Novel Capture Methods (sorbents, membranes and enzymes)

1. 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. Alternative capture technologiesWhy? • Physical and chemical solvent systems leading technologies for pre and post combustion capture respectively. • Current CO2 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 CO2 on a global scale.

3. The ChallengeConditions for Capture aLinde Rectisol, 7th European Gasification Conference; bPennline (2000), Photochemical removal of mercury from flue gas, NETL

4. 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, SOx and NOx 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. Heating cycles 323 – 1273 K CO2 capture Cooling + separate process avoided. Source: Feng et al., (1) Pre-combustion captureSorbent 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 (Li4SiO4). • Developing stable, attrition resistant, regenerable (low energy penalty), H2S resistant material key Overall reaction: C + H20 → H2 + CO (steam gasification) CO + H2O → CO2 + H2 (wgs) CAM + CO2→ CAM – CO2 (CO2 adsorption) 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), 22nd + 23rd International Pittsburgh Coal Conference.

6. Adorption capacity increasing with surface area Pre-combustion captureSorbent systems Low temperaturesorbents – Microporous materials (activated carbons(1), MOFs) after wgs reaction, direct replacement of Rectisol / Selexsol Potentially regenerate CO2 at high pressure (TSA) – saving compression costs. • 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 CO2 at relatively high pressure, (i.e 10 bar) would have a significant impact in reducing CO2 compressor cost • If higher (20+%) cyclic adsorption capacities can be achieved, TSA cycles can potentially be employed leading to significant benefits, CO2 recovered at 30 – 40 bar. 40 bar 30 C 1 Drage et al., Fuel (in press) / Research Fund for Coal and Steel (CT-2006-00003) 2 DTI Cleaner coal technology programme (project 406)

7. Pre-Combustion CaptureMembranes • High temperature and CO2 partial pressure operation • Advantages: • Single stage separation – one-step process • Can promote reaction by shifting equilibrium (lower reaction temp) • CO2 retainedat relatively high pressure • Key to efficient operation: • Permeance - determines membrane area required • Selectivity - influences % recovery of H2 • Range of membranes explored • Inorganic – e.g. silica / alumina / zeolites / palladium • Improvements by surface chemistry modification of silica / alumina • Palladium high H2 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. Post-combustion captureMembranes • Polymeric Gas Separation Membranes • Used in CO2 removal from natural gas – low CO2 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. Flue gas Temperature Amine-CO2 chemical adsorption CO2 + 2R2NH  R2NH + R2NCOO- <1> CO2 + 2R3N  R4N+ + R2NCOO- <2> CO2 + H2O +R2NH  HCO3- + R2NH2+ <3> Maximising sorption capacity key 3 – 6 mmol g-1 required to make competitive (1,2) Gray et al.,(3) Post-combustion capture Adsorbent Development • Many groups developing solid sorbents for CO2 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 (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.

10. Post-combustion captureeconomic studies • NETL study: • based on: • 90 % CO2 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 Source: Tarka et al., 2006, Prep. Pap.-Am. Chem. Soc., Div. Fuel. Chem. 51(1), 104. 1T.C. Drage, A. Arenillas, K.M. Smith, and C.E. Snape. Microporous and Mesoporous Materials – In Press

11. Enzymes Fast reaction rate + Low regeneration energy Fast reaction + low regeneration energy. Enzyme used by higher plants and mammals CO2 + H2O → HCO3- + H+ <1> HCO3- + H+ → H2CO3 → CO2 + H2O <2> Reactions catalysed by carbonic anhydrase Source: Carbozyme Inc – Proceeding of 8th International Conference on Greenhouse Gas Control Technologies + refs within.

12. 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 CO2 sorbents