Cathode plate for electrolysis, electrolytic cell, electrolysis method, and method for producing nickel

Abstract

To provide a cathode plate for electrolysis configured such that the formation of a metal lump precipitated on a cathode plate constituting a cathode for an electrolysis cell is suppressed to prevent partial damage to the electrolysis cell caused by the contact of the metal lump.SOLUTION: A cathode plate for electrolysis is a cathode plate 1 in which the shape of both lower corners 11 in a plan view is an arc shape or an elliptical arc shape with no corners.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a cathode plate for electrolysis, an electrolytic cell, an electrolysis method, and a method for producing nickel. More specifically, the present invention relates to a cathode plate for electrolysis constituting the cathode (negative electrode) of an electrolytic cell widely used in various non-ferrous metal refining processes, an electrolytic cell using this cathode plate, an electrolysis method using the electrolytic cell, and a method for producing nickel using them. [Background technology]

[0002] For example, in the hydrometallurgical process for recovering nickel from sulfides, the raw material nickel matte or nickel-cobalt mixed sulfide is leached with chlorine, impurities are removed from the resulting leachate, and after a purification process in which nickel and cobalt are separated, electrolytic nickel and electrolytic cobalt are produced in an electrolytic process. This hydrometallurgical process includes a copper removal electrolytic process in which excess copper contained in the leachate is removed by electrowinning. In this copper removal electrolytic process, the copper contained in the leachate is precipitated on the cathode in the electrolytic cell.

[0003] In the copper removal electrolysis process carried out in an electrolytic cell, the metallic copper powder precipitated on the surface of the cathode plate is peeled off and recovered by, for example, a rocking mechanism that drops the cathode plate a small distance to apply an impact.

[0004] On the other hand, it is known that during operation of the electrolytic cell, the above-mentioned cathode plate is prone to the formation of gigantic granular or lumpy solids (hereinafter also referred to as "metal lumps" in this specification) consisting of dendrites (branch-like electrodeposits), particularly near the lower end thereof.

[0005] When the cathode plate is dropped a small distance and subjected to an impact as described above, this "metal lump" may come into contact with the anode constituting the electrolytic cell or with the body of the electrolytic cell, and partial damage to the electrolytic cell due to such contact often occurs. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 11-80986 [Patent Document 2] JP 2018-199858 A Summary of the Invention [Problem to be solved by the invention]

[0007] An object of the present invention is to suppress the formation of metal lumps that deposit on a cathode plate that constitutes the cathode of an electrolytic cell, and to prevent partial damage to the electrolytic cell caused by contact with the metal lumps. [Means for solving the problem]

[0008] As a result of extensive research, the inventors discovered that the above-mentioned problem could be solved by making the shape of both corners of the lower side of a cathode plate for electrolysis having a substantially rectangular planar shape into an arc shape, thereby eliminating the corners, and thus completed the present invention.

[0009] (1) A cathode plate for electrolysis, the shape of both corners of the lower side in a plan view being a circular arc or an elliptical arc with no corners.

[0010] (1) The cathode plate for electrolysis can suppress the formation of giant granular or lumpy solids (metal lumps) formed from dendrites on the cathode plate constituting the electrolytic cell, thereby preventing partial damage to the electrolytic cell caused by contact with the metal lumps.

[0011] (2) The cathode plate according to (1), wherein the radius of the circular arc shape or the elliptical arc shape is 10% to 20% of the width of the lower side of the cathode plate.

[0012] The electrolytic cathode plate (2) can more reliably exert the above-mentioned effects provided by the cathode plate (1).

[0013] (3) A combination of a cathode plate and an anode plate for electrolysis, comprising the cathode plate described in (1) or (2) and an anode plate having a height shorter than that of the cathode plate.

[0014] According to the combination of the cathode plate and the anode plate of (3), the generation of the "metal lump" in the cathode plate described in (1) or (2) can be more effectively suppressed. Furthermore, in an existing electrolytic cell, the effect of the invention of (1) or (2) can be enjoyed only by optimizing the combination of the cathode plate and the anode plate to a specific shape combination, without changing the arrangement or size of the structure for suspending the cathode plate and the anode plate (for example, the beam member described below, or the hanger member for hanging the cathode plate and the anode plate from the beam member, etc.).

