Copyright by Le Li 2015rochelle.che.utexas.edu/files/2015/02/Li-dissertation-final-version.pdf · The Dissertation Committee for Le Li Certifies that this is the approved version

Copyright

by

Le Li

2015

The Dissertation Committee for Le Li Certifies that this is the approved version of

the following dissertation:

Carbon Dioxide Solubility and Mass Transfer in Aqueous Amines for

Carbon Capture

Committee:

Gary T. Rochelle, Supervisor

Benny D. Freeman

Isaac C. Sanchez

Hallvard F. Svendsen

Ross E. Dugas

Carbon Dioxide Solubility and Mass Transfer in Aqueous Amines for

Carbon Capture

by

Le Li, B.S.E.

Dissertation

Presented to the Faculty of the Graduate School of

The University of Texas at Austin

in Partial Fulfillment

of the Requirements

for the Degree of

Doctor of Philosophy

The University of Texas at Austin

August 2015

Dedication

to my mother,

for teaching me how to think, and how to enjoy life.

v

Acknowledgements

First and foremost, I would like to thank my advisor, Dr. Gary Rochelle, for his

guidance and mentorship during the past six years. His (often outrageously creative)

ideas and his patience with me made this work possible. Dr. Rochelle’s enthusiasm

about research and his scientific curiosity has been an inspiration for me to find joy and

value in my own work. His dedication to his family and community taught me the

importance of work-life balance. Most importantly, his love for teaching and generosity

for his students are values I hope to carry on in my career and in my life. Beyond the

technical expertise and scientific knowledge I have learned, I also treasure the memories

from the extra-curricular activities organized by Dr. Rochelle, such as: backpacking trips

in the mountains, descending into caves, and exploring in exotic foreign cities. Joining

his research group was one of the easiest and best decisions I have made.

This work and my graduate studies were supported financially by the Luminant

Carbon Management Program, and later the Texas Carbon Management Program. I

received additional financial assistance from the Thrust Fellowship through the Cockrell

School of Engineering at UT Austin. I am very grateful to these programs as they

allowed me to not only survive, but enjoy my life during the past six years in Austin.

I would like to thank Prof. Benny Freeman, Prof. Issac Sanchez, Prof. Hallvard

Svedsen, and Dr. Ross Dugas for offering their time and professional expertise as

members of my dissertation committee. I’m especially grateful to Dr. Svendsen’s extra

efforts in his participation from very far away. Moreover, Dr. Svendsen and his

research group at NTNU gave me important alternative perspectives on the science of

amine scrubbing, which were very valuable in the development of my research ideas.

vi

The faculty and staff at the McKetta Department of Chemical Engineering at The

University of Texas in Austin offered invaluable support for this work and my learning.

Prof. Michael Baldea offered important assistance to my MATLAB modeling activity in

this work. I also enjoyed working with Prof. Hal Alper in the organization of the

Graduate Seminar class. I am thankful to Prof. Keith Freidman for letting me regularly

use the rheometer under his care for my viscosity measurements.

I greatly appreciate our administrative assistance, Maeve Cooney, for her hard

work to take care of the many important logistics during my time in the research group.

I must thank her especially for putting up with me missing the deadline for many

quarterly reports. The graduate program coordinators at the department, T Stockman

and Kate Baird, provided assistance during my enrollment, through my preliminary

exams, and most importantly with my graduation paperwork and logistics. Jim

Smitherman and Butch Cunningham, along with the machine shop, was a great resource

for hardware problems in the lab. Eddie Ibarra and Kevin Haynes helped with my many

purchase orders and deliveries of chemicals and equipments. Randy Rife and Patrick

Danielewski helped me with several computer software related issues. Carrie Brown

and Kay Costales-Swift provided numerous assistance with arranging meeting rooms and

other administrative matters.

The cryogenic lab operated by the Department of Physics offered a convenient

source of liquid nitrogen, which was crucial to the mass transfer experiments. On

several occasion, the glass shop in the Department of Chemistry and the glass technician

Mike Ronalter provided efficient support for the glassware that was used in this work.

During the past six years I received daily support and inspirations from my

colleagues in the Rochelle group. I am especially thankful for the detailed and patient

mentorship offered by Dr. Xi Chen, with whom I learned to operate the wetted wall

vii

column. I really appreciate Dr. Fred Closmann and Dr. Stephanie Freeman for training

me on the basics in the lab, as well as for maintaining several shared apparatus in the lab

during their time in the group. Their work ethics, thoroughness, and dedication to

excellence set an important example for me. I very much value the experience of

working closely with Dr. Qing Xu, Dr. Alex Voice, Steven Fulk, Humera Rafique, Dr.

Nathan Fine, and Yang Du. I’m also thankful for the support and friendship of Dr.

David Van Wagner, Dr. Jorge Plaza, Dr. Peter Frailie, Dr. Omkar Namjoshi, Darshan

Sachde, Tarun Madan, Brent Sherman, Matt Walters, Yu-Jeng Lin, Di Song, Kent

Fischer, and our exchange scholar Dr. Han Li from Tsinghua University.

I was fortunate to have had excellent help from my undergraduate assistants:

Trang Nguyen, Joseph Ming-Han Lee, and Nina Salta.

I would like to thank my mother, who provided constant support, guidance, as

well as home cooked deliciousness during my graduate studies. Her firm belief in the

value and importance of graduate education and her faith in me are what kept me going

through my challenges and doubts. I would like to also thank her husband Victor Pol,

for his understanding and many helps with my apartment and life in Austin. I am very

thankful for the love and support from my grandparents, aunt, uncle, and cousins (Lei and

Chen) in China. I also appreciate the support and thoughts from my father.

Through the Department of Chemical Engineering I am honored to have met great

friends including Dr. Nathan Crook, Dr. Erwan Chabert, Dr. Zach Frye, Peach Kasamset,

Dr. Avni Jain, Dr. Sunmi Lee, Dr. Kate Curran, Dr. Jie Sun, Dr. Jong Suk Kim, Dr.

Leqian Liu, Dr. Wenzong Li, Dr. Bo Lu, Joseph Cheng, and Jorge Vasquez. During my

time at UT, I also became close friends with Dr. Man Liang and (soon to be Dr.) Beatrice

Mabrey. The times shared and support I received from these friendships I will always

treasure.

viii

Last but not least I would like to thank Brent Sherman, for his love and company

during the last few years. Our relationship, much like the experience of this Ph.D. work,

has been very challenging and rewarding at the same time. The writing of this

dissertation would’ve been much more painful without his encouragement and support

along the way.

ix

Carbon Dioxide Solubility and Mass Transfer in Aqueous Amines for Carbon Capture

Le Li, Ph.D.

The University of Texas at Austin, 2015

Supervisor: Gary T. Rochelle

Amine scrubbing is the state of the art technology for CO2 capture, and solvent

selection can significantly reduce the capital and energy cost of the process. This work

presents rigorous CO2 mass transfer and solubility data at expected process conditions for

more than 20 aqueous amines and amino acid salts.

Amino acid salts are generally not competitive with aqueous amines as solvents

for CO2 capture, particularly from coal fired power plants. The capacity of amino acid

salts is intrinsically low (0.2 – 0.35 mol/mol alkalinity).

Piperazine (PZ) blends have good overall performance. 3.5 m PZ/3.5 m 2-

amino-2-hydroxymethyl-propane-1,3-diol (Tris) shows good absorption rates, good

capacity, and low solvent viscosity. 6 m PZ/2 m hexamethylenediamine (HMDA) has

moderate absorption rates, capacity, and a high viscosity.

High solvent viscosity has been shown to reduce CO2 absorption rate and increase

sensible heat cost.

A simplified speciation model (SSM) was developed in MATLAB to represent

CO2 VLE in a mono-amine solvent using only four adjustable parameters. The model

can also predict liquid phase speciation. Primary and secondary amines were shown to

have different CO2 VLE dependence on amine pKa. At pKa higher than 8, secondary

x

amines have lower carbamate stability than primary amines. A correlation was

developed to predict the SSM parameters based on the amine type and amine pKa.

The third order overall reaction kinetic expression better explains the mass

transfer data at process conditions than the more widely applied second order overall

expression. A new Bronsted correlation was developed to represent the third order

concentration based kinetic constant at 40 °C for primary and secondary amines:

𝑙𝑜𝑔10(𝑘𝑐−3∗) = −11.728 + 1.113 ∙ 𝑝𝐾𝑎𝑎𝑚𝑖𝑛𝑒

.

This work shows the absorption rate of CO2 at process conditions do not always

increase with amine pKa. As the reaction rate constant increases with amine pKa, the

free amine available for CO2 absorption decreases. As the result, for primary and

secondary mono-amines, the optimum amine pKa for the best mass transfer performance

is around 8.7 (at 40 °C).

xi

Table of Contents

List of Tables ..................................................................................................... xviii

List of Figures ......................................................................................................xxx

Chapter 1: Introduction .........................................................................................1

1.1 Motivations ...............................................................................................1

1.2 Amine scrubbing for CO2 Capture ............................................................4

1.2.1 Current technical challenges .........................................................5

1.2.2 Solvent screening for amine scrubbing .........................................6

1.3 Previous studies on CO2 absorption rates and capacity ............................7

1.4 Objective and Scope of This Work .........................................................13

1.4.1 Rigorous screening of new amine solvents .................................13

1.4.2 Estimate process performance ....................................................14

1.4.3 Generalize solvent performance .................................................14

Chapter 2: Theoretical review .............................................................................15

2.1 General Chemistry ..................................................................................15

2.1.1 Acid base catalysis ......................................................................15

2.1.2 Types of amine structures ...........................................................16

2.1.3 Kinetic mechanisms ....................................................................20

2.1.4 Reversible reaction......................................................................23

2.1.5 Activity vs. concentration based rate expression: .......................24

2.2Mass Transfer Theories ............................................................................24

2.2.1 Mass transfer coefficients ...........................................................25

2.2.2 Physical mass transfer .................................................................26

2.2.3 Mass transfer with chemical reaction .........................................29

Chapter 3: Experimental methods .......................................................................37

3.1 Wetted Wall Column ..............................................................................37

3.1.1 Introduction .................................................................................37

3.1.2 Apparatus and set up ...................................................................38

xii

3.1.3 WWC Data analysis ....................................................................42

3.1.4 Error and reproducibility.............................................................46

3.2 Total Pressure Apparatus ........................................................................52

3.2.1 Introduction .................................................................................52

3.2.2 Apparatus and set up ...................................................................52

3.2.3 Data analysis ...............................................................................53

3.3 Analytical Methods .................................................................................55

3.3.1 Total Inorganic Carbon (TIC) .....................................................55

3.3.2 Total alkalinity titration ..............................................................55

3.3.3 Viscosity .....................................................................................56

Chapter 4: Data Applications ..............................................................................57

4.1 CO2 VLE .................................................................................................57

4.1.1 CO2 loading .................................................................................59

4.1.2 Semi-empirical model for CO2 VLE ...........................................59

4.1.3 Estimation of heat of absorption .................................................59

4.2 Process performance parameters.............................................................61

4.2.1 Standard operating conditions.....................................................61

4.2.2 Average mass transfer rate ..........................................................63

4.2.3 CO2 capacity ...............................................................................64

4.2.4 Stripping performance ................................................................67

Chapter 5: Amino Acid Salts for CO2 Capture ...................................................70

5.1 Introduction .............................................................................................70

5.1.1 Motivations .................................................................................70

5.1.2 CO2/amino acid salt/H2O Chemistry ..........................................70

5.1.3 Literature review .........................................................................72

5.1.4 Scope ...........................................................................................78

5.1.5 Solvent preparation .....................................................................79

5.2 Physical properties ..................................................................................80

5.2.1 Solid solubility ............................................................................80

5.2.2 Viscosity .....................................................................................85

xiii

5.3. Absorption rate.......................................................................................88

5.3.1 CO2 mass transfer data ................................................................88

5.3.2 Mass transfer performance in an absorber ..................................96

5.4 CO2 VLE .................................................................................................97

5.4.1 CO2 solubility data ......................................................................98

5.4.2 CO2 Capacity ............................................................................109

5.4.3 Heat of CO2 absorption .............................................................112

5.5 Oxidative Degradation of Aqueous Amino Acid Salts .........................114

5.6 Conclusions ...........................................................................................115

Chapter 6: Concentrated Piperazine Blends for CO2 Capture ..........................117

6.1 Introduction ...........................................................................................117

6.1.1 Motivation .................................................................................117

6.1.2 Literature review .......................................................................118

6.1.3 Scope .........................................................................................121

6.1.4 Solvent preparation ...................................................................124

6.2 Physical Properties ................................................................................124

6.2.1 Solid Solubility .........................................................................124

6.2.2 Viscosity ...................................................................................129

6.3 Absorption Rate Results .......................................................................136

6.3.1 CO2 mass transfer data ..............................................................137

6.3.2 Effect of solvent viscosity .........................................................146

6.3.3 Effect of amine structure ...........................................................148

6.3.4 Effect of blend ratio ..................................................................152

6.3.5 Performance in an absorber ......................................................153

6.4 CO2 Solubility .......................................................................................155

6.4.1 CO2 VLE data ...........................................................................156

6.4.2 Effect of structure .....................................................................174

6.4.3 Effect of blend ratio ..................................................................178

6.4.4 CO2 Capacity ............................................................................179

6.4.4 Heat of Absorption ....................................................................180

xiv

6.4.5 Stripping performance ..............................................................183

6.5 Solvent Management ............................................................................185

6.5.1 Solvent degradation ..................................................................185

6.5.2 Amine volatility ........................................................................189

6.6 Conclusions ...........................................................................................192

Chapter 7: CO2 Solubility and absorption rate measurements in aqueous primary

and secondary amines .................................................................................194

7.1 Introduction ...........................................................................................194

7.1.1 Scope .........................................................................................194

7.1.2 Literature review .......................................................................196


7.2 Absorption rate results ..........................................................................198

7.2.1 CO2 mass transfer data ..............................................................199

7.2.2 Effect of amine type ..................................................................203

7.2.4 Process performance .................................................................204

7.2.5 Effect of base strength ..............................................................205

7.3 CO2 VLE Results ..................................................................................206

7.3.1 CO2 solubility data ....................................................................206

7.3.1 Effect of amine type ..................................................................215

7.3.2 CO2 Capacity ............................................................................217

7.3.2 Heat of Absorption ....................................................................217

7.4 Conclusions ...........................................................................................220

Chapter 8: Other solvents and overall comparison ...........................................221

8.1 Introduction ...........................................................................................221

8.2 Aqueous Amines and Blends ................................................................221

8.2.1 MEA/MDEA .............................................................................221

8.2.2 8 m Bis(amnioethyl)ether (BAE) ...........................................228

8.3 Enzyme Catalyzed Aqueous Amine .....................................................235

8.4 Proprietary Systems ..............................................................................240


xv

8.4.2 Viscosity ...................................................................................241

8.4.3 Absorption rate results ..............................................................245

8.4.3 CO2 solubility............................................................................248

8.5 Rate and capacity comparison of amine solvents .................................256

8.5.1 Single amine solvents ...............................................................258

8.5.2 PZ blends ..................................................................................261

8.5.3 Amino acids ..............................................................................265

8.5.4 Rates and viscosity normalized capacity ..................................265

8.6 Master solvent table ..............................................................................267

Chapter 9: Simplified stoichiometric model for CO2 VLE in aqueous amines ...272

9.1 Introduction ...........................................................................................272

9.1.1 CO2 VLE in aqueous amines .....................................................272

9.1.2 Types of CO2 VLE modeling methods .....................................274

9.1.3 Previous stoichiometric models ................................................275

9.1.4 Scope .........................................................................................276

9.2 Simplified stoichiometric model (SSM) ...............................................278

9.2.1 Model equations ........................................................................278

9.2.2 Numerical tools .........................................................................281

9.2.3 Model statistics .........................................................................283

9.2.4 Base case results for 7 m MEA .................................................284

9.3 Model results of aqueous amines ..........................................................290

9.3.1 CO2 VLE fit ..............................................................................290

9.3.2 Liquid phase speciation prediction ...........................................299

9.3.3 Regressed parameters and statistics ..........................................304

9.4 Physical significance of model parameters ...........................................305

9.4.1 First equilibrium constant (K1*) ................................................307

9.4.2 Second equilibrium constant (K2*)............................................310

9.4.4 Predicting CO2 VLE .................................................................316

9.5 Conclusions ...........................................................................................318

xvi

Chapter 10: Mass transfer and kinetics in aqueous mono-amines ....................321

10.1 Introduction .........................................................................................321

10.1.1 Process condition ....................................................................322

10.1.2 Scope .......................................................................................323

10.2 Experimental Data ..............................................................................323

10.2.1 CO2 mass transfer rates ...........................................................323

10.2.2 CO2 VLE .................................................................................325

10.2.3 Viscosity .................................................................................326

10.2.4 Density ....................................................................................326

10.3 Estimating components of liquid film mass transfer coefficient ........328

10.3.1 Free amine concentration ........................................................328

10.3.2 Diffusion coefficient of CO2 ...................................................329

10.3.3 Henry’s constant of CO2 .........................................................331

10.3.4 Activity coefficients ................................................................331

10.3.5 Calculating reaction rate constant ...........................................332

10.4 Predicting mass transfer rates for unhindered mono-amines ..............339

10.4.1 Mass transfer rate in a generic primary and secondary amine 340

10.4.2 Error analysis ..........................................................................345

10.5 Conclusions .........................................................................................347

Chapter 11: Conclusions and Recommendations .............................................348

11.1 Conclusions .........................................................................................348

11.1.1 Primary and secondary mono-amines .....................................348

11.1.2 Generalization of CO2 mass transfer rates at process conditions348

11.1.3 Generalization of CO2 VLE ....................................................349

11.1.4 Solvent viscosity .....................................................................350

11.1.5 Piperazine blends ....................................................................351

11.1.6 Amino acid salts ......................................................................352

11.2 Recommendations ...............................................................................353

11.2.1 Solvent screening ....................................................................353

11.2.2 High temperature mass transfer data.......................................354

xvii

11.2.3 CO2 VLE and simplified speciation model (SSM) .................354

11.2.4 Hindrance effect on CO2 VLE ................................................355

11.2.5 CO2 absorption rate in hindered amines .................................355

Appendix A: Background and Theory .................................................................356

Appendix B: Additional Experimental Data ........................................................372

B.1 Additional mass transfer and CO2 solubility data ................................372

B.2 Detailed WWC data .............................................................................386

Appendix C: Simplified stoichiometric model ....................................................474

Appendix D: Spreadsheet model for process performance ..................................480

Appendix E: Standard Operating Procedures (SOP) ...........................................488

E.1 Wetted Wall Column SOP .................................................................488

E.2 Total pressure apparatus SOP ...............................................................501

References ............................................................................................................515

Vita .....................................................................................................................529

xviii

List of Tables

Table 1.1: Summary of published solvent rate screening results.............................9

Table 1.2: Summary of published CO2 capacity screening results ........................10

Table 1.3: Previous absorption rate measurements by at the University of Texas at

Austin using a wetted wall column ...................................................11

Table 1.3 (continued) .............................................................................................12

Table 2.1: General structure of different types of amines .....................................17

Table 2.2: Summary of kl dependence on diffusion coefficient by various physical

mass transfer models .........................................................................29

Table 3.1: CO2 solubility and kg’ in 8 m PZ measured in three separate experiments

from 2010-2012 ................................................................................51

Table 4.1: Standard operating conditions for CO2 capture process used in this work,

for coal and natural gas combined cycle flue gas .............................62

Table 5.1: Journal Publications on Amino Acid Solvents from the University of

Twente...............................................................................................74

Table 5.2: Journal Publications on Amino Acid Solvents by various sources ......76

Table 5.3: Patents on the use of amino acid salts for CO2 capture ........................77

Table 5.4: Summary of amino acid salt systems screened in this work ................78

Table 5.5: Materials used for solvent preparation .................................................80

Table 5.6 : Solid solubility measured for amino acid salts at room temperature, the

solubility of the amino acid salt is between the before and after

concentrations ...................................................................................85

Table 5.7: Viscosity of amino acid salts measured at 40 ad 60 °C ........................87

Table 5.8: Semi-empirical model parameters of the amino acid salt solvents .....103

xix

Table 5.9: CO2 Solubility and kg’ for 3.55m GlyK..............................................104

Table 5.10: CO2 Solubility and kg’ for 6 m GlyK................................................104

Table 5.11: CO2 solubility and kg’ for 6 m SarK .................................................105

Table 5.12: CO2 Solubility and kg’ for 4.5 m SarNa ...........................................106

Table 5.13: CO2 Solubility and kg’ for 6.5 m β-AlaK .........................................107

Table 5.14: CO2 Solubility and kg’ for 5 m TauK ...............................................107

Table 5.15: CO2 Solubility and kg’ for 3 m TauK/5 m HomotauK .....................108

Table 5.16: CO2 Solubility and kg’ for 6.5 m ProK .............................................108

Table 5.17: Summary of performance parameters evaluated at coal flue gas conditions

(0.5-5 kPa) for amino acid salt solvents..........................................113

Table 5.18: Summary of performance parameters evaluated at natural gas conditions

(0.1 – 1 kPa) for amino acid salt solvents .......................................114

Table 5.19: Summary of the oxidative stability of amino acid salts studied by Voice

(2013) ..............................................................................................115

Table 6.1: Selected literature on three popular PZ blends ...................................119

Table 6.2: Literature on other PZ blends .............................................................120

Table 6.3: List of PZ blends tested in this work ..................................................122

Table 6.3: (continued) ..........................................................................................123

Table 6.4: Materials Used for Solvent Preparation ..............................................124

Table 6.5: Solid solubility measurement of concentrated PZ blends in literature128

Table 6.6: Solid solubility observation for PZ blends at room temperature ........129

Table 6.7: Viscosity of 6 m PZ/2 m EDA at 25, 40, and 60 °C ...........................131

Table 6.7: (continued) ..........................................................................................132

Table 6.8: Viscosity of 6 m PZ/2 m HMDA at 40, 60, 80, and 100 °C ...............132

Table 6.9: Viscosity of 6 m PZ/2 m BAE at 40 °C ..............................................133

xx

Table 6.10: Viscosity of 5 m PZ/5 m DGA® at 40 °C .........................................133

Table 6.11: Viscosity of 6 m PZ/2 m HEP at 40 °C ............................................134

Table 6.12: Viscosity of 5 m PZ/5 m 2-PE at 40 °C ............................................135

Table 6.13: Viscosity of 3.5 m PZ/3.5 m Tris at 20 and 40 °C ...........................136

Table 6.14: Absorption rate performance of concentrated PZ blends for coal flue gas

conditions, compared with literature results of other PZ blends ....154

Table 6.15: Parameter values for the semi-empirical VLE model for PZ blends 164

Table 6.16: CO2 solubility and absorption rates for 6 m PZ/2 m EDA by the WWC

.........................................................................................................165

Table 6.17: CO2 solubility for 6 m PZ/2 m EDA at high temperature by the total

pressure apparatus ...........................................................................165

Table 6.18: CO2 solubility and absorption rates in 6 m PZ/2 m DAB by the WWC166

Table 6.19: CO2 solubility for 6 m PZ/2 m DAB at high temperatures by the total


Table 6.20: CO2 solubility and absorption rates for 6 m PZ/2 m HMDA by the WWC

.........................................................................................................167

Table 6.21: CO2 solubility and absorption rates for 6 m PZ/2 m BAE by the WWC

.........................................................................................................167

Table 6.22: CO2 solubility for 6 m PZ/2 m BAE at high temperatures by the total


Table 6.23: CO2 solubility and absorption rates for 5 m PZ/5 m DGA® by the WWC

.........................................................................................................169

Table 6.24: CO2 solubility and absorption rates of 5 m PZ/2 m AEP by the WWC170

Table 6.25: CO2 solubility and absorption rates of 5 m PZ/2.3 m AMP by the WWC

.........................................................................................................171

xxi

Table 6.26: CO2 solubility and absorption rates for 6 m PZ/2 m HEP by the WWC172

Table 6.27: CO2 solubility and absorption rates for 5 m PZ/5 m 2-PE by the WWC

.........................................................................................................173

Table 6.28: CO2 solubility and absorption rates for 3.5 m PZ/3.5 m Tris by the WWC

.........................................................................................................174

Table 6.29: Summary of cyclic loading, capacity, and heat of absorption for PZ

blends ..............................................................................................183

Table 6.30: Summary of stripping performance for selected PZ blends .............184

Table 6.31: Summary of thermal degradation rate, activation energy, and maximum

stripper temperature for PZ blends and amines in the blends .........186

Table 6.32: Ammonia production rates (mmol/kg/hr) from various solvents in the

HGF apparatus by Voice (2013); with air and 2% CO2 at 70 °C with iron

(Fe), copper (Cu) and manganese (Mn) added at 1 mM concentration188

Table 6.33: Total formate production rates in various solvents in the LGF apparatus

with oxygen and 2% CO2 at 70 °C with various metals (SSM=Fe, Ni,

Cr) ...................................................................................................188

Table 6.34: Parameters for the structural property correlation for Hamine (Equation 6.5)

.........................................................................................................190

Table 6.35: The practical Henry’s constant and amine partial pressure at 40 °C for the

PZ blends ........................................................................................191

Table 7.1: Structure and solvent concentration for amine solvents tested in this work

.........................................................................................................195

Table 7.2: Selected literature on CO2 reaction kinetics and solubility for amine

solvents included in this work.........................................................196

xxii

Table 7.3: Available WWC data for other primary and secondary amines collected

using the same method ....................................................................196

Table 7.4: Chemicals used in solvent preparation ...............................................198

Table 7.5: Semi-empirical CO2 VLE model parameter values ............................211

Table 7.6: CO2 Solubility and kg’ for 7 m monoisopropanolamine (MIPA) .......211

Table 7.7: CO2 Solubility and kg’ results for 7 m monopropanolamine (MPA)..212

Table 7.8: CO2 Solubility and kg’ results for 7 m diethanolamine (DEA) ..........213

Table 7.9: CO2 Solubility and kg’ results for 7 m methylmonoethanolamine (MMEA)

.........................................................................................................214

Table 7.10: CO2 Solubility and kg’ results for 7 m diisopropanolamine (DIPA) 215

Table 8.1: Materials used for preparation of the MEA/MDEA ...........................222

Table 8.2: Viscosity of 3.4 m (20 wt %) MDEA/9.8 m (30 wt %) MEA at 40 °C223

Table 8.3: Semi-empirical VLE model parameters for 3.4 m MDEA/9.8 m MEA

(Equation 4.4) .................................................................................226

Table 8.4: Predicted performance parameters of 3.4 m MDEA/9.8 m MEA ......227

Table 8.5: PCO2* and kg’ measurement for 3.4 m MDEA/9.8 m MEA by the WWC227

Table 8.6: Viscosity for 8 m BAE at 25, 40, and 60 °C.......................................230

Table 8.7: Parameters of the equilibrium model for 8 m BAE (Equation 4.4) ....234

Table 8.8: Performance parameters of 8 m BAE, compared with 8 m PZ, 7 m MEA

(Dugas 2009, Xu 2011), 10 m DGA®(Chen 2011), and 6 m PZ/2 m BAE

(Chapter 6) ......................................................................................234

Table 8.9: PCO2* and kg’ measurement for 8 m BAE...........................................235

Table 8.10: Materials Used for Solvent Preparation ............................................237

Table 8.11: Chemical Composition in 4.8 m AMP Solution ...............................237

Table 8.12: Species Composition in Enzyme Promoted AMP Solutions ............238

xxiii

Table 8.13: Measured kg’ of 4.8 m AMP Promoted by Enzyme ........................240

Table 8.14: Materials Used for Solvent Preparation ............................................241

Table 8.15: Composition of the initial solution used in the wetted wall column

experiment.......................................................................................241

Table 8.16: Parameters of the viscosity correlation for the Company A solvents244

Table 8.17: Viscosity measurements of the Company A solvents .......................244

Table 8.18: Parameters of the modified semi-empirical VLE model (Equation 8.4) for

the proprietary solvents ...................................................................251

Table 8.19: Performance of the proprietary solvents at coal flue gas conditions,

compared with 7 m MEA and 8 m PZ (Dugas 2009, Xu 2011) .....252

Table 8.20: WWC measurements for Company A1 ............................................253

Table 8.21: WWC measurements for Company A2 ............................................253

Table 8.22: Total pressure apparatus CO2 solubility results for the Company A

solvents ...........................................................................................254

Table 8.23: WWC measurements for the Company B solvent ............................255

Table 8.24: Performance summary of amine solvents characterized at the University

of Texas in Austin ...........................................................................268

Table 8.24 (Continue’d): Performance summary of amine solvents characterized at

the University of Texas in Austin ...................................................269





Table 9.1: The structure, type and pKa of the amines analyzed using the simplified

speciation model .............................................................................276

xxiv

Table 9.1: (continued) ..........................................................................................277

Table 9.2: SSM parameter values and standard deviation for 7 m MEA ............289

Table 9.3: Correlation matrix of the SSM parameters for 7 m MEA ..................289

Table 9.4: Experimental data used for each amine system in the regression of SSM

equilibrium parameters and the AARD of the final data fit ............304

Table 9.5: The SSM model parameter values and standard error for each amine304

Table 9.6: Chemical equilibrium constants at 40 °C calculated by the SSM ......316

Table 10.1: Parameters of the polynomial fit for kg' (40 °C) as a function of CO2

loading (Equation 10.2), and the interpolated kg' value at standard

operating conditions (40 °C, 0.5 and 5 kPa) for coal flue gas ........324

Table 10.2: Source of solvent viscosity and density data and/or method of estimation

.........................................................................................................327

Table 10.3: The molar mass, density (also in Table 10.3), and molar density of amine

solvents at the standard operating conditions (40 °C, 0.5 and 5 kPa) for

coal flue gas ....................................................................................328

Table 10.4: Free amine concentration at standard operating CO2 loadings (40 °C, 0.5

and 5 kPa), calculated by the simplified stoichiometric model (Chapter

9) .....................................................................................................329

Table 10.5: Viscosity and diffusion coefficient of CO2 at the standard operating

conditions (40 °C, 0.5 and 5 kPa ) for coal flue gas .......................330

Table 10.7: Standard error and R2 values for the overall and separate Bronsted

correlations for primary and secondary monoamines .....................339

Table 10.8: Calculated diffusion coefficient, standard operating CO2 loadings, free

amine concentration for the generic primary and secondary amine with

varying pKa at 40 °C. ......................................................................342

xxv

Table 10.9: Calculated effective reaction kinetic constant (kc-3*), and mass transfer

coefficients at process conditions using two types of Bronsted

correlation .......................................................................................343

Table B-1: Parameter values of two semi-empirical VLE models (Equation 4.4) for 8

m MAPA .........................................................................................373

Table B-2: Capacity, -Habs, and operating loading range of 8 m MAPA predicted

using two empirical models (Table 3). ...........................................375

Table B-3: PCO2* for 8 m MAPA at high temperature ..........................................376

Table B-4: CO2 Solubility and kg’ Measured for 7 m MDEA 2 m PZ at 30 and 40 °C

.........................................................................................................377

Table B-5: CO2 solubility and absorption rates of 5 m MDEA/5 m PZ blend at low

temperatures ....................................................................................379

Table B-6: Semi-empirical model (Equation 4.4) parameters for PRC pilot plant

sample and 8 m PZ ..........................................................................382

Table B-7: Detailed high temperatures PCO2* results for PRC 8 m PZ Fall 2011 pilot

plant sample ....................................................................................383

Table B-8: Detailed high temperatures PCO2* results for 8 m PZ + 100 mM Inh A384

Table B-9: Detailed Wetted Wall Column Data for 3.55 m GlyK (part 1) .........386

Table B-10: Detailed Wetted Wall Column Data for 3.55 m GlyK (part 2) .......387

Table B-11: Detailed Wetted Wall Column Data for 3.55 m GlyK (part 3) .......388

Table B-12: Detailed Wetted Wall Column Data for 6 m GlyK (part 1) ............389

Table B-13: Detailed Wetted Wall Column Data for 6 m GlyK (part 2) ............390

Table B-14: Detailed Wetted Wall Column Data for 6 m SarK (part 1) .............391



xxvi

Table B-17: Detailed Wetted Wall Column Data for 3 m TauK/5 m HomotauK (part

1) .....................................................................................................394


2) .....................................................................................................395


3) .....................................................................................................396

Table B-20: Detailed Wetted Wall Column Data for 5 m TauK .........................397

Table B-21: Detailed Wetted Wall Column Data for 6.5 m β-AlaK (part 1) ......398




Table B-25: Detailed Wetted Wall Column Data for 4.5 m SarNa (part 1) ........402



Table A-28: Detailed Wetted Wall Column Data for 4.5 m SarNa (part 4) ........405

Table B-29: Detailed Wetted Wall Column Data for 6.5 m ProK .......................405

Table B-30: Detailed Wetted Wall Column Data for 6 m PZ/2 m HMDA (part 1)407

Table B-31: Detailed Wetted Wall Column Data for 6 m PZ/2 m HMDA (part 2)408

Table B-32: Detailed WWC data for 6 m PZ/2 m DAB (part 1) .........................409



Table B-35: Detailed WWC data for 6 m PZ/2 m BAE (part 1) .........................412




xxvii

Table B-39: Detailed WWC data for 6 m PZ/2 m EDA (part 1) .........................416



Table B-42: Detailed WWC data for 5 m PZ/2 m AEP (part 1) ..........................419




Table B-46: Detailed WWC data for 5 m PZ/2.3 m AMP (part 1) ......................423




Table B-50: Detailed WWC data for 6 m PZ/2 m HEP (part 1) ..........................426




Table B-54: Detailed WWC data for 5 m PZ/5 m 2PE (part 1) ...........................430





Table B-59: Detailed WWC data for 5 m PZ/5 m DGA (part 1) .........................435



Table B-62: Detailed WWC data for 3.5 m PZ/3.5 m Tris (part 1) .....................438


xxviii


Table B-65: Detailed WWC data for 7 m 3 amino 1 propanol (part 1) ...............441




Table B-69: Detailed WWC data for 7 m MIPA (part 1) ....................................445




Table B-73: Detailed WWC results for 7 m DEA (part 1) ..................................449

Table B-74: Detailed WWC results for 7 m DEA (part 2) ..................................450

Table B-75: Detailed WWC data for 7 m DEA (part 3) ......................................451

Table B-76: Detailed WWC data for 7 m DEA (part 4) ......................................452

Table B-77: Detailed WWC data for 7 m MMEA (part 1) ..................................452




Table B-81: Detailed WWC data for 7 m DIPA (part 1) .....................................456

Table B-82: Detailed WWC data for 7 m DIPA (part 2) .....................................457

Table B-83: Detailed WWC data for 9.8 m MEA/3.4 m MDEA (part 1) ...........459




Table B-87: Detailed WWC data for 8 m BAE (part 1) ......................................463


xxix


Table B-90: Detailed WWC data for 2011 8 m PZ pilot plant campaign sample (part

1) .....................................................................................................466

Table B-91: Detailed WWC data for 2011 8 m PZ pilot plant campaign sample (part

2) .....................................................................................................467

Table B-92: Detailed Wetted Wall Column Data for 7 m MDEA/2 m PZ (part 1)468

Table B-93: Detailed Wetted Wall Column Data for 7 m MDEA/2 m PZ (part 2)469

Table B-94: Detailed WWC data for 5 m MDEA/5 m PZ (part 1)......................470

Table B-95: Detailed WWC data for 5 m MDEA/5 m PZ (part 2)......................471

Table B-96: Detailed Wetted Wall Column Data for Enzyme Promoted 4.8 m AMP

(part 1) .............................................................................................472

Table B-97: Detailed Wetted Wall Column Data for Enzyme Promoted 4.8 m AMP

(part 3) .............................................................................................473

Table D-1: Flue Gas Properties of 500 MW Coal Plant ......................................480

Table D-2: VLE Models and Parameters .............................................................480

Table D-3: Wetted Wall kg’ Measurements (40 °C) ............................................481

Table D-4: Parameters of kg’ Correlation ............................................................482

Table D-5: Input Values of First Calculation Stage.............................................482

Table D-6: Output Values of First Calculation Stage ..........................................483

Table D-7: Isothermal Spreadsheet Model Results (40 °C, 90% Removal) ........485

xxx

List of Figures

Figure 1.1: World energy consumption and CO2 emission from 1980 to 2011 (EIA

2014a) .................................................................................................2

Figure 1.2: U.S. energy consumption in 2013 by fuel source (EIA 2014b) ............2

Figure 1.3: The amine scrubbing process for CO2 capture (Rochelle 2009). ..........4

Figure 2.1: Reaction complex proposed by the Termolecular Reaction Mechanism22

Figure 2.2: Steady state concentration profile of CO2 absorption without chemical

reaction in the liquid phase, using film theory (not drawn to scale). 27

Figure 2.3: Steady state concentration profile of CO2 absorption with chemical

reaction in the liquid phase, with the pseudo first order assumption (not

drawn to scale). .................................................................................31

Figure 2.4: Steady state concentration profile of CO2 absorption with instantaneous

reversible reaction in the liquid phase (not drawn to scale). .............33

Figure 2.5: Steady state concentration profile of CO2 absorption with fast reversible

chemical reaction in the liquid phase (not drawn to scale). ..............35

Figure 3.1: Detailed dimensions of the wetted wall column .................................38

Figure 3.2: The wetted wall column apparatus and supplementary equipment .....40

Figure 3.3: Experimental CO2 flux and partial pressure driving force measured for 5

m PZ/2m AEP with 0.25 mol/mol alk CO2 loading at 80 °C ...........45

Figure 3.4: Equilibrium partial pressure of CO2 for 8 m PZ measured by the WWC

from four separate experiments, compared with the lines from a semi-

empirical VLE model (Xu 2011). .....................................................47

xxxi

Figure 3.5: Parity plot of PCO2* measured by the WWC compared with results from a

semi-empirical VLE model, assuming the CO2 loading measured for the

samples are accurate (Xu 2011). .......................................................48

Figure 3.6: Parity plot of potential errors in CO2 loading in the WWC samples,

estimated using a semi-empirical VLE model and assumes accuracate

PCO2* (Xu 2011). ...............................................................................49

Figure 3.7: Liquid film mass transfer coefficient (kg’) measured by the WWC for 8 m

piperazine (PZ) in four separate experiments ...................................50

Figure 3.8: Diagram of the total pressure equilibrium reactor ...............................52

Figure 3.9: Example total pressure measurement of a pilot plant sample of 8 m PZ

during the 2011 campaign at the University of Texas in Austin Pickle

Research Center. ...............................................................................53

Figure 4.1: Simplified diagram of the two phase CO2-amine-H2O system ...........57

Figure 4.2: Example CO2 VLE plot. Solid points: WWC data for 6.5 m β-ala(K);

lines: semi-empirical model results (Equation 4.4). .........................58

Figure 4.3: Heat of absorption of 6 m PZ/2 m BAE predicted by three semi-empirical

VLE models ......................................................................................61

Figure 4.4: Simplified diagram of an absorber for CO2 capture from coal flue gas62

Figure 4.5: CO2 VLE curves at 40 C for PZ (Xu 2011) and 3.5 m PZ/3.5 m Tris (this

work) and the corresponding delta loading (Δldg). ..........................65

Figure 5.1. Chemical structure of amino acid in various charged forms ...............70

Figure 5.2: Highest soluble concentration measured for the amino acid salts at room

temperature (approximately 25 °C) ..................................................82

Figure 5.3: Statistics of the solid solubility data for SarK at room temperature. ..83

xxxii

Figure 5.4: Solubility of amino acid salt (solid) compared to the solubility of the

amino acid in water (dashed line) at room temperature (highest soluble

concentration measured). ..................................................................84

Figure 5.5: Viscosity of amino acid salts at 40 °C .................................................86

Figure 5.6: CO2 Liquid Phase Mass Transfer Coefficient (kg’) in 3.55 m GlyK.

Compared to 7 m MEA and 8 m PZ at 40 °C (Dugas 2009) ............88

Figure 5.7: CO2 Liquid Phase Mass Transfer Coefficient (kg’) in 6 m GlyK.

Compared to 7 m MEA (Dugas 2009) and 3.55 GlyK at 40 °C. ......89

Figure 5.8: CO2 Liquid Phase Mass Transfer Coefficient (kg’) in 6 m SarK, compared

to 7 m MEA and 8 m PZ (Dugas 2009). ...........................................90

Figure 5.9: CO2 Liquid Phase Mass Transfer Coefficient (kg’) in 4.5 m SarNa....91

Figure 5.10: CO2 Liquid Phase Mass Transfer Coefficient (kg’) in 6.5 m β-AlaK92

Figure 5.11: CO2 Liquid Phase Mass Transfer Coefficient (kg’) for 5 m TauK.

Compared to 7 m MEA and 8 m PZ at 40 °C (Dugas 2009), and 3.55 m

GlyK and 6 m SarK at 40 °C. ...........................................................93

Figure 5.12: CO2 Liquid Phase Mass Transfer Coefficient (kg’) for 3 m TauK/5 m

HomotauK .........................................................................................94

Figure 5.13: CO2 Liquid Phase Mass Transfer Coefficient (kg’) in 6.5 m ProK.

Compared to 8 m ProK (Chen 2011), 7 m MEA, and 8 m PZ at 40 °C

(Dugas 2009) .....................................................................................95

Figure 5.14: CO2 Liquid Phase Mass Transfer Coefficient (kg’) for amino acid salts at

40 °C. Compared to 7 m MEA and 8 m PZ (Dugas 2009). ...........96

xxxiii

Figure 5.15: CO2 solubility data in 3.55 m GlyK (filled) and 6 m GlyK (empty), and

the semi-empirical VLE model results (solid lines). Compared to semi-

empirical VLE model for 7 m MEA at 40 and 100 °C (dashed lines, Xu

2011). ................................................................................................98

Figure 5.16: CO2 Solubility for sarcosine based amino acid salt solvents. Empty

points: 3 M SarK (Aronu et al. 2011c). Filled points: 6 m SarK .

Asterisk: 4.5 m SarNa. Lines: semi-empirical model (Table 6.8) .99

Figure 5.17: CO2 solubility data for 6.5 m β-AlaK (points), and semi-empirical model

fit (solid lines). Compared to semi-empirical model results for MEA at

40 and 100 °C (Xu 2011). ...............................................................100

Figure 5.18: CO2 solubility in 5 m TauK (points). Compared to the semi-empirical

model result for MEA (dashed lines, Xu 2011). .............................101

Figure 5.19: CO2 Solubility data for 3 m TauK/5 m HomotauK (points), and semi-

empirical model fit (solid lines). Compared to semi-empirical model

result of MEA at 40 and 100 °C(dashed lines, Xu 2011). ..............102

Figure 5.20: CO2 Solubility for 6.5 m ProK (solid) and 8 m ProK (empty, Chen

2011), with semi-empirical model fit (solid) for both solvents. Compared

with semi-empirical model result for MEA (dashed line, Xu 2011).102

Figure 5.21: Solvent capacity and heat of absorption estimated for β-alaK at coal and

natural gas conditions. Compared to 7 m MEA (Xu 2011). ........109

Figure 5.22: CO2 solubility curves of amino acid solvents (Table 6.8) at 40 °C and

coal flue gas conditions. Compared to the PZ and MEA (Xu 2011).110

Figure 5.23: CO2 solubility curves of amino acid solvents (Table 6.8) at 40 °C and

natural gas conditions. Compared to the PZ and MEA (Xu 2011).111

xxxiv

Figure 5.24: Heat of absorption of CO2 for amino acid salts at coal flue gas

conditions. Compared to MEA and PZ (Xu 2011). ........................112

Figure 5.25: Heat of absorption of CO2 for amino acid salts at natural gas flue gas

conditions. Compared to MEA and PZ (Xu 2011). ........................113

Figure 6.1: Molecular structure of piperazine (PZ) .............................................117

Figure 6.2: Solid solubility of concentrated PZ blends compared to 8 m PZ. Solid

lines: transition temperature curve. Dash lines: approximate transition

temperature curve. Empty points: soluble condition. Filled point:

precipitation condition. ...................................................................127

Figure 6.3: Viscosity of concentrated PZ blends at 40 °C. Compared with 7 m MEA

(empirical model by Weiland 1998) and 8 m PZ (Freeman 2011) at 40

°C. ...................................................................................................130

Figure 6.4: Absorption rate of 6 m PZ/2 m EDA. Empty diamonds: 8 m PZ; empty

squares: 7 m MEA (Dugas 2009). Empty circles: 12 m EDA (Chen

2011). ..............................................................................................137

Figure 6.5: Absorption rate of 6 m PZ/2 m DAB compared with dashed lines for 8 m

PZ and 7 m MEA at 40 °C (Dugas 2009). ......................................138

Figure 6.6: Absorption rate of 6 m PZ/2 m HMDA compared with dashed lines for

8 m PZ and 7 m MEA at 40 °C (Dugas 2009). ...............................139

Figure 6.7: Absorption rate of 6 m PZ/2 m BAE compared with dashed lines for 8 m

PZ (Dugas 2009) and 8 m BAE (Chapter 8) at 40 °C. ....................140

Figure 6.8: Absorption rate of 5 m PZ/5 m DGA®. Dashed lines: 8 m PZ at 40 ˚C

(Dugas 2009). Dotted lines: 10 m DGA® at 40 ˚C (Chen 2011). 141

Figure 6.9: Absorption rate of 5 m PZ/2 m AEP compared with dashed lines for 8 m

PZ, 7 m MEA (Dugas 2009), and 6 m AEP at 40 °C (Chen 2011).142

xxxv

Figure 6.10: Absorption rate of 6 m PZ/2 m HEP. Dashed lines: 8 m PZ at 40 ˚C

(Dugas 2009). Dotted lines: 7.7 m HEP at 40 ˚C (Chen 2011). ..142

Figure 6.11: Absorption rate of 5 m PZ/5 m 2-PE. Dashed lines: 8 m PZ at 40 ˚C

(Dugas 2009). Dotted lines: 8 m 2PE at 40 ˚C (Chen 2011). ......143

Figure 6.12: Absorption rate of 5 m PZ/2.3 m AMP. Dashed lines: 8 m PZ at 40 °C

(Dugas 2009); dotted lines: 4.8 m AMP at 40 °C. ..........................144

Figure 6.13: Absorption rate of 3.5 m PZ/3.5 m Tris. Dashed line: 8 m PZ at 40 °C;

dotted line: 7 m MEA at 40 °C (Dugas 2009). ...............................145

Figure 6.14: Comparison of 40 °C absorption rate (kg’) and viscosity normalized

absorption rate (kg’*) for 6 m PZ/2 m HMDA and 5 m PZ/5 m 2-PE with

8 m PZ (Dugas 2009). .....................................................................147

Figure 6.15: Comparison of CO2 absorption rate at 40 °C for PZ blends with three

primary di-amines of increasing chain length and 8 m PZ (Dugas 2009).

.........................................................................................................148

Figure 6.16: Comparison of CO2 absorption rates at 40 °C for PZ blends with primary

amines of similar chain length and 8 m PZ (Dugas 2009). .............149

Figure 6.17: Comparison of CO2 absorption rates at 40 °C for PZ blends with PZ

derivatives and 8 m PZ (Dugas 2009).............................................150

Figure 6.18: Comparison of CO2 absorption rates at 40 C for PZ blends with

equimolar mono-amines: 5 m PZ 5 m DGA®, 5 m PZ 5 m 2-PE, 3.5 m

PZ 3.5 m Tris, 5 m PZ 5 m MDEA (Chen 2011), and 8 m PZ (Dugas

2009). ..............................................................................................151

Figure 6.19: Comparison of CO2 absorption rate at 40 °C for PZ blends with hindered

amines and 8 m PZ (Dugas 2009) ................................................152

xxxvi

Figure 6.20: Comparison of CO2 absorption rate at 40 °C at different PZ-amine ratios

for PZ blends with AMP (Li 2013) and MDEA (Chen 2011). .......153

Figure 6.21: CO2 absorption rates as functions of the lower pKa of the second amine

for PZ blends with long chain primary di-amines: 6 m PZ/2 m HMDA, 6

m PZ/2 m DAB, 6 m/2 m BAE, 6 m PZ/2 m EDA. .......................155

Figure 6.22: CO2 solubility in 6 m PZ/2 m EDA. Diamond: WWC; filled circles:

total pressure. Solid lines: empirical model (Table 6.15). Dashed

line: semi-empirical model of 8 m PZ (Xu 2011). Dotted line: semi-

empirical model of 12 m EDA; empty circles: WWC for 12 m EDA

(Chen 2011). ...................................................................................156

Figure 6.23: CO2 solubility in 6 m PZ/2 m DAB. Diamonds: WWC results; Circles:

total pressure results; Solid lines: model prediction (Table 6.15); Dashed

lines: model for 8 m (Xu 2011).......................................................157

Figure 6.24: CO2 solubility in 6 m PZ/2 m HMDA. Diamonds: WWC results; Circles:

total pressure results (Namjoshi et al. 2013); Solid lines: model

prediction (Table 6.15); Dashed lines: model for 8 m PZ at 40 and 160

°C (Xu 2011). ..................................................................................158

Figure 6.25: CO2 solubility in 6 m PZ/2 m BAE. Diamonds: WWC results; Circles:

total pressure results; Solid lines: model prediction (Table 6.15); Dashed

lines: model for 8 m PZ (Xu 2011). Dotted lines: model for 8 m BAE;

empty circles: WWC data for 8 m BAE (Chapter 8). .....................159

Figure 6.26: CO2 solubility in 5 m PZ/5 m DGA®. Diamond: WWC results. Solid

lines: empirical model (Table 6.15). Dashed line: empirical model of

PZ at 40 ˚C (Xu 2011). Dotted line: 10 m DGA® at 40 ˚C (Chen 2011).

.........................................................................................................160

xxxvii

Figure 6.27: CO2 solubility in 5 m PZ/2 m AEP. Diamonds: WWC results; Circles:

total pressure results (Du et al. 2013); Solid lines: semi-empirical model

result (Table 6.15); Dashed lines: model for 8 m PZ at 40 and 160 °C

(Xu 2011). .......................................................................................161

Figure 6.28: CO2 solubility in 6 m PZ/2 m HEP. Diamond: WWC results. Solid


PZ at 40 °C (Xu 2011); dotted line: semi-empirical model for 7.7 m HEP

at 40 °C (Chen 2011) ......................................................................162

Figure 6.29: CO2 solubility in 5 m PZ/5 m 2PE. Diamond: WWC results. Solid


PZ (Xu 2011), dotted line: empirical model of 8 m 2-PE (Chen 2011).

.........................................................................................................162

Figure 6.30: CO2 solubility of 5 m PZ/2.3 m AMP. Diamonds: WWC; square: total

pressure apparatus (Li et al. 2013). Dashed lines: semi-empirical model

for PZ at 40 °C (Xu 2011); dotted line: semi-empirical model for 4.8 m

AMP at 40 °C (Chen 2011) .............................................................163

Figure 6.31: CO2 solubility of 3.5 m PZ/3.5 m Tris. Solid curves: semi-empirical

model result (Table 6.15). Dashed line: 8 m PZ at 40 °C (Xu 2011).

.........................................................................................................164

Figure 6.32: CO2 solubility at 40 °C for PZ blends with primary di-amines, compared

to 8 m PZ, 7 m MEA (Xu 2011), and 12 m EDA (Chen 2011). .....175

Figure 6.33: CO2 solubility at 40°C in PZ blends with primary amines of similar

chain length, compared with 8 m PZ, 7 m MEA (Xu 2011), 8 m BAE

(Chapter 8) and 10 m DGA® (Chen 2011). ....................................176

xxxviii

Figure 6.34: CO2 solubility at 40° C in PZ blends with PZ derivatives, compared to8

m PZ (Xu 2011), 7.7 m HEP, and 6 m AEP (Chen 2011). ..........177

Figure 6.35: CO2 solubility at 40 °C for PZ blends with hindered amines, compared

with 8 m PZ (Xu 2011), 4.8 m AMP, and 8 m 2-PE (Chen 2011). 178

Figure 6.36: Comparison of CO2 solubility at 40 °C of PZ blends with AMP and

MDEA with different PZ-amine ratio .............................................179

Figure 6.37: Heat of absorption of CO2 at process conditions for PZ blends with

primary di-amines, compared with MEA and PZ ...........................181

Figure 6.38: Heat of absorption of CO2 at process conditions for PZ blends with AMP

and 5 m PZ/2 m AEP ......................................................................182

Figure 7.1: CO2 Liquid Phase Mass Transfer Coefficient (kg’) for 7 m MIPA, and 7 m

MEA at 40 °C (Dugas 2009). ..........................................................199

Figure 7.2: CO2 Liquid Phase Mass Transfer Coefficient (kg’) for 7 m MPA, and 7 m

MEA at 40 °C (Dugas 2009). ..........................................................200

Figure 7.3: CO2 Liquid Phase Mass Transfer Coefficient (kg’) for 7 m DEA,

compared with 7 m MEA at 40 °C (Dugas 2009). ..........................201

Figure 7.4: CO2 Liquid Phase Mass Transfer Coefficient (kg’) for 7 m MMEA,

compared with 7 m MEA and 8 m PZ at 40 °C (Dugas 2009). ......201

Figure 7.5: CO2 Liquid Phase Mass Transfer Coefficient (kg’) for 7 m DIPA,

compared with 7 m MEA at 40 °C (Dugas 2009) and 7 m DEA....202

Figure 7.6: CO2 absorption rates in primary amines at 40 °C, compared with 7 m

MEA (Dugas 2009); 10 m DGA® and 4.8 m AMP (Chen et al. 2011).

.........................................................................................................203

xxxix

Figure 7.7: CO2 absorption rates in secondary amines at 40 °C, compared with 7 m

MEA and 8 m PZ (Dugas 2009); and 8 m 2PE (Chen and Rochelle

2011). ..............................................................................................204

Figure 7.8: The kg’avg at coal flue gas conditions and the pKa of the amine. Dashed

lines: potential trends; empty points: hindered amine solvents ......205

Figure 7.9: CO2 solubility data (solid diamonds) and the semi-empirical model fit

(Table 7.5, solid lines) for 7 m MIPA, compared with 40 °C solubility

curve for MEA (dashed line, Xu 2011) and 40 °C data for 30 wt% MIPA

(empty circles, Rebolledo-Morales et al. 2010). .............................207

Figure 7.10: CO2 solubility data (solid diamonds) and the semi-empirical model result

(solid lines, Table 7.5) for 7 m MPA, compared with CO2 solubility

curve at 40 °C for MEA (Xu 2011). ...............................................208

Figure 7.11: CO2 solubility data (solid diamonds) the semi-empirical model fit (solid

lines, Table 7.5) for 7 m DEA, compared with data for 5 M DEA

(asterisk, Lee et al. 1972), and MEA at 40 °C (dashed line, Xu 2011)208

Figure 7.12: CO2 solubility data (solid diamonds) and the semi-empirical model fit

(solid curves) for 7 m MMEA, compared with MEA at 40 °C (dashed

lines, Xu 2011) ................................................................................209

Figure 7.13: CO2 solubility data (solid diamonds) and semi-empirical model (solid

lines) for 7 m DIPA, compared with data at 25 °C for 34 wt% DIPA

(Dell’Era et al. 2010), and MEA at 40 °C ......................................210

Figure 7.14: CO2 solubility curves at 40 °C for primary amines, compared with MEA

(Dugas 2009), 10 m DGA®, GlyK, and 6.5 m β-alaK (Chapter 5). 215

xl

Figure 7.15: CO2 solubility at 40 °C for secondary amine solvents, compared with

MEA and PZ (Dugas 2009), 8 m 2PE (Chen and Rochelle 2011), and

SarK(Na) (Chapter 5). .....................................................................216

Figure 7.16: Heat of absorption of CO2 in 7 m MIPA and 7 m MPA compared with

MEA (Xu 2011). .............................................................................218

Figure 7.17: Heat of absorption of CO2 in 7 m DEA, 7 m MMEA, and 7 m DIPA,

compared with MEA and PZ (Xu 2011). ........................................218

Figure 8.1: Viscosity of 3.4 m (20 wt %) MDEA/9.8 m (30 wt %) MEA at 40 °C

(solid diamonds). Compared with experimental data (solid circles) and

model prediction (dashed lines) by Weiland (1998) for 7 m MEA and 20

wt % MDEA/30 wt% MEA at 40 °C, and three MDEA/MEA solvents at

25 °C. ..............................................................................................222

Figure 8.2: CO2 absorption rate for 3.4 m MDEA/9.8 m MEA. Dashed lines: 7 m

MEA (Dugas 2009). ........................................................................224

Figure 8.3: CO2 absorption rate at 40 °C for 3.4 m MDEA/9.8 m MEA, compared

with 7 m MEA, 8 m PZ (Dugas 2009), 5 m PZ 5 m MDEA, and 2 m PZ

7 m MDEA (Chen et al. 2011) ........................................................224

Figure 8.4: CO2 solubility in 3.4 m MDEA/9.8 m MEA. Diamond: WWC results.

Solid lines: empirical model (Table 8.3). Dashed line: empirical model

of 7 m MEA (Xu 2011). ..................................................................225

Figure 8.5: Molecular structure of bis(aminoethyl)ether (BAE) .........................228

Figure 8.6: Viscosity of 8 m BAE (solid diamonds), compared with 8 m PZ (Freeman

2011) and 6 m PZ/2 m BAE (Chapter 6) at 40 °C ..........................229

xli

Figure 8.7: Absorption rate of 8 m BAE. Empty circles: 8 m PZ. Empty squares: 7

m MEA (Dugas 2009). Empty square: 6 m PZ/2 m BAE (Chapter 6).

.........................................................................................................231

Figure 8.8: Absorption rate at 40 °C for 8 m BAE, compared with 8 m PZ, 7 m

MEA (Dugas 2009), 6 m PZ/2 m BAE (Chapter 6), and 10 m DGA®

(Chen and Rochelle 2011). .............................................................232

Figure 8.9: CO2 solubility in 8 m BAE. Squares: WWC. Circles: total pressure.

Solid lines: empirical model (Equation 4.4). Dashed line: MEA (Xu

2011). ..............................................................................................233

Figure 8.10: Molecular Structure of 2-amino-2-methyl-propane (AMP) ............236

Figure 8.11: Absorption Rates of 4.8 m AMP Promoted by Enzyme, compared with

rates of 4.8 m AMP (Chen 2011) ....................................................239

Figure 8.12: Viscosity of Company A solvent #1. Data points: experiment values.

Solid lines: viscosity correlation (Equation 8.2, Table 8.16) ..........242

Figure 8.13: Viscosity of Company A solvent #2. Data points: experiment values.

Solid lines: viscosity correlation (Equation 8.2, Table 8.16) ..........242

Figure 8.14: Absorption rates of the Company A solvent #1. Compared with 8 m PZ

and 7 m MEA at 40 °C (Dugas 2009) .............................................245

Figure 8.15: Absorption rates of the Company A solvent #2. Compared with 8 m PZ

and 7 m MEA at 40 °C (Dugas 2009) .............................................246

Figure 8.16: CO2 absorption rate of the Company B solvent. Dashed line: 8 m PZ at

40 °C; dotted line: 7 m MEA at 40 °C (Dugas 2009). ....................247

Figure 8.17: Absorption of the three proprietary solvents at 40 °C, compared with 7 m

MEA and 8 m PZ (Dugas 2009). ....................................................247

xlii

Figure 8.18: CO2 solubility in Company A solvent #1. Experimental data: ♦ - WWC;

■ – total pressure. Semi-empirical model: solid lines (Table 8.18).

.........................................................................................................249

Figure 8.19: CO2 solubility in Company A solvent #2. Experimental data: ♦ - WWC;

■ – total pressure. Semi-empirical model: solid lines (Table 8.18).

.........................................................................................................249

Figure 8.20: CO2 VLE of the Company B solvent. Points: WWC result. Solid lines:

semi-empirical VLE curves (Table 8.18)........................................250

Figure 8.21: Absorption rates and CO2 capacity for 7 m MEA and 8 m PZ, compared

with MEA and PZ solvents at other amine concentrations .............257

Figure 8.22: Absorption rate and CO2 capacity for primary amines and amino acids

.........................................................................................................258

Figure 8.23: Absorption rate and CO2 capacity for primary diamines ................259

Figure 8.24: Absorption rate and CO2 capacity for secondary amines ................259

Figure 8.25: Absorption rate and CO2 capacity for hindered amines ..................260

Figure 8.26: Absorption rate and CO2 capacity for PZ derivatives .....................261

Figure 8.27: Absorption rate and CO2 capacity for PZ blends with primary diamines

.........................................................................................................262

Figure 8.28: Absorption rate and CO2 capacity for PZ blends with primary amines262

Figure 8.29: Absorption rate and CO2 capacity for PZ blends with PZ derivatives263

Figure 8.30: Absorption rate and CO2 capacity for PZ blends with hindered amines

.........................................................................................................263

Figure 8.31: Absorption rate and CO2 capacity for PZ and MEA blended with MDEA

.........................................................................................................264

Figure 8.32: Absorption rate and CO2 capacity for amino acids .........................265

xliii

Figure 8.33: Absorption rate and viscosity normalized CO2 capacity (Equation 4.17)

.........................................................................................................266

Figure 9.1: SSM fit of CO2 VLE for 7 m MEA (solid lines), compared with data by

Dugas (2009, diamonds), Hillard (2008, squares), Xu (2011, triangles)

Ma’mum et al. (2006, asterisk), and Jou et al. (2009, circles). .......285

Figure 9.2: SSM fit (blue line) of CO2 VLE for 7 m MEA at 40 °C, compared with

semi-empirical model (Xu 2011, orange dotted line), Phoenix in

AspenPlus® (Plaza 2011, black line); and data by Jou et al. (circle),

Dugas (2009, diamond), and Hillard (2008, Square). .....................286

Figure 9.3a: Liquid phase composition predicted by the SSM for 7 m MEA,

compared with NMR speciation data (Hillard 2008) and prediction by

the Pheonix model in Aspen Plus® (Plaza 2011) ............................287

Figure 9.3b: Liquid phase composition predicted by the SSM for 7 m MEA,

compared with NMR speciation data (Hillard 2008) and prediction by

the Pheonix model in Aspen Plus® (Plaza 2011) (Logarithmic scale)288

Figure 9.4: SSM fit of CO2 VLE for 7 m MPA (solid lines: SSM; solid diamonds:

WWC data) .....................................................................................290

Figure 9.5: SSM fit of CO2 VLE for 7 m MIPA (solid lines: SSM; solid diamonds:

WWC data), and 5.7 m MIPA (dashed lines: SSM; empty squares:

Morales et al. 2010) ........................................................................291

Figure 9.6: SSM fit of CO2 VLE for 10 m DGA® (solid lines: SSM; solid diamonds:

Chen et al. 2011), and prediction for 7 m DGA®............................291

Figure 9.7: SSM fit of CO2 VLE for 3.55 m GlyK (solid lines: SSM; solid diamonds:

WWC). ............................................................................................292

xliv

Figure 9.8: SSM fit of CO2 VLE for 6 m GlyK (solid lines: SSM; solid diamonds:

WWC). ............................................................................................293

Figure 9.9: SSM fit of CO2 VLE for 6.5 m β-alaK (solid lines: SSM; solid diamonds:

WWC data). ....................................................................................293

Figure 9.10: SSM fit of CO2 VLE for 7 m MMEA (solid lines: SSM; solid diamonds:

WWC data). ....................................................................................294

Figure 9.11: SSM fit of CO2 VLE for 5 M (9.4 m) DEA (solid lines: SSM; solid

squares: Lee et al. 1972). ................................................................295

Figure 9.12: SSM fit of CO2 VLE for 7 m DEA (solid lines: SSM; solid diamonds:

WWC). ............................................................................................295

Figure 9.13: SSM fit of CO2 VLE for 7 m DIPA (solid lines: SSM; solid diamonds:

WWC data), and 34 wt % (3.9 m) DIPA at 25 °C (dash lines: SSM;

empty squares: data by Dell’Era et al. 2010). .................................296

Figure 9.14: SSM fit of CO2 VLE for 3 M (2.8 m) SarK (solid lines: SSM; solid

squares: Aronu et al. 2011). ............................................................297

Figure 9.15: SSM fit of CO2 VLE for 6 m SarK (solid lines: SSM; solid diamonds:

WWC). ............................................................................................297

Figure 9.16: SSM prediction of CO2 VLE for 4.5 m SarNa (solid lines: SSM; empty

diamonds: WWC). ..........................................................................298

Figure 9.17: SSM fit of CO2 VLE for 4.8 m AMP (solid lines: SSM; empty

diamonds: WWC data by Chen et al. 2011). ..................................298

Figure 9.18: SSM fit of CO2 VLE for 8 m 2-PE (solid lines: SSM; empty diamonds:

WWC data by Chen et al. 2011). ....................................................299

Figure 9.19: SSM prediction of liquid phase free amine composition at 40 °C for

selected primary and secondary amines at 7 m total amine ............300

xlv

Figure 9.20: SSM prediction of liquid phase amine carbamate composition at 40 °C

for selected primary and secondary amines at 7 m total amine ......301

Figure 9.21: SSM prediction of liquid phase bicarbonate composition at 40 °C for

selected primary and secondary amines at 7 m total amine ............301

Figure 9.22: Liquid phase composition predicted by the SSM for 4.8 m AMP at 25

°C, compared with NMR speciation data (Cifjia et al. 2014) and

prediction by the Sherman AMP model in Aspen Plus® (Rochelle et al.

2014) ...............................................................................................302

Figure 9.23: Liquid phase composition predicted by the SSM for 4.8 m AMP at 25

°C, compared with prediction by the Sherman AMP model in Aspen

Plus® (Rochelle et al. 2014) ............................................................303

Figure 9.24: The first equilibrium constant for the SSM (Equation 9.28) at 40 °C with

base strength of the amine. ..............................................................308

Figure 9.25: The mole fraction based carbamate formation constant (Equation 9.32) at

40 °C estimated by the SSM ...........................................................309

Figure 9.26: The second equilibrium constant in the SSM (Equation 9.33) at 40 °C

with base strength of the amine. .....................................................310

Figure 9.27a: The mole fraction based bicarbonate formation constant (Equation

9.37a) at 40 °C estimated by the SSM, compared with literature values

(Equation 9.41) ...............................................................................313

Figure 9.27b: The effect of activities on the bicarbonate reaction at high amine

concentration and CO2 loading (Equation 9.37b) ...........................314

Figure 9.28: The mole fraction based carbamate stability constant (Equation 9.43) at

40 °C estimated by the SSM with the base strength of the amine ..315

xlvi

Figure 9.29: CO2 VLE predicted for a generic primary amine (red) and a generic

secondary amine (blue) at 40 °C and 7 m total amine, at four amine pKa

values ..............................................................................................317

Figure 9.30: Free amine concentrations for a generic primary (red) and secondary

(blue) amine and the pKa of the amine at 40 °C, estimated at 7 m total

amine and the operating lean (solid lines) and rich (dashed lines) loading

for coal flue gas, compared with the SSM predicted results of real

amines .............................................................................................318

Figure 10.1: Alternative methods of interpolating measured kg' at standard conditions

for 7 m MIPA and 7 m MEA ..........................................................325

Figure 10.2: Effective concentration based second order kinetic rate constant for

primary, secondary, and hindered amines, at standard operating

condition for coal flue gas...............................................................333

Figure 10.3: Effective concentration based second order kinetic rate constant

compared with literature value for MEA (Versteeg et al. 1988). ...334

Figure 10.4: Effective concentration based third order kinetic rate constant for

primary, secondary, and hindered amines, at standard operating

condition for coal flue gas...............................................................335

Figure 10.5: Effective concentration based third order kinetic rate constant compared

with literature values for PZ, DEA, DIPA (Cullinane 2005), and activity

based third order rate constant for MEA (Dugas 2009). .................336

Figure 10.6: Bronsted correlation for the third order reaction rate constant

representing both primary and secondary amines ...........................337

Figure 10.7: Bronsted correlations for the third order reaction rate constant

representing primary amines and secondary amine separately .......338

xlvii

Figure 10.8: CO2 mass transfer rates (Equation 4.6) calculated for primary and

secondary amines at varying pKa, at the same total amine concentration

of 7 m, with the density and viscosity of MEA (Weiland 1998), using the

overall Bronsted correlation (Equation 10.16)................................341

Figure 10.9: CO2 mass transfer rates (Equation 4.6) calculated for primary and

secondary amines at varying pKa, at the same total amine concentration

of 7 m, with the density and viscosity of MEA (Weiland 1998), using

separate Bronsted correlation for each amine type (Equation 10.17).341

Figure 10.10: Sensitivity of the effective mass transfer rate (kg'avg) at process

conditions on each of the PFO parameters for primary amines ......344

Figure 10.11: Sensitivity of the effective mass transfer rate (kg'avg) at process

conditions on each of the PFO parameters for secondary amines ..345

Figure 10.12: Parity plot of measured kg' and calculated kg' at the standard operating

CO2 loadings and 40 °C. .................................................................346

Figure 10.13: Parity plot of measured kg' and calculated kg' as function of amine pKa,

at the standard operating CO2 loadings and 40 °C ..........................346

Figure A-2: U.S. CO2 emission (from primary fuel consumption) in 2013 by sector

(EIA 2014b) ....................................................................................357

Figure A-3: U.S. electricity generation in 2013 by fuel source (EIA 2014b) ......358

Figure A-4: Sherwood plot of industrial separation processes cost dependence on

concentration in the source stream (House et al. 2011) ..................359

Figure A-5: Total CO2 emission by the U.S. and China from 1980 to 2013 (EIA

2014a) .............................................................................................362

Figure A-6: CO2 emission and energy consumption in the U.S. and China as fraction

of world total since 1980 (EIA 2014a). ..........................................363

xlviii

Figure B-1: CO2 solubility in 8 m MAPA at high temperature. Solid circles: total

pressure results. Solid lines: 1st empirical model (Table B-1). .....372

Figure B-2: CO2 solubility in 8 m MAPA. Diamond: WWC (Chen, 2011). Circles:

total pressure. Solid lines: 1st empirical model. Dashed line: 2nd

empirical model (Table B-1). ..........................................................373

Figure B-3: CO2 heat of absorption in 8 m MAPA predicted by two empirical models

(Table B-2) ......................................................................................376

Figure B-4: CO2 Liquid Phase Mass Transfer Coefficient (kg’) in 7 m MDEA 2 m PZ

at 30°C ............................................................................................377

Figure B-5: CO2 Liquid Phase Mass Transfer Coefficient (kg’) in at low temperatures

in 5 m MDEA/5 m PZ .....................................................................378

Figure B-6: CO2 solubility in 5 m MDEA/5 m PZ ..............................................379

Figure B-7: CO2 Liquid Phase Mass Transfer Coefficient (kg’) in 2011 8 m PZ pilot

plant sample ....................................................................................381

Figure B-8: CO2 solubility in PRC 8 m PZ Fall 2011 campaign pilot plant sample.

Circle: total pressure; diamond: wetted wall column; solid lines: pilot

plant semi-empirical model; dashed lines: 8 m PZ semi-empirical model

(Table B-6). .....................................................................................382

Figure B-9: CO2 solubility at high temperatures for 8 m PZ + 100 mM Inh A. Solid

circle: PRC pilot plant sample; empty circle: 8 m PZ + Inh A; solid

lines: pilot plant semi-empirical model (Table B-6). ......................384

Figure D-1: Empirical fit of kg’ as function of PCO2* ..........................................481

Figure D-2: Liquid Flow Rate Optimization (7 m MEA, lean loading = 0.438, 90%

removal) ..........................................................................................484

Figure D-3: Liquid Flow Rate of Different Solvents and Lean Loadings ...........484

xlix

Figure D-4: Spreadsheet model result of absorber packing requirement versus total

work requirement in a process using 7 m MEA .............................487

Figure E-1: Overall flow diagram of the wetted wall column system .................496

Figure E-2: Detailed section diagram. Section A: Solvent Reservoir .................497

Figure E-4: Detailed section diagram. Section C: Outlet gas ..............................498

Figure E-5: Detailed section diagram. Section D: Saturator................................498

Figure E-6: Detailed drawing of the ZipperClave set up (sideview) ...................511

Figure E-7: Detailed drawing of the ZipperClave set up (top view) ...................512

Figure E-8: ZipperClave part list part 1 ...............................................................513

Figure E-9: ZipperClave part list part 2 ...............................................................513

1

Chapter 1: Introduction

1.1 MOTIVATIONS

The phenomenon of climate change is the main environmental issue facing our

world today. Since the beginning of the industrial era, the world economy has been

mostly powered by energy stored in various types of fossil fuels. As fossil fuels are

converted into usable energy, such as electricity, large amounts of CO2 are generated as a

byproduct and released into the atmosphere. In the last 160 years, atmospheric CO2

concentration has increased by approximately 38%, from 280 ppm in the pre-1850 years

(Etheridge 1998) to 385 ppm in 2008 (Keeling 2009). This accumulation of the emitted

CO2 in the atmosphere is the cause of the change in world climate that is observed by

scientists today. To minimize the impact of human activities on the environment, the

method of combustion of fossil fuels for energy must be adapted to reduce the amount of

CO2 released to the atmosphere. This need to reduce CO2 emissions from the energy

sector offers a potential market for new technologies and innovations.

The world energy demand is still increasing. Along with it is the same increase in

world CO2 emission (Figure 1.1). The challenge of mitigating climate change is in the

reduction of CO2 while meeting the rising energy demand. While renewable and

alternative energy sources seems to be the obvious solutions to the emission problem, as

CO2 is not produced as the byproduct, the capacity of these clean sources are limited and

cannot meet the world energy demand as of today or in the near future. The distribution

of U.S. energy consumption in 2013 by fuel source suggests the current energy sector is

still heavily dependent on the use of fossil fuels (82% BTU) (Figure 1.2). Substantial

reduction of world CO2 emission necessitates the controlling of emissions from fossil fuel

sources. The development and deployment of CO2 emission reduction technologies for

2

fossil fuel sources and meeting the associated economic costs is the key solution to

climate change.

Figure 1.1: World energy consumption and CO2 emission from 1980 to 2011 (EIA

2014a)

Figure 1.2: U.S. energy consumption in 2013 by fuel source (EIA 2014b)

200

250

300

350

400

450

500

550

15000

20000

25000

30000

35000

1980 1990 2000 2010

CO

2 e

mis

sio

n (

MM

ton

)

Ener

gy c

on

sum

pti

on

(Q

uad

BTU

)

Nuclear Electric

8%

Renewable10%

Coal19%

Natural Gas27%

Petroleum36%

Fossil Fuels82%

Unit: BTU

3

Among the various sources of CO2 in the economy, coal fired power generation is

one of the largest and most important category to be targeted for emission control.

Coal-fired power plants contributed to 30% of the total U.S. CO2 emission in 2013,

second only to the entire transportation sector. Within the electric sector, coal fired

plants are the largest CO2 emitter, which contributed to 78% of the emission from all U.S.

power plants in 2013 (EIA 2014b). Thus, effective emission control of the coal fired

power plants will be significant to the overall CO2 reduction of the electric sector and the

entire country. Moreover, the electric sector is an important part of the economy, as the

energy it generates is partially used to power other industries. The cost of adding CO2

reduction technologies will affect other sectors of the economy. Therefore, reducing the

cost of emission control technologies is of high priority for researchers and developers.

The technical solution to the reduction of CO2 emission from power plants and

other large point sources is Carbon Capture and Sequestration (CCS). The CCS process

involves the capture of CO2 from various emission sources, followed by the

transportation of the separated and compressed CO2 from the emission site to storage

locations, and lastly the long term storage of CO2 at appropriate natural underground

formations. The cost of CCS is more advantages if applied to large point sources, such

as power plants, as favored by the economy of scale. As estimated by the

Intergovernmental Panel on Climate Change (1995), the capture of CO2 is the largest cost

component of CCS for most large point sources. Thus, development and cost reduction

of the CO2 capture technologies are critical in lowering the overall cost the deployment of

CCS.

4

1.2 AMINE SCRUBBING FOR CO2 CAPTURE

Figure 1.3: The amine scrubbing process for CO2 capture (Rochelle 2009).

Currently, amine scrubbing is the choice post combustion CO2 capture technology

for CCS. It is the most mature and technically ready for commercial deployment

(Rochelle 2009). This chemical separation process (Figure 1.3) involves first directly

contacting post-combustion flue gas with an aqueous amine solvent at 40°C, where CO2

is separated from the gas into the liquid by chemically reacting with the amine molecules

and mass transfer in to the liquid phase. The main cost of the separation of CO2 from

the flue gas is in the capital cost of the absorber column and packing materials to

facilitate the mass transfer of CO2 into the solvent. To regenerate the solvent, CO2 is

stripped from the liquid with water vapor at high temperature (100-150 °C). A stream

of CO2 mixed with water vapor is produced, and the regenerated solvent is recycled back

to the absorber. To maximize the heat integration of the process, a cross exchanger is

used between the two solvent streams entering and leaving the stripper, where the

regenerated solvent is used to partially heat the cold solvent from the absorber. The

5

main cost associated with the regeneration of the solvent is in the heat added into the

stripper and the equipment cost of cross exchanger. The stripped CO2 stream is further

purified by knocking out the water vapor, which then needs to be compressed before it

can be transported for long term storage. The compression cost is another major

component of the overall process.

1.2.1 Current technical challenges

While amine scrubbing is the state of the art technology for post combustion CO2

capture, the cost of the application of this technology still has room for reduction. The

energy cost of amine scrubbing is significant and consists of heat required to regenerate

the solvent and compression work for the CO2 product. The capital cost of the process

is also significant, dominated by the cost of the absorber, cross exchanger, and

compressors; which is estimated to be similar to the energy cost in some cases. Overall,

base case capture process is expected to cost about 20-30% of total power plant output to

remove 90% of CO2 in the flue gas (Rochelle 2009). Also, degradation of the amine

solvent, controlling and treatment of degradation products, and amine loss due to volatile

emissions also add to the cost and affect performance.

The improvement of the amine scrubbing process can be approached in three

areas. First, finding new solvents with optimum chemical and physical properties at low

costs can potentially reduce the energy requirement of the process as well as lowering the

capital cost. Second, optimization of the process design and enhancing the heat

integration and recovery can improve the efficiency of the process and reduce energy

cost. Third, the potential environmental impact of the amine scrubbing process itself

must be considered and addressed. The degradation of the amine over time results in

accumulation of potentially hazardous materials, as well as reduction in process

6

performance. The potential emission of the amine and its degradation products through

entrainment and aerosol formations in the absorber columns are relevant concerns to the

safety of the process.

1.2.2 Solvent screening for amine scrubbing

The search for new and better solvents has been a major part of the research and

development efforts for amine scrubbing. A good solvent is largely defined by two

performance criteria: a high rate of CO2 mass transfer and a large CO2 carrying capacity.

The rate of CO2 mass transfer directly affects the equipment size and cost of the absorber

column, which is a major part of the total capital cost of the process. The CO2 capacity

of a solvent is often loosely defined as the amount of CO2 the solvent is expected to

absorb between the top and bottom of the absorber. This is an important criterion

because higher CO2 capacity corresponds to less solvent recirculation rate required to

remove the same amount of CO2. The cost of sensible heat required and the cross

exchanger equipment can be reduced in the process if the solvent rates are lowered.

Several other solvent properties also affect the performance of the process.

The solvents with higher heat of CO2 absorption can reduce the energy cost of the

process (by lowering the compression work and improving the stripping efficiency).

The viscosity of the solvent affects its heat transfer performance in the cross exchangers,

which then contributes to the equipment cost of the process. The stability of the amine

solvent at high temperature determines the operating temperature of the stripper, which

affects the compression cost in the process. The oxidative stability of the amine can

also limit the temperature of the stripper, as well as incur additional cost for oxidation

inhibitors or additional solvent make up cost. The volatility of the amine affects the

7

emission of the amine from the process, which is an environmental concern and would

require additional equipment cost to minimize.

All of these properties contribute to the performance of a solvent in the process.

However, there is no perfect solvent. The best solvents, which are significantly better

than the average solvents in most respects, still have minor disadvantages that need to be

managed. The relative performance of the solvents can also be affected by the

conditions of the application. For example, flue gas with higher oxygen content would

favor solvents with higher oxidative stability over other properties. The task of solvent

selection is the trade off analysis for all relevant solvent properties at different flue gas

conditions. The objectives for solvent screening studies, beyond identifying solvents

with better properties, is also to collect representative data for which can be used to

quantify the variability of each property and its affect on overall process cost.

The base case solvent for post combustion amine scrubbing processes is 30 wt%

monoethanolamine (MEA), which has been commonly used for gas treating. Recent

research suggest a solvent using 40 wt% piperazine (PZ) to have superior performance to

30 wt% MEA in absorption rate, capacity, stability, and volatility (Freeman 2009).

Current solvent development efforts aim to improve the performance of 30 wt% MEA,

and compete with 40 wt% PZ.

1.3 PREVIOUS STUDIES ON CO2 ABSORPTION RATES AND CAPACITY

A number of solvent screening studies have focused on CO2 absorption rate and

capacity, as they are expected to have significant effects on the cost the process. There

are more than ten journal articles on the systematic screening of amine solvents for

absorption rates and CO2 carrying capacity in the application of post-combustion CO2

capture (Table 1.1). With the exception of Chen et al. (2011), the other screening works

8

are limited for several reasons. First, absorption rates were often measured with no CO2

loading in the solvents. Optimized process designs always require amine solvents in the

absorber to have various level of CO2 loading (usually significant enough to drastically

change the ionic and physical properties of the solvent). Thus, the relative performance

of CO2 free amine solvent cannot be used to represent real process performance. Also,

the gas sparging apparatus typically used provide hydrodynamic conditions very different

from those of structured packings, which further confound the reported results.

Moreover, the hydrodynamics of gas sparging experiments are typically inconsistent and

cannot be accurately quantified. While data from this type of experiment suggests an

apparent rate of absorption specific to the experimental conditions, it cannot provide

fundamental mass transfer properties of the solvent and cannot be used to accurately

predict rates at process conditions.

Thus, the abundance of previous screening work still leaves room for continuous

testing of both new and tested amine solvents with experimental conditions that better

match the real process and rigorous methods that generate fundamental mass transfer

data.

Rigorous evaluation of solvent performance is often time consuming and

experimentally demanding. At the University of Texas at Austin, a bench scale wetted

wall column has been used by many researchers to perform rigorous CO2 mass transfer

experiments for different amine solvents. The published works on solvent performance

using this rigorous method are summarized in Table 1.3. Recent works, by Dugas

(2009) and Chen et al. (2011), greatly improved the efficiency of the experimental effort

required for the mass transfer and VLE measurements. This work uses the same WWC

apparatus for the screening of new amine solvents for CO2 capture.

9

Table 1.1: Summary of published solvent rate screening results

Author Amines Conc CO2

loading

T

(°C) Apparatus Data type

Hook, 1997 MEA, AMP,

6 amino acids 2.5 M n/a

22

/26

/120

Stirred

reactor

Total CO2 absorbed

as function of time

Ma’mun et

al., 2007

8

(AEEA,

MEA based

structures)

30 wt% yes 40 Gas

sparging

Rate of CO2

absorption (mol/L/s)

Singh et al.

2007

14

(unbranched,

primary:

alkanolamine,

akylamine,

di-amine

0.1-2.5

M

not

quantified ~30

Stirred

absorption

screening

apparatus

Total CO2 absorbed

as function of time

Singh et al.

2009

33

(various

functional

groups, cyclic

structures)

0.5-

2.5M

not

quantified ~30

Stirred

screening

apparatus

Total CO2 absorbed

as function of time

Puxty et

al., 2009 76 amines

< 30

wt% no 40

Isothermal

gravimetric

analysis.

Gas

sparging

Initial rate of CO2

absorption

(mol/L/s)

Aronu et

al. 2009

MEA, 5

amines and

their mixtures

approx

30 wt% yes 40/80

Gas

sparging

Rate of CO2

absorption (mol/L/s)

Chowdhury

et al. 2009

11 amines

(7 novel) 30 wt% estimated 40/70

Gas

sparging

Absorption rate /

total CO2 at 50% of

saturated CO2

loading

Chen et al.

2011

14 amines

and blends

4.8 –

12 m 0.05-0.6

40-

100

Wetted

wall

column

Liquid film mass

transfer coefficient

(kg’)

Dubois and

Thomas

2012

6 amines 5-50

wt% no 25

Cable-

bundle

scrubber

Fraction of CO2

absorbed, kapp

Brœder and

Svendsen

2012

amines and

blends using

7 structures

4 - 8 M 0 –

(0.2-0.8)

40 /

80

Gas

sparging

Rate of CO2

absorption/desorption

(mol/L)

Song et al.

2012

16 amino

acids, blends

w/ PZ

1 M no 40 /

80

Gas

sparging

Initial

absorption/desorption

rate (mol/L/s)

10

Table 1.2: Summary of published CO2 capacity screening results

Author Amines T (°C) Method Result type

Hook, 1997 MEA, AMP, 6

amino acids 100

Heated

regeneration

apparatus

CO2 loading after 1 hour

of heating

Ma’mun el al.

2007 2.9 M AEEA 40 / 120

VLE apparatus

for atmospheric

and medium

pressures

Vapor-liquid equilibrium,

capacity (mol/L solution)

Singh et al. 2007,

2009 47 amines ~ 30

Stirred

absorption

screening

apparatus

Total capacity: maximum

loading after absorption for

a long time

Puxty et al. 2009 76 amines 40

Isothermal

gravimetric

analysis. Gas

sparging.

Total CO2 uptake at

apparent equilibrium

Aronu et al. 2009

MEA, 5 amines

and their

mixtures

40 / 80

Absorption /

desorption by

gas sparging

Difference between

maximum rich and

minimum lean loading

Chowdhury et al.

2009

IPAE, IBAE,

IPDEA, 1M-

2PPE

40 / 120 Glass autoclave

equilibrium cell Vapor-liquid equilibrium

Chen, 2011 14 amines and

blends 40-100

Wetted wall

column Vapor-liquid equilibrium

Porcheron et al.

2011 30 amines 40

High throughput

screening

equilibrium

apparatus

Vapor-liquid equilibrium

Dubois and

Thomas, 2012 6 amines

boiling

point

Temperature

controlled glass

stirred

regeneration

device

Regeneration efficiency:

(𝛼𝑟𝑖𝑐ℎ − 𝛼𝑙𝑒𝑎𝑛

𝛼𝑟𝑖𝑐ℎ)

Brœder and

Svendsen, 2012

amines and

blends using 7

structures

40 / 80

Absorption /

desorption by

gas sparging

Difference between

maximum rich and

minimum lean loading

Song et al. 2012 16 amino acids,

blends w/ PZ 40 Gas sparging

Approximate degree of

CO2 saturation at 40 °C

11

Table 1.3: Previous absorption rate measurements by at the University of Texas at Austin

using a wetted wall column

Category Amine Con

(m) T (°C)

CO2

loading (mol/mol

alk)

Author /

Year

Primary

monoamine

Monoethanolamine

(MEA) 7-13

40-

100 0.2-0.5

Dugas,

2009

Diglycolamine

(DGA®)

3.2, 17.7 25-60 0-0.45 Al-juaied,

2004

3.8, 11.5 25-

110 0.02-0.55

Pacheco

1998

10 40-

100 0.3-0.5

Chen

2011

Primary

(mono-

hindered)

2-amino-2methyl-1

propanol

(AMP)

4.8 40-

100 0.15-0.56

Chen

2011

Primary

(diamine)

Ethylenediamine

(EDA) 12

40-

100 0.36-0.49

Zhou et

al. 2010

Chen

2011

1,2-Diaminopropane

(MEDA) 8

40-

100 0.36-0.42

Chen

2011

(Methylamino)propylamine

(MAPA) 8

40-

100 0.25-0.52

Chen

2011

Secondary

(mono, non-

cyclic)

Diethanolamine

(DEA) 4.8

40-

120 0.02-0.46

Mshewa

1995

Secondary

(mono,

cyclic)

2-piperidineethanol

(2-PE) 8

40-

100 0.21-0.7

Chen

2011

12

Table 1.3: Previous absorption rate measurements by at the University of Texas at Austin

using a wetted wall column (continued)

Secondary

(di-amine,

cyclic)

Piperazine

and

derivatives

Piperazine (PZ) 2-12 40-

100 0.2-0.5

Dugas

2009

1-Methylpiperazine

(1MPZ) 8

40-

100 0.1-0.26

Chen

2011

2-Methylpiperazine

(2MPZ) 8

40-

100 0.1-0.37

Chen

2011

1-(2-

Aminoethyl)piperazine

(AEP)

6 40-

100 0.1-0.36

Chen

2011

N-(2-

hydroxyethyl)piperazine

(HEP)

8 40-

100 0.06-0.28

Chen

2011

2,5-trans-

dimethylpiperazine

(2,5DMPZ)

2 40-

100 0.15-0.26

Chen

2011

Tertiary Methyldiethanolamine

(MDEA)

4.5, 8.4 25-

110 0.02-0.55

Pacheco

1998

8.4 40-

120 0.02-0.46

Mshewa

1995

PZ based

blend

MDEA/PZ

7.6/0.2-0.6 25-70 0-0.31 Bishnoi

2000

7/2, 5/5 40-

100

0.09-0.27

0.18-0.37

Chen

2011

K+/PZ 0-6.2 /

0.6-3.6

25-

110 0-0.45

Cullinane

2005

MEA/PZ 7/2 40-

100 0.2-0.5

Dugas

2009

2MPZ/PZ 8 40-

100 0.16-0.39

Chen

2011

1,4-DMPZ/1MPZ/PZ 0.5/3.75/3.75 40-

100 0.21-0.32

Chen

2011

Amine blend

DGA®/ Morpholine 14/3.5 25-60 0-0.45 Al-Juaied

2004

MDEA/ DGA® 0.8/10.3 25-

110 0.02-0.55

Pacheco

1998

MDEA/DEA 7.6/1, 4.2/4.8 40-

120 0.02-0.46

Mshewa

1995

13

1.4 OBJECTIVE AND SCOPE OF THIS WORK

1.4.1 Rigorous screening of new amine solvents

This work aims to collect CO2 VLE and absorption rate data at the amine

concentration, CO2 loading, and temperature that corresponds to the expected operating

conditions of a real process.

More than 20 aqueous amine, amine blend, and amino acid solvents are tested in

this work. Each solvent was chosen for at least one of the following reasons: 1) one or

more expected attractive properties in the amine scrubbing process; 2) suggested in the

literature to be an attractive molecule or structure group; 3) systematic study of the effect

of amine structure on absorption performance. All of the amines and amino acids tested

in this work are currently commercially available and financially affordable (less than

$1000 for 1 kg).

For many of the solvents included, this work is the first effort to evaluate their

potential for CO2 capture. Some solvents have been tested as solvents for CO2 capture

previously, with available results found in literature. In these cases, this work provides

a more rigorous measurement of CO2 mass transfer and capacity, such that the direct

contribution to process cost can be inferred from the data.

The CO2 mass transfer and VLE data reported in this work is collected using a

pre-existing experimental apparatus, with a mature operating method developed by

previous researchers (Dugas 2009; Chen 2011). Little modification was made to the

pre-existing apparatus and method. However, the operating range of the experimental

apparatus was widened to included 20 °C as part of this work. Also, the error and

reproducibility of the pre-existing method was quantified in this work.

14

1.4.2 Estimate process performance

This work aims to interpret and analyze the screening data with considerations of

the operating conditions and trade-offs of a capture process. New parameters are

introduced to represent the relative capital and operating cost of each solvent in the

process.

1.4.3 Generalize solvent performance

This work aims to demonstrate the relationship between amine structure and

solvent performance. The CO2 VLE and absorption rate in several primary and

secondary mono-amines were collected and studied. The effect of amine pKa on the

CO2 VLE and speciation in the solvent is evaluated using a simplified speciation model

(SSM). The effect of amine pKa on the CO2 mass transfer rate at CO2 loaded conditions

are studied by considering the pseudo first order (PFO) analytical representation of the

mass transfer coefficient.

15

Chapter 2: Theoretical review

In this chapter, the relevant theories on the reaction mechanism of the CO2/amine

reaction are presented. The theories of acid base catalysis are necessary to understand

why amines react differently with CO2, and how does this difference in chemistry affect

the absorption of CO2 in a capture process. These theories are directly applied in

Chapter 10 to demonstrate the effect of chemical reaction on the mass transfer

coefficient.

The origin of kg', the liquid film mass transfer coefficient with gas side units, is

explained using mass transfer theories. The pseudo first order (PFO) analytical

expression for kg' is also presented in this chapter, which relates kg' to the physical and

chemical properties of the solvent. kg' is used in this work to represent CO2 absorption

rates, these backgrounds are helpful in the understanding and interpretation of data

presented in this work. The PFO expression is used to generalize the mass transfer rate

of CO2 based on the structure of the amine (Chapter 10). The relevant assumptions

involved in the development of the PFO kg' is useful in understanding the applications

and limitations of this work.

2.1 GENERAL CHEMISTRY

2.1.1 Acid base catalysis

The liquid phase reactions between amines and CO2 are categorized as base

catalysis reaction (Equation 2.1).

HA + B A- + BH+ (2.1)

Acid and base catalysis are the most common types of homogeneous catalysis

reactions. As originally defined by Bronsted (1927), and Lowry (1927), a base (B) is

16

the molecule with gains a hydrogen proton in a reaction, and the corresponding molecule

which gives up the hydrogen proton is defined as the acid (HA). Moreover, the

protonated base (BH+) is defined as the conjugated acid, and the de-protonated acid (A-)

the conjugated base, such the reverse reaction is also an acid-base catalysis reaction.

The Bronsted-Lowry definition of acid and base emphasizes that acid and base exist in

pairs, and their roles are specific to each chemical reaction. A molecule can behave like

an acid in one reaction but as a base in another.

Bronsted also suggests the catalytic effect of the acid or base on the kinetic rate

of the reaction is proportional to the strength of acid/base. For a general form of base

catalysis reaction (Equation 2.2), this relationship can be represented as shown in

Equation 2.3.

𝑅 + 𝑏𝑘𝑏→ 𝑃 (2.2)

𝑙𝑜𝑔10𝑘𝑏 = 𝑥 + 𝜒 ∙ 𝑝𝐾𝑎,𝑏 (2.3)

In Equation 2.3, 𝑥 and 𝜒 are reaction specific constants, and 𝑝𝐾𝑎,𝑏 is the acid

dissociation constant of the base in water. This correlation derived Bronsted theory has

been widely applied to the reaction between CO2 and amines, such that the reaction rate

constants of the amine-CO2 reactions are commonly correlated with the basic strength of

the amine (Versteeg and Swaaij 1988a; Cullinane 2005).

2.1.2 Types of amine structures

In general, amines can be divided into three groups depending on the number of

hydrogen atoms attached to the basic nitrogen. Primary amines carry two hydrogen

atoms on the nitrogen. Secondary amines have one additional substitution group on the

nitrogen and one less hydrogen on than primary amines. Tertiary amines are fully

substituted and carry no hydrogen on their nitrogen. A fourth category of amine is also

17

relevant for the application of CO2 capture, which is commonly referred to as hindered

amines. Loosely defined by shapes of the substitution groups on the nitrogen, hindered

amines are primary or secondary amines with substitution groups that directly interferes

with the interaction of its nitrogen with CO2. The general structure of each type of

amine is shown in Table 2.1, where the structure of 2-amino-2-methyl-1propanol is used

as an example for hindered amines.

Table 2.1: General structure of different types of amines

Amine category General structure

Primary R NH2

Secondary R NH

R'

Tertiary R'N

R"

R

Hindered NH2

CH3

OH CH3 (2-amino 2-methyl 1propanol)

Primary and Secondary Amines

The overall equilibrium of the reversible reaction between CO2 and a primary or

secondary amine can be represented using Equation 2.4. A nitrogen on a primary or

secondary amine can form a covalent bond with the carbon on CO2, forming a carbamate

product. This reaction is catalyzed by a base, which becomes protonated in the process

(Crooks and Donnellan 1989).

(2.4)

18

In an aqueous amine system, the available bases for this reaction (Equation 2.4)

are H2O and the amine. At moderate to high amine concentrations, the amine is the

favored base, as it is a stronger base than H2O. And the carbamate formation reaction

can be re-written as Equation 2.5.

(2.5)

The stoichiometry of this reaction shows for each mole of reacted CO2, two moles

of free amine are consumed. In a CO2 capture process, a high ratio of amine

consumption per mole of CO2 absorbed means a larger amount of amine is required to

capture the same amount of CO2.

The rate of carbamate formation reaction is believed to be second order in the

amine at high amine concentrations (Equation 2.6). Two proposed mechanisms for this

reaction are discussed in section 2.1.3.

−𝑟𝐶𝑂2 = 𝑘 ∙ [𝐴𝑚𝑖𝑛𝑒]2 ∙ [𝐶𝑂2] (2.6)

Tertiary amines

Tertiary amines cannot react with CO2 and form carbamates, as their nitrogen is

fully substituted. Instead, tertiary amines act as a base and catalyze the CO2 and water

reaction, which forms bicarbonate and protonated amine (Equation 2.7).

(2.7)

The rate of CO2 production for the bicarbonate reaction can be written as:

−𝑟𝐶𝑂2 = 𝑘 ∙ [𝐴𝑚𝑖𝑛𝑒] ∙ [𝐶𝑂2] ∙ [𝐻2𝑂] ≈ 𝑘[𝐴𝑚𝑖𝑛𝑒] ∙ [𝐶𝑂2] (2.8)

19

Unlike primary and secondary amines, the amine catalyzed bicarbonate formation

reaction is first order to the amine. The reaction rate constants for bicarbonate

formation reactions (Equation 2.7) are typically much lower than for carbamate formation

reactions (Equation 2.4). However, the stoichiometry of the bicarbonate reaction is

favorable for the CO2 capacity of the amine, as for each mole of CO2 reacted only one

mole of free amine is consumed.

Hindered Amines

Hindered amines are special primary and secondary amines with bulky functional

groups which interfere with the formation of stable carbamates (Satori an Savage 1983).

Still, hindered amines can react with CO2 to form carbamate similar to unhindered

amines, but at a much lower equilibrium concentration. As shown in Equation 2.9b, the

hindered amine carbamate is believed to dissociate in water, which produces a free amine

and bicarbonate. Thus, the hindered carbamate can be considered as an intermediate for

converting free CO2 to bicarbonates.

(2.9a)

(2.9b)

(2.10)

Hindered amines can also produce bicarbonate by catalyzing the CO2 and H2O

reaction (Equation 2.10), similar to tertiary amines (Equation 2.7). Since the amount of

20

stable carbamate in hindered amine systems is very low, for each mole of reacted CO2,

about one mole of amine is consumed. The capacity of hindered amine solvents is

expected to be higher than primary and secondary amines.

2.1.3 Kinetic mechanisms

The reaction order and mechanism of the carbamate formation reaction (Equation

2.4) by a primary or secondary amine and CO2 has been the subject of much debate in

literature. Based on the large amount of literature data accumulated over time, it

appears that the order of the carbamate formation reaction depends on the concentration

of free amine. Two reaction mechanisms have been widely applied in literature for the

carbamate formation reaction: the Zwitterion and Termolecular mechanisms. While

both mechanisms allow for the varying of reaction order with amine concentration, it has

been widely suggested the Termolecular mechanism offers more reasonable explanations

of the physical system (Crooks and Donnellan, 1989; da Silva and Svendsen, 2004;

Aboudheir et.al., 2003). Both reaction mechanisms and their application to

concentrated amine systems are discussed here.

Zwitterion mechanism

The Zwitterion mechanism was originally proposed by Caplow (Caplow 1968)

and later used by Danckwerts (1979) in several influential studies of CO2 reactions with

amines. This mechanism describes the reaction as a two step process. During the first

step, the CO2 and amine molecules combine and form an unstable zwitterion intermediate

(Equation 2.11a). This intermediate is then quickly deprotonated by a base in the system,

which produces a negatively charged carbamate and a protonated base (Equation 2.11b).

21

(2.11a)

(2.11b)

The overall rate of reaction of CO2 using this mechanism can be written as shown

in Equation 2.12:

− 𝑟𝐶𝑂2 =𝑘𝑓[𝐶𝑂2][𝐴𝑚𝑖𝑛𝑒]

(1+𝑘𝑟

∑ 𝑘𝐵𝑖[𝐵𝑖]𝑖

) (2.12)

The subscript “Bi” represents the available bases in the solvent, which are H2O

and free amine molecules. In the case where the base extraction step (kBi) is much faster

than the reverse rate of the zwitterion formation (kr), or ∑ 𝑘𝐵𝑖[𝐵𝑖]𝑖 ≫ 𝑘−1, the rate

expression in Equation 2.12 simplifies into Equation 2.13, where the rate of reaction is

first order to the amine.

− 𝑟𝐶𝑂2 = 𝑘𝑓[𝐶𝑂2][𝐴𝑚𝑖𝑛𝑒] (2.13)

For the zwitterion mechanism to show a second order rate dependence with the

amine, it is necessary to assume that the base extraction reaction is much slower than the

reverse reaction of zwitterion formation (∑ 𝑘𝐵𝑖[𝐵𝑖]𝑖 ≪ 𝑘𝑟). In this case, the rate of

reaction can be simplified into Equation 2.14a. At high amine concentration where the

amine is the dominating base, the expression further reduces to a second order

dependence on amine (Equation 2.14b).

− 𝑟𝐶𝑂2 = ∑ 𝑘𝐴𝑚−𝐵𝑖[𝐵𝑖]𝑖 [𝐶𝑂2][𝐴𝑚𝑖𝑛𝑒], 𝑘𝐴𝑚−𝐵𝑖

=𝑘𝑓 𝑘𝐵𝑖

𝑘𝑟 (2.14a)

−𝑟𝐶𝑂2 = 𝑘[𝐶𝑂2][𝐴𝑚𝑖𝑛𝑒]2 (2.14b)

22

Though the Zwitterion mechanism allows for the representation of experimental

data with both first and second (and in between) order dependence on amine

concentration, the necessary assumptions are questionable (Crooks and Donnellan 1989;

da Silva and Svendsen 2004).

Termolecular mechanism

Alternatively to the Zwitterion mechanism, Crooks and Donnellan (1989)

proposed the Termolecular mechanism for the formation of carbamate, where three

molecules (amine, CO2, base) form a loosely associated complex (Figure 2.1). Bonds

form and charges shift simultaneously, and the reaction is a single step.

Figure 2.1: Reaction complex proposed by the Termolecular Reaction Mechanism

The reaction rate of CO2 expressed using the Termolecular mechanism is

essentially the sum of all possible base catalysis reactions (Equation 2.15). This rate

expression is identical to the Zwitterion expression in the limit of a relatively slow base

extraction step (Equation 2.15).

− 𝑟𝐶𝑂2 = ∑ 𝑘𝐴𝑚−𝐵𝑖[𝐵𝑖]𝑖 [𝐶𝑂2][𝐴𝑚𝑖𝑛𝑒], 𝑘𝐴𝑚−𝐵𝑖

=𝑘𝑓 𝑘𝐵𝑖

𝑘𝑟 (2.15)

The Termolecular rate expression can be used to represent data with first to

second order dependence on amine concentration, by considering the effect of the

available bases only. In the case of low amine concentration, H2O is the most available

base, and Equation 2.15 can simplify into a first order dependence on the amine. At

23

high amine concentration, as the amine becomes the dominating base, the reaction is

second order to the amine, the same as shown in Equation 2.14b.

2.1.4 Reversible reaction

In the earlier sections, the reaction rate expressions are written only for the

forward reactions for simplicity. However, all amine and CO2 reactions are reversible,

which allows for the amine solvent to regenerate in the stripper section of a CO2 capture

process. Conveniently, at most relevant conditions, this reversibility can be accounted

for with a simple modification of the reaction rate expressions.

A general form of the CO2 and amine reaction, for all amine types and

mechanisms, can be written as Equation 2.16 with the corresponding reaction rate

expression as shown in Equation 2.17.

CO2 + Rkr←

kf → P (2.16)

−𝑟𝐶𝑂2 = 𝑘𝑓[𝐶𝑂2][𝑅] − 𝑘𝑟[𝑃] (2.17)

Substituting the equilibrium condition (Equation 2.18) into the rate expression

(Equation 2.17) results in Equation 2.19.

𝐾𝑒𝑞 =𝑘𝑓

𝑘𝑟=

[𝑃]𝑒𝑞

[𝐶𝑂2]𝑒𝑞[𝑅]𝑒𝑞 (2.18)

−𝑟𝐶𝑂2 = 𝑘𝑓[𝐶𝑂2][𝑅] −𝑘𝑓

𝐾𝑒𝑞[𝑃] = 𝑘𝑓 ([𝐶𝑂2][𝑅] −

[𝑃𝑟𝑜𝑑𝑢𝑐𝑡]

𝐾𝑒𝑞) (2.19)

At high amine concentrations with moderate CO2 loading (expected for CO2

capture processes), the concentration of CO2 is much smaller than the free amine and

product species, such that:

[𝑃]𝑒𝑞 ≈ [𝑃]; [𝑅]𝑒𝑞 ≈ [𝑅]; [𝐶𝑂2] ≪ [𝑅], [𝑃] (2.20)

Substituting the approximations in Equation 2.20 into the rate expression

(Equation 2.19) results in the reversible rate expression:

−𝑟𝐶𝑂2 = 𝑘𝑓[𝑅]([𝐶𝑂2] − [𝐶𝑂2]𝑒𝑞) (2.21)

24

In Equation 2.21 the reversibility of the reaction is expressed as a CO2

concentration driving force for the chemical reaction.

2.1.5 Activity vs. concentration based rate expression:

The reaction rate expressions are commonly written with concentrations of the

reactants (Equation 2.22), which is also used in earlier sections for simplicity.

−𝑟𝐶𝑂2 = 𝑘𝑐[𝐶𝑂2[𝐴𝑚𝑖𝑛𝑒] (2.22)

The concentration based rate expression is valid at conditions close to infinite

dilution in water, where the activity coefficients of the reacting species are approximately

one. However, for highly concentrated aqueous amines with moderate CO2 loading, the

liquid environment is highly ionic and significantly away from infinite dilution. To

account for the ionic effect on reaction kinetics, an activity based rate expression should

be used (Equation 2.23).

−𝑟𝐶𝑂2 = 𝑘𝑎𝑎𝐶𝑂2𝑎𝑎𝑚𝑖𝑛𝑒𝜌𝑚2 (2.23)

The activity based reaction rate constant is related to the concentration based

constant as shown in Equation 2.24.

𝑘𝑎 =𝑘𝑐

𝛾𝐶𝑂2𝛾𝑎𝑚𝑖𝑛𝑒 (2.24)

2.2MASS TRANSFER THEORIES

The mass transfer problem of CO2 absorption from flue gas into aqueous amines

involves four phenomena: molecular diffusion in the gas phase, physical solubility at the

gas-liquid interface, molecular diffusion in the liquid phase, and chemical reactions in the

liquid. The role of gas phase diffusion and gas-liquid equilibrium at the interface are

rather straightforward and can be easily accounted for. However, the mass transfer

process in the liquid with both diffusion and reversible chemical reactions is the complex

25

component of the process. Moreover, while the properties of the solvent or amine does

not affect the mass transfer of CO2 in the gas phase and at the interface, they contribute

significantly to the mass transfer in the liquid phase. Understanding the reactive mass

transfer of CO2 in liquid amine is critical for choosing the best solvent.

Various mass transfer theories are discussed and applied to the CO2 absorption

case in this section. The most appropriate representation for the CO2-amine system is

presented.

2.2.1 Mass transfer coefficients

The mole flux (NCO2) is commonly used to represent the rate of mass transfer per

unit area. As defined by Fick’s law, the mole flux of CO2 across the gas-liquid interface

(x=0) can be written as Equation 2.25.

𝑁𝐶𝑂2 = −𝐷𝐶𝑂2𝜕[𝐶𝑂2]

𝜕𝑥|𝑥=0

(2.25)

The mole flux can also be written as proportional to the concentration driving

force for mass transfer. In the case of CO2 absorption from bulk gas to bulk liquid, CO2

flux can be written for the driving force in the gas film, liquid film, or overall (Equation

2.26). The proportionality constant between mole flux and its corresponding driving

force is the mass transfer coefficient.

𝑁𝐶𝑂2 [𝑚𝑜𝑙

𝑠∙𝑚2] =

{

𝐾𝐺∙(𝑃𝐶𝑂2,𝑏𝑢𝑙𝑘−𝑃𝐶𝑂2

∗ )

𝑘𝑔(𝑃𝐶𝑂2,𝑏𝑢𝑙𝑘−𝑃𝐶𝑂2,𝑖)

𝑘𝑙(𝐶𝑂2,𝑖−𝐶𝑂2,𝑏𝑢𝑙𝑘)

𝑘𝑔′ (𝑃𝐶𝑂2,𝑖−𝑃𝐶𝑂2

∗ )=𝑘𝑙

𝐻𝐶𝑂2(𝑃𝐶𝑂2,𝑖−𝑃𝐶𝑂2

∗ )

(2.26)

The overall gas side mass transfer coefficient (KG) corresponds to the

concentration driving force between bulk gas and bulk liquid (where PCO2* is in

equilibrium with [CO2]bulk). The gas film mass transfer coefficient (kg) corresponds to

the driving force across the gas film, and kg is a function of relevant properties of the gas.

At the gas-liquid interface, the CO2 in the gas and liquid are in equilibrium, and can be

26

related using the Henry’s constant. The liquid film mass transfer coefficient (kl)

corresponds to the CO2 gradient in the liquid film. The parameter kg’ is also the liquid

film mass transfer coefficient, which differs from kl only in that it has partial pressure

units. Both kl and kg’ are functions of relevant liquid properties, and are the focus of

this work. An illustration of the mass transfer of CO2 (without chemical reaction) is

shown in Figure 2.2.

If the mass transfer process is at steady state, the flux across each mass transfer

films are the same, and the mass transfer coefficients can be written in the series

resistance form (Equation 2.27). 1

𝐾𝐺=

1

𝑘𝑔+

𝐻𝐶𝑂2

𝑘𝑙=

1

𝑘𝑔+

1

𝑘𝑔′ (2.27)

2.2.2 Physical mass transfer

First, the case of physical mass transfer of CO2 without chemical reaction is

considered to evaluate the effect of molecular diffusion on the liquid film mass transfer

coefficient (kl or kg’). The dependence of kl on the diffusion coefficient can be

determined by solving the simplified continuity equation (Equation 2.28), which assumes

mass transfer of CO2 occurs only in the x direction via molecular diffusion.

𝐷𝐶𝑂2𝜕2[𝐶𝑂2]

𝜕𝑥2=

𝜕[𝐶𝑂2]

𝜕𝑡 (2.28)

Several mass transfer models have been proposed to describe the physical process

and solve the differential equation with its own specified boundary conditions.

Film Theory

Film theory proposes a steady state model, which assumes the diffusion of CO2

occurs within a boundary layer close to the interface (Whitman 1962). The diffusion

boundary has some finite thickness (). Also, the bulk liquid is assumed to be well

mixed, and the convection in the liquid bulk ultimately determines the film thickness.

27

The effect of convection is neglected within the diffusion boundary. The governing

equation and boundary conditions based on film theory is: 𝜕2[𝐶𝑂2]

𝜕𝑥2= 0; @ 𝑥=0,[𝐶𝑂2]=[𝐶𝑂2]𝑖

@ 𝑥=𝛿,[𝐶𝑂2]=[𝐶𝑂2]𝑏𝑢𝑙𝑘 (2.29)

The solution of Equation 2.29 gives a first order dependence of kl on DCO2:

𝑘𝑙 =𝐷𝐶𝑂2

𝛿 (2.30)

The CO2 concentration profile in the gas and liquid film as proposed by the film

theory is shown in Figure 2.2.

