Electrolyser for hydrogen production

Abstract

The present invention refers to an electrolyser (1) for the production of hydrogen from an alkaline electrolyte. The electrolyser (1) comprises a first header (2) and a second header (3) between which a plurality of elementary cells (4) and a plurality of bipolar plates (5) are stacked. Each bipolar plate (5) separates two adjacent elementary cells. The electrolyser (1) further comprises a plurality of clamping elements (20) that mechanically connect said headers (2, 3). Each of the elementary cells (4) comprises a frame (6) defining a chamber (6A), having an anodic section and a cathodic section, in which an anodic electrode (7) and a cathodic electrode (8) are at least in part housed. Each of the elementary cells (4) further comprise a separator element (10) that separates the anodic section from the cathodic section. According to the invention, each of the frames (6) comprises first through holes (61) and each of the bipolar plates (5) comprises second through holes (51), wherein each of said first through holes (61) of one frame (6) is mutually aligned with a corresponding first through holes (61) of each of the another frames (6) and with one of said second through holes (51) of each bipolar plate (5), wherein each one of said clamping means (20) extends through said through holes (51, 61) mutually aligned.

Description

[0001] ELECTROLYSER FOR HYDROGEN PRODUCTION

[0002] FIELD OF THE INVENTION

[0003] The present invention falls within the scope of the realization of devices for the production of hydrogen by water electrolysis. In particular, the invention refers to an electrolyser for the production of hydrogen and oxygen preferably, but not exclusively, from an alkaline electrolyte. STATE OF THE ART

[0004] Over the past few years, the demand for hydrogen has greatly increased in various production areas, such as the production of electricity without polluting emissions. Hydrogen can be easily stored and transported, for example through pipelines such as those used for gas, and it therefore can be easily made available for different applications.

[0005] The use of electrolysers is known for the production of hydrogen, in which water electrolysis is carried out, that is, the dissociation of the same into hydrogen and oxygen under the effect of an electric current. The existence of different types of electrolysis is also known, including alkaline water electrolysis and polymer membrane electrolysis.

[0006] A plant for the production of hydrogen at an industrial level, based on alkaline water electrolysis, typically comprises an electrolyser including a plurality of elementary cells stacked between two headers and blocked by using clamping means. In each of the elementary cells, alkaline water dissociation reaction is carried out, which very frequently consists of an electrolyte based on potassium hydroxide (also commonly known as “potash”).

[0007] In each elementary cell, an anodic portion and a cathodic portion separated by a separator element are identified. The anodic portion and the cathodic portion respectively comprise an anodic electrode and a cathodic electrode, between which the separator element is placed. The anodic portion comprises an anodic chamber in which an anodic electrode is at least partially housed. Similarly, the cathodic portion comprises a cathodic chamber in which a cathodic electrode is partially housed. The anodic and cathodic chambers are created by means of a dedicated frame for each chamber. Between the two electrodes (anodic and cathodic) there is a separator element involved in the electrolysis process according to widely known principles. Between two adjacent elementary cells a bipolar plate is arranged. Each bipolar plate is made of metallic material, and it comprises a first face / side in electrical contact with a cathodic electrode of a cell. A second face / side, opposite to the first one, is in electrical contact with the anodic electrode of an adjacent cell.

[0008] Typically, the elementary cell frames and the bipolar plates comprise openings arranged and configured in such a way as to define, following the stacking of the cells between the electrolyser headers, a first potash distribution channel, a second potash distribution channel, a first collection channel of a first reaction product and a second collection channel of a second reaction product.

[0009] The first distribution channel and the first collection channel are in hydraulic communication, through the frames, with the anodic section of each elementary cell, while the second distribution channel and the second collection channel are in hydraulic communication, through the frames, with the cathodic section of each elementary cell. Through the distribution channel (first or second), the corresponding portion (anodic or cathodic) of each elementary cell is fed with potash. For each elementary cell, the gas that is generated following the electrolysis reaction and / or any non-dissociated potash leaves the respective portion (cathodic or anodic) of the cell and flows into the corresponding collection channel (first or second).

[0010] To efficiently carry out the processes described above, the electrolysers must withstand difficult operating conditions, in terms of pressure and chemical stability, without compromising the operation efficiency and the overall costs of the components, also considering the assembly and disassembly operations. In this regard, it has been seen that the known solutions are not sufficiently effective especially for what concerns mechanical resistance allowed by the components defining the elementary cells. At the same time, also the assembly operations of the known electrolysers take too long having a strong impact on the final costs.

[0011] Further, it has been found the need to provide a new structure of the electrolysers that can minimize both waste production and the overall amount of expensive materials used. Furthermore, it is desirable that electrolyser components can be manufactured without resorting to very expensive materials and techniques. SUMMARY

[0012] The main task of the present invention is therefore to provide an electrolyser that allows to overcome or at least to mitigate the above problems. Within this task, a first object of the present invention is to provide an electrolyser that allows the electrolyte to operate effectively, with particular regard to the capacity of operating at high pressure (for example at 30 bar relative). A further object of the present invention is to provide an electrolyser that allows to reduce production costs, especially those linked to the assembly operations. Not least object is to provide an electrolyser that is reliable and easy to build at competitive costs as well as with easy and economical maintenance in case of disassembly and reassembly.

[0013] The scope and the purposes above are achieved by an electrolyser according to Claim 1. The dependent claims specify preferred embodiment of the electrolyser. More in detail, the electrolyser according to the invention is usable to produce hydrogen from an alkaline electrolyte and it comprises: a first header and a second header made of metal material; a plurality of elementary cells and a plurality of bipolar plates arranged between said headers, wherein said elementary cells are separated from each other by one of said bipolar plates; a plurality of clamping elements that mechanically connect said headers, said elementary cells and said bipolar plates; wherein each elementary cell comprises: a frame defining a chamber, having an anodic section and a cathodic section, in which an anodic electrode and a cathodic electrode are at least in part housed, a separator element that separates the anodic section from the cathodic section.

