Thermophysical parameters of coal with various levels of preoxidation

Heat transfer in a coal mass is governed by thermophysical properties such as thermal diffusivity, specific heat capacity, and thermal conductivity. Coal samples were preoxidized at 90, 150, and 200 °C in a temperature-programmed oxidation apparatus, with raw coal acting as the control group. A laser flash method was employed to examine the thermophysical properties of the coal samples and establish a relationship between the thermophysical properties and the coal’s microcrystalline structure/pore structure. The results indicated that thermal diffusivity decreased and specific heat capacity and thermal conductivity raised when the temperature increased. Furthermore, when the preoxidation temperature increased, aromatic microcrystalline structures developed and the specific surface area of the coal samples first decreased and then increased. Moreover, thermal diffusivity and thermal conductivity increased with the elevated preoxidation temperature, and specific heat capacity was the highest at 90 °C. The reason for this was that preoxidation of the coal samples influenced the development of aromatic microcrystalline structures and pore structures, promoting the heat transfer on coal mass.