JP6996277B2 - Electrorefining method for non-ferrous metals - Google Patents

Description

The present invention is a method for electrolytic refining of non-ferrous metals such as copper and nickel, and in particular, a target metal such as copper and nickel dissolved in the electrolytic solution by energizing between an anode and a cathode immersed in the electrolytic solution. The present invention relates to an electrolytic refining method for non-ferrous metals, which is electrodeposited on the cathode surface.

Electrorefining of non-ferrous metals is widely known as a method for smelting non-ferrous metals such as copper (Cu) and nickel (Ni). In the electrolytic refining of non-ferrous metals, the target metal (for smelting) such as copper and nickel dissolved in the electrolytic solution is energized between the anode (anodic plate) and the cathode (cathode plate) immersed in the electrolytic solution. By electrolyzing the target metal) onto the surface of the cathode, it is possible to obtain a high-purity target metal.

The electrorefining method for non-ferrous metals is classified into an electrolytic refining method in which the target metal in the electrolytic solution is supplied from the anode and an electrolytic sampling method in which the target metal is separately dissolved in the electrolytic solution. Of these, in the electrolytic purification method in which the target metal is supplied from the anode, the target metal anode made of the target metal before purification is used as the anode, but in the electrolytic sampling method, an insoluble anode made of an insoluble electrode is used as the anode.

Further, the electrolytic refining method for non-ferrous metals is classified into a permanent cathode method in which the target metal after electrodeposition is stripped from the cathode and a seed plate electrolysis method in which the electrodeposited cathode is used as a product. In the permanent cathode method, a base plate such as titanium or stainless steel is used for the cathode before electrodeposition, but in the seed plate electrolysis method, the seed plate is made by processing the target metal stripped by the permanent cathode method into a rectangular plate shape. Is used.

For example, in the copper electrolytic purification method using the seed plate electrolysis method, generally, a blister copper anode and a pure copper cathode are alternately suspended in an electrolytic cell and energized in an electrolytic bath. Will be.

As for the seed plate used for the cathode, the anode made of blister copper and the cathode, which is a master plate made of stainless steel, are alternately suspended in the electrolytic cell, and energization is performed in the electrolytic bath, and the target metal (copper, etc.) is attached to the master plate. The electrodeposited material was thinly electrodeposited, and the electrodeposited material was peeled off from the main plate and processed into a rectangular plate shape. To use this seed plate as a cathode for electrolytic refining, another seed plate obtained in the same manner was cut to obtain a ribbon formed in a loop shape, and this ribbon was attached to the upper part of the seed plate as a hanging hand. The seed plate is suspended from the cathode beam (conductive rod) via a ribbon. In the cathode produced in this way, the cathode beam is spread over the upper portions of the opposite side walls of the electrolytic cell, so that most of the lower side of the rectangular plate-shaped portion of the seed plate constituting the cathode is immersed in the electrolytic solution in the electrolytic cell.

On the other hand, the anode is provided with ear portions (support portions) having a shape protruding in the horizontal direction at both upper corners of a rectangular plate shape, and is manufactured by casting or the like. By supporting the selvage portion by the upper portions of the opposite side walls of the electrolytic cell, most of the lower side of the rectangular plate-shaped portion constituting the anode is immersed in the electrolytic solution in the electrolytic cell.

In the permanent cathode method, a cathode is manufactured using a base plate made of titanium or stainless steel instead of a seed plate, and the base plate can be fixed to the cathode beam by welding or the like without using a ribbon. The method of dipping the cathode, the shape of the anode, the method of dipping the anode, etc. are the same as those of the seed plate electrolysis method.

By the way, in order to energize a large number of anodes and cathodes at one time and efficiently perform electrolytic refining, a plurality of insoluble anodes or target metal anodes and a plurality of mother plates or a plurality of mother plates are provided in each of a plurality of electrolytic cells arranged in a row. The seed plates are arranged alternately and parallel to each other, and energization is performed at the same time. For example, in the copper electrolytic purification method, 30 anodes connected in parallel and 29 cathodes connected in parallel are alternately and parallel to each other in each of a plurality of electrolytic cells arranged in a row. After immersion, the plurality of anodes and the plurality of cathodes are connected in series between two adjacent electrolytic cells. The specific number of cathodes and anodes to be installed is arbitrarily set according to the amount of electrodeposition of the target metal, the size of the electrolytic cell, and the like.

In order to realize the electrical connection of the plurality of cathodes and the plurality of anodes as described above, a bus bar made of a conductor is installed on the electrolytic cell. The bus bar is usually placed on the upper end surface of a partition wall or a partition plate located between adjacent electrolytic cells among the wall portions constituting the electrolytic cell, and is placed from one end to the other along the electrolytic cell. It is composed of a long conductive member that extends to.

