United States
Environmental
Protection Agency
Air and Radiation
(6207-J)
EPA Publication:
EPA-430-R08-004
January 2008
Upgrading Drained Coal Mine
Methane to Pipeline Quality:
A Report on the Commercial
Status of System Suppliers
,i •
OUTREACH
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Upgrading Drained Coal Mine Methane
to Pipeline Quality: A Report on the
Commercial Status of System Suppliers
EPA Publication: EPA430-R08-004
January 2008
Coalbed Methane Outreach Program
U. S. Environmental Protection Agency
Cover Photos: Left, BCCK Nitech field installation (courtesy ofBCCK Engineering, Inc.);
remainder, stock coal mine images
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Acknowledgments
This report was prepared under Environmental Protection Agency Contract EPA-430-
R08-004 by BCS, Incorporated. The principal authors were F. Peter Carothers and H.
Lee Schultz. The authors gratefully acknowledge the contributions of all the vendors
who provided technology characterization information summarized in this report.
Disclaimer
This report was prepared forthe U.S. Environmental Protection Agency (USEPA). This
preliminary analysis uses publicly available information in combination with information obtained
through direct contact with equipment vendors and project developers. USEPA does not:
(a) make any warranty or representation, expressed or implied, with respect to the accuracy,
completeness, or usefulness of the information contained in this report, or that the use of
any apparatus, method, or process disclosed in this report may not infringe upon privately
owned rights;
(b) assume any liability with respect to the use of, or damages resulting from the use of, any
information, apparatus, method, or process disclosed in this report; or
(c) imply endorsement of any technology supplier, product, or process mentioned in this report.
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Preface
In 1997, the U.S. Environmental Protection Agency (USEPA) published a report titled
Technical and Economic Assessment of Potential to Upgrade Gob Gas to Pipeline
Quality. At the time, only one commercial upgrade facility was being established.
During the ensuing years, three additional gas processing system suppliers have made
significant progress in bringing upgrade facilities on line. This paper serves to update
the 1997 report to provide information about coal mine methane upgrade system options
that currently are at or near commercial readiness.
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Contents
Abbreviations and Units v
1. Introduction 1
2. Background 1
Using Drained CMM for Natural Gas Pipeline Sales 1
Gas Upgrading Options 2
3. Gas Upgrading Technologies 3
Nitrogen Rejection Technologies 3
Oxygen, Carbon Dioxide, and Water Vapor Removal Technologies 5
4. Commercial Applications 6
Example #1 7
Example #2 8
Example #3 8
5. Summary of Gas Upgrading Technologies 8
Appendix: NRU Vendor Profiles 10
A.1 Advanced Extraction Technologies, Inc. (AET) 11
A.2 BCCK Engineering, Inc 12
A.3 D'Amico Technologies 13
A.4 Guild Associates, Inc 14
A.5 Engineered Gas Systems Worldwide (EGSWW) 16
A.6 Gas Separation Technologies, LLC (GST) 17
A.7 Membrane Technology and Research, Inc. (MTR) 18
A.8 Northwest Fuel Development, Inc. (NWFuel) 19
A.9 Velocys, Inc 20
List of Figures
Figure 1. Molecular Gate NRU Technology 5
Figure 2. Locations of Operating CMM Upgrade Facilities 6
List of Tables
Table 1. Typical Methane Pipeline Specifications 2
Table 2. Operating CMM Upgrade Facilities 7
Table 3. Current and Upcoming CMM Upgrade Technology Vendors 9
IV
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Abbreviations and Units
AMM Abandoned mine methane
CBM Coal bed methane
CMM Coal mine methane
NRU Nitrogen rejection unit
PSA Pressure swing adsorption
N2 Nitrogen
O2 Oxygen
CO2 Carbon dioxide
H2O Water vapor
H2S Hydrogen sulfide
Btu/scf British thermal unit per standard cubic foot
Mmscfd Million standard cubic feet per day
ppm Parts per million
psig Pound per square inch, gauge
scfd Standard cubic feet per day
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1. Introduction
In today's scenario of growing energy demands worldwide and rising natural gas prices,
any methane emitted into the atmosphere is an untapped resource of energy and
potentially a lost opportunity for additional revenue. In 2005, 9.7 percent of the total U.S.
anthropogenic emissions of methane were attributed to coal production. In recent years,
many gassy coal mines have seized the opportunity to recover coal mine methane
(CMM) and supply it to natural gas pipeline systems. With natural gas prices in the U.S.
exceeding $7.00 per million Btu,1 CMM pipeline sales brought in an annual revenue
topping $97 million in 2005. However, significant opportunity still exists for tapping into
this resource as 22 percent of the drained CMM remains unutilized as of 2005,2 primarily
because its quality does not meet the requirements of natural gas pipeline systems.
Recent advances in technologies now offer off-the-shelf options in the U.S. that can
upgrade the drained CMM to pipeline quality. These gas upgrading technologies are not
only opening up the market to lower-quality methane resources but are also providing
significant means for reducing emissions, since methane is over 20 times a more potent
greenhouse gas than carbon dioxide.
This report reviews current gas upgrading technologies available in the market for
removal of typical CMM contaminants (section 3), provides examples of their successful
commercial implementation (section 4), and compiles a list of vendors specific to
nitrogen rejection systems (section 5), since nitrogen poses the biggest challenge to
upgrading CMM.
