JP7095606B2 - Method for producing nickel-cobalt mixed sulfide from nickel oxide ore by hydrometallurgy - Google Patents

Description

The present invention relates to a method for producing a nickel-cobalt mixed sulfide from a nickel oxide ore by a wet smelting method, and in particular, dezincination for separating and removing zinc and copper contained in the nickel oxide ore as 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-oxidized ore, a high-pressure acid leaching method also called HPAL (High Pressure Acid Leaching), in which the ore raw material is leached using sulfuric acid under high temperature and high pressure, is known. This high-pressure acid leaching method is different from the dry smelting method, which is a conventional general method for smelting nickel oxide ore, and treats the raw material nickel oxide ore in a consistent wet process without going through a reduction step or a drying step. Therefore, it is advantageous in terms of energy and cost, and it is possible to obtain a smelter containing nickel and cobalt (hereinafter, also referred to as nickel-cobalt mixed smelter) having a high purity of nickel grade of 50 to 60% by mass. Has advantages.

In the above high-pressure acid leaching method, generally, a leaching step of adding sulfuric acid to a slurry of nickel oxide ore as a raw material and leaching treatment under high temperature and high pressure, and a multi-stage washing of the leaching slurry obtained in the leaching step are performed. A solid-liquid separation step of obtaining a leachate containing an impurity element together with nickel and cobalt by separating the leachate residue, and a neutralized starch containing an impurity element by adjusting the pH of the leachate to promote the sedimentation rate. Therefore, to the slurry containing the neutralized starch, a part of the leachate residue separated in the solid-liquid separation step is added together with a coagulant and a coagulant, and the neutralized starch is precipitated and separated to obtain nickel and cobalt. A neutralization step of obtaining a neutralized final solution containing the mixture, and a dezincination step of treating the neutralized final solution with hydrogen sulfide gas to generate zinc or copper sulfide, which is separated and removed to obtain a dezincinated final solution. And, the dezincification final liquid is treated with hydrogen sulfide gas to produce a mixed sulfide containing nickel and cobalt, and the nickel recovery step of recovering the mixed sulfide is included.

By the way, under the conditions for producing zinc sulfide in the dezincination step, some nickel may also precipitate as sulfide, and the recovery rate of nickel may be reduced. Therefore, Patent Document 1 states that in the dezincination step, the turbidity of the neutralized final liquid is maintained high in order to promote the sulfurization treatment in which zinc contained in the neutralized final liquid is fixed and separated in the form of sulfide. A technique for sulfurization treatment has been proposed. This makes it possible to coarsen the zinc sulfide to improve the filterability of the slurry containing the neutralized starch and to increase the nickel recovery rate. Further, Patent Document 2 proposes a technique for supplying a neutralizing final 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 coprecipitating with impurities such as zinc and copper and increase the nickel recovery rate.

Japanese Unexamined Patent Publication No. 2010-37626 Japanese Unexamined Patent Publication No. 2018-90889

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, the nickel can be recovered obtained through the dezincification step. The dezincified final solution, which is the mother liquor, tends to have a large amount of impurities remaining, and the nickel-cobalt mixed sulfide obtained by sulphurizing this mother liquor (sulfurization reaction starting solution) 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 neutralization final solution obtained in the neutralization step.

As described above, the conditions for producing nickel sulfide starch and the conditions for producing zinc sulfide starch are close to each other, and nickel coprecipitates and loses in the zinc starch produced in the dezincification step. was there. Since the loss of nickel reduces the nickel recovery rate, which greatly affects the economic efficiency of the process, it is desired to reduce the loss of nickel as much as possible.

