JP6726411B2 - Power control device and power control method for use in electrolytic refining equipment - Google Patents

Description

The present invention relates to a safety device for preventing adverse effects on equipment and people in an electrolytic refining facility, and specifically, in an electrolytic refining facility, a power control device for electrolytic refining for safe operation, and its control. Regarding the method.

A nonferrous electrolytic refining method is widely known as a refining method for nonferrous metals such as copper and nickel. This non-ferrous electrolytic refining method is a refining target metal such as Cu or Ni that is dissolved in the electrolytic solution by energizing between the anode (anode plate) and the cathode (cathode plate) immersed in the electrolytic solution in the electrolytic cell. (Hereinafter, referred to as a target metal) is electrodeposited on the cathode surface to obtain a high-purity target metal.

Specifically, after energization is continued to electrodeposit the target metal on the surface of each cathode to a predetermined thickness, the cathode is pulled up from the electrolytic solution in the electrolytic cell to recover the electrodeposited target metal, The cathode before electrodeposition is immersed in the electrolytic cell and energized repeatedly. Also, with respect to the anode, the anode is consumed with the passage of time, and thus the consumed anode is pulled out of the electrolytic cell and replaced with a new one. After pulling up the cathode or anode, the electrolytic solution is removed by pulling out a plug from a pipe installed at the bottom of the electrolytic cell, and the electrolytic cell is regularly cleaned.

By the way, when a plurality of electrolyzers are used, there are a method of connecting those electrolyzers in series to a power source and energizing, and a method of connecting these electrolyzers to a power source in parallel with each other to energize, and the former series method is It is commonly used.
The reason for this is that as the electrodeposition progresses, the cathode easily comes into contact with the anode, and when it comes into contact, the current concentrates on the contact portion, but this current loss and the accompanying production loss are small in the series method. To be Specifically, in the series method, the current of the electrolytic cell in which the contact occurs is wasted. On the other hand, in the parallel system, the electric current that should flow through the electrolytic cells in parallel is concentrated on the contact portion and is wasted.

The power supply used is roughly classified into a constant current power supply that keeps the current amount constant and a constant voltage power supply that keeps the voltage value constant. In the series system, the constant current power supply is generally used.
When this constant current power source is used, the current can be evenly distributed to each tank even if there is a difference in electrical resistance, so the production amount and quality of the target metal obtained by electrodeposition can be maintained. In addition, when pulling up the cathode or anode from the electrolytic cell or when temporarily changing the circuit so as to bypass the electrolytic cell, the constant current power supply can be used to suppress the temporal fluctuation of the current flowing in each cell. Therefore, the production amount and quality of the target metal obtained by electrodeposition can be maintained. The power supply may be a DC power supply, and may have a function such as pulse energization or reverse energization.

By the way, the cathode, the anode, and the fragments that have fallen off from the cathode during energization are heavy, and may fall to damage the bottom surface of the electrolytic cell. If the bottom surface is damaged or the plug is loosened and pulled out, the electrolyte solution is lost from the inside of the electrolytic cell.As the electrolyte level decreases, the contact area of the cathode and anode with the bulk electrolytic solution decreases. However, this contact area finally becomes zero. At this time, a huge electric current is concentrated on a small contact area, and there is a risk that the overheated electrolytic solution may bump and cause burns or chemicals. In addition, there is a risk that blindness or a fire may occur due to the spark of air discharge.

These dangers can be prevented by temporarily changing the circuit so as to bypass the electrolytic cell, if a cell in which the electrolyte level is lowered can be found early. However, since there are cathodes and anodes in the upper part of the electrolytic cell to block the view, the liquid level of the electrolytic solution and the state of the cell bottom cannot be seen from a distance, and the electrolytic cell has several m ² per cell. Generally, it occupies the site area of, and it is often housed in the building away from the electrolytic refining control room in units of several hundreds, and early visual detection was difficult.

Therefore, in order to remove the dangerous state, when a stable voltage value of the electrolysis device is read and stored as shown in Patent Document 1, a fluctuation allowable range is set for this value, and the voltage value deviates from the allowable range. In addition, a technique for protecting an electrolysis device is known. However, in an electrolysis plant, many electrolyzers are connected to a power source (especially in series), so the voltage of the electrolyzer is stabilized by the number of electrolyzers, and there is a risk of lowering the electrolyte level. Could not be removed.
As described above, there has been a demand for a system that accurately detects a decrease in the liquid level in the electrolytic cell and reliably prevents a danger.

