Pressurized electrolytic cell, electrolytic apparatus, and electrolysis method

Abstract

The present invention relates to a pressurized electrolytic cell (100) having a cell stack (10) including a plurality of electrolytic cells (12) and a pressure vessel (18) in which the cell stack is arranged and sealed against ambient pressure. One inner seal (14) is positioned between each of the two cell frames. The electrolytic cells (12) are positioned between a first stack end plate (22) and a further stack end plate (24). The pressure vessel has a pressure-resistant housing body (20) and a first stack end plate (22) as an upper surface and the further stack end plate (24) as a base surface. At least one of the first stack end plate (22) or the further stack end plate (24) has an axial end plate projection (28), and an outer seal (26) is positioned radially (Y) between the housing body (20) and the sealing portion of the end plate projection (28). The sealing portion has a cross-section that coincides with the cross-section of the working portion and protrudes into the working portion. The end plate projection (28) has a pressing surface (23), which presses the cell stack (10) in the axial direction (X).

Description

Technical Field

[0001] The present invention relates to a pressurized electrolytic cell configured based on the superordinate concept of claim 1, specifically a high-pressure electrolytic cell, for example, an alkaline electrolytic cell for water electrolysis. The present invention further relates to an electrolysis device equipped with a related pressurized electrolytic cell, specifically a water electrolysis device, and an electrolysis method carried out in the electrolytic cell.

Background Art

[0002] Electrolytic cells operating under a pressure increased relative to atmospheric pressure are known, for example, from Patent Document 1 and Patent Document 2. Such pressurized electrolytic cells have a pressure-supporting frame structure for protecting the electrolytic blocks, that is, for protecting the cell stack equipped with electrolytic cells, for reasons of mechanical integrity. Known pressurized electrolytic cells are carried out at a pressure of about 2 - 5 MPa.

[0003] Patent Document 3 discloses a pressurized electrolytic cell equipped with a cell block incorporated into a cylindrical pressure tube. The ends of the pressure tube are closed by end plates, and these end plates are also the end plates of the cell block at the same time. In this way, the same pressure state is formed inside and outside the cell space of the electrolytic cell. In the case of such an electrolytic cell, both the inner seal of the electrolytic cell and the outer seal of the tube pressure vessel are carried out by axial seals. Therefore, the electrolytic cell must operate with extremely narrow tolerances. Such axial seals enable the proper sealing action of the electrolytic cell only when the operating pressure of the electrolytic cell is relatively low.

[0004] In the case of the pressurized electrolytic cell known from FIG. 4 of Patent Document 4, the end plates of the cell block are formed within a common seal. Such a seal serves both to seal the electrolytic cells from each other and to seal the internal space of the pressure vessel from the surroundings. Based on the high pressure load, such a seal must be formed extremely strongly in order to withstand the pressure state acting on the seal.

[0005] A pressurized electrolytic cell that performs electrolysis under high pressure, for example, at least 20 MPa, for example, 35 MPa or 70 MPa, is called a high-pressure electrolytic cell. High-pressure electrolytic cells can provide compressed hydrogen that can be used, for example, as fuel or as an energy carrier.

[0006] A pressurized electrolytic cell configured based on the broader concept of claim 1 is known from Patent Document 5. Such a pressurized electrolytic cell is a high-pressure electrolytic cell and is useful for producing hydrogen. To protect the electrolytic block from mechanical loads due to pressure, Patent Document 5 teaches that a cell stack, i.e., a so-called stack of electrolytic cells, is placed in a cup-shaped pressure vessel that is sealed against ambient pressure and supplied with the operating pressure of the electrolytic cell. A closing plate of the cell stack forms a stationary head, which is formed as a single piece with the lid of the cup-shaped pressure vessel and is equipped with electrical anode and cathode connections. A second closing plate of the cell stack forms a movable head, which can move freely longitudinally relative to the stationary head in response to thermal expansion or contraction of the electrolytic cell. To seal the cell frames of each electrolytic cell to each other, the electrolytic cells have an internal O-ring seal, which surrounds the cell frame. To isolate the internal space of the pressure vessel from ambient pressure, additional external seals are provided, which are positioned axially between the stationary head and the anode plate of the cell stack (Figure 2 of Patent Document 5). The drawback of such a system is that it is complex in its configuration, and strong mechanical forces act on the anode plate of the cell stack due to the presence of pressure differences.

[0007] Patent Document 6 discloses a pressurized electrolytic cell with a cell block incorporating a cylindrical tube pressure vessel. The tube pressure vessel includes a pressure tube and two end plates, the end plates closing one end of each pressure tube in the use position. The end plates have axial throughs for threaded rods, which, by attached nuts, position the electrolytic cells axially between the two end plates. To prevent short circuits between the electrodes of the cell block, a disc made of an electrically insulating material is provided between the nut and the end plate. The disc allows for simultaneous centering of the threaded rods within each through, thus ensuring radial free space between the threaded rods and the end plates. At each end, the end wall of the pressure tube has a circumferentially extending housing groove that opens radially toward the interior of the pressure tube. Each end plate has a projection that protrudes axially and supports a radial seal, which is configured to be tightly housed within the housing groove in the use position. A retaining plate is provided between each end plate and cell block. In the operating position, the retaining plate holds the cells of the cell block axially and simultaneously contacts the bottom of the housing groove. When the end plates are pressed together, the surfaces of the inwardly oriented projections make fixed contact with the retaining plates, so that each retaining plate contacts the bottom of the respective housing groove and holds the cells together. In such an electrolytic cell, the internal seal of the electrolytic cells is provided by an axial seal, and the external seal of the tube pressure vessel is provided by a radial seal. The structure of the electrolytic cell requires the machining of the end walls, specifically the fabrication of the housing groove, which requires tight tolerances. The housing groove must allow the retaining plates to contact the bottom of the housing groove and the cell block simultaneously in the axial direction. Furthermore, in order to enable and maintain such contact during operation, and to prevent the mechanical load on the retaining plates and outer seal from causing a loss of sealing performance, the electrolytic cell must operate with extremely tight tolerances, specifically the cell thickness tolerances. During operation, the electrolytic cell experiences a temperature rise that causes cell expansion, resulting in additional stress on the retaining plate. In this case, the disk, which is made of insulating material, can become mechanically damaged and deteriorate over time.

