Electrolysis cell with support members

Abstract

An electrolysis cell 1 comprises: first electrode chamber and second electrode chambers 2, 3, the first electrode chamber 2 being defined by a back wall 4 and a sidewall 5; first and second electrodes 6, 7 accommodated in the respective electrode chambers 2, 3; a separator 8 arranged between the first and second electrodes 6, 7 and extending in a height direction H and a width direction W of the electrolysis cell 1; and columns of support members 10 for elastic support of the first electrode 6 on the back wall 4, the columns of support members 10 being arranged between the first electrode 6 and the back wall 4 and extending parallel to each other along the height direction H. Each support member 10 comprises a plurality of spring portions 15, at least some 15a of the spring portions extending from sides of the support member 10, said at least some 15a of the spring portions being independent from each other by a plurality of side openings 16 formed in the sides of the support member 10. The electrolysis cell 1 further comprises a rectifying member 18 arranged between two adjacent columns of support members 10 and extending at least partially along the adjacent columns of the support members 10 in the height direction H.

Description

[0001] M / THYS-392-PC

[0002] ELECTROLYSIS CELL WITH SUPPORT MEMBERS

[0003] Technical Field

[0004] The invention relates to an electrolysis cell having electrodes supported with support members.

[0005] Background

[0006] Electrolysis cells for chlor-alkali and / or alkaline water electrolysis typically comprise two electrode chambers each containing one electrode. The electrode chambers are separated from one another by a sheet-like separator. The electrodes within each chamber are supported by a support structure on a back wall of the electrode chamber.

[0007] In the past, the electrodes are positioned with a gap to the separator ("finite-gap con-figuration") in order to prevent damages of the separator during assembly and to allow for the product gases to bubble up freely also on the separator side of the electrodes. However, for an increased efficiency of the cell the so-called "zerogap configuration" has been developed in which the electrodes are brought substantially into contact with the separator on both sides. In order to reduce the risk of damaging the separator during assembly and to provide for a homogeneous contact pressure, the support structure of at least one electrode usually contains at least one resilient or elastic member in an electrolysis cell of zero-gap design.

[0008] From the prior art, zero-gap electrolysis cells with elastic electrode support structures of differing designs are known. M / THYS-392-PC

[0009] WO 2017 / 217427 Al describes an electrolytic cell comprising a support structure arranged between an electrode and a back wall of an electrode chamber and supporting the electrode on the back wall . The support structure comprises a pair of side sections standing on the back wall and extending in the height direction of the electrolysis cell, a web section connecting the pair of support sections in the width direction, and a plurality of spring portions. In order to allow sufficient elastic deformation of the spring portions, some of the spring portions are so formed as to extend from the side sections of the support structure whilst forming a plurality of openings in the side sections to separate elastic deformation areas of said spring portions from the side sections.

[0010] Another support structure is disclosed in EP 3 794 165 Al. The support structure has a plurality of ring-shaped spring portions each formed by shaping one or two strip portions into a ring. The ringshaped spring portions are arranged in an orientation where their opening axes are aligned with the cell height direction.

[0011] In a common chlor-alkali or alkaline electrolyser, electrolysis is performed whilst electrolyte is continuously fed from a supply port toward a discharge port. Homogeneous concentration of electrolyte is preferable. However, the inventors have found that when using the support members such as described in WO 2017 / 217427 Al or EP 3 794 165 Al, the concentration of electrolyte near the supply port becomes different from the concentration of electrolyte near the discharge port, as electrolysis progresses. In addition, due to the flow of the liquid in the chamber, drifting may occur due to the differential pressure in the chamber, resulting in that the electrolyte M / THYS-392-PC concentration in the electrolysis cell also varies in the cell width direction. Since the concentration of the electrolyte is a factor that greatly influences the electrolytic resistance value, the concentration distribution within the electrolytic cell greatly affects the current distribution. If the electrolyte concentration distribution in the electrolytic cell is unbalanced, the current distribution may also be unbalanced and the current may thus increase in the areas with low electric resistance, resulting in deterioration of the electrolysis performance.

