Particle size control method of zinc sulfide

Abstract

To provide a particle size control method of zinc sulfide capable of improving filterability of zinc sulfide to be formed and of suppressing deterioration of a nickel recovery rate.SOLUTION: A particle size control method of zinc sulfide to be separated in hydrometallurgy of nickel oxide ore, wherein hydrometallurgy of nickel oxide ore has at least the above-described leaching step S2, a solid-liquid separation step S4, a neutralization step S5, a dezincification step S6, and a nickel recovery step S7, and in the neutralization step, part of the leach residue is added to the leachate to adjust so that the pH of the neutralization end is 3.0-3.5, and a part of the zinc sulfide precipitate in the dezincification step is repeatedly added to the neutralization end solution as seed crystals, so that a median diameter D 50 of the zinc sulfide is adjusted so that it becomes precipitate of a particle size of 5 μm or more, and the particle size of the zinc sulfide is characterized in measuring a calcium grade ratio expressed by the following equation 1 of zinc sulfide to increase or decrease addition amount of the seed crystal to per zinc one mole of the neutralization end solution. (Calcium grade ratio)=(Ca grade / (Ni grade + Co grade + Cu grade + Fe grade)) is Equation 1.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a method for controlling the particle size of zinc sulfide in the dezincification process in the hydrometallurgy of nickel oxide ore. [Background technology]

[0002] One of the hydrometallurgical methods for nickel oxide ore is the high pressure acid leaching (HPAL) method using sulfuric acid. This method does not include dry processing steps such as drying and roasting, and instead consists of a continuous hydrometallurgical process, so it is advantageous in terms of energy and cost, and has the advantage of being able to obtain nickel-cobalt mixed sulfide with nickel content improved to about 50 mass%.

[0003] The high-pressure acid leaching (HPAL) method includes a leaching process in which sulfuric acid is added to an ore slurry and stirred at a temperature condition of 220 to 280°C to form a leaching slurry; a solid-liquid separation process in which the leaching slurry is washed in multiple stages to obtain a leachate containing nickel and cobalt and a leach residue; a neutralization process in which the pH of the leachate is adjusted and a neutralized precipitate containing impurity elements is generated, which is then sedimented and separated in a thickener to remove the neutralized precipitate and obtain a neutralized final solution containing nickel and cobalt; a dezincification process in which a sulfiding agent such as hydrogen sulfide is added to the neutralized final solution to generate a mixed sulfide containing zinc, which is then separated and removed to obtain a dezincification final solution; and a nickel recovery process in which hydrogen sulfide gas is blown into the dezincification final solution to form a sulfide containing nickel and cobalt and a barren solution.

[0004] In the dezincing step, the neutralized end solution is introduced into a sulfurization reaction tank, and a sulfurizing agent such as hydrogen sulfide gas or sodium hydrosulfide is added to sulfurize the zinc, copper, etc. contained in the neutralized end solution, and then the solution is separated into solid and liquid by a filter to obtain a mother liquor for nickel recovery containing zinc sulfide, nickel, and cobalt. Since the slurry containing the dezincified precipitate produced in the dezincing step contains hydrogen sulfide, a closed pressure filter or the like is used as the filter. In the solid-liquid separation by the filter, the dezincified precipitate adheres to the surface of the filter cloth, causing resistance, and the flow rate gradually decreases with the increase in the liquid passing time. For this reason, it is necessary to periodically stop the liquid passing and remove the dezincified precipitate adhered to the filter cloth. When the particle size of the dezincified precipitate is small, the filter cloth is easily clogged, the liquid passing flow rate decreases significantly, and the frequency of stopping the liquid passing and removing the precipitate increases. Therefore, it is desirable to keep the particle size large in terms of maintaining a stable operating load.

[0005] On the other hand, in the neutralization step preceding the dezincing step, it is known that it is desirable to adjust the pH of the final neutralization solution to 3.0 to 3.5 (in this specification, "to" means not less than the lower limit and not more than the upper limit; the same applies hereinafter) in order to increase the degree of sulfidation in the dezincing step, thereby improving the sulfiding reactivity of zinc, and to reduce the amount of sulfiding agent added to prevent co-precipitation of nickel (see, for example, Patent Document 3).

