430F98087
United States
Environmental Protection Agency
Air and Radiation Draft
6202J June 1998
EPA Coalbed Methane Outreach Program Technical Options Series
USE OF COAL MINE METHANE IN 1C ENGINES AT COAL MINES
225 kW Synchronous Skid-Mounted Generator at Nelms No. 1 Mine, Ohio
(Photo courtesy Northwest Fuel Development, Inc. and U.S. DOE)
A PRACTICAL APPROACH TO POWER GENERATION AT COAL MINES. ..
4 Economic benefits to coal mines, power producers and end users
* Improved on-site power supply reliability
* Modular design accommodates fluctuations in gas supply
* Commercially proven at the Nelms No. 1 Mine, Ohio, USA and at the
Appin and Tower Collieries, New South Wales, Australia
* Reduces emissions of coal mine methane, a greenhouse gas
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Capital costs of small
1C engine power
generating sets are
economically
competitive
Why Consider Using Coal Mine Methane in 1C Engines?
M
Maintenance and
parts for 1C engines
are readily available
Iinmg of underground coal deposits releases large quantities of
methane gas, which presents a safety hazard to miners and
therefore must be ventilated or removed. Mines can drain methane
ahead of mining operations through the drilling of vertical wells in the
surrounding coal seam. Vertical wells usually produce high quality gas, (over
90% methane concentration) with a heating value of over 900 Btu/cf, In
contrast, gob wells (drilled into collapsed rock over mined-out areas) produce
medium quality gas that generally contains 30-80% methane.
Most methane recovery operations inject pipeline quality gas directly into a
pipeline and sell it to utility companies. Mines often vent the medium quality
gas they drain from gob wells into the atmosphere instead of using it,
because gob gas requires enrichment prior to pipeline injection. However,
fuel for power generators does not require pipeline quality gas. Generally, 1C
engines can be adapted to generate electricity using coal mine gas with a
methane concentration as low as 20%. (For safety reasons, however, mines
usually cease production of gob gas if the methane concentration drops
below 25%).
In Ohio, Northwest Fuel Development, Inc. (NW Fuel), with the assistance of the
U.S. DOE, has developed power generators that use medium quality gas. The
"prime mover" in NW Fuel's power generating set is a TOO hp 1C engine
manufactured by General Motors, Properly configured carburetors in this light
truck engine allow for the use of fuels ranging from 20% to 100% methane.
The engines generally provide service for over 12,000 hours (or one and one-
half years) before any significant maintenance is required. After
maintenance, the engines are placed back in service for another 8,000 to
10,000 hours before they are replaced.
NW Fuel recovers methane from the Nelms Mine No. 1 and generates power
for on-site use at the neighboring Nelms Cadiz Portal Mine. Through the use of
common mass-produced GM engines, the power-generating equipment
developed at the Nelms Mines produces low-cost electricity by keeping
capital and operating costs to a minimum. Currently, the project also sells
some electricity directly to American Electric Power Company, a local utility.
SOME FACTS ABOUT POWER GENERATION AT THE NELMS COAL MINES. .
• Current nine-unit system capable of generating 675 kW of electricity
• System uses about 225,000 cubic feet of coal mine methane per day
1C engines operate on • Existing units produce three-phase electricity at 480 volts
gas at atmospheric
pressure; they do not • installed costs of generator sets and utility-required protective relays are
require compressed less than $800/kW
fuels like gas turbines
• Produce power for less than $0.025/kW-hr
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EXHAUST MINE AIR
CONTAINING LOW
HOLES OKILLCD IN
ROCK AND COAL STRATA
Use of methane at the Appin Colliery for power generation in 1C engines
(Schematic courtesy of Energy Developments, Ltd.)
On a larger scale, Energy Developments Ltd. (EDL) has developed a power project in
Australia that uses coal mine methane (supplied by BHP's Appin and Tower Collieries) to
generate electricity for the local utility grid. The project cuts the mines' methane
emissions in half and delivers a total of 94 MW of power to the utility grid during peak demand
hours. Of this, 4-10 MW is fed back from the utility grid to meet the mines' equipment energy
requirements, such as ventilation fans, power equipment, and other critical loads. The
remaining power is supplied to Integral Energy Australia, By purchasing power from this
project. Integral Energy, a local distribution company and energy trader, expects to save its
customers more than $US 2.4 million annually. To ensure consistent gas quality and quantity,
EDL uses an electronic monitoring and control system to supplement the coal mine gas with
natural gas when necessary.
As with the Nelms Mines, this innovative project converts coal mine methane to electricity
using a conventional internal combustion engine. In this case, a 16-cylinder Caterpillar G3516
bulldozer engine is connected to a Cat SR4 brushless generator. Housed in soundproof sheds,
the 94 generator sets convert over 20 million cu ft/day of coal mine methane to 94 MW of
electricity. Each generator set is expected to operate up to 8000 hours a year, A gas turbine-
based system was not considered as cost-effective because of the need to compress the
gas before fueling, and because experience had shown that maintenance could be a
problem at the site.
SOME FACTS ABOUT THE USE OF 1C ENGINES AT THE APPIN POWER PROJECT. ..
• Each engine directly drives one 415 volt 1 megawatt generator
• Fuel gas composition varies from 50 - 85% methane, 0-5% C02, and up to 50% air
• Modular design provides for off-site fabrication, ease of relocation, and staged expansion
• Mine ventilation air from Appin Colliery, containing 0.5 -1.0% methane, supplies all of the
combustion air to the 54 units at the Appin plant (mine design prohibits this option at Tower)
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For More Information.
The economic success at the Nelms Mines
in Ohio and the Appin and Tower Collieries
in Australia is prompting coal and electricity
producers worldwide to take a new look at
using methane-fueled internal combustion
engines for power generation. This ap-
proach has the added benefit of reducing
methane emissions by converting a waste
product into electricity.
To obtain more information about using
coalbed methane in gas engines, contact:
Mr. William Lazarus
General Manager
Energy Developments, Ltd.
P.O. Box 535
Richlands, QLD
Australia
Tel: (61) (7) 3275 5555
Fax: (61) (7) 3217 0733
Dr. Peet Soot
Northwest Fuel Development, Inc.
4064 Orchard Drive
Lake Oswego, OR 97035
Tel: (503) 699-9836
Fax: (503) 699-9847
Or contact the EPA's Coalbed Methane Outreach Program for information about this and
other profitable uses for coal mine methane:
Coalbed Methane Outreach Programs
U.S. EPA
401 M Street, SW (6202J)
Washington, DC 20460 USA
Tel: (202) 564-9468 or (202) 564-9481
Fax: (202) 565-2077
e-mail:fernandez.roger@epa.gov
schultz.karl@epa.gov
http://www.epa .gov/coalbed
M E T H A N
OUTREACH
PROGRAM
The mention of products or services in this case study does not constitute an endorsement by EPA.
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