Kinetics of CO 2 Absorption into MEA-AMP Blended Solution

1. Kinetics of CO2 Absorption into MEA-AMP Blended Solution Roongrat Sakwattanapong Adisorn Aroonwilas Amornvadee Veawab Faculty of Engineering University of Regina Saskatchewan, 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 Process Design Absorption solvents

4. Introduction (Solvent Characteristics) Blended-alkanolamines • Blended alkanolamines have been receiving a great deal of interest. • Low energy requirement with acceptable absorption rate

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. Research Objective • 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

7. CO2 Absorption Experiment • 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) 8

9. System Verification • Measurement of diffusion coefficient for CO2-water system • T = 298 – 325 K 9

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 10

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 11

12. Test Condition for MEA-AMP Blend

13. Experimental Results • Overall rate constant (kOV) • Parametric effects on kOV (Temperature, Amine conc., MEA-AMP mixing ratio) Regression of diffusion coefficient and Henry’s constant for MEA-AMP blend. 13

14. Effect of Temperature • General representation MEA : AMP = 1 : 1

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)

16. Effect of Amine Concentration • General representation T = 318 K

17. Effect of Amine Concentration (cont’d) • Individual temperatures 17

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) AMP MEA

19. Single AMP Single MEA Effect of Mixing Ratio (cont’d) • Individual Temperatures

20. Kinetic Model for MEA-AMP System • 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) • CO2-MEA System • CO2-AMP System • 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.

21. Overall reaction of CO2-MEA-AMP System Apparent reaction rate Kinetic Model(cont’d)

22. Speciation • [MEA], [AMP], [H2O], [OH-] • CO2 Absorption Reaction

23. Comparison (Model & Experimental data) Single AMP Single AMP Single AMP Single AMP Single AMP Single MEA Single MEA Single MEA Single MEA Single MEA

24. Conclusions • 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.

25. Further work • 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.

26. Acknowledgement • 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)

27. Thank You