Sealing arrangement for sealing electrolysis cells

Abstract

The invention relates to a sealing arrangement for sealing electrolysis cells in an electrolysis device, in particular in alkaline pressure electrolysis, comprising an outer sealing element (8) and an inner sealing element (7), which are interlockingly arranged relative to each other.

Description

[0001] Sealing arrangement for sealing electrolysis cells

[0002] The present invention relates to a sealing arrangement for sealing electrolysis cells in an electrolysis device. In particular, it concerns a sealing arrangement for sealing electrolysis cells in water electrolysis for the production of hydrogen and oxygen. For alkaline electrolysis, aqueous alkaline electrolytes such as potassium hydroxide (KOH) or sodium hydroxide (NaOH) solutions are typically used, whereas for acidic electrolysis, e.g., sulfuric acid or phosphoric acid electrolyte solutions are used. The sealing arrangement is provided and intended to seal the electrolysis cells in an electrolysis device in a liquid-tight and gas-tight manner with a low leakage rate after they have been pre-assembled and clamped to form an electrolysis stack during operation.The operation of the electrolysis device may also include standby phases in which the pressure and temperature of the electrolysis device change repeatedly, sometimes even periodically, such as in alkaline pressure electrolysis.

[0003] EP 0 261 827 A1 discloses a seal for use in an electrolytic cell, which seal has a plurality of projections and / or recesses in its surface, wherein the projections and recesses are adapted to interact with the surface of an anode or cathode. The projections and recesses secure the seals to the cathode or anode during assembly of the seal.

[0004] The present invention is based on the object of providing a sealing arrangement that achieves good technical tightness using the simplest possible means and has a long service life. According to the invention, this object is achieved by a sealing arrangement having the features of claim 1. Advantageous embodiments form the subject matter of the subclaims.

[0005] The sealing arrangement according to the invention is provided and intended for sealing electrolysis cells in an electrolysis device. In particular, the proposed sealing arrangement is provided and intended for effectively sealing the electrolysis cell with a low leakage rate in alkaline or acidic water electrolysis, preferably in alkaline pressure electrolysis. The sealing arrangement has a first, inner sealing element and a second, outer sealing element. According to the invention, the inner and outer sealing elements are arranged in a form-fitting manner with respect to one another, in particular can be connected to one another in a form-fitting manner. The form-fitting arrangement is created by blocking the relative movement of the two sealing elements by design details on the sealing elements. The form-fitting arrangement blocks the movement of the two sealing elements relative to one another in one or more directions.It can preferably be formed between an inner circumference of the outer sealing element and an outer circumference of the inner sealing element. The sealing elements can be positively connected to one another at the inner circumference of the outer sealing element and at the outer circumference of the inner sealing element. The advantage of positively connected sealing elements is that they can assume a defined position with one another in order to achieve a better sealing effect. The positive connection between the two sealing elements can be established before the sealing arrangement is installed. However, it is also possible to mount one of the two sealing elements in advance or to position it on the electrolysis cell and then arrange the other sealing element in a positive fit with the already installed sealing element.In an electrolysis cell stack, several electrolysis cells are typically arranged side by side in series and clamped together by pressing the resulting cell stack together. The sealing arrangement according to the invention is installed between the sealing surfaces of oppositely arranged electrolysis cells, so that during clamping, the sealing arrangement is subjected to a surface pressure, which is applied to the sealing arrangement via the sealing surfaces of the electrolysis cells. For this purpose, the sealing elements have contact surfaces that are placed against the sealing surfaces of the electrolysis cells and are preferably each subjected to a surface pressure perpendicularly.

[0006] According to the invention, the sealing arrangement is subjected to surface pressure in the main force connection. The positive connection between the outer and inner sealing elements is formed on the inner circumference of a contact surface of the outer sealing element and on the outer circumference of a contact surface of the inner sealing element. The surface pressure is applied perpendicular to the circumferential direction of these contact surfaces. The sealing surfaces of the electrolysis cells in the cell stack are usually aligned parallel, in particular plane-parallel, to one another. Accordingly, the contact surfaces of the sealing elements can also be oriented parallel to one another.

[0007] The sealing elements can preferably be designed as flat gaskets, in particular as annular flat gaskets, where annular means circular, oval or polygonal. Polygonal sealing elements can in particular be square or hexagonal sealing elements. The outer contour of the sealing arrangement can be adapted to the outer contour of the sealing surface, e.g. correspond to it. For electrolysis cells with a circular cross-section, the inner and outer sealing elements can, for example, be designed as an annular disc with one or more annular segments. The positive connection between the sealing elements, e.g. annular discs, occurs in the circumferential direction, so that forces normal to the circumferential direction, i.e. in the radial direction, can be transmitted between the outer circumference of the inner sealing element and the inner circumference of the inner sealing element.

[0008] In a preferred embodiment, a positive connection in the radial direction is also provided between the inner and the outer sealing element, so that forces can be transmitted in the circumferential direction between the sealing elements. The positive connection in the radial direction makes it particularly easy to assemble both sealing elements when they are fixed to one another, because the relative movement of the sealing elements to one another is blocked in two directions of movement. The positive connection in the radial direction between the inner and the outer sealing element is achieved, for example, by means of formations and / or recesses on the circumferential surfaces. The formations, which can also be referred to as projections, and / or the recesses on the outer circumference of the inner sealing element are shaped complementarily to the respective recesses or formations on the inner circumference of the outer sealing element. The formations or recesses, which are shaped complementarily to one another.Recesses can be formed, for example, as fingers, tenons, or prongs. In a particularly preferred embodiment, the recesses or recesses are formed with an undercut, e.g., as a dovetail joint or buttonhole joint. In these joints, the undercut prevents relative movement of the sealing elements in the circumferential direction of the sealing elements.

[0009] The outer or inner sealing element can be provided with both protrusions and recesses, or only protrusions or only recesses. It has proven particularly advantageous if the inner sealing element has only protrusions and the outer sealing element has only complementary recesses. With a higher cold heading value of the inner sealing element compared to the outer sealing element, the protrusions of the inner sealing element, particularly in buttonhole connections with rounded or oval protrusions, adapt particularly well to the recesses of the outer sealing element in the area of ​​the positive fit, thus achieving improved sealing.