Figure 2.2: Steady state concentration profile of CO2 absorption without chemical

reaction in the liquid phase, using film theory (not drawn to scale).

The film model is largely criticized as the first order dependence of kl on DCO2 has

been shown to be inaccurate when compared with experimental data (Danckwerts, 1970).

Moreover, the discontinuity in the concentration profile at the diffusion boundary is

highly unrealistic. However, this model is still used widely to represent the diffusion of

CO2 in the liquid phase due to its simplicity.

28

Unsteady State Theories

Two unsteady state models have been proposed to better represent the diffusion of

a dissolved gas in a non-reacting liquid. The governing equation for both models is the

continuity equation as shown in Equation 2.28.

The Penetration theory (Higbie 1935) suggests the liquid film behaves like

currents with bulk motion. As a result, each current element spends only a finite

amount of time at the interface participating in the diffusion process. The times spent at

the interface are assumed to be constant among all the liquid elements. The solution

derived using this model shows a half order dependence of kl on DCO2:

𝑘𝑙 = √4𝐷𝐶𝑂2

𝜏𝜋 (2.31)

In Equation 2.31, the parameter τ is the time constant.

The Surface Renewal theory (Danckwerts 1951) improves on the Penetration

Theory model by abandoning the constant time distribution assumption. Instead, it uses

a convenient probability distribution function to represent the range of time spend at the

interface by each liquid element. The result also shows a half order dependence of kl on

DCO2:

𝑘𝑙 = √𝐷𝐶𝑂2𝑠 (2.32)

In Equation 2.32, the parameter s represents the fraction of renewal surface.

The square root dependence on DCO2 is in close agreement with experimental

data, and these models are believed to be better representatives of reality (Danckwerts

1970).

Eddy Diffusivity Theory

The Eddy Diffusivity theory is a steady state model which proposes the presence

of eddy currents in the liquid film that affect the diffusion of CO2 in the solvent. This

29

microscopic convection effect is introduced by modifying the continuity equation as

Equation 2.33.

𝜕

𝜕𝑥(𝐷𝐶𝑂2 + 휀𝑥)

𝜕[𝐶𝑂2]

𝜕𝑥= 0 (2.33)

The parameter 휀 effectively varies the size of the current as function of the depth

into the liquid film, where the current is assumed to be smallest close to the interface and

will increase as CO2 moves into the liquid film (King 1966). The solution using this

model shows the square root dependence of kl on DCO2:

𝑘𝑙 =√4𝐷𝐶𝑂2

𝜋 (2.34)

The Eddy Diffusivity model is attractive as it correctly predicts the half order

dependence of kl on DCO2. Moreover, it is still a steady state model, which makes it

easier to use than the unsteady state models.

The dependence of kl on DCO2 predicted by the mass transfer models are

summarized in Table 2.2.

Table 2.2: Summary of kl dependence on diffusion coefficient by various physical mass

transfer models

Theory n: 𝑘𝑙 = 𝑓(𝐷𝐶𝑂2𝑛) Model form

Film 1 Steady State

Penetration 0.5 Unsteady State

Surface Renewal 0.5 Unsteady State

Eddy Diffusivity 0.5 Steady State

2.2.3 Mass transfer with chemical reaction

For the reactive absorption of CO2 by aqueous amines, the effects of both

molecular diffusion and chemical reaction need to be accounted for. The general

continuity equation for this reactive mass transfer problem is:

𝐷𝐶𝑂2𝜕[𝐶𝑂2]

𝜕𝑥2− 𝑘𝑛[𝐴𝑚𝑖𝑛𝑒]

𝑛−1([𝐶𝑂2] − [𝐶𝑂2]𝑒𝑞) =𝜕[𝐶𝑂2]

𝜕𝑡 (2.35)

30

Solving this partial differential equation requires another differential equation

accounting for the mass balance of amine, making the problem difficult to solve

mathematically. Therefore, two relevant assumptions are considered instead, both of

which allows for significant simplification of the mathematical problem.

In the analysis of mass transfer with chemical reaction, the parameter 𝑘𝑙° is

useful. Applied for CO2 absorption into aqueous amines by Cullinane (2005) and Dugas

and Rochelle (2011), 𝑘𝑙° is the physical mass transfer coefficient in the liquid phase. In

the previous case where physical mass transfer is the only considered phenomenon, 𝑘𝑙° is

the same as kl. In the case where chemical reaction occurs together with molecular

diffusion, 𝑘𝑙° only contributes partially to the liquid side mass transfer (kl), and thus a

separate parameter is necessary. The previously developed kl expressions in the

physical mass transfer only case are required to develop the solutions in the reactive mass

transfer case.

Pseudo first order approximation

The first limiting case of reactive mass transfer assumes the concentration of

available amines for the reaction with CO2 is much higher relative to the CO2 flux.

Therefore, the concentration of free amine and reaction products are approximately

constant from the gas-liquid interface to the liquid bulk, and the rate of CO2 reaction can

be expressed as pseudo first order (PFO).

𝑘𝑛[𝐴𝑚𝑖𝑛𝑒]𝑛−1 ≈ 𝑘1 (2.36)

In Figure 2.3, the concentration profile of CO2 from bulk gas into bulk liquid is

illustrated for the PFO case. The PFO assumption requires the concentration of free

amine reactant and reaction products to be constant from the gas liquid interface to bulk

liquid. At the interface, the CO2 in the gas (PCO2,i) is in equilibrium with free CO2 in the

31

liquid ([CO2]i). However, at and near the interface, the absorbed free CO2 ([CO2]i) is

not in chemical equilibrium with the other species in the liquid because the reaction rate

is finite. It can be imagined that there exists a [CO2]i,e, which is the concentration of

free CO2 that is in chemical equilibrium with the amine and products. And the distance

between [CO2]i and [CO2]i,e is the driving force for the chemical reaction of CO2. There

exists a distance close to the interface (𝛿′) within which the mass transfer of CO2 is

driven by reaction, and this is referred to as the reaction film.

Figure 2.3: Steady state concentration profile of CO2 absorption with chemical reaction in

the liquid phase, with the pseudo first order assumption (not drawn to scale).

The continuity equation for the PFO approximation can be solved using film

theory or the surface renewal model to account for the diffusion effect. If film theory is

applied, the continuity equation to be solved and the boundary conditions are:

DCO2∂2[CO2]

∂x2− k1([CO2] − [CO2]eq) = 0 (2.37)

32

{@𝑥 = 0, [𝐶𝑂2] = [𝐶𝑂2]𝑖

@ 𝑥 = 𝛿, [𝐶𝑂2] = [𝐶𝑂2]𝑏𝑢𝑙𝑘 (2.38)

Using the surface renewal model, the governing equation and boundary

conditions are:


𝜕𝑥2− 𝑘1([𝐶𝑂2] − [𝐶𝑂2]𝑒𝑞) =

𝜕[𝐶𝑂2]

𝜕𝑡 (2.39)

{

@𝑥 = 0, [𝐶𝑂2] = [𝐶𝑂2]𝑖@𝑥 = 𝑓𝑖𝑛𝑖𝑡𝑒, [𝐶𝑂2] = [𝐶𝑂2]𝑏𝑢𝑙𝑘@𝑡 = 0, [𝐶𝑂2] = [𝐶𝑂2]𝑏𝑢𝑙𝑘

(2.40)

The solution of using both mass transfer models arrives at the same flux

expression in the limit of high Hatta number (𝐻𝑎 = √𝐷𝐶𝑂2𝑘1

𝑘𝑙°2

), where the amount of

absorbed CO2 consumed by the reaction in the reaction film relative to the unreacted CO2

which reached the bulk liquid. A large Hatta number represents fast or strong effect of

the chemical reaction. In the limit of high Hatta number, the CO2 concentration at the

reaction interface ([𝐶𝑂2]𝛿′) is about the same as [CO2]bulk, and the reaction and diffusion

film collapse together (𝛿′ = 𝛿). The analytical expression of CO2 flux at the limit of

high Hatta number is shown in Equation 2.41, and the corresponding expression for kg’ in

Equation 2.42.

𝑁𝐶𝑂2 =√𝐷𝐶𝑂2𝑘1

𝐻𝐶𝑂2

(𝑃𝐶𝑂2𝑖 − 𝑃𝐶𝑂2∗ ) =

√𝐷𝐶𝑂2𝑘𝑛[𝐴𝑚𝑖𝑛𝑒]𝑛−1

𝐻𝐶𝑂2

(𝑃𝐶𝑂2𝑖 − 𝑃𝐶𝑂2∗ ) (2.41)

𝑘𝑔,𝑃𝐹𝑂′ =

√𝐷𝐶𝑂2𝑘𝑛[𝐴𝑚𝑖𝑛𝑒]𝑛−1

𝐻𝐶𝑂2

(2.42)

The analytical expression in Equation 2.42 is believed to be valid for a significant

portion of the experimental kg’ collected in this work.

33

Instantaneous

The case of instantaneous reaction rates is relevant in the analysis of high

temperature absorption rates. Reaction rates increase exponentially with temperature,

and can be assumed to be instantaneous relative to diffusion at high temperature

conditions. The instantaneous limit is also helpful in demonstrating the mass transfer

behavior in the diffusion film for systems with moderate Hatta numbers. At moderate

Hatta numbers, a diffusion film exists where the chemical reactions are at equilibrium

across the entire film, which is similar to the case of instantaneous reaction. In both

cases, the ongoing mass transfer is driven by the diffusion of reactants and products.

Figure 2.4: Steady state concentration profile of CO2 absorption with instantaneous

reversible reaction in the liquid phase (not drawn to scale).

The reversible CO2 reaction with amines can be written as Equation 2.43, with the

corresponding equilibrium constant in Equation 2.44.

𝐶𝑂2 + 𝑅 ↔ 𝑃 (2.43)

34

𝐾 =[𝑃]𝑒

[𝐶𝑂2]𝑒[𝑅]𝑒=

[𝑃]𝑖

[𝐶𝑂2]𝑖[𝑅]𝑖=

[𝑃]𝑏𝑢𝑙𝑘

[𝐶𝑂2]𝑏𝑢𝑙𝑘[𝑅]𝑏𝑢𝑙𝑘 (2.44)

The condition of instantaneous reaction requires the species to be at chemical

equilibrium at the gas liquid interface. The concentration profile of CO2 for the case of

instantaneous reaction is shown in Figure 2.4. At the gas-liquid interface, [CO2]i is not

in equilibrium with PCO2i, and instead it is in chemical equilibrium with the other species

in the liquid. In Figure 2.4, [CO2]i* is the CO2 concentration in equilibrium with PCO2i,

which is reduced instantaneously to [CO2]i at the interface.

Mathematically, the mass balance of this case can be written as shown in

Equation 2.45:


𝜕𝑥2+ 𝐷𝑃

𝜕2[𝑃]

𝜕𝑥2= 0 (2.45)

With the boundary conditions of:

@𝑥=0,[𝑃]=[𝑃]𝑖;[𝐶𝑂2]=[𝐶𝑂2]𝑖;[𝑅]=[𝑅]𝑖

@𝑥=𝛿,[𝑃]=[𝑃]𝑏𝑢𝑙𝑘;[𝐶𝑂2]=[𝐶𝑂2]𝑏𝑢𝑙𝑘;[𝑅]=[𝑅]𝑏𝑢𝑙𝑘 (2.46)

As shown by Danckwerts (1970), the flux expression derived from Equation 2.45

and 2.46 is:

𝑁𝐶𝑂2 = 𝑘𝑙° [([𝐶𝑂2]𝑖 +

𝐷𝑃[𝑃]𝑖

𝐷𝐶𝑂2) − ([𝐶𝑂2]𝑏𝑢𝑙𝑘 +

𝐷𝑃[𝑃]𝑏𝑢𝑙𝑘

𝐷𝐶𝑂2)] (2.47)

At the condition of moderate to high CO2 loading, the concentration of free CO2

is much lower than the reaction products, and Equation 2.47 can be simplified into

Equation 2.48.

𝑁𝐶𝑂2 = 𝑘𝑙° 𝐷𝑃

𝐷𝐶𝑂2([𝑃]𝑖 − [𝑃]𝑏𝑢𝑙𝑘) ≈ 𝑘𝑙

° 𝐷𝑃

𝐷𝐶𝑂2([𝐶𝑂2]𝑇,𝑖 − [𝐶𝑂2]𝑇,𝑏𝑢𝑙𝑘) (2.48)

To convert the CO2 concentration driving force in Equation 2.48 into partial

pressure driving force, the slope of the equilibrium can be used (∆𝑃𝐶𝑂2

∗

∆[𝐶𝑂2]𝑇). If kl

◦

expression from film theory is used, the flux expression can be further reduced to:

𝑁𝐶𝑂2 = 𝑘𝑙−𝑝𝑟𝑜𝑑° (

∆𝑃𝐶𝑂2∗

∆[𝐶𝑂2]𝑇) ∙ (𝑃𝐶𝑂2,𝑖 − 𝑃𝐶𝑂2

∗ ) (2.49)

35

If a square root dependence of kl◦ on DCO2 is assumed, the flux expression

becomes:

𝑁𝐶𝑂2 = 𝑘𝑙−𝑝𝑟𝑜𝑑° (√

𝐷𝑝

𝐷𝐶𝑂2) (

∆𝑃𝐶𝑂2∗

∆[𝐶𝑂2]𝑇) ∙ (𝑃𝐶𝑂2,𝑖 − 𝑃𝐶𝑂2

∗ ) (2.50)

The expression in Equation 2.50 agrees with the expression proposed by

Cullinane (2005). The corresponding kg’ can be expressed by analogy:

𝑘𝑔,𝐼𝑁𝑆𝑇′ = 𝑘𝑙−𝑝𝑟𝑜𝑑

° (∆𝑃𝐶𝑂2

∗

∆[𝐶𝑂2]𝑇) 𝑜𝑟 𝑘𝑙−𝑝𝑟𝑜𝑑

° (√𝐷𝑝

𝐷𝐶𝑂2) (

∆𝑃𝐶𝑂2∗

∆[𝐶𝑂2]𝑇) (2.51)

Fast reaction

Figure 2.5: Steady state concentration profile of CO2 absorption with fast reversible

chemical reaction in the liquid phase (not drawn to scale).

At some relevant conditions for CO2 absorption into amines, the reaction is not

pseudo first order nor instantaneous. The overall mass transfer process carries the

combined effect of reaction kinetics, molecular diffusion of CO2, and the diffusion of

reactants and products. The CO2 concentration profile for the case of fast chemical

36

reactions is shown in Figure 2.5, where a reaction film and a diffusion film are both

significant, and the concentrations of reactants and products vary between the interface

and bulk liquid.

To develop an analytical expression for kg’ in this case, Dugas (2009) represents

the reaction film and diffusion film in the liquid with the film resistance theory. Similar

to the case of series resistance between the gas and liquid film (Equation 2.26 and 2.27),

the mass transfer coefficients in the liquid film can be related by Equations 2.52 and 2.53:

𝑁𝐶𝑂2 =

{

𝑘𝑔′ (𝑃𝐶𝑂2,𝑖 − 𝑃𝐶𝑂2

∗ )

𝑘𝑔" (𝑃𝐶𝑂2,𝑖 − 𝑃𝐶𝑂2,𝛿′

∗ )

𝑘𝑔−𝐷𝑖𝑓𝑓′ ∙ (𝑃𝐶𝑂2,𝛿′

∗ − 𝑃𝐶𝑂2∗ )

(2.52)

1

𝑘𝑔′ =

1

𝑘𝑔" +

1

𝑘𝑔−𝐷𝑖𝑓𝑓′ (2.53)

Assuming the mass transfer in the reaction film is similar to the PFO case with

high Hatta number (reaction is fast), kg” can be substituted with Equation 2.42.

Similarly, the behavior in the diffusion film is expected to be the same as the

instantaneous case, only the boundary of the diffusion film is at 𝛿′ for the case of fast

reaction, as opposed to the interface for the instantaneous reaction case. By analogy,

𝑘𝑔−𝐷𝑖𝑓𝑓′ can be substituted by Equation 2.51. And the general expression for the liquid

film mass transfer coefficient is: 1

𝑘𝑔′ =

𝐻𝐶𝑂2

√𝐷𝐶𝑂2𝑘𝑛[𝐴𝑚𝑖𝑛𝑒]𝑛−1+

1

𝑘𝑙−𝑝𝑟𝑜𝑑° (

∆𝑃𝐶𝑂2∗

∆[𝐶𝑂2]𝑇)

(2.54)

In this work, the PFO expression of kg' is assumed to represent the experimental

data collected at 40 °C and low to moderate CO2 loadings. The PFO kg' is a convenient

approximation, which can be used to demonstrate the effect of solvent properties on the

overall absorption performance.

37

Chapter 3: Experimental methods

3.1 WETTED WALL COLUMN

3.1.1 Introduction

A bench scale wetted wall column (WWC) was used to measure the CO2

absorption rates and VLE in various amine solvents. During a WWC experiment, the

CO2 loaded amine solvent flows downward along the smooth surface of a vertical

cylindrical column. A gas stream counter currently contacts the downward flowing

liquid, during which CO2 mass transfer occurs between the gas and liquid phase. The

steady state CO2 concentration change is measured, which is used to calculate the mass

transfer rates and CO2 VLE.

The gas-liquid contact area of the WWC can be estimated rather accurately using

momentum transfer first principles, as long as the liquid flow maintains a smooth surface

(without rippling or dry spots). Compared to other types of mass transfer measurement

devices, such as the laminar jet or the stirred cell, the WWC is the best fit for measuring

the overall liquid film mass transfer with fast chemical reactions. Stirred cell contactors

are typically restricted by low kl◦, and the effect of fast chemical reaction cannot be

observed. Laminar jet contactors usually operate with low gas-liquid contact time, and

are ideal for measuring reaction kinetics and for systems with high overall mass transfer

rates. However, the mass transfer of CO2 in amines at process conditions is too slow for

the laminar jet range. Moreover, the geometry of the WWC is more comparable to

structured packing than the other two contactor types.

The WWC used in this work was first constructed by Mshewa (1995).

Correlation of physical mass transfer coefficients (liquid and gas side) for this contactor

was later completed by Pacheco (1998). This apparatus was used in numerous other

38

studies for CO2 absorption into amines, including Bishnoi (2000), Cullinane (2005),

Dang (2000), Dugas (2009), and Chen (2011). The set up and data interpretation

method used in this work is closest to Dugas and Chen. The standard operating

procedure (SOP) for the WWC was developed as part of this work and can be found in

Appendix E.

3.1.2 Apparatus and set up

WWC contactor

Figure 3.1: Detailed dimensions of the wetted wall column

The detailed geometry of the wetted wall column is shown in Figure 3.1. The

metal cylinder is enclosed by an inner glass tube, within which the gas-liquid contact

occurs. This contacting chamber is housed within a larger glass tube. The space

between the two glass tubes functions as a heating jacket, which is filled with heating oil

pumped from an external heater to control the temperature of the chamber. The inner

diameter of the small glass tube is 2.54 cm. The diameter of the metal cylinder is 1.26

39

cm. The exposed height of the cylinder is 9.1 cm. The hydraulic diameter of the

contact chamber is 0.44 cm, and the cross area for gas flow is 1.3 cm2.

The liquid enters the chamber via the hollow center of the metal cylinder, and

overflows the top, then flows downward along the outer wall of the cylinder forming a

smooth film. The liquid then exits from the bottom of the chamber. The gas enters the

bottom of the chamber between the cylinder and the glass wall, and leaves from the top.

The liquid film properties of the WWC were estimated by Pacheco (1998) and the

equations from the momentum balance of a falling film (Bird et al. 2002) were used.

The liquid film thickness of the WWC (δ) is a function of the viscosity (µ), volumetric

flow rate (Qsol), density (ρ), gravitational constant (g), and the wetted perimeter (W)

(Equation 3.1). The superficial velocity of the liquid is a function of the film thickness

(Equation 3.2). The gas-liquid contact time (τ) is the height of the column (h) divided

by the superficial velocity (Equation 3.3).

𝛿 = √3𝜇𝑄𝑠𝑜𝑙

𝜌𝑔𝑊

3 (3.1)

𝑢𝑠 =𝜌𝑔𝛿2

2𝜇 (3.2)

𝜏 =ℎ

𝑢𝑠 (3.3)

The total gas-liquid contact area can be calculated by adding the side area of the

cylinder with the area of the cylinder top (Equation 3.4). The contact area on the side of

the cylinder can be estimated by assuming the diameter of the liquid surface is the sum of

the cylinder diameter plus the film thickness (Equation 3.5). The liquid at the top of the

cylinder is assumed to have a half dome shape with diameter that is also the cylinder

diameter plus the film thickness (Equation 3.6).

𝐴𝑟𝑒𝑎 = 𝐴𝑟𝑒𝑎𝑆𝑖𝑑𝑒 + 𝐴𝑟𝑒𝑎𝑇𝑜𝑝 (3.4)

𝐴𝑟𝑒𝑎𝑆𝑖𝑑𝑒 = 𝜋 ∙ (𝑑𝑐𝑦𝑙𝑖𝑛𝑑𝑒𝑟 + 2 ∙ 𝛿) ∙ ℎ (3.5)

40

𝐴𝑟𝑒𝑎𝑇𝑜𝑝 = 4𝜋 ∙ ((𝑑𝑐𝑦𝑙𝑖𝑛𝑑𝑒𝑟+2∙𝛿)

2)2

∙1

2 (3.6)

The contact area of the WWC will vary slightly with temperature, liquid flowrate,

density, and viscosity of the solvent. In this work, the contact area is assumed to be at a

constant value of 38.52 cm2 for all experiments.

WWC experimental process

Figure 3.2: The wetted wall column apparatus and supplementary equipment

The process diagram of the WWC apparatus, including the contactor and

supplementary equipment, is shown in Figure 3.2. The liquid solvent for the mass

transfer experiments is pumped from a storage reservoir which is about 1 liter. A gear

pump, which consists of a Cole Parmer gear pump drive (EW-75211-70) and a

Micropump pump head (#GAT23PKSA/L27391E), is used. The liquid circulates

through the WWC at approximately 2.4 × 10-4 m3/min, and returns to the reservoir

forming a closed loop. The liquid rate of this WWC is monitored with a rotameter.

41

The rotameter reading is related to the volumetric flow rate by an empirical correlation

developed by Bishnoi (2000):

𝑄𝑠𝑜𝑙 = (0.4512𝑥 − 0.2901)√7.83−𝜌𝑇𝑟𝑒𝑓

(7.83−0.997)𝜌𝑇𝑟𝑒𝑓∙ √

7.83−𝜌2

7.83−𝜌𝑇𝑟𝑒𝑓2 (3.7)

In Equation 3.7, “x” is the flow meter reading, which is set to 10 for all

experiments in this work.

A total gas flow of 5 SLPM is prepared by mixing CO2 with N2 using mass flow

controllers (Brooks Instrument Model 5850). The gas stream first enters a water

saturator where it bubbles through about 1 ft of water. The water saturated gas then

enters the WWC contacting chamber where it counter currently contacts the liquid and

mass transfer occurs. The exit gas leaves from the top of the chamber and is sent

through a water knock out tank followed by solid drierite desiccants, where all moisture

is removed from the gas. The dry gas then enters a CO2 analyzer (Horiba Infrared

Detector VIA510) where the concentration of CO2 is measured. A bypass pathway on

the gas line can be used to direct the saturate gas stream directly for concentration

measurement without entering the contacting chamber. The bypass gas line is used to

determine the CO2 concentration of the inlet gas into the WWC chamber.

The temperature of the system is measured at the liquid side exit of the contacting

chamber by an Omega® type T thermocouple. The temperature of the solvent is

maintained at the target temperature, and is controlled manually and continuously during

the measurement by adjusting the set point of the oil baths. The WWC apparatus uses

maintained two oil baths for temperature control. First is a Fisher ScientificTM

IsotempTM heated bath circulator (model 5150 H11), a shown as HX-02 in Figure 3.2,

which heats the gas line and liquid line upstream of the contacting chamber. Also the

heating oil in HX-02 is pumped into the heating jacket of the WWC chamber. The set

42

point of this oil bath is adjusted during the experiment to keep the measured liquid

temperature on target. A second heat exchanger (HX-01: LAUDA Alpha A6 Heating

thermostat) is used to set the temperature at the saturator. This oil bath is typically kept

at 3 – 5 °C lower than the set point of HX-02 and not adjusted during an experiment. As

part of this work, the HX-02 is replaced with a new unit (Fisher Scientific #5150 R28).

The new HX-02 contains an additional refrigeration unit which expands the temperature

range of the WWC apparatus to include 20 °C.

The WWC chamber is pressurized using a needle valve, which is placed

downstream of the exit of the contactor. In this work, the WWC is operated with total

system pressure between 0.5 MPa and 0.7 MPa (20 to 80 psig).

3.1.3 WWC Data analysis

Gas film resistance

The gas film mass transfer coefficient (kg) of this WWC was first characterized by

Pacheco (1998) by measuring the absorption rate of CO2 into unloaded 2 M MEA. The

system is thus gas film controlled and can be used to quantify the kg of the contactor.

Pacheco used a Sherwood number correlation developed by Hobbler ( 1966) for short

WWC contactors (Equation 3.8).

𝑆ℎ = 𝐴 ∙ 𝑅𝑒𝐵 ∙ 𝑆𝑐𝐶 ∙ (𝑑ℎ

ℎ)𝐷

(3.8)

In Equation 3.8, “Sh” is the Sherwood number; “Re” is the Reynolds number;

“Sc” is the Schmidt number, “dh” is the hydraulic diameter of the wetted wall column

(0.44 cm); “h” is the height of the column (9.1 cm); the values of A, B, C, and D are

parameters specific to each contactor and systems. Pacheco experimentally determined

43

the kg of the contactor and calculated the corresponding Sherwood number using

Equation 3.9.

𝑆ℎ =𝑅𝑇𝑘𝑔𝑑ℎ

𝐷𝐶𝑂2 (3.9)

By fitting the experimental results to Equation 3.8, Pacheco determined the

parameters of the correlation to be:

𝑆ℎ = 1.075 ∙ [𝑅𝑒 ∙ 𝑆𝑐 ∙ (𝑑ℎ

ℎ)]

0.85

(3.10)

Bishnoi (2005) later confirmed the parameters regressed by Pacheco by

measuring the absorption rate of SO2 into NaOH. The results are within 10% of the

values calculated by Equation 3.10 and 3.9.

In this work, kg is determined using the Sherwood correlation by Pacheco

(Equation 3.10) and Equation 3.9. In Equation 3.9, the diffusion coefficient of CO2 in

the gas phase (𝐷𝐶𝑂2) is estimated as the binary diffusion coefficient of CO2 in N2 ((Bird

et. al., 2002).

Liquid film resistance (physical mass transfer)

The liquid film physical mass transfer coefficient was first characterized for this

WWC by Mshewa (1995) by measuring desorption of CO2 from water and various

concentrations of aqueous ethylene glycol. Pacheco (1998) later added temperature

dependence to the kl correlation. A theoretical model developed by Pigford (1941) was

used to fit the experimental data, where kl° is expressed as a function of gas-liquid contact

area (A), total liquid flow rate (Qsol), and a dimensionless driving force Θ, as shown in

Equation 3.11.

𝑘𝑙° =

𝑄𝑠𝑜𝑙

𝐴(1 − Θ) (3.11)

The dimensionless driving force is calculated by:

44

Θ =

{

0.7857 exp(−5.121𝜂) + 0.1001 exp(39.21𝜂) + 0.036 exp(−105.6𝜂) + 0.0181 exp(−204.7𝜂)

𝑓𝑜𝑟 𝜂 > 0.01

1 − 3√𝜂

𝜋 𝑓𝑜𝑟 𝜂 < 0.01

(3.12)

In Equation 3.12, η is the dimensionless penetration distance. For conditions

included in this work, η can be estimated using Equation 3.13.

𝜂 =𝐷𝐶𝑂2𝜏

𝛿2 (3.13)

In Equation 3.13, DCO2 is the diffusion coefficient of CO2 in the liquid solvent. δ

is the film thickness and τ is the contact time, calculated in Equation 3.1 and 3.3

respectively.

Measuring flux

In this work, the WWC is used to measure the liquid film mass transfer

coefficient of CO2 (kg’) and the CO2 VLE (PCO2*) in CO2 loaded aqueous amines. Both

kg’ and PCO2* are determined from direct measurements of CO2 flux.

The CO2 flux is calculated as the difference in CO2 concentration between the

inlet gas and exit gas to the contacting chamber as read by the CO2 analyzer. First,

readings in CO2 concentrations are converted into pressure units using Equation 3.14.

𝑃𝐶𝑂2 = [𝐶𝑂2] ∙ 𝑃𝑇𝑜𝑡𝑎𝑙 ∙ (𝑄𝑠𝑎𝑡

𝑄𝑑𝑟𝑦) (3.14)

Second, flux is calculated from the difference in CO2 partial pressure measured at

the inlet and exit of the contactor using Equation 3.15, in which 𝑉�̂� is the molar

volume of an ideal gas.

𝑓𝑙𝑢𝑥𝐶𝑂2[𝑚𝑜𝑙 𝑠 ∙ 𝑐𝑚2⁄ ] = (𝑃𝐶𝑂2,𝑖𝑛−𝑃𝐶𝑂2,𝑜𝑢𝑡

𝑃𝑇𝑜𝑡𝑎𝑙) ∙ 𝑄𝑠𝑎𝑡 ∙

1

𝑉�̂�∙𝐴𝑟𝑒𝑎 (3.15)

At each CO2 loading and temperature, six CO2 flux measurements were collected

at different inlet CO2 partial pressures by varying the CO2/N2 ratio in the gas. An

example of a typical set of WWC is shown in Figure 3.3.

45

Figure 3.3: Experimental CO2 flux and partial pressure driving force measured for 5 m

PZ/2m AEP with 0.25 mol/mol alk CO2 loading at 80 °C

The PCO2 were chosen between zero and double the equilibrium partial pressure of

the solvent (PCO2*), such that driving force for mass transfer is balanced between the

absorption points and desorption points. Also, for each set of six fluxes, three points

was measured for absorption conditions and the other three at desorption conditions.

The measured CO2 flux should form a straight line when plotted with the partial pressure

driving force on the x-axis, as described by Equation 3.16.

𝐶𝑂2 𝑓𝑙𝑢𝑥 = 𝐾𝐺(𝑃𝐶𝑂2,𝑔 − 𝑃𝐶𝑂2∗ )𝐿𝑀 (3.16)

Measuring CO2 VLE

The x-axis in Figure 3.3 is the log mean driving force of the WWC, and is

calculated by Equation 3.17.

(𝑃𝐶𝑂2 − 𝑃𝐶𝑂2∗)log 𝑚𝑒𝑎𝑛

=(𝑃𝐶𝑂2,𝑡𝑜𝑝−𝑃𝐶𝑂2

∗)−(𝑃𝐶𝑂2,𝑏𝑜𝑡𝑡𝑜𝑚−𝑃𝐶𝑂2∗)

𝑙𝑛(𝑃𝐶𝑂2,𝑡𝑜𝑝

−𝑃𝐶𝑂2∗

𝑃𝐶𝑂2,𝑏𝑜𝑡𝑡𝑜𝑚−𝑃𝐶𝑂2

∗)

(3.17)

-4000 -2000 0 2000 4000

CO

2fl

ux (

mo

l/(s

∙ c

m2))

Log mean driving force (Pa)

6x 10-7

-2x 10-7

2x 10-7

46

While the CO2 flux can be directly calculated from the analyzer readings, the

PCO2* (equilibrium partial pressure of CO2) values in Equation 3.16 and 3.17 is unknown.

The value for PCO2* is inferred from the flux measurements by satisfying the condition

where CO2 flux is zero when the driving force is zero. Graphically this criteria means

the linear fit of the six flux points should pass through the origin with the correct PCO2* in

Figure 3.3.

Measuring liquid film mass transfer coefficient (kg’)

The slope of the linear fit of the flux measurements is the overall gas side mass

transfer coefficient (KG) (Equation 3.16). The liquid film mass transfer coefficient (kg’)

is calculated by subtracting the gas film resistance (1/kg) from the overall resistance

(Equation 3.18).

1

𝑘𝑔′ =

1

𝐾𝐺−

1

𝑘𝑔 (3.18)

The gas film mass transfer coefficient (kg) in Equation 3.18 is calculated using the

Pacheco correlation (Equation 3.9 and 3.10) for each set of fluxes.

3.1.4 Error and reproducibility

To determine the error and reproducibility in the kg’ and PCO2* measured using the

current WWC method, three separate experiments was performed using 8 m PZ. In

these experiments, fresh PZ solutions were prepared for each set. The results are

compared with 8 m PZ data reported by Dugas (2009) using the same WWC.

Error analysis of CO2 VLE data

47

Figure 3.4: Equilibrium partial pressure of CO2 for 8 m PZ measured by the WWC from

four separate experiments, compared with the lines from a semi-empirical

VLE model (Xu 2011).

The CO2 VLE measurement for 8 m PZ by the WWC can be compared with

results from other studies, as available data for PZ is abundant (Figure 3.4). A semi-

empirical VLE model developed by Xu (2011) is used as the standard for comparison

(Equation 3.19).

ln(𝑃𝐶𝑂2∗ ) = (35.3 ± 0.3) −

(11054±120)

𝑇− (18.9 ± 2.7) ∙ 𝛼𝐶𝑂2

2 + (4958 ± 347) ∙

𝛼𝐶𝑂2

𝑇+ (10163 ± 1085) ∙

𝛼𝐶𝑂22

𝑇 (3.19)

The regression of the PZ model by Xu (Equation 3.19) included the PCO2* data by

Dugas, as well as literature data. It does not include the three sets of PCO2* data

collected in this work.

Each data point in Figure 3.4 involves the determination of PCO2* (y-axis value)

from the absorption/desorption flux results, and the determination of CO2 loading (x-axis

10

100

1000

10000

100000

0.2 0.25 0.3 0.35 0.4 0.45

PC

O2*

(Pa)

CO2 ldg (mol/mol alk) TIC/Acid titration

Diamond: Dugas (2009)Circles: May 2010

Triangles: March 2012Squares: August 2012

40 °C

60 °C

80 °C

100 °C

20 °C

48

value) by analysis of liquid samples taken during the WWC experiment. For each VLE

data point, there are expected errors associated with value in both x and y dimensions.

Figure 3.5: Parity plot of PCO2* measured by the WWC compared with results from a

semi-empirical VLE model, assuming the CO2 loading measured for the

samples are accurate (Xu 2011).

Potential errors in both PCO2* and CO2 loading values can be estimated by

considering each individually. First, the errors in PCO2* can be evaluated by comparing

the experimental PCO2* with the semi-empirical VLE model value calculated at the same

experimental loading, which assumes the loading values are accurate and all experimental

errors are contributed by the PCO2* measurement. The parity plot of the PCO2* results are

shown in Figure 3.5, and the experimental PCO2* shows a less than 5% error with the

model values on a log scale (base 10). The average absolute error in PCO2* is calculated to

be about 30% (Equation 3.20).

𝐴𝐴𝐸 =|𝑃𝐶𝑂2,𝑒𝑥𝑝

∗ −𝑃𝐶𝑂2,𝑚𝑜𝑑𝑒𝑙∗ |

𝑃𝐶𝑂2,𝑚𝑜𝑑𝑒𝑙∗ (3.20)

1

2

3

4

5

1 2 3 4 5

Log 1

0(P

exp

eri

me

nt)

Log10 (Pmodel)

- 5%

Diamond: Dugas(2009)

Circles: May 2010Triangles: March 2012Squares: August 2012

+ 5%

49

Figure 3.6: Parity plot of potential errors in CO2 loading in the WWC samples, estimated

using a semi-empirical VLE model and assumes accuracate PCO2* (Xu

2011).

Alternatively, the errors observed can be considered as from the CO2 loading

measurements. In Figure 3.6, the errors between experimentally measured CO2 loading

and model values (calculated using Equation 3.19 with experimental PCO2*) are shown in

a parity lot. For most of the experimental data, the potential error in measured CO2

loading is less than 5%, with an average error of about 3%.

0.2

0.3

0.4

0.5

0.2 0.3 0.4 0.5

CO

2ld

g(m

ol/

mo

l alk

) Ex

per

imen

tal

CO2 ldg (mol/mol alk) Model

Diamond: Dugas (2009)Circles: May 2010

Triangles: March 2012Squares: August 2012

- 5%

+ 5%

50

Reproducibility of mass transfer data

Figure 3.7: Liquid film mass transfer coefficient (kg’) measured by the WWC for 8 m

piperazine (PZ) in four separate experiments

The liquid film mass transfer coefficient (kg’) measured in the four 8 m PZ

experiments are compared in Figure 3.7. It is difficult to evaluate the absolute error in

measured kg’ due to a lack of reliable standard for comparison. Alternatively, the

reproducibility of the method can be quantified by comparing the multiple measurements

collected at the same conditions. The kg’ measured at each temperature from the four 8 m

PZ experiments are regressed together in a quadratic equation (Equation 3.21) as a

function of PCO2*. The regressed equations represent the mathematical average of the four

experiments. The difference between the measured values and the equation values at the

same PCO2* is assumed to represent the deviation between each set of experimental

1E-07

1E-06

1E-05

10 100 1000 10000 100000

k g’ (

mo

l/P

a s

m2)

PCO2* (Pa)

Diamond: Dugas

(2009)

Circles: May 2010

Triangles: March 2012

Squares: August 2012

40 °C 60

°C 80 °C

100 °C

7 m MEA @ 40 °C

51

results. The average deviation in the measured kg’ of the four 8 m PZ experiments is

about 8.5%.

ln(𝑘𝑔′ ) = 𝑎 + 𝑏 ∙ ln(𝑃𝐶𝑂2

∗ ) + 𝑐 ∙ ln (𝑃𝐶𝑂2∗ )2 (3.21)

It has been observed that during the course of this work, the total gas rate (Qdry)

shifted from the expected condition of 5 SLPM by up to 10%. It has been estimated this

shift in gas flow rate has introduced an error of up to 5% for some of the kg’ reported in

this work.

The measured kg’ and PCO2* from the three sets of 8 m PZ experiments are


Table 3.1: CO2 solubility and kg’ in 8 m PZ measured in three separate experiments from

2010-2012

Date

CO2 loading T PCO2 kg'

mol/mol alk °C kPa mol/Pa s

m2

May

2010

0.326 40 0.54 22.43

0.422 40 5.41 3.95

0.326 60 2.87 24.95

0.422 60 27.96 3.08

0.326 80 8.71 18.60

0.326 100 32.72 10.96

March

2012

0.307 20 0.07 26.80

0.394 20 0.60 7.19

0.307 40 0.42 22.60

0.394 40 3.60 7.21

0.307 60 2.35 24.80

0.394 60 19.87 5.02

0.307 80 9.64 14.78

0.307 100 39.31 7.94

August

2012

0.322 20 0.10 23.20

0.322 40 0.52 22.38

0.322 60 2.81 20.63

0.322 80 11.60 16.48

0.322 100 41.30 8.69

52

3.2 TOTAL PRESSURE APPARATUS

3.2.1 Introduction

A total pressure apparatus was used to measure CO2 VLE at high temperatures for

some of the amine solvents included in this work. The total pressure experimental

method used in this work was developed by Xu (2011). The apparatus and method are

briefly summarized in this section. The standard operating procedure (SOP) for the

WWC was developed as part of this work and can be found in Appendix E.

3.2.2 Apparatus and set up

The total pressure apparatus, as shown in Figure 3.8, involves a 500 mL stainless

steel autoclave which acts as an equilibrium reactor. Mechanical agitation of both gas and

liquid phase in the reactor is provided by a stainless steel agitator powered by a magnetic

air motor. The temperature of the reactor is controlled by an electric heating jacket.

Figure 3.8: Diagram of the total pressure equilibrium reactor

53

During an experiment, approximately 350 mL of liquid solvent with CO2 loading

is placed in the 500 mL equilibrium reactor. The head space of the reactor is flushed

with N2 before the reactor is sealed, and the reactor is assumed to be a closed system

which contains the solvent sample and gaseous nitrogen (N2) only. The pressure of the

reactor is measured continuously as it is heated to target temperatures. The reactor is

kept at each temperature for at least 20 minutes after the reactor temperature stabilizes in

order to ensure equilibrium is reached. The measured system pressure during the

equilibrium is averaged and reported as Pmeas. An example of the total pressure raw

experimental data is shown in Figure 3.9.

3.2.3 Data analysis

Figure 3.9: Example total pressure measurement of a pilot plant sample of 8 m PZ during

the 2011 campaign at the University of Texas in Austin Pickle Research

Center.

The CO2 partial pressure of the system (PCO2) is calculated from the measured

Pmeas.

0

2

4

6

8

10

12

14

16

0 1 2 3 4 5 6 7

Pm

eas

ure

d(b

ar)

Time (hr)

120

140

160

150

130

110100˚C

54

𝑃𝐶𝑂2∗ = 𝑃𝑚𝑒𝑎𝑠 − 𝑃𝑁2 − 𝑃𝐻2𝑂 − 𝑃𝑎𝑚𝑖𝑛𝑒 = 𝑃𝑚𝑒𝑎𝑠 − 𝑇 ∙

𝑃𝑁2 𝑖𝑛𝑖𝑡𝑖𝑎𝑙

𝑇𝑖𝑛𝑖𝑡𝑖𝑎𝑙 − 𝑃𝐻2𝑂,𝑣𝑎𝑝 ∙ 𝑥𝐻2𝑂

(3.22)

The initial pressure of N2 (PN2initial) and temperature are recorded and used in the

ideal gas law to calculate PN2 at each experimental temperature (Equation 3.22). The

partial pressure of water is calculated using Raoult’s law. Literature values for water

vapor pressures are used for PH2O* (DIPPR 1998). Vapor pressure of the amine

(Pamine*) is assumed to be zero since its value is expected to be negligible relative to the

vapor pressure of other species.

To accurately report the CO2 content in the liquid phase, the liquid sample is

analyzed at room temperature at the beginning and the end of each experiment.

However, the true liquid phase CO2 loading during the experiment is expected to change

significantly from measured values due to the high CO2 partial pressure at high

temperatures. To correct for this effect, the reported CO2 loading values are calculated

by subtracting the moles CO2 in the vapor phase (𝑛𝐶𝑂2𝑉) from total CO2 in the original

sample (𝑛𝐶𝑂2𝑇) as in Equation 3.23. The vapor phase CO2 (𝑛𝐶𝑂2𝑉) is calculated using

ideal gas law (Equation 3.24), where Vvap is the vapor volume of the equilibrium reactor

(approx 135 mL).

∝=𝑛𝐶𝑂2𝑇−𝑛𝐶𝑂2𝑉

𝑛𝑎𝑙𝑘𝑎𝑙𝑖𝑛𝑖𝑡𝑦 (3.23)

𝑛𝐶𝑂2𝑉 =𝑃𝐶𝑂2𝑉𝑣𝑎𝑝

𝑅𝑇 (3.24)

The total pressure apparatus can operate from 100 to 160 °C, and measures PCO2*

accurately in the range of 0.1–2.0 MPa.

55

3.3 ANALYTICAL METHODS

3.3.1 Total Inorganic Carbon (TIC)

The CO2 content in a loaded liquid sample is measured using a total inorganic

carbon apparatus. The method involves injecting small amount of a sample of know mass

into a solution of strong acid (H3PO4). The strong acid affects the chemical equilibrium

of the CO2/amine reactions, and reverses all CO2 associated reaction products back to

free CO2. A stream of inert carrier gas (N2) continuously passes through the acid solution,

which carries free CO2 in the solution into a CO2 analyzer (Horiba PIR 200 infrared

detector) for quantification. This method provides CO2 concentration in the liquid

samples with units of mol CO2/kg sample.

3.3.2 Total alkalinity titration

The total alkalinity of a CO2 loaded amine sample should correspond to the

concentration of total amines. An automatic Titrando series titrator with automatic

equivalence point detection (Metrohm USA) was used to determine the total alkalinity in

the liquid sample via acid titration. The acid used is 0.1 N H2SO4, which is added

incrementally into a beaker containing a sample of known mass (approximately 0.2 g)

diluted in 60 mL of DDI water. Titration automatically ends when the pH of the sample

beaker reaches 2.4. The amount of acid added to reach the appropriate equivalence point

of the titration curve is assumed to correspond to the total moles of alkalinity in solution.

This method generates alkalinity concentration results in the unit of mol alkalinity/kg

sample.

The total inorganic carbon and acid titration methods are used together to

calculate the CO2 loading in the sample (mol CO2/mol alkalinity). The average deviation

56

between a set of triplicates of the same sample is approximately 2% for each of the two

methods.

3.3.3 Viscosity

A Physica MCR 301 cone and plate rheometer (Anton Paar GmbH, Graz, Austria)

is used to measure the viscosity of CO2 loaded amine solvents from 25 – 60 °C. For each

measurement, about 0.8 mL of the liquid sample is placed between the sample plate and

the rotating cone. The angular speed of the rotating of the cone is varied, and the

corresponding torque required is recorded continuously. For Newtonian fluids in fully

developed flow, the shear stress of the fluid is proportional to the velocity gradient

perpendicular to the direction of fluid flow, with the proportionality constant defined as

the viscosity of the fluid (Equation 3.25).

𝜏𝑇𝑜𝑟𝑞 = 𝜇𝜕𝑣

𝜕𝑥 (3.25)

Detailed descriptions and standard operating procedures (SOP) of all three

analytical apparatus and experimental methods are discussed by Freeman (2011).

57

Chapter 4: Data Applications

The liquid film mass transfer coefficient (kg’) and equilibrium CO2 partial

pressure (PCO2*) data can be used to suggest the relative performance of each solvent in a

real CO2 capture process. This section describes the use of experimental data to

estimate the key process performance parameters for CO2 capture from flue gas.

4.1 CO2 VLE

Figure 4.1: Simplified diagram of the two phase CO2-amine-H2O system

As illustrated in Figure 4.1, the CO2 VLE in an aqueous amine solvent is affected

byby two equilibria: the physical solubility of gaseous CO2 in the solvent, and the

chemical equilibrium between dissolved CO2 and other species in the solvent. The

physical solubility of CO2 is often represented using Henry’s law (Equation 4.1).

𝑃𝐶𝑂2∗ = 𝐻𝐶𝑂2−𝑠𝑜𝑙𝑣𝑒𝑛𝑡 ∙ 𝑥𝐶𝑂2 = 𝐻𝐶𝑂2−𝑤𝑎𝑡𝑒𝑟 ∙ 𝛾𝐶𝑂2 ∙ 𝑥𝐶𝑂2 (4.1)

The dissolved free CO2 in the liquid is in chemical equilibrium with the amines,

amine products, and CO2 products. The total CO2 in the liquid phase ([CO2]T) is the

58

sum of the dissolved free CO2 and the other CO2 containing product species (Equation

4.2).

[𝐶𝑂2]𝑇 = [𝐶𝑂2] + [𝐴𝑚𝐶𝑂𝑂−] + [𝐻𝐶𝑂3−] + [𝐶𝑂3

2−] (4.2)

Due to the strong effect of the chemical reactions, the free CO2 in the liquid phase

is very low at most relevant conditions. Therefore, in most representations of CO2 VLE,

[CO2]T is used instead of free CO2 (Figure 4.2).

Figure 4.2: Example CO2 VLE plot. Solid points: WWC data for 6.5 m β-ala(K); lines:

semi-empirical model results (Equation 4.4).

In Figure 4.2, the CO2 VLE curve represents the effect of both physical solubility

and chemical equilibrium. Practically, [CO2]T is a useful parameter as the total CO2

absorbed by the liquid corresponds directly to changes in total CO2, not free CO2.

Moreover, [CO2]T can be easily quantified experimentally, while measuring

concentration of free CO2 is difficult.

0.001

0.01

0.1

1

10

100

0.3 0.4 0.5 0.6

PC

O2*

(kP

a)

CO2 loading (mol CO2/mol Alk)

7m MEA40◦C

40◦C

60◦C

80◦C

100◦

7m MEA @ 100◦C

59

4.1.1 CO2 loading

In this work, the total CO2 concentration in the liquid phase is always written as

CO2 loading (Equation 4.3).

𝛼𝐶𝑂2 =[𝐶𝑂2]𝑇

∑𝑛𝑖∙[𝐴𝑚𝑖𝑛𝑒𝑖]𝑇[=]

𝑚𝑜𝑙 𝐶𝑂2

𝑚𝑜𝑙 𝑎𝑙𝑘𝑎𝑙𝑖𝑛𝑖𝑡𝑦 (4.3)

CO2 loading is the concentration of total CO2 normalized by the concentration of

total alkalinity. In Equation 4.3, ni is the number of basic nitrogen per amine molecule.

The total alkalinity in a blended amine solvent is the sum of the active nitrogen from each

amine in the solvent.

4.1.2 Semi-empirical model for CO2 VLE

To obtain CO2 VLE curves from PCO2* data, a semi-empirical model is used

which relates PCO2* to temperature, CO2 loading, and their cross terms in a linear

combination (Equation 4.4).

ln(𝑃𝐶𝑂2∗ ) = 𝑎 +

𝑏

𝑇+ 𝑐 ∙ 𝛼𝐶𝑂2 + 𝑑 ∙ 𝛼𝐶𝑂2

2 + 𝑒 ∙𝛼𝐶𝑂2

𝑇+ 𝑓 ∙

𝛼𝐶𝑂22

𝑇 (4.4)

This specific form of the semi-empirical model was developed by Xu (2011) by

fitting the CO2 VLE data of several amine solvents with various combinations of

temperature, loading, and cross terms. The terms with low statistical significance were

eliminated systematically. The combination of the five terms in Equation 4.4 was found

to be the minimum number of total terms required to fit a wide range of CO2 VLE

behaviors.

4.1.3 Estimation of heat of absorption

The heat of CO2 absorption for each solvent can be estimated from the

temperature dependence of the PCO2* data. This thermodynamic relationship can be

applied to the semi-empirical model to obtain an analytical expression for ΔHabs

(Equation 4.5):

60

−∆𝐻𝑎𝑏𝑠 = 𝑅 ∙ (𝜕ln (𝑃𝐶𝑂2

∗ )

𝜕(1 𝑇⁄ ))𝑃,𝑥

= 𝑏 + 𝑒 ∙ 𝛼𝐶𝑂2 + 𝑓 ∙ 𝛼𝐶𝑂22 (4.5)

In the work by Xu (2011), it was shown the thermodynamic expression in

Equation 4.5 can be derived using two methods. The first method begins with the

definition of molar fugacity of CO2, and makes use of other thermodynamic first

principles. The second method considers the overall energy balance of a typical CO2

capture process and assumes the Carnot Cycle reversibility for the system. Both

methods require assumptions of constant total system pressure and CO2 loading. It was

shown for the pressure range of the total pressure and WWC experiments, the errors

associated with total system pressure change is small. This expression of heat of

absorption also requires the total pressure of the system to be low, which is necessary for

the use of partial pressure in place of fugacity a valid approximation.

Error of heat of absorption estimation

The main relevant error in the ΔHabs estimated using Equation 4.5 is the accuracy

in the temperature behaviour of the experimental data. In Figure 4.3, three estimations

of ΔHabs for 6 m PZ/2 m EDA are shown, using he semi-empirical model regressed

with: 1) WWC data only, 2) total pressure data only, and 3) both sets of data. The

results show the WWC model and total pressure model both over predict the value from

the combined model by approximately 10%. The deviation between the three results is

because of inherent bias in the temperature measurement of both experimental

apparatuses. In this work, the combined model is used in the case where both WWC

and total pressure results are available. In the cases where only WWC data was used,

the estimated ΔHabs is expected to be higher than the combined results by up to 10 %.

61

Figure 4.3: Heat of absorption of 6 m PZ/2 m BAE predicted by three semi-empirical

VLE models

4.2 PROCESS PERFORMANCE PARAMETERS

4.2.1 Standard operating conditions

To compare the performance of different amine solvents, it is necessary to

establish a common basis. In this work, the standard operating condition is used for this

purpose, which is determined by considering the CO2 concentration in a specific type of

flue gas.

The mass transfer driving force in the absorber is an important variable in the

design of the process. As shown in Figure 4.4, the PCO2* in the solvent must be lower

than the PCO2 in the gas for the entire column in order to provide a positive driving force

for mass transfer. An absorber design with a large mass transfer driving force would

require less packing area and cost. However, it also introduces significant irreversibility

to the process, which will be penalized in the regeneration energy cost (Van Wagner

50

55

60

65

70

75

80

85

90

95

0.3 0.35 0.4 0.45 0.5

-∆H

abs

(kJ)

CO2 loading (mol/mol alk)

2) WWC

1) Total pressure

3) All data

62

2011). The optimum process design requires the driving force in the absorber to

minimize the total cost of absorber capital and regeneration energy.

Figure 4.4: Simplified diagram of an absorber for CO2 capture from coal flue gas

Table 4.1: Standard operating conditions for CO2 capture process used in this work, for

coal and natural gas combined cycle flue gas

Coal

Flue gas

(PCO2)

CO2 loading (PCO2* @ 40 °C)

Top 1.3 kPa 0.5 kPa Lean

Bottom 12 kPa 5 kPa Rich

Natural gas combined cycle

Flue gas

(PCO2)

CO2 loading

(PCO2*@ 40 °C)

Top 0.3 kPa 0.1 kPa Lean

Bottom 3 kPa 1 kPa Rich

In this work, solvents are compared at the same mass transfer driving force in the

absorber. In the case of coal flue gas (Figure 4.4) which contains about 12 % CO2, the

standard operating condition is lean and rich CO2 loadings which corresponds to PCO2* of

0.5 and 5 kPa at 40 °C. In the case of natural gas combined cycle plants, with flue gas

63

containing much less CO2 (about 3%), the standard operating condition is at 0.1 and 1

kPa at 40 °C (Table 4.1).

4.2.2 Average mass transfer rate

The measured kg’ values are used to estimate the rate performance in an

isothermal absorber for some specified flue gas properties. This method was first used

by Dugas (2009) and later by Chen (2011) for coal flue gas.

First, the log mean average absorption rate (kg’avg) can be calculated using

Equation 4.6:

𝑘𝑔′

𝑎𝑣𝑔=

𝐹𝑙𝑢𝑥𝐶𝑂2,𝐿𝑀

(𝑃𝐶𝑂2−𝑃𝐶𝑂2∗ )𝐿𝑀

=(𝐹𝑙𝑢𝑥𝐶𝑂2,𝑡𝑜𝑝−𝐹𝑙𝑢𝑥𝐶𝑂2,𝑏𝑜𝑡𝑡𝑜𝑚) 𝐿𝑛(𝐹𝑙𝑢𝑥𝐶𝑂2,𝑡𝑜𝑝/𝐹𝑙𝑢𝑥𝐶𝑂2,𝑏𝑜𝑡𝑡𝑜𝑚)⁄

(𝑃𝐶𝑂2,𝑡𝑜𝑝−𝑃𝐶𝑂2,𝑙𝑒𝑎𝑛∗ )−(𝑃𝐶𝑂2,𝑏𝑜𝑡𝑡𝑜𝑚−𝑃𝐶𝑂2,𝑟𝑖𝑐ℎ

∗ ) 𝐿𝑛(𝑃𝐶𝑂2,𝑡𝑜𝑝

−𝑃𝐶𝑂2,𝑙𝑒𝑎𝑛∗

𝑃𝐶𝑂2,𝑏𝑜𝑡𝑡𝑜𝑚−𝑃𝐶𝑂2,𝑟𝑖𝑐ℎ

∗ )⁄

(4.6)

𝐹𝑙𝑢𝑥𝐶𝑂2,𝑡𝑜𝑝 = 𝑘𝑔′𝑡𝑜𝑝

∙ (𝑃𝐶𝑂2,𝑡𝑜𝑝 − 𝑃𝐶𝑂2,𝑙𝑒𝑎𝑛∗ ) (4.7a)

𝐹𝑙𝑢𝑥𝐶𝑂2,𝑏𝑜𝑡𝑡𝑜𝑚 = 𝑘𝑔′𝑏𝑜𝑡𝑡𝑜𝑚

∙ (𝑃𝐶𝑂2,𝑏𝑜𝑡𝑡𝑜𝑚 − 𝑃𝐶𝑂2,𝑟𝑖𝑐ℎ∗ ) (4.7b)

In the definition of kg’avg, the absorber is assumed to be isothermal at 40 °C. The

experimental kg’ values are fitted as a function of PCO2* using a second order polynomial,

in order to interpolate the kg’ at the standard operating conditions. The kg’ at operating

conditions are used to calculate the CO2 flux at the top and bottom of the isothermal

absorber (Equation 4.). The kg’avg of the solvent is the log mean of CO2 flux between

the top and bottom of the column divided by the log mean of the driving force. This

single parameter (kg’avg) represents the complex and variable rate behaviour of a solvent

across an absorber column, and allows for easier comparison of rate performance of

different solvents.

Moreover, kg’avg can be used to calculate the corresponding packing area (Ap) per

volumetric unit of flue gas rate (Vg) in the same isothermal column (Equation 4.8)

64

𝐴𝑝

𝑉𝑔=

𝑅𝑒𝑚𝑜𝑣𝑎𝑙 ∙ 𝑥𝐶𝑂2 ∙ 𝑃/𝑅𝑇

𝐹𝑙𝑢𝑥𝐶𝑂2,𝐿𝑀=

90% ∙12%∙𝑃/𝑅𝑇

𝑘𝑔′𝑎𝑣𝑔


(4.8)

This estimation of packing area only considers the variation in the kg’ of the

solvent, and assumes a high kg, such that the gas film resistance is negligible. With

higher absorption rate (kg’avg), less packing (Ap/Vg) is required to achieve the same level

of removal.

4.2.3 CO2 capacity

The CO2 carrying capacity (∆Csolv) of a solvent is the difference in CO2

concentration between the standard lean and rich loading. It represents the amount of

CO2 removed per unit mass of solvent (amine and H2O). With higher ∆Csolv, less

solvent (mass) is required to remove the same amount of CO2. Thus, ∆Csolv directly

relates to the sensible heat requirement, pump work, and the size and overall cost of the

cross-exchanger.

As shown in Equation 4.9, ∆Csolv is calculated as the product of two parts. First

is the delta loading (Δldg), which is the difference between the standard rich and lean

loadings of the solvent.

∆𝐶𝑠𝑜𝑙𝑣 =(∝𝑟𝑖𝑐ℎ − ∝𝑙𝑒𝑎𝑛)∙𝑚𝑜𝑙 𝑎𝑙𝑘𝑎𝑙𝑖𝑛𝑖𝑡𝑦

𝑘𝑔 (𝑎𝑚𝑖𝑛𝑒+ 𝐻2𝑂)=


𝑘𝑔(𝑎𝑚𝑖𝑛𝑒+𝐻2𝑂) (4.9)

Delta loading is determined by the solvent CO2 VLE curve at 40 °C. Solvents

with a flat VLE curve, such as hindered or tertiary amines, have large delta loadings.

Whereas solvents with steep VLE curves have lower delta loadings (Figure 4.5). The

second part of ∆Csolv is the concentration of total alkalinity in the solvent. This part is

inversely proportional to the molecular weight of the amine, which suggests high

molecular weight amines are less competitive than smaller molecules. Overall, ∆Csolv

can be considered as the product of the carrying effectiveness of the amine and the

concentration of the amine.

65

Figure 4.5: CO2 VLE curves at 40 C for PZ (Xu 2011) and 3.5 m PZ/3.5 m Tris (this

work) and the corresponding delta loading (Δldg).

Viscosity normalized CO2 capacity

The CO2 carrying capacity is an important solvent parameter because it is

proportional to the sensible heat cost of solvent regeneration and the cost of the cross

exchanger in the process. Besides ∆Csolv, the viscosity of the solvent can also

significantly affect the cost of the cross exchanger. Thus, to compare solvents based on

their corresponding total cross exchanger cost, the effect of ∆Csolv and viscosity must be

considered together.

An optimization of the cross exchanger cost is performed, which considers the

trade-off between the capital cost of the exchanger and the value of sensible heat cost.

This analysis neglects the trade off the exchanger size with the pump cost associated with

100

1000

10000

0.1 0.2 0.3 0.4

PC

O2*

(Pa)

CO2 ldg (mol/mol alk)

Δldg = 0.13

Δldg = 0.09

PZ

3.5 m PZ / 3.5 m Tris

66

the pressure drop across the exchanger. The capital cost of the exchanger is a function

of the cost per unit area (A$), solvent heat capacity (Cp), temperature difference between

two solvent streams (∆T), the liquid film heat transfer coefficient (h), solvent capacity

(∆Csolv), and the temperature gain by the rich solvent (Equation 4.10). 𝐻𝑋 𝑐𝑜𝑠𝑡

𝑚𝑜𝑙 𝐶𝑂2=

𝐴$(𝑇𝑟𝑖𝑐ℎ,𝑜𝑢𝑡− 𝑇𝑟𝑖𝑐ℎ,𝑖𝑛)∙ 𝐶𝑝

ℎ ∙∆𝑇∙∆𝐶𝑠𝑜𝑙𝑣 (4.10)

The sensible heat requirement is the result of cross-exchanger inefficiency, which

increases with ∆T and also depends on Cp and capacity (Equation 4.11).

𝑄𝑠𝑒𝑛𝑠𝑖𝑏𝑙𝑒 =𝐶𝑝

∆𝐶𝑠𝑜𝑙𝑣∙ ∆𝑇 (4.11)

In order to assign value to sensible heat, the equivalent electric work by the steam

used in the reboiler is calculated assuming a Carnot cycle efficiency and 0.75 turbine

efficiency (Equation 4.12), and W$ representing the cost per unit of electricity. 𝑆𝑒𝑛𝑠𝑖𝑏𝑙𝑒 ℎ𝑒𝑎𝑡 𝑐𝑜𝑠𝑡

𝑚𝑜𝑙 𝐶𝑂2= 𝑊$ ∙ 0.75

𝑇𝑠𝑡𝑒𝑎𝑚−𝑇𝑠𝑖𝑛𝑘

𝑇𝑠𝑡𝑒𝑎𝑚∙ 𝑄𝑠𝑒𝑛𝑠𝑖𝑏𝑙𝑒 (4.12)

The total cost associated with heating the solvent equals the sum of the two costs

with the assumption of constant ∆T, h, and Cp across the exchanger (Equation 4.13). 𝑇𝑜𝑡𝑎𝑙 𝑐𝑜𝑠𝑡

𝑚𝑜𝑙 𝐶𝑂2=

𝐴$(𝑇𝑟𝑖𝑐ℎ,𝑜𝑢𝑡− 𝑇𝑟𝑖𝑐ℎ,𝑖𝑛)∙ 𝐶𝑝

ℎ ∙∆𝑇∙ ∆𝐶𝑠𝑜𝑙𝑣+𝑊$ ∙ 0.75

𝑇𝑠𝑡𝑒𝑎𝑚−𝑇𝑠𝑖𝑛𝑘

𝑇𝑠𝑡𝑒𝑎𝑚

𝐶𝑝

∆𝐶𝑠𝑜𝑙𝑣∙ ∆𝑇 (4.13)

The total cost function can be minimized to find the optimum ΔT (∆Topt), with

quantity Trich,out – Trich,in assumed to have negligible dependence on ∆T and treated as a

constant (Equation 4.14).

∆𝑇𝑜𝑝𝑡 = √(𝑇𝑟𝑖𝑐ℎ,𝑜𝑢𝑡− 𝑇𝑟𝑖𝑐ℎ,𝑖𝑛)𝑇𝑠𝑡𝑒𝑎𝑚

0.75(𝑇𝑠𝑡𝑒𝑎𝑚−𝑇𝑠𝑖𝑛𝑘)

𝐴$

𝑊$

1

ℎ (4.14)

An analysis performed by Lin studied the dependence of heat transfer coefficients

on liquid viscosity with a focus on plate and frame exchangers (PHE) for the application

of CO2 capture processes (Rochelle et al. 2015). The results show the heat transfer

coefficient (h) is a function of the Nusselt number (Nu), which is proportional to the

Reynolds number (Re) and inversely proportional to the Prandtl number (Pr). Both Re

67

and Pr has its own dependence on viscosity, and the overall viscosity dependence of ℎ is

the combined effect the two (Equation 4.15)

ℎ =𝑘

𝐷𝑒𝐶𝑁𝑢𝑅𝑒

𝑚𝑃𝑟𝑛 = 𝐶𝑁𝑢𝜌𝑚𝐷𝑒

𝑚−1𝑘1−𝑛𝐶𝑃𝑛𝑢𝑚𝜇𝑛−𝑚 (4.15)

Based on the literature review performed by Lin, the value of n-m has the value

range of -0.3 to -0.4. In this work, the value of -0.3 is used as the exponent of the heat

transfer coefficient dependence on viscosity. Substituting Equation 4.15 into 4.14 with

a 𝑛 −𝑚 value of -0.3, the expression for minimum exchanger cost becomes:

(𝑇𝑜𝑡𝑎𝑙 𝑐𝑜𝑠𝑡

𝑚𝑜𝑙 𝐶𝑂2)𝑚𝑖𝑛𝑖𝑚𝑢𝑚

=2∙𝐶𝑝

∆𝐶𝑠𝑜𝑙𝑣√0.75∙𝐴$𝑊$(𝑇𝑟𝑖𝑐ℎ 𝑜𝑢𝑡− 𝑇𝑟𝑖𝑐ℎ,𝑖𝑛)(𝑇𝑠𝑡𝑒𝑎𝑚−𝑇𝑠𝑖𝑛𝑘)

𝑎∙𝜇−0.3 ∙𝑇𝑠𝑡𝑒𝑎𝑚 (4.16)

In Equation 4.16, the total minimum cost of the exchanger is inversely

proportional to ∆𝐶𝑠𝑜𝑙𝑣 and proportional to solvent viscosity to the 0.3 power. Based on

this relationship, the viscosity normalized capacity is defined in Equation 4.17.

∆𝐶𝜇 =∆𝐶𝑠𝑜𝑙𝑣

(𝜇𝛼𝑚𝑖𝑑

10 𝑐𝑃⁄ )0.15 (4.17)

In ∆Cμ, the viscosity term is normalized to 10 cP, which is the viscosity of 8 m PZ

at 40 °C with moderate CO2 loading. As the result, ∆Cμ represents the relative sensible

heat and cross exchanger cost of the solvent relative to that of 8 m PZ.

4.2.4 Stripping performance

Maximum stripper temperature

While the rate of amine loss increases with temperature, the energy cost of the

process decreases with higher stripper operating temperature. Stripper operating

temperature is determined by the trade off of solvent loss and energy cost savings. The

definition of maximum stripper temperature (Tmax) considers this trade off and was first

introduced by Freeman (2011). The definition of Tmax was based on previous work by

Davis (2009), which suggests the acceptable rate of degradation (k1) for 7 m MEA is

68

2.9x10-8 s-1 with stripper temperature at 121 °C. This optimum is calculated by the

trade-off between the cost of MEA loss and the energy benefits of higher stripper

temperature and pressure. Assuming this trade-off is consistent for different amines, the

optimum stripper operating temperature (Tmax) for each solvent was defined as the

temperature which corresponds to an overall amine degradation rate of 2.9x10-8 s-1.

Tmax can be calculated using the first order degradation rate (k1) and the activation

energy (Eact) extracted from thermal degradation data (Freeman 2011). Tmax affects

process cost by contributing to the maximum stripper pressure of the process (Pmax).

Maximum stripper pressure

A better solvent is one that can be used at higher stripper pressure, which

corresponds to lower Wcompression and lower overall work (Equation 4.18) (Oyenekan and

Rochelle 2006).

𝑊𝑡𝑜𝑡𝑎𝑙 = 𝑊𝑟𝑒𝑏𝑜𝑖𝑙𝑒𝑟 +𝑊𝑝𝑢𝑚𝑝 +𝑊𝑐𝑜𝑚𝑝𝑟𝑒𝑠𝑠𝑖𝑜𝑛 (4.18)

Pmax can be calculated as the sum of the partial pressure of water and CO2 exiting

the stripper, with the partial pressure of the amine assumed to be negligible (Equation

4.19).

𝑃𝑚𝑎𝑥 = 𝑃𝐶𝑂2|𝑇𝑚𝑎𝑥+ 𝑃𝐻2𝑂|𝑇𝑚𝑎𝑥

= 𝑃𝐶𝑂2,𝑙𝑒𝑎𝑛∗ |

𝑇𝑚𝑎𝑥+ 𝑥𝐻2𝑂 ∙ 𝑃𝐻2𝑂,𝑣𝑎𝑝|𝑇𝑚𝑎𝑥

(4.19)

The vapor pressure of water is calculated using data from the DIPPR database

(1998) and the partial pressure of water is assumed to follow Raoult’s law. The mole

fraction of water is assumed to be equal to one minus the mole fraction of total amine in

the solvent. The partial pressure of CO2 in the stripper is assumed to be at equilibrium

with the lean loading of the solvent at Tmax, which can be calculated by integrating the

thermodynamic relationship in Equation 4.20 from a standard temperature (40 °C) to

Tmax:

69

ln (𝑃𝐶𝑂2,𝑙𝑒𝑎𝑛∗ |

𝑇𝑚𝑎𝑥

𝑃𝐶𝑂2,𝑙𝑒𝑎𝑛∗ |

40°𝐶

) = 𝑙𝑛 (𝑃𝐶𝑂2,𝑙𝑒𝑎𝑛∗ |

𝑇𝑚𝑎𝑥

0.5 𝑘𝑃𝑎) =

−∆𝐻𝑎𝑏𝑠,𝑙𝑒𝑎𝑛

𝑅(

1

𝑇𝑚𝑎𝑥−

1

40°𝐶) (4.20)

Alternatively, PCO2,lean* can be calculated using a semi-empirical model at solvent

lean loading and Tmax.

The Pmax of a solvent is a function of both Tmax and the heat of absorption

(Equation 4.20). Solvents with greater heat of absorption will have higher stripper

pressure if operated at the same temperature as some other low heat of absorption

solvent.

H2O/ CO2/ ratio

𝑃𝐻2𝑂

𝑃𝐶𝑂2|𝑇𝑚𝑎𝑥

=𝑥𝐻2𝑂∙𝑃𝐻2𝑂,𝑣𝑎𝑝|𝑇𝑚𝑎𝑥

𝑃𝐶𝑂2,𝑙𝑒𝑎𝑛∗ |

𝑇𝑚𝑎𝑥

(4.21)

Water is vaporized along with CO2 during the stripping process, and the heat loss

associated with this stripping steam contributes to the work loss at the reboiler. The

ratio of PH2O and PCO2 exiting the stripper represents the amount of heat loss through

stripping steam relative to the total moles of CO2 removed. A high ratio of PH2O/ PCO2

corresponds to less efficient stripping and greater energy cost per mole of CO2 removed.

Similarly with Pmax, PH2O/ PCO2 improves (decreases) with increase in solvent ∆Habs and

Tmax. Solvents with high Pmax correspond to low PH2O/ PCO2, but PH2O/ PCO2 is more

sensitive to variations in ∆Habs.

70

Chapter 5: Amino Acid Salts for CO2 Capture

5.1 INTRODUCTION

5.1.1 Motivations

Amino acid salts have been proposed as potential solvents for post combustion

CO2 capture because of low environmental impact. Amino acids are expected to have

zero volatility as they are anions in the solvent. Amino acid based solvents have been

shown to have low ecotoxicity, and high biodegradability compared to conventional

amine solvents (Eide-Haugmo et al. 2009). Some literature also reports an expected

superior resistance to oxidative degradation (Kumar et al. 2003).

Amino acid salts have been suggested for variations of the amine scrubbing

process for CO2 capture, such as membrane contactors, submarine scrubbers, and

precipitation processes. This work evaluated the performance of amino acid salts as

aqueous solvents in traditional amine scrubbing processes for post combustion CO2

capture from coal or natural gas power plants.

5.1.2 CO2/amino acid salt/H2O Chemistry

Amino acids are organic compounds with an amino group and a carboxylic acid

group attached to a central carbon (Figure 4.1.a).

Figure 5.1. Chemical structure of amino acid in various charged forms

71

The side chain group (-R) attached to the central carbon varies between different

amino acids, giving them unique chemical properties. Amino acids differ from other

amines by the addition of the carboxylic acid group (or other acid groups such as sulfonic

acid). When dissolved in water, the neutral amino acid molecule transforms into its

zwitterion form (Figure 5.1b), where the carboxylic acid group loses a proton and the

amino group becomes protonated. In this protonated form, the amino group cannot

react with CO2 for absorption. To “activate” the amino group for CO2 absorption, the

amino acid is usually treated with an equimolar amount of a base (such as potassium

hydroxide) via the following reaction:

NH3+ - R – COO- + KOH ↔ NH2 – R – COO-(K+) + H2O (5.1)

The resulting amino acid salt (Figure 5.1c) has an unprotonated amino group, which can

react with CO2 like other amines. Any chemical with higher basic strength than the

amino group can be effectively used as the base to activate the amino acid.

Terminology for amino acid salt solvent systems

In this work, the term “amino acid salt” is used to refer to the associated

molecular pair of amino acid and base, denoted as “aminoacid(base)”. For example, the

amino acid salt of Glycine(K) refers to the associated molecules of glycine (amino acid)

and potassium (base). Variations of this expression include GlyK, or potassium

glycinate, which is common in literature. The term and abbreviations are also used to

describe the aqueous solvent composed of the amino acid salt.

Alkalinity of amino acid salt solvents

Due to the presence of an additional carboxylic acid group and base ions, amino

acid salt solvents have different acid-base composition compared to conventional amine

72

systems. Therefore, the concept of alkalinity is redefined to particularly address amino

acid salt solvents such that:

𝑎𝑙𝑘𝑎𝑙𝑖𝑛𝑖𝑡𝑦𝑡𝑜𝑡𝑎𝑙 = 𝑛𝑁𝐻2 − 𝑛𝐶𝑂𝑂− + 𝑛𝐾+ (5.2)

According to Equation 5.2, with the assumption that the amino acid molecule has the

same number of carboxylic acid groups and amino groups, the total alkalinity of the

system can be reduced to simply the number of moles of potassium ions in the system.

In the case where an equimolar amount of base and amino acid is used in the solvent, the

total alkalinity also equals the total moles of amino acid.

Reaction chemistry

Once the amino acid zwitterion is deprotonated with a strong base, the amine

group can react with CO2 in the same way as other amines. For primary and secondary

amino acids, the amino group will bond to the carbon of the CO2 forming an amino acid-

carbamate in the presence of a catalyzing base. At concentrated amino acid salt, a

second deprotonated amino acid is the most likely catalyzing base for this carbamate

forming reaction (Equation 5.3).

2 NH2-R-COO-(K+) + CO2 ↔ -OOC-NH-R-COO-(K+) + +NH3-R-COO- + K+ (5.3)

In the case of Equation 5.3, the products of the carbamate reaction include one mole of

the amino acid zwitterion per mole of CO2 reacted. The addition of CO2 into the solvent

effectively converts deprotonated amino acid back into its zwitterion form.

5.1.3 Literature review

Hook (1997)

Hook (1997) screened 5 amino acids for CO2 capture: glycine, alanine, Alkazid M

(N-methyl alanine), methylamino propionic acid, methyl-2 (methylamino) propionic acid,

and 2-methyl-2-[2’(-hyroxyethyl)-1’-(amino)] propionic acid. Absorption and

73

desorption experiments were conducted using laboratory scale apparatuses similar to a

stirred cell. Only qualitative conclusions on the absorption/desorption rates were made,

where the rates of the amino acid solvents are compared to the rates of

monoethanolamine (MEA) and 2-amino-2-methyl-propanol (AMP). All experiments

were conducted using solvents at 2.5 M amino acid. Crystallization upon CO2 loading

was observed for several amino acids at this concentration. The author proposed a

relationship between the position of methyl groups and the crystallization behavior of the

solvent.

University of Twente

The published works on amino acid salts from The University of Twente are

summarized in Table 5.1. The research efforts initially focused on the analysis of

taurine based solvents for CO2 absorption. The majority of the data reported are

physical properties of the solvents, which includes: density, viscosity, diffusivity of the

solvent in water, critical CO2 loadings, and solid precipitant analysis (Kumar et al. 2001;

2003). Many experiments were conducted using N2O, measuring the diffusivity of N2O,

solubility of N2O, and the physical mass transfer coefficient of N2O into taurine solvents.

Subsequent analysis regarding the solubility of CO2 into taurine solvents was derived

from applying the N2O-CO2 analogy to the N2O. A CO2-taurine reaction kinetics study

was performed using a stirred cell apparatus, and the reaction rates were reported and the

mechanism of the reaction analyzed (Kumar et al. 2003). One other experiment where

CO2 was used as the absorbent gas was a membrane contactor study. While CO2

absorption rate data was reported from this experiment, the measured values are specific

for the conditions in a membrane fiber contactor (Kumar et al. 2002).

74

Table 5.1: Journal Publications on Amino Acid Solvents from the University of Twente

Amino

Acid Base

C

(M)

T

(K)

αCO2

mol/mol

Properties

Analyzed

Author

Year Taurine

Glycine K 0.5 – 4

293-328

295 /

Solubility, diffusivity,

density, viscosity, DNO2

Kumar et

al. 2001

(N/A)

Taurine K 1.0 – 2 295 0-0.32

Absorption in

membrane fiber

contactor

Kumar et

al. 2002

Taurine K 1.0 – 4 298 0-0.7

Critical loading for

solubility; K2CO3 effect;

kL∙a of N2O;

solids analysis (13C

NMR)

Kumar et al.

2003

Taurine

Glycine K 0.1 – 4

285, 295,

305

295

/ Reaction rate constant Kumar et

al. 2003

Glycine K 0.1-3 293-313 / Density, viscosity,

N2O solubility, kapp

Portugal et

al. 2007

β-alanine, 6-

aminohexanoic

acid

Taurine

Glycine

Methionine

Phenylala-nine

Glutamic acid

Aspartic acid

/ / 293-353 /

Dissociation constant K,

thermodynamic

properties

Hamborg

et al. 2007

Taurins

Glycine

Sarcosine

Proline

K 0 – 3 293-368 /

Solvent diffusion

coefficient;

diffusivity of N2O

Hamborg et

al. 2008

Threonine K 0.1 – 3 293-313 /

Density, viscosity, DN2O,

N2O solubility, physical

mass transfer

coefficient, reaction

kinetics

Portugal et

al. 2008

β-alanine, 6-

aminohexanoic

acid, arginine,

Aspartic acid,

Glutamic acid,

Methionine,

Phenylalanine,

Proline,

sarcosine

K 0.25-3.5 298-333 /

Density, viscosity,

physical solubility of

N2O

Holst et al.

2008

Alanine

Sarcosine

Proline

Taurine

K,

Na,

Li

Saturation 293-313 /

Saturation

concentration;

conditions effecting

solubility

Majchrowicz

et al. 2009

75

Recent works on amino acid based solvents at the University of Twente include a

major screening effort using a wide range of amino acids (Hamborg et al. 2007, 2008;

Holst et al. 2008; Majchrowicz et al. 2009). The reported properties for the amino acids

are: solvent density, viscosity, solvent solubility, thermodynamic parameters, diffusivity

of N2O, and the physical solubility of N2O. There were no experiments reported where

CO2 was used in the gas phase in these screening works. A more in-depth effort was

invested in the analysis of two amino acids: glycine and threonine. The study of these

two amino acid solvents was within the scope of the earlier taurine study. The data

available for these solvents include: density and viscosity measurements, physical

solubility of N2O, and the kinetic rate analysis using a stirred cell reactor (Portugal et al.

2007; 2008).

Other Works

Among other published amino acid works, glycine was studied by three research

groups. Researchers at Yonsei University in South Korea conducted experiments very

similar in scope to the studies at the University of Twente. The reported analyses

include the measurement of physiochemical properties and the diffusivity and solubility

of N2O in glycine solvents. All of the reported CO2 absorption data were generated

using the N2O analogy without performing experiments using CO2 in the gas phase (Lee

et al. 2005, 2006; 2007). The glycine studies at the Universiti Teknologi Petronas in

Malaysia included direct CO2 solubility measurements obtained using an equilibrium cell

(Harris et al. 2009). Sarcosine is currently being studied at Norwegian University of

Science and Technology, where the CO2 solubility of loaded sarcosine solvents is

measured in an equilibrium cell (Aronu et al. 2011c).

76

Table 5.2: Journal Publications on Amino Acid Solvents by various sources

Amino

Acid Base Concentration T(K) αCO2 Properties Analyzed

Author/Year

Institution

Glycine Na 10-50 wt% 303-

353 /

Density, viscosity,

surface tension,

physical solubility,

DN2O , kinetics,

EActivation

Lee et al. 2005,

2006, 2007

Yonsei

University

Glycine K 1-3 (M) 303-

323 /

Membrane wetting,

Kinetics

Yan et al. 2007

Zhejiang Univ.,

China

Glycine Na 10-30 wt% 298-

353 0.5-3.5

Density, CO2

solubility

Harris et al. 2009

Universiti

Teknologi

Petronas,

Malaysia

Glycine K 0.1-0.5 M

298,

303,

308

5-7

kPa Kinetics

Vaidya,

Konduru, and

Vaidyanathan

2010

Sarcosine K,

MAPA

3.5M

5M

313-

353 0.1-0.6

CO2 solubility,

speciation, kinetics

Aronu et al.

2011b, 2011c

NTNU

Sarcosine K 3.5 M 393 0.3-

0.55

Pilot plant study:

KG, energy

performance

Knuutila et al.

2011

NTNU

Sarcosine K 0.5-3.8 M 313 0 Kinetics: WWC

Simons et al.

2010

University of

Twente

L-Alanine

L-Proline K 2.5 M

298-

313

0.45-

0.7

NMR speciation,

max CO2 loading

Lim et al. 2012

Kyungpook

National

University,

Republic of

Korea

Proline K 0.5-2 M 303-

323 Kinetics

Paul and

Thomsen 2012

Patent publications

More than half of the published patents on the use of amino acid salts for CO2

separation suggest the use of a precipitating slurry process. This is designed to target

77

the solid solubility limit of most amino acid salts, which leads to solid precipitation at

optimum operating conditions. Compared to conventional aqueous absorption stripping

processes, a slurry process requires special equipment to handle the solid particles. A

few patents suggest the use of amino acids as an aqueous solvent. In some of these

cases, the amino acid is used as a promoter or is promoted by other catalysts.

Table 5.3: Patents on the use of amino acid salts for CO2 capture

Organization Amino acid Base Process Application Data Number /

Date (Filing)

Siemens

Secondary

amino acid

with primary

amino acid

promoter

Na, K,

Li, Mg,

Ca, Be

Liquid

Power /

incineration

plant

/ EP2640491 A1

Jan, 2012

Nonspecific

amino acid

salt

/ Precipitation Combustion

process /

WO2014122000

A1

Jan, 2014

Carbon Clean

Solutions

Pvt.Ltd.

Amino

carboxylic

acid/Amino

sulfonic acid

(taurine)

/ Liquid

Gaseous

CO2

separation

Rate

WO2013144730

A2

March, 2013

CO2 Solution

Inc.

Amino acid

salt with

biocatalyst

(enzyme)

K

Liquid/

mineral

regeneration

Power Rate,

capacity

WO2011014955

A1

Aug, 2010

Svendsen et al.

Amino acid

promoted

carbonate

/ Precipitation

CO2 capture

from flue

gas

/

WO2008072979

A1

Dec 2007

Versteeg et al.

non-

sterically

hindered

Na, K Precipitation/

Slurry

Acid gas

treating/H2S

removal

Solid

solubility

WO2003095071

A1

May 2003

Among the previous studies on amino acid salts, there is a lack of quantitative

CO2 mass transfer data at concentrated amino acid salt conditions with CO2 loading in the

liquid phase. Two studies offer CO2 VLE data for glycine and sarcosine based solvents.

While there is an abundance of physical properties data, the majority of these

78

measurements were performed without CO2 loading in the liquid phase, which is a

significant deviation from process conditions. Patent publications suggest significant

improvements in energy cost for amino acid salts compared to conventional amines, but

little data is presented.

5.1.4 Scope

Table 5.4: Summary of amino acid salt systems screened in this work

Amino acid Structure Amino

group type Base

pKa @ 40 °C

(Hamborg

et al.

2007)

Solvent

Concentration

(m)

Glycine

OH

ONH2

Primary K+ 9.41 3.5

6

Sarcosine

OH

ONHCH3

Secondary K+

9.89 6

Na+ 4.5

β-alanine

OH

ONH2

Primary K+ 9.94 6.5

Proline

NH

O

OH

Secondary,

ring K+ 10.41 6.5

Taurine S

O

O

OH

NH2

Primary K+ 8.71 5

Homotaurine S

O

O

OH

NH2

Primary K+ N/A 5/3 m Tau

79

The molecular structures and concentration of the amino acid salts tested in this

work are summarized in Table 5.4, which only includes simple amino acid structures that

are commercially available and affordable. The GlyK solvent was tested at two

concentrations to observe the effect on solvent performance. The amino acid sarcosine

was tested using potassium and sodium as the neutralizing base.

The amino acid salts were tested for their performance as aqueous solvents in a

conventional scrubbing process. The results for the amino acids are compared to the

performance of base case aqueous amines such as 7 m MEA and 8 m PZ. The physical

properties of the amino acid salts were measured, including the solid solubility of the

solvent and solvent viscosity. The absorption rates of the solvents were measured and

used to estimate the performance and size of the absorber. The CO2 VLE in each

solvent was measured and analyzed to report the CO2 capacity and heat of absorption,

both of which affect the energy cost of the process. The oxidative degradation of the

amino acid salts were summarized from literature (Voice 2013).

5.1.5 Solvent preparation

The solvents were prepared gravimetrically by mixing the amino acid with water.

A mixture of potassium carbonate (K2CO3) and potassium hydroxide was added to the

solvent at the appropriate ratio to achieve the desired CO2 loading and neutralize the

amino acid zwitterion. Alternatively, in some cases, only KOH was used to neutralize

the solvent, while gaseous CO2 (99.99%, Matheson Tri-Gas) was bubbled into the solvent

to achieve the desired CO2 loading.

The CO2 concentration in the liquid phase was verified using a total inorganic

carbon (TIC) method (Section 3.3.1). The total alkalinity of the solvent was confirmed

using acid titration (Section 3.3.1). In some cases, the total cation in the solvent was

80

quantified using cation chromatography (Freeman 2011). The chemicals used in the

preparation of solvents used in this work are summarized in Table 6.5.

Table 5.5: Materials used for solvent preparation

Chemical Source Purity

Glycine Fisher BioReagents 98.50 %

Sarcosine Acros Organics 98.00 %

Taurine Alfa Aesar 99.00 %

Homotaurine AK Scientific 98.00 %

β - alanine Acros Organics 98.00 %

Proline BP Chemicals 99.00 %

KOH (solid) Fisher Chemical 87.00 %

KOH (aqueous) Fisher Chemical 45.5 %

K2CO3 Fisher Chemical 100.00 %

NaOH Fisher Chemical 40 %

5.2 PHYSICAL PROPERTIES

5.2.1 Solid solubility

Amino acid salts have been observed to precipitate solid particles as CO2 is

loaded into the solvent. The solubility of amino acid salts in water increases with

temperature; and decreases with total amino acid salt concentration and CO2 loading.

To be used as an aqueous solvent in a conventional absorption/stripping process, the

amino acid salt solvent should remain in a liquid state over the entire range of process

temperature and CO2 loading. The lowest temperature expected in the process is 40 °C

and the maximum CO2 loading of typical amine solvents is around 0.5 mol/mol. The

solid solubility of candidate amino acid salts was measured at room temperature and

three CO2 loadings between zero and 0.5 mol/mol. The results suggest the maximum

amino acid salt concentration that is acceptable for this application.

81

Experimental method

All amino acid salts tested use potassium as the neutralizing base. For each

amino acid salt, three samples were prepared at CO2 loading of zero, 0.25, and 0.5

mol/mol. All samples contained a solid phase that is in equilibrium with an aqueous

phase. For the zero loading samples, the amino acid was simply mixed with equimolar

amount potassium hydroxide (KOH) in water. For the samples at 0.25 loading, the

amino acid was mixed with potassium carbonate (K2CO3) to achieve the CO2 loading,

and additional KOH was added to achieve an equimolar amount of potassium in solution.

For the 0.5 loading samples, the appropriate amount of K2CO3 was added to the amino

acid in water to achieve an equimolar K+ concentration and the desired CO2 loading.

At the beginning of the experiment, each sample contained some un-dissolved

amino acid solid particles in a liquid. To ensure the solid particles were in equilibrium

with rest of the system, the samples were shaken vigorously then stirred overnight.

Next, water was added to each sample in small increments until all solids dissolved.

Between each addition of water, the solution was constantly stirred and sufficient time

was allowed for the solvent to reach equilibrium. The amount of water added was

recorded after each addition. The concentration of the amino acid salt before and after

the observed dissolution of all solid particles brackets the solid solubility limit of the

solvent.

82

Solid solubility data

Figure 5.2: Highest soluble concentration measured for the amino acid salts at room

temperature (approximately 25 °C)

The solid solubility of six amino acid salts was measured and the results are

plotted in Figure 5.2, where the concentration at which all solids becomes dissolved is

shown. The true solubility limit (saturation concentration) is slightly lower than the

value plotted. Among the systems tested, TauK and α-alaK are the least soluble systems

at 0.5 CO2 loading. And SarK, ProK, and β-alaK all have high soluble concentration at

0.5 loading, which offers potential as solvents for CO2 capture.

The solubility experiment for SarK was repeated and the results are plotted in

Figure 5.3. The variability between the three data points measured at 0.5 CO2 loading

suggest the error associated with the experimental method used is up to ± 1 m.

0

5

10

15

20

0 0.1 0.2 0.3 0.4 0.5 0.6

Mo

lalit

y (m

)

CO2 loading (mol /mol alk)

α - alanine (K)

β - alanine (K)

Proline (K)

Sarcosine (K)

Glycine (K)

Taurine (K)

83

Figure 5.3: Statistics of the solid solubility data for SarK at room temperature.

Along with the solubility of the amino acid salt mixture, the solubility of the

amino acid in water was also measured using the same method. In Figure 5.4, the

solubility of two amino acid salts, TauK and ProK, is compared to the solubility of the

amino acid. These two systems represent two types of solubility behaviors observed.

For TauK, the solubility of the amino acid salt approaches the solubility of the amino acid

as CO2 loading approaches 0.5 mol/mol. Consider the reaction stoichiometry of the

carbamate formation reaction between amino acids and CO2 (Equation 6.3), the decrease

in amino acid salt solubility with increasing CO2 loading corresponds to the accumulation

of amino acid zwitterions in the system as CO2 is added. For TauK, and other systems

with similar behavior (Table 6.6: GlyK, β-alaK, and α-alaK), the solubility of the amino

acid salt is limited by the solubility of the amino acid zwitterion. For ProK, the

solubility behavior differs from TauK, such that the solubility of the solvent is less than

the solubility of the amino acid zwitterion. The same behavior was observed for SarK

(Table 5.6). Other phenomena besides the zwitterions, possibly the increase in ionic

5

10

15

0 0.1 0.2 0.3 0.4 0.5 0.6

Mo

lalit

y (m

)

CO2 loading (mol/mol alkalinity)

Error bar: ± 95 % confidence interval

84

strength or the solubility of the carbamate speices, limit the solubility of these amino acid

salt solvents.

Figure 5.4: Solubility of amino acid salt (solid) compared to the solubility of the amino

acid in water (dashed line) at room temperature (highest soluble

concentration measured).

The solubility data collected at room temperature for amino acid salt solvents are

summarized in Table 5.6. The solubility is reported as concentrations before and after

the complete dissolution of solids is observed.

0

5

10

15

0 0.1 0.2 0.3 0.4 0.5 0.6

Mo

lalit

y (m

)


Proline (K)

Taurine (K)

Taurine solubility

Prolinesolubility

85

Table 5.6 : Solid solubility measured for amino acid salts at room temperature, the

solubility of the amino acid salt is between the before and after

concentrations

β-alaine (K) α-alanine (K) Glycine (K)

CO2 ldg Solubility

CO2 ldg Solubility

CO2 ldg Solubility

After Before After Before After Before

0 15.79 16.18 0 18.59 19.31 0 11.89 12.63

0.25 8.76 9.31 0.25 3.08 3.42 0.25 8.30 9.05

0.5 6.93 7.28 0.5 2.81 3.08 0.5 5.19 5.47

amino acid 7.69 8.32 amino acid 1.97 2.13 amino acid 3.10 3.20

Proline (K) Taurine (K) Sarcosine (K)

0 12.50 13.90 0 13.61 14.11 0 13.63 14.02

0.25 10.69 11.96 0.25 4.92 5.27 0.25 9.30 9.95

0.5 6.74 7.23 0.5 1.82 2.11 0.5 9.34 9.95

amino acid 11.06 12.46 amino acid 0.84 1.01 0 15.06

/ 0.25 9.06

0.49 6.45

0.51 7.38

amino acid 16.39 17.16

5.2.2 Viscosity

The viscosity of the amino acid salt solvents was measured using a Physica MCR

301 cone and plate rheometer (Chapter 4) at 40 and 60°C over the a range of CO2 loading

(Table 5.7). The viscosity result at 40 °C is plotted in Figure 5.5. Among the solvents

tested, 3 m TauK/5 m HtauK has the highest viscosity. This blend is also unique as its

viscosity decreases with increase in CO2 loading, which is the opposite trend from other

amino acid salts and most amine solvents. For most amino acid salts, the viscosity of

the solvent varied little with increase in CO2 loading. The data for 3.5 m and 6 m GlyK

show an increase in solvent viscosity with amino acid salt concentration. However, the

viscosity of 4.5 m SarNa is higher than 6 m SarK, even though the amino acid salt

86

concentration is lower. This suggests the choice of base also significantly affects the

viscosity of the solvent.

The viscosity of amino acid salt based solvents compares favorably to 8 m PZ,

which has a viscosity around 10 cP at 40 °C (Freeman et al. 2010). In the case of 3.5 m

GlyK, 6 m GlyK, 6 m SarK, and 5 m TauK, the viscosity is also competitive to 7 m MEA

(3 cP at 40 °C).

Figure 5.5: Viscosity of amino acid salts at 40 °C

0

3

6

9

12

0.2 0.25 0.3 0.35 0.4 0.45 0.5 0.55 0.6

Vis

cosi

ty (

cP)


3.55m GlyK

3/5 m Tau/HtauK

6.5m BetaAlaK

6m SarK 6m GlyK

5m TauK

4.5 m SarNa

87

Table 5.7: Viscosity of amino acid salts measured at 40 ad 60 °C

Amino acid salt T CO2 ldg µ % deviationi

°C mol/mol cP cP

GlyK 3.55m

40 0.35 1.67 0.17

40 0.35 1.74 0.17

40 0.41 1.71 0.17

40 0.47 2.15 0.21

40 0.53 1.84 0.18

60 0.47 1.26 0.13

TauK 5m 40 0.2 2.28 0.23

SarK 6m

40 0.2 3.63 0.36

40 0.35 3.84 0.38

40 0.42 4.60 0.46

40 0.5 4.07 0.41

40 0.55 4.11 0.41

SarNa 4.5 m

40 0.22 4.59 0.76

40 0.33 4.67 4.78

40 0.4 4.57 0.61

40 0.48 4.79 0.91

40 0.51 5.18 0.82

60 0.22 3.07 0.45

60 0.33 2.96 2.43

60 0.4 2.89 1.43

60 0.48 3.07 1.33

60 0.51 3.28 1.44

40 0.22 4.59 0.76

TauK/HomoTauK

3 m /5 m

40 0.28 11.91 1.19

40 0.32 6.98 0.70

40 0.35 8.42 0.84

40 0.42 8.24 0.82

Beta AlaK 6.5m

40 0.32 4.67 0.47

40 0.4 5.22 0.52

40 0.45 5.34 0.53

40 0.5 5.13 0.51

40 0.54 5.28 0.53

GlyK 6m

40 0.35 3.06 0.31

40 0.4 3.51 0.35

40 0.45 2.94 0.29

60 0.35 1.95 0.19

80 0.35 1.61 0.16 i % deviation is the standard deviation of 10 viscosity measurements - within a single rheometer run,

divided by their average

88

5.3. ABSORPTION RATE

The absorption rate of CO2 in eight amino acid salt solvents was quantified by

measuring the liquid film mass transfer coefficient (kg’) of CO2. The data was collected

using a bench scale wetted wall column (WWC). The apparatus and methods are

described in Chapter 3.1. The CO2 mass transfer rate was measured at 40, 60, 80, and

100 °C. The results at 40 °C are important as it is the target operation temperature of

the absorber column. The reported kg’ values directly suggest the relative rate

performance of each solvent in an absorber. The data at 40° C was further analyzed to

estimate the expected packing area in optimized absorbers for coal and natural gas flue

gas. The data at other temperatures offer information on the temperature dependence of

CO2 mass transfer rates, which addresses the effect of temperature bulge in the absorber.

5.3.1 CO2 mass transfer data

Figure 5.6: CO2 Liquid Phase Mass Transfer Coefficient (kg’) in 3.55 m GlyK. Compared

to 7 m MEA and 8 m PZ at 40 °C (Dugas 2009)

1.E-07

1.E-06

10 100 1000 10000

k g' (

mo

l/s∙

Pa∙

m2)

PCO2* @ 40 °C (Pa)

7m MEA @ 40◦C

8m PZ@ 40◦C40◦C60◦C

80◦C

100◦C

89

The kg’ measured for 3.55 GlyK are shown in Figure 5.6 together with the 40 ºC

data for 7 m MEA and 8 m PZ for comparison. The CO2 loading was varied across the

expected operation range for both coal and natural gas conditions. The rate of

absorption for 3.55 m GlyK is competitive to 7 m MEA at the lean loadings, but is lower

than 7 m MEA at rich loadings. There is no change in the kg’ between 40 – 80 °C,

while the kg’ at 100 °C is lower than other temperatures.

Figure 5.7: CO2 Liquid Phase Mass Transfer Coefficient (kg’) in 6 m GlyK. Compared

to 7 m MEA (Dugas 2009) and 3.55 GlyK at 40 °C.

The CO2 absorption rate was measured at only three CO2 loadings for 6 m GlyK,

as the solvent began to precipitate at higher loadings. In Figure 5.7, the kg’ of 6 m GlyK

is compared to 7 m MEA and 3.55 m GlyK. At low loadings, 6 m GlyK has similar

absorption rates as 7 m MEA and 3.55 m GlyK. At the third loading, the kg’ of 6 m

GlyK is lower than both 7 m MEA and 3.55 m GlyK. Also, relative to kg’ at higher

temperatures, the data at 40 C decreases much faster between the second and third

1.00E-07

1.00E-06

1.00E-05

10 100 1000 10000

k g' (

mo

l/s∙

Pa∙

m2)

PCO2* @ 40 °C (Pa)

7m MEA @ 40 °C

3.55m GlyK @ 40 °C

40 ◦C

60 ◦C

80 ◦C

100 ◦C

90

loadings. Absorption rates are not measured at coal conditions and rich loading

conditions for natural gas due to solid precipitation.

The kg’ for 6 m SarK was measured at six CO2 loading across the operation range

for both natural gas and coal conditions. The results are plotted in Figure 5.8 compared

to 7 m MEA and 8 m PZ at 40 °C. At 40 °C, the kg’ of 6 m SarK is similar to 7 m MEA

at low loading, but higher than 7 m MEA between 100 and 1000 Pa. At the highest

loading, the kg’ of 6 m SarK drops to about the same as 7 m MEA. The rate of 6 m

SarK is still lower than 8 m PZ over the entire experimental range. Little temperature

dependence in kg’ was observed for 6 m SarK.

Figure 5.8: CO2 Liquid Phase Mass Transfer Coefficient (kg’) in 6 m SarK, compared to

7 m MEA and 8 m PZ (Dugas 2009).

Liquid phase mass transfer coefficient (kg’) for 4.5 m SarNa was measured at five

loadings. The results are compared to 7 m MEA, 8 m PZ, 6 m SarNa at 40 °C (Figure

1.E-07

1.E-06

1.E-05

0.1 1 10 100 1000 10000

kg'(

mo

l/P

a s

m2)

PCO2* @ 40 °C (Pa)

8 m PZ 40 ◦C

60 ◦C

80 ◦C

100 ◦C

7m MEA @ 40 °C

91

5.9). The kg’ at 40 °C for 4.5 m SarNa is lower than 8 m PZ. At the two low loadings,

4.5 m SarNa is faster than 7 m MEA. And the rate drops to be about the same rate as 7

m MEA at the three higher loadings. Compared to 6 m SarK, 4.5 m SarNa has higher

rates at low loadings, but lower rates at high loadings. At low loadings, the absorption

rate of 4.5 m SarNa is higher at 40 °C. At the higher loadings, kg’ values changed little

at the four different temperature conditions.

Figure 5.9: CO2 Liquid Phase Mass Transfer Coefficient (kg’) in 4.5 m SarNa

1.E-07

1.E-06

1.E-05

1 10 100 1000 10000

k g' (

mo

l/s∙

Pa∙

m2)

PCO2 @ 40◦C (Pa)

40°C60°C

80°

100°

7m MEA @

8m PZ @ 40°C

6 m SarK@ 40°C

92

Figure 5.10: CO2 Liquid Phase Mass Transfer Coefficient (kg’) in 6.5 m β-AlaK

The liquid film mass transfer coefficient (kg’) was measured for 6.5 m β-AlaK at

five loadings across the operation range for natural gas and coal. The measured kg’ is

compared to results for 7 m MEA and 8 m PZ at 40 °C (Dugas 2009) in Figure 5.10.

Over the entire experimental loading range, the kg’ for 6.5 m β-AlaK at 40 °C is lower

than 7 m MEA. The absorption rate of 6.5 m β-AlaK is not a function of temperature

between 40 and 100 °C.

1.E-07

1.E-06

1.E-05

1 10 100 1000 10000

k g' (

mo

l/s∙

Pa∙

m2)

PCO2 @ 40◦C (Pa)

40°C

60°C

80°

100°

7m MEA @ 40°C

8m PZ @ 40°C

93

Figure 5.11: CO2 Liquid Phase Mass Transfer Coefficient (kg’) for 5 m TauK. Compared to 7 m MEA and 8 m PZ at 40 °C (Dugas 2009), and 3.55 m GlyK and 6 m

SarK at 40 °C.

The rate of CO2 absorption of 5 m TauK was measured at 0.2 CO2 loading (40 Pa)

only. The measured kg’ is compared to 7 m MEA, 8 m PZ, 3.55 m GlyK, and 6 m SarK

(Figure 5.11). At 40 °C and low CO2 loading, 5 m TauK has higher absorption rate than

7 m MEA, 3.55 m GlyK, and 6 m SarK, but still lower than 8 m PZ. Rate

measurements for 5 m TauK were not collected at the higher loadings because the solvent

was expected to precipitate. Solvent using TauK at lower concentrations have good

potentials of attractive CO2 absorption rate.

1.E-07

1.E-06

1.E-05

10 100 1000 10000

k g' (

mo

l/s∙

m2∙P

a)

PCO2* @ 40°C (Pa)

3.55 m GlyK

8m PZ7m MEA

6m SarK40°C

80°C60°C

100°C

94

Figure 5.12: CO2 Liquid Phase Mass Transfer Coefficient (kg’) for 3 m TauK/5 m

HomotauK

The absorption rate for the blend of 3 m TauK/5 m HomotauK was measured at

five loadings across the operation range for natural gas and coal conditions. The kg’ for

the blend is plotted with the absorption rate of 7 m MEA and 8 m PZ at 40 °C (Figure

5.12). At 40 °C, the blend has much higher kg’ than 7 m MEA at lean loading

conditions, but its rate decreases significantly as solvent loading increases. The rate

behavior of the blend demonstrated consistent temperature dependence, where the rate

decreases with increasing temperature.

1.E-08

1.E-07

1.E-06

1.E-05

1 10 100 1000 10000 100000

k g' (

mo

l/s∙

Pa∙

m2)

PCO2* @ 40°C (Pa)

40°C

60°C

80°C

100°C

7m MEA @ 40°C

8m PZ @ 40°C

95

Figure 5.13: CO2 Liquid Phase Mass Transfer Coefficient (kg’) in 6.5 m ProK. Compared to 8 m ProK (Chen 2011), 7 m MEA, and 8 m PZ at 40 °C (Dugas 2009)

Liquid film mass transfer coefficients (kg’) were measured for 6.5 m ProK at two

lean loadings. The results are compared to previous data for 8 m ProK (Chen 2011), as

well as 7 m MEA and 8 m PZ at 40 °C (Figure 5.13). The measured kg’ for the 6.5 m

solvent matches those of 8 m ProK solvent 40°C. The 6.5 m solvent is tested only at

two low loadings due to solid precipitation at higher loadings. However, no solid

precipitation was observed in the study for 8 m ProK (Chen 2011), which conflicts with

the general trend of solid solubility dependence on amino acid salt concentration and CO2

loading. It is possible that in the previous study, 8 m ProK appeared aqueous while it is

a supersaturated liquid, or that the solid phase formed in small and indistinguishable to

the naked eye. The kg’ for 8 m ProK significantly decreased at the highest CO2 loading

of the experiment (1kPa), which is uncharacteristic of other aqueous solvents. This

1E-07

1E-06

1E-05

0.01 0.1 1 10

k g' (

mo

l/s. P

a. m2)

P*CO2 @ 40°C (kPa)

7 m MEA@40°C

8 m PZ@40°C

100°C

80°C

60°C

40°C

Solid: 6.5 m ProK (this work)

Empty: 8 m ProK (Chen, 2011)

96

decrease in kg’ can also be explained by a shift in liquid phase speciation as solid

precipitation begins to form, thus depleting reactants for the reaction and absorption of

CO2. At loadings lower than 0.5 kPa, the kg’ of both ProK solvents are competitive

with 7 m MEA, but they are still slower than 8 m PZ.

The kg’ data for these amino acid salt solvents are summarized in Table 6.9-6.16.

5.3.2 Mass transfer performance in an absorber

Figure 5.14: CO2 Liquid Phase Mass Transfer Coefficient (kg’) for amino acid salts at 40 °C. Compared to 7 m MEA and 8 m PZ (Dugas 2009).

The kg’ of CO2 in amino acid salts at 40 °C is compared to 7 m MEA and 8 m PZ

in Figure 5.14. The amino acid salt with the highest kg’ is 6 m SarK, which is higher

1.E-07

1.E-06

1.E-05

10 100 1000 10000

k g' (

mo

l/s∙

Pa∙

m2)

PCO2 @ 40◦C (Pa)

8m PZ

Tau/HomotauK 3/5m

GlyK 3.55m

SarK 6m

MEA 7m

ProK6 and 8m

6.5 m βAlaK

4m TauK

GlyK 6 m

40

97

than 7m MEA at 200 – 1000 Pa, but is still lower than 8 m PZ over the entire range of

expected operating conditions. Other amino acid salts including 3.55 m and 6 m GlyK,

4.5 m SarNa, 6 m ProK, and 3 m TauK 5 m HtauK have higher kg’ than 7 m MEA at low

CO2 loadings but lower kg’ at rich loadings. For 6 m β-alaK, the kg’ is consistently 10%

lower than 7 m MEA over the entire range of experiments.

The kg’ data at 40 °C is used to estimate the average absorption rate of each

solvent in an isothermal absorber for both coal and natural gas conditions using Equation

4.6. The corresponding packing requirement is calculated using Equation 4.8. Coal flue

gas is assumed to contain 12% CO2 and natural gas with 3% CO2. The results are

summarized in Table 5.17 and 5.18.

5.4 CO2 VLE

The CO2 VLE in amino acid salts was measured using the WWC (Chapter 3).

The equilibrium CO2 partial pressure (PCO2*) was measured at 40, 60, 80, and 100 °C.

The CO2 loading in the liquid phase was varied across the operating range of coal and

natural gas conditions. For each amino acid salt, a semi-empirical VLE model was

developed to represent the data. The model can be used to interpolate within the

experimental CO2 loadings, temperatures, and amino acid concentrations; as well as

extrapolate near the experimental conditions.

The CO2 VLE behavior at 40 °C was analyzed to estimate the CO2 capacity of

each solvent for coal and natural gas conditions. The temperature dependence of the

CO2 VLE was analyzed to estimate the heat of CO2 absorption in each solvent. Both of

these properties contribute to the relative energy cost of the process.

98

5.4.1 CO2 solubility data

Figure 5.15: CO2 solubility data in 3.55 m GlyK (filled) and 6 m GlyK (empty), and the

semi-empirical VLE model results (solid lines). Compared to semi-empirical VLE model for 7 m MEA at 40 and 100 °C (dashed lines, Xu 2011).

The CO2 solubility data for GlyK at two concentrations (3.55 m and 6 m) are

plotted together in Figure 5.15. The solubility of CO2 is the same for the two GlyK

concentrations, as expected for primary and secondary unhindered amines – where the

PCO2* is a function of CO2 loading and independent of amine concentration (Dugas

2009). A semi-empirical model (Equation 4.4) is regressed using the experimental data

at the two concentrations to describe the CO2 VLE in GlyK solvents across and near the

experimental conditions. The fit of the model is also plotted in Figure 5.15, which

agrees well with experimental data. The solubility data at 0.48 CO2 loading for 3.55 m

GlyK is much lower than the trend suggested by the rest of the data, and was left out of

0.01

0.1

1

10

100

0.3 0.4 0.5 0.6

PC

O2*

(kP

a)

CO2 Loading (mol CO2/mol alk)

7m MEA 100◦C100◦C

80◦C

60◦C

40◦C

7m MEA 40◦C

99

the regression. Compared to the CO2 solubility curves of 7 m MEA, GlyK solvents

have higher CO2 solubility at the same CO2 loading.

Figure 5.16: CO2 Solubility for sarcosine based amino acid salt solvents. Empty points: 3

M SarK (Aronu et al. 2011c). Filled points: 6 m SarK . Asterisk: 4.5 m

SarNa. Lines: semi-empirical model (Table 6.8)

The CO2 solubility in 6 m SarK and 4.5 m SarNa are plotted in Figure 5.16 and

compared to literature results for 3 M SarK (Aronu et al. 2011c). The two amino acid

salt solvents using sarcosine but different neutralizing base have the same solubility of

CO2. The results of 6 m SarK and 4.5 SarNa also match those for 3 M SarK. In this

case, the CO2 solubility of the amino acid salt solvent is not only independent of the

amino acid salt concentration, it is also independent of the neutralizing base. A single

semi-empirical model is then used to describe all sarcosine based amino acid salt solvents

0.01

0.1

1

10

100

1000

0.1 0.3 0.5 0.7 0.9

PC

O2*

(kP

a)

40 °C60 °C

80 °C

100 °C

120 °C

100

near the experimental conditions. The result of the model fit is also shown in Figure

5.16, which fits all three data sets well.

Figure 5.17: CO2 solubility data for 6.5 m β-AlaK (points), and semi-empirical model fit

(solid lines). Compared to semi-empirical model results for MEA at 40 and 100 °C (Xu 2011).

The CO2 solubility in 6.5 m β-AlaK is shown in Figure 5.17. The semi-

empirical VLE model for this solvent was regressed using the experimental data and the

model fit also plotted. The data for this solvent show good internal consistency, and the

model fits the data well over the entire range of CO2 loading and temperature.

Compared at the same CO2 loading, the CO2 solubility of 6.5 m β-AlaK is higher than 7

m MEA.