The present invention has been made in view of this situation, and is used in wet smelting of nickel oxide ore by a high-pressure acid leaching method when removing impurities such as zinc and copper contained in the nickel oxide ore. It is an object of the present invention to provide a method for producing a nickel-copper mixed sulfide capable of reducing the amount of nickel that sinks and thereby increasing 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 is a leaching step in which sulfuric acid is added to a slurry of nickel oxide ore as a raw material and leached 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 leachate residue while washing the leachate slurry in multiple stages, and a neutralized starch containing an impurity element by adjusting the pH of the leachate. A neutralization step of obtaining a neutralized final solution containing nickel and cobalt by adding a part of the leachate residue together with a flocculant to precipitate and separate the neutralized starch in order to promote the sedimentation rate. After producing sulfides of zinc and copper by treating the neutralized final solution with hydrogen sulfide gas, a dezincination step of separating the sulfides to obtain a dezincified final solution and sulfurizing the dezincinated final solution. Production of nickel-cobalt mixed sulfide from nickel oxide ore by high-pressure acid leaching method including a nickel recovery step of recovering the mixed sulfide after producing a mixed sulfide containing nickel and cobalt by treatment with hydrogen gas. The method is characterized in that the Fe (III) concentration of the neutralization final solution obtained in the neutralization step is adjusted to 0.18 g / L or less.

According to the present invention, it is possible to suppress the loss of nickel due to coprecipitation in the dezincification step, and thus it is possible to increase the nickel recovery rate.

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

1. 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 as a raw material to a predetermined particle size by pulverization and sieving, and to add water to the nickel oxide slurry. Nickel is separated by separating the leaching residue by performing the leaching step S1 in which sulfuric acid is added and the leaching treatment is performed under high temperature and high pressure, and the leaching slurry obtained in the leaching step S1 is washed in multiple stages in a plurality of continuous settling separation tanks in series. In the solid-liquid separation step S2 for obtaining a leachate consisting of a crude nickel sulfate solution containing impurities together with cobalt, and by adding a neutralizing agent to the leachate, a neutralized starch containing impurities is produced, and this is separated and removed. Zinc sulfide is produced by adding a sulfide agent to the neutralization step S3 for obtaining a neutralization final solution containing nickel and cobalt and impurities such as zinc, and this is separated and removed to obtain nickel and nickel. A dezincification step S4 for obtaining a dezincification final solution (mother solution for recovering nickel) containing cobalt, and a nickel-cobalt mixed sulfide containing nickel and cobalt are produced by adding a sulfide agent to the dezincification final solution, and then solidified. It has a nickel recovery step S5 for recovering the nickel-cobalt mixed sulfide by liquid separation. Hereinafter, each of these steps will be described.

(1) Leaching Step In the leaching step S1, an ore slurry containing nickel oxide ore having a predetermined particle size prepared by pulverization and wet classification treatment in the pretreatment step of the previous step is charged into a pressure container called an autoclave together with sulfuric acid. 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 of nickel, cobalt, etc. as sulfate and immobilization of leached iron sulfate as hematite are performed, and a leaching slurry consisting of a leaching solution and a leaching residue is performed. Is generated.

As the nickel oxide ore as a raw material to be treated in the leaching step S1, so-called laterite ore such as limonite ore and saprolite ore is mainly used. The nickel content of the laterite ore is generally 0.8 to 2.5% by mass, and is contained as a hydroxide or a siliceous earth (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), and some divalent iron is caustic. It is contained in minerals. In addition to the above-mentioned laterite ore, an oxide ore such as a manganese aneurysm present on the deep sea bottom containing valuable metals such as nickel, cobalt, manganese, and copper may be used as the raw material.

The amount of sulfuric acid added to the autoclave is not particularly limited, but nickel and cobalt, which are valuable metals contained in the ore of the raw material, are efficient so that the amount of sulfuric acid used does not become excessively large. It is preferable to add it economically to the extent that it is leached into the water. The pH of the leachate is adjusted to 0.1 to 1.0 so that the leachate residue containing hematite generated by the above immobilization does not reduce the solid-liquid separability in the solid-liquid separation step S2 in the subsequent step. It is preferable to do so. Further, before the leaching slurry obtained in the leaching step S1 is treated in the solid-liquid separation step S2 in the subsequent step, the free sulfuric acid contained in the leaching slurry (excess sulfuric acid not involved in the leaching reaction, hereinafter referred to as free sulfuric acid) is also used. You may perform a pre-neutralization treatment for neutralizing (referred to as).