[0012] Summary

[0013] The object of the invention is to provide an electrolysis cell with support members for an electrode, which allows for good elastic support for the electrode, whilst preventing the deterioration of the electrolysis performance due to the inhomogeneous electrolyte concentrations in the chamber.

[0014] This object is achieved by an electrolysis cell according to the features of claim 1. An electrolysis cell comprises: first electrode chamber and second electrode chambers, the first electrode chamber being defined by a back wall and a sidewall; first and second electrodes accommodated in the respective electrode chambers; a separator arranged between the first and second electrodes and extending in a height direction and a width direction of the electrolysis cell; and columns of support members for elastic support of the first electrode on the back wall, the columns of support members being arranged between the first electrode and the back wall and extending parallel to each other along the height direction. Each support member comprises a plurality of spring portions, at least some of the spring portions extending from sides of the support member, said at least some of M / THYS-392-PC the spring portions being independent from each other by a plurality of side openings formed in the sides of the support member. The electrolysis cell further comprises a rectifying member arranged between two adjacent columns of support members and extending at least partially along the adjacent columns of the support members in the height direction. Here, "rectifying" refers to rectification of gas and liquid flow inside the chamber, and is to guide the flow in a predetermined direction.

[0015] A good elastic support can be achieved by the spring portions extending from the sides of the support member. Also, the rectifying member prevents the deflected flow through the side openings in the sides of the support members. As such, electrolyte concentration in the chamber is homogenised within the first chamber.

[0016] Further advantages of the invention are described in the following with regard to the embodiments shown in the attached drawings.

[0017] Brief Description of the Drawings

[0018] Fig. 1 shows schematically a cross-sectional view of an electrolysis cell of an embodiment according to the present invention,

[0019] Fig. 2 shows schematically a cross-sectional view of an electrolysis cell of another embodiment according to the present invention,

[0020] Fig. 3 shows the A-A cross section of Fig. 1,

[0021] Fig. 4 shows a perspective view of a support member,

[0022] Fig. 5 is a similar cross section to Fig. 3, showing another support member having ring-shaped spring portions, M / THYS-392-PC

[0023] Fig. 6 illustrates electrolyte concentration distribution in a conventional electrolysis cell,

[0024] Fig. 7 illustrates non-uniform gas and liquid flow in the chamber,

[0025] Fig. 8 illustrates rectified gas and liquid flow in the chamber by means of rectifying members,

[0026] Fig. 9 illustrates electrolyte concentration distribution in the electrolysis cell according to the present invention, and

[0027] Figs. 10 and 11 illustrate a method to attach the rectifying members to the support members.

[0028] Detailed Description

[0029] In the drawings same or similar parts are identified by the same or similar reference signs and are therefore generally described and duplicate explanations may be omitted.

[0030] Fig. 1 shows a cross-sectional view of an electrolyser having electrolysis cells each according to the invention. This electrolyser may be used for chloralkali or alkaline water electrolysis, or the like. The electrolysis cell 1 as shown is an electrolysis cell for a bipolar type electrolyser, which contains a plurality of individual electrolysis cell elements 1A, 1A..., electrically and mechanically connected in series. Each electrolysis cell 1, which in this type is configured by part of two adjacent cell elements 1A, 1A, comprises a first electrode chamber 2 and a second electrode chamber 3. The first electrode chamber 2 is defined by a back wall 4 and a sidewall 5. The second electrode chamber 3 may also be defined by a back wall 4 and a side wall 5 of the adjacent cell element 1A. The side wall 5 may extend from the periphery of the back wall 4. M / THYS-392-PC

[0031] The electrolysis cell 1 further comprises first and second electrodes 6, 7 accommodated in the respective electrode chambers 2, 3. In this type of electrolyser, a sheet-like separator 8, such as ion exchange membrane or diaphragm, may be arranged between the respective adjacent cell elements 1A, 1A to separate the first chamber 2 of one cell element 1A from the second chamber 3 of the other cell element 1A. In any cases, the separator 8 is arranged between the first and second electrodes 6, 7 and extending in a height direction H and a width direction W of the electrolysis cell 1. The height direction H is perpendicular to the ground on which the electrolysis cell 1 is displaced; and the width direction W is perpendicular to the height direction H. The direction perpendicular to the height direction H and the width direction W is a thickness or depth direction T, which may also be referred to as a cell stacking direction.

