WO2024235704A1

WO2024235704A1 - Method for reactivating an electrolysis cell unit

Info

Publication number: WO2024235704A1
Application number: PCT/EP2024/062430
Authority: WO
Inventors: Sebastian Austenfeld
Original assignee: ThyssenKrupp Nucera AG and Co KGaA
Current assignee: ThyssenKrupp Nucera AG and Co KGaA
Priority date: 2023-05-15
Filing date: 2024-05-06
Publication date: 2024-11-21
Anticipated expiration: 2025-11-15
Also published as: EP4464821A1

Abstract

A method for reactivating an electrolysis cell unit (10) is provided. The electrolysis cell unit (10) comprises a back wall (12), a first electrode element (14) arranged over a first side (12A) of the back wall (12) facing said first side (12A), and one or more existing support elements (16), wherein the one or more existing support elements (16) extend between the back wall (12) and the first electrode element (14) to support said first electrode element (14). The method comprises: removing the first electrode element (14); removing at least part of the one or more existing support elements (16); placing one or more new support elements (16', 24, 26) on the first side (12A) of the back wall (12); and welding each new support element (16', 24, 26) to the back wall (12) from a second side (12B) of the back wall (12) opposite to the first side (12A) of the back wall (12).

Description

thyssenkrupp nucera AG & Co. KGaA

METHOD FOR REACTIVATING AN ELECTROLYSIS CELL UNIT

Description

Field of Invention

The present invention relates to a method for reactivating or regenerating an existing electrolysis cell unit, the electrolysis cell unit comprising a back wall, a first electrode element arranged over a first side of the back wall facing said first side, and one or more existing support elements, wherein the one or more existing support elements extend between the back wall and the first electrode element to support said first electrode element.

Description of Related art

The present invention relates in particular to electrolysis cell units for hydrochloric acid electrolysis with an oxygen-depolarized cathode (ODC). Depending on the material used for internal components such as electrode support elements, however, they are to some extent attacked by corrosion, especially at anode side due to acid and chlorine contact. In order to reactivate the electrolysis cells after certain period of operation, it can be economic to reuse the existing electrolysis cell components to a large extent, because major portions of the components are made of expensive material such as Titanium alloy, stabilized with costly Palladium. Replacement of only limited components such as existing electrode support elements is thus desired.

Replacement of the existing electrode support elements may also be desirous in order to modify media flow, adjust electrode level and/or replace corroded elements. Additionally or alternatively, further economic benefits are expected if a so-called "zero gap" configuration is retrofittingly applied using existing finite gap or nonzero gap type electrolysis cells. In the "zero-gap" configuration, the anode electrode element and the cathode electrode element should be in direct contact with a separator such as a membrane or the like. Such a configuration may be used in chlor-alkali electrolysis.

From WO 03/014419 A2 there is known an electrolysis cell for the electrochemical production of chlorine, in which an anode, a cation-exchange membrane, a gas diffusion electrode and a current collector are elastically held together so that there are no gaps between the individual components. The elastic cohesion is achieved by the current collector being elastically fixed to the cathode frame or the anode being elastically fixed to the anode frame. Holding elements are thereby used which are configured as spring elements and extend, for example, in the cathode chamber between a back wall and the current collector. Helical springs are used, which on the one hand are fastened at one end via Z-profiles to the back wall and on the other hand at their other end exert a pressing force on the current collector in their axial direction. These helical springs extend with their axial direction in the transverse direction of the electrolysis cell, that is to say perpendicular to the plane of the electrodes.

In US 2009/0050472 Al there is described an electrolysis cell having an anode chamber and a cathode chamber which are separated from one another by an ion-exchange membrane, wherein the electrolysis cell further comprises a gas diffusion electrode. The arrangement of the individual structural elements in the electrolysis cell is such that the anode is followed by the ion-exchange membrane, then a percolator, then the cathode, an elastic current collector and the cathode back wall. The electrolysis cell is a chlor-alkali cell with an oxygen-depolarized cathode. The elastic current collector used here consists of a type of mattress of nickel. Alternatively, it is possible to use a current collector with elastic spring tags in a comb-like arrangement or with projecting spring plates fixed on one side, which push against the cathode or against the anode and press them against the ion-exchange membrane.

