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
Patent Application -
WO2008039783
1st
Meeting of the High Temperature Solid Looping Cycles NetworkSeptember 15th
–September 17th
U.S. Patent Application No. 61/116,172
Equilibrium Limited Water Gas Shift Reaction (WGSR)
Temperature (0C)
100 200 300 400 500 600 700 800 900 1000 1100
KW
GS
1
10
100
1000
10000CO + H2
O CO2 + H2
Cu
Fe
MoS2
High Steam/CO
H2/CO ratio can be improved
But can never maximize H2
production
Further CO cleanup will be required for PEM fuel Cells (ppm levels)
Steam Gasification:
Coal + H2
O CO + H2
Hydrogen Synthesis from Coal
+ H2
S CaS + H2O+ COS CaS + CO2+ HCl CaCl2 + H2O
Specific Objectives
Simultaneous WGSR, CO2 removal, sulfur and halide capture integrated in one module
High purity H2 production
Reduce excess steam requirement
Remove H2S, COS and HCl to ppm levels
CO + H2
O CO2 + H2
+
CaO
CaCO3
Patent Application # WO2008039783 (2008)
Sulfur By-Product
Sulfur By-Product
Fly Ash By-Product
Fly Ash By-Product
Slag By-Product
Slag By-Product
Sulfur By-Product
Sulfur By-Product
Sulfur By-Product
Sulfur By-Product
Fly Ash By-Product
Fly Ash By-Product
Fly Ash By-Product
Fly Ash By-Product
Slag By-Product
Slag By-Product
Slag By-Product
Slag By-Product
Conventional Syngas Process
Steigel and Ramezan, 2006
Fuels &ChemicalsAir
Separation
Hydrogen
FuelCell
Steam
Slag SteamTurbine
Gas Turbine
AirCompressor
Stack
HRSG
RotaryCalciner
INTEGRATEDWGS +H2S
+COS + HCLCAPTURE
Generator
Gasifier
BFW
To SteamTurbine
CO2
Air
AirOxygen
CaO
CaCO3
SteamH2+O2
Calcium Looping Process
Patent Application # WO2008039783 (2008)
Hydrator
U.S. Patent Application No. 61/116,172
Calcium Looping Process
Net HeatOutput Heat
Input
Pure CO 2 gas
Calcination: CaCO3 CaO + CO2CO + H2O CO2 + H2
CaO + CO2 CaCO3
CaO + H2S CaS + H 2O
Syngas
Hydrogen
reactor
RegenerationReaction
2 gas
Calcination: CaCO3 CaO + CO2WGSR : O CO2 removal : CaO + CO2 CaCO3
Sulfur : CaO 2S CaS O
IntegratedHydrogen
CaCO3
CaO
Calciner
H2O
Reactivation
HydratorCa(OH)2
CaOHydration :CaO + H2O Ca(OH)2
OutputHeat
Ca(OH)2 CaO + H2ODehydration :
Halide : CaO + 2HX CaX2 + H2O
Net HeatOutput Heat
Input
Pure CO 2 gas
Calcination: CaCO3 CaO + CO2Calcination: CaCO3 CaO + CO2CO + H2O CO2 + H2
CaO + CO2 CaCO3
CaO + H2S CaS + H 2O
Syngas
Hydrogen
reactor
RegenerationReaction
2 gas
Calcination: CaCO3 CaO + CO2Calcination: CaCO3 CaO + CO2WGSR : O CO2 removal : CaO + CO2 CaCO3
Sulfur : CaO 2S CaS O
IntegratedHydrogen
CaCO3
CaO
Calciner
H2O
Reactivation
HydratorCa(OH)2
CaOHydration :CaO + H2O Ca(OH)2
OutputHeat
Ca(OH)2 CaO + H2ODehydration :
Halide : CaO + 2HX CaX2 + H2O
Patent Application # WO2008039783 (2008)U.S. Patent Application No. 61/116,172
Thermodynamic Analyses
Carbonation :Temperatures below 800C for a CO2
partial pressure of .4 atmTemperatures below 1000C for a CO2
partial pressures of 4.6 atm
Sulfidation :Outlet H2S concentration as steam partial
pressure and temperatureConventional System - 1000 ppm H2SCalcium looping - <1 ppm H2S
Temperature (oC)
400 500 600 700 800 900 1000
Equi
libriu
m H
2S C
onc
(ppm
)w
ith 3
0 at
m to
tal p
ress
ure
0.01
0.1
1
10
100
1000
1000020 atm 2 atm0.2 atm0.02 atm
CaO+ H2S CaS + H2OCaO+ H2S CaS + H2O
