Thermal properties and microstructural evolution of coal spontaneous combustion

With the increase of coal energy mining depth in China, coal spontaneous combustion phenomenon becomes more frequent, which makes the safe mining of coal energy in China under serious threat. In order to prevent coal spontaneous combustion, it is significant to investigate the process of coal oxidation and spontaneous combustion by combining thermal and microstructural properties, which is a necessary study to figure out the mechanism of coal spontaneous combustion. A series of coal oxidation experiments were conducted with the aid of high precision Calorimeter and X-ray diffractometer. The results show that the thermal properties of coal spontaneous combustion have obvious segmentation characteristics which is not affected by the degree of metamorphism and heating rates, and the initial exothermic temperature is positively correlated with heating rates. The effect of temperature on microscopic characteristics is not uniform, but the degree of metamorphism has a regular change for microscopic characteristics. Although temperature does not play a decisive role, the spatial structure of coal oxidation process has some reversibility with the change of temperature. Besides, thermal dynamic balance is an important cause of microstructure changes. It is expected that this work will contribute to the refinement of the theory of coal spontaneous combustion.