rate based mea mdea model

8/9/2019 Rate Based MEA MDEA Model

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Aspen Plus

Rate-Based Model of theCO2 Capture Process byMEA+MDEA AqueousSolution using Aspen

Plus


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Copyright (c) 2008-2010 by Aspen Technology, Inc. All rights reserved.

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Revision History 1

Revision HistoryVersion Description

V7.1 First version

V7.1 CP1 Add O2, CO and H2to the model as Henry components

V7.2 Update results for V7.2


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2 Contents

ContentsIntroduction ............................................................................................................3

1 Components .........................................................................................................4

2 Process Description ..............................................................................................5

3 Physical Properties...............................................................................................6

4 Reactions ...........................................................................................................20

5 Simulation Approaches.......................................................................................25

6 Simulation Results .............................................................................................28

7 Conclusions ........................................................................................................29

References ............................................................................................................30


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Introduction 3

Introduction

This file describes an Aspen Plus rate-based model of the CO2capture processby mixed MEA and MDEA aqueous solution from a gas mixture of CO2and N2.The model consists of an absorber. The operating data for a bench-scalepacked column from Aroonwilas (2004)[1] were used to specify feed conditionsand unit operation block specifications in the model. Thermophysical propertymodels and reaction kinetic models are based on the recent works of U.T.Austin (1988)[2], the work of Aspen Technology (2007)[3], Hikita (1977)[4] andRamachandran (2006)[5] and Pinsent (1956)[6]. Transport property modelsand model parameters have been validated against experimental data fromopen literature[17-24].

The model includes the following key features:

True species including ions

Electrolyte NRTL method for liquid and RK equation of state for vapor Concentration-based reaction kinetics

Electrolyte transport property models

Rate-based models for absorber with packing


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4 1 Components

1 Components

The following components represent the chemical species present in theprocess:

Table 1. Components Used in the Model

ID Type Name Formula

MEA Conventional MONOETHANOLAMINE C2H7NO

H2O Conventional WATER H2O

CO2 Conventional CARBON-DIOXIDE CO2

H3O+ Conventional H3O+ H3O+

OH- Conventional OH- OH-

HCO3- Conventional HCO3- HCO3-

CO3-2 Conventional CO3-- CO3-2

MEAH+ Conventional MEA+ C2H8NO+

MEACOO- Conventional MEACOO- C3H6NO3-

MDEA Conventional METHYL-DIETHANOLAMINE C5H13NO2MDEAH+ Conventional MDEA+ C5H14NO2+

N2 Conventional NITROGEN N2

H2S Conventional HYDROGEN SULFIDE H2S

HS- Conventional HS- HS-

S-2 Conventional S-- S-2

O2 Conventional OXYGEN O2

CO Conventional CARBON-MONOXIDE CO

H2 Conventional HYDROGEN H2


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2 Process Description 5

2 Process Description

The flowsheet for the bench-scale absorption unit[1] for CO2capture byMEA+MDEA aqueous solution includes an absorber. Table 2 represents theabsorbers typical operation data:

Table 2. Data of the Absorber Used in the CO2 CaptureProcess by MEA+MDEA Aqueous Solution

Absorber

Diameter 0.02mPacking Type Sulzer DXPacking Height 2m

Feed Gas

Flow rate 2.3648kmol/hrCO2in Sour Gas 10%(mole fraction)Temperature 298K

Pressure 1atmLean Amine

Flow rate 0.4906m3/hrMEA concentration 1.5MMDEA concentration 1.5MCO2concentration 0.75MTemperature 298KPressure 1atm


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6 3 Physical Properties

3 Physical Properties

The electrolyte NRTL method is used for liquid and RK equation of state forvapor in this Rate-based MEA+MDEA model. The phase equilibrium modelparameters for the sub-systems CO2-MEA-H2O, CO2-MDEA-H2O and H2S-MDEA-H2O, together with the Henrys constant parameters and/or chemicalequilibrium constant parameters, were regressed against:

