Filter candle with reinforced collar

Abstract

The present invention relates to a filter element, in particular a filter candle for filtering exhaust gases or process gases, having a filter body that is closed at one end and open at its opposite end, wherein an outwardly projecting collar is formed on the open end of the filter body and the filter body is divided into at least a collar portion containing the collar and a filter portion connected to it, characterized in that the collar portion has a higher O-ring strength than the filter portion, wherein the O-ring strength is determined as defined in the description. The invention further relates to a method for producing such a filter element and to its use and further to the use of a collar portion having a higher O-ring strength than the filter portion for such a filter element.

Description

[0001] The present invention relates to a filter element, in particular a filter candle for filtering exhaust gases or process gases, comprising a filter body that is closed at one end and open at its opposite end, wherein an outwardly projecting collar is formed on the open end of the filter body and the filter body is divided into at least one collar section containing the collar and a filter section connected to the collar. The invention further relates to a method for producing such a filter element and its use, as well as to the use of a collar section with a higher O-ring strength than the filter section for such a filter element.

[0002] Process or exhaust gases occur in a wide variety of industrial sectors, for example exhaust gases from combustion plants, gas turbines, waste incineration plants, and combustion engines. Due to environmental, safety, and health regulations, such process or exhaust gases, often referred to as raw gases, must be mechanically and, if necessary, catalytically treated. For the purification of process or exhaust gases, which usually occur as hot gases, filter elements are known from the state of the art. These filter elements are used to largely remove toxic pollutants contained in the raw gas by means of catalysis and / or solid particles or dust. Such filter elements are often so-called filter candles, which can be part of a larger filter module or filter system. Within such a filter module, the filter candles are often suspended at one end.

[0003] For a variety of reasons, particularly for process-related reasons, long filter elements are desirable, for example, with a length of several meters. This is because increasing filter element length allows for higher filter performance, for example. To obtain such long filter elements, it is known to divide a filter body of a filter element, which defines a longitudinal direction, into several essentially tubular filter body elements along the longitudinal direction. The filter body elements are connected in pairs at their mutually facing end sections, so that, in particular, a hollow-cylindrical filter candle body is formed.

[0004] In DE 87 15 130, the connection is achieved by pushing the filter body elements into each other at the ends and additionally gluing them together. Since the filter element is suspended during operation and the gravitational force acts parallel to its longitudinal direction, such an adhesive connection is subject to high mechanical stress due to the weight of the filter body elements. This can lead to the filter body elements breaking off and / or falling off.

[0005] In EP 0 730 896 A2, the connection is achieved by screwing the filter body elements together using interacting internal and external threads. Such a screw connection is relatively stable and will not come loose, or only with great difficulty, even if the filter element is suspended. However, a screw connection alone cannot ensure that the separation gap between the screw-connected filter body elements is sealed in such a way that no fluids can penetrate from an outer area of ​​the filter element into the interior of the filter element and / or escape from the interior to the outer area. However, this is necessary to achieve high filter performance.

[0006] To overcome these disadvantages, EP 3 448 542 B1 proposes screwing several filter body elements together and additionally gluing them in the screw connection area. This allows filter candles of, for example, 6 meters in length to be created.

[0007] Although this makes it possible to provide very long filter elements with correspondingly good filter performance, it has been shown in practice in some cases that precisely because of the great length and the associated higher weight, greater mechanical stress can be found in the collar area of ​​the filter candles, where the filter candles are typically suspended in the filter module. Added to this is the additional weight caused by adhering dust. If fluctuating exhaust gas velocities occur during operation, mechanical vibrations can occur in the filter candles, which puts additional strain on the collar area. This is particularly true for systems in which the filter candles are blown from the side. In individual cases, the strain can be so great that cracks appear in the collar area or the filter candle may even break in the collar area.

[0008] To address this problem, hot gas filters with a higher bulk density have been offered on the market, for example, by using a higher fiber content. However, this has disadvantages in terms of filter performance because it increases the differential pressure, which increases operating costs.

