GB2031293A

GB2031293A - A filter belt press for dewatering sludge and similar substances, particularly for water purfication plants

Info

Publication number: GB2031293A
Application number: GB7904928A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1978-10-13
Filing date: 1979-02-12
Publication date: 1980-04-23
Also published as: GB2031293B; DE2844715A1; DE2844715C2

Abstract

A filter press leading from a sludge chamber 2 comprises a continuous filter band 15 carried on a carrier belt 16 of high lateral rigidity and the band 15 and belt 16 advance together so that frictional drag is avoided. The belt 16 is formed with open top channels 25, preferably extending at 45 DEG to the direction of movement of the belt, through which filtrate can be diverted as the solids accumulate on the filter band. The belt and band assembly is simply guided during advancement by rings, rims or flanges mounted on the ends of rollers 38, 39, 40 for supporting, deflecting or driving the belt and band assembly. Various embodiments are described and preferably the filter band/carrier belt forms the bottom wall 14 of the sludge chamber. Additional similar pressure applying filter band assemblies may co-act to squeeze the sludge, and rotating drum filter elements 5 may be provided in the sludge chamber 2, these having associated cleaning devices. <IMAGE>

Description

SPECIFICATION A filter belt press for de-watering sludge and similar substances, particularly for water purification plants This invention relates to a filter belt press for de-watering, or removing water from sludges and similar substances, particularly as occurring in water purification plants, of the kind wherein revolving filter bands are provided and the sludge is carried along between these bands and dewatered under pressure.

Basically, this type of filter belt press is known, and there are many constructional variations with regard to the means and arrangements for guiding and supporting the filter bands between which the sludge is carried along, and also with regard to the generation and application of the operative pressure. It is also known to subject the sludge between the filter bands to a pulling, or squeezing action by conducting it through sinuous or serpentine pressure-application stages designed to augment water release and discharge from the sludge.

One drawback of conventional filter belt presses resides in that a considerable amount of friction tends to occur between the pressing elements and the filter bands whether these be press rollers of V-belt arrays. This imposes severe limitations with regard to the magnitude of applicable pressure. Furthermore, owing to inevitable slipping and other relative movement of the filter bands, it is virtually impossible to provide lateral seals for the space between the bands containing the sludge because the relative position of the filter bands in the course of their circulation through the press cannot be precisely determined.

Moreover, comparatively complex and expensive arrangements are needed to ensure that the filter bands run true through the whole of the press, and this is usually done with the aid of conventional conveyor guide and control means and devices. Another serious drawback of conventional filter belt presses resides in that water emerging on the rear of the filter bands is liable to become dammed up in front of the press rollers, and subsequently re-absorbed by the sludge as soon as this has cleared the rollers.

It is the aim of the present invention to avoid these drawbacks which afflict conventional filter belt presses.

This invention consists of a filter belt press for de-watering sludge and similar substances, particularly as occurring in water purification plants, wherein continuous filter bands are provided and the sludge is carried along between these bands and de-watered under pressure, characterised in that the press is provided with at least one carrier belt of comparatively high lateral rigidity which advances with the filter band supported thereon, the carrier belt being provided with open-top channels and guide means are provided on rollers for supporting and deflecting the direction of the carrier belt and the filter band.

The main advantage achieved by the invention resides in the elimination of all relative movement between filter bands and carrier belts, so that the earlier described disadvantages are avoided and, particularly, that the equipment may also be used for pressing highly abrasive or agressive media. The carrier belts are never separated from the filter bands in the operative de-watering stages of the press. Due to the high lateral rigidity of the carrier belts the problem of keeping the bands straight can also be solved in a comparatively very simple manner. The rear faces of the carrier belts provide at the same time a perfectly smooth surface for the application thereto to press or squeeze rollers whilst the water which is squeezed out of the sludge does not reach these surfaces so that the earlier described adverse effects cannot arise.

A preferred embodiment of the invention is characterised in that the guide means take the form of track-holding rings, flanges or rims adjacent the roller ends. This is possible because, in view of the firm lateral rigidity of the carrier belts, only simple track-holding is required to keep the carrier belts with the filter bands supported thereon true and perfectly centered on the supporting rollers.

In a preferred embodiment of the invention these track-holding rings are rubber rings fitted on the roller ends.

According to a further feature of this invention, the open top channels in the carrier belts may extend mutually parallel and in the transverse direction at an angle which is larger or smaller than 900, and preferably an angle of 450 to the longitudinal or major axis of the carrier belt.