[0006] In addition, the pH adjuster added in the neutralization process is generally a calcium salt such as limestone, and calcium remains in the liquid as ions within the range of its solubility, and the portion that exceeds its solubility combines with sulfate ions in the liquid to form gypsum. In the neutralization process, the generated gypsum is separated by settling in a thickener to obtain a neutralization end liquid. When the pH is 3.0 to 3.5, the amount of unreacted neutralizer in the neutralization reaction tank increases with an increase in the amount of neutralizer added, and fine particles cannot be removed by the thickener and are carried to the next process. In this case, gypsum is generated in the neutralization end liquid storage tank and the dezincification reaction tank, and it has been confirmed that it is collected by a filter together with the dezincification precipitate, causing clogging of the filter cloth.

[0007] Table 1 shows the change in turbidity components when the neutralization end solution of pH 2.9 and pH 3.2 is incubated and left for 4 hours. For example, when two neutralization end solutions with pH 2.9 and 3.2 immediately after the neutralization sediment is separated by settling in a thickener in the neutralization process are incubated and left for 4 hours, which is the same as the residence time in a dezincification reaction tank, the turbidity components increased to 6 times the relative ratio only in the case of pH 3.2 due to gypsum generation (see Table 1), and clogging of the filter cloth occurred in the dezincification filter, and the liquid flow rate decreased. Therefore, a method for preventing clogging of the dezincification filter by fine gypsum while maintaining the pH of the neutralization end solution at 3.0 to 3.5 was required.

[0008] [Table 1]

[0009] In response to such conventional problems, for example, Patent Document 1 proposes a technique for lowering the zinc concentration of the mother liquor for nickel recovery by controlling the amount of seed crystals added in the dezincing step. Patent Document 2 proposes a technique for extending the life of the filter cloth in the dezincing step by lowering the turbidity components of the end solution of the neutralization step, which is the step preceding the dezincing step. Patent Document 3 proposes a technique for improving filterability by adjusting the pH of the end solution of the neutralization step to 3.0 to 3.5 and leaving suspended matter so that the turbidity of the end solution of the neutralization step is 100 to 400 NTU.

[0010] Although the techniques disclosed in the above Patent Documents 1 to 3 are said to improve filtration performance, there is no specific mention of the cause thereof, and the technical solution to the problem of clogging of the filter cloth by gypsum is insufficient, so further technological development is desired. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] JP 2019-137903 A [Patent Document 2] JP 2014-074233 A [Patent Document 3] JP 2010-037626 A Summary of the Invention [Problem to be solved by the invention]

[0012] The present invention has been made to solve the above-mentioned problems, and aims to provide a method for controlling the particle size of zinc sulfide, which can improve the filterability of zinc sulfide formed in the dezincification step of a hydrometallurgical method for nickel oxide ore and suppress a decrease in the nickel recovery rate. [Means for solving the problem]

[0013] In order to achieve the above object, the present inventors have conducted extensive research and have found that by changing the amount of seed crystals added per zinc in a solution depending on the calcium content ratio of zinc sulfide (dezincified precipitate), a precipitate with excellent filterability and a median diameter of 5 μm or more can be produced, thereby completing the present invention.

