JP2011213502A - Method of recovering nickel from copper electrolyte - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a space-saving method of recovering nickel from a copper electrolyte.SOLUTION: In a method of recovering nickel from a copper-removed electrolyte comprising concentrating a copper-removed electrolyte by heating, depositing a crude nickel sulfate by cooling the concentrate, and separating the deposited crude nickel sulfate from the liquid, the concentration of the copper-removed electrolyte by heating is made in a vacuum evaporator.

Description

  The present invention relates to a method and system for recovering nickel from a copper electrolyte. More specifically, the present invention relates to a method and system for recovering nickel as crude nickel sulfate from a copper-free electrolyte in copper electrolytic purification.

  Crude copper used as an anode in copper electrolytic refining contains impurities such as arsenic, bismuth, antimony, nickel, and these are eluted in the electrolytic solution. Among the impurities, nickel has an electrodeposition potential extremely lower than the electrodeposition potential of copper, and is thus particularly easily concentrated in the electrolytic solution. When the nickel concentration in the electrolytic solution increases, the voltage rises due to an increase in the liquid resistance of the electrolytic solution, and thus there is a problem that the production cost of electrolytic copper increases due to an increase in power consumption. Further, it is known that when the nickel concentration in the electrolytic solution increases too much, a slime layer that hinders elution of copper ions is formed on the anode surface, and so-called passivation occurs.

  Therefore, nickel concentration in the copper electrolyte is maintained below a certain value by recovering nickel from the copper electrolyte. As a method for recovering nickel from the copper electrolyte, after removing copper, removing impurities such as arsenic, antimony and bismuth by electrolysis, sulfurization, solvent extraction, precipitation, etc., and then crystallizing nickel in the form of nickel sulfate Is common. Since nickel sulfate at this time contains a small amount of impurities, it is called crude nickel sulfate in this field.

  Japanese Patent Laying-Open No. 2006-283047 (Patent Document 1) describes the following nickel recovery method. The copper electrolyte is heated and concentrated, and then cooled to remove copper as copper sulfate. Next, impurities such as copper, arsenic, antimony, and bismuth are reduced and removed on the cathode side in an electrowinning process. After the electrolytic collection, the liquid is cooled, and the nickel in the liquid is crystallized as crude nickel sulfate using the difference in solubility, and then the nickel is recovered from the liquid by centrifugation.

  In JP2003-222408A (Patent Document 2), a submerged combustion method is used as a step of precipitating Ni in a solution after electrolytic collection. In the submerged combustion method, the liquid to be treated is concentrated, and the solubility of Ni is lowered by increasing the concentration of sulfuric acid. It is also described that the crystallization of crude nickel sulfate can be increased by cooling the concentrated liquid after combustion in liquid in a cooling tank.

JP 2006-283047 A JP 2003-222408 A

The method described in Patent Document 2 is a method in which the crystallization efficiency of Ni is increased by using a submerged combustion method and a cooling method in combination, and is a practical method. However, the submerged combustion device not only requires fuel for combustion, but also requires exhaust gas treatment, internal scale removal by steam agitation, and periodic maintenance of the burner. Management also takes time. In addition, many installation spaces such as an electric dust collector and exhaust gas scrubber installed for exhaust gas treatment are required.
When installing a new Ni recovery system, it is possible to secure the necessary installation space from the beginning. However, when considering increasing the processing capacity of existing facilities, a lot of space in the factory is filled. Therefore, it is necessary to keep the equipment as compact as possible.

  Therefore, the main object of the present invention is to provide a method for recovering nickel from a copper electrolyte at low cost and space saving. Moreover, this invention makes it another subject to provide the nickel recovery system which can implement such a method.

  As a result of repeated studies to solve the above-mentioned problems, the present inventors have found that it is effective to concentrate nickel using a vacuum evaporator. The vacuum evaporator is a device that heats and concentrates the liquid to be treated while lowering the boiling point of the electrolyte by reducing the boiling point of the electrolyte, and can be obtained together with the concentrate by vacuum evaporation and the ability to use waste heat generated in the factory. There is a merit that the condensed water (weakly acidic) can be used for process water (reduction of water usage). Moreover, the vacuum evaporation apparatus contributes to space saving because no gas treatment is required. Combustion gas can be used as a heat source for the vacuum evaporator, but waste steam discharged from a flash smelting furnace installed at a copper smelting plant can be used. The required fuel is no longer needed.