[0010] In a preferred embodiment, for easier production, the outer sealing element and / or the inner sealing element can each be formed from a plurality of segments that are connectable or connected to one another. Annular sealing elements can, for example, be divided into segments in the radial direction. In a preferred embodiment, the inner and / or outer sealing element is each divided or segmented into two or more circular ring segments that are connected to one another in the circumferential direction; in particular, these can also be glued to one another in the circumferential direction.

[0011] The segments can be connected at joining surfaces which are preferably complementary to one another on two adjacent segments to be connected. The joining surfaces can also be referred to as contact surfaces. They can, for example, be knurled or designed with an undercut, e.g. as a dovetail connection and / or as a buttonhole connection, whereby these positive-locking connections with an undercut also allow a detachable connection, without gluing, so that simple production of the sealing arrangement is possible. Knurled means that the respective joining surfaces of adjacent segments are complementary and flat to one another, each designed at an acute or obtuse angle to the contact surfaces of the sealing element, in particular at an acute angle in the range of 3.5° to 20°, preferably from 3.5° to 15°, particularly preferably from 3.5° to 10°.an obtuse angle of 160° to 176.5°, preferably 165° to 176.5°, particularly preferably 170° to 176.5°. Such inclined joining surfaces can be produced, for example, by grinding the contact surfaces.

[0012] The length 1 of a joining surface of a segment can, in the circumferential direction of the sealing element, be at least 8 times the thickness d of the respective sealing element or segment in the uncompressed state, for example 8 to 20 times, preferably more than 10 times the thickness d, particularly preferably at least 11 or 12 times the thickness d, for example 12 to 20 times. The length of the joining surface is preferably considered in a projection perpendicular to the contact surface.

[0013] In the case of annular sealing elements, the joining surfaces between adjacent segments can be formed on opposite sides of a segment, which do not form circumferential surfaces of the sealing elements. For simple assembly, the joining surfaces of a segment can each have an acute angle between the contact surface and the joining surface on the opposite contact surfaces of the segment. The joining surfaces can, in particular, be beveled in the same direction, preferably also aligned parallel to one another. Alternatively, in embodiments, it is possible for the joining surfaces of a segment to each have an acute angle to only one of the contact surfaces and only obtuse angles to the opposite contact surface.

[0014] In a particularly preferred embodiment, the thickness D of the inner and / or outer sealing element is increased in areas of division or segmentation, i.e., in the area of ​​the joining surfaces, relative to the thickness d of the respective sealing element. It is therefore greater than the thickness d in the areas that do not have joining surfaces. The thickness D at the joining surfaces can be up to 120%, preferably between 102% and 120%, of the thickness d of the respective sealing element. The increased thickness exerts greater contact pressure on the joining surfaces, and a high level of tightness is achieved despite the segmentation.

[0015] The thickness can be increased, for example, by introducing an additional material, such as an adhesive, into the joining surfaces, which remains as a thicker layer in the joint gap, thereby increasing the thickness. However, this is cumbersome, and the increase in thickness is difficult to control.

[0016] In a preferred embodiment, the thickness is increased by arranging the segments in the sealing element offset from one another so that the knurled joining surfaces project beyond one another. With such an offset, oblique butt joint of the segments, that part of the joining surface which projects beyond the associated complementary joining surface overlaps a contact surface of the sealing element and thereby increases the thickness of the sealing element by the maximum height that the segment has at the overlapping part of the joining surface. The offset by which the segments are offset from one another or shifted towards one another can be selected depending on the oblique angle of the knurled joining surfaces, the length of the joining surface and the thickness d of the segment such that the thickness D in the region of the joining surfaces is up to 120%, preferably between 102% and 120%, of the thickness d of the respective segment or sealing element in the uncompressed state.

[0017] In the case of annular sealing elements, the segments of the respective sealing element can be arranged offset from one another in the circumferential direction. For this purpose, the segments are preferably designed rotationally symmetrically to an axis through the centroids of the contact surfaces, in particular as circular ring segments. This allows the segments to be arranged offset from one another very easily by rotation in the circumferential direction, so that the knurled joining surfaces protrude beyond one another and the thickness of the segments overlapping at the joining surfaces is increased in the joining or overlapping area.

[0018] For particularly precise positioning and alignment of the offset segments in the sealing arrangement, the inner and outer sealing elements can have the previously described positive locking in the radial direction, which can be achieved, for example, by means of protrusions and / or recesses on the inner circumference of the outer sealing element and the outer circumference of the inner sealing element, in particular by means of connections with an undercut, such as dovetail and / or buttonhole connections. This prevents the segments from twisting or shifting relative to one another in the circumferential direction of the sealing elements and thus enables precise adjustment and fixing of the offset of the joining surfaces relative to one another and thus also of the thickness increase in the area of ​​the knurled connection.

[0019] In an advantageous embodiment, the segments of the outer sealing element are arranged offset from the segments of the inner sealing element in the sealing arrangement. This means that the divisions or joining surfaces between the segments of the sealing elements are arranged at different locations on the outer and inner sealing elements in the circumferential direction. This results in a meandering or labyrinth-like path along the joining surfaces of the segments and the circumferential surfaces of the sealing elements between the inner circumference of the inner sealing element and the outer circumference of the outer sealing element, along which the sealing elements are sealed against one another. This extended sealing path increases the tightness of the sealing arrangement.For a maximum sealing distance, the divisions between the segments of the outer sealing element can preferably be arranged in the circumferential direction at equal distances from the divisions between the segments of the inner sealing element, or vice versa. Particularly preferably, the sealing distance is also increased by positive-locking connections with an undercut, in particular by buttonhole connections, between the outer and inner sealing elements and / or between the segments of the inner and / or outer sealing elements.

