Calcium Enhanced H 2 Production with CO 2 Capture Douglas P. Harrison Voorhies Professor Emeritus Cain Department of Chemical Engineering Louisiana State University Baton Rouge, LA USA ISCR 2008 Imperial College July 2008

Potential Applications Hydrogen Production: ≈95% to >99% Electricity Generation: from CH 4 from coal Other Candidate Sorbents K-Hydrotalcite Mixed metal oxides of: Lithium Sodium

Reforming CH 4 (g) + H 2 O(g) ↔ CO(g) + 3H 2 (g) ∆H r o = 226 kJ/mol CH 4 Shift CO(g) + H 2 O(g) ↔ CO 2 (g) + H 2 (g) ∆H r o = -38 kJ/mol CO Carbonation CO 2 (g) + CaO(s) ↔ CaCO 3 (s) ∆H r o = -178 kJ/mol CO 2 Overall CH 4 (g) + 2H 2 O(g) + CaO(s) ↔ 4H 2 (g) + CaCO 3 (s) ∆H r o = -13 kJ/mol CH 4 Calcium Enhanced Hydrogen Production

Potential Advantages Simplification (or in some cases elimination) of the H 2 purification section. Elimination of the shift reactor(s) and shift catalysts. Replacement of high temperature, high alloy steels in the reforming reactor with less expensive materials of construction. Reduction or possible elimination of carbon deposition in the reforming reactor. Reduced energy requirement.

Thermodynamics

Equilibrium H 2 as Function of T and P

Product Impurities at 15 bar

Reactor Packing 6.70 g CaO 7.00 g catalyst P = 15 atm Feed CH 4 6% H 2 O 24% N 2 70% Feed Rate 500 cm 3 (STP)/min Postbreakthrough Prebreakthrough 100 % Conversion of CH 4 to H 2 Mol Percent H 2 (Dry Basis) Temperature, o C Fixed-Bed Reactor Results at 15 bar (Balasubramanian et al., 1999)

Fixed-Bed Reactor Results at 1 bar (Yi and Harrison, 2005) 96.4% H 2 50 ppmv CO

Fluidized-Bed Results at 600 o C, 1 atm, and S/C =3 (Johnsen et al., 2006)

Time, min Sulfur Impurity in the Sorbent (Lopez et al., 2001)

Regeneration for Multicycle Operation This is where the problems arise. Researchers are studying: Naturally occurring sorbents (limestone and dolomite). Synthetic sorbents. Sorbent reactivation.

Carbonation Calcination Temperature, oC oC CaO(s) + CO 2 (g)  CaCO 3 (s) Equilibrium CO 2 Pressure, bar Regeneration Thermodynamics P CO2 = 0.1 bar T > 750 o C P CO2 = 1 bar T > 850 o C P CO2 = 15 bar T > 1100 o C

Performance Deterioration With Naturally Occurring Sorbents (Bandi et al., 2002)

500-Cycle Results (Grasa and Abanades, 2006) Piasek Limestone: Calcination 850 o C 1 atm 5 min Carbonation 650 o C 1 atm 5 min P CO2 = 0.01 Mpa in air (both steps)

1000-Cycle Results (Sun et al., 2008) Carbonation 100% CO o C Calcination 100%N o C Asymptotic limit of 17% carbonation with 15 min carbonation time.

Synthetic Sorbent: CaO (75%) and Ca 12 Al 14 O 33 (25%): (Li et al., 2006) CaO-CA o C calcination during preparation Carbonation: 650 o C, 1 atm, 16% CO 2 /N 2, 30 min Calcination 850 o C, 1 atm 100% N 2 5 min

Synthetic Sorbent: 90% CaO/10% Al 2 O 3 (Stevens et al., 2007) 420-cycle experimental data was curve fit and extrapolated to 4380 cycles (1 year operation) to give a predicted capacity of 18.5% CO 2. Oxide powers produced using spray conversion powder technology by Cabot Superior MicroPowders. Carbonation: 600 o C, 1 atm, 100% CO 2, 1 hr Calcination: 800 o C, 1 atm, 100% N 2, 30 min

Steam Activation: Ca(OH) 2 Formation 20 calcination-carbonation cycles without activation Calcination 850 o C, 1 atm, 100% N 2, 30 min Carbonation 650 o C, 1 atm, 20%CO 2 /N 2 Activation Parr bomb, 200 o C, 30 min, saturated steam (Manovic & Anthony, 2007)

Reactivation with Humid Air (Fennell et al., 2007) Three Limestones: Havelock, Purbeck, Cadomin Fluid Bed Carbonation: 750 o C, 1 atm 14% CO 2 in N 2 Calcination: 750 o C, 1 atm 100% N 2 Hydration: Overnight at 20 o C, 1 atm, in Air with P CO2 ≈0.023 bar

SEHP Process With Steam Activation ReformerRegenerator Hydrator Regeneration Gas Spent Sorbent Regenerated Sorbent Hydrogen Product Regeneration Gas + CO 2 Natural Gas/Steam Sorbent Purge Sorbent Makeup Regeneration Energy

Regeneration Energy Options Regeneration Gas Energy Input Fuel/Oxidant Comment CO 2 Indirect H 2 /Air Max Temp/ Direct H 2 /O 2 No H 2 O CO 2 /H 2 O Indirect H 2 /Air Direct CH 4 /O 2 H 2 O Indirect H 2 /Air Min Temp/ Direct CH 4 /O 2 Max H 2 O

Process Analysis CH 4 to H 2 -- (Ochoa-Fernandes et al. 2006) CH 4 to Electricity – (Reijers et al., 2006) Coal to Electricity – (MacKenzie et al., 2007) Coal to Electricity – (Li et al., 2008)

