Modeling Entrained Flow Gasifiers

Mike BockelieMartin Denison, Dave Swensen, Connie Senior, Adel Sarofim

Reaction Engineering International

2010 Workshop on Multiphase Flow ScienceMay 4-6, 2010, Pittsburgh, PA USA

2

Acknowledgement“This material is based upon work supported by the Department of Energy under

award number DE-FC26-00FNT41047 and DE-FC26-05NT42444”

Vision 21 Program“Computational Workbench Environment for Virtual Power Plant Simulation”DOE NETL (COR=John Wimer, Bill Rogers, DE-FC26-00FNT41047)

Clean Coal R+D Project“A Virtual Engineering Framework for Simulating Advanced Power Systems”DOE NETL (COR=Ron Breault, DE-FC26-05NT42444 )

"This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof.“

3

Advanced Power Systems

[J. Phillips, “IGCC 101”, GTC 2009] http://www.gasification.org/library/overview.aspx

Why Use Modeling?

Cost effective approach for evaluating performance, operational impacts & emissions

Improve understanding

Estimate performance

Assist with conceptual design

Identify operational problems

Cheaper than testing

More detailed information than testing

Helps engineers make better, more informed decisions

4

5

Entrained Flow Gasifier Model• Model Development

– CFD + Process models• Allows modification of

– Process conditions, burner characteristics– Fuel type, slurry composition– gross geometry

• Generic Configurations: – downflow / upflow– 1 stage / 2 stage – based on public information

• Define Parameters with DOE– Improved physical models

• pressure effects on radiation heat transfer • reaction kinetics

– high pressure, gasification w / inhibition • slag, ash (vaporization), tar, soot

• Collaboration– N. Holt (EPRI)– T.Wall,.. (Black Coal CCSD, Australia) – K.Hein (IVD, U. of Stuttgart)

[Clearwater 2001-2008], [PCC 2002-2009],

Axial Gas Velocity, m/sAxial Gas

Particle Char Fraction

1 stage

H2H2H2

2 stage

Glacier Software

• Glacier is REI’s in-house, CFD-based combustion simulation software

• Over 30 years of development• Over 15 years of industrial application• Designed to handle “real-world” applications

– Judicious choice of sub-models & numerics– Qualified modelers

6

Modeling Coal Combustion

• Computer model represents– Furnace geometry – Operating conditions– Combustion processes– Pollutant formation

• Accuracy depends on– Input accuracy– Numerics– Representation of physics

& chemistry

Turbulence

Radiation &Convection

Surface Properties

Particle Deposition

Combustion Chemistry

Coal-firedCombustion

Finite-rateChemistry

Particle Reactions

7

Flowing Slag Model• Model accounts for:

– Wall refractory properties– Back side cooling– Fire side flow field + heat transfer– Particle deposition on wall

• Local Deposition Rate• Fuel ash properties• Composition (ash, carbon)• Burning on wall

• Slag model computes– Slag viscosity

• Tcv = critical viscosity• ash composition

– Slag surface temperature– Liquid & frozen slag layer thickness– Heat transfer through wall

Based on work by [Benyon], [CCSD], [Senior], [Seggiani]

[Dogan et al, GTC2002]

For model details see - Pittsburgh Coal Conference 2002

8

9

Gasifier Slag Viscosity ModelDerived for a range of coal ashesCurve fit as a function of SiO2, TiO2, Al2O3, Fe2O3, CaO, FeO, MgO, Na2O, K2O and temperature.References:Kalmanovitch , D.P. And Frank, M., “An Effective Model of Viscosity of Ash Deposition Phenomena,” in Proceedings of the Engineering Foundation Conference on Mineral Matter and Ash Deposition from Coal, ed., Bryers, R.W. And Vorres, K.S.,Feb. 22-26, 1988.Urbain, G., Cambier, F., Deletter, M., and Anseau, M.R., Trans. J. Gr. Ceram. Soc., Vol. 80, p. 139, 1981.

10

Viscosity Model

Gasifier slag data from Mills, K.C., and Rhine, J.M., “The measurement and estimation of the physical properties of slags formed during coal gasification 1. Properties relevant to fluid flow.,” Fuel vol. 68, pp. 193-198, 1989.

