Filter sectors for filter discs and disc filters with filter sectors

Abstract

The invention relates to a filter sector (1) for a filter disc (11) or disc filter (10), having a perforated and structured filter plate (2), wherein the filter plate (2) can be pumped. Characterized in that the filter plate (2) comprises at least one arched structure (3) with a polygonal base (4). This leads to an improved separation capacity or separation efficiency.

Description

TECHNICAL FIELD

[0001] The invention relates to a filter segment for a rotating filter disc of a disc filter, comprising at least one perforated and structured filter plate and an inner space of the filter segment, wherein the filter plate can be sucked through the inner space of the filter segment for separating a liquid from a suspension. The invention further relates to a disc filter having a filter segment according to the invention. BACKGROUND

[0002] Disc filters are used for separating a liquid from a suspension and are used in the field of pulp and paper production. In the latter field of application, disc filters can also be used, in particular, for recovering fibrous material from a fibrous suspension.

[0003] Usually, several filter segments form a filter disc, wherein the filter discs in a disc filter are designed to be rotatable. Usually, the filter disc or the filter segments are connected to a hollow shaft, wherein the filter segments can be sucked through the hollow shaft. Due to the suction of the filter segments, the liquid is sucked out of the suspension into the inner space of the filter segments and the solid material, for example fibrous material, is deposited on the filter plates, thus forming a filter cake on the filter plates. The filter cake is removed from the filter segments at the appropriate place in the disc filter, for example with a doctor blade, so that the filter segments are ready for a new filtering process. In general, the filter segments are designed in such a way that a maximum separation performance of the filter segments or a maximum efficiency of the disc filter is achieved. At the same time, the filter segments are mechanical load components with corresponding requirements in terms of rigidity, wherein the filter segments in turn exert a mechanical load on the hollow shaft.

[0004] For example, DE 10 2017 118 050 A1 discloses a filter segment for a disc filter, wherein the filter segment comprises a perforated filter plate having a corrugated profile and the corrugated profile has a specific arrangement of recesses and protrusions. The corrugated profile increases the surface area available for dewatering, thus increasing the efficiency of the disc filter.

[0005] It should be noted that according to the prior art, an increase in filter plate surface area often also means an increase in filter segment mass, and a filter disc with a greater mass also means a greater mechanical load on the hollow shaft. In particular in the case of a retrofit of an existing disc filter, the hollow shaft remains unchanged, but the heavier filter segments after the retrofit lead to a failure of the hollow shaft in the medium or long term.

[0006] US2006261001A1 further discloses a filter sector for a rotary filter disc, wherein a filtrate chamber is formed between a first rigid mesh and a second rigid mesh, the rigid meshes forming a profiled filter wall and having concavities and peaks, each concavity and peak being formed by a multitude of mesh openings of the mesh. Advantageously, a special weaving technique is used to form the concavities and peaks.

[0007] US10894226B2 discloses a filter element of a rotary disc filter, comprising two filter plates, which are perforated and profiled, wherein at least one of the filter plates is wavelike in cross section and each outer side of the filter plates has a protrusion, which is circular or elongated in cross section.

[0008] Finally, DE102017107665A1 discloses a filter disc for a disc filter, wherein the circular filter sectors are formed by filter plates having a multitude of perforated openings. In particular, a filter sector is disclosed, which is formed by a wavelike profiled plate, having flat filter plates and circular recesses thereon. SUMMARY

[0009] It is an object of the present invention to provide a filter sector for a disc filter, which improves the separation performance or increases the efficiency of the disc filter. Another object is to reduce the amount of material used for the filter sector while increasing the efficiency. Finally, the filter sector should also have improved properties of the separated filter cake or fiber mat.

[0010] According to the application, this is achieved in that the filter sector comprises at least one arched structure having a polygonal base. Polygonal base means a substantially planar geometric figure formed by a closed series of segments. Arched structure thus means a shell formed on this base. The term shell means an arched object, the thickness of which is smaller than the remaining dimensions thereof. Preferably, the shell is arched and free of edges (Kanten). Free of edges means the shape of the shell. Since the arched structure itself is porous, edges naturally occur at the pores, which are irrelevant for the shape of the shell. The design of the filter plate with the arched structure according to the application has a positive effect on the separation efficiency, since the filter plate forms an increased surface area by means of the arched structure, which immediately increases the efficiency. Surprisingly, it was found that the formation of the filter plate with the arched structure having a polygonal base has a positive effect on the strength of the filter plate, whereby sufficient filter plate strength or rigidity values are achieved even with less material used on the filter plate. In this way, the filter plate can be produced with a lower weight, so that a filter sector of lower weight is produced. The increase in the surface area of the filter plate has an unexpected synergistic effect. Advantageously, the filter plate according to the application comprises a large number of arched structures according to the application. It is likewise advantageous if the structure of the filter plate can vary at least in local regions. According to the application, the polygonal base of the arched structure is hexagonal.

