Effects of different factors on the minimum ignition temperature of the mixed dust cloud of coal and oil shale

Abstract The effects of particle size, oil shale content, dust concentration, dispersion pressure and inert dust on the minimum ignition temperature (MIT) of coal and oil shale mixed dust clouds (COSMD) were investigated in a dust cloud MIT testing system to understand the intrinsic mechanisms of these factors affecting the MIT of COSMD. The results demonstrated that 1) COSMD with larger particle size have higher MIT; with particle size increasing, MIT of COSMD with 50% oil shale content increases from 425 °C to 542 °C, 2) with the oil shale content increasing, MIT of COSMD exhibit the trend of increase, decrease and increase again with the two critical points at 50% and 80% oil shale content; 3) COSMD has an optimal ignition concentration and optimal ignition pressure to exhibit the lowest MIT; 4) the inhibitory effects of inert dusts NH4H2PO4, NaCl and CaCO3 on the MIT of COSMD show the order of NH4H2PO4>NaCl > CaCO3 with their critical concentrations at 30%, 40% and 60%, respectively; when the content of inert dust is 80%, all three inert dusts almost completely suppress the ignition and combustion of COSMD. The results and the underlying mechanism presented are extremely useful, not only in research and advancement of knowledge on the COSMDC ignition process, but also in taking necessary measures for preventing COSMDC explosions in underground coal mines.