CALCIUM LOOPING PROCESS FOR CLEAN FOSSIL FUEL CONVERSION Shwetha Ramkumar, Robert M. Statnick, Liang-Shih Fan William G. Lowrie Department of Chemical and Biomolecular Engineering The Ohio State University Columbus, Ohio, USA Daniel P. Connell CONSOL Energy Inc. Research & Development South Park, PA, USA 1 st Meeting of the High Temperature Solid Looping Cycles Network September 15 th September 17 th Patent Application - WO2008039783 U.S. Patent Application No. 61/116,172
Hydrogen Synthesis from Coal Steam Gasification: Coal + H 2 O CO + H 2 Equilibrium Limited Water Gas Shift Reaction (WGSR) High Steam/CO H 2 /CO ratio can be improved But can never maximize H 2 production Further CO cleanup will be required for PEM fuel Cells (ppm levels) K WGS 10000 1000 100 10 1 CO + H 2 O CO 2 + H 2 Cu MoS 2 Fe 100 200 300 400 500 600 700 800 900 1000 1100 Temperature ( 0 C)
Specific Objectives CO + H 2 O CO 2 + H 2 + CaO CaCO 3 + H 2 S CaS + H 2 O + COS CaS + CO 2 + HCl CaCl 2 + H 2 O Simultaneous WGSR, CO 2 removal, sulfur and halide capture integrated in one module High purity H 2 production Reduce excess steam requirement Remove H 2 S, COS and HCl to ppm levels Patent Application # WO2008039783 (2008)
Conventional Syngas Process Sulfur By-Product Fly Ash By-Product Slag By-Product Steigel and Ramezan, 2006
Calcium Looping Process Steam INTEGRATED WGS +H 2 S +COS + HCL CAPTURE Hydrogen Air Fuel Cell To Steam Turbine CaO CaCO 3 Hydrator Steam H 2 +O 2 Gas Turbine BFW Rotary Calciner Air Compressor Generator Gasifier Air Oxygen CO 2 HRSG Stack Slag U.S. Patent Application No. 61/116,172 Patent Application # WO2008039783 (2008) Air Separation Fuels & Chemicals Steam Turbine
Calcium Looping Process Reaction Hydrogen CaCO 3 Regeneration Pure CO 2 gas Integrated Hydrogen reactor Syngas Net Heat Output Heat Input Calciner Dehydration : Ca(OH) 2 CaO + H 2 O WGSR : CO 2 removal : CO + H 2 O CO 2 + H 2 CaO + CO2 CaCO3 Sulfur : CaO + H2S CaS + H 2O Halide : CaO + 2HX CaX 2 + H 2 O Calcination: CaCO3 CaO + CO2 Reactivation Ca(OH) 2 Hydrator Heat Output CaO H 2 O U.S. Patent Application No. 61/116,172 Patent Application # WO2008039783 (2008) Hydration : CaO + H 2 O Ca(OH) 2
Thermodynamic Analyses Equlibrium Partial Pressure (atm) 10 2 10 1 10 0 10-1 10-2 10-3 10-4 10-5 10-6 10-7 10-8 CaO + CO 2 CaCO 3 CaO + H 2 O Ca(OH) 2 Hydration Carbonation 400 600 800 1000 Temperature (C) P H2O P CO2 Equilibrium H 2 S Conc (ppm) with 30 atm total pressure 10000 1000 100 10 1 0.1 CaO+ H 2 S CaS + H 2 O 20 atm 2 atm 0.2 atm 0.02 atm CLP 0.01 400 500 600 700 800 900 1000 Temperature ( o C) Conventional IGCC Carbonation : Temperatures below 800C for a CO 2 partial pressure of.4 atm Temperatures below 1000C for a CO 2 partial pressures of 4.6 atm Sulfidation : Outlet H 2 S concentration as steam partial pressure and temperature Conventional System - 1000 ppm H 2 S Calcium looping - <1 ppm H 2 S Patent Application # WO2008039783 (2008)
Experimental Setup Combined WGSR and CO 2 Removal 500-1500 sccm 3-15 % CO Steam/CO =1:1-3:1 600 700 o C 5000 ppm H 2 S Hydrocarbon Analyzer Analyzers (CO, CO 2, H 2, H2S) Back Pressure Regulator Thermocouple Heat Exchanger Steam & Gas Mixture Steam Generator Quartz Wool Packing Sorbent & Catalyst Powder Mixture Heated Steel Tube Reactor Cold Fluid Out Water In Water Syringe Pump Mixture Mixture MFC MFC MFC MFC H 2 CO CO 2 N 2 Water Trap Cold Fluid In N 2
Catalyst/Sorbent WGS System CO Conversion (%) 1.0 0.8 0.6 0.4 0.2 0.0 Temperature ( o C) H2 Gas Composition (%) 100 14.7 0 psig Psi 20 14.7 0 psig Psi CaO Sorbent 150 psig Psi 150 Psi psig 300 psig Psi 300 Psi psig 0 500 600 700 800 0 500 1000 1500 2000 Catalyst 80 60 40 Increasing Pressure Time (sec) CO + H 2 O Catalyst CO 2 + H 2 CO + H 2 O CO 2 + H 2 CaO Patent Application # WO2008039783 (2008)