JP, 03-130385, A

The present invention, in an electrolysis plant in which a plurality of electrolytic cells are connected in series to a DC power supply, detects a phenomenon associated with a decrease in the liquid level in the electrolytic cell, and reliably prevents the risk caused by the decrease in the liquid level. An object of the present invention is to provide a power supply control device for electrolytic refining equipment and a control method therefor.

The inventors observed changes in the amount of the electrolytic solution in the electrolytic cell when the electrolytic solution decreased from the electrolytic cell in the operating state, and found that the rate of change was constant. In addition, we examined the change in the voltage (cell voltage) applied to the electrolytic cell when the electrolytic solution decreased from the electrolytic cell, and found that the voltage applied to the electrolytic cell increased at an accelerated rate as the amount of electrolytic solution decreased. I found it.
Therefore, if the change rate of the voltage fluctuation rate per unit time is used for determination, it is possible to accurately detect the decrease in the liquid level in the electrolytic cell.
Next, the inventors examined a method of discovering a change in the voltage fluctuation rate within a fixed time, for example, made a group in which 10 to 20 electrolytic cells were connected in series, and measured the voltage of the group. As a result, they have found that a drop in the liquid level in the electrolytic cell can be detected in a short period of time, and have completed the present invention.

A first aspect of the present invention is an electrolysis system comprising a power source having a transformer function section for stepping down a received high voltage current to supply a low voltage current, and a plurality of electrolytic cells connected in series to the power source to form a closed circuit. A power supply control device for use in an electrolytic refining facility for supplying an electrolytic current from a power supply to an electrolysis section, the electrolysis section comprising one or more and m electrolyzers connected in series to each other. Groups or more, n groups, which are connected in series, and the difference between the voltage applied to any one of the n groups and the voltage applied to another group different from the one is a voltage equal to or higher than the cutoff voltage value. In the case shown, the power supply control device is characterized in that the supply of the electrolysis current from the power supply to the electrolysis section is stopped.

A second invention of the present invention is the power supply control device characterized in that the supply of the electrolytic current in the first invention is stopped by interrupting the high-voltage current to the transformer function section.

A third invention of the present invention uses the power supply control device according to the first or second invention to detect an increase in voltage applied to a group of m electrolyzers connected in series, and from the power supply to the electrolysis section. After the supply of the electrolytic current is stopped, the set in which the voltage increase is detected includes a tank in which the amount of the electrolytic solution has decreased, and a conduction path that bypasses this tank is constructed, and the supply of the electrolytic current is restarted. This is the power control method.

According to the present invention, in an electrolytic refining facility in which a plurality of electrolysis cells are connected in series to a DC power source, it is possible to detect a decrease in the liquid level of the electrolytic solution in the electrolysis cell and reliably prevent the risk resulting from the decrease in the liquid level. It is possible to provide a system that can.

It is the schematic which shows the equivalent circuit of one specific example of the electrolysis process using the power supply control apparatus of this invention. It is a figure which shows a general electrolysis cell, (a) is sectional drawing, (b) is schematic which shows the flow path of a copper ion and an electric current (* same arrow). FIG. 3 is a schematic diagram showing an energization path that bypasses a tank with a reduced amount of electrolyte in the present invention. It is a schematic flow chart which shows the power supply control device concerning Example 1 of the present invention. It is a schematic flowchart which shows the power supply control apparatus which concerns on Example 2 of this invention. It is the schematic which shows the equivalent circuit of the conventional electrolysis process. It is a schematic diagram showing an equivalent circuit when the electrolytic solution is lost from one electrolytic cell in the electrolysis step.

Hereinafter, the power supply control device and the power supply control method of the present invention will be described in detail.
According to the present invention, the voltage applied to the set constituted by connecting the electrolytic cells in series is measured, and when the measured voltage value becomes excessive, the supply of the electrolytic current from the power source to the electrolytic cell is stopped. In the present invention, the voltage is measured so that the measured value is a positive value.
To determine whether or not the measured voltage value is excessive, the evaluation voltage value is calculated from the measured voltage value, and when the evaluation voltage value shows a value equal to or higher than the preset cutoff voltage value, the measured voltage value is It is judged to be excessive.