  The present invention completed on the basis of the above knowledge, in one aspect, the concentrated copper sulfate is heated and concentrated, and then cooled to precipitate crude nickel sulfate, and the precipitated crude nickel sulfate is separated into solid and liquid, In the method for recovering crude nickel sulfate from a copper removal electrolyte, the copper concentration is heated and concentrated in a vacuum evaporator.

  In one embodiment, the crude nickel sulfate recovery method according to the present invention is performed by heating and concentrating the copper removal electrolyte using a vacuum evaporator and a submerged combustion device arranged in series in the subsequent stage.

  In another embodiment of the crude nickel sulfate recovery method according to the present invention, the heat source of the vacuum evaporator is water vapor.

  In yet another embodiment, the method for recovering crude nickel sulfate according to the present invention is water vapor generated using waste heat discharged from a flash smelting furnace or converter by a heat source of a vacuum evaporator.

  In yet another embodiment of the method for recovering crude nickel sulfate according to the present invention, the copper removal electrolyte is concentrated 1.85 to 2.15 times in the former vacuum evaporator, and further in the latter submerged combustion apparatus. It is concentrated 1.85 to 2.15 times, and is concentrated 3.42 to 4.62 times in total.

In another aspect of the present invention,
A vacuum evaporator for heating and concentrating the copper removal electrolyte,
A cooling bath for cooling the copper removal electrolyte concentrated in the vacuum evaporator to deposit crude nickel sulfate;
A solid-liquid separator for removing the crude nickel sulfate precipitated in the cooling bath from the copper removal electrolyte,
Is a system for recovering crude nickel sulfate from a copper removal electrolyte solution.

  In one embodiment, the crude nickel sulfate recovery system according to the present invention further comprises a submerged combustion device for further heating and concentrating the copper removal electrolyte concentrated by the vacuum evaporator, and the cooling tank is concentrated by the submerged combustion device. The removed copper removal electrolyte is cooled to deposit crude nickel sulfate.

  In another embodiment of the crude nickel sulfate recovery system according to the present invention, the heat source of the vacuum evaporator is water vapor.

  In yet another embodiment, the crude nickel sulfate recovery system according to the present invention is steam generated by using waste heat discharged from a flash smelting furnace or converter by a heat source of a vacuum evaporator.

  According to the present invention, nickel recovery from a copper electrolyte can be performed in a smaller space than before.

  When there is an existing crude nickel sulfate recovery facility using a submerged combustion device, the ability to recover nickel from the electrolyte can be easily increased by adding a vacuum evaporator. When the nickel recovery capability is strengthened, it is possible to keep the nickel concentration in the electrolyte low even if the tolerance of nickel grade in crude copper in copper electrolysis is increased. The raw material can be used.

  By using water vapor as a heat source of the vacuum evaporator, there is an advantage that condensed water (weak acidity) obtained together with the concentrate by vacuum evaporation can be used as process water. In particular, by using the heat in exhaust gas discharged from flash smelting furnaces and converters installed in copper smelters, water vapor is no longer needed, and the fuel required for submerged combustion is no longer necessary. The cost for collection can be reduced.

It is a flow figure showing an example of the rough nickel sulfate recovery method concerning the present invention.

  An embodiment of the present invention will be described with reference to the drawings. When the copper removal electrolytic solution is introduced into the vacuum evaporator 11, it is heated and concentrated there. The concentrated copper removal electrolyte leaving the vacuum evaporator 11 enters the submerged combustion device 12 and undergoes further concentration. Next, the highly concentrated copper removal electrolyte is introduced into the cooling bath 13 and cooled, whereby crude nickel sulfate is crystallized. The precipitated crude nickel sulfate is separated by a filter press (solid-liquid separator) 14. Through these series of steps, crude nickel sulfate is recovered from the copper removal electrolyte.

