Combustion of single CWF droplets of either pulverized or micronized coal

This paper reports on new experimental findings on the combustion behavior of coal-water fuels (CWF) consisting of either pulverized coal (average size ca. 40{mu}m) or of micronized coal (averaae size ca. 4{mu}m). The former CWF is considered as a fuel in, utility boilers to substitute petroleum. The latter is considered as a fuel in diesel engines, gas turbines, etc. There are differences in the physical and chemical properties of these fuels since the size of the coal particles differs by an order of magnitude, the resulting packing factor is unequal and the mineral content is different by an order of magnitude as well, since the micronized slurries are also beneficiated. This work concentrated on the combustion of the solid agglomerated particles that remain upon completion of water evaporation. Experiments were conducted in a bench scale high-temperature drop-tube furnace, electrically heated to gas temperatures of 1450 K. Single CWF agglomerates (200--500 {mu}m, in diameter) were introduced in the furnace, and upon ignition their combustion behavior was monitored with a specially developed three wavelength (640, 810 and 998 nm) pyrometer. Results showed that the overall combustion behavior of Agglomerates of the same size from the two coal grinds was similar when burned under the same conditions.