[0020] In a preferred embodiment, the inner sealing element is provided with a greater cold heading value than the outer sealing element. The cold heading value is a measure of the adaptability of the seal to the sealing surface. The determination of the deformation values ​​is specified, for example, in DIN 28090-2:2014-11. In the two-part sealing arrangement according to the invention, it has proven particularly advantageous if the quotient of the cold heading values ​​of the outer sealing element to the inner sealing element is equal to or less than 0.6. The cold heading values ​​from the quotient indicate that the cold heading value of the outer sealing element is only 60% or less than the cold heading value of the inner sealing element. The quotient of the cold heading values ​​can in particular be in a range between 0.1 and 0.6, preferably between 0.2 and 0.5.Due to the higher cold heading value of the inner sealing element, the inner sealing element not only adapts favorably to the sealing surfaces of the electrolysis cells, but also to the outer sealing element in the area of ​​the positive connection to the outer sealing element. In pressure electrolysis, this effect is further enhanced by the overpressure in the electrolysis cells, which presses the inner sealing element against the outer sealing element.

[0021] In embodiments, the cold compression value of the outer sealing element can, for example, be in a range of 4% to 8%, preferably 5% to 7%. Furthermore, it is advantageous, particularly for electrolysis at temperatures above room temperature, such as alkaline pressure electrolysis, for the outer sealing element to be designed with a lower hot compression value than the inner sealing element. The hot compression behavior is a measure of the creep behavior of the seal. The hot compression value can be determined according to DIN 28090-2:2014-11.

[0022] The quotient of the heat settling values ​​of the outer sealing element to the inner sealing element can preferably be less than or equal to 0.8. The heat settling value of the outer sealing element can therefore be only 80% or less than the heat settling value of the inner sealing element. The quotient of the heat settling values ​​can in particular be in a range between 0.1 and 0.8, preferably between 0.2 and 0.4. Because the heat settling value of the outer sealing element is lower than that of the inner sealing element, meaning that the outer sealing element has better creep behavior than the inner sealing element, the outer sealing element offers an additional sealing function should the inner sealing element become leaky due to creep.

[0023] In embodiments, the heat setting value of the outer sealing element can in particular be in a range from 3% to 8%, preferably from 4% to 6%.

[0024] A configuration in which the outer sealing element has a higher springback value than the inner sealing element is also preferred. The springback value describes the percentage by which a material recovers after being subjected to a predetermined pressure for a predetermined period of time. It can be determined according to ASTM F 36 J - 2015 and is a measure of the ability of a seal to compensate for an increase in the sealing gap between the sealing surfaces. Due to its higher springback, the outer sealing element offers an additional sealing function should the inner sealing element become leaky due to changes in the sealing gap.

[0025] The springback values ​​also result in a preferred ratio of the outer sealing element to the inner sealing element. The ratio is preferably between 1.4 and 3.5, meaning that the springback value of the outer sealing element is preferably at least 1.4 times greater than the springback value of the inner sealing element.

[0026] The inner sealing element preferably has a springback value of 20% to 50%, preferably 30% to 40%. The outer sealing element has a springback value of 40% to 70%, preferably 50% to 70%, with the springback values ​​being determined, for example, according to ASTM F 36 J - 2015.

[0027] A particular advantage of the sealing arrangement consisting of two sealing elements is that it allows the use of different materials, thus enabling a better adaptation of the sealing arrangement to the challenges of sealing electrolysis cells. The outer and inner sealing elements are preferably made of electrically insulating material or materials, particularly non-metallic materials. Electrically insulating materials are those with an electrical conductivity of less than 10'. 8 ' S / m, preferably not more than 10' 10 S / m, particularly preferably not more than 10' 16 S / m.

[0028] The outer sealing element can advantageously consist of a composite material comprising a binder and fillers. The binder can be an elastomer, which is preferably chemically resistant to alkaline and / or acidic electrolyte solutions, such as KOH or NaOH, sulfuric acid, or phosphoric acid solutions. It can be a material selected from the group of rubbers, e.g., a synthetic rubber, such as ethylene propylene diene (monomer) rubber (EPDM) or acrylonitrile butadiene rubber (NBR). The binder typically has a proportion of <30% by weight, preferably <20% by weight, particularly preferably <15% by weight.

[0029] Fillers can consist of particles or fibers. For high compressive strength and thermal resistance, they can be made, for example, of a material selected from the group of temperature-resistant polymers, in particular from the group of aromatic polyamides, polyaryl ether ketones, and polyaryl sulfides, for example from aramids, polyether ether ketone (PEEK), and / or polyphenylene sulfide (PPS). Their proportion can be up to 30% by weight. Particles or fibers can preferably be randomly oriented in the composite material. Fibers or elongated particles can preferably be no longer than 5 mm, particularly preferably no longer than 2 mm.

[0030] Other functional fillers to improve fire protection, tensile strength and / or tear resistance can be, for example, aluminum silicates, such as kaolin, with a proportion of between 30% and 60% by weight, silicon dioxides, such as silica gel or diatomaceous earth, with a proportion of between 10% and 30% by weight, and / or calcium silicates with a proportion of between 10% and 30% by weight.

[0031] In a preferred embodiment, the inner sealing element consists of a particle- and / or fiber-reinforced composite material that is chemically resistant to alkaline and / or acidic electrolyte solutions, such as KOH or NaOH, sulfuric acid or phosphoric acid solutions, as well as to oxygen and hydrogen. The composite material can, for example, consist of a binder from the group of polyhaloolefins, in particular polytetrafluoroethylene (PTFE) or polyvinylidene fluoride (PVDF), as well as particulate and / or fibrous fillers, e.g. fillers made of ceramic and / or glass. When using composite material for the inner sealing element, glass spheres, in particular hollow glass spheres, with a diameter of 1 pm to 99 pm, preferably 10 pm to 90 pm, can preferably be used as the filler.Such particle composite materials have good compressive and thermal strength and are therefore particularly suitable as an internal sealing element for sealing the electrolysis cell.

[0032] The inner sealing element expediently has a greater thickness than the outer sealing element. The thickness is defined as the distance between the contact surfaces of the respective sealing element in an area without segmentation or without shank. The thickness difference Ad between the inner and outer sealing elements without surface pressure, i.e., in the uncompressed state, can preferably be at least the difference in compression between the inner sealing element Si and the outer sealing element S a in the compressed state: Ad > Si - S a. Compression can be understood as the difference in thickness of a sealing element between the uncompressed and compressed state, as can be determined, for example, using the heat compression values ​​according to DIN 28090-2:2014-11.

