Fluid dynamics of gas-liquid-particle flow in the draft tube and liquid-particle flow in the annulus were studied for a draft-tube fluidized bed (DTFB) operating in the circulating regime. The local concentrations 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 extended to take into account the momentum transfer between all phases in the three-phase system studied, and used to describe the circulating flow in the DTFB. Additional momentum transfer from gas bubbles to solid particles was identified and attributed to the changes in relative velocities and drag forces induced by bubble motion in three-phase flow.