Electrolytic cell

Abstract

The present invention relates to an electrolytic cell (1) for producing hydrogen from an alkaline electrolyte. The electrolytic cell (1) includes a first header (11) and a second header (12), between which a plurality of single cells (20) and a plurality of bipolar plates (5, 5', 5") are stacked. Each bipolar plate (5) separates two adjacent single cells. According to the present invention, each of the bipolar plates (5, 5', 5") includes two plate-like components (5A, 5B) coupled to each other and configured to define one or more internal cavities (66) for the circulation of a cooling fluid. Furthermore, each bipolar plate (5, 5', 5") includes an inlet (SI) and an outlet (SV) corresponding to the inlet and outlet of the cooling fluid to the one or more internal cavities (66), respectively.

Description

TECHNICAL FIELD

[0001] Technical field to which the invention belongs The present invention belongs to the manufacturing field of an apparatus for producing hydrogen by electrolysis of water. In particular, the present invention preferably, but not exclusively, relates to an electrolytic cell for producing hydrogen and oxygen using an alkaline electrolyte (for example, using an aqueous potassium hydroxide solution). BACKGROUND ART

[0002] prior art In recent years, the demand for hydrogen has increased remarkably in various manufacturing fields, such as power generation that does not emit pollutants. Hydrogen can be easily stored and transported through, for example, pipelines similar to those used for gaseous fuels, and can therefore be easily supplied for various applications.

[0003] For the production of hydrogen, the use of an electrochemical reactor, also called an electrolytic cell, is known. In the reactor, electrolysis of water is performed, that is, a reaction that splits water into hydrogen and oxygen by the action of electric current. It is also well known that there are various types of electrolysis, such as alkaline water electrolysis, polymer electrolyte membrane electrolysis, and ceramic membrane electrolysis.

[0004] A plant for producing hydrogen on an industrial scale based on alkaline water electrolysis is usually provided with an electrolytic cell, which comprises a plurality of unit cells stacked between two headers, and is fastened by clamping means (typically screws) that apply a traction force between the two headers. The splitting reaction of alkaline water is carried out in each unit cell, and the alkaline water often consists of an electrolyte mainly composed of potassium hydroxide (generally also referred to as "potash").

[0005] Each single cell has an anode and a cathode, separated by a separator element. The anode and cathode sections each have an anode electrode and a cathode electrode, with the separator element positioned between these electrodes. The anode section includes an anode chamber that houses at least a portion of the anode electrode. Similarly, the cathode section includes a cathode chamber that houses at least a portion of the cathode electrode. The anode and cathode chambers are defined by a specific frame shared by both chambers, or by frames specific to each chamber. The separator element involved in the electrolysis process, based on widely known principles, is positioned between the two electrodes (anode and cathode).

[0006] A bipolar plate made of a metallic material is placed between two adjacent single cells, with one side electrically in contact with the cathode electrode of the cathode portion of one cell, and the opposite side electrically in contact with the anode electrode of the anode portion of the other adjacent cell. In each cell, a sealing plate, usually made of a polymer material, is typically provided between each frame and the adjacent bipolar plate, and between the frames of each chamber (if they are separate).

[0007] Typically, the frame, sealing plate, and bipolar plate of a single cell are provided with openings arranged and configured to define a first potassium distribution channel, a second potassium distribution channel, a first collection channel for the first reaction product, and a second collection channel for the second reaction product, respectively, when cells are stacked between the headers of an electrolytic cell. The reaction product consists of a two-phase solution comprising a reaction gas (hydrogen or oxygen) and unreacted electrolyte / potassium. The first distribution channel and the first collection channel are fluidically connected to the anode of each single cell via their respective frames, and the second distribution channel and the second collection channel are fluidically connected to the cathode of each single cell via their respective frames. Potassium is supplied to the corresponding part (anode or cathode) of each single cell via the distribution channel (first or second). In each single cell, the gas (hydrogen or oxygen) and / or undissociated potassium produced by the electrolysis reaction flows out from the respective part (cathode or anode) of the cell and flows into the corresponding collection channel (first or second).

[0008] Figure 1 is a schematic diagram of a known type of plant (600) in which an electrolytic cell (E) having the structure described above is installed. Such a plant (600) is provided with a first circuit (C1) and a second circuit (C2) for supplying to the electrolytic cell (E). Each of these circuits includes a fluid-connected supply branch pipe (RM1, RM2) fluidly connected to a corresponding distribution channel, and a return branch pipe (RR1, RR2) fluidly connected to a corresponding collection channel in the electrolytic cell. Each circuit (C1, C2) has a circulation pump (P1, P2) along the supply branch pipe (RM1, RM2) that delivers electrolyte / potassium to a single cell of the electrolytic cell (E). Meanwhile, degassing devices (D1, D2) are located along the return branch pipes (RR1, RR2) to which the two-phase solution (gas and unreacted liquid solution) flowing out of the single cell is introduced and recovered into the corresponding collection channel. In each degassing unit (D1, D2), the corresponding gas (hydrogen or oxygen) is separated from the liquid component and stored in a suitable container (tank, cylinder, etc.) via the first outlet (D1-A, D2-A). Meanwhile, the liquid component is returned to the liquid supply branch pipe (RM1, RM2) via the second outlet (D1-B, D2-B) by suction of the circulation pump (P1, P2). This liquid component is mixed with other electrolytes / potassium supplied from external tanks (T1, T2) (for example, at the outlets of the corresponding degassing units D1, D2) and adjusted to an operating flow rate for being pumped to the electrolytic cell by the corresponding circulation pump (P1, P2).

[0009] As schematically shown in Figure 1, each supply circuit (C1, C2) has a liquid / liquid type or liquid / air type heat exchanger (S1, S2) arranged along the corresponding liquid supply branch pipe. Through these heat exchangers, the liquid solution is cooled before returning to the electrolytic cell, suppressing the subsequent temperature rise that occurs when passing through the single cell. Thus, such heat exchangers cool the liquid solution before it enters the electrolytic cell, preventing a subsequent temperature rise.

[0010] Typically, the installation of heat exchangers (S1, S2) is necessary because, as is well known, the electrolytic reaction is extremely exothermic. In fact, the two-phase mixture (gas and undissociated / unreacted liquid solution) discharged from each part of the electrolytic cell (anode and cathode) has a higher temperature than the incoming liquid solution. The operating flow rate of potassium is set to exceed the nominal flow rate of the electrolytic reaction. As a result, the heat generated by the exothermic reaction is carried out of the electrolytic cell at a flow rate fraction exceeding the nominal flow rate. Therefore, the working potassium supplied to the electrolytic cell (E) via the heat exchangers (S1, S2) is cooled in order to suppress the subsequent temperature rise caused by the hydrolysis reaction, that is, to maintain the temperature gradient between the inlet and outlet within a predetermined range. [Overview of the project] [Problems that the invention aims to solve]

[0011] However, the applicant has found that such a temperature gradient causes significant non-uniformity in the temperature distribution within the electrolytic cell. This leads to a decrease in the efficiency of the electrolysis process, because the electrolyte / potassium cannot reach and maintain the ideal temperature conditions (typically 88±8°C) throughout the entire single cell to achieve maximum electrical conductivity and, consequently, maximum efficiency of the electrolysis process. In addition, the heat exchanger, like other components of a gas production plant, is sized based on the assumed operating flow rate of potassium, which exceeds the nominal value required for the reaction, as mentioned above. This is particularly important not only in terms of the construction cost of the plant, but also in terms of the overall size, i.e., the final dimensions of the plant itself. Furthermore, the circuits (C1, C2) and related components for ensuring the circulation of potassium / electrolyte usually have a complex configuration. This is because it requires the use of extremely chemically resistant and particularly expensive materials that can withstand harsh operating conditions, namely high pH and relatively high temperature environments.

