Process for manufacturing protective elements for chlorine-alkaline electrolytic cells and alkaline water electrolytic cells

Abstract

The present invention relates to articles for electrolyte cells, particularly chlorine-alkaline electrolytic cells and alkaline water electrolytic cells, the cells comprising a nickel-based protective element and a conductive pocket, the pocket substantially surrounding the protective element on its entire surface, and the present invention also relates to batches of two or more such articles and processes for manufacturing these batches.

Description

[Technical Field]

[0001] The present invention relates to the field of industrialized batch production of protective elements for chlorine-alkaline electrolytic cells and alkaline water electrolytic cells. [Background technology]

[0002] Industrial electrolytic devices typically consist of multiple adjacent cells, each containing two opposing electrodes, which may be coated with a catalyst to facilitate the desired electrochemical reaction. Depending on the application, the electrode coating composition may contain one or more precious metals, such as Ru, Rh, Ir, and / or Pt, in varying proportions. These materials are rare and expensive, significantly impacting electrode costs and procurement, but often play a crucial role in ensuring the economics and performance of the electrolytic system, particularly in chlorine-alkali (C / A) and alkaline water electrolysis (AWE) applications. In these scenarios, ruthenium is often preferred due to its low cost, and typically replaces all or part of the other relatively expensive precious metals in the catalyst coating composition.

[0003] During nominal operating conditions, excluding maintenance work, the C / A and AWE electrolytic units operate at a specific current density, which is kept substantially constant during operation.

[0004] However, unplanned interruptions can occur, causing the cell to suddenly cease functioning and the current to be cut off. These events can negatively impact the cell's medium- and long-term performance, degrading its performance under standard operating conditions and potentially leading to premature breakdown of the coating.

[0005] In fact, unplanned interruptions can lead to an undesirable phenomenon known as current reversal. In this case, the reversal current generated during the shutdown event flows through the electrolytic device in the opposite direction to the electrolytic current, causing cathode degradation due to the leaching of catalyst materials (especially ruthenium), which can have a serious impact on the performance of the electrolytic device over time.

[0006] Several solutions have been developed to address this problem, and particularly successful approaches are described in European Patent Publication No. 3330409 (EP3330409), European Patent Publication No. 3330410 (EP3330410), and European Patent Publication No. 2615195 (EP2615195).

[0007] In these inventions, a protective element, i.e., a body made of a material suitable for absorbing reverse current, is placed within the cell in electrical contact with the cathode itself.

[0008] Suitable protective elements include porous nickel-based compacted materials, such as sintered nickel tablets.

[0009] In fact, nickel can be oxidized more readily than Ru in alkaline solutions, such as the cathode solution used in C / A and AWE cells. When porous nickel is electrically connected to an activated cathode, the potentials of the porous nickel and the cathode can be maintained at the same level. When a reverse current flows, Ni is oxidized preferentially over Ru, thus preserving the catalytic coating of the cathode and the operating parameters of the cell.

[0010] Therefore, the above solution has been proven to be effective in maintaining the performance of the electrolytic device over time.

[0011] However, until today, the aforementioned protective elements have been handled one by one by hand, making the process time-consuming, cumbersome, and inefficient when applied at an industrial level.

[0012] In addition, the reverse current absorber may fail due to its brittleness during operation, or during transportation and in-house operation before assembly, which can negatively impact the cell's performance or the overall cost of the system.

[0013] Therefore, for AWE and C / A applications, an automated or semi-automated process for batch manufacturing of reverse current protection elements is desirable. Furthermore, it is desirable that the batch requires minimal work for the installation of individual elements within the electrochemical cell. The individual elements thus prepared should exhibit the same desired protection characteristics as individually handcrafted elements, and should avoid the negative effects of damage to the current reverse protection material during transport or operation. Automated or semi-automated machinery to implement this process is also desirable.

[0014] Detailed explanation In one embodiment, the present invention relates to an article for electrolytic cells, particularly AWE cells and C / A cells, comprising a nickel-based protective element (501) and a conductive pocket, wherein the pocket substantially surrounds the protective element on all sides.

