CA2101732A1 - Method and device for separating liquid/solid mixtures - Google Patents
Method and device for separating liquid/solid mixturesInfo
- Publication number
- CA2101732A1 CA2101732A1 CA002101732A CA2101732A CA2101732A1 CA 2101732 A1 CA2101732 A1 CA 2101732A1 CA 002101732 A CA002101732 A CA 002101732A CA 2101732 A CA2101732 A CA 2101732A CA 2101732 A1 CA2101732 A1 CA 2101732A1
- Authority
- CA
- Canada
- Prior art keywords
- filter
- tank
- press
- pressure
- mixture
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D25/00—Filters formed by clamping together several filtering elements or parts of such elements
- B01D25/12—Filter presses, i.e. of the plate or plate and frame type
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D25/00—Filters formed by clamping together several filtering elements or parts of such elements
- B01D25/30—Feeding devices ; Discharge devices
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D25/00—Filters formed by clamping together several filtering elements or parts of such elements
- B01D25/32—Removal of the filter cakes
- B01D25/38—Removal of the filter cakes by moving parts, e.g. scrapers, contacting stationary filter elements sprayers
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D25/00—Filters formed by clamping together several filtering elements or parts of such elements
- B01D25/32—Removal of the filter cakes
- B01D25/38—Removal of the filter cakes by moving parts, e.g. scrapers, contacting stationary filter elements sprayers
- B01D25/386—Nozzles
Landscapes
- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Filtration Of Liquid (AREA)
Abstract
The invention concerns a method and device for separating mixtures of liquid and solid materials by squeezing out or filtering off the liquid component. 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.
Description
Method and Device for Separating Liquid-Solid Mixtures The invention relates to a methocl according to the prearnble to Patent Claim 1. In addition, the invention relates to a separating device for implementing this method according to ~he preamble to Patent Claim 13.
5 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 fil~er 10 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 15 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 20 in such mixtures the dewatering characteristics depend to a large degree on the thickness of the filter cake.
C:hemical conditioning, i.e. adding lime and iron chloride, permi~s Filter cake thicknesses of up to 40 mm to be achieved, if the squeezing is carried out using a filter on both sides of the Filter cake and, for example in the case . .
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5 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 fil~er 10 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 15 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 20 in such mixtures the dewatering characteristics depend to a large degree on the thickness of the filter cake.
C:hemical conditioning, i.e. adding lime and iron chloride, permi~s Filter cake thicknesses of up to 40 mm to be achieved, if the squeezing is carried out using a filter on both sides of the Filter cake and, for example in the case . .
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of municipal sludges, it yields dry matter contents of max. 40 to 4~%; 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 5 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 10 more than 60% dry matter using polymer conditioning in membrane cylinder presses. However, squeeziny the water frorn these fibre-containin~ slud~es 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 procedural steps must be taken since 15 the liquid is initially fairly easy to squeeze out, but as pressing continues so the liquid becomes extremely hard to expel.
It is the object of 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 watef 20 treatment plants, can to a large extent be separated into a liquid fraction and a solids fraction having dry matter contents of at least 4û%, and in particular 50% and more, even if these sludges have been aerobically stabilized. Using ~he ~raditional methods, aerobically stabilized sludges are extremely difficult to dewater down to dry matter contents of more than ?5 30%. Thus, it is the purpose of the invention to design a method of the kind .. . . . .
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mentioned 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 squee~ed to yield the highest possible dry matter conten~s.
A method of the type mentioned at the beginning is characterized~
according to the invention, by the features listed in the characterizing section of Patent Claim 1. A separating device according to the inVentiQr~ is characterized by the features listed in the characterizing section of Paten-t Claim 13.
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 ~o 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 3 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.
Once the press chamber, which is subdivided by filter plates into a large number of sub-chambers or compartments, has been filled, ~he 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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chamber or tank when the sliding plate is closed, so that when squee2ing is carried out, i.e. when the lamellar filters are displaced alon0 the longitudinalaxis of the press chamber, thereby reducing the size o-F the individuai compartments, the edges of the lamellar filters almost touch or come as 5 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 housiny; ~he 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 ~he 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 !amellar filter plates is squeezed. However, because ~he distance between the filter plates is from the start not very large, namely 15 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 tha~ rnix~ure, i.e. Iiquid 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 20 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 ;3 ~ er 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 25 be recycled bacl< into the process. This filter represents the lower boundary - - - . . . . . . . .