[0032] The form of the electrode 6, 7 is not particularly limited and any known electrodes, such as expanded metal, a net-like body, and a woven body may be used.

[0033] Fig. 2 shows another type of electrolysis cell element, which may be referred to as 'single-element'. In this type, one cell element constitutes one electrolysis cell. In other words, a single cell element IB has the first and second chambers 2, 3, the first and second electrodes 6, 7 and the separator 8 to form the electrolytic cell 1 as a module. The separator 8 may be interposed in a joint 9 between the first chamber 2 and the second chamber 3 with being interposed between the first and second electrodes 6 and 7. This type of electrolysis cell may be assembled and tested before inserting it into the electrolyser stack.

[0034] In both types, it is preferable that the electrodes 6, 7 are brought substantially into contact with the separator 8 to form a zero-gap M / THYS-392-PC configuration. To prevent the separator 8 from damage or reduce the risk of damage, an elastic support means is provided in at least one of the chambers 2, 3. In Fig. 1, columns of support members 10 as the elastic support means are provided in the first chamber 2, preferably in a cathode chamber. The columns of support members 10 support the first electrode 6 on the respective back wall 4. The columns of support members 10 are arranged between the first electrode 6 and the back wall 4 and extending parallel to each other along the height direction H. Fig. 3 shows an A-A section in Fig. 1. The columns of support members 10 are arranged next to each other in the width direction W.

[0035] Each support member 10 may be made of conductive material and welded or connected to the back wall 4.

[0036] Fig. 4 shows an exemplary support member, which comprises a pair of side sections 12, 13 standing on the back wall 4 and extending in the height direction H of the electrolysis cell 1, a web section 14 connecting the pair of side sections 12, 13 in the width direction W, and a plurality of spring portions 15. At least some 15a of the spring portions 15 may extend from the side sections 12, 13. A plurality of side openings 16 are formed in the side sections 12, 13 to define part of the spring portions 15a extending from the side sections 12, 13. The side openings 16 partially separate the spring portions 15a from the side sections 12, 13.

[0037] The spring portions 15 may also include spring portions 15b extending from the web section 14, wherein the spring portions 15a extending from the side sections 12, 13 and the spring portions 15b extending from the web section 14 may cross each other in an X-shape when viewed in the height direction H. In Fig. 4, two rows of spring portions 15a and 15b, i.e., two rows X- shaped crossings, are provided on the web section 14. The spring portions M / THYS-392-PC

[0038] 15 may include leaf springs or plate springs. Preferably, the spring portions

[0039] 15 may be formed by cutting around the spring portions and bending the respective portions from the side sections 12, 13 and the web section 14.

[0040] It should be noted that the X-shaped crossings are not necessary. The only important feature in the support member 10 is that, at least some 15a of the spring portions 15 extends from the sides of the support member 10 so that a larger region of this spring portion 15a is elastically deformed, ensuring improvement in elasticity. The spring portions 15a with sufficient elasticity gently presses the electrode 6 against the separator 8 (e.g. ion exchange membrane), which thus protects the separator 8 from mechanical damage and at the same time improves the operating environment of the separator 8. This feature, however, involves the above-mentioned side openings 16 in the sides of the support member 10, leading to the aforementioned drawback, which is the inhomogeneous concentrations in the chamber, particularly in the cathode chamber.

