WO2020149122A1 - Method for manufacturing nickel/cobalt mixed sulfide from nickel oxide ore by wet smelting method - Google Patents

Abstract

Provided is a wet smelting method whereby the amount of nickel coprecipitated with impurities is reduced and nickel yield can be increased.　The present invention provides a method for manufacturing a nickel/cobalt mixed sulfide, the method including: a leaching step S1 for performing sulfuric acid leaching of a nickel oxide ore slurry under high temperature and high pressure and obtaining a leached slurry; a solid/liquid separation step S2 for separating a leaching residue from the leached slurry and obtaining a leachate including an impurity together with nickel and cobalt; a neutralization step S3 for sedimentation-separating a neutralized sediment formed by adjusting the pH of the leachate, and obtaining a neutral final liquid including nickel and cobalt; a dezincification step S4 for separating zinc and other sulfides obtained by treating the neutral final liquid with hydrogen sulfide, and obtaining a dezincified final liquid; and a nickel recovery step S5 for recovering a mixed sulfide including nickel and cobalt obtained by treating the dezincified final liquid with hydrogen sulfide; wherein the Fe(III) concentration of the neutral final liquid is adjusted to 0.18 g/L or less.

Description

Method for producing nickel-cobalt mixed sulfide from nickel oxide ore by hydrometallurgy

The present invention relates to a method for producing a nickel-cobalt mixed sulfide from nickel oxide ore by a hydrometallurgical method, and in particular, dezincification for separating and removing zinc and copper contained in the nickel oxide ore as a sulfide by adding hydrogen sulfide gas. The present invention relates to a method for producing a nickel-cobalt mixed sulfide having a step.

As a hydrometallurgical method for nickel oxide ores, a high-pressure acid leaching method, which is also called HPAL (High Pressure Acid Leaching), in which sulfuric acid is leached with sulfuric acid under high temperature and high pressure is known. This high-pressure acid leaching method, unlike the conventional general smelting method of nickel oxide ore, treats the raw material nickel oxide ore with a consistent wet process without undergoing a reduction process or a drying process. Therefore, in addition to being advantageous in terms of energy and cost, it is possible to obtain a sulfide containing nickel and cobalt (hereinafter also referred to as nickel-cobalt mixed sulfide) that is highly purified to a nickel grade of 50 to 60 mass %. Have advantages.

The high-pressure acid leaching method is generally a leaching step in which sulfuric acid is added to a slurry of nickel oxide ore as a raw material and leaching is performed under high temperature and high pressure, and while the leaching slurry obtained in the leaching step is washed in multiple stages. A solid-liquid separation step of obtaining a leachate containing an impurity element together with nickel and cobalt by separating the leaching residue, and a neutralized precipitate containing an impurity element is produced by adjusting the pH of the leachate to accelerate the sedimentation rate. Therefore, nickel and cobalt are separated by adding a part of the leaching residue separated in the solid-liquid separation step together with a flocculant and a coagulant to the slurry containing the neutralized starch to precipitate and separate the neutralized starch. A neutralization step for obtaining a neutralized final solution containing the same, and a dezincification step for treating the neutralized final solution with hydrogen sulfide gas to produce sulfides of zinc and copper, which are separated and removed to obtain a dezincified final solution. And a step of recovering nickel for treating the dezincified final solution with hydrogen sulfide gas to generate a mixed sulfide containing nickel and cobalt, and recovering the mixed sulfide.

By the way, under the conditions for producing zinc sulfide in the above dezincification step, some nickel may also precipitate as sulfide, which may reduce the nickel recovery rate. Therefore, in Patent Document 1, in the dezincification step, the turbidity of the neutralization final liquid is maintained high in order to promote the sulfurization treatment in which zinc contained in the neutralization final liquid is fixed and separated in the form of sulfide. Then, the technique of performing the sulfurating treatment is proposed. This makes it possible to coarsen the zinc sulfide to improve the filterability of the slurry containing the neutralized precipitate and to increase the nickel recovery rate. Further, Patent Document 2 proposes a technique of supplying a final neutralization solution to a plurality of reaction tanks connected in series in a dezincification step and adjusting the addition ratio of hydrogen sulfide to these reaction tanks. This makes it possible to reduce the amount of nickel that co-precipitates with impurities such as zinc and copper, and increase the nickel recovery rate.

