Water electrolyser stack using alkaline media

Abstract

Various embodiments of the present invention disclose a water electrolyser using an alkaline medium, including a first end plate and a second end plate, and a plurality of cells stacked between the first end plate and the second end plate. Each cell includes an anode cell frame and a cathode cell frame, each cell frame further including a central opening, at least one inlet channel laterally through the cell frame, and at least one inlet path slotted in the cell frame for connecting the inlet channel to the central opening. The inlet path includes an inlet aperture characterized by a minimum cross-sectional area in the inlet path. A cross-sectional area of the inlet channel in the cell stack is greater than a sum of cross-sectional areas of the plurality of inlet holes in the cell stack by at least a predetermined coefficient greater than 1 and less than or equal to 4.

Description

TECHNICAL FIELD

[0001] The present invention relates to an electrolyser stack, in particular to a water electrolyser using alkaline media. BACKGROUND

[0002] In alkaline water electrolysis, water is electrochemically converted into hydrogen and oxygen in an alkaline medium: H2O = H2+ 0.5O2. The electrolyser cell comprises two electrodes (anode and cathode) and an electrolyte. The electrolyte comprises a liquid alkaline medium, such as an aqueous solution of hydroxide and / or carbonate. The alkaline electrolyte flows through the anode and cathode compartments of the electrolyser cell, which are fluidically in parallel, thus immersing the electrodes in the electrolyte. During operation, an electric potential is applied between the two electrodes, causing an electrolytic current to flow through the electrolyser cell. During operation, hydrogen is produced at the cathode according to the hydrogen evolution reaction (HER): 2H2O + 2e - = H2+ 2OH - and oxygen is produced at the anode according to the oxygen evolution reaction (OER): 2OH - = 0.5O2+ H2O + 2e - The electrolyser cell further comprises a porous separator (membrane) and / or an ion exchange membrane, which is able to conduct hydroxide ions and separates the two half-cells to prevent mixing of the product gases. The electrodes are placed in a sandwich fashion on both sides of the membrane.

[0003] It is advantageous to place the electrodes in a sandwich fashion as close to the membrane as possible on both sides, which on the one hand minimizes the distance between the electrodes, thus reducing the ionic resistance, and on the other hand ensures that hydrogen bubbles are mainly produced at the back side of the electrodes, which leads to a reduction of the overpotential. This arrangement, often referred to as "zero-gap configuration", thus increases the cell efficiency. The positioning of the electrodes in this configuration is achieved by pressing the electrodes and the separator together and adjusting the contact pressure by elastic or rigid spacers placed next to the electrodes on the side opposite to the side facing the separator. Furthermore, the electrical contact to the electrodes is established by bipolar plates in contact with the spacers.

[0004] The cells are usually electrically assembled in series between a first and a second end plate into a cell stack. The more cells in the electrolyser stack, the more hydrogen and oxygen is produced per time. Similarly, the larger the surface area (footprint) of each cell in the electrolyser stack, the more hydrogen and oxygen can be produced by each cell at a fixed current density.

[0005] Alkaline electrolysis cell stacks can be operated either at atmospheric pressure or at high pressure. The advantage of operating at high pressure is that hydrogen (and optionally oxygen) is produced at high pressure, thus requiring less compressor and less energy to compress the gas to the required pressure level. For pressurized alkaline electrolyzers, typical operating pressures are in the range of 10 barg to 35 barg. Pressurized operation typically requires that the cells are circular (or substantially circular). Furthermore, pressurized electrolyzer stacks typically comprise a cell frame, i.e. a component that at least houses the electrodes and the pressurized fluid. The cell frame comprises a central opening that forms a reaction chamber in the cell. Furthermore, the cell frame provides mechanical support to the cell components and, in combination with a gasket, prevents leakage of the alkaline electrolyte as well as the product hydrogen and oxygen into the environment.

[0006] When stacking the cell stack components to form an electrolyzer stack, a plurality of channels resulting from the holes and openings in the cell frame extend through the cell stack from the first end plate to the second end plate. The channels branch through multiple paths into the respective cells. The electrolyte solution enters the electrolyzer stack through the channels and is fed to each individual cell through the paths branching from the channels. The electrolyte enters and exits the electrolyzer stack through the same end plates (sometimes referred to as a “U-shaped design”), or the electrolyte enters the electrolyzer stack through one end plate and exits the electrolyzer stack through the other end plate (sometimes referred to as a “Z-shaped design”). The U-shaped design is particularly advantageous for use in alkaline electrolyzers as it significantly reduces shunt (parasitic) currents in the electrolyzer stack, i.e. a portion of the applied current that bypasses the active cell area and thus does not contribute to the desired electrochemical reaction.

[0007] When the electrolyte is supplied to an electrolyzer stack having a U-shaped design at a particular time, the electrolyte supplied to each cell is unequal. The cells closest to the first end plate receive the majority of the electrolyte, while the cells further along the electrolyzer stack receive less electrolyte than the preceding cells. This phenomenon occurs because the flow path for the electrolyte through the cells closest to the first end plate is the shortest, and the flow path distance increases as the electrolyte moves away from the first end plate. This results in an uneven distribution of electrolyte within the cells. As the number of cells in the electrolyzer stack increases, certain cells at the end of the cell stack no longer receive the same amount of electrolyte as the other cells. This results in “electrolyte starvation” of the cells in the back portion of the electrolyzer stack. In other words, the cells at different locations along the electrolyzer stack receive a progressively decreasing flow of electrolyte in order from the first end plate to the second end plate.

[0008] Inhomogeneous distribution of electrolyte leads to thermal variations and low current efficiency. Furthermore, thermal variations can lead to failure of electrolyser stack components: for example, the most commonly used separator material starts to degrade rapidly when exposed to temperatures above certain critical temperatures. In an electrolyser stack with inhomogeneous electrolyte distribution between cells, the first cells (receiving higher than average electrolyte flow) will be cooled more efficiently, leading to lower cell temperature, higher cell resistance, and thus lower cell efficiency. The high overpotential in these first cells can lead to faster degradation of cell components, such as electrodes. In a cell stack with inhomogeneous electrolyte distribution between cells, the last cells (receiving lower than average KOH flow) cool less efficiently, leading to higher cell temperatures. If this cell temperature exceeds the critical temperature of the separator, the separator can fail before reaching its designed lifetime. Therefore, it is highly desirable to ensure that the distribution of electrolyte in the electrolyser stack is as uniform as possible. Furthermore, in cells with low electrolyte flow rates, the effectiveness of bubble removal is reduced. When bubbles stick to the electrodes, the cell has a high resistance, which in turn negatively impacts the performance of the electrolyser.

