JP2019099881A - Method for electrolytically refining nonferrous metal - Google Patents

Abstract

To provide the method for electrolytically refining the nonferrous metal, that can prevent nonuniform current distribution in an electrolytic tank brought about by an increase in electrical resistance due to a reduction in a contact area of a contact part between a cathode beam and a bus bar.SOLUTION: The method for electrolytically refining the nonferrous metal comprises a step of flat-polishing the contact part 2b of cathode beams 2 used in an electrolytic operation using an abrasive material whose thickness does not change when polishing the contact part of the cathode beam while pressing the abrasive material, as a result, the contact part between the contact part 2c of a plurality of the cathode beams 2 and the contact part 11a of the bus bar 11 has an average contact area of 10 mmor more, and the contact area of the contact part has a standard deviation σ of 3 mmor less. Preferably, the method further comprises a step of measuring the contact area using a pressure-sensitive paper after flat-polishing.SELECTED DRAWING: Figure 5

Description

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

  As a method of smelting and refining nonferrous metals such as copper (Cu) and nickel (Ni), electrolytic refining of nonferrous metals is widely known. In the electrorefining of nonferrous metals, a target metal such as copper or nickel dissolved in an electrolyte is supplied by supplying electricity between an anode (anode plate) and a cathode (cathode plate) immersed in the electrolyte. It is possible to obtain a high purity target metal by electrodepositing the target metal) on the cathode surface.

  Electrolytic refining methods of non-ferrous metals are classified into an electrolytic refining method in which the target metal in the electrolytic solution is supplied from the anode, and an electrolytic collection method in which the target metal is separately dissolved in the electrolytic solution. Among 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 collection method, the insoluble anode made of insoluble electrode is used as the anode.

  In addition, electrolytic refining methods of non-ferrous metals are classified into a permanent cathode method in which the target metal after electrodeposition is peeled off from the cathode, and a seed plate electrolysis method in which the electrodeposited cathode remains 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, a seed plate obtained by processing the target metal peeled off by the permanent cathode method into a rectangular plate Is used.

  For example, in the electrolytic refining method of copper using a seed plate electrolytic method, generally, an anode made of crude copper and a cathode made of pure copper are alternately suspended in an electrolytic cell, and electricity is supplied in an electrolytic bath. It will be.

  The seed plate used for the cathode was a stainless steel base plate as the cathode, and the same electrolysis was performed, and when the target metal was thinly electrodeposited, this electrodeposition was peeled off from the base plate and processed into a rectangular plate shape It is a thing. In order to make this seed plate a cathode for electrolytic refining, another seed plate obtained in the same manner is cut to obtain a ribbon formed in a loop shape, and this ribbon is attached to the top of the seed plate as a hanger, The seed plate is suspended to the cathode beam (conduction weir) via the ribbon (hanger). In FIG. 1, the cathode beam is bridged over upper opposite side walls of the electrolytic cell, and the lower major part of the rectangular plate-like portion of the seed plate constituting the cathode for copper electrolytic purification is loaded in the electrolytic cell. An example is shown.

  As shown in FIG. 1, an anode plate 10 made of crude copper (Cu purity is about 97% to 99.5%) and a cathode plate 1 which is a seed plate made of pure copper (Cu purity of 99.9% or more) are A plurality of sheets are arranged alternately in parallel. In one of the cell walls on both sides of the electrolytic cell (not shown), a first bus bar 11 for realizing the electrical connection of the plurality of cathode plates 1 is provided, and in the other, the plurality of electrically conductive anode plates 10 are provided. The second bus bars 12 for realizing the connection are respectively arranged. The first end portion 2 a of the cathode beam 2 supporting the cathode plate 1 is mounted on the first bus bar 11 in a state of being electrically connected, and the second bus bar 12 is mounted on the first bus bar 11. The first ear portion 10a is placed in an electrically connected state. The second end 2 b of the cathode beam 2 is placed on the second bus bar 12 via the insulator 6, and the second ear 10 b of the anode plate 10 is an insulator for the first bus bar 11. Placed through 6.

  Further, by suspending the ribbon 3 attached to the cathode plate 1 to the cathode beam 2, the cathode plate 1 is supported by the cathode beam 2. The specific number of cathode plates 1 and anode plates 10 is arbitrary according to the size of the electrolytic cell, but it is preferable to reduce the number of anode plates 10 by one more than the number of cathode plates 1. For example, when 51 anode plates 10 are disposed per one electrolytic cell, a total of 50 cathode plates 1 are disposed one by one between each of the anode plates 10, or one anode plate is disposed per one electrolytic cell. When 27 pieces of 10 are arranged, a total of 26 pieces of cathode plates 1 are arranged between the anode plates 10 one by one.

  The current flows from the cathode through the electrical contact between the second busbar 12 and the first ear 10a of the anode plate 10, the electrolyte between the anode plate 10 and the cathode plate 1, and the ribbon 3 in this order. A current flows through the electrical contact between the first end 2 a of the beam 2 and the first bus bar 11.