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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 10 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 sun-~p 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 complete!y clear. Subsequently, the lamellar 15 filters are moved back to their original position, this movement and ~heir position being determined or restricted by a limiting device, e.g. chain link or similar, attached to the individual larnellar filters. A scraper device, or compressed air lances or similar vvhich can be introduced into the press compartments, can be provided to detach the filter cakes adhering ~o the 20 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 volurne. It is advantageous if 25 the method is applied in accordance with the features described in Patent .. . . :
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. ., . ~, , 7 ~ 7 3 2 Claims 9 and 10. In this way a rela-tively large reduc-tion in volume can be achieved during the first squee~ing step, so that a drive unit wi-th a correspondingly large stroke should be provided for the press device, although it does not have to exert especially high forces. The linear vol;.ime 5 reduction or the end pressure aimed for in the second squeezing step rnay 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 s~r multi-stage construction because ~he pressure in the second squeezing step or towards the end of the squee~ing 10 process increases subs~antially 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 ~he 15 drawing. Fig. 1 shows a purely diagrammatic view of a separatin~ 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 diagramrnatically the emptying of the device. Figs. 6 and 6a are detailed 20 views of filter plates. Fig. 7 shows the interconnections betvveen the filter plates and the detachment of the Filter cake~ Figs. ~ and 8a are cross sections throuyh 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.
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Fi~3. 1 shows in diagrammatic form an embodiment of a separa~irlg device according to the invention. This device comprises an elon0ated housing or tank 8 formed by sheet metal walls, having front, rear,and side walls 51 indicated by dashed lines in the Figure; the tank 8 is closed off at 5 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 w~311 as a pressure plate 2 aré 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 par~ with the front and rear walls, and in 10 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 5 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 15 end plate 4 and the pressure plate 2 is subdivided into a large nurnber of separate compartments 22 located between filter plates 3, and these compartments or fractional volumes 22 which make up the press chamber 3a 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 20 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 af~er i~
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 " ., .. ; - -, . . . , :
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g horizontally oriented filter 25 which is positioned directly agains~ ~he undersides of the filter plates 3 or at a distance from thern; in addition, the sump 1 1 possesses an outlet 2~' for filtrate 16 as well as an outlet Z4 for liquid-solid mixtures which escape from the press compartments 22 wihen 5 the squeezing is carried out and which can be flushed away by a flushirlg 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 ion~
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 exampl0, a 10 kind of spindle press 6' can be provided which is Fitted with a pressur0 plate 5' 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 5', while hydraulic press 6 remains in its starting posi~ion, and the first stage of the pressing is completed, pressure plate 5' is lockedl 15 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 abutmen~.
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 ~ank 8 or the filter 25 in the 20 sump 11 or the sliding plate 18 fit close to the edges of the fil~er 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 fil~rate but also mixture escapes, this 25 can be caught on or by the filter plate 25 arranged in the sump 11, so that ' .... . . . . .
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, 2 ~ 2 ~;. 1o-a large build-up of pressure in the press chamber 30, which would s~ress 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 reslJI~
of the increase in the angle of friction in the filter cake, no more solids but 5 only filtrate liquid escapes and is either carried away by the filter 2~ f:3r drips into the tilted sump 11. The high pressure is absorbed by the abutrnents 5 or 5', the longitudinal struts 1 and the end plate ~. It ~s~ 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 10 sump 11 can in addition also be equipped at suitable points, especially laterally, with filters which, like filter 25, permit filtrate to emerge.
Fig. 3 shows the separating device according to the invention s~ar~ing 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 15 by means of a flushing device 27 into a line 51 which may recirculate the 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, 20 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 importan~ ~ha~ ~he press chamber 30 be subdivided into a large number of separate compartnments 22 which are lateral!y bounded in the direction of pressing 25 by filter plates 3, which in their starting and ending positions are : : . , . : ', .
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substantially 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 S0071 attained in the filter cake at which the escape of solids is prevented se ~ha~
5 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 8 have been returned to ~heir 10 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 wi~h frame attachments 46 which engage around the vertical side edges olF the 15 filter plates 3 so that the scraper blades 15, which are oriented horizon~aily 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 20 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, ~1e eyes 18 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 25 mixture which sprays out during the first squee~ing step and return it via ; ~. . . .
21~ ~ ~32 r recirculation line 51 to the charging container 7. The space 26 below the filter ~5 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 o~
5 the separating device; the guides may be formed, for example, by the uppeY
surface ~2 of 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 15 elernent 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 35, 36 do not in any way impede the movement of the fil$er plates towards each other but they do prevent the plates from rnoving more than a given 20 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 35 depicted, other devices such as chains or cables 4~ running along the separating device may be used to which the filter plates 3 may be attached .
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~:~01732 at cer~ain 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. 8, the filter plates 3 may comprise two plates provided with holes 41 and an intermediate plate 45 provided wi-th vertically 5 oriented longitudinal slits 40, and the holes 41 of the perforated plates 14 open into ~he lonyitudinal slits 4û of the central pla~e 45. At least one filter layer 13 is fitted to the plates 1~. 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 10 through exit holes or the lower, open longitudinal slits ~0.
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 15 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 metal filter mesh could be placed one on top of the other and securely loined with each other to give a stiff filter lamella. The mesh widths of the metal filters would 20 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.