[0014] That is, one aspect of the present invention is a method for controlling the particle size of zinc sulfide separated in the hydrometallurgy of nickel oxide ore, the hydrometallurgy of nickel oxide ore including at least a leaching process in which sulfuric acid is added to a slurry of nickel oxide ore and leached under high temperature and high pressure to obtain a leaching slurry, a solid-liquid separation process in which the leaching slurry is washed in multiple stages and the leaching residue is separated to obtain a leaching solution containing nickel, cobalt and impurity elements, a neutralization process in which the pH of the leaching solution is adjusted and a neutralization precipitate containing impurity elements is separated to obtain a neutralization end solution containing zinc as well as nickel and cobalt, and a de-Ammonia process in which hydrogen sulfide gas is added to the neutralization end solution to form zinc sulfide, the zinc sulfide is separated, and a mother liquor for nickel recovery containing nickel and cobalt is obtained. The method includes a lead process, and a nickel recovery process in which hydrogen sulfide gas is added to a mother liquor for nickel recovery to form a mixed sulfide containing nickel and cobalt, and the mixed sulfide is separated. In the neutralization process, a part of the leaching residue is added to the leachate, and the pH of the neutralization end solution is adjusted to 3.0 to 3.5. At the same time, a part of the zinc sulfide precipitate from the dezincing process is repeatedly added to the neutralization end solution as seed crystals, thereby adjusting the zinc sulfide precipitate to have a particle size of 5 μm or more. The particle size of the zinc sulfide is adjusted by measuring the calcium content ratio of the zinc sulfide, which is represented by the following formula 1, and increasing or decreasing the amount of seed crystals added per mole of zinc in the neutralization end solution according to the value of the calcium content ratio. (Calcium content ratio) = (Ca content / (Ni content + Co content + Cu content + Fe content)) Equation 1

[0015] In this case, in one embodiment of the present invention, the amount of seed crystals added in adjusting the particle size of the zinc sulfide may be increased when the value of the calcium content ratio becomes relatively large, and decreased when the value of the calcium content ratio becomes relatively small.

[0016] In one embodiment of the present invention, the relationship between the calcium content ratio of zinc sulfide and the amount of seed crystals added per mole of zinc may be based on the following criteria (1) to (3). (1) When the calcium content ratio of zinc sulfide is 0.01 or more and less than 0.05, the amount of seed crystals added per mole of zinc is 5 g / mol-Zn or more and 50 g / mol-Zn or less. (2) When the calcium content ratio of zinc sulfide is 0.05 or more and less than 0.1, the amount of seed crystals added per mole of zinc is 15 g / mol-Zn or more and 50 g / mol-Zn or less. (3) When the calcium content ratio of zinc sulfide is 0.1 or more and less than 0.5, the amount of seed crystals added per mole of zinc is 25 g / mol-Zn or more and 50 g / mol-Zn or less. Effect of the Invention

[0017] According to the present invention, in the dezincification step in the hydrometallurgical smelting of nickel oxide ore, the filterability of the formed zinc sulfide can be improved and a decrease in the nickel recovery rate can be suppressed. That is, a decrease in the particle size of the dezincification precipitate due to fine gypsum in the dezincification step can be suppressed. [Brief description of the drawings]

[0018] [Figure 1] FIG. 1 is a process diagram showing a hydrometallurgical process for nickel oxide ore by high-pressure acid leaching. [Diagram 2] FIG. 2 is a diagram showing the relationship between the amount of seed crystals added and the particle size of the dezincified precipitate according to the calcium content ratio of the dezincified precipitate in the dezincification step. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] The method for controlling the particle size of zinc sulfide according to the present invention will be described below with reference to the drawings in the following order. Note that the present invention is not limited to the following examples, and can be modified as desired without departing from the gist of the present invention. 1. Hydrometallurgy of nickel oxide ore 2. Method for controlling particle size of zinc sulfide

[0020] <1. Hydrometallurgical refining method for nickel oxide ore> First, prior to a more specific description of the method for controlling the particle size of zinc sulfide, a hydrometallurgical method for nickel oxide ore to which the method for controlling the particle size of nickel zinc sulfide according to the present invention is applied will be briefly described. This hydrometallurgical method for nickel oxide ore is a hydrometallurgical method for leaching and recovering nickel and cobalt from nickel oxide ore using a high-pressure acid leaching method (HPAL method). Figure 1 shows an example of a process diagram of a hydrometallurgical method for nickel oxide ore using the high-pressure acid leaching method.

[0021] In the slurry preparation step S1, nickel oxide ore is used as the raw material ore, and several types of nickel oxide ore are mixed to obtain a specified Ni content and impurity content, which are then mixed with water to form a slurry, which is then sieved to classify the slurry at a specified classification point to remove oversized ore particles, and only the undersized ore is used.

