Sealing concept for alkali electrolysis (AEL) electrolysis

Abstract

In order to provide a seal for an electrolysis cell arrangement which has a long service life and is easy to handle and assemble in practical use when sealing electrolysis cells, a seal (10) for an electrolysis cell arrangement is proposed, wherein the seal (10) has a first, inner sealing element (12) and a second, outer sealing element (14) which adjoin one another in a form-fitting manner in a sealing plane (20), and wherein the first, inner sealing element (12) has a greater compressibility or pressability than the second, outer sealing element (14). Furthermore, a use of the seal (10) and an electrolysis cell arrangement are disclosed.

Description

The invention relates to a seal for an electrolysis cell arrangement and to an electrolyser having the abovementioned seal.The electrolyser is referred to as an apparatus in which material conversion as a result of a chemical reaction, an electrolysis, is brought about with the aid of electrical current.Over the course of the energy reversal, electrolysers could assume an important role for the generation of hydrogen in the near future. In order to meet the ever increasing demands, it is necessary to clearly increase the size and reliability of the electrolyzers and to make them marketable.As in the other types of electrolysis, in the alkali electrolysis (hereinafter also AEL) water is split into hydrogen and oxygen. The cleavage usually takes place on two nickel-based electrodes which are separated from one another by a diaphragm. The diaphragm is an ion conductive membrane through which the negatively charged hydroxide ions can pass and move toward the anode. This ion permeability allows directed charge exchange, at the same time the membrane is gas impermeable and prevents the oxygen from mixing with the hydrogen. The electrodes are located in an alkaline electrolyte, which usually consists of potassium hydroxide solution. Hydroxide ions and hydrogen are formed at the cathode from water with electron absorption. The hydroxide ions diffuse through the diaphragm to the anode because of their negative charge, where they react to form oxygen and water with electrode discharge.Electrolysis cells are used inter alia for the production of chromic acid, H 2, and O 2, from H 2 O, or chlorine and alkali metal hydroxides by electrolysis of aqueous alkali metal chloride solutions, electrolysis cells of the membrane type being used in particular. In membrane-type electrolytic cells, a membrane of an ion exchange material formed in a sheet shape is generally used, such cells generally having monopolar or bipolar electrode constructions. The membrane in film form is clamped or otherwise held between the sides of frame elements. In addition, a seal is provided which is inserted between at least one of the frame elements and the surface of the membrane in order to form a liquid- and gas-tight seal when the frames and the seals are braced, so that electrolyte and end product cannot escape. Liquid-tight is to be understood as meaning that no visible liquid drop leakage occurs during operation of the arrangement, while gas-tight is to be understood as meaning that the leakage rate is <10 mg / ms at an area pressure of 10 MPa.Bracing of the frames is typically performed manually or mechanically using hydraulic pistons or other types of pressurizing devices to compress the electrode frames and the separating seals. In this case, it is in particular a condition to achieve such a seal without damage to the membrane.The sealing material commonly used between the membrane and an electrode frame member of an electrolytic cell is made of a chemically resistant, resilient material, for example an elastomer. Commercially available bipolar and monopolar electrolytic cell assemblies with membranes generally use ethylene propylene (EP) or ethylene propylene diene (EPD) as the sealing material between the membrane and the electrode frames.Specific seals made for this purpose are, for example, flat-layer or O-ring EPD seals, which are usually incorporated into the cells. Recently, ePTFE gaskets of sintered PTFE sheets have also been increasingly used in conjunction with an laid-on ePTFE cord.However, the above-mentioned materials tend to deform and expand outwardly when pressure is applied to the seal via the frame members. As the gaskets deform outward, some separators in contact with the gaskets tend to expand under the action of the outwardly deforming gaskets. This stretching of the separator or membrane can cause the membranes to tear when the frames are compressed into a fluid-tight and gas-tight cell. Moreover, it may happen that the known resilient seals require such a high compressive force as to risk damage or rupture of the membrane.Moreover, such resilient seals tend to recover their original size and shape upon release of compressive stress applied thereto. As a result, these resilient gaskets cannot be pre-compressed, so that the membrane with the gasket must be installed between the cell frames before the gasket can be compressed. This increases the likelihood that the diaphragm will be damaged when compressed together with such a resilient seal.In modular constructions, several electrolysis cells of the above-described type are connected in parallel, which