Experimental study on the influence of oxygen concentration on spontaneous combustion characteristics of sulfur-containing anthracite

In order to study the influence of different oxygen concentrations on low-temperature oxidation and spontaneous combustion of sulfur-containing coal, coal samples of No. 14 and No. 15 coal seams of Shanxi Shigang Coal Industry Co., Ltd. were selected as test samples to carry out temperature-programming experiments of tube furnaces under different oxygen concentrations. There are 6 groups in total, the oxygen concentrations of No. 14 and No. 15 coal samples are 21.0% and 21.0%, 12.2% and 12.1%, 10.2% and 10.1%, 7.1% and 7.2%, 5.0% and 5.1%, 2.9% and 2.8%, respectively. And the gas composition was analyzed by parallel gas chromatograph. By calculating the oxygen consumption rate and heat release intensity at different oxygen concentrations and temperatures, the corresponding relationship between the oxygen consumption rate, heat release intensity and temperature was analyzed, and the oxygen consumption rate and heat release intensity of No. 14 coal sample and No. 15 coal sample were fitted when the oxygen concentration was 21%. The apparent activation energy of low temperature oxidation of No. 14 and No. 15 coal samples under different oxygen concentrations was calculated, the relationship between oxygen concentration and apparent activation energy was analyzed. According to the critical temperature of spontaneous combustion oxidation and the change characteristics of apparent activation energy, the critical oxygen concentration of No. 14 and No. 15 coal samples was obtained. In the test range(oxygen concentration 2.8%−21%, temperature 30−300 ℃), the results show that increasing the oxygen concentration is helpful for the oxidation development of No. 14 and No. 15 coal samples, while reducing the oxygen concentration will inhibit its development. The spontaneous combustion tendency of No. 14 coal sample is greater than that of No. 15 coal sample, and the critical oxygen concentration of spontaneous combustion of No. 14 and No. 15 coal seams is 5.0% and 7.2% respectively. When the oxygen concentration is constant, the CO release volume, oxygen consumption rate and heat release intensity all increase with the increase in temperature, which conforms to the exponential function. The CO release volume, oxygen consumption rate and heat release intensity of No. 14 coal sample at each temperature point of the same group are larger than that of No. 15 coal sample, while the apparent activation energy and critical temperature of spontaneous combustion are smaller than that of No. 15 coal sample. When the temperature is constant, the CO release, oxygen consumption rate and heat release intensity decrease with the decrease of oxygen concentration, while the apparent activation energy and critical temperature of spontaneous combustion increase. The fitting curve of oxygen consumption rate and heat release intensity with temperature and the critical oxygen concentration value of spontaneous combustion can provide important parameters for numerical simulation of spontaneous combustion characteristics of coal in goaf and classification of spontaneous combustion risk area.