The CO2 solubility in 5 m TauK was measured only at 0.2 CO2 loading, as the

solvent begins to precipitate at higher loadings. The result at 0.2 loading is plotted in

Figure 5.18 and compared to the CO2 VLE curves for MEA (Xu 2011). Compared to

0.001

0.01

0.1

1

10

100

0.3 0.4 0.5 0.6

PC

O2*

(kP

a)


7m MEA40◦C

40◦C

60◦

80◦

100◦

7m MEA @

101

MEA and other amino acid salts tested in this work, 5 m TauK has the lowest CO2

solubility. The structure of taurine is similar to β-alanine, only taurine has a sulfonic

acid group whereas β-alanine has a carboxylic acid group. The lowered CO2 solubility

is possibly the result of this difference in acid group of the amino acid.

Figure 5.18: CO2 solubility in 5 m TauK (points). Compared to the semi-empirical

model result for MEA (dashed lines, Xu 2011).

The CO2 solubility of the blend 3 m TauK/5 m HomotauK is plotted in Figure

5.19 and compared to MEA at 40 and 100 °C. A semi-empirical model for this blend is

calculated by fitting the experimental data to Equation 4.4. The fit of the model is

compared with the data in the same figure and show good agreement over the

experimental CO2 loading range and temperatures. The CO2 solubility in this blend is

very similar to 7 m MEA and higher than 5 m TauK at the tested CO2 loadings. Thus,

the addition of homotaurine to the solvent effectively increased the CO2 solubility of

TauK.

0.001

0.01

0.1

1

10

0.1 0.2 0.3 0.4 0.5

PC

O2

*(k

Pa)

CO2 Loading (mol CO2/mol alk)

40°C

60°C

80°C

100°C

7m MEA

102

Figure 5.19: CO2 Solubility data for 3 m TauK/5 m HomotauK (points), and semi-

empirical model fit (solid lines). Compared to semi-empirical model result of MEA at 40 and 100 °C(dashed lines, Xu 2011).

Figure 5.20: CO2 Solubility for 6.5 m ProK (solid) and 8 m ProK (empty, Chen 2011),

with semi-empirical model fit (solid) for both solvents. Compared with

semi-empirical model result for MEA (dashed line, Xu 2011).

0.001

0.01

0.1

1

10

100

0.2 0.25 0.3 0.35 0.4 0.45 0.5

PC

O2*

(kP

a)


7m MEA

40◦C

60◦

80◦

100◦

7m MEA @

1.E+01

1.E+02

1.E+03

1.E+04

1.E+05

0.45 0.46 0.47 0.48 0.49 0.5 0.51 0.52

PC

O2*

(Pa)

equ

Solid: 6.5 m ProK (this work)Empty: 8 m ProK (Chen, 2011)

100°C

80°C

60°C

40°C

7 m MEA @ 100 °C

7 m MEA @ 40 °C

103

The CO2 solubility in 6.5 m ProK was measured at two loadings only as the

solvent begins to precipitate at higher loadings. The results are plotted in Figure 5.20

and compared to results for 8 m ProK (Chen 2011). The CO2 solubility data for 8 m

ProK was collected at higher CO2 loadings than 6.5 m ProK, and no precipitation was

observed in the study. The solid solubility observations of 8 m ProK are inconsistent

with this work and the results of the solid solubility experiments (Section 4.2.1), as the

solvent is expected to be less soluble at higher amino acid salt concentrations. It is

possible that the 8 m ProK maintained a stable super-saturated liquid phase during those

experiments, which is common of amino acid salt solvents. Alternatively, the solid

precipitants could be small and not observed by the naked eye for 8 m ProK. Despite

the inconsistent solid solubility observations, the CO2 solubility of 6.5 m ProK matches

the results of 8 m ProK with some minor scatter in the data around 0.48 CO2 loading. A

semi-empirical model was developed for both ProK solvents by regressing both sets of

CO2 solubility data using Equation 4.4. The model fit the experimental data well.

Compared to MEA, the solubility of CO2 in ProK solvents is much higher.

The parameters of the semi-empirical models for each amino acid salt are

summarized in Table 6.8. The CO2 solubility data for each solvent are summarized in

Table 5.9-5.16.

Table 5.8: Semi-empirical model parameters of the amino acid salt solvents

ln(𝑃𝐶𝑂2∗ ) = 𝑎 +

𝑏


2 + 𝑒 ∙𝛼𝐶𝑂2

𝑇+ 𝑓 ∙

𝛼𝐶𝑂22

𝑇

Solvent a b c d e f R2

GlyK 40.41±3.28 -14188±1102 -16.4±8.04 / 12468±2695 / 0.995

SarK (Na) 46.4±1.7 -15975±605 -34.2±3.2 / 17742±1157 / 0.994

3/5 m

Tau/HtauK / 1525±672 233.2±20.8 -354±59.0 -82716±6109 136486±17194 0.999

6.5 m β-AlaK 44.3±4.28 -13003±1409 -52.1±11.6 54.0±9.49 9974±3245 / 0.995

ProK 162.6±44.38 -59625±14684 -258.0±90.6 / 101934±29967 / 0.984

104

Table 5.9: CO2 Solubility and kg’ for 3.55m GlyK

Loading T kg' PCO2*

(mol CO2/mol alk) (◦C) (x107mol/s∙Pa∙m2) (kPa)

0.348 40 22.60 0.037

0.4 40 17.54 0.075

0.489 40 8.01 0.260

0.57 40 1.92 5.361

0.348 60 15.70 0.180

0.4 60 13.82 0.462

0.489 60 8.62 1.641

0.57 60 1.59 20.079

0.348 80 20.40 1.063

0.4 80 12.99 2.341

0.489 80 7.70 6.735

0.57 80 1.56 47.888

0.348 100 19.30 4.435

0.4 100 10.46 9.949

0.489 100 5.83 23.325

Table 5.10: CO2 Solubility and kg’ for 6 m GlyK

Loading Temperature kg' P*CO2

(mol CO2/mol alk) (◦C) (Х 107 mol/Pa∙s∙m2) (kPa)

0.33 40 38.79 0.018

0.41 40 12.43 0.1

0.45 40 5.58 0.204

0.33 60 21.40 0.095

0.41 60 9.42 0.62

0.45 60 7.16 1.531

0.33 80 17.58 0.536

0.41 80 8.84 3.243

0.45 80 7.06 6.619

0.33 100 20.45 2.549

0.41 100 8.40 13.529

0.45 100 5.23 23.675

105

Table 5.11: CO2 solubility and kg’ for 6 m SarK

loading T PCO2* kg'

(mol CO2/mol alk) (◦C) (Pa) (x107mol/s∙Pa∙m2)

0.192 40 1* NA

0.295 40 8* NA

0.359 40 18 26.40

0.450 40 201 19.91

0.482 40 612 10.20

0.540 40 4477 3.25

0.295 60 116 64.83

0.359 60 164 39.10

0.450 60 826 12.69

0.482 60 2430 8.75

0.540 60 6263* 2.77

0.192 80 102 78.90

0.295 80 368* 46.19

0.359 80 1023* 23.56

0.450 80 7096 17.17

0.482 80 12260 10.72

0.192 100 691 87.16

0.295 100 2266 50.94

0.359 100 3947 26.48

0.450 100 16699 11.08

0.482 100 31295 5.33

106

Table 5.12: CO2 Solubility and kg’ for 4.5 m SarNa

CO2 loading T kg' PCO2*

mol CO2/mol alk °C Х107 (mol/s∙Pa∙m2) (kPa)

0.243 40 / 0.0065

0.333 40 49.75 0.020

0.398 40 22.45 0.053

0.477 40 7.19 0.365

0.514 40 4.64 1.252

0.243 60 60.50 0.026

0.333 60 30.30 0.106

0.398 60 23.33 0.312

0.477 60 8.23 1.977

0.514 60 5.58 4.611

0.243 80 45.87 0.148

0.333 80 31.22 0.577

0.398 80 19.29 1.851

0.477 80 9.31 6.676

0.514 80 5.16 13.66

0.243 100 52.35 0.638

0.333 100 21.40 2.772

0.398 100 15.65 6.496

0.477 100 7.42 19.48

0.514 100 4.53 35.31

107

Table 5.13: CO2 Solubility and kg’ for 6.5 m β-AlaK



0.32 40 29.3 0.009

0.39 40 24.7 0.017

0.45 40 10.5 0.081

0.50 40 4.5 0.516

0.54 40 1.9 2.28

0.32 60 31.9 0.036

0.39 60 16.8 0.102

0.45 60 9.8 0.471

0.50 60 4.5 2.52

0.54 60 1.9 8.82

0.32 80 30.6 0.201

0.39 80 18.7 0.575

0.45 80 10.1 2.657

0.50 80 4.5 9.08

0.54 80 2.2 23.1

0.32 100 29.2 0.867

0.39 100 18.4 2.71

0.45 100 9.0 9.80

0.50 100 4.3 26.1

Table 5.14: CO2 Solubility and kg’ for 5 m TauK

Loading T kg' PCO2*

(mol CO2/mol alk) (°C) Х 107 (mol/s∙Pa∙m2) (kPa)

0.2 40 31.60 0.041

0.2 60 21.32 0.234

0.2 80 18.16 1.259

0.2 100 24.05 7.73

108

Table 5.15: CO2 Solubility and kg’ for 3 m TauK/5 m HomotauK

Loading T kg' PCO2*

(mol CO2/mol alk) (°C) Х 10-7 (mol/s∙Pa∙m2) (kPa)

0.25 40 96.98 0.0098

0.305 40 50.01 0.027

0.365 40 14.22 0.114

0.43 40 6.83 0.443

0.5 40 0.38 30.982

0.25 60 55.01 0.061

0.305 60 22.48 0.204

0.365 60 11.39 0.696

0.43 60 5.29 3.112

0.25 80 31.29 0.389

0.305 80 16.75 1.351

0.365 80 7.56 4.958

0.43 80 2.63 20.299

0.25 100 22.81 2.051

0.305 100 12.94 6.2

0.365 100 5.06 21.232

Table 5.16: CO2 Solubility and kg’ for 6.5 m ProK



0.45 40 33.1 0.019

0.48 40 8.57 0.213

0.45 60 20.3 0.226

0.48 60 8.61 1.417

0.45 80 13.8 1.86

0.48 80 8.1 5.111

109

5.4.2 CO2 Capacity

Figure 5.21: Solvent capacity and heat of absorption estimated for β-alaK at coal and

natural gas conditions. Compared to 7 m MEA (Xu 2011).

The CO2 capacity of a solvent determines the amount of the solvent circulation

required in the scrubbing process, and in turn the energy cost associated with the

regeneration of the solvent. As defined in Section 4.2.3, solvent capacity is the product

of the delta loading and the concentration of the amine (or amino acid salt) in the solvent.

The delta loading is the difference between the CO2 concentration in the solvent at the

top (lean loading) and bottom (rich loading) of the absorber, which is a function of the

CO2 VLE in the solvent and the flue gas properties. In this work, the lean and rich

loading of 0.5 and 5 kPa is chosen as the basis for comparison for coal flue gas; and 0.1

and 1 kPa is used as the basis for natural gas flue gas. As shown in Figure 5.21, the

delta loading of a solvent is calculated using the CO2 VLE curve at 40 °C by finding the

lean and rich loadings that corresponds to the partial pressure conditions for each types of

40

45

50

55

60

65

70

75

80

85

90

0.001

0.01

0.1

1

10

100

0.3 0.4 0.5 0.6

Hab

s(k

J/m

ol)

P* C

O2

(kP

a)

CO2 loading (mol CO2/mol alk)

β-AlaK @ 40◦C

7m MEA@ 40◦C

Habs β-AlaK

Habs 7m MEA

Capacity Gas = 0.29

CapacityCoal =0.25

110

flue gas. The CO2 solubility data and the corresponding semi-empirical model are

critical in the accurate estimation of delta loading and capacity for each solvent.

Figure 5.22: CO2 solubility curves of amino acid solvents (Table 6.8) at 40 °C and coal

flue gas conditions. Compared to the PZ and MEA (Xu 2011).

The CO2 solubility curve at 40 °C for each amino acid salt solvent was compared

at coal and natural gas conditions (Figure 5.22 and 5.23 respectively). At both coal and

natural gas conditions, β-alanine and the blend of Tau/HtauK have steep solubility curves

which correspond to low delta loadings. Whereas the sarcosine based solvents and

GlyK have similar or higher delta loadings than MEA.

In general, amino acid salts have lower CO2 capacity than amine based solvents,

despite several amino acid systems having VLE behavior that are competitive with

amines. This is because of the low amino acid salt concentrations for all of the solvents

tested. Two factors contribute to the low concentration of amino acid salt solvents:

500

5000

0.3 0.35 0.4 0.45 0.5 0.55 0.6

PC

O2

(Pa)


SarK/SarNa

3/5 m TauK/HomoTauK

β - akaK

GlyK

PZMEA

40 °C

111

solid solubility and the high molecular weight of the amino acid salt. The solid

solubility limit restricts the maximum amino acid concentration to around 5 – 6 m for

natural gas conditions. For coal flue gas, where the solvent is expected to operate at

higher CO2 loadings, the amino acid salt concentration needs to be lowered further to

prevent precipitation. Compared to 7 m MEA and 8 m PZ (which has 16 m alkalinity),

amino acids are 15 % to four times lower in CO2 carrying capacity. Moreover, amino

acids have higher molecular weight than their amine counterparts because of the acid

group on the molecule and the addition of neutralizing base in the solvent. In effect,

additional solvent mass needs to be recirculated in the process for each mole of CO2

absorbed.

Figure 5.23: CO2 solubility curves of amino acid solvents (Table 6.8) at 40 °C and natural

gas conditions. Compared to the PZ and MEA (Xu 2011).

The calculated CO2 capacity for each amino acid solvent at both coal and natural

gas conditions is summarized in Table 5.17 and 5.18.

100

1000

0.2 0.25 0.3 0.35 0.4 0.45 0.5 0.55

PC

O2

(Pa)


PZ

MEA

3 m Tau/5 m HtauK

SarK/SarNa

β - akaK

GlyK

ProK

40 °C

112

5.4.3 Heat of CO2 absorption

The heat of absorption of CO2 for each amino acid salt was estimated for both

coal and natural gas conditions and plotted in Figure 5.24 and 5.25 respectively. At coal

conditions, the blend of 3 m TauK 5 m HtauK has the highest –Habs, which is competitive

with PZ but still lower than MEA. The other amino acid salts have similar or lower –

Habs than PZ and are not competitive with MEA. The –Habs for all solvents are high at

natural gas conditions relative to coal, due to the lower operating CO2 loadings. At

natural gas conditions 3 m TauK 5 m HtauK has competitive –Habs to MEA. And ProK

has a high –Habs at low loadings, which decreases significantly with increase in CO2

loading. Other amino acid salts do not have competitive –Habs. The –Habs at the mid

points of the CO2 loading range for both types of flue gas are summarized in Table 5.17

and 5.18.

Figure 5.24: Heat of absorption of CO2 for amino acid salts at coal flue gas conditions.

Compared to MEA and PZ (Xu 2011).

40

50

60

70

80

90

500 5000

-Hab

s(k

J/m

ol)

PCO2 @ 40 °C (Pa)

SarK/SarNa

3/5 m TauK/HomoTauK

β - akaK

GlyK

PZ MEA

113

Figure 5.25: Heat of absorption of CO2 for amino acid salts at natural gas flue gas

conditions. Compared to MEA and PZ (Xu 2011).

Table 5.17: Summary of performance parameters evaluated at coal flue gas conditions

(0.5-5 kPa) for amino acid salt solvents

Amino acid Base C

(m)

kg’avg

(mol/Pa s

m2)

Ap/Vg

m2/(m3/s)

Capacity

(mol/kg solv)

µ (cP)

40 °C

-ΔHabs

(kJ/mol)

Solid

solubility

(m)

x 107@ 40

°C x10-3 ΔCsolv mid ldg 1.5 kPa

25 °C, 0.5

CO2 ldg

Glycine K 3.55 3 5.1 0.25 2 64 5.2

Sarcosine K 6 5 3.0 0.35 4.1

54 7.7

Na 4.5 4.5 3.4 0.31 5.0 NA

β-Alanine K 6.5 2* 7.6* 0.25* 5.2 64 6.9

Taurine/

Homotaurine K 3/5 2.2* 6.8* 0.18* 8 69 NA

MEA / 7 4.3 3.5 0.47 1.8 72 /

* solid precipitation occurred only near the rich loading

40

50

60

70

80

90

100 1000

-Hab

s(k

J/m

ol)

PCO2 @ 40 °C (Pa)

SarK/SarNa

3/5 m TauK/HomoTauK

β - akaK

GlyKPZ

MEA

ProK

114

Table 5.18: Summary of performance parameters evaluated at natural gas conditions (0.1

– 1 kPa) for amino acid salt solvents

Amino acid Base C

(m)

kg’avg

(mol/Pa s m2)

Ap/Vg

m2/(m3/s) Capacity µ -ΔHabs

Solid

solubility

x 107@ 40 °C x10-3 ΔCsolv mid

ldg 0.5 kPa

25 °C, 0.5

CO2 ldg

Glycine K 6 3.2* 4.7* 0.35* 3 69 5.2

Sarcosine K 6 18.9 0.20 0.35 4

62 7.7

Na 4.5 11.4 0.33 0.31 4.6 NA

β-Alanine K 6.5 7.4 0.51 0.29 5.1 67 6.9

Taurine/

Homotaurine K 3/5 10.3 0.36 0.22 8 77 NA

Proline K 6.5 3.6* 1.04* 0.18* / 68 6.7

MEA / 7 11.7 0.32 0.55 1.7 78 /

* solid precipitation occurred only near the rich loading

5.5 OXIDATIVE DEGRADATION OF AQUEOUS AMINO ACID SALTS

The oxidation of amino acid salts was systematically screened by Voice (2013)

using a high gas flow apparatus (HGF). In these experiments, an air stream is

continuously sparged into the amino acid solvent in a semi-batch reactor. The CO2

loading in the solvent is maintained at approximately 2 kPa by adding CO2 to the air

stream at 2 vol%. The temperature of the reactor is maintained at 70 or 80 °C, which is

expected to around the absorber temperature bulge where oxidation is at its maximum.

The oxidation of the amino acid is monitored by gas phase analysis for volatile

degradation products, mainly ammonia (NH3). Various common metals, potential

catalysts and inhibitors were added to the solvent sequentially to observe their effects on

the oxidation of the amino acid. The results of these experiments are summarized in

Table 5.19.

The amino acid salts are divided into three categories based on their stability in

the presence of gas phase oxygen: susceptible to oxidation with similar or less stability

than MEA (GlyK), susceptible to oxidation but more stable than MEA (SarK/Na and

TauK), do not oxidize or only oxidize in the presence of Cu (β-AlaK and ProK). It was

115

also concluded that amino acid based solvents as a group do not exhibit unique stability

in the presence of oxygen. And the oxidative stability is more strongly associated with

the number of carbons between nucleophilic groups, as opposed to the presence of acidic

functional groups on the molecule. Moreover, though β-AlaK and ProK are stable at

70-80 °C, it is still possible that they will oxidatively degrade if cycled to stripper

temperatures, as it was observed for many other amine systems.

Table 5.19: Summary of the oxidative stability of amino acid salts studied by Voice

(2013)

Amino acid

salt

Amino acid

structure T (°C) Observations Oxidative stability

GlyK

OH

ONH2

70

NH3 production.

Catalyst: Fe, Inh

A

Oxidizes, similar

or less stable than

MEA

SarK/Na

OH

ONHCH3

80 CH3NH2, no NH3

Oxidizes but more

stable than MEA

TauK S

O

O

OH

NH2

80 NH3, Catalyst: Fe

Inhibitors: Inh A

β-AlaK

OH

ONH2

70 No NH3 with Cu

and Fe Do not oxidize, or

only oxidizes with

Cu ProK

NH

O

OH

80 No NH3 with Fe

5.6 CONCLUSIONS

Amino acid salts, in general, are not competitive with conventional aqueous

amines as solvents for CO2 capture. All amino acid salts suffer from low CO2 carrying

116

capacity, which is an intrinsic disadvantage due to the high molecular weight of the

amino acid salt and the low alkalinity concentration as limited by the solid solubility of

the solvents. Most amino acids have CO2 absorption rates that are about the same or

lower than 7 m MEA, and are not competitive with 8 m PZ. Most amino acids have low

heat of absorption, which are lower than both MEA and PZ. Most amino acid salts are

attractive in terms of viscosity, which are in the same range as 7 m MEA and much lower

than 8 m PZ. Amino acid salts, as a category, are not immune from oxidation.

Amino acid salts have more competitive performance at natural gas conditions

than coal, because of the lower flue gas CO2 concentration. With less CO2 in the flue

gas, the amino acid salts can operate at leaner CO2 loading, where the absorption rate and

heat of absorption are more competitive with amines. Also, at lower CO2 loading, the

amino acid salt concentration can be increased in the solvent to maximize CO2 capacity

without solid precipitation.

The most attractive amino acid salt is 6 m SarK, which has a higher absorption

rate than 7 m MEA and is not limited by solid precipitation. It also has lower viscosity

than 8 m PZ. However, it has low CO2 capacity, low heat of absorption, and is not

oxidatively stable.

The blend of 3 m TauK 5 m HtauK has an attractive high heat of absorption,

which is better than 8 m PZ. The solvents using ProK and β-AlaK were found to be

oxidatively stable at absorber temperatures.

117

Chapter 6: Concentrated Piperazine Blends for CO2 Capture

6.1 INTRODUCTION

6.1.1 Motivation

Recent studies show 8 m piperazine (40 wt% PZ) has superior performance to the

previous industry standard, 7 m monoethanolamine (30 wt% MEA). As shown in

Figure 6.1, PZ contains two secondary amine groups in a six member ring structure.

The two pKa values of PZ at 40 °C are 9.35 and 5.13 (Hamborg et al. 2009). At process

conditions, 8 m PZ has double the absorption rate and cyclic CO2 capacity of 7 m MEA.

Compared to MEA, PZ is more stable at high temperature and less prone to oxidation.

Also, 8 m PZ has lower volatility than 7 m MEA. These physical and chemical

advantages of 8 m PZ translate into an expected energy cost of 220 kWh/tonne CO2 with

optimized process design, which is the new standard for amine scrubbing (Rochelle et al.

2011a).

NH

NH

Figure 6.1: Molecular structure of piperazine (PZ)

The major disadvantage of 8 m PZ is limited solvent solubility, where solid

precipitation occurs at both low and high CO2 loading at reduced temperature. While 8

m PZ can be safely used as an aqueous solvent at its optimum loading range (between

0.26 and 0.42 mol CO2/ equivPZ) above 20 °C, it can be problematic in case of process

upsets and temperature fluctuations in the capture plant. Advanced control mechanisms

can help ensure proper operation, though these would incur additional cost and demand

advanced handling techniques. Due to its solubility limitations, historically PZ has been

118

mainly used at low concentration (< 10 wt %) as a promoter for amines with slow

absorption rates, such as tertiary amines and potassium carbonates. In these solvents,

PZ is the only component which directly reacts and binds with CO2. The other

component, the tertiary amine or carbonates, does not react with CO2, and instead acts as

a buffer to maintain a high solvent pH and store the absorbed CO2 in solution. Most of

these PZ-promoted solvents lose one or more other performance advantages of 8 m PZ

because the amount of PZ present is too low.

This work evaluates the performance of amine blends using concentrated PZ (25–

35 wt%). Using a larger amount of PZ is expected to maximize the advantages of PZ.

Since the solid solubility window for PZ solvents becomes more limited with increased

PZ, slightly reducing the PZ from 8 m by replacing it with other high performing amines

is expected to improve or eliminate the precipitation problem. Also, this work studies

PZ with other fast amines, where the second amine competes with PZ in reaction with

CO2. The CO2 absorption rates of these blends are expected to be higher than PZ

promoted tertiary amines and carbonates.


A major portion of literature work on PZ blends was devoted to three systems:

potassium carbonate (K2CO3), methyldiethanolamine (MDEA), and 2-amino-2-methyl-1

propanol (AMP). Abundant literature data are available for each of these three systems

in terms of CO2 absorption kinetics, VLE, physical properties, and NMR liquid phase

speciation. Selected previous works for these blended solvents are summarized in Table

6.1. For PZ/MDEA and PZ/K2CO3, the works by Cullinane (2005) and Chen (2011)

shows increasing PZ in the blend enhances the overall performance of the solvent at

119

process conditions for CO2 capture from coal flue gas. For PZ/AMP, the work by Li

(2013) shows the blend to have competitive performance with PZ at 10 – 40 wt %.

Table 6.1: Selected literature on three popular PZ blends

Blend name Result type Author

PZ promoted K2CO3 CO2 solubility, kinetics Cullinane (2005)

NMR speciation Kim et al. (2011)

PZ/MDEA

Physical solubility, diffusivity Dash et al. (2011)

Kinetics, CO2 solubility Derks et al. (2006)

CO2 solubility Bishnoi (2000)

Solvent degradation Closmann (2011)

CO2 solubility, mass transfer Chen et al. (2011)

ASPEN modeling Frailie (2014)

PZ/AMP

Density and Viscosity Samanta and

Bandyopadhyay (2006)

CO2 solubility Dash (2011)

Density and viscosity Paul and Mandal (2006)

Rigorous mass transfer, CO2 VLE,

degradation, volatility Li H et al. (2013)

Some previous work also investigated blending PZ with other amines, as

summarized in Table 6.2. More than half of these studies look at blending PZ with

either a tertiary amine or hindered amine. The only unhindered primary and secondary

amines tested in blends with PZ are MEA, DEA, and MMEA. Most of these works use

a small amount of PZ (5 wt % or less) in the blend to act as an absorption rate enhancer.

A major weakness of some of these works is that the effect of CO2 loading is not studied.

Dubois and Thomas (2009, 2013) and Aronu et al. (2011a) are screening studies, where

the absorption rates and stripping efficiencies reported are not intended for further

analysis and interpretation, as it is not rigorous mass transfer and CO2 VLE

measurements.

120

Table 6.2: Literature on other PZ blends

PZ blend w/ C T

(K) CO2 ldg Data type Author

2-piperidineethanol

(2PE)

Total amine: 30

wt %

288 -

333 /

Density,

viscosity, surface

tension

Paul and

Mandal

2006

Monoethanolamine

(MEA)

PZ: 2 m

Am: 7 m

313 -

373

0.2-0.5

(mol/mol

alk)

Rigorous mass

transfer rates,

CO2 VLE

Dugas

2009

PZ: 5 – 12.5 wt

%

Am: 15 – 30 wt

%

298 /

Mass transfer

rates, modeling,

regeneration

Dubois

and

Thomas

2009

Diethanolamine

(DEA)

PZ: 5 wt %

Am: 30 wt % 298 /

Absorption rates,

regeneration

efficiency

Dubois

and

Thomas

2013

PZ: 0.02-0.6 M

Total: 2-3 M

303-

353

0.4-0.75

(mol/mol

am)

CO2 solubility Monoj

2009

2-amino-2-

hydroxymethyl-1,3

propanediol

(AHDP)

PZ: 0.1-0.4 M

Am: 1 M

303-

323 /

Density,

viscosity, N2O

analogy

Bougie

et al.

2009

PZ: 5 wt %

Am: 30 wt % 298 /

Absorption rates,

regeneration

efficiency

Dubois

and

Thomas

2013

Methyl-

monoethanolamine

(MMEA)

PZ: 5 wt %

Am: 30 wt % 298 /

Absorption rates,

regeneration

efficiency

Dubois

and

Thomas

2013

N,N-

Diethylethanolamine

(DEEA)

PZ:0.1-0.5 M

Am: 2 M

298-

308 PCO2

*: 5 kPa Absorption rates,

kinetics

Konduru

et al.

2010

(TMBPA) PZ: 1 M

Am: 1.5 M

313,

353

0.81-1.9

(mol/mol

am)

Absorption

stripping

screening

Aronu et

al.

2011a

2-methylpiperazine

(2MPZ)

PZ: 4 m

Am: 4 m

313-

373 0.2-0.4

Mass transfer

rates, CO2 VLE,

viscosity

Chen

2011

1-methylpiperazine /

1,4dimethylpiperazine

1MPZ/1,4DMPZ

PZ:3.75 m

Am: 4.25 m

313-

373

0.1 – 0.35

(mol/mol

alk)

Mass transfer

rates, CO2 VLE

Chen

2011

121

Dugas (2009) and Chen (2011) evaluated 2 m PZ/7 m MEA, 4 m PZ/4 m

2MPZ, and 3.75 m PZ/3.75 m 1MPZ 0.5 m 1,4DMPZ and other CO2 VLE and absorption

rates data over a wide range of temperature. Also, the effect of CO2 loading is

considered. The experimental conditions and the use of the WWC contactor focus on

evaluation of the solvents at process conditions. However, only three different

structures were tested in blends with PZ so any generalization based on structure is not

feasible.

6.1.3 Scope

In this work, PZ is blended with three different categories of amines: primary

unhindered amines, PZ derivatives, and hindered amines. All of the blends have a PZ to

amine molar ratio of at least 1:1, which is at higher PZ concentration compared to

literature solvents which use PZ as a promoter. Among the five primary unhindered

amines tested, EDA, DAB, HMDA, and BAE are long chain diamines, where two

primary amine groups are attached the ends of a straight carbon chain. The chain length

increases by two carbons in the following order: EDA (2) < DAB (4) < HMDA (6). The

pKa of these three amines increases with increase in its carbon chain length. The

molecular structure of BAE differs from HMDA only in the ether group in the middle of

the carbon chain, which lowers the pKa of BAE. The fifth primary amine tested is

DGA®, which contains only one amine group. The structure of DGA® is similar to

BAE, only the second amine group of BAE is replaced by an hydroxyl group on DGA®,

which further reduces the pKa of the molecule. The second category of structures

includes two PZ derivatives: AEP and HEP. Both AEP and HEP were tested previously

by Chen (2011), where both demonstrated good absorption rates. The third category

includes three hindered amines: 2-PE, AMP, and Tris. The pKa of these hindered amines

122

range from 7.72 (Tris) to 9.68 (2-PE). The structures, pKa, and solvent concentration of

the PZ blends tested in this work are summarized in Table 6.3.

Table 6.3: List of PZ blends tested in this work

Amine Structure Type pKa

(40 °C)

Blend

concentratio

n

Ethylenediamine

(EDA)

NH2

NH2

Primary

diamine

9.51,6.46

(Everett et

al.,

1952)

6 m PZ/2 m

EDA

Diaminobutane

(DAB)

NH2

NH2

Primary

diamine

10.17

8.74

(Christense

n et al.,

1969)

6 m PZ/2 m

DAB

Hexamethylenediamine

(HMDA)

NH2

NH2

Primary

diamine

10.44 9.35

(Everett et

al. 1952)

6 m PZ/2 m

HMDA

Bis(aminoethyl)ether

(BAE)

NH2

O

NH2

Primary

diamine

9.32

8.32

(Christense

n et al.

1969)

6 m PZ/2 m

BAE

Diglycolamine

(DGA)®

OH

O

NH2

Primary

monoamine

9.08

(Hamborg

et al. 2009)

5 m PZ/5 m

DGA®

N-

2(aminoethyl)piprazine

(AEP)

N

NH

NH2

Piperazine

derivative

9.13

8.06

(Pagano et

al.

1961)

5 m PZ/3 m

AEP

123

Table 6.3: List of PZ blends tested in this work (continued)

Hydroxyethylpiperazine

(HEP)

N

NH

OH

Piperazine

derivative

8.75

3.74

(Khalili et

al. 2009)

6 m PZ/2 m

HEP

2-piperidineethanol

(2-PE)

NH

OH

Hindered

secondary

9.68

(Xu et al.

1992)

5 m PZ/5 m

2PE

2-amino-2-methyl-

1propanol

(AMP)

NH2

CH3

OH CH3

Hindered

primary

9.17

(Hamborg

et al. 2009)

5 m PZ/2.3

m AMP

2-amino-2-

hydroxymethyl-

propane-1,3-diol

(Tris) OH

NH2

OH

OH

Hindered

primary

7.72

(Angus

Chemical,

2000)

3.5 m PZ/3.5

m Tris

The solid solubility window of the PZ blends is first discussed and compared with

8 m PZ and other PZ blends. The viscosity of the PZ blends was measured and the

results are applied to demonstrate its effect on CO2 mass transfer and sensible heat cost of

the solvent in the process. The focus of this work is the measurement and comparison

of CO2 absorption rate and solubility in the PZ blends. The CO2 mass transfer and

solubility data are first reported. The effect of molecular structure and blend ratio on the

rate and solubility of CO2 are discussed. The experimental data are then used to

estimate the relative performance of each solvent in a capture process for coal flue gas.

Lastly, the degradation and volatility of the amines as measured by others are

summarized by reviewing and reanalysis of experimental results from literature.

124


Table 6.4: Materials Used for Solvent Preparation

Chemical Purity Source

Piperazine 99% Sigma-Aldridge

Hexamethylenediamine (HMDA) 99% Acros Organics

Diaminobutane (DAB) 99% Acros Organics

Ethylenediamine (EDA) 99% Sigma-Aldridge

Bis(aminoethyl)ether (BAE) 99% Huntsman Chemicals

Diglycolamine® (DGA®) 99% Sigma-Aldridge

N-2(aminoethyl)piprazine (AEP) 99% Acros Organics

N-(hydroxyethyl)piperazine (HEP) 98% Sigma-Aldridge

2-piperidineethanol (2PE) 95% Huntsman

2-amino-2-methyl-1propanol (AMP) 99% Acros Organics

2-amino-2-hydroxymethyl-propane-1,3-

diol (Tris) 99% Sigma-Aldridge

DDI Water 100.00% Millipore, Direct-Q

6.2 PHYSICAL PROPERTIES

6.2.1 Solid Solubility

The solubility of piperazine (PZ) in water is low. When the concentration of PZ

in water is higher than the liquid-solid equilibrium point, PZ and the surrounding water

molecules form solid piperazine hexahydrate (PZ∙6H2O), which precipitates from the

liquid phase (Freeman 2011). Adding CO2 to the PZ/H2O mixture enhances the

solubility of the solution. At moderate CO2 loading, the absorbed CO2 reacts with free

piperazine and forms more soluble reaction products, so the concentration of the less

soluble free piperazine is reduced. However, one of the PZ – CO2 reaction products,

protonated piperazine carbamamte (H+PZCOO-), also has limited solubility. At high

125

CO2 loading, the built up of H+PZCOO- will cause precipitation in the form of protonated

piperazine carbamate hydrate (H+PZCOO-∙H2O) (Xu 2008).

The solid solubility of the base case PZ solvent 8 m PZ (40 wt %) was measured

by Freeman (2011). As shown in Figure 6.2, 8 m PZ has an aqueous operating window

between CO2 loading of 0.28 and 0.42 at 20 °C. While the performance of 8 m PZ

within the solubility range is highly competitive with other candidate solvents, the

possibility of solid precipitation if the window is breeched during operation is a major

cause for concern. The solubility window of 8 m PZ can be improved by simply

reducing the concentration of PZ, which will also reduce the total alkalinity and CO2

carrying capacity of the solvent. The solubility challenge for PZ solvents is to improve

the operating window without significantly reducing the total alkalinity and CO2 capacity

of 8 m PZ.

For concentrated PZ blends, a small portion of the PZ in 8 m PZ is replaced with

other high performance amines. The solubility window of the blended solvent is

expected to be improved as the concentration of the less soluble PZ species (piperazine

hexahydrate and protonated piperazine carbamate) is reduced, while the total alkalinity of

the solvent is kept close to 8 m PZ by the presence of the other amine(s). Replacing part

of the PZ with a second amine can affect the solubility of the solvent in several other

ways. First, the solid-liquid equilibrium of the PZ species in the blended solvent

depends on the interaction of these species with the second amine, which could enhance

or reduced their solubility. Second, the second amine or their reaction products with

CO2 can have low solubility in the blended solvent. Third, the change in the ionic

environment of the solvent due to the addition of a second amine will alter the activities

of the species, which can lead to subtle changes in the reaction equilibrium and the

concentration of the less soluble PZ species.

126

Experimental method

The solid solubility window of a solvent can be determined by measuring the

solid-liquid transition temperature as a function of CO2 loading. First, several samples

of a solvent is prepared at different CO2 loadings between 0 and 0.45, where the solid

solubility window is expected to occur. Each sample was shaken and stirred vigorously

for ensure the solution is homogeneous. Next, the samples which contain solid particles

are heated in an oil bath at increments of 1 °C. At each temperature, the samples were

shaken and stirred frequently to achieve thermal equilibrium. A short time of

approximately 10 minutes is allotted at each temperature to allow for the solids to

potentially melt. This process is repeated until all of the solids disappear to the naked

eye. The temperature at which this occurs is recorded as the transition temperature.

For the samples that contain no solids at room temperature, the samples are cooled to

zero degree and left overnight for solids to precipitate. Next, the samples with solid

precipitation are heated at 1°C increments using a refrigerated oil bath from 0 °C until the

transition temperature is measured. Using this method, the solid solubility window for 5

m PZ 2 m AEP (Du et al. 2013) and 6.5 m PZ 3 m AMP (Li et al. 2013) was measured

(Table 6.5).

For the other PZ blends studied in this work, the solid solubility window was not

measured rigorously using the above method. For the WWC and total pressure

experiments, samples are prepared at room temperature by estimating the soluble CO2

loading range. The solid solubility observations made during these experiments are

summarized in Table 6.6. The lowest and highest CO2 loading without solid

precipitation is reported. The solvents are soluble between these loadings. It is

possible for solid precipitation to occur at lower or higher CO2 loadings.

127

Results

The solid solubility results for 5 m PZ/2 m AEP and 6.5 m PZ/3 m AMP are

compared with 8 m PZ (Freeman 2008), 4 m PZ/4 m 2MPZ, and 3.75 m PZ/3.75 m

1MPZ/0.5 m 1,4 dimethylpiperazine (DMPZ) (Rochelle et al. 2011) in Figure 6.2. The

solid solubility observations for 6 m PZ/2 m HMDA and 6 m PZ/2 m DAB are also

shown in Figure 6.2.

Figure 6.2: Solid solubility of concentrated PZ blends compared to 8 m PZ. Solid lines:

transition temperature curve. Dash lines: approximate transition temperature

curve. Empty points: soluble condition. Filled point: precipitation

condition.

At high CO2 loadings, no solid solubility limit was observed for the PZ blends at

room temperature. For 5 m PZ 2 m AEP and 6.5 m PZ/3 m AMP, the solvent is soluble

down to zero 0 °C at about 0.45 CO2 loading. This is an advantage over 8 m PZ which

precipitates at CO2 loading of 0.45 mol/mol N up to 40 °C. At lower CO2 loadings, all

0

10

20

30

40

50

0 0.1 0.2 0.3 0.4 0.5

Ttr

ans

(°C

)


8 m PZ

5 m PZ/2 m AEP

4 m PZ/4 m 2MPZ

3.75 m PZ/3.75 m/ 1MPZ 0.5 m DMPZ

6 m PZ/2 m HMDA

6 m PZ/2 m DAB

6.5 m PZ/3 m AMP

128

of the PZ blends, except for 6 m PZ/2 m HMDA, have better solid solubility than 8 m PZ.

For 6 m PZ/2 m HMDA, at room temperature, the solvent precipitates at 0.3 CO2 loading,

which is less soluble than 8 m PZ. It is possible that HMDA is limiting the solid

solubility of the solvent at low loadings, as HMDA itself has low solubility in water.

Alternatively, HMDA could have reduced the solubility of free PZ in the solvent.

Table 6.5: Solid solubility measurement of concentrated PZ blends in literature

Solvent

CO2 ldg Ttrans

Solvent

CO2 ldg Ttransition

(°C)

(mol/mol

alkalinity)

4 m PZ/4 m 2MPZ

(Rochelle et al. 2011)

0.008 23

6.5 m PZ/3 m

AMP

(Rochelle et al.

2012b)

0 37

0.108 21.5 0.043 34

0.159 17.5 0.097 30

0.209 11 0.145 26

0.25 0 0.163 24

5 m PZ/2 m AEP

(Rochelle et al. 2012a)

0 40 0.225 15

0.05 37 0.292 3

0.1 34 0.309 0

0.15 31 0.337 0

0.2 21.5 0.341 40

0.23 19

0.25 4

0.3 0

3.75 m PZ/3.75 m//0.5

m DMPZ


0.00 34

0.04 29

0.16 23

0.23 2

129

Table 6.6: Solid solubility observation for PZ blends at room temperature

Solvent T (°C) Soluble loadings (mol/mol alkalinity)

Lowest observed Highest observed

6 m PZ/2 m EDA Room (21) 0.34 0.44

6 m PZ/2 m DAB Room (21) 0.30 0.43

6 m PZ/2 m HMDA Room (21) 0.35

(precipitation at 0.3) 0.46

6 m PZ/2 m BAE Room (21) 0.31 0.42

6 m PZ/2 m HEP Room (21) 0.25 0.37

5 m PZ/5 m DGA® Room (21) 0.32 0.44

5 m PZ/2.3 AMP

(Li et al. 2013) 0 0.3 0.5

5 m PZ/5 m 2-PE Room (21) 0.19 0.52

3.5 m PZ/3.5 m Tris Room (21) 0.20 0.37

6.2.2 Viscosity

The viscosity of the PZ blends was measured using a rheometer (Chapter 3.3.3).

The CO2 loading in the solvent was varied across the expected operating range in a

capture process. For all PZ solvents, viscosity was measured at 40 °C. For 6 m PZ/2

m EDA, 6 m PZ/2 m HMDA, and 3.5 m PZ/3.5 m Tris, viscosity was also measured at

other temperatures. The measured results are summarized in Table 6.7 - 6.13.

130

Figure 6.3: Viscosity of concentrated PZ blends at 40 °C. Compared with 7 m MEA

(empirical model by Weiland 1998) and 8 m PZ (Freeman 2011) at 40 °C.

The viscosity results at 40 °C are plotted in Figure 6.3, where the PZ blends are

compared with 8 m PZ (Freeman 2011) and 7 m MEA (Weiland 1998). The viscosity

of all PZ blends is significantly higher than 7 m MEA. Most of the PZ blends have

viscosity similar to 8 m PZ (about ±2 cP). The viscosity of 6 m PZ/2 m HMDA is

higher than 8 m PZ and other PZ blends, at about 15 cP. The blend with the highest

viscosity is 5 m PZ /5 m 2-PE, which is around 25 cP and about twice that of 8 m PZ and

other PZ blends. The viscosity of 3.5 m PZ/3.5 m Tris is lower than the other PZ

blends, which is likely due to the lower total amine concentration of this blend. For all

of the PZ blends, solvent viscosity increases with increase in CO2 loading.

0

5

10

15

20

25

30

0.1 0.2 0.3 0.4 0.5 0.6

Vis

cosi

ty (

cP)


5 m PZ/5 m 2-PE

6 m PZ/2 m HMDA

6 m PZ/2 m BAE

5 m PZ/5 m DGA

8 m PZ

5 m PZ/2.3 AMP

6 m PZ/2 m EDA

3.5 m PZ /3.5 m Tris

5 m PZ/2 m AEP

6 m PZ/2 m HEP

7 m MEA

131

Table 6.7: Viscosity of 6 m PZ/2 m EDA at 25, 40, and 60 °C

T CO2 loading µ St. Dev µavg St.Dev

°C mol/mol alkalinity cP cP cP cP

25

0.300

14.60 0.08

14.47 0.11 14.44 0.08

14.38 0.09

0.349

14.63 0.13

14.63 0.01 14.62 0.09

14.64 0.11

0.397

15.33 0.12

15.32 0.01 15.33 0.13

15.31 0.11

0.410

15.93 0.08

16.02 0.10 16.12 0.15

16.01 0.11

0.446

16.60 0.12

16.58 0.06 16.51 0.15

16.62 0.12

40

0.300

8.61 0.20

8.61 0.01 8.60 0.17

8.62 0.15

0.349

8.90 0.19

8.86 0.06 8.79 0.19

8.90 0.17

0.397

9.87 0.14

9.50 0.34 9.23 0.17

9.39 0.14

0.410

9.78 0.19

9.79 0.03 9.76 0.20

9.83 0.22

0.446

10.25 0.20

10.21 0.12 10.08 0.18

10.31 0.23

132

Table 6.7: Viscosity of 6 m PZ/2 m EDA at 25, 40, and 60 °C (continued)

Table 6.8: Viscosity of 6 m PZ/2 m HMDA at 40, 60, 80, and 100 °C

T CO2 loading µ St Dev

°C mol/mol alkalinity cP cP

40

0.35 14.61 0.41

0.40 14.9 0.11

0.43 15.71 0.12

0.46 16.53 0.13

60

0.35 7.88 0.15

0.40 10.21 1.24

0.43 9.98 0.81

80 0.35 6.57 1.52

0.40 10.15 3.14

100 0.35 3.24 0.04

60

0.300

5.22 0.21

5.14 0.08 5.06 0.20

5.13 0.19

0.349

5.53 0.15

5.56 0.08 5.50 0.16

5.65 0.22

0.397

5.79 0.22

5.89 0.09 5.92 0.13

5.95 0.22

0.410

6.54 0.20

6.36 0.16 6.25 0.18

6.28 0.22

0.446

6.30 0.20

6.50 0.22 6.73 0.14

6.46 0.18

133

Table 6.9: Viscosity of 6 m PZ/2 m BAE at 40 °C

CO2 loading µ St. Dev µavg St.Dev

mol/mol alkalinity cP cP cP cP

0.336

11.75 0.32

11.18 0.53 11.09 0.13

10.7 0.16

0.357

11.44 0.12

11.47 0.03 11.47 0.12

11.49 0.14

0.401

12.76 0.16

12.43 0.29 12.31 0.13

12.23 0.14

0.467

13.77 0.15

13.84 0.19 14.06 0.17

13.7 0.20

Table 6.10: Viscosity of 5 m PZ/5 m DGA® at 40 °C



0.321

10.89 0.251

10.84 0.068 10.86 0.259

10.76 0.227

0.368

11.03 0.226

11.10 0.070 11.17 0.221

11.1 0.211

0.418

11.98 0.169

11.68 0.260 11.52 0.290

11.54 0.237

0.437

11.83 0.226

11.76 0.081 11.67 0.245

11.77 0.254

0.456

12.27 0.271

12.47 0.250 12.39 0.273

12.75 0.341

134

Table 6.11: Viscosity of 6 m PZ/2 m HEP at 40 °C



0.309

11.96 0.250

12.24 0.246 12.43 0.330

12.32 0.326

0.341

12.22 0.220

12.46 0.230 12.68 0.322

12.47 0.327

0.358

13.51 0.338

13.43 0.127 13.28 0.308

13.49 0.331

0.373

13.23 0.211

13.13 0.091 13.05 0.201

13.12 0.175

0.251

11.78 0.312

11.59 0.249 11.31 0.256

11.69 0.314

0.273

11.53 0.275

11.53 0.235 11.3 0.327

11.77 0.330

135

Table 6.12: Viscosity of 5 m PZ/5 m 2-PE at 40 °C



0.194

19.70 0.19

19.66 0.05 19.60 0.23

19.68 0.18

0.228

20.06 0.21

20.08 0.08 20.17 0.21

20.01 0.19

0.271

21.23 0.19

21.25 0.15 21.41 0.16

21.12 0.21

0.324

23.24 0.13

23.18 0.19 23.34 0.18

22.97 0.27

0.393

25.02 0.18

24.92 0.09 24.84 0.19

24.90 0.21

0.453

25.70 0.19

25.53 0.32 25.16 0.21

25.73 0.18

0.488

27.87 0.18

27.18 0.60 26.88 0.25

26.80 0.34

0.518

28.29 0.22

28.02 0.30 28.07 0.22

27.69 0.51

136

Table 6.13: Viscosity of 3.5 m PZ/3.5 m Tris at 20 and 40 °C

T CO2 loading µ St. Dev µavg St.Dev

C mol/mol alkalinity cP cP cP cP

20 0.203

11.27 0.11

11.17 0.08 11.12 0.08

11.13 0.05

40 0.203

5.93 0.20

5.86 0.07 5.79 0.15

5.87 0.17

40 0.255

5.80 0.18

5.84 0.04 5.88 0.16

5.85 0.19

40 0.315

6.11 0.18

6.11 0.07 6.18 0.19

6.05 0.16

40 0.349

6.34 0.19

6.34 0.09 6.25 0.19

6.44 0.18

40 0.367

6.77 0.21

6.75 0.04 6.77 0.19

6.71 0.18

6.3 ABSORPTION RATE RESULTS

The CO2 absorption rate into PZ blends was measured using a bench scale WWC

(Chapter 3.1). For each solvent, the liquid film mass transfer coefficient (kg’) of CO2

was measured at 20, 40, 60, 80, and 100 °C. The CO2 loading in the solvent is varied

across the expected operating range for coal flue gas. The kg’ results at 40 °C are used

to compare the rate performance of the solvents in a capture process. The effect of

solvent viscosity, molecular structure, and blend ratio are studied.

137


Figure 6.4: Absorption rate of 6 m PZ/2 m EDA. Empty diamonds: 8 m PZ; empty

squares: 7 m MEA (Dugas 2009). Empty circles: 12 m EDA (Chen 2011).

The kg’ for 6 m PZ/2 m EDA was measured at four CO2 loadings. The results

are plotted in Figure 6.4, and are compared with 8 m PZ, 7 m MEA (Dugas 2009), and 12

m EDA (Chen 2011) at 40 °C. The absorption rate of this blend shows little

temperature dependence between 40 and 60 °C at low loading. At 80 and 100 °C, the

absorption rate is much lower than the rate at low temperature. At the high CO2

loading, the kg’ at 60 °C becomes lower than at 20 and 40 °C. Where this temperature

effect is more apparent at high CO2 loadings and high temperature, it is likely the result

of the diffusion of CO2-amine reactants and products (Dugas 2009). At high

temperature, the CO2 absorption/desorption flux in the WWC column is higher than at

1.E-7

1.E-6

100 1000 10000

k g' (

mo

l/P

a ∙s

∙m2)

PCO2* (Pa)

40 °C

60 °C

80 °C

20 °C

100 °C

8 m PZ @ 40 °C

12 m EDA @ 40 °C

7 m MEA@ 40 °C

138

low temperature, which depletes the free amine at the reaction boundary layer. In this

case, the diffusion of free amine from bulk liquid to the reaction boundary becomes the

limiting phenomena for CO2 mass transfer. At high CO2 loading, the concentration of

free amine is low which is quickly depleted even at low temperature and low CO2 flux.

At these conditions, the diffusion of reactants and products begins to limit the mass

transfer of CO2 even at low temperature.

Compared to the base case solvents, the kg’ of 6 m PZ/2 m EDA is about twice

that of 7 m MEA, and is about the same as 8 m PZ. Compared to its components, the

kg’ of the blend is much more similar to 8 m PZ than 12 m EDA. In other words, the

substitution of part of the PZ with EDA has little effect on its kg’.

Figure 6.5: Absorption rate of 6 m PZ/2 m DAB compared with dashed lines for 8 m PZ

and 7 m MEA at 40 °C (Dugas 2009).

The absorption rate of CO2 in 6 m PZ/2 m DAB was measured at five CO2

loadings, and the results are plotted in Figure 6.4 where they are compared with 8 m PZ

1.E-07

1.E-06

100 1000 10000

k g' (

mo

l/P

a s

m2

)

PCO2*(Pa)

40 °C

60 °C80 °C

20 °C

8 m PZ@ 40 °C

7 m MEA@ 40 °C

139

and 7 m MEA at 40 °C. The kg’ of this blend exhibits temperature dependence starting

at moderate CO2 loading. At 40 °C, the kg’ of 6 m PZ 2 m DAB is slightly lower than 8

m PZ, but is still significantly higher than 7 m MEA.

The absorption rate of 6 m PZ/2 m HMDA is plotted in Figure 6.6, and is

compared with 8 m PZ and 7 m MEA. The kg’ of the blend shows significant

temperature dependence. At 40 °C, the kg’ of 6 m PZ/2 m HMDA is much lower than 8

m PZ. At low CO2 loading, the blend is faster than 7 m MEA. However, as CO2

loading increases, the kg’ of the blend drops and is lower than 7 m MEA beyond 5 kPa.

The low kg’ of this blend is partially determined by the high viscosity of the solvent

(Figure 6.3), which is 50% higher than 8 m PZ.

Figure 6.6: Absorption rate of 6 m PZ/2 m HMDA compared with dashed lines for 8 m

PZ and 7 m MEA at 40 °C (Dugas 2009).

5E-8

5E-7

100 1000 10000

k g' (

mo

l/P

a∙s∙

m2)

PCO2* @ 40 °C (Pa)

40 °C

60 °C

80 °C

100 °C

8 m PZ@ 40 °C

7 m MEA@ 40 °C

140

Figure 6.7: Absorption rate of 6 m PZ/2 m BAE compared with dashed lines for 8 m PZ

(Dugas 2009) and 8 m BAE (Chapter 8) at 40 °C.

The kg’ of 6 m PZ/2 m BAE is shown in Figure 6.7, where it is compared to 8 m

PZ and 8 m BAE at 40 °C. The kg’ of the blend is similar to 8 m PZ and much higher

than 8 m BAE. The absorption rate of the blend varies with temperature between 40-

100 °C. At high CO2 loading, kg’ at 40 °C is much lower than 20 °C, which suggests

rate of CO2 mass transfer at 40 °C is dominated by the rate of diffusion of reactant and

products.

The rate of CO2 absorption in 5 m PZ/5 m DGA® is plotted in Figure 6.8, and is

compared with 8 m PZ and 10 m DGA® (Chen 2011). At low CO2 loading, the kg’ of

this blend decreases with temperature between 60 to 100 C. At moderate CO2 loading,

small temperature dependence is observed between 40 – 60 °C. Between 20 – 40 °C,

The temperature dependence in kg’ only becomes significant at rich loading. Compared

1.E-07

1.E-06

100 1000 10000

k g' (

mo

l/P

a∙s

∙m2)

PCO2* @ 40 °C (Pa)

40 °C

60 °C80 °C

20 °C

8 m PZ@ 40 °C

8 m BAE@ 40 °C

100 °C

141

to 10 m DGA®, the blend has much higher kg’. And the rate of the blend is only

slightly lower than 8 m PZ.

Figure 6.8: Absorption rate of 5 m PZ/5 m DGA®. Dashed lines: 8 m PZ at 40 ˚C

(Dugas 2009). Dotted lines: 10 m DGA® at 40 ˚C (Chen 2011).

The rate of CO2 absorption in 5 m PZ/ 2 m AEP and 6 m PZ/2 m HEP is plotted

in Figure 6.9 and 6.10 respectively. The two blends have similar rate behaviour, where

the kg’ of the blend is higher than the PZ derivative and about the same as 8 m PZ. Both

blends show less temperature dependence than the previous blends. In these two blends,

kg’ does not change between 20 – 60 °C. Significant effect of temperature is only

observed between 80 – 100 °C

1.E-07

1.E-06

100 1000 10000

k g' (

mo

/Pa

s m

2)

PCO2* @ 40 ˚C (Pa)

40 °C

80 °C

60 °C100 °C

20 °C

8 m PZ @ 40 °C

10 m DGA® @ 40 °C

142

Figure 6.9: Absorption rate of 5 m PZ/2 m AEP compared with dashed lines for 8 m PZ,

7 m MEA (Dugas 2009), and 6 m AEP at 40 °C (Chen 2011).

Figure 6.10: Absorption rate of 6 m PZ/2 m HEP. Dashed lines: 8 m PZ at 40 ˚C

(Dugas 2009). Dotted lines: 7.7 m HEP at 40 ˚C (Chen 2011).

1E-7

1E-6

100 1000 10000

k g' (

mo

l/P

a∙m

2∙s

)

PCO2* 40 °C (Pa)

40 °C

60 °C

80 °C

20 °C

8 m PZ@ 40 °C

100 °C

6 m AEP@ 40 °C

1.E-07

1.E-06

100 1000 10000

k g' (

mo

l/P

a s

m2)

PCO2* @ 40 ˚C (Pa)

40 °C

80 °C

60 °C

100 °C

20 °C

8 m PZ @ 40 °C

7.7 m HEP @ 40 °C

143

Figure 6.11: Absorption rate of 5 m PZ/5 m 2-PE. Dashed lines: 8 m PZ at 40 ˚C

(Dugas 2009). Dotted lines: 8 m 2PE at 40 ˚C (Chen 2011).

The measured kg’ for 5 m PZ/5 m 2-PE is plotted in Figure 6.11 and compared

with 8 m PZ (Dugas 2009) and 8 m 2-PE (Chen 2011). Unlike the previous PZ blends,

the kg’ at 40 °C for 5 m PZ/5 m 2-PE is much lower than 8 m PZ, and slightly higher than

8 m 2-PE. The low kg’ for this blend corresponds to a high viscosity of the solvent,

which is around 25 cP and more than twice that of 8 m PZ. This blend also has little

temperature dependence from 40 to 80 °C. At 100 °C, the kg’ is only slightly lower than

other temperatures.

1.E-08

1.E-07

1.E-06

1.E-05

10 100 1000 10000

k g' (

mo

l/P

a s

m2)

PCO2* @ 40 ˚C (Pa)

40 °C

80 °C

60 °C

100 °C

20 °C

8 m PZ @ 40 °C

8 m 2PE @ 40 °C

144

Figure 6.12: Absorption rate of 5 m PZ/2.3 m AMP. Dashed lines: 8 m PZ at 40 °C

(Dugas 2009); dotted lines: 4.8 m AMP at 40 °C.

The kg’ results for 5 m PZ/2.3 m AMP are plotted in Figure 6.12, and are

compared with 8 m PZ and 4.8 m AMP at 40 °C. The kg’ of this blend has little

temperature dependence between 20 and 60 C. The kg’ at 100 °C is much lower than

other temperatures. And the kg’ at 80 °C begins to drop below other temperatures only at

moderate loading. The kg’ of the blend is competitive with 8 m PZ and is much higher

than 4.8 m AMP.

The CO2 absorption rate measured for 3.5 m PZ/3.5 m Tris is plotted in Figure

6.13, and compared with 8 m PZ and 7 m MEA at 40 C. At low CO2 loadings, the 40 C

result for this blend is between 7 m MEA and 8 m PZ. At high CO2 loadings, the 40 C

kg’ is about the same as 8 m PZ. Thus, the kg’ of the blend decreases with CO2 loading

at a lower rate than 8 m PZ. This kg’ of this blend exhibits strong temperature

1.E-07

1.E-06

100 1000 10000

k g' (

mo

l/P

a∙s∙

m2)

PCO2* 40˚C (Pa)

40 °C

60 °C80 °C

20 °C

100 °C

8 m PZ @ 40 ˚C

4.8 m AMP @ 40˚CChen (2011)

145

dependence between 80 and 100 °C at low loading, which extends to 40 °C at high CO2

loadings.

Figure 6.13: Absorption rate of 3.5 m PZ/3.5 m Tris. Dashed line: 8 m PZ at 40 °C;

dotted line: 7 m MEA at 40 °C (Dugas 2009).

In general, the kg’ of PZ blends are competitive with 8 m PZ. The CO2

absorption rate of the blends are typically close to 8 m PZ and much higher than the

second amine in the blend, regardless of the kg’ of the second amine. In the two cases

where the kg’ of the blend is lower than 8 m PZ, the low absorption rate is observed to

correlate with high solvent viscosity. The temperature dependence of kg’ in the PZ

blends varies depending on the solvent. The decrease in kg’ with increase in

temperature is evident of the CO2 mass transfer becoming controlled by the diffusion of

reactants and products into the reaction boundary. This effect is observed at different

CO2 loadings and temperature ranges for different solvents because of the combination of

1.E-07

1.E-06

100 1000

k g' (

mo

l/P

a s

m2)

PCO2* @ 40°C (Pa)

40 °C

80 °C

60 °C

100 °C

20 °C

8 m PZ @ 40 °C

7m MEA@ 40 °C

146

two properties: the viscosity of the solvent and the shape of the CO2 solubility curves (as

shown in Equation 2.54 in Chapter 2.2).

6.3.2 Effect of solvent viscosity

Two of the PZ blends tested in this work have much higher viscosity than other

solvents: 6 m PZ/2 m HMDA and 5 m PZ/5 m 2-PE. The viscosity of the solvent

affects the kg’ (Equation 2.54) of CO2 through the diffusion coefficient of CO2 (DCO2) and

the diffusion coefficient of reactant and products (DR-P). A study by Versteeg and van

Swaaij (1988) suggests, in aqueous amines, DCO2 and DR-P correlates with the viscosity of

the solvent to the 0.8 and 0.6 power respectively (Equation 6.1).

(𝐷𝐶𝑂2𝜇0.8)

𝑎𝑚𝑖𝑛𝑒 𝑠𝑜𝑙𝑣𝑒𝑛𝑡= 𝑐𝑜𝑛𝑠𝑡𝑎𝑛𝑡 = (𝐷𝐶𝑂2𝜇

0.8)𝑤𝑎𝑡𝑒𝑟

(6.1-a)

(𝐷𝑎𝑚𝑖𝑛𝑒𝜇0.6)𝑎𝑚𝑖𝑛𝑒 𝑠𝑜𝑙𝑣𝑒𝑛𝑡 = 𝑐𝑜𝑛𝑠𝑡𝑎𝑛𝑡 ((𝐷𝑎𝑚𝑖𝑛𝑒𝜇

0.6)𝑤𝑎𝑡𝑒𝑟 (6.1-

b)

To quantify the effect of viscosity on kg’, the viscosity normalized kg’ (kg’*) is

used (Equation 6.2).

𝑘𝑔′ ∗ = 𝑘𝑔

′ ∙ (𝜇𝑠𝑜𝑙𝑣

10𝑐𝑃)0.4

=√𝑘2𝐷𝐶𝑂2−10𝑐𝑃𝑎𝑎𝑚𝑖𝑛𝑒

𝐻𝐶𝑂2

(6.2)

To derive the definition for kg’*, first, the PFO (pseudo first order) analytical

expression for kg’ is assumed (Equation 2.42). Next, the DCO2 term in kg’PFO is

substituted with the diffusion coefficient of CO2 at the viscosity of 10 cP (DCO2-10cP) using

Equation 6.1-a. The viscosity of 10 cP was chosen because it is conveniently the

viscosity of 8 m PZ at 40 °C. By this definition, kg’* represents the kg’ of the solvent if

its viscosity is the same as 8 m PZ. This parameter demonstrates the effect of solvent

viscosity on its kg’; also, it can be used to study the effect of other solvent properties on

kg’. This definition of kg’* only accounts for the effect of viscosity on DCO2, and

147

neglects its effect on DR-P. This approximation only becomes problematic when the kg’

data deviates from the PFO regime. In this work, kg’* is only applied to kg’ at 40 °C,

where the PFO assumption is mostly valid.

Figure 6.14: Comparison of 40 °C absorption rate (kg’) and viscosity normalized

absorption rate (kg’*) for 6 m PZ/2 m HMDA and 5 m PZ/5 m 2-PE with 8

m PZ (Dugas 2009).

In Figure 6.14, the kg’ and kg’* are compared for 6 m PZ/2 m HMDA, 5 m PZ/5

m 2-PE, and 8 m PZ at 40 °C. For 6 m PZ/2 m HMDA, the effect of solvent viscosity is

minor in comparison to its deviation in kg’ from 8 m PZ. For 5 m PZ/5 m 2-PE, its kg’*

is about the same as 8 m PZ at low loadings. At rich loadings, the kg’* of 5 m PZ/5 m

2-PE is still much lower than 8 m PZ. For both blends, their high viscosity cannot fully

account for the low kg’. The presence of the second amine contributes to changes in

other solvent properties which lowered the kg’ of the solvent.

1.E-07

1.E-06

100 1000 10000

k g’ (

mo

l/P

a s

m2)

PCO2* (Pa)

Dash lines: kg'Solid lines: kg'* (viscosity normalized at 10 cP)

40 °C

8 m PZ

6 m PZ/2 m HMDA

5 m PZ/5 m 2-PE

148

6.3.3 Effect of amine structure

Figure 6.15: Comparison of CO2 absorption rate at 40 °C for PZ blends with three

primary di-amines of increasing chain length and 8 m PZ (Dugas 2009).

For the PZ blends with EDA, DAB, and HMDA, the absorption rates at 40 °C are

compared in Figure 6.15 with 8 m PZ. These three are all primary alkyl di-amines, with

increase carbon chain length which corresponds to increase in the pKa of both amine

groups on the molecule. The kg’* (Equation 6.2) of 6 m PZ/2 m HMDA is compared

with the kg’ of other solvents, such that all of the solvents are compared at about the same

solvent viscosity. At low loadings, the kg’ of the three blends are all lower than 8 m PZ,

while the differences between the solvents are small. At rich loadings, the kg’ of the

three blends are inversely proportional to the pKa of the second amine. The kg’* of 6 m

PZ/2 m HMDA is lower than the kg’ of all other solvents over the entire loading range of

the experiments.

1.E-07

1.E-06

100 1000 10000

k g' (

mo

l/P

a s

m2)

PCO2* (Pa)

8 m PZ

6 m PZ/2 m EDA

6 m PZ /2 m DAB

6 m PZ /2 m HMDA kg'*

149

Figure 6.16: Comparison of CO2 absorption rates at 40 °C for PZ blends with primary

amines of similar chain length and 8 m PZ (Dugas 2009).

In Figure 6.16, the absorption rates of PZ blends with BAE, DGA®, and HMDA

are compared at 40 C. All three amines are linear molecules, with BAE and DGA®

having the same chain length, and HMDA is one carbon longer than the other two. The

two pKa values of BAE are lower than those of HMDA due to the ether group in the

middle of its carbon chain. The pKa of DGA® is lower than the first pKa of BAE because

of the additional hydroxyl group on DGA®. The kg’* of 6 m PZ/2 m HMDA is lower

than the kg’ of all other solvents. At low loading, the kg’ of the BAE and DGA® blends

are about the same as the HMDA blend. At high loading, the BAE and DGA® have kg’

that is only slight lower than 8 m PZ and is higher than the HMDA blend.

In Figure 6.17, two PZ blends with PZ derivatives are compared with the PZ

derivatives themselves (Chen 2011) and 8 m PZ (Dugas 2009). And the kg’ of the

blends are about the same as 8 m PZ, and much higher than the PZ derivatives.

1.E-07

1.E-06

100 1000 10000

k g' (

mo

l/P

a s

m2)

PCO2* (Pa)

8 m PZ

6 m PZ/ 2 m BAE

6 m PZ/ 2 m HMDAkg'*

5 m PZ /5 m DGA®

150

Figure 6.17: Comparison of CO2 absorption rates at 40 °C for PZ blends with PZ

derivatives and 8 m PZ (Dugas 2009).

In Figure 6.18, the PZ blends with monoamines of different hindrance and pKa are

compared at 40 °C. All of the blends also have equimolar amounts of PZ and the

second amine. The kg’* of the 2-PE and Tris blends is used to compare with the kg’ of

the other solvents to normalize the high viscosity of the 2-PE blend and the low viscosity

of the Tris blend. For the 2-PE blend, the kg’* is about the same as 8 m PZ at low

loading; after which it decreases much faster than other solvents as loading increases.

For the two blends with MDEA and Tris, which both have lower pKa, the kg’ is lower

than 8 m PZ at low loading, but they decrease at a slower rate with loading. At high

loading, the absorption rate of these two blends is about the same as 8 m PZ. The kg’ of

the DGA® blend lies in the middle of the other solvents across the entire loading range of

the experiments.

1.E-07

1.E-06

100 1000 10000

k g' (

mo

l/P

a s

m2)

PCO2* (Pa)

5 m PZ /2 m AEP

6 m PZ/2 m HEP

6 m AEP

7.7 m HEP

8 m PZ

151

Figure 6.18: Comparison of CO2 absorption rates at 40 C for PZ blends with equimolar

mono-amines: 5 m PZ 5 m DGA®, 5 m PZ 5 m 2-PE, 3.5 m PZ 3.5 m Tris, 5

m PZ 5 m MDEA (Chen 2011), and 8 m PZ (Dugas 2009).

The absorption rates of PZ blends with hindered amines are compared in Figure

6.19. The kg’ of all three blends are lower than 8 m PZ at 40 °C. The kg’of 5 m PZ/2.3

m AMP and the Tris blend are lower than 8m PZ a low loading, but about the same as PZ

at high loading. The blend with 2-PE has absorption rate with the opposite trend, where

it is about the same as 8 m PZ, but is much less than PZ at high loading.

1.E-07

1.E-06

100 1000 10000

k g' (

mo

l/P

a s

m2)

PCO2* (Pa)

5 m PZ /5 m MDEA

8 m PZ

5 m PZ /5 m 2-PE: kg'*

3.5 m PZ/ 3.5 m Tris: kg'*

5 m PZ/ 5 m DGA®

152

Figure 6.19: Comparison of CO2 absorption rate at 40 °C for PZ blends with hindered

amines and 8 m PZ (Dugas 2009)

6.3.4 Effect of blend ratio

The PZ and amine ratio was varied in the blend of PZ/AMP (2013) and

PZ/MDEA (Chen 2011). The kg’ of four blends are compared in Figure 6.20. For the

PZ/MDEA blends, higher PZ relative MDEA increases the kg’ at low and mid loading.

For the PZ/AMP blends, the opposite is observed, where the blend with lower PZ

concentration has slightly higher kg’ at low loading.

1.E-07

1.E-06

100 1000 10000

k g' (

mo

l/P

a s

m2)

PCO2* (Pa)

5 m PZ/ 5 m 2-PE: kg'*

3.5 m PZ/ 3.5 m Tris: kg'*

5 m PZ /2.3 m AMP

8 m PZ

153

Figure 6.20: Comparison of CO2 absorption rate at 40 °C at different PZ-amine ratios for

PZ blends with AMP (Li 2013) and MDEA (Chen 2011).

6.3.5 Performance in an absorber

The kg’ data at 40 °C are used to estimate the overall mass transfer rate of each

solvent in an absorber column for coal flue gas (kg’avg) using Equation 4.6. The

calculated kg’avg and its corresponding packing area required (Ap/Vg, Equation 4.8) are

summarized in Table 6.14. The same kg’avg is calculated using kg’* (Equation 6.2) to

estimate the effect of solvent viscosity on the overall performance of the solvent in a

column. Results of 8 m PZ, 7 m MEA, and other PZ blends also tested using the same

WWC method are also included for comparison.

1.E-07

1.E-06

1.E-05

100 1000 10000

k g' (

mo

l/P

a s

m2)

PCO2* (Pa)

8 m PZ

2 m PZ/4 m AMP

5 m PZ/2.3 m AMP

5 m PZ/5 m MDEA

2 m PZ/7 m MDEA

154

Table 6.14: Absorption rate performance of concentrated PZ blends for coal flue gas

conditions, compared with literature results of other PZ blends

Solvent kg’ avg (40 °C) kg’*avg Ap/Vg Amine Type Source

m x 107 mol/Pa s m2 x103 m2/(m3/s)

6 m PZ/2 m EDA 8.6 8.5 1.7

Primary

diamine

This work

6 m PZ/2 m DAB 7.1 7.5 2.1

6 m PZ/2 m HMDA 4.9 5.8 3.1

6 m PZ/2 m BAE 7.3 7.8 2.1

5 m PZ/5 m DGA® 6.7 7.1 2.2 Primary

6 m PZ/2 m HEP 8.7 9.4 1.7 PZ derivative

5 m PZ/2 m AEP 8.1 9.0 1.8

5 m PZ/5 m 2-PE 4.2 6.2 3.6 Hindered

secondary

5 m PZ/2.3 m AMP 7.5 7.6 2.0 Hindered

Primary 2 m PZ/4 m AMP 8.3 6.7 1.8 Li (2013)

3.5 m PZ/3.5 m Tris 7.4 6.1 2.0 This work

5 m PZ/5 m MDEA 8.5

/

1.8 Tertiary

Chen

(2011)

2 m PZ/7 m MDEA 7.2 2.1

4 m PZ/4 m 2MPZ 7.1 2.1 PZ derivative

3.75 m PZ/ 3.75 m 1MPZ / 0.5 m 1,4DMPZ 8.5 1.8

2 m PZ/7 m MEA 6.9 2.2 Primary Dugas

(2009) 8 m PZ 8.5 8.7 1.8

/ 7 m MEA 4.3 / 3.5

In Figure 6.21, the kg’avg* of four PZ blends with primary di-amines are compared

as a function of the second pKa of the di-amine. The lower pKa of the two is used in this

comparison because at the corresponding CO2 loading, it is the second pKa of the amine

which could affect the reaction with CO2. And the absorption rate of the solvent at

process conditions is inversely proportional to the effective pKa of the second amine.

155

Figure 6.21: CO2 absorption rates as functions of the lower pKa of the second amine for

PZ blends with long chain primary di-amines: 6 m PZ/2 m HMDA, 6 m

PZ/2 m DAB, 6 m/2 m BAE, 6 m PZ/2 m EDA.

6.4 CO2 SOLUBILITY

The CO2 solubility in the PZ blends was measured in the WWC at low

temperatures: 20, 40, 60, 80, and 100 °C. The CO2 loading in the solvent was varied

across the expected operating conditions for coal flue gas. For 6 m PZ/2 m EDA, 6 m

PZ/2 m DAB, and 6 m PZ/2 m BAE, a total pressure apparatus (Chapter 3.2) was used to

measure the CO2 solubility in the solvent at high temperatures (100 – 160 °C). For 6 m

PZ/2 m HMDA, 5 m PZ/2 m AEP, and 5 m PZ/2.3 AMP, high temperature data collected

using the same total pressure method are available in literature by Namjoshi et al. (2013),

Du et al. (2013), and Li et al. (2013) respectively. The experimental CO2 VLE data for

PZ blends are summarized in Table 6.16-6.28.

5

6

7

8

9

6 7 8 9 10

kg'*

avg

x10

7m

ol/

Pa

s m

2)

2nd pKa at 40 °C

6 m PZ/2 m HMDA

6 m PZ/2 m DAB

6 m PZ/2 m EDA

6 m PZ/2 m BAE

156

For each solvent, a semi-empirical CO2 VLE model is calculated by regressing all

of the available VLE data using Equation 4.4. The regressed model parameters for each

solvent are summarized in Table 6.15. The model can be used to interpolate within the

experimental temperatures and CO2 loadings, and extrapolate near the experimental

conditions. The CO2 solubility curve at 40 °C is used to estimate the operating CO2

loading range, solvent capacity, and heat of absorption of each solvent.

6.4.1 CO2 VLE data

Figure 6.22: CO2 solubility in 6 m PZ/2 m EDA. Diamond: WWC; filled circles: total

pressure. Solid lines: empirical model (Table 6.15). Dashed line: semi-

empirical model of 8 m PZ (Xu 2011). Dotted line: semi-empirical model of

12 m EDA; empty circles: WWC for 12 m EDA (Chen 2011).

The CO2 solubility data by the WWC and total pressure apparatus are shown

together in Figure 6.22. The two sets of VLE results agree well with each other, and the

1.E+01

1.E+02

1.E+03

1.E+04

1.E+05

1.E+06

0.28 0.33 0.38 0.43

PC

O2*

(Pa)


40 °C

60 °C

80 °C

20 °C

100 °C

120 °C

140 °C

PZ @ 40 °C

160 °C

12 m EDA@ 40 °C

157

semi-empirical model shows a good fit over the entire experimental range. Compared to

PZ and 12 m EDA, the 40 °C solubility curve of the blend lies between the two amines

and is closer to PZ, which corresponds to the higher concentration of PZ in the blend.

Figure 6.23: CO2 solubility in 6 m PZ/2 m DAB. Diamonds: WWC results; Circles: total

pressure results; Solid lines: model prediction (Table 6.15); Dashed lines:

model for 8 m (Xu 2011).

The CO2 solubility measurement by the WWC and total pressure apparatus are

plotted in Figure 6.23. The high temperature results by the total pressure show slight

scatter. The semi-empirical model regressed using both sets of data fits the WWC data

at low CO2 loadings and fits the total pressure data at high loadings. The model under

predicts the WWC data at 0.35-0.42 CO2 loading and 40 – 80 °C, which is because more

total pressure data were used to regress the model. Thus, the model is biased to the

trend of the total pressure data as the two sets of data showed different temperature

dependence for this solvent. Nonetheless, the overall fit of the model is satisfactory,

1E+1

1E+2

1E+3

1E+4

1E+5

1E+6

0.28 0.33 0.38 0.43 0.48

PC

O2*

(Pa)


40 °C

60 °C

80 °C

100 °C

140 °C

120 °C

160 °C

20 °C

PZ

PZ

158

with a high R2 of 0.992. Compared with PZ, the CO2 solubility in the blend is slightly

higher due to the higher pKa of DAB.

Figure 6.24: CO2 solubility in 6 m PZ/2 m HMDA. Diamonds: WWC results; Circles:

total pressure results (Namjoshi et al. 2013); Solid lines: model prediction (Table 6.15); Dashed lines: model for 8 m PZ at 40 and 160 °C (Xu 2011).

The CO2 solubility data for 6 m PZ 2 m HMDA by the WWC are compared with

total pressure results by Namjoshi et al. (2013) in Figure 6.24. The two sets of data

show good agreement, and the semi-empirical model fits both sets of experimental data

well. Compared to PZ at 40 °C, the CO2 solubility in the blend is higher, which is a

result of the higher pKa of HMDA.

The CO2 solubility was measured for 6 m PZ/2 m BAE using the WWC and the

total pressure apparatus (Figure 6.25). The two sets of experimental results agree well

1E+2

1E+3

1E+4

1E+5

1E+6

0.32 0.37 0.42 0.47

PC

O2*(

Pa)


40 °C

60 °C

80 °C

100 °C

140 °C

120 °C

160 °C

PZ @ 40 °C

PZ @ 160 °C

159

with each other, and the semi-empirical model fits the data over the entire experimental

range. The CO2 solubility of the blend is similar to PZ between 40 and 160 °C, with a

slightly enhanced solubility in the blend at 40 °C. Compared to 8 m BAE, the solubility

of CO2 in the blend is greatly reduced.

Figure 6.25: CO2 solubility in 6 m PZ/2 m BAE. Diamonds: WWC results; Circles: total

pressure results; Solid lines: model prediction (Table 6.15); Dashed lines:

model for 8 m PZ (Xu 2011). Dotted lines: model for 8 m BAE; empty

circles: WWC data for 8 m BAE (Chapter 8).

For 5 m PZ/5 m DGA®, CO2 solubility was only measured using the WWC at low

temperatures, and the results are plotted in Figure 6.26. The WWC data show good

internal consistency, and the semi-empirical model fits the data over the entire

experimental range. Compared with PZ, the CO2 solubility in the blend at 40 °C is

1.E+01

1.E+02

1.E+03

1.E+04

1.E+05

1.E+06

0.3 0.32 0.34 0.36 0.38 0.4 0.42

PC

O2*

(Pa)


40 °C

60 °C

80 °C

100 °C

140 °C

120 °C

160 °C

20 °C

PZ @ 40 °C

8 m BAE @ 40 °C

160

enhanced at low CO2 loading and reduced at high loading. The solubility of CO2 is

much lower in the blend than 10 m DGA® (Chen 2011).

Figure 6.26: CO2 solubility in 5 m PZ/5 m DGA®. Diamond: WWC results. Solid lines:

empirical model (Table 6.15). Dashed line: empirical model of PZ at 40 ˚C

(Xu 2011). Dotted line: 10 m DGA® at 40 ˚C (Chen 2011).

The CO2 solubility in 5 m PZ/2 m AEP was measured using the WWC, which is

plotted in Figure 6.27 and compared with total pressure results by Du et al. (2013). The

WWC and total pressure results show good agreement over the entire experimental CO2

loading range. The semi-empirical model fits both sets of data well. Compared with

PZ, CO2 is slightly less soluble in the blend at both 40 and 160 °C.

For 6 m PZ/2 m HEP, 5 m PZ/5 m 2-PE, and 3.5 m PZ/3.5 m Tris, CO2 solubility

was measured using the WWC at low temperatures only. The results are shown in

Figure 6.28, 6.29, and 6.31, respectively. For all three solvents, the WWC data show

good internal consistencies and the semi-empirical model match the data well. For 6 m

100

1000

10000

100000

0.3 0.35 0.4 0.45

PC

O2*

(Pa)


40 °C

80 °C

60 °C

100 °C

20 °C

PZ @ 40 °C

10 m DGA@ 40 °C

161

PZ/2 m HEP, the 40 C solubility curve lies between PZ and 7.7 m HEP (Chen 2011).

For 5 m PZ/5 m 2-PE, the CO2 solubility at high CO2 loading is higher than PZ due to the

high CO2 solubility of 2-PE. The CO2 solubility in 3.5 m PZ/3.5 m Tris is much lower

than PZ, due to the low pKa of Tris. However, solubility in the blend decreases much

slower than PZ with increase in CO2 loading (solubility curve has a lower slope), as

characteristic of Tris being a hindered amine.

Figure 6.27: CO2 solubility in 5 m PZ/2 m AEP. Diamonds: WWC results; Circles: total

pressure results (Du et al. 2013); Solid lines: semi-empirical model result (Table 6.15); Dashed lines: model for 8 m PZ at 40 and 160 °C (Xu 2011).

1E+1

1E+2

1E+3

1E+4

1E+5

1E+6

0.24 0.29 0.34 0.39

PC

O2*

(Pa)


40 °C

60 °C

80 °C

100 °C

140 °C

120 °C

160 °C

20 °C

PZ @ 40 °C

162

Figure 6.28: CO2 solubility in 6 m PZ/2 m HEP. Diamond: WWC results. Solid lines:

empirical model (Table 6.15). Dashed line: empirical model of PZ at 40 °C (Xu 2011); dotted line: semi-empirical model for 7.7 m HEP at 40 °C

(Chen 2011)

Figure 6.29: CO2 solubility in 5 m PZ/5 m 2PE. Diamond: WWC results. Solid lines:

empirical model (Table 6.15). Dashed line: empirical model of PZ (Xu

2011), dotted line: empirical model of 8 m 2-PE (Chen 2011).

10

100

1000

10000

100000

0.23 0.28 0.33 0.38

PC

O2

(Pa)


40 °C

80 °C

60 °C

100 °C

20 °CPZ @ 40 °C

7.7 m HEP@ 40 °C

10

100

1000

10000

100000

0.17 0.27 0.37 0.47

PC

O2*

(Pa)


40 °C

80 °C

60 °C

100 °C

20 °CPZ @ 40 °C

8 m 2-PE@ 40 °C

163

Figure 6.30: CO2 solubility of 5 m PZ/2.3 m AMP. Diamonds: WWC; square: total

pressure apparatus (Li et al. 2013). Dashed lines: semi-empirical model for PZ at 40 °C (Xu 2011); dotted line: semi-empirical model for 4.8 m AMP at

40 °C (Chen 2011)

The CO2 solubility results measured by the WWC for 5 m PZ/2.3 m AMP are

shown together with total pressure results (Li et al. 2013) in Figure 6.30. The two sets

of measurements agree well with each other, and the semi-empirical model fits both sets

of data. Compared to PZ, the 40 C solubility curve for the blend is slightly enhanced.

The slope of the solubility curve for the blend is about the same as PZ, and much steeper

than 4.8 m AMP (Chen 2011). The overall CO2 solubility behavior of the blend is more

similar to PZ because of the low AMP concentration, which reduced its effect on the

blend.

1.E+01

1.E+02

1.E+03

1.E+04

1.E+05

1.E+06

1.E+07

0.27 0.32 0.37 0.42 0.47

PC

O2

(Pa)


40 °C

60 °C

80 °C100 °C

140 °C

120 °C

160 °C

20 °C

164

Figure 6.31: CO2 solubility of 3.5 m PZ/3.5 m Tris. Solid curves: semi-empirical model

result (Table 6.15). Dashed line: 8 m PZ at 40 °C (Xu 2011).

Table 6.15: Parameter values for the semi-empirical VLE model for PZ blends

ln(𝑃𝐶𝑂2∗ ) = 𝑎 +

𝑏

𝑇(𝐾)+ 𝑐 ∙ 𝑙𝑑𝑔 + 𝑑 ∙ 𝑙𝑑𝑔2 + 𝑒 ∙

𝑙𝑑𝑔

𝑇(𝐾)+ 𝑓 ∙

𝑙𝑑𝑔2

𝑇(𝐾) :

(m) PZ /(m) Am a b x 10-3 c d e x 10-3 f x 10-3 R2

6 / 2 EDA 47.3±1.7 -16.89±0.64 -36.2±4.3 / 22.58 ±1.654 / 0.998

6 / 2 DAB 41.2 ± 4.1 -16.40 ± 1.23 -27.3 ± 10.4 0 30.30 ± 4.31 -1.64 ± 0.66 0.992

6 / 2 HMDA 0 0 230.1±8.1 -368.1±21.0 -72.49±2.90 13.10 ± 0.00 0.9998

6 / 2 BAE 0 0 189.7±6.8 -263.5±18.1 -56.67 ± 2.39 9.19 ± 0.64 0.9998

5 / 5 DGA® 0 2.93±0.87 183.6±11.1 -210.2±29.4 -71.49 ± 3.98 9.84 ± 0.78 0.9999

5 / 2 AEP 58.3±12.3 -17.59 ± 4.18 -138.2 ± 80.7 200.2 ± 131.4 42.83 ± 27.31 -4.73 ± 4.41 0.9984

6 / 2 HEP 0 3.46 ± 0.87 219.4 ± 15.7 -328.9 ± 49.6 -86.11 ± 5.44 14.52 ± 1.39 0.9949

5 / 2.3 AMP 23. 9± 6.6 -6.58 ± 2.53 88.5 ± 35.6 -160 ± 47 -28.17 ± 13.52 6.07 ± 1.79 0.999

2 / 4 AMP 31.4 ± 4.2 -8.65 ± 1.56 32.4 ± 23.1 -55.9 ± 30.9 -9.56 ± 8.36 2.28 ± 1.10 0.999

5 / 5 2-PE 18.7 ± 7.3 -4.52 ± 2.43 131 ±45 -206 ± 63 -44.55 ± 14.88 7.74 ± 2.09 0.9924

3.5 / 3.5 Tris 33.3 ± 1.7 -9.42 ± 0.35 10.4 ± 5.4 / / 0.40 ± 0.31 0.9931

100

1000

10000

100000

0.18 0.23 0.28 0.33 0.38

PC

O2*

(Pa)


40 °C

80 °C

60 °C

100 °C

20 °C8 m PZ @ 40 °C

165

Table 6.16: CO2 solubility and absorption rates for 6 m PZ/2 m EDA by the WWC

T ldg PCO2* kg'

˚C mol/mol kPa Х107 mol/Pa s m2

20 0.376 0.16 11.2

20 0.409 0.52 7.8

20 0.435 1.74 3.8

40 0.335 0.24 23.4

40 0.376 1.14 11.9

40 0.415 3.99 6.8

40 0.436 11.40 3.5

60 0.335 1.35 24.3

60 0.376 6.86 11.5

60 0.411 19.74 4.9

80 0.335 7.82 18.3

80 0.376 27.31 7.6

100 0.335 30.43 11.3

Table 6.17: CO2 solubility for 6 m PZ/2 m EDA at high temperature by the total pressure

apparatus

T ldg PCO2 Pmeas Ptotal T ldg PCO2* Pmeas Ptotal

˚C mol/mol kPa kPa kPa ˚C mol/mol kPa kPa kPa

100 0.388 74 283 162 130 0.383 433 797 669

100 0.406 160 376 249 130 0.398 796 1143 1032

100 0.447 435 652 523 130 0.435 1352 1718 1588

110 0.344 61 309 186 140 0.301 187 642 503

110 0.387 153 400 279 140 0.340 350 802 666

110 0.404 327 557 452 140 0.380 672 1120 988

110 0.444 678 928 804 140 0.394 1144 1586 1459

120 0.303 42 351 216 140 0.430 1810 2263 2125

120 0.343 102 409 276 150 0.299 330 889 746

120 0.385 257 557 430 150 0.337 574 1130 990

120 0.402 498 805 671 150 0.376 1016 1567 1432

120 0.440 973 1282 1146 150 0.388 1608 2153 2023

130 0.302 102 472 338 160 0.296 558 1246 1100

130 0.342 203 568 439 160 0.333 900 1583 1441

160 0.370 1474 2152 2014

166

Table 6.18: CO2 solubility and absorption rates in 6 m PZ/2 m DAB by the WWC

T αCO2 PCO2* kg' Х107

°C mol/mol kPa (mol/s∙Pa∙m2)

20

0.372 0.24 9.4

0.398 0.64 5.9

0.425 1.75 3.9

40

0.300 0.11 30.0

0.351 0.72 12.3

0.372 1.51 10.5

0.398 3.57 5.2

0.425 11.66 2.4

60

0.300 0.92 30.0

0.351 4.55 9.4

0.372 7.94 6.8

0.398 19.81 3.5

80

0.300 3.68 24.8

0.351 19.77 7.2

0.372 37.21 3.5

Table 6.19: CO2 solubility for 6 m PZ/2 m DAB at high temperatures by the total

pressure apparatus

2nd experiment 1st experiment

T Loading Pmeas Ptotal PCO2* T Loading Pmeas Ptotal PCO2*

˚C mol/mol alk kPa kPa kPa ˚C mol/mol alk kPa kPa kPa

130 0.367 527 446 210 130 0.363 574 434 199

140 0.366 740 629 314 140 0.360 832 689 375

150 0.363 1080 966 551 150 0.357 1216 1069 656

160 0.359 1530 1413 874 160 0.352 1727 1577 1040

110 0.421 467 362 236 110 0.409 398 275 150

120 0.419 665 533 359 120 0.408 554 422 249

130 0.416 965 853 617 130 0.406 798 669 434

140 0.412 1371 1245 928 140 0.402 1126 990 676

150 0.406 1888 1759 1343 150 0.398 1581 1442 1028

160 0.400 2554 2422 1881 160 0.392 2171 2028 1491

100 0.471 564 437 349 100 0.418 400 271 183

110 0.467 820 728 603 110 0.416 584 455 331

120 0.464 1160 1027 853 120 0.413 830 693 521

130 0.458 1597 1500 1264 130 0.409 1189 1054 819

140 0.453 2135 2016 1700 140 0.405 1653 1512 1198

150 0.399 2261 2117 1703

100 0.459 429 302 214

110 0.456 654 574 449

120 0.453 948 814 641

130 0.448 1344 1260 1025

140 0.443 1857 1744 1429

150 0.436 2489 2373 1959

167

Table 6.20: CO2 solubility and absorption rates for 6 m PZ/2 m HMDA by the WWC

T CO2 loading P*CO2 kg' Х107 °C mol/mol (kPa) (mol/s∙Pa∙m2)

40

0.35 0.28 13.6

0.40 1.19 8.7

0.43 5.11 2.6

0.46 18.2 0.78

60

0.35 1.82 15.1

0.40 7.82 6.3

0.43 28.7 1.4

80 0.35 9.18 12.9

0.40 35.7 4.0

100 0.35 35.5 8.1

Table 6.21: CO2 solubility and absorption rates for 6 m PZ/2 m BAE by the WWC

T CO2 loading kg' PCO2

˚C mol/mol alk Х107 (mol/s∙Pa∙m2) kPa

20 0.333 17.2 0.072

20 0.362 13.4 0.128

20 0.392 7.79 0.385

20 0.42 4.14 1.527

40 0.305 23.4 0.262

40 0.333 16.2 0.509

40 0.362 11.1 1.196

40 0.392 6.89 3.519

40 0.42 2.31 15.75

60 0.305 18.2 1.958

60 0.333 17 3.355

60 0.362 8.86 8.729

60 0.392 3.77 21.84

80 0.305 15 9.523

80 0.333 9.89 16.17

80 0.362 5.16 37.92

100 0.305 11.5 36.72

168

Table 6.22: CO2 solubility for 6 m PZ/2 m BAE at high temperatures by the total pressure

apparatus

T CO2 ldg PCO2 Raw Data Sample analysis

Pmeas Ptot CO2 Alkalinity CO2 ldg

(°C) mol/mol kPa kPa kPa mol/kg mol/kg mol/mol

130 0.339 223 598 460

2.71 7.91 0.343 140 0.338 372 841 690

150 0.334 635 1208 1053

160 0.330 995 1697 1538

110 0.357 120 373 246

2.84 7.90 0.359

120 0.356 207 516 382

130 0.354 379 750 616

140 0.351 609 1065 926

150 0.346 955 1515 1373

160 0.341 1418 2106 1961

100 0.396 169 391 257

3.23 8.11 0.399

110 0.394 320 577 444

120 0.392 518 831 691

130 0.388 827 1201 1062

140 0.383 1221 1680 1535

150 0.377 1745 2308 2159

100 0.428 476 694 565

3.34 7.66 0.435

110 0.423 820 1009 946

120 0.419 1099 1410 1273

130 0.412 1598 1902 1836

140 0.406 2077 2500 2394

169

Table 6.23: CO2 solubility and absorption rates for 5 m PZ/5 m DGA® by the WWC

CO2 ldg T PCO2* kg' Х 107

mol/mol alk ˚C kPa mol/Pa s m2

0.382 20 0.21 7.99

0.420 20 0.82 3.92

0.443 20 2.81 2.08

0.321 40 0.29 17.59

0.353 40 0.66 13.36

0.382 40 2.04 7.65

0.420 40 7.05 3.29

0.443 40 25.51 1.12

0.321 60 2.21 18.20

0.353 60 5.00 11.25

0.382 60 11.40 6.60

0.420 60 44.80 1.97

0.321 80 10.25 13.56

0.353 80 24.75 6.55

0.382 80 69.17 2.61

0.321 100 51.74 6.71

170

Table 6.24: CO2 solubility and absorption rates of 5 m PZ/2 m AEP by the WWC

T CO2 loading kg' PCO2


20 0.288 21.70 0.054

20 0.328 13.20 0.165

20 0.360 7.38 0.505

20 0.386 4.35 1.854

40 0.251 32.70 0.16

40 0.288 20.60 0.365

40 0.328 12.90 1.109

40 0.360 6.84 3.763

40 0.386 4.01 10.08

60 0.251 28.50 0.907

60 0.288 20.20 2.201

60 0.328 10.90 7.075

60 0.360 6.62 17.54

60 0.386 2.53 44.81

80 0.251 29.40 4.505

80 0.288 16.30 10.20

80 0.328 7.73 28.99

100 0.251 15.40 19.65

100 0.288 8.17 42.43

171

Table 6.25: CO2 solubility and absorption rates of 5 m PZ/2.3 m AMP by the WWC

T CO2 loading kg’ PCO2


20 0.35 12.90 0.093

20 0.38 9.53 0.229

20 0.42 5.19 0.676

20 0.45 2.62 2.963

40 0.31 18.90 0.325

40 0.35 12.60 0.844

40 0.38 10.01 2.204

40 0.42 5.62 5.325

40 0.45 2.36 17.62

60 0.31 17.10 2.742

60 0.35 13.00 5.979

60 0.38 9.16 11.46

60 0.42 4.56 26.45

80 0.31 18.20 11.15

80 0.35 10.10 27.78

80 0.38 5.69 49.17

100 0.31 6.59 59.91

172

Table 6.26: CO2 solubility and absorption rates for 6 m PZ/2 m HEP by the WWC



0.312 20 0.11 10.82

0.344 20 0.30 8.45

0.358 20 0.62 7.39

0.371 20 1.51 4.11

0.251 40 0.25 23.05

0.273 40 0.46 19.77

0.309 40 1.04 12.17

0.341 40 2.18 9.08

0.358 40 4.98 5.98

0.373 40 10.08 3.60

0.250 60 1.38 28.39

0.276 60 2.79 20.94

0.313 60 5.92 12.42

0.340 60 11.08 8.91

0.358 60 22.29 4.99

0.250 80 6.36 24.97

0.273 80 12.02 17.86

0.309 80 25.26 8.37

0.251 100 25.51 12.01

173

Table 6.27: CO2 solubility and absorption rates for 5 m PZ/5 m 2-PE by the WWC

CO2 loading T PCO2 kg' Х 107


0.488 20 0.61 2.97

0.518 20 3.27 0.94

0.194 40 0.03 41.52

0.228 40 0.05 32.47

0.271 40 0.08 30.69

0.324 40 0.17 22.10

0.393 40 0.45 11.81

0.453 40 1.43 5.87

0.488 40 4.86 2.46

0.518 40 19.29 0.57

0.194 60 0.24 41.01

0.228 60 0.37 38.60

0.271 60 0.61 27.20

0.324 60 1.19 20.90

0.393 60 3.23 12.60

0.453 60 8.75 5.62

0.488 60 25.22 2.12

0.194 80 1.31 52.80

0.228 80 2.46 39.23

0.271 80 3.70 27.95

0.324 80 7.71 18.57

0.393 80 19.14 8.93

0.453 80 39.05 3.86

0.194 100 7.54 34.55

0.228 100 11.98 19.10

0.271 100 16.84 16.00

0.324 100 30.22 11.50

174

Table 6.28: CO2 solubility and absorption rates for 3.5 m PZ/3.5 m Tris by the WWC



0.315 20 0.30 7.58

0.349 20 0.58 6.49

0.367 20 0.97 4.64

0.203 40 0.33 14.50

0.255 40 1.04 10.40

0.315 40 2.29 8.99

0.349 40 4.40 5.33

0.367 40 7.19 4.34

0.203 60 1.88 16.79

0.255 60 5.67 9.56

0.315 60 12.49 5.94

0.349 60 22.73 3.79

0.367 60 40.92 2.89

0.203 80 8.00 12.20

0.255 80 24.99 6.25

0.315 80 48.00 3.62

0.203 100 46.70 5.76

6.4.2 Effect of structure

The CO2 solubility behavior at 40 °C determines the operating loading range of a

solvent in a capture process, and ultimately the cyclic capacity of the solvent. The

variation in CO2 solubility between different amine solvents is determined by the

differences in chemical equilibrium of the amine-CO2 reactions, and, to a lesser extent,

the ionic environment of the solvent. The chemical equilibrium of amine-CO2 reactions

is determined by the molecular structure of the amine, as the steric hindrance of amine

group affects the carbamate stability constant, and the electronegativities of various

functional groups affects the pKa of the amine groups.

175

Figure 6.32: CO2 solubility at 40 °C for PZ blends with primary di-amines, compared to 8

m PZ, 7 m MEA (Xu 2011), and 12 m EDA (Chen 2011).

The CO2 solubility curves for the PZ blends with primary alkyl di-amines are

shown in Figure 6.32, where they are compared to PZ, MEA, and 12 m EDA. At the

same PCO2* range of 0.5 – 5 kPa, the solubility of CO2 is higher in the blends than in PZ.

The presence of the primary di-amines enhanced the solubility of CO2 as they are added

to PZ. Compared to 12 m EDA and MEA, the CO2 solubility in the blends is

significantly reduced, which corresponds to lower CO2 loading at the same PCO2*. The

CO2 solubility curves of the blends lies in between that of PZ and the second amine.

The CO2 loading range that corresponds to the operation loading range of 0.5 and 5 kPa

directly affects the kg’ of the solvent, as at higher loading less free amine is available for

absorption of CO2. The slopes of the solubility curves for the PZ blends are increased

from PZ, which corresponds to a reduction in the corresponding cyclic loading of the

solvent.

500

5000

0.3 0.35 0.4 0.45 0.5 0.55

PC

O2*

(Pa)


PZ

MEA

12 m EDA

6 m PZ/2 m HMDA

6 m PZ/2 m EDA

6 m PZ/2 m DAB

176

Figure 6.33: CO2 solubility at 40°C in PZ blends with primary amines of similar chain

length, compared with 8 m PZ, 7 m MEA (Xu 2011), 8 m BAE (Chapter 8)

and 10 m DGA® (Chen 2011).

In Figure 6.33, the CO2 solubility for three PZ blends with primary amines of

similar chain length are compared at 40 °C. The main difference in structure between 6

m PZ/2 m BAE and 6 m PZ/2 m HMDA is the ether group on BAE, which lowered both

pKa of BAE from that of HMDA. As the result, the CO2 solubility in 6 m PZ/2 m BAE

is much lower than 6 m PZ/2 m HMDA. Also, at the same PCO2*, the corresponding

CO2 loading in the BAE blend is lower than that of the HMDA blend. The solubility of

CO2 in 6 m PZ/2 m BAE and 5 m PZ/5 m DGA® is similar, even though the pKa of BAE

and DGA® differs by about 1. Compared to the solubility curves for 10 m DGA® and 8

m BAE, which are similar with each other, the solubility in the corresponding blends is

lower and much closer to PZ.

500

5000

0.3 0.35 0.4 0.45 0.5 0.55

PC

O2*

(Pa)


8 m PZ

7 m MEA

6 m PZ/2 m HMDA

10 m DGA®

5 m PZ/5 m DGA®

6 m PZ/2 m BAE

8 m BAE

177

Figure 6.34: CO2 solubility at 40° C in PZ blends with PZ derivatives, compared to8 m

PZ (Xu 2011), 7.7 m HEP, and 6 m AEP (Chen 2011).

The CO2 solubility in 5 m PZ/2 m AEP and 6 m PZ/2 m HEP is compared at 40

°C in Figure 6.34. The solubility curves of the blends lies between that of PZ and the

second amine.

In Figure 6.35, the CO2 solubility in PZ blends with hindered amines are plotted

with PZ and the hindered amine solvents. Hindered amines have CO2 solubility

behavior relative to unhindered primary and secondary amines, where the PCO2* varies

with CO2 loading at a lower rate. Thus, the cyclic loading corresponding to the same

operation range of 0.5 and 5 kPa is much higher for hindered amines. When blended

with PZ, in some case of 3.5 m PZ/3.5 m Tris and 2 m PZ/4 m AMP, the hindered amine

significantly changed the slope of the solubility curve of PZ and enhanced the cyclic

loading of the solvent. For 5 m PZ/2.3 m AMP and 5 m PZ/5 m 2-PE, the CO2

500

5000

0.1 0.2 0.3 0.4

PC

O2*

(Pa)


8 m PZ

5 m PZ/2 m AEP

6 m PZ/2 m HEP

6 m AEP

7.7 m HEP

178

solubility curve of the blend is about the same as PZ. For all hindered amine blends, the

CO2 loading range increases with the pKa of the hindered amine.

Figure 6.35: CO2 solubility at 40 °C for PZ blends with hindered amines, compared with

8 m PZ (Xu 2011), 4.8 m AMP, and 8 m 2-PE (Chen 2011).

6.4.3 Effect of blend ratio

For PZ blends with hindered and tertiary amines, the effect of PZ and amine ratio

is studied with PZ/AMP and PZ/MDEA systems. For PZ/MDEA, CO2 VLE data was

collected by Chen (2011) and Xu (2011) at two concentrations of 5 m PZ/5 m MDEA and

2 m PZ/7 m MDEA. For the PZ/AMP blend, the result of 5 m PZ/2.3 m AMP is

compared with 2 m PZ/4 m AMP (Li 2013). For both PZ/MDEA and PZ/AMP,

increasing the relative concentration of the second amine increased the cyclic loading of

the blend.

500

5000

0.2 0.3 0.4 0.5 0.6 0.7

PC

O2*

(Pa)


8 m PZ

8 m 2-PE4.8 m AMP

2 m PZ/4 m AMP (Li 2013)

5 m PZ/5 m 2-PE

5 m PZ/2.3 m AMP

3.5 m PZ/3.5 m Tris

179

Figure 6.36: Comparison of CO2 solubility at 40 °C of PZ blends with AMP and MDEA

with different PZ-amine ratio

Overall, the CO2 solubility of the concentrated PZ blends is only slightly affected

by the second amine. For PZ blends with primary di-amines, and PZ derivatives, the

cyclic loading of the blend is reduced from PZ. Only for two PZ/hindered amine

blends, 3.5 m PZ/3.5 m Tris and 2 m PZ/4 m AMP, the cyclic loading of the blend is

significantly enhanced by the second amine.

6.4.4 CO2 Capacity

The cyclic loadings, corresponding to the 0.5 and 5 kPa operating PCO2* for coal

flue gas, are critical, as they contribute to the cyclic capacity of the solvent. The cyclic

capacity of the solvent is one indicator of the relative energy cost of using one amine over

others. As discussed in Chapter 4.2.3, cyclic capacity is determined by the cyclic

loading (Δldg) of the solvent, the total alkalinity in the solvent, and the molecular weight

of the amine per mole of alkalinity (Equation 4.9). The calculated cyclic capacity of PZ

500

5000

0.1 0.2 0.3 0.4 0.5 0.6

PC

O2*

(P

a)


5 m PZ/ 5 m MDEA

2 m PZ/ 7 m MDEA

8 m PZ4.8 m AMP

5 m PZ /2.3 m AMP

2 m PZ /4 m AMP

180

blends is summarized in Table 6.29. In general, PZ blends with all primary amines have

lower capacity than 8 m PZ. For the two blends with PZ derivatives, their capacity is also

lower than 8 m PZ. Though the total alkalinity of these blends is the same as 8 m PZ,

both the cyclic loading and the molecular weight of the amine per mole of alkalinity

contributes a lower capacity of the blend. The two hindered amine blends with high

cyclic loadings, 3.5 m PZ/3.5 m Tris and 2 m PZ/4 m AMP, both have higher capacity

than 8 m PZ, even though these blends suffer from low total alkalinity and high

molecular weight.

Viscosity normalized capacity

The cyclic capacity is important to the energy cost of a solvent because it directly

suggests the solvent rate required in the process and the corresponding sensible heat cost

of heating the solvent. The viscosity of the solvent also affects the sensible heat cost

of the process. As discussed in Chapter 4.2.3, viscosity affects the heat transfer

coefficient of the solvent and thus the size and equipment of the cross exchanger. To

fully represent the effect of solvent choice on the overall sensible heat cost of the process,

the effect of capacity and viscosity is combined using the viscosity normalized capacity

(ΔCµ).

The ΔCµ of the PZ blends are calculated using viscosity data (Chapter 6.2.2) and

the results are summarized in the Table 6.29. The ΔCµ comparison shows 2 m PZ/4 m

AMP and 3.5 m PZ/3.5 m Tris to be competitive solvents in terms of sensible heat cost

due to the combination of high cyclic capacity and low viscosity.

6.4.4 Heat of Absorption

The heat of CO2 absorption in the PZ blends is estimated from the CO2 solubility

data using the semi-empirical VLE model (Equation 4.4). The calculated ∆Habs at 1.5

181

kPa is summarized in Table 6.29. As discussed in Chapter 4, this method of estimating

the heat of absorption depends on the range and quality of CO2 VLE data. If only the

WWC or the total pressure data is used, larger error can be expected in the estimation of

∆Habs (generally over predicting the value). Therefore, only the PZ blends with both

WWC and total pressure VLE data are further discussed in terms of their ∆Habs.

Figure 6.37: Heat of absorption of CO2 at process conditions for PZ blends with primary

di-amines, compared with MEA and PZ

The estimated ∆Habs of PZ blends with primary di-amines are plotted in Figure

6.37. The blend with the best ∆Habs is 6 m PZ/2 m BAE, with higher ∆Habs than 8 m PZ

over the entire loading range. However, its ∆Habs is still lower than MEA. The blends

of 6 m PZ/2 m HMDA and 6 m PZ/2 m EDA have ∆Habs higher than PZ at low loading,

but they decrease fast with loading and ∆Habs becomes lower than PZ at high loading.

The blend of 6 m PZ/2 m DAB has lower ∆Habs than other PZ blends and PZ.

55

60

65

70

75

80

500 5000

-∆H

abs

(kJ/

mo

l)

PCO2* @ 40 °C (Pa)

PZ

MEA6 m PZ/2 m BAE

6 m PZ/ 2 m HMDA

6 m PZ /2 m DAB

6 m PZ /2 m EDA

182

Figure 6.38: Heat of absorption of CO2 at process conditions for PZ blends with AMP

and 5 m PZ/2 m AEP

The ∆Habs of PZ blends with AMP and AEP is compared in Figure 6.38. The

blend of 2 m PZ/4 m AMP has the greatest ∆Habs, which is higher than MEA at low

loading. 5 m PZ/2.3 m AMP has ∆Habs that is higher than PZ at low loading, which is

about the same as PZ at high loading. 5 m PZ/2 m AEP also has ∆Habs that is

competitive with MEA.

60

65

70

75

80

500 5000

-∆H

abs

(kJ/

mo

l)

PCO2* @ 40 °C (Pa)

PZ

MEA2 m PZ/4 m AMP

5 m PZ/2.3 m AMP

5 m PZ/2 m AEP

183

Table 6.29: Summary of cyclic loading, capacity, and heat of absorption for PZ blends

PZ (m) /

Amine (m)

αCO2

(mol/mol N) ∆ αCO2 Capacity

- ∆Habsa

(kJ/mol) μ b

lean rich ∆Csolv ∆Cμ αmid a

cP

6 / 2 EDA 0.36 0.42 0.06 0.63 0.64 67 9.4

6 / 2 DAB 0.33 0.41 0.08 0.71 0.69 62 11.6

6 / 2 HMDA 0.37 0.43 0.06 0.55 0.51 68 15.4

6 / 2 BAE 0.33 0.41 0.07 0.69 0.67 70 11.7

5 /5 DGA® 0.34 0.41 0.07 0.53 0.52 83* 11.2

5 / 2 AEP 0.30 0.37 0.07 0.68 0.67 71 10.9

6 / 2 HEP 0.29 0.36 0.07 0.66 0.64 76* 12.3

5 / 5 2-PE 0.39 0.48 0.09 0.67 0.57 76* 25.3

5 / 2.3 AMP 0.33 0.43 0.09 0.71 0.72 70 9.5

2 / 4 AMP 0.33 0.48 0.15 0.77 0.86 73 5.4

3.5 / 3.5 Tris 0.23 0.35 0.13 0.78 0.85 76* 6.0

5 / 5 MDEA 0.21 0.35 0.13 0.98 0.93 69 13.2

2 / 7 MDEA 0.13 0.28 0.15 0.80 0.81 68 9 c

4 / 4 2MPZ 0.29 0.39 0.10 0.89 0.88 66 10.5

3.75 / 3.75 1MPZ 0.5

1,4DMPZ 0.23 0.33 0.10 0.87 0.84 71 12.4 d

2 / 7 MEA 0.38 0.46 0.09 0.59 / 73* /

8 0.31 0.40 0.09 0.86 0.84 67 10.8

7 MEA 0.43 0.53 0.10 0.50 0.67 72 3 * Estimated with only CO2 VLE data at 40 – 100 °C by the WWC a Calculated at the CO2 loading corresponding to PCO2* of 1.5 kPa b Calculated at the algebraic mean of the rich and lean loadings c Measured at solvent lean loading (PCO2* = 0.5 kPa) d Viscosity for 5 m PZ/2 m 1MPZ/1 m 1,4DMPZ. (Freeman 2011)

6.4.5 Stripping performance

The estimation of stripping performance of a solvent involve calculating the

maximum stripping temperature (Pmax) and the selectivity of CO2 relative to water in the

stripper (PCO2/PH2O), which are both discussed and defined in Chapter 4.3. The

calculations of both stripping parameters require the maximum stripping temperature

(Tmax), which is determined by the rate of thermal degradation of the solvent. For PZ

blends where thermal degradation data and Tmax results are available (Chapter 6.5.1), the

stripping parameters were calculated (Table 6.30).