2. Background
Using Drained CMM for Natural Gas Pipeline Sales
In general, about half of the domestic CMM emissions come from ventilation fans used
to keep methane levels at underground mines within the safe range. However, many
particularly gassy coal mines need to supplement their ventilation systems by drilling and
operating wells to drain methane from the coal seam either before or during mining. The
drained CMM typically finds end-use in the U.S. in natural gas pipeline injection.
A project manager must consider several factors for pipeline injection, including the
distance and terrain to the nearest pipeline and its available capacity, the volume of
methane expected to be available over the lifetime of the drainage and injection project
and most importantly, the quality of the drained methane. The methane injected into the
November 2007 Henry Hub prices from http://tonto.eia.doe.gov/ooq/info/nqw/nqupdate.asp. The Henry
Hub, physically located at Sabine's Henry Gas Processing Plant in Louisiana, connects nine interstate and
four intrastate pipelines, comprising about 49% of total US wellhead production. The Henry Hub represents
the largest centralized location for natural gas spot trading in the U.S. (Philip Budzik, Energy Information
Administration, U.S. Natural Gas Markets: Relationship between Henry Hub Spot Prices and U.S.
Wellhead Prices, available at http://www.eia.doe.gov/oiaf/analysispaper/henryhub).
2 EPA Coalbed Methane Outreach Program Accomplishments
http://www.epa.gov/cmop/accomplishments.htmltfreducing
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natural gas transmission or distribution system must meet stringent pipeline quality
specifications as suggested in Table 1.
Table 1. Typical Natural Gas Pipeline Specifications3
Oxygen
Nitrogen
Carbon Dioxide
Heat Value
Water Vapor
Sales Gas Pressure
<0.2%
3% maximum
2% maximum
>967 Btu/scf minimum
7 Ibs/mmscf
800 psig
(range -200 - 1 ,500
psig)
Methane drained before mining may often be of high enough quality to meet the natural
gas pipeline specifications stated in Table 1 with little or no processing, generating a
ready stream for substantial revenue for mine owners. However, the gas drained during
mining from gob wells4 does not typically meet natural gas pipeline specifications
outright because it is more susceptible to nitrogen, oxygen, carbon dioxide, and water
contamination. The same is often also true for abandoned mine methane (AMM), gas
that is liberated from closed coal mines through fissures, vents, and boreholes. The
methane concentration in gob gas and AMM varies widely with site-specific conditions
but typically falls between 30 and 80 percent.
Gas Upgrading Options5
Currently, gob gas containing 50 percent methane is considered to be the low end of the
range for economically viable gas upgrading. Gas containing over 90 percent methane
requires relatively little cleanup for pipeline sales. Therefore, gob gas and AMM within
the range of 50 to 90 percent are good candidates for upgrade.
There are four primary options to upgrade gas to pipeline quality:
1. Invest in techniques designed to improve recovery so that the gas maintains the
highest possible quality. Such techniques include well and borehole design
optimization and continuous monitoring systems.
2. Blend lower-quality CMM with higher-quality CMM, possibly in combination with
an upgrading system. If access to high-grade blending gas is available, a less
costly upgrade facility can be employed in conjunction with blending the drained
CMM with higher-quality gas to bring up the CMM's quality to pipeline
specifications.
Gas pressure values are from The Transportation of Natural Gas, available at
http://www.naturalqas.orq/naturalqas/transport.asp, and personal experience. Other values are from
Interstate Natural Gas - Quality Specifications & Interchangeability, Center for Energy Economics, Bureau
of Economic Geology, University of Texas at Austin, December 2004, available at
http://www.beq.utexas.edu/enerqyecon/lnq/documents/CEE Interstate Natural Gas Quality Specification
s and lnterchanqeabilitv.pdf.
1 Gob (or goaf) refers to the rubble zone which results when longwall mining advances and the mine roof
collapses into the mined-out void. Although the primary coal seam is gone, considerable amounts of
methane may continue to be released into the gob area from fractured adjacent rock strata and other, non-
mined coal seams, and that methane can be extracted through wells drilled to contact the gob zone.
' Adapted from Technical and Economic Assessment of Potential to Upgrade Gob Gas to Pipeline Quality,
U.S. Environmental Protection Agency, December 1997.
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3. Increase the energy content of the drained gas by spiking it with higher
hydrocarbon gases such as propane. This option is usually available only if the
receiving pipeline is willing to accept spiked gas.
4. Install an upgrading system or enrichment plant that removes one or more of the
four most prevalent contaminants.
While blending or spiking the drained CMM may help dilute the concentration of
contaminants in methane, it is often necessary to employ more aggressive technologies
to remove the contaminants to bring up the methane quality to pipeline specifications.
3. Gas Upgrading Technologies
Currently, several technologies are commercially available for removing the major CMM
contaminants (i.e., nitrogen, oxygen, carbon dioxide, and water vapor), while some
others have reached field demonstration stage of development.
Nitrogen Rejection Technologies
Nitrogen is usually the most technically difficult contaminant to remove from CMM, as
well as the most expensive. Currently there are five types of available nitrogen rejection
unit (NRU) technologies:
• Cryogenic Technology
• Pressure Swing Adsorption
• Solvent Absorption
• Molecular Gate
• Membrane
Cryogenic Technology: The cryogenic process uses a series of heat exchangers to
liquefy the high-pressure feed gas stream. The mixture is then flashed and a nitrogen-
rich stream vents from a distillation separator, leaving the methane-rich stream.