[0008] The pressurized electrolytic cell for hydrogen production disclosed in Patent Document 7 includes a positive end plate and a negative end plate. A flat cylindrical seal and a cell frame assembly are positioned offset between the positive and negative end plates. A threaded rod is guided through the positive and negative end plates to position the combined seal and cell frame assembly. Sealing against ambient pressure is performed axially via the flat cylindrical seal. Unlike the pressurized electrolytic cell disclosed in Patent Document 6, the cell block of the pressurized electrolytic cell is not incorporated within a cylindrical tubular pressure vessel. For this reason, when high operating pressure is applied, the cell frame assembly is subjected to high mechanical loads. [Prior art documents] [Patent Documents]

[0009] [Patent Document 1] German Patent Application Publication No. 102014010813 [Patent Document 2] European Patent Application Publication No. 1464730 [Patent Document 3] German Patent Application Publication No. 4418999 Specification [Patent Document 4] European Patent Application Publication No. 0212240 [Patent Document 5] U.S. Patent Application Publication No. 2011 / 0210012 [Patent Document 6] U.S. Patent No. 4210511 [Patent Document 7] Chinese Patent No. 104911626 Specification [Overview of the Initiative] [Problems that the invention aims to solve]

[0010] Starting from the aforementioned problems and shortcomings, and based on the evaluation of the prior art outlined, the fundamental objective of the present invention is to improve the type of pressurized electrolytic cell described at the beginning, so that it can be manufactured as simply and inexpensively as possible. Furthermore, the pressure vessel should be able to seal against ambient pressure easily, reliably, and for a long period of time. Specifically, the high-pressure electrolytic cell should be constructed such that the mechanical forces acting on the inner and outer seals are as small as possible, and the number of separate individual parts in the high-pressure electrolytic cell is as small as possible. Furthermore, the high-pressure electrolytic cell should have reliable and long-lasting insulation to prevent short circuits.

[0011] Furthermore, the fundamental problem of the present invention is to provide an electrolytic apparatus including a high-pressure electrolytic cell, and a method for providing at least one gas product by the electrolytic cell, wherein the method is carried out within the high-pressure electrolytic cell. [Means for solving the problem]

[0012] These problems are solved by a high-pressure electrolytic cell having the features described in claim 1, an electrolytic apparatus having the features described in claim 14, and a method having the features described in claim 15. Advantageous configurations and further configurations suitable for the purpose of the present invention are characterized in each dependent claim.

[0013] The present invention relates to a pressurized electrolytic cell for providing at least one gas product, comprising a cell stack containing a plurality of electrolytic cells formed for electrochemical electrolysis, and a pressure vessel sealed to ambient pressure. [Effects of the Invention]

[0014] Advantageously, a high-pressure electrolytic cell is designed to electrolyze water into its elements, oxygen and hydrogen. These elements are produced as gaseous products.

[0015] The electrolytic cells are connected in series in the axial direction and are positioned between a first stack end plate and a further stack end plate. Furthermore, each electrolytic cell has one cavity to which an operating pressure is applied, and a stabilizing cell frame surrounding the cavity.

[0016] Within the cell stack, an inner seal is positioned between each of the two cell frames, and the inner seal surrounds each cavity of the electrolytic cell, sealing the periphery of the electrolytic cell. The inner seal is positioned axially between the cell frames and between the stack end plates.

[0017] The advantageous cylindrical pressure vessel has a pressure-resistant housing body having end walls at each axial end of the pressure vessel, and also has the first stack end plate as the top surface and the further stack end plate as the base surface. The housing body has at least one outer seal that is fitted between the first stack end plate and the further stack end plate and is formed to seal the internal space of the pressure vessel against the ambient pressure.

[0018] The cell stack is housed within the internal space of the pressure vessel and within the operating section of the housing body, and the operating pressure of the electrolytic cell is applied to the inside of the pressure vessel.

[0019] 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 outer seal is positioned radially between the housing body and the sealing portion of the end plate projection.

[0020] According to the present invention, the sealing section has a cross-section that coincides with the cross-section of the operating section in the use position. Further, the sealing section protrudes into the operating section of the housing body. Further, the end plate protrusion has a pressing surface on the side facing the cell stack of the end plate protrusion, and the pressing surface presses the cell stack in the axial direction at the use position of the pressurized electrolytic cell in order to clamp the cell stack between the first stack end plate and the further stack end plate.

[0021] Specifically, at least one of the first stack end plate or the further stack end plate includes a closing plate that can act as an upper surface or a base surface, and an end plate protrusion. The end plate protrusion protrudes inward in the axial direction from the closing plate and protrudes into the operating section.

[0022] In order to arrange the electrolytic cell axially between the stack end plates, the pressurized electrolytic cell advantageously has fixing elements or fixing rods for arranging the stack end plates relative to each other. For example, the fixing element can have a threaded rod as a tie rod. The threaded rod arranges the electrolytic cell axially between the stack end plates by means of attached nuts. Preferably, the fixing element is electrically insulated from the first stack end plate and the further stack end plate.

[0023] By having the sealing section have a cross-section that coincides with the cross-section of the operating section in the use position, the sealing section can be pushed into the pressure vessel. In this case, the end plate protrusion protrudes into the pressure vessel by at least the insertion length of the end plate protrusion. Here, the cross-section defines a cross-section that extends perpendicular to the axial direction.

[0024] The end plate protrusions that extend into the operating section of the housing body allow for larger tolerances during the assembly of the pressurized electrolytic cell, specifically in the thickness tolerance of the electrolytic cells. The end plate protrusions can thus protrude more or less into the housing body depending on the deviation from the nominal thickness of the cell stack. This is done without compromising the sealing performance, because the outer seal is located radially between the sealing section of the end plate protrusions and the housing body.

[0025] Furthermore, the sealing performance of the pressure vessel can be guaranteed independently of the configuration of the end walls of the housing body. This is because the outer seal is formed within the operating section in the operating position and not between the end wall and the closing plate.

[0026] In one embodiment, at least one of the first stack end plate or the further stack end plate is formed integrally as a single piece. That is, the end plate projection and the closing plate form an inseparable unit, preferably made of a single material.

[0027] A pressurized electrolytic cell may contain more than 100 electrolytic cells. Each of these electrolytic cells has a nominal thickness and a thickness tolerance. As a result, when the total thickness of the cell stack is calculated, the thickness tolerance is multiplied by more than 100. Since the thickness tolerance of the electrolytic cells is ±0.1 mm, the deviation of the cell stack dimensions, i.e., from the nominal dimensions, is ±10 mm. The end plate projection protrudes into the operating section of the housing body, so the end plate projection can protrude more or less depending on the dimensions while its pressing surface is pressing the cell stack axially. The end plate projection can thus compensate for the dimensions of the cell stack. In this case, the operating pressure remains maintained within the pressure vessel because the outer seal is located radially between the housing body and the end plate projection. Therefore, a larger thickness tolerance is allowed during manufacturing. This is advantageous because it makes the manufacture of electrolytic cells considerably easier and, consequently, cheaper.