CO2solubility data in aqueous MEA solutions from Jou et al. (1995)[7],

Maddox et al. (1987)[8], Isaacs et al. (1980)[9], Lawson and Garst(1976)[10], Muhlbauer and Monaghan (1957)[11]

CO2solubility data in aqueous MDEA solutions from Jou et al. (1982,1993)[ 12-14], Kuranov et al. (1996)[15] and Kamps et al. (2001)[16]

H2S solubility data in aqueous MDEA solutions from Kuranov et al.(1996)[15] and Kamps et al. (2001)[16]

Predictions for CO2solubility in mixed MEA and MDEA aqueous solutionsbased on the phase equilibrium model parameters from the sub-systems werecompared with literature data from Shen and Li (1992)[17].

CO2, H2S, N2, O2, CO and H2are selected as Henry-components to whichHenrys law is applied. Henrys constants for these components with water areretrieved from the Aspen Plus databanks. For solvents MEA and MDEA, theHenrys constants are obtained as follows: For CO2with MEA, regressed from CO2 solubility data

[7-11] in aqueous MEAsolutions

For CO2with MDEA, regressed from CO2solubility data[12-16] in aqueous

MDEA solutions

For H2S with MDEA, regressed from H2S solubility data[15-16] in aqueous

MDEA solutions

In the reactions calculations, the activity coefficient basis for the Henryscomponents (solutes) is chosen to be Aqueous. Therefore, in calculating theunsymmetric activity coefficients (GAMUS) of the solutes, the infinite dilutionactivity coefficients are calculated based on infinite-dilution condition in purewater, instead of in mixed solvents.

The liquid molar volume model and transport property model parameters areregressed from literature experimental data[18-25] for the sub-systems CO2-MEA-H2O and CO2-MDEA-H2O. Predictions for the mixed MEA and MDEAaqueous solutions loaded with CO2are compared against literature data whenpossible. However, we did not evaluate these properties of the MEA and/or


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3 Physical Properties 7

MDEA systems loaded with H2S. Specifications of the transport propertymodels include:

For liquid molar volume, the Clarke model, called VAQCLK in Aspen Plus,is used with option code 1 to use the quadratic mixing rule for solvents.The interaction parameter VLQKIJ for the quadratic mixing rule betweenMEA and H2O is regressed against experimental MEA-H2O density datafrom Kapadi et al. (2002) [18] and VLQKIJ between MDEA and H2O isregressed against experimental MDEA-H2O density data from Bernal-Garcia (2003)[19].

The Clarke model parameter VLCLK/1 is also regressed for mainelectrolytes (MEAH+, HCO 3), (MEAH+, MEACOO

) and (MEAH+, CO 23 )

against experimental CO2-MEA-H2O density data from Weiland (1996)[20]

and for (MDEAH+, HCO 3) and (MDEAH+, CO 23 ) against experimental

density data of the CO2-MDEA-H2O system from Weiland (1998)[21].

For liquid viscosity, the Jones-Dole electrolyte correction model, calledMUL2JONS in Aspen Plus, is used with the mass fraction based ASPENliquid mixture viscosity model for the solvent. There are three models forelectrolyte correction and the MEA+MDEA model always uses the Jones-Dole correction model. The three option codes for MUL2JONS are set to 1(mixture viscosity weighted by mass fraction), 1 (always use Jones andDole equation when the parameters are available), and 2 (ASPEN liquidmixture viscosity model), respectively.

The interaction parameters between MEA and H2O in the ASPEN liquidmixture viscosity model, MUKIJ and MULIJ, are regressed againstexperimental MEA-H2O viscosity data from Kapadi et al. (2002)

[18] andWadi et al. (1995) [22]. MUKIJ and MULIJ between MDEA and H2O areregressed against experimental viscosity data of the MDEA-H2O systemfrom Teng et al. (1994)[23].The Jones-Dole model parameters, IONMUB, for MEAH+, and MEACOO- areregressed against CO2-MEA-H2O viscosity data from Weiland (1996)[20];for MDEAH+, is regressed against CO2-MDEA-H2O viscosity data fromWeiland (1998)[21]; for HCO3

-, is regressed against KHCO3-H2O viscositydata from Palaty (1992)[24] and for CO3

2-, is regressed against K2CO3-H2Oviscosity data from Pac et al. (1984)[25].

