Hydrogen Production from Lignite and Subbituminous Coals
Panel 3: Coal to Hydrogen4th Annual Hydrogen Implementation Conference
Laramie, Wyoming
Steve Benson
July 22–24, 2008
2
National Center for Hydrogen Technology (NCHT)
1945 1955 1965 1975 1985 1995 2005 2010
Annular ExternallyHeated Retort
Slagging Fixed-Bed Gasifier
CatalyticGasification/SOFC
Mild Gasification
Transport ReactorDevelopment Unit
Microgasifier
Tec
hn
olo
gy
Dem
on
stra
tio
ns
Refractory and slag flowLignite properties – moisture friability
Gasification Kinetics
Coal water slurries
CABRE I – Ash behavior Entrained flow gasifiers
CABRE II – Computer model for entrained flow
gasifiers
CABRE III – Systems Engineering modeling – design of future systems
Trace elementsin gasification
Lignite Gasification – ashbehavior
Res
earc
h a
nd
Dev
elo
pm
ent
Entrained flow Slagging gasifier
Dakota GasificationSupport
Selected Gasification ActivitiesSelected Gasification Activities at the EERCat the EERC
4
Overview
• Gasification of coal
• Lignite and subbituminous coals
• Key challenges
• Bench- and pilot-scale testing
• Future opportunities
5
Conventional Gasification
Air
O2
Coal
Steam
Steam
AcidGas
Tail Gas
CO2
S
Hydrogen
Tail
Electricity
Power Generation
Gasification
Quench Coolerand Scrubber
Water–Gas Shift(sour high temperature)
Sulfur Removal
CO Capture(physical scrubbbng)
2
Pressure SwingAdsorption
Air SeparationUnit
Claus Plant
Gas
6
“Advanced” Gasification System
Air
O2
Coal
Steam
Electricity
Gasification
Hot-Gas CleanupAnd Sulfur Removal
High-Temperature Shift
Membrane Separation
O Combustor2
Air SeparationUnit
Mercury Capture
Hydrogen
Power Generation
TurbineExpander
CO2-Rich Gas
O2
CO2 H2O
7
Key Challenges
Air
O2
Coal
Steam
O2
CO2 H2O
Electricity
Gasification
Hot-Gas Cleanupand Sulfur Removal
High-Temperature Shift
Membrane Separation
O Combustor2
Air SeparationUnit
Mercury Capture
Hydrogen
Power Generation
TurbineExpander
CO2-Rich Gas
8
What Is the Best Conversion Technology?
Key Fuel Properties• Moisture content• Coal reactivity• Caking properties• Inorganic materials
– Ash/slag and trace elements
• Sulfur levels• Oxygen content
Lignite and Subbituminous – High Reactivity
IncludedMinerals
ExcludedMinerals
Na+Ca++Mg++
Reactivity• Organic structure• Inorganic components
Catalytic ActivityNa, Ca, Mg
1.4
1.0
0.6
0.2
70 9080
Carbon Content of Raw Coal,% d.a.f.
Rela
tive
Reac
tivity
Fac
tor Lignite
SubbituminousBituminous
Anthracite
Steam O2
10
Distribution of Inorganic Phases Low- and High-Temp. Gasifiers
• Predicted using equilibrium thermodynamics
• Assumes equilibrium distribution of phases
Test Temperature 900C
1.0000E-05
1.0000E-04
1.0000E-03
1.0000E-02
1.0000E-01
1.0000E+00
1.0000E+01
1.0000E+02
Solid Liquid Gas Solid Liquid Gas Solid Liquid Gas
Beulah Illinois #6 Black Thunder
% In
org
anic
Ph
ase
s
Test Temperature 900C
1.0000E-05
1.0000E-04
1.0000E-03
1.0000E-02
1.0000E-01
1.0000E+00
1.0000E+01
1.0000E+02
Solid Liquid Gas Solid Liquid Gas Solid Liquid Gas
Beulah Illinois #6 Black Thunder
% In
org
anic
Ph
ase
s
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Bench- and Pilot-Scale Testing – Lignite and Subbituminous Coals
• Bench-scale testing – fluidized bed – 4 lb/hr– Range of lignite and subbituminous coals– Test hot-gas cleanup for particulate, S, alkali, Cl, Hg– Test shift catalysts– Test membrane separation
• Pilot-scale testing – transport reactor – 250 lb/hr– Lignite from Texas– Test hot-gas cleanup for particulate, S, alkali, Cl, Hg– Test shift catalysts– Test hydrogen membrane separation
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Water–Gas Shift (WGS) and Hydrogen Separation
• High- and low-temperature WGS catalyst to maximize hydrogen yields.
