Dynamics and mechanisms of methane–deposited coal dust–methane continuous explosions: Effects of coal metamorphism and deposition mass

Abstract

Methane–deposited coal dust–methane continuous explosion seriously threatens mine safety and the environment, and its explosion mechanism requires further research. This study employed a self-designed pipeline to examine how coal dust metamorphic degree and deposition mass affect dynamics. Explosion overpressure, flame propagation, and residue characteristics were analyzed. Furthermore, the contribution of each factor to the explosion hazard was quantitatively evaluated using grey relational analysis. Results showed the most severe explosion at 4 g of deposited coal dust. When the methane explosion entered the dust zone, the resulting shock wave entrained dust, intensifying combustion and increasing flame brightness and speed. In the downstream methane-air premixed region, thermal buoyancy, turbulence, and particle motion caused stratified combustion and upward flame deflection. Reflected shock waves led to secondary entrainment and re-ignition of coal dust, producing oscillatory flame propagation. Explosion pressure and flame velocity correlated strongly with coal O/C ratio, volatile matter, and pyrolysis characteristics, confirming that chemical reactivity, volatility, and pyrolysis kinetics govern explosion intensity. Low-rank coals exhibited markedly higher hazard indices than high-rank coals across all metrics. This work elucidates the evolution and mechanisms of methane–coal dust–methane continuous explosions and offers practical guidance for enhancing intrinsic mine safety.