Electrolysis Cell

Abstract

The present invention relates to an electrolytic cell for chlor-alkali or alkaline water electrolysis, comprising two cell elements (2, 3) each defining an electrode chamber (4, 5) by providing a rear wall (6) and a side wall (7) of the electrode chamber (4, 5), electrodes (8, 9) housed in each of the electrode chambers (4, 5), and a sheet-like separator (10) extending in the height direction (H) and width direction of the electrolytic cell (1), interposed at the joint (11) between the two cell elements (2, 3) and between the electrode chambers (4, 5). and a sheet-like separator (10) providing a separating wall (17) between the electrodes (8, 9), wherein at least one of the electrodes (8, 9) is made from a sheet (16) of metal mesh supported by a plurality of webs (12) attached to the rear wall (6) of the respective electrode chamber (4, 5), the webs (12) extending in a height direction (H) of the electrolytic cell (1), the webs (12) carrying a plurality of ribs (13) extending in a width direction of the electrolytic cell (1), and the electrodes (8, 9) being positioned on the plurality of ribs (13).

Description

[Background technology]

[0001] The present invention relates to an electrolysis cell for chlor-alkali or alkaline water electrolysis according to the preamble of claim 1.

[0002] Electrolytic cells for chlor-alkali and alkaline water electrolysis comprise two electrode chambers separated by a sheet-like separator, typically a membrane or diaphragm. The performance of such electrolytic cells is closely related to two parameters: first, the distance between the electrodes that must be traversed by the ions carrying the charge through the separator, and second, the surface structure and properties of the electrodes where the electrochemical reaction takes place.

[0003] Optimizing the distance between the electrodes has resulted in so-called zero-gap electrolysis cells, where the electrodes are in direct contact with the separator at a specific contact pressure. The contact pressure is maintained by elastic components within the cell that transmit a specific mechanical pressure to the other components of the cell, in particular the electrodes. Furthermore, additional mechanical loads are exerted on the electrodes by the internal cell operating pressure, in particular the pressure difference between the anode and cathode chambers.

[0004] In order to have uniform reaction conditions over the entire electrode area, it is important to ensure a uniform pressure distribution over the surface area of ​​the electrode. Conventionally, this is achieved by a sufficiently rigid electrode that distributes the mechanical pressure introduced by the vertical support web attached to the rear wall of the respective electrode chamber uniformly over the entire electrode area due to its high bending modulus. Electrode structures of this kind are known, for example, from US Patent Application Publication No. 2020 / 0283919 and US Patent Application Publication No. 2011 / 0259735.

[0005] However, known solutions have the drawback of not being able to fully realize the efficiency gains achievable through electrode structure design. The most efficient electrodes in terms of energy efficiency and material usage have a fine mesh structure that creates a large reaction surface area in close proximity to the separator. The finer the mesh structure, the weaker the electrode material in terms of mechanical rigidity, and there is a trade-off between uniform reaction conditions across the electrode area and a highly efficient electrode structure. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] US Patent Application Publication No. 2020 / 0283919 [Patent Document 2] US Patent Application Publication No. 2011 / 0259735 Summary of the Invention

[0007] It is an object of the present invention to provide an electrolytic cell for chlor-alkali or alkaline water electrolysis with electrodes made from metal mesh that improves the uniformity of reaction conditions across the electrode area.

[0008] This object is achieved by an electrolysis cell having the features of claim 1.

[0009] Thereby, an electrolytic cell for chlor-alkali or alkaline water electrolysis is provided, comprising two cell elements, each of which defines an electrode chamber by providing a rear wall and a side wall of the electrode chamber. The electrolytic cell further comprises an electrode housed in each of the electrode chambers and a sheet-like separator extending in the height and width directions of the electrolytic cell. The separator is interposed at the junction between the two cell elements and provides a separation wall between the electrode chambers. At least one of the electrodes is made from a sheet of metal mesh supported by a number of webs attached to the rear wall of the respective electrode chamber, the webs extending in the height direction of the electrolytic cell. According to the invention, the electrolytic cell further comprises a number of ribs extending in the width direction of the electrolytic cell, the ribs being carried by the webs and the electrodes being placed on the ribs.