For liquid surface tension, the Onsager-Samaras model, called SIG2ONSGin Aspen Plus, is used with its option codes being -9 (exponent in mixingrule) and 1 (electrolyte system), respectively. Predictions for the sub-systems CO2-MEA-H2O and CO2-MDEA-H2O are within the range of theexperimental data from Weiland (1996)[20].

For thermal conductivity, the Riedel electrolyte correction model, calledKL2RDL in Aspen Plus, is used.

For binary diffusivity, the Nernst-Hartley model, called DL0NST in AspenPlus, is used with option code of 1 (mixture viscosity weighted by massfraction).

In addition to the updates with the above transport properties, heat capacityat infinite dilution (CPAQ0) for MDEAH+, MEAH+ and MEACOO- are adjusted tofit to heat capacity data from Weiland (1996)[20].


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The aqueous phase heat of formation at infinite dilution and 25C (DHAQFM)for MEAH+ and MEACOO- are adjusted to fit to the literature heat of solutiondata from Carson et al. (2000)[26] of the sub-system CO2-MEA-H2O. ForMDEAH+, the databank value of DHAQFM is -5.0471x108 J/kmol, which resultsin heat of solution predictions for the sub-system CO2-MDEA-H2O as shown inFigure 6b-1 together with the data from Carson et al. (2000)[26]. However, to

match the temperature profile data of an plant absorber for CO 2capture byaqueous MDEA solutions[27], it was found that a value of -5.0 x108J/kmol forDHAQFM of MDEAH+ is better. This value is used in the current simulationand results in heat of solution predictions for sub-system CO2-MDEA-H2O asshown in Figure 6b-2.

The estimation results of various transport and thermal properties aresummarized in Figures 1-8:

900

950

1000

1050

1100

1150

1200

0 0.1 0.2 0.3 0.4 0.5

CO2 Loading

Density,

kg/m3

EXP MEA 10w t%EXP MEA 20w t%EXP MEA 30w t%EXP MEA 40w t%

EST MEA 10w t%EST MEA 20w t%EST MEA 30w t%EST MEA 40w t%

Figure 1a. Liquid Density of MEA-CO2-H2O at 298.15K, experimental datafrom Weiland (1996)[20]


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900

950

1000

1050

1100

1150

1200

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7

CO2 Loading, m ol/mol

Density,

kg/m3

EXP MDEA 30w t%

EXP MDEA 40w t%

EXP MDEA 50w t%

EXP MDEA 60w t%

EST MDEA 30w t%

EST MDEA 40w t%

EST MDEA 50w t%

EST MDEA 60w t%

Figure 1b. Liquid Density of MDEA-CO2-H2O at 298.15K, experimental datafrom Weiland (1998)[21]

900

950

1000

1050

1100

1150

1200

0 0.1 0.2 0.3 0.4 0.5

CO2 Loading

Density,

kg/m3

EXP MEA5w t%+MDEA45w t%

EST MEA5w t%+MDEA45w t%





Figure 1c. Liquid Density of MEA+MDEA-CO2-H2O at 298.15K, experimentaldata from Weiland (1998)[21]


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0.1

1

10

100

0 0.1 0.2 0.3 0.4 0.5

CO2Loading, mol/mol

Viscosity,m

PaS

EXP MEA 20w t%

EXP MEA 30w t%

EXP MEA 40w t%

EST MEA 20w t%

EST MEA 30w t%

EST MEA 40w t%

Figure 2a. Liquid Viscosity of MEA-CO2-H2O at 298.15K, experimental datafrom Weiland (1996)[20]

1.00

10.00

100.00

1000.00

0 0.1 0.2 0.3 0.4 0.5

CO2 Loading

Log(Viscosity

,mPaS)