The cutoff voltage value serving as the criterion can be obtained by linearly combining the average value of the evaluation voltage value and the fluctuation range of the evaluation voltage value, as described in detail in the following equations (1) to (8). Moreover, it is preferable that the evaluation voltage value and the cutoff voltage value are recalculated and set at regular intervals. By doing so, an abnormality such as a decrease in the liquid level in the electrolytic cell can be detected at an early stage and erroneous detection can be reduced.
It is desirable that the data period used for calculation of the cutoff voltage value be longer than the update interval of the cutoff voltage value. By doing so, the cutoff voltage value becomes stable, and the detection accuracy of the abnormality can be improved.

As a method of calculating the evaluation voltage value and the cutoff voltage value, a first or second evaluation method described later is used.
[First evaluation method]
As the evaluation voltage value, the measured voltage value E[V] is used as it is.
At this time, as the cutoff voltage value [V], any of the following expressions (1) to (3) can be used.

In particular, in the electrolytic refining of copper, the value calculated by the following formula (3) can be used as the cutoff voltage value. The number of measurement cells is the number of electrolysis cells arranged in a group of electrolysis cells connected in series (that is, the range to which the measurement voltage value E is applied) when measuring the measurement voltage value E. ..

In this method of the present invention, since the measured voltage value E of the voltage applied to the set in which the electrolytic cells are connected in series is used as the evaluation voltage value, the evaluation voltage value is large and has little fluctuation. Therefore, when the evaluation voltage value (=measured voltage value E) reaches the cutoff voltage value represented by the above formula (1) or formula (2), it means that there is an abnormality such as a drop in the liquid level in the electrolytic cell. it can.

Particularly, in electrolytic refining of copper, the measured voltage value E of the voltage is generally 0.2 V/tank to 0.4 V/tank, and is generally 0.25 V/tank to 0. It is in the range of 35 V/tank. Therefore, it can be said that the measured voltage value E of the voltage reaches the cutoff voltage value represented by the above formula (3) at the time of an abnormality such as a decrease in the liquid level in the electrolytic cell.

[Second evaluation method]
As an evaluation voltage value, the absolute value of the difference between the measured voltage value E and the measured value E′ of the voltage applied to another set in which the same number of electrolytic cells as the set of electrolytic cells in which the measured voltage value E is recorded are connected in series. , |EE'| is used. One of the following values is used as the cutoff voltage value at this time.

In this evaluation method, since the absolute value |E−E′| of the difference between the voltages applied to the set in which the same number of electrolytic cells are connected in series is used as the evaluation voltage value, the fluctuation of the evaluation voltage value is reduced, so that evaluation It can be said that the voltage value |EE′| reaches the cutoff voltage value represented by the above formula (4) or formula (5) at the time of an abnormality such as a decrease in the liquid level in the electrolytic cell. In addition, since E×1.0≦E′×1.1 and E′×1.0≦E×1.1 are normally satisfied, the equations (4) to (5), (6), and (7) can be obtained, and it can be more easily operated. Further, in the normal state, almost the same current flows in each set, so that the evaluation voltage value |E−E′| has an advantage that it can be stably operated even if the current amount is changed.

(When there are many pairs)
In an electrolytic refining facility that includes a large number of sets composed of a plurality of electrolytic cells, it is expected that it will be difficult to operate the evaluation voltage value and the cutoff voltage value because there are numerous combinations of the sets.

For example, in the above equation (4), the maximum value and the minimum value of |E−E′| are different from the average value, and cannot be obtained from the average value of E or the average value of E′. This difficulty can be reduced by setting the cutoff voltage value to the following equation (8).

When there are a large number of sets composed of a plurality of electrolytic cells, the cutoff voltage value obtained from any combination is used as the cutoff voltage value while using various evaluation voltage values |EE′| It may be represented by a value. As a result, the cost and time required for recording and calculating the cutoff voltage value can be significantly reduced.
At this time, erroneous detection can be prevented by selecting E and E′ so that the breaking voltage value becomes the largest in the calculation of the breaking voltage value.