[0010] The ribs carried by the webs form a plurality of cross stiffeners between the webs providing additional support of the electrodes between the webs in the width direction of the cell. The horizontal support of the ribs allows the mechanical stiffness of the electrode mesh to be reduced without reducing the distance between the webs. Reducing the distance between adjacent webs would adversely affect the flow characteristics of the electrolyte / gas mixture through the cell. Preferably, in an electrolysis cell according to the invention, adjacent webs are spaced apart by at least 100 mm. The electrodes may preferably be secured to the ribs and / or webs, for example by spot welding.

[0011] In a preferred embodiment, the ribs are inserted into recesses in the webs. This ensures that the manufacturing effort of the electrode support structure is low. Even more preferably, the ribs are accommodated in recesses in the webs such that the webs and the ribs form a flush support grid for the electrode. The electrode is then supported by a grid of transverse and longitudinal stiffeners that improves the uniformity of the pressure distribution across the electrode.

[0012] Preferably, the ribs have a rib height and a rib thickness that define an elongated cross section of the rib, the rib height being greater than the rib thickness. The ribs are preferably arranged in the cell such that the electrodes are located on the narrow side of the rib defined by the rib thickness. The elongated cross section of the ribs provides an advantageous geometric moment of inertia for loads acting perpendicular to the surface of the electrodes. In addition to mechanical reasons, the orientation of the ribs is selected to ensure good liquid supply through the electrodes to the separator with sufficient open area. Particularly preferably, the rib height is at least twice the rib thickness.

[0013] Preferably, the rib height is at most 1 / 3 of the depth of the electrode chamber in which it is located, thereby maintaining a large free cross section for vertical electrolyte flow in the electrode chamber.

[0014] In a preferred embodiment, the ribs have a rectangular cross section. A simple rectangular cross section has the advantage that the ribs can be made from sheet metal without the need for a metal forming step. If the amount of material needs to be further reduced, ribs with S-shaped, I-shaped, T-shaped or L-shaped cross sections can alternatively be used, which provide a high geometric moment of inertia with less material usage.

[0015] In a preferred embodiment, the rib height is at least three times the thickness of the sheet of metal mesh to provide a high level of support for the electrode.

[0016] Preferably, the ribs are arranged at an angle to the electrode in the range of 70°-90°, particularly preferably in the range of 75°-85°. In particular, it is preferred that the ribs are arranged perpendicular to the electrode or inclined downwards. The perpendicular arrangement has the advantage of forming the most stable support for the electrode. Downwardly inclined ribs have the positive effect that gas bubbles formed at the electrode do not accumulate under the horizontal ribs but are guided away from the electrode into the vertical electrolyte flow behind the ribs.

[0017] In certain embodiments, the webs are regularly spaced at a first interval and the ribs are regularly spaced at a second interval, and the ratio of the first interval to the second interval is within the range of 1.5 to 3.5.

[0018] In certain embodiments, the supported electrode has a first bending modulus across the width of the electrolytic cell and a second bending modulus across the height of the electrolytic cell, the ratio of the first bending modulus to the second bending modulus being within the range of 1.5 to 3.5.

[0019] Preferably, the sheet of metal mesh is a perforated or expanded metal sheet. Alternatively, a woven wire mesh may be used for the electrode.

[0020] Preferably, the ribs are attached to the webs by spot welding or clip connections, which allow for easy assembly that can also be automated.

[0021] The ribs are preferably made from a metal, in particular nickel or titanium.

