Electrode assembly for electrochemical process and method for restoring the same

Abstract

The invention relates to an electrode assembly (10) for an electrochemical process, the electrode assembly comprising: a current supply element (1), the current supply element comprising at least one recessed hole (4); at least one current distribution rod (2), the at least one current distribution rod comprising a first end (5) and a second end (6), the first end being releasably arranged at the at least one recessed hole; and an electrode substrate (3), the electrode substrate being arranged at the at least one current distribution rod. The current distribution rod comprises a core (7) and an outer layer (8), the core being completely covered by the outer layer. The invention also relates to a method for recovering an electrode substrate of an electrode assembly without removing the electrode substrate from the at least one current distribution rod.

Description

Technical Field

[0001] The present invention relates to the field of electrodes, and more particularly to an electrode assembly for an electrochemical process and a method for recovering an electrode substrate of such an electrode assembly. Background Art

[0002] Electrowinning is an example of an electrochemical process in which metals can be recovered from solutions containing them in ionic form. These processes take place in an electrolytic cell, which includes alternating electrodes in the form of one or more cathodes and one or more anodes, which are immersed in a solution. When an electric current is passed through the electrolytic cell, the desired metal is plated onto the cathodes.

[0003] A typical electrode assembly for electrowinning includes a current supply rod (commonly referred to as a suspension rod) arranged to extend horizontally above the electrolytic cell. The electrode assembly further includes current distribution rods, which are attached to the current supply rods and extend vertically therefrom, and the electrochemically active electrode substrate is attached to these current distribution rods, for example, by welding. The electrode substrate is generally composed of a base structure and an electrochemically active coating applied to the base structure. The materials of the base structure and the coating, and the materials of the current distribution rods are suitable for the process of using the electrode assembly. The current distribution rod is composed of a conductive material for conducting current from the suspension rod to the electrode substrate. For example, for the anode used in electrowinning, the conductive materials commonly used are copper and aluminum. Due to the low corrosion resistance of these materials, for example, it is necessary to apply a metal coating with chemical resistance to the electrolyte solution used on these materials. Typically, for the anode, a titanium coating or another valve metal coating is used. Valve metals are also commonly used in the base structure of the electrode substrate. These metals are referred to as film-forming metals and, when connected as electrodes in the electrolyte in which the electrode assembly is intended to operate, have the property of rapidly forming a passive oxide film, thereby protecting the underlying metal from corrosion by the electrolyte.

[0004] US 2010 / 0276281 discloses such a typical electrode assembly.

[0005] During the use of the electrode assembly, the electrochemically active coating of the electrode substrate loses activity or effectiveness over time, resulting in ohmic losses and high cell voltages in the electrolytic cell, which in turn leads to increased power consumption. Therefore, in order to keep the electrode effective, it is necessary to restore the electrochemical activity of the electrode substrate. At present, in order to restore the electrochemical activity, the electrode substrate is generally removed from the current distribution rod and replaced with a new coated electrode substrate. Considering the value of the materials constituting the electrode substrate and its coating, replacing a new electrode substrate with an old one involves high costs. The electrode assembly disclosed in US 2010 / 0276281 is not arranged to be detachable, and there is no teaching on whether restoration can be performed.

[0006] US 4088558 discloses a method for rejuvenating the electrode surface of a metal electrode, wherein, after removing the electrode component from a supporting riser, the electrode component is recoated and then reinstalled at the supporting riser. The removal of the electrode component involves punching or drilling out weld joints by which the electrode component is attached to the supporting riser. The recoated electrode component is then installed at the supporting riser by spot welding. This results in a rather time-consuming and energy-consuming process. Summary of the invention

[0007] It would be advantageous to provide more efficient recoverable electrode assemblies for electrochemical processes.

[0008] In order to better solve this problem, in a first aspect of the present invention, an electrode assembly for an electrochemical process is provided, the electrode assembly comprising: a current supply element, the current supply element comprising at least one recessed hole; at least one current distribution rod, the at least one current distribution rod comprising a first end and a second end, the first end being releasably arranged at the at least one recessed hole; and an electrode substrate, the electrode substrate being arranged at the at least one current distribution rod. The current distribution rod comprises a core and an outer layer, the core being completely covered by the outer layer.

