Method for reactivating an electrolytic cell unit

Abstract

A method for reactivating an electrolytic cell unit (10) is provided. The electrolytic cell unit (10) comprises a rear wall (12), a first electrode element (14) positioned on and facing a first side surface (12A) of the rear wall (12), and one or more existing support elements (16), the one or more existing support elements (16) extending between the rear wall (12) and the first electrode element (14) and supporting the first electrode element (14). The method includes removing a first electrode element (14), removing at least a portion of one or more existing support elements (16), placing one or more new support elements (16', 24, 26) on a first side surface (12A) of the rear wall (12), and welding each new support element (16', 24, 26) to the rear wall (12) from a second side surface (12B) of the rear wall (12) opposite to the first side surface (12A).

Description

Technical Field

[0001] The present invention relates to a method for reactivating or regenerating an existing electrolytic cell unit, the electrolytic cell unit comprising a rear wall, a first electrode element disposed on a first side of the rear wall and facing the first side, and one or more existing support elements, the one or more existing support elements extending between the rear wall and the first electrode element and supporting the first electrode element.

Background Art

[0002] The present invention relates in particular to an electrolytic cell unit for hydrochloric acid electrolysis having an oxygen depolarized cathode (ODC). However, depending on the materials used for internal components such as electrode support elements, the internal components are subject to some corrosion, particularly on the anode side, due to contact with acids and chlorine. To reactivate an electrolytic cell after a certain period of operation, it may be economical to significantly reuse existing electrolytic cell components, since most of the components are made of expensive materials such as titanium alloys stabilized with costly palladium. Therefore, it is desirable to replace only limited components such as existing electrode support elements.

[0003] The replacement of existing electrode support elements may also be desirable to change the flow of the medium, adjust the electrode level, and / or replace corroded elements.

[0004] Additionally or alternatively, further economic benefits are expected when a so-called "zero-gap" configuration is retrofitted using an existing finite-gap or non-zero-gap type electrolytic cell. In a "zero-gap" configuration, the anode electrode element and the cathode electrode element need to be in direct contact with a separator such as a membrane. Such a configuration may also be used for chlor-alkali electrolysis.

[0005] From International Publication No. 03 / 014419, an electrolytic cell for the electrochemical production of chlorine is known in which an anode, a cation exchange membrane, a gas diffusion electrode, and a current collector are elastically held together so as to have no gaps between the individual components. Elastic aggregation is achieved by elastically fixing the current collector to the cathode frame or by elastically fixing the anode to the anode frame. This is achieved by using a retaining element configured as a spring element, for example, extending between the rear wall and the current collector in the cathode chamber. A helical spring is used, fastened at one end to the rear wall via a Z-shaped member and at the other end applying pressure to the current collector in their axial direction. These helical springs extend axially in the lateral direction of the electrolytic cell, i.e., perpendicular to the plane of the electrodes.

[0006] U.S. Patent Application Publication No. 2009 / 0050472 describes an electrolytic cell having an anode chamber and a cathode chamber separated from each other by an ion exchange membrane, the electrolytic cell further comprising a gas diffusion electrode. The arrangement of the individual structural elements within the electrolytic cell is such that the anode is followed by the ion exchange membrane, then a percolator, then a cathode, an elastic current collector, and a cathode back wall. The electrolytic cell is a chlor-alkali cell having an oxygen depolarizing cathode. The elastic current collector used here consists of a type of nickel mattress. Alternatively, it is possible to use a current collector that presses the cathode or anode and presses them against the ion exchange membrane, using a comb-shaped arrangement of elastic spring tags or a protruding spring plate fixed to one side.

[0007] These cells for hydrochloric acid electrolysis are very expensive.

[0008] In either case, replacing the electrode support element requires removing the old support element and welding the new support element to the back wall. However, the weld area where the old weld line is present may be susceptible to surface corrosion, at least. Such weld areas may contain residues that hinder high-quality welding of the new support element. Furthermore, the anode chamber is in a harsh acidic environment, and the pressure in the anode chamber is higher than that in the cathode chamber, resulting in a greater risk of corrosion.

