Electrolysis cell with support members having first and second spring means

Abstract

Electrolysis cell for chlor-alkali or alkaline water electrolysis comprises: two cell elements each defining an electrode chamber by providing a back wall and sidewalls of the electrode chambers; an electrode accommodated in each of the electrode chambers; a sheet-like separator extending in a height direction and a width direction of the electrolysis cell, the separator being interposed in a joint between the two cell elements and providing a separating wall between the electrode chambers; and a plurality of support members supporting at least one of the electrodes on the respective back wall. The support members each comprise: two support portions standing upright on the back wall and extending in the height direction of the electrolysis cell; a body portion connecting the two support portions in the width direction; and one or more first spring means provided in the body portion or the support portions for providing a resilient force with respect to the supported electrode when deflected by a load applied from said electrode. Each support member further comprises one or more second spring means each having a higher stiffness than that of the first spring means.

Description

[0001] ELECTROLYSIS CELL WITH SUPPORT MEMBERS HAVING FIRST AND SECOND SPRING MEANS

[0002] Technical Field

[0003] The invention relates to an electrolysis cell having electrodes supported with support members.

[0004] Background

[0005] Electrolysis cells for chlor-alkali and / or alkaline water electrolysis typically comprise two electrode chambers containing one electrode each. 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.

[0006] In the past, the electrodes used to be 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 in touching 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 member in an electrolysis cell of zero-gap design.

[0007] From the prior art, zero-gap electrolysis cells with resilient electrode support elements of differing designs are known.

[0008] WO 2017 / 217427 Al describes an electrolytic cell including an elastic member disposed in the cathode chamber. The elastic member is constituted by a bonding part, a plurality of spring retaining parts and two spring rows provided on each spring retaining part. The bonding part is bonded to a flat panel-shaped electrolytic partition wall. The spring rows contact the cathode. Each spring row is constituted by a plurality of first flat spring-like bodies. Similar elastic members with flexible tongues supporting the electrodes are known from EP 1 865 092 A2, EP 1 900 851 A2 and EP 1 378 589 Al.

[0009] Another type of resilient support elements in an electrolytic cell is known from US 2021 / 222 306 Al. The resilient support elements contain annular elements, the axis of which is oriented in the height direction of the electrolysis cell.

[0010] In these support structures according to the prior art, only one spring means or functionality is implemented in the direction of supporting the electrode, which might not be sufficient in terms of compensating possible tolerances in practice.

[0011] The problem is, that the spring means needs to be chosen in order to achieve a smooth contact surface to the electrode that will be put on top of the elastic part of the support member. In that case the deflection is low compared to possible dimensional tolerances that have to anticipated for the spring means itself and for the other relevant parts in the assembly. The deflection of the sole spring means could be used completely (spring is at block), before all the required travel of the supported electrode during assembly is done, depending on tolerances (certain travel during assembly and squeezing of the cells is required). On the other hand, situations may occur in which the required deflection for smooth contact surface is not reached completely due to unfavorable tolerance situations.

[0012] Summary

[0013] The object of the invention is to provide an electrolysis cell with resilient support members for an electrode, which is able to compensate occurring tolerances in the assembly setup of the electrolysis cell whilst ensuring proper deflection for smooth contact between the support member and the electrode. This object is achieved by an electrolysis cell according to the features of claim 1.

[0014] Hereby, an electrolysis cell for chlor-alkali or alkaline water electrolysis is provided. The electrolysis cell comprises: two cell elements each defining an electrode chamber by providing a back wall and sidewalls of the electrode chambers; an electrode accommodated in each of the electrode chambers; a sheet-like separator extending in a height direction and a width direction of the electrolysis cell, the separator being interposed in a joint between the two cell elements and providing a separating wall between the electrode chambers; and a plurality of support members supporting at least one of the electrodes on the respective back wall. The support members each comprise: two support portions standing upright on the back wall and extending in the height direction of the electrolysis cell; a body portion connecting the two support portions in the width direction; and one or more first spring means provided in the body portion or the support portions for providing a resilient force with respect to the supported electrode when deflected by a load applied from said electrode. Each support member further comprises one or more second spring means each having a higher stiffness than that of the first spring means.