[0009] When it is necessary to restore the electrochemical activity of the electrode substrate, or for any other reason, the releasably arranged current distribution rod allows the current distribution rod with the electrode substrate to be easily removed. In addition, since the outer layer completely covers the core of the current distribution rod, the electrode substrate can be subjected to a recovery treatment without removing the electrode substrate from the current distribution rod. This recovery treatment may include, for example, cleaning the electrode substrate and removing any residual coating therefrom by immersing the electrode and therefore the current distribution rod in a salt bath, and then re-coating the electrode substrate. Subjecting the portion of the current distribution rod that is not covered by the outer layer (i.e., where the core is exposed) to a treatment for removing any residual coating from the substrate typically causes the core to dissolve at a higher rate than the substrate coating because the material of the core has a higher chemical reactivity. This is highly undesirable because it will damage the current distribution rod. According to the electrode assembly of the present invention, by providing a core that is completely covered by the outer layer, the core will not be exposed and such adverse reactions are prevented. Therefore, the electrode substrate can be treated to remove the residual coating while still attached to the current distribution rod.

[0010] Recoating the electrode substrate generally involves a heat treatment at a temperature between 300°C and 600°C. In a current distribution rod, the thermal expansion coefficient of the core is generally higher than the thermal expansion coefficient of the outer layer. In known electrode assemblies, the current distribution rod comprising a core and an outer layer is usually coated and provided as a long rod, which is then cut into the desired length so that the end of the cut rod is without any coating layer. When such a rod is subjected to thermal cycling, the thermal expansion of the core material is greater than the thermal expansion of the coating material, which may cause the core material to extend out of the outer layer at the end of the rod (where it can expand freely). However, it is convenient to find that the current distribution rod according to the present invention, which includes a core (including at its end) completely covered by an outer layer, does not allow such free expansion of the core, thereby providing dimensional stability of the current distribution rod. This in turn allows the current distribution rod to be reinstalled in the recessed hole of the current supply element together with the electrode substrate attached thereto after the electrode is subjected to a recovery treatment. Therefore, an electrode assembly that can be effectively restored when necessary is provided, which does not require the electrode substrate to be separated from its current distribution rod.

[0011] Further, in known solutions of the prior art, the first end of the current distribution rod, which is arranged in contact with the current supply element, is stripped of the coating so as to provide a good conductive contact surface for contact between them to keep the power losses to a minimum. However, for the disclosed electrode assembly of the present invention, it was surprisingly found that the power losses caused by the outer layer of the current distribution rod are negligible for the process. This is attributed to the relatively thin thickness of the outer layer, which is generally included in the range of 0.1 mm to 5 mm. In a preferred embodiment, the thickness of the outer layer is included in the range of 0.5 mm to 3 mm. Providing the outer layer of the releasably arranged current distribution rod to cover the entire core (including its end surface) thus allows the current distribution rod to be removed from the current supply element together with the electrode substrate and the resulting unit to be subjected to a recovery process without compromising the energy consumption of the process of operating the electrode assembly.

[0012] According to an embodiment, the electrode comprises a plurality of current distributing bars and the current supply element comprises a corresponding number of recessed holes, such that the first end of each current distributing bar is arranged in a recessed hole of the current supply element.

[0013] According to an embodiment of the electrode assembly, the first end of at least one current distribution rod is arranged in at least one recessed hole in a press-fit engagement. A press-fit tool can be used to install one or more current distribution rods at the current supply element and to remove one or more current distribution rods from the current supply element. The press-fit can be performed at an elevated temperature to ensure good engagement of the current distribution rod with the current supply element. However, according to an embodiment of the electrode assembly, the first end of at least one current distribution rod is tapered, and at least one recessed hole has a corresponding tapered shape. Providing a tapered first end of the current distribution rod and a corresponding tapered shape of the recessed hole facilitates press-fitting the first end into the recessed hole and allows the current distribution rod to be installed at the current supply element at room temperature. Therefore, time and energy are saved during the installation process of the electrode assembly.

