Prediction of fluidized bed behaviour in the presence of liquid bridges

The need to understand defluidization due to free surface liquid in gas-sol id fluidized bed processes gave rise to a study of the effect of addition o f non-volatile liquids with different viscosity and surface tension to a co ld model gas-solid fluidized bed. The incremental addition of liquid to a f luidized bed of Geldart group B particles was observed, in general, to resu lt in a transition to group A behaviour and eventually to group C behaviour . The BA and AC boundaries are shown to be associated with the balance betw een the interparticle liquid bridge forces and the fluid drag force. Using liquid bridge forces calculated from measurements of bridge geometry, the r atios of interparticle force to fluid drag force were found to vary between 0.6 and 1.07 for the AC boundary and between 0.02 and 0.06 for the BA tran sition boundary. Based on this approach, a practical diagram is developed e nabling fluid bed behaviour to be predicted from a knowledge of particle, f luid and liquid properties and the quantity of liquid in the bed. (C) 2001 Elsevier Science S.A. All rights reserved.