[0015] After the first spring means with a lower stiffness that is ensuring the proper contacting for the respective electrode is deflected, the second spring means is deformed, as the second spring has a higher stiffness than that of the first spring means. With the lower and higher stiffness of the springs, occurring tolerances in the assembly setup of the electrolysis cell can be compensated, whilst ensuring proper deflection for smooth contact between the support member and the electrode. It is preferable that the one or more second spring means have a load limit after which plastic deformation of the second spring means occurs, particularly within a possible maximum tolerance in the assembly setup of the electrolysis cell. By this feature of plastic deformation, the overall load to the support member is limited. In case the load limit is exceeded, the geometry of the second spring means keeps deforming until the load to the first spring means is reduced. This would be for example the case when the travel is limited due to high tolerances of neighboring parts. Once the second spring means has adjusted its height to the neighboring parts, the load will adapt itself. Thus the overall support member is able to compensate occurring tolerances in the assembly setup of an electrolysis cell whilst ensuring proper contact conditions by means of the first spring means. Put another way, the plastic deformation of the second spring means may avoid or release the blocked state of the first spring member due to the dimensional tolerances of the components of the electrolysis cell, and thus maintains the proper cushioning support for the electrode by the first spring means.

[0016] It is preferable that the one or more second spring means are configured to be plastically deformed when a load greater than that required to complete the deflection of first spring means is applied from the supported electrode to the support member as we as the second spring means reached the load limit thereof, especially due to dimensional tolerances of components of the electrolysis cell.

[0017] It is preferable that the one or more second spring means are configured to be elastically deformed until the load limit of thereof. This allows that the second spring means provides elastic support for the electrode if the load on the support member does not exceed the load limit of the second spring means.

[0018] It is preferable that the second spring means is provided in each of the support portions. This ensures improved homogeneity of the contact pressure between electrode and separator.

[0019] It is preferable that each second spring means includes one or more bent sections formed by the respective support portion being partially bent in the width direction. This allows the second spring means to be implemented without the use of additional components such as additional coil springs or disc springs.

[0020] It is preferable that each bent section has a U-shape or V-shape having two opposing walls in a cross-sectional view perpendicular to the height direction. Such a bent section can easily be produced, for example, by press working.

[0021] The ability to deflect plastically might be a potential danger during operation. This might be for example the case when an unintended differential pressure case occurs, causing persistent high mechanical loads to the half part of the cell in which these support members are used. In such a case the mechanical integrity of the separator / membrane could be at risk, a crack or even rupture of it could be the consequence. Hence, excessive deflections of the separator / membrane need to be prevented. To achieve this, a third highest stiffness is designed by providing an end stop for the second spring means, preventing further deflection thereof. More specifically, in a preferred embodiment, the two opposing walls of the U- shaped or V-shaped bent section are configured to come into contact each other when an excessive load is applied from the electrode to the support member, thereby forming a stopper for preventing a further displacement of the body portion towards the back wall.

[0022] In a preferable embodiment, the support member forms an arc-spring as the first spring means. The support members may be a single piece construction providing at the same time a static support component by the upright support portions as well as an elastic support component by the deflectable arched portion. The functions of support, current distribution and homogeneous contact pressure of the electrode are all provided by the support members.

[0023] Moreover, the bearing surface for the electrode may be enlarged upon inwards-directed deflections of the arched portion, which is advantageous for both, the supported electrode and the support member.

[0024] As the bearing surface enlarges during assembly of the cell e.g. by providing a contact pressure in the joint of the cell elements, the load acting between the electrode and the respective back wall is dissipated through the larger contact area of the enlarged bearing surface. Thus, the pressure is distributed over a larger part of the area of the electrode and results in an improved homogeneity of the contact pressure between electrode and separator.

[0025] In preferred embodiments, the foot portions are attached to the back wall by a detachable mechanical connection. If the foot portions are fixed by detachable mechanical connections to the back wall, the support members can be mounted and replaced easily and individually. The foot portions may be part of the second spring means, preferably part of one of the two opposing walls of the U-shaped or V-shaped bent section, which faces the back wall.

[0026] Preferably, the foot portions are subdivided by indentations into latches that are engaged in pockets provided on the back wall. Even more preferred, the support members are fixed in a mounted position by a form-locked engagement of the latches in the pockets. This mounted position can be achieved, for example, by exploiting the elastic properties of the support member to deflect the foot portions during assembly, in order to bring the latches of both foot portions into engagement with the respective pockets on the back wall. The pockets can preferably be provided on the back wall by means of corrugated metal strips. The metal strips can be intermittently fixed to the back wall by spot welding, for example.

[0027] In further preferred embodiments, the indentations are continued into the respective support portion for a lateral suspension of the individual latches. With the indentations continuing into the support portions, the latches become individually deflectable in a lateral direction. Thereby, the mounting of the support members in the cell is simplified as the latches can be plugged into the pockets on a one-by- one basis.