Designers locate the deoxygenation system at the plant inlet to avoid the danger of
explosion within the plant. Cryogenic plants have the highest methane recovery rate
(about 98 percent) of any of the technologies and have become standard practice for
large-scale projects where they achieve economies-of-scale; however, they tend to be
less cost-effective at capacities below 5 Mmscfd which are more typical of CMM
drainage projects.
Pressure Swing Adsorption (PSA): Gases when under pressure tend to get adsorbed on
solid surfaces; while more gas is adsorbed with increase in pressure, reducing the
pressure releases or desorbs the gas. PSA utilizes the property of varying affinities of
gases for a given solid surface to separate a mixture of gases. In case of CMM, nitrogen
is removed from low-quality gas by passing the gas mixture under pressure through a
vessel containing an adsorbent bed that preferentially adsorbs nitrogen, leaving the gas
coming out of the vessel to be rich in methane. When the adsorbent bed is saturated,
the pressure is reduced to release the adsorbed nitrogen, preparing the bed for another
cycle.
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Usually very porous materials are selected as adsorbents for PSA systems because
they provide surface areas large enough to adsorb significant amount of gas even
though the adsorbed layer may be one or only a few molecules thick. Adsorbents
typically used are activated carbon, silica gel, alumina, and zeolite.
Some specialty adsorbents like zeolites and carbon molecular sieves selectively adsorb
gases based on the size of their molecules; only those gases are allowed into the
adsorbent structure that have molecules smaller than the pore size of the absorbents. In
most PSA NRU systems, wide-pore carbon molecular sieves selectively adsorb nitrogen
and methane at different rates in an equilibrium condition. The use of zeolites as
adsorbent for CMM has so far been tested only on bench scale.
PSA recovers up to 95 percent of available methane and can operate on a continuous
basis with minimal onsite attention. PSA systems have excellent turndown capability, so
they are able to operate effectively with gas flowing at a fraction of rated capacity.
Solvent Absorption: Sometimes referred to as Selective Absorption, this process uses
specific solvents that have different absorption capacities with respect to different gases.
In CMM applications, a solvent selectively absorbs methane while rejecting a nitrogen-
rich stream in a refrigerated environment. The petroleum industry commonly uses
selective absorption to enrich gas streams.
Molecular Gate: This process removes nitrogen and other contaminants from the
methane, whereas other processes remove the methane from the nitrogen. The process
uses a new type of molecular sieve that has the unique ability to adjust pore size
openings within an accuracy of 0.1 angstrom. For CMM, the sieve pore size is set
smaller than the molecular diameter of methane and above the molecular diameters of
nitrogen, oxygen, carbon dioxide, and water, as indicated in Figure 1. This permits the
nitrogen and other contaminants to enter the pores and be adsorbed while excluding the
methane, which passes through the fixed bed of adsorbent at essentially the same
pressure as the feed.
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Starting Material - 4 Angstroms
4.0 Angstroms
3.6 A
3.8 A
a
Molecular Gate - Pore Contracted to 3.7 Angstroms
3.6 A IMN2)
\r AfxXr^ ^r^«^
3.7 Angstroms
3.8 A
'"
Figure 1. Molecular Gate NRU Technology (courtesy of Engelhard)
The molecular gate process employs a PSA operation by "swinging" the adsorbent bed
pressure from a high-pressure feed step that adsorbs the contaminants to a low-
pressure regeneration step to remove the previously adsorbed contaminants.
Membrane: This process uses membranes to selectively pass methane, ethane, and
higher hydrocarbons while retaining nitrogen. A simple one-stage membrane unit is
appropriate for feed gas containing about 6 to 8 percent nitrogen. However, more
commonly, nitrogen concentrations are higher and require a two-step or two-stage
membrane system.
Oxygen, Carbon Dioxide, and Water Vapor Removal Technologies
Systems to remove oxygen, carbon dioxide, or water vapor can stand alone, but
typically, an integrated enrichment facility is installed to remove all four contaminants
with a series of connected processes at one location. When a facility consists of
components from more than one vendor, a single company usually takes responsibility
for the design and performance of the entire upgrade facility. Such a "turn-key"
arrangement protects the system owner from potential disputes over the failure of one
system component.
The following technologies are commercially available to remove the remaining three of
the four major CMM contaminants:
Oxygen Removal: After nitrogen rejection, deoxygenation is the most technically
challenging and expensive process. It is especially important since most pipelines have
very strict oxygen limits (typically 0.1 percent or 1,000 parts per million). NRU
technologies such as PSA will experience oxygen rejection in proportion to nitrogen
rejection and may need very little deoxygenation as a final processing step. Oxygen
rejection associated with cryogenic or solvent absorption NRUs is more critical due to
explosion danger, and it must be the first system component. Since deoxygenation
results in a substantial temperature rise, if inlet gas is likely to contain over 1.5 percent
oxygen, a two-stage recycle system is needed to avoid unacceptably high temperatures.
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Carbon Dioxide Removal: Several technologies are available commercially, including
amine units, membrane technology, and selective adsorption. Amine units are tolerant
of only low levels of oxygen in the feed stream, so the amine unit must be downstream
of the deoxygenation unit.
