Cell frame for a cell stack of a pressurized electrolyzer and electrolyzer cell stack including a plurality of cell frames

Abstract

A cell frame (1) adapted for use in a pressurized electrolyzer cell stack (3) is provided, having circumferential radial shelves (5) tapering inwardly from an inner peripheral rim (4) of the cell frame (1) to provide an annular space between a given circumferential radial shelf (5) and an adjacent circumferential radial shelf (5) when the cell frames (1) are stacked in alignment with one another, and having movable links (6) on the outside of the circumferential radial shelves (5) connecting the radial shelves (5) to the rest of the cell frames (1).

Description

[Technical Field]

[0001] The present invention relates to a cell frame for a cell stack of a pressurized electrolyzer.The present invention also relates to an electrolyzer cell stack comprising a plurality of cell frames. [Background technology]

[0002] In the electrolyzer stack, cell frames are placed adjacent to each other with alternating diaphragms and bipolar plates between the frames, and similarly, alternating catholyte and anolyte chambers may be provided on either side of the diaphragms and on either side of the bipolar plates.

[0003]

[0004]

[0005]

[0006] Summary of the Invention [Problem to be solved by the invention]

[0007] It is important that fluid does not flow between adjacent anolyte and catholyte chambers, for example by leaking from one side of the diaphragm / bipolar plate to the other.

[0008] Such leakage can occur when there is no reliable seal against the passage of fluid around the edges of the bipolar plate / diaphragm.

[0009] It is therefore an object of the present invention to prevent mixing of anolyte and catholyte within the cells during electrolysis by fluid flow from one half-cell to the next via channels around the rims of the diaphragms and / or bipolar plates in the electrolyzer stack.

[0010] Furthermore, it is an object to ensure a leak-tight enclosure for the half-cell process in a novel and patentably different way.

[0011] It is a further object of the present invention to ensure that engravings and unique markings on the bipolar plates remain protected from the combined corrosive action of oxygen and caustic liquid in the individual half cells. [Means for solving the problem]

[0012] The object of the invention can be achieved in a first aspect of the invention by a cell frame as claimed in claim 1.

[0013] A cell frame for a stack of cells in a pressurized electrolysis device is provided, the cell frame having circumferential radial shelves of a thickness tapering inward from an inner peripheral rim of the cell frame such that when the cell frames are stacked together annular spaces are provided between adjacent cell frame radial shelves, and movable links are provided on the outer sides of the radial shelves connecting the radial shelves to the remaining cell frames.

[0014] The combined effect of the radial ledge and movable link allows the radial ledge to pivot and / or translate slightly relative to the rest of the cell frame, thus allowing an element inserted into the annular space to transfer movement, and therefore pressure, between the two opposing sides of the radial ledge. This movement of the radial ledge allows the radial ledge to compensate for variations in tolerances of the elements inserted into the annular space. For stacks with multiple cell frames, this configuration ensures a more even distribution of forces between the individual radial ledges of the annular space and the inserted elements throughout the stack.

[0015] In one embodiment, the movable link is comprised of an annular radial section of reduced thickness of the cell frame.

[0016] Any other means of providing a movable link could be used, such as bonding the shelf to the cell with flexible cement, but the reduced thickness radial section is preferred because it is easily manufactured from an injection molded part and is easily modifiable.

[0017] In one embodiment, the reduced thickness portion has a thickness m that is greater than or equal to 10% and less than or equal to 75% less than the nominal thickness t of the cell frame.

[0018] The compliance of the cell frame material allows the reduced thickness to act as a link between the cell frame and the inward circumferential radial ledge. The added compliance between the radial ledge and the remainder of the cell frame caused by the reduced thickness can be easily adjusted by modifying the injection mold.

[0019] In one embodiment, the movable link extends radially of the cell frame greater than or equal to the reduced thickness and less than or equal to three times the reduced thickness.

[0020] The extent of the movable links in the radial and axial directions determines, among other things, whether the movement is purely pivotal or includes a translational component in the longitudinal direction of the cell stack.

[0021] The object of the present invention can further be achieved by a second aspect of the invention, which relates to an electrolyzer cell stack, for example as set forth in claim 5.

[0022] The cell stack may comprise a plurality of cell frames, the cell frames being pressed together between a plurality of end plates, and successive cell frames in the stack supporting corresponding diaphragms and bipolar plates in an alternating manner.

