Solid-liquid separation four stages

Solid-liquid separation systems generally consist of four stages, which are 1) pretreatment to increase particle size 2) solid concentration in thickeners 3) solid separation in filters and centrifuges and 4) posttreatment to remove solubles and reduce liquid content. Fig. 6 shows the relationship among these stages. 

Fig. 8 Equipment used for the four stages of solid-liquid separation.

Solid-liquid separation systems generally consist of four stages including pretreatment, solid concentration in thickeners, solid separation in filters or centrifuges, and post-treatment by expression and washing operations. There are different types of SLS equipment served for different functions in relation to the four stages. Product specification, characteristics of solid-liquid suspension, solid settling velocity, rate of cake... 

Water is the most commonly used liquid in industry and in all human activities. Thus most liquid-solids separation equipment is specifically designed for treating aqueous systems. In water suspensions, the sizes of solid partieles are usually very small (in the micron and submicron size range) and surface-active forces often play an important role. Representative examples are the mineral slurries, lyophilie eolloids, slimes, and wastewater mixtures. The treatment of aqueous systems involves four stages floeeulation (elarification), sedimentation (settling), consolidation (compression or compaction), and phase separation (filtration or centrifugation). 

Although adsorption has been used as a physical-chemical process for many years, it is only over the last four decades that the process has developed to a stage where it is now a major industrial separation technique. In adsorption, molecules distribute themselves between two phases, one of which is a solid whilst the other may be a liquid or a gas. The only exception is in adsorption on to foams, a topic which is not considered in this chapter. 

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