A group of laboratory and production operations whereby the components of a polyphase mixture are separated by mechanical methods into two or more fractions of different mechanical characteristics. The separated fractions may be homogeneous or heterogeneous, particulate or nonparticulate.
The techniques of mechanical separation are based on differences in phase density, in phase fluidity, and in such mechanical properties of particles-as size, shape, and density; and on such particle characteristics as wettability, surface charge, and magnetic susceptibility. Obviously, such techniques are applicable only to the separation of phases in a heterogeneous mixture. They may be applied, however, to all kinds of mixtures containing two or more phases, whether they are liquid-liquid, liquid-gas, liquid-solid, gas-solid, solid-solid, or gas-liquid-solid.
Methods of mechanical separations fall into four general classes: (1) those employing a selective barrier such as a screen or filter cloth; (2) those depending on difference in phase density alone (hydrostatic separators); (3) those depending on fluid and particle mechanics; and (4) those depending on surface or electrical characteristics of particles. A wide variety of separation devices have been devised and are in use. The more important kinds of equipment are listed in the table, grouped according to the phases involved. See also Centrifugation; Clarification; Electrostatic precipitator; Filtration; Sedimentation (industry).
Materials separated | Separators |
|---|---|
Liquid from liquid | Settling tanks, liquid cyclones, centrifugal decanters, coalescers |
Gas from liquid | Still tanks, deaerators, foam breakers |
Liquid from gas | Settling chambers, cyclones, electrostatic precipitators, impingement separators |
Solid from liquid | Filters, centrifugal filters, clarifiers, thickeners, sedimentation centrifuges, liquid cyclones, wet screens, magnetic separators |
Liquid from solid | Presses, centrifugal extractors |
Solid from gas | Settling chambers, air filters, bag filters, cyclones, impingement separators, electrostatic and high-tension precipitators |
Solid from solid | |
By size | Screens, air and wet classifiers, centrifugal classifiers |
By other characteristics | Air and wet classifiers, centrifugal classifiers, jigs, tables, spiral concentrators, flotation cells, dense-medium separators, magnetic separators, electrostatic separators |