For example, as described in Japanese Patent Application Laid-Open No. 10-245690, a plurality of units charged in one side of an electrolytic tank and in one of the electrolytic tanks located on the side of the one side. 1 The support part of the electrode plate (for example, the end of the cathode beam that supports the cathode) is electrically connected, and the other side of the electrolytic tank is connected to the other side of the electrolytic tank. The support portion (for example, the ear portion of the anode) of a plurality of second electrode plates, which is the opposite electrode to the first electrode plate, is electrically connected to each other, and is between the two electrolytic tanks. The support part of the plurality of second electrode plates in one electrolytic tank and the support part of the plurality of first electrode plates in the other electrolytic tank are electrically connected via the bus bar on the partition wall located at. ing.

With such a configuration, it becomes possible to efficiently energize a plurality of cathodes and a plurality of anodes at one time. By this energization, the target metal is electrodeposited on the surfaces of a plurality of cathodes to a predetermined thickness, and then the cathode is pulled up from the electrolytic solution in the electrolytic cell to recover the electrodeposited target metal and again before electrodeposition. Immersing the cathode in the electrolytic cell and energizing it is repeated.

For example, in the seed plate electrolysis method, after electrolysis is performed by energizing between the anode immersed in the electrolytic solution and the cathode of the seed plate, the electrodeposited cathode is pulled up from the electrolytic solution and the cathode beam is extracted. , Shipped as a product with the ribbon attached, a new seed plate with a ribbon is hung on the cathode beam, immersed in the electrolytic solution as a cathode, and energized between the cathode and the anode via the electrolytic solution. The process is repeated.

On the other hand, in the permanent cathode method, after electrolytic refining is performed by energizing between the anode immersed in the electrolytic solution and the cathode of the seed plate, the electrodeposited cathode is pulled up from the electrolytic solution and the target metal is used from the mother plate. A certain electrodeposition is peeled off and shipped, and the mother plate is supported in the electrolytic solution by a cathode beam, so that the electrodeposition is immersed in the electrolytic solution, and the process of energizing between the cathode and the anode via the electrolytic solution is repeated.

Japanese Unexamined Patent Publication No. 2000-345380 describes a cathode beam composed of a rectangular parallelepiped crossbar made of pure copper as a cathode beam used in electrolytic refining including a seed plate electrolysis method and a permanent cathode method. Further, Japanese Patent Application Laid-Open No. 01-319695 describes a cathode beam composed of an iron core rod and a coating layer made of copper covering the surface of the core rod. A cathode beam composed of such a core rod and a copper coating layer can secure high strength and can keep costs low as compared with a cathode beam made of pure copper.

By the way, in the configuration in which the cathode and the anode are electrically connected using the bus bar, the connection state of the electrical connection portion (contact portion) between the bus bar and the ear portion of the anode, and the electrical connection portion (contact portion) between the bus bar and the cathode beam. ) Connection state greatly affects the efficiency of electrolytic refining. However, in electrolytic refining, the cathode is repeatedly pulled up and charged with respect to the electrolytic solution, so that the electrolytic solution tends to scatter on the cathode. A film of substances, sulfates, chlorides, etc. is formed, and power consumption increases.

Furthermore, the position on the cathode beam where the film is formed and the thickness of the film vary, and the current decreases at the electrical connection part where the film is formed, whereas the electrical connection part where the film is not formed is formed. Then, the current increases, and the current flowing between each cathode and the anode may vary.

Due to such variations in current, local current concentration occurs, so that the electrodeposition has a dendritic shape, a short circuit occurs, and the current is wasted. In addition, the anode that is charged so as to sandwich the cathode where the current is concentrated causes excessive wear, and the part of the worn anode that is located below the electrolyte surface and is immersed in the electrolyte. However, it may fall into the electrolytic cell, or it may break from the central portion of the anode due to wear and fall into the electrolytic cell. When a part of the anode comes off, a part of the removed anode breaks through the bottom of the electrolytic cell and causes the electrolyte to flow out, or a short circuit occurs when the surrounding cathode is pushed and moved to contact another anode. There is a possibility, and it takes time to monitor the presence or absence of dropping and remove a part of the falling anode.

In addition, the area of the available anode decreases due to the drop into the tank, and the current density increases. Therefore, if energization is continued as it is, the voltage rises, causing deterioration of the product appearance such as granular electrodeposition. there is a possibility.

As described above, the critical current amount in the electrolytic operation is determined by one anode, which has the largest amount of current due to the current distribution and is severely worn, among the plurality of anodes. From this, the non-uniformity of the current distribution limits the amount of current, and a large amount of used anode remains. Since the remaining anode is repeated in the smelting process (casting furnace, etc.) as anode scrap, transportation costs and fuel costs increase.

In addition, the increased current at the electrical connection can overheat and deform the cathode beam. Deformation of the cathode beam also requires replacement work, which reduces the production efficiency of electrolytic refining.

In order to prevent such a problem caused by film formation, Japanese Patent Application Laid-Open No. 2000-345380 and Japanese Patent Application Laid-Open No. 2013-019018 propose to perform a regeneration operation for polishing the surface of the cathode beam.

Further, Japanese Patent Application Laid-Open No. 2009-019018 proposes that the thickness of the coating layer of the cathode beam is stratified in a narrow range and charged into one electrolytic cell.

