Hydrometallurgical method for nickel oxide ore, method for producing nickel-containing sulfide, and method for producing nickel-containing hydroxide

Abstract

The present invention provides a hydrometallurgical method for a nickel oxide ore, with which it is possible to effectively utilize an ore that contains magnesium at a high concentration.　Provided is a hydrometallurgical method for a nickel oxide ore, the hydrometallurgical method including: a first step S1 in which a leaching step S11, a solid-liquid separation step S12, and a neutralization step S13 are performed; and a second step S2 in which a dissolvability improvement treatment step S21, in which the dissolvability of a magnesium-containing ore that has a magnesium concentration exceeding 5 mass% is improved, and a carbonate production step S22, in which the magnesium-containing ore, which has passed through the dissolvability improvement treatment step S21, is put into a solution and magnesium dissolved in the solution is reacted with carbon dioxide so as to produce magnesium carbonate, are performed. The magnesium carbonate produced in the carbonate production step S22 is used as a neutralizing agent in the neutralization step S13.

Description

Hydrometallurgical method for nickel oxide ore, method for producing nickel-containing sulfide, and method for producing nickel-containing hydroxide

[0001] The present invention relates to a hydrometallurgical method for producing nickel oxide ore, a method for producing nickel-containing sulfide, and a method for producing nickel-containing hydroxide. More specifically, the present invention relates to a hydrometallurgical method for producing nickel oxide ore by high pressure acid leaching (hereinafter also referred to as "HPAL process"), which can effectively utilize ore containing magnesium at a high concentration.

[0002] In recent years, the high-temperature pressure acid leaching (HPAL process), which is a hydrometallurgical method for leaching metal ions into a liquid phase using concentrated sulfuric acid under high temperature and pressure, has become widely used as a hydrometallurgical method for nickel oxide ore, replacing conventional pyrometallurgical methods. This "HPAL process" is a process that consists of a consistent hydrometallurgical process and is therefore superior to conventional pyrometallurgical methods in terms of economic efficiency.

[0003] Conventionally, so-called laterite ores such as limonite ore and saprolite ore have been widely used as raw material ores in the hydrometallurgy of nickel oxide ores. However, in the hydrometallurgy of nickel smelting (nickel smelting by the "HPAL process"), for example, if saprolite ore with a high magnesium concentration (nickel concentration: approximately 1.8% by mass to 3.0% by mass, magnesium concentration: 6% by mass or more) is used, Mg is preferentially ionized over valuable metals such as nickel, which increases the amount of concentrated sulfuric acid required to leach valuable metals, thereby reducing the economic advantages of the "HPAL process." Therefore, in the hydrometallurgy of nickel smelting (nickel smelting by the "HPAL process"), limonite ore with a relatively low magnesium concentration (nickel concentration: approximately 0.8% by mass to 1.8% by mass, magnesium concentration: 5% by mass or less) has mainly been used as the nickel oxide ore, although it is not necessarily particularly high in nickel concentration.

[0004] However, in various fields of metal smelting, technological development is underway to use low-grade ores that have been avoided under conventional technologies due to their cost disadvantages, or ores that have been considered waste ores.In line with this trend, in the field of nickel smelting using the "HPAL process," technological development is underway to use raw material ores containing high concentrations of Mg, which have not been actively used in the past, without reducing the inherent economic advantages of the "HPAL process."

[0005] For example, Patent Document 1 discloses an "HPAL process" in which nickel oxide ore, which is a mixture of ores with various Mg concentrations, is sieved into a fine particle fraction with a low magnesium concentration and a coarse particle fraction with a high magnesium concentration, and the separated and recovered coarse particle fraction is further separated by specific gravity, and only the portion with a high specific gravity is charged into a leaching step.

[0006] However, the process disclosed in Patent Document 1 is a process that is premised on the presence of a certain amount of fine grains with a low magnesium concentration in the raw ore, and the accuracy of separation of Mg from the ore rejected to the coarse grains and recovery of nickel is not necessarily sufficient, leaving room for further improvement. For example, there has been a demand for a technical means that can effectively utilize ores that contain a high concentration of magnesium, such as saprolite ore.

[0007] JP 2019-65340 A

[0008] The present invention has been proposed in view of the above circumstances, and aims to provide a method for hydrometallurgy of nickel oxide ore that can effectively utilize ores containing high concentrations of Mg, such as saprolite ore, which have not been actively used in hydrometallurgy nickel smelting such as the "HPAL process."

[0009] The present inventors have carried out a hydrometallurgical process for nickel oxide ore by adding carbon dioxide (CO ２ ) was fixed and MgCO ３The present inventors have found that the above-mentioned problems can be solved by carrying out a first step of producing a hydroxybenzoate in parallel with a second step of producing a hydroxybenzoate, and have thus completed the present invention.

[0010] (1) A method for hydrometallurgical smelting of nickel oxide ore, comprising: a first step of leaching a nickel oxide ore with a mineral acid to obtain a leach slurry; a solid-liquid separation step of separating the leach slurry into a leachate and a leach residue; and a neutralization step of separating a neutralized precipitate from the leachate to obtain a neutralized end solution. A second step of carrying out a leachability improvement treatment step of improving the leachability of magnesium by changing the crystal structure of a magnesium-containing ore having a magnesium concentration of more than 5% by mass, and a carbonate production step of placing the magnesium-containing ore that has been subjected to the leachability improvement treatment step into a solution and reacting the magnesium eluted into the solution with carbon dioxide to produce magnesium carbonate. The magnesium carbonate produced in the carbonate production step of the second step is used as a neutralizing agent in the neutralization step of the first step.

