Study on low temperature oxidation and high temperature pyrolysis characteristics of coal spontaneous combustion with different oxygen concentration

The oxygen concentration in the environment of the residual coal in the underground goaf is not uniform. The study on the characteristics of low temperature oxidation and high temperature pyrolysis of coal under different oxygen concentrations is of great significance to prevent the spontaneous combustion of the residual coal in the goaf. Based on this, this paper studies the generation of O2, CO, C2H4 and C2H6 gases during coal low temperature oxidation at 21%, 15% and 5% oxygen concentrations, and compares the oxygen consumption rate at different temperatures. The weight loss characteristics and characteristic point temperature of coal pyrolysis at high temperature under different oxygen concentrations were further studied, and the influence mechanism of different oxygen concentrations on coal spontaneous combustion characteristics was finally revealed. The results show that in the three oxygen concentration experiments, the decrease of oxygen concentration will lead to the decrease of CO, C2H4 and C2H6 concentrations generated in the low temperature oxidation process of coal, and the oxygen consumption and oxygen consumption rate are significantly reduced, and the temperature at the intersection is significantly increased. The decrease of oxygen concentration will lead to the decrease of mass loss percentage of coal during high temperature pyrolysis, and the increase of critical temperature and maximum weight loss rate temperature. The decrease of oxygen concentration leads to less active structure in coal involved in the coal-oxygen composite reaction, which inhibits the coal-oxygen composite reaction.