[0014] According to an embodiment of the electrode assembly, the tapered first end of the current distributing bar is obtained by a gradual reduction in thickness of the outer layer at the first end. The gradual reduction in thickness of the outer layer of the first end of the current distributing bar can be obtained, for example, by machining the outer layer of the first end (for example by turning) to remove increasingly larger portions of the outer layer towards the end of the first end. Other alternatives for obtaining the tapered first end of the current distributing bar are also possible within the concept of the invention, such as by isostatic pressing or mechanical pressing.

[0015] According to an embodiment of the electrode assembly, the recessed hole of the current supply element is a through hole. This facilitates removal of one or more current distribution bars from the current supply element.

[0016] According to an embodiment of the electrode assembly, the outer layer comprises a coating of the longitudinally extending surface of the core of the current distributor bar, and a first outer end layer and a second outer end layer covering the lateral end surfaces of the core, wherein the outer end layers are arranged at the respective ends of the core by welding. Thus, the current distributor bar can be obtained by cutting a long bar including the coating into the required length and then welding the outer end layers (e.g. caps) to the exposed lateral end surfaces of the core to completely cover these lateral end surfaces. Alternative ways of covering the lateral end surfaces with the outer end layers, such as by fastening elements or coating methods, are also possible within the concept of the present invention.

[0017] According to an embodiment of the electrode assembly, the material of the outer end layer is the same as the material of the coating layer. The outer layer is composed of a material that is inert in the process environment. In an embodiment of an electrode assembly for use in a relatively acidic to weakly alkaline environment (i.e., an oxidizing environment), the outer layer typically includes a valve metal, such as titanium or tantalum. In an embodiment of an electrode assembly for use in an alkaline or reducing environment, the outer layer includes nickel or stainless steel.

[0018] According to an embodiment of the electrode assembly, the core comprises a good electrical conductor. Typically, the material of the core is selected from copper, aluminum, silver and zinc.

[0019] According to a second aspect of the present invention, there is provided an electrolytic cell comprising one or more electrode assemblies as disclosed herein. According to an embodiment, the electrode assembly is adapted to be used as an anode. According to another embodiment, the electrode assembly is adapted to be used as a cathode.

[0020] According to a third aspect of the present invention, there is provided a method for installing an electrode assembly, the electrode assembly comprising a current supply element, at least one current distribution rod, and an electrode substrate, the current supply element comprising at least one recessed hole, the at least one current distribution rod comprising a first end and a second end, the first end being arranged at the recessed hole, the electrode substrate being arranged at the at least one current distribution rod. The first end is tapered, and the at least one recessed hole has a corresponding tapered shape. The method comprises the following steps: attaching the electrode substrate to the at least one current distribution rod; and arranging the first end of the current distribution rod at the at least one recessed hole of the current supply element by press fitting, wherein the step of arranging the current distribution rod at the current supply element is performed at room temperature. The tapered first end of the current distribution rod and the corresponding tapered recessed hole facilitate the press-fit engagement of the current distribution rod and the current supply element, and allow the press fitting to be performed at room temperature. This provides an effective installation of the electrode assembly.

[0021] According to an embodiment of the method of mounting an electrode assembly, the step of arranging the at least one current distribution bar at the current supply element is performed before attaching the electrode substrate to the current distribution bars.

[0022] According to a fourth aspect of the present invention, a method for restoring an electrode assembly as disclosed herein is provided. The method comprises the following steps: removing the at least one current distribution rod from the current supply element, subjecting the electrode substrate to a cleaning process, recoating the electrode substrate with an electrochemically active coating, and arranging the first end of the at least one current distribution rod at the current supply element. Since the entire outer surface of the current distribution rod is inert in the processing environment of the electrode assembly, it is not necessary to remove the electrode substrate from the current distribution rod to clean and recoat it. Instead, the releasably arranged current distribution rod can be conveniently removed from the current supply element and subjected to a restoration process without suffering surface damage or dimensional deformation. This allows saving time and energy. Relative to solutions involving replacing the electrode substrate with a new electrode substrate, the method for restoring the electrode assembly as disclosed herein further provides significant economic advantages.

[0023] According to an embodiment of the method for restoring an electrode assembly, the step of arranging the first end of the at least one current distribution bar at the current supply element is performed by press fitting. A press fitting tool can be used to achieve a press fit engagement between the current distribution bar and the current supply element, thereby providing easy and fast installation thereof.