[0009] The object of the present invention is to provide a method for reactivating an electrolytic cell unit that has a lower risk of corrosion and enables high-quality welding between a new support element and the existing back wall. [Prior art documents] [Patent Documents]

[0010] [Patent Document 1] International Publication No. 03 / 014419 [Patent Document 2] U.S. Patent Application Publication No. 2009 / 0050472 [Overview of the Initiative]

[0011] This objective is achieved by the method described in independent claim 1. The dependent claims provide advantageous embodiments.

[0012] Specifically, this objective is solved by a method for reactivating an electrolytic cell unit, the electrolytic cell unit comprising a rear wall, a first electrode element positioned on and facing a first side surface of the rear wall, and one or more existing support elements, the one or more existing support elements extending between the rear wall and the first electrode element and supporting the first electrode element. The method includes removing the first electrode element, removing at least a portion of one or more existing support elements, placing one or more new support elements on the first side surface of the rear wall, and welding each new support element to the rear wall from a second side surface of the rear wall opposite to the first side surface of the rear wall.

[0013] Since the new support element is welded from the second side of the rear wall, the new weld can be performed while avoiding the old weld line on the first side of the rear wall, enabling a high-quality weld between the new support element and the existing rear wall. Furthermore, there are no or very few weld lines on the first side of the rear wall that could be prone to corrosion. This is particularly advantageous when the first side is the anode side, which is in a harsh acidic environment.

[0014] Advantageously, the electrolytic cell unit is positioned on a second side of the rear wall and further comprises a second electrode element facing the second side, the method further includes removing the second electrode element before welding each new support element to the rear wall. This facilitates access from the second side of the rear wall for welding.

[0015] One or more existing support elements may be fixed to the rear wall via welded joints. In this case, advantageously, removing at least a portion of one or more existing support elements includes removing one or more existing support elements while leaving the old welded joints on the rear wall. This allows the existing weld lines of the existing support elements to remain unchanged. Thus, the reactivation of the electrolytic cell unit can be simplified. Furthermore, damage to the rear wall, such as perforation, which may occur when the old support elements are completely removed can be avoided.

[0016] Advantageously, placing one or more new support elements on the first side surface of the rear wall involves bringing one or more new support elements into contact with the rear wall between adjacent old welds. This makes it possible to place the new support elements while avoiding interference between new and old welds. For this purpose, it is even more advantageous that welding each new support element to the rear wall involves welding at a position where one or more new support elements are in contact with the rear wall between adjacent old welds.

[0017] In one example, the new support element may have the same shape and material as the existing support element. This is advantageous when replacing a corroded element with a new one to reactivate the electrolytic cell unit.

[0018] In another example, the new support element may have a different height from the existing support element to adjust the level of the first electrode element. This is advantageous for corrosion replacement and / or electrode level adjustment (i.e., adjustment of the distance between the back wall and the first electrode element).

[0019] In yet another example, the new support element may be a resilient support element to achieve a zero-gap configuration. This is advantageous for retrofitting a finite-gap or non-zero-gap electrolytic cell unit to a zero-gap electrolytic cell unit, and is significantly less expensive than constructing a zero-gap electrolytic cell unit from scratch. Advantageously, the resilient support element comprises one or more ring portions.

[0020] It is preferable that the removal of at least a portion of one or more existing support elements be carried out by cutting or machining. Machining or machine cutting is more economical and less prone to failure than manual cutting. Machining or machine cutting can be performed using a milling machine while the electrolytic cell unit is held in the machine bed. More preferably, machining or machine cutting can be performed using a side milling cutter.

[0021] Boldly, the method further includes welding each new support element to the rear wall, and then installing the new first electrode element in place of the existing first electrode element. With the new first electrode element having a new coating of catalyst material, improved cell performance can be expected. Similarly, it is more advantageous to install a new second electrode element having a new coating of catalyst material in place of the existing second electrode element.

