Effect of sulfur content on spontaneous combustion characteristics of anthracite

The spontaneous combustion process of coal is influenced by multiple factors. Existing studies mainly investigate coal spontaneous combustion characteristics from aspects such as coal metamorphic degree, oxygen concentration, air supply rate, air humidity, particle size, and moisture content rate. However, the sulfur content in coal is also one of the important factors affecting coal spontaneous combustion. To investigate the effects of sulfur content on the spontaneous combustion characteristics and oxidation kinetic parameters of anthracite, oxidation processes of five coal samples with different sulfur contents were tested using a programmed temperature-rise experiment system with a tube furnace. The effects of different sulfur contents on CO and CO₂ gas release characteristics and characteristic temperatures of spontaneous combustion during the low-temperature oxidation process of coal were quantitatively analyzed. By calculating the oxygen consumption rates of coal samples with different sulfur contents under different temperature conditions, the variation pattern of the oxygen consumption rate with temperature was quantitatively examined. Based on chemical reaction kinetics, the apparent activation energies of coal samples under different sulfur contents were calculated, and the variation pattern of apparent activation energy with sulfur content was quantitatively analyzed. The results showed that when the sulfur content remained constant, the concentrations of CO and CO₂ and the oxygen consumption rate increased exponentially with increasing temperature, while the apparent activation energy gradually decreased. With increasing sulfur content, the concentrations of CO and CO₂ and the oxygen consumption rate at each temperature point first increased and then decreased, reaching maximum values at a sulfur content of 5.14%. In contrast, the characteristic temperature of spontaneous combustion and the apparent activation energy showed opposite trends and reached minimum values at a sulfur content of 5.14%, at which point the coal sample exhibited the strongest spontaneous combustion tendency. Therefore, the critical sulfur content affecting the spontaneous combustion tendency of anthracite was 5.14%.