Pressure electrolyser, electrolysis system and electrolysis method
Patent Information
- Application Number
- EP2023793802
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2022-10-25
- Filing Date
- 2023-10-20
- Publication Date
- 2025-09-03
Smart Images
Figure 1.1
Abstract
Description
[0001] Pressure electrolyzer, electrolysis plant and electrolysis process
[0002] Technical area
[0003] The present invention relates to a pressure electrolyzer designed according to the preamble of claim 1, in particular a high-pressure electrolyzer, such as an alkaline electrolyzer for water electrolysis. The present invention further relates to an electrolysis system, in particular a water electrolysis system, with a corresponding pressure electrolyzer, and to an electrolysis process carried out in the electrolyzer.
[0004] State of the art
[0005] Electrolyzers that operate at a pressure higher than atmospheric pressure are known, for example, from publications DE 10 2014 010 813 A1 and EP 1 464 730 A1. For reasons of mechanical integrity, these pressure electrolyzers have a pressure-bearing frame structure to protect the electrolysis block, i.e., the cell stack with electrolysis cells. Known pressure electrolyzers perform electrolysis at a pressure of approximately 20 to 50 bar.
[0006] The document DE 44 18 999 A1 discloses a pressure electrolyzer with a cell block installed in a cylindrical pressure tube. The pressure tube is closed at its ends by end flanges, which also serve as the end flanges of the cell block. This ensures the same pressure conditions inside and outside the cell spaces of the electrolysis cells. In this electrolyzer, both the internal sealing of the electrolysis cells and the external sealing of the tubular pressure vessel are provided by an axial seal. Therefore, the electrolyzer must operate with very tight tolerances. This axial seal enables proper sealing of the electrolyzer only at a relatively low operating pressure of the electrolysis cells.
[0007] Figure 4 of EP 0 212 240 A1 discloses a pressure electrolyzer in which the end flanges of the cell block are cast into a common seal. This seal serves both to seal the electrolysis cells from each other and to seal the interior of the pressure vessel from the environment. Due to the high pressure load, this seal must be very strong to withstand the pressure conditions acting on it.
[0008] Pressure electrolyzers that perform electrolysis under high pressure, for example, at a pressure of at least 200 bar, such as 350 bar or 700 bar, are called high-pressure electrolyzers. A high-pressure electrolyzer can, for example, produce compressed hydrogen, which can be used as a fuel or as an energy source.
[0009] A pressure electrolyzer designed according to the preamble of claim 1 is known from document US 2011 / 0210012 A1. This pressure electrolyzer is a high-pressure electrolyzer and is used to produce hydrogen. To protect the electrolysis block from pressure-induced mechanical stresses, document US 2011 / 0210012 A1 teaches arranging the cell stack, the so-called electrolyzer stack, in a cup-shaped pressure vessel sealed against ambient pressure and subjected to the electrolyzer's working pressure. An end plate of the cell stack forms a stationary head, which is integrally formed with a lid of the cup-shaped pressure vessel and is equipped with electrical anode and cathode connections.The second end plate of the cell stack forms a moving head, which can move freely longitudinally relative to the stationary head in response to thermally induced expansion or contraction of the electrolysis cells. To seal the cell frames of the respective electrolysis cells from one another, these have internal O-ring seals surrounding the cell frames. To separate the interior of the pressure vessel from the ambient pressure, external seals are also provided, which are axially clamped between the stationary head and an anode plate of the cell stack (Figure 2 of US 2011 / 0210012 A1). The disadvantage of this system is that it is complex in design, and strong mechanical forces act on the anode plate of the cell stack due to the existing pressure difference.
[0010] US4210511 discloses a pressure electrolyzer with a cell block installed in a cylindrical tubular pressure vessel. The tubular pressure vessel comprises a pressure tube and two end flanges, each of which closes one end of the pressure tube in the operating position. The end flanges have axial passages for threaded rods, which clamp the electrolysis cells axially between the end flanges by means of attached nuts. To prevent a short circuit between the poles of the cell block, washers made of electrically insulating material are provided between the nuts and the end flanges. The washers also allow the threaded rods to be centered in the respective passages, thus ensuring radial clearance between the threaded rods and the end flanges. At each end, the end wall of the pressure tube has a circumferentially extending receiving groove that is open radially toward the interior of the pressure tube.The end flanges each have an axially projecting projection carrying a radial seal, which, in the use position, is designed to be sealingly received in the receiving groove. A retaining plate is provided between each end flange and the cell block. In the use position, this retaining plate holds the cells of the cell block axially and simultaneously comes into contact with the bottom of the receiving groove. When the end flanges are pressed against each other, the inward-facing surface of the projections comes into firm contact with the retaining plates, so that each retaining plate comes into contact with the respective bottom of the receiving groove and holds the cells together. In this electrolyzer, the internal sealing of the electrolysis cells is provided by an axial seal, and the external sealing of the tubular pressure vessel is provided by a radial seal.The design of the electrolyzer requires machining of the end walls, particularly the manufacturing of the mounting groove, which requires tight tolerances. The mounting groove must allow simultaneous axial contact between the holding plate and the bottom of the mounting groove and with the cell block. Furthermore, the electrolyzer must operate with very tight tolerances, particularly the cell thickness tolerance, to enable and maintain this contact during operation, so that mechanical stress on the holding plates and the external seal does not cause a loss of tightness. During operation, the electrolyzer experiences an increase in temperature, which causes the cells to expand, thus placing further stress on the holding plates. This can cause the insulating material discs to suffer mechanical stress and become damaged over time.
[0011] CN104911626B discloses a pressure electrolyzer for hydrogen production, comprising a positive end plate and a negative end plate. Flat cylindrical seals and cell frame assemblies are arranged offset between the positive end plate and the negative end plate. Threaded rods are passed through the positive end plate and the negative end plate to clamp the combined seal and cell frame assemblies. Sealing against ambient pressure is achieved via the flat cylindrical seals in the axial direction. In contrast to the pressure electrolyzer disclosed in US4210511, the cell block of the pressure electrolyzer is not installed in a cylindrical tubular pressure vessel. For this reason, the cell frame assemblies are subjected to high mechanical stress when a high working pressure is applied.
[0012] Description of the invention
[0013] Based on the disadvantages and deficiencies outlined above, and taking into account the prior art outlined above, the present invention is based on the object of developing a pressure electrolyzer of the type mentioned above in such a way that the pressure electrolyzer can be manufactured as simply and cost-effectively as possible. Furthermore, the pressure vessel should seal itself against the ambient pressure in a simple, reliable, and durable manner. In particular, the pressure electrolyzer should be designed such that the mechanical forces acting on the internal seals and the external seal are as low as possible, and the pressure electrolyzer should have as few separate components as possible. Furthermore, the pressure electrolyzer should have reliable and durable insulation that prevents short circuits.
