AU656169B2 - Method and device for separating liquid/solid mixtures - Google Patents

Description

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pages 1/3-3/3, drawings, renumbered as pages 1/5-3/5; pages 792 PC 4/5 and 5/5 added INTERNATIONALE ANMELDUNG VEROFFENTLICHT NACH DEM VERTRAG OBER DIE INTERNATIONALE ZUSAMMENARBEIT AUF DEM GEBIET DES PATENTWESENS (PCT) (51) Internationale Patentklassifikation 5 (11) Internationale Veroffentlichungsnummer: WO 92/13624 BO1D 25/12, 25/30, 25/38 Al (43) Internationales Veroffentlichungsdatum: 20. August 1992 (20.08.92) (21) Internationales Aktenzeichen: PCT/AT92/00010 (81) Bestimmungsstaaten: AT, AT (europdisches Patent), AU, BB, BE (europiisches Patent), BF (OAPI Patent), BG, (22) Internationales Anmeldedatum: 29. Januar 1992 (29.01.92) BJ (OAPI Patent), BR, CA, CF (OAPI Patent), CG (OAPI Patent), CH, CH (europiisches Patent), CI (OA- PI Patent), CM (OAPI Patent), CS, DE, DE (Ge- Priorititsdaten: brauchsmuster), DE (europaisches Patent), DK, DK (eu- A 225/91 1. Februar 1991 (01.02.91) AT ropdisches Patent), ES, ES (europiisches Patent), FI, FR (europlisches Patent), GA (OAPI Patent), GB, GB (europiisches Patent), GN (OAPI Patent), GR (europii- (71)(72) Anmelder und Erfinder: GUGGEMOS, Horst [AT/ sches Patent), HU, IT (europiisches Patent), JP, KP, AT]; Sonnleitenweg 33, A-8043 Graz HASLAU- KR, LK, LU, LU (europhisches Patent), MC (europii- ER, Edwin [AT/AT]; Annaweg 2, A-8020 Graz sches Patent), MG, ML (OAPI Patent), MR (OAPI Pa- HASLAUER, Robert [AT/AT]; Thal 659, A-8051 Graz tent), MW, NL, NL (europaisches Patent), NO, PL, RO, RU, SD, SE, SE (europdisches Patent), SN (OAPI Patent), TD (OAPI Patent), TG (OAPI Patent), US.

(74) Anwilte: BRAUNEISS, Leo usw.; Landstrager Hauptstrae 50, A-1030 Wien Ieuinr.. h Veriffentlicht Mit intern lem e e e AUSTRALIAN

INDUSTRIAL

-6 AUG 1993 (54)Title: METHOD AND DEVICE FOR SEPARATING LIQUID/SOLID MIXTURES (54)Bezeichnung: VERFAHREN UND EINRICHTUNG ZUR TRENNUNG VON FLiSSIGKEIT-FESTSTOFF-GEMI-

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(57) Abstract The invention concerns a method and device for separating mixtures of liquid and solid materials by squeezing out or filtering off the liquid compo- i nent. The mixture is divided into a multiplicity of adjacent or consecutive portions which are simultaneously and jointly compressed or reduced in size by the action of an external compressive force which is substantially the same for all portions and which acts in the direction in which the portions are disposed next to each other, and is propagated through all the portions. The solids in the portions are retained as filter cake, while the liquid is squeezed out as filtrate. The invention calls for the filtrate squeezed out of the portions, or out of the filter cake formed in the portions/filter cakes, to be removed through the end faces of the portions as well as through at least the bottom and, if possible, also the top surfaces, and preferably also through the sides, and advantageously through the entire top surface of the portions or filter cakes, i.e. through the end and peripheral surfaces of the portions/filter cakes.

(57) Zusammenfassung Die Erfindung betrifft ein Verfahren sowie eine Einrichtung zur Trennung von vermengten flilssigen und festen Medien durch Auspressen bzw. Ausfiltern des fliissigen Anteils, wobei das aufzutrennende Gemisch in eine Vielzahl von nebeneinanderliegenden bzw. aufeinanderfolgend angeordneten Teilvolumina aufgeteilt wird, die gleichzeitig und gemeinsam durch Ausibung eines im wesentlichen filr alle Teilvolumina gleichen, auf die Teilvolumina von augen aufgebrachten, in der Richtung, in der die Teilvolumina nebeneinander angeordnet sind, ausgefibten und sich durch alle Teilvolumina fortsetzenden Preedruckes eingeengt bzw. verringert werden, wobei die Feststoffe in den Teilvolumina als Filterkuchen zuriickgehalten und das fliissige Medium als Filtrat ausgepret wird. Erfindun-sgemlig ist vorgesehen, dag das Filtrat aus den Teilvolumina bzw. den sich in den Teilvolumina bildenden Filterkuchen iber ihre bzw. die jeweiligen Stirnflichen und auch fiber zunmindest die untere und gegebenenfalls auch die oberen Umfangsflichen, vorzugsweise auch ilber die seitlichen Umfangsfldchen, vorteilhafterweise somit Oiber die gesamte Oberflliche der Teilvolumina bzw. Filterkuchens, d.h. fiber die Stirn- und Umfangsflichen abgeffihrt bzw. ausgepreft wird.

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Method and Device for Separating Liquid-Solid Mixtures The invention relates to a method according to the preamble to Patent Claim 1. In addition, the invention relates to a separating device for implementing this method according to the preamble to Patent Claim 13.

A method and a device of this type, in which dewatering is carried out exlusively through the filter plates forming the boundaries of the press compartments are known from EP-A-318 732. Such presses or separating devices differ in principle from those separating devices in which the mixture to be separated is forced under pressure through filters or filter plates; such filter plates may also form the boundaries of press compartments, but these compartments do not change their volume as the mixture is pressed through the filter plates.

Furthermore, a number of methods of separating liquid-solid mixtures are known which may also comprise conditioning processes, e.g. polymer conditioning by adding organic flocculation agents, thermal conditioning, or chemical conditioning (addition of lime and iron chloride).

