WO2016034185A1 - Electrolyser stack divided into sub-stacks - Google Patents

Electrolyser stack divided into sub-stacks Download PDF

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Publication number
WO2016034185A1
WO2016034185A1 PCT/DK2015/050265 DK2015050265W WO2016034185A1 WO 2016034185 A1 WO2016034185 A1 WO 2016034185A1 DK 2015050265 W DK2015050265 W DK 2015050265W WO 2016034185 A1 WO2016034185 A1 WO 2016034185A1
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WO
WIPO (PCT)
Prior art keywords
electrolysis stack
electrolysis
stack
frames
cell
Prior art date
Application number
PCT/DK2015/050265
Other languages
French (fr)
Inventor
Jørgen Krogsgaard Jensen
Anders Rønne Rasmussen
Original Assignee
Greenhydrogen.Dk Aps
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Publication date
Application filed by Greenhydrogen.Dk Aps filed Critical Greenhydrogen.Dk Aps
Publication of WO2016034185A1 publication Critical patent/WO2016034185A1/en

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B1/00—Electrolytic production of inorganic compounds or non-metals
    • C25B1/01—Products
    • C25B1/02—Hydrogen or oxygen
    • C25B1/04—Hydrogen or oxygen by electrolysis of water
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B9/00—Cells or assemblies of cells; Constructional parts of cells; Assemblies of constructional parts, e.g. electrode-diaphragm assemblies; Process-related cell features
    • C25B9/05—Pressure cells
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B9/00—Cells or assemblies of cells; Constructional parts of cells; Assemblies of constructional parts, e.g. electrode-diaphragm assemblies; Process-related cell features
    • C25B9/70—Assemblies comprising two or more cells
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/30—Hydrogen technology
    • Y02E60/36—Hydrogen production from non-carbon containing sources, e.g. by water electrolysis

Definitions

  • the present invention generally relates to an electrolyser for pressurised electrolysis,
  • the present invention more particularly relates to an electrolysis stack for a pressurised electrolyser.
  • An electrolyser is a device that splits water (H 2 0) into hydrogen (H 2 ) and oxygen (0 2 ) by means of electrical energy.
  • An electrolyser comprises a number of modules including one or more electrolyser modules, a water supply module for supplying purified water and power supply modules for supplying direct current to the electrolysis process,
  • the electrolyser modules consist of an electrolysis stack as well as a degassing system (chambers), a gas purification system and a pressure control system .
  • the electrolysis stack comprises a series of stacked electrolysis cells comprising electrodes (e.g. bipolar electrodes) and one gas separating porous membrane.
  • the stacked electrolysis ceils are typically mounted in a ring-shaped polymer cell frame having a channel that supplies electrolyte to the cell compartment and a channel that evacuates the gas generated.
  • the channels may be connected to manifolds that either distribute electrolyte to all cells in a stack or collect oxygen or hydrogen from ail cells in a stack.
  • An electrolyser generates a specific mass of hydrogen from a given amount of electrical energy. Calculation of the efficiency of an electrolyser is based on the higher heating value of hydrogen which is 141.80 MJ/kg . The electrolyser efficiency is given as the ratio of the mass of hydrogen multiplied by the higher heating value to the amount of electrical energy. Several mechanisms influence the efficiency of an electrolyser. The efficiency can never exceed 100% and for practical reasons it will always be below 100%.
  • stray currents may also give rise to loss of energy in an electrolysis stack.
  • supply and evacuation channels together with the manifolds form alternative current pathways for ionic currents between the ceils in a stack. These currents are called stray currents,
  • the electrolysis stack according to the invention is an electrolysis stack method for an electrolyser, which electrolysis stack comprises a plurality of electrolysis cells each comprising two electrodes and a gas separating membrane and a cell frame, which ceil frames are arranged adjacent to each other, which electrolysis stack comprises means for supplying electrolyte feed to the interior of the electrolysis cells and means for removing oxygen gas and hydrogen gas from the electrolysis cells, which electrolysis stack comprises electric power point members constituting either a cathode, an anode or a cathode and an anode, wherein the electrolysis stack is divided into a plurality of electrically separated cell frame modules.
  • the electrolysis stack comprises a plurality of insulation bushings configured to electrically insulate the electrolyte within the electrolysis stack from the current terminals and/or electric power point members during use of the electrolysis stack.
  • the electrical potential between the first and last cells in each of the ceil frame modules is reduced. Accordingly, it is possible to provide an electrolysis stack that reduces the energy losses including the stray currents. Moreover, the insulation bushings reduce the stray currents giving rise to loss of energy in the electrolysis stack.
  • the amount of energy loss due to stray currents increases with the number of cells in the cell frame module, because the electrical potential between the first cell frame and the last cell frame in a cell frame module depends on the number of ceil frames in the ceil frame module.
  • the present invention suggests a construction in which the electrolysis stack is divided into a plurality of electrically separated cell frame modules. In this manner, the electrical potential difference between the first cell and the last ceil in a cell frame module can be significantly reduced.
  • the electrolysis stack may comprise any suitable number of electrolysis cells (e.g. 25, 50, 100, or 400).
  • the electrolysis cells may be arranged in the same or in several different modules.
  • the electrolysis stack according to the invention may be adapted to handle a strong alkali electrolyte comprising potassium hydroxide (KOH) (e.g. 30wt% KOH).
  • KOH potassium hydroxide
  • the bipolar electrodes may comprise sheet material (e.g. a metal sheet), and the separating membrane may be a porous gas separating membrane.
  • the membrane may comprise any suitable material e.g. two layers of a polymer comprising Zr0 2 . It may be an advantage that each eel! frame has a circular outer periphery, Hereby it is possible to provide a strong and reliable electrolysis stack.
  • the ceil frames are arranged adjacent to each other, and it may be an advantage that the cell frames are sealed with Or!ng gaskets made in a resilient material (e.g. EPDM rubber).
  • the electrolysis stack comprises means for supplying electrolyte feed to the interior of the electrolysis cells.
  • the means for supplying electrolyte feed to the interior of the electrolysis ceils may be of any suitable type and geometry.
  • the means for supplying electrolyte feed to the interior of the electrolysis cells may comprise a channel structure constituted by the plurality of cell frames arranged side by side along the longitudinal axis of the electrolysis stack.
  • the electrolysis stack comprises means for removing oxygen gas and hydrogen gas from the electrolysis ceils. These means may comprise a channel structure constituted by the plurality of cell frames arranged side by side along the longitudinal axis of the electrolysis stack.
  • each cell frame is provided with a plurality of through-bores extending through the axial length of the cell frame.
  • These through-bores may, together with other structures, constitute a channel structure constituted by the plurality of cell frames arranged side by side along the longitudinal axis of the electrolysis stack.
  • the electrolysis stack comprises electric power point members constituting a cathode, an anode or a cathode and an anode. These electric power point members may have any suitable geometry.
  • the electric power point members may e.g. be plate-shaped.
  • the electrolysis stack may be divided into a plurality of electrically separated cell frame modules by several means; however, it may be an advantage that the electrolysis stack is divided into a plurality of electrically separated cell frame modules by means of electric power point members extending along the length of the cell frames.
  • the electric power point members electrically separating the cell frame modules are plate-shaped.
  • each of the electrically separated cell frame module comprises 10-40, preferably 15-35, such as 20-35 ceil frames.
  • 15-35 such as 20-35 ceil frames.
  • each of the electrically separated cell frame modules comprises 25 cell frames.
  • each of the electrically separated cell frame modules comprises the same number of cell frames.
  • each of the electrically separated cell frame modules are electrically separated from each other by means of current terminals and/or electric power point members arranged between adjacent cell frame modules. Hereby it is possible to supply electrical current to the cell frame modules through these current terminals and/or electric power point members. It may be an advantage that each of the electrically separated ceil frame modules comprises insulation bushings configured to electrically insulate the electrolyte within the electrolysis stack from the current terminals and/or electric power point members arranged between adjacent cell frame modules during use of the electrolysis stack. Hereby it is possible to reduce the stray currents giving rise to loss of energy in the electrolysis stack,
  • the bushings may preferably have a cylindrical shape.
  • the bushings are arranged in the channels that are provided in the cell frames to distribute electrolyte to all the cells frames in the cell frame module.
  • the bushings extend between two adjacent ceil frame modules.
  • At least one support member is arranged at the outside periphery of the cell frames.
  • the support member reduces deformation in the circumferential direction of the ceil frames.
  • the support member is cylindrical and extends along the axial length of the cell frame.
  • a support member having the required mechanical properties.
  • a cylindrical support member will be fit to enclose cell frames having a circular outer periphery.
  • the cell frames are arranged between two flanges and that the flanges are mechanically attached to each other by means of a plurality of threaded rods and nuts.
  • an electrolysis stack that is configured to resist large forces acting in the axial direction (causing expansion of the electrolysis stack along its longitudinal axis). It may be an advantage that the cell frames are arranged between two flanges and that the flanges are mechanically attached to each other by means of a plurality of threaded rods, nuts and washers, It may be advantageous that the support member is arranged in such a manner that it is not in mechanical contact with the flanges, Hereby it is achieved that the support member can expand in the axial direction.
  • the cell frames are mounted in an outer support member made in a high strength composite material. It may be an advantage that the outer support member extends longer in the axial direction than the cell frames contained within the outer support member. Hereby it is possible to support the cell frames when the cell frames extend axially.
  • the support member is constructed in such a way that the gap between the outer diameter of the cell frames and the inner diameter of the support member is as small as possible.
  • the support member is a cylindrical tube made in a composite material (fibre-reinforced polymer) made of a polymer matrix reinforced with fibres (e.g. glass, carbon or aramid).
  • the polymer may be any suitable polymer material, e.g. epoxy, polyphenylsulfone (PPSU) or polyether ether ketone (PEEK).
  • the elastic modulus of the support member is significantly larger than the elastic modulus of the cell frames.
  • the support member is configured to keep its geometrical shape and prevent radial expansion of the cell frames.
  • the coefficient of thermal expansion of the support member is smaller than the coefficient of thermal expansion of the cell frames.