[0014] Furthermore, the present invention is based on the object of providing an electrolysis plant comprising the pressure electrolyzer and a method for providing at least one gas product by means of electrolysis, which method is carried out in the pressure electrolyzer.
[0015] This object is achieved by a pressure electrolyzer having the features specified in claim 1, an electrolysis system having the features specified in claim 14, and a method having the features specified in claim 15. Advantageous embodiments and expedient further developments of the present invention are characterized in the respective dependent claims.
[0016] The invention relates to a pressure electrolyzer for providing at least one gas product, comprising a cell stack with several electrolysis cells designed for electrochemical electrolysis and a pressure vessel sealed against the ambient pressure.
[0017] Preferably, the pressure electrolyzer is designed to carry out the electrolysis of water into its elements oxygen and hydrogen, which are produced as gas products.
[0018] The electrolysis cells are connected in series in an axial direction and clamped between a first stack end plate and another stack end plate. Furthermore, the electrolysis cells each have a cavity in which a working pressure is applied, as well as a stabilizing cell frame surrounding the cavity.
[0019] In the cell stack, an internal seal is arranged between each cell frame. The internal seals surround the respective cavities of the electrolysis cells and seal them off from the surroundings. The internal seals are arranged axially between the cell frames and clamped between the stack end plates.
[0020] The preferably cylindrical pressure vessel comprises a pressure-resistant housing body with an end wall at each axial end, as well as the first stack end plate as the top surface and the second stack end plate as the base surface. The housing body is clamped between the first stack end plate and the second stack end plate and has at least one external seal designed to seal the interior of the pressure vessel against the ambient pressure.
[0021] The cell stack is accommodated in the interior of the pressure vessel in a working section of the housing body, in which pressure vessel the working pressure of the electrolysis cells is applied.
[0022] At least one of the first stack end plate or the further stack end plate has an axial end plate projection. In other words, the first stack end plate or the further stack end plate, or both stack end plates, have an axial end plate projection. Furthermore, the external seal is clamped in the radial direction between the housing body and a sealing portion of the end plate projection.
[0023] According to the invention, the sealing section has a cross-section that, in the use position, is inscribed in the cross-section of the working section. Furthermore, the sealing section protrudes into the working section of the housing body. Furthermore, the end plate projection has a stamping surface on its side facing the cell stack, which, in the use position of the pressure electrolyzer, presses the cell stack in the axial direction to clamp the cell stack between the first and the further stack end plates.
[0024] Specifically, at least one of the first stack end plate or the further stack end plate comprises a closing plate, which can act as a cover surface or as a base surface, and the end plate projection, which projects axially inwardly from the closing plate and projects into the working section.
[0025] To clamp the electrolysis cells axially between the stack end plates, the pressure electrolyzer advantageously comprises fastening elements or fastening rods that clamp the stack end plates together. For example, the fastening elements can comprise threaded rods as tie rods, which clamp the electrolysis cells axially between the stack end plates by means of attached nuts. The fastening elements are preferably electrically insulated from the first stack end plate and the other stack end plate.
[0026] Because the sealing section of the end plate projection has a cross-section that, in the operating position, is inscribed in the cross-section of the working section, the sealing section can be inserted into the pressure vessel. The end plate projection protrudes into the pressure vessel by at least the insertion length of the end plate projection. In this case, the cross-section defines the cross-section running perpendicular to the axial direction.
[0027] The end plate projection extending into the working section of the housing body allows for greater tolerance in the design of the pressure electrolyzer, particularly in the thickness tolerance of the electrolysis cells. The end plate projection can extend more or less into the housing body depending on the deviation from the nominal thickness of the cell stack. This is achieved without compromising the tightness because the external seal is arranged radially between the sealing section of the end plate projection and the housing body.
[0028] Furthermore, the tightness of the pressure vessel can be ensured independently of the design of the end walls of the housing body because the external seal is formed in the working section in the use position and not between the end walls and the closing plate.
[0029] In one embodiment, one of the first stack end plate or the further stack end plate is formed integrally and in one piece, ie the end plate projection and the closing plate form an inseparable unit, preferably made of a single material.
[0030] A pressure electrolyzer can comprise one hundred or more electrolysis cells, each with a nominal thickness and a thickness tolerance. Consequently, the thickness tolerance is multiplied by a factor of one hundred or more when calculating the total thickness of the cell stack. With an electrolysis cell thickness tolerance of + / - 0.1 mm, this corresponds to a dimension deviation, i.e. a deviation from the nominal dimension, of + / - 10 mm for the cell stack. Since the end plate projection protrudes into the working section of the housing body, it can protrude more or less depending on the dimension, while its stamping surface presses the cell stack in the axial direction. The end plate projection can thus compensate for the dimension of the cell stack. The working pressure in the pressure vessel is maintained because the external seal is clamped radially between the housing body and the end plate projection. A larger thickness tolerance is therefore permitted during production.This is advantageous because the production of the electrolysis cells is simplified and thus cheaper.
[0031] This is not possible in a pressure electrolyzer such as that in US4210511, even though the external seal is axially sealed between each end plate projection of the stack end plates. In US4210511, the end plate projection is designed to be received in a groove in the end wall, in which the end plate projection presses a retaining plate axially against the bottom of the groove in the use position. At the same time, the retaining plate must hold the electrolysis cells of the cell block axially. This design requires electrolysis cells with very small thickness tolerances. Otherwise, if the lower dimension of the cell block is too large, the electrolysis cells can no longer be held by the retaining plates. In this case, a gap forms between the cell block and the retaining plates, which impairs the tightness of the internal seal.Conversely, the retaining plates no longer come into contact with the respective bottom of the receiving groove if the upper dimension of the cell block is too large.
[0032] In this case, the nominal thickness of the cell stack is the sum of the nominal thicknesses of the electrolysis cells. The deviation of the cell stack is the cumulative deviation of the thicknesses of the electrolysis cells from their nominal thickness. The upper deviation of the cell stack is the highest positive tolerance, i.e. the maximum positive deviation from the nominal thickness. This occurs when each electrolysis cell has the maximum positive deviation from its nominal thickness. The lower deviation of the cell stack is the highest negative tolerance, i.e. the maximum negative deviation from the nominal thickness. The nominal thickness plus the upper deviation equals the maximum dimension, i.e. the maximum thickness of the cell stack. The nominal thickness minus the lower deviation equals the minimum dimension, i.e. the minimum thickness of the cell stack.