[0014] The electrolyser further comprises: at least one first distribution channel of an alkaline electrolyte wherein, for each of said elementary cells, said channels are in hydraulic communication with said sections of said chamber defined by said frame; at least a first collection channel of a first reaction product mainly comprising oxygen, wherein, for each of said element cells, said first collection channel is in hydraulic communication with the anodic section of said chamber; a second collection channel of a second reaction product mainly comprising hydrogen, wherein, for each of said elementary cells, said second distribution channel is in hydraulic communication with the cathodic section of said chamber; wherein each of the frames comprises first through holes and each of the bipolar plates comprises second through holes, wherein each of said first through holes of one frame is mutually aligned with a corresponding first through holes of each of another frames and with one of said second through holes of each bipolar plate, wherein each one of said clamping means extends though said through holes mutually aligned.

[0015] According to a preferred embodiment, each of said bipolar plates comprises:

[0016] - one or more channels for the circulation of a cooling fluid;

[0017] - an entry section and an exit section respectively for the entry and exit of said cooling fluid in said one or more channels, wherein said electrolyser further comprises:

[0018] - at least one delivery channel of said cooling fluid in hydraulic communication with said entry section of each of said bipolar plates; and at least one return channel of said cooling fluid in hydraulic communication with said exit section of each of said bipolar plates.

[0019] According to a possible embodiment, at least one of said bipolar plates comprises three components configured and assembled so as to define a plurality of inner channels, wherein an inner components is placed between two outer components and wherein a first plurality of channels is defined between said inner component and one of said outer components and a second plurality of channels is defined between said inner component and the other outer component, wherein said inner component separates said first plurality of channels from said second plurality of channels. According to a possible embodiment, the frame has first face and a second face opposite to the first face, said first through holes extending from said first face to said second face, said frame comprising at least one distribution opening of said electrolyte, a first collection opening for said first reaction product and a second collection opening for said second reaction product. Said frame further comprises at least two opening for the passage of the cooling fluid circulating in said internal channels of the bipolar plate.

[0020] According to a preferred embodiment, the frame comprises a metal core at least partially covered by elastomeric material layer.

[0021] According to a possible embodiment, for at least one of said through holes of the frame a bushing is provided in its inside, wherein said bushing is axially holed to receive a corresponding of said clamping means and wherein said bushing is made of non-compressible material.

[0022] According to a possible embodiment, the first face and / or side second face of the frame comprises corrugations adapted to be compressed against a surface of a corresponding bipolar plate to generate leak-tightness of the electrolyser during the stacking.

[0023] Preferably, each one of the faces of the frame is provided with first grooves that make the at least one distribution opening communicating with the chamber of the frame and second groves that make one of the collection opening communicating with the same chamber.

[0024] According to a possible embodiment, the electrolyser comprises a first distribution channel and a second distribution channel of an alkaline electrolyte and wherein, for each of said elementary cells, each one of said distribution channels is in hydraulic communication with one of the sections of said chamber defined by the frame, wherein the frame comprises a first distribution opening and a second distribution opening of the electrolyte.

[0025] According to a possible embodiment, the electrolyser comprises: two delivery channels of said cooling fluid each of which is in hydraulic communication with said entry section of at least one of said bipolar plates, and two delivery channels of said cooling fluid each of which is in hydraulic communication with said exit section of at least one each of said bipolar plates, wherein such frame comprises at least four through openings for the passage of the cooling fluid circulating in said internal channels of said bipolar plates.

[0026] According to a possible embodiment, the frame is provided with a sealing groove defined on said first surface and / or on said second surface, wherein said sealing groove as a loop configuration so that said distribution opening of said electrolyte, said collection openings of said reaction products and said openings for the passage of said cooling fluid are positioned inside said loop, wherein said sealing grove is suitable to be filled with sealing material or a sealing element.

[0027] According to a possible embodiment, each of the bipolar plates comprises a plurality of openings each of which for the passage of said electrolyte, wherein, following the stacking of the elementary cells, each of said openings is aligned with a distribution opening or with a collection opening of said frame, wherein said openings develops from a first surface to a second surface of the bipolar plate and wherein a sealing member is placed in each of said openings of the bipolar plate so as to provide leak-tightness between the components thereof.

[0028] According to a possible embodiment, each of said bipolar plates comprises a couple of delivery opening which are hydraulically communicating with said internal channels and a couple of return openings for collecting the cooling fluid after its passage in said internal channels, each of said openings for the circulation of said cooling fluid is configured so as to match with a corresponding opening of said frame, so as to define, following the stack of the cells, one of said delivery channels or one of said return channels.

[0029] Preferably, said delivery openings are defined at a first side of the bipolar plate, each one near one of its corners, said return openings being defined at a second e side of said bipolar plate, each one near one of its corners; each of said openings for the passage of said electrolyte being defined between said delivery openings or between said return openings.

[0030] According to a possible embodiment, said bipolar plate comprises a sealing groove defined on a first surface and / or a second surface of said bipolar plate, wherein said sealing grove is suitable to be filled with sealing material or a s sealing element. According to a possible embodiment, for at least one of the elementary cells, said frame comprises anchoring means to arrange said separator inside the corresponding chamber so as to generate said anodic section and said cathodic section.

[0031] According to a its possible embodiment, the anchoring means comprise an internal edge that develops at least partially along the perimeter of said chamber, wherein said internal edge defines an attachment surface at an intermediate position between said first face and said second face, said anchoring means further comprising a plurality of connecting pins on one side of said internal edge, wherein said pins are suitable to enter with corresponding holes defined through said separator close to its perimetral edge, wherein said separator is fixed to the frame following the insertion of the each of the connecting pins in a corresponding of said holes, said anchoring means further comprise a perimetral frame that is fitted on said internal edge so as to block the position of the separator with respect to the frame.

[0032] According to a possible embodiment, a centering element is provided for at least one of said bushing, said centering element being axially holed so as to receive one of said clamping elements, said centering elements being arranged inside a corresponding bushing so that one of its ends emerges with respect to one of the surfaces of the frame, wherein said emerging end is suitable to be inserted in one of said through holes of said bipolar plate.