According to another feature of this invention, a gravitationally effective preliminary de-watering stage is provided in the form of a sludge chamber whereof the bottom is formed by the carrier belt with the filter band supported thereon.

This feature of the invention may be developed further by arranging the bottom of the sludge chamber in such a manner that it presents an upwardly directed gradient from the sludge inlet towards the sludge outlet, and by providing filter elements which are wholly or partially submerged in the sludge in the sludge chamber and comprise filtrate discharge outlets which conduct the filtrate out of the sludge chamber.

Advantageously such filter elements comprise filter drums with at least one filtrate discharge outlet in the side wall of the sludge chamber.

The filter elements may be associated with internally or externally cleaning devices, preferably in the form of internally rotating brushes.

The filter elements may be rotated, preferably all the elements being driven for rotation in the same direction of rotation towards the sludge outlet. In this kind of arrangement locally fixed or stationary cleaning devices may be provided inside or outside of the filter elements, and conveniently such devices could take the form of brushes of nylon or similar materials. The application of brushes has the special advantage that the brush bristles penetrate periodically through the holes in the filter material and detach any adhering sludge particles, thereby eliminating the need for special cleaning of the filter elements whilst at the same time enhancing the discharge of filtrate throtigh the filter material.

A further development in respect of this kind of cleaning device rotating brushes can be provided inside the filter elements and counter-rotate relative to the filter element.

It is also an advantage that the bottom of the sludge chamber can be arranged to merge into an adjoining preliminary de-watering stage where a further continuous band is applied to the top of the sludge carried on the filter band leading from the bottom of the sludge chamber Preferably, this further band comprises flexible transverse blades or ribs which are adapted to engage with the lower filter band. Accordingly, by providing this additional band which co-operates with the sludge chamber side walls, the blades form a plurality of successively advancing chambers travelling in the direction towards the sludge outlet.

A further feature of the invention comprises the provision of a further continuous carrier belt which is associated with a further filter band and cooperates with the first combination assembly of carrier belt and filter band to provide at least one generally wedge-shaped pressure application stage, and the combination of two such pressureapplication stages, which are arranged one above the other, provides special advantages.

The pressure application stages are preferably inclined i.e. extend at a gradient, and conveniently they are inclined in the same direction and, preferably, the bottom of the sludge chamber has the same gradient.

The pressure application stages may alternatively extend in a straight line or may be conducted once, or several times, around a drum of comparatively large diameter. In each case, the pressure application stage is formed by virtue of the provision of spring-loaded guide rollers for the respectively uppermost carrier belt along this stretch of belt advancement, so that these springloaded rollers can function as squeezing elements by applying pressure to the belt.

In another advantageous development of the invention the filtrate which is evacuated through the channels in the carrier belts above and below the sludge cake is collected in laterally provided collector or drainage means.

Since there is no relative movement between filter bands it is preferred to provide a lateral seal.

Such lateral seal may take the form of a pair of independently circulating, elastically deformable sealing strips which are firmly pressed into place between the filter bands. Alternatively the lateral seals may be provided by sealing beads secured to the filter bands, and these would also be elastically deformable, and preferably adapted to interengage to provide a tight seal when their respectively associated filter bands are mutually opposed and adjacent.

In a particularly preferred embodiment, the open top channels in the carrier belts are arranged to extend in such a manner that they intersect or cross one another in the pressure application stages.

Further details of the invention will be noted from the following specific description which explains the invention more specifically with reference to some embodiments illustrated by way of example in the accompanying drawings wherein: FIGURE 1 is a schematic sectional side elevation of a first embodiment of the invention; FIGURE 2 is a section taken on line Il-Il in Figure 1; FIGURE 3 is a schematic sectional side view similar to Figure 1 but of a second embodiment of the invention; FIGURE 4 is a detail sectional view depicting the carrier belts and filter bands; FIGURE 5 is a plan view of the carrier belts shown in Figure 4; FIGURE 6 is a diagrammatic top view of the resulting arrangement of the superimposition of the carrier belts shown in Figure 4;; FIGURE 7 is a schematic sectional side view similar to Figure 1 but of an extremely simple further embodiment of the invention; FIGURE 8 shows yet another embodiment of the invention viewed as in Figure 1; FIGURE 9 shows a modification of this invention, again viewed as in Figure 1; FIGURE 10 is a part-sectional detail of one kind of lateral seal; FIGURE 11 is a part-sectional detail depicting a modification of the seal shown in Figure 1 0; and FIGURE 12 is a part-sectional detail of an alternative type of lateral sealing means.