JP, 2010-37626, A JP, 2008-90889, A

However, in the method of Patent Document 1, it is necessary to appropriately combine the conditions of the neutralization step and the dezincification step according to the concentration of impurities contained in the leachate, and if this is insufficient, for recovering nickel obtained through the dezincification step. In the dezincification final liquid, which is the mother liquor, a large amount of impurities may rather remain, and the nickel-cobalt mixed sulfide obtained by sulfidizing this mother liquor (sulfurization reaction start liquid) contains a large amount of impurities. .. Further, in the method of Patent Document 2, the amount of nickel precipitated in the dezincification step may vary depending on the liquid composition of the final solution for neutralization obtained in the neutralization step.

As described above, the conditions for forming the nickel sulfide and the zinc sulfide are similar to each other, and when nickel is coprecipitated in the zinc starch produced in the dezincification step and loss occurs. was there. When nickel is lost, the nickel recovery rate, which greatly affects the economical efficiency of the process, is reduced. Therefore, it is desired to reduce nickel loss as much as possible.

The present invention has been made in view of such circumstances, and in the hydrometallurgy of nickel oxide ore by the high-pressure acid leaching method, when impurities such as zinc and copper contained in the nickel oxide ore are removed, the impurities are mixed with the impurities. It is an object of the present invention to provide a method for producing a nickel-cobalt mixed sulfide that can reduce the amount of nickel that is precipitated and thereby increase the nickel recovery rate.

In order to achieve the above object, the method for producing a nickel-cobalt mixed sulfide according to the present invention comprises a leaching step in which sulfuric acid is added to a slurry of nickel oxide ore as a raw material and leaching is performed under high temperature and high pressure to obtain a leached slurry. A solid-liquid separation step of obtaining a leachate containing an impurity element together with nickel and cobalt by separating the leach residue while washing the leach slurry in multiple stages; and a neutralized precipitate containing an impurity element by adjusting the pH of the leachate A neutralization step for producing a neutralized final solution containing nickel and cobalt by adding a part of the leaching residue together with a coagulant to accelerate the sedimentation rate, and separating the neutralized precipitate by sedimentation. After the neutralization final solution is treated with hydrogen sulfide gas to produce sulfides of zinc and copper, a dezincification step of separating the sulfide to obtain a dezincification final solution, and a step of sulfiding the dezincification final solution Production of nickel-cobalt mixed sulfide from nickel oxide ore by high-pressure acid leaching method including a mixed sulfide containing nickel and cobalt produced by treatment with hydrogen gas, and a nickel recovery step of recovering the mixed sulfide. The method is characterized in that the concentration of Fe(III) in the neutralized final solution obtained in the neutralization step is adjusted to 0.18 g/L or less.

According to the present invention, nickel loss due to coprecipitation in the dezincification step can be suppressed, and thus the nickel recovery rate can be increased.

It is a process flow which shows embodiment of the manufacturing method of the nickel cobalt mixed sulfide of this invention. 3 is a graph showing the relationship between the ORP and Fe(III) concentration of the final neutralization solution obtained in the neutralization step of the embodiment of the production method of the present invention. It is a graph showing the relationship between the concentration of Fe(III) in the final neutralization solution obtained in the neutralization step of the embodiment of the production method of the present invention and the hydrogen sulfide addition equivalent in the dezincification step S4. It is a graph showing the relationship between the hydrogen sulfide addition equivalent and the nickel precipitation rate in the dezincification step which the embodiment of the production method of the present invention has.