entails a higher rated output of the entire plant.The AEL is operated in a temperature range between 40° C. and 90° C. and at a pressure of 1-30 bar.The low investment costs compared with the other types of electrolysis, which result from the market life of the technology, are advantageous in AEL. The AEL is the most recently established type of electrolysis. Technical maturation has already been achieved in the 1950's. In addition, the AEL is distinguished by a high long-term stability. It also makes do virtually without critical raw materials.However, in modular operation, particularly at larger scales, there is a great challenge in the selection of the sealing material between the modules and between the cells.Large, high-performance alkali electrolysers of 4 MW consist of up to 550 cell frames with a diameter of 1.8 metres and have an overall length of up to 10 metres.Operating conditions:temperature: 90° C. (design 120° C.)- pressure: 38 bar (design 54 bar)Medium: high-concentration 30% potassium hydroxide solutionoxygen at 90° C. (very critical)hydrogen90,000 hours of service life are requiredNumber of seals per stack 560This requires a seal with high chemical resistance, temperature and mechanical strength.The sealing materials must be non-conductive (therefore carbon fibre composites and graphite are excluded from the beginning).Without exception, all fibrous material seals currently available on the market do not meet these conditions.Only PTFE (polytetrafluoroethylene) is sufficiently chemically stable. Due to the mechanical instability (creep) of PTFE, it is not possible to ensure a leak-tightness that is at least non-durable.Asbestos seals which were used inexpensively in the past have fulfilled the purpose with very long service lives of 20 years and more, but from the present point of view they no longer satisfied the increasing physical requirements in addition to the asbestos ban.Added to this is the economic component which, from the standpoint of the manufacturers of the electrolysers, should also be located for substitutes in the area of asbestos seals.Therefore, alternatives to the proven asbestos concept are provided, which, however, up to now never fulfil all of the requirements.From EP 0 195 072 B1 and DD 243 052 A5 (The Dow Chemical Company) respectively, an electrolytic cell arrangement of the kind defined in the opening paragraph is known, in which the seal consists of a non-elastic, compressible material which is already completely pre-compressed in the absence of the separator to such an extent that it is already subjected to the main part of the compressive forces necessary to form a liquid- and gas-tight seal. The seal can be fitted with a seal portion into a depression of the electrolysis frame, thereby facilitating the assembly of the seal.EP 0 280 359 (Metalgesellschaft AG) discloses a seal for the electrode frames of a membrane electrolysis arrangement pressed onto one another for producing sodium hydroxide solution, hydrogen and chlorine from a NaCl brine, the membrane being situated with its edge between a two-part seal. At least one sealing part consists of a flat core frame made of asbestos and two sealing frames made of graphite placed on opposite surfaces of the core frame, this structure being surrounded by a foil sheath.From EP 0 416 031 B1 (W.L. Gore & Associates) a seal is known which is formed from a flexible polymeric material, this seal having at least a first region and at least a second region which has a lower density than the first region in order to enable an effective seal under low pressure loads. For this purpose, the polymeric material consists of a body of porous polytetrafluoroethylene which would normally be deformable under its own weight. However, since the first portion of the seal is compacted, the seal is allowed to bear itself against deformation under heavy dead weight.Furthermore, for electrolytic cell seals, two-part seals have already been used in which a separate first sealing component, which is primarily designed in the form of a spacer frame, and a separate second sealing component, in particular in the form of a sealing cord made of ePTFE, have been joined, wherein after the insertion of these two sealing components between a first frame or a second frame and a separator, in particular in the form of a membrane, and after the application of a compressive force to this arrangement, the first sealing component primarily has to provide for a spacing and the second sealing component primarily has to provide for a liquid- and gas-tight seal. The above-mentioned spacing function of the first sealing component is required in order to keep the distance between separator and electrode constant, that is to say the seal must not set in practice, in particular during continuous operation. In the practical application of these known two-part seals, it has been found that their assembly is extremely complicated and expensive, especially since, in particular during the pressing of the seal, for example by screw forces in the case of a flange connection, the maximum stress must be as central as possible to the pressed sealing section.In general, seals of this type are required to have a considerably reduced transverse flow and an extraordinarily low setting behavior.In addition, seals made of multidirectionally