Figure 1 shows an embodiment of the invention wherein a filter belt press is associated with a preliminary gravitational de-watering stage which is also provided in the arrangements according to Figures 3 and 7, and in slightly modified form in the arrangements shown in Figures 8 and 9.

The preliminary de-watering stage 1 comprises a sludge chamber 2 having a sludge inlet 3 which is located below the upper sludge level 4, and this enables the sludge to be very gently introduced into the chamber 2. Inside the sludge chamber 2 a row of filter elements 5 is provided, and these filter elements 5 are wholly or partially submerged in the sludge and comprise cylindrical drums of a pervious filter material. These filter elements 5 may be rotationally driven. With reference to Figure 2, each filter element 5 is carried on an axle 6 of which the opposed ends are mounted in the side walls 7 of the sludge chamber 2. The filter elements 5 are driven by a suitable drive transmission, not shown.

Each filter element 5 comprises at least one filtrate outlet 8 which opens through the side wall 7 of the sludge chamber, and through which the filtrate passing from the sludge into the filter element is laterally discharged from the sludge chamber 2 and may then be carried away in a side drainage orcollectorchannel 9.

Associated with each filter element 8 is an external scraper blade 10. Inside the filter element 8 there is a cleaning device as an alternative or as an addition to the external scraper or strippers 10.

The cleaning devices comprise brushes, made of nylon or similar material, which extend across the whole width of the filter element and during rotation of these brushes relative to the cylindrical pervious filter material 11 the brush bristles poke through the holes in the filter material and this continually detach any adhering sludge particles.

This action also assists and augments the discharge of filtrate from the filter body 8.

In modified arrangements, not illustrated, the filter elements 8 may be stationary and provided with lateral outlets leading out of the sludge chamber 2 and the brushes may be rotatable inside the filter bodies. Another alternative which might be adopted would provide revolving brushes as well as counter-rotating filter elements, the relatively independent speed controls would be chosen.

If the sludge chamber 2 is equipped with rotatable filter elements 5, all of these would be driven in the same direction of rotation, preferably in the direction towards an outlet 13 of the sludge chamber 2.

The bottom wall 14 of the sludge chamber 2 is formed by a continuous filter band 15 which is supported on a continuous carrier belt 16, and this combination of filter band 1 5 and carrier belt 1 6 are arranged to move or advance together. This combination is, at the same time, one of the advancing filter belts of the filter belt press.

The bottom wall 14 of the sludge chamber 2 is inclined upwardly from the sludge inlet 3, and the carrier belt 16 with its filter band 1 5 advance from the lower end to the top end of the sludge chamber being carried on supporting rollers 1 7 which run on the rear side of the carrier belt 1 6.

In the upper half of the sludge chamber which is nearer to the outlet 1 3, a further belt 1 8 is mounted above the filter band 15 and engages with the top of the sludge carried thereon. The further belt 18 is a conveyor belt of rubber or like material and provided with flexible, transverse blades or vanes 1 9, and it moves at the same speed as belt 16 with band 15 in the same sense.

As illustrated, the transverse blades 19 carry the sludge along in separate compartments or chambers formed by the belt 18, the filter band 1 5, two adjacent transverse blades 19 and the side walls 7 of the sludge chamber. In this stage it is possible to apply pressure to the sludge because the flexible transverse blades 19 can adapt their shape, and because the space between belt 18 and filter band 15 is substantially wedge-shaped by providing for the belt 1 8 to the convergent relative to filter band 15.

At the sludge chamber outlet 13, the combined filter band 15 and the belt 1 6 assembly is conducted over a return pulley or roller 20, and at this position the sludge is transferred to a second filter band 21 which also advances in combination with an associated carrier belt 22.

The special design of filter bands and carrier belts according to this invention will now be described with reference to Figures 4 to 6, and 10 to 12.

As shown in the detail section of Figure 4, the carrier belts 1 6,22 are made from a plastic or rubber belting material with comparatively high lateral rigidity and a smooth rear face 23,25. On the frontal side, i.e. facing the filter bands 15,21, the carrier belts 1 6,22 are provided with open-top channels 25.26 which are relatively separated by intervening strips or lands 27,28 of belting material. The spaced filter bands 15,21 rest on these intervening lands or strips 27,28 and the filter cake is held between the filter bands 1 5,21.