  • the support member is configured to maintain its geometrical shape and prevent radial expansion of the ceil frames during operation of the electrolysis stack, It may be beneficial that the support member is made in an electrical insulation material e.g. a fibre reinforced plastic material.
  • the fibres may be glass fibre, armid fibre or carbon fibre by way of example.
  • the electrolysis stack comprises a plurality of support members arranged with mutual end-to-end contact and substantially in axial extension of each other.
  • the electrolysis stack comprises a first support member and at least one additional support member arranged at the outside of the first support member.
  • the object of the invention may be achieved by an electrolyser comprising an electrolysis stack according to the invention.
  • the electrolysis stack can be a single electrolysis stack or split in sections. It is preferred that the cell frames are made in a material that is suitable for handling high pH values (pH values above 14)
  • the support member may be mechanically attached outside the cell frames. It is possible to apply a metal (steel) support structure provided with an inner isolation structure.
  • the bipolar electrodes may comprise sheet material (e.g. a metal sheet) and the separating membrane may be a porous gas separating membrane.
  • the membrane may comprise any suitable material e.g. two layers of a polymer comprising Zr0 2 .
  • each cell frame has a circular outer periphery. Hereby it is possible to provide a strong and reliable electrolysis stack.
  • the cell frames are arranged adjacent to each other and it may be an advantage that the cell frames are sealed with O-ring gaskets made in a resilient material (e.g. EPDM rubber).
  • a resilient material e.g. EPDM rubber
  • the electrolysis stack comprises means for supplying electrolyte feed to the interior of the electrolysis cells.
  • the means for supplying electrolyte feed to the interior of the electrolysis ceils may be of any suitable type and geometry.
  • the means for supplying electrolyte feed to the interior of the electrolysis ceils may comprise a channel structure constituted by the plurality of cell frames arranged side by side along the longitudinal axis of the electrolysis stack.
  • the electrolysis stack comprises means for removing oxygen gas and hydrogen gas from the electrolysis cells. These means may comprise a channel structure constituted by the plurality of cell frames arranged side by side along the longitudinal axis of the electrolysis stack. It may be an advantage that each ceil frame is provided with a plurality of through-bores extending through the axial length of the cell frame.
  • These through-bores may, together with other structures, constitute a channel structure constituted by the plurality of cell frames arranged side by side along the longitudinal axis of the electrolysis stack.
  • the at least one support member arranged at the outside periphery of the cell frames may have any suitable geometry and be made in any suitable material.
  • the inner portion of the support member is made in an electrically insulating material, such as a plastic material.
  • the support member is cylindrical and extends along the axial length of the cell frame.
  • a support member having the required mechanical properties.
  • a cylindrical support member wil l be fit to enclose cell frames having a circular outer periphery.
  • the cell frames are arranged between two flanges and that the flanges are mechanically attached to each other by means of a plurality of threaded rods and nuts.
  • the cell frames are arranged between two flanges and that the flanges are mechanically attached to each other by means of a plurality of threaded rods, nuts and washers. It may be advantageous that the support member is arranged in such a manner that it is not in mechanical contact with the flanges. Hereby it is achieved that the support member can expand in the axial direction.
  • ceil frames are mounted in an outer support member made in a high strength composite material. It may be an advantage that the outer support member extends longer In the axial direction than the cell frames contained within the outer support member, Hereby it is possible to support the cell frames when the cell frames extend axialiy.
  • the support member is constructed in such a way that the gap between the outer diameter of the cell frames and the inner diameter of the support member is as small as possible.
  • the support member is a cylindrical tube made in a composite material (fibre-reinforced polymer) made of a polymer matrix reinforced with fibres (e.g. glass, carbon or aramid).
  • the polymer may be any suitable polymer material, e.g. epoxy, polyphenylsulfone (PPSU) or polyether ether ketone (PEEK).
  • the elastic modulus of the support member is significantly larger than the elastic modulus of the cell frames.
  • the support member is configured to keep its geometrical shape and prevent radial expansion of the cell frames.
  • the coefficient of thermal expansion of the support member is smaller than the coefficient of thermal expansion of the cell frames.
  • the support member is configured to maintain its geometrical shape and prevent radial expansion of the cell frames during operation of the electrolysis stack. It may be beneficial that the support member is made in an electrical insulation material e.g. a fibre reinforced plastic material.
  • the fibres may be glass fibre, armid fibre or carbon fibre by way of example.
  • the electrolysis stack comprises a plurality of support members arranged with mutual end-to-end contact and substantially in axial extension of each other, Hereby it is possible to provide an electrolysis stack provided with modular support members. It is thus possible to build a long electrolysis stack and apply the same support member that is used for shorter electroiysis stacks. It may be an advantage that the electrolysis stack comprises a first support member and at least one additional support member arranged at the outside of the first support member.
  • the object of the invention may be achieved by an electrolyser comprising an electrolysis stack according to the invention,
  • the electrolysis stack can be a single electrolysis stack or split in sections.
  • the cell frames are made in a material that is suitable for handling high pH values (pH values above 14)
  • the support member may be mechanically attached outside the cell frames.
  • the support members are arranged in such a manner that they are not in mechanical contact with the flanges.
  • the cell frames can be compressed in axial direction (e.g. during tensioning of the nuts). Furthermore, the support member can expand in the axial direction.
  • the support member can expand in the axial direction without pressing against the flanges. it may be advantageous that a gap is provided between at least some of the adjacent support members.
  • the cell frames can be compressed in axial direction (e.g. during tensioning of the nuts).
  • the support member can expand in the axial direction.
  • the cell frames can be compressed in axial direction (e.g. during tensioning of the nuts) without damaging the support members.
  • the support member can expand in the axial direction.
  • the metal structure may be a current terminal made of a metal plate.
  • the metal structure may be an electrical power member shaped as a plate. It may be beneficial that an electric connection is provided between adjacent support members, wherein at least the distal portion of the electric connections protrudes from the support members.
  • the electric connections may preferably extent radially perpendicular to the support member. Hereby, easy access can be provided.
  • the electric power point members are easily accessible electrically.
  • Fig. 1 shows two schematic views of an electrolysis stack according to the invention
  • Fig. 2 shows a schematic perspective top view of an electrolyser according to the invention
  • Fig. 3 illustrates schematic perspective top views of an electrolysis stack according to the invention
  • Fig. 4 shows schematic cross-sectional views of an electrolysis stack according to the invention
  • Fig. 5 shows two schematic perspective top views of an electrolysis stack according to the invention
  • Fig. 6 shows a schematic perspective top view of an electrolysis stack according to the invention
  • Fig. 7 a shows an end view of an electrolysis stack according to an embodiment of the invention
  • Fig, 7 b shows a close-up cross-sectional view of the bushing electrically insulating the electric power point member from the electrolyte within the electrolysis stack;
  • Fig. 7 c shows a close-up cross-sectional view of a bushing electrically insulating a current terminal from the electrolyte
  • Fig, 7 d shows a cross-sectional view of the electrolysis stack shown in Fig, 7 a);
  • Fig, 7 e shows a perspective view of the bushing shown in Fig. 7 c);
  • Fig. 7 f shows a perspective view of the bushing shown in Fig. 7 b);
  • Fig. 8 a shows a top view of an electrolysis stack according to an embodiment of the invention
  • Fig. 8 b shows a close-up cross-sectional view of the electrical connection shown in Fig. 8 a)
  • Fig. 8 c shows a close-up cross-sectional view of the joint structure of the adjacent support members.
  • an electrolysis stack 2 of the present invention is illustrated in Fig. 1.
  • Fig, 1 illustrates two different schematic views of an electrolysis stack 2 according to the invention.
  • Fig. 1 a illustrates a schematic top view of an electrolysis stack 2 comprising a cylindrical support member 12 enclosing a plurality of disk-shaped cell frames 6 stacked within the support member 12.
  • the electrolysis stack 2 comprises a series of stacked electrolysis cells. Each of these electrolysis cells contains two bipolar electrodes (metal sheets). A gas separating porous membrane is provided between every bipolar electrode.
  • Each electrolysis ceil comprises a disk-shaped polymer cell frame 6, in Fig. 1, however, the membrane and bipolar electrodes of the ceil frames 6 have been removed for illustration purposes. It may be an advantage that the cell frames are sealed with O-ring gaskets of a resilient material (e.g. EPDM rubber).
  • Each ceil frame 6 comprises four axialiy extending through bores 8, 8', 10, 10'.
  • Each cell frame 6 comprises a centrally arranged aperture 14.
  • Each ceil frame 6 comprises a membrane (not shown).
  • the membrane is exposed to high temperatures (up to 100° Celsius) and pH values above 14 during operation of the electrolysis stack 2. Accordingly, the membrane must be capable of being exposed to a demanding chemical environment.
  • the membrane may comprise any suitable material e.g. two layers of a polymer comprising Zr0 2 .
  • the electrolysis stack 2 according to the invention may be adapted to handle a strong alkali electrolyte comprising potassium hydroxide (KOH) (e.g. 30 wt% KOH).
  • KOH potassium hydroxide
  • Some of the through bores 8, 8 f , 10, 10 f may be used to transport oxygen (0 2 ) and hydrogen (H 2 ) generated by means of the electrolysis stack 2.
  • FIG. 1 b illustrates a schematic perspective top view of the electrolysis stack 2 shown in Fig. 1 a).
  • the electrolysis stack 2 comprises a cylindrical support member 12 arranged at the outside of a stack of cell frames 6, 6', 6" stacked within the support member 12. Even though the cell frames 6, 6', 6" comprise membranes and bipolar electrodes, these have been removed for illustrating that the ceil frames 6, 6', 6" are stacked on top of each other within the cylindrical support member 12.
  • the cell frames 6, 6', 6" may be manufactured in a polymer material, e.g. polyphenylsuifone (PPSU) or poiyether ether ketone (PEEK).
  • PPSU polyphenylsuifone
  • PEEK poiyether ether ketone
  • Fig. 2 illustrates a schematic perspective top view of an eiectrolyser 20 according to the invention.
  • the eiectrolyser 20 comprises a frame 36 having a lower frame member 38 and an upper frame member 38' interconnected by four (only three are visible in Fig. 2) connection members 40, 40', 40" shaped as angle bars 40, 40', 40".