1. Method for Producing Nickel-Cobalt Mixed Sulfide Hereinafter, an embodiment of a method for producing a nickel-cobalt mixed sulfide by the high pressure acid leaching method according to the present invention will be described with reference to the process flow of FIG. The method for producing the nickel-cobalt mixed sulfide shown in FIG. 1 is to adjust the nickel oxide ore as a raw material to a predetermined particle size by crushing and sieving and to add water to the nickel oxide ore slurry, The leaching step S1 in which sulfuric acid is added to perform leaching treatment under high temperature and high pressure, and the leaching residue obtained by separating the leaching residue while performing multistage washing of the leaching slurry obtained in the leaching step S1 in a plurality of sedimentation separation tanks connected in series And a solid-liquid separation step S2 for obtaining a leachate consisting of a crude nickel sulfate solution containing impurities together with cobalt, and adding a neutralizing agent to the leachate to produce a neutralized precipitate containing impurities, which is separated and removed. A neutralization step S3 for obtaining a neutralization final solution containing impurities such as zinc together with nickel and cobalt, and a zinc sulfide is generated by adding a sulfidizing agent to the neutralization final solution, which is separated and removed to remove nickel and cobalt. A dezincification step S4 for obtaining a dezincification final solution containing cobalt (a mother liquor for nickel recovery), and a nickel-cobalt mixed sulfide containing nickel and cobalt are produced by adding a sulfidizing agent to the dezincification final solution, and then solidified. And a nickel recovery step S5 for recovering the nickel-cobalt mixed sulfide by liquid separation. Each of these steps will be described below.

(1) Leaching Step In the leaching step S1, an ore slurry containing nickel oxide ore having a predetermined particle size prepared by crushing and wet classification in the pretreatment step of the previous step is charged together with sulfuric acid into a pressure vessel called an autoclave. Here, the ore slurry is subjected to high pressure acid leaching treatment under high temperature and high pressure conditions of about 3 to 4.5 MPaG and about 220 to 280° C. while being stirred. As a result, a leaching reaction and a high-temperature thermal hydrolysis reaction occur, leaching as a sulfate of nickel, cobalt, etc. and immobilization of the leached iron sulfate as hematite are carried out, and a leaching slurry consisting of a leaching liquid and a leaching residue. Is generated.

The so-called laterite ore such as limonite ore and saprolite ore is mainly used as the nickel oxide ore as a raw material processed in the leaching step S1. The nickel content of the laterite ore is generally 0.8 to 2.5 mass% and is included as a hydroxide or a magnesia silicate (magnesium silicate) mineral. This nickel oxide ore has an iron content of 10 to 50% by mass, which is mainly in the form of trivalent hydroxide (goethite). Included in minerals. In addition to the laterite ore described above, an oxide ore containing valuable metals such as nickel, cobalt, manganese, and copper such as manganese nodules existing in the deep sea floor may be used as the raw material.

The addition amount of sulfuric acid charged into the autoclave is not particularly limited, but nickel or cobalt of valuable metals, which are recovery objects contained in the ore of the raw material, are efficient so that the amount of sulfuric acid used is not excessively large. It is preferably added economically to such an extent that it is leached into The pH of the leachate is adjusted to 0.1 to 1.0 so that the leaching residue containing hematite generated by the above immobilization does not deteriorate the solid-liquid separation property in the subsequent solid-liquid separation step S2. Preferably. In addition, before the leaching slurry obtained in this leaching step S1 is processed in the solid-liquid separation step S2 in the subsequent step, free sulfuric acid (excess sulfuric acid not involved in the leaching reaction, hereinafter referred to as free sulfuric acid which is not involved in the leaching reaction) You may perform the preliminary neutralization process which neutralizes the said.

(2) Solid-Liquid Separation Step In the solid-liquid separation step S2, preferably, the above-mentioned leaching slurry and the cleaning liquid are continuously introduced into the plurality of settling separation tanks connected in series so that they are countercurrent to each other. Method (CCD method), the leach residue is separated by gravity settling while washing the leach slurry in multiple stages. As a result, the leaching residue slurry is extracted from the bottom of the most downstream sedimentation separation tank in the form of a concentrated slurry, and nickel and cobalt as well as impurity elements such as zinc are used as a supernatant liquid from the overflow port of the most upstream sedimentation separation tank. A leachate consisting of a crude nickel sulphate solution containing is obtained.

