JP6168000B2 - Method for producing nickel sulfate solution - Google Patents

Description

  The present invention relates to a method for producing a nickel sulfate solution by pressure leaching a nickel raw material, and more particularly to a method for suppressing leaching of selenium in a nickel raw material during pressure leaching.

  In general, nickel metal is mainly used as an alloy component such as steel, and nickel salts are used as a plating raw material, an aluminum color former, a catalyst, a battery material, an electronic component material, and the like. Nickel salts used for such applications are required to have high purity, and high purity containing no iron, copper, selenium or the like is particularly desired. Therefore, in the manufacturing process of nickel salts, separation of impurities is an important elemental technology.

  For example, nickel sulfate, which is one of nickel salts, is generally produced by the following method. First, a nickel sulfate solution is obtained by dissolving a raw material such as sulfide or metal scrap containing nickel by an operation such as pressure leaching or acid leaching. After removing impurities from this nickel sulfate solution in the liquid purification process, the resulting high-purity nickel sulfate solution is concentrated by an operation such as heating and evaporation, and then the concentrated nickel sulfate solution is cooled to form a supersaturated nickel sulfate solution. To precipitate nickel sulfate crystals.

  Usually, nickel sulfide, metal scrap, and the like, which are raw materials for nickel sulfate, contain impurities such as iron and copper in addition to nickel. These impurities are leached into the liquid together with nickel when the raw material is dissolved by pressure leaching or acid leaching. Therefore, in order to produce high-purity nickel sulfate, not only the removal method and reaction conditions in the removal process of each impurity as a unit process, but also the overall configuration such as the order and combination of a plurality of impurity removal processes is optimal. At the same time, it is important to set the conditions of the crystallization process for precipitating nickel sulfate crystals, and the raw material melting method and conditions.

By the way, in the smelting of nickel ore, nickel sulfide obtained by melting nickel sulfide ore in a blast furnace, nickel sulfide obtained by adding sulfur to nickel oxide ore and melting in an electric furnace, so-called dry type Nickel mats mainly composed of nickel sulfide such as Ni ₃ S ₂ obtained by a smelting method are produced. As a method for obtaining a nickel sulfate solution by dissolving the nickel mat, a pressure leaching method using an autoclave has been industrialized.

  In the industrialized nickel mat pressure leaching method, first, as a first step, water is added to the nickel mat and wet pulverized to form a nickel mat slurry. In the second step, a sulfur slurry is formed by adding water to sulfur and performing wet pulverization in order to supplement the sulfur component which is equivalently insufficient with respect to nickel contained in the nickel mat in producing nickel sulfate. The obtained sulfur slurry is mixed with the nickel matte slurry obtained in the first step.

  Next, in the third step, the mixed slurry is charged into an autoclave and subjected to pressure leaching by blowing compressed air to obtain a nickel sulfate solution. In the pressure leaching in the third step, impurities such as iron, copper, cobalt and the like contained in the raw material nickel mat are eluted in the nickel sulfate solution in addition to nickel as a recovery target metal. Especially for selenium contained in nickel mats, some of the selenium remains in the leaching residue as undissolved material after pressure leaching, but some selenium together with other impurities such as iron, copper, cobalt etc. in the nickel sulfate solution. Elute.

Selenium eluted in the nickel sulfate solution takes the form of an oxo acid, and is stabilized in the form of an anion as selenious acid (SeO ₃ ²⁻ ) or selenic acid (SeO ₄ ²⁻ ). For this reason, selenium eluted in the nickel sulfate solution is difficult to separate in a normal liquid purification process aimed at removing heavy metal impurities mainly in the form of cations. Therefore, even if a very small amount of selenium is eluted into the nickel sulfate solution, there is a high possibility that the high-purity nickel sulfate as the final product will be contaminated.