[0009] EP4071277A1 discloses a method to address the inhomogeneous flow of electrolyte into the cells of an electrolyser stack by providing a bypass that directs electrolyte flow to one of the flow-split sections, which bypasses another of the flow-split sections that is axially closer to the electrolyte inlet than said one flow-split section. The bypass supplies electrolyte to the cells further away from the inlet and then to the cells closer to the inlet. With said bypass, the pressure drop characteristics over the cells become more balanced or uniform and either better performance can be obtained over a fixed number of cells or the number of cells can be increased without deteriorating performance relative to a conventional electrolyser with fewer cells. The prior art additionally discloses the need to manufacture at least two different structures of cell frames for this arrangement, which increases the cost of the electrolyser. Typically, cell frames are manufactured using injection moulding. To manufacture different structures of cell frames, different injection moulds are required, which increases the cost and complexity of the cell frame manufacturing process. Furthermore, the cell frames proposed in EP4071277A1 have additional channels to incorporate the bypass sections, which are closed when the cell frames are used before the bypass sections. This arrangement can lead to leaks in the electrolyser stack. Furthermore, to accommodate the additional flow and bypass channels, the size of the cell frames needs to be larger, leading to a larger volume of the electrolyser stack, which reduces the volumetric hydrogen production rate of the electrolyser stack. For certain applications, the available space is limited and using the above-mentioned method can make the electrolyser stack less suitable for these applications.

[0010] US11326267B2 discloses a polymer electrolyte membrane (PEM) electrolyzer with a fluid supply unit comprising a first fluid supply path extending at least partially through a first electrochemical cell and at least one second fluid supply path extending at least partially through a second electrochemical cell. The fluid supply unit is designed such that the volumetric flow rates of the fluid through the first and second electrochemical cells are at least substantially the same. To achieve uniform distribution, the fluid supply path must extend from an inlet channel to an outlet channel in each individual cell, and the fluid is distributed to half of the electrochemical cell. Designs disclosed in the prior art involve a single supply channel and a single outlet channel for both the anode and cathode, resulting in gas mixing. The prior art discloses high pressure drops in the channel and low pressure drops in the path. Furthermore, the first and second cells have different pressure drops, which still leads to inefficient distribution of the electrolyte to each cell in the electrolyzer. Moreover, to achieve different pressure drops in each cell, the cell structures need to be different from each other. This design increases the manufacturing cost of the electrolyzer stack. Therefore, this method is usually limited to PEM electrolyzers, and the design used in the prior art is not ideal for use in alkaline electrolyzers.

[0011] US20230155143A1 discloses a fuel cell interconnect comprising a central fuel channel and a peripheral fuel channel disposed on a first side of the interconnect, and a central air channel and a peripheral air channel disposed on a second opposite side of the interconnect. Prior art suggests modifying the cross-sectional area of ​​the central fuel / air channel to be smaller than that of the peripheral fuel / air channel. This arrangement provides a greater fuel mass flow rate to the central portion of the adjacent fuel cell than to the peripheral portion, thereby directing more hydrogen fuel to the region with higher operating temperatures and improving thermal stability. However, the method in the prior art, when applied to alkaline electrolyzers, generates excessive shunt currents (stray currents) through the alkaline electrolyte solution in the electrolyzer stack due to the large channel size, resulting in unacceptably large efficiency losses. The elevated operating temperatures (500°C to 900°C) and the cell design optimized for fuel cell applications are unsuitable for alkaline electrolyzer stacks. Furthermore, in US20120155143A1, the electrolyte is an immobile solid oxide material and is part of the cell structure. In the present invention, the electrolyte is an alkaline medium, which is supplied to each cell through an inlet channel and an inlet path, and removed from each cell through an outlet path and an outlet channel.

[0012] US6554978B1 discloses an electrolyzer stack including a battery frame, which further includes an inlet channel and an inlet path connecting the inlet channel to a central opening. Prior art discloses inlet channel diameters of 1.5 cm to 2.5 cm and inlet path diameters (also considered inlet orifices) of 0.5 mm to 3 mm. However, prior art does not propose solutions for optimizing the distribution of KOH on electrolyzer stacks of different sizes.

[0013] KR20220065541A and KR102324396B1, submitted by the Korea Energy Research Institute, disclose a battery frame used in an electrolyzer stack, which has an electrolysis space at its center. An electrolyte flow path connects multiple supply / discharge conduits to the electrolysis space. KR102324396B1 discloses that the electrolyte flow also includes multiple protrusions to vary the thickness of the flow path. This structure is provided to apply resistance to the electrolyte flowing from the supply conduits to the electrolysis space. Changing the resistance to the electrolyte flow helps reduce the shunt current flowing through the electrolyzer stack. KR20220065541A discloses that the electrolyte flow path includes a flow path reduction unit and an outlet, wherein the width of the flow reduction unit is smaller than the width of the outlet, and the outlet has a conical shape. This design is configured to control the electrolyte flow from the outlet to the electrolyte reaction unit.

[0014] Industrie de Nora SpA, EP4130340A1, discloses an electrolyzer comprising a cathode cell and an anode cell, the cathode cell and anode cell comprising a cathode frame and an anode frame, respectively. Each frame includes a feed channel connecting a feed inlet to a hole in the frame to a feed outlet leading to a central empty space in the cell frame. However, the prior art does not provide an adaptable system for achieving uniform electrolyte dispersion that can be modified based on the length of the electrolyzer stack. Given all the above methods, there is a need for a scalable electrolyzer stack, particularly an alkaline electrolyzer stack, in which uniform electrolyte distribution can be achieved regardless of the cell coverage area and the number of cells in the stack, resulting in higher efficiency and improved stack lifetime. Summary of the Invention

[0015] The purpose of this invention is to achieve a uniform distribution of electrolyte to each cell in an alkaline electrolytic cell stack.

[0016] Another objective of this invention is to ensure a uniform voltage drop across the battery, thereby improving the performance of the electrolyzer stack.

[0017] Another objective of this invention is to reduce stray currents in the electrolytic cell stack channels to ensure high current (Faraday) efficiency of the electrolytic cell stack.

[0018] Furthermore, the purpose of this invention is to maintain the thermal stability of the electrolyzer stack by establishing a uniform temperature distribution and uniform heat dissipation in the cells within the electrolyzer stack.

[0019] The above-mentioned objectives of the present invention can be achieved through the following technical solutions:

[0020] Various embodiments of the present invention disclose an alkaline electrolyzer stack comprising: a first end plate and a second end plate, and a plurality of cells stacked between the first end plate and the second end plate. Each cell includes an anode cell frame and a cathode cell frame, each cell frame further including a central opening, at least one inlet channel transversely through the cell frame, and at least one inlet path slotted in the cell frame for connecting the inlet channel to the central opening. The inlet path includes at least one inlet hole, characterized by a minimum cross-sectional area in the inlet path. The cross-sectional area of ​​the inlet channel in the electrolyzer stack is greater than the sum of the cross-sectional areas of the plurality of inlet holes in the electrolyzer stack by at least a predetermined factor. In order to obtain a uniform distribution on the cells in the electrolyzer stack and maintain the required voltage drop at the inlet hole, the predetermined factor needs to be greater than 1 and less than or equal to 4.

