Deironization equipment for crude nickel sulfate solution

Abstract

To provide an iron removal facility for a crude nickel sulfate aqueous solution that can reduce nickel loss while sufficiently removing iron.SOLUTION: An iron removal facility is equipped with a neutralization tank 10 that performs oxidation neutralization treatment with respect to a crude nickel sulfate aqueous solution containing iron and discharges a neutralization slurry containing iron hydroxide as a precipitate, and a neutralizer supply pipe 15 that supplies a neutralizer to the neutralization tank 10. In the neutralizer supply pipe 15, a plurality of addition ports 15a for discharging the neutralizer are provided for one neutralization tank 10. Since the neutralizing agent is dispersed and added from the plurality of addition ports 15a, a region of locally high pH is unlikely to occur. Therefore, the formation of nickel hydroxide can be suppressed and nickel loss can be reduced.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to an apparatus for removing iron from an aqueous solution of crude nickel sulfate. More specifically, the present invention relates to an apparatus for removing iron from an aqueous solution of crude nickel sulfate. [Background technology]

[0002] Aqueous solutions of crude nickel sulfate obtained by leaching nickel raw materials such as nickel matte and nickel hydroxide contain impurity elements such as iron and arsenic. A known method for removing iron from aqueous solutions of crude nickel sulfate is the oxidation neutralization method, in which compressed air is blown into the aqueous solution of crude nickel sulfate to oxidize it, while a neutralizing agent is added to precipitate and remove the iron.

[0003] After iron is removed from the aqueous solution of crude nickel sulfate, the remaining impurities are removed by solvent extraction to obtain an aqueous solution of nickel sulfate with high purity. Iron is removed before solvent extraction because iron, an impurity element, forms crud, mainly composed of hydroxides, during the solvent extraction process, which may clog pipes and the like. Furthermore, a large amount of acid is required to strip and remove the iron extracted into the organic solvent, increasing production costs. Furthermore, if crud is formed, it may interfere with the process and deteriorate oil-water separation. Therefore, it is desirable to thoroughly remove iron from the aqueous solution of crude nickel sulfate before the solvent extraction process.

[0004] In the iron removal process using the oxidation neutralization method, compressed air is blown into the crude nickel sulfate solution to remove the Fe contained in the solution. 2+ Fe 3+ The iron is oxidized to iron hydroxide (Fe(OH)3), and a neutralizing agent is added to cause a neutralization reaction, which generates ferric hydroxide (Fe(OH)3), which is removed as a primary residue. Patent Document 1 discloses that, in order to promote the oxidation of iron and facilitate the generation of ferric hydroxide, hydrogen peroxide is added in addition to the injection of compressed air, and preliminary oxidation is carried out in advance.

[0005] During the oxidation neutralization process, iron hydroxide precipitates and a small amount of nickel also co-precipitates. As a result, the primary residue contains nickel. Therefore, a process to recover nickel from the primary residue is carried out. For example, the primary residue is repulped by adding water or a crude nickel sulfate solution with a low nickel concentration, and after heating, sulfuric acid is added. This dissolves the nickel hydroxide contained in the primary residue, allowing it to be recovered as a crude nickel sulfate solution.

[0006] The secondary residue remaining after dissolution is discharged outside the system, and therefore, the higher the nickel grade of the secondary residue, the greater the nickel loss. Furthermore, the more nickel hydroxide remains in the secondary residue, the poorer the filterability of the slurry becomes, and the higher the moisture content of the secondary residue. As a result, more nickel adheres to the secondary residue and is discharged, increasing nickel loss. Therefore, it is desirable to dissolve as much nickel hydroxide contained in the primary residue as possible.

[0007] Regarding this point, Patent Document 2 discloses that adding sulfuric acid to a slurry containing the primary residue and then stirring for a certain period of time increases the nickel leaching rate while maintaining the facility capacity. However, this method limits the stirring time from the perspective of the treatment cycle. In addition, iron leaching must be suppressed, and there is a limit to the amount of nickel that can be dissolved in the aqueous solution, making it difficult to reduce the nickel grade of the secondary residue below a certain level.