[0033] LIST OF FIGURES

[0034] Further characteristics and advantages of the invention will become better apparent upon examination of the following detailed description of preferred, but not exclusive, embodiments of the electrolyser according to the invention, illustrated by way of non-limiting example, with the support of the accompanying drawings, in which:

[0035] - Figure 1 is an exploded view of a first embodiment of an electrolyser according to the present invention;

[0036] - Figure 2 is a lateral view of the electrolyser of Figure 1 in an assembled configuration;

[0037] - Figures 2A and 2B are enlargement views respectively of the detail A and B of Figure 2;

[0038] - Figure 3 and 3A are views from opposite point of view of a frame of the electrolyser of Figures 1 and 2; - Figure 4 is a cross section view of a frame of the electrolyser of Figures 1 and 2;

[0039] - Figure 4A is a cross section showing a possible alternative of the frame of Figure 4;

[0040] - Figures 5 and 5A are views from opposite point of view of a bipolar plate of the electrolyser of Figures 1 and 2;

[0041] - Figures 6 and 7 are section views respectively according to the line VI and VII of Figure 5;

[0042] - Figure 8 is an exploded view of a second embodiment of an electrolyser according to the present invention;

[0043] - Figure 9 is a lateral view of the electrolyse of Figure 8 in an assembled configuration;

[0044] - Figure 9 A is an enlargement view of the detail C of Figure 9;

[0045] - Figures 10 and 10A are views from opposite points of view of a frame of the electrolyser of Figures 8 and 9;

[0046] - Figures 11 and 12 are section views respectively according to line XI-XI and XII-XII of Figure 10;

[0047] - Figure 13 is a frontal view of a bipolar plate of the electrolyser of Figures 8 and 9;

[0048] - Figure 14 is a section view according to the line XIV-XIV of Figure 13.

[0049] The same reference numbers and letters in the figures identify the same elements or components.

[0050] DETAILED DESCRIPTION

[0051] With reference to the aforementioned figures, the present invention therefore relates to an electrolyser 1 that is a device for the electrolysis of water, in particular alkaline water (hereinafter referred to as potash).

[0052] The electrolyser 1 according to the invention comprises a plurality of electrolysis cells 4 (hereinafter also referred to by the expression “elementary cells”) stacked between a first header 2 (or anodic header) and a second header 3 (or cathodic header) opposite each other and made of metallic material. In particular, the elementary cells are stacked along a longitudinal direction 401. Each elementary cell is separated from the adjacent one through a bipolar plate (indicated in the figures with reference 5). The electrolyser 1 is provided with a plurality of clamping elements 20 (preferably in the form of stud screw) that mechanically connect the two headers 2, 3, the cells 4 and the bipolar plates 5 by exerting a traction force such that the elementary cells 4 and the bipolar plates 5 indicated above define, as a whole, a compact, substantially “sandwich” structure.

[0053] For descriptive purposes only, in the following description the expression “first cell” is intended to mean the elementary cell immediately adjacent to the anodic header 2, while the expression “last cell” is intended to mean the cell immediately adjacent to the cathodic header 3.

[0054] According to the invention, each elementary cell comprises an anodic electrode 7 (or first electrode 7), a cathodic electrode 8 (or second electrode 8) and a frame 6 delimiting a chamber 6 A, with an anodic section and a cathodic section ( not shown in the figures), in which the anodic electrode 7 and the cathodic electrode 8 are at least partially housed. For each elementary cell, the anodic electrode 7 and the cathodic electrode 8 are separated by a separator element 10 ( e.g. a diaphragm or a membrane) which divides the anodic section from the cathodic section. For each elementary cell, the chamber 6A is axially delimited (i.e. delimited along the longitudinal direction 401) between two bipolar plates 5, while the relative frame 6 delimits said chamber 6A laterally, that is according to at least two directions each of which perpendicular to the longitudinal direction 401.

[0055] As below better explained, preferably, but not exclusively, the frame 6 provided for each elementary cell comprises an inner metal part 11 surrounded by a part of elastomeric material 25. In any case, the chamber 6 A defined by the frame 6 has an axial extension sufficient to house at least the electrodes 7, 8 and the separator 10.

[0056] In any case, in each elementary cell each of the electrodes 7 or 8 are in electrical contact with one of the immediately adjacent bipolar plates 5 that delimit axially the elementary cell. In this regard, in the case of the first cell, the anodic electrode 7 is in electrical contact with the anodic header 2, while the cathodic electrode 8 is in electrical contact with a bipolar plate 5. Similarly, for the last cell, the anodic electrode 7 is in electrical contact with a bipolar plate 5, while the cathodic electrode 8 is in electrical contact with the cathodic header 3. According to a possible embodiment of the invention, the electrolyser 1 comprises at least a first potash distribution channel 11A which, for each elementary cell, is in hydraulic communication with the chamber 6 A defined by the frame 6. Such a first distribution channel 11A is provided for delivery the potash in the sections of the elementary cells. As shown in the embodiment of Figure 1, preferably, but not exclusively, the electrolyser 1 may comprise two potash distribution channels 11 A, 12A. In this case, for each elementary cell, a first distribution channel 11A is in hydraulic communication with the anodic section of the clamber 6 A defined by the relative frame 6, while a second distribution channel 12A is in hydraulic communication with the cathodic section of the chamber 6 A (cathodic section).

[0057] The electrolyser 1 also comprises a first collection channel 11B of a first reaction product mainly comprising oxygen. For each elementary cell, said first collection channel 11B is in hydraulic communication with the anodic section of each elementary cell. The electrolyser 1 also comprises a second collection channel 12B of a second reaction product mainly comprising hydrogen. For each elementary cell, said second collection channel 12B is in hydraulic communication with the cathodic section of each elementary cell.

[0058] In practice, the first collection channel 11B has the purpose of conveying the oxygen generated by the electrolysis reaction and possibly a part of unreacted, i.e. not dissociated, potash. Similarly, the second collection channel 12B conveys the hydrogen generated by the electrolysis reaction and possibly a part of unreacted potash. Thus, the two collection channels 11B, 12B collect a monophasic or biphasic solution depending on the presence or absence of unreacted potash.

[0059] The at least one distribution channels (or in the case both the distribution 11 A, 12A) and the collection channels 11B, 12B are defined following the stacking of the elementary cells. To this end, as better specified below, the frame 6 and the bipolar plates 5 comprise openings 31, 32, 33, 34 - 52, 53, 54, 55 that, by effect of stacking, align with each other defining each of said channels 11 A, 12A, 11B, 12B.

