CO2 Separation from Flue Gas Using Carbonation/Calcination
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
1st Meeting of the High Temperature Solid Looping Cycles Network September 15th –September 17th
Patent Application - WO2008039783 U.S. Patent Application No. 61/116,172
Hydrogen Synthesis from Coal
Steam Gasification: Coal + H2O Æ CO + H2
Equilibrium Limited Water Gas Shift Reaction (WGSR)
¾ High Steam/CO CO + H2O Æ CO2 + H2 10000
¾ H2/CO ratio can be
improved 1000 ¾ But can never Cu maximize H2 100 WGS production K MoS2 ¾ Further CO cleanup 10 Fe will be required for
PEM fuel Cells (ppm 1 levels) 100 200 300 400 500 600 700 800 900 1000 1100
Temperature0 (C) Specific Objectives
CO + H2O Æ CO2 + H2
+ + H2S Æ CaS + H2O CaO + COS Æ CaS + CO2 + HCl Æ CaCl2 + H2O
CaCO3
¾ Simultaneous WGSR, CO2 removal, sulfur and halide capture integrated in one module
¾ High purity H2 production ¾ Reduce excess steam requirement
¾ Remove H2S, 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
INTEGRATED
WGS +H2S Steam +COS + HCL Hydrogen Air CAPTURE Fuel Cell
To Steam CaO Gas Turbine Turbine Steam CaCO 3 H2+O2 Hydrator Rotary BFW Air Generator Calciner Compressor
CO2 HRSG Air Oxygen Gasifier Stack
Fuels & Chemicals Slag Air Steam Separation Turbine U.S. Patent Application No. 61/116,172 Patent Application # WO2008039783 (2008) Calcium Looping Process
CaCO Reaction 3 Regeneration
Hydrogen Pure CO 2 gas
Integrated Hydrogen Net Heat Output Heat Calciner reactor Input Syngas
Dehydration : Ca(OH)2 Æ CaO + H2O Calcination: CaCO3 Æ CaO + CO2 WGSR : CO + H2O Æ CO2 + H2 CO2 removal : CaO + CO2 Æ CaCO3 Sulfur : CaO + H2S Æ CaS + H 2 O Æ Halide : CaO + 2HX CaX2 + H2O
Reactivation
Heat CaO Ca(OH)2 Hydrator Output
H2O
Hydration : CaO + H2O Æ Ca(OH)2 U.S. Patent Application No. 61/116,172 Patent Application # WO2008039783 (2008) Thermodynamic Analyses
CaO + CO 2 CaCO 3 CaO + H O Ca(OH) CaO+ H2S CaS + H2O 102 2 2 10000 20 atm 101 Hydration 2 atm 1000 Conventional 0 0.2 atm 10 0.02 atm IGCC -1 10 100 -2 10 Carbonation S Conc (ppm)S Conc 10-3 2 10
10-4 1 10-5
-6 10 P H2O 0.1 CLP -7 10 with total 30 atm pressure P CO2 H Equilibrium 0.01 -8 10 400 500 600 700 800 900 1000 400 600 800 1000 Equlibrium Partial Pressure (atm) Pressure (atm) Partial Partial Equlibrium Equlibrium o Temperature (C) Temperature ( C)
Carbonation : Sulfidation : ¾Outlet H S concentration as steam partial ¾Temperatures below 800C for a CO2 2 partial pressure of .4 atm pressure and temperature
¾Temperatures below 1000C for a CO2 ¾Conventional System - 1000 ppm H2S
partial pressures of 4.6 atm ¾Calcium looping - <1 ppm H2S
Patent Application # WO2008039783 (2008) Experimental Setup Combined WGSR and CO2 Removal Thermocouple Steam Generator •500-1500 sccm Mixture •3-15 % CO Steam & Mixture Gas Mixture Water In •Steam/CO =1:1- 3:1 Quartz •600 – 700 oC Wool Packing •5000 ppm H S 2 Sorbent & Catalyst Powder MFC MFC MFC MFC Mixture H CO CO N Hydrocarbon Heated Steel Tube 2 2 2 Analyzer Reactor Back Pressure Regulator Cold Fluid Out Analyzers (CO, Heat CO , H , H2S) Water Syringe 2 2 Exchanger Pump
Water Trap Cold Fluid In
N2 Catalyst/Sorbent WGS System
1.0 100 Increasing 0.8 80 Pressure
0.6 60
0.4 40 CO Conversion (%) CO Conversion 0.2 0 psig
H2 GasComposition (%) 14.7 Psi Catalyst 14.70 psig Psi 20 CaO Sorbent 150 psigPsi 150150 Psipsig 300 psigPsi 300300 Psipsig 0.0 0 500 600 700 800 0 500 1000 1500 2000
Temperature (oC) Time (sec)
Catalyst CO + H2O CO2 + H2 CO + H2O CO2 + H2 CaO
Patent Application # WO2008039783 (2008) H2 Production with H2S removal Non catalytic - Effect of Steam to CO ratio
