Study on the Explosion Characteristics of CH₄ with the Addition of Coal Spontaneous Combustion Gases

Combustible gases produced during the coal spontaneous combustion (CSC) process will cause hidden danger for mine safety. For studying the effect of the addition of CSC gas on CH4 explosion characteristics, a 20 L explosive device was adopted to obtain the explosion characteristics of CH4 (7%, 9.5%, and 11% in vol.) and CSC gas (0–2% in vol.) premixed fuel, and the effect of CSC gas on CH4 explosion characteristics was analyzed. Results show that for 7% CH4, CSC gas promotes the CH4 explosion. However, for 11% CH4, CSC gas inhibits the explosion of CH4. Based on the chemical reaction kinetics analysis, it indicates that adding CSC gas at different stages changes the sensitivity coefficients, which affects the concentration of active radicals. With the increase of CSC gas in CH4, the concentration of H increased, the concentration of O decreased, and the concentration of OH increased first and then decreased. The variations of O and OH are regarded to be the main reason for promoting the explosion of dilute CH4 and inhibiting the explosion of concentrated CH4. The variations of H, O, and OH indicate that the addition of the self-heating oxidation stage of CSC gas has a more evident effect on the CH4 explosion characteristics.