Water Vapor Removal: Dehydration of CMM is the simplest part of any integrated
system design. Inadequate water removal, however, can result in corrosion damage to
delivery pipes and can be quite serious. Most system suppliers will employ a molecular
sieve dehydration stage because of its proven record and economical operation.
4. Commercial Applications
The first CMM upgrade facility in the U.S. was installed by BCCK Engineering, Inc. in
1997 in Southwestern Pennsylvania. Since then, 13 additional commercial-scale CMM
upgrade facilities have come on line at active and abandoned mines, and three
additional facilities are awaiting start up. Figure 2 shows the locations of these projects,
while Table 2 lists these facilities, including their location, type of feed gas, and
throughput capacity.
1 (CMM)
2 (CMM)
5(CBM, CMM.AMM)
16(AMM)
14 (CMM)
13(AMM)
-15(CBM)
(AMM)
17(AMM)/4
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Table 2. Operating CMM Upgrade Facilities
Vendor
AET
(Vendor profile
on pg. 11)
BCCK
(Vendor profile
on pg. 12)
BCCK
BCCK
D'Amico
Technologies
(Vendor profile
on pg. 13)
Guild (Molecular
Gate)**
(Vendor profile
on pg. 14)
Guild (Molecular
Gate)
Guild (Molecular
Gate)
Guild (Molecular
Gate)
Guild (Molecular
Gate)
Guild (Molecular
Gate)
Guild (Molecular
Gate)
Guild (Molecular
Gate)
Guild (Molecular
Gate)
Guild (Molecular
Gate)
Guild (Molecular
Gate)
Guild (Molecular
Gate)
Location
Price, Utah
Waynesburg, PA
Brookwood, AL
Marion, IL
Northern Appalachia
Illinois Basin
Raleigh, Illinois Basin
Southwestern PA
Virginia
West Virginia
West Virginia
Virginia
PennsylvaniaA
Pennsylvania
West VirginiaA
PennsylvaniaA
Illinois
Feed
Gas
CMM
CMM
CMM
AMM
CBM*,
CMM,
AMM
AMM
AMM
AMM
CMM
AMM
AMM
CMM
AMM
CMM
CBM
AMM
AMM
Inlet
Capacity
(Mmscfd)
8
12
12
12
5
1.0
2.5
2.0
1.5
0.8
1.5
10
1.5
1.5
1.0
2.0
0.5
Inlet N2
Concentration
-15%
10-25%
28-32%
15-30%
2-3%
<10%(plus1%
C02)
<1 5% (plus 3%
C02)
13% (plus 2%
C02)
17% (plus 3%
C02)
6% (plus 1%
C02)
30% (plus 3%
C02)
17% (plus 3%
C02)
40% (plus 1%
C02)
15% (plus 5%
C02)
8% CO2 only
40% (plus 1%
C02)
< 10% (plus 1%
C02)
* Coalbed methane
**The Guild / Molecular Gate™ technology is licensed to Guild from Engelhard (now BASF).
A Awaiting start-up
The following examples demonstrate how some CMM drainage projects have
successfully combined various gas upgrading technology options to purify lower-quality
CMM to pipeline quality specifications.
Example #1
The D'Amico Technologies project underway in northern Appalachia performs limited
CMM processing for sale to a natural gas pipeline. The developer avoids the costly
NRU step by employing three techniques to maintain acceptable product specifications:
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• Feed gas control - accepting only the high-grade or lightly contaminated CMM,
especially with respect to nitrogen.
• Carbon dioxide and water vapor removal - using a proprietary technique to reject
carbon dioxide.
• Blending - using a supply of very high-grade CMM, the project employs
controlled blending to bring into compliance a substantial flow of slightly off-
specification product.
Example #2
In 2000, Jim Walter Resources (JWR) began operating a BCCK gas processing plant at
their Brookwood, Alabama mine to supplement their high-quality methane production by
upgrading low-quality gas. The fully integrated plant removes water, CO2, nitrogen, and
oxygen. Early in the plant's operation, the low-quality gas was determined to contain
sulfur, a not so common CMM contaminant. Although the gas contained only a few ppm
of sulfur, it nevertheless caused problems over time for the amine tower (the CO2
removal component); JWR had to add a sulfur removal component to the overall plant.
The plant has continued to operate since startup and currently processes an estimated 8
to 9 Mmscfd of raw gas, producing about 4 Mmscfd of treated gas. During the first five
years of operation, the plant was managed on site by BCCK staff under contract to JWR.
Subsequently it has been operated directly by the JWR staff.
Example #3
In southern Illinois, Grayson Hill Energy, LLC is employing the Molecular Gate®
technology to remove water, nitrogen, and carbon dioxide from abandoned mine
methane and low-quality natural gas to produce pipeline quality gas. The plant, which is
powered by an onsite tail-gas-fueled generator, removes nitrogen and carbon dioxide in
a single step. Gas flow rates to the plant are of the order of 2.5 Mmscfd.
5. Summary of Gas Upgrading Technologies
Five system vendors are currently supplying CMM upgrading technologies to the natural
gas market: AET, BCCK, D'Amico Technologies, Guild Associates, and MTR. Another,
Northwest Fuel Development, has operated a nitrogen removal system with 1 Mmscfd
capacity at two mines in Ohio.