Japanese Patent Application Laid-Open No. 10-245690 Japanese Unexamined Patent Publication No. 01-319695 Japanese Unexamined Patent Publication No. 2000-345380 Japanese Unexamined Patent Publication No. 2013-0190118 Japanese Unexamined Patent Publication No. 2009-0190118

However, in the methods and devices disclosed in JP-A-2000-345380 and JP-A-2013-0190118, the amount of polishing required for removing the film is unknown, and excess or deficiency of polishing occurs. As a result, the electrical resistance varies greatly from cathode beam to cathode beam, resulting in local current concentration. In order to prevent local current concentration, it is necessary to identify a cathode beam with a large electrical resistance, and the electrical resistance of the identified cathode beam is increased by any of the contradictory factors such as residual film or thinning of the cathode beam. It is necessary to judge whether it is.

Further, in the method disclosed in Japanese Patent Application Laid-Open No. 2009-0190118, the thickness of any part of the cathode beam in which the thickness is uneven due to repeated use due to polishing or the like is measured. It is unclear if this is desirable. Therefore, when sorting is performed based on the thickness of the cathode beam, it becomes necessary to measure the thickness of several places of the cathode beam, and there is a problem that the work load increases.

The present invention has been made in view of the problems of the prior art, and is caused by an increase in the electrical resistance of the contact portion of the cathode beam by processing the cathode beam used in the electrolytic refining method of copper or nickel. The purpose is to prevent non-uniformity of the current distribution in the electrolytic cell.

The present inventors have investigated the cathode beam from various viewpoints and found that the variation in electrical resistance is greatly affected by the surface roughness of the electrical connection with the bus bar.

Then, the positional relationship between the cathode beam and the polishing tool was also examined, and a polishing means capable of reducing the surface roughness and the electrical resistance and its variation was found.

Further, when the cathode beam is stratified, the cathode beam can be stratified more accurately and easily by stratifying by the weight of the cathode beam instead of the thickness of the coating layer of the cathode beam, and thus the cathode current. It was found that the distribution can be made uniform.

The present invention has been completed based on these findings.

That is, the method of electrolytic refining of a non-ferrous metal according to one aspect of the present invention includes a polishing step of polishing a plurality of cathode beams that are repeatedly used to smooth the surface of the plurality of cathode beams. In particular, in the method of electrolytic refining of a non-ferrous metal of the present invention, in the polishing step, a process of polishing each of the plurality of cathode beams in the major axis direction and a process of polishing each of the plurality of cathode beams in the minor axis direction. It is characterized by having.

Further, in the electrolytic refining method for non-ferrous metal according to one aspect of the present invention, after the polishing step, a part or all of the plurality of cathode beams is selected, and the surface roughness (Ra) of the electrical connection portion thereof is measured. , The plurality of cathode beams are sorted into a lot having a large average value of the surface roughness (Ra) or the surface roughness (Ra) and a lot having a small average value, and the surface roughness (Ra) or the surface roughness (Ra). It is possible to provide a step of installing the plurality of cathode beams belonging to a lot having a small average value of Ra) in an electrolytic tank and energizing them.

In this case, as a lot having a small surface roughness (Ra), a cathode beam having a surface roughness (Ra) of 5.0 μm or less is selected from the plurality of cathode beams, or the surface roughness (Ra) is selected. It is preferable to select a lot composed of the plurality of card beams having an average value of Ra) of 5.0 μm or less.

On the other hand, among the plurality of cathode beams, the cathode beam having the surface roughness (Ra) of more than 5.0 μm or the plurality of cathode beams having the average value of the surface roughness (Ra) of more than 5.0 μm. It is preferable that the lot is subjected to the polishing step again.

Alternatively, the method of electrolytic refining a non-ferrous metal according to one aspect of the present invention selects a part or all of the plurality of cathode beams after the polishing step and determines the surface roughness (Ra) of the electrical connection portion thereof. The lot to which the plurality of cathode beams belong is sorted into a lot having a large standard deviation of the surface roughness (Ra) and a lot having a small standard deviation of the surface roughness (Ra), and the lot belongs to the lot having a small standard deviation of the surface roughness (Ra). It is possible to provide a step of installing a plurality of cathode beams in an electrolytic tank and energizing them.

In this case, it is preferable to select a lot having a standard deviation of the surface roughness (Ra) of 2.5 μm or less as a lot having a small standard deviation of the surface roughness (Ra).

On the other hand, it is preferable that the plurality of cathode beams belonging to a lot having a standard deviation of the surface roughness (Ra) of more than 2.5 μm are subjected to the polishing step again.

In another aspect of the present invention, the method for electrolytic refining of a non-ferrous metal stratifies a plurality of cathode beams that are repeatedly used according to the respective weights of the plurality of cathode beams, and the plurality of cathode beams are stratified for each lot stratified by the weight. It is characterized by having a step of installing the cathode beam of the above in an electrolytic cell and energizing it.

In the stratification by weight, the relationship between the average unit weight (Ave) and the unit weight standard deviation (σ) of the plurality of cathode beams belonging to the lot stratified by the weight is less than σ / Ave = 0.1. It is preferable to do so.

