Influence of CO on Explosion Limits and Characteristics of the CH₄/Air Mixture

The study of gas explosion under the influence of CO generated by spontaneous combustion of coal has practical value for preventing and controlling such accidents. The explosion limit and the explosion characteristic parameters of the CO/CH₄/air mixture were measured with a 20 L explosion tank. The changes in free radical concentration and temperature sensitivity in the process of mixture explosion reaction were analyzed using the GRI-mech 3.0 mechanism. The test results show that with the increase of the CO concentration in the mixture, both the lower explosion limit and the upper explosion limit of CH₄ explosion decreased, the explosion limit range became wider, and the maximum explosion pressure of the mixture decreased. The time for the H•, O•, and •OH radical molar fractions to reach the peak value was found to be prolonged with the increase of the CO ratio in the mixture. Under oxygen-enriched conditions, the •OH and O• mole fractions were larger than those under oxygen-lean conditions, while the H• concentration was reversed. The higher the proportion of CO in the premixed gas, the higher the value of the temperature sensitivity coefficient. The reaction processes R155 CH₃ + O₂ ⇌ O• + CH₃O and R158 2•CH₃ (+M) ⇌ C₂H₆ (+M) had the greatest influence on the temperature of the reaction process. Explosion suppression techniques can be developed for similar explosive environments based on this study.