184

Table 6.30: Summary of stripping performance for selected PZ blends

PZ (m) /

Amine (m)

- ∆Habsa

(kJ/mol) Tmax Pmax PH2O/

PCO2/ αmid

a αleam °C bar

6 / 2 DAB 63 69 157 11.7 0.77

6 / 2 HMDA 68 75 163 21.8 0.37

6 / 2 BAE 70 72 162 17.3 0.50

5 / 2 AEP 71 75 155 15.4 0.45

5 / 2.3 AMP 71 77 128 5.3 0.71

2 / 4 AMP 73 77 128 5.6 0.69

5 / 5 MDEA 69 74 138 7.2 0.66

2 / 7 MDEA 68 72 138 6.3 0.85

4 / 4 2MPZ 66 72 155 12.8 0.59

3.75 / 3.75 1MPZ 0.5

1,4DMPZ 71 74 159 17.0 0.45

2 / 7 MEA 73 78 104 1.8 1.27

8 67 71 163 16.5 0.56

7 MEA 72 76 121 3.8 0.91 a mid loading: PCO2* = 1.5 kPa

Solvent Pmax depends most significantly on thermal stability (Tmax). All

thermally stable PZ blends have high Pmax (above 10 bar), such as 6 m PZ/2 m HMDA, 6

m PZ/2 m BAE, and 5 m PZ/2 m AEP. Whereas the alkanolamine blends (MEA,

MDEA, AMP), which are thermally unstable with low Tmax, have Pmax about 50–80%

lower than the other blends. Solvent Pmax depends, to a lesser degree, on solvent ∆Habs

at lean loading. While 6 m/PZ 2 m BAE, 6 m PZ/2 m DAB, and 5 m PZ/2 m AEP all

have similar Tmax, 5 m PZ/2 m AEP and 6 m PZ/2 m BAE have higher Pmax because of

their high ∆Habs. Like Pmax, PCO2/PH2O increases with increase in solvent ∆Habs and Tmax.

Solvents with high Pmax also have high PCO2/PH2O, but PCO2/PH2O is more sensitive to

variations in ∆Habs.

185

6.5 SOLVENT MANAGEMENT

6.5.1 Solvent degradation

Thermal degradation

Thermal degradation experiments were performed at 135–175 °C by Namjoshi

(2013). The experimental methods are describes by Freeman (2011). Amine

degradation was measured as the change in amine concentration with time, and the

degradation rate is reported as the apparent first order rate constant of amine loss (k1).

For a blend, k1 values can be measured for each amine and also for the total amines (TA)

in the solvent. The degradation reactions are assumed to be first order with amine

concentration. Thus, using k1 measurements at multiple temperatures, the activation

energy (Eact) for degradation can be calculated using the Arrhenius equation for reaction

rate constants:

𝑘1 = 𝐴 ∙ 𝑒−𝐸𝑎𝑐𝑡𝑅𝑇 (6.3)

For a blend, Eact can be calculated for each amine species and for the total amine.

While the rate of amine loss increases with increase in temperature, the energy

performance of the process improves with higher stripper operating temperature.

Stripper operating temperature is limited by the rate of thermal degradation, and the

optimum corresponds to the maximum tolerable rate of amine loss. Previous work by

Davis suggests the acceptable rate of degradation (k1) for 7 m MEA is 2.9x10-8 s-1 with

stripper temperature at 121 °C. This optimum is calculated by the trade-off between the

cost of MEA loss and the energy benefits of higher stripper temperature and pressure

(Davis, 2008). Assuming this trade-off is consistent for different amines, the optimum

stripper operating temperature (Tmax) for each solvent is defined as the temperature which

corresponds to an overall amine degradation rate of 2.9x10-8 s-1. Tmax can be calculated

186

using k1 and Eact measured at the practical amine concentration and CO2 loading, which is

important as k1 depends strongly on these conditions (Freeman 2011). In cases where

Eact is not available, the Eact of other amines with similar structures and degradation

mechanisms is used. This approximation is acceptable since the Eact does not change

significantly between amines with similar degradation characteristics (Freeman 2011).

The results for k1 at 150 °C, Eact, and Tmax for each blend are summarized in Table 6.31.

The blends are compared with the degradation rate of the amine by itself.

Table 6.31: Summary of thermal degradation rate, activation energy, and maximum

stripper temperature for PZ blends and amines in the blends

Blend Amine

PZ (m) /

Amine (m) αCO2

k1 (Х 109) * Tmax Eact

b

Ref Amine

αCO2 k1 * Tmax Eact Ref

PZ Am TAa °C kJ/mol m Х 109 °C kJ/mol

6 / 2 HMDA c 0.4 / / 6 163 PZ f 8 0.3 9 c 160 PZ e

6 / 2 DAB c 0.4 9 90 13 157 PZ f 8 0.4 147 c 127 PZ f

6 / 2 BAE c 0.35 6.9 7.2 7.0 162 PZ f 8 0.4 11 c 158 PZ f

5 / 2 AEP 0.3 10 28 15 155 PZ i 2.33 0.4 1306

d 121 PZ e

5 / 2.3 AMP 0.4 90 256 133 138 99 h 7 0.4 86 137 MEA e

4 / 4 2MPZ 0.3 / / 16 155 PZ e 8 0.3 25 151 PZ e

3.75 / 3.75

1MPZ

/0.5 1,4DMPZ

0.3 8 / 10 159 PZ e 8

(1MPZ) 0.3 36 148 PZ e

2 / 7 MEA 0.4 1200 683 608 104 84 e 7 0.4 828 121 157 e

2 / 7 MDEA 0.11 486 42 61 138 PZ g 7 0.1 283 128 MEA g

8 PZ 0.3 6 / 6 163 184 e

7 MEA 0.4 / 828 828 122 157 e

* k1 is the apparent rate of amine loss at 150 °C, with the unit of s-1 b Eact is calculated based on the k1 value for total amine loss (TA) c Extrapolated from data collected at 175 °C using listed Eact d Extrapolated from data collected at 135 °C using listed Eact

e Freeman 2011; f Namjoshi et al. 2013; g Closmann 2011; h Li et al. 2013; i Du et al. 2013

When PZ is used together with HMDA, BAE, 2MPZ, 1MPZ, which are thermally

stable by themselves, the blends are also stable. DAB and AEP are both less stable

amines, but when blended with PZ they do not affect the stability of PZ. Also, DAB

and AEP are present at low concentration in the blends, the overall degradation rate of the

187

blends is still competitive with other stable solvents. Also, AEP is identified as a major

stable degradation product of PZ. Thus, in a blend of PZ and AEP, the two amines are

close to chemical reaction equilibrium which inhibits degradation reactions. The blends

of PZ with MEA, MDEA, and AMP all degrade at much higher rates than the amines if

used by themselves. This is because PZ, as a strong nucleophile, will react with

alkanolamines (or their respective oxalzolidinone) such as MEA, MDEA and AMP in a

blend and result in additional degradation pathways (Freeman 2011).

Oxidation

The oxidation of 6 m PZ/4 m AMP, 6 m PZ/2 m HMDA, and 6 m PZ/2 m DAB

was measured by Voice (2013) a high gas flow (HGF) apparatus at absorber temperatures

(70 °C). A few of the amines used in the PZ blend, such as BAE, AEP, 2-PE, were also

tested for oxidation using the same method. The HGF method involves a semi-batch

reactor, where the CO2 loaded amine solvent is held. An air stream mixed with 2% CO2

is continuously sparged into the amine solvent. An exit air stream leaves the reactor and

into a FTIR (Fourier-Transform Infrared spectroscopy), where its components are

continuously analyzed. Only the gas phase of the oxidation reactor is analyzed in the

HGF method, and ammonia is used as the sole indicator for amine oxidation. The

results and conditions of the HGF experiments are summarized in Table 6.32.

Alternatively, a low gas flow apparatus (LGF) was used to measure solvent

oxidation at 70 °C. With the LGF method, liquid samples from a amine oxidation

reactor is collected periodically, and analyzed for signs of amine oxidation. In this case

total formatted is used as the main indicator for amine oxidation. The LGF method was

used to measure the oxidation of 6 m PZ/2 m HMDA, 5 m PZ/2 m AEP, 4 m PZ/4 m

188

2MPZ. The results are summarized in Table 6.33 and compared with the oxidation of 8

m PZ and 7 MEA.

Table 6.32: Ammonia production rates (mmol/kg/hr) from various solvents in the HGF

apparatus by Voice (2013); with air and 2% CO2 at 70 °C with iron (Fe),

copper (Cu) and manganese (Mn) added at 1 mM concentration

m Amine / m

PZ Fe Fe/Cu Fe/Cu/Mn

7 BAE 5.46 13.9 13.6

8 AEP 2.42 -- --

4 AMP / 6 <0.02 1.89 0.12

2 HMDA / 6 0.03 1.35 2.56

2 DAB / 6 <0.02 1.1 0.53

8 m 2PE <0.02 -- --

8 m PZ <0.02 0.37 0.03

7 MEA 0.9 6.6 11.6

Table 6.33: Total formate production rates in various solvents in the LGF apparatus with

oxygen and 2% CO2 at 70 °C with various metals (SSM=Fe, Ni, Cr)

m Amine

/ m PZ

Total Formate

Rate

(mmol/kg/hr)

Catalyst

2 AEP a 0.089 SSM+Mn

2 AEP /5 a 0.076 SSM+Mn

2 HMDA / 6 e 0.095 SSM+Mn

MDEA b 0.039 SSM

7 MDEA/ 2 b 0.072 SSM

4 m 2MPZ /4 c,e 0.021 SSM+Mn

8 m PZ d 0.031 SSM

8 m PZ a 0.026 SSM+Mn

7 MEA e 6.65 Mn+Fe

7 MEA e 3.64 Fe a Du et al. (2013); b Closmann (2011); c Sherman et al. (2013); d Freeman (2011); e Voice (2013)

The results from both apparatus show 6 m PZ/2 m HMDA to be stable towards

oxidation. Its ammonia and formate rates are much lower than 7 m MEA, and only

189

slightly higher than 8 m PZ. The HGF results show 6 m PZ/4 m AMP and 6 m PZ 2m

DAB to have low rates of ammonia production in the presence of oxygen. Also, 7 m

BAE shows higher ammonia rates than 7 m MEA, which suggest the blend of BAE with

PZ is also prone to oxidation. The result for 8 m 2-PE was performed with only Fe, and

the ammonia rates are competitive with 8 m PZ. The LGF results shows 5 m PZ/2 m

AEP, 2 m PZ/7 m MDEA, and 4 m PZ/4 m 2MPZ all have low rates of total formate

production, which are competitive with 8 m PZ.

A HTCS (High temperature cycling system) was used by Voice (2013) to measure

the effect of the temperature swing in a real process on the oxidation of amine solvents.

The CO2 loaded amine solvent first absorbs O2 at absorber temperatures (55 °C). Next,

the solvent is cycled through a high temperature reactor (120-150 °C) before returning to

the low temperature reactor. The results of HTSC shows 4.8 m AMP is more stable

than 8 m PZ for oxidation, and 4 m PZ/4 m 2MPZ is less stable than 8 m PZ but more

stable than 7 m MEA.

6.5.2 Amine volatility

Amine volatility was measured by Nguyen (2013) using an equilibrium reactor

with a re-circulating gas stream, with the gas phase composition analyzed online by a

multi-component FTIR. The experimental apparatus and methods are described by

Nguyen et al. (2010).

Intrinsic volatility of the amines was studied by measuring the VLE of amine-

water systems. The Henry’s constant is calculated from experimental data (Equation

22).

𝐻𝑎𝑚𝑖𝑛𝑒,𝑇 =𝑃𝑎𝑚𝑖𝑛𝑒

𝑥𝑎𝑚𝑖𝑛𝑒∙𝛾𝑎𝑚𝑖𝑛𝑒∞ (6.4)

190

For Henry’s constant experiments, dilute amine concentrations were used. At

dilute conditions, the activity coefficient of the amine at infinite dilution (𝛾𝑎𝑚𝑖𝑛𝑒∞ ) is

approximately one, and the Henry’s constant can be calculated from amine partial

pressure (Pamine) measurements. A structure property correlation for Hamine* was

developed using experimental results and literature data (Equation 23).

𝑙𝑛(𝐻𝑎𝑚𝑖𝑛𝑒(𝑃𝑎)) = 𝐼𝑛𝑡𝑒𝑟𝑐𝑒𝑝𝑡 + 𝐵 ∙ (1/313𝐾 − 1/𝑇(𝐾)) + ∑(𝑐𝑜𝑒𝑓𝑓𝑖𝑐𝑖𝑒𝑛𝑡 𝑖)(# 𝑔𝑟𝑜𝑢𝑝𝑠) (6.5)

Table 6.34: Parameters for the structural property correlation for Hamine (Equation 6.5)

Parameter Value Standard

error

N -7.10 0.49

NH -4.29 0.26

O -3.19 0.16

Ncyc -2.83 0.16

NH2 -1.29 0.21

OH -0.34 0.19

Ocyc 0 0

C 0.013 0.05

CH3-(C) 0.260 0.09

CH3-(Ccyc) 0.281 0.20

Ccyc 0.660 0.07

CH3-(Ncyc) 1.88 0.10

CH3-(N) 3.92 0.25

Intercept 6.95 0.31

B 6840 423

Hamine for new amines can be predicted using Equation (6.5). The measured or

predicted Hamine for the amines used in the PZ blends at 40 °C are summarized in Table

6.35. High amine volatility leads to higher amine loss with the exit flue gas at the top of

the absorber. For the amines used in the new PZ blends, BAE and AEP have lower

191

Hamine than PZ. HMDA and DAB have Hamine slightly higher than PZ, but still lower

than MEA. AMP is a volatile amine, with Hamine about 3.5 times that of MEA.

While Henry’s constant represents intrinsic volatility of the amine, the practical

volatility of the solvent in the absorber also depends on the concentration of the amine in

solution and solvent CO2 loading. At zero CO2 loading, the expected Pamine over the

solvent equals to Hamine multiplied by the mole fraction of the amine in the liquid (Table

6.25). HMDA and DAB have high Hamine, but the volatility for 6 m/PZ 2 m HMDA and

6 m PZ/2 m DAB at process conditions is expected to be low due to the low

concentration of the volatile amines.

Table 6.35: The practical Henry’s constant and amine partial pressure at 40 °C for the PZ

blends

PZ (m) / (m) Amine

Zero CO2 loading Loaded solvent

Hamine Pamine Pamine PPZ αCO2

Pa Pa Pa Pa

6 / 2 m HMDA 85 2.7

6 / 2 m DAB 83 # 2.6

6 / 2 m BAE 3.4 # 0.1

5 / 2 m AEP 14.4 # 0.5

5 / 2.3 AMP 350 12.8 5.7 c 0.6 c 0.3 c

5 / 5 m MDEA 22.9 1.7 0.16 0.5 0.21

4 / 4 m 2MPZ 66.8 4.2 0.85 0.1 0.32

3.75 / 3.75 m 1MPZ

0.5 m 1,4DMPZ

1MPZ 332

DMPZ 2183

1MPZ 19.6

DMPZ 17.6

2 / 7 m MEA 98.7 10.7

2 / 7 m MDEA 22.9 2.5 0.61 d 0.18 d 0.1 d

8 m PZ 50.9 6.4

0.77 a 0.31

7 m MEA 98.7 11.0 1.27 b

0.43

a 𝑙𝑛(𝑃𝑃𝑍 𝑥𝑃𝑍)⁄ = −123 + 21.6𝑙𝑛(𝑇) + 20.2𝛼 − 18174𝛼2/𝑇; Xu 2011 b 𝑙𝑛(𝑃𝑀𝐸𝐴 𝑥𝑀𝐸𝐴)⁄ = 30 − 8153/𝑇 − 2594𝛼2/𝑇; Xu 2011

c Li et al. 2013; d Nguyen et al. 2010; # Values predicted using Equation 6.5

192

6.6 CONCLUSIONS

In general, concentrated PZ blends have a larger solid solubility window than 8 m

PZ, where the rich loading limit is removed and the low loading limit is less restrictive.

The only exception is with 6 m PZ/2 m HMDA, which precipitates up to 0.3 ldg at 20 °C.

The viscosity of concentrated PZ blends is about the same as 8 m PZ. Only for 5

m PZ/5 m 2-PE, the viscosity is about 25 cP, which is more than twice that of 8 m PZ at

40 °C. The blends 3.5 m PZ/3.5 m Tris and 2 m PZ/4 m AMP have low viscosity at

around 5 cP, which is due to the low total amine concentration in the solvent.

All of the PZ blends have better CO2 absorption rates than 7 m MEA, and most

are competitive with 8 m PZ. Only 6 m PZ/2 m HMDA and 5 m PZ/5 m 2-PE have

lower kg’ than 8 m PZ and other blends, which are partially contributed by the high

viscosity of the solvents.

For PZ blends with primary diamines or primary amines, the solvent capacity is

lower than 8 m PZ due to lower Δldg (shape of CO2 VLE curve at 40 °C) and a higher

molecular weight of the blended amines than PZ. Hindered amines enhanced the Δldg

of PZ when the two amines are used in a blend, which contributes to a high solvent

capacity of the blends.

The blends of PZ/AMP and 5 m PZ/2 m AEP show high ∆Habs, which is

competitive with MEA. Mainly due to their high thermal stability, PZ blends with long

chain primary diamines are expected to have good stripping performance.

The amines AEP and BAE are expected to have low volatility, while AMP has the

highest volatility.

3.5 m PZ/3.5 m Tris has good absorption rates, good capacity, and low solvent

viscosity. 2 m PZ/4 m AMP shows competitive performance in all aspects, except for

its high volatility. 5 m PZ/2 m AEP also has good overall performance, only its

193

capacity is moderate. 6 m PZ/2 m HMDA has moderate absorption rates, capacity, and

a high viscosity. But it is thermally stable with a high heat of absorption, which

contributes to a high stripping performance that is competitive with 8 m PZ.

The CO2 absorption rates for PZ blends with primary di-amines increases with

decreasing pKa of the amine (2nd pKa). Increase in the concentration of PZ increases the

kg’ of the blend for AMP and MDEA.

194

Chapter 7: CO2 Solubility and absorption rate measurements in

aqueous primary and secondary amines

7.1 INTRODUCTION

Five amines were tested using the WWC to study the effect of molecular structure

on the mass transfer rate and CO2 solubility at process conditions. The structures

chosen are simple variations of MEA. This chapter summarizes these measurements

and the relevant analysis.

7.1.1 Scope

Two primary amines and three secondary amines are tested in this work. The

primary amines are monoisopropanolamine (MIPA) and monopropanolamine (MPA),

both have structure similar to MEA. MIPA has an additional methyl group on the beta

carbon and about the same pKa. MPA differs from MEA with one additional carbon

between the nitrogen and the hydroxyl group. The pKa of MPA is slightly higher than

MEA. The three secondary amines are diethanolamine (DEA),

methylmonoethanolamine (MMEA), and diisopropanolamine (DIPA). DEA contains

two ethanol groups. And DIPA has two more methyl groups than DEA. The pKa of

DIPA is about the same as DEA. MMEA is MEA with an additional methyl group on

the nitrogen. The pKa of MMEA is higher than MEA and similar to MPA. The

structures and pKa of the amines tested in this work are summarized in Table 7.1.

195

Table 7.1: Structure and solvent concentration for amine solvents tested in this work

Amine Structure Type pKa (40

°C) Solvent

Monoisopropanolamine

(1-amino-2-propanol)

(MIPA)

CAS# 78-96-6

Primary

9.04

(Hamborg

and

Versteeg

2009)

7 m

MIPA

Monopropanolamine

or 3 amino 1 propanol

(MPA)

CAS# 156-87-6

NH2

OH

Primary

9.48

(Hamborg

and

Versteeg

2009)

7 m

MPA

Diethanolamine

(DEA)

CAS# 111-42-2

OH

NH

OH

Secondary

8.52

(Bower et

al. 1962)

7 m

DEA

Methylmonoethanolamine

(MMEA)

CAS# 109-83-1

CH3 NH

OH

Secondary

9.46

(Hamborg

and

Versteeg

2009)

7 m

MMEA

Diisopropanolamine

(DIPA)

CAS# 110-97-4

NH

OH

OH

CH3

CH3

Secondary

8.51

(Hamborg

and

Versteeg

2009)

7 m

DIPA

Each amine is tested at a concentration of 7 m, which is the same as the base case

MEA concentration (30 wt%, 7 m). The absorption rate of CO2 and CO2 solubility in

each solvent was measured using the WWC at 20 – 100 °C. The effect of pKa and

structure on the CO2 absorption rate and capacity are studied by comparing results in this

work with relevant results in literature.

NH2

CH3

OH

196


Table 7.2: Selected literature on CO2 reaction kinetics and solubility for amine solvents

included in this work

Amine C T (K) CO2

loading Data type Source

MIPA

10 – 50

wt % 313, 393 0.2 – 0.9 CO2 VLE

Rebolledo-Morales

et al. 2011

0.025-

0.082 M

298, 303,

308, 313 0

Reaction

kinetics Henni et al. 2008

MPA 0.027-

0.061 M

298, 303,

308, 313 0

Reaction

kinetics

DEA

0.01-1 M 298 0

Reaction

kinetics

(review)

Little et a. 1992b

0.5-5M 298, 393 0.1-827

psia CO2 VLE Lee et al. 1972

25 wt% 313, 353, 393

0.04-0.5

mol/mol

amine

Absorption

rates by

WWC

Mshewa 1995

MMEA 0.2-3.5 M 293, 318 0 Reaction

kinetics Littel et al. 1992a

DIPA

0.2-4 M 293, 298 0 Reaction

kinetics Little et a. 1992b

10, 11, 34

wt% 298

0.5 – 0.9

mol/mol

amine

CO2 VLE Dell’Era et al. 2010

All of the five amines tested in this work have been studied previously, with

various level of rigor, for the application of CO2 absorption. The most thoroughly

studied amine is DEA, with data available for both reaction kinetics and CO2 solubility.

Reaction kinetics data are also available for all other amines tested in this work.

However, literature kinetic studies are all performed without CO2 loading in the liquid

phase. Also, most of the available kinetic data are collected at low amine concentration,

which is different from expected operating conditions of a real process. Moreover,

reaction kinetics alone does not fully represent the overall mass transfer rate of CO2,

197

where the diffusion of species can become important at process conditions. Literature

data are also available for CO2 VLE in MIPA and DIPA, which were compared with

results in this work. Selected literature studies on the amines tested in this work are


The mass transfer rate measured in this work is best compared with mass transfer

data collected at similar conditions. Previous results in literature on the mass transfer

rate of primary and secondary amines at CO2 loaded conditions and high amine

concentration are summarized in Table 7.3, and are used in the analysis of this work.

Table 7.3: Available WWC data for other primary and secondary amines collected using

the same method

Amine Structure pKa (40 °C) C (m) Source

Monoethanolamine

(MEA)

NH2

OH

9.03

(Hamborg) 7, 9, 11

Dugas

(2009)

Glycine (GlyK)

OH

ONH2

9.41

(Hamborg

2007)

3.5, 6

This work

(Chapter 5)

β-alanine (β-alaK)

OH

ONH2

9.94

(Hamborg

2007)

6.5

Diglycolamine

(DGA®)

OH

O

NH2

8.25 10

Chen et al.

(2011) 2-amino -2 methyl -1

propanol

(AMP)

NH2

CH3

OH CH3

9.24 4.8

2 piperideneethanol

(2PE)

NH

OH

9.68

(Xu et al.

1992)

8

Chen and

Rochelle

(2011)

Sarcosine (SarK)

OH

ONHCH3

9.88

(Hamborg

2007)

6 This work

(Chapter 5)

198


The amine solvents were prepared gravimetrically by mixing the amine with

water. To achieve the desired CO2 loading, gaseous CO2 (99.99%, Matheson Tri-Gas)

were bubbled into the amine water mixture.

For most of the WWC experiments, the CO2 concentration in the liquid phase is

verified using a total inorganic carbon (TIC) method (Section 3.3.1). The total

alkalinity of the solvent is confirmed using acid titration (Section 3.3.1). In some cases

(7 m DIPA and 7 m MMEA), gravimetrically measured CO2 and amine mass are used to

calculate CO2 loading. The chemicals used in the preparation of solvents used are


Table 7.4: Chemicals used in solvent preparation


Monoisopropanolamine

(1 amino 2 propanol)

(MIPA)

99% Sigma-Aldridge

Monopropanolamine

(3 amino 1 propanol)

(MPA)

99% Sigma-Aldridge

Diethanolamine

(DEA) 99% Fisher Scientific

Methylmonoethanolamine

(MMEA) 99% Sigma-Aldridge

Diisopropanolamine

(DIPA) 99% Acros Organics

7.2 ABSORPTION RATE RESULTS

The absorption rate of CO2 in the amine solvents is quantified by measuring the

liquid film mass transfer coefficient (kg’) of CO2. The data was collected using the

WWC (Section 3.1). The CO2 mass transfer rate was measured at 20, 40, 60, and 80 °C.

199

For 7 m MIPA, 7 m MPA, and 7 m MMEA, kg’ was also measured at 100 °C. The data

at 40° C is further analyzed to estimate the expected packing area in optimized absorbers

for coal and natural gas flue gas.


Figure 7.1: CO2 Liquid Phase Mass Transfer Coefficient (kg’) for 7 m MIPA, and 7 m MEA at 40 °C (Dugas 2009).

The CO2 absorption rate results at 40 oC for 7 m MIPA are compared with 7 m

MEA in Figure 7.1. The kg’ of 7 m MIPA is comparable to 7 m MEA, which shows

little temperature dependence over the entire temperature and CO2 loading range. The

structure of MIPA differs from MEA only in the addition of a methyl group on the beta

carbon of the amine group. It has little effect on the kg’ of the solvent.

The kg’ of 7 m MPA is shown in Figure 7.2 and compared with 7 m MEA at 40

°C. The kg’ of 7 m MPA shows little temperature dependence, except at the highest

1.E-07

1.E-06

1.E-05

10 100 1000 10000

k g' (

mo

l/P

a∙s∙

m2)

PCO2* @ 40 °C (Pa)

40 °C

80 °C

60 °C100 °C

20 °C

7m MEA@ 40 °C

200

CO2 loading condition where kg’ drops at 40 °C. At 40 °C, the kg’ of 7 m MPA is lower

than 7 m MEA. The molecular structure of MPA differs from MEA by one additional

carbon in the carbon chain, which contributes to a higher pKa of MPA (9.48) than MEA

(9.03). In this case, the kg’ of the solvent is 25 to 50 % lower than 7 m MEA at 40 oC.

Figure 7.2: CO2 Liquid Phase Mass Transfer Coefficient (kg’) for 7 m MPA, and 7 m

MEA at 40 °C (Dugas 2009).

The measured kg’ for 7 m DEA is plotted in Figure 7.3, and compared with 7 m

MEA at 40 °C. The kg’ of 7 m DEA shows little temperature dependence over the

entire temperature and CO2 loading range of the experiment. At 40 °C, the kg’ of 7 m

DEA is slightly higher than 7 m MEA. The pKa of DEA is much lower than MEA.

DEA is a secondary amine with a much longer carbon chain than MEA. Also, the pKa

of DEA is much lower than MEA. In this comparison, the amine with lower pKa (DEA)

has a kg that is about 15 % greater at 40 °C than MEA.

1.E-08

1.E-07

1.E-06

1.E-05

10 100 1000 10000 100000

k g' (

mo

l/P

a∙s∙

m2)

PCO2* @ 40 ˚C (Pa)

40 °C

80 °C

60 °C100 °C

20 °C

7 m MEA @ 40 °C

201

Figure 7.3: CO2 Liquid Phase Mass Transfer Coefficient (kg’) for 7 m DEA, compared

with 7 m MEA at 40 °C (Dugas 2009).

Figure 7.4: CO2 Liquid Phase Mass Transfer Coefficient (kg’) for 7 m MMEA, compared

with 7 m MEA and 8 m PZ at 40 °C (Dugas 2009).

1.E-07

1.E-06

100 1000 10000

k g' (

mo

l/P

a s

m2)

PCO2* @ 40 °C (Pa)

40 °C

80 °C

60 °C

20 °C

7m MEA@ 40 °C

1.E-07

1.E-06

1.E-05

10 100 1000 10000 100000

k g' (

mo

l/P

a s

m2)

PCO2* @ 40 °C (Pa)

7m MEA@ 40 °C

40 °C

80 °C

60 °C

100 °C

20 °C

8 m PZ@ 40 °C

202

The kg’ for 7 m MMEA is plotted in Figure 7.4, and compared with 7 m MEA and

8 m PZ at 40 °C. At 40 °C, the kg’ of 7 m MMEA is twice that of 7 m MEA at 40 oC

which is about the same as 8 m PZ. The structure of MMEA differs from MEA only in

an additional methyl group on the nitrogen, making MMEA a secondary amine. The

pKa of MMEA is higher than MEA. In this case, the secondary amine with higher pKa

has higher kg’ than the primary amine with lower pKa.

Figure 7.5: CO2 Liquid Phase Mass Transfer Coefficient (kg’) for 7 m DIPA, compared

with 7 m MEA at 40 °C (Dugas 2009) and 7 m DEA.

Unlike the three previous solvents, the kg’ of 7 m MMEA shows significant

temperature dependence between 60 and 100 °C, where kg’ decreases with temperature.

The temperature dependence in kg’ for 7 m MMEA can be explained by its high rates at

40 °C. With increase in temperature, the kinetics of the reaction becomes instantaneous,

and the mass transfer of CO2 becomes diffusion controlled at 80 °C. In other words, the

kg’ at 80 and 100 °C are essentially the kl° of the solvent, while the kg’ at 20 – 60 °C is

1.E-07

1.E-06

100 1000 10000 100000

k g' (

mo

l/P

a s

m2)

PCO2* @ 40 °C (Pa)

40 °C

80 °C 60 °C

20 °C

7m MEA@ 40 °C

7 m DEA@ 40 °C

203

the pseudo first order kg’. Therefore, the temperature dependence in the measured kg’

varies distinctly between the two temperature ranges.

The kg’ of 7 m DIPA is plotted in Figure 7.5 and compared with 7 m MEA at 40

°C. The kg’ of 7 m DIPA shows little temperature dependence. At 40 °C, the kg’ of 7

m DIPA is 50 % that of 7 m MEA. The kg’ of 7 m DIPA is much lower than 7 m DEA,

although the two amines have similar pKa.

7.2.2 Effect of amine type

Figure 7.6: CO2 absorption rates in primary amines at 40 °C, compared with 7 m MEA

(Dugas 2009); 10 m DGA® and 4.8 m AMP (Chen et al. 2011).

The kg’ at 40 °C for the two primary amine solvents, 7 m MIPA and 7 m MPA,

are compared with other primary amines in Figure 7.6. Among the five solvents, the

variation in kg’ is small. The kg’ of the hindered amine solvent, 4.8 m AMP, is the

1.E-08

1.E-07

1.E-06

1.E-05

10 100 1000 10000 100000

k g' (

mo

l/P

a s

m2)

PCO2* @ 40 °C (Pa)

7 m MPA

10 m DGA®

7 m MIPA

7 m MEA

4.8 m AMP

40 °C

204

lowest. The kg’ of 7 m MPA is slightly higher than 4.8 m AMP at low loadings, and

they are about the same at high loadings.

Figure 7.7: CO2 absorption rates in secondary amines at 40 °C, compared with 7 m MEA

and 8 m PZ (Dugas 2009); and 8 m 2PE (Chen and Rochelle 2011).

The kg’ at 40 °C for the three secondary amine solvents, 7 m DEA, 7 m MMEA,

and 7 m DIPA are plotted in Figure 7.7, and compared with 7 m MEA, 8 m PZ, and 8 m

2-PE. The CO2 absorption rate in secondary amines varies greatly among themselves.

7 m MMEA is the fastest, with kg’ about the same as 8 m PZ, and much faster than 7 m

MEA. The kg’ for 7 m DIPA is much slower than all other solvents. For 7 m DEA, its

kg’ is slightly higher than 7 m MEA despite its low pKa.

7.2.4 Process performance

As discussed in Section 4.2.2, the kg’ measurement at 40 °C can be used to

estimate the performance of the solvent in an isothermal absorber. The calculated kg’avg

1.E-07

1.E-06

1.E-05

10 100 1000 10000 100000

k g' (

mo

l/P

a s

m2)

PCO2* (Pa)

40 °C

7 m MMEA

8 m PZ

7 m DEA

8 m 2-PE

7 m DIPA

8 m PZ

205

and average packing area (Ap/Vg) for coal flue gas conditions are summarized in Table

7.11.

7.2.5 Effect of base strength

Figure 7.8: The kg’avg at coal flue gas conditions and the pKa of the amine. Dashed lines:

potential trends; empty points: hindered amine solvents

The effective CO2 absorption rate (kg’avg) at process conditions (coal) is compared

with the pKa of the amine in Figure 7.8. Primary and secondary amines show different

kg’avg dependence on pKa. The secondary amines are about twice as fast as the primary

amines. The maximum rate occurs at pKa 8.5-9.0 for primary amines and pKa 9-9.5 for

secondary amines. Hindered amines have slightly lower kg’avg than their unhindered

equivalent. Still, 8 m 2-PE, a hindered secondary amine, has higher kg’avg than all

unhindered primary amines with similar pKa. Also, 4.8 m AMP, a hindered primary

amine, has competitive kg’avg with other primary amines with higher pKa.

0

2

4

6

8

8 8.5 9 9.5 10

k g' a

vg @

40

°C

(m

ol/

Pa

s m

2)

pKa @ 40 °C

7 m MMEA

7 m DEA 6 m SarK

7 m DIPA

10 m DGA®

7 m MEA

7 m MIPA

6.5 m β-alaK

3.5 m GlyK

7 m MPA4.8 m AMP

8 m 2PE

Secondary

Primary

206

7.3 CO2 VLE RESULTS

The CO2 VLE of the amine solvents was measured using the WWC (Section 3.1).

For 7 m DEA and 7 m DIPA, PCO2* was measured at 20, 40, 60, and 80 °C. For 7 m

MIPA, 7 m MPA, and 7 m MMEA, data was also collected at 100 °C. The CO2 loading

in the liquid phase is varied across the operating range for coal flue gas. For each

solvent, a semi-empirical VLE model is developed to represent the data using Equation

4.4 (Table 7.5). The model can be used to interpolate within the experimental CO2

loading and temperature; as well as extrapolate near the experimental conditions.

The CO2 VLE curve at 40 °C is used to estimate the CO2 capacity of each solvent

for coal flue gas conditions. The temperature dependence of the CO2 VLE used to

estimate the heat of absorption in each solvent.

7.3.1 CO2 solubility data

The CO2 solubility data for 7 m MIPA is plotted in Figure 7.9, which is compared

with data for 30 wt% MIPA at 40 °C by Morales et al. (2010). Also shown in the plot is

the fit of the semi-empirical model and the CO2 solubility curve at 40 °C for MEA (Xu

2011). The semi-empirical model was regressed using only WWC data, and the results

fit the data well. Most of the 30 wt% MIPA data are at much higher CO2 loading than

this work. The only overlapping point suggests good agreement between the two sets of

results. The semi-empirical model does not fit the 30 wt% MIPA data at high CO2

loadings, and should not be used to extrapolate beyond the WWC experimental loading.

Compared to MEA, 7 m MIPA has similar CO2, which is expected as the two amines

have similar pKa and hindrance.

207

Figure 7.9: CO2 solubility data (solid diamonds) and the semi-empirical model fit (Table 7.5, solid lines) for 7 m MIPA, compared with 40 °C solubility curve for

MEA (dashed line, Xu 2011) and 40 °C data for 30 wt% MIPA (empty

circles, Rebolledo-Morales et al. 2010).

The CO2 solubility measurements for 7 m MPA are plotted in Figure 7.10. The

semi-empirical model fits the experimental data well except for the lowest CO2 loading at

40 °C. This is most likely due to large error associated with this data point, which is

collected at the limit of the experimental method. Thus, the PCO2* estimated by the

semi-empirical model is reported instead (Table 7.7). At CO2 loading below 0.5, CO2 is

more soluble in 7 m MPA than MEA, as MPA has higher pKa than MEA and is expected

to have stronger chemical interactions with CO2.

10

100

1000

10000

100000

1000000

0.25 0.35 0.45 0.55 0.65 0.75 0.85

40 °C

80 °C

60 °C

20 °C

7 m MEA @ 40 °C

100 °C

30 wt % MIPA(Rebolledo-

Morales et al. 2010)

208

Figure 7.10: CO2 solubility data (solid diamonds) and the semi-empirical model result

(solid lines, Table 7.5) for 7 m MPA, compared with CO2 solubility curve at 40 °C for MEA (Xu 2011).

Figure 7.11: CO2 solubility data (solid diamonds) the semi-empirical model fit (solid

lines, Table 7.5) for 7 m DEA, compared with data for 5 M DEA (asterisk, Lee et al. 1972), and MEA at 40 °C (dashed line, Xu 2011)

10

100

1000

10000

100000

0.3 0.35 0.4 0.45 0.5 0.55 0.6

PC

O2*

(Pa)


40 °C

80 °C

60 °C

100 °C

20 °C7 m MEA @ 40 °C

100

1000

10000

100000

1000000

0.15 0.35 0.55 0.75

PC

O2*

(Pa)


5 M DEA

40 °C

80 °C

60 °C

20 °C

MEA @ 40 °C

209

The CO2 solubility data in 7 m DEA is plotted in Figure 7.11. The semi-

empirical model fits the WWC data well. Compared with data for 5 M DEA at 40 °C,

both the WWC data and semi-empirical model shows good agreement. At low loading,

DEA has lower CO2 solubility than MEA due to its low pKa.

Figure 7.12: CO2 solubility data (solid diamonds) and the semi-empirical model fit (solid curves) for 7 m MMEA, compared with MEA at 40 °C (dashed lines, Xu

2011)

The CO2 solubility data for 7 m MMEA is plotted in Figure 7.12. The semi-

empirical model fits the data well. The solubility of CO2 in 7 m MMEA is very similar

to MEA at 40 °C, although the pKa of MMEA is higher than MEA. Compared to

primary amines with similar pKa, such as MPA, CO2 is less soluble in MMEA. The

reduced CO2 solubility could be the result of the second functional group on the nitrogen,

which reduces its affinity to CO2.

10

100

1000

10000

100000

0.15 0.25 0.35 0.45 0.55

PC

O2

(Pa)


40 °C

80 °C

60 °C

20 °C

100 °C

MEA @ 40 °C

210

The CO2 solubility data for 7 m DIPA is shown in Figure 7.13. The semi-

empirical model fits the WWC data well. The model is extrapolated to 25 °C and CO2

loading much higher than the WWC experiment to compare with literature data for 34

wt% DIPA (Era et al. 2010). The model agrees well with the 34 wt% data despite the

extrapolation. Compared to MEA, the CO2 solubility in 7 m DIPA is much lower,

which is a result of the much lower pKa of DIPA.

Figure 7.13: CO2 solubility data (solid diamonds) and semi-empirical model (solid lines) for 7 m DIPA, compared with data at 25 °C for 34 wt% DIPA (Dell’Era et

al. 2010), and MEA at 40 °C

The regressed parameters of the semi-empirical model for the five amine solvents

and their statistics are summarized in Table 7.5. The CO2 solubility and kg’ data for the

solvents are tabulated in Table 7.6-7.10.

100

1000

10000

100000

0.05 0.15 0.25 0.35 0.45 0.55 0.65

PC

O2

(Pa)


40 °C

80 °C

60 °C

20 °C

25 °C34 wt%

DIPA(Dell'Era et

al. 2010)

MEA @ 40 °C

211

Table 7.5: Semi-empirical CO2 VLE model parameter values

(ln(𝑃𝐶𝑂2∗ ) = 𝑎 +

𝑏


2 + 𝑒 ∙𝛼𝐶𝑂2

𝑇+ 𝑓 ∙

𝛼𝐶𝑂22

𝑇

a b x 10-3 c d e x 10-4 f x 10-4 R2

7 m MIPA -23.0±20.2 8.99±6.63 357±108 -485±140 -11.91±3.52 17.03±4.53 0.993

7 m MPA 53.5±1.7 -14.76±0.38 -36±3.2 0 0 2.27±0.12 0.995

7 m DEA 33.5±0.1 -9.05±0.20 5.1±2.0 0 0 0.32±0.99 0.995

7 m MMEA 25.0±3.8 -7.09±1.29 91±23 -156±32 -2.99±0.76 5.83±1.04 0.999

7 m DIPA 42.8±2.4 -12.41±0.79 -39.5±26.1 98.3±66.1 1.83±0.83 -3.19±2.08 0.999

Table 7.6: CO2 Solubility and kg’ for 7 m monoisopropanolamine (MIPA)

CO2 ldg T kg' Х 107 PCO2*

mol/mol alk ˚C mol/Pa s m2 kPa

0.455 20 4.51 0.11

0.487 20 2.58 0.38

0.514 20 1.21 2.30

0.278 40 20.50 0.04

0.333 40 14.20 0.10

0.398 40 8.67 0.34

0.455 40 5.64 1.04

0.487 40 3.36 3.34

0.514 40 1.15 15.12

0.278 60 22.80 0.28

0.333 60 15.80 0.83

0.398 60 9.69 2.72

0.455 60 6.51 7.07

0.487 60 3.13 18.60

0.514 60 3.79 22.73

0.278 80 25.50 2.12

0.333 80 18.30 5.39

0.398 80 9.79 16.03

0.278 100 21.60 12.83

0.333 100 12.05 27.81

212

Table 7.7: CO2 Solubility and kg’ results for 7 m monopropanolamine (MPA)

CO2 loading T kg' Х 107 PCO2*


0.553 20 1.18 1.75

0.586 20 0.60 6.34

0.325 40 23.20 0.01a

0.385 40 14.15 0.03

0.472 40 7.84 0.25

0.508 40 3.58 1.06

0.553 40 1.37 8.66

0.586 40 0.32 39.95

0.325 60 23.10 0.14

0.385 60 17.10 0.30

0.472 60 8.87 1.77

0.508 60 4.28 7.12

0.553 60 1.22 31.08

0.325 80 27.20 0.92

0.385 80 19.41 2.11

0.472 80 9.43 10.11

0.508 80 3.36 31.28

0.325 100 24.90 6.56

0.385 100 16.40 12.12

0.472 100 5.99 42.06 a Calculated using semi-empirical model (Table 1)

213

Table 7.8: CO2 Solubility and kg’ results for 7 m diethanolamine (DEA)



0.314 20 6.18 0.22

0.349 20 5.61 0.31

0.412 20 3.25 0.73

0.470 20 2.28 1.71

0.189 40 10.10 0.41

0.253 40 7.07 0.76

0.303 40 5.65 1.36

0.348 40 5.44 2.23

0.414 40 3.37 5.95

0.455 40 2.14 12.59

0.188 60 9.48 2.04

0.250 60 7.29 4.35

0.309 60 5.76 7.26

0.349 60 5.54 11.39

0.431 60 3.13 24.97

0.188 80 8.21 9.76

0.251 80 6.53 19.08

0.303 80 5.06 29.64

0.342 80 5.80 46.84

214

Table 7.9: CO2 Solubility and kg’ results for 7 m methylmonoethanolamine (MMEA)



0.470 20 9.98 0.22

0.524 20 3.89 1.47

0.554 20 2.21 4.84

0.208 40 185.09 0.02

0.312 40 37.71 0.08

0.405 40 21.90 0.30

0.470 40 11.56 1.36

0.524 40 4.78 6.03

0.554 40 2.28 16.41

0.208 60 69.68 0.13

0.312 60 42.39 0.49

0.405 60 22.10 2.04

0.470 60 11.06 6.72

0.524 60 4.63 20.54

0.208 80 74.63 0.80

0.312 80 35.41 2.83

0.405 80 15.48 10.64

0.470 80 7.19 28.64

0.208 100 61.92 5.13

0.312 100 25.97 14.09

0.405 100 7.70 47.76

215

Table 7.10: CO2 Solubility and kg’ results for 7 m diisopropanolamine (DIPA)



0.238 20 1.99 0.21

0.315 20 1.28 0.78

0.100 40 6.83 0.16

0.165 40 3.20 0.54

0.238 40 2.30 1.71

0.315 40 1.26 6.89

0.100 60 4.42 1.19

0.165 60 3.59 3.73

0.238 60 2.42 11.46

0.100 80 4.30 8.27

0.165 80 3.37 20.46

7.3.1 Effect of amine type

Figure 7.14: CO2 solubility curves at 40 °C for primary amines, compared with MEA

(Dugas 2009), 10 m DGA®, GlyK, and 6.5 m β-alaK (Chapter 5).

100

1000

10000

0.35 0.45 0.55

PC

O2

(Pa)


6.5 mβ alaK

GlyK

10 m DGA®

7 m MIPA 7 m MPA

MEA

216

The CO2 solubility in two primary amine solvents, 7 m MIPA and 7 m MPA, is

compared in Figure 7.14. Also included in the plot are MEA (Xu 2011) and 10 m

DGA® (Chen et al. 2011) and two primary amino acids, GlyK and 6.5 m β-alaK. All of

the unhindered primary amines have similar CO2 solubility, with lean loadings around 0.4

and rich loadings around 0.5. The slope of the equilibrium curves is also similar for the

unhindered primary amines.

Figure 7.15: CO2 solubility at 40 °C for secondary amine solvents, compared with MEA

and PZ (Dugas 2009), 8 m 2PE (Chen and Rochelle 2011), and SarK(Na)

(Chapter 5).

The CO2 solubility in the three secondary amines is compared in Figure 7.15, with

PZ and MEA (Xu 2011), 8 m 2PZ (Chen and Rochelle 2011), and SarK(Na) (Chapter 5).

For 7 m MMEA, its CO2 solubility is about the same as MEA. For the sarcosine based

solvents, where sarcosine is a secondary amino acid, its CO2 solubility curve have about

the same slope as MEA and MMEA, only it operates at higher loadings than the other

solvents. For 7 m DIPA and 7 m DEA, the CO2 solubility is great reduced compared to

100

1000

10000

0 0.2 0.4 0.6 0.8

PC

O2

(Pa)


8 m 2PE

MEA

SarK/SarNa

7 m MMEA

7 m DIPA

7 m DEAPZ

217

MMEA and MEA due to their low pKa values. The slope of the CO2 solubility curves

differs significantly between DIPA and DEA, where the slope for DEA is much lower

and similar to hindered amines. The CO2 solubility curve for 8 m 2PE, a hindered

secondary amine, has a lower slope than DEA.

7.3.2 CO2 Capacity

The CO2 solubility at 40 °C suggests the CO2 capacity of the solvent in a capture

process, which can be calculated using Equation 4.9 (Section 4.2.3). The CO2 capacity

of a solvent is determined by the slope of the solubility curve (Δldg), as well as the

molecular weight of the amine and the total concentration of alkalinity in the solvent.

The capacity of the two primary amine solvents, 7 m MIPA and 7 m MPA, is lower

than 7 m MEA because of their low Δldg and their slightly higher molecular weight.

The capacity of the secondary amine solvent 7 m MMEA is only slightly lower than 7 m

MEA due to a higher molecular weight. The Δldg for 7 m DEA is much higher than 7

m MEA, which gives it a greater capacity despite the high molecular weight of DEA.

For 7 m DIPA, its high Δldg is counter balanced by the high molecular weight of DIPA

and results in a capacity that is similar to 7 m MEA.

The calculated capacity, Δldg, and the lean/rich loadings for the five solvents are

summarized in Table 7.11 and compared with other amines.

7.3.2 Heat of Absorption

The heat of absorption for each amine solvent is estimated from CO2 solubility

data as discussed in Section 4.1.3. The results at the operating range for coal flue gas

are plotted in Figure 7.16 for the primary amines and in Figure 7.17 for the secondary

amines. The estimated ∆Habs for 7 m MIPA is higher than MEA at lean loadings. For

7 m MPA, the estimated ∆Habs is about the same as MEA.

218

Figure 7.16: Heat of absorption of CO2 in 7 m MIPA and 7 m MPA compared with MEA

(Xu 2011).

Figure 7.17: Heat of absorption of CO2 in 7 m DEA, 7 m MMEA, and 7 m DIPA,

compared with MEA and PZ (Xu 2011).

The ∆Habs for 7 m DEA is lower than MEA at lean loadings but competitive with

MEA at rich loadings. For 7 m DIPA, the estimated –Habs is much higher than MEA.

50

60

70

80

90

100

500 5000

-∆H

abs

(kJ/

mo

l)

PCO2* @ 40 °C (Pa)

7 m MIPA

7 m MPA

MEA

50

60

70

80

90

100

500 5000

-∆H

abs

(kJ/

mo

l)

PCO2* @ 40 °C (Pa)

MEA

PZ

7 m DIPA

7 m MMEA

7 m DEA

219

The high ∆Habs for DIPA and moderate ∆Habs for DEA despite their low pka is due to the

lower operating CO2 loading. The ∆Habs for 7 m MMEA is about the same as MEA at

lean loading, but it decreases significantly with loading and is much lower than MEA at

rich loading.

The ∆Habs for the solvents at 1.5 kPa is summarized in Table 7.11. As discussed

in Section 4.1.3, there is uncertainty associated with the estimated ∆Habs for the five

solvents in this work, as only WWC solubility data is used. The estimation method

potentially over-predicts the ∆Habs by up to 5-10 kJ/mol.

Table 7.11: Summary of solvent performance for coal flue gas compared to related

solvents in the literature

Conc kg'avg

@ 40 ˚C Capacity* ∆ldg ldglean ldgrich

∆Habs @

PCO2* = 1.5

kPa

(m) x 107 mol/ Pa s

m2

mol/kg

solv

mol/mol

alkalinity

mol/mol

alkalinity kJ/mol

MIPA 7 4.22 0.35 0.080 0.42 0.50 80

MPA 7 2.65 0.27 0.055 0.49 0.54 73

DEA 7 4.86 0.80 0.199 0.21 0.41 73

MMEA 7 8.36 0.43 0.093 0.43 0.52 68

DIPA 7 1.99 0.48 0.133 0.16 0.30 82

MEA

(Dugas 2009, Xu

2011)

7 4.25 0.5 0.096 0.43 0.53 73

DGA®

(Chen et al. 2011) 10 3.61 0.38 0.08 0.41 0.49 81

AMP

(Chen et al. 2011) 4.8 2.39 0.96 0.29 0.27 0.56 73

2PE

(Chen and Rochelle

2011)

8 3.5 1.23 0.31 0.37 0.68 73

PZ

(Dugas 2009,

Xu 2011)

8 8.5 0.79 0.08 0.31 0.39 64

* ∆𝐶𝑠𝑜𝑙𝑣 =(∝𝑟𝑖𝑐ℎ − ∝𝑙𝑒𝑎𝑛)∙𝑚𝑜𝑙 𝑎𝑙𝑘𝑎𝑙𝑖𝑛𝑖𝑡𝑦



𝑘𝑔(𝑎𝑚𝑖𝑛𝑒+𝐻2𝑂) (Equation 4.9)

220

7.4 CONCLUSIONS

In general, secondary amines have up to double the effective CO2 mass transfer

rates than primary amines at process conditions for coal. At pKa above 9, the kg’avg of

primary amines decreases with increase in amine pKa. The highest absorption rate for

primary amines occurs between pKa of 8.5 and 9. For secondary amines, highest kg' is

observed at amine pKa of 9.5. Hindered amines have lower kg’avg than the unhindered

amines at the same pKa. Still, secondary hindered amines have higher absorption rates

than most of the primary amines. Among the five solvents tested, 7 m MMEA has the

highest absorption rate, which is competitive with 8 m PZ.

Primary and secondary amines with similar pKa and hindrance, such as MPA and

MMEA, have similar CO2 solubility. Amines with higher pKa have higher CO2

solubility, which corresponds to higher CO2 loadings at the same PCO2*. Hindered

amines have CO2 solubility curves that are more flat than unhindered amines, which

correspond to greater CO2 carrying capacity. Among the solvents tested in this work, 7

m DEA has the greatest capacity, which is greater than 7 m MEA, but still less than 8 m

PZ.

221

Chapter 8: Other solvents and overall comparison

8.1 INTRODUCTION

In the first section of this chapter, the CO2 absorption rate and solubility

measurements in five additional solvents are presented and compared with other related

solvents. In the second section, all amine solvents tested by the current method are

compared together. Specifically, the absorption rate and CO2 capacity of the solvents

are generalized based on amine structures.

8.2 AQUEOUS AMINES AND BLENDS

8.2.1 MEA/MDEA

The blend of 3.4 m methyldiethanolamine (MDEA)/9.8 m monoethanolamine

(MEA) (equivalent of 20 wt % MDEA, 30 wt % MEA) is potentially an attractive solvent

for CO2 absorption. Compared to 7 m MEA (30 wt %), the blend has higher alkalinity

which provides higher CO2 carrying capacity. The blend is expected to have good

absorption rate, as the addition of MDEA will allow more free MEA species in the

absorption process. Also, MDEA has been shown to be an effective oxidation inhibitor

in 7 m MEA at absorber conditions (Voice 2013).

The absorption/desorption rates and CO2 solubility of 3.4 m MDEA/9.8 m MEA

were measured in the WWC at 20,40, 60, 80, 100 °C and variable CO2 loadings. The

cyclic capacity and heat of absorption of the blend is estimated from CO2 solubility

results. The viscosity of this solvent is measured at 40 °C. The performance of this

blend is compared to 7 m MEA.

222

Solvent preparation

The amine solvents were prepared gravimetrically. To achieve each CO2

loading, gaseous CO2 (99.99%, Matheson Tri-Gas) was bubbled into the solvent. The

chemicals used in solvent preparation are listed in Table 8.1. The CO2 loading in the

liquid solvent was verified by measuring total alkalinity using acid titration and the CO2

concentration using the total inorganic carbon method (Section 3.3).

Table 8.1: Materials used for preparation of the MEA/MDEA


Monoethanolamine 98% Acros

Methyldiethanolamine 99% Huntsman


Viscosity

Figure 8.1: Viscosity of 3.4 m (20 wt %) MDEA/9.8 m (30 wt %) MEA at 40 °C (solid

diamonds). Compared with experimental data (solid circles) and model

prediction (dashed lines) by Weiland (1998) for 7 m MEA and 20 wt % MDEA/30 wt% MEA at 40 °C, and three MDEA/MEA solvents at 25 °C.

0

4

8

12

0 0.1 0.2 0.3 0.4 0.5

Vis

oci

sty

(cP

)


25 °C

40 °C

7 m (30 wt %) MEA @40 °C

20 wt % MDEA/ 30 wt % MEA




223

The viscosity of this blend was measured using a rheometer (Section 3.3.3) at 40

°C and six CO2 loadings. The experimental data are shown in Figure 8.1 (solid

diamonds). The data agrees well with the predictions of an empirical viscosity model

developed by Weiland (1998). The viscosity of the blend at 40 °C is greater than 7 m

MEA. Viscosity data was collected by Weiland (1998) for MEA/MDEA at three

different amine ratios at 25 °C. The ratio of the amines does not significantly affect the

viscosity of the solvent. The viscosity data for 3.4 m MDEA/9.8 m MEA are


Table 8.2: Viscosity of 3.4 m (20 wt %) MDEA/9.8 m (30 wt %) MEA at 40 °C



0.249

6.50 0.21

6.41 0.08 6.37 0.16

6.36 0.14

0.288

6.43 0.19

6.46 0.04 6.45 0.20

6.50 0.19

0.335

6.79 0.09

6.67 0.10 6.61 0.17

6.62 0.16

0.366

6.75 0.17

6.80 0.06 6.77 0.15

6.87 0.22

0.408

7.48 0.25

7.50 0.02 7.51 0.25

7.51 0.25

0.44

7.60 0.26

7.61 0.02 7.61 0.27

7.63 0.25294

224

Absorption rate

Figure 8.2: CO2 absorption rate for 3.4 m MDEA/9.8 m MEA. Dashed lines: 7 m MEA

(Dugas 2009).

Figure 8.3: CO2 absorption rate at 40 °C for 3.4 m MDEA/9.8 m MEA, compared with 7

m MEA, 8 m PZ (Dugas 2009), 5 m PZ 5 m MDEA, and 2 m PZ 7 m

MDEA (Chen et al. 2011)

1.E-07

1.E-06

10 100 1000 10000

k g' (

mo

l/P

a s

m2)

PCO2* @ 40 C (Pa)

40 °C

80 °C

60 °C100 °C

20 °C

7 m MEA @ 40 °C

1.E-07

1.E-06

10 100 1000 10000

k g' (

mo

l/P

a s

m2 )

PCO2* @ 40 °C (Pa)

40 °C8 m PZ

7 m MEA

3.4 m MDEA/9.8 m MEA

5 m MDEA/5 m PZ

7 m MDEA/2 m PZ

225

The CO2 absorption rate for 3.4 m MDEA/9.8 m MEA is given in Figure 8.2.

The measured kg’ shows little temperature dependence between 40 and 100 °C. At high

CO2 loading, the kg’ at 20 °C is slightly lower than other temperatures. Compared to 7

m MEA, the blend has about the same kg’ at 40 °C.

The absorption rate of the blend at 40 °C is further compared with other solvents

in Figure 8.3. Compared to two PZ/MDEA blends, where the kg’ of the blend is lower

than 8 m PZ, the addition of MDEA to MEA does not show the same effect.

The kg’ data at 40 °C were used to estimate the rate performance of this solvent in

an isothermal absorber for coal flue gas (kg’avg , Equation 4.6). The result is summarized

in Table 8.6.

CO2 solubility

Figure 8.4: CO2 solubility in 3.4 m MDEA/9.8 m MEA. Diamond: WWC results. Solid

lines: empirical model (Table 8.3). Dashed line: empirical model of 7 m

MEA (Xu 2011).

10

100

1000

10000

100000

0.2 0.25 0.3 0.35 0.4 0.45

PC

O2*

(Pa)


40 °C

80 °C

60 °C

100 °C

20 °C

7 m MEA @ 40 °C

226

The CO2 solubility results for 3.4 m MDEA/9.8 m MEA are plotted in Figure 8.4.

The semi-empirical model (Equation 4.4) fits the experimental data well. The blend has

higher PCO2* than 7 m MEA at the same CO2 loading. The addition of MDEA reduced

the CO2 solubility of 30 wt % MEA. As a result of this reduced solubility, the operation

lean and rich loading for the blend are lower than 7 m MEA.

Table 8.3: Semi-empirical VLE model parameters for 3.4 m MDEA/9.8 m MEA

(Equation 4.4)

ln(𝑃𝐶𝑂2∗ ) = 𝑎 +

𝑏


2 + 𝑒 ∙𝛼𝐶𝑂2

𝑇+ 𝑓 ∙

𝛼𝐶𝑂22

𝑇

Parameter Standard Error

a 39.5 1.0

b -11636.2 311.2

c 0 /

d -28.9 8

e 0 /

f 19893.6 2591.5

R2 0.997

The semi-empirical model is used to estimate the cyclic capacity and heat of

absorption of 3.4 m MDEA/9.8 m MEA. The cyclic capacity of the blend is calculated

to be 0.58 mol/kg solvent (Equation 4.9), which is slightly higher than 7 m MEA. The

blend has a relatively high alkalinity concentration (12.2 m), which is offset by its low

delta loading (corresponding to the steep slope of the equilibrium curve) and resulted in a

moderate capacity. The viscosity normalized capacity (Cµ) for this blend is calculated

using the measured viscosity data and Equation 4.17. The calculated Cµ is about the

same as 7 m MEA. The high solvent capacity of the blend is offset by is high viscosity.

The estimated heat of absorption of CO2 (Equation 4.5) at the mid-point between

the operation lean and rich loading (PCO2* at 1.5 kPa) is about 73 kJ/mol of CO2, which is

about the same as 7 m MEA.

227

The calculated kg’avg, capacity, heat of absorption, and operation lean and rich

loading for coal flue gas are summarized in Table 8.4 and compared to 7 m MEA. The

measured values kg’ and PCO2* by the WWC are summarized in Table 8.5.

Table 8.4: Predicted performance parameters of 3.4 m MDEA/9.8 m MEA

Con kg'avg @ 40 ˚C Csolv Cµ

-∆Habs @

PCO2* =1.5

kPa

(m) Х107 mol/Pa s m2 mol/kg solv kJ/mol

MDEA/MEA 3.4 / 9.8 3.9 0.58 0.62 73

MEA 7 4.3 0.50 0.61 72

MDEA/PZ 5 / 5 8.3 0.98 0.95 69

7 / 2 6.9 0.8 0.82 68

PZ 8 8.5 0.79 0.79 64

Table 8.5: PCO2* and kg’ measurement for 3.4 m MDEA/9.8 m MEA by the WWC

T ldg PCO2* kg'

˚C mol/mol kPa Х107 mol/Pa s m2

20 0.365 0.15 4.39

20 0.404 0.49 2.91

20 0.438 1.40 1.60

40 0.249 0.09 14.54

40 0.288 0.19 10.92

40 0.335 0.41 7.12

40 0.366 1.05 5.46

40 0.408 3.79 3.40

40 0.440 7.77 2.22

60 0.248 0.67 16.72

60 0.290 1.19 13.63

60 0.338 2.79 8.94

60 0.364 6.26 6.27

60 0.410 15.62 3.76

60 0.438 34.91 2.38

80 0.252 3.97 19.62

80 0.291 8.18 12.85

80 0.343 18.23 8.02

100 0.253 17.60 12.23

228

8.2.2 8 m Bis(amnioethyl)ether (BAE)

A new amine solvent, 8 m Bis(aminoethyl)ether (BAE), was tested for CO2

absorption. BAE was previously tested in a blend with PZ as 6 m PZ/2 m BAE

(Chapter 6). Based on the blend result, BAE is expected to have attractive heat of

absorption and thermal stability. Absorption rate and low temperature VLE were

measured for 8 m BAE using the WWC, and high temperature VLE was measured using

the total pressure apparatus. An empirical equilibrium model was regressed using VLE

data, and the solvent capacity and heat of absorption are calculated using the model.

NH2

O

NH2

Figure 8.5: Molecular structure of bis(aminoethyl)ether (BAE)

Solvent preparation

The 8 m BAE solvent was prepared gravimetrically by mixing BAE (Huntsman,

99%) with water (Millipore, Direct-Q). To achieve each CO2 loading, gaseous CO2

(99.99%, Matheson Tri-Gas) was bubbled into the solvent. The CO2 loading in the

solvent was verified using TIC and acid titration (Section 3.3).

229

Viscosity

Figure 8.6: Viscosity of 8 m BAE (solid diamonds), compared with 8 m PZ (Freeman 2011) and 6 m PZ/2 m BAE (Chapter 6) at 40 °C

The viscosity of 8 m BAE was measured at 25, 40, and 60 °C, and the results are

plotted in Figure 8.6. At 40 °C, the viscosity of 8 m BAE is about the same as 8 m PZ

and 6 m PZ/2 m BAE.

5

10

15

20

25

30

0.20 0.25 0.30 0.35 0.40 0.45 0.50

Vis

cosi

ty (

cP)


25 °C

40 °C

60 °C

8 m PZ

8 m BAE

6 m PZ 2 m BAE

230

Table 8.6: Viscosity for 8 m BAE at 25, 40, and 60 °C

T (°C) CO2 loading µ St. Dev µavg St.Dev

C mol/mol alkalinity cP cP cP cP

25

0.331

17.56 0.15

17.43 0.23 17.57 0.12

17.17 0.10

0.413

21.91 0.17

21.84 0.12 21.70 0.09

21.92 0.15

0.425

21.96 0.12

21.86 0.19 21.64 0.12

21.99 0.19

0.474

28.82 0.16

28.69 0.12 28.61 0.13

28.63 0.15

40

0.331

10.50 0.16

10.21 0.25 10.10 0.15

10.03 0.17

0.413

12.75 0.18

12.71 0.04 12.67 0.19

12.70 0.20

0.425

12.69 0.19

12.67 0.05 12.71 0.21

12.62 0.20

0.474

16.64 0.21

16.55 0.20 16.32 0.24

16.69 0.17

60

0.331

6.56 0.19

6.64 0.27 6.41 0.23

6.94 0.11

0.413

7.14 0.15

7.06 0.09 7.08 0.23

6.97 0.23

0.425 8.48 0.24

8.72 0.35 8.97 0.16

0.474

7.72 0.18

7.66 0.06 7.64 0.16

7.60 0.23

231

Absorption rate

The kg’ results of 8 m BAE are plotted in Figure 8.7. The absorption rate of 8 m

BAE is compared with 7 m MEA and 8 m PZ at 40 ˚C. 8 m BAE has similar rate to 7 m

MEA at low loadings. At high loadings, the kg’ of 8 m BAE is lower than 7 m MEA. 8

m BAE is significantly slower than 8 m PZ, though they have the same total alkalinity.

The measured kg’ for 8 m BAE shows significant temperature dependence at rich loading

and high temperature.

Figure 8.7: Absorption rate of 8 m BAE. Empty circles: 8 m PZ. Empty squares: 7 m

MEA (Dugas 2009). Empty square: 6 m PZ/2 m BAE (Chapter 6).

5.E-8

5.E-7

5.E-6

50 500 5000

k g' (

mo

l/P

a s

m2)

PCO2* 40 C (Pa)

40 °C

60 °C

80 °C

20 °C

7 m MEA@ 40 °C

100 °C

8 m PZ@ 40 °C

232

Figure 8.8: Absorption rate at 40 °C for 8 m BAE, compared with 8 m PZ, 7 m MEA

(Dugas 2009), 6 m PZ/2 m BAE (Chapter 6), and 10 m DGA® (Chen and

Rochelle 2011).

The kg’ at 40 °C for 8 m BAE is further compared with 8 m PZ, 7 m MEA, 10 m

DGA®, and 6 m PZ/2 m BAE in Figure 8.8. The kg’ of 6 m PZ/2 m BAE is about the

same as 8 m PZ and much higher than 8 m BAE, which suggests PZ is the main reaction

species in the 6 m PZ/2 m BAE. The rate of 8 m BAE is similar to 10 m DGA®, as the

two amines are both primary amines and have similar pKa.

The average absorption rate (kg’avg) of the solvent in an isothermal absorber at 40

˚C for 90% CO2 removal from coal flue gas is calculated using Equation 4.6 and the

value is shown in Table 8.8. The kg’avg for 8 m BAE is only 40% of 8 m PZ and also

15% less than 7 m MEA.

1.E-08

1.E-07

1.E-06

1.E-05

10 100 1000 10000

k g' (

mo

l/P

a s

m2)

PCO2* (Pa)

40 °C

7 m MEA

8 m PZ6 m PZ 2 m BAE

10 m DGA®

8 m PZ

233

CO2 solubility

Figure 8.9: CO2 solubility in 8 m BAE. Squares: WWC. Circles: total pressure.

Solid lines: empirical model (Equation 4.4). Dashed line: MEA (Xu 2011).

The CO2 solubility data for 8 m BAE are plotted in Figure 8.9. The semi-

empirical VLE model (Equation 4.4) was regressed by fitting both WWC and total

pressure data. The model parameters are summarized in Table 8.7. Overall, the total

pressure results show good agreement with WWC measurements. The model-predicted

equilibrium curves show good agreement with measured data. However, the WWC

measurements at high temperature are under-predicted, and the 40 ˚C results are slightly

over-predicted. The WWC result demonstrates higher temperature dependence than the

high temperature result and the model prediction. The overall fit of the model has an R2

value of 0.993. At 40 °C, 8 m BAE has similar VLE to MEA (dashed lines in Figure

8.9).

1E+1

1E+2

1E+3

1E+4

1E+5

1E+6

0.32 0.36 0.4 0.44 0.48 0.52

PC

O2*

(Pa)


40 °C

60 °C

80 °C

20 °C

100 °C

130 °C120 °C

110 °C

150 °C140 °C

160 °C

234

Table 8.7: Parameters of the equilibrium model for 8 m BAE (Equation 4.4)

ln(𝑃𝐶𝑂2∗ ) = 𝑎 +

𝑏


2 + 𝑒 ∙𝛼𝐶𝑂2

𝑇+ 𝑓 ∙

𝛼𝐶𝑂22

𝑇

8 m BAE

Coefficient Std.err

a 39.0 1.7

b -11867 641

c 0 /

d 0 /

e -18.0 9.5

f 14853 3441

R2 0.993

The semi-empirical model is used to estimate the cyclic capacity and heat of

absorption for 8 m BAE. The cyclic capacity of the blend is calculated to be 0.63

mol/kg solvent (Equation 4.9), which is higher than 7 m MEA and about 20 % less than 8

m PZ. The viscosity normalized capacity (∆Cµ) for this blend is calculated using the

measured viscosity data and Equation 4.17. The calculated Cµ is about the same as 7 m

MEA. The estimated –Habs (Equation 4.5) for 8 m BAE is about the same as 7 m MEA.

Table 8.8: Performance parameters of 8 m BAE, compared with 8 m PZ, 7 m MEA

(Dugas 2009, Xu 2011), 10 m DGA®(Chen 2011), and 6 m PZ/2 m BAE

(Chapter 6)

kg'avg Х107

@ 40 ˚C ΔCsolv ΔCµ

-∆Habs

(PCO2* = 1.5 kPa)

mol/Pa∙m∙s2 mol/kg solv kJ/mol

8 m BAE 3.2 0.63 0.61 73

6 m PZ/ 2 m BAE 7.3 0.69 0.68 63

10 m DGA® 3.6 0.38 0.38 81*

8 m PZ 8.5 0.79 0.79 67

7 m MEA 4.3 0.5 0.61 72

* estimated with WWC data only, potentially overpredict true value (Section 4.1.3)

235

Table 8.9: PCO2* and kg’ measurement for 8 m BAE

T Loading PCO2* kg' Х 107 T Loading PCO2* Pmeas Ptotal

˚C mol/mol alk kPa mol/ Pa∙m∙s2 ˚C mol/mol alk kPa bar bar

20 0.488 0.35 2.85 100 0.498 245 4.61 3.34

20 / 1.35 1.25 110 0.494 478 7.04 6.03

40 0.352 0.09 21.4 120 0.491 701 10.10 8.75

40 0.404 0.24 9.89 120 0.425 203 5.13 3.78

40 0.444 0.74 6.14 130 0.347 110 4.81 3.47

40 0.488 3.55 2.31 130 0.422 390 7.60 6.27

40 / 13.53 0.52 130 0.420 318 6.73 5.55

60 0.352 0.86 16.8 130 0.485 1104 14.47 13.41

60 0.404 2.15 11.2 140 0.417 543 9.91 8.60

60 0.444 6.84 5.35 140 0.346 213 6.69 5.30

60 0.488 33.08 1.21 140 0.418 663 11.20 9.80

80 0.352 5.81 13.6 140 0.478 1557 19.99 18.74

80 0.404 13.48 6.95 150 0.412 913 14.66 13.31

80 0.444 41.47 2.21 150 0.412 1083 16.44 15.01

100 0.352 30.57 7.55 150 0.343 419 9.79 8.36

160 0.405 1428 23.19 21.73

160 0.338 723 14.11 12.65

160 0.405 1630 21.07 19.69

8.3 ENZYME CATALYZED AQUEOUS AMINE

Carbonic anhydrase is a class of enzymes which catalyze the bicarbonate

formation reaction between water and CO2 (Equation 8.1). HHCOOHCO Enzyme

322 (8.1)

It has been suggested this catalytic nature can be used to enhance the absorption

rate of amine solvents (Salmon 2009). Studies have shown carbonic anhydrase to have

a fast catalytic reaction rate and a high turnover rate (Khalifa 1971). However, it is

unclear whether these properties can result in good absorption performance at process

conditions.

236

In this work, an enzyme provided by Novozymes North America Inc., NS81239

carbonic anhydrase, was tested as a rate promoter for 4.8 m 2-amino-2-methyl-propane

(AMP).

Figure 8.10: Molecular Structure of 2-amino-2-methyl-propane (AMP)

As a hindered primary amine, AMP reacts with CO2 mainly by the bicarbonate

formation reaction (Equation 3), and the carbamate formation reaction is not favored.

Since the bicarbonate reaction is much slower than the carbamate reaction, the overall

absorption rate of this amine is slower than other primary amines (Section 2.1.2). On

the other hand, AMP has the advantage of having a large CO2 capacity. Adding the

enzyme to AMP can potentially improve its slow rates while maintaining the large

capacity.

The wetted wall column was used to measure the absorption rates. The enzyme

promoted solvent was tested at the lean and rich conditions (0.5 kPa and 5 kPa) for coal

flue gas. The temperatures of the experiments were 40 °C and 60 °C, which are typical

temperatures in the absorber. Two enzyme concentrations were tested: 100 ppm and

1000 ppm (mass of enzyme/mass of solvent). The measured rates with enzyme are

compared with rates for 4.8 m AMP (Chen 2011)

237

Solvent preparation

The materials used to prepare the enzyme promoted AMP solvent are summarized

in Table 8.10,



AMP 99.00% Acros Organics


NS81239 Enzyme

Solution 38g/L

Novozyme North

American Inc.

A solution of 4.8 m AMP was first prepared gravimetrically without the addition

of enzymes. The composition of the original solution is summarized in Table 8.11.

The solution was loaded to optimum lean loading (PCO2* = 0.5 kPa) by bubbling of

gaseous CO2 (99.99%, Matheson Tri-Gas). A baseline experiment measured the rate of

the solvent without enzyme acceleration at both 40 °C and 60 °C. Next, enzyme was

added to the same solution to make the 100 ppm concentration enzyme promoted

solution. Additional enzyme was then added to the same solution after the 100 ppm rate

experiments to reach the next concentration level at 1000 ppm enzyme. After these lean

loading experiments, more gaseous CO2 was added to the solution to reach the rich

condition of 4.8 m AMP (PCO2* = 5 kPa).

Table 8.11: Chemical Composition in 4.8 m AMP Solution

Chemical Species Mass (g) wt frac

AMP 522.1 0.303

Water 1199.8 0.697

238

Table 8.12: Species Composition in Enzyme Promoted AMP Solutions

Chemical

Species

Enzyme Concentration

None 100 ppm 1000 ppm

(g) (g) (g)

AMP 522.1 477.6 476.3

Water 1199.8 1097.5 1094.7

CO2 68.3 62.5 62.3

NS81239

Solution / 4.3 44.7

(Enzyme) / 0.16 1.7

The enzyme NS81239 carbonic anhydrase was provided by Novozymes North

America Inc. as a proprietary material. Only preliminary safety information is available

on the material, specifically regarding temperature and pH stability of the enzyme and

hazardous information.

Absorption rate results

The absorption rate measurements for enzyme promoted 4.8 m AMP are plotted

in Figure 8.11. The kg’ of the solvent without added enzyme agrees with the data

collected by Chen et al. (2011) at both 40 and 60 °C.

At 40 °C, addition of 100 ppm enzyme increases the kg’ of the solvent by 20%.

Increasing the enzyme concentration 10 times further increased the kg’ to about 40%

higher than the base case. These results suggest, at 40 °C and solvent lean loading, the

rate enhancement of the enzyme is proportional to the enzyme concentration.

239

Figure 8.11: Absorption Rates of 4.8 m AMP Promoted by Enzyme, compared with

rates of 4.8 m AMP (Chen 2011)

At 60 °C and lean loading, the addition of 100 ppm enzyme shows no rate

enhancement for 4.8 m AMP. With 1000 ppm enzymes added, the measured kg’ was

increased by approximately 15% from the base case. Thus, as temperature increases,

the enzyme is less effective for rate enhancement. At the rich loading, the addition of

1000 ppm enzymes increased the kg’ of the solvent by approximately 20% at both 40

°C and 60 °C.

The rate of the enzyme enhanced solvent decreases with increase of solvent CO2

loading. This suggests the activity of the enzymes is affected by CO2 loading in the

solvent, similar to amine based rate promoters.

The measured kg’ for the enzyme enhanced 4.8 m AMP is summarized in Table

8.13.

1.E-07

1.E-06

100 1000 10000 100000

k g'(

mo

l/P

a∙s∙

m2)

PCO2* (Pa)

Diamond: no enzyme, Xi Chen (2009)

Circles: no enzyme. this workTriangle (filled): 100 ppm enz

Triangle (empty): 1000 ppm enz (0.1wt %)

40 °C 60 °C

240

Table 8.13: Measured kg’ of 4.8 m AMP Promoted by Enzyme

Enzyme

Concentration

40 °C 60 °C

kg' PCO2* kg' PCO2*

ppm Х107

mol/s.Pa.m2 (kPa)

Х107

mol/s.Pa.m2 (kPa)

Lean

0 (Chen, 2010) 4.82 0.52 5.57 3.8

0 4.93 0.55 5.52 3.8

100 5.8 0.47 5.58 3.6

1000 6.65 0.51 6.33 3.4

Rich 0 (Chen, 2010) 1.67 5.4 1.58 30.2

1000 2.01 7.2 1.9 34.4

8.4 PROPRIETARY SYSTEMS

Proprietary materials provided by two companies (referred to as Company A and

Company B) were tested for their absorption rate and CO2 solubility performance. In

both cases, PZ was added in the solvent as a rate promoter.

The performance of the PZ promoted unknown solvents are experimentally

measured at conditions targeted for coal flue gas. Specifically, the liquid phase CO2

concentration range corresponds to CO2 equilibrium partial pressures (PCO2*) of 500 to

5000 Pa. The results these solvents are compared with the base case solvents for post

combustion amine scrubbing, 7 m MEA and 8 m PZ, as well as other potential solvents

for CCS.


The material provided by Company A is an ionic liquid (IL) based amine. The

ratio of IL to PZ is fixed at 9:1 in mass. Using this ratio of IL and PZ, two solvent

concentrations were tested with 50 wt % IL+PZ, and 30 wt % IL+PZ.

241

The material provided by Company B is an unknown amine. The Company B

solvent is composed of 50 wt % unknown amine with 7 wt % PZ in water.

The source of the components in the solvent are listed in Table 8.14. The

composition of the unknown solvents is listed in Table 8.15.



Piperazine 99% Sigma-Aldridge

Ionic liquid material 98% Company A

Unknown amine material 99% Company B


Table 8.15: Composition of the initial solution used in the wetted wall column

experiment

Company A #1 Company A#2 Company B

Chemical Mass fraction

PZ 0.5 0.3 0.071

Unknown 0.45 0.27 0.500

Water 0.50 0.70 0.429

Each solvent was prepared by gravimetrically mixing the amines with water.

To achieve each CO2 loading, gaseous CO2 (99.99%, Matheson Tri-Gas) was bubbled

into the solvent. At each CO2 loading, the composition of the CO2 free solvent stays the

same (Table 8.15). The concentration of CO2 in the solvent was quantified at each

experimental condition using the total inorganic carbon (TIC) method (Section 3.3).

8.4.2 Viscosity

The viscosity of the Company A solvents was measured at 20, 40, and 60 °C. At

each temperature, viscosity was measured at five different liquid phase CO2

concentrations (CCO2). The measured results of Company A solvent #1 and #2 are

plotted in Figure 8 and 9 respectively. In Figure 8.12 and 8.13, each data point is the

242

average of three separate measurements. The measured viscosity data for both solvents

are summarized in Table 8.17.

Figure 8.12: Viscosity of Company A solvent #1. Data points: experiment values. Solid

lines: viscosity correlation (Equation 8.2, Table 8.16)

Figure 8.13: Viscosity of Company A solvent #2. Data points: experiment values. Solid

lines: viscosity correlation (Equation 8.2, Table 8.16)

5

10

15

20

0.035 0.045 0.055 0.065 0.075

Vis

cosi

ty (

cP)

CCO2 (weight fraction)

40 °C

60 °C

20 °C

1.5

2

2.5

3

3.5

4

0.02 0.025 0.03 0.035 0.04 0.045

Vis

cosi

ty (

cP)

CO2 Mass Fraction

40 °C

60 °C

20 °C

243

The viscosity of solvent #1 is much higher than solvent #2 due to the higher

overall concentration of IL+PZ. The viscosity data were used to develop a viscosity

correlation, which can be used to predict the viscosity of the Company A solvents within

and close to the range of the experiment conditions. The mathematical form of the

correlation is shown in Equation 8.2a and 8.2b, where the ratio of solvent viscosity and

the viscosity of water (𝜇 𝜇𝑤𝑎𝑡𝑒𝑟⁄ ) is related to temperature, the mass fraction of each

amine in the solvent (Camine1 and Camine2, where amine 1 is the ionic liquid and amine 2 is

PZ), and the mass fraction of CO2.

𝑙𝑛 (𝜇

𝜇𝑤𝑎𝑡𝑒𝑟) = 𝑎 + Φ1 +

Φ2

T (8.2a)

Φ𝑖 = 𝑏𝑖 ∙ 𝐶𝑎𝑚𝑖𝑛𝑒1 + 𝑐𝑖 ∙ 𝐶𝑎𝑚𝑖𝑛𝑒2 + 𝑑𝑖 ∙ 𝐶𝐶𝑂2 + 𝑒𝑖 ∙ (𝐶𝑎𝑚𝑖𝑛𝑒1 + 𝐶𝑎𝑚𝑖𝑛𝑒2) ∙ 𝐶𝐶𝑂2 (8.2b)

The regressed parameters of Equation 8.2 are summarized in Table 8.16. The

correlation has an R2 value of 0.998, and the results are plotted with the experimental

data in Figures 7 and 8. The absolute average deviation (AAD) of the correlation is

calculated using Equation 10, which is 2.6%.

𝐴𝐴𝐷 =1

𝑁∑

|𝜇𝑐𝑎𝑙𝑐,𝑖−𝜇𝑒𝑥𝑝,𝑖|

𝜇𝑒𝑥𝑝,𝑖

𝑁𝑖=1 (8.3)

This model should only be used for IL/PZ s with the same mass fraction ratio as

the Company A solvents.

Solvent viscosity is an important parameter affecting the energy cost of the

capture process. To address this effect of viscosity, the effective capacity (∆Cμ) is

calculated using Equation 4.17, which is the capacity of the solvent normalized by the

viscosity of the solvent. The results are listed in Table 8.17.

244

Table 8.16: Parameters of the viscosity correlation for the Company A solvents

Parameter Value Standard Error

a -0.786 0.147

b1 3.25 1.74

c1 / /

d1 67.0 18.2

e1 -150.3 34.5

b2 / /

c2 1309.9 521.7

d2 -21736.8 5605.7

e2 52870.7 10439.2

R2 0.998 /

AAD 2.6% /

Table 8.17: Viscosity measurements of the Company A solvents

Solvent #1

CCO2 T Viscosity

wt frac °C cP

0.0396 20 17.13

0.0461 20 16.89

0.0461 20 16.83

0.0539 20 16.96

0.0611 20 17.30

0.0699 20 17.65

0.0396 40 8.72

0.0461 40 8.93

0.0461 40 9.08

0.0539 40 9.17

0.0611 40 9.11

0.0699 40 9.69

0.0396 60 6.02

0.0461 60 5.70

0.0461 60 5.67

0.0539 60 5.92

0.0611 60 6.04

0.0699 60 6.48

Solvent #2

CCO2 T Viscosity

wt frac °C cP

0.0222 20 3.70

0.0286 20 3.68

0.0350 20 3.61

0.0394 20 3.81

0.0420 20 3.74

0.0222 40 2.24

0.0286 40 2.24

0.0350 40 2.30

0.0394 40 2.38

0.0420 40 2.35

0.0222 60 1.72

0.0286 60 1.63

0.0286 60 1.61

0.0350 60 1.63

0.0394 60 1.58

0.0394 60 1.65

0.0420 60 1.68

245

8.4.3 Absorption rate results

The kg’ results for Company A solvent #1 and #2 are shown in Figure 8.14 and

8.15. The absorption rates of Company A solvents are compared with 8 m PZ and 7 m

MEA at 40 °C (Dugas 2009).

Figure 8.14: Absorption rates of the Company A solvent #1. Compared with 8 m PZ and

7 m MEA at 40 °C (Dugas 2009)

1.E-07

1.E-06

100 1000 10000

k g' (

mo

l/P

a s

m2)

PCO2* @ 40 °C (Pa)

40 °C

60 °C

20 °C

80 °C100 °C

8 m PZ @ 40 °C

7 m MEA @ 40 °C

246

Figure 8.15: Absorption rates of the Company A solvent #2. Compared with 8 m PZ and

7 m MEA at 40 °C (Dugas 2009)

The two Company A solvents have similar absorption rates of CO2. For both

solvents, the kg’ is independent of temperature at 20-60 °C. Significant temperature

dependence is observed between 60 and 100 °C, where kg’ decreases with increase in

temperature. At 40 °C, the kg’ of both solvents are competitive with 7 m MEA but

lower than 8 m PZ. The difference in IL+PZ concentration between the two solvents

does not affect their kg’.

1.E-07

1.E-06

100 1000 10000

k g' (

mo

l/P

a s

m2)

PCO2* @ 40 °C (Pa)

40 °C

60 °C

80 °C

100 °C 7 m MEA @ 40 °C

8 m PZ@ 40 °C

20 °C

247

Figure 8.16: CO2 absorption rate of the Company B solvent. Dashed line: 8 m PZ at 40

°C; dotted line: 7 m MEA at 40 °C (Dugas 2009).

Figure 8.17: Absorption of the three proprietary solvents at 40 °C, compared with 7 m

MEA and 8 m PZ (Dugas 2009).

1.E-07

1.E-06

1.E-05

10 100 1000 10000

k g' (

mo

l/P

a ∙ s

∙ m

2)

PCO2* @ 40 °C (Pa)

20 °C

40 °C

60 °C

80 °C

100 °C

8 m PZ @ 40 °C

7 m MEA @ 40 °C

1.E-07

1.E-06

1.E-05

10 100 1000 10000

k g' (

mo

l/P

a s

m2)

PCO2* @ 40 °C (Pa)

Company A #2

Company A #1

7 m MEA

8 m PZ

40 °C

Company B

248

In Figure 8.16, the kg’ of the Company B solvent is shown and compared with 8

m PZ and 7 m MEA at 40 °C. The kg’ of Company B solvent shows significant

temperature dependence between 60 and 100 °C. The absorption rate of CO2 in the

Company B solvent at 40 °C is slightly lower than that of 8 m PZ and much higher than 7

m MEA over the entire range of CO2 loading of the experiment.

In Figure 8.17, the kg’ of the three proprietary solvents are compared together at

40 °C. The kg’ of the two Company A solvent #2 is slightly higher than solvent #1.

Both Company A solvents have kg’ that is competitive with 7 m MEA, but are lower than

8 m PZ. The kg’ of Company B solvent is about 25 % less than 8 m PZ, and is better

than both Company A solvents. Despite using about the same amount of PZ as a

promoter, the effective absorption rate of Company B solvent is much higher than

Company A #1.

The kg’ data at 40 °C were used to predict rate performance and packing

requirement in an isothermal absorber for coal flue gas. The results are listed in Table

8.19.

8.4.3 CO2 solubility

The CO2 solubility in Company A solvents were measured using the WWC and

the total pressure apparatus. Data was collected at 20 – 150 °C, and the results are

plotted in Figure 8.18 and 8.19.

249

Figure 8.18: CO2 solubility in Company A solvent #1. Experimental data: ♦ - WWC; ■ –

total pressure. Semi-empirical model: solid lines (Table 8.18).

Figure 8.19: CO2 solubility in Company A solvent #2. Experimental data: ♦ - WWC; ■ –

total pressure. Semi-empirical model: solid lines (Table 8.18).

1.E+01

1.E+02

1.E+03

1.E+04

1.E+05

1.E+06

1.E+07

0.03 0.04 0.05 0.06 0.07

PC

O2

*(P

a)


20 °C

100 °C110 °C120 °C130 °C

140 °C

150 °C

80 °C

60 °C

40 °C

1.E+01

1.E+02

1.E+03

1.E+04

1.E+05

1.E+06

0.02 0.025 0.03 0.035 0.04 0.045

PC

O2

*(P

a)


20 °C

100 °C110 °C120 °C

130 °C

140 °C150 °C

80 °C

60 °C

40 °C

250

The CO2 solubility in Company B was measured using only the WWC at 20 – 100

°C. The results are plotted in Figure 8.20.

Figure 8.20: CO2 VLE of the Company B solvent. Points: WWC result. Solid lines: semi-

empirical VLE curves (Table 8.18)

To represent the CO2 solubility data of these proprietary solvents, the

mathematical form of the semi-empirical model (Equation 4.4) was modified. The

modified semi-empirical model (Equation 8.4) relates PCO2* to the mass fraction of total

CO2 in the solvent, as opposed to CO2 loading. This modification is necessary as for

proprietary solvents where the molecular weight and alkalinity of some or all of its

components are unknown, CO2 loading cannot be calculated.

ln(𝑃𝐶𝑂2∗) = 𝑎 +

𝑏

𝑇+ 𝑐 ∙ 𝐶𝐶𝑂2 + 𝑑 ∙ 𝐶𝐶𝑂2

2 + 𝑒 ∙𝐶𝐶𝑂2

𝑇+ 𝑓 ∙

𝐶𝐶𝑂22

𝑇∙ 1000 (8.4)

The modified model was used to fit the CO2 solubility data of all three proprietary

solvents. The model fits the experimental data well for all three solvents. The

regressed model parameters are summarized in Table 8.18.

10

100

1000

10000

100000

0.015 0.035 0.055

PC

O2*

(Pa)

CO2 mass fraction

20 °C

40 °C

60 °C

80 °C

100 °C

251

Table 8.18: Parameters of the modified semi-empirical VLE model (Equation 8.4) for the

proprietary solvents

ln(𝑃𝐶𝑂2∗) = 𝑎 +

𝑏

𝑇+ 𝑐 ∙ 𝐶𝐶𝑂2 + 𝑑 ∙ 𝐶𝐶𝑂2

2 + 𝑒 ∙𝐶𝐶𝑂2

𝑇+ 𝑓 ∙

𝐶𝐶𝑂22

𝑇∙ 1000

Company A #1 Company A #2 Company B

Value Standard

Error Value

Standard

Error Value

Standard

Error

a 21.6 4.6 48.6 2.9 34.9 1.3

b -5174.0 1595.1 -15273.4 1003.0 -10179.1 449.2

c 513.5 176.4 -474.0 77.3 98.7 32.0

d -4888.7 1661.8 / / -728.8 173.6

e -174391.4 60573.9 213814.5 26513.1 13465.7 11137.8

f 2028.3 564.8 / / / /

R2 0.9992 0.995 0.995

The CO2 capacity of each proprietary solvent was calculated similar to other

amine solvents. The capacity calculation as shown in Equation 8.5 was used to express

capacity as a function of CO2 mass fraction (and not CO2 loading).

𝐶𝑠𝑜𝑙𝑣 =𝑚𝑜𝑙 𝐶𝑂2

𝑘𝑔 (𝑎𝑚𝑖𝑛𝑒+𝐻2𝑂)=

(𝐶𝐶𝑂2,𝑟𝑖𝑐ℎ

𝐶(𝑎𝑚𝑖𝑛𝑒+𝐻2𝑂),𝑟𝑖𝑐ℎ−

𝐶𝐶𝑂2,𝑙𝑒𝑎𝑛

𝐶(𝑎𝑚𝑖𝑛𝑒+𝐻2𝑂),𝑙𝑒𝑎𝑛)

44𝑔 𝐶𝑂2 𝑚𝑜𝑙 𝐶𝑂2⁄∙1000𝑔

1𝑘𝑔

(8.5)

In Equation 8.5, 𝐶𝐶𝑂2,𝑙𝑒𝑎𝑛 and 𝐶𝐶𝑂2,𝑟𝑖𝑐ℎ are the CO2 weight fraction in the liquid

which corresponds to PCO2* of 0.5 and 5 kPa at 40 °C respectively, which were calculated

using the semi-empirical VLE model. The CO2 capacity for the three solvents is

summarized in Table 8.19. The Company A solvent #1 has similar capacity as 7 m

MEA, but is only 60% of 8 m PZ. The capacity of Company A solvent #2 is half of

solvent #1 due to its lower IL+PZ concentration. The capacity of Company B solvent is

competitive with 8 m PZ.

The -Habs of the proprietary solvents were estimated similarly to the method used

for other amines. The -Habs definition (Equation 4.5) is applied to the modified semi-

empirical model to obtain an modified expression for estimating -Habs (Equation 8.6).

252

−∆𝐻𝑎𝑏𝑠 = 𝑅 ∙ (𝜕ln (𝑃𝐶𝑂2

∗ )

𝜕(1 𝑇⁄ ))𝑃,𝑥

= 𝑏 + 𝑒 ∙ 𝛼𝐶𝑂2 + 𝑓 ∙ 𝛼𝐶𝑂22 ∙ 1000 (8.6)

The calculated -Habs for the proprietary solvent at the mid loading for the coal

operating range are summarized in Table 8.19. The -Habs of Company A solvent #1 is

moderate, less attractive than 7 m MEA but competitive with 8 m PZ. The -Habs of

Company A solvent #2 is lower than both 7 m MEA and 8 m PZ. The -Habs for

Company B solvent is higher than both 7 m MEA and 8 m PZ. However, since only

WWC VLE data was used in the estimation of -Habs for Company B solvent, the value

potentially overpredicts the true value (Table 8.19).

Table 8.19: Performance of the proprietary solvents at coal flue gas conditions, compared

with 7 m MEA and 8 m PZ (Dugas 2009, Xu 2011)

Amine kg’avg (40 °C) Ap/Vg ∆Csolv ∆Cµ -Habs

(1.5 kPa)

(m) x 107 mol/Pa s m2 x 103 m2/(m3/s) mol/kg solv kJ/mol

7 m MEA 4.3 3.5 0.50 0.62 76

8 m PZ 8.5 1.8 0.79 0.79 71

Company A1 4.2 3.6 0.47 0.48 72

Company A2 4.8 3.1 0.27 0.34 64

Company B 6.4 2.3 0.82 / 79* * estimated with WWC data only, potentially overpredict true value (Section 4.1.3)

The WWC and total pressure data for the proprietary solvents are summarized in

Table 8.20 – 8.23.

253

Table 8.20: WWC measurements for Company A1

CCO2 T kg' × 107 PCO2*

wt fraction °C mol/Pa∙s∙m2 kPa

0.0461 20 7.85 0.09

0.0539 20 5.05 0.20

0.0611 20 2.92 0.68

0.0699 20 1.08 3.59

0.0396 40 12.54 0.31

0.0461 40 7.92 0.66

0.0539 40 5.47 1.43

0.0611 40 3.09 4.54

0.0699 40 1.00 16.33

0.0396 60 11.90 1.85

0.0461 60 8.27 3.77

0.0539 60 4.98 8.75

0.0611 60 2.61 21.89

0.0396 80 9.46 8.94

0.0461 80 5.65 17.07

0.0539 80 3.15 34.11

0.0396 100 4.24 41.00

Table 8.21: WWC measurements for Company A2

CCO2 T kg' × 107 PCO2*

wt fraction °C mol/Pa∙s∙m2 kPa

0.0350 20 6.28 0.16

0.0394 20 4.55 0.56

0.0420 20 2.30 2.05

0.0222 40 13.38 0.13

0.0286 40 11.21 0.31

0.0350 40 7.69 0.93

0.0394 40 4.46 3.08

0.0420 40 1.89 10.15

0.0222 60 13.79 0.80

0.0286 60 11.05 1.59

0.0350 60 7.36 4.85

0.0394 60 4.11 11.05

0.0222 80 11.65 3.97

0.0286 80 9.18 8.06

0.0350 80 4.75 19.60

0.0222 100 6.40 17.01

0.0408 100 4.48 34.50

254

Table 8.22: Total pressure apparatus CO2 solubility results for the Company A solvents

Solvent #1

CCO2 T PCO2

wt fraction °C kPa

0.0365 140 242

0.0439 110 86

0.0432 130 265

0.0426 140 422

0.0556 100 117

0.0550 110 284

0.0545 120 398

0.0532 130 741

0.0521 140 1039

0.0501 150 1592

0.0655 100 491

0.0645 110 749

0.0631 120 1102

0.0614 130 1539

0.0592 140 2142

Solvent #2

CCO2 T PCO2

wt fraction °C kPa

0.0388 120 233

0.0381 130 411

0.0373 140 609

0.0362 150 900

0.0428 100 121

0.0424 110 202

0.0419 120 317

0.0412 130 475

0.0402 140 686

0.0391 150 951

0.0387 120 253

0.0381 130 407

0.0372 140 610

255

Table 8.23: WWC measurements for the Company B solvent

CO2 mass

frac

T PCO2* kg'

°C kPa x 107 mol/Pa s m2

0.044 20 0.16 8.35

0.055 20 0.26 5.09

0.063 20 0.66 3.31

0.018 40 0.11 29.30

0.026 40 0.27 19.10

0.034 40 0.64 13.51

0.044 40 1.47 8.79

0.055 40 2.64 5.67

0.063 40 5.33 3.76

0.018 60 0.70 27.09

0.026 60 1.68 19.60

0.034 60 4.10 11.50

0.044 60 8.45 7.04

0.055 60 13.50 5.17

0.063 60 27.15 3.17

0.018 80 3.59 21.60

0.026 80 9.18 12.70

0.034 80 19.85 7.24

0.044 80 39.75 4.37

0.018 100 20.28 7.57

0.026 100 40.67 6.06

Conclusions

The kg’ for the two Company A solvents are about the same as 7 m MEA and

much lower than 8 m PZ. The kg’ of the Company A solvent is not a strong function of

total IL+PZ concentration, since the rates of the two solvents are about the same. The

CO2 capacity (∆Csolv) of solvent #1 is about the same as 7 m MEA. For solvent #2, its

∆Csolv is half of solvent #1 due to its low IL+PZ concentration. The viscosity of solvent

#1 is about 10 cP at 40 °C, which is similar to that of 8 m PZ, and higher than 7 m MEA.

256

The viscosity of solvent #2 is about 3 cP at 40 °C, which lower than both 8 m PZ and 7 m

MEA. The low viscosity of solvent #2 improves the effective capacity (∆Cµ) of the

solvent, but not significant enough for the solvent to be competitive. The -Habs of

solvent #1 is competitive with 8 m PZ but lower than 7 m MEA. The -Habs of solvent #2

is low, and not competitive with other solvents.

The kg’ for the Company B solvent at 40 °C is only 25 % less than 8 m PZ, and

higher than both Company A solvents and 7 m MEA. The CO2 carrying capacity of the

Company B solvent is competitive with 8 m PZ and much higher than 7 m MEA. The

heat of CO2 absorption of the Company B solvent estimated from the WWC VLE data is

higher 7 m MEA (though the estimated value is likely an overprediction).

8.5 RATE AND CAPACITY COMPARISON OF AMINE SOLVENTS

Absorption rate and CO2 capacity are two significant properties of a solvent, both

of which affect the cost of the capture process. In this section, these two properties are

compared together for all of the amine solvents that have been tested using the WWC.

Coal flue gas condition is used as a common operating condition for this comparison.

To represent the overall effective absorption rate, the kg’avg at 40 °C is used (Equation

4.6) which suggests the relative capital cost of the absorber. The capacity of the solvent

(Equation 4.9) is inversely proportional to the solvent rate in the process, and thus the

cost of solvent regeneration. A good solvent should have high kg’avg and high CO2

capacity.

257

Figure 8.21: Absorption rates and CO2 capacity for 7 m MEA and 8 m PZ, compared

with MEA and PZ solvents at other amine concentrations

In Figure 8.21, the kg’avg and capacity of two base case solvents, 7 m MEA and 8

m PZ, are compared with other MEA and PZ solvents at different amine concentrations.

For both amines, kg’avg decreases with increase of amine concentration; and CO2 capacity

increases with amine concentration. PZ solvents have higher kg’avg than MEA

solvents, and PZ solvents have higher CO2 capacity than MEA solvents at the same

amine concentration. 8 m PZ and 7 m MEA are used as the base case solvents for

comparison is this section.

The kg’avg and capacity values used in this section are summarized in Table 8.24.

3

6

12

0 0.2 0.4 0.6 0.8 1

k g' a

vg x

10

7@

40

°C

(m

ol/

Pa

s m

2)

CO2 Capacity (mol/kg solvent)

5 m PZ

8 m PZ

7 m MEA

9 m MEA

11 m MEA

258

8.5.1 Single amine solvents

Figure 8.22: Absorption rate and CO2 capacity for primary amines and amino acids

Primary amines have similar kg’avg as the MEA solvents (Figure 8.22). The

capacity of the three primary amines and two primary amino acids is all lower than 7 m

MEA, mainly due to the higher molecular weight of these amines than MEA. Primary

diamine solvents have about the same kg’avg as MEA solvents and other primary amines,

despite their higher total alkalinity in the solvent (Figure 8.23). In general, the capacity

of primary diamine solvents is not significantly enhanced by their high alkalinity.

0

2

4

6

8

10

12

0 0.5 1 1.5

k g' a

vg x

10

7@

40

°C

(m

ol/

Pa

s m

2)


3.5 m GlyK

6.5 m β-alaK

7 m MIPA

10 m DGA®

7 m MPA

8 m PZ

7 m MEA

259

Figure 8.23: Absorption rate and CO2 capacity for primary diamines

Figure 8.24: Absorption rate and CO2 capacity for secondary amines

The secondary amine solvents included in this work have kg’avg and capacity

which vary significantly from each other. The capacity of 7 m DEA is about the same

0

2

4

6

8

10

12

0 0.5 1 1.5

k g' a

vg x

10

7@

40

°C

(m

ol/

Pa

s m

2)


Primary amines

8 m PZ

12 m EDA

8 m BAE

8 m MAPA

7 m MEA

0

2

4

6

8

10

12

0 0.5 1 1.5

k g' a

vg x

10

7@

40

°C

(m

ol/

Pa

s m

2)


7 m MMEA

7 m DEA

7 m DIPA

6 m SarK

4.5 m SarNa

8 m PZ

7 m MEA

260

as 8 m PZ, while the other secondary amine has similar or lower capacity as 7 m MEA.

The kg’avg of 7 m MMEA is about the same as 8 m PZ, and higher than all other

secondary amines. On the other hand, the kg’avg for 7 m DIPA is lower than other

secondary amines and 7 m MEA.

Figure 8.25: Absorption rate and CO2 capacity for hindered amines

Hindered amines are compared with unhindered primary and secondary amines in

Figure 8.25. Both hindered amine solvents, 4.8 m AMP and 8 m 2PE, have higher

capacity than both 8 m PZ and 7 m MEA. The effective absorption rates of both

hindered amine solvents are competitive with most unhindered primary and secondary

amines. The steric hindrance of the amine ground does not significantly reduce the

effective absorption rate of the solvent.

PZ derivatives have good CO2 capacity (Figure 8.26), mainly due to their high

total alkalinity in the solvent. The kg’avg of three PZ derivatives is less than 8 m PZ,

0

2

4

6

8

10

12

0 0.5 1 1.5

k g' a

vg x

10

7@

40

°C

(m

ol/

Pa

s m

2)


Primary amines

Secondary amines

8 m PZ

7 m MEA

4.8 m AMP

8 m 2PE

261

which is due to the steric hindrance of the nitrogen (2MPZ) or the low pKa of the amine

group (HEP and AEP). 8 m 1MPZ has the greatest kg’avg among the PZ derivatives,

which is competitive with 8 m PZ.

Figure 8.26: Absorption rate and CO2 capacity for PZ derivatives

8.5.2 PZ blends

The kg’avg and CO2 capacity of PZ blends with primary diamines are compared in

Figure 8.27. The capacity of these blends is lower than 8 m PZ, despite having the same

total alkalinity. With the exception of 6 m PZ/2 m EDA, the kg’avg of the blends is

lower than 8 m PZ. Thus, the addition of primary diamines reduced the effective

absorption rate of PZ.

The kg’avg of PZ blends with primary amines is similar to PZ/primary diamine,

which is higher than primary amines but lower than 8 m PZ. The capacity of

PZ/primary amine is lower than 8 m PZ.

0

2

4

6

8

10

12

0 0.5 1 1.5

k g' a

vg x

10

7@

40

°C

(m

ol/

Pa

s m

2)


8 m PZ

7 m MEA

8 m 1MPZ

7.7 m HEP

6 m AEP

8 m 2MPZ

262

Figure 8.27: Absorption rate and CO2 capacity for PZ blends with primary diamines

Figure 8.28: Absorption rate and CO2 capacity for PZ blends with primary amines

The kg’avg and capacity of PZ blends with PZ derivatives are all competitive with

8 m PZ (Figure 8.29). As a category, these blends have the best overall performance

among the amine solvents studied in this work.

0

2

4

6

8

10

12

0 0.5 1 1.5

k g' a

vg x

10

7@

40

°C

(m

ol/

Pa

s m

2)


8 m PZ

7 m MEA6 m PZ/2 m HMDA

6 m PZ/2 m DAB

6 m PZ/2 m EDA

6 m PZ/2 m BAE

0

2

4

6

8

10

12

0 0.5 1 1.5

k g' a

vg x

10

7@

40

°C

(m

ol/

Pa

s m

2)


PZ/Primary Diamine

2 m PZ/7 m MEA

5 m PZ/5 m DGA®

8 m PZ

7 m MEA

263

Figure 8.29: Absorption rate and CO2 capacity for PZ blends with PZ derivatives

Figure 8.30: Absorption rate and CO2 capacity for PZ blends with hindered amines

The performance of PZ/AMP and PZ/2PE are all competitive with 8 m PZ and

PZ/PZ derivatives (Figure 8.30). In the case of PZ/AMP, increasing the AMP/PZ ratio

0

2

4

6

8

10

12

0 0.5 1 1.5

k g' a

vg x

10

7@

40

°C

(m

ol/

Pa

s m

2)


8 m PZ

7 m MEA

4 m PZ/4 m 2MPZ

3.75m PZ/3.75m 1MPZ/0.5 m DMPZ

5 m PZ/2 m AEP

6 m PZ/2 m HEP

0

2

4

6

8

10

12

0 0.5 1 1.5

k g' a

vg x

10

7@

40

°C

(m

ol/

Pa

s m

2)


PZ/PZ derivative

3.5 m PZ/3.5 m Tris

5 m PZ/5 m 2PE

5 m PZ/2.3 m AMP

2 m PZ/4 m AMP 8 m PZ

7 m MEA

264

improved both the kg’avg and capacity of the solvent. The performance of PZ/Tris is less

attractive than other PZ/hindered amine. The kg’avg of PZ/Tris is about the same as 7 m

MEA, due to the low pKa of Tris. The capacity of PZ/Tris is low because of the low

concentration of alkalinity and the high molecular weight of Tris.

Figure 8.31: Absorption rate and CO2 capacity for PZ and MEA blended with MDEA

The PZ/MDEA blends have competitive performance with 8 m PZ, PZ/hindered

amine, and PZ/PZ derivative. Unlike PZ/AMP, increasing the ratio of MDEA/PZ

reduced the kg’avg and capacity of the solvent. The MEA/MDEA has about the same

kg’avg as 7 m MEA, but higher CO2 capacity. For both MEA and PZ, blending with

MDEA slightly reduced the kg’avg of the solvent, while the capacity is enhanced.

0

2

4

6

8

10

12

0 0.5 1 1.5

k g' a

vg x

10

7@

40

°C

(m

ol/

Pa

s m

2)


PZ/PZ derivative

PZ/Hinderedamine

9.8 m MEA/3.4 m MDEA

2 m PZ/7 m MDEA

5 m PZ/5 m MDEA

8 m PZ

7 m MEA

265

8.5.3 Amino acids

Figure 8.32: Absorption rate and CO2 capacity for amino acids

All amino acid based solvents have lower capacity than their amine counterparts.

This is due to both the low alkalinity of these solvents and the high molecular weight of

the amino acid with added neutralizing base. The kg’avg of the secondary amino acid,

sarcosine, is higher than primary amino acids.

8.5.4 Rates and viscosity normalized capacity

Viscosity normalized capacity (∆Cµ) of a solvent, as introduced in Chapter 4.2.3,

more directly correlates with the overall sensible heat cost of the process. As defined by

Equation 4.17, ∆Cµ increases with solvent capacity but decreases with solvent viscosity.

A comparison of ∆Cµ with the CO2 absorption rate of the solvents is shown in Figure

8.23.

0

2

4

6

8

10

12

0 0.5 1 1.5

k g' a

vg x

10

7@

40

°C

(m

ol/

Pa

s m

2)


6 m SarK

4.5 m SarNa

8 m PZ

7 m MEA

3.5 m GlyK

6.5 m β-alaK3 m TauK/5 m HTauK

Primary

Secondary

266

Figure 8.33: Absorption rate and viscosity normalized CO2 capacity (Equation 4.17)

0

2

4

6

8

10

12

0 0.2 0.4 0.6 0.8 1 1.2

k g' a

vg@

40

°C

(m

ol/

Pa

s m

2)

∆Cµ (mol/kg solvent)

8 m PZ

7 m MEA

Amino acid salt

PZ/Primaryand PZ/Primary Di-amine

Primary Di-amine

PZ derivative(emptydiamond)

PZ /PZ derivative(filled diamond)

PZ /AMP

PZ/MDEA

PZ/2PE

PZ/Tris

5 m PZ

AMP

2-PE

267

8.6 MASTER SOLVENT TABLE

The experimentally measured performances of all amine solvents tested at the

University of Texas in Austin are summarized in Table 8.24. All solvents are evaluated

at coal flue gas conditions.

