Research on the Intrinsic correlation mechanism between stage oxidation characteristics and spontaneous combustion tendency of coals with different metamorphic degrees

This study explored the internal correlation mechanism between the stage oxidation characteristics and spontaneous combustion tendency of coals with different degrees of metamorphism.Through TG-DSC, in-situ infrared spectroscopy and programmed temperature-rise experiments, the patterns of oxygen consumption and heat release, gas generation and functional group changes during the spontaneous combustion process of coal were analyzed.The research indicates that before the ignition temperature, the coal-oxygen reaction is mainly the oxidation of aliphatic side chains and oxygen-containing active functional groups, mainly generating CO,CO₂,H₂O and -C=O. As the degree of coalification deepens, the content and reaction activity of aliphatic side chains decrease, and the characteristic temperature points of coal spontaneous combustion shift to higher temperatures.Meanwhile, the scale of “oxygen consumption-heat release-product”in the oxidation-pyrolysis stage decreases by about 36 %(in terms of heat release) to 70 %(in terms of CO generation), and the heat-release proportion in the combustion stage increases, with a maximum of 77.79 %. By using the Pearson correlation analysis method, it is obtained that the oxidative pyrolysis behavior of aliphatic side chains has a significant negative correlation with the spontaneous combustion tendency of coal(oxygen consumption R =-0.992, CO generation R =-0.978), confirming the dominant role of the oxidation of aliphatic side chains in coal spontaneous combustion.The study systematically correlates the macroscopic thermal effects, oxidation behaviors, gas products and micro-group evolution, determines that the content and reaction activity of aliphatic side chains are the core factors determining the differences in the spontaneous combustion tendency of coals,and is of great significance for the prediction and precise prevention and control of coal spontaneous combustion.