Hydrodynamics of a swirling fluidised bed

A novel variant of the fluidised bed, the swirling fluidised bed, featuring an annular bed and inclined injection of gas through the distributor blades, is studied in the present work. The hydrodynamic characteristics in the swirling regime of operation are studied in detail, experimentally as well as by an analytical model. Unlike a conventional bed, the swirling bed presents three, or sometimes four regimes of operation depending on the bed weight. Bed pressure drop studies have been carried out in a swirling bed for two different sizes of spherical PVC particles. A striking feature that distinguishes the swirling bed from a conventional fluidised bed is that, the bed pressure drop in the swirling mode, (Δp)b,s increases with air velocity. A physically plausible explanation for this behaviour is that, (Δp)b,s is proportional to the centrifugal weight of the bed. This idea leads to the development of an approximate model that predicts the mean angular velocity of the bed, and hence, (Δp)b,s, at a given air flow rate. The good agreement between the theoretical and experimentally obtained (Δp)b,s values at moderate air flow rates, and the results of an uncertainty analysis performed on the model indicate that the present model describes the fluidised regime of a swirling bed satisfactorily.