  Specifically, as shown in FIG. 2, among the first bus bars 11, a plurality of places where the first end 2 a of each cathode beam 2 is placed, and, of the second bus bars 12, In a plurality of places where the first ears 10a of the respective anode plates 10 are placed, in plan view, it is an oval (oval shape) extending in the longitudinal direction of the bus bars 11 and 12, other in the height direction The contact portions 11a and 12a which are dome-shaped and bulging upward from the portion of (1) are provided by pressing the bus bars 11 and 12.

  As shown in FIG. 3, the contact portion between the first bus bar 11 and the cathode beam 2 is a contact portion 2 c which is the lower surface of the first end portion 2 a of the cathode beam 2 at the contact portion 11 a of the first bus bar 11. By placing the The contact portion between the contact portion 11a of the first bus bar 11 and the contact portion 2c of the cathode beam 2 needs to maintain an electrically good contact state.

  After the end of the energization period, the cathode beam 2 removed from the ribbon 3 attached to the cathode plate 1 is repeatedly used. That is, in the electrolytic refining of copper, copper is electrodeposited to a predetermined thickness on the cathode plate (seed plate) 1, and then the cathode plate 1 after electrodeposition is pulled out of the electrolytic cell, and the cathode beam 2 is removed. The cathode plate 1 with the ribbon 3 attached is shipped as a product, and the cathode beam 2 is incorporated in another cathode (combination of the cathode plate 1, the ribbon 3 and the cathode beam 2).

  In the permanent cathode method, as described above, mother plates made of titanium, stainless steel or the like are used as the cathode, but these mother plates are permanently attached to the cathode beam to constitute a cathode. In addition, cathodes and anodes having the same configuration as the electrolytic refining method of copper are used in electrowinning methods for other non-ferrous metals such as nickel, except that the target metal is different, and the seed plate or base plate of the cathode is a cathode beam. The electrodes are suspended in the electrolytic cell, and the connection of the cathode beam and the bus bar realizes the electrical connection of the cathode.

  Such a cathode beam is formed of, for example, a core rod made of iron and a covering layer made of copper covering the surface of the core rod as disclosed in JP-A-01-1319695, and has a rectangular cross section. And a cathode beam formed of a rectangular crossbar made of copper as described in JP-A-2000-345380.

  However, in view of cost and strength, in many cases, as shown in FIG. 3, a cathode beam 2 is formed of a core rod 4 made of iron and a covering layer 5 of copper and has a rectangular cross section. It is used.

  By the way, on the surface of the cathode beam, during electrolytic operation, a film of oxide due to heat generation and oxidation caused by air, or a film of sulfate due to adhesion of an electrolytic solution and an acid mist or the like is formed. The thicker the oxide or sulfate film, the higher the electrical resistance on the surface of the cathode beam and the greater the power consumption. Since the location of the film and its thickness vary, the amount of increase in electrical resistance also varies from location to location. As a result, current is not distributed equally to a plurality of cathode beams used in a certain electrolytic cell, and the current (that is, current distribution) flowing to each cathode (or the anode opposed to them) becomes uneven. .

  When the current distribution in the tank becomes uneven, local current concentration occurs, causing the electrodeposit to have a dendritic form, causing a short circuit, resulting in a decrease in current efficiency. In addition, excessive wear of the anode plate constituting the anode inserted in a form sandwiching the cathode plate constituting the cathode where the current is concentrated causes the worn anode plate to be positioned lower than the electrolyte surface. As a result, the portion immersed in the electrolytic solution may fall into the electrolytic cell or may be broken from the central portion of the anode due to wear and may fall into the electrolytic cell. A part of the anode plate is broken because a part of the dropped anode pierces the bottom of the electrolytic cell to cause the electrolyte to flow out or lean on the surrounding cathode plate to cause a short circuit. It takes

  In addition, the area of the available anode is reduced by a portion of the anode plate dropped into the tank, and the current density is increased. Therefore, if the current is continued as it is, the voltage of the tank is increased and current efficiency is increased. The appearance of the product may deteriorate due to the decrease of

  As described above, the limit applied current amount in the electrolytic operation is determined by one anode plate having the largest amount of current and the most worn out due to the current distribution among the plurality of anodes. That is, as the variation in the current distribution becomes larger due to the variation in the degree of wear of the anode plate, it is stronger to reduce the applied current so that a part of the most worn anode plate does not fall off. Be However, when the current is reduced, there is a problem that the amount of electrodeposition (that is, the amount of production) of the target metal such as copper and nickel is also reduced.

  In order to reduce variations in current distribution, as described in JP-A-2000-345380, when oxide or sulfate film is generated, a regeneration operation of polishing the surface of the cathode beam may be performed. it can.

Japanese Patent Application Laid-Open No. 01-319695 JP 2000-345380 A

  In the conventional cathode beam regenerating operation by polishing, it is an object to remove the film present on the surface of the cathode beam without grinding the copper (coating layer) itself on the surface of the cathode beam as much as possible. Since the thickness of the cathode beam varies depending on the age of use, it is usually polished using a brush-type abrasive so that the tip can reach regardless of the thickness of the cathode beam.

