Sumedh Warudkar PhD Candidate Chemical and Biomolecular Engineering

1. Evaluation of performance of various alkanolamines for CO2 capture from a pulverized coal-fired power plant Sumedh Warudkar PhD Candidate Chemical and Biomolecular Engineering

2. Outline • The CO2 problem • Current CO2 capture technology • Scope of Study • Amine Absorption Process • Comparison of absorbents properties • Comparison of Energy Consumption • Comparison of Absorber and Stripper Sizing • Comparison of Rich Amine Loading • Contribution of various processes and utilities to energy consumption • Conclusions

3. The CO2 problem Fig 1. Worldwide energy consumption in TW (2004) Fig 2. Atmospheric CO2 variation (1860-2000)

4. Current CO2 Capture Technology Figure 2.a. Membrane Separation Figure 2.b. Gas Adsorption Figure 2.c. Gas Absorption

5. Scope of Study • With available technology, CCS will increase the cost of electricity from a conventional power plant by 21% - 91%.7 • Current technology for CO2 separation was designed primarily for natural gas sweetening – high pressure feed gas, large variance in acid gas (CO2, H2S) content and generates value added product. • Problem at hand involves power plant flue gas – near atmospheric, low variance in CO2 content and will be a parasitic load for electricity generation utilities. • Due to the low variance in flue gas composition, it might be possible to come up with a generic “best” absorbent for CO2 capture. • Need to better optimize current technology by changing process parameters.

6. Amine Absorption Flow-sheet

7. CO2 compression train

8. Simulation Parameters

9. Amine AbsorbentsComparison Monoethanolamine (MEA) Advantage • Primary amine with very high reaction rate with CO2 • Low amine circulation rate • Low molecular weight Drawbacks • High heat of reaction • MEA concentrations above 30-35% (wt) are corrosive • Highly corrosive at CO2 loadings above 0.35-0.4 • Highly volatile Diglycolamine (DGA) Advantage • High DGA concentrations around 50-70% (wt) can be used due to low volatility • High reaction rate with CO2 • Low amine circulation rate Drawbacks • High heat of reaction • Highly corrosive at CO2 loadings above 0.35-0.4 Diethanolamine (DEA) Advantage • Low volatility • Low heat of reaction Drawbacks • High amine circulation rate • Secondary amine, low reaction rate • DEA concentrations above 30-35% (wt) are corrosive • Forms highly corrosive at CO2 loadings above 0.35-0.4. Reacts irreversibly with O2 in flue gas. 2-amino-2-methyl-1-propanol (AMP) Advantage • High theoretical CO2 loading capacity • Low volatility and few corrosion problems • Low heat of reaction Drawbacks • Very low reaction rate • High amine circulation rate • High steam consumption to heat amine solution in stripper

10. Reaction Rate Constant & Heat of Reaction

11. Energy Required for CO2 captureEffect of Amine Absorber Entry Temperature (MEA & DEA 40% wt)

12. Energy Required for CO2 captureComparison of Effect of Stripper Pressure on MEA & DGA

13. Energy Required for CO2 captureComparison of Effect of Stripper Pressure on DEA & AMP

14. Stripper DiameterComparison of Effect of Stripper Pressure on MEA & DGA

15. Stripper DiameterComparison of Effect of Stripper Pressure on DEA & AMP

16. CO2 loading of Rich Amine LoadingComparison of DEA-AMP

17. CO2 loading of Rich Amine LoadingComparison of DEA-AMP

18. Energy ConsumptionContribution of various processes and utilities

19. CO2 CompressionEffect of stripper pressure on specific volume of compressed vapor and energy consumption

20. Conclusions • 4 amines – MEA, DEA, DGA and AMP were compared to evaluate their performance for CO2 capture application. • 3 absorber-stripper train configuration was investigated for 90% CO2 removal from 500 MW coal fired power plant flue gas. This permits estimation of reasonable absorber and stripper sizes. • MEA and DGA require only 2 ideal (6 real) stages to achieve 90%+ CO2 capture. • DEA requires 10 ideal (30 real) stages to achieve 90% CO2 capture. • AMP requires a 10 absorber/stripper train to achieve 90% CO2 capture with reasonable absorber/stripper sizes. • Increasing the stripper pressure from 1.5 atm to 3 atm results in a 40% decrease in the energy consumption of CO2 capture (separation + compression) on an average. Compression duty reduces by 25% on an average. • Based on these considerations, DGA is the absorbent of choice across all stripper pressures. It has a high reaction rate, it can be used in concentrations up to 60-70% and is non-volatile.

21. Acknowledgements • Prof. George Hirasaki Prof. Mike Wong and Prof. Ken Cox. • Dr. Brad Atkinson and Dr. Peter Krouskop from Bryan Research and Engineering • Loewenstern Graduate Fellowship • Energy and Environmental Systems Institute (EESI) at Rice University • Rice Consortium on Processes in Porous Media • Schlumberger • Office of Dean of Engineering, Rice University • Hirasaki Group & Wong Group members

22. References • ProMax Foundations, Bryan Research and Engineering. • Vaidya, CO2-Alkanolamine Reaction Kinetics: A review of recent studies, Chem. Eng. Technol (2007), 30, No 11, 1467-1474. • Alper, Kinetics of Reactions of Carbon Dioxide with Diglycolamine and Morpholine, Chem. Eng. J, (1990), 44, 107-111. • http://msdssearch.dow.com/PublishedLiteratureDOWCOM/dh_017d/0901b8038017d302.pdf?filepath=amines/pdfs/noreg/111-01375.pdf&fromPage=GetDoc • http://msdssearch.dow.com/PublishedLiteratureDOWCOM/dh_004e/0901b8038004e5da.pdf?filepath=angus/pdfs/noreg/319-00016.pdf&fromPage=GetDoc • http://www.bre.com/portals/0/technicalarticles/Selecting%20Amines%20for%20Sweetening%20Units.pdf • D. Aaron and C. Tsouris. Separation of CO2 from flue gas: a review. Separation Science and Technology, 40(1):321, 2005.

23. Questions