EXP MDEA 30w t%EST MDEA 30w t%EXP MDEA 40w t%EST MDEA 40w t%EXP MDEA 50w t%EST MDEA 50w t%EXP MDEA 60w t%EST MDEA 60w t%

Figure 2b. Liquid Viscosity of MDEA-CO2-H2O at 298.15K, experimental datafrom Weiland (1998)[21]


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0.001

0.01

0.1

0 0.1 0.2 0.3 0.4 0.5

CO2 Loading

Viscosity,

PaS







Figure 2c. Liquid Viscosity of MEA+MDEA-CO2-H2O at 298.15K, experimentaldata from Weiland (1998)[21]

0

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

0.09

0.1

0 0.1 0.2 0.3 0.4 0.5 0.6

CO2 Loading, mol/mol

SurfaceTension,

N/m

EXP MEA 10wt%EXP MEA 20wt%EXP MEA 30wt%EXP MEA 40wt%EST MEA 10wt%EST MEA 20wt%EST MEA 30wt%EST MEA 40wt%

Figure 3a. Surface tension of MEA-CO2-H2O at 298.15K, experimental data

from Weiland (1996)[20]


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0.03

0.04

0.05

0.06

0.07

0.08

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7

CO2 Loading

SurfaceTension,N

/m

EXP MDEA 30w t%EST MDEA 30w t%EXP MDEA 40w t%EST MDEA 40w t%EXP MDEA 50w t%EST MDEA 50w t%EXP MDEA 60w t%

EST MDEA 60w t%

Figure 3b. Surface tension of MDEA-CO2-H2O at 298.15K, experimental datafrom Weiland (1996)[20]

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 0.1 0.2 0.3 0.4 0.5

CO2 Loading

ThermalConductivity

,Watt/m-K

EST MEA 10w t%

EST MEA 20w t%

EST MEA 30w t%

EST MEA 40w t%

Figure 4a. Liquid Thermal Conductivity of MEA-CO2-H2O at 298.15K


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0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0 0.1 0.2 0.3 0.4 0.5

CO2 Loading, mol/mol

ThermalConductivity,W

att/mK

EST MDEA 30w t%

EST MDEA 40w t%

EST MDEA 40w t%

EST MDEA 60w t%

Figure 4b. Liquid Thermal Conductivity of MDEA-CO2-H2O at 298.15K

2000

2500

3000

3500

4000

4500

0 0.1 0.2 0.3 0.4 0.5

CO2Loading

HeatCapac

ity(J/kg)

EXP MEA 10w t%EXP MEA 20w t%EXP MEA 30w t%EXP MEA 40w t%EST MEA10w t%EST MEA 20w t%EST MEA 30w t%EST MEA 40w t%

Figure 5a. Liquid Heat Capacity of MEA-CO2-H2O at 298.15K, experimentaldata from Weiland (1996)[20]


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0

20

40

60

80

100

120

140

160

0 0.1 0.2 0.3 0.4 0.5

CO2 Loading

HeatCapacity,

J/mol-

K

EXP MDEA 30w t%

EXP MDEA 40w t%

EXP MDEA 50w t%

EXP MDEA 60w t%

EST MDEA 30w t%

EST MDEA 40w t%

EST MDEA 50w t%

EST MDEA 60w t%

Figure 5b. Liquid Heat Capacity of MDEA-CO2-H2O at 298.15K, experimentaldata from Weiland (1996)[20]

0

500

1000

1500

2000

2500

3000

3500

4000

0 0.1 0.2 0.3 0.4 0.5

CO2 Loading

HeatCapacity,

J/kg-K

EXP MEA5w t%+MDEA45w t%5






Figure 5c. Liquid Heat Capacity of MEA+MDEA-CO2-H2O at 298.15K,experimental data from Weiland (1997)[28]