  Therefore, in order to obtain a high-purity nickel solution for the recovery of nickel salts and nickel metal, a method for removing these impurities simply and efficiently from the eluate of nickel raw materials containing copper, iron and selenium as impurities is patented. It is proposed in Document 1. That is, the method described in Patent Document 1 adds an oxidizing agent and a neutralizing agent to an eluate of an acidic nickel raw material containing copper, iron, and selenium, and raises the pH to 5 or more. After neutralizing and precipitating selenium, the neutralized starch is washed with an acidic solution having a pH of 4 or higher, and nickel in the neutralized starch is re-eluted and recovered.

  However, according to the method described in Patent Document 1, it is necessary to add an oxidizing agent and a neutralizing agent and to raise the pH to 5 or more in order to remove selenium and the like from the eluate of the nickel raw material. Along with iron, copper and selenium, a large amount of nickel precipitates as neutralized starch. For this reason, it is necessary to wash the obtained neutralized starch with an acidic solution having a pH of 4 or more and re-exude nickel in the neutralized starch.

  Furthermore, since selenium is leached together with nickel in the obtained acid cleaning liquid, finally, by electrolyzing metal nickel as an anode and metal copper as a cathode, and electrodepositing copper and selenium on the cathode for the first time, Nickel and selenium are separated. Therefore, in the method described in Patent Document 1, the process is complicated, and a processing device such as an electrolysis device is separately required, and a large amount of chemicals such as a neutralizing agent and washing sulfuric acid and electrolysis power are required. Therefore, it was difficult to say an efficient and economical method.

  For example, a method described in Patent Document 2 is known as a method for treating selenium-containing water. In this method, the step of causing 5 moles or more of aluminum and 5 moles or more of iron to exist in 1 mole of selenium in selenium-containing water, and the pH of selenium-containing water in which aluminum and iron are present within the range of 4 to 9 A step of adjusting, a step of stirring the selenium-containing water whose pH is adjusted, and a step of removing the generated precipitate.

  However, when this method is applied to the removal of selenium contained in a nickel sulfate solution, iron is already contained in the nickel sulfate solution as an impurity, but in addition, a large amount of aluminum salt and neutralizing agent are required. In addition, since a large amount of precipitates are generated and the loss of nickel increases, it is still not an efficient and economical method.

In general, selenious acid (SeO ₃ ²⁻ ) can be coprecipitated and removed by trivalent iron hydroxide, but selenic acid (SeO ₄ ²⁻ ) is trivalent iron hydroxide. Then it is difficult to remove coprecipitation. Therefore, it was necessary to perform coprecipitation after reducing selenic acid to selenious acid.

JP 2000-054040 A JP 2001-276847 A

  The present invention has been devised in view of such problems of the prior art, and requires special processing equipment when producing a nickel sulfate solution from a nickel raw material such as a nickel mat by a pressure leaching method. In addition, an object is to provide a method for producing a nickel sulfate solution having a particularly low selenium concentration by efficiently and economically removing impurities without using a large amount of chemicals such as a neutralizing agent.

In order to achieve the above object, the present inventor has studied to efficiently remove impurities from a nickel raw material such as a nickel mat only by a pressure leaching method to produce a high-purity nickel sulfate solution. At that time, quaternary selenious acid (SeO ₃ ²⁻ ) can be removed by coprecipitation with trivalent iron hydroxide and the like, while hexavalent selenic acid (SeO ₄ ²⁻ ) is trivalent hydroxylated. Focusing on the fact that coprecipitation is difficult to remove with iron or the like, in order to remove selenium efficiently, impurities in the pressure leaching process are more important than optimizing the method of removing selenium in the liquid purification process after leaching. It was concluded that it is important to suppress the oxidation of selenium to hexavalent selenate.

  That is, selenium leached in the form of tetravalent selenious acid contains trivalent iron hydroxide if it can be suppressed that selenium in the nickel raw material is oxidized to hexavalent selenic acid in the pressure leaching. It was considered that the amount of selenium distributed to the leaching residue could be increased if co-precipitation could be removed by the leaching residue, and if it could be dissolved in the undissolved sulfur contained in the leaching residue.

