Aspen RateSep Absorber Model for Aspen RateSep Absorber Model for COCO22 Capture Capture CASTOR Pilot PlantCASTOR Pilot Plant

IFP – Lyon, FranceIFP – Lyon, France

by: Ross Dugasby: Ross Dugas

January 11, 2008January 11, 2008

(ross@che.utexas.edu)(ross@che.utexas.edu)

Scope of the PresentationScope of the Presentation

• ObjectiveObjective• IntroductionIntroduction• Data Improvements in AspenData Improvements in Aspen

• DensityDensity• ViscosityViscosity• Thermodynamics – Heat of Formation, Heat CapacityThermodynamics – Heat of Formation, Heat Capacity• KineticsKinetics

• Model ParametersModel Parameters• kkgg, k, kLL, liquid holdup, film discretization, etc., liquid holdup, film discretization, etc.

• ResultsResults• ConclusionsConclusions

ObjectiveObjective

• Create an Aspen RateSep model to Create an Aspen RateSep model to simulate absorber pilot plant data from simulate absorber pilot plant data from the CASTOR projectthe CASTOR project• COCO22 profiles, Temp profiles profiles, Temp profiles

• The absorber model will aid in the The absorber model will aid in the evaluation and optimization of operating evaluation and optimization of operating conditionsconditions• liquid rate, lean loading, gas temperature, liquid rate, lean loading, gas temperature,

packing heightpacking height, packing type, etc., packing type, etc.

IntroductionIntroduction• CASTOR ProjectCASTOR Project

• 12 experimental runs12 experimental runs• 1.1 meter diameter absorber1.1 meter diameter absorber• Four 4.25 meter beds of IMTP-50 (17m Four 4.25 meter beds of IMTP-50 (17m

total)total)• MEA Concentration: 30 – 33 wt% (COMEA Concentration: 30 – 33 wt% (CO22-free -free

basis)basis)• Lean Loading: 0.16 - 0.28 mol/molLean Loading: 0.16 - 0.28 mol/mol• Lean Flow Rate: 13 – 24 mLean Flow Rate: 13 – 24 m33/m/m22hh• TTLEANLEAN = 40C T = 40C TFGFG ≈ 48C ≈ 48C

• yyCO2CO2 = 10 – 12% (Saturated basis) = 10 – 12% (Saturated basis)

• QQFGFG ≈ 5000 Nm ≈ 5000 Nm33/h/h

Data Improvements – Data Improvements – DensityDensity

• Aspen defaults incorrectly predicted Aspen defaults incorrectly predicted decreasing density with increasing decreasing density with increasing loadingloading

• Adjust Aspen parametersAdjust Aspen parameters• Weiland (1998), 30-35 wt%, 40-80C Weiland (1998), 30-35 wt%, 40-80C

correlationscorrelations• Parameters for MEA redefinedParameters for MEA redefined• MEAHMEAH++/MEACOO/MEACOO-- and MEAH and MEAH++/HCO/HCO33

-- defined defined

35wt% MEA

0.96

0.98

1.00

1.02

1.04

1.06

1.08

1.10

1.12

1.14

1.16

35 40 45 50 55 60 65 70 75 80 85

Temperature (C)

De

ns

ity

(g

/cm

3 )

0.0 Aspen 0.1 Aspen 0.2 Aspen 0.3 Aspen 0.4 Aspen 0.5 Aspen0.0 Weiland 0.1 Weiland 0.2 Weiland 0.3 Weiland 0.4 Weiland 0.5 Weiland

Data Improvements – Data Improvements – ViscosityViscosity

• Aspen defaults underestimated Aspen defaults underestimated viscosityviscosity

• Adjust Aspen parametersAdjust Aspen parameters• Weiland (1998), 30-35 wt%, 40-80C Weiland (1998), 30-35 wt%, 40-80C

correlationscorrelations• Parameters for MEA redefinedParameters for MEA redefined• MEAHMEAH++, MEACOO, MEACOO-- and HCO and HCO33

-- defined defined

35wt% MEA

0.5

1.0

1.5

2.0

2.5

3.0

3.5

35 40 45 50 55 60 65 70 75 80 85

Temperature (C)

Vis

cosi

ty (

cP)

0.0 ldg Aspen 0.0 ldg Weiland0.2 ldg Aspen 0.2 ldg Weiland0.3 ldg Aspen 0.3 ldg Weiland0.4 ldg Aspen 0.4 ldg Weiland0.5 ldg Aspen 0.5 ldg Weiland

Data Improvements –Data Improvements –Heat of FormationHeat of Formation

• Heat of absorption was inconsistent within Heat of absorption was inconsistent within AspenAspen• 5 reactions (Freguia (2002))5 reactions (Freguia (2002))• KKeqeq data - Van't Hoff equation data - Van't Hoff equation• Heat of formation data in AspenHeat of formation data in Aspen

• Heat of formation defined at 25CHeat of formation defined at 25C• updated: MEAHupdated: MEAH++, MEACOO, MEACOO--, HCO, HCO33

--, CO, CO33-2-2

R

H

Td

Kd abs

)/1(

lnreactfprodfabs HHH ,,

Data Improvements –Data Improvements –Heat CapacityHeat Capacity

• CCpp used to match ∆H used to match ∆Habsabs at higher at higher temperaturestemperatures• 40, 60, 80, 100, 120C40, 60, 80, 100, 120C

• CCpp of MEAH of MEAH++ and MEACOO and MEACOO-- set to C set to Cpp of MEAof MEA• Empirically known from heat exchangersEmpirically known from heat exchangers