These cells for electrolysis of hydrochloric acid are quite expensive. In any cases, for replacement of the electrode support elements, new support elements need to be welded to the back wall after removing the old electrode support elements. However, welded areas where old welding lines exist may be prone to at least surface corrosion. Such welded areas might contain residuals that prevent high quality welding for the new support elements. Furthermore, the anode chamber is in harsh acidic environment resulting in more corrosion risk, as the pressure of anode chamber is higher than that of cathode chamber.

The purpose of the present invention is to provide a method for reactivating an electrolysis cell unit which allows high quality welding between new support elements and the existing back wall with lower risk of corrosion.

Brief Summary of the Invention

This purpose is achieved by a method according to independent claim 1. Dependent claims give advantageous embodiments.

Specifically, the aim is solved by a method for reactivating an electrolysis cell unit, the electrolysis cell unit comprising a back wall, a first electrode element arranged over a first side of the back wall facing said first side, and one or more existing support elements, wherein the one or more existing support elements extend between the back wall and the first electrode element to support said first electrode element. The method comprises: removing the first electrode element; removing at least part of the one or more existing support elements; placing one or more new support elements on the first side of the back wall; and welding each new support element to the back wall from a second side of the back wall opposite to the first side of the back wall.

Since the new support element is welded from the second side of the back wall, the new welding can be performed avoiding the old welding lines on the first side of the back wall, allowing high quality welding between the new support elements and the existing back wall. Further, no or only little welding lines, which might be prone to corrosion, appears on the first side of the back wall. This is particularly advantageous if the first side is an anode side which is harsh acidic environment.

Advantageously, the electrolysis cell unit further comprises a second electrode element arranged over the second side of the back wall facing said second side, the method further comprising removing the second electrode element before welding each new support element to the back wall. This facilitates access from the second side of the back wall for welding.

The one or more existing support elements may be fixed to the back wall via welded portions. In this case, it is advantageously that the removing at least part of the one or more existing support elements includes removing the one or more existing support elements whilst leaving the old welded portions on the back wall. This allows that the existing welding lines of the existing support element remain unchanged. The reactivation of the electrolysis cell unit can thus be simplified. Further, damages in the back wall such as perforation, which might occur when completely removing the old support elements, can be avoided.

Advantageously, the placing the one or more new support elements on the first side of the back wall includes bringing the one or more new support element into contact with the back wall between the adjacent old welded portions. This allows the new support elements to be placed whilst avoiding interference between new and old welding lines. To this end, it is further advantageous that the welding each new support element to the back wall includes welding at locations where the one or more new support elements contact the back wall between the adjacent old welded portions.

In one example, the new support element may be the same in shape and material as the existing support element. This is advantageous when replacing corroded elements with new elements to reactivate the electrolysis cell unit.

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

In yet another example, the new support element may be a resilient support element for achieving a zero-gap configuration. This is advantageous for retrofitting a finite-gap or non-zero gap electrolysis cell unit into a zero-gap type electrolysis cell unit, with significant lower costs than constructing a zero-gap type electrolysis cell unit from scratch. Advantageously, the resilient support element comprises one or more ring portions.

It is preferable that the removing at least part of the one or more existing support elements is done by cutting or machining. Machining or machined cutting is more economical and less prone to failure than manual cutting. Machining or machined cutting may be performed using milling machine whilst retaining the electrolysis cell unit to a machine bed. More preferably, machining or machined cutting may be performed using a side milling cutter.

Adventurously, the method further comprises installing a new first electrode element in place of the existing first electrode element, after welding each new support element to the back wall. Improved cell performance may be expected with the new first electrode element, which is equipped with a fresh coating of catalyst material. Likewise, it is more advantageous that a new second electrode element with a fresh coating of catalyst material is installed in place of the existing second electrode element.

Advantageously, the method further comprises welding the new first electrode element to the new support element. This allows good electrical and mechanical connection.

Advantageously, the electrolysis cell unit is a bipolar electrolysis cell unit in which an anode chamber and a cathode chamber are partitioned by the back wall, wherein the welding each new support element to the back wall includes welding each support element to the back wall from the cathode side.

