Spontaneous Combustion and Oxidation of Coal

Coal spontaneous combustion arises from the exothermic reaction between coal and atmospheric oxygen at ambient or mildly elevated temperatures. As coal adsorbs oxygen, heat evolves progressively; if this heat is not dissipated through conduction, convection or ventilation, the local temperature can climb to the ignition point, resulting in self-sustaining combustion. The propensity for self-heating depends on the intrinsic properties of the coal—rank, moisture content, porosity, mineral inclusions such as pyrite—and on external factors including ventilation rate, ambient temperature and the geometry of coal seams or waste piles. Low-temperature oxidation is the initial stage of spontaneous combustion and is marked by the generation of CO, CO₂ and volatile organic compounds. Modern monitoring techniques—gas analysis, infrared thermography and fibre-optic sensors—enable early detection of incipient heating. Control strategies range from inertisation with nitrogen or carbon dioxide to chemical inhibitors and physical isolation of heat-prone zones. Given the global reliance on coal for power generation and industrial heat, understanding and mitigating spontaneous combustion is critical to reduce greenhouse-gas emissions, safeguard labour and avert infrastructure loss in mining, storage and transport operations.

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Spontaneous Combustion and Oxidation of Coal publication trend

The graph below shows the total number of articles in spontaneous combustion and oxidation of coal across all publications each year (not limited to Nature Index journals).

Technical terms

Spontaneous combustion: Self-ignition of coal through progressive heat accumulation from exothermic oxidation without an external flame source.

Low-temperature oxidation: Chemical reaction of coal with oxygen at moderate temperatures that generates heat and combustion by-products.

Goaf: Voids or caved-in spaces left after the extraction of coal, often prone to gas accumulation and self-heating.

Free radical: Highly reactive atom or molecule possessing an unpaired electron, central to chain reactions in coal oxidation.

Retarding gel: Inorganic composite material applied to coal surfaces to impede oxygen diffusion and inhibit exothermic reactions.

References

1. Disasters of gas-coal spontaneous combustion in goaf of steeply inclined extra-thick coal seams. Journal of Rock Mechanics and Geotechnical Engineering (2024).
2. Effects of pyrite on the spontaneous combustion of coal. International Journal of Coal Science & Technology (2015).
3. The Method of Combating Coal Spontaneous Combustion Hazard in Goafs—A Case Study. Energies (2020).
4. A novel composite inorganic retarding gel for preventing coal spontaneous combustion. Case Studies in Thermal Engineering (2021).
5. Oxidation Characteristics of Functional Groups in Relation to Coal Spontaneous Combustion. ACS Omega (2021).