HYDRODYNAMICS OF THE FREEBOARD REGION OF A FLUIDIZED BED WITH SECONDARY AIR INJECTION

Gas and particle flow dynamics in the freeboard region of a bubbling fluidized bed was investigated. The results of the swirling lateral air injection measurements showed that the presence of swirl increased the solid internal circulation and residence time. In the experiments without the secondary air injection, the particles were accelerated in the axial direction reaching a maximum velocity at a certain height in the freeboard due to high drag forces exerted on the particles by the gas puffs emerging from bubbles coalescing near the bed surface. The theoretical part of this study involves a 2-D Eulerian-Eulerian (two-fluid) approach using kinetic theory of granular solids to model the bubbling dense region and the freeboard together.