[0015] (4) An electrolytic cell in which the cathode plate according to (1) or (2) is suspended, and the position of the lower edge of the cathode plate is lower than the position of the lower edge of the anode plate.

[0016] According to the electrolytic cell of (4), in an electrolytic cell in which the cathode plate described in (1) or (2) is installed, the generation of "metal lumps" on the cathode plate can be more effectively suppressed.

[0017] (5) The electrolytic cell according to (4), wherein the difference in height between the position of the lower edge of the cathode plate and the position of the lower edge of the anode plate is 3% or more of the vertical length of the anode plate.

[0018] According to the electrolytic cell of (5), in the electrolytic cell described in (4), the generation of "metal lumps" on the cathode plate can be more reliably suppressed.

[0019] (6) An electrolytic cell according to (4) or (5), further comprising a rocking mechanism for rocking the cathode plate in a direction parallel to the plate surface as a mechanism for separating and dropping the metal deposited on the surface of the cathode plate.

[0020] In the electrolytic cell of (6), it is possible to effectively avoid contact between the "metal mass" and the body of the electrolytic cell, which occurs when the cathode plate is swung to separate and drop the deposited metal, thereby suppressing damage to the electrolytic cell caused by such contact.

[0021] (7) An electrolysis method, comprising depositing a metal on the surface of the cathode plate in the electrolytic cell according to any one of (4) to (6).

[0022] In the electrolysis method of (7), the above-mentioned effects provided by the electrolytic cell of any one of (4) to (6) can be enjoyed, and electrolysis can be carried out efficiently.

[0023] (8) The electrolysis method according to (7), wherein the metal is copper.

[0024] In the electrolysis method (8), it is possible to suppress the formation of granular or lumpy solids (metal lumps) formed from giant dendrites on the cathode plate constituting the electrolytic cell, which occurs particularly notably during the extraction of copper powder.

[0025] (9) A method for producing nickel, comprising a copper removal electrolysis step of removing copper from a copper-containing aqueous nickel chloride solution by the electrolysis method according to (8).

[0026] In the nickel production method of (9), the above-mentioned effects of the electrolysis method described in (8) can be enjoyed, and this can contribute to improving the production efficiency of nickel production. Effect of the Invention

[0027] According to the present invention, it is possible to suppress the formation of metal lumps depositing on the cathode plate constituting the cathode of the electrolytic cell, and to prevent partial damage to the electrolytic cell caused by contact with the metal lumps. [Brief description of the drawings]

[0028] [Figure 1] FIG. 2 is a plan view of a cathode plate for electrolysis according to the present invention. [Diagram 2]FIG. 1 is a cross-sectional view showing the overall configuration of an electrolytic cell according to the present invention. [Diagram 3] FIG. 1 is a plan view of a cathode plate for a conventional electrolysis. [Figure 4] FIG. 1 is a cross-sectional view showing the overall configuration of a conventional electrolytic cell. [Diagram 5] 4 is a diagram illustrating the operation of a rocking mechanism provided in the electrolytic cell of the present invention. [Figure 6] FIG. 1 is an equipment flow diagram showing a configuration of a copper removal electrolysis equipment for performing a nickel hydrometallurgy process, which is an example of an embodiment of the electrolysis method of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0029] Hereinafter, preferred embodiments of the cathode plate for electrolysis, the electrolytic cell comprising the same, and the electrolysis method using them of the present invention will be described.

[0030] <Cathode plate for electrolysis> As shown in Fig. 1, the cathode plate 1 for electrolysis of the present invention has a substantially rectangular shape in plan view (planar shape) like a conventionally known general cathode plate 1B (see Fig. 3). More specifically, the cathode plate 1 is a substantially rectangular plate surrounded by both side edges 13, an upper edge 14, and a lower edge 15, and upper oblique edges 12 are formed at both ends of the upper edge 14, which cross the upper edge 14 and the side edges 13 at an angle. In this specification, the "upper edges" of the cathode plate and the anode plate refer to the vertically upper edges when these plates are used while hanging down in an electrolytic cell. Similarly, the "lower edges" refer to the vertically lower edges when used.

