1. Nottingham Fuel & Energy Centre Novel Capture Methods (sorbents, membranes and enzymes) Trevor C. Drage and Colin E. Snape School of Chemical and Environmental Engineering, University of Nottingham, University Park, Nottingham NG7 2RD trevor.drage@nottingham.ac.uk International workshop on “Power Generation and Carbon Capture and Storage in India” Delhi 2008

2. Nottingham Fuel & Energy Centre Alternative capture technologies Why? Current CO 2 capture technologies consume power and can significantly increase the cost of electricity. Need for the development of alternative low cost technologies to provide a more effective route for the capture and storage of CO 2 on a global scale. Physical and chemical solvent systems leading technologies for pre and post combustion capture respectively.

3. Nottingham Fuel & Energy Centre The Challenge Conditions for Capture Pre-combustion capture (after water gas shift) a Post-combustion capture b Gas composition CO 2 35.5 %15 – 16 % H2OH2O0.2 %5 – 7 % H2H2 61.5 %- O2O2 -3 – 4 % CO1.1 %20 ppm N2N2 0.25 %70 – 75 % SO x -< 800 ppm NO x -500 ppm H2SH2S1.1%- Conditions Temperature40 °C50 – 75 °C Pressure50 – 60 bar1 bar a Linde Rectisol, 7 th European Gasification Conference; b Pennline (2000), Photochemical removal of mercury from flue gas, NETL

4. Nottingham Fuel & Energy Centre Alternative capture technologies Range of technologies being developed Technologies to demonstrate clear competitive edge If plant is build as “capture ready” technologies can be integrated Technologies need to overcome challenges of other acids gases, SO x and NO x etc Rapid development required Risk that technologies will not scale up Source: Figueroa et al. 2008 – Int. J. Greenhouse Gas Control 2;9-20.

5. Nottingham Fuel & Energy Centre Pre-combustion capture Sorbent systems High temperature sorbents – Metal oxides (1,2), Hydrotalcite-like compounds and carbonate / silicate (3) compounds. Operate at high temp – capture combined with the water gas shift reaction (wgs) / gasification, reduced CAPEX and increased thermal efficiency + can promote wgs reaction (Li 4 SiO 4 ). Developing stable, attrition resistant, regenerable (low energy penalty), H 2 S resistant material key 1 Feng et al., 2007, Energy & Fuels, 21:426-434 2 Siriwardane et al., 2007, Prep. Pap. Am. Chem. Soc., Div. Fuel Chem. 52(2) 5. 3 Li et al., (RTI International), 22 nd + 23 rd International Pittsburgh Coal Conference. Heating cycles 323 – 1273 K Overall reaction: C + H 2 0 → H 2 + CO(steam gasification) CO + H 2 O → CO 2 + H 2 (wgs) CAM + CO 2 → CAM – CO 2 (CO 2 adsorption) CO 2 capture Source: Feng et al., (1) Cooling + separate process avoided.

6. Nottingham Fuel & Energy Centre Pre-combustion capture Sorbent systems Low temperature sorbents – Microporous materials (activated carbons (1), MOFs) after wgs reaction, direct replacement of Rectisol / Selexsol Potentially regenerate CO 2 at high pressure (TSA) – saving compression costs. 1 Drage et al., Fuel (in press) / Research Fund for Coal and Steel (CT-2006-00003) 2 DTI Cleaner coal technology programme (project 406) Feasibility study (2) based on a conservative adsorption capacity of 12 wt.% Fixed bed adsorption with pressure swing regeneration potential economic benefits over physical solvent systems Ability to produce CO 2 at relatively high pressure, (i.e 10 bar) would have a significant impact in reducing CO 2 compressor cost If higher (20+%) cyclic adsorption capacities can be achieved, TSA cycles can potentially be employed leading to significant benefits, CO 2 recovered at 30 – 40 bar. Adorption capacity increasing with surface area 40 bar 30 C