(Measurement period)
The starting point of the data used for the calculation of the average value, the maximum value, and the minimum value of the present invention is “10 days ago”, “the time when the liquid levels of all the electrolytic cells of the group in which the electrolytic cells are connected in series are stable”, “energization” It is preferable to be the later one of "the time when the number of cells changes" and "the time when the electrolytic current is intentionally changed".
Furthermore, the end of the data should be at the time of calculation or immediately before the time of calculation.

(Electrolyzers that make up a set)
It is preferable that the electrolyzers constituting one set are not all of the electrolyzers connected in series to the power source, but only some of the electrolyzers. By doing so, it is possible to make the voltage change sensitive and detect it with high sensitivity.
The number m of electrolytic cells constituting one set may be one or more, but is preferably two or more. If the measurement takes time, it is recommended that the number of tanks is 9 or more, or 18 or more. This makes it easier to finish the measurement in time, since there are fewer sets to measure.

Regarding the number n of sets to be set, as shown in FIG. 6 which is a schematic diagram showing an equivalent circuit of a conventional electrolysis process, the electrolytic cell is formed by folding back and forth inside the building. Due to the circumstances, it is better to have one set of electrolytic cells from the turning point to the turning point. It is more preferable to make a set of electrolytic cells until they are returned with an odd number of turns. Specifically, the parts to which the voltages E _a and E _{b in} FIG. 1 are applied are set.
FIG. 1 is a schematic diagram showing an equivalent circuit of a specific example of an electrolysis step using the power supply control device of the present invention.

In FIG. 1 and FIG. 6, V _jk is an electrolytic cell (j group, k-th electrolytic cell), j is a group number, k is an electrolytic cell number in the group, N is a single electrolytic cell, 3 is a power supply device, Reference numeral 4 is a cutoff portion, 5 is a transformer function portion, 6 is an AC power source, E ₁₁ and E ₁₂ are voltages applied to one electrolytic cell, E _a and E _b are voltages applied to a pair of electrolytic cells, and E _all is a series. It is the voltage across all electrolyzers connected to.
Here, E ₁₁ , E ₁₂ , E _a , E _b , and E _all represent the measured voltage values, and E ₁₁ and E ₁₂ are the measured voltages of the first set of the first electrolytic cell and the second set of electrolytic cell, respectively. The values, E _a and E _b, are the measured voltage values of a group consisting of 12 electrolytic cells and their adjacent groups, and E _all is the measured voltage value when _all the electrolytic cells are combined, and is applied to the electrolytic cells. Voltage.

As shown in FIG. 1, the power supply device 3 of the electrolysis plant equipped with the electrolytic refining equipment according to the present invention includes a transformer function unit 5 therein, and the transformer function unit 5 receives a high-voltage current to step down the voltage to obtain a high voltage current. The generated large amount of low-voltage current is supplied to the electrolytic cell.
Therefore, when the supply of the electrolytic current from the power supply to the electrolytic cell is stopped, the high-voltage current to the transformer function unit 5 is cut off to stop it. By doing so, the current passing through the breaking unit 4 (so-called switch) is a high-voltage side current, which is smaller than that in the case of breaking the low-voltage current. Therefore, the capacity of the breaking unit can be reduced, and It consumes less.
When the high-voltage current is alternating current, the power supply device 3 may convert (rectify) to direct current at the same time as stepping down as shown in FIG. 1, or may convert (rectify) to direct current before stepping down. After that, it may be converted (rectified) to direct current.

FIG. 2 is a view showing a general electrolytic cell, (a) is a cross-sectional view, (b) is a schematic view showing flow paths of copper ions (black single-headed arrow) and current (black single-headed arrow). And current flow through the flow path in the same direction. In FIG. 2, V is an electrolytic cell, L is an electrolytic solution, A is an anode, C is a cathode, and 11 is a liquid level of the electrolytic solution.
Since the electrolytic solution L in the electrolytic cell V constitutes a circuit through which copper ions and current pass as shown in FIG. 2B, the higher the liquid level 11, the larger the cross-sectional area through which copper ions and current pass. Become. It is widely known that the resistance value of the conductor is inversely proportional to the cross-sectional area, and the resistance value increases at an accelerating rate even if the liquid level of the electrolytic solution in the electrolytic cell decreases at a constant speed. This is the first factor that causes the voltage applied to the group to increase at an accelerating rate.