[0024] According to an embodiment of the method for restoring an electrode assembly, wherein the first end of the at least one current distribution bar and the at least one recessed hole of the current supply element are tapered, the step of arranging the first end of the at least one current distribution bar at the current supply element is performed at room temperature. This allows saving time and energy during the installation of the electrode assembly.

[0025] According to an embodiment of the method for restoring an electrode assembly, the cleaning process includes removing any residues of the electrochemically active coating from the electrode substrate by at least one of a salt bath treatment and blasting. Removing possible coating residues by a salt bath treatment allows the metals contained in these residues to be recovered later, which are generally high-value materials. When blasting is used to remove the residual coating from the electrode substrate, the metal can also be recovered in a subsequent mineral refining step. This increases the value of the restoration process and achieves economic and environmental benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The invention will now be described in more detail and with reference to the accompanying drawings, in which:

[0027] Figure 1 is a perspective view of an electrode assembly according to an embodiment of the present invention;

[0028] Figure 2 yes Figure 1 An exploded view of the electrode assembly is shown;

[0029] Figure 3 yes Figure 1 a partial cross-sectional view of a portion of the electrode assembly shown;

[0030] Figure 4 yes Figure 1 a cross-sectional view of a portion of a current supply element and current distribution bars of the electrode assembly shown; and

[0031] Figure 5 is a perspective view of an electrode assembly according to another embodiment of the present invention. DETAILED DESCRIPTION

[0032] refer to Figure 1, presents an electrode assembly 10 for an electrochemical process, for an electrolytic cell. The electrode assembly 10 comprises a current supply element 1, a current distribution rod 2, and an electrode substrate 3 arranged at the current distribution rod 2. The current supply element 1 is here an elongated rod, which can generally be arranged to extend horizontally across the electrolytic cell. However, the current supply rod 1 is not necessarily straight, but can be, for example, curved, or bent at one or more portions thereof. In the illustrated embodiment, the current supply element 1 has a rectangular cross-section. However, the cross-section of the current supply element 1 can be any other suitable shape, such as square, circular or elliptical. The current supply element 1 is preferably made of a conductive material, such as but not limited to copper, aluminum, silver and zinc. In a preferred embodiment, the current supply element 1 is made of copper. The current supply element 1 is further provided with at least one recessed hole 4 for engaging with the current distribution rod 2. The current distribution rod 2 is arranged to extend perpendicularly to the longitudinal extension of the current supply element 1. Each current distribution rod 2 comprises a first end 5 (see Figure 2 ) and the second end 6. The first end 5 of the current distribution bar 2 is arranged in the corresponding recessed hole 4 of the current supply element 1. In general, and according to Figure 1 In the illustrated embodiment, the current distribution bars 2 extend vertically downward from the horizontally arranged current supply element 1. Figure 1 In the exemplary embodiment of the present invention, the electrode assembly 10 includes four recessed holes 4 at the current supply element 1, and four current distribution bars 2. However, the number of recessed holes 4 is not limited to four, but can vary from one to more depending on the size of the electrode assembly 1. Accordingly, the number of current distribution bars 2 can vary to correspond to the number of recessed holes 4 of the current supply element 1. The current distribution bar 2 is cylindrical in shape here. However, any other suitable shape is also possible for the current distribution bar 2, such as a rectangle.

[0033] The electrode substrate 3 is arranged at the current distribution rod 2, extending from the portion of the current distribution rod 2 near the corresponding first end 5 toward its corresponding second end 6. In the illustrated embodiment, the electrode substrate 3 is a rectangular sheet. However, the electrode substrate 3 can also be a mesh, or have any other suitable shape and structure for this purpose. The electrode substrate 3 generally includes a base structure of a material that is inert to the processing environment, and an electrochemically active coating arranged at the base structure. Examples of such electrochemically active coatings and base structures are known in the art, for example, disclosed in EP 1670973. In a preferred embodiment, the base structure of the electrode substrate includes titanium, and the coating includes ruthenium and iridium. However, other materials of the base structure and the coating are also possible, such as those disclosed in the above-mentioned EP 1670973.