0.1

1

10

100

1550 1600 1650 1700 1750 1800 1850

Temperature (K)

Visc

osity

(Pa

s)

Slag A measuredSlag A modelSlag B measuredSlag B modelSlag F measuredSlag F modelSlag G measuredSlag G modelSlag K measuredSlag K model

Flowing Slag Model

0

1

2

3

4

5

6

7

8

1400 1700 2000 2300 2600

Slag surface temperature, K

Gas

ifier

heig

ht, m

0

1

2

3

4

5

6

7

8

0 0.005 0.01 0.015 0.02

Liquid slag thickness, m

0

1

2

3

4

5

6

7

8

0 0.02 0.04 0.06 0.08

Solid slag thickness, m

Seggiani

Benyon

REI

Test case: - 1 stage, upflow Prenflo Gasifier

at Puertollano, Spain IGCC plant- 2600 tpd, dry feed, opposed fired- water jacket to cool refractory

Slag SurfaceTemperature

Liquid SlagThickness

Solid Slag Thickness

Gas temperature, K

CO 11

12

Carbon Conversion• Carbon Conversion vs Time in PFR• Contributions of Volatile Release and Gasification Rxns [Roberts, Tinney, & Harris, CCSD, 2005] symbols refer to different coals

[Bockelie et al, 2002]

13

Effect of CO Inhibition on Carbon Gasification Rate• [Roberts, Tinney, & Harris, CCSD, 2005]• symbols refer to different coals

CO reduces gasification rate

increase CO conc.

decrease relative gasification rate

14

Gasification Kinetics – with inhibition• CO, CO2, H2, H2O

0.01

0.1

1

1.0E-03 1.0E-01 1.0E+01

PCO/PCO2

rs/rs

(PC

O=0

)

0.0010.0100.0200.0400.0800.1000.1500.200

PCO2, atm

1600K, 60 atm

DrySlurry

[van Heek & Muhlen, 1991]

222

22

6543

21

1)/1(

HOHCOCO

OHCOs PkPkPkPk

PkPksr

++++

+=

−⋅=

RTEkk i

ii exp0

15

Gasification Kinetics – CO effects

0

1

2

3

4

5

6

0 1 2 3Time, s

Gas

ifica

tion

Rat

e, g

/g/s

0

0.1

0.2

0.3

0.4

0.5

CO

mol

e fra

ctio

n

H2O gasification

CO2 gasification

CO

0

1

2

3

4

5

6

0 1 2 3Time, s

Gas

ifica

tion

Rat

e, g

/g/s

0

0.1

0.2

0.3

0.4

0.5

CO

mol

e fra

ctio

n

H2O gasification

CO2 gasification

COSlurry feed SR=0.52 70 atm.

012345678

0 2 4 6 8Time, s

Gas

ifica

tion

Rat

e, g

/g/s

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

CO

mol

e fra

ctio

n

H2O gasificationCO2 gasification

Dry feedSR = 0.4870 atm.

Presence of CO reduces gasification rate

Gasification rate for H2O is greater than for CO2

16

Humphrey Pittsburg #8

93

94

95

96

97

98

99

0 10 20 30 40 50Liner Life (Months)

Carb

on C

onve

rsio

n (%

Per

Pas

s)

Startup Liner

Commercial Liner

Reduce carbon conversion increase refractory liner Life (Tampa Electric Polk Plant)

[TECO, July 2000]

Gasifier Issues

17

70

75

80

85

90

95

100

0 1 2 3 4

Residence time, s

Carb

on C

onve

rsio

n, %

1531 K, SR = 0.451707 K, SR = 0.521797 K, SR = 0.57

Effect of Temp. on Carbon Conversion• Increase gasifier volume (residence time) small benefit• Increase temperature increase carbon conversion

BUT can reduce refractory life

(2300F)(2610F)(2775F)

70 atm.

Carbon Conversion vs. Residence Time

Increase StoichiometricRatio

= dry feed, SR = 0.482079K (3200F)

Tar & Soot Model

• Semiempirical model*– Coal-derived soot is assumed to form from only tar.– Tar yields is calculated by CPD model† based on

measured coal characteristics.– Three equations for conservation of the mass of soot

and tar, and the number of soot particles.

* Brown, A.L.; Fletcher, T.H. Energy Fuels 1998, 12, 745-757.† Fletcher, T.H.; Kerstein, A. R.; Pugmire, R. J.; Solum, M. S.; Grant, D. M. Energy Fuels 1992, 6, 414-431.

