1 kinetics of co 2 absorption into mea-amp blended solution roongrat sakwattanapong adisorn...
TRANSCRIPT
1
Kinetics of CO2 Absorption into
MEA-AMP Blended Solution
Roongrat Sakwattanapong Adisorn Aroonwilas
Amornvadee Veawab
Faculty of EngineeringUniversity of ReginaSaskatchewan, Canada
Presented at the Annual Research Review Meeting, University of Texas at Austin, Jan 10-11, 2008
2
Outline
Introduction & Research Motivation
Research Objective
CO2 Absorption Experiments
Experimental Results and Discussion
Kinetic Model for MEA-AMP System
Conclusions
Acknowledgement
3
Introduction CO2 capture technology Reduction in GHG emissions
Low pressure flue gas Chemical absorption into amines
Performance of CO2 absorption
Higher performance [Smaller unit] Lower cost
Feed Gas
Treated Gas CO2
Liquid Solvent (Lean)
Liquid Solvent (Rich)
REGENERATIONCOLUMN
ABSORPTIONCOLUMN
Absorption solventsAbsorption solvents
Process DesignProcess Design
4
Introduction (Solvent Characteristics)
Blended-alkanolamines Blended alkanolamines have been receiving a great deal of interest.
Low energy requirement with acceptable absorption rate
MEA DEA MDEA
Absorption efficiency or rate
rCO2 = k2 [CO2][Amine]
k2 ~ 6000 to 7500
m3/kmol-s
k2 ~ 550 to 1600
m3/kmol-s
k2 ~ 5
m3/kmol-s
Heat of reaction (kJ/mol CO2) 85.6 76.3 60.9
Energy requirement for regeneration (kJ/kg CO2)
High Medium Low
CO2 solubility
(mol CO2/mol Amine)
0.5 0.5 1.0
5
Research Motivation MDEA-based solvents Low rate of CO2 absorption.
AMP can absorb CO2 with the similar capacity with MDEA but at a much
higher rate.
The knowledge of CO2 absorption kinetics for MEA-AMP is minimum
and limited.
Aroonwilas and Veawab, 2004. (Ind. Eng. Chem. Res.)
6
To measure kinetic rate of CO2 absorption into
aqueous MEA-AMP solution
To investigate the effects of process parameters on the kinetic rate of the blend. (The parameters of interest are temperature, total amine concentration, and MEA-AMP mixing ratio.)
To understand the kinetic rate data using reaction mechanism model
Research Objective
7
CO2 Absorption Experiment
Water Bath
Feed Tank
Receiver
Bubble Flow Meter
Gas Flow Meter
Saturation Cell
Heat Exchanger
Wetted Wall Cell
Equalizer
Condenser
Gas in
Gas out
Wetted Wall Column Diameter = 12 mm, OD (stainless steel)
Column height = up to 100 mm.