[0028] Preferably, the resilient bearing surface comprises openings for passage of gas produced at the supported electrode. Thus, the gas produced at the electrode does not need to dissipate through the mesh-like structure of the electrode alone, but enters the portion of the electrode chamber behind the support members, which is filled with electrolyte during operation of the cell. In addition, the openings improve the supply of the electrode with fresh electrolyte. Both effects contribute to an improved efficiency of the cell. However, if the openings are chosen too large, the stability of the support member and mechanical resistance of the arched portion are weakened. Therefore, the opening ratio defined as the area of the openings divided by the complete bearing surface is preferably chosen within the range of 0.6 to 0.85, and more preferably within the range of 0.7 to 0.8.

[0029] In preferred embodiments, the openings are provided with bent rim portions facing away from the supported electrode. The bent rim portions enlarge the geometrical moment of inertia of the arched portions. Thus, the bent rim portions allow for a larger area of the openings by strengthening the supportive effect of the arched portions at the same time.

[0030] In some embodiments, the foot portions of laterally adjacent support members are arranged side-by-side on the back wall. Such an arrangement enlarges the contact area of the support members on the back wall and thus improves current distribution by the support members.

[0031] In alternative embodiments, the foot portions of laterally adjacent support members are arranged on top of each other on the back wall. This arrangement has the advantage that the gap between bearing surfaces of the laterally adjacent support members is reduced, such that the electrode is supported even more homogeneously over its complete area.

[0032] In certain preferred embodiments, the bearing surface extends laterally beyond the support portions at least to one side by means of an extension portion of the support member. The extension portion thus extends the arched portion on the side of the support portion that faces away from the arched portion. Extension portions of this kind may be used to reduce or even close the gap between the bearing surfaces of laterally adjacent support members.

[0033] Preferably, the arched portion has an arch height and the support portions have a supporting height, wherein the ratio of the arch height and the supporting height is within the range from 1:3 to 1:30, and more preferred in the range of 1: 15 to 1 :25, in an undeflected state of the arched portion. Thus, the larger part of the space between the back wall and the electrode is preferably bridged by the support portions, whilst the arch is comparatively flat. This cross- sectional form of the support member is preferred as it results in a wide bearing surface for the electrode and thus optimizes both, resilient support of the electrode and uniform current distribution.

[0034] Further advantages of the invention are described in the following with regard to the embodiments shown in the attached drawings.

[0035] Brief Description of the Drawings

[0036] Fig. 1 shows schematically a cross-sectional view of an electrolysis cell, which can be an embodiment according to the invention if a second spring means as described later is incorporated therein,

[0037] Fig. 2A shows schematically a first perspective view of the right-hand side cell element of Fig. 1 containing a plurality of support members mounted on the back wall, which can be an embodiment according to the invention if a second spring means as described later is incorporated therein, Fig. 2B shows schematically a second close-up perspective view of the cell element of Fig. 2A, which can be an embodiment according to the invention if a second spring means as described later is incorporated therein,

[0038] Fig. 3 shows schematically a perspective view of one of the support elements shown in Figs. 1, 2A and 2B, which can be an embodiment according to the invention if a second spring means as described later is incorporated therein,

[0039] Figs. 4A and 4B show schematically a cross-sectional view of the support element according to Fig. 3, in a load-free state and a loaded state, respectively, which can be an embodiment according to the invention if a second spring means as described later is incorporated therein,

[0040] Figs 5A to 5Eshow schematically in a cross-sectional view different configurations of support members and their arrangement on the back wall of the cell, which can be an embodiment according to the invention if a second spring means as described later is incorporated therein,

[0041] Fig. 6 shows schematically a perspective view of a support member, which can be another embodiment according to the invention if a second spring means as described later is incorporated therein,

[0042] Fig. 7 shows schematically a cross-sectional view of the support member according to Fig. 6,

[0043] Fig. 8A shows schematically a cross-sectional view of a support member having a second spring means, which may also be used in the electrolysis cell of Figs. 1 to 3 to thus be part of the present invention,

[0044] Fig. 8B shows a perspective view of the support member of Fig. 8A, Fig. 9 shows schematically in a cross-sectional view of a plurality of support members of Fig. 8A and their arrangement on the back wall of the cell,

[0045] Fig. 10 illustrates undeflected and different deflected states of the support member of Fig. 8A along with a corresponding force-deflection curve,

[0046] Fig. 11 shows schematically a cross-sectional view of a support member according to another embodiment of the present invention;

[0047] Fig. 12 shows schematically a cross-sectional view of a support member according to another embodiment of the present invention; and

[0048] Fig. 13 shows schematically a cross-sectional view of a support member according to yet another embodiment of the present invention.