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~ 211~:~732 ~; -14-One alternative means of separating the filter cake 19 frorn 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 s-tarting position; the nozzles 32 of this 5 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 10 preliminary dewatering of the mixture while the filter plates 3 are statiorlary 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 me~al 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 hcrizontally.
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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 th0 5 inven-tion 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 d0watering 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 10 been pre-dewatered then undergoes the squeezing process.
Separating devices according to the invention may be several rnetres long; their cross sectional dimensions are, for example, lOO x 100 cm Advantageously, steps are taken to ensure that the pressure exerted cluring the first squeezing step is adjusted to a value of 0.5 to 6 bar, preferably 11 15 to 5 bar, and in particular 2 to 4 bar, and the final va!ue of the pressure in the second squeezing step is adjusted to at least 10 bar and in particular to 20 to 50 bar or higher. The pressure applied during the first squeezing s~ep is held substantially constant; this is possible because along the relatively long path through which the press travels, the high liquid content of the 20 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 constan~ 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 : . , .
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' efficiency of the separating process is guaranteed because of the lar0e 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 5 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 10 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 rernoved 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 15 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 20 produce; high-pressure devices which only have to operate over short distances in the second step of the squeezin3 operation are complex and costly.
In the case of mixtures produced by the pulp and paper industry, their behaviour in the press permits the separa~ion to be carried out in just one 25 step.
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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 rnore charging containers for the mixture 5 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 compartrnents 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 10 compartments 22 can be simultaneously and rapidly filled. As Figs. 6 and 12 show, several rnixture 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 emptyin~ can 15 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 the pressure plate 2, and since the mixture can escape almost without any 20 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 ~, the abutment 2 and the longitudinal strut 1, which connects the end plate 4 with the abutrnent 5 for the press unit 6 are subjected to any stress.
The mixture in the press chamber 30 may contain about 7 to 15%
25 dry matter and the dry matter content of the mixture to be charged may be ,'' . , . ~
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21~1732 increased as long as the mixture remains flowable and can be filled into the separating device.
Figs. 10 and 1Oa depict a variant of the separating device accosding to the invention. In these Figs. the tank ~ takes the form of a soncre~e ~ank, 5 especially a steel-reinforced concrete tank, which may be open a~ 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 an5 applying pressure to a number of filter plates 3 via appropriate pressure 10 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 waV
the pressure distribution in the individual compartments is evened out. At their sides, the compartments are bordered by side walls 66 which rnay contain filter sections or may be -formed by filter walls so that filtrate can 15 emer~e easily at the side without the need for seals.
The side wails 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 20 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 bottcn1 part of the the separating device away to the side.
Fig. 11 shows a mobile device for removing the filter cake from the ~5 press compar$ments. This mobile device can be travellingly arranged on rails : "-: ~' ' ' :
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21~732 ~,`'5 -19-69 above the press chamber, and i-t comprises a number of scraper b~ades 15 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 5 means of a drive pinion 72, and i~ carries a crosspiece 73 at both ends of which - as shown in Fig. 11 b - scraper blades 62 are arranged on spring-loaded legs 63. As Fig. 11 b shows, a guide 74 which is inserted into ~he press compartrnents and pivots around a pivoting point 75 is arranged laterally in the area of the mobile system 61; this guide is inserted with its 10 tapered end 76 into the press compartments or into the upper parts thereof, as shown successively in Fig. 11 b. 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 par~ 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 siiding plate 18.
It should also be noted that the tanlc can be made of any suitable 20 material, e.g. also plastic.
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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 5 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 10 more than 60% dry matter using polymer conditioning in membrane cylinder presses. However, squeeziny the water frorn these fibre-containin~ slud~es 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 procedural steps must be taken since 15 the liquid is initially fairly easy to squeeze out, but as pressing continues so the liquid becomes extremely hard to expel.
It is the object of 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 watef 20 treatment plants, can to a large extent be separated into a liquid fraction and a solids fraction having dry matter contents of at least 4û%, and in particular 50% and more, even if these sludges have been aerobically stabilized. Using ~he ~raditional methods, aerobically stabilized sludges are extremely difficult to dewater down to dry matter contents of more than ?5 30%. Thus, it is the purpose of the invention to design a method of the kind .. . . . .
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mentioned 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 squee~ed to yield the highest possible dry matter conten~s.
A method of the type mentioned at the beginning is characterized~
according to the invention, by the features listed in the characterizing section of Patent Claim 1. A separating device according to the inVentiQr~ is characterized by the features listed in the characterizing section of Paten-t Claim 13.
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 ~o 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 3 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.
Once the press chamber, which is subdivided by filter plates into a large number of sub-chambers or compartments, has been filled, ~he 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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chamber or tank when the sliding plate is closed, so that when squee2ing is carried out, i.e. when the lamellar filters are displaced alon0 the longitudinalaxis of the press chamber, thereby reducing the size o-F the individuai compartments, the edges of the lamellar filters almost touch or come as 5 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 housiny; ~he 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 ~he 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 !amellar filter plates is squeezed. However, because ~he distance between the filter plates is from the start not very large, namely 15 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 tha~ rnix~ure, i.e. Iiquid 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 20 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 ;3 ~ er 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 25 be recycled bacl< into the process. This filter represents the lower boundary - - - . . . . . . . .