[0023] In this stack, the bipolar plates and corresponding diaphragms may be selected to have a thickness such that a gasket force always exists between the cell frame and its corresponding bipolar plate / diaphragm when the frames are pressed together between the end plates.

[0024] In one embodiment, both the bipolar plate and the corresponding diaphragm have a diameter no larger than the outer diameter of the movable link and no smaller than the inner diameter of the groove in the movable link.

[0025] In this way, the diaphragm is compressed along its entire edge between the radial ledges of the successive cell frames between which it is placed, ensuring that the diaphragm maintains sealing contact with each of the two cell frames it is held in. Similarly, the bipolar plate is sandwiched between the radial ledges on both sides. This structure eliminates the need for actual gasket material between the bipolar plate and the cell frames, a significant advantage in both reduced structural complexity and assembly costs.

[0026] The predetermined diameter constraint ensures that the diaphragm and bipolar plate fit radially within the annular space. Preferably, the diameter of the bipolar plate is slightly smaller than the outermost diameter of the movable link groove to prevent the bipolar plate from being unintentionally pinched between two consecutive cell frames in the area where the frames are supposed to lie flat against each other. The movable link groove defines the movable link, as it contours the remaining cell frame material within the movable link.

[0027] In an embodiment of the electrolyzer cell stack, the radial shelves are adapted to pivot and / or translate in the axial direction of the cell stack when two cell frames with a bipolar plate disposed therebetween are pressed together.

[0028] This mobility allows for the transmission of forces and motion from one side of the radial shelf to the other, and the transmission of forces and / or motion allows minor irregularities caused by manufacturing tolerances to be accommodated within the corresponding diaphragm.

[0029] In one embodiment of the electrolysis device, a diaphragm provided between two adjacent cell frames is adapted to be sandwiched between two radial shelves of two adjacent cell frames when the radial shelves move by two bipolar plates arranged on opposite sides of the two adjacent cell frames.

[0030] The diaphragm is made of a sponge-like material, which locally absorbs pinching movements, but because the diaphragm also contains elastic polymer elements, it maintains its elastic properties and therefore continues to function in its gasketing capacity, preventing fluid flow around the edge between the two sides. The pinching of the diaphragm is based on the fact that when the cell frames with oversized bipolar plates are pressed together, the thickness of the diaphragm exceeds at least the minimum distance between consecutive cell frames in the annular space. This is ensured by ensuring that the average sum of the thicknesses of the diaphragms and bipolar plates over the entire stack exceeds the nominal distance between two cell frames in the annular space.

[0031] In one embodiment, the annular space between adjacent cell frames covers a rim portion of each bipolar plate in the annular space, and the bipolar plates at this rim portion have product markings embedded within the bipolar plate material.

[0032] The bipolar plates are immersed in a chemically aggressive caustic or electrolyte solution, which also contains oxygen on one side of the plate, which accelerates the deterioration of the metal surface of the bipolar plates. However, the outer rim regions of the bipolar plates arranged in a stack, which lie in the annular spaces between the radial shelves of successive cell frames, provide some shielding of the surface of the bipolar plates from the aggressive oxygen, and the surface markings in this region are maintained. To further guarantee the life of the markings, it is preferable to provide the markings on the cathode side of the bipolar plates, where only minimal oxygen is present during use of the electrolysis device.

[0033] In one embodiment, the product marking is provided by laser or etching and is coded for computer identification, such as a quick response (QR) code, bar code, or the like.

[0034] Barcode or CR coding is common, but in this case it is not clear whether the markings that make up the code will remain viable and readable. However, placing the code in the rim area of ​​the bipolar plate ensures that it will remain readable by computer processing of the photograph.

[0035] Various exemplary and non-limiting embodiments, both as to structure and method of operation, together with further objects and advantages thereof, will be best understood from the following description of certain exemplary and non-limiting embodiments when read in conjunction with the accompanying drawings. The verbs "comprise" and "include" are used herein in an open-ended manner that does not exclude or require the presence of unrecited features. Features recited in dependent claims may be freely combined with each other unless expressly stated otherwise. Furthermore, it should be understood that the use of "a" or "an," i.e., the singular, throughout this specification does not exclude the plural.