[0031] The cathode plate 1 for electrolysis of the present invention is similar to the conventional cathode plate 1B in that its planar shape is generally rectangular. However, as shown in Fig. 1, the cathode plate 1 for electrolysis of the present invention has both lower corners 11 formed into a circular or elliptical arc shape without corners, which is its main characteristic in terms of shape.

[0032] Here, in conventional cathode plates 1B, the above-mentioned "metal lumps" are often formed starting from the corners of both lower corners 11B. In the cathode plate 1 for electrolysis of the present invention, both lower corners 11 are formed into a cornerless circular or elliptical arc shape, eliminating the angular portions that tend to be the starting points for the formation of "metal lumps," and thus the generation of "metal lumps" in the cathode plate can be significantly suppressed.

[0033] The radius of the circular or elliptical arc shape of both bottom corners 11 of the cathode plate 1 for electrolysis is preferably 10% to 20% of the width of the bottom side 15 of the cathode plate 1. The radius of the elliptical arc shape being 10% to 20% of the width of the bottom side 15 of the cathode plate 1 means an elliptical arc whose minor axis is 10% or more and whose major axis is 20% or less.

[0034] 3 is a diagram showing the shape (planar shape) of a conventionally known general cathode plate 1B for electrolysis. As shown in the figure, a general cathode plate 1B for electrolysis is also a substantially rectangular plate material surrounded by both side edges 13, both upper oblique edges 12, an upper edge 14, and a lower edge 15. However, in the conventionally known general cathode plate 1B for electrolysis, the shape of both lower corners 11B is an angle having a right angle or an angle close to that, as shown in the figure.

[0035] If the lower corners 11B of the cathode plate 1B for electrolysis, which are immersed in the electrolyte in the electrolytic cell, were to be shaped by removing the corners, the surface area of ​​the cathode plate, i.e., the area on which metal is electrolytically deposited, would be reduced. This would result in an increase in voltage due to an increase in current density, or a decrease in the efficiency of metal recovery due to a decrease in the area of ​​the cathode plate. Furthermore, shaping the cathode plate would require extra costs and labor in electrolysis operations that handle a large number of cathode plates. Therefore, in the past, the lower corners of the cathode plate for electrolysis were not processed to remove the corners of the plate material, and were made into a square shape as shown in FIG. 3.

[0036] <Electrolytic cell> By constructing a cathode (negative electrode) using the cathode plate 1 described in detail above, an existing electrolytic cell can be made into an electrolytic cell that can enjoy the effects of the present invention. As shown in Figures 2 and 5, in the electrolytic cell 10 of the present invention, similar to a conventionally known general electrolytic cell 10B (see Figure 4), the cathode plate 1 is suspended so that most of it is immersed in the electrolyte inside the electrolytic cell 10 in a state where it is joined to a rod-shaped beam member 17 (see Figure 5) via a plurality of bolt holes 16 formed in the vicinity of the upper side 14.

[0037] In the electrolytic cell 10, as shown in FIG. 2, the position c of the lower side 15 of the hanging cathode plate 1 0 The lower edge of the anode plate 2 is suspended at position a. 0 It is preferred that all of the cathode plates 1 and anode plates 2 are suspended so that the height of the cathode plates 1 and anode plates 2 is lower than the

[0038] This change in the relative position of the cathode plate and the anode plate is the same as the position of the cathode and the anode in the conventional electrolytic cell 10B, i.e., the position c of the lower side 15 of the hanging cathode plate 1B. 0 The lower edge of the anode plate 2 is suspended at position a. 0 This is based on the finding that when all of the cathode plates 1B and anode plates 2 are suspended so that the vertical axis of the cathode plates 1B and the anode plates 2 is higher than the vertical axis of the cathode plates 1B (see FIG. 4), a "metal lump" is likely to form, particularly around the lower edge 15 of the cathode plate 1B, where the current density is likely to become excessive.