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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 10 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 sun-~p 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 complete!y clear. Subsequently, the lamellar 15 filters are moved back to their original position, this movement and ~heir position being determined or restricted by a limiting device, e.g. chain link or similar, attached to the individual larnellar filters. A scraper device, or compressed air lances or similar vvhich can be introduced into the press compartments, can be provided to detach the filter cakes adhering ~o the 20 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 volurne. It is advantageous if 25 the method is applied in accordance with the features described in Patent .. . . :
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. ., . ~, , 7 ~ 7 3 2 Claims 9 and 10. In this way a rela-tively large reduc-tion in volume can be achieved during the first squee~ing step, so that a drive unit wi-th a correspondingly large stroke should be provided for the press device, although it does not have to exert especially high forces. The linear vol;.ime 5 reduction or the end pressure aimed for in the second squeezing step rnay 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 s~r multi-stage construction because ~he pressure in the second squeezing step or towards the end of the squee~ing 10 process increases subs~antially 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 ~he 15 drawing. Fig. 1 shows a purely diagrammatic view of a separatin~ 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 diagramrnatically the emptying of the device. Figs. 6 and 6a are detailed 20 views of filter plates. Fig. 7 shows the interconnections betvveen the filter plates and the detachment of the Filter cake~ Figs. ~ and 8a are cross sections throuyh 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.
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Fi~3. 1 shows in diagrammatic form an embodiment of a separa~irlg device according to the invention. This device comprises an elon0ated housing or tank 8 formed by sheet metal walls, having front, rear,and side walls 51 indicated by dashed lines in the Figure; the tank 8 is closed off at 5 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 w~311 as a pressure plate 2 aré 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 par~ with the front and rear walls, and in 10 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 5 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 15 end plate 4 and the pressure plate 2 is subdivided into a large nurnber of separate compartments 22 located between filter plates 3, and these compartments or fractional volumes 22 which make up the press chamber 3a 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 20 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 af~er i~
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 " ., .. ; - -, . . . , :
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g horizontally oriented filter 25 which is positioned directly agains~ ~he undersides of the filter plates 3 or at a distance from thern; in addition, the sump 1 1 possesses an outlet 2~' for filtrate 16 as well as an outlet Z4 for liquid-solid mixtures which escape from the press compartments 22 wihen 5 the squeezing is carried out and which can be flushed away by a flushirlg 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 ion~
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 exampl0, a 10 kind of spindle press 6' can be provided which is Fitted with a pressur0 plate 5' 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 5', while hydraulic press 6 remains in its starting posi~ion, and the first stage of the pressing is completed, pressure plate 5' is lockedl 15 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 abutmen~.
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 ~ank 8 or the filter 25 in the 20 sump 11 or the sliding plate 18 fit close to the edges of the fil~er 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 fil~rate but also mixture escapes, this 25 can be caught on or by the filter plate 25 arranged in the sump 11, so that ' .... . . . . .
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, 2 ~ 2 ~;. 1o-a large build-up of pressure in the press chamber 30, which would s~ress 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 reslJI~
of the increase in the angle of friction in the filter cake, no more solids but 5 only filtrate liquid escapes and is either carried away by the filter 2~ f:3r drips into the tilted sump 11. The high pressure is absorbed by the abutrnents 5 or 5', the longitudinal struts 1 and the end plate ~. It ~s~ 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 10 sump 11 can in addition also be equipped at suitable points, especially laterally, with filters which, like filter 25, permit filtrate to emerge.
Fig. 3 shows the separating device according to the invention s~ar~ing 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 15 by means of a flushing device 27 into a line 51 which may recirculate the 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, 20 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 importan~ ~ha~ ~he press chamber 30 be subdivided into a large number of separate compartnments 22 which are lateral!y bounded in the direction of pressing 25 by filter plates 3, which in their starting and ending positions are : : . , . : ', .
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substantially 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 S0071 attained in the filter cake at which the escape of solids is prevented se ~ha~
5 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 8 have been returned to ~heir 10 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 wi~h frame attachments 46 which engage around the vertical side edges olF the 15 filter plates 3 so that the scraper blades 15, which are oriented horizon~aily 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 20 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, ~1e eyes 18 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 25 mixture which sprays out during the first squee~ing step and return it via ; ~. . . .
21~ ~ ~32 r recirculation line 51 to the charging container 7. The space 26 below the filter ~5 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 o~
5 the separating device; the guides may be formed, for example, by the uppeY
surface ~2 of 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 15 elernent 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 35, 36 do not in any way impede the movement of the fil$er plates towards each other but they do prevent the plates from rnoving more than a given 20 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 35 depicted, other devices such as chains or cables 4~ running along the separating device may be used to which the filter plates 3 may be attached .