[0022] Advantageously, the method further includes welding a new first electrode element to the new support element, which enables a good electrical and mechanical connection.

[0023] Advantageously, the electrolytic cell unit is a bipolar electrolytic cell unit in which the anode chamber and the cathode chamber are partitioned by a rear wall, and welding each new support element to the rear wall includes welding each support element to the rear wall from the cathode side.

[0024] Advantageously, welding each new support element to the rear wall is performed by keyhole welding. Keyhole welding is a welding technique in which a concentrated heat source partially or completely penetrates the workpiece (i.e., the rear wall in the present invention) to form a hole (keyhole) at the leading edge of the weld pool (ISO / TR 25901, 2.1.8.3). This makes it possible to prevent the weld line from appearing at all or hardly appearing on the first side of the rear wall. Such keyhole welding can be achieved by laser welding. Laser welding is accurate and efficient.

[0025] The present invention will be better understood with the aid of the description of the embodiments given as examples illustrated by the figures.

Brief Description of the Drawings

[0026] [Figure 1A] It is a cross-sectional view of an existing electrolytic cell unit as a starting point in a method for reactivating or generating an electrolytic cell unit according to the present invention. [Figure 1B] It is a view showing the removal of the electrode element of the existing electrolytic cell unit of FIG. 1A. [Figure 1C] It is a view showing the removal of the internal support element. [Figure 1D] It is a view showing the installation of a new support element on the rear wall of an existing electrolytic cell for upgrading to a zero-gap type electrolytic cell unit. [Figure 1E] It is a view showing the installation of a new electrode element. [Figure 2]This figure shows another method for reactivating or regenerating an existing electrolytic cell unit according to the present invention. [Figure 3] This figure shows another method for reactivating or regenerating an existing electrolytic cell unit according to the present invention. [Modes for carrying out the invention]

[0027] One exemplary electrolytic cell to which the method of the present invention can be applied is a bipolar electrolytic cell, such as an ion-exchange membrane process electrolytic cell, in which multiple bipolar electrolytic cell units are arranged in series, i.e., stacked back-to-back, using an ion-exchange membrane or diaphragm as a separator interposed between adjacent cell units. By utilizing filter press technology, adjacent cell units can be joined such that there is substantially no gap between the electrode elements on both sides of the separator. However, the electrolytic cell may also be a unipolar electrolytic cell, in which each cell unit has either a cathode or anode electrode element on its side.

[0028] The electrolytic cell unit can be used in chlor-alkali electrolysis. In another example, the electrolytic cell unit can be used in alkaline water electrolysis (AWE). More generally, the electrolytic cell unit may be applicable to any electrolytic process that uses a first electrode element, a second electrode element, and a separator interposed between the first and second electrode elements.

[0029] Referring to Figure 1, an existing bipolar electrolytic cell unit 10 is shown, starting from a finite-gap or non-gap electrolytic cell unit. The existing bipolar electrolytic cell unit 10 is shown upgraded to a zero-gap electrolytic cell unit by the method according to the present invention. The electrolytic cell unit 10 comprises a rear wall 12, a first electrode element 14 positioned on and facing a first side surface 12A of the rear wall 12, and one or more existing support elements 16, the one or more existing support elements 16 extending between the rear wall 12 and the first electrode element 14 and supporting the first electrode element 14. The first electrode element 14 may be in the form of a current distributor mesh or includes a current distributor mesh. Examples of the first electrode element 14 include woven mesh, weave mesh, perforated metal, lattice, expanded metal, foamed metal, etc. More preferably, the electrode element is made of a lattice or expanded metal. The first electrode element 14 may also have a highly reactive catalyst layer on the surface of its substrate. The material of the substrate is not limited and may be steel, stainless steel, nickel, or a nickel-based alloy.