[0012] Furthermore, in addition to the dimensions of the heat exchanger, other components necessary for processing potassium and two-phase mixtures (e.g., filters and / or degassing equipment) also directly and proportionally affect the time and cost associated with maintenance work, and consequently, the overall plant management costs. Furthermore, in addition to the technical challenges mentioned above, there is a phenomenon known as the "battery effect." This occurs when the supply of current that powers the electrolytic cell header is interrupted. After the current is cut off, a series of reverse current phenomena occur due to the formation of parasitic redox pairs that are generated during operation. This phenomenon is mainly driven by the reduction reaction of Ni(IV) to Ni(II) in the section that functions as the anode during operation, and the oxidation reaction of Ni(O) to Ni(II) in the section that functions as the cathode during operation. This battery effect has adverse effects on the metal components inside the electrolytic cell, namely the electrodes and structural components, particularly by accelerating corrosion. Moreover, the intensity of the battery effect becomes more pronounced the higher the temperature of the electrolytic cell when it is stopped (when the ohmic component that resists the battery effect decreases). This effect is even more pronounced when the electrolytic cell is kept under electrolyte circulation, because in that case, electrical communication occurs between the various chambers via the flushing duct.

[0013] Summary of the Invention Therefore, the primary object of the present invention is to provide an electrolytic cell that can overcome or at least mitigate the limitations of the solutions described above. Within the scope of this object, a first object of the present invention is to provide an electrolytic cell that can operate the electrolyte more effectively, particularly in terms of maintaining the temperature at which maximum conductivity is observed. Another object of the present invention is to provide an electrolytic cell that can reduce the electrolyte flow rate compared to that used in known solutions, under conditions where other properties are equivalent. Yet another object of the present invention is to provide an electrolytic cell that can eliminate or at least suppress damage that may result from the aforementioned battery effect. A further object of the present invention is to provide an electrolytic cell that can reduce the construction cost of the plant in which the electrolytic cell is installed. Yet another object related to this object is to provide an electrolytic cell that can reduce the complexity and dimensions of other components in the plant in which the electrolytic cell is installed. At a minimum, it is an object to provide an electrolytic cell that is reliable and can be easily manufactured at a competitive cost. [Means for solving the problem]

[0014] The applicant has found that the above problems and objectives can be achieved by removing the heat generated by the hydrolysis reaction at the point where the heat is generated, using a cooling fluid different from the electrolyte involved in the reaction. In particular, the applicant has found that such heat can be removed in the bipolar plate of the electrolytic cell, and more specifically, by configuring the bipolar plate to form an internal cavity that functions as one or more cooling chambers, and providing an inlet and outlet for the cooling fluid in the internal cavity. Furthermore, in each part of the single cell, a spacer made of a metallic material is provided between the corresponding electrode (anode or cathode) and the corresponding bipolar plate. Overall, the applicant has found that by using a bipolar plate having an internal cooling structure and being in thermal contact with a spacer, the heat generated in the electrolytic reaction can be effectively dissipated.

[0015] Specifically, the applicant has found that the above problems and objectives can be achieved by the electrolytic cell described in claim 1. In particular, the electrolytic cell according to the present invention enables the production of hydrogen from an alkaline electrolyte and comprises the following: -A first header and a second header made of metal material; - A plurality of single cells and a plurality of bipolar plates arranged between the headers, wherein two adjacent cells are separated by one of the bipolar plates; - Clamping elements for mechanically connecting the headers so that the single cells and the bipolar plates remain stably stacked between the headers.

[0016] According to the present invention, each single cell includes the following: - An anode portion comprising an anode electrode and an anode frame defining a chamber in which at least a portion of the anode electrode is housed, wherein the anode portion includes at least one sealing plate interposed between the anode frame and one of the bipolar plates, and the anode portion further includes an anode spacer made of a metallic material interposed between the one of the bipolar plates and the anode electrode; -A cathode portion comprising a cathode electrode and a cathode frame defining a chamber in which at least a portion of the cathode electrode is housed, wherein the cathode portion comprises at least one sealing plate interposed between the cathode frame and another of the bipolar plates, and the cathode portion further comprises a cathode spacer made of a metallic material interposed between the other of the bipolar plates and the cathode electrode; -A separator element that separates the anode portion from the cathode portion; - At least one additional sealing plate interposed between the anode frame of the anode portion and the cathode frame of the cathode portion.

[0017] The electrolytic cell according to the present invention further comprises the following: - a first distribution channel for the alkaline electrolyte and a first collection channel for a first reaction product mainly containing oxygen, wherein in each of the unit cells, the channels are fluidly connected to the chamber of the anode portion via a groove defined by the anode frame; - a second distribution channel for the alkaline electrolyte and a second collection channel for a second reaction product mainly containing hydrogen, wherein in each of the unit cells, the second distribution channel and the second collection channel are fluidly connected to the chamber of the cathode portion via a groove defined by the cathode frame.

[0018] According to the present invention, each of the bipolar plates comprises two plate-shaped members coupled to each other and configured to define at least one internal cavity for circulation of a cooling fluid, and each bipolar plate comprises an inlet portion and an outlet portion respectively corresponding to the inlet and outlet of the fluid to / from said one or more internal cavities. The electrolytic cell according to the present invention further comprises: - a cooling fluid supply channel fluidly connected to the inlet portion of each of the bipolar plates; and - a cooling fluid return channel fluidly connected to the outlet portion of each of the bipolar plates.

[0019] Advantageously, the electrolytic cell is cooled from the inside, that is, from the position where heat is generated by the hydrolysis reaction. Since this cooling is performed via a fluid different from the electrolyte, on one hand, the operating flow rate of the electrolyte itself can be limited, and on the other hand, it becomes possible to reduce the size and volume of plant components involved in electrolyte circulation. A spacer made of a metallic material is in thermal contact with the bipolar plate. This arrangement advantageously increases the heat transfer from each portion (the anode and the cathode) to the cooling fluid circulating in the internal cavity of the bipolar plate.

[0020] By separating the cooling of the electrolyte from the circulation of the electrolyte passing through the electrolyzer cells, the circulation of the cooling fluid can be continuously operated even when the electrolyzer is stopped, that is, even when the circulation of the electrolyte is interrupted. Thereby, the amount of heat to be removed from the electrolyzer is limited only to the fluid present in the anode chamber and the cathode chamber. Due to the cooling performed via the bipolar plate and the interruption of the flow of the circulating electrolyte, the internal resistance of the electrolyzer rises rapidly, and thus the battery effect and the resulting adverse effect on the integrity of the electrolyzer itself are greatly reduced.

[0021] According to a possible embodiment, the cooling fluid is water. However, as the cooling fluid, various fluids that can operate in either the range of sensible heat (heat not accompanied by a phase change from liquid to gas) or latent heat (heat removed through a phase change from liquid to gas) can be used. These cooling fluids are preferably, but not limited to, aqueous fluids, which are pure water, or water added with glycol, polyelectrolyte, or colloid, or organic fluids having a phase change temperature close to the operating temperature of the electrolyzer. According to a possible embodiment, the liquid feed channel is provided with an inlet, and the return channel is provided with an outlet. Both the inlet and the outlet are arranged on one of the headers.

[0022] According to a possible embodiment, the first distribution channel and the second distribution channel for the electrolyte each comprise a first inlet and a second inlet located on one of said headers opposite to the side where said inlet and said outlet of the cooling fluid feed channel and return channel are respectively located, and said first collection channel and said second collection channel for reaction products each comprise a first outlet and a second outlet also located on said one of said headers.

[0023] According to a possible embodiment, for each individual cell, each frame comprises: -A first distribution opening and a first collection opening fluidly connected to a corresponding chamber defined by the frame, wherein the first distribution opening and the first collection opening are defined diagonally opposite to each other; - A second distribution opening and a second collection opening that are not fluidly connected to the corresponding chamber defined by the frame, wherein the second distribution opening and the second collection opening are defined diagonally opposite to each other; - A liquid supply opening and a return opening configured to allow the cooling fluid to pass through while the electrolytic cell is in use. According to a possible embodiment, the sealing plate has six openings, each of which is configured and positioned to fit into each corresponding opening of the frame. Furthermore, each bipolar plate also has six openings, each of which is configured and positioned to fit into one of the six openings of each of the frame and one of the six openings of each of the sealing plate.

