Method for refining nickel oxidation ore in wet process, method for manufacturing nickel containing sulfide and method for manufacturing nickel containing hydroxide

Abstract

To provide a method for refining nickel oxidation ore in a wet process, capable of effectively using ore including magnesium at a high concentration.SOLUTION: A method for refining nickel oxidation ore in a wet process comprises: a first step S1 of performing a leach step S11, a solid-liquid separation step S12 and a neutralization step S13; and a second step S2 of performing a dissolution improvement step S21 of improving the dissolution of magnesium containing ore having a magnesium concentration of more than 5 mass% and a carbonate production step S22 of entering the magnesium containing ore through the dissolution improvement step S21 into a solution to react magnesium dissolved in the solution with carbon dioxide and produce magnesium carbonate. The magnesium carbonate produced in the carbonate production step S22 is used as a neutralizer in the neutralization step S13.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for hydrometallurgy of 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 method for hydrometallurgy of nickel oxide ore by high pressure acid leaching (hereinafter also referred to as "HPAL process"), which can effectively utilize ore containing high concentration of magnesium. [Background technology]

[0002] In recent years, the high-temperature pressure acid leaching process (HPAL process), which uses concentrated sulfuric acid under high temperature and pressure to leach metal ions into the liquid phase, has become widely used as a hydrometallurgical method for nickel oxide ore instead of the conventional dry smelting method. This "HPAL process" is a process that is economically superior to the conventional dry smelting method because it consists of a consistent wet process.

[0003] Conventionally, so-called laterite ores such as limonite ore and saprolite ore have been widely used as nickel oxide ores used as raw materials in the wet smelting of nickel oxide ores. However, in the above-mentioned wet nickel smelting (nickel smelting by the "HPAL process"), if saprolite ore with a high magnesium concentration (nickel concentration: about 1.8% by mass to about 3.0% by mass, magnesium concentration: 6% by mass or more) is used, Mg is preferentially ionized over valuable metals such as nickel, and the amount of concentrated sulfuric acid required to leach valuable metals increases, reducing the economic advantage of the "HPAL process". Therefore, in wet nickel smelting (nickel smelting by the "HPAL process"), limonite ore with a relatively low magnesium concentration (nickel concentration: about 0.8% by mass to about 1.8% by mass, magnesium concentration: 5% by mass or less) has been mainly used as 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 disadvantage, 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 compromising 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 part with a high specific gravity is charged to a leaching step.

[0006] However, the process disclosed in Patent Document 1 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 into 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. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2019-65340 A Summary of the Invention [Problem to be solved by the invention]

[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". [Means for solving the problem]

[0009] The present inventors have found that the above-mentioned problems can be solved by performing a nickel oxide ore hydrometallurgical process in parallel with a second step of producing MgCO3 by fixing carbon dioxide (CO2) to a high-magnesium ore having a magnesium concentration of more than 5 mass%, and have completed the present invention. That is, the present invention provides the following.

[0010] (1) A method for hydrometallurgy 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 neutralization end solution; and a second step of changing a 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 leachate dissolved in 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.

[0011] According to the nickel oxide ore hydrometallurgy method of (1), in the field of nickel smelting by the "HPAL process", raw ores containing high concentrations of Mg, such as saprolite ore, which have not been actively used in the past, 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 process and have been excluded from the production line of the final product, can be effectively utilized in the neutralization process.

[0012] (2) The method for hydrometallurgy of 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 formation step of the second step.

[0013] According to the nickel oxide ore hydrometallurgy method in (2), the CO2 gas emitted during the nickel smelting process, such as the CO2 gas emitted from the neutralization process in the first step, is used as the CO2 to be reacted with Mg in the carbonate production process in the second step, thereby contributing to a reduction in the total amount of CO2 gas emissions from the nickel smelting plant.

[0014] (3) A method for producing a nickel-containing sulfide, comprising adding a sulfurizing agent to a neutralization end solution obtained in the neutralization step of the method for hydrometallurgy of 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), the above-mentioned effects of the method for hydrometallurgy of nickel oxide ore of (1) or (2) can be obtained, and the productivity of nickel-containing sulfides, which is the target product in nickel smelting by the "HPAL process", can be improved.

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

[0017] According to the method for producing nickel-containing sulfide of (4), the above-mentioned effects of the method for hydrometallurgy of nickel oxide ore of (1) or (2) can be obtained, and the productivity of nickel-containing hydroxide, which is the target product in nickel smelting by the "HPAL process", can be improved. Effect of the Invention

[0018] According to the present invention, it is possible to effectively utilize ores containing high concentrations of Mg, such as saprolite ore, which has not been actively used in the past in hydrometallurgical nickel smelting. [Brief description of the drawings]

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

[0020] Hereinafter, specific embodiments of the "hydrometallurgical method for producing nickel oxide ore" of the present invention will be described in detail. Note that the present invention is not limited to the following embodiments, and various modifications are possible without departing from the gist of the present invention.