oriented expanded polytetrafluoroethylene (ePTFE) in the form of a strip or segment are generally known, wherein such seals are distinguished by higher transverse strength than, for example, multidirectionally oriented ePTFE. However, multidirectional ePTFE also already has lower, but still continuous, setting behavior and flow behavior compared to nonexpanded PTFE.A more promising sealing principle is based on a combination of a mechanically stable aramid fiber seal with a chemically stable sealing material provided in front. The sophisticated design and manufacture of this design is correspondingly complicated and results in far higher costs than the asbestos gasket. The market therefore requires a concept of a seal made of a material, which is however currently not possible because of the lack of chemically resistant and mechanically stable materials.In addition, the aramid fibers are not permanently stable to the highly concentrated potassium hydroxide solution (KOH).The object of the present invention is to provide an improved seal for an electrolytic cell arrangement of the type defined at the beginning, an electrolytic cell arrangement having such a seal, the use of such a seal for sealing an electrolytic cell, which seal is distinguished in particular by a long service life with respect to the media and physical parameters used, and easy handling and simple assembly in practical use in the sealing of electrolytic cells. In this case, the seal, in addition to the sealing function, is intended to simultaneously provide effective insulation against electrical bridging and to function as a spacer.This object is achieved by a seal and its use with the features of the independent claims. Thus, a first aspect of the invention relates to a seal for an electrolysis cell arrangement, wherein the seal has a first, inner sealing element and a second, outer sealing element which adjoin one another in a form-fitting manner in a sealing plane, and wherein the first, inner sealing element has a greater compressibility or compressibility than the second, outer sealing element.The seal according to the invention acts as a sealing element because of the positive connection, since during assembly or pressing, as well as during the service life, it is ensured that the sealing elements remain in contact. This allows a high accuracy during assembly with comparatively little outlay. The two sealing elements can thus combine properties, in particular compressibility in a seal. Sealing properties such as high chemical resistance, in particular to bases and high compressibility, are not compatible in the same material, thus the inner sealing element can serve as a fluid barrier and thus prevent contact of the outer sealing element with the fluid. The seal according to the invention therefore has chemical resistance, high temperature and mechanical strength. Furthermore, the seal according to the invention made of two different materials enables a more specific adaptation to the applications, and a controlled setting, much less maintenance effort, even in the case of many seals located one behind the other. A follow-up after application of temperature or under temperature is made possible without the tightness being impaired. This is a great advantage, since the design and the startup of an AEL device takes up to 6 weeks. A tightening and tightening of the tightening of the seal is associated with a high risk of a distortion of the entire device during a tightening of the flanges and is also correspondingly time-consuming. Finally, it has been shown that the seal according to the invention also resists load changes occurring without being destroyed.In the art, a seal is referred to as elements or constructions which have the task of preventing or limiting undesired material transfers from one location to another.In the present case, greater compressibility of the inner sealing element is to be understood as meaning a higher cold compression value. The material of the first inner sealing element preferably has a cold compression value according to DIN 28090-2 in a range of at least 13%, in particular at least 15%, preferably more than 20%, more preferably more than 23%.The second, outer sealing element, on the other hand, preferably has a cold compression value according to DIN 28090-2 in the range from 2% to 10%, in particular in the range from 4% to 8%.A cold-compression ratio between the first and second sealing elements is preferably in the range from 0.1 to 0.5, in particular in the range from 0.2 to 0.4.Due to the higher cold compression value of the inner sealing element compared to the outer sealing element, a seal at the connection point between the sealing elements is also achieved. The material of the first sealing element is compressed during installation by the installation surface pressure and pressed to the connection point of the second, outer sealing element. This can make adhesion superfluous.In a preferred embodiment of the invention, it is provided that the first, inner sealing element predominantly consists of a polymer and the second, outer sealing element predominantly consists of a mineral material.In the present case, mineral material is to be understood as meaning, in particular, an asbestos-free material. In the present case, predominantly is to be