[0036] In the following, the present invention will be described in more detail with reference to the embodiments illustrated by the accompanying drawings. The illustrated embodiments are used for illustrative purposes only and should not be used to limit the scope of the present invention. [Brief explanation of the drawings]

[0037] [Figure 1] FIG. 2 is an enlarged cross-sectional view including the inner periphery of a plurality of cell frames. [Figure 2] A larger portion of the cell stack 2 is shown in cross section, tilted slightly to show the upper side of the cell frame. [Figure 3] 3D representation of the cell stack 3 with end plates, current injectors and insulating plates, showing the top side of the cell frame 1. [Figure 4] 1 is a cross-sectional view through the radial ledge 5 and the movable link 19. FIG. [Figure 5] 1, but with the bipolar plate 11 and diaphragm 10 inserted. [Figure 6] FIG. 2 is an enlarged plan view of a portion of a bipolar plate. DETAILED DESCRIPTION OF THE INVENTION

[0038] 1 shows a cross-sectional view of the inner periphery of a cell frame stack 3, in which identical cell frames 1 are stacked. The cell frame 1 shown at the top is rotated 180 degrees relative to the adjacent cell frame and is adapted to receive a diaphragm 10 that extends inside the inner rim 4 of the cell frame 1. A second cell frame 1 in the stack is adapted to receive a bipolar plate 11. The first and second cell frames are identical, but rotated relative to each other about the longitudinal axis of the cell stack.

[0039] Figure 2 shows a larger section of the cell stack 3, with multiple identical cell frames 1 stacked on top of each other, with every other cell frame 1 rotated 180 degrees around the cell stack axis. O-ring seals 9 are provided between each frame 1, and steel rings 13 are attached to the outer regions of each cell frame 1 for safety reasons and to ensure containment of internal pressure within the cell stack 3 during electrolysis. Because this electrolysis device 3 is used in a pressurized alkaline electrolysis process, it is important to keep the electrolytes in any two half cells separated and prevent cross-flow across the diaphragms, as cross-flow can compromise the purity of the gases generated in the two chambers. Preventing fluid flow around the edges of the diaphragms and bipolar plates can be difficult, especially when pressures of 30 to 100 bar are used.

[0040] In Figure 3, a three-dimensional view of the electrolyzer stack 3 is shown with some elements missing, allowing the axial surfaces of the cell frames to be seen. Although in Figures 1, 2, 4 and 5 the cell frames 1 are shown in a horizontal position, the cell frames are typically arranged stacked in a vertical or upright position as disclosed in Figure 3 when the cell stack 3 is operating as an electrolyzer 3. The longitudinal and central axis of the cell stack is therefore along the horizontal line in Figure 3.

[0041] 2 and 3, the cell frame 1 has four through openings 8, which function as supply and discharge manifolds 8 for each half cell in the stack. Cell frame flow channels 14 are provided from two openings toward the inlet and outlet, respectively.

[0042] Any two such flow channels 14 and corresponding supply and exhaust manifolds are adapted to be in fluid communication with a half-cell, such as a cathode chamber, located on a first side of the diaphragm 10. On the opposite side of the same diaphragm 10 is an anode chamber, which is supplied by two flow channels 14 in the adjacent cell frame in the stack. For this purpose, the next frame is mounted rotated 180° about the longitudinal axis of the stack so that the cell frame flow channels 14 and two corresponding supply and exhaust manifolds 8 form an anolyte supply and exhaust manifold. In Figures 1, 2 and 5, the cross-sectional views show that the cell frame flow channels 14 in the indicated cross sections are visible in every other cell frame cross section.

[0043] In FIG. 5, the diaphragm 10 and bipolar plate 11 are shown schematically between two cell frames 1. On each side of any diaphragm 10, an electrolysis chamber defined by the bipolar plate 11 and diaphragm 10 is provided. Electrodes (not shown) are provided on both sides of the dipolar plate 11 to stimulate the production of hydrogen and oxygen and abut the diaphragm from both sides. Each cell includes two half-cells, each positioned on either side of the diaphragm, each radially bounded by a cell frame 1. The diaphragm 10 is shown with a dashed line; in reality, the diaphragm may have small openings that allow the flow of ions and / or liquid between the two half-cells while simultaneously preventing the passage of gas bubbles from one side of the diaphragm to the other.

[0044] 1, 2, 4, and 5 show the inner rim 4 of the cell frame 1. The inner rim 4 is the innermost portion of the radial shelves 5. The radial shelves 5 extend inward from the movable links 6 and taper inward from the movable links 6 toward the inner rim 4. The tapered radial shelves 5 form annular spaces 7 between the radial shelves when the cell frames are stacked adjacent to one another, as shown in FIG.

