Effect of moisture content on the R70 self-heating rate of Callide coal

Strip samples from the Boundary Hill pit at Callide have been tested in an adiabatic oven to assess the effect of moisture on the R70 self-heating rate of coal. The two strip samples tested had R70 self-heating rate values of 10.23 and 8.61 °C/h. As the moisture content of the coal was progressively increased, from the dry state of the test, the R70 value decreased dramatically. At approximately 40-50% of the moisture holding capacity of the coal, the self-heating rate becomes measurable. Above this critical level of moisture content, the heat produced by oxidation is dissipated by moisture evaporation and coal self-heating is significantly delayed.