268

Table 8.24: Performance summary of amine solvents characterized at the University of Texas in Austin

Category Solvent

name Amine

MW Concentration (m) kg'avg @ 40 °Ca

Capacity -Habs

@ 1.5

kPa

µ Tmax Pmax

Solid

solubility

limit

Author(s)

ΔCsolvb ΔCµ

c

kg/mol amine alkalinity wt

frac

x 107

mol/Pa

s m2

mol/mol alkalinity kJ/mol cP °C bar Lean Rich

PZ 8 m PZ Piperazine

86.14 8 16 0.41 8.5 0.79 0.79 64 10.8 163 14.3 yes yes Dugas, Xu, Freeman

5 m PZ Piperazine 5 10 0.3 11.3 0.63 0.76 64 3 / / yes no Dugas, Xu, Freeman

PZ

derivatives

8 m

1MPZ 1-methyl piperazine 100.16 8 16 0.445 8.4 0.83 0.83 67 11 148 6.4 / / Chen, Xu, Freeman

8 m

2MPZ 2-methyl piperazine 100.16 8 16 0.445 5.9 0.93 0.89 72 15 151 9.9 yes no Chen, Xu, Freeman

7.7 m

HEP N-(2-hydroxyethyl)piperazine 130.19 7.7 15.4 0.5 5.3 0.68 0.64 79 17 130 2.3 no no Chen, Freeman

8 m 2PE 2-piperidineethanol 129.2 8 8 0.51 3.5 1.23 1.14 73 18 127 3.3 no no Chen, Freeman

6 m AEP 1-(2-Aminoethyl)piperazine 129.2 6 18 0.44 3.5 0.66 0.59 72 23 121 1.8 no no Chen, Freeman

Primary

monoamine

7 m MEA

monoethanolamine 61.08

7 7 0.3 4.3 0.5 0.62 71 2.5 121 2.2

no

Dugas, Freeman, Xu

9 m MEA 9 9 0.355 3.3 0.59

71

125 2.7 Dugas, Freeman, Xu

11 m

MEA 11 11 0.4 3.6 0.67 71 125 2.7 Dugas, Freeman, Xu

7 m

MIPA monoisopropanolamine 75.11 7 7 0.345 3.7 0.35 80 114f

Li L

7 m MPA 3 amino propanol 75.11 7 7 0.345 2.5 0.27 73 126f Li L

10 m

DGA® Diglycolamine (R) 105.1 10 10 0.51 3.6 0.38 0.38 81 10 132 9.1 Chen X, Freeman

Secondary

monoamine

7 m DEA Diethanolamine 105.14 7 7 0.42 4.9 0.8

73

103f

no

Li L

7 m

MMEA Methylmonoethanolamine 75.11 7 7 0.345 7.8 0.43 68 102f Li L

7 m DIPA Diisopropanolamine 133.19 7 7 0.48 2 0.48 82

Li L

Hindered

monoamine

4.8 m

AMP 2-amino-2-methyl-1 propanol 89.14 4.8 4.8 0.3 2.4 0.96 1.14 73 3.5 140 6.1 no Chen X

8 m 2PE 2-piperidineethanol 129.2 8 8 0.51 3.5 1.23 1.14 73 18 127 3.3 no no Chen, Freeman

269

Table 8.24: Performance summary of amine solvents characterized at the University of Texas in Austin (continued)

Category Solvent name Amine MW amine

(m)

alkalinity

(m) wt frac

kg'avg

@ 40 °C

ΔCsolv ΔCµ

-Habs

@

1.5

kPa

µ

(cP)

Tmax

°C Pmax

bar

Solubility

limit Author(s)

Lean Rich

Diamines

12 m EDA Ethylenediamine 60.1 12 24 0.42 2.5 0.78 0.79 81 10 117 2.6

no

Chen X, Zhou S,

Freeman

8 m MAPA (Methylamino)propylamine 88.15 8 16 0.41 3.1 0.42

84

114 3 Chen X, Valvstat S,

Freeman

8 m BAE Bis(aminoethyl)ether 104.1 8 16 0.45 3.2 0.63 0.61 79 13 158 24 Li L, Namjoshi

PZ blends

2 m PZ 7 m

MDEA

Piperazine 86.14 2 11

0.09 6.9 0.8 0.82 68 9 120 1.4

no

Chen X, Closmann N-methyldiethanolamine 119.16 7 0.42

5 m PZ 5 m

MDEA


0.21 8.3 0.98 0.95 69 13 120 1.8 Chen X, Closmann

N-methyldiethanolamine 119.16 5 0.29

4 m PZ 4 m

2MPZ


0.2 7.1 0.88 0.88 66 11 155 10.3 yes no Chen X, Freeman

2-Methylpiperazine 100.16 4 0.23

3.75 m PZ

3.75 m 1MPZ

0.5 m DMPZ

Piperazine 86.14 3.75

16

0.18

8.5 0.83 0.82 67 12 159 9.8 no Chen X, Freeman 1-Methylpiperazine 100.16 3.75 0.21

1,4 Dimethylpiperazine 114.19 0.5 0.03

5 m PZ 2.3 m

AMP

Piperazine 86.14 5 12.3

0.28 7.5 0.71 0.72 71 10 134 4.5 yes no Li H, Li L,

2-amino-2-methyl-1 propanol 89.14 2.3 0.11

2 m PZ 4 m

AMP


0.11 8.3 0.77 0.86 73 5 128 3.4 no Li H

2-amino-2-methyl-1 propanol 89.14 4 0.23

5 m PZ 2 m

AEP


0.26 8.1 0.68 0.68 71 11 138 5 yes no Li L, Du Y

1-(2-Aminoethyl)piperazine 129.2 2 0.15

6 m PZ 2 m

HMDA


0.3 4.9 0.55 0.52 68 15 163 15.2 yes no Li L, Namjoshi

Hexamethylenediamine 116.21 2 0.13

6 m PZ 2 m

DAB


0.31 7.1 0.68 0.67 63 12 157 13.7 n.a. no Li L, Namjoshi

Diaminobutane 88.15 2 0.1

6 m PZ 2 m

BAE


0.3 7.3 0.69 0.68 70 12 162 16.2 n.a. no Li L, Namjoshi

Bis(aminoethyl)ether 104.1 2 0.12

270


Category Solvent

name Amine MW

amine

(m)

alkalinity

(m)

wt

frac

kg'avg

@ 40 °C

ΔCsolv ΔCµ -Habs

@ 1.5

kPa

µ

(cP)

Tmax

°C Pmax

bar

Solid

solubility limit Author(s)

Lean Rich

PZ blends

6 m PZ 2 m EDA


0.32 8.6 0.66 0.67 74 10

n.a. no Li,L Ethylenediamine 60.1 2 0.07

6 m PZ 2

m HEP

Piperazine 86.14 6

16

0.29

8.7 0.66 0.65 78 12 n.a. no Li L N-(2-hydroxyethyl)piperazine

130.1

9 2 0.15

5 m PZ 5 m 2PE


0.21 4.2 0.67 0.59 75 26 n.a. no Li L

2-piperidineethanol 129.2 5 0.31

5 m PZ 5

m DGA


0.22 6.7 0.48 0.48 83 11 n.a. no Li L

Diglycolamine (R) 105.1 5 0.27

3.5 m PZ 3.5 m

Tris


10.5

0.17

7.4 0.78 0.85 76 6 no Li L 2-amino-2-hydroxymethyl-

1,3-propanediol

121.1

4 3.5 0.25

2 m PZ/ 7 m

MEA


0.11 6.9 0.59

73

104 0.7 no

Dugas,

Freeman Monoethanolamine 61.08 7 0.27

Company

A #1


0.05 4.2 0.47 0.48 72 9

no Li L Unknown IL NA NA 0.45

Company A #2

Piperazine 86.14 0.5 0.03 4.8 0.27 0.34 64 2.4 no Li L

Unknown IL NA NA 0.27

Company

B

Piperazine 86.14 1.9 0.07 6.4 0.82

79

no Li L

Unknown amine NA NA 0.5

271


Categor

y

Solvent

name Amine MW amine (m)

wt

frac

kg'avg

@ 40 °C

ΔCsolv ΔCµ

-Habs

@ 1.5

kPa

µ

(cP)

Solid

solubility

limit Author(s)

Lean Rich

Amino

Acids

6 m

Glycine(K) Glycine (Potassium) 75.1 (39.1)

6 6 0.41 0.2 0.35 0.42 64 3 no yes Li L

3.5 m

Glycine(K) 3.5 3.5 0.29 3.1 0.25 0.32 64 1.9 no

Li L,

Voice A

6 m

Sarcosine(K) Sarcosine (Potassium) 89.1 (39.1) 6 6 0.43 5 0.35 0.41 57 4

no

Li L,

Voice A

4.5 m

Sarcosine(N

a)

Sarcosine (Sodium) 89.1 (23) 4.5 4.5 0.33 4.5 0.31 0.35 54 5 Li L

6.5 m beta-

alanine(K)

beta-alanine

(Potassium) 89.1 (39.1) 6.5 6.5 0.45 2 0.25 0.28 64 5 no

Li L,

Voice A

3 m Taurine

5 m

Homotaurine

(K)

Taurine (Potassium) 125.1 (39.1) 3 3 0.21

2.2 0.2 0.21 75 8 no yes Li L,

Voice A Homotaurine

(Potassium)

139.17

(39.1) 5 5 0.37

6.5 m

Proline (K) Proline (Potassium)

115.13

(39.1) 6.5 6.5 0.5 3.6* 0.14*

63*

no yes

Li L, Chen

X, Voice A

Others MEA

MDEA

Monoethanolamine 61.08 9.9 13.3

0.3 3.9 0.58 0.62 75 7 no

Li L,

Voice A Methyldiethanolamine 119.16 3.4 0.2

a Equation 4.6 at 0.5 and 5 kPa: 𝑘𝑔

′

𝑎𝑣𝑔=

𝐹𝑙𝑢𝑥𝐶𝑂2,𝐿𝑀


=(𝐹𝑙𝑢𝑥𝐶𝑂2,𝑡𝑜𝑝−𝐹𝑙𝑢𝑥𝐶𝑂2,𝑏𝑜𝑡𝑡𝑜𝑚) 𝐿𝑛(𝐹𝑙𝑢𝑥𝐶𝑂2,𝑡𝑜𝑝/𝐹𝑙𝑢𝑥𝐶𝑂2,𝑏𝑜𝑡𝑡𝑜𝑚)⁄

(𝑃𝐶𝑂2,𝑡𝑜𝑝−𝑃𝐶𝑂2,𝑙𝑒𝑎𝑛∗ )−(𝑃𝐶𝑂2,𝑏𝑜𝑡𝑡𝑜𝑚−𝑃𝐶𝑂2,𝑟𝑖𝑐ℎ

∗ ) 𝐿𝑛(𝑃𝐶𝑂2,𝑡𝑜𝑝

−𝑃𝐶𝑂2,𝑙𝑒𝑎𝑛∗

𝑃𝐶𝑂2,𝑏𝑜𝑡𝑡𝑜𝑚−𝑃𝐶𝑂2,𝑟𝑖𝑐ℎ

∗ )⁄

b Equation 4.9: ∆𝐶𝑠𝑜𝑙𝑣 =(∝𝑟𝑖𝑐ℎ − ∝𝑙𝑒𝑎𝑛)∙𝑚𝑜𝑙 𝑎𝑙𝑘𝑎𝑙𝑖𝑛𝑖𝑡𝑦



𝑘𝑔(𝑎𝑚𝑖𝑛𝑒+𝐻2𝑂)

c Equation 4.17: ∆𝐶𝜇 =∆𝐶𝑠𝑜𝑙𝑣


10 𝑐𝑃⁄ )0.15

d Equation 4.5: −∆𝐻𝑎𝑏𝑠 = 𝑅 ∙ (𝜕ln (𝑃𝐶𝑂2

∗ )

𝜕(1 𝑇⁄ ))𝑃,𝑥

= 𝑏 + 𝑒 ∙ 𝛼𝐶𝑂2 + 𝑓 ∙ 𝛼𝐶𝑂22

f Cited by Freeman (2011)

272

Chapter 9: Simplified stoichiometric model for CO2 VLE in aqueous

amines

9.1 INTRODUCTION

The VLE of CO2 in aqueous amines directly affects the performance of the CO2

capture process in both operating and capital cost. The CO2 solubility in a solvent

determines the operating condition of the process, as well as the CO2 capacity of the

solvent. The speciation of CO2 in the liquid solvent, as dictated by chemical

equilibrium with the amine species, affects the mass transfer rate of CO2, and thus the

rate of CO2 absorption.

This chapter presents a simplified stoichiometric model (SSM) for the accurate

representation of CO2 VLE in aqueous amines. The model also represents the chemical

equilibria of the CO2 and amine ionic species in the liquid phase. This model is used to

represent 11 aqueous amines, including primary, secondary, hindered amines, and amino

acid salts. The regressed model parameters for these amines are used to develop a

general correlation, which predicts the CO2 VLE and speciation of primary and

secondary amines at 40 °C based on the pKa of the amine.

9.1.1 CO2 VLE in aqueous amines

The VLE of CO2 refers to the equilibrium of CO2 in the gas with its concentration

in the liquid phase. This equilibrium is commonly represented using Henry’s law,

where the gas and liquid concentrations are related by the Henry’s constant (Equation

9.1). With the ideal gas assumption, the CO2 in the gas can be approximated with the

partial pressure of CO2. For a solvent such as concentrated aqueous amines, where the

liquid composition is substantially away from infinite dilution in water, the solute (CO2)

273

is best represented as its activity to account for the nonideality of the liquid phase. In

Equation 9.1, the activity based Henry’s constant has the unit of 1 𝑃𝑎⁄ .

𝑃𝐶𝑂2 = 𝑎𝐶𝑂2 ∙ 𝐻𝐶𝑂2−𝐻2𝑂𝑎 = 𝑥𝐶𝑂2 ∙ 𝛾𝐶𝑂2 ∙ 𝐻𝐶𝑂2−𝐻2𝑂

𝑎 (9.1)

In an aqueous amine solvent, free molecular CO2 is in chemical equilibria with

the amine, water, and reaction products. The VLE of CO2 in these solvents is highly

coupled with the chemical equilibria in the liquid phase. And the chemistry of the

amine can significantly affect the VLE of CO2.

Chemical equilibria in CO2 loaded aqueous amines

The relevant chemical equilibria in CO2 loaded aqueous amines can be written as

the following five equations.

Carbamate formation (primary and secondary amine):

𝐻2𝑂 + 𝐴𝑚𝑖𝑛𝑒 + 𝐶𝑂2 𝐾𝐴𝑚𝐶𝑂𝑂−𝑓 ⇔ 𝐻3𝑂

+ + 𝐴𝑚𝐶𝑂𝑂− (9.2)

Dissociation of free CO2 (bicarbonate formation):

2𝐻2𝑂 + 𝐶𝑂2 𝐾𝑎,𝐶𝑂2

⇔ 𝐻3𝑂+ +𝐻𝐶𝑂3

− (9.3)

Dissociation of protonated amine (base strength of the amine):

𝐻2𝑂 + 𝐴𝑚𝐻+ 𝐾𝑎 ⇔ 𝐻3𝑂

+ + 𝐴𝑚𝑖𝑛𝑒 (9.4a)

𝑝𝐾𝑎 = −𝑙𝑜𝑔10(𝐾𝑎) (9.4b)

Dissociation of bicarbonate (carbonate formation):

𝐻2𝑂 + 𝐻𝐶𝑂3−

𝐾𝑎,𝐻𝐶𝑂3−

⇔ 𝐻3𝑂+ + 𝐶𝑂3

2− (9.5)

Ionization of water:

2𝐻2𝑂 𝐾𝐻2𝑂

⇔ 𝐻3𝑂+ + 𝑂𝐻− (9.6)

The carbamate formation and bicarbonate reactions directly influence CO2 VLE

as they directly affect the free molecular CO2. The basicity of the amine is also an

important equilibrium, as it affects the availability of the free amine for the carbamate

274

formation. For unhindered primary and secondary amines, the formation of carbamate

is much more favorable compared to the formation of bicarbonate. At CO2 loading

lower than 0.5, the free CO2 is largely determined by the carbamate formation reaction

(Equation 9.2) and the pKa of the amine (Equation 9.4). At CO2 loading higher than 0.5,

as the free amine in the liquid is mostly depleted, the bicarbonate formation

determines the free CO2. The carbonate formation and ionization of water affects free

CO2 to a lesser extent, mainly by affecting the non-CO2 species in the first three

equilibria.

9.1.2 Types of CO2 VLE modeling methods

The modeling of CO2 VLE for the purpose of CO2 capture from flue gas or acid

gas treating represents the changes in gas phase CO2 with important process conditions,

mainly temperature and CO2 loading. Many different methods have been used to model

the CO2 VLE in aqueous amines. These methods can be roughly divided into three

categories based on their rigorousness and complexity.

Semi-empirical

The semi-empirical method is a simple method which can be used to fit the

available CO2 VLE data. A simple mathematical equation is generally used to relate the

dependent variable with the relevant experimental conditions. The form and value of

the model equation typically have little physical significance. This approach only

allows for the interpolation of CO2 VLE behavior within the experimental range.

Extrapolation beyond the data conditions is prone to significant errors.

This method is used in the previous chapters to interpolate the experimental CO2

VLE data.

275

Rigorous methods

More rigorous approaches towards CO2 VLE modeling typically use an existing

thermodynamic framework. One of the most appropriate choices is the electrolyte Non-

Random Two-Liquid (eNRTL) framework in Aspen Plus®, which has the capacity to

represent liquid phase non-idealities of typical CO2 loaded aqueous amine systems.

These rigorous methods use thermodynamic first principles to represent the physical

system.

However, rigorous thermodynamic modeling is much more involved in terms of

model development as well as data requirement. In addition to the CO2 VLE data,

thermodynamic data of the amine/H2O system is typically required.

Stoichiometric model

A method referred to as “stoichiometric” modeling has been used to represent the

CO2 VLE in aqueous amines. A model of this type developed by Kent and Eisenberg

(1976) later received widespread use in the representation of CO2 VLE (Dang 2001).

The stoichiometric modeling method describes the liquid phase composition by the

chemical equilibria of the reacting species. This method relies on a good understanding

of the chemical reaction stoichiometry to correctly represent the system.

The stoichiometric approach is considerably more rigorous than the semi-

empirical methods, and it is much simpler and easier to use than the rigorous

thermodynamic models. However, it is difficult to represent liquid phase non-ideality

using this approach.

9.1.3 Previous stoichiometric models

The CO2 VLE modeling method used in this work is based on a stoichiometric

type model by Dang (2001), which was adapted from a model for piperazine first

276

developed by Bishnoi (2000). The Dang model uses all of the five chemical equilibria

(Equation 9.2-9.6) to describe the chemistry in the liquid phase. Together with four

mass balances and the Henry’s law, a total of ten equations were used to represent the

CO2/amine/H2O gas-liquid system. The model neglects non-idealities in both the liquid

and gas phase, and uses mole fraction based chemical equilibrium expressions.

The Dang model was coded in FORTRAN, and was used to represent the CO2

VLE for MEA.

9.1.4 Scope

The model developed in this work is used to represent the CO2 VLE in 12

aqueous amines and amino acids, including primary, secondary, and hindered structures.

The amines are summarized in Table 9.1. The amino acids are all used with one

equivalent of KOH to neutralize the carboxylic acid.


speciation model

Amine Structure Type pKa (40 °C)

MEA

Primary

9.03

(Hamborg and

Versteeg 2009)

MIPA

Primary

9.04

(Hamborg

andVersteeg

2009)

MPA

NH2

OH

Primary

9.48

(Hamborg and

Versteeg 2009)

Diglycolamine

(DGA)®

OH

O

NH2

Primary 9.08

(Hamborg and

Versteeg 2009)

NH2OH

NH2

CH3

OH

277


speciation model (continued)

Glycine (K)

OH

ONH2

Primary

amino acid

9.41

(Hamborg et al.

2007)

β-alanine (K)

OH

ONH2

Primary

amino acid

9.94

(Hamborg et al.

2007)

DEA

OH

NH

OH

Secondary

8.52

(Bower et al.

1962)

MMEA

CH3 NH

OH

Secondary

9.46

(Hamborg and

Versteeg 2009)

DIPA NH

OH

OH

CH3

CH3

Secondary

8.51

(Hamborg and

Versteeg 2009)

Sarcosine (K/Na)

OH

ONHCH3

Secondary

amino acid

9.89

(Hamborg et al.

2007)

AMP NH2

CH3

OH CH3

Primary

hindered

9.17

(Hamborg and

Versteeg 2009)

2PE NH

OH

Secondary

hindered

9.68

(Xu et al.

1992)

278

9.2 SIMPLIFIED STOICHIOMETRIC MODEL (SSM)

The SSM is a simplified version of the Dang model. Only two chemical

equilibria are used to describe the chemical interaction between the amine and CO2.

Along with three mass balance equations, only five equations are used to represent the

system.

Several simplifying assumptions were used to reduce the equation set to five.

First, the Henry’s law, which was used to describe the gas-liquid equilibrium of free CO2

in the Dang model, is combined with the chemical equilibria in the SSM. As the result,

molecular CO2 is not represented in the liquid phase, which is expected to introduce

small errors at CO2 loading less than 1. Second, the dissociation of bicarbonate into

carbonate is eliminated from the reaction chemistry, which affects the speciation for

systems with significant carbonate and at high CO2 loading. Lastly, the ionization of

water is also eliminated from the reaction set, and water is assumed to be an inert species.

9.2.1 Model equations

The two chemical equilibria used in the SSM are shown in Equation 9.7 and 9.8.

The first equilibrium (Equation 9.7) involves the reaction of CO2 with two amine

molecules, which produces a protonated amine and an amine carbamate. This

equilibrium is combination of the carbamate formation equilibrium (Equation 9.2) with

the amine protonation (Equation 9.4) and Henry’s law (Equation 9.1).

2𝐴𝑚𝑖𝑛𝑒 + 𝐶𝑂2(𝑔) 𝐾1 ⇔ 𝐴𝑚𝐻+ + 𝐴𝑚𝐶𝑂𝑂− (9.7a)

279

Ion-pair interpretation for hindered amines

In the high pKa hindered amines (AMP and 2PE), the equilibrium reaction (9.7a)

is stoichiometrically equivalent to the equilibrium producing the ion pair of carbonate and

protonated amine.

2𝐴𝑚𝑖𝑛𝑒 + 𝐶𝑂2(𝑔) + 𝐻2𝑂 𝐾1 ⇔ 𝐴𝑚𝐻+ + 𝐴𝑚𝐻+𝐶𝑂3

= (9.7b)

Therefore the inclusion of this equilibrium reaction can be interpreted as the

formation of carbamate in unhindered amines or as the formation of the carbonate ion

pair in hindered or tertiary amines. Since the divalent carbonate ion is likely to be

strongly associated with the amine cation, this is a satisfactory representation even in the

hindered amines.

The second equilibrium (Equation 9.8) describes the dissociation of amine

carbamate into bicarbonate and protonated amine, as well as the reaction of gaseous CO2

with water into bicarbonate. This equilibrium is the combination of the bicarbonate

formation equilibrium (Equation 9.3) with carbamate formation (Equation 9.2), the amine

protonation (Equation 9.4), and Henry’s law.

𝐴𝑚𝐶𝑂𝑂− + 2𝐻2𝑂 + 𝐶𝑂2(𝑔) 𝐾2 ⇔ 2 ∙ 𝐻𝐶𝑂3

− + 𝐴𝑚𝐻+ (9.8)

These two equilibria were chosen as they directly represent the overall chemical

stoichiometry of primary and secondary amine systems. For unhindered amines, at CO2

loading lower than 0.5, the first equilibrium determines the distribution of CO2. At CO2

loading higher than 0.5, the second equilibrium becomes important as the free amine is

low.

The reaction equilibria are represented using mole fraction based constants, as

shown in Equations 9.9 and 9.10. The non-ideality in the liquid is neglected by

assuming the activity coefficient of the species to be one. Also, the constants in

280

Equation 9.9 and 9.10 are the product of the chemical equilibrium constant and the

Henry’s constant.

𝐾1∗ =

𝑥𝑎𝑚𝐶𝑂𝑂− ∙𝑥𝑎𝑚𝐻+

𝑥𝑎𝑚2∙𝑃𝐶𝑂2 (9.9)

The second equilibrium constant also includes the square of the mole fraction of

water, which is assumed to be a constant in this model.

𝐾2∗ =

𝑥𝐻𝐶𝑂3−2∙𝑥

𝑎𝑚𝐻+

𝑥𝑎𝑚𝐶𝑂𝑂− ∙𝑃𝐶𝑂2 (9.10)

An Arrhenius relationship was used to describe the temperature dependence of the

equilibrium constants, where the temperature dependent term is centered at 40 °C.

ln(𝐾𝑖∗) = 𝐶𝑖−𝑎 + 𝐶𝑖−𝑏 ∙ (

1

313.15−

1

𝑇) (9.11)

The SSM has five unknown variables, the mole fractions of four liquid phase

species and the partial pressure of CO2 in the gas (Equation 9.12).

𝑈𝑛𝑘𝑛𝑜𝑤𝑛 =

{

𝑥𝑎𝑚𝑥𝑎𝑚𝐻+

𝑥𝑎𝑚𝐶𝑂𝑂−

𝑥𝐻𝐶𝑂3−

𝑃𝐶𝑂2

(9.12)

To solve the chemical equilibria and determine the values of the five unknowns,

three mass balances are added to the model. These are the total CO2 and amine

balances in the liquid, and the charge balance (Equation 9.13). Together these five

equations specify the components in the system.

{

𝐶1−𝑎 + 𝐶1−𝑏 ∙ (

1

313.15−

1

𝑇) = 𝑙𝑛 (𝑥𝑎𝑚𝐶𝑂𝑂−) + 𝑙 𝑛(𝑥𝑎𝑚𝐻+) − 2 ∙ ln(𝑥𝑎𝑚) − ln (𝑃𝐶𝑂2)

𝐶2−𝑎 + 𝐶2−𝑏 ∙ (1

313.15−

1

𝑇) = 2 ∙ ln(𝑥𝐻𝐶𝑂3−) + ln (𝑥𝑎𝑚𝐻+) − ln (𝑥𝑎𝑚𝐶𝑂𝑂−) − ln (𝑃𝐶𝑂2)

𝑥𝑎𝑚𝐶𝑂𝑂− + 𝑥𝐻𝐶𝑂3− = 𝑥𝐶𝑂2,𝑡𝑜𝑡𝑎𝑙𝑥𝑎𝑚𝐻+ + 𝑥𝑎𝑚𝐶𝑂𝑂− + 𝑥𝑎𝑚 = 𝑥𝑎𝑚𝑡𝑜𝑡𝑎𝑙

𝑥𝑎𝑚𝐶𝑂𝑂− + 𝑥𝐻𝐶𝑂3− = 𝑥𝑎𝑚𝐻+

(9.13)

281

In Equation 9.13, three terms are the conditions for the system, which are

specified as input values to the model (Equation 9.14). These are the temperature, total

CO2 and amine mole fractions in the liquid phase.

𝐼𝑛𝑝𝑢𝑡 = {

𝑇𝑥𝐶𝑂2,𝑡𝑜𝑡𝑎𝑙𝑥𝑎𝑚,𝑡𝑜𝑡𝑎𝑙

(9.14)

The four parameters (Equation 9.15) for the two equilibrium constants are specific

to each amine.

𝑀𝑜𝑑𝑒𝑙 𝑝𝑎𝑟𝑎𝑚𝑒𝑡𝑒𝑟𝑠 = {

𝐶1−𝑎𝐶1−𝑏𝐶2−𝑎𝐶2−𝑏

(9.15)

In the case where the model parameters are known, the SSM can be used to

determine the liquid phase speciation and CO2 partial pressure in an aqueous amine at

some specified temperature and CO2 loading that is less than 1. If the model parameters

are unknown, they can be determined using a parameter regression component of the

model. The values of the parameters are adjusted until the model predictions match the

experimental data.

9.2.2 Numerical tools

The SSM was coded using MATLAB. To implement the model numerically, the

model equations were transformed and the model parameters were scaled.

As shown in Equation 9.16, the five unknowns are transformed into natural log

values. This is because the mole fractions of the species are very small numbers, and

they differ from each other by several orders of magnitude; whereas PCO2, in the unit of

Pascal, can have very large values. A system of equations with variables of different

magnitudes is difficult to solve numerically. The natural log transformation of these

terms brings them to the same order of magnitude, and the equations can be solved easily.

282

𝑀𝑜𝑑𝑒𝑙 𝑢𝑛𝑘𝑛𝑜𝑤𝑛 =

{

𝑥1 = ln (𝑥𝑎𝑚)𝑥2 = ln (𝑥𝑎𝑚𝐻+)

𝑥3 = ln (𝑥𝑎𝑚𝐶𝑂𝑂−)𝑥4 = ln (𝑥𝐻𝐶𝑂3−)

𝑥5 = ln (𝑃𝐶𝑂2)

(9.16)

The four adjustable parameters of the model equations are also scaled to the same

order of magnitude, as shown in Equation 9.17.

𝐴𝑑𝑗𝑢𝑠𝑡𝑎𝑏𝑙𝑒 𝑝𝑎𝑟𝑎𝑚𝑒𝑡𝑒𝑟𝑠 = {

𝐶1 = 𝐶1−𝑎𝐶2 = 𝐶1−𝑏 10000⁄

𝐶3 = 𝐶2−𝑎 10⁄

𝐶4 = 𝐶2−𝑏 1000⁄

(9.17)

After the transformation and scaling of the unknowns and parameters, the model

equations implemented into MATLAB are shown in Equation 9.18.

𝑓𝑢𝑛̅̅ ̅̅ ̅ =

{

𝐶1 + 𝐶2 ∙ 10000 ∙ (

1

313.15−

1

𝑇) = 𝑥3 + 𝑥2 − 2 ∙ 𝑥1 − 𝑥5

𝐶3 ∙ 10 + 𝐶4 ∙ 1000 ∙ (1

313.15−

1

𝑇) = 2 ∙ 𝑥4 + 𝑥2 − 𝑥3 − 𝑥5

exp (𝑥3) + exp (𝑥4) = 𝑥𝐶𝑂2,𝑡𝑜𝑡𝑎𝑙exp (𝑥2) + exp (𝑥3) + exp (𝑥1) = 𝑥𝑎𝑚𝑡𝑜𝑡𝑎𝑙

exp (𝑥3) + exp (𝑥4) = exp (𝑥2)

(9.18)

Nonlinear equation solver

In the SSM, the system of equations is solved using a built in solver in MATLAB,

the fsolve function. This solver handles systems of equations and can be used for

nonlinear systems (MathWorks 2015).

Parameter regression

The parameter regression component of the SSM is implemented as an

optimization problem. For a set of CO2 VLE data with n points, the SSM is evaluated at

each data point conditions with some arbitrary initial guesses for the model parameters.

Then the error between the model and data is written as Equation 9.19.

283

𝑒𝑟𝑟𝑜𝑟 = ∑ (𝑙𝑛𝑃𝐶𝑂2𝑀𝑜𝑑𝑒𝑙 (

𝐶1𝐶2𝐶3𝐶4

)− 𝑙𝑛𝑃𝐶𝑂2𝑑𝑎𝑡𝑎)

2

𝑖=𝑛𝑖=1 (9.19)

The parameter regression component of the model then finds the best set of

parameter values by minimizing the error function (Equation 9.20).

min(𝐶)

𝑒𝑟𝑟𝑜𝑟 (𝐶) = ∑ (𝑙𝑛 𝑃𝐶𝑂2𝑀𝑜𝑑𝑒𝑙(𝐶) − 𝑙𝑛 𝑃𝐶𝑂2𝑑𝑎𝑡𝑎)2

𝑛𝑖=1 (9.20)

The built in MATLAB function of fmincon was used to solve this optimization

problem.

9.2.3 Model statistics

The fit of the SSM to the experimental data was quantified by calculating the

average absolute relative deviation (AARD), as shown in Equation 9.21.

𝐴𝐴𝑅𝐷 =1

𝑛∙ (

|𝑃𝐶𝑂2𝑚𝑜𝑑𝑒𝑙−𝑃𝐶𝑂2𝑑𝑎𝑡𝑎

|

𝑃𝐶𝑂2𝑚𝑜𝑑𝑒𝑙

) (9.21)

To determine the standard deviation and correlation of the four regressed

parameters, the hessian of the error function is calculated. The hessian is the square

matrix which has dimensions that are the same as the total number of adjusted

parameters. The elements of the hessian are the second derivatives of the error function

with respect to each parameter pair (Equation 9.22).

𝐻(𝑒𝑟𝑟𝑜𝑟) =

[ 𝜕2𝑒𝑟𝑟𝑜𝑟

𝜕𝐶12

𝜕2𝑒𝑟𝑟𝑜𝑟

𝜕𝐶1 𝜕𝐶2


𝜕𝐶2 𝜕𝐶1


𝜕𝐶22


𝜕𝐶1 𝜕𝐶3


𝜕𝐶1 𝜕𝐶4


𝜕𝐶2 𝜕𝐶3


𝜕𝐶2 𝜕𝐶4


𝜕𝐶3 𝜕𝐶1


𝜕𝐶3 𝜕𝐶2


𝜕𝐶4 𝜕𝐶1


𝜕𝐶4 𝜕𝐶2


𝜕𝐶32


𝜕𝐶3 𝜕𝐶4


𝜕𝐶4 𝜕𝐶3


𝜕𝐶42 ]

(9.22)

284

Numerically, the second derivative was estimated using the second order

centered difference, as introduced by Press (2008). The MATLAB code for the

calculation of hessian was adapted from Baldea (2014)

The inverse of the hessian is referred to as the covariance matrix of the function.

And the standard deviation of the parameters is the square root of the diagonal elements

of the covariance matrix (Equation 9.23).

𝑆𝑡. 𝐷𝑒𝑣 = √𝑑𝑖𝑎𝑔(𝑖𝑛𝑣(𝐻)) (9.23)

The correlation matrix of the adjusted parameters is calculated as the linear

correlation of the covariance matrix (Equation 9.24). The MATLAB command corr

was used to calculate the correlation matrix of the covariance matrix.

The MATLAB code of the SSM, along with the parameter regression and the

statistics functions are included in the Appendix C.

9.2.4 Base case results for 7 m MEA

The CO2 VLE data for 7 m MEA was regressed using the SSM as a base case

analysis of the model. Experimental data over a wide range of CO2 loading (0.1-0.9

mol/mol alkalinity) and temperature (40 – 170 °C) were used in the regression of model

parameters. With an abundance of experimental data, the model can be tested over

much of the relevant process conditions. The liquid phase speciation is also available

for 7 m MEA, which is used to compare with the predictions of the SSM and to

demonstrate the accuracy of the model.

285

CO2 solubility

Figure 9.1: SSM fit of CO2 VLE for 7 m MEA (solid lines), compared with data by

Dugas (2009, diamonds), Hillard (2008, squares), Xu (2011, triangles)

Ma’mum et al. (2006, asterisk), and Jou et al. (2009, circles).

Five sets of data for 7 m MEA were regressed to determine the equilibrium

constants in the SSM. The fit of the model to the data is plotted in Figure 9.1. The

model results fit the data over the entire range of CO2 loading and temperature. In

Figure 9.2, the SSM model result is compared with the semi-empirical model (Xu 2011)

and the Pheonix model developed in Aspen Plus® (Plaza 2011) at 40 °C. All three

models fit the data reasonably well over most of the CO2 loading range. The SSM

better captures the curvatures in the data than the semi-empirical model, particularly at

very low and high CO2 loading. The SSM and the semi-empirical model both deviate

from the Aspen Plus® model between CO2 loading of 0.3 and 0.5.

1.E+00

1.E+01

1.E+02

1.E+03

1.E+04

1.E+05

1.E+06

1.E+07

0.1 0.3 0.5 0.7 0.9

PC

O2*

(Pa)


40 °C

120 °C100 °C

80 °C

60 °C

140 °C

160 °C

286

Figure 9.2: SSM fit (blue line) of CO2 VLE for 7 m MEA at 40 °C, compared with semi-

empirical model (Xu 2011, orange dotted line), Phoenix in AspenPlus®

(Plaza 2011, black line); and data by Jou et al. (circle), Dugas (2009,

diamond), and Hillard (2008, Square).

Liquid phase speciation

The liquid phase composition predicted by the SSM for 7 m MEA is plotted in

Figure 9.3, and compared with the result by Aspen and experimental data (Hillard 2008).

The SSM and Aspen result agree well with each other. Around CO2 loading of 0.5, the

two models deviate slightly, where Aspen shows better agreement with the data for

bicarbonate. Both models under predict the data for carbamate.

1.E+00

1.E+01

1.E+02

1.E+03

1.E+04

1.E+05

1.E+06

0.1 0.3 0.5 0.7 0.9

PC

O2*

(Pa)


40 °C

287

Figure 9.3a: Liquid phase composition predicted by the SSM for 7 m MEA, compared

with NMR speciation data (Hillard 2008) and prediction by the Pheonix

model in Aspen Plus® (Plaza 2011)

0

0.02

0.04

0.06

0.08

0.1

0.12

0 0.2 0.4 0.6 0.8 1

x


MEA/MEAH+

MEA

MEAH+

MEACOO-

HCO3-

Solid lines: SSMDashed lines: AspenPlus®

288

Figure 9.3b: Liquid phase composition predicted by the SSM for 7 m MEA, compared

with NMR speciation data (Hillard 2008) and prediction by the Pheonix

model in Aspen Plus® (Plaza 2011) (Logarithmic scale)

In Figure 9.3b, the lower ranges of the speciation values use the logarithmic scale

for the mole fractions. The SSM substantially over predicts the bicarbonate at CO2

loading lower than 0.5. At CO2 loading higher than 0.5, the SSM predicts higher free

amine than Aspen. This error exhibited by the SSM at low concentrations is because the

model neglects the ionization of water and the formation of carbonate in the model

chemistry. These two chemical equilibria have small effects on the overall chemistry,

and neglecting them introduced a greater relative error only at low concentrations.

1E-05

0.0001

0.001

0.01

0.1

1

0 0.2 0.4 0.6 0.8 1

x


MEA/MEAH+

MEA

MEAH+

MEACOO-

HCO3-

Solid lines: SSMDashed lines: AspenPlus®

289

Parameter statistics

The value and statistics of the model parameters are summarized in Table 9.2 and

9.3. All four adjusted parameters are statistically significant based on their standard

deviations. The correlation matrix suggests the four parameters are highly correlated

with each other.

Table 9.2: SSM parameter values and standard deviation for 7 m MEA

Value St.Dev

C1 - 4.23 0.13

C2 - 1.16 0.04

C3 - 1.72 0.02

C4 - 4.36 0.75

Table 9.3: Correlation matrix of the SSM parameters for 7 m MEA

C1 C2 C3 C4

C1 1.000 -0.940 -0.913 0.900

C2

1.000 0.997 -0.995

C3

1.000 -0.999

C4 1.000

290

9.3 MODEL RESULTS OF AQUEOUS AMINES

9.3.1 CO2 VLE fit

Figure 9.4: SSM fit of CO2 VLE for 7 m MPA (solid lines: SSM; solid diamonds: WWC

data)

The SSM result for 7 m MPA is plotted in Figure 9.4, which is compared with the

data used for the parameter regression. The SSM fits the data well over the entire range

of temperature and CO2 loading of the experiments. The model is also well behaved at

CO2 loading beyond the range of the data.

The model result for MIPA is shown in Figure 9.5. For MIPA, data at 7 m

(Chapter 7) and 5.7 m MIPA (Morales et al. 2010) were regressed together. The model

fits both sets of data well. Only at high CO2 loading, around 0.9, the model over-

predicts the data. This may be because the model omits explicit dissolved free CO2,

which is expected to have a significant effect on the solvent VLE at high CO2 loading.

1

10

100

1000

10000

100000

1000000

0.1 0.3 0.5 0.7 0.9

PC

O2*

(Pa)


40 °C

100 °C

80 °C

60 °C

20 °C

291

Figure 9.5: SSM fit of CO2 VLE for 7 m MIPA (solid lines: SSM; solid diamonds: WWC

data), and 5.7 m MIPA (dashed lines: SSM; empty squares: Morales et al.

2010)

Figure 9.6: SSM fit of CO2 VLE for 10 m DGA® (solid lines: SSM; solid diamonds:

Chen et al. 2011), and prediction for 7 m DGA®.

1.E+01

1.E+02

1.E+03

1.E+04

1.E+05

1.E+06

1.E+07

0.1 0.3 0.5 0.7 0.9

PC

O2*

(Pa)


40 °C

100 °C80 °C

60 °C

20 °C

120 °C

Solid lines: 7 mDashed lines: 5.7 m

1

10

100

1000

10000

100000

1000000

0.1 0.2 0.3 0.4 0.5 0.6 0.7

PC

O2*

(Pa)


40 °C

100 °C

80 °C

60 °C

Solid lines: 10 mDashed lines: 7 m

292

The SSM result for DGA® at 10 m and 7 m amine is shown in Figure 9.6. Only

data for 10 m DGA® (Chen et al. 2011) were used to regress the model parameters.

The model results shown little difference in CO2 VLE at the two amine concentrations at

CO2 loading lower than 0.5. At the high CO2 loading, where the bicarbonate formation

reaction begins to affect CO2 VLE, PCO2* increases with amine (at the same CO2 loading).

In other words, CO2 solubility is reduced per mole of DGA® as the total amineincreases.

At high CO2 loading, the CO2 VLE curves at different temperature begin to collapse,

which is not physically realistic. This is because the model parameter representing the

temperature dependence of the second equilibrium (C4/C2-b) was set to zero in the

regression. A statistically significant value cannot be obtained for this parameter as no

data at high CO2 loading was included in the regression.

Figure 9.7: SSM fit of CO2 VLE for 3.55 m GlyK (solid lines: SSM; solid diamonds:

WWC).

10

100

1000

10000

100000

0.1 0.3 0.5 0.7

PC

O2*

(Pa)


40 °C

100 °C

80 °C

60 °C

293

Figure 9.8: SSM fit of CO2 VLE for 6 m GlyK (solid lines: SSM; solid diamonds:

WWC).

The results for GlyK are shown in Figure 9.7 and 9.8. The CO2 VLE data for

3.55 m and 6 m GlyK (Chapter 5) were used together in the parameter regression. The

SSM model for GlyK fits data at both concentration well. And the model extrapolations

beyond the experimental loading are well behaved.

Figure 9.9: SSM fit of CO2 VLE for 6.5 m β-alaK (solid lines: SSM; solid diamonds:

WWC data).

10

100

1000

10000

100000

0.1 0.3 0.5 0.7

PC

O2*

(Pa)


40 °C

100 °C

80 °C

60 °C

10

100

1000

10000

100000

1000000

0.1 0.3 0.5 0.7 0.9

PC

O2*

(Pa)


40 °C

100 °C

80 °C

60 °C

294

The model CO2 solubility result for 6.5 m β-alaK is shown in Figure 9.9. And

the model fits the regressed data well.

Figure 9.10: SSM fit of CO2 VLE for 7 m MMEA (solid lines: SSM; solid diamonds:

WWC data).

For 7 m MMEA, the SSM model fits the experimental data well (Figure 9.10).

However, like the case for 10 m DGA®, not enough data at CO2 loading higher than 0.5

were used in the regression to obtain a statistically significant value for the temperature

dependence of the second equilibrium. Thus, the temperature behavior of this model at

high CO2 loading is not physically realistic.

Two sets of experimental data at 9.4 m (Lee et al. 1972) and 7 m amine were

regressed in the SSM for DEA. The results are shown in Figure 9.11 and 9.12. The

model fits the data at both amine concentrations. At CO2 loading around 0.9, the model

over-predicts the data at 9.4 m DEA. This is due to the absence of explicit dissolved

CO2 in the model.

1

10

100

1000

10000

100000

0.1 0.3 0.5 0.7

PC

O2*

(Pa)


40 °C

100 °C

80 °C

60 °C

20 °C

295

Figure 9.11: SSM fit of CO2 VLE for 5 M (9.4 m) DEA (solid lines: SSM; solid squares:

Lee et al. 1972).

Figure 9.12: SSM fit of CO2 VLE for 7 m DEA (solid lines: SSM; solid diamonds:

WWC).

100

1000

10000

100000

1000000

10000000

0.0 0.2 0.4 0.6 0.8 1.0

PC

O2*

(Pa)


40 °C

100 °C

75 °C

50 °C

25 °C

120 °C

140 °C

100

1000

10000

100000

1000000

0.1 0.3 0.5 0.7 0.9

PC

O2*

(Pa)


40 °C

80 °C

60 °C

20 °C

296

Figure 9.13: SSM fit of CO2 VLE for 7 m DIPA (solid lines: SSM; solid diamonds: WWC data), and 34 wt % (3.9 m) DIPA at 25 °C (dash lines: SSM; empty

squares: data by Dell’Era et al. 2010).

For DIPA, data at 7 m and 3.9 m amine was regressed in the SSM. The model

fit of both data sets are shown in Figure 9.13. The model fits the 7 m data well, but

under-predicts the 3.9 m data at 0.5-0.7 CO2 loading.

The SSM results for SarK are shown in Figure 9.14 and 9.15. Experimental data

at 3 M (2.8 m) (Aronu et al. 2011) and 6 m (Chapter 5) amino acid were both used in the

parameter regression. The model fits both sets of data well. Moreover, the model for

SarK was used to predict the CO2 VLE at 4.5 m amino acid. The result is compared

with data for 4.5 m SarNa. The model prediction at 4.5 m fits the data of SarNa well.

This shows the model can be used to adequately interpolate the CO2 VLE behavior within

the amine concentration of the data used in the parameter regression.

10

100

1000

10000

100000

1000000

0.1 0.3 0.5 0.7 0.9

PC

O2*

(p

a)


40 °C

80 °C

60 °C

20 °C

25°C

297

Figure 9.14: SSM fit of CO2 VLE for 3 M (2.8 m) SarK (solid lines: SSM; solid squares:

Aronu et al. 2011).

Figure 9.15: SSM fit of CO2 VLE for 6 m SarK (solid lines: SSM; solid diamonds:

WWC).

1

10

100

1000

10000

100000

1000000

0.1 0.3 0.5 0.7 0.9

PC

O2*

(Pa)


40 °C

80 °C

60 °C

100 °C

120 °C

1

10

100

1000

10000

100000

1000000

0.1 0.3 0.5 0.7 0.9

PC

O2*

(Pa)


40 °C

80 °C

60 °C

100 °C

298

Figure 9.16: SSM prediction of CO2 VLE for 4.5 m SarNa (solid lines: SSM; empty

diamonds: WWC).

Figure 9.17: SSM fit of CO2 VLE for 4.8 m AMP (solid lines: SSM; empty diamonds:

WWC data by Chen et al. 2011).

1

10

100

1000

10000

100000

0.1 0.3 0.5 0.7

PC

O2*

(Pa)


40 °C

80 °C

60 °C

100 °C

10

100

1000

10000

100000

1000000

0.1 0.3 0.5 0.7 0.9

PC

O2*

(Pa)


40 °C

80 °C

60 °C

100 °C

299

Figure 9.18: SSM fit of CO2 VLE for 8 m 2-PE (solid lines: SSM; empty diamonds:

WWC data by Chen et al. 2011).

The SSM results for 4.8 m AMP and 8 m 2-PE are plotted in Figure 9.17 and

9.18. For both hindered amines, the model fits the regressed data (Chen et al. 2011).

The model is also well behaved over a wide range of CO2 loading beyond the data range.

9.3.2 Liquid phase speciation prediction

The SSM prediction of liquid phase composition of three primary amines and

three secondary amines are compared together at the same amine concentration of 7 m

and 40 °C.

The model predictions of free amine mole fraction (xam) for the amines are shown

in Figure 9.19. The calculated xam are plotted as functions of the equilibrium partial

pressure of CO2 at 40 °C. The standard operating conditions for coal flue gas, between

500 and 5000 Pa in PCO2* are identified along the x-axis. This result shows, at the same

PCO2*, the amount of free amine available in the solvent increases as the pKa of the amine

decreases. The exception to this trend is DIPA, which has the same pKa as DEA, but

10

100

1000

10000

100000

1000000

0.1 0.3 0.5 0.7 0.9

PC

O2*

(Pa)


40 °C

80 °C

60 °C

100 °C

300

much higher free amine. Also, the secondary MMEA has slightly more free amine than

MPA, though they have the same pKa. The difference in free amine between the amines

is up to a factor of three. Moreover, the free amine in the solvent decreases by about 50

% between the standard lean and rich loading of the solvent.

Figure 9.19: SSM prediction of liquid phase free amine composition at 40 °C for selected

primary and secondary amines at 7 m total amine

The model predicted amine carbamate mole fractions are compared for the amines

in Figure 9.20. The model results show, at the same CO2 loading, the carbamate

generally increases with the pKa of the amine. However, the stability of the carbamate

has different dependence on pKa for primary and secondary amines. This is suggested

by the difference in predicted carbamate between MMEA and MPA, which have the pKa.

Also, DIPA and DEA have the same pKa and are both secondary amines, while DIPA has

much less carbamate than DEA. The low carbamate in DIPA suggests it is more

structurally hindered than DEA.

0

0.03

0.06

0.09

100 1000 10000

x am

PCO2* (Pa)

DIPA

DEAMIPA

MMEA

MEA

MPA

40 °C

500 5000

7 m Amine

301

Figure 9.20: SSM prediction of liquid phase amine carbamate composition at 40 °C for

selected primary and secondary amines at 7 m total amine

Figure 9.21: SSM prediction of liquid phase bicarbonate composition at 40 °C for

selected primary and secondary amines at 7 m total amine

0

0.03

0.06

0.1 0.3 0.5 0.7 0.9

x car

bam

ate


DIPA

DEA

MIPA

MMEA

MEAMPA40 °C

7 m Amine

0.0001

0.001

0.01

0.1

0.1 0.3 0.5 0.7 0.9

x bic

arb

on

ate


DIPA

DEA

MIPAMMEA

MEA

MPA

40 °C

7 m Amine

302

The bicarbonate in the six amines is compared in Figure 9.21. At CO2 loading

below 0.5, the bicarbonate in the solvent increases with decrease in amine pKa. Trends

are observed in the bicarbonate as for the carbamate and free amine, where MMEA has

higher bicarbonate than its primary counter-part. Also, DIPA has higher bicarbonate

than DEA, while both are secondary amines and have the same pKa. At CO2 loading

higher than 0.7, the bicarbonate of different amines begins to converge together.

Speciation prediction of 30 wt % AMP

Using the ion-pair formation reaction as one of the two main interactions between

CO2 and a hindered amine, the SSM shows a good representation of NMR data as well as

good agreement with AspenPlus® predictions.

Figure 9.22: Liquid phase composition predicted by the SSM for 4.8 m AMP at 25 °C,

compared with NMR speciation data (Cifjia et al. 2014) and prediction by

the Sherman AMP model in Aspen Plus® (Rochelle et al. 2014)

0.00

0.02

0.04

0.06

0.08

0.10

0.1 0.3 0.5 0.7 0.9

x (m

ol/

mo

l)


AMP/AMPH+

HCO3-/CO3

2-

AMPCOO-

Solid: SSMDashed: AspenPlus(Rochelle et al. 2014)

303

The liquid phase speciation of 4.8 m AMP predicted by the SSM is compared

with quantitative NMR data by Cifjia et al. (2014) and the prediction of an eNRTL model

in Aspen Plus® by Sherman (Rochelle et al. 2014) in Figure 9.22. The speciation

calculated by the SSM is interpreted using the ion-pair reaction (Equation 9.7b). And

the SSM results agree well with the data and Aspen Plus® results. The SSM does not

predict AMP carbamate, as it is not included as a species in the model. Since AMP

carbamate exists in very low concentration in the solvent, this approximation does not

significantly affect the accuracy in the prediction of other species.

Figure 9.23: Liquid phase composition predicted by the SSM for 4.8 m AMP at 25 °C,

compared with prediction by the Sherman AMP model in Aspen Plus®


The SSM and Aspen Plus® results for 4.8 m AMP are further compared in Figure

9.23. The Aspen results are interpreted using the ion-pair reaction (Equation 9.7b) by

0

0.02

0.04

0.06

0.08

0.1 0.3 0.5 0.7 0.9

x (m

ol/

mo

l)


AMP

HCO3-

AMPCOO-

AMPH+

AMPH+CO32-

Solid: SSMDashed: AspenPlus(Rochelle et al.2014)

304

representing the carbonate species as the AMP cation and carbonate anion pair, and the

“free” AMPH+ is calculated from total AMPH+ minus the carbonate . The comparison

shows good agreement in the predicted AMPH+ between the two models. At low

CO2 loading, the SSM under predicts the Aspen results for AMP and bicarbonate, while it

over predicts the Aspen results for the ion pair.

9.3.3 Regressed parameters and statistics

The experimental data used in the parameter regression of the SSM and the

AARD (Equation 9.21) of the fit are summarized in Table 9.4. The regressed SSM

parameter values and their standard deviations are summarized in Table 9.5. The

correlation matrix of the parameters for each amine is included in the Appendix C.

Table 9.4: Experimental data used for each amine system in the regression of SSM

equilibrium parameters and the AARD of the final data fit

𝐴𝐴𝑅𝐷 =1

𝑛∙ (

|𝑃𝐶𝑂2𝑚𝑜𝑑𝑒𝑙−𝑃𝐶𝑂2𝑑𝑎𝑡𝑎

|

𝑃𝐶𝑂2𝑚𝑜𝑑𝑒𝑙

)

Amine [Am]t CO2 loading T (°C) # data AARD

MEA 7 m 0.1– 0.95 40 - 170 171 0.26

MPA 7 m 0.3 – 0.6 20 - 100 20 0.24

MIPA 30 wt% (5.7 m), 7 m 0.25 – 0.95 20 - 120 36 0.24

DGA® 10 m 0.2 – 0.5 40 - 100 15 0.21

DEA 7 m, 5M (9.4 m) 0.05 – 0.95 20 - 80 78 0.21

MMEA 7 m 0.2 – 0.53 20 - 100 19 0.17

DIPA 7 m, 34 wt% (3.9 m) 0.1 – 0.97 20 - 80 21 0.35

GlyK 3.55 m, 6 m 0.3 – 0.57 40 - 100 27 0.23

SarK

SarNa 6 m, 3M (2.8 m), 4.5 m 0.14 – 0.72 40 - 100 70 0.17

β-alaK 6.5 m 0.32 – 0.54 40 - 100 19 0.096

2PE 8 m 0.2 – 0.7 40 - 100 14 0.105

AMP 4.8 m 0.15 – 0.6 40 - 100 13 0.108

Table 9.5: The SSM model parameter values and standard error for each amine

305

Amine C1 C2 C3 C4

V Std.dev V Std.dev V Std.dev V Std.dev

MEA - 4.23 0.13 - 1.16 0.04 - 1.72 0.02 - 4.36 0.75

MPA - 2.66 0.40 - 1.21 0.14 - 1.72 0.03 - 4.72 1.81

MIPA - 4.71 0.28 - 1.14 0.09 - 1.77 0.03 - 5.18 1.14

DGA - 4.30 0.39 - 1.32 0.13 - 1.91 0.11 /

DEA - 8.06 0.02 - 1.05 0.04 - 1.74 0.02 - 3.97 0.05

MMEA - 4.69 0.35 - 1.29 0.11 - 1.71 0.06 /

DIPA - 9.72 0.25 - 1.00 0.01 - 1.75 0.01 - 5.51 1.35

GlyK - 3.10 0.34 - 1.03 0.12 - 1.72 0.07 - 5.12 2.86

SarK

SarNa - 3.16 0.16 - 0.96 0.06 - 1.76 0.02 - 4.17 0.59

β-alaK - 2.03 0.41 - 0.99 0.14 - 1.66 0.07 - 5.49 2.82

2PE - 8.67 1.37 - 1.60 0.01 - 1.13 0.12 - 2.48 1.42

AMP - 9.54 3.24 - 1.78 0.25 - 1.30 0.37 /

9.4 PHYSICAL SIGNIFICANCE OF MODEL PARAMETERS

In liquid systems involving weak electrolytes, such as CO2 loaded aqueous

amines, chemical equilibria are defined as functions of the activities of the reacting

species (Equation 9.24).

𝐾𝑒𝑞 =∏𝑎𝑝𝑟𝑜𝑑𝑢𝑐𝑡

∏𝑎𝑟𝑒𝑎𝑐𝑡𝑎𝑛𝑡=

∏𝑥𝑝𝑟𝑜𝑑𝑢𝑐𝑡

∏𝑥𝑟𝑒𝑎𝑐𝑡𝑎𝑛𝑡∙∏𝛾𝑝𝑟𝑜𝑑𝑢𝑐𝑡

∏𝛾𝑟𝑒𝑎𝑐𝑡𝑎𝑛𝑡 (9.24)

In the SSM, the equilibrium constants are approximated as functions of the mole

fractions of the species. And they are denoted by the asterisk (*) superscript in the

equilibrium constant (Equation 9.25a).

𝐾𝑒𝑞∗ =

∏𝑥𝑝𝑟𝑜𝑑𝑢𝑐𝑡

∏𝑥𝑟𝑒𝑎𝑐𝑡𝑎𝑛𝑡≈ (𝐾𝑒𝑞) (9.25a)

The mole fraction based equilibrium constant in the SSM can be related to the

activity based equilibrium constants by the activity coefficients of the reacting species

(Equation 9.25b).

306

𝐾𝑒𝑞 = 𝐾𝑒𝑞∗ ∙ (

∏𝛾𝑝𝑟𝑜𝑑𝑢𝑐𝑡

∏𝛾𝑟𝑒𝑎𝑐𝑡𝑎𝑛𝑡) (9.25b)

The activity coefficients also represent the error of using the mole fraction basis

to represent the chemical equilibria (Equation 9.25c).

𝑒𝑟𝑟𝑜𝑟𝐾𝑒𝑞∗ =𝐾𝑒𝑞∗

𝐾𝑒𝑞=

∏𝛾𝑟𝑒𝑎𝑐𝑡𝑎𝑛𝑡

∏𝛾𝑝𝑟𝑜𝑑𝑢𝑐𝑡 (9.25b)

In this section, the equilibrium constants in the SSM are used together with acid

dissociation constant of the amines found in literature. Also, the SSM constants are

compared with values found in literature when they are available. In both of these

cases, Equation 9.25b was used to account for the neglected activity coefficients for the

SSM constants.

The two chemical equilibria in the SSM are both written as the combination of

two or more fundamental chemical equilibria: the carbamate formation (Kcarb form), acid

dissociation of the protonated amine (Ka), and the formation of bicarbonate (Ka,CO2).

Measured values of Ka are available in literature for the amines analyzed in this Chapter

(Table 9.1). Using literature Ka values, the values for Kcarb form and Ka,CO2 can be

calculated from the SSM parameters.

The Ka values in literature are always reported at the condition of infinite dilution

in water (Equation 9.26).

𝐾𝑎𝑥𝑎𝑚→0=

𝑥𝐻3𝑂

+ ∙𝑥𝑎𝑚

𝑥𝐻2𝑂𝑥𝑎𝑚𝐻+ (9.26)

The infinite dilution value can be related to the Ka value at concentrated amine

and CO2 loaded conditions by the activity coefficient of the species (Equation 9.27).

𝐾𝑎 =𝑎𝐻3𝑂

+ ∙𝑎𝑎𝑚

𝑎𝐻2𝑂𝑎𝑎𝑚𝐻+ = (

𝑥𝐻3𝑂

+ ∙𝑥𝑎𝑚

𝑥𝐻2𝑂∙𝑥𝑎𝑚𝐻+) ∙ (

𝛾𝐻3𝑂

+ ∙ 𝛾𝑎𝑚

𝛾𝐻2𝑂∙ 𝛾𝑎𝑚𝐻+) = 𝐾𝑎

𝑥𝑎𝑚→0

∙ (𝛾𝐻3𝑂

+ ∙ 𝛾𝑎𝑚

𝛾𝐻2𝑂∙ 𝛾𝑎𝑚𝐻+) (9.27)

In this work, equation 9.26 was used to represent experimental Ka values.

307

The CO2 VLE in an amine solvent is related to the physical structure of the amine

molecule and its corresponding chemical properties, particularly the base strength of the

amine. In this section, this relationship is examined by looking at the correlation of the

equilibrium constants with the structure and Ka of the amine.

The asterisk in the superscript of the equilibrium constants signifies a SSM

specific equilibrium constant. The SSM constants are related to the true activity based

constants of the same chemical equilibrium through various activity coefficients and

other neglected parameters.

9.4.1 First equilibrium constant (K1*)

The first equilibrium constant in the SSM (K1*) is a concentration based

equilibrium constant, with a gas phase partial pressure used in place of liquid mole

fraction for CO2. The Henry’s constant can be used to interchange between the two

representations of CO2 concentration (Equation 9.28).

𝐾1∗ =


𝑥𝑎𝑚2∙𝑃𝐶𝑂2=


𝑥𝑎𝑚2∙(𝑎𝐶𝑂2 ∙𝐻𝐶𝑂2−𝐻2𝑂) (9.28)

This SSM constant can be related to the activity based constant of the same

chemical reaction via the activity coefficient of the carbamate, free amine, and the

protonated amine (Equation 9.29).

𝐾1 =𝑎𝑎𝑚𝐶𝑂𝑂− ∙𝑎𝑎𝑚𝐻+

𝑎𝑎𝑚2∙𝑎𝐶𝑂2 ∙𝐻𝐶𝑂2−𝐻2𝑂= 𝐾1

∗ ∙ (𝛾𝑎𝑚𝐶𝑂𝑂− ∙𝛾𝑎𝑚𝐻+

𝛾𝑎𝑚2 ) (9.29)

308

Figure 9.24: The first equilibrium constant for the SSM (Equation 9.28) at 40 °C with

base strength of the amine.

The dependence of K1* on the base strength of the amine (Ka) is shown in Figure

9.24 at 40 °C. At the same Ka, primary amines have higher K1* than secondary amines.

And hindered amines have lower Ka than both primary and secondary amines. For both

primary and secondary amines, the K1* value decreases with decrease in amine Ka.

The first equilibrium in the SSM is the combination of the carbamate formation

equilibrium (Equation 9.2), the acid dissociation equilibrium of the amine (Equation 9.4),

and the Henry’s constant of CO2, as shown in Equation 9.30.

𝐾1 =𝐾𝐴𝑚𝐶𝑂𝑂−,𝑓

𝐾𝑎∙𝐻𝐶𝑂2−𝐻2𝑂 (9.30)

Based on Equation 9.30, an approximation of the carbamate formation

equilibrium constant can be written using the SSM parameter and the literature Ka values

of the amine (Equation 9.31).

1.E-05

1.E-04

1.E-03

1.E-02

1.E-01

1.E+00

1.E-10 1.E-09 1.E-08

K1

*

Ka, xam→0

40 °C

Primary amine

Secondary amine

AMP

2-PE

DIPA

309

𝐾𝐴𝑚𝐶𝑂𝑂−,𝑓 ∗ = 𝐾1

∗ ∙ 𝐾𝑎𝑥𝐻2𝑂→1=

𝑥𝑎𝑚𝐶𝑂𝑂− ∙ 𝑥𝐻3𝑂+

𝑥𝑎𝑚∙𝑥𝐻2𝑂∙(𝑎𝐶𝑂2 ∙𝐻𝐶𝑂2−𝐻2𝑂) (9.31)

The SSM approximated carbamate formation equilibrium constant is related to the

activity based constant by the Henry’s constant of CO2 and the activity coefficients of the

species as shown in Figure 9.32.

𝐾𝐴𝑚𝐶𝑂𝑂−,𝑓 ∗ =

𝐾𝐴𝑚𝐶𝑂𝑂−,𝑓

𝐻𝐶𝑂2−𝐻2𝑂∙ (

𝛾𝐻2𝑂∙𝛾𝑎𝑚

𝛾𝐻3𝑂+∙𝛾𝑎𝑚𝐶𝑂𝑂−

) (9.32)

The SSM approximated constant for the carbamate formation equilibrium is

compared with the Ka of the amine at 40 C in Figure 9.25. The plot shows primary

amines to have higher values of the carbamate formation equilibrium constant than

secondary amines, which are both higher than hindered amines. Also, the carbamate

formation constant decreases with the base strength of the amine. For primary amines,

the change in the carbamate formation constant with Ka is small, particularly when

compared with secondary amines. In other words, the likelihood to form carbamates is

less affected by the amine base strength for primary amines than it is for secondary

amines.

Figure 9.25: The mole fraction based carbamate formation constant (Equation 9.32) at 40 °C estimated by the SSM

1.E-14

1.E-13

1.E-12

1.E-11

1.E-10 1.E-09 1.E-08

Kam

,CO

O-*

Ka,xam→0

40 °CPrimary amine

Secondary amine

AMP2-PE

DIPA

310

9.4.2 Second equilibrium constant (K2*)

Figure 9.26: The second equilibrium constant in the SSM (Equation 9.33) at 40 °C with

base strength of the amine.

The second chemical equilibrium constant in the SSM is shown with the base

strength of the amine at 40 °C in Figure 9.26. The K2* value for unhindered amines

does not vary with the pKa of the amine. Hindered amines have higher values of K2*

than unhindered amines. K2* is a concentration based equilibrium constant, however, a

gas phase partial pressure is used in place of liquid mole fraction for CO2. The Henry’s

constant can be used to interchange between the two representations of CO2

concentration (Equation 9.33).

𝐾2∗ =


𝑎𝑚𝐻+

𝑥𝑎𝑚𝐶𝑂𝑂− ∙𝑃𝐶𝑂2=


𝑎𝑚𝐻+

𝑥𝑎𝑚𝐶𝑂𝑂− ∙𝑥𝐶𝑂2 ∙𝛾𝐶𝑂2 ∙𝐻𝐶𝑂2−𝐻2𝑂 (9.33)

The second constant in the SSM can be related to the activity based equilibrium

constant by the activity coefficients of the non-CO2 species (Equation 9.34).

𝐾2 =𝑎𝐻𝐶𝑂3

−2∙𝑎𝑎𝑚𝐻+

𝑎𝑎𝑚𝐶𝑂𝑂− ∙𝑎𝐶𝑂2 ∙𝐻𝐶𝑂2−𝐻2𝑂= 𝐾2

∗ ∙ (𝛾𝐻𝐶𝑂3

−2∙𝛾𝑎𝑚𝐻+

𝛾𝑎𝑚𝐶𝑂𝑂−) (9.34)

1.E-09

1.E-08

1.E-07

1.E-06

1.E-05

1.E-04

1E-10 1E-09 1E-08

K2*

Ka,xam→0

40 °C

Primary amine

Secondary amine

AMP

2-PE

DIPA

Unhinderdamineaverage

311

The second chemical equilibrium in the SSM is the combination of the

bicarbonate formation equilibrium (Equation 9.3), the carbamate formation equilibrium

(Equation 9.2), the acid dissociation of protonated amine (Equation 9.4), and the Henry’s

constant of CO2 in water (Equation 9.1), as shown in Equation 9.35. Moreover, the

second equilibrium constant can be written as a function of the first chemical equilibrium

constant of the SSM.

𝐾2 =𝐾𝑎,𝐶𝑂2

2∙𝑎𝐻2𝑂2

𝐾𝐴𝑚𝐶𝑂𝑂−,𝑓∙𝐾𝑎∙𝐻𝐶𝑂2−𝐻2𝑂=

𝐾𝑎,𝐶𝑂22∙𝑎𝐻2𝑂

2

𝐾1∙𝐾𝑎2∙𝐻𝐶𝑂2−𝐻2𝑂

2 (9.35)

Using the relationship between K2 and other equilibrium constants, an expression

can be written for the bicarbonate formation constant (Equation 9.36).

𝐾𝑎,𝐶𝑂2 = 𝐾𝑎 ∙ √𝐾1𝐾2 ∙ (𝐻𝐶𝑂2−𝐻2𝑂

𝑎𝐻2𝑂) (9.36)

Based on the relationship shown in Equation 9.36, the bicarbonate formation

equilibrium constant can be calculated using the SSM constants and the pKa of the amine

at infinite dilution in water. This bicarbonate formation constant is related to the

activity based constant through the Henry’s constant, activity coefficients, and the

activity of water (Equation 9.37a).

𝐾𝑎,𝐶𝑂2∗ = 𝐾𝑎𝑥𝐻2𝑂→1

∙ √𝐾1∗ ∙ 𝐾2

∗ = (𝐾𝑎,𝐶𝑂2

𝐻𝐶𝑂2−𝐻2𝑂) ∙ (

𝛾𝐻2𝑂∙𝑎𝐻2𝑂

𝛾𝐻3𝑂+∙𝛾𝐻𝐶𝑂3

−) (9.37a)

The activity coefficient terms in Equation 9.37a represents the deviation between

the SSM equilibrium constant for the bicarbonate reaction and literature value of this

reaction in water. In other words, these terms represent the non-idealities of an

concentrated and CO2 loaded amine solvent.

𝐾𝑎,𝐶𝑂2∗

𝐾𝑎,𝐶𝑂2−𝐻2𝑂= 𝐾𝑎,𝐶𝑂2

∗ (𝐾𝑎,𝐶𝑂2

𝐻𝐶𝑂2−𝐻2𝑂)⁄ = (

𝛾𝐻2𝑂∙𝑎𝐻2𝑂

𝛾𝐻3𝑂+∙𝛾𝐻𝐶𝑂3

−) (9.37b)

312

The bicarbonate formation constant calculated using the SSM parameters can be

compared with literature values. A mole fraction based bicarbonate formation constant

was reported by Edwards et al. (1978) and used later by Posey (1996) and Cullinane

(2005) (Equation 9.38).

𝑙𝑛 (𝐾𝑎,𝐶𝑂2𝑥) = 231.4 −12092

𝑇− 36.78 ∙ ln (𝑇) (9.38)

The Henry’s constant and the molar density of water are needed to relate the

literature constant with the SSM constant. The Henry’s constant of CO2 in water

reported by Versteeg and Van Swaaij (1988) is used (Equation 9.39).

𝐻𝐶𝑂2−𝐻2𝑂𝑐= 2.82 ∙ 106 exp(−2044 𝑇⁄ )𝑃𝑎 ∙ 𝑚3 ∙ 𝑚𝑜𝑙−1 (9.39)

The molar density of water at 40 °C is reported by DIPPR (1998) as shown in

Equation 9.40.

𝜌𝑚 = 54.9𝑘𝑚𝑜𝑙

𝑚3 = 5.5 ∙ 104𝑚𝑜𝑙

𝑚3 (9.40)

The ratio of the mole fraction based bicarbonate equilibrium constant and the

Henry’s constant of CO2 is calculated as shown in Equation 9.41, which is compared with

the Ka,CO2* from the SSM (Figure 9.27a).

𝐾𝑎,𝐶𝑂2𝑥

𝐻𝐶𝑂2−𝐻2𝑂(40 ℃) =

𝐾𝑎,𝐶𝑂2𝑥

𝐻𝐶𝑂2−𝐻2𝑂𝑐∙𝜌𝑚

= 3.78 ∙ 10−17 𝑃𝑎−1 (9.41)

313

Figure 9.27a: The mole fraction based bicarbonate formation constant (Equation 9.37a) at

40 °C estimated by the SSM, compared with literature values (Equation

9.41)

In Figure 9.27a, the Ka,CO2* calculated using the SSM is plotted with the base

strength of the amine measured at infinite dilution (Equation 9.26). The Ka,CO2* of the

amines appears to be independent of the base strength of the amine. This is physically

realistic, as the bicarbonate formation is not expected to be affected by the chemistry of

the amine. Also in Figure 9.27a, the Ka,CO2* of the amines are compared with the ratio

of the mole fraction based equilibrium constant of the bicarbonate formation reaction

(Equation 9.38) and the Henry’s constant of CO2 (Equation 9.41) . Compared to

literature results, the Ka,CO2* from the SSM has higher values. This difference can be

explained by the activity coefficient and water activity terms in Equation 9.37b.

The values of the activity terms in Equation 9.37b are plotted in Figure 9.27b.

1.E-18

1.E-17

1.E-16

1.E-15

1.E-14

1.E-13

1.E-12

1.E-10 1.E-09

Ka,

CO

2*

Ka,xam→0

40 °C

Primary amine

Secondary amineAMP

2-PE

DIPA

Equation 9.41

314

Figure 9.27b: The effect of activities on the bicarbonate reaction at high amine

concentration and CO2 loading (Equation 9.37b)

The carbamate stability constant is defined as the ratio of the carbamate formation

equilibrium and the bicarbonate formation equilibrium (da Silva and Svendsen 2006)

(Equation 9.42).

𝐾𝐶𝑎𝑟𝑏.𝑆𝑡𝑎𝑏 =𝑎𝑎𝑚𝐶𝑂𝑂−

𝑎𝑎𝑚∙𝑎𝐻𝐶𝑂3−=

𝐾𝑎,𝑎𝑚𝐶𝑂𝑂−

𝐾𝑎,𝐶𝑂2 (9.42)

Physically, this equilibrium represents the preference of CO2 for the carbamate

form versus the bicarbonate form in an aqueous amine solvent. For unhindered primary

or secondary amines, the carbamate is expected to be strongly favored over the

bicarbonate form at CO2 loading of 0.5 or lower. For hindered amines, the bicarbonate

form is favored over the carbamate even at low CO2 loading. Carbamate stability is an

important amine property for CO2 capture processes, as it indicates CO2 VLE behavior

which can affect the capacity of CO2 in the process. Moreover, carbamate stability is

also a direct indication of the steric hinderance of the nitrogen on the amine.

64

128

256

512

1,024

1.E-10 1.E-09

Ka,

CO

2*/

Ka,

CO

2-H

2O

(Eq

. 9.3

7b

)

Ka,xam→0

Primary amine

Secondary amine

AMP

2-PE

DIPA

40 °C

315

The mole fraction based carbamate stability constant can be calculated from the

SSM parameters as shown in Equation 9.43.

𝐾𝐶𝑎𝑟𝑏.𝑆𝑡𝑎𝑏∗ =

𝐾1∗∙𝐾𝑎,𝑥𝑎𝑚→0

𝐾𝑎,𝐶𝑂2∗ =

𝑥𝑎𝑚𝐶𝑂𝑂−

𝑥𝑎𝑚∙𝑥𝐻𝐶𝑂3−

(9.43)

The calculated mole fraction based carbamate stability constant is plotted in

Figure 9.28 with base strength of the amine at 40 °C. The plot shows unhindered

amines to have higher carbamate stability than hindered amines. In the case of DIPA,

the calculated carbamate stability constant suggests it is more hindered than other

secondary amines. The plot shows primary amines to have higher carbamate stability

constant than secondary amines at the same pKa. For both primary and secondary

amines, the carbamate stability constant decreases with the pKa of the amine.

Figure 9.28: The mole fraction based carbamate stability constant (Equation 9.43) at 40

°C estimated by the SSM with the base strength of the amine

The calculated values for all equilibrium constants using the SSM are summarized

in Table 9.6.

1.E+00

1.E+01

1.E+02

1.E+03

1.E+04

1.E-10 1.E-09

KC

arb

.Sta

b*

Ka,xam→0

40 °CPrimary amine

Secondary amine

AMP2-PE

DIPA

316

Table 9.6: Chemical equilibrium constants at 40 °C calculated by the SSM

Ln(K1

*) Ln(K2*) pKa 𝐾𝑎,𝑥𝑎𝑚→0 KamCOO-f

* Ka,CO2* KCarb.Stab

*

MEA -4.23 -17.17 9.03 9.26E-10 1.35E-11 2.10E-14 6.44E+02

MPA -2.66 -17.24 9.48 3.27E-10 2.29E-11 1.56E-14 1.47E+03

MIPA -4.71 -17.74 9.04 9.08E-10 8.16E-12 1.21E-14 6.74E+02

DGA -4.30 -19.12 9.08 8.38E-10 1.13E-11 6.87E-15 1.65E+03

GlyK -3.10 -17.21 9.41 3.92E-10 1.77E-11 1.52E-14 1.16E+03

AlaK -2.03 -16.65 9.94 1.16E-10 1.52E-11 1.02E-14 1.49E+03

MMEA -4.69 -17.13 9.46 3.48E-10 3.20E-12 6.37E-15 5.02E+02

DEA -8.06 -17.38 8.52 3.04E-09 9.66E-13 9.10E-15 1.06E+02

SarK -3.16 -17.59 9.89 1.28E-10 5.45E-12 4.00E-15 1.36E+03

DIPA -9.72 -17.52 8.51 3.11E-09 1.87E-13 3.79E-15 4.94E+01

AMP -9.54 -13.00 9.24 5.79E-10 4.15E-14 7.37E-15 5.64E+00

2PE -8.67 -11.31 9.68 2.09E-10 3.57E-14 9.58E-15 3.73E+00

9.4.4 Predicting CO2 VLE

Base on the correlation between the two SSM equilibrium constants with the pKa

of the amine, CO2 VLE behavior can be predicted at 40 °C based on the amine type and

pKa.

For the first equilibrium constant of the SSM, primary amines and secondary

amines have different dependence on pKa (Figure 9.24). Assuming a linear correlation

between the natural log of the equilibrium constant and natural log of the amine Ka, the

regressed model parameter are fitted as shown in Equation 9.44 for both types of amines.

𝑙𝑛 (𝐾1∗40℃

) = {−1.251 ∙ 𝑙 𝑛 (𝐾𝑎𝑥𝑎𝑚→040℃

) − 30.38 𝑃𝑟𝑖𝑚𝑎𝑟𝑦

−1.547 ∙ 𝑙 𝑛 (𝐾𝑎𝑥𝑎𝑚→040℃) − 38.40 𝑆𝑒𝑐𝑜𝑛𝑑𝑎𝑟𝑦

(Equation 9.44)

The second equilibrium constant in the SSM does not vary systematically with

amine pKa. The average K2* value for the unhindered amines analyzed in this work

(Table 9.6) is assumed to apply for all unhindered and hindered amines (Equation 9.45).

𝑙 𝑛(𝐾2∗40℃

) = −17.474 (Equation 9.45)

317

Using Equation 9.44 and 9.45, the CO2 VLE at 40 °C of an unhindered primary or

secondary amine can be predicted using the SSM. Figure 9.29 shows the predicted CO2

VLE of primary and secondary amines at four different amine pKa’s. The prediction

shows CO2 solubility is reduced with decrease in amine pKa for both primary and

secondary amines. With the same pKa of 8, a secondary amine has higher CO2 partial

pressures than a primary amine. This difference between the two amine types decreases

with increase in amine pKa. At high amine pKa, the difference in CO2 VLE is small

between primary and secondary amines.

Figure 9.29: CO2 VLE predicted for a generic primary amine (red) and a generic secondary amine (blue) at 40 °C and 7 m total amine, at four amine pKa

values

Using Equation 9.44 and 9.45, the liquid phase speciation of a generic primary or

secondary amine can also be predicted. Among the molecular and ionic species in a

CO2 loaded aqueous amine solvent, the free molecular amine is important as it affects the

1.E-02

1.E+00

1.E+02

1.E+04

1.E+06

0.1 0.3 0.5 0.7 0.9

PC

O2*

(Pa)


40 °C7 m Amine

pKa = 8

pKa = 9

pKa = 10

pKa = 11

318

effective CO2 mass transfer rate and volatility of the amine. The predicted free amine as

a function of the pKa of the amine is shown in Figure 9.30, where the free amine is

calculated by the SSM at the operating lean and rich loading for coal flue gas (Section

4.2.1). The results show the available free amine in the solvent at process conditions

decreases by an order of magnitude between amine pKa of 8 and 10. Also, at the same

amine pKa, secondary amines have more available free amine than primary amines.

Figure 9.30: Free amine concentrations for a generic primary (red) and secondary (blue) amine and the pKa of the amine at 40 °C, estimated at 7 m total amine and

the operating lean (solid lines) and rich (dashed lines) loading for coal flue

gas, compared with the SSM predicted results of real amines

9.5 CONCLUSIONS

A simplified stoichiometric model (SSM) was developed in MATLAB to

represent the CO2 VLE and liquid phase speciation of primary and secondary amines.

The model was used to represent the CO2 VLE data of 12 solvent systems including

0.001

0.002

0.004

0.008

0.016

0.032

0.064

8 8.5 9 9.5 10 10.5 11

x am

pKa

40 °C7 m Amine

319

primary and secondary amines, and amino acids. For each amine solvent, four

adjustable parameters are varied to fit the experimental data.

The SSM model parameters are physically significant, as they represent the

chemistry between CO2 and the amines in the solvent. These parameters can be related

to fundamental chemical equilibria, and their values agree reasonably with literature

values.

The SSM can be used to predict the liquid phase speciation of a CO2 loaded

aqueous amine solvent. The model prediction show good agreement with experimental

NMR data and rigorous Aspen Plus® model prediction for 7 m MEA. For hindered

amines, the carbonate and amine cation ionic-pair formation reaction was used as one of

the two chemical reactions included in the SSM. Using the ionic pair reaction gave

good speciation results for 4.8 m AMP, which agree well with NMR data as well as

Aspen Plus® predictions. Thus, the formation of the ionic pair is likely an useful

interpretation of the chemical interactions of species in aqueous AMP and potentially all

hindered amines.

The analysis of SSM parameters shows primary and secondary amines to have

different CO2 VLE dependence on amine pKa. At pKa higher than 8, secondary amines

has lower carbamate stability than primary amines. A correlation is developed to

predict the SSM parameter based on the amine type and amine pKa, such that the first

equilibrium constant of the SSM can be calculated by:

𝑙𝑛 (𝐾1∗40℃

) = {−1.251 ∙ 𝑙 𝑛 (𝐾𝑎𝑥𝑎𝑚→040℃



And the second equilibrium constant of SSM is the same for all primary and

secondary amines:

𝑙 𝑛(𝐾2∗40℃

) = −17.474

320

Using this method, CO2 VLE and liquid phase speciation can be predicted for

any primary and secondary amine based on the amine pKa.

321

Chapter 10: Mass transfer and kinetics in aqueous mono-amines

10.1 INTRODUCTION

The mass transfer rate of CO2 determines the size and cost of the absorber column

in the capture process. For post combustion CO2 capture processes, the mass transfer of

CO2 is controlled by the reaction kinetics, equilibrium, and the molecular diffusion of the

reactant and products. Variation in these chemical and physical properties of the solvent

can significantly affect the rate of CO2 absorption and thus the overall cost.

Most of the published studies on the absorption rate of CO2 in aqueous amine

focus on reaction kinetics between CO2 and amines. These studies explain the two ways

in which CO2 reaction rate is related to amine structure. First, the application of the

Bronsted theory of acid-base reactions, which suggests the rate of reaction between CO2

and amines increases with the basic strength of the amine, has been shown to be mostly

valid (Versteeg et al. 1988a, Bishnoi and Rochelle 2000, Cullinane 2005). Second, the

structural hindrance of the basic nitrogen in an amine can reduce the rate of its reaction

with CO2. In other words, the rate of the reaction depends on the physical accessibility

of the basic nitrogen atom on the amine (Satori and Savage 1983). These two effects,

basic strength and steric hindrance, are believed to account for the main differences in

CO2 reaction rates for amines of varying structures.

A major weakness in the general published literature on the testing and analysis of

CO2 mass transfer rates in aqueous amines is the use of the reaction rate constant to

suggest mass transfer performance. It is often assumed or implied in these works that

amines with high reaction rate constants will also have high CO2 mass transfer rates.

This assumption has usually not been challenged because CO2 mass transfer rates are

rarely measured or analyzed.

322

Also problematic is that most kinetic studies do not consider the effect of

dissolved CO2 in the liquid, which is an essential condition for a real capture process.

Thus the results of these works do not represent operating performance.

New experimental data (Chapter 7) show the mass transfer coefficient of CO2

(kg') at process condition does not always increase with the base strength of the amine

(Figure 7.8). This result suggests some important amine properties, other than reaction

rate constants, that significantly affect the mass transfer of CO2. According to the

pseudo first order expression of kg' (Equation 10.1, previously discussed in Chapter 2),

free amine concentration ([Amine]) in the solvent and the diffusion coefficient of CO2

(DCO2) are candidates for having significant effects on the overall rate of CO2 mass

transfer.

𝑘𝑔′ =

√𝑘𝑐−𝑛∙[𝐴𝑚𝑖𝑛𝑒]𝑛−1𝐷𝐶𝑂2

𝛾𝐶𝑂2𝐻𝐶𝑂2−𝐻2𝑂 (10.1)

In this work, the dependence of kg' on free amine concentration and DCO2 are

evaluated, while the rate constants of the CO2-amine reaction are interpreted at process

conditions and compared with literature values.

10.1.1 Process condition

An optimized CO2 capture process is expected to operate with a significant

amount of total dissolved CO2 in the solvent. To compare different solvents at the same

process condition, the standard operation condition for coal flue gas (Chapter 4) is used

in this analysis. Specifically, the CO2 loadings which correspond to PCO2* of 0.5 and 5

kPa at 40 °C are considered the standard lean and rich loadings of the solvent

respectively.

323

The concentration of total reacted CO2 species is critical to the mass transfer of

CO2 because it affects the free amine ([Amine]) in the solvent. Since CO2-amine

reactions are reversible, free amine available with a given amount of dissolved CO2

depends on the chemical equilibrium of the reaction. At the same PCO2*, total amine ,

and temperature, the amine which forms the most stable products with CO2 will have the

least amount of free amine remaining in the solvent. One of the main contributions of

this analysis is the quantification of free amine in various amine solvents at process

conditions, and the analysis of its effect on CO2 mass transfer rate.

10.1.2 Scope

Twelve amines and amino acids are included in this analysis, which includes six

primary amines and amino acids with pKa between 9 and 10, four secondary amines and

amino acids with pKa between 8.5 and 10, and three hindered amines with pKa between

8.5 and 10. All of the amine and amino acids are mono-amines, as they each contain

one basic nitrogen in its structure. With the exception of 2-piperidineethanol (2PE),

none of the amines and amino acids contain any ring structures. Half of the solvents

have 7 m total amine, while the rest range between 3 m to 10 m. The molecular

structure and pKa of the solvents are summarized in Table 9.1.

10.2 EXPERIMENTAL DATA

Four types of data are used in this analysis: CO2 mass transfer coefficients, CO2

VLE, viscosity, and density. Most of the data used are collected in this work and

reported in previous chapters (Chapter 5 and 7), with additional data from literature.

10.2.1 CO2 mass transfer rates

The liquid film mass transfer coefficient (kg') of CO2 for each solvent was

measured using the same WWC apparatus (Chapter 3). The results for the amino acid

324

salts used in this analysis are reported in Chapter 5, and the results for the primary and

secondary amines are in Chapter 7. The kg' for 10 m DGA, 4.8 m AMP, and 8 m 2PE

was measured by Chen (2011).

This analysis only considers the kg' at 40 C. For each solvent, kg' as measured over

a range of PCO2* near the standard condition of 0.5 and 5 kPa. To simplify the analysis,

the kg' data are interpolated at 0.5 and 5 kPa using a second order polynomial (Equation

10.2).

ln(𝑘𝑔′ ) = 𝑎 + 𝑏 ∙ ln(𝑃𝐶𝑂2

∗ ) + 𝑐 ∙ (ln (𝑃𝐶𝑂2∗ ))

2 (10.2)

For each solvent, the set of four to five kg' data points is reduced to two values

corresponding to the standard conditions. In the case of 6.5 m β-alaK and 4.5 m SarNa,

because data was not collected around 5 kPa, only the interpolated value at 0.5 kPa is

considered. The parameters of the polynomial fit of kg' for each solvent, and its

interpolated kg' value at 0.5 and 5 kPa are summarized in Table 10.1.

Table 10.1: Parameters of the polynomial fit for kg' (40 °C) as a function of CO2 loading

(Equation 10.2), and the interpolated kg' value at standard operating conditions (40 °C, 0.5 and 5 kPa) for coal flue gas

Solvent

Empirical fit

(Equation 10.2)

kg' kg'avgi

(40° C) mol/Pa s m2

a b c R2 0.5 kPa 5 kPa (Equation 4.)

7 m MEA -4.798 -0.636 0.050 0.9965 7.01E-07 3.37E-07 4.35E-07

-5.049 -0.396 / 0.9883 7.64E-07 3.07E-07 4.23E-07

7 m MPA -5.333 -0.267 -0.031 0.995 5.26E-07 1.8E-07 2.65E-07

7 m MIPA -5.063 -0.397 / 0.999 7.35E-07 2.95E-07 4.07E-07

-5.490 -0.020 -0.077 0.9965 7.86E-07 2.41E-07 3.71E-07

10 m DGA® -5.220 -0.107 -0.077 1 8.58E-07 2.17E-07 3.61E-07

3.55 m GlyK -4.709 -0.618 0.021 0.9969 5.99E-07 1.97E-07 2.95E-07

6.5 m β-alaK -5.134 -0.374 -0.029 0.9979 4.42E-07 / /

7 m MMEA -5.234 0.076 -0.097 0.9993 1.84E-06 5.28E-07 8.36E-07

7 m DEA -4.620 -0.634 0.039 0.9711 8.93E-07 3.67E-07 5.03E-07

6 m SarK -5.840 0.422 -0.165 0.9917 1.25E-06 2.9E-07 5.02E-07

325

4.5 m SarNa -3.855 -1.341 0.175 1 6.28E-07 / /

7 m DIPA -4.590 -0.891 0.076 0.9891 3.63E-07 1.43E-07 1.99E-07

4.8 m AMP -5.726 -0.075 -0.057 0.9887 4.56E-07 1.67E-07 2.39E-07

8 m 2PE -4.482 -0.528 -0.020 0.9994 8.9E-07 1.98E-07 3.49E-07 i Log mean average kg' between the standard operating CO2 loadings of 0.5 and 5 kPa, calculated using

Equation 4.6.

For 7 m MEA, using a second order polynomial results in unrealistic prediction of

kg' at high CO2 partial pressure, and a linear fit is used instead. In the case of 7 m

MIPA, the kg' data at the highest CO2 partial pressure is excluded from the empirical fit,

as it is likely to be beyond the PFO regime of mass transfer. The comparisons of the

different empirical fits for 7 m MEA and 7 m MIPA are shown in Figure 10.1.

Figure 10.1: Alternative methods of interpolating measured kg' at standard conditions for

7 m MIPA and 7 m MEA

10.2.2 CO2 VLE

Experimental data for CO2 VLE are essential to the calculation of free amine in

this analysis. For the primary and secondary amines, CO2 VLE are reported and

1.E-07

1.E-06

10 100 1000 10000

k g' (

mo

l/P

a s

m2)

PCO2* @ 40 °C (Pa)

7 m MIPA 7 m MEA

5 kPa0.5 kPa

Dashed: 2nd order polynomialSolid: linear fit

326

discussed in Chapter 7. For the amino acid salts, the measured CO2 VLE are reported in

Chapter 5. In the case of 10 m DGA®, 4.8 m AMP, and 8 m 2PE, CO2 VLE collected

by Chen (2011) are used. In some cases, additional CO2 VLE found in literature are

also included in the analysis (Chapter 9).

10.2.3 Viscosity

For most of the solvents used in this analysis, viscosity data is available at the

CO2 loadings that correspond to the standard operating conditions. In the case of 7 m

MIPA and 7 m DIPA, viscosity data is available but not at the standard operating CO2

loading and (or) temperature. For these two solvents, Equation 10.3 is used to estimate

solvent viscosity at desired conditions.

𝜇𝑠𝑜𝑙𝑣−𝑥|𝑇,𝑙𝑑𝑔,[𝐴𝑚𝑖𝑛𝑒 𝑥]

𝜇𝑠𝑜𝑙𝑣−𝑥|𝑇𝑟𝑒𝑓,𝑙𝑑𝑔𝑟𝑒𝑓,[𝐴𝑚𝑖𝑛𝑒 𝑥]𝑟𝑒𝑓

=𝜇𝑠𝑜𝑙𝑣−𝑦|𝑇,𝑙𝑑𝑔,[𝐴𝑚𝑖𝑛𝑒 𝑦]

𝜇𝑠𝑜𝑙𝑣−𝑦|𝑇𝑟𝑒𝑓,𝑙𝑑𝑔𝑟𝑒𝑓,[𝐴𝑚𝑖𝑛𝑒 𝑦]𝑟𝑒𝑓

(10.3)

In Equation 10.3, a known amine solvent (Amine y and solv-y) with viscosity

data available over a wide range of CO2 loading, amine concentration, and temperature, is

used to estimate the change in solvent viscosity that corresponds to the deviation between

the experimental condition of the available data (subscript “ref”) and the standard

operating conditions. In the case of 7 m MPA and 7 m MMEA, viscosity data is not

available, and the viscosity of 7 m MEA is used as an approximation. The sources of

solvent viscosity data are summarized in Table 10.2, and the values of viscosities used for

each solvent are summarized in Table 10.4.

10.2.4 Density

The density of the solvents used in this analysis is mostly not available. Only for

7 m MEA and 7 m DEA, experimental data were found at the standard operating CO2

loadings. For 3.55 m GlyK, density data is available at zero CO2 loading, and Equation

327

10.4 was used to estimate the effect of CO2 loading on solvent density based on the

density behavior of MEA.

𝜌𝑠𝑜𝑙𝑣−𝑥|𝑇,𝑙𝑑𝑔,[𝐴𝑚𝑖𝑛𝑒 𝑥]

𝜌𝑠𝑜𝑙𝑣−𝑥|𝑇𝑟𝑒𝑓,𝑙𝑑𝑔𝑟𝑒𝑓,[𝐴𝑚𝑖𝑛𝑒 𝑥]𝑟𝑒𝑓

=𝜌𝑠𝑜𝑙𝑣−𝑦|𝑇,𝑙𝑑𝑔,[𝐴𝑚𝑖𝑛𝑒 𝑦]

𝜌𝑠𝑜𝑙𝑣−𝑦|𝑇𝑟𝑒𝑓,𝑙𝑑𝑔𝑟𝑒𝑓,[𝐴𝑚𝑖𝑛𝑒 𝑦]𝑟𝑒𝑓

(10.4)

For the other amine solvents, the density values of either MEA or DEA were

used. For the other amino acid salt solvents, the estimated density values of GlyK were

used. The sources of solvent viscosity data are summarized in Table 10.2. The

measured or estimated density values for all solvents in this analysis are summarized in

Table 10.3.

Table 10.2: Source of solvent viscosity and density data and/or method of estimation

Solvent Viscosity Density

7 m MEA Weiland et al. (1998)

7 m MPA Value of MEA Value of MEA

7 m MIPA Hikita (1981)1

10 m DGA® Chen (2011) Value of DEA

3.55 m GlyK Chapter 5 Portugal3

6.5 m β-alaK Chapter 5 Value of GlyK4

7 m MMEA Value of MEA

7 m DEA Weiland et al. (1998)

6 m SarK Chapter 5 Value of GlyK4

4.5 m SarNa Chapter 5

7 m DIPA Henni (2003) 2 Value of DEA

4.8 m AMP Chen (2011) Value of MEA

8 m 2PE Chen (2011) Value of DEA 1 Data collected at zero loading, 25 °C, and around 7 m, extrapolated using Equation 10.3 and MEA as Amine y 2 Data collected at zero loading, 40 °C, and around 7 m, extrapolated using Equation 10.3 and DEA as Amine y

3 Data collected at zero loading, 40 °C, and near 3.55 m, extrapolated using Equation 10.4 and MEA as Amine y

4 Value for GlyK at zero loading was used and extrapolated to the target amino acid salt concentration, CO2 loading

extraploted using Equation 10.4 and MEA as Amine y

328

10.3 ESTIMATING COMPONENTS OF LIQUID FILM MASS TRANSFER COEFFICIENT

10.3.1 Free amine concentration

The free amine concentration (M) at the standard CO2 loadings is calculated as

the product of the mole fraction of free amine (xamine) and the molar density of the solvent

(Equation 10.5).

[𝐴𝑚𝑖𝑛𝑒] = 𝑥𝑎𝑚𝑖𝑛𝑒 ∙ 𝜌𝑚[=]𝑘𝑚𝑜𝑙

𝑚3 (10.5)

The molar density of the solvent is calculated from the molar mass and density of

the solvent. The values of these density related solvent properties at the standard

operating conditions are summarized in Table 10.3.

Table 10.3: The molar mass, density (also in Table 10.3), and molar density of amine

solvents at the standard operating conditions (40 °C, 0.5 and 5 kPa) for coal

flue gas

Solvent CO2 ldg (mol/mol)

Molar mass

(g/mol) Density (g/mL)

Molar density

(kmol/m3)

0.5 kPa 5 kPa 0.5 kPa 5 kPa 0.5 kPa 5 kPa 0.5 kPa 5 kPa

7 m MEA 0.440 0.525 25.0 25.4 1.09 1.11 43.8 43.8

7 m MPA 0.478 0.538 26.7 27.0 1.08 1.09 40.5 40.4

7 m MIPA 0.418 0.506 26.4 26.9 1.07 1.09 40.5 40.4

10 m DGA® 0.425 0.487 34.1 34.6 1.12 1.13 32.7 32.6

3.55 m GlyK 0.485 0.579 25.1 25.3 1.27 1.29 50.5 51.0

6.5 m β-alaK 0.498 / 31.8 / 1.33 / 41.8 /

7 m MMEA 0.424 0.519 26.5 26.9 1.07 1.09 40.5 40.4

7 m DEA 0.238 0.406 28.9 29.7 1.08 1.11 37.4 37.4

6 m SarK 0.470 0.537 30.8 31.0 1.32 1.34 42.9 43.1

4.5 m SarNa 0.475 / 26.6 / 1.29 / 48.5 /

7 m DIPA 0.144 0.306 31.6 32.4 1.07 1.09 33.7 33.7

4.8 m AMP 0.265 0.571 24.6 25.7 1.04 1.08 42.2 42.1

8 m 2PE 0.361 0.694 34.0 35.8 1.11 1.17 32.7 32.7

The mole fraction of free amine at the operating conditions is calculated using the

simplified stoichiometric model (SSM) for CO2 VLE. This model uses CO2 VLE data

over a range of CO2 loading and temperature, as well as pre-established reaction

329

stoichiometry, to calculate the liquid phase species that is in equilibrium with some CO2

in the gas phase. The details of the SSM and CO2 VLE data used are described in

Chapter 9. The calculated values of free amine mole fraction and concentration are


Table 10.4: Free amine concentration at standard operating CO2 loadings (40 °C, 0.5 and

5 kPa), calculated by the simplified stoichiometric model (Chapter 9)

Solvent xamine [Amine] kmol/m3

0.5 kPa 5 kPa 0.5 kPa 5 kPa

7 m MEA 0.0175 0.0062 0.767 0.272

7 m MPA 0.0087 0.0029 0.352 0.117

7 m MIPA 0.0213 0.0077 0.863 0.311

10 m DGA® 0.0246 0.0087 0.804 0.284

3.55 m GlyK 0.0054 0.0018 0.273 0.092

6.5 m β-alaK 0.0055 / 0.230 /

7 m MMEA 0.0211 0.0076 0.855 0.307

7 m DEA 0.0622 0.0316 2.327 1.182

6 m SarK 0.0087 0.0029 0.373 0.125

4.5 m SarNa 0.0068 / 0.330 /

7 m DIPA 0.0829 0.053 2.798 1.789

4.8 m AMP 0.0536 0.028 2.259 1.180

8 m 2PE 0.071 0.0299 2.320 0.977

10.3.2 Diffusion coefficient of CO2

The molecular diffusion of CO2 in the solvent depends on solvent viscosity. The

relationship between solvent viscosity and the diffusion coefficient of CO2 is described

by the modified Stokes-Einstein correlation (Equation 10.6):

𝐷𝐶𝑂2−𝑠𝑜𝑙𝑣𝑒𝑛𝑡 ∙ 𝜇𝑠𝑜𝑙𝑣𝑒𝑛𝑡𝑛 = 𝐷𝐶𝑂2−𝐻2𝑂 ∙ 𝜇𝐻2𝑂

𝑛 (10.6)

The exponent of the viscosity term in Equation 10.6 was determined by Versteeg

et al. (1988b) to be 0.8 for the diffusion of CO2 in aqueous amines. Later, based on new

330

diffusion coefficient data, Dugas (2009) regressed the exponent to be 0.72, which is

reasonably close to the value by Versteeg.

In this analysis, the value of 0.8 is used for the exponent of the viscosity term in

Equation 10.6. The diffusion coefficient of CO2 in water was estimated using a

correlation developed by Versteeg et al (1988b) (Equation 10.7).

𝐷𝐶𝑂2−𝐻2𝑂 = 2.35 ∙ 10−6 exp (−2119

𝑇)𝑚2 ∙ 𝑠−1 (10.7)

The value from DIPPR (1998) is used for the viscosity of water at 40 °C. The

calculated values for the diffusion coefficient of CO2 for each solvent at process

conditions are summarized in Table 10.5.

Table 10.5: Viscosity and diffusion coefficient of CO2 at the standard operating

conditions (40 °C, 0.5 and 5 kPa ) for coal flue gas

Solvent Viscosity (cP) DCO2 (m

2/s)

0.5 kPa 5 kPa 0.5 kPa 5 kPa

7 m MEA 2.48 2.67 9.52E-10 8.97E-10

7 m MPA 3.37 3.60 7.44E-10 7.06E-10

7 m MIPA 6.70 7.37 4.30E-10 3.98E-10

10 m DGA® 7.19 8.69 4.06E-10 3.49E-10

3.55 m GlyK 1.70 1.80 1.29E-09 1.23E-09

6.5 m β-alaK 5.20 / 5.26E-10 /

7 m MMEA 3.17 3.52 7.81E-10 7.18E-10

7 m DEA 3.83 3.99 6.72E-10 6.50E-10

6 m SarK 4.60 4.10 5.80E-10 6.36E-10

4.5 m SarNa 4.50 / 5.90E-10 /

7 m DIPA 6.79 7.10 4.25E-10 4.10E-10

4.8 m AMP 3.07 4.05 8.02E-10 6.43E-10

8 m 2PE 14.48 23.84 2.32E-10 1.56E-10

331

10.3.3 Henry’s constant of CO2

The physical solubility of CO2 in a solvent is typically represented using the

Henry’s constant (HCO2-solvent). In the PFO expression for kg', HCO2-solvent is shown as the

product of the activity of CO2 and Henry’s constant of CO2 in water (HCO2-H2O).

𝐻𝐶𝑂2−𝑠𝑜𝑙𝑣𝑒𝑛𝑡 = 𝛾𝐶𝑂2 ∙ 𝐻𝐶𝑂2−𝐻2𝑂 (10.8)

In this analysis, a correlation for HCO2-H2O developed by Versteeg (1988) based on

experimental data is used (Equation 10.9).

𝐻𝐶𝑂2−𝐻2𝑂 = 2.82 ∙ 106 exp (−2044

𝑇)𝑃𝑎 ∙ 𝑚3𝑚𝑜𝑙−1 (10.9)

10.3.4 Activity coefficients

At concentrated amine and CO2 loaded conditions typical for a real capture

process, the system is sufficiently non-ideal such the activity coefficient of CO2 and

amine both affect the mass transfer of CO2. The activity coefficient of CO2 affects the

physical solubility of CO2 as shown in Equation 10.8. The activity coefficient of both

CO2 and the amine contribute to the rate of chemical reaction. While concentration

based reaction rate constants are more commonly used, for non-ideal systems it is more

accurate to used activity based reaction expressions and rate constants (Equation 10.10).

−𝑟𝐶𝑂2 = 𝑘𝑐−𝑛 ∙ [𝐶𝑂2] ∙ [𝐴𝑚𝑖𝑛𝑒]𝑛−1 = 𝑘𝑎−𝑛 ∙ 𝑎𝐶𝑂2 ∙ 𝑎𝐴𝑚𝑖𝑛𝑒

𝑛−1𝜌𝑚𝑛 (10.10)

The activity based kinetic constant (ka-n) is related to the concentration based

constant (kc-n) by the activity coefficient of CO2 and amine (Equation 10.11).

𝑘𝑐−𝑛 = 𝑘𝑎−𝑛 ∙ 𝛾𝐶𝑂2 ∙ 𝛾𝐴𝑚𝑖𝑛𝑒𝑛−1 (10.11)

Using the activity based reaction expression (Equation 10.10), the activity based

PFO expression for kg' can be written as shown in Equation 10.12.

𝑘𝑔′ =

√𝑘𝑎−𝑛∙𝛾𝐴𝑚𝑖𝑛𝑒𝑛−1𝑥𝐴𝑚𝑖𝑛𝑒

𝑛−1𝜌𝑚𝑛−1𝐷𝐶𝑂2

𝛾𝐶𝑂21/2𝐻𝐶𝑂2−𝐻2𝑂

(10.12)

332

While Equation 10.12 is a more rigorous representation of kg', the activity

coefficient of the amine and CO2 are both difficult to quantify, particularly at CO2 loaded

conditions. In this analysis, the concentration based PFO expression for kg' is used

(Equation 10.1), where only the activity of CO2 as it affects the physical solubility of CO2

is considered.

10.3.5 Calculating reaction rate constant

With values for DCO2, [Amine], and HCO2-H2O, the effective concentration based

kinetic constant is calculated from the measured kg' data as shown in Equation 10.13.

𝑘𝑐−𝑛∗ =

𝑘𝑐−𝑛

𝛾𝐶𝑂22 =

(𝑘𝑔′ ∙𝐻𝐶𝑂2−𝐻2𝑂)

2

[𝐴𝑚𝑖𝑛𝑒]𝑛−1𝐷𝐶𝑂2 (10.13)

The term “effective” is used to specify the rate constant (kc-n*) in Equation 10.13

because it is the true concentration based rate constant divided by the activity of CO2

squared. The effective concentration based constant can be related to the activity based

constant by the activity coefficient of CO2 and amine as shown in Equation 10.14.

𝑘𝑐−𝑛∗ =

𝑘𝑐−𝑛

𝛾𝐶𝑂22 = 𝑘𝑎−𝑛 ∙ (

𝛾𝑎𝑚𝑖𝑛𝑒𝑛−1

𝛾𝐶𝑂2) (10.14)

Reaction order

The subscript “n” that is associated with all of the kinetic constants represents the

order of the chemical reaction. There has been much debate in open literature regarding

the correct order of the carbamate formation reaction between CO2 and the amine,

specifically with respect to the amine. The theory for a kinetic expression that is second

order over all, and first order to the amine, was developed first and more widely used.

However, much of the kinetic data, particularly those collected at high amine

concentrations, suggest the reaction has a greater than first order dependence on the

amine. Thus, recent kinetic studies have used kinetic expression that is second order to

333

the amine, or a combined expression which results in an overall order that is in between

first and second to the amine.

In this analysis, both regimes of kinetic expression are considered: second order

overall (first order to the amine) where the subscript n has value of 2, and third order

overall (second order to the amine) where n equals 3.

Figure 10.2: Effective concentration based second order kinetic rate constant for primary,

secondary, and hindered amines, at standard operating condition for coal

flue gas.

The second order rate constants calculated using Equation 10.14 (with n equal to

2) at the operating lean and rich loadings of 0.5 and 5 kPa and 40 °C are shown in Figure

10.2. The calculated rate constant roughly increases with the pKa of the amine, as

expected based on the Bronsted theory, though the data exhibit significant scatter. In

most cases, the rate constant at rich loading (5 kPa) is lower than that at lean loading (0.5

kPa). This should not be the case, as the rate constant is not expected to be a function of

CO2 loading. Contributing to this difference between the rate at lean and rich loadings

0

1

10

100

8.0 8.5 9.0 9.5 10.0 10.5

k c-2

*(m

3/m

ol/

s)

pKa (40 °C)

Empty: 0.5 kPaSolid: 5 kPa

40 °C

Primary

Secondary

Hindered

334

is the activity coefficient of CO2 and amine, which is embedded in the calculated

effective reaction rate constants and they are both functions of CO2 loading. However,

the activity coefficient effect cannot explain the differences observed in the data entirely.

Also problematic is the rate constant for the hindered amines is about the same as those

for primary and secondary amines. This is contradictory with the established

understanding that hindered amines have lower reaction rates with CO2 than un-hindered

primary and secondary amines. Both of these effects combined to suggest the second

order kinetic regime does not represent kinetic data at process conditions.

Figure 10.3: Effective concentration based second order kinetic rate constant compared

with literature value for MEA (Versteeg et al. 1988).

The literature value of second order rate constant for MEA (Versteeg et al. 1988a)

agrees well with the effective second order rate constants calculated for primary amines

at the same amine pKa (Figure 10.3).

The third order rate constants calculated using Equation 10.14 (with n equal to 3)

at the operating lean and rich loadings of 0.5 and 5 kPa and 40 °C are shown in Figure

0

1

10

100

8.0 8.5 9.0 9.5 10.0 10.5

k c-2

*(m

3/m

ol/

s)

pKa (40 °C)

40 °C

Primary

Secondary

Hindered

MEA (Versteeg 1988)

335

10.4. For primary and secondary amines, the calculated third order rate constants at rich

and lean loadings agree well with each other. For hindered amines, the values at 5 kPa

are lower than those at 0.5 kPa, but the difference is much smaller than those for the

second order rate constants (Figure 10.3). Moreover, the rate constants for hindered

amines are significantly lower than the un-hindered amines at the same pKa, which is

consistent with the existing understanding of the effect of molecular hindrance on

reaction kinetics.

Figure 10.4: Effective concentration based third order kinetic rate constant for primary,

secondary, and hindered amines, at standard operating condition for coal

flue gas.

The calculated third order rate constants are compared with literature values for

PZ, DEA, and DIPA (Cullinane 2005), as well as the activity based third order constant

for MEA (Dugas 2009) in Figure 10.5. The results in this analysis agree well with the

literature values despite differences in the type of data and how they are analyzed.

1.E-04

1.E-03

1.E-02

1.E-01

1.E+00

8.0 8.5 9.0 9.5 10.0 10.5

k c-3

*(m

6/m

ol2

/s)

pKa (40 °C)


40 °C

Primary

Secondary

Hindered

336

Figure 10.5: Effective concentration based third order kinetic rate constant compared

with literature values for PZ, DEA, DIPA (Cullinane 2005), and activity

based third order rate constant for MEA (Dugas 2009).

Table 10.6: The calculated concentration based second order (kc-2*) and third order (kc-3

*) overall reaction rate constant at standard operating CO2 loadings and 40 °C

Solvent Amine

CO2 ldg

(mol/mol alk)

kc-2*

(m3/mol/s)

kc-3*

(m6/mol2/s)

pKa 0.5 kPa 5 kPa 0.5 kPa 5 kPa 0.5 kPa 5 kPa

7 m MEA 9.03 0.440 0.525 13.62 6.61 0.0178 0.0243

7 m MPA 9.48 0.478 0.538 17.95 6.64 0.0510 0.0567

7 m MIPA 9.04 0.418 0.506 24.79 11.92 0.0287 0.0383

10 m DGA® 9.08 0.425 0.487 38.39 8.07 0.0477 0.0284

3.55 m GlyK 9.41 0.485 0.579 17.41 5.88 0.0638 0.0641

6.5 m β-alaK 9.94 0.498 / 27.42 / 0.1191 /

7 m MMEA 9.46 0.424 0.519 86.84 21.52 0.1016 0.0701

7 m DEA 8.52 0.238 0.406 8.69 2.99 0.0037 0.0025

6 m SarK 9.89 0.470 0.537 122.57 18.07 0.3284 0.1447

4.5 m SarNa 9.89 0.475 / 34.43 / 0.1043 /

7 m DIPA 8.51 0.144 0.306 1.88 0.48 0.0007 0.0003

4.8 m AMP 9.24 0.265 0.571 1.96 0.63 0.0009 0.0005

8 m 2PE 9.68 0.361 0.694 25.08 4.38 0.0108 0.0045

1.E-04

1.E-03

1.E-02

1.E-01

1.E+00

8.0 8.5 9.0 9.5 10.0 10.5

k c-3

*(m

6/m

ol2

/s)

pKa (40 °C)

Primary

Secondary

Hindered

MEA (ka-3

Dugas 2009)

PZ(Cullinane

2005)

DEA(Cullinane

2005)

DIPA(Cullinane

2005)

40 °C

337

According to this analysis, the third order reaction expression better represents the

data collected at high amine and high CO2 loading conditions, relative to the second order

expression. Therefore, only the third order reaction expression will be applied in the

rest of this chapter.

The calculated values of second order and third order reaction rate constants at the

standard operating conditions for coal flue gas are summarized in Table 10.6.

Brønsted correlation for the effective third order reaction rate constant (kc-3*)

Figure 10.6: Bronsted correlation for the third order reaction rate constant representing

both primary and secondary amines

A Bronsted correlation was developed for the effective third order concentration

based rate constants by fitting the kc-3* for primary and secondary amines together with

Equation 10.15.

𝑙𝑜𝑔10(𝑘𝑐−3∗) = 𝑎 + 𝑏 ∙ 𝑝𝐾𝑎𝑎𝑚𝑖𝑛𝑒

(10.15)

0.001

0.004

0.016

0.064

0.256

8.0 8.5 9.0 9.5 10.0 10.5

(kc-

3* )

pKa (40 °C)

Primary

Secondary

40 °C

log10(y) = 1.113x - 11.728R2 = 0.8656

338

The parameters of this overall Bronsted correlation are shown in Equation 10.16.

𝑙𝑜𝑔10(𝑘𝑐−3∗) = −11.728 + 1.113 ∙ 𝑝𝐾𝑎𝑎𝑚𝑖𝑛𝑒

(10.16)

Previous kinetic studies have all used the same Bronsted correlation to represent

the pKa dependence of rate constants for both primary and secondary amines. This

overall correlation (Equation 10.16) fits the kc-3* data in this work reasonablely well.

However, the overall fit over predicts the rate constant for primary amines at the pKa of

10, and underpredicts at the pKa of 9. Also, the rate constant for the secondary amine at

the pKa of 8 is overpredicted by the overall Bronsted correlation.

As the data suggest a slight difference in the pKa dependence for primary and

secondary amines, an alternative Bronsted correlation was explored by fitting the primary

and secondary amine results separately (Figure 10.7).

Figure 10.7: Bronsted correlations for the third order reaction rate constant representing

primary amines and secondary amine separately

0.001

0.004

0.016

0.064

0.256

8 8.5 9 9.5 10 10.5

k c-3

*

pKa (40 °C)

40 °C

Primary

Secondary

log10(y) = 0.706x - 7.918R2 = 0.782

log10(y) = 1.285x - 13.400R2 = 0.940

339

The parameters of the alternate Bronsted correlations for primary and secondary

amines are shown in Equation 10.17.