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~:~01732 at cer~ain 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. 8, the filter plates 3 may comprise two plates provided with holes 41 and an intermediate plate 45 provided wi-th vertically 5 oriented longitudinal slits 40, and the holes 41 of the perforated plates 14 open into ~he lonyitudinal slits 4û of the central pla~e 45. At least one filter layer 13 is fitted to the plates 1~. 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 10 through exit holes or the lower, open longitudinal slits ~0.
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 15 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 metal filter mesh could be placed one on top of the other and securely loined with each other to give a stiff filter lamella. The mesh widths of the metal filters would 20 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.
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~ 211~:~732 ~; -14-One alternative means of separating the filter cake 19 frorn 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 s-tarting position; the nozzles 32 of this 5 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 10 preliminary dewatering of the mixture while the filter plates 3 are statiorlary 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 me~al 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 hcrizontally.
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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 th0 5 inven-tion 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 d0watering 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 10 been pre-dewatered then undergoes the squeezing process.
Separating devices according to the invention may be several rnetres long; their cross sectional dimensions are, for example, lOO x 100 cm Advantageously, steps are taken to ensure that the pressure exerted cluring the first squeezing step is adjusted to a value of 0.5 to 6 bar, preferably 11 15 to 5 bar, and in particular 2 to 4 bar, and the final va!ue of the pressure in the second squeezing step is adjusted to at least 10 bar and in particular to 20 to 50 bar or higher. The pressure applied during the first squeezing s~ep is held substantially constant; this is possible because along the relatively long path through which the press travels, the high liquid content of the 20 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 constan~ 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 : . , .
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' efficiency of the separating process is guaranteed because of the lar0e 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 5 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 10 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 rernoved 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 15 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 20 produce; high-pressure devices which only have to operate over short distances in the second step of the squeezin3 operation are complex and costly.
In the case of mixtures produced by the pulp and paper industry, their behaviour in the press permits the separa~ion to be carried out in just one 25 step.
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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 rnore charging containers for the mixture 5 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 compartrnents 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 10 compartments 22 can be simultaneously and rapidly filled. As Figs. 6 and 12 show, several rnixture 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 emptyin~ can 15 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 the pressure plate 2, and since the mixture can escape almost without any 20 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 ~, the abutment 2 and the longitudinal strut 1, which connects the end plate 4 with the abutrnent 5 for the press unit 6 are subjected to any stress.
The mixture in the press chamber 30 may contain about 7 to 15%
25 dry matter and the dry matter content of the mixture to be charged may be ,'' . , . ~
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21~1732 increased as long as the mixture remains flowable and can be filled into the separating device.
Figs. 10 and 1Oa depict a variant of the separating device accosding to the invention. In these Figs. the tank ~ takes the form of a soncre~e ~ank, 5 especially a steel-reinforced concrete tank, which may be open a~ 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 an5 applying pressure to a number of filter plates 3 via appropriate pressure 10 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 waV
the pressure distribution in the individual compartments is evened out. At their sides, the compartments are bordered by side walls 66 which rnay contain filter sections or may be -formed by filter walls so that filtrate can 15 emer~e easily at the side without the need for seals.
The side wails 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 20 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 bottcn1 part of the the separating device away to the side.
Fig. 11 shows a mobile device for removing the filter cake from the ~5 press compar$ments. This mobile device can be travellingly arranged on rails : "-: ~' ' ' :
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21~732 ~,`'5 -19-69 above the press chamber, and i-t comprises a number of scraper b~ades 15 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 5 means of a drive pinion 72, and i~ carries a crosspiece 73 at both ends of which - as shown in Fig. 11 b - scraper blades 62 are arranged on spring-loaded legs 63. As Fig. 11 b shows, a guide 74 which is inserted into ~he press compartrnents and pivots around a pivoting point 75 is arranged laterally in the area of the mobile system 61; this guide is inserted with its 10 tapered end 76 into the press compartments or into the upper parts thereof, as shown successively in Fig. 11 b. 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 par~ 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 siiding plate 18.
It should also be noted that the tanlc can be made of any suitable 20 material, e.g. also plastic.
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Claims (34)
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, by 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 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 a filtrate, characterized in that 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 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 portions or of the filter cakes, i.e. through the front and rear surfaces and all peripheral surfaces.
2. A method according to Claim 1, characterized 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, characterized in shaft the value of the pressure in the first squeezing step is determined by the frictional resistance inherent in the equipment and acting against the pressure piston when the discrete portions of mixture are being reduce in volume, and this pressure value only slightly exceeds the value of the frictional resistance.