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

A part of the above-mentioned leachate residue slurry is transferred to the neutralization step S3 in the subsequent step, and the rest is detoxified by adding a neutralizing agent as necessary to remove heavy metals. , Transferred to the tailing dam. It is preferable to use an aqueous solution having a pH of about 1.0 to 3.0 as the cleaning liquid, and a poor liquid discharged from the nickel recovery step S5 in the subsequent step can be preferably used. Further, a flocculant or a part of the neutralized starch slurry separated in the following neutralization step S3 may be added to the plurality of sedimentation separation tanks as needed.

(3) Neutralization Step In the neutralization step S3, the leachate separated from the leachate residue in the solid-liquid separation step S2 is charged into at least one neutralization reaction tank equipped with a stirrer, and the leachate is further charged with the above-mentioned leachate. A part of the leachate 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 precipitated as neutralized starch.

The slurry containing the neutralized starch is introduced into a sedimentation separation tank such as a thickener together with a predetermined amount of a flocculant and a coagulant, and sedimentation separation is performed. As a result, the neutralized starch slurry in the form of a concentrated slurry is extracted from the bottom of the sedimentation separation tank, and neutralization containing nickel and cobalt as well as impurity elements mainly composed of zinc from the overflow port of the sedimentation separation tank. The final liquid is collected as a supernatant liquid. If necessary, a part of the neutralized starch slurry may be repeated in the solid-liquid separation step S2.

(4) Dezincification step In the dezincification step S4, the neutralization final solution obtained in the neutralization step S3 is introduced into the slightly pressurized sulfurization reaction tank, and further sulfurized in the gas phase in the sulfurization reaction tank. The neutralized final liquid is sulfurized by blowing hydrogen gas. As a result, zinc is selectively sulfurized 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 dezincified final solution (mother solution 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 the reaction tank pressurized slightly higher than the sulfurization reaction tank, and hydrogen sulfide gas is further applied to the dezincification final solution. By adding a sulfurizing agent such as the above and performing a sulfurization treatment, a nickel-cobalt mixed sulfurized product is produced. The produced nickel-cobalt mixed sulfide can be recovered by solid-liquid separation such as filtration. The nickel-poor liquid discharged to the liquid phase side by this solid-liquid separation contains impurity metal ions such as iron, aluminum, and manganese, as well as unreacted Ni ions. It may be repeated.

2. 2. Method for reducing the amount of nickel precipitate in the dezincification step In the wet smelting of nickel oxide ore by the high-pressure acid leaching method as described above, the neutralized final solution obtained in the neutralization step generally has a Ni concentration of 3.0 to 4 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 dezincified liquid obtained in the dezincification step has 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 the liquid composition of, and its pH is about 2.6 to 3.4.

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

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 to be sent to the hydrometallurgical facility by the above-mentioned hydrometallurgy method. Attempts were made to adjust the redox potential (ORP) of the neutralized final solution. As a result, it was found that the ORP could be satisfactorily adjusted and that there was 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 concentration of Fe (III) 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 of the ORP is not particularly limited, but is preferably 300 mV or more. Further, 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 the present specification is measured using a silver-silver chloride electrode as a standard electrode.

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

Therefore, by lowering the concentration of Fe (III) in the final neutralizing liquid as described above, the amount of hydrogen sulfide gas consumed in the reduction reaction of Fe (III) is reduced, so that zinc sulfide is sulfided in the dezincination step S4. The amount of hydrogen sulfide gas added for the treatment can be significantly reduced. As described above, by significantly reducing the amount of hydrogen sulfide gas added in the dezincification step S4, the sulfurization reaction of nickel locally generated due to the excessive supply of the sulfurizing agent can be suppressed, and thus the sulfurization reaction of nickel in the dezincification step S4 can be suppressed. The amount of nickel precipitation can be reduced.

