Solid-Liquid Separation Techniques

Even though surtace-property-based liquid-solid-liquid separation techniques have yet to be widely used in significant industrial applications, several studies which demonstrate their effectiveness have appeared in literature. 

Rgure 4-54. Size ranges where particular solid-solid/solid-liquid separation techniques can be applied. By permission, Roberts, E. J. et. al.. Chemical Engineering, June 29,1970 [35]. 

Flocculation or clarification processes are solids-liquid separation techniques used to remove suspended solids and colloidal particles such as clays and organic debris from water, leaving it clear and bright. Certain chemicals used (such as alums) also exhibit partial dealkaliz-ing properties, which can be important given that the principal alkaline impurity removed is calcium bicarbonate—the major contributory cause of boiler and heat exchanger scales (present in scales as carbonate), although closely followed by phosphate. 

Figure 10.10. Solid-liquid separation techniques (after Dahlstrom and Cornell, 1971)...

As we discussed earlier for the solid-liquid separation technique, filtration separates particles by forcing the fluid through a filtering medium on which solids are deposited. The conventional filtration involves the separation of large particles (dp > 10 pm) by using canvas, synthetic fabrics, or glass fiber as filter medium. 

Bioproducts are usually secreted from animal cells in culture, and can be purified after cell removal by solid-liquid separation techniques (see Chapter 11). However, the product can sometimes be found within the cell and this requires its extraction from the cellular mass, which contains numerous molecular species that can have high viscosity and proteolytic activity, which increases the difficulty of sample handling. 

Sequence of steps in selecting a solid-liquid separation technique (a) definition of basic characteristics of the process, (b) coding sludge settling characteristics, and (c) coding filtering characteristics. 

We are concerned primarily here with the process filter - its selection and design, and calculations for simulation and scale-up. During preparation of the current text a conscious decision was taken to largely limit the contents to cake filtration. However, although most chapters concentrate on cake filtration, it is not possible to give a balanced account of the practical aspects of filtration without some presentation of other separation techniques. To present information to a similar depth about all of these other processes would have made the book encyclopaedic. While there is certainly a technical need for such a book, or series of books, the authors did not set out to include all solid/liquid separation techniques in the current volume. This should not be seen as an attempt to diminish the importance of depth filtration, crossflow filtration or other solid/liquid separation techniques it is... 

Figure 7.12 Impurity content as a result of suspension (melt) crystallization of diphenyl from 80% diphenyl/20% naphthalene mixtures and application of different solid-liquid separation techniques (reproduced with permission from Ref (6j).

Crystallization is the (natural or artificial) process of formation of solid crystals precipitating from a solution, melt or more rarely deposited directly from a gas. Crystallization is also a chemical solid-liquid separation technique, in which mass transfer of a solute from the liquid solution to a pure solid crystalline phase occurs. 

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