Solids Circulation and Attrition Rates and Gas Bypassing in an Internally Circulating Fluidized Bed

Abstract

Solids circulation and attrition rates and gas bypassing in an internally circulating fluidized bed (ICFB) were studied. The bed materials used were mixtures of silica sand and calcium particles. The effects of the superficial gas velocities in the annulus and the draft tube, average diameter of the calcium particles, and geometry of the draft tube on the solids circulation and attrition rates and gas-bypassing fractions were investigated. It was found that the solids circulation rate first increased with increasing superficial gas velocity in the annulus and then leveled off. It also increased with increasing superficial gas velocity in the draft tube and the orifice diameter. However, it decreased with increasing average diameter of the calcium particles. When the draft tube height increased from 25 to 35 cm, a minimum solids circulation rate occurred at 30 cm. Moreover, when the inner diameter of the draft tube increased from 3 to 5 cm, a maximum solids circulation rate occurred at 4 cm. Gas-bypassing ...