[0033] In a preferred embodiment, the end plate projection has a cross-section over its entire axial length that, in the use position, is inscribed in the cross-section of the working section. The manufacture of the end plate projection is thus simplified. Furthermore, the end plate projection can, if necessary, be inserted into the working section over its entire length, thereby compensating for larger thickness tolerances.
[0034] In a preferred embodiment, the stamping surface is oriented perpendicular to the axial direction in order to have a stamping surface running parallel to the electrolysis cells, which can press the cell stack homogeneously.
[0035] Preferably, the stamping surface is in direct contact with the electrolysis cell facing the stamping surface in order to avoid interfaces.
[0036] Furthermore, the present invention is based on arranging the cell stack in a pressure vessel designed as a closed pressure compartment and clamping it between two stack end plates. At least one external seal designed to seal the interior of the pressure vessel from the ambient pressure is arranged in such a way that the forces clamping the cell stack and the forces bracing the external seal act in different directions. In the present invention, the forces acting on the cell stack and the forces acting on the external seal are thus aligned differently and thus distributed more evenly. This reduces the requirements for the stability of the cell stack and the stability of the external seal, and allows the latter to be manufactured from a wider range of materials.This also has the advantage that the electrolysis cells are free of the external seal and are therefore easier to manufacture.
[0037] In a preferred embodiment, the end plate projection comprises an inner portion and an outer portion. In the use position, the inner portion is arranged in the housing body and comes into contact with the cell stack. The sealing portion is part of the inner portion. Furthermore, in the use position, the outer portion is arranged outside the housing body and is intended to form an axial air gap between the end wall of the housing body and at least one of the first stack end plates or the further stack end plates.
[0038] The axial air gap between the housing body, in particular its end wall, electrically insulates the housing body from at least one of the first stack end plates or from the further stack end plate in the axial direction. In the radial direction, the external seal arranged between the end plate projection and the housing body electrically insulates the housing body from at least one of the first stack end plates or from the further stack end plate. Thus, insulation of the fastening elements which clamp the first stack end plate and the further stack end plate together is only necessary for the first stack end plate or the further stack end plate. In a preferred embodiment, the end plate projection is electrically insulated from the housing body by an electrically insulating support element. The support element supports a coaxial arrangement of the housing body to the end plate projection.This also ensures that a short circuit between the housing body and the end plate projection is more reliably prevented. The support element extends radially between the end plate projection and the housing body and preferably lies directly axially against the external seal to prevent the external seal from slipping.
[0039] The axial section of the pressure vessel in which the cell stack is arranged in the operating position defines the working section of the pressure vessel. The working section extends over an axial length that is at least equal to the sum of the nominal thickness of the cell stack, the upper dimension of the cell stack, and an axial reserve length.
[0040] The reserve length is intended to accommodate the inner section of the end plate projection into the housing body, so that the end plate projection, particularly its stamping surface, comes into contact with the cell stack in the operating position. At least the sealing section is located in the working section. Depending on the actual dimensions of the cell stack, the length corresponding to the upper dimension can also be intended to accommodate the inner section of the end plate projection.
[0041] The total axial length of the end plate projection includes the insertion length, which corresponds to the inner portion, and may include a residual length corresponding to an outer portion of the end plate projection extending outside the housing body. The total axial length of the end plate projection extends from the punch surface to the base of the end plate projection, which base is located at the level of the closing plate.
[0042] In a preferred embodiment, the total length of the end plate projection is calculated such that an axial air gap is present between the closure plate and the corresponding end wall of the housing body in the use position. This enables electrical insulation between the housing body and the stack end plate.
[0043] The total axial length of the endplate projection is at least equal to the sum of the bottom dimension of the cell stack, ensuring that the endplate projection comes into contact with the cell stack, and the thickness of the sealing section, ensuring that the sealing section is within the working section for the tightness of the pressure vessel. In the operating position, the insertion length of the endplate projection depends on the actual dimension of the cell stack.
[0044] For the sake of completeness, it should be mentioned that the reserve length can also be calculated so that additional electrolysis cells can optionally be incorporated into the cell stack. In such an embodiment, the total axial length of the end plate projection is calculated so that the end plate projection comes into contact with the cell stack in the use position.
[0045] Furthermore, it should be mentioned that the operating position of the pressure electrolyzer corresponds to an assembled state of the pressure electrolyzer.
[0046] The working section has a cross-section that allows for the cell stack to be accommodated. The cross-section of the cell stack is inscribed within the cross-section of the working section, whereby a radial clearance may be maintained between an inner surface of the housing body and the cell stack over the entire circumference of the cell stack. This allows for electrical insulation between the cell stack and the housing body.
[0047] Preferably, the working section has the same cross-section across its entire length. Particularly preferably, the housing body has the same cross-section as the cross-section of the housing body across its entire length. This simplifies the manufacture of the housing body and consequently reduces its cost. In a preferred embodiment, the working section extends across the entire axial length of the housing body. Thus, the cell stack can be flexibly arranged within the housing body. The cross-section of the housing body can remain constant across its entire length.
[0048] In a preferred embodiment, the end plate projection has the same cross-section as the cross-section of the electrolysis cells. This embodiment ensures that the cell stack is pressed homogeneously in the axial direction by the end plate projection.
[0049] The housing body is preferably cylindrical, particularly preferably circularly cylindrical, in order to create a radial distribution of the forces exerted by the working pressure. In the circular-cylindrical embodiment, the cross section of the housing body forms a circular cross section that has the same diameter over the axial length of the housing body. Furthermore, the end plate projection has a cross section that, in the use position, is inscribed in the circular cross section of the working section. Specifically, the longest dimension of the cross section of the end plate projection is smaller than the diameter of the circular cross section.
[0050] In a preferred embodiment, the end plate projection is formed as a circular, axially centered disc, which, in the use position, extends at least partially into the working section. This embodiment ensures that the cell stack is pressed evenly in the axial direction by the end plate projection.
[0051] Preferably, the working section extends over the entire length of the housing body so that the housing body can accommodate as many electrolysis cells as possible.
[0052] In the present pressure electrolyzer, the internal seals preferably act in the axial direction and the external seal in the radial direction, i.e., the internal seals seal in the axial direction and the external seals seal in the radial direction. In other words, the forces acting on the internal seals are aligned along the longitudinal axis of the pressure vessel housing body, for example, horizontally. The forces acting on the external seal are aligned along the radius of the pressure vessel housing body, i.e., in the radial direction. Due to this different alignment of the internal seals and the external seal, the overall mechanical stress acting on these seals is reduced.This ensures that the seals, both internal and external, reliably fulfil their sealing function even under very high pressure conditions, can be manufactured from cost-effective materials and are designed to be durable.