4. A method according to one of the Claims 1 to 3, characterized in that the second squeezing step is initiated when, by squeezing out the liquid fraction of the mixture in the first squeezing step, the coefficient of friction of the mixture or of the filter cake is increased to a value which substantially prevents any entrainment of solids particles in the expressed liquid when further squeezing is applied or the pressure is further increased.
5. A method according to one of the Claims 1 to 3, characterized in that in a single squeezing step, as the pressure rises correspondingly, a linear reduction or compression of the individual portions of mixture by about 50 to 95%, preferably 75 to 85%, is achieved over the sequence of portions in the direction in which the pressure is applied.
6. A method according to one of the Claims 1 to 5, characterized in that in the squeezing steps the liquid is for the most part squeezed out of discrete portions of mixture arranged without seals or at least open at the bottom.
7. A method according to one of the Claims 1 to 6, characterized in that solids entrained in the filtrate escaping when the machine is filled, Ofsqueezed out in the first squeezing step, are filtered out or retained in or below the portions of mixture by a filter unit, e.g. a screen arranged below the portions of mixture.
8. A method according to one of the Claims 1 to 7, characterized in that filtrate emerging in the second squeezing step is allowed to drain 3 away freely, i.e. the filter unit is removed.
9. A method according to one of the Claims 1 to 8, characterized in that in the first squeezing step a linear reduction or compression of the portions of mixture by 40 to 85%, preferably 60 to 75%, is achieved over 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 extent of the portions of mixture in the direction in which the pressure is applied is reduced to a value of approximately 50 to 95%, preferably 75 to 85% of the original or starting value.
10. A method according to one of the Claims 1 to 9, characterized in that the pressure applied in the course of the first squeezing step is adjusted to a value of 0.5 to 6 bar, preferably 1 to 5 bar, in particular 2 to 4bar, 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 higher.
11. A method according to one of the Claims 1 to 10, characterized in that prior to carrying out the first squeezing step, a pre-dewatering of the mixture is achieved by directly applying pressure to the 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, wherein the pre-dewatering is preferably carried out at a lower pressure than the first squeezing step.
12. A method according to one of the Claims 1 to 11, characterized in that the squeezing takes place in a second, possibly multi-stage squeezing step, to an end content of at least 40% dry matter, preferably at least 50% dry matter.
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 similar, by squeezing or filtering out the liquid fraction in a large number of separate compartments arranged adjacently or consecutively, and bounded by a large number of at least ten, preferably at least twenty, filter plates, preferably bearing filter layers or their surfaces 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 one of the Claims 1 to 12, characterized in that the filter plates are enclosed at least in their lower and in particular also intheir lateral and/or upper sections, without seals, by an elongated tank (8), and the plates are slidingly arranged in the longitudinal direction of the tank (8), 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 (3) can be drained away through at least one wall surface, designed as a filter wall surface, of the tank (8).
14. A filter press according to Claim 13, characterized in that a filter (25), which can be removed, tilted, or slid away to the side, is arranged close below the press compartments and the filter plates (3) to allow filtrate to pass through, and/or the tank (8) may be closed at the top by a removable wall surface, e.g. a sliding plate.
15. A filter press according to Claim 13 or 14, characterized in that the bottom (11) of the tank (8) is designed as a removable sump (11) which in particular may be tilted or pivoted aside, and which is used to 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 advantageously by washed clean by means of a flushing device (27) mounted on the tank (8) or the sump (11).
16. A filter press according to one of the Claims 13 to 15, characterized in that the filter plates (3) are spaced a maximum of 0.5 to 6 cm, preferably 0.5 to 4 cm, in particular 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 (3) is determined by connecting devices attached to the filter plates (3) which permit the filter plates (3) to move together but which prevent there from moving apart by more than the predetermined maximum distance, and for this purpose pins (36) are provided on the filter plates (3) and adjacent pins (36) are encircled by a ring (35), 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 (3) 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 (8) possesses longitudinal guides (37) Of longitudinal guides are formed in the tank, and the filter plates (3) 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 (8), and the filter plates (3) are preferably supported in or on the guides (37)by means of projections (38).
20. A filter press according to one of the Claims 13 to 19, characterized in that at least one (reinforcing) strut (1) runs along both sidesof the tank (8) and is connected to the end plate (4) which forms one end of the tank (8) or press chamber (30) and with which also the abutment 15) of the press unit (6) is connected or by means of which the abutment (5) is supported possibly in selectable positions (39), the said press unit (6) being arranged between the pressure plate (2) and the abutment (5), and further characterized in that the guides (37) may be formed on the (reinforcing) strut (1 ) running from the end plate (4) of the tank (8) to the abutment (5) of the drive unit.
21. A filter press according to one of the Claims 13 to 20, characterized in that at least one press unit comprising possibly different and/or sequentially arranged press devices or drives, and/or a multi-stage press unit, e.g. an hydraulic (6) and a spindle-driven (6') press device, a multi-stage cylinder press, or similar, are arranged between the abutment (5) and the pressure plate (2).