Table 3 summarizes the system providers that have the technical capability to design
and provide gas upgrading systems and that have targeted their systems to the CMM
market. The Appendix contains a more detailed profile of each of these vendors.
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Table 3. Current and Upcoming CMM Upgrade Technology Vendors
Vendor
Advanced Extraction
Technology
(Vendor profile: pg. 11)
BCCK
(Vendor profile: pg. 12)
D'Amico Corporation
(Vendor profile: pg. 13)
Engelhard (Guild)
(Vendor profile: pg. 14)
Engineered Gas
Systems Worldwide
(Vendor profile: pg. 16)
Gas Separation
Technology
(Vendor profile: pg. 17)
Membrane Technology
and Research (with
ABB)
(Vendor profile: pg. 18)
Northwest Fuel
Development
(Vendor profile: pg. 19)
Velocys
(Vendor profile: pg. 20)
NRU
Technology
Solvent
Absorption
Cryogenic
PSA
Molecular Gate
Cryogenic and
membrane
PSA with Zeolites
Membrane
PSA
MicroChannel
thermal swing
absorption
Size Range
(inlet Mmscfd)
2 and over
5 and over
1 and over
1 and over
1 and over
1 and over
1 and over
1 and over
1 and over
Contaminants
Removed
N2, H2O
N2, 02
O2, H2O
N2, O2 (partial),
CO2, H2O
N2, CO2, H2O
N2, O2, CO2, H2O
N2, CO2,
N2
N2
Turnkey?
Y
Y
Y
Y
Y
N
Y
N
N
Status
Full-scale operation
at coal mine
Full-scale operation
at coal mine
Demonstrated in
natural gas fields
and commercially
available
Full-scale operation
at coal mine
CMM field
demonstration
needed
Bench-scale testing
phase
Full-scale operation
at natural gas fields
Pilot NRU has been
demonstrated under
field conditions
Under development
Comments
Engineering for N2 & H2O only. Has
designated HNNG Development to
be their representative in North
America.
Cost competitive at larger scale
(e.g., >5 Mmscfd). Provide a fully
integrated plant incorporating third-
party CO2 and H2O removal
technologies.
In addition, the company has
implemented a gas upgrade project
using an advanced gas production
and management approach,
avoiding the need for nitrogen
rejection.
May need to add a supplemental
deoxygenation system depending on
pipeline quality requirements and
source gas concentrations.
Can design integrated, turnkey
systems.
System will need supplemental
deoxygenation system. Has not
moved past the bench-scale stage;
still seeking development capital.
Continuous process yields steady
product stream. Systems can be
designed to meet various gas
contamination levels and product
requirements.
Lower methane yield. Can be
competitive with molecular sieve at
low N2 concentrations.
Third-party components needed for
CO2, H2O, and O2 removal.
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Appendix: NRU Vendor Profiles
Following are vendor profiles for nitrogen rejection technologies that have targeted CMM
applications. Integrated upgrading systems that a vendor can offer are also profiled.
These profiles were developed based on publicly available information as well as that provided
directly by vendor representatives. In some cases (e.g., technologies that have only been
demonstrated at bench scale), vendor claims with respect to "proven performance" may not hold
true under actual mine conditions. Deviation from proven performance may occur for a number
of reasons, including the following:
• Presence of contaminants in CMM that are not usually found in low-grade natural gas
• Variation of CMM flows as wells are disconnected and reconnected
• Variation of CMM contaminant levels over time and location
• Integration of system components that may not be fully compatible (e.g., supplied by a
subcontractor)
10
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A.1 Advanced Extraction Technologies, Inc. (AET)
Nitrogen rejection: Solvent Absorption
Other contaminants removed: H2O
Third party equipment needed to remove: CO2, O2
Flow rate limitations: None
Feed quality limitations: None
Status: Commercially available
Contact: Name: Tom Gaskin, VP Technology
Address: 2 Northpoint Drive, Suite 820
Houston, TX 77060-3237 USA
Tel: (281) 447-0571
Fax: (281) 447-5601
E-mail: tomg@aet.com
Website: http ://www. aet. com
Commercial history: AET offers full-scale 5 Mmscfd and 15 Mmscfd plants for rejection of
nitrogen, with feed gas nitrogen content of about 15 percent. AET's first CMM application
began operation at the Aberdeen Mine near Price, Utah in June 2007.
Description of system(s) and performance: AET's process requires oxygen and carbon
dioxide removal prior to removing nitrogen and water.
Following O2 and CO2 removal, the partially processed feed gas is chilled with propane
refrigeration and ethylene glycol injection. Ethylene glycol and water separate, water exits, and
ethylene glycol is regenerated, while the cold feed gas is brought into contact with an
appropriate chilled solvent in an absorption tower. Nitrogen exits the absorber as the
"overhead" product. Methane is absorbed, and the rich solvent is the "bottoms" product of the
absorber. Flash separation removes the absorbed methane and heavier hydrocarbons from the
solvent by reducing the pressure of the absorber bottoms stream in multiple steps to minimize
gas compression. Methane released during flash separation is compressed to sales pressure.
After methane release, the lean solvent is pumped to higher pressure, chilled, and returned to
the absorber.
AET notes that its technology exhibits infinite CO2 tolerance without freezing and flexibility in
terms of its response to feed rate and compositional changes.
