Mechanical separation techniques

Mechanical separation techniques

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.

Types of mechanical separator

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	Air and wet classifiers, centrifugal classifiers, jigs, tables,
characteristics	spiral concentrators, flotation cells, dense-medium
	separators, magnetic separators, electrostatic
	separators

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 Centrifugation, Clarification, Dust and mist collection, Filtration, Flotation, Magnetic separation methods, Mechanical classification, Screening, Sedimentation (industry)