Coal Mine Turns Greenhouse Gas into 'Green Energy'
July 1, 2008
"Coal mines are one of the largest single emitters of methane gas," said Richard Mattus, business manager for methane-gas abatement projects at Megtec Systems. "And among greenhouse gases, methane [CH4] is second only to carbon dioxide in global impact. In fact, methane is more than 20 times more potent at warming the atmosphere than CO2."
To help mines address the emission of these greenhouse gases, Megtec Systems, DePere, Wis., developed a patented combination of emission control and steam-cycle technologies, called the VOCsidizer.
Most coal-mine ventilation of air methane (VAM) is, for mine safety reasons, diluted to concentrations of less than 1 percent, and enormous volumes are being emitted, Mattus noted. "[So,] it's even harder to design technically and economically viable systems to dispose of this greenhouse gas," Mattus said.
The world's first commercially viable VAM-converting installation has been installed at WestVAMP in Australia with the help of the VOCsidizer from Megtec.
Four VOCsidizers are up-and-running at West Cliff Colliery, BHP Billiton, Australia. Megtec development manager Ake Kallstrand reported that, for more than one year, these systems have been converting the energy of the coal mine's 0.9 percent VAM concentration into electrical power.
Kallstrand explained, "The VOCsidizer turns VAM into high-grade, superheated steam that operates a 6 MW conventional steam turbine. The electricity generated by the plant is fed into the local area power grid."
"Of course," he added, "at British Coal in the UK, starting in 1994, a VOCsidizer showed it could efficiently oxidize the very dilute VAM. And in 2001, an installation at Appin Colliery, BHP, Australia, demonstrated twelve full months of efficient heat recovery, using VAM as fuel to generate steam. Here, we're going all the way."
Measurable returns from multiple sources demonstrated that new installations could pay for themselves 2 to 3 years.
Colin Bloomfield, president of BHP Billiton, Illawarra Coal said, "We are very pleased with results from Megtec's VOCsidizer system. To date, we have abated some 250,000 tons of greenhouse gas -- 200,000 by direct methane emission and the balance by displaced electricity emission reduction. And the installation is only taking 20 percent of the full air volume from the ventilation shaft. Also, the facility generates revenue from Greenhouse Abatement Certificates, issued under the NSW (New South Wales) Government's Greenhouse Reduction program."
"Such certificates often are referred to generically as 'carbon credits,'" noted Lars Sundback, managing director of Megtec's Sweden office. "They are key currency for investments in global greenhouse gas emission abatement and conversion technologies."
Valuable credits can be earned with Megtec's VAM technology, he pointed out, by VAM abatement. Converting VAM to thermal energy, or into electrical power, as with WestVAMP, can generate direct income and/or savings in addition -- amounts that could be considerable, depending on local area conditions and power needs. Although the United States is not a Kyoto Protocol signatory, Sundback said there is an increasing market in voluntary carbon trading in the United States. And, in a demonstration project at Consol Energy's Windsor coal mine, a system from Megtec has been abating simulated VAM, generating the ultra-low mine gas concentrations typical for VAM by diluting abandoned-mine methane into fresh air, since May of 2007. The project is partially funded by the U.S. EPA and the Department of Energy (DOE).
As rapidly developing global carbon credit trading and investment options evolve, Sundback suggested that the potential exists for coal mines to realize full payback from a new VAM plant in two or three years. "Of course, 'environmental payback' from these systems benefits everyone."