Services offered: AET licenses the use of its NRU and water removal technology and provides
process engineering support. HNNG Development (Glen Rector; (713) 225-6801;
www.hnngdevelopment.com) is the sole representative for licensing the process in North
America.
11
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A.2 BCCK Engineering, Inc.
Nitrogen rejection: Cryogenic
Other contaminants removed: O2
Third party equipment needed to remove: CO2, H2O
Flow rate limitations: The BCCK process is most cost effective at raw gas inflow rates higher
than 5 Mmscfd.
Feed quality limitations: None
Status: Commercially available
Contact: Name: Gregory L. Hall, P.E., Sales Manager or
R. Clark Butts, P.E., President
Address: 2500 North Big Spring Street, Suite 230
Midland, TX 79705
Tel: (432) 685-6095
Fax: (432) 685-7021
E-mail: Greg Hall: greghall@bcck.com
Website: www.bcck.com
Commercial history: BCCK Engineering has installed three full-scale CMM upgrade facilities
to date. The first was installed in Pennsylvania in 1997. All three facilities upgrade methane to
meet natural gas pipeline requirements.
Description of system(s) and performance: BCCK's CMM upgrading plants are completely
integrated facilities, including a proprietary oxygen extraction process (catalytic oxidation) and
BCCK's patented Nitech™ nitrogen extraction process. The system integrates conventional
CO2 removal (amine process) and dehydration equipment supplied by other vendors. BCCK's
plants operate over a wide range of inlet conditions while meeting sales gas specifications.
BCCK specializes in nitrogen extraction using cryogenic technology. The Nitech™ process is
capable of providing over 99 percent hydrocarbon recovery. Nitrogen vented from the NRU
contains only a small amount of methane and no volatile organic compounds. This efficiency
eliminates the need to flare residue product from the facility. The company's catalytic oxygen
extraction process can meet stringent oxygen specifications (e.g., up to 10 ppm) in the sales
gas. BCCK has integrated the oxygen extraction process with other plant components in order
to utilize the heat produced, thus reducing fuel gas demand.
Services offered: BCCK's services include designing, procuring, and installing all plant
equipment; start-up; and operation (if requested).
12
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A.3 D'Amico Technologies
Nitrogen rejection: PSA
Other contaminants removed: None
Third party equipment needed to remove: CO2, H2O, O2
Flow rate limitations: None
Feed quality limitations: The D'Amico Technologies' currently active CMM drainage and
treatment project uses advanced techniques for gas capture and handling that minimize the
level of contamination in the gas fed to the upgrade plant, avoiding the need for nitrogen
rejection (the costliest step in CMM processing). The company also employs high-quality gas
for blending to increase the energy content of the product stream.
Status: Commercially available, but currently not employed at a coal mine
Contact: Name: Joseph D'Amico, President
Address: 6422 Oak Park Court
Linthicum, MD 21090
Tel: (410) 859-3044
Fax: (410)859-3044
E-mail: damico.corp@verizon.net
Website: N/A
Commercial history: D'Amico Technologies' patented nitrogen rejection technology has been
tested in natural gas fields in Texas, Colorado and Kansas, and is commercially available
though not as yet put into operation at a coal mine. The company has successfully developed
and implemented a gas upgrading and pipeline injection project that avoids the need for
nitrogen rejection; the facility, located in the Northern Appalachian coal basin, is currently active.
Description of system(s) and performance: D'Amico Technologies employs a patented PSA
nitrogen rejection process that includes a carbon molecular sieve in the bed. It preferentially
adsorbs the hydrocarbon and lets the contaminants (nitrogen, some oxygen, and water) pass.
Third-party components can be added for removal of other contaminants. There are no data on
performance of this technology at an actual mine, since it has yet to be implemented for CMM
processing. The gas management approach being employed at D'Amico's current project
includes use of small, satellite gas-processing plants at the wellheads upstream of the larger
centralized processing facility.
Services offered: D'Amico Technologies can design and implement fully integrated gas
processing systems using advanced technologies. In addition, the company is able to provide
gas drainage expertise to produce gas with as little contamination as possible, thereby reducing
the gas-processing requirement and maximizing project profitability. Their approach to gas
management enables handling daily changes in gas supply. The company also offers
consultation services and assistance in securing pipeline interconnection, gas sales, and carbon
offset agreements.
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A.4 Guild Associates, Inc.
(Exclusive U.S. licensee of Engelhard's Molecular Gate technology)
Nitrogen rejection: Molecular gate
Other contaminants removed: CO2, H2O, O2 (partial - see text below), H2S (if necessary)
Third party equipment needed to remove: O2,when required to be removed to low levels
Flow rate limitations: None
Feed quality limitations: None
Status: Commercially available
Contact: Name: Michael Mitariten
Address: 5750 Shier-Rings Road
Dublin, OH 43016
Tel: (908) 752-6420
Fax: (614)798-1972
E-mail: Mike@moleculargate.com
Website: www.moleculargate.com
Commercial history: Twelve full-scale plants are in or are nearing operation (25 in total on
natural gas): one processing virgin coalbed methane for CO2 removal, three processing CMM,
and eight processing methane from abandoned mines.
Description of system(s) and performance: The technology consists of specialty adsorbents
and advanced PSA processes that are jointly offered as fabricated equipment by Guild
Associates, Inc. and is based on the Molecular Gate technology licensed by Guild from
Engelhard (now BASF) Corporation. The Molecular Gate process will remove all the water and
CO2 and a portion of the N2 and O2 in a single step. If required, the process can also remove
H2S. In most cases, the nitrogen specification is 4 percent and typically the methane recovery
rate is 92 percent.