Advantageously, the welding each new support element to the back wall is performed by keyhole welding. The keyhole welding is a welding technique in which a concentrated heat source penetrates partially or completely through a workpiece (i.e., the back wall in the present invention), forming a hole (keyhole) at the leading edge of the weld pool (ISO/TR 25901, 2.1.8.3). This allows that no or less welding lines appear on the first side of the back wall. Such a keyhole welding may be achieved by laser welding. The laser welding is precise and efficient.

Brief Description of Drawings This invention will be better understood with the aid of the description of embodiments given by way of example illustrated by the figures, in which:

Fig. 1A shows a section through an existing electrolysis cell unit as a starting point in a method for reactivating or generating the electrolysis cell unit according to the present invention;

Fig. IB shows a removal of electrode elements of the existing electrolysis cell unit of Fig. 1A;

Fig. 1C shows a removal of internal support elements;

Fig, ID shows an installation of new support elements onto the back wall of the existing electrolysis cell to upgrade to a zero-gap type electrolysis cell unit;

Fig. IE shows an installation of new electrode elements;

Fig. 2 shows another method for reactivating or regenerating an existing electrolysis cell unit according to the present invention; and

Fig. 3 shows another method for reactivating or regenerating an existing electrolysis cell unit according to the present invention.

One exemplary electrolyzer in which the inventive method may be applied is a bipolar electrolyzer, such as ion-exchange membrane process electrolyzer, in which a plurality of bipolar electrolysis cell units are arranged in series, i.e., stacked back to back, with an ion exchange membrane or diaphragm as a separator being interposed between the adjacent cell units. The filter press technology may be utilized to join the adjacent cell units so that there is substantially no gap between electrode elements on both sides of the separator. However, the electrolyzer may be a monopolar electrolyzer in which each cell unit has either a cathode or anode electrode element on the side.

The electrolysis cell units may be used for Chlor-Alkali electrolysis. In another example, the electrolysis cell units may be used for alkaline water electrolysis (AWE). More generally, the electrolysis cell units may be applicable to any electrolysis process using a first electrode element, a second electrode element, and a separator interposed between the first and second electrode elements.

With reference to Fig. 1, an existing bipolar electrolysis cell unit 10, which is finite gap or non-gap type electrolysis cell unit as a starting point, is shown. The existing bipolar electrolysis cell unit 10 is upgraded to a zero-gap type electrolysis cell unit by a method according to the present invention is shown. The electrolysis cell unit 10 comprises a back wall 12, a first electrode element 14 arranged over a first side 12A of the back wall 12 facing said first side 12A, and one or more existing support elements 16, wherein the one or more existing support elements 16 extend between the back wall 12 and the first electrode element 14 to support said first electrode element 14. The first electrode element 14 may be in the form of, or includes, a current distributor mesh. Examples of the first electrode element 14 include woven mesh, weave mesh, perforated metal, grid element, expanded metal, metal foam, or the like. More preferably, the electrode element is made of grid element or expanded metal. The first electrode element 14 may also have a catalyst layer with high reaction activity on the surface of its base material. The material of the base material is not restricted, but may be steel, stainless steel, nickel or nickel-based alloys.

The back wall 12 in this example physically partitions an anode chamber and a cathode chamber of the bipolar electrolysis cell unit. The anode chamber may be defined by the first side 12A of the back wall 12 and a separator, and the cathode camber may be defined by the second side 12B of the back wall 12 and another separator. The back wall 12 is retained within a frame 18 of the electrolysis cell unit 10.

The one or more existing support elements 16 may have any shape as long as they can support the first electrode element 14 against the back wall 12. In Fig. 1A, the support element 16 is corrugated, specifically, the support element 16 comprises a plurality of bases 16a welded to the first side 12A of the back wall 12, legs 16b extending from the base 16a toward the first electrode element 14, and a top 16c spanning between the adjacent legs 16b and attached to the first electrode element 14. On a second side 12B of the back wall 12 opposite to the first side 12A, a second electrode element 20 is arranged over the second side 12B of the back wall 12 facing said second side 12B. The above description regarding the first electrode element 14 may equally apply to the second electrode element 20. A plurality of ribs or Z-profiles 22 may be arranged between the second side 12B of the back wall 12 and the second electrode element 20 to support the second electrode element 20 against the back wall 12. The ribs or Z-profiles 22 may be spaced apart from each other in the horizontal direction of the electrolysis unit (left and right direction in Fig. 1A).

