Mine Site Greenhouse Gas Mitigation » Mine Site Greenhouse Gas Mitigation
Currently, utilisation of coal mine methane is generally limited to d rained methane. Mine ventilation air exhaust (MVAE) now represents the single largest opportunity in coal mining for further reduction of methane emissions and hence greenhouse gas emissions. There is also the potential for energy recovery and utilisation.
MVAE is characterised by large volumetric flows and low methane concentrations (<1% by volume). Due to its low energy concentration, MVAE cannot be utilised in conventional combustion systems, such as gas turbines or engines. It can and has been used as a fuel laden combustion air; however, efficient combustion systems allow only a small proportion of the total available MVAE to be utilised, or require the presence of a large mine mouth power station.
Two similar technologies, based on a flow-reversal reactor utilising a regenerative heat exchange bed, are capable of combusting hydrocarbons at low concentrations in air streams.
One of these technologies, developed by MEGTEC Systems AB and known as the VOCSIDIZER™, has been demonstrated over a period of a year on MVAE at Appin Colliery, on the NSW South Coast. The test unit operated safely and without any observable effect on the performance of the mine's ventilation system. The test unit, fitted with heat exchange media and designed to utilise up to 6000 Nm3 of MVAE per hour, has shown promising results, recovering up to 88% of the chemical energy of the input methane (lower heating value). The test unit has also been operated on methane concentrations as low as 0.19% by volume. These results meet or exceed expected results from a range of technical evaluations made by a number of parties.
In addition to the significant greenhouse gas emissions abated as a result of oxidising methane in the MVAE, the results of this demonstration trial indicate that a high proportion of the energy release can be made available for a conventional steam cycle power plant.