  • Each angle bars 40, 40', 40" is mechanically attached to both the lower frame member 38 and an upper frame member 38'.
  • the eiectrolyser 20 comprises two electrolysis stacks 2, 2' mounted in the lower portion of the eiectrolyser 20.
  • Each of the electrolysis stacks 2, 2' comprises a cylindrical support member 12 like the one shown in Fig. 1.
  • Each of the two electrolysis stacks 2, 2' is arranged between two flanges 24, 24'. These flanges 24, 24' are mechanically attached to each other by means of a plurality of threaded rods 26, nuts 22 and washers 44.
  • the two electrolysis stacks 2, 2' are identically constructed and extend parallel to each other.
  • the eiectrolyser 20 comprises degassing chambers, a gas purification system and a pressure control system.
  • the two electrolysis stacks 2, 2' are electrically connected to separate power supplies.
  • Fig. 3 a) and Fig. 3 b) illustrate two different schematic perspective top views of an electrolysis stack 2 according to the invention.
  • the electrolysis stack 2 is arranged between two parallel, plate-shaped flanges 24, 24'.
  • the flanges 24, 24' are mechanically attached to each other by means of a plurality of threaded rods 26 and corresponding nuts 22 and disks 44.
  • the disks 44 are compressible disks allowing the eel! frames to expand along the longitudinal axis X of the electrolysis stack 2.
  • the stack may for example comprise 18 disks 44, This assembly prevents the flanges from being displaced from each other along the longitudinal axis X of the electrolysis stack 2 ,
  • threaded rods 26 extend parallel to each other and to the longitudinal axis X of the electrolysis stack 2.
  • the electrolysis stack 2 comprises three cylindrical support members 11, 11', 12 arranged end to end at the periphery of a plurality of ceil frames (not shown) within the interior of the electrolysis stack 2 ,
  • electrical connections 50, 50', 52, 52' are provided along the periphery of the support members 11, 11', 12.
  • the electrical connections 50, 50', 52, 52' protrude radially from the periphery of the support members 11, 11', 12.
  • Fig . 4 illustrates two schematic cross-sectional views of an electrolysis stack 2 according to the invention .
  • Fig . 4 a) shows a side view
  • Fig . 4 b) illustrates a perspective view.
  • the electrolysis stack 2 is arranged between two flanges 24, 24' mechanically attached to each other by means of a plurality of threaded rods 26, 26' and corresponding nuts 22, 22' and washers 44.
  • the threaded rods 26, 26' extend along the longitudinal axis X of the electrolysis stack 2.
  • the electrolysis stack 2 comprises a cylindrical support member 12 arranged at the periphery of a plurality of cell frames 6.
  • the electrolysis stack 2 comprises three cylindrical support members 11, 11', 12 arranged end to end at the periphery of a plurality of ceil frames 6 of the electrolysis stack 2.
  • Fig . 4 b shows that a gas outlet pipe 16 and a KOH inlet pipe 18 are provided in the flange 24.
  • Channels extending parallel to the longitudinal axis X of the electrolysis stack 2 are provided in continuation of the gas outlet pipe 16 and of the KOH inlet pipe 18.
  • the channels extend through the plurality of eel! frames 6.
  • the electrolysis stack 2 comprises three cell frame modules M lf M 2 , M 3 arranged end to end along the longitudinal axis X of the electrolysis stack 2. Fifty cell frames 6 are arranged in each of the three cell frame modules Mi, M 2 , M 3 . Accordingly, the total number of cell frames 6 in the electrolysis stack 2 is 150,
  • An insulating plate member 32, 32' is arranged in each end of the electrolysis stack 2.
  • Two electric power point members (current terminals) 46, 46' are arranged next to each of the insulating plate members 32, 32'.
  • the electric power point member 46 is a cathode, while the electric power point member 46' is an anode,
  • two electric power point members formed as bipolar electrodes 48, 48' are arranged between the first cell frame module Mi and the second cell frame module M 2 as well as between the second cell frame module M 2 and the third cell frame module M 3 , respectively.
  • a first bushing 34, a second bushing 34' and a third bushing 34" are arranged to electrically insulate the electrolyte from the electric power point members 48, 48', 46, 46' in order to prevent unwanted currents from running through the electrolysis stack 2.
  • the bushings 34, 34', 34" may be made in any suitable insulating material capable of resisting the demanding working conditions (temperatures up to 100° Celsius and pH values above 14 as well as a high concentration of oxygen and hydrogen gasses).
  • the bushings 34, 34', 34" may be made in poiyphenylsulfone (PPSU) or poiyether ether ketone (PEEK) by way of example.
  • the electrolysis stack 2 is equipped with a gas outlet channel 16 (oxygen or hydrogen gasses) and a media inlet 18 (for demineralised water with KOH, e.g. demineralised water with 30wt% KOH).
  • the electrolysis stack 2 is enclosed by three support members 11, 11', 12 shaped like cylindrical tubes.
  • the support members 11, 11', 12 are constructed in such a way that they are configured to support the cell frames 6 in radial direction. It is possible to apply one large support member instead of three support members 11, 11', 12.
  • the total length of the stack of ceil frames 6 wil l change with temperature and over time due to thermal expansion, change of elastic modulus with temperature and compressive stress, and creep due to compressive stress.
  • the support members 11, 11', 12 are not subjected to any significant stress in the axial direction. Accordingly, only thermal expansion will cause changes in the length of the support members 11, 11', 12 in the direction of their longitudinal axis X.
  • the electrolysis stack 2 is designed with a modular concept in mind.
  • the electrolysis stack 2 contains??? a number of cell frame modules Mi, M 2 , M 3 providing a total number of cell frames 6 of e.g. 100, 150 or 200 with a volume ranging from e.g. 4 L to 10 L or more of electrolyte inside.
  • a number of cell frame modules M lf M 2/ M 3 it is possible to provide large configurations of e.g. 50, 75, 100 or 200 ceil frames 6 by combining a number of cell frame modules M lf M 2/ M 3 .
  • the cell frame modules Mi, M 2 , M 3 are separated from one.
  • the cell frame modules M i? M 2 , M 3 each comprises 50 cell frames 6. Each cell frame module comprises electrical power point members constituting either a cathode, an anode or a cathode and an anode. A diaphragm or membrane is provided to separate the gasses generated.
  • the cell frame modules M i? M 2/ M 3 are connected to fittings in the flanges 24, 24'.
  • a 150 cell frame electrolysis stack 2 is built up by the three cell frame modules Mi, M 2 , M 3 with a total of 150 small chambers (anode, cathode, anode, cathode and so on) where 75 of the chambers are connected by channels to the oxygen producing part of the stack, and the remaining 75 chambers are connected to the hydrogen producing part.
  • the electrolysis stack 2 may be considered to take the form of two vessels; one carrying H 2 and one carrying 0 2 .
  • each cell comprises two cell frames 6) in the cell frame module Mi, M 2 , M 3 , dividing the potential between each cell frame in the cell frame module Mi, M 2 , M 3 .
  • the potential of each cell frame 6 is determined by the current passing through each cell frame 6, the temperature, the chemical composition of the (bipolar) electrode and the thickness of the electrolyte.
  • Fig. 5 a illustrates a schematic perspective top view of an electrolysis stack 2 according to the invention.
  • the electrolysis stack 2 comprises only one ceil frame 6 since the remaining ceil frames have been removed.
  • the ceil frame 6 has a circular outer periphery and is provided with a centrally and symmetrically arranged aperture 14.
  • the aperture 14 is defined by two circular arcs connected by two parallel straight lines.
  • the cell frame 6 is arranged within a cylindrical support member 12 having an inner geometry that fits the outer geometry of the eel! frame 6.
  • Fig, 5 b illustrates a top view of an electrolysis stack 2 according to the invention.
  • the electrolysis stack 2 comprises a plurality of cell frames 6 (only one is visible) corresponding to the one illustrated in Fig, 5 a).
  • the cell frame 6 is arranged within a cylindrical support member 12 having an inner geometry that fits the outer geometry of the cell frame 6.
  • gaseous 0 2 and H 2 are generated within the centra! portion of the cell frame 6 by means of two electrodes (metal sheets) and a gas separating porous membrane (these are not shown).
  • the pressure is increased significantly (up to 3 MPa). Therefore, an outwardly directed force F is created.
  • the force F acts in all radial directions causing a need to ensure a rather large mechanical strength of the electrolysis stack 2.
  • a large mechanical strength of the electrolysis stack 2 is achieved by means of the cylindrical support member 12 enclosing the ceil frames 6 of the electrolysis stack 2.
  • the ceil frame 6 bears against the inside portion of the support member 12, and hereby the mechanical strength of the support member 12 can directly be used to prevent radial expansion of the ceil frames 6.
  • the mechanical strength of the cell frames 6 may be reduced provided that the mechanical strength of the support member 12 is sufficiently large.
  • Fig. 6 a illustrates a schematic perspective top view of an electrolysis stack 2 according to the invention.
  • the electrolysis stack 2 comprises a plurality of ceil frames 6, 6', 6" arranged within a cylindrical support member 12. Additional support members 42, 42', 42" are provided at the outside of the cylindrical support member 12.
  • the additional support members 42, 42', 42" are made as separate bands configured to fit the outer periphery of the cylindrical support member 12. However, it would be possible to apply one large additional support member 42 having the same axial extension as the cylindrical support member 12. Alternatively, it is possible to apply a larger number (e.g. four or more) of additional support members 42, 42', 42".
  • Fig. 6 b illustrates a schematic top view of an electrolysis stack 2 according to the invention.
  • the electrolysis stack 2 comprises a plurality of cell frames 6 arranged within a first cylindrical support member 12 having an inner geometry that fits the outer geometry of the cell frame 6.
  • a second and additional support member 12' is arranged at the outside of the first cylindrical support member 12.
  • gaseous 0 2 and H 2 are generated within the central portion of the ceil frames 6.
  • the gaseous 0 2 and H 2 can be generated through use of two electrodes (not shown) and a gas separating porous membrane (not shown).
