Ignition and Flame Propagation Characteristics of Residual Coal Dust Following a Methane Explosion-Induced Deposited Coal Dust Explosion

To assess the re-explosion severity of residual coal dust following a methane-induced deposited coal dust explosion, horizontal pipeline tests were conducted. The residual dust was collected and characterized, and its ignition sensitivity and flame evolution were subsequently examined. The results reveal that explosion significantly coarsened the residual dust, increasing its median particle size. The substantial release of volatiles created pore structures on particle surfaces, while surface carbon content decreased markedly, accompanied by noticeable enrichment of oxygen and sulfur. The starting temperature of the main decomposition stage for the residual dust was higher than that of the original dust, but decreased with increasing fuel-richness of the primary explosion. Although the post-explosion dust remained ignitable in air and exhibited even higher ignitability, its flame propagation ability was significantly weakened. The flames appeared bright yellow but with reduced luminosity and enhanced discontinuity; both the maximum flame height and propagation velocity were substantially lower than those of the original dust. The flame parameters of re-explosion were positively correlated with the fuel equivalence ratio of the primary explosion; however, a nonlinear coupling effect existed between the contributions of methane and dust. The present work offers new insights into the re-explosion risk posed by the products of methane–coal dust explosions.