JP2003160893A - Method for controlling voltage of electrolytic vessel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for controlling voltage on an electrolytic vessel, which enables a proper operation, and enables the electrolytic vessel showing abnormal voltage to be easily found, by individually determining the voltage on the electrolytic vessel corresponding to difference or a change of operating conditions with calculation, and comparing the voltage determined by the calculation with a measured voltage value. <P>SOLUTION: This method comprises, when controlling electrolytic cell voltage in a chloride bath of nonferrous metal, previously determining voltage drops ΔE<SB>a</SB>and ΔE<SB>c</SB>from contact resistance of an anode and a cathode, voltage drops ΔEL<SB>a</SB>and ΔEL<SB>c</SB>from resistance of an electrolytic solution, a voltage drop ΔE<SB>f</SB>from resistance of a membrane, theoretical electrolytic voltage ΔET<SB>he</SB>when the objective metal electrodeposits from the electrolytic solution containing nonferrous metal ions and chlorine ions, and voltage E(ca) calculated as a total of overvoltage η, and comparing the calculated voltage E(ca) with measured voltage E(me) in the electrolytic cell, to control the cell voltage. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is intended to detect abnormalities such as contact failure and short circuit of electrodes during operation when electrolytically extracting or electrolytically refining non-ferrous metals such as nickel, cobalt and copper from a chloride bath. The present invention relates to a method for managing the voltage of an electrolytic cell.

[0002]

2. Description of the Related Art In electrowinning or electrorefining of non-ferrous metals such as nickel, several tens to several hundreds of electrolytic cells are simultaneously operated. In order to detect abnormalities such as poor contact between anodes and cathodes or short-circuits among these many electrolytic cells, it has been customary to manage the voltage of the electrolytic cells.

The conventional electrolytic cell voltage control method is as follows:
Periodically measure the voltage of each electrolytic cell at a certain time of day,
A list containing the measured values was created to check the highest and lowest electrolytic cell voltage measured values, or the transition of electrolytic cell voltage. As a result, it can be determined that an abnormality such as a contact failure or short circuit of the anode or cathode has occurred in the electrolytic cell in which the electrolytic cell voltage has significantly increased or decreased.

[0004]

In the above-mentioned conventional control method, since the relative level or transition of the measured value of the electrolytic cell voltage is merely checked, is the electrolytic cell voltage suitable for the operating conditions? There was no way to judge and it was not possible to manage the electrolytic cell voltage appropriately. For example, when the operating conditions were changed, it was difficult to judge whether the measured value of the electrolytic cell voltage was an appropriate value corresponding to the changed operating conditions.

Further, when there are differences in the operating conditions of a large number of electrolytic cells, it is difficult to detect abnormalities with high accuracy from among them. For example, a tank with a small number of electrodes, or a tank operating under conditions where the concentration of non-ferrous metal ions in the liquid supply is low,
It was always prioritized to be checked as a cell showing a high electrolysis cell voltage, and there was a high possibility that a cell with an abnormal electrolysis cell voltage could be overlooked due to an increase in contact resistance or a short circuit.

The present invention has been made in view of such conventional circumstances.
Obtain an appropriate electrolytic cell voltage corresponding to the difference or change in operating conditions by individual calculation, and compare the calculated voltage value with the actual measured voltage value to determine an electrolytic cell that can operate properly and shows abnormal voltage. It is an object of the present invention to provide a method of controlling the electrolytic cell voltage that can be easily found.

[0007]

In order to achieve the above object, the method of controlling the electrolytic cell voltage in a chloride bath of a non-ferrous metal provided by the present invention is: electrode contact resistance of cathode and anode, electrolytic solution resistance, and diaphragm resistance. From the calculated voltage drop, the theoretical electrolysis voltage when the target metal is electrodeposited from the electrolyte containing non-ferrous metal ions and chloride ions, and the calculated voltage E (ca) is calculated in advance as the sum of the overvoltages. Measured voltage E measured in the electrolytic cell against calculated voltage E (ca)
Characterized by comparing and managing (me).

Further, in the above-mentioned electrolytic cell voltage management method of the present invention, the calculated voltage E (ca) and the measured voltage E (me) actually measured in each electrolytic cell are previously obtained for a plurality of electrolytic cells having different operating conditions. Is compared with each other, and the electrolytic cell in which the difference ΔE between the two becomes equal to or more than a predetermined value is detected.

In the electrolytic cell voltage control method of the present invention, the electrolytic solution resistance is at least a non-ferrous metal ion concentration, a chlorine ion concentration, a SO ₄ ion concentration, a Na ion concentration, a liquid composition of a chloride bath, an energizing current, It is characterized in that the number of electrodes, energization time, electrode plate area, and temperature inside the electrolytic cell are used as parameters. Further, the diaphragm resistance is calculated by using the temperature in the electrolytic cell and the water permeability of the diaphragm as parameters.

Further, in the above-described electrolytic cell voltage management method of the present invention, the overvoltage is defined as a difference between the sum of the voltage drops and the theoretical electrolytic voltage and the electrolytic cell voltage measured in normal operation, and the value is determined. Purpose It is characterized by calculating non-ferrous metal ion concentration, energizing current, and temperature in the electrolytic cell as parameters.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Constituent factors for determining the electrolytic cell voltage are, as conceptually shown in FIG. 1, a voltage drop ΔE _a due to a contact resistance of an anode, a voltage drop ΔE _c due to a contact resistance of a cathode, Voltage drop in the anode electrolytic bath due to the resistance of the electrolytic solution that occurs when an electric current passes through the solution ΔE
There is a voltage drop △ _{E Lc} in _La and cathode electrolytic bath.
In addition, since chlorine gas is generated from the anode during electrowinning from a chloride bath, the anode is installed in an anode box whose counter surface is covered with a filter cloth, and the voltage drop caused by the diaphragm resistance due to this filter cloth Δ E _f occurs.

Further, on the surface of the anode and cathode,
Electrode potential E based on electrochemical reaction_AAnd E_COccurs.
The electrode potentials of this anode and cathode are
As the sum of the equilibrium potential E (eq) of the redox reaction and the overvoltage η,
It is expressed as. Anode electrode potential E_A= E_A(eq) ＋ η_a Electrode potential E of the cathode_C= E_C(eq) ＋ η_c

Therefore, the electrolytic cell voltage E is reduced by the above voltage reduction.
Down △ E_a, △ E_c, △ E_La, △ E _LcAnd △ E_fWhen,
It can be expressed as the total electrode potential as follows:
It E = △ E_a+ △ E_c+ △ E_La+ △ E_Lc+ △ E_f+
{E_A(eq) ＋ η_a}-{E_C(eq) ＋ η_c}

Here, it is considered that the liquid quality of the anode electrolytic bath and the liquid quality of the cathode electrolytic bath are the same, and it is assumed that ΔE _L = E _{L a} + ΔE _Lc . The difference E _A (eq) −E _C (eq) of the equilibrium electrode potential, that is, the theoretical electrolysis voltage is expressed as E _The . Further, in order to comprehensively evaluate the overvoltages of the anode and the cathode, if the overvoltage η = η _a −η _c , the electrolytic cell voltage E can be expressed as follows. E = ΔE _a + ΔE _c + ΔE _L + ΔE _f + E _The + η

That is, the electrolytic cell voltage E is the voltage drop ΔE _a and ΔE _c due to the electrode contact resistance of the anode and cathode,
The voltage drop ΔE _L due to the electrolytic solution resistance, the voltage drop ΔE _f due to the diaphragm resistance, the theoretical electrolytic voltage E _The , and the overvoltage η can be obtained by calculation.

The method of calculating the voltage for each constituent factor will be described in more detail below. (1) Voltage drop due to electrode contact resistance (ΔE _a , ΔE _c ) Letting the contact resistance values of the anode and the cathode be R _a and R _c , respectively, the energizing current is I, and the number of electrodes is n, the anode and cathode The voltage due to contact resistance is given as follows according to Ohm's law. ΔE _a = R _a × I / n ΔE _c = R _c × I / n

(2) Voltage drop due to diaphragm resistance (ΔE _f ) The voltage drop due to the diaphragm resistance is the same as the voltage drop due to the electrode contact resistance of the anode and cathode, and the diaphragm resistance R
According to Ohm's law, it is represented by the following formula by _f , the energizing current I and the number of electrodes n. ΔE _f = R _f × I / n Further, the diaphragm resistance R _f changes depending on the temperature in the electrolytic cell and the water permeability of the diaphragm and is represented by the following formula. R _f = a × electrolysis cell temperature + b × water flow rate + c

(3) Voltage drop due to electrolyte resistance (△
E _L ) Assuming that there is no flow or convection of the liquid when the ions move in the electrolytic solution, that is, when a current flows, the electrolytic solution resistance is R _L , the applied current is I, and the number of electrodes is n, The following potential difference represented by Ohm's law occurs in the electrolytic solution. ΔE _L = R _L × I / n Further, the electrolytic solution resistance R _L is expressed by the following relational expression with the specific resistance ρ of the electrolytic solution, the electrode plate area S, and the interelectrode distance d. here,
The specific resistance ρ of the electrolytic solution can be determined from the composition and temperature of the electrolytic solution, and the inter-electrode distance d can be determined from the energizing current and the energizing time. R _L = ρ × d / S

(4) Theoretical electrolysis voltage (E _The ) Taking nickel electrolysis as an example, chlorine ions are oxidized on the surface of the anode electrode to generate chlorine gas, and nickel ions are deposited as electric nickel on the surface of the cathode electrode. . It is known that when this electrochemical reaction occurs, the anode equilibrium potential E _A (eq) and the cathode equilibrium potential E _C (eq) are obtained by the following mathematical formulas 1 and 2, respectively.

[0020]

[Equation 1]

[0021]

[Equation 2]

_The theoretical electrolysis voltage E _The is the difference between the anode equilibrium potential E _A (eq) and the cathode equilibrium potential E _C (eq), and nickel electrolysis will occur unless a potential higher than the theoretical electrolysis voltage is applied. It is a voltage that does not hold. That is, the theoretical electrolysis voltage E _The can be obtained by the following mathematical formula 3.

[0023]

[Equation 3]

(5) Overvoltage (η) The overvoltage η means a driving force that causes a current to flow depending on the deviation of the anode and cathode electrode potentials from the equilibrium potential, that is, the degree of polarization. It is represented by the relationship of.

In the present invention, the above (1) to
Overvoltage η is defined as the difference between the total voltage drop of (3) and the theoretical electrolysis voltage of (4) and the electrolysis cell voltage measured in the electrolysis cell of the normal operation, and the target non-ferrous metal ion concentration is defined. Calculation is performed by using the following formulas that regress to three types of parameters, that is, the applied current and the temperature inside the electrolytic cell. η = a × non-ferrous metal ion concentration + b × carrying current + c × electrolytic cell temperature + d

As described above, the voltage drops ΔE _a and ΔE _c due to the contact resistance between the anode and the cathode, the voltage drop ΔE _L due to the electrolytic solution resistance, the diaphragm resistance based on all the constituent factors that determine the electrolytic cell voltage. The voltage drop ΔE _f , the theoretical electrolysis voltage E _The , and the overvoltage (η) due to
The calculation voltage E (ca) can be calculated as the sum of these values by calculating from the actual operating conditions according to (5).

In the present invention, the calculated voltage E (ca) thus obtained is compared with the measured voltage E (me) actually measured in the electrolytic cell, and the electrolytic cell voltage is controlled based on the difference between the two. Therefore, by maintaining a small difference between the two, it is possible to always perform an appropriate operation, and even when the operating conditions are changed, it is immediately determined whether the electrolytic cell current is appropriate for the changed operating conditions. can do.

Further, even when a plurality of electrolytic cells having different operating conditions are operated at the same time, the calculated voltage E (ca) obtained in advance and the measured voltage E (me) actually measured in each electrolytic cell are compared. Then, by detecting the electrolytic cell in which the difference between the two becomes a predetermined value or more, it is possible to easily find the electrolytic cell in which an abnormality such as a poor contact between the anode and the cathode or a short circuit has occurred. Needless to say, an abnormality such as a contact failure or a short circuit can be easily detected from the difference between the two electrolysis cells even when there is only one.

[0029]

[Example] In a factory where electrolytic extraction of nickel is performed from a chloride bath, the measured voltage values are taken in every morning at 5 o'clock in the morning, and at the same time, the Ni concentration, energizing current, electrolyzer temperature, energizing time, etc. The calculated voltage value E (c) calculated from the above operating conditions based on the above-mentioned formulas (1) to (5).
a) was determined for each electrolytic cell. Difference between measured voltage E (me) and calculated voltage E (ca) for each electrolytic cell ΔE (ΔE = E (me) −
E (ca)) was prepared in the list, and the electrolytic cell whose electrolytic cell voltage was abnormally high or abnormally low was checked.

As a result of performing the operation while controlling the voltage of the electrolytic cell in this way, as shown in Table 1 below, the measured voltage E (me) and the calculated voltage E ( The day when the difference ΔE from (ca) was abnormally high continued. 12
Inspection of the No. 9 tank revealed that the cathode beam generated heat and the surface was blackened due to oxidation, increasing the contact resistance. By changing the cathode beam, the electrolytic cell voltage returned to the normal value from December 12.

[0031]

[Table 1]

As shown in Table 2 below, since ΔE gradually increased from May 19 in tank No. 130, 5
When the cathode beam was replaced on the 21st of March, the electrolytic cell voltage dropped temporarily but showed an abnormal voltage value again.
When the No. 130 tank was further inspected, the nickel plating on the coma type pedestal on which the cathode beam was placed was peeled off, and the contact resistance between the coma type pedestal and the cathode beam increased,
It was found that the electrolyzer voltage was high. There 5
By replacing the pedestal on the 24th of the month, the electrolytic cell voltage returned to the normal value.

[0033]

[Table 2]

Further, as shown in Table 3 below, the value of ΔE in the No. 207 tank was lower than usual from August 12th. Therefore, when the cathode was pulled up on August 15, it was found that nickel was short-circuited due to the electrodeposition by winding the filter cloth. By using a new anode box from August 15, the electrolytic cell voltage returned to the normal value.

[0035]

[Table 3]

[0036]

According to the present invention, since the calculated voltage is calculated in consideration of all the operating conditions that affect the electrolytic cell voltage, it is appropriate to compare the calculated voltage value with the actual measured voltage value. It is possible to perform various operations, and it is possible to easily and accurately find an electrolytic cell that exhibits an abnormality. In particular, according to the calculated voltage of the present invention, the cause of the actual electrolytic cell voltage being higher than the calculated voltage is only due to the increase of the electrode contact resistance, and therefore the cause of the abnormality can be found very easily.

Further, since the calculated voltage according to the present invention represents a near-ideal electrolysis cell voltage corresponding to the operating conditions, it is possible to predict the electrolysis cell voltage according to various operating conditions without actually performing the operation. In particular, it has high reliability even when estimating the electrolytic cell voltage under conditions that are significantly different from the actual operation.

[Brief description of drawings]

FIG. 1 is a conceptual diagram of constituent factors that determine an electrolytic cell voltage.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Nobumasa Iemori             3-5-3 Nishihara-cho, Niihama-shi, Ehime Sumitomo Kin             Besshi Works, Inc. F-term (reference) 4K058 AA13 AA25 BA17 BA21 BB03                       BB04 CA04 CA05 CA07 FB01                       FB03

Claims (5)

[Claims] 1. A method of controlling an electrolytic cell voltage in a chloride bath of non-ferrous metal, wherein voltage drop, non-ferrous metal ion and chlorine ion calculated respectively from electrode contact resistance of cathode and anode, electrolytic solution resistance, and diaphragm resistance. Calculated voltage E (ca) is calculated in advance as the total of the theoretical electrolysis voltage and overvoltage when the target metal is electrodeposited from the electrolyte containing, and the measured voltage E (ca) is measured in the electrolytic cell. A method for controlling an electrolytic cell voltage, which is characterized by comparing and managing a voltage E (me). 2. For a plurality of electrolytic cells having different operating conditions, the calculated voltage E (ca) obtained in advance and the measured voltage E (me) actually measured in each electrolytic cell are compared, and the difference ΔE between the two is found. The electrolytic cell voltage management method according to claim 1, wherein an electrolytic cell having a predetermined value or more is detected. 3. The electrolyte resistance is at least non-ferrous metal ion concentration, chloride ion concentration, SO ₄ ion concentration, Na
3. The electrolytic cell according to claim 1 or 2, wherein the liquid composition of the chloride bath including the ion concentration, the applied current, the number of electrodes, the applied time, the electrode plate area, and the temperature inside the electrolytic cell are calculated as parameters. How to control voltage. 4. The method for controlling the electrolytic cell voltage according to claim 1, wherein the diaphragm resistance is calculated using the temperature inside the electrolytic cell and the water permeability of the diaphragm as parameters. 5. The overvoltage is defined as the difference between the total of the voltage drops and the theoretical electrolysis voltage and the electrolysis cell voltage measured in normal operation, and the values are determined as the target non-ferrous metal ion concentration, the energizing current, and the electrolysis cell. The method for controlling the electrolytic cell voltage according to claim 1, wherein the internal temperature is calculated as a parameter.