Study on test method of heat release intensity and thermophysical parameters of loose coal

Accurate determination of basic parameters of coal spontaneous combustion process can not only directly or indirectly characterize the spontaneous combustion of coal, but also provide a reliable theoretical basis for the accurate prediction of coal spontaneous combustion period and the proposition of prevention measures of spontaneous combustion. In this paper, based on the theory of porous medium heat transfer, the mathematical models of parameters such as oxidative heat release intensity, thermal conductivity, heat capacity and activation energy of loose coal were established by using element balance method. Then, an integrated experiment system for testing characteristic parameters of coal spontaneous combustion was designed and set up, and the characteristic parameters of loose coal spontaneous combustion were accurately tested through the spontaneous combustion heating experiment on large-volume coal. The results show that the thermal conductivities of loose coal samples all decrease with the increase of voidage and rise with the increase of metamorphic grade. The heat capacity grows with the increase of volatile content. The oxidative heat release intensities of samples were increased exponentially with the rising temperature, which first rises slowly in the temperature range of 60-70 °C and then increases rapidly after 70 °C. The sample with a lower metamorphic grade and a stronger spontaneous combustion tendency owns greater oxidative heat release intensity, which grows with the increase of dynamic absorbed oxygen. At the same temperature, the large-size sample has smaller oxidative heat release intensity. The activation energy of coal samples increases with the rise of temperature and metamorphic grade. The experimental results indicate that the test system and method are reliable and can achieve the goal of rapid test.