Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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Description
Filtration System for Removing Solid Particles
The invention concerns a filtration system for removing solid particles from liquids
using a cover plate and a filtration device adjoining the underside of the cover plate.
Mechanical removal processes and devices are familiar, these ser~ing to separate what
are mostly solid particles from liquids or suspensions as well as insoluble droplets of liquid
from another liquid or emulsion aided by porous filter units flat in shape such as filter cloths
or wire-fabric screen cloths or thick gravel-pack layers. The physical ~riving force as
15 applied to filtration is the difference in pressure between the inlet and outlet ends of the
filter brought about by the weight of the liquid column located above the filter. This force
can, however, also be generated, or at least boosted, by presses on the inlet side or by
applying vacuum on the outlet side (pressure or vacuum filtration).
Using automatic filter presses, for example, an attempt is made to shorten the process
of filtration as well as setting-up times spent on replacing or separating the filter cake. In the
case of the automatic chamber filter press, which is fitted with horizontal filter chambers
located one on top of the other and an endless-belt type filter cloth, the filter plates can be
25 moved up and down by means of an electro-mechanical opening and closing device. During
this process the filter cake is separated sideways on the filter cloth. Replacement of a new
unreeled filter cloth is effected by laterally mounted roller elements.
30It has been shown on the conventional type of automatic vertical chamber filter press
incorporating movable filter plates that evenness of ascent and descent on the filter plates,
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controlled by laterally mounted lifting systems mounted on the side of the filter plates, is
inadequate, thus resulting in leakages occurring on the filtration chambers acted upon by
high pressure. Leakages are to be observed in particular on sealing elements used to seal off
the sides of the filtration chambers. Leakages are incapable of being prevented even if
5 equipping the filter chambers with fle~;ible sealing elements as it becomes apparent that the
more flexible a seal is, all the higher is the potential fragility of the material and thus all the
shorter the service life of the sealing elements is bound to be. Guidance of the endless belt-
type filter cloth is likewise oroblematic and involves a complex roller system, in other words
a large number of moving parts which are susceptible to disturbance.
The disadvantage of pressure filters designed with rigidly mounted rect~n~ r duct-
like filter chambers, whose ports, located opposite, can be closed offwith tube-like seals for
the filtration process, is that the filter cloth resting on the perforated base of the chamber
15 develops a corrugated shape through constant use, this resulting in the solid matter seeping
through. S-shaped distortion of the filter cloth is also inevitable and causes increased wear
along the edges while the cloth is rendering service or leads to the formation of dead
filtration zones.
Dead filtration zones are interpreted as being those areas which, despite their being
covered over by the filter cloth, do not reveal any pores or inlet for the filtrate.
The disadvantage of chamber filter presses designed with horizontally movable filter
plates is that the filter cloths are immobile for the purpose of improving cake discharge or
for carrying out efficient cloth washing after each filtration process as a means of protection
against blinding.
The term 'blinding' is used to describe clogging of the pores on the filter cloth.
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The chamber filter press disclosed under DE 37 03 696 A1 is provided with two end
plates interposed by a set of filter plates around which a closed-loop filter cloth belt runs,
this bein, tensioned by means of rollers. These rollers run inside the grooves of gibbets
rigidly mounted to the plates. The chamber filter press also reveals a device providing
5 contact pressure for the set of filter plates as well as manifolds lin};ed to the feed and
discharge lines of the matter due to be removed. The disadvantage observed here is that,
although the load generated by the filter cloth belt while in motion is taken over by the
plates, a heavy degree of strain is nevertheless exerted on tensioning elements.