[0009] The invention is therefore based on the object of providing a filter element of the type mentioned at the outset which has a higher stability and mechanical load-bearing capacity even with great lengths of the filter element and is more resistant to the occurrence of cracks, particularly in the collar area.

[0010] This object is achieved according to the invention by a filter element, in particular a filter candle for filtering exhaust gases or process gases, with a filter body which is closed at one end and open at its opposite end, wherein an outwardly projecting collar is formed on the open end of the filter body and the filter body is divided into at least one collar section containing the collar and a filter section connected to it, wherein the filter element is characterized in that the collar section has a higher O-ring strength than the filter section, wherein the O-ring strength is determined as defined in the description.

[0011] The basic idea of ​​the invention is to make the collar area more mechanically stable than the rest of the filter element and thus more resistant to the aforementioned stresses. This can be achieved by various measures, such as • Selection of a higher density of the material of the collar section compared to the material of the filter section, • Selection of a material with higher tensile strength in the collar section compared to the material of the filter section, • Setting a different flocculation size during the vacuum forming process of the collar section compared to the material of the filter section, • Selection of a higher filler quantity for the material of the collar section compared to the material of the filter section, • Selection of a higher fiber content for the material of the collar section compared to the material of the filter section and / or • Selection of a fiber material with higher tensile strength for the collar section material compared to the filter section material.

[0012] Regarding the possibility of setting a different flocculation size during the vacuum forming process of the collar section compared to the material of the filter section, this can be achieved by a lower solid content in the suspension. If less solid in 1 m 3 When flocculation is carried out with water, the resulting flocculation size is smaller. This is also used in the paper industry. Details can be found in "E. Gruber: Paper Chemistry, Lecture Notes for the Paper Technology Course (Karlsruhe)," version 2011-12, page 12-1.

[0013] The O-ring strength is determined in the context of the present invention in the manner disclosed in the examples section below.

[0014] In contrast to the solution proposed in EP 3 448 542 B1, the collar area can be designed not to be the same length as the other filter body elements, but to be significantly shorter, for example only with a length of around 10 to 100 cm. In this case, a material can be selected for the collar area which is primarily designed for mechanical resilience and therefore has lower or possibly hardly any appreciable filter performance, since with the short collar section the loss in filter performance relative to the overall length of the filter candle is not so significant. In principle, it is sufficient if the collar section has a length that the collar protrudes above the perforated plate and there is still sufficient length available below the perforated plate for a connection to the filter section, such as a screw connection between these two components.

[0015] In other words, the collar area can be formed separately, which means you are not tied to the bulk density of the rest of the filter element, for example. The collar area can therefore be formed with a significantly higher bulk density, for example by using a higher fiber content, which increases strength. It is also possible to specifically use different raw materials in the collar area than in the filter area, such as chopped glass fibers or chopped continuous aluminum oxide fibers. These fibers are cost-intensive and, in the solution according to the invention, are only needed in the area of ​​greatest load. If the collar has a higher bulk density, the differential pressure is also higher here, but this is not so significant due to the collar's small proportion of the total length of the filter candle. The length of the collar section preferably accounts for 3 to 30% of the total length of the filter element.For example, for a filter candle with a length of 3 meters, the collar section can have a length of 10 cm to 1.00 m.

[0016] The raw gases filtered with the filter element according to the invention can, in principle, be exhaust gases or process gases at a wide range of temperatures. However, the filter element according to the invention is particularly suitable for filtering exhaust gases or process gases with temperatures up to 750°C.

[0017] In an advantageous embodiment of the filter element according to the invention, the collar section has an O-ring strength that is at least 3% higher than the filter section, in particular by 3% to 50%, preferably by at least 4%, and more preferably by at least 5%. This allows for particularly high stability compared to filter elements in which the collar and filter body are made of the same material.