[0015] For the purposes of the present invention, a conductive pocket means a conductive container having a cavity, which is adapted to house a protective element inside the cavity. The conductive pocket is adapted to protect the protective element from damage during operation or outside of operation (e.g., during storage or transport). Preferably, the conductive pocket is adapted to ensure that the protective element functions even if it is inside the pocket and is damaged. Preferably, the conductive pocket is adapted to prevent the protective element from scattering within the cell in the event of damage.

[0016] A protective element refers to an element made of a material known in the art for its ability to absorb current reversal during a power outage in the electrolytic device and / or during the shutdown of the C / A and AWE cells, either in its final or intermediate preparation stage. These protective elements are typically nickel-based in both their final and intermediate preparation stages; that is, they contain nickel in the form of nickel metal or nickel alloy.

[0017] In the implementation of the present invention, the protective element observed to work particularly well is a heat-treated compressed body (e.g., a tablet) containing nickel. The protective element preferably has a nickel content of 45 to 90% by mass and / or a density of 2.00 to 6.51 g / cm³. 3 It is preferable that this be the case.

[0018] These materials can be obtained by heat-treating raw material powders consisting of Raney nickel alloy particles containing nickel and alkali-soluble metallic elements, metallic nickel particles, and mixtures of Raney nickel alloy particles and metallic nickel particles. These may, for example, be made of Ni-Al compositions or Ni-Al alloys. It is preferable that Al or the optional alkali-soluble metallic element is removed by leaching before the protective element is placed in the cell and during element operation, thereby providing a porous structure to the Ni-based elements.

[0019] Typically, one protective element is located within a single elemental cell, often corresponding to the cathode.

[0020] Therefore, in a second aspect, the present invention relates to an electrolytic apparatus comprising one or more articles according to the present invention. Preferably, it is an electrolytic apparatus for chlorine-alkali or alkaline water electrolysis.

[0021] When placing a protective element inside an electrochemical cell, it may be advantageous to leave the protective element inside a pocket: The pocket can be more easily handled without impairing the functionality of the protective element and can be connected to the cathode or other parts of the cell. The latter can be a brittle and porous compact that is difficult to firmly attach and connect to other elements of the cell by itself.

[0022] When a pocket containing a protective element is welded or connected to a conductive pocket, the conductive pocket should ensure electrical contact between the protective element and the electrolyte and / or between the protective element and the cathode.

[0023] In a third aspect, the present invention relates to a batch of two or more articles according to the present invention, the batch comprising a plurality of protective elements made of a nickel-based material housed within a conductive envelope, the envelope being made of a material compatible with an alkaline environment and comprising a plurality of pockets, at least two of the pockets each housing at least one protective element, and the at least two pockets each completely surrounding the at least one protective element.

[0024] The conductive envelope is characterized in that a base surface and a cover are joined together to form an enclosure having an outer periphery and provided with a plurality of pockets.

[0025] The pockets are created by joining the base surface and the cover of the conductive envelope along one or more paths (joining paths), thereby providing a plurality of receptacles suitable for containing and surrounding one or more protective elements.

[0026] When each pocket is substantially completely closed, it means that the gap in the path joining the pockets is small enough that one or more integral protective elements contained within the pocket are prevented from spontaneously exiting the pocket when the latter is moved or shaken without actively cutting or tearing the pocket.

[0027] Joining the envelope base surface and the cover to form its overall shape, and the joining path for forming pockets within the enclosure can be obtained by any technique suitable for creating a permanent or semi-permanent joint or bond between the envelope surfaces. Non-limiting examples of suitable techniques are heat welding, laser welding, soldering, resistance welding, microplasma welding, or mechanical joining (e.g., by folding or packaging).

[0028] The fact that multiple protective elements constitute an ensemble or batch enables easier handling and shipping, as well as a reduction in manufacturing time, as can be evaluated below.

