SORPTION-ENHANCED REFORMING OF NATURAL GAS FOR PRE- COMBUSTION DECARBONISATION

Transcription

1 ECN-RX SORPTION-ENHANCED REFORMING OF NATURAL GAS FOR PRE- COMBUSTION DECARBONISATION R.W. van den Brink H.T.J. Reijers P.D. Cobden R. Smit D. Jansen A. de Groot Presented at the International CO2 Capture Network. 10 September, 2004, Vancouver, Canada APRIL 2005

2 Sorption-Enhanced Reforming of natural gas for PRE-Combustion Decarbonisation Ruud van den Brink, Rick Reijers, Paul Cobden, Ruben Smit, Daniel Jansen, Arend de Groot Energy research Centre of The Netherlands Vancouver, 10 September 2004 Greenhouse gas mitigation is essential to the Energy Research Centre of the Netherlands Petten Amsterdam

3 ECN Priority Areas Biomass Solar Energy Wind Energy Renewable Energy in the Built Environment Fuel Cell Technologies Policy Studies Clean Fossil Fuels Energy Efficiency in Industry ECN Priority Areas Biomass Solar Energy Wind Energy Renewable Energy in the Built Environment Fuel Cell Technologies Policy Studies Clean Fossil Fuels Energy Efficiency in Industry

4 Pre-combustion decarbonisation Coal Natural Gas gasification reforming CO + H 2 CO + H 2 Water-gas Shift Storage H 2 + CO 2 Separation GT, Fuel Cell CO 2 H 2 Separation-enhanced reactors Steam reforming: CH 4 + H 2 O 3 H 2 + CO (ΔH = 206 kj/mol) Water-gas shift: CO + H 2 O H 2 + CO 2 (ΔH = - 41 kj/mol) CH H 2 O 4 H 2 + CO 2 CH 4 + H 2 O CH 4 + H 2 O H 2 H 2 Pd-membrane catalyst CO 2 + H 2 O Membrane reactors H 2 SMR-catalyst + CO 2 adsorbent Sorption-enhanced reactors

5 Sorption Enhanced Reaction Process (SERP) CH H 2 O 4 H 2 + CO 2 CH 4 + H 2 O H 2 + CO 2 CO 2 CO 2 CO 2 catalyst adsorbent catalyst adsorbent CO2 CO2 Conventional steam reforming of natural gas CH 4 + H 2 O flue gas H 2 O reformer HT shift LT shift PSA H 2 CH 4 burner CH 4,H 2 O, CO, CO 2

6 Sorption-enhanced reforming CH 4 + H 2 O SER reactor 1: adsorption mode burner H 2, CH 4 CH 4 PSA H 2 CO 2 + H 2 O SER reactor 2: desorption mode H 2 O Sorption-enhanced reforming CO 2 + H 2 O SER reactor 1: desorption mode H 2 O burner H 2, CH 4 CH 4 PSA H 2 CH 4 + H 2 O SER reactor 2: adsorption mode

7 Results SERP Base case system analysis Three main challenges: - High conversion of CH 4 (>95%) needed - Reduction of CO 2 stripping steam - 85% CO 2 capture High Approach - Improved/new catalyst and adsorbent - Process optimization (cycle times) - Innovative system configurations Experiments and Materials Experimental conditions ml/min flows grams adsorbent - pressure 1 to 5 bar(a) A s Materials s - Commercially e available (pre)reform s catalysts or WGS catalysts s m - Hydrotalcite adsorbents e n

8 Adsorbent: hydrotalcite Al(OH) 6 -octahedron general formula: Mg 1-x Al x (OH) 2 (CO 3 ) x/2.nh 2 O Promoted with K 2 CO 3 H 2 O Mg(OH) 6 -octahedron CO 3 2- High average CH 4 conversion over 100 cycles Reaction conditions: 2.9% CH 4, 17.5% H 2 O, 79.5% N 2, 400 C 9 100% 8 Average CH 4 conversion during 400 C Equilibrium CH 4 conversion at 800 C 90% 80% CO 2 uptake/release [ml] 7 6 adsorbed CO 2 Equilibrium CH 4 conversion at 400 C 70% 60% 50% 40% 30% CH 4 conversion [%] 5 desorbed CO 2 20% 10% 4 0% Cycle

