Exploitation of shear and compression rheology in disposal of bauxite residue

Abstract

The paper presents an overview of the research conducted in the Department of Chemical Engineering at the University of Melbourne in conjunction with Alcoa of Australia Limited. The first part of the presentation reviews the shear rheology of bauxite residue suspensions and emphasises how an understanding of the fundamental flow properties of concentrated bauxite residue suspensions can be exploited in developing a semi-dry waste disposal scheme, which has been developed and proven by Alcoa in Western Australia and is now under consideration by a number of international alumina producing companies. The paper compares the rheology of highly concentrated bauxite residue suspensions in shear to results obtained in compression using techniques for compressive yield stress measurement developed at the University of Melbourne. It is shown how the compressive yield stress properties are particularly useful in the design and specification of thickeners for dewatering red mud suspensions. The techniques presented for both shear and compression rheology measurement are applicable not only in the disposal of bauxite residue but are also useful in examining dewatering processes in other mineral system applications and for other waste disposal problems, for example, in the disposal of coal tailings.