Depending on the type of conditioning used, the various mixtures or slurries which are to be dewatered vary in sensitivity with regard to the destruction of their flocculate structure as further treatment is applied, and in such mixtures the dewatering characteristics depend to a large degree on the thickness of the filter cake.

Chemical conditioning, i.e. adding lime and iron chloride, permits filter cake thicknesses of up to 40 mm to be achieved, if the squeezing is carried utLIAas ut using a filter on both sides of the filter cake and, for example in the case kO

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rE i; a~ L-,r- 4 -3of municipal sludges, it yields dry matter contents of max. 40 to 45%; this type of conditioning is used mainly in the case of chamber filter presses.

However, one disadvantage is that the volume of the filter cake increases by about 30% when lime is added, as a result of which the actual dry matter content of the solids to be filtered out is considerably reduced.

In the case of sludges containing fibres, e.g. from the waste water treatment systems of pulp and paper plants, or other easily dewatered industrial sludges, the restrictions mentioned above do not apply. In particular, sludges from pulp and paper plants can easily be dewatered to more than 60% dry matter using polymer conditioning in membrane cylinder presses. However, squeezing the water from these fibre-containing sludges cannot be compared with squeezing the water from the sludges which are to be dewatered in an improved manner according to the invention, because in the latter case special structural and procedur il steps must be taken since 1 5 the liquid is initially fairly easy to squeeze out, but as pressing continues so the liquid becomes extremely hard to expel.

-lt is the-objet -The present invention to create a method and separating device by means of which even sludges that are difficult to dewater, such as municipal sludges and/or sludges from waste water treatment plants, can to a large extent be separated into a liquid fraction j and a solids fraction having dry matter contents of at least 40%, and in particular 50% and more, even if these sludges have been aerobically stabilized. Using the traditional methods, aerobically stabilized sludges are extremely difficult to dewater down to dry matter contents of more than Thus, it is the purpose of the invention to design a method of the kind I 1 1 -4mentioned at the beginning, such that liquid-solid mixtures which are easily squeezed to remove the water as well as mixtures, sludges, slurries, etc. which are extremely difficult to separate, can be optimally squeezed to yield the highest possible dry matter contents.

In accordance with a first aspect of the present invention there is provided a method for separating mixtures of liquid and solid media or for separating or dewatering liquid-solid mixtures, sludges, slurres, municipal effluents, municipal sludges, or similar, comprising squeezing or filtering out the liquid component, wherein the mixture to be separated, which may have been conditioned by polymers or the application of heat, is divided up into a large number of preferably equal-sized, discrete portions arranged adjacently or consecutively in sequence, and these portions are simultaneously and jointly compressed or reduced in size by the application of pressure, which is substantially the same for all the portions and acts throughout all the portions, said pressure being applied from the outside oin the direction in which the individual portions are consecutively arranged, and wherein o: 15 also the solids are retained as filter cake in the individual portions while the liquid medium is squeezed out as filtrate, characterised in that filter plates are almost in a seal free contact with all sides to the boundary surface of a tank or housing or press chamber and :3 the filtrate from the discrete portions of mixture or from the filter cakes formed. in the discrete portions of mixture is drained away or squeezed out through the front and rear 20 surfaces of the discrete portions or of the filter cakes and also through the lower and possibly also the upper and/or the lateral peripheral surface(s), advantageously therefore through the entire surface area of the discrete portion or of the filter cakes, i.e. through •the front and rear surfaces and all peripheral surfaces.

:00 In accordance with a second aspect of the present invention there is provided a filter press for separating mixtures of liquid and soEd media or for separating or dewatering liquidsolid mixtures, sludges, slurries, municipal effluents or municipal sludges, or simnilar, comprising a large number of separate compartments in which the liquid fraction is squeezed or filtered out adjacently or consecutively, and bounded by a large number of at least ten, preferably at least twenty, filter plates, preferably bearing filter layers on their

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-4asurfaces and arranged substantially parallel to each other, through which filtrate is drained away, and the linear extent of these filter plates in the direction of squeezing can be reduced by the application of pressure, and at least one drive unit is provided to generate the pressure and in particular to implement the method according to the first aspect hereinbefore stated of the present invention, characterised in that the filter plates are enclosed at least in their lower and in particular also in their lateral and/or upper sections, without seals, by an elongated tank, and the plates are slidingly arranged in the longitudinal direction of the tank, and the lateral peripheral surface of the separate compartments is left open at the bottom and possibly also at the top and/or laterally to permit the filtrate to emerge, and the filtrate from the press compartments and from the filter plates can be drained away through at least one wall surface, designed as a filter wall surface, of the tank.

i",..The invention is based on the following concept: A press chamber, bounded on all sides by a closed tank, is subdivided into a large number of non-watertight compartments which are open at least at the bottom, possibly also laterally and at the top; the subdividing is accomplished by providing lamellar filter plates, preferably suspended and arranged parallel to one another at a given maximum spacing, to define the boundaries of the individual compartments; the chamber itself is preferably gravity charged from above via a charging container or feed hopper with conditioned, preferably pre-dewatered sludge, or the sludge is forced into the chamber with the assistance of a suitable charging device, e.g. a piston having a large head area.

C Once the press chamber, which is subdivided by filter plates into a large number of subchambers or compartments, has been filled, the charging container is sealed off from the compartments by a sliding plate. The surface dimensions of the lamellar filters correspond substantially to those of the press chamber or tank, or to the clearance width of the

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,i N chamber or tank when the sliding plate is closed, so that when squeezing is carried out, i.e. when the lamellar filters are displaced along the longitudinal axis of the press chamber, thereby reducing the size of the individual compartments, the edges of the lamellar filters almost touch or come as close as possible on all sides to the boundary surfaces of the tank or housing or press chamber; no seal is provided between the peripheral surfaces or edges of the lamellar filters and the interior of the housing; the contact between the lamellar filters and the wall of the tank or the sliding plate is accomplished without seals.

