Low-capacity high-voltage electrolysis device

Abstract

The present invention provides a small high-voltage electrolyzer for generating hydrogen and oxygen, the small high-voltage electrolyzer comprising: one or more cells each comprising a plurality of high-voltage electrolysis cells wherein the electrolysis cells of the respective cells are electrically connected in series; and a central electrolyte header functionally connected to each of the electrolytic cells for supplying a liquid electrolyte to the cell; a central hydrogen header connected to each of the electrolytic cells for discharging the generated hydrogen from the cells; a central oxygen header connected to each of the electrolytic cells for discharging the generated oxygen from the cells; the direct-current power supply is used for supplying power to each unit of the electrolytic bath which is connected in series; wherein the cells of the electrolytic cells connected in series are electrically connected in parallel.

Description

Technical Field

[0001] The present invention relates to a novel high-pressure electrolysis device for generating hydrogen and oxygen, and is particularly suitable for small factories (<500 kW). Background Art

[0002] The electrolytic production of hydrogen is well known. For example, see WO 2004 / 076721 and the US patent publications cited therein.

[0003] As described in the introduction of WO 2004 / 076721, known electrolysis equipment for generating hydrogen using a liquid electrolyte (also known in the art as an "electrolyzer") operates as follows. Two electrodes are placed in a bath of a liquid electrolyte, such as an aqueous solution of potassium hydroxide (KOH). A wide range of potassium hydroxide concentrations can be used, but a KOH solution with a concentration of about 25 to 30 wt% is typically used. The electrodes are separated from each other by a separation membrane that selectively allows the liquid to pass through but not the gas. When a voltage is applied across the electrodes, typically about 2 - 3 volts, an electric current flows through the electrolyte between the electrodes. Hydrogen gas is produced at the cathode and oxygen gas is produced at the anode. As the generated bubbles rise through the liquid electrolyte, the separation membrane keeps the hydrogen and oxygen separated. There is a disengagement space above the liquid electrolyte, which contains two separate chambers or two sections that are isolated from each other by an airtight barrier divided into two separate sections. One chamber or section is used to receive hydrogen, and the other is used to receive oxygen. These two gases are removed from the corresponding sections of the disengagement space respectively for storage or discharge.

[0004] Currently available electrolyzers are mainly low-pressure electrolyzers with a stack design, where multiple sets of prefabricated components are stacked to assemble the electrolyzer. Due to the nature of the stack design, the pressure is limited to about 30 bar.

[0005] High-pressure electrolyzers are becoming the focus of attention because they have advantages over low-pressure electrolyzers as they are suitable for high-pressure applications, transportation, and storage without the need for downstream compressor stages. A variety of designs of high-pressure electrolyzers have been documented in the art, and these designs are generally based on polymer electrolyte membrane ("PEM") technology. For example, see WO 2011 / 012507 A1. However, an important disadvantage of PEM technology is that it requires expensive rare metal material catalysts, and the catalyst layer in the electrolytic cell degrades faster under varying load requirements compared to alkaline electrolysis.

[0006] NL 2023212 discloses a high-pressure electrolysis unit, which includes a mass of conductive metal that forms an anode or a cathode. The high-pressure electrolysis unit has an arrangement of interconnected vertical and horizontal cylindrical channels that are closed except for the channels for the water inlet connection, the hydrogen and oxygen outlet connections. The inner surfaces of the channel arrangement are partially coated with an electrically insulating coating, and the counter electrodes that respectively form the cathode or the anode are positioned in the vertical channels, enclosed by a cylindrical membrane, and supported and connected by electrode support rods in the horizontal channels installed in the upper part of the housing.

[0007] WO 2021 / 029768 A1 discloses a high-pressure alkaline electrolysis unit, which includes an assembly of pipes and pipe fittings of conductive metal that form an anode or a cathode. The high-pressure alkaline electrolysis unit has an arrangement of interconnected vertical and horizontal pipe fittings and pipes that are closed except for the pipe fittings for the water inlet connection, the hydrogen and oxygen outlet connections. The inner surfaces of the channel arrangement are coated with an electrically insulating coating, and the counter electrodes that respectively form the cathode or the anode are positioned in the vertical pipe fittings, enclosed by a cylindrical membrane, and supported and connected by electrode support rods in the horizontal pipe fittings installed in the upper part of the housing. The high-pressure electrolysis device also includes more than one pressure-tight isolated electrical conductor to conduct electrical power supply from the outside of the electrolysis device to the inside.

[0008] WO 2004 / 076721 A2 (corresponding to EP 1597414 B1) discloses an electrolytic cell for electrolyzing water, which includes a cathode of a generally tubular configuration, an anode is arranged inside the cathode, and a generally tubular separation membrane separates the anode from the cathode and divides the electrolyte chamber into an anode sub-chamber and a cathode sub-chamber. The electrolyzer device includes an array of individual cells, and a DC generator applies a potential across the individual cells via electrical leads. Hydrogen generated from the electrolyte in the cell is removed via a hydrogen extraction pipeline and a hydrogen manifold pipeline. The by-product oxygen is removed from the cell via an oxygen extraction pipeline and an oxygen manifold pipeline.