[0030] In this example, the rear wall 12 physically separates the anode chamber and the cathode chamber of the bipolar electrolytic cell unit. The anode chamber may be defined by a first side surface 12A of the rear wall 12 and a separator, and the cathode camber may be defined by a second side surface 12B of the rear wall 12 and another separator. The rear wall 12 is held within the frame 18 of the electrolytic cell unit 10.

[0031] One or more existing support elements 16 may have any shape as long as it is capable of supporting the first electrode element 14 against the rear wall 12. In Figure 1A, the support element 16 is corrugated. Specifically, the support element 16 comprises a plurality of bases 16a welded to the first side surface 12A of the rear wall 12, legs 16b extending from the bases 16a toward the first electrode element 14, and an upper part 16c attached to the first electrode element 14, straddling adjacent legs 16b.

[0032] On the second side surface 12B of the rear wall 12, opposite to the first side surface 12A, the second electrode element 20 is positioned on the second side surface 12B of the rear wall 12 and faces the second side surface 12B. The above description relating to the first electrode element 14 can also be applied to the second electrode element 20. Multiple ribs or Z-shaped members 22 can be positioned between the second side surface 12B of the rear wall 12 and the second electrode element 20 to support the second electrode element 20 relative to the rear wall 12. The ribs or Z-shaped members 22 may be spaced apart from each other in the horizontal direction of the electrolytic unit (left-right direction in Figure 1A).

[0033] Starting with the existing electrolytic cell unit 10 shown in Figure 1A, the existing electrolytic cell unit 10 can be reactivated or regenerated according to the following procedure, and preferably can be upgraded as shown: Removing the first electrode element 14 (Figure 1B), Removing at least a portion of one or more existing support elements 16 (Figure 1C), Placing one or more new support elements 24 on the first side surface 12A of the rear wall 12 (Figure 1D), and Each new support element 24 is welded to the rear wall 12 from the second side 12B of the rear wall 12, opposite to the first side 12A of the rear wall 12 (Figure 1E).

[0034] More specifically, in the first step shown in Figure 1B, the method according to the present invention includes removing the first electrode element 14. If the existing first electrode element 14 is welded to the existing support element 16, this step includes cutting the welded area. Alternatively, if the existing first electrode element 14 is fixed to the existing support element by fasteners or clips, this step includes removing the fasteners or clips.

[0035] Advantageously, the method also includes removing the second electrode element 20. In Figure 1B, the second electrode element 20 is also removed to provide easy access to the second side surface 12B of the rear wall 12 for welding.

[0036] In the next step shown in Figure 1C, the method involves removing at least a portion of one or more existing support elements 16 on one side (e.g., the anode side) of the electrolytic cell unit 10. In Figure 1C, the existing support elements 16 are removed while the welded portion (e.g., base 16a) remains on the rear wall 12. This can be done by cutting or machining the existing support elements 16 from its upper surface near the rear wall 12 so that only the base 16a of the existing support element remains welded to the rear wall 12. In this way, the existing weld lines of the previous profile remain unchanged. Subsequent welding of the new support elements 24, which will be described later, can be performed on the rear wall 12 in good shape without much laborious prior processing (e.g., grinding). Machining or cutting can be performed using a milling machine while the electrolytic cell unit 10 is held on the machine bed. More preferably, machining or cutting can be performed using a side milling cutter. However, manual cutting may also be applicable.

[0037] The ribs or Z-shaped members 22 on the other side (for example, the cathode side) may remain connected to the rear wall 12.

