Application of Bulk Coal Self-Heating Tests to Longwall Operations

A new laboratory has been established in the Division of Mining and Minerals Process Engineering, which has refurbished and recommissioned a 2-metre self-heating column built at The University of Queensland (UQ). This equipment overcomes the limitations associated with previous large-scale testing. Repeatable test results are achievable within days instead of months and are far more advanced than any previous work at this scale. The column is ideal for simulating goaf behaviour and for teaching the fundamentals of heating development, including gas detection and analysis. Seventeen test runs have now been completed since the initial recommissioning test in late 2001, with a 100% success rate. Results to date clearly show that moisture transfer is the key factor in coal self-heating development. There is a critical moisture content below which coal oxidation and resultant self-heating is inevitable. This has significant implications for detecting and reducing the risk of a heating in longwall operations. Dried coal as a result of gas drainage will be more susceptible to selfheating as it is predisposed to both heat of wetting from moisture adsorption and accelerated coal oxidation due to ease of access of air to oxidation sites. The off-gas signature associated with the self-heating process appears to be quite complex.