Temperature measurement at different locations
8
CO2 Absorption Experiment (cont’d)
9
0
1
2
3
4
3.0 3.1 3.2 3.3 3.4 3.5
1000 K/T
109
DC
O2 (
m2/s
ec)
This study
Versteeg and van Swaaij, 1988
Nijsing et al., 1959
Yoon et al., 2003
Rowley et al., 1997Perez and Sandall, 1973
Takahashi et al., 1982
Perry and Green, 1984
System Verification Measurement of diffusion coefficient for CO2-water
system
T = 298 – 325 K
2
2
2
22
2 2 CO
cCOCOCO
p
tHND
THCO
2044exp108249.2 6
2
3/13/23
3
2
gV
dht
Lc
10
System Verification (cont’d)
Measurement of reaction rate constant for CO2-MEA system
Temperature = 298 – 318 K (at Various liquid flow rates)
MEA concentration = 1 – 4 kmol/m3
MEAkDH
pN MEAMEACO
MEACO
COMEACO ,2,
,, 2
2
2
2
MEADp
HNk
MEACOCO
MEACOMEACOMEA
,
2,,
,222
22 1
11
System Verification (cont’d)
Measurement of reaction rate constant for CO2-AMP system
Temperature = 298 – 318 K (at Various liquid flow rates)
AMP concentration = 1 – 4 kmol/m3
12
Test Parameters Condition
Molar mixing ratio MEA : AMP 1 : 0 (xMEA = 1.0) 4 : 1 (xMEA = 0.8) 1 : 1 (xMEA = 0.5) 1 : 4 (xMEA = 0.2) 0 : 1 (xMEA = 0.0)
Temperature 298, 303, 308, 313, and 318 K
Total amine concentration
1.0 , 1.5, 2.0, 3.0, and 4.0 kmol/m3
Test Condition for MEA-AMP Blend
13
Experimental Results Overall rate constant (kOV)
Parametric effects on kOV (Temperature, Amine conc., MEA-AMP
mixing ratio)
ovBlendCOBlendCO
COBlendCO kD
H
pN ,
,, 2
2
2
2
BlendCOCO
BlendCOBlendCOov Dp
HNk
,
2,,
22
22 1
DN2O-mixed (109 m2/s)
0.5
0.75
1
1.25
1.5
1.75
2
0.5 0.75 1 1.25 1.5 1.75 2Correlation from this study
Rep
ort
ed
data
Mandal et al., 2005
Li and Lai, 1995
HN2O-mixed (kPa.m3/kmol)
3500
4000
4500
5000
5500
6000
6500
7000
3500 4000 4500 5000 5500 6000 6500 7000Correlation from this study
Rep
ort
ed
data
Mandal et al., 2005
Li and Lai, 1995
Regression of diffusion coefficient and Henry’s constant for MEA-AMP blend.
14MEA : AMP = 1 : 1
General representation
Effect of Temperature
15
Effect of Temperature (cont’d)
Individual Mixing Ratio
MEA : AMP ratio
1 : 0 (xMEA = 1.0)
4 : 1 (xMEA = 0.8)
1 : 1 (xMEA = 0.5)
1 : 4 (xMEA = 0.2)
0 : 1 (xMEA = 0.0)
MEA : AMP ratio
1 : 0 (xMEA = 1.0)
4 : 1 (xMEA = 0.8)
1 : 1 (xMEA = 0.5)
1 : 4 (xMEA = 0.2)
0 : 1 (xMEA = 0.0)
16T = 318 K
General representation
Effect of Amine Concentration
17
Individual temperatures
Effect of Amine Concentration (cont’d)
18
Without Synergy Effect
Effect of Mixing Ratio General Representation
MEA : AMP ratio
1 : 0 (xMEA = 1.0)
4 : 1 (xMEA = 0.8)
1 : 1 (xMEA = 0.5)
1 : 4 (xMEA = 0.2)
0 : 1 (xMEA = 0.0)
MEA : AMP ratio
1 : 0 (xMEA = 1.0)
4 : 1 (xMEA = 0.8)
1 : 1 (xMEA = 0.5)
1 : 4 (xMEA = 0.2)
0 : 1 (xMEA = 0.0)
AMP MEA
19
Single AMP
Single MEA
Individual Temperatures
Effect of Mixing Ratio (cont’d)
20
Xiao et al. (2000) proposed a model based on a hybrid reaction rate
Ali (2005) expressed the reaction rates of both AMP and MEA based on the zwitterion mechanism (for low amine concentration)
Xiao, J., Li, C.W., and Li, M.H., “Kinetics of absorption of carbon dioxide into aqueous solutions of 2-amino-2-methyl-1-propanol + monoethanolamine,” Chemical Engineering Science, 55(1), 161-175 (2000). Ali, S.H., “Kinetics of the Reaction of Carbon Dioxide with Blends of Amines in Aqueous Media Using the Stopped-Flow Technique,” International Journal of Chemical Kinetics, 37(7), 391-405, July 2005.