[0060] According to the present invention, the frame 6 and the plates 5 of each elementary cell of the electrolyser 1 comprise through holes 61, 51 that receive one of said clamping means 20. The term “through” wants to mean that the corresponding hole extends along the entire axial thickness of the relative component (frame 6 or plate 5). More precisely, each of the frames 6 of the electrolyser 1 comprises first through holes 61 and each of the bipolar plates 5 comprises second through holes 51. For each of the frame, each first through hole 61 is mutually aligned with a corresponding first through hole 61 of each the other frames 6 and mutually aligned with a corresponding second through hole 51 of each bipolar plate 5. According to the invention, each of the clamping means extends, between the two headers 2, 3, through corresponding holes 51, 61 mutually aligned. Therefore, by effect of the through holes 61, 51, the frames 6 and the bipolar plates 5, following their stacking, overall define a plurality of channels 71 extending between the two header 2,3. Each of such as channels 71 receives / accommodates one of said clamping means 20 ( see Figure 2A ).

[0061] Differently from the prior art solutions, the clamping means 20 mechanically connect the two headers 2, 3 by extending through the components (frames 6 and the bipolar plates 5) that define the elementary cells 4 of the electrolyser 1. Hence, the clamping means 20 are positioned inside the structure of the electrolyser 1. This arrangement allows a more effective distribution of the clamping forces that develop between the components (frames 6 and bipolar plates 5) in positions extremely close to the active regions (namely the anodic section and the cathodic section) of the elementary cells in which the electrolysis reaction develops. Further, it has been seen that the use of internal clamping means makes the assembly operation easier. Indeed, the clamping means 20 can be advantageously used as a sort of guides to stack the components of the electrolyser 1. In this regard, the internal clamping means 20 allow also a “vertical assembly ” of the electrolyser avoiding, or at least strongly reducing, the need to use of jigs or other tools to favour the assembly. In general, by the present invention, the times and costs of the assembly operation can be strongly contained.

[0062] A first possible embodiment of an electrolyser 1 according to the invention is shown in Figures 1-7. With reference to Figure 1, the elementary cell comprises an anodic spacer 9 A at least partially housed in the housing chamber 6 A defined by the frame 6. The anodic spacer 9 A is interposed between the bipolar plate 5 (or anodic header 2 in the case of the first cell) and the anodic electrode 7 so as to improve the electrical continuity between these parts. For a similar purpose, the elementary cell comprises a cathodic spacer 9B in metal material interposed between the cathodic electrode 8 and the bipolar plate 5 (or cathodic header 3 in the case of the last cell). Preferably, the spacers 9 A, 9B are made of metal material and can be in various forms known in the art (for example in the form of a mesh) and configured so as to allow the diffusion of the electrolyte in the chamber 6A (both in the anodic and cathodic section) defined by the frame 6 and in which they are positioned. The anodic spacer and the cathodic spacer may be separate components or components integral (e.g., by welding) with the respective bipolar plates.

[0063] Figure 2 is a lateral view of the electrolyser of Figure 1 that shows the arrangement of the clamping means 20 in form of screw bolts ( indicated with the same reference number 20). Both the headers 2, 3 comprises through holes 91 (indicated in Figure 1) which are aligned with a corresponding one of the channel defined by the through holes 51, 61. The screw bolts 20 are arranged parallel to the longitudinal direction 401.

[0064] Figures 2A and 2B are details of the stack of the elementary cells from which it is possible to observe the alignment of the holes 51, 61 defined through the components (frames 6, bipolar plates 5) and in particular the channels 71 generated from such an alignment.

[0065] Preferably, the bipolar plates 5 of the electrolyser 1 in the Figures 1- 7 comprises a plurality of components 5A, 5B and 5C configured and assembled so as to define one or more internal channels 66 A, 66B (i.e. passages) for the circulation of a cooling fluid, preferably a cooling liquid (e.g. water). Each bipolar plate 5 comprises an entry section SI and an exit section SU respectively for the entry and exit of the cooling fluid in / from internal channels 66A, 66B.

[0066] In order to allow the circulation of the cooling fluid, the electrolyser 1 comprises a delivery channel 4A of the cooling fluid in hydraulic communication with the entry section SI of each bipolar plate 5 and a return channel 4B of the same fluid hydraulically connected with the exit section SU of each bipolar plate 5. Advantageously, the passage of the cooling fluid in the bipolar plates 5 counteracts the heat increase to which they, and in general all the components of the elementary cells, are subjected due to the electrolysis reaction. In the following, the cooling fluid is also referred to by the expression of cooling water (or water / cooling fluid), but this does not mean that a different liquid or a different fluid could not be used as cooling fluid. In addition, in the following the electrolyte will also be indicated with the term potash, without any limitation on the use of another type of electrolyte.

[0067] Figure 6 shows in detail an embodiment of a bipolar plate 5 of the electrolyser 1. Such a plate 5 is defined by the assembly of three components 5A, 5B and 5C. More precisely, an inner component 5C is placed between two outer components 5 A, 5B. The three components 5 A, 5B, 5C are preferably, but not exclusively made of nickel, steel or other conductive metal alloy resistant to the operation condition.

[0068] Following the assembly of the components 5A, 5B and 5C, internal channels 66A, 66B are generated between the three components 5 A, 5B and 5C in which the cooling fluid flows. Preferably, the inner component 5C is preferably made of a flat metal plate and the two outer components 5A, 5B are corrugated metal plates, preferably obtained by a stamping operation from a metal foil. Following the assembly of the three components 5A, 5B, 5C, a first plurality of channels 66A is defined between a first outer component 5A and the inner component 5C, while a second plurality of channels are defined between the second outer component 5B and the inner component 5C. Therefore, the first plurality of channels 66A and the second plurality of channels 66B are defined on opposite sides of the inner component 5C. In other words, the first plurality of channels 66A are separated from the second plurality of channels 66B by means of the inner component 5C.

[0069] Flowing through the segments of the internal channels 66 A, 66B, the cooling fluid subtracts heat from the two components 5A, 5B and 5C of the bipolar plate 5 so that to contain the increase the heating to which the bipolar plates 5, and in general all the components of the elementary cell, are subjected due to the electrolysis reaction.

[0070] Figures 3 and 3A show the frame 6 of the electrolyser of Figures 1 and 2. The frame 6 comprise a first surface 611 and a second surface 612 opposite to the second surface wherein such surfaces 611, 612 develops transversally with respect to the stacking direction 401 (see Figure 1). The frame 6 comprise a central opening 600 defined through the entire thickness thereof. The central opening 600 delimits the chamber 6A in which the components of the relative cell (electrodes, separator and preferably spacers are housed) are arranged. As shown, preferably the frame 6 comprises a couple of opposite thin sides 67A and a couple of large sides 67B that develop transversally with respect to the thin sides 67A. The chamber 6A is defined between such cupules of sides 67A-67B.

