MELT PELLETIZATION IN A HIGH-SHEAR MIXER .4. EFFECTS OF PROCESS VARIABLES IN A LABORATORY-SCALE MIXER

Melt pelletization of lactose in an 8 litre high shear mixer was exami ned by a factorially designed experiment. Polyethylene glycol (PEG) 30 00 was used as melting binder in a concentration of 23% m/m. The load of the mixer was varied at 600, 800 and 1000 g of lactose. Effects wer e investigated of: massing time, impeller speed and mixer load on mean granule size and size distribution, amount of lumps, intragranular po rosity, adhesion of material to the bowl, product temperature and powe r input. The process was found to be the most reproducible and to give rise to the optimum pellets at a mixer load of 1000 g. A lower mixer load gave rise to a larger amount of lumps. The highest impeller speed resulted in the largest and most rounded pellets. The agglomerate gro wth was found to be dependent on the power input.