From the existing electrolysis cell unit 10 of Fig. 1A as a starting point, the existing electrolysis cell unit 10 can be reactivated or regenerated, preferably upgraded as illustrated, according to the following procedures: removing the first electrode element 14 (Fig. IB); removing at least part of the one or more existing support elements 16 (Fig. 1C); placing one or more new support elements 24 on the first side 12A of the back wall 12 (Fig. ID); and welding each new support element 24 to the back wall 12 from the second side 12B of the back wall 12 opposite to the first side 12A of the back wall 12 (Fig. IE).

More specifically, in the first step as shown in Fig. IB, the method according to the present invention includes removing the first electrode element 14. In case where the existing first electrode element 14 is welded to the existing support element 16, this step includes cutting the welded areas. Alternatively, in case where the existing first electrode element 14 is secured to the existing support element with fixtures or fasteners, this step includes removing the fixtures or fasteners.

Advantageously, the method also includes removing the second electrode element 20. In Fig. IB, the second electrode element 20 is also removed for easy access to the second side 12B of the back wall 12 for welding. In the next step as shown in Fig. 1C, the method includes removing at least part of the one or more existing support elements 16 on one side of the electrolysis cell unit 10 (e.g., anode side). In Fig. lC, the existing support element 16 is removed whilst the welded portions (e.g., the bases 16a) remains on the back wall 12. This can be done by cutting or machining the existing support element 16 from its top side close to the back wall 12 so that only the bases 16a of the existing support element are left and remained welded to the back wall 12. In this way, the existing welding lines of the former profiles remain unchanged. A subsequent welding of new support elements 24, which will be described later, may be done on the back wall 12 in good shape, without prior treatment (e.g., grinding) which is subject to much effort. Machining or machined cutting may be performed using milling machine whilst the electrolysis cell unit 10 is retained on a machine bed. More preferably, machining or machined cutting may be performed using a side milling cutter. However, manual cutting may also be applicable.

The ribs or Z-profiles 22 on the other side (e.g., cathode side) may remain connected to the back wall 12.

In the next step as shown in Fig. ID, the one or more new support elements 24 are placed on one side (e.g., anode side) of back wall 12 in which the existing support elements 16 are at least partially removed. Advantageously, the new support element 24 is a resilient support element for achieving a zero-gap configuration. The resilient support element 24 may comprise one or more ring or tubular portions 24a, the axis of which is oriented in the height direction or in the longitudinal direction of the electrolysis cell unit 10. The one or more ring or tubular portions 24a may be oriented in another direction, such as the horizontal direction of the electrolysis cell unit 10. The ring or tubular portions 24a adjacent in the height direction of the electrolysis cell unit 10 may be connected to each other via a base strip. The one or more ring or tubular portions 24a are resilient so that the fist electrode element 14 is pressed toward a separator of an electrolyzer (e.g. membrane) to retrofit the existing finite or non-zero gap type electrolysis cell unit into the zero gap type electrolysis cell unit. However, other resilient support elements such as having coil springs or leaf springs may also be applicable for the same purpose. As such, the existing electrolysis cell unit can be upgraded to the zero gap type electrolysis cell unit with lower costs. Advantageously, the new support elements 24 are placed between the adjacent welded portions 16a left on first side 12A (e.g., anode side) of the back wall 12. In the example of Fig. ID, the ring or tubular portions 24a and the welded portions 16a are arranged alternately to each other in the horizontal direction of the electrolysis cell unit 10.

After placing the new support elements 24, these are welded to the first side 12A of the back wall 12 from the second side 12B (e.g., cathode side) of the back wall 12 (see, arrows A in Fig. 1A). As discussed above, if the new support elements 24 are placed where no former welded portions 16a exist, no prior treatments (e.g., grinding) are in general necessary. In Fig. ID, at locations where the new support elements 24 contact the back wall 12, welding is performed. Advantageously, the welding is performed by keyhole welding. The keyhole welding is a welding technique in which a concentrated heat source penetrates partially or completely through a workpiece (i.e., the back wall 12 in the present invention), forming a hole (keyhole) at the leading edge of the weld pool. This allows that no or less welding lines appear on the first side 12A of the back wall 12. Such a keyhole welding may be achieved by laser welding. The laser welding is precise and efficient.

