Experimental Study on the Effect of Ultraviolet Light on Spontaneous Combustion of Coal under the Action of a Photosensitive Reagent

In the process of open-pit coal mining, storage, and transportation, coal is subjected to ultraviolet light for a long time, and the photosensitizing substances in the coal can react with ultraviolet light. In order to further study the influence mechanism of ultraviolet light on the spontaneous combustion process of coal under photosensitizing reagents, azobenzene photosensitizing reagents were selected as reactants and fully mixed with coal. The changes in the spontaneous combustion characteristics of coal by UV light under the action of the photosensitive reagent were analyzed by using programmed heating experiments, TG-DSC experiments, and infrared spectroscopy experiments. The results show that the isomerization reaction of the photosensitive reagent under ultraviolet light irradiation produces a large amount of energy stored in chemical bonds, which reduces the characteristic temperature of coal by 3.7–5.6 °C and the oxidative activation energy by 0.65 times. At the same time, the number of active sites in the coal increases after irradiation, enhancing the oxygen absorption capacity of the −C–O– bond, making the coal more inclined to produce CO, and exhibiting a more pronounced catalytic effect on spontaneous combustion.