The unit weight of the cathode beam means the weight per cathode beam.

Further, it is preferable that the stratification by weight is performed after the polishing step in one aspect of the present invention.

Any aspect of the present invention can be widely applied to a known cathode beam, but is suitable for a copper electrolytic refining method using a cathode beam composed of an iron core and a copper coating layer provided on the surface of the iron core. Applicable.

According to the present invention, the cathode beam used in the electrolytic refining method for non-ferrous metals such as copper and nickel is appropriately processed, and the current value distributed to a plurality of cathode beams used for electrolytic refining arranged in the same tank. Is made uniform. As a result, the amount of electrodeposition to each cathode and the weight variation of the anodes arranged so as to sandwich each cathode can be made uniform, and the anode scrap can be reduced.

As described above, according to the present invention, the energizing current can be appropriately increased, and the productivity of the non-ferrous metal electrolytic refining method can be remarkably improved.

FIG. 1 is a flowchart showing an electrolytic refining process according to an embodiment of the present invention. FIG. 2 is a schematic diagram of a cathode used in the seed plate electrolysis method. FIG. 3 is a schematic diagram of the cathode used in the permanent cathode method. FIG. 4 is a schematic view showing the polishing direction of the cathode beam.

As a result of careful study on each resistance value that determines the current value flowing through the cathode and the current flowing through each cathode in the electrolytic cell, the present inventors have found that the variation in the electrical resistance of each cathode beam is found in the electrolytic cell. It was found that it is the main cause of the non-uniformity of the current distribution within.

Further, in particular, the variation in the contact resistance of the cathode beam with the busbar is directly linked to the variation in the current distribution in the electrolytic cell, and the variation in the contact resistance is the electrical contact of each cathode beam with the busbar. It was found that the surface roughness of the part is affected.

The present invention has been completed based on these findings.

The present invention is suitably applicable to the cathode and the cathode beam having the structure shown in FIG. 2 or FIG. The cathode is, for example, detachably attached to the cathode beam 3 via the target metal ribbon 2 on the target metal seed plate 1 as shown in FIG. 2, or as shown in FIG. 3, stainless steel. It is configured by permanently attaching a base plate 1 made of stainless steel to the cathode beam 3.

One aspect of the present invention relates to a method for electrolytic refining of a non-ferrous metal, comprising a polishing step of polishing a plurality of cathode beams that are repeatedly used to smooth the surface of the plurality of cathode beams. In particular, in the method of electrolytic refining of a non-ferrous metal according to the first aspect of the present invention, the polishing step performs a process of polishing each of the plurality of cathode beams in the long axis direction and a process of polishing each of the plurality of cathode beams in the short axis. It is characterized by being provided with a process of polishing in a direction.

Depending on the shape of the polishing tool, the surface of the cathode beam is polished from different angles by performing both the process of polishing the cathode beam in the long axis direction and the process of polishing the cathode beam in the short axis direction. It is possible to eliminate polishing omissions and to form a finely polished surface with few grooves. Even if a groove is formed on the polished surface of the cathode beam, the cathode beam and the bus bar not only come into contact with each other at the two ridges sandwiching the groove, but also come into contact with each other at four or more ridges surrounding the groove from all four sides. The resistance can be reduced. It does not matter which of the major axis direction and the minor axis direction is polished first.

The polishing tool used in the polishing step in the present invention is not limited as long as the variation in the surface roughness of the electrical contact portion of the cathode beam can be reduced, and any known polishing tool can be used. .. As an example, Scotch-Brite ™ industrial pad 7440 manufactured by 3M Japan Ltd. can be mentioned.

As shown in FIG. 1, in order to polish the surface of the cathode beam to a necessary and sufficient degree, a part or all of the cathode beam after the polishing step is selected and the surface roughness of the electrical connection portion is measured. It is desirable to judge whether or not it can be used in an electrolytic cell based on the measurement results. Cathode beams that are not desirable for use in the electrolytic cell are either subjected to the polishing process again or discarded. By selecting the cathode beam in this way, it is possible to efficiently exclude the cathode beam having a high resistance value, which affects the non-uniformity of the current distribution in the electrolytic cell, and to achieve more uniform and efficient energization. Is possible.

As the surface roughness, a Ra value based on JIS B0031: 2003 can be used, and the surface roughness can be measured by a known means such as a roughness measuring instrument.

More specifically, it is preferable that the cathode beam having a surface roughness (Ra) of 5.0 μm or less is sorted into lots having a small surface roughness (Ra) and used in an electrolytic cell.

That is, the cathode beams polished by the same polishing method have almost the same surface roughness (Ra), and the cathode beams having the same surface roughness (Ra) have the same electric resistance value when used under the same conditions. This is to show. Therefore, by sorting the cathode beams based on the surface roughness (Ra), the electrical resistance values of the cathode beams belonging to each lot after sorting can be made substantially the same. When the cathode beam divided into lots is installed in the electrolytic cell, the variation in resistance value becomes small among a plurality of cathode beams in the lot, and it becomes possible to avoid local current concentration. In particular, a cathode beam having a small surface roughness (Ra) has a small resistance value when installed in an electrolytic cell, so that power consumption can be suppressed. Therefore, it is preferable to select a lot to which the cathode beam having a small surface roughness (Ra) belongs, install it in an electrolytic cell, and energize it.

