Electrolyzer system comprising an electrolyzer in a pressure vessel with an electrical feedthrough
Patent Information
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- STIESDAL HYDROGEN AS
- Filing Date
- 2024-08-27
- Publication Date
- 2026-07-08
AI Technical Summary
Existing high-pressure electrolyzer systems face challenges in securely and safely feeding high currents through gas-tight feedthroughs, as conventional methods are either complex, costly, or limited in flexibility and safety.
The electrolyzer system employs a gas-tight polymer bushing and a rigid, electrically conducting metal rod, which are securely insulated and sealed using elastomeric sealing rings and a shoulder design, preventing the rod from being pushed out by internal pressure.
This solution provides a simple, cost-effective, and flexible high-current feedthrough that is securely sealed against gas leakage, even under high pressures, thus enhancing safety and adaptability compared to traditional methods.
Smart Images
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Abstract
Description
[0001] Electrolyzer system comprising an electrolyzer in a pressure vessel with an electrical feedthrough
[0002] FIELD OF THE INVENTION
[0003] The present invention relates to an electrolyzer system comprising an electrolyzer in a pressure vessel having a high-current electrical feedthrough for supply of power to the electrolyzer.
[0004] BACKGROUND OF THE INVENTION
[0005] For certain electrolyzer systems, the electrolyzer is contained in a pressurised vessel. An example for an electrolyzer in a hydrogen tank is disclosed in WO2022 / 156868. In other systems, the electrolyzer is contained in a pressurised vessel with a protective nitrogen gas, which also improves safety in case of hydrogen leakage from the electrolyzer. A large scale electrolyzer need high currents, which have to be fed to the electrolyzer through the wall of the pressurised vessel, typically through correspondingly arranged flanges. Due to the high pressure, for example in the range of 20-60 bars, these current feedthroughs have to be gas-tight.
[0006] For pressurised vessels, cable feedthroughs are typically not useful, as the pressurised gas may pass through the cables between the conducting wires. Accordingly, it is customary to provide copper rods through the wall of the vessel.
[0007] GB 1498488 discloses a conductor extending through an opening in a wall of an electrolyte cell. A seal is provided which comprises a silicone rubber part and a neoprene part, both of which fill an opening between the cell wall and the conductor. The seal is held in place by a washer and packing nut, the latter being engaged in a thread of collar plate, which in turn is fastened to the wall by screws. Disadvantageously, there is no secure measure on the inner side of the wall to prevent the rod from being pressed out. This has a severe consequence in that the conductor is only held in place by the friction against the compressed seal. If the seal ages and loses elasticity and friction due to hardening, the conductor is at risk for being pressed out of the cell by the pressure inside the cell. It would be desirable to provide a feedthrough with a higher safety.
[0008] Cable feedthroughs are disclosed in GB1346578A and US4741199. Other principles are disclosed in CN206779629U. CN104911626A, JP2000309367A, WO95 / 32803A2, and US2018 / 162754A1.
[0009] For higher safety, GB2072769A warns against using insulating sheaths, particularly if they are made from plastics resilient material, e.g. PTFE, as these tend to crack in the fastening area between the sealing shoulders.
[0010] Examples of rigid feedthroughs are disclosed in US8378221 in which a metal tube is fused in a glass insulator, and a metal rod is mounted in the metal tube by means of soldering, prior to the sealing of the tube in the glass insulator. However, this is a complex and costly method for providing a current feedthrough.
[0011] Commercially, similar types of rod conductors through flanges are commercially available either as portion of a flange or as insertion assemblies for correspondingly prepared flanges. The corresponding production method with the surrounding ceramics is complex and costly, which is also reflected in the pricing of such items, the high pricing being a general disadvantage. Furthermore, due to the complex production method, commercially available assemblies are limited to a few standard sizes. Accordingly, there is a general lack of flexibility for adapting commercially available feedthrough assemblies to actual needs. Rather, the design for a machine has to be adapted to the few commercially available systems for feeding current into a pressurised vessel.