[0071] Always with reference to Figures 3-3A, the frame 6 comprises a first distribution opening 31 and a second distribution opening 32 for delivering the electrolyte and a first collection opening 33 and a second collection opening 34 for collection the reaction products. With reference to Figure 1, each of the distribution opening 31, 32 and each one of the collection openings 33, 34 are shaped and positioned in a compliant manner to a corresponding opening 52, 53, 54, 55 defined through each of the bipolar plate 5. Following the stack of the elementary cells, each of the openings 31, 32, 33, 34 contributes to create one of the two distribution channels 11 A, 12A or one of the two collection channels 11B, 12B. Each of the openings 31, 32, 33, 34 is defined at one of said large side 67B near a corner formed on the frame 6 according to an arrangement for which each one of the distribution openings 31, 32 is diametrically opposite to one of the collection openings 33, 34.

[0072] The frame 6 also comprises two openings 45 A, 45B for the passage of the cooling fluid used at the bipolar plates 5 to remove heat generated by the electrolysis reaction. A first opening 45A is defined between the first distribution opening 31 and the second distribution opening 32, while the second opening 45B is defined between the two collection openings 33, 34.

[0073] The first side 611 is provided with first grooves 26A that make the first distribution opening 31 communicating with the chamber 6A and second grooves 26A’ that make the second collection opening 34 communicating with the same chamber 6A. Similarly, the second face 612 is provided with first grooves 26B that makes the second distribution opening 32 communicating with the chamber 6A and second groves 26B’ that makes the first collection opening 33 communicating with the chamber 6A. Following the stack of the elementary cells, each of the faces 611, 612 of the frame 6 contacts one of the bipolar plates 5 so that each of the grooves 26A, 26 A’, 26B, 26B’ is axially closed by a surface of said one of the bipolar plates 5. Therefore, the grooves 26A, 26 A’ of the first surface 611 allow the circulation of the potash in one of the portions (cathodic or anodic) of the chamber 6A, while the grooves 26B, 26B’ of the second surface 612 allow the circulation of the potash in the other portions of the chamber 6A.

[0074] With reference to the partial cross section of Figure 4, preferably the frame 6 comprises a metal core 11 covered at least in part with an elastomeric material layer 25. Preferably, the metal core 11 is totally embedded in a layer of elastomeric material 25. The metal core 11 can be made of a single element or it can comprise a plurality of plurality of elements.

[0075] The grooves 26A, 26A’, 26B, 26B’ adapted to let flow the process electrolyte inside the sections of the elementary cells are defined on the elastomeric material layer 25. Preferably, the first face 611 and the second surface 612 also comprise corrugations 21 adapted to be compressed in the stacking phase to generate leak-tightness of the electrolyser. Indeed, such corrugations 21 are part of the elastomeric layer 25. Due to the clamping forces, the corrugations 21 deform against the surface of a bipolar plate 5 assuring the leak- tightness between the frame 6 and the same bipolar plate 5.

[0076] With reference to Figures 1 and 4, according to the principles of the present invention, for each of the through holes 61 of the frame 6, a bushing 13 is provided in its inside. Such a bushing is made of non-compressible and insulating material such as, for example, ceramic material (such as alumina) or metal material suitably surface treated (such as steel with insulation material coating). The bushing 13 has the function of keeping the thickness of the frames fixed. Each bushing 13 is internally holed so as to allow the passage of the clamping means 20. Therefore, for each of the though holes 61, the relative clamping means 20 extends through the hole of the corresponding bushing 13.

[0077] According to a possible alternative, shown in Figure 4A, preferably, a plurality of centering elements 133 are provided, each one for a corresponding bushing 13. More precisely, the centering element 133 is axially holed and suitable to receive one of the clamping elements 20. Each of the centering elements 133 is arranged inside the hole of a corresponding bushing 13 so that one of its ends 133A emerges with respect to one of the surfaces 611, 612 of the frame 6. During the stack of the cells, the emerging end 133A of each element 133 is suitable to be inserted in one of the through holes 51 of a bipolar plate 5. This solution makes easier the connection of the frame 6 with the corresponding bipolar plates 5 and in general quicker the assembly operations.

[0078] Figure 5 is a frontal view of the bipolar plate 5 of the electrolyser of Figure 1. More precisely, Figure 1 shows a first face 511 of the bipolar plate 5. Figure 5A shows a second face 512 of the bipolar plate 5, opposite to the first face 511, indicated also in the section view of Figure 7. The second through holes 51 above defined extend from the first face 511 to the second face 512. According to the purposes of the present invention, following the stack of the elementary cells, each of the second through holes 51 receives one of the clamping means 20.

[0079] The bipolar plate 5 comprises four openings 52, 53, 54, 55 each of one aligned, following of the stacking of the elementary cells, with one of the openings 31, 32, 33, 34 of the frames 6. Each of the four openings 52, 53, 54, 55 of the plate 5 is not hydraulically communicating with the internal channels 66A, 66B provided for the cooling fluid circulation. With reference to the section view of Figure 7, for each of the openings 51, 52, 53, 54 a sealing element 14 is provided therein. The main purpose of such a sealing element 14 is to guarantee, at the corresponding opening 52, 53, 54, 55 leak-tightness between the components of the bipolar plate 5.

[0080] Always with reference to Figures 5 and 5 A, two further opening 56 A, 56B are provided respectively for the distribution, and for collection of, the cooling fluid circulating in the internal channels 66A, 66B of the bipolar plate 5. Each of the openings 56A, 56B is defined through the entire thickness of the bipolar plate 5 and it is configured and arranged so as to match a corresponding opening 45A, 45B of the frames 6 provided for the passage of the cooling fluid. This in order to define, following the stack of the cells 4, the distribution channel 4A and the collection channel 4B of the cooling fluid.

[0081] Figures 8-14 refer to a second embodiment of an electrolyser according to the invention that differs from that above described mainly for a different configuration of the components (frames 6 and bipolar plate 5 ) that delimit the elementary cells 4 as showing in the exploded view of Figure 8. Figures 9 and 9A are respectively a lateral view and a detail view of the electrolyser of Figure 8 from which it is possible to observe the sequence of the elementary cells 4 as well as the alignment of the through holes 61, 51 provided for the frame 6 and the bipolar plates 5 according to the principles of the invention already above explained.

