Experimental investigation on effects of particle size, dust concentration and dust-dispersion-air pressure on minimum ignition temperature and combustion process of coal dust clouds in a G-G furnace

Abstract

The present study investigates the effects of three important parameters, namely, particle size, dust concentration and dust-dispersion-air pressure on Minimum Ignition Temperature (MIT) and explosion process of coal dust cloud using Godbert-Greenwald furnace. The coal sample collected from Jharia Coalfield, India was used for experimentation. The effects of particle size and concentration of coal dust on MIT of coal dust cloud were studied at five different particle size ranges, that is, <38 µm, 38 to <75 µm, 75 to <212 µm, 212 to <425 µm and 425 to <850 µm. However, the effect of dust-dispersion-air pressure was studied only with the initial three finer particle size ranges, because at coarser sizes it was not possible to maintain a dust cloud of sufficient concentration due to high particle settling velocity and the dust cloud became non-explosive beyond dust-dispersion-air pressure of 30–35 kPa, even at ignition temperature of 1000 °C, which is the limiting temperature of the apparatus. The results indicate that MIT of coal dust cloud increases exponentially from 420 to 730 °C with increase in coal dust particle size. MIT was also found to decrease with the coal dust concentration till a stoichiometric concentration was reached, beyond which MIT slightly increased for the three finer particle size ranges. Nevertheless, in the case of the coarser particle size ranges tested, initially a trivial decrease in MIT was observed only up to certain dust concentration, after which, the MIT increased faintly. The results and the underlying mechanism presented are extremely useful, not only in research and advancement of knowledge on the coal dust explosion process, but also in taking necessary measures for preventing coal dust explosions in underground coal mines.