Comparative study of the kinetic characteristics of coal spontaneous combustion

Coal spontaneous combustion often occurs in coal seam mining, which may lead to mine fires and other disasters. It is essential to investigate the detailed differences in combustion processes, characteristic temperatures, characteristic parameters of mass loss, combustion characteristic indices, and reaction kinetic characteristics of coal with different metamorphic degrees. Therefore, long-flame coal, non-caking coal, gas coal, and anthracite were selected as experimental samples. The microphysical properties of coal were studied by the proximate and ultimate analyzer, and scanning electron microscope, then the coal combustion characteristics were compared by simultaneous thermal analyzer. The results clearly indicated that the heating rate was positively correlated with the five characteristic temperatures, two mass loss rates, and two combustion characteristic indices of coal. Moreover, with the increase of metamorphic degree, the porosity of the coal surface structure decreased, the corresponding five characteristic temperatures increased, and the two combustion characteristic indices decreased. Significantly, the burnout temperature was mainly affected by the heating rate, and the maximum exothermic peak temperature was affected by the metamorphic degree. The combustion of the four kinds of coal as the first-order chemical reaction, the apparent activation energy of long-flame coal was the lowest, the easiest to burn, and the risk of spontaneous combustion was the greatest. These results revealed the thermodynamic characteristics of coal spontaneous combustion in specific mines from a microscopic viewpoint and provided basic data for the prevention of mine fires.