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-90000

-88000

-86000

-84000

-82000

-80000

-78000

-76000

-74000

-72000

-70000

0 0.02 0.04 0.06 0.08 0.1 0.12 0.14

O Loading

H

o

S

u

o

J

m

o

EXP MEA 10wt%

EXP MEA 20wt%

EXP MEA 30wt% 1

EXP MEA 30wt% 2

EST MEA 10wt%

EST MEA 20wt%

EST MEA 30wt%

Figure 6a. Heat of Solution of CO2 in MEA-H2O at 298.15K, experimental datafrom Carson et al. (2000)[26]

Figure 6b-1. Heat of Solution of CO2 in MDEA-H2O using ASPEN databankDHAQFM(MDEAH+) value (-5.0471E8J/kmol), experimental data from Carsonet al. (2000)[26]


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Figure 6b-2. Heat of Solution of CO2 in MDEA-H2O using DHAQFM(MDEAH+)=-

5.0E8J/kmol, experimental data from Carson et al. (2000)[26]

-100000

-80000

-60000

-40000

-20000

0

0 0.02 0.04 0.06 0.08 0.1 0.12

CO2 Loading

HeatofSolu

tion,

J/mol

EXP1 MEA7w t%+MDEA27w t%

EXP2 MEA7w t%+MDEA27w t%


EST MEA34w t%

EST MDEA34w t%

Figure 6c. Heat of Solution of CO2 in MEA+MDEA-H2O at 298.15K,

experimental data from Carson et al. (2000)[26]


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0.001

0.01

0.1

1

10

100

1000

10000

100000

1000000

0.001 0.01 0.1 1 10

CO2 Loading

CO2Pressure,kP

a

EXP 40CEST 40C

EXP 60CEST 60CEXP 80C

EST 80CEXP 100C

EST 100CEXP 120CEST 120C

Figure 7a-1. CO2 Partial Pressure of MEA-CO2-H2O (MEA mass fraction = 0.3),experimental data from Jou et al. (1995)[7]

0.1

1

10

100

1000

10000

0.1 1 10

CO2 Loading

CO2Press

ure,

KPa

EXP 298.15KEST 298.15KEXP 333.15KEST 333.15KEXP 353.15KEST 353.15K

Figure 7a-2. CO2 Partial Pressure of MEA-CO2-H2O (MEA mass fraction =

0.153), experimental data from Maddox et al. (1987)[8]


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0.1

1

10

100

1000

10000

0.1 1

CO2 Loading

CO2Pressure,K

Pa

EXP 40CEST 40CEXP 60CEST 60C

EXP 80CEST 80C

EXP 100CEST 100C

Figure 7c-2. CO2 Partial Pressure of MEA+MDEA-CO2-H2O (MEA mass fraction= 0.24 and MDEA mass fraction = 0.06), experimental data from Shen and Li(1992)[17]

0.1

1

10

1 10

m_H2S, mol/kg

H2SPressure,M

Pa

EXP 313.15KEST 313.15KEXP 333.15KEST 333.15KEXP 373.15KEST 373.15KEXP 393.15KEST 393.15K

EXP 413.15KEST 413.15K

Figure 8. H2S Partial Pressure of MDEA-H2S-H2O (MDEA molality = 4),experimental data from Kuranov et al. (1996)[15]


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20 4 Reactions

4 Reactions

MEA is a primary ethanolamine, as shown in Figure 9. It can associate with H +

to form an ion MEAH+, and react with CO2to form a carbamate ion MEACOO-.

Figure 9. MEA Molecular Structure

MDEA is a tertiary ethanolamine, as shown below in Figure 10. It canassociate with H+ to form MDEAH+ but cannot react with CO2to producecarbamate as is the case for primary or secondary ethanolamines.

Figure 11. MDEA Molecular Structure

The electrolyte solution chemistry for the mixed amines, MEA+MDEA with CO2and H2S, has been modeled with a CHEMISTRY model with CHEMISTRY ID =MEAMDEA. This CHEMISTRY ID is used as the global electrolyte calculationoption in the simulation by specifying it on the Globalsheet of theProperties | Specificationsform. Chemical equilibrium is assumed with allthe ionic reactions in the CHEMISTRY MEAMDEA. In addition, a kineticREACTION model called RMEAMDEA has been created and used in thecalculations of the absorber by specifying it in the Reactionpart of theabsorber specifications. In RMEAMDEA, all reactions are assumed to be inchemical equilibrium except those of CO2with OH

-, CO2with MEA and CO2with MDEA.