  • the pressure within the central portion of the cell frames 6 is increased significantly (up to 3 MPa) due to the generated gasses, and an outwardly directed force F acting in all radial directions is created.
  • the first cylindrical support member 12 as well as the second additional support member 12' provide the required mechanical strength of the electrolysis stack 2. Thus, radial expansion of the ceil frames 6 can be prevented.
  • Fig. 7 A illustrates an end view of an electrolysis stack 2 according to an embodiment of the invention, in which the threaded rods, washers and nuts have been removed for better illustrating the remaining structures.
  • the electrolysis stack 2 comprises an outlet 16 and an inlet 18 protruding from the flange 24 of the electrolysis stack 2. A line A going through the outlet 16 and the inlet 18 is indicated.
  • Fig, 7 d) illustrates a cross-sectional view of the electrolysis stack 2 shown in Fig, 7 a), wherein the cross is made along the line A shown in Fig. 7 a),
  • the electrolysis stack 2 comprises a first flange 24 and a second flange 24' arranged in the opposite end of the first flange 24.
  • the electrolysis stack 2 comprises a plurality of ceil frames 6 arranged in a first cell frame module Mi and in a second ceil frame module M 2 .
  • the electrolysis stack 2 comprises a first support member 11 and a second support member 11' arranged in axial extension of each other.
  • the support members 11, 11' are arranged at the outside periphery of the cell frames 6,
  • the first support member 11 is arranged between a first plate-shaped current terminal 46 and a plate-shaped electrical power point member 48 positioned centrally in the electrolysis stack 2.
  • the second support member 11' is arranged between a second plate-shaped current terminal 46 and the plate-shaped electrical power point member 48.
  • a gap 54 is provided between the second support member 11' and the second flange 24'. The gap 54 allows for compressing the cell frames 6 in axial direction e.g. during tensioning of the nuts (not shown) without damaging the support members 11, 11'. Further, the support members 11, 11' can expand in the axial direction without pressing against the flanges.
  • the electrolysis stack 2 comprises a first insulation bushing 34 arranged and configured to electrically insulate the electrolyte within the electrolysis stack 2 from the current terminal 46'.
  • the electrolysis stack 2 comprises a second insulation bushing 34' and a third insulation bushing 35 arranged and configured to eiectricaiiy insulate the electrolyte within the electrolysis stack 2 from the electrical power point member 48.
  • the bush ings 34, 34', 35 reduce the stray currents giving rise to loss of energy in the electrolysis stack 2.
  • Fig , 7 b) illustrates a close-up cross-sectional view of the bushing 34' electrically insulating the electric power point member 48 from the electrolyte with in the electrolysis stack 2.
  • a perspective close-up view of the bushing 34' is shown in Fig , 7 f) . I n Fig . 7 f), it can be seen that the bushing 34' com prises an inner cyl indrical portion 33 su rrounded by an outer cylindrical portion 33' which is an integrated part of the bushing 34'.
  • the bushings 34', 35 extend between the two adjacent cell frame modules M i f M 2 .
  • the bushings 34', 35 are arranged in the channels provided in the ceil fra mes 6 to distri bute electrolyte to all the cel l frames 6 in the cell frame modules M 2 , Fu rther, in Fig . 7 f) it can be seen that the bushing 34 is provided with an outlet 30 for gas.
  • the outlet 30 is provided in the inner cylindrical portion 33.
  • Fig . 7 c) i llustrates a close-up, cross-sectional view of the bushing 34 electrically insulating the current term inal 46' from the electrolyte that flows through the through-going hole 56 during use of the electrolysis stack 2. It can be seen that the bushing 34 is arranged in the channel provided in the cel l frames 6 to distribute electrolyte to all the cell frames 6 in the cel l frame module Mi .
  • FIG. 7 e A perspective close-up view of the bushing 34 is shown in Fig . 7 e) in which it can be seen that the bushing 34 comprises a central ly arranged inner cylindrical portion 33 surrounded by an outer cylindrical portion 33' wh ich is an integrated part of the bush ing 34'. Besides, the bushing 34 is provided with an outlet 30 for gas. The outlet 30 is provided in the inner cylindrical portion 33.
  • Fig . 8 a i llustrates a top view of an electrolysis stack 2 according to an em bodiment of the invention .
  • the threaded rods, washers and nuts have been removed for better il lustrating the remain ing structures of the electrolysis stack 2.
  • Part of the support mem bers 11 , 11 ' has been removed in order to see the structures underneath the support members 11, 11'.
  • the electrolysis stack 2 comprises a first flange 24 and a second flange 24' arranged in the opposite end of the first flange 24.
  • the electrolysis stack 2 comprises a plurality of ceil frames 6 arranged between the flanges 24, 24'.
  • the electrolysis stack 2 comprises a first support member 11 and a second support member 11' arranged in axial extension of each other.
  • the support members 11, 11' are arranged at the outside periphery of the cell frames 6.
  • a plate-shaped electrical connection 52 protrudes from the outside surface of the support members 11, 11 '.
  • the electrical connection 52 is an integrated portion of the electrical power point member 48 arranged centrally in the electrolysis stack 2.
  • Fig . 8 b illustrates a close-up, cross-sectional view of the electrical connection 52 shown in Fig , 8 a) . It can be seen that the electrical connection 52 extends through a gap provided between the support members 11, 11'. The electrical connection 52 is provided with a through-going hole 60. Further, it can be seen that the electrical connection 52 is an integrated part (the peripheral portion) of the electrical power point member 48. The electrical connection 52 can easily be accessed from outside of the electrolysis stack 2.
  • Fig . 8 c illustrates a close-up, cross-sectional view of the joint structure 58 of the adjacent support members 11, 11'. It can be seen that a gap 62 is provided between at least some of the adjacent support members 11, 11'.
  • the ceil frames can be compressed in axial direction (e.g. during tensioning of the nuts) . Further, the support member can expand in the axial direction .

Abstract

An electrolysis stack (2) for an electrolyser (20) is disclosed. The electrolysis stack (2) comprises a plurality of electrolysis cells each comprising two electrodes and a (porous) gas separating membrane and a cell frame (6, 6', 6"). The cell frames (6, 6', 6") are arranged adjacent to each other. The electrolysis stack (2) comprises means (18) for supplying electrolyte feed to the interior of the electrolysis ceils and means (16) for removing oxygen gas and hydrogen gas from the electrolysis cells. The electrolysis stack (2) comprises electric power point members (46, 46', 48, 48') constituting either a cathode, an anode or a cathode and an anode. The electrolysis stack (2) is divided into a plurality of electrically separated cell frame modules (M1; M2, M3).

Description

Electrolyser Stack Divided into Sub-stacks
Field of invention
The present invention generally relates to an electrolyser for pressurised electrolysis, The present invention more particularly relates to an electrolysis stack for a pressurised electrolyser.
Prior art
The need for storing electric energy generated from solar panels or wind turbines is increasing due to the need of greener energy sources. Storing the electric energy in hydrogen by using electrolysers to convert water to hydrogen and oxygen has been known for decades.
An electrolyser is a device that splits water (H20) into hydrogen (H2) and oxygen (02) by means of electrical energy. An electrolyser comprises a number of modules including one or more electrolyser modules, a water supply module for supplying purified water and power supply modules for supplying direct current to the electrolysis process,
The electrolyser modules consist of an electrolysis stack as well as a degassing system (chambers), a gas purification system and a pressure control system . The electrolysis stack comprises a series of stacked electrolysis cells comprising electrodes (e.g. bipolar electrodes) and one gas separating porous membrane. The stacked electrolysis ceils are typically mounted in a ring-shaped polymer cell frame having a channel that supplies electrolyte to the cell compartment and a channel that evacuates the gas generated. The channels may be connected to manifolds that either distribute electrolyte to all cells in a stack or collect oxygen or hydrogen from ail cells in a stack.
An electrolyser generates a specific mass of hydrogen from a given amount of electrical energy. Calculation of the efficiency of an electrolyser is based on the higher heating value of hydrogen which is 141.80 MJ/kg . The electrolyser efficiency is given as the ratio of the mass of hydrogen multiplied by the higher heating value to the amount of electrical energy. Several mechanisms influence the efficiency of an electrolyser. The efficiency can never exceed 100% and for practical reasons it will always be below 100%.
The electrochemical hydrogen and oxygen generation over-potentials the ohmic losses (IR losses) in all components carrying electrical current or ionic current, electrical energy used for the auxiliary components (e.g. electrically controlled valves, control electronics, compressors in water supply modules) and loss of energy in the power supply influences the efficiency of an electrolyser. A phenomenon called stray currents may also give rise to loss of energy in an electrolysis stack. The above mentioned supply and evacuation channels together with the manifolds form alternative current pathways for ionic currents between the ceils in a stack. These currents are called stray currents,
All of the above mentioned losses of energy cause heating of the electrolyser. The generated heat has to be removed from the electrolyser in order to avoid increased temperatures, which may damage the electrolyser. Furthermore, in most cases the heat generated is purely waste; therefore in order to make the most cost- effective use of the supplied electrical energy, the electrolyser must have the highest possible efficiency.
The typical way of limiting energy loss due to stray currents, is by carefully choosing the dimensions of supply and evacuation channels and manifolds. The resistance to ionic currents is inversely related to the cross-section and directly related to the length of the channel . Accordingly, channels and pipe members (e.g . of a manifold) with a smaller geometrical cross-section and longer length have higher resistance to ionic currents. The American patent application US2881123A describes a stack design having optimised channel and manifold dimensions with the purpose of reducing the energy loss due to stray currents. The problem associated with application of this strategy is that channels and manifolds having too small cross-sections may be critical to the circulation of electrolyte and gas in the stack. A reduced circulation of electrolyte and gas in the stack may cause a malfunction of the electrolysis stack and the electrolyser.
Thus, there is a need for an improved electrolysis stack in which the energy losses including the stray currents can be reduced in an alternative way. Accordingly, it is an object of the present invention to provide an electrolysis stack that reduces the energy losses including the stray currents.
