Low-Temperature Oxidation Characteristics and Spontaneous Combustion Limit Parameters of Residual Coal in Deep Mine Goafs

As mining depth increases, the temperature of coal seams increases gradually, which increases the risk of spontaneous coal combustion in goaf areas. This paper uses a programmed temperature rise experiment to analyze the oxidation combustion characteristics of high ground temperature coal and calculates the oxidation kinetic parameters and limit characteristic parameters. The results show that, above 100 °C, the ratios C₃H₈/C₂H₆ and C₂H₄/C₂H₆ change with the same trend. The CO and CO₂ release rates, oxygen consumption rate, heating rate and heat release intensity are positively correlated with the ground temperature. There is a good exponential relationship between the release rate of CO and CO₂ and the coal temperature. The activation energy increases and then decreases as the oxidation temperature increases (above 100 °C). In the later stage of low-temperature oxidation, the higher the ground temperature is, the lower the activation energy, the more active the organic active groups and the more violent the oxidation reaction. As the oxidation temperature increases, the lower-limit oxygen concentration (C_min) and the minimum floating coal thickness (h_min) increase and then decrease, and the high ground temperature reduces the temperature at which the maximum is reached. With increasing ground temperature, h_min and C_min increase, and the maximum air leakage intensity decreases. The research results provide a theoretical basis for the prevention and control of spontaneous coal combustion in high ground temperature coal seam mining in deep mines.