[0034] Continue to refer Figure 1 and Figure 2, the first end 5 of each current distributing bar 2 is releasably arranged in a corresponding recessed hole 4 of the current supply element 1. Therefore, the size of the recessed hole 4 is such that the current distributing bar 2 can be inserted therein. Preferably, the first end 5 of each current distributing bar 2 is arranged in the corresponding recessed hole 4 by press fitting. Therefore, the diameter of the recessed hole 4 is slightly smaller than the diameter of the first end 5 of the current distributing bar 2. Although the current distributing bar 2 and the recessed hole 4 are shown here as circular cross-sections, it is also possible within the concept of the disclosed electrode assembly 10 to provide the current distributing bar 2 and the recessed hole 4 with another shape (e.g. rectangular).

[0035] In order to press fit the current distribution rod 2 of constant diameter into the recessed hole 4 of constant diameter, it is generally necessary to heat the first end 5 of the current distribution rod 2 and / or the recessed hole 4 of the current supply element 1. However, it has been found that according to this embodiment of the electrode assembly, Figure 3 As shown, providing a slightly tapered first end 5 of the current distribution bar 2 and a correspondingly tapered recessed hole 4 enables the first end 5 to be arranged in the recessed hole 4 by press-fitting at room temperature (i.e., without changing the temperature of the current supply element 1 or the current distribution bar 2 so that the temperature of the current supply element 1 is higher than the temperature of the current distribution bar 2). This allows the current distribution bar 2 to be mounted quickly and with low energy consumption at the current supply element 1, and thus allows a more efficient mounting of the electrode assembly 10. In an alternative embodiment, the first end 5 of the current distribution bar 2 and the recessed hole 4 have constant dimensions and are therefore not tapered.

[0036] Continue to refer Figure 3 , the recessed hole 4 is a through hole. Providing the through hole 4 at the current supply element 1 for engaging the current distribution bar 2 facilitates the removal of the current distribution bar 2 from the current supply element 1. When the through hole 4 has a slightly tapered shape, according to Figure 3 The embodiment shown particularly facilitates disassembly if the first end 5 of the current distribution bar 2 has a complementary tapered shape. However, according to alternative embodiments, it is also possible to provide a recessed hole 4 that is not a through hole. Such a non-through hole may further be slightly tapered in order to engage with a correspondingly tapered first end 5 of the current distribution bar 2. According to another embodiment, the non-through hole may also have a constant cross-section in order to engage with a first end 5 of the current distribution bar 2 having a correspondingly constant size.

[0037] To install Figure 3In the electrode assembly 10 partially shown in the figure, the electrode substrate 3 is attached to the current distribution rod 2. In an embodiment, the attachment of the electrode substrate 3 to the current distribution rod 2 is achieved by welding. Other alternatives include the use of fastening elements, soldering or conductive adhesives. The current distribution rod 2 is then arranged at the recessed hole 4 (here a through hole) of the current supply element 1 by press fitting. More specifically, the first end 5 of the current distribution rod 2 is inserted into the recessed hole 4. Due to the tapered first end 5 and the through hole 4, the arrangement of the current distribution rod 2 at the current supply element 1 can be performed at room temperature. In another embodiment in which the first end 5 and the through hole 4 have constant dimensions, the press fitting of the current distribution rod 2 into the current supply element 1 is performed at an elevated temperature.

[0038] According to an alternative method of mounting the electrode assembly 10 , the step of arranging one or more current distribution bars 2 at the current supply element 1 is performed before arranging the electrode substrate 3 at the one or more current distribution bars 2 .

[0039] Reference now Figure 4 According to an embodiment of the electrode assembly 10, the current distribution rod 2 consists of a core 7 and an outer layer 8. The core 7 is made of a conductive material, such as copper, aluminum and silver. Such a material will typically react with the processing environment in which the electrode assembly 10 is used, i.e., with the electrolyte solution of the electrolytic cell. Therefore, the current distribution rod 2 further includes an outer layer 8, which is arranged to prevent the core 7 from chemically reacting with the processing environment (e.g., electrolyte), which may, for example, cause severe corrosion of the core 7 and thus result in a short durability of the electrode assembly 10. The core 7 is here coated in the outer layer 8, which is selected from a material that is inert in the processing environment. In an embodiment of the electrode assembly 10 used as an anode, for example, the outer layer 8 is preferably selected from a valve metal group, such as but not limited to titanium and tantalum. In a preferred embodiment, the outer layer 8 is made of titanium and the core 7 is made of copper.

