A core-annulus model for the radial flow structure in a liquid-solid circulating fluidized bed (LSCFB)

A core-annulus model is developed to describe the radial nonuniform flow structure in a liquid-solid circulating fluidized bed (LSCFB). Good agreement is obtained between the model predictions and the experimental results of the radial distributions in the bed voidages and liquid velocities under different superficial liquid velocities and particle circulation rates. The variations of the liquid velocity, particle velocity, bed voidage and slip velocity in the core and annular regions are predicted with the model under different superficial liquid velocities and different particle circulation rates. The variation of the radial non-uniformity of the flow structure is also discussed and a mechanistic explanation is presented. A radial uniformity index is proposed to characterize the radial flow structure. The similarities and differences between gas-solid and liquid-solid fluidization systems are compared. (C) 1997 Published by Elsevier Science S.A.