US PS 50 94 760 merely describes a filtration system designed to run on intermittent
lines incorporating several vertical filter plates rigidly mounted next to one another and
whose interstices are acted upon by matter due to undergo filtration. These interstices are
rigidly mounted to two opposite sides and are capable of being locked at the top and
15 bottom with tube-like seals for the process of filtration. In addition, a double-sided
diaphragm is installed centrally between the filter plates and can be acted upon by a pressure
medium for re-pressing the filter cake formed during the process of filtration. Here,
however, due to the inadequate sealing of the filter media against the filter plates on the
closed sides of the interstices, solid matter seepage occurs as well as premature blinding of
20 the filter cloth due to single-sided washing.
The object of the invention presented here is not only to eliminate the above-
mentioned shortcomings revealed in the current state of the art, but also to create a
25 universal filtration system capable of being constructed and operated at low cost owing to
the simplicity of its design and thus having a favourable impact on industrial use for tasks
encountered in the sector of environmental protection. In addition, facilities were needed for
pressing out the possible formation of a compressible filter cake after filtration of the
suspension or liquid.
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Accordingly it appeared desirable to make provision for a filtration system which,
under working conditions, would facilitate ascent and descent of evenly spaced filter plates
while pressing the same against the cover plates. Another advantage-would be to cater for
higher dehydration of a compressible filter cake by means of an additional pressing process
5 making use of existing equipment so as to dispense with the necessity of employing costly
diaphragms used on con- entional-type filtration systems for compressing filter cakes.
It was further deemed necessary to make provision for filtration to proceed on
10 continuous lines, in which case replacement of filter cloths and/or separation of the filter
cake might be rendered possible during filtration without disturbing, slowing down or even
interrupting the filtration process. Here, it was regarded as being desirable to provide a
filtration system that would be easy to handle while enabling a whole variety of different
filtration processes to be perforrned without much conversion such as parallel- or series-
15 connected filtration methods.
This task is solved by the main claim. The subordinate claims concern preferreddesign versions.
The invention concems a filtration system for removing solid particles from liquids or
suspensions and is provided with a cover plate as well as filtration device located on the
underside of the cover plate, characterised in that the said filtration device comprises
25 flexible sealing elements and a filter plate, whereby the filter plate, which is aligned so as
to run essentially parallel to the cover plate, is capable of being moved perpendicularly
relative to the longitudinal axis of the cover plate, further that sealing elements are located
between the cover plate and filter plate to form a filtration chamber and a filter unit is
located between the sealin~ elements and the filter plate, further that a base plate is located
30 underneath the filter plate at a distance from the filter plate, further that one or more flexible
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lifting elements are located between the filter plate and base plate and are connected via as
pressure medium to a pressure-generating device.
The filter plate is essentially aligned so as to run parallel to the cover plate owing to
some slight deviations in its position likely to occur on account of the flexibility of the
sealing elements. The sealing elements are also capable of acting as spacers between the
filter plate and cover plate when the filter plate is pressed by the lifting elements against the
sealing elements, e.g. while the filtration operation is in progress. Minor differences may
occur in the formability or deforrnability of the sealing elements due to the nature of the
material from which they made which, however, have had no noticeable effect on restricting
the success of the invention.
There is also a likelihood of a slight difference occurring in the position of the filter
plate on account of varying deformability of the lifting elements due to the resilience of the
material, a circumstance which, however, does not deter from the outstanding success of
the invention, especially as facilities are provided for carrying out appropriate adjustments
to the position of the filter plate, e.g. by varying pressure using pressure-loadable sealing
elements.
For example, plerelled fiexible lifting elements may assume the form of moulded
cushions or air cushions usable as large- and/or small-area units. It is also possible to make
use of tubes to serve as flexible lifting elements.
A type of tube capable of being used may be designed in such a way for example that,
prior to pressure-loading, the circumference of the tube remains essentially unchanged in the
cross-sectional area in the relieved state as well as when pressure-loading takes place but
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that the shape of the tube cross-sectional area differs before and during pressure-loading.
For example, a fabric-reinforced tube usable as a lifting element re-eals a variable cross-
sectional shape in the relieved state but its circumference in the cross-sectional area remains
essentially unchanged.
