Dispersion Behavior and Entrapment Time of Low Density Particles into a Water Bath under Mechanical Agitation

Abstract

Investigations have been carried out on the dispersion behavior and entrapment time of low density particles into a water bath. Particle holdup, vortex initiation time and vortex arrival time have been measured. The particle holdup is defined as the ratio of the sum of particle passing time at a laser beam to the total measurement time. The vortex initiation time is defined as the period from the start of impeller rotation to the initiation of a vortex tube, and the vortex arrival time is defined as the period from the start of impeller rotation to the moment at which the vortex tube arrives at the impeller. The following results are obtained. (1) The particle holdup in offset agitation is higher than that in centric agitation. (2) The mass of the particles placed on the bath surface affects the particle holdup. (3) Empirical equations are proposed for the two characteristic times as functions of the rotation frequency of impeller and the geometrical parameters such as the depth of the water bath and the height of the impeller position.