[0041] Another exemplary elastic support member is shown in Fig. 5. The support member 10' includes a plurality of ring-shaped spring portions 15'. Each spring portion 15' may be formed by shaping one or two strip portions into a ring. The ring-shaped spring portions may be arranged in an orientation where their opening axes are aligned with the height direction H. The ring-shaped spring portions 15' are spaced apart from each other in the height direction H. Side openings (gaps) are thus formed between respective adjacent spring sections in the height direction H. Since the spring portions 15' extends from the sides of the support member 10', a larger region of this spring portion 15' can be elastically deformed, ensuring improvement in elasticity. The spring portions 15' with sufficient elasticity gently presses the electrode 6 against the M / THYS-392-PC separator 8, which thus protects the separator 8 from mechanical damage and at the same time improves the operating environment of the separator 8. This feature, however, involves the above-mentioned side openings (gaps) in the sides of the support member 10', leading to the aforementioned drawback, which is the inhomogeneous concentrations in the chamber, particularly in the cathode chamber.

[0042] As such, each support member comprising a plurality of spring portions, at least some of the spring portions extending from sides of the support member, said at least some of the spring portions being independent from each other by a plurality of openings formed in the sides of the support member. However, the use of such support members causes inhomogeneous electrolyte concentration distribution due to the side openings or gaps of the support members, as discussed above.

[0043] Fig. 6 shows an example of sodium hydroxide (NaOH) solution concentration distribution within a cathode chamber in a chlor-alkali electrolysis process, using a conventional electrolysis cell. This conventional electrolysis cell uses the support members as described in WO 2017 / 217427 Al, wherein the support members includes a plurality of side openings in the sides of the support members.

[0044] Electrolysis produces chlorine on the anode and the sodium ions move through the ion exchange membrane as the separator to the cathode chamber. Hydrogen is generated on the cathode and at the same time hydroxide ions are formed, generating NaOH solution in the cathode chamber. A lower concentration of NaOH solution is supplied from an inlet at the bottom of the cathode chamber and distributed into the chamber by means of a distribution pipe in the bottom of the cathode chamber. The NaOH solution increases in concentration (wt%) M / THYS-392-PC through electrolysis and is discharged from an outlet at the top of the cathode chamber. This figure shows concentration ratios of sodium hydroxide solution at three different portions within the chamber, which are left, centre and right portions, with respect to an average concentration of sodium hydroxide solution inside the chamber as 1.00. As shown, the concentration within the chamber varies in the width direction W. More specifically, the concentration in the left portion, which is the closest to the inlet and outlet of the chamber, is lowest; and the concentration in the right portion, which is farthest from the inlet and outlet of the chamber, is highest.

[0045] Further studies by the inventors revealed that such an inhomogeneous concentration distribution was caused by non-uniform flows of gas and liquid in the chamber. The electrolyte distributed from the distribution pipe at the bottom of the chamber initially forms a vertical upward flow. However, as indicated by arrows in Fig. 7, as the electrolyte moves towards the top of the chamber, it becomes a lateral flow as a result of short-passing of the electrolyte through the side openings of the support members.

[0046] Returning to Fig. 3, a solution to this problem is described. The electrolysis cell 1 according to the present invention further comprises a rectifying member 18 arranged between two adjacent columns of support members 10 and extending at least partially along the adjacent columns of the support members 10 in the height direction H. In this example, more than one rectifying member 18 is provided so as to be arranged between respective adjacent columns of support members 10. The rectifying member 10 prevents the deflected flow through the side openings 16 in the sides of the support members 10. This is illustrated in Fig. 8; the electrolyte distributed from the bottom of the chamber 2 flows upwardly with being rectified by the M / THYS-392-PC rectifying members 18 placed between the adjacent columns of support members 10 and towards the top of the chamber 2. As such, as shown in Fig. 9, the electrolyte concentration in the chamber is homogenised. This figure shows concentration ratios of sodium hydroxide solution measured at three different portions within the chamber, which are left, centre and right portions, with respect to an average concentration of sodium hydroxide solution inside the chamber as 1.00.

