Experimental Study of the Influence of H2/CO on the CH4 Explosion Pressure and Thermal Behaviors

In a spontaneous coal combustion environment and in the coal chemical process, multiple gases, such as CH4, H2, and CO, coexist, and explosion accidents are prone to occur. The causes of these disasters and the explosion characteristics are key to formulating preventive measures. To explore the effect of H2/CO on the explosion pressure and thermal behavior of methane-air, CH4 with initial volume fractions of 7, 9.5, and 12%, which correspond to three states of oxygen enrichment, equivalence ratio, and oxygen depletion, was selected. Moreover, a mixed fuel system is composed of H2/CO with different volume ratios. A 20 L spherical gas explosion experimental system was used to test the peak explosion overpressure Pmax, the maximum explosion overpressure rise rate (dP/dt)max, and the corresponding time parameters of the H2/CO-CH4 mixed system. Combined with the thermodynamic calculation model, laminar burning velocity SL, explosion heat loss qtra, and other parameters were obtained. The results show that due to the existence of the damping effect, CO has the dual characteristic of promoting or weakening methane explosions. Compared with CO, the effect of H2 on the methane explosion is more significant, and the improvement or weakening of the laminar combustion rate of the reaction system by CO "lags" behind that of H2. The heat loss in the process of a gas explosion is affected by factors such as the heat release rate, the propagation speed of the combustion wave, and the heat dissipation effect of the container wall. When H2/CO increases the laminar burning velocity of the mixed system, the heat loss decreases accordingly. This study also found that the laminar burning velocity model of the mixed gas based on the ideal spherical flame propagation theory is not fully applicable to the H2/CO/CH4 mixed system in a spherical closed space, and the calculation results have large errors when the mixed system is close to the upper limit of the explosion.