Study on Spontaneous Combustion Characteristics and Oxidation Kinetic Parameters of Lignite at Different Oxygen Concentrations

Abstract The spontaneous combustion parameters of lignite at different oxygen concentrations and temperatures were studied by temperature-programmed oxidation experiments. The characteristic parameters, tendency, oxygen consumption rate, kinetic parameters of oxidation reaction, and heat release intensity of coal’s spontaneous combustion were studied. The results show that the variation of export oxygen volume fraction of coal samples under different oxygen concentrations is similar. It has a general s-shaped downward trend. The change trend of the CO concentration of the coal sample export is basically the same at different oxygen concentrations. The CO concentration at the outlet of the coal sample increases with the increase in coal temperature. The CO concentration at 0–200 °C increased exponentially with the coal temperature. The distribution pattern of CO/CO2 ranging from 0 to 320 °C was similar at different oxygen concentrations. With the increase of coal temperature, CO/CO2 first increases and then decreases after reaching the extreme point. The change curve of CH4 with coal temperature under different oxygen concentrations meets the exponential change rule. At different oxygen concentrations, the concentration of ethylene at 0–300 °C changes exponentially, but at 300–400 °C there is no rule. When the oxygen concentration is 20.9%, according to the comprehensive judgment index method and cross temperature method, the comprehensive determination of the spontaneous combustion trend of coal samples is grade II. Under different oxygen concentrations, the oxygen consumption rate of coal increases with the increase of temperature; the oxygen consumption rate increases with the increase of oxygen concentration at the same temperature. The activation energy of coal samples increases with the decrease of oxygen supply concentration or the increase of temperature. The thermal strength of the coal sample is consistent with the change trend of the oxygen consumption rate. The heat release intensity of coal samples conforms to an exponential function and polynomial function in the early and late stages, respectively.