[0011] An advantageous embodiment of the filter sector is characterized in that the polygonal base of the arched structure is an equilateral hexagon. By designing the base of the arched structure as a hexagon, in particular as an equilateral hexagon, the advantages according to the application are particularly evident. In addition to the increase in the surface area of the filter plate by means of the arched structure, the use of a hexagonal base is particularly advantageous in improving the strength or rigidity of the filter plate, which can further reduce the amount of material used. In particular, a synergistic effect is highlighted, i.e. the efficiency of the filter sector is increased while the amount of material is reduced, with the same strength or rigidity.

[0012] Optionally, the base is designed as a hexagon having six segments, on two opposite segments a saddle surface can be designed, on the other four segments in the form of two opposite ridge surfaces, wherein two segments each form a ridge surface and the ridge surfaces are connected by a saddle surface. Thus, the other four segments of the base lie substantially in one plane, wherein the respective channel of the saddle surface lies between this plane and the interior space. This design of the arched structure, i.e. with a saddle surface on two opposite segments of the base, has a further positive effect on the strength or rigidity of the filter plate. The flow of the liquid in the interior space of the filter sector is preferably also in the direction of the ridge surfaces.

[0013] A further advantageous embodiment of the filter sector is characterized in that the arched structure is oriented towards the interior space of the filter sector, thus appearing convex when viewed from the interior space towards the filter plate. In this case, the filter sector comprises an interior space which is at least delimited by the surrounding filter plate. When the interior space is connected to a source of negative pressure, liquid is drawn through the filter plate from the suspension surrounding the filter sector, forming a filter cake, for example a fiber mat, on the surface area of the filter plate. Advantageously, the height of the arched structure is no more than 25 mm, preferably no more than 10 mm, above the base. Surprisingly, this has a positive effect on the detachment or rolling behavior of the filter cake or fiber mat from the filter sector. In the case of a filter plate designed with a corrugated profile, the direction of the corrugations makes detachment of the filter cake more difficult, since the direction of the corrugations and the direction of rolling of the filter cake or fiber mat diverge during the rolling process, which impedes the rolling process. In contrast, a filter sector with an advantageous arched structure does not form a dominant direction, having a near-isotropic effect, which also means that there is no divergence from the direction of rolling of the filter cake or fiber mat.

[0014] An equally advantageous embodiment of the filter sector is characterized in that the filter plate has perforations with a hydraulic diameter of 0.2 mm to 3 mm, preferably with a hydraulic diameter of 0.4 mm to 0.8 mm, for example 0.6 mm. This ensures a good permeation and retention ratio. Typically, round holes are used, in which case the hydraulic diameter corresponds to the circular diameter. However, perforations of other geometries (elliptical arcs, slots, etc.) with the above-mentioned hydraulic diameter are also possible, wherein the hydraulic diameter is defined as the quotient of the four times the perforation area and the perforation circumference. It is also advantageous for the filter plate to be designed with an open area of 10% to 40%, in particular with an open area of 15% to 30%.

[0015] An advantageous design of the filter sector is characterized in that a segment of the polygonal base of the first arched structure is also a segment of the polygonal base of the second arched structure. Advantageously, a filter plate comprises a large number of arched structures, wherein the individual arched structures are directly adjacent. This means that a segment of the polygonal base of the first arched structure is also a segment of the polygonal base of the second adjacent arched structure. In this way, a dense arrangement of the arched structures can be achieved, which increases the surface area of the filter plate. In addition, the dense arrangement has a positive effect on the strength or stiffness of the structure.