  The purpose of surface polishing using such a brush-type abrasive is to remove the oxide or sulfate film attached to the surface of the cathode beam, and the surface of the cathode beam after the film is removed. The change in the contact area due to the shape or the shape is not considered. For this reason, in the case of using a brush-type abrasive material, a striking force is applied to the corner from the periphery at the time of contact with the square cathode beam, and the abrasion of the corner is repeated each time polishing is repeated. Becomes noticeable, and the lower surface of the end portion which is the contact portion of the cathode beam is curved. Similarly, in the case of a non-rectangular cathode beam, the portion to which the brush first hits is more worn and curved due to rotational movement and reciprocation. When the lower surface of the end portion of the cathode beam is thus curved, the contact area with the bus bar is reduced, and the contact resistance between the cathode beam and the bus bar is increased.

  Also, due to handling during movement and storage for repeated use of the cathode beam, scratches and irregularities may occur on the surface of the cathode beam, which also causes a decrease in the contact area with the bus bar. There is.

  Thus, the presence of scratches and irregularities on the cathode beam contact point and the shape of the curved contact point lead to a reduction in the contact area between the cathode beam and the bus bar and an increase in contact resistance, and the cathode beam and the bus bar Cause the current to flow less easily.

  According to the present invention, not only the film attached to the contact portion of the cathode beam but also the flaws and irregularities formed on the contact portion of the cathode beam and the shape of the curved contact portion form the contact portion of the cathode beam and the contact portion of the bus bar By effectively preventing uneven current distribution in the electrolytic cell due to the increase in electrical resistance associated with the reduction in contact area, the thickness reduction of the anode can be made uniform, and the area of the anode necessary for electrolytic operation can be reduced. A method of electrorefining of non-ferrous metals, which can also reduce the amount of target metals such as copper and nickel circulating in the smelting process and the electrolysis process by maintaining and further reducing the repetitive amount of anode scrap The purpose is to provide.

  The invention relates to a nonferrous metal such as copper or nickel using a cathode beam having a rectangular cross-section at least at its longitudinal ends, in which the surface of the iron core is provided with a copper coating. Regarding the electrolytic refining method, the contact portion of the cathode beam used in the electrolytic operation is surface-grounded to remove not only the film such as oxide or sulfate adhering to the contact portion, but also a scratch or a scratch generated on the contact portion. By effectively removing the unevenness and appropriately evaluating the smoothing of the contact portion, the contact area between the contact portion of the cathode beam and the contact portion of the bus bar is increased, and the variation of the contact area is Using a small cathode beam, it is possible to suspend and charge the cathode plate to carry out the electrolysis operation.

  In particular, the invention is non-ferrous, using a plurality of cathode beams each having a rectangular shape in cross-section at least at its longitudinal ends and made of copper or provided with a copper coating on its surface. It relates to a method of electrolytic refining of metal. In this electrolytic refining method, the plurality of cathode beams have contact portions capable of making electrical contact with bus bars provided in the electrolytic cell.

In particular, in the electrolytic refining method for non-ferrous metals according to the present invention, the contact portions of the plurality of cathode beams used in the electrolytic operation are planarly polished to make contact between the contact portions of the plurality of cathode beams and the bus bar. The average contact area with the part is 10 mm ² or more, preferably 13 mm ² or more, more preferably 16 mm ² or more, and the contact area between the contact portion of the plurality of cathode beams and the contact portion of the bus bar It is characterized in that the standard deviation σ is maintained at 3.9 mm ² or less, preferably 3.5 mm ² or less, more preferably 3 mm ² or less.

  In the method of electrolytic refining of non-ferrous metals according to the present invention, it is preferable to further include the step of measuring the contact area of the contact portions of the plurality of cathode beams and the contact portions of the bus bar using a pressure sensitive paper.

  Further, in the planar polishing, it is preferable that the polishing is performed while pressing the abrasive, and the thickness of the abrasive is not changed in the polishing. For this purpose, in the case of an abrasive whose thickness changes, the position of the abrasive is adjusted so that the pressing pressure becomes constant while measuring the pressing pressure. Alternatively, as the abrasive, it is possible to use an abrasive such as a grindstone or sandpaper whose thickness does not change.

  When using an abrasive whose thickness does not change, as the abrasive, an abrasive having a grain size of # 60 or more according to the standard of the abrasive for JIS R6001 grinding wheel (# 60 or finer than # 60) It is preferred to use. It is preferable to use an abrasive (grindstone or sandpaper) in the range of # 60 to # 300.

  Even when a plurality of cathode beams used in the electrolytic refining method of nonferrous metals such as copper and nickel arranged in the same tank by the electrolytic refining method of nonferrous metals of the present invention are used plural times, respectively Of the cathode beams, the contact portions in contact with the contact portions of the bus bars are properly polished by the planar polishing without deteriorating the surface quality, and the contact area between the contact portions of the plurality of cathode beams and the contact portions of the bus bars Since the reduction can be suppressed and the variation in the contact area can be reduced, it becomes possible to make the current value distributed to each of the plurality of cathode beams uniform.

  More specifically, in planar polishing, polishing is performed while pressing the abrasive material, and the thickness of the abrasive material is not changed in this polishing, so that the contact portion of the plurality of cathode beams and the contact portion of the bus bar By increasing the contact area and reducing the variation in the contact area, the current applied to the electrolytic cell is uniformly distributed to the cathode and the anode respectively, and the amount of copper deposited on the cathode, the dissolution of the anode Weight loss (weight change of anode) can be made uniform.