The Molecular Gate system (explained in section 3) for upgrading nitrogen-contaminated CMM
uses molecular sieves with pore size of 3.7 angstroms, nitrogen and methane molecular
diameters being approximately 3.6 angstroms and 3.8 angstroms, respectively. This adsorbent
permits nitrogen and the much smaller CO2 (3.3 angstroms) and O2 (3.5 angstroms) molecules
to enter the pore and be adsorbed while excluding the methane, which passes through the fixed
bed of adsorbent at essentially the same pressure as the feed. One major advantage of the
process is that the CO2 is completely removed in a single step being much smaller in size, while
the nitrogen and oxygen are removed to pipeline specifications. Water is also a small molecule
and adsorbs strongly; typically, the system is designed to remove water so the feed is pre-
dehydrated to moderate levels.
The Molecular Gate system can operate over a feed pressure range from as low as 50 psig to
600 psig or more, which suits CMM feed pressure which is typically in the range of 100 psig.
This fits the conditions for an oil-flooded screw compressor with atmospheric pressure suction
and discharge as required in a single stage. A pressure of about 100 psig offers an optimal
balance between the needs of the compressor and the Molecular Gate unit because it provides
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product at 90 psig, which allows the product compressor to be a two-stage reciprocating
machine. Since the product at the suction point is dry and CO2-free, there are no corrosion
issues; this advantage voids the need for special materials and extends the life of the
compressor.
Although the Molecular Gate process will remove O2 at about the same or slightly lower rate as
N2, O2 removal is recommended ahead of the Molecular Gate, since accumulating
concentrations of O2 in the low-pressure tail gas pose a risk of explosion. As the rejected O2
concentration approaches about 10 percent (the lower explosive limit of O2 in methane) in the
tail gas, a safety issue can develop since the tail gas continue to contain small amounts of
methane.
Guild states that it removes the N2 from the methane, leaving methane at high pressure, while
all other processes remove the methane from the N2, producing methane at low pressure—a
significant economic advantage over other technologies.
Services offered: Guild Associates will design, build, and start up an integrated CMM upgrade
plant, including providing compression and peripheral equipment, and will train the operators.
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A.5 Engineered Gas Systems Worldwide (EGSWW)
Nitrogen rejection: Cryogenic
Other contaminants removed: CO2, H2O, O2
Third party equipment needed to remove: N/A
Flow rate limitations: None
Feed quality limitations: None, although their process is more cost effective at higher inlet
flows and methane concentrations
Status: Field demonstration needed
Contact: Name: George Timberlake, CEO
Address: 141 Aspen Lane
Gilbertsville, PA 19525
Tel: (610) 367-2340
Fax: (610)367-2324
E-mail: info@enggas.com
Website: http://www.enggas.com
Commercial history: EGSWW has targeted biogas and landfill gas upgrading (among other
applications) in their technology portfolio and could engineer an integrated system for upgrading
coal mine methane. As of this report, however, they have not demonstrated their process in the
field.
Description of system(s) and performance: The proprietary EGSWW process involves an
initial dewatering step followed by a cryogenic stage for nitrogen removal and a hollow-fiber
membrane stage for CO2 removal.
Services offered: EGSWW can provide fully integrated, turnkey CMM upgrade systems for
domestic applications. They can custom design systems that are tailored to meet the specific
gas processing needs of a given project.
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A.6 Gas Separation Technologies, LLC (GST)
Nitrogen rejection: PSA with natural zeolites
Other contaminants removed: CO2, O2 (partial - see text below)
Third party equipment needed to remove: H2O, O2
Flow rate limitations: The process is designed to be economical for relatively small gas flows
from 0.5 to several million cubic feet per day.
Feed quality limitations: Less than 40 percent nitrogen
Status: Research and development; field demonstration needed
Contact: Name: Major Seery, President
Address: 345 West 62nd Ave., Suite C203
Denver, CO 80216
Tel: (303) 430-1430
Fax: (303) 657-6075
E-mail: mseery@gassep.com
Website: http://www.gassep.com
Commercial history: The technology has not yet been proven beyond bench-scale testing,
and the process for removing oxygen and nitrogen is not yet perfected. The low oxygen
specification for pipeline gas (0.1 percent) might be the most difficult to meet. As of this writing,
the developer was still seeking sources of development capital to move the technology past the
bench-scale stage.
Description of system(s) and performance: Gas Separation Technologies uses two distinct
pressure swing adsorption systems: the patented Carbo-X™ process for carbon dioxide
removal and Air-X™ for air/nitrogen removal. Both systems employ a natural zeolite adsorbent.
Inlet gas is pressurized and dehydrated, after which it travels to the Carbo-X™ unit which
reduces CO2 to about 0.5 percent. Upgraded gas then travels to the Air-X system. A
supplemental deoxygenation step will probably be necessary for most CMM applications. The
Carbo-X™ component uses an air rinse instead of pressure reduction for regeneration, and can
achieve a high level of separation at low operating pressures—a feature that reduces both
operating and capital costs. Increasing operating pressures will improve the purity even further.
Services offered: Once GST has perfected both system designs, it will offer a full-scale facility.