A flexible lifting element may assume the form of a hollow body with resilient walls
rnadc of flexible material which increases in diameter in the cross-sectional area when
p e.i~ e is applied and which reduces its diameter in the absence of pressure due, for
10 inslance, to the inherent elasticity or internal stress of its material.
The flexible li~ing elements are mounted between the filter plate and base plate in
such a way that the flexible lifting elements - due to their deformability when acted upon by
15 pressure - reduce the distance between the cover plate and filter plate when under pressure
caused by the filter plate ascending perpendicularly to the longitudinal axis of the cover
plate in the direction of the cover plate, i.e. upwards. When pressure is released, the
diameter of the flexible lifting elements for example is reduced and the filter plate travels in
the direction of the base plate, i.e. downwards. On account of the arrangement of the
20 flexible lifting elements, the filter plate remains essentially aligned parallel to the longitudinal
axis of the cover plate during the ascending and descending motions.
It is observed as being an advantage when the diameter of the tubes undergoes change
25 when pressure-loaded and the tubes reveal an approximately identical shape in the cross-
sectional area when acted upon by a defined pressure. Owing to the use of tubes, whose
shape is capable of undergoing change when acted upon by pressure, the filtration system
on which the invention is based caters for even distribution of forces over the filter plate so
that ideal running up to the cover plate is rendered possible.
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In addition, it has been established that the use of flexible tubes enables the filter
plates to be pressed with adequate evenness in the direction of the cover plate after filtration
involving compressible filter cal;e, so much so that the filter cake is dehydrated to such an
extent that adequate drying or dehydration of the filter cake is rendered possible without the
5 necessity of employing additional costly diaphragms used on conventional-type filter
systems.
In oi:e ver,lon of the invention-related object, the tubes can be made to form a10 parallel, meander-shaped and/or circular arrangement. The preferable arrangement is to
have the tubes arranged so as to be approximately parallel with one another. Thearrangement of the tubes is dependent on the design of the filter plate, e.g. in the form of a
round filter or rectangular-shaped filter. It proves an advantage if the tubes are linked to one
another, for example using flexible connections, via a pressure medium. These flexible
1~ connections as well as the manifolds may assume same form, material and size as the tubes,
again warranting homogeneous action of the contact-pressure forces produced by the tubes
on the filter plate and by means of which the filter plate is pressed against the cover plate via
the sealing elements.
In another version of the invention-related filtration system the tubes can be acted
upon by the pressure-generating device via a pressure medium, preferably air, water and/or
liquids containing oil. The use of pressure media is dependent on the designated application
of the filtration system, although air or water (air in particular) will prove advisable, for
25 example as a means of minimi.cing corrosion on the pressure-generating device. Use can be
made of machines to serve as a pressure-generating device that convey the energy fed to it
from a drive unit to the gas and/or liquid, e.g. electric pumps and the like.
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The design of the filter plates used on the invention-related filtration system is such
that they provide free passage for the liquid, chiefly rendered possible by the filter plate
being porous. The pores on the upper side of the filter plate are interlinked by ducts, at least
to a partial extent, the liquid flowing through the ducting and/or via the pores located on the
5 underside of the filter plate into a filtrate drain. For example, in the course of filtration, the
liquid - having been freed from solid particles - passes through the filter unit via the pores
located on the upper side of the filter plate and, by means of ducts, to the pores located on
the underside. On the in;ention-related filtration system the filter plate can be, and is
preferably designed with pOI es, in which case a number of the pores are interconnected via
10 ducts, those ducts located on the outlet side being linked to a filtrate drain and those on the
inlet side being connected up to the filtration chamber.
It is an advantage to load the tubes - located on the underside of the filter plate - with
15 pressure in such a way that their diameter undergoes change, preferably as viewed from the
cross-sectional angle. However, deformability as regards length has no disturbing effect.