[0022] In the leaching step S2, the nickel oxide ore slurry obtained in the slurry preparation step S1 is subjected to a leaching treatment using, for example, a high-pressure acid leaching method. Specifically, sulfuric acid is added to an ore slurry obtained by mixing the raw nickel oxide ore, and nickel, cobalt, etc. are leached from the ore by applying a pressure of 3 to 5 MPa under a high temperature condition of 220 to 280°C using, for example, a heat-resistant and pressure-resistant vessel (autoclave), to form a leaching slurry consisting of a leachate and a leach residue.

[0023] In the leaching step S2, an excess of sulfuric acid is added in order to improve the leaching rate. Therefore, the resulting leaching slurry contains excess sulfuric acid that was not involved in the leaching reaction, and its pH is very low.

[0024] For this reason, in the preliminary neutralization step S3, the pH of the leaching slurry obtained in the leaching step S2 is increased and adjusted to a predetermined range so that washing can be performed efficiently in the multi-stage washing in the next solid-liquid separation step S4. The pH can be adjusted to a predetermined range by adding a neutralizing agent such as limestone (calcium carbonate) slurry, for example.

[0025] In the solid-liquid separation step S4, the leaching slurry whose pH has been adjusted in the preliminary neutralization step S3 is washed in multiple stages to obtain a leachate containing nickel, cobalt and zinc as an impurity element, and a leach residue.

[0026] In the neutralization step S5, the pH of the leachate separated in the solid-liquid separation step S4 is adjusted, and the neutralized precipitate containing impurity elements is separated to obtain a neutralized end solution containing zinc as well as nickel and cobalt. The pH of the leachate is adjusted by adding a neutralizing agent such as limestone (calcium carbonate) slurry.

[0027] In the dezincing step S6, a sulfurizing agent such as hydrogen sulfide gas is added to the neutralization end solution obtained in the neutralization step S5 to perform sulfurization treatment, thereby generating zinc sulfide (dezincified precipitate), and the zinc sulfide is separated and removed to obtain a mother liquor for nickel recovery (dezincified end solution) containing nickel and cobalt. In the dezincing step S6, a sulfurizing agent such as hydrogen sulfide gas is added to the crude nickel sulfate solution in a slightly pressurized reaction tank to sulfurize the zinc contained therein, thereby generating zinc sulfide and a mother liquor for nickel recovery. The method for controlling the particle size of zinc sulfide according to the present invention is applied to this dezincing step S6. Details will be described later.

[0028] Thereafter, in the nickel recovery step S7, the dezincification final liquor, which is the mother liquor for nickel recovery after the dezincification step S6, is used as a sulfurization reaction starting liquor, and hydrogen sulfide gas is blown into the sulfurization reaction starting liquor as a sulfurizing agent to cause a sulfurization reaction, thereby producing a mixed sulfide of nickel and cobalt with few impurity components and a barren liquor in which the concentrations of nickel and cobalt are stabilized at low levels.

[0029] The final neutralization step S8 neutralizes the leaching residue containing free sulfuric acid transferred from the solid-liquid separation step S4 described above, and the filtrate (barren liquid) containing impurities such as magnesium, aluminum, and iron transferred from the nickel recovery step S7. The leaching residue and filtrate are adjusted to a predetermined pH range using a neutralizing agent, and become a waste slurry (tailings). The generated tailings are transferred to a tailings dam (waste storage site).

[0030] <2. Method for controlling particle size of zinc sulfide> So far, we have explained the flow of the hydrometallurgical method for smelting nickel oxide ore. However, the method for controlling the particle size of zinc sulfide according to the present invention is mainly a method for controlling the particle size of zinc sulfide to a predetermined size or more in order to prevent clogging of the filter cloth with fine particles when generating zinc sulfide (dezincification precipitate) to be separated and removed in the dezincification step S6.