[0009] EP 3 498 886 A1 discloses an electrolysis system for performing oxidation and reduction reactions, the electrolysis system comprising: more than one electrolytic cell, the electrolytic cell being formed by at least a pair of electrodes and an electrolyte between the electrodes, wherein the components of the more than one electrolytic cell define an electrolyzer; an energy source for supplying an electrical signal to the electrolyzer. The electrical signal received by the electrolytic cell forming the electrolyzer corresponds to a direct current pulse, the direct current pulse being configured such that for the electrolytic cells of each electrolyzer: during the current electrical pulse, each cell operates in a charging transient state; during the time between the direct current pulses, each cell operates in a discharging transient state; wherein the charging transient state and the discharging transient state are defined by the construction of each electrolytic cell in the form of a cylindrical plate capacitor.

[0010] US 3,984,303 discloses an electrolytic cell for producing halogen gas and alkali metal hydroxide, the electrolytic cell having a hollow tubular cathode member, the hollow tubular anode member being concentrically arranged within the cathode, each electrode member having a liquid-permeable wall to allow electrolyte circulation. The anode is covered with a conductive film on its outer surface, thereby separating the anode surface from the cathode surface. The film is tubular in shape and is mounted above the outer surface of the anode. The tubular film may have a material that is selectively permeable to ion passage and impermeable to the hydrodynamic flow of the electrolyte. Such electrolytic cells may also be connected in series to form a larger multi-cell electrolyzer.

[0011] In the unpublished international patent application PCT / NL 2022 / 050648 (corresponding to NL 2029726), a high-voltage electrolysis device is disclosed, the high-voltage electrolysis device comprising a plurality of high-voltage electrolysis units arranged in series, wherein each unit comprises a body of conductive metal, the body of conductive metal being composed of a component of interconnected horizontal pipes and vertical pipes, which constitutes an electrode connectable to a DC power source. The component comprises three horizontal pipes and at least two vertical pipes, each vertical pipe accommodating an elongated central electrode and a tubular membrane, wherein each vertical pipe together with the central electrode, the membrane and the electrolyte constitutes an electrolytic cell. The electrolytic cells within each unit are connected in parallel, wherein each unit further comprises at least two vertical pipes that do not accommodate central electrodes: a first vertical pipe connecting the lower horizontal pipe to the first upper horizontal pipe, and a second vertical pipe connecting the lower horizontal pipe to the second upper horizontal pipe.

[0012] The differential voltage across the series-connected units is equal to the number of units multiplied by the voltage drop across a single unit, the voltage drop being in the range of 2 - 3 Vdc. The current is equal to the number of parallel-connected cells multiplied by the current through a single cell, which depends on the detailed design of the cell and the voltage applied across the cell.

[0013] The system described in PCT / NL 2022 / 050648 is very suitable for large-scale applications because the high-pressure electrolysis device consists of electrolytic cells connected in parallel, which can accept a large current passing through the unit.

[0014] However, for a small-capacity system with a small number of electrolytic cells, such a system will result in a very low voltage, which is not optimal for the design of the upstream power conversion and rectification system necessary for the operation of the electrolyzer system. In particular, for small units, the system described in PCT / NL 2022 / 050648 will result in low voltage and high current, which is inefficient and uneconomical. The ideal conversion and rectification system design is based on the highest possible voltage and the lowest possible current.

[0015] Small-capacity high-pressure electrolyzer systems have a major advantage over large-scale systems because high-pressure technology is easier to apply, there have been many advancements in such application areas, and importantly, the use of compressors can be avoided.

[0016] Therefore, there is a need for a simple, efficient, and cost-effective small high-pressure electrolyzer for hydrogen production and other industrial processes, which is compact, flexible, modular, scalable, and requires low maintenance. An object of the present invention is to provide a small high-pressure electrolysis device having such beneficial properties. Summary of the Invention

[0017] In one aspect of the present invention, there is provided a small high-pressure electrolyzer for generating hydrogen and oxygen, the small high-pressure electrolyzer comprising:

[0018] - More than one unit, each of the more than one unit containing a plurality of high-pressure electrolytic cells, wherein the electrolytic cells of each unit are connected in series electrically;

[0019] - A central electrolyte header, the central electrolyte header being functionally connected to each electrolytic cell for supplying liquid electrolyte to the cell;

[0020] - A central hydrogen header, the central hydrogen header being functionally connected to each electrolytic cell for discharging the generated hydrogen from the cell;

[0021] - A central oxygen header, the central oxygen header being functionally connected to each electrolytic cell for discharging the generated oxygen from the cell;

[0022] - A DC power supply, the DC power supply being functionally connected to each unit of the electrolytic cells connected in series for supplying power to each unit of the cells connected in series;

[0023] - Wherein the units of the electrolytic cells connected in series are connected in parallel electrically.

[0024] In a preferred embodiment, the functional connections between the central electrolyte header and the electrolytic cells, between the central hydrogen header and the electrolytic cells, and between the central oxygen header and the electrolytic cells are achieved through non-conductive hydraulic hoses.

