JPH05156482A - Quality control method for electrolytically refining metal - Google Patents

Abstract

PURPOSE:To provide a quality control method capable of relatively easily judging whether a cathode plate is good or bad, capable of being easily mechanized or automated and also used for improving the electrolytic operation. CONSTITUTION:The quality is judged from the average current density of a cathode calculated from the weight of a cathode plate or the weight difference between the cathode plates before and after electrolysis and electrolyzing time, and the current distribution in the succeeding stage is uniformized to conduct electrolysis.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a quality control method for determining the quality of a cathode plate and improving electrolysis conditions in electrolytic refining of metals.

[0002]

2. Description of the Related Art The actual case of electrolytic refining of metal will be described in the case of copper. Electrolytic refining of copper uses crude copper or purified crude copper as an anode and an electrodeposited copper seed plate as a cathode, which are alternately suspended in an electrolytic cell and electrolyzed in an electrolytic solution containing a copper sulfate solution as a main component to form a seed plate. It is common to electrodeposit pure copper on top. The cathode in which copper is electrodeposited to a predetermined thickness on the seed plate in this manner is called electrolytic copper.

Impurity elements are present not only in the crude copper but also in the refined crude copper, and these impurities are eluted with the copper into the electrolytic solution in accordance with the electrolysis, and a part thereof becomes slime and settles on the bottom of the tank. For this reason, a certain amount of the electrolytic solution is extracted during electrolysis, and a part of the electrolytic solution is purified so that the electrolytic solution is repeated.

The electrolytic copper thus obtained is washed and the crossbars are taken out, bundled in a predetermined number of sheets and shipped. This electrolytic copper has a purity of 99.99% or more, but those with large surface irregularities generally have a somewhat high impurity content, so a visual inspection is finally performed and electrolytic copper judged to be defective is smelted. I am trying to repeat the process.

[0005]

Conventionally, the visual inspection has been conducted by visual inspection, but some sort of sensor is necessary to automate the visual inspection. However, this visual inspection comprehensively evaluates the degree of unevenness on the surface of the cathode plate, and cannot be used as a substitute unless a sensor capable of such evaluation is separately developed.

It is an object of the present invention to provide a quality control method which can determine the quality of a cathode plate relatively easily, is easy to mechanize and automate, and can be used for improving electrolytic operation. ..

[0007]

In order to achieve the above object, the present inventors have found that the surface of the cathode plate is rough because the current density is too high. If the current density is high, the amount of electrodeposition is large. Therefore, it was thought that there is a correlation between the weight of the cathode plate and the defective product, and as a result of various experiments, this was confirmed and the present invention was reached.

That is, the first quality control method of the present invention is to measure the weight of each cathode plate after electrolytic refining one by one and determine the quality of the cathode plate based on the magnitude of the measured value.

In the second aspect of the present invention, the weight of the cathode is measured one by one before the start of electrolytic refining, and the weight of the cathode is measured after electrolysis to calculate the amount of electrodeposited metal of each cathode, and at the same time from the electrolysis time. The average current density of the cathode is obtained, and the quality of the cathode plate is determined by the magnitude of the current density.

A third aspect of the present invention is to carry out electrolysis so that the current distribution state in each electrolytic cell is known from the average current density and the current distribution in the next electrolytic refining is made uniform.

[0011]

[Function] Current density is one of the most important conditions for electrolysis. If this is too small, the productivity will be low, so it is desirable to make it as high as possible, but naturally there is a limit to obtaining a good quality cathode plate. This is because if the current density is too high, impurities are likely to be deposited on the cathode, abnormal metal deposition is likely to occur, and a short circuit may occur. Although economic conditions are selected to prevent such precipitation of impurities and abnormal precipitation, operation is actually carried out, but due to changes in various factors, it is possible to eliminate short circuits between electrode plates during electrolytic operation. No
Monitoring during electrolysis is essential because of the need to detect and correct short circuits early.

Even if the cathode plates obtained from the same electrolytic cell are monitored and corrected as described above, some cathode plates may be determined to be defective by visual inspection. It is presumed that the cause of this is that a portion with a high current density locally occurred for some reason, resulting in impurity precipitation or abnormal precipitation. As the current density increases, the electrodeposition amount naturally increases, so that the electrodeposition amount can be used as a means instead of the visual inspection.

The amount of electrodeposition can be approximated by the weight of the cathode plate, and the weight of each cathode plate may be measured one by one, and a cathode plate having an abnormally large weight may be determined to be defective. When the appearance inspection and the weight measurement were actually performed, there was a good correlation, and it was found that the gravimetric method was effective. According to this gravimetric method, mechanization and automation can be performed relatively easily.