[0040] The outer layer 8 completely covers the core 7 of the current distribution bar 2 (including its end surfaces). In the embodiment shown, the end surfaces of the core 7 are covered by corresponding outer end layers 9, which consist of caps welded to the corresponding end surfaces of the core 7. Such caps are here the same material as the cladding of the core of the current distribution bar 2. In another embodiment, the caps are made of a material different from the cladding. In any case, the material of the outer end layer 9 is selected from a material that is inert in the processing environment in which the electrode assembly 10 is used, that is, a material that does not chemically react with the processing environment. It is understood by those skilled in the art that the outer end layer 9 can be provided in a manner different from the cap welded to the end surface of the core 7. For example, the outer end layer 9 can be fastened by fastening elements, by soldering, or by means of a conductive adhesive. In another embodiment, the outer end layer 9 is deposited as a coating at the corresponding end surface of the core 7. The thickness and joints of the outer end layer 9 make it withstand the forces applied thereto, especially the thickness and joints of the outer end layer 9 of the first end 5 when the current distribution bar 2 is removed from the current supply element 1.

[0041] Further, in Figure 4 In an exemplary embodiment of the invention, the first end of the current distribution bar 2 is tapered. The tapered shape is provided here by the outer layer 8 of the first end 5, which has a thickness that gradually decreases toward the end of the first end 5. The gradually decreasing thickness of the outer layer 8 is generally obtained by machining the first end 5 so that the outer layer 8 is gradually thinned toward the end of the first end 5. The total thickness reduction of the outer layer 8 is lower than the thickness of the outer layer at the portion of the current distribution bar 2 that is not subjected to the thickness reduction. Therefore, the outer layer 8 is not completely eliminated at any point of the current distribution bar 2. That is, the outer layer 8 completely surrounds the core 7. This is very advantageous because even after the current distribution bar 2 is removed from the current supply element 1, the core material that generally reacts is still completely encapsulated by the outer layer 8. This in turn allows the substrate 3 attached to the current distribution bar 2 to be subjected to a recovery process, including, for example, removing the residual coating from the substrate 3 and re-coating the substrate after the current distribution bar 2 is removed from the current supply element 1 but without having to disassemble the electrode substrate 3 from the current distribution bar 2.

[0042] refer to Figure 5 , presents an alternative embodiment of an electrode assembly 20 for an electrochemical process. According to this embodiment, the electrode assembly 20 includes two current supply elements 21 in the form of blocks. The current supply elements 21 of this embodiment can be arranged on opposite sides of the electrolytic cell. The current supply elements 21 each include two recessed holes 24 extending from one side of the block-shaped current supply element 21 to its opposite side. The recessed holes 24 are through holes, such as Figure 5 In an alternative embodiment, the recessed hole 24 is not a through hole, ie, does not extend completely through the current supply element 21. Figures 1 to 4As described for the previous embodiment, the recessed hole 24 may be tapered. However, it is also possible within the concept of the present invention to provide a recessed hole 24 with a constant diameter.

[0043] The electrode assembly 20 further includes four current distribution bars 22, which include respective first ends 25 and second ends 26. The first end 25 and each current distribution bar 22 are arranged in a recessed hole 24 of one of the current supply elements 21. The first end 25 of this exemplary embodiment is slightly tapered, thereby facilitating the press-fitting of the current distribution bar 22 into the recessed hole 24. In another embodiment, the first end 25 has a constant size. The number of recessed holes 24 and current distribution bars 22 is not limited to four, but can be adapted to the requirements of the process in which the electrode assembly is to be used.