Therefore, the present inventors changed the way of thinking and did not separate and remove the selenium eluted in the aqueous solution by the pressure leaching in the liquid purification process, but eluted the selenium in the nickel raw material in the aqueous solution in the pressure leaching process. We examined from the viewpoint of not letting. As a result, by controlling the oxygen partial pressure in the pressure leaching apparatus, selenium in the nickel raw material can be prevented from being oxidized to hexavalent selenic acid (SeO ₄ ²⁻ ), and sulfuric acid having a low selenium concentration can be suppressed. The inventors have found that a nickel solution can be produced, and have completed the present invention.

That is, the method for producing a nickel sulfate solution according to the present invention is a method for producing a nickel sulfate solution by pressure leaching from a nickel raw material containing iron, copper, cobalt, and selenium as impurities , wherein water is added to the nickel raw material. in addition nickel raw material by wet grinding a first step of obtaining a slurry, a slurry was obtained by wet grinding by adding to a slurry of the nickel raw material by adding water to the solid body sulfur, nickel raw material and sulfur Second step of preparing the mixed slurry, and charging the mixed slurry into a pressure leaching device, blowing compressed air, pressure leaching the nickel in the nickel raw material, and then reducing the pressure leaching solution to atmospheric pressure And a third step of obtaining a nickel sulfate solution, wherein the pressure in the pressure leaching apparatus in the third step is set to 1.6 to 1.9 MPa, and the oxygen partial pressure is set to 0.311 MPa or less. Characterized by lifting.

  In the method for producing a nickel sulfate solution according to the present invention, the mixed slurry of nickel raw material and sulfur in the second step has a reaction equivalent amount necessary for pressure leaching the metal component contained in the nickel raw material as sulfate. When the amount of sulfur is 1, it is preferable to adjust so that the sum of the amount of sulfur contained in the nickel raw material and the amount of sulfur added in the second step is 0.7 or more.

In the method for producing a nickel sulfate solution according to the present invention, a nickel mat produced by dry smelting can be used as the nickel raw material. In this case, the slurry concentration of the nickel raw material and sulfur mixed slurry is adjusted to 100 to 400 g / l in the second step, and the temperature in the pressure leaching apparatus is maintained at 140 to 180 ° C. in the third step. preferable. Furthermore, it is preferable to adjust the amount of compressed air blown into the pressure leaching apparatus in the third step to 4000 to 6000 Nm ³ per ton of nickel raw material.

  According to the present invention, a nickel raw material containing iron, copper, cobalt, and selenium as impurities does not require a special processing apparatus, the process becomes complicated, and a large amount of chemicals such as a neutralizing agent are used. In addition, it is possible to provide a method for efficiently and economically removing impurities and producing a nickel sulfate solution having a particularly low selenium concentration.

  Therefore, the nickel sulfate solution having a low selenium concentration obtained by the present invention is efficiently and economically produced without increasing the loss of nickel by precipitating nickel sulfate crystals after being subjected to a normal cleaning treatment. In particular, high-purity nickel sulfate with a low selenium content can be produced.

It is the graph which showed the relationship between the oxygen partial pressure in the autoclave which is a pressure leaching apparatus, and the selenium density | concentration in a leaching solution for every sulfur addition ratio.

  The nickel sulfate solution manufacturing method according to the present invention includes a first step of obtaining a nickel raw material slurry by wet-grinding a nickel raw material containing iron, copper, cobalt, selenium, etc. as impurities, and the nickel obtained in the first step. The second slurry is prepared by mixing the raw material slurry with the wet-pulverized solid sulfur slurry to prepare the nickel raw material / sulfur mixed slurry, and the mixed slurry obtained in the second step is charged into the pressure leaching device. And a third step of obtaining a nickel sulfate solution by blowing compressed air and pressurizing and leaching the nickel in the nickel raw material to the atmospheric pressure.

  And in the manufacturing method of the nickel sulfate solution of the present invention, the pressure in the pressure leaching apparatus in the third step is set to 1.6 to 1.9 MPa and the oxygen partial pressure is maintained at 0.311 MPa or less, Suppressing the oxidation of selenium in the nickel raw material to hexavalent selenic acid during pressure leaching and fixing the selenium in the nickel raw material to undissolved sulfur contained in the leaching residue it can. As a result, the selenium concentration in the nickel sulfate solution obtained as the leachate can be reduced to 0.5 mg / l or less only by the pressure leaching method.