[0025] In another preferred embodiment, the central hydrogen header and the central oxygen header are each functionally connected to the central electrolyte header, preferably through non-conductive hoses to the central electrolyte header.

[0026] In still another preferred embodiment, the central electrolyte header further includes a supply connection for supplying softened water to the electrolyte header, the central hydrogen header further includes a discharge connection for discharging hydrogen from the hydrogen header, and the central oxygen header further includes a discharge connection for discharging oxygen from the oxygen header.

[0027] In a further embodiment of the present invention, each electrolytic cell is composed of the following parts: a pressure-resistant, vertically arranged conductive metal pipe constituting the anode; an elongated cathode accommodated in the center of the vertical pipe; and a separation membrane surrounding the cathode, which divides the electrolytic cell into an anodic sub-chamber and a cathodic sub-chamber.

[0028] In another embodiment of the present invention, the vertical pipe of each electrolytic cell has a lower end and an upper end, the lower end is closed, and the upper end is sealed with an electrically insulating, airtight and pressure-resistant seal.

[0029] In still another embodiment of the present invention, the elongated central cathode extends from the lower part of the vertical pipe and protrudes beyond the upper end of the vertical pipe through an electrically insulating seal.

[0030] In a further embodiment, the vertical pipe has at least three openings at different heights in the pipe sidewall: a lower opening at the lower end of the pipe for supplying softened water or electrolyte; an upper opening for discharging the generated hydrogen; and a middle opening for discharging the generated oxygen.

[0031] In still a further embodiment, an airtight seal is provided at the height between the upper opening and the middle opening between the separation membrane and the inner wall of the vertical pipe, and the seal also supports the separation membrane.

[0032] In another embodiment, the separation membrane has a lower end and an upper end, the lower end extends downward beyond the lower end of the central cathode, and the upper end is connected to the airtight seal. The separation membrane seals to prevent gas from passing through, but allows liquid and ions of the electrolyte contained therein to pass through.

[0033] In the following specific embodiments referring to specific embodiments of the present invention (i.e., producing hydrogen and oxygen by high-pressure electrolysis of water), these and other aspects of the present invention will be more fully outlined. However, those skilled in the art will recognize that the present invention can also be used in other embodiments.

[0034] Conventional known devices, such as pressure sensing devices and flow sensing devices, as well as the control of operating valves and pumps, have been largely omitted from the description because such devices and their uses are well known in the art. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 is a schematic view of an embodiment of a high-pressure electrolyzer according to the present invention;

[0036] Figure 2 is Figure 1 a flowchart of the electrolyzer;

[0037] Figure 3 is a perspective view of a schematic prototype of an electrolyzer according to the present invention;

[0038] Figure 4 is a perspective view of an embodiment of an electrolytic cell forming part of a high-pressure electrolyzer according to the present invention;

[0039] Figure 5 is Figure 4 a detailed view of the upper part of two electrolytic cells as shown in

[0040] The following detailed description should be read with reference to the drawings, in which the same elements in different drawings are identically numbered. These drawings are not necessarily to scale, depict the selected embodiments, and are not intended to limit the scope of the present invention. DETAILED DESCRIPTION

[0041] According to the present invention, there is provided a small high-pressure electrolyzer for generating hydrogen and oxygen, the small high-pressure electrolyzer comprising more than one unit, each of the more than one unit comprising a plurality of electrolytic cells, such as three to twenty and up to more than 100 electrolytic cells, the electrolytic cells being connected in series. A preferred range for a row of serially connected electrolytic cells is between 20 and 100 cells, more preferably between 50 and 100 cells. As a result, the current through the system is equal to the current of one cell, which depends on the detailed design of the cell and the voltage applied across the cell. In addition, the differential voltage across the serially connected cells is equal to the number of cells multiplied by the voltage drop across a single cell, the voltage drop being in the range of 2 - 3 Vdc. Currently, the preferred range for the units of serially connected electrolytic cells is from 1 to 10 units, more preferably from 1 to 5 units.

[0042] One advantage of the present invention is that the voltage across the series-connected cells is relatively high and the current passing through the cells is relatively low. This is advantageous for a power conversion system. The voltage drop from the supplied AC voltage to the desired voltage is relatively small, resulting in a smaller transformer. The lower current will reduce the overall materials required for rectification and current transmission, thereby reducing the cost of the complete system.

[0043] Each high-pressure electrolytic cell comprises: a pair of electrodes; a separation membrane; and a liquid electrolyte between the cells, wherein the cell is constituted by a pressure-resistant, vertically arranged pipe of conductive metal, the pipe constituting the first electrode (anode or cathode), and an elongated central second electrode or counter electrode (cathode or anode respectively) is in the middle of the vertical pipe, electrically insulated from the vertical pipe and the separation membrane surrounding the counter electrode. The first electrode of the electrolytic cell can be connected to a DC power source or can be connected to the elongated central counter electrode of the previous electrolytic cell. The second electrode or counter electrode of the (same) electrolytic cell can be connected to the first electrode of the subsequent electrolytic cell (which is the vertically arranged pipe of the cell) or can be connected to a DC power source. Preferably, the vertical pipes, the separation membrane and the central electrodes of each electrolytic cell are arranged coaxially with respect to each other.

