JP2020128579A - Drain method of electrolytic solution in electrolytic refining - Google Patents

Abstract

To provide a drain method of electrolytic solution in electrolytic refining, capable of improving productivity through homogenizing a copper ion concentration in the electrolytic solution in an electrolytic bath and suppressing passivation of an anode, when performing the electrolytic refining of copper with high current density.SOLUTION: In a drain method of electrolytic solution from an electrolytic bath that performs electrolytic refining of a metal, there is provided a piping for drainage in which one end side is immersed as a suction port in the electrolytic solution stored in the electrolytic bath from upward of the electrolytic bath, and the other side is connected to a pump for drainage that can control a flow rate. The drain method of electrolytic solution changes an installation position of the suction port of the piping for drainage so as to suck and drain the electrolytic solution from an arbitrary position ranging from a bottom of the electrolytic bath to a vicinity of a liquid level of the electrolytic solution.SELECTED DRAWING: Figure 2

Description

The present invention relates to a method of draining an electrolytic solution in electrolytic refining.

As the electrolytic refining carried out industrially, electrolytic refining of copper is mentioned as the main one. In this electrolytic refining of copper, an anode plate (hereinafter, referred to as an anode) made of crude copper produced in a dry process of copper smelting is placed in an electrolytic cell charged with an electrolytic solution containing copper sulfate as a main component, A cathode plate made of copper, stainless steel, titanium, or the like (hereinafter, referred to as a cathode) is arranged so as to be opposed to each other at regular intervals, and a constant current is applied.
By this energization, the anode is eluted as copper ions in the electrolytic solution, and the copper ions are electrodeposited on the cathode. At the same time, impurities such as nickel, antimony and arsenic contained in the anode, noble metal elements such as gold and silver do not elute in the electrolytic solution, and even if they elute, they do not deposit on the cathode. Has the characteristic that high-purity copper (electrolytic copper) can be obtained.

However, a factor that hinders such a reaction is passivation of the anode. The passivation of the anode is caused mainly by the precipitation of copper sulfate crystals on the surface of the anode. Since the copper sulfate crystal is non-conductive, no current flows, which hinders the production of high-purity copper (electrolytic copper) as a product.
The precipitation of copper sulfate crystals, which is the main cause of anode passivation, occurs when the copper ions eluted on the anode surface exceed the solubility of copper sulfate in the vicinity of the anode and are crystallized. Normally, production (refining) is performed under the condition that the ion concentration of copper and sulfuric acid does not exceed the solubility of copper sulfate, but due to the recent increase in demand for copper, it is required to produce a large amount of copper in a shorter time. ..

Here, the amount of copper produced, that is, the amount of electrodeposition, is represented by the relationship of “current-carrying time×electrode area for current-carrying×current density (per unit area)”. Since the energization time is close to the constant energization, there is little room for extension, and it is difficult to change the electrode area without renewing the equipment. Therefore, efforts have been made to increase the current density.

However, when the current density is increased, the dissolution rate of copper is increased, which causes a problem of passivation of the anode.
On the other hand, the copper ion concentration in a general electrolytic cell is not uniform and has a concentration gradient. As seen in Patent Document 1, the copper ion concentration is high in the lower part of the electrolytic cell and the copper ion concentration is low in the upper part of the electrolytic cell. Therefore, passivation of the anode is more likely to occur at the bottom of the electrode than at the top of the electrode.

Against this background, efforts have been made to make the copper ion concentration in the electrolytic cell uniform.
The method as seen in Patent Document 2 and Patent Document 3 is to dip a stirring blade in an electrolytic bath and stir the liquid in the bath with a dedicated motor or the like to make the copper ion concentration uniform. Since the equipment becomes very complicated, it was not suitable for large-scale production.

