EPA/600/A-33/242
LANDFILL GAS PRETREATMENT FOR FUEL CELL APPLICATIONS
Authors:
G. J. Sandelli/J. C. Trocciola
International Fuel Cells Corporation
195 Governors Highway
South Windsor, CT 06074
U.S.A.
R. J. Spiegel
U.S. Environmental Protection Agency
Air and Energy Engineering
Research Laboratory
Research Triangle Park, NC 27711
U.S.A.
Introduction
The U.S. Environmental Protection Agency (EPA) has proposed regulations1 to control
air emissions from municipal solid waste landfills. If these regulations are adopted, they
would require waste methane mitigation in order to prevent emission into the atmo-
sphere and reduce the effect on global warming. One potential use of the waste methane
is in a device which produces energy, the fuel cell. This device would reduce air emissions
affecting global warming, acid rain, and other health and environmental issues. By pro-
ducing useable energy, it would also reduce our dependency on foreign oil.
' This paper discusses the U.S. EPA program underway at International Fuel Cells Corpo-
ration to demonstrate landfill methane control, and the fuel cell energy recovery concept.
In this program, two critical issues needed to be addressed: 1) a landfill gas cleanup meth-
od that would remove contaminants from the gas sufficient for fuel cell operation, and
2) successful operation of a commercial fuel cell power plant on that lower-heating value
waste methane gas.
Program Description
International Fuel Cells Corporation (IFC) was awarded a contract by the U.S. EPA to
demonstrate methane control with energy recovery from landfill gas using a commercial
200 kW phosphoric acid fuel cell. IFC is conducting a three-phase program to show that
this concept is economically and environmentally feasible in commercial operation.
Work was initiated in January 1991 on Phase I that consisted primarily of a conceptual
design, cost, and evaluation study. The Phase II work addressed the issue of contaminant
removal from the gas. This consisted of construction and testing of a landfill gas cleanup
pretreatment module designed to remove those contaminants. Phase in of this program,
which is scheduled to begin in October 1993, has as its goal the demonstration of meth-
ane control and the fuel cell energy recovery concept at Penrose Station, an existing land-
fill gas-to-energy facility owned by Pacific Energy Corporation in Sun Valley, California.
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Methane Mitigation and the Fuel Cell Advantage
There are several methods of reducing the quantity of methane emissions from landfills.
These include:
Flaring
Combustion combined with heat recovery
Conversion to electricity
Conversion to pipeline gas
Conversion to vehicular fuel
Of these methods, flaring is the least desirable since it converts the methane into carbon
dioxide (CO2), another greenhouse gas, and it results in no useful by-products such as
heat or electricity. While either combusting the methane with heat recovery or convert-
ing it to electricity also produces CO2, there is a total CO2 emission reduction that is
realized. The fuel cell, itself, emits less CO2 per kilowatt-hour than any other heat recov-
ery or electrical generating equipment. In addition, by producing electricity this way at
a landfill, less electricity needs to be generated by a central utility station and therefore
less CO2 is emitted from that utility.
The fuel cell method of converting the methane to electricity offers a number of other
advantages:
As shown in Figure 1, the fuel cell produces very few pollutants
compared to other electric generators;
Its electrical efficiency, shown in Figure 2, is higher than that of con-
ventional generators; and
The fuel cell is factory constructed and truck transportable; there-
fore, as a landfill age increases and it is no longer economical to
utilize the methane, the fuel cell can be easily moved to a new site.
Commercial 200 kW Landfill Gas Fuel Cell
The landfill gas-to-energy concept would incorporate a 200 kW commercial phosphoric
acid fuel cell. The basis for the landfill gas fuel cell would be the PC25 natural gas fuel
cell power plant commercially produced by ONSI Corporation2, an IFC subsidiary.
This unit is a packaged, truck transportable, fuel cell power plant which has been in natu-
ral gas commercial service since early 1992. Today, power plants operate for 26 utility
customers in 11 countries on 3 continents. These power plants have accumulated over
100,000 hours of operation in commercial service, with an overall availability of 92 per-
cent. They produce electricity at 40 percent efficiency, based on the lower heating value,
and exhibit an overall efficiency of 85 percent when fuel cell waste heat is utilized in co-
generation applications. Their air emissions are lower than the background air quality
in many U.S. cities. These measured characteristics, when incorporated in the landfill
gas fuel cell concept, would verify the estimated emissions benefits generated in the
Phase I study.