The squeezing process itself is carried out by reducing the size of the press chamber in the longitudinal direction, i.e. in the direction perpendicular to the surface of the filter plates, and as a result the mixture filling the spaces between the lamellar filter plates is squeezed. However, because the distance between the filter plates is from the start not very large, namely about 10 to 50 mm, and therefore the portion of mixture between the plates is not very thick, also because of the loss of liquid, the angle of internal friction of the filter cake increases relatively rapidly so that mixture, i.e. liquid and solids together, is forced out around the edges of the lamellar filters only in the initial phase of the squeezing process while the pressure applied is still low.

However, steps are taken to ensure that any solids flowing out together with filtrate during the initial squeezing phase are caught by a filter arranged below the filter plates so that at most only the liquid can pass through the filter while the solids are retained, or the escaping mixture can be recycled back into the process. This filter represents the lower boundary it

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i i sF- of the press chamber and is arranged at a distance from the bottom of a sump in which the liquid passing through the filter is collected.

Once a certain degree of dewatering has been attained,.or after the first squeezing step has been performed, the solids can be flushed from the 5 sump or from the filter, or further filtrate emerging from the filter plates and the filter cake during the subsequent stage of the pressing can drip into the possibly tilted sump and drain away. Once the point is reached at which no more solids can escape because of the increased angle of internal friction, the sump is cleaned by washing it out using a flushing device, but until the second squeezing step is over it remains in the tilted position and drains away any filtrate dripping from the press.

Once the pressing is over, the sump can be tilted laterally or it may be moved away to the side or in the longitudinal direction so that the space below the lamellar filters is completely clear. Subsequently, the lamellar filters are moved back to their original position, this movement and their position being determined or restricted by a limiting device, e.g. chain links or similar, attached to the individual lamellar filters. A scraper device, or compressed air lances or similar which can be introduced into the press compartments, can be provided to detach the filter cakes adhering to the filter surfaces.

Advantageously it is ensured that the pressure exerted during the volume reduction phase in a first squeezing step is held substantially constant and is then increased to a final value in a subsequent squeezing step which brings about a further reduction in volume. It is advantageous if the method is applied in accordance with the features described in Patent 1 -7- Claims 9 and 10. In this way a relatively large reduction in volume can be achieved during the first squeezing step, so that a drive unit with a correspondingly large stroke should be provided for the press device, although it does not have to exert especially high forces. The linear volume reduction or the end pressure aimed for in the second squeezing step may alternatively also be attained in one single step in which the pressure is preferrably steadily increased. It may be advantageous if the drive unit or the press device is of two-stage or multi-stage co.istruction because the pressure in the second squeezing step or towards the end of the squeezing process increases substantially and thus much higher press forces are needed, although the press travel is shorter.

Further advantageous embodiments of the invention are contained in the following description, the drawings and the patent claims.

In the following, the invention is described on the basis of the drawing. Fig. 1 shows a purely diagrammatic view of a separating device according to the invention. Fig. 2 is a diagrammatic view of one embodiment of a separating device according to the invention. Figs. 3 and 4 show the device in various operating positions. Fig. 5 depicts diagrammatically the emptying of the device. Figs. 6 and 6a are detailed views of filter plates. Fig. 7 shows the interconnections between the filter plates and the detachment of the filter cake. Figs. 8 and 8a are cross sections through some filter plates. Fig. 9 is a diagrammatic view of a stripping device for removing filter cake from filter plates and it also shows a connecting element between the filter plates.

P Lia !b i Li' I ~I -I Fig. 1 shows in diagrammaI;c form an embodiment of a separating device according to the invention. This device comprises an elongated housing or tank B formed by sheet metal walls, having front, .rear,ant side walls 51 indicated by dashed lines in the Figure; the tank 8 is closed off at the bottom by a tiltable sump 11; the upper covering of the housing may be formed by a sliding plate 18. In addition, an end plate 4 as well as a pressure plate 2 are arranged on or in the tank 8 or are an integral part of it; also, outside or inside the housing run longitudinal struts or guide supports 1, which may form an integral part with the front and rear walls, and in order to apply the pressure these struts are attached at one end of the tank 8 to the end plate 4 and at the other end to abutment 5, against which a press unit 6 is braced. The press unit 6 arranged between the abutment and the pressure plate 2 applies pressure to pressure plate 2, moving it in the direction of end plate 4. The press chamber 30 situated between the end plate 4 and the pressure plate 2 is subdivided into a large rumber of separate compartments 22 located between filter plates 3, and these compartments or fractional volumes 22 which make up the press chamber are reduced in size as the pressing is carried out. At the top and/or to the side of the housing 8 a charging container 7 and/or a number of charging ducts 7 (Fig..6, 12) open into the press chamber 30 or they can be closed off from the press chamber 30 by means of a sliding plate 18 or other shut-off devices. As a rule, the press chamber 30 is shut off after it has been filled, but this need not be the case.

The sump 11 is tightly attached to the tank walls by means of -25 possibly inflatable seals 41. The sump 11 contains a substantially Z

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-9horizontally oriented filter 25 which is positioned dirPtly against the undersides of the filter plates 3 or at a distance from them; in addition, the sump 11 possesses an outlet 26' for filtrate 16 as well as an outlet 24 for liquid-solid mixtures which escape from the press compartments 22 when the squeezing is carried out and which can be flushed away by a flushing device 27 mounted on the sump and/or on the housing (Fig. 3).

Since the press may be very long and since it also has a very long travel when in operation it is possible, as shown in Fig. 2, to subdivide the press unit into two press or drive units 6 and 6' respectively. For example, a kind of spindle press 6' can be provided which is fitted with a pressure plate which is adjustable by the spindle press 6' with regard to the pressure plate 5. Once the squeezing process has been initiated by displacing pressure plate while hydraulic press 6 remains in its starting position, and the first stage of the pressing is completed, pressure plate 5' is locked in place at one of a number of given end positions 39 and the hydraulic press 6 is brought into action with pressure plate 5' acting as the abutment.

