The availability of industrial purge gas: Experimental and kinetic study of explosion characteristics of low-concentration H2/CH4 mixtures

This study focuses on the resource utilization of purge gas from the coal chemical industry and evaluates its theoretical flammability. The explosion characteristics of low concentration H2-CH4 mixtures with nitrogen were investigated, analyzing the effects of equivalence ratio and nitrogen on explosion intensity. Kinetic mechanisms were employed to simulate the impact of equivalence ratio and nitrogen on OH radicals during the explosion process. Results indicate that as equivalence ratio increases, both the Pmax and (dP/dt)max initially increase and then decrease. Increasing the nitrogen proportion gradually reduces explosion intensity, with Pmax positively correlated to flame propagation speed. Comparative analysis reveals that nitrogen's suppressive effect on low concentration hydrogen is significantly greater than that on methane. Simulations show that changes in OH radicals during the explosion process are more pronounced in mixtures with higher hydrogen content. At the same equivalence ratio, hydrogen exhibits greater sensitivity to nitrogen, followed by methane, consistent with experimental findings. Nitrogen primarily affects the generation rate of OH radicals and ROP, with this effect becoming more pronounced as equivalence ratio increases. These findings provide a theoretical basis for utilizing explosion energy from purge gas and for risk prevention.