Effect of thermal damage on pore development and oxidation reaction of coal

With the coal entering deep mining, the thermal damage to the destruction of the coal body structure, causing the phenomenon of coal spontaneous combustion is more and more common. To better understand the effect of thermal damage on coal spontaneous combustion, the law of thermal damage on pore structure and free radical of coal was studied by automatic specific surface area analyzer and electron spin resonance spectrometer. It was concluded that 225 degrees C was a key point of thermal damage on coal spontaneous combustion. The pore structure analysis indicates that the specific surface area and pore volume of coal decrease with the increase of thermal damage temperature, while the average pore diameter increases gradually. While the specific surface area of Qianyingzi coal is the lowest at 225 degrees C, which is 67.5% of that of raw coal. The average pore size of Zhaotong coal continues to increase by 18.9%. In addition, the pore structure of coal changes greatly in the thermal damage temperature range of 150-225 degrees C, and the connectivity of coal pore is greatly strengthened at this range. The free radical results show that the free radical concentration in thermally damaged coal soars, compared with that in raw coal, and reaches the maximum value at 225 degrees C, indicating that the active groups in coal are greatly active at this temperature. The g factor value declines firstly, then increases, and finally falls. These investigations may serve to reveal the internal mechanism of thermal damage on coal structure and natural oxidation characteristics and provide experimental basis for the prevention and control of coal spontaneous combustion affected by thermal damage.