[0053] The pressure vessel is formed from the two stack end plates of the cell stack and a tubular or shell-like housing geometry, which forms the housing body and is pressure-tightly connected to the end plates, also called stack end plates, of the electrolysis cell stack.
[0054] Since the base and top surfaces of the pressure vessel are formed from end plates of the cell stack, the pressure vessel has a particularly simple design and very few individual parts. The first stack end plate can be designed as an anodic end plate in its area facing the electrolysis cells, particularly in an area designed as a stamping surface, and the other stack end plate can be designed as a cathodic end plate in its area facing the electrolysis cells, or vice versa. The electrical insulation of the pressure electrolyzer is designed such that an electrical current can flow between the end plates, thereby avoiding potential electrical short circuits caused, for example, by fastening elements or the housing body.
[0055] The anodic end plate and / or the cathodic end plate may be split into two parts, as described in more detail below.
[0056] In a preferred embodiment, the first stack end plate and the further stack end plate each have an end plate projection. This allows for a symmetrical design of the pressure electrolyzer. The end plate projection is preferably designed identically for the first stack end plate and the further stack end plate. Particularly preferably, the first stack end plate and the further stack end plate are designed identically, so that only a single stack end plate needs to be designed, which fits both ends of the housing body.
[0057] In a preferred embodiment, the first stack end plate or the further stack end plate has an end plate projection. This embodiment has the advantage that only one stack end plate, e.g., the first stack end plate, needs to be machined to form the end plate projection. The further stack end plate can be sealingly connected to the housing body via an external seal arranged between the corresponding end wall of the housing body and the further stack end plate.
[0058] In a preferred embodiment, the plunger surface lies directly against the electrolysis cell facing the plunger surface. This allows for a compact design of the pressure electrolyzer to be produced.
[0059] In a preferred embodiment, at least one of the first stack end plate or the further stack end plate is the first stack end plate, which first stack end plate is detachably connectable to the housing body and is designed to close an axial opening in the housing body in a pressure-tight manner. This means that only one of the two stack end plates has an end plate projection, in this case the first stack end plate, wherein the external seal is clamped in the radial direction between the housing body and the end plate projection. The further stack end plate is formed integrally and pressure-tightly with the housing body. Integral is to be understood as meaning that the housing body and the further stack end plate are connected to one another to form a single complete piece. For example, the housing body and the further stack end plate can be welded together tightly.The pressure vessel can thus be designed as simply as possible because no external seal is required on this side. In a preferred embodiment, the external seal runs around the outer circumference of the end plate projection, which end plate projection preferably has a circumferential sealing groove in the sealing section to accommodate the external seal. The production of the sealing groove in the end plate projection, particularly in the sealing section of the end plate projection, is less complex than in the inner wall of the housing body. Furthermore, the wall thickness of the housing body can be selected to be thinner if the sealing groove is formed in the end plate projection. This is advantageous for manufacturing costs. In the assembled state, the external seal acts radially. The external seal is designed as a separate element which is clamped between the housing body and a radial sealing surface, wherein the sealing surface forms a bottom of the sealing groove.Preferably, the bottom of the sealing groove, seen in the longitudinal cross-section, runs parallel to the axial direction.
[0060] In a preferred embodiment, the outer circumference of the stack end plates is larger than the outer circumference of the housing body, so that the stack end plates have an outer region extending away from an outer surface of the pressure vessel. Furthermore, the stack end plates are arranged parallel to one another. Furthermore, the stack end plates are clamped together at their outer region by means of at least three fastening elements extending in the direction of the longitudinal axis of the housing body, i.e., in the axial direction, such that the cell stack is clamped axially between the stack end plates, in particular between the die surface and the opposite stack end plate.
[0061] Each electrolysis cell has a surrounding cell frame for stability. To seal adjacent electrolysis cells from each other, the internal seal is located between two cell frames in the cell stack.
[0062] The internal seals are each clamped between two cell frames, each with a frame groove for accommodating an internal seal. The frame grooves each have a sealing surface that forms a bottom of the frame groove. Preferably, the bottom of the frame groove runs parallel to the plane of the respective cell frame.
[0063] Preferably, the sealing surface of the frame grooves is arranged perpendicular to the sealing surface of the sealing groove.
[0064] In a preferred embodiment, the external seal is designed as a double seal. In this embodiment, an additional external seal runs around the outer circumference of the end plate projection, which end plate projection preferably has a further circumferential sealing groove for accommodating the additional external seal. This better ensures the tightness of the pressure vessel.
[0065] In a preferred embodiment, the end wall of the housing body which faces the at least one of the first stack end plates or the further stack end plate runs in a plane extending at right angles to the axial direction. The housing body can therefore be manufactured cost-effectively because the end formed by the end wall can be produced via a cut without complex machining of the end wall, e.g. without a groove or without a step. The end wall runs in a plane which can be created from a cut transverse to the axial direction. In other words, the end wall runs from the outer surface of the housing body to the inner surface of the housing body in one plane, i.e. the transition from the outer surface to the inner surface runs without interruption, e.g. without interruption by a recess or a groove.Preferably, both ends of the housing body each extend in a plane extending perpendicular to the axial direction. Preferably, the end wall of the housing body extends at both ends in a plane extending perpendicular to the axial direction.
[0066] When clamping the stack end plates, the fastening elements can be electrically insulated from the stack end plates by insulating elements to prevent an electrical short circuit between the cell block poles. The stack end plates can have axial passages for the fastening elements, e.g., threaded rods. For insulation, insulating elements made of electrically insulating material can be provided between the fastening elements and the stack end plates. The insulating elements can be discs, which simultaneously allow centering of the fastening elements in the respective passages, thus ensuring radial clearance between the fastening elements and the stack end plates. It is also possible to provide a housing body made of electrically insulating material.
[0067] In a preferred embodiment, at least one of the first stack end plate or the further stack end plate is designed in the form of an assembly, wherein the closure plate, which acts as a cover surface or as a base surface, and the end plate projection are designed separately, wherein the closure plate and the end plate projection are electrically insulated from one another by a separating layer made of electrically insulating material. In other words, the first stack end plate or the further stack end plate, or both stack end plates, are designed as an assembly.