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4 Reactions 21

A. Chemistry ID: MEAMDEA

1 Equilibrium OHOHO2H 32

2 Equilibrium 3322 HCOOHO2HCO

3 Equilibrium 23323 COOHOHHCO

4 Equilibrium OHMEAOHMEAH 32

5 Equilibrium 32 HCOMEAOHMEACOO

6 Equilibrium OHMDEAOHMDEAH 32

7 Equilibrium OHHSSHOH 322

8 Equilibrium OHSHSOH 32

2

B. Reaction ID: RMEAMDEA

1 Equilibrium

OHMEAOHMEAH 32

2 Equilibrium OHOHO2H 32

3 Equilibrium OHCOOHHCO 32

323

4 Equilibrium OHMDEAOHMDEAH 32

5 Equilibrium OHHSSHOH 322

6 Equilibrium OHSHSOH 32

2

7 Kinetic 32 HCOOHCO

8 Kinetic

OHCOHCO 23

9 Kinetic OHMEACOOOHCOMEA 3-

22

10 Kinetic 223-

COOHMEAOHMEACOO

11 Kinetic -322 HCOMDEAHOHCOMDEA

12 Kinetic OHCOMDEAHCOMDEAH 22-

3

The equilibrium expressions for the reactions are taken from the work ofAustgen et al.[2] and Jou et al.[12-14], as well as the parameters for theequilibrium constants. However, for the fifth equilibrium reaction, itsequilibrium constant parameters were regressed using the CO

2solubility

data[7-11] in aqueous MEA solutions together with the NRTL parameters andthe Henrys constants parameters. The power law expressions (T0notspecified) are used for the rate-controlled reactions (reactions 7-12 inRMEAMDEA):

N

i

a

i

n iC)RT

E(kTr

1

exp (1)

Where:


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22 4 Reactions

r= Rate of reaction;

k= Pre-exponential factor;

T= Absolute temperature;

n= Temperature exponent;

E= Activation energy;R= Universal gas constant;

N= Number of components in the reaction;

Ci= Concentration of component i;

ai= The stoichiometric coefficient of component iin the reaction equation.

In equation (1), the concentration basis is Molarity, the factor n is zero, kand Eare given in Table 3.

Ramachandran et al.[5] reported that reaction kinetics of the mixed MEA andMDEA system cannot be interpreted by the mechanism of the single amines.We assume that free MEA can transfer CO2to MDEA and then regenerate byitself simultaneously:

(A) 22 COMEACOMEA

(B) MEACOMDEAMDEACOMEA 22

(C) -322 HCOMDEAHOHCOMDEA

We combine these three reactions and obtain the following reaction:

(D) -322 HCOMDEAHOHCOMDEA

Reaction (D) is used to represent the chemical equilibrium between MDEA and

CO2, and the following rate expression is used to represent the catalytic effectof MEA on reaction (D):

2exp COMEAMDEA

nCC)C

RT

E(kTr (2)

To implement the catalytic effect of MEA on reaction (D), we set thestoichiometric coefficient of MEA to 0 and the concentration exponent of MEAto 1 when we edit reactions 11 and 12 of RMEAMDEA in Reactions(Figures11a and 11b).


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4 Reactions 23

Figure 11a. Specifications of Reaction 11

Figure 11b. Specifications of Reaction 12

The kinetic parameters for reactions 7, 9 and 11 in Table 3 are derived fromthe work of Pinsent[6], Hikita[3] and Ramachandran[5]. The kinetic parameters

for the corresponding reversible reactions 8, 10 and 12 are calculated byusing the kinetic parameters and the equilibrium constants of the forwardreactions 7, 9 and 11.