[0018] It is further preferred that the collar section has an O-ring strength that is at least 35 N higher than the filter section, in particular by 35 to 200 N, preferably by at least 40 N, more preferably by at least 45 N higher.

[0019] Preferably, in the filter element according to the invention, the O-ring strength is related to the same wall thickness in the collar section and filter section.

[0020] In an advantageous development of the filter element according to the invention, the filter section is divided into at least two interconnected sections. This facilitates the transport of particularly long filter elements, which are then assembled at the destination.

[0021] Within the scope of the present invention, the connection between the collar section and the filter section and / or the sections of the filter section to one another is realized by means of internal and external threads formed on their adjacent end sections and corresponding to one another, an adhesive bond, a plug connection optionally secured with pins, and / or by means of a bayonet lock. In this case, the collar section and the filter section and / or the sections of the filter section can further preferably be additionally adhesively bonded to one another in their contact areas using an adhesive. The adhesive bond further increases the stability of the connection. Furthermore, the adhesive bond ensures a fluid-tight connection and thus high filter performance.

[0022] The internal and external threads are preferably trapezoidal, round, and / or rectangular threads. Trapezoidal threads have a relatively high friction and can therefore be designed to be self-locking, preventing them from loosening on their own. Round threads are relatively durable because they do not have delicate edges. The internal and external threads can each have a length of 50 to 200 mm in the longitudinal direction of the filter element.

[0023] In the filter element according to the invention, the filter element can furthermore have the shape of a filter candle with a substantially hollow-cylindrical filter candle body, the closed end of which is in particular hemispherical in shape.

[0024] In the filter element of the present invention, the collar can be formed so as to project radially outwards, in particular as a substantially cylindrical collar or a substantially conical collar that tapers towards the filter section. The filter element can be attached to a suspension device of a filter module via the collar. Due to the special design of the filter element as a filter candle, raw gas to be cleaned can flow from a raw gas chamber through the filter candle body into the interior of the filter candle during operation of the filter element. In this process, the raw gas is largely freed of dust particles and / or pollutants and can then leave the interior of the filter candle at its open end and flow into a clean gas chamber.

[0025] In an advantageous embodiment of the filter element, the collar section and / or the filter section can be formed as a vacuum-formed part, in particular as a fired or unfired vacuum-formed part containing inorganic fibers, such as mineral wool, glass fibers, aluminum silicate wool, alkaline earth silicate wool, and / or polycrystalline high-temperature wool. The inorganic fibers are preferably selected from the group comprising or consisting of aluminum silicate wool, alkaline earth silicate wool, polycrystalline wool, mineral fibers, silica fibers, glass fibers, basalt fibers, ceramic fibers, or mixtures thereof. This vacuum-forming technique also allows the production of relatively complex molded parts. If desired, at least one catalyst can also be incorporated into the vacuum-formed part. Within the scope of the invention, however, the filter element can also be catalyst-free.

[0026] In addition to the aforementioned fiber materials, the collar section and / or the filter section may contain at least one filler, preferably selected from the group comprising or consisting of alumina, quartz sand, silica, mullite, sillimanite, andalusite, silicon carbide, spinel, barium sulfate, boron carbide, or mixtures thereof. However, the collar section and / or the filter section may also be manufactured without filler.

[0027] Furthermore, the collar section and / or the filter section can contain at least one binder. The binder can contain starch, starch derivatives, or cellulose derivatives such as cellulose ethers, as well as at least one colloidal dispersion, preferably a silica sol. In principle, all conventional forming processes, such as injection molding and vacuum forming, can be used to form the filter body, with vacuum forming being preferred, especially to achieve higher porosity.

[0028] In an advantageous embodiment of the filter element, a catalyst can be contained at least in the material of the filter section, wherein in particular the content of catalyst in the material of the collar section is lower than in the filter section, wherein preferably the material of the collar section does not contain a catalyst.