[0008] In order to further reduce the nickel grade in the secondary residue, it is conceivable to reduce the nickel grade at the stage of the primary residue. That is, the amount of nickel precipitation in the oxidation neutralization step can be reduced. Patent Document 3 discloses that when the iron concentration of an aqueous solution of crude nickel sulfate is 0.5 g / L or less, nickel loss can be reduced by adjusting the pH to 4.2 to 5.0. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Japanese Patent Publication No. 2020-158381 [Patent Document 2] Japanese Patent Application Laid-Open No. 2013-253273 [Patent Document 3] Japanese Patent Application Publication No. 2018-177547 Summary of the Invention [Problem to be solved by the invention]

[0010] However, when a neutralizing agent is added to an aqueous solution of crude nickel sulfate, areas with high pH are created, resulting in the formation of nickel hydroxide. If the amount of neutralizing agent added is reduced to prevent this, the average pH of the entire aqueous solution of crude nickel sulfate drops, making it difficult to produce iron hydroxide, which is the intended purpose. Therefore, it is difficult to reduce nickel loss while sufficiently removing iron by managing the pH alone.

[0011] In view of the above circumstances, an object of the present invention is to provide an iron removal system for an aqueous solution of crude nickel sulfate, which can sufficiently remove iron while reducing nickel loss. [Means for solving the problem]

[0012] The deironization equipment of the first invention comprises a neutralization tank that performs oxidation neutralization treatment on an aqueous solution of crude nickel sulfate containing iron and discharges a neutralized slurry containing iron hydroxide as a precipitate, and a neutralizer supply pipe that supplies a neutralizer to the neutralization tank, and the neutralizer supply pipe is provided with a plurality of addition ports for discharging the neutralizer for each neutralization tank. And, In a cylindrical coordinate system in which the agitation shaft of the agitation device provided in the neutralization tank is defined as the central axis, the distance from the central axis is defined as radius r, the direction around the central axis is defined as angle θ, the rotation direction of the agitation device is defined as the positive direction of angle θ, and the direction from the agitation shaft toward the discharge outlet of the neutralized slurry is defined as θ=0°, the multiple addition ports are arranged in the range of 30°≦θ≦210°. No. 2 The iron removal equipment of the invention is No. 1In the present invention, the plurality of addition ports are arranged in the range of 0.3R≦r≦0.7R (R is the radius of the neutralization tank). Third The iron removal equipment of the present invention is or the second invention a first solid-liquid separator for separating the neutralized slurry into a primary residue and a de-ironization final liquid; a dissolution tank for adding sulfuric acid to the primary residue to dissolve nickel hydroxide contained in the primary residue and obtain a dissolved slurry; and a second solid-liquid separator for separating the dissolved slurry into a secondary residue and a nickel recovery liquid. 。 [Effects of the Invention]