Specifically, in order to make the electrical resistance low without excessive polishing, a cathode beam having a surface roughness (Ra) of 5.0 μm or less is selected for a lot having a small surface roughness (Ra). It is preferable to do so. The surface roughness (Ra) in this case is preferably 4.5 μm or less. The lower limit of the surface roughness (Ra) is not limited, but in the conventional polishing means used for polishing the cathode beam, the lower limit is about 3.0 μm.

The surface roughness (Ra) of this cathode beam is evaluated for each cathode beam, and the evaluation result is used to select a cathode beam to be distributed to a specific lot, a cathode beam to be re-polished, a cathode beam to be discarded, and the like. It is possible. That is, when measuring the surface roughness (Ra) of all the cathode beams, the cathode beams having a surface roughness (Ra) of 5.0 μm or less are selected, and the plurality of cathode beams selected in this way are used. , It is possible to form a lot having a small surface roughness (Ra). Alternatively, it is also possible to evaluate each lot and use the evaluation result to select a lot to be re-polished, a lot to be discarded, and the like. That is, for example, when a part or all of the cathode beam is taken out and the surface roughness (Ra) is measured, the lot to which the cathode beam having the surface roughness (Ra) of 5.0 μm or less belongs is selected as the surface roughness. It is a small lot of (Ra).

In the case of evaluation for each lot, it is also possible to use the average value of the measured surface roughness (Ra) of the cathode beam for the evaluation. In this case, as a lot having a small surface roughness (Ra), a lot consisting of a plurality of card beams having an average surface roughness (Ra) of 5.0 μm or less is selected. On the other hand, a lot consisting of a plurality of cathode beams having an average surface roughness (Ra) of more than 5.0 μm is subjected to the polishing step again or discarded depending on the degree of surface roughness (Ra).

Instead of evaluating by the average value of the surface roughness (Ra), or in addition to the evaluation by the surface roughness (Ra), the standard deviation (σ) of the surface roughness (Ra) can be used. Specifically, a cathode beam having a small standard deviation (σ) of surface roughness (Ra) may be sorted into lots having a small standard deviation (σ) of surface roughness (Ra) and used in an electrolytic cell. preferable. Cathode beam groups with a small standard deviation (σ) of surface roughness (Ra) have almost the same surface roughness (Ra), so when installed in an electrolytic cell and energized, they show almost the same electrical resistance value and are localized. The current concentration can be avoided. Therefore, it is possible to select a lot to which the cathode beam having a small standard deviation (σ) of surface roughness (Ra) belongs and install it in an electrolytic cell to energize.

Specifically, in order to suppress the variation in electrical resistance without excessive polishing, the standard deviation (σ) of the surface roughness (Ra) is small for lots with a small standard deviation (σ) of the surface roughness (Ra). ) Is preferably 2.5 μm or less. The standard deviation (σ) of the surface roughness (Ra) in this case is preferably 1.5 μm or less. The lower limit of the standard deviation (σ) of the surface roughness (Ra) is not limited, but in the conventional polishing means used for polishing the cathode beam, the lower limit is about 0.5 μm.

Similarly, a plurality of cathode beams belonging to lots in which the standard deviation (σ) of the surface roughness (Ra) exceeds 2.5 μm are divided into lots according to the surface roughness (Ra), and the surface roughness (Ra) is divided. ) Is particularly large, the cathode beam is subjected to the polishing step again, or is discarded depending on the degree.

The cathode beam for which the surface roughness (Ra) is to be measured does not have to be all of the plurality of cathode beams, but can be a part thereof. However, it is recommended that the number of cathode beams for measuring the surface roughness (Ra) be such that it is statistically considered to represent the population. In order to prevent local current concentration in the electrolysis process, the cathode beams used in an electrically parallel relationship are required to have similar electrical resistances. Therefore, for the number of cathode beams used in one tank, it is practical to extract and measure samples to the extent that the tendency of electrical resistance can be estimated, and the number of samples required for that purpose is determined in advance and measured. It is desirable to do.

Specifically, it is preferable to use 5 or more and half or less of the number of cathode beams used in one tank as a sample. When calculating the average value of the surface roughness (Ra) and the standard deviation (σ), a plurality of samples are required, but in this case as well, 5 or more samples are used in one lot. It is preferable to use less than half of the number of cathode beams as a sample.

One aspect of the non-ferrous metal electrolytic refining method of the present invention is not limited by the structure of the cathode beam. Usually, the cathode beam used in the electrolytic operation, that is, the cathode beam to be polished in the present invention has a square cross-sectional shape.

As the cathode beam, a cathode beam having a structure composed of an iron core and a copper coating layer is preferably used as in the conventional case, but a cathode beam made entirely of copper can also be used. In the cathode beam having a structure composed of an iron core and a copper coating layer, the cross-sectional shape of the iron core may be square or circular.