After part of the above-mentioned leaching residue slurry is transferred to the subsequent neutralization step S3, and the rest is subjected to detoxification treatment by addition of a neutralizing agent to remove heavy metals, if necessary. , Transferred to the tailing dam. An aqueous solution having a pH of about 1.0 to 3.0 is preferably used as the cleaning liquid, and a poor liquid discharged from the nickel recovery step S5 as a post step can be preferably used. Moreover, you may add a coagulant|flocculant and a part of neutralized-starch slurry isolate|separated by the following neutralization process S3 to the said several settling-separation tank.

(3) Neutralization Step In the neutralization step S3, at least one neutralization reaction tank equipped with a stirrer is charged with the leachate separated from the leach residue in the solid-liquid separation step S2, and the leachate is further treated as described above. A part of the leaching residue slurry discharged from the solid-liquid separation step S2 and a neutralizing agent such as calcium carbonate are added. As a result, the pH is adjusted and mainly trivalent iron ions and aluminum ions contained in the leachate are deposited as neutralized precipitates.

The slurry containing this neutralized precipitate is introduced into a sedimentation separation tank such as thickener together with a predetermined amount of coagulant and coagulant, and sedimentation is performed. As a result, a neutralized starch slurry in the form of a concentrated slurry is extracted from the bottom of the settling separation tank, and at the same time, neutralization containing impurity elements mainly consisting of zinc in addition to nickel and cobalt from the overflow port of the settling separation tank. The final solution is collected as a supernatant. A part of the neutralized starch slurry may be repeated in the solid-liquid separation step S2, if necessary.

(4) Dezincification step In the dezincification step S4, the neutralized final solution obtained in the above-mentioned neutralization step S3 is introduced into the sulfurization reaction tank slightly pressurized, and further sulfurization is carried out in the gas phase in the sulfurization reaction tank. The sulfurization treatment is performed on the neutralized final liquid by blowing hydrogen gas. As a result, zinc is selectively sulfided with respect to nickel and cobalt, so that zinc sulfide is produced. This zinc sulfide is separated and removed by a filtration device such as a filter press, and a final dezincification solution (a mother liquor for nickel recovery) consisting of a sulfuric acid solution containing nickel and cobalt is obtained as a filtrate.

(5) Nickel recovery step In the nickel recovery step S5, the dezincification final solution is introduced into a reaction tank pressurized slightly higher than the sulfurization reaction tank, and hydrogen sulfide gas is further added to the dezincification final solution. A nickel-cobalt mixed sulfide is generated by adding a sulfiding agent such as the above to the sulfurating treatment. The generated nickel-cobalt mixed sulfide can be recovered by solid-liquid separation such as filtration. The poor nickel liquid discharged to the liquid phase side by this solid-liquid separation contains unreacted Ni ions in addition to impurity metal ions such as iron, aluminum, and manganese. You may repeat.

2. Method for Reducing Nickel Precipitation in Dezincification Step In the hydrometallurgy of nickel oxide ore by the high pressure acid leaching method as described above, the final neutralization solution obtained in the neutralization step generally has a Ni concentration of 3.0 to 4 It has a liquid composition of 0.0 g/L, Zn concentration of 0.06 to 0.10 g/L, total Fe concentration of 0.4 to 2.0 g/L, and Fe(III) concentration of 0.3 g/L or less. Its pH is about 2.6 to 3.4, and ORP is about 320 to 440 mV. The final zinc removal solution obtained in the zinc removal step had a Ni concentration of 3.0 to 4.0 g/L, a Zn concentration of 0.001 to 0.005 g/L, and a total Fe concentration of 0.4 to 2.0 g/L. It has a liquid composition of, and its pH is about 2.6 to 3.4.

On the other hand, in the method for producing the nickel-cobalt mixed sulfide of the embodiment of the present invention, the ORP of the final neutralization solution obtained in the neutralization step S3 is preferably 370 mV or less by adjusting the raw material nickel oxide ore. The concentration of Fe(III) in the neutralized final solution is adjusted to 0.18 g/L or less by adjusting As a result, the nickel precipitation rate in the dezincification step S4 can be suppressed to 1.0% or less.