[0022] Further advantages of the present invention will be described below with reference to the embodiments shown in the accompanying drawings. [Brief description of the drawings]

[0023] [Figure 1] 1 shows diagrammatically in vertical cross section two electrolysis cells according to the invention; [Diagram 2] FIG. 2 shows a schematic front view of a support grid for electrodes formed by webs and ribs in an electrode chamber of an electrolysis cell according to FIG. 1; [Figure 3A] 1 shows a schematic representation of an assembly of webs and ribs having a shaped cross-section. [Figure 3B] 13A-13C show schematic diagrams of web and rib assemblies having alternative cross-section shapes; [Figure 4] 1 shows a detailed view of an electrode supported by ribs in schematic form; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] In the drawings, like parts are identified with the same reference numerals throughout and therefore will be generally described and referenced only once.

[0025] In Figure 1, two electrolysis cells 1 are shown in a side-by-side arrangement. The electrolysis cells 1 are suitable for chlor-alkali or alkaline water electrolysis.

[0026] Each electrolysis cell 1 has two cell elements 2, 3, each of which defines an electrode chamber 4, 5 by providing a rear wall 6 and a side wall 7 of the electrode chamber 4, 5. Each of the electrode chambers 4, 5 houses an electrode 8, 9. The electrode chambers 4, 5 may or may not have equal depths perpendicular to the electrodes 8, 9. In particular, electrode chambers 4, 5 in which a greater amount of foaming is expected, such as the anode chambers in chlor-alkali electrolysis, may be chosen to have a greater depth.

[0027] At the joint 11 between the two cell elements 2, 3, a sheet-like separator 10 is interposed, providing a separation wall 17 between the electrode chambers 4, 5. The sheet-like separator 10 extends in the height direction H and width direction W (see FIG. 2) of the electrolytic cell 1. The sheet-like separator 10 is preferably an ion exchange membrane or a porous diaphragm. The joint 11 is also provided with a seal 18 sealing the electrode chambers 4, 5. The joint 11 may be a screw connection of two metal frames, which clamp the cell elements 2, 3 forming the half shells of the cell 1 into an individually sealed unit, i.e. a single-element type electrolytic cell 1.

[0028] At least one of the electrodes 8, 9 is made from a sheet of metal mesh 16. Preferably, the sheet of metal mesh 16 is a perforated metal sheet or an expanded metal sheet. However, a wire mesh, for example a woven wire mesh, may also be used as the electrodes 8, 9.

[0029] The metal meshes of the electrodes 8, 9 are supported by a number of webs 12 attached to the rear wall 6 of each electrode chamber 4, 5. The webs 12 extend in the height direction H of the electrolytic cell 1. The webs 12 carry a number of ribs 13 extending in the width direction W of the electrolytic cell 1, on which the electrodes 8, 9 are positioned.

[0030] 1 and 2, the ribs 13 are preferably inserted into recesses 14 in the web 12, where the ribs 13 are received, such that the web 12 and the ribs 13 form a flush support grid 15 for the electrodes 8, 9. Preferably, the ribs 13 are attached to the web 12 by spot welding or clip connections for easy assembly.

[0031] The ribs 13 are preferably made of metal in order to obtain a sufficiently high bending resistance. In particular, nickel or titanium are preferred. Titanium is particularly preferred in chlorine production electrode chambers or low PH liquids, while nickel is selected especially for high PH applications. In general, the use of stainless steel for the ribs 13 can also be envisaged depending on the application case.

[0032] As shown in FIG. 2, the webs 12 are regularly spaced apart with a first spacing I1 and the ribs 13 are preferably regularly spaced apart with a second spacing I2, the ratio of the first spacing I1 to the second spacing I2 being preferably in the range of 1.5 to 3.5. The spacing I2 between the ribs 13 being smaller than the spacing I1 between the webs 12 ensures good support of the electrodes 8, 9 while leaving sufficient space between the webs 12 for an unhindered vertical flow of electrolyte through the electrode chambers 4, 5. The spacing I1 is preferably in the range of 70 mm to 200 mm, more preferably in the range of 100 mm to 150 mm. The spacing I2 is preferably selected in the range of 20 mm to 135 mm, more preferably in the range of 30 mm to 100 mm, most preferably in the range of 40 mm to 80 mm.