Summary of the invention
The object of the present invention can be achieved by an electrolysis stack as defined in claim 1 and by an electrolyser having the features as defined in claim 15. Preferred embodiments are defined in the dependent sub claims and explained in the following description and illustrated in the accompanying drawings.
The electrolysis stack according to the invention is an electrolysis stack method for an electrolyser, which electrolysis stack comprises a plurality of electrolysis cells each comprising two electrodes and a gas separating membrane and a cell frame, which ceil frames are arranged adjacent to each other, which electrolysis stack comprises means for supplying electrolyte feed to the interior of the electrolysis cells and means for removing oxygen gas and hydrogen gas from the electrolysis cells, which electrolysis stack comprises electric power point members constituting either a cathode, an anode or a cathode and an anode, wherein the electrolysis stack is divided into a plurality of electrically separated cell frame modules. The electrolysis stack comprises a plurality of insulation bushings configured to electrically insulate the electrolyte within the electrolysis stack from the current terminals and/or electric power point members during use of the electrolysis stack.
Hereby, the electrical potential between the first and last cells in each of the ceil frame modules is reduced. Accordingly, it is possible to provide an electrolysis stack that reduces the energy losses including the stray currents. Moreover, the insulation bushings reduce the stray currents giving rise to loss of energy in the electrolysis stack.
The amount of energy loss due to stray currents increases with the number of cells in the cell frame module, because the electrical potential between the first cell frame and the last cell frame in a cell frame module depends on the number of ceil frames in the ceil frame module. The present invention suggests a construction in which the electrolysis stack is divided into a plurality of electrically separated cell frame modules. In this manner, the electrical potential difference between the first cell and the last ceil in a cell frame module can be significantly reduced.
The electrolysis stack may comprise any suitable number of electrolysis cells (e.g. 25, 50, 100, or 400). The electrolysis cells may be arranged in the same or in several different modules.
The electrolysis stack according to the invention may be adapted to handle a strong alkali electrolyte comprising potassium hydroxide (KOH) (e.g. 30wt% KOH).
The bipolar electrodes may comprise sheet material (e.g. a metal sheet), and the separating membrane may be a porous gas separating membrane. The membrane may comprise any suitable material e.g. two layers of a polymer comprising Zr02. It may be an advantage that each eel! frame has a circular outer periphery, Hereby it is possible to provide a strong and reliable electrolysis stack. The ceil frames are arranged adjacent to each other, and it may be an advantage that the cell frames are sealed with Or!ng gaskets made in a resilient material (e.g. EPDM rubber).
The electrolysis stack comprises means for supplying electrolyte feed to the interior of the electrolysis cells. The means for supplying electrolyte feed to the interior of the electrolysis ceils may be of any suitable type and geometry. The means for supplying electrolyte feed to the interior of the electrolysis cells may comprise a channel structure constituted by the plurality of cell frames arranged side by side along the longitudinal axis of the electrolysis stack.
The electrolysis stack comprises means for removing oxygen gas and hydrogen gas from the electrolysis ceils. These means may comprise a channel structure constituted by the plurality of cell frames arranged side by side along the longitudinal axis of the electrolysis stack.
It may be an advantage that each cell frame is provided with a plurality of through-bores extending through the axial length of the cell frame. These through-bores may, together with other structures, constitute a channel structure constituted by the plurality of cell frames arranged side by side along the longitudinal axis of the electrolysis stack.
The electrolysis stack comprises electric power point members constituting a cathode, an anode or a cathode and an anode. These electric power point members may have any suitable geometry. The electric power point members may e.g. be plate-shaped.
The electrolysis stack may be divided into a plurality of electrically separated cell frame modules by several means; however, it may be an advantage that the electrolysis stack is divided into a plurality of electrically separated cell frame modules by means of electric power point members extending along the length of the cell frames.
It may be an advantage that the electric power point members electrically separating the cell frame modules are plate-shaped.
It may be beneficial that the electrolysis stack is divided into two, three or more electrically separated ceil frame modules. It may be advantageous that each of the electrically separated cell frame module comprises 10-40, preferably 15-35, such as 20-35 ceil frames. Hereby it is possible to apply standard power supplies.
It may be an advantage that each of the electrically separated cell frame modules comprises 25 cell frames. Hereby it is possible to apply a standard power supply.
It may be advantageous that each of the electrically separated cell frame modules comprises the same number of cell frames. Hereby it is possible to build an electrolysis stack by using a plurality of identical ceil frame modules.
It may be beneficial that each of the electrically separated cell frame modules are electrically separated from each other by means of current terminals and/or electric power point members arranged between adjacent cell frame modules. Hereby it is possible to supply electrical current to the cell frame modules through these current terminals and/or electric power point members. It may be an advantage that each of the electrically separated ceil frame modules comprises insulation bushings configured to electrically insulate the electrolyte within the electrolysis stack from the current terminals and/or electric power point members arranged between adjacent cell frame modules during use of the electrolysis stack. Hereby it is possible to reduce the stray currents giving rise to loss of energy in the electrolysis stack,
The bushings may preferably have a cylindrical shape.
It may be an advantage that the bushings are arranged in the channels that are provided in the cell frames to distribute electrolyte to all the cells frames in the cell frame module. Preferably, the bushings extend between two adjacent ceil frame modules.
It may be an advantage that at least one support member is arranged at the outside periphery of the cell frames.
Hereby it is possible to provide an electrolysis stack that is capable of being operated at elevated pressure, where thickness of the cell frame can be reduced. The support member reduces deformation in the circumferential direction of the ceil frames.
It may be beneficial that the support member is cylindrical and extends along the axial length of the cell frame.
Hereby it is possible to provide a support member having the required mechanical properties. Moreover, a cylindrical support member will be fit to enclose cell frames having a circular outer periphery.
It may be beneficial that the cell frames are arranged between two flanges and that the flanges are mechanically attached to each other by means of a plurality of threaded rods and nuts.
Hereby it is possible to provide an electrolysis stack that is configured to resist large forces acting in the axial direction (causing expansion of the electrolysis stack along its longitudinal axis). It may be an advantage that the cell frames are arranged between two flanges and that the flanges are mechanically attached to each other by means of a plurality of threaded rods, nuts and washers, It may be advantageous that the support member is arranged in such a manner that it is not in mechanical contact with the flanges, Hereby it is achieved that the support member can expand in the axial direction.
It is preferred that the cell frames are mounted in an outer support member made in a high strength composite material. It may be an advantage that the outer support member extends longer in the axial direction than the cell frames contained within the outer support member. Hereby it is possible to support the cell frames when the cell frames extend axially.
It may be beneficial that the support member is constructed in such a way that the gap between the outer diameter of the cell frames and the inner diameter of the support member is as small as possible. In one embodiment according to the invention, the support member is a cylindrical tube made in a composite material (fibre-reinforced polymer) made of a polymer matrix reinforced with fibres (e.g. glass, carbon or aramid). The polymer may be any suitable polymer material, e.g. epoxy, polyphenylsulfone (PPSU) or polyether ether ketone (PEEK).
It may be beneficial that the elastic modulus of the support member is significantly larger than the elastic modulus of the cell frames.
Hereby the support member is configured to keep its geometrical shape and prevent radial expansion of the cell frames.
It may be advantageous that the coefficient of thermal expansion of the support member is smaller than the coefficient of thermal expansion of the cell frames. Hereby the support member is configured to maintain its geometrical shape and prevent radial expansion of the ceil frames during operation of the electrolysis stack, It may be beneficial that the support member is made in an electrical insulation material e.g. a fibre reinforced plastic material. The fibres may be glass fibre, armid fibre or carbon fibre by way of example.
It may be an advantage that the electrolysis stack comprises a plurality of support members arranged with mutual end-to-end contact and substantially in axial extension of each other.
Hereby it is possible to provide an electrolysis stack provided with modular support members. It is thus possible to build a long electrolysis stack and apply the same support member that is used for shorter electrolysis stacks.
It may be an advantage that the electrolysis stack comprises a first support member and at least one additional support member arranged at the outside of the first support member.
Hereby it is possible to provide additional strength to the electrolysis stack so that is configured to resist the pressure within the cell stacks.
The object of the invention may be achieved by an electrolyser comprising an electrolysis stack according to the invention.
The electrolysis stack can be a single electrolysis stack or split in sections. It is preferred that the cell frames are made in a material that is suitable for handling high pH values (pH values above 14)
The support member may be mechanically attached outside the cell frames. It is possible to apply a metal (steel) support structure provided with an inner isolation structure.
The bipolar electrodes may comprise sheet material (e.g. a metal sheet) and the separating membrane may be a porous gas separating membrane. The membrane may comprise any suitable material e.g. two layers of a polymer comprising Zr02.
It may be an advantage that each cell frame has a circular outer periphery. Hereby it is possible to provide a strong and reliable electrolysis stack.
The cell frames are arranged adjacent to each other and it may be an advantage that the cell frames are sealed with O-ring gaskets made in a resilient material (e.g. EPDM rubber).
The electrolysis stack comprises means for supplying electrolyte feed to the interior of the electrolysis cells. The means for supplying electrolyte feed to the interior of the electrolysis ceils may be of any suitable type and geometry. The means for supplying electrolyte feed to the interior of the electrolysis ceils may comprise a channel structure constituted by the plurality of cell frames arranged side by side along the longitudinal axis of the electrolysis stack. The electrolysis stack comprises means for removing oxygen gas and hydrogen gas from the electrolysis cells. These means may comprise a channel structure constituted by the plurality of cell frames arranged side by side along the longitudinal axis of the electrolysis stack. It may be an advantage that each ceil frame is provided with a plurality of through-bores extending through the axial length of the cell frame. These through-bores may, together with other structures, constitute a channel structure constituted by the plurality of cell frames arranged side by side along the longitudinal axis of the electrolysis stack. The at least one support member arranged at the outside periphery of the cell frames may have any suitable geometry and be made in any suitable material.
It may be an advantage that the inner portion of the support member is made in an electrically insulating material, such as a plastic material.
It may be beneficial that the support member is cylindrical and extends along the axial length of the cell frame.
Hereby it is possible to provide a support member having the required mechanical properties. Moreover, a cylindrical support member wil l be fit to enclose cell frames having a circular outer periphery.