[0033] A preferred embodiment of the invention is presented below. It shows:

[0034] Fig. 1 is a perspective view of an electrolyzer,

[0035] Fig. 2 shows a section of an electrolysis cell with an example of a sealing arrangement,

[0036] Fig. 3 a detailed view of the inner and outer sealing element, Fig. 4 a detailed view of exemplary embodiments for formations and recesses on sealing elements,

[0037] Fig. 5 is a sectional view of an embodiment of segments of a sealing element with a socketed connection and

[0038] Fig. 6 is a sectional view of another embodiment of segments of a sealing element with a knurled connection.

[0039] Figure 1 shows a perspective view of an electrolyzer with at least one electrolysis cell and two end plates 2, 9, which can be attached and aligned to a cylindrical housing 1 of the electrolyzer using positioning pins. Typically, several electrolysis cells are arranged one behind the other in a cell stack.

[0040] An electrolysis cell consists of a cell frame, two electrodes 3, 6, and a membrane 5. The membrane 5 can be arranged between two optional intermediate grids 4, each located between an electrode 3, 6 and the membrane 5. The cell frame can comprise an intermediate plate with which the cells are spatially separated from an adjacent cell. In the first and last cell of a cell stack, the cell frame can be designed as an end plate 2, 9, as in Figure 1, or integrated into it. The sealing arrangement is arranged between the cell frames of adjacent cells and comprises an inner sealing element 7 and an outer sealing element 8. The sealing elements 7, 8 are thus designed as static seals between stationary parts that form detachable contact seals. The sealing pressure is generated by an external force. The sealing arrangement is preferably a flat seal.

[0041] Figure 2 shows a schematic sectional view of a section of an electrolysis cell with a sealing arrangement. Identical reference numerals in this and subsequent figures denote identical or corresponding components or features. The sealing arrangement is arranged in the main force connection between the cell frames 10 of adjacent electrolysis cells.

[0042] The outer sealing element 8 of the sealing arrangement is typically dimensioned such that its outer diameter rests against the outer edges or in an outer region of the end faces of the cell frames 10. The inner sealing element 7 of the sealing arrangement can be designed such that it is flush with an inner edge of the cell frame 10 or projects beyond it. In embodiments, it can rest against an electrode 3, 6 or another part of the electrolysis cell in a region on the inner circumference.

[0043] Figure 3 shows a section of the sealing arrangement 22 according to the invention. The inner sealing element 7 and the outer sealing element 8 are circular ring discs. The circular ring discs are positively connected to one another via buttonhole connections 30, a section of which is shown in Figure 4. A head 32 forming the connection has a maximum width B and is preferably rounded. However, the head 32 does not have to be circular but can, for example, also be oval. As on the right in Figure 4, a trapezoidal or wedge-shaped head 36 can also be provided for the buttonhole connection. The head 32, 36 can each be mounted on a stem 34. The head 32, 36 and / or the stem 34 have a width b that is smaller than the width B of the head 32, 36. Because the width B of the head 32, 36 is greater than the width b, an undercut is created. The transitions or edges between head 32 and stem 34 and / oror between head 36 and sealing element 7, 8 and / or between stem 34 and sealing element 7, 8 can be rounded. Head 32, 36 and stem 34 form a projection or a formation on the outer circumference of the inner sealing element 7. The recess or cutout 38 on the inner circumference of the outer sealing element 8 is designed to be complementary to the head 32, 36 and stem 34 of the inner sealing element 7, so that head 32, 36 and stem 34 can be inserted into the recess, resting against the inner wall of the inner sealing element 7, and can rest against it over their entire surface.

[0044] In the illustrated, preferred embodiment of Figure 3, the head 32 and stem 34 are arranged on the inner sealing element 7 as projections, which engage in the recess 38 on the outer sealing element 8. The positive connection between the inner sealing element 7 and the outer sealing element 8 can also be created by other connections with an undercut. It is also possible for the connections to be designed differently along the circumferential direction. Likewise, if the same connection is used, it is possible to arrange it alternately between the inner sealing element 7 and the outer sealing element 8.

[0045] The inner and / or outer sealing elements 7, 8 can consist of segments 24a, 24b; 28a, 28b. In the case of annular sealing elements, the sealing elements 7, 8 can be divided radially into segments 24a, 24b; 28a, 28b, as shown in Figure 3. The segments 24a, 24b of the outer sealing element 8 are advantageously arranged offset in the circumferential direction from the segments 28a, 28b of the inner sealing element 7, so that the sealing section between the inner circumference of the inner sealing element 7 and the outer circumference of the outer sealing element 8 is extended in a meandering or labyrinthine manner. The divisions between the segments 28a, 28b of the inner sealing element 7 are preferably evenly spaced from the divisions between the segments 24a, 24b of the outer sealing element 8 in the circumferential direction.The segments of the sealing elements 7, 8 can be connected to one another via knurled joining surfaces 26, like the segments 24a, 24b in Figure 3, or, like the segments 28a, 28b in Figure 3, can be connected to one another in the circumferential direction, preferably also via a buttonhole connection 20. While knurled joining surfaces 26 are formed at an acute or obtuse angle to the contact surfaces 39 of the sealing elements or segments 24a, 24b, the joining surfaces of connections 20, 30 with an undercut are preferably formed perpendicular to the contact surfaces 39 of the sealing elements or segments 28a, 28b for ease of production.

[0046] Advantageously, all connections between the circumferential surfaces of the sealing elements 7, 8 can be designed with an undercut, in particular as a buttonhole connection, and all connections between the segments of the sealing elements 7, 8 can be designed as knurled connections, i.e. as connections with knurled joining surfaces 26. The length of the joining surfaces 26 in at least one of the sealing elements 7, 8, preferably in both sealing elements 7, 8, in the uncompressed state can be at least 8 times the thickness of the respective sealing element in the unknuckled areas. Preferably, it is more than 10 times, particularly preferably at least 11 or 12 times the thickness d. In the region of the knurled connections, the sealing elements 7, 8 can, in the uncompressed state, particularly advantageously have a greater thickness than the thickness of the unknuckled areas.The greater thickness can be adjusted, for example, as shown in Figure 5 or Figure 6, by offsetting the segments and thus also the joining surfaces 26 relative to one another.

