Industrial Filtration
Filtration is the removal of solid particles from a fluid by passing the fluid through a filtering medium, or ‘septum’ on which the solid are deposited.
Industrial filtrations range from simple straining to highly complex separations.
Firstly the feed is modified by some means of pretreatment i.e. heating, or adding a ‘filter aid’ such as cellulose, to increase filtration rate. In industrial filtration the solid content of the feed ranges from a trace to a very high percentage.
Fluid flows through a filter medium by virtue of a pressure differential across the medium. Pressures above atmospheric may be developed by the force of gravity acting on a column of liquid, by a pump or blower, or by centrifugal force .
Types of Industrial Filters: -
These are mainly divided into three main groups:
Cake Filters,
Clarifying Filters, and Cross flow Filters.
Cake filters: - They separate relatively large amount of
solids as a cake of crystals and sludge. Before the discharge of filtered fluid,
they often include provision for washing the cake and for removing some of the
liquid from the solids.
Clarifying filters: - They are operated to produce a clean
gas or sparkling clear liquid such as beverages (cold drinks & juices).
They remove small amount and size of solids, which are trapped inside the
filter medium, or on its external surfaces.
Crossflow filters: - In this type of filters the feed
suspension flows under pressure at a fairly high velocity across the filter
medium. A thin layer of solid may form on the surface of the medium, but the
high liquid velocity keeps the layer from building up.
The filter medium is a ceramic, metal, or polymer membrane
with pores small enough to exclude most of the suspended particles.
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