22. A filter press according to one of the Claims 13 to 21, characterized in that a charging container or duct (7) for the mixture opens into the tank (8), said container or duct being arranged preferably at the top and/or at least at one side of the tank and extending preferably over the entire length of the press chamber (30), and possibly having the same width as the latter, and in particular being arranged above the the press compartments (22), and in this container or duct (7) is arranged at least one piston (9) for forcibly loading the compartments (22) with mixture and/or for pre-dewatering the mixture supplied to the press compartments (22).
23. A filter press according to Claim 22, characterized in that the press compartments (22) can be sealed off against the charging container (7) or charging duct(s) by means of at least one sliding plate (18) which, without using seals, makes direct contact with the upper or lateral edges or peripheral surfaces of the filter plates (3).
24. A filter press according to one of the Claims 13 to 23, characterized in that the tank (8), in particular its side walls which may contain filter wall sections, also the sliding plate (13) and the filter (25) surround the peripheral or narrow edges of the filter plates (3) closely but without seals.
25. A filter press according to one of the Claims 13 to 24, characterized in that in order to remove the filter cakes (19) adhering to the filter plates (3), stripping devices are provided which advantageously take the form of scrapers (15) which may be slidingly moved along each filter plate (3) or they take the form of air-jet nozzles (21), or similar, which can be introduced between the filter plates (3).
26. A filter press according to one of the Claims 13 to 25, characterized in that drainage ducts (33) for the expressed liquid are formed in the filter plates (3) laterally bordering the press compartments (22) and bearing filter layers (13) preferably on both sides.
27. A filter press according to one of the Claims 13 to 26, characterized in that the filter plates (3) are of multilayer construction and comprise two perforated plates (14) provided on their outer surfaces with at least one filter layer (13) and having interposed between them a plate (45) bearing vertical longitudinal slots (40) into which the holes (41) of the perforated plates (14) open.
28. A filter press according to one of the Claims 13 to 27, characterized in that the filter plates (3) are provided at the surface, preferably on both sides, with vertical, longitudinal ducts (33) which are covered over on the outside with at least one filter layer (13).
29. A filter press according to one of the Claims 13 to 28, characterized in that a recirculating line (51) is provided which leads from the tank (8) or the sump (11) to the charging container (7).
30. A filter press according to one of the Claims 25 to 29, characterized in that the scraper devices (62) are carried on a trolley (611 ) which can be moved longitudinally over the tank (8).
31. A filter press according to Claim 30, characterized in that the scraper devices (15) possess scraper blades (62) which are pressed by means of spring action or with spring-loaded legs (63) against the surfaces of the filter plates (3).
32. A filter press according to one of the Claims 13 to 31, characterized in that the tank (8) is formed by a (steel-reinforced) concrete tank or frame, possibly open at both the bottom and the top, and the abutments (5) for at least one press device (6) which is provided are formed by the end walls of the concrete tank (8).
33. A filter press according to Claim 32, characterized in that sliding side wall and/or bottom wall surfaces (66, 67), possibly possessing filter wall sections, are provided which may be moved close up to or positioned against the filter plates (3), without the use of seals, or they may be moved in front of the bottom and side surfaces of the compartments (22).
34. A filter press according to one of the Claims 13 to 33, characterized in that a pressure plate (64) rigidly mounted in the tank (8) or on the struts (1 ) or on the concrete tank (8) is arranged in the central part of the press chamber, i.e. in the middle of the package of filter plates (3).