[0047] The sealing arrangement 22 described above is intended for alkali electrolysis, in particular pressurized alkali electrolysis. The sealing arrangement consists of an outer sealing element 8 and an inner sealing element 7. The multi-part design of the sealing elements allows the use of different materials and thus better adaptation to the requirements of the electrolysis process. Different thicknesses can also be selected for the sealing elements.

[0048] The outer sealing element 8 is preferably made of a material having the following properties:

[0049] • low compressibility, especially according to ASTM F 36 J - 2015 in the range of 8% to 12%, preferably 9% to 10%,

[0050] • high compressive strength, in particular according to DIN 52913:2002-04 at 100° C in the range of 20 to 50 N / mm based on the thickness of the sealing element, preferably in the range of 30 to 50 N / mm,

[0051] • high springback, especially according to ASTM TF 36 J - 2015 in the range of 40% to 70%, preferably 55% to 66%

[0052] • low cold heading value, especially according to DIN 28090-2:2014-11 in the range of 4% to 8%, preferably 5% to 7%

[0053] • low warm setting value, especially according to DIN 28090-2:2014-11 in a range of 3% to 8%, preferably 4% to 6%

[0054] • Low cold recovery value according to DIN 28090-2:2014-11 of <3%, preferably <2%, and low hot recovery value at 100°C according to DIN 28090-2:2014-11 of <3%, preferably <2%

[0055] The outer sealing element 8 preferably comprises a material selected from the group of rubbers, in particular the group of synthetic rubbers, such as ethylene-propylene-diene (monomer) rubber or acrylonitrile-butadiene rubber. The material is particularly preferably a composite material in which the rubber forms a matrix or a binder into which one or more fillers, such as particles and / or fibers, can be embedded or cast. The matrix or the binder can have a proportion of <30% by weight, preferably <20% by weight, particularly preferably <15% by weight. The fibers and / or particles can, for example, be made of a material selected from the group of aromatic polyamides, polyaryletherketones and polyarylsulfides, for example poly(p-phenyleneterephthalamide), poly(m-phenylenisophthalamide), polyetheretherketone (PEEK) and / or polyphenylene sulfide (PPS).Their proportion can be up to 30% by weight.

[0056] When using composite material for the outer sealing element 8, the fillers can be introduced in any orientation. However, it is also possible to specify a preferred direction, which results, for example, from the use of the sealing elements.

[0057] Other functional fillers to improve fire protection, tensile strength and / or tear resistance can be, for example, aluminum silicates, such as kaolin, for example with a proportion of between 30% by weight and 60% by weight, silicon dioxides, such as silica gel or diatomaceous earth, for example with a proportion of between 10% by weight and 30% by weight, and / or calcium silicates, for example with a proportion of between 10% by weight and 30% by weight.

[0058] Furthermore, it is possible to provide the outer sealing element 8 with a non-stick coating. This can be selected, for example, from a material from the group of polyhaloolefins, such as polytetrafluoroethylene (PTFE).

[0059] The advantage of the above material specifications lies in the high mechanical stability during manufacture and operation of the electrolysis device. Furthermore, the use of composite material prevents creep of the material under load.

[0060] For the inner sealing element 7, a material is preferably provided that is chemically resistant to aqueous, alkaline electrolyte solutions, in particular KOH lye, as well as oxygen and hydrogen. The material preferably has the following properties:

[0061] • No or low swelling behavior towards aqueous electrolyte solutions, preferably <0.2 vol.%, at temperatures up to at least 100°C,

[0062] • high compressive strength, especially according to DIN 52913:2002-04 in the range of 10 to 50 N / mm 2 at 100° C based on the thickness of the sealing element,

[0063] • a lower springback than the material of the outer sealing element, in particular a springback in the range of 20% to 50% according to ASTM F 36 J - 2015, preferably 30% to 40%,

[0064] • a higher cold heading value than the material of the outer sealing element, in particular according to DIN 28090-2:2014-11, a cold heading ratio of the outer sealing element to the inner sealing element in the range of 0.1 to 0.6, preferably 0.2 to 0.5, particularly preferably 0.2 to 0.3. Values ​​of 13% to 40%, preferably 14% to 36%, particularly preferably 17% to 32%, can be provided as cold heading values ​​for the inner sealing element.

[0065] • a higher cold recovery value according to DIN 28090-2:2014-11 than the material of the outer sealing element, in particular a cold recovery value of <6%, preferably <4%, and a higher hot recovery value at 100°C according to DIN 28090-2:2014-11 than the material of the outer sealing element, in particular a hot recovery value of <6%, preferably <4%. For use in acidic electrolysis, the material can be chemically resistant to an acidic aqueous electrolyte solution instead of alkalis.

[0066] The inner sealing element 7 preferably comprises a material selected from the group of polyhaloolefins, such as polytetrafluoroethylene (PTFE). The material is preferably a particle- and / or fiber-reinforced composite material in which the PTFE serves as a base into which fillers—for example, particles and / or fibers, in particular glass spheres, e.g., made of borosilicate glass—are embedded or cast. The glass spheres can preferably be glass microspheres with an outer diameter in the range of 1 μm to 99 μm. Hollow glass microspheres can also be provided. Such materials are advantageously chemically resistant to both aqueous alkaline and acidic electrolyte solutions.

[0067] With the specified materials, specific leakage rates of L<0.001 mg / m / s can be achieved, for example, at an initial surface load or surface pressure of at least 40 MPa, preferably at least 50 MPa, and a surface load after unloading between at least 26 MPa and at least 40 MPa. Higher leakage rates, e.g., 0.01 mg / m / s or more, can be achieved even at a lower surface load after unloading. The sealing arrangement is therefore also suitable for cyclic loading.