[0011] According to the hydrometallurgical method for nickel oxide ore (1), raw ores containing high concentrations of Mg, such as saprolite ore, which have not been actively used in the field of nickel smelting using the "HPAL process," or other low-grade ores or waste ores, which contain trace amounts of nickel but have a high proportion of gangue components and have not been used in the leaching step and have been excluded from the production line for the final product, can be effectively utilized in the neutralization step.

[0012] (2) The hydrometallurgical method for producing nickel oxide ore according to (1), wherein the carbon dioxide gas discharged from the neutralization step of the first step is used as carbon dioxide to react with the magnesium dissolved in the solution in the carbonate production step of the second step.

[0013] According to the hydrometallurgical method for producing nickel oxide ore in (2), the CO reacted with Mg in the carbonate production step of the second step is ２ CO emitted from the neutralization step in the first step ２ CO emitted in the nickel smelting process, such as gas ２By utilizing gas, CO from nickel smelting plants can be reduced. ２ It can also contribute to reducing the total amount of gas emissions.

[0014] (3) A method for producing a nickel-containing sulfide, comprising adding a sulfiding agent to the final neutralization solution obtained in the neutralization step of the hydrometallurgical method for producing a nickel oxide ore according to (1) or (2), to produce a nickel-containing sulfide.

[0015] According to the method for producing nickel-containing sulfides of (3), it is possible to enjoy the above-mentioned effects of the hydrometallurgical method for nickel oxide ore of (1) or (2), and improve the productivity of nickel-containing sulfides, which are the target product in nickel smelting by the "HPAL process."

[0016] (4) A method for producing a nickel-containing hydroxide, comprising adding a neutralizing agent to the final neutralization solution obtained in the neutralization step of the hydrometallurgical method for producing a nickel oxide ore according to (1) or (2), to produce a nickel-containing hydroxide.

[0017] According to the method for producing nickel-containing sulfide of (4), it is possible to enjoy the above-mentioned effects of the hydrometallurgical method for producing nickel oxide ore of (1) or (2), and improve the productivity of nickel-containing hydroxide, which is the target product in nickel smelting by the "HPAL process."

[0018] According to the present invention, ores containing high concentrations of Mg, such as saprolite ore, which have not been actively used in the past in hydrometallurgical nickel smelting, can be effectively utilized.

[0019] Fig. 1 is a flow diagram showing the flow of the hydrometallurgical method for producing nickel oxide ore according to the present invention. Fig. 2 is a graph showing the change in particle size distribution of "high-magnesium ore" when "mechanochemical treatment", which is an example of a treatment for improving leaching property in the hydrometallurgical method for producing nickel oxide ore according to the present invention, is carried out. Fig. 3 is a graph showing that "high-magnesium ore" is made amorphous by "mechanochemical treatment", which is an example of a treatment for improving leaching property in the hydrometallurgical method for producing nickel oxide ore according to the present invention.

[0020] Specific embodiments of the "hydrometallurgical method for producing nickel oxide ore" of the present invention will be described in detail below. Note that the present invention is not limited to the following embodiments, and various modifications are possible within the scope of the present invention.

[0021] <Method for Hydrometallurgy of Nickel Oxide Ore> An example of the overall flow of the hydrometallurgy process of nickel oxide ore that can be performed by the "method for hydrometallurgy of nickel oxide ore" of the present invention (hereinafter also simply referred to as "method for hydrometallurgy of nickel oxide ore") is shown in FIG. 1. The "method for hydrometallurgy of nickel oxide ore" includes a first step S1 of producing nickel-containing sulfide or nickel-containing hydroxide from nickel oxide ore by hydrometallurgy, and a second step S2 of producing MgCO from Mg contained in magnesium-containing ore having a magnesium concentration exceeding 5 mass % (also referred to as "high-magnesium ore" in this specification), which has been difficult to utilize in conventional hydrometallurgy processes. ３ In this "hydrometallurgical method for producing nickel oxide ore", the second step S2 produces MgCO3 from the "high magnesium ore". ３ The main feature of the overall process is that the above is used as a neutralizing agent in the first step S1.

[0022] [First Step] The first step S1 is a hydrometallurgical method for producing nickel oxide ore. As shown in Fig. 1 , the first step S1 is similar to a conventionally known hydrometallurgical method (HPAL process), in which a leaching step S11, a solid-liquid separation step S12, and a neutralization step S13 are sequentially performed. In the first step S1, as in the conventional method, limonite ore having a magnesium concentration of 5 mass% or less can be preferably used as the nickel oxide ore used as the raw material ore.

[0023] Furthermore, by performing a smelting process consisting of the above three steps (leaching step S11, solid-liquid separation step S12, and neutralization step S13), a sulfurization step S14 in which a sulfiding agent is added to the neutralization end solution obtained in the neutralization step S13, or a hydroxide step S15 in which a neutralizing agent is added to the neutralization end solution, a nickel-containing sulfide or a nickel-containing hydroxide can be produced in each step.