[0029] The pockets for containing the protective elements are suitable for being removed from the envelope and separated from each other. Thus, once prepared to install the protective elements in individual cells, the pockets can be separated from each other or removed in some other way and installed individually within the cells. Since the pockets completely surround the protective elements, if the latter are damaged, that part will remain confined within the receiving portion of the pocket without impairing the protective function of the element and without substantial loss of material, regardless of whether the damage occurred during transportation or within the cell.

[0030] With a batch of articles containing protective elements, it becomes possible to perform specific manufacturing processes on the protective elements within the batch, in contrast to processing each element individually.

[0031] For example, protective elements obtained by leaching Al from a Ni-Al composition before batch preparation can be used, but it is also possible to leach Al from the Ni-Al protective elements after they have entered the batch, thus completing the preparation of these elements by leaching the entire batch at once. For this purpose, it is sufficient that the envelope be selected as a perforated structure that allows the leaching agent to flow within the pockets.

[0032] Using a perforated structure allows for lighter materials and enables electrolytes to flow within each pocket.

[0033] For manufacturing purposes, it is advantageous for conductive envelopes or pockets to have an elongation of >20%, a yield strength of >80 MPa, and a tensile strength of >345 MPa. These elastic properties ensure that the envelope can be folded, pressed, or bent, thus ensuring that opposing surfaces can easily adhere to and / or to each other.

[0034] The conductive envelope or pocket may be advantageously made of nickel, stainless steel, or an alloy thereof. These materials have been observed to exhibit desired chemical, electrical, and elastic properties and can also be manufactured as a mesh, net, or cloth with a perforated structure.

[0035] In preferred embodiments of the present invention, the conductive envelope or pocket is a nickel flynet (i.e., a net of nickel wires with a diameter of >0.14 mm), a nickel elastic mattress, or a nickel expanded mesh.

[0036] The conductive envelope may have a substantially flat base surface, which may optionally be provided with receptors suitable for housing protective elements and for forming pockets.

[0037] In a preferred embodiment of the present invention, the pockets are substantially coplanar and evenly distributed within the plane xy. The pockets are arranged at a first fixed distance from one another along a first direction x of the plane, and at a second fixed distance from one another along a second direction y of the plane, which is perpendicular to direction x, where the first and second distances are equal or different from each other.

[0038] In a fourth aspect, the present invention relates to a process for manufacturing the batch previously described herein. This process includes the following steps: (a) A step of placing an upper cover on a plurality of protective elements made of nickel-based material distributed on a base surface, wherein the upper cover and the base surface are made of a conductive structure; (b) A step of forming a conductive envelope by joining the upper cover and the base surface together with a bonding means to create an enclosure for housing the multiple protective elements; (c) A step of providing the envelope with at least one joining path obtained by joining means to form a plurality of pockets to be housed within the envelope, wherein at least two of the plurality of pockets each comprises at least one protective element.

[0039] It should be noted that steps (b) and (c) may be performed sequentially or simultaneously. Since it may be advantageous to select the same joining means for steps (b) and (c), a joining pattern can be devised that creates both the envelope and the pockets simultaneously. The envelope may be formed from an ensemble containing multiple pockets. Steps (a) to (c) may be performed manually.

[0040] It is understood that step (a0) may precede step (a) by distributing multiple protective elements made of nickel-based material onto a conductive base surface, either manually or by automated means.

[0041] By the process according to the invention, the effort required for the preparation of a plurality of protective elements can be reduced. This is because by supplying the plurality of protective elements in batches, the production time of the protective elements is significantly shortened.

[0042] The envelope can be manufactured by using separate sheets for the base surface and the upper cover, or by using a single manufacturing sheet that is folded in on itself over the entire area A. m In the latter case, the process according to the invention can be carried out by distributing a plurality of protective elements over the production surface within the perimeter that defines the base surface and divides the area A, leaving an area A on the production surface that is greater than A. p <1 / 2A m Thereafter, step (a) can be carried out by folding the remaining area A, which will form the upper cover of the envelope, over A. e が、A e >A p で残る。その後、工程(a)は、エンベロープの上部カバーとなる空いた面積A e をA p 上に折りたたむことによって行われ得る。

[0043] If the protective elements are made of Ni - Al alloy, the process according to the invention may include an additional step (d) of leaching Al from the Ni - Al protective elements to obtain a plurality of porous nickel - based protective elements. This step can be carried out by chemically removing Al from the batch by dissolving it in an alkaline medium by immersion. The batch can be immersed at a temperature of 15°C to 100°C for 1 to 48 hours.

