Inhibiting effect of coal fly ash on minimum ignition temperature of coal dust clouds

The inhibiting effect of coal fly ash on the combustion of a coal dust cloud was studied for three typical types of coal: anthracite, bituminous coal, and lignite. Using a Godbert–Greenwald furnace, the minimum ignition temperature (MIT) of coal dust clouds containing various quantities of coal fly ash was measured. The results show that the MIT of coal dust clouds increases linearly with increasing quantities of coal fly ash. Compared with calcium carbonate as a common inhibitor, coal fly ash was found to have a better inhibiting effect owing to its larger heat capacity. Furthermore, at the same concentration of coal fly ash, the larger the coal dust particle size, the higher the MIT of the coal dust cloud. Moreover, at the same concentration of coal fly ash, the higher the content of volatile matter in the coal dust, the lower the MIT of the coal dust cloud. Coal fly ash has the strongest inhibiting effect on lignite, the second strongest inhibiting effect on bituminous coal, and the weakest inhibiting effect on anthracite. Combining all the factors examined in this work, a simple empirical model is presented that provides a reasonable estimation of MIT.