More specifically, the present inventor obtains in the neutralization step S3 by adjusting the carbon grade in the nickel oxide ore contained in the ore slurry sent to the hydrometallurgical equipment by the high pressure acid leaching method. Attempts were made to adjust the redox potential (ORP) of the final neutralized solution. As a result, it was found that the ORP can be adjusted well and that there is a positive correlation between the ORP and the Fe(III) concentration in the neutralized final solution as shown in FIG.

That is, the higher the Fe(III) concentration having oxidizing power, the higher the ORP. Therefore, by adjusting the ORP to 370 mV or less, the Fe(III) concentration can be suppressed to 0.18 g/L or less. The lower limit value of the ORP is not particularly limited, but is preferably 300 mV or higher. The lower limit of the Fe(III) concentration is not particularly limited, but is preferably 0.05 g/L or more. The redox potential shown in this specification is measured by using a silver-silver chloride electrode as a standard electrode.

By the way, the order of the Fe(III) concentration and the Zn concentration in the final neutralization solution obtained in the neutralization step S3 is almost the same, and the hydrogen sulfide gas added in the dezincification step S4 is represented by the following formula 1. It is mainly consumed in the sulfurization reaction of zinc and the reduction reaction of Fe(III) shown in the following formula 2.
[Formula 1]
Zn ²⁺ +H ₂ S=ZnS+2H ⁺
[Formula 2]
2Fe ³⁺ +H ₂ S=2Fe ²⁺ +S+2H ⁺

Therefore, since the amount of hydrogen sulfide gas consumed in the reduction reaction of Fe(III) is reduced by lowering the Fe(III) concentration in the final neutralization solution as described above, zinc sulfidization in the dezincification step S4 is performed. The amount of hydrogen sulfide gas required for processing can be greatly reduced. Thus, by significantly reducing the amount of hydrogen sulfide gas added in the dezincification step S4, it is possible to suppress the sulfidation reaction of nickel that locally occurs due to the excessive supply of the sulfiding agent, and thus the zinc removal step S4 The amount of nickel precipitation can be reduced.

FIG. 3 shows the addition equivalent of hydrogen sulfide (mol-H ₂ S/mol-Zn) necessary for the sulfurization treatment of 1 mol of Zn contained in the neutralization final solution obtained in the neutralization step S3 and the neutralization final solution. The relationship with the Fe(III) concentration is shown. From this FIG. 3, it can be seen that the hydrogen sulfide addition equivalent can be reduced as the Fe(III) concentration in the final neutralization solution decreases. With the above hydrogen sulfide addition equivalent, the sulfide required for adjusting the Zn/Ni mass concentration ratio of the dezincification final solution (mother liquor for nickel recovery) obtained in the dezincification step S4 to 0.0004 or more and 0.0005 or less. It is the molar amount of hydrogen gas.

FIG. 4 shows the relationship between the hydrogen sulfide addition equivalent in the dezincification step S4 and the nickel precipitation rate in the dezincification step S4. It can be seen from FIG. 4 that the nickel precipitation rate increases as the hydrogen sulfide addition equivalent increases. The nickel precipitation rate shown on the vertical axis of FIG. 4 is the nickel concentration of the neutralization final solution, which is the starting solution of the dezincification step S4, of N ₁ [g/L] and the dezincification step obtained in the dezincification step S4. When the nickel concentration of the liquid is N ₂ [g/L], it is calculated by the following formula 3.
[Formula 3]
Nickel precipitation rate [%]=(N ₁ −N ₂ )/N ₁ ×100

Further, since the carbon has a function as a reducing agent, the inventor of the present invention has a relationship between the carbon grade in the nickel oxide ore as a raw material and the ORP of the final neutralization solution obtained in the neutralization step S3. It has been found that there is a negative correlation, and thus the higher the carbon grade, the lower the ORP of the final neutralization solution tends to be. Therefore, as a result of further intensive studies by the present inventor, in order to adjust the ORP to 370 mV or less in the above-mentioned neutralization final solution, the mixture ratio of a plurality of nickel oxide ore lots having different carbon grades was appropriately adjusted. It was found that it can be adjusted by using as a raw material. Specifically, the carbon quality of the mixed raw material obtained by mixing a plurality of nickel oxide ore lots is adjusted to preferably 0.20 mass% or more, more preferably 0.18 mass% or more.