CLP
ConventionalIGCC
Hydration
Carbonation
Temperature (C)400 600 800 1000Eq
ulib
rium
Par
tial P
ress
ure
(atm
)
10-8
10-7
10-6
10-5
10-4
10-3
10-2
10-1
100
101
102
P H2O P CO2
CaO + CO2 CaCO3CaO + H2O Ca(OH)2
Hydration
Carbonation
Temperature (C)400 600 800 1000Eq
ulib
rium
Par
tial P
ress
ure
(atm
)
10-8
10-7
10-6
10-5
10-4
10-3
10-2
10-1
100
101
102
P H2O P CO2
CaO + CO2 CaCO3CaO + H2O Ca(OH)2
Patent Application # WO2008039783 (2008)
Experimental Setup Combined WGSR and CO2
Removal
•500-1500 sccm•3-15 % CO•Steam/CO =1:1-
3:1•600 –
700 oC•5000 ppm H2
S
N2
Steam Generator
QuartzWool
Packing
Water InSteam &
Gas Mixture
Sorbent&
CatalystPowderMixture
Heated Steel TubeReactor
Thermocouple
Water Trap
Analyzers (CO,CO2, H2, H2S)
Cold Fluid In
Cold Fluid Out
Water SyringePump
HeatExchanger
MixtureMixture
COH2 CO2
MFC MFC MFC MFC
N2
BackPressureRegulator
HydrocarbonAnalyzer
Temperature (oC)
500 600 700 800
CO
Con
vers
ion
(%)
0.0
0.2
0.4
0.6
0.8
1.0
0 psig 150 psig 300 psig
CO + H2
O Catalyst
CO2
+ H2
Time (sec)
0 500 1000 1500 2000
H2
Gas
Com
posi
tion
(%)
0
20
40
60
80
100
0 psig150 psig 300 psig
CO + H2
O CO2
+ H2
CaO
Catalyst/Sorbent WGS System
Catalyst CaO Sorbent
IncreasingPressure
14.7 Psi 14.7 Psi150 Psi300 Psi
150 Psi300 Psi
Patent Application # WO2008039783 (2008)
H2
Production with H2
S removal Non catalytic -
Effect of Steam to CO ratio
Time(sec)1000 2000 3000 4000
H2S
con
cent
ratio
n (p
pm)
0
200
400
600
800Steam to CO = 0.75:1Steam to CO = 1:1Steam to CO = 3:1
25 ppmH2
S 8 ppmH2
S0 ppm H2
S
Time(sec)
0 1000 2000 3000C
O C
onve
rsio
n0.0
0.2
0.4
0.6
0.8
1.03-1 1-1 0.75-1
CO + H2
O H2
+ CO2
CaO
H2
S
CaCO3 CaS
Pressure : 14.7 Psia
Patent Application # WO2008039783 (2008)
H2
Production with H2
S removal Non catalytic –
Effect of Temperature
H2S Outlet Concentration with Temperature
Lowest at 560-600C
Time(sec)500 1000 1500 2000 2500 3000
H2S
con
cent
ratio
n (p
pm)
0
200
400
600
800600C560C650 C700C
Time(sec)0 500 1000 1500 2000 2500 3000
Gas
Com
posi
tion
(%)
0
20
40
60
80
100560C600C650C700C
S/C ratio = 1:1P= 0 psig
Greater extent of carbonation 600-650C
Optimum temperature for sulfidation and carbonation– 600C
Patent Application # WO2008039783 (2008)
H2
Production with H2
S removal Non catalytic –
Effect of Pressure
Time (sec)0 1000 2000 3000 4000 5000
H2S
con
cent
ratio
n (p
pm)
0
200
400
600
800300 psig0 psig
300 psig
0 psig
< 1 ppm
Time(sec)0 1000 2000 3000 4000
H2
Gas
Com
posi
tion
(%)
0
20
40
60
80
100
0 psig300 psig
300 psig
0 psig
High purity H2
S/C ratio = 1:1T = 600C
Higher pressure favors sulfidationH2S in the outlet
0 psig – 20 ppm 300 psig <1 ppm
High pressure favors combined carbonation and WGSR
H2 in the outlet0 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
0
10
20
30
40
50
60
70
OriginalSorbent
0% 33% 50%
Steam Concentration in Carrier Gas
W
t% C
aptu
re
0
10
20
30
40
50
60
70
OriginalSorbent
1 2 3
Number of Cycles
W
t% C
aptu
re
Sorbent reactivity reduced to half during calcinationEffect of sintering reduced by steam calcinationIncrease in steam concentration improves reactivity
Calcination at 900C with 50% steam and 50% CO2
Reduced sintering over multiple cyclesReactivity reduced to half in 4 cycles