[0012] It would be desirable to have alternative flexible, low cost options available. DESCRIPTION / SUMMARY OF THE INVENTION
[0013] It is therefore an objective of the invention to provide an improvement in the art. In particular, it is an objective to provide flexible, low cost feedthrough assemblies for an electrolyzer in a pressurised vessel.
[0014] This objective and further advantages are achieved with an electrolyzer in a pressure vessel having an electrical conductor assembly extending through a wall section of the vessel, in particular through a flange cover, as set forth below. The assembly comprises a gas tight polymer bushing and a rigid, electrically conducting metal rod extending through in the bushing and electrically insulated from the wall section by the bushing.
[0015] For example, the voltage is in the range up to kV, and the material of the bushing insulates correspondingly.
[0016] The electrolyzer system comprises a vessel with an inner volume that contains pressurized gas and an electrolyzer in the pressurised gas. For example, the vessel is filled with pressurised nitrogen gas. Typical pressures are in the range of 10-60 bar. Typically, the electrolyzer comprises a stack of electrolytic cells for producing hydrogen gas by electrolysis of water.
[0017] An electrical conductor assembly is provided as a high-current feedthrough, extending through a wall section of the vessel from outside the vessel to the inner volume. It is used for providing electrical current to the electrolyzer. Typically, the wall section of the vessel is provided as a flange cover that is mounted to a flange on the remaining portion of the vessel.
[0018] The assembly comprises a bushing made of an electrically insulating, gas-tight polymer and has a first portion of the bushing inside the inner volume and a second portion of the bushing extending from the first portion through an opening in the wall section to outside of the vessel. The first and the second portion of the bushing are made as a single piece of insulating polymer. The second portion has a cross section corresponding to the opening and extends through the opening. The first portion, which is inside the vessel, comprises a shoulder that has a cross section larger than the opening and extends around the opening along a rim of the opening. Typically, the opening has a circular cross section. A first elastomeric sealing ring, for example O-ring, is provided between the shoulder and the wall section, providing a gas tight sealing between the first portion and the wall section and, correspondingly, between the opening and the inner volume of the vessel.
[0019] After installation of the electrical conductor assembly, when the vessel is pressurised, the gas exerts pressure on the rod and the bushing, and, accordingly, is pressing the shoulder with the gas tight sealing against the wall section. By orienting the bushing with the shoulder against the inner side of the wall section, a safe and secure tight connection is provided. In comparison, if the shoulder would be provided on the outer side, there would have to be provided means, such as a nut on the inner side to pull the bushing tight on the sealing ring. However, such means imply the risk of the nut becoming lose and the connection leaking.
[0020] A rigid, electrically conducting metal rod extends through a passage of the bushing and is electrically insulated from the wall section by the bushing. The metal rod comprises a first electrical connector piece inside the vessel and a second electrical connector piece outside the vessel. Both electrical connector pieces are connected to conductors that provide power to the electrolyzer through the rod. One or more elastomeric sealing rings are provided inside the passage to achieved a gas-tight connection between the metal rod and the bushing.
[0021] This system is simple, can be produced at low cost, is efficiently adaptable to different sizes of openings, and is safely sealing against gas leakage. Despite its simplicity, it is fulfilling its purpose and a low-cost alternative to sintered or glued solutions.
[0022] Optionally, the bushing has a third portion, which in extension of the second portion is provided outside the vessel. This third portion has a counter-holder to keep the bushing in place in the opening, for example an outer threading that is secured against the wall of the vessel by a threaded nut. For example, the nut is made of the same material as the bushing. Advantageously, a stopper is provided on the rod inside the vessel. The stopper has a cross section larger than the passage and is abutting the bushing, thus, preventing the rod from being pushed through the bushing by the pressure in the vessel.
[0023] For example, the rod, at the location of the first electrical connector piece, has a cross section not larger than the passage, and the stopper is provided by an electrical terminal of the conductor, optionally with additional connector blocks, mounted onto the first electrical connector piece. For example, the first connector piece is provided with screw holes, through which screws extend, which hold the conductor terminal and the optional connector blocks to the first connector piece.
