Flame Propagation in CH4/Air and CH4/Air/Coal Dust Mixtures in a Closed Vertical Channel

We investigated the possibility of the existence of combustion waves in CH $$_{4}$$ /air mixtures with a methane content $$\alpha = 5{-} 8$$ vol % and in CH $$_{4}$$ /air/coal dust mixtures in a closed vertical channel 6.75 m long and 0.07 m in diameter when ignited at the top. The experiments were carried out at an initial pressure of 0.1 MPa using dust with an average volume concentration of 100–530 g/m3 and a particle size 0–200 μm. It was found that combustion was not initiated in gas and gas/coal dust mixtures with $$\alpha \;\leqslant \;5{-} 5.5$$ vol %. The results of the study indicate that the direction of gravity influences the ignition and combustion of the mixtures and that the energy contribution of coal particles is low compared to that of methane.