Solid Circulation Characteristics in an Internally Circulating Fluidized Bed with Orifice-Type Draft Tube

Abstract

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. x 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 (DeltaP(or)). However, the values of G(s) decrease by 7-21% with increasing particle size from 86 to 288 mum. The pressure drop across the orifice increases with increasing U-d and U-a. However, DeltaP(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 DeltaP(or).