The
choice of a recessed filter press, plate
and frame filter or membrane plate filter
press is determined by the application
which normally falls into one of three
categories, namely:
1. The separation of solids and liquids
under conditions where there is sufficient
solid material in the feed slurry to form
a filter cake.
2. The separation of solids and liquids
where there is sufficient solids to form
only a thin layer on the filtering media.
3. The removal from a liquid of small
quantities of finely divided solids, sometimes
with the assistance of filter aids, this
operation is normally described as clarification
or polishing. In the first category the
filter press criteria is to provide filtration
area and volume for cake filtration, in
the second and third categories the filter
press essentially provides filtration
area and the capacity for cake filtration
is unimportant. For the first application
a recessed plate filter press is usually
recommended with the plate and frame design
normally recommended for second and third
category applications.
Recessed Plate Filter Press
In the recessed type of press the recess
is formed by a raised rim which stands
above the drainage surface and the thickness
of cake formed therefore twice the depth
of the recess on individual plates. The
slurry to be filtered is normally fed
into the filter press through a central
hole that feeds each chamber at the same
time. The solids are retained within the
recessed hollow chamber and the filtrate
passes through the media into an internal
manifold or away through drain cocks or
directional bibs.
Plate and Frame Filter Press
In the plate and frame type of press
the chambers are formed by the use of
a hollow frame which is placed between
two plates whose rim or joint surfaces
are nearly flush with their drainage surfaces.
The slurry to be filtered is fed into
the press through a manifold formed by
ports in each plate and frame and delivered
into each frame by suitable connecting
ports. The solids are retained within
the hollow frame whilst filtrate delivers
through the media into a collection manifold
by way of additional ports in the plates
or through drain cocks or directional
bibs.
Membrane Plate Filter Press
The membrane system has proved to be
useful in certain applications, typical
of which are the filtration of dyes, pigments
and yeast slurries.
1. 630 x 630mm square, recessed plate
filter press used for dewatering metal
hydroxide sludges from a plating shop
effluent treatment plant
2. 800 x 800mm square, recessed membrane
plate filter press used in filteration
of fermenting vessel bottoms on a brewery
installation.
3. 1500 x 1500mm square, recessed plate
filter presses used for treatment of drinking
water in a large Scottish town.
