4% ¶	United States	Air and Radiation Draft
^S^tr^r\	Environmental Protection Agency	6202J	November 1998
EPA Coalbed Methane Outreach Program Technical Options Series
Conversion Of Coal Mine Methane
Into Synthetic

Commercial scale gas-to-liquids plant in Pueblo, Colorado fueled by landfill methane gas (1992)
(Photo courtesy of Rentech, Inc.)
Coal Mine Methane Use In Synfuel Production...
~	Use of coal mine methane as a feedstock gas can improve synfuel economics
~	Produces high-quality liquid fuels that can be easily transported
~	Ideal for methane recovered from coal mines without pipeline access
~	Use of coal mine methane reduces greenhouse gas emissions
~	Can operate on medium-quality gob gas

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Coal mine methane
may be a low-cost
alternative to
conventional natural
gas for small gas-to-
liquids plants
Synthetic fuels are
environmentally
superior to
conventional petroleum
products
Why Consider Coal Mine Methane for Synfuel Production?
For safety reasons, many gassy underground coal mines drain methane
from their coal seams. Most coal mines vent this methane to the
atmosphere, which not only represents the loss of a valuable fuel source,
but also contributes to global warming, as methane is a potent
greenhouse gas. While an increasing number of coal mines recover methane
for pipeline injection, mines producing medium quality gas (typically less than
80% methane), or those not located near pipelines, look to other gas-use
options. Recently, there has been a renewed interest in the conversion of
methane into liquid hydrocarbon fuels such as diesel, kerosene, and naphtha.
Because liquids can be transported more efficiently than gas, energy producers
are developing methane-to-liquid fuel technologies in areas where pipeline
facilities may not be economically justified. As a result, locating a synfuel plant
near a coal mine could enhance the economic viability of both methane
recovery and synfuel production.
Although gas-to-liquids technologies have existed since the 1920s, the capital
cost of conversion plants has hindered the economic feasibility of synfuels
production. The most successful conversion of methane to liquid fuels to date
is through Fischer-Tropsch Synthesis technology. The discovery of advanced
catalysts during the past decade has greatly reduced the costs of the
technology, thus making methane conversion plants smaller than 5,000 barrels
per day economically possible. Currently, Syntroleum Corporation refines the
Fischer-Tropsch chemistry using a proprietary catalyst that allows up to 30% N2
and C02 in the feedstock gas. Using an iron-based catalyst, Rentech, Inc.
successfully converts gas with methane concentrations as low as 40%. In
addition, the Department of Energy is working with Air Products and Chemicals,
Inc. to develop a novel ceramic membrane that could reduce the cost of
converting natural gas to transportation-grade liquid fuels by 50%.
The products produced from these conversion processes are environmentally
superior to many fuels because they are free of aromatics, nitrogen, and sulfur,
and have a high centane number (clean burning properties). The quality of
synthetic diesel fuel produced by the Fischer-Tropsch process is excellent, and
therefore would be of special interest to underground coal mines operating or
considering operating diesel equipment. In fact, these properties make
synthetic diesel suitable as a blending component for upgrading conventional
diesel fuels to meet stringent mining specifications.
Some Facts About Synfuel Production...
The market for high-
quality diesel is
increasing worldwide
Ten thousand cubic feet (10 mcf) of methane will produce
approximately one barrel of liquid products
Plant sizes typically range from 2,000 to 20,000 barrels/day, but smaller
plants may be feasible if low cost gas is available
At $0.50-1.00/mcf of methane, feedstock gas costs are $5-10/barrel,
while estimated operating and maintenance costs (at 5,000 barrels/day)
are $5-6/barrel
Typical 1998 synthetic diesel prices are about $US 27 to $32 per barrel
(typically $8/barrel more than conventional diesel prices)

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Synthesis Fuel Flowchart
Q >
Z Z
- O