In order to accurately measure the electrodeposition amount, it is preferable to measure the cathode weights one by one before starting the electrorefining and to calculate the difference from the weight of the cathode plate after electrolysis. The cathode weight may be measured by the weight including the crossbar. The average current density during electrolysis of each cathode can be calculated from the amount of electrodeposited metal and the electrolysis time, and an abnormally large current density can be determined to be defective. According to this method, it is possible to more accurately determine the quality.

Further, this method can be used as follows.
That is, the array of the average current densities of the cathodes during electrolysis indicates the current distribution state in the entire electrolytic cell. Therefore, it is possible to know the cathode position that shows an abnormally large current density or an abnormally small current density as a result of one-life electrolysis operation, and adjust the power supply equipment at this position before the next operation to average the current distribution. Can be planned. The presence of a cathode having an abnormally small current distribution also increases the amount of current flowing to the other cathode, and also induces abnormal deposition.

The method of the present invention can be applied not only to electrolytic refining of copper but also to electrolytic refining of other metals.

[0017]

【Example】

Experiment No. 1 ... 23 cathodes for one electrolysis tank (length: 1050 mm, width: 1070 mm, thickness: about 0.6 mm, weight: about 7 kg), excluding the cathodes at both ends, the total weight (including crossbar) ) Was charged in the electrolytic cell, and 22 purified anodes were charged, and electrolysis was performed for 216 hours with the cathode current density of the entire electrolytic cell set to 260 A / m ² and then obtained. Was measured in the same manner except for both ends, and the amount of electrodeposited copper of each cathode was determined from the weight difference. The electrolytic copper was also visually inspected and scored with a perfect score of 100. As a result, 3 out of 21 rejected products were rejected.

The weight of electrolytic copper including the crossbar and the appearance rating are plotted in FIG. In FIG. 1, open corner points indicate acceptable products, and black corner points indicate rejected products. It can be seen from this figure that there is a correlation between the weight of electrolytic copper and the external appearance score, and the pass / fail judgment may be made on the basis of 180 kg of electrolytic copper.

The average current density during electrolysis was calculated from the amount of electrodeposited copper on each cathode. FIG. 2 is a plot of the current density and the appearance rating. It can be seen from FIG. 2 that there is a good correlation between these factors and the appearance inspection can be replaced by the current density. In this case, the current distribution ratio (σ _n-1 / average value x) was 0.092.

Experiment No. 2 ... Experiment No. In No. 1, electric copper having a small current density and a small amount of electrodeposited copper was observed, and it was found that the current distribution rate was also large. Therefore, in order to improve this, contact with the ears of the anode, the crossbar of the cathode, and these The bus bar contact part was well polished, and the others were the same as the experimental No.
Electrolysis was performed in the same manner as 1. However, the cathode is 27
The number of sheets and the number of anodes were 26, and the electrolysis time was 231 hours.

The appearance of the obtained electrolytic copper was visually inspected, but no rejected product was found. The relationship between the weight of electrolytic copper and the appearance score and the relationship between the current density and the appearance score are plotted in FIGS. 3 and 4, respectively.

According to FIGS. 3 and 4, the variations in the data of electrolytic copper weight or current density became small, and the correlation between these and the appearance scores became small, but the scores were generally high,
It shows that the third method of the present invention is extremely effective. The current distribution ratio was 0.039.

[0023]

As described above, according to the present invention, a simple means for discriminating the quality of electrolytic copper can be obtained. However, it is possible to obtain not only the simple means but also the means for improving the quality variation. This can greatly contribute to the quality improvement of electrolytic copper.

[Brief description of drawings]

FIG. 1 Experiment No. FIG. 2 is a plot diagram of electrolytic copper weight and appearance score in FIG.

2] Experiment No. 2 is a plot diagram of the cathode current density and the appearance score in FIG.

[Fig. 3] Experiment No. 2 is a plot diagram of electrolytic copper weight and appearance score in FIG.

4] Experiment No. 2 is a plot diagram of the cathode current density and the appearance score in FIG.

Claims (3)

[Claims] 1. A quality control method in electrolytic refining of metal, wherein the weight of each cathode plate after electrolytic refining is measured one by one, and the quality of the cathode plate is discriminated by the size of the weight. 2. The weight of each cathode is measured one by one before the start of electrolytic refining, and the amount of electrodeposited metal of each cathode is calculated from the difference between the weight of the cathode plate after electrolysis and the amount of electrodeposited metal and electrolysis. A quality control method in electrolytic refining of a metal, characterized in that the average current density of each cathode is obtained from time, and the quality of the cathode plate is determined by the magnitude of the current density. 3. The cathode weight is measured one by one before starting electrorefining in each electrolytic cell, and the amount of electrodeposited metal of each cathode is calculated from the difference with the weight of the cathode plate after electrolysis, Knowing the current distribution state in the electrolytic cell by obtaining the average current density of each cathode from the amount of electrodeposited metal and the electrolysis time, the next step of electrorefining the current distribution of the metal is characterized by uniform electrolysis Quality control method in electrolytic refining.