In the next step as shown in Fig. IE, a first new electrode element 14' is installed in place of the old electrode element 14 as removed in Fig. IB. In this example, a second new electrode element 20' is also installed in place of the old electrode element 20 as removed in Fig. IB. Of course, the removed first and/or second electrode element 14, 20 may be reused if the conditions allow. Additionally, the new first electrode element 14' may be welded to the new support element 24. This may be done by laser welding. As such, the ring-shaped resilient support elements 24a are joined with the reused cell component (i.e., back wall) as well as with the new electrode element 14', allowing good electrical and mechanical connection.

With reference to Fig. 2, another method for reactivating or regenerating an existing electrolysis cell unit 10, according to the present invention, is illustrated. A step similar to the step as shown in Fig. ID is illustrated. This embodiment differs from the embodiment of Figs. 1A-1E only in that the existing support element 16 is replaced with a new support element 16' which is the same in shape and mate- n rial as the existing support element 16. The new support element 16' thus includes bases 16a', legs 16b' and tops 16c'. The bases 16a' of the new support element 16' are arranged to avoid the old bases 16a, preferably between the adjacent old bases 16a. The new bases 16a are welded to the first side 12A of the back wall 12 from the second side of the back wall, preferably by means of keyhole welding. Other features described in connection with Figs. 1A-1E may equally apply to the embodiment of Fig. 2. This embodiment is advantageous for replacing corroded or damaged support elements with new ones with lower costs.

With reference to Fig. 3, another method for reactivating or regenerating an existing electrolysis cell unit 10, according to the present invention, is illustrated. This embodiment differs from the embodiment of Fig. 1 only in that the existing support element 16 is replaced with a new support element 26 that has a height (i.e., length measured along the direction perpendicular to the back wall 12) different from that of the existing support element 16. The new support element 26 may have Z-profile. Each new support element 26 may be arranged between the old welded portions 16a. Each new support element 26 is then welded to the first side 12A of the back wall 12 from the second side 12B of the back wall 12, preferably by means of keyhole welding. Other features described in connection with Figs. 1A-1E may equally apply to the embodiment of Fig. 3. This embodiment is advantageous for corrosion replacement as well as level adjustment of the first electrode element 14.

Reference sign list

10 electrolysis cell unit

12 back wall

12A first side of the back wall (e.g., anode side)

12B second side of the back wall (e.g., cathode side)

14 existing first electrode element

14' new first electrode element

16 existing support element

16' new support element frame existing second electrode element ' new second electrode element Z-profile resilient support element a ring portion new support element

Claims

1. A method for reactivating an electrolysis cell unit (10), the electrolysis cell unit (10) comprising a back wall (12), a first electrode element (14) arranged over a first side (12A) of the back wall (12) facing said first side (12A), and one or more existing support elements (16), wherein the one or more existing support elements (16) extend between the back wall (12) and the first electrode element (14) to support said first electrode element (14), the method comprising:

- removing the first electrode element (14);

- removing at least part of the one or more existing support elements (16);

- placing one or more new support elements (16', 24, 26) on the first side (12A) of the back wall (12); and

- welding each new support element (16', 24, 26) to the back wall (12) from a second side (12B) of the back wall (12) opposite to the first side (12A) of the back wall (12).

2. The method according to claim 1, wherein the electrolysis cell unit (10) further comprising a second electrode element (20) arranged over the second side (12B) of the back wall (12) facing said second side (12B), the method further comprising:

- removing the second electrode element (20) before welding each new support element (16', 24, 26) to the back wall (12).

3. The method according to claim 1 or 2, wherein the one or more existing support elements (16) are fixed to the back wall (12) via welded portions, wherein the removing at least part of the one or more existing support elements (16) includes removing the one or more existing support elements (16) whilst leaving the welded portions on the back wall (12).

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

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

6. The method according to any one of claims 1 to 5, wherein the new support element (16') is the same in 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 height different from that of the existing support element (16) for level adjustment of the first electrode element.

8. The method according to any one of claims 1 to 5, wherein the new support element (24) is a resilient support element for achieving a zerogap configuration.

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

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

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

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

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

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

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