Study of multi-scale thermal effects and mechanism of oxidized coal spontaneous combustion by correlation analysis

The thermal effect of coal oxidation has a deep connection with the coal microstructure. A long flame coal, prone to spontaneous combustion is selected for the Differential scanning calorimetry (DSC) experiment and Fourier transform infrared experiment (FTIR) to identify the multi-scale thermal effects and mechanism of oxidized coal at different pre-oxidation temperatures. A model of the relationship between macro thermal effect and microstructure during coal oxidation is established by adopting multiple linear regression. It indicated that, with the increase of pre-oxidation temperature, the oxidizing property and exothermic of oxidized coal first decrease and then increase. The FTIR illustrated that the intramolecular hydrogen bond and free and linked hydrogen bond in the hydroxyl group have multiple collinearities. The result showed that the coal oxidation process is divided into three stages. In the heat absorption stage, aliphatic hydrocarbons and C=C double bond are negatively correlated with the exothermic rate. In the slow heat release stage, the variance predicted by the regression model is 0.722, which characterizes and predicts the degree of coal spontaneous combustion. In the heat release stage, the key factors affecting the heat release rate are aliphatic hydrocarbons and carboxyl groups, and the amount of heat release increases exponentially.