[0024] (Leaching Step) The leaching step S11 is a step of carrying out a leaching treatment in which a mineral acid such as sulfuric acid is added to nickel oxide ore that has been mixed with water to form a slurry (nickel oxide ore slurry), and the mixture is stirred under pressure at a high temperature of approximately 220° C. to 280° C. to produce a leaching slurry consisting of a leachate and a leaching residue. Specifically, this leaching treatment can be carried out by charging the above-mentioned "nickel oxide ore slurry" into a pressure leaching reaction vessel such as an autoclave.

[0025] For example, in the second step S2, when a "nickel oxide ore" having a high magnesium concentration, such as "saprolite ore," is used as the "high-magnesium ore," MgCO ３ The slurry remaining after the recovery of Mg can be charged into the leaching step S11 as a "nickel oxide ore slurry" with a reduced Mg concentration.

[0026] (Solid-liquid separation step) The solid-liquid separation step S12 is a step of separating the leaching slurry that has been subjected to the leaching step S11 into a leachate containing nickel (Ni), cobalt (Co) and other impurity elements and a leaching residue while washing the leached slurry in multiple stages. The solid-liquid separation step S12 can be performed, for example, by mixing the leached slurry with a washing solution and then subjecting the mixture to solid-liquid separation treatment using solid-liquid separation equipment such as a thickener.

[0027] (Neutralization Step) The neutralization step S13 is a step of adjusting the pH of the leachate separated in the solid-liquid separation step S12 and separating impurity elements as a neutralized precipitate to obtain a neutralized end solution containing Ni and Co. Specifically, in the neutralization step S13, a neutralizing agent is added to the leachate while suppressing oxidation of the separated leachate so that the pH of the resulting neutralized end solution is 4.0 or less, preferably 3.0 to 3.5, and more preferably 3.1 to 3.2, to produce a neutralized end solution and a neutralized precipitate slurry containing impurity elements such as trivalent iron (Fe) and aluminum (Al). In this way, impurities are removed as a neutralized precipitate to produce a neutralized end solution that serves as a mother liquor for nickel recovery.

[0028] Common neutralizing agents used in the neutralization process of nickel oxide ore hydrometallurgy include calcium carbonate and MgCO ３ The above-mentioned various neutralizing agents can also be used in the neutralization step S13 of the first step S1 of the "hydrometallurgical method for producing nickel oxide ore" of the present invention. In the neutralization step S13, at least a part of the neutralizing agent used in the neutralization step S13 is MgCO 3 produced in the carbonate production step S22 of the second step S2. ３ In the "hydrometallurgical method for producing nickel oxide ore" of the present invention, 5% or more of the total amount of neutralizing agent used in the neutralization step S13 is used as the MgCO 3 produced in the carbonate production step S22 of the second step S2. ３ It is preferable that the total amount of neutralizing agent (100%) is MgCO ３ It is most preferable to set the following.

[0029] In the neutralization step S13, MgCO was used as the neutralizing agent as described above. ３ The neutralization reaction that proceeds when the solution is added is, for example, as shown in the following (Equation 1), and iron (Fe) and the like in the solution are removed as a neutralized precipitate slurry. (Equation 1) Fe ２ (SO ４ ) ３ + 3MgCO ３ +H ２ O → 3MgSO ４ (aq)+2FeOOH↓+3CO ２ ↑

[0030] (Sulfurization Step) As described above, the sulfurization step S14 is a step of adding a sulfurizing agent to the mother liquor for nickel recovery from which Fe and other elements have been removed in the neutralization step S13, and further separating the resulting mixture into a nickel-containing sulfide and a barren liquor. In the sulfurization step S14, a sulfurizing agent is blown into the end-neutralization liquor, which is the mother liquor for nickel recovery, to cause a sulfurization reaction and produce a nickel-containing sulfide and a barren liquor. Examples of sulfurizing agents that can be used in the sulfurization step S14 include hydrogen sulfide, sodium hydrogen sulfide, and sodium sulfide. Of these, hydrogen sulfide is particularly preferred. The "hydrometallurgical method for producing nickel oxide ore" of the present invention can produce the target product, a nickel-containing sulfide, by further performing the sulfurization step S14. That is, the process including the above three steps (leaching step S11, solid-liquid separation step S12, and neutralization step S13) and this sulfurization step S14 is the "method for producing nickel-containing sulfide" of the present invention.

[0031] The nickel-containing sulfide is generally called MS (mixed sulfide) and refers to a nickel-cobalt mixed sulfide. Specifically, it contains 50.0 to 60.0 mass% Ni, 0.1 to 26.0 mass% Co, and approximately 0.1 to 2.0 mass% Fe and other impurities. These nickel-containing sulfides can be subjected to chlorine leaching and electrowinning to produce electrolytic nickel, or to purification to produce nickel sulfate, or subjected to ammonia leaching and hydrogen reduction to produce nickel powder or nickel briquettes. Furthermore, the nickel-containing sulfides produced by the "method for producing nickel-containing sulfides" of the present invention can be processed into final products such as nickel sulfate, electrolytic nickel, nickel powder, and nickel briquettes using these existing methods.