Further, as the amount of the electrolytic solution L in the electrolytic cell V decreases, the electrolytic current concentrates on the remaining small amount of electrolytic solution, and the evaporation of the electrolytic solution proceeds at an accelerated rate. As a result, crystals are deposited on the surface of the anode A and the surface of the cathode C to prevent energization. The resistance value also increases at an accelerated rate due to the accelerated evaporation of the electrolytic solution and the precipitation of crystals. This is the second factor that causes the voltage applied to the group to increase at an accelerating rate.

When constant current electrolysis is performed while the resistance value is acceleratedly increased by the first factor or the second factor described above, the voltage applied to the electrolytic cell is proportional to the resistance value. Increase. This is utilized to stop the supply of the electrolytic current from the power source to the electrolytic cell only when the voltage or the voltage difference increases at an accelerating rate.
By doing so, the supply of the electrolytic current is not erroneously stopped when the amount of the electrolytic solution has not decreased, so that unnecessary stop can be reduced and the production amount can be increased.

In addition, after detecting an increase in voltage or voltage difference and stopping the supply of electrolytic current from the power supply to the electrolytic cell, identify the cause of it and build an energizing path that bypasses the electrolytic solution-reduced cell. , Restart the supply of electrolytic current. By doing so, while repairing a tank having a reduced amount of electrolytic solution or supplementing the electrolytic solution, it is possible to supply current to another electrolytic cell for production.
More specifically, for example, when the electrolyte of the electrolytic cell V ₂₂ within the dotted line is washed away as in Figure 7, after stopping the supply of electrolysis current in the present invention, a short circuit 10 the black part of FIG. 3 By short-circuiting, the current is diverted as shown by the white arrow, and the supply of electrolytic current is restarted. In FIG. 3, “white x” corresponds to the second electrolyzer V ₂₂ of the second set in FIG. 7, and is an electrolyzer that is not functioning because the electrolytic solution has flowed out.

(Evaporated electrolyte)
As the evaporation of the electrolytic solution accelerates, a large amount of water vapor is supplied above the electrolytic cell. Since water vapor is evaporated from the electrolytic cell in the electrolytic building and the humidity is high, a large amount of supplied water vapor forms dew in the air to form fog. This fog can be detected using light, such as a photocell. Only when such detection is performed, the supply of the electrolytic current from the power source to the electrolytic cell may be stopped. By doing so, the supply of the electrolytic current is not erroneously stopped when the amount of the electrolytic solution has not decreased, so that unnecessary stop can be reduced and the production amount can be increased.
Such detection using light can be suitably used when there are a large number of electrolytic cells, and also makes it easy to identify the cell in which the electrolytic solution has decreased.

As described above, the present invention provides a system capable of detecting a decrease in the liquid level in an electrolytic cell in an electrolytic plant in which a plurality of electrolytic cells are connected in series to a DC power source and reliably preventing a danger. You can The current supplied from the DC power source is preferably a DC current, but may have a pulsating current or the current direction may be temporarily reversed.

Hereinafter, the present invention will be further described with reference to examples.

As the power supply control device of the present invention, electrolytic purification of copper was performed using the power supply control device shown in the schematic flowchart of the power supply control device according to the first embodiment of FIG.
The power supply control device shown in FIG. 4 measures the voltage of a group in which a plurality of electrolytic cells are connected in series, and sends the voltage of this group to an alarm setter via a transformer for an instrument, and the input value of the alarm setter is Outputs a DC overvoltage signal when the set value is exceeded.
Further, when the DC overvoltage signal is output, a serious failure alarm is issued and the protection circuit is operated to automatically stop the power supply device.
In addition, each electrolyzer is connected to the power supply device in series to form a closed circuit.

A high-voltage current was stepped down and rectified by a power supply unit to energize each electrolytic cell, and a value corresponding to 1.1 times the voltage of the set at this time was set as the set value of the alarm setter. When the plug at the bottom of a certain electrolytic cell was removed while electricity was still flowing, the amount of electrolyte in the electrolytic cell gradually decreased, and electricity was automatically stopped.
The voltage of the set at the time when the energization was stopped was the voltage at the time when the alarm setter was set.