[0033] The metal meshes used in the electrodes 8 and 9 often have a bending modulus that varies depending on the bending direction. For example, an expanded metal sheet has a lower bending resistance (lower bending modulus) in the expansion direction and a higher bending resistance (higher bending modulus) in the direction perpendicular to the expansion direction. In the case of punched metal meshes and wire meshes, the bending modulus in each direction depends on the hole pattern and structure of the mesh.

[0034] For uniform support of electrodes 8, 9 made from such metal mesh materials, the spacing of the supports in the direction of higher bending resistance can be larger, but the spacing of the supports in the direction of lower bending resistance needs to be smaller. Therefore, when the supported electrodes 8, 9 have a direction-dependent bending modulus, it is preferred to arrange the electrodes 8, 9 in the electrode chambers 4, 5 such that the first bending modulus in the width direction W and the second bending modulus in the height direction H of the electrolytic cell 1 have a ratio of the first bending modulus to the second bending modulus in the range of 1.5 to 3.5. This results in uniform support of the electrodes while allowing a relatively large spacing between the webs 12 for unimpeded electrolyte flow.

[0035] In Fig. 3A and Fig. 3B the assembly of the ribs 13 and the web 12 is shown diagrammatically. The web 12 has recesses 14 that fit the cross section of the ribs 13. In the case of rectangular, S-shaped 13.1 or I-shaped 13.2 cross sections, an approximately rectangular recess 14 is preferred, as shown in Fig. 3A. In the case of T-shaped 13.3 or L-shaped 13.4 cross sections, a slot-like recess is sufficient depending on the mounting direction. For easy assembly, the ribs 13 are placed in dedicated recesses 14 in the web 12. Fixation is performed by spot welding or by a press fit, for example in a clip connection. The ribs 13 are accommodated in the recesses 14 in such a way that they directly contact the electrodes 8, 9 when the latter are placed on the support grid 15 of the web 12 and the ribs 13.

[0036] Figure 4 is a detailed view of a rib 13 supporting the electrode 9. The rib 13 has a rib height h and a rib thickness t that define an elongated cross-section of the rib 13, the rib height h being greater than the rib thickness t. Preferably, the rib height h is at least twice the rib thickness t. In the simplest case, the rib 13 has a rectangular cross-section, as shown in Figure 4.

[0037] To provide the best support for the electrode 9, the rib height h is preferably at least three times the thickness tm of the metal mesh sheet 16 of the electrode 9. The rib height h is even more preferably at most ⅓ of the depth of the electrode chamber in which the ribs 13 are located.

[0038] The rib height h may preferably be selected in the range of 4 mm to 12 mm. The rib thickness t is preferably in the range of 1 mm to 2 mm. In general, the rib thickness and rib height are preferably selected as low as possible to provide the desired stability without undesirably impeding the electrolyte flow and to keep material costs down. Due to the low modulus of elasticity of titanium typically used in chlor-alkali electrolysis cells, the rib height and rib thickness are greater for these ribs than for nickel ribs typically used in alkaline water electrolysis cells.

[0039] The ribs 13 are preferably arranged orthogonally towards the electrodes 8, 9 or inclined downwards. As a result of the orthogonal arrangement, the rib height is oriented parallel to the main direction of mechanical pressure on the electrodes 8, 9 and therefore provides excellent support. In the inclined arrangement, the angle β between the ribs 13 and the electrodes 8, 9 must not be too small. Preferably, the ribs 13 are arranged at an angle β in the range of 70° to 90° relative to the electrodes 8, 9. To optimize the guidance of the gas bubbles, an angle β in the range of 75° to 85° is preferred. This prevents stagnation of the gases generated during electrolysis.