Filter material capable of being used can assume the form of belt-type fabric filters of
20 cloth or non-woven fabric as well as metal, natural, plastic- or glass-fibre, filtering paper, or
filter diaphragms, e.g. from cellulose derivates, ceramic or plastic material. At the opposite
ends of the filtration system or filtration device, roller elements can be fitted which, apart
from guiding the filter unit, can if need be serve to wind it on or unreel it. The filter unit is
guided on the filter plate of the invention-related filtration system in such a way that the
25 entire area of the filter plate acts as a support to the filter unit, thus precluding the formation
of dead zones which tend to restrict the filtration area on conventional systems.
Another advantage on the invention-related filtration system is that two or more30 filtration devices can be combined, in which case the base plate on one of the filtration
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devices is designed as a cover plate with another filtration device then located on, or
forming contact with the underside of that cover plate. A further advantage on the
invention-related filtration system is that the filtrate drains are provided with a common
outlet line, thus facilitating parallel connection of the filtration devices. On the other hand, it
5 is also possible to link the filtrate drain on one of the filtration devices to the inlet line of the
filtration chamber on another filtration device so as to facilitate series connection of the
filtration devices. Connecting the filter devices up in series enables a higher stage of
filtration to be carried out.
Resorting to parallel connection of the filtration devices provides the user with a
continuous process by operating one filtration device, while on another such device the filter
cake that has meanwhile accumulated can be separated laterally after shutting down the
filter plate and winding on or unreeling the filter medium.
Design Versions:
Design versions are described in the following description with reference made to the
drawings. The drawings are int~nllP~ to provide a simplified portrayal in enlarged diagram
form and thus lay no claim to being true to scale. They depict the following:
Fig. 1 Side view of the invention-related filtration system during the process of
filtration and with the tubes being acted upon by compressed air.
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- Fig. 2 Side view of the invention-related filtration system following completion
of the filtration process and after the tubes have been evacuated.
Fig. 3 Top view focusing on the filter plate fitted with the filter unit.
The invention-related filtration system comprises a cover plate 1. Located underneath
the cover plate 1 and parallel to it is a filter plate 2 (Fig. 1). Flexible sealing elements 3
10 made of conventional rubber-like material can also be designed as flexible tubes so as to
increase the lateral sealing efficiency on the filter chamber 4 of the invention-related
filtration system. For example, tubes 7 and the sealing elements 3 designed as tubes can be
linked to one another and acted upon simultaneously by air as a pressure medium.
Tubes 3 are arranged on the underside of the cover plate l in such a way that, when
tubes 7 are acted upon by pressure, tubes 3 and the filter plate 2 seal off against the filter
cloth 5. The cover plate 1 reveals feed lines capable of conveying the liquid due to be
20 filtrated to the filtration chamber 4. Located on the underside of the filter plate 2 are flexible
tubes 7, e.g. made of silicon and/or a rubber-like material and forming a parallel
arrangement to one another. Pressure-loading here is effected by means of compressed air.
Tube 7 can be a fabric-reinforced type made of standard commercial plastic or
material containing rubber and whose cross-sectional shape undergoes change when acted
upon by pressure, but whose cross-sectional circumference remains essenti~lly unchanged.
Use can also be made of tubing material not containing any fabric reinforcement made of
standard commercial plastic or material containing rubber and on which the cross-sectional
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circumference and cross-sectional shape both undergo change as pressure-loading of the
tube varies.
As a result of pressure-loading, the filter plate 2 is made to move in the direction of
the cover plate 1, thus sealing offthe sides of filtration chamber 4 via the sealing elements 3
so as to prevent escape of the liquid that is under pressure and due to undergo filtration.
It is important that the filter plate 2 can be made to proceed in essentially parallel
motion to the cover plate, perpendicularly to its lon~itu-lin~l axis so as to warrant adequate
sealing off of the filter chamber 4.
Located on the upper side of the filter plate 2 is a standard commercial filter cloth 5.