Data Improvements – ∆HData Improvements – ∆Habsabs

• ∆∆HHabsabs – K – Keqeq equations vs Aspen (∆H equations vs Aspen (∆Hformform, , CCpp) parameters) parameters• COCO22 Loading - 0.2, 0.3, 0.4, 0.45, 0.5 Loading - 0.2, 0.3, 0.4, 0.45, 0.5• Temperature – 25, 40, 60, 80, 100, 120CTemperature – 25, 40, 60, 80, 100, 120C

• Discrepancy of ±3%Discrepancy of ±3%• Improves energy-material balance Improves energy-material balance

consistencyconsistency

Data Improvements – Data Improvements – KineticsKinetics

• Over 25 sources of MEA kinetics for dilute, Over 25 sources of MEA kinetics for dilute, unloaded solutionsunloaded solutions

• Currently only 1 data source for highly Currently only 1 data source for highly concentrated, highly loaded MEA solutionsconcentrated, highly loaded MEA solutions• Aboudheir (2002), laminar jet absorberAboudheir (2002), laminar jet absorber

• Rate constants from dilute, unloaded Rate constants from dilute, unloaded systems don't directly apply to CASTOR systems don't directly apply to CASTOR conditionsconditions

• Aboudheir data was verified by matching to Aboudheir data was verified by matching to dilute, unloaded literature datadilute, unloaded literature data• Activity coefficient and DActivity coefficient and DCO2CO2 corrections corrections

Aboudheir data presented on unloaded basisAboudheir data presented on unloaded basis

Versteeg Correlationy = -5400x + 26.810

7.0

7.5

8.0

8.5

9.0

9.5

10.0

10.5

11.0

11.5

12.0

0.0028 0.0029 0.0030 0.0031 0.0032 0.0033 0.0034 0.0035 0.0036 0.0037

Temp-1 (1/K)

ln (

k 2)

(dm

3/m

ol. s)

Literature Data

Aboudheir Data 3M

Aboudheir Data 5M

Aboudheir Data 7M

Linear (Versteeg)

Data Improvements – Data Improvements – KineticsKinetics• Ionic strength effect quantified and Ionic strength effect quantified and

implemented into Aspen kineticsimplemented into Aspen kinetics

5M MEA6

7

8

9

10

11

0 0.1 0.2 0.3 0.4 0.5

CO2 Loading (mol/mol)

ln (

k2)

(dm

3/m

ol. s

)

20C

30C

40C

50C

60C

Model ParametersModel Parameters

• Aspen RateSepAspen RateSep• 1.1 m diameter1.1 m diameter• 17m of IMTP-50 17m of IMTP-50

packingpacking

• Aspects ConsideredAspects Considered• Solvent DegradationSolvent Degradation• Heat LossHeat Loss• Number of StagesNumber of Stages• Reaction Film DiscretizationReaction Film Discretization• Pressure DropPressure Drop• Interfacial AreaInterfacial Area• Liquid HoldupLiquid Holdup• Gas Film MT Coefficient (kGas Film MT Coefficient (kGG))

• Liquid Film MT Coefficient (kLiquid Film MT Coefficient (kLL))

Model ParametersModel Parameters

• Reaction Film DiscretizationReaction Film Discretization• RateSep feature allows the reaction film RateSep feature allows the reaction film

to be subdivided.to be subdivided.• Reaction rates calculated for each Reaction rates calculated for each

segmentsegment• Reaction film broken into 6 non-equal Reaction film broken into 6 non-equal

segmentssegments• Larger segments near bulk liquidLarger segments near bulk liquid• Smaller segments near gas-liquid interfaceSmaller segments near gas-liquid interface

Model ParametersModel Parameters• Pressure DropPressure Drop

• Billet-Schultes pressure drop model to determine ∆P in Billet-Schultes pressure drop model to determine ∆P in packingpacking

• Matched very well with dataMatched very well with data• ≈ ≈ 70% of measured ∆P attributed to packing70% of measured ∆P attributed to packing

• Implemented into AspenImplemented into Aspen• >80% capacity factor – high vapor rates>80% capacity factor – high vapor rates

• Interfacial AreaInterfacial Area• CASTOR testsCASTOR tests• aaee = f(Q = f(QLL, V, VsGsG, , ρρGG))

• aaee≈1.5a≈1.5app

Model ParametersModel Parameters• Liquid HoldupLiquid Holdup

• Gamma topography with 400mm transparent Gamma topography with 400mm transparent columncolumn

• hhLL = f( = f(μμLL, V, VsLsL, , ρρLL, a, aGG))

• Gas Film MT Coefficient (kGas Film MT Coefficient (kGG))• Calculated from Onda (1968)Calculated from Onda (1968)

• Liquid Film MT Coefficient (kLiquid Film MT Coefficient (kLL))• A value of 5x10A value of 5x10-4-4 m/s m/s• Absorber operated >80% capacityAbsorber operated >80% capacity

Case 1ACase 1A

50

55

60

65

70

75

80

0 5 10 15 20 25 30

Stage

Tem

per

atu

re (

C)

Case 1ACase 1A

0

2

4

6

8

10

12

14

0 5 10 15 20 25 30

Stage

Vap

or

CO

2 (D

ry m

ole

%)

ConclusionsConclusions• An Aspen RateSep absorber model was An Aspen RateSep absorber model was

created using CASTOR dimensionscreated using CASTOR dimensions• Improved thermodynamic, kinetic and Improved thermodynamic, kinetic and

physical property data for Hphysical property data for H22O-MEA-O-MEA-COCO22 system were implemented into the system were implemented into the Aspen modelAspen model

• The absorber model was not adjusted The absorber model was not adjusted to fit experimental performance.to fit experimental performance.

• The absorber model did a very good The absorber model did a very good job of predicting the temperature and job of predicting the temperature and COCO22 profiles of the CASTOR data profiles of the CASTOR data