Published in the December 2009 Coal USA Magazine
Developed and implemented by Canadian company Biothermica Technologies, the Vamox coal mine methane abatement system uses regenerative thermal oxidation to capture and destroy ventilation air methane (VAM) emissions before they are released into the atmosphere. Each ton of methane oxidized reduces greenhouse gas emissions by about 18 tons of carbon dioxide equivalent.
VAM makes up 60-70% of the greenhouse gas emissions from underground coal mines. Globally, these emissions account for about 5% of the 300 million tonnes a year of CO2 equivalent man-induced greenhouse gas emissions. The US is the second-largest contributor, after China, with about 18% of the total.
The first system of its kind to be used in a coal mine in the US, the Vamox unit has been installed and is operational at Jim Walter Resources’ Mine No. 4. The project is also the first of its kind to receive approval from the US Mine Safety and Health Administration (MSHA).
Biothermica director of development Nicolas Duplessis told Coal USA the key design feature that convinced MSHA to approve the project was a configuration which prevented a potentially flammable gas mixture – mine air containing more than 5% methane – from entering the system.
“This is achieved by positioning a fast-acting methane detector at the inlet of the mine air capture duct coupled to a cut-off damper located downstream, just before the system’s inlet,” he said. “Factoring in the air velocity and the reaction time of all the components, the length of the duct is selected to ensure that the cut-off damper will close before the potentially flammable mixture reaches it. By design, this system is failsafe.”
Capturing 30,000 cubic feet per minute of mine ventilation air, the medium-sized Vamox unit is capable of achieving greenhouse gas emission reductions amounting to some 40,000t of CO2 equivalent each year. That is the same as taking 8000 cars off the road.
Historically considered as waste, ventilation air can now be turned into a valuable asset that can be sold as carbon credits on the market. According to Biothermica, one shaft emitting 300,000cu.ft/min of mine ventilation air at 0.5% methane has the potential to generate up to $US2.5 million per year.
JWR spokesman Michael Monahan said Biothermica approached the company, presented the concept and asked for their involvement in the project. He said JWR had been looking at using VAM for several years, both as a potential revenue source as well as developing a strategy to offset any adverse effects of potential “cap and trade” legislation.
The company is working with Biothermica to assess further opportunities for the Vamox system to be installed at its other mines.
Duplessis said Biothermica chose to partner with JWR because the company was one of the few pioneers in the capture and utilization of coal mine methane. “From the beginning, they were receptive to the potential and many benefits of our technology,” he said.
According to Biothermica, the project will be one of the first in the world to generate an income stream based on the selling of carbon credits as a result of VAM destruction.
The company plans to develop VAM oxidation projects based on the monetization of carbon credits around the world under different greenhouse gas emission schemes such as the Clean Development Mechanism of the Kyoto Protocol.
Duplessis said the focus of the JWR project was to gather long-term operational experience and performance data and optimize the Vamox system. The company then plans to develop and demonstrate a full-scale project featuring one or more large units, possibly with a capacity of up to 100,000cu.ft/min. Duplessis said of all the possibilities for reducing the coal mining industry’s carbon footprint, VAM oxidation was arguably the most promising one in terms of emission reduction potential.
JWR also believes VAM abatement systems such as the Vamox will provide a methodology for confronting issues arising from greenhouse gas legislation which may be introduced in the future.
There are currently 220 coal mine methane projects worldwide in 14 countries, helping to lower methane emissions by 3.8 million cubic meters (134.2Mcu.ft) each year. Global mining giant BHP Billiton has had its $A30 million ($US25.04 million) ventilation air methane project, WestVAMP, operational at Illawarra Coal’s West Cliff Colliery in New South Wales, Australia, since September 2007.
WestVAMP utilizes 20% of West Cliff’s available mine ventilation air, reducing greenhouse gas emissions by 250,000 tonnes (275,577 tons) of CO2-e per year.
The project also generates 5 megawatts of electricity from the steam turbine, which is used to meet some of the mine’s energy requirements.
The technology was first piloted at Illawarra Coal’s Appin Colliery in 2001. Biothermica believes the potential for VAM oxidation projects can extend to trona mines which also release significant amounts of methane.