[0039] Also, the position c of the lower side 15 of the cathode plate 1 in the electrolytic cell 10 0 and the height a of the lower edge of the anode plate 2 0It is more preferable that the difference is 3% or more and 10% or less of the vertical length of the anode plate 2. By making the above ratio 3% or more, it becomes easier to fully enjoy the effect of suppressing the generation of "metal lumps". However, if this ratio exceeds 10%, the effect of suppressing the generation of "metal lumps" does not change, and the cathode plate 1 is unnecessarily lengthened, which deteriorates the efficiency of the equipment and increases the cost. In addition, in the case of an electrolytic cell 10 with a quadrangular pyramid-shaped lower part as shown in FIG. 2 in order to collect the metal powder dropped from the cathode plate 1, if the cathode plate 1 is lengthened, there is a risk that the lower corners 11 of the cathode plate 1 may come into contact with the main body of the electrolytic cell 10 when the cathode plate 1 is slightly dropped. In such a case, the object of the present invention of preventing partial damage to the anode and the electrolytic cell may not be achieved.

[0040] The electrolytic cell 10 can be configured, for example, by adjusting the positions of the cathode plate 1 and the anode plate 2, which have no corners at their lower corners 11, respectively, to optimize the positional relationship between the lower ends of the respective plates.

[0041] Alternatively, the electrolytic cell 10 can be constructed by combining a cathode plate 1 having no corners at both corners 11 of its lower side with an anode plate 2 having a shorter height than the cathode plate 1, thus forming a "combination of a cathode plate 1 and an anode plate 2."

[0042] In the "combination of the cathode plate 1 and the anode plate 2", the ratio of the height of the cathode plate 1 to the height of the anode plate 2 is the ratio of the height of the lower side 15 of the cathode plate 1 to the height of the anode plate 2 when the cathode plate 1 is suspended in the electrolytic cell 10. 0 and the height a of the lower edge of the anode plate 2 0 It is preferable to design and form the anode plate 2 so that the difference is 3% to 10% of the vertical length of the anode plate 2.

[0043] Here, FIG. 4 is a cross-sectional view showing the overall configuration of a conventional electrolytic cell 10B configured using the above-mentioned conventional cathode plate 1B. As shown in the figure, in the conventional electrolytic cell 10B, the position c of the lower side of the hanging cathode plate 1B 0The lower edge of the anode plate 2 is suspended at position a. 0 or at least the position a of the lower edge of the anode plate 2 0 The cathode plate 1B and the anode plate 2 are hung down so that the height of the cathode plate 1B is the same as that of the anode plate 2. This is based on the idea that by positioning the cathode plate 1B and the anode plate 2 in this way, it is easier to electrodeposit a larger amount of metal over the entire surface, including the lower end of the cathode plate 1B. In contrast, in the electrolytic cell 10 of the present invention, contrary to the above idea, the position c of the lower side 15 of the cathode plate 1 is deliberately 0 is the position a of the lower edge of the anode plate 2 0 In this way, the electrolytic cell 10 of the present invention prevents the current density from becoming excessive around the lower edge of the cathode plate 1, and as a result, the generation of a "metal lump" around the lower edge of the cathode plate 1 is suppressed.

[0044] Moreover, the electrolytic cell 10 is preferably provided with a swinging mechanism for swinging the cathode plate 1 in a direction parallel to the plate surface as a mechanism for peeling off and dropping the metal deposited on the surface of the cathode plate 1. The manner of swinging by this swinging mechanism is not limited to a specific movement, so long as the cathode plate 1 moves in a direction parallel to its plate surface and, as a result of this movement, it is possible to give an impact to the surface of the cathode plate 1 to an extent that promotes the peeling off and dropping of the metal.

[0045] A preferred specific embodiment of the above-mentioned movement that applies an impact strong enough to promote the peeling and falling of metal from the surface of the cathode plate 1 is a movement in which the beam end of the cathode plate 1 that is not connected to the busbar drops suddenly a very small distance. The rocking mechanism shown in FIG. 5 is an example of a preferred embodiment of a rocking mechanism that can move the cathode plate 1 in such a manner. In this rocking mechanism, the vicinity of one end of the beam member 17 is used as a fulcrum 171, and the other end is used as a force point 172 for rotating the beam member 17 in the d direction, and the cathode plate 1 is dropped suddenly a very small distance. This movement can apply an impact of sufficient strength to the surface of the cathode plate 1 to promote the peeling and falling of metal.