Further, the method as seen in Patent Document 4 is to supply the liquid from the upper part of the electrolytic cell and drain the liquid from the lower part of the electrolytic cell, but the copper ion concentration becomes low in the upper part in the electrolytic cell, There is a problem that the surface quality of the cathode is deteriorated. Since there is a problem even when the copper ion concentration is low, it is important to make it uniform in the tank.
Further, the following technique is also found in Patent Document 4. Liquid is supplied from the upper and lower parts of the electrolyzer and drained from the upper part of the electrolyzer. However, as in a general electrolyzer, the copper ion concentration increases in the lower part of the electrolyzer, and the copper ion concentration increases. The effect of homogenization was slight.

Further, in the methods as seen in Patent Documents 5 to 7, the diameter of each liquid supply or drainage is reduced, so that the adhesion of the sparingly soluble substance causes blockage in a short time, or the assumed flow rate is There was a problem that could not be maintained. Although cleaning work is effective as a measure to eliminate the blockage, before performing the cleaning work, it is necessary to extract an electrolytic solution harmful to the human body such as strong acidity from the electrolytic cell to expose the blocked pipe. Therefore, since the production is stopped during the cleaning work or the work of extracting the electrolytic solution, it is necessary to finish the work promptly, but it is not easy to extract the electrolytic solution using the blocked pipe. However, it was difficult to extract quickly.

Japanese Patent Publication No. 60-45127 JP, 2017-048438, A Japanese Patent No. 3952766 Japanese Patent No. 6065706 JP 2002-105684A Japanese Patent No. 4342522 JP-A-52-33824

The present invention, when electrolytically refining crude copper at a high current density to obtain electrolytic copper, the concentration of copper ions in the electrolytic solution in the electrolytic cell is made uniform, passivation of the anode can be suppressed, and further maintenance is easy. The present invention also provides a method for draining an electrolytic solution from an electrolytic cell, which maintains good production efficiency with simplified equipment.

Usually, the passivation of the anode that occurs during the electrolytic refining of copper is that the copper ions eluted on the surface of the anode reach the solubility of copper sulfate near the anode to form a non-conductive copper sulfate crystal film. In a general copper electrolytic refining method, the copper ion concentration is high in the lower part of the electrolytic cell, so that the passivation of the anode is likely to occur preferentially in the lower part of the electrode.

Thus, when passivation occurs at the lower part of the electrode, the current concentrates on the upper part of the electrode, so the current density at the upper part of the electrode and the elution rate increase, and passivation easily occurs at the upper part of the electrode. Become.
Since the passivation of the anode proceeds in a chain-like manner as described above, it is important to suppress the passivation at the lower part of the electrode, which is the generation source. It is important to make the copper ion concentration in the liquid uniform.
Therefore, the present inventors have found that it is possible to make the concentration of the electrolytic solution in the electrolytic cell uniform by changing the method of discharging the electrolytic solution, and have completed the present invention.

A first aspect of the present invention is a method of draining an electrolytic solution from an electrolytic cell for electrolytically refining a metal, wherein one end side is in the electrolytic solution stored in the electrolytic cell from above the electrolytic cell. As a suction port, the other end side is provided with a drainage pipe connected to a drainage pump whose flow rate is controllable, and by changing the installation position of the suction port of the drainage pipe, the electrolytic cell The method for draining an electrolytic solution in electrolytic refining is characterized in that the electrolytic solution is sucked and discharged from an arbitrary position from the tank bottom to the vicinity of the electrolytic solution surface.

A second invention of the present invention controls the drainage flow rate of the drainage pump of the first invention to be equal to or less than the supply flowrate of the electrolytic solution supplied to the electrolytic cell, A method for draining an electrolytic solution in electrolytic refining, which enables draining due to overflow from the liquid surface simultaneously with the draining of the electrolytic solution.

A third invention of the present invention is a method for draining an electrolytic solution in electrolytic refining, wherein the drainage pump in the first and second inventions is a manual pump utilizing the siphon principle. ..