[0047] The rectifying member 18 are not limited in shape, size or number as long as it prevents the short-passing of electrolyte through the side openings of the support member 10. For example, the rectifying member 18 may be a plate. The rectifying member 18 may be divided into several parts in the height direction H or may extend continuously in the height direction.

[0048] Preferably, the rectifying member 18 is configured to cover at least part of the side openings 16 in the sides of the support members 10. In other words, the rectifying member 18 is positioned in close proximity to the side openings 16 of the support members. The short pass of electrolyte through the side openings 16 of the support members 10 can effectively be prevented. More preferably, the rectifying member 18 is positioned on the outer surface of the side section 12, 13 of the support member 10.

[0049] If the rectifying member(s) 18 extends 50% or more of the adjacent support columns in the height direction H, more improved rectification of the electrolyte flow within the chamber and thus more homogeneous electrolyte concentration within the chamber is achieved. More preferably, the rectifying member(s) 18 extends 60% or more, more preferably 70% or more, more preferably 80% or more, more preferably 90% or more, of the adjacent support columns in the height direction H. Most preferably, the rectifying M / THYS-392-PC member(s) 18 extends to the same extent as the adjacent support member 10 in the height direction H.

[0050] As shown in Fig. 3, the rectifying member 18 (s) may include a rectangular or U-shape channel creating an inner passage P extending in the height direction H. Preferably, in the height direction H, both ends of the channel are open, allowing the electrolyte to flow through the channel. For example, if each distribution hole in the distribution pipe at the bottom of the chamber is located between the pair of side sections 12, 13 of the support member 10 and does not communicate with the passage P of the channel, it may be expected that the electrolyte, which has moved upwards, circulates downwards through the passage of the channel (down-comer effect), contributing to a more homogeneous concentration distribution within the chamber.

[0051] As shown in Fig. 3, the rectifying member 18 has a thickness 18t measured from the back wall 4 in the thickness direction T. The thickness 18t is not limited to the illustrated example and the front surface of the rectifying member 18 may be located within any distance from the back wall 4 as long as it does not hinder the displacement of the electrode 6 supported by the spring portion 15. Preferably, the front surface of the rectifying member 18 facing the electrode 6 is flush with the front surface of the support member 10. Alternatively, the front surface of the rectifying member 18 may be located closer to the back wall 4 than the front surface of the support member 10. In other words, the rectifying member 18 does not protrude from the outer surface level of the web section 14 of the support member 10 towards the electrode 6.

[0052] With reference to Figs. 10 and 11, an exemplary mounting structure of the rectifying member 18 is described. The rectifying member 18 has one or M / THYS-392-PC more wings 19 or protruding pieces at one or both ends thereof in the height direction H. In the illustrated example, at each end, two wings 19, 19 extend from the respective sides of the rectangular channel 18. As shown in Fig. 10, the channel-shaped rectifying member 18 is inserted between the adjacent columns of support members 10. After inserting the member 18 between the adjacent columns of support members 10, the wings 19, 19 are folded around the respective side sections 12, 13 of the adjacent support members 10, thereby retaining the rectifying member 18 with the adjacent support members 10. No welding or other fixing means is thus required. Such a mounting structure is particularly advantageous for retroactively applying the rectifying members 18 of the present invention to existing electrolysis cell.

[0053] Returning to Fig. 5, it is confirmed that the rectifying members 18 are provided between the adjacent ring-shaped spring portions 10. The above description of the rectifying members applies equally to this embodiment.

[0054] Although the application of rectifying member(s) is particularly advantageous when used in the electrolysis cell with a zero-gap configuration, the rectifying member(s) may be used in a finite-gap configuration in which the electrodes are positioned with gaps with respect to the separator.

[0055] Further, the elastic support members and the rectifying member(s) may be provided in the anode chamber, or in both the anode and cathode chambers (not shown).