[0029] Catalysts that are particularly suitable for the decomposition of toxic gases, such as nitrogen oxides, are known to those skilled in the art. Suitable catalysts for this purpose are known to those skilled in the art. These are based on metal compounds, for example, selected from the group comprising or consisting of platinum, palladium, ruthenium, aluminum, tungsten, titanium, vanadium, and mixtures thereof, in particular comprising or consisting of titanium and vanadium, and optionally tungsten.

[0030] The filter element can be impregnated with a catalyst solution on the inside and / or outside, preferably on the inside. Impregnation can be carried out, for example, by spraying, brushing, coating, or the like with dissolved or dispersed metal compounds of the aforementioned type. Furthermore, the catalyst can also be introduced into the suspension from which the filter element is produced during the molding process. These possibilities are described, for example, in WO 2021 / 245080 A1.

[0031] The catalyst solution used contains at least one solvent and at least one metal compound dissolved or dispersed in the at least one solvent. Suitable solvents include all solvents capable of dissolving or dispersing the suitable metal compounds. Protic solvents such as water, alcohols, and mixtures thereof are preferably used in the present invention. Particularly preferred solvents are water, methanol, ethanol, or mixtures thereof. Furthermore, the catalyst solution may contain other common auxiliaries, such as dispersants and / or emulsifiers.

[0032] In the filter element according to the invention, the filter body can have a length of 1 to 6 m, preferably 2 to 6 m, and / or the collar section can have a length of 10 to 100 cm, preferably 12 to 50 cm, more preferably 15 to 30 cm and / or the sections of the filter section can each independently have a length of 0.5 to 4.5 m, preferably 1.0 to 4.0 m.

[0033] In the filter element of the present invention, the length of the collar section can be 1.5 to 30% of the length of the entire filter body, preferably 1.8 to 25%, particularly preferably 2 to 20%. Particularly preferred specific embodiments are a collar of 15 cm (=2.5%) for a 6 m long filter element, a collar of 15 cm (=3.75%) for a 4 m long filter element, and a collar of 15 cm (=7.5%) for a 2 m long filter element. The stated lengths of the filter candles are furthermore preferably understood with a deviation of approximately + / -10%.

[0034] The filter body can have an outer diameter of 30 to 300 mm and / or a wall thickness of 5 to 30 mm, preferably 10 to 25 mm, wherein the wall thickness of the collar section outside the actual collar is substantially equal to the wall thickness of the filter section.

[0035] In the filter element according to the invention, it is further preferred that the material of the filter body has a porosity of 50 to 90%, determined according to DIN EN 993-1 - 2019-03, preferably greater than 70%. This ensures high filter performance while maintaining sufficient mechanical stability.

[0036] The filter element according to the invention is particularly preferably characterized in that the porosity value of the filter body material in the collar section is at least 10% lower in absolute terms than in the filter section, preferably at least 20% lower in absolute terms. This allows the stability in the collar section to be significantly increased without noticeably reducing the filtering performance of the entire filter element, especially since the collar is partially secured in a holder during operation anyway, so that no gas filtration can take place in this area.

[0037] The object mentioned at the outset is further achieved within the scope of the present invention by a method for producing a filter element according to the invention, in which a filter body which is closed at one end and open at its opposite end is formed by connecting a collar section at the open end of the filter body with an outwardly projecting molded-on collar at the end opposite the collar to a filter section, wherein the collar section has a higher O-ring strength than the filter section, wherein the O-ring strength is determined as defined in the description.

[0038] The present invention further relates to the use of a collar section with a higher O-ring strength than the filter section, for a filter element with a filter body which is closed at one end and open at its opposite end, wherein an outwardly projecting collar is formed on the open end of the filter body, in particular for a filter element according to the invention.

[0039] Finally, the invention also relates to the use of a filter element according to the invention for the filtration of exhaust gases or process gases, in particular in the form of a filter candle.

