Identification of Signs of Spontaneous Combustion and Delineation of Hazardous Areas in Coal Seam Goafs Prone to Spontaneous Combustion

The problem of spontaneous combustion in goafs of coal seams prone to spontaneous combustion is significant; however, due to the complex and highly hazardous nature of the goaf environment, predicting spontaneous combustion in goafs has always been a major challenge for the industry. To understand and predict the development and evolution of coal spontaneous combustion in goafs, this study employed Fourier transform infrared spectroscopy (FTIR) experiments combined with program-controlled temperature (PCT) experiments to characterize oxygen-containing functional groups, aliphatic structures, hydrogen bonding evolution, oxygen consumption and other indicator gases. A multi-stage kinetic model was established based on the Coats–Redfern integration method. The results indicate that, in the wavenumber range of 1000–1800 cm−1, oxygen-containing functional groups account for more than 50% of the peak area, providing abundant active sites for oxygen adsorption and peroxide formation. Significant oxygen consumption begins to occur above 150°C, accompanied by a major CO peak at approximately 265°C (approximately 1.25 × 104 ppm) and a minor peak at 300–350°C (>1.30 × 104 ppm). CO2 increases sharply above 300°C, whilst CH4 exhibits a broad peak (~0.11%) near 300°C. The activation energies for the slow and fast oxidation stages are 9.99 kJ/mol and 38.43 kJ/mol, respectively. Based on the above findings, the optimal mining speed was determined through the selection of spontaneous combustion indicators. These results provide constructive insights for predicting coal spontaneous combustion in goaf areas, optimizing the selection of spontaneous combustion indicators, and implementing fire prevention and suppression measures in goaf areas.