Analysis of the Thermal Behavior Characteristics and Dynamics of Coal Under High Primary Temperature Conditions in Deep Mines

The exposure to spontaneous combustion of coal subjected to high ground temperatures increases as the depth of mine excavation increases. To research the oxidative heat release characteristics of deep coal, a study was carried out to characterize the oxidation kinetics and thermal effects on coal in deep thermal environments; deep coals (heat-treated coals) in 30°C (T30), 45°C (T45) and 60°C (T60) environments were prepared using a simultaneous thermal analysis, and the thermal weight characteristics (TG) and thermal release characteristics (DSC) of heat-treated coals were tested by simulating coal samples in different deep thermal environments; the thermal effects of heat-treated coals were analyzed by oxidation kinetic theory. The findings indicated that the characteristic point temperature of the coal gradually reduces (T60 has the lowest oxidation characteristic temperature) as the heat treatment temperature increases, and the maximum mass loss (63.76%) during thermal treatment coal oxidation occurs in the combustion stage. The oxidation reaction mechanism function for the low-temperature oxidation phases of the deep coal conforms to the Z-L-T equation with a three-dimensional diffusion reaction mechanism. As the temperature of the thermal environment is increased, the apparent activation energy of the coal decreases and the exothermic heat increases. This increases the tendency for oxidation of the deep coal, making it more amenable to spontaneous combustion as the ambient temperature at depth rises. The results contribute to a theoretical framework for monitoring and preventing coal spontaneous combustion fires in deep mine excavations.