9 Typical experiment steam reforming of methane 1.0 Reaction conditions: 2.9% CH 4, 17.5% H 2 O, 79.5% N 2, 400 C ads desorption ads desorption ads desorption ads 100% CH4,CO2,CO concentration [vol%] CH4 CO2 Conversion 90% 80% 70% 60% 50% 40% 30% 20% CH4 conversion [%] % 0.0 0% Time [min] Breakthrough of methane before CO 2 Long tail in desorption Efficiency Improvement in Water-Gas Shift Reaction CO + H 2 O H 2 + CO 2 Reaction conditions: 16% CO, 14.5% H 2 O, 2.5% CO 2, 12% H 2, 65% N 2, 400 C Concentration [%] Equilibrium CO Conversion CO Conversion Using Dummy Adsorbent CO conversion CO 2 concentration Conversion [%] 2 CO concentration Time [min] : New catalyst sorbent combination mix of htc and pre-reforming catalyst 0

10 Regeneration of CO 2 -loaded adsorbent CO 2 [ml/min] Reaction conditions: 29% H 2 O in N C CO2 (ml/min) Time (min) blank 1stcycle 10th cycle 20th cycle 30th cycle 40th cycle Time [min] Modeling of the adsorption: Langmuir isotherm c Adsorption z c Desorption z For complete regeneration > 50 moles steam per mole CO 2 adsorbed is needed

11 Systems modeling Hot flue gas Extra Recycle Recycle Hot flue gas External burner Non-used feed steam H2 CH4 Steam production CH4 Feed Feed Reaction heat SER Adsorption mode Steam CH4, H2 PSA Product H2 Steam CO2 Steam Purge SER Desorption mode Steam Non-used purge steam Systeemberekeningen steam/co 2 PSA ratio (-) feed steam purge steam H 2 production CO 2 capture Low steam demand very important - lower desorption pressure - shallow desorption = input = result = changed parameter S/C 6 T = 491 C P ads = 1.7 bar kat/ads =2:3 (w/w)

12 Effect of shallow desorption Desorption percentage [%] min ads 10 min des 10 min ads 25 min des 10 min ads 75 min des 75 min adsorption 75 min desorption Cumulative purge flow [mol purge gas/mol adsorbed CO 2 ] Systeemberekeningen steam/co 2 PSA ratio (-) feed steam purge steam H 2 production CO 2 capture Low steam demand very important - lower desorption pressure - shallow desorption - novel adsorbents = input = result = changed parameter S/C 6 T = 491 C P ads = 1.7 bar kat/ads =2:3 (w/w)

13 Development of novel adosrbents Modification of adsorbent: - Promising new hydrotalcites and promoters found Alkali metal carbonates - Further development on going in cooperation with Utrecht University Conclusions and future work SERP Conclusions - Methane conversion > 98% feasible at T=400 C - < 100 ppm levels of CO, CO 2 in H 2 gas - CO 2 removal of 85 % feasible R&D issues - Steam/CO 2 ratio < 5 (shallow ad- desorption mode) - Integration in GT-cycle - Reactor design CH4 20 mol kj (feed) + 2 mol 2148 kj (reactie) η = 80 % 122 mol 4882 kj (feed) mol 4661 kj (purge) SER CH4 conversie = 66 % SER (ATR) + Compressor + Turbine H2O CH4,H2 N2,CO 54 mol kj (H2) + 7 mol 6086 kj (CH4) Steam 1588 kj 40 mol (non-used steam) LP AIR Compressor Combustion Chamber HP AIR Rendement =?? % Turbine 17 mol Hot flue gas Electricity CO2

14 Acknowledgements Colleagues and co-workers Sponsors: CATO project Netherlands Ministry of Economic Affairs