  Thus, by operating (electrolytic operation) electrolytic refining of non-ferrous metals, the amount of limit applied current is increased, anode scrap is decreased, and a target metal such as copper or nickel circulating in the smelting process and the electrolysis process The cost can be reduced by reducing the amount of

  Therefore, the present invention has a remarkable effect of easily realizing low-cost operation in the field of nonferrous metal electrolytic refining method, and its technical contribution is large.

FIG. 1 is a schematic perspective view showing an example of an anode, a cathode and a cathode beam in a state of being loaded into an electrolytic cell (not shown) provided with a bus bar. FIG. 2A is a schematic view showing an example of a side view shape of a pressed bus bar contact portion, and FIG. 2B is a schematic view showing an example of a plan view shape of the bus bar contact portion. FIG. 3 is a schematic cross-sectional view showing the contact portion between the contact portion of the cathode beam and the contact portion of the bus bar. FIG. 4 shows the respective cathode beam contact points and busbar contact points of the pressure-sensitive paper for the 26 cathode beams used in the electrolytic operation and in an unpolished state in Example 1 It is a figure which shows the shape of a contact part with. FIG. 5 shows the shapes of the contact parts of the contact parts of the respective cathode beams and the contact parts of the bus bars by the pressure-sensitive paper for the 26 cathode beams in the state after planar polishing in Example 1 FIG.

  The present inventors examine the state of an electrolytic cell, a cathode beam, etc. used in the operation (electrolytic operation) of nonferrous metal electrolytic refining, and during the electrolytic operation, the current is an anode (anode plate) in the electrolytic cell. Flowing from the electrolyte to the bus bar through the electrolyte and the cathode (cathode plate, ribbon and cathode beam) in order, and when the inside of one electrolytic cell is viewed as a parallel circuit, the cathode beam and the bus bar contact As a result of considering that the contact resistance of the part is directly linked to uneven current distribution etc., it is found that the variation of the current value flowing to the cathode beam at the time of energization causes the wear and drop of the anode plate. The present invention has been achieved.

  In the electrolytic refining of non-ferrous metals such as copper and nickel, the cathode beam is repeatedly used in the electrolysis operation. Specifically, a plurality (predetermined number) of cathode beams are incorporated into one set of cathodes (the same number of cathode plates), these cathode plates are inserted into an electrolytic cell, and the target metal has a sufficient thickness as a product by energization. Then, the target metal deposited on the cathode plate is recovered as a product, the surface of the cathode beam is polished if necessary, and then the cathode beam is The cathode plate incorporated into the cathode again and constituting the cathode is inserted into the electrolytic cell to conduct electricity.

  During polishing, the entire cathode beam including the contact portion is usually polished by brush-type polishing or polishing using a sponge-like abrasive, but when pressing while pressing the abrasive, In surface polishing using abrasives of varying thickness, excessive force is applied to the corners to change the shape or thickness of the copper surface layer or copper covering layer at the contact point of the cathode beam. As a result, the contact portion of the cathode beam is curved.

  In addition, the contact portion may be scratched or uneven at the time of transportation or installation of the cathode beam.

  That is, while the cathode beam is new, the contact portion of the cathode beam is in surface contact or line contact with the bus bar, but the above-mentioned surface polishing or transportation is carried out every time the cathode beam is repeatedly used for electrolytic operation. Also, due to the contact at the time of installation, the shape of the contact portion of the cathode beam is changed, and the contact portion gradually approaches the point contact with the bus bar. That is, the contact area between the contact portion of the cathode beam and the bus bar gradually decreases.

  However, since the reduction rate of the contact area of the contact portion of the cathode beam is different for each cathode beam, every time the copper electrorefining using a plurality of cathode beams is repeated, A bias occurs in the current flowing between them.

  In particular, electrodeposition on the seed plate or base plate does not progress so much from the first day to the second day of the electrolysis operation, and the weight of the cathode plate is light, so the contact portion of the cathode beam and the contact portion of the bus bar The contact resistance of the contact portion is high, and the bias of the current flowing to the cathode beam is not only the contact area between the contact portion of the cathode beam and the contact portion of the bus bar, but also the weight per cathode beam (hereinafter Greatly dependent on From the second day of the current application period, as the weight of the cathode plate increases due to electrodeposition, the contact resistance between the contact portion of the cathode beam contact portion and the contact portion of the bus bar decreases and the cathode beam contact portion and bus bar The contact area between the cathode beam and the contact point is increased, and the bias of the current flowing through the cathode beam depends only on the contact area, so that the contact area between the cathode beam contact point and the bus bar contact area is uneven. As it becomes smaller, the current flowing to the cathode beam is made uniform.

  The present invention suppresses variation in cathode beam single weight, and reduces the contact resistance of the contact portion between the cathode beam contact portion and the bus bar contact portion, even when the weight of the cathode plate is light, thereby making the cathode In the electrolytic refining method of nonferrous metals using a plurality of cathode beams made of copper or having a copper coating layer on the surface in order to minimize the bias of the current flowing in the beams, the cathode beam used in the electrolytic operation The contact portion may be planarly polished to increase the contact area between the contact portion and the bus bar, and the current value distributed to each of the plurality of cathode beams may be made uniform.

