Liquid velocity and gas holdup in three-phase internal loop airlift reactors were investigated. Air and water were used as the gas and liquid phase, respectively, and the solid particles used were calcium alginate beads with different particle size. The liquid velocity in the riser and the downcomer were obtained by tracer analysis. The gas holdup in the riser and the downcomer were determined by manometric technique. It was found that the liquid velocity did not show any significant variations with top clearance. The liquid velocity increased with an increase in aeration rate or draught tube length, whereas it decreased as the diameter of the particles was increased. Moreover, the liquid velocity and the gas holdup decreased with increasing solids loading. A hydrodynamic model based on the drift-flux model was developed to describe satisfactorily the liquid velocity and gas holdup in air-water-calcium alginate internal loop airlift reactors.