[0016] A particularly advantageous embodiment of the filter sector is characterized in that the polygonal base of the first arcuate structure is formed by segments, wherein each segment of the polygonal base of the first arcuate structure is also formed as a segment of the polygonal base of the arcuate structure surrounding the first arcuate structure. In this particularly dense arrangement of arcuate structures, the first arcuate structure is surrounded by another adjacent arcuate structure at each segment or each side of the polygonal base. This results in a large surface area of the filter plate, while at the same time having an advantageous structural strength or stiffness.

[0017] A further advantageous embodiment of the filter sector is characterized in that the perforated and structured filter plate is an arcuately structured perforated plate. The process of arcuate structuring is disclosed, for example, in EP 0693 008 A1. The perforated plate formed in this way can achieve advantageous arcuate structures, for example, the base is formed as a hexagon, in particular as an equilateral hexagon. Also, the perforated plate formed in this way has very advantageous strength or stiffness properties and allows the provision of a filter sector with a very small material usage.

[0018] In an advantageous embodiment, the filter sector is shaped like a circular arc sector. Usually, a plurality of filter sectors make up a filter disc of a disc filter. The design of the circular arc sector makes the assembly of a filter disc consisting of a plurality of filter sectors particularly simple.

[0019] In a particularly advantageous design, the filter sector is fastened to the circumference of a hollow shaft. The filter plate extends essentially in the radial and circumferential direction of the hollow shaft. On both sides of the inner space of the filter sector, there are arranged filter plates opposite to each other, wherein the arcuate structures of the filter plates opposite to each other are arranged either symmetrically with respect to the inner space or offset by half a base in the radial direction with respect to the hollow shaft with respect to each other. As already explained, the filter sector comprises an inner space which is limited by the surrounding filter plates. When the filter plates opposite to each other are arranged symmetrically with respect to the inner space, the filter plates can be in contact with each other, wherein the arcuate surfaces opposite to each other are in contact with each other. At the contact points of the arcuate surfaces, the opposite filter plates can be connected, for example, by spot welding, which can thus increase the strength of the filter sector.

[0020] When the filter plates opposite to each other are arranged in an offset manner, offset by half a base in the radial direction with respect to the hollow shaft, a mutual contact of the filter plates can be avoided. In this way, flow obstructions of the inner space can be avoided, which is advantageous for the separation performance of the filter sector or the efficiency of the disc filter.

[0021] The present application also relates to a disc filter having a rotating hollow shaft and at least one filter disc, wherein the filter disc comprises a plurality of filter sectors according to the present application. The filter sectors extend substantially in the radial and circumferential direction of the hollow shaft. Furthermore, the filter sectors are arranged on the circumference of the hollow shaft and can be suctioned through the hollow shaft, wherein the liquid separated from the suspension can be fed from the interior space of the filter sectors substantially in the radial direction of the hollow shaft. Radial is to be understood as the radial direction of the hollow shaft. The disc filter with filter sectors according to the present application has advantageous separation performance or higher efficiency, wherein this can be achieved while reducing the material usage.

[0022] A further advantageous embodiment of the disc filter is characterized in that the filter plate comprises a plurality of arch structures adjacent to one another, the base of the arch structures being hexagonal, in particular equilateral hexagonal, wherein the filter plate is oriented with respect to the hollow shaft such that the connecting line of the centers of the opposite segments of the base points substantially towards the hollow shaft. A filter plate with arch structures adjacent to one another, oriented in this way, can advantageously guide the liquid from the interior space of the filter sectors in the direction of the hollow shaft, wherein a direct liquid guidance as far as possible is provided. BRIEF DESCRIPTION OF DRAWINGS

[0023] The present application will now be described with reference to the examples in the accompanying drawings.

[0024] Figure 1 A disc filter according to the prior art is shown.

[0025] Figure 2 A filter sector with a structured filter plate according to the prior art is shown.

[0026] Figure 3 A design of an advantageous filter sector is shown.

[0027] Figure 4 and Figure 5 A filter plate with an advantageous arch structure is shown.

[0028] Figure 6a and Figure 6b Two opposite filter plates with an advantageous arch structure are shown. DETAILED DESCRIPTION

[0029] Figure 1A disc filter according to the prior art is shown. Here, a plurality of filter sectors 1 form a filter disc 11, wherein the filter disc 11 is at least partially immersed in a suspension. The filter sectors 1 are fastened on the circumference of a hollow shaft 12 and extend essentially in the radial and circumferential direction of the hollow shaft 12. The filter sectors 1 can be further sucked by means of the hollow shaft 12, whereby liquid can be separated from the suspension surrounding the filter sectors 1 through the filter plates 2 into the respective interior spaces 13 of the filter sectors 1. The separated liquid is fed into the hollow shaft in accordance with the suction of the filter sectors 1 by means of the hollow shaft 12.

