Experimental Study on the Activation Energy of Coal Oxidation Under Different Oxygen Concentrations

To investigate the effect of oxygen concentration on the activation energy of coal oxidation, low-temperature oxidation experiments were carried out on coal samples under controlled oxygen levels (21%, 12%, 10%, 7%, 5%, and 3%) using a programmed-temperature apparatus. The oxygen consumption rates and gas production were measured in relation to temperature, and critical temperatures were identified for each condition, enabling the division of the oxidation process into two distinct stages. Kinetic analyses were conducted for each stage based on the Arrhenius equation derived from the oxygen consumption rate. The apparent activation energy was determined from the slope of the linearized Arrhenius plot. The results demonstrate a strong dependence of activation energy on oxygen concentration, with values increasing from 12.98 kJ·mol−1 at 21% O2 to 25.11 kJ·mol−1 at 3% O2. A marked difference in activation energy was observed across the critical temperature—for instance, under 21% O2, activation energies were 12.98 kJ·mol−1 below and 41.72 kJ·mol−1 above the critical point. Furthermore, a safety threshold of 6% O2 was identified for goaf atmospheres, providing critical guidance for the prevention of coal spontaneous combustion.