As shown in Figure 5, the channels 25.26 are inclined relative to the major axis of the carrier belts 1 6,22, preferably at an angle of 45 , and arranged in such a way that the axes of opposed channels cross over or intersect one another.

Figure 6 shows this cross-over and mutual intersection of relatively opposite channels 25,26, and the areas 30 shown in deep black in Figure 6 indicate where the lands or strips 27 of the belt 1 6 intersect with the intervening lands or strips 28 between channels 26 in the opposite belt 22. It will be understood that due to this arrangement, the filter bands 1 5,21 cannot, even under considerable pressure application, be forced into the channels 25,26 if the latter should, at any given time or point happen to touch one another.

As shown by the arrows in Figures 5 and 6, the filtrate emerging on the rear side of the filter bands 21,15 can be diverted and run off on both sides, depending on the chosen gradient of the dewatering stages. This also applies to the second or upper half of the sludge chamber where the upper filter band 15 with its carrier belt 1 6 closes on the filter cake 29 so that the pressure applied to the filter cake 29 effectively precludes any back-flow of filtrate.

Due to the comparatively high lateral rigidity of carrier belts 16,22 it is possible to keep the belts running true throughout the filter belt press by the simple means, as illustrated, by way of example, in Figures 10 and 11, namely by providing trackholding rings or rims or flanges 31,32 at the ends of all supporting, pressing and return rollers of the press. Such simple rings of the kind will effectively prevent skewing of the filter bands and carrier belts since there is no relative movement whatsoever between filter bands 1 5,2 2 on the one hand and carrier belts 1 6,22 on the other.

For precisely the same reason it is now also possible to provide inexpensive but effective lateral seals for the pressure spaces enclosed between the relatively opposed filter bands and carrier belts.

Figures 10 and 12 illustrating various kinds of seals which may be used for this purpose. As shown, generally referenced 33 on both sides of the filter bands may be provided by sealing beads which are secured to the filter bands 15,21 and resiliently deformable to compensate for alterations in the distance between filter bands caused by increasing pressure. One arrangement is illustrated in Figure 10 where a sealing strip or bead 34 of hollow triangular cross section is secured to each lateral edge of each filter band and the sealing beads co-act to provide a lateral seal for the space between the filter bands, the provision of an internal cavity 35 in the bead permits considerable elastic deformation.

Figure 11 shows a modification in this type of lateral sealing device 33, wherein two complementary sealing elements are provided to co-act together.

The lateral sealing means shown in Figure 12 is another variant wherein the seal for each'side of the belt and carrier combination comprises a continuously advancing hollow sealing element which is adapted to be inserted between the filter bands 1 5,21. The sealing element is a flexible tubular or hose-like rubber element of circular cross-section in unstressed condition, and this configuration enables the sealing element 33 to be guided for continuous advancement on both sides of the press over suitable pulleys or similar means.

With reference again to Figure 1, as aforementioned, the sludge 29 is transferred from the outlet 13 of sludge chamber 2 to the second combination assembly of filter band 21 and carrier belt 22 and carried to position 36 where it is introduced into a first, wedge-shaped pressure stage 37. In this stage 37 the arrangement of the lower carrier belt 22, with filter band 21 resting thereon, is supported on rollers 38 which have track-holding rims or flanges and run with a minimum of friction on the smooth rear face of the carrier belt. The upper carrier belt 1 6 with filter band 15 resting thereon is subjected to pressure in the direction towards the filter band 21 by spring-loaded pressing rollers 39, also running on the smooth rearface of the carrier belt.Instead of the rollers 39 suitable similar devices may be provided for the purpose, and, in contrast with all prior arrangements, the rollers 39 may be more closely spaced than previously possible. This is because the filtrate which is squeezed out of the filter cake does not penetrate to the rear side of the carrier belts and cannot, therefore build up forwardly of the squeezing rollers and subsequently return to the filter cake. When the filtrate is squeezed out, it is laterally evacuated through the channels 25 and drains away because of the gradient of the first pressure stage 37.

Due to the foregoing provisions, the invention offers yet another advantage in as much as the large water collecting boxes which had to be provided beneath all de-watering stages in conventional systems may now be safely dispensed with and replaced by simple lateral gutters or drain channels.

