Low-Temperature Oxidation Characteristics and Apparent Activation Energy of Pressurized Crushed Coal Under Stress Loading

With increasing mining depth, coal is more affected by ground and mining stresses. In order to study the characteristics and activation features of coal spontaneous combustion (CSC) under different stress conditions, experiments on low-temperature oxidation under six different stress conditions were conducted using a newly developed multi-field loading and permeability experimental device for stress-loaded and crushed coal. The experimental results showed that, with increase in axial stress from 0 to 15 MPa, the amounts of CO, CO₂, C₂H₄ generated and the rate of oxygen consumption all first followed an increasing trend, reached maximum at 9 MPa, and then a decreasing trend. In three temperature stages—I (20 ℃ < T < 80 ℃), II (90 ℃ < T < 120 ℃), and III (120 ℃ < T < 150 ℃)—all under increasing axial stress from 0 to 15 MPa, the apparent activation energy (AAE) followed a decreasing and then relatively increasing trend. The AAE in all three temperature stages reached a minimum of 9.60 kJ mol⁻¹, 60.57 kJ mol⁻¹, and 19.61 kJ mol⁻¹, respectively, at 9 MPa. Combining the characteristics of gas generation, oxygen consumption, and changes in AAE during the low-temperature oxidation of stress-bearing crushed coal, it was found that stress loading to a certain extent promotes the occurrence of CSC.