Solid/liquid separation equipment

This chapter attempts to provide a descriptive overview of the generic equipment types and the main alternatives available to the design engineer. It highlights the advantages and disadvantages of equipment, and provides quantitative values whenever possible. Gravity thickeners and clarifiers represent a class of solid-walled separator, where gravitational forces are used to raise the concentration of a suspension through sedimentation to produce a thickened sludge with a clear liquid as overflow. The rate of sedimentation should be as high as reasonably possible to both increase throughput and reduce floor area. Sedimentation rates are often artificially increased by the addition of coagulants or flocculants. Cyclones designed for use with liquids are referred to as hydrocyclones, hydraulic cyclones, or hydroclones. The basic principle employed to effect either concentration or classification of the solids is centrifugal sedimentation, which is caused by introducing the feed suspension tangentially into the unit; they are particularly attractive for many applications because they have no moving parts. Centrifuges are designed to either thicken or filter suspensions, which leads to two general classes of machine: sedimenting centrifuges and filtering centrifuges.