[0038] In the next step shown in Figure 1D, one or more new support elements 24 are placed on one side (e.g., the anode side) of the rear wall 12 from which the existing support elements 16 have been at least partially removed. Advantageously, the new support elements 24 are resilient support elements for achieving a zero-gap configuration. The resilient support elements 24 may comprise one or more rings or tubular portions 24a whose axes are oriented in the height or longitudinal direction of the electrolytic cell unit 10. One or more rings or tubular portions 24a may be oriented in another direction, such as the horizontal direction of the electrolytic cell unit 10. Rings or tubular portions 24a adjacent to each other in the height direction of the electrolytic cell unit 10 may be connected to each other via a base strip. Because one or more rings or tubular portions 24a are resilient, the fist electrode elements 14 are pressed toward the separator (e.g., a membrane) of the electrolytic cell, retrofitting an existing finite-gap or non-zero-gap electrolytic cell unit to a zero-gap electrolytic cell unit. However, other elastic support elements, such as coil springs or leaf springs, may also be applicable to the same purpose. Therefore, existing electrolytic cell units can be upgraded to zero-gap type electrolytic cell units at a lower cost.

[0039] Advantageously, the new support element 24 rests between adjacent welded portions 16a remaining on the first side surface 12A (e.g., the anode side) of the rear wall 12. In the example of Figure 1D, the ring or tubular portion 24a and the welded portion 16a are arranged alternately with respect to each other in the horizontal direction of the electrolytic cell unit 10.

[0040] After the new support elements 24 are placed, they are welded from the second side 12B (e.g., the cathode side) of the rear wall 12 to the first side 12A of the rear wall 12 (see arrow A in Figure 1A). As mentioned above, if the new support elements 24 are placed in a location where no previous welded portion 16a exists, pretreatment (e.g., grinding) is generally not required. In Figure 1D, welding is performed at the location where the new support elements 24 contact the rear wall 12. Advantageously, the welding is performed by keyhole welding. Keyhole welding is a welding technique in which a concentrated heat source partially or completely penetrates the workpiece (i.e., the rear wall 12 in this invention) and forms a hole (keyhole) at the leading edge of the weld pool. This makes it possible to have no or very visible weld line on the first side 12A of the rear wall 12. Such keyhole welding can be achieved by laser welding. Laser welding is precise and efficient.

[0041] In the next step, as shown in Figure 1E, a first new electrode element 14' is installed in place of the old electrode element 14, as removed in Figure 1B. In this example, a second new electrode element 20' is also installed in place of the old electrode element 20, as removed in Figure 1B. Of course, if conditions permit, the removed first and / or second electrode elements 14, 20 may be reused. In addition, the new first electrode element 14' may be welded to the new support element 24. This can be done by laser welding. Thus, the ring-shaped elastic support element 24a is joined to the reused cell components (i.e., the back wall) as well as the new electrode element 14', enabling good electrical and mechanical connections.

[0042] Referring to Figure 2, another method for revitalizing or regenerating an existing electrolytic cell unit 10 according to the present invention is shown. Steps similar to those shown in Figure 1D are shown. This embodiment differs from the embodiments in Figures 1A to 1E only in that an existing support element 16 is replaced with a new support element 16' which is of the same shape and material as the existing support element 16. Thus, the new support element 16' includes a base 16a', a leg 16b', and an upper part 16c'. The base 16a' of the new support element 16' is preferably positioned between adjacent old bases 16a so as to avoid the old base 16a. The new base 16a is preferably welded from a second side of the rear wall to a first side 12A of the rear wall 12 by keyhole welding. Other features described in relation to Figures 1A to 1E can also be applied to the embodiment in Figure 2. This embodiment is advantageous for replacing a corroded or damaged support element with a new support element at a lower cost.

[0043] Referring to Figure 3, another method for revitalizing or regenerating an existing electrolytic cell unit 10 according to the present invention is shown. This embodiment differs from the embodiment in Figure 1 only in that the existing support element 16 is replaced with a new support element 26 having a different height (i.e., a length measured along the direction perpendicular to the rear wall 12) than the height of the existing support element 16. The new support element 26 may have a Z-shape. Each new support element 26 may be positioned between the old welded portions 16a. Each new support element 26 is then welded from the second side 12B of the rear wall 12 to the first side 12A of the rear wall 12, preferably by keyhole welding. Other features described in relation to Figures 1A to 1E can also be applied to the embodiment in Figure 3. This embodiment is advantageous not only for leveling the first electrode element 14 but also for corrosion replacement. [Explanation of Symbols]

