Post Post-Combustion Capture of carbon dioxide by Clathrate Hydrate crystallization Rajnish Kumar 1, Praveen Linga 1, Adebola Adeyemo 1, Peter Englezos 1 and John Ripmeester 2 1. Clean Energy Research Center Department of Chemical and Biological Engineering The University of British Columbia Vancouver, BC 2. Steacie Institute for Molecular Sciences National Research Council of Canada 100 Sussex Drive Ottawa, ON

2 Post-combustion capture of CO 2 from power plants involves separation of CO 2 from flue gas Fossil Fuels COMBUSTION Flue Gas Air CO 2 capture CO 2, N 2, O 2 MIXTURE CO 2

3 Flue gas from a coal-fired power plant 15-20% CO 2, 5% O 2 and balance N 2 Low concentration of CO 2 Absorption in MEA solutions: most promising current method Development of ceramic membranes could be more efficient Aaron, D and C. Tsouris, Separation Science and Technology, 40: 321–348, 2005

The clathrate hydrate process Hydrate formation is a very new concept for CO 2 Capture that is still in lab testing (Aaron and Tsouris, 2005).

5 Gas Hydrates are Crystals waterFormed by water and small molecules like (CH 4, C 2 H 6, C 3 H 8, CO 2, N 2, O 2, H 2 ) No chemical reaction only physical bonding CO 2 hydrate 277.1K and 4.1 MPa cages H 2 O forms cages enclosing CH 4

6 FEED CO 2 /N 2 Composition of Hydrate Crystals Different than Feed Gas Hydrate Formation from gas mixtures Treated flue gas (CO 2, N 2, O 2 ) is considered a CO 2 /N 2 mixture Basic Idea/Concept Kang S.P. and H. Lee (2000),Environ. Sci. Technol.,Vol. 34, No. 20, pp

7 Laboratory scale CO 2 capture Temperature controlled water bath T2T2 Crystallizer (CR) GC DPDP GASSUPPLyGASSUPPLy Motor SV RV CR – Crystallizer DP – Differential Pressure RV – Reference VesselGC – Gas Chromatography SV – Supply VesselCV – Control Valve CV DAQ & PC Crystallizer volume: 323 cm 3 Semi-batch operation at constant T & P We can determine, Operating P-T conditions for hydrate crystallization Rate of hydrate formation Split fraction or CO 2 recovery

Post-combustion CO 2 capture CO 2 /N 2 separation via hydrate formation Flue gas mixture: 17 mol% CO 2 and rest N 2

9 Hydrate crystal formation P & T Min pressure to form crystals At T = 0.6 C, P = 7.7 MPa Pure N 2 hydrate Hydrate from Flue Gas (17% CO 2 ) phase equilibrium Pure CO 2 hydrate

10 CO 2 prefers hydrate phase Hydrate formation experiments were carried out at C and at two pressures 10 MPa and 11 MPa (Peq = 7.7 MPa)

11 CO 2 /N 2 separation & recovery at 0.6 o C Split fraction or CO 2 recovery Separation factor Gas Hydrate 83.1 mol% N mol% CO 2 Stage 1 Stage 2Stage 3

12 Post-Combustion Capture of CO 2 water Flue Gas Residual flue gas removal Hydrate layer Hydrate decomposition Gas released from hydrate decomposition (CO 2 enriched) Hydrate formation Water Hydrate Layer Water Single Stage Hydrate Process

13 Post-Combustion Capture of CO 2 Membrane Process CO 2 N 2 T = 0.6 o C P = 10 MPa T = 0.6 o C P = 5 MPa T = 0.6 o C P = 2.5 MPa Gas Hydrate Process 17% CO 2 83% N 2 H2OH2O 57% CO 2 10% CO 2 First Stage 50% CO 2 83% CO 2 Gas Hydrate Process H2OH2O Second Stage Gas Hydrate Process H2OH2O 98-99% CO 2 70% CO 2 Third Stage

14 Process Drawbacks Flue gas requires compression to high pressure (~10 MPa) for hydrate formation ~385MW (77%) of the output of a 500MW power plant required for compression alone

15 Hydrate formation pressure decreases in presence of THF 16.9 % CO 2 and rest N 2 gas mixture Min pressure to form crystals At T = 0.6 C, P = 0.35 MPa At T = 0.6 C, P = 7.7 MPa

16 CO 2 /N 2 separation & recovery at 0.6 o C (in presence of THF) Split fraction or CO 2 recovery Separation factor % THF Solution Gas Hydrate 83.1 mol% N mol% CO 2 Stage 1 Stage 2Stage 3

17. Gas Hydrate Process (1) Gas Hydrate Process (2) Gas Hydrate Process (3) Membrane Process 17 % CO 2 83 % N 2 1 mol% THF 94 % CO 2 for Disposal/Storage 10 % CO 2 37 % CO 2 28 % CO 2 62 % CO 2 70 % CO 2 CO 2 N 2 CO 2 -lean CO 2 -rich 1 mol% THF T = 0.6 o C P = 2.5 MPa T = 0.6 o C P = 2.5 MPa T=0.6 o C P= 2.5 MPa First Stage Second Stage Third Stage Post-Combustion Capture of CO 2 in presence of THF and lower pressure

18 Concluding Remarks CO 2 can be separated from flue gas by hydrate formation –CO 2 prefers the hydrate phase High purity CO 2 can be recovered from a flue gas mixture in three hydrate formation stages –Coupled with a single stage membrane process Additives such as THF (1mol% solution) reduce the hydrate formation pressure –Making it more suitable for industrial application

19 Slow kinetics due to mass transfer restriction Current Challenges water Hydrate layer Gas Slow gas diffusion through hydrate layer

20 Current challenges: work underway To determine the best contact mode between water and gas in order to speed up hydrate formation Hydrate formation with water adsorbed on silica gel Hydrate formation with micro water droplets

21 Acknowledgements Greenhouse Gas Mitigation ProgramNatural Resources Canada- Greenhouse Gas Mitigation Program Canada Foundation for Innovation (CFI) –Clean Energy Research Center

22 Compression Cost Calculated for a 500MWe PC power plant ~2,439,000kg/hr flue gas produced* Compression from atmospheric pressure to 10 MPa was considered with 4 staged compressor with equal compression ratio for each stage ~385MW would be required to achieve compression *MIT Report on The Future of Coal