The cathode beam used in the copper electrorefining method of the present invention is composed of, for example, an iron core having an outer diameter of 22.0 mmφ and a copper coating layer having a thickness of 1 mm or more and 10 mm or less, and has a cross-sectional width of 24.0 mm. A rectangular cathode beam having a height of 42.0 mm is preferably used. The length of the cathode beam is appropriately determined by the structure of the electrolytic cell. Further, a cathode beam having a width and height of 26.0 mm having a cross section of 26.0 mm and a copper coating layer having a thickness of 3.0 mm and having a thickness of 32.0 mm can also be preferably used. In addition, the present invention is applicable to a cathode beam having an arbitrary cross section having a square cross section.

The method of electrolytic refining of a non-ferrous metal according to another aspect of the present invention is widely applied to a known cathode beam, and is particularly suitable for a cathode beam composed of an iron core and a copper coating layer provided on the surface of the iron core. Applies to.

In particular, in the method of electrolytic refining of a non-ferrous metal according to another aspect of the present invention, as shown in FIG. 1, a plurality of repeatedly used cathode beams are layered according to the weight of each of the plurality of cathode beams, and the weight thereof is increased. Each lot is characterized by having a step of installing the plurality of cathode beams in an electrolytic cell and energizing them.

The cathode beam is used repeatedly during the electrolytic operation. At this time, the copper coating layer, which is the conductive layer of the cathode beam, is gradually worn, and the thickness of the copper coating layer is reduced. Polishing the cathode beam is basically performed to remove the film adhering to the cathode beam, so it does not directly affect the thickness of the copper film layer, but it is repeated multiple times (for example, repeatedly). Every time it is used), the polishing may affect the thickness of the copper coating layer.

In any case, the rate of decrease in the thickness of such a copper coating layer differs depending on the cathode beam even when the film is removed by the polishing step. Therefore, the electric resistance differs for each cathode beam, and when a lot consisting of a plurality of cathode beams having such a large variation in electrical resistance is used, the current distribution in one electrolytic cell varies, that is, becomes non-uniform. Occurs.

In order to prevent such non-uniformity of the current distribution, it is necessary to use a cathode beam having an electric resistance in the same range as possible for each lot used in one electrolytic cell.

Therefore, it is preferable to measure the unit weight, which is the weight per cathode beam, for each cathode beam and perform stratification according to the weight of the cathode beam. In particular, for each lot, the relationship between the average unit weight (Ave) and the unit weight standard deviation (σ) of a plurality of cathode beams belonging to the lot may be less than σ / Ave = 0.1. preferable.

By charging lots in which the unit weights are stratified in a narrow range into the same electrolytic cell as a cathode beam, it is possible to effectively equalize the current distribution in the electrolytic cell. That is, such stratification of the cathode beam makes it possible to efficiently exclude the cathode beam having a high resistance value, which affects the non-uniformity of the current distribution in the electrolytic cell. As a side effect, the voltage can be lowered and the power consumption can be suppressed.

When the relationship between the average unit weight (Ave) and the unit weight standard deviation (σ) of a plurality of cathode beams belonging to one lot is σ / Ave = 0.1 or more, the current distribution in the electrolytic cell is made uniform. The effect is not fully obtained.

The weight range of the cathode beam of one lot is preferably in the range of σ / Ave = 0.02 to 0.05, more preferably in the range of σ / Ave = 0.02 to 0.03. ..

The stratification of the cathode beam in another aspect of the present invention basically evaluates the influence of the thickness reduction of the copper coating layer of the cathode beam, and the stratification of the cathode beam by weight in this embodiment. Is preferably performed after the polishing step in one aspect of the present invention.

The two embodiments of the present invention, the electrorefining method for non-ferrous metals, can be applied in combination as long as they are not inconsistent with each other, and the cathode beam can be stratified into one lot and for each lot. The evaluation of the cathode beam can be performed by the plurality of means disclosed above, and is preferable.

Hereinafter, the present invention will be further described with reference to Examples. In addition, Example 1, Reference Example 1 and 2, and Comparative Example 1 are an example of a copper electrorefining method using a permanent cathode method, and Example 2 and Comparative Example 2 are copper electrorefining using a seed plate electrorefining method. Regarding an example of the method. However, the present invention is not limited to this embodiment, and is applicable to various types of non-ferrous metal electrolytic refining methods using a cathode beam.

(Example 1)
As shown in FIG. 3, as a cathode (cathode plate) used in the permanent cathode (PC) method, a stainless steel plate 1 having a width of 1100 mm, a height of 1100 mm, and a thickness of 3 mm was prepared. A notch for transportation was provided on the upper portion of the stainless steel plate 1, and then welded to the cathode beam 3.

As the cathode beam 3, a stainless steel square tube having a cross section of 30 mm in width × 20 mm in height and a thickness of 3 mm (both ends sealed) and a copper coating layer having a thickness of 2 mm on the outer surface of the square tube (pure copper: 99). 1.9% or more) was used.