[0021] According to one embodiment of the invention, the surface of the inlet path is formed with protrusions to form an inlet orifice by reducing the width and / or depth of the inlet path.

[0022] According to another embodiment of the invention, the battery frame includes an insert mounted on the inlet path to form an inlet aperture by reducing the depth and / or width of the inlet path. The surface of the inlet path and the inner side of the insert facing the inlet path together define the inlet aperture.

[0023] According to an alternative embodiment of the invention, the insert includes a vacuum feedthrough that, when installed in the inlet path, forms an inlet orifice.

[0024] According to one embodiment of the invention, the thickness of the insert or the size of the vacuum lead wire defines the cross-sectional area of ​​the inlet orifice.

[0025] According to another alternative embodiment of the invention, the inner side of the insert is configured in a dome shape to form a larger cross-sectional area of ​​the hole; alternatively, the protruding portion of the inner side of the insert is configured to form a smaller cross-sectional area of ​​the hole.

[0026] According to one embodiment of the invention, a plurality of inserts of predetermined thickness and / or size for vacuum introduction lines and / or structures are mounted along the electrolyzer stack in a plurality of battery frames to create an inlet orifice having a predetermined cross-sectional area.

[0027] According to one embodiment of the invention, multiple inserts of varying thicknesses and / or sizes of vacuum lead wires and / or structures are mounted along an electrolytic cell stack within multiple cell frames to create a gradient in the cross-sectional area of ​​the holes. The holes at different locations along the electrolytic cell stack have progressively increasing cross-sectional areas from the first end plate to the second end plate.

[0028] According to one embodiment of the invention, the inlet hole is configured to be located anywhere within the inlet path. However, the inlet hole is preferably located closer to the central opening of the battery frame, such that the distance between the hole and the central opening is less than the distance between the inlet channel and the hole.

[0029] According to another embodiment of the invention, the insert is an additional / removable component or an integrated part of the battery frame.

[0030] According to another embodiment of the invention, the inlet path is a single path, wherein the inlet path may alternatively include multiple paths branching from the region near the hole.

[0031] According to a preferred embodiment of the invention, the sum of the cross-sectional areas of the plurality of holes is smaller than the total area of ​​the inlet channel by at least a predetermined coefficient, wherein the predetermined coefficient is 1 to 4, preferably 1.2 to 2.

[0032] According to an embodiment of the invention, the anode battery frame is the same as the cathode battery frame, wherein the anode battery frame is rotated 180 degrees to serve as the cathode battery frame.

[0033] According to one embodiment of the invention, at least the anode or cathode is operated under high pressure, preferably from 1.5 bar to 700 bar, and more preferably from 16 bar to 45 bar.

[0034] According to one embodiment of the invention, an inlet channel through the battery frame extends from the first end plate through the electrolytic cell stack to the second end plate, wherein an alkaline medium enters and exits the electrolytic cell stack through the first end plate.

[0035] These and other aspects of the embodiments described herein will be better understood and appreciated when considered in conjunction with the following description and accompanying drawings. However, it should be understood that while the following description points to preferred embodiments and many specific details therein, it is given by way of illustration and not limitation. Many changes and modifications may be made within the scope of the embodiments of the invention without departing from the spirit of the invention, and the embodiments of the invention encompass all such modifications. Attached Figure Description

[0036] The above-described invention and the specific implementation of the illustrative embodiments below can be better understood when read in conjunction with the accompanying drawings. For the purpose of illustrating the invention, exemplary constructions of embodiments of the invention are shown in the drawings, with reference to the following diagrams, wherein: Figure 1 is a schematic diagram of a battery frame according to an embodiment of the present invention. Figure 1a This is a front view of the battery frame. Figure 1b This is a cross-sectional view of the battery frame inlet side.

[0037] Figure 2 is a schematic diagram of a battery frame according to another embodiment of the present invention. Figure 2a This is a front view of the battery frame. Figures 2b to 2e This is a cross-sectional view of the battery frame inlet side, showing the structure of the insert according to different embodiments of the present invention.

[0038] Figure 3 This is a schematic side view of an electrolytic cell stack according to a preferred embodiment of the present invention.

[0039] Figure 4 This is a schematic diagram of a model system for computational fluid dynamics (CFD) simulation of inlet path and inlet orifice according to a preferred embodiment of the present invention.

[0040] Figure 5 This illustrates a preferred embodiment of the invention, from Figure 4 The pressure distribution curve along the inlet path obtained from the CFD simulation of the model system.

[0041] Figure 6 This is a preferred embodiment of the invention for CFD simulation. Figure 3 A schematic diagram of the model system of the electrolytic cell stack.

[0042] Figure 7 This illustrates a preferred embodiment of the invention. Figure 6 The curves showing the electrolyte flow velocity distribution in the electrolyzer stack for different inlet channel areas obtained from the CFD simulation of the model system.

[0043] Figure 8 This illustrates a preferred embodiment of the invention from Figure 6 The curves showing the electrolyte flow velocity distribution in the electrolyzer stack for different inlet orifice areas obtained from the CFD simulation of the model system.

[0044] Figure 9 This illustrates a preferred embodiment of the invention from Figure 6 The curves of electrolyte flow velocity distribution in the electrolyzer stack with different inlet flow velocities obtained from the CFD simulation of the model system.

[0045] Figure 10 It is a graph showing the electrolyte flow rate of each cell in an electrolytic cell stack of 17 cells according to an embodiment of the present invention, which is plotted as a function of predetermined coefficients.

[0046] Figure 11 This is a graph showing the voltage drop of each cell in a stack of 17 cells as a function of predetermined coefficients according to an embodiment of the present invention.

[0047] Figure 12 It is a graph showing the electrolyte flow rate of each cell in an electrolyzer stack of 90 cells according to an embodiment of the present invention, which is plotted as a function of predetermined coefficients.

[0048] However, it should be understood that although the following description points out preferred embodiments and many specific details therein, these descriptions are given by way of illustration and not by way of limitation. Many changes and modifications can be made within the scope of the embodiments of the invention without departing from the spirit of the invention, and the embodiments of the invention include all such modifications. Detailed Implementation

[0049] In the following detailed description, reference is made to the accompanying drawings, which form part of this specification, illustrating specific embodiments that may be practiced. These embodiments have been described in sufficient detail to enable those skilled in the art to practice them, and it should be understood that logical, mechanical, and other changes may be made without departing from the scope of these embodiments. Therefore, the following detailed description should not be considered limiting.

[0050] Various embodiments of the present invention disclose an electrolyzer stack for electrochemically splitting water to produce hydrogen and oxygen, particularly an alkaline electrolyzer stack. The electrolyzer stack includes a first end plate, a second end plate, and a plurality of cells stacked between the end plates. The end plates serve as negative and positive terminals, respectively, to which DC power is supplied. Each cell in the electrolyzer stack consists of multiple cell components, including, but not limited to, at least two electrodes (one as an anode and the other as a cathode) placed on both sides of a membrane, a bipolar plate placed between the cells, and at least two spacers placed beside the electrodes on both sides of the electrode-membrane-electrode assembly. The positioning of the electrodes near the cell membrane is achieved by applying pressure to the spacers.