[0024] According to a preferred embodiment, the stack of single cells between the headers is as follows: -One of the distribution openings in each frame, the corresponding first opening in each sealing plate, and the corresponding first opening in each bipolar plate, together, define a first electrolyte distribution channel; -The other of the distribution openings in each frame, the corresponding second openings in each sealing plate, and the corresponding second openings in each bipolar plate, together, define a second electrolyte distribution channel; -One of the collection openings in each frame, the corresponding third opening in each seal plate, and the corresponding third opening in each bipolar plate, together, define a first electrolyte collection channel; -The other of the collection openings in each frame, the corresponding fourth opening in each seal plate, and the corresponding fourth opening in each bipolar plate, together, define a second electrolyte collection channel; -The fluid delivery openings in each frame, the corresponding fifth openings in each seal plate, and the corresponding fifth openings in each bipolar plate, together, define a first fluid delivery channel for the cooling fluid, configured to pass through the interior of the bipolar plate; - The return openings of each frame, the corresponding sixth openings of each seal plate, and the corresponding sixth openings of each bipolar plate, together, define the return channel for the cooling fluid discharged from the bipolar plate.

[0025] According to a possible embodiment, each component of the bipolar plate includes a flat portion and a molded portion surrounded by the flat portion, wherein in each of the components, the molded portion is recessed with respect to a reference plane on which the flat portion is located, the components are joined at the corresponding flat portions and configured to be symmetrical with respect to a contact surface coinciding with the reference plane, the molded portion of the first component is positioned opposite the molded portion of the second component, and the one or more internal cavities of the bipolar plate are defined between the opposing molded portions of the components. Preferably, in each component, the molded portion includes at least one region having a substantially wavy shape in which grooves and raised portions are alternately formed, and after the components are joined, each raised portion in the molded portion of the first component comes into contact with the corresponding raised portion in the molded portion of the second component, and after the joining, an internal cavity for the circulation of a cooling fluid is defined between two opposing grooves in the molded portion of the component.

[0026] According to an alternative embodiment, in each component of the bipolar plate, the molded portion comprises a recess recessed with respect to a reference plane on which a flat portion is located, and a plurality of protrusions projecting from the recess beyond the reference plane, and after joining the components, the recess in the molded portion of the first component remains on the opposite side from the side on which the recess in the molded portion of the second component is located, defining an internal cavity effective for the flow of cooling fluid between the recesses, the protrusions of the first component contact the inner surface of the recess of the second component, and the protrusions of the second component contact the inner surface of the recess of the first component.

[0027] In a preferred embodiment, the components of the bipolar plate consist of two flat metal plates, each having an inner surface and an outer surface facing the inner surface, each metal plate having a plurality of grooves extending from the corresponding inner surface in the thickness direction of the plate itself, the components are joined such that the inner surface of one component is in contact with the inner surface of the other component, and as a result following such contact, the grooves of one component are positioned to face the corresponding grooves of the other component, and the pair of opposing grooves define one of the internal cavities for the flow of cooling fluid. In this embodiment, in each metal plate, the corresponding outer surfaces are flat. [Brief explanation of the drawing]

[0028] List of drawings Further features and advantages of the present invention will become more apparent by considering the following detailed description relating to preferred but non-exclusive embodiments of the electrolytic cell according to the present invention, illustrated for illustrative and non-limiting purposes with reference to the accompanying drawings. Figure 1 is a schematic diagram of a hydrogen production plant known in the prior art. Figure 2 is a diagram of the components of a hydrogen production plant equipped with an electrolytic cell according to the present invention. Figure 3 is a perspective view of the electrolytic cell shown in Figure 2. Figure 4 is a side view of the electrolytic cell shown in Figure 3. Figure 5 is a front view along the VV section of Figure 4. Figure 6 is a perspective view along the VI-VI section in Figure 4. Figure 7 is a perspective view along the VV section of Figure 4. Figure 8 is an exploded view of the electrolytic cell shown in Figure 2. Figure 9 is an exploded view of a single cell of the electrolytic cell shown in Figure 2. Figure 10 shows a first embodiment of the bipolar plate of an electrolytic cell according to the present invention. Figures 11 and 12 are front and perspective views, respectively, of different components of the bipolar plate shown in Figure 10. Figure 13 is a diagram along the XIII-XIII section of Figure 10. Figure 14 shows a second embodiment of the bipolar plate of an electrolytic cell according to the present invention. Figure 15 is a front view of the components of the bipolar plate shown in Figure 14. Figure 16 is a diagram along the XVI-XVI section of Figure 14. Figure 17 shows a third embodiment of the bipolar plate of an electrolytic cell according to the present invention. Figures 18 and 19 are front and perspective views, respectively, of a different component of the bipolar plate shown in Figure 10. Figure 20 is a diagram along the XX-XX cross-section of Figure 17. Figure 21 is a diagram of a hydrogen production plant equipped with an electrolytic cell according to the present invention. Identical reference numbers and letters in the diagram indicate the same element or component. [Modes for carrying out the invention]

[0029] Detailed explanation Referring to the aforementioned drawings, the present invention relates to an apparatus for electrolyzing water, particularly alkaline water. Figure 2 is a perspective view of a hydrogen production plant 100 equipped with an electrolytic cell 1 according to the present invention. Preferably, hydrogen and oxygen are obtained from an alkaline electrolyte, such as a liquid solution containing potassium hydroxide (hereinafter referred to as "potassium"), via the electrolytic cell 1. However, the electrolytic cell 1 can also be used to obtain hydrogen and oxygen from other liquid solutions, such as a sodium hydroxide solution or a concentrated and alkalized neutral salt solution such as potassium chlorate.

[0030] The electrolytic cell 1 according to the present invention has a plurality of electrolytic cells 20 (hereinafter also referred to as "single cells") stacked along the longitudinal direction 401 (shown in Figures 8 and 9) between a first header 11 (or anode header) and a second header 12 (or cathode header) made of a metal material that face each other. Each single cell 20 is separated from adjacent cells by a pair of bipolar plates (shown as reference numeral 5 in Figures 8 and 9). The electrolytic cell 1 is provided with clamp elements 3 (preferably in the shape of stud bolts) that mechanically connect the two headers 11 and 12 by applying tensile force, so that the single cells 20 and bipolar plates 5 define a substantially "sandwich-like" compact structure as a whole. For the sake of explanation, in the remainder of the explanation, the term "first cell" will refer to the single cell closest to the anode header 11, and the term "final cell" will refer to the single cell closest to the cathode header 12.

[0031] Figures 3 and 4 are perspective and side views of the electrolytic cell 1, respectively, and Figure 8 is an exploded view of the same electrolytic cell, showing how multiple single cells 20 are arranged (stacked) in a continuous manner. On the other hand, Figure 9 shows the structure of one single cell 20 in the same electrolytic cell 1 in detail. Referring to these drawings, each single cell 20 comprises an anode section 20A including an anode electrode 21A and an anode frame 22A. This demarcates a chamber 200A in which the anode electrode 21A is at least partially housed. The chamber 200A is demarcated axially by one of the bipolar plates 5 (i.e., demarcated along the longitudinal direction 401). Thus, the anode frame 22A demarcates the chamber 200A from the sides along two directions perpendicular to the longitudinal direction 401.

[0032] Each single cell 20 also comprises a cathode section 20B including a cathode electrode 21B and a cathode frame 22B, the cathode frame 22B defining a chamber 200B in which the cathode electrode 21B is at least partially housed. The chamber 200B of the cathode section 20B is axially defined by a separate bipolar plate 5, which is different from the one defining the chamber 200A of the anode section 20A. The cathode frame 22B defines the cathode section 20B laterally. In each single cell 20, the two parts 20A and 20B described above are separated from each other by a separator element 2 (e.g., a membrane). Preferably, but not limited to, the two frames 22A and 22B used in the single cell 20 are made of polymer material, but may be made of metal material in part, as long as they are electrically insulated from the outside.

[0033] For the purposes of this invention, the terms "anode" and "cathode" for the two frames 22A and 22B do not refer to the charge of the frame itself, but are used to indicate the cell portion (anode or cathode) to which each frame belongs. In all cases, in each part 20A, 20B of the single cell 20, the corresponding electrode 21A or 21B is in electrical contact with the nearest bipolar plate 5 that demarcates the single cell along the longitudinal direction 401. In this regard, in the case of the first cell, the electrode 21A of the anode part 20A is in electrical contact with the anode header 11, and the electrode 21B of the cathode part 20B is in electrical contact with the bipolar plate 5. Similarly, in the final cell, the electrode of the anode part 20A is in electrical contact with the bipolar plate 5, and the electrode 21B of the cathode part 20B is in electrical contact with the second header 12.