[0024] As alternative, for achieving the stopper function, preventing the rod from being pushed through the bushing, the rod comprises a thickened first electrical connector piece to which the terminal of the electrical conductor is mounted.
[0025] As a further alternative, the stopper is obtained by a thickened further section of the rod, provided between the first connector piece and a middle section that extends through the bushing. The thickened further section is provided in extension of the middle section and has a larger cross section than the middle section and, thus, a larger cross section than the passage, and is acting as a stopper against the bushing. The first electrical connector piece, the second electrical connector piece, the middle section, and the further section are made as a single piece of metal.
[0026] If the vessel has a pressure in the order of 30 bar, the pressure on a rod n a passage with a cross section of 2 cm2is 60 kg. Accordingly, without an enlarged piece on the rod in the inner volume, there would be a risk that the rod is pressed out of the bushing. The stopper is a useful feature for preventing such accidents.
[0027] For example, the bushing is made of Polyphenylene sulphide (PPS), polytetrafluoroethylene (PTFE), Polyether ether ketone (PEEK), or Polyether ketone (PEK). Optionally, the sealing rings are made of ethylene propylene diene monomer rubber (EPDM) or a fluoro-elastomer, such as commercially available under the name Viton®. However, other polymers may be found to fulfil the requirements of mechanical stability at sub- zero temperatures, in case of an outdoor position in winter at times when the electrolyzer is not in used, to 80°C when the electrolyzer is heating up the pressurised gas and the vessel wall.
[0028] The rod is typically made of copper but may also be made of other metals, advantageously heat conducting, such as aluminium.
[0029] SHORT DESCRIPTION OF THE DRAWINGS
[0030] The invention will be explained in more detail with reference to the drawing, where FIG. 1 is a sketch of an electrolyzer system;
[0031] FIG. 2 illustrates a flange cover holding an electrical conductor assembly, in A) perspective view, B) side view, and C) cross sectional view:
[0032] FIG. 3 is a photograph of parts for the electrical conductor assembly.
[0033] DETAILED DESCRIPTION / PREFERRED EMBODIMENT
[0034] FIG. 1 illustrates an electrolyzer system 1 comprising a vessel 2 with an inner volume 3 that contains pressurized gas. An electrolyzer 5, typically provided as a stack of electrolysis cells, is provided inside the inner volume 3, surrounded by the pressurised gas, for example nitrogen gas. Alternatively, other pressurized gases can be used in the vessel, for example hydrogen gas as a buffer, as described in WO2022 / 156868. Typically, the pressure in the vessel is in the range of 10-50 bar (1 bar = 100 kPa).
[0035] The electrolyzer 5 is used to produce hydrogen gas, H2, by splitting water and producing also oxygen gas, 02, as a by-product. For example, the electrolyzer 5 is working with an alkaline electrolyte, such as KOH-based or NaOH-based electrolyte. The electrolyzer 5 comprises an anode chamber and a cathode chamber separated by an ion- permeable membrane embedded in the electrolyte. The cells, and the water passages and gas passages are not shown in the drawings but are well known in the art, for example as described in WO2022 / 156868. Typically, the electrolyzer 5 receives electrical current through multiple power cables 7. However, for simplicity, only a single power cable 7 is shown and the electrolyser 5 grounded to the conducting metal vessel 2 by a ground connection 6.
[0036] The terminal 8 has to be connected to a power source through an opening 4 in a flange 9. The open flange 9 is covered by flange cover 25 holding an electrical conductor assembly 10, which is illustrated in FIG. 2 in A) perspective view, B) side view, and C) cross sectional view.
[0037] As best seen in FIG. 2B, a bolt / washer / nut 23 / 22 / 24 combination clamps the flange cover 25 against the flange 9, with a sealing in between, typically an O-ring around the opening 4 of the flange 9. This is a well-known fastening method.
[0038] The electrical conductor assembly 10 extends through the flange cover 25. The flange cover 25 forms a wall section of the vessel 2 when mounted onto the flange 9. The assembly 10 extends from outside the vessel 2 into the inner volume 3.