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24 4 Reactions

Table 3. Parameters k and E in Equation (1)

Reaction No. k E, cal/mol

7 4.32e+13 13249

8 2.38e+17 294519 9.77e+10 9856

10 2.80e+20 17230

11 2.21e+8 7432

12 8.89e+11 15334


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5 Simulation Approaches 25

5 Simulation Approaches

The case from Aroonwilas[1] is used in this simulation.

Simulation Flowsheet The bench-scaled absorber has been modeled withthe following simulation flowsheet in Aspen Plus, shown in Figure 12.

LEANIN

GASIN

GASOUT

RICHOUT

ABSORBER

Figure 12. Rate-Based MEA+MDEA Simulation Flowsheet in Aspen Plus


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26 5 Simulation Approaches

Unit Operations- Major unit operations in this model have been representedby Aspen Plus Blocks as outlined in Table 4. As there is no Sulzer DX in thepacking type option of Aspen Plus, the Sulzer BX packing is used, the columndiameter is scaled up to 0.25m and the packing height is set to 6m.

Table 4. Aspen Plus Unit Operation Blocks Used in theRate-Based MEA+MDEA Model

Unit Operation Aspen Plus Block Comments / Specifications

Absorber RadFrac 1. Calculation type: Rate-Based

2. 20 Stages

3. Top Pressure: 1atm

4. Reaction condition factor: 0.5

5. Film discretization ratio: 2

6. Heater Cooler: Heat loss is ignored for the absorber

7. Reaction: Reaction ID is RMEAMDEA for all stages

8. Packing Type: Sulzer BX

9. Section Diameter: 0.25m

10. Packing Height: 6m

11. Mass transfer coefficient method: Bravo et al (1985)

12. Interfacial area method: Bravo et al (1985)

13. Interfacial area factor: 0.5

14. Heat transfer coefficient method: Chilton and Colburn

15. Holdup correlation: Bravo et al (1992)

16. Film resistance: Discrxn for liquid film; Film for vaporfilm

17. Additional discretization points for liquid film: 5

18. Flow model: CounterCurrent


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5 Simulation Approaches 27

Streams- Feeds to the absorber are GASIN containing N2and CO2andLEANIN containing aqueous MEA and MDEA solution loaded with some CO2.Feed conditions are summarized in Table 5. The flow rates of feeds are scaledup in accordance with the scaled-up column diameter.

Table 5. Feed specificationsStream ID GASIN LEANIN

Substream: MIXED

Temperature: K 298 298

Pressure: atm 1 1

Total flow 2.3648kmol/hr 0.4906cum/hr

Mole-Frac Mole-Conc

H2O 0 solvent

CO2 0.1 0.75kmol/cum

MEA 0 1.5kmol/cum

MDEA 0 1.5kmol/cumN2 0.9 0

Prop-Sets- A Prop-Set, XAPP, has been created to report apparent molefraction of CO2, MEA and MDEA in liquid streams to facilitate calculations ofCO2loadings of the streams.


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28 6 Simulation Results

6 Simulation Results

The simulation was performed using Aspen Plus V7.2. The measured versuscalculated absorber CO2concentration profile in the gas phase is shown inFigure 13.

0

0.5

1

1.5

2

0 0.02 0.04 0.06 0.08 0.1

CO2 concentration in gas(%)

Heightfrom

bottom,

m

Figure 13. The Absorber CO2 concentration Profile in Gas Phase

() Experimental data of 3M MEA, () Experimental data of 1.5M MEA and 1.5M MDEA,() Experimental data of 3M MDEA, () Simulation results of 3M MEA, ()Simulation results of 1.5M MEA and 1.5M MDEA, (----) Simulation results of 3M MDEA


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7 Conclusions 29

7 Conclusions

The Rate-Based MEA+MDEA model provides a rate-based rigorous simulationof the process. Key features of this rigorous simulation include electrolytethermodynamics and solution chemistry, reaction kinetics for the liquid phasereactions, rigorous transport property modeling, rate-based multi-stagesimulation with Aspen Rate-Based Distillation which incorporates heat andmass transfer correlations accounting for columns specifics and hydraulics.