[0028] This is not possible, for example, in a pressurized electrolytic cell as described in U.S. Patent No. 4210511, even though the outer seal is axially performed between each end plate projection of the stack end plates. In other words, in U.S. Patent No. 4210511, the end plate projections are specified to be housed in housing grooves in the end walls, and within the housing grooves, the end plate projections, in the use position, press the retaining plates axially against the bottom of the housing grooves. At the same time, the retaining plates must hold the electrolytic cells of the cell block axially. Such a structure requires electrolytic cells with extremely small thickness tolerances. Otherwise, if the lower dimension of the cell block is too large, the electrolytic cells will no longer be held by the retaining plates. In such cases, a tear will occur between the cell block and the retaining plates, and this gap will impair the sealing performance of the inner seal. Conversely, if the upper dimension of the cell block is too large, the retaining plates will no longer contact the bottom of each housing groove.

[0029] Here, the nominal thickness of the cell stack is the sum of the nominal thicknesses of the electrolytic cells. The dimensions of the cell stack are the cumulative deviations of the thickness from the nominal thickness of the electrolytic cells. The top dimension of the cell stack is the maximum positive tolerance, i.e., the largest positive deviation from the nominal thickness. This occurs when each electrolytic cell has the largest positive deviation from the nominal thickness. The bottom dimension of the cell stack is the maximum negative tolerance, i.e., the largest negative deviation from the nominal thickness. Adding the top dimension to the nominal thickness gives the maximum dimension, i.e., the maximum thickness of the cell stack. Subtracting the bottom dimension from the nominal thickness gives the minimum dimension, i.e., the minimum thickness of the cell stack.

[0030] In a preferred embodiment, the end plate projection has a cross-section that coincides with the cross-section of the operating section at the point of use, along its entire axial length. Therefore, the end plate projection is easily manufactured. Furthermore, the end plate projection can optionally be introduced into the operating section along its entire length. This allows for greater tolerance compensation.

[0031] In a preferred embodiment, the pressing surface is oriented perpendicular to the axial direction so that it extends parallel to the electrolytic cell. Such a pressing surface can uniformly press the cell stack.

[0032] Preferably, the pressing surface is in direct contact with the electrolytic cell facing the pressing surface in order to avoid an interface.

[0033] Furthermore, the present invention is based on arranging a cell stack within a pressure vessel formed as a closed pressure compartment and crimping it between two stack end plates, with at least one outer seal formed to seal the internal space of the pressure vessel against ambient pressure, positioned such that the force crimping the cell stack and the force positioning the outer seal act in different directions. In other words, in the present invention, the forces acting on the cell stack and the forces acting on the outer seal are directed in different directions and thus distributed more uniformly. This reduces the requirements for the stability of the cell stack and the outer seal, and allows them to be manufactured from a wider range of materials. This also has the advantage that the electrolytic cell does not have an outer seal and can therefore be manufactured more easily.

[0034] In a preferred embodiment, the end plate projection includes an inner section and an outer section. In the use position, the inner section is located within the housing body and in contact with the cell stack. The sealing section is part of the inner section. Furthermore, in the use position, the outer section is located outside the housing body, and the outer section is defined to form an axial gap between the end wall of the housing body and at least one of the first stack end plate or the further stack end plates.

[0035] The housing body, specifically the axial gap between its end walls, electrically insulates the housing body axially from at least one of the first stack end plates or the further stack end plates. In the radial direction, the outer seal positioned 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 the further stack end plates. This makes insulation of the fixing elements that position the first stack end plate and the further stack end plates relative to each other necessary only at the first stack end plate or the further stack end plate.

[0036] In a preferred embodiment, the end plate projection is electrically insulated from the housing body by an electrically insulating support element. The support element assists in coaxial positioning the housing body with respect to the end plate projection. This further reliably prevents short circuits between the housing body and the end plate projection. The support element extends radially between the end plate projection and the housing body and, advantageously, directly abuts the outer seal axially, thereby preventing the outer seal from sliding.

[0037] The axial section of the pressure vessel, where the cell stack is positioned in use, defines the operating section of the pressure vessel. The operating section extends over the axial length. The axial length corresponds to at least the sum of the nominal thickness of the cell stack, the top dimension of the cell stack, and the axial reserve length.

[0038] The reserve length is specified so that the inner portion of the end plate projection, specifically its pressing surface, is housed within the housing body so that it contacts the cell stack at the operating position. In this case, at least the sealing portion is located within the operating portion. Depending on the actual dimensions of the cell stack, the length corresponding to the upper dimension may also be specified to house the inner portion of the end plate projection.

[0039] The axial length of the end plate projection includes an introduction length corresponding to the inner section and the remaining length. The remaining length corresponds to the outer section of the end plate projection, which extends outside the housing body. The axial length of the end plate projection extends from the pressing surface to the base of the end plate projection. This base is located at the height of the closing plate.

[0040] In a preferred embodiment, the total length of the end plate projection is calculated such that an axial gap exists between the closing plate and the corresponding end wall of the housing body at the point of use. This enables electrical insulation between the housing body and the stacked end plate.

[0041] The axial length of the end plate projection is at least equal to the sum of the lower dimensions of the cell stack to ensure that the end plate projection contacts the cell stack, and the thickness of the sealing section to ensure that the sealing section is located within the working section for sealing of the pressure vessel. In the operating position, the introduction length of the end plate projection depends on how large the actual dimensions of the cell stack are.

[0042] For completeness, the reserve length may also be calculated to accommodate any additional electrolytic cells within the cell stack. In such embodiments, the axial length of the end plate projection is calculated so that the end plate projection contacts the cell stack at the point of use.

[0043] Furthermore, the usage location of the pressurized electrolytic cell corresponds to the assembled state of the pressurized electrolytic cell.

[0044] The operating section has a cross-section that allows for the accommodation of the cell stack. The cross-section of the cell stack coincides with the cross-section of the operating section. A radial gap may exist between the inner side of the housing body and the cell stack around the entire circumference of the cell stack. This allows for electrical insulation between the cell stack and the housing body.

[0045] Preferably, the operating section has the same cross-section along its length. Particularly preferably, the housing body has the same cross-section along its entire length. This makes the manufacturing of the housing body easier and therefore less expensive.

[0046] In a preferred embodiment, the operating section extends along the entire axial length of the housing body. This allows the cell stack to be flexibly positioned within the housing body, while the cross-section of the housing body remains constant along its entire length.

[0047] In a preferred embodiment, the end plate projection has the same cross-section as the electrolytic cell. In such an embodiment, uniform pressure is ensured on the cell stack in the axial direction of the end plate projection.

[0048] Advantageously, the housing body is formed in a cylindrical shape, particularly preferably a circular cylindrical shape, to form a radial distribution of the force applied by the operating pressure. In the circular cylindrical embodiment, the cross-section of the housing body forms a circular cross-section. The circular cross-section has the same diameter along the axial length of the housing body. Furthermore, the end plate projection has a cross-section that coincides with the circular cross-section of the operating section at the point of use. Specifically, the longest dimension of the cross-section of the end plate projection is smaller than the diameter of the circular cross-section.