[0056] Reference sign list

[0057] 1 electrolysis cell M / THYS-392-PC

[0058] 1A, IB cell element

[0059] 2, 3 electrode chamber

[0060] 4 back wall

[0061] 5 sidewall 6, 7 electrode

[0062] 8 sheet-like separator

[0063] 9 joint

[0064] 10 support member

[0065] 12, 13 side section 14 web section

[0066] 15 spring portion

[0067] 15' ring-shaped spring portion

[0068] 15a spring portion extending from side section

[0069] 15b spring portion extending from web section 16 side opening

[0070] 18 rectifying member

Claims

M / THYS-392-PCCLAIMS1. An electrolysis cell (1) comprising: first electrode chamber and second electrode chambers (2, 3), the first electrode chamber (2) being defined by a back wall (4) and a sidewall (5), first and second electrodes (6, 7) accommodated in the respective electrode chambers (2, 3); a separator (8) arranged between the first and second electrodes (6, 7) and extending in a height direction (H) and a width direction (W) of the electrolysis cell (1); and columns of support members (10) for elastic support of the first electrode (6) on the back wall (4), the columns of support members (10) being arranged between the first electrode (6) and the back wall (4) and extending parallel to each other along the height direction (H), wherein each support member (10) comprises a plurality of spring portions (15), at least some (15a) of the spring portions extending from sides of the support member (10), said at least some (15a) of the spring portions being independent from each other by a plurality of side openings (16) formed in the sides of the support member (10), characterized in that the electrolysis cell (1) further comprises a rectifying member (18) arranged between two adjacent columns of support members (10) and extending at least partially along the adjacent columns of the support members (10) in the height direction (H).M / THYS-392-PC2. The electrolysis cell (1) according to claim 1, wherein each support member (10) comprises: a pair of side sections (12, 13) standing on the back wall (4) and extending in the height direction (H) of the electrolysis cell (1); a web section (14) connecting the pair of side sections (12, 13) in the width direction (W); the plurality of spring portions (15), at least some (15a) of the spring portions extending from the side sections (12, 13); and the plurality of openings (16) formed in the side sections (12, 13) to define part of the spring portions (15a) extending from the side sections (12, 13).

3. The electrolysis cell (1) according to claim 2, wherein the spring portions (15) further include spring portions (15b) extending from the web section (14), the spring portions (15a) extending from the side sections (12, 13) and the spring portions (15b) extending from the web section (14) cross each other in an X-shape when viewed in the height direction (H).

4. The electrolysis cell (1) according to any one of claims 1 to 3, wherein the rectifying member (18) is positioned to cover at least part of the side openings (16).

5. The electrolysis cell (1) according to any one of claims 1 to 4, wherein the rectifying member (18) extends 50% or more, preferably 60% or more, more preferably 70% or more, more preferably 80% or more, moreM / THYS-392-PC preferably 90% or more, of the adjacent columns of support members (10) in the height direction (H).

6. The electrolysis cell (1) according to any one of claims 1 to 5, wherein the rectifying member (18) extends to the same extent as the adjacent columns of support member (10) in the height direction (H).

7. The electrolysis cell (1) according to any one of claims 1 to 6, comprising a plurality of the rectifying members (18) each arranged between respective adjacent columns of support members (10).

8. The electrolysis cell (1) according to any one of claims 1 to 7, wherein the rectifying member (18) includes a rectangular or U-shape channel defining an inner passage (P) which extends in the height direction (H).

9. The electrolysis cell (1) according to any one of claims 1 to 8, wherein the rectifying member (18) has a thickness (18t) measured in a direction (T) perpendicular to the height direction and to the width direction (W) so that the rectifying member (18) does not hinder a displacement of the first electrode (6) which is supported by the support member (10).

10. The electrolysis cell (1) according to any one of claims 1 to 9, wherein the rectifying member (18) is retained by at least one of the adjacent columns of support members (10).

11. The electrolysis cell (1) according to any one of claims 1 to 10, wherein the support members (10) are configured to bring the first electrode (6) substantially into contact with the separator (8), thereby forming a zerogap configuration.17M / THYS-392-PC12. The electrolysis cell (1) according to any one of claims 1 to 11, wherein the first electrode (6) is a cathode electrode.

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