Pressure : 14.7 Psia 1.0 Steam to CO = 0.75:1 800 3-1 Steam to CO = 1:1 Steam to CO = 3:1 1-1 0.8 0.75-1
600
0.6
400 25 ppm H2S 8 ppm 0 ppm 0.4
H2S H2S CO Conversion 200 0.2 H2S concentration (ppm) H2S concentration
0 0.0 1000 2000 3000 4000 0 1000 2000 3000 Time(sec) Time(sec) H S CO + H2O H2 +CO2 2
CaO CaCO3 CaS
Patent Application # WO2008039783 (2008) H2 Production with H2S removal Non catalytic – Effect of Temperature
800 100 600C 560C 560C 600C 650 C 650C 700C 80 700C 600
60
400 S/C ratio = 1:1 P= 0 psig 40
200 Gas Composition (%) 20 H2S concentration (ppm) concentration H2S
0 0 500 1000 1500 2000 2500 3000 0 500 1000 1500 2000 2500 3000 Time(sec) Time(sec)
¾H2S Outlet Concentration with Temperature ¾Greater extent of carbonation 600-650C
¾Lowest at 560-600C
¾ Optimum temperature for sulfidation and carbonation– 600C
Patent Application # WO2008039783 (2008) H2 Production with H2S removal Non catalytic – Effect of Pressure
800 100 300 psig 0 psig 0 psig High purity H2 80 300 psig 600 0 psig
60 300 psig 400 S/C ratio = 1:1 T = 600C 40
200 0 psig S concentration (ppm) S concentration 2
300 psig H2 Gas Composition(%) 20 H < 1 ppm
0 0 0 10002000300040005000 0 1000 2000 3000 4000 Time (sec) Time(sec) ¾Higher pressure favors sulfidation ¾High pressure favors combined carbonation and WGSR ¾H2S in the outlet ¾0 psig – 20 ppm ¾H2 in the outlet ¾300 psig <1 ppm ¾0 psig – 70% ¾300 psig – 99.97% ¾Presence of calcium oxide removes equilibrium limitation of WGSR
Patent Application # WO2008039783 (2008) Sorbent Reactivity and Recyclability Effect of Realistic Calcination Conditions
70
70 60 60 50 50 40
40 30 30 20 20 Capture Wt% Wt% Capture Wt%
10 10
0 0 Original 0% 33% 50% Original 123 Sorbent Sorbent Steam Concentration in Carrier Gas Number of Cycles
¾Sorbent reactivity reduced to half during calcination ¾Calcination at 900C with 50% steam and 50% CO2 ¾Effect of sintering reduced by steam calcination ¾Reduced sintering over multiple cycles ¾Increase in steam concentration improves reactivity ¾Reactivity reduced to half in 4 cycles
U.S. Patent Application No. 61/116,172 Reactivation of the Sorbent
60 50
50 40 e 40 30
30 20 Wt % Capture Wt % Wt % Captur % Wt 20 10
10 0 Calcined 100 psig 150 psig 300 psig 0 Sorbent Original Calcined Water Steam Hydration Pressure Sorbent Sorbent Hydration Hydration
¾Sorbent reactivity reduced to a third after calcination at 1000C ¾Calcined 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
¾ 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
¾ 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 compressed to 151 bar 2
¾ Results obtained from Aspen Plus® and spreadsheet-based models
¾ This is a work-in-progress; results are preliminary Coal-to-Hydrogen Process
Quench Steam Air Turbine Coal Water Syngas Scrubber Radiant Cooler Shift Reactors Boiler Flue Gas Coal Prep and Feed Syngas Cooling Pressure Gasifier Swing Pure H2 Mercury Adsorber Removal Air Separation 2-Stage Unit CO2 Selexol Compression CO2 Dehydration Slag Handling Claus Air Plant Sulfur Slag Coal-to-Hydrogen Process
Steam Turbine Coal Water Calcium Coal Radiant Looping Limestone Cooler Process Solid Waste
Coal Prep and Feed
Pressure Gasifier Swing Pure H2 Adsorber Air Separation Unit CO2 Compression CO2 Dehydration Slag Handling
Air Slag CLP Aspen Plus® Process Model Process Flow Diagram
Oxygen FSPLIT Hydrator from ASU
FSPLIT MIXER
CO2 to
Compressor FSPLIT MIXER RG I BBS
Syngas from Limestone Radiant MIXER Carbonator Cooler Calciner
FSPLIT