18

19

Assumed Soot Formation Mechanism

Coal Tar

Light Gas

Char

Soot AgglomeratesPrimary Soot

Light GasDevolatilization

Formation

Gasification

Agglomeration

Brown, A.L.; Fletcher, T.H. Energy Fuels 1998, 12, 745-757.

CPD Soot Model

Motivation:1. Coal-derived soot undergoes different mechanism than

gaseous fuel (limited acetylene involvement)2. The sum of soot and tar is relatively constant during

pyrolysis.

20

Soot Model Evaluation

0.8 0.9 1.0 1.1

Burner Stoichiometric Ratio

130

140

150

160

170

180

190

200

210

220

230

240

NO

x, p

pm

0.0E+000

5.0E-008

1.0E-007

1.5E-007

2.0E-007

2.5E-007

3.0E-007

3.5E-007

4.0E-007

4.5E-007

Soot

Vol

ume

Frac

tion

100 150 200 250Exit NOx, ppm

0.0E+000

5.0E-008

1.0E-007

1.5E-007

2.0E-007

2.5E-007

3.0E-007

3.5E-007

4.0E-007

4.5E-007

5.0E-007

Soot

Vol

ume

Frac

tion

MeasurementsGLACIER

Mineral Matter Transformation Pathways

1) Fly ash (residual solid)2) Organometallics (solid + vapor)3) Vapor (fume) created by reduction of stable condensed metal oxide (SiO2, MgO,

CaO, Al2O3, FeO) to more volatile suboxides (SiO, Al2O) or metals (Mg, Ca, Fe)

21 )()( COvMOCOcMO nn +⇔+ −

21

[Lee, 2000]

2 Stage Gasifier – Vaporization Along Representative Particle Trajectories

25 to 60 micron

22

Ash Vaporization SummaryMass Fraction of Inlet Ash Vaporized

(relative to initial total ash mass)

23

0.00E+00

5.00E-03

1.00E-02

1.50E-02

2.00E-02

2.50E-02

3.00E-02

SiO2 Al2O3 FeO CaO MgO Total

Slurry Feed

Dry Feed

Syngas Cooler Fouling24

• REI fouling model mechanistic model that includes impacts of

– ash properties (individual particle composition, particle size, temperature, density, viscosity, surface tension),

– included/excluded minerals (e.g., pyrite),– local conditions (gas composition, temperature, heat

flux to surfaces)– properties of deposits (composition, temperature,

density, viscosity, surface tension (if wet)). – refine model to account for data from NETL gasification

studies [Gibson, 2009] • Model predicts

– properties of particles exiting furnace in-flight, – deposition rate (growth rate) – properties of sintered deposits on walls, – impacts of fouling on gas phase properties, overall heat

transfer, etc. – emissions of Ca, Mg, Fe, SiO from ash that react in the

gas phase to produce submicron aerosols (e.g., FeS ) observed by Brooker [1993, 1995] which forms part of the glue for the sticking

• Model builds on work of many investigators– [Walsh et al., 1990, 1992], [Wall et al., 1979, 1993],

[Gallagher et al., 1990, 1996], [Senior and Srinivaschar, 1995], [Wang et al., 1997, 1999], [Quann and Sarofim, 1982]

1.0

0.0

Deposition Rate

(lb/hr-ft)

Figure 4. Predicted deposition rate on rear wall of 800 MWe coal fired boiler.

Hot Gas

Gas Flow

Particulate Deposit

Highly sintered Deposit

Steam/ water

Heat Transfer

Q conv + Q inc

Q ref + Q emi

Q cond

T surf T steam

Figure 2. Schematic of REI Fouling Model.

Figure 1. Example of plugged CSC inlet tubesheet [Polk, 2002].

Gasifier - CFD Model - transient

RECOM Services / IVD Gas Temperature

25

Challenges for IGCC / Gasification26

http://tonto.eia.doe.gov/oog/info/ngw/ngupdate.asp

Coal-fired gasification power plant cost rises by $530 million16 April 2010 – Duke Energy Indiana told regulators the cost of its 618 MW Edwardsport coal gasification plant under construction in southwest Indiana will rise from $2.35 billion (or $3,800/kW) to $2.88 billion (or $4,660/kW).[http://www.duke-energy.com/indiana.asp]