[0032] (Hydroxylation Step) As described above, the hydroxylation step S15 is a step in which a neutralizing agent is added to the mother liquor for nickel recovery from which Fe and other elements have been removed in the neutralization step, and the resulting solution is further separated into a nickel-containing hydroxide and a barren liquor. Examples of neutralizing agents that can be used in the hydroxylation step S15 include calcium carbonate, calcium hydroxide, magnesium hydroxide, sodium hydroxide, quicklime, and magnesium oxide. Among these, magnesium hydroxide and magnesium oxide are particularly preferred. In the hydroxylation step S15, a neutralizing agent such as MgO is added to the end neutralization liquor, which is the mother liquor for nickel recovery, to cause a hydrolysis reaction, as exemplified by the following formulas (2) and (3), to proceed, thereby producing a nickel-containing hydroxide and a barren liquor. The "hydrometallurgical method for producing nickel oxide ore" of the present invention can produce the target product, a nickel-containing hydroxide, by further performing the hydroxylation step S15. In other words, the process including the above three steps (leaching step S11, solid-liquid separation step S12, and neutralization step S13) and this hydroxide step S15 is the "method for producing a nickel-containing hydroxide" of the present invention. ４ (aq)+MgO(s)+H ２ O(l) = MgSO ４ (aq)+Ni(OH) ２ (s) (Formula 3) CoSO ４ (aq)+MgO(s)+H ２ O(l) = MgSO ４ (aq)+Co(OH) ２ (s)

[0033] The nickel-containing hydroxide is generally called MHP (Mixed Hydroxide Precipitate) and refers to a mixture of nickel hydroxide and cobalt hydroxide. Specifically, it contains 5% by mass to 50% by mass of Ni, 0.05% by mass to 10.0% by mass of CO, and approximately 0.01% by mass to 10.0% by mass of impurities such as Mg, manganese (Mn), Al, and Fe. These nickel-containing hydroxides can be dissolved, purified, and then electrolytically won to produce electrolytic nickel. Furthermore, the nickel-containing hydroxides produced by the present invention can be processed into final products such as electrolytic nickel using these existing methods.

[0034] The neutralization end liquid, which is the mother liquor for recovering nickel, is a sulfuric acid solution in which impurity components have been reduced by passing the leachate through the neutralization step S13. Note that this mother liquor for recovering nickel may contain impurity components such as Fe, Mg, and Mn at a concentration of several g / L, but these impurity components have low stability as sulfides and will not be contained in the nickel-containing sulfide produced.

[0035] [Second step] The second step S2 is a process for converting MgCO , which can be used in the first step S1, from Mg contained in "high magnesium ore," which was difficult to use in conventional hydrometallurgical processes. ３ As shown in Fig. 1 , in the second step S2, a leaching improvement treatment step S21 and a carbonate production step S22 are essential steps that are carried out in this order. The produced carbonate may be recovered, for example, by a carbonate recovery step S23. However, the carbonate recovery step S23 is not an essential step in the "hydrometallurgical method for producing nickel oxide ore" of the present invention. As long as the magnesium carbonate produced in the carbonate production step S22 of the second step S2 is used as a neutralizing agent in the neutralization step S13 of the first step S1, the present invention can be carried out regardless of whether or not the carbonate recovery step S23, i.e., the separation and recovery process of the produced carbonate and the solution, which will be described in detail below, is carried out, and such an embodiment is naturally within the technical scope of the present invention.

[0036] In the "hydrometallurgical method for producing nickel oxide ore" of the present invention, ore having a magnesium concentration exceeding 5 mass % ("high-magnesium ore") is charged not in the first step S1 but in the second step S2. However, it is not essential that all of the "high-magnesium ore" be charged only in the second step S2. Even if some of the "high-magnesium ore" containing nickel is mixed in with the ore charged in the first step S1, it is within the technical scope of the present invention as long as the "high-magnesium ore" is charged in the second step S2, which is carried out in parallel.

[0037] In the "hydrometallurgical method for producing nickel oxide ore" of the present invention, ores other than "nickel oxide ore" having a magnesium concentration exceeding 5 mass% can also be treated with MgCO ３ However, the "high-magnesium ore" used in the second step S2 is preferably a "nickel oxide ore" having a high magnesium concentration, such as saprolite ore, which is ore normally used as a raw material ore in nickel smelting. By carrying out the present invention in such a manner that "nickel oxide ore" having a high magnesium concentration is used as the "high-magnesium ore" in the second step S2, for example, by carrying out the carbonate recovery step S23, MgCO ３ The residue remaining after the recovery of the "nickel oxide ore with a low magnesium concentration" derived from the "nickel oxide ore with a high magnesium concentration" can be effectively utilized by being charged into the leaching step S11.

[0038] In addition, examples of ores that can be used as "high-magnesium ores" in the second step S2 and that contain Mg as a silicate mineral include "nickel oxide ores" such as saprolite ore, as well as lizardite, chrysotile, enstatite, forestellite, talc, magnesite, serpentine, olivine, and smectite.

[0039] In the "high magnesium ore" that can be used in the second step S2, most of the Mg is contained in silicate minerals (magnesium silicate (Mg ３ Si２ O ５ (OH) ４ ) and the like). Magnesium silicate has a three-dimensional, complex crystal structure, and Mg is present at the center of the structure, so leaching of Mg from the magnesium silicate into the solution is difficult. Therefore, in the "method for hydrometallurgy of nickel oxide ore" of the present invention, a leaching improvement treatment step S21, which will be described in detail below, is made an essential step in the second step S2 as a treatment for sufficiently promoting the leaching of the silicate mineral into the solution, and within this step, a leaching improvement treatment for the "high-magnesium ore" is performed as will be described in detail below.