The subsequent second squeezing step requires higher forces because the dewatering now takes place at elevated pressure.

It should be noted that the housing or tank 8 or the filter 25 in the sump 11 or the sliding plate 18 fit close to the edges of the filter plates, but no seals are used. This is advantageous because it means that the housing or the tank 8 do not have to be pressure-resistant and they need only withstand the filling pressure or the pressure of the first squeezing step. If, as the pressure is increased, not only filtrate but also mixture escapes, this can be caught on or by the filter plate 25 arranged in the sump 11, so that

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a large build-up of pressure in the press chamber 30, which would stress the walls of the housing 8, is avoided. When high pressures are applied in the second squeezing step, a seal is no longer needed because, as a result of the ino. ease in the angle of friction in the filter cake, no more solids but only filtrate liquid escapes and is either carried away by the filter 25 or it drips into the tilted sump 11. The high pressure is absorbed by the abutments 5 or the longitudinal struts 1 and the end plate 4. It is, of course, also possible to build the housing or the tank out of steel-reinforced concrete so that it will withstand the pressures. The housing 8 and/or the sump 11 can in addition also be equipped at suitable points, especially laterally, with filters whic..:, like filter 25, permit filtrate to emerge. Fig. 3 shows the separating device according to the inventiorn starting its first operating step, in the course of which, with the sump 11 closed or slightly inclined, solid-liquid mixture emerging from the press can be flushed by means of a flushing device 27 into a line 51 which may recirculate the 7 mixture back into the charging container 7 to permit it to go through the squeezing process once more. It can be seen that the filter plates 3 are brought close together to each other by the action of the hydraulic press 6; in the course of a second squeezing step conducted at elevated pressure, the plates are brought even closer together until a desired end position is reached as indicated in Fig. 4.

If the separating device is to function properly, it is important that the press chamber 30 be subdivided into a large number of separate compartnments 22 which are laterally bounded in the direction of pressing by filter plates 3, which in their starting and ending positions are I i i j S 11substantially parallel to and at a given spacing from one another; the individual press compartments are however open on all sides. Since the predetermined spacing between the plates is small, a friction value is soon attained in the filter cake at which the escape of solids is prevented so that finally, in the second squeezing step, an extremely high degree of dewatering and a high content of dry matter is achieved by raising the pressure but without any solids emerging.

Fig. 5 shows the end position of the separating device according to the invention. In this position the filter plates 3 have been returned to their starting position in order to remove the filter cake 19, possibly using scraper blades 15 moving vertically over the surfaces of the filter plates 3 to detach and discharge the filter cake.

As shown in Figs. 6, 6a and 8, the scraper blades 15 are fitted with frame attachments 46 which engage around the vertical side edges of tht filter plates 3 so that the scraper blades 15, which are oriented horizonrSly on both sides of the filter plates 3, can be moved over the filter plate surfaces 31 in the direction indicted by the arrow 50. In their lower end section, the frame attachments 46 are provided with recesses or eyes 18 .through which are inserted rods 17 running longitudinally on both sides of the separating device (Fig. 5) and these rods can be moved up and down by means of actuating devices 20. This up and down motion takes place when sump 11 is removed from the housing 8; when the sump 11 is in place, the eyes 13 and the rods 17 fit into recesses 24 between the sump 11 and the filter 25. It should further be noted that the recesses 24 serve to catch the mixture which sprays out during the first squeezing step and return it via

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bii 4 -12recirculation line 51 to the charging container 7. The space 26 below the filter 25 leads to an outlet 26' through which the filtrate is removed or sent on to a treatment plant for further processing.

The filter plates 3 are slidingly arranged in the longitudinal direction of the separating device; the guides may be formed, for example, by the upper surface 52of the the longitudinal strut 1, on which rest projections 38 of the filter plates 3. In the same way, however, recesesses or guides 37 could be formed in the housing 8 in which the projections 38 of the filter plates 3 are slidingly mounted.

In order to move the filter plates 3 back into a defined starting position after each squeezing cycle, adjacent filter plates 3 are connected, as shown in Fig. 7 or 9, by at least one connecting device, for which purpose at least one pin 36 is mounted on both sides of each filter plate 3 and the pins 36 of adjacent filter plates 3 are encircled by an annular element 35. The last connecting device 35 connects the filter plate 3 to the end plate 4 or to the pressure plate 2 so that the filter plates 3 can be precisely returned to their starting positions. These connecting elements 36 do not in any way impede the movement of the filter plates towards each other but they do prevent the plates from moving more than a given maximum distance apart, i.e. they guarantee a constant width of the -individual press compartments.

It is obvious that instead of the pins 36 and annular elements depicted, other devices such as chains or cables 48 running along the separating device may be used to which the filter plates 3 may be attached

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i! ULIUiIS U mixture is arainec away or squeezed out through the 1 front and rear surfaces of the discrete portions or of the filter cakes and also through the lower and possibly also the upper and/or the lateral peripheral surface(s), advantageously therefore through the entire surface area of the discrete portion or of the filter cakes, i.e. i through the front and rear surfaces and all peripheral surfaces.

-13at certain intervals by means of clamp bolts 49 or similar. The ends of the cables are connected to the end plate 4 or the pressure plate 2 (Fig. 9).

As shown in Fig. 13, the filter plates 3 may comprise two plates provided with holes 41 and an intermediate plate 45 provided with vertically oriented longitudinal slits 40, and the holes 41 of the perforated plates 14 open into the longitudinal slits 40 of the central plate 45. At least one filter layer 13 is fitted to the plates 14. When a pressure is applied, the fluid is pressed through the filter layer 13 and the holes 41 into the vertically oriented slits 40 and then emerges in the lower section of the filter plates through exit holes or the lower, open longitudinal slits Fig. 8a shows an alternative design for a filter plate 3. This filter plate 3 possesses vertical ducts 33 preferably arranged offset to each other on both sides of the plate, and the surfaces of the filter plates 3 are covered with filter layers 13. In this way, it is possible to conduct the expressed liquid through the vertical ducts 33 to the bottom of the plate and to collect it in the sump 11.

