Thermal effects and kinetics behaviors of coal spontaneous combustion via synchronous thermal analyzer under different heating rates

This study aimed to dissect the thermal effects and kinetic behaviors of coal spontaneous combustion (CSC) under different heating rates (5, 10, 15, and 20°C/min). The charred coal, nonstick coal, and gas-fat coal were collected as coal samples, and thermogravimetric (TG)-differential scanning calorimeter (DSC) were performed. First, four characteristic temperatures were determined, and the CSC process was divided into four stages. Second, the characteristic temperatures, reaction stages, mass loss and thermal effects were investigated. The results indicated that as the characteristic temperatures increased, mass loss changed little, the TG-DSC curve peak shifted to high temperature, and the total heat release increased as the increases of heating rates. In addition, kinetic parameters of the conversion rate and activation energy was calculated. The apparent activation energies for the collected coal samples found by the Flynn-Wall-Ozawa method were 104.84, 95.51, and 129.84 kJ/mol, respectively, and those found when using the Kissinger method were 86.75, 78.90, and 110.54 kJ/mol, respectively. The results revealed that CSC occurred more difficultly in gas-fat coal than in charred coal. The results can provide theoretical support for the prediction and prevention of CSC in various applications.