[0040] Furthermore, among the above-mentioned "high-magnesium ores," those containing Mg as magnesium silicate and having a mass ratio of Mg to Si (Mg / Si) of 0.5 or more are particularly preferred. Those with a Mg / Si ratio of 1.0 or more are even more preferred. A Mg / Si ratio of 0.5 or more allows for a greater amount of Mg to be eluted into the solution after elution improvement treatment. Compounds containing a higher Si content relative to Mg tend to have a more complex crystal structure, making Mg less elutable. The Si content (mass) in "alkaline earth metal-containing ores" can be determined by mixing 2.5 g each of sodium peroxide and sodium carbonate with 0.5 g of ore, heating and melting the mixture in an electric furnace to 800°C, cooling, and then leaching the mixture with hydrochloric acid, followed by ICP atomic emission spectroscopy. Similarly, the magnesium concentration (mass) in the "alkaline earth metal-containing ore" can be determined by leaching 0.5 g of the ore in hydrochloric acid and measuring it by ICP emission spectrometry.

[0041] (Leachability Improvement Treatment Step) As described above, the leaching improvement treatment step S21 is a step of performing a treatment to change the crystal structure of a "high-magnesium ore," which has a complex crystal structure and tends to make Mg difficult to leach, thereby improving the leaching of Mg from the "high-magnesium ore" into a solution. The specific treatment method for improving leaching is not limited to a specific treatment method, and any known or unknown treatment method can be used. Examples of conventionally known treatment methods for improving leaching include a treatment method of calcining a "high-magnesium ore," as disclosed in Japanese Patent Laid-Open No. 10-249153 and Japanese Patent Publication No. 2012-500718, or a treatment method of crushing a "high-magnesium ore" to a fine powder and then heating it. In this way, by changing the crystal structure of the "high-magnesium ore" by dehydration or the like, the leaching of Mg from the "high-magnesium ore" into a solution can be improved. It is preferable to use water as the solution used in carrying out the present invention.

[0042] As an example, when the "elution property improvement treatment" is performed by heating the "high-magnesium ore" by calcination or the like, the heating temperature in the "elution property improvement treatment" is preferably 500°C or more and 800°C or less (furnace atmosphere temperature), and more preferably 600°C or more and 750°C or less, as verified and confirmed in the "magnesium elution test" described below. The heating time is preferably 2 hours or more, and more preferably 4 hours or more.

[0043] Furthermore, in the "hydrometallurgical method for producing nickel oxide ore" of the present invention, the "high-magnesium ore" may be crushed to a particle size of approximately 300 μm or less as a pretreatment before being charged into the leaching property improvement treatment step S21, from the viewpoint of ease of handling. The "high-magnesium ore" may be crushed by any conventional method, and specific examples include crushing using a rod mill or a ball mill. However, the particle size of the "alkaline-earth metal-containing ore" does not significantly affect the leaching property of the alkaline-earth metal.

[0044] Table 1 below shows the results of a "magnesium elution test" conducted on a nickel oxide ore (saprolite ore: particle size 150 μm to 300 μm) having a magnesium concentration of 6% by mass or more as a specific example of a "high-magnesium ore" to confirm how the elution rate of Mg into solution changes depending on the heating temperature when the "elution improvement treatment" in the elution improvement treatment step S21 is performed by heating. The heating time (calcination time) in each test example was 4 hours, and the heating temperature was as shown in Table 1.

[0045] In this "magnesium elution test," 5 g of the above "high-magnesium ore (nickel oxide ore)" was placed in 200 mL of a solution (pure water at a temperature of 60°C) under different heating conditions during the "elution improvement treatment." CO was then added to the solution while stirring at a rotation speed of 450 rpm for 2 hours. ２ Gas (manufactured by Takamatsu Teisan Co., Ltd., concentration 99.995 vol.%) was blown in at a rate of 0.1 L / min. The magnesium elution rates (%) in Table 1 were measured and calculated after the above-mentioned two hours of stirring had elapsed using the "Method for measuring the amount of eluted magnesium and the method for calculating the elution rate" below. (Method for measuring the amount of eluted magnesium and the method for calculating the elution rate) Magnesium elution rate = magnesium concentration in solution (mg / L) × volume of eluate (L) / (magnesium concentration in ore (mass %) ÷ 100 × mass of ore (mg)) Each of the above magnesium concentrations was measured by ICP atomic emission spectrometry.

[0046] The results of this "magnesium elution test" showed that the magnesium elution rate was 1.8% when the "elution improvement treatment" by firing was not performed. It was also found that the "elution improvement treatment" at a heating temperature of 600°C, which is 500°C or higher, could sufficiently improve the magnesium elution rate to 32.0%. It was also confirmed that the magnesium elution rate decreased to 2.0% at a heating temperature of 900°C, which is higher than 800°C. The reason why the magnesium elution rate decreased by heating at 900°C is that the complex crystalline structure of magnesium silicate (Mg ３ Si ２ O ５ (OH) ４ ) is Mg２ SiO ４ This is thought to be due to the fact that the crystals are re-crystallized in the form of

[0047]

[0048] In addition, whether the complex crystalline structure of the minerals contained in the "high magnesium ore" has actually been sufficiently destroyed and made amorphous (i.e., whether the elution property has been improved) can be confirmed by XRD analysis. ３ SiO ５ (OH) ４ The XRD analysis can be performed by checking the peak of the (002) plane. For example, an X-ray diffractometer "Empyrean (manufactured by Malvern Instruments)" can be suitably used.