[0044] In a preferred embodiment of the present invention, the vertical pipe constitutes the anode (+) of the electrolytic cell and the elongated central electrode in the middle of the pipe constitutes the cathode (-) of the electrolytic cell.

[0045] The terms "pipe" and "pipe fitting" are frequently used interchangeably in the art, although there are differences between a pipe and a pipe fitting. For example, reference can be made to http: / / www.wermac.org / pipes / pipe vs tube.html . As used herein, unless otherwise specified, "pipe" and "pipe fitting" are collectively referred to as "pipe". Those skilled in the art should have no problem understanding which materials are required when applying the design according to the present invention.

[0046] The vertical pipe has a lower end and an upper end, the lower end is closed, and the upper end is sealed with an electrically insulating, airtight and pressure-resistant seal. In a preferred embodiment, the upper end of the vertical pipe is threaded to facilitate the maintenance of the electrolytic cell. The vertical pipe can be closed with available pressure fittings known in the art (such as threaded pressure fittings).

[0047] The elongated central cathode extends from the lower part of the vertical pipe and protrudes beyond the upper end of the vertical pipe through an electrically insulating seal. The central cathode can be connected to a DC power source or can be connected to the first electrode of the subsequent electrolytic cell. In a preferred embodiment, the elongated central electrode is a solid cylindrical rod-shaped or bar-shaped electrode.

[0048] The vertical pipe has at least three openings at different heights in the pipe sidewall: a lower opening at the lower end of the pipe for supplying softened water or electrolyte; an upper opening for discharging the generated hydrogen; and a middle opening for discharging the generated oxygen. In one embodiment, the openings are connected to corresponding headers through non-conductive connectors for further separate conveyance to a pressurized vessel (for further processing and storage of the gas) and supply from a softened water storage tank. In another embodiment, the openings are provided with suitable non-conductive fittings for connecting hydraulic hoses, pipe fittings, etc. to the corresponding headers. The high-pressure electrolyzer and electrolytic cell according to the present invention are further combined through a common feed conduit for the liquid electrolyte and softened water and a withdrawal conduit for hydrogen and oxygen.

[0049] To overcome short circuits between serially connected cells, the electrolyte supply and collection of the generated gas are achieved by connecting the electrolytic cells to a central header (also called a manifold) through non-conductive connectors. The central header and the connectors form part of the electrolyzer according to the present invention.

[0050] Softened water or liquid electrolyte is supplied to a pressurized electrolyte header, which is connected to the corresponding electrolytic cell through a non-conductive connector for distributing the liquid into the cell.

[0051] The generated hydrogen and oxygen, together with a part of the electrolyte, are discharged from the electrolytic cell in a mixture form and transferred through non-conductive connectors to corresponding central hydrogen and central oxygen headers for collection, separation from the electrolyte, and further conveyance.

[0052] In each electrolytic cell, between the separation membrane and the inner wall of the vertical pipe, in the upper half of the vertical pipe, at a position between the upper opening and the middle opening of the pipe, a sleeve or disk-shaped airtight seal is provided, and the seal also supports the membrane.

[0053] The separation membrane is preferably of a tubular construction, disposed within each vertical pipe, surrounding the central electrode, thereby dividing the vertical pipe into an anodic sub-chamber and a cathodic sub-chamber. The separation membrane prevents the gas from passing therethrough, but allows the liquid and liquid-borne ions to pass. The separation membrane is supported at the top by a sleeve or disk-shaped seal and extends from the lower outer end of the central electrode until beyond the seal. Preferably, the separation membrane is open at the lower side. In another preferred embodiment, the membrane is a ZIRFON® (ZIRFON® is a registered trademark) separation membrane.

[0054] The upper part of the elongated central electrode, i.e., the part above the sleeve or disk-shaped airtight seal in the vertical pipe, is preferably electrically insulated upwards around its periphery from the seal to prevent gas generation in the upper part of the cathodic sub-chamber, enabling the production of high-quality gas.

[0055] The electrolytic cell is filled with a liquid electrolyte, typically a solution of potassium hydroxide (KOH) in softened water. A wide range of KOH concentrations can be applied, but a KOH solution with a concentration of about 25 to 30 wt% is typically used. The electrodes, namely the vertical pipes constituting the anode and the elongated central cathode, are exposed to and in contact with the liquid electrolyte to generate gas during operation.

[0056] During operation, hydrogen is produced at the cathode of each electrolytic cell and oxygen is produced at the anode. As the generated bubbles rise through the liquid electrolyte, the separation membrane keeps the hydrogen and oxygen gases separated.