understood as meaning that, with respect to the inner sealing element, more than 80 vol %, in particular more than 90 vol %, consist of a polymer. Thus, also included are materials of this type which, in addition to a polymer, also have additives in customary amounts and / or fibers or mineral materials of a different material class. In the case of the outer seal, predominantly mineral is understood to mean a material which consists to an extent of at least 80% by weight, in particular more than 90% by weight, preferably more than 95% by weight, of a mineral material. Thus, for example, materials are also included which comprise an organic or inorganic binder to a small extent.The polymer is advantageously an EPDM or a fluorinated polymer or comprises such. It is particularly preferred that this is PTFE, FKM, FFKM or a mixture thereof.These materials exhibit a particularly high chemical resistance, also and in particular to bases and at higher temperatures.The polymer is particularly advantageously filled with a mineral material, preferably borosilicate glass, silicon dioxide or barium sulfate. The filling gives the first sealing element a higher dimensional stability and thus reduced compressibility without reducing its chemically inert properties.Such material mixtures have a high cold dip value and a low heat setting value according to DIN 28090-2.In a further preferred embodiment, it is provided that the mineral material is a silicate mineral, preferably mica.Materials of the mica group, or mica for short, are a group of minerals from the division of the sheet silicates having the same atomic structure.The prominent feature of mica is its layer structure and the very weak bond between these layers. This results in the perfect splittability, which is characteristic of these minerals, parallel to these layer packages. They have a low Mohs hardness of 2 (parallel to the layer planes) to 4 (all other directions). Their color varies from white to brown black; less frequently green or pink. The line color is white. For many industrial applications, the very low electrical conductivity of the mica is decisive.Mica is among the most common rock forming minerals and is an important component of many magic (e.g., Graminites, Diorites, Pegmatites) and metamorphic (mica slate, Gnieise) rocks.Other leafy or flaky fracturing minerals other than mica group are also referred to as mica, such as iron mica. However, the latter are not suitable as sealing material in the present case because of their conductivity.These materials are distinguished by high mechanical stability in use in the electrolyser. The final thickness in the pressed state should no longer change under all load cases. Cyclic loads occur during operation of the system, which leads to changes in the sealing surface pressure. Compliance with the tightness class 0.01 is ensured under all load changes when mica is used. In addition, mica is chemically very resistant, so that in the event of boundary surface leakage of the inner sealing element occurring, the functionality of the outer sealing element remains. Surprisingly, it has been found that when mica is used in the outer seal, controlled seating is observed and controlled seating is also achieved when a plurality of cells are connected in series, even when load changes occur in succession. A follow-up is moreover not required.Preferably, the outer seal comprises an additive, in particular an elastomer, in addition to the mineral component. This serves as a binder for the mineral, intrinsically non-adhering constituents.The seal is advantageously designed as a flat seal, in particular a flat seal of circular or rectangular design. This enables reproducible production in large numbers, production in a segmented manner.The seal preferably has a thickness or thickness in the range from 0.5 mm to 5 mm, 1 mm to 3 mm or else 1.5 mm and 2 mm. These dimensions are necessary in order to be able to exclude fluid-conducting cavities and to achieve a complete tightness despite the demanding architecture of the surfaces to be sealed with a multiplicity of different sized recesses and grooves. The profiles of the surfaces to be sealed also vary between the users, in order nevertheless to ensure sealing uniformly, the thicknesses specified have the necessary tolerance.Depending on the configuration, i.e. on the combination of the materials used and their cold compression values of the first and second sealing elements, it can be advantageous if the thicknesses of the sealing elements differ, so that during the pressing of the sealing elements during the assembly in the installation, the sealing elements can be pressed in such a way that during the assembly they have the same thickness as the respective adjacent one.In other words, the difference in thickness (difference) of the primary sealing member and the secondary sealing member is compensated by the compression in the compressed state.In the pressed state, the different sealing thicknesses then reach the calculated and defined height of the necessary deformation for adaptation to the flange surfaces, compacting the inner structure and for achieving the constant technical tightness of the electrolysis cells even during alternating operation, such as driving up and down or starting up and back again the plant.This also