[0082] Differently from the first embodiment above, in the second embodiment the electrolyser 1 comprises a sole distribution channel 11A which is hydraulically communicating with the sections (anodic and cathodic) of each elementary cell. Further, differently from the first embodiment above, the electrolyser 1 comprises two delivery channels 4A, 4A’ of a cooling fluid and two return channels 4B, 4B’ of the same cooling fluid, wherein such a cooling fluid is suitable to circulate in one or more channels 66A, 66B defined between at least two components defining a bipolar plate 5. Therefore, according to a principle already above explained, each of the delivery channel 4A, 4A’ is in hydraulic communication with an entry section SI of each of the bipolar plates, while each of the return channels 4B, 4B’ is in hydraulic communication with an exit section SU of each of the bipolar plates 5.

[0083] Figures 10 and 10A are views respectively of a first face 611 and of a second face 612 of a frame 6 of the electrolyser 1 of Figure 8. The frame 6 comprises four openings 45A, 45 A’, 45B, 45B’ for the passage of the cooling fluid, a sole distribution opening 31 of the electrolyte, a first collection opening 33 of a and a second collection opening 34 wherein, following the stack of the elementary cells, said distribution opening 31 contributes to define the distribution channel 11 A, while the first collection opening 33 and the second collection opening 34 contribute to define respectively a first collection channel 12A of a first reaction product and a second collection channel 12B of a second reaction product.

[0084] Always with reference to Figures 10 and 10A, the distribution opening 31 of the electrolyte is defined at a first large side 67B of the frame 6, in a position comprised between two openings 45 A, 45 A’ each of one contributes to define, following the stack of the elementary cells, one of said delivery channels 4A, 4A’ of the cooling fluid. The two collection openings 33, 34 are defined at a second large side 67B of the frame 6 each of which in a position comprised between two opening 45B, 45B’. Each one of the latter contributes to define, following the stack of the elementary cells, one of the return channels 4B, 4B’ of the cooling fluid. With reference to Figure 10, the first face 611 of the frame comprises first grooves 26A that make the distribution opening 31 communicating with a first section (anodic or cathodic) of the chamber 6A wherein the sections of the chamber 6A are defined following the placement of the separator 10 on the frame 6. On the first face 611 second grooves 26 A’ are defined to make the first collection opening 33 communicating with said first section of said chamber 6A. With reference to Figure 10A, also on the second surface 612, first groves 26B are defined to make the distribution opening 31 communicating with a second section (cathodic or anodic) of the chamber 6A. Further, on the second surface 612 second groves 26B’ are provided to make the second distribution opening 34 communicating with said second section of the chamber 6A. With reference again to figure 10 and 10A, preferably, the first surface 611 is provided with a first sealing groove 35 that develops as a loop. More in detail, such a sealing groove 35 develops so that the distribution opening 31 and the two collection openings 33, 34 of the electrolyte are defined inside said loop. At the same time, also the openings 45A, 45A’, 45B, 45B’ for the passage of the cooling fluid are defined inside the loop.

[0085] Analogously, on the second surface 612 a second sealing groove 36 is provided. Also, the second sealing groove 36 develops as a loop so that the distribution opening 31 of the electrolyte, the two collection openings 33, 34 of the electrolyte and the openings 45A, 45 A’, 45B, 45B’ for the passage of the cooling fluid are inside the loop.

[0086] Both the sealing groove 35, 36 are suitable to be filled with a sealing material or a sealing element so as to form, following the stack of the elementary cells 4, a corresponding sealing loop between each face 611, 612 of the frame 6 and a corresponding face 511, 512 of a bipolar plate 5. This in order to avoid that the cooling water circulating in the openings 45A, 45 A’, 45B, 45B’ can reach the two sections of the chamber 6 A defined by the frame 6.

[0087] As show in Figure 13, preferably, a corresponding sealing groove 135 can be defined on one or both the surfaces 511, 512 of the bipolar plate 5. Also, such a sealing groove 135 can be filled with sealing material or a sealing element for the same purpose above indicated for the sealing groove 35, 36 of the frame 6. It is worth notice that the sealing grooves could be provided also on the surface 611, 612 of the frame 6 provided for the first embodiment of the electrolyser to which the figures 1 to 7 refer. Analogously a sealing groove could be provided also on one or both the surfaces 511, 512 of the bipolar plate 5 of the first embodiment (Figures 1 to 7).

[0088] As shown in Figure 10 and 10A, according to the principles of the present inventions, the frame 6 is provided with a plurality of first through holes 61 each of which receives a corresponding clamping means 20. Also in this case, for each of the through holes 61 a bushing 13 of non- compressible material is provided for the purposes already above indicated. On this regards, Figure 11 is a section view that specifically shows the arrangement of a bushing 13 in a corresponding through holes 61. Also in this case, a centering element 133 is preferably provided for the bushing 13 for the same purposes above explained with reference to Figure 4A.

[0089] Figure 13 is a front view of the bipolar plate 5 of the electrolyser 1 of Figures 8 and 9. Also in this case the structure of the bipolar plate 5 is defined by the assembly of three components 5A, 5B, 5C, an inner component 5C and two outer component 5A and 5B each one connected, preferably welded, to one of the flat surfaces of the inner component 5C. This in order to define a first plurality of channels 66A and a second plurality of channels 66B that are separated by the inner component 5C. The channels 66A, 66B are provided for the circulation of a cooling fluid for purposes already indicated.

[0090] As shown also in Figure 8, the outer components 5A, 5B have a configuration different from that of the similar components provided for the first embodiment. Such a different configuration determines clearly a different development of the internal channels 66A, 66B.

[0091] Always with reference to Figure 13, the bipolar plate 5 comprises a couple of delivery opening 56 A, 56 A’ which are hydraulically communicating with the channels 66 A, 66B by means of a corresponding inlet section SI. The delivery openings 56A, 56A’ are defined at a first side 57A of the bipolar plate 5, each one near one of its corners. A couple of return openings 56B, 56B’ are also provided for collecting the cooling fluid after its passage in the channels 66A, 66B. The latter are hydraulically communicating with such return openings 56B, 56B’ by means of a corresponding outlet section SU. The return openings 56B, 56B’ are defined at a second side 57B of the bipolar plate 5 (opposite to the first side 57 A), each one near one of its corners. Each of said sides 57 A of the bipolar plate 5 corresponds to one of the large sides 67B of the frame 6.

