Case Study: U.S. Demonstration ^
of Ventilation Air Methane
Oxidation Technology
U.S. EPA
Coalbed Methane
JTBEACH PROGRAM
JULY 2010
Project Overview
Methane (CH4) released to the atmosphere
from gassy underground coal mine ventilation
systems constitutes a major source of
greenhouse gas emissions. As concern over
climate change grows worldwide, mitigating
ventilation air methane (VAM) emissions is
drawing increasing attention. Field
demonstrations of VAM oxidation technology
have paved the way for the emergence of a
new industry focused on capturing the energy
embodied in VAM exhaust flows and putting it
to beneficial use. The first such
demonstration in North America was carried
out by CONSOL Energy1, using a MEGTEC
Systems2 single-bed VOCSIDIZER™
(commercial-sized units are twin-bed).
Project Specifications
Name: VAM Oxidation Demonstration project
Site: Windsor Mine, West Liberty, West Virginia
Host: CONSOL Energy
Funding Agencies: USDOE and USEPA
Dates of Operation: Feb. 2007 - Oct. 2008
Equipment: MEGTEC Systems VOCSIDIZER™
Efficiency: >95%
End Use: Abatement only
Emission Reduction: 14,849 tonnes CO2e
CONSOL conducted the project at their
abandoned Windsor coal mine to (1)
demonstrate that the oxidizer can reliably
convert very low concentrations of methane
present in mine ventilation exhaust air to
carbon dioxide and water and (2) determine
CONSOL Energy is the largest producer of high-Btu
coal in the United States, with 17 bituminous coal
mines in six states. CONSOL is a recognized
pioneer in the production and use of coal mine
methane and they provided the host site and
extensive engineering support for the VAM
demonstration project.
the quantity of useful energy that can be
produced by the oxidation reaction. Given
that the project was conducted at an
abandoned mine, drained methane from the
closed workings was diluted to simulate
typical VAM concentrations.
VAM Oxidation Project Site
(Photo courtesy: CONSOL Energy)
Technology Design
Electric heating elements are used to preheat
ceramic heat transfer material in the
VOCSIDIZER's™ core up to or above the
oxidation temperature of methane (1,000°C or
1,832°F), at which point the preheating
system is turned off and VAM inflow is
initiated. As a safety feature, methane cannot
enter the oxidizer unless the electric
preheaters are turned off. Ducting conveys
the (simulated) ventilation exhaust flow into
the oxidizer core where it encounters the
preheated heat exchange material (ceramic
pieces with a high surface area to volume
ratio) and oxidizes the methane, releasing
heat, water, and carbon dioxide. This heat is
transferred to the bed, thereby maintaining its
temperature at or above the temperature
MEGTEC Systems manufactures oxidizers for
industrial air pollutant emission control. They
adapted their technology to abate VAM emissions
at gassy underground coal mines. Their VAM
oxidation system (VOCSIDIZER™) has been
operating successfully in the field, including at the
largest commercial-scale VAM-to-power project in
the world (West Cliff mine in Australia).
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necessary to support auto-thermal operation.
To preclude cooling of the bed, dampers and
valves redirect the flow of incoming ventilation
exhaust air from one side of the bed to the
other, typically on a timeframe of every two or
three minutes. This flow-reversal process,
which is managed by a programmable logic
controller, maintains the hot area of the bed in
the middle of the oxidizer, where it is available
to support oxidation of a constant stream of
VAM overtime.
It should be noted that the oxidation process
is flameless and, following the initial bed
preheating, requires no auxiliary fuel so long
as adequate inflow methane concentrations
are maintained.
Project Operation
The project commenced processing methane
on February 11, 2007 and all components
were found to perform as required, with the
exception of the air compressor and two
methane sensors - one for mine gas and one
for the simulated VAM entering the oxidizer.
Both had an unacceptably long response time
and the VAM sensor showed an inaccurate
reading. Therefore, the methane analyzers
(both mine gas and VAM inflow) and the
compressor were replaced.
Initially the system was run under six different
combinations of methane concentration and
airflow to test the effect of changes in each on
bed temperature, methane conversion, and
bed pressure drop. Following those
parametric tests, the system operated at a
constant methane concentration of 0.6
percent and inlet airflow of 30,000 scfm.
From May through November of 2007, the
system ran unattended for a total of 1,301
hours, with availability in one month reaching
nearly 60 percent. During this period, some
shutdowns were experienced due to
equipment problems and operational
problems. The system's remote unattended
location meant that longer shutdown-response
times were incurred than would have been the
case at an active mine with on-site
maintenance staff available. Following a bed
rebuild, the system ran unattended for a total
of 2,833 hours from May through October of
2008, reflecting an improved availability of 64
percent overall and a peak of almost 95
percent in one month, thus evidencing
substantially improved performance as
compared with the initial operational period.
Overall during the project, the performance of
the oxidizer bed itself was as expected. Inlet
temperatures were essentially steady and
outlet temperatures fluctuated with the
actuation of the flow reversal valves.
CONSOL characterizes the overall operation
of the bed as being "very stable" and
evidenced a methane destruction efficiency of
better than 95 percent. The system operated
safely and all mechanical and logical safeties
performed as designed. CONSOL estimates
that a commercial-scale system at one of their
mines could produce enough energy to
generate 3.3 to 8.2 MW of electricity (or 11 to
27 MW of thermal power).
To improve long-term system availability,
MEGTEC is investigating other, better-
performing ceramic media that may be
employed in place of that used in the
demonstration. Taking all of their experience
with this demonstration project into account,
CONSOL hopes to move the unit to an active
mine and is optimistic that availability can
ultimately be increased to 97 percent.
For further information, contact:
Dr. Jayne Somers, Program Manager
Coalbed Methane Outreach Program
U.S. Environmental Protection Agency
Washington, DC USA
E-mail: somers.iavne@epa.gov
Website: http://www.epa.gov/coalbed
www.epa.gov/cmop
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