Kinetic Model for MEA-AMP System
COONHRRNHRRCO k
k'
1'
2
2 NCOORRBHBCOONHRR Bk ''
CO2-MEA System
Bk
k
AMPCOkr
B
AMPAMPCO
1
2,2,
12
Bkk
MEACOkr
B
MEAMEACO
1
2,2,
12
CO2-AMP System
21
Overall reaction of CO2-MEA-AMP System
Apparent reaction rate
OHCOAMPCOMEACOovov rrrCOkr ,,,2222
Kinetic Model (cont’d)
][* OHkkk
OHOVapp
][][][
11][
][][][
11][
][
1
,2
1
,22
1
,2,2
1
,2
1
,22
1
,2,2
*
22 MEAk
kkAMP
k
kkOH
k
kkk
AMP
AMPk
kkMEA
k
kkOH
k
kkk
MEAOHkk
MEAAMPAMPAMPOHAMPAMPAMPMEAMEAMEAOHMEAMEA
OHOV
)(
3.4340095.15,2 KT
k AMP
)(
758.10067.0
1
,2
KTk
kk AMPAMP
)(
32.4164825.1
1
,2
KTk
kk MEAAMP
)(
0852.00003.0
1
,2
KTk
kk WAMP
)(
4945018.171,2 KT
k MEA
)(
29.935979.0
1
,2
KTk
kk MEAMEA
)(
78.3532459.1
1
,2
KTk
kk AMPMEA
)(
7754.00027.0
1
,2
KTk
kk WMEA
22
Speciation [MEA], [AMP], [H2O], [OH-]
CO2 Absorption Reaction
( 1 ) 2332 '' 1 NHROHNHROH K 2' NHR
( 2 ) 232 '' 2 NHRHCONHCOOROH K 3' NHR
( 3 ) 332232 HCOOHOHCO K NHCOOR '
( 4 ) OHOHOH K32
42 2CO
( 5 ) 23332
5 COOHHCOOH K 3HCO
( 6 ) 332226 HCORNHOHRHNCO K 2
3CO
2RNH
( 7 ) E l e c t r o - n e u t r a l i t y 3RNH
( 8 ) M E A B a l a n c e OH 3
( 9 ) A M P B a l a n c e OH
( 1 0 ) C a r b o n B a la n c e
0.1ix OH 2
( 1 ) 2332 '' 1 NHROHNHROH K 2' NHR
( 2 ) 232 '' 2 NHRHCONHCOOROH K 3' NHR
( 3 ) 332232 HCOOHOHCO K NHCOOR '
( 4 ) OHOHOH K32
42 2CO
( 5 ) 23332
5 COOHHCOOH K 3HCO
( 6 ) 332226 HCORNHOHRHNCO K 2
3CO
2RNH
( 7 ) E l e c t r o - n e u t r a l i t y 3RNH
( 8 ) M E A B a l a n c e OH 3
( 9 ) A M P B a l a n c e OH
( 1 0 ) C a r b o n B a la n c e
0.1ix OH 2
23
Comparison (Model & Experimental data)
Single AMPSingle MEASingle AMPSingle MEASingle AMP
Single MEASingle AMPSingle MEA
Single AMPSingle MEA
24
The overall rate constant increases with the absolute temperature.
At the same mixing ratio, the overall rate constant increases when the total concentration increases.
An increase in MEA concentration in the blended solution causes the overall rate constant to change in a nonlinear manner.
Rate constant => 1:1 < 4:1 < 1:0 < 1:4 < 0:1 (MEA:AMP)
Existing model developed for low amine concentration provides reasonable prediction for single amine, but not for the blend.
Conclusions
25
Mechanism of CO2 absorption into MEA-AMP blended solution
will be further investigated.
CO2-loaded solution will be tested.
Degraded solution will be tested.
Empirical correlation of absorption kinetics will be developed.
Further work
26
Faculty of Graduate Studies and Research (FGSR), University of Regina
Faculty of Engineering, University of Regina
The Natural Sciences and Engineering Research Council of Canada (NSERC)
Acknowledgement
27
Thank You