[0049] Another example of a specific method for "elution improvement treatment" is a "mechanochemical treatment" that applies mechanical stress to "high-magnesium ore" to change its crystal structure. "Mechanochemical treatment" is a new ore treatment method independently developed by the inventors of the present application, and refers to "a treatment in which mechanical stress is applied to the "high-magnesium ore," which is the treatment target of the "elution improvement treatment," thereby changing the crystal structure of the magnesium-containing mineral contained in the treatment target ("high-magnesium ore") by mechanical energy."

[0050] The above-mentioned "mechanochemical treatment" is not limited to a specific treatment method, and can be carried out using various industrial devices capable of applying mechanical stress by stirring or kneading (preferably kneading with a grinding medium (media, etc.)). Specific implementation methods include various stirring and kneading methods using a ball mill or a spikey hammer. Furthermore, the above-mentioned "mechanochemical treatment" can also be carried out using various other known or unknown stirring or kneading devices that can exert similar effects.

[0051] Unlike typical "pulverization," mechanochemical processing is not intended to reduce particle size. While the particle size of individual particles may decrease during mechanochemical processing due to the destruction of the ore being processed, the purpose of mechanochemical processing is to amorphize the ore by reducing its crystallinity (i.e., by changing its structure (destruction)). Therefore, mechanochemical processing is a novel processing method with a different purpose and effect from, for example, a pulverization process for particle size adjustment, which is performed to increase the specific surface area of ​​the material being processed, as a pretreatment prior to amorphization processing, which reduces crystallinity through conventional heat treatment. Figure 2 shows the change in particle size distribution of a "high-magnesium ore" after mechanochemical processing. The fact that the particle size distribution shown in the figure remains almost unchanged indicates that mechanochemical processing, which can be used as a means for implementing the leaching improvement processing step S21 in the present invention, is a novel processing method distinct from typical "pulverization" aimed at adjusting particle size distribution.

[0052] When "mechanochemical treatment" is performed using a ball mill, the ball mill rotation speed should be 10 rpm or higher, and the treatment time should be 80 minutes or longer. Furthermore, the rotation speed is preferably 100 rpm or higher, more preferably 300 rpm or higher, and the treatment time should also be 150 minutes or higher, more preferably 270 minutes or higher. If the treatment time is further extended while the ball mill rotation speed is set to 300 rpm, the effect of amorphizing the treated material (alkaline earth metal-containing mineral) increases, but even in this case, the rate of increase in the amorphization effect reaches a plateau at a treatment time of about 400 minutes. Therefore, the combination of ball mill rotation speed and treatment time should preferably be 300 rpm or higher, and the treatment time should be 270 minutes or longer. The "mechanochemical treatment" can be performed either dry or wet.

[0053] 3 shows the results of an "amorphization test" conducted to verify the effect of amorphization of a "high-magnesium ore" when the "elution improvement treatment" in the elution improvement treatment step S21 is performed by the above-mentioned "mechanochemical treatment" on nickel oxide ore (saprolite ore: particle size 150 μm to 300 μm) having a magnesium concentration of 14 mass % or more, as a specific example of "high-magnesium ore." The "mechanochemical treatment" was performed under "Test Condition 1" below, with the kneading time in a ball mill varied for each sample, and then each sample was subjected to "crystal structure analysis by X-ray diffraction" to confirm whether or not amorphization had progressed. (Test condition 1): A planetary ball mill (Star-shaped ball mill, Classikline P-5, manufactured by Fritsch) was used as a kneading device for mechanochemical treatment to amorphize the ore. A sample consisting of 50 g of the high-magnesium ore and 300 g of zirconia balls (10 mm diameter) were added as grinding media. The table rotation speed of the planetary ball mill was set to 300 rpm, and mechanochemical treatment was performed for a predetermined time and at a predetermined table rotation speed. Then, for each sample after the kneading treatment under the above conditions, an X-ray diffraction crystal structure analysis was performed using an Empyrean X-ray diffractometer (manufactured by Malvern Instruments).

[0054] As shown in Figure 3, the mechanochemical treatment reduced the amount of lizardite (Mg ３ Si ２ O ５ (OH) ４ It was confirmed that the peak of the (002) plane of the ore sample decreased. This indicates that the crystallinity of the ore sample has changed.