H 2 Production with H 2 S removal Non catalytic - Effect of Steam to CO ratio H2S concentration (ppm) 800 600 400 200 Steam to CO = 0.75:1 Steam to CO = 1:1 Steam to CO = 3:1 25 ppm H 2 S 8 ppm H 2 S Pressure : 14.7 Psia 0 ppm H 2 S CO Conversion 1.0 0.8 0.6 0.4 0.2 3-1 1-1 0.75-1 0 1000 2000 3000 4000 0.0 0 1000 2000 3000 Time(sec) Time(sec) CO + H 2 O H 2 +CO 2 CaO H 2 S CaCO 3 CaS Patent Application # WO2008039783 (2008)
H 2 Production with H 2 S removal Non catalytic Effect of Temperature H2S concentration (ppm) 800 600 400 200 600C 560C 650 C 700C S/C ratio = 1:1 P= 0 psig Gas Composition (%) 100 80 60 40 20 560C 600C 650C 700C 0 500 1000 1500 2000 2500 3000 Time(sec) 0 0 500 1000 1500 2000 2500 3000 Time(sec) H 2 S Outlet Concentration with Temperature Greater extent of carbonation 600-650C Lowest at 560-600C Optimum temperature for sulfidation and carbonation 600C Patent Application # WO2008039783 (2008)
H 2 Production with H 2 S removal Non catalytic Effect of Pressure H 2 S concentration (ppm) 800 600 400 200 < 1 ppm 300 psig 0 psig S/C ratio = 1:1 T = 600C 0 psig 300 psig H2 Gas Composition (%) 100 80 60 40 20 High purity H 2 300 psig 0 psig 0 psig 300 psig 0 0 1000 2000 3000 4000 5000 0 0 1000 2000 3000 4000 Time (sec) Higher pressure favors sulfidation H 2 S in the outlet 0 psig 20 ppm 300 psig <1 ppm Time(sec) High pressure favors combined carbonation and WGSR H 2 in the outlet 0 psig 70% 300 psig 99.97% Presence of calcium oxide removes equilibrium limitation of WGSR Patent Application # WO2008039783 (2008)
Sorbent Reactivity and Recyclability
Effect of Realistic Calcination Conditions 70 70 60 Wt% Capture 60 50 40 30 20 Wt% Capture 50 40 30 20 10 10 0 Original Sorbent 0% 33% 50% 0 Original Sorbent 1 2 3 Steam Concentration in Carrier Gas Number of Cycles Sorbent reactivity reduced to half during calcination Effect of sintering reduced by steam calcination Increase in steam concentration improves reactivity Calcination at 900C with 50% steam and 50% CO 2 Reduced sintering over multiple cycles Reactivity reduced to half in 4 cycles U.S. Patent Application No. 61/116,172
Reactivation of the Sorbent 60 50 50 40 Wt % Capture 40 30 Wt % Capture 30 20 20 10 10 0 Original Sorbent Calcined Sorbent Water Hydration Steam Hydration 0 Calcined Sorbent 100 psig 150 psig 300 psig Hydration Pressure Sorbent reactivity reduced to a third after calcination at 1000C Calcined sorbent regenerated completely by hydration U.S. Patent Application No. 61/116,172
Techno-Economic Evaluation CLP for High-Purity Hydrogen Production
Techno-Economic Evaluation CLP for High-Purity Hydrogen Production Compare the technical and economic performance of the Calcium Looping Process (CLP) with the performance of the conventional coal-to-hydrogen process for a commercial-scale plant Both processes modeled using a common basis Illinois No. 6 coal (27,135 kj/kg HHV, 2.5% sulfur as received) GE Energy gasifier with 226 tonne/h coal feed Hydrogen produced at 99.9% purity, 20.7 bar CO 2 compressed to 151 bar Results obtained from Aspen Plus and spreadsheet-based models This is a work-in-progress; results are preliminary
Coal-to-Hydrogen Process Coal Coal Prep and Feed Air Separation Unit Air Water Radiant Cooler Gasifier Slag Handling Slag Quench Syngas Scrubber Shift Reactors Syngas Cooling Mercury Removal 2-Stage Selexol Claus Plant Sulfur Air Boiler Pressure Swing Adsorber CO 2 Compression Dehydration Steam Turbine Flue Gas Pure H 2 CO 2
Coal-to-Hydrogen Process Coal Water Radiant Cooler Calcium Looping Process Coal Limestone Solid Waste Steam Turbine Coal Prep and Feed Gasifier Pressure Swing Adsorber Pure H 2 Air Separation Unit Slag Handling CO 2 Compression Dehydration CO 2 Air Slag
CLP Aspen Plus Process Model Process Flow Diagram MIXER FSPLIT Oxygen from ASU FSPLIT Hydrator CO 2 to Compressor FSPLIT FSPLIT RG IBBS MIXER MIXER Limestone Calciner Carbonator Syngas from Radiant Cooler Solid Waste RGIBBS Hydrogen Product RYIELD Coal
CLP Aspen Plus Process Model Key Assumptions Carbonator T = 677 C P = 22 bar Ca/C molar ratio = 1.3 All required steam provided by hydrated lime and syngas Calciner T = 840 C P = 1 bar Fuel: coal (Illinois No. 6) and PSA tailgas with oxyfiring Solids purge = 6 % Heat is recovered from the following sources for steam generation: Syngas radiant cooler Carbonator Hydrator CO 2 stream (HRSG) H 2 stream (firetube boiler and condensing heat exchanger)