In a fourth aspect of the present invention, the electrolytic cell according to any one of the first to third aspects includes a plurality of electrodes whose electrode surfaces are arranged in parallel, and the electrolytic cell is electrolyzed on one side of an electrolytic cell wall in a direction normal to the electrode surface. Discharge of electrolytic solution in electrolytic refining characterized by having a supply port for supplying the solution into the electrolytic cell and having a movable suction port for sucking the electrolytic solution in the electrolytic cell on the other side electrolytic cell wall It is a liquid method.

A fifth aspect of the present invention is characterized in that the ratio of the amount of electrolytic solution drained from the suction port in the second aspect is 25% or more and 75% or less of the total amount of drained liquid from the electrolytic cell. Is a method of draining the electrolytic solution in the electrolytic refining.

A sixth invention of the present invention is characterized in that the suction port according to the first to fifth inventions is installed at a position of 10% or more from the bottom of the electrolytic bath with respect to the depth inside the electrolytic bath. This is the liquid drainage method.

A seventh invention of the present invention is a method for draining an electrolytic solution in electrolytic refining, characterized in that the flow velocity at the liquid supply port and the suction port in the fourth to sixth inventions is 2.5 cm/s or less. ..

According to the present invention, when electrolytically refining copper at a high current density, the copper ion concentration in the electrolytic solution in the electrolytic cell can be made uniform. Thereby, passivation of the anode can be suppressed and productivity can be improved.

It is a figure which shows the electrolytic cell which used the drainage method of the electrolyte solution in the general electrolytic refining of copper. It is a figure which shows the electrolytic cell which used the drainage method of the electrolyte solution by this Embodiment. FIG. 3 is a diagram showing a drainage device A used in the present embodiment, where (a) is an example of the drainage device A having an intermediate portion 13 that expands and contracts, the intermediate portion 13 is in a contracted state, and (b) is an intermediate portion. A state in which the portion 13 is extended, (c) is a drainage device A of a type in which the position of the suction port 12 is changed by fixing the suction pipe 12a with a fixture 14, and the suction port 12 is installed at the upper position. In this case, (d) is a diagram showing a case where the suction port 12 is installed at the lower position or the middle position.

Specific contents of the present embodiment in which the concentration of the electrolytic solution in the electrolytic cell can be made uniform by optimizing the drainage method of the electrolytic solution will be described in detail with reference to examples.
In the general electrolytic refining of copper, a method of supplying and discharging an electrolytic solution is as follows. lower than the lower end portion of the tank wall w ¹ side of the electrode, and supply fluid from the liquid supply ports 30, the liquid supply side of the electrolytic cell walls w ¹ and drainage port provided in the upper part of the opposite electrolytic cell wall w ² is It is discharged from 31 (see FIG. 1). In FIG. 1, 100 is a conventional electrolytic cell, 2 is an electrolytic solution, 2a is an electrolytic solution surface, 3 is an anode, 4 is a cathode, 5 is an electrode composed of a cathode and an anode, the right side is the cathode surface, and the left side is An electrode arranged as an anode surface, an electrode arranged on the right side as an anode surface and an electrode arranged as a cathode surface on the left side, and 30a is a liquid supply pipe for supplying an electrolytic solution.

In such a conventional liquid supply and drainage method, a concentration gradient of the copper ion concentration due to gravity occurs in the depth direction (the direction of the broken line arrow) of the electrolytic solution held in the electrolytic cell 100. For example, if the solution is supplied to an electrolytic cell of about 9 m ³ at about 30 L/min and electrolyzed at a current density of about 300 A/m ² , the copper ion concentration at the upper and lower parts of the electrode will be about several days after electrolysis. A difference of 10 g/L occurs.
The electrolytic refining of copper is carried out at about 60° C., and the copper ion concentration in a saturated solution of copper sulfate at 60° C. is 158 g/L. However, practically, sulfuric acid is added to reduce the bath resistance during energization. When the electrolytic solution is formed only of sulfuric acid, copper sulfate and water, and the temperature is 60° C. and the sulfuric acid concentration is 200 g/L, the solubility of copper sulfate is lowered and the copper ion concentration in the saturated solution is lowered to 95 g/L.