<1. Copper removal electrolyte>
In the present invention, the copper removal electrolytic solution is used in the copper electrolytic purification process, and is used for the used copper electrolytic solution after elution of copper ions, impurities such as arsenic, bismuth, antimony and nickel from the anode. The liquid after washing | cleaning after performing the reduction process of a copper concentration at least by the well-known arbitrary means. The copper removal electrolytic solution is preferably a post-cleaning solution after reduction treatment of impurities such as arsenic, bismuth and antimony as well as copper from the viewpoint of improving the nickel recovery rate.

  The method for reducing the copper concentration in the copper electrolyte is not limited. For example, it is concentrated by heating and then cooled to remove copper as copper sulfate, or by removing the copper by electrodeposition on the cathode side. Electrolytic collection method is included.

  The method for reducing the concentration of impurities such as arsenic, bismuth and antimony in the copper electrolyte is not limited, but for example, an electrowinning method in which impurities such as arsenic, antimony and bismuth are electrodeposited and removed on the cathode side, Examples thereof include a method of passing through an ion exchange resin or a chelate resin. Of these, the electrowinning method is preferable from the viewpoints of impurity removal efficiency and ease of operation.

  Typically, the used copper electrolyte is mainly removed of copper by heat concentration and cooling treatment, and further, impurities such as copper and arsenic, antimony, bismuth and the like are further removed by an electrowinning process. A copper removal electrolyte to be treated is obtained.

  An example will be described of how the concentration of each component in the copper electrolyte solution changes due to the cleaning of the copper electrolyte solution. Copper electrolyte is copper: 45-50 g / L, nickel: 12-15 g / L, sulfuric acid: 170-200 g / L, arsenic: 7-10 g / L, antimony: 0.1-0.3 g / L, bismuth: When 0.1 to 0.3 g / L is contained, when heated and concentrated, copper: 90 to 100 g / L, nickel: 24 to 30 g / L, sulfuric acid: 340 to 400 g / L, arsenic: 14 to 20 g / L , Antimony: 0.2 to 0.6 g / L, bismuth: 0.2 to 0.6 g / L. By cooling the concentrate to 10 ° C., copper sulfate is precipitated. This copper sulfate can be purified separately after solid-liquid separation to obtain product copper sulfate. The liquid after cooling is, for example, copper: 10-20 g / L, nickel: 24-30 g / L, sulfuric acid: 260-330 g / L, arsenic: 14-20 g / L, antimony: 0.2-0.6 g / L, bismuth : 0.2 to 0.6 g / L. By sending this solution to the electrolytic collection step, copper, arsenic, antimony and bismuth are removed, and the post-electrolytic collection solution (that is, the copper removal electrolytic solution) is, for example, copper 0.5 g / L, nickel 24-30 g / L, Sulfuric acid: 280-350 g / L, Arsenic: 3.0-5.0 g / L, Antimony: 00.01-0.1 g / L, Bismuth: 0.01-0.05 g / L.

<2. Vacuum evaporator>
The copper removal electrolyte introduced into the vacuum evaporator 11 is concentrated as the water in the electrolyte evaporates.
The vacuum evaporator 11 is operated with the inside of the apparatus at atmospheric pressure or lower using a vacuum pump. The inside of the apparatus is preferably set to a pressure of about 0.05 to 0.1 MPa, more preferably about 0.01 to 0.05 MPa, for reasons of vaporizer partition pressure resistance and airtightness. In the apparatus, the heat source of the vacuum evaporation apparatus 11 includes water vapor, combustion gas, etc. However, if waste heat can be used, it can be operated at a low running cost. For example, waste steam discharged from a flash smelting furnace, a converter, etc. installed in a copper smelting factory can be used.

  The vacuum evaporator 11 may have a single evaporator. Alternatively, a plurality of vacuum evaporators may be arranged in series, and a multi-effect formula may be employed in which steam used in the previous stage is used for subsequent evaporation. I can do it. Thereby, evaporation efficiency can be improved. At this time, the electrolytic solution in the evaporator 11 is 60 to 80 ° C. for the first effect can and 40 to 60 ° C. for the second effect can, typically 68 to 73 ° C. for the first effect can and the second effect. It can be 43-48 degreeC with a can.