[0057] The electrolytic cells connected in series of the electrolyzer according to the present invention are preferably arranged in an electrically insulated adjacent array. As Figure 1 and Figure 5 shown in the embodiment of, the electrolytic cells are electrically connected such that the anode (+) of the body of the first unit is connected to a DC power supply, the cathode (-) of the central cathode of the first unit is connected to the body of the second adjacent electrolytic cell, the central cathode of the second electrolytic cell is connected to the body of the next adjacent electrolytic cell, and so on, and the central cathode (-) of the last one is connected to the DC power supply. The differential voltage across the series-connected cells is equal to the number of cells multiplied by the voltage drop across a single cell, and the voltage drop is in the range of 2 - 3 Vdc. The current through one unit of the series-connected cells is equal to the current through a single cell and depends on the detailed design of the cell and the voltage applied across the cell.

[0058] The wall thickness of the vertical pipe is indicated by the desired generation pressure and by material properties (such as the yield strength and electrical conductivity of the metal from which the pipe is made). Generally, the wall thickness can vary from about 0.65 to 1.60 cm. Generally, the length of the vertical pipe fittings of the high-pressure cells is in the range of 500 to 2000 mm and can be further developed up to 4000 mm. Generally, the diameter of the central cathode is in the range of 10 to 30 mm and can be further developed up to 100 mm. These values are merely indicative and should not be construed as limiting the present invention in any way.

[0059] In a preferred embodiment of the present invention, a cooling and drying device is provided, and the device forms part of a high-pressure electrolyzer. The device includes more than one cooling and drying unit, and the units are connected to the extraction ducts of the generated hydrogen and oxygen from the central hydrogen manifold and the central oxygen manifold. The gas is conveyed to the cooling and drying device to be cooled down by a cooling medium (e.g., cooling water). After cooling, the oxygen is reduced to atmospheric pressure, which causes an additional temperature drop due to the thermodynamic behavior of oxygen. Then, the hydrogen still under high pressure is further cooled using oxygen under ambient conditions. The gas cooling unit is designed such that the condensed water returns to the electrolysis unit. Condensation of water vapor in the downstream system is avoided. Thus, by cooling the hydrogen to a temperature lower than the ambient temperature and drying the hydrogen to a saturation temperature lower than the atmospheric conditions, condensation of water in the downstream system is prevented.

[0060] In another aspect of the present invention, more than one pressure vessel is provided, and the pressure vessel forms part of the electrolysis device according to the present invention. The pressure vessel is preferably releasably connected to the cooling and drying unit for storing the dried and purified gas.

[0061] Compared with prior art electrolyzers of similar types, the electrolyzer according to the present invention has several advantages. These advantages particularly relate to: a) high-pressure environment, b) gas-liquid separation, c) natural circulation and removal of the generated gas from the electrolytic cell by the gravity effect, d) isolation of the central cathode, e) simplified equipment maintenance, f) cooling of the generated gas.

[0062] Regarding the high-pressure environment, the pressure containment is also one of the electrodes. The coaxial anode / cathode configuration allows for the generation of very high-pressure hydrogen within the pressure containment body provided by the anode with the actual wall thickness of conventional materials. The conventional stacking concept has large plates, which enables a high current to flow through the system. The perimeter of the plates is also the perimeter where pressure sealing must be maintained. This electrolyzer is designed such that the perimeter of the anode / cathode configuration and the opening at the top of the cell is significantly smaller than the perimeter of the plates in the stacking concept, which reduces the area of potential leakage of combustible gas.

[0063] The high pressure in the electrolysis unit results in a smaller gas volume in the electrode region, thereby a larger electrolyte volume, which in turn leads to a lower resistance and thus higher efficiency.

[0064] The ability of the devices and methods of the present invention to produce hydrogen (and oxygen) at pressures up to or even exceeding 1000 bar exceeds the highest pressures of known prior art electrolyzers. The devices and methods of the present invention can produce such high-pressure hydrogen without the need for a separate compressor to pressurize the product hydrogen. The main advantage of a high-pressure electrolyzer system in a small system is that the use of a small-capacity and low-efficiency downstream compressor can be avoided. Small compressors are relatively expensive compared to large compressors.

[0065] The device according to the present invention allows for high-pressure hydrogen production in a unique way, which reduces component costs and system complexity, making the device easily affordable. The device can be scaled up to any given production capacity.

[0066] The gas produced is removed from the electrode surface by natural ventilation, which improves the capacity of the system. An active circulation system is not required. A collection manifold is included in the electrolyzer according to the present invention to achieve or improve natural circulation and gas separation in the high-pressure electrolysis unit.

[0067] Regarding the maintenance of the device, the outer upper part of the vertical pipe that houses the central electrode is preferably threaded and provided with a releasable threaded pressure fitting. In addition, the central cathode and the surrounding separation membrane are preferably supported only at the top, enabling easy removal of the central electrode and the membrane for maintenance or replacement. Thus, the maintenance of the device is simplified, more efficient, and less expensive.

[0068] Regarding the cooling of the gas produced, the gas cooling unit according to the present invention provides for drying the hydrogen by cooling it to a temperature below the saturation temperature of atmospheric conditions, thereby preventing water condensation in downstream systems. This feature is not taught by the prior art.

[0069] The devices and methods of the present invention can be applied to generate high-pressure hydrogen on-site, for example, at factory, office building, or residential area sites, for on-site energy storage and / or as fuel for fuel cells, internal combustion engines, or heating applications.

