Highlights of 5th Session

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Highlights of 5th Session Kynchs
theory Introduction to filtration Theory of
filtration Filtration Equipment
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Rotary Drum Filter In rotary filters, the flow
passes through a rotating cylindrical cloth
from which the filter cake can be continuously
scraped. Either pressure or vacuum can provide
the driving force, but a particularly useful form
is the rotary vacuum filter. In this, the cloth
is supported on the periphery of a horizontal
cylindrical drum that dips into a bath of the
slurry.
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Vacuum is drawn in those segments of the drum
surface on which the cake is building up. A
suitable bearing applies the vacuum at the
stage where the actual filtration commences and
breaks the vacuum at the stage where the cake is
being scraped off after filtration. Filtrate is
removed through trunnion bearings. Rotary
vacuum filters are expensive.
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This press is an alternate assembly of plates
covered on both sides with a filter medium,
usually a cloth, and hollow frames that provide
space for cake accumulation during filtration.
The frames have feed and wash manifold ports,
while the plates have filtrate drainage ports.
The plates and frames usually are rectangular,
although circles and other shapes also are
used.
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They are hung on a pair of horizontal support
bars and pressed together during filtration to
form a watertight closure between two end
plates, one of which is stationary. The press
may be closed manually, hydraulically, or by a
motor drive. Several feed and filtrate
discharge arrangements are possible.
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Plate
Frame
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• The filter press has the advantage of
• Simplicity
• 2) Low capital cost,
• 3) Flexibility,
• 4) Ability to operate at high pressure in either
  a cake-filter or a clarifying-filter application.
• 5) Floor-space and headroom needs per unit of
  filter area are small.
• 6) Capacity can be adjusted by adding or removing
  plates and frames.

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• Several Disadvantages of Plate And Frame
  Press are
• Improper washing due to variable cake density
• Short filter cloth life
• The mechanical wear of emptying and cleaning the
  press (often involving scraping the cloth)
• High labor requirements.
• Presses frequently drip or leak and thereby
  create housekeeping problems

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Air Filters Air
Filters are used quite extensively to remove
suspended dust or particles from air streams. The
air or gas moves through a fabric and the dust is
left behind. These filters are particularly
useful for the removal of fine particles. The bag
filter consists of a number of vertical
cylindrical cloth bags 15-30 cm in diameter, the
air passing through the bags in parallel. Air
bearing the dust enters the bags, usually at the
bottom and the air passes out through the cloth.
A familiar example of a bag filter for dust is to
be found in the domestic vacuum cleaner. Some
designs of bag filters provide for the mechanical
removal of the accumulated dust.
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Biotechnological Application Removal of
particles less than 5 mm diameter in modern air
sterilization units using (1) Paper filters
(2) Packed tubular filters These cover the
range of sizes of bacterial cells and spores.
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• Mixing is required for
• Blending of two miscible liquids and solids
• 2) Dissolving of solids in Liquids.
• 3) Dispersing a gas in a liquid as fine bubbles
  such as oxygen from air in a suspension of
  microorganisms in fermentation or for the
  activated sludge process in water treatment.
• 4) Suspending of fine solid particles in a liquid
  such as in the catalytic hydrogenation of a
  liquid where solid catalyst particles and
  hydrogen bubbles are dispersed in liquid.
• 5) Agitation of the fluid to increase heat
  transfer between the fluid and a coil or jacket
  in the vessel wall.

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Selection Of Mixing Equipment The
following factors must be taken into account when
choosing equipment for mixing liquids 1. Batch
of continuous operation. 2. Nature of the
process miscible liquids, preparation of
solutions, or dispersion of immiscible
liquids. 3. Degree of mixing required. 4.
Physical properties of the liquids, particularly
the viscosity. 5. Whether the mixing is
associated with other operations reaction,
heat transfer.
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End of Session 6