[0049] In a preferred embodiment, the end plate projection is formed in a circular cylindrical shape as a circular disc centered in the axial direction. The circular disc protrudes at least partially into the operating section in the operating position. In such an embodiment, it is ensured that the cell stack is pressed uniformly in the axial direction by the end plate projection.

[0050] Advantageously, since the operating section extends along the entire length of the housing, the housing can accommodate as many electrolytic cells as possible.

[0051] Preferably, in this pressurized electrolytic cell, the inner seal acts axially and the outer seal acts radially. That is, the inner seal seals axially and the outer seal seals radially. In other words, the force acting on the inner seal is directed along the longitudinal axis of the housing body of the pressure vessel. The force acting on the outer seal is directed radially, i.e., radially, along the radius of the housing body of the pressure vessel. Based on these different orientations of the inner and outer seals, the overall mechanical load acting on these seals is reduced. As a result, the seals, i.e., the inner and outer seals, can reliably perform their sealing function even under extremely high pressure conditions, can be manufactured from inexpensive materials, and are formed to have a long lifespan.

[0052] The pressure vessel is formed from two stack end plates of the cell stack, as well as a tubular or jacket-shaped housing geometry, the housing geometry forming the housing body and compactly coupled to the end plates, also called stack end plates, of the electrolytic cell stack.

[0053] Since the base and top surfaces of the pressure vessel are formed from the end plates of the cell stack, the pressure vessel is particularly simply constructed, and the individual parts of the pressure vessel are extremely few. The first stack end plate may be formed as an anode end plate in the region facing its electrolytic cell, specifically in the region formed as a pressing surface, and the further stack end plate may be formed as a cathode end plate in the region facing its electrolytic cell, or vice versa. The electrical insulation of the pressurized electrolytic cell is formed so that current can flow between the end plates, thereby avoiding electrical short circuits that may be caused, for example, by fixed elements or the housing body.

[0054] The anode end plate and / or cathode end plate may be divided into two sections, as detailed below.

[0055] In a preferred embodiment, the first stack end plate and the further stack end plate each have one end plate projection. This allows for a symmetrical structure of the pressurized electrolytic cell. Advantageously, the end plate projection is formed identically for the first stack end plate and the further stack end plate. Particularly preferred is that the first stack end plate and the further stack end plate are formed identically, so only one stack end plate suitable for both ends of the housing body needs to be conceived.

[0056] In a preferred embodiment, the first stack end plate and the further stack end plate each have a single end plate projection. An advantage of this embodiment is that only one stack end plate, for example, the first stack end plate, needs to be machined to form the end plate projection. The further stack end plate may be tightly coupled to the housing body via an external seal positioned between the corresponding end wall of the housing body and the further stack end plate.

[0057] In a preferred embodiment, the pressing surface is in direct contact with the electrolytic cell facing the pressing surface. This allows for the manufacture of a compact embodiment of the pressurized electrolytic cell.

[0058] 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 can be detachably coupled to the housing body and is formed to compactly close an axial opening in the housing body. That is, only one of the two stack end plates, in this case the first stack end plate, has an end plate projection. An outer seal is located radially between the housing body and the end plate projection. The further stack end plate is formed integrally and compactly with the housing body. Integral can be understood as the housing body and the stack end plate being coupled to each other to form individual complete pieces. For example, the housing body and the stack end plate can be tightly welded to each other. The pressure vessel can thus be constructed as simply as possible because an outer seal is not required on such a side.

[0059] In a preferred embodiment, the outer seal surrounds the outer circumference of the end plate projection, and the end plate projection has an annular sealing groove within the sealing section, preferably for housing the outer seal. Manufacturing the sealing groove within the end plate projection, specifically within the sealing section of the end plate projection, is less labor-intensive than manufacturing it within the inner wall of the housing body. Furthermore, when the sealing groove is formed within the end plate projection, a thinner wall thickness can be selected for the housing body, which is advantageous in terms of manufacturing costs. When assembled, the outer seal acts radially. The outer seal is formed as a separate element, which is located between the housing body and the radial sealing surface. The sealing surface forms the bottom of the sealing groove. Advantageously, the bottom of the sealing groove extends parallel to the axial direction when viewed in a longitudinal cross-section.

[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 the outer side surface of the pressure vessel. Furthermore, the stack end plates are arranged parallel to each other. In addition, the stack end plates are positioned relative to each other in their outer regions by at least three fixing elements extending in the direction of the longitudinal axis of the housing body, i.e., in the axial direction, so that the cell stack is compressed axially between the stack end plates, specifically between the pressing surface and the opposite stack end plate.

[0061] Each electrolytic cell has a ring-shaped cell frame for stabilization. To seal adjacent electrolytic cells from each other, an inner seal is placed within each of the two cell frames in the cell stack.

[0062] Each inner seal is crimped between two cell frames. Each cell frame has one frame groove for housing the inner seal. Each frame groove has one sealing surface. The sealing surface forms the bottom of the frame groove. Advantageously, the bottom of the frame groove extends parallel to the plane of each cell frame.

[0063] Preferably, the sealing surface of the frame groove is positioned perpendicular to the sealing surface of the sealing groove.

[0064] In a preferred embodiment, the outer seal is formed as a double seal. In such an embodiment, a further outer seal surrounds the outer circumference of the end plate projection, which preferably has an annular additional sealing groove for accommodating the further outer seal. This ensures better sealing of the pressure vessel.

[0065] In a preferred embodiment, the end wall of the housing body, facing at least one of the first stack end plate or the further stack end plate, extends in a plane perpendicular to the axial direction. This allows the housing body to be manufactured at a low cost because the end formed by the end wall can be manufactured through a cross section without significant processing of the end wall, for example, without grooves or steps. The end wall extends in a plane that can arise from a cross section transverse to the axial direction. In other words, the end wall extends in a single plane from the outer surface of the housing body to the inner surface of the housing body. That is, the transition from the outer surface to the inner surface extends without interruption, for example, without notches or grooves. Advantageously, both ends of the housing body each extend in a plane perpendicular to the axial direction. Advantageously, the end walls of the housing body extend in a plane perpendicular to the axial direction at both ends of the housing body.

[0066] When stack end plates are positioned, the fixed elements may be electrically insulated from the stack end plates by insulating elements to prevent electrical short circuits between the poles of the cell block. The stack end plates may have axial throughs for the fixed elements, such as threaded rods. For insulation, insulating elements made of electrical insulating material may be provided between the fixed elements and the stack end plates. The insulating elements may be discs. These discs simultaneously allow for centering of the fixed elements within their respective throughs, thus ensuring radial free space between the fixed elements and the stack end plates. A housing body made of electrical insulating material may also be provided.

[0067] In a preferred embodiment, at least one of the first stack end plate or the further stack end plate is formed in the form of an assembly, with a closing plate acting as the top or base surface and the end plate projection being formed separately, and the closing plate and the end plate projection being electrically insulated from each other by a separation layer formed of an electrically insulating material. In other words, the first stack end plate or the further stack end plate or both stack end plates are formed as an assembly.