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PPMv
(15% 02
DRY) 30
CO Non-methane
hydrocarbons
Fuel Cell2
Federal New New Boiler1 New Combined Commercial 200 kW
Source Performance Cycle Gas Phosphoric Acid
Standards1 Turbine1
1. From Staff Recommendations for Generic Power Plant Emissions Factors,
California Energy Commission, August 1989.
2. Source: ONSI Corporation.
Figure L Power Plant Emissions Comparison (Natural Gas)
HP2U-01q
Rft3140Ť
EFFICIENCY.
(%)
GASOLINE
ELECTRIC
J I I I lllll ' I I mill
ADVANCED
CONCEPTS
FUEL CELL SYSTEMS
FIRST V
GENERATION
^^ x.
DIESa
ELECTRIC
1 10
Source: International Fuel Cells Corporation.
100 1000
POWER OUTPUT (kW)
STEAM &
GAS TURBINE
SYSTEMS
I I l_L
10,000 100,000
HP2*3-02q
931447
Figure 2. Power System Efficiency Comparison Based on
Lower Heating Value
HP 283
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Landfill Gas Availability and Characterization
In Phase I of the contract, Municipal Solid Waste (MSW) landfills in the U.S. were eva-
luated. From this evaluation, the potential power generation market available for fuel
cell energy recovery was estimated to be 4,370 MW. The evaluation also identified a mar-
ket niche segment, based on potential power rating, for a 200 kW fuel cell power plant
module. This segment contained 1,700 sites with a combined potential power rating of
1010 MW.
The assessment concluded that these sites are ideally suited for fuel cell operation. The
commercial 200 kW fuel cell can provide a generating capacity tailored to the site be-
cause of its modular nature. Sites in this range could also be served by competing options,
such as a gas turbine, which exhibit poorer emission characteristics (Figure 1).
The Phase I study also characterized landfill gas contaminants. Contaminant levels for
one site (i.e., the Penrose Landfill, located in Sun Valley, California) are shown in Tkble
I. (The data in the table are based on a number of years of measurements taken at the
Penrose site by a variety of methods; the values shown are "worst case" scenarios; i.e.,
"high values.") This characterization, reported in the Phase I Final Report3, was used
to design the Gas Pretreatment Module, built and tested in Phase II.
Gas Pre treatment Module
One essential element of Phase II was construction and testing of a gas cleanup system
at the Penrose Landfill site. Landfill gases consist primarily of CO2, methane, and oxygen
plus trace amounts of sulfides, organic halides, and non-methane hydrocarbons. The spe-
cific contaminants in the landfill gas of concern to the fuel cell are sulfur and halides.
Both of these ingredients can "poison" and therefore reduce the life of the power plant's
fuel processor. The fuel processor is the unit which converts methane in the gas stream
into hydrogen and CO2 over a catalyst bed. The catalyst in this bed can react with the
halides and sulfides and lose its activity.
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TABLE I
Raw Landfill Gas Contaminants and Concentrations for Penrose Test Site
Landfill Gas Trace Contaminants
Design Raw Gas Concentration Level
(ppm - by volume)
Aromatics
Benzene
2
Chlorobenzene
1
Ethylbenzene
13
Styrene
0.5
Toluene
35
Xylenes
22
Total
73.5
Halogenated Hydrocarbons
Cis-1,2-Dichloroethene
5
Dichloroethane
3
Dichloroethene
3
Methylene Chloride
12
Tetrachlorethylene
6
Trichloroethylene
70
Trichlorofluoroethane
0.6
Vinyl Chloride
1.4
Total
101
Hydrocarbons
Hexane
297
Isobutane
95
Isopentane
963
n-Pentane
198
Octane
81
Total
1634
Sulfides
Dimethyl Disulfide
0.02
Dimethyl Sulfide
8
Ethyl Mercaptan
5
Hydrogen Sulfide
103
Methyl Mercaptan
5
Total
121
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Process
The system designed to remove fuel cell contaminants is shown in Figure 3. Hydrogen
sulfide is first removed by adsorption on a packed bed. Several materials including zinc
oxide, activated carbon, and carbon impregnated with various compounds to increase
sulfur capacity can be used for this purpose. This bed is not regenerable on site, but must
be removed to another site if regeneration is desired.
