Experimental study on the spatial and temporal variations of temperature and indicator gases during coal spontaneous combustion

Abstract

Coal spontaneous combustion is one of the main potential hazards in the process of mining. To study the spatial and temporal variations of higher-temperature area and indicator gases, an adiabatic oxidation testing system was developed to simulate the whole process of coal spontaneous combustion. The experimental results show that the entire process of coal spontaneous combustion could be divided into three stages: slow-oxidation, accelerated-oxidation and combustion stages. In the slow-oxidation stage, the higher-temperature area shifted slowly from the bottom to the top and then stayed at the top until accelerated-oxidation stage was reached; [Formula: see text] and [Formula: see text] concentration remained more or less constant as well as the oxygen concentration. In accelerated-oxidation stage, the higher-temperature area moved to the bottom rapidly and subsequently stayed approximately in the center of the coal; [Formula: see text], [Formula: see text] concentration and oxygen consumption increased sharply. In addition, the occurrence of higher-temperature area is accompanied by higher oxygen consumption. The obtained results show that higher air supply rate could shorten spontaneous combustion period and there exists a hyperbolic relationship between the temperature and time.