A FLUID DYNAMIC-MODEL OF THE DRAFT TUBE GAS-LIQUID-SOLID FLUIDIZED-BED

Fluid dynamics of gas-liquid-particle flow in the draft tube and liqui d-particle flow in the annulus were studied for a draft-tube fluidized bed (DTFB) operating in the circulating regime. The local concentrati ons and velocities of the continuous liquid phase, solid particles and air bubbles were assessed in flow visualization studies, using a two- dimensional column, 1 cm thick x 8 cm wide x 105 cm high, with a 4 cm wide x 83 cm high internal draft tube. The drift-flux model was extend ed to take into account the momentum transfer between all phases in th e three-phase system studied, and used to describe the circulating flo w in the DTFB. Additional momentum transfer from gas bubbles to solid particles was identified and attributed to the changes in relative vel ocities and drag forces induced by bubble motion in three-phase flow.