Effect of depth and particle size on spontaneous combustion of coal in deep underground mines of Jharia coalfield.
Debashish Mishra, D.P. Mishra, N.K. Mohalik, S.K. Ray, J.K. Pandey.
Journal of Sustainable Mining, 24(1), 117-129 (2025);
DOI: https://doi.org/10.46873/2300-3960.1443
Abstract
Since their inception, the deep mines have faced the challenges of spontaneous heating and fire. The study examines the impact of coal seam depth and particle size on the spontaneous combustion of coal. A spontaneous heating study of seven coal samples shows moisture, volatile matter, and ash do not exhibit any clear trend except for fixed carbon, which shows a direct relationship. However, crossing point temperature (CPT) and thermo-gravimetric (TGignition) temperature reveal an inverse relationship between spontaneous combustion and the depth of the coal seam. Five size ranges: < 106, 106–212, 212–425, 425–2000, and 0–212 µm are studied, which displayed an increase in mean specific surface area (SSA) by 87% and a decrease in mean D90 value by 93%, with a decrease in particle size from 2000 to 106 µm. The reduction in particle size increases the spontaneous heating tendency by nearly 12–14%. The results show that external factors like coal seam depth, particle size, specific surface area (SSA), mining methods, and others influence spontaneous heating and fire in the Jharia coalfield. Additionally, we develop three mathematical models to forecast spontaneous heating in deep underground coal mines, considering CPT, TGignition, particle size (D90), SSA, and coal seam depth.
KEYWORDS: Deep underground coal mines; TG ignition; CPT; Particle size; Specific Surface Area (SSA); Spontaneous heating.
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