[0051] According to embodiments of the present invention, the electrode can be formed into a perforated metal plate, woven metal mesh, expanded metal plate, porous metal foam, porous metal felt, etc., with a porous surface. The electrode needs to be corrosion-resistant in an alkaline environment for a long time and have good conductivity and high electrochemical activity.

[0052] In the context of this invention, the term "membrane" is used interchangeably with the terms "separator" and "diaphragm," referring to a porous or non-porous electrolytic cell stack component comprising a polymer, used to separate the anode from the cathode, through which hydroxide ions are transported. This membrane needs to have high heat resistance, chemical resistance, and electrochemical resistance. Zirconia-polysulfonic acid membranes are preferred; however, membranes with different configurations are also suitable, the base material of which is an inorganic oxide supported by a polymer fabric. Materials considered for the membrane include, but are not limited to, oxide ceramic materials, sulfonated polymers, perfluorinated sulfonated polymers, and glass fiber reinforced polyphenylene sulfide or polysulfone having an inorganic oxide component.

[0053] The bipolar plates and gaskets are primarily made of nickel or nickel-coated steel. The gaskets need to be designed to have spring-like properties so that the electrodes can be gently pressed onto the membrane.

[0054] The battery frame includes a central opening that accommodates or receives other battery components, such as gaskets, electrodes, bipolar plates, and membranes. The electrolyzer stack assembly is sealed together by gaskets. Each cell includes two battery frames: an anode battery frame for the anode side and a cathode battery frame for the cathode side. The anode battery frame includes at least one inlet path connecting the inlet channel to the central opening for supplying a liquid electrolyte solution into the anode chamber. The anode battery frame also includes at least one outlet path connecting the central opening to an outlet channel for receiving a mixture of liquid electrolyte and generated oxygen from the anode chamber. Additional inlet channels may be present in the anode battery frame for supplying a liquid electrolyte solution through the anode battery frame to the inlet channel of an adjacent (cathode) battery frame. The anode battery frame also includes at least one additional outlet channel for conveying a mixture of liquid electrolyte solution and generated hydrogen to the outlet channel of an adjacent (cathode) battery frame. According to one embodiment of the invention, the electrolyte is supplied to the battery via a common inlet channel, i.e., there are no separate inlet channels for the anolyte and catholyte in the anode cell frame. The cathode cell frame includes at least one inlet path connecting the inlet channel to a central opening for supplying the liquid electrolyte solution to the cathode chamber of the battery. The cathode cell frame also includes at least one outlet path connecting the central opening to an outlet channel for receiving a mixture of liquid electrolyte and generated hydrogen from the cathode chamber. Additional inlet channels may be present in the cathode cell frame for supplying the liquid electrolyte solution through the cathode cell frame to the inlet channels of adjacent (anode) cell frames. The cathode cell frame also includes at least one additional outlet channel for conveying a mixture of liquid electrolyte solution and generated oxygen to the outlet channel of adjacent (anode) cell frames. According to one embodiment of the invention, the electrolyte is supplied to the electrolytic cell via a common inlet channel, i.e., there are no separate inlet channels for the anolyte and catholyte in the cathode cell frame.

[0055] According to one embodiment of the invention, the anode battery frame is identical to the cathode battery frame, and the anode battery frame is rotated 180 degrees to serve as the cathode battery frame. The end plates and batteries are pressed and clamped together using tie rods and bolts. The clamping provides sealing pressure and proper pressure distribution between the different battery components. The clamping also ensures electrical connection between the bipolar plates.

[0056] The battery frame is primarily made of plastics, including but not limited to polysulfone, polyetheretherketone, acetal copolymers, polyethersulfone, polyphenylene, polyphenylene sulfide, polyphenylene oxide, polybenzimidazole, polyethyleneimine, polyamide-imides, and other plastic polymers. The battery frame material may contain fillers such as fibers, polyphenylene oxide, and other suitable materials to provide additional strength and temperature resistance. However, the battery frame can also be made of metals, ceramics, and other materials, as well as combinations thereof, possessing appropriate mechanical strength, heat resistance, electrical insulation properties, and chemical resistance to withstand alkaline environments.

[0057] like Figure 1a As shown, the battery frame (100) includes a central opening (101) configured to accommodate battery components. The central opening (101) serves as a container for containing the electrolyte required for the electrolysis process. A plurality of channels (102a, 102b, 104a, 104b) passing through the battery frame (100) include at least one inlet channel (102a) for transporting the electrolyte within the electrolytic cell stack. To ensure fluid communication between the inlet channel (102a) and the central opening (101), at least one inlet path (103) is provided. Electrolyte from the inlet channel (102a) is conveyed from one end to the inlet path (103) and discharged from the other end of the inlet path (103) to the central opening (101). The channels also include at least one outlet channel (104a) arranged on the opposite side of the inlet channel (102a). The outlet channel (104a) is connected to the central opening (101) via an outlet path (105), which is configured to convey the humidified gas generated during the electrolysis process from the corresponding electrolytic cell to the outlet channel (104a). The inlet channel (102a) and the outlet channel (104a) are positioned to ensure that the gas generated in the electrolytic cell by the electrolysis process rises and is removed from the electrolytic cell in the electrolyte flow through the outlet channel (104a).

[0058] Figure 1b A cross-sectional view of the inlet side of a battery frame (100) according to an embodiment of the present invention is shown. The inlet path (103) includes an inlet hole (106), characterized by having a minimum cross-sectional area compared to the regions along the front and rear of the inlet path (103). Protrusions on the surface of the inlet path (103) are made to reduce the width of the inlet path (103) (e.g., Figure 1a (as shown) or depth (as shown) Figure 1b(as shown) or a combination of both, thus forming an inlet orifice (106). The inlet orifice (106) can be positioned anywhere within the inlet path (103) as needed to achieve specific fluid flow control characteristics. The inlet orifice (106) is preferably located closer to the central opening (101) of the cell frame (100). The large cross-sectional area of ​​the inlet channel (102a) and the inlet path (103) ensures a smaller electrolyte pressure drop before the inlet orifice (106) compared to the pressure drop on either side of the inlet orifice (106). This mechanism applies to each cell in the electrolyzer stack, thereby ensuring that each individual cell, regardless of its position in the electrolyzer stack, receives a controlled and consistent amount of liquid electrolyte. Furthermore, it ensures that the electrolyte is efficiently delivered throughout the electrolyzer stack, even to the cell furthest from the first endplate.