allows a cyclical manner of driving the system through the seal according to the invention. The final thickness of the seals in the pressed state is defined in such a way that dropping below the absolutely minimum seal height under all operating parameters is avoided.In particular, in the preferred combination of polymer (first sealing element) and mica (second sealing element), the first, inner sealing element has a greater thickness than the second, outer sealing element. The first, inner sealing element can be pressed in such a way that it has the same thickness as the second, outer sealing element, so that the second, outer sealing element has the function of spacing and the first, inner sealing element has the function of sealing.The surface pressure should reach at least 30 MPa during the production of an electrolysis device, i.e. during the bracing of the electrolysis cells to form the cell stack, and at least 15 MPa during the relief, given by creep or relaxation of the bracing during operation, is to maintain the required tightness class. The seal for the electrolyser can be annular or have an freely selectable shape. The seal can also be used to seal the electrolyser in a tongue and groove flange or a recess flange. However, the sealing height in the pressed state should be selected such that under all operating states the seal always remains a force-fit.The outer diameter of the secondary sealing member may be in a range of 200 mm to 2000 mm or more.With regard to the arrangement of the sealing elements with respect to one another, it is preferred that the first, inner sealing element is arranged centrally with respect to the second, outer sealing element.It is particularly advantageous for the first, inner sealing element on the outer circumference and the second, outer sealing element on the inner circumference to each have at least two formations and / or recesses for the positive connection of the first, inner sealing element to the second, outer sealing element. This allows a dimensionally accurate arrangement of both sealing elements in the electrolyser in only one working step.In a preferred embodiment, the first, inner sealing element on the outer circumference and the second, outer sealing element on the inner circumference have all 15-20° formations or recesses.Alternatively or additionally, the first, inner sealing element on the outer circumference and the second, outer sealing element on the inner circumference have all 10-20 cm protrusions or recesses.The formations or recesses are formed correspondingly to one another, so that in each case a pair of formation and recess engage in one another when the first sealing element is arranged on the second. Interlocking formations / recesses prevent slipping during the production / bracing of the cell stacks to form an electrolysis device.For this purpose, it is necessary for the formations on one of the sealing elements to be precisely adjacent to the corresponding recesses on the adjacent sealing element when the sealing elements are arranged on one another.In a preferred embodiment of the invention, it is provided that the first, inner sealing element has protrusions on the outer circumference and the second, outer sealing element has recesses on the inner circumference. It has been found that, surprisingly, formations on the inner sealing element instead of on the outer one increase the resistance to alkaline solution, because alkaline solution penetrates from the inside and more alkaline solution-resistant material is present for alkaline solution-resistant sealing due to formations on the inner sealing element.Alternatively, it is provided that the first, inner sealing element on the outer circumference and the second, outer sealing element on the inner circumference have formations and recesses in alternation. In this embodiment, the stability of the connection between the first and second sealing elements, which connection is produced by the interlocking formations and recesses, is significantly increased.Further preferably, the formations and recesses of the first, inner sealing element and of the second, outer sealing element are each at a maximum or irregularly spaced apart from one another. The arrangement of the two sealing elements relative to one another is facilitated in this case with a maximum and thus regular arrangement of the recesses and formations. In the case of irregular spacings, it is to be ensured that there is at least one arrangement of the first sealing element on the second sealing element, in which arrangement all the formations completely adjoin recesses.Particularly preferably, the formations have a cross-sectional tapering perpendicular to the plane of the flat seal, such that the formations on one sealing element can be hooked into a recess of inversely congruent shape on the respective other sealing element. Cross-sectional tapering means that the formation in the plane of the flat gasket has a first diameter b and a second diameter B, wherein the first diameter b is arranged closer to the circumferential surface of the sealing element than the second diameter B and the first diameter b is smaller than the second diameter B. In particular, the ratio of the first diameter b to the second diameter B can be between 0.5 and 0.95, preferably between 0.6 and 