Designing for Paste Thickening Testwork and Sizing for Paste Thickeners

Abstract

In the mineral processing industries, there is an increasing need to design thick-eners which are able to produce high density underflows usually referred to as "paste". The behaviour of a flocculated suspension in compression needs to be well understood in order to arrive at a reliable thickener tank configuration (i.e. diameter , cone angle and depth) for a required paste result. As a suspension approaches paste consistency, its fluid characteristics change markedly. It develops a high yield stress, and may have an increased tendency to form agglomerates, which in thickener tanks leads to a phenomenon known as "rotating beds", "donuts", or "islands". These characteristics present challenges to the designer of the rake mechanism. The subject paper addresses the requirements for designing a paste thickener, covering the following topics: • Testwork for thickener sizing. • Design of rake mechanisms. • Suspension rheology and effect on design.