[0040] The invention particularly relates to the following embodiments: 1. Filter element, in particular a filter candle for filtering exhaust gases or process gases, with a filter body which is closed at one end and open at its opposite end, wherein an outwardly projecting collar is formed on the open end of the filter body and the filter body is divided into at least a collar section containing the collar and a filter section connected to it, characterized in that the collar section has a higher O-ring strength than the filter section, wherein the O-ring strength is determined as defined in the description. 2. Filter element according to embodiment 1, characterized in that the collar section has an O-ring strength that is at least 3% higher than the filter section, in particular by 3% to 50%, preferably by at least 4%, more preferably by at least 5% higher. 3. Filter element according to embodiment 1 or 2, characterized in that the collar section has an O-ring strength that is at least 35 N higher than the filter section, in particular by 35 to 200 N, preferably by at least 40 N, more preferably by at least 45 N higher. 4. Filter element according to one of the preceding embodiments, characterized in that the O-ring strength is related to the same wall thickness in the collar section and filter section. 5. Filter element according to one of the preceding embodiments, characterized in that the filter section is divided into at least two interconnected sections. 6. Filter element according to one of the preceding embodiments, characterized in that the connection between the collar section and the filter section and / or the sections of the filter section to one another is realized by means of internal and external threads formed on their adjacent end sections and corresponding to one another, an adhesive bond, a plug connection optionally secured with pins and / or by means of a bayonet lock. 7. Filter element according to embodiment 6, characterized in that the collar section and the filter section and / or the sections of the filter section are additionally glued to one another in their contact areas by means of an adhesive. 8. Filter element according to one of the preceding embodiments, characterized in that the filter element has the shape of a filter candle with a substantially hollow cylindrical filter candle body, the closed end of which is in particular hemispherical. 9. Filter element according to one of the preceding embodiments, characterized in that the collar is formed so as to project radially outwards, in particular as a substantially cylindrical collar or a substantially conical collar which tapers in the direction of the filter section. 10. Filter element according to one of the preceding embodiments, characterized in that the collar section and / or the filter section are designed as a vacuum formed part, in particular as a fired or unfired vacuum formed part containing mineral wool, glass fibers, aluminum silicate wool, alkaline earth silicate wool and / or polycrystalline high-temperature wool. 11. Filter element according to one of the preceding embodiments, characterized in that a catalyst is contained at least in the material of the filter section, wherein in particular the content of catalyst in the material of the collar section is lower than in the filter section, wherein preferably the material of the collar section does not contain any catalyst. 12. Filter element according to one of the preceding embodiments, characterized in that the filter body has a length of 1 to 6 m, preferably 2 to 6 m, and / or the collar section has a length of 10 to 100 cm, preferably 12 to 50 cm, more preferably 15 to 30 cm and / or the sections of the filter section each independently have a length of 0.5 to 4.5 m, preferably 1.0 to 4.0 m. 13. Filter element according to one of the preceding embodiments, characterized in that the length of the collar portion is 1.5 to 30% of the length of the entire filter body, preferably 1.8 to 25%, particularly preferably 2 to 20%. 14. Filter element according to one of the preceding embodiments, characterized in that the filter body has an outer diameter of 30 to 300 mm and / or a wall thickness of 5 to 30 mm, preferably of 10 to 25 mm, wherein the wall thickness of the collar section outside the actual collar is substantially equal to the wall thickness of the filter section. 15. Filter element according to one of the preceding embodiments, characterized in that the material of the filter body has a porosity of 50 to 90%, determined according to DIN EN 993-1 - 2019-03, preferably greater than 70%. 16. Filter element according to one of the preceding embodiments, characterized in that the value of the porosity of the material of the filter body in the collar section is absolutely at least 10% lower than in the filter section, preferably absolutely at least 20%. 17. Filter element according to one of the preceding embodiments, characterized in that the higher O-ring strength of the collar section is adjusted by • Selection of a higher density of the material of the collar section compared to the material of the filter section, • Selection of a material with higher tensile strength in the collar section compared to the material of the filter section, • Setting a different flocculation size during the vacuum forming process of the collar section compared to the material of the filter section, • Selection of a higher filler quantity for the material of the collar section compared to the material of the filter section, • Selection of a higher fiber content for the material of the collar section compared to the material of the filter section and / or • Selection of a fiber material with higher tensile strength for the collar section material compared to the filter section material. 18. A method for producing a filter element according to any one of embodiments 1 to 17, wherein a filter body which is closed at one end and open at its opposite end is formed by connecting a collar portion at the open end of the filter body with an outwardly projecting molded-on collar at the end opposite the collar to a filter portion, characterized in that the collar portion has a higher O-ring strength than the filter portion, the O-ring strength being determined as defined in the description. 19. Use of a collar portion having a higher O-ring strength than the filter portion for a filter element having a filter body which is closed at one end and open at its opposite end, wherein an outwardly projecting collar is formed on the open end of the filter body, in particular for a filter element according to one of embodiments 1 to 17. 20. Use of a filter element according to one of embodiments 1 to 17 for the filtration of exhaust gases or process gases, in particular in the form of a filter candle.