[0059] Figure 2a A battery frame according to an embodiment of the present invention is depicted. The inlet path (103) further includes an insert (107) placed on the inlet path (103) to form an inlet hole (106). The insert (107) is a plate of predetermined thickness, inserted into a portion of the inlet path (103) such that the inner side of the insert (107) forms a cap on the inlet path (103). The insert (107) is inserted and secured within the inlet path (103), resulting in a defined gap between the insert (107) and the inlet path (103) serving as the inlet hole (106). The inlet hole (106) is defined by the thickness of the insert (107) and the depth of the inlet path (103). Figure 2b As shown, one side of the inlet hole (106) is formed by the inlet path (103), and the other side is formed by the inner side of the insert (107) facing the inlet path. Alternatively, in a modified version of the invention, the insert (107) includes a vacuum introduction line that forms the inlet hole (106) when the insert (107) is fully pushed into the inlet path (103), as... Figure 2c As shown. The insert (107) is an additional / removable part made of any metal or plastic or the same material as the battery frame (100), which can be clipped onto the inlet path (103). However, the insert (107) can also be an integrated part of the battery frame (100) as an extension onto the inlet path (103).

[0060] An insert (107) with a desired thickness and / or desired size for the vacuum inlet wire defines the cross-sectional area of ​​the inlet aperture (106). Alternatively, the structure of the inner side of the insert (107) is modified to achieve the desired cross-sectional area of ​​the inlet aperture (106). Figure 2d As shown, the inner side of the insert (107) is dome-shaped to increase the cross-sectional area of ​​the inlet hole (106). As Figure 2eAs shown, the inner side of the insert (107) includes a portion that protrudes in the inlet path (103) to reduce the cross-sectional area of ​​the inlet hole (106).

[0061] An insert (107) can be placed anywhere along the inlet path (103) to form an inlet hole (106), preferably placed closer to the central opening (101) of the battery frame (100). However, according to another embodiment of the invention, the battery frame (100) includes an additional component, such as an annular structure, mounted on the inner surface of the central opening (101). This additional component includes the inlet hole (106) and is positioned such that the inlet hole (106) is aligned at the exit of the inlet path (103).

[0062] Figure 3 An electrolytic cell stack according to an embodiment of the invention is depicted. Inlet channels (102a) and outlet channels (104a) are holes passing through a battery frame (100); when the battery frames (100) are studded together, the through holes in the battery frames form inlet channels (102a) and outlet channels (104a) for conveying electrolyte and humidifying gas. Paths are slotted in the battery frames (100) for transferring electrolyte to the corresponding cells and collecting the mixture of liquid electrolyte and product gas in the outlet channel (104a).

[0063] refer to Figure 3 Electrolyte is supplied to inlet channel 102a at the first end plate (108). Inlet channel (102a) extends from the first end plate (108), through the electrolytic cell stack, and to the cell next to the second end plate (109). Electrolyte reaches each individual cell via a path extending from the channel. Humidifying gas generated in the cell is discharged through outlet path (105) and exits the electrolytic cell stack through outlet channel (104a), returning to the first end plate (108). However, the invention is applicable to implementations in electrolytic cell stacks characterized by varying channel configurations. This includes configurations where the inlet channel is located at the first end plate and the outlet channel at the second end plate, and configurations where the inlet channel is located at both end plates and the outlet channel is located at the intermediate plate of the electrolytic cell stack.

[0064] To achieve uniform electrolyte distribution in each cell at a given time, the pressure in the inlet path (103) of all cells in the electrolyzer stack must be as equal as possible. This is achieved when the cross-sectional area of ​​the inlet channel (102a) in the electrolyzer stack is greater than the sum of the cross-sectional areas of the multiple inlet holes (104) in the electrolyzer stack. The sum of the cross-sectional areas of the multiple inlet holes is calculated by adding the cross-sectional areas of all inlet holes (106) of the inlet path (103) connected to the inlet channel (102a). The high pressure drop within the inlet path (103) plays a crucial role in maintaining the controlled flow of electrolyte from the inlet channel (102a) to the individual cells. The pressure difference established by this design ensures that the electrolyte supplied to the inlet channel (102a) is uniformly distributed to the successive cells.

[0065] The sum of the cross-sectional areas of the multiple holes is smaller than the total area of ​​the inlet channel (102a) by at least a predetermined factor. The predetermined factor ranges from 1 to 4, and is preferably from 1.2 to 2.

[0066] To achieve uniform distribution of electrolyte among the cells in the electrolytic cell stack, the conditions in equation (1) need to be met.

[0067] 1 A T IN ≤ 4 A T A T = A PH1 + A PH2 + A PH3 +……+ A PHn (1) A IN A is the cross-sectional area of ​​the entrance channel (102a). T A is the cross-sectional area of ​​multiple inlet holes. PH1 A is the cross-sectional area of ​​the inlet hole (106) of the first path's inlet path. PH2 A is the cross-sectional area of ​​the inlet hole (106) of the second path's inlet path. PHn It is the cross-sectional area of ​​the inlet hole (106) of the inlet path of the nth path, where n is the number of inlet paths connected to the inlet channel (102a).

[0068] For the predetermined inlet channel (102a) cross-sectional area (A) IN ​Given a predetermined number of cells and considering the use of the same cell frame (100) in the electrolyzer stack, different configurations of inlet holes (106) can be used to ensure uniform distribution of the electrolyte. In one configuration, all inserts (107) in the electrolyzer stack have a predetermined thickness to create inlet holes (106) with a predetermined cross-sectional area. In another configuration, the inserts (107) in the electrolyzer stack have varying thicknesses to create a gradient in the cross-sectional area of ​​the holes. The inserts (107) used in the first cell frame are the thickest, and inserts (107) with continuously decreasing thickness are used along the electrolyzer stack. Thus, the holes at different locations along the electrolyzer stack (i.e., from the first end plate to the second end plate) have gradually increasing cross-sectional areas. This configuration ensures that the earlier cells receive a controlled amount of electrolyte, and that the electrolyte in the inlet channel (102a) reaches the cell furthest from the first end plate.

[0069] The cross-sectional area of ​​the channel / path is measured based on the shape of the channel / path and in a plane perpendicular to the electrolyte flow direction. The cross-sectional area of ​​the inlet channel (102a) varies along the length of the electrolyzer stack because the gasket can extend inward into the channel when the electrolyzer stack is compressed together. The cross-sectional area of ​​the inlet channel (102a) used for calculation is the average cross-sectional area of ​​the inlet channel (102a) over the length of the electrolyzer stack. When closer to the central opening (101), the inlet path (103) can have a single path that branches into multiple paths after the inlet orifice.

[0070] Figure 5 Depicting the example shown from such Figure 4The graph shows the pressure distribution along the inlet path obtained from a CFD simulation of the model system (400). The model system (400) includes an inlet channel (401) and an inlet path (402) with an inlet orifice (403), wherein the cross-sectional area of ​​the inlet path (402) is reduced to half at the inlet orifice (403). The simulation was performed using the finite element method with typical geometric parameters found in electrolytic cells of the type described above. Due to the high Reynolds number (over 2000) characteristic of the model system (400), a turbulent (k-ε) flow model was used to simulate the flow of water + KOH (30%) through the system (400). The inlet mass flow rate was set to 0.015 kg / s, and the outlet boundary condition was set to 0 bar pressure. The simulation results are a static pressure field in which the electrolyte pressure was measured at different locations along the inlet path (402), starting near the inlet channel (401) and continuing until near the outlet of the inlet path (402). In the model system (400), the inlet orifice (403) is located near the central opening approximately 10 cm from a reference point. The intersection of the inlet channel (401) and the inlet path (402) is considered the reference point, from which points along the inlet path (402) are measured to estimate the corresponding pressure. The figure shows a sudden drop in electrolytic hydraulic pressure 10 mm from the reference point, which is the location of the inlet orifice (403).

