Design of small-rate feeders for non-free-flowing materials: A case study

Abstract

This paper uses a case study to illustrate the problems which can occur when using small feeders to dose at low rates, with materials which are not totally free flowing. The general principles of good design for small feeders are enlarged upon, together with issues to look for when trouble shooting these equipment items.

The system in question used a screw to dose a moist pelleted talc into a process at a nominal rate which was variable at around 1 t/h and originally suffered from poor flow in the hopper, a variable dosing rate and binding of the screw, thus needing constant attention from the operator to keep it working. Various types of mechanical flow assistance device had been tried, most of which made the problem worse. The Wolfson Centre redesigned the screw and hopper of the unit, and the performance problems were cleared. The problems with the original and intermediate designs serve to illustrate very well the points that need to be observed, in obtaining good performance from small feeders.