Joint-free sealing of filter elements

Abstract

The invention relates to a filter element (1) or a system of filter elements (1) for wet filtration, comprising a sealing edge (6) and at least one seal (16) in a sealing region (12) in the sealing edge. The aim of the invention is to be able to clean the filter element or system less frequently, more quickly and above all more efficiently while complying with the required hygiene regulations. To achieve this aim, a sealing material (16) is inserted in or applied to the sealing region (12) in such a way that the sealing material (16) at least partially thermally and / or chemically bonds with the base material.

Description

[0001] Description

[0002] Seamless sealing of filter elements

[0003] The invention relates to a method for producing a filter plate for wet filtration, comprising a filter frame made of a base material and at least one groove in the filter frame. Furthermore, the invention relates to a filter plate, a system comprising at least two filter plates, and a filter press.

[0004] Wet filtration is a process for separating solids from liquids. A suspension is passed through a filter medium that retains the solids, also called the filter cake, while allowing the purified liquid, also called the filtrate, to pass through. In wet filtration using filter presses, filter elements are used to reduce the residual moisture in the filter cake, further compressing it through pressure. The filter elements have a drainage area to collect the filtrate, as well as a filtrate discharge area for removing the filtrate or for introducing a liquid or gaseous medium for further treatment of the filter cake in the filter chambers. In such filter presses, a plurality of filter elements are arranged one behind the other.

[0005] Filter elements typically comprise a sealing edge in the form of a frame and a centrally positioned filter surface surrounded by the sealing edge on all four sides. The filter elements, or in particular the combination of two filter elements arranged one behind the other, can be designed in different ways.

[0006] The combination of a filter plate and a filter frame refers to two filter elements arranged one behind the other. The filter plate has no recessed chamber, meaning the surface of the drainage nubs or grooves on the filter surface is flush with the sealing edge surrounding the filter surface. To form a filter chamber, the filter plate is assigned a filter frame, which essentially consists only of the sealing edge and has an open area in the center to form a chamber. The chamber is then formed by another filter plate on the other side of the filter frame. This combination is the simplest system for industrial solid-liquid separation.

[0007] Filter elements can also be designed as chamber filter plates, with the filter chamber integrated into the filter element. This filter chamber is created by a recessed arrangement of the filter surface or the drainage nubs or grooves relative to the sealing edge. When two chamber filter plates are placed side by side, a filter chamber is formed between the two chamber filter plates due to the recessed filter surfaces on both sides. Typically, a so-called sealing edge slope is arranged between the filter surface and the sealing edge, which allows the formed filter cake to fall out of the filter chambers more easily when the press is opened.

[0008] Filter elements can also be designed as membrane chamber plates. The membrane chamber plate is a further development of the chamber filter plate, designed to further dewater the filter cake by exerting pressure on it via the membrane, thus shortening long filtration times purely through the pump pressure of the feed pump. The membrane chamber plate also usually has the filter chamber integrated.

[0009] A membrane combination plate is also possible as a filter element. This type of membrane combination plate is essentially a chamber filter plate, but the boundary surfaces of the filter chamber are adapted to the contours of the membranes.

[0010] All these configurations of a filter element are the subject of the present application.

[0011] Certain wet filtration applications with filter presses require a seal between the filter elements, preferably on the opposing flat surfaces of the sealing edge. Various sealing profiles are used for this purpose, such as a round cord or an O-ring, which are installed in a corresponding groove in the sealing surfaces. This is primarily done at openings or recesses that interrupt the flat sealing surfaces of a filter plate. These are usually holes or the filter chamber.

[0012] Installing the sealing profiles, in particular, is labor-intensive and difficult. It is not always possible to guarantee a consistent seal across all areas. Cleaning the filter elements around the seals is also very time-consuming, especially when additional hygiene regulations are important. Germs can easily form in the areas between the grooves and the seals, increasing the cleaning cycles. To achieve optimal cleaning results, the sealing profiles must be removed and reinstalled each time after cleaning.

