Abstract Axial dispersion coefficients in the liquid phase of gas—liquid (three-phase) fluidized beds have been determined from tracer concentration measurements upstream of the injection plane by using the steady state injection technique and applying the axially dispersed plug-flow model. Water, air and glass beads of 0.45, 0.96, 2 and 3 mm diameter particles were used as the liquid, gas and solid phases, respectively. The superficial velocities ranged from 1.15 to 12.8 cm/s for the liquid phase and from 1.3 to 7 cm/s for the gas phase. The calculated dispersion coefficients increased with increasing gas flow rate and their variation with the liquid flow rate depended on particle size. These coefficients were higher for three-phase fluidized beds than those for the corresponding two-phase particle-free systems. The mixing length decreased with increasing particle size.
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