Characteristics of self–ignition and smoldering of coal dust layer under inclination conditions

In many actual industrial scenes, the coal body and coal dust are not always in the tiled state, but in the inclined situation. A two – dimensional transient numerical model of coal oxidation reaction was established to study the self–ignition and smoldering characteristics of coal dust layers in the presence of inclination angle. The effects of gravity and thermal buoyancy were considered to solve the coupling problem of coal oxidation reaction and air flow. The results show that the growth coefficients of minimum ignition temperature of coal dust with thicknesses of 6.4 mm, 12.7 mm, 19.1 mm and 25.4 mm are 0.117 °C/°, 0.0467 °C/°, 0.033 °C/° and 0.033 °C/°, respectively. With the increase of hot plate temperature, the inclination of coal dust can greatly shorten the ignition delay time (IDT). The ΔIDT of coal dust inclination of 60° is 128 s/°C greater than that of 0°. The movement of high temperature point of coal dust in self–heating development stage is from the inside to the outside, and that in decaying stage is from the outside to the inside. In addition, some interesting phenomena in the process of coal self–ignition and smoldering have also been found. The influence of coal dust inclination on its self–heating is mainly reflected in the location of high temperature points and the spread of smoldering. This study is helpful to understand the characteristics of coal dust self–ignition and smoldering spread in inclined situation, and can guide the prevention of coal dust self–ignition. © 2021 Institution of Chemical Engineers