In another possible design for the filter plate 3 layers of meta! filter mesh could be placed one on top of the other and securely joined with each other to give a stiff filter lamella. The mesh widths of the metal filters would become progressively finer in the outer layers so that only the filtrate can penetrate into the lamella and flow to the bottom in the coarse metal mesh.

Whatever the case, the edges of the filter plate or the filter plate itself are always spaced apart from each other during the squeezing process and they are open at least at one peripheral surface and preferably over their 25 entire peripheral surface.

(I :i -i 1 bzw. verringert werden, wobei die Feststoffe in den Teilvolumina als Filterkuchen zuriickgehalten und das flissige Medium als Filtrat ausgepreSt wird. Erfindun-sgemal ist vorgesehen, dai das Filtrat aus den Teilvolumina bzw. den sich in den Teilvolumina bildenden Filterkuchen fiber ihre bzw. die jeweiligen Stirnflichen und auch fiber zumindest die untere und gegebenenfalls auch die oberen Umfangsflichen, vorzugsweise auch iber die seitlichen Umfangsflichen, vorteilhafterweise somit fiber die gesamte Oberflache der Teilvolumina bzw. Filterkuchens, d.h. fiber die Stirn- und Umfangsflichen abgefiihrt bzw. ausgepreat wird.

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~i L C- I ~C -I i 1 l~il i I \.2-1 r -14- One alternative means of separating the filter cake 19 from the filter surfaces 31 may be to introduce an air-jet lance 21 into the upper area of the respective press compartment 22 between two filter plates 3, once they have been moved back into their starting position; the nozzles 32 of this lance are arranged adjacent to the surfaces 31 of the filter plates 3 and they loosen the filter cake 19 with a jet of air, causing the cake to fall out at the bottom.

A piston 9 may be arranged in the charging container 7 to provide forced charging of the press chamber 30 and thus a certain amount of preliminary dewatering of the mixture while the filter plates 3 are stationary in their starting positions. In order alternately to supply new material and also to exert this pressure, the piston 9 has a non-return valve which prevents mixture charged into the press chamber 30 from moving back upwards.

The filter material 13 applied to the filter plates 3 may be a woven plastic or metal fabric; the filter plates 3 may be made of plastic, cast metal or profiled sheet steel. The embodiment illustrated in Fig. 8a is advantageously made of plastic plates which are provided by appropriate processing methods with the longitudinal ducts 33.

The filter plates 3 may in principle possess any type of profiled or perforated surface; all that is necessary is that the filtrate passing through the filter material 13 can flow away between the filter material 13 and the filter plate 3 or in the filter plate 3. The drainage ducts may also be arranged on a slant or horizontally.

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cake thicknesses of up to 40 mm to be achieved, if the squeezing is carried Ut using a filter on both sides of the filter cake and, for example in the case 4 J ;4 i ii-i m ii tiB iia2 .nar,,, a~; i-i -4 The filter cake 19 emerging or ejected from the separating device may be taken away by a transporting device or it falls into an appropriate container in which it is then taken away.

One major advantage of the separating device according to the invention is that a certain amount of dewatering takes place even before the first squeezing step is executed, because the liquid can pass to a certain extent through the filter 25 and/or lateral filter walls, and this preliminary dewatering effect can be reinforced by the pressure of the piston 9 during its downward travel, so that a mixture which has already to some extent been pre-dewatered then undergoes the squeezing process.

Separating devices according to the invention may be several metres long; their cross sectional dimensions are, for example, 100 x 100 cm.

Advantageously, steps are taken to ensure that the pressure exerted during the first squeezing step is adjusted to a value of 0.5 to 6 bar, preferably 1 to 5 bar, and in particular 2 to 4 bar, and the final value of the pressure in the second squeezing step is adjusted to at least 10 bar and in particular to to 50 bar or higher. The pressure applied during the first squeezing step is held substantially constant; this is possible because along the relatively long path through which the press travels, the high liquid content of the mixture being processed, the large areas through which the filtrate can emerge, and the narrow width of the press compartments, all mean that instead of increasing the pressure tends to remain constant despite the fact that the individual press compartments are compressed. In particular, by forming only thin filter cakes, clogging by the cake is avoided, or the j fi i

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Thus, it is the purpose of the invention to design a method of the kind i

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I.iv, i 4 -16efficiency of the separating process is guaranteed because of the large number of cakes to be pressed.

As soon as the pressure increases, the second squeezing step commences, and in this second step the pressure increases either linearly, in stages, or more steeply than linearly until the predetermined end value is attained and can be held for a certain period of time. At the start of the second squeezing step no more solids-containing mixture emerges from the individual compartments of the press chamber; instead, despite the increasing pressure only substantially pure filtrate liquid now emerges. For this reason, the sump 11 is also rinsed just before the start of the second squeezing step, i.e. any mixture which has escaped is removed by the recirculation line 51 so that the pure filtrate 16 can be appropriately discharged. In this way the mixture is very cleanly separated.

The number of filter plates 3 provided may be 160 to 200 in a separating device which is, for example, 8 m long, depending on the maximum spacing selected between the filter plates 3 in their starting position. A major advantage of the press is that only low pressures need to be applied in the course of the first squeezing step, but the pressure has to be applied over a long distance; such drive devices are relatively simple to produce; high-pressure devices which only have to operate over short distances in the second step of the squeezing operation are complex and costly.

411 In the case of mixtures produced by the pulp and paper industry, their behaviour in the press permits the separation to be carried out in just one f step.

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ii c- -17- The number of guides provided for or on the filter plates 3 is arbitrary; advantageously the guides are arranged on the lateral vertical surfaces or edges of the filter plates 3.

It is advantageous if one or more charging containers for the mixture discharge into the housing 8, said container(s) being preferably arranged over the entire length of the press chamber 30 and possibly extending over its width, and being located in particular above the press compartments 22.