[0031] One aspect of the present invention is a method for controlling the particle size of zinc sulfide separated in the hydrometallurgy of nickel oxide ore, the hydrometallurgy of nickel oxide ore including at least the above-mentioned leaching step S2, solid-liquid separation step S4, neutralization step S5, dezincification step S6, and nickel recovery step S7, in which a part of the leaching residue is added to the leaching solution in the neutralization step, and the pH of the neutralization end solution is adjusted to 3.0 to 3.5, and a part of the zinc sulfide precipitate in the dezincification step is repeatedly added to the neutralization end solution as seed crystals to adjust the zinc sulfide to a particle size of precipitate having a median diameter D50 of 5 μm or more, and the particle size of the zinc sulfide is adjusted by measuring the calcium content ratio of the zinc sulfide represented by the following formula 1, and increasing or decreasing the amount of seed crystals added per mole of zinc in the neutralization end solution according to the value of the calcium content ratio. (Calcium content ratio) = (Ca content / (Ni content + Co content + Cu content + Fe content)) Equation 1

[0032] In the method for controlling the particle size of zinc sulfide according to the present invention, in the neutralization step S5, a part of the leaching residue generated in the leaching step S2 is added to the leaching solution, and the pH of the final neutralization solution is adjusted to 3.0 to 3.5. Under reaction conditions where the final pH is less than 3.0, the neutralization of free sulfuric acid is insufficient, so the hydrolysis reaction does not proceed, and the concentrations of impurity elements such as iron, aluminum, and chromium do not decrease to the target values. In addition, the zinc sulfide generated in the next step, the dezincing step S6, is redissolved. On the other hand, under reaction conditions where the final pH exceeds 3.5, it is difficult to control the amount of SS (fine particle components) contained in the solution, and the amount of particles brought to the dezincing step S6 increases, which deteriorates the filterability of the slurry in the dezincing step. In addition, not only zinc but also some of nickel and cobalt are precipitated in the dezincing step S6.

[0033] By adding the leaching residue to the leaching solution, the sulfurization reaction proceeds with the suspended matter in the solution as a nucleus, so the ratio of fine particles in the zinc sulfide produced is smaller than that in the case of zinc sulfide without suspended matter. Therefore, compared to the case of zinc sulfide without suspended matter, zinc sulfide with low viscosity is formed. In this way, by adding the leaching residue to the leaching solution, the ratio of fine particles in the zinc sulfide is reduced, the viscosity of the zinc sulfide is reduced, etc., and the filterability of the zinc sulfide is improved, so that clogging of the filter cloth is unlikely to occur, and the frequency of cleaning and replacing the filter cloth can be significantly reduced. The amount of leaching residue to be added can be, for example, an amount (7 to 22.5 g per 1 L of leaching solution) that results in a turbidity of 100 to 400 NTU in the neutralization end solution, as described in Patent Document 3.

[0034] In the dezincing step S6, the neutralization end solution transferred through the neutralization step S5 is supplied to a sulfurization reaction tank, and then hydrogen sulfide gas is blown into the gas phase of the sulfurization reaction tank to cause a sulfurization reaction, producing zinc sulfide (dezincification precipitate) contained in the solution. The slurry containing zinc sulfide is then supplied to a filtration device such as a filter press, and a filtration process is performed. In the filtration device, the residue containing zinc sulfide contained in the slurry (dezincification residue) is separated from the mother liquor for nickel recovery.

[0035] The median diameter D50 of the dezincified precipitate is preferably 5 μm or more. If it is less than 5 μm, the filterability is significantly deteriorated. The median diameter D50 means the particle size at which the volume of each particle is accumulated from the smallest particle size side and the accumulated volume is 50% of the total volume of all particles. The median diameter D50 can be calculated from the integrated volume measured by a laser light diffraction scattering type particle size analyzer.

[0036] In the present invention, a part of the dezincification residue containing the separated and recovered zinc sulfide is repeatedly added to the sulfurization reaction tank in the dezincification step S6. The zinc sulfide in the dezincification residue repeatedly added to the sulfurization reaction tank acts as a seed crystal for the sulfurization reaction occurring in the sulfurization reaction tank, and increases the efficiency of sulfurization of zinc in the starting liquid. In addition, by adding the seed crystal and reacting it, the particle size of the zinc sulfide produced can be controlled, and the filterability in the filtration device can be improved.