[0092] In general, each of the openings 56A, 56A’, 56B, 56B’ provided for the circulation of the cooling fluid is configured so as to match with a corresponding of the openings 45 A, 45 A’, 45B. 45B’ of the frame 6 (see Figures 10, 10A). This in order to generate, following the stack of the cells, one of delivery channels 4A, 4A’ or of the return channels 4B, 4B’.

[0093] Always with reference to Figure 13, the bipolar plate 5 also comprises a first opening 52 for the passage of the potash. Such a first opening 52 is defined at the first side 57 A between the two delivery openings 56A, 56A’. Two further openings 54, 55 for the passage of the potash are provided at the second side 57B between the two return openings 56B, 56B’.

[0094] Following the stack of the cells 4 of the electrolyser of Figure 8, the first opening 52 matches the corresponding distribution opening 31 of a frame 6, while each one of the other openings 54, 55 matches one of the collection opening 33, 34 of the same frame 6. This in order to generate the distribution channel 11A and the two collection channels 12A, 12B of the potash. With reference to Figure 13 and 14, preferably, a sealing member 14 is provided for each of the openings 52, 54, 55 of the bipolar plate 5 defined for the passage of the potash. Such a sealing member 14 has a ring shape and has the purpose to avoid the enter of the potash in the internal channels 66, 66B of the bipolar plate 5. Such a sealing member 14 has the purpose of providing a leak- tightness at each of the openings 52, 54, 55 as above already indicated for the first embodiment, in particular with reference to Figure 7.

[0095] With reference to Figure 8, for at least one of the elementary cells 4, preferably for all of them, the frame 6 comprise anchoring means for positioning the separator 10 inside the chamber 6A so as to generate the two sections thereof. Figure 12 shows in detail a preferred embodiment of the anchoring means that comprise an internal edge 41 which develops at least partially along the perimeter of the chamber 6A. The internal edge 41 defines an attachment surface 415 at an intermediate position between the first face 611 and the second face 612 of the frame 6. A plurality of connecting pins 611 is provided on one side of the internal edge 41. These pins 411 emerge with respect to the attachment surface 415 and are suitable to enter with corresponding holes 101 (indicated in Figure 8) defined through the separator 10 close to its perimetral edge. The separator 10 is fixed to the frame 6 at the internal edge 41 following the insertion of the each of the connecting pins 411 in a corresponding of said holes 101. In order to block the position of the separator 10 on the internal edge 41, a perimetral frame 450 is fitted on the internal edge 41 (in particular on the connecting pin 411) so that the perimetral edge of the separator 10 is comprised between the internal edge 41 and such perimetral frame 450. The use of the latter avoids the detachment of the separator 10.

[0096] It is worth notice that also the frames 6 of the cells 4 of the first embodiment of the electrolyser (figures 1 to 7) could be provided with anchoring means corresponding to that shown in Figures 8 and 12 or with other means functionally equivalent.

[0097] The solutions described above make it possible to fully fulfil the task and objectives set. In particular, the proposed device allows the electrolyte to operate effectively at high pressure, in particular around 30 bar relative. Further the solutions described allow to reduce production costs, especially those linked to the assembly operations. Further, the electrolyser according to the invention is reliable and easy to build at competitive costs as well as with easy and economical maintenance in case of disassembly and reassembly.

