Investigation into the spontaneous combustion characteristics and microstructure change of pre-oxidation coal

To study the macro and micro characteristics of the spontaneous combustion of pre-oxidation coals (POC) with different pre-oxidation temperatures (80°C, 120°C, 160°C, 200°C), we used programmed temperature experiments, BET, and in situ FTIR. The results show that the spontaneous combustion characteristic parameters (oxygen consumption rate, gas release rate (CO and CO2), and exothermic intensity) of POC show disparities. Especially after the functional group content of coals reaches the extreme value at 160°C, the differences are further enlarged. Different primary oxidation processes change the specific surface area (SSA) and functional group content to varying degrees. The 80°C pre-oxidation process increases SSA and functional group content. 80°C POC reacts more violently than Y (raw coal), which can produce more reducing groups (-OH, -CH3, and -CH2-) and lower oxidizing groups (C = O and -COO-), showing a stronger ability to combine with oxygen. Moreover, it consumes more oxygen and releases more CO, CO2, and heat. The macro and micro spontaneous combustion characteristics of 200°C POC are the weakest. It can be judged that the coal under a pre-oxidation temperature of 80°C has a stronger tendency to spontaneous combustion, and the pre-oxidation process at 200°C reduces the tendency of coal to spontaneous combustion.