[0044] The portion of the current distribution bar 22 adjacent to its first end 25 extends horizontally from the recessed hole 24 of the current supply element 21. The current distribution bar 22 further includes one or two bends 27, by which the current distribution bar 22 is bent so that its second end 26 extends substantially perpendicularly to the extension of the first end 25, i.e., vertically. The angle of the bend 27 of the current distribution bar 22 can vary from current distribution bar 22 to current distribution bar 22, so that the vertical extensions of the current distribution bar 22 are arranged in parallel and with a distance between them. The electrode substrate 3 of the electrode assembly 20 can thus be fastened to the current distribution bar 22 in the same manner as described in the previous embodiment. In the illustrated embodiment, the angle of the bend 27 of the two outermost current distribution bars 22 of the electrode assembly 20 is approximately 90°. The two centrally arranged current distribution bars 22 of the electrode assembly 20 each include two bends 27 having an angle greater than 90°, more particularly approximately 135°. However, as will be appreciated by those skilled in the art, it is also possible to provide the bending portions 27 with different angles within the concept of the electrode assembly 20 .

[0045] As in the previously described embodiments, the current distribution bar 22 comprises a core 7 and an outer layer 8. The outer layer further comprises an outer end layer 9, so that the entire core 7 is surrounded by the outer layer 8. The current supply element 21 is made of a conductive material for conducting current to the current distribution bar 22. The current distribution bar is also made of a conductive material for conducting current to the electrode substrate 3. Possible materials for the components of the electrode assembly 20 are the same as previously described herein.

[0046] When the efficiency of the electrode substrate 3 of the disclosed electrode assembly 10, 20 is reduced and needs to be restored, the electrode assembly 10, 20 can be disassembled and the electrode substrate 3 restored according to the following method, which includes: a first step of removing one or more current distribution bars 2, 22 from the current supply element 1, 21; a second step of subjecting the electrode substrate 3 to a cleaning process; a third step of re-coating the electrode substrate 3 with an electrochemically active coating; and a fourth step of arranging the current distribution bars 2, 22 at the current supply element 1, 21. As previously mentioned, the first step of removing one or more current distribution bars 2, 22 from the current supply element 1, 21 is facilitated by providing a tapered first end of the current distribution bar 2, 22 and a recessed hole 4, 24. This first step is further facilitated by providing the recessed hole 4, 24 as a through hole at the current supply element 1, 21. However, performing the removal step at an elevated temperature allows the removal of the current distribution bars 2, 22 including the first end 5, 25 also having a constant cross-section.

[0047] After removing the current distribution bars 2, 22 and the electrode substrate 3 attached thereto, a step of subjecting the electrode substrate 3 to a cleaning process is performed. The cleaning process generally comprises removing the residues of the worn electrochemically active coating from the electrode substrate 3 so that the electrode substrate is clean before applying a new coating thereto. The cleaning process is preferably performed by a treatment as disclosed in US 5141563, which involves a salt bath heated to a temperature of up to 450°C. This treatment allows the valuable elements of the residual coating to be recovered for reuse. Another possible cleaning process is spraying. Other alternative methods for cleaning the electrode substrate to remove any residual coating therefrom may also be used.

[0048] The re-coating of the third step is generally performed in steps at different temperatures between 300° C. and 600° C. Since the outer surface (such as the outer layer 8) of the current distribution bars 2, 22 has a material that is inert in the processing environment of the electrode assembly 10, 20, it is not necessary to remove the current distribution bars 2, 22 from the electrode base plate 3 for cleaning and re-coating. Instead, the structure including the current distribution bars 2, 22 and the electrode base plate 3 can be subjected to the cleaning and coating process together without causing damage to the current distribution bars 2, 22.

[0049] The step of arranging the current distributing bars 2, 22 at the current supply element 1 is generally performed by press-fitting the first ends 5, 25 of the current distributing bars 2, 22 into the recessed holes 4, 24 of the current supply element 1, 21. In embodiments in which the first ends 5, 25 of the current distributing bars 2, 22 and the recessed holes 4, 24 of the current supply element 1 are tapered electrode assemblies, the arranging step is preferably performed at room temperature.

[0050] Although the invention has been shown and described in detail in the drawings and the foregoing description, such showing and description are to be regarded as illustrative or exemplary rather than restrictive. The invention is not limited to the disclosed embodiments. The invention is generally applicable to any process using an electrode assembly including a current distributor rod having a core and an outer layer. Examples of such processes are electrowinning, electrogalvanizing, electroliberation, chlor-alkali diaphragm processes, and processes using monopolar chlorate anodes.

[0051] Other variations of the disclosed embodiments may be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, this disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. The mere fact that certain measures are cited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope.

