LAUSR

Abstract Although the mechanical grinding process is often involved in coal mining and processing, the effect of this process on coal spontaneous combustion has been scarcely investigated in the literature. The changes of the content of oxygen-containing functional groups in coal caused by mechanochemical effect and their effects on coal spontaneous combustion were studied. The low-temperature oxidation experiment, grinding experiment, infrared spectrum experiment, and electron spin resonance (ESR) experiment were carried out. Firstly, the cross-point temperatures (CPTs), CO gas production, and the content of oxygen-containing functional groups of coal with different particle sizes were compared. Furthermore, changes in gas composition and functional groups during the grinding of coal samples under different gas conditions were also analyzed. Finally, the mechanism of mechanochemical reaction was revealed by studying the change of free radical concentration during the grinding process. The experiments have shown that coal will oxidize and generate large amounts of oxygen-containing functional groups under mechanical grinding. The effect of particle size on coal spontaneous combustion is not only caused by the change of surface area which was traditionally considered, but also the mechanochemical action during the crushing and grinding process. The research results can provide a new way for the prevention of coal spontaneous combustion.