  Basically, the method of the present invention for electrolytic refining of non-ferrous metals is characterized in that the contact portion of the cathode beam used in the electrolytic operation is planarly polished to increase the contact area between the contact portion and the bus bar. Therefore, the method of electrolytic refining of non-ferrous metals according to the present invention can be widely applied to known known methods of electrolytic refining of non-ferrous metals, including permanent cathode method and seed plate electrolysis method. .

  In addition, an electrolytic cell, a bus bar, an anode (anode plate with ears), a cathode (a cathode plate consisting of a base plate or a seed plate, a ribbon, and a cathode beam) used in an electrolytic refining method of nonferrous metals, and electrolysis Known conditions can be applied to the operating conditions and the like. Accordingly, the structures shown in FIGS. 1 to 3 and the description thereof, and further, the contents described in Japanese Patent Application Laid-Open Nos. 01-319695 and 2000-345380 are incorporated herein by reference. I assume.

  In the electrolytic refining method for non-ferrous metals of the present invention, the cathode beam used for the electrolytic operation, that is, the cathode beam to be subjected to the surface grinding of the contact portion in the present invention, has a rectangular cross section at least at its longitudinal end. It has a shape. The cathode beam is preferably configured by a prismatic column whose cross-sectional shape does not change in the length direction, that is, a so-called rectangular cross bar.

  As such a cathode beam, a cathode beam having a structure constituted by an iron core and a copper coating layer is suitably used as in the prior art, but a cathode beam made entirely of copper can also be used. In the cathode beam of the structure constituted by the iron core and the copper covering layer, the cross-sectional shape of the iron core may be square or circular.

  The width W and height H of the cross section of the cathode beam are arbitrary, but usually the width W is 10 mm to 100 mm, preferably 20 mm to 40 mm, and the height H is 10 mm to 100 mm, preferably 30 mm or more It is 50 mm or less. The length of the cathode beam is appropriately determined by the structure of the electrolytic cell.

  The thickness of the copper coating layer is optional, but usually the thickness is 0.5 mm or more and 15 mm or less, preferably 1 mm or more and 10 mm or less, and more preferably 2 mm or more and 8 mm or less. When the cross-sectional shape of the iron core is not parallel to the copper coating layer, such as circular, the thickness of the copper coating layer is the same as that of the upper surface or lower surface of the cathode beam at both ends constituting the contact portion of the cathode beam. The shortest distance on the outer surface.

  Specifically, as a cathode beam used for the copper electrolytic refining method of the present invention, for example, it has an iron core with an outer diameter of 22.0 mm and a copper coating layer with a thickness of 1 mm or more and 10 mm or less. A rectangular cathode beam 24.0 mm wide and 42.0 mm high is preferably used. In addition, a cathode beam having a width and a height of 32.0 mm square, which is constituted by an iron core having a width and a height of 26.0 mm square and a copper covering layer having a thickness of 3.0 mm, is also included. Are also preferably usable. In this case, any surface of both ends of the cathode beam can be a contact portion.

  One of the longitudinal ends of such a cathode beam is mounted at the contact point of the bus bar for achieving the electrical connection of the plurality of cathodes. That is, the lower surface of one of the longitudinal end portions of the cathode beam is a flat surface contact portion which can be electrically connected to the contact portion of the bus bar.

  The bus bar for the cathode, that is, the bus bar for achieving the electrical connection of the plurality of cathodes, is a flat plate made of a conductive metal such as copper. A plurality of contacts in the longitudinal direction of the bus bar are oval-shaped (oval-shaped) extending in the longitudinal direction in plan view, and the contact portions which bulge in a dome shape above the other portions in the height direction are bus bar Are provided by press molding.

  The length d and the width w of the contact portion of the bus bar are arbitrary, but the length d is usually 20 mm or more and 70 or less, preferably 30 mm or more and 50 mm or less, and the width w is 30 mm or more and 50 mm or less.

  The height h of the most bulging part of the contact portions of the bus bar is optional, but the height h is usually 4 mm or more and 20 mm or less, preferably 5 mm or more and 10 mm or less.

  The surface polishing of the present invention differs from the conventional polishing in that not only removal of the oxide or sulfate film on the contact portion of the cathode beam but removal of scratches and irregularities on the contact portion of the cathode beam is performed. That is, the main object of the known polishing is to remove the oxide or sulfate film at the contact portion between the cathode beam and the ribbon, and the oxide or sulfate film at the contact portion between the cathode beam and the ribbon It is for suppressing the rise of the electrical resistance by existence.

  In order to suppress the variation in the current flowing to the cathode beam, it is desirable that the variation in the contact area between the contact portion of the cathode beam and the contact portion of the bus bar be small. That is, in one electrolytic cell, it is most desirable that the contact area between the contact portion of each cathode beam and the contact portion of each bus bar be substantially constant. For this purpose, a plurality of cathode beams constituting one lot are used in which scratches and irregularities on the respective contact portions are removed by plane polishing, and the respective cathode beam contact portions and bus bars are used. It is effective to reduce the variation in the contact area with the contact portion and to increase each contact area.