{𝑃𝑟𝑖𝑚𝑎𝑟𝑦 𝑎𝑚𝑖𝑛𝑒: 𝑙𝑜𝑔10(𝑘𝑐−3

∗) = −7.918 + 0.706 ∙ 𝑝𝐾𝑎𝑎𝑚𝑖𝑛𝑒

𝑆𝑒𝑐𝑜𝑛𝑑𝑎𝑟𝑦 𝑎𝑚𝑖𝑛𝑒: 𝑙𝑜𝑔10(𝑘𝑐−3∗) = −13.4 + 1.285 ∙ 𝑝𝐾𝑎𝑎𝑚𝑖𝑛𝑒

(10.17)

Table 10.7: Standard error and R2 values for the overall and separate Bronsted

correlations for primary and secondary monoamines

Bronsted Slope Intercept

R2 Value Std. Error Value Std. Error

Overall 1.11 0.11 -11.73 1.02 0.866

Primary only 0.71 0.12 -7.92 1.15 0.782

Secondary only 1.27 0.14 -13.34 1.27 0.96

10.4 PREDICTING MASS TRANSFER RATES FOR UNHINDERED MONO-AMINES

The Bronsted correlation (Equation 10.16 and Equation 10.17) can be used to

predict the effective reaction rate constant of a primary or secondary amine based on its

pKa at 40 °C. The CO2 solubility at 40 °C in a primary or secondary amine can be

predicted using the simplified stoichiometric model based on the pKa of the amine

(Equation 9.44 and 9.45), which can also be used to predict the free amine concentration

at process conditions. Using these two methods, and if the viscosity and density of an

aqueous amine solvent are also known, the mass transfer rate of CO2 (kg') at process

conditions can be estimated. Moreover, this approach can also be used to demonstrate

the effect of amine pKa on the rate of CO2 mass transfer.

340

10.4.1 Mass transfer rate in a generic primary and secondary amine

The effect of pKa on CO2 mass transfer rates was studied by varying the pKa of a

“generic” primary or secondary amine while holding all other relevant solvent properties

constant, and calculating the solvent kg'. For this analysis, the total amine concentration

is fixed at 7 m for all cases. The viscosity and density of MEA, as correlated by

Weiland (1998) was used for all cases. The Henry’s constant of CO2 in water (HCO2-

H2O) as correlated by Versteeg (1988) was used. The change in free amine concentration

with pKa is estimated using the simplified speciation model and Equation 9.44 and 9.45.

The change in reaction rate constant (kc-3*) with amine pKa is estimated using two

methods: the overall Bronsted correlation, and the separate Bronsted correlations for

primary and secondary amines.

The calculated results of kg'avg (Equation 4.6) for a generic primary amine and a

generic secondary amine over the pKa range of 8 – 11 are shown in Figure 10.8. The

overall Bronsted correlation (Equation 10.16) was used for both the primary and

secondary amine cases. The results show, with the same viscosity, density, and total

amine concentration, secondary amines have greater kg'avg than primary amines at the

same amine pKa. Since the same Bronsted correlation is used for both sets of amines,

the difference in the calculated kg'avg between primary and secondary amines is due to

their different CO2 VLE. This analysis also shows there exists an optimum pKa which

corresponds to the greatest kg'avg, which is around 8.8 for both primary and secondary

amine.

341

Figure 10.8: CO2 mass transfer rates (Equation 4.6) calculated for primary and secondary

amines at varying pKa, at the same total amine concentration of 7 m, with

the density and viscosity of MEA (Weiland 1998), using the overall

Bronsted correlation (Equation 10.16).

Figure 10.9: CO2 mass transfer rates (Equation 4.6) calculated for primary and secondary

amines at varying pKa, at the same total amine concentration of 7 m, with

the density and viscosity of MEA (Weiland 1998), using separate Bronsted

correlation for each amine type (Equation 10.17).

2.E-07

5.E-07

1.E-06

8 8.5 9 9.5 10 10.5 11

k g' a

vg(m

ol/

Pa/

s/m

2)

pKa @ 40 °C

Primary

Secondary

Total amine: 7 mT: 40 °C

1.E-07

2.E-07

5.E-07

1.E-06

8 9 10 11

k g' a

vg(m

ol/

Pa/

s/m

2)

pKa @ 40 °C

Primary

Secondary

Total amine: 7 mT: 40 °C

342

Table 10.8: Calculated diffusion coefficient, standard operating CO2 loadings, free amine

concentration for the generic primary and secondary amine with varying pKa

at 40 °C.

pKa

40 °C

CO2 ldg

(mol/mol alk) DCO2 (m

2/s) xam [Am]

(mol/m3)

lean rich lean rich lean rich lean rich

Primary amine

8 0.282 0.437 1.06E-09 9.52E-10 0.0522 0.0241 2271 1046

8.25 0.326 0.465 1.03E-09 9.34E-10 0.0424 0.0180 1843 781

8.5 0.366 0.487 1.00E-09 9.19E-10 0.0334 0.0132 1451 573

8.75 0.401 0.503 9.77E-10 9.09E-10 0.0256 0.0096 1112 414

9 0.430 0.515 9.57E-10 9.01E-10 0.0192 0.0069 833 297

9.25 0.452 0.524 9.42E-10 8.95E-10 0.0141 0.0049 613 211

9.5 0.470 0.531 9.30E-10 8.91E-10 0.0103 0.0034 444 149

9.75 0.483 0.535 9.22E-10 8.88E-10 0.0074 0.0024 319 105

10 0.492 0.539 9.16E-10 8.86E-10 0.0052 0.0017 227 74

10.25 0.499 0.541 9.11E-10 8.85E-10 0.0037 0.0012 160 52

10.5 0.504 0.542 9.08E-10 8.84E-10 0.0026 0.0008 113 36

10.75 0.507 0.544 9.06E-10 8.83E-10 0.0018 0.0006 79 25

11 0.510 0.544 9.04E-10 8.83E-10 0.0013 0.0004 56 18

Secondary amine

8 0.135 0.295 1.18E-09 1.05E-09 0.0848 0.0554 3701 2409

8.5 0.233 0.401 1.10E-09 9.77E-10 0.0630 0.0323 2744 1400

9 0.342 0.474 1.02E-09 9.27E-10 0.0387 0.0160 1682 692

9.5 0.426 0.514 9.59E-10 9.02E-10 0.0200 0.0072 866 310

10 0.475 0.532 9.27E-10 8.9E-10 0.0092 0.0031 397 132

10.5 0.498 0.540 9.12E-10 8.85E-10 0.0040 0.0013 171 55

11 0.508 0.544 9.05E-10 8.83E-10 0.0017 0.0005 72 23

The generic amine analysis is performed using separate Bronsted correlations for

primary and secondary amines (Equation 10.17). The results are plotted in Figure 10.9.

For the secondary amine, the behavior in kg'avg does not change significantly from the

previous case, with an optimum pKa at round pKa of 9. On the other hand, the kg'avg for

primary amines decreases with increase in pKa, and an optimum pKa does not appear

within the range of this analysis. The kg'avg for the generic primary amine is more

343

sensitive to variation in the Bronsted correlation than the secondary amine. While the

alternate Bronsted correlations (Equation 10.17) shows the effect of the scatter in the kc-3*

on the generic amine kg'avg, it will not be used further as there are little theoretical basis

for the primary and secondary amines to have different Bronsted dependence on pKa.

Table 10.9: Calculated effective reaction kinetic constant (kc-3*), and mass transfer

coefficients at process conditions using two types of Bronsted correlation

pKa

(40 °C)

Method 1(Equation 10.16) Method 2 (Equation 10.17)

kc-3* kg' (mol/Pa/s/m2) kc-3

* kg' (mol/Pa/s/m2)

m6/

mol2/s 0.5 kPa 5 kPa kg'avg

m6/

mol2/s 0.5 kPa 5 kPa kg'avg

Primary amine

8 0.001 6.95E-07 3.03E-07 4.06E-07 0.005 1.31E-06 5.73E-07 7.68E-07

8.25 0.003 7.65E-07 3.09E-07 4.26E-07 0.008 1.29E-06 5.19E-07 7.16E-07

8.5 0.005 8.18E-07 3.09E-07 4.38E-07 0.012 1.22E-06 4.63E-07 6.55E-07

8.75 0.010 8.53E-07 3.07E-07 4.42E-07 0.018 1.14E-06 4.08E-07 5.89E-07

9 0.019 8.71E-07 3.01E-07 4.41E-07 0.027 1.03E-06 3.57E-07 5.23E-07

9.25 0.037 8.76E-07 2.94E-07 4.36E-07 0.041 9.22E-07 3.1E-07 4.59E-07

9.5 0.070 8.69E-07 2.86E-07 4.27E-07 0.062 8.15E-07 2.68E-07 4.00E-07

9.75 0.133 8.55E-07 2.77E-07 4.16E-07 0.092 7.13E-07 2.31E-07 3.47E-07

10 0.252 8.36E-07 2.67E-07 4.04E-07 0.139 6.19E-07 1.98E-07 3.00E-07

10.25 0.479 8.12E-07 2.58E-07 3.91E-07 0.208 5.36E-07 1.7E-07 2.58E-07

10.5 0.909 7.87E-07 2.48E-07 3.78E-07 0.313 4.62E-07 1.46E-07 2.22E-07

10.75 1.725 7.61E-07 2.39E-07 3.64E-07 0.469 3.97E-07 1.25E-07 1.90E-07

11 3.273 7.34E-07 2.3E-07 3.51E-07 0.705 3.41E-07 1.07E-07 1.63E-07

Secondary amine

8 0.001 1.19E-06 7.34E-07 8.65E-07 0.001 8.48E-07 5.22E-07 6.15E-07

8.5 0.005 1.62E-06 7.79E-07 1.01E-06 0.003 1.27E-06 6.12E-07 7.89E-07

9 0.019 1.81E-06 7.13E-07 9.93E-07 0.015 1.57E-06 6.18E-07 8.61E-07

9.5 0.070 1.72E-06 5.98E-07 8.74E-07 0.064 1.65E-06 5.72E-07 8.37E-07

10 0.252 1.47E-06 4.8E-07 7.21E-07 0.282 1.55E-06 5.08E-07 7.62E-07

10.5 0.909 1.19E-06 3.79E-07 5.75E-07 1.237 1.39E-06 4.42E-07 6.71E-07

11 3.273 9.46E-07 2.97E-07 4.53E-07 5.433 1.22E-06 3.83E-07 5.83E-07

344

Parameter sensitivity

The sensitivity of the calculated kg'avg to each PFO parameter is demonstrated in

Figure 10.10 and 10.11. In these figures, each PFO parameters is scaled to the same

order of magnitude and plotted on the right hand side axis, and compared with the kg'avg

(left axis) over the pKa range of 8-11. For both generic amines, the reaction rate

constant increases with the pKa of the amine, while the free amine concentration

decreases with amine pKa. The combined effect of reaction rate and free amine results

in the optimum pKa for each amine. The generic secondary amine has higher kg'avg than

primary amine because it has more free amine available at the same amine pKa. The

diffusion coefficient of CO2 has little effect on the kg'avg for the generic amines because

the viscosity of MEA is assumed for all cases. The difference in viscosity between real

amine solvents can still lead to significant change in solvent kg'avg.

Figure 10.10: Sensitivity of the effective mass transfer rate (kg'avg) at process conditions

on each of the PFO parameters for primary amines

0.1

1

10

1.E-07

1.E-06

8 8.5 9 9.5 10 10.5 11

PFO

Par

amet

ers

k g' a

vg(m

ol/

Pa/

s/m

2)

pKa @ 40 °C

kg'avg

(kc-3*)1/2 x10

[Amine] x10(kmol/m3)

DCO21/2 x 105

Dashed line: 0.5 kPaSolid line: 5 kPa

345

Figure 10.11: Sensitivity of the effective mass transfer rate (kg'avg) at process conditions

on each of the PFO parameters for secondary amines

10.4.2 Error analysis

The potential error in the proposed method of estimating CO2 mass transfer rates

based on amine pKa is quantified by comparing the calculated and measured kg' at the

standard operating conditions for real primary and secondary amine solvents. The

parity plot (Figure 10.12) shows the error in the calculated kg' is evenly distributed

between the lean and rich CO2 loadings and it is consistent over the range of kg' values.

The error of this method is further examined in a second parity plot where the

ratio of the calculated kg' with the measured kg' is compared with the pKa of the amine

(Figure 10.13). The result shows no significant bias with amine pKa. However, for

primary amines, the kg' around pKa of 9 is slightly under-predicted, while it is over

predicted at higher pKa. This trend is consistent with the bias in the overall Bronsted

correlation fit of the primary amine data (Figure 10.6).

0.1

1

10

1.E-07

1.E-06

8 8.5 9 9.5 10 10.5 11

PFO

par

amet

ers

k g' a

vg(m

ol/

Pa/

s/m

2)

pKa (40 °C)

kg'avg

(kc-3*)1/2 x10

[Amine] x10(kmol/m3)

DCO21/2 x 105

Dashed line: 0.5 kPaSolid line: 5 kPa

346

Figure 10.12: Parity plot of measured kg' and calculated kg' at the standard operating CO2 loadings and 40 °C.

Figure 10.13: Parity plot of measured kg' and calculated kg' as function of amine pKa, at

the standard operating CO2 loadings and 40 °C

1.E-07

1.E-06

1.E-07 1.E-06

k g' m

easu

red

(m

ol/

Pa/

s/m

2)

kg' calculated (mol/Pa/s/m2)

Primary

Secondary


0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

8.0 8.5 9.0 9.5 10.0 10.5

k g'c

alcu

late

d/k

g'm

easu

red

pKa (40 °C)

Primary

Secondary


347

The AARD (Equation 9.21) of the calculated kg' for the primary and secondary

amine solvents is 21%.

10.5 CONCLUSIONS

The effective concentration based reaction rate constant is calculated from

measured kg' data for primary, secondary, and hindered amines. The third order overall

reaction kinetic expression as shown to better explain the kinetic data at process

conditions than the more widely applied second order overall expression. The

calculated third order rate constant for the primary and secondary amine show good

consistency with the Bronsted theory of acid-base reactions, as well as literature values of

kinetic constants. A new Bronsted correlation was developed to represent the third

order concentration based kinetic constant at process conditions for primary and

secondary amines, which is 𝑙𝑜𝑔10(𝑘𝑐−3∗) = −11.728 + 1.113 ∙ 𝑝𝐾𝑎𝑎𝑚𝑖𝑛𝑒

. It was

demonstrated that in general, the kg'avg of secondary amines is higher than primary amines

at the same pKa, which is due to the differences in CO2 VLE behavior between the two

amine types. For both primary and secondary amines, their kg' increases from pKa of 8

to around 8.8, then decreases as their pKa increases from 8.8. The optimum pKa for the

best kg'avg for both amines is around 8.8. The sensitivity analysis shows the kg'avg of a

solvent at process conditions is most significantly affected by the reaction rate constant,

as well as the free amine concentration which is determined by the CO2 VLE in the

solvent. The error analysis shows the CO2 mass transfer rate in a primary or secondary

amine can be estimated based on the pKa of the amine with an average error of about 20

%.

348

Chapter 11: Conclusions and Recommendations

11.1 CONCLUSIONS

11.1.1 Primary and secondary mono-amines

In general, secondary amines have up to double the effective CO2 mass transfer

rates than primary amines at process conditions for coal. The maximum rate occurs at

pKa 8.5-9.0 for primary amines and pKa 9-9.5 for secondary amines. Hindered amines

have lower kg’avg than the unhindered amines at the same pKa. Still, secondary hindered

amines have higher absorption rates than most of the primary amines. Among the five

solvents tested, 7 m methyl-monoethanolamine (MMEA) has the highest absorption rate,

which is competitive with 8 m PZ.

Primary and secondary amines with similar pKa and hindrance, such as methyl-

propanolamine (MPA) and MMEA, have similar CO2 solubility. Amines with higher

pKa have higher CO2 solubility, which corresponds to higher CO2 loading at the same

PCO2*. Hindered amines have CO2 solubility curves that are more flat than unhindered

amines, which correspond to greater CO2 carrying capacity. Among the solvents tested

in this work, 7 m diethanolamine (DEA) has the greatest capacity, which is greater than 7

m MEA, but still less than 8 m PZ.

11.1.2 Generalization of CO2 mass transfer rates at process conditions

The third order overall reaction kinetic expression was shown to better explain the

kinetic data at process conditions than the more widely applied second order overall

expression. The calculated third order rate constant for the primary and secondary

amine show good consistency with the Bronsted theory of acid-base reactions, as well as

literature values of kinetic constants. A new Bronsted correlation was developed to

349

represent the third order concentration based kinetic constant at process conditions for

primary and secondary amines, which is 𝑙𝑜𝑔10(𝑘𝑐−3∗) = −11.728 + 1.113 ∙ 𝑝𝐾𝑎𝑎𝑚𝑖𝑛𝑒

.

It was demonstrated that in general, the kg'avg of secondary amines are higher than

primary amines at the same pKa, which is due to the differences in CO2 VLE behavior

between the two amine types. For both primary and secondary amines, their kg'

increases from pKa of 8 to around 8.8, then decreases as their pKa increases from 8.8.

The optimum pKa for the best kg'avg for both amines is around 8.8. The sensitivity

analysis shows the kg'avg of a solvent at process conditions is most significantly affected

by the reaction rate constant, as well as the free amine concentration which is determined

by the CO2 VLE in the solvent. The error analysis shows the CO2 mass transfer rate in a

primary or secondary amine can be estimated based on the pKa of the amine with an

average error of about 20 %.

11.1.3 Generalization of CO2 VLE

A simplified stoichiometric model (SSM) was developed in MATLAB to

represent the CO2 VLE and liquid phase speciation of primary and secondary amines.

The model was used to represent the CO2 VLE data of 12 solvent systems including

primary and secondary amines, and amino acids. For each amine solvent, four

adjustable parameters are varied to fit the experimental data.

The SSM can be used to predict the liquid phase speciation of a CO2 loaded

aqueous amine solvent. The model prediction show good agreement with experimental

NMR data and rigorous Aspen Plus® model prediction for 7 m monoethanolamine

(MEA). For hindered amines, the carbonate and amine cation ionic-pair formation

reaction was used as one of the two chemical reactions included in the SSM. Using the

ionic pair reaction gave good speciation results for 4.8 m 2-amino-2-methyl-1-propanol

350

(AMP), which agree well with NMR data as well as Aspen Plus® predictions. Thus, the

formation of the ionic pair is likely an useful interpretation of the chemical interactions of

species in aqueous AMP and potentially all hindered amines.

The analysis of SSM parameters shows primary and secondary amines to have

different CO2 VLE dependence on amine pKa. At pKa higher than 8, secondary amines

has lower carbamate stability than primary amines. A correlation is developed to

predict the SSM parameter based on the amine type and amine pKa, such that the first

equilibrium constant of the SSM can be calculated by:

𝑙𝑛 (𝐾1∗40℃

) = {−1.251 ∙ 𝑙 𝑛 (𝐾𝑎𝑥𝑎𝑚→040℃



And the second equilibrium constant of SSM is the same for all primary and

secondary amines:

𝑙 𝑛(𝐾2∗40℃

) = −17.474

Using this method, CO2 VLE and liquid phase speciation can be predicted for

any primary and secondary amine based on the amine pKa.

11.1.4 Solvent viscosity

A new parameter was developed to capture the effect of solvent viscosity on the

sensible heat cost of the process. Specifically the viscosity dependence of the heat

transfer coefficient in a plate and frame exchanger is considered. The viscosity

normalized solvent capacity is defined as:

∆𝐶𝜇 =∆𝐶𝑠𝑜𝑙𝑣


10 𝑐𝑃⁄ )0.15

The viscosity normalized capacity represents the effect of solvent choice on the

sensible heat cost.

351

Solvent viscosity also affects the absorption rate of CO2. Using the pseudo first

order (PFO) expression for kg' and the modified Stokes Einstein equation, it was

demonstrated for high viscosity solvents such as 5 m PZ/5 m 2-piperidineethanol (2-PE)

and 6 m PZ/2 m hexamethylenediamine (HMDA) that viscosity reduced the kg' of the

solvent by up to 45 %.

11.1.5 Piperazine blends

In general, piperazine (PZ) blends have about the same performance as 8 m PZ

and are better than 7 m MEA. PZ blends with hindered amines show the best potential

as competitive solvents. PZ blends with high pKa primary diamines are less attractive

than other blends.

Most of the PZ blends have larger solid solubility window than 8 m PZ, where the

rich loading limit is removed and the low loading limit is less restrictive. The only

exception is with 6 m PZ/ 2 m HMDA, which precipitates up to 0.3 ldg at 20 °C. The

viscosity of concentrated PZ blends is about the same as 8 m PZ. Only for 5 m PZ/5 m

2-PE, the viscosity is about 25 cP, which is more than twice that of 8 m PZ at 40 °C.

The blends 3.5 m PZ/ 3.5 m 2-amino-2-hydroxymethyl-propane-1,3-diol (Tris) and 2 m

PZ/ 4 m AMP have low viscosity at around 5 cP, which is due to the low total amine.

All of the PZ blends have better CO2 absorption rates than 7 m MEA, and most

are competitive with 8 m PZ. Only 6 m PZ/2 m HMDA and 5 m PZ/5 m 2-PE have

lower kg’ than 8 m PZ and other blends, resulting fromthe high viscosity of these

solvents.

With PZ blends with primary diamines or primary amines, the solvent capacity is

lower than 8 m PZ due to lower Δldg (shape of CO2 VLE curve at 40 °C) and a higher

molecular weight of the blended amines than PZ. Hindered amines, such as Tris, AMP,

352

and 2-PE, enhance the Δldg of PZ in a blend, which contributes to a high solvent

capacity.

PZ/AMP and 5 m PZ/ 2 m N-2(aminoethyl)piprazine (AEP) have high -∆Habs,

which is competitive with MEA. Mainly due to their high thermal stability, PZ blends

with long chain primary diamines are expected to have good stripping performance.

2 m PZ/ 4 m AMP shows competitive performance in all aspects, except for its

high volatility. 5 m PZ/ 2 m AEP also has good overall performance, except for its

moderate capacity. 6 m PZ 2 m HMDA has moderate absorption rates, capacity, and a

high viscosity. But it is thermally stable with a high heat of absorption, which

contributes to a high stripping performance that is competitive with 8 m PZ.

The CO2 absorption rate for PZ blends with primary di-amines increases with

decreasing pKa of the amine (2nd pKa). Increase in the concentration of PZ increases

the kg’ of the blend for AMP and methyldiethanolamine (MDEA).

11.1.6 Amino acid salts

Amino acid salts, in general, are not competitive with conventional aqueous

amines as solvents for CO2 capture. All amino acid salts suffer from low CO2 carrying

capacity, which is an intrinsic disadvantage due to the high molecular weight of the

amino acid salt and the low alkalinity concentration as limited by the solid solubility of

the solvents. Most amino acids have CO2 absorption rates that are about the same or

lower than 7 m MEA, and are not competitive with 8 m PZ. Most amino acids have

heat of absorption less than both MEA and PZ. Most amino acid salts are attractive in

terms of viscosity, which are in the same range as 7 m MEA and much lower than 8 m

PZ. Amino acid salts, as a category, are not immune from oxidation.

353

Amino acid salts have more competitive performance at natural gas conditions

than coal, because of the lower flue gas CO2. With less CO2 in the flue gas, the amino

acid salts can operate at leaner CO2 loading, where the absorption rate and heat of

absorption are more competitive with amines. Also, at lower CO2 loading, the amino

acid salt concentration can be increased to maximize CO2 capacity without solid

precipitation.

The most attractive amino acid salt is 6 m potassium sarcosine (SarK), which has

a higher absorption rate than 7 m MEA and is not limited by solid precipitation. It also

has lower viscosity than 8 m PZ. However, it has low CO2 capacity, low heat of

absorption, and is not oxidatively stable. The blend 3 m potassium taurine (TauK)/5 m

homotaurine (HtauK) has an attractive high heat of absorption, which is better than 8 m

PZ. The solvents using potassium proline (ProK) and potassium beta-alanine (β-AlaK)

potentially have oxidatively stable properties at absorber temperatures.

11.2 RECOMMENDATIONS

11.2.1 Solvent screening

PZ blends with hindered amines and tertiary amines offer good opportunities for

the discovery of competitive solvents. Both hindered amines and tertiary amines can

enhance the capacity of PZ, while PZ can maintain a high absorption rate. The CO2

VLE of these blends is sensitive to the molar ratio of PZ and the second amine, which

should be evaluated systematically.

Hindered and tertiary amines with good thermal stability in the presence of PZ,

good oxidative stability, low viscosity when blended with PZ, and low volatility are good

candidates for blending with PZ.

354

11.2.2 High temperature mass transfer data

The kg' data at 80 and 100 °C can be used to study the physical liquid film mass

transfer coefficient (klo). At high temperatures, the chemical reaction kinetics will

approach instantaneous, and the mass transfer of CO2 in the liquid is controlled by the

diffusion of reactants and products to and from the interface. The measured CO2 mass

transfer flux (Appendix B.2) at these conditions can be used to calculate the klo of the

solvent. The effect of solvent properties, such as viscosity and density, on klo can be

evaluated.

11.2.3 CO2 VLE and simplified speciation model (SSM)

The SSM can be modified to represent tertiary amine and di-amine systems. For

tertiary amines, only one chemical equilibria (bicarbonate formation) would be included

in the model. The reaction needs to be re-written to eliminate the carbamate species.

For di-amines, the total number of reactions and the corresponding equilibrium constants

(adjustable parameters) will increase, and should be first tested with amines such as PZ

where a large number of data is available for CO2 VLE and speciation.

The SSM can also be used to represent amine blends. The efficiency of the

model will be improved by including the appropriate chemical equilibria as model

equations.

The ion-pair reaction representation should be further evaluated in other hindered

amines, such as 2-PE or DIPA. The model using the ion-pair equation can be compared

with a separate model using the carbonate formation equation, to evaluate the

significance of the ion-pair interaction. Quality NMR speciation data is also important to

the study of hindered amine chemistry.

355

11.2.4 Hindrance effect on CO2 VLE

Steric hindrance, together with pKa of the amine, determines the CO2 VLE in a

solvent, and ultimately the performance and cost of the process. The effect of hindrance

on CO2 VLE can be studied using the SSM. The hindered amine structure for this

analysis should cover over a range of hindrance and pKa between 8.5 and 10.

11.2.5 CO2 absorption rate in hindered amines

Currently, the effect of hindrance on the absorption rate of CO2 is not well

understood beyond the observation that it generally lowers the kg' of the solvent. A

better understanding of hindrance can better guide solvent screening for CO2 capture,

particularly if the hindered amine can be used in a blend with PZ. Moreover, this topic

contributes to improve the general understanding of the interaction and reaction between

CO2 and amines. Structures with various degree of hindrance should be studied to

understand the effect. CO2 absorption rate results should be analyzed along with CO2

VLE and speciation data to fully account for the effect of speciation on absorption rate.

356

Appendix A: Background and Theory

A.1. CO2 CAPTURE BACKGROUND

A.1.1 Emissions from coal fired power plants

Figure A-1: U.S. energy consumption from primary sources in 2013 by sector (EIA

2014b)

Currently, a major portion of the energy in the world is being used for the

generation of electricity, which is then used to power other sectors of the economy. As

Figure A-1 shows, the electric power sector consumed nearly 40% of primary energy

sources in 2013, leading both the transportation and industrial sector. At the same time,

the electric power sector is the largest contributor of CO2 emission. In the U.S., the

electric power sector was responsible for close to 40% of the total CO2 emitted in 2013

(Figure A-2). Not only is the electricity sector an important target for the reduction of

CO2 emission, the industry has one characteristic which makes it convenient for the

Residential7%

Commercial4%

Industrial22%

Transportation

28%

Electric power39%

357

application of necessary technologies. Electric power plants are mostly large point

sources of CO2 emissions, generating large amounts of CO2 continuously at set locations.

Considering the economies of scale, which suggests the cost of industrial products is

lower for larger process units, as the equipment cost of the plant is shared among a larger

total number of products. Thus, the application of CO2 emission control technologies to

power plants is expected to be more cost effective compared to small moving sources

(such as the transportation sector).

Figure A-2: U.S. CO2 emission (from primary fuel consumption) in 2013 by sector (EIA

2014b)

The generation of electricity in the world today is mostly through the combustion

of fossil fuels. As Figure A-3 shows, in the U.S., coal is the largest fuel source for the

electric sector (39% kwhr), followed by natural gas (28%), leading both the renewable

and nuclear fuel sources. While coal is the largest fuel source for the electric sector, it

also produces more CO2 than natural gas per unit of electricity generated (EIA). As a

result, coal fired power plants are currently responsible for nearly 80 % of the CO2

Residential5.1%

Commercial4.2%

Industrial17.9%

Transportation

34.5%Coal

29.5%

Gas8.3%

Petroleum0.4%

Electric Power38%

358

emitted by the electric sector in the U.S. (Figure A-2). Moreover, compared to natural

gas power plants, coal fired power plants generate flue gas with higher CO2 content

(approximately 4 times that of natural gas combined cycle power plants). As the

Sherwood plot (Figure A-4) suggests, the cost of separation decreases linearly with

increase in the concentration of the material in the source stream. The application of

CO2 separation technologies would be cheaper for coal fired power plants compared to

natural gas plants.

Figure A-3: U.S. electricity generation in 2013 by fuel source (EIA 2014b)

It is essential for potential CO2 emission regulations to target coal fired power

plants, as the emission from these plants is significant relative to other sectors. It is

also likely that regulation strategies will first focus on coal power plants, as it is expected

to be cheaper and easier to remove the CO2 from these sources than others (such as cars

or natural gas power plants). Therefore, the main application of this work is the

conventional coal fired power plants. The typical conditions of such a plant in the U.S.

are used as the basis for the majority of the technical analysis.

Other gases0.3%

Nuclear19.5%

Renewable12.9%

Coal39.2%

Natural gas27.5%

Petroleum0.7%

Fossil fuels68%

Unit: kilowatthours

359

Figure A-4: Sherwood plot of industrial separation processes cost dependence on

concentration in the source stream (House et al. 2011)

A.1.2 Potential of CO2 Regulation

With the reality of climate change confirmed by all scientific research on the

topic, few action have been taken to address the issue and the world CO2 emission

continues to rise. Without an effective policy either limiting or penalizing carbon

emission, there is no economic incentive for the power industry to reduce the production

of CO2 in the current world market.

The regulation of CO2 emission for the purpose of mitigating climate change is

challenging for two main reasons. First, while climate change is a global environmental

issue, the emission of CO2 is a matter of international economy as it is directly associated

360

with the production of goods and energy. Each country contributes differently in their

CO2 emissions; at the same time the effect of climate change is likely to harm some

countries more than others. It is difficult to form an agreement when each country has

different degrees of, and sometimes conflicting, motivation and economic priorities with

regard to climate change and emission control. To make matters worse, as the global

trading of energy and goods increases, the economy of CO2 becomes more complex.

The countries producing the emissions are not usually the same as the countries

consuming them, making assigning appropriate responsibilities even more difficult. The

second challenge is the complexity of the solution itself. To achieve the necessary CO2

emission reduction, the policy solution is likely to involve all sectors of the world

economy, as well as the deployment of many new technologies, and changing the way the

world as a whole distributes and uses energy. Due to these challenges, effective

regulation has yet to be implemented for the reduction of worldwide CO2 emission.

History of International Climate Change Policies

The international discussion for a plan to mitigate climate change and reduce

world CO2 emission began over 30 years ago. The first official international

collaboration was the formation of the Intergovernmental Panel on Climate Change

(IPCC) in 1988. Formulated by the World Meteorological Organization (WMO) and the

United Nations Environment Program (UNEP), the IPCC aimed to “prepare, based on

available scientific information, assessments on all aspect of climate change and its

impacts, with a view of formulating realistic response strategies” (IPCC 2014). With the

Fifth Assessment Report (AR5) released recently, along with the previous reports and

other activities, the IPCC provides comprehensive and publicly available scientific

information on the issue of climate change. Even though the IPCC does not directly

361

produce emission reduction policies, its reports and other work products laid the

scientific foundation for the development of all future international policies and treaties.

Based on the results of IPCC, the United Nations Framework Convention on

Climate Change (UNFCCC) was negotiated and signed in 1992. The objective of the

UNFCCC treaty is to “stabilize greenhouse gas concentrations in the atmosphere at a

level that would prevent dangerous anthropogenic interference with the climate system”

(UN General Assembly 1994). Even though the UNFCCC has nearly universal

membership, with participants including all United Nation member states, the European

Union, and two other small countries, the treaty included no binding limits on greenhouse

gases emissions for any individual member. Instead, the UNFCCC aimed to facilitate

negotiations of subsequent emission binding treaties among its members with the

convening of annual Conference of the Parties (COP) which began in 1995. The most

significant outcome of the COPs is the signing of the Kyoto Protocol in 1997. The

Kyoto Protocol established binding targets for a group of developed countries (Annex I)

to collectively reduce CO2 emission by 5% from 1990 emission levels during the first

commitment period of 2008–2012. The Annex I group originally included the European

Union and 42 other nations. Despite being a key member of the Annex I group to the

Kyoto Protocol, the U.S. eventually refused to ratify the treaty under the Bush

administration, as the treaty did not pass through the Senate. Prior to the targeted

deadline of the first commitment period, Canada, Japan, and Russia also withdrew from

the protocol. Even though the remaining Annex I countries ultimately met the adjusted

collective emission reduction target, it can be argued the Kyoto Protocol achieved little in

terms of global reduction of CO2 emission (Helm 2008), mainly because the failure to

bring forth the participation of the United States and China. Perhaps the most significant

362

contribution of the Kyoto Protocol is the facilitation of an international discussion of

climate policy, as well as the lessons learned through the experience (Böhringer 2003).

Post- Kyoto Climate Policies

Figure A-5: Total CO2 emission by the U.S. and China from 1980 to 2013 (EIA 2014a)

Based on the experience of Kyoto, it is apparent that the involvement of U.S. and

China are crucial to the effective regulation of global CO2 emissions. As shown in

Figure A-5, the CO2 emission from China has increased rapidly since 2000; whereas the

U.S. has historically produced large amounts of CO2. Currently, U.S. and China are the

largest energy consumers and CO2 emitters in the world (Figure A-6). Historically, both

countries have held back from making international commitments with regards to the

climate change. However, new promises have been made by the leaders of the two

countries to reduce CO2 emission. In June 2013, with his Climate Action Plan, President

Obama re-affirmed the goal of 17 percent CO2 emission reduction from 2015 level by

2020 (Executive Office of the President 2013). Specifically, the plan called for cutting

0

3000

6000

9000

1970 1980 1990 2000 2010 2020

CO

2em

issi

on

(M

Mto

n)

Year

United States

China

363

carbon pollution from power plants, with clean coal technologies as part of the solution.

Following this announcement, an unprecedented collaboration was formulated between

the leaders of the U.S. and China. In November 2014, during the Asian Pacific

Economic Cooperation summit, President Obama committed the U.S. to reduce 26 to 28

percent carbon by 2025 (relative to 2005). As part of the agreement, President Xi

Jinping pledged for China to reach its carbon peak by 2030, with at least 20 percent of the

energy produced to come from clean energy sources by the same time. However, the

implementation of specific regulations to achieve these goals faces significant challenges,

likely more so for the U.S. As the U.S. Congress is currently controlled by the

Republican party which historically held anti-climate change views, and is expected to

block any regulation for CO2 emission (Landler 2014). Nonetheless, this agreement

between U.S. and China provides significant motivation for the continuous research and

development of technologies to achieve the goal (Buchele 2014).

Figure A-6: CO2 emission and energy consumption in the U.S. and China as fraction of

world total since 1980 (EIA 2014a).

0

0.05

0.1

0.15

0.2

0.25

0.3

1970 1980 1990 2000 2010 2020

% W

orl

d T

ota

l (M

ton

; BT

U)

U.S

China

Dotted line: CO2 emissionDiamond curve: energy

364

A.1.3 Current cost of implementing absorption/stripping unit for CO2 capture:

The cost of implementing amine scrubbing to power plant depends on 1) the

efficiency (heat rate) of the power plant, 2) the carbon content of the coal (relative to its

energy density), 3) the energy and capital cost of the amine scrubbing unit, and 4)

electricity price. Calculation of capture cost is performed with best approximations

based on available data in all four items.

Power plant and coal type specifications:

Coal fired power plant heat rate (depending on both plant type and coal

type): 8000-10000 BTU/kwh (EPA 2009).

Carbon emission factor (lb CO2/BTU, depend on coal type) in U.S. (EIA

1994): 227 (anthracite), 216.3 (lignite), 211.9 (subbituminous), and 205.3

(bituminous).

CO2 emission rate (mol CO2/MWh) = power plant heat rate (x) emission factor


𝑀𝑊𝐻=

205.3 (227)𝑙𝑏 𝐶𝑂2

𝐵𝑇𝑈∙8000 (10,000)𝐵𝑇𝑈

𝑘𝑤ℎ∙453.6𝑔

𝑙𝑏∙𝑡𝑜𝑛𝑛𝑒 𝐶𝑂2

1000000𝑔∙1000 𝑘𝑊ℎ

𝑀𝑊ℎ=

0.74 (1)𝑡𝑜𝑛𝑛𝑒 𝐶𝑂2

𝑀𝑊ℎ≈ 1

𝑡𝑜𝑛𝑛𝑒 𝐶𝑂2

𝑀𝑊ℎ (A-1)

A conservative estimate of CO2 emission rate, for a less efficient power plant and

high carbon content coal, is approximately 1 tonne CO2/MWh. An optimum estimate is

about 25% less CO2 emission.

Capture unit performance:

Equivalent work of the energy required in a capture unit is about 30 kJ/mol CO2

(Van Wagner 2011). This value assumes Carnot efficiency of the reboiler, and 0.75

turbine efficiency, and unit it does not account for pressure drop in the absorber and

intercooler pump.

365

Energy cost of operating the capture unit: $

𝑀𝑊ℎ= (

30 𝑘𝐽

𝑚𝑜𝑙 𝐶𝑂2∙

ℎ𝑟

3600𝑠∙𝑚𝑜𝑙 𝐶𝑂2

44𝑔) (

1 𝑡𝑜𝑛𝑛𝑒 𝐶𝑂2

𝑀𝑊ℎ∙1𝑀𝑊ℎ

103𝑘𝑊ℎ∙106𝑔

𝑡𝑜𝑛𝑛𝑒) (

10𝑐

𝑘𝑊ℎ∙1000𝑘𝑊ℎ

𝑀𝑊ℎ∙

$

100𝑐) =

$19

𝑀𝑊ℎ (A-2)

Capital cost of the capture unit can be estimated by considering:

approx $1 billion for a 1000 MW power plant (Rochelle 2009)

assume 15% (conservative estimates 30-40%) annual rate of return

30 year operating life of capture unit

8000 hr total operating time/year

(1 𝑚𝑖𝑙𝑙𝑖𝑜𝑛 $

1𝑀𝑊∙0.15(0.15+1)30

(0.15+1)30−1)

1

𝑦𝑟∙ (

1𝑦𝑒𝑎𝑟

8000 ℎ𝑟) =

$19

𝑀𝑊ℎ (A-3)

Calculated capital cost: 19-50 $/MWh (corresponding to 15 and 40% annual rate

of return). Assuming an average electricity price of 10c/kWh (Texas 2013), the total

cost of building and operating the CO2 capture unit is:

(19/50+19)$

𝑀𝑊ℎ∙

100𝑐

1000𝑘𝑊ℎ=

4/7𝑐

𝑘𝑊ℎ= 40 𝑡𝑜 70% 𝑖𝑛𝑐𝑟𝑒𝑎𝑠𝑒 𝑖𝑛 𝑒𝑙𝑒𝑐 𝑝𝑟𝑖𝑐𝑒 (A-4)

A.2 DERIVATION OF PSEUDO FIRST ORDER (PFO) EXPRESSION

CO2 mass balance in the liquid film

𝑓𝑙𝑢𝑥 𝑖𝑛 − 𝑓𝑙𝑢𝑥 𝑜𝑢𝑡 + 𝑟𝐶𝑂2 = 𝑎𝑐𝑐𝑢𝑚𝑢𝑙𝑎𝑡𝑖𝑜𝑛 (A-5)

A.2.1 Film theory: steady state

−𝜕𝑁𝐶𝑂2

𝜕𝑥+ 𝑟𝐶𝑂2 = 0 (A-6)

𝑁𝐶𝑂2 = −𝐷𝐶𝑂2𝜕[𝐶𝑂2]

𝜕𝑥 (A-7)

366

DCO2∂2[CO2]

∂x2+ rCO2 = 0 (A-8)

Substitute CO2 reaction rate expression:

DCO2∂2[CO2]

∂x2− k2[Amine]([CO2] − [CO2]eq) = 0 (A-9)

Apply the pseudo first order assumption:

DCO2∂2[CO2]

∂x2− k1([CO2] − [CO2]eq) = 0 (A-10)

{@𝑥 = 0, [𝐶𝑂2] = [𝐶𝑂2]𝑖@ 𝑥 = 𝛿, [𝐶𝑂2] = [𝐶𝑂2]𝑏

(A-11)

Re-define the variable:

[𝐶𝑂2]̅̅ ̅̅ ̅̅ ̅ = [𝐶𝑂2] − [𝐶𝑂2]𝑒𝑞 (A-12)

Transform governing DFQ and boundary conditions:

DCO2∂2[CO2]̅̅ ̅̅ ̅̅ ̅̅

∂x2− k1[CO2]̅̅ ̅̅ ̅̅ ̅ = 0 (A-13)

{@𝑥 = 0, [𝐶𝑂2]̅̅ ̅̅ ̅̅ ̅ = [𝐶𝑂2]𝑖 − [𝐶𝑂2]𝑒𝑞 = 𝑎

@ 𝑥 = 𝛿, [𝐶𝑂2]̅̅ ̅̅ ̅̅ ̅ = [𝐶𝑂2]𝑏 − [𝐶𝑂2]𝑒𝑞 = 𝑏 (A-14)

Standard solution to governing equation:

[𝐶𝑂2]̅̅ ̅̅ ̅̅ ̅ = 𝐶1 cosh (√𝑘1

𝐷𝐶𝑂2𝑥) + 𝐶2 𝑠𝑖𝑛ℎ (√

𝑘1

𝐷𝐶𝑂2𝑥) (A-15)

Apply boundary conditions

[𝐶𝑂2]̅̅ ̅̅ ̅̅ ̅ = 𝑎 𝑐𝑜𝑠ℎ (√𝑘1

𝐷𝐶𝑂2𝑥) +

(

𝑏

𝑠𝑖𝑛ℎ(√𝑘1

𝐷𝐶𝑂2𝛿)

−𝑎

𝑡𝑎𝑛ℎ(√𝑘1

𝐷𝐶𝑂2𝛿)

)

𝑠𝑖𝑛ℎ (√

𝑘1

𝐷𝐶𝑂2𝑥)

(A-16)

367

Rearrange and apply identity of hyperbolic functions: sinh(a)cosh(b)-

sinh(b)cosh(a) = sinh(a-b)

[𝐶𝑂2]̅̅ ̅̅ ̅̅ ̅ = 𝑎 ∙


𝐷𝐶𝑂2(𝛿−𝑥))


𝐷𝐶𝑂2𝛿)

+ 𝑏 ∙


𝐷𝐶𝑂2𝑥)


𝐷𝐶𝑂2𝛿)

(A-17)

Re-substitute expressions for constants and transformed function:

[𝐶𝑂2] =

([𝐶𝑂2]𝑖−[𝐶𝑂2]𝑒𝑞)𝑠𝑖𝑛ℎ(√𝑘1

𝐷𝐶𝑂2(𝛿−𝑥))+([𝐶𝑂2]𝑏−[𝐶𝑂2]𝑒𝑞)𝑠𝑖𝑛ℎ(√

𝑘1𝐷𝐶𝑂2

𝑥)


𝐷𝐶𝑂2𝛿)

+ [𝐶𝑂2]𝑒𝑞 (A-18)

Take derivative:

𝑑[𝐶𝑂2]

𝑑𝑥|𝑥=0

= −

([𝐶𝑂2]𝑖−[𝐶𝑂2]𝑒𝑞)√𝑘1

𝐷𝐶𝑂2

𝑡𝑎𝑛ℎ(√𝑘1

𝐷𝐶𝑂2𝛿)

+

([𝐶𝑂2]𝑏−[𝐶𝑂2]𝑒𝑞)√𝑘1

𝐷𝐶𝑂2


𝐷𝐶𝑂2𝛿)

(A-19)

Substitute expression for 𝛅 (diffusion film thickness): = 𝐷𝐶𝑂2 𝑘𝐿°⁄ , and use the

dimensionless Hatta number (M): 𝑀 = 𝐷𝐶𝑂2𝑘1 𝑘𝐿° 2⁄ :

𝑑[𝐶𝑂2]

𝑑𝑥|𝑥=0

= −

([𝐶𝑂2]𝑖−[𝐶𝑂2]𝑒𝑞)√𝑘1

𝐷𝐶𝑂2

𝑡𝑎𝑛ℎ(𝑀)+

([𝐶𝑂2]𝑏−[𝐶𝑂2]𝑒𝑞)√𝑘1

𝐷𝐶𝑂2

𝑠𝑖𝑛ℎ(𝑀) (A-20)

As reaction rate increases (𝑘1 → ∞), the Hatta number (M) also increases, at

which𝑡𝑎𝑛ℎ(𝑀) → 1, and ([𝐶𝑂2]𝑏 − [𝐶𝑂2]𝑒𝑞) → 0

𝑑[𝐶𝑂2]

𝑑𝑥|𝑥=0

= ([𝐶𝑂2]𝑖 − [𝐶𝑂2]𝑒𝑞)√𝑘1

𝐷𝐶𝑂2 (A-21)

Use expression of derivative in Fick’s law:

368

𝑁𝐶𝑂2 = −𝐷𝐶𝑂2𝑑[𝐶𝑂2]

𝑑𝑥|𝑥=0

= 𝑘𝐿°√𝑀([𝐶𝑂2]𝑖 − [𝐶𝑂2]𝑒𝑞) (A-22)

𝑁𝐶𝑂2 =√𝐷𝐶𝑂2𝑘1

𝐻𝐶𝑂2

(𝑃𝐶𝑂2𝑖 − 𝑃𝐶𝑂2∗ ) =

√𝐷𝐶𝑂2𝑘2[𝐴𝑚𝑖𝑛𝑒]

𝐻𝐶𝑂2

(𝑃𝐶𝑂2𝑖 − 𝑃𝐶𝑂2∗ ) (A-23)

A.2.2 Surface renewal theory (model by Danckwerts 1970): unsteady state

Surface renewal models characterize the liquid film as individual liquid elements,

which are continuously replaced by fresh elements from the interior at certain time

intervals. The instantaneous rate of mass transfer of CO2 is then time dependent. The

fresh elements have the local mean bulk composition, and absorb gas as though it were

quiescent and infinitely deep. The instantaneous rate of absorption can be simply

assumed to be a function of the time of exposure of the element, though with little

physical basis.

Danckwerts describes the surface renewal process by assuming the chance of each

liquid element to be replaced by a fresh element as independent of its exposure time.

Mathematically, he assumed a stationary distribution of surface ‘age’ that at any given

instant, the fraction of surfaces with 𝑑𝑡 exposure time is 𝑠𝑒−𝑠𝑡𝑑𝑡, where s is the fraction

of exposed area that is replaced by fresh liquids at a given time. The average rate of

absorption (�̅�) can be described as the flux at each position (R) multiplied by its exposure

area, integrated over all elements of the surface with ages between 0 and ∞:

�̅� = 𝑠 ∫ 𝑅 ∙ 𝑒−𝑠𝑡𝑑𝑡∞

0 (A-24)

According to this equation, while the rate of absorption at each unit area is time

dependent, the average absorption rate over the entire liquid element is not time

dependent.

For physical absorption, this surface renewal theory shows a relationship between

the fraction of renewed surface (s) and the liquid side physical mass transfer coefficient

(kL).

369

𝑠 =𝑘𝐿

2

𝐷𝐶𝑂2 (A-25)

The physical behavior of this model can help solve the partial differential

equation of this unsteady state mass balance of CO2 absorption:


𝜕𝑥2− 𝑘1([𝐶𝑂2] − [𝐶𝑂2]𝑒𝑞) =

𝜕[𝐶𝑂2]

𝜕𝑡 (A-26)

{

@𝑥 = 0, [𝐶𝑂2] = [𝐶𝑂2]𝑖@𝑥 = 𝑓𝑖𝑛𝑖𝑡𝑒, [𝐶𝑂2] = [𝐶𝑂2]𝐵@𝑡 = 0, [𝐶𝑂2] = [𝐶𝑂2]𝐵

(A-27)

Function transformation:

[𝐶𝑂2]∗ = [𝐶𝑂2] − [𝐶𝑂2]𝑒𝑞 (A-28)


∗

𝜕𝑥2− 𝑘1[𝐶𝑂2]

∗ =𝜕[𝐶𝑂2]

∗

𝜕𝑡 (A-29)

{

@𝑥 = 0, [𝐶𝑂2]∗ = [𝐶𝑂2]𝑖 − [𝐶𝑂2]𝑒𝑞 = 𝑎

@𝑥 = ∞, [𝐶𝑂2]∗ = [𝐶𝑂2]𝐵 − [𝐶𝑂2]𝐵 = 0

@𝑡 = 0, [𝐶𝑂2]∗ = [𝐶𝑂2]𝐵 − [𝐶𝑂2]𝑩 = 0

(A-30)

Apply Laplace Transform:

𝑐(𝑥)̅̅ ̅̅ ̅̅ = 𝐿(𝑐(𝑥, 𝑡)) = 𝑠 ∙ ∫ 𝑐(𝑥, 𝑡)𝑒−𝑠𝑡𝑑𝑡∞

0 (A-31)

𝐷𝐶𝑂2𝜕2[𝐶𝑂2]∗̅̅ ̅̅ ̅̅ ̅̅ ̅

𝜕𝑥2− (𝑘1 + 𝑠)[𝐶𝑂2]∗̅̅ ̅̅ ̅̅ ̅̅ ̅ = 0 (A-32)

{@𝑥 = 0, [𝐶𝑂2]

∗̅̅ ̅̅ ̅̅ ̅̅ ̅ = 𝑎

@𝑥 = ∞, [𝐶𝑂2]∗̅̅ ̅̅ ̅̅ ̅̅ ̅ = 0 (A-33)

The ordinary differential equation has the following standard solution:

[𝐶𝑂2]∗̅̅ ̅̅ ̅̅ ̅̅ ̅ = 𝐶1𝑒(√

𝑘1+𝑠

𝐷𝐶𝑂2 𝑥)

+ 𝐶2𝑒(−√

𝑘1+𝑠

𝐷𝐶𝑂2 𝑥)

(A-34)

370

Apply the boundary conditions and obtain:

[𝐶𝑂2]∗̅̅ ̅̅ ̅̅ ̅̅ ̅ = 𝑎 ∙ 𝑒(−√

𝑘1+𝑠

𝐷𝐶𝑂2 𝑥)

(A-35)

Due to the identical mathematical form between the average rate of absorption (�̅�)

and the definition of Laplace transform, the physical significance of �̅� can be applied to

[𝐶𝑂2]∗̅̅ ̅̅ ̅̅ ̅̅ ̅, which by analogy represents the average CO2 concentration in the liquid. The

expression of s from the physical mass transfer solution (Equation A-25) can be used in

Equation A-35.

[𝐶𝑂2]∗̅̅ ̅̅ ̅̅ ̅̅ ̅ = ([𝐶𝑂2]𝑖 − [𝐶𝑂2]𝑒𝑞) ∙ 𝑒(−√

𝑘1𝐷𝐶𝑂2

+𝑘𝐿

2

𝐷𝐶𝑂22 𝑥)

(A-36)

[𝐶𝑂2]̅̅ ̅̅ ̅̅ ̅ = ([𝐶𝑂2]𝑖 − [𝐶𝑂2]𝑒𝑞) ∙ 𝑒(−𝑥

𝑘𝐿𝐷𝐶𝑂2

√𝑘1𝐷𝐶𝑂2

𝑘𝐿2 +1 )

+ [𝐶𝑂2]𝑒𝑞 (A-37)

Apply Fick’s law:

𝑁𝐶𝑂2 = 𝑘𝐿 (√𝑘1𝐷𝐶𝑂2

𝑘𝐿2 + 1) ([𝐶𝑂2]𝑖 − [𝐶𝑂2]𝑒𝑞) (A-38)

𝑁𝐶𝑂2 = 𝑘𝐿√𝑀 + 1([𝐶𝑂2]𝑖 − [𝐶𝑂2]𝑒𝑞) (A-39)

At conditions with high Hatta number (fast reaction), simplifies to the same

expression as:

𝑁𝐶𝑂2 = 𝑘𝐿√𝑀([𝐶𝑂2]𝑖 − [𝐶𝑂2]𝑒𝑞) =√𝐷𝐶𝑂2𝑘2[𝐴𝑚𝑖𝑛𝑒]

𝐻𝐶𝑂2

(𝑃𝐶𝑂2𝑖− 𝑃𝐶𝑂2

∗) (A-40)

Equation A-40 is identical to the solution from film theory (Equation A-23).

Since the liquid film mass transfer coefficient (kg’) is defined as:

𝑘𝑔′ =

𝑁𝐶𝑂2

(𝑃𝐶𝑂2𝑖−𝑃𝐶𝑂2

∗) (A-41)

371

By analogy with Equation B.60, the expression for kg’ with the PFO assumption

is:

𝑘𝑔′ =

√𝐷𝐶𝑂2𝑘2[𝐴𝑚𝑖𝑛𝑒]

𝐻𝐶𝑂2

(A.42)

372

Appendix B: Additional Experimental Data

B.1 ADDITIONAL MASS TRANSFER AND CO2 SOLUBILITY DATA

B.1.1 High temperature VLE for 8 m MAPA

Figure B-1: CO2 solubility in 8 m MAPA at high temperature. Solid circles: total

pressure results. Solid lines: 1st empirical model (Table B-1).

CO2 equilibrium partial pressure (PCO2*) in 8 m MAPA was measured at 100–160

˚C and rich CO2 loading (higher than 0.5 mol/mol alk). The high temperature results

show good internal consistency and suggest a reasonable trend with CO2 loading and

temperature dependence (Figure B-1). Compared with WWC results, high temperature

data match low temperature VLE well at two low loadings, and show slight inconsistency

around 0.5 loading (Figure B-2).

5E+4

5E+5

0.5 0.52 0.54 0.56 0.58

PC

O2*

(Pa)


110 °C

100 °C

120 °C

140 °C

160 °C

150 °C

130 °C

373

The measured CO2 partial pressure data are regressed to generate the parameters

of the semi-empirical VLE model for 8 m MAPA.

Figure B-2: CO2 solubility in 8 m MAPA. Diamond: WWC (Chen, 2011). Circles:

total pressure. Solid lines: 1st empirical model. Dashed line: 2nd empirical

model (Table B-1).

Table B-1: Parameter values of two semi-empirical VLE models (Equation 4.4) for 8 m

MAPA

1st 2nd

Value Std. Err Value Std. Err

a 24.2 12.0 0 NA

b -7587.8 4154.7 3028 661

c 93.4 57.3 210 21

d -144.7 66.9 -271 49

e -31274.5 20010.6 -85700 7666

f 57360.1 23609.6 123113 16476

R2 0.999 0.999

1E+0

1E+1

1E+2

1E+3

1E+4

1E+5

1E+6

0.25 0.35 0.45 0.55

PC

O2*

(Pa)


40 °C

60 °C

80 °C

110 °C

100 °C

120 °C

140 °C

160 °C150 °C

130 °C

374

Data used Total pressure and WWC

results at two low loadings WWC only

Data # 26 12

The inconsistencies between the two models are due to the inconsistency in the

experimental data. At loadings close to 0.5 mol/mol alk, the WWC measurements are

significantly higher than the values suggested by high temperature results.

Experimentally, accurately measuring CO2 loading at rich loadings can be difficult and

slightly affect the quality of data. Physically, at around 0.5 CO2 loading, carbamate

forming species, free MAPA and MAPA carbamate, are mostly consumed. As a result,

the CO2 solubility of the solvent reduces significantly faster than at lower loadings. Due

to its simple mathematical form, the semi-empirical model cannot describe the physical

change in VLE around 0.5 loading and low temperature while maintaining good fit with

data at other conditions.

The semi-empirical models are used to predict the operating lean and rich loading

of 8 m MAPA, which correspond to PCO2* of 0.5 and 5 kPa at 40 ˚C. The cyclic

capacity (∆Csolv) of the solvent is calculated using Equation 4.9.

The calculated lean/rich loadings and ∆Csolv of 8 m MAPA are summarized in

Table 4. The results of the two models are very different from each other. The first

model predicts lean/rich loadings that are much higher than the second model

(approximately 0.06 mol/mol alk). Also, the first model predicts a ∆Csolv more than 50%

higher than the second. This is because of the uncertainties in the shape of the VLE

curve at 40 ˚C (Figure B-2). The loadings and ∆Csolv calculated by the second model

should be used since this model better match the available experimental data at

conditions critical to these properties.

375

Table B-2: Capacity, -Habs, and operating loading range of 8 m MAPA predicted using

two empirical models (Table 3).

1st 2nd

αlean (mol/mol alk) 0.494 0.464

αrich (mol/mol alk) 0.562 0.507

∆Csolv (mol/kg solv) 0.63 0.40

-Habs at αlean (kJ/mol) 75 85 81*

-Habs at αmid(kJ/mol) 67 80 77* * Calculated using the first model at loadings calculated by the second model

The heat of absorption of CO2 in 8 m MAPA is calculated as the temperature

dependence of the CO2 VLE using in Equation 4.5

The ∆Habs of a solvent is a function of CO2 loading, and not dependent on

temperature. Also, the calculation of ∆Habs depends on the semi-empirical model. The

∆Habs calculated using two models for 8 m MAPA are summarized in Table B-2 and

plotted in Figure B-3. Since ∆Habs decreases with an increase in CO2 loading, the first

model calculates a lower ∆Habs than the second model mostly due to the higher loadings

suggested by the first model. The ∆Habs predicted by the two models are similar, as

shown in Figure B-3. The second model (WWC only) predicts slightly higher ∆Habs at

low loadings and lower ∆Habs at rich loadings. However, the differences between the

two models are within 5 kJ/mol at the operating condition. The ∆Habs of 8 m MAPA

should be calculated using the first model, since it is regressed using more data and from

a greater temperature and loading range. Typically, the ∆Habs of a solvent is reported at

its lean loading and mid-loading (PCO2* at 1.5 kPa). In the case of 8 m MAPA, these

loadings are to be calculated using the second model. The ∆Habs calculated by a

combination of the two models is slightly lower than the first model and much higher

than the second.

The PCO2* experimental data at high temperature are summarized in Table B-3.

376

Figure B-3: CO2 heat of absorption in 8 m MAPA predicted by two empirical models

(Table B-2)

Table B-3: PCO2* for 8 m MAPA at high temperature

T CO2 ldg PCO2* Pmeas Ptotal

˚C mol/mol alk kPa

100 0.532 81 298 170

100 0.557 166 390 255

100 0.569 234 451 322

110 0.531 162 412 287

110 0.555 284 543 409

110 0.567 353 629 478

120 0.529 272 580 445

120 0.553 450 766 624

120 0.564 571 880 745

130 0.527 449 817 685

130 0.550 667 1044 903

130 0.561 809 1203 1044

140 0.523 712 1167 1028

140 0.545 976 1438 1291

140 0.556 1174 1642 1489

40

50

60

70

80

90

100

0.35 0.4 0.45 0.5 0.55 0.6

-Hab

s(k

J/m

ol)


Lean

Rich

LeanRich

1st model2nd model

377

150 0.518 1064 1621 1479

150 0.540 1375 1941 1790

150 0.550 1614 2185 2029

160 0.512 1507 2191 2046

B.1.2 Low temperature performance of MDEA/PZ blends

The kg’ of 7 m MDEA/2 m PZ was measured at 30°C and compared with results

at 40°C, 60 °C, 80°C, and 100°C (Figure B-4). Five CO2 loadings across the lean and

rich loading range were tested. The absorption rate of this blend at 30°C is about the

same as its rate at 40°C and 60°C when compared at the same PCO2* (40°C).

Figure B-4: CO2 Liquid Phase Mass Transfer Coefficient (kg’) in 7 m MDEA 2 m PZ at

30°C

Table B-4: CO2 Solubility and kg’ Measured for 7 m MDEA 2 m PZ at 30 and 40 °C

1.E-07

1.E-06

0.1 1 10 100

k g' (

mo

l/s∙

Pa∙

m2)

PCO2 * @ 40°C (kPa)

40°C

30°C

60°C80°C

100°C

378

CO2 loading Temperature kg' PCO2*


0.133 30 13.70 0.217

0.195 30 7.53 0.732

0.249 30 5.23 2.175

0.298 30 3.58 4.154

0.356 30 2.33 8.262

0.356 40 2.42 16.712

Figure B-5: CO2 Liquid Phase Mass Transfer Coefficient (kg’) in at low temperatures in 5

m MDEA/5 m PZ

The absorption rate of 5 m MDEA/5 m PZ at temperatures 10, 20, 30 and 40 ˚C

are approximately the same (Figure B-5). At low temperatures, high solvent viscosity

will significantly reduce the diffusivity of all species in solution. The physical mass

transfer will dominate the overall absorption process, and the value of kl˚ will become the

limiting factor in the measured kg’. Compared to previous rate measurement of the

blend at 40 ˚C, the new values are slightly lower at lean loadings. The rate at rich

loadings agrees well with previous data.

1.E-07

1.E-06

100 1000 10000

k g' (

mo

l/p

a ∙s

∙m2)

PCO2*@ 40 ˚C (Pa)

10 °C

40 °C30 °C

20 °C

Chen 2011

379

The PCO2* measured at low temperatures are plotted together with previously

measured high temperature data (Figure B-6). The new equilibrium measurements agree

well with the high temperature data. The two sets of data were regressed together and

the result VLE model fits the experimental data well over the entire temperature range.

Figure B-6: CO2 solubility in 5 m MDEA/5 m PZ

Table B-5: CO2 solubility and absorption rates of 5 m MDEA/5 m PZ blend at low

temperatures

Temperature CO2 loading kg' PCO2


10 0.24 12.4 0.046

10 0.28 7.96 0.089

20 0.24 9.04 0.103

20 0.28 8.85 0.275

30 0.20 14.4 0.13

30 0.24 13.8 0.288

30 0.28 8.79 0.825

30 0.33 5.55 1.749

1.E+01

1.E+02

1.E+03

1.E+04

1.E+05

0.15 0.2 0.25 0.3 0.35 0.4

PC

O2*

(P

a)


10 °C

40 °C

60 °C

80 °C

100 °C

30 °C

20 °C

Empty points: Chen 2011

380

40 0.20 15 0.326

40 0.24 12.5 0.843

40 0.28 8.88 2.245

40 0.33 5.86 4.906

B.1.3 Pilot Plant Samples

The absorption rate of the lean amine sample from the 2011 8 m PZ pilot plant

campaign was measured at 40, 60, 80, and 100 ˚C (Figure B-7). The sample was tested

at the collected loading and two higher loadings. At 40 ˚C, the pilot plant sample has

similar absorption rate than 8 m PZ. Only the 40 ˚C kg’ measured at the initial loading

is slightly higher than 8 m PZ. At all three loadings, the absorption rate of pilot plant

sample exhibits more significant temperature dependence than 8 m PZ. This

temperature dependence in kg’ could be a result in change in physical properties of the

solvent which will affect the mass transfer of CO2.

The CO2 solubility of the pilot plant sample distinctly differs from 8 m PZ (Figure

B-8). At rich loadings, PCO2* is higher in the pilot plant sample than 8 m PZ. The

decrease of CO2 solubility of the pilot plant samples suggests changes in active species in

solution from that of 8 m PZ. As a result, the cyclic capacity of the pilot plant sample is

lower than 8 m PZ.

Using the semi-empirical VLE model regressed from the solubility data, the

capacity and heat of absorption of the sample are calculated (Table B-8). The calculated

capacity of the pilot plant sample is approximately 10 % less than 8 m PZ. The heat of

absorption of the sample is higher than 8 m PZ by 19 %. The kg’avg for the pilot plant

sample is slightly higher than 8 m PZ.

381

Figure B-7: CO2 Liquid Phase Mass Transfer Coefficient (kg’) in 2011 8 m PZ pilot plant

sample

For the PRC 8 m PZ Fall 2011 pilot plant campaign sample, 18 PCO2* data points

were collected using the total pressure method at 100–160 °C between the nominal lean

and rich loading of the solvent. Together with 9 PCO2* data points collected at low

temperature using the WWC (Rochelle, 2012), a total of 27 data points were regressed to

obtain the semi-empirical model for the pilot plant sample (Table B-6). The measured

PCO2* plotted with the semi-empirical model result, is also compared with the semi-

empirical model result of 8 m PZ (Figure B-8). The measured values from the two

different methods agreed well with each other. The semi-empirical model is able to fit

both sets of data closely. The model regression has a relatively high R2 value (0.997)

Compared to the model results of 8 m PZ, the CO2 solubility curve of the pilot plant

sample has a smaller slope. Considering the errors associated with the experimental

data, this observed difference in the model results is likely within the variability of the

1.E-07

1.E-06

1.E-05

100 1000 10000

k g' (

mo

l/P

a∙s∙

m2)

PCO2* @ 40 ˚C (kPa)

40 °C

60 °C

80 °C

100 °C

Dashed lines: 8 m PZ (Dugas 2009)

382

data used. Mathematically, the regressed model for PRC pilot plant and 8 m PZ differs

in the functional dependency of PCO2* and loadings and temperatures. The predicted

capacity of the pilot plant sample is significantly lower than 8 m PZ, by 18%. The

calculated heat of absorption for the pilot plant sample is 6% higher than 8 m PZ.

Detailed PCO2* data for the pilot plant sample are summarized in Table B-7.

Figure B-8: CO2 solubility in PRC 8 m PZ Fall 2011 campaign pilot plant sample. Circle:

total pressure; diamond: wetted wall column; solid lines: pilot plant semi-

empirical model; dashed lines: 8 m PZ semi-empirical model (Table B-6).

Table B-6: Semi-empirical model (Equation 4.4) parameters for PRC pilot plant sample

and 8 m PZ

PRC pilot plant 8 m PZ (Xu, 2011)

Value Std Error Value Std Error

a 45.8 1.9 35.3 0.3

b -15604.3 727.7 -11054 120

c -35.4 6.0 / /

d / / -18.9 2.7

1.E+02

1.E+03

1.E+04

1.E+05

1.E+06

0.22 0.27 0.32 0.37

PC

O2*

(Pa)


120 ˚C130 ˚C

100 ˚C

110 ˚C

140 ˚C

150 ˚C

160 ˚C

40 ˚C

60 ˚C

80 ˚C

383

e 21322.6 2227.7 4958 347

f / / 10163 1085

R2 0.997 0.993

Capacity

(mol/kg solv) 0.65 0.79

-Habs @ 1.5 kPa

(kJ) 68 64

Table B-7: Detailed high temperatures PCO2* results for PRC 8 m PZ Fall 2011 pilot plant

sample

Temperature CO2 ldg PCO2 Raw Data Sample analysis



120 0.260 47 372 220

2.22 8.53 0.261

130 0.259 113 499 348

140 0.258 205 677 521

150 0.256 360 936 775

160 0.253 586 1289 1125

110 0.318 95 323 220

2.62 8.19 0.320

120 0.318 132 439 306

130 0.316 301 646 538

140 0.314 457 899 774

150 0.310 755 1300 1172

160 0.306 1116 1789 1658

100 0.355 100 322 189

2.95 8.26 0.356

110 0.354 207 460 332

120 0.352 329 642 502

130 0.349 554 924 789

140 0.346 837 1295 1152

150 0.341 1230 1791 1645

160 0.335 1722 2411 2261

384

Figure B-9: CO2 solubility at high temperatures for 8 m PZ + 100 mM Inh A. Solid

circle: PRC pilot plant sample; empty circle: 8 m PZ + Inh A; solid lines:

pilot plant semi-empirical model (Table B-6).

PCO2* data are collected at high temperature using the total pressure method for 8

m PZ with 100 mM Inh A. The 8 m PZ/Inh A data are plotted with measurements and

model results for the PRC pilot plant sample (Figure B-9). At high temperatures, the

CO2 solubility for 8 m PZ/Inh A compares closely to that of the pilot plant sample. The

measured PCO2* values for 8 m PZ/Inh A are systematically lower than both the measured

data and model results for the PRC sample. However, the difference is small and within

the error margin of the experimental method. Thus, additional data at low temperatures

are necessary to perform further comparison on the CO2 solubility of the two systems.

The detailed measurement of high temperature PCO2* for 8 m PZ/Inh A is summarized in

Table B-8.

Table B-8: Detailed high temperatures PCO2* results for 8 m PZ + 100 mM Inh A

1.E+04

1.E+05

1.E+06

0.23 0.28 0.33 0.38

PC

O2*

(Pa)


130 ˚C

100 ˚C

110 ˚C

140 ˚C

120 ˚C

150 ˚C

160 ˚C

385

T CO2 ldg PCO2 Raw Data Sample analysis



120 0.288 69 405 243

2.39 8.28 0.289

130 0.287 153 552 390

140 0.285 259 744 576

150 0.283 446 1035 863

160 0.280 724 1442 1266

110 0.321 74 334 199

2.64 8.20 0.322

120 0.321 124 441 298

130 0.319 250 628 487

140 0.317 409 873 725

150 0.314 664 1232 1081

160 0.310 1023 1720 1565

100 0.355 101 319 190

2.89 8.09 0.357

110 0.354 188 423 314

120 0.352 321 630 495

130 0.350 502 855 739

140 0.346 756 1203 1072

150 0.342 1115 1666 1533

160 0.336 1575 2253 2117

386

B.2 DETAILED WWC DATA

B.2.1 Amino acid salt solvents

Table B-9: Detailed Wetted Wall Column Data for 3.55 m GlyK (part 1)

GlyK CO2 ldg PCO2* T P GasDry Gaswet PCO2in, dry PCO2in, wet PCO2out, dry PCO2out, wet CO2 flux KG kg

KG/kg

kg'

m mol CO2/mol

alk Pa C psig Std L/min Std L/min Pa Pa Pa Pa mol/s m2

mol/s Pa m2

mol/s Pa m2

mol/s Pa m2

3.55 0.35 37 40 20 5 5.16

0 0.00 14.5 14.05 -5.85E-09

1.51E-06 4.57E-06 0.33 2.26E-06

10 9.69 17.8 17.25 -3.15E-09

20 19.38 23.1 22.39 -1.25E-09

60 58.15 51.7 50.10 3.35E-09

70 67.84 62.4 60.47 3.07E-09

80 77.53 67.2 65.13 5.17E-09

3.55 0.35 180 60 20 5 5.45

0 0.00 50 45.83 -2.02E-08

1.18E-06 4.83E-06 0.25 1.57E-06

50 45.83 81.5 74.71 -1.27E-08

100 91.67 120.5 110.46 -8.27E-09

250 229.17 238 218.17 4.84E-09

300 275.00 277 253.92 9.28E-09

350 320.83 313 286.92 1.49E-08

3.55 0.35 1063 80 40 5 5.72

0 0.00 395 345.37 -1.01E-07

1.25E-06 3.21E-06 0.39 2.04E-06

500 437.18 773 675.88 -6.99E-08

1000 874.36 1079 943.43 -2.02E-08

1500 1311.53 1420 1241.58 2.05E-08

2000 1748.71 1710 1495.15 7.43E-08

2500 2185.89 2050 1792.43 1.15E-07

3.55 0.35 4435 100 40 5 6.84

0 0.00 1825 1334.58 -4.67E-07

1.28E-06 3.76E-06 0.34 1.93E-06

2500 1828.19 3665 2680.12 -2.98E-07

5000 3656.37 5330 3897.69 -8.45E-08

10000 7312.75 8720 6376.72 3.28E-07

12500 9140.93 10460 7649.13 5.23E-07

15000 10969.12 12370 9045.87 6.74E-07

3.55 0.4 75 40 20 5 5.16

0 0.00 25 24.23 -1.01E-08

1.27E-06 4.57E-06 0.28 1.75E-06

25 24.23 35 33.92 -4.04E-09

50 48.46 55 53.30 -2.02E-09

150 145.37 129 125.02 8.48E-09

175 169.60 156 151.19 7.67E-09

200 193.83 164 158.94 1.45E-08

3.55 0.4 462 60 40 5 5.28

0 0.00 161 152.49 -4.12E-08

9.44E-07 2.98E-06 0.32 1.38E-06 150 142.07 244 231.10 -2.41E-08

300 284.14 332 314.45 -8.19E-09

387

600 568.28 579 548.39 5.38E-09

750 710.35 676 640.26 1.90E-08

850 805.07 741 701.83 2.79E-08


GlyK CO2 ldg PCO2* T P GasDry Gaswet PCO2in,

dry PCO2in, wet

PCO2out,

dry PCO2out,

wet CO2 flux KG kg

KG/kg

kg'

m mol CO2/mol

alk Pa C psig

Std L/min

Std L/min

Pa Pa Pa Pa mol/s

m2 mol/s Pa m2

mol/s Pa m2

mol/s Pa m2

3.55 0.4 2341 80 40 5 5.71

0 0.00 688 601.56 -1.76E-07

9.25E-07 3.21E-06 0.29 1.30E-06

1000 874.36 1512 1322.03 -1.31E-07

2000 1748.71 2180 1906.09 -4.60E-08

4000 3497.42 3630 3173.91 9.46E-08

5000 4371.78 4345 3799.07 1.67E-07

6000 5246.13 5120 4476.70 2.25E-07

3.55 0.4 9949 100 60 5 6.22

0 0.00 3350 2690.80 -6.28E-07

7.41E-07 2.54E-06 0.29 1.05E-06

5000 4016.11 7050 5662.72 -3.84E-07

10000 8032.23 10720 8610.55 -1.35E-07

14000 11245.12 13360 10731.05 1.20E-07

19000 15261.23 17350 13935.91 3.09E-07

24000 19277.34 20800 16707.03 5.99E-07

3.55 0.49 260 40 20 5 5.16

0 0.00 41 39.73 -1.66E-08

6.81E-07 4.57E-06 0.15 8.01E-07

75 72.69 103 99.82 -1.13E-08

150 145.37 168 162.82 -7.27E-09

300 290.74 297 287.83 1.21E-09

375 363.43 357 345.98 7.27E-09

450 436.11 423 409.95 1.09E-08

3.55 0.49 1641 60 40 5 5.28

0 0.00 353 334.34 -9.04E-08

6.69E-07 2.98E-06 0.22 8.62E-07

500 473.57 785 743.50 -7.30E-08

1000 947.14 1185 1122.36 -4.74E-08

2000 1894.27 1932 1829.87 1.74E-08

2500 2367.84 2341 2217.24 4.07E-08

3000 2841.41 2710 2566.74 7.43E-08

3.55 0.49 6735 80 40 5 5.72

0 0.00 1480 1294.05 -3.79E-07

6.21E-07 3.21E-06 0.19 7.70E-07

3000 2623.07 3890 3401.24 -2.28E-07

6000 5246.13 6340 5543.41 -8.71E-08

10000 8743.55 9540 8341.35 1.18E-07

13000 11366.62 11980 10474.78 2.61E-07

16000 13989.68 14430 12616.95 4.02E-07

3.55 0.49 23325 100 60 5 6.22 0 0.00 5660 4546.24 -1.06E-06 4.74E-07 2.54E-06 0.19 5.83E-07

388

12000 9638.67 15080 12112.60 -5.77E-07

24000 19277.34 24650 19799.44 -1.22E-07

36000 28916.01 34380 27614.79 3.03E-07

48000 38554.68 44650 35863.89 6.28E-07

60000 48193.35 54520 43791.69 1.03E-06


GlyK CO2 ldg PCO2* T P GasDry Gaswet PCO2in, dry PCO2in, wet PCO2o

ut, dry PCO2out,

wet CO2 flux KG kg

KG/kg

kg'

m mol CO2/mol

alk Pa C psig

Std L/min

Std L/min

Pa Pa Pa Pa mol/s m2 mol/s Pa

m2 mol/s Pa m2

mol/s Pa m2

3.55 0.53 5361 40 20 5 5.16

0 0.00 248 240.35 -1.00E-07

1.84E-07 4.57E-06 0.04 1.92E-07

1500 1453.71 1670 1618.46 -6.86E-08

3000 2907.42 3117 3020.81 -4.72E-08

7000 6783.98 6893 6680.29 4.32E-08

8500 8237.70 8390 8131.09 4.44E-08

10000 9691.41 9820 9516.96 7.27E-08

3.55 0.53 20079 60 40 5 5.28

0 0.00 1380 1307.05 -3.53E-07

1.51E-07 2.98E-06 0.05 1.59E-07

5000 4735.68 5730 5427.09 -1.87E-07

10000 9471.35 10480 9925.98 -1.23E-07

30000 28414.06 29500 27940.50 1.28E-07

35000 33149.74 34250 32439.39 1.92E-07

40000 37885.42 39050 36985.64 2.43E-07

3.55 0.53 47888 80 60 5 5.51

0 0.00 4190 3804.50 -7.86E-07

1.46E-07 2.28E-06 0.06 1.56E-07

20000 18159.90 21800 19794.29 -3.38E-07

40000 36319.80 40390 36673.92 -7.32E-08

60000 54479.71 59210 53762.39 1.48E-07

67500 61289.67 66800 60654.07 1.31E-07

75000 68099.63 73800 67010.04 2.25E-07

389

Table B-12: Detailed Wetted Wall Column Data for 6 m GlyK (part 1)

GlyK CO2 ldg PCO2* T P GasDry Gaswet PCO2in,

dry PCO2in, wet PCO2out, dry PCO2out, wet CO2 flux KG kg

KG/kg

kg'

m mol CO2/mol

alk Pa C psig

Std L/min

Std L/min

Pa Pa Pa Pa mol/s m2 mol/s Pa m2

mol/s Pa m2

mol/s Pa m2

6 0.35 18 40 20 5 5.16

0 0.00 7.15 6.93 -2.89E-09

2.10E-06 4.57E-06 0.46 3.88E-06

5 4.85 9.45 9.16 -1.80E-09

10 9.69 14.75 14.29 -1.92E-09

30 29.07 25.7 24.91 1.74E-09

35 33.92 29.1 28.20 2.38E-09

40 38.77 30.6 29.66 3.79E-09

6 0.35 95 60 20 5 5.45

0 0.00 27.9 25.57 -1.13E-08

1.48E-06 4.83E-06 0.31 2.14E-06

30 27.50 54.8 50.23 -1.00E-08

60 55.00 72.1 66.09 -4.88E-09

120 110.00 112.2 102.85 3.15E-09

150 137.50 136 124.67 5.65E-09

180 165.00 160.1 146.76 8.03E-09

6 0.35 536 80 40 5 5.72

0 0.00 177 154.76 -4.53E-08

1.14E-06 3.21E-06 0.35 1.76E-06

200 174.87 353 308.65 -3.92E-08

400 349.74 476 416.19 -1.95E-08

800 699.48 735 642.65 1.66E-08

1000 874.36 877 766.81 3.15E-08

1200 1049.23 1007 880.48 4.94E-08

6 0.35 2549 100 40 5 6.84

0 0.00 995 727.62 -2.55E-07

1.33E-06 3.76E-06 0.35 2.05E-06

1000 731.27 1904 1392.35 -2.32E-07

2000 1462.55 2480 1813.56 -1.23E-07

4500 3290.74 4185 3060.38 8.07E-08

5500 4022.01 4820 3524.74 1.74E-07

6500 4753.29 5560 4065.89 2.41E-07

6 0.4 100 40 20 5 5.16

0 0.00 24.9 24.13 -1.01E-08

9.77E-07 4.57E-06 0.21 1.24E-06

25 24.23 37.8 36.63 -5.17E-09

50 48.46 60.2 58.34 -4.12E-09

150 145.37 139.8 135.49 4.12E-09

175 169.60 161.8 156.81 5.33E-09

200 193.83 178.6 173.09 8.64E-09

6 0.4 620 60 40 5 5.28

0 0.00 129 122.18 -3.30E-08

7.16E-07 2.98E-06 0.24 9.42E-07

200 189.43 323 305.92 -3.15E-08

400 378.85 472 447.05 -1.84E-08

800 757.71 772 731.19 7.17E-09

1000 947.14 916 867.58 2.15E-08

1200 1136.56 1065 1008.70 3.46E-08

390

Table B-13: Detailed Wetted Wall Column Data for 6 m GlyK (part 2)

GlyK CO2 ldg PCO2* T P GasDry Gaswet PCO2in, dry PCO2in, wet PCO2out,

dry PCO2out, wet CO2 flux KG kg KG/kg kg'

m mol

CO2/mol alk Pa C psig

Std L/min

Std L/min


mol/s Pa m2

mol/s Pa m2

6 0.4 3243 80 40 5 5.72

0 0.00 728 636.53 -1.86E-07

6.93E-07 3.21E-06 0.22 8.84E-07

1000 874.36 1619 1415.58 -1.59E-07

2000 1748.71 2386 2086.21 -9.89E-08

4000 3497.42 3930 3436.22 1.79E-08

5000 4371.78 4730 4135.70 6.91E-08

6000 5246.13 5504 4812.45 1.27E-07

6 0.4 13529 100 60 5 6.22

0 0.00 3970 3188.79 -7.44E-07

6.32E-07 2.54E-06 0.25 8.40E-07

5000 4016.11 7785 6253.09 -5.22E-07

10000 8032.23 11680 9381.64 -3.15E-07

20000 16064.45 19276 15482.92 1.36E-07

25000 20080.56 23040 18506.25 3.67E-07

30000 24096.68 26870 21582.59 5.86E-07

6 0.45 225 40 20 5 5.16

0 0.00 21 20.35 -8.48E-09

5.12E-07 4.57E-06 0.11 5.77E-07

75 72.69 97 94.01 -8.88E-09

150 145.37 163 157.97 -5.25E-09

350 339.20 338 327.57 4.84E-09

425 411.88 399 386.69 1.05E-08

500 484.57 469 454.53 1.25E-08

6 0.45 1530 60 40 5 5.28

0 0.00 318 301.19 -8.14E-08

5.78E-07 2.98E-06 0.19 7.16E-07

750 710.35 917 868.52 -4.28E-08

1500 1420.70 1529 1448.17 -7.43E-09

2500 2367.84 2300 2178.41 5.12E-08

3250 3078.19 2935 2779.84 8.07E-08

4000 3788.54 3558 3369.91 1.13E-07

6 0.45 6619 80 40 5 5.72

0 0.00 1330 1162.89 -3.41E-07

5.79E-07 3.21E-06 0.18 7.06E-07

3000 2623.07 3850 3366.27 -2.18E-07

6000 5246.13 6271 5483.08 -6.94E-08

10000 8743.55 9580 8376.32 1.08E-07

13000 11366.62 12045 10531.61 2.45E-07

16000 13989.68 14462 12644.93 3.94E-07

6 0.45 23675 100 60 5 6.22

0 0.00 5385 4325.35 -1.01E-06

4.34E-07 2.54E-06 0.17 5.23E-07

10000 8032.23 13050 10482.05 -5.71E-07

20000 16064.45 21430 17213.06 -2.68E-07

40000 32128.90 38020 30538.52 3.71E-07

50000 40161.13 46560 37398.04 6.44E-07

60000 48193.35 55020 44193.31 9.33E-07

391

Table B-14: Detailed Wetted Wall Column Data for 6 m SarK (part 1)

SarK CO2 ldg PCO2* T P GasDry Gaswet PCO2in, dry PCO2in,

wet PCO2out,

dry PCO2out,

wet CO2 flux KG kg

KG/kg

kg'

m mol


Std L/min

Std L/min


mol/s Pa m2

mol/s Pa m2

6 0.2 102 80 20 5 6.23

0 0.00 68.7 55.09 -2.77E-08

3.22E-06 5.45E-06 0.59 7.89E-06

30 24.06 74.5 59.74 -1.79E-08

60 48.12 88 70.57 -1.13E-08

150 120.29 131.6 105.53 7.42E-09

180 144.35 154.3 123.74 1.04E-08

210 168.41 179 143.55 1.25E-08

6 0.2 690 100 20 5 8.67

0 0.00 681 392.52 -2.75E-07

3.96E-06 7.26E-06 0.55 8.72E-06

250 144.10 695 400.59 -1.80E-07

500 288.19 736 424.22 -9.52E-08

1500 864.58 1282 738.93 8.79E-08

1750 1008.68 1531 882.45 8.83E-08

2000 1152.78 1647 949.31 1.42E-07

6 0.29 115 60 20 5 5.45

0 0.00 65 59.58 -2.62E-08

2.77E-06 4.83E-06 0.57 6.48E-06 50 45.83 77 70.58 -1.09E-08

150 137.50 141 129.25 3.63E-09

175 160.42 166 152.17 3.63E-09

6 0.29 1136 80 20 5 6.23

0 0.00 596 477.95 -2.40E-07

2.50E-06 5.45E-06 0.46 4.62E-06

250 200.48 701 562.16 -1.82E-07

500 400.97 809 648.77 -1.25E-07

1500 1202.91 1461 1171.63 1.57E-08

1750 1403.39 1642 1316.78 4.36E-08

2000 1603.88 1767 1417.02 9.40E-08

6 0.29 2266 100 40 5 6.84

0 0.00 1526 1115.93 -3.91E-07

2.16E-06 3.76E-06 0.58 5.09E-06

750 548.46 1823 1333.11 -2.75E-07

1500 1096.91 2052 1500.58 -1.41E-07

4500 3290.74 3835 2804.44 1.70E-07

6000 4387.65 4846 3543.76 2.96E-07

12000 8775.30 7832 5727.34 1.07E-06

6 0.35 19 40 20 5 5.16

0 0.00 15.5 15.02 -6.26E-09

1.67E-06 4.57E-06 0.37 2.64E-06

40 38.77 29.3 28.40 4.32E-09

80 77.53 50.3 48.75 1.20E-08

120 116.30 86.7 84.02 1.34E-08

150 145.37 107.1 103.79 1.73E-08

180 174.45 131 126.96 1.98E-08

392


SarK CO2 ldg PCO2* T P GasDry Gaswet PCO2in, dry PCO2in, wet PCO2out, dry PCO2out, wet CO2 flux KG kg

KG/kg

kg'

m mol

CO2/mol alk

Pa C psig Std

L/min Std

L/min Pa Pa Pa Pa mol/s m2

mol/s Pa m2

mol/s Pa m2

mol/s Pa m2

6 0.35 164 60 20 5 5.45

0 0.00 76.5 70.12 -3.09E-08

2.16E-06 4.83E-06 0.45 3.91E-06

50 45.83 93 85.25 -1.73E-08

100 91.67 130 119.17 -1.21E-08

200 183.33 192 176.00 3.23E-09

250 229.17 225 206.25 1.01E-08

300 275.00 253 231.92 1.90E-08

6 0.35 2330 80 40 5 5.72

0 0.00 1058 925.07 -2.71E-07

1.36E-06 3.21E-06 0.42 2.36E-06

2000 1748.71 2190 1914.84 -4.87E-08

4000 3497.42 3393 2966.69 1.55E-07

5000 4371.78 4193 3666.17 2.07E-07

6000 5246.13 4802 4198.65 3.07E-07

6 0.35 3947 100 40 5 6.84

0 0.00 2031 1485.22 -5.20E-07

1.55E-06 3.76E-06 0.41 2.65E-06

2000 1462.55 3075 2248.67 -2.75E-07

4000 2925.10 4460 3261.49 -1.18E-07

8000 5850.20 7180 5250.55 2.10E-07

10000 7312.75 8450 6179.27 3.97E-07

12000 8775.30 9510 6954.42 6.38E-07

6 0.43 201 40 20 5 5.16

0 0.00 66.7 64.64 -2.69E-08

1.39E-06 4.57E-06 0.30 1.99E-06

25 24.23 76.7 74.33 -2.09E-08

50 48.46 86.3 83.64 -1.47E-08

250 242.29 232 224.84 7.27E-09

275 266.51 255 247.13 8.07E-09

300 290.74 280 271.36 8.07E-09

6 0.43 826 60 20 5 5.45

0 0.00 176 161.33 -7.10E-08

1.01E-06 4.83E-06 0.21 1.27E-06

500 458.33 585 536.25 -3.43E-08

2000 1833.33 1797 1647.25 8.19E-08

2250 2062.50 1985 1819.58 1.07E-07

2500 2291.67 2146 1967.17 1.43E-07

6 0.43 7096 80 40 5 5.72

0 0.00 2837 2480.55 -7.27E-07

1.12E-06 3.21E-06 0.35 1.72E-06

4000 3497.42 4982 4356.04 -2.51E-07

10000 8743.55 9335 8162.11 1.70E-07

12000 10492.26 10770 9416.81 3.15E-07

14000 12240.97 12260 10719.60 4.46E-07

6 0.43 16699 100 40 5 6.84

0 0.00 5730 4190.20 -1.47E-06

8.56E-07 3.76E-06 0.23 1.11E-06

4000 2925.10 7680 5616.19 -9.43E-07

8000 5850.20 10720 7839.26 -6.97E-07

24000 17550.59 23510 17192.27 1.26E-07

28000 20475.69 27030 19766.35 2.48E-07

393

30000 21938.24 28660 20958.33 3.43E-07


SarK CO2 ldg PCO2* Temp Pressure GasDry Gaswet PCO2in, dry PCO2in, wet PCO2out, dry PCO2out, wet CO2 flux KG kg

KG/kg

kg'

m mol


Std L/min

Std L/min


m2 mol/s Pa m2

mol/s Pa m2

6 0.48 610 40 20 5 5.16

0 0.00 112 108.54 -4.52E-08

8.36E-07 4.57E-06 0.18 1.02E-06

250 242.29 327 316.91 -3.11E-08

500 484.57 519 502.98 -7.67E-09

1500 1453.71 1343 1301.56 6.34E-08

1750 1696.00 1547 1499.26 8.19E-08

2000 1938.28 1751 1696.97 1.01E-07

6 0.48 2430 60 20 5 5.45

0 0.00 422 386.83 -1.70E-07

7.41E-07 4.83E-06 0.15 8.75E-07

1000 916.67 1228 1125.67 -9.19E-08

2000 1833.33 2116 1939.67 -4.68E-08

8000 7333.33 7165 6567.91 3.37E-07

9000 8249.99 8072 7399.33 3.74E-07

10000 9166.66 8820 8084.99 4.76E-07

6 0.48 12260 80 40 5 5.72

0 0.00 4413 3858.53 -1.13E-06

8.04E-07 3.21E-06 0.25 1.07E-06

4000 3497.42 5720 5001.31 -4.41E-07

8000 6994.84 8821 7712.69 -2.10E-07

22000 19235.82 20210 17670.72 4.58E-07

26000 22733.24 23180 20267.56 7.22E-07

30000 26230.66 26240 22943.08 9.63E-07

6 0.48 31295 100 60 5 6.22

0 0.00 12180 9783.25 -2.28E-06

4.41E-07 2.54E-06 0.17 5.33E-07

10000 8032.23 15090 12120.63 -9.54E-07

20000 16064.45 23080 18538.38 -5.77E-07

45000 36145.02 44250 35542.60 1.41E-07

50000 40161.13 47890 38466.33 3.95E-07

6 0.51 4477 40 20 5 5.16

0 0.00 412 399.29 -1.66E-07

3.03E-07 4.57E-06 0.07 3.25E-07

1000 969.14 1215 1177.51 -8.68E-08

2000 1938.28 2118 2052.64 -4.76E-08

6000 5814.84 5880 5698.55 4.84E-08

7000 6783.98 6855 6643.46 5.85E-08

8000 7753.13 7781 7540.88 8.84E-08

6 0.51 17877 60 60 5 5.2

0 0.00 6995 6724.22 -1.31E-06

2.45E-07 2.16E-06 0.11 2.77E-07

5000 4806.45 7030 6757.86 -3.80E-07

10000 9612.89 10680 10266.57 -1.27E-07

40000 38451.57 37040 35606.16 5.55E-07

45000 43258.02 41710 40095.38 6.17E-07

50000 48064.47 46800 44988.34 6.00E-07

394

Table B-17: Detailed Wetted Wall Column Data for 3 m TauK/5 m HomotauK (part 1)

TauK/ Homotau

K CO2 ldg PCO2* T P GasDry Gaswet PCO2in, dry PCO2in, wet PCO2out, dry PCO2out, wet CO2 flux KG kg KG/kg kg'

m mol

CO2/mol alk

Pa C psig Std

L/min Std


mol/s Pa m2

mol/s Pa m2

mol/s Pa m2

(3 / 5) 0.26 9.8 40 20 5 5.16

0.0 0.0 5.3 5.1 -2.12E-09

3.11E-06 4.57E-06 0.680 9.70E-06

8.4 8.1 9.1 8.8 -2.90E-10

18.4 17.8 13.2 12.7 2.12E-09

34.9 33.8 23.2 22.5 4.73E-09

93.0 90.2 50.0 48.4 1.74E-08

125.8 121.9 64.3 62.4 2.48E-08

(3 / 5) 0.26 61 60 20 5 5.45

0.0 0.0 31.8 29.2 -1.28E-08

2.57E-06 4.83E-06 0.532 5.50E-06

32.5 29.8 46.4 42.5 -5.59E-09

61.5 56.3 63.6 58.3 -8.68E-10

87.8 80.5 75.1 68.8 5.11E-09

121.5 111.4 95.2 87.3 1.06E-08

182.7 167.5 133.5 122.3 1.99E-08

(3 / 5) 0.26 389 80 40 5 5.72

0.0 0.0 206.6 180.7 -5.29E-08

1.59E-06 3.21E-06 0.494 3.13E-06

195.7 171.1 280.9 245.6 -2.18E-08

367.6 321.4 383.4 335.3 -4.06E-09

578.8 506.0 530.1 463.5 1.25E-08

742.4 649.1 623.2 544.9 3.05E-08

911.3 796.8 716.0 626.0 5.00E-08

(3 / 5) 0.26 2051 100 20 5 5.16

0.0 0.0 972.8 711.4 -2.96E-07

1.42E-06 3.76E-06 0.377 2.28E-06

1048.2 766.5 1613.7 1180.1 -1.72E-07

2066.2 1510.9 2254.7 1648.8 -5.74E-08

4102.2 2999.8 3725.1 2724.1 1.15E-07

5384.1 3937.3 4516.9 3303.1 2.64E-07

6741.5 4929.9 5421.8 3964.8 4.02E-07

(3 / 5) 0.3 27 40 20 5 5.16

0.0 0.0 12.9 12.5 -5.21E-09

2.39E-06 4.57E-06 0.522 5.00E-06

14.8 14.4 21.5 20.9 -2.70E-09

35.9 34.8 30.9 29.9 2.03E-09

48.6 47.1 38.7 37.6 3.96E-09

59.6 57.7 45.2 43.8 5.79E-09

70.1 67.9 53.6 51.9 6.66E-09

(3 / 5) 0.3 204 60 20 5 5.45

0.0 0.0 72.2 66.2 -2.91E-08

1.53E-06 4.83E-06 0.318 2.25E-06

67.4 61.8 109.1 100.0 -1.68E-08

119.4 109.4 145.4 133.3 -1.05E-08

292.8 268.4 270.8 248.2 8.87E-09

345.1 316.4 310.2 284.4 1.41E-08

403.0 369.4 351.8 322.5 2.06E-08

395


TauK/ HomotauK

CO2 ldg PCO2* Temp Pressure GasDry Gaswet PCO2in,

dry PCO2in, wet PCO2out, dry PCO2out, wet CO2 flux KG kg

KG/kg

kg'

m mol


Std L/min

Std L/min


mol/s Pa m2

mol/s Pa m2

(3 / 5) 0.3 1351 80 40 5 5.72

0.0 0.0 512.8 448.3 -1.31E-07

1.10E-06

3.21E-06

0.343 1.68E-

06

678.7 593.4 953.9 834.1 -7.05E-08

1338.5 1170.3 1364.9 1193.4 -6.76E-09

3382.0 2957.1 2790.1 2439.5 1.52E-07

4064.5 3553.8 3280.2 2868.1 2.01E-07

4694.1 4104.3 3725.1 3257.1 2.48E-07

(3 / 5) 0.3 6200 100 40 5 6.84

0.0 0.0 2111.4 1544.0 -5.41E-07

9.63E-07

3.76E-06

0.256 1.29E-

06

1998.3 1461.3 3544.2 2591.8 -3.96E-07

4034.3 2950.2 5052.3 3694.6 -2.61E-07

9350.6 6837.8 9048.9 6617.3 7.73E-08

11311.2 8271.6 10632.5 7775.3 1.74E-07

13196.4 9650.2 12140.7 8878.2 2.70E-07

(3 / 5) 0.365 114 40 20 5 5.16

0.0 0.0 31.6 30.6 -1.27E-08

1.09E-06

4.57E-06

0.237 1.42E-

06

11.2 10.9 34.9 33.8 -9.56E-09

44.7 43.3 59.6 57.7 -5.99E-09

164.3 159.2 150.0 145.3 5.79E-09

226.0 219.1 201.6 195.4 9.85E-09

282.2 273.5 247.1 239.5 1.42E-08

(3 / 5) 0.365 696 60 20 5 5.45

0.0 0.0 162.9 149.3 -6.57E-08

9.22E-07

4.83E-06

0.191 1.14E-

06

246.6 226.0 327.9 300.6 -3.28E-08

457.1 419.0 509.7 467.2 -2.12E-08

1272.7 1166.6 1162.7 1065.8 4.44E-08

1466.4 1344.2 1332.5 1221.4 5.40E-08

1653.0 1515.2 1497.5 1372.7 6.27E-08

(3 / 5) 0.365 4958 80 40 5 5.72

0.0 0.0 1150.0 1005.5 -2.95E-07

6.12E-07

3.21E-06

0.190 7.56E-

07

1979.5 1730.7 2658.1 2324.1 -1.74E-07

4090.9 3576.9 4317.1 3774.7 -5.79E-08

13252.9 11587.8 11782.5 10302.1 3.77E-07

15175.8 13269.1 13366.0 11686.7 4.63E-07

17023.3 14884.4 14949.6 13071.3 5.31E-07

(3 / 5) 0.365 21232 100 40 5 6.84

0.0 0.0 3921.2 2867.5 -1.00E-06

4.46E-07

3.76E-06

0.119 5.06E-

07

8634.2 6314.0 10934.1 7995.9 -5.89E-07

16665.1 12186.8 17683.1 12931.2 -2.61E-07

44603.7 32617.6 42756.3 31266.6 4.73E-07

51842.9 37911.4 49165.9 35953.8 6.86E-07

59383.7 43425.8 55839.5 40834.0 9.08E-07

396


TauK/ HomotauK

CO2 ldg PCO2* Temp Pressure GasDry Gaswet PCO2in, dry PCO2in, wet PCO2out,

dry PCO2out, wet CO2 flux KG kg

KG/kg

kg'

m mol

CO2/mol alk

Pa C psig Std

L/min Std


mol/s Pa m2

mol/s Pa m2

mol/s Pa m2

(3 / 5) 0.42 21232 40 20 5 5.16

0.0 0.0 71.8 69.5 -2.90E-08

5.94E-07 4.57E-06 0.130 6.83E-

07

138.7 134.4 181.8 176.2 -1.74E-08

275.1 266.6 287.0 278.2 -4.83E-09

487.9 472.9 478.4 463.6 3.86E-09

767.8 744.1 724.7 702.4 1.74E-08

911.3 883.2 858.7 832.2 2.12E-08

(3 / 5) 0.42 3112 60 20 5 5.45

0.0 0.0 406.6 372.7 -1.64E-07

4.77E-07 4.83E-06 0.099 5.29E-

07

1078.7 988.8 1294.0 1186.1 -8.68E-08

2131.1 1953.5 2226.8 2041.2 -3.86E-08

4312.5 3953.1 4195.3 3845.6 4.73E-08

5264.4 4825.7 5025.2 4606.4 9.65E-08

6388.6 5856.2 6149.4 5636.9 9.65E-08

(3 / 5) 0.42 20299 80 40 5 5.72

0.0 0.0 2299.9 2011.0 -5.89E-07

2.43E-07 3.21E-06 0.076 2.63E-

07

6070.3 5307.6 7390.0 6461.5 -3.38E-07

11235.8 9824.1 11763.6 10285.6 -1.35E-07

32161.5 28120.5 31218.9 27296.4 2.41E-07

42266.1 36955.6 40833.4 35702.9 3.67E-07

52295.3 45724.7 50146.2 43845.6 5.50E-07

(3 / 5) 0.51 30982 40 20 5 5.16

0.0 0.0 358.8 347.7 -1.45E-07

3.74E-08 4.57E-06 0.008 3.77E-

08

1243.7 1205.4 1530.8 1483.5 -1.16E-07

6673.2 6467.3 6864.5 6652.7 -7.72E-08

13035.4 12633.2 13155.0 12749.1 -4.83E-08

19373.8 18775.9 19445.5 18845.4 -2.90E-08

41737.3 40449.3 41689.4 40402.9 1.93E-08

397

Table B-20: Detailed Wetted Wall Column Data for 5 m TauK

TauK CO2 ldg PCO2* Temp Pressure GasDry Gaswet PCO2in, dry PCO2in, wet PCO2out, dry PCO2out, wet CO2 flux KG kg KG/kg

kg'

m mol


Std L/min

Std L/min


mol/s Pa m2

mol/s Pa m2

5 0.2 32 40 20 5 5.16

0.00 0.00 12.6 12.21 -5.09E-09

1.99E-06 4.57E-06 0.44 3.53E-06

2.87 2.78 15.5 15.02 -5.10E-09

5.98 5.80 15.6 15.12 -3.88E-09

42.81 41.49 38.1 36.92 1.90E-09

72.71 70.47 58.2 56.40 5.86E-09

87.78 85.07 69.8 67.65 7.26E-09

5 0.2 234 60 20 5 5.45

0.00 0.00 83 76.08 -3.35E-08

1.48E-06 4.83E-06 0.31 2.13E-06

33.96 31.13 92 84.33 -2.34E-08

116.72 106.99 150 137.50 -1.34E-08

295.87 271.21 279 255.75 6.81E-09

375.99 344.66 344 315.33 1.29E-08

464.49 425.78 407 373.08 2.32E-08

5 0.2 1259 80 40 5 5.72

0.00 0.00 492 430.18 -1.26E-07

1.16E-06 3.21E-06 0.36 1.82E-06

490.15 428.57 819 716.10 -8.42E-08

904.89 791.20 1051 918.95 -3.74E-08

2752.39 2406.56 2330 2037.25 1.08E-07

6899.82 6032.89 5087 4447.85 4.64E-07

19869.97 17373.41 13853 12112.44 1.54E-06

5 0.2 7730 100 40 5 6.84

0.00 0.00 4245 3104.26 -1.09E-06

1.47E-06 3.76E-06 0.39 2.40E-06

11424.29 8354.29 10390 7597.94 2.65E-07

22019.09 16102.01 17930 13111.76 1.05E-06

27033.72 19769.07 21375 15631.00 1.45E-06

32123.75 23491.28 25145 18387.90 1.79E-06

398

Table B-21: Detailed Wetted Wall Column Data for 6.5 m β-AlaK (part 1)

GlyK CO2 ldg PCO2* Temp Pressure GasDry Gaswet PCO2in, dry PCO2in, wet PCO2out, dry PCO2out, wet CO2 flux KG kg

KG/kg

kg'

m mol CO2/mol

alk Pa C psig

Std L/min

Std L/min


m2 mol/s Pa

m2 mol/s Pa

m2

6.5 0.32 9 40 20 5 5.16

0.0 0.0 2.9 2.8 -1.2E-09

1.79E-10 4.57E-10 0.390 2.93E-10

8.8 8.6 10.3 10.0 -5.8E-10

16.3 15.8 14.1 13.7 8.69E-10

54.3 52.6 38.3 37.1 6.47E-09

67.2 65.1 46.4 45.0 8.4E-09

125.6 121.7 85.6 83.0 1.61E-08

6.5 0.32 36 60 20 5 5.45

0.0 0.0 14.4 13.2 -5.8E-09

1.92E-10 4.83E-10 0.398 3.19E-10

13.4 12.3 22.7 20.8 -3.8E-09

23.9 21.9 29.9 27.4 -2.4E-09

57.2 52.4 49.5 45.4 3.09E-09

82.5 75.6 67.2 61.6 6.18E-09

162.4 148.9 119.4 109.4 1.74E-08

6.5 0.32 201 80 40 5 5.72

0.0 0.0 96.5 84.4 -2.5E-08

1.57E-10 3.21E-10 0.488 3.06E-10

89.4 78.1 145.5 127.3 -1.4E-08

165.1 144.4 188.1 164.5 -5.9E-09

274.5 240.0 259.0 226.5 3.96E-09

359.7 314.5 308.4 269.7 1.31E-08

432.1 377.8 344.6 301.3 2.24E-08

6.5 0.32 867 100 40 5 6.84

0.0 0.0 455.8 333.3 -1.2E-07

1.65E-10 3.76E-10 0.437 2.92E-10

255.3 186.7 588.6 430.4 -8.5E-08

490.5 358.7 763.1 558.1 -7E-08

1401.1 1024.6 1300.4 951.0 2.58E-08

1636.0 1196.3 1455.7 1064.6 4.61E-08

1847.9 1351.3 1623.5 1187.2 5.74E-08

6.5 0.385 17 40 20 5 5.16

0.0 0.0 6.0 5.8 -2.41E-09

1.60E-10 4.57E-10 0.350 2.47E-10

13.9 13.4 15.1 14.6 -4.83E-10

24.2 23.4 22.0 21.3 8.69E-10

56.7 54.9 44.2 42.9 5.02E-09

67.9 65.8 52.1 50.5 6.37E-09

399


β-AlaK CO2 ldg PCO2* Temp Pressure GasDry Gaswet PCO2in, dry PCO2in, wet PCO2out, dry PCO2out, wet CO2 flux KG kg

KG/kg

kg'

m mol CO2/mol

alk Pa C psig

Std L/min

Std L/min


m2 mol/s Pa

m2 mol/s Pa

m2

6.5 0.385 102 60 20 5 5.45

0.0 0.0 28.5 26.1 -1.1E-08

1.25E-10 4.83E-10 0.258 1.68E-10

30.1 27.6 50.0 45.8 -8E-09

56.7 52.0 69.4 63.6 -5.1E-09

189.2 173.4 169.3 155.2 8.01E-09

213.4 195.6 187.8 172.1 1.03E-08

239.2 219.3 208.8 191.4 1.23E-08

6.5 0.385 575 80 40 5 5.72

0.0 0.0 226.2 197.8 -5.8E-08

1.18E-10 3.21E-10 0.368 1.87E-10

226.2 197.8 365.7 319.8 -3.6E-08

429.8 375.8 497.7 435.2 -1.7E-08

712.6 623.1 693.8 606.6 4.83E-09

806.9 705.5 757.8 662.6 1.25E-08

912.4 797.8 833.3 728.6 2.03E-08

6.5 0.385 2708 100 40 5 6.84

0.0 0.0 1104.7 807.9 -2.8E-07

1.24E-10 3.76E-10 0.329 1.84E-10

1036.9 758.2 1840.0 1345.5 -2.1E-07

2047.3 1497.2 2499.8 1828.0 -1.2E-07

4034.3 2950.2 3977.8 2908.8 1.45E-08

5078.7 3713.9 4679.1 3421.7 1.02E-07

6134.4 4486.0 5387.9 3940.0 1.91E-07

6.5 0.45 81 40 20 5 5.16

0.0 0.0 18.7 18.1 -7.5E-09

8.56E-11 4.57E-10 0.187 1.05E-10

31.6 30.6 39.7 38.5 -3.3E-09

55.5 53.8 57.9 56.1 -9.7E-10

140.9 136.5 129.6 125.6 4.54E-09

163.6 158.6 149.0 144.4 5.89E-09

191.3 185.4 172.2 166.9 7.72E-09

6.5 0.45 471 60 20 5 5.45

0.0 0.0 91.6 84.0 -3.7E-08

8.13E-11 4.83E-10 0.168 9.77E-11

150.2 137.7 209.0 191.6 -2.4E-08

289.6 265.5 322.9 296.0 -1.3E-08

649.6 595.5 627.6 575.3 8.88E-09

792.6 726.6 743.9 681.9 1.97E-08

925.9 848.7 858.9 787.3 2.7E-08

400


β-AlaK CO2 ldg PCO2* Temp Pressure GasDry Gaswet PCO2in, dry PCO2in, wet PCO2out, dry PCO2out, wet CO2 flux KG kg

KG/kg

kg'

m mol CO2/mol

alk Pa C psig

Std L/min

Std L/min


m2 mol/s Pa

m2 mol/s Pa

m2

6.5 0.45 2657 80 40 5 5.72

0.0 0.0 735.2 642.8 -1.9E-07

7.7E-11 3.21E-10 0.240 1.01E-10

818.2 715.4 1315.9 1150.5 -1.3E-07

1576.0 1378.0 1892.7 1654.9 -8.1E-08

4181.4 3656.0 3909.9 3418.6 6.95E-08

4965.6 4341.7 4516.9 3949.4 1.15E-07

5749.8 5027.4 5139.0 4493.4 1.56E-07

6.5 0.45 9799 100 40 5 6.84

0.0 0.0 2631.7 1924.5 -6.7E-07

7.25E-11 3.76E-10 0.193 8.98E-11

5697.1 4166.1 7054.4 5158.7 -3.5E-07

11088.7 8108.9 11465.8 8384.6 -9.7E-08

21645.8 15829.0 20024.6 14643.5 4.15E-07

26849.0 19634.0 24360.5 17814.2 6.37E-07

32089.8 23466.5 28658.8 20957.4 8.78E-07

6.5 0.5 516 40 20 5 5.16

0.0 0.0 56.4 54.7 -2.3E-08

4.14E-11 4.57E-10 0.090 4.55E-11

150.7 146.0 182.0 176.4 -1.3E-08

285.6 276.8 305.7 296.2 -8.1E-09

652.2 632.1 641.7 621.9 4.25E-09

787.4 763.1 762.5 739.0 1E-08

923.2 894.8 888.1 860.7 1.42E-08

6.5 0.5 2519 60 40 5 5.28

0.0 0.0 388.4 367.8 -9.9E-08

3.93E-11 2.98E-10 0.132 4.53E-11

803.1 760.6 1048.2 992.8 -6.3E-08

1549.6 1467.7 1674.1 1585.6 -3.2E-08

3597.0 3406.8 3453.7 3271.1 3.67E-08

4377.4 4146.0 4147.4 3928.2 5.89E-08

5135.3 4863.8 4818.6 4563.8 8.11E-08

6.5 0.5 9080 80 40 5 5.72

0.0 0.0 1417.7 1239.5 -3.6E-07

3.97E-11 3.21E-10 0.123 4.52E-11

3498.9 3059.3 4373.7 3824.1 -2.2E-07

6865.9 6003.2 7201.5 6296.6 -8.6E-08

20130.1 17600.9 18772.8 16414.1 3.48E-07

23335.0 20403.0 21751.4 19018.4 4.05E-07

26426.7 23106.3 24466.1 21392.0 5.02E-07

6.5 0.5 26093 100 40 5 6.84

0.0 0.0 4106.0 3002.6 -1.1E-06

3.82E-11 3.76E-10 0.102 4.25E-11

11835.3 8654.8 14135.2 10336.7 -5.9E-07

22656.3 16568.0 23561.2 17229.7 -2.3E-07

43582.0 31870.4 42790.2 31291.4 2.03E-07

54139.1 39590.5 52216.2 38184.4 4.92E-07

401

64394.5 47090.1 61604.4 45049.8 7.14E-07


β-AlaK CO2 ldg PCO2* Temp Pressure GasDry Gaswet PCO2in, dry PCO2in, wet PCO2out, dry PCO2out, wet CO2 flux KG kg KG/kg kg'

m mol CO2

/mol alk Pa C psig

Std L/min

Std L/min


m2 mol/s Pa

m2 mol/s Pa

m2

6.5 0.54 2282 40 20 5 5.16

0.0 0.0 122.0 118.2 -4.9E-08

1.85E-11 4.57E-10 0.040 1.93E-11

708.0 686.1 765.4 741.8 -2.3E-08

1380.1 1337.5 1416.0 1372.3 -1.4E-08

4171.3 4042.6 4087.6 3961.5 3.38E-08

4853.0 4703.2 4733.4 4587.3 4.83E-08

5498.8 5329.1 5379.2 5213.2 4.83E-08

6.5 0.54 8834 60 40 5 5.28

0.0 0.0 693.8 657.1 -1.8E-07

1.79E-11 2.98E-10 0.060 1.90E-11

3465.0 3281.8 3842.0 3638.9 -9.7E-08

6922.4 6556.5 6952.6 6585.1 -7.7E-09

19979.3 18923.1 19262.9 18244.6 1.83E-07

23221.8 21994.2 22354.7 21172.9 2.22E-07

26389.0 24993.9 25333.3 23994.0 2.7E-07

6.5 0.54 23113 80 40 5 5.72

0.0 0.0 2069.9 1809.9 -5.3E-07

2.08E-11 3.21E-10 0.065 2.22E-11

6175.9 5399.9 7495.5 6553.8 -3.4E-07

11567.6 10114.2 12321.6 10773.5 -1.9E-07

32794.9 28674.4 32380.1 28311.7 1.06E-07

37696.4 32960.0 36866.9 32234.8 2.12E-07

42937.2 37542.4 41919.2 36652.3 2.61E-07

402

Table B-25: Detailed Wetted Wall Column Data for 4.5 m SarNa (part 1)