[0013] According to the first aspect of the present invention, the neutralizing agent is added in a dispersed manner from multiple addition ports, which makes it difficult for localized areas of high pH to occur, thereby suppressing the generation of nickel hydroxide and reducing nickel loss. Also, Since the addition port is located in a region distant from the discharge port in terms of the path along the swirling flow of the crude nickel sulfate aqueous solution, it is possible to suppress short-path discharge in which the neutralizing agent added through the addition port and the locally generated nickel hydroxide are discharged from the discharge port in a short time, thereby allowing the neutralizing agent to act sufficiently and enabling sufficient removal of iron. No. 2 According to the present invention, the neutralizing agent is added to the region where the swirling flow velocity of the crude nickel sulfate aqueous solution is high, so that the occurrence of locally high pH regions is unlikely, thereby suppressing the generation of nickel hydroxide and reducing nickel loss. Third According to the invention, nickel hydroxide contained in the primary residue is dissolved and recovered as a nickel recovery solution, which further reduces nickel loss. 。 [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 2 is an explanatory diagram of an iron removal equipment according to an embodiment. [Figure 2] FIG. 2 is a vertical cross-sectional view of a neutralization tank according to one embodiment. [Figure 3] FIG. 2 is a plan view of a neutralization tank according to one embodiment. [Figure 4] FIG. 2 is a schematic diagram showing a high concentration region of a neutralizing agent. [Figure 5] Figure (A) is a graph showing the change in the insoluble nickel content of the primary residue of the exchange system. Figure (B) is a graph comparing the insoluble nickel content of the secondary residue of the exchange system. [Figure 6] Figure (A) is a graph showing the change in the insoluble nickel content of the primary residue of the extraction system. Figure (B) is a graph comparing the insoluble nickel content of the secondary residue of the extraction system. DETAILED DESCRIPTION OF THE INVENTION

[0015] Next, an embodiment of the present invention will be described with reference to the drawings. The iron removal equipment according to one embodiment of the present invention is equipment for removing iron from an aqueous solution of crude nickel sulfate. The aqueous solution of crude nickel sulfate to be treated contains at least iron as an impurity. The aqueous solution of crude nickel sulfate may further contain impurities other than iron.

[0016] Examples of crude nickel sulfate aqueous solutions include: (1) an aqueous solution obtained in the electrolytic nickel production process by dissolving nickel and cobalt hydroxides, obtained by purifying the chlorine leachate of a mixed sulfide containing nickel and cobalt, in sulfuric acid; (2) an aqueous solution obtained by pressure leaching nickel matte together with sulfur and oxygen; (3) an aqueous solution obtained by mixing (1) and (2); and (4) an aqueous solution obtained in the electrolytic copper production process by dissolving crude nickel sulfate crystals, which are produced in the process of crystallizing and removing nickel concentrated in copper electrolyte, and then removing impurities such as copper and zinc contained in the crystals by sulfurization precipitation using hydrogen sulfide gas.

[0017] In this specification, the aqueous solutions (1), (2), and (3) are referred to as "exchange-type crude nickel sulfate aqueous solutions," and the aqueous solution (4) is referred to as "extract-type crude nickel sulfate aqueous solution." The exchange-type crude nickel sulfate aqueous solution has a nickel concentration of 100 to 120 g / L and an iron concentration of 0.1 to 0.5 g / L. The extract-type crude nickel sulfate aqueous solution has a nickel concentration of 100 to 120 g / L and an iron concentration of 0.4 to 0.8 g / L. These crude nickel sulfate aqueous solutions contain impurities such as aluminum, chromium, copper, zinc, and arsenic in addition to iron.

[0018] As shown in FIG. 1, the deironization equipment AA of this embodiment has multiple stages of neutralization tanks 10A, 10B, and 10C connected in series (hereinafter, reference numeral 10 will be used when the order of arrangement is not to be distinguished). The aqueous solution of crude nickel sulfate is continuously supplied to the first neutralization tank 10A, and then flows sequentially toward the last neutralization tank 10C. Compressed air is introduced as an oxidizing agent into each neutralization tank 10. A neutralizing agent is also added to each neutralization tank 10. The number of stages of neutralization tanks 10 is not particularly limited. The number of stages of neutralization tanks 10 may be one.

[0019] When air is blown into a crude nickel sulfate solution, the Fe contained in the solution 2+ Fe 3+ When a neutralizing agent is added to the aqueous solution to cause a neutralization reaction, ferric hydroxide (Fe(OH)3) is produced. In this way, in the neutralization tank 10, the crude nickel sulfate aqueous solution is subjected to an oxidation neutralization treatment, producing a precipitate containing iron hydroxide. Hereinafter, the slurry containing this precipitate will be referred to as the neutralized slurry.