[0071] Figure 6A model system is shown for computational fluid dynamics (CFD) simulations to study the relationship between an inlet channel and multiple inlet paths. The model system (500) includes an inlet channel (501) and an outlet channel (506) arranged parallel to each other at a distance along the x-direction. At the upstream end (low x-value), the inlet channel (501) connects to an electrolyte source; at the downstream end (high x-value), the inlet channel terminates. At the downstream end, the outlet channel (506) connects to an electrolyte sink; at the upstream end, the outlet channel terminates. The model system (500) also includes 17 inlet paths (502), each inlet path (502) connecting one end to the inlet channel (501) and the other end to an intermediate channel (504). Inlet orifices (503) are located at the inlet paths (502), closer to the intermediate paths. Outlet paths (505) connect one end to the intermediate channel and the other end to the outlet channel (506). Electrolyte originating from inlet channel (501) is injected across the entire width of inlet channel (501) in a direction perpendicular to the x-axis. Electrolyte travels along the y-axis through inlet path (502) and through inlet orifice (503) into intermediate path (504). Electrolyte from intermediate path (504) is collected and subsequently delivered to the tank via outlet path and outlet channel. CFD simulations are performed to observe / understand the distribution of electrolyte in different inlet paths (502) by measuring the flow rate at the inlet orifice (503) end of inlet path (502).

[0072] like Figure 7 As shown, the figure plots the flow velocity measured at the inlet orifice (503) as a function of the number of paths (502) (path 1 refers to the path closest to the first end plate, and path 17 refers to the path furthest from the first end plate). As mentioned above, in order to have equal flow velocities in all inlet paths (502), the 17 inlet channels (501) (A) in the electrolytic cell stack... IN The cross-sectional area of ​​(503) must be larger than the cross-sectional area of ​​multiple inlet holes (A) in the electrolytic cell stack. T The sum of the cross-sectional areas of the inlet channel (501) and outlet channel. To observe the effect of the above relationship, the diameters of the inlet channel (501) and outlet channel were varied as shown in Table 1, while all other conditions remained constant. Inlet hole (503) (A PH The cross-sectional area of ​​is the same in all paths, which is 0.1.169E [cm]. 2 ]. 17 inlet holes (503) (A T The total cross-sectional area of ​​) is 2.873 [cm 2 ].

[0073] Table 1: Diameter and cross-sectional area of ​​the inlet channel considered for simulation.

[0074]

[0075] Within the framework of the model system (500), for various configurations of the inlet channel, the flow velocity at the inlet orifice (503) was systematically measured, as detailed in Table 1, and... Figure 7 The diagram shows that in Case 1, the cross-sectional area of ​​the inlet channel (501) is smaller than the sum of the cross-sectional areas of the multiple inlet holes (503), resulting in non-uniform flow velocity at the inlet holes (503). Subsequently, a significant improvement was observed as the cross-sectional area of ​​the inlet channel (501) increased. In Cases 4 and 5, the cross-sectional area of ​​the inlet channel (501) is significantly larger than the sum of the cross-sectional areas of the multiple inlet holes (503), achieving uniform distribution of the electrolyte within the path. Furthermore, when the cross-sectional area of ​​the inlet channel (501) is kept within the range of 1 to 4 times larger than the sum of the cross-sectional areas of the inlet holes (503), a uniform flow velocity is consistently observed in the inlet path (502).

[0076] For each case in Table 1, the flow velocity at the inlet orifice (503) of the model system (500) with different inlet channels was measured, such as Figure 7The graphs shown indicate that in case 1, the flow velocity at the inlet orifice (503) is non-uniform, where the cross-sectional area of ​​the inlet channel (501) is much smaller than the sum of the cross-sectional areas of the multiple inlet orifices (503). Specifically, the electrolyte flow velocity through path 1 is 0.026 kg / s, while the corresponding flow velocity through path 17 is 0.016 kg / s. For case 1, the ratio of the electrolyte flow velocity through path 1 to that through path 17 is 1.625, which is far from uniform. The situation improves as the cross-sectional area of ​​the inlet channel (501) increases. In case 2, the electrolyte flow velocity through path 1 is 0.022 kg / s, while the corresponding flow velocity through path 17 is 0.017 kg / s. For case 2, the ratio of the electrolyte flow velocity through path 1 to that through path 17 is 1.29, which is also non-uniform. In case 3, the electrolyte flow rate through path 1 is 0.021 kg / s, while the corresponding flow rate through path 17 is 0.017 kg / s. In case 3, the ratio of the electrolyte flow rate through path 1 to that through path 17 is 1.23. With a further increase in the cross-sectional area of ​​the inlet channel (501), a uniform distribution of the electrolyte can be achieved. In case 4, the electrolyte flow rate through path 1 is 0.0195 kg / s, while the corresponding flow rate through path 17 is 0.0186 kg / s. In case 4, the ratio of the electrolyte flow rate through path 1 to that through path 17 is 1.048. In other words, the flow rate difference between path 1 and path 17 is less than 20% of the electrolyte flow rate, which is considered uniform in the context of this invention. For case 5, the electrolyte flow rate through path 1 is 0.0190 kg / s, while the corresponding flow rate through path 17 is 0.0186 kg / s. For case 5, the ratio of the electrolyte flow rate through path 1 to that through path 17 is 1.022. The electrolyte flow rate distribution in case 5 is considered uniform. A uniform flow rate is observed in the inlet path (502) when the cross-sectional area of ​​the inlet channel (501) is greater than 1.095 times the sum of the cross-sectional areas of the inlet orifices (503).