[0034] As shown in Figure 9, each anode section 20A, 20B includes sealing plates 26A, 26B interposed between the corresponding frames 22A, 22B and the corresponding bipolar plates 5 (or, in the case of the first and final cells, the headers 11, 12). Each single cell 20 also includes at least one further sealing plate 26C (as shown in Figure 8) positioned between the two frames 22A, 22B inside the cell. In this regard, the configuration example shown in Figure 8 includes at least two sealing plates 26C. Preferably, the sealing plates 26A, 26B, and 26C are all made of a heat-resistant polymer material and each is intended to ensure a hydraulic seal between the two components in which it is interposed.

[0035] Referring to Figure 8, according to the present invention, in each single cell 20, the anode section 20A comprises an anode spacer 23A at least partially housed in a housing chamber defined by the anode frame 22A. The anode spacer 23A is interposed between the bipolar plate 5 (or, in the case of the first cell, the anode header 11) and the anode electrode 21A, and is configured to ensure electrical conductivity between these components. For a similar purpose, the cathode section 20B comprises a cathode spacer 23B made of a metallic material interposed between the cathode electrode 21B and the bipolar plate 5 (or, in the case of the final cell, the cathode header 12). Preferably, the spacers 23A and 23B are made of a metallic material (e.g., a mesh) and are defined by their respective frames (anode and cathode) and configured to allow the electrolyte to diffuse within the chambers 200A and 200B (anode or cathode) in which they are respectively located. Therefore, each of the spacers 23A and 23B is in thermal contact with the corresponding bipolar plate 5, and the heat generated by the electrolytic reaction can be transferred to the bipolar plate by thermal conduction. Advantageously, the spacers 23A and 23B also serve to balance the internal pressure between the cell parts (anode and cathode), thereby advantageously reducing the stress applied to the separator element 2 and improving its durability.

[0036] Referring particularly to the cross-sectional views in Figures 5, 6, and 7, the electrolytic cell 1 according to the present invention includes a first potassium distribution channel 11A for each single cell 20 which is fluidly connected to a chamber 200A defined by an anode frame 22A that accommodates at least a portion of the corresponding anode electrode 21A, and the electrolytic cell 1 further includes a second potassium distribution channel 12A for each single cell 20 which is fluidly connected to a chamber 200B defined by a cathode frame 22B that accommodates at least a portion of the corresponding cathode electrode 21B. In particular, the first potassium distribution channel 11A and the second potassium distribution channel 12A are fluidly connected to the corresponding chambers 200A and 200B by grooves 9A and 9B defined by the corresponding frames 22A and 22B (cathode or anode), respectively.

[0037] Figure 6 shows the anode frame 22A, and Figure 7 shows the cathode frame 22B in the same single cell. Cell components (separator, electrodes, and sealing plate) located between frames 22A and 22B are not shown in these figures. The electrolytic cell 1 also includes a first collection channel 11B for a first reaction product mainly containing oxygen. In each single cell 20, the first collection channel 11B is fluidically connected to the chamber 200A defined by the anode frame 22A. The electrolytic cell 1 also includes a second collection channel 12B for a second reaction product mainly containing hydrogen. In each single cell 20, the second collection channel 12B is fluidically connected to the cathode portion 20B of each single cell 20. In particular, the first collection channel 11B and the second collection channel 12B are fluidically connected to the associated chambers 200A and 200B by grooves 9A' and 9B' defined by the corresponding frames 22A and 22B (cathode or anode), respectively.

[0038] In practice, the first collection channel 11B is intended to transport oxygen produced by the electrolysis reaction and, if applicable, some unreacted, i.e., undissociated, potassium. Similarly, the second collection channel 12B transports hydrogen produced by the electrolysis reaction and, if applicable, some unreacted potassium. Therefore, the two collection channels 11B and 12B collect single-phase or two-phase solutions depending on the presence or absence of unreacted potassium. The distribution channels 11A, 12A and collection channels 11B, 12B are defined as a result of stacking the single cells 20. For this purpose, as will be described in more detail below, the frames 21A, 21B, bipolar plate 5, and sealing plates 26A, 26B, 26C each have openings, which are aligned with each other by the stacking effect, thereby defining the channels 11A, 12A, 11B, and 12B, respectively. In this regard, for frames 22A, 22B, the terms “grooves” 9A, 9A', 9B, 9B' refer collectively to a plurality of fluid passages defined on the structure of the corresponding frames 22A, 22B, which fluidly connect the corresponding distribution channels 11A, 12A or collection channels 11B, 12B to the corresponding parts 20A, 20B of the single cell.

[0039] According to the present invention, each bipolar plate 5 is defined by two components 5A and 5B that are coupled to each other and configured to define one or more internal cavities (i.e., flow paths) for the circulation of a cooling fluid, preferably a refrigerant (e.g., water). Each bipolar plate 5 is provided with an inlet portion SI and an outlet portion SV corresponding to the inlet and outlet of the cooling fluid to the internal cavities (indicated by reference numeral 66 in Figures 13, 14, 16, and 20). According to the present invention, the electrolytic cell 1 includes a cooling fluid supply channel 4A that is fluidically connected to the inlet SI of each bipolar plate 5, and a return channel 4B for the same fluid that is fluidically connected to the outlet SV of each bipolar plate 5. In practice, fluid supplied from a supply source (e.g., a tank 400) located outside the electrolytic cell 1 flows through the supply channel 4A and is distributed into the internal cavities 66 of each bipolar plate 5 via the corresponding inlet SI. The cooling fluid discharged from the internal cavities of each bipolar plate 5 is collected in the return channel 4B via the corresponding outlet SV and returned to the outside of the electrolytic cell 1 through the channel.

[0040] Advantageously, the cooling fluid passing through the bipolar plate 5 suppresses the rise in heat generated by the electrolytic reaction, thereby preventing the bipolar plate 5 itself, and even all components of the single cell 20, from overheating. Therefore, heat can be advantageously removed from the heat-generating area, i.e., the electrolytic cell 1 where the electrolysis reaction takes place. In this regard, as mentioned above, the spacers 23A and 23B, made of metal and positioned on both sides of the single cell, promote heat transfer to the bipolar plate 5. This heat is removed using a cooling fluid (preferably a liquid) different from the electrolyte involved in the electrolytic reaction. Therefore, the operating flow rate of the electrolyte can be advantageously set to a value close to the nominal flow rate of the electrolytic reaction. This makes it possible to miniaturize the plant components located outside the electrolytic cell that are necessary for circulating the electrolyte and reaction products. In this respect, the internal cooling structure of the electrolytic cell eliminates the need for external heat exchangers (S1, S2 shown in Figure 1) that are currently used to cool the electrolyte before it is introduced into the electrolytic cell.

[0041] In the following explanation, the cooling fluid will be referred to as "cooling water (or cooling water / fluid)," but this does not mean that other liquids or other fluids can be used as the cooling fluid. Furthermore, the term "potassium" will be used below for the electrolyte, but this does not preclude the use of other types of electrolytes.

[0042] According to a possible embodiment shown in the figure, the fluid delivery channel 4A has an inlet 41A on one of the two headers 11, 12, and the return channel 4B has an outlet 41B on the same headers 11, 12 (see Figure 2 in particular). Preferably, these inlets and outlets are located on the same header (cathode header 12 in the figure), and more specifically, on the opposite side of the header (anode header 11 in the figure) from which the inlets 111A, 111B of the potassium distribution channels 11A, 12A are defined. According to an alternative embodiment, the inlets 41A and outlets 41B defined above may be defined on different headers.

[0043] Referring to Figures 3, 6, and 7, according to the preferred embodiment shown in the figures, the first potassium distribution channel 11A and the second potassium distribution channel 12A each comprise a first inlet 111A and a second inlet 112A, respectively, located on the header (anode header in the figure) opposite to the header (cathode header in the figure) of the electrolytic cell 1 where the inlet 41A of the cooling fluid supply channel 4A and the outlet 41B of the return channel 4B are located. Furthermore, the first reaction product collection channel 11B and the second reaction product collection channel 12B each comprise a first outlet 111B and a second outlet 112B, respectively, which are also located on the same header where the first inlet 111A and the second inlet 112A of the distribution channels 11A and 12A are located. In other words, according to the preferred configuration, electrolyte / potassium management is assumed to be in the header opposite to the header provided for the conduction (intake / exhaust) of the cooling fluid, with respect to the introduction and discharge of the electrolyte into and out of the electrolytic cell. In particular, as shown in Figure 2, the electrolyte flow path is preferably formed on the header closest to the degassers 451, 452 into which the first reaction product, transported via the first collection channel 11B, and the second reaction product, transported via the second collection channel 12B, flow.