[0068] As a result, at least one of the first stack end plate or the further stack end plate is formed in two parts. The elements of the assembly, namely the closing plate, the end plate projection, and the isolation layer, can be manufactured more easily because the three functions of the stack end plate—stability of the high-pressure electrolytic cell, compaction, and electrical insulation—can be separated. Therefore, the selection of elements for the stack end plate can be optimized according to the function of the element. The closing plate acts axially as a pressurizing element and must contribute to the stabilization of the pressurized electrolytic cell. In contrast, the end plate projection supporting the outer seal acts as a sealing element. Furthermore, the isolation layer acts as an insulating element between the poles of the cell block. Electrical contact with the cell stack can be made through through-passages formed in the closing plate and the isolation layer.

[0069] Manufacturing stack end plates as an assembly becomes easier because milling of the base plate to form the end plate protrusions is eliminated. For clarification, the electrolytic cell housing body may be up to 2.5 meters long and have a diameter of up to 1.5 meters. In this case, to ensure the sealing and mechanical stability of the pressure vessel, the milling must adhere to narrow tolerances. Machining the base plate can be particularly difficult when the diameter is large.

[0070] Such embodiments have the further advantage that further electrical insulation of the fixed elements is no longer required. Unlike embodiments in which electrical insulation is provided between the fixed elements and the stack end plates, the isolation layer provides insulation between the electrodes of the cell block. Therefore, fewer components are required. Furthermore, the pressurized electrolytic cell is less susceptible to insulation failures, allowing for more reliable operation. Insulation is performed in one place, namely the isolation layer. The isolation layer is uniformly pressed axially between the end plate projection and the closing plate. The isolation layer is hardly exposed to other mechanical loads. In contrast, insulating elements are mechanically loaded during the assembly of the pressurized electrolytic cell. When disc-shaped insulating elements are used, each insulating element is pressed between the nut and the stack end plate and is exposed to shear load when the nut is tightened. Such drawbacks can be avoided in this embodiment.

[0071] Electrical contact with the end plate projection can be made via an electrical connection. The electrical connection extends while being electrically insulated by the separation layer and the closing plate.

[0072] In a preferred embodiment, the first stack end plate, or the further stack end plate, is formed in the form of an assembly. This allows for a symmetrical structure of the pressurized electrolytic cell. Advantageously, since the first stack end plate and the further stack end plate are formed identically, only one stack end plate suitable for both ends of the housing body needs to be conceived.

[0073] The features of the end plate projection disclosed in the embodiment comprising the one portion of the stacked end plate can also be applied to the end plate projection as an element of an assembly.

[0074] In a preferred embodiment, the closing plate is formed as a flat plate of uniform thickness, which is inexpensive to manufacture. In a preferred embodiment, the end plate projection extends between a pressing surface and an intermediate surface that axially separates the end plate projection from the pressing surface, i.e., from the cell stack. Advantageously, the pressing surface and the intermediate surface extend parallel to each other and perpendicular to the axial direction.

[0075] In this embodiment, the entire axial length of the end plate projection extends from the pressing surface to the base of the end plate projection. This base is located at the height of the intermediate surface.

[0076] In a preferred embodiment, the separation layer has the same shape as the intermediate surface, specifically the same cross-section, thereby shielding the intermediate surface at the point of use. This makes it possible to insulate the end plate projection from the closing plate through the entire intermediate surface of the end plate projection. Preferably, the separation layer extends across the entire cross-section of the housing body. Therefore, the area of ​​the separation layer is larger than that of the intermediate surface. This prevents electrical bridging between the end plate projection and the closing plate.

[0077] In a preferred embodiment, the entire axial length of the end plate projection is formed such that an axial gap exists between the closing plate and the end wall of the housing body at the point of use. This enables electrical insulation between the housing body and the closing plate. Advantageously, to ensure reliable insulation, the entire axial length of the end plate projection and the thickness of the separation layer are formed such that an axial gap exists between the closing plate and the end wall at the point of use.

[0078] In a preferred embodiment, the end plate projection is formed as an electrolytic cell, and the cell frame of the electrolytic cell has a thick wall on the side facing the closing plate, and the thick wall is defined to accommodate the outer seal. Therefore, the thick wall includes a sealing section. This allows for optimization of the production capacity of the pressurized electrolytic cell.

[0079] The pressure vessel is sealed against ambient pressure, has a cell stack within its internal section, and is supplied with pressure during electrolysis. Specifically, the pressure vessel may be supplied with a pressure of at least 0.5 MPa, preferably at least 3 MPa, and particularly preferably at least 4 MPa during electrolysis. Higher pressures of at least 20 MPa, for example 35 MPa or 70 MPa are also possible and preferred. Particularly preferably, the pressure vessel is supplied with the operating pressure of the electrolytic cells during electrolysis.

[0080] By arranging the cell stack within a pressure vessel, substantially the same pressure conditions are created inside the electrolytic cell, i.e., inside the cavity of the electrolytic cell, and outside the electrolytic cell during electrolysis, and it is possible to have no or almost no pressure difference acting on the cell stack, specifically the end plates of the cell stack. As a result, the pressure on the individual cell frames of the electrolytic cell is almost the same inside and outside the electrolytic cell. The mechanical forces acting on the cell frames and inner seals of the electrolytic cell are significantly less than when the cell stack is surrounded by atmospheric pressure. As a result, the cell frames and inner seals of the electrolytic cell are subjected to less mechanical load, and therefore they can be made from thinner and / or less expensive materials, and have a longer lifespan than in pressurized electrolytic cells operating at ambient pressure, as known from, for example, German Patent Application Publication No. 102014010813 and European Patent Application Publication No. 1464730.

[0081] In this pressurized electrolytic cell, as well as in this method, the cell frame, the so-called stack frame, and the attached internal seals between the cell frames are not exposed to the pressure difference between the operating pressure and the ambient pressure, and operate at most with a very small pressure difference. This reduces the risk of internal seal failure and, consequently, the risk of alkaline solution leakage from each electrolytic cell. Failure of the internal seal leads to a deterioration of the output and / or lifespan of the cell stack.

[0082] Based on the placement of the cell stack within a pressure vessel, no pressure difference is formed between the surroundings of the electrolytic cell and the cavity of the electrolytic cell. This reduces the pressure resistance requirements on the cell stack. This significantly extends the lifespan of the cell stack, specifically the cell frame and inner seal. When the operating pressure of the electrolytic cell is 3 MPa and the pressure applied to the pressure vessel is approximately 3 MPa, the lifespan of the cell frame and inner seal is approximately twice that of a conventional cell stack operating under ambient pressure. Furthermore, the cell frame and inner seal can also be manufactured from a wider range of materials because the mechanical loads they are subjected to are smaller. For example, the cell frame may be made from ethylene-propylene-diene-(monomer)-rubber, so-called EPDM.

