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.

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Authors are grateful to Commonwealth Scholarship Commission, UK and The University of Nottingham for their financial support (Commonwealth Scholarship and Fellowship Plan—2010, INCS-2010-192). The authors are obliged to Ministry of Human Resources and Development, Government of India and Council of Scientific and Industrial Research (CSIR) for their kind permission to avail the above fellowship. Authors acknowledge thanks to Director, CSIR-CIMFR, all staffs of Mine Fire, Ventilation and Miner’s Safety Research Group, CSIR-CIMFR for necessary help for the sample collection.

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Correspondence to Niroj Kumar Mohalik.

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See Figs. 811 and Table 6.

Fig. 8

Repeatability of sample 3 at heating rate 5 °C min−1

Fig. 9

DTG curve for different mass of the sample 2, 3, 9, 10 and 11

Fig. 10

DTG curve for different fraction size of the sample 2, 3, 9, 10 and 11

Fig. 11

DTG curve for different flow rate of the sample 2, 3, 9, 10 and 11

Table 6 TGA results

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Mohalik, N.K., Lester, E. & Lowndes, I.S. Application of TG technique to determine spontaneous heating propensity of coals. J Therm Anal Calorim 143, 185–201 (2021).

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  • Coal
  • Thermogravimetric analysis (TG)
  • Spontaneous heating
  • Jharia coalfield