6/29/11

1

CO2CapturebyAmineScrubbingBy

GaryT.Rochelle

LuminantCarbonManagementProgram

DepartmentofChemicalEngineering

TheUniversityofTexasatAusJn

RECS

June9,2011

CentralMessages

•  AmineScrubbingisTHEtechnologyforCO2capturefromCoalPowerplants

•  EnergyconsumpJonbyaminesisapproaching20%oftheplantoutput,apracJcallowerlimit.

•  SolventdegradaJon&contaminaJonwillprobablylimitthechemicalcosttolessthan$5/lb.

6/29/11

2

IbelievethatCO2willberegulated

becauseourscienJstshaveshownthatsignificantglobalwarmingisresulJngfromconJnuingemissionsofCO2

CoalCombusJonisanimportantcontrollablesourceofCO2emissions.

CarbonCapture&Storage(CCS)isanimportantopJonforexisJngcoal‐firedpowerplants

SourcesofGlobalWarming(IPCC,2007)

‐1 ‐0.5 0 0.5 1 1.5 2

Netanthropogenic

CO2

CH4,etc

directaerosols

cloudaerosols

solar

Radia%veForcing(W/m2)

6/29/11

3

ModelswithonlynaturalforcingsModelswithbothnatural&anthropogenicforcings

40%ofUSCO2emissionsareFromElectricityGeneraJon

78%

6/29/11

4

6/29/11

5

6/29/11

6

Other Solutions for Coal •  Oxy-Combustion

– O2 plant & compression require more energy – Gas recycle, boiler modification for high CO2 – Gas cleanup, compression including air leaks

•  Coal Gasification / Combined Cycle – O2 plant, complex gasifier, cleanup, CO2 removal – Not ready for deployment – Relatively more expensive on PRB or lignite – New plants only

•  Neither is Tail end: More suitable for new plants – Require higher development cost, time, and risk – Not suitable for on/off to address peaking

6/29/11

7

HistoryRepeatsCaCO3Slurry:::AmineScrubbing

CaCO3 Event Amine 1936 1st commercial plant 1980

1958 Too commercial for Gov. support “Nearly Insurmountable” issues

1991

1960-75 Government funds advanced alts 1990-

1970-85 Govern. & EPRI fund test facilities 2010-

1968 60-250 MW prototypes 2015

1977 500+ MW deployed per regulations First choice dominates

2020

MessagesonEnergy•  ReversibilityisKing•  GreaterCapacityreducesSensibleQ•  SaturaJonStrippingismorereversible

•  FasterSolventsEnhanceReversibility•  GreaterHeatofAbsorpJonReducesEnergy•  GreaterStrippingTismorereversible•  EnhancedStrippingismorereversible

•  Energyisapproaching50%oftheoreJcal,apracJcallimit

6/29/11

8

Carbonate & Tertiary/Hindered Amines

HO-CH2-CH2-N-CH2-CH2-OH ↔ MDEAH+ + HCO- ׀ 3

CH3 60 kJ/gmol, slow Methyldiethanolamine (MDEA)

CH3 ׀ ׀ HO-CH2-CH2-NH2 + CO2 ↔ AMPH+ + HCO-

׀ 3 CH3 60 kJ/gmol, slow 2-Aminomethylpropanolamine (AMP, KS-1(?))

CO3= + CO2 + H2O ↔ 2 HCO-

3 20 kJ/gmol Carbonate Bicarbonate very slow

+ CO2 ↔ +HPZ-COO-

Piperazine (PZ)

Primary and Secondary Amines 60-85 kJ/gmol, fast

CH2-CH2

HN NH CH2-CH2

2 HO-CH2-CH2-NH2 + CO2 ↔ HO-CH2-CH2-NH-COO- + MEAH+

Monoethanolamine (MEA) MEA Carbamate (MEACOO-)

2 NH3 + CO2 ↔ NH2-COO- + NH4+

Ammonia

6/29/11

9

6/29/11

10

6/29/11

11

Sensibleheatloss–25kwh/tonne•  Q=CpΔT/capacity

=3.5J/mol‐K*5K/(0.88moles/kg)

=20kJ/moleCO2,Steamat155oC

Mass transfer coefficients

Bulk gas

Bulk liquid

Gas film Liquid film

22 4/19/2011

KG

CO2 flux = k (∆ CO2)

PCO2, b PCO2, i

[CO2]i

[CO2]b (=PCO2*)

∙(PCO2,b – PCO2*) CO2 flux =

CO2 flux = kg (PCO2,b- PCO2,i) = kl ([CO2]i – [CO2]b) = kg’ (PCO2,i – PCO2*)