  In order to further reduce the concentration of selenium in the leachate and obtain high-purity nickel sulfate having a lower selenium content, when adjusting the mixed slurry of nickel raw material and sulfur in the second step, When the sulfur amount of the reaction equivalent necessary for pressurizing and leaching the contained metal component as sulfate is 1, the total amount of sulfur contained in the nickel raw material and the amount of sulfur to be added is 0.7 or more. It is preferable to adjust so that.

  The nickel raw material may be a solid containing at least iron, copper, cobalt, selenium as impurities, for example, nickel matte obtained by dry smelting method, nickel sulfide ore, nickel oxide ore, nickel-containing Nickel sulfide or nickel oxide such as sludge, nickel-containing metal scraps, or the like can be used.

  The nickel matte, which is a typical nickel raw material, will be described. The chemical composition is generally 74 to 80% by weight of Ni, about 1% by weight of Co, and 0.1 to 0.4% by weight of Cu. Fe is 0.1 to 0.7% by weight, and S is 18 to 23% by weight. Moreover, the Se content of the nickel mat is usually in the range of 3 to 10 ppm by weight.

  An example of the particle size distribution of the nickel mat is less than 0.1% by weight exceeding 1680 μm, 2.9% by weight exceeding 1840 μm and exceeding 840 μm, and 17 exceeding μμm and 420 μm. 5 wt%, 420 μm or less and over 250 μm 30.6 wt%, 250 μm or less over 149 μm 30.0 wt%, 149 μm or less over 105 μm 12.5 wt%, 105 μm or less 74 μm The amount exceeding 4.5% is 4.5% by weight, and that below 74 μm is 1.9% by weight.

  Hereinafter, the method for producing a nickel sulfate solution according to the present invention will be described in detail step by step while exemplifying a case where a nickel mat having the above-described general chemical composition is used as a nickel raw material as necessary.

<First step>
In the first step of the present invention, a nickel raw material such as a nickel mat is charged into a pulverizer such as a vibration mill and wet pulverized to produce a nickel raw material slurry. The particle diameter of the nickel raw material after pulverization is not particularly limited, but it is preferable that the nickel raw material is smaller in order to increase the nickel leaching reaction rate. For example, 50% D (number-based 50% particle diameter) is preferably less than 50 μm, and more preferably less than 30 μm.

<Second step>
In the second step of the present invention, first, solid sulfur is charged into a vibration mill or the like and wet pulverized to produce a sulfur slurry. Next, this sulfur slurry is mixed with the nickel raw material slurry prepared in the first step to prepare a mixed slurry of nickel raw material and sulfur. At that time, the amount of sulfur added to the nickel raw material slurry, the slurry concentration of the mixed slurry, and the like are preferably prepared as described later.

  The reason why the sulfur slurry is added to and mixed with the nickel raw material slurry in this second step is basically that when nickel sulfate or the like is generated in the pressure leaching in the next third step (see Formula 3 to be described later). 4), in order to replenish the sulfur component which is equivalently insufficient with respect to metal components such as nickel in the nickel raw material. For example, when the nickel raw material is a nickel mat having the above-described general chemical composition, the desirable sulfur addition amount is 80 kg or more, preferably about 80 to 200 kg per ton of nickel mat.

  However, when the addition amount of sulfur is excessive with respect to a metal component such as nickel in the nickel raw material, sulfur oxidation reaction shown in the following chemical formula 1 occurs and sulfuric acid is generated. Since the produced sulfuric acid dissolves metallic nickel in the nickel raw material and generates hydrogen gas as shown in the following chemical formula 2, a safety problem arises. Further, if the amount of sulfur added is increased, the amount of required oxygen also increases, so that restrictions due to the equipment capacity of the air compressor, piping, or exhaust gas treatment process also occur.