[0013] Cleaning the filter plates, especially in the area of ​​the seals and in filtration processes where special hygiene regulations apply due to the nature of the filtrate, has therefore been both labor-intensive and time-consuming.

[0014] The object of the present invention is therefore to provide filter elements which can be cleaned less frequently, more quickly and, above all, more efficiently while complying with the required hygiene regulations.

[0015] The object is achieved according to the invention by the independent claims. Advantageous embodiments are the subject of the subclaims.

[0016] The invention is based on the consideration that the formation of gaps between the seal and the groove of the filter elements in particular promotes germ formation, which leads to shorter cleaning cycles. Only because of the formation of germs in the gaps is it necessary to remove, clean, replace, or reinsert the entire seal. The consideration within the scope of the invention was therefore that an external seal inserted into the groove should be dispensed with. Instead, the sealing material should be introduced directly into or onto the sealing area of ​​a sealing edge, namely during the manufacturing process of the seal, namely in such a way that the sealing material bonds thermally and / or chemically with the base material of the sealing edge or the sealing area. This material composite avoids gaps between the seal and the sealing area that could promote germ growth.

[0017] The process for applying or inserting a sealing material onto or into the sealing edge now makes it possible to apply the seal to the planar surface of the sealing edge. In an advantageous embodiment, however, the sealing area is designed as a groove. Such irreversible insertion of the seal onto the sealing edge or into the groove of a filter element can be achieved, for example, by welding or another additive process.

[0018] In a preferred embodiment, the groove is completely filled with sealing material, so that even in the edge area, no gaps remain that could promote germ formation. In an additional or alternative embodiment, the sealing material can also protrude from the groove, so that its cross-section extends beyond the surface of the filter element or the sealing edge.

[0019] After the sealing material has been inserted or applied, the seal can advantageously be reworked using a mechanical and / or thermal process to achieve the desired shape. In particular, it is conceivable for the seal to be ground flush with the surface of the sealing edge, creating a flat surface that, however, exhibits a different elasticity in the area of ​​the seal. Alternatively, the seal can protrude from the surface of the sealing edge and receive the desired contour or cross-sectional profile through mechanical processing.

[0020] The seal is preferably made of an elastomer or a thermoplastic elastomer with a lower Shore hardness than the base material of the filter plate, particularly in the area of ​​the sealing edge. Furthermore, a hardness of 20 Shore A to 50 Shore D according to DIN ISO 815-1 has proven advantageous for the seal. The sealing materials also have a restoring force with a preferred compression set of less than 50%. In filter presses, several filter elements are arranged one behind the other in such a way that a base surface of a sealing edge of a filter element is assigned to a base surface of a sealing edge of an adjacent filter element. In use, these base surfaces of adjacent sealing edges lie essentially flat on one another. In a particularly preferred embodiment, at least one base surface of a sealing edge has a material bead whose position and design is adapted to a seal of the adjacent filter element.When the filter elements are in use, i.e., when these two filter elements are arranged directly on top of or next to each other, the material bead engages with the seal of the adjacent filter element, thus sealing the space between the filter elements. The material bead and the seal can be designed in such a way that the material bead penetrates the seal and deforms it.

[0021] In an advantageous embodiment, the material bead is made of the base material of the filter frame, i.e. it protrudes from it in the form of a molding.

[0022] In a preferred embodiment, the material bead is designed in the form of one or more sealing ridges. In the case of multiple sealing ridges, these can run essentially parallel to one another. The sealing ridges are selected from a material that has a higher hardness than the respective sealing material of the associated and opposite filter plate. The geometries of the ridges can be designed in various ways, from spherical, to flattened, or even pointed at the point where they penetrate the sealing material. The geometry can be specifically adapted to the required internal pressure against which the seal must be protected and the corresponding hardness of the sealing material.