[0044] Furthermore, as particularly shown in Figure 2, the fluid delivery channel 4A (and its inlet 41A) is defined as being located vertically below the return channel 4B (and its outlet 41B), as clearly indicated by the arrows indicating the inlet and outlet directions of the cooling fluid. Preferably, the potassium distribution channels 11A and 12A are also located vertically below the reaction product collection channels 11B and 12B. In particular, as can be seen from Figures 6 and 7, the first collection channel 11B is defined as being vertically above the second distribution channel 12A, and the second collection channel 12B is defined as being vertically above the first distribution channel 11A.

[0045] Referring particularly to Figures 5, 6, 7, 8, and 9, in each single cell 20, both frames 22A and 22B are provided with first distribution openings 31A and 33B and first collection openings 32A and 34B, respectively, which are fluidly connected to the corresponding chambers 200A and 200B. Such connections are preferably achieved by grooves 9A, 9B, 9A', and 9B' (shown in Figures 5 and 8) defined on the side opposite to the side facing the adjacent bipolar plate 5. In particular, the grooves indicated by reference numerals 9A and 9B connect the distribution openings 31A and 33B to the corresponding chambers 200A and 200B. These chambers 200A and 200B are fluidly connected to the collection openings 32A and 34B by grooves indicated by reference numerals 9A' and 9B'.

[0046] Each frame 22A, 22B further comprises second distribution openings 33A, 31B and second collection openings 34A, 32B, which are not fluidly connected to the chambers 200A, 200B. Preferably, the first distribution openings 31A, 33B and their respective corresponding first collection openings 32A, 34B are positioned diagonally opposite to each other. In each frame 22A, 22B, the corresponding first distribution openings 31A, 33B and first collection openings 32A, 34B are "active" openings because they are provided to circulate potassium within chambers 200A, 200B defined by the frame itself during operation of the electrolytic cell. On the other hand, the second distribution openings 33A, 31B and second collection openings 34A, 32B are "passive" because they do not participate in the circulation of potassium within the same containment chambers 200A, 200B.

[0047] Referring particularly to Figure 9, it can be seen that in each single cell 20, the anode frame 22A and cathode frame 22B are oriented such that each "active" opening of the anode frame 22A aligns with and fits the "passive" opening of the cathode frame 22B, and vice versa. Thus, the first distribution opening 31A (active) and the second distribution opening 33A (passive) of the anode frame 22A align with and fits the second distribution opening 31B (passive) and the first distribution opening 33B (active) of the cathode frame 22B, respectively. In each single cell 20, each frame 22A, 22B is provided with fluid supply openings 35A, 35B and return openings 36A, 36B configured for the cooling fluid to pass through when the electrolytic cell 1 is in operation. As shown in the figure, preferably the fluid supply openings 35A, 35B and the return openings 36A, 36B are defined between one of the "active" openings and one of the "passive" openings, respectively.

[0048] Referring to Figures 8 and 9, in each single cell 20, the sealing plates 26A, 26B, and 26C each have six openings 41, 42, 43, 44, 45, and 46, and each opening is formed and positioned to fit the openings 31A, 32A, 33A, 34A, 35A, 36A and 31B, 32B, 33B, 34B, 35B, and 36B of the two frames 22A and 22B. Similarly, each bipolar plate 5 also has six openings 51, 52, 53, 54, 55, 56, each opening formed and positioned to correspond to one of the six openings 31A, 32A, 33A, 34A, 35A, 36A and 31B, 32B, 33B, 34B, 35B, 36B of each frame 22A, 22B, and the six openings 41, 42, 43, 44, 45, 46 of the sealing plates 26A, 26B, 26C.

[0049] Overall, the stack of single cells 20 between the two headers 11 and 12 is as follows, i.e., the assembly of the electrolytic cell 1 is as follows: - One of the two distribution openings 31A or 31B of each frame 22A, 22B, the corresponding first opening 41 of each seal plate 26A, 26B, 26C, and the corresponding first opening 51 of each bipolar plate 5 collectively define the first potassium distribution channel 11A; - The other of the two distribution openings 33A or 33B of each frame 22A, 22B, the corresponding second opening 43 of each sealing plate 26A, 26B, 26C, and the corresponding second opening 52 of the bipolar plate 5 collectively define the second potassium distribution channel 12B; -The collection opening 32A or 34B of each frame 22A, 22B, the corresponding third opening 42 of each sealing plate 26A, 26B, 26C, and the corresponding third opening 53 of each bipolar plate 5 collectively define the first potassium collection channel 11B; -The other of the collection openings 34A, 34B of each frame 22A, 22B, the corresponding fourth opening 44 of each sealing plate 26A, 26B, 26C, and the corresponding fourth opening 54 of each bipolar plate 5 collectively define the second potassium collection channel 12B; -The fluid delivery openings 35A and 35B of each frame 22A and 22B, the corresponding fifth openings 45 of each seal plate 26A, 26B, and 26C, and the corresponding fifth openings 55 of each bipolar plate 5 collectively define the first fluid delivery channel 4A for the cooling fluid passing through the inside of the bipolar plate 5; finally, - The return openings 36A and 36B of each frame 22A and 22B, the corresponding sixth openings 46 of each seal plate 26A, 26B, and 26C, and the corresponding sixth openings 56 of each bipolar plate 5 collectively define the return channel 4B for the cooling fluid flowing out of the bipolar plate 5.

[0050] Figures 10 to 13 show in detail the shape of the bipolar plate 5 of the electrolytic cell 1 shown in Figure 9 (exploded view). In particular, Figure 10 is a front view of the bipolar plate 5 extending mainly along the longitudinal direction Y, which is perpendicular to the transverse direction X. Considering the bipolar plate 5 in use (as shown in Figures 2 and 3), i.e., when it is placed inside the electrolytic cell 1, the longitudinal direction Y substantially coincides with the vertical direction. Hereinafter, the terms "longitudinal plane" and "transverse plane" refer to planes parallel to the longitudinal direction Y and the transverse direction X, respectively. According to the present invention, the bipolar plate 5 is defined by the joining of two components 5A and 5B, and in the embodiments shown in Figures 10 to 13, these two components 5A and 5B are obtained by forming metal plates, which are preferably but not limited to steel. Figures 11 and 12 are a front view of the first component 5A and a perspective view of the second component 5B, respectively. Each component is characterized by flat portions 501A and 501B, and molded portions 502A and 502B surrounded by these flat portions 501A and 501B. Each of the openings 51, 52, 53, 54, 55, and 56 provided in the bipolar plate 5 is defined by connecting the corresponding openings (indicated by the letters A, B, C, D, E, and F defined in each of the two components 5A and 5B). More precisely, in each component 5A and 5B, four openings (A, B, C, and D) are defined in the corresponding flat regions 501A and 501B, respectively, and by connecting the two components 5A and 5B, four openings 51, 52, 53, and 54 of the bipolar plate 5 are formed. The latter contribute to defining the potassium distribution channels 11A and 12A and the reaction product collection channels 11B and 12B after the stacking of the single cells 20.

[0051] On the other hand, in each component 5A and 5B, two further openings (E and F) are formed in the molding regions 502A and 502B, respectively, and the connection of the two components 5A and 5B forms the fifth opening 55 and the sixth opening 56 of the bipolar plate 5. The latter contributes to defining the cooling fluid supply channel 4A and return channel 4B after the stacking of the single cells 20. In each component 5A and 5B, the molded regions 502A and 502B are recessed relative to the reference plane PR on which the corresponding flat regions 501A and 501B extend. More precisely, the molded regions 502A and 502B include a substantially rectangular central region 502', which has a substantially wave-like shape with alternating grooves S and raised portions CR. Therefore, the cross-section of such a central region has a profile that includes the minimum point on a plane away from the reference plane PR and the maximum point on a plane coinciding with the reference plane PR (see cross-sectional view in Figure 13).