[0068] The sealing elements 7, 8 are essentially designed as flat gaskets. Typically, the sealing arrangement or the sealing elements 7, 8 in the direction of the surface pressure to be applied, i.e. perpendicular to the plane of the flat gasket or the contact surfaces, in the uncompressed state has a thickness d in the range from 0.5 mm to 5 mm, preferably from 1 mm to 3 mm, particularly preferably from 1 mm to 2 mm, wherein the inner sealing element 7 in the uncompressed state typically has a greater thickness d than the outer sealing element 8. The thickness difference Ad between the thickness di of the inner sealing element 7 and the thickness d a of the outer sealing element 8 without surface pressure, ie in the uncompressed state, is at least the difference in compression of the inner sealing element Si and the outer sealing element S a in the compressed state: Ad > Si - S a. Compression can be understood as the difference in height or thickness of the respective sealing element between the uncompressed and compressed state, as can be determined, for example, using the hot settling values ​​according to DIN 28090-2:2014-11.

[0069] A compressed state is, in particular, a state under surface pressure for bracing the cell stack at temperatures up to a maximum operating temperature of the electrolysis device. The maximum operating temperature can be up to 95°C during alkali electrolysis. In the compressed state, the thickness of the sealing elements 7, 8 can typically be between 0.5 and 1.5 mm. The surface pressure can be at least 40 MPa, preferably at least 50 MPa, during manufacture of the electrolysis device, in particular when bracing the electrolysis cells to form the cell stack, and in the range from at least 26 MPa to at least 50 MPa during electrolysis operation for a leakage rate L < 0.001 mg / (ms), wherein operation can also include standby phases or temporary shutdown of the electrolysis device. The sealing arrangement can therefore also be advantageously used under cyclic loads.

[0070] The diameter and shape of the sealing elements 7, 8 are preferably selected so that they can be used to seal electrolysis cells at their edges. The sealing elements 7, 8 are arranged in a space between two electrolysis cells for this purpose. The sealing elements 7, 8 are typically arranged in the circumferential direction as a flat seal with the outer diameter of the outer sealing element 8 on an outer edge of the electrolysis cell to be sealed or its cell frame 10, wherein the outer sealing element 8 can be flush with the outer edge or can have a preferably uniform distance from it. In embodiments, the seal can therefore be an annular, e.g., circular, oval or polygonal, in particular rectangular, flat seal adapted to the basic shape or circumferential contour of the electrolysis cell.

[0071] Typically, the maximum outer diameter of the outer sealing element 8 is in a range from 1,000 mm to 2,000 mm, preferably from 1,400 mm to 1,800 mm, particularly preferably from 1,500 mm to 1,600 mm. The surface of the inner circumference of the outer sealing element 8 is shaped to complement the surface of the outer circumference of the inner sealing element 7, so that the sealing elements 7, 8 engage with each other in a form-fitting manner when joined together. The form-fitting connection can be achieved, for example, via buttonhole connections and / or dovetail connections.

[0072] The sealing elements 7, 8 preferably have formations or projections on the inner circumference of the outer sealing element 8 and / or on the outer circumference of the inner sealing element 7. These can in particular be designed as formations for a dovetail or buttonhole connection, i.e. be prism-shaped, trapezoidal, or rounded, whereby the term “rounded” includes circular, elliptical, and other oval shapes. Due to the complementary shaped circumferential surface of the sealing elements 7, 8, the sealing arrangement 22 has a corresponding recess on the other, outer sealing element 8 for each formation of the inner sealing element 7, which recesses engage with one another in a form-fitting manner when joined together. The formations or recesses are accordingly arranged on the respective sealing elements 7, 8 at the same distances on the outer circumference of the inner sealing element 7 and on the inner circumference of the outer sealing element 8.In embodiments, both protrusions and recesses can be formed for each sealing element, in particular alternating with one another. However, in embodiments, either only protrusions or only recesses can be formed on the outer or inner sealing element 7, 8. In a preferred embodiment, only protrusions are formed on the outer circumference of the inner sealing element 7, and only recesses are formed on the inner circumference of the outer sealing element 8.

[0073] Interlocking formations / recesses prevent the sealing elements 7, 8 from slipping during manufacture of the electrolysis cell and during clamping of the cell stack to form an electrolysis device. Formations on the inner sealing element 7 instead of on the outer sealing element 8 increase the alkali or acid resistance and thus the service life of the sealing arrangement because, during electrolysis operation, the alkaline or acidic electrolyte solution penetrates into the sealing arrangement 22 from the inside, i.e. from the direction of the inner sealing element 7, to the outer sealing element 8, and there, formations on the inner sealing element 7 in the penetration direction provide more alkali- or acid-resistant material for the alkali- or acid-resistant seal than recesses. This applies not only to the electrolyte solution, but also to the electrolysis gases.In addition, the formations on the inner sealing element 7, particularly in buttonhole connections with rounded, for example circular or oval, formations, adapt particularly well to the inner wall of the recesses on the outer sealing element 8 in the region of the positive connection when the inner sealing element 7 has a higher cold heading value than the outer sealing element 8, so that improved sealing is achieved. The formations or recesses can preferably be evenly spaced from one another on the respective sealing element, for example each at an angle to one another which, in embodiments, can be between 10° and 15° inclusive, preferably between 11° and 12°. In embodiments, however, the formations or recesses can be formed at any desired, different distances from one another on the respective circumferential surfaces of the sealing elements 7, 8.

[0074] The formations particularly preferably have an undercut so that the formation in one sealing element can be hooked or buttoned into a complementarily shaped recess on the other sealing element, as shown, for example, in Figure 4. Undercut means that the formation has a cross-sectional taper. For this purpose, the formation on the sealing element can have a first diameter b and a second diameter B in the plane of the flat gasket, 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, as shown, for example, in Figure 4. In the case of annular sealing elements, the cross-sectional taper is formed in the radial direction. The ratio of the first diameter b to the second diameter B can in particular be between 0.4 and 0.95, preferably between 0.6 and 0.8.

[0075] Formations on the circumferential surfaces of the sealing elements 7, 8 can typically have a maximum extension of 10 to 50%, preferably 10% to 35% of the total width of the respective sealing element 7, 8 in the plane of the flat gasket, in the case of annular sealing elements 7, 8 in the radial direction, for example in the range from 5 to 20 mm. Formations between segments 28a, 28b of the sealing elements 7, 8 can have a maximum width of 10 to 80%, preferably 10% to 60% of the total width of the respective segment 28a, 28b in the plane of the flat gasket, in the case of annular sealing elements 7, 8 in the radial direction. In embodiments, the formations in a region at the beginning of the sealing element 7, 8 can have a constant diameter in the plane of the flat gasket, e.g. B. be designed as a stem 34 which, for example, connects a rounded area of ​​the formation 32 with the peripheral surface of the sealing element or segment.