[0044] In another aspect, the invention relates to the semi - automatic preparation of a batch of nickel - based protective elements, where the machine automatically implements the process steps (a) - (c) or (a) - (d) described above. In this case, the protective elements can be manually placed on the base structure.

[0045] When step (a0) is carried out using automation means, the invention also relates to the automatic preparation of a batch of nickel - based protective elements, where the machine automatically implements the process steps (a0) - (c) or (a0) - (d).

[0046] Automatic or semi-automatic machinery for preparing batches of protective elements significantly improves the time and cost-effectiveness of manufacturing these parts, thus offering an attractive alternative to the current state of the art manual and one-piece techniques.

[0047] Several embodiments of the present invention are described illustratively by the following examples with reference to the accompanying drawings, the purpose of which is solely to illustrate the relative arrangement of various elements relating to embodiments of the present invention. The drawings are not to scale. The same numbers are used to indicate features having the same purpose / effect. The coordinate axes x, y, and z are used in the same way in all drawings. The xy plane is substantially parallel to the main surface of the separator and other main functional elements of the cell (electrodes, frame, bipolar plate), while z is orthogonal to such a plane and identifies the main longitudinal axis of the electrolytic apparatus according to the present invention. [Brief explanation of the drawing]

[0048] [Figure 1] This is a schematic diagram of a batch (100) of articles containing a protective element according to an embodiment of the present invention.

[0049] Specifically, Figure 1.a) is a top view of batch (100) with 52 protective elements such as (501, 502). The envelope is demarcated by the outer perimeter of the batch, and its boundaries are joined together, with each protective element housed in a single pocket (invisible). Each pocket is obtained by laser welding opposing faces of the envelope along a joining path positioned between any adjacent protective elements. Some of these paths, in terms of direction and arrangement, are indicated by dashed lines h1, h2, h3 and v1, v2.

[0050] Figure 1.b) shows a schematic exploded view of a portion of batch (100) shown in Figure 1.a). The upper cover portion (300) should be positioned on the base surface portion (200) where the protective elements (501, 502, 503, 504) are distributed during assembly. The upper cover and the base surface will be pressed against each other. In a preferred embodiment, they are made to adhere to the protective elements where present, and to adhere to each other wherever otherwise. Two opposing surfaces (200, 300) will be laser-welded together along specific paths to create pockets, each pocket enclosing one protective element. For example, two opposing surfaces (200, 300) may be welded along their periphery and along joining paths running in the directions of h1 and v1, with other parallel directions running between the protective elements, creating adjacent rectangular pockets, each accommodating one protective element. It may be advantageous that the pockets accommodating the protective elements are not adjacent and not connected to each other. For this effect, an additional bonding path may be formed between surfaces (200) and (300) to ensure that two pockets containing at least one protective element do not share a bonding path. In this way, the protective element can be retrieved by cutting the pocket out of the envelope between the bonding paths, or along a bonding path that does not belong to the perimeter of the pocket containing the protective element. In this way, the integrity of the pocket enclosure (if a protective element is contained in the pocket) is maintained because the bonding path forming its perimeter does not directly exert mechanical stress to separate the pocket from the envelope. This integrity allows the protective element to remain within the pocket when attached to the cathode or other structural elements of the cell, thereby enabling easier and safer assembly and preventing the protective element from scattering within the cell in the event of failure.

[0051] In the specification and claims of this application, the word “comprise,” and its variations, such as “comprising” and “comprises,” do not preclude the presence of other additional elements, components, or stages.

[0052] For the purposes of this invention, the terms “to comprise” or “to include” also include the terms “to consist in” or “essentially consist of…”.

