Analysis of temporal and spatial evolution characteristics of temperature and oxygen in spontaneous combustion process of cylindrical coal bunker

The cylindrical coal bunker is widely utilized in coal mining sites because of its relatively sound ventilation conditions and short storage of time. It is mainly used to store coal samples for a long time or temporarily. However, based on the current research results, studies into the variation of spontaneous combustion temperature and oxygen concentration is relatively few, and so further research on typical cylindrical coal bunkers is needed. To that end, this study was conducted to look into the shortcomings of the existing test device associated with coal storage in cylindrical coal bunkers, according to the characteristics of actual coal storage in mines, and so an experimental system for spontaneous combustion evolution of coal bunkers was built independently. The Zijing coal sample from Luoyang, Henan Province, was chosen as the research object, the temporal and spatial changes of transverse and longitudinal temperature in the process of spontaneous combustion of coal (SCC) bunker were tested, and the development stage of SCC bunker was divided. Furthermore, an ananlysis of the variation trend of oxygen concentration and oxygen consumption rate at each measuring point in different stages of coal bunker spontaneous combustion was made. The results demonstrated that the spontaneous combustion process of coal bunker were divided into the stages of slow heating, rapid heating, constant temperature, rapid cooling, and slow cooling. Besides, when the air leakage occurred at the position of the coal outlet, the lower coal body could gradually spontaneously combust. In the process of temperature migration, the high temperature points were mainly concentrated in the middle and lower part of the coal bunker, and the temperature of the second layer of coal body tended to reach 655.7 °C. The spontaneous combustion of the lower coal body formed internal voids and was in a high temperature state for a long time. The lowest coal sample in the coal bunker was observed to basically maintain between 400 and 600 °C in the constant temperature stage. The coal sample near the lower air leakage port had a fast combustion rate and a low peak temperature. The duration of the cooling stage was different due to the different oxidation degree of the coal body. The research results have vital theoretical guiding significance for the prevention and control of coal bunker's spontaneous combustion disaster.