[0083] As a further advantageous boundary criterion (Abgrenzungskriterium) of the present invention over the prior art, the fact that electrolysis in a pressure vessel can be carried out at operating pressures greater than 10 MPa and up to 70 MPa, i.e., at a pressure difference relative to the surroundings of the electrolytic cell where the electrolytic cells and their seals can hardly or never mechanically withstand the pressure, should be appreciated. However, the higher the operating pressure in the cell stack, the better the efficiency, and therefore such an operating pressure is advantageous. That is, the water is under pressure, which supports the electrolytic reaction. Furthermore, at higher operating pressures, compressed gas products can be generated; for example, water can be generated under pressures of 30 MPa or higher, so that an additional compressor to compress the gas products is no longer necessary for use.

[0084] In a preferred embodiment, the end plate projection is positioned radially away from the inner side surface of the housing body, specifically from the inner side surface of the operating section, and the outer seal extends through the radial gap. This allows the outer seal to act as a spacer, supporting the coaxial alignment of the inner side surface of the housing body with respect to the stack end plate. In a particularly preferred embodiment, the cell stack is also positioned radially away from the inner side surface of the housing body, preferably at the same radial gap as the end plate projection.

[0085] A pressurized electrolytic cell is advantageously designed to provide hydrogen through the electrochemical electrolysis of water.

[0086] The present invention further relates to an electrolytic apparatus having a pressurized electrolytic cell based on the above-described form and at least one gas storage container, wherein the gas storage container is configured to contain gaseous products and to separate the gaseous products from the entrained electrolyte. Such an electrolytic apparatus benefits from the advantages of a pressurized electrolytic cell, which manifests as greater reliability and lower maintenance costs.

[0087] The present invention also relates to a method for providing at least one gas product, specifically hydrogen, by electrolysis. This method is carried out in a pressurized electrolytic cell based on one of the embodiments described above. When electrolysis is performed, a pressure of at least 0.5 MPa, for example at least 3 MPa, advantageously 4 MPa to 5 MPa, and similarly preferably more than 10 MPa, specifically 15 MPa to at least 20 MPa, for example up to 35 MPa, or up to 70 MPa is applied to the internal space of the pressure vessel. Such an operating pressure is possible by the embodiments described above because the electrolytic cell is insulated from the ambient pressure of the pressurized electrolytic cell by the housing body. The housing body can be designed to be optimized for such an electrolytic cell as described. The higher the operating pressure in the pressure vessel, the better the efficiency. Furthermore, higher operating pressures can generate compressed gas products. This allows the gas product, for example hydrogen, to be provided in a compressed state and does not require additional compression following electrolysis to be useful as fuel or for storage. This saves energy and costs for pressure compressors or avoids the use of further pressure compressors. [Brief explanation of the drawing]

[0088] As discussed previously, there are various possibilities for advantageously structuring and improving the teachings of the present invention. Further configurations, features, and advantages of the present invention will be described in detail below, particularly based on the embodiment shown in Figure 1. [Figure 1] Figure 1 is a side view showing a first embodiment of a pressurized electrolytic cell according to the present invention, operating according to a method according to the present invention. [Figure 2] Figure 2 is a longitudinal cross-sectional view of the pressurized electrolytic cell shown in Figure 1, along line AA shown in Figure 1. [Figure 3] Figure 3 is a longitudinal cross-sectional view of the pressurized electrolytic cell shown in Figure 1, along the line BB shown in Figure 1. [Figure 4] Figure 4 is a detailed view showing the region indicated by "C" in Figure 2. [Figure 5]Figure 5 is a longitudinal cross-sectional view showing a further embodiment of the pressurized electrolytic cell. [Figure 6] Figure 6 is a detailed view showing the region indicated by "D" in Figure 5. [Modes for carrying out the invention]

[0089] Figure 1 relates to a high-pressure electrolytic cell 100 for providing at least one gas product, i.e., an alkaline electrolytic cell for providing hydrogen and oxygen by electrochemically decomposing water.

[0090] To perform electrolysis, the high-voltage electrolytic cell 100 has a cell stack 10 comprising a plurality of electrolytic cells 12 connected in series in the axial direction X. The cell stack has a plurality of electrolytic cells, specifically at least 10, for example 20, for example 60, and even 120. In the axial direction X, the cell stack 10 has a first stack end plate 22 formed as an anode end plate and a further stack end plate 24 formed as a cathode end plate.

[0091] Each electrolytic cell 12 has a cavity positioned between the anode plate and the cathode plate, and a stabilizing cell frame surrounding the cavity. An operating pressure of, for example, 3 MPa, 35 MPa, or 70 MPa is applied to this cavity during electrolysis. Each electrolytic cell 12 is thus configured to operate under a predetermined operating pressure. A membrane is placed within each cavity of the electrolytic cell 12 to separate the anode plate and the cathode plate from each other. A potassium hydroxide aqueous solution is suitable as the electrolyte.

[0092] To seal the cavity of the electrolytic cell from the surroundings and / or to seal adjacent electrolytic cells from each other, an inner seal 14 is positioned between each pair of cell frames within the cell stack 10. Figure 4 shows the stacked electrolytic cells and the inner seals 14. These inner seals are located between the cell frames. Each inner seal is screwed between each pair of cell frames. Each cell frame has one frame groove for housing the inner seal. Each frame groove has one sealing surface. The sealing surface forms the bottom of the frame groove. Here, the bottom of the frame groove extends parallel to the plane of each cell frame. The sealing surfaces of the frame grooves act on the inner seals, for example, horizontally, in the direction of the longitudinal axis X of the housing body.

[0093] The high-pressure electrolytic cell includes a pressure vessel 18. The pressure vessel 18 includes a pressure-resistant tubular, circular cylindrical housing body 20, a 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 can be detachably coupled to the housing body 20 and is formed to compactly close the axial opening of the housing body 20.

[0094] The cell stack 10 is housed within the internal space of the pressure vessel 18, in the operating section 21 of the housing body. Such a pressure vessel is supplied with positive pressure, preferably the operating pressure of the cells, for example, 3 MPa, 35 MPa, or 70 MPa, when electrolysis is performed.

[0095] In other words, in the case of the illustrated high-pressure electrolytic cell 100, the cell stack 10 is inserted into a pressure-resistant circular cylindrical housing body 20, for example, into a pressure-supporting tube. This tube is axially coupled to the stack end plates 22 and 24 of the cell stack 10. The stack end plates 22 and 24 are compactly coupled to the housing body 20 at the operating position of the pressure vessel.

[0096] The housing body has an end wall 20a at the axial end facing the first stack end plate 22. The end wall extends in a plane perpendicular to the axial direction X.

[0097] At least one of the first stack end plate or the further stack end plate has an axial end plate projection. Here, the first stack end plate 22 has an end plate projection 28.