[0041] The invention is explained in more detail below using exemplary embodiments and comparative examples: Examples:

[0042] In the following design and comparison examples, collar sections for filter elements with identical geometries were produced from different compositions. The dimensions of the collar sections were as follows: Outer diameter [mm]: 150 Inner diameter [mm]: 110 Wall thickness [mm]: 20 Length [mm]: 100

[0043] The following raw materials were used: Fiber 1: Alsitra NCK; RATH Mönchengladbach, Krefelder Str. 680 / 682, 41066 Mönchengladbach; NCK, sieve size of the chopping system 50 mm Fiber 2: Altra B72 C25; RATH Mönchengladbach, Krefelder Str. 680 / 682, 41066 Mönchengladbach Filler: Martoxid DN-206; Huber Advanced Materials, Martinswerk GmbH, Kölner Str. 110, 50127 Bergheim Binder: Köstrosol 1540 KD; Chemiewerk Bad Köstritz GmbH, Heinrichshall 2, 07586Bad Köstritz, Flocking aids: Solvitose PLV (Avebe); Avebe, Prins Hendrikplein 20, 9641 GK Veendam, Netherlands

[0044] The collar sections for the filter elements were produced by mixing the raw materials together to form a slurry and then forming them into blanks on a vacuum forming machine. To do this, the fiber was first dispersed in the water using stirring tools and then the fillers and binder were added. After the fillers and binder were homogeneously introduced into the suspension by further stirring, the flocculating agent was added. This flocculating agent was then stirred for 8 minutes so that it could perform its task of forming flocculates. This is because the flocculating agent has to change from a solid to a dissolved / partially dissolved state. The stirring times in the previous steps only need to be long enough to achieve the required effect of dispersing and homogenizing. Stirring for too long during these steps is not possible because the solids are insoluble, inorganic solids.After the flocculation time has been reached, the finished suspension is drained into the forming tank. Further details on the preparation are described in DE 10 2021 114 190 A1, particularly in sections

[0013] to

[0024] . The compositions of the individual experiments are summarized in the following table: Indication in parts by weight Fiber 1 Fiber 2 filler binder Flocking aids Water Weight [kg] Experiment 1(cf.) 1 0 0 0,3 0,07 260 0,3 Experiment 2 (Experiment) 1 0 0 0,3 0,07 130 0,28 Experiment 3(cf.) 1 0 0,15 0,3 0,07 130 0,29 Experiment 4(Experiment) 1 0 0,3 0,3 0,07 130 0,32 Experiment 5(cf.) 0 1 0 0,3 0,07 260 0,16 Experiment 6(Experiment) 0 1 0 0,3 0,07 130 0,18