[0052] In each component 5A and 5B, the molded regions 502A and 502B further include two bottleneck regions 502'' and 502'''' positioned opposite each other with respect to the central rectangular region 502'. Referring again to Figures 11 and 12, it can be seen that these bottleneck regions 502'' and 502'''' have a wavy portion (indicated by reference numeral P), and that this wavy portion is formed symmetrically with respect to the longitudinal axis Y of each component 5A and 5B. Overall, it is preferable that the two bottleneck regions 502'' and 502'''' are also symmetrical with respect to the lateral direction X. Referring to Figures 11 and 12, the two components 5A and 5B are connected by welding in their respective flat regions 501A and 501B, and are configured to be mirror-symmetric with respect to the contact surface (which coincides with the reference surface PR). After such connection, the molded region 502A of the first component 5A faces / opposes the molded region 502B of the second component 5B. The wavy protrusions of the central region 502' and the bottleneck regions 502'' and 502'''' in the molded region 502A of the first component 5A contact the corresponding wavy protrusions in the molded region 502B of the second component (see cross-sectional view in Figure 13). Thus, after the connection between the components 5A and 5B, internal cavities 66 are formed, each partitioned between the two opposing grooves S of the two components 5A and 5B. Referring particularly to Figure 10, these internal cavities 66 extend in the longitudinal direction and are parallel to each other and adjacent in the lateral direction.

[0053] Referring again to Figure 10, the bipolar plate 5 is provided with a first chamber CI, which is defined by two bottleneck regions 502'' (of their respective components 5A and 5B) that face each other across the contact surface PR. A second chamber CV is also recognized, which is defined by two other bottleneck regions 502''' (of their respective components 5A and 5B) that face each other across the same contact surface PR. The first chamber CI forms a passage for the cooling fluid to flow into the internal cavity 66, and thus defines an inlet SI into which the fluid flows between the two components 5A and 5B of the bipolar plate 5. The second chamber CV transports the cooling fluid flowing out of the internal sliding cavity 66, and thus defines an outlet SV for the cooling fluid. In practice, during normal operation of the electrolytic cell 1, the cooling fluid first flows into and is distributed in the inlet chamber CI of the bipolar plate 5, and then passes through the internal cavity 66 defined by the connection of the two central regions 502' of the two components 5A and 5B of the bipolar plate 5. After passing through the internal cavity 66, the fluid is transported into the outlet chamber CV and finally led to the outlet SV. Therefore, together with the internal cavity 66, the first chamber CI and the second chamber CV contribute to the circulation of the cooling fluid and, consequently, to the removal of heat.

[0054] Figures 14, 15, and 16 show possible embodiments of the bipolar plate for an electrolytic cell according to the present invention, as an alternative to the one described above. To distinguish it from the previous embodiment, the plate of this embodiment is denoted by reference numeral 5', and its two components are denoted by reference numerals 5A and 5B, which have already been used. Specifically, in this embodiment, the two components 5A and 5B are composed of two flat metal plates that extend mainly along the longitudinal direction Y. These two components 5A and 5B have the same shape and are preferably symmetric with respect to two mutually orthogonal planes of symmetry (longitudinal and transverse directions). For simplification, only the first component 5A is shown in Figure 15.

[0055] Each component 5A, 5B has an inner surface 51A and an outer surface 51B facing the inner surface 51A. Each component has four openings A, B, C, and D intended to form four corresponding openings 51, 52, 53, and 54 of the bipolar plate 5' after the connection of the two components 5A, 5B. These openings contribute to defining potassium distribution channels and reaction product collection channels after the stacking of single cells 20. Each component 5A, 5B also has two other openings E and F, which define a supply opening 55 and a return opening 56 for forming a cooling water supply channel 4A and a return channel 4B after the connection of the two components 5A, 5B. Each component 5A, 5B is provided with a plurality of grooves 65 formed in the thickness direction from the corresponding inner surface 51A. These grooves 65 are preferably formed by machining, such as milling. To define the bipolar plate 5', the two components 5A, 5B are joined so as to be mirror-symmetric with respect to a contact plane CP (shown in Figure 16). More precisely, the inner surface 51A of one component 5A is in contact with the inner surface 51A of the other component 5B. Furthermore, the grooves 65 of one component face the corresponding grooves of the other component 5B, forming a pair of opposing grooves. Each pair of grooves defines an internal cavity 66 through which a cooling fluid flows.

[0056] As can be seen from the cross-sectional view in Figure 16, preferably, the internal cavity 66 has a cross-sectional surface that is generally ellipsoidal in shape, and this cross-sectional surface is evaluated on a cross-sectional plane perpendicular to the longitudinal extension direction. However, in other alternative embodiments, the shape of the cross-section may be circular or other shapes. Referring to Figures 14 and 15, in this embodiment, for each component 5A of the bipolar plate 5', the groove 65 includes a first curved portion 65', a second longitudinal portion 65'', and a third portion 65''' that is symmetric with respect to the lateral plane of symmetry (XX) with respect to the first portion 66'. As a result of this shape, when the two components 5A and 5B are joined, the internal cavity 66 for water has a first portion 66' that communicates with an inlet portion SI (defined as a liquid delivery opening 55), through which water reaches the second longitudinal portion 66''. Through the third portion 66''', the water is transported toward an outlet portion SV defined as a return opening 56 (see Figure 14). As the cooling fluid passes through all portions 66', 66”, 66''' of the internal cavity 66, particularly the second longitudinal portion 66”, it removes heat from the two components 5A and 5B of the plate 5' in accordance with the objectives of the present invention.

[0057] In the embodiments shown in Figures 14, 15, and 16, the outer surfaces 51B of each component 5A, 5B are advantageously flat. This configuration improves thermal contact with the spacers 23A, 23B provided within the single cell. Furthermore, the flatness of the outer surface 51B facilitates the placement of the sealing plates 26A, 26C, which are positioned between the bipolar plate 5 and the adjacent frames 22A, 22B. Overall, this configuration improves the sealing performance of the single-cell laminate. Figures 17 to 20 show yet another possible embodiment of the bipolar plate for electrolytic cells according to the present invention. To distinguish it from the previous embodiment, the plate is denoted by reference numeral 5” (shown in Figure 17), and reference numerals 5A and 5B are again used to indicate the two components that make it up.

[0058] Figures 18 and 19 are a front view of the first component 5A and a perspective view of the second component 5B of the bipolar plate 5”, respectively. Similar to the bipolar plate 5 in Figure 10, the components 5A and 5B of this bipolar plate 5”, are formed by molding and then welded as detailed below. The two components 5A and 5B of plate 5" have the same shape. Each component 5A, 5B is identified with flat sections 501A, 501B and molded sections 502A, 502B surrounded by these flat sections 501A, 501B. The flat sections 501A, 501B define four openings A, B, C, and D (shown only in Figure 18), which, through the connection of the two components, form four openings 51, 52, 53, and 54 of the bipolar plate 5''. These openings 51-54 contribute to defining potassium distribution channels (11A, 12A) and reaction product collection channels (11B, 12B) after the stacking of single cells 20.

[0059] Meanwhile, in each component 5A and 5B, the corresponding molded regions 502A and 502B define a first opening E and a second opening F, which, after the two components 5A and 5B are joined, define a fifth opening 55 and a sixth opening 56 of the bipolar plate 5''. These fifth and sixth openings 55 and 56 contribute to defining the supply channel 4A and return channel 4B for the cooling fluid circulating within the electrolytic cell 1. Each component 5A, 5B has molded portions 502A, 502B which are recessed portions 503A, 503B with respect to the reference plane PR on which the flat portions 501A, 501B are located (see Figure 20). The molded portions 502A, 502B are provided with a plurality of protrusions 504A, 504B that project from the recesses 503A, 503B beyond the reference plane PR. Preferably, the protrusions 504A, 504B are arranged at predetermined intervals along two mutually orthogonal directions (longitudinal direction X and transverse direction Y).