It may be beneficial that the cell frames are arranged between two flanges and that the flanges are mechanically attached to each other by means of a plurality of threaded rods and nuts.
Hereby it is possible to provide an electrolysis stack that is configured to resist large forces acting in the axial direction (causing expansion of the electrolysis stack along its longitudinal axis).
It may be an advantage that the cell frames are arranged between two flanges and that the flanges are mechanically attached to each other by means of a plurality of threaded rods, nuts and washers. It may be advantageous that the support member is arranged in such a manner that it is not in mechanical contact with the flanges. Hereby it is achieved that the support member can expand in the axial direction.
It is preferred that the ceil frames are mounted in an outer support member made in a high strength composite material. It may be an advantage that the outer support member extends longer In the axial direction than the cell frames contained within the outer support member, Hereby it is possible to support the cell frames when the cell frames extend axialiy.
It may be beneficial that the support member is constructed in such a way that the gap between the outer diameter of the cell frames and the inner diameter of the support member is as small as possible. In one embodiment according to the invention, the support member is a cylindrical tube made in a composite material (fibre-reinforced polymer) made of a polymer matrix reinforced with fibres (e.g. glass, carbon or aramid). The polymer may be any suitable polymer material, e.g. epoxy, polyphenylsulfone (PPSU) or polyether ether ketone (PEEK).
It may be beneficial that the elastic modulus of the support member is significantly larger than the elastic modulus of the cell frames.
Hereby the support member is configured to keep its geometrical shape and prevent radial expansion of the cell frames.
It may be advantageous that the coefficient of thermal expansion of the support member is smaller than the coefficient of thermal expansion of the cell frames.
Hereby the support member is configured to maintain its geometrical shape and prevent radial expansion of the cell frames during operation of the electrolysis stack. It may be beneficial that the support member is made in an electrical insulation material e.g. a fibre reinforced plastic material.
The fibres may be glass fibre, armid fibre or carbon fibre by way of example. It may be an advantage that the electrolysis stack comprises a plurality of support members arranged with mutual end-to-end contact and substantially in axial extension of each other, Hereby it is possible to provide an electrolysis stack provided with modular support members. It is thus possible to build a long electrolysis stack and apply the same support member that is used for shorter electroiysis stacks. It may be an advantage that the electrolysis stack comprises a first support member and at least one additional support member arranged at the outside of the first support member.
Hereby it is possible to provide additional strength to the electrolysis stack so that is configured to resist the pressure within the cell stacks.
The object of the invention may be achieved by an electrolyser comprising an electrolysis stack according to the invention, The electrolysis stack can be a single electrolysis stack or split in sections.
It is preferred that the cell frames are made in a material that is suitable for handling high pH values (pH values above 14)
The support member may be mechanically attached outside the cell frames.
It is possible to apply a metal (steel) support structure provided with an inner isolation structure.
It may be advantageous that the support members are arranged in such a manner that they are not in mechanical contact with the flanges.
Hereby, it is achieved that the cell frames can be compressed in axial direction (e.g. during tensioning of the nuts). Furthermore, the support member can expand in the axial direction.
It may be an advantage that a gap is provided between a flange and the adjacent support member.
This allows for compressing the cell frames in axial direction (e.g. during tensioning of the nuts) without damaging the support members. Furthermore, the support member can expand in the axial direction without pressing against the flanges. it may be advantageous that a gap is provided between at least some of the adjacent support members. Hereby, the cell frames can be compressed in axial direction (e.g. during tensioning of the nuts). Furthermore, the support member can expand in the axial direction.
It may be beneficial that a metal structure is provided under the gap.
This facilitates that the cell frames can be compressed in axial direction (e.g. during tensioning of the nuts) without damaging the support members. Furthermore, the support member can expand in the axial direction.
The metal structure may be a current terminal made of a metal plate. The metal structure may be an electrical power member shaped as a plate. It may be beneficial that an electric connection is provided between adjacent support members, wherein at least the distal portion of the electric connections protrudes from the support members.
Hereby, it is possible to arrange the electric connections in more positions providing greater design freedom with respect to the electrical system of the electrolysis stack.
The electric connections may preferably extent radially perpendicular to the support member. Hereby, easy access can be provided.
It may be beneficial that an electric connection is provided at the outermost axial end of each of the outermost support members.
Hereby, the electrical system can be simplified.
It may be an advantage that the electric connections extend as extension of the electric power point members.
Hereby, the electric power point members are easily accessible electrically.
Description of the Drawings
The invention will become more fully understood from the detailed description given herein below. The accompanying drawings are given by way of illustration only, and thus, they are not limitative of the present invention. In the accompanying drawings:
Fig. 1 shows two schematic views of an electrolysis stack according to the invention;
Fig. 2 shows a schematic perspective top view of an electrolyser according to the invention;
Fig. 3 illustrates schematic perspective top views of an electrolysis stack according to the invention;
Fig. 4 shows schematic cross-sectional views of an electrolysis stack according to the invention;
Fig. 5 shows two schematic perspective top views of an electrolysis stack according to the invention;
Fig. 6 shows a schematic perspective top view of an electrolysis stack according to the invention
Fig. 7 a shows an end view of an electrolysis stack according to an embodiment of the invention;
Fig, 7 b shows a close-up cross-sectional view of the bushing electrically insulating the electric power point member from the electrolyte within the electrolysis stack;
Fig. 7 c shows a close-up cross-sectional view of a bushing electrically insulating a current terminal from the electrolyte;
Fig, 7 d) shows a cross-sectional view of the electrolysis stack shown in Fig, 7 a);
Fig, 7 e) shows a perspective view of the bushing shown in Fig. 7 c);
Fig. 7 f) shows a perspective view of the bushing shown in Fig. 7 b);
Fig. 8 a) shows a top view of an electrolysis stack according to an embodiment of the invention;
Fig. 8 b) shows a close-up cross-sectional view of the electrical connection shown in Fig. 8 a) and
Fig. 8 c) shows a close-up cross-sectional view of the joint structure of the adjacent support members.
Detailed description of the invention
Referring now in detail to the drawings for the purpose of illustrating preferred embodiments of the present invention, an electrolysis stack 2 of the present invention is illustrated in Fig. 1.
Fig, 1 illustrates two different schematic views of an electrolysis stack 2 according to the invention. Fig. 1 a) illustrates a schematic top view of an electrolysis stack 2 comprising a cylindrical support member 12 enclosing a plurality of disk-shaped cell frames 6 stacked within the support member 12.
The electrolysis stack 2 comprises a series of stacked electrolysis cells. Each of these electrolysis cells contains two bipolar electrodes (metal sheets). A gas separating porous membrane is provided between every bipolar electrode. Each electrolysis ceil comprises a disk-shaped polymer cell frame 6, in Fig. 1, however, the membrane and bipolar electrodes of the ceil frames 6 have been removed for illustration purposes. It may be an advantage that the cell frames are sealed with O-ring gaskets of a resilient material (e.g. EPDM rubber).
Each ceil frame 6 comprises four axialiy extending through bores 8, 8', 10, 10'. Each cell frame 6 comprises a centrally arranged aperture 14.
Each ceil frame 6 comprises a membrane (not shown). The membrane is exposed to high temperatures (up to 100° Celsius) and pH values above 14 during operation of the electrolysis stack 2. Accordingly, the membrane must be capable of being exposed to a demanding chemical environment. The membrane may comprise any suitable material e.g. two layers of a polymer comprising Zr02. The electrolysis stack 2 according to the invention may be adapted to handle a strong alkali electrolyte comprising potassium hydroxide (KOH) (e.g. 30 wt% KOH). Some of the through bores 8, 8f, 10, 10f may be used to transport oxygen (02) and hydrogen (H2) generated by means of the electrolysis stack 2. Some of the through bores 8, 8', 10, 10f may be used to transport the electrolyte (e.g. demineralised water with 30 wt% KOH). Fig. 1 b) illustrates a schematic perspective top view of the electrolysis stack 2 shown in Fig. 1 a). The electrolysis stack 2 comprises a cylindrical support member 12 arranged at the outside of a stack of cell frames 6, 6', 6" stacked within the support member 12. Even though the cell frames 6, 6', 6" comprise membranes and bipolar electrodes, these have been removed for illustrating that the ceil frames 6, 6', 6" are stacked on top of each other within the cylindrical support member 12.
The cell frames 6, 6', 6" may be manufactured in a polymer material, e.g. polyphenylsuifone (PPSU) or poiyether ether ketone (PEEK). When the stack is pressurised and the ceil frames 6, 6', 6" are brought into mechanical contact with the support member 12, the support member 12 (a cylindricai tube) wi ll significantly reduce further deformation in the circumferential direction of the ceil frames 6, 6', 6". Accordingly, the use of the support member 12 makes it possible to operate the electrolysis stack 2 at high pressures (e.g. up to 3 MPa) without critical deformation of the ceil frames 6, 6', 6",
Fig. 2 illustrates a schematic perspective top view of an eiectrolyser 20 according to the invention. The eiectrolyser 20 comprises a frame 36 having a lower frame member 38 and an upper frame member 38' interconnected by four (only three are visible in Fig. 2) connection members 40, 40', 40" shaped as angle bars 40, 40', 40". Each angle bars 40, 40', 40" is mechanically attached to both the lower frame member 38 and an upper frame member 38'.
The eiectrolyser 20 comprises two electrolysis stacks 2, 2' mounted in the lower portion of the eiectrolyser 20. Each of the electrolysis stacks 2, 2' comprises a cylindrical support member 12 like the one shown in Fig. 1. Each of the two electrolysis stacks 2, 2' is arranged between two flanges 24, 24'. These flanges 24, 24' are mechanically attached to each other by means of a plurality of threaded rods 26, nuts 22 and washers 44. The two electrolysis stacks 2, 2' are identically constructed and extend parallel to each other.