[0021] <Hydrometallurgy method for nickel oxide ore> FIG. 1 shows an example of a flow of the entire process of the hydrometallurgy of nickel oxide ore that can be performed by the "hydrometallurgy method for nickel oxide ore" (hereinafter, also simply referred to as "hydrometallurgy method for nickel oxide ore") of the present invention. The "hydrometallurgy method for nickel oxide ore" is a composite process in which 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 MgCO3 from Mg contained in magnesium-containing ore (also referred to as "high magnesium ore" in this specification) having a magnesium concentration exceeding 5 mass%, which was difficult to utilize in conventional hydrometallurgy processes, are performed in parallel. In addition, the "hydrometallurgy method for nickel oxide ore" is mainly characterized as an entire process in that MgCO3 produced from the "high magnesium ore" in the second step S2 is utilized as a neutralizing agent in the first step S1.

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

[0023] Furthermore, by going through 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 sulfurizing agent is added to the neutralization end liquid obtained in the neutralization step S13, or a hydroxide step S15 in which a neutralizing agent is added to the neutralization end liquid, can be performed, and a nickel-containing sulfide or nickel-containing hydroxide can be produced by each step.

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

[0025] In addition, for example, when "nickel oxide ore" having a high magnesium concentration, such as "saprolite ore", is used as the "high-magnesium ore" in the second step S2, the slurry, which is the residue after MgCO3 is recovered in the carbonate recovery step S23 of the second step S2, can be charged into the leaching step S11 as "nickel oxide ore slurry" with a reduced Mg concentration.

[0026] (Solid-liquid separation process) The solid-liquid separation step S12 is a step in which the leaching slurry that has been subjected to the leaching step S11 is washed in multiple stages to separate a leaching solution containing nickel (Ni), cobalt (Co) and other impurity elements from a leaching residue. The solid-liquid separation step S12 can be performed, for example, by mixing the leaching 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 process) The neutralization step S13 is a step of adjusting the pH of the leachate separated in the solid-liquid separation step S12, separating impurity elements as neutralized precipitates, and obtaining 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 obtained neutralized end solution is 4 or less, preferably 3.0 to 3.5, 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 the neutralization step S13, impurities are removed as neutralized precipitates in this way, and a neutralized end solution that becomes a mother liquor for nickel recovery is produced.

[0028] As the neutralizing agent used in the neutralization step of a general nickel oxide ore hydrometallurgy process, various alkaline earth metal carbonates such as calcium carbonate and MgCO3 can be preferably used. The above-mentioned various neutralizing agents can also be used in the neutralization step S13 of the first step S1 of the "nickel oxide ore hydrometallurgy process" of the present invention, but in the neutralization step S13, MgCO3 generated in the carbonate generation step S22 of the second step S2 is used as at least a part of the neutralizing agent used in the neutralization step S13. In the "nickel oxide ore hydrometallurgy process" of the present invention, it is preferable that 5% or more of the total amount of the neutralizing agent used in the neutralization step S13 is MgCO3 generated in the carbonate generation step S22 of the second step S2, and it is most preferable that the total amount of the neutralizing agent used (100%) is MgCO3.

[0029] In addition, the neutralization reaction that proceeds when MgCO3 is added as a neutralizing agent in the neutralization step S13 as described above is, for example, as shown in the following (formula 1), and iron (Fe) and the like in the solution are removed as a neutralized precipitate slurry. (Formula 1) Fe2(SO4)3+3MgCO3+H2O→3MgSO4(aq)+2FeOOH↓+3CO2↑

[0030] (Sulfurization process) 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 the like have been removed in the neutralization step S13, and further separating the mother liquor into nickel-containing sulfides and poor liquor. In the sulfurization step S14, a sulfurizing agent is blown into the neutralization end liquor, which is the mother liquor for nickel recovery, to cause a sulfurization reaction and generate nickel-containing sulfides and poor liquor. Examples of the sulfurizing agent that can be used in the sulfurization step S14 include hydrogen sulfide, sodium hydrogen sulfide, and sodium sulfide. Among these, hydrogen sulfide is particularly preferably used. The "hydrometallurgical method for nickel oxide ore" of the present invention can produce nickel-containing sulfides, which are the target product, by further carrying out the sulfurization step S14. In other words, the process including the above three steps (leaching step S11, solid-liquid separation step S12, and neutralization step S13) and the sulfurization step S14 is, in other words, the "method for producing nickel-containing sulfides" of the present invention.

[0031] Nickel-containing sulfides are generally called MS (Mixed Sulfide) and refer to nickel-cobalt mixed sulfides. Specifically, they contain 50% to 60% Ni, 0.1% to 26% Co, and about 0.1% to 2% Fe and other impurities. These nickel-containing sulfides can be electrolytically won through chlorine leaching, or nickel sulfate after purification, or nickel powder or nickel briquettes can be produced through ammonia leaching and hydrogen reduction. The nickel-containing sulfides produced by the "method for producing nickel-containing sulfides" of the present invention can be produced as final products such as nickel sulfate, electrolytic nickel, nickel powder, and nickel briquettes by these existing methods.