Electrolytic refining of copper was performed using the power supply control device shown in the schematic flow chart showing the power supply control device according to the second embodiment of the present invention in FIG. 5 of the present invention.
The power supply control device of FIG. 5 measures the voltage of a group in which 18 electrolytic cells are connected in series, and sends the maximum of the voltage difference of each group to the alarm setter via the instrument transformer, Outputs a DC overvoltage signal when the input value of the setter exceeds the set value. Further, when a DC overvoltage signal is output, a serious failure alarm is issued and the protection circuit is activated to automatically stop the power supply device.
Each pair is connected in series to the power supply device to form a closed circuit.

A high-voltage current was stepped down and rectified by a power supply unit to energize each electrolytic cell, and a value corresponding to 0.1 times the voltage of the set at this time was set as the set value of the alarm setter. Then, when the plug at the bottom of a certain electrolytic cell was removed while energizing each electrolytic cell, the electrolytic solution in the electrolytic cell decreased and the energization automatically stopped.
The largest voltage difference among the groups at the time when the energization was stopped was the voltage at the time when the alarm setter was set.

As the power supply control device of the present invention, electrolytic purification of copper was performed using the power supply control device shown in the schematic flowchart of the power supply control device according to the first embodiment of FIG.
The power supply control device shown in FIG. 4 measures the voltage of a group in which a plurality of electrolytic cells are connected in series, and sends the voltage of this group to an alarm setter via a transformer for an instrument, and the input value of the alarm setter is Outputs a DC overvoltage signal when the set value is exceeded.
Further, when the DC overvoltage signal is output, a serious failure alarm is issued and the protection circuit is operated to automatically stop the power supply device.
It should be noted that the power supply device is connected in series with one set in which two electrolytic cells are connected in series and one set in which four electrolytic cells are connected in series to form a closed circuit. ing.

A high-voltage current was stepped down and rectified by a power supply unit to energize each electrolytic cell, and the set value of the alarm setter was set to a value corresponding to 0.4 times the number of cells. When the plug at the bottom of the electrolytic cell belonging to the group of two tanks was removed while the power was on, the electrolytic solution in the electrolytic cell gradually decreased, and the power was automatically stopped.
The voltage of the set at the time when the energization was stopped was the voltage at the time when the alarm setter was set.

A current of 20 kA was passed through the electrolytic cell to carry out electrolytic refining of copper.
When a plug at the bottom of a certain electrolytic cell was removed while applying an electric current, the electrolytic solution in the electrolytic cell decreased, and the voltage applied to the electrolytic cell was measured every 5 minutes after the plug was removed.
The voltage was measured 7 times, but the voltage increased monotonously, and the rate of increase was accelerated as the number of measurements was increased.

After Example 1, a short-circuiting device was arranged to form a circuit bypassing the electrolytic cell from which the plug was removed, and then energization was restarted.
Periodically observing the cathode surface of the electrolyzing cell under electricity with a magnifying glass, it was confirmed that the electrodeposition of copper was progressing without any particular problems.

V _jk , V Electrolyzer j Number of electrolyzer set k Number of electrolyzer in set L Electrolyte A Anode C Cathode 3 Power supply unit 4 Breaking unit 5 Transformer function unit 6 AC power supply 10 Short circuiter 11 Liquid level of electrolyte

Claims (3)

The power supply includes a transformer function unit that reduces the received high-voltage current to supply a low-voltage current, and an electrolysis unit including a plurality of electrolytic cells that are connected in series to the power supply to form a closed circuit. Is a power supply control device used in an electrolytic refining facility for supplying an electrolytic current to a section,
The electrolysis section has a configuration in which one or more sets connected in series, two or more sets consisting of m electrolysis cells, and n sets are connected in series,
When a difference between a voltage applied to any one of the n sets and a voltage applied to another set different from the one set indicates a voltage equal to or higher than a cutoff voltage value, an electrolytic current from the power source to the electrolysis unit A power supply control device for use in electrolytic refining equipment, characterized in that the supply of electricity is stopped. The power supply control device used in the electrolytic refining equipment according to claim 1, wherein the supply of the electrolytic current is stopped by interrupting a high-voltage current to the transformer function unit. After detecting an increase in voltage applied to a set of m electrolytic cells connected in series using the power supply control device according to claim 1 or 2 , and stopping the supply of electrolytic current from the power supply to the electrolysis section,
The set in which the voltage increase is detected includes a tank with a reduced amount of electrolyte, and an energization path that bypasses the tank is constructed.
A power supply control method used for electrolytic refining equipment, characterized in that the supply of the electrolytic current is restarted.

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