The model is meant to be used as a guide for modeling the CO2captureprocess with MEA+MDEA. Users may use it as a starting point for moresophisticated models for process development, debottlenecking, plant andequipment design, among others.


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30 References

References

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[3] Aspen Technology Inc., 2007

[4] H. Hikita, S. Asai, H. Ishikawa, M. Honda, The Kinetics of Reactions ofCarbon Dioxide with Monoethanolamine, Diethanolamine, andTriethanolamine by a Rapid Mixing Method, Chem. Eng. J., 13, 7-12 (1977).

[5] N. Ramachandran, A. Aboudheir, R. Idem, P. Tontiwachwuthikul, Kineticsof the Absorption of CO2into Mixed Aqueous Loaded Solutions ofMonoethanolamine and Methyldiethanolamine, Ind. Eng. Chem. Res., 45,2608-2616 (2006)

[6] B.R. Pinsent, L. Pearson, F.J.W. Roughton, The Kinetics of Combination ofCarbon Dioxide with Hydroxide Ions, Trans. Faraday Soc., 52, 1512-1520(1956)

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[8] R.N. Maddox, A.H. Bhairi, J.R. Diers, P.A. Thomas, Equilibrium Solubilityof Carbon Dioxide or Hydrogen Sulfide in Aqueous Solutions ofMonoethanolamine, Diglycolamine, Diethanolamine andMethyldiethanolamine, GPA Research Report No.104, 1987

[9] E.E. Isaacs, F.D. Otto, A.E. Mather, "Solubility of Mixtures of H 2S and CO2in a Monoethanolamine Solution at Low Partial Pressures", J. Chem. Eng. Data,

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[14] F.-Y. Jou, J.J. Carroll, A.E. Mather, F.D. Otto, The Solubility of CarbonDioxide and Hydrogen Sulfide in a 35 wt% Aqueous Solution ofMethyldiethanolamine, Can. J. Chem. Eng., 71, 264-268 (1993)

[15] G. Kuranov, B. Rumpf, N.A. Smirnova, G. Maurer, "Solubility of SingleGases Carbon Dioxide and Hydrogen Sulfide in Aqueous Solutions of N-Methyldiethanolamine in the Temperature Range 313-413 K at Pressures upto 5 MPa", Ind. Eng. Chem. Res., 35, 1959-1966 (1996)

[16] . P.-S. Kamps, A. Balaban, M. Jdecke, G. Kuranov, N.A. Smirnova, G.Maurer, "Solubility of Single Gases Carbon Dioxide and Hydrogen Sulfide inAqueous Solutions of N-Methyldiethanolamine at Temperatures from 313 to393 K and Pressures up to 7.6 MPa: New Experimental Data and Model

Extension", Ind. Eng. Chem. Res., 40, 696-706 (2001)

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[20] R.H. Weiland, Physical Properties of MEA, DEA, MDEA and MDEA-BasedBlends Loaded with CO2,GPA Research Report No. 152, August 1996

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[26] J.K Carson, K.N. Marsh, A.E. Mather, "Enthalpy of solution of carbondioxide in (water + monoethanolamine, or diethanolamine, or N-
http://www.ingentaconnect.com/content/els/03783812/2002/00000201/00000002/art00095;jsessionid=b8n0gl9mmmig.alexandrahttp://www.ingentaconnect.com/content/els/03783812/2002/00000201/00000002/art00095;jsessionid=b8n0gl9mmmig.alexandrahttp://www.ingentaconnect.com/content/els/03783812/2002/00000201/00000002/art00095;jsessionid=b8n0gl9mmmig.alexandrahttp://www.ingentaconnect.com/content/els/03783812/2002/00000201/00000002/art00095;jsessionid=b8n0gl9mmmig.alexandrahttp://www.ingentaconnect.com/content/els/03783812/2002/00000201/00000002/art00095;jsessionid=b8n0gl9mmmig.alexandrahttp://www.ingentaconnect.com/content/els/03783812/2002/00000201/00000002/art00095;jsessionid=b8n0gl9mmmig.alexandra


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rate based mea mdea model

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