[0068] Thus, at least one of the first stack end plate or the further stack end plate is split in two. The elements of the assembly, i.e. the closing plate, the end plate projection and the separation layer, are easier to manufacture because three functions of the stack end plate, namely stability of the pressure electrolyzer, pressure tightness and electrical insulation, can be separated. The selection of materials for the elements of the stack end plate can thus be optimized depending on the function of the elements. The closing plate must act as a pressure element in the axial direction and thereby contribute to the stability of the pressure electrolyzer. In contrast, the end plate projection, which carries the external seal, acts as a sealing element. In addition, the separation layer acts as an insulating element between the poles of the cell block. Electrical contact with the cell stack can be established via a passage formed in the closing plate and the separation layer.Manufacturing the stack end plate as a single assembly is simplified because milling a base plate to create the end plate projection is eliminated. It should be noted that the housing body of an electrolyzer can be up to 2.5 meters long and have a diameter of up to 1.5 meters. The milling must adhere to tight tolerances to ensure the tightness and mechanical stability of the pressure vessel. Machining the base plate can therefore be difficult, especially with large diameters.
[0069] This design also has the advantage that no further electrical insulation of the fastening elements is required. In contrast to the design in which electrical insulation is provided between the fastening elements and the stack end plates, the separating layer assumes the function of insulation between the poles of the cell block. Consequently, fewer components are required. Furthermore, the pressure electrolyzer is less susceptible to insulation failure, allowing it to be operated more safely. The insulation is provided in one location, namely at the separating layer, which is homogeneously pressed axially between the end plate projection and the closing plate. The separating layer is hardly exposed to any other mechanical stresses. In contrast, the insulating elements are subjected to mechanical stress during assembly of the pressure electrolyzer.When disc-shaped insulation elements are used, they are each pressed between a nut and the stack end plate and subjected to shear stress when the nut is screwed in tightly. These disadvantages can be avoided in the present embodiment.
[0070] The electrical contact to the end plate projection can be made via an electrical connection which is electrically insulated through the separating layer and the closing plate.
[0071] In a preferred embodiment, the first stack end plate and the further stack end plate are each designed as an assembly. This allows for a symmetrical design of the pressure electrolyzer. Preferably, the first stack end plate and the further stack end plate are designed identically, so that only a single stack end plate needs to be designed, which fits both ends of the housing body.
[0072] The features of the end plate projection disclosed in the above-described one-piece embodiment of the stack end plate are also applicable to the end plate projection as an element of the assembly.
[0073] In a preferred embodiment, the closing plate is designed as a flat plate of uniform thickness throughout, which is inexpensive to manufacture. In a preferred embodiment, the end plate projection extends between the punch surface and an intermediate surface facing away from the punch surface, i.e., facing away from the cell stack, which delimits the end plate projection in the axial direction. Preferably, the punch surface and the intermediate surface extend parallel to one another and perpendicular to the axial direction.
[0074] In such an embodiment, the total axial length of the end plate projection extends from the punch surface to the foot of the end plate projection, which foot is located at the level of the intermediate surface
[0075] In a preferred embodiment, the separating layer has the same shape as the intermediate surface, in particular the same cross-section, in order to cover the intermediate surface in the use position. This allows the end plate projection to be insulated from the locking plate across its entire intermediate surface. Preferably, the separating layer extends across the entire cross-section of the housing body. Thus, the surface area of the separating layer is larger than the intermediate surface. This prevents electrical bridging between the end plate projection and the locking plate.
[0076] In a preferred embodiment, the overall axial length of the end plate projection is designed such that an axial air gap is present between the locking plate and the end wall of the housing body in the use position. This enables electrical insulation between the housing body and the locking plate. Preferably, the overall axial length of the end plate projection and the thickness of the separating layer are designed such that the axial air gap is present between the locking plate and the end wall in the use position to ensure more reliable insulation.
[0077] In a preferred embodiment, the end plate projection is designed as an electrolysis cell whose cell frame has a thickened wall on the side facing the closure plate, wherein the thickened wall is designed to accommodate the external seal. The thickened wall thus encompasses the sealing section. This allows the production capacity of the pressure electrolyzer to be optimized.
[0078] The pressure vessel is sealed against ambient pressure, contains the cell stack in its interior, and is pressurized during electrolysis. In particular, the pressure vessel can be pressurized to a pressure of at least 5 bar, preferably at least 30 bar, and particularly preferably at least 40 bar during electrolysis. A higher pressure of at least 200 bar, such as 350 bar or 700 bar, is also possible and preferred. Particularly preferably, the pressure vessel is pressurized to the working pressure of the electrolysis cells during electrolysis.
[0079] The arrangement of the cell stack in the pressure vessel ensures that, during electrolysis, essentially the same pressure conditions prevail inside the electrolysis cells (i.e., in the cavities of the electrolysis cells) and outside the electrolysis cells, and that no or only a slight pressure difference acts on the cell stack, particularly on the end plates of the cell stack. The pressure acting on the individual cell frames of the electrolysis cells is therefore approximately the same on the inside and outside of the electrolysis cells. As a result, the mechanical forces acting on the cell frames and the internal seals of the electrolysis cells are significantly lower than if the cell stack were surrounded by atmospheric pressure.Cell frames and internal seals of the electrolysis cells are therefore subjected to less mechanical stress, which is why they can be made of thinner and / or cheaper material and are more durable than, for example, the pressure electrolyzers known from the documents DE 10 2014 010 813 A1 and EP 1 464 730 A1, which operate at ambient pressure.
[0080] In both the pressure electrolyzer and the process described, the cell frames, so-called stack frames, and the associated internal seals between the cell frames are not exposed to the pressure difference between the working pressure and the ambient pressure, but operate at a very small pressure difference at most. This reduces the risk of internal seal failure and thus the risk of lye leakage from the respective electrolysis cells. Failure of the internal seal would lead to a deterioration in the performance and / or service life of the cell stack.
[0081] Due to the arrangement of the cell stack in the pressure vessel, there is no pressure difference between the environment of the electrolysis cells and the cavities of the electrolysis cells. This places lower demands on the pressure resistance of the cell stack. This significantly increases the service life of the cell stack, especially the cell frames and internal seals. With an electrolysis cell working pressure of 30 bar and a pressure in the pressure vessel of approximately 30 bar, the service life of the cell frames and internal seals is approximately doubled compared to a conventional cell stack operating at ambient pressure. Furthermore, the cell frames and internal seals can be made from a wider range of materials because they are exposed to lower mechanical stress. For example, the cell frames can be made of ethylene propylene diene (monomer) rubber, so-called EPDM.A further advantageous criterion distinguishing the present invention from the prior art is the fact that electrolysis in the pressure vessel can be carried out at a working pressure of over 100 bar and up to 700 bar, i.e. at a pressure difference to the environment of the electrolyzer which the electrolysis cells and their seals can hardly or not at all mechanically withstand. Higher working pressures in the cell stack, however, lead to better efficiency and are therefore advantageous. Water is under pressure, which supports the electrolysis reaction. Furthermore, at a higher working pressure, a compressed gas product can be produced, e.g. hydrogen at a pressure of 300 bar or higher, so that an additional compressor to compress the gas product is no longer required for use.