Aspen Plus Modeling Results Calcium Looping Process vs. Conventional Process Conventional Calcium Looping % Coal-to-H 2 Process Difference Coal Feed Rate (tonne/h) 226 313 +38 O 2 Consumption a (tonne/h) 221 472 +114 Solid Waste (tonne/h) 23 137 +489 CO 2 Sequestered (tonne/h) 469 741 +58 Net CO 2 Emissions (tonne/h) 54 1-98 H 2 Production (tonne/h) 23 22-6 Net Electric Power (MW e ) 31 254 +719 a 95% (v/v) purity
Technical Challenges Solids Handling Scale For 1.3 Ca/C molar ratio, solids feed rate to calciner is 1705 tonne/h (by comparison, coal feed rate to gasifier is only 226 tonne/h) Ca/C ratio and solids circulation rate would be much larger without hydration Significant capital cost and maintenance requirements associated with handling this quantity of solids Small particle size Hydration results in micron-sized particles Fluidization behavior needs to be confirmed at larger scale Possible problems with thermophoresis Heat transfer to/from solids Use of gases as heat carriers Fluidized beds with downstream particle separators Effect of coal ash in calciner is uncertain Concerns about erosion, plugging, scaling, etc.
Technical Challenges Unconventional / Unproven Equipment Items High-temperature hydrator with heat recovery Turboexpander with 65 bar inlet pressure Flash calciner with oxyfuel combustion High-pressure condensing heat exchanger for H 2 stream Very large, high-temperature lockhoppers High-temperature (675 C) metallic filters with fine particles
Economic Analysis Key Assumptions 2008 U.S. dollars Capacity factor = 90% Capital charge factor = 0.175 O&M levelizing factors Coal = 1.25 Electricity = 1.19 General O&M = 1.18 Variable O&M unit cost assumptions: Coal Electric power CO 2 emission allowances Solid waste disposal Limestone $1.69 / GJ $91.10 / MWh $40.00 / tonne $17.71 / tonne $27.56 / tonne Water $0.12 / m 3 Water treatment chemicals Selexol solution Shift catalyst Claus catalyst $0.37 / kg $3.55 / L $17.45 / L $4.59 / L
Process Economic Summary Levelized Cost of Hydrogen ($/kg H 2 ) Conventional Coal-to-H 2 Capital $1.38 Calcium Looping Process < $1.99 Fixed O&M $0.22 $0.30 Coal $0.55 $0.82 Variable O&M $0.04 $0.30 Credit Net Difference in Electricity - -$1.11 Credit Net Difference in CO 2 Emissions - -$0.11 TOTAL $2.19 < $2.19 CLP Total Plant Cost must be < $1,959,000,000 to compete with conventional process
Next Steps Techno-Economic Evaluation Determine the technical feasibility and capital cost of nonconventional equipment items Optimize operating conditions for the carbonator, calciner, and hydrator Optimize solid purge and make-up rates Optimize heat integration Evaluate sulfur management Fate of sulfur in calciner Trade-offs between extent of CaS oxidation in calciner, coal demand, oxygen demand, and hydrogen production rate Perform sensitivity analyses (e.g., prices, reactor conditions, solid purge rate) and study different plant configurations (e.g., IGCC)
Calcium Looping Process Efficiently integrates the water-gas shift reaction and the removal of CO 2, sulfur species, and halides into a single reactor for high-purity hydrogen production Obviates the need for water-gas shift catalyst and excess steam Hydration reverses the effect of sintering and maintains sorbent reactivity, permitting the use of a relatively low Ca/C molar ratio Offers essentially zero CO 2 emissions and significantly greater co-production of electricity than the conventional coal-to-hydrogen process, but at the expense of increased coal and oxygen consumption Large solids handling requirement poses an operating and maintenance challenge We are currently evaluating capital costs and the technical feasibility of unconventional equipment items (e.g., hydrator with heat recovery, high-pressure turboexpander) to determine the viability of the process