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

11

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

12

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

13

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

15

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

17

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.

19

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.

20

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) 777-5177sbenson@undeerc.org