[0044] 10 Electrolytic Cell Units 12 Back wall 12A First side of the rear wall (e.g., anode side) 12B Second side of the rear wall (e.g., cathode side) 14 Existing first electrode element 14' New first electrode element 16 Existing support elements 16' New support elements 18 frames 20 Existing second electrode element 20' New second electrode element 22 Z-shaped material 24 Elastic support elements 24a Ring portion 26 New Supporting Elements

Claims

1. A method for reactivating an electrolytic cell unit (10), wherein the electrolytic cell unit (10) comprises a rear wall (12), a first electrode element (14) positioned on and facing a first side surface (12A) of the rear wall (12), and one or more existing support elements (16), the one or more existing support elements (16) extending between the rear wall (12) and the first electrode element (14) and supporting the first electrode element (14), and the method is as follows: Removing the first electrode element (14), Removing at least a portion of one or more existing support elements (16), Placing one or more new support elements (16', 24, 26) on the first side surface (12A) of the rear wall (12), Each new support element (16', 24, 26) is welded to the rear wall (12) from the second side (12B) of the rear wall (12) opposite to the first side (12A) of the rear wall (12). Methods that include...

2. The electrolytic cell unit (10) is positioned on the second side surface (12B) of the rear wall (12) and further comprises a second electrode element (20) facing the second side surface (12B), and the method is as follows: Remove the second electrode element (20) before welding each new support element (16', 24, 26) to the rear wall (12). The method according to claim 1, further comprising:

3. The one or more existing support elements (16) are fixed to the rear wall (12) via a welded portion. Removing at least a portion of one or more existing support elements (16) includes removing one or more existing support elements (16) while leaving the welded portion on the rear wall (12), The method according to claim 1 or 2.

4. The method according to claim 3, wherein placing the one or more new support elements (16', 24, 26) on the first side surface (12A) of the rear wall (12) includes bringing the one or more new support elements (16', 24, 26) into contact with the rear wall (12) between the adjacent welded portions.

5. The method according to claim 4, wherein welding each new support element (16', 24, 26) to the rear wall (12) includes welding one or more new support elements (16', 24, 26) at a position where they contact the rear wall (12) between adjacent welded portions.

6. The method according to any one of claims 1 to 5, wherein the new support element (16') has the same shape and material as the existing support element (16).

7. The method according to any one of claims 1 to 5, wherein the new support element (24) has a different height from the existing support element (16) for leveling the first electrode element.

8. The method according to any one of claims 1 to 5, wherein the new support element (24) is an elastic support element for achieving a zero-gap configuration.

9. The method according to claim 8, wherein the elastic support element (24) comprises one or more ring portions (24a).

10. The method according to any one of claims 1 to 9, wherein the removal of at least a portion of the one or more existing support elements (16) is performed by cutting or machining.

11. The method according to any one of claims 1 to 10, further comprising welding each new support element (16', 24, 26) to the rear wall (12), and then installing a new first electrode element (14') in place of the first electrode element (14).

12. The method according to claim 11, further comprising welding the new first electrode element (14') to the new support elements (16', 24, 26).

13. The method according to any one of claims 1 to 12, wherein the electrolytic cell unit (10) is a bipolar electrolytic cell unit (10) in which an anode chamber and a cathode chamber are separated by the rear wall (12), and welding each new support element (16', 24, 26) to the rear wall (12) includes welding each support element (16', 24, 26) to the rear wall (12) from the cathode side.

14. The method according to any one of claims 1 to 13, wherein the welding of each new support element (16', 24, 26) to the rear wall (12) is carried out by keyhole welding.

15. The method according to any one of claims 1 to 14, wherein welding each new support element (16', 24, 26) to the rear wall (12) is performed by laser welding.

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