Solid circulation characteristics in an internally circulating fluidized bed with orifice-type draft tube

Effects of superficial gas velocities to a draft tube, to an annulus section and particle size on the solid circulation rate (G_s) have been determined in an internally circulating fluidized bed (0.28 m I.D.×2 m high) with an orifice type draft tube. The solid circulation rate from the draft tube to an annulus section increases with increasing gas velocities to the draft tube (U_d) and annulus section (U_a) and consequent increase in pressure drop across the orifice (δP_or). However, the values of G_s decrease by 7-21% with increasing particle size from 86 to 288 um. The pressure drop across the orifice increases with increasing U_d and U_a. However, δP_or decreases by 5-23% with increasing particle size. To predict G_s in an internally circulating fluidized bed, a correlation is proposed as a function of δP_or.