Gas-Liquid Interface

Henry’s Law: PCO2i= He * [CO2]i

6/29/11

12

Gas Film Reaction Film Diffusion Film

Bulk Gas Bulk Liquid

PCO2,b PCO2,i

G-L Interface

[CO2]i

[CO2]b

(PCO2*)

fast chemical rxn

23 4/19/2011

Pseudo 1st order kinetics

CO2 removal = area∙KG(∆PCO2)≈f(area,kg’) Packing Solvent

EsJmateareafromk’g•  Lnmeank’gΔP=2.4e‐3mol/s‐m2

–  Lean:2.2e‐6*(0.012–0.005)*105–  Rich:5e‐7*(0.12‐0.05)*105

•  Absorberpackingvolume–  1.9e3m3for800MW,250M2/M3

•  0.9tonneCO2/MW‐hr–  25X25X13.5m–  1.5m/sgasvelocity

•  Exergylost/moleCO2–  RTln(0.12/0.05)=14kwh/tonneCO2

6/29/11

13

6/29/11

14

GreaterTstrip&ΔHCO2reduceWeq

MEA120°C

PZ

Singlestageflashat90‐150°CCompressionto150barLeanPCO2=0.5kPaat40°C

90°C 150°C

6/29/11

15

6/29/11

16

6/29/11

17

6/29/11

18

0

2

4

6

8

10

0 0.2 0.4 0.6 0.8 1 1.2

k g' av

g (x

107

mol

/pa∙

s∙m

2 )

CO2 Capacity (mol CO2/kg solvent) 4/19/2011 35

Amino Acids

SarK

PZ Derivatives

Primary Amine

MEA

EDA Hindered Amines

2-PE

5/5 MDEA/PZ

PZ based solvents

PZ

2MPZ

Two-dimension comparison of solvents

FastSolvents

Amine (m)Capacity -∆Habs

@PCO2 =1.5kPa kg,

’avg x1e-7

@40 °C

DegT(oC)k1=3e‐6s

mol/kg solv kJ/mol mol/s·Pa·m2 3e‐9s‐1

PZ 8 0.79 70 8.5 163

1-MPZ 8 0.83 67 8.4 148

MDEA/PZ 5/5 0.99 70 8.3 138

2-MPZ/PZ 4/4 0.84 70 7.1 155

MDEA/PZ 7/2 0.80 68 6.9 138

2-MPZ 8 0.93 72 5.9 151

HEP 7.7 0.68 69 5.3 130

MEA 7 0.47 82 4.3 120

6/29/11

19

SlowSolvents

Amine (m)Capacity -∆Habs

@PCO2 =1.5kPa kg,

’avg x1e-7

@40 °C

DegTk1=3e‐9s‐1

mol/kg solv kJ/mol mol/s·Pa·m2 oC

PZ 8 0.79 70 8.5 163

MEA 7 0.47 82 4.3 120

DGA® 10 0.38 81 3.6 132

AEP 6 0.66 72 3.5 121

2-PE 8 1.23 73 3.5 120

MAPA 8 0.42 84 3.1 114

AMP 4.8 0.96 73 2.4 137

MessagesonSolventManagement•  ThermalDegradaJon

–  LimitsmaxStripperT–  TMEA<TMDEA<TAMP<TPZ

•  FreeRadicalAutooxidaJon–  Iffast,inabsorber::ifslow,inheatexchanger– Alkanolamine>terJary>Hindered>cyclic(PZ)–  CatalyzebyFe+2,Cu+2,Mn+2

–  Inhibitbyperoxide/radicalscavengers,terJaryamine

•  VolaJlityofaminesanddegradaJonproducts– Absorberwaterwashmaywork–  Reducedbyhydrophilicgroups&speciaJon– NitrosaminesfromNO2/NO2

‐+secondaryamine–  ReclaimingrequiredforcoalimpuriJes

6/29/11

20

5MechanismsforThermalDegradaJon

•  1.CarbamatePolymerizaJon‐MEA•  2.CyclicUrea‐Ethylenediamine

•  3.ArmSwitching/EliminaJon‐TerJaryAmine

•  4.SN2RingOpening–Piperazine•  5.BlendSynergism–Piperazine/MEA

6/29/11

21

O2solubility&MassTransfer

0.E+0

2.E‐5

4.E‐5

6.E‐5

2.E‐04 2.E‐03 2.E‐02

AmineOxida

%on

(mol/m

olCO2)

OxygenRateConstant(s‐1)

Total

Absorber

ExchangerSump

PZ

MEAMDEA

6/29/11

22

VolaJlityIssues

•  AminevolaJlity–  InH2O–  InloadedsoluJon– AsamethylateddegradaJonproduct,e.g.1.4dimethylpiperazine,methylamine

•  OxidaJonproducts– HEI–  Formamide– Ammonia– NitrosaminefromsecamineandNO2/NO2

‐

Amine Volatility (Pa) at 40 oC Amine Ldg = 0 Ldg: PCO2=500 Pa

@ 40oC

5m MDEA/5m PZ 0.17/3.43 0.16/0.51

7m MDEA/2m PZ 0.56/0.91 0.42/0.21

8m PZ (8.8) 0.78

12m EDA 87 1

7m MEA 10 2.7

5m AMP 14.2 11.2

6/29/11

23

Conclusions

•  AmineScrubbingcanbeDeployedby2019•  ImprovedAmineSolventsandProcesses

– ReduceEnergyfrom400%to200%ofMinimumW– ProvideStable,BenignSolvents– SimplifysystemstoreducecapitalCost

•  AsLimestoneSlurryRulesFGDauer30yrs;AmineScrubbingwilldominateCO2capture.

•  OthertechnologiesareunlikelytocompeteforPost‐combusJoncapture.