[0039] As best seen in FIG. 2c, the assembly 10 comprises a bushing 11 made of an electrically insulating, gas-tight polymer. It has a first portion 11 A inside the inner volume 3 of the vessel, a second portion 11B that is extending from the first portion 11A through an opening 25 A in the flange cover 25, and a third portion 11C outside of the vessel 2. The first portion 11 A, the second portion 1 IB, and the third portion 11C in combination are provided as a single piece of polymer for preventing creep of gas through the bushing 11 material. The second portion 11B has a cross section corresponding to the opening 25 A, and the third portion 11C is also not larger than the opening, so that the third portion 11C and then the second portion 1 IB can be pushed through the opening 25 A of the flange cover 25 for mounting. The first portion 11 A of the bushing 11 comprises a shoulder 30 having a cross section larger than the opening 25 A and extends around the opening 25A.
[0040] As best seen in FIG. 3, which is a photograph of some of the components of the assembly, the shoulder 30 has a flat, ring shaped face 30A around the opening 25 A and parallel with the inwards-directed surface of the flange cover 25 A so that it abuts the flange cover 25 and prevents the bushing 11 from being pressed out of the opening 25 A by the pressure in the inner volume 3 of the vessel 2.
[0041] As illustrated in FIG. 2C, a first elastomeric sealing ring 16 is provided between flange cover 25 and the shoulder 30, providing a gas-tight sealing between the first portion 11A of the bushing 11 and the flange cover 25A, and, correspondingly, between the opening 25A and the inner volume 3 of the vessel 2. For further securing the bushing 11, the third portion 11C has an outer threading 31 that is secured against the flange cover 25 by two threaded nuts 15 resting against a washer 26 and gasket 17.
[0042] Even in the event of the first elastomeric sealing ring 16 between the flange cover 25 and the shoulder 30 becoming pressed and changing shape with time and the nut 15 being insufficient to maintain a tight connection by its force, this would potentially not lead to a leak, because the shoulder 32 would be pressed onto the flange cover 25 by the gas pressure in the vessel 2 and result in maintaining a gas-tight sealing.
[0043] A rigid, electrically conducting metal rod 12 extends through a passage 32 in the bushing 11 and is electrically insulated from the flange cover 25, and thus from the vessel wall, by the bushing 11. The metal rod 12 comprises a first electrical connector piece 12A inside the vessel and a second electrical connector piece 12B outside the vessel 2.
[0044] For good electrical contact of the connector pieces 12A, 12B to the respective terminals, connector blocks 14 are mounted to the connector pieces 12 A, 12B. These connector blocks 14 have a cross section larger than the passage 32 and are abutting the bushing 11 so as to function as a stopper on the rod 12 inside the vessel 2, preventing the rod 12 from being pushed through the bushing 11 by the pressure in the vessel 2.
[0045] As an alternative, the terminal 8 could be screwed to the first connector piece 12A without the connector blocks and function as a stopper.
[0046] As a further alternative, the connector blocks 14 could be substituted by a thickened first electrical connector piece 12A to which the terminal 8 of the electrical conductor 7 is mounted. As an even further alternative, the stopper could be obtained by a thickened further section of the rod 12, which is not shown in the drawings, however. In such embodiment, the rod 12 not only has a middle section 12C inside the bushing 11 between the first electrical connector piece 12A and the second electrical connector piece 12B, but the rod 12 comprises additionally a further, thickened section (not shown) between the middle section 12C and the first connector piece 12A. The stopper is, thus, provided by the thickened further section in extension of the middle section 12C, as it has a larger cross section that the middle section 12C and, thus, larger than the passage 32. The first electrical connector piece 12A, the second electrical connector piece 12B, the middle section 12C, and the further section are made as a single piece of metal.