It is advantageous when the charging container(s) 7 for the mixture extend(s) over the entire length of the press chamber so that all the press compartments 22 can be simultaneously and rapidly filled. As Figs. 6 and 12 show, several mixture supply ducts 7, which may be closed off by sliding plates, extend along the tank 8. In order to ensure continuous processing of the mixture, several separating devices according to the invention can be set up so that the charging, dewatering and emptying can occur in a rhythmical sequence and continuously accumulating mixture can be quasi-continuously disposed of.

Since the pressure acts on the filter plates 3, or through them on the contents of the press compartments 22, only between the end plate 4 and

I

the pressure plate 2, and since the mixture can escape almost without any pressure building up, the walls of the housing are not stressed and can be used as guides for the filter plates 3 etc. Only the end plate 4, the abutment 2 and the longitudinal strut 1, which connects the end plate 4 with the abutment 5 for the press unit 6 are subjected to any stress. P The mixture in the press chamber 30 may contain about 7 to 15% dry matter and the dry matter content of the mixture to be charged may be y t -18increased as long as the mixture remains flowable and can be filled into the separating device.

Figs. 10 and 10a depict a variant of the separating device according to the invention. In these Figs. the tank 8 takes the form of a concrete tank, especially a steel-reinforced concrete tank, which may be open at the bottom or may be provided with tiltable or pivotable or laterally sliding filters 67. The surrounding concrete walls, i.e. the concrete tank 8, provide the abutment for the press devices 6 arranged at either end of the tank and applying pressure to a number of filter plates 3 via appropriate pressure plates 2. A middle plate 64, against which the filter plates 3 are pressed, is firmly anchored in the middle of the filter plates 3 in the tank 8. In this way the pressure distribution in the individual compartments is evened out. At their sides, the compartments are bordered by side walls 66 which may contain filter sections or may be formed by filter walls so that filtrate can emerge easily at the side without the need for seals.

The side walls 66 may be forced laterally by hydraulic cylinders against the filter plates 3 and they may be removed for the second stage of pressure application or to remove the filter cake. The filter plates 3 may also be covered or closed off at the top by means of a sliding plate 68. It is also possible to arrange a lowerable filter 25 in a lowerable sump in the bottom zone of the concrete tank 8, and hydraulic devices may be provided to carry out the lowering function; it would also be possible to move the bottom part of the the separating device away to the side.

Fig. 11 shows a mobile device for removing the filter cake from the press compartments. This mobile device can be travellingly arranged on rails I-1- r- r- be recycled back into the process. This filter represents the lower boundary

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II

-19- 69 above the press chamber, and it comprises a number of scraper blades which can be lowered either manually or by a motor-powered or electric drive unit 70 into the press compartments, as shown in Fig. 11 a. The scrapers 15 consist of a push rod 71 which is movable up and down by means of a drive pinion 72, and it carries a crosspiece 73 at both ends of which as shown in Fig. 11 b scraper blades 62 are arranged on springloaded legs 63. As Fig. 11 b shows, a guide 74 which is inserted into the press compartments and pivots around a pivoting point 75 is arranged laterally in the area of the mobile system 61; this guide is inserted with its tapered end 76 into the press compartments or into the upper parts thereof, as shown successively in Fig. 1 lb. As soon as the guide 74 has achieved a firm fit, the blades 62 of the scrapers are lowered along the inner surfaces of the guide 74 and scrape the filter cake 19 from the filter surfaces of the filter plates 3.

Fig. 12 shows a cross section through a tank 8, the upper part of which possesses an inlet duct 7 which extends over a number of separate press compartments in the longitudinal direction of the tank 8 and the duct can be shut off by means of sliding plate 18.

It should also be noted that the tank can be made of any suitable material, e.g. also plastic.

J

Claims (5)

1. A method for separating mixtures of liquid and solid media or for separating or dewatering liquid-solid mixtures, sludges, slurries, municipal effluents, municipal sludges, or similar, comprising squeezing or filtering out the liquid component, wherein the mixture to be separated, which may have been conditioned by polymers or the application of heat, is divided up into a large number of preferably equal-sized, discrete portions arranged adjacently or consecutively in sequence, and these portions are simultaneously and jointly compressed or reduced in sized by the application of pressure, which is substantially the same for all the portions and acts throughout all the portions, said pressure being applied from the outside in the direction in which the individual portions are consecutively arranged, and wherein also the solids are retained as filter cake in the individual portions while the liquid medium is squeezed out as filtrate, characterised in that filter plates are .0 almost in a seal free contact with all sides to the boundary surface of a tank or housing or press chamber and the fltrate from the discrete portions of mixture or from the filter cakes formed in the discrete portions of mixture is drained away or squeezed out through the front and rear surfaces ofthe discrete po oo r ofthe filter cakes and also through the lower and possibly also the upper and/or the lateral peripheral surface(s), advantageously therefore through the entire surface area of the discrete portion or of the filter cakes, i.e. S 20 through the front and rear surfaces and all peripheral surfaces.

2. A method according to Claim 1, characterised in that the pressure applied in the course of volume reduction in a first squeezing step is maintained at a substantially constant low value, and is then increased to an end value in a subsequent squeezing step, thereby bringing about a further reduction in volume.