It will probably have to work through a turnkey constructor that has sufficient financial strength
to stand behind system guarantees.
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A.7 Membrane Technology and Research, Inc. (MTR)
Nitrogen rejection: Membrane
Other contaminants removed: CO2, with a separate membrane
Third party equipment needed to remove: H2O, O2
Flow rate limitations: The process is most cost effective at flows ranging from 1-20 Mmscfd.
Feed quality limitations: None
Status: Commercially available
Contact: Name: Kaaeid Lokhandwala, Product Manager- Natural Gas
Address: 1360 Willow Road, Suite 103
Menlo Park, CA 94025-1516 USA
Tel: (650) 328-2228, ext. 140
Fax: (650) 328-6580
E-mail:
Website: http://www.mtrinc.com/index.html
Commercial history: MTR's membrane systems have been field-proven in natural gas
processing applications such as nitrogen removal and fuel gas processing.
Description of system(s) and performance: The MTR NitroSep™ process uses a selective
membrane that allows hydrocarbons to pass through but retains nitrogen. Typically their
process creates two treated streams: a low-nitrogen (<4 percent N2) product stream that is
enhanced in hydrocarbons, and a high-nitrogen (30-50 percent N2) side stream that will contain
some methane and can be used as a fuel for compressors powering the membrane separation
process. In some applications, a third concentrated-nitrogen (60-85 percent N2) waste stream is
also generated.
Treatment of gas streams with low levels of nitrogen contamination may require only a single
membrane to achieve product gas specifications. Two or more membranes may be required for
more concentrated streams. The company can engineer its treatment systems specifically to
meet requisite product gas specifications depending on the quality of the feed gas stream.
The MTR process is continuous (not batch mode) and is able to produce a steady product flow
with 80-90 percent methane recovery.
Services offered: MTR can provide a system combining one membrane for nitrogen removal
and another for CO2 removal. Third party processes for water removal and oxygen removal
must be added, either upstream or downstream of the MTR membrane(s), to create a fully
integrated CMM upgrade system.
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A.8 Northwest Fuel Development, Inc. (NW Fuel)
Nitrogen rejection: Continuous PSA
Other contaminants removed: None
Third party equipment needed to remove: CO2, H2O, O2
Flow rate limitations: None
Feed quality limitations: Yes - feed should contain >90 percent methane
Status: Demonstrated under field conditions
Contact: Name: Peet Soot, PhD, President
Address: 4064 Orchard Drive
Lake Oswego, OR 97035
Tel: (503) 699-9836
Fax: (503) 699-9847
E-mail: nwfuel(S)northwestf uel.com
Website: http://www.northwestfuel.com
Commercial history: The NW Fuel Continuous Pressure Swing Adsorption (CPSA) process
has been demonstrated at full scale (1 Mmscfd unit) at two coal mines for a limited term.
Description of system(s) and performance: The CPSA process is a simple, high-throughput
process capable of separating methane from nitrogen in lightly contaminated CMM gas streams.
Given its simplicity, the process can be applied economically to small sources of CMM. A unit
capable of processing 1 Mmscfd of CMM is about the size of a pickup truck.
The NW Fuel system uses a methane-selective absorbent. A disadvantage of the NW Fuel
system is that it does not have high product recovery efficiency. About 30 percent of the
methane in the feed stream goes into the byproduct stream that is available for onsite power
generation or other applications.
Services offered: NW Fuel can provide an integrated CPSA system by adding the appropriate
carbon dioxide, oxygen, and water vapor removal systems from third party suppliers. The
company has installed and operated such systems, although its experience with oxygen
removal systems is limited.
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A.9 Velocys, Inc.
Nitrogen rejection: Thermal swing absorption
Other contaminants removed: None
Third party equipment needed to remove: CO2, H2O, O2
Flow rate limitations: Velocys is targeting small flow-rate CMM applications rather than trying
to compete with cryogenic systems which are economical for large flow-rate applications.
Feed quality limitations: None for CMM applications
Status: Under development
Contact: Name: Jeff McDaniel, Manager of Business Development
Address: 7950 Corporate Boulevard
Plain City, OH 43064
Tel: (614) 733-3300
Fax: (614) 733-3301
E-mail: mcdaniel@velocys.com
Website: http://www.velocvs.com/home.php
Commercial history: Velocys Inc. is pursuing a breakthrough in nitrogen rejection gas
processing efficiency through the application of their microchannel chemical processing
technology. By combining that technique with selected adsorbents, Velocys is striving to
achieve ultra-fast thermal swing adsorption. Bench-scale testing has been conducted using
microporous carbon as the adsorbent and employing a thermal swing time of 10 seconds and a
bed differential temperature of 20°C. In testing, a feed gas stream of 70 percent methane and
30 percent nitrogen was separated into a product stream of 92 percent methane and 8 percent
nitrogen. Further testing and development is underway.
Description of system(s) and performance: The Velocys microchannel technology is based
on the principal that increased surface area results in increased chemical reaction rates. Their
goal is to dramatically increase the rate at which temperature swings can occur and to direct a
greater amount of heat where it is needed to increase the nitrogen removal rate.
Services offered: The Velocys system at present is solely targeting nitrogen removal. Third
party components would need to be secured for carbon dioxide, water, and oxygen removal for
a fully integrated gas processing plant.
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