Real-time analysis of the changing trends of functional groups and corresponding gas generated law during coal spontaneous combustion

In the process of spontaneous combustion, coal samples undergo oxidation and pyrolysis reactions, and various gases are produced when functional groups transform with each other. This paper conducted in situ FTIR and high-temperature oxidation experiments on raw coal samples to investigate the changing trends of functional groups and corresponding gas generated law. Experimental results show that at the early stage of low-temperature oxidation (before 90 degrees C), CO production is the result of oxidation and decomposition reactions, and water evaporation leads to significant changes in =OH. At the late stage of low-temperature oxidation (100-200 degrees C), CO increased exponentially with the increase of oxygen consumption. After 200 degrees C, the activity of each functional group increased significantly and the O-2 supplied were completely consumed. Meanwhile, the thermal decomposition of aromatic hydrocarbons C=C in coal produced large amounts of CH4. When the oxygen-nitrogen ratio reaches 0.15 or less, the nitrogen injection has a significant inhibitory effect on the late stage of the low-temperature oxidation process. However, the higher the temperature, the less obvious the inhibition effect of nitrogen on the activity of functional groups. The results are applicable to the study on the thermodynamic disaster warning, prevention and control.