• Hydrogen separation membrane for warm-gas purification of hydrogen.
Coal Feed
CFBReactor
Transport Sulfur
Removal
Hot-Gas Filter Vessel
Sulfur Polishing
H2/CO2 Separation
LT WGS
Mercury ControlHT
WGS
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Sulfur Removal ResultsPolishing Bed
• Achieved as low as 0.01 ppm H2S.
% R
emov
al
99%
99.9%
99.99%
99.999%
%H2S Slip for Polishing Bed Runs
0.000
0.001
0.010
0.100
1.000
Red Hills Arkansas Oak Hill Coteau
% S
lip
, Lo
g S
cale
Air O2
Freedom
14
Mercury ResultsMetal-Based Sorbent
• Red Hills Lignite
• 410°F
• ~95% Removal
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Hydrogen Separation at Elevated Temperature
• Slipstream pulled from TRDU for warm-gas cleanup and hydrogen separation
• All cleanup and separation operations performed above 400°F
Transport Reactor for
Sulfur Removal
Hot-Gas Filter Vessel
Sulfur Polishing
H2 Separation Membrane
Chlorine Guard/LT
WGS
Mercury/Trace
Element Control
HT WGS
TRDU
TRDUSlipstream ~300 scfh
Raffinate
PureHydrogen
Gas Analysis Results
Sulfur Reactor Inlet Sulfur Reactor OutletHigh-Temp. WGS Outlet
Low-Temp. WGS Outlet
Transport Reactor for
Sulfur Removal
Hot-Gas Filter Vessel
Sulfur Polishing
H2 Separation Membrane
Chlorine Guard/LT
WGS
Mercury/Trace
Element Control
HT WGS
TRDU
TRDUSlipstream~300 scfh
Raffinate
PureHydrogen
Component Concentration UnitH2 8.3 %CO 4.8 %
CO2 15.0 %N2 69.1 %
CH4 1.7 %H2S 3455 ppm
H2/CO 1.7 ratio
Component Concentration UnitH2 7.7 %CO 4.4 %
CO2 13.8 %N2 72.3 %
CH4 1.5 %H2S 4.4 ppm
H2/CO 1.8 ratio
Component Concentration UnitH2 10.9 %CO 1.0 %
CO2 16.7 %N2 68.6 %
CH4 1.5 %H2S 3.0 ppm
H2/CO 11.0 ratio
Component Concentration UnitH2 13.3 %CO 0.1 %
CO2 18.4 %N2 65.5 %
CH4 1.6 %H2S 0 ppm
H2/CO 98.3 ratio
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Hydrogen Stream Characteristics
• After nearly 50 hours of operation, CO2 concentration in the permeate was nearly zero.
• Oxygen and nitrogen were present because of a leak in the sample system (a vacuum pump was used).
• About >99.9% purity of hydrogen is anticipated without a leak in the sample system.
mol% Measured Normalized Measured Normalized Measured NormalizedHydrogen 96.48 96.86 97.48 97.67 96.74 96.76Carbon Dioxide 0.69 0.69 0.54 0.54 0.07 0.07Oxygen/Argon 2.44 2.45 1.79 1.79 0.43 0.43Nitrogen 2.74 2.74Total 99.61 100.00 99.81 100.00 99.98 100.00
Real Btu (saturated) 309.52 312.10 309.20Real Btu (dry) 315.00 317.63 314.68
Ideal Specfic Gravity 0.10 0.09 0.10Real Specific Gravity 0.10 0.09 0.10Ave. Molecular Weight 2.86 2.64 2.89
Date: 6/10/2008 Date: 6/11/2008 Date: 6/13/2008
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Coal-to-Hydrogen Demonstration
• Demonstrated the technical capability to produce a pure stream of hydrogen from lignite coal while maintaining gas temperature above 400°F.
• Demonstration was completed using commercial or near-commercial technologies.
• Texas lignite was gasified in the EERC’s transport reactor development unit (TRDU), and a slipstream was cleaned and purified.
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Future Testing
• The hydrogen flux was very low because the TRDU runs at 120 psig.
• The highest driving force for hydrogen through the membrane was only 3.4 psi.
• Additional testing will take place on higher-pressure systems, including a 300-psi bench-scale entrained-flow gasifier.
• This will eliminate the need for a vacuum pump to pull hydrogen product gas and should result in pure hydrogen samples.
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Contact Information
Energy & Environmental Research CenterUniversity of North Dakota
15 North 23rd Street, Stop 9018Grand Forks, North Dakota 58202-9018
World Wide Web: www.undeerc.orgTelephone No. (701) 777-5000
Fax No. (701) 777-5181
Steven A. Benson, Ph.D.Senior Research Manager
(701) [email protected]