[0046] In the conventional electrolytic cell 10B, "metal lumps" were easily generated starting from the corners of both lower corners 11 of the cathode plate 1B, and thus the generated "metal lumps" often contacted various parts of the electrolytic cell 10B during the oscillation of the cathode plate 1B, causing partial damage to the electrolytic cell 10B. In contrast, according to the electrolytic cell 10 of the present invention, by changing the shape of both lower corners 11 of the cathode plate 1 to a cornerless shape, and more preferably by changing the positional relationship between the cathode plate 1 and the anode plate 2 to the above-mentioned positional relationship different from that of the conventional one, it is possible to suppress the generation of "metal lumps" starting from the corners of both lower corners 11B, and to significantly reduce the risk of the above-mentioned damage during the oscillation of the cathode plate 1B.

[0047] <Electrolysis method> In one preferred embodiment, the "electrolysis method" of the present invention, which can be suitably carried out using the electrolytic cell 10, is used in a "copper removal electrolysis step", which is one step in a nickel production method in which copper is removed by electrowinning from a copper-containing nickel chloride aqueous solution (copper-containing nickel chloride aqueous solution). Hereinafter, an embodiment of the "electrolysis method" of the present invention will be described in which an electrolytic treatment is carried out in the above-mentioned "copper removal electrolysis step" to deposit copper powder on the cathode plate of the electrolytic cell.

[0048] [Copper removal electrolytic process] 6, the copper removal electrolysis step, which is one step of the nickel smelting process, is carried out in a copper removal electrolysis facility 500 including a copper removal electrolysis cell 100, a copper removal repulping cell 200, and a solid-liquid separator 300, according to the flow shown in the figure. In carrying out the copper removal electrolysis step of the present invention, the electrolysis cell 10 described in detail above is used as the copper removal electrolysis cell 100.

[0049] The electrolytic solution supplied to the copper removal electrolytic cell 100 is a copper-containing nickel chloride aqueous solution, with a nickel concentration of about 200 g / L and a copper concentration of 25 to 60 g / L. In the copper removal electrolytic cell 100, copper powder is deposited on the cathode plate 1 constituting the cathode by electrowinning. After copper is removed from the electrolytic solution in the copper removal electrolytic cell 100, the electrolytic solution overflows from the copper removal electrolytic cell 100 and is discharged as a post-electrolysis solution. Meanwhile, the copper powder electrodeposited on the cathode plate 1 is caused to fall off from the surface of the cathode plate 1 by rocking the cathode plate 1 by the above-mentioned rocking mechanism. When a predetermined amount of copper powder is accumulated at the bottom of the copper removal electrolytic cell 100, the copper powder is extracted from the bottom of the electrolytic cell 10. The extracted copper powder has the electrolytic solution attached thereto and is in a liquid-containing state (slurry state). The bottom of the copper removal electrolytic bath 100 and the copper removal repulping bath 200 are connected by a flow path, and the discharged copper powder in a liquid state is supplied to the copper removal repulping bath 200 through the flow path.

[0050] The copper-removal repulping tank 200 is equipped with an agitator, in which the copper powder and repulping water are mixed. The slurry discharged from the repulping tank is fed to a solid-liquid separator 300, where it is separated into copper powder and filtrate. The copper powder recovered by this process is discharged outside the system, and the copper-removal filtrate from which the copper powder has been separated is sent via the copper-removal filtrate tank 400 to be recycled to the upstream process.

[0051] In the "copper removal electrolysis step", copper contained in the copper-containing aqueous nickel chloride solution is precipitated on the cathode in the copper removal electrolysis bath 100 (electrolysis bath 10) by the reactions of the following chemical formulas (1) and (2). Cu + +e - =Cu 0 (1) Cu 2+ +2e - =Cu0 (2) In this case, if the copper-containing nickel chloride aqueous solution contains a large amount of divalent copper ions, the copper powder (metallic copper) that was once precipitated on the cathode and dropped off will be redissolved by the reaction of the following chemical formula (3). Therefore, if the copper-containing nickel chloride aqueous solution contains a large amount of divalent copper ions, the current efficiency (copper powder recovery rate) will decrease. In addition, since chlorine gas is generated at the anode, a small amount of chlorine gas that has been back-diffused from the anode chamber and dissolved in the electrolyte will redissolve metallic copper by the reaction of the following chemical formula (4), which will also decrease the current efficiency, i.e., the copper powder recovery rate. Therefore, it is desirable to separate the precipitated metallic copper into solid and liquid in as short a time as possible. Cu 0 +Cu 2+ =2Cu + (3) Cu 0 +Cl 2 =CuCl 2 (4) The current efficiency is defined by the following formula. Current efficiency [%] = [produced copper powder x copper grade [%]] / [Cu 2+ Electrochemical equivalent × current application time × current application