As the bus bar, a copper bus bar (length 6000 mm) having a pitch of 100 mm and a thickness of 6 mm was used.

For these 110 cathodes, the electrolytic operation of copper electrolytic refining was repeated. Specifically, 110 cathode beams were set as one lot, 110 cathodes were assembled, charged into two electrolytic cells, energized with a current of 40 kA for a cathode life of 6 days, and an electrolytic operation was performed. When one electrolysis operation was completed, another lot of cathode was charged into the electrolytic cell, and the same electrolysis operation was performed. Each lot was used for 5 electrolysis operations.

After that, the electrical contact portion of the cathode beam with the bus bar was polished with the following tools to make the surface roughness uniform.

Manufacturer: 3M Japan Ltd. Product name: Scotch-Brite Industrial Pad 7440
As shown in FIG. 4, the polishing method was sequentially performed in both the long axis direction and the short axis direction of the cathode beam.

The cathode beam was used for electrolytic refining of copper using 110 polished cathodes. The current flowing through the cathode and the voltage drop at the contact point with the bus bar were measured on the 4th day of energization.

(Reference example 1)
In the polishing step, electrolytic refining was performed in the same manner as in Example 1 except that the cathode beam was polished only in the long axis direction.

(Reference example 2)
In the polishing step, electrolytic refining was performed in the same manner as in Example 1 except that the cathode beam was polished only in the minor axis direction.

(Comparative Example 1)
Electrorefining was performed in the same manner as in Example 1 except that the polishing step was not performed.

Table 1 shows the average value and standard deviation (σ) of the surface roughness (Ra) of the electrical contact portion in the cathode beams of Examples 1, Reference Examples 1 and 2, and Comparative Example 1. The number of each sample was 20, and the surface roughness (Ra) was measured at one location per cathode beam (the central portion of the electrical contact portion).

By performing polishing, the average value of surface roughness (Ra) was reduced. Further, it can be said that the standard deviation (σ) is reduced and the variation in surface roughness (Ra) is reduced. Example 1 had a sufficiently smaller standard deviation than Reference Examples 1 and 2, and was effective in equalizing the surface roughness.

Further, in Table 2, the contact portion of the cathode beam with the bus bar when the cathode having the polished cathode beam according to Example 1 and the unpolished cathode according to Comparative Example 1 are used for electrolytic purification, respectively. Shows the average value and standard deviation of voltage drop and contact resistance. The measurement standard for each is 110 cathode beams.

By polishing by the method of Example 1, the average values of both the voltage drop and the contact resistance were sufficiently reduced in comparison with the unpolished Comparative Example 1. Also, in Example 1, these standard deviations were also reduced by about 70% compared to Comparative Example 1.

Further, Table 3 shows a comparison of the standard deviations of the current values flowing through the cathode. The measurement standard for each is 110 cathode beams.

With the reduction in the variation in the contact resistance between the cathode beam and the bus bar described above in Example 1, the standard deviation of the current value in Example 1 was also reduced by about 30% as compared with the unpolished Comparative Example 1. Can be understood.

From the above results, it is understood that the current distribution in the electrolytic cell in the electrolytic refining method can be made uniform by performing the polishing according to the present invention. Further, this equalization of the current distribution is achieved by reducing both the surface roughness of the electrical contact portion of the cathode beam with the bus bar and its standard deviation by performing the polishing according to the present invention. It is understood that this is because the standard deviation of the contact resistance of the part is reduced.

(Example 2)
As shown in FIG. 2, as a cathode used in the seed plate electrolysis method, a copper plate 1 having a width of 1070 mm, a height of 1050 mm, and a thickness of 1 mm is prepared, and a copper loop-shaped ribbon is inserted so as to sandwich the copper plate 1. Two pieces of 2 (width 100 mm, length 300 mm, thickness 1 mm) were attached, and the cathode beam 3 was passed through each of the two ribbons to obtain a cathode.

The cathode beam 3 is composed of an iron core having a cross-sectional area of 26 mm and a height of 26 mm and a copper coating layer having a thickness of 3 mm (pure copper: 99.9% or more) formed on the surface of the iron core. Those having an area width of 32 mm and a height of 32 mm were used.

As the bus bar, a copper bus bar (length 5000 mm) having a pitch of 100 mm and a thickness of 6 mm was used.

50 cathode beams were placed on the bus bar, and the electrolytic operation of copper electrolytic refining was repeated for 50 cathodes. Specifically, 50 cathode beams were set as one lot, 50 cathodes were assembled, charged into an electrolytic cell, energized with a current of 35 kA for a cathode life of 10 days, and an electrolytic operation was performed. After each electrolysis operation (10 days) is completed, the cathode beam is polished, and at the same time, the cathode beam of another lot that has been polished is used to assemble the cathode and charged into the electrolytic cell, and the same electrolysis operation is repeated. rice field.

The cathode beam was then stratified by its weight. As a criterion for stratification, the relationship between the unit weight of the cathode beam and the average unit weight (Ave) and the unit weight standard deviation (σ) of a plurality of cathode beams belonging to the selected lot is σ / Ave = 0.05. I went as follows.