Furthermore, the concentration gradient occurs not only in the vertical direction but also in the horizontal direction. That is, since copper is eluted on the surface of the anode, the closer to the anode and the higher the current density, the higher the copper ion concentration. As a specific example, when the electrolytic solution is collected on the liquid surface and the copper ion concentration is 50 g/L, it is possible to elute up to a copper ion concentration 45 g/L higher than that in the vicinity of the anode. The vicinity of the lower end of the electrode, which has a vertical concentration gradient as high as about 10 g/L, is 60 g/L, and therefore, when the copper ion concentration is eluted by 35 g/L in the vicinity of the anode, it saturates, and crystals rise when it rises. become. Therefore, passivation of the anode is likely to occur on the lower end side of the electrode. In addition, since the actual electrolytic solution contains impurities, it is saturated when the copper ion concentration in the saturated solution is lower than 95 g/L, and the passivation of the anode is likely to occur.

As a factor for alleviating this situation, there is a supply of an electrolytic solution. By supplying the electrolytic solution having an appropriate concentration, the electrolytic solution can be brought close to the target concentration. For example, by supplying a low-concentration electrolytic solution from the liquid supply port 30, the electrolytic solution near the lower end side of the electrode is diluted. The copper ion concentration is high near the lower end of the electrode, but if the concentration is higher than the supply liquid by about 10 g/L, the density difference between the two at about 60° C. is about 0.01 g/cm ³ . Therefore, the electrolytic solution supplied to the electrolysis tank bottom Bo side forms an upward flow, and then moves to the upper drainage port 31 provided at the upper part of the electrolytic bath and is drained. In such a flow, since the supplied electrolytic solution does not sufficiently diffuse between the electrodes, the function of suppressing the concentration gradient of the copper ion concentration in the depth direction of the electrolytic cell is limited as described above.

Therefore, as means for suppressing such a concentration gradient of the copper ion concentration, the drainage method and the liquid supply method of the electrolytic solution were focused and studied.
As a result, in order to suppress the concentration gradient of the copper ion concentration, it was found that it is important to sufficiently disperse the supplied electrolytic solution between the electrodes, and drainage of the electrolytic solution according to the present invention from the electrolytic cell. The method was obtained.
That is, from the upper part of the electrolytic cell, in the electrolytic solution stored in the electrolytic cell, one end side is immersed as a suction port, and the other end side is connected to a drainage pump whose flow rate is controllable. By changing the installation position of the suction port corresponding to the opening of the drainage of the drainage pipe, the electrolyte is sucked and discharged from an arbitrary position from the electrolytic cell bottom Bo to the vicinity of the electrolyte level 2a. Can be liquefied.
Thereby, the concentration gradient of the copper ion concentration can be suppressed. Further, by controlling the drainage flow rate by the drainage pump to be equal to or less than the feed rate of the electrolyte solution supplied to the electrolytic cell, the drainage pump simultaneously drains the electrolyte solution and overflows the electrolyte solution surface 2a. It becomes possible to drain the liquid.

For blockage, by changing the installation position of the drainage pipe, it is possible to perform cleaning without taking time to extract the electrolytic solution. In the separated environment, maintenance such as maintenance and cleaning can be performed, service life and performance deterioration can be prevented, and it is possible to continue electrolytic refining of metal without lowering production efficiency.
In addition, if maintenance and cleaning are difficult, the pump can be immediately discarded or replaced.

