Variation of CO2/CO ratio during pure-oxidation of feed coal

Since the CO2/CO ratio was found to be unaffected by the ventilation flow rate, it is an excellent tool to evaluate the state of coal spontaneous combustion. However, the existing studies generally regard coal-oxygen reaction as a total package reaction, which leads to the mutual interference of CO2/CO produced by pure oxidation, pyrolysis and physical desorption. Besides, the reasons for the change of CO2/CO ratio are not clear. Therefore, a method was designed to obtain the gas production characteristics of pure oxidation pathway. At the same time, the relationship between the change of active groups and CO2/CO during pure oxidation was investigated by means of in-situ FTIR and model compounds. The experimental results show that at lower temperatures, the CO2 produced in coal mainly comes from physical desorption and pyrolysis, which will interfere with the change of CO2/CO. The new method can eliminate the influences of them. It is also concluded that the ratio of CO2/CO produced by pure oxidation pathway exhibits obvious segmentation. With the increase of temperature, it can be divided into four stages, gradual participation of different active groups in coal is the main reason for the segmentation and determines the initial temperature range in each stage. The CO2/CO ratio and equilibrium value are mainly affected by the hydroxyl content in coal. The accuracy of coal spontaneous combustion can be improved based on the segmentation of CO2/CO production by pure oxidation.