[0037] FIG. 2 is a diagram showing the relationship between the amount of seed crystals added and the particle size of the dezincified precipitate according to the calcium content ratio of the dezincified precipitate in the dezincification step S6. (Calcium content ratio) = (Ca content / (Ni content + Co content + Cu content + Fe content)) Equation 1 The unit of the amount of seed crystals added to the dezincified precipitate, "g / mol-Zn", indicates the amount of seed crystals added (g) per mole of Zn concentration in the final neutralization solution.

[0038] As shown in Fig. 2, the present inventors have found that there is a correlation between the amount of seed crystals added, classified according to the calcium content ratio, and the particle size of the dezincified precipitate. In particular, when the calcium content ratio of the dezincified precipitate increases, i.e., when the amount of gypsum produced increases, the particle size of the dezincified precipitate decreases relatively, and the frequency of occurrence of precipitates of 5 µm or less, which cause clogging of the filter cloth, increases. Therefore, when the calcium content ratio in the zinc sulfide (dezincified precipitate) is high, the particle size of the zinc sulfide produced can be increased by increasing the amount of seed crystals added to the final neutralization solution.

[0039] Therefore, in one embodiment of the present invention, the amount of seed crystals added in adjusting the particle size of zinc sulfide is preferably increased when the calcium content ratio becomes relatively large, and decreased when the calcium content ratio becomes relatively small.

[0040] More specifically, the relationship between the calcium content ratio of zinc sulfide and the amount of seed crystals added per mole of zinc is preferably based on the following criteria (1) to (3). (1) When the calcium content ratio of zinc sulfide is 0.01 or more and less than 0.05, the amount of seed crystals added per mole of zinc is 5 g / mol-Zn or more and 50 g / mol-Zn or less. (2) When the calcium content ratio of zinc sulfide is 0.05 or more and less than 0.1, the amount of seed crystals added per mole of zinc is 15 g / mol-Zn or more and 50 g / mol-Zn or less. (3) When the calcium content ratio of zinc sulfide is 0.1 or more and less than 0.5, the amount of seed crystals added per mole of zinc is 25 g / mol-Zn or more and 50 g / mol-Zn or less.

[0041] The means for measuring the metal content in the zinc sulfide is not particularly limited, but for example, fluorescent X-ray analysis, ICP emission spectrometry, atomic absorption spectrometry, etc. can be used. As an example, a portion of the zinc sulfide (dezincified precipitate) obtained after filtration in the dezincification step S6 may be extracted and measured.

[0042] As described above, in the method for controlling the particle size of zinc sulfide according to the present invention, in the dezincification step in which zinc sulfide is formed by adding hydrogen sulfide gas to a neutralization end solution containing zinc together with nickel and cobalt, and the zinc sulfide is separated to obtain a mother liquor for nickel recovery containing nickel and cobalt, the filterability of the formed zinc sulfide can be improved, clogging of the filter cloth can be prevented, and the frequency of cleaning and replacing the filter cloth can be reduced. Therefore, it is possible to recover nickel that was lost accompanying the zinc sulfide, and therefore the industrial value is extremely great.

[0043] Furthermore, according to the present invention, the pH of the neutralization end solution is kept at 3.0 to 3.5, and an efficient reaction in the dezincification step is maintained while the particle size of the dezincification precipitate is increased, thereby making it possible to prevent a significant decrease in the liquid flow rate through the filter and clogging of the filter cloth. EXAMPLES

[0044] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples in any way.

[0045] Six samples were extracted from the samples obtained by dezincification treatment under various conditions, and the relationship between the pH of the neutralization end solution, the calcium content ratio of the dezincification precipitate, the amount of seed crystals added (g / mol-Zn), and the particle size of the dezincification precipitate (D50) was examined. The results are shown in Table 2.

[0046] As shown in Table 2, it was found that when the amount of seed crystals added is 25 g / mol-Zn or more, even when the calcium content ratio of the dezincified precipitate is as high as 0.1 to 0.5, that is, when the amount of gypsum produced is large and the calcium content of the dezincified precipitate is high, the particle size of the dezincified precipitate can be made 5 μm or more.