0.8.Preferably, these cross-sectional tapers of the formations and the corresponding recesses are shaped in a dovetail shape or puzzle shape or as a button hole connection.Puzzle-shaped is to be understood here as meaning that the formations typically have a maximum extent of 5% to 10% of the total width of the respective sealing element in the plane of the flat seal, i.e. in the radial direction in the case of annular sealing elements, e.g. lie in a range of 2 to 10 mm. In embodiments, the formations can have a constant diameter in the plane of the flat seal in a region on the circumference of the sealing element, that is to say can be formed with a web which connects, for example, a rounded region of the formation to the circumferential surface of the sealing element.In a further preferred embodiment of the invention, it is provided that the first, inner sealing element and / or the second, outer sealing element are segmented, wherein the segments of the first, inner sealing element and of the second, outer sealing element have formations and / or recesses for the form-fitting connection of the segments, preferably the formations and the corresponding recesses are connected in a materially bonded manner. Further embodiments correspond to those in the case of the sealing elements. This offers great advantages, in particular with regard to production and material economy, since the sealing elements do not have to be manufactured integrally from solid material.The segments can have formations and / or recesses in the circumferential direction according to the previously described principle in order to connect the segments to one another in a form-fitting manner, or can be sealed, i.e. can be formed with oblique contact surfaces. In addition, in embodiments, a bonded connection is also possible, for example by adhesive bonding to the contact surfaces, preferably with an ethyl cyanoacrylate-based adhesive, in particular ethyl 2-cyanoacrylate. Each sealing element can advantageously have between 3 and 7 segments. Business means that the respective contact surface of mutually adjacent segments for joining the segments to the contact surfaces are designed to be inversely congruent with each other at an acute angle to the plane of the surface seal, in particular at an angle of 2° to 20°, preferably 5° and 15°. In embodiments, the formations or recesses on the peripheries of the sealing elements can be arranged symmetrically or asymmetrically with respect to a center line of the respective segment, which runs in the radial direction in the case of annular sealing elements. In preferred embodiments, the formations or recesses on the peripheries of the sealing elements are each arranged asymmetrically with respect to the centre lines of the segments.The segments are preferably arranged in the respective sealing elements in such a way that the segments of the inner sealing element are each arranged offset from the segments of the outer sealing element after the sealing elements have been joined together for sealing.It is further preferably provided that the contact surfaces of the first, inner sealing element and the second, outer sealing element are sealed. In this embodiment, a partial overlap of the two sealing elements is realized without relative height differences occurring with respect to the entire sealing height. In embodiments where the sealing elements have different cold crush values and the inner sealing element therefore has a greater thickness prior to compression, the thickness of the sealed area towards the outer seal decreases in proportion to the overlap. The overlap reduces the likelihood of leakage of the seal and ensures that the seal members are reliably in contact with each other.The contact surfaces of the first, inner sealing element and of the second, outer sealing element are advantageously connected to one another in a materially integral manner. The material-to-material connection can be achieved either by an additional adhesive, which is applied to one of the joint edges on one of the sealing elements. Alternatively or additionally, the cohesive connection arises by a connection of the polymer portions of the sealing elements during pressing and or temperature action in the process.In a preferred embodiment of the invention, it is provided that the first, inner sealing element and the second, outer sealing element have through-openings for media passage, for connecting pieces and / or for pins for positioning the sealing elements on the electrolysis cell. This embodiment represents a prefabricated arrangement which facilitates assembly, since no further feedthroughs need to be provided when arranging the seal in the electrolyser. Since introducing media feedthroughs after the segments are assembled and on site during assembly is complicated and can lead to damage to the seal.A further aspect of the invention relates to the automated production of a seal according to the invention, in particular in a segmented manner.Furthermore, one aspect of the invention relates to the use of a seal according to the invention for sealing an electrolysis cell, in which the seal is inserted between at least a first frame or a second frame and a separator and compressed, wherein the separator separates an anode space and a cathode space from one another, which