[0070] Turning to the drawings, and particularly referring to Figure 1 And also referring to Figure 2 The flowchart of shows an embodiment of a high-pressure electrolyzer 100 that includes a unit of four electrolytic cells 50 electrically connected in series. Each electrolytic cell is composed of: a pipe 1 of a pressure-resistant, vertically arranged conductive metal that forms the anode; an elongated central cathode 2 housed in the center of the vertical pipe; and a separation membrane 3 surrounding the cathode that divides the electrolytic cell into an anodic sub-chamber 8 and a cathodic sub-chamber 9. The bottom end 10 of the vertical pipe 1 is closed, while the top end is sealed with an insulating pressure-resistant seal 5. The elongated cathode 2 projects through the seal.

[0071] The electrolytic cells are electrically connected by electrical series connectors 6 such that: the anode (+) of the body of the first cell is connected to the DC power supply, the cathode (-) of the central cathode of the first cell is connected to the body of the second adjacent electrolytic cell, the central cathode of the second electrolytic cell is connected to the body of the next adjacent electrolytic cell, and so on until the last central cathode (-) is connected to the DC power supply.

[0072] Each electrolytic cell is interconnected with three manifolds 15, 16, and 17 by non-conductive hydraulic hoses 1g, 1h, and 1i, which extend from the openings 21, 22, and 23 of the cell to the respective electrolyte manifold 15, oxygen manifold 16, and hydrogen manifold 17.

[0073] The oxygen manifold and the hydrogen manifold are connected by hydraulic hoses 1e and 1f respectively, so that the separated electrolyte can return to the electrolyte manifold. Due to the gravity difference between the electrolytic cell 50 and the assembled components 15, 16, 17, 1e, and 1f, the electrolyte will establish a natural circulation flow.

[0074] The hydrogen outlet 12 releases excess hydrogen to a downstream system, such as a storage tank or pipeline.

[0075] The oxygen outlet 13 releases excess hydrogen to a downstream system, such as a storage tank or pipeline.

[0076] To compensate for the water in the electrochemical reaction, softened water is supplied via the softened water inlet 10.

[0077] The softened water will be intermittently incorporated from the softened water tank 18 through the valve 24. The softened water tank 18 will be filled under atmospheric conditions with the aid of a simple pumping device, which is not part of the present invention.

[0078] When filling the tank 18 with softened water, oxygen from the electrolytic cell 50 is fed into the tank via the valve 20 to pressurize the tank 18. During this filling period, the pressure in the electrolytic cell 50 is temporarily increased to achieve a higher pressure in the tank 18 than during the normal operation of the electrolytic cell 50. Once the pressure in the tank 18 (as the water volume decreases) drops to a value close to the electrolyzer operating pressure, the electrolytic cell 50 will start operating again at a higher pressure to refill the tank 18 with pressurized oxygen via the valve 20. This process is repeated until the tank 18 is empty. Once the tank 18 is empty, depressurization via the valve 19 allows the softened water to be filled again.

[0079] Figure 3 A schematic prototype of a compact small electrolyzer according to the present invention is shown, having five pressurized softened water tanks 18 for supplying softened water to the central electrolyte manifold 15. Two units of electrolytic cells 50 connected in series are shown, as well as the central oxygen manifold 16 and the central hydrogen manifold 17. Connectors and connecting fittings or hoses are not shown in this drawing.

[0080] Figure 4 A modular electrolyzer for small high-pressure applications is shown. The individual electrolyzers are connected to three manifolds 15, 16, and 17 by non-conductive hydraulic hoses 1g, 1h, and 1i, which extend from the openings 21, 22, and 23 of the cells to the respective manifolds. The series connection is achieved by a connector 6, which in this embodiment has a special design that enables the vertical anode pipe 1 of one cell to be connected to the concentrically positioned central cathode 2 of an adjacent cell, thereby forming a compact array of series-connected electrolyzers. This is further shown in Figure 5 the detailed view of, which shows the tops of two electrolyzers connected by the connector 6. The connector 6 is matched to the anode pipe 1 by a threaded connection and to the threaded upper end of the left cathode 2 by means of a fixing nut 25.

[0081] Operation (See Figure 1 and Figure 2 )

[0082] The empty electrolyzers of the unit are filled with electrolyte (first filling, the electrolyte is a solution of 25%-30% potassium hydroxide in softened water) via the central electrolyte manifold 15, with all venting devices in the open position until the liquid levels in the central hydrogen manifold 17 and the central oxygen manifold 16 are ensured.

[0083] Then, the electrolysis process is started by connecting the electrolyzer to a DC power supply and generating a voltage drop of 2 - 3 V across each individual electrolyzer. Hydrogen will be produced at the surface of the central electrode (cathode), and oxygen will be produced at the inner surface of the surrounding vertical pipes (anodes). The gases produced will rise and be collected in the hydrogen and oxygen manifolds. When all downstream volumes have been purged by the gases produced and no air remains in the downstream system, the venting devices on the manifolds will be closed. Since the volume of the gases produced is much larger than the volume of the converted water, pressure will build up in the system.