[0047] [Table 2]

[0048] From the above, it has been demonstrated that the method for controlling the particle size of zinc sulfide according to one embodiment of the present invention makes it possible to produce zinc sulfide having a desired particle size and to improve the filterability of the zinc sulfide thus formed.

[0049] Although one embodiment of the present invention and each example have been described in detail above, it will be readily apparent to those skilled in the art that many modifications are possible without substantially departing from the novel features and effects of the present invention. Therefore, all such modifications are intended to be included within the scope of the present invention.

[0050] For example, a term described at least once in the specification or drawings together with a different term having a broader meaning or the same meaning can be replaced with the different term anywhere in the specification or drawings. The configuration of the zinc sulfide particle size control method is not limited to the embodiment of the present invention and the examples described in each embodiment, and various modifications are possible. [Explanation of symbols]

[0051] S1 slurry preparation process, S2 leaching process, S3 preliminary neutralization process, S4 solid-liquid separation process, S5 neutralization process, S6 dezincification process, S7 nickel recovery process, S8 final neutralization process

Claims

1. A method for controlling particle size of zinc sulfide separated during hydrometallurgy of nickel oxide ore, comprising the steps of: The hydrometallurgy of the nickel oxide ore comprises at least a leaching step of adding sulfuric acid to the nickel oxide ore slurry and leaching the nickel oxide ore under high temperature and pressure to obtain a leaching slurry; a solid-liquid separation step of separating the leaching residue while washing the leaching slurry in multiple stages to obtain a leachate containing nickel and cobalt as well as impurity elements; a neutralization step of adjusting the pH of the leachate and separating a neutralized precipitate containing impurity elements to obtain a neutralized final solution containing zinc as well as nickel and cobalt; a dezincing step of adding hydrogen sulfide gas to the neutralization end liquid to form zinc sulfide, and separating the zinc sulfide to obtain a mother liquor for nickel recovery containing nickel and cobalt; a nickel recovery step of adding hydrogen sulfide gas to the nickel recovery mother liquor to form a mixed sulfide containing nickel and cobalt, and separating the mixed sulfide; having In the neutralization step, a part of the leaching residue is added to the leaching solution, and the pH of the neutralization end solution is adjusted to 3.0 to 3.

5. At the same time, a part of the zinc sulfide precipitate in the dezincing step is repeatedly added as seed crystals to the neutralization end solution, thereby adjusting the zinc sulfide precipitate to have a particle size of 5 μm or more in median diameter D50; The particle size of the zinc sulfide is adjusted by measuring a calcium content ratio of the zinc sulfide represented by the following formula 1, and increasing or decreasing the amount of the seed crystals added per mole of zinc in the neutralization end solution according to the value of the calcium content ratio. (Calcium content ratio)=(Ca content / (Ni content+Co content+Cu content+Fe content)) Formula 1

2. 2. The method for controlling the particle size of zinc sulfide according to claim 1, characterized in that the amount of seed crystals added in adjusting the particle size of the zinc sulfide is increased when the value of the calcium content ratio becomes relatively large, and the amount of seed crystals added is decreased when the value of the calcium content ratio becomes relatively small.

3. 2. The method for controlling particle size of zinc sulfide according to claim 1, characterized in that the relationship between the calcium content ratio of the zinc sulfide and the amount of the seed crystals added per mole of zinc is based on the following criteria (1) to (3). (1) When the calcium content ratio of the zinc sulfide is 0.01 or more and less than 0.05, the amount of the seed crystals added per mole of zinc is 5 g / mol-Zn or more and 50 g / mol-Zn or less. (2) When the calcium content ratio of the zinc sulfide is 0.05 or more and less than 0.1, the amount of the seed crystals added per mole of zinc is 15 g / mol-Zn or more and 50 g / mol-Zn or less. (3) When the calcium content ratio of the zinc sulfide is 0.1 or more and less than 0.5, the amount of the seed crystals added per mole of zinc is 25 g / mol-Zn or more and 50 g / mol-Zn or less.

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