are bounded by the first and the second frame.In principle, the seal according to the invention is suitable for other types of electrolysers, for example PEM.Thus, a final aspect of the invention relates to an electrolytic cell arrangement having an anode space and a cathode space, which comprises:a first frame in the anode compartment,a second frame in the cathode space,a separator interposed between the frames to separate the anode compartment and the cathode compartment from each other, and,a seal between at least one of the first frame and the second frame and the separator, characterized in that the seal is a seal according to the invention.The invention is explained in more detail below with reference to figures. They show FIG. 1 is a plan view of a flat gasket for alkaline electrolysis according to the invention, with a first, inner sealing element and a second, outer sealing element, FIG. 2 shows a sectional side view of a flat gasket according to the invention according to FIG. 1, FIG. 3 shows a sectional detailed view of a flat gasket according to the invention with a sealed first and a second sealing element, FIG. 4 is a detailed view of a flat gasket according to the invention with dovetail joints between the first and the second sealing element, FIG. 5 is a detailed view of a flat gasket according to the invention with button hole connections between the first and the second sealing element, and FIG. 6 is a detailed view of a segmented flat gasket according to the invention with button hole connections between the segments of the first and second sealing elements.FIGS. 1 to 6 show seals 10 according to the invention, which are designed as flat seals, in various embodiments. The gaskets 10 have a first inner sealing element 12 and a second outer sealing element 14, both of which are circular and concentrically arranged. According to the invention, the shape of the seal 10 in the sealing plane 20 can be arbitrary, i.e. also angular, in particular quadrangular. However, this ultimately depends on the circumstances of the device to be sealed.The outer edge (outer circumference) 16 of the first sealing element 12 adjoins the inner edge (inner circumference) 18 of the second sealing element 14 in such a way that both sealing elements 12, 14 are positive-locking with respect to one another.The two adjoining edges 16 and 18 of the two sealing elements 12, 14 can be formed at right angles to the sealing plane 20, as shown in FIG. 2, or can be sealed, as shown in FIG. 3, in order to provide a greater contact area between the two sealing elements 12, 14. This is advantageous in particular if the two sealing elements 12, 14 are connected to one another in a materially integral manner by suitable adhesive.A further possibility for fixing the position of the first and the second sealing element 12, 14 in relation to one another is to provide, adjacent to the edges 16, 18 of the two sealing elements 12, 14, formations 22 and corresponding recesses 24, which engage in one another. These are preferably designed as dovetail joints 26 (FIG. 4 ) or as button hole joints 28 (FIG. 5 ), since these cannot be pulled apart in the sealing plane 20 due to the geometric configuration. In addition, the formations 22 and the corresponding recesses 24 can additionally be glued to one another, wherein here too, in order to enlarge the glue surface, the edges 16, 18 can be sealed, including the formations 22 and the recesses 24.FIG. 6 shows a preferred embodiment of the flat gasket according to the invention, in which, because of the sometimes very large dimensioning of the gaskets 10, these are divided into several segments 30, which are then only connected to one another at the location of use. For this purpose, formations 22 and corresponding recesses 24 are also provided, which connect the segments to one another. For this purpose, although not shown again, the first and the second segmented sealing element 12, 14 can be connected to one another as described above with formations 22 and corresponding recesses 24. Otherwise, all other features, such as adhesive bonding and shafts, can also be used.List of reference characters10 Seal / flat seal 12 first, inner sealing element 14 second, outer sealing element 16 edge / outer circumference of the first sealing element 18 edge / inner circumference of the second sealing element 20 sealing plane 22 formation 24 recesses 26 dovetail joints 28 button hole joints 30 segmentsReferences included in the specificationThis list of documents cited by the applicant has been produced in an automated manner and is only included for the better information of the reader. The list is not part of the German patent application or utility model application. The DPMA does not take any adhesion for any faults or omissions.Patent Literature citedEP 0 195 072 B1

[0024] DD 243 052 A5

[0024] EP 0 280 359

[0025] EP 0 416 031 B1

[0026]

Claims