[0082] In a preferred embodiment, the end plate projection is arranged at a radial distance from the inner surface of the housing body, in particular from the inner surface of the working section, with the external seal extending through the radial distance. The external seal thus also serves as a spacer and supports a coaxial arrangement of the inner surface of the housing body with the stack end plates. In a particularly preferred embodiment, the cell stack is also arranged at a radial distance from the inner surface of the housing body, preferably at the same radial distance as the radial distance of the end plate projection.
[0083] The pressure electrolyzer is preferably designed to provide hydrogen by electrochemical electrolysis of water.
[0084] The present invention also relates to an electrolysis plant comprising a pressure electrolyzer according to the type described above and at least one gas storage container that receives the gas product and is designed to separate the gas product from the entrained electrolyte. This electrolysis plant benefits from the advantages of the pressure electrolyzer, which translates into greater safety and lower maintenance costs.The present invention also relates to a process for providing at least one gas product by electrolysis, in particular hydrogen, which process is carried out in a pressure electrolyzer according to one of the embodiments set out above, wherein, when the electrolysis is carried out, a pressure of at least 5 bar, approximately at least 30 bar, preferably between 40 bar and 50 bar, likewise preferably above 100 bar, in particular between 150 bar and at least 200 bar, approximately up to 350 bar or up to 700 bar, is present in the interior of the pressure vessel. Such a working pressure is possible with the embodiments set out because the electrolysis cells are insulated from the ambient pressure of the pressure electrolyzer by the housing body. The housing body can be designed to be optimized for this, as set out. Higher working pressures in the pressure vessel lead to better efficiency.Furthermore, a compressed gas product can be produced at a higher operating pressure. The gas product, e.g., hydrogen, can thus be provided in compressed form and does not need to be further compressed after electrolysis to serve as fuel or for storage. This saves energy and costs for the pressure compressor or avoids the use of an additional pressure compressor.
[0085] Description of the characters
[0086] As already discussed above, there are various possibilities for advantageously embodying and developing the teachings of the present invention. Further embodiments, features, and advantages of the present invention are explained in more detail below, among other things, with reference to the exemplary embodiment illustrated in Figure 1.
[0087] It shows: Fig. 1 in side view a first embodiment of a pressure electrolyzer according to the present invention, which operates according to the method according to the present invention;
[0088] Fig. 2 shows a longitudinal section of the pressure electrolyzer from Figure 1 along the line AA shown in Figure 1;
[0089] Fig. 3 shows a longitudinal section of the pressure electrolyzer from Figure 1 along the line BB shown in Figure 1;
[0090] Fig.4 shows a detailed view of the area marked «C» in Figure 2;
[0091] Fig. 5 is a longitudinal section of another embodiment of the pressure electrolyzer; and
[0092] Fig. 6 shows a detailed view of the area marked «D» in Figure 5.
[0093] Figure 1 shows a pressure electrolyzer 100 for providing at least one gas product, namely an alkaline electrolyzer for providing hydrogen and oxygen by electrochemical electrolysis of water.
[0094] To carry out the electrolysis, the pressure electrolyzer 100 has a cell stack 10 with a plurality of electrolysis cells 12 connected in series in the axial direction X. The cell stack has a plurality of electrolysis cells, in particular at least 10, for example 20, approximately 60, or even 120. In the axial direction X, the cell stack 10 is arranged between a first stack end plate 22, which is designed as an anodic end plate, and a further stack end plate 24, which is designed as a cathodic end plate.
[0095] Each electrolysis cell 12 has a cavity arranged between an anodic plate and a cathodic plate, and a stabilizing cell frame surrounding the cavity. During electrolysis, a working pressure of, for example, 30 bar, 350 bar, or 700 bar is present in this cavity. The respective electrolysis cells 12 are therefore designed to operate under a working pressure. To separate the anodic plate and the cathodic plate from each other, a membrane is arranged in the cavity of each electrolysis cell 12. Potassium hydroxide serves as the electrolyte.
[0096] In order to seal the cavity of the electrolysis cell from the environment and / or to seal adjacent electrolysis cells from one another, an internal seal 14 is arranged in the cell stack 10 between each two cell frames. Figure 4 shows stacked electrolysis cells and internal seals 14, which internal seals are located between the cell frames. The internal seals are each clamped between two cell frames, whereby the cell frames each have a frame groove for receiving the internal seal. The frame grooves each have a sealing surface which forms a bottom of the frame groove. In this case, the bottom of the frame groove runs parallel to the plane of the respective cell frame. The sealing surfaces of the frame grooves each act on the internal seals in the direction of the longitudinal axis X of the housing body, for example in a horizontal direction.
[0097] The pressure electrolyzer comprises a pressure vessel 18, which comprises a pressure-resistant, tubular, circular-cylindrical housing body 20, the first stack end plate 22 as the top surface, and the further stack end plate 24 as the base surface. The first stack end plate 22 is detachably connectable to the housing body 20 and is designed to pressure-tightly close an axial opening of the housing body 20.
[0098] The cell stack 10 is housed in the interior of the pressure vessel 18 in a working section 21 of the housing body. This pressure vessel is pressurized during electrolysis, preferably at the working pressure of the cells, for example, 30 bar, 350 bar, or 700 bar.
[0099] In the pressure electrolyzer 100 shown, the cell stack 10 is inserted into a pressure-resistant, circular-cylindrical housing body 20, such as a pressure-bearing tube, which is axially connected to the stack end plates 22, 24 of the cell stack 10. The stack end plates 22, 24 are connected to the housing body 20 in a pressure-tight manner when the pressure vessel is in the operating position.
[0100] At its axial end, which faces the first stack end plate 22, the housing body has an end wall 20a which extends in a plane extending at right angles to the axial direction X.
[0101] At least one of the first stack end plate or the further stack end plate has an axial end plate projection. In the present case, the first stack end plate 22 has the end plate projection 28.
[0102] In order to seal the interior of the pressure vessel against the ambient pressure of the pressure electrolyzer 100, an external seal 26 is clamped in the radial direction Y between the housing body 20 and a sealing portion 28a of the end plate projection 28.
[0103] The end plate projection 28 has a circular cross-section over its entire axial length. Thus, the sealing section 28a has the same circular cross-section, which, in the use position, is inscribed in the circular cross-section of the working section 21.