FIG. 3 shows the addition equivalent of hydrogen sulfide (mol _— H 2S / mol—Zn) required 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 FIG. 3, it can be seen that the hydrogen sulfide addition equivalent can be reduced as the Fe (III) concentration in the neutralized final liquid decreases. In the above hydrogen sulfide addition equivalent, the sulfide required to reduce the Zn / Ni mass concentration ratio of the dezincified final solution (mole solution for nickel recovery) obtained in the dezincification step S4 to 0.0004 or more and 0.0055 or less. 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. From FIG. 4, it can be seen that the nickel precipitation rate increases as the hydrogen sulfide addition equivalent increases. The nickel sedimentation rate shown on the vertical axis of FIG. 4 is the nickel concentration of the neutralized final solution, which is the starting solution of the dezincination step S4, N ₁ [g / L], and the dezincification final solution 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.
[Equation 3]
Nickel precipitation rate [%] = (N ₁ -N ₂ ) / N ₁ × 100

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

As for the amount of hydrogen sulfide added in the dezincification step S4, the hydrogen sulfide addition equivalent increases as described above when the Zn concentration or Fe ³⁺ concentration of the neutralization final 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 dezincinated 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.

By blending multiple nickel oxide ore lots, the ore raw materials of Samples 1 to 15 having various carbon grades are prepared, and each of them is treated according to the process flow shown in FIG. 1 to prepare a nickel-cobalt mixed sulfide. 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. The ORP (Ag / AgCl standard electrode) and pH of the neutralization final solution obtained in the neutralization step S3 at that time are shown in Table 1 below together with the Fe ³⁺ concentration, Zn concentration and Ni concentration of the neutralization final solution.

As can be seen from Table 1 above, the nickel precipitation rate was 1.0% or less in all of the samples 1 to 10 satisfying the condition that the Fe (III) concentration of the neutralization final solution was 0.18 g / L or less. .. On the other hand, in the samples 11 to 15 in which the Fe ³⁺ concentration of the neutralization final solution exceeded 0.18 g / L, the nickel precipitation rate exceeded 1.0% in each of the samples. The carbon grade was measured by using an oxygen airflow combustion-infrared absorption method (LECO CS-230). The Fe ³⁺ concentration was measured by the oxidation-reduction titration method (Aqua Counter Autumn Titrator COM-1700), and the Zn concentration and the Ni concentration were measured by the ICP emission spectroscopic analysis method (Thermo scientific iCAP 6000).

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

Claims (3)

Sulfide is added to a slurry of nickel oxide ore as a raw material and leached under high temperature and high pressure to obtain a leached slurry, and the leached residue is separated while cleaning the leached slurry in multiple stages to separate impurities together with nickel and cobalt. A solid-liquid separation step for obtaining a leachate containing an element and a neutralized starch containing an impurity element are produced by adjusting the pH of the leachate, and a part of the leachate residue is added together with a flocculant to promote the sedimentation rate. Then, a neutralization step of obtaining a neutralized final solution containing nickel and cobalt by precipitating and separating the neutralized starch, and a sulfide of zinc and copper by treating the neutralized final solution with hydrogen sulfide gas. After the formation, a dezincification step of separating the sulfide to obtain a dezincified final solution and a mixed sulfide containing nickel and cobalt by treating the dezincinated final solution with hydrogen sulfide gas are produced, and then the sulfide is formed. A method for producing a nickel-cobalt mixed sulfide from nickel oxide ore by a high-pressure acid leaching method including a nickel recovery step for recovering the mixed sulfide, wherein Fe (III) of the neutralized final solution obtained in the neutralization step is used. A method for producing a nickel-cobalt mixed sulfide, which comprises adjusting the concentration to 0.18 g / L or less. The first aspect of claim 1, wherein the redox potential (Ag / AgCl standard electrode) of the neutralized final solution is adjusted to 370 mV or less by adjusting the carbon grade in the nickel oxide ore as a raw material. A method for producing a nickel-cobalt mixed sulfide. The nickel-cobalt mixed sulfide according to claim 2, wherein the carbon grade in the nickel oxide ore as a 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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