[0020] As a neutralizing agent, slaked lime, sodium hydroxide, etc. can be used. The amount of neutralizing agent added is preferably an amount that causes the pH of the aqueous crude nickel sulfate solution in the neutralization tank 10 to be 2.6 to 5.9, and more preferably an amount that causes the pH to be 4.6 to 5.9. In this way, it is possible to suppress the generation of nickel hydroxide while generating iron hydroxide.

[0021] When the oxidation neutralization treatment is carried out using multiple neutralization tanks 10A, 10B, and 10C, it is preferable to increase the pH stepwise from the first neutralization tank 10A to the last neutralization tank 10C. Since the impurity concentration in the final deironization solution depends mainly on the pH of the last neutralization tank 10C, it is preferable to set the pH of the aqueous crude nickel sulfate solution in the last neutralization tank 10C to 4.6 to 5.9.

[0022] The neutralized slurry discharged from the final-stage neutralization tank 10C is introduced into a first solid-liquid separator 20. The first solid-liquid separator 20 separates the neutralized slurry into a primary residue and a deironization end liquid. A filter press can be suitably used as the first solid-liquid separator 20.

[0023] The de-ironized final solution is a solution in which iron has been removed from the aqueous solution of crude nickel sulfate. For example, when an exchange-type crude nickel sulfate solution is used, the de-ironized final solution has a nickel concentration of 100 to 120 g / L and an iron concentration of less than 5 mg / L. When an extraction-type crude nickel sulfate solution is used, the de-ironized final solution has a nickel concentration of 100 to 120 g / L and an iron concentration of less than 15 mg / L. The de-ironized final solution is sent to a solvent extraction step. In the solvent extraction step, impurities remaining in the de-ironized final solution are removed by solvent extraction to obtain a high-purity aqueous solution of nickel sulfate.

[0024] When oxidation neutralization treatment is performed, iron hydroxide precipitates are formed, and a small amount of nickel also co-precipitates. Therefore, the primary residue contains nickel. For example, when an exchange-type crude nickel sulfate aqueous solution is used, the nickel content of the primary residue is 2 to 6 wt. %. When an extraction-type crude nickel sulfate aqueous solution is used, the nickel content of the primary residue is 10 to 20 wt. %.

[0025] Discharging the primary residue directly from the system results in a large loss of nickel, so a process to recover nickel from the primary residue is carried out. The primary residue is discharged to a dissolution tank 30. In the dissolution tank 30, water or a crude nickel sulfate solution with a low nickel concentration is added to the primary residue to repulp it, and after the temperature is raised, sulfuric acid is added. The nickel hydroxide contained in the primary residue is dissolved by the sulfuric acid.

[0026] The amount of sulfuric acid added is preferably an amount that makes the liquid phase of the slurry (dissolved slurry) in the dissolution tank 30 have a pH of 3.0 to 4.1. By adjusting the pH of the dissolution tank 30 to 3.0 to 4.1, the nickel hydroxide contained in the primary residue can be sufficiently dissolved.

[0027] The post-dissolution slurry discharged from the dissolution tank 30 is introduced into a second solid-liquid separator 40. The second solid-liquid separator 40 separates the post-dissolution slurry into a secondary residue and a nickel recovery solution. A filter press can be suitably used as the second solid-liquid separator 40.

[0028] The secondary residue is discharged outside the system. For example, when an exchange-type crude nickel sulfate aqueous solution is used, the nickel content of the secondary residue is 0.7 to 1.4 wt %. When an extraction-type crude nickel sulfate aqueous solution is used, the nickel content of the secondary residue is 0.6 to 1.3 wt %.

[0029] The nickel recovery solution is recycled within the system. The nickel recovery solution is used, for example, as a repulping aqueous solution when nickel and cobalt hydroxides are used as raw materials and dissolved with sulfuric acid, as a dissolution aqueous solution when dissolving crude nickel sulfate crystals, and as a crude nickel sulfate aqueous solution with a low nickel concentration for repulping the primary residue. In this way, nickel hydroxide contained in the primary residue is dissolved and recovered as a nickel recovery solution, thereby further reducing nickel loss.