The hydrogen sulfide gas addition amount in the dezincification step S4 increases the hydrogen sulfide addition equivalent as described above when the Zn concentration or the Fe ³⁺ concentration in the final neutralization solution obtained in the neutralization step S3 increases. Therefore, it is preferable to appropriately adjust according to the measured values of the Zn concentration and Fe ³⁺ concentration of the neutralized final solution and the Zn concentration of the dezincified final solution obtained in the dezincification step S4. Next, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.

The ore raw materials of Samples 1 to 15 having various carbon grades were prepared by blending a plurality of nickel oxide ore lots, and each of them was treated according to the process flow shown in FIG. 1 to obtain nickel-cobalt mixed sulfide. Was manufactured. In the dezincification step S4, sulfurization is performed based on the measurement results of the Zn concentration and Fe ³⁺ concentration of the neutralization final solution obtained in the neutralization step S3 and the Zn concentration of the dezincification final solution obtained in the dezincification step S4. Hydrogen gas was added. Table 1 below shows the ORP (Ag/AgCl standard electrode) and pH of the final neutralization solution obtained in the neutralization step S3 together with the Fe ³⁺ concentration, Zn concentration, and Ni concentration of the final neutralization solution.

As can be seen from Table 1 above, in each of Samples 1 to 10 satisfying the Fe(III) concentration of the neutralization final solution of 0.18 g/L or less, the nickel precipitation rate was 1.0% or less in all cases. .. On the other hand, in all of Samples 11 to 15 in which the Fe ³⁺ concentration in the neutralized final solution exceeded 0.18 g/L, the nickel precipitation rate exceeded 1.0% in all samples. The above-mentioned carbon quality was measured by an oxygen stream combustion-infrared absorption method (LECO CS-230). The Fe ³⁺ concentration was measured using a redox titration method (Aqua Counter Automatic Titler COM-1700), and the Zn concentration and the Ni concentration were measured by ICP emission spectroscopy (Thermo Scientific iCAP 6000).

S1 Leaching step S2 Solid-liquid separation step S3 Neutralization step S4 Dezincification step S5 Nickel recovery step

Claims (3)

Impurities along with nickel and cobalt by separating the leaching residue while multi-stage washing the leaching slurry by adding sulfuric acid to the slurry of nickel oxide ore as a raw material and leaching it under high temperature and high pressure to obtain a leaching slurry A solid-liquid separation step of obtaining a leachate containing an element, and a neutralized precipitate containing an impurity element is produced by adjusting the pH of the leachate, and a part of the leach residue is added together with a coagulant to accelerate the sedimentation rate. Then, a neutralization step of obtaining a neutralized final solution containing nickel and cobalt by sedimenting and separating the neutralized precipitate, and treating the final neutralized solution with hydrogen sulfide gas to remove sulfides of zinc and copper. After the production, a dezincification step of separating the sulfide to obtain a dezincified final solution, and a step of treating the dezincified final solution with hydrogen sulfide gas to produce a mixed sulfide containing nickel and cobalt, A method for producing a nickel-cobalt mixed sulfide from a nickel oxide ore by a high-pressure acid leaching method, which comprises a nickel recovery step for recovering a mixed sulfide, wherein the neutralized final solution of Fe(III) obtained in the neutralization step is A method for producing a nickel-cobalt mixed sulfide, characterized in that the concentration is adjusted to 0.18 g/L or less. The redox potential (Ag/AgCl standard electrode) of the neutralization final liquid is adjusted to 370 mV or less by adjusting the carbon grade in the nickel oxide ore as the raw material. Method for producing nickel-cobalt mixed sulfide of. The nickel-cobalt mixed sulfide according to claim 2, wherein the carbon grade in the nickel oxide ore as the raw material is adjusted by changing the mixing ratio of a plurality of nickel oxide ore lots having different carbon grades. Production method.

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