SarNa CO2 ldg P*CO2 T P GasDry Gaswet PCO2in, dry PCO2in, wet PCO2out, dry PCO2out, wet CO2 flux KG kg

KG/kg

kg'

m mol

CO2/mol alk

Pa °C psig Std

L/min Std

L/min Pa Pa Pa Pa mol/s cm2

mol/s Pa cm2

mol/s Pa cm2

mol/s Pa cm2

4.5 0.243 6.5 40 20 5 5.16

0 0 3.83 3.71 -1.545E-09

4.59E-10 4.57E-10 1.00 /

3.35 3.25 5.02 4.87 -6.758E-10

5.50 5.33 6.22 6.03 -2.896E-10

12.68 12.29 8.37 8.11 1.738E-09

14.59 14.14 9.09 8.81 2.22E-09

17.70 17.15 9.57 9.27 3.282E-09

4.5 0.243 26 60 20 5 5.45

0 0 12.68 11.62 -5.116E-09

2.69E-10 4.83E-10 0.56 6.05E-10

7.89 7.24 17.46 16.01 -3.861E-09

14.35 13.16 20.57 18.86 -2.51E-09

39.23 35.96 33.72 30.91 2.22E-09

45.92 42.10 38.75 35.52 2.896E-09

52.14 47.80 40.66 37.27 4.634E-09

4.5 0.243 148 80 40 5 5.72

0 0 79.56 69.56 -2.037E-08

1.89E-10 3.21E-10 0.59 4.59E-10

46.00 40.22 104.06 90.99 -1.487E-08

87.85 76.81 127.06 111.10 -1.004E-08

247.34 216.26 210.39 183.95 9.461E-09

291.07 254.50 229.62 200.77 1.574E-08

331.04 289.45 255.63 223.51 1.931E-08

4.5 0.243 637 100 40 5 6.84

0 0 391.37 286.20 -1.002E-07

2.19E-10 3.762E-10 0.58 5.23E-10

198.32 145.03 545.20 398.69 -8.881E-08

466.02 340.79 635.69 464.86 -4.344E-08

1333.21 974.94 1118.30 817.78 5.503E-08

1559.43 1140.37 1229.53 899.12 8.447E-08

1729.10 1264.45 1340.75 980.46 9.943E-08

4.5 0.333 20 40 20 5 5.16

0 0 10.52 10.20 -4.248E-09

2.38E-10 4.57E-10 0.52 4.98E-10

9.33 9.04 13.87 13.44 -1.834E-09

13.39 12.98 15.31 14.84 -7.723E-10

40.90 39.64 31.57 30.60 3.765E-09

53.10 51.46 37.31 36.16 6.371E-09

64.82 62.82 47.12 45.66 7.144E-09

403



KG/kg

kg'

m mol

CO2/mol alk

Pa °C psig Std

L/min Std


mol/s Pa cm2

mol/s Pa cm2

mol/s Pa cm2

4.5 0.333 106 60 20 5 5.45

0 0 40.18 36.83 -1.622E-08

1.862E-10 4.83E-10 0.39 3.03E-10

30.62 28.06 59.56 54.59 -1.168E-08

57.16 52.40 78.45 71.91 -8.592E-09

160.01 146.68 141.84 130.02 7.337E-09

187.04 171.45 164.80 151.06 8.978E-09

212.39 194.69 179.15 164.22 1.342E-08

4.5 0.333 577 80 40 5 5.72

0 0 279.39 244.28 -7.153E-08

1.583E-10 3.21E-10 0.49 3.12E-10

113.11 98.90 338.58 296.04 -5.773E-08

218.31 190.88 401.55 351.09 -4.692E-08

701.67 613.51 684.70 598.67 4.344E-09

798.19 697.90 741.26 648.12 1.458E-08

4.5 0.333 2772 100

40 5 6.84

0 0 1129.99 826.33 -2.893E-07

1.364E-10 3.76E-10 0.36 2.14E-10

1379.96 1009.13 2235.84 1635.02 -2.191E-07

2786.32 2037.57 3143.38 2298.67 -9.142E-08

5583.95 4083.40 5058.74 3699.33 1.345E-07

6914.90 5056.69 5842.98 4272.82 2.745E-07

8219.46 6010.68 6781.81 4959.36 3.681E-07

4.5 0.398 53 40 20 5 5.16

0 0 19.37 18.78 -7.819E-09

1.506E-10 4.57E-10 0.33 2.25E-10

29.18 28.28 34.92 33.84 -2.317E-09

56.93 55.17 55.01 53.31 7.723E-10

109.78 106.40 93.04 90.17 6.758E-09

135.14 130.97 110.74 107.32 9.847E-09

159.77 154.84 128.92 124.94 1.245E-08

4.5 0.398 312 60 20 5 5.45

0 0 110.74 101.51 -4.47E-08

1.573E-10 4.83E-10 0.33 2.33E-10

109.55 100.42 176.04 161.37 -2.684E-08

213.11 195.35 242.05 221.88 -1.168E-08

409.00 374.92 385.32 353.21 9.557E-09

500.85 459.11 459.47 421.18 1.67E-08

4.5 0.398 1851 80 40 5 5.72

0 0 739.00 646.15 -1.892E-07

1.205E-10 3.21E-10 0.38 1.93E-10

542.94 474.72 1021.78 893.40 -1.226E-07

1063.25 929.66 1451.60 1269.22 -9.943E-08

2560.10 2238.43 2409.28 2106.57 3.861E-08

3114.34 2723.04 2756.16 2409.86 9.171E-08

3619.58 3164.80 3129.43 2736.23 1.255E-07

404


SarNa CO2 ldg P*CO2 T P GasDry Gaswet PCO2in, dry PCO2in, wet PCO2out, dry PCO2out, wet CO2 flux KG kg KG/kg kg'

m mol CO2/mol

alk Pa °C psig

Std L/min

Std L/min

Pa Pa Pa Pa mol/s cm2 mol/s Pa

cm2 mol/s Pa

cm2 mol/s Pa

cm2

4.5 0.398 6496 100 40 5 6.84

0 0 2439.44 1783.90 -6.246E-07

1.105E-10 3.76E-10 0.29 1.56E-10

3461.22 2531.10 4931.67 3606.41 -3.765E-07

6929.98 5067.72 7420.13 5426.16 -1.255E-07

13603.58 9947.95 12208.53 8927.79 3.572E-07

16733.00 12236.42 14772.40 10802.68 5.02E-07

19862.43 14524.89 16846.12 12319.14 7.723E-07

4.5 0.477 365 40 20 5 5.16

0 0 58.12 56.33 -2.346E-08

6.216E-11 4.57E-10 0.14 7.19E-11

152.36 147.66 181.54 175.94 -1.178E-08

281.28 272.60 287.02 278.16 -2.317E-09

621.16 601.99 586.24 568.14 1.409E-08

745.77 722.76 699.61 678.02 1.863E-08

884.97 857.66 813.22 788.12 2.896E-08

4.5 0.477 1977 60 20 5 5.45

0 0 325.29 298.18 -1.313E-07

7.032E-11 4.83E-10 0.15 8.23E-11

681.67 624.86 901.72 826.57 -8.881E-08

1360.95 1247.53 1468.58 1346.20 -4.344E-08

4135.46 3790.83 3836.48 3516.77 1.207E-07

4786.03 4387.20 4398.56 4032.01 1.564E-07

5443.79 4990.13 4965.42 4551.63 1.931E-07

4.5 0.477 6676 80 40 5 5.72

0 0 1674.05 1463.72 -4.286E-07

7.219E-11 3.21E-10 0.22 9.31E-11

2741.08 2396.67 3721.38 3253.81 -2.51E-07

5531.17 4836.20 5983.61 5231.80 -1.158E-07

10960.53 9583.40 10319.57 9022.97 1.641E-07

13562.10 11858.10 12393.28 10836.13 2.993E-07

19858.66 17363.52 17068.57 14923.99 7.144E-07

4.5 0.477 19478 100 40 5 6.84

0 0 4494.31 3286.57 -1.151E-06

6.195E-11 3.76E-10 0.16 7.42E-11

9037.63 6608.99 11714.61 8566.60 -6.854E-07

17030.86 12454.24 18425.91 13474.40 -3.572E-07

37918.84 27729.09 36335.28 26571.07 4.055E-07

45987.48 33629.48 42933.46 31396.16 7.819E-07

53980.71 39474.73 49380.84 36110.95 1.178E-06

4.5 0.514 1252 40 20 5 5.16

0 0 124.37 120.54 -5.02E-08

4.216E-11 4.57E-10 0.09 4.64E-11

552.51 535.46 626.66 607.32 -2.993E-08

1131.33 1096.42 1143.29 1108.01 -4.827E-09

1724.50 1671.29 1679.06 1627.24 1.834E-08

2150.25 2083.89 2073.71 2009.72 3.089E-08

405

2843.88 2756.12 2693.19 2610.08 6.082E-08

Table A-28: Detailed Wetted Wall Column Data for 4.5 m SarNa (part 4)


KG/kg

kg'

m mol CO2/mol

alk Pa °C psig

Std L/min

Std L/min


cm2 mol/s Pa

cm2 mol/s Pa

cm2

4.5 0.514 4611 60 20 5 5.45

0 0 562.08 515.24 -2.269E-07

5.005E-11 4.83E-10 0.10 5.58E-11

2901.28 2659.50 3068.71 2812.98 -6.758E-08

4240.70 3887.31 4336.37 3975.01 -3.861E-08

8330.71 7636.48 8019.78 7351.46 1.255E-07

10387.68 9522.03 9837.56 9017.76 2.22E-07

12444.65 11407.58 11607.51 10640.21 3.379E-07

4.5 0.514 1366

1 80 40 5 5.72

0 0 2345.18 2050.52 -6.005E-07

4.449E-11 3.21E-10 0.14 5.16E-11

6277.70 5488.94 7446.53 6510.91 -2.993E-07

11971.00 10466.90 12423.44 10862.50 -1.158E-07

23206.77 20290.96 22226.47 19433.83 2.51E-07

28598.43 25005.19 26713.23 23356.86 4.827E-07

34065.50 29785.35 31501.63 27543.62 6.564E-07

4.5 0.514 3530

9 100 40 5 6.84

0 0 5708.37 4174.39 -1.462E-06

4.047E-11 3.76 E-10 0.11 4.53E-11

23240.70 16995.34 25276.71 18484.22 -5.213E-07

55439.86 40541.76 54836.59 40100.61 1.545E-07

66260.88 48454.91 64262.58 46993.60 5.116E-07

71124.69 52011.69 68749.34 50274.65 6.082E-07

Table B-29: Detailed Wetted Wall Column Data for 6.5 m ProK

ProK CO2 ldg P*CO2 T P GasDry Gas PCO2in, dry PCO2in, wet PCO2out, dry PCO2out, wet CO2 flux KG kg KG/kg kg'

m mol CO2/mol alk Pa C psig Std L/min Std L/min Pa Pa Pa Pa mol/s cm2 mol/s Pa cm2 mol/s Pa

cm2

mol/s Pa cm2

6.5 0.45 19 40 20 5 5.16

0.0 0.0 7.2 7.0 -2.9E-09

1.92E-10 4.57E-10 0.42 3.31E-10

3.6 3.5 9.3 9.0 -2.3E-09

10.3 10.0 14.4 13.9 -1.6E-09

25.6 24.8 23.7 22.9 7.72E-10

28.7 27.8 24.6 23.9 1.64E-09

36.6 35.5 30.6 29.7 2.41E-09

6.5 0.45 226 60 20 5 5.45 0.0 0.0 72.2 66.2 -2.9E-08 1.43E-10 4.83E-10 0.296 2.03E-10

406

53.8 49.3 106.0 97.1 -2.1E-08

209.3 191.8 216.7 198.6 -3E-09

307.1 281.5 287.7 263.8 7.82E-09

402.1 368.6 358.1 328.2 1.78E-08

495.1 453.8 429.8 394.0 2.64E-08

6.5 0.45 1860 80 40 5 5.72

0.0 0.0 658.3 575.6 -1.7E-07

9.63E-11 3.21E-10 0.3 1.38E-10

673.4 588.8 1089.6 952.7 -1.1E-07

1247.2 1090.5 1450.8 1268.6 -5.2E-08

2551.8 2231.2 2363.3 2066.3 4.83E-08

3962.7 3464.8 3423.5 2993.4 1.38E-07

4743.2 4147.2 4075.8 3563.7 1.71E-07

6.5 0.483 213 40 20 5 5.16

0.0 0.0 35.9 34.8 -1.4E-08

7.22E-11 4.57E-10 0.158 8.57E-11

55.3 53.5 80.6 78.1 -1E-08

106.7 103.4 123.9 120.1 -7E-09

297.1 287.9 285.6 276.8 4.63E-09

350.6 339.8 329.8 319.7 8.4E-09

395.6 383.4 367.1 355.8 1.15E-08

6.5 0.483 1417 60 20 5 5.45

0.0 0.0 251.9 230.9 -1E-07

7.31E-11 4.83E-10 0.151 8.61E-11

535.8 491.1 676.9 620.5 -5.7E-08

1057.2 969.1 1129.2 1035.1 -2.9E-08

2076.1 1903.1 1985.2 1819.8 3.67E-08

2607.1 2389.8 2449.2 2245.1 6.37E-08

3116.5 2856.8 2882.1 2642.0 9.46E-08

6.5 0.483 1860 80 40 5 5.72

0.0 0.0 1202.8 1051.6 -3.1E-07

6.47E-11 3.21E-10 0.201 8.10E-11

2088.8 1826.4 2805.2 2452.7 -1.8E-07

4275.6 3738.4 4539.6 3969.2 -6.8E-08

7103.4 6210.9 6839.5 5980.1 6.76E-08

8498.5 7430.7 8046.0 7035.1 1.16E-07

9893.5 8650.4 9064.0 7925.2 2.12E-07

407

B.2.2 Piperazine blends

Table B-30: Detailed Wetted Wall Column Data for 6 m PZ/2 m HMDA (part 1)

HMDA PZ CO2 ldg P*CO2 Temp Pressure GasDry Gaswet PCO2in, dry PCO2in, wet PCO2out, dry PCO2out, wet CO2 flux KG kg

KG/kg

kg'

m mol CO2/mol

alk Pa °C psig

Std L/min

Std L/min


cm2 mol/s Pa

cm2 mol/s Pa

cm2

2 6 0.349 282 40 20 5 5.16

0 0 69.4 67.2 -2.8E-08

1.05E-10 4.57E-10 0.23 1.36E-10

103.1 99.9 137.5 133.3 -1.39E-08

192.8 186.8 216.0 209.3 -9.364E-09

445.8 432.1 414.0 401.2 1.2839E-08

531.2 514.8 479.3 464.5 2.0948E-08

607.0 588.3 533.9 517.4 2.954E-08

2 6 0.349 1820 60 20 5 5.45

0 0 466.2 427.3 -1.881E-07

1.15E-10 4.83E-10 0.24 1.51E-10

449.9 412.4 775.4 710.8 -1.314E-07

1007.0 923.0 1258.1 1153.3 -1.014E-07

2523.4 2313.1 2396.6 2196.9 5.1164E-08

3023.3 2771.3 2762.6 2532.3 1.0522E-07

3544.7 3249.3 3202.6 2935.8 1.3805E-07

2 6 0.349 9180 80 40 5 5.72

0 0 3016.3 2637.3 -7.723E-07

9.22E-11 3.21E-10 0.29 1.29E-10

4166.3 3642.8 5768.7 5043.9 -4.103E-07

8238.3 7203.2 8690.8 7598.8 -1.158E-07

10877.6 9510.9 10689.1 9346.0 4.8268E-08

14874.2 13005.3 13856.2 12115.2 2.6065E-07

19888.8 17389.9 17362.7 15181.1 6.4679E-07

2 6 0.349 3549

2 100 40 5 6.84

0 0 9139.4 6683.4 -2.34E-06

6.66E-11 3.76E-10 0.18 8.09E-11

22448.9 16416.3 26181.6 19145.9 -9.557E-07

43638.5 31911.8 43864.8 32077.2 -5.792E-08

58946.3 43106.0 57174.2 41810.1 4.5372E-07

64526.5 47186.6 62000.3 45339.3 6.4679E-07

66487.1 48620.3 63772.4 46635.2 6.9506E-07

2 6 0.396 1187 40 20 5 5.16

0 0 215.0 208.4 -8.679E-08

7.28E-11 4.57E-10 0.16 8.66E-11

465.7 451.3 576.0 558.2 -4.45E-08

897.4 869.7 935.0 906.1 -1.516E-08

1519.5 1472.6 1464.5 1419.3 2.2203E-08

1708.5 1655.8 1631.9 1581.6 3.0892E-08

1899.8 1841.2 1806.5 1750.8 3.7649E-08

2 6 0.396 7824 60 20 5 5.45 0 0 1128.9 1034.9 -4.557E-07

5.55E-11 4.83E-10 0.11 6.27E-11 2829.5 2593.7 3451.4 3163.8 -2.51E-07

408

5508.4 5049.3 5771.5 5290.5 -1.062E-07

13329.6 12218.8 12731.7 11670.7 2.4134E-07

15984.5 14652.5 15123.5 13863.2 3.4753E-07

18567.7 17020.4 17419.6 15968.0 4.6337E-07

Table B-31: Detailed Wetted Wall Column Data for 6 m PZ/2 m HMDA (part 2)

HMDA PZ CO2 ldg P*CO2 Temp Pressure GasDry Gaswet PCO2in, dry PCO2in,

wet PCO2out, dry

PCO2out,

wet CO2 flux KG kg

KG/kg

kg'

m mol CO2/mol

alk Pa °C psig

Std L/min

Std L/min


cm2 mol/s Pa

cm2 mol/s Pa

cm2

2 6 0.396 35669 80 40 5 5.72

0 0 5553.8 4856.0 -1.422E-06

3.58E-11 3.21E-10 0.11 4.03E-11

11925.8 10427.3 14866.7 12998.7 -7.53E-07

22671.4 19822.8 24066.4 21042.6 -3.572E-07

54418.1 47580.7 52608.3 45998.3 4.6337E-07

64937.5 56778.4 62411.3 54569.7 6.4679E-07

75192.9 65745.3 71460.3 62481.7 9.5571E-07

2 6 0.426 5110 40 20 5 5.16

0 0 337.2 326.8 -1.361E-07

2.48E-11 4.57E-10 0.05 2.62E-11

1399.2 1356.0 1614.5 1564.7 -8.688E-08

2858.2 2770.0 2977.8 2885.9 -4.827E-08

5584.9 5412.6 5537.1 5366.2 1.9307E-08

6972.2 6757.0 6876.5 6664.3 3.8615E-08

8263.7 8008.7 8120.2 7869.6 5.7922E-08

2 6 0.426 28662 60 40 5 5.28

0 0 2571.4 2435.5 -6.584E-07

1.97E-11 2.98E-10 0.07 2.11E-11

6217.4 5888.7 7838.6 7424.3 -4.151E-07

11986.1 11352.4 12891.0 12209.5 -2.317E-07

39170.6 37099.9 38416.5 36385.7 1.9307E-07

44750.8 42385.1 43619.7 41313.7 2.8961E-07

50067.0 47420.3 48709.7 46134.7 3.4753E-07

55270.2 52348.4 53724.3 50884.2 3.958E-07

2 6 0.458 18221 60 20 5 5.16

0 0 545.3 528.5 -2.201E-07

7.63E-12 4.57E-10 0.02 7.76E-12

6005.9 5820.5 6269.0 6075.5 -1.062E-07

11531.0 11175.1 11626.6 11267.9 -3.861E-08

27484.4 26636.3 27317.0 26474.0 6.7575E-08

32818.2 31805.4 32579.0 31573.6 9.6536E-08

38271.5 37090.5 38056.3 36881.9 8.6883E-08

43414.0 42074.2 43126.9 41796.1 1.1584E-07

409

Table B-32: Detailed WWC data for 6 m PZ/2 m DAB (part 1)

PZ/DAB

CO2 ldg P*CO2 T P GasDr

y Gas PCO2in, dry PCO2in, wet PCO2out, dry PCO2out, wet CO2 flux KG kg

KG/kg

kg'

m mol CO2/mol alk Pa C psig Std

L/min Std

L/min Pa Pa Pa Pa mol/s cm2 mol/s Pa cm2 mol/s Pa cm2 mol/s Pa cm2

6 2 0.301 114 40 20 5 5.16

0.00 0.00 41.86 40.57 -1.69E-08

1.81E-10 4.57E-10 0.40 3.00E-10

28.70 27.82 58.60 56.79 -1.21E-08

46.64 45.20 73.19 70.93 -1.07E-08 154.27 149.51 138.49 134.21 6.37E-09

177.47 172.00 156.90 152.06 8.30E-09

193.02 187.06 167.67 162.49 1.02E-08

6 2 0.301 924 60 20 5 5.45

0.00 0.00 349.21 320.11 -1.41E-07

1.85E-10 4.83E-10 0.38 2.99E-10

275.06 252.14 519.03 475.77 -9.85E-08 550.12 504.28 703.20 644.60 -6.18E-08

1614.48 1479.94 1427.92 1308.92 7.53E-08

1860.84 1705.77 1566.64 1436.09 1.19E-07 2116.76 1940.36 1724.50 1580.79 1.58E-07

6 2 0.301 4982 80 40 5 5.72

0.00 0.00 2103.88 1839.54 -5.39E-07

1.40E-10 3.21E-10 0.44 2.48E-10

1402.59 1226.36 3136.97 2742.82 -4.44E-07 2820.25 2465.90 3872.19 3385.67 -2.69E-07

8528.63 7457.05 7510.62 6566.95 2.61E-07

9810.56 8577.92 8189.29 7160.35 4.15E-07 11356.42 9929.55 9207.30 8050.45 5.50E-07

6 2 0.351 718 40 20 5 5.16

0.00 0.00 205.49 201.46 -5.26E-08

8.61E-11 2.87E-10 0.30 1.23E-10

145.91 143.06 321.61 315.32 -4.50E-08

412.48 404.41 495.81 486.10 -2.13E-08

779.72 764.45 754.83 740.06 6.37E-09 923.75 905.66 864.93 848.00 1.51E-08

1082.10 1060.92 993.50 974.05 2.27E-08

1266.10 1241.31 1119.81 1097.89 3.75E-08

6 2 0.351 6148 60 40 5 5.28

0.00 0.00 1696.68 1606.98 -4.34E-07

7.13E-11 2.98E-10 0.24 9.37E-11

1440.29 1364.15 2699.60 2556.89 -3.22E-07

2933.37 2778.29 3687.44 3492.51 -1.93E-07 8965.99 8492.01 8211.92 7777.80 1.93E-07

11831.49 11206.03 10398.74 9849.02 3.67E-07 23632.82 22383.48 19824.73 18776.70 9.75E-07

410


PZ/DAB

CO2 ldg P*CO2 T P GasDry Gas PCO2in, dry PCO2in, wet PCO2out, dry PCO2out, wet CO2 flux KG kg KG/kg

kg'

m mol

CO2/mol alk Pa C psig Std L/min Std L/min Pa Pa Pa Pa mol/s cm2 mol/s Pa

cm2 mol/s Pa

cm2 mol/s Pa cm2

6 2 0.351 26739 80 40 5 5.72

0.00 0.00 5866.73 5129.61 -1.50E-06

5.88E-11 3.21E-10 0.18 7.20E-11 5776.24 5050.49 10059.41 8795.50 -1.10E-06

31437.54 27487.57 30947.38 27059.01 1.25E-07

36565.27 31971.04 35358.74 30916.10 3.09E-07

41806.12 36553.40 40147.14 35102.87 4.25E-07

6 2 0.372 242 20 40 5 5.03

0.00 0.00 60.33 59.95 -1.54E-08

7.06E-11 2.82E-10 0.25 9.42E-11

60.33 59.95 105.19 104.54 -1.15E-08

117.64 116.91 144.41 143.51 -6.85E-09 227.35 225.95 233.39 231.94 -1.54E-09

429.45 426.79 380.06 377.70 1.26E-08 627.02 623.13 538.04 534.70 2.28E-08

835.14 829.97 627.02 623.13 5.33E-08

6 2 0.372 1513 40 40 5 5.10

0.00 0.00 429.82 421.41 -1.10E-07

7.67E-11 2.87E-10 0.27 1.05E-10

395.14 387.40 665.85 652.82 -6.93E-08

774.82 759.65 957.68 938.93 -4.68E-08

1851.26 1815.02 1734.38 1700.43 2.99E-08 2209.45 2166.20 2051.09 2010.94 4.05E-08

2556.33 2506.28 2322.56 2277.10 5.99E-08

6 2 0.372 10734 60 40 5 5.28

0.00 0.00 2262.24 2142.64 -5.79E-07

5.51E-11 2.98E-10 0.18 6.76E-11

4441.52 4206.72 5610.34 5313.76 -2.99E-07

8890.59 8420.59 9305.33 8813.41 -1.06E-07 16016.63 15169.92 14998.62 14205.73 2.61E-07

20427.99 19348.07 18693.61 17705.38 4.44E-07

24763.94 23454.81 22464.00 21276.45 5.89E-07

6 2 0.372 50322 80 70 5 5.44

0.00 0.00 9475.48 8706.62 -1.57E-06

3.00E-11 1.99E-10 0.15 3.53E-11

13708.21 12595.89 19546.46 17960.41 -9.65E-07

25384.71 23324.93 29179.57 26811.87 -6.27E-07 73958.95 67957.74 70397.62 64685.38 5.89E-07

86803.10 79759.68 82015.74 75360.78 7.92E-07

96669.74 88825.72 90831.49 83461.20 9.65E-07

6 2 0.398 642 20 40 5 5.03

0.00 0.00 118.01 117.28 -3.02E-08

4.86E-11 2.82E-10 0.17 5.88E-11 196.81 195.59 265.44 263.79 -1.76E-08 368.37 366.08 417.01 414.42 -1.25E-08

1123.95 1116.99 1041.38 1034.93 2.11E-08

1286.08 1278.11 1177.12 1169.82 2.79E-08

411

1471.21 1462.09 1329.44 1321.20 3.63E-08


PZ/DAB

CO2 ldg P*CO2 T P GasDry Gas PCO2in, dry PCO2in, wet PCO2out, dry PCO2out, wet CO2 flux KG kg KG/kg

kg'

m mol CO2/mol

alk Pa C psig Std

L/min Std


mol/s Pa cm2

mol/s Pa cm2

mol/s Pa cm2

6 2 0.398 4821 40 40 5 5.10

0.00 0.00 833.26 816.94 -2.13E-07

4.40E-11 2.87E-10 0.15 5.20E-11

1425.21 1397.31 1953.06 1914.83 -1.35E-07

2895.66 2838.98 3121.89 3060.77 -5.79E-08

8815.18 8642.61 8211.92 8051.16 1.54E-07

10172.52 9973.38 9418.44 9234.06 1.93E-07

11756.08 11525.95 10662.67 10453.94 2.80E-07

6 2 0.398 26787 60 40 5 5.28

0.00 0.00 3713.84 3517.51 -9.51E-07

3.13E-11 2.98E-10 0.11 3.50E-11

9075.34 8595.57 10847.42 10273.98 -4.54E-07

17521.02 16594.78 18312.80 17344.70 -2.03E-07

36787.72 34842.96 35618.90 33735.93 2.99E-07

45836.67 43413.53 43913.77 41592.29 4.92E-07

54093.83 51234.18 51605.37 48877.27 6.37E-07

6 2 0.425 2364 20 40 5 5.03

0.00 0.00 320.48 318.50 -8.21E-08

3.41E-11 2.82E-10 0.12 3.88E-11

565.56 562.05 784.24 779.38 -5.60E-08

1108.50 1101.62 1240.46 1232.77 -3.38E-08

3268.93 3248.67 3152.05 3132.51 2.99E-08

3826.95 3803.23 3653.51 3630.87 4.44E-08

4377.43 4350.29 4136.12 4110.48 6.18E-08

6 2 0.425 15774 40 40 5 5.10

0.00 0.00 1504.39 1474.94 -3.85E-07

2.23E-11 2.87E-10 0.08 2.42E-11

4520.70 4432.20 5414.28 5308.29 -2.29E-07

9045.17 8868.10 9459.92 9274.73 -1.06E-07

25031.64 24541.61 24239.86 23765.33 2.03E-07

29405.29 28829.65 28274.18 27720.67 2.90E-07

33778.95 33117.69 32459.31 31823.88 3.38E-07

412

Table B-35: Detailed WWC data for 6 m PZ/2 m BAE (part 1)

PZ/BAE CO2 ldg

P*CO2 T P GasDry Gas PCO2in, dry PCO2in, wet PCO2out, dry PCO2out,

wet CO2 flux KG kg

KG/kg

kg'

m mol

CO2/mol alk

Pa C psig Std

L/min Std


mol/s Pa cm2

mol/s Pa cm2

mol/s Pa cm2

6 2 0.305 262 40 20 5 5.16

0 0 86 83 -3.47E-08

1.55E-10 4.57E-10 0.34 2.34E-10

62 61 126 122 -2.58E-08

120 117 166 160 -1.82E-08

439 425 384 373 2.20E-08

491 475 423 410 2.71E-08

547 531 463 449 3.42E-08

6 2 0.305 1958 60 20 5 5.45

0 0 492 451 -1.99E-07

1.32E-10 4.83E-10 0.27 1.82E-10

567 520 1028 943 -1.86E-07

1112 1020 1409 1291 -1.20E-07

2973 2725 2786 2554 7.53E-08

3322 3045 2930 2686 1.58E-07

3887 3563 3463 3175 1.71E-07

6 2 0.305 9523 80 40 5 5.72

0 0 3137 2743 -8.03E-07

1.02E-10 3.21E-10 0.32 1.50E-10

3039 2657 5591 4889 -6.54E-07

6116 5347 7239 6330 -2.88E-07

17702 15478 15779 13797 4.92E-07

20756 18148 18305 16005 6.27E-07

23923 20917 19663 17192 1.09E-06

6 2 0.305 36717 100 40 5 6.84

0 0 11292 8258 -2.89E-06

8.80E-11 3.76E-10 0.23 1.15E-10

6881 5032 17023 12449 -2.60E-06

12914 9443 20492 14985 -1.94E-06

64568 47217 61401 44901 8.11E-07

76709 56095 70865 51821 1.50E-06

6 2 0.333 72 20 20 5 5.05

0 0 21 21 -8.59E-09

1.24E-10 4.46E-10 0.28 1.72E-10

15 14 29 29 -5.99E-09

25 25 36 36 -4.44E-09

194 192 162 160 1.28E-08

227 225 188 186 1.59E-08

182 181 153 151 1.20E-08

413


PZ/BAE CO2 ldg

P*CO2 T P GasDry Gas PCO2in, dry PCO2in, wet PCO2out, dry PCO2out,

wet CO2 flux KG kg

KG/kg

kg'

m mol

CO2/mol alk

Pa C psig Std

L/min Std


mol/s Pa cm2

mol/s Pa cm2

mol/s Pa cm2

6 2 0.333 509 40 20 5 5.16

0 0 136 132 -5.48E-08

1.20E-10 4.57E-10 0.26 1.62E-10

106 102 204 198 -3.98E-08

206 199 287 279 -3.30E-08

975 945 864 837 4.49E-08

1061 1028 923 894 5.58E-08

1155 1120 1001 970 6.25E-08

6 2 0.333 3355 60 40 5 5.28

0 0 1191 1128 -3.05E-07

1.08E-10 2.98E-10 0.36 1.70E-10

577 546 1576 1493 -2.56E-07

1127 1068 1908 1807 -2.00E-07

4457 4221 4023 3810 1.11E-07

5007 4742 4562 4321 1.14E-07

5569 5274 4969 4707 1.53E-07

6 2 0.333 16170 80 40 5 5.72

0 0 4400 3847 -1.13E-06

7.56E-11 3.21E-10 0.24 9.89E-11

4313 3771 7480 6541 -8.11E-07

7971 6969 10157 8881 -5.60E-07

30216 26419 27577 24112 6.76E-07

33911 29650 30631 26782 8.40E-07

37417 32716 32931 28793 1.15E-06

6 2 0.362 128 20 20 5 5.05

0 0 29 29 -1.17E-08

1.03E-10 4.46E-10 0.23 1.34E-10

26 25 47 46 -8.59E-09

50 49 70 69 -8.11E-09

183 181 169 167 5.60E-09

206 204 192 190 5.79E-09

227 225 204 202 9.36E-09

6 2 0.362 1196 40 20 5 5.16

0 0 257 249 -1.04E-07

8.92E-11 4.57E-10 0.20 1.11E-10

260 252 432 419 -6.93E-08

506 491 644 624 -5.55E-08

1923 1863 1781 1726 5.70E-08

2531 2452 2289 2218 9.75E-08

2655 2573 2528 2450 5.12E-08

414


PZ/BAE CO2 ldg P*CO2 T P GasDry Gas PCO2in, dry PCO2in,

wet PCO2out, dry

PCO2out,

wet CO2 flux KG kg

KG/kg kg'


L/min Std L/min Pa Pa Pa Pa mol/s cm2

mol/s Pa cm2

mol/s Pa cm2

mol/s Pa cm2

6 2 0.362 8729 60 40 5 5.28

0 0 2176 2061 -5.57E-07

6.83E-11 2.98E-10 0.23 8.86E-11

1497 1418 3163 2996 -4.27E-07

3062 2900 4374 4142 -3.36E-07

15240 14434 13732 13006 3.86E-07

16635 15756 15127 14327 3.86E-07

18068 17113 16107 15256 5.02E-07

6 2 0.362 37920 80 40 5 5.72

0 0 6523 5703 -1.67E-06

4.45E-11 3.21E-10 0.14 5.16E-11 25793 22552 27754 24267 -5.02E-07

50301 43981 48906 42761 3.57E-07

64741 56607 62253 54431 6.37E-07

6 2 0.392 385 20 20 5 5.05

0 0 58 58 -2.36E-08

6.63E-11 4.46E-10 0.15 7.79E-11

108 107 149 148 -1.68E-08

202 200 232 229 -1.21E-08

683 676 636 630 1.88E-08

780 772 720 713 2.39E-08

874 866 804 796 2.85E-08

6 2 0.392 3519 40 20 5 5.16

0 0 505 489 -2.04E-07

5.99E-11 4.57E-10 0.13 6.89E-11

749 726 1179 1143 -1.74E-07

1461 1416 1720 1667 -1.04E-07

3030 2937 3052 2958 -8.69E-09

6747 6539 6365 6168 1.54E-07

7513 7281 6987 6771 2.12E-07

8182 7930 7704 7466 1.93E-07

6 2 0.392 21838 60 40 5 5.28

0 0 3133 2968 -8.02E-07

3.35E-11 2.98E-10 0.11 3.77E-11

6715 6360 8487 8038 -4.54E-07

12748 12074 13539 12824 -2.03E-07

37293 35321 35408 33536 4.83E-07

43929 41607 41780 39571 5.50E-07

49924 47285 46832 44356 7.92E-07

415


PZ/BAE CO2 ldg P*CO2 T P GasDry Gas PCO2in, dry PCO2in,

wet PCO2out, dry

PCO2out,

wet CO2 flux KG kg KG/kg kg'


L/min Std L/min Pa Pa Pa Pa mol/s cm2

mol/s Pa cm2

mol/s Pa cm2

mol/s Pa cm2

6 2 0.420 1527 20 20 5 5.05

0 0 148 147 -5.98E-08

3.79E-11 4.46E-10 0.08 4.14E-11

205 203 317 314 -4.52E-08

399 395 493 489 -3.81E-08

2001 1982 1963 1944 1.54E-08

2131 2110 2083 2062 1.93E-08

2300 2278 2229 2207 2.90E-08

6 2 0.420 15745 60 40 5 5.28

0 0 926 897 -3.74E-07

2.20E-11 4.57E-10 0.05 2.31E-11

2830 2742 3461 3354 -2.55E-07

5174 5014 5700 5524 -2.12E-07

24954 24184 24499 23743 1.83E-07

27537 26687 26939 26108 2.41E-07

29953 29028 29283 28379 2.70E-07

416

Table B-39: Detailed WWC data for 6 m PZ/2 m EDA (part 1)

PZ/EDA CO2 ldg P*CO2 T P Gas Dry Gas

PCO2in,

dry PCO2in, wet

PCO2out,

dry

PCO2out,

wet CO2 flux KG kg

KG/kg

kg'

m mol

CO2/mol alk Pa °C psig

Std

L/min

Std


mol/s Pa

cm2

mol/s Pa

cm2

mol/s Pa

cm2

6 2 0.335 237 40 40 5 5.1

0.0 0.0 87.5 85.8 -2.24E-08

1.29E-10 2.87E-10 0.449 2.34E-10

35.1 34.4 116.5 114.2 -2.09E-08

61.1 59.9 136.9 134.2 -1.94E-08

337.5 330.8 300.9 295.0 9.36E-09

446.4 437.7 368.4 361.2 2.00E-08

539.9 529.4 420.8 412.5 3.05E-08

6 2 0.335 1348 60 40 5 5.28

0.0 0.0 557.6 528.2 -1.43E-07

1.34E-10 2.98E-10 0.449 2.43E-10

268.5 254.3 711.1 673.5 -1.13E-07

518.1 490.7 876.6 830.3 -9.18E-08

1961.4 1857.7 1750.2 1657.7 5.41E-08

2432.7 2304.1 2048.1 1939.8 9.85E-08

2888.9 2736.2 2308.2 2186.2 1.49E-07

6 2 0.335 7816 80 50 5 5.59

0.0 0.0 2925.5 2614.8 -6.33E-07

1.09E-10 2.67E-10 0.407 1.83E-10

2773.9 2479.3 5026.1 4492.2 -4.88E-07

5480.9 4898.7 6832.2 6106.5 -2.93E-07

12130.3 10841.8 11060.0 9885.2 2.32E-07

14806.1 13233.3 12576.3 11240.4 4.83E-07

17348.1 15505.3 14092.6 12595.6 7.05E-07

6 2 0.335 30432 100 50 5 6.47

0.0 0.0 10252.8 7923.5 -2.22E-06

8.25E-11 3.03E-10 0.272 1.13E-10

11724.5 9060.8 18547.8 14333.9 -1.48E-06

17076.1 13196.6 22829.1 17642.5 -1.25E-06

61405.3 47454.6 55607.7 42974.1 1.25E-06

70636.8 54588.8 62475.6 48281.7 1.77E-06

79645.4 61550.7 69700.3 53865.0 2.15E-06

6 2 0.376 155 20 20 5 5.05

0.0 0.0 31.8 31.5 -1.28E-08

8.92E-11 4.46E-10 0.200 1.12E-10

36.8 36.5 59.3 58.7 -9.07E-09

73.0 72.2 90.4 89.5 -7.05E-09

185.1 183.3 178.4 176.7 2.70E-09

227.2 225.0 212.2 210.1 6.08E-09

328.9 325.7 296.3 293.5 1.31E-08

6 2 0.376 1141 40 40 5 5.1

0.0 0.0 307.3 301.3 -7.87E-08

8.44E-11 2.87E-10 0.294 1.19E-10

315.2 309.0 564.4 553.4 -6.38E-08

620.6 608.5 769.2 754.1 -3.80E-08

1755.1 1720.8 1602.4 1571.0 3.91E-08

1969.7 1931.1 1743.4 1709.3 5.79E-08

2354.2 2308.1 2018.7 1979.2 8.59E-08

417


PZ/EDA CO2 ldg P*CO2 T P

Gas

Dry Gas

PCO2in,

dry

PCO2in,

wet PCO2out, dry

PCO2out,

wet CO2 flux KG kg

KG/kg

kg'

m mol


Std

L/min

Std


mol/s Pa

cm2

mol/s Pa

cm2

mol/s Pa

cm2

6 2 0.376 6861 60 40 5 5.28

0.0 0.0 1941.8 1839.1 -4.97E-07

8.28E-11 2.98E-10 0.278 1.15E-10

1353.6 1282.0 2884.4 2731.9 -3.92E-07

2744.8 2599.7 3868.4 3663.9 -2.88E-07

12174.6 11531.0 10930.4 10352.5 3.19E-07

16058.1 15209.2 13833.6 13102.3 5.70E-07

21148.1 20030.1 17377.7 16459.1 9.65E-07

6 2 0.376 27313 80 50 5 5.28

0.0 0.0 6537.9 5843.4 -1.42E-06

5.89E-11 2.67E-10 0.221 7.56E-11

5217.8 4663.6 10921.8 9761.6 -1.23E-06

9628.4 8605.7 13865.1 12392.3 -9.17E-07

66667.7 59585.9 59487.7 53168.6 1.55E-06

71127.4 63571.9 62654.0 55998.6 1.83E-06

76657.4 68514.5 65909.6 58908.3 2.33E-06

6 2 0.409 516 20 20 5 5.05

0.0 0.0 82.3 81.5 -3.32E-08

6.62E-11 4.46E-10 0.149 7.77E-11

158.3 156.8 206.4 204.4 -1.94E-08

318.4 315.2 352.6 349.1 -1.38E-08

716.4 709.4 680.5 673.8 1.45E-08

860.3 851.9 813.7 805.7 1.88E-08

1003.4 993.6 932.1 923.0 2.88E-08

6 2 0.415 3989 40 40 5 5.1

0.0 0.0 780.5 765.2 -2.00E-07

5.49E-11 2.87E-10 0.191 6.79E-11

739.0 724.5 1364.9 1338.2 -1.60E-07

1478.0 1449.1 1960.6 1922.2 -1.24E-07

7152.4 7012.4 6586.9 6457.9 1.45E-07

8585.2 8417.1 7718.0 7566.9 2.22E-07

10017.9 9821.8 8886.8 8712.8 2.90E-07

6 2 0.411 19742 60 40 5 5.28

0.0 0.0 3178.4 3010.4 -8.14E-07

4.22E-11 2.98E-10 0.142 4.92E-11

6481.3 6138.7 8547.5 8095.6 -5.29E-07

12053.9 11416.7 13109.7 12416.6 -2.70E-07

43612.1 41306.6 40256.5 38128.3 8.59E-07

48212.0 45663.3 44517.0 42163.7 9.46E-07

53264.3 50448.5 48438.2 45877.6 1.24E-06

6 2 0.435 1742 20 20 5 5.05

0.0 0.0 147.6 146.1 -5.96E-08

3.50E-11 4.46E-10 0.078 3.79E-11

330.1 326.8 444.9 440.5 -4.63E-08

633.8 627.6 724.7 717.6 -3.67E-08

2688.4 2662.1 2614.3 2588.7 2.99E-08

3090.2 3060.0 2985.0 2955.8 4.25E-08

3386.8 3353.7 3248.1 3216.4 5.60E-08

418


PZ/EDA CO2 ldg P*CO2 T P Gas Dry Gas PCO2in, dry

PCO2in,

wet

PCO2out,

dry

PCO2out,

wet CO2 flux KG kg

KG/kg

kg'

m mol


Std

L/min

Std


mol/s Pa

cm2

mol/s Pa

cm2

mol/s Pa

cm2

6 2 0.436 11401 40 40 5 5.1

0.0 0.0 1315.9 1290.1 -3.37E-07

3.10E-11 2.87E-10 0.108 3.47E-11

1398.8 1371.4 2499.8 2450.8 -2.82E-07

2775.0 2720.7 3785.5 3711.4 -2.59E-07

26302.3 25787.4 24643.3 24160.9 4.25E-07

31316.9 30703.8 29205.5 28633.7 5.41E-07

36331.5 35620.3 33503.7 32847.8 7.24E-07

419

Table B-42: Detailed WWC data for 5 m PZ/2 m AEP (part 1)

PZ/AEP CO2 ldg P*CO2 T P GasDry Gas PCO2in, dry PCO2in,

wet PCO2out,

dry PCO2out,

wet CO2 flux KG kg

KG/kg

kg'

m mol

CO2/mol alk Pa C psig Std L/min Std

L/min Pa Pa Pa Pa

mol/s cm2

mol/s Pa cm2

mol/s Pa cm2

mol/s Pa cm2

5 2 0.251 160 40 20 5 5.16

0.0 0.0 65.3 63.3 -2.64E-08

1.91E-10 4.57E-10 0.417 3.27E-10

59.8 58.0 91.4 88.5 -1.27E-08

116.2 112.7 135.6 131.4 -7.82E-09

223.2 216.3 199.5 193.3 9.56E-09

325.0 315.0 271.5 263.1 2.16E-08

426.7 413.5 327.9 317.8 3.99E-08

5 2 0.251 907 60 20 5 5.45

0.0 0.0 316.9 290.5 -1.28E-07

1.79E-10 4.83E-10 0.371 2.85E-10

104.0 95.4 425.0 389.6 -1.30E-07

201.2 184.4 456.6 418.5 -1.03E-07

1226.0 1123.9 1132.8 1038.4 3.76E-08

1302.6 1194.0 1202.1 1102.0 4.05E-08

1398.3 1281.7 1269.1 1163.3 5.21E-08

5 2 0.251 4505 80 40 5 5.72

0.0 0.0 2077.5 1816.5 -5.32E-07

1.54E-10 3.21E-10 0.478 2.94E-10

1417.7 1239.5 2967.3 2594.5 -3.97E-07

2899.4 2535.1 3804.3 3326.3 -2.32E-07

7359.8 6435.1 6507.7 5690.0 2.18E-07

8830.3 7720.8 7322.1 6402.1 3.86E-07

10263.0 8973.5 8151.6 7127.4 5.41E-07

5 2 0.251 19649 100 40 5 6.84

0.0 0.0 6884.7 5034.6 -1.76E-06

1.09E-10 3.76E-10 0.290 1.54E-10

5942.1 4345.3 11544.9 8442.5 -1.43E-06

11846.6 8663.1 16031.7 11723.6 -1.07E-06

37259.0 27246.6 35373.8 25868.0 4.83E-07

38314.7 28018.6 34959.1 25564.7 8.59E-07

44762.1 32733.4 40539.3 29645.3 1.08E-06

49814.4 36428.0 42650.7 31189.4 1.83E-06

5 2 0.288 54 20 20 5 5.05

0.0 0.0 17.9 17.8 -7.24E-09

1.46E-10 4.46E-10 0.328 2.17E-10

11.5 11.4 23.4 23.2 -4.83E-09

24.9 24.6 33.5 33.2 -3.48E-09

92.8 91.9 81.6 80.8 4.54E-09

114.8 113.7 96.6 95.7 7.34E-09

116.0 114.9 97.8 96.9 7.34E-09

420


PZ/AEP CO2 ldg P*CO2 T P GasDry Gas PCO2in, dry PCO2in, wet PCO2out, dry PCO2out, wet CO2 flux KG kg

KG/kg

kg'

m mol

CO2/mol alk Pa C psig Std

L/min Std L/min Pa Pa Pa Pa

mol/s cm2

mol/s Pa cm2

mol/s Pa cm2

mol/s Pa cm2

5 2 0.288 365 40 20 5 5.16

0.0 0.0 110.7 107.3 -4.47E-08

1.42E-10 4.57E-10 0.310 2.06E-10

79.9 77.4 165.5 160.4 -3.46E-08

152.8 148.1 216.0 209.3 -2.55E-08

534.6 518.1 479.8 465.0 2.21E-08

605.8 587.2 547.2 530.4 2.37E-08

669.2 648.6 585.0 567.0 3.40E-08

5 2 0.288 2201 60 40 5 5.28

0.0 0.0 833.3 789.2 -2.13E-07

1.21E-10 2.98E-10 0.404 2.02E-10

573.1 542.8 1180.1 1117.7 -1.55E-07

1116.0 1057.0 1576.0 1492.7 -1.18E-07

3310.4 3135.4 2967.3 2810.4 8.78E-08

3845.8 3642.5 3299.1 3124.7 1.40E-07

4392.5 4160.3 3634.7 3442.5 1.94E-07

5 2 0.288 10201 80 60 5 5.51

0.0 0.0 4093.4 3716.8 -7.67E-07

9.49E-11 2.28E-10 0.417 1.63E-10

2811.3 2552.7 5890.4 5348.5 -5.77E-07

6065.5 5507.4 7991.2 7256.0 -3.61E-07

17727.9 16096.8 15513.8 14086.5 4.15E-07

20611.3 18715.0 17213.0 15629.3 6.37E-07

24009.6 21800.6 19118.1 17359.1 9.17E-07

5 2 0.288 42428 100 50 5 6.47

13610.9 10518.7 22128.9 17101.4 -1.84E-06

6.44E-11 3.03E-10 0.212 8.17E-11

25250.7 19514.0 31003.7 23959.9 -1.25E-06

37113.4 28681.6 41038.0 31714.5 -8.50E-07

62355.2 48188.7 61017.3 47154.7 2.90E-07

82290.0 63594.4 76492.4 59114.0 1.25E-06

5 2 0.328 165 20 20 5 5.05

0.0 0.0 37.6 37.2 -1.52E-08

1.02E-10 4.46E-10 0.228 1.32E-10

60.8 60.2 83.5 82.7 -9.17E-09

118.6 117.5 128.9 127.7 -4.15E-09

226.5 224.3 212.6 210.6 5.60E-09

279.6 276.9 255.2 252.7 9.85E-09

333.2 329.9 296.6 293.7 1.48E-08

5 2 0.328 1109 40 40 5 5.10

0.0 0.0 330.7 324.2 -8.47E-08

8.89E-11 2.87E-10 0.309 1.29E-10

262.8 257.7 517.7 507.5 -6.53E-08

499.6 489.8 679.4 666.1 -4.60E-08

1462.9 1434.3 1348.7 1322.3 2.93E-08

1917.2 1879.7 1687.3 1654.2 5.89E-08

2151.0 2108.9 1872.0 1835.4 7.14E-08

421



wet PCO2out,

dry PCO2out,

wet CO2 flux KG kg

KG/kg

kg'

m mol


L/min Pa Pa Pa Pa

mol/s cm2

mol/s Pa cm2

mol/s Pa cm2

mol/s Pa cm2

5 2 0.328 7075 60 40 5 5.28

0.0 0.0 1855.0 1757.0 -4.75E-07

8.00E-11 2.98E-10 0.268 1.09E-10

1489.3 1410.6 3072.9 2910.4 -4.05E-07

3008.8 2849.7 4166.3 3946.0 -2.96E-07

12792.9 12116.7 11360.2 10759.6 3.67E-07

13810.9 13080.8 12302.8 11652.4 3.86E-07

15055.2 14259.3 13056.9 12366.6 5.12E-07

5 2 0.328 28989 80 40 5 5.72

0.0 0.0 6213.6 5432.9 -1.59E-06

6.23E-11 3.21E-10 0.194 7.73E-11

6854.6 5993.3 12227.4 10691.1 -1.38E-06

12981.5 11350.4 16450.2 14383.3 -8.88E-07

51100.1 44679.7 48310.0 42240.1 7.14E-07

57321.3 50119.2 53098.4 46426.9 1.08E-06

64522.7 56415.8 57660.6 50415.9 1.76E-06

5 2 0.360 505 20 20 5 5.05

0.0 0.0 75.1 74.4 -3.03E-08

6.33E-11 4.46E-10 0.142 7.38E-11

105.0 104.0 163.8 162.2 -2.37E-08

197.6 195.6 241.1 238.7 -1.76E-08

758.7 751.3 716.4 709.4 1.71E-08

852.9 844.6 806.8 798.9 1.86E-08

940.0 930.8 880.9 872.3 2.38E-08

5 2 0.360 3763 40 40 5 5.10

0.0 0.0 761.6 746.7 -1.95E-07

5.53E-11 2.87E-10 0.192 6.84E-11

576.9 565.6 1183.9 1160.7 -1.55E-07

1104.7 1083.1 1617.5 1585.8 -1.31E-07

4358.6 4273.2 4219.1 4136.5 3.57E-08

5436.9 5330.5 5161.7 5060.6 7.05E-08

6549.2 6421.0 6036.4 5918.2 1.31E-07

5 2 0.360 17534 60 40 5 5.28

0.0 0.0 3514.0 3328.2 -9.00E-07

5.42E-11 2.98E-10 0.182 6.62E-11

6598.2 6249.4 8604.0 8149.2 -5.14E-07

12600.7 11934.5 13467.8 12755.9 -2.22E-07

37070.5 35110.8 34129.6 32325.4 7.53E-07

49362.0 46752.5 43668.7 41360.2 1.46E-06

63086.2 59751.2 54866.8 51966.3 2.10E-06

422



wet PCO2out,

dry PCO2out,

wet CO2 flux KG kg

KG/kg

kg'

m mol


L/min Pa Pa Pa Pa

mol/s cm2

mol/s Pa cm2

mol/s Pa cm2

mol/s Pa cm2

5 2 0.386 1854 20 20 5 5.05

0.0 0.0 177.0 175.3 -7.14E-08

3.97E-11 4.46E-10 0.089 4.35E-11

741.5 734.2 841.9 833.7 -4.05E-08

1026.1 1016.1 1102.6 1091.9 -3.09E-08

2980.2 2951.1 2875.0 2846.9 4.25E-08

4436.8 4393.5 4212.0 4170.8 9.07E-08

5915.0 5857.2 5532.3 5478.2 1.54E-07

5 2 0.386 10083 40 40 5 5.10

0.0 0.0 1285.7 1260.5 -3.29E-07

3.52E-11 2.87E-10 0.123 4.01E-11

2816.5 2761.3 3774.2 3700.3 -2.45E-07

5964.8 5848.0 6421.0 6295.3 -1.17E-07

20484.5 20083.5 19391.1 19011.5 2.80E-07

23274.6 22819.0 21691.1 21266.4 4.05E-07

29307.3 28733.5 26743.4 26219.9 6.56E-07

5 2 0.386 44806 60 40 5 5.10

0.0 0.0 4505.6 4267.4 -1.15E-06

2.33E-11 2.98E-10 0.078 2.53E-11

12902.3 12220.2 15466.2 14648.5 -6.56E-07

25042.9 23719.1 26324.9 24933.2 -3.28E-07

63387.8 60036.9 62030.5 58751.3 3.48E-07

69571.3 65893.4 67987.7 64393.6 4.05E-07

74849.8 70892.9 72587.6 68750.3 5.79E-07

423

Table B-46: Detailed WWC data for 5 m PZ/2.3 m AMP (part 1)

PZ/AMP CO2 ldg P*CO2 T P GasDry Gas PCO2in, dry PCO2in, wet PCO2out, dry PCO2out, wet CO2 flux KG kg KG/kg

kg'

m mol CO2/mol

alk Pa C psig Std

L/min Std


mol/s Pa cm2

mol/s Pa cm2

mol/s Pa cm2

5 2.3 0.31 325 40 20 5 5.16

0.00 0.00 93.04 90.17 -3.76E-08

1.34E-10 4.57E-10 0.292 1.89E-10

62.90 60.96 138.01 133.75 -3.03E-08

109.31 105.93 170.78 165.51 -2.48E-08

475.49 460.82 432.44 419.10 1.74E-08

527.40 511.12 477.65 462.91 2.01E-08

570.21 552.61 507.07 491.42 2.55E-08

5 2.3 0.31 2742 60 20 5 5.45

0.00 0.00 755.82 692.83 -3.05E-07

1.27E-10 4.83E-10 0.262 1.71E-10

557.29 510.85 1131.33 1037.05 -2.32E-07

1112.20 1019.51 1604.91 1471.17 -1.99E-07

3274.40 3001.53 3233.74 2964.26 1.64E-08

3826.91 3508.00 3590.12 3290.94 9.56E-08

5 2.3 0.31 11146 80 40 5 5.72

0.00 0.00 4098.42 3583.47 -1.05E-06

1.16E-10 3.21E-10 0.361 1.82E-10

4441.52 3883.47 7065.72 6177.95 -6.72E-07

8019.63 7012.00 9490.08 8297.70 -3.76E-07

12732.62 11132.83 12921.14 11297.66 -4.83E-08

23704.46 20726.12 20575.03 17989.89 8.01E-07

27474.85 24022.78 22837.27 19967.89 1.19E-06

31132.13 27220.55 24571.65 21484.35 1.68E-06

5 2.3 0.31 59912 100 60 5 6.22

0.00 0.00 16250.13 13052.47 -3.05E-06

5.23E-11 2.54E-10 0.206 6.59E-11

25981.67 20869.07 33859.59 27196.79 -1.48E-06

50233.30 40348.52 55330.77 44442.92 -9.56E-07

89005.00 71490.82 86533.49 69505.65 4.63E-07

95492.69 76701.88 91270.54 73310.56 7.92E-07

102598.26 82409.24 92403.31 74220.43 1.91E-06

5 2.3 0.35 93 20 20 5 5.05

0.00 0.00 21.29 21.08 -8.59E-09

1.00E-10 4.46E-10 0.224 1.29E-10

22.00 21.79 37.55 37.18 -6.27E-09

34.44 34.11 47.84 47.37 -5.41E-09

59.56 58.97 65.78 65.13 -2.51E-09

141.84 140.45 130.83 129.55 4.44E-09

191.11 189.24 170.78 169.11 8.21E-09

424



kg'

m mol CO2/mol alk Pa C psig Std L/min Std L/min Pa Pa Pa Pa mol/s cm2 mol/s Pa cm2 mol/s Pa cm2 mol/s Pa cm2

5 2.3 0.35 844 40 20 5 5.16

0.00 0.00 186.32 180.57 -7.52E-08

9.85E-11 4.57E-10 0.215 1.26E-10

202.59 196.34 324.81 314.79 -4.93E-08

385.80 373.90 486.50 471.48 -4.06E-08

758.21 734.81 793.61 769.12 -1.43E-08

1124.63 1089.93 1098.32 1064.43 1.06E-08

1486.04 1440.18 1344.92 1303.42 5.70E-08

1832.85 1776.29 1619.98 1569.99 8.59E-08

5 2.3 0.35 5979 60 40 5 5.28

0.00 0.00 1760.77 1667.69 -4.51E-07

9.06E-11 2.98E-10 0.304 1.30E-10

1474.22 1396.29 2846.65 2696.16 -3.51E-07

2933.37 2778.29 3940.06 3731.77 -2.58E-07

9033.86 8556.29 8317.49 7877.79 1.83E-07

10391.20 9841.88 9184.68 8699.13 3.09E-07

11823.95 11198.88 10240.39 9699.03 4.05E-07

5 2.3 0.35 27778 80 40 5 5.72

0.00 0.00 8095.03 7077.94 -2.07E-06

7.70E-11 3.21E-10 0.240 1.01E-10

6786.71 5933.99 11903.13 10407.56 -1.31E-06

12732.62 11132.83 17143.98 14989.93 -1.13E-06

37466.39 32758.94 36222.16 31671.04 3.19E-07

49870.99 43604.96 44818.66 39187.43 1.29E-06

63142.77 55209.21 56582.29 49473.02 1.68E-06

5 2.3 0.38 229 20 20 5 5.05

0.00 0.00 43.05 42.63 -1.74E-08

7.85E-11 4.46E-10 0.176 9.53E-11

59.56 58.97 88.26 87.40 -1.16E-08

116.00 114.87 134.90 133.58 -7.63E-09

328.40 325.19 308.78 305.77 7.92E-09

378.63 374.93 354.23 350.77 9.85E-09

429.09 424.90 395.61 391.74 1.35E-08

5 2.3 0.38 2204 40 20 5 5.16

0.00 0.00 406.61 394.06 -1.64E-07

8.23E-11 4.57E-10 0.180 1.00E-10

727.11 704.68 1002.17 971.25 -1.11E-07

1449.44 1404.71 1583.39 1534.52 -5.41E-08

3011.30 2918.38 2906.06 2816.38 4.25E-08

3736.03 3620.73 3501.63 3393.57 9.46E-08

4470.31 4332.36 4039.79 3915.12 1.74E-07

5 2.3 0.38 11464 60 40 5 5.28

0.00 0.00 2752.39 2606.88 -7.05E-07

7.01E-11 2.98E-10 0.235 9.16E-11

2925.82 2771.15 4905.28 4645.97 -5.07E-07

6021.32 5703.00 7491.77 7095.72 -3.76E-07

17634.13 16701.91 16616.12 15737.72 2.61E-07

20537.33 19451.63 18576.73 17594.68 5.02E-07

425

23440.53 22201.36 20688.15 19594.48 7.05E-07



kg'


5 2.3 0.38 49169 80 50 5 5.59

0.00 0.00 11265.15 10068.51 -2.44E-06

4.69E-11 2.67E-10 0.176 5.69E-11

12915.23 11543.31 19337.17 17283.07 -1.39E-06

25268.54 22584.38 29282.25 26171.74 -8.69E-07

75796.70 67745.18 72987.10 65234.03 6.08E-07

82129.44 73405.23 78338.71 70017.17 8.21E-07

88997.35 79543.59 81817.26 73126.21 1.55E-06

5 2.3 0.42 676 20 20 5 5.05

0.00 0.00 75.58 74.84 -3.05E-08

4.65E-11 4.46E-10 0.104 5.19E-11

107.39 106.34 168.62 166.98 -2.47E-08

200.20 198.24 250.90 248.45 -2.05E-08

960.08 950.70 929.94 920.85 1.22E-08

1136.35 1125.25 1086.84 1076.22 2.00E-08

1314.55 1301.70 1247.57 1235.38 2.70E-08

5 2.3 0.42 5325 40 20 5 5.16

0.00 0.00 662.53 642.09 -2.67E-07

5.01E-11 4.57E-10 0.109 5.62E-11

734.29 711.63 1260.49 1221.59 -2.12E-07

1475.75 1430.21 1896.71 1838.18 -1.70E-07

8911.93 8636.91 8529.24 8266.03 1.54E-07

9581.64 9285.95 9127.19 8845.53 1.83E-07

10299.18 9981.36 9749.06 9448.21 2.22E-07

5 2.3 0.42 26451 60 40 5 5.28

0.00 0.00 3989.08 3778.20 -1.02E-06

3.96E-11 2.98E-10 0.133 4.56E-11

6809.33 6449.36 9448.60 8949.11 -6.76E-07

12841.96 12163.07 14727.15 13948.61 -4.83E-07

24982.62 23661.93 25397.37 24054.75 -1.06E-07

43570.66 41267.32 41836.28 39624.62 4.44E-07

50168.85 47516.70 47303.35 44802.68 7.34E-07

62988.18 59658.34 57860.45 54801.68 1.31E-06

5 2.3 0.45 2963 20 20 5 5.05

0.00 0.00 196.13 194.21 -7.92E-08

2.48E-11 4.46E-10 0.056 2.62E-11

751.03 743.69 875.41 866.85 -5.02E-08

1112.20 1101.33 1219.83 1207.91 -4.34E-08

2190.91 2169.50 2222.00 2200.29 -1.25E-08

5895.84 5838.23 5728.41 5672.44 6.76E-08

6709.06 6643.51 6493.80 6430.35 8.69E-08

7450.52 7377.73 7187.42 7117.20 1.06E-07

426



kg'


5 2.3 0.45 17617 40 40 5 5.10

0.00 0.00 1564.71 1534.08 -4.01E-07

2.18E-11 2.87E-10 0.076 2.36E-11

6692.45 6561.43 7484.23 7337.72 -2.03E-07

10085.80 9888.36 10651.36 10442.85 -1.45E-07

24828.04 24342.00 24337.89 23861.44 1.25E-07

30898.37 30293.50 29842.66 29258.45 2.70E-07

37421.15 36688.58 35875.29 35172.99 3.96E-07

Table B-50: Detailed WWC data for 6 m PZ/2 m HEP (part 1)

PZ/HEP CO2 ldg P*CO2 T P Gas Dry Gas PCO2in, dry PCO2in, wet

PCO2out,

dry

PCO2out,

wet CO2 flux KG kg

KG/kg

kg'

m mol


Std

L/min

Std


mol/s Pa

cm2

mol/s Pa

cm2

mol/s Pa

cm2

6 2 0.251 253 40 40 5 5.10

0 0 103 101 -2.63E-08

1.28E-10 2.87E-10 0.445 2.31E-10

63 62 138 136 -1.92E-08

122 119 175 172 -1.36E-08

547 537 435 427 2.88E-08

644 631 488 478 4.00E-08

955 936 690 676 6.79E-08

6 2 0.250 1376 60 40 5 5.28

0 0 597 566 -1.53E-07

1.45E-10 2.98E-10 0.488 2.84E-10

217 206 756 716 -1.38E-07

410 389 828 784 -1.07E-07

2395 2268 2003 1897 1.00E-07

2640 2500 2135 2022 1.29E-07

3017 2858 2376 2250 1.64E-07

6 2 0.250 6358 80 60 5 5.51

0 0 2981 2707 -5.59E-07

1.19E-10 2.28E-10 0.523 2.50E-10

1406 1276 3821 3469 -4.53E-07

2816 2557 4680 4250 -3.49E-07

11333 10290 9582 8701 3.28E-07

14165 12862 11075 10056 5.79E-07

24514 22259 16739 15199 1.46E-06

6 2 0.251 25513 100 60 5 6.22

0 0 9448 7589 -1.77E-06

8.16E-11 2.54E-10 0.321 1.20E-10 7394 5939 14417 11580 -1.32E-06

54425 43715 47834 38421 1.24E-06

427

59265 47603 51953 41730 1.37E-06

64465 51780 54013 43384 1.96E-06

6 2 0.273 461 40 40 5 5.10

0 0 173 170 -4.44E-08

1.17E-10 2.87E-10 0.408 1.98E-10

63 62 215 211 -3.89E-08

121 119 242 237 -3.09E-08

844 827 709 695 3.45E-08

893 875 750 735 3.66E-08

948 929 770 754 4.57E-08

6 2 0.276 2637 60 60 5 5.20

0 0 1251 1136 -2.35E-07

1.06E-10 2.16E-10 0.493 2.09E-10

551 500 1545 1403 -1.86E-07

1081 982 1802 1636 -1.35E-07

5185 4708 4227 3838 1.80E-07

5690 5166 4516 4100 2.20E-07

6215 5643 4835 4390 2.59E-07


PZ/HEP CO2 ldg P*CO2 T P Gas Dry Gas

PCO2in,

dry

PCO2in,

wet

PCO2out,

dry

PCO2out,

wet CO2 flux KG kg

KG/kg

kg'

m mol


Std

L/min

Std


mol/s Pa

cm2

mol/s Pa

cm2

mol/s Pa

cm2

6 2 0.273 12018 80 60 5 5.51

0 0 5345 4853 -1.00E-06

1.00E-10 2.28E-10 0.440 1.79E-10

2111 1917 6292 5713 -7.84E-07

4366 3965 7332 6658 -5.56E-07

27233 24727 22444 20379 8.98E-07

40002 36322 29601 26878 1.95E-06

48910 44410 35008 31787 2.61E-06

6 2 0.312 144 20 40 5 5.03

0 0 36 36 -9.27E-09

7.82E-11 2.82E-10 0.278 1.08E-10

34 34 63 63 -7.43E-09

63 62 88 88 -6.56E-09

235 233 207 206 6.95E-09

340 338 290 288 1.28E-08

449 446 370 368 2.02E-08

6 2 0.309 1038 40 40 5 5.10

0 0 296 290 -7.58E-08

8.55E-11 2.87E-10 0.297 1.22E-10

164 161 425 417 -6.68E-08

310 303 506 496 -5.03E-08

1932 1894 1686 1653 6.27E-08

2395 2348 2026 1986 9.46E-08

2836 2781 2339 2293 1.27E-07

6 2 0.313 5922 60 40 5 5.28 0 0 1648 1561 -4.22E-07

8.77E-11 2.98E-10 0.294 1.24E-10 1395 1321 2783 2635 -3.55E-07

428

2843 2693 3755 3557 -2.34E-07

13687 12963 11801 11177 4.83E-07

16213 15356 13498 12784 6.95E-07

21529 20391 17155 16248 1.12E-06

6 2 0.309 25264 80 60 5 5.20

0 0 6987 6717 -1.31E-06

6.03E-11 2.16E-10 0.280 8.37E-11

6766 6504 11951 11488 -9.72E-07

12466 11983 16018 15398 -6.66E-07

45985 44205 40939 39355 9.46E-07

55099 52966 47788 45938 1.37E-06

64213 61727 53709 51630 1.97E-06

6 2 0.344 296 20 40 5 5.03

0 0 63 63 -1.61E-08

6.50E-11 2.82E-10 0.231 8.45E-11

64 63 119 118 -1.42E-08

122 121 161 160 -9.94E-09

453 450 420 417 8.50E-09

654 650 575 571 2.03E-08

789 784 678 674 2.84E-08



PCO2in,

dry

PCO2in,

wet

PCO2out,

dry

PCO2out,

wet CO2 flux KG kg

KG/kg

kg'

m mol


Std

L/min

Std


mol/s Pa

cm2

mol/s Pa

cm2

mol/s Pa

cm2

6 2 0.341 2177 40 40 5 5.10

0 0 505 495 -1.29E-07

6.90E-11 2.87E-10 0.240 9.08E-11

747 732 1078 1057 -8.50E-08

1440 1412 1633 1601 -4.92E-08

4294 4210 3834 3759 1.18E-07

7054 6916 5923 5807 2.90E-07

12597 12350 10184 9984 6.18E-07

6 2 0.340 11084 60 60 5 5.20

0 0 3033 2915 -5.69E-07

6.30E-11 2.16E-10 0.293 8.91E-11

3589 3450 5705 5484 -3.97E-07

7255 6974 8424 8098 -2.19E-07

21013 20199 18902 18170 3.96E-07

27501 26436 23073 22179 8.30E-07

40270 38711 32083 30841 1.53E-06

6 2 0.358 616 20 40 5 5.03

0 0 125 124 -3.21E-08

5.86E-11 2.82E-10 0.208 7.39E-11

125 124 223 222 -2.51E-08

216 214 301 299 -2.18E-08

1003 997 929 924 1.89E-08

1095 1088 998 991 2.48E-08

1288 1280 1149 1142 3.55E-08

429

6 2 0.358 4983 40 40 5 5.10

0 0 886 869 -2.27E-07

4.95E-11 2.87E-10 0.172 5.98E-11

1429 1401 2040 2000 -1.56E-07

2922 2865 3292 3227 -9.46E-08

8525 8358 7959 7803 1.45E-07

11240 11020 10184 9984 2.70E-07

13917 13644 12371 12128 3.96E-07

6 2 0.358 22289 60 60 5 5.20

0 0 4351 4182 -8.16E-07

4.06E-11 2.16E-10 0.188 4.99E-11

7559 7266 10442 10038 -5.41E-07

12203 11731 14108 13562 -3.57E-07

53858 51773 48915 47022 9.27E-07

63590 61128 55763 53605 1.47E-06

73373 70532 63590 61128 1.83E-06

6 2 0.371 1510 20 40 5 5.03

0 0 197 193 -5.04E-08

3.60E-11 2.87E-10 0.125 4.11E-11

207 203 385 377 -4.56E-08

399 391 541 530 -3.64E-08

1904 1867 1856 1819 1.25E-08

2815 2759 2652 2601 4.15E-08

3237 3174 3018 2959 5.60E-08



PCO2in,

dry

PCO2in,

wet

PCO2out,

dry

PCO2out,

wet CO2 flux KG kg

KG/kg

kg'

m mol


Std

L/min

Std


mol/s Pa

cm2

mol/s Pa

cm2

mol/s Pa

cm2

6 2 0.373 10083 40 40 5 5.10

0 0 1233 1209 -3.16E-07

3.20E-11 2.87E-10 0.111 3.60E-

11

2820 2765 3654 3582 -2.13E-07

5652 5541 6138 6018 -1.25E-07

21416 20997 20172 19777 3.19E-07

23942 23473 22472 22032 3.76E-07

26280 25765 24319 23843 5.02E-07

430

Table B-54: Detailed WWC data for 5 m PZ/5 m 2PE (part 1)

PZ/2PE CO2 ldg P*CO2 T P Gas Dry Gas

PCO2in,

dry

PCO2in,

wet

PCO2out,

dry

PCO2out,

wet CO2 flux KG kg

KG/kg

kg'

m mol


Std

L/min

Std


mol/s Pa

cm2

mol/s Pa

cm2

mol/s Pa

cm2

5 5 0.194 31 40 40 5 5.10

0 0 15 15 -3.96E-09

1.70E-10 2.87E-10 0.591 4.15E-10

8 7 18 18 -2.70E-09

16 16 25 24 -2.22E-09

54 53 43 43 2.80E-09

61 60 47 46 3.57E-09

5 5 0.194 241 60 40 5 5.28

0 0 118 111 -3.01E-08

1.73E-10 2.98E-10 0.579 4.10E-10

51 48 146 139 -2.45E-08

98 93 177 168 -2.02E-08

426 403 337 320 2.26E-08

481 456 377 357 2.65E-08

523 496 399 377 3.20E-08

5 5 0.194 1309 80 60 5 5.51

0 0 818 743 -1.53E-07

1.59E-10 2.28E-10 0.699 5.28E-10

206 187 851 773 -1.21E-07

602 547 1021 927 -7.84E-08

2401 2181 1871 1699 9.94E-08

2798 2541 2113 1919 1.28E-07

3303 2999 2283 2073 1.91E-07

5 5 0.194 7542 100 60 5 6.22

0 0 3996 3209 -7.49E-07

1.47E-10 2.54E-10 0.576 3.45E-10

2889 2320 5829 4682 -5.51E-07

5715 4591 8038 6456 -4.35E-07

24293 19513 17239 13847 1.32E-06

27125 21787 18835 15129 1.55E-06

27125 21787 18835 15129 1.55E-06

5 5 0.228 48 40 20 5 5.16

0 0 17 16 -6.66E-09

1.76E-10 4.57E-10 0.384 2.85E-10

13 13 25 24 -4.83E-09

25 24 36 35 -4.34E-09

81 78 69 67 4.63E-09

102 99 82 79 8.40E-09

163 158 125 121 1.52E-08

5 5 0.228 368 60 40 5 5.28

0 0 177 167 -4.53E-08

1.68E-10 2.98E-10 0.564 3.86E-10

64 61 215 204 -3.86E-08

121 115 247 234 -3.22E-08

652 617 535 506 3.00E-08

698 661 560 531 3.52E-08

744 705 569 539 4.48E-08

431


PZ/2PE CO2 ldg P*CO2 T P Gas Dry Gas PCO2in, dry

PCO2in,

wet

PCO2out,

dry

PCO2out,

wet CO2 flux KG kg

KG/kg

kg'

m mol


Std

L/min

Std


mol/s Pa

cm2

mol/s Pa

cm2

mol/s Pa

cm2

5 5 0.228 2461 80 40 5 5.72

0 0 1256 1098 -3.21E-07

1.77E-10 3.21E-10 0.550 3.92E-10

1437 1256 1983 1734 -1.40E-07

2108 1843 2455 2146 -8.88E-08

4340 3794 3729 3260 1.56E-07

5720 5001 4453 3893 3.24E-07

9841 8604 6598 5769 8.30E-07

5 5 0.228 11982 100 60 5 6.84

0 0 5392 3943 -1.38E-06

1.27E-10 3.76E-10 0.337 1.91E-10

4389 3209 7805 5707 -8.75E-07

8672 6342 10708 7830 -5.21E-07

25978 18997 23037 16846 7.53E-07

30012 21947 26016 19025 1.02E-06

33632 24594 26883 19659 1.73E-06

5 5 0.271 84 40 40 5 5.10

0 0 38 37 -9.65E-09

1.48E-10 2.87E-10 0.517 3.07E-10

23 23 50 49 -6.85E-09

43 42 61 60 -4.73E-09

176 173 138 135 9.94E-09

202 198 152 149 1.26E-08

215 211 158 155 1.46E-08

5 5 0.271 606 60 40 5 5.28

0 0 270 256 -6.91E-08

1.42E-10 2.98E-10 0.477 2.72E-10

111 105 324 307 -5.45E-08

213 202 382 362 -4.33E-08

1154 1093 935 886 5.60E-08

1253 1187 1007 954 6.29E-08

1349 1277 1062 1006 7.33E-08

5 5 0.271 3701 80 60 5 5.51

0 0 1854 1683 -3.48E-07

1.26E-10 2.28E-10 0.551 2.80E-10

638 580 2235 2029 -2.99E-07

1375 1248 2564 2328 -2.23E-07

8398 7625 6524 5924 3.51E-07

9747 8850 7070 6419 5.02E-07

11328 10286 8038 7298 6.17E-07

5 5 0.271 16843 100 60 5 6.22

0 0 6858 5509 -1.29E-06

9.83E-11 2.54E-10 0.387 1.60E-10

4258 3420 10128 8135 -1.10E-06

8362 6716 12975 10422 -8.65E-07

40728 32714 34086 27379 1.25E-06

44487 35733 36300 29157 1.53E-06

44487 35733 36300 29157 1.53E-06

432


PZ/2PE CO2 ldg P*CO2 T P Gas Dry Gas PCO2in, dry PCO2in, wet PCO2out, dry PCO2out, wet CO2 flux KG kg

KG/kg

kg'

m mol CO2/

mol alk Pa °C psig

Std

L/min

Std


mol/s Pa

cm2

mol/s Pa

cm2

mol/s Pa

cm2

5 5 0.324 166 40 40 5 5.10

0 0 63 62 -1.61E-08

1.25E-10 2.87E-10 0.434 2.21E-10

64 63 105 103 -1.04E-08

121 119 142 139 -5.21E-09

290 284 244 239 1.18E-08

339 333 273 267 1.71E-08

444 435 341 334 2.64E-08

5 5 0.324 1186 60 40 5 5.28

0 0 453 429 -1.16E-07

1.23E-10 2.98E-10 0.412 2.09E-10

272 257 643 609 -9.50E-08

506 480 770 729 -6.74E-08

2401 2274 1967 1863 1.11E-07

2620 2481 2133 2021 1.25E-07

2835 2685 2258 2138 1.48E-07

5 5 0.324 7710 80 60 5 5.51

0 0 3383 3072 -6.34E-07

1.02E-10 2.28E-10 0.449 1.86E-10

2132 1936 4603 4180 -4.63E-07

4305 3908 5865 5325 -2.93E-07

15231 13829 12656 11492 4.83E-07

16724 15185 13428 12193 6.18E-07

17960 16307 14304 12988 6.85E-07

5 5 0.324 30221 100 60 5 6.22

0 0 10803 8677 -2.03E-06

7.99E-11 2.54E-10 0.314 1.16E-10

7677 6166 17342 13929 -1.81E-06

14613 11737 19968 16038 -1.00E-06

68522 55039 60336 48463 1.53E-06

78202 62814 66051 53054 2.28E-06

5 5 0.393 449 40 40 5 5.10

0 0 121 118 -3.09E-08

8.37E-11 2.87E-10 0.291 1.18E-10

65 64 183 180 -3.02E-08

120 118 208 204 -2.26E-08

838 821 727 712 2.85E-08

898 880 787 771 2.85E-08

951 932 813 797 3.53E-08

5 5 0.393 3232 60 40 5 5.28

0 0 984 932 -2.52E-07

8.86E-11 2.98E-10 0.297 1.26E-10

445 421 1252 1186 -2.07E-07

886 839 1580 1496 -1.78E-07

5509 5217 4920 4660 1.51E-07

5957 5642 5267 4989 1.77E-07

6153 5828 5373 5089 2.00E-07

433



PCO2in,

dry

PCO2in,

wet

PCO2out,

dry

PCO2out,

wet CO2 flux KG kg

KG/kg

kg'

m mol CO2/mol

alk Pa °C psig

Std

L/min

Std


mol/s Pa

cm2

mol/s Pa

cm2

mol/s Pa

cm2

5 5 0.393 19142 80 60 5 5.51

0 0 5535 5026 -1.04E-06

6.41E-11 2.28E-10 0.282 8.93E-11

1411 1281 6673 6059 -9.87E-07

2956 2684 7883 7158 -9.24E-07

50712 46046 42834 38893 1.48E-06

51793 47028 43555 39548 1.54E-06

53544 48618 44018 39969 1.79E-06

5 5 0.453 1429 40 40 5 5.10

0 0 263 258 -6.74E-08

4.87E-11 2.87E-10 0.170 5.87E-11

216 211 422 413 -5.27E-08

407 399 580 569 -4.44E-08

1768 1733 1702 1669 1.67E-08

2517 2468 2340 2294 4.54E-08

3064 3004 2796 2741 6.85E-08

5 5 0.453 8749 60 60 5 5.20

0 0 1921 1846 -3.60E-07

4.46E-11 2.16E-10 0.207 5.62E-11

1416 1361 2966 2851 -2.91E-07

2883 2772 4104 3945 -2.29E-07

24859 23897 21615 20779 6.08E-07

26198 25184 22851 21967 6.27E-07

27691 26619 23778 22857 7.34E-07

5 5 0.453 39049 80 60 5 5.51

0 0 6853 6223 -1.28E-06

3.30E-11 2.28E-10 0.145 3.86E-11

6694 6078 12090 10977 -1.01E-06

12347 11211 16363 14858 -7.53E-07

74753 67875 69501 63106 9.85E-07

86132 78207 79799 72457 1.19E-06

90354 82041 83866 76150 1.22E-06

5 5 0.488 605 20 40 5 5.03

0 0 60 60 -1.53E-08

2.69E-11 2.82E-10 0.095 2.97E-11

62 62 117 116 -1.39E-08

119 118 171 170 -1.32E-08

964 958 921 915 1.12E-08

1271 1263 1209 1201 1.58E-08

1456 1447 1374 1365 2.09E-08

5 5 0.488 4862 40 40 5 5.10

0 0 411 403 -1.05E-07

2.26E-11 2.87E-10 0.079 2.46E-11

415 407 807 791 -1.00E-07

829 813 1158 1135 -8.40E-08

11688 11459 11123 10905 1.45E-07

12028 11792 11462 11238 1.45E-07

12518 12273 11877 11644 1.64E-07

434



PCO2in,

dry

PCO2in,

wet

PCO2out,

dry

PCO2out,

wet CO2 flux KG kg

KG/kg

kg'

m mol CO2/mol

alk Pa °C psig

Std

L/min

Std


mol/s Pa

cm2

mol/s Pa

cm2

mol/s Pa

cm2

5 5 0.488 25224 60 60 5 5.20

0 0 2863 2752 -5.37E-07

1.93E-11 2.16E-10 0.089 2.12E-11

3666 3524 5736 5514 -3.88E-07

6462 6212 8079 7766 -3.03E-07

44024 42319 42016 40389 3.76E-07

54425 52318 51696 49694 5.12E-07

64620 62118 61324 58950 6.18E-07

5 5 0.518 3270 20 40 5 5.03

0 0 121 120 -3.09E-08

9.07E-12 2.82E-10 0.032 9.37E-12

577 573 664 659 -2.22E-08

7168 7123 7028 6984 3.57E-08

7918 7869 7767 7719 3.86E-08

8634 8581 8446 8393 4.83E-08

5 5 0.518 19293 40 40 5 5.10

0 0 430 421 -1.10E-07

5.61E-12 2.87E-10 0.020 5.72E-12

2899 2843 3310 3246 -1.05E-07

5241 5138 5475 5367 -5.99E-08

39736 38958 39321 38552 1.06E-07

44298 43431 43770 42914 1.35E-07

435

Table B-59: Detailed WWC data for 5 m PZ/5 m DGA (part 1)

PZ/DGA CO2 ldg P*CO2 T P Gas Dry Gas

PCO2in,

dry

PCO2in,

wet

PCO2out,

dry

PCO2out,

wet CO2 flux KG kg

KG/kg

kg'

m mol


Std

L/min

Std


mol/s Pa

cm2

mol/s Pa

cm2

mol/s Pa

cm2

5 5 0.321 291 40 40 5 5.10

0 0 103 101 -2.65E-08

1.09E-10 2.87E-10 0.380 1.759E-10

63 61 143 140 -2.07E-08

122 120 181 177 -1.51E-08

547 537 456 447 2.35E-08

647 635 530 519 3.01E-08

750 735 598 587 3.88E-08

5 5 0.321 2205 60 40 5 5.28

0 0 773 732 -1.98E-07

1.13E-10 2.98E-10 0.379 1.823E-10

656 621 1252 1186 -1.53E-07

3695 3500 3254 3082 1.13E-07

4208 3985 3544 3357 1.70E-07

4747 4496 3917 3710 2.12E-07

5 5 0.321 10254 80 60 5 5.51

0 0 3784 3436 -7.10E-07

8.50E-11 2.28E-10 0.373 1.356E-10

2775 2520 5736 5208 -5.55E-07

5036 4572 7049 6400 -3.77E-07

28206 25611 22748 20655 1.02E-06

33818 30707 25940 23554 1.48E-06

38349 34821 29287 26593 1.70E-06

5 5 0.321 51739 100 60 5 6.22

0 0 13320 10699 -2.50E-06

5.31E-11 2.54E-10 0.209 6.706E-11

12085 9707 23206 18640 -2.09E-06

17594 14132 26347 21163 -1.64E-06

95240 76499 88804 71330 1.21E-06

97609 78402 91070 73149 1.23E-06

99977 80304 92769 74514 1.35E-06

5 5 0.369 664 40 40 5 5.10

0 0 206 202 -5.27E-08

9.12E-11 2.87E-10 0.317 1.336E-10

163 159 310 304 -3.78E-08

317 311 420 411 -2.63E-08

1082 1061 963 944 3.06E-08

1181 1158 1028 1008 3.91E-08

1285 1260 1111 1089 4.46E-08

5 5 0.369 4997 60 40 5 5.28

0 0 1372 1300 -3.51E-07

8.17E-11 2.98E-10 0.274 1.125E-10

543 514 1772 1678 -3.15E-07

1071 1014 2179 2064 -2.84E-07

9573 9067 8442 7996 2.90E-07

10742 10174 9309 8817 3.67E-07

11835 11210 10139 9603 4.34E-07

436



PCO2in,

dry

PCO2in,

wet

PCO2out,

dry

PCO2out,

wet CO2 flux KG kg

KG/kg

kg'

m mol


Std

L/min

Std


mol/s Pa

cm2

mol/s Pa

cm2

mol/s Pa

cm2

5 5 0.369 24745 80 60 5 5.51

0 0 5736 5208 -1.08E-06

5.09E-11 2.28E-10 0.223 6.552E-11

6153 5587 11271 10234 -9.60E-07

11889 10795 14927 13554 -5.70E-07

54110 49132 49116 44597 9.36E-07

64563 58623 55243 50161 1.75E-06

84850 77043 72595 65916 2.30E-06

5 5 0.418 214 20 40 5 5.03

0 0 46 45 -1.17E-08

6.23E-11 2.82E-10 0.221 7.995E-11

38 38 79 79 -1.05E-08

62 62 93 93 -7.92E-09

414 412 369 367 1.15E-08

443 440 394 392 1.24E-08

467 464 414 412 1.34E-08

5 5 0.418 2042 40 40 5 5.10

0 0 437 429 -1.12E-07

6.04E-11 2.87E-10 0.210 7.654E-11

339 333 705 691 -9.36E-08

645 632 928 909 -7.24E-08

3627 3556 3303 3238 8.30E-08

3748 3674 3408 3342 8.69E-08

3936 3859 3555 3486 9.75E-08

5 5 0.418 11397 60 60 5 5.20

0 0 2693 2589 -5.05E-07

5.06E-11 2.16E-10 0.235 6.604E-11

1905 1831 4217 4054 -4.33E-07

4135 3975 5849 5623 -3.21E-07

24092 23159 21466 20635 4.92E-07

27233 26179 23577 22664 6.85E-07

32536 31277 27233 26179 9.94E-07

5 5 0.418 69167 80 60 5 5.51

0 0 8207 7452 -1.54E-06

2.34E-11 2.28E-10 0.103 2.612E-11 5787 5255 13331 12104 -1.41E-06

93963 85318 91749 83308 4.15E-07

103438 93921 100606 91349 5.31E-07

5 5 0.437 821 20 40 5 5.03

0 0 104 104 -2.67E-08

3.44E-11 2.82E-10 0.122 3.922E-11

106 105 198 197 -2.37E-08

204 203 284 282 -2.04E-08

883 877 866 861 4.15E-09

1633 1622 1531 1522 2.60E-08

1815 1804 1696 1685 3.05E-08

437



PCO2in,

dry

PCO2in,

wet

PCO2out,

dry

PCO2out,

wet CO2 flux KG kg

KG/kg

kg'

m mol


Std

L/min

Std


mol/s Pa

cm2

mol/s Pa

cm2

mol/s Pa

cm2

5 5 0.437 7052 40 40 5 5.10

0 0 818 802 -2.09E-07

2.95E-11 2.87E-10 0.103 3.286E-11

1059 1039 1693 1660 -1.62E-07

2081 2041 2602 2551 -1.33E-07

12929 12676 12288 12047 1.64E-07

14927 14635 14097 13822 2.12E-07

17001 16668 15983 15670 2.61E-07

5 5 0.437 44803 60 60 5 5.20

0 0 4536 4361 -8.50E-07

1.81E-11 2.16E-10 0.084 1.970E-11

6462 6212 9886 9503 -6.42E-07

12090 11622 14767 14196 -5.02E-07

90560 87054 86853 83491 6.95E-07

95246 91559 91281 87747 7.43E-07

99983 96112 94834 91163 9.65E-07

5 5 0.457 2806 20 40 5 5.03

0 0 219 217 -5.60E-08

1.94E-11 2.82E-10 0.069 2.080E-11

215 214 403 401 -4.83E-08

434 431 599 596 -4.25E-08

3318 3297 3265 3245 1.35E-08

4340 4313 4223 4197 2.99E-08

5147 5115 4996 4965 3.86E-08

5 5 0.457 25511 40 40 5 5.10

0 0 1244 1220 -3.19E-07

1.07E-11 2.87E-10 0.037 1.116E-11 6353 6229 6926 6791 -1.47E-07

56100 55001 54893 53819 3.09E-07

58287 57145 57005 55889 3.28E-07

438

Table B-62: Detailed WWC data for 3.5 m PZ/3.5 m Tris (part 1)

PZ Tris CO2 ldg P*CO2 T P Gas Dry Gas

PCO2in,

dry

PCO2in,

wet

PCO2out,

dry

PCO2out,

wet CO2 flux KG kg

KG/kg

kg'

m m mol


Std

L/min

Std


mol/s Pa

cm2

mol/s Pa

cm2

mol/s Pa

cm2

3.5 3.5 0.203 332 40 40 5 5.1

0 0 111 109 -2.85E-08

9.63E-11 2.87E-10 0.335 1.45E-10

107 105 180 177 -1.86E-08

162 159 214 210 -1.33E-08

701 688 583 571 3.04E-08

987 967 780 765 5.29E-08

1478 1449 1135 1113 8.79E-08

3.5 3.5 0.203 1877 60 40 5 5.28

0 0 667 632 -1.71E-07

1.07E-10 2.98E-10 0.360 1.68E-10

324 307 890 843 -1.45E-07

660 625 1075 1018 -1.06E-07

3152 2985 2749 2603 1.03E-07

3654 3460 3062 2900 1.52E-07

5252 4975 4223 4000 2.64E-07

3.5 3.5 0.203 7999 80 40 5 5.72

0 0 2541 2222 -6.51E-07

8.83E-11 3.21E-10 0.275 1.22E-10

2632 2301 4460 3900 -4.68E-07

5524 4830 6470 5657 -2.42E-07

17642 15425 15191 13282 6.27E-07

23674 20700 19602 17139 1.04E-06

44977 39326 35890 31381 2.33E-06

3.5 3.5 0.203 46703 100 50 5 6.47

0 0 9802 7575 -2.12E-06

4.84E-11 3.03E-10 0.159 5.76E-11

6743 5211 15778 12194 -1.96E-06

12389 9574 19168 14813 -1.47E-06

81826 63236 79150 61168 5.79E-07

86910 67165 82406 63684 9.75E-07

3.5 3.5 0.255 1038 40 40 5 5.1

0 0 272 267 -6.97E-08

7.64E-11 2.87E-10 0.266 1.04E-10

178 175 420 411 -6.18E-08

510 500 629 617 -3.05E-08

1486 1456 1365 1338 3.10E-08

1959 1920 1736 1702 5.70E-08

2434 2386 2091 2050 8.78E-08

3.5 3.5 0.255 5669 60 40 5 5.28

0 0 1452 1375 -3.72E-07

7.24E-11 2.98E-10 0.243 9.56E-11

2142 2028 3035 2875 -2.29E-07

2647 2507 3416 3235 -1.97E-07

11835 11210 10365 9817 3.76E-07

15229 14424 13117 12424 5.41E-07

17604 16673 14889 14102 6.95E-07

439



PCO2in,

dry

PCO2in,

wet

PCO2out,

dry

PCO2out

, wet CO2 flux KG kg

KG/k

g

kg'

m m mol


Std

L/min

Std


mol/s Pa

cm2

mol/s Pa

cm2

mol/s Pa

cm2

3.5 3.5 0.255 24986 80 40 5 5.72

0 0 4773 4174 -1.22E-06

5.23E-11 3.21E-10 0.163 6.25E-11

3752 3280 7944 6946 -1.07E-06

6285 5496 9716 8496 -8.78E-07

44102 38561 41388 36187 6.95E-07

49305 43110 45987 40209 8.50E-07

54923 48022 50700 44330 1.08E-06

3.5 3.5 0.315 297 20 40 5 5.03

0 0 61 61 -1.56E-08

5.97E-11 2.82E-10 0.212 7.58E-11

64 63 114 113 -1.28E-08

121 120 159 158 -9.65E-09

543 540 491 488 1.33E-08

644 640 567 564 1.95E-08

849 844 739 735 2.81E-08

3.5 3.5 0.315 2297 40 40 5 5.1

0 0 566 554 -1.45E-07

6.85E-11 2.87E-10 0.238 8.99E-11

347 340 792 776 -1.14E-07

671 658 1041 1020 -9.46E-08

4234 4151 3804 3730 1.10E-07

4743 4650 4178 4096 1.45E-07

5275 5172 4604 4514 1.72E-07

3.5 3.5 0.315 12485 60 40 5 5.28

0 0 2323 2200 -5.95E-07

4.96E-11 2.98E-10 0.166 5.94E-11

2677 2535 4419 4185 -4.46E-07

5320 5039 6523 6178 -3.08E-07

23256 22026 21521 20384 4.44E-07

28761 27240 26234 24848 6.47E-07

33775 31990 30306 28704 8.88E-07

3.5 3.5 0.315 48003 80 40 5 5.72

0 0 6481 5667 -1.66E-06

3.25E-11 3.21E-10 0.101 3.62E-11

12016 10506 16277 14232 -1.09E-06

23177 20265 25778 22539 -6.66E-07

72493 63385 70910 62000 4.05E-07

75359 65890 73210 64011 5.50E-07

3.5 3.5 0.349 584 20 40 5 5.03

0 0 124 123 -3.18E-08

5.28E-11 2.82E-10 0.187 6.49E-11

118 117 203 202 -2.17E-08

207 206 264 262 -1.44E-08

1103 1096 995 989 2.77E-08

1207 1199 1102 1096 2.66E-08

1308 1300 1178 1171 3.34E-08

440



PCO2in,

dry

PCO2in,

wet

PCO2out,

dry

PCO2out,

wet CO2 flux KG kg

KG/kg

kg'

m m mol


Std

L/min

Std


mol/s Pa

cm2

mol/s Pa

cm2

mol/s Pa

cm2

3.5 3.5 0.349 4401 40 40 5 5.1

0 0 735 721 -1.88E-07

4.50E-11 2.87E-10 0.157 5.33E-11

1097 1076 1648 1615 -1.41E-07

2130 2089 2477 2429 -8.88E-08

8517 8351 7839 7685 1.74E-07

9837 9644 8970 8794 2.22E-07

11948 11714 10817 10605 2.90E-07

3.5 3.5 0.349 22725 60 40 5 5.28

0 0 3084 2921 -7.90E-07

3.36E-11 2.98E-10 0.113 3.79E-11

4306 4078 6572 6224 -5.80E-07

7650 7246 9309 8817 -4.25E-07

46975 44492 44223 41885 7.05E-07

49992 47349 46787 44313 8.21E-07

55383 52455 51952 49206 8.78E-07

3.5 3.5 0.367 974 20 40 5 5.03

0 0 132 132 -3.39E-08

3.99E-11 2.82E-10 0.141 4.64E-11

211 210 331 329 -3.06E-08

409 407 492 489 -2.11E-08

1479 1470 1407 1398 1.84E-08

1678 1668 1573 1563 2.70E-08

1870 1858 1746 1735 3.17E-08

3.5 3.5 0.367 7191 40 40 5 5.1

0 0 995 976 -2.55E-07

3.77E-11 2.87E-10 0.131 4.34E-11

1086 1065 1934 1896 -2.17E-07

2142 2100 2813 2758 -1.72E-07

12209 11970 11568 11341 1.64E-07

15300 15001 14245 13966 2.70E-07

17562 17219 16167 15851 3.57E-07

3.5 3.5 0.367 40915 60 40 5 5.28

0 0 4313 4085 -1.10E-06

2.63E-11 2.98E-10 0.088 2.89E-11

4321 4092 7873 7456 -9.09E-07

7835 7421 10851 10278 -7.72E-07

66728 63201 64542 61130 5.60E-07

71064 67308 68312 64701 7.05E-07

76494 72450 73591 69700 7.43E-07

441

B.2.3 Primary Amines

Table B-65: Detailed WWC data for 7 m 3 amino 1 propanol (part 1)

3amino

1propanol CO2 ldg P*

CO2 T P Gas Dry Gas PCO2in,

dry

PCO2in,

wet

PCO2out,

dry

PCO2out,

wet CO2 flux KG kg

KG/kg

kg'

m mol


Std

L/min

Std


mol/s Pa

cm2

mol/s Pa

cm2

mol/s Pa

cm2

7 0.325 25 40 40 5 5.10

0 0 9 9 -2.41E-09

1.28E-10 2.87E-10 0.447 2.318E-10

5 5 12 12 -1.83E-09

10 10 17 16 -1.74E-09

48 47 38 37 2.70E-09

75 74 53 52 5.60E-09

122 119 85 84 9.36E-09

7 0.325 137 60 40 5 5.28

0 0 56 53 -1.44E-08

1.30E-10 2.98E-10 0.437 2.309E-10

31 30 74 70 -1.10E-08

61 58 93 88 -8.01E-09

341 323 266 252 1.93E-08

392 371 297 282 2.41E-08

440 416 327 310 2.88E-08

7 0.325 915 80 60 5 5.51

0 0 455 413 -8.53E-08

1.24E-10 2.28E-10 0.544 2.722E-10

196 178 559 508 -6.82E-08

1562 1418 1311 1191 4.69E-08

1755 1593 1442 1310 5.86E-08

1952 1772 1503 1365 8.42E-08

401 364 752 683 -6.57E-08

7 0.325 6560 100 60 5 6.22

0 0 3414 2742 -6.40E-07

1.26E-10 2.54E-10 0.495 2.493E-10

1056 848 3990 3205 -5.50E-07

2013 1617 4577 3677 -4.81E-07

14098 11324 11678 9380 4.54E-07

16569 13309 13120 10538 6.47E-07

18835 15129 14304 11489 8.50E-07

7 0.385 32 40 40 5 5.10

0 0 9 9 -2.41E-09

9.48E-11 2.87E-10 0.330 1.415E-10

6 6 15 14 -2.22E-09

17 17 21 21 -1.06E-09

68 67 58 57 2.70E-09

90 89 74 72 4.25E-09

113 111 88 86 6.56E-09

7 0.385 302 60 40 5 5.28

0 0 104 98 -2.65E-08

1.09E-10 2.98E-10 0.365 1.711E-10 31 30 129 122 -2.51E-08

60 57 145 137 -2.18E-08

478 453 427 404 1.31E-08

442

505 478 443 420 1.57E-08

521 494 453 429 1.75E-08


3amino


CO2 T P Gas

Dry Gas

PCO2in,

dry

PCO2in,

wet

PCO2out,

dry

PCO2out,

wet CO2 flux KG kg

KG/kg

kg'

m mol


Std

L/min

Std


mol/s Pa

cm2

mol/s Pa

cm2

mol/s Pa

cm2

7 0.385 2114 80 60 5 5.51

0 0 880 799 -1.65E-07

1.05E-10 2.28E-10 0.460 1.941E-10

527 479 1339 1216 -1.52E-07

1010 917 1508 1369 -9.34E-08

3837 3484 3147 2858 1.29E-07

4295 3900 3564 3236 1.37E-07

4738 4302 3796 3447 1.77E-07

7 0.385 12116 100 60 5 6.22

0 0 5041 4049 -9.45E-07

9.99E-11 2.54E-10 0.393 1.644E-10

2636 2118 7023 5641 -8.22E-07

5221 4194 8779 7051 -6.67E-07

23371 18772 20591 16539 5.21E-07

28520 22908 23989 19269 8.50E-07

34132 27416 27284 21915 1.28E-06

7 0.472 245 40 40 5 5.10

0 0 51 50 -1.31E-08

6.16E-11 2.87E-10 0.214 7.838E-11

33 33 80 78 -1.19E-08

62 61 104 102 -1.06E-08

337 330 315 309 5.50E-09

461 452 417 409 1.13E-08

534 524 476 467 1.49E-08

7 0.472 1770 60 40 5 5.28

0 0 420 398 -1.08E-07

6.84E-11 2.98E-10 0.229 8.869E-11

263 249 621 588 -9.15E-08

506 480 808 766 -7.73E-08

3290 3116 2973 2816 8.11E-08

3508 3323 3150 2984 9.17E-08

3757 3559 3327 3151 1.10E-07

7 0.472 10110 80 60 5 5.51

0 0 2786 2529 -5.22E-07

6.67E-11 2.28E-10 0.293 9.430E-11

2858 2595 5144 4671 -4.29E-07

5355 4862 6992 6349 -3.07E-07

17867 16223 16425 14914 2.70E-07

23170 21039 20029 18187 5.89E-07

34292 31137 27547 25013 1.26E-06

7 0.472 42059 100 60 5 6.22 0 0 10246 8230 -1.92E-06

4.85E-11 2.54E-10 0.191 5.990E-11 6503 5223 15133 12155 -1.62E-06

443

12558 10087 19458 15629 -1.29E-06

90308 72537 83717 67243 1.24E-06

95199 76466 87064 69932 1.53E-06

100091 80395 90823 72951 1.74E-06


3amino


CO2 T P Gas

Dry Gas

PCO2in,

dry

PCO2in,

wet

PCO2out,

dry

PCO2out,

wet CO2 flux KG kg

KG/kg

kg'

m

mol

CO2/mol

alk

Pa °C psig Std

L/min

Std


mol/s Pa

cm2

mol/s Pa

cm2

mol/s Pa

cm2

7 0.508 1509 40 40 5 5.10

0 0 173 169 -4.42E-08

3.19E-11 2.87E-10 0.111 3.585E-11

269 264 420 412 -3.88E-08

521 510 638 625 -2.99E-08

2668 2616 2536 2487 3.38E-08

2887 2830 2725 2672 4.15E-08

3121 3060 2947 2890 4.44E-08

7 0.508 7116 60 60 5 5.20

0 0 1318 1267 -2.47E-07

3.57E-11 2.16E-10 0.166 4.280E-11

1081 1039 2106 2024 -1.92E-07

2121 2039 2950 2836 -1.55E-07

16575 15933 15030 14448 2.90E-07

18686 17962 16832 16180 3.48E-07

20848 20041 18583 17863 4.25E-07

7 0.508 31282 80 60 5 5.51

0 0 4789 4348 -8.98E-07

2.93E-11 2.28E-10 0.129 3.361E-11

6483 5886 10174 9238 -6.92E-07

12296 11164 14716 13362 -4.54E-07

70582 64088 66308 60208 8.01E-07

75371 68436 70633 64135 8.88E-07

90766 82415 82425 74841 1.56E-06

7 0.553 1747 20 40 5 5.03

0 0 77 77 -1.98E-08

1.14E-11 2.82E-10 0.040 1.183E-11

223 222 290 289 -1.72E-08

510 507 562 558 -1.33E-08

938 933 972 966 -8.50E-09

2886 2868 2841 2823 1.16E-08

3316 3295 3248 3228 1.74E-08

3565 3542 3485 3464 2.03E-08

7 0.553 8657 40 40 5 5.10

0 0 456 447 -1.17E-07

1.31E-11 2.87E-10 0.046 1.371E-11 682 669 1082 1061 -1.02E-07

1704 1671 2032 1992 -8.40E-08

18279 17921 17789 17440 1.25E-07

444

20315 19917 19749 19363 1.45E-07

23256 22801 22577 22135 1.74E-07


3amino


CO2 T P Gas

Dry Gas

PCO2in,

dry

PCO2in,

wet

PCO2out,

dry

PCO2out,

wet CO2 flux KG kg

KG/kg

kg'

m mol CO2/mol

alk Pa °C psig

Std

L/min

Std


mol/s Pa

cm2

mol/s Pa

cm2

mol/s Pa

cm2

7 0.553 31081 60 60 5 5.20

0 0 2152 2069 -4.04E-07

1.16E-11 2.16E-10 0.054 1.220E-11

5839 5613 7384 7098 -2.90E-07

11940 11478 12816 12320 -1.64E-07

75891 72953 73162 70329 5.12E-07

85983 82654 82842 79635 5.89E-07

95096 91415 91749 88198 6.27E-07

7 0.586 6338 20 40 5 5.03

0 0 162 161 -4.15E-08

5.87E-12 2.82E-10 0.021 5.990E-12

1961 1948 2059 2046 -2.51E-08

3763 3740 3808 3784 -1.16E-08

11948 11874 11798 11724 3.86E-08

15116 15022 14927 14834 4.83E-08

17038 16933 16812 16708 5.79E-08

7 0.586 39953 40 60 5 5.07

0 0 886 873 -1.66E-07

3.17E-12 2.09E-10 0.015 3.221E-12

6184 6095 6725 6628 -1.01E-07

12038 11866 12296 12119 -4.83E-08

95709 94337 94782 93423 1.74E-07

100909 99463 99931 98499 1.83E-07

445

Table B-69: Detailed WWC data for 7 m MIPA (part 1)

MIPA CO2 ldg P*CO2 T P Gas Dry Gas PCO2in, dry PCO2in, wet PCO2out, dry PCO2out, wet CO2 flux KG kg