Hydrogen Product Solid Waste RGIBBS
RYIELD
Coal CLP Aspen Plus® Process Model Key Assumptions ¾ Carbonator – T = 677 °C – P = 22 bar
– Ca/C molar ratio = 1.3 – All required steam provided by hydrated lime and syngas
¾ Calciner – T = 840 °C – P = 1 bar
– Fuel: coal (Illinois No. 6) and PSA tailgas with oxyfiring
¾ Solids purge = 6 %
¾ Heat is recovered from the following sources for steam generation: – Syngas radiant cooler – Carbonator – Hydrator – CO stream (HRSG) 2 – H2 stream (firetube boiler and condensing heat exchanger)
Aspen Plus® Modeling Results Calcium Looping Process vs. Conventional Process
Conventional Calcium Looping %
Coal-to-H2 Process Difference Coal Feed Rate (tonne/h) 226 313 +38
a O2 Consumption (tonne/h) 221 472 +114
Solid Waste (tonne/h) 23 137 +489
CO2 Sequestered (tonne/h) 469 741 +58
Net CO2 Emissions (tonne/h) 54 1 -98
H2 Production (tonne/h) 23 22 -6
Net Electric Power (MWe) 31 254 +719 a95% (v/v) purity Technical Challenges Solids Handling ¾ 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
¾ Small particle size – Hydration results in micron-sized particles – Fluidization behavior needs to be confirmed at larger scale – Possible problems with thermophoresis
¾ Heat transfer to/from solids – Use of gases as heat carriers – Fluidized beds with downstream particle separators
¾ Effect of coal ash in calciner is uncertain
¾ Concerns about erosion, plugging, scaling, etc. Technical Challenges Unconventional / Unproven Equipment Items
¾ High-temperature hydrator with heat recovery
¾ Turboexpander with 65 bar inlet pressure
¾ Flash calciner with oxyfuel combustion
¾ High-pressure condensing heat exchanger for H2 stream
¾ Very large, high-temperature lockhoppers
¾ High-temperature (675°C) metallic filters with fine particles Economic Analysis Key Assumptions ¾ 2008 U.S. dollars ¾ Capacity factor = 90% ¾ Capital charge factor = 0.175 ¾ O&M levelizing factors – Coal = 1.25 – Electricity = 1.19 – General O&M = 1.18 ¾ Variable O&M unit cost assumptions:
Coal $1.69 / GJ Electric power $91.10 / MWh
CO2 emission allowances $40.00 / tonne Solid waste disposal $17.71 / tonne Limestone $27.56 / tonne Water $0.12 / m3 Water treatment chemicals $0.37 / kg Selexol solution $3.55 / L Shift catalyst $17.45 / L Claus catalyst $4.59 / L Process Economic Summary Levelized Cost of Hydrogen ($/kg H ) 2 Conventional Calcium Looping
Coal-to-H2 Process Capital $1.38 < $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 CO2 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
¾ Determine the technical feasibility and capital cost of nonconventional equipment items
¾ Optimize operating conditions for the carbonator, calciner, and hydrator
¾ Optimize solid purge and make-up rates
¾ Optimize heat integration
¾ 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
¾ Perform sensitivity analyses (e.g., prices, reactor conditions, solid purge rate) and study different plant configurations (e.g., IGCC) Calcium Looping Process
¾ Efficiently integrates the water-gas shift reaction and the removal of CO2, sulfur species, and halides into a single reactor for high-purity hydrogen production
¾ Obviates the need for water-gas shift catalyst and excess steam
¾ Hydration reverses the effect of sintering and maintains sorbent reactivity, permitting the use of a relatively low Ca/C molar ratio
¾ Offers essentially zero CO2 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
¾ Large solids handling requirement poses an operating and maintenance challenge
¾ 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