Application of TG technique to determine spontaneous heating propensity of coals

The TG method is applied to eleven coal samples of varying rank collected from across the Jharia coalfield, India, to determine spontaneous heating susceptibility. Previous literature does not agree as to the TG experimental parameter that characterizes the spontaneous heating susceptibility of coal. A series of TG experiments were performed on triplicate samples of each coal to determine the susceptibility of coal to spontaneous heating. Each prepared sample had the following properties: mass–10 mg, size distribution − 212 µm, and was subjected to a sample gas flow rate of 40 mL min−1 and a balance gas flow rate of 60 mL min−1 under the following four different heating rates: 1, 5, 15 and 30 °C min−1. The study concludes that the heating rate of 5 °C min−1 should be used to determine the spontaneous heating susceptibility. The experimental data obtained are subjected to chemo-metric tools, i.e. principal component analysis and hierarchical clustering analysis to establish any linkage between the coal characteristics parameters and spontaneous heating susceptibility indices. These analyses reveal that the self-heating (Tsh) and ignition temperature (Tign) determined from the TG experiment results may indicate the susceptibility of coal to spontaneous heating, which is corroborated by well-established standard experiments as well as with field observations