[0077] Figure 8 The flow velocity at the inlet orifice (503) measured using the model system (500) is depicted, with the inlet channel (501) kept constant, i.e., inlet channel (501) diameter: 18 mm, cross-sectional area: 2.534 cm². 2The cross-sectional areas of the multiple inlet orifices (503) vary in three cases, as shown in Table 2. As can be seen from the figures, in case 6, where the cross-sectional area of ​​the inlet channel (501) is less than the sum of the areas of the 17 inlet orifices (503), a significant deviation in the flow velocity occurs in the channel. Specifically, the electrolyte flow velocity through path 1 is 0.024 kg / s, while the corresponding flow velocity through path 17 is 0.016 kg / s. For case 6, the ratio of the electrolyte flow velocity through path 1 to that through path 17 is 1.5, which is non-uniform. As shown in cases 7 and 8, the flow velocity distribution improves as the cross-sectional area of ​​the inlet orifice (503) decreases. Specifically, for case 7, the electrolyte flow velocity through path 1 is 0.022 kg / s, while the corresponding flow velocity through path 17 is 0.017 kg / s. For case 7, the ratio of the electrolyte flow rate through path 1 to that through path 17 is 1.29, which is non-uniform. For case 8, the electrolyte flow rate through path 1 is 0.0207 kg / s, while the corresponding flow rate through path 17 is 0.0176 kg / s. For case 8, the ratio of the electrolyte flow rate through path 1 to that through path 17 is 1.18. In other words, the flow rate difference between path 1 and path 17 is less than 20% of the electrolyte flow rate, which is considered uniform in the context of this invention. To achieve uniform flow rate with minimal deviation in all channels, the area of ​​the inlet orifice (503) is made smaller, such that A IN ≥1.18A T .

[0078] Table 2: Cross-sectional area of ​​the inlet orifice considered for simulation.

[0079]

[0080] Figure 9 The figure shows the relationship between the electrolyte flow rate supplied to the inlet channel (501) and the electrolyte flow rate at the inlet orifice (503). A model system (500) was considered for the flow rate study. The figure shows that the lower flow rate at the inlet channel (501) results in better uniformity of electrolyte distribution along the battery. As the flow rate at the inlet channel (501) increases, we can observe an increase in the deviation between the flow rates at the inlet orifice (503) of the first inlet path and the inlet orifice (503) of the last inlet path.

[0081] The dimensions of an electrolytic cell stack with a maximum number of cells, which can be used to ensure uniform electrolyte distribution, can be determined based on the parameters of the inlet channel and inlet orifice. For a predetermined A IN and A PH The maximum number of cells in an electrolytic cell stack can be derived as follows: Where N is the cross-sectional area of ​​the predetermined entrance channel (A)IN ) and the cross-sectional area of ​​a single inlet hole (A PH The maximum number of cells in an electrolytic cell stack.

[0082] Therefore, in order to increase the number of cells in the electrolyzer stack, the cross-sectional area of ​​the inlet channel or the cross-sectional area of ​​the inlet path, or a combination thereof, is increased accordingly. Similarly, given a predetermined electrolyzer stack size that includes the necessary number of cells, the design and arrangement of the cell frames and / or inserts are customized to establish the dimensions of the inlet channels and inlet orifices according to the specifications required in Equation (1). This configuration ensures a uniform distribution of the electrolyte throughout the electrolyzer stack.

[0083] exist Figure 10 Another simulation of an electrolyzer stack with 17 cells is shown to illustrate the electrolyte flow rate (in kg / s) through each cell as a function of predetermined coefficients. The inlet channel remains constant with a diameter of 18 mm and a cross-sectional area A. IN It is 254.34 mm. 2 The size of the inlet orifice was varied to obtain a series of simulations with different predetermined coefficients. A total electrolyte flow rate of 0.35 kg / s was applied to the electrolyzer stack.

[0084] In one case, the predetermined coefficient A IN / A T It is 0.71, the cross-sectional area of ​​the inlet orifice is A. PH It is 21.10 mm 2 Therefore, the area A of the 17 inlet holes T The total is 358 mm 2 The electrolyte flow rate through path 1 is 0.0231 kg / s, while the corresponding flow rate through path 17 is 0.0154 kg / s. Therefore, the ratio of the electrolyte flow rate through path 1 to that through path 17 is 1.50. The electrolyte distribution is highly uneven, with cells closer to the electrolyzer inlet receiving significantly more electrolyte than those furthest from the inlet.

[0085] In the second case, the pre-determined coefficient is 0.98, A PH It is 15.21 mm 2 A T It is 258.57 mm 2 The electrolyte flow rate through path 1 is 0.0212 kg / s, while the corresponding flow rate through path 17 is 0.0166 kg / s. The electrolyte flow rate ratio of path 1 to path 17 is 1.28. In this case, we observe that compared to the previous case, the electrolyte distribution received by the first cell is more uniform, but still relatively uneven, with the cells closer to the electrolyzer inlet receiving significantly more electrolyte than the cells furthest from the inlet.

[0086] In the third case, the pre-determined coefficient is 1.36, A PH It is 10.98 mm 2 A T It is 186.75 mm 2 The electrolyte flow rate through path 1 is 0.0196 kg / s, while the corresponding flow rate through path 17 is 0.0173 kg / s. The electrolyte flow rate ratio of path 1 to path 17 is 1.13. In this case, we see that the electrolyte received by the first cell is almost equal to that received by the 17th cell.

[0087] As the predetermined coefficient further increases, the electrolyte distribution becomes more uniform. At a predetermined coefficient of 1.97, A PH It is 7.60 mm 2 And A T It is 129.29 mm. 2 The electrolyte flow rate through path 1 is 0.0187 kg / s, while the corresponding flow rate through path 17 is 0.0176 kg / s, thus establishing a uniform distribution of electrolyte in all 17 cells.

[0088] When A PH =4.23 mm 2 and A T = 71.91 mm 2 At that time, the predetermined coefficient was 3.54. The flow rate through all 17 cells was 0.018 kg / s, and the electrolyte supplied in all cells was substantially equal (the ratio of the flow rate to path 1 to the flow rate to path 17 was 1.02).

[0089] In A PH =3.38 mm 2 and A T = 57.46 mm 2 In this case, the predetermined coefficient is 4.43. The flow rate through all 17 cells is 0.018 kg / s, and the electrolyte supplied in all cells is substantially equal (the ratio of the flow rate to path 1 to the flow rate to path 17 is 1.01).

[0090] When A PH =2.54 mm 2 and A T = 41.10 mm 2 At that time, the predetermined coefficient was 5.90. The flow rate through all 17 cells was 0.018 kg / s, and the electrolyte supplied in all cells was substantially equal (the ratio of the flow rate to path 1 to the flow rate to path 17 was 1.007).

[0091] Therefore, from Figure 10 It can be observed that when the cross-sectional area of ​​the inlet channels is less than the sum of the cross-sectional areas of the inlet orifices, the electrolyte distribution in different cells is uneven. When the cross-sectional area of ​​the inlet channels is greater than the sum of the cross-sectional areas of the inlet orifices, the uniform distribution of the electrolyte improves. As the predetermined coefficient increases to greater than 1.0, the distribution becomes increasingly uniform (i.e., the variation between the first and last cells is less than 20%). Further increases in the predetermined coefficient further improve flow uniformity, but this improvement limits further technological advantages.

[0092] Increasing the pre-determined coefficient indefinitely is not beneficial: when the pre-determined coefficient increases to greater than 4, the pressure drop in the inlet orifice increases significantly. (Reference) Figure 11 It can be noted that for a predetermined coefficient between 0.71 and 2, the pressure drop is minimal (below 100 mbar). When the predetermined coefficient is greater than 2, the pressure drop begins to increase sharply. When the predetermined coefficient is 3.54, the pressure drop at the inlet orifice is 293 mbar, and when the predetermined coefficient is 4.43, the pressure drop is 503 mbar. As the predetermined coefficient increases to 5.90, the pressure drop doubles to 1016 mbar.