[0049] Detailed Description

[0050] 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. Figures 1 to 7 are presented to help readers understand the present invention. Features described in relation to these figures may be combined with embodiments as shown in figures 8 to 13 to be part of the present invention. In other words, by providing a second spring means to the support member shown in figures 1 to 7, the resultant embodiments would be part of the present invention.

[0051] Fig. 1 shows a cross-sectional view of an electrolysis cell 1 for chlor-alkali or alkaline water electrolysis according to the invention. The electrolysis cell 1 comprises two cell elements 2, 3, which each define an electrode chamber

[0052] 4, 5 by providing a back wall 6 and sidewalls 7 of the electrode chambers 4,

[0053] 5, and an electrode 8, 9 accommodated in each of the electrode chambers 4, 5.

[0054] Figs. 2A, 2B and Fig. 3 show additional details of the inner structure of the electrolysis cell 1 according to Fig. 1 in perspective views. The structure of the cell 1 will therefore be explained in the following in more detail with reference to Figs. 1 to 3.

[0055] The cell 1 further comprises a sheet-like separator 10 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 separator 10 is interposed in a joint 11 between the two cell elements 2, 3 and provides a separating wall 12 between the electrode chambers 4, 5. Within the cell 1 a plurality of support members 13 supporting one of the electrodes 8 on the respective back wall 6 is provided. The support members 13 each comprise two support portions 14, 15 standing upright on the back wall 6 and extending in the height direction H of the electrolysis cell 1, and two foot portions 16, 17 attached to the respective support portion 14, 15 in an angled manner for a planar contact with the back wall 6. According to the invention, the support portions 14, 15 of the support members 13 are connected to each other by a body portion 18. Preferably, the body portion 18 is an arched portion as a first spring means. The arched portion 18 is arched outwardly towards the supported electrode 8 and provides a resilient bearing surface 19 for the supported electrode 8. Upon inwards-directed deflections of the arched portion 18 the bearing surface 19 is enlarged.

[0056] In operation, one of the electrodes 8, 9 acts as the anode and the other one as the cathode of the electrolysis. Since different chemical products are obtained at the anode (chlorine, oxygen) and the cathode (hydrogen), the electrode chambers 4, 5 may be designed differently. In particular, the harsher conditions typically prevail within the anode chamber due to the oxidative effect of the chlorine or oxygen produced there in chlor-alkali and alkaline water electrolysis, respectively. The resilient support members according to the invention can generally be used in both, the anode and / or the cathode chamber.

[0057] As can be best seen in Figs. 2A and 2B, the foot portions 16, 17 may be attached to the back wall 6 by a detachable mechanical connection. In particular, the foot portions 16, 17 can be subdivided by indentations 20 into latches 21 (cf. Fig. 3) that are engaged in pockets 22 provided on the back wall 6. The pockets 22 can be provided on the back wall 6 by means of metal strips 23, preferably corrugated metal strips that are intermittently fixed to the back wall 6 by spot welding.

[0058] The structure of the support member 13 is explained in more detail with reference to Fig. 3. The support portions 14, 15 together with the arched portion 18 and the back wall 6 form a hollow channel in the height direction H of the cell for an unobstructed passage of electrolyte and / or gases produced at the supported electrode 8. Along the height direction H the support member 13 may be subdivided into a plurality of individual arches 27, e.g. seven arches 27 as shown in Fig. 3 or 26 thinner arches as shown in Fig. 6. Those individual arches are formed preferably by the indentations 20 being continued into the respective support portion 14, 15 and result in a lateral suspension of the individual latches 21 forming the foot portions of 16, 17 of the individual arches 27. The individual arches 27 may be connected to each other within the region of the support portions 14, 15 by bridges 28, as shown in Fig. 3. Alternatively, the indentations may continue up to the arched portion 18, such that the individual arches J are only connected to each other within the region of the arched portion 18.

[0059] Preferably, the resilient bearing surface 19 comprises openings 24 for passage of gas produced at the supported electrode 8. As depicted in Fig. 3, the openings 24 may be slit-shaped openings that preferably extend in the width direction W of the cell 1. It is preferred to provide a plurality of openings 24 within each individual arch 27.

[0060] The opening ratio of the openings 24 to the complete bearing surface 19 (including the openings 24) may be within the range 0.6 to 0.85. As depicted in Fig. 3, the openings 24 are preferably provided with bent rim portions 25 that face away from the supported electrode 8.

[0061] The support portions 14, 15 may include cutouts 29. The cutouts 29 allow for an improved flow of electrolyte along the width direction W of the cell 1 and reduce the amount of material needed to build the support members 13.