  When carrying out the heat concentration of the copper removal electrolyte only with the vacuum evaporator 11 or when the submerged combustion device 12 is installed in the previous stage, the concentration of the copper removal electrolyte is such that Ni in the electrolyte is supersaturated. Therefore, it is preferably 3.5 to 4.5 times and more preferably about 4 times. On the other hand, when the submerged combustion device 12 is installed in the subsequent stage, if the concentration rate is too high, the viscosity of the concentrated liquid increases in the submerged combustion device or scale (nickel sulfate) is generated in the liquid feeding pipe. Or On the other hand, if the concentration rate is too low, the recovered amount of crude nickel sulfate is reduced or the load of the submerged combustion apparatus is increased. Therefore, it is preferably 3 to 5 times, and 3.5 to 4.5 times. More preferably. The concentration rate here is defined as a value obtained by dividing the sulfuric acid concentration in the concentrated solution by the sulfuric acid concentration in the stock solution.

<3. Submerged combustion device>
In addition to the vacuum evaporation apparatus 11, the submerged combustion apparatus 12 can also be provided in the front | former stage or a back | latter stage. The submerged combustion apparatus evaporates the copper removal electrolyte by heating it to about 130 to 160 ° C. with a submerged combustion flame to concentrate it. At this time, a part of nickel (about 75 to 85%) in the copper removal electrolytic solution can be precipitated as crude nickel sulfate. If the concentration rate of the copper removal electrolyte solution by the submerged combustion device 12 is too high, the concentration can is operated for a longer time, and the upper limit of the temperature in the can is exceeded. On the other hand, if it is too low, the precipitation amount of the crude nickel sulfate is lowered and the recovery efficiency is lowered. Therefore, it is preferably 3 to 5 times, more preferably 3.5 to 4.5 times. Since the copper removal electrolyte is already concentrated by the vacuum evaporator 11 in the previous stage, the submerged combustion device 12 does not need to set a high concentration rate.

  The submerged combustion device 12 is preferably provided in the subsequent stage of the vacuum evaporator 11. That is, a procedure in which a low concentrated liquid is produced by the vacuum evaporator 11 and then a high concentrated liquid is produced by the submerged combustion apparatus 12 is preferable. This is because the vacuum evaporator 11 tends to generate scale in the apparatus and does not like a highly concentrated liquid.

  Table 1 shows that the submerged combustion device 12 is used alone to concentrate the copper removal electrolyte four times A, the vacuum evaporator 11 is used alone to concentrate the copper removal electrolyte four times, B, vacuum When the evaporator 11 is installed at the front stage and concentrated twice, and the submerged combustion apparatus 12 is installed at the rear stage and further concentrated twice, C, the submerged combustion apparatus 12 is installed at the front stage and concentrated twice, and vacuum The advantages and disadvantages of the four patterns D are summarized when the evaporator 11 is installed in the latter stage and concentrated twice.

  In the case of A, there is no problem of scale because the vacuum evaporator is not used, but there are problems of fuel cost and installation space. In the case of B, since the submerged combustion device is not used, the problem of fuel cost and space is solved, but there is room for improvement in that the scale is easily generated and the resulting crude nickel sulfate becomes hexahydrate. There is. Since monohydrate has less crystal water, it has high Ni quality and can keep logistics costs low. Therefore, it is preferable to recover crude nickel sulfate as monohydrate. In the case of C, the fuel cost problem, scale problem, crude nickel sulfate quality problem, and space problem are solved in a well-balanced manner. In the case of D, the problem of fuel cost and space is reduced, but there is room for improvement in the same way as B in that a new scale is likely to occur and the obtained crude nickel sulfate becomes hexahydrate.