[0060] Referring to Figures 18 and 19, the two components 5A and 5B are connected on their respective flat portions 501A and 501B, i.e., contact surfaces that coincide with the aforementioned reference plane PR. With respect to these contact surfaces, the recess 503A of the molded portion 502A of the first component 5A is positioned on the opposite side from where the recess 503B of the molded portion 502B of the second component 5B is located (see the cross-section in particular of Figure 20). This arrangement creates an internal cavity 66 between the two recesses 503A and 503B, which is used for the flow of water / cooling fluid. Referring again to the cross-sectional view in Figure 20, it can be observed that the protrusion 504A of the first component 5A is in contact with the inner surface of the recess 503B of the second component 5B, and conversely, the protrusion 504B of the second component 5B is in contact with the inner surface of the recess 503A of the first component 5A. Overall, the fluid can flow around the protrusions 504A and 504B within the internal cavity 66, and this flow cools the components 5A and 5B of the bipolar plate 5”. Advantageously, the contact between the protrusions 504A and 504B of one component 5A and 5B and the recesses 503A and 503B of the other component 5A and 5B contributes to the structural strength of the bipolar plate 5”.

[0061] In the illustrated embodiment, the protrusions 504A and 504B have substantially frustoconical shapes, and this shape is evaluated on a plane parallel to the reference plane PR (see again Figure 20). However, the possibility of such protrusions having different configurations is within the scope of the present invention. As described above, the two members 5A and 5B have the same configuration. In Figure 19, it can be observed that the second component 5B is shown with the molded portion 502B positioned in front of the corresponding flat portion 501B. In other words, Figure 19 shows the outside of the second component 5B with respect to the internal cavity 66 through which the water / cooling fluid flows. On the other hand, Figure 18 shows the inside of the first component 5A, i.e., the side that is in contact with the second component 5B. When making the connection from the state shown in Figure 19, the second member 5B is placed on top of the first member 5A so that the respective flat portions 501A and 501B are in contact with each other, and each convex portion 504A formed on one of the members 5A and 5B is in contact with the inner surface of the recesses 503A and 503B formed on the other member. In the final state after connection, it can be observed that each convex portion 504B of the second member 5B is surrounded by the convex portions 504A of the first member 5A, and vice versa. In other words, along each of the orthogonal directions (X, Y) in which the convex portions 504A and 504B are arranged, the convex portions 504B of the second member 5B are dispersed between the convex portions 504A of the first member 5A, and vice versa (see Figure 17).

[0062] Referring to Figure 17, in the bipolar plate 5”, the internal cavity 66 formed by the joining of two molded regions 502A and 502B of two members 5A and 5B comprises a substantially rectangular central region 502' extending along two principal directions (X, Y), and two bottleneck regions 502'' and 502''' located opposite the central region 502' and formed between the central region 502' and the corresponding openings 55A and 56A. The two bottleneck regions 502'' and 502''' constitute the inlet SI and outlet SV of the cooling fluid in the fluid supply opening 55 and the return opening 56, respectively, of the bipolar plate 5”.

[0063] Referring again to Figure 17, during normal operation, the cooling fluid flows through the inlet SI between members 5A and 5B of the bipolar plate 5”, and is first distributed between the protrusions 504A and 504B in the first bottleneck region 502”, and then distributed to the protrusions in the central region 502'. After that, the fluid passes through the second bottleneck region 502'''' and is discharged outside the bipolar plate 5”, from the outlet SV. The present invention also relates to a plant 100 for the industrial production of hydrogen, which includes an electrolytic cell 1 according to the present invention. Figure 21 shows a schematic diagram of the plant according to the present invention, which, in addition to the electrolytic cell 1, includes a first circuit C1 for the circulation of electrolyte and a second circuit C2 for the circulation of electrolyte. Each circuit C1, C2 includes fluid delivery branch pipes RM1, RM2 which are fluidly connected to either of the distribution channels 11A, 12A via corresponding inlets 111A, 112A. Each circuit C1, C2 further includes return branch pipes RR1, RR2 which are connected to either of the collection channels 11B, 12B via corresponding outlets 111B, 112B. Each circuit C1, C2 further includes degassing devices 451, 452 which are positioned between the corresponding fluid delivery branch pipes RM1, RM2 and the return branch pipes RR1, RR2. Each circuit C1, C2 is also provided with circulation pumps P1, P2 along the corresponding return branch pipes RR1, RR2.

[0064] According to the present invention, the plant 100 includes a further circuit C3 for circulating the cooling fluid. Such a further circuit C3 includes a tank 400 and a fluid supply lamp RM3 fluid-connected to the fluid supply channel 4A of the electrolytic cell 1 via a corresponding inlet 41A. The circuit also includes a return branch pipe RR3 fluid-connected to the return channel 4B of the electrolytic cell 1 via a corresponding outlet 41B. A circulation pump P3 is positioned along the fluid supply branch pipe RM3, which supplies the cooling fluid pumped from the tank 400 to the fluid supply channel 4A. Through the return branch pipe RR3 of the third circuit C3, the cooling fluid discharged from the return channel 4B of the electrolytic cell is returned to the tank 400 for subsequent recirculation. Preferably, the circulation pump P3 of the third circuit C3 can be driven independently of the circulation pumps P1 and P2 of the two circuits C1 and C2 through which the electrolyte circulates. This allows the circulation of the cooling fluid to continue even when the electrolytic cell is stopped, i.e., when the circulation of the electrolyte inside the electrolytic cell has stopped. This condition makes it possible to effectively counteract damage that may occur due to the aforementioned "battery effect".

[0065] Comparing the schematic diagram in Figure 21 with the schematic diagram in Figure 1 relating to a known type of plant, it can be inferred that using the electrolytic cell according to the present invention eliminates the need for the two heat exchangers that are normally used to cool the electrolyte before it is introduced into the electrolytic cell. Furthermore, compared to a conventional plant as shown in Figure 1, the present invention can reduce the operating flow rate of the electrolyte, thereby shortening the residence time in the degassing device installed in the plant, and as a result, a clear advantage in terms of productivity can be obtained. The solutions described above fully achieve the pre-defined challenges and objectives. In particular, the proposed apparatus is highly convenient, practical, effective, and can be easily manufactured at low cost.

Claims

1. An electrolytic cell (1) for producing hydrogen from an alkaline electrolyte, The electrolytic cell (1) is: - A first header (11) and a second header (12) made of a metal material; - A plurality of single cells (20) and a plurality of bipolar plates (5, 5', 5") arranged between the headers (11, 12); Here, the single cells (20) are separated from each other by one of the bipolar plates (5, 5', 5"), - Clamp elements (3) for mechanically connecting the headers (11, 12) so as to maintain the state in which the single cell (20) and the bipolar plates (5, 5', 5") are stably stacked between the headers (11, 12); Each of the aforementioned single cells (20) is: - An anode portion (20A) including an anode electrode (21A) and an anode frame (22A) defining a chamber (200A) in which the anode electrode (21A) is at least partially housed; Here, the anode portion (20A) includes at least one sealing plate (26A) interposed between the anode frame (22A) and one of the bipolar plates (5, 5', 5"), and the anode portion further includes a metallic anode spacer (23A) interposed between one of the bipolar plates (5) and the anode electrode (21A). - A cathode portion (20B) including a cathode electrode (21B) and a cathode frame (22B) defining a chamber (200B) in which the cathode electrode (21B) is at least partially housed; Here, the cathode portion (20B) includes at least one sealing plate (26B) interposed between the cathode frame (22B) and another of the bipolar plates (5, 5', 5"), and the cathode portion (20B) further includes a metal cathode spacer (23B) interposed between the cathode electrode (21B) and another of the bipolar plates (5), - A separator element (2) that separates the anode portion (20A) from the cathode portion (20B); - comprising at least one further sealing plate (26C) interposed between the anode frame (22A) of the anode portion (20A) and the cathode frame (22B) of the cathode portion (20B); The electrolytic cell (1) is: - The first distribution channel (11A) of the alkaline electrolyte and the first collection channel (11B) of the first reaction product mainly containing oxygen; Here, for each of the single cells (20), the channels (11A, 11B) are fluidly connected to the chamber (200A) of the anode portion (20A) by grooves (9A, 9A') defined by the anode frame (22A). - The second distribution channel (12A) for the alkaline electrolyte and the second collection channel (12B) for the second reaction product mainly containing hydrogen; Here, for each of the single cells (20), the second distribution channel (12A) and the second collection channel (12B) are fluidly connected to the chamber (200B) of the cathode portion (20B) by grooves (9B, 9B') defined by the cathode frame (22B). It further includes, Each of the bipolar plates (5, 5', 5") comprises two plate-like components (5A, 5B) connected to each other and configured to define one or more internal cavities (66) for the circulation of a cooling fluid, and each bipolar plate (5, 5', 5") includes an inlet (SI) and an outlet (SV) corresponding to the inlet and outlet of the cooling fluid to the one or more internal cavities (66), respectively. The electrolytic cell (1) is: - A fluid supply channel (4A) for the cooling fluid is fluidly connected to the inlet (SI) of each of the bipolar plates (5, 5', 5"); - An electrolytic cell (1) further comprising: a return channel (4B) for the cooling fluid, which is fluidly connected to the outlet (SV) of each of the bipolar plates (5, 5', 5");

2. The electrolytic cell (1) according to claim 1, wherein the liquid delivery channel (4A) includes an inlet (41A), the return channel (4B) includes an outlet (41B), and both the inlet (41A) and the outlet (41B) are located on one of the headers (11, 12).

