Solid/liquid separation of flocculated suspensions

Solid-liquid separation operations leading to the concentration and isolation of fine particles dispersed in liquids are important in the chemical and mineral processing industries. In spite of this, the procedures available for the prediction of equipment performance remain crude. Almost all major mineral and chemical processing companies now have a clear priority in R&D budgets to develop new approaches to waste minimization; a major part of the problem faced by these industries relates to the effect of management of waste slurries. The processes that manage final waste slurries are often classical “end-of-pipe” solutions. One of the key aims of the present broad program is to understand how to manipulate the structure of slurries within the process so that finally it is possible to engineer clear liquor and simultaneously manageable or tractable waste solids. The best way to process such wastes relies on understanding how to control the compressibility and viscosity of these materials.A generalized approach to understanding and prediction of solid-liquid separation methods based on the measurement of fundamental material properties is reviewed here. This is of value in designing more efficient methods and ultimately to optimizing the performance of solid-liquid separation methods and the selection of flocculants for any given slurry. The model identifies two key parameters, the compressional yield stress Py(φ) and the hindered settling factor r(φ) and laboratory test procedures for the direct measurement of both have been developed. The application of this model to a variety of thickening and filtration processes is demonstrated and a direct relationship between the model parameters and the conventional cake resistance as utilised by current filtration engineers is provided.