Experimental investigation on residual gas re-explosion behaviors following primary fuel-rich explosions of methane-bituminous coal powder mixtures

This study aims to identify the re-explosion hazard after a primary explosion of a fuel-rich methane and bituminous coal powder mixture. Primary and re-explosion experiments were conducted using a spherical explosion testing apparatus. The results reveal that once the mixture of methane and bituminous coal powder reaches a certain degree of fuel enrichment, an explosion can occur under the condition of reintroducing a certain volume of air and igniting. However, the pressure rise rate and explosion pressure of re-explosions are both lower than those recorded in the primary explosion. Nonetheless, the residual gas re-explosion exhibits a maximum pressure exceeding 0.3 MPa, with the maximum rate of pressure rise surpassing 1.8 MPa/s. The residual gas mixture with explosibility significantly reduces the lower explosion limit of methane and increases the risk of re-explosion. The re-explosion characteristics exhibited significant variations with the changing re-added methane concentration after a primary explosion. The premixed laminar burning velocity and flame temperature followed consistent trends with the explosion characteristic parameters. Furthermore, the key elementary reactions governing the combustion kinetics were identified. The results provide new insights into the re-explosion phenomenon and provide data support for assessing the hazards of a re-explosion accident in coal mines.