Methods for design of hoppers. Silos, bins and bunkers for reliable gravity flow, for pharmaceutical, food, mineral and other applications

Abstract

It is now four and a half decades since Andrew Jenike introduced the first integrated method for characterising powders for flow, and using this information to design a hopper that would discharge without hang-up. Sadly, many users and designers of hoppers still do not benefit from this, so a lot of process vessels in industry still suffer from rat-holing, arching and bridging. Objections of cost, time and questionable accuracy were levelled at the original hopper design method, in spite of the breakthrough it represented. However, over the last 40 years these problems have been overcome with the introduction of faster, easier to use and more sensitive powder flowability measurement techniques, and a lot of experience of what measurements matter with which materials and in what operational scenarios. This paper will pull together various lessons learned from many years of hopper and silo design projects, and show a practical approach to deciding (i) what flow pattern is required (mass flow or core flow), (ii) what measurements need to be made of the powder properties, and (iii) what design models should be used, based on the material being handled and the operational requirements of any given case