The effect of particle shape on the pressure drop across the dust cake

In order to observe the effect of particle shape of poly-dispersed dusts on filter performance, the pressure drop across the dust cakes of fly ashes from a conventional power plant (PC), fluidized bed combustion (FBC), and paint incinerator (FI) was measured over a metal filter element in the accurate conditions. A fluidized bed column was used to prepare the dust feed stream of uniform particle distribution. The fine particles of FI ash have a tendency to be agglomerated at low transport velocity. The aggregates were broken at high velocity of more than 21 cm/sec. FBC ash composed of jagged type particles and containing high concentration of unbumed-carbon showed higher pressure drop than that of PC ash composed mostly of spherical particles. FI ash composed of aggregates of very fine carbon particles presented the highest pressure drop among the fly ashes tested. The shape factors of PC, FBC, and FI ash were estimated as 0.91, 0.76, and 0.65, respectively, by the Ergun equation. The results implied that the irregular particle tends to form a higher pressure drop and to be more compressible than spherical one.