Spontaneous combustion characteristics of hydrothermal erosion coal from deep mining and its microscopic mechanism

With the gradual depletion of shallow coal resources, deep mining has become a new normal for coal resource development. During deep mining, hydrothermal erosion leads to changes in the physical and chemical properties of coal, which in turn profoundly affects coal spontaneous combustion (CSC). To study the CSC characteristics and micromechanisms under the influence of hydrothermal erosion, oxidation temperature rise experiments and molecular dynamics calculations were conducted to analyze the oxygen consumption characteristics, changes in indicator gases, and generation paths of active sites. The results show that hydrothermal erosion coal has a greater ability to oxidize, and the higher the hydrothermal temperature is, the higher the oxygen consumption and CO and CO2 concentrations are during the rapid oxidation stage. The adsorption capacity of coal for water molecules gradually decreases with increasing temperature, and the removal of water in the pores provides more channels for oxygen. Hydrothermal erosion can accelerate the activation of active sites in coal and generate high levels of oxidative free radicals, and at the same time, the high-temperature environment promotes microdegradation of coal macromolecular structures, generating a large amount of heat and improving coal reaction activity, increasing the risk of CSC.