[0053] Discussions concerning documents, actions, materials, apparatus, articles, etc., are included hereinafter solely for the purpose of providing context for the present invention; however, this material, or any part thereof, should not be understood to constitute general knowledge in the art relating to inventions prior to the priority date of each claim attached to this application.

Claims

1. An article for an electrolyte cell comprising a nickel-based protective element (501) and a conductive pocket, wherein the pocket substantially surrounds the protective element over its entire surface.

2. The article according to claim 1, wherein the protective element is made of Ni, Ni-Al, or an alloy thereof, Ni powder mixed with an alkali-soluble metal, or a Ni alloy with an alkali-soluble metal.

3. The article according to claim 1 or 2, wherein the protective element is a sintered compacted body containing nickel, preferably having a nickel content of 45 to 90% by mass.

4. The protective element is a sintered compacted body containing nickel, preferably with a density of 2.00 to 6.51 g / cm³. ３ The article according to any one of claims 1 to 3.

5. The article according to any one of claims 1 to 4, wherein the conductive pocket has an elongation of >20%, a yield strength of >80 MPa, and a tensile strength of >345 MPa.

6. The article according to any one of claims 1 to 5, wherein the conductive pocket is made of a perforated material.

7. The article according to any one of claims 1 to 6, wherein the conductive pocket is made of nickel, stainless steel, or an alloy thereof.

8. The article according to claim 7, wherein the conductive pocket is nickel flynet, woven mesh, nickel elastic mattress, or nickel expanded mesh.

9. An electrolytic apparatus comprising an article according to any one of claims 1 to 8.

10. A batch (100) of two or more articles according to any one of claims 1 to 8, A batch (100) comprising a plurality of nickel-based protective elements (501, 502, 503, 504) housed within a conductive envelope, wherein the envelope comprises a plurality of pockets, at least two pockets each housing at least one protective element, and each of the at least two pockets substantially surrounds the at least one protective element over its entire surface.

11. The batch according to claim 10, wherein the pockets are substantially coplanar and evenly distributed within the XY plane, and the pockets are arranged at a first fixed distance from each other along a first direction x of the plane, and at a second fixed distance from each other along a second direction y of the plane that is perpendicular to direction x.

12. The following steps: (a) A step (200) of placing an upper cover (300) on a plurality of protective elements made of nickel-based material distributed on a base surface (200), wherein the upper cover and the base surface are made of a conductive structure; (b) A step of forming a conductive envelope by joining the upper cover and the base surface together with a bonding means to create an enclosure for housing the multiple protective elements; (c) A step of providing the envelope with at least one joining path obtained by joining means to form a plurality of pockets to be housed within the envelope, wherein at least two of the plurality of pockets each comprises at least one protective element. A process for manufacturing the batch according to claim 10 or 11, including the process described above.

13. The process according to claim 12, wherein steps (b) and (c) are performed simultaneously.

14. Process (a) includes the following steps: (a ０ ) A process of distributing multiple protective elements made of nickel-based material onto a base surface, wherein the base surface has a conductive structure. The process according to claim 12 or 13, wherein the preceding step is performed.

15. - The base surface and upper cover have a total area of ​​A ｍ Belonging to one of the same manufacturing surfaces having; • Multiple protective elements define the base surface, and A ｐ < 1 / 2A ｍ It is distributed on the manufacturing surface within the periphery that divides the area, and this A ｅ > A ｐ The remaining empty area is; - Step (a) is performed by folding the empty area A ｍ of A ｅ onto A ｐ as follows: The process according to any one of claims 12 to 14.

16. Multiple protective elements are made of Ni-Al or an alloy thereof, and the following additional steps are taken: (d) Obtain multiple porous nickel-based protective elements by leaching Al from Ni-Al elements. The process according to any one of claims 12 to 15, including the process described in any one of claims 12 to 15.

17. The process according to any one of claims 12 to 16, wherein the joining means is selected from the following techniques: thermal welding, laser welding, soldering, resistance welding, microplasma welding, mechanical joining, and any combination thereof.

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