[Chemical Formula 1]
2S + 3O ₂ + 2H ₂ O → 2H ₂ SO ₄
[Chemical formula 2]
Ni + H ₂ SO ₄ → NiSO ₄ + H ₂

  Under such circumstances, in order to prevent the generation of hydrogen gas and to suppress the decrease in the processing amount of nickel raw materials and the increase in processing costs due to the restrictions on the equipment capacity of air compressors, etc., the amount of sulfur added to the nickel raw material slurry The amount of sulfur in the mixed slurry of nickel raw material and sulfur is defined as the amount of sulfur of the reaction equivalent necessary for pressurizing and leaching the metal component contained in the nickel raw material as sulfate. It is preferable to adjust so that the ratio of the total amount of sulfur contained in the raw material and the amount of sulfur to be added (hereinafter also referred to as sulfur addition ratio) is 0.7 or more.

  Moreover, by adjusting the amount of sulfur in the mixed slurry of nickel raw material and sulfur so that the sulfur addition ratio is 0.7 or more, selenium in the nickel raw material is reduced in the pressure leaching in the next third step. It can be fixed to undissolved sulfur contained in the leach residue.

  Further, the slurry concentration of the mixed slurry of nickel raw material and sulfur is 100 to 400 g at an industrial level when the nickel raw material is nickel mat, for example, in consideration of handling problems and diffusibility of blown air in the autoclave. / L is preferable.

<Third step>
In the third step of the present invention, the nickel raw material / sulfur mixed slurry prepared in the second step is charged into a pressure leaching apparatus such as an autoclave, and compressed air is blown to pressurize nickel in the nickel raw material. Leaching.

The pressure leaching reaction of the nickel mat in the third step proceeds mainly based on the following chemical formulas 3-6.
[Chemical formula 3]
Ni ₃ S ₂ + S + 6O ₂ → 3NiSO ₄
[Chemical formula 4]
Ni + S + 2O ₂ → NiSO ₄

[Chemical formula 5]
2Ni ₃ S ₂ + 9O ₂ + 2H ₂ O → 4NiSO ₄ + 2NiO · H ₂ O
[Chemical formula 6]
2Ni + O ₂ → 2NiO

  In the pressure leaching in the third step, the pressure in the pressure leaching apparatus is set to 1.6 to 1.9 MPa. When the pressure in the pressure leaching apparatus is less than 1.6 MPa, the leaching reaction does not proceed sufficiently and nickel cannot be leached efficiently from the nickel raw material. Conversely, even if the pressure in the pressurized leaching device exceeds 1.9 MPa, the nickel leaching rate reaches a peak at 99% or more, and it is a good idea to consider the equipment cost of special pressurized leaching device and the power cost of compressed air. It will not be.

  Moreover, the oxygen partial pressure in the pressure leaching apparatus is set to 0.311 MPa or less. In order to increase the leaching rate of nickel, it is desirable that the oxygen partial pressure is high. However, it suppresses the oxidation reaction of selenite ion represented by the following chemical formula 7 and substantially prevents the formation of selenate that is difficult to remove by coprecipitation. Therefore, it is important to keep the oxygen partial pressure necessary for nickel leaching at a minimum, and specifically, it is necessary to maintain the oxygen partial pressure in the pressure leaching apparatus at 0.311 MPa or less. is there.

[Chemical formula 7]
2SeO ₃ ²⁻ + O ₂ → 2SeO ₄ ²⁻

  The oxygen partial pressure is monitored with an exhaust gas oxygen concentration meter installed in a pressure leaching device such as an autoclave, and the oxygen partial pressure is adjusted by adjusting the operating pressure and the compressed air flow rate of the pressure leaching device such as an autoclave. Can be implemented.

As the pressure leaching conditions other than the pressure in the pressure leaching apparatus and the oxygen partial pressure, in addition to the purpose of suppressing oxidation of selenium to hexavalent selenic acid (SeO ₄ ²⁻ ), exhaust gas Taking into account the increase in heat removal loss due to heat, the capacity of air compressors and exhaust gas treatment facilities, etc., the flow rate of compressed air blown into a pressure leaching device such as an autoclave should be minimized. Is nickel matte, the unit weight (ton) is preferably 4000 to 6000 Nm ³ / t. Moreover, it is preferable that the temperature in a pressure leaching apparatus exists in the range of 140-180 degreeC.

