PROCESS VARIABLES OF INSTANT GRANULATOR AND SPHERONISER .3. SHAPE ANDSHAPE DISTRIBUTIONS OF PELLETS

The complete 2(6) study design was used to investigate the influence o f the process variables of a continuously working granulator, and a sp heroniser on the shape and shape distributions of pellets. Shape param eters were derived from size parameters measured by image analysis. Of seven shape parameters suggested, roundness and elongation most effec tively distinguished pellets from each other. For a homogeneous pellet batch, 200 pellets need to be measured, but in the case of a heteroge neous batch, even up to 800 measurements were required to achieve reli able and reproducible results. The most important process variables af fecting the shape of pellets were the size of the granule outlet in th e granulator, the speed of the friction plate and the residence time: rounder pellets could be produced using larger granule outlet, faster speed of the friction plate and longer residence time.