[0098] In order to seal the internal space of the pressure vessel against the ambient pressure of the high-pressure electrolytic cell 100, the outer seal 26 is positioned in the radial direction Y between the housing body 20 and the sealing section 28a of the end plate projection 28.

[0099] The end plate projection 28 has a circular cross-section along its entire axial length. As a result, the sealing section 28a has a circular cross-section that matches the circular cross-section of the operating section 21 at the point of use.

[0100] Furthermore, the end plate projection has a pressing surface 23 on the side of the end plate projection facing the cell stack 10, which is located within the internal space of the pressure vessel and oriented perpendicular to the axial direction. The pressing surface presses the cell stack axially in the operating position of the pressurized electrolytic cell 100 in order to tighten the cell stack 10 between the first stack end plate 22 and the further stack end plate 24. Here, the further stack end plate 24 also has a pressing 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 tightened between the stack end plates 22 and 24. Furthermore, the sealing section 28a protrudes into the operating section 21 of the housing body 20.

[0101] In the illustrated embodiment, as better seen in Figure 4, the first stack end plate 22 is formed as an assembly. Specifically, the first stack end plate 22 includes a closing plate 22a acting as the top surface, an end plate projection 28, and a separation layer 33 formed from an electrically insulating material. Thus, the closing plate and the end plate projection are electrically insulated from each other by the separation layer.

[0102] The first stack end plate 22 is divided into two parts, and these parts are electrically insulated from each other by the isolation layer 33, thereby preventing a short circuit between the two stack end plates 22 and 24. The outer seal 26 surrounds the outer circumference of the end plate projection 28.

[0103] The outer seal 26 is a double O-ring, as shown in Figure 4. In this embodiment, the end plate projection 28 has two annular sealing grooves for accommodating the double O-rings. Each O-ring is positioned between the housing body 20 and the radial sealing surface 29, the sealing surface 29 forming the bottom of the sealing groove. Here, the bottom extends parallel to the axial direction X when viewed in a longitudinal cross-section.

[0104] The two sealing grooves are separated from each other by the spacer element 27 of the end plate projection 28.

[0105] In the illustrated embodiment, the additional stack end plates 24 are directly, specifically integrally, coupled to the housing body 20. As shown in Figure 1, the stack end plates 22, 24 are arranged parallel to each other. The outer periphery of the stack end plates 22, 24 protrudes beyond the outer periphery of the housing body 20, so that the stack end plates 22, 24 have an outer region or projection extending radially outward from the internal space of the pressure vessel. To ensure particularly reliable closure of the pressure vessel, the stack end plates 22, 24 are positioned relative to each other in these projection regions by fixing elements 30, 32, specifically tie rods, extending in the direction of the longitudinal axis X of the housing body 20, so that the cell stack 10 is tightened axially between the pressing surface 23 and the additional stack end plates 24. The functions of sealing the cavity of the electrolytic cell and sealing the internal space of the pressure vessel are performed by two separate elements, namely the inner seal and the outer seal.

[0106] Figure 4 shows a detailed view of the outer seal 26 positioned between the cell stack 10 and the first stack end plate 22. The cell stack is positioned radially apart from the pressure vessel, specifically from the housing body 20, at a distance of 44.

[0107] The fixing elements 30 and 32 have threaded rods. The threaded rods, by attached nuts, position the electrolytic cells axially between a plurality of stack end plates. In the embodiments of Figures 5 and 6, the fixing elements must be electrically insulated from the first stack end plate and the further stack end plates if they are conductive. In the embodiments of Figures 1 and 4, the isolation layer 33 ensures that the further stack end plate 24 and the end plate projection 28 are electrically insulated. Furthermore, the housing body is insulated from the cell stack via radial spacing 44. Electrical contact with the end plate projection 28 is made via an electrical connection 31. The connection extends electrically isolated by the isolation layer and the closing plate.

[0108] Furthermore, one support element 54 is positioned within each sealing groove. The support element 54 extends through a radial gap 44 located between the cell stack 10 and the housing body 20 of the pressure vessel. The support element 54 extends radially between the inner side surface of the housing body and the end plate projection 28, and axially between the outer seal 26 and the radial wall of the sealing groove. The support element 54 helps to coaxially position the inner side surface of the housing body with respect to the end plate projection. Furthermore, the support element 54 supports the outer seal 26. This is advantageous in specifically preventing the outer seal 26 from sliding under high pressure. Advantageously, the support element 54 is formed from an electrically insulating material and acts as an insulating element. This reliably prevents short circuits between the inner side surface of the housing body and the end plate projection 28.

[0109] The total length of the end plate projection 28 in the axial direction and the thickness of the separation layer 33 are configured such that an axial gap 56 exists between the closing plate 22a and the end wall 20a at the point of use.

[0110] The pressure space around the cell stack 10 can be cleaned with the generated gas. An inlet 50 is provided for the inflow of the generated gas, for example, hydrogen (see Figure 3). Furthermore, an outlet 52 may be provided for the caustic solution that may be generated, for example, an aqueous potassium hydroxide solution.

[0111] In other words, in the case of the pressurized electrolytic cell shown in the drawing, the cell stack 10 is located within a pressure vessel supplied with the operating pressure of the cell stack 10. As a result, there is little to no pressure difference between the cavity inside the electrolytic cell and the surrounding area of ​​the electrolytic cell. The cell stack 10 and its inner seal 14 are located between the stack end plates in the axial direction. That is, the inner seal 14 acts in the axial direction. The outer seal 26, formed to seal the pressure vessel, is located between the stack end plates 22 and the housing body 20 in the radial direction. That is, the outer seal 26 acts in the radial direction. Since the inner seal 14 is located within the pressure space and the outer seal 26 is an independent element of the inner seal, the mechanical loads to which the inner seal 14 and the outer seal 26 are subjected are significantly smaller than in a conventional electrolytic cell operating under ambient pressure.

[0112] The pressurized electrolytic cell shown in Figures 5 and 6 is configured similarly to the embodiment disclosed in Figures 1-4. Only the differences are described below. The same features are characterized by the same reference numerals.

[0113] Unlike the first embodiment shown in Figures 1-4, the first stack end plate 22 is formed integrally and as a single piece. That is, the end plate projection and the closing plate form a unit. As can be seen more clearly in Figure 6, the outer seal 26 is also positioned in the radial direction Y between the housing body 20 and the sealing section 28a of the end plate projection 28 in order to seal the internal space of the pressure vessel against the ambient pressure of the pressurized electrolytic cell 100. Furthermore, the sealing section 28a protrudes into the operating section 21 of the housing body 20.

