Comparisons Between Solid Plug Model Predictions for a Powder Roll Compactor Screw Feeder and Experimental Measurements

Comparisons between solid plug model predictions for a powder roll compactor screw feeder and experimental measurements

T. Patterson and C. Wassgren, Purdue University

Abstract

Solid plug models previously developed to predict the pressure distribution in extruded plastic pellets fed by a screw feeder are evaluated in the present work for feeding pharmaceutical powders, specifically to the inlet of the nip region in a roll compactor.  Experimental measurements of the screw torque required to feed the powder at a given feed rate, the pressure at the outlet of the feeder, and the powder bulk density distribution along the axis of the screw are compared to corresponding predictions from the solid plug models.  The screw rotational speed and outlet pressure are varied in the experiments. The goal of the work is to use the measured screw feeder torque, a parameter often available in commercial roll compactors, and the solid plug model to predict the stress at the exit of the feed screw, and use this stress as an input to Johanson's one-dimensional model for predicting the ribbon density exiting the roll compactor.