Specifically, in the copper electrolytic refining method of the present invention, the contact portions of the plurality of cathode beams used in the electrolytic operation are planarly polished, and the contact area between the contact portions of the plurality of cathode beams and the contact portions of the bus bar the standard deviation σ of the contact area, 3.9 mm ² or less, preferably 3.5 mm ² or less, more preferably so as to maintain the 3.0 mm ² or less.

When the standard deviation σ of the contact area between the contact portions of the plurality of cathode beams and the contact portion of the bus bar is larger than 3.9 mm ² , that is, the variation of the contact area is large, the currents flowing to the respective cathodes become biased. Therefore, the effect of making the current values distributed to each of the plurality of cathode beams uniform is not sufficiently obtained. At this time, it is considered that a curved surface portion, a flaw or unevenness is present at the contact portion of the cathode beam having a small contact area.

The lower limit of the standard deviation σ of the contact area is not limited, but is preferably about 1.0 mm ^{2 in} consideration of work efficiency and work cost associated therewith.

In addition, the larger the average contact area between the contact portions of the cathode beams and the contact portions of the bus bar, the more the heating of the contact portions between the contact portions of the cathode beam and the contact portions of the bus bar and the accompanying growth of oxides. Instead, a large current can be supplied to the cathode or the anode. For example, in the case of passing a current of 650 A to 850 A per sheet, it is preferably 10 mm ² or more, more preferably 13 mm ² or more, and preferably 16 mm ² or more. More preferable.

The average for the upper limit of the contact area, is not particularly limited, considering the working efficiency and operation cost associated with it, preferably 100 mm ^2, more preferably 50 mm ^2, more preferably about 25 mm ^2.

  In the present invention, the values of the contact area and the standard deviation thereof are as follows: the length of both ends of the cathode plate and the cathode beam where the ribbon is not suspended is set to a pair of bus bars arranged on the cell walls on both sides of the electrolytic cell However, one of the busbars is placed in such a way as to be spread across the insulator), that is, in a state where the weight of the cathode beam alone is applied, the contact portion of each cathode beam and the busbar It means the value of the contact area with the contact portion and its standard deviation.

  In the planar polishing in the present invention, in order to prevent over-polishing to the corner of the cathode beam, it is preferable to keep the thickness of the abrasive constant by the pressing pressure when polishing while pressing the abrasive. A specific method for keeping the thickness constant is not particularly limited. For example, in the case of an abrasive such as a brush or a sponge-like abrasive whose thickness changes depending on the pressing pressure, the pressing pressure is measured. There is a method of adjusting the position of the abrasive so that the pressing pressure becomes constant.

  Alternatively, instead of a brush or a sponge-like abrasive, an abrasive such as a grindstone or a sandpaper whose thickness does not change due to pressing pressure can be used. Such abrasives that do not vary in thickness typically include those with non-elastic and / or flat surfaces, such as grinding wheels or sandpaper. When using an abrasive whose thickness does not change, there is an advantage that the pressing pressure can be easily maintained by means of placing the cathode beam on the abrasive or placing the abrasive on the cathode beam, so pressing pressure Measurement is not required.

  The material of the abrasive is preferably diamond or alumina from the viewpoint of the life, but is not limited thereto. The oxide or sulfate film on the cathode beam contact point can be removed, and the contact area between the cathode beam contact point and the busbar contact point can be increased by removing the irregularities on the cathode beam contact point Abrasives of any other material may also be used as long as

  When using an abrasive whose thickness does not change, such as a grindstone or sand paper, as the abrasive, the grain size of the abrasive according to the standard of the abrasive for JIS R 6001 grinding stone is # 60 or more (# 60 or finer than # 60) ) It is preferable to use an abrasive. Although the upper limit of the particle size of the abrasive is not limited, it is more preferable to use an abrasive in which the particle size of the abrasive is in the range of # 60 to # 300, in consideration of the labor of the polishing process and the working time. If the grain size of the abrasive grains is in the range of # 80 to # 140, a suitably smooth contact portion can be obtained in a short time.

  In this case, as a method of planarly polishing the contact portion of the cathode beam, the contact portions of a plurality of cathode beams, which are aligned with the surface constituting the contact portion of the cathode beam facing up, are electrically Cutting with an abrasive tool such as a grinder or a grindstone can be mentioned. These polishing tools may be operated manually, but in order to reduce work efficiency, work man-hours, and cost, after being removed from the ribbon of the cathode after the current-carrying period, from when it is installed again on the cathode Preferably, the polishing apparatus is installed at a place where the cathode beam is transported or stocked between them so that the polishing is automatically performed on the lower end surface including the contact part of the cathode beam. .

  In addition, it is preferable to polish only the contact portion of the lower surface of the end portion of the cathode beam, in consideration of delaying the shortening of the life of the cathode beam by preventing the reduction of the weight due to the thickness reduction of the cathode beam.

