Influence of deposited methane and microstructure of bituminous coal on the characteristics of its oxidation and gas production under different oxygen concentration

The coupling of coal spontaneous combustion and high methane is ubiquitously observed in coal mining and poses a significant jeopardy to production safety. The extant studies are largely focused on altering external methane conditions and fail to investigate the spontaneous combustion properties of methane-laden coal samples. This study conducted an evaluation of the microstructure of typical coal samples, followed by a fractal analysis. It discovered that the surface structure of the specimen is relatively homogeneous, and the mesopores (2-4 nm) exhibit a significant influence on the specific surface distribution. The overall pore structure is characterized by a multiplicity of peaks, which renders the coal sample markedly segmented during methane desorption, oxygen consumption, and gas products generation. The low-temperature oxidation tests under various working conditions reveal that methane desorption is a crucial factor in determining the spontaneous combustion pattern of the coal sample. The degree of methane desorption bears a close association with the oxygen concentration, and at an oxygen concentration of approximately 2 %, there is a turning point for gas generation and oxygen consumption. The present investigation provides a qualitative and quantitative exposition of the relevant laws, offering guidance for fire prevention and suppression in pertinent mines.