Effect of Impeller and Chopper Design on Granulation in a High Speed Mixer

Abstract

Effects of impeller and chopper design upon granule growth are investigated by granulation of dicalcium phosphate in a Fielder PMAT 25 laboratory high speed mixer. It is shown that the effects of the impeller design with respect to the blade inclination and impeller rotation speed can be described in terms of the volume swept out by the impeller. A high swept volume causes high densification of the agglomerates and narrow granule size distributions. Chopper size and rotation speed have no effect upon the granule size distribution. It is suggested that the primary function of the chopper is to disturb the uniform flow pattern of the mass. Effects of deposition of moist mass on the wall of the bowl on granule growth are demonstrated, and suggestions for reducing the deposition are given.