[0062] The support members 13 are preferably made of a metallic material, in particular preferably made of nickel or titanium.

[0063] In Fig. 4A the support member 13 is shown in undeflected, load-free state. The arched portion 18 has an arch height hl and the support portions 14, 15 have a supporting height h2. The arch height 1 may be measured in the undeflected state from the point between the support portions 14, 15 and the arched portion 18 to the uppermost point of the arched portion, along the direction perpendicular to the back wall 6, i.e., along a direction perpendicular to the height direction H the electrolysis cell 1 and to the width direction W of the electrolysis cell 1 (see, Fig. 2A). Likewise, the supporting height h2 may be measured in the undeflected state from the lower end of the support portions 14, 15 to the upper end thereof, along the direction perpendicular to the back wall 6. In the undeflected state, the ratio of the arch height hl and the supporting height h2 is within the range from 1:3 to 1:30, and in particular within the range 1:3 to 1:6. The total height of the support member is denoted h3. In one example, the ratio of the arch height hl and the total height h3, hl:h3, is 1:9. If an electrode is put on the top of the arched portion 18 in the load-free undeflected state, the resilient bearing surface 19 is concentrated to the upmost part of the arch and has a load-free supporting width wl. In Fig. 4B, the support member 13 is shown in a state under load. Upon the load- induced inwards-directed deflection of the arched portion 18, the bearing surface 19 is increased, resulting in an increased supporting width w2 under load. The supporting width w2 under load is preferably at least 50 %, and even more preferred at least 75 % of the total width w3 of the arched portion 18. The supporting width w2 under load may reach up to 100% of the total width w3 of the arched portion 18.

[0064] Figs. 5A to 5E show in a cross-sectional view five variants of the arrangement of several laterally adjacent support members 13 on the back wall 6 of an electrolytic cell according to the invention.

[0065] Fig. 5A shows support members 13 having foot portions 16, 17 that are bent outwards from the bottom of the support portions 14, 15. The foot portions 16, 17 are introduced in pockets 22 formed beneath a metal strip 23 from both sides in a side-by-side arrangement. This arrangement results in a large contact area with the back wall 6, but also leads to a relatively large unsupported gap 30 of the electrode between the arched portions 18 of adjacent support members 13.

[0066] In order to reduce the gap 30, a configuration as shown in in Fig. 5B can be used, in which the foot portions 17, 16 of laterally adjacent support members 13 are arranged on top of each other on the back wall 6. Thus, the width of the stripes 23 and the width of the gap 30 is reduced.

[0067] An alternative configuration is shown in Fig. 5C. If the foot portions 16, 17 are bent to the same side, the gap 30 between the arched portions 18 of adjacent support members 13 can be reduced to the width of one foot portion 16; 17. The foot portions 16; 17 are introduced in the pockets beneath the metal stripes 23 from one side. Either both or only one of the foot portions 16, 17 as shown in Fig. 5C may fixed to the back wall 6.

[0068] Fig. 5D shows a configuration with a minimal gap 30. The foot portions 16, 17 are both bent inwards, such that the support portions 14, 15 of adjacent support members 13 are immediately adjacent to each other. This configuration has a comparatively high assembly effort since twice the number of metal stripes 23 are required.

[0069] Finally, Fig 5E shows a configuration in which the bearing surface 19 extends laterally beyond the support portions 14, 15 to both sides by means of extension portions 26 of the support member 13. Thus, the extension portions 26 are configured to support the electrode in the gap 30 between the adjacent support members 13.

[0070] Figs. 6 and 7 show another embodiment of a support member 13 according to the invention. Rather than being subdivided into a plurality of individual arches, the bearing surface 19 in Fig. 6 is configured as a regular grating. The openings 24 are thus arranged at regular intervals throughout the whole bearing surface 19. This has the positive effect that gas discharge and electrolyte exchange through the bearing surface's 19 openings 24 is homogenized throughout the electrode 8. Further, the surface pressure on the bearing surface 19 is equalized by the regular structure.

[0071] In this embodiment, the opening ratio of the openings 24 to the complete bearing surface 19 may be within the range 0.6 to 0.85, in particular within the range 0.7 to 0.8. This opening ratio also enhances the exchange of electrolyte and gas through the bearing surface 19, while providing still sufficient support for the electrode 8. The embodiment of Figs. 6 and 7 is further characterized by a particularly flat arched portion 18. The ratio of the arch height hl and the supporting height h2 (cf. Fig. 7) is within the range from 1:3 to 1:30, and in particular within the range of 1:10 to 1:20 in an undeflected state of the arched portion 18. It has been found that a rather flat arched portion 18 helps to provide an equalized surface pressure in the width direction W of the support element.