3. The electrolytic cell (1) according to claim 2, wherein the first distribution channel (11A) and the second distribution channel (12A) of the electrolyte include a first inlet (111A) and a second inlet (112A) located on one side of the header (11, 12) opposite to the location of the inlet (41A) of the liquid delivery channel (4A) and the outlet (41B) of the return channel (4B), and the first collection channel (11B) and the second collection channel (12B) of the reaction product include a first outlet (111B) and a second outlet (112B) located on one side of the header (11, 12).

4. For each of the single cells (20), each frame (22A, 22B) is: - The chambers (200A, 200B) defined by the corresponding frames (22A, 22B) are fluid-connected to the first distribution openings (31A, 33B) and the first collection openings (32A, 34B) via the grooves (9A, 9A', 9B, 9B'); Here, the first distribution openings (31A, 33B) and the first collection openings (32A, 34B) are defined at diagonal positions relative to each other. - Second distribution openings (33A, 31B) and second collection openings (34A, 32B) that are not fluid-connected to the chambers (200A, 200B) defined by the corresponding frames (22A, 22B); Here, the second distribution openings (33A, 31B) and the second collection openings (34A, 32B) are defined at diagonal positions relative to each other. - An electrolytic cell (1) according to any one of claims 1 to 3, comprising: a liquid supply opening (35A, 35B) and a return opening (36A, 36B) intended for the cooling fluid to pass through when the electrolytic cell (1) is in use;

5. - The sealing plates (26A, 26B, 26C) include six openings (41, 42, 43, 44, 45, 46) each configured and positioned to fit the corresponding openings (31A, 32A, 33A, 34A, 35A, 36A-31B, 32B, 33B, 34B, 35B, 36B) of the frames (22A, 22B), - The electrolytic cell (1) according to claim 4, wherein each bipolar plate (5, 5', 5") includes six openings (51, 52, 53, 54, 55, 56) respectively configured and positioned to fit one of the six openings (31A, 32A, 33A, 34A, 35A, 36A-31B, 32B, 33B, 34B, 35B, 36B) of each of the frames (22A, 22B) and one of the six openings (41, 42, 43, 44, 45, 46) of each of the sealing plates (26A, 26B, 26C).

6. The stack of the single cells (20) between the headers (11, 12) is as follows: - One of the distribution openings (31A or 31B) of each of the frames (22A, 22B), the corresponding first opening (41) of each of the seal plates (26A, 26B, 26C), and the corresponding first opening (51) of each of the bipolar plates (5, 5', 5") together define the first distribution channel (11A) of the electrolyte. - The other of the distribution openings (33A or 33B) of each of the frames (22A, 22B), the corresponding second openings (43) of each of the seal plates (26A, 26B, 26C), and the corresponding second openings (52) of each of the bipolar plates (5, 5', 5") together define the second distribution channel (12A) of the electrolyte. - One of the collection openings (32A or 32B) of each of the frames (22A, 22B), the corresponding third opening (42) of each of the seal plates (26A, 26B, 26C), and the corresponding third opening (53) of each of the bipolar plates (5, 5', 5"), together define the first collection channel (11B) of the electrolyte. - The other of each of the collection openings (34A, 34B) of the frame (22A, 22B), the corresponding fourth opening (44) of each of the seal plates (26A, 26B, 26C), and the corresponding fourth opening (54) of each of the bipolar plates (5, 5', 5") together define the second collection channel (12B) of the electrolyte. - The fluid delivery openings (35A, 35B) of each of the frames (22A, 22B), the corresponding fifth openings (45) of each of the seal plates (26A, 26B, 26C), and the corresponding fifth openings (55) of each of the bipolar plates (5, 5', 5"), together define the first fluid delivery channel (4A) for the cooling fluid, which is intended to pass through the interior of the bipolar plates (5, 5', 5"), and finally - The electrolytic cell (1) according to claim 5, wherein the return openings (36A, 36B) of each of the frames (22A, 22B), the corresponding sixth openings (46) of each of the seal plates (26A, 26B, 26C), and the corresponding sixth openings (56) of each of the bipolar plates (5, 5', 5") together define the return channel (4B) of the cooling fluid exiting the bipolar plates (5, 5', 5").

7. Each component (5A, 5B) of the bipolar plate (5) includes a flat portion (501A, 501B) and a molded portion (502A, 502B) surrounded by the flat portion (501A, 501B), and in each component (5A, 5B), the molded portion (502A, 502B) is formed in a concave shape with respect to the reference surface (PR) on which the flat portion (501A, 501B) unfolds, and the component (5A, 5B) has a flat portion (501A, 501B) The electrolytic cell (1) according to any one of claims 1 to 6, wherein the cells are connected and configured to be symmetric with respect to a contact surface that coincides with the reference surface (PR), the molded region (502A) of the first component (5A) faces the molded region (502B) of the second component (5B), and the one or more internal cavities (66) of the bipolar plates (5, 5') are defined between the mutually opposing molded regions (502, 502) of the components (5A, 5B).

8. 5A, 5B) wherein each of the constituent members (5A, 5B) has a molded portion (502A, 502B) comprising at least one substantially corrugated region (502') in which grooves (S) and raised portions (CR) are alternately formed, and as a result of connecting the constituent members (5A, 5B), each of the raised portions (CR) of the molded portion (502A) of the first constituent member (5A) contacts the corresponding raised portion (CR) of the molded portion (502B) of the second constituent member (5B), and as a result of the connection, the internal cavity (66) for the circulation of the cooling fluid is defined between two opposing grooves (S) of the molded portions (502A, 502B) of the constituent members (5A, 5B), the electrolytic cell (1) according to claim 7.

9. Each of the aforementioned components (5A, 5B) has a molded portion (502A, 502B) which includes a recess (503A, 503B) recessed with respect to the reference surface (PR) and a plurality of protrusions (504A, 504B) that extend beyond the reference surface (PR) from the recess (503A, 503B), and as a result of connecting the components (5A, 5B), the recess (503A) of the molded portion (502A) of the first component (5A) is the same as the recess (502B) of the molded portion (502B) of the second component (5B). The electrolytic cell (1) according to claim 7, wherein (503B) remains positioned on the opposite side from the side in which it is located, and the at least one internal cavity (66) for the circulation of the cooling fluid is defined between the recesses (503A, 503B), the convex portion (504A) of the first component (5A) contacts the inner surface of the recess (503B) of the second component (5B), and the convex portion (504B) of the second component (5B) contacts the inner surface of the recess (503A) of the first component (5A).

10. The electrolytic cell (1) according to any one of claims 1 to 9, wherein the constituent members (5A, 5B) include two flat metal plates, each metal plate including an inner surface (51A) and an outer surface (51B) opposite to the inner surface (51A), each metal plate including a plurality of grooves (65) formed in the thickness direction from the corresponding inner surface (51A), the constituent members (5A, 5B) are joined such that the inner surface (51A) of one constituent member (5A) is in contact with the inner surface (51A) of the other constituent member (5B), and as a result of the contact, the grooves (65) of one constituent member (5A) face the corresponding grooves of the other constituent member (5B), and a pair of opposing grooves define an internal cavity (66) for the circulation of the cooling fluid, and the outer surface (51B) of the metal plate is flat.

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