[0114] The fixing elements 30 and 32 may have threaded rods. The threaded rods, by attached nuts, position the electrolytic cells axially between the stack end plates. In the embodiment of Figure 5, the fixing elements are electrically insulated from the first stack end plate and the further stack end plates. Furthermore, the housing body is electrically insulated from the cell stack. [Explanation of Symbols]

[0115] 10 Cell stack with multiple electrolytic cells 12 12 electrolytic cells 14 Cell stack 10 inner seal 18 Pressure vessel 20. Housing body of pressure vessel 20a End wall of the housing body 21 Operating sections of the housing body 22 First stack end plate 22a Closure plate 23 Pressing surface of end plate protrusion 24 Further stack end plates formed as the base surface of the pressure vessel 25 Further pressing surface of stack end plate 24 26 Outer seal 27 Spacer element of end plate protrusion 28 End plate protrusion 28a Sealing division 29 Radial sealing surface 30 1st fixed element 31 Electrical connection 32 Further fixed elements 33 Separation layer 44 Radial distance between the cell stack 10 and the housing body 20 of the pressure vessel 50 Entrance 52 Outlet, for example, an outlet for electrolytes that may be generated, such as alkaline solutions. 54 Support element for outer seal 26 56 Axial gap 100 Pressurized electrolytic cells, specifically high-pressure electrolytic cells Directions arranged in the direction of the X axis, or the longitudinal axis of the housing body 20. Direction positioned in the Y radial direction, or in the radial direction of the housing body 20.

Claims

1. A pressurized electrolytic cell (100) for providing at least one type of gas product, The system comprises a cell stack (10) containing a plurality of electrolytic cells (12) formed for electrochemical electrolysis, and a pressure vessel (18) sealed against ambient pressure. The electrolytic cell (12) is connected in series in the axial direction (X) and is positioned between a first stack end plate (22) and a further stack end plate (24), and has one cavity to which an operating pressure is applied, as well as a stabilizing cell frame surrounding the cavity. Within the cell stack (10), an inner seal (14) is positioned between each of the two cell frames, the inner seal (14) surrounds each cavity of the electrolytic cell and seals the periphery of the electrolytic cell, the inner seal (14) is positioned between the two cell frames in the axial direction (X) and between the stack end plates (22, 24), The cell stack (10) is housed within the operating section of the housing body (20) in the internal space of the pressure vessel (18), and the operating pressure of the electrolytic cell (12) is applied within the internal space. The pressure vessel (18) has a pressure-resistant housing body (20) having end walls at each axial end of the pressure vessel, and a first stack end plate (22) as an upper surface and a further stack end plate (24) as a base surface, and the housing body (20) has at least one outer seal (26) that is fitted between the first stack end plate and the further stack end plate and is formed to seal the internal space of the pressure vessel against the ambient pressure, In a pressurized electrolytic cell (100), at least one of the first stack end plate (22) or the further stack end plate (24) has an axial end plate projection (28), and the outer seal (26) is positioned radially (Y) between the housing body (20) and the sealing portion of the end plate projection (28), The sealing section has a cross-section that coincides with the cross-section of the operating section at the usage position, the sealing section protrudes into the operating section of the housing body (20), the end plate protrusion (28) has a pressing surface (23) on the side of the end plate protrusion facing the cell stack (10), and the pressing surface (23) presses the cell stack (10) in the axial direction (X) at the usage position of the pressurized electrolytic cell (100) in order to tighten the cell stack (10) between the first stack end plate (22) and the further stack end plate (24).

2. The pressurized electrolytic cell (100) according to claim 1, characterized in that the outer seal (26) surrounds the outer circumference of the end plate projection (28), and the end plate projection has an annular sealing groove within the sealing section, which is advantageous for housing the outer seal.

3. The pressurized electrolytic cell (100) according to claim 1 or 2, characterized in that the end wall (20a) of the housing body (20) facing at least one of the first stack end plate (22) or the further stack end plate (24) extends in a plane that extends perpendicular to the axial direction (X).

4. The pressurized electrolytic cell (100) according to any one of claims 1 to 3, characterized in that the pressing surface is in direct contact with the electrolytic cell facing the pressing surface.

5. The end plate projection includes an inner portion and an outer portion including the sealing portion, and in the usage position, the inner portion is located inside the housing body (20) and in contact with the cell stack via the pressing surface, and in the usage position, the outer portion is located outside the housing body (20) and is configured to form an axial 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), as described in any one of claims 1 to 4.

6. The pressurized electrolytic cell (100) according to any one of claims 1 to 5, characterized in that the operating section has the same cross-section over the length of the operating section.

7. The pressurized electrolytic cell (100) according to any one of claims 1 to 6, characterized in that at least one of the first stack end plate (22) or the further stack end plate (24) is formed in the form of an assembly, and the closing plate acting as the top surface or base surface and the end plate protrusion are formed separately, and the closing plate and the end plate protrusion are electrically insulated from each other by a separation layer formed of an electrically insulating material.

8. The pressurized electrolytic cell (100) according to claim 7, characterized in that the end plate projection (28) is formed as an electrolytic cell, the cell frame of the electrolytic cell has a thick wall on the side facing the closing plate, and the thick wall is defined to accommodate the outer seal.

9. The pressurized electrolytic cell (100) according to claim 7 or 8, characterized in that the entire axial length of the end plate projection is formed such that an axial gap exists between the closing plate and the end wall of the housing body at the point of use.

10. The separation layer is oriented away from the pressing surface (23) and has the same cross-section as the intermediate surface of the end plate projection that defines the end plate projection in the axial direction, and the intermediate surface is covered at the usage position, as described in any one of claims 7 to 9, for the pressurized electrolytic cell (100).

11. The pressurized electrolytic cell (100) according to any one of 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), and the support element (54) assists in coaxially positioning the housing body with respect to the end plate projection.

12. The pressurized electrolytic cell (100) according to any one of claims 1 to 11, characterized in that the end plate projection is positioned at a radial distance (44) from the inner side surface of the housing body, and the outer seal (26) extends through the radial distance (44).

13. The pressurized electrolytic cell (100) according to any one of claims 1 to 12, wherein at least one of the first stack end plate (22) or the further stack end plate (24) is the first stack end plate (22), the first stack end plate (22) can be detachably coupled to the housing body (20) and is formed to compactly close an axial opening of the housing body (20), and the further stack end plate (24) is integrally and press-fitted with the housing body (20).

14. An electrolytic apparatus comprising a pressurized electrolytic cell (100) according to at least one of claims 1-13 and at least one gas storage container, An electrolytic apparatus in which the at least one gas storage container is configured to contain a gas product and to separate the gas product from an entrained electrolyte.

15. In a method for providing at least one gas product, specifically hydrogen, by electrolysis, The method is carried out in a pressurized electrolytic cell (100) configured according to at least one of claims 1-13, characterized in that when electrolysis is performed, a pressure of at least 0.5 MPa, for example at least 3 MPa, preferably 4 MPa to 5 MPa, similarly preferably more than 10 MPa, specifically 15 MPa to at least 20 MPa, for example up to 35 MPa, or up to 70 MPa is applied to the internal space of the pressure vessel.

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