Claims

CLAIMS1) Electrolyser (1) for the production of hydrogen from an alkaline electrolyte, wherein said electrolyser (1) comprises:- a first header (2) and a second header (3) made of metal material;- a plurality of elementary cells (4) and a plurality of bipolar plates (5) arranged between said headers (2, 3), wherein said elementary cells (4) are separated from each other by one of said bipolar plates (5);- a plurality of clamping elements (20) that mechanically connect said headers (2, 3), said elementary cells (4) and said bipolar plates (5); wherein each elementary cell (4) comprises:- a frame (6) defining a chamber (6A), having an anodic section and a cathodic section, in which an anodic electrode (7) and a cathodic electrode (8) are at least in part housed,- a separator element (10) that separates the anodic section from the cathodic section; wherein said electrolyser (1) further comprises:- at least one first distribution channel ( 11 A, 12A) of an alkaline electrolyte wherein, for each of said elementary cells, said channels (11A, 12A) is in hydraulic communication with said sections of said chamber (6A) defined by said frame (6);- at least a first collection channel (11B) of a first reaction product mainly comprising oxygen, wherein, for each of said element cells, said first collection channel (11B) is in hydraulic communication with the anodic section of said chamber (6A);- a second collection channel (12B) of a second reaction product mainly comprising hydrogen, wherein, for each of said elementary cells (4), said second distribution channel (12B) is in hydraulic communication with the cathodic section of said chamber (6A); wherein each of the frames (6) comprises first through holes (61) and each of the bipolar plates (5) comprises second through holes (51), wherein each of said first through holes (61) of one frame (6) is mutually aligned with a corresponding first through holes (61) of each of the another frames (6) and with one of said second through holes (51) of eachbipolar plate (5), wherein each one of said clamping means (20) extends through said through holes (51, 61) mutually aligned.2) Electrolyser (1) according to Claim 1, wherein each of said bipolar plates (5) comprises:- one or more channels (66 A, 66B) for the circulation of a cooling fluid;- an entry section (SI) and an exit section (SU) respectively for the entry and exit of said cooling fluid in said one or more channels (66A, 66B), wherein said electrolyser (1) further comprises:- at least one delivery channel (4A) of said cooling fluid in hydraulic communication with said entry section (SI) of each of said bipolar plates (5); and- at least one return channel (4B) of said cooling fluid in hydraulic communication with said exit section (SU) of each of said bipolar plates (5).3) Electrolyser (1) according to claim 2, wherein at least one of said bipolar plates (5) comprises three components configured and assembled so as to define a plurality of inner channels (66A, 66B), wherein an inner components (5C) is placed between two outer components (5A, 5B) and wherein a first plurality of channels (66A) is defined between said inner component (5A) and one of said outer components (5A) and a second plurality of channels (66B) is defined between said inner component (5C) and the other outer component (5B), wherein said inner component (5C) separates said first plurality of channels (66A) from said second plurality of channels (66B).4) Electrolyser (1) according to anyone of the claims 1 to 3, wherein said frame (6) has a first face (611) and a second face (612) opposite to said first face (611), said first through holes (61) extending from said first face (611) to said second face (612), said frame (6) comprising at least one distribution opening (31, 32) of said electrolyte, a first collection opening (33) for said first reaction product and a second collection opening (34) for said second reaction product, said frame (6) further comprising at least two opening (45A, 45B) for the passage of the cooling fluid circulating in said internal channels (66A, 66B) of said bipolar plate (5).5) Electrolyser (1) according to anyone of the previous claims, wherein said frame (6) comprises a metal core (11) at least partially covered by elastomeric material layer (25).6) Electrolyser (1) according to any of the claims 1-5, wherein for at least one of said through holes (61) of the frame (6) a bushing (13) is provided in its inside, wherein said bushing (13) is axially holed to receive a corresponding of said clamping means (20) and wherein said bushing (13) is made of non-compressible material.7) Electrolyser (1) according to claim 5 or 6, wherein said first face (611) and / or side second face (612) comprise corrugations (21) adapted to be compressed against a surface (511, 512) of a corresponding bipolar plate (5) to generate leak-tightness of the electrolyser during the stacking.8) Electrolyser (1) according to any of the claims 4 to 7, wherein each of said faces (611, 612) of said frame (6) is provided with first grooves (26A, 26B) that make said at least one distribution opening (31, 32) communicating with said chamber (6A) and second groves (26A’, 26B’) that make one of the collection opening (33, 34) communicating with said chamber (6A).9) Electrolyser (1) according to any of the claims 4 to 8, wherein said electrolyser comprise a first distribution channel (11 A) and a second distribution channel (12A) of an alkaline electrolyte and wherein, for each of said elementary cells, each one of said distribution channels (11 A, 12A) is in hydraulic communication with one of the sections of said chamber (6A) defined by said frame (6), wherein said frame (6) comprises a first distribution opening (31) and a second distribution opening (32) of said electrolyte.10) Electrolyser (1) according to any of the claims 4 to 9, wherein said electrolyser (1) comprises:-two delivery channels (4A, 4A’) of said cooling fluid each of which in hydraulic communication with said entry section (SI) of at least one of said bipolar plates (5), and two delivery channels (4B, 4B’) of said cooling fluid each of which in hydraulic communication with said exit section (SU) of at least one each of said bipolar plates (5),wherein such frame (6) comprises at least four through openings (45A, 45A’, 45B, 45B’) for the passage of the cooling fluid circulating in said internal channels (66A, 66B) of said bipolar plates (5).11) Electrolyser (1) according to any of the claims 4 to 10, wherein said frame (6) is provided with a sealing groove (35, 36) defined on said first surface (611) and or on said second surface (612), wherein said sealing groove (35, 36) has a loop configuration so that said distribution opening (31, 32) of said electrolyte, said collection openings (33, 34) of said reaction products and said openings (45A, 45A’, 45B, 45B’) for the passage of said cooling fluid are positioned inside said loop, wherein said sealing grove (35, 36) is suitable to be filled with sealing material or a sealing element.12) Electrolyser (1) according to any of the claims 1 to 11, wherein each of the bipolar plates (5) comprises a plurality of openings (52, 53, 54, 55) each of which for the passage of said electrolyte, wherein, following the stacking of the elementary cells, each od said opening (52, 53, 54, 55) is aligned with a distribution opening (31, 32) or with a collection opening (33, 34) of said frame (6), wherein said openings (52, 53, 54, 55) develops from a first surface (511) and a second surface (512) of said bipolar plate (5) and wherein a sealing member (14) is placed in each of said openings (52, 53, 54, 55) of the bipolar plate (5) so as to provided leak-tightness between the components thereof.13) Electrolyser (1) according to claim 12 when dependent on Claim 11, wherein each of said bipolar plates (5) comprises a couple of delivery opening (56A, 56A’) which are hydraulically communicating with said internal channels (66A, 66B) and a couple of return openings (56B, 56B’) for collecting the cooling fluid after its passage in said internal channels (66A, 66B), each of said openings (56A, 56A’, 56B, 56B’) for the circulation of said cooling fluid is configured so as to match with a corresponding opening (45A, 45A’, 45B. 45B’) of said frame (6), so as to define, following the stack of the cells, one of said delivery channels (4A, 4A’) or one of said return channels (4B, 4B’).14) Electrolyser (1) according to claim 13, wherein said delivery openings (56A, 56A’) are defined at a first side (57A) of said bipolar plate (5), each one near one of its corners, saidreturn openings (56B, 56B’) being defined at a second side (57B) of said bipolar plate (5), each one near one of its corners, each of said openings (52, 54, 55) for the passage of said electrolyte being defined between said delivery openings (56A, 56A’) or between said return openings (56B, 56B’).15) Electrolyser (1) according to any of the claims 12 to 14, wherein said bipolar plate (5) comprises a sealing groove (135) defined on a first surface (511) and / or a second surface (512) of said bipolar plate (5), wherein said sealing groove (135) is suitable to be filled with sealing material or a sealing element.16) Electrolyser (1) according to anyone of the previous claims, wherein for at least one of the elementary cells (4) said frame (6) comprises anchoring means to arrange said separator (10) inside the corresponding chamber (6A) so as to generate said anodic section and said cathodic section.17) Electrolyser (1) according to claim 16, wherein said anchoring means comprise an internal edge (41) that develops at least partially along the perimeter of said chamber (6A), wherein said internal edge (41) defines an attachment surface (415) at an intermediate position between said first face (611) and said second face (612), said anchoring means further comprising a plurality of connecting pins (411) at one side of said internal edge (41), wherein said pins (411) are suitable to enter corresponding holes (101) defined through said separator (10) close to its perimetral edge, wherein said separator (10) is fixed to the frame (6) following the insertion of each of the connecting pins (411) in a corresponding of said holes (101), said anchoring means further comprise a perimetral frame (450) that is fitted on said internal edge (41) so as to block the position of the separator (10) with respect to the frame (6).18) Electrolyser (1) according to any of the claims 6 to 17, wherein a centering element (133) is provided for at least one of said bushing (13), said centering element (133) being axially holed so as to receive one of said clamping elements (20), said centering element (133) being arranged inside a corresponding bushing (13) so that one of its end (133A) emerges with respect to one of the surfaces (611, 612) of said frame (6), wherein said emergingend (133 A) is suitable to be inserted in one of said through holes (51) of said bipolar plate

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