[0076] The width of the sealing elements 7, 8 or segments 24a, 24b, 28a, 28b in the plane of the flat gasket, i.e., in the case of annular sealing elements, the width in the radial direction, can be 0.5% to 10% of the outer circumference of the outer sealing element 8 without any protrusions, for example, in the range from 10 to 60 mm, preferably between 20 and 40 mm, particularly preferably between 25 and 30 mm. The width ratio of the outer sealing element 8 to the inner sealing element 7 in the plane of the flat gasket can be in a range from 0.8 to 1.2.

[0077] The segments of the sealing elements 7, 8 can, as shown in Figure 3 by way of example on segments 28a and 28b, have formations and / or recesses in the circumferential direction in order to releasably connect the segments to one another in a form-fitting manner or, as shown in Figure 3 by way of example on segments 24a and 24b, can be designed to be serrated to one another, i.e. with contact surfaces or joining surfaces running obliquely to the contact surfaces 39 and coming to rest at least partially on one another. In addition, in embodiments, a material bond is also possible, for example by gluing the contact or joining surfaces. An adhesive based on cyanoacrylic acid ethyl ester, in particular ethyl-2 cyanoacrylate, is preferably used. Each sealing element 7, 8 can advantageously have between three and nine segments."Squared" means that the respective contact surfaces of adjacent segments 24a, 24b are complementary and flat to one another for joining the segments at the contact surfaces, each at an oblique angle to the plane of the flat gasket, in particular at an acute angle α, β in the range of 3.5° to 20°, preferably 3.5° to 15°, particularly preferably 3.5° to 10°. The acute angles α, β have the same value in Figures 5 and 6, but can also assume different values, as explained below.

[0078] In embodiments, the formations or recesses on the circumferences of the sealing elements 7, 8 can be arranged symmetrically or asymmetrically to a center line of the respective segment, which, in the case of annular sealing elements 7, 8, runs in the radial direction. In preferred embodiments, the formations or recesses on the circumferences of the sealing elements 7, 8 can each be arranged asymmetrically to the center line of the segments.

[0079] In embodiments, the sealing elements 7, 8, in particular the outer sealing element 8, can have through-openings for media feedthrough, for connecting pieces, and / or for pins for positioning the sealing elements 7, 8 on the electrolysis cell. The outer contours or circumferential surfaces of the sealing elements 7, 8 or segments are typically produced using a punching or cutting process, for example, using a laser cutting process, a waterjet process, or a cutting process with hand-guided and / or automatically guided cutting tools, such as a CNC cutter.Any unevenness on the respective surfaces or associated edges, such as can occur with sealing materials containing fibers and / or particles during certain punching or cutting processes, can be well compensated for by the described cold heading value and hot setting value ratios, especially on the peripheral surfaces where the inner and outer sealing elements are positively connected to one another.

[0080] Figure 5 shows a lateral sectional view (not to scale) of a section of a sealing element 7, 8 with knurled joining surfaces or contact surfaces 26. The segments 24a, 24b are arranged offset from one another in the circumferential direction of the sealing element 7, 8 such that the joining surfaces 26 of the adjacent segments 24a, 24b each project beyond one another and cover part of the contact surfaces 39. Firstly, due to this offset, the length L of the knurled connection is greater than the length l of the joining surfaces 26. The lengths l and L are considered here relative to the horizontal. The connecting length L of the segments 24a, 24b is longer than the length l of the joining surfaces 26 by the offset length v, by which the segments 24a, 24b are offset from one another.On the other hand, due to the offset of the segments 24a, 24b, the thickness D of the respective sealing element 7, 8 in the uncompressed state in the area of ​​the segmentation is also greater than the thickness d in the remaining, uncut areas of the sealing element 7, 8, outside the connection length L. The thickness d is increased by the maximum height that the overlapping segment 24a, 24b has in the area of ​​the overlap of the joining surface 26 and the respective contact surface 39.

[0081] The edges between the joining surfaces 26 and the contact surfaces 39 should be burr-free and can be rounded or broken for manufacturing reasons, as indicated by dotted lines in Figures 5 and 6. The acute angles α, β between the contact surface 39 and the joining surface 26 are each formed on the opposite contact surfaces 39 or sides of a segment 24b, i.e. on a diagonal connecting line between the edges of the segment. The angles α and β of a segment can have different values, but for simple manufacturing they are preferably the same size so that the joining surfaces 26 of the segment run parallel to one another. The lengths of the joining surfaces 1, the connecting lengths L or the angles α, β of the segments can be different from one another or the same size within one sealing element or in both sealing elements 7, 8.For simple production, in particular the lengths 1 of the joining surfaces 26 or the angles a between the joining surfaces 26 and the contact surfaces 39 can be the same for all segments of a sealing element or both sealing elements 7, 8.

[0082] The offset v = (L - 1) of the segments 24a, 24b relative to one another can be achieved very easily in the case of rotationally symmetrical sealing elements 7, 8 by rotating the segments 24a, 24b relative to one another in the circumferential direction of the respective sealing element 7, 8. The offset v is selected as a function of the angle α, β of the knurled joining surfaces 26, the length 1 of the joining surfaces and the thickness d of the uncompressed segment such that the thickness D in the area of ​​the joining surfaces 26 in the uncompressed state is up to 120%, preferably between 102% and 120%, of the thickness d of the respective sealing element 7, 8. Due to the increased thickness D, the contact pressure in the area of ​​the knurled connection is increased and thus very good sealing is possible despite segmentation.