DEHYDRATION
LFQ
CLEAN
LFQ TO
FUEL
CONDENSATION ADSORPTION
=^r ^
HYDROCARBONS INCLUDING ORGANIC
SULFUR AND HALOGEN COMPOUNDS
260 °C
REGENERATION
CONDENSATION
OF WATER
HYDROCARBONS
ADSORPTION
OF WATER
REGENERATION
11.1 it en/Mc
260°C
REGENERATION
TO ^
FLARE
TO
FLARE
COOLER
CONDENSER
PARTICULATE
FILTER
HjS
ADSORBER
low
TEMPERATURE
COOLER
CONDENSER
ACT
CARBON
DESKCANTS
WATER
DESORPTION
25.9 ltters/sŤC landfill
gas
Major CH4/CO2/N2
0.5% 02
3ppmv Ct
3ppmv S
OUTPUT CONDITIONS
37.6 liters/sŤc landfill
gas
Major CH4/CO2/N2
0.5% 02
130-475ppmv
hydrocarbons
78-95ppmv halldes
100ppmv H2S
INPUT CONDITIONS
Figure 3. LFG Pretreatment System
Two stage, low temperature condensation followed by activated carbon adsorption are
included in the process steps used to remove the heavy and chlorinated hydrocarbons.
The first stage condenser is designed to operate at slightly above the freezing point of
water followed by another condenser which is designed to operate at below 0°C. To pre-
vent freezing of water in the second condenser, a dehydration bed is located between the
condensers. This bed is designed to reduce the dew point of the gas to significantly below
the freezing point of water prior to its entering the second condenser. These dehydration
beds are designed to be regenerated by heating a purge gas flowing through the bed.
T\vo desiccant modules operate in parallel so that one is always operational while the
other is being regenerated.
Dry landfill gas is then fed to the second stage refrigeration condenser. This condenser
is operated to condense a mixture of hydrocarbons, aromatics, and halogenated hydro-
carbons. Condensates are collected and transferred to the enclosed flare for thermal de-
struction. If the second stage condenser is ineffective in removing hydrocarbon contami-
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nants, the downstream carbon adsorption unit, whose temperature is controlled by the
second stage condenser, is conservatively sized to remove all heavy hydrocarbon and ha-
logen contaminant species. Two activated carbon beds operate in parallel so one is al-
ways operational when the other is being regenerated. Finally, the gas passes through
a particulate filter and is warmed indirectly by an ambient air-finned tube heat exchanger
before being fed to the fuel cell unit. The process operating pressure is designed to re-
main steady at 2.43 kg/cm2 with only nominal pressure loss across the equipment. Thus
the process can be controlled easily without any critical pressure control problems.
Initially it was planned to remove hydrogen sulfide downstream in the process using a
bed of zinc oxide. This bed was to be located after the bed of activated carbon. However,
initial field testing of this configuration showed that the hydrogen sulfide was converted
to carbonyl sulfide (COS) upstream of the zinc oxide bed. The zinc oxide bed will not
effectively remove the generated COS. However, as shown in Tkble II, other impurities
present in the landfill gas, which are believed detrimental to the fuel cell, were effectively
removed by the unit.
Laboratory testing to identify the cause of the COS formation showed that the COS is
formed by the reaction of hydrogen sulfide with the CO2 present in the gas stream accord-
ing to
co2 + H2S - COS + h2o (1)
Table II. Gas Pretreatment Unit Test Results*
(Without Upstream H2S Removal)
Raw Penrose LFG At Carbon Bed Exit
CH4 (%)
43
Not Measured
co2 (%)
39
Not Measured
n2 (%)
17
Not Measured
02 (%)
1.2
Not Measured
C3 - Cg Alkanes (ppm)
92
Not Measured
H2S (ppm)
83
None Detected
COS (ppm)
None Detected
76
Organic Sulfur Compounds (ppm)
9
None Detected
Organic Halogen Compounds (ppm)
24
None Detected
Other NMOCs** (ppm)
170
0.02
* Analysis by gas chromotography and mass spectrometry
** Nonmethane organic compounds
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The amount of COS formed may be predicted by use of the equilibrium equation:
Keq = [COS] [H20] (2)
[H2S] [C02]
[COS] = K [C02] [H2S] (3)
[W]
It was found that a large fraction of the hydrogen sulfide in the inlet gas stream is con-
verted to COS. This high conversion is believed due to the removal of product water
by absorption on the desiccant material. This removal lowers the concentration of water
in the gas phase, reducing the denominator in equation (3) and resulting in an increase
in the concentration of COS.
Based on these laboratory results, the unit has been modified to remove hydrogen sulfide
upstream of the process; i.e., prior to the desiccant bed. The modified unit with upstream
removal of the hydrogen sulfide is currently undergoing testing at the Penrose Site.