[0045] For the pairings, tests 1 and 2, 3 and 4, and 5 and 6 represent the comparison between conventional material for the collars (1, 3 and 5) and the inventive material (2, 4 and 6) with a comparable formulation but increased O-ring strength. The pairings are based on the following test strategy: Explanation Attempt 1 without filler, different floc size Attempt 2 without filler Attempt 3 with filler Attempt 4 more filler Attempt 5 without filler, other fiber, other floc size Attempt 6 without filler, other fiber

[0046] The tables above show that different weights were achieved in tests 5 and 6 due to the different fibers. The flocculation size was adjusted by the water-to-solids ratio. While 260 units of water were used in tests 1 and 5, 130 units were used in the other tests. This results in a different flocculation size. The flocculation is generally larger with this fiber because the fiber is more stable and is not crushed as much with the same mixing times. This explains the lower weight.

[0047] The O-ring strength was determined on the collars produced as follows: The testing machine is a ZwickRoell zwickiLine Z2.5 TN. The test jaws, into which the specimens are inserted, have a horizontal width of 60 mm and a depth of 60 mm, with a radius of 92.5 mm across the width into which the specimen is inserted.

[0048] The specimens, which are 100 mm long, are placed centrally in the testing machine and the test program is started. The test program sequence is as follows: 1. The test jaws close until a pre-pressure of 1.5N is reached on the test specimen. 2. The test jaws move together at a speed of 200 mm / min until the component breaks.

[0049] The force applied is recorded throughout the entire test procedure. The maximum force encountered is defined as the O-ring strength.

[0050] The specimens are inserted in such a way that they are only subjected to radial loading in the vertical direction. No external loading is applied in the longitudinal direction or from any other directions other than the vertical radial loading.

[0051] The following results were obtained: Pre-load [N] Test speed [mm / min] O-ring strength[N] D ORing (%) Δ ORing (abs) Attempt 1 1,5 200 670 Attempt 2 1,5 200 720 6,94% 50 Attempt 3 1,5 200 805 Attempt 4 1,5 200 877 8,21% 72 Attempt 5 1,5 200 448 Attempt 6 1,5 200 572 21,68% 124

[0052] The results show that the O-ring strength of the collar sections can be increased using the various options shown, allowing the collar section to be specifically reinforced compared to the respective comparison example. The remaining part of the filter element, i.e., the actual filter body, can then be manufactured, for example, from the formulation of the respective comparison example. This has the advantage that, for example, the thermal expansion behavior of the collar and filter section is very similar due to the otherwise high similarity in the formulation, and thermally induced material stresses between the collar and filter section can be kept to a minimum. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] DE 87 15 130

[0004] EP 0 730 896 A2

[0005] EP 3 448 542 B1 [0006, 0014] WO 2021 / 245080 A1

[0030] DE 10 2021 114 190 A1

[0044] Cited non-patent literature

[0000] E. Gruber: Paper Chemistry, Lecture notes for the Paper Technology course (Karlsruhe)“, Version 2011-12, page 12-1

[0012] DIN EN 993-1 - 2019-03

[0035]