[0030] In the oxidation neutralization treatment, the pH of the crude nickel sulfate aqueous solution is adjusted to Ni in order to suppress the generation of nickel hydroxide. 2+ However, when a neutralizing agent is added to the aqueous solution of crude nickel sulfate in the neutralization tank 10, the pH is set to the stable range of Ni 2+Even if the stability region of nickel hydroxide is set to 0.05, nickel hydroxide is produced. When a neutralizing agent is added to the neutralization tank 10, the concentration of the neutralizing agent becomes locally high in the aqueous solution of crude nickel sulfate in the neutralization tank 10, especially near the inlet for adding the neutralizing agent. In such a high concentration region, the pH of the aqueous solution of crude nickel sulfate becomes high. As a result, the stability region of nickel hydroxide (Ni(OH)2) may be locally reached, which is produced and co-precipitates with iron hydroxide. The pH of the aqueous solution of crude nickel sulfate is 2+ Since the stability region of the neutralization tank 10 is set at 100°C, the generated nickel(II) hydroxide will re-dissolve once the equilibrium state is completely restored. However, since it takes a long time to completely restore the equilibrium state, nickel(II) hydroxide will remain during the residence time in the neutralization tank 10. Therefore, the deironization equipment AA of this embodiment is devised to add a neutralizing agent to the neutralization tank 10 in order to prevent the occurrence of a high concentration region of the neutralizing agent.

[0031] As shown in Fig. 2, neutralization tank 10 is provided with a supply port 11 for a crude nickel sulfate aqueous solution (neutralization slurry in the case of second-stage or later neutralization tanks 10B and 10C). Neutralization tank 10 is also provided with a discharge port 12 for the neutralization slurry. The neutralized slurry in neutralization tank 10 is discharged from discharge port 12 by overflow. The locations of supply port 11 and discharge port 12 are not particularly limited, but they are usually located at opposing positions within neutralization tank 10, i.e., at the furthest positions.

[0032] Discharge port 12 is preferably disposed inside hydrostatic cylinder 13. Hydrostatic cylinder 13 is a cylindrical member that extends in the vertical direction along the inner wall surface of neutralization tank 10 from near the bottom to above the liquid level. The neutralized slurry flows into hydrostatic cylinder 13 from the lower end thereof and is discharged from discharge port 12. The presence of hydrostatic cylinder 13 makes it possible to suppress short-pass discharge, in which the aqueous crude nickel sulfate solution supplied from supply port 11 is discharged from discharge port 12 in a short time.

[0033] Neutralization tank 10 is provided with an air inlet pipe 14 for blowing air into the interior (crude nickel sulfate aqueous solution) of neutralization tank 10. Neutralization tank 10 also has a neutralizer supply pipe 15 for supplying a neutralizer into the interior of neutralization tank 10. The open end at the end of neutralizer supply pipe 15, from which the neutralizer is discharged, is referred to as addition port 15a.

[0034] The neutralization tank 10 is provided with an agitator 16. The aqueous solution of crude nickel sulfate in the neutralization tank 10 is agitated by driving the agitator 16. A cylindrical tank is usually used as the neutralization tank 10. The agitator shaft 16a of the agitator 16 is disposed in the center of the neutralization tank 10.

[0035] As shown in FIG. 3, the neutralizing agent supply pipe 15 branches into multiple parts and has multiple addition ports 15a. A plurality of addition ports 15a are provided for each neutralization tank 10. In this way, the neutralizing agent is added in a dispersed manner through the multiple addition ports 15a, which prevents localized high pH regions from occurring. In other words, an oxidation neutralization reaction close to an equilibrium state can be caused throughout the entire neutralization tank 10. This can suppress the generation of nickel hydroxide and reduce nickel loss.

