Research on the influence of air humidity on coal spontaneous combustion characteristics and oxidation kinetics parameters

Air humidity has an important impact on the spontaneous combustion process of coal in mines. In order to study the influence characteristics of air humidity on the natural oxidation characteristics and oxidation kinetics parameters of coal, a programmed heating experiment was conducted on coal samples from 4105 fully mechanized caving face of Wenjiapo Coal Mine. The oxidation spontaneous combustion characteristics of coal samples were analyzed under different air humidity conditions, and a formula was constructed to calculate the apparent activation energy and pre-exponential factor of different oxidation stages based on the oxygen consumption rate. The research results indicate that under different air humidity conditions, CO gas and oxygen consumption rate both exhibit an exponential growth trend with increasing temperature. C₂H₄ gas is a product of coal high-temperature pyrolysis and only appears after 90 °C. The critical temperature of coal samples in Wenjiapo Coal Mine is 60-80 °C, and the dry-cracking temperature is 100-120 °C. By calculating the coal oxidation kinetics parameters before and after the critical temperature, the apparent activation energy of the coal sample gradually decreases with the increase of air humidity. When the air humidity exceeds 60%, the apparent activation energy gradually increases, and the pre-exponential factor shows a similar pattern, indicating that the coal spontaneous combustion process exists in the critical humidity, which plays a certain promoting role in coal spontaneous combustion, and the coal sample is more prone to spontaneous combustion in this environment.