The ignitability of coal dust-air and methane-coal dust-air mixtures

Abstract

An experimental investigation of coal dust explosions was conducted in a 26 1 spherical chamber. Channel (mine-face) samples of coal from the Prince and Phalen mines of the Cape Breton Development Corporation were used. The objective of the work was to investigate the ignitability characteristics of the coals, alone and with admixed methane. The apparent lean flammability limit of the coal dust-air mixtures was observed to decrease with increasing ignition energy. The decrease was rapid at low energies, with an approach to an asymptotic value of the lean limit at high energies. A stored ignition energy of 5 kJ was required to measure these asymptotic values which represent the true lean flammability limit. The apparent lean limit at a given ignition energy was found to decrease in the presence of methane, with a reduction in mass mean diameter of the parent coal, and with an increase in coal volatile matter. These three conditions also enhanced the ignitability of the coal dust-air mixtures, meaning that ignition of a given coal dust concentration was possible with lower energies. The lowering of the lean limit with methane admixture, particle size reduction and increase in volatiles was more pronounced at lower ignition energies.