[0045] The movable link 6, seen in the enlarged cross-sectional view of FIG. 4, is defined by a groove 19 having an outermost diameter 12 (in the direction of the cell frame periphery) and a radial extension d that defines a region of reduced thickness of the cell frame material. The reduction is indicated by arrow h, and is greater than 10% of the nominal thickness of the cell frame indicated by arrow t, and constitutes less than 75% of the nominal cell thickness t. The groove 19 may be deeper, with h comprising more than 99% of the nominal thickness t, leaving only a film-like hinge between the cell frame and the radial shelf. However, this construction may be hindered by the limitations of available injection molding technology, given the frame materials and size.

[0046] The movable link extends radially as indicated by arrow d. The extension d is at least equal to the reduced thickness h, but not more than three times the reduced thickness h. The movable link groove 19 has a box-shaped profile in the cross section of the cell frame 1, as shown in FIG. 4. However, other types of shapes, such as curved or angled, may also be realized.

[0047] As shown in Figure 3, when the cell frames 1 are stacked to a certain extent, any two cell frames 1 house a bipolar plate 11 and a diaphragm 10 (not shown in Figure 3), each of which spans the inner region of the inner periphery of the cell frame 4 and extends to the outermost part of the movable link. However, the annular space 7 is dimensioned so that the minimum axial distance between successive radial shelves 5 in the annular space 7 is slightly shorter than the thickness of the bipolar plate 11. In this context, "slightly shorter" should be interpreted as 10% to 45% shorter, and preferably the distance is nominally 20% shorter than the thickness of the bipolar plate. By this means, it is ensured that a bipolar plate 11, having a manufacturing tolerance in combination with that of the cell frame 1, is contacted from two opposite sides by the circumferential radial shelves of an adjacent cell frame when the cell frames are pressed together in the electrolyzer stack 2. In particular, when the cells in the stack of cell frames are pressed together by the tension rods 17, a pressure or sealing force is applied between the bipolar plate 11 and the two opposing sides of the radial shelves 5 because the distance between the radial shelves 5 in the annular space 7 is less than the thickness of the bipolar plate 11.

[0048] As shown in FIG. 5, any diaphragm 10 residing in the annular space 7 between two consecutive radial shelves 5 has bipolar plates 11 on both sides that also reside in adjacent annular spaces 7. When the cell frames 1 are pressed together between two end plates 16 (one of which is shown in FIG. 3) by the tension rods 17 configured with fastening knots 18, the cell frames 1 cannot occupy more space in the longitudinal direction of the cell stack than the nominal length of the cell stack. This length of the cell stack is given by the nominal thickness of the cell frames 1 multiplied by the number of cell frames (see FIG. 5). Because the bipolar plates 11 are made from an alloy such as a nickel alloy and the diaphragm is made from a compliant material, the movable links 6 allow the radial shelves 5 to pivot away from the bipolar plates 11 and toward the diaphragms 10, elastically compressing the diaphragms 10 on both sides of the plates 11.

[0049] This action effectively pinches each diaphragm 10, forming a seal between the two sides of any diaphragm. Furthermore, the bipolar plates are also pressurized from both sides because their size is larger than the annular space 7 around which they are secured. Therefore, any two adjacent half-cells in the cell stack 3 are isolated from each other, and electrolyte does not pass from one half-cell to the next, even if a pressure difference occurs during use of the cell stack 3. The thickness of the diaphragms themselves may be oversized or undersized relative to the annular space between any two cell frames. If oversized, the diaphragms, which are somewhat elastic, may deflect when the cell frames are pressed toward each other. If undersized, the movement of the movable link caused by the oversized bipolar plates pressurizes the rim of the diaphragm in the annular space, thereby creating a seal to prevent fluid flow between the two sides of the diaphragm around the diaphragm's edge. In the disclosed example, the oversized thickness of the bipolar plate ensures a seal both around the edge of the bipolar plate and around the edge of the diaphragm.

[0050] As shown in FIG. 4, grating surfaces 21 are provided on both sides of the radial shelf 5. These surfaces are provided to increase the pull-out force on the diaphragm. The gratings may be provided as annular ridges protruding 0.03 mm to 0.05 mm from the surface and evenly spaced across the surface. Other types of gratings, such as bumps, spikes, or similar elements, may also be used to increase friction between the radial shelf surface and the diaphragm. As is evident from FIG. 4, the surfaces 21 may also form opposing conical shapes. However, stepped inward tapers, such as two, three, or more steps, are also possible, with each step consisting of a flat annular surface portion disposed in a plane extending perpendicular to the cell stack axis or cell frame axis. Stepped tapered surfaces, combining flat and conical surfaces, may also be provided on the upper and lower surfaces 21 of the upper and lobe sides of the shelf 5.