[0093] Excessive pressure drop is undesirable because pumping the KOH electrolyte into the electrolyzer stack requires more energy. Ideally, the pressure drop should be high enough to ensure uniform distribution of KOH among the cells in the electrolyzer stack, but not so high as to significantly reduce the overall system efficiency. Therefore, simulations and graphs show that if the pre-determined coefficient is less than or equal to 1, the KOH distribution becomes uneven. If the pre-determined coefficient is greater than 4, the pressure drop increases significantly, requiring a more powerful and energy-intensive KOH pump.

[0094] To support the above observation, Figure 12 The diagrams depict a simulation of an electrolyzer stack with 90 cells. CFD simulations were performed to observe the electrolyte distribution in larger electrolyzer stacks with a greater number of cells. The sizes of the inlet channels and inlet orifices were varied to obtain simulations with a range of different predetermined coefficients, as shown in Table 3.

[0095] Table 3: Cross-sectional areas of the inlet channel and inlet orifice considered for simulation.

[0096]

[0097] When the predetermined coefficient A IN / A T When the value is 0.71, the cross-sectional area A of the entrance channel is... IN It is 254.34 mm. 2 The cross-sectional area of ​​the inlet hole is A PH 16.9 mm 2 The total area of ​​the 90 inlet holes, AT 1521 mm 2 The electrolyte distribution is highly uneven, with cells closer to the inlet of the electrolyzer receiving significantly more electrolyte than those furthest from the inlet. Specifically, when a total electrolyte flow rate of 1.5 kg / s is applied to the electrolyzer stack, the electrolyte flow rate through path 1 is 0.070 kg / s, while the corresponding flow rate through path 90 is 0.002 kg / s. Therefore, the ratio of the electrolyte flow rate through path 1 to that through path 90 is 35, which is highly uneven. Many cells in the electrolyzer stack with the aforementioned predetermined coefficients will exhibit KOH deficiency, and the efficiency and performance of the electrolyzer stack will be very low.

[0098] In case 10, where the predetermined coefficient is 0.33, A IN It is 254.34 mm 2 A PH It is 8.45 mm 2 A T It is 760.5mm 2 The electrolyte flow rate through path 1 is 0.040 kg / s, while the corresponding flow rate through path 90 is 0.0055 kg / s. The ratio of the electrolyte flow rate through path 1 to that through path 90 is 7.3. The electrolyte distribution is significantly better than in the previous case, but the electrolyte is still not uniform in different cells of the electrolytic cell stack.

[0099] When the predetermined coefficient is 1.29, a uniform electrolyte distribution is observed, where A IN 490.62 mm 2 A PH It is 4.23mm 2 A T It is 380.7 mm. 2 The electrolyte flow rate through path 1 is 0.016 kg / s, and the corresponding flow rate through path 90 is 0.013 kg / s, which are approximately equal.

[0100] The foregoing description of the specific implementation scheme will so fully reveal the general nature of the implementation scheme herein that others can readily modify and / or adapt such specific implementation scheme for various applications by applying present knowledge without departing from the general conception. Therefore, such adaptations and modifications should and are intended to be understood within the meaning and scope of equivalents of the disclosed implementation scheme.

[0101] It should be understood that the wording or terminology used herein is for descriptive purposes and not for limitation. Therefore, although embodiments thereof have been described in accordance with preferred embodiments, those skilled in the art will recognize that modifications may be made to embodiments thereof within the spirit and scope of the appended claims.

[0102] Although the embodiments described herein are based on various specific implementations, it will be apparent to those skilled in the art that the invention can be practiced with modifications. However, all such modifications are considered to be within the scope of the claims.

[0103] It should also be understood that the following claims are intended to cover all general and specific features of the embodiments described herein, as well as all statements regarding the scope of the embodiments, which, in terms of language, may fall between them.

Claims

1. A water electrolyzer using alkaline media, comprising: a first end plate and a second end plate and a plurality of cells stacked between the first end plate and the second end plate; wherein each cell comprises an anode cell frame and a cathode cell frame; wherein each cell frame further comprises: a central opening, at least one inlet channel passing through the cell frame, and at least one inlet path slotted in the cell frame for connecting the inlet channel to the central opening; wherein the inlet path comprises at least one inlet hole characterized by a minimum cross-sectional area in the inlet path; and wherein a cross-sectional area of the inlet channel in the electrolyzer stack is at least a predetermined factor larger than a sum of cross-sectional areas of a plurality of the inlet holes in the electrolyzer stack, wherein the predetermined factor is larger than 1 and less than or equal to 4.

2. The electrolyzer stack of claim 1, wherein a surface of the inlet path constitutes a protrusion to form the inlet hole by reducing a width and / or depth of the inlet path.

3. The electrolyzer stack of claim 1, wherein the cell frame comprises an insert mounted on the inlet path to form the inlet hole by reducing a depth and / or width of the inlet path.

4. The electrolyzer stack of claim 3, wherein the surface of the inlet path and an inner side of the insert facing the inlet path combine to define the inlet hole.

5. The electrolyzer stack of claim 3, wherein the insert comprises a vacuum lead that forms the inlet hole when mounted in the inlet path.

6. The electrolyzer of claim 4, wherein an inner side of the insert is configured in a dome shape to constitute a larger cross-sectional area of the hole; alternatively, a protruding portion of the inner side of the insert is configured to constitute a smaller cross-sectional area of the hole.

7. The electrolyzer stack of claims 3 to 6, wherein the vacuum lead and / or the plurality of inserts of varying thickness and / or dimensions are mounted in the plurality of cell frames along the electrolyzer stack to create a gradient in the cross-sectional area of the hole, the hole at different locations along the electrolyzer stack having a cross-sectional area that gradually increases in sequence from the first end plate towards the second end plate.

8. The electrolyzer stack of any of the preceding claims, wherein the inlet hole is positioned such that a distance between the hole and the central opening is less than a distance between the inlet channel and the hole.

9. The electrolyzer stack of claim 1, wherein the inlet path is a single path, wherein the inlet path alternatively comprises a plurality of paths branching at the hole.

10. The electrolyzer stack of any of the preceding claims, wherein the predetermined factor is preferably 1.2 to 2.

11. The electrolyzer stack of any of the preceding claims, wherein the anode cell frame is identical to the cathode cell frame, wherein the anode cell frame is rotated 180 degrees to serve as the cathode cell frame.

12. The electrolyzer stack of any of the preceding claims, wherein the electrolyzer stack is configured for at least the anode or the cathode to operate at high pressure, the high pressure being 1.5 bar to 700 bar, preferably 16 bar to 45 bar.

13. The electrolyzer stack of claim 1, wherein the electrolyzer stack is configured for the alkaline medium to enter and exit the electrolyzer stack through the first end plate.

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