[0072] In all other respects, the description of the embodiment shown in Figs. 1 to 4 also applies to the embodiment shown in Figs. 6 and 7.

[0073] With reference to Figs. 8 to 10, an embodiment of the present invention is described. This embodiment differs from the embodiment shown in Figs. 1 to 7 in that the support member has a second spring means. Therefore, only the details of the support member will be described here, but it should be noted again that the description of the embodiments shown in Figs, 1 to 7 are also applicable to the embodiments shown in Figs. 8 to 10.

[0074] The structure of the support member 13A is explained in detail with reference to Figs. 8A and 8B.

[0075] The support member 13A includes the two support portions 14, 15 standing upright on the back wall 6 and extending in the height direction H of the electrolysis cell 1. The support member 13A also includes the body portion 18 connecting the two support portions 14, 15 in the width direction W. In this preferable example, the body portion 18 is the arched portion, which functions as a fist spring means for providing a resilient force with respect to the supported electrode 8, 9 when deflected by a load applied from said electrode 8, 9. The support member 13A in this embodiment further includes one or more second spring means each having a higher stiffness than that of the arched portion 18. Preferably, the one or more second means has a load limit after which plastic deformation of the second spring means occurs.

[0076] Preferably, the one or more second spring means are configured to be plastically deformed when a load greater than that required to complete the deflection of the arched portion 18 is applied from the supported electrode to the support member as well as the second spring means reached the load limit thereof, especially due to dimensional tolerances of components of the electrolysis cell. The deflection of the first spring shall in any case be accomplished. Loads that are only slightly higher then this value shall not yet create plastic but elastic deflection at the second spring means. When the load is further increased, the second spring deflects plastically in order to limit the effective loads created by unfortunate dimensional tolerances.

[0077] In the depicted example, each of the support portions 14, 15 includes a bent section 32, 33, which is formed by the respective support portion 14, 15 being partially bent in the width direction W. Preferably, these bent sections 32a, 32b are arranged with their inflection points facing each other. This avoids interference with adjacent support members 13A in the width direction W, resulting in a denser arrangements of the support members 13A.

[0078] In order to enable plastic deformation, the material used has to be ductile. In case of thin Nickel sheet metal, soft-annealed material may be used to prevent too high yield strength. Such a softening treatment may be partially performed with respect to the region to become the bent sections 32, 33.

[0079] Preferably, the material, its thickness and / or treatments of the bent section are selected so that the bent section is elastically deformed until the load limit of thereof. The support member 13A including the bent section 32, 33 may be made of Nickel, Titanium or Stainless steel, and most preferably Nickel. The support member 13A including the bent section 32, 33 may have a thickness between 0.1 to 1 mm, more preferably between 0.2 to 0.4 mm.

[0080] As shown in Fig. 8A, each bent section 32, 33 has a U-shape having two opposing walls 32a, 32b; 33a, 33 in a cross-sectional view perpendicular to the height direction H.

[0081] The ratio of the arch height hl and the total height h3 may be within the range from 1:3 to 1:30 in an undeflected state of the arched portion 18, more preferably within the range from 1:15 to 1:25, such as 1: 23.

[0082] Fig. 9 shows schematically in a cross-sectional view of a plurality of support members 13A of Fig. 8A and their arrangement on the back wall of the cell. The support members 13A are detachable with respect to the back wall 6. In an alternative embodiment, no foot portion is provided, and the support members may be fixed to the back wall 6 with fasteners or may be directly welded to the back wall 6.

[0083] The foot portions 16, 17 extends from the one 32b, 33b of the opposing walls in contact with the back wall 6. The foot portions 16, 17 are introduced in pockets 22 formed beneath a metal strip 23 from both sides in a side-by- side arrangement. This arrangement results in a large contact area with the back wall 6, but also leads to a relatively large unsupported gap 30 of the electrode between the arched portions 18 of adjacent support members 13.

[0084] It is also confirmed from this figure that the bent sections 32a, 32b are arranged with their inflection points facing each other, so that interference with adjacent support members 13A in the width direction W is avoided. The distance between the two opposing walls 32a, 32b; 33a, 33b in the direction perpendicular to the back wall 6 may be designed such that the two opposing walls 32a, 32b; 33a, 33b come into contact each other when an excessive load is applied from the electrode to the support member 13A, thereby forming a stopper for preventing a further displacement of the body portion 18 toward the back wall 6.