[0030] Figure 2 A filter sector 1 with a perforated and structured filter plate 2 according to the prior art is shown. Here, the filter plate 2 has a corrugated profile, wherein the corrugated profile has recesses and protrusions.

[0031] Figure 3 An advantageous design of a filter sector 1 is shown. The filter sector 1 comprises a perforated and structured filter plate 2, wherein the interior space 13 of the filter sector 1 is at least delimited by the surrounding filter plate 2. According to the invention, the filter plate comprises at least one arch structure 3 with a polygonal base 4. Advantageously, the polygonal base 4 of the arch structure 3 is formed as a hexagon, in particular an equilateral hexagon, wherein the arch structure 3 is oriented towards the interior space 13 of the filter sector 1. Advantageously, several arch structures 3 are arranged next to one another, wherein each segment 5 of the polygonal base 4 of a first arch structure 3 is also formed as a segment of the polygonal base 4 of several arch structures 3 surrounding the first arch structure 3.

[0032] Figure 4 and Figure 5 A filter plate 2 with an advantageous arch structure 3 is shown. The arch structure 3 comprises a polygonal base 4, wherein the polygonal base 4 is an equilateral hexagon. Advantageously, the arch structure 3 forms a height 6 above the base 4 of not more than 25 mm, preferably not more than 10 mm, wherein the filter plate 2 has perforations with a hydraulic diameter of 0.2 mm to 3 mm, preferably perforations with a hydraulic diameter of 0.4 mm to 0.8 mm, for example 0.6 mm. In Figure 4 and Figure 5In this case, several arcuate structures 3 are arranged next to one another, wherein each segment 5 of the polygonal base 4 of the first arcuate structure 3 is also formed as one segment of the polygonal base 4 of several arcuate structures 3 around the first arcuate structure 3. Advantageously, the individual arcuate structures are designed in such a way that two opposite segments 5 are formed as a saddle surface 7 and the other four segments 5 form two opposite ridge surfaces 9, wherein two segments 5 each form one ridge surface 9, which is connected by a saddle surface 7. In this case, the other four segments 5 of the polygonal base 4 lie substantially in one plane, and the respective channel 8 of the saddle surface 7 is arranged between this plane and the interior space 13.

[0033] Figure 6a and Figure 6b Two opposite filter plates 2 of the filter sector 1 are shown. The filter plates 2 have an advantageous arcuate structure 3. In Figure 6a In this case, the viewing direction is parallel to the filter plates. As a result, the interior space 13 of the filter sector 1 is clearly visible, as is the height 6 formed by the arcuate structure 3 above the respective base 4. Figure 6b is a plan view of a portion of the filter sector 1, in which the opposite filter plates 2 and the interior space 13 can be seen. The opposite filter plates 2 are arranged on both sides of the interior space 13. In this case, the arcuate structures 3 of the opposite filter plates 2 are arranged symmetrically about the interior space 13 and the arcuate structures 3 of the opposite filter plates 2 are arranged in mirror-opposite fashion. An advantageous disc filter (not shown) comprises filter sectors in which the filter plates 2 are oriented with respect to the hollow shaft 12 (not shown) in such a way that the connecting line of the centers of the opposite segments 5 of the base 4 of the arcuate structure 3 points substantially towards the hollow shaft 12. Furthermore, the opposite filter plates 2 can be arranged symmetrically or mirror- symmetrically about the interior space 13, wherein in a particularly advantageous arrangement the filter plates 2 are offset by half the base 4 in the radial direction with respect to the hollow shaft 12.

[0034] The invention has a number of advantages. This makes it possible to increase the surface area of the filter plates, while also increasing the strength or rigidity of the filter plates. This improves the separation or efficiency of the filter sector, so that the material usage in the filter sector can be reduced. Likewise, the invention can also improve the separation or rolling behavior of the filter cake from the filter sector.