Seal (10) for an electrolysis cell arrangement, wherein the seal (10) has a first, inner sealing element (12) and a second, outer sealing element (14) which border one another in a form-fitting manner in a sealing plane (20), and wherein the first, inner sealing element (12) has a greater compressibility or compressibility than the second, outer sealing element (14).The seal of claim 1, wherein the first inner sealing element (12) is predominantly made of a polymer and the second outer sealing element (14) is predominantly made of a mineral material.The gasket according to claim 2, wherein the polymer is an EPDM or a fluorinated polymer, preferably PTFE, FKM or FFKM.The seal according to any one of claims 1 to 3, wherein the polymer is filled with a mineral particle / material, preferably borosilicate glass, silicon dioxide or barium sulfate.A gasket according to any one of claims 1 to 4, wherein the mineral material is a silicate mineral, preferably mica.The seal of claim 1, wherein the first inner seal member (12) is made of polytetrafluoroethylene filled with borosilicate glass, silica, or barium sulfate.Seal according to one of Claims 1 to 6, wherein the second, outer sealing element (14) comprises a binder or an elastomer.Seal according to one of the preceding claims, wherein the seal (10) is designed as a flat seal.A seal according to any preceding claim, wherein the seal (10) is circular or rectangular.A seal according to any preceding claim, wherein the first inner seal member (12) has a greater thickness than the second outer seal member (14), the first inner seal member (12) being compressible to have the same thickness as the second outer seal member (14) such that the second outer seal member (14) performs the function of spacing and the first inner seal member (12) performs the function of sealing.A seal according to any preceding claim, wherein the first inner seal member (12) is centrally located with respect to the second outer seal member (14).Seal according to one of the preceding claims, wherein the first, inner sealing element (12) on the outer periphery (16) and the second, outer sealing element (14) on the inner periphery (18) each have at least two formations and / or recesses (22, 24) for the positive connection of the first, inner sealing element (12) to the second, outer sealing element (14).Seal according to Claim 12, wherein the first, inner sealing element (12) on the outer circumference (16) and the second, outer sealing element (14) on the inner circumference (18) have all 15-20° formations or recesses (22, 24).The seal of claim 12, wherein the first inner seal element (12) on the outer periphery (16) and the second outer seal element (14) on the inner periphery (18) have all 10-20 cm formations or recesses (22, 24).Seal according to one of Claims 12 to 14, wherein the first, inner sealing element (12) has formations (22) on the outer periphery (16) and the second, outer sealing element (14) has recesses (24) on the inner periphery (18).Seal according to one of Claims 12 to 14, wherein the first, inner sealing element (12) on the outer circumference (16) and the second, outer sealing element (14) on the inner circumference (18) have formations (22) and recesses (24) in alternating fashion in each case.Seal according to one of Claims 12 to 16, wherein the formations (22) and recesses (24) of the first, inner sealing element (12) and of the second, outer sealing element (14) are in each case at a maximum or irregular distance from one another.Seal according to one of Claims 12 to 17, wherein the formations (22) have a cross-sectional tapering perpendicular to the plane of the seal (20), and the corresponding recesses (24) are shaped in an inversely congruent manner.A seal according to claim 18, wherein the formations (22) and the corresponding recesses (24) are formed as a dovetail joint or as a button hole joint.Seal according to one of the preceding claims, wherein the first, inner sealing element (12) and / or the second, outer sealing element (14) are segmented, wherein the segments (30) of the first, inner sealing element (12) and of the second, outer sealing element (14) have formations (22) and / or recesses (24) for the positive connection of the segments (30), preferably the formations (22) and the corresponding recesses (24) are connected in a materially integral manner.A seal according to any preceding claim, wherein the contact surfaces of the first inner seal member (12) and the second outer seal member (14) are sealed.Seal according to one of the preceding claims, wherein the contact surfaces of the first, inner sealing element (12) and of the second, outer sealing element (14) are connected to one another in a materially integral manner.Seal according to one of the preceding claims, wherein the first, inner sealing element (12) and / or the second, outer sealing element (14) have through-openings.Use of a gasket (10) according to any one of claims 1 to 23 for sealing an electrolytic cell in which the gasket (10) is inserted and compressed between at least one first frame or a second frame and a separator, the separator separating an anode space and a cathode space defined by the first and second frames.An electrolytic cell assembly having an anode compartment and a cathode compartment, comprising: a first frame in the anode compartment, a second frame in the cathode compartment, a separator inserted between the frames to separate the anode compartment and the cathode compartment from each other, and a gasket (10) between at least one of the first frame and the second frame and the separator, wherein the gasket (10) is a gasket (10) according to any one of claims 1 to 23.

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