[0036] Figure 4 shows the state in which a high concentration region HD of the neutralizing agent has occurred. The crude nickel sulfate aqueous solution is flowing to the right in Figure 4. When the neutralizing agent is added to the crude nickel sulfate aqueous solution, the concentration of the neutralizing agent becomes locally high near the addition port 15a. The high concentration region HD of the neutralizing agent has a high pH and is thought to be a region where nickel hydroxide nucleation occurs. According to the concept of turbulent diffusion, the volume V of the high concentration region HD is thought to be proportional to the square of the neutralizing agent flow rate q [mol / s] and inversely proportional to the flow rate u [m / s] of the crude nickel sulfate aqueous solution.

[0037] Therefore, the more the number of addition ports 15a, that is, the smaller the neutralizing agent flow rate q, the smaller the volume V of the high concentration region HD can be. For example, if the addition ports are distributed to three locations, even if the total flow rate of the neutralizing agent is the same, the volume V of the high concentration region HD can be reduced by (1 / 3) 2 × 3 = (1 / 3), so the total volume V of the high concentration region HD is (1 / 3). As a result, it is thought that the generation of nickel hydroxide is suppressed.

[0038] It is not necessary to reduce the total flow rate of the neutralizing agent added to the neutralization tank 10. Therefore, the average pH of the entire aqueous crude nickel sulfate solution in the neutralization tank 10 does not decrease, so iron hydroxide is easily produced and iron can be sufficiently removed.

[0039] Hereinafter, as shown in Figures 2 and 3, a cylindrical coordinate system will be defined with the neutralization tank 10 as the reference. The agitation shaft 16a of the agitation device 16 is defined as the central axis (z-axis). The distance from the central axis to the addition port 15a is defined as the radius r. The direction around the central axis is defined as the angle θ. The rotation direction of the agitation device 16 is defined as the positive direction of the angle θ. In the example shown in Figure 3, the positive direction of the angle θ is defined as clockwise. Furthermore, the direction from the agitation shaft 16a toward the discharge port 12 is defined as θ = 0°.

[0040] As shown in Fig. 3, it is preferable to arrange the plurality of addition ports 15a in the range of 30°≦θ≦210°. In this way, when viewed along the path of the swirling flow of the crude nickel sulfate aqueous solution, all of the addition ports 15a are arranged in an area away from the discharge port 12. This makes it possible to prevent a short pass, in which the neutralizing agent added through the addition ports 15a is discharged from the discharge port 12 in a short time. This allows the neutralizing agent to act sufficiently, and iron can be sufficiently removed.

[0041] To add a neutralizing agent to the neutralization tank 10, the addition port 15a needs to be located within the range of the neutralization tank 10. If the neutralization tank 10 is cylindrical with a radius R and the stirring shaft 16a is located at the center, then the multiple addition ports 15a should be located within the range 0≦r≦R.

[0042] However, it is preferable that the plurality of addition ports 15a are arranged in the range of 0.3R≦r≦0.7R. As shown in FIG. 2, the angular velocity of the swirling flow in the cylindrical stirring vessel is equal to the radius of rotation r c In other words, the larger the radius r, the faster the flow rate. On the other hand, the solid rotation radius r c The flow rate decreases as the radius r increases outside the tank 10. Therefore, the flow rate is fastest near the center of the radius R of the neutralization tank 10. It is preferable to place the addition port 15a in this region where the flow rate is fast.

[0043] As mentioned above, the faster the flow rate u of the crude nickel sulfate aqueous solution, the smaller the volume V of the high-concentration region HD. If a neutralizing agent is added to the region where the flow rate u of the crude nickel sulfate aqueous solution is fast, it is difficult for a region with a locally high pH to occur. Therefore, the generation of nickel hydroxide can be suppressed, and nickel loss can be reduced.

