Abrasion of Particle by Small Impeller in an Agitated Vessel

概要

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There are a number of operations carried out in the process industries by small impeller in an agitated vessel in which particles are suspended and thus the possible abrasion of particles should be considered precisely to understand the operation. To investigate the abrasion of particles in an agitated vessel, an aggregated spherical silica particle, the diameter of which was set at about 2.0 mm or 1.0 mm, was prepared purposely and put into a vessel and agitated by a Rushton turbine impeller, RT or an edged turbine impeller, ET. The change of diameter of the particle with time elapse was measured by using a CCD camera as an area equivalent diameter. And the frequency of the particle which was passing through the impeller swept region was also measured by 3-D PTV method. As a result, it is found that an ET is superior to a RT for the abrasion of the particle at same power input per unit volume. For both impellers, the power efficiency of the particle abrasion at too high impeller speed condition is worse than that at low impeller speed condition. However, it is also found that with increasing impeller speed, the particle abrasion rate per the number of circulation of the particle passing through the impeller swept region, Rω, increases, especially at high tip velocity condition with an ET. At the same maximum impact energy condition, the Rω by an ET is superior to that by a RT.