[0085] With reference to Fig. 10, undeflected state (a) and different deflected states (b)-(d) of the support member 13A along with a corresponding overall resulting force vs. deflection characteristic of the spring components are shown. At the state (a) in this figure, no load is applied to the support member 13A and thus no deflection occurs. At the state (b), as a load is applied, the arched portion 18 as the first spring means is deflected in accordance with its stiffness cl (section 1 of the curve), resulting in a large contact surface area with respect to the supported electrode 8, 9. The deflection of the arched portion 18 ends at block state, i.e., at the end of section 1 of the curve. At the subsequent state (c), the bent sections 32, 33 as the second harder spring means start deflecting in accordance with its stiffness c2, which is higher than the stiffness cl, resulting in an assimilation to target load (section 2 of the curve) even in the block state of the first spring means. When the applied load reaches the load limit of the bent sections 32, 33 at the end of the section 2, the bent sections 32 and 33 enter a plastification state (section 3 of the curve), compensating possible unfortunate tolerance situations. At the final state (d), the opposing walls 32a, 32b; 33a, 33b of the bent sections 32; 33 come into contact with each other to act as a stopper. Yet higher loads may be carried with the highest stiffness c3 (section 4 of the curve) without further deflection of the spring means. This prevents damage or rupture of separator 10 or membrane, due to, e.g., an unfortunate high differential pressure between the anode and cathode chambers 4, 5. In the embodiments of Figs. 8 to 10, the first spring means is configured by the arced portion 18, but the form of the first spring means is not limited thereto. The second spring means is not limited to the U-shaped section. Figs. 11 to 13 show in a cross-sectional view of variants of the first and second spring means.

[0086] In Fig. 11, the first spring means is configured by a wave-shaped body portion 19', which has the lower stiffness cl than that c2 of the second spring means. In undeflected state, the convex part of the wavy body 19' is positioned more distant from the back wall 6 than the upper end of the support portions 14, 15 (i.e., hl>0). The wavy body 19' is elastically deformable by the load from the supported electrode, up to the position where the convex part is at the upper end of the support portion 14, 15 (i.e., hl=0).

[0087] Further, the second spring means provided in each support portion 14, 15 includes a V-shaped bent section 32'; 33', which includes opposing walls 32a', 32b'; 33a', 33b'. Although not shown, the wavy body 19' as the first spring means may be combined with a U-shaped bent section or other second spring members as shown in Figs. 12 and 13.

[0088] When leaving the field of sheet metal to achieve a proper design for the first and second spring means, the use of common spring parts is also possible. Such components could be spiral springs (Fig. 12) or disc springs (Fig. 13). The stiffness cl, c2 of such springs can be modified by the choice of material thickness or overall dimensions (e.g. diameter). These spring kinds all provide a defined blockage state that would allow to limit the deflection. To achieve the ability of plastic deformation such springs would have to be kind of special; usually standard springs are built such, that plastic deformations even in block state are prevented. However, plastic deformation would be possible by choosing different material, for example.

[0089] Reference sign list

[0090] I electrolysis cell 2, 3 cell elements

[0091] 4, 5 electrode chamber

[0092] 6 back wall

[0093] 7 sidewall

[0094] 8, 9 electrodes 10 sheet-like separator

[0095] II joint

[0096] 12 separating wall

[0097] 13, 13A support member

[0098] 14, 15 support portions 16, 17 foot portions

[0099] 18 body portion, arched portion

[0100] 19 resilient bearing surface 19' wavy portion

[0101] 20 indentation

[0102] 21 latch

[0103] 22 pocket 23 metal strip

[0104] 24 opening

[0105] 25 rim portion

[0106] 26 extension portion

[0107] 27 arch 28 bridge

[0108] 29 cutout

[0109] 30 gap

[0110] 32, 33 bent section

[0111] 32a, 32b opposing wall 33a, 33b opposing wall

[0112] 32', 33' bent section

[0113] 32a', 32b' opposing wall 33a', 33b' opposing wall

[0114] H height direction hl arch height, deflectable height of first spring means h2 supporting height h3 total height of support member

[0115] W width direction wl load-free supporting width w2 supporting width under load w3 width of arched portion