3. A method according to Claims 1 or 2, characterised in that the value of the pressure in the first squeezing step is determined by the frictional resistance inherent in the equipment and acting against the ein liudsldmxtrs ldeslris uiiplefuns uncplsugs or i iar co p14gs u ei g o ilei g o tt elq i o po e t h ri h t r e sprtd c a aebe odtoe yplmr rteapiaino et sdvd du noalrenu b ro)rfrbye ulsze ,dsrt oto sarn e a connecung. element between the filter plates. I I i i

21- 4 pressure piston when the discrete portions of mixture are being reduced in volume, and this pressure value only slightly exceeds the value of the 6 frictional resistance. 1 4. A method according to one of the Claims 1 to 3, characterized 2 in that the second squeezing step is initiated when, by squeezing out the 3 liquid fraction of the mixture in the first squeezing step, the coefficient of 4 friction of tte mixture or of the filter cake is increased to a value which substantially prevents any entrainment of solids particles in the expressed 6 liquid when further squeezing is applied or the pressure is further increased. 1 5. A method according to one of the Claims 1 to 3, characterized 2 in that in a single squeezing step, as the pressure rises correspondingly, a 3 linear reduction or compression of the individual portions of mixture by 4 about 50 to 95%, preferably 75 to 85%, is achieved over the sequence of portions in the direction in which the pressure is applied. 1 6. A method according to one of the Claims 1 to 5, characterized 2 in that in the squeezing steps the liquid is for the most part squeezed out of 3 discrete portions of mixture arranged without seals or at least open at the 4 bottom. 1 7. A method according to one of the Claims 1 to 6, characterized 2 in that solids entrained in the filtrate escaping when the machine is filled, or 3 squeezed out in the first squeezing step, are filtered out or retained in or 4 below the portions of mixture by a filter unit, e.g. a screen arranged below the portions of mixture. 1 8. A method according to one of the Claims 1 to 7, characterized 2 in that filtrate emerging in the second squeezing step is allowed to drain 3 away freely, i.e. the filter unit is removed. REPLACEMENT SHEET i. the- potin ofv- mixture. I lilt suilp I I Is LiyIILIy LLd IIU LU LIIl LaIs r -25 possibly inflatable seals 41. The sump 11 contains a substantially 1 9. A method according to one of the Claims 1 to 8, characterized 2 in that in the first squeezing step a linear reduction or compression of the 3 portions of mixture by 40 to 85%, preferably 60 to 75%, is achieved over 4 the sequence of portions in the direction in which the pressure is applied, and further characterized in that in the following squeezing step the linear 6 extent of the portions of mixture in the direction in which the pressure is 7 applied is reduced to a value of approximately 50 to 95%, preferably 75 to 8 85% of theloriginal or starting value. 1 10. A method according to one of the Claims 1 to 9, characterized 2 in that the pressure applied in the course of the first squeezing step is 3 adjusted to a value of 0.5 to 6 bar, preferably 1 to 5 bar, in particular 2 to 4 4 bar, and the end value of the squeezing pressure is adjusted in the second, possibly multi-stage, step to at least 10 bar, in particular to 20 to 50 bar or 6 higher. 1 11. A method according to one of the Claims 1 to 2 characterized in that prior to carrying out the first squeezing step, a pre- 3 dewatering of the mixture is achieved by directly applying pressure to the 4 mixture to be squeezed, after it has been filled into the machine but while the volume of the discrete portions of the mixture remains unchanged, 6 wherein the pre-dewatering is preferably carried out at a lower pressure than 7 the first squeezing step. 1 12. A method according to one of the Claims 1 to 11, 2 characterized in that the squeezing takes place in a second, possibly multi- 3 stage squeezing step, to an end content of at least 40% dry matter, 4 preferably at least 50% dry matter. 1 13. A filter press for separating mixtures of liquid and solid media 2 or for separating or dewatering liquid-solid mixtures, sludges, slurries, 3 municipal effluents, or municipal sludges, or similat, q6 -g r. filt 4 .out tho tiqo a large number of separate compartments We r ed REPLACEMENT SHE T U in t 3 I tonttA an fute chrceie nta ntefllwn qezn ttelna can be caught on or by the filter plate 25 arranged in the sump i i, su uLIIO 1 t adjacently or consecutively, and bounded by a large number of at least ten, 6 preferably at least twenty, filter plates, preferably bearino filter layers on 7 their surfaces and arranged substantially parallel to each other, through 8 which filtrate is drained away, and the linear extent of these filter plates in 9 the direction of squeezing can be reduced by the application of pressure, and at least one drive unit is provided to generate the pressure and in -41 particular to implement the method according to one of the Claims 1 to 12, 12 characterized in that 13 the filter plates are enclosed at least in their lower and in particular also in 14 their lateral and/or upper sections, without seals, by an elongated tank and the plates are slidingly arranged in the longitudinal direction of the tank 16 and the lateral peripheral surface of the separate compartments is left 17 open at the bottom and possibly also at the top and/or laterally to permit the 18 filtrate to emerge, and the filtrate from the press compartments and from 19 the filter plates can be drained away through at least one wall surface, designed as a filter wall surface, of the tank 1 14. A filter press according to Claim 1 characterized in that a 2 filter which can be removed, tilted, or slid away to the side, is 3 arranged close below the press compartments and the filter plates to 4 allow filtrate to pass through, and/or the tank may be closed at the top by a removable wall surface, e.g. a sliding plate. 1 15. A filter press according to Claim 13 or 14, characterized in that 2 the bottom (11) of the tank is designed as a removable sump (11), 3 which in particular may be tilted or pivoted aside, and which is used to 4 collect escaping mixture and/or expressed filtrate, and the filter (25) is arranged at a distance from the bottom of the sump (11) and may 6 advantageously by washed clean by means of a flushing device (27) 7 mounted on the tank or the. sump (11). REPLACEMENT SHEET i "W i il-"a i ~I h~ -II 1 2 3 16. A filter press according to one of the Claims 13 to characterized in that the filter plates are spaced a maximum of 0.5 to 6 cm, preferably 0.5 to 4 cm, in rp:rticular 1.5 to 3 cm, apart. 17. A filter press according to one of the Claims 13 to 16, characterized in that the maximum spacing between the filter plates is determined by connecting devices attached to the filter plates which permit the filter plates to move together but which prevent them from moving apart by more than the predetermined maximum distance, and for this purpose pins (36) are provided on the filter plates and adjacent pins (36) are en':ircled by a ring and when spaced apart the filter plates (3) are connected by chain links or cables, or similar. 