PARTIAL
OXIDATION

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ió;>


f
OXYGEN (OR AIR)
1

RE-FORMING

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¶=!>


COALMINE "
METHANE "
SYNTHESIS
MIXED
HYDROCARBONS
(AND NITROGEN)
GAS (AND
NITROGEN)
FISCHER-
TROPSCH
SYNTHESIS
REF N NG
METHANOL
METHANOL
SYNTHESIS
CHEMICAL
PROCESSING
SYNTHESIS
GAS
GASOLINE,
DIESEL,
WAXES
AND OLEFINS
GASOLINE,
DIESEL ALTERNATIVES,
OCTANE ENHANCERS
AND OTHER CHEMICALS

REACTION USING
CONVENTIONAL
CATALYSTS

i=t>
ió;>


f
OXIDANTS
1

REACTION USING
LIQUID CATALYSTS

¶=£>
¶=£>


OLEFINS
AND OTHER
CHEMICALS
METHANOL
AND OTHER
CHEMICALS
In an era of increasing environmental concerns, high-quality, sulfur-free diesel is readily sold on
worldwide markets. For example, Royal Dutch/Shell Group produced synthetic diesel at its 12,500 b/d
plant in Malaysia and sold it in California, because it met the stringent emission standards imposed by
the California Air Resources Board. Moreover, the Mine Safety and Health Administration (MSHA)
proposed a rule in April 1998 to reduce diesel particulate matter in underground coal mines. As a
result, diesel engines used in these mines may require particulate filters in the future. Synthetic diesel
use can reduce particulate emissions by up to 30%. In addition, synthetic diesel can reduce NOx
emissions (which represent a major problem for diesel engine exhaust) by 10%. U.S. EPA is
proposing new diesel engine emission standards in 1999 for a wide range of highway and off-road
applications. Coal mine methane-produced synthetic fuels could help reduce emissions that cause
ground-level ozone (primarily NOx and particulate matter).
The success of coal mine methane recovery and use requires a reliable market for the gas, and
synfuel plants seek ample (five million standard cubic feet per day or more) methane sources. A coal
mine or a group of coal mines located close together could supply low-cost methane feedstock to gas-
to-liquid plants. In return, the mines would have access to high-quality diesel and other fuels to meet
the fuel needs of their mining equipment. The recovery of coal mine methane for use as a synfuel
feedstock reduces emissions of this greenhouse gas into the atmosphere.
Properties of High-Quality Synthetic Diesel
FUEL PROPERTIES
MSHA
RECOMMENDATIONS
CONVENTIONAL
DIESEL
SYNTHETIC
DIESEL
Centane Number*
> 48
40-57
> 65
Aromatic Content
< 20%
<35%
< 1%
Sulfur Content
< 0.05%
<0.25%
< 0.0001%
* The centane number refers to the volatility of a fuel. Higher numbers indicate lower hydrocarbon emissions.

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For More Info
The continued development and refinement of
gas-to-liquid technologies offers opportunities
for coal mine operators and synfuel
producers. Synfuel production provides a
market opportunity for gassy coal mines with-
out ready access to pipelines, while producers
of liquid synthetic fuels may find the
opportunity to purchase low-cost coal mine
methane attractive.
To obtain more information about gas-to-
liquids technologies, contact:
Mark Koenig
Rentech, Inc.
1331 17th Street
Suite 720
Denver, Colorado 80202
(303) 298-8008
Fax: (303) 298-8010
John Ford
Syntroleum Corporation
1350 South Boulder
Suite 1100
Tulsa, Oklahoma 74119
(918) 592-7900
Fax: (918) 592-7979
Or contact EPA's Coalbed Methane Outreach Program for information about this and other
profitable uses for coal mine methane:
Coalbed Methane Outreach Program
U.S. EPA (6202J)
401 M Street, SW
Washington, DC 20460 USA
(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
c
O
A L B E
D
M
E
THAN
E
O
U
T R E A C
H
P
R
O C R A
M
The mention of products or services in this case study does not constitute an endorsement by
EPA.

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