Characteristics of coal dust ignited by a hot particle

Abstract

Ignition of coal dust caused by hot particles (ICDHP) will lead to serious combustion or explosion. In this work, the coupling details of multi–physical fields of the ICDHP were established. Two different chemical reactions of flaming combustion of volatiles and smoldering of coal dust were established to understand the mechanism and process of the ICDHP. The evolution of temperature, volatiles molar concentration and heat release characteristics under different particle temperatures and contact conditions between the hot particle and coal dust were investigated. Results show that there are two ways of the ICDHP, which are volatiles ignition and coal smoldering ignition. The ignition delay time (IDT) increases exponentially with the decrease of the hot particle temperature. The temperature of the hot particle is 1100 K, and thermal runaway occurs in the way of coal smoldering ignition. When the temperature of the hot particle is higher than 1100 K, thermal runaway occurs in the way of volatiles ignition. In addition, it is found that the IDT decreases exponentially with the increase of the buried depth (lp) of the hot particle in coal dust for the hot particle temperature of 1186 K. The IDT shows a trend of decreasing – increasing – decreasing with the increase of lp for the hot particle temperatures of 1271 K and 1369 K. If the hot particle is completely embedded in the coal dust, the smoldering combustion of the coal dust is found. In addition, the volatiles first react on the side of the hot particle, and the thermal runaway occurs at the position where the concentration and temperature of volatiles are high enough.