[0044] The position of the addition port 15a in the z direction is not particularly limited. Usually, the addition port 15a is disposed above the liquid surface of the aqueous solution of crude nickel sulfate. [Example]

[0045] Next, an example will be described. 1. Exchange system The iron removal equipment AA shown in Figure 1 was used to remove iron from a crude nickel sulfate aqueous solution. The crude nickel sulfate aqueous solution used was a mixture of two aqueous solutions (3): (1) an aqueous solution obtained by dissolving nickel and cobalt hydroxides, obtained by purifying the chlorine leach solution of a mixed sulfide containing nickel and cobalt in an electrolytic nickel production process, in sulfuric acid, and (2) an aqueous solution obtained by pressure leaching nickel matte together with sulfur and oxygen. The crude nickel sulfate aqueous solution at the time of supply to the front-stage neutralization tank 10A had a nickel concentration of 100-120 g / L, an iron concentration of 0.1-0.5 g / L, and a pH of 1-2.

[0046] The deironization equipment AA has three neutralization tanks 10A, 10B, and 10C. Slaked lime slurry was added to each of the neutralization tanks 10A, 10B, and 10C to adjust the pH. Specifically, the pH of the front neutralization tank 10A was adjusted to 2.7±0.1, the pH of the middle neutralization tank 10B to 4.6±0.1, and the pH of the final neutralization tank 10C to 4.7±0.1. Furthermore, sulfuric acid was added to the dissolution tank 30 to adjust the pH to 3.3±0.1.

[0047] Operation was carried out with one neutralizing agent addition port 15a in each of neutralization tanks 10A, 10B, and 10C (hereinafter referred to as single-point addition). Subsequently, operation was carried out with the addition ports 15a in the front-stage neutralization tank 10A and the middle-stage neutralization tank 10B increased to three (hereinafter referred to as multi-point addition). During operation, samples of the primary residue and secondary residue were taken at predetermined time intervals, and the insoluble nickel grade was measured.

[0048] The nickel contained in the primary and secondary residues consists of two types: water-soluble nickel derived from nickel sulfate carried over from the adhesion solution, and insoluble nickel derived from nickelous hydroxide produced by the neutralization reaction. The purity of the insoluble nickel was measured using the following procedure. First, 1 g of the primary residue was dissolved in nitric acid, and the nickel concentration in the solution was analyzed. This analytical value corresponds to the total nickel content, which is the sum of the insoluble and water-soluble nickel content. Next, 1 g of the primary residue was washed with 150 mL of boiling water for 10 minutes to elute the water-soluble nickel. The nickel concentration in the eluate was analyzed to determine the water-soluble nickel content. The insoluble nickel content of the primary residue was then calculated by subtracting the water-soluble nickel content from the total nickel content. The nickel concentration was analyzed using ICP atomic emission spectroscopy. The insoluble nickel content of the secondary residue was also determined using the same procedure.

[0049] Figure 5(A) shows the change in the insoluble nickel content of the primary residue. Figure 5(B) shows a graph comparing the insoluble nickel content of the secondary residue. The insoluble nickel content of the primary residue averaged 5.67 wt% (standard deviation 2.08 wt%) with single-point addition, but decreased to an average of 4.02 wt% (standard deviation 0.75 wt%) with multi-point addition. The insoluble nickel content of the secondary residue averaged 1.91 wt% (standard deviation 0.54 wt%) with single-point addition, but decreased to an average of 0.93 wt% (standard deviation 0.12 wt%) with multi-point addition.

[0050] 2.Extraction system The crude nickel sulfate aqueous solution was deionized using the deionization equipment AA shown in Figure 1. The crude nickel sulfate aqueous solution was prepared by dissolving crude nickel sulfate crystals produced in the (4) electrolytic copper production process, in which nickel concentrated in the copper electrolyte is crystallized and removed, and then removing impurities such as copper and zinc contained in the crystals by sulfurization precipitation using hydrogen sulfide gas. The crude nickel sulfate aqueous solution at the time of supply to the front-stage neutralization tank 10A had a nickel concentration of 100 to 120 g / L, an iron concentration of 0.4 to 0.8 g / L, and a pH of 1 to 2.