  In addition, as a pressure leaching reaction apparatus, an autoclave equipped with a stirrer and a cooling serpentine tube is generally used, but it is not particularly limited as long as it can perform a pressure leaching reaction. The material and structure of a pressure leaching reaction apparatus such as an autoclave is industrially used, for example, an apparatus in which lead lining is applied to the inner surface of a rolled steel can body and acid-resistant bricks are laminated on the inner surface of the lead lining. . However, any material or structure having pressure resistance, heat resistance, and corrosion resistance to the leachate may be used, such as stainless steel or titanium.

  In the pressure leaching reaction of the nickel raw material in the third step, since the pressure leaching is performed in a state where sulfur is insufficient with respect to the nickel raw material, the reaction product is a nickel sulfate aqueous solution containing solid basic nickel sulfate. Become. The nickel sulfate solution as the reaction product is recovered by extracting a nickel sulfate aqueous solution containing basic nickel sulfate in the pressure leaching reactor and reducing the pressure to atmospheric pressure by a flash device or the like.

  As explained in detail above, according to the method for producing a nickel sulfate solution of the present invention having the first to third steps, not only efficiently removing impurities such as selenium contained in the nickel raw material, By suppressing the oxidation reaction of selenite ions, it is possible to substantially eliminate the production of selenate that is difficult to remove by coprecipitation. Moreover, by adjusting the amount of sulfur added to the nickel raw material, selenium in the nickel raw material can be fixed to undissolved sulfur contained in the leaching residue.

  Since the nickel sulfate solution recovered after depressurization in the third step contains basic nickel sulfate, the basic solution contained in the nickel sulfate solution is represented by the following chemical formula 8 after the third step. The nickel sulfate is dissolved in sulfuric acid and filtered, whereby the leaching residue is separated to obtain an aqueous nickel sulfate solution.

[Chemical formula 8]
3NiO.2NiSO ₄ + 3H ₂ SO ₄ → 5NiSO ₄ + 3H ₂ O

  As a nickel raw material, a nickel mat containing 78% by weight of nickel (Ni), 20% by weight of sulfur (S), and 4% by weight of selenium (Se) was used. This nickel mat was mixed with water and finely pulverized to 30 μm at 50% D (number-based 50% particle size) using a rod mill to prepare a nickel mat slurry.

  On the other hand, solid sulfur was mixed with water, and finely pulverized to 30 μm at 50% D using a ball mill to prepare a sulfur slurry. This sulfur slurry was added and mixed with the nickel mat slurry so that the total amount of sulfur was 73 kg / t per unit weight of the nickel mat, and water was further added to add a mixed slurry (sample) with a slurry concentration of 224 g / l. 1) was prepared. In addition, the addition amount of the said sulfur is 0.64 in the sulfur addition ratio.

While continuously supplying the obtained mixed slurry of Sample 1 to an autoclave having an effective capacity of 10 m ³ , compressed air was blown at a flow rate of 6089 Nm ³ / ton per ton of nickel mat, and the pressure in the autoclave was 1.63 MPa and oxygen The pressure was leached while controlling the partial pressure to 0.343 MPa. The slurry after pressure leaching is discharged into a vacuum tank and depressurized to atmospheric pressure with a flash device, and the slurry obtained by dissolving basic nickel sulfate with sulfuric acid is filtered to recover a leachate (nickel sulfate solution). .

  The recovered nickel sulfate solution of Sample 1 was divided into two parts, and one was added with hydrochloric acid and boiled, and then the tetravalent selenium concentration (A) was measured. The other is not subjected to boiling treatment with the addition of hydrochloric acid, and the tetravalent selenium concentration (B) is measured as it is, and the hexavalent selenium concentration is determined from the tetravalent selenium concentration (A) and the tetravalent selenium concentration (B). The selenium removal rate was calculated. The selenium concentration was measured by ICP-MS method.