Furthermore, it is possible to apply higher pressures even in this first stage because the lateral seals 33 effectively prevent the sludge from being squeezed laterally out of the space between the filter bands even under high pressure.

A deflector roller 40 then conveys and conducts the combined assembly comprising carrier belts 16,22, with filter bands 15,21 and filter cake therebetween into the second pressure stage 41 wherein the previously described arrangement is inverted, in as much as here the elastically biassed pressure roller arrays 39 engage with the plain rear side of carrier belt 22 whilst the plane rear side of carrier belt 16 is supported by supporting rollers 38. The filtrate evacuation method and resulting advantages are however precisely the same.

When the filter cake has passed through the second pressure stage 41 it is ejected at position 42, and the filter bands pass through rinsing or cleaning stations 43,44 whereupon they return to join with their respective carrier belts as shown in Figure 1.

Figure 3 shows a modification according to this invention which differs from the arrangements shown in Figure 1 in that the ejector or discharge position 42 is arranged at a higher level. A deflector roller 45 directs the assembly of filter bands and carrier belts upwards on leaving the second pressure stage 41 so that it passes through a short further pressure stage 46 before it arrives at the ejection point 42. Apart from the additional pressure application stage 46, the advantage of this arrangement resides in the elevated position of discharge of the sludge cake because this allows direct sludge delivery into conveyor tubs or the like. Another advantage arises from the deflection of the carrier belts 1 6,22 with their filter bands 1 5,21 around roller 45 as well as the deflector rollers 47,48 higher up.

These repeated direction changes in the feed path tend to break up the filter cake so that this is easily detached from the filter bands.

Figure 7 illustrates the invention embodied in a much simplified and correspondingly cheaper kind of filter belt press which comprises only one filter band 1 5 with associated carrier belt 16 designed with the same principle as shown in the upper half of the embodiment of Figure 1 and wherein only a light amount of pressure is applied to the sludge by the additional belt 18 with its flexible transversely extending blades 19. Further similar details as aforementioned may be noted from Figure 7.

Figure 8 shows an arrangement according to this invention wherein the bottom of the sludge chamber 2 has two oppositely directed gradients.

One of the filter bodies 5 in the sludge chamber 2 is arranged to serve as a deflector roller for the combined assembly of carrier belt 1 6. The filter band 1 5 is studded with a number of relatively spaced apart rubber rings which also enable a free discharge of filtrate from the sludge through filter band 15 in this region of the sludge chamber 2. In the arrangement according to Figure 8 the pressure application stages 37 and 41 are arranged successively behind one another and have oppositely directed gradients with the additional advantage that the discharge or ejection station 42 is again at a slightly higher lever.

This embodiment of the invention has the further advantage that it provides a substantially longer preliminary de-watering stage for the same overall construction height.

Figure 9 shows an embodiment of the invention wherein the pressure application stages are conducted around a drum 51 of comparatively large diameter, and here the pressing or squeezing roller arrays 39 of the pressure stage 41 are at the same time the supporting rollers for pressure stage 37, thus achieving a particularly compact construction of the apparatus as a whole. With regard to its advantages and manner of operation this plant is similar to the earlier described embodiments.

In all embodiments of the invention, friction problems in pressure-application stages are avoided due to the plain and smooth rear faces of the carrier belts 1 6,22 whilst fast and safe filtrate evacuation is guaranteed in all pressure stages, and friction-free seals can be readily provided for sealing the space between filter bands. Owing to the absence of relative movement between filter bands any aggressive medium may be safely processed.

Further modifications and variations in the illustrated arrangements beyond the described forms of execution will be readily apparent and suggested to the skilled man without departing from the basic principle of the invention.

Claims

1. A filter belt press for de-watering sludge and similar substances, particularly as occurring in water purification plants, wherein continuous filter bands are provided and the sludge is carried along between these bands and de-watered under pressure, characterised in that the press is provided with at least one carrier belt of comparatively high lateral rigidity which advances with the filter band supported thereon, the carrier belt being provided with open-top channels and guide means are provided on rollers for supporting and deflecting the direction of the carrier belt and the filter band.

2. A filter band press according to claim 1, characterised in that the said guide means are track-holding flanges or rims adjacent the roller ends.

3. A filter belt press according to ciaim 2, characterised in that the track-holding rims are rubber rings.

4. A filter belt press according to any preceding claim, characterised in that the channels are mutually parallel and extend in a direction transverse to the length of the carrier belt.