[0051] The deironization equipment AA has three neutralization tanks 10A, 10B, and 10C. Slaked lime slurry was added to each of the neutralization tanks 10A, 10B, and 10C to adjust the pH. Specifically, the pH of the front neutralization tank 10A was adjusted to 3.5±0.1, the pH of the middle neutralization tank 10B to 5.7±0.1, and the pH of the final neutralization tank 10C to 5.8±0.1. Furthermore, sulfuric acid was added to the dissolution tank 30 to adjust the pH to 4.0±0.1.

[0052] Operation was carried out with one neutralizing agent addition port 15a in each of the neutralization tanks 10A, 10B, and 10C (single-point addition). Subsequently, the number of addition ports 15a in the front-stage neutralization tank 10A and the rear-stage neutralization tank 10C was increased to two, and the number of addition ports 15a in the middle-stage neutralization tank 10B was increased to three (multi-point addition). During the operation period, samples of the primary and secondary residues were taken at specified intervals, and the insoluble nickel grade was measured using the same procedure as for the exchange system.

[0053] Figure 6(A) shows the change in the insoluble nickel content of the primary residue. Figure 6(B) shows a graph comparing the insoluble nickel content of the secondary residue. The insoluble nickel content of the primary residue averaged 17.75 wt% (standard deviation 2.64 wt%) with single-point addition, but decreased to an average of 13.89 wt% (standard deviation 2.24 wt%) with multi-point addition. The insoluble nickel content of the secondary residue averaged 1.67 wt% (standard deviation 0.94 wt%) with single-point addition, but decreased to an average of 0.94 wt% (standard deviation 0.14 wt%) with multi-point addition.

[0054] From the above, it was confirmed that the insoluble nickel grade in both the primary residue and the secondary residue was reduced by increasing the number of neutralizing agent addition ports 15a. [Explanation of symbols]

[0055] AA de-ironizing equipment 10(10A, 10B, 10C) Neutralization tank 11 Supply port 12 Outlet 13 Still water bottle 14 Air inlet tube 15 Neutralizer supply pipe 15a Addition port 16 Mixing device 16a Agitator shaft 20 1st solid-liquid separator 30 Dissolution tank 40 Second solid-liquid separator

Claims

1. a neutralization tank for performing an oxidation neutralization treatment on the iron-containing crude nickel sulfate aqueous solution and discharging a neutralized slurry containing iron hydroxide as a precipitate; a neutralizing agent supply pipe for supplying a neutralizing agent to the neutralization tank; The neutralizing agent supply pipe has a plurality of addition ports for discharging the neutralizing agent provided for each neutralization tank, In a cylindrical coordinate system in which the agitation shaft of the agitation device provided in the neutralization tank is defined as the central axis, the distance from the central axis is defined as the radius r, the direction around the central axis is defined as the angle θ, the rotation direction of the agitation device is defined as the positive direction of the angle θ, and the direction from the agitation shaft toward the discharge port of the neutralized slurry is defined as θ=0°, the multiple addition ports are arranged within a range of 30°≦θ≦210°. The iron removal equipment is characterized by the above.

2. The plurality of addition ports are arranged in the range of 0.3R≦r≦0.7R (R is the radius of the neutralization tank).

2. The iron removal equipment according to claim 1.

3. a first solid-liquid separator for separating the neutralized slurry into a primary residue and a deironation final liquid; a dissolution tank in which sulfuric acid is added to the primary residue to dissolve the nickel hydroxide contained in the primary residue and obtain a slurry after dissolution; a second solid-liquid separator for separating the post-dissolution slurry into a secondary residue and a nickel recovery solution.

3. The iron removal equipment according to claim 1 or 2.

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