An example of such a specific embodiment according to the present invention is such that a flow rate controllable drainage pump P is connected as shown in FIG. 2, one end of which is connected to the pump P and the other end (suction port 12) is electrolyzed. The electrolytic solution is discharged by performing the drainage operation using the electrolytic cell 1 which is immersed in the electrolytic solution from above the solution and is equipped with the drainage device A in which the suction pipe 12a whose adjustable immersion position is freely adjustable is combined. The depth of the drainage port (the suction port 12 in FIG. 2) in the electrolytic solution in the electrolytic cell that can be adjusted can be adjusted appropriately, and even when a hardly soluble substance is generated in the suction pipe 12a, the pipe or pump is By replacing it with a new one, the drainage operation can be restarted immediately, and the production of copper by electrolytic refining can be restarted without delay.
Further, the drainage from the drainage device A and the drainage from the existing upper drainage port 11 can be merged by the drainage gutter 11a to be collectively discharged to the outside, which simplifies the drainage process and equipment. Is possible.

The drainage device A includes a pump P capable of controlling the flow rate, a suction pipe 12a connected to the pump P, and a drain pipe 12b for discharging the electrolytic solution sucked by the pump P to a drain gutter 11a. The pipe 12a has a suction port 12 opened on the side opposite to the connecting portion with the pump P, and is immersed to a predetermined position in the electrolytic solution. The electrolytic solution in the electrolytic bath is sucked through the suction pipe 12a, mixed with the drainage from the upper drainage port 11a in the drainage gutter 11a connected to the upper drainage port 11, and discharged to the outside of the electrolytic bath.

This drainage device A has a mechanism as shown in FIG. 3(a), (b), or (c), (d). In other words, when the drainage device A is installed in the electrolytic bath 1, the position of the suction port 12 at the tip portion immersed in the electrolytic solution of the suction pipe 12a can be changed within the movable range δ. With this mechanism, the distance from the electrolytic cell bottom portion Bo can be appropriately set. The drainage device A is not limited to the type shown in FIG. 3 and may be provided with a mechanism capable of sucking and discharging the electrolytic solution in the electrolytic cell from various liquid levels.

The drainage device A shown in FIGS. 3A and 3B is a device having a mechanism that changes the length of the suction pipe 12a by including the intermediate portion 13 that can expand and contract like a bellows.
Further, the drainage device A shown in FIGS. 3(c) and 3(d) is provided with a fixture 14 that is attached to and fixed to the electrolytic bath, and the fixture 14 has suction pipes 12a at different positions in the depth direction of the electrolytic bath. The device has a gripping mechanism.
In both of the drainage device A shown in FIGS. 3A and 3B and the drainage device A shown in FIGS. 3C and 3D, by moving at least a part of the suction pipe 12a, The suction port 12 can be arranged at a predetermined position including the electrolytic bath bottom area S.

Further, as the pump P capable of controlling the flow rate used in the drainage device A, a manual type (siphon type drainage) pump utilizing the siphon principle is preferable in that the flow rate can be maintained without power supply. In the case of a pump using such a siphon principle, the flow rate can be adjusted by changing the pipe diameter of the suction pipe 12a and the opening diameter of the suction port 12, but the diameter of the pipe and the opening diameter can be optimized in advance. It is desirable to do.

By the way, in the embodiment of the present invention shown in FIG. 2, when all the drainage is discharged from the electrolytic cell bottom region S, the copper ion concentration near the electrode upper part (electrolyte surface side) decreases, and the surface properties of the cathode and Since the purity may be deteriorated, the drainage of the electrolytic solution from the bottom area S of the electrolytic cell, that is, the drainage of the electrolytic solution using the suction port 12 is preferably 75% or less of the total drainage amount. Further, if the amount of liquid drained from the electrolytic bath bottom region S is small, the effect of sufficiently dispersing the supplied electrolytic solution between the electrodes is poor, so the amount of drained liquid from the electrolytic bath bottom region S is less than the total amount of drained liquid. It is better to be 25% or more.

Further, the purity of the cathode is deteriorated by the inclusion of the anode slime. The anode slime refers to an insoluble substance that does not dissolve in the anode during electrolytic refining of copper.
The anode slime drops off from the surface of the anode and deposits on the bottom Bo of the electrolytic cell. When the drainage from the electrolyzer bottom area S is carried out at a position close to the electrolyzer bottom Bo, the anode slime deposited on the electrolyzer bottom Bo is rolled up between the electrodes to raise the impurity concentration of the cathode. When the liquid is drained from the electrolyzer bottom area S, by setting the position of the suction port 12 at a position that is 10% or more of the depth inside the electrolyzer from the electrolyzer bottom Bo, the winding of the anode slime can be suppressed.