[0052] For example, in the "copper removal electrolysis process" shown in FIG. 6, by configuring the copper removal electrolysis cell 100 with the electrolysis cell 10 of the present invention, it is possible to minimize the risk of equipment damage resulting from contact between the copper powder (metallic copper) deposited on the cathode plate 1 and each part of the electrolysis cell 10, which leads to temporary operation stoppage. Furthermore, according to the present invention, it is possible to prevent re-dissolution of metallic copper due to the reactions of the above chemical formulas (3) and (4) that proceed during temporary operation stoppage due to various troubles caused by the generation of "metal lump", and to maintain high current efficiency in the above "copper removal electrolysis process". The above-mentioned various troubles include not only partial damage to the electrolysis cell, but also, for example, damage to the anode due to the occurrence of a short circuit originating from the above-mentioned "metal lump", damage to the electrolysis cell due to the fall of the "metal lump", and blockage of the removal nozzle of the electrolysis cell. [Explanation of symbols]

[0053] 1. Cathode plate for electrolysis 11 Bottom corners 12 Upper hypotenuse 13 side 14 Top 15 Bottom 16 Bolt holes 17 Beam member 171 Fulcrum 172 Emphasis 2. Anode plate for electrolysis 10 Electrolytic cell 100 Copper removal electrolyzer 200 Copper removal repulping tank 300 Solid-liquid separation equipment 400 Decopper filtrate tank 500 Copper removal electrolysis equipment

Claims

1. A cathode plate for electrolysis used in an electrolytic cell having a rocking mechanism for rocking the cathode plate in a direction parallel to the plate surface as a mechanism for separating and dropping metal deposited on the surface of the cathode plate, comprising: The shape of both corners of the lower side in a plan view is a circular arc shape or an elliptical arc shape without any corners, The radius of the circular arc shape or the elliptical arc shape is 10% to 20% of the width of the lower side of the cathode plate. Cathode plate for electrolysis.

2. The metal deposited on the surface of the cathode plate is copper, and the metal is used in a copper removal electrolytic treatment for removing copper from a copper-containing nickel chloride aqueous solution.

2. A cathode plate for electrolysis according to claim 1.

3. A combination of a cathode plate and an anode plate for electrolysis used in an electrolytic cell having a rocking mechanism for rocking the cathode plate in a direction parallel to the plate surface as a mechanism for peeling off and dropping metal deposited on the surface of the cathode plate, comprising: A cathode plate for electrolysis according to claim 1 or 2; and an anode plate having a height shorter than that of the cathode plate for electrolysis. A combination of a cathode and an anode plate.

4. An electrolytic cell having a rocking mechanism for rocking the cathode plate in a direction parallel to the plate surface as a mechanism for peeling off and dropping the metal deposited on the surface of the cathode plate, The electrolytic cathode plate according to claim 1 is suspended, The position of the lower side of the cathode plate for electrolysis is lower than the position of the lower side of the anode plate. electrolytic cell.

5. An electrolytic cell having a rocking mechanism for rocking the cathode plate in a direction parallel to the plate surface as a mechanism for peeling off and dropping the metal deposited on the surface of the cathode plate, The cathode plate for electrolysis according to claim 2 is suspended, The position of the lower side of the cathode plate for electrolysis is lower than the position of the lower side of the anode plate. electrolytic cell.

6. The difference in height between the position of the lower side of the cathode plate for electrolysis and the position of the lower side of the anode plate is 3% or more of the vertical length of the anode plate; 5. An electrolytic cell according to claim 4.

7. 7. A method for electrolysis, comprising depositing a metal on the surface of the cathode plate for electrolysis in an electrolytic cell as claimed in claim 4 or 6.

8. 8. The electrolytic process of claim 7, wherein the metal is copper.

9. The copper removal electrolysis step includes removing copper from the copper-containing nickel chloride aqueous solution by the electrolysis method according to claim 8. How nickel is produced.

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