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| AT0022591A AT396923B (en) | 1991-02-01 | 1991-02-01 | METHOD AND SEPARATING DEVICE FOR SEPARATING OR DRAINING LIQUID-SOLID MIXTURES |
| ATA225/91 | 1991-02-01 | ||
| PCT/AT1992/000010 WO1992013624A1 (en) | 1991-02-01 | 1992-01-29 | Method and device for separating liquid/solid mixtures |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2101732A1 true CA2101732A1 (en) | 1992-08-02 |
Family
ID=3484865
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002101732A Abandoned CA2101732A1 (en) | 1991-02-01 | 1992-01-29 | Method and device for separating liquid/solid mixtures |
Country Status (10)
| Country | Link |
|---|---|
| EP (1) | EP0569459A1 (en) |
| JP (1) | JPH06506141A (en) |
| AT (1) | AT396923B (en) |
| AU (1) | AU656169B2 (en) |
| BR (1) | BR9205579A (en) |
| CA (1) | CA2101732A1 (en) |
| CZ (1) | CZ154493A3 (en) |
| HU (1) | HUT67819A (en) |
| SK (1) | SK82793A3 (en) |
| WO (1) | WO1992013624A1 (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE4425755C1 (en) * | 1994-07-21 | 1995-09-14 | Netzsch Erich Holding | Filtrate catcher tray assembly moves on continuous guide rails |
| DE19707070C2 (en) * | 1997-02-22 | 1999-04-01 | Netzsch Erich Holding | Filter press |
| CN112757680A (en) * | 2019-11-01 | 2021-05-07 | 王树岩 | Kitchen waste material receiving and extruding all-in-one machine |
Family Cites Families (16)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR1314040A (en) * | 1960-12-12 | 1963-01-04 | Almasfuezitoi Timfoldgyar | Filter press and method for separating solids from liquids, in particular for the filtration of cloudy liquors and the like |
| DE1190315B (en) * | 1962-11-24 | 1965-04-01 | Heidenau Maschf Veb | Hydraulic pot press for oiling cocoa mass |
| US3708072A (en) * | 1970-10-13 | 1973-01-02 | Industrial Filter Pump Mfg Co | Method and apparatus for controlling filter cake thickness and for compressing a filter cake |
| DE2813236A1 (en) * | 1978-03-28 | 1979-10-11 | Rittershaus & Blecher Gmbh | FILTER PRESS WITH A SPRAY DEVICE |
| US4222873A (en) * | 1978-08-23 | 1980-09-16 | Exxon Research & Engineering Co. | Plate and frame filter press having modified flow pattern method |
| AT376642B (en) * | 1979-07-31 | 1984-12-10 | Oestreicher Friedrich Ing | DEVICE FOR DRAINING AND TRANSPORTING SLUDGE OD. DGL. MEASURE |
| US4519903A (en) * | 1983-01-24 | 1985-05-28 | Johnson Willard L | Filter machine |
| GB2159724A (en) * | 1984-06-08 | 1985-12-11 | Johnson Progress Ltd | Filter press |
| DE3520171C2 (en) * | 1985-06-05 | 1993-10-28 | Seitz Enzinger Noll Masch | Filter press of horizontal design |
| AU584461B2 (en) * | 1985-09-06 | 1989-05-25 | Kurita Machinery Manufacturing Co., Limited | Filter press |
| SE453726B (en) * | 1986-07-10 | 1988-02-29 | Sala International Ab | PROCESS FILTER PROCEDURE AND DEVICE |
| DE3636799A1 (en) * | 1986-10-29 | 1988-05-05 | Rittershaus & Blecher Gmbh | METHOD FOR REGULATING THE FILTER PLATE SYSTEM PRESSURE IN FILTER PRESSES AND DEVICE FOR CARRYING OUT THE METHOD |
| ES2024452B3 (en) * | 1987-01-29 | 1992-03-01 | Lenser Kunststoff-Presswerk Gmbh & Co Kg | FILTER PRESS WITH A CERTAIN AMOUNT OF MEMBRANE FILTER PLATES |
| FI78843C (en) * | 1987-11-13 | 1989-10-10 | Larox Ag | FOERFARANDE FOER RENGOERING AV FILTERTYGET I ETT KAMMARFILTER SAMT KAMMARFILTER ENLIGT FOERFARANDET. |
| DE3833391A1 (en) * | 1987-11-28 | 1989-06-08 | Kloeckner Humboldt Deutz Ag | DEVICE FOR EXPRESSING LIQUID FROM SHEET AND / OR GIANT MATERIAL |
| EP0337218B1 (en) * | 1988-04-14 | 1995-01-25 | Hoppe + Partner | Process and dewatering device of mud |
-
1991
- 1991-02-01 AT AT0022591A patent/AT396923B/en not_active IP Right Cessation
-
1992
- 1992-01-29 EP EP92904360A patent/EP0569459A1/en not_active Ceased
- 1992-01-29 SK SK827-93A patent/SK82793A3/en unknown
- 1992-01-29 CZ CS931544A patent/CZ154493A3/en unknown
- 1992-01-29 WO PCT/AT1992/000010 patent/WO1992013624A1/en not_active Application Discontinuation
- 1992-01-29 HU HU9302184A patent/HUT67819A/en unknown
- 1992-01-29 CA CA002101732A patent/CA2101732A1/en not_active Abandoned
- 1992-01-29 BR BR9205579A patent/BR9205579A/en unknown
- 1992-01-29 JP JP4503849A patent/JPH06506141A/en active Pending
- 1992-01-29 AU AU12007/92A patent/AU656169B2/en not_active Ceased
Also Published As
| Publication number | Publication date |
|---|---|
| AU1200792A (en) | 1992-09-07 |
| AU656169B2 (en) | 1995-01-27 |
| HUT67819A (en) | 1995-05-29 |
| AT396923B (en) | 1993-12-27 |
| WO1992013624A1 (en) | 1992-08-20 |
| ATA22591A (en) | 1993-05-15 |
| BR9205579A (en) | 1994-10-11 |
| HU9302184D0 (en) | 1993-10-28 |
| EP0569459A1 (en) | 1993-11-18 |
| JPH06506141A (en) | 1994-07-14 |
| SK82793A3 (en) | 1994-01-12 |
| CZ154493A3 (en) | 1994-03-16 |
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