The eiectrolyser 20 comprises degassing chambers, a gas purification system and a pressure control system. The two electrolysis stacks 2, 2' are electrically connected to separate power supplies. Fig. 3 a) and Fig. 3 b) illustrate two different schematic perspective top views of an electrolysis stack 2 according to the invention. The electrolysis stack 2 is arranged between two parallel, plate-shaped flanges 24, 24'. The flanges 24, 24' are mechanically attached to each other by means of a plurality of threaded rods 26 and corresponding nuts 22 and disks 44. The disks 44 are compressible disks allowing the eel! frames to expand along the longitudinal axis X of the electrolysis stack 2. The stack may for example comprise 18 disks 44, This assembly prevents the flanges from being displaced from each other along the longitudinal axis X of the electrolysis stack 2 ,
It can be seen that the threaded rods 26 extend parallel to each other and to the longitudinal axis X of the electrolysis stack 2.
The electrolysis stack 2 comprises three cylindrical support members 11, 11', 12 arranged end to end at the periphery of a plurality of ceil frames (not shown) within the interior of the electrolysis stack 2 ,
Four electrical connections 50, 50', 52, 52' are provided along the periphery of the support members 11, 11', 12. The electrical connections 50, 50', 52, 52' protrude radially from the periphery of the support members 11, 11', 12.
Fig . 4 illustrates two schematic cross-sectional views of an electrolysis stack 2 according to the invention . Fig . 4 a) shows a side view, while Fig . 4 b) illustrates a perspective view. The electrolysis stack 2 is arranged between two flanges 24, 24' mechanically attached to each other by means of a plurality of threaded rods 26, 26' and corresponding nuts 22, 22' and washers 44. The threaded rods 26, 26' extend along the longitudinal axis X of the electrolysis stack 2.
The electrolysis stack 2 comprises a cylindrical support member 12 arranged at the periphery of a plurality of cell frames 6. The electrolysis stack 2 comprises three cylindrical support members 11, 11', 12 arranged end to end at the periphery of a plurality of ceil frames 6 of the electrolysis stack 2.
Fig . 4 b) shows that a gas outlet pipe 16 and a KOH inlet pipe 18 are provided in the flange 24. Channels extending parallel to the longitudinal axis X of the electrolysis stack 2 are provided in continuation of the gas outlet pipe 16 and of the KOH inlet pipe 18. The channels extend through the plurality of eel! frames 6.
The electrolysis stack 2 comprises three cell frame modules Mlf M2, M3 arranged end to end along the longitudinal axis X of the electrolysis stack 2. Fifty cell frames 6 are arranged in each of the three cell frame modules Mi, M2, M3. Accordingly, the total number of cell frames 6 in the electrolysis stack 2 is 150,
An insulating plate member 32, 32' is arranged in each end of the electrolysis stack 2. Two electric power point members (current terminals) 46, 46' are arranged next to each of the insulating plate members 32, 32'. The electric power point member 46 is a cathode, while the electric power point member 46' is an anode, Furthermore, two electric power point members formed as bipolar electrodes 48, 48' are arranged between the first cell frame module Mi and the second cell frame module M2 as well as between the second cell frame module M2 and the third cell frame module M3, respectively.
A first bushing 34, a second bushing 34' and a third bushing 34" are arranged to electrically insulate the electrolyte from the electric power point members 48, 48', 46, 46' in order to prevent unwanted currents from running through the electrolysis stack 2.
The bushings 34, 34', 34" may be made in any suitable insulating material capable of resisting the demanding working conditions (temperatures up to 100° Celsius and pH values above 14 as well as a high concentration of oxygen and hydrogen gasses). The bushings 34, 34', 34" may be made in poiyphenylsulfone (PPSU) or poiyether ether ketone (PEEK) by way of example.
The electrolysis stack 2 is equipped with a gas outlet channel 16 (oxygen or hydrogen gasses) and a media inlet 18 (for demineralised water with KOH, e.g. demineralised water with 30wt% KOH). The electrolysis stack 2 is enclosed by three support members 11, 11', 12 shaped like cylindrical tubes. The support members 11, 11', 12 are constructed in such a way that they are configured to support the cell frames 6 in radial direction. It is possible to apply one large support member instead of three support members 11, 11', 12.
Along the longitudinal axis X of the electrolysis stack 2, the total length of the stack of ceil frames 6 wil l change with temperature and over time due to thermal expansion, change of elastic modulus with temperature and compressive stress, and creep due to compressive stress.
The support members 11, 11', 12 are not subjected to any significant stress in the axial direction. Accordingly, only thermal expansion will cause changes in the length of the support members 11, 11', 12 in the direction of their longitudinal axis X.
By using support members 11, 11', 12 like the ones illustrated in Fig. 3- 4, it is possible to reduce the dimensions of the ceil frames 6, 6', 6".
The electrolysis stack 2 is designed with a modular concept in mind. The electrolysis stack 2 contains??? a number of cell frame modules Mi, M2, M3 providing a total number of cell frames 6 of e.g. 100, 150 or 200 with a volume ranging from e.g. 4 L to 10 L or more of electrolyte inside. Depending on the customer's needs, it is possible to provide large configurations of e.g. 50, 75, 100 or 200 ceil frames 6 by combining a number of cell frame modules Mlf M2/ M3.
When assembled, the cell frame modules Mi, M2, M3 are separated from one.
The cell frame modules Mi? M2, M3 each comprises 50 cell frames 6. Each cell frame module comprises electrical power point members constituting either a cathode, an anode or a cathode and an anode. A diaphragm or membrane is provided to separate the gasses generated. When the cell frames 6 are combined into an electrolysis stack 2, three cell frame modules i, M2, M3 are positioned end to end. The cell frame modules Mi? M2/ M3 are connected to fittings in the flanges 24, 24'.
Accordingly, a 150 cell frame electrolysis stack 2 is built up by the three cell frame modules Mi, M2, M3 with a total of 150 small chambers (anode, cathode, anode, cathode and so on) where 75 of the chambers are connected by channels to the oxygen producing part of the stack, and the remaining 75 chambers are connected to the hydrogen producing part.
The oxygen and the hydrogen sides are completely separated from each other by membranes/diaphragms and (bipolar) electrodes. Accordingly, the electrolysis stack 2 may be considered to take the form of two vessels; one carrying H2 and one carrying 02.
When direct current is applied to the first and the last ceil of a cell frame module Mi, M2, M3, it causes current to flow through each ceil (each cell comprises two cell frames 6) in the cell frame module Mi, M2, M3, dividing the potential between each cell frame in the cell frame module Mi, M2, M3. The potential of each cell frame 6 is determined by the current passing through each cell frame 6, the temperature, the chemical composition of the (bipolar) electrode and the thickness of the electrolyte.
Fig. 5 a) illustrates a schematic perspective top view of an electrolysis stack 2 according to the invention. The electrolysis stack 2 comprises only one ceil frame 6 since the remaining ceil frames have been removed. The ceil frame 6 has a circular outer periphery and is provided with a centrally and symmetrically arranged aperture 14. The aperture 14 is defined by two circular arcs connected by two parallel straight lines. The cell frame 6 is arranged within a cylindrical support member 12 having an inner geometry that fits the outer geometry of the eel! frame 6.
Fig, 5 b) illustrates a top view of an electrolysis stack 2 according to the invention. The electrolysis stack 2 comprises a plurality of cell frames 6 (only one is visible) corresponding to the one illustrated in Fig, 5 a).
The cell frame 6 is arranged within a cylindrical support member 12 having an inner geometry that fits the outer geometry of the cell frame 6. During operation, gaseous 02 and H2 are generated within the centra! portion of the cell frame 6 by means of two electrodes (metal sheets) and a gas separating porous membrane (these are not shown). Hereby, the pressure is increased significantly (up to 3 MPa). Therefore, an outwardly directed force F is created. The force F acts in all radial directions causing a need to ensure a rather large mechanical strength of the electrolysis stack 2.
A large mechanical strength of the electrolysis stack 2 is achieved by means of the cylindrical support member 12 enclosing the ceil frames 6 of the electrolysis stack 2. The ceil frame 6 bears against the inside portion of the support member 12, and hereby the mechanical strength of the support member 12 can directly be used to prevent radial expansion of the ceil frames 6. Thus, the mechanical strength of the cell frames 6 may be reduced provided that the mechanical strength of the support member 12 is sufficiently large.
Fig. 6 a) illustrates a schematic perspective top view of an electrolysis stack 2 according to the invention. The electrolysis stack 2 comprises a plurality of ceil frames 6, 6', 6" arranged within a cylindrical support member 12. Additional support members 42, 42', 42" are provided at the outside of the cylindrical support member 12.
Hereby, it is possible to enlarge the mechanical strength of the electrolysis stack 2. The additional support members 42, 42', 42" are made as separate bands configured to fit the outer periphery of the cylindrical support member 12. However, it would be possible to apply one large additional support member 42 having the same axial extension as the cylindrical support member 12. Alternatively, it is possible to apply a larger number (e.g. four or more) of additional support members 42, 42', 42".
Fig. 6 b) illustrates a schematic top view of an electrolysis stack 2 according to the invention. The electrolysis stack 2 comprises a plurality of cell frames 6 arranged within a first cylindrical support member 12 having an inner geometry that fits the outer geometry of the cell frame 6. A second and additional support member 12' is arranged at the outside of the first cylindrical support member 12. Hereby, the mechanical strength of the construction can be increased further. During operation of the electrolysis stack 2, gaseous 02 and H2 are generated within the central portion of the ceil frames 6. The gaseous 02 and H2 can be generated through use of two electrodes (not shown) and a gas separating porous membrane (not shown). The pressure within the central portion of the cell frames 6 is increased significantly (up to 3 MPa) due to the generated gasses, and an outwardly directed force F acting in all radial directions is created.
The first cylindrical support member 12 as well as the second additional support member 12' provide the required mechanical strength of the electrolysis stack 2. Thus, radial expansion of the ceil frames 6 can be prevented.