[0083] Figure 6 shows a side sectional view of another example of a sealing element 7, 8 with knurled joining surfaces or contact surfaces 26. As in Figure 5, the segments 24a, 24b are also arranged in an offset, oblique butt joint, so that the congruently shaped joining surfaces 26 of the segments 24a, 24b project beyond one another and each partially overlap a contact surface 39. As a result, the thickness d of the sealing element is increased by the maximum height that the segment has at the overlapping area of ​​the joining surfaces 26. In contrast to the segments of Figure 5, however, the joining surfaces 26 of the segments 24a, 24b of Figure 6 have acute angles a, ß only to one of the contact surfaces 39, ie on one of the sides of the respective segment, while on the opposite contact surface 39 or side only obtuse angles are formed, so that the joining surfaces 26 of the respective segment are inclined to one another.The angles α and β can be equal for ease of manufacturing. However, different angles α and β are also possible, both within a segment and with respect to the segments of the inner and outer sealing elements 7, 8.

[0084] The lengths of the joining surfaces 1, the connection lengths L or the angles α, β between joining surfaces 26 and contact surfaces 39 of the segments can be different or the same in one or both sealing elements 7, 8. For simple production, in particular the lengths 1 of the joining surfaces 26 or the angles α and β between the joining surfaces 26 and the contact surfaces 39 can be the same in one or both sealing elements 7, 8. The inner and / or outer sealing element can, for example, have joining surfaces 26 with a length 1 = 15.0 mm in the uncompressed state. The outer sealing element 7 can have a thickness d of 1.0 mm and a connection length L of 16.5 mm. The inner sealing element 8 can have a thickness d of 1.5 mm and a connection length L of 15.3 mm. For equal angles, the angles a and ß can, for example, be 3.8 degrees in one or both sealing elements 7, 8.The outer sealing element 7 can have a thickness d of 1.0 mm and a connection length L of 16.5 mm. The inner sealing element 8 can have a thickness d of 1.5 mm and a connection length L of 23.0 mm.

[0085] List of reference symbols

[0086] 1 housing

[0087] 2 end plate

[0088] 3 Electrode, anode

[0089] 4 intermediate grilles

[0090] 5 Membran

[0091] 6 Electrode, cathode

[0092] 7 Inner sealing element

[0093] 8 Outer sealing element

[0094] 9 End plate

[0095] 10 cell frames

[0096] 11 Intermediate plate

[0097] 20 buttonhole connection

[0098] 22 Sealing arrangement

[0099] 24a, 24b segments

[0100] 26 Business Connection

[0101] 28a, 28b segments

[0102] 30 buttonhole connection

[0103] 32, 36 head

[0104] 34 handle

[0105] 38 recess

[0106] 39 Contact surface b Width of a stem of a connection

[0107] B Width at the head of a connection d Thickness of a sealing element outside a connection

[0108] D Thickness of a sealing element at a connection

[0109] 1 Length of a joining surface

[0110] L Connection length of interconnected segments

Claims

Claims 1. Sealing arrangement for sealing electrolysis cells in an electrolysis device, in particular in an alkaline pressure electrolysis, with an inner sealing element (7) and an outer sealing element (8), characterized in that the sealing elements (7, 8) are designed as flat seals which are arranged in a form-fitting manner with respect to one another on an inner circumference of the outer sealing element (8) and an outer circumference of the inner sealing element (7).

2. Sealing arrangement according to claim 1, characterized in that the inner sealing element (7) and / or the outer sealing element (8) is designed as an annular disc, in particular as a circular disc, with one or more ring segments (24a, 24b; 28a, 28b) in the circumferential direction.

3. Sealing arrangement according to one of the preceding claims, characterized in that the positive connection is formed in the circumferential direction between the inner sealing element (7) and the outer sealing element (8).

4. Sealing arrangement according to one of the preceding claims, characterized in that the positive connection is also formed in the radial direction between the inner sealing element (7) and the outer sealing element (8), in particular via recesses and formations with an undercut, preferably via a dovetail connection or a buttonhole connection (30).

5. Sealing arrangement according to claim 4, characterized in that formations (32, 34, 36) with undercut on the outer circumference of the inner Sealing element (7) are arranged and recesses (38) complementary to the formations (32, 34, 36) are arranged on the inner circumference of the outer sealing element (8).

6. Sealing arrangement according to one of the preceding claims, characterized in that the inner and / or the outer sealing element (7, 8) have two or more ring segments (24a, 24b; 28a, 28b) which are connected to one another in the circumferential direction via shouldered joining surfaces (26) and / or via an undercut, in particular an undercut of a dovetail connection or a buttonhole connection (20).

7. Sealing arrangement according to claim 6, characterized in that the ring segments (24a, 24b; 28a, 28b) have an increased thickness D in the region of the knurled joining surfaces (26) compared to regions without joining surfaces.

8. Sealing arrangement according to one of claims 6 or 7, characterized in that the knurled joining surfaces (26) are arranged offset from one another in the circumferential direction, so that they each overlap with a contact surface (39).

9. Sealing arrangement according to one of claims 2 to 8, characterized in that the ring segments (24a, 24b) of the outer sealing element (8) are arranged offset from the ring segments (28a, 28b) of the inner sealing element (7).

10. Sealing arrangement according to one of the preceding claims, characterized in that the inner sealing element (7) has a greater cold heading value than the outer sealing element (8).

11. Sealing arrangement according to one of the preceding claims, characterized in that a quotient of a cold upsetting value of the outer sealing element (8) to a cold upsetting value of the inner sealing element (7) is less than 0.

6.

12. Sealing arrangement according to one of the preceding claims, characterized in that a quotient of a heat setting value of the outer sealing element (8) to a heat setting value of the inner sealing element (7) is less than 0.

8.

13. Sealing arrangement according to one of the preceding claims, characterized in that the outer sealing element (8) has a higher springback value than the inner sealing element (7).

14. Sealing arrangement according to one of the preceding claims, characterized in that the quotient of a springback value of the outer sealing element (8) to a springback value of the inner sealing element (7) is greater than 1.

4.

15. Sealing arrangement according to one of the preceding claims, characterized in that the outer sealing element (8) consists of a composite material consisting of a rubber and at least one filler made of particles or fibers.

16. Sealing arrangement according to one of the preceding claims, characterized in that the inner sealing element (7) consists of a composite material consisting of polytetrafluoroethylene (PTFE) and at least one filler made of particles or fibers.

17. Sealing arrangement according to one of the preceding claims, characterized in that the inner sealing element (7) has a greater thickness than the outer sealing element (8).

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