[0084] The natural circulation via the hydrogen and oxygen manifolds and the connected electrolyte manifold will support the removal of the gases produced from the electrolyzer area and collect the gases in the manifolds.

[0085] When the operating pressure has been reached, the gas pressure control system will blow the excess gas into the downstream system, such as a storage and / or pipeline system. When the water level reaches the low water level or a controllable water level, softened water will replenish the amount of water converted. The softened water is incorporated into the electrolyte manifold 15 from a pressurized tank or a series of pressurized tanks 18 in which the softened water is stored.

[0086] The stored softened water will be pressurized batch by batch with the generated oxygen: 1) First, fill the tank 18 with softened water under atmospheric conditions; 2) After filling, supply the oxygen from the electrolyzer 50 to the tank via the valve 20 to pressurize the tank 18. During this filling period, the pressure in the electrolyzer 50 is temporarily increased to achieve a higher pressure in the tank 18 than during the normal operation of the electrolyzer 50; 3) After pressurizing the tank 18, controlled by the control valve 24, the softened water will flow into the electrolyzer; 4) Once the pressure in the tank 18 (as the water volume decreases) drops to a value close to the electrolyzer operating pressure, the electrolyzer 50 will start operating again at a higher pressure to fill the tank 18 with pressurized oxygen via the valve 20 again; 5) Repeat this process until the tank 18 is empty; 6) When the tank 18 is empty, depressurize via the valve 19 and fill it with softened water again.

[0087] The generated hydrogen and oxygen are separated from the liquid electrolyte in the central headers 17 and 16 respectively and then transported to the cooling device. The cooling device is not shown. In this regard, reference is made to the unpublished patent application PCT / NL2022 / 050648 of the same applicant, in which the same cooling and drying devices are shown and explained (see Figures 8 - 11). This PCT application is incorporated herein by reference. The gas is cooled by a cooling medium (e.g., cooling water). After cooling, the oxygen pressure will be reduced to atmospheric pressure, resulting in an additional temperature drop due to the thermodynamic behavior of oxygen. Then, the cold oxygen at atmospheric pressure is used to further cool the still pressurized hydrogen. The cooling device is designed such that the condensed water vapor will return to the electrolyzer.

[0088] After cooling the hydrogen as described above, the hydrogen is dried to a temperature below the saturation temperature under atmospheric conditions, thereby preventing water vapor condensation in the downstream system.

[0089] From the above description, those skilled in the art can easily determine the basic features of the present invention, and various changes and modifications can be made without departing from the gist and scope of the present invention to adapt it to various uses and conditions. Therefore, these modifications and adjustments are considered to fall within the scope of the present invention as claimed in the appended claims.

[0090] Reference Signs

[0091] 1. A vertical pipe of conductive metal, constituting the first electrode of the electrolyzer

[0092] 1e. A connecting piece between the electrolyte header 15 and the oxygen header 16

[0093] 1f. A connecting piece between the electrolyte header 15 and the hydrogen header 17

[0094] 1g. A connecting piece between the electrolyte header 15 and the opening 21 of the vertical pipe 1

[0095] 1h. Connector between the oxygen manifold 16 and the opening 22 of the vertical pipe 1

[0096] 1i. Connector between the hydrogen manifold 17 and the opening 23 of the vertical pipe 1

[0097] 2. Elongated second electrode of the electrolytic cell

[0098] 3. Separation membrane of the electrolytic cell

[0099] 4. Hermetic sleeve or disc seal

[0100] 5. Electrical insulation seal at the top of the vertical pipe 1

[0101] 6. Electrical series connector

[0102] 7. Electrical insulation ring or nut

[0103] 8. Anode sub-chamber

[0104] 9. Cathode sub-chamber

[0105] 10. Bottom end of the vertical pipe 1

[0106] 11. Softened water inlet

[0107] 12. Hydrogen outlet

[0108] 13. Oxygen outlet

[0109] 15. Electrolyte manifold

[0110] 16. Oxygen manifold

[0111] 17. Hydrogen manifold

[0112] 18. Pressurized softened water tank

[0113] 19. Softened water tank pressure relief valve

[0114] 20. Softened water pressure valve

[0115] 21. Opening in the vertical pipe for softened water supply

[0116] 22. Opening in the vertical pipe for oxygen discharge

[0117] 23. Opening in the vertical pipe for hydrogen discharge

[0118] 25. Fixing screw or nut

[0119] 50. Electrolytic cell

[0120] 100. Electrolyzer according to the present invention

Claims

1. A high-pressure electrolyzer (100) for the production of hydrogen and oxygen, in particular in small plants, the high-pressure electrolyzer (100) comprising: - More than one unit, each of the more than one unit containing a plurality of high-pressure electrolytic cells (50), wherein the electrolytic cells of each unit are electrically connected in series with each other; - A central electrolyte distribution holder (15) functionally connected to each electrolytic cell (50) of the electrolyzer for supplying liquid electrolyte to the electrolytic cells; - A central storage and separation container (17) functionally connected to each electrolytic cell (50) of the electrolyzer for collecting and processing hydrogen generated from the electrolytic cells; - A central storage and separation container (16) functionally connected to each electrolytic cell (50) of the electrolyzer for collecting and processing oxygen generated from the electrolytic cells; and - A DC power supply electrically connected to each unit of the serially connected electrolytic cells for powering each unit of the serially connected electrolytic cells; wherein the units of the serially connected electrolytic cells are electrically connected in parallel.

