Study on the Characteristics of Coal Spontaneous Combustion during the Development and Decaying Processes

Abstract Large-scale experiments could reflect the real status of coal spontaneous combustion and therefore were conducted to investigate the characteristics of coal oxidation during the development and decaying processes. Three coals with different metamorphic grades were collected and tested to acquire the information including the temperature profiles, movement of the hottest spots, gaseous products, limiting parameters and so forth. The results indicated that the trajectories of hottest spots did not overlap for the development and decaying processes. Meanwhile, compared to the development process, CO productions during the decaying process were higher in the air circumstance and lower in the nitrogen. Coupled with the changes of C2H4 and oxygen consumptions, it could be concluded that both the oxygen concentrations and the stages (development or decaying process) must be taken into account when judging the status of coal spontaneous combustion. Additionally, the discussions about the limiting parameters of the coal spontaneous combustion showed that during the decaying process, the lower limit of coal thickness was smaller, the lower limit of oxygen concentration became less and the upper limit of air leakage turned larger. These results implied that the experience of high temperatures would raise the hazard of coal spontaneous combustion.