Inertisation of highwall mining to control methane concentrations at the Moura mine

Abstract

Methane, a highly explosive gas, which is released during coal mining, presents an imminent problem when mixed with oxygen in regard to maintaining safe working conditions. The Moura Mine’s previous highwall coal mining operation in Central Queensland identified that production rates and penetration depths of mining equipment has been restricted for mines with high methane concentrations in comparison to regions with lower methane concentrations. A number of inert gases have been identified to inertise the highwall drive, including Carbon Dioxide, Nitrogen and Boiler Gas, which is a combination of carbon dioxide, oxygen and nitrogen. The objective of this paper is to determine which of these gases is the most effective in improving the mine’s efficiency with regard to safety and production rates at a chosen penetration depth of 300m. A 2D, steady, non-reacting species transport model of the highwall drive was used to obtain methane and oxygen concentrations using CFD software (Fluent). Results indicate that applying the inert gases at high angles is more effective in minimising the methane/oxygen concentrations within the drive than at lower angles. Carbon Dioxide was the most effective when applied at a 60 degree angle, followed closely by Nitrogen, while Boiler Gas came last.