[0035] List of reference signs

[0036] (1) filter sector

[0037] (2) filter plate

[0038] (3) arcuate structure

[0039] (4) polygonal base

[0040] (5) subsection

[0041] (6) height

[0042] (7) saddle surface

[0043] (8) channel

[0044] (9) ridge surface

[0045] (10) disc filter

[0046] (11) filter disc

[0047] (12) hollow shaft

[0048] (13) interior space

Claims

1. A filter sector (1) for a rotating filter disc (11) of a disc filter (10), comprising at least one perforated and structured filter plate (2) and an inner space (13) of the filter sector (1), wherein, The filter plate (2) can be sucked through the interior space (13) of the filter sector (1) for separating liquid from a suspension, characterized in that the filter plate (2) comprises at least one arched structure (3) with a polygonal base (4), wherein the polygonal base (4) of the arched structure (3) is hexagonal.

2. Filter sector (1) according to claim 1, characterized in that The polygonal base (4) of the arched structure (3) is equilateral hexagonal.

3. Filter sector (1) according to claim 1 or 2, characterized in that The arched structure (3) is oriented towards the interior space (13) of the filter sector (1) and is therefore convex when viewed from the interior space (13) in the direction of the filter plate (2).

4. Filter sector (1) according to claim 1 or 2, characterized in that The height (6) of the arched structure (3) above the base (4) is no more than 25 mm.

5. The filter sector (1) according to claim 4, characterized in that The height (6) of the arched structure (3) above the base (4) is no more than 10 mm.

6. The filter sector (1) according to claim 1 or 2, characterized in that The filter plate (2) has perforations with a hydraulic diameter of 0.2 mm to 3 mm.

7. The filter sector (1) according to claim 6, characterized in that The filter plate (2) has perforations with a hydraulic diameter of 0.4 mm to 0.8 mm.

8. Filter sector (1) according to claim 7, characterized in that The filter plate (2) has perforations with a hydraulic diameter of 0.6 mm.

9. The filter sector (1) according to claim 1 or 2, characterized in that One segment (5) of the polygonal base (4) of a first arched structure (3) is formed at the same time as one segment (5) of the polygonal base (4) of a second arched structure (3).

10. The filter sector (1) according to claim 1 or 2, characterized in that The polygonal base (4) of a first arched structure (3) is formed from several segments (5), wherein each segment (5) of the polygonal base (4) of the first arched structure (3) is also formed as a segment of the polygonal base (4) of several arched structures (3) around the first arched structure (3).

11. Filter sector (1) according to claim 1 or 2, characterized in that The hexagon is formed from six segments (5), wherein two mutually opposite segments (5) are formed as a saddle surface (7) and the other four segments (5) form two mutually opposite ridge surfaces (9), wherein two segments (5) each form a ridge surface (9) and the ridge surfaces (9) are connected by a saddle surface (7).

12. Filter sector (1) according to claim 11, characterized in that The other four segments (5) of the polygonal base (4) lie essentially in one plane and the respective channel (8) of the saddle surface (7) is arranged between the plane and the interior space (13).

13. The filter sector (1) according to claim 1 or 2, characterized in that The structure of the filter plate (2) is varied at least locally.

14. The filter sector (1) according to claim 1 or 2, characterized in that The filter sector (1) is in the shape of an arc segment.

15. The filter sector (1) according to claim 1 or 2, characterized in that The perforated and structured filter plate (2) is a punched plate of arched structures.

16. The filter sector (1) according to claim 1 or 2, characterized in that The filter sectors (1) are fastened on the circumference of a hollow shaft (12) and mutually opposite filter plates (2) are arranged on both sides of the interior space (13), wherein the arched structures (3) of the mutually opposite filter plates (2) are arranged symmetrically with respect to the interior space (13) or offset by half the base (4) in the radial direction with respect to the hollow shaft (12).

17. A disc filter (10) comprising a rotating hollow shaft (12) and at least one filter disc (11), wherein The filter disc (11) comprises a plurality of filter sectors (1) according to any one of claims 1 to 16, which are fastened on the circumference of the hollow shaft (12) and can be pumped through the hollow shaft (12), wherein the liquid separated from the suspension can be transported from the inner space (13) of the filter sector (1) to the hollow shaft (12).

18. The disc filter (10) according to claim 17, wherein The filter plate (2) of the filter sector (1) comprises a plurality of arch structures (3) adjacent to one another, and the filter plate (2) is oriented relative to the hollow shaft (12) such that the connecting line of the centers of the opposite segments (5) of the base (4) of the arch structure (3) essentially points to the hollow shaft (12).

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