November 5, 2007 A new power plant that generates electrical power using ventilation air methane (VAM) from coal mining is now in operation. The technology significantly reduces harmful emissions of methane (a gas 20 times more potent than CO2) released in the mining process, while producing power that can be delivered to the grid or used directly in the mine.
Developed by MEGTEC, the technology for the BHP Billiton project was is based on a patented combination of emission control and steam-cycle technologies. By using a compact and flameless VOCSIDIZER regenerative thermal oxidizer as an energy source, it is possible to generate high grade, super-heated steam from a fuel with 0.9% methane content. The steam has the same quality as used at traditional power plants. It is used to drive a conventional steam turbine which generates electricity.
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Each hour, the installation is treating 0.9% of methane content in 250,000 square meters (2.69 million square feet) of ventilation air. The energy produced from the methane is utilized to generate steam suitable for running a conventional six Megawatt turbine. The volume of ventilation air treated amounts to only 20% of the total volume of ventilation air available from the ventilation shaft. When coal is formed, so is methane. When the coal is excavated, methane is released. Since methane in air is explosive in concentrations between 5 and 15%, ventilation air is used to dilute the methane to levels below 1% - well below the explosion limit.
Methane is a greenhouse gas over 20 times more potent than CO2. BHP Billiton can now convert the emission reduction to carbon credits corresponding to 250,000 tons of CO2e (CO2-equivalents). A VAM Power Plant treating the full volume of ventilation air can generate approximately one million carbon credits. In comparison, methane emissions of a cow amounts annually to between 1 and 2 tons of CO2e while a car annually generates emissions corresponding to a typical 2 to 4 tons of CO2e.
The power plant is now in full operation at the West Cliff Colliery of BHP Billiton, located in the state of New South Wales on the Australian east coast.