2. The high-pressure electrolyzer according to claim 1, wherein the functional connection between the central electrolyte distribution container (15) and the electrolytic cells, and the functional connections between the central hydrogen storage and separation container (17) for hydrogen or the central oxygen storage and separation container (16) for oxygen and the electrolytic cells respectively are achieved via non-conductive connectors, for example via non-conductive hydraulic hoses.

3. The high-pressure electrolyzer according to claim 1 or 2, wherein the central storage and separation container (17) for hydrogen and the central storage and separation container (16) for oxygen are each functionally connected to the central distribution container (15) for electrolyte.

4. The high-pressure electrolyzer according to any one of claims 1 to 3, wherein the central distribution container (15) for electrolyte further comprises a supply line (10) for supplying softened water, the central storage and separation container (17) further comprises a discharge line (12) for discharging hydrogen, and the central storage and separation container (16) further comprises a discharge line (13) for discharging oxygen.

5. The high-pressure electrolyzer according to any one of claims 1 to 4, wherein each electrolytic cell (50) is constructed of: A pressure-resistant, substantially vertically arranged conductive metal pipe (1), the pipe (1) constituting a first electrode, an anode (+) or a cathode (-); An elongated central second electrode (2), the second electrode (2) being received in the center of the substantially vertical pipe and constituting a counter electrode, a cathode (-) or an anode (+); and A separation membrane (3) surrounding the central second electrode, the separation membrane (3) dividing the electrolytic cell into an anodic sub-chamber (8) and a cathodic sub-chamber (9).

6. The high-pressure electrolyzer according to claim 5, wherein the substantially vertical pipe (1) constituting the first electrode is the anode (+), and the central second electrode (2) constituting the counter electrode is the cathode (-).

7. The high-pressure electrolyzer according to claim 6, wherein the substantially vertical pipe (1) has a lower end (10) and an upper end, wherein the lower end is closed, and the upper end is sealed with an electrically insulating, airtight and pressure-resistant seal (5).

8. The high-pressure electrolyzer according to claim 6 or 7, wherein the elongated central second electrode (2) extends from the lower part of the vertical pipe (1) and projects through the electrically insulating seal (5) beyond the upper end of the vertical pipe.

9. The high-pressure electrolyzer according to any one of claims 1 to 8, wherein the vertical pipe (1) has at least three openings (21, 22, 23) at different heights in the side wall: a lower opening (21) in the lower part of the pipe for supplying the electrolyte; an upper opening (22) for discharging the generated hydrogen; and a middle opening (23) for discharging the generated oxygen.

10. The high-pressure electrolyzer according to any one of claims 1 to 9, wherein an airtight seal (4) is provided between the separation membrane (3) and the inner wall of the vertical pipe at the height between the upper opening (22) and the middle opening (23) of the pipe.

11. The high-pressure electrolyzer according to any one of claims 1 to 10, wherein the separation membrane (3) has a lower end and an upper end, the lower end extends downward beyond the lower end of the central second electrode (2), and the upper end is connected to the airtight seal (4), wherein the separation membrane seals to prevent gas passage but allows liquid and ions of the electrolyte contained therein to pass through.

12. The high-pressure electrolyzer according to any one of claims 1 to 11, wherein the substantially vertical tubular first electrode (1) of the electrolytic cell is conductively electrically connected to a DC power source or conductively electrically connected to the central second electrode (2) of a previous electrolytic cell, and the central second electrode (2) is connected to the vertical tubular first electrode (1) of a subsequent electrolytic cell or connected to a DC power source.

13. The high-pressure electrolyzer according to any one of claims 1 to 12, wherein the electrolytic cells are conductively electrically connected to each other by means of connectors (6).

14. The high-pressure electrolyzer according to any one of claims 1 to 13, wherein the elongated central second electrode (2) is rod-shaped or cylindrical.

15. The high-pressure electrolyzer according to any one of claims 1 to 14, wherein the substantially vertical pipe (1) forming the first electrode, the central second electrode (2) and the separation membrane (3) are arranged coaxially with each other.

16. The high-pressure electrolyzer according to any one of claims 1 to 15, wherein the upper end of the central second electrode (2) of the electrolytic cell (50) is electrically insulated around its periphery above the seal (4).

17. The high-pressure electrolyzer according to any one of claims 1 to 16, wherein the electrolyzer further comprises a cooling and drying unit for the generated hydrogen, The cooling and drying unit is functionally connected to the central storage and separation container (17) for hydrogen.

18. The high-pressure electrolyzer according to any one of claims 1 to 17, wherein the electrolyzer further comprises more than one container (18) for storing and incorporating softened water, The container (18) is functionally connected to the central electrolyte distribution container (15).

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