Study on Natural Characteristics of Coal Gangue Oxidation under the Action of Water

The exposed accumulation of coal gangue undergoes changes when it is soaked by rainwater, exhibiting varying tendencies for spontaneous combustion in different precipitation regions. This study investigates the effects of moisture on the oxidation and spontaneous combustion of coal gangue in high-sulfur coal gangue from the Qipanjing area of Inner Mongolia. Initially, coal gangue samples were subjected to soaking and air-drying treatments at different moisture contents. The dried coal gangue samples were then placed into a self-designed programmable heating furnace for thermal experiments, during which the gases generated were collected and characterized using gas chromatography. By comparing the oxygen consumption and volume fractions of gases such as CO, CH₄, and C₂H₆ produced from coal gangue treated at different moisture contents, it was found that the low-temperature oxidation characteristics were optimal at a moisture content of 25%. At this level, the initial formation temperatures of gases like CO, CH₄, and C₂H₆ were the lowest, with peak concentrations observed at 390 °C. Conversely, when the moisture content exceeded 70%, a significant amount of combustible material in the coal gangue was dissolved and dispersed by water, leading to a marked decrease in the concentrations of indicator gases produced at 390 °C. In fact, these concentrations fell below those of the control group, which was not subjected to water soaking or subsequent drying. The water immersion treatment also lowered the initial temperature points for the generation of various indicator gases by approximately 15 °C, making spontaneous combustion more likely.