This filter cloth 5 is guided by roller elements 9 and wound or unwound on reels. The liquid
due to be filtered is conveyed via feed lines through the cover plate l into the filter chamber
4, is pressed through the filter cloth 5 and then proceeds via the filtrate drains to a collecting
basin After a suitable filter cake has formed, the filtrate still present inside the filtration
chamber 4 can be pressure-forced via the feed lines located in thecover plate 1 through the
filter cake and into the filter plate 2. The filter cake can be dehydrated even further by
blowing air into the filtration chamber 4. On a compressible filter cake, it is also possible to
apply a far higher pressure-load on tubes 7, thus reducing the distance between the cover
plate 1 and the filter plate 2 - by deforrning the sealing elements 3, or even by relieving
pressure on these sealing elements 3 - in such a way that pressing out of the filter cake can
be carried out. The ducts of the filter plate 2 opening out via pores on the underside of the
filter plate 2 lead to the filtrate drain or drains.
Tubes 7 are linked at one end by a manifold 12 (Fig. 3) which is connected up to a
pump. The other end oftubes 7 are hermetically sealed offby means of dummy plugs 14.
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To effect disposal of the filter cake that has accumulated on the filter cloth 5, tubes 7
can be evacuated by pumping the pressure medium out of tubes 7. By opening a valve on
the manifold 12 It is also possible to allow the pressure medium to escape from tubes 7
5 under inherent stress and the wei;,ht load of the filter plate 2 (Fig. 2).
A~er the filter plate 2 has been lowered, the filter cloth 5 can be made to travel
sideways by means of roller elements 9 so as to remove the filter cake. In this case it is
possible for the filter cloth 5 to be run back following separation of the filter cake or for it
0 to remain on the roller elements 9. When running back the filter cloth 5, it can be cleaned by
means of a pressure medium forced through a jet-nozzle unit mounted between the roller
elements 9. While pressure is exerted on tubes 7, the filter plate 2 runs on guide rails
arranged at the side of the filter plate 2, proceeding upwards in the direction of the cover
plate 1 so that the longitudinal plane of the filter plate 2 is brought into parallel alignment
15 with the longitudinal axis 11 of the cover plate 1 chiefly as a result of the evenly applied
force coming from tubes 7, apart from revealing consistent spacing.
Besides it is possible, though not necessary or compulsory, for the sealing elements 3
20 to be linked to the same pressure-generating device used to load pressure on tubes 7.
Conversely, it is also possible for the sealing elements 3 to be coupled separately to a
pressure-generating device.
Control equipment used to control the pressure-generating devices, the pumps used
for supplying the filtration chamber 4 with filtration solution, etc. are not described in
further detail here as these are conventional devices sufficiently familiar to the expert.
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The fact that the invention-related filtration system can also be operated in such a way
that the liquid due to be fed to it can be handled under pressure by the filter unit 5 or by
applying vacuum on the outlet side of the filter plate 2 is regarded as an advantagJe.
The invention-related filtration system unites the optimum filtration properties of a
laboratory-scale pressure suction filter with industrial requirements. The pressure-loaded
lub- ;ystem for lifting and lowering the filter plate applying virtually ideal distribution of
fo-~ . ~ombines with the mobility of the filter medium for discharging the solid particles and
10 subs;~quent cleaning of the filter cloth within a very short period of time so as to warrant
extremely low downtime and thus a high degree of ser~/ice time. The simplicity of the
invention-related filtration system, e g. by the use of easily replaceable tubes for the filter-
plate lifting system as well as easily exchangeable filter cloths for each filtration device cater
for extremely high system availability.
By coupling up additional filtration devices, the filtration system is easily adapted to
individual requirements where increase in capacity is called for. A computer control
function incorporated in the filtration system facilitates optimum adaptation of the individual
JO cycles to given operating requirements. For the expert, these are factors serving to eliminate
the familiar disadvantages associated with the current state of the art, while providing an
ideal combination of the advantages brought about by the invention-related filtration system.