  Next, using the same nickel mat slurry and sulfur slurry as in sample 1, the sulfur amount is 90 to 154 kg / t per unit weight of nickel mat (0.68 to 0.83 in terms of sulfur addition). Then, water was added so that the slurry concentration was 219 to 249 g / l, and each mixed slurry of Samples 2 to 8 was prepared. In addition, the addition amount of the said sulfur is 0.68-0.83 in a sulfur addition ratio.

While continuously supplying each of the obtained mixed slurries of Samples 2 to 8 to an autoclave having the same effective capacity of 10 m ³ as described above, compressed air was supplied at a flow rate of 4389 to 5268 Nm ³ / ton per ton of nickel mat for each sample. The pressure was leached by controlling the pressure in the autoclave at 1.63 to 1.73 MPa and the oxygen partial pressure at 0.290 to 0.311 MPa.

  Each slurry of Samples 2 to 8 after pressure leaching is discharged to a vacuum tank and depressurized to atmospheric pressure by a flash device, and each slurry obtained by dissolving basic nickel sulfate with sulfuric acid is filtered and filtered. The nickel sulfate solution was recovered. Each of the collected nickel sulfate solutions of Samples 2 to 8 was divided into two, and tetravalent selenium concentration and hexavalent selenium concentration were determined by the same method as described above, and the selenium removal rate was calculated. The obtained results are shown in the following Table 1 and FIG. 1 together with the sulfur addition ratio, slurry concentration, oxygen partial pressure, and compressed air flow rate of each sample.

  From the results shown in Table 1 and FIG. 1, by controlling the oxygen partial pressure in the autoclave to 0.311 MPa or less, the hexavalent Se concentration in the nickel sulfate solution as the leachate is reduced to 0.5 mg / l or less. It can be seen that this can be reduced. Moreover, it turns out that the hexavalent Se density | concentration in the nickel sulfate solution which is a leaching solution reduces by increasing sulfur usage-amount.

Claims (6)

A method for producing a nickel sulfate solution by pressure leaching from a nickel raw material containing iron, copper, cobalt, and selenium as impurities, wherein a nickel raw material slurry is obtained by adding water to the nickel raw material and wet-pulverizing it. a first step, a slurry was obtained by wet grinding by adding water to the solid body sulfur is added to a slurry of the nickel raw material, a second step of preparing a mixed slurry of nickel raw material and sulfur, said mixed slurry The third step is to obtain a nickel sulfate solution by charging the pressure leaching device, blowing compressed air, pressure leaching the nickel in the nickel raw material, and then reducing the pressure leaching solution to atmospheric pressure. The method for producing a nickel sulfate solution, characterized in that the pressure in the pressure leaching apparatus in the third step is set to 1.6 to 1.9 MPa and the oxygen partial pressure is maintained at 0.311 MPa or less. .   In the mixed slurry of nickel raw material and sulfur in the second step, when the sulfur amount of reaction equivalent necessary for pressurizing and leaching the metal component contained in the nickel raw material as sulfate is 1, the nickel raw material The method for producing a nickel sulfate solution according to claim 1, wherein the total amount of sulfur contained and the amount of sulfur added in the second step is adjusted to be 0.7 or more.   The nickel sulfate solution according to claim 2, wherein the total amount of sulfur contained in the nickel raw material and the amount of sulfur added in the second step is adjusted to be 0.7 or more and less than 1.0. Manufacturing method.   The method for producing a nickel sulfate solution according to any one of claims 1 to 3, wherein the nickel raw material is a nickel mat produced by dry smelting.   In the second step, the slurry concentration of the mixed slurry of nickel raw material and sulfur is adjusted to 100 to 400 g / l, and the temperature in the pressure leaching apparatus is maintained at 140 to 180 ° C. in the third step. The manufacturing method of the nickel sulfate solution of Claim 4. The amount of blown compressed air in pressure leaching in the apparatus in the third step, and adjusting the nickel raw material per ton 4000～6000Nm ^3, the production of nickel sulfate solution according to claim 4 or 5 Method.

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