Further, when the drainage device A is installed such that the suction port 12 of the drainage device A is located on the bottom side, that is, the lower side of the electrolysis bath, the drainage from the bottom region S of the electrolytic bath is performed. When the flow velocity near the suction port 12 which is the liquid port is high, the anode slime is locally rolled up, and the impurity concentration of the cathode is increased.
Therefore, the size of the suction port 12 serving as the lower drainage port is set so that the flow velocity of the electrolytic solution (drainage liquid) passing through the drainage port is 2.5 cm/s or less. Winding up of was suppressed. Further, also in the liquid supply port 10, similarly, the size of the liquid supply port is set so that the flow velocity at the time of passing through the liquid supply port is 2.5 cm/s or less, whereby the winding of the anode slime is suppressed. It was

1 Electrolyzer 2 Electrolyte 2a Electrolyte Liquid Level 3 Anode 4 Cathode 5 Electrode 5u Electrode Lower Ends 10, 30 Liquid Supply Ports 10a, 30a Liquid Supply Pipes 11, 31 Upper Drain Port 11a Drain Trough 12 Suction Port 12a Suction Pipe 12b Drainage pipe 13 Intermediate part 14 Fixture 100 Electrolysis tank A Drainage device Bo Electrolysis tank bottom P (Siphon type drainage) pump S Electrolysis tank bottom area ho Ho drainage height w ¹ , w ² Electrolyte wall ( (Tank wall in the direction normal to the electrode surface)
δ movable range

Claims (7)

A method for draining an electrolytic solution from an electrolytic cell for electrolytically refining a metal,
In the electrolytic solution stored in the electrolytic bath from above the electrolytic bath, one end side is immersed as a suction port, and the other end side is a drainage pipe connected to a drainage pump whose flow rate is controllable. Prepare,
By changing the installation position of the suction port of the drainage pipe, the electrolytic solution is sucked and drained from any position from the bottom of the electrolytic cell to the vicinity of the electrolytic solution surface. Method of draining electrolyte in purification. The drainage flow rate of the drainage pump is controlled to be equal to or lower than the feed rate of the electrolyte solution supplied to the electrolytic cell, so that the drainage pump drains the drainage fluid at the same time as the drainage flow rate overflow The method for draining an electrolytic solution in electrolytic refining according to claim 1, wherein the electrolytic solution is made liquid. The drainage method of an electrolytic solution in electrolytic refining according to claim 1 or 2, wherein the drainage pump is a manual pump utilizing a siphon principle. The electrolytic cell comprises a plurality of electrodes having electrode surfaces arranged in parallel,
On one side of the electrolytic cell wall in the normal direction of the electrode surface, a liquid supply port for supplying an electrolytic solution into the electrolytic cell is provided,
The drainage of the electrolytic solution in the electrolytic refining according to any one of claims 1 to 3, wherein the electrolytic cell in the electrolytic cell has a movable suction port for sucking the electrolytic solution in the electrolytic cell on the other side. Method. The electrolytic solution in electrolytic refining according to claim 2, wherein the ratio of the amount of electrolytic solution drained from the suction port is 25% or more and 75% or less of the total amount of drained liquid from the electrolytic cell. Drainage method. The drainage of the electrolytic solution in the electrolytic refining according to any one of claims 1 to 5, wherein the suction port is installed at a position of 10% or more from the bottom of the electrolytic bath with respect to the depth of the electrolytic bath. Liquid method. The drainage method of the electrolytic solution in the electrolytic refining according to any one of claims 4 to 6, wherein the flow rates at the liquid supply port and the suction port are 2.5 cm/s or less.

Images