5. A filter belt press according to claim 4, characterised in that the channels extend at an angle which is smaller or larger than 900 relative to the major axis of the carrier belt.

6. A filter belt press according to claim 5, characterised in that the angle is 450.

7. A filter belt press according to any one of the preceding claims, characterised in that it is provided with a preliminary gravitational dewatering stage consisting of a sludge chamber whereof the bottom wall is formed by a carrier belt with an associated filter band.

8. A filter belt press according to claim 7, characterised in that the bottom wall of the sludge chamber slopes upwards from a sludge inlet to a sludge outlet, and filter elements are wholly or partially submerged in the sludge contained in the sludge chamber and provided with filtrate outlets leading from the sludge chamber.

9. A filter belt press according to claim 8, characterised in that the filter elements comprise filter drums and the filtrate outlet extends through the side walls of the sludge chamber.

10. A filter belt press according to claim 8 or claim 9, characterised in that cleaning devices are associated with the filter elements.

11. A filter belt press according to claim 1 0, characterised in that the cleaning devices are brushes mounted internally of the filter element.

12. A filter belt press according to any one of claims 8 to 11, characterised in that the filter elements are rotationally driven.

13. A filter belt press according to claim 12, characterised in that the filter elements rotate in a common direction to advance the sludge towards the sludge outlet.

14. A filter belt press according to any one of claims 8 to 13, characterised in that additional cleaning devices are provided externally of the filter elements.

1 5. A filter belt press according to any one of claims 11 to 14, characterised in that the cleaning devices are brushes.

16. A filter belt press according to claim 1 5.

characterised in that the brushes are driven to rotate in the opposite direction of rotation of the filter elements.

17. A filter belt press according to any one of the preceding claims, characterised in that the bottom wall of the sludge chamber merges contiguously into a preliminary de-watering stage.

1 8. A filter belt press according to claim 1 7, characterised in that a further continuous advancing belt is mounted above the preliminary dc-watering stage to engage with the upper side of the sludge.

1 9. A filter belt press according to claim 18, characterised in that said further belt comprises flexible transverse blades or ribs which are directed towards the filter band.

20. A filter belt press according to any one of the preceding claims, characterised in that it is provided with a further continuous carrier belt associated with a further filter band which, in cooperation with the first combination of carrier belt and filter band form at least one wedge-shaped pressure application stage.

21. A filter belt press according to claim 20, characterised in that two pressure-application stages are provided.

22. A filter belt press according to claim 21, characterised in that the two pressure-application stages extend at an inclination to the horizontal at a gradient.

23. A filter belt press according to claim 22, characterised in that both pressure-application stages slope in the same direction.

24. A filter belt press according to claim 22 or 23, characterised in that the two pressureapplication stages extend in the same direction as the bottom wall of the sludge chamber.

25. A filter belt press according to any one of claims 21 to 24, characterised in that the pressure-application stages are rectilinear stretches along which guide rollers of the uppermost carrier belt are biassed and arranged to act as pressing or squeezing rollers.

26. A filter belt press according to any one of the preceding claims, characterised by the provision of lateral collector means for catching filtrate discharged through the open top channels.

27. A filter belt press according to any one of the preceding claims, characterised in that the filter bands have associated sealing means.

28. A filter belt press according to claim 27, characterised in that the lateral sealing means are elastically deformable sealing beads secured to the filter bands.

29. A filter belt press according to claim 28, characterised in that the sealing beads of mutally opposite filter bands, interengage.

30. A filter belt press according to claim 27, characterised in that the lateral sealing means are independently continuous advancing hollow elements made of rubber or the like.

31. A filter belt press according to any one of the preceding claims 20 to 30, characterised in that the directions of the open top channels in the opposed carrier belts are arranged in such a way that they intersect or cross-over one another in the pressure-application stages.

32. A filter belt press according to any one of the preceding claims 20 to 30, characterised in that the pressure-application stages are conducted during the advancement of the filter band and carrier belt around a drum of comparatively large diameter.

33. A filter belt press according to claim 32, characterised in that the rollers for applying pressure in the second pressure-application stage are supporting rollers of the first pressureapplication stage.

34. A filter belt press for de-watering sludge and similar substances substantially as hereinbefore described with reference to the various embodiments depicted in the accompanying drawings.