[0040] All the embodiments shown in the drawings relate to single element type electrolysis cells, where all the cells are individually replaceable sealed units, however, it will be clear to a person skilled in the art that the invention is equally applicable to other types of electrolysis cells, in particular filter press type electrolysis cells. [Explanation of symbols]

[0041] 1 Electrolysis cell 2,3 Cell elements 4,5 Electrode chamber 6 Back wall 7 side wall 8,9 electrode 10 Separator 11 Joint 12. Web 13 Ribs 13.1 S-shaped cross section 13.2 I-shaped cross section 13.3 T-shaped cross section 13.4 L-shaped cross section 14 Recess 15 Support Grid 16 Metal mesh sheet 17 Separation wall 18 Sealing H Cell height direction W Cell width direction h Rib height t Rib Thickness tm Metal mesh thickness I1 First Interval I2 Second Interval β angle

Claims

1. An electrolytic cell for chlor-alkali or alkaline water electrolysis, comprising: two cell elements (2, 3), each of said two cell elements (2, 3) defining an electrode chamber (4, 5) by providing a rear wall (6) and a side wall (7) of said electrode chamber; an electrode (8, 9) housed in each of said electrode chambers (4, 5); a sheet-like separator (10) extending in the height direction (H) and width direction (W) of the electrolysis cell (1), which is interposed at the joint (11) between the two cell elements (2, 3) and provides a separation wall (17) between the electrode chambers (4, 5); Equipped with An electrolysis cell, wherein at least one of the electrodes (8, 9) is made from a sheet (16) of metal mesh supported by a plurality of webs (12) attached to the rear wall (6) of each of the electrode chambers (4, 5), the webs (12) extending in the height direction (H) of the electrolysis cell (1), Electrolysis cell, characterized in that the web (12) carries a plurality of ribs (13) extending in the width direction (W) of the electrolysis cell (1), and the electrodes (8, 9) are arranged on the plurality of ribs (13).

2. 2. Electrolysis cell according to claim 1, characterized in that the ribs (13) are inserted into recesses (14) in the webs (12).

3. 3. An electrolysis cell according to claim 2, characterized in that the ribs (13) are received in the recesses (14) of the webs (12) such that the webs (12) and the ribs (13) form a flush support grid (15) for the electrodes (8, 9).

4. 4. The electrolysis cell according to claim 1, wherein the ribs (13) have a rib height (h) and a rib thickness (t) that define an elongated cross-section of the rib (13), the rib height (h) being greater than the rib thickness (t).

5. 5. The electrolysis cell of claim 4, wherein said rib height (h) is at least twice said rib thickness (t).

6. Electrolysis cell according to claim 4 or 5, characterized in that the ribs (13) have a rectangular cross section.

7. 6. Electrolysis cell according to claim 4 or 5, characterized in that the ribs (13) have an S-shaped (13.1), I-shaped (13.2), T-shaped (13.3) or L-shaped (13.4) cross section.

8. 8. Electrolysis cell according to claim 4 or 7, characterized in that the rib height (h) is at least three times the thickness (tm) of the sheet of metal mesh (16).

9. Electrolysis cell according to any one of the preceding claims, characterized in that the ribs (13) are arranged at an angle (β) in the range of 70° to 90° relative to the electrodes (8, 9).

10. Electrolysis cell according to any one of the preceding claims, characterized in that the ribs (13) are arranged perpendicularly or inclined downwards towards the electrodes (8, 9).

11. Electrolysis cell according to any one of claims 1 to 10, characterized in that the webs (12) are regularly spaced with a first interval (I1) and the ribs (13) are regularly spaced with a second interval (I2), the ratio of the first interval (I1) to the second interval (I2) being in the range of 1.5 to 3.

5.

12. 12. The electrolytic cell according to any one of claims 1 to 11, characterized in that the supported electrodes (8, 9) have a first flexural modulus in the width direction (W) and a second flexural modulus in the height direction (H) of the electrolytic cell (1), the ratio of the first flexural modulus to the second flexural modulus being in the range of 1.5 to 3.

5.

13. Electrolysis cell according to any one of the preceding claims, characterized in that the sheet (16) of metal mesh is a perforated metal sheet or an expanded metal sheet.

14. Electrolysis cell according to any one of the preceding claims, characterized in that the ribs (13) are attached to the webs (12) by spot welding or clip connections.

15. Electrolysis cell according to any one of the preceding claims, characterized in that the ribs (13) are made of metal, in particular nickel or titanium.

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