CH 4 to H 2 (Ochoa-Fernandes et al., 2006) SMRSESMR-CaO Reformer1mol CH 4, 1193K, 25 bar, S/C =2.31 mol CH 4, 848K, 10 bar, S/C =3 Reformer HeatPSA Off-gas mol CH 4 in O HT Shift623K, 25 bar----- LT Shift423 K, 25 bar----- Sorbent Regenerator K, 1 bar, steam Regenerator Heat-----PSA Off-gas mol CH 4 in O 2 Product Compressor bar PSA303 K, 25 bar H 2 in Feed77%94% H 2 Product Recovery90% H 2 Product Purity99.9%99.8% Carbon Capture79%100% Thermal Efficiency (w/o CO 2 Capture)86% (vs. 88% literature)82% Net Efficiency (w CO 2 Capture)71%79%

CH 4 to Electricity (Reijers et al., 2006) Design Basis: Natural gas combined cycle based on 380 MWe Siemens V94.3A gas turbine coupled with steam cycle Standard steam-methane reforming: η = 57.1% without CO 2 capture η = 48% with 85% CO 2 capture using MEA Sorption Enhanced H 2 Production using CaO sorbent: Hydrogen Production: 600 o C, 17 bar, H 2 O/CH 4 = 3 Sorbent Regeneration: 1000 o C, 17 bar, H2O/CO 2 = 1.8 η = 52.6% with 85% CO 2 capture

Coal to Electricity (MacKenzie et al. 2007) Order-of-Magnitude Economic Study 360 MWe Pressurized Fluid Bed Combustor 85% CO 2 Capture Capture Cost $23.70/metric ton CO 2 (Canadian) MEA Capture Cost $39 – $96/metric ton CO 2 (range from 11 literature sources)

Sensitivity Analysis (MacKenzie et al., 2007) Reference Case Parameters Limestone Cost $25/tonne CaO Recycle Rate 92.5% Ca/C Ratio 4 CaO Deactivation Rate 15%/cycle

Coal to Electricity (Li et al., 2008) ProcessCOE, ¢/kWhη, % HHV *Amine, subcritical *Amine, supercritical *Amine, ultra supercritical *Oxyfuel IGCC Limestone (X = 0.1) Dolomite (X = 0.14) CaO/25Ca 12 Al 14 O 33 (X = 0.27) * Results from Beer, 2007

Conclusions H 2 Production All looks good. Sorbent Regeneration No problem. Sorbent Durability Good progress. Process Simulation Favorable numbers.

References Balasubramanian, B. et al., Hydrogen from Methane in a Single –Step Process, ChemEngSci, 1999, 54, 3543 Yi, K., Harrison D., Low Pressure Sorption Enhanced Hydrogen Production, IECRes., 2005, 44, 1665 Lopez, A., Harrison, D., Hydrogen Production Using Sorption Enhanced Reaction, IECRes, 2001, 40, 5102 Johnsen, K. et al., Sorption Enhanced Steam Reforming of Methane in a Fluidized Bed Reactor, ChemEngSci, 2006, 61, 1195 Bandi, A. et al., In Situ Gas Conditioning on Fuel Reforming for Hydrogen Generation, Proc. 5 th Intl Symp Gas Cleaning, Pittsburgh, Sept Grasa, G.S., Abanades, J.C. CO 2 Capture Capacity of CaO in Long Series of Carbonation/Calcination Cycles, IECRes., 2006, 45, 8846 Sun, P. et al., Cyclic CO 2 Capture of Limestone-Derived Sorbent During Prolonged Calcination/Carbonation Cycling, AIChE J., 2008, 54, 1668 Li, Z. et al., Effect of Preparation Temperature on Cyclic CO 2 Capture and Multiple Carbonation-Calcination Cycles for a New Ca-Based CO 2 Sorbent, IECRes., 2006, 45, 1911 Stevens, J.F. et al., Development of 50 kW Fuel Processor for Stationary Fuel Cell Applications, Final Report, DOE/GO/ , 2007 Manovic, V., Anthony, E.J. Steam Reactivation of Spent CaO-Based Sorbent for Multiple CO 2 Capture Cycles, EnvSciTech., 2007, 41, 1420

References (cont) Fennell, P. S., Davidson, J. F., Dennis, J.S., and Hayhurts, A. N., Regeneration on Sintered Limestone for the Sequestration of CO 2 from Combustion and Other Systems, JInstEnergy, 2007, 80, 116 Ochoa-Fernandez, E., Haugen, G., Zhao, T., Ronning, M., Aartun, I., Borresen, B., Rytter, E., Ronnekleiv, M., and Chen, D. Process Design Simulation of H 2 Production by Sorption Enhanced Steam Methane Reforming: Evaluation of Potential CO 2 Acceptors, GreenChem, 2007, 9, 654 Reijers, H., van Beurden, P., Elzinga, G., Kluiters, S., Dijkstra, J., van den Brink, R. A New Route for Hydrogen Production with Simultaneous CO 2 Capture, World Hydrogen Energy Conference, Lyon, France, 2006 MacKenzie, A., Granatstein, D., Anthony, E., and Abanades, J., Economics of CO 2 Capture Using the Calcium Cycle with a Pressurized Fluidized Bed Combustor, EnergyFuels, 21, 920, Li, Z., Cai, N., and Croiset, E., Process Analysis of CO 2 Capture from Flue Gas Using Carbonation/Calcination Cycles, AIChE J, 2008, (online early publication) Beer, J., High Efficiency Electric Power Generation. The Environmental Role, ProgrEnergy & Comb Sci., 2007, 33, 107. More details: Harrison, D., Sorption Enhanced Hydrogen Production: A Review, IECRes, accepted for publication, May 2008