As a result, the average unit weight (Ave) of 50 cathode beams of the lot was 10.1 kg, the unit weight standard deviation (σ) was 0.3 kg, and σ / Ave = 0.03. The cathode assembled with these cathode beams was charged into an electrolytic cell, and the cathode current was measured.

A Keysight U1213A clamp meter manufactured by Keysight Technology Co., Ltd. was used for the current measurement. Specifically, the cathode current was measured by sandwiching the cathode beam so as to enter the ring of the clamp portion of this measuring instrument. The portion where the cathode beam is sandwiched is the intermediate point between the contact portion with the bus bar and the ribbon closest to the bus bar.

(Comparative Example 2)
A lot was composed of 50 cathode beams that were not selected in Example 2. The average unit weight (Ave) of the 50 cathode beams of the lot was 10.3 kg, the unit weight standard deviation (σ) was 1.0 kg, and σ / Ave = 0.1. The cathode assembled with these cathode beams was charged into an electrolytic cell, and the cathode current was measured.

Table 4 shows a comparison of the cathode beam unit weight (kg) and the standard deviation (σ) of the cathode current (A) for Example 2 and Comparative Example 2. The measurement standard for each is 50 cathode beams.

With the reduction of the standard deviation (σ) of the cathode beam unit weight, the standard deviation of the cathode current was also reduced by about 44%. From the above results, it is understood that in the examples, the cathode current distribution was made uniform by using a lot of cathode beams having a small standard deviation of the cathode beam unit weight.

It is also understood that this sorting means makes it possible to efficiently discharge the cathode beam whose wall thickness has been reduced due to repeated use and whose resistance value has increased, and that the voltage can be reduced more efficiently.

1 Cathode plate (seed plate or mother plate)
2 Ribbon 3 Cathode beam

Claims (8)

A polishing step of polishing a plurality of cathode beams to smooth the surface of the plurality of cathode beams,
After the polishing step, a part or all of the plurality of cathode beams is selected, the surface roughness (Ra) of the electrical connection portion thereof is measured, and the plurality of cathode beams have the surface roughness (Ra). It is provided with a step of sorting into a large lot and a small lot, and installing the plurality of cathode beams belonging to the lot having a small surface roughness (Ra) in an electrolytic cell to energize .
The polishing step is characterized by performing a process of polishing each of the plurality of cathode beams in the major axis direction and a process of polishing each of the plurality of cathode beams in the minor axis direction. Refining method. The method for electrolytic refining of a non-ferrous metal according to claim 1 , wherein a cathode beam having a surface roughness (Ra) of 5.0 μm or less is selected as a lot having a small surface roughness (Ra). The method for electrolytic refining of a non-ferrous metal according to claim 1 or 2 , wherein the cathode beam having a surface roughness (Ra) of more than 5.0 μm is subjected to the polishing step again. A polishing step of polishing a plurality of cathode beams to smooth the surface of the plurality of cathode beams,
After the polishing step, a part or all of the plurality of cathode beams is selected, the surface roughness (Ra) of the electrical connection portion thereof is measured, and the lot to which the plurality of cathode beams belong is referred to as the surface roughness (the surface roughness (Ra). It is provided with a step of sorting into a lot having a large standard deviation of Ra) and a lot having a small standard deviation, and installing the plurality of cathode beams belonging to the lot having a small standard deviation of the surface roughness (Ra) in an electrolytic tank to energize .
The polishing step is characterized by performing a process of polishing each of the plurality of cathode beams in the major axis direction and a process of polishing each of the plurality of cathode beams in the minor axis direction. Refining method. The method for electrolytic refining of a non-ferrous metal according to claim 4 , wherein a lot having a standard deviation of the surface roughness (Ra) of 2.5 μm or less is selected as a lot having a small standard deviation of the surface roughness (Ra). The method for electrolytic refining of a non-ferrous metal according to claim 4 or 5, wherein the plurality of cathode beams belonging to a lot having a standard deviation of surface roughness (Ra) of more than 2.5 μm are subjected to the polishing step again. A polishing step of polishing a plurality of cathode beams to smooth the surface of the plurality of cathode beams,
A step is provided in which the plurality of cathode beams are stratified according to the weight of each of the plurality of cathode beams, and the plurality of cathode beams are installed in an electrolytic cell to energize each lot stratified by the weight .
In the polishing step, a process of polishing each of the plurality of cathode beams in the major axis direction and a process of polishing each of the plurality of cathode beams in the minor axis direction are performed.
In the stratification by weight, the relationship between the average unit weight (Ave) and the unit weight standard deviation (σ) of the plurality of cathode beams belonging to the lot stratified by the weight is less than σ / Ave = 0.1. A method for electrolytic refining of non-ferrous metals, which is characterized in that it is performed so as to be . The copper electrorefining method according to any one of claims 1 to 7 , wherein as the plurality of cathode beams, a cathode beam composed of an iron core and a copper coating layer provided on the surface of the iron core is used.

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