Heat Release Characteristic of Key Functional Groups during Low-Temperature Oxidation of Coal

Coal spontaneous combustion involves the process of functional group distribution and heat accumulation in coal. Therefore, analyzing the thermal reaction process of coal spontaneous combustion and the law of thermal effect generation to determine the key reaction links and functional groups and reveal the mechanism of coal spontaneous combustion is of great significance for the development of relevant control technology and materials. Three weakly caking coal samples were collected from the Chao Yuan, Huang Ling, and Hei Lapan coal mines in the Shaanxi Province of China. The characteristic heat release parameters of the weakly caking coal during low-temperature oxidation were analyzed using a micro-calorimeter (C80) and Fourier transform infrared spectroscopy (FTIR). A correlation analysis between the heat release rate and functional groups was carried out by the Pearson correlation coefficient method. The results showed that the low-temperature oxidation process of coal has obvious in stages and characteristics. Furthermore, while the heat release rate is influenced by the reaction of the functional groups in the coal molecular structure, the different functional groups exhibit different effects on the oxidation. The formation and consumption of hydroxyl, carbonyl, carboxyl, and various substituted aromatic hydrocarbons were observed to play a crucial role in low-temperature oxidation.