PROPER FILTER OPERATION
IMPROVES EFFICIENCY
n practice filtration is the
recovery of a material
that is either wanted so
as to reuse it or unwanted
so that it can be readily
withdrawn from the system. It is the
separation process where gas steam or
liquid slurry is purified by the use of a filter.
Filters are the equipment used to achieve
selective recovery of a certain component
or compound from a mixture. That is
accomplished when the material passes
through a filter medium. The driving
force across the medium could be the
differential pressure between the medium
or gravity or even the concentration,
however there are factors such as the
mechanism of operation of the system,
the nature of material being handled, the
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size specification of filter medium, the
operating condition (cycle, temperature,
flow rate etc) and hydraulic properties
of the fluid which affect the process.
The choice of a filter media is often very
important as factors such as minimum
propensity to bleed which is the ability
to create solid bridge across its pores in
less time, minimum propensity to blind
that is the wedging of solids between the
interstices of the pores should be less too,
the minimum resistance to flow of filtrate,
resistance to attack by corrosive tendency
of the fluid being handled, and resistance
to mechanical wear, etc.
Filters can be classified by their
characteristic applications for example air
filters, oil filters, flush filters, sand filters
etc or by their operational provisions
such as rotary vacuum filters, or by design
principle e.g. cake gravity, pressure and
press filters and so no. Cake filters are
such that accumulate appreciable visible
quantities of filtered solids on the surface
of the medium, pressure filters are those
which operate under super-atmospheric
pressure at the filtering surface and more
or same at it downstream. Whereas gravity
filters operate at the available hydrostatic
pressure of the fluid above it, hydraulic
filters combines the principles of filters and
the hydraulic press, etc.
The filter media are manufactured from
cotton, polymers, asbestos, glass, cellulose.
metals, fabrics, refractories, ceramics, sands,
particulate solids, etc. Apart from the media