  In the case of newly installing a nickel recovery system, it is not always necessary to use the vacuum evaporator 11 and the submerged combustion apparatus 12 together. The vacuum evaporator 11 is sufficient, but the submerged combustor 12 is already in the nickel recovery facility. If installed, discarding the submerged combustion device 12 and installing the vacuum evaporation device 11 conversely increases the equipment cost. Therefore, in such a case, the processing capacity can be easily increased by using the existing submerged combustion apparatus 12 and adding the vacuum evaporation apparatus 11. Even in this case, the total nickel processing capacity can be increased while reducing the load of the submerged combustion device 12, and therefore there is an advantage of reducing the running cost. When the vacuum evaporator 11 and the submerged combustion apparatus 12 are used in combination, the vacuum evaporator 11 depends on the maintenance frequency of each facility (vacuum canister twice / year, submerged combustion can once / month) and the operation mode. Is preferably provided at the front stage, and the submerged combustion device 12 is preferably provided at the rear stage.

<4. Cooling tank>
The cooling tank 13 cools the concentrated liquid discharged from the vacuum evaporator 11 or, if present, the in-liquid combustion apparatus 12, and crystallizes undeposited Ni in the concentrated liquid as crude nickel sulfate. Cooling can be performed, for example, by making the cooling tank 13 into a jacket structure, or by inserting a serpentine tube into the cooling tank, and passing a refrigerant through the jacket or serpentine tube. It is also possible to cool naturally without using a special refrigerant. Furthermore, it is also possible to employ a refrigeration crystal method that cools to about −20 ° C. The serpentine method is preferred because of the cooling efficiency of the concentrate and the simplicity of the cooling operation.

  Moreover, it is preferable to stir the concentrated liquid in the cooling tank 13 with an impeller or the like for the purpose of preventing precipitation (crude nickel sulfate) in the cooling tank. Also, if the cooling temperature is too low, the cooling time increases and the recovery time decreases due to the increase in recovery time. If it is too high, the load on the solid-liquid separation device increases, so that the concentrated liquid is about 0-50 ° C. in the cooling tank 13. Preferably, it cools to 15-30 degreeC.

<5. Solid-liquid separator>
The precipitated crude nickel sulfate passes through the solid-liquid separator 14 and is recovered from the copper removal electrolyte. Examples of the solid-liquid separation include sedimentation separation, centrifugation, filtration (gravity filtration, vacuum filtration, pressure filtration, etc.), and these may be used alone or in combination. A filtration method is preferred for reasons of recovery efficiency. The electrolytic solution after recovering the nickel is sent to the copper electrolytic purification process and reused. The recovered crude nickel sulfate can be sold externally.

  Examples of the present invention will be described below together with comparative examples, but these examples are provided for better understanding of the present invention and its advantages, and are not intended to limit the invention.

(1) Preparation of Decopper Electrolytic Solution A copper removal electrolytic solution having the following composition was obtained by performing electrowinning on the copper electrolytic solution after being used in copper electrolytic purification.
<Composition>
Copper 0.1 g / L, Nickel 20 g / L, Sulfuric acid: 200 g / L, Arsenic: 4 g / L, Antimony: 0.05 g / L, Bismuth: 0.02 g / L

(2) Comparative Example The copper removal electrolyte obtained in (1) was introduced into a submerged combustion apparatus, concentrated by heating, and then cooled in a cooling tank to crystallize crude nickel sulfate. Crude nickel sulfate was recovered with a solid-liquid separator.

The operating conditions were as follows.
A) Amount of copper removal electrolyte treatment: 35 m ³ / day b) Operating condition of submerged combustion system:
Electrolyte heating temperature: 138 to 143 ° C
・ Concentration rate: 4 times ・ Fuel consumption: 900-1200 L / day (kerosene)
C) Cooling tank ・ Cooling method: Heat exchange cooling ・ Cooling temperature: 30 ° C.
· Capacity: 4m ³ / tank × 3 group d) solid-liquid separation method: centrifugation

  As a result, the production amount of crude nickel sulfate was 80 t / month. Moreover, the nickel concentration in the copper removal electrolyte after nickel recovery was about 3 g / L. As a result of analysis by a powder X-ray diffraction method, the recovered crude nickel sulfate was mainly a monohydrate.