[0104] In addition, the end plate projection 28 has, on its side facing the cell stack 10, a stamping surface 23 arranged in the interior of the pressure vessel and oriented perpendicular to the axial direction, which, when the pressure electrolyzer is in the operating position, presses the cell stack in the axial direction in order to clamp the cell stack between the first and the further stack end plate 24. In the present case, the further stack end plate 24 also has a stamping surface 25 oriented perpendicular to the axial direction, which is formed by the wall of the further stack end plate 24 facing the cell stack. In this way, the cell stack 10 is clamped between the stack end plates 22, 24. Furthermore, the sealing section 28a protrudes into the working section 21 of the housing body 20. In the embodiment shown, the first stack end plate 22 is designed as an assembly, as can be seen more clearly in Fig. 4.Specifically, the first stack end plate 22 comprises a closing plate 22a, which acts as a cover surface, the end plate projection 28, and a separating layer 33 formed from electrically insulating material. The closing plate and the end plate projection are thus electrically insulated from each other by the separating layer.
[0105] A short circuit between the two stack end plates 22, 24 can be prevented by dividing the first stack end plate 22 into two parts, which are electrically insulated from each other by the separating layer 33. The external seal 26 runs around the outer circumference of the end plate projection 28.
[0106] The external seal 26 is a double O-ring, as also shown in Fig. 4. In this embodiment, the end plate projection 28 has two circumferential sealing grooves for receiving the double O-ring. Each O-ring is clamped between the housing body 20 and a radial sealing surface 29, with the sealing surface 29 forming a bottom of the sealing groove. In this case, the bottoms run parallel to the axial direction X, viewed in longitudinal cross-section.
[0107] The two sealing grooves are spaced apart from each other by a spacer element 27 of the end plate projection 28.
[0108] The further stack end plate 24 is directly, in particular integrally, connected to the housing body 20 in the embodiment shown. As shown in Figure 1, the stack end plates 22, 24 are arranged parallel to one another. The outer circumference of the stack end plates 22, 24 projects beyond the outer circumference of the housing body 20, so that the stack end plates 22, 24 have an outer region or projection extending radially outward from the interior of the pressure vessel. In order to close the pressure vessel particularly reliably, the stack end plates 22, 24 are clamped together at their protruding region by means of fastening elements 30, 32, in particular tension rods, which extend in the direction of the longitudinal axis X of the housing body 20, such that the cell stack 10 is clamped axially between the punch surface 23 and the further stack end plate 24.The functions of sealing the cavity of the electrolysis cells and sealing the interior of the pressure vessel are performed by two separate elements, namely the internal seals and the external seal.
[0109] Fig. 4 shows a detailed view of the external seal 26 clamped between the cell stack 10 and the first stack end plate 22. The cell stack is arranged at a radial distance 44 from the pressure vessel, in particular from the housing body 20.
[0110] The fastening elements 30 and 32 have threaded rods which, by means of attached nuts, clamp the electrolysis cells axially between the stack end plates. In the embodiment of Fig. 5 and Fig. 6, the fastening elements must be electrically insulated from the first stack end plate and the further stack end plate if they are electrically conductive. In the embodiment of Fig. 1 and Fig. 4, the separating layer 33 ensures that the further end plate 24 and the end plate projection 28 are electrically insulated. Furthermore, the housing body is electrically insulated from the cell stack over a radial distance 44. The electrical contact to the end plate projection 28 is made via an electrical connection 31 which runs electrically insulated through the separating layer and the closing plate.
[0111] Furthermore, a support element 54 is arranged in each of the sealing grooves. The support element 54 extends through the radial gap 44 arranged between the cell stack 10 and the housing body 20 of the pressure vessel. The support element 54 extends in the radial direction between the inner circumferential surface of the housing body and the end plate projection 28, and in the axial direction between the external seal 26 and a radial wall of the sealing groove. The support element 54 supports a coaxial arrangement of the inner circumferential surface of the housing body to the end plate projection 28. In addition, the support element 54 supports the external seal 26, which is particularly advantageous at high pressure in order to prevent the external seal 26 from slipping. The support element 54 is advantageously formed from electrically insulating material and acts as an insulator element.This has the effect of more reliably preventing a short circuit between the inner surface of the housing body and the end plate projection 28.
[0112] The total axial length of the end plate projection 28 and the thickness of the separating layer 33 are designed such that an axial air gap 56 is present between the closing plate 22a and the end wall 20a in the position of use.
[0113] The pressure chamber surrounding the cell stack 10 can be purged with product gas. An inlet 50 is provided for admitting the product gas, for example, hydrogen (see Fig. 3). An outlet 52 can also be provided for any escaping lye, such as potassium hydroxide.
[0114] In the pressure electrolyzer shown in the figures, the cell stack 10 is arranged in a pressure vessel pressurized to the working pressure of the cell stack 10. Thus, there is no, or at most only a slight, pressure difference between the cavity within the electrolysis cells and the surroundings of the electrolysis cells. The cell stack 10 and its internal seals 14 are clamped axially between the stack end plates. The internal seals 14 therefore act in the axial direction. The external seal 26, designed to seal the pressure vessel, is clamped radially between the stack end plate 22 and the housing body 20. The external seal 26 therefore acts in the radial direction.Since the internal seals 14 are arranged in the pressure chamber and the external seal 26 is an element independent of the internal seals, the internal seal 14 and the external seal 26 are exposed to significantly lower mechanical stresses than in conventional electrolyzers operating under ambient pressure.
[0115] The pressure electrolyzer according to Fig. 5 and Fig. 6 is constructed similarly to the embodiment disclosed in Figs. 1 to 4. Only the differences will be discussed below. Identical features are designated by the same reference numerals. In contrast to the first embodiment of Figs. 1 to 4, the first stack end plate 22 is integrally formed in one piece, i.e., the closing plate and the end plate projection form a unit. In order to seal the interior of the pressure vessel from the ambient pressure of the pressure electrolyzer 100, as is better visible in Fig. 6, the external seal 26 is also clamped in the radial direction Y between the housing body 20 and the sealing portion 28a of the end plate projection 28. Furthermore, the sealing portion 28a projects into the working portion 21 of the housing body 20.
[0116] The fastening elements 30 and 32 comprise threaded rods that, by means of attached nuts, clamp the electrolysis cells axially between the stack end plates. In the embodiment shown in Fig. 5, the fastening elements are electrically insulated from the first stack end plate and the second stack end plate. Furthermore, the housing body is electrically insulated from the cell stack.