7. Nottingham Fuel & Energy Centre Pre-Combustion Capture Membranes High temperature and CO2 partial pressure operation Advantages:  Single stage separation – one-step process  Can promote reaction by shifting equilibrium (lower reaction temp)  CO 2 retained at relatively high pressure Key to efficient operation:  Permeance - determines membrane area required  Selectivity - influences % recovery of H 2 Range of membranes explored Inorganic – e.g. silica / alumina / zeolites / palladium  Improvements by surface chemistry modification of silica / alumina  Palladium high H 2 selectivity + permeability (300 – 600 C) Organic Polymers  Supported Liquid Membrane – ionic liquids (1) Source (1) Ilconich et al., 2007 J. Memb Sci (In Press) (2) IPCC Special report on CCS 2005

8. Nottingham Fuel & Energy Centre Post-combustion capture Membranes Polymeric Gas Separation Membranes Used in CO 2 removal from natural gas – low CO 2 partial pressure leads to low driving force for gas separation Illusive balance between permeability and selectivity Hybrid membrane systems Membrane acts as high surface area contactor between gas stream and solvent Avoids operational problems of conventional adsorption (flooding, foaming, channelling and entrainment), impurities blocked from reaching solvent Reduced plant size, CAPEX, gas / liquid flow rates flexible Many types of membrane explored – e.g. Facilitated transport membranes Membrane is crucial – hydrophobic, permeable, physical strength Challenges – large scale manufacture, avoiding imperfections, cost Source: Franco et al., 2006 – GHGT-8.

9. Nottingham Fuel & Energy Centre Post-combustion capture Adsorbent Development (1) Drage, T.C., Arenillas, A., Smith, K., Pevida, C., Pippo, S., and Snape, C.E. (2007) Fuel, 86, 22-31 (2) Arenillas, A., Drage, T.C., Smith, K.M, and Snape C.E. (2005). JAAP, 74, 298- 306. (3) Gray et al (2008) J. Greenhouse Gas Control, 2:3-8. Many groups developing solid sorbents for CO 2 by developing porous substrates (e.g MCM-41, SBA-15) enhanced with basic nitrogen groups (Penn State, NETL, Monash, Dartford, Nottingham etc..) Critical to operation is:  Adsorption capacity  Energy requirement for regeneration  Sorbent lifetime, attrition resistance  Cost Gray et al., (3) Flue gas Temperature Amine-CO 2 chemical adsorption CO 2 + 2R 2 NH  R 2 NH + R 2 NCOO - CO 2 + 2R 3 N  R 4 N + + R 2 NCOO - CO 2 + H 2 O +R 2 NH  HCO 3 - + R 2 NH 2 + Maximising sorption capacity key 3 – 6 mmol g -1 required to make competitive (1,2)

10. Nottingham Fuel & Energy Centre Post-combustion capture economic studies Source: Tarka et al., 2006, Prep. Pap.-Am. Chem. Soc., Div. Fuel. Chem. 51(1), 104. NETL study: based on: 90 % CO 2 removal Pressure drop < 6 psi Use of enriched amine SBA-15 substrate Adsorption offers potential cost saving over MEA scrubber Fixed bed not viable due to large footprint Nottingham study: Proposed novel moving bed design (Carbon Trust Funded) Minimising temperature difference between adsorption and regeneration key (1) System has potential to reduce capture cost Current research looking to scale-up to Kg operation 1 T.C. Drage, A. Arenillas, K.M. Smith, and C.E. Snape. Microporous and Mesoporous Materials – In Press

11. Nottingham Fuel & Energy Centre Enzymes Source: Carbozyme Inc – Proceeding of 8 th International Conference on Greenhouse Gas Control Technologies + refs within. Fast reaction rate + Low regeneration energy Fast reaction + low regeneration energy. Enzyme used by higher plants and mammals CO 2 + H 2 O → HCO 3 - + H + HCO 3 - + H + → H 2 CO 3 → CO 2 + H 2 O Reactions catalysed by carbonic anhydrase

12. Nottingham Fuel & Energy Centre Acknowledgements Thank the following for invite: Integrated Research and Action for Development (IRADe) Department for Environment Food and Rural Affairs (DEFRA) British High Commission (BHC) Ministry of Science and Technology – Government of India Engineering and Physical Science Research Council, UK (EPSRC) – Advanced Research Fellowship to TD (EP-543203/1) for funding continued research in CO 2 sorbents