[0032] (Hydroxylation process) As described above, the hydroxide step S15 is a step of adding a neutralizing agent to the mother liquor for nickel recovery from which Fe and the like have been removed in the neutralization step, and further separating the mother liquor into nickel-containing hydroxide and poor liquor. Examples of neutralizing agents that can be used in the hydroxide step S15 include calcium carbonate, calcium hydroxide, magnesium hydroxide, sodium hydroxide, quicklime, magnesium oxide, and the like. Among these, magnesium hydroxide and magnesium oxide are particularly preferably used. In the hydroxide step S15, a neutralizing agent such as MgO is added to the neutralization end liquor, which is the mother liquor for nickel recovery, and a hydrolysis reaction, for example, as exemplified by the following formulas (2) and (3), is allowed to proceed, thereby producing nickel-containing hydroxide and poor liquor. In the "wet smelting method for nickel oxide ore" of the present invention, the hydroxide step S15 is further performed to produce the nickel-containing hydroxide, which is the target product. That is, the process including the above three steps (the leaching step S11, the solid-liquid separation step S12, and the neutralization step S13) and this hydroxide step S15 is the "method for producing a nickel-containing hydroxide" of the present invention. (Formula 2) NiSO4(aq)+MgO(s)+H2O(l)=MgSO4(aq)+Ni(OH)2(s) (Formula 3) CoSO4(aq)+MgO(s)+H2O(l)=MgSO4(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 or more and 50% by mass or less of Ni, 0.05% by mass or more and 10% by mass or less of CO, and about 0.01% by mass or more and 10% by mass or less of impurities such as Mg, manganese (Mn), Al, and Fe. These nickel-containing hydroxides can be made into electric nickel by electrowinning through dissolution and purification. The nickel-containing hydroxide produced by the present invention can be made into a final product such as electric nickel by these existing methods.

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

[0035] [Second process] The second step S2 is a step of producing MgCO3 that can be used in the first step S1 from Mg contained in "high magnesium ore" that was difficult to use in the conventional hydrometallurgical process. As shown in FIG. 1, in the second step S2, the elution improvement treatment step S21 and the carbonate formation step S22 are performed in sequence as essential steps. In addition, the generated carbonate may be recovered by the carbonate recovery step S23, for example. However, the carbonate recovery step S23 is not an essential step in the "hydrometallurgical method for nickel oxide ore" of the present invention. If the magnesium carbonate generated in the carbonate formation step S22 of the second step S2 is used as a neutralizing agent in the neutralization step S13 of the first step S1, it is possible to carry out the present invention regardless of whether or not the carbonate recovery step S23, i.e., the separation and recovery process of the generated carbonate and the solution, which will be described in detail below, is performed, and such an embodiment is naturally within the technical scope of the present invention.

[0036] In the "hydrometallurgical method for 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" is charged only in the second step S2, and even if a portion 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 carried out in parallel.

[0037] In the "hydrometallurgical smelting method for nickel oxide ore" of the present invention, ores other than "nickel oxide ore" having a magnesium concentration of more than 5 mass% can also be used as a material ore for generating MgCO3 in the second step S2. 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 usually used as a raw material ore for nickel smelting. By carrying out the present invention in such an embodiment 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, the residue after MgCO3 is recovered, "nickel oxide ore slurry having a low magnesium concentration" derived from the above-mentioned "nickel oxide ore having a high magnesium concentration", can be charged into the leaching step S11 and effectively utilized.

[0038] In addition, examples of ores that can be used as "high magnesium ore" in the second step S2 and 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] Here, in the "high magnesium ore" that can be used in the second step S2, most of the Mg is contained as silicate minerals (such as magnesium silicate (Mg3Si2O5(OH)4)). Magnesium silicate has a three-dimensional complex crystal structure, and since Mg is present at the center, it is difficult for Mg to dissolve from the magnesium silicate into the solution. Therefore, in the "method for hydrometallurgy of nickel oxide ore" of the present invention, in the second step S2, first, a leaching improvement treatment step S21, which will be described in detail below, is set as an essential step 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] Among the above-mentioned "high magnesium ores", ores containing Mg as magnesium silicate and having a mass ratio (Mg / Si) of Mg to Si in the ore of 0.5 or more can be particularly preferably used. Ores having the ratio of 1.0 or more can be more preferably used. If the Mg / Si ratio is 0.5 or more, more Mg can be eluted into the solution after the elution improvement treatment. In addition, compounds having a large amount of Si relative to Mg tend to have a complex crystal structure, making it difficult for Mg to be eluted. The content (mass) of Si in the "alkaline earth metal-containing ore" can be specified by a method in which 2.5 g each of sodium peroxide and sodium carbonate are mixed with 0.5 g of ore, the mixture is heated and melted in an electric furnace to 800°C, cooled, and then leached with hydrochloