JPS58147578A - Electrolytic refining method of nickel - Google Patents

Abstract

PURPOSE:To prevent the cracking of product nickel and to decrease electrolysis voltage by maintaining the temp. of the feed liquid which is the electrolyte discharged from an electrolytic cell and is to be returned to a cathode box after refining and cooling at a prescribed temp. or above in the initial period when the electrolysis is started. CONSTITUTION:In an electrolytic refining method of nickel wherein electrolysis is accomplished by using nickel matt as anode and maintaining the current density of cathode at >=1.5A/dm<2>, the temp. of the feed light for a cathode box in the initial period when the electrolysis is started is maintained at >=45 deg.C to reduce electrodeposition stress, whereby the craking to be generated in the stage of cutting electric nickel to product nickel as well as the cracking of the seed plate in speed plate electrolysis are prevented. The electrolysis voltage is decreased by an increase in the temp. of the electrolyte, whereby the cost of electric power for electrysis is reduced. The temp. of the feed liquid is maintained at >=45 deg.C, more preferably about 45-60 deg.C by allowing the reflux electrolyte in the initial period when the electrolysis is started to bypass a cooler partially or if necessary through a heater.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improved nickel electrolytic refining method using a nickel matte as an anode.

In the nickel electrolytic refining method, which uses a nickel matte as an anode and a metal nickel plate as a cathode,
The cathode is suspended in a cathode box equipped with a diaphragm, and the electrolyte is continuously extracted from the electrolytic cell and undergoes purification processes such as copper removal, iron removal, and cobalt removal, and is further adjusted to remove impurities. After making a pure liquid, the electrolyte is continuously injected into the cathode deck and electrolyzed while circulating the electrolyte. During this electrolytic refining, the cathode current density is set to 1.5.
When A/d is maintained at about 1 or more, the temperature of the electrolytic solution increases in the electrolytic cell due to Joule heat.

Therefore, in order to keep the liquid temperature in the electrolytic cell constant (usually kept at 70 to 80°C), after purifying the electrolyte discharged from the electrolytic cell, it is passed through a heat exchanger using water to maintain the temperature of the pure liquid. A method has been adopted in which the temperature is lowered to approximately 35°C and the liquid is supplied into the container.

However, in the case of electrolytic refining using nickel matte as an anode, slime containing sulfur as the main component is generated on the anode surface as the electrolysis progresses.

In order to take out the slime from the electrolytic cell without causing any trouble while adhering to the anode scrap, it is necessary to drain the electrolytic solution inside the electrolytic cell to the outside. When a new nickel matte anode is placed in the electrolytic cell and electrolytic refining is started, the electrolytic cell is refilled with electrolytic solution, so the temperature of the liquid in the electrolytic cell at the beginning of electrolysis is about 35℃. However, it takes a considerable amount of time for the temperature to rise again due to Joule heat and return to normal temperature.

Additionally, the life of the cathode is about half of the life of a nickel matte anode, so at least once the power must be turned off, the can-r (electrolytic nickel) removed, and the cathode replaced with a new seed plate cathode. At this time as well, an operation is performed to remove the slime on the anode surface and the electrolytic solution is temporarily extracted from the electrolytic cell, so that the same drop in solution temperature occurs as in the case of starting electrolysis with a new nickel matte anode described above.

In addition, in seed plate electrolysis to produce seed plates used in electrolytic refining, a nickel plate is obtained by electrodepositing nickel using a nickel matte as an anode and stainless steel as a base plate. The liquid temperature in the electrolytic cell becomes low for the same reason as in electrolytic refining.

The present inventors believe that the drop in liquid temperature in the electrolytic cell at the beginning of electrolysis is the cause of cracks that occur when electrolytic nickel is cut into product nickel, and cracks in the seed plate during seed plate electrolysis. According to the present invention, the first object of the present invention is to cut electrolytic nickel obtained by electrolytic refining to obtain product nickel in a desired shape. The purpose is to significantly reduce the amount of electrolytic nickel that causes cracks.

The second object of the present invention is to prevent cracks from occurring in the first type plate during seed plate electrolysis and to improve the rate of seed plate collection. The purpose is to measure the decline.

To achieve these objectives, the present invention uses a nickel matte as Ano-P and a cathode current density of L 5 A/a.
- In the nickel electrolytic refining method in which electrolysis is carried out by maintaining the temperature above
The temperature should be 5°C or higher.

The inventors investigated the relationship between the temperature of the electrolytic solution and the electrodeposition stress using a Snoquiral plating stress meter. An example of this is shown in FIG.

Figure 1 shows an electrolytic solution (Ni g 7 f /J!, Ot56) used in nickel electrolytic refining using a normal nickel matte as an anode, using a spiral plating tester.
f/', Ibr30311ri/l, 804 14
3'/l, Na5st/l, PII3) with a cathode current density of 2,4 A/6W? These are the results of measuring the electrodeposition stress at an electrodeposition film thickness of 20 μm under the following conditions, with the liquid temperature changed to 35° C., 45° C., and 65° C. As is clear from Figure 1, the lower the liquid temperature, the greater the electrodeposition stress, especially when the liquid temperature is 45°C.
Below this, the electrodeposition stress becomes significantly large. At the beginning of the electrolytic refining process using the conventional nickel matte as an anode, the temperature of the liquid in the electrolytic cell drops to about 35°C, so the electrodeposited layer is deposited with a particularly large stress at the beginning of the electrolysis. This is thought to be the cause of the separation of the seed plate from the new electrodeposited layer when the electrolytic nickel finally obtained is cut into product nickel, causing cracks. Similarly, in seed plate electrolysis, the electrodeposition stress is high at the beginning of electrolysis, which can cause cracks in the seed plate, or in severe cases, it may peel off from the mother plate. Conceivable.

Note that if the temperature of the liquid in the electrolytic cell decreases, the sliding voltage will increase, which is disadvantageous in terms of power consumption.

Based on the above findings, the present inventors set the temperature of liquid supplied to the candodex at 45° C. or higher at the beginning of electrolysis in actual nickel electrolytic refining.

In other words, the electrolytic solution that is continuously drawn out from the electrolytic cell and supplied into the cathode NOx after going through a liquid purification process is normally lowered in temperature by a cooling heat exchanger as described above before being supplied into the cathode NOx. However, at the beginning of electrolysis, the pure liquid that had undergone the liquid purification process was supplied into the cathode XX without passing through the cooling heat exchanger. To do this, a branched pipe is installed in front of the cooling heat exchanger after the liquid purification process, which is separate from the normal system. If a valve is provided at the branch point and the connecting portion, the liquid can be supplied without passing through a cooling heat exchanger by opening and closing the valve.

In addition, if it is not possible to obtain a supply liquid temperature of 45°C or higher simply by not passing the cooling heat exchanger due to piping equipment, etc., use a heating heat exchanger using steam, etc. The pure liquid may be supplied by heating it to a higher temperature.

The supply liquid temperature is 45°C according to the results of the electrodeposition stress measurement test using the spiral plating stress needle mentioned above and the experience of actual operation.
The higher the temperature is, the better it is, but the temperature of the electrolyte increases in the electrolytic cell, so setting the supply liquid temperature to 60°C or higher has a limit in terms of the heat resistance of the electrolytic cell, which is not desirable. Therefore, the most preferred liquid supply temperature is 45-60°C.

In addition, if electrolysis is started with the supply liquid temperature set to 45°C or higher,
The temperature of the liquid in the electrolytic cell gradually rises due to Joule heat and reaches the normal temperature (70 to 80 degrees Celsius), so at that time, the above-mentioned valve is operated to supply the liquid through the cooling heat exchanger in a normal circulation system. Switch to. The time required for this switching varies depending on the temperature of the supplied liquid, but is approximately 48 minutes from the start of electrolysis.
Within hours.

If the supply liquid temperature is set to 45°C or higher at the beginning of electrolysis using the method described in detail above, cracks may occur when the nickel obtained by electrolysis is cut into product nickel, and in seed plate electrolysis. It is also possible to effectively prevent the occurrence of seed plate cracking and improve the seed plate collection rate. It also has the effect of preventing a rise in electrolysis voltage at the beginning of electrolysis and reducing power consumption.

The present invention provides a method for electrolyzing a nickel cell which performs electrolysis at a cathode current density of 1,5 Al1- or higher, which requires cooling the electrolyte in a purified liquid circulation system in order to suppress the rise in liquid temperature in the electrolytic cell due to Joule heat. The nickel electrolytic refining method using matte as an anode has a great effect, and the composition of the electrolytic bath used is not particularly limited.
o, -Ni Ct, nickel ion concentration 4 in mixed bath
0-909/l chloride ion concentration 40-5ot7, sulfate ion concentration 100-150 F/z, sodium ion concentration 30-60 t/l, boric acid concentration 5-309/l.

In the case of PH2,0-4°5 and N15o4 bath, the nickel ion concentration is 40-50 f/l and the boric acid concentration is 20-50.
25 f/l, pH 4 to 5, or other chloride baths may be used.

"1" YuNl74゜0wt%, S20゜6wt%, Ou3.43
Weight'tXsooO, 74% by weight, F-〇. 23% by weight nickel mat 975cm (vertical) x 755cm (horizontal) x 5
The anode has a shape of 0■ (thickness), 987■ x 787■
The metal nickel seed plate of
Cjl 50-70'/l + HsPOs
7~12'/l *804100~l 50'/j
*Na 30-50'/l, P u 2. B
In one electrolytic cell, 39 of the above 7 nodes and 38 of the above cathodes are arranged alternately with the same distance between the electrodes of 150cm, and 50 such electrolytic cells are provided, and the cathode current density is 2A/a.
- Electrolysis was carried out for 9 days. At that time, the electrolyte should not be cooled in the purified liquid circulation system at the beginning of electrolysis.
The temperature of the liquid supplied to the cathode XX was set at 50°C, and after 36 hours from the start of electrolysis, the system was switched to a purified liquid circulation system that performs normal cooling. The number of electrolytic nickels produced was 1,900 pieces.

In addition, as a comparative example, a non-nickel matte anode with the same composition and shape as above was used, except for the conventional method in which liquid was supplied to the cathode NOx at the initial stage of electrolysis through a purified liquid circulation system that performs normal cooling. Electrolysis was carried out under the same electrolytic conditions, and 1900 pieces of electrolytic nickel were produced in the same manner.

Table 1 shows a comparison of the number of cracked sheets during electrolytic nickel cutting and the average sliding voltage over 9 days between the method of the present invention and the comparative example.

Table 1 Example 2 After removing the slime that had formed on the surface of the Anor-R, which had consumed approximately half of its capacity in Example 1, it was put back into the electrolytic tank, a new seed plate was inserted as a cathode, and 50 electrolytic cells were used. Electrolysis was carried out for 9 days under the same electrolytic conditions as in Example 1, and 1900 pieces of electrolytic nickel were produced. At this time, at the beginning of electrolysis, the electrolyte is not cooled in the purified liquid circulation system, and the temperature of the liquid supplied to the cathode 2x is set at 48°C, and after 38 hours from the start of electrolysis, the normal purified liquid circulation system is switched on. Switched.

Further, approximately half of the amount was consumed in the electrolysis of the comparative example described in Example 1. After removing the slime on the surface of the anode, it is returned to the electrolytic cell, a new seed plate is inserted as a cand, and the supplied liquid at the beginning of electrolysis is cooled through a normal purified liquid circulation system. Electrolysis was carried out for 9 days under the same electrolytic conditions as above, and 1900 pieces of electrolytic nickel were produced.

Table 2 shows a comparison of the number of cracked sheets during electrolytic nickel cutting and the average sliding voltage over 9 days between the method of the present invention and the conventional method.

Example 3 Nickel pine with the same composition as Example 1) t-975w (
1f1) x 755 m (horizontal) x 30 wa
(N) f) 7/-do, 10109O vertical)X
840cm (horizontal) (electrodeposited part 1015cm x 806cm) stainless steel split mother plate is used as a cand, and the canard is r11? The composition of the liquid supplied to the box was the same as in Example 1, and the distance between the same poles was M 15 by alternating the 139 sheets of anodes per cypress and the 38 sheets of the motherboard.
0-, and four of these electrolytic cells were installed to give a current density of 2 A.
Seed plate electrolysis was performed for 9 days at /-. The seed plates electrodeposited on both sides of the mother plate were peeled off six times during the process to produce 1824 seed plates. At this time, at the beginning of the seed plate electrolysis, the electrolyte is not cooled in the purified liquid reflux system, and the temperature of the liquid supplied to Cando Switched to.

In addition, seed plate electrolysis was performed for 9 days under the same electrolytic conditions as above, except that the conventional method of cooling the supplied liquid at the beginning of electrolysis through a normal purified liquid circulation system was used to produce 1824 seed plates in the same manner. .

Table 3 shows a comparison of the number of electric currents at which cracks occurred between the method of the present invention and the conventional method.

Table 3

[Brief explanation of drawings]

FIG. 1 is a diagram showing the results of measuring the relationship between the temperature of the electrolytic solution and the electrodeposition stress υ using a spiral plating stress needle. In the figure, the horizontal axis is the liquid temperature (℃), and the vertical axis is the electrodeposition stress (kf
/-). trap/diagram

Claims (1)

[Claims] In the nickel electrolytic refining method in which electrolysis is carried out using a nickel matte as an anode and maintaining the cathode current density at 1°5 A/d- or higher, the temperature at which the liquid is supplied to the cathode current density at the beginning of electrolysis is set at 45° C. or higher. Nickel electrolytic refining method.