Experimental Study on the Entrainment Characteristics of Ultrafine Powder in a Fluidized Bed with Vibrator and Agitator

The entrainment characteristics of Geldart group C powder from solid mixtures (groups A and C) were investigated in a fluidized bed (inner diameter of 40 mm and height of 150 mm) equipped with two vibrators and an agitator. Silicon powders of mean size 2.2 and 0.9 mu m were adopted as entrained material (group C), hollow alumina pellets of mean sizes 359, 505, 650, 775, 996, and 1200 mu m were used as coarse particles (group A), and industrial nitrogen was applied as carrier gas. At ambient temperature (20 degrees C) and atmospheric pressure, the effects of the size of coarse particles (D, 359-1200 mu m), mass ratio of coarse to fine particles (M, 0-1.5), ratio of static bed height to diameter (H, 0.875-1.625), rotational speed of agitator (omega, 27-54 rps), vibration intensity (Gamma, 0-5.0) and superficial velocity of nitrogen gas (V, 0.22-0.55 m/s) on the entrainment characteristics were experimentally studied in sequence. In the scope of this work, the increase of M, Gamma, or V could always improve the entrainment characteristics, while there exists an optimal value for D, H, or omega to obtain the optimum entrainment characteristics. The entrainment rate constant is an order of magnitude larger than that without vibration and agitation, which shows the significant effects of vibration and agitation on the improvement of entrainment characteristics. A relational expression is derived to unify the experimental data, which gives a good fitting result.