[0055] Furthermore, Table 2 below shows the results of a "dissolution acceleration test" conducted on nickel oxide ore (saprolite ore: particle size 150 μm to 300 μm) having a magnesium concentration of 6 mass% or more as a specific example of "high-magnesium ore" to confirm how the dissolution rate of Mg into solution changes depending on the treatment time when the "dissolution improvement treatment" in the dissolution improvement treatment step S21 is performed by the above-mentioned "mechanochemical treatment." In this test, after the amorphization treatment under the following (Test Condition 2), 5 g of each "ore sample" after the treatment was introduced into 200 mL of solution (pure water at a temperature of 60°C), and CO was introduced into the solution while stirring at a rotation speed of 450 rpm. ２ The test was performed by injecting a gas (manufactured by Takamatsu Teisan Co., Ltd., concentration 99.995% by volume) at a rate of 0.1 L / min, and the elution rate of Mg or Ca into the solution was measured and calculated using the "Method for Measuring the Amount of Leaching of Alkaline Earth Metal (Mg) and the Method for Calculating the Elution Rate" described below. The test results are shown in Table 2 below. (Test Condition 2): For various "ore samples," mechanochemical amorphization treatment was performed by placing 50 g of each "ore sample" and 300 g of zirconia balls (diameter 10 mm) as milling media into the same planetary ball mill as in the above-mentioned "amorphization treatment test." However, the table rotation speed of the planetary ball mill was 300 rpm, and the treatment time was the treatment time listed in Table 2 below. (Method for measuring the amount of eluted alkaline earth metal (Mg) and method for calculating the elution rate) Magnesium elution rate = magnesium concentration in solution (mg / L) × amount of eluate (L) / (magnesium concentration in ore (mass %) ÷ 100 × mass of ore (mg)) Each of the magnesium concentrations was measured by ICP emission spectrometry.

[0056]

[0057] From the above, it has been confirmed that the mechanochemical amorphization treatment described above improves the elution of Mg from magnesium silicate in the ore. The effect of this mechanochemical amorphization treatment is the result of a uniquely discovered novel method, but it is believed to be due to the fact that the crystalline structure of the alkaline earth metal-containing mineral in the alkaline earth metal-containing ore is changed by externally applied mechanical stress, making it easier for the alkaline earth metal to elute into solution. Therefore, the effect of the mechanochemical treatment described above is not limited to stirring or kneading using a ball mill, but is also believed to be an effect that is exhibited when similar treatments are performed using various other known or unknown stirring or kneading devices.

[0058] The "mechanochemical treatment" described above, i.e., the treatment of amorphizing "high-magnesium ore" by applying mechanical stress, is a novel, unprecedented technical means for amorphizing minerals, based on the findings uniquely discovered by the present inventors.

[0059] (Carbonate Forming Step) In the carbonate forming step S22, Mg is sufficiently eluted into a solution from the “high-magnesium ore” in which the elution property of Mg into a solution has been improved through the elution property improving treatment step S21, and CO is added to the solution. ２ A gas was blown in, and the dissolved Mg and the CO blown in as a gas were mixed in the solution. ２ by reacting with MgCO ３ This is a process in which a treatment is carried out to precipitate and generate carbonate (hereinafter also referred to as "carbonate generation treatment").

[0060] The ratio of the "high magnesium ore" to the solution into which Mg is eluted is preferably 2% by mass or more and 30% by mass or less, and more preferably 5% by mass or more and 20% by mass or less. By making the amount (mass ratio) of the "high magnesium ore" in the solution 2% by mass or more, MgCO ３ Furthermore, by making the amount (mass ratio) 30 mass % or less, the viscosity of the solution that becomes a slurry can be maintained at an appropriate level, and the handleability of the slurry material is improved.

[0061] CO in solution２ The method of blowing gas is not particularly limited. For example, CO 2 is blown into the gas using a disk-type diffuser or a cylindrical diffuser. ２ This can be done by blowing gas into the solution. ２ Gas CO ２ The concentration should be 10% or more. However, if the concentration exceeds 10%, ２ By making it into a gas, MgCO ３ The production of can be promoted more efficiently.

[0062] In addition, the CO used in the carbonate production step S22 ２ The supply source and supply method of CO are not particularly limited. However, in the neutralization step S13 of the first step S1, CO generated in the neutralization step using a neutralizing agent derived from fossil fuels or carbonates is ２ gas, which can be used to reduce CO from nickel smelting plants. ２ This can contribute to reducing the total amount of gas emissions.

[0063] (Carbonate recovery step) The carbonate recovery step S23 is a step of recovering MgCO 3 produced in the carbonate production step S22. ３ This is a process to recover MgCO from the solution. ３ The specific method for recovering the is not particularly limited, but examples thereof include a method of recovering the liquid by separating it using a filter such as a filter press, or a method of recovering the water content of the solution by volatilizing it.

[0064] [Other Steps] In the "hydrometallurgical method for producing nickel oxide ore" of the present invention, in addition to the four basic steps in the first step S1 (leaching step S11, solid-liquid separation step S12, neutralization step S13, and sulfurization step S14) and the three basic steps in the second step S2 (leachability improvement treatment step S21, carbonate production step S22, and carbonate recovery step S23), an ore screening step may be performed upstream of the leaching step S11 and the leachability improvement treatment step S21. It is also preferable to further perform a final neutralization step downstream of the sulfurization step S14 in the first step S1. These steps are not necessarily required for the "hydrometallurgical method for producing nickel oxide ore" of the present invention. Regardless of whether or not these steps are performed, or the implementation of these steps, any smelting process that performs the above-described five basic steps in a manner that satisfies the requirements of the present invention falls within the technical scope of the present invention.