KG/kg

kg'

m

mol

CO2/mol

alk

Pa °C psig Std

L/min

Std


mol/s Pa

cm2

mol/s

Pa cm2

mol/s Pa

cm2

7 0.278 36 40 40 5 5.10

0 0 13 13 -3.38E-09

1.20E-10 2.87E-

10 0.416 2.05E-10

4 4 17 16 -3.19E-09

9 9 19 18 -2.61E-09

59 58 51 50 2.12E-09

77 75 61 60 4.05E-09

91 89 72 71 4.92E-09

7 0.278 276 60 40 5 5.28

0 0 104 99 -2.66E-08

1.29E-10 2.98E-

10 0.434 2.28E-10

62 59 153 145 -2.33E-08

117 111 190 180 -1.87E-08

440 416 379 359 1.54E-08

543 514 446 423 2.47E-08

746 707 575 545 4.37E-08

7 0.278 2120 80 60 5 5.51

0 0 1041 945 -1.95E-07

1.20E-10 2.28E-

10 0.529 2.55E-10

262 238 1180 1071 -1.72E-07

517 470 1307 1187 -1.48E-07

3831 3478 3177 2885 1.23E-07

4330 3932 3445 3128 1.66E-07

4778 4339 3697 3357 2.03E-07

7 0.278 12833 100 60 5 6.22

0 0 5695 4574 -1.07E-06

1.17E-10 2.54E-

10 0.459 2.16E-10

3264 2622 8630 6932 -1.01E-06

6194 4975 9989 8023 -7.11E-07

23366 18768 21152 16990 4.15E-07

34436 27660 27691 22242 1.26E-06

39276 31548 29184 23442 1.89E-06

7 0.333 96 40 40 5 5.10

0 0 31 30 -7.82E-09

9.49E-11 2.87E-

10 0.330 1.42E-10

21 21 42 41 -5.41E-09

34 33 55 54 -5.41E-09

203 199 172 169 7.82E-09

229 224 187 184 1.06E-08

446 437 340 333 2.71E-08

7 0.333 826 60 40 5 5.28

0 0 274 259 -7.01E-08

1.03E-10 2.98E-

10 0.346 1.58E-10

118 112 363 344 -6.26E-08

209 198 416 394 -5.31E-08

1582 1498 1355 1284 5.80E-08

1689 1600 1437 1361 6.47E-08

1776 1682 1484 1406 7.47E-08

446


MIPA CO2 ldg P*CO2 T P Gas Dry Gas PCO2in, dry PCO2in, wet

PCO2out,

dry

PCO2out,

wet CO2 flux KG kg

KG/k

g

kg'

m mol


Std

L/min

Std


mol/s Pa

cm2

mol/s Pa

cm2

mol/s Pa

cm2

7 0.333 5393 80 60 5 5.51

0 0 2090 1898 -3.92E-07

1.02E-10 2.28E-10 0.446 1.83E-10

1066 968 3017 2740 -3.66E-07

2142 1945 3682 3343 -2.89E-07

10293 9346 8825 8013 2.75E-07

13382 12151 10550 9580 5.31E-07

18171 16499 13228 12011 9.27E-07

7 0.333 27814 100 60 5 6.22

0 0 10159 8160 -1.90E-06

8.18E-11 2.54E-10 0.321 1.20E-10

6065 4872 15025 12068 -1.68E-06

12038 9669 18217 14632 -1.16E-06

76400 61366 63888 51317 2.35E-06

81137 65171 68419 54956 2.38E-06

85565 68728 69707 55990 2.97E-06

7 0.398 344 40 40 5 5.10

0 0 72 71 -1.85E-08

6.66E-11 2.87E-10 0.232 8.67E-11

32 32 110 108 -1.98E-08

60 59 126 123 -1.69E-08

647 634 587 576 1.53E-08

697 683 615 603 2.10E-08

751 736 658 645 2.37E-08

7 0.398 2721 60 40 5 5.28

0 0 675 639 -1.73E-07

7.32E-11 2.98E-10 0.245 9.69E-11

283 268 909 861 -1.60E-07

554 525 1101 1043 -1.40E-07

4257 4032 3910 3703 8.88E-08

4766 4514 4332 4103 1.11E-07

5279 5000 4709 4460 1.46E-07

7 0.398 16030 80 60 5 5.51

0 0 4866 4418 -9.12E-07

6.85E-11 2.28E-10 0.301 9.79E-11

3609 3277 7528 6835 -7.35E-07

6205 5634 9381 8518 -5.96E-07

28881 26223 26152 23746 5.12E-07

34235 31086 29756 27018 8.40E-07

45718 41511 37376 33938 1.56E-06

7 0.455492 111 20 40 5 5.03

0 0 17 17 -4.34E-09

3.89E-11 2.82E-10 0.138 4.51E-11

17 17 30 30 -3.28E-09

39 39 48 48 -2.32E-09

204 203 191 190 3.38E-09

232 230 215 214 4.25E-09

447


MIPA CO2 ldg P*CO2 T P Gas Dry Gas PCO2in, dry

PCO2in,

wet

PCO2out,

dry

PCO2out,

wet CO2 flux KG kg

KG/kg

kg'

m mol


Std

L/min

Std


mol/s Pa

cm2

mol/s Pa

cm2

mol/s Pa

cm2

7 0.455 1035 40 40 5 5.10

0 0 177 173 -4.53E-08

4.72E-11 2.87E-10 0.164 5.64E-11

115 112 269 264 -3.96E-08

214 210 350 343 -3.48E-08

1470 1442 1404 1377 1.69E-08

1708 1674 1604 1573 2.65E-08

1958 1920 1804 1768 3.96E-08

7 0.455 7065 60 60 5 5.20

0 0 1684 1619 -3.16E-07

5.00E-11 2.16E-10 0.232 6.51E-11

1092 1049 2523 2425 -2.68E-07

2137 2054 3352 3222 -2.28E-07

14360 13805 12764 12270 2.99E-07

17038 16378 14618 14052 4.54E-07

23371 22466 19921 19150 6.47E-07

7 0.487 383 20 40 5 5.03

0 0 32 32 -8.30E-09

2.37E-11 2.82E-10 0.084 2.58E-11

33 33 68 67 -8.98E-09

66 66 92 91 -6.56E-09

690 685 663 659 6.85E-09

740 735 705 701 8.88E-09

795 790 763 758 8.30E-09

7 0.487 3337 40 40 5 5.10

0 0 373 366 -9.56E-08

3.01E-11 2.87E-10 0.105 3.36E-11

298 292 637 625 -8.69E-08

603 591 909 891 -7.82E-08

4132 4051 4046 3966 2.22E-08

5207 5105 5003 4905 5.21E-08

6236 6114 5938 5822 7.63E-08

7 0.487 18602 60 40 5 5.28

0 0 2040 1932 -5.22E-07

2.83E-11 2.98E-10 0.095 3.13E-11

4170 3950 5663 5364 -3.82E-07

7609 7206 8740 8278 -2.90E-07

44445 42096 42070 39846 6.08E-07

54663 51773 51081 48381 9.17E-07

63561 60201 59225 56094 1.11E-06

7 0.514 2297 20 40 5 5.03

0 0 106 106 -2.72E-08

1.16E-11 2.82E-10 0.041 1.21E-11

318 316 408 406 -2.31E-08

945 939 997 991 -1.32E-08

2905 2887 2878 2860 6.76E-09

3346 3325 3297 3276 1.25E-08

3798 3775 3738 3715 1.54E-08

448


A2P CO2 ldg P*CO2 T P Gas Dry Gas PCO2in, dry PCO2in, wet PCO2out, dry

PCO2out,

wet CO2 flux KG kg

KG/kg

kg'

m mol


Std

L/min

Std


mol/s Pa

cm2

mol/s Pa

cm2

mol/s Pa

cm2

7 0.514 15123 40 40 5 5.10

0 0 720 706 -1.84E-07

1.11E-11 2.87E-10 0.039 1.15E-11

3382 3316 3834 3759 -1.16E-07

5169 5068 5527 5419 -9.17E-08

39020 38256 38115 37369 2.32E-07

44072 43209 42903 42063 2.99E-07

54893 53819 53196 52155 4.34E-07

7 0.514 22725 60 40 5 5.28

0 0 3084 2921 -7.90E-07

3.36E-11 2.98E-10 0.113 3.79E-11

4306 4078 6572 6224 -5.80E-07

7650 7246 9309 8817 -4.25E-07

46975 44492 44223 41885 7.05E-07

49992 47349 46787 44313 8.21E-07

55383 52455 51952 49206 8.78E-07

449

B.2.4 Secondary Amines

Table B-73: Detailed WWC results for 7 m DEA (part 1)

DEA CO2 ldg P*CO2 T P GasDry Gas PCO2in, dry PCO2in, wet PCO2out, dry PCO2out, wet CO2 flux KG kg

KG/kg

kg'

m mol/mol Pa °C psig Std L/min Std L/min Pa Pa Pa Pa mol/s cm2 mol/s Pa

cm2

mol/s Pa

cm2

mol/s Pa

cm2

7 0.348 2234 40 40 5 5.1

0 0 381 373 -9.8E-08

4.57E-11 2.87E-10 0.159 5.44E-11

573 562 837 821 -6.8E-08

1139 1116 1312 1286 -4.4E-08

3341 3275 3175 3113 4.25E-08

4434 4347 4095 4014 8.69E-08

5550 5441 5022 4924 1.35E-07

0 0 381 374 -9.8E-08

1136 1114 1296 1271 -4.1E-08

3330 3265 3164 3102 4.25E-08

7 0.349 11386 60 40 5 5.28

0 0 1987 1882 -5.1E-07

4.67E-11 2.98E-10 0.157 5.54E-11

2251 2132 3778 3578 -3.9E-07

3363 3185 4675 4428 -3.4E-07

18810 17816 17717 16780 2.8E-07

21638 20494 20130 19066 3.86E-07

24881 23566 22845 21637 5.21E-07

7 0.342 46835 80 60 5 5.51

0 0 10437 9477 -2E-06

4.62E-11 2.28E-10 0.203 5.80E-11

12497 11347 20477 18593 -1.5E-06

22537 20464 28046 25466 -1E-06

80308 72920 75056 68151 9.85E-07

89062 80868 80823 73387 1.54E-06

97454 88488 88547 80400 1.67E-06

7 0.253 760 40 40 5 5.1

0 0 159 156 -4.1E-08

5.67E-11 2.87E-10 0.197 7.07E-11

253 248 363 356 -2.8E-08

419 411 472 463 -1.4E-08

1175 1152 1092 1071 2.12E-08

1726 1692 1544 1513 4.67E-08

2272 2228 1982 1943 7.43E-08

7 0.250 4354 60 60 5 5.2

0 0 1056 1015 -2E-07

5.45E-11 2.16E-10 0.253 7.29E-11

1159 1114 1951 1876 -1.5E-07

2240 2153 2832 2722 -1.1E-07

9639 9266 8485 8157 2.16E-07

11997 11533 10195 9800 3.38E-07

17352 16680 14160 13612 5.99E-07

450

Table B-74: Detailed WWC results for 7 m DEA (part 2)


KG/kg

kg'

m mol/mol Pa °C psig Std

L/min

Std


mol/s Pa

cm2

mol/s Pa

cm2

mol/s Pa

cm2

7 0.251 19082 80 60 5 5.51

0 0 4279 3885 -8E-07

5.07E-11 2.28E-10 0.223 6.53E-11

11992 10889 13846 12572 -3.5E-07

32948 29917 30889 28047 3.86E-07

51896 47122 45563 41371 1.19E-06

71565 64981 60032 54509 2.16E-06

7 0.314 217 20 20 5 5.05

0 0 27 27 -1.1E-08

5.43E-11 4.46E-10 0.122 6.18E-11

41 41 64 63 -9.2E-09

75 75 93 92 -7.2E-09

402 398 379 375 9.27E-09

514 509 478 473 1.48E-08

7 0.303 1356 40 40 5 5.1

0 0 234 229 -5.99E-08

4.72E-11 2.87E-10 0.164 5.65E-11

310 303 486 476 -4.52E-08

592 581 718 703 -3.21E-08

2272 2228 2117 2076 3.96E-08

2544 2494 2370 2324 4.44E-08

2856 2801 2604 2553 6.47E-08

7 0.309 7257 60 60 5 5.2

0 0 1509 1450 -2.8E-07

4.55E-11 2.16E-10 0.211 5.76E-11

1740 1673 2971 2856 -2.3E-07

3419 3287 4289 4123 -1.6E-07

11899 11439 11075 10647 1.54E-07

14474 13913 13084 12577 2.61E-07

17203 16537 15092 14507 3.96E-07

7 0.303 29640 80 60 5 5.51

0 0 5782 5250 -1.1E-06

4.14E-11 2.28E-10 0.182 5.06E-11

6524 5924 11637 10566 -9.6E-07

12203 11080 15704 14259 -6.6E-07

76411 69380 68481 62181 1.49E-06

85421 77562 75741 68773 1.81E-06

93042 84481 82126 74570 2.05E-06

7 0.412 732 20 40 5 5.03

0 0 79 79 -2E-08

2.91E-11 2.82E-10 0.103 3.25E-11

131 130 193 192 -1.6E-08

247 245 297 296 -1.3E-08

903 897 892 886 2.8E-09

1156 1148 1116 1109 1.02E-08

1388 1380 1311 1302 1.99E-08

451

Table B-75: Detailed WWC data for 7 m DEA (part 3)


KG/kg

kg'


L/min

Std


mol/s Pa

cm2

mol/s Pa

cm2

mol/s Pa

cm2

7 0.414 5952 40 40 5 5.1

0 0 709 695 -1.8E-07

3.02E-11 2.87E-10 0.105 3.37E-11

2828 2772 3118 3057 -7.4E-08

5222 5120 5309 5205 -2.2E-08

12597 12350 11918 11685 1.74E-07

14859 14568 13917 13644 2.41E-07

16895 16564 15689 15381 3.09E-07

7 0.431 24971 60 60 5 5.2

0 0 3429 3296 -6.4E-07

2.73E-11 2.16E-10 0.127 3.13E-11

6616 6360 9134 8781 -4.7E-07

12563 12077 14263 13711 -3.2E-07

23067 22174 23428 22521 -6.8E-08

42994 41330 40728 39152 4.25E-07

62508 60089 57977 55733 8.5E-07

81560 78402 74145 71275 1.39E-06

7 0.470 1705 20 40 5 5.03

0 0 145 144 -3.7E-08

2.11E-11 2.82E-10 0.075 2.28E-11

306 304 416 414 -2.8E-08

581 578 665 661 -2.1E-08

2275 2261 2211 2197 1.64E-08

2837 2819 2758 2741 2.03E-08

3342 3321 3221 3201 3.09E-08

7 0.455 12591 40 40 5 5.1

0 0 1052 1031 -2.7E-07

1.99E-11 2.87E-10 0.069 2.14E-11

3695 3623 4366 4281 -1.7E-07

6372 6247 6757 6624 -9.8E-08

42232 41405 39932 39151 5.89E-07

51658 50647 48906 47948 7.05E-07

61122 59925 57615 56487 8.98E-07

7 0.189 410 40 40 5 5.1

0 0 100 98 -2.6E-08

7.50E-11 2.87E-10 0.261 1.01E-10

127 125 200 196 -1.9E-08

238 233 293 288 -1.4E-08

689 676 617 605 1.85E-08

912 895 782 766 3.35E-08

1354 1327 1125 1103 5.84E-08

7 0.188 2037 60 60 5 5.2

0 0 608 584 -1.1E-07

6.59E-11 2.16E-10 0.306 9.48E-11

587 564 994 955 -7.6E-08

1159 1114 1457 1401 -5.6E-08

3960 3806 3460 3326 9.36E-08

4516 4341 3841 3692 1.26E-07

5530 5316 4521 4346 1.89E-07

452

Table B-76: Detailed WWC data for 7 m DEA (part 4)


KG/kg

kg'


L/min

Std


mol/s Pa

cm2

mol/s Pa

cm2

mol/s Pa

cm2

7 0.188 9760 80 60 5 5.2

0 0 2430 2207 -4.6E-07

6.04E-11 2.28E-10 0.265 8.21E-11

4444 4035 6184 5615 -3.3E-07

7729 7018 8619 7826 -1.7E-07

22547 20473 19715 17901 5.31E-07

27490 24961 23423 21268 7.63E-07

33103 30057 27130 24634 1.12E-06

Table B-77: Detailed WWC data for 7 m MMEA (part 1)

MMEA CO2 ldg P*CO2 T P GasDry Gas PCO2in, dry PCO2in, wet PCO2out,

dry

PCO2out,

wet CO2 flux KG kg

KG/kg

kg'

m mol/mol Pa C psig Std

L/min

Std


mol/s Pa

cm2

mol/s Pa

cm2

mol/s Pa

cm2

7 0.208 18 40 60 5 5.1

0.0 0.0 12.1 11.8 -3.09E-09

2.49E-10 2.87E-10 0.866 1.85E-09

7.5 7.4 14.3 14.0 -1.74E-09

23.0 22.5 19.6 19.2 8.69E-10

35.1 34.4 23.8 23.3 2.90E-09

44.5 43.6 29.8 29.2 3.76E-09

136.9 134.2 78.4 76.9 1.50E-08

7 0.208 129 60 60 5 5.2

0.0 0.0 64.4 61.9 -1.21E-08

1.65E-10 2.16E-10 0.764 6.97E-10

34.0 32.7 91.7 88.1 -1.08E-08

74.7 71.8 108.6 104.4 -6.37E-09

196.7 189.1 157.0 151.0 7.43E-09

221.4 212.8 173.0 166.3 9.07E-09

261.1 250.9 190.0 182.6 1.33E-08

7 0.208 802 80 60 5 5.51

0.0 0.0 448.0 406.7 -8.40E-08

1.75E-10 2.28E-10 0.766 7.46E-10

294.0 267.0 630.7 572.7 -6.31E-08

587.5 533.4 748.7 679.8 -3.02E-08

1138.4 1033.7 1009.7 916.8 2.41E-08

1426.3 1295.0 1115.8 1013.1 5.82E-08

1658.5 1505.9 1208.5 1097.3 8.44E-08

7 0.208 5132 100 60 5 6.62 0.0 0.0 2950.4 2369.8 -5.53E-07

1.80E-10 2.54E-10 0.709 6.19E-10 1189.4 955.4 3928.7 3155.6 -5.14E-07

453

2306.7 1852.8 4453.9 3577.4 -4.03E-07

9051.9 7270.7 7960.3 6393.9 2.05E-07

12609.8 10128.5 9211.5 7398.9 6.37E-07

13330.7 10707.5 9417.5 7564.3 7.34E-07

7 0.312 75 40 20 5 5.16

0.0 0.0 34.7 33.6 -1.40E-08

2.07E-10 4.57E-10 0.452 3.77E-10

18.4 17.8 41.4 40.1 -9.27E-09

33.2 32.2 50.9 49.4 -7.14E-09

97.3 94.3 87.5 84.8 3.96E-09

133.9 129.8 107.4 104.1 1.07E-08

371.9 360.5 258.8 250.8 4.57E-08


MMEA CO2 ldg P*CO2 T P GasDry Gas PCO2in,

dry

PCO2in,

wet

PCO2out,

dry

PCO2out,

wet CO2 flux KG kg

KG/kg

kg'


L/min

Std


mol/s Pa

cm2

mol/s Pa

cm2

mol/s Pa

cm2

7 0.312 486 60 40 5 5.28

0.0 0.0 255.3 241.8 -6.54E-08

1.75E-10 2.98E-10 0.587 4.24E-10

120.3 113.9 304.6 288.5 -4.72E-08

234.1 221.8 359.3 340.3 -3.21E-08

785.0 743.5 647.8 613.5 3.51E-08

1024.8 970.6 780.8 739.6 6.25E-08

1133.0 1073.1 844.2 799.6 7.39E-08

7 0.312 2825 80 60 5 5.51

0.0 0.0 1489.1 1352.1 -2.79E-07

1.39E-10 2.28E-10 0.609 3.54E-10

1149.2 1043.5 2142.0 1944.9 -1.86E-07

2256.3 2048.7 2688.8 2441.4 -8.11E-08

3914.2 3554.1 3528.1 3203.5 7.24E-08

4460.0 4049.7 3785.5 3437.2 1.26E-07

5016.1 4554.6 4079.0 3703.7 1.76E-07

7 0.312 14089 100 60 5 6.62

0.0 0.0 7486.6 6013.4 -1.40E-06

1.29E-10 2.54E-10 0.505 2.60E-10

7574.1 6083.7 11513.1 9247.6 -7.39E-07

13881.6 11150.0 15374.8 12349.4 -2.80E-07

25209.3 20248.7 22377.4 17974.0 5.31E-07

37257.9 29926.4 29019.6 23309.2 1.54E-06

48328.2 38818.3 35043.9 28148.0 2.49E-06

7 0.405 300 40 20 5 5.16

0.0 0.0 91.1 88.3 -3.68E-08

1.48E-10 4.57E-10 0.324 2.19E-10 69.4 67.2 145.2 140.7 -3.06E-08

131.8 127.7 183.5 177.8 -2.09E-08

474.3 459.7 421.2 408.2 2.14E-08

454

532.4 516.0 468.6 454.1 2.58E-08

588.6 570.5 505.6 490.0 3.35E-08

7 0.405 2041 60 40 5 5.28

0.0 0.0 784.2 742.8 -2.01E-07

1.27E-10 2.98E-10 0.426 2.21E-10

595.7 564.2 1229.1 1164.2 -1.62E-07

1176.4 1114.2 1515.7 1435.6 -8.69E-08

2873.0 2721.2 2620.4 2481.9 6.47E-08

3446.1 3264.0 2940.9 2785.4 1.29E-07

3985.3 3774.6 3306.6 3131.8 1.74E-07

7 0.405 10638 80 60 5 5.51

0.0 0.0 4031.6 3660.7 -7.56E-07

9.22E-11 2.28E-10 0.405 1.55E-10

2888.6 2622.8 6281.7 5703.8 -6.36E-07

5699.9 5175.5 7862.5 7139.1 -4.05E-07

20220.0 18359.6 17182.1 15601.3 5.70E-07

22588.5 20510.3 18623.8 16910.3 7.43E-07

25935.3 23549.2 19962.5 18125.9 1.12E-06


MMEA CO2 ldg P*CO2 T P GasDry Gas PCO2in, dry PCO2in, wet PCO2out,

dry PCO2out, wet CO2 flux KG kg

KG/kg

kg'


L/min

Std


mol/s Pa

cm2

mol/s Pa

cm2

mol/s Pa

cm2

7 0.405 47758 100 60 5 6.62

0.0 0.0 13691.1 10997.0 -2.57E-06

5.91E-11 2.54E-10 0.232 7.70E-11

14206.0 11410.6 24606.9 19764.8 -1.95E-06

25997.1 20881.5 32484.8 26092.5 -1.22E-06

80164.2 64389.7 76714.4 61618.8 6.47E-07

90925.6 73033.5 82738.7 66457.6 1.53E-06

95559.6 76755.6 87784.7 70510.6 1.46E-06

101223.5 81305.0 87166.8 70014.4 2.64E-06

7 0.470 217 20 20 5 5.05

0.0 0.0 40.9 40.5 -1.65E-08

8.16E-11 4.46E-10 0.183 9.98E-11

71.0 70.3 98.1 97.1 -1.09E-08

137.3 135.9 150.4 149.0 -5.31E-09

317.9 314.8 299.9 297.0 7.24E-09

374.3 370.7 346.3 343.0 1.13E-08

430.5 426.3 392.7 388.9 1.53E-08

7 0.470 1356 40 40 5 5.1

0.0 0.0 388.4 380.7 -9.94E-08

8.24E-11 2.87E-10 0.287 1.16E-10

305.4 299.4 586.3 574.8 -7.19E-08

596.5 584.8 803.8 788.1 -5.31E-08

2278.1 2233.5 2033.0 1993.2 6.27E-08

2828.5 2773.2 2444.0 2396.1 9.85E-08

3409.2 3342.5 2858.7 2802.7 1.41E-07

7 0.470 6717 60 40 5 5.28 0.0 0.0 1794.7 1699.8 -4.60E-07 8.07E-11 2.98E-10 0.271 1.11E-10

455

1726.8 1635.6 3091.7 2928.3 -3.49E-07

4686.6 4438.8 5327.6 5045.9 -1.64E-07

13373.6 12666.6 11865.4 11238.2 3.86E-07

17407.9 16487.6 14730.9 13952.2 6.85E-07

20725.8 19630.2 17144.0 16237.7 9.17E-07

7 0.470 28638 80 60 5 5.51

0.0 0.0 7254.9 6587.4 -1.36E-06

5.46E-11 2.28E-10 0.240 7.19E-11

14087.6 12791.4 18361.2 16671.9 -8.01E-07

25827.2 23451.0 27577.9 25040.6 -3.28E-07

60428.2 54868.5 54455.4 49445.3 1.12E-06

76338.5 69315.0 66710.0 60572.3 1.81E-06

91631.0 83200.5 77110.9 70016.3 2.72E-06

7 0.524 1467 20 40 5 5.03

0.0 0.0 190.0 188.8 -4.87E-08

3.42E-11 2.82E-10 0.121 3.89E-11

308.4 306.5 455.5 452.6 -3.76E-08

580.6 577.0 689.2 685.0 -2.78E-08

1683.9 1673.4 1643.9 1633.7 1.02E-08

2236.6 2222.7 2138.6 2125.3 2.51E-08

2783.3 2766.1 2632.5 2616.2 3.86E-08


MMEA CO2 ldg P*CO2 T P GasDry Gas PCO2in, dry PCO2in, wet PCO2out, dry PCO2out,

wet CO2 flux KG kg

KG/kg

kg'


L/min

Std

L/min Pa Pa Pa Pa

mol/s

cm2

mol/s Pa

cm2

mol/s Pa

cm2

mol/s Pa

cm2

7 0.524 6031 40 40 5 5.1

0.0 0.0 938.8 920.4 -2.40E-07

4.10E-11 2.87E-10 0.143 4.78E-11

2601.6 2550.6 3088.0 3027.5 -1.25E-07

4596.1 4506.1 4795.9 4702.1 -5.12E-08

12091.6 11854.9 11224.5 11004.7 2.22E-07

13863.7 13592.3 12732.6 12483.4 2.90E-07

16201.4 15884.2 14768.6 14479.5 3.67E-07

7 0.524 20544 60 60 5 5.2

0.0 0.0 3789.6 3642.9 -7.11E-07

3.81E-11 2.16E-10 0.177 4.63E-11

7692.6 7394.8 9963.2 9577.6 -4.26E-07

14144.2 13596.7 15225.5 14636.1 -2.03E-07

20374.5 19585.7 20683.4 19882.7 -5.79E-08

37366.0 35919.6 34946.0 33593.2 4.54E-07

48796.7 46907.8 43905.2 42205.6 9.17E-07

81338.2 78189.5 70525.4 67795.3 2.03E-06

7 0.554 4842 20 40 5 5.03

0.0 0.0 399.7 397.2 -1.02E-07

2.05E-11 2.82E-10 0.073 2.21E-11 599.5 595.8 908.7 903.0 -7.92E-08

1176.4 1169.1 1447.8 1438.9 -6.95E-08

10998.2 10930.1 10508.1 10443.0 1.25E-07

456

12091.6 12016.7 11563.8 11492.1 1.35E-07

13260.5 13178.3 12619.5 12541.3 1.64E-07

7 0.554 16408 40 60 5 5.07

0.0 0.0 1863.9 1837.2 -3.49E-07

2.06E-11 2.09E-10 0.098 2.28E-11

4289.1 4227.6 5545.4 5465.9 -2.36E-07

7502.0 7394.5 8289.8 8171.0 -1.48E-07

13933.1 13733.4 14190.5 13987.1 -4.83E-08

37669.8 37129.8 35507.3 34998.3 4.05E-07

59655.9 58800.7 55279.3 54486.9 8.21E-07

91116.1 89809.9 84937.3 83719.7 1.16E-06

Table B-81: Detailed WWC data for 7 m DIPA (part 1)

DIPA CO2 ldg P*CO2 T P GasDry Gas PCO2in,

dry

PCO2in,

wet

PCO2out,

dry

PCO2out,

wet CO2 flux KG kg

KG/kg

kg'


L/min

Std


mol/s Pa

cm2

mol/s Pa

cm2

mol/s Pa

cm2

7 0.1 156 40 40 5 5.1

0 0 34 33 -8.59E-09

5.52E-11 2.87E-10 0.192 6.83E-11

38 37 58 57 -5.21E-09

70 68 86 85 -4.25E-09

256 251 234 230 5.60E-09

310 304 284 279 6.56E-09

368 361 341 334 7.05E-09

7 0.1 1187 60 40 5 5.28

0 0 177 168 -4.54E-08

3.85E-11 2.98E-10 0.129 4.42E-11

223 211 358 339 -3.46E-08

430 407 535 507 -2.68E-08

1611 1526 1551 1469 1.54E-08

2094 1983 1981 1876 2.90E-08

2663 2522 2486 2354 4.54E-08

7 0.1 8265 80 60 5 5.51

0 0 1534 1393 -2.88E-07

3.62E-11 2.28E-10 0.159 4.30E-11

3954 3591 4758 4320 -1.51E-07

7245 6578 7415 6732 -3.19E-08

16374 14867 15344 13932 1.93E-07

19154 17392 17506 15896 3.09E-07

24972 22675 22398 20337 4.83E-07

7 0.165 541 40 40 5 5.1

0 0 63 62 -1.61E-08

2.88E-11 2.87E-10 0.100 3.20E-11

119 116 164 160 -1.15E-08

234 230 263 258 -7.43E-09

893 875 849 832 1.12E-08

1093 1071 1043 1022 1.28E-08

1300 1275 1223 1200 1.97E-08

7 0.165 3727 60 60 5 5.2 0 0 566 544 -1.06E-07 3.08E-11 2.16E-10 0.143 3.59E-11

457

1143 1099 1524 1465 -7.14E-08

2235 2148 2477 2381 -4.54E-08

5453 5242 5262 5059 3.57E-08

6606 6350 6225 5984 7.14E-08

7682 7385 7085 6811 1.12E-07

7 0.165 20458 80 60 5 5.51

0 0 2992 2716 -5.61E-07

2.94E-11 2.28E-10 0.129 3.37E-11

7353 6676 9495 8621 -4.02E-07

13387 12156 14469 13137 -2.03E-07

24818 22535 24406 22161 7.72E-08

35734 32446 34035 30903 3.19E-07

46238 41984 43251 39272 5.60E-07

56690 51474 52056 47267 8.69E-07

Table B-82: Detailed WWC data for 7 m DIPA (part 2)

DIPA CO2 ldg P*CO2 T P GasDry Gas PCO2in,

dry

PCO2in,

wet

PCO2out,

dry

PCO2out,

wet CO2 flux KG kg

KG/kg

kg'


L/min

Std


mol/s Pa

cm2

mol/s Pa

cm2

mol/s Pa

cm2

7 0.238 208 20 40 5 5.03

0 0 15 15 -3.86E-09

1.86E-11 2.82E-10 0.066 1.99E-11

38 38 50 50 -3.09E-09

72 72 80 80 -2.12E-09

371 369 361 359 2.61E-09

427 425 414 411 3.48E-09

484 481 463 460 5.41E-09

7 0.238 1713 40 40 5 5.1

0 0 143 140 -3.67E-08

2.13E-11 2.87E-10 0.074 2.30E-11

305 299 415 407 -2.80E-08

596 584 679 665 -2.12E-08

2828 2772 2749 2695 2.03E-08

3378 3312 3254 3190 3.19E-08

4536 4447 4313 4229 5.70E-08

7 0.238 11458 60 60 5 5.2

0 0 1282 1232 -2.40E-07

2.18E-11 2.16E-10 0.101 2.42E-11

4052 3895 4938 4747 -1.66E-07

7322 7038 7734 7434 -7.72E-08

24190 23253 22800 21917 2.61E-07

27743 26669 26146 25134 2.99E-07

30575 29391 28618 27510 3.67E-07

7 0.315 780 20 40 5 5.03

0 0 41 41 -1.05E-08

1.23E-11 2.82E-10 0.044 1.28E-11 138 138 166 165 -7.14E-09

242 241 268 266 -6.47E-09

841 836 836 831 1.16E-09

458

902 896 889 884 3.19E-09

998 992 992 986 1.64E-09

1641 1631 1604 1594 9.46E-09

1917 1905 1875 1864 1.06E-08

7 0.315 6894 40 40 5 5.1

0 0 339 333 -8.69E-08

1.21E-11 2.87E-10 0.042 1.26E-11

1154 1131 1410 1383 -6.56E-08

2258 2214 2443 2395 -4.73E-08

13113 12857 12887 12635 5.79E-08

18882 18512 18317 17958 1.45E-07

24538 24057 23821 23355 1.83E-07

459

B.2.5 Other solvents

Table B-83: Detailed WWC data for 9.8 m MEA/3.4 m MDEA (part 1)

MEA/MDEA CO2 ldg P*CO2 T P Gas Dry Gas

PCO2in,

dry

PCO2in,

wet

PCO2out,

dry

PCO2out,

wet CO2 flux KG kg

KG/kg

kg'

m

mol

CO2/mol

alk

Pa °C psig Std

L/min

Std


mol/s Pa

cm2

mol/s Pa

cm2

mol/s Pa

cm2

9.8 3.4 0.249 91 40 40 5 5.1

0 0 27.5 27.0 -7.05E-09

9.65E-11 2.87E-10 0.336 1.45E-10

27.9 27.4 49.0 48.1 -5.41E-09

42.2 41.4 57.7 56.6 -3.96E-09

127.8 125.3 116.9 114.6 2.80E-09

159.5 156.4 138.8 136.0 5.31E-09

184.4 180.8 155.7 152.7 7.34E-09

9.8 3.4 0.248 670 60 40 5 5.28

0 0 225.8 213.9 -5.78E-08

1.07E-10 2.98E-10 0.359 1.67E-10

204.7 193.9 374.4 354.6 -4.34E-08

403.8 382.5 505.2 478.5 -2.60E-08

1177.5 1115.2 1023.3 969.2 3.95E-08

1549.6 1467.7 1273.3 1206.0 7.08E-08

1896.9 1796.6 1507.8 1428.1 9.96E-08

9.8 3.4 0.252 3969 80 60 5 5.51

0 0 1900.0 1725.2 -3.56E-07

1.05E-10 2.28E-10 0.463 1.96E-10

643.6 584.4 2142.0 1944.9 -2.81E-07

1364.5 1238.9 2425.2 2202.0 -1.99E-07

5514.5 5007.2 5061.4 4595.8 8.50E-08

8295.0 7531.8 6642.2 6031.1 3.10E-07

13665.4 12408.1 10009.6 9088.7 6.85E-07

9.8 3.4 0.253 17599 100 50 5 6.47

0 0 6100.8 4714.8 -1.32E-06

8.72E-11 3.03E-10 0.287 1.22E-10

4218.9 3260.4 9111.1 7041.2 -1.06E-06

8388.7 6482.8 12322.1 9522.6 -8.51E-07

35155.6 27168.6 31677.1 24480.3 7.53E-07

38589.6 29822.4 34486.7 26651.6 8.88E-07

42826.3 33096.5 37474.7 28960.8 1.16E-06

9.8 3.4 0.288 188 40 40 5 5.1

0 0 50.9 49.9 -1.30E-08

7.91E-11 2.87E-10 0.275 1.09E-10

65.6 64.3 99.2 97.2 -8.59E-09

123.7 121.2 139.5 136.8 -4.05E-09

369.5 362.3 321.2 314.9 1.24E-08

394.4 386.7 342.7 336.0 1.32E-08

450.2 441.4 383.1 375.6 1.72E-08

9.8 3.4 0.290 1194 60 40 5 5.28

0 0 376.3 356.4 -9.63E-08

9.35E-11 2.98E-10 0.314 1.36E-10 214.5 203.2 519.2 491.7 -7.80E-08

426.4 403.9 662.5 627.4 -6.04E-08

460

1398.8 1324.9 1360.0 1288.1 9.94E-09

1596.8 1512.3 1493.1 1414.1 2.65E-08

1784.5 1690.2 1637.1 1550.6 3.77E-08


MEA/MDEA CO2 ldg P*CO2 T P Gas Dry Gas

PCO2in,

dry PCO2in, wet PCO2out, dry

PCO2out,

wet CO2 flux KG kg

KG/kg

kg'

m mol


Std

L/min

Std


mol/s Pa

cm2

mol/s Pa

cm2

mol/s Pa

cm2

9.8 3.4 0.291 8184 80 40 5 5.51

0 0 2806.2 2548.0 -5.26E-07

8.22E-11 2.28E-10 0.361 1.29E-10

2198.6 1996.3 4711.3 4277.8 -4.71E-07

4386.9 3983.3 5833.8 5297.0 -2.71E-07

12939.3 11748.9 11549.1 10486.6 2.61E-07

15565.3 14133.2 13402.8 12169.6 4.05E-07

18139.8 16470.9 15204.9 13806.0 5.50E-07

9.8 3.4 0.335 409 40 20 5 5.16

0 0 59.6 57.7 -2.40E-08

6.16E-11 4.57E-10 0.135 7.12E-11

107.2 103.8 151.4 146.7 -1.79E-08

198.0 191.9 226.5 219.5 -1.15E-08

681.2 660.2 644.4 624.5 1.49E-08

774.7 750.8 725.0 702.6 2.01E-08

866.3 839.6 808.0 783.0 2.36E-08

9.8 3.4 0.338 2792 60 40 5 5.28

0 0 640.2 606.4 -1.64E-07

6.88E-11 2.98E-10 0.231 8.94E-11

1051.9 996.3 1474.2 1396.3 -1.08E-07

1542.1 1460.6 1892.7 1792.7 -8.98E-08

4573.5 4331.7 4215.3 3992.5 9.17E-08

5086.3 4817.4 4592.3 4349.6 1.26E-07

5602.8 5306.6 5003.3 4738.8 1.53E-07

9.8 3.4 0.343 18232 80 50 5 5.59

0 0 4713.9 4213.1 -1.02E-06

6.17E-11 2.67E-10 0.231 8.02E-11

3576.7 3196.7 7438.7 6648.6 -8.36E-07

7028.5 6281.9 9820.2 8777.1 -6.04E-07

39432.5 35243.8 35106.6 31377.4 9.36E-07

42465.1 37954.2 37291.8 33330.5 1.12E-06

45586.8 40744.4 40190.6 35921.4 1.17E-06

9.8 3.4 0.360 146 20 20 5 5.05

0 0 12.7 12.6 -5.12E-09

4.00E-11 4.46E-10 0.090 4.39E-11 24.6 24.4 36.4 36.0 -4.73E-09

305.2 302.2 290.4 287.5 5.99E-09

327.0 323.8 309.5 306.5 7.05E-09

9.8 3.4 0.361 1050 40 40 5 5.1

0 0 182.1 178.5 -4.66E-08

4.59E-11 2.87E-10 0.160 5.46E-11 401.9 394.1 507.5 497.6 -2.70E-08

797.4 781.8 830.6 814.4 -8.50E-09

1444.8 1416.5 1383.4 1356.3 1.57E-08

461

1634.8 1602.8 1542.8 1512.6 2.36E-08

2184.6 2141.8 2011.1 1971.8 4.44E-08


MEA/MDEA CO2 ldg P*CO2 T P

Gas

Dry Gas

PCO2in,

dry

PCO2in,

wet

PCO2out,

dry

PCO2out,

wet CO2 flux KG kg

KG/kg

kg'

m mol CO2/mol

alk Pa °C psig

Std

L/min

Std


mol/s Pa

cm2

mol/s Pa

cm2

mol/s Pa

cm2

9.8 3.4 0.359 6260 60 40 5 5.28

0 0 1195.2 1132.0 -3.06E-07

5.18E-11 2.98E-10 0.174 6.27E-11

1402.6 1328.4 2296.2 2174.8 -2.29E-07

2793.9 2646.2 3431.1 3249.7 -1.63E-07

10907.7 10331.1 10153.7 9616.9 1.93E-07

13471.6 12759.4 12265.1 11616.7 3.09E-07

19881.3 18830.3 17581.3 16651.9 5.89E-07

9.8 3.4 0.404 487 20 40 5 5.03

0 0 50.5 50.2 -1.29E-08

2.64E-11 2.82E-10 0.094 2.91E-11

65.6 65.2 109.0 108.3 -1.11E-08

119.5 118.8 151.9 151.0 -8.30E-09

649.6 645.6 628.5 624.6 5.41E-09

854.7 849.5 820.1 815.0 8.88E-09

954.3 948.4 912.4 906.8 1.07E-08

9.8 3.4 0.408 3787 40 40 5 5.1

0 0 422.3 414.0 -1.08E-07

3.04E-11 2.87E-10 0.106 3.40E-11

701.3 687.6 1059.5 1038.7 -9.17E-08

1398.8 1371.4 1655.2 1622.8 -6.56E-08

7031.8 6894.1 6684.9 6554.0 8.88E-08

7767.0 7615.0 7325.9 7182.5 1.13E-07

8370.3 8206.4 7880.1 7725.9 1.25E-07

9.8 3.4 0.410 15621 60 40 5 5.28

0 0 1998.3 1892.7 -5.12E-07

3.34E-11 2.98E-10 0.112 3.76E-11

3555.5 3367.5 5029.7 4763.8 -3.77E-07

6202.3 5874.4 7333.4 6945.7 -2.90E-07

28089.4 26604.5 26769.8 25354.6 3.38E-07

33254.9 31496.9 31256.6 29604.2 5.12E-07

43736.6 41424.4 40607.1 38460.5 8.01E-07

9.8 3.4 0.438 1396 20 40 5 5.03

0 0 85.2 84.7 -2.18E-08

1.52E-11 2.82E-10 0.054 1.60E-11

316.3 314.4 377.8 375.5 -1.57E-08

608.9 605.1 648.5 644.5 -1.01E-08

2397.2 2382.4 2340.7 2326.2 1.45E-08

2834.6 2817.0 2755.4 2738.3 2.03E-08

3298.3 3277.9 3189.0 3169.2 2.80E-08

9.8 3.4 0.437 7770 40 40 5 5.1 0 0 622.1 609.9 -1.59E-07

2.06E-11 2.87E-10 0.072 2.22E-11 2812.7 2757.7 3201.1 3138.4 -9.94E-08

462

5719.7 5607.7 5878.0 5763.0 -4.05E-08

13833.6 13562.8 13381.1 13119.2 1.16E-07

16435.1 16113.4 15756.5 15448.0 1.74E-07

26652.9 26131.1 25257.9 24763.4 3.57E-07


MEA/MDEA CO2 ldg P*CO2 T P Gas Dry Gas PCO2in, dry PCO2in, wet

PCO2out,

dry

PCO2out,

wet CO2 flux KG kg

KG/kg

kg'

m mol


Std

L/min

Std


mol/s Pa

cm2

mol/s Pa

cm2

mol/s Pa

cm2

9.8 3.4 0.438 34906 60 60 5 5.2

0 0 4181.0 4019.1 -7.84E-07

2.14E-11 2.16E-10 0.099 2.38E-11

6415.6 6167.3 9391.7 9028.2 -5.58E-07

12300.9 11824.7 14463.4 13903.6 -4.05E-07

63945.0 61469.6 61010.1 58648.3 5.50E-07

68991.0 66320.3 65644.1 63103.0 6.27E-07

74139.9 71269.9 70278.2 67557.7 7.24E-07

463

Table B-87: Detailed WWC data for 8 m BAE (part 1)

BAE CO2 ldg P*CO2 T P

Gas

Dry Gas

PCO2in,

dry

PCO2in,

wet

PCO2out,

dry

PCO2out,

wet CO2 flux KG kg

KG/kg

kg'

m mol


Std

L/min

Std


mol/s Pa

cm2

mol/s Pa

cm2

mol/s Pa

cm2

8 0.352 92 40 40 5 5.10

0 0 37.7 37.0 -9.65E-09

1.23E-10 2.87E-10 0.43 2.14E-10

15.1 14.8 44.1 43.3 -7.43E-09

21.5 21.1 47.1 46.2 -6.56E-09

136.5 133.8 118.4 116.1 4.63E-09

163.6 160.4 137.2 134.6 6.76E-09

205.1 201.1 165.1 161.9 1.02E-08

8 0.353 864 60 40 5 5.28

0 0 297.9 282.1 -7.63E-08

1.08E-10 2.98E-10 0.36 1.68E-10

111.6 105.7 377.4 357.5 -6.81E-08

207.0 196.1 437.4 414.2 -5.90E-08

1425.6 1350.2 1255.5 1189.2 4.35E-08

1718.9 1628.1 1456.1 1379.1 6.73E-08

1902.5 1802.0 1576.4 1493.1 8.35E-08

8 0.354 5811 80 50 5 5.59

0 0 2158.5 1929.2 -4.67E-07

9.00E-11 2.67E-10 0.34 1.36E-10

1373.6 1227.7 3179.8 2842.0 -3.91E-07

2702.6 2415.5 3625.7 3240.6 -2.00E-07

12125.9 10837.8 10119.0 9044.1 4.34E-07

16986.9 15182.5 13642.2 12193.0 7.24E-07

19528.9 17454.5 15738.2 14066.4 8.21E-07

8 0.354 30570 100 50 5 6.47

0 0 7849.0 6065.8 -1.70E-06

6.05E-11 3.03E-10 0.20 7.55E-11

6457.6 4990.5 13285.4 10267.1 -1.48E-06

11501.5 8888.5 16318.0 12610.7 -1.04E-06

73535.6 56829.0 66979.9 51762.7 1.42E-06

79154.8 61171.5 71484.2 55243.6 1.66E-06

79154.8 61171.5 71484.2 55243.6 1.66E-06

8 0.404 243 40 40 5 5.10

0 0 61.1 59.9 -1.56E-08

7.36E-11 2.87E-10 0.26 9.89E-11

35.1 34.4 87.5 85.8 -1.34E-08

63.7 62.5 108.6 106.5 -1.15E-08

447.9 439.2 397.4 389.6 1.29E-08

546.7 536.0 474.3 465.0 1.85E-08

848.3 831.7 665.9 652.8 4.67E-08

8 0.413 2154 60 40 5 5.28

0 0 610.8 578.5 -1.56E-07

8.15E-11 2.98E-10 0.27 1.12E-10

271.5 257.1 772.9 732.1 -1.28E-07

520.3 492.8 984.1 932.1 -1.19E-07

2993.7 2835.4 2790.1 2642.6 5.21E-08

3472.5 3289.0 3140.7 2974.7 8.50E-08

3966.5 3756.8 3555.5 3367.5 1.05E-07

464


BAE CO2 ldg P*CO2 T P Gas Dry Gas PCO2in, dry PCO2in, wet PCO2out, dry

PCO2out,

wet CO2 flux KG kg

KG/kg

kg'

m mol


Std

L/min

Std


mol/s Pa

cm2

mol/s Pa

cm2

mol/s Pa

cm2

8 0.413 13477 80 40 5 5.72

0 0 2835.3 2479.1 -7.26E-07

5.71E-11 3.21E-10 0.18 6.95E-11

3446.1 3013.1 5659.4 4948.3 -5.67E-07

5881.8 5142.8 7352.3 6428.5 -3.76E-07

29710.7 25977.7 27146.8 23736.0 6.56E-07

31407.4 27461.2 28541.9 24955.7 7.34E-07

33330.3 29142.5 30238.6 26439.2 7.92E-07

8 0.444 735 40 40 5 5.10

0 0 135.4 132.7 -3.47E-08

5.06E-11 2.87E-10 0.18 6.14E-11

211.9 207.7 303.1 297.2 -2.34E-08

415.9 407.7 473.2 463.9 -1.47E-08

1000.7 981.1 958.4 939.7 1.08E-08

1472.3 1443.5 1344.5 1318.2 3.27E-08

1282.3 1257.2 1207.3 1183.6 1.92E-08

8 0.460 6844 60 40 5 5.28

0 0 1187.7 1124.9 -3.04E-07

4.53E-11 2.98E-10 0.15 5.35E-11

980.3 928.5 1915.4 1814.1 -2.39E-07

2051.1 1942.7 2839.1 2689.0 -2.02E-07

9991.5 9463.3 9463.7 8963.4 1.35E-07

12668.5 11998.8 11801.3 11177.5 2.22E-07

14440.6 13677.2 13422.6 12713.0 2.61E-07

8 0.465 41473 80 50 5 5.59

78441.3 70108.8 75720.9 67677.4 5.89E-07

2.05E-11 2.67E-10 0.08 2.21E-11

80983.3 72380.8 78262.9 69949.4 5.89E-07

83971.3 75051.4 80983.3 72380.8 6.47E-07

13954.3 12472.0 16897.7 15102.8 -6.37E-07

17076.1 15262.2 19127.6 17095.7 -4.44E-07

22115.5 19766.3 23453.4 20962.1 -2.90E-07

8 0.488 353 20 20 5 5.05

0 0 21.8 21.6 -8.78E-09

2.68E-11 4.46E-10 0.06 2.85E-11

51.7 51.2 72.7 72.0 -8.50E-09

106.9 105.9 122.0 120.8 -6.08E-09

592.2 586.4 576.7 571.0 6.27E-09

643.9 637.6 627.1 621.0 6.76E-09

700.8 694.0 677.8 671.2 9.27E-09

8 0.494 3552 40 40 5 5.10

0 0 403.4 395.5 -1.03E-07

2.14E-11 2.87E-10 0.07 2.31E-11

972.8 953.7 1199.0 1175.5 -5.79E-08

2149.1 2107.1 2247.2 2203.2 -2.51E-08

8219.5 8058.6 7842.4 7688.9 9.65E-08

9576.8 9389.3 9124.4 8945.7 1.16E-07

5048.6 4949.7 4878.9 4783.4 4.34E-08

465


BAE CO2 ldg P*CO2 T P Gas Dry Gas

PCO2in,

dry PCO2in, wet

PCO2out,

dry

PCO2out,

wet CO2 flux KG kg

KG/kg

kg'

m mol


Std

L/min

Std


mol/s Pa

cm2

mol/s Pa

cm2

mol/s Pa

cm2

8 0.496 33079 60 40 5 5.28

0 0 2024.7 1917.7 -5.18E-07

1.16E-11 2.98E-10 0.04 1.21E-11

3857.1 3653.2 5252.2 4974.5 -3.57E-07

7363.6 6974.3 8441.9 7995.6 -2.76E-07

54855.4 51955.5 53912.8 51062.8 2.41E-07

64997.8 61561.7 63829.0 60454.7 2.99E-07

69371.5 65704.2 68164.9 64561.4 3.09E-07

8 0.505 1352 20 20 5 5.05

212.9 210.8 246.4 244.0 -1.35E-08

1.22E-11 4.46E-10 0.03 1.25E-11

107.6 106.6 145.9 144.5 -1.54E-08

313.3 310.3 344.4 341.1 -1.25E-08

1789.1 1771.6 1772.3 1755.0 6.76E-09

2291.4 2269.0 2267.4 2245.3 9.65E-09

2791.3 2764.0 2784.1 2756.9 2.90E-09

8 0.505 13528 40 40 5 5.10

4049.4 3970.1 4275.6 4191.9 -5.79E-08

5.11E-12 2.87E-10 0.02 5.20E-12

6986.5 6849.8 7099.6 6960.7 -2.90E-08

26577.5 26057.2 26275.9 25761.5 7.72E-08

28613.5 28053.4 28311.9 27757.6 7.72E-08

36493.6 35779.2 36078.9 35372.6 1.06E-07

466

Table B-90: Detailed WWC data for 2011 8 m PZ pilot plant campaign sample (part 1)

Alkalinity [CO2] CO2 ldg P*CO2 T P GasDry Gas PCO2in, dry PCO2in, wet PCO2out, dry PCO2out, wet CO2 flux KG kg KG/kg kg'

mol alk/kg mol/kg mol


L/min Std


mol/s Pa cm2

mol/s Pa cm2

mol/s Pa cm2

0.351 0.104 0.291 244 40 40 5 5.10

0.0 0.0 86.3 84.7 -2.21E-08

1.67E-10 2.87E-10 0.581 3.99E-10

95.8 93.9 170.4 167.1 -1.91E-08

184.0 180.4 202.8 198.9 -4.83E-09

431.3 422.9 355.2 348.2 1.95E-08

523.7 513.5 403.1 395.2 3.09E-08

735.2 720.8 494.7 485.0 6.16E-08

0.351 0.104 0.291 1248 60 40 5 5.28

0.0 0.0 565.2 535.3 -1.45E-07

1.47E-10 2.98E-10 0.493 2.89E-10

300.9 285.0 712.2 674.6 -1.05E-07

576.1 545.7 885.7 838.8 -7.93E-08

1853.5 1755.5 1623.5 1537.7 5.89E-08

2113.7 2001.9 1793.2 1698.4 8.21E-08

2392.7 2266.2 1936.5 1834.1 1.17E-07

0.351 0.104 0.291 7740 80 40 5 5.72

0.0 0.0 3023.9 2643.9 -7.74E-07

1.24E-10 3.21E-10 0.386 2.02E-10

2217.0 1938.4 4603.6 4025.2 -6.11E-07

4471.7 3909.8 5953.5 5205.4 -3.79E-07

10361.0 9059.2 9720.1 8498.8 1.64E-07

12510.2 10938.3 11303.6 9883.4 3.09E-07

14621.6 12784.5 12661.0 11070.2 5.02E-07

0.351 0.104 0.291 34204 100 40 5 6.47

0.0 0.0 10560.5 8161.3 -2.29E-06

8.45E-11 3.03E-10 0.278 1.17E-10

11095.7 8574.8 20817.8 16088.2 -2.10E-06

24920.7 19258.9 30138.5 23291.3 -1.13E-06

61846.8 47795.8 57075.0 44108.0 1.03E-06

74824.5 57825.0 66574.1 51449.0 1.79E-06

87757.6 67819.8 76608.4 59203.6 2.41E-06

0.329 0.111 0.330 756 40 20 5 5.16

0.0 0.0 191.3 185.4 -7.72E-08

1.17E-10 4.57E-10 0.256 1.57E-10

152.8 148.1 300.9 291.6 -5.98E-08

268.6 260.3 400.6 388.3 -5.33E-08

941.9 912.8 900.0 872.3 1.69E-08

1070.1 1037.1 999.8 968.9 2.84E-08

1202.6 1165.5 1100.0 1066.1 4.14E-08

467

Table B-91: Detailed WWC data for 2011 8 m PZ pilot plant campaign sample (part 2)

Alkalinity [CO2] CO2 ldg P*CO2 T P GasDry Gas PCO2in, dry PCO2in, wet PCO2out, dry PCO2out, wet CO2 flux KG kg KG/kg kg'

mol alk/kg mol/kg mol


L/min Std


mol/s Pa cm2

mol/s Pa cm2

mol/s Pa cm2

0.329 0.111 0.330 5510 60 20 5 5.45

0.0 0.0 1284.4 1177.4 -5.18E-07

1.09E-10 4.83E-10 0.225 1.41E-10

1439.9 1319.9 2458.8 2253.9 -4.11E-07

2963.5 2716.5 3635.6 3332.6 -2.71E-07

7362.0 6748.5 7098.9 6507.3 1.06E-07

10208.3 9357.6 9299.4 8524.4 3.67E-07

11643.4 10673.1 10375.7 9511.1 5.12E-07

0.329 0.111 0.330 21352 80 40 5 5.72

0.0 0.0 5421.8 4740.6 -1.39E-06

6.98E-11 3.21E-10 0.217 8.92E-11

6703.8 5861.5 10398.7 9092.2 -9.46E-07

12849.5 11235.0 14998.6 13114.1 -5.50E-07

37055.4 32399.6 34529.3 30190.8 6.47E-07

42861.8 37476.5 38978.3 34080.9 9.94E-07

49573.1 43344.5 44181.5 38630.3 1.38E-06

0.336 0.136 0.397 5891 40 20 5 5.16

0.0 0.0 653.0 632.8 -2.64E-07

4.44E-11 4.57E-10 0.097 4.91E-11

2167.0 2100.1 2561.6 2482.6 -1.59E-07

4345.9 4211.8 4477.5 4339.3 -5.31E-08

8627.3 8361.1 8340.3 8082.9 1.16E-07

12813.0 12417.6 12167.2 11791.7 2.61E-07

0.336 0.136 0.397 37794 60 40 5 5.28

0.0 0.0 4317.1 4088.9 -1.11E-06

2.61E-11 2.98E-10 0.087 2.86E-11

6737.7 6381.5 9527.8 9024.1 -7.14E-07

12544.1 11881.0 14542.4 13773.6 -5.12E-07

48928.4 46341.8 48212.0 45663.3 1.83E-07

55036.4 52127.0 53415.2 50591.4 4.15E-07

61408.4 58162.1 59674.0 56519.4 4.44E-07

468

Table B-92: Detailed Wetted Wall Column Data for 7 m MDEA/2 m PZ (part 1)

MDEA PZ CO2 ldg P*CO2 T P GasDry Gaswet PCO2in, dry PCO2in, wet PCO2out, dry PCO2out,

wet CO2 flux KG kg KG/kg kg'

m mol CO2/ mol alk

Pa °C psig Std L/min Std


mol/s Pa cm2

mol/s Pa cm2

mol/s Pa cm2

7 2 0.1335 217 30 20 5 5.09

0 0 51.9 51.0 -2.1E-08

1.05E-10 4.5E-10 0.23 1.37E-10

43.8 43.0 82.8 81.3 -1.6E-08

113.6 111.6 137.5 135.1 -9.7E-09

287.0 281.9 266.9 262.2 8.11E-09

334.9 328.9 310.7 305.2 9.75E-09

382.7 375.9 348.5 342.3 1.38E-08

7 2 0.195 732 30 20 5 5.09

0 0 110.7 108.8 -4.5E-08

6.46E-11 4.5E-10 0.14 7.53E-11

210.2 206.5 290.6 285.5 -3.2E-08

382.5 375.7 432.0 424.3 -2E-08

892.4 876.6 862.7 847.4 1.2E-08

1058.4 1039.6 1012.7 994.7 1.84E-08

1205.5 1184.1 1145.4 1125.1 2.42E-08

7 2 0.249 2750 30 20 5 5.09

0 0 275.1 270.2 -1.1E-07

4.06E-11 4.51E-

10 0.09 4.46E-11

1062.0 1043.1 1219.8 1198.2 -6.4E-08

2004.3 1968.8 2088.1 2051.0 -3.4E-08

3085.4 3030.7 3052.0 2997.8 1.35E-08

3525.5 3463.0 3470.5 3409.0 2.22E-08

3936.9 3867.1 3836.5 3768.5 4.05E-08

7 2 0.245 2175 30 20 5 5.09

0 0 251.1 246.7 -1E-07

4.69E-11 4.51E-

10 0.10 5.23E-11

684.1 671.9 839.5 824.6 -6.3E-08

1408.8 1383.8 1487.7 1461.3 -3.2E-08

4180.9 4106.8 3982.4 3911.8 8.01E-08

4860.2 4774.0 4573.2 4492.1 1.16E-07

5506.0 5408.3 5147.2 5055.9 1.45E-07

7 2 0.298 4154 30 20 5 5.09

0 0 344.4 338.3 -1.4E-07

3.32E-11 4.51E-

10 0.07 3.58E-11

1370.5 1346.2 1581.0 1553.0 -8.5E-08

2800.8 2751.2 2896.5 2845.1 -3.9E-08

9426.2 9259.0 9043.5 8883.1 1.54E-07

10741.7 10551.2 10239.4 10057.8 2.03E-07

12081.1 11866.9 11459.2 11256.0 2.51E-07

469

Table B-93: Detailed Wetted Wall Column Data for 7 m MDEA/2 m PZ (part 2)

MDEA PZ CO2 ldg P*CO2 T P GasDry Gaswet PCO2in, dry PCO2in, wet PCO2out, dry PCO2out,

wet CO2 flux KG kg

KG/k

g kg'

m mol CO2/ mol alk

Pa °C psig Std

L/min Std


mol/s Pa cm2

mol/s Pa cm2

mol/s Pa cm2

7 2 0.356 8262 30 20 5 5.09

0 0 459.2 451.1 -1.9E-07

2.22E-11 4.51E-10 0.05 2.33E-11

2829.5 2779.4 3114.2 3058.9 -1.1E-07

5580.1 5481.2 5699.7 5598.6 -4.8E-08

13425.3 13187.2 13210.0 12975.8 8.69E-08

16199.8 15912.6 15769.3 15489.7 1.74E-07

18759.1 18426.4 18208.9 17886.1 2.22E-07

7 2 0.356 16712 30 20 5 5.09

0 0 1470.5 1441.7 -3.8E-07

2.23E-11 2.87E-10 0.08 2.42E-11

5625.4 5515.3 6530.3 6402.5 -2.3E-07

11054.8 10838.4 11394.1 11171.1 -8.7E-08

21461.1 21040.9 21234.9 20819.2 5.79E-08

26701.9 26179.2 25947.8 25439.9 1.93E-07

31905.1 31280.5 30623.1 30023.6 3.28E-07

470

Table B-94: Detailed WWC data for 5 m MDEA/5 m PZ (part 1)

MDEA/PZ CO2 ldg P*CO2 T P GasDry Gas PCO2in, dry PCO2in, wet PCO2out, dry PCO2out, wet CO2 flux KG kg KG/kg kg'

m mol


cm2 mol/s Pa

cm2 mol/s Pa

cm2

5 5 0.202 130 30 20 5 5.09

0.00 0.00 26.55 26.08 -1.07E-08

1.09E-10 4.50E-10 0.24 1.44E-10

59.80 58.74 80.60 79.18 -8.40E-09

110.74 108.78 118.16 116.06 -2.99E-09

209.52 205.81 191.11 187.72 7.43E-09

259.03 254.44 229.61 225.54 1.19E-08

302.09 296.73 260.95 256.32 1.66E-08

5 5 0.202 326 40 20 5 5.16

0.00 0.00 79.17 76.73 -3.20E-08

1.13E-10 4.57E-10 0.25 1.50E-10

93.28 90.40 151.88 147.19 -2.37E-08

140.16 135.84 189.19 183.35 -1.98E-08

377.67 366.01 365.47 354.19 4.92E-09

450.38 436.48 422.63 409.59 1.12E-08

499.41 484.00 462.10 447.84 1.51E-08

5 5 0.242 46 10 20 5 5.03

0.00 0.00 14.11 14.04 -5.70E-09

9.68E-11 4.42E-10 0.22 1.24E-10

13.87 13.80 17.46 17.37 -1.45E-09

27.03 26.89 29.66 29.51 -1.06E-09

78.69 78.29 71.75 71.39 2.80E-09

92.09 91.61 83.95 83.52 3.28E-09

104.52 103.99 90.65 90.18 5.60E-09

5 5 0.242 103 20 20 5 5.05

0.00 0.00 19.37 19.18 -7.82E-09

7.52E-11 4.46E-10 0.17 9.04E-11

32.05 31.74 43.29 42.87 -4.54E-09

59.56 58.97 66.73 66.08 -2.90E-09

166.47 164.84 154.51 153.00 4.83E-09

217.89 215.77 198.28 196.34 7.92E-09

316.92 313.82 282.23 279.48 1.40E-08

5 5 0.242 288 30 20 5 5.09

0.00 0.00 66.01 64.84 -2.66E-08

1.06E-10 4.50E-10 0.23 1.38E-10

61.47 60.38 116.96 114.89 -2.24E-08

114.81 112.77 152.84 150.13 -1.53E-08

315.24 309.65 309.26 303.78 2.41E-09

372.65 366.04 356.62 350.30 6.47E-09

419.29 411.85 390.11 383.19 1.18E-08

5 5 0.242 843 40 20 5 5.16

0.00 0.00 182.74 177.10 -7.38E-08

9.75E-11 4.57E-10 0.21 1.24E-10

297.30 288.13 418.81 405.88 -4.90E-08

567.10 549.60 627.61 608.25 -2.44E-08

1099.28 1065.36 1047.86 1015.52 2.08E-08

1390.37 1347.46 1282.73 1243.15 4.34E-08

1557.79 1509.72 1416.68 1372.96 5.70E-08

471

Table B-95: Detailed WWC data for 5 m MDEA/5 m PZ (part 2)

MDEA/PZ CO2 ldg P*CO2 T P GasDry Gas PCO2in, dry PCO2in, wet PCO2out, dry PCO2out, wet CO2 flux KG kg KG/kg kg'

m mol


cm2 mol/s Pa

cm2 mol/s Pa

cm2

5 5 0.282 89 10 20 5 5.03

0.00 0.00 14.11 14.04 -5.70E-09

6.75E-11 4.42E-10 0.15 7.96E-11 57.88 57.59 61.95 61.63 -1.64E-09

213.83 212.73 197.33 196.31 6.66E-09

238.46 237.24 213.59 212.49 1.00E-08

5 5 0.282 275 20 20 5 5.05

0.00 0.00 54.77 54.24 -2.21E-08

7.40E-11 4.46E-10 0.17 8.87E-11

59.80 59.21 87.54 86.69 -1.12E-08

110.50 109.42 136.81 135.48 -1.06E-08

459.71 455.22 429.33 425.14 1.23E-08

504.44 499.51 468.08 463.51 1.47E-08

5 5 0.282 825 30 20 5 5.09

0.00 0.00 136.33 133.92 -5.50E-08

7.36E-11 4.50E-10 0.16 8.79E-11

236.79 232.59 346.81 340.66 -4.44E-08

454.45 446.39 507.07 498.08 -2.12E-08

1609.70 1581.15 1482.93 1456.64 5.12E-08

1848.88 1816.10 1683.84 1653.99 6.66E-08

2045.01 2008.75 1848.88 1816.10 7.92E-08

5 5 0.282 2245 40 20 5 5.16

0.00 0.00 310.94 301.34 -1.25E-07

7.43E-11 4.57E-10 0.16 8.88E-11

571.65 554.00 863.45 836.80 -1.18E-07

1097.85 1063.97 1289.19 1249.41 -7.72E-08

3245.70 3145.54 3090.23 2994.87 6.27E-08

3532.72 3423.70 3341.37 3238.26 7.72E-08

3807.78 3690.27 3561.42 3451.52 9.94E-08

5 5 0.329 1749 30 20 5 5.09

0.00 0.00 196.13 192.65 -7.92E-08

4.94E-11 4.50E-10 0.11 5.55E-11

710.37 697.78 837.14 822.29 -5.12E-08

1439.88 1414.35 1478.15 1451.94 -1.54E-08

2922.81 2870.98 2798.43 2748.81 5.02E-08

3666.66 3601.65 3451.40 3390.20 8.69E-08

4415.30 4337.01 4113.93 4040.99 1.22E-07

5 5 0.329 4906 40 20 5 5.16

0.00 0.00 583.60 565.59 -2.36E-07

5.20E-11 4.57E-10 0.11 5.86E-11

1447.05 1402.40 1853.66 1796.46 -1.64E-07

2953.90 2862.74 3240.92 3140.91 -1.16E-07

8789.94 8518.69 8335.50 8078.27 1.83E-07

10177.20 9863.14 9579.24 9283.64 2.41E-07

11612.29 11253.95 10846.91 10512.18 3.09E-07

1.

472

Table B-96: Detailed Wetted Wall Column Data for Enzyme Promoted 4.8 m AMP (part 1)

AMP CO2 ldg [Enz] PCO2* Temp Pressure GasDry Gaswet PCO2in, dry PCO2in, wet PCO2out, dry PCO2out, wet CO2 flux KG kg KG/kg kg'

m mol CO2/ mol alk

ppm Pa C psig Std

L/min Std

L/min Pa Pa Pa Pa

mol/s cm2

mol/s Pa m2

mol/s Pa m2 mol/s Pa

m2

4.8 0.256 0 551 40 20 5 5.16

0.0 0.0 61.7 59.8 -2.49E-08

4.45E-07 4.57E-06 0.10 4.93E-07

102.8 99.7 147.6 143.0 -1.81E-08

190.6 184.7 226.3 219.3 -1.44E-08

717.1 694.9 702.2 680.6 5.99E-09

810.1 785.1 786.0 761.7 9.75E-09

892.4 864.9 859.9 833.3 1.31E-08

4.8 0.256 0 3835 60 20 5 5.45

0.0 0.0 478.4 438.5 -1.93E-07

4.95E-07 4.83E-06 0.10 5.52E-07

1368.1 1254.1 1655.1 1517.2 -1.16E-07

2803.2 2569.6 2922.8 2679.2 -4.83E-08

5577.7 5112.9 5410.3 4959.4 6.76E-08

6941.1 6362.6 6654.0 6099.5 1.16E-07

8184.8 7502.7 7778.2 7130.0 1.64E-07

4.8 0.256 100 474 40 20 5 5.16

0.0 0.0 60.3 58.4 -2.43E-08

5.14E-07 4.57E-06 0.11 5.80E-07

105.0 101.8 148.1 143.5 -1.74E-08

189.4 183.6 222.4 215.6 -1.33E-08

710.1 688.2 680.2 659.2 1.21E-08

793.8 769.3 760.8 737.4 1.33E-08

879.5 852.3 835.9 810.1 1.76E-08

4.8 0.256 100 3590 60 20 5 5.45

0.0 0.0 432.9 396.8 -1.75E-07

5.00E-07 4.83E-06 0.10 5.58E-07

1315.5 1205.9 1590.6 1458.0 -1.11E-07

2750.6 2521.4 2867.8 2628.8 -4.73E-08

5415.1 4963.8 5247.7 4810.3 6.76E-08

6754.5 6191.6 6443.6 5906.6 1.25E-07

8046.1 7375.6 7615.6 6980.9 1.74E-07

4.8 0.256 1000 512 40 20 5 5.16

0.0 0.0 75.6 73.2 -3.05E-08

5.81E-07 4.57E-06 0.13 6.65E-07

93.8 90.9 146.4 141.9 -2.12E-08

184.6 179.0 224.6 217.7 -1.61E-08

693.1 671.8 674.7 653.9 7.43E-09

798.9 774.2 763.5 739.9 1.43E-08

882.1 854.9 835.2 809.4 1.89E-08

4.8 0.256 1000 3383 60 20 5 5.45

0.0 0.0 447.3 410.0 -1.81E-07

5.60E-07 4.83E-06 0.12 6.33E-07

1396.8 1280.4 1683.8 1543.5 -1.16E-07

2831.9 2595.9 2903.7 2661.7 -2.90E-08

5534.7 5073.4 5319.4 4876.1 8.69E-08

6945.8 6367.0 6563.2 6016.2 1.54E-07

8261.4 7572.9 7783.0 7134.4 1.93E-07

473

Table B-97: Detailed Wetted Wall Column Data for Enzyme Promoted 4.8 m AMP (part 3)

AMP CO2 ldg [Enz] PCO2* Temp Pressure GasDry Gaswet PCO2in, dry PCO2in, wet PCO2out, dry PCO2out, wet CO2 flux KG kg KG/kg kg'

m mol CO2/ mol alk

ppm Pa C psig Std

L/min Std


mol/s Pa m2

mol/s Pa m2 mol/s Pa

m2

4.8 0.56 1000 7231 40 20 5 5.16

0.0 0.0 339.6 329.2 -1.37E-07

1.92E-07 4.57E-06 0.04 2.01E-07

1392.0 1349.1 1679.1 1627.2 -1.16E-07

2851.1 2763.1 3042.4 2948.5 -7.72E-08

10911.5 10574.8 10744.1 10412.5 6.76E-08

12274.8 11896.0 12059.6 11687.4 8.69E-08

13518.6 13101.4 13255.5 12846.4 1.06E-07

4.8 0.56 1000 3444

0 60 40 5 5.1

0.0 0.0 2420.6 2373.2 -6.20E-07

1.78E-07 2.87E-06 0.06 1.90E-07

12080.3 11843.9 13513.1 13248.6 -3.67E-07

23014.5 22563.9 23806.3 23340.2 -2.03E-07

49595.7 48624.9 48577.7 47626.8 2.61E-07

66487.1 65185.5 64413.4 63152.4 5.31E-07

74895.1 73428.9 72331.2 70915.2 6.56E-07

474

Appendix C: Simplified stoichiometric model

C.1 MATLAB CODE

C.1.1 Model equations

function [error] = TwoRegionTrans (c)

% This model takes data from the specified spreadsheets

% This is a simplified equation set which describes the CO2 VLE into

primary % or secondary (unhindered) amines

% This function is to be used together with a parameter regression code % ParamRegTransT

% The governing chemical equilibrium were chosen to represent two

distinct % regions of CO2 loading: Carbamate formation, and bicarbonate

formation

% The governing chemical equilibrium equations are transformed in order

to % improve convergence of the nonlinear solver

% This function takes the equilibrium parameter values and reads the

experimental % conditions and calculates PCO2 and liquid phase species (at the % experimental conditions)

% This model neglects carbonate formation, and does not account for the % dissociation of water

% The equilibrium parameters are center around 40C % clear all

%k(1) is the carbamate stability constant %k(2) MEA protonation constant

% x are the experimental conditions: temperature, total CO2, total

amine

T=xlsread('Specmodeldatatemplate','Result conditions','A46:A131'); xaminetotal=xlsread('Specmodeldatatemplate','Result

conditions','B46:B131');

475

xCO2total=xlsread('Specmodeldatatemplate','Result

conditions','C46:C131'); LnPCO2data=xlsread('Specmodeldatatemplate','Result

conditions','F46:F131');

x=[T xaminetotal xCO2total];

% y are the outputs of the function VLE % y(1): ln(xMEA) % y(2): ln(xMEAH+) % y(3): ln(xMEACOO-) % y(4): ln(xHCO3-) % y(5): ln(PCO2)

[m,n]=size(T);

options=optimset('TolFun',1.0e-12,'TolX',1e-12);

for i=1:m xi=x(i,:);

VLE=@(y)[-y(3)-y(2)+y(5)+2*y(1)-c(1)-c(2)*(1/313.15-1/T(i))*10000; -2*y(4)-y(2)+y(3)+y(5)-c(3)*10-c(4)*(1/313.15-1/T(i))*1000; exp(y(1))+exp(y(2))+exp(y(3))-xi(2); exp(y(2))-exp(y(3))-exp(y(4)); exp(y(3))+exp(y(4))-xi(3)];

yo=[log(xi(2))-log(xi(3)) log(xi(3)) log(xi(3)) log(xi(3))/10 LnPCO2data(i)];

[yi fval] = fsolve(VLE,yo,options); % % % xMEA(i)=exp(yi(1)); % xMEAp(i)=exp(yi(2)); % xMEACOO(i)=exp(yi(3)); % xHCO3(i)=exp(yi(4)); % LnPCO2calc(i)=yi(5);

end

LnCalc=LnPCO2calc' AARD=sum(abs(exp(LnPCO2data)-

exp(LnCalc))./exp(LnPCO2data))/merror=sum(((LnPCO2data-LnCalc).^2))

C.1.2 Parameter regression

476

% this script performs nonlinear parameter regression for CO2 VLE

models

clear all

co =[8.6725 1.5976 1.1305 2.4795]; %initial guess for the equilibrium constant parameters

A=[]; b=[]; Aeq=[]; beq=[];

lb=[1 0.1 0.1 1];

ub=[15 5 2 10];

[c,error] = fmincon(@TwoRegionTrans,co,Aeq,beq,A,b,lb,ub)

C.1.3 Model statistics clear all

c=[8.6725 1.5976 1.1305 2.4795];

H=hessianVLE(@TwoRegionTrans,c,0.0001 )%calculated the Hessian of the

system of nonlinear equations

covar = inv(H) %0.0000001)); calculates the convariance matrix stdev_param = sqrt(diag(covar)) % calculates the standard deviation of

the parameters

corr(covar) %calculate the correlation matrix

HessianVLE file

function h = hessianVLE(fun,c,del) %implementation by Prof. William Press %http://www.nr.com/CS395T/lectures2008/12-

MaxLikelihoodEstimationAgain.pdf

477

%part of the course material provided by Dr.Michael Baldea for CHE384 %slightly adapted

h = zeros(4); for i=1:4 for j=1:i ca = c; ca(i) = ca(i)+del; ca(j) = ca(j)+del; cb = c; cb(i) = cb(i)-del; cb(j) = cb(j)+del; cc = c; cc(i) = cc(i)+del; cc(j) = cc(j)-del; cd = c; cd(i) = cd(i)-del; cd(j) = cd(j)-del; h(i,j) = (fun(ca)+fun(cd)-fun(cb)-fun(cc))/(4*del^2); h(j,i) = h(i,j); end end

end

C.2 Correlation matrix for amine models

MEA

C1 C2 C3 C4

C1 1 -0.940 -0.913 0.900

C2

1 0.997 -0.995

C3

1 -0.999

C4

1

7 m MPA

C1 C2 C3 C4

C1 1 -0.277 -0.620 -0.156

C2

1 -0.572 -0.905

C3

1 0.854

C4

1

MIPA

C1 C2 C3 C4

C1 1 -0.850 -0.843 0.741

C2

1 0.995 -0.983

C3

1 -0.983

C4

1

478

10 m DGA®

C1 C2 C3

C1 1 -0.953 -0.841

C2 1 0.638

C3 1

GlyK

C1 C2 C3 C4

C1 1 -0.986 -0.970 0.962

C2

1 0.996 -0.994

C3

1 -0.999

C4

1

6.5 m β-alaK

C1 C2 C3 C4

C1 1 -0.972 -0.926 0.911

C2

1 0.987 -0.981

C3

1 -0.999

C4

1

7 m MMEA

C1 C2 C3

C1 1 -0.917 -0.938

C2 1 0.721

C3 1

DEA

C1 C2 C3 C4

C1 1 0.763 -0.931 -0.950

C2

1 -0.826 -0.617

C3

1 0.938

C4

1

DIPA

C1 C2 C3 C4

C1 1 0.019 -0.406 -0.305

479

C2

1 -0.905 -0.936

C3

1 0.994

C4

1

Sar(K or Na)

C1 C2 C3 C4

C1 1 -0.883 -0.016 -0.008

C2

1 0.457 -0.439

C3

1 -0.999

C4

1

4.8 m AMP

C1 C2 C3

C1 1 0.986 -0.9999

C2 1 -0.988

C3 1

480

Appendix D: Spreadsheet model for process performance

D.1 ISOTHERMAL ABSORBER MODELING

Microsoft Excel 2007 was used to build the absorber model. The absorber is

assumed to be isothermal at 40 °C. Pressure drop across the column is assumed to be

zero, and the operating pressure is atmospheric. Flue gas properties used in the model

correspond to typical coal-fired power plants. The gas flow rate is ¼ of the total flue

gas rate of a 500 MW plant (Table 5).

Table D-1: Flue Gas Properties of 500 MW Coal Plant

Flow rate

(kmol/s)

total 23.55

per train (1/4) 5.89

Composition

(mol%)

CO2 12.38

N2 70.03

O2 4.65

H2O 12.94

To represent the CO2 vapor liquid equilibrium of the solvent, the semi-empirical

expression is used (Table D-2). The expression relates PCO2* with temperature and

solvent CO2 loading. The parameters were obtained by regression of multiple sets of

experimental data. The absorption rate of the solvent is represented by a correlation

which relates solvent mass transfer coefficients (kg’) with PCO2* (Equation D-1). The

experimentally measured kg’ values are fitted using a second order polynomial with

experimental PCO2* using three parameters (Figure 3, Table 8).

ln(kg’) = a ∙ ln(PCO2*)2 + b∙ ln(PCO2

*) + c (D-1)

Table D-2: VLE Models and Parameters

7 m MEA

(Xu, 2010)

2* )ln(/)ln(2

eTdcTbaPCO

a b c d e

481

-402.0 10489.6 -16.5 64.7 52.74

6 m SarK

2* //)ln(2

eTdcTbaPCO

a b c d e

46.5 -15982.5 -34.4 17766 0.08

Table D-3: Wetted Wall kg’ Measurements (40 °C)

7 m MEA

(Dugas, 2009) 6 m SarK

PCO2* kg' PCO2

* kg'

Pa mol/Pa∙s ∙m2 Pa mol/Pa∙s ∙m2

15.7 3.34E-06 18 2.64E-06

77 1.4E-06 201 1.99E-06

465 7.66E-07 612 1.02E-06

4216 3.47E-07 4477 3.25E-07

Figure D-1: Empirical fit of kg’ as function of PCO2*

-16

-15

-14

-13

-12

2 3 4 5 6 7 8 9

ln(k

g')

ln(PCO2*)

7m MEA

6m SarK

482

Table D-4: Parameters of kg’ Correlation

7 m MEA 6 m SarK

a 0.0215 -0.0716

b -0.6362 0.4219

c -11.048 -13.448

The absorber column set up as 30 calculation stages. Stage 1 represents the top

of the absorber, where the lean solvent enters and the clean flue gas leaves. Stage 30

corresponds to flue gas entrance and rich solvent condition. CO2 removal and species

mass balance are calculated at each stage, which gives the gas and liquid compositions of

the subsequent stage.

Two values need to be chosen as initial guesses: inlet liquid flow rate (kmol/s)

and effective mass transfer area per stage (m2). At stage 1, the flow rate and CO2 mol%

of the gas are set by assuming 90% of the CO2 in the inlet flue gas are removed in the

column (Table D-5). On the liquid side, the CO2 loading is set as the lean loading of the

solvent (correspond to 0.5 kPa). The flow rate of each species in the solvent are then

calculated using total inlet liquid flow rate and amine concentration of the solvent. The

calculated output of each stage is the total CO2 removed (kmol/s), which is calculated

using the input values and the effective mass transfer area of the stage (Table D-6). The

calculated removal then gives the input values of the next stage by setting the CO2 flow

rate of both the gas and liquid. The flow rates of all non-CO2 species are assumed to be

constant at all stages.

Table D-5: Input Values of First Calculation Stage

Gas Liquid

Flow rate CO2 flow

rate CO2% CO2 ldg

Flow rate

CO2 H2O Amine

Segment kmol/s kmol/s mol% (mol CO2/mol alk) kmol/s kmol/s kmol/s

1 5.25 0.0706 0.0135 0.438 3.26 59.1 7.45

483

Table D-6: Output Values of First Calculation Stage

PCO2 Pa 1479.8 Ptotal Х CO2 mol%

PCO2* Pa 502.2 Table 5

kg' mol/s.Pa.m2 7.0E-07 Equation 4

CO2 flux mol/s.m2 0.00068 kg' Х (PCO2 - PCO2*)

∆ CO2 kmol/s 0.0083 CO2 flux Х Area

As the calculation sequence reaches stage 30, the gas properties should agree with

the assumed inlet flow rate and composition (Table D-5). The values of the liquid flow

rate and effective area are adjusted by trial and error to match calculated results to

expected values (and the model converges). At a constant liquid flow rate, there is a

corresponding value of effective area which results in a converged model. The model

can be used to calculate this relationship between liquid rate and effective area. As

liquid flow rate decreases, the effective area required will increase to achieve the desired

removal. The theoretical minimum liquid flow rate requires an infinite amount of

transfer area to achieve the target removal rate. This minimum can be found by plotting

liquid flow rate values with model calculated area (Figure D-2). The reported liquid

rate is set to equal to 1.1 times the Lmin, which is assumed to be a reasonable optimum

point in the tradeoff between packing area and solvent rate (Table D-7).

484

Figure D-2: Liquid Flow Rate Optimization (7 m MEA, lean loading = 0.438, 90%

removal)

Figure D-3: Liquid Flow Rate of Different Solvents and Lean Loadings

55

60

65

70

75

80

85

250000 300000 350000 400000 450000 500000 550000 600000

Liq

uid

Flo

w R

ate

(km

ol/

s)

Total Column Area (m2)

Lmin

L = 1.1 ХLmin

Lean loading = 0.438(0.5 kPa)

15

25

35

45

55

65

75

85

30000 130000 230000 330000 430000 530000 630000 730000 830000

Liq

uid

Flo

w R

ate

(km

ol/

s)

Total Column Area (m2)

7m MEA lean ldg @ 0.5 kPa

6m SarK lean ldg @ 0.5 kPa

6m SarK (overstripping)

7m MEA (overstripping)

485

The model is used to compare 7 m MEA and 6 m SarK at two conditions:

optimum lean loading (PCO2* = 500 Pa) and overstripping (PCO2*= 8 Pa). In the case of

optimum lean loading, 6 m SarK has better performance than 7 m MEA, because it

requires slightly less effective packing area and less total liquid flow rate to achieve 90%

CO2 removal. The low liquid rate of 6 m SarK is not expected since it has a smaller

capacity than 7 m MEA. A possible explanation is the unit of reported liquid rate which

uses a molar basis, while the capacity is a mass-based parameter. The relative

performance of the two solvents switches at the condition of overstripping. When the

lean loading is low, 7 m MEA performs better than 6 m SarK, requiring 50% less packing

area and also less liquid rate. The required liquid rate and packing area for both

solvents decreases with decreased lean loading, and 7 m MEA performs better at low lean

loadings. The isothermal spreadsheet model results are compared with predictions using

the log mean (LM) flux method (Table 11). The log mean flux calculation assumes the

rich loading at 10 times the lean loading PCO2*, and the log mean average of the flux at

the top (lean) and bottom (rich) of the absorber are used to calculate the expected packing

area (Equations 5, 6). For the optimum lean loading condition, the LM flux method

results in higher packing area than the model, by approximately 30%. The two methods

demonstrate the same relative performance between the two solvents at this condition,

with 6 m SarK as the better solvent.

Table D-7: Isothermal Spreadsheet Model Results (40 °C, 90% Removal)

Solvent

Lean loading Isothermal Model LM Flux

Liquid Rate Apacking kg'avg Apacking

mol CO2/

mol alk

PCO2*

(Pa) kmol/s Х10-5 m2

Х107

mol/s.Pa.m2 Х 10-5 m2

7 m MEA 0.44 500 66.55 3.62 4.35 4.82

0.2 8 17.15 1.21 / /

486

6 m SarK 0.48 500 54.45 3.49 5.02 4.17

D.2 EQUIVALENT WORK SPREADSHEET CALCULATION

The energy performance of the process is represented using equivalent work

(Weq), which account for the equivalent work corresponding to the sensible heat cost of

heating to solvent to high temperatures, pump work, and compression work. The

following equations were used to calculate Weq, which were written based on principles

outlines by Van Wagner (2011).

𝑊𝑒𝑞 = 𝑊ℎ𝑒𝑎𝑡 +𝑊𝑐𝑜𝑚𝑝𝑟𝑒𝑠𝑠𝑖𝑜𝑛 +𝑊𝑝𝑢𝑚𝑝 (D-2)

𝑊ℎ𝑒𝑎𝑡 = 0.75𝑄𝑟𝑒𝑏 (𝑇ℎ𝑒𝑎𝑡−𝑇𝑠𝑖𝑛𝑘

𝑇𝑠𝑖𝑛𝑘) (D-3)

𝑄𝑟𝑒𝑏 = 𝑄𝑙𝑎𝑡𝑒𝑛𝑡 + 𝑄𝑠𝑒𝑛𝑠𝑖𝑏𝑙𝑒 (D-4)

𝑄𝑙𝑎𝑡𝑒𝑛𝑡 = 𝑄𝑎𝑏𝑠𝑜𝑟𝑝𝑡𝑖𝑜𝑛 + 𝑄𝑠𝑡𝑒𝑎𝑚 (D-5)

𝑄𝑎𝑏𝑠𝑜𝑟𝑝𝑡𝑖𝑜𝑛 =∫ 𝐻𝑎𝑏𝑠(𝛼)𝑑𝛼𝛼𝑟𝑖𝑐ℎ𝛼𝑙𝑒𝑎𝑛

(𝛼𝑟𝑖𝑐ℎ−𝛼𝑙𝑒𝑎𝑛) (D-6)

𝑄𝑠𝑡𝑒𝑎𝑚 =𝑛𝐻2𝑂

𝑛𝐶𝑂2𝐻𝑣𝑎𝑝,𝐻2𝑂 (D-7)

𝑄𝑠𝑒𝑛𝑠𝑖𝑏𝑙𝑒 =𝐶𝑝

∆𝐶𝑠𝑜𝑙𝑣(𝑇𝑠𝑡𝑟𝑖𝑝𝑝𝑒𝑟 − 40°𝐶) (D-8)

The compression work was calculated using an empirical correlation developed

by Van Wagner (2011), as shown in Equation D-9.

𝑊𝑐𝑜𝑚𝑝 (𝑘𝐽

𝑚𝑜𝑙 𝐶𝑂2) = {

4.572 ln (150 𝑃𝑖𝑛⁄ ) − 4.096, 𝑃𝑖𝑛 ≤ 4.56𝑏𝑎𝑟

4.023 ln (150 𝑃𝑖𝑛⁄ ) − 2.181, 𝑃𝑖𝑛 ≥ 4.56𝑏𝑎𝑟

(D-9)

The pump work is estimated by considering the pressure difference between the

stripper and the absorber, and the liquid flowrate. The pump efficiency is not included

in this estimation (Equation D-10).

𝑊𝑝𝑢𝑚𝑝 =(𝑃𝑠𝑡𝑟𝑖𝑝𝑝𝑒𝑟−𝑃𝑎𝑡𝑚)∙�̇�

𝜌∙𝑛𝐶𝑂2 (D-10)

Figure D-4 shows the equivalent work and required absorber packing at different

solvent lean loadings calculated using the spreadsheet.

487

Figure D-4: Spreadsheet model result of absorber packing requirement versus total work

requirement in a process using 7 m MEA

5.E+04

5.E+05

0

50

100

150

200

250

300

0.2 0.25 0.3 0.35 0.4 0.45

Pac

kin

g ar

ea (

m2)

We

q(k

J/m

ol C

O2)

Lean Loading (mol CO2/mol alk)

488

Appendix E: Standard Operating Procedures (SOP)

E.1 WETTED WALL COLUMN SOP

E.1.1 Preparation

Wash solvent reservoir tank

o flush with distilled water (open V-L02), then drain all liquids from tank

Wash system liquid lines (Figure E.1 and E.2)

o Open valve V-L01; adjust V-L03 to the downward direction

o Close V-G07 and needle valve

o Prepare: beaker #1 with 300 mL of DI water, beaker #2 empty

o Immerse tip of solvent loading line in beaker #1, position beaker #2 at liquid

exit

o Switch on power button on pump, adjust setting to 50%

o Set pump setting to zero when beaker #1 is empty, and liquids stops at the

liquid exit. Empty beaker #2 into a waste container.

o Refill beaker #1 with 200 mL of solvent, repeat steps 4 – 6

o Close V-L01 and V-L03.

Refill saturator (Figure E-5)

o Disconnect the plastic-plastic swadglok connection downstream of the

saturator

o Push DDI water into the saturator with a 200 mL plastic syringe, until water

level is about 85%

Desiccant column (Figure E-3)

o In case of desiccant in column is saturated (color turns pink), refill with fresh

desiccant

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Water knockout flask (Figure E-3)

o Rinse three times with water (DDI for final rinse); dry the inside of the flask

E.1.2 Start up

Liquid solvent (Figure E-2)

o Connect drum to system at swadglok connections C-1 and C-3 (finger tight)

o Load solvent into system

Open valves V-L01, V-L02, open V-L03 to downward position

Fill a 500 mL beaker with solvent, immerse tip of solvent loading line

into beaker, position the open end of liquid line bridge to point the

beaker

Turn pump setting to about 50% until beaker is empty

Turn off pump; follow by immediately switching on V-G07 (to avoid

significant flooding of WWC chamber due residue suction)

When liquid level in WWC chamber is stable, close V-G07

Repeat steps ii – v (3-4 times) until liquid flows out of the open end of

bridge (at C-2)

o Close valves V-L01, V-L02, V-L03

o Connect C-2, then tighten all connections (C-1, C-2, C-3) using ranches

o Open valves V-L01, V-L02, V-L03

o Turn on pump and adjust setting until liquid flow rate reach target (typically

10 on flow meter)

o Turn on and set HX-02 to 5 -15 ˚C higher than target temperature

Gas stream:

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o Adjust pressure of all gas tanks to about 20 psi higher than target system

pressure

o (Not pictured in diagrams) Open all valves between N2 gas tank and the

MFC-1.

o Ensure V-G03 and V-G05 are closed

o Open valves downstream to MFC-1 (V-G01, V-G02, V-G04, V-G06)

o Quickly follow by open MFC-1 using the MFC control box to settings at 10%

or lower (system pressure will increase as result of gas flow)

o Immediately adjust needle valve to lower system pressure

o Adjust MFC-1 setting to target flow rate, follow by re-adjusting system

pressure iteratively until target pressure and flow rate are reached

o the system pressure responds quickly to increase in total gas rate, but slower

to needle valve adjustments. Therefore it is important to start the gas flow

by small intervals, and quickly adjusting the needle valve to avoid over-

pressuring the system

o Turn on and set HX-01 to 3 to 10 C higher than target system temperature

o Make ice bath by immersing water knock-out flask in fresh ice water

o Set V-G09 to direct gas flow to the appropriate CO2 analyzer

o Connect electric signal cable from CO2 analyzer to receiver on the WWC

computer

o Adjust V-G08 to ensure flow rate into CO2 analyzer is optimum (X.1)

Steady state

o Stabilize system pressure by tuning needle valve setting (MFC setting might

fluctuate as result of significant shift in system pressure, adjust accordingly)

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o Readjust pump setting to target flow rate (typically setting 10 on flow meter is

used to provide stable film on WWC)

o Inject additional solvent into system using a 1.5 mL syringe via the sample

valve, until visible liquid level in the WWC chamber (approximately ½ to 1

inch) is observed

No air bubbles should be passing through the transparent section of

flow meter

Film should cover entire WWC without dry spots, surface should be

smooth.

o Adjust setting of HX-02 until temperature of the system (as displayed by

thermocouple reader) reaches target

o Remove just enough solvent from the sample valve so the liquid level in

chamber disappears, without generating air bubbles visible at the flow meter

o In the following order: open V-G05, close V-G06, wait about 5 seconds, open

V-G06, close V-G05

o this step brings the gas stream into the WWC chamber, then switch back to the

bypass line immediately after to minimize the contact time. Excess liquids in

the gas line will be pushed into the WWC chamber

o Remove additional solvent if liquid level becomes visible as result of step 6

o CO2 analyzers need to be flushed with N2 until a stable reading is obtained (15

minutes or longer)

o The system needs to be actively maintained at steady state by constantly

monitoring and readjusting: system pressure (needle valve), temperature (HX-

02), liquid flow rate (pump setting), use sample valve to adjust liquid level

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o the liquid level need to be maintained such that there are no visible in the

WWC chamber (too much liquid), also no gas bubble is visible (too little

liquid)

E.1.3 Operation

Turn on PicoLog software on WWC computer

o Click: File

New data: save under appropriate file name

o Click: View

Graph

o Start recording

o The computer software is used only to monitor the trend of output data.

The recording is not used in the analysis and calculations of

experimental results

Record in data sheet: system pressure (gauge), temperature, total gas flow rate

Record in data sheet: the CO2 concentration baseline reading (N2 only) as shown

on the front of the analyzer

Connect appropriate MFC (MFC 2, 3, 4) with CO2 tank and the gas line, open V-

G03 and all valves between MFC and gas tank

For each experimental point:

o Adjust MFCs to target settings, wait until analyzer reading is stable,

record in data sheet stable reading (as shown on analyzer) “bypass CO2

concentration”

o Open V-G05 first, then close V-G06 (gas stream now contacts the liquid

solvent)

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In case of liquid splash in the WWC chamber, withdraw solvent

from sample valve until splashing stops (without introducing air

bubbles)

Tune needle valve settings to maintain stable system pressure

Monitor the PicoLog graph until the data reach steady state

Record analyzer reading as “operation CO2 concentration”

o Open V-G06 first, then close V-G05. Gas stream now by-passes the

WWC chamber

o When switching the gas stream between the WWC path and the bypass

line, it is important to NOT close the two valves at the same time.

Therefore, always first OPEN the closed valve, then close the other valve.

o For a typical CO2 absorption experiment, repeat step e) using six different

CO2/N2 ratios: three absorption and three desorption conditions.

o For a typical CO2 absorption experiment, three solvent samples are

collected, one after two flux measurements

While the gas line is on bypass (V-G06 open, V-G05 close), inject

1.5 mL of fresh solvent into sample valve

After about 5 minutes, withdraw excess solvent from sample valve,

store as sample

E.1.4 Change system temperature

Set the CO2 stream MFC to zero, close all valves between MFC and CO2 tank, and V-

G03

Set the N2 stream to about 1-2 SLPM (MFC-1), system pressure will decrease (do not

adjust)

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Set HX-02 and HX-01 to new condition, wait until thermocouple reading is within 2C

of target

While waiting

o If significant water is collected in the knockout flask, rinse and dry the flask

o Refill ice if it has mostly melted

Bring gas flow rate, liquid flow rate, pressure to operating conditions

Readjust HX-02 setting to reach target temperature

E.1.5 Shut down

Set the CO2 stream MFC to zero, close all valves between MFC and CO2 tank, and V-

G03

Close CO2 tank, or reset tank pressure to original conditions

Set the N2 stream to about 1-2 SLPM (MFC-1), system pressure will decrease (do not

adjust)

Lower pump speed to about 2-5 on flow meter

Power off HX-01 and HX-02, wait until system cool down to below 40 C

Set MFC-1 to zero, close V-G01, V-G02, V-G04, and needle valve (stop gas flow)

Solvent reservoir

o Turn off pump

o Close V-L01, V-L02, set V-L03 to point in horizontal direction

o Disconnect C-1, C-2, C-3, use beaker to collect solvent from bridge

o Pour solvent from the reservoir into storage containers

Liquid lines

o Position empty beaker at solvent loading line, set V-L03 to point down,

collect any liquid solvent

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o Position empty beaker at liquid exit, open V-L01, V-L02, set V-L03 to point

upward

o Turn on pump to 50% setting, collect solvent residue in the liquid lines

o Turn off pump, and power off

Lower N2 tank pressure

Remove and clean ice bath

Double check for

o Power off: HX-01, HX-02, pump

o All gas and liquid valves closed (except V-G06)

o All MFC are set to zero

E.1.6 Data analysis

The CO2 mass transfer flux can be calculated from raw WWC experiment data by

first calculating the bypass and operation 𝑃𝐶𝑂2 from measured [CO2]:

𝑃𝐶𝑂2 = ([𝐶𝑂2]𝑒𝑥𝑝 − [𝐶𝑂2]𝑏𝑎𝑠𝑒𝑙𝑖𝑛𝑒) ∙ 𝑃𝑡𝑜𝑡𝑎𝑙 (E-1)

[𝐶𝑂2]𝑏𝑎𝑠𝑒𝑙𝑖𝑛𝑒 is the analyzer reading with pure N2 in the gas stream; Ptotal is the

pressure of the WWC chamber, and 𝑃𝑡𝑜𝑡𝑎𝑙 = 𝑃𝑔𝑎𝑢𝑔𝑒 + 𝑃𝑎𝑡𝑚.

𝑓𝑙𝑢𝑥(𝑚𝑜𝑙

𝑐𝑚2𝑠) =

(𝑃𝐶𝑂2,𝑏𝑦𝑝𝑎𝑠𝑠−𝑃𝐶𝑂2,𝑜𝑝𝑒𝑟𝑎𝑡𝑖𝑜𝑛)

𝑃𝑡𝑜𝑡𝑎𝑙∙ 𝑄𝑔𝑎𝑠 ∙

𝑚𝑜𝑙

22.4𝐿 ∙𝑚𝑖𝑛

60𝑠∙

1

38.52𝑐𝑚2 (E-2)

Flux can then be calculated using the gas-liquid contact area of the WWC, which

is about 38.52 cm2; and the total gas flow rate Qgas (L/min).

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Figure E-1: Overall flow diagram of the wetted wall column system

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Figure E-2: Detailed section diagram. Section A: Solvent Reservoir

Figure E-3: Detailed section diagram. Section B: Inlet gas

498

Figure E-4: Detailed section diagram. Section C: Outlet gas

Figure E-5: Detailed section diagram. Section D: Saturator

E.1.5 System equipment details

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CO2 analyzers

Two CO2 analyzers are used in typical CO2 absorption experiments. Each

analyzer measures different concentration ranges: 0-1 vol% (top), and 0 – 20 vol%

(bottom). The accuracy of the analyzer depends on the flow rate of the sample gas.

The optimum flow rate is about 0.5 L/min, and it is monitored by the small flow meter on

the front of the analyzers. The gas flow rate of typical WWC experiments are much

higher than 0.5 L/min, so only part of the gas exiting the WWC chamber is sent to the

analyzers by adjust V-G08 (Figure E-4). Also, at the beginning of each experiment day,

it is important to flush the analyzer with N2 gas for sufficient amount of time (until the

analyzer reading is very close to zero and stable). The analyzers are sensitive to

moisture in the sample gas, and will be damaged. Therefore, it is important to regularly

upkeep the water knockout and desiccant column to dry the sample gas (Figure E-4).

Calibration

The analyzers should be calibrated every 6 months or more frequently. To

calibrate, first send a zero gas through the analyzers until reading is stable, then set the

zero reading by pressing the zero button on the analyzer screen. Then a span gas is sent

with CO2 concentration in the range of 80-95 % of the analyzer. To set the span

condition, the absolute concentration of the span gas is entered by first press the span

button then adjusting the reading values. To prepare the span gas for the 0-20 vol%

analyzer (bottom), newly calibrated MFCs are used to mix N2 and CO2 gas in order to

obtain high confidence in the CO2 concentration of the span gas.

MFC

Four mass flow controllers are used for typical CO2 absorption experiments to

generate different CO2 concentrations in the gas phase. The controllers are operated

using a control box, and is connected to the MFCs by electronic cables. The MFCs

500

require a positive pressure drop between its gas entrance and exit (20 psi), so the

pressures of the gas tanks need to be higher than the WWC. Typically MFC for N2 gas

is always connected to the gas line and the control box. For CO2 gas, three MFCs with

different flow rate ranges are switched during each experiment.

Calibration

The MFC should be calibrated every six months or more frequently. The bubble

column method is used to measure the absolute gas flow rate through the analyzers at

different settings across its range. The performance of the MFCs is specific to the gas

type. Therefore, it is important to use the corresponding gas as the calibration gas to

obtain the best results.

Temperature baths (HX-01, HX-02)

Two heated oil baths are used for temperature control in the WWC system. HX-

01 only controls the temperature of the water saturator. HX-02 controls the temperature

of the WWC reactor chamber, and also the gas and liquid lines. The settings of the oil

baths must allow proper temperature driving force for heat exchange into or out of the

system. For HX-01, its setting is typically 2-10 ˚C lower than HX-02. This is to avoid

over saturation of the gas line, which will result in excess water entering the liquid

solvent. Typical approximate settings of the oil baths are show in the bottom table, the

exact setting will vary slightly depending on the experiment day.

Experiment (˚C) HX-02 (˚C)

G-L lines

HX -01 (˚C)

Saturator

20 18 off

40 45 43

60 69 66

80 92 90

100 115 110

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E.2 TOTAL PRESSURE APPARATUS SOP

This procedure is developed to measure CO2 VLE in amine/water solutions at

high temperatures. The part numbers (#) mentioned in the procedure refers to the

Figures in the following section.

The personal protection equipment for the operator include: safety goggles, lab

coat, gloves, closed toed shoes.

E.2.1 Start up

Sample Preparation

Approximately 500 mL of CO2 loaded amine/water solutions is prepared and stored

in a sample jar.

Add approximately 350 mL of the prepared sample into the reactor body (#1), until

the liquid level reaches the top horizontal metal bar inside the reactor.

o Note: Measure and record the mass of the sample added into the reactor (by

measuring the mass of the sample jar before and after the sample addition).

Collect approximately 20 mL of the remaining sample into a 40 mL sample vial for

future analysis.

Autoclave setup

Place the reactor body (#1) containing the sample on the lab jack (#37).

Position the opening of the reactor body (#1) directly under the agitation

impeller (#19).

502

Slowly raise the reactor body by turning the knob of the lab jack (#37)

clockwise. Make sure the reactor does not hit the impeller, the

thermowell (#15), or the baffle bar (#16) in the process.

As the mouth of the reactor sits into the cover weldment (#2), it will

require additional force to keep raising the lab jack. This is the result of

the resistance provided by the O-ring (#17), which is acting part that seals

the autoclave. To properly seal the autoclave, periodically turn the

reactor horizontally back and forth as the reactor is being raised. Keep

turning the knob on the lab jack until the top of the reactor body meets the

cover weldment (at this point the knob will become very difficult to turn).

The sleeve of the spring on the reactor body (#1) should be perpendicular

to the edge of the cover top.

Insert the spring (#22) into the spring sleeve on the reactor body (#1), and

lock the spring in place using the safety lock (#14).

Mechanical hazard: If the safety lock is misplaced, the spring will be pushed

out of the sleeve in projectile motion as the autoclave is pressurized.

Hazard control:

o Push, pull, and turn on the handle of the spring (#11) to ensure the spring

is locked in place.

o Do not increase the temperature of the autoclave without double checking

the safety lock.

N2 flushing

The lettering in this section refers to the openings on the cover weldment (#2), as

drawn in Figure E-7.

503

Close the valves at opening C and E.

Open the valve at opening A (this valve serves as the exit during the

flushing process).

Connect the N2 gas line to the closed valve at opening E (this valve serves

as the N2 inlet).

Note: It is critical to flush the reactor head space at a very slow rate. This is

to prevent entrainment of the liquid sample, and to minimize stripping of loaded CO2 in

the sample.

To ensure N2 is flushed slowly, first turn on the N2 gas with the valve at

opening E remaining closed. Then slowly open the valve at E until a

light pressure can be felt at opening A. Leave the valve at E partially

opened for approximately 1-2 minutes.

Close valve E, followed immediately by closing valve A.

Turn off the N2 gas, and disconnect the N2 gas line from valve E.

Final check of autoclave prior to increasing the reactor temperature

Ensure all three valves (A, C, and E) on the cover weldment (#2) are

closed. Cap all three openings with Swagelok caps.

Check the safety lock (#14) of the spring again to ensure it is locking the

spring (#22) in place.

E.2.2 Measure initial condition

Use the LabView® SignalExpress® data logger to record the pressure of the

autoclave at room temperature for approximately 2-3 minutes at 1 second intervals. At

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the end of the recording period, stop the data logger, and copy the data file into

MicrosoftExcel®. Record the initial temperature of the autoclave.

E.2.3 CO2 total pressure measurements

Heating jacket: Place the heating jacket around the autoclave. Lock the

jacket using the two buckle locks.

Burn hazard: the apparatus body is at elevated temperatures during

operation and can cause burns if the operator touches it without proper protection.

Hazard control: Do not attempt to remove the heating jacket until the reactor is

sufficiently cooled. Use leather cloves if necessary to touch the apparatus body.

Turn on the temperature controller, set the target temperature to the

desired experimental condition

Agitator: Turn on the agitator using the air motor pressure gauge. The

desired pressure drop is between 60 and 65 psig.

Data collection: Use LabView® SignalExpress® data logger to record the

pressure of the autoclave at 10s intervals.

Monitoring equilibrium: When the temperature of the autoclave stabilizes

at the target temperature, begin monitoring the pressure of the autoclave at

5-10 minute intervals. Note the time at which the pressure of the reactor

reaches a stable range of approximately ±0.2 bar. Continue recording for

another 10-15 minutes, which ensures the reactor is at equilibrium.

Note: For typical CO2 VLE measurements, at each CO2 loading the total

pressure of the autoclave is measured at seven temperatures. The temperatures are

measured in the following sequence: 100, 120, 140, 160, 150, 130, 110 °C.

505

At the end of the measurement, stop the data logger and copy the recorded

data file into MicrosoftExcel®.

E.2.4 Unexpected shutdown

In case the reactor begins to leak, immediately shut off the temperature jacket and

allow the system to cool down to room temperature before disassembling and cleaning up

(step 7 and 8).

E.2.5 Cool down

Turn off the heating jacket. Wait until the reactor temperature is lowered

to room temperature. This step typically takes up to 10 hours

(overnight).

Burn hazard: the apparatus body is at elevated temperatures during

operation and can cause burns if the operator touches it without proper protection.

Hazard control: Do not attempt to remove the heating jacket until the reactor is

sufficiently cooled. Use leather cloves if necessary to touch the apparatus body.

Remove heating jacket (only after reactor is cooled).

Turn off agitation using the pressure gauge at the air motor.

E.2.6 Measure final condition

Use the LabView® SignalExpress® data logger to record the pressure of the

autoclave at room temperature for approximately 2-3 minutes at 1 second intervals. At

the end of the recording period, stop the data logger, and copy the data file into

MicrosoftExcel®. Record the final temperature of the autoclave.

506

E.2.7 Disassemble

Remove the cap at valve A, then open valve A to release any residual

pressure in the autoclave.

Unlock the safety lock (#14) and remove the spring (#22) from the

autoclave.

Pressure hazard: residual pressure in the autoclave can eject the spring if it

is not properly released prior to disassembling the reactor.

Hazard control: valve A must be open prior to the removal of the spring.

Lower the autoclave by turning the lab jack (#37) counter clockwise.

Turn the autoclave horizontally to loosen it from the over weldment (The

autoclave is likely to stay attached to the cover due to the resistance

provided by the O-ring).

Collect approximately 20-30mL of the amine sample from the autoclave

into a 40 mL sample vial.

E.2.8 Clean up

Dispose the remaining samples from the autoclave into an EHS specified

waste container.

Wash the autoclave twice with water, and a third time with de-ionized

water.

Thoroughly dry the autoclave with paper towels and compressed air.

Washing the agitator

507

Fill a 1 liter glass beaker with water and position it on the lab jack

(#17) in position of the autoclave. Raise the glass beaker until as

much of the agitator is emerged as possible without the hitting the

bottom of the glass beaker.

Turn on the agitator with the compressed air pressure regulators

(set the regulator to approximately 60-65 psig). Keep the agitator

on for 2-3 minutes, then turn off the agitator.

Hazard: the agitator could hit and break the glass beaker and the broken

glass could cut the operator

Hazard control:

o Make sure the bottom of the agitator does not touch the bottom and the

edge of the glass beaker BEFORE turning on the agitator

o Use the windows of the hood as a shield between the operator and the

apparatus

o Consider upgrading to a plastic container to replace the glass beaker

Connect air gas line to valve E, turn on air inlet to flush valve E and the

connected sparge line for about 1 minute. Turn off air inlet and

disconnect the air gas line from valve E.

Connect air gas line to valve D, turn on air inlet to flush valve E and the

connected sparge line for about 1 minute. Turn off air inlet and

disconnect the air gas line from valve D.

Repeat steps i-iv two more times. The 2nd time with water, the 3rd time

with de-ionized water. Rinse the glass beaker in between each time

508

With the glass beaker still on the lab jack and directly under the agitator.

Use a squirt water bottle to wash the top of the cover (not emerged in the

glass beaker). Lower and remove the glass beaker.

Remove the O-ring (#17), and wash with water. Replace the washed O-

ring back on the cover weldment.

Dry the agitator using a paper towel.

Turn on the agitator to spin out the remaining water. Clean up the water

around the apparatus.

Note: Use the glass window of the hood as a shield, as the remaining water on the

agitator will be splashed around the apparatus.

E.2.9 Hazardous waste disposal

All chemical waste generated should be disposed following the instruction of

University of Texas at Austin Department of Environmental Health & Safety:

http://www.utexas.edu/safety/ehs/disposal/

E.2.10 Safety hazards and precautions

High pressure operation

a) The ZipperClave apparatus contains a built in pressure release, which will

fail first in case the reactor pressure exceeds the limit of the design.

b) The spring seal (#22) of the autoclave is a potential hazard when the

autoclave is pressurized. The spring can potentially slide out of position as result of

pressure built up in the autoclave and hit the experimentalist. To prevent this, it is to be

ensured that the spring is properly set up and held in place using the safety lock (#14).

i. Prior to heating of autoclave, the set up of the spring and safety

lock is to be examined to ensure it is properly set up.

509

ii. At the end of the experiment, the venting valve (A) should be

opened to release any residue pressure in the autoclave before attempting to

disassemble the spring and safety lock.

High temperature operation

a) The temperature of the autoclave is set and controlled using an electrical

heating jacket attached to a temperature probe. This is a potential hazard in case the

probe fails, or if the controller fails. If the temperature controller fails, the jacket will

potentially keep heating the autoclave past the set point of the experiment. As the

result, the temperature of the autoclave can exceed the tolerance of the body parts (such

as the O-rings).

i. A secondary temperature probe is to be added to the apparatus to

provide an alternative reading of the reactor temperature. This secondary probe

can be used as an indicator in case the primary probe fails.

ii. The pressure of the autoclave is to be monitored continuously

(every 5-10 minutes) for increase in autoclave temperature past the experimental

set point. The heating jacket is to be turned off completely in case the controller

has failed.

b) The heating jacket is a potential hazard at high temperatures. The

experimentalist should not touch the heating jacket without proper heat-proof gloves.

At the end of the experiment, the heating jacket should not be removed while it is still at

high temperatures. In case when removing the heating jacket is necessary, use proper

gloves.

510

c) At high temperatures, the entire body part of the autoclave and the cover

weldment are safety hazards. Do not touch the autoclave and the cover weldment

before the system is completely cooled (or wear proper gloves).

Mechanical agitation

The agitator is a potential hazard during the clean up step as it can break the glass

beaker used to clean the agitator. To prevent potential damage, ensure the agitator does

not touch the glass beaker prior to turning on the agitator. Also, using plastic bottles as

an alternative cleaning vessel is being considered.

511

E.2.11 Detailed apparatus drawings

Figure E-6: Detailed drawing of the ZipperClave set up (sideview)

512

Figure E-7: Detailed drawing of the ZipperClave set up (top view)

513

Figure E-8: ZipperClave part list part 1

Figure E-9: ZipperClave part list part 2

514

E.2.12 Maintenance

Two O-rings on the ZipperClave apparatus (#17 and # 35) need to be routinely

inspected and replaced. After each experiment, remove both O-ring for inspection.

Any visible signs of erosion (as result of corrosion) require replacement with new O-ring.

E.2.13 Training

New operators should trained by experienced operators. In case this is not an

option, the standard operating procedure should be used as a guide for operation.

515

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Vita

Le (Lynn) Li was born in Beijing, China to Qian Wang and Jun Li. She moved

with her mother to Tulsa, Oklahoma in 2000. In May 2005, she graduated from Jenks

High School in Oklahoma. She then entered Tulane University in New Orleans, LA, in

the fall of 2005. However, due to hurricane Katrina, which devastated the city of New

Orleans and Tulane, she studied at the University of Tulsa for the fall of 2005. She

returned to Tulane in the spring of 2006, and graduated in May 2009 with a B.S.E. degree

in chemical engineering and a minor in mathematics. In August 2009, she started her

graduate studies at the University of Texas at Austin, where she pursued a Ph.D. degree

in chemical engineering advised by Dr. Gary Rochelle.

She has accepted a full-time employment offer with Shell Global Solution, at the

Shell Technology Center in Houston, Texas.

Permanent email address: [email protected]

This dissertation was typed by the author.

Documents

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