Ventilation air methane: a simulation of an optimised process of abatement with power and cooling

ABSTRACT Ventilation air methane is low concentration methane (below 1 vol. %) emitted from an underground coal mine. High ventilation air volumes circulated through the mine, ensure that the methane remains at a safe concentration. In 2016, the Australian Government reported fugitive emissions of methane from underground coal mines at approximately 19.0 million tonnes (CO2-equivalent) which was about 4.0% of Australia's national greenhouse gas emissions. Therefore, an optimised process of heat recovery from a fluidised-bed VAM abatement reactor, to produce power and cooling was studied. For a ventilation flow rate of 20 m3/s, the minimum methane concentration for a direct gas turbine was 0.45 vol. % at a reactor temperature of 630°C and compressor pressure of 1.5 bar. An indirect gas turbine process operated with a minimum methane concentration was 0.4 vol. % at a reactor temperature of 630°C, compressor pressure of 4.0 bar and turbine flow rate of 2.2 kg/s.