Effect of C₂H₆、C₂H₄、CO and H₂ on the explosion pressure and kinetic characteristics of methane

The gas composition of spontaneous coal combustion in a high-temperature mine fire area is extremely complex. Due to the low-temperature oxidation or pyrolysis of coal, a variety of combustible and explosive gases are produced, such as CH₄, CO, H₂, C₂H₆, C₂H₄, C₃H₈, and C₂H_2. The paper provided associated basic data to quantify potential hazards caused by flammable gases and design containers that can withstand explosion during gas fuel processing, storage, and transportation. Under different initial temperatures (298–373 K) and varying volume fractions of the premixed gases (CO, H₂, C₂H₄, and C₂H₆: 0.4%–2.0%), when volume fraction of methane is 7% and 11%, the explosion pressure characteristic parameters were obtained in a 20 L spherical gas explosion system. In addition, the change in trend of the mole fraction of H·, O·, and OH radicals of the gas mixture during the explosion process was analyzed and simulated. Sensitivity analysis was performed using the CHEMKIN software. Results show that at the same volume fractions of the premixed gases, the maximum explosion pressure linearly decreases with increasing initial temperature and the maximum pressure rise rate is almost constant or slightly decreasing. At the same initial temperature, when volume fraction of methane is 7%, as the volume fractions of the premixed gases increases to 2%, the maximum explosion pressure and the maximum pressure rise rate show an increasing trend. However, a decreasing trend is observed with 11% methane–air mixture. When volume fraction of methane is 7%, with the increased gas mixture volume fraction, the maximum mole fraction of the free radicals, H·, O·, and ·OH increases. When volume fraction of methane is 11%, the maximum mole fraction of O· and ·OH radicals indicated a downward trend, whereas that of the H· radical increases with increase in volume fractions of the premixed gases. When volume fraction of methane is 7% and 11%, chemical kinetics analysis revealed that the addition of premixed gases had little effect on the key elementary reactions. Moreover, the sensitivity coefficient of CH₄ decreases with increase in volume fractions of the premixed gases.