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 fl ow structure in a liquid-solid circulating fluidized bed (LSCFB). Good agreement is obtained between the model predictions and the experimen tal 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 ve locity, bed voidage and slip velocity in the core and annular regions are predicted with the model under different superficial liquid veloci ties and different particle circulation rates. The variation of the ra dial non-uniformity of the flow structure is also discussed and a mech anistic explanation is presented. A radial uniformity index is propose d to characterize the radial flow structure. The similarities and diff erences between gas-solid and liquid-solid fluidization systems are co mpared. (C) 1997 Published by Elsevier Science S.A.