Claims

1. An electrode assembly (10, 20) for an electrochemical process, comprising: A current supply element (1, 21), the current supply element comprising at least one recessed hole (4, 24); at least one current distributing bar (2, 22), comprising a first end (5, 25) and a second end (6, 26), the first end being releasably arranged at the at least one recessed hole; and an electrode substrate (3) arranged at the at least one current distributing rod, The current distribution rod comprises a core (7) and an outer layer (8), wherein the core is completely covered by the outer layer, wherein the outer layer (8) comprises a coating layer on the longitudinally extending surface of the core (7) of the current distribution rod (2, 22), and a first outer end layer and a second outer end layer (9) covering the transverse end surface of the core.

2. The electrode assembly (10, 20) according to claim 1, wherein: The first end (5, 25) of the current distributing bar (2, 22) is arranged in a press-fit engagement at the recessed hole (4, 24) of the current supply element (1, 21).

3. The electrode assembly (10, 20) according to claim 1 or 2, wherein: The recessed hole (4, 24) of the current supply element (1, 21) is a through hole.

4. The electrode assembly (10, 20) according to claim 1 or 2, wherein: The outer end layers are arranged at these lateral end surfaces by means of welded joints.

5. The electrode assembly (10, 20) according to claim 1 or 2, wherein: The first end (5, 25) of the at least one current distributing bar (2, 22) is tapered, and the at least one recessed hole (4, 24) of the current supply element (1, 21) has a correspondingly tapered shape.

6. The electrode assembly (10, 20) according to claim 5, wherein: The tapered first end portion (5, 25) is obtained by a gradual reduction in thickness of the outer layer (8) of the at least one current distributing bar (2, 22) at the first end portion.

7. The electrode assembly (10, 20) according to claim 4, wherein: The outer end layer (9) is made of the same material as the coating layer of the outer layer (8).

8. An electrolytic cell comprising an electrode assembly (10, 20) according to any one of the preceding claims.

9. A method for installing an electrode assembly (10, 20), the electrode assembly comprising a current supply element (1, 21), at least one current distribution rod (2, 22) and an electrode substrate (3), the current supply element comprising at least one recessed hole (4, 24), the at least one current distribution rod comprising a first end (5, 25) and a second end (6, 26), the first end being arranged at the recessed hole, the electrode substrate being arranged at the at least one current distribution rod, wherein: The first end portion is tapered and the at least one recessed hole has a correspondingly tapered shape, and wherein the current distribution bar comprises a core (7) and an outer layer (8), the core being completely covered by the outer layer, wherein the outer layer (8) comprises a coating of a longitudinally extending surface of the core (7) of the current distribution bar (2, 22), and a first outer end layer and a second outer end layer (9) covering a transverse end surface of the core, the method comprising the following steps: attaching the electrode base plate to the at least one current distribution bar; and The first end of the current distributing bar is arranged at the at least one recessed hole of the current supply element by press fitting, wherein the step of arranging the current distributing bar at the current supply element is performed at room temperature.

10. The method according to claim 9, wherein: The step of arranging the at least one current distributing bar (2, 22) at the current supply element (1, 21) is performed before arranging the electrode substrate (3) at the current distributing bar.

11. A method for restoring an electrode substrate (3) of an electrode assembly (10, 20) according to any one of claims 1 to 7, the method comprising the following steps: removing the at least one current distributing rod (2, 22) from the current supply element (1, 21); subjecting the electrode base plate (3) arranged at the at least one current distributing bar to a cleaning process; recoating the electrode substrate with an electrochemically active coating; as well as The first end (5, 25) of the at least one current distributing bar is arranged on the current supply element.

12. The method according to claim 11, wherein: The cleaning process includes removing any residues of the electrochemically active coating from the electrode substrate (3) by at least one of a salt bath treatment and a spray.

13. The method according to claim 11 or 12, wherein: The step of arranging the first end (5, 25) of the at least one current distributing bar (2, 22) at the current supply element (1, 21) is performed by press-fitting.

14. The method according to claim 13, wherein: The step of arranging the first end (5, 25) of the at least one current distributing bar (2, 22) at the current supply element (1, 21) is performed at room temperature.

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