Fig. 7 A) illustrates an end view of an electrolysis stack 2 according to an embodiment of the invention, in which the threaded rods, washers and nuts have been removed for better illustrating the remaining structures. The electrolysis stack 2 comprises an outlet 16 and an inlet 18 protruding from the flange 24 of the electrolysis stack 2. A line A going through the outlet 16 and the inlet 18 is indicated. Fig, 7 d) illustrates a cross-sectional view of the electrolysis stack 2 shown in Fig, 7 a), wherein the cross is made along the line A shown in Fig. 7 a), The electrolysis stack 2 comprises a first flange 24 and a second flange 24' arranged in the opposite end of the first flange 24. The electrolysis stack 2 comprises a plurality of ceil frames 6 arranged in a first cell frame module Mi and in a second ceil frame module M2. The electrolysis stack 2 comprises a first support member 11 and a second support member 11' arranged in axial extension of each other. The support members 11, 11' are arranged at the outside periphery of the cell frames 6,
The first support member 11 is arranged between a first plate-shaped current terminal 46 and a plate-shaped electrical power point member 48 positioned centrally in the electrolysis stack 2. Likewise, the second support member 11' is arranged between a second plate-shaped current terminal 46 and the plate-shaped electrical power point member 48. A gap 54 is provided between the second support member 11' and the second flange 24'. The gap 54 allows for compressing the cell frames 6 in axial direction e.g. during tensioning of the nuts (not shown) without damaging the support members 11, 11'. Further, the support members 11, 11' can expand in the axial direction without pressing against the flanges.
An outlet 16 and an inlet 18 are provided in the first flange 24. The electrolysis stack 2 comprises a first insulation bushing 34 arranged and configured to electrically insulate the electrolyte within the electrolysis stack 2 from the current terminal 46'.
The electrolysis stack 2 comprises a second insulation bushing 34' and a third insulation bushing 35 arranged and configured to eiectricaiiy insulate the electrolyte within the electrolysis stack 2 from the electrical power point member 48.
By electrically insulating the electrolyte within the electrolysis stack 2 from the current terminals 46, 46' and the electric power point member 48, the bush ings 34, 34', 35 reduce the stray currents giving rise to loss of energy in the electrolysis stack 2.
Fig , 7 b) illustrates a close-up cross-sectional view of the bushing 34' electrically insulating the electric power point member 48 from the electrolyte with in the electrolysis stack 2. A perspective close-up view of the bushing 34' is shown in Fig , 7 f) . I n Fig . 7 f), it can be seen that the bushing 34' com prises an inner cyl indrical portion 33 su rrounded by an outer cylindrical portion 33' which is an integrated part of the bushing 34'. Moreover, it can be seen that the bushings 34', 35 extend between the two adjacent cell frame modules Mi f M2. and that the bushings 34', 35 are arranged in the channels provided in the ceil fra mes 6 to distri bute electrolyte to all the cel l frames 6 in the cell frame modules M2, Fu rther, in Fig . 7 f) it can be seen that the bushing 34 is provided with an outlet 30 for gas. The outlet 30 is provided in the inner cylindrical portion 33.
Fig . 7 c) i llustrates a close-up, cross-sectional view of the bushing 34 electrically insulating the current term inal 46' from the electrolyte that flows through the through-going hole 56 during use of the electrolysis stack 2. It can be seen that the bushing 34 is arranged in the channel provided in the cel l frames 6 to distribute electrolyte to all the cell frames 6 in the cel l frame module Mi .
A perspective close-up view of the bushing 34 is shown in Fig . 7 e) in which it can be seen that the bushing 34 comprises a central ly arranged inner cylindrical portion 33 surrounded by an outer cylindrical portion 33' wh ich is an integrated part of the bush ing 34'. Besides, the bushing 34 is provided with an outlet 30 for gas. The outlet 30 is provided in the inner cylindrical portion 33.
Fig . 8 a) i llustrates a top view of an electrolysis stack 2 according to an em bodiment of the invention . The threaded rods, washers and nuts have been removed for better il lustrating the remain ing structures of the electrolysis stack 2. Part of the support mem bers 11 , 11 ' has been removed in order to see the structures underneath the support members 11, 11'.
It can be seen that the electrolysis stack 2 comprises a first flange 24 and a second flange 24' arranged in the opposite end of the first flange 24. The electrolysis stack 2 comprises a plurality of ceil frames 6 arranged between the flanges 24, 24'. The electrolysis stack 2 comprises a first support member 11 and a second support member 11' arranged in axial extension of each other. The support members 11, 11' are arranged at the outside periphery of the cell frames 6.
A plate-shaped electrical connection 52 protrudes from the outside surface of the support members 11, 11 '. The electrical connection 52 is an integrated portion of the electrical power point member 48 arranged centrally in the electrolysis stack 2.
Fig . 8 b) illustrates a close-up, cross-sectional view of the electrical connection 52 shown in Fig , 8 a) . It can be seen that the electrical connection 52 extends through a gap provided between the support members 11, 11'. The electrical connection 52 is provided with a through-going hole 60. Further, it can be seen that the electrical connection 52 is an integrated part (the peripheral portion) of the electrical power point member 48. The electrical connection 52 can easily be accessed from outside of the electrolysis stack 2.
Fig . 8 c) illustrates a close-up, cross-sectional view of the joint structure 58 of the adjacent support members 11, 11'. It can be seen that a gap 62 is provided between at least some of the adjacent support members 11, 11'. Hereby, the ceil frames can be compressed in axial direction (e.g. during tensioning of the nuts) . Further, the support member can expand in the axial direction . List of referenc1 numerals
2 Electrolysis stack
6, 6', 6" Cell frame
8, 8' Bore
10, 10' Bore
11, 11' Support member
12, 12' Support member
14 Aperture
16 Pipe (gas outlet)
18 Pipe (KOH inlet)
20 Electrolyser
22, 22' Nut
24, 24' Flange
26 Threaded rod
30 Outlet
32, 32' Plate member
33 Inner portion
33' Outer portion
34, 34', 34", 35 Bushing (insulation)
36 Frame
38, 38' Frame member
40, 40', 40" Connection member
42, 42', 42" Additional support member 44 Disk
46, 46' Current terminal
48, 48' Electric power point member
50, 50', 52, 52' Electrical connection
54, 62 Gap
56 Through-going hole
58 Joint structure
60 Hole
M1? M2, M3 Cell frame module
X Longitudinal axis
Force

Claims

Claims
1. An electrolysis stack (2) for an electrolyser (20), which electrolysis stack (2) comprises a plurality of electrolysis ceils each comprising two electrodes and a gas separating membrane and a cell frame (6, 6', 6"), which ceil frames (6, 6', 6") are arranged adjacent to each other, which electrolysis stack (2) comprises means (18) for supplying electrolyte feed to the interior of the electrolysis ceils and means (16) for removing oxygen gas and hydrogen gas from the electrolysis ceils, which electrolysis stack (2) comprises electric power point members (46, 46', 48, 48') constituting either a cathode, an anode or a cathode and an anode, characterised in that the electrolysis stack (2) is divided into a plurality of electrically separated cell frame modules (Mlf M2, M3), wherein the electrolysis stack (2) comprises a plurality of insulation bushings (34, 34', 34", 35) configured to electrically insulate the electrolyte within the electrolysis stack (2) from the current terminals (46, 46') and/or electric power point members (48, 48') during use of the electrolysis stack (2).
2. An electrolysis stack (2) according to claim 1, characterised in that the electrolysis stack (2) is divided into a plurality of electrically separated cell frame modules (Mi, M2, M3) by means of electric power point members (48, 48') extending along the length of the cell frames (6, 6', 6").
3. An electrolysis stack (2) according to claim 1 or claim 2, characterised in that the electrolysis stack (2) is divided into two, three or more electrically separated ceil frame modules (Mi, M2, M3).
4, An electrolysis stack (2) according to one of the preceding claims, characterised so that each of the electrically separated cell frame modules (Mi, M2, M3) comprises 10-40, preferably 15-35, such as 20-35 cell frames (6, 6', 6"),
5. An electrolysis stack (2) according to claim 4, characterised in that each of the electrically separated cell frame modules (Mi, M2, M3) comprises 25 cell frames (6, 6', 6").
6. An electrolysis stack (2) according to one of the claims 4-5, characterised in that each of the electrically separated cell frame modules (Mi, M2, M3) comprise the same number of cell frames (6, 6', 6").
7. An electrolysis stack (2) according to one of the claims, characterised in that each of the electrically separated cell frame modules (Mif M2, M3) are electrically separated from each other by means of current terminals (46, 46') and/or electric power point members (48, 48') arranged between adjacent cell frame modules (Mi, M2i M3).
8. An electrolysis stack (2) according to one of the claims, characterised in that each of the electrically separated cell frame modules (Mi, M2, M3) comprises insulation bushings (34, 34', 34") configured to electrically insulate the electrolyte within the electrolysis stack (2) from the current terminals (46, 46') and/or electric power point members (48, 48') arranged between adjacent cell frame modules (Mlf M2, M3) during use of the electrolysis stack (2).
9. An electrolysis stack (2) according to one of the preceding claims, characterised in that at least one support member (12, 12', 42, 42',
42") is arranged at the outside periphery of the ceil frames (6, 6', 6").
10. An electrolysis stack (2) according to claim 3, characterised in that a gap (54) is provided between a flange (24') and the adjacent support member (11'),
11. An electrolysis stack (2) according to one of the preceding claims, characterised i that a gap (62) is provided between at least some of the adjacent support members (11, 11', 12).
12. An electrolysis stack (2) according to claim 5 or claim 6, characterised in that a metal structure (46, 46', 48) is provided under the gap (54, 62).
13. An electrolysis stack (2) according to one of the preceding claims, characterised in that an electric connection (52, 52') is provided between adjacent support members (11, 11', 12), wherein at least the distal portion of the electric connections (52, 52') protrudes from the support members (11, 11', 12).
14. An electrolysis stack (2) according to one of the preceding claims, characterised in that an electric connection (50, 50', 52, 52') is provided at the outermost axial end of each of the outermost support members (11, 11', 12).
15. An electroiyser (20) comprising an electrolysis stack (2) according to one of the preceding claims.
PCT/DK2015/050265 2014-09-05 2015-09-04 Electrolyser stack divided into sub-stacks WO2016034185A1 (en)

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DKPA201400506 2014-09-05
DK201400506A DK178317B1 (en) 2014-09-05 2014-09-05 Electrolyser Stack Divided into Sub-stacks

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