Summary
In summary, methane emissions from landfills and other sites are potential contributors
to global warming. Conventional methods to mitigate these emissions, such as flaring,
produce other greenhouse gases such as carbon dioxide. By operating a fuel cell at a
landfill site, methane is destroyed while efficiently generating electric power and lower-
ing carbon dioxide emissions. In order to operate a fuel cell on landfill gas, the gas must
be purified or "cleaned up." A landfill gas cleanup pretreatment module was designed,
constructed, and is undergoing testing at a landfill site. Initial results indicate that the
unit removed all impurities detrimental to the fuel cell with the exception of hydrogen
sulfide. The unit was modified to remove this compound and testing is continuing. Based
on successful completion of this testing, it is anticipated that operation of a commercial
fuel cell power plant on the cleaned-up methane gas will help demonstrate the economic
and environmental feasibility of this concept.
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References:
1. U.S. Federal Register, May 30, 1991. Part III Environmental Pro-
tection Agency, 40 CFR Parts 51,52 and 60: Standards of Perform-
ance for New Stationary Sources and Guidelines for Control of Ex-
isting Sources, Municipal Solid Waste Landfills, Proposed Rule,
Guideline and Notice of Public Hearing. Washington, D.C.:
United States Government Printing Office.
2. ONSI Corporation. 1993. The PC25 Fuel Cell Power Plant: Product
Brochure. South Windsor, Connecticut.
3. Sandelli, G. J. January 1992. "Demonstration of Fuel Cells to Re-
cover Energy From Landfill Gas. Phase I Final Report: Conceptual
Study." EPA - 600-R-92-007 (NTIS PB92-137520).
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a ,rrRT .p.1,11 TECHNICAL REPORT DATA
/l xiiHiXXi. r 1.111 (Please read fnimctions on the reverse before completing)
1. REPORT NO,
EPA/600/A-93/242
2.
3. RECIPIENT'S ACCESSION NO.
PEftH -!o79Ł-o
4. title and subtitle
Landfill Gas Pretreatment for Fuel Cell Applications
5. REPORY DATE
6. PERFORMING ORGANIZATION CODE
7 authoR(si G. J. Sandelli and J. C. Trocciola (IFC), and
R. J. Spiegel (EPA)
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING OROANIZATION NAME AND ADDRESS
International Fuel Cells Corporation.
10. PROGRAM ELEMENT NO.
195 Governors Highway
South Windsor, Connecticut 06074
11. CONTRACT/GRANT NO.
68-D1-0008
12. SPONSORING AGENCY NAME AND ADDRESS
EPA, Office of Research and Development
Air and Energy Engineering Research Laboratory
Research Triangle Park, NC 27711
13. TYPE OF REPORT AND PERIOD COVERED
Published paper; 1/91-9/93
14. SPONSORING AGENCY CODE
EPA/600/13
15. SUPPLEMENTARY NOTES pR L
541-7542. Presented at 3rc
Technology, and Medicine,
project officer is Ronald J. Spiegel, Mail Drop 63, 919/
Grove Fuel Cell Symposium, Imperial College of Science,
London. 9/28-10/1/93.
16. abstract paper discusses the U. S. EPA's program, underway at International
Fuel Cells Corporation, to demonstrate landfill methane control and the fuel cell
energy recovery concept. In this program, two critical issues are being addressed:
(l) a landfill gas cleanup method that would remove contaminants from the gas suf-
ficient for fuel cell operation, and (2) successful operation of a commercial fuel cell
power plant on that lower-heating-value waste methane gas. (NOTE: The EPA has
proposed regulations to control air emissions from municipal solid waste landfills.
If these regulations are adopted, they would require waste methane mitigation in or-
der to prevent emission into the atmosphere and reduce the effect on global warming.
One potential use of the waste methane is in a device that produces energy, a fuel
cell. This device would reduce air emissions affecting global warming, acid rain,
and other health and environmental issues. By producing useable energy, it would
also reduce U.S. dependency on foreign oil.)
17.
KEY WORDS AND DOCUMENT ANALYSIS
3. DESCRIPTORS
b.IDENTIFIERS/OPEN ENDED TERMS
c. COS ATI Field/Group
Pollution Electric Power Plants
Fuel Cells Greenhouse Effect
Methane
Earth Fills
Energy
Gas Scrubbing
Pollution Control
Stationary Sources
Energy Recovery
Gas Cleaning
Global Warming
Acid Rain
13B
10B 04A
07 C
13 C
14 G
07A, 13H
13. DISTRIBUTION STATEMENT
19. SECURITY CLASS (This Report)
Unclassified
21. NO. OF PAGES
9
Release to Public
20. SECURITY CLASS {This page)
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)
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