[0065] (Ore sieving step) When using a raw ore that is a mixture of multiple types of nickel oxide ores with different magnesium concentrations, it is preferable to perform an ore sieving step in which the raw ore is sieved into a coarse ore and a fine ore prior to the second step S2. When the ore sieving step is performed, the coarse ore sieved into the coarse part is regarded as a "high-magnesium ore" and charged into the second step S2, and the subsequent steps are carried out. On the other hand, the fine ore sieved into the fine part in this ore sieving step can be charged into the leaching step S11 without passing through the second step S2.

[0066] When the ore sieving step is performed, the sieving is preferably performed in a manner that sieving a portion in which the proportion of particles having a particle size of less than 45 μm is 40 mass% or less of the solid content into the coarse particle portion, and the remaining portion into the fine particle portion. By treating the portion sieved into the coarse particle portion in this way as coarse ore and as "high magnesium ore," a portion containing a relatively high concentration of Mg can be separated from a raw ore comprising a mixture of multiple types of nickel oxide ores with different magnesium concentrations, and charging the separated portion into the second step S2, thereby achieving the effects of the "hydrometallurgical method for producing nickel oxide ore" of the present invention.

[0067] (Final Neutralization Step) The final neutralization step is a step of neutralizing the barren solution containing impurity elements such as Fe, Mg, and Mn discharged in the sulfurization step S14 to adjust the pH to a predetermined range that satisfies the discharge standard (detoxification treatment). The method of detoxification in the final neutralization step, i.e., the method of adjusting the pH, is not particularly limited. For example, a calcium carbonate (limestone) slurry, a calcium hydroxide (slaked lime) slurry, or the MgCO 3 separated and recovered in the second step S2 as described above may be used. ３ As a neutralizing agent, the concentration of MgCO can be adjusted to a predetermined range by adding MgCO as a neutralizing agent. ３ As a neutralizing agent, this process is also a neutralization step in that it is a treatment for separating the neutralized precipitate to obtain a neutralization final solution. Therefore, as a neutralizing agent to be used in this final neutralization step, MgCO produced in the carbonate production step S22 is used. ３ Of course, an embodiment using the above is also within the technical scope of the present invention.

[0068] [Characteristics of the Overall Process] The overall process of the "hydrometallurgical method for producing nickel oxide ore" consisting of the above steps is characterized by the following: first, the MgCO ３ As a second feature, in the "hydrometallurgical method for producing nickel oxide ore", MgCO is used as a neutralizing agent in the carbonate production step S22 of the second step S2. ３ CO used to generate ２ CO generated in the smelting plant ２ Furthermore, as a third feature, in the "hydrometallurgical method for producing nickel oxide ore", MgCO ３The nickel oxide ore slurry, which is the residue (of the "high magnesium ore") after the magnesium content is recovered, can be charged into the leaching step S11 of the first step S1 as a raw material that has been treated to reduce the magnesium concentration. The "nickel oxide ore hydrometallurgy method" is a composite process that performs the first step S1 and the second step S2 in parallel, making it possible to effectively utilize the "high magnesium ore" that was difficult to utilize in conventional hydrometallurgy processes. In addition to simply being able to effectively utilize ore that was previously unused, it also reduces the amount of neutralizing agent used and reduces CO2 emissions throughout the process. ２ Furthermore, the magnesium carbonate production process carried out in the "hydrometallurgical method for nickel oxide ore" of the present invention reduces CO emissions from the ore. ２ In other words, the "hydrometallurgical method for nickel oxide ore" of the present invention is also a suitable process for specifically implementing "Mineral Carbonation Technology," which is one of the "Carbon Sequestration and Utilization Technologies (CCSU)."

[0069] S1 First step S11 Leaching step S12 Solid-liquid separation step S13 Neutralization step S14 Sulfurization step S15 Hydroxylation step S2 Second step S21 Elution improvement treatment step S22 Carbonate generation step S23 Carbonate recovery step

Claims

1. A method for hydrometallurgy of nickel oxide ore, comprising: a first step of leaching nickel oxide ore with a mineral acid to obtain a leach slurry; a solid-liquid separation step of separating the leach slurry into a leachate and a leach residue; and a neutralization step of separating a neutralized precipitate from the leachate to obtain a neutralization end liquid; and a second step of changing the crystal structure of a magnesium-containing ore having a magnesium concentration of more than 5 mass% to improve the leachability of magnesium, and a carbonate formation step of placing the magnesium-containing ore that has been subjected to the leachability improvement treatment step into a solution and reacting the magnesium eluted into the solution with carbon dioxide to produce magnesium carbonate, wherein the magnesium carbonate produced in the carbonate formation step of the second step is used as a neutralizing agent in the neutralization step of the first step.

2. The method for hydrometallurgy of nickel oxide ore according to claim 1, wherein the carbon dioxide gas discharged from the neutralization step of the first step is used as carbon dioxide to react with the magnesium dissolved in the solution in the carbonate formation step of the second step.

3. A method for producing nickel-containing sulfides, comprising adding a sulfurizing agent to the end neutralization solution obtained in the neutralization step of the hydrometallurgical method for producing nickel oxide ore according to claim 1 or 2, to produce nickel-containing sulfides.

4. A method for producing nickel-containing hydroxide, comprising adding a neutralizing agent to the end neutralization solution obtained in the neutralization step of the hydrometallurgical method for producing nickel oxide ore according to claim 1 or 2, thereby producing nickel-containing hydroxide.

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