(3) Invention Example The nickel recovery system shown in FIG. 1 was constructed by installing a vacuum evaporator with respect to the nickel recovery system of the comparative example. The copper removal electrolyte obtained in (1) is introduced into a two-stage effect type vacuum evaporator and heated and concentrated, then further introduced into a submerged combustion apparatus and heated and concentrated, and then cooled in a cooling tank to be coarse. Nickel sulfate was crystallized. Crude nickel sulfate was recovered with a solid-liquid separator.

The operating conditions were as follows.
A) Decopper electrolyte treatment amount: 55 m ³ / day 1) Vacuum evaporator operating conditions • Heat source: Waste steam from flash furnace • Electrolyte heating temperature: 40-80 ° C. (first effect can about 81 ° C., Second effect can about 67 ℃)
・ Internal pressure: 0.1 MPa
・ Concentration rate: 2 times a) 2) Submerged combustion device operating conditions ・ Electrolyte heating temperature: 138 to 143 ° C.
・ Concentration rate: double ・ Fuel consumption: 900-1200 L / day (kerosene)
C) Cooling tank ・ Cooling method: Heat exchange cooling ・ Cooling temperature: 30 ° C.
· Capacity: 4m ³ / tank × 4 groups d) solid-liquid separation method: pressure filtration

The nickel concentration in the copper removal electrolyte after nickel recovery was about 3 g / L, which was about the same as the comparative example, but the amount of copper removal electrolyte treatment increased by 55 m ³ / day, and the amount of crude nickel sulfate produced Increased to 120 t / month. The production amount was 1.5 times that of the comparative example. The burden on the submerged combustion device has been reduced, and the fuel consumption rate has also decreased. As a result of analysis by a powder X-ray diffraction method, the recovered crude nickel sulfate was mainly a monohydrate.

11 Vacuum evaporation device 12 Submerged combustion device 13 Cooling tank 14 Filter press (solid-liquid separation device)

Claims (9)

  In the method of recovering the crude nickel sulfate from the decopper electrolyte by precipitating crude nickel sulfate by heating and concentrating the decopper electrolyte and then cooling it, and separating the precipitated crude nickel sulfate by solid-liquid separation, A method characterized in that the heating and concentration of the electrolytic solution is carried out in a vacuum evaporator.   The crude nickel sulfate recovery method according to claim 1, wherein the copper concentrate electrolytic solution is heated and concentrated using a vacuum evaporator and a submerged combustion apparatus arranged in series in a subsequent stage.   The crude nickel sulfate recovery method according to claim 1 or 2, wherein the heat source of the vacuum evaporator is water vapor.   The crude nickel sulfate recovery method according to claim 3, wherein the heat source of the vacuum evaporator is water vapor generated using waste heat discharged from the flash smelting furnace or converter.   The copper removal electrolytic solution is concentrated 1.85 to 2.15 times in the vacuum evaporator at the front stage, and further concentrated 1.85 to 2.15 times in the submerged combustion apparatus at the rear stage, so that the total of 3.42 to The crude nickel sulfate recovery method according to any one of claims 2 to 4, which is concentrated 4.62 times. A vacuum evaporator for heating and concentrating the copper removal electrolyte,
A cooling bath for cooling the copper removal electrolyte concentrated in the vacuum evaporator to deposit crude nickel sulfate;
A solid-liquid separator for removing the crude nickel sulfate precipitated in the cooling bath from the copper removal electrolyte,
A system for recovering crude nickel sulfate from copper-free electrolytic solution.   It is further equipped with a submerged combustion device for further heating and concentrating the copper removal electrolyte concentrated in the vacuum evaporator, and in the cooling tank, the copper removal electrolyte concentrated in the submerged combustion device is cooled to deposit crude nickel sulfate. The crude nickel sulfate recovery system according to claim 6.   The crude nickel sulfate recovery system according to claim 6 or 7, wherein the heat source of the vacuum evaporator is water vapor.   The crude nickel sulfate recovery system according to claim 8, wherein the heat source of the vacuum evaporator is water vapor generated using waste heat discharged from the flash smelting furnace or converter.

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