[0117] List of reference symbols
[0118] 10 cell stacks with a variety of electrolysis cells 12
[0119] 12 electrolysis cell
[0120] 14 internal seal of the cell stack 10
[0121] 18 pressure vessels
[0122] 20 Housing body of the pressure vessel
[0123] 20a Front wall of the housing body
[0124] 21 Working section of the housing body
[0125] 22 first stack end plate
[0126] 22a locking plate
[0127] 23 Stamp surface of the end plate projection
[0128] 24 further stacking end plate designed as the base of the pressure vessel
[0129] 25 Stamping surface of the further stack end plate 24
[0130] 26 external seal
[0131] 27 Spacer element of the end plate projection 28 End plate projection
[0132] 28a Sealing section
[0133] 29 radial sealing surface
[0134] 30 first fastening element 31 electrical connection
[0135] 32 additional fastening element
[0136] 33 Separating layer
[0137] 44 radial distance between the cell stack 10 and housing body 20 of the
[0138] Pressure vessel 50 inlet
[0139] 52 Outlet, for example, drain for any electrolyte that may leak out, for example for
[0140] lye
[0141] 54 Support element for the external seal 26
[0142] 56 axial air gap 100 pressure electrolyzer, especially high-pressure electrolyzer
[0143] X axial direction or direction arranged in the direction of the longitudinal axis of the housing body 20
[0144] Y radial direction or direction arranged in the direction of the radius of the housing body 20
Claims
Patent claims 1. Pressure electrolyzer (100) for providing at least one gas product, comprising a cell stack (10) which comprises a plurality of electrolysis cells (12) designed for electrochemical electrolysis, and a pressure vessel (18) sealed against the ambient pressure, - wherein the electrolysis cells (12) are connected in series in an axial direction (X) and clamped between a first stack end plate (22) and a further stack end plate (24), and each have a cavity in which a working pressure is applied, as well as a stabilizing cell frame surrounding the cavity, - wherein in the cell stack (10) an internal seal (14) is arranged between each two cell frames, wherein the internal seals (14) encircle the respective cavities of the electrolysis cells and seal them off from the environment of the electrolysis cells, which internal seals (14) are arranged in the axial direction (X) between the cell frames and are clamped between the stack end plates (22, 24), and - wherein the cell stack (10) is accommodated in the interior of the pressure vessel (18) in a working section of the housing body (20), and wherein the working pressure of the electrolysis cells (12) is present in the interior, - wherein the pressure vessel comprises a pressure-resistant housing body (20) having an end wall at its respective axial end, as well as the first stack end plate (22) as the cover surface and the further stack end plate (24) as the base surface, wherein the housing body (20) is clamped between the first stack end plate and the further stack end plate, and has at least one external seal (26) designed to seal the interior of the pressure vessel against the ambient pressure, - wherein at least one of the first stack end plate (22) or of the further stack end plate (24) has an axial end plate projection (28) and the external seal (26) is arranged in the radial direction (Y) between the Housing body (20) and a sealing section of the end plate projection (28), characterized in that the sealing section has a cross section which, in the use position, is inscribed in the cross section of the working section, that the sealing section projects into the working section of the housing body (20), and that the end plate projection (28) has, on its side facing the cell stack (10), a stamping surface (23) which, in the use position of the pressure electrolyzer (100), presses the cell stack (10) in the axial direction (X) in order to clamp the cell stack (10) between the first and the further stack end plate (22, 24).
2. Pressure electrolyzer according to claim 1, characterized in that the external seal (26) runs around the outer circumference of the end plate projection (28), which end plate projection in the sealing section preferably has a circumferential sealing groove for receiving the external seal.
3. Pressure electrolyzer according to claim 1 or 2, characterized in that the end wall (20a) of the housing body (20), which faces the at least one of the first stack end plate (22) or the further stack end plate (24), extends in a plane extending at right angles to the axial direction (X).
4. Pressure electrolyzer according to one of the preceding claims 1 to 3, characterized in that the stamp surface lies directly against the electrolysis cell facing the stamp surface.
5. Pressure electrolyzer according to one of the preceding claims 1 to 4, characterized in that the end plate projection comprises an inner section, which comprises the sealing section, and an outer section, wherein in the position of use the inner section is arranged in the housing body (20) and comes into contact with the cell stack via the stamping surface, and wherein in the position of use the outer section is outside the housing body (20) and is intended to form an axial air gap between the end wall of the housing body and at least one of the first stack end plate (22) or the further stack end plate (24).
6. Pressure electrolyzer according to one of the preceding claims 1 to 5, characterized in that the working section has the same cross-section over its length.
7. Pressure electrolyzer according to one of the preceding claims 1 to 6, characterized in that at least one of the first stack end plate (22) or of the further stack end plate (24) is designed in the form of an assembly, wherein a closing plate, which acts as a cover surface or as a base surface, and the end plate projection are designed separately, wherein the closing plate and the end plate projection are electrically insulated from one another by a separating layer formed from electrically insulating material.
8. Pressure electrolyzer according to claim 7, characterized in that the end plate projection (28) is designed as an electrolysis cell, the cell frame of which has a thickened wall on the side facing the closing plate, the thickened wall being intended to accommodate the external seal.
9. Pressure electrolyzer according to claim 7 or 8, characterized in that the total axial length of the end plate projection is designed such that an axial air gap is present between the closing plate and the end wall of the housing body in the position of use.
10. Pressure electrolyzer according to one of claims 7 to 9, characterized in that the separating layer has the same cross-section as an intermediate surface of the end plate projection facing away from the stamping surface and delimiting the end plate projection in the axial direction in order to cover the intermediate surface in the position of use.
11. Pressure electrolyzer according to one of the preceding claims 1 to 10, characterized in that the end plate projection (28) is electrically insulated from the housing body by an electrically insulating support element (54) which supports a coaxial arrangement of the housing body to the end plate projection.
12. Pressure electrolyzer according to one of the preceding claims 1 to 11, characterized in that the end plate projection is arranged at a radial distance (44) from the inner circumferential surface of the housing body, wherein the external seal (26) extends through the radial distance (44).
13. Pressure electrolyzer according to one of the preceding claims 1 to 12, characterized in that the at least one of the first stack end plate (22) or of the further stack end plate (24) is the first stack end plate (22), which first stack end plate (22) is detachably connectable to the housing body (20) and is designed to close an axial opening of the housing body (20) in a pressure-tight manner, and that the further stack end plate (24) is designed integrally and pressure-tightly with the housing body (20).
14. Electrolysis plant comprising a pressure electrolyzer (100) according to at least one of claims 1 to 13, and at least one gas storage container which receives the gas product and is designed to separate the gas product from entrained electrolyte.
15. A process for providing at least one gas product, in particular hydrogen, by means of electrolysis, characterized in that the process is carried out in a pressure electrolyzer (100) designed according to at least one of claims 1 to 13, wherein when carrying out the electrolysis in the interior of the pressure vessel a pressure of at least 5 bar, approximately at least 30 bar, preferably between 40 bar and 50 bar, likewise preferably above 100 bar, in particular between 150 bar and at least 200 bar, approximately up to 350 bar or up to 700 bar, is present.