U.S. Patent Application No. 61/116,172
Reactivation of the Sorbent
Sorbent reactivity reduced to a third after calcination at 1000C
Calcined sorbent regenerated completely by hydration
0
10
20
30
40
50
60
OriginalSorbent
CalcinedSorbent
WaterHydration
SteamHydration
W
t % C
aptu
re
0
10
20
30
40
50
CalcinedSorbent
100 psig 150 psig 300 psig
Hydration Pressure
Wt %
Cap
ture
U.S. Patent Application No. 61/116,172
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– CO2
compressed to 151 bar
Results obtained from Aspen Plus® and spreadsheet-based models
This is a work-in-progress; results are preliminary
Techno-Economic Evaluation CLP for High-Purity Hydrogen Production
Coal-to-Hydrogen Process
Air Separation
Unit
Gasifier
Quench
Shift Reactors
Syngas Scrubber
2-Stage Selexol
Coal Prep and Feed
Slag Handling
CO2
Compression Dehydration
Pressure Swing
Adsorber
Boiler
Radiant Cooler
Syngas Cooling
Mercury Removal
Claus
Plant
Steam Turbine
Coal Water
AirSlag
Sulfur
Flue Gas
Pure H2
CO2
Air
Coal-to-Hydrogen Process
Air Separation
Unit
Gasifier
Coal Prep and Feed
Slag Handling
CO2
Compression Dehydration
Pressure Swing
Adsorber
Radiant Cooler
Steam Turbine
Coal Water
AirSlag
Pure H2
CO2
CalciumLooping Process
Coal
Limestone
Solid Waste
CLP Aspen Plus®
Process Model Process Flow Diagram
Syngas from
Radiant Cooler
Hydrogen Product
Coal
Oxygen from ASU
Solid Waste
Limestone
CO2
to Compressor
Hydrator
CarbonatorCalciner
FSPLIT
MIXER
MIXERRGIBBS
FSPLIT MIXER
FSPLIT
RYIELD
RGIBBS
FSPLIT
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
–
CO2
stream (HRSG)– H2
stream (firetube boiler and condensing heat exchanger)
Aspen Plus®
Modeling Results Calcium Looping Process vs. Conventional Process
Conventional Coal-to-H2
Calcium Looping Process
% Difference
Coal Feed Rate (tonne/h) 226 313 +38
O2 Consumptiona (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
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 Solids Handling
High-temperature hydrator with heat recovery
Turboexpander with 65 bar inlet pressure
Flash calciner with oxyfuel combustion
High-pressure condensing heat exchanger for H2 stream
Very large, high-temperature lockhoppers
High-temperature (675°C) metallic filters with fine particles
Technical Challenges Unconventional / Unproven Equipment Items
Economic Analysis Key Assumptions
2008 U.S. dollarsCapacity factor = 90%Capital charge factor = 0.175O&M levelizing factors
– Coal = 1.25
–
Electricity = 1.19
–
General O&M = 1.18Variable O&M unit cost assumptions:
Coal $1.69 / GJElectric power $91.10 / MWhCO2 emission allowances $40.00 / tonneSolid waste disposal $17.71 / tonneLimestone $27.56 / tonneWater $0.12 / m3
Water treatment chemicals $0.37 / kgSelexol solution $3.55 / LShift catalyst $17.45 / LClaus catalyst $4.59 / L
Process Economic Summary Levelized Cost of Hydrogen ($/kg H2
)
Conventional Coal-to-H2
Calcium Looping Process
Capital $1.38
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
< $1.99
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 CO2, 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 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
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