[0051] As shown schematically in FIG. 6, a bipolar plate may be provided with a unique identification mark 20, such as a bar code or alphanumeric characters, on one or both sides of its periphery. This surface portion is fixed in the annular space between the radial shelves. Such markings are susceptible to erosion by the harsh chemical environment within the cell stack, i.e., high temperature, high ash concentration, and potentially high oxygen concentration. However, at least in the space between the radial shelves of the bipolar plate, where the oxygen concentration is expected to be lower, and at least in the area of ​​the rim of the bipolar plate in pressure contact with the cell frame material, the corrosive attack of the layer and oxygen is expected to be less pronounced, and the surface etching or laser engraving will remain readable for a longer period of time. Preferably, the cathode side, where hydrogen evolution and low oxygen concentrations exist, is used for the identification marking.

[0052] It should be noted that the drawings and the above description illustrate exemplary embodiments in a simplified and schematic manner, and many specific mechanical details have not been shown, as those skilled in the art would be familiar with those details and showing them would only unnecessarily complicate the present specification. [Explanation of symbols]

[0053] 1 Cell Frame 2. Pressurized electrolysis device 3-cell stack 4. Cell frame inner rim 5 Radial shelf 6 Movable Link 7 Circular Space 8 Supply manifold and discharge manifold 9 O-ring seal 10 diaphragm 11 Bipolar Plate 12 Outer diameter of movable link groove 13 Steel Ring 14 Cell frame flow path 16 End plate 17 Tensile Rod 18 Fastening Knot 19 Movable link groove 20 Identification Marker 21 Grating Surface t Nominal thickness of the cell frame h reduced thickness of movable link 6 m thickness of movable link th d Radial extent of movable link groove

Claims

1. A cell frame (1) configured for use in a cell stack of a pressurized electrolysis device, comprising: Circumferential radial shelves (5) of tapering thickness project inward from the inner peripheral rim (4) of the cell frame (1), so that when the cell frames (1) are stacked in alignment with one another, an annular space (7) is provided between a given circumferential radial shelf (5) and an adjacent circumferential radial shelf (5); a movable link (6) is provided on the outside of the circumferential radial shelf (5) connecting the radial shelf (5) to the rest of the cell frame (1); Cell frame (1).

2. said movable link (6) is composed of an annular radial section with a reduced thickness of the cell frame material; A cell frame (1) according to claim 1.

3. the portion of reduced thickness is 10% or more and 75% or less thinner than the nominal thickness (t) of the cell frame; A cell frame (1) according to claim 2.

4. The movable link (6) extends in the radial direction of the cell frame by more than the reduced thickness and not more than three times the reduced thickness. A cell frame (1) according to claim 3.

5. A plurality of cell frames (1) according to any one of claims 1 to 4, A plurality of cell frames (1) are pressed against each other between a plurality of end plates (16), and successive cell frames (1) in the cell stack (3) alternately support diaphragms (10) and bipolar plates (11). Electrolyzer cell stack (3).

6. The bipolar plate (11) and the diaphragm (10) each have a diameter not larger than the outer diameter of the groove (19) of the movable link and not smaller than the inner diameter of the groove (19) of the movable link. Electrolyzer cell stack (3) according to claim 5.

7. The radial shelves (5) are adapted to pivot and / or translate in the axial direction of the cell stack (3) when two cell frames (1) with the bipolar plate (11) therebetween are pressed together. The electrolysis device cell stack of claim 5 .

8. The diaphragm (10) provided between two adjacent cell frames (1) is adapted to be sandwiched between the two radial shelves (5) of the two adjacent cell frames (1) when the radial shelves (5) are moved by the two bipolar plates (11) arranged on opposite sides of the two adjacent cell frames (1).

8. The electrolyzer cell stack of claim 7.

9. The annular spaces (7) between adjacent cell frames cover the rim of each bipolar plate (11), whereby the bipolar plates (11) at this rim contain identification markers (20) embedded in the bipolar plate material.

9. The electrolyzer cell stack of claim 8.

10. The identification marker (20) is provided by laser or etching and is coded for computer identification, such as a quick response (QR) code, a bar code, etc.

10. The electrolyzer cell stack of claim 9.

Images