[0047] As seen in FIG. 3 in combination with FIG. 2C, the first connector piece 12A is connected to the terminal 8 of the conductor 7 shown in FIG. 1. The second connector piece 12B is connected to a respective conductor terminal (not shown) that provides power to the electrolyzer 5 through the rod 12. The terminals 8 and the connector blocks 14 are safely secured to the rod 12 by bolt / washer / nut combinations 19 / 18 / 20.
[0048] In order to provide a gas tight connection between the flange cover 25 and the flange 9 of the vessel 2, a corresponding gasket 21 is provided around the opening 4 of the flange 9, which is illustrated in FIG. 2C.
[0049] Two elastomeric sealing rings 13 inside the passage 32 provides a gas-tight connection between the metal rod 12 and the bushing 11 so that no gas creeps between the rod 12 and the bushing 11.
[0050] This system is simple, can be produced at low cost, is efficiently adaptable to different sizes of openings, and is safely sealing against gas leakage. For example, for special dimensions, the rod 12 and bushing 11 can easily be produced in a workshop with a few hours of work. Despite its simplicity, it is fulfilling its purpose and a low-cost alternative to sintered or glued solutions, even when produced automatically in large numbers.
Claims
CLAIMS1. An electrolyzer system (1) comprising a vessel (2) with an inner volume (3) that contains pressurized gas and an electrolyzer (5) in the pressurised gas, wherein an electrical conductor assembly (10) extends through a wall section (25) of the vessel (2) from outside the vessel (2) to the inner volume (3) for providing electrical current to the electrolyzer (5); wherein the assembly (10) comprises a bushing (11) made of an electrically insulating, gas-tight polymer and which has a first portion (11 A) and a second portion (1 IB) extending from the first portion (11 A) through an opening (25 A) in the wall section (25) to outside of the vessel (2), wherein the second portion (1 IB) has a cross section corresponding to the opening (25 A) wherein a rigid, electrically conducting metal rod (12) extends through a passage (32) in the bushing (11) and is electrically insulated from the wall section (25) by the bushing (11), wherein the metal rod (12) comprises a second electrical connector piece (12B) outside the vessel (2), which is connected to a corresponding conductor (7) that provides power to the electrolyzer (5) through the rod (12), wherein an elastomeric sealing ring (13) inside the passage (32) provides a gastight connection between the metal rod (12) and the bushing (11), characterized in that the bushing has a first portion (11 A) inside the inner volume and a second portion (11B) extending from the first portion (11 A) through the opening (25A) in the wall section (25) to outside of the vessel (2), that the first portion (11 A) and the second portion (11B) are a single piece of the polymer, that the first portion (11 A) comprises a shoulder (30) inside the inner volume, the shoulder having a cross section larger than the opening (25 A) and which extends around the opening (25 A), and that a first elastomeric sealing ring (16) is provided between the shoulder (30) and the wall section (25), providing a gas tight sealing between the first portion (11 A) and the wall section (25) and, correspondingly, between the opening (25 A) and the inner volume (3) of the vessel (2); wherein the metal rod (12) comprises a first electrical connector piece (12A) inside the vessel (2).
2. The system according to claim 1, wherein a stopper (14) is provided on the rod (12) inside the vessel (2), the stopper (14) having a cross section larger than the passage (32) and is abutting the bushing (11) so as to secure the rod (12) from being pushed through the bushing (11) by the gas pressure in the vessel (2).
3. The system according to claim 2, wherein the rod (12) at the location of the first electrical connector piece (12A) has a cross section not larger than the passage (32) and the stopper is provided by a connector terminal (8) or by connector blocks (14) as part of a connector terminal (8) mounted onto the first electrical connector piece (12A).
4. The system according to any preceding claim, wherein the bushing (11), in extension of the second portion (11B), has a third portion (11C) outside the vessel (2), wherein the third portion (11C) has an outer threading (31) and is secured against the wall section (25) of the vessel (2) by a threaded nut (15).
5. The system according to any preceding claims, wherein the vessel (2) is pressurised to at least 10 bar, corresponding to 1 MPa, relatively to the outside of the vessel (2).
6. The system according to any preceding claim, wherein the bushing is made of PPS,PTFE, PEEK or PEK.