Entrainment characteristics of fine particles in fluidized bed under preheating conditions

• The initial loading quantity has significant effect on powder–gas ratio R.
• The gas velocity and initial loading quantity have effect on entrainment rate Wi.
• The increased preheating temperature greatly improves entrainment characteristics.
• The optimal entrainment characteristics (Wi 9.27 g/min, R 0.19 g/g) are achieved.

The entrainment characteristics of fine silicon particles from solid mixtures (Geldart groups C and B) are investigated in a cylindrical fluidized bed with an inner diameter of 30 mm and a height of 450 mm and that is equipped with an agitator and an electromagnetic vibration table. Silicon particles (mean size of 2.7 μm) are used as entrained materials (group C), hollow alumina pellets (mean size of 1200 μm) are used as coarse particles (group B), and nitrogen gas is applied as carried gas. The effects of the superficial velocity of nitrogen gas at room temperature (U, 0.39 m/s to 0.98 m/s), the initial loading quantity of fine particles (M, 5 g to 20 g), the vibration intensity (Γ, 1.3 to 4.83), the stirring speed of agitator (V, 75 rpm to 195 rpm), the mass ratio of coarse to fine particles (N, 0 to 1.5), and the preheating temperature of nitrogen gas (T, 20 °C to 170 °C) on the entrainment characteristics (entrainment rate Wi and entrained powder–gas ratio R) are experimentally studied under atmospheric pressure. Significance analyses of U, M, Γ, and V are performed via the analysis of variance. M and U both significantly affect Wi, but only M significantly affects R. The experimental results show that an increase in U, M, N, and T constantly improves the entrainment characteristics, an increase in Γ deteriorates such characteristics, whereas there exists an optimal value for V to obtain the optimum entrainment characteristics. This study also determines that an optimal operating condition can result in optimal entrainment characteristics (Wi, 9.27 g/min and R, 0.19 g/g), which can be achieved with a U of 0.98 m/s, M of 20 g, Γ of 1.3, V of 155 rpm, N of 1.0, and T of 170 °C.

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