  The amount of polishing in each plane polishing is adjusted by adjusting the pressing pressure or polishing time of the abrasive according to the type of the abrasive and the polishing apparatus. In particular, in the case where the contact portion has a flaw or unevenness, it is important to remove the flaw or unevenness. It is desirable that the pressing pressure and the polishing time be previously examined through experiments and the like. For example, cathode beams that have not been polished for many years have longer scratches and irregularities, so polishing takes longer. Also, the value of the average contact area between the contact portion of each cathode beam and the contact portion of each bus bar in the previous polishing and the value of the standard deviation σ of the contact area for the same set are fed back to the abrasive It is also possible to adjust the pressing pressure and polishing time of

  In addition, planar polishing can be performed each time the electrolytic operation is performed, but it is also possible to experimentally determine in advance the possible number of repetitions of the electrolytic operation and to perform it every number of times (a plurality of times).

  In the present invention, it is preferable to further include the step of measuring the contact area between the contact portions of the respective cathode beams and the respective contact portions of the bus bars using a pressure-sensitive paper after planar polishing.

  Specifically, the pressure-sensitive paper is placed on the upper surface of the bus bar or on the surface corresponding to the upper surface of the bus bar, and a plurality of cathode beams (or base plates are attached) on which the seed plate or ribbon is not suspended. The plurality of cathode beams) are placed to color only the portion corresponding to the contact portion between the contact portion of each cathode beam and the contact portion of the bus bar to obtain the shape of each contact portion. The area of the colored portion of the pressure-sensitive paper corresponding to the shape of each contact portion is measured, and the average value of the contact area (average contact area) and the standard deviation σ can be obtained from the measurement results.

  It is possible to evaluate the smoothing of the contact portion of the cathode beam by other means. For example, it is conceivable to measure the current distribution at the contact points using an ammeter. However, in this method, the current distribution varies depending on how the terminals are applied, and hence the evaluation results vary. On the other hand, a pressure sensitive paper is used to measure the contact area between the contact part of each cathode beam and each contact part of the bus bar, and based on this, the average contact area and the standard deviation σ of the contact area are It is advantageous to find and use this for evaluation of the smoothing of the contact part of the cathode beam in that it is simpler and that there is no variation in the results.

  The present invention is applicable not only to a structure in which a plurality of cathodes and anodes are suspended alternately and in parallel in one electrolytic cell, but also when such electrolytic cells are connected in series. It is applicable. In this case, the standard contact area σ of the contact area between the contact portion of the cathode busbar and the contact portion of each cathode beam installed in each electrolytic cell and the standard deviation σ of the contact area are restricted within the above range.

The invention is further illustrated by the following examples. In addition, an Example relates to an example of the copper electrolytic refining method using seed plate electrolysis. However, the present invention is not limited to this embodiment, and is applicable to various types of nonferrous metal electrolytic refining methods using a cathode beam.
Example 1
As an inner core, an iron core having a cross-sectional width of 18.0 mm and a height of 36.0 mm, and a 3.0 mm-thick copper covering layer (pure copper, 99.9% or more) formed on the surface of the iron core 52 cathode beams each having a cross-sectional width of 24.0 mm and a height of 42.0 mm (see FIG. 3).

  As a cathode bus bar, a cathode bus bar (2900 mm in length; pure copper, 99.9% or more) having a thickness of 10 mm was used, in which 26 cathode contact portions were pressed at a cycle of 105 mm (FIG. 2). As a busbar for the anode, 27 anode contact parts were pressed at a cycle of 105 mm (Fig. 2), and a busbar made of copper with a thickness of 10 mm (length 2900 mm; pure copper, 99.9% or more) It was. Each of the anode contact portion and the cathode contact portion is an oval extending in the longitudinal direction in plan view, and has a dome shape bulging upward than the other portions in the height direction, and has a length of 50 mm and a width of 20 mm , Height 10 mm.

  As a seed plate, a copper plate (pure copper, 99.9% or more) with a height of 1000 mm, a width of 1000 mm and a thickness of 1 mm, a copper plate with a width of 100 mm, a thickness of 1 mm and a length of 300 mm (pure copper, 99.9% or more) Two U-shaped ribbons were attached to the left and right sides of the upper side of the seed plate. Further, as the anode, a copper plate of rough copper having a size of approximately 1000 mm in height, 1000 mm in width and 40 mm in thickness excluding the ear portion was used (99% Cu).

  The electrolytic operation of copper electrorefining was repeated using these bus bars, a cathode (seed plate (cathode plate), a ribbon, and a cathode beam) and an anode (anode plate with ears). Specifically, one set of 26 cathode beams is incorporated into the cathode consisting of 26 cathode plates, and is inserted into the electrolytic cell so as to be sandwiched by 27 anode plates constituting the anode. Electricity was supplied at the cathode life of the day to carry out electrolysis operation. Thereafter, another set of 26 cathode beams was used to carry out electrolysis similarly. The cathode beams of each set were used alternately. Each set was used repeatedly in six electrolysis runs.