18. A filter press according to one of the Claims 13 to 17, characterized in that pressure can be applied to the press compartments (22) by means of one or two pressure plates, adjustable by means of at least one drive unit, arranged at one or both ends of the tank. 19. A filter press according to one of the Claims 13 to 18, characterized in that the tank possesses longitudinal guides (37) or longitudinal guides are formed in the tank, and the filter plates are suspended on or in these guides or are carried by them in such a way that the plates can be slidingly moved in the longitudinal direction of the tank and the filter plates are preferably supported in or on the guides (37) by means of projections (38). 20. A filter press according to one of the Ciaims 13 to 19, characterized in that at least one (reinforcing) strut runs along both sides of the tank and is connected to the end plate which forms one end of the tank or press chamber (30) and with which also the abutment of the press unit is connected or by means of which the abutment is supported possibly in selectable positions the said press unit being arranged between the pressure plate and the abutment and further 'I :sl 1 xCD c9 REPLACEMENT SHEET vl ii i; mixture which sprays out during the first squeezing step and return it via -6- 8 characterized in that the guides (37) may be formed on the (reinforcing) 9 strut running from the end plate of the tank to the abutment of the drive unit. 1 21. A filter press according to one of the Claims 13 to 2 characterized in that at least one press unit comprising possibly different 3 and/or sequentially arranged press devices or drives, and/or a multi-stage 4 press unit, e.g. an hydraulic and a spindle-driven press device, a multi-stage cylinder press, or similar, are arranged between the abutment 6 and the pressure plate 1 22. A filter press according to one of the Claims 13 to 21, 2 characterized in that a charging container or duct for the mixtur3 opens 3 into the tank said container or duct being arranged preferably at the top 4 and/or at least at one side of the tank and extending preferably over the entire length of the press chamber and -'ossibly having the same width 6 as the latter, and in particular being arranged above the the press 7 compartments and in this container or duct is arranged at least one 8 piston for forcibly loading the compartments (22) with mixture and/or for 9 pre-dewatering the mixture supplied to the press compartments (22). 1 23. A filter press according to Claim 22, characterized in that the 2 press compartments (22) can be sealed off against the charging container 3 or charging duct(s) by means of at least one sliding plate (18) which, 4 without using seals, makes direct contact with the upper or lateral edges or peripheral surfaces of the filter plates 1 24. A filter press according to one of the Claims 13 to 23, 2 characterized in that the tank (8),in particular its side walls which may 3 contain filter wall sections, also the sliding plate (18) and the filter 4 surround the peripheral or narrow edges of the filter plates closely but without seals. F REPLACEMENT SHEET /ii -i 1 25. A filter press according to one of the Claims 13 to 24, 2 characterized in that in order to remove the filter cakes (19) adhering to the 3 filter plates stripping devices are provided which advantageously take 4 the form of scrapers (15) which may be slidingly moved along each filter plate or they take the form of air-jet nozzles or similar, which can 6 be introduced be-'Neen the filter plates 1 26. -A filter press according to one of the Claims 13 to 2 characterized in that drainage ducts (33) for the expressd liquid are formed 3 in the filter plates laterally bordering the press compartments (22) and 4 bearing filter layers (13) preferably on both sides. 1 27. A filter press according to one of the Claims 13 to 26, 2 characterized in that the filter plates are of multilayer construction and 3 comprise two perforated plates (14) provided on their outer surfaces with at 4 least one filter layer (13) and having interposed between them a plate bearing vertical longitudinal slots (40) into which the holes (41) of the 6 perforated plates (14) open. 1 28. A filter press according to one of the Claims 13 to 27, 2 characterized in that the filter plates are provided at the surface, 3 preferably on both sides, with vertical, longitudinal ducts (33) which are 4 covered over on the outside with at least one filter layer (13). 1 29. A filter press according to one of the Claims 13 to 28, 2 characterized in that a recirculating line (51) is provided which leads from 3 the tank or the sump (11) to the charging container 1 30. A filter press according to one of the Claims 25 to 29, 2 characterized in that the scraper devices (62) are carried on a trolley (61) 3 which can be moved longitudinally over the tank m2 REPLACEMENT SHEET j co ee *n -h 'usd 'it fi, ite ay r( 1 31. A filter press according to Claim 30, characterized in that the 2 scraper devices (15) possess scraper blades (62) which are pressed by 3 means of spring action or with spring-loaded legs (63) against the surfaces 4 of the filter plates 1 32. A filter press according to one of the Claims 13 to 31, characterized in that the tank is formed by a (steel-reinforced) concrete 3 tank or frame, possibly open at both the bottom and the top, and the 4 abutments for at least one press device which is provided are formed by the end walls of the concrete tank 1 33. A filter press according to Claim 32, characterized in that 2 sliding side wall and/or bottom wall surfaces (66, 67), possibly possessing 3 filter wall sections, are provided which may be moved close up to or 4 positioned against the filter plates without the use of seals, or they may be moved in front of the bottom and side surfaces of the compartments 6 (22). 1 34. A filter press according to one of the Claims 13 to 33, 2 'characterized in that a pressure plate (64) rigidly mounted in the tank or 3 on the struts or on the concrete tank is arranged in the central part 4 of the press chamber, i.e. in the middle of the package of filter plates .REPLACEMENT SHEET I 1 Fl- W dewatering liquid-solid mixtures, sludges, slurries, municipal effluents, municipal sludges, or similar, substantially as hereinbefore described.

36. A filter press substantially as hereinbefore described with reference to the accompanying drawings. DATED THIS 19TH DAY OF AUGUST 1994 HORST GUGGEMOS EDWIN HASLAUER ROBERT HASLAUER By their Patent Attorneys KELVIN LORD AND COMPANY PERTH, WESTERN AUSTRALIA 9 aI o 0 *a 9 a 'a P a a -28-• 3id k q OOS GUGEO EDINHALAE ROETHSAE 15B herPtetAtony KEVI LOR AN OPN O .PRHWSENAUTAI 0 t 0 o oa 0