Claims

CLAIMS1. Electrolysis cell for chlor-alkali or alkaline water electrolysis comprising: two cell elements (2, 3) each defining an electrode chamber (4, 5) by providing a back wall (6) and sidewalls (7) of the electrode chambers (4, 5); an electrode (8, 9) accommodated in each of the electrode chambers (4, 5); a sheet-like separator (10) extending in a height direction (H) and a width direction (W) of the electrolysis cell (1), the separator (10) being interposed in a joint (11) between the two cell elements (2, 3) and providing a separating wall (12) between the electrode chambers (4, 5); and a plurality of support members (13) supporting at least one (8) of the electrodes (8, 9) on the respective back wall (6), wherein the support members (13) each comprise: two support portions (14, 15) standing upright on the back wall (6) and extending in the height direction (H) of the electrolysis cell (1); a body portion (18) connecting the two support portions (14, 15) in the width direction (W); and one or more first spring means provided in the body portion or the support portions for providing a resilient force with respect to the supported electrode (8, 9) when deflected by a load applied from said electrode (8, 9),characterized in that each support member (13) further comprises one or more second spring means each having a higher stiffness (c2) than that (cl) of the first spring means.

2. Electrolysis cell according to claim 1, wherein the one or more second spring means have a load limit after which plastic deformation of the second spring means occurs, preferably, wherein the one or more second spring means are configured to be plastically deformed when a load greater than that required to complete the deflection of first spring means is applied from the supported electrode to the support member as we as the second spring means reached the load limit thereof, especially due to dimensional tolerances of components of the electrolysis cell.

3. Electrolysis cell according to claim 2, wherein the one or more second spring means are configured to be elastically deformed until the load limit of thereof.

4. Electrolysis cell according to any one of claims 1 to 3, wherein the second spring means is provided in each of the support portions (14, 15).

5. Electrolysis cell according to claim 4, wherein each second spring means includes one or more bent sections (32, 33, 32', 339 formed by the respective support portion being partially bent in the width direction (W).

6. Electrolysis cell according to claim 5, wherein each bent section (32, 33, 32', 339 has a U-shape or V-shape having two opposing walls (32a, 32b, 33a, 33b, 32a', 32b', 33a', 33b7) in a cross-sectional view perpendicular to the height direction (H).

7. Electrolysis cell according to claim 6, wherein the two opposing walls (32a, 32b, 33a, 33b, 32a', 32b', 33a', 33b7) of the U-shaped or V-shaped bent section (32, 33, 32', 339 are configured to come into contact each other when an excessive load is applied from the supported electrode to the support member (13A), thereby forming a stopper for preventing a further displacement of the body portion toward the back wall (6).

8. Electrolysis cell according to any one of claims 1 to 7, wherein each support portion (14, 15) include a foot portion (16, 17), which is connected to the back wall (6), preferably, wherein the foot portions (16, 17) are attached to the back wall (6) by a detachable mechanical connection, preferably, wherein the foot portions (16, 17) are subdivided by indentations(20) into latches (21) that are engaged in pockets (22) provided on the back wall (6), preferably, wherein the pockets (22) are provided on the back wall (6) by means of corrugated metal strips (23) that are intermittently fixed to the back wall (6) by spot welding, preferably, wherein the indentations (20) are continued into the respective support portion (14, 15) for a lateral suspension of the individual latchespreferably, wherein the foot portions (17, 16) of laterally adjacent support members (13) are arranged on top of each other on the back wall (6).

9. Electrolysis cell according to claim 8, wherein the one or more second spring means are provided in the respective support portions, and the foot portions (16, 17) are part of the second spring means.

10. Electrolysis cell according to any one of claims 1 to 9, wherein the body portion is an arched portion (18) functioning as the first spring means, which is arched outwardly towards the supported electrode (8) and providing a resilient bearing surface (19) for the supported electrode (8), wherein the bearing surface (19) is enlarged upon inwards-directed deflections of the arched portion (18).

11. Electrolysis cell according to claim 10, wherein the resilient bearing surface (19) comprises openings (24) for passage of gas produced at the supported electrode (8), preferably, wherein the opening ratio of the openings (24) to the complete bearing surface (19) is within the range 0.6 to 0.85, more preferably within the range 0.7 to 0.8.

12. Electrolysis cell according to claim 10 or 11, wherein the openings (24) are provided with bent rim portions (25) facing away from the supported electrode (8).

13. Electrolysis cell according to any one of the claims 10 to 12, wherein the bearing surface (19) extends laterally beyond the support portions (14,15) at least to one side by means of an extension portion (26) of the support member (13).

14. Electrolysis cell according to any one of the claims 10 to 13, wherein the arched portion (18) has an arch height (hl) and the support portions (14, 15) have a total height (h3), wherein the ratio of the arch height (hl) and the total height (h3) is within the range from 1:3 to 1:30 in an undeflected state of the arched portion (18).

15. Electrolysis cell according to claim 14, wherein the ratio of the arch height (hl) and the total height (h3) is within the range from 1:15 to 1:25 in an undeflected state of the arched portion (18).

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