Claims

[1] Filter element, in particular a filter candle for filtering exhaust gases or process gases, with a filter body which is closed at one end and open at its opposite end, wherein an outwardly projecting collar is formed on the open end of the filter body and the filter body is divided into at least one collar section containing the collar and a filter section connected to the collar, characterized by that the collar portion has a higher O-ring strength than the filter portion, wherein the O-ring strength is determined as defined in the description. [2] Filter element according to claim 1, characterized by that the collar section has an O-ring strength that is at least 3% higher than the filter section, in particular 3% to 50%, preferably at least 4%, more preferably at least 5% higher. [3] Filter element according to claim 1 or 2, characterized bythat the collar section has an O-ring strength that is at least 35 N higher than the filter section, in particular 35 to 200 N, preferably at least 40 N, more preferably at least 45 N higher. [4] Filter element according to one of the preceding claims, characterized by that the O-ring strength is based on the same wall thickness in the collar section and filter section. [5] Filter element according to one of the preceding claims, characterized by that the filter section is divided into at least two interconnected sections. [6] Filter element according to one of the preceding claims, characterized bythat the connection between the collar section and the filter section and / or the sections of the filter section to one another is realized by means of internal and external threads formed on their adjacent end sections and corresponding to one another, an adhesive bond, a plug connection possibly secured with pins and / or by means of a bayonet lock. [7] Filter element according to claim 6, characterized by that the collar section and the filter section and / or the sections of the filter section are additionally bonded to one another in their contact areas by means of an adhesive. [8] Filter element according to one of the preceding claims, characterized by that the filter element has the shape of a filter candle with a substantially hollow cylindrical filter candle body, the closed end of which is in particular hemispherical. [9] Filter element according to one of the preceding claims, characterized by that the collar is formed so as to project radially outwards, in particular as a substantially cylindrical collar or a substantially conical collar which tapers in the direction of the filter section. [10] Filter element according to one of the preceding claims, characterized by that the collar section and / or the filter section are designed as a vacuum formed part, in particular as a fired or unfired vacuum formed part containing mineral wool, glass fibers, aluminum silicate wool, alkaline earth silicate wool and / or polycrystalline high-temperature wool. [11] Filter element according to one of the preceding claims, characterized by that at least in the material of the filter section a catalyst is contained, wherein in particular the content of catalyst in the material of the collar section is lower than in the filter section, wherein preferably the material of the collar section does not contain a catalyst. [12] Filter element according to one of the preceding claims, characterized by that the filter body has a length of 1 to 6 m, preferably 2 to 6 m, and / or the collar section has a length of 10 to 100 cm, preferably 12 to 50 cm, more preferably 15 to 30 cm and / or the sections of the filter section each independently have a length of 0.5 to 4.5 m, preferably 1.0 to 4.0 m. [13] Filter element according to one of the preceding claims, characterized by that the length of the collar portion is 5 to 30% of the length of the entire filter body, preferably 1.8 to 25%, particularly preferably 2 to 20%. [14] Filter element according to one of the preceding claims, characterized bythat the filter body has an outer diameter of 30 to 300 mm and / or a wall thickness of 5 to 30 mm, preferably of 10 to 25 mm, wherein the wall thickness of the collar section outside the actual collar is substantially equal to the wall thickness of the filter section. [15] Filter element according to one of the preceding claims, characterized by that the material of the filter body has a porosity of 50 to 90%, determined according to DIN EN 993-1 - 2019-03, preferably greater than 70%. [16] Filter element according to one of the preceding claims, characterized by that the porosity value of the material of the filter body in the collar section is at least 10% lower in absolute terms than in the filter section, preferably at least 20% lower in absolute terms. [17] Filter element according to one of the preceding claims, characterized by that the higher O-ring strength of the collar section is set by • Selection of a higher density of the material of the collar section compared to the material of the filter section, • Selection of a material with higher tensile strength in the collar section compared to the material of the filter section, • Setting a different flocculation size during the vacuum forming process of the collar section compared to the material of the filter section, • Selection of a higher filler quantity for the material of the collar section compared to the material of the filter section, • Selection of a higher fiber content for the material of the collar section compared to the material of the filter section and / or • Selection of a fiber material with higher tensile strength for the collar section material compared to the filter section material. [18] A method for producing a filter element according to any one of claims 1 to 17, wherein a filter body which is closed at one end and open at its opposite end is formed by connecting a collar portion at the open end of the filter body with an outwardly projecting molded collar at the end opposite the collar to a filter portion, characterized by that the collar portion has a higher O-ring strength than the filter portion, wherein the O-ring strength is determined as defined in the description. [19] Use of a collar portion having a higher O-ring strength than the filter portion, for a filter element having a filter body which is closed at one end and open at its opposite end, wherein an outwardly projecting collar is formed on the open end of the filter body, in particular for a filter element according to one of claims 1 to 17. [20] Use of a filter element according to one of claims 1 to 17 for the filtration of exhaust gases or process gases, in particular in the form of a filter candle.