[0023] The advantages achieved by the invention are, in particular, that the firm bond between the seal and the filter element eliminates the need for maintenance, particularly the replacement of the seal. Furthermore, the manufacturing process eliminates gaps between a groove and the seal, thus meeting the highest hygiene standards and requirements. Due to the uniformity of the seal and the possibility of post-processing, a particularly uniform pressure distribution of the sealing profile can be achieved. The invention is further described with reference to the exemplary embodiments illustrated in the drawings. They show:

[0024] FIG. 1 two filter elements arranged one behind the other with a circumferential seal,

[0025] FIG. 2 a system of two adjacent filter elements with a seal, and

[0026] FIG. 3 a system of two adjacent filter elements with a material bead,

[0027] FIG. 4 a system of two adjacent filter elements with two rounded sealing bars,

[0028] FIG. 5 shows a system of two adjacent filter elements with two flattened sealing bars.

[0029] The illustrations in the figures are partly simplified and schematic. Different views of parts may be scaled differently. Identical reference numbers are used for identical or similarly constructed parts.

[0030] An embodiment of two filter elements 1 arranged one behind the other is shown in the embodiment according to FIG. 1. FIG. 1 shows a system comprising a filter plate 2 and a filter frame 4 arranged in front of it. As described in the introduction, the invention and thus also the illustrations in all figures are not limited to the combination of a filter plate 2 with a filter frame 4, but also apply to all conceivable filter elements, in particular chamber filter plates, membrane chamber plates and membrane combination plates. The front, visible filter element 1 in FIG. 1 is designed as a filter frame 4. Behind the filter frame 4, a second filter element 1 is visible as a filter plate 2. This filter plate 2 comprises a sealing edge 6 and a centrally arranged filter surface 8 which is surrounded by the sealing edge 6 on all four sides.Filtrate drainage channels 10 are provided in all corners of the sealing edge 6 of the filter frame 4 and the filter plate 2, through which the filtrate can drain. However, it is also possible to provide a filtrate drainage channel 10 only in certain corners. For this purpose, corresponding holes 11 are provided in the filter frame, which connect the filtrate chamber to the filtrate drainage channel 10 and through which the filtrate can drain.

[0031] The filter frame according to FIG. 1 has a sealing area 12 surrounding the sealing edge 6 in the form of a groove 14 filled with a sealing material 16. Additionally, a groove 14 with a sealing material 16 is also provided around each filtrate drainage channel 10. This seals each filtrate drainage channel 10 individually and also the filter surface 8 or the filter chamber to the outside.

[0032] The embodiments according to FIG. 2 and FIG. 3 show two adjacent filter elements 1, again as an example in the form of a filter plate 2 and a filter frame 4, in cross-section A. FIG. 2 and FIG. 3 are not an exact cross-section of FIG. 1 but show alternative embodiments that differ in particular in the positioning and design of the seals.

[0033] Even though the filter elements 1 are shown spaced apart from one another for clarity, the base surfaces 18 of the sealing edges 6 lie essentially directly on top of one another during use, so that the seals 16 are in direct contact with the adjacent filter element 1. Even though in the exemplary embodiments according to FIGS. 2 and 3, only one filter element 1 shows a seal 16 on both sides, it may also be possible for the other filter element 1 to have the seals 16, or for each filter element 1 to have a seal 16 on only one or both sides. This also applies to the material bead 20, which will be described later.

[0034] In the exemplary embodiment according to FIG. 2, the filter plate 2 has two grooves 14 in the sealing edge 6, both of which are completely filled with a sealing material 16 in such a way that the seal 16 protrudes beyond the base surface 18 of the sealing edge 6. The adjacent filter frame 4 in this exemplary embodiment has no groove and no seal, but rather shows a planar base surface 18 of the sealing edge 6. When the two filter elements 1 are in use, the two base surfaces 18 of the sealing edges 6 lie directly on one another (in the illustration), so that the protruding seal 16 of the filter plate 2 presses against the planar base surface 18 of the filter frame 4 and seals the space between the two filter elements 1. The restoring force of the sealing material 16 makes this process repeatable, i.e. the filter elements 1 can be moved apart and together without restricting the sealing effect.

[0035] The seal 16 is designed slightly differently in the embodiment according to FIG. 3. In contrast to FIG. 2, the seal 16 does not protrude, but is flush with the base surface 18 of the sealing edge 6 of the filter plate 2. Alternatively, the seal 16 can also be designed with a slight recess from the base surface 18. For this purpose, the filter frame 4 includes a material bead 20 in the sealing edge, such that the material bead 20 engages or dips into the seal 16 of the adjacent filter plate 2 when the filter elements 1 are moved together. This achieves not only the sealing effect through compression when the filter elements 1 are pressed together, but also a positive seal.

[0036] A similar system to that shown in FIG. 3 is shown in the embodiments shown in FIG. 4 and FIG. 5. The difference is that the material bead 20 shown in FIG. 3 is now designed as two parallel sealing ridges 22 with adjacent displacement zones 24. The sealing ridges 22 are rounded in the embodiment shown in FIG. 4, while they are flattened in the embodiment shown in FIG. 5. Theoretically, tapered sealing ridges 22 are also conceivable, or combinations of different designs within a filter plate.

[0037] The hard, protruding sealing ribs 22 penetrate the soft, planar sealing material 16 on the opposite side, thereby creating a type of positive fit by displacing the sealing compound between the sealing ribs 22. This is achieved by the closing force of the filter press, i.e., by pressing the filter elements together. In this case, the sealing material 16 penetrates in particular into the displacement zones 24, which are arranged laterally next to each sealing rib 22. In the illustrated embodiments according to FIGS. 4 and 5, the displacement zones 24 even penetrate into the base area 18, thus forming a recess. The restoring force of the sealing material 16 enables a seal between the filter elements 1 that can be repeated many times.

[0038] List of reference symbols

[0039] 1 filter element

[0040] 2 filter plate

[0041] 4 filter frames

[0042] 6 Sealing edge

[0043] 8 filter area

[0044] 10 Filtrate drain channel

[0045] 12 Sealing area

[0046] 14 grooves

[0047] 16 Seal / sealing material

[0048] 18 floor space

[0049] 20 material beads

[0050] 22 Sealing bar

[0051] 24 Displacement zone

Claims

Claims 1. A method for producing a filter element (1) for wet filtration comprising a sealing edge (6) made of a base material and at least one sealing region (12) in the sealing edge (6), wherein sealing material (16) is introduced into or applied to the sealing region (12) in such a way that the sealing material (16) bonds at least partially thermally and / or chemically to the base material.

2. A method for producing a filter element (1) according to claim 1, characterized in that the sealing area (12) is designed as a groove (14).

3. A method for producing a filter element (1) according to claim 2, characterized in that the sealing material (16) essentially completely fills the groove (14) and / or protrudes from the base surface (18) of the sealing edge (6).

4. A method for producing a filter element (1) according to one of claims 1 to 3, characterized in that the sealing material (16) is subsequently reworked by a mechanical and / or thermal manufacturing process.

5. Filter element (1) for wet filtration comprising a sealing edge (6) and at least one seal (16) in a sealing area (12) in the sealing edge (6), manufactured according to one of claims 1 to 4.

6. Filter element (1) for wet filtration according to claim 5, characterized in that the sealing material (16) is an elastomer or a thermoplastic elastomer.

7. Filter element (1) for wet filtration according to claim 5 or 6, characterized in that the hardness of the sealing material (16) according to DIN ISO 815-1 is between 20 Shore A and 45 Shore A.

8. System comprising at least two filter elements (1) for use in the wet filtration of a filter press, with at least one filter element (1) according to one of claims 5 to 7 and wherein at least one filter element (1) has a material bead (20) in the region of the sealing edge (6), which is adapted in position and design to the sealing material (16) of the adjacent filter element (1), such that when the filter elements (1) are in use, the material bead (20) engages in the sealing material (16) of the adjacent filter element (1).

9. System comprising at least two filter elements (1) according to claim 8, characterized in that the material bead (20) is formed from the base material of the sealing edge (6).

10. Filter press for wet filtration with a number of filter elements (1) according to one of claims 5 to 7 and / or a system of filter plates (1) according to one of claims 8 to 9.

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