  Each cathode beam was considered to have lost the flatness of the contact portion in contact with the bus bar by repeated use and to have a small contact area with the bus bar. The shape of the contact portion was confirmed using a pressure sensitive paper (manufactured by Fujifilm Corporation). That is, a pressure-sensitive paper is placed on the upper surface of a cathode busbar, and a single cathode beam is quietly placed on the pressure-sensitive sheet, and the contact point which is the lower surface of the end of each cathode beam and the cathode The contact portions of the bus bars with the respective contact portions were colored. As a result, the shapes of the contact portions were as shown in FIG.

  Subsequently, the area of the colored portion was measured, and the contact area of the contact portion of each cathode beam contact portion with the contact portion of the bus bar was determined. The average contact area of the contacts and the standard deviation σ of the contact area for one set of cathode beams obtained from these measured values are shown in Table 1, respectively.

  About the contact point part of these 26 cathode beams, the abrasive grain according to the standard of the abrasives for JIS R 6001 grinding wheel is cut by using a whetstone of # 120 with a hand grinder (Mini-angle sander MX-80E made by Office Mine, Inc.) Planar polishing was performed for 5 minutes to smooth each contact portion. The shape of each contact portion after smoothing (planar polishing) was similarly measured with a pressure-sensitive paper. The results are shown in FIG.

  Similarly, 26 cathodes were loaded into the electrolytic cell using one set of cathode beams after smoothing, and energization was resumed with a current of 18700 A and a cathode life of 9 days.

The current flowing through one set of cathode beams in the resumed energization was measured using a hot-wire ammeter (a clamp meter, clamp-on AC / DC high tester 3265 manufactured by Hioki Electric Co., Ltd.). The average current value obtained from the measurement results and the standard deviation of the current value are shown in Table 1.
Comparative Example 1
Using the same cathode beam set and bus bar as in Example 1 except that the contact portion of the cathode beam was not polished, energization was resumed under the same conditions and operation as in Example 1. The average current value flowing to one set of cathode beams in the resumed energization and the standard deviation of the current values were determined. The results are shown in Table 1. Table 1 also shows the average contact area of the contact portion and the standard deviation σ of the contact area, which were measured using a pressure-sensitive paper after repeated use and before resumption of energization.
[Reference Example 1]
The electrolytic operation was performed in the same manner as in Example 1 except that the surface of the contact portion of the cathode beam was polished by brush polishing using a cup brush as an abrasive. At this time, the pressing pressure was measured, and the position of the abrasive was not adjusted based on the measured value so that the pressing pressure became constant. The average current value flowing to one set of cathode beams in the resumed energization and the standard deviation of the current values were determined. The results are shown in Table 1.
[Reference Example 2]
The electrolysis operation was performed in the same manner as in Example 1 except that a # 300 grinding stone was used as the abrasive. The average current value flowing to one set of cathode beams in the resumed energization and the standard deviation of the current values were determined. The results are shown in Table 1.

  From the above results, in the case where the contact portion of the cathode beam is not polished as in Comparative Example 1, the scratches and irregularities on the contact portion are not sufficiently removed. At this time, the standard deviation σ of the contact area between the contact portion of each cathode beam and each contact portion of the bus bar is large. As described above, it is understood that the standard deviation of the current value in the current application period is also increased when the cathode beam having a large standard deviation σ of the contact area of each contact portion is used.

  On the other hand, in the case of the cathode beam in Example 1, it can be understood that the contact area of each contact portion becomes sufficiently large and the standard deviation σ becomes small by plane polishing in comparison with Comparative Example 1. . Therefore, it was found that the standard deviation of the current value in the current application period becomes small, and stable current application can be continued.

  In addition, in the reference example 2, since the particle size of the abrasive grain was too small, under the same polishing condition as that of the example 1, the improvement of the surface property can be seen but it is inferior to the example 1. However, by continuing the polishing further, it is considered that the surface texture of the contact portion of the cathode beam similar to that of the present invention can be obtained.

1 cathode plate 2 cathode beam 2a, 2b end 2c contact portion 3 ribbon (hand strap)
DESCRIPTION OF SYMBOLS 4 core rod 5 coating layer 6 insulator 10 anode plate 10a, 10b ear part 11 1st bus bar 11a contact part 12 2nd bus bar 12a contact part

Claims (4)

A copper electrorefining method using a plurality of cathode beams each having a rectangular shape in cross section at least at its longitudinal end and made of copper or provided with a copper covering layer on the surface,
The plurality of cathode beams have contact portions capable of making electrical contact with bus bars provided in the electrolytic cell,
The contact portions of the plurality of cathode beams used in the electrolytic operation are flat-polished to have an average contact area of 10 mm ² or more between the contact portions of the plurality of cathode beams and the contact portions of the bus bar, and The standard deviation σ of the contact area between the contact portion of the plurality of cathode beams and the contact portion of the bus bar is maintained at 3 mm ² or less.
Copper electrolytic refining method.   The copper electrolytic refining method according to claim 1, further comprising the step of measuring the contact area using a pressure sensitive paper.   The copper electrolytic refining method according to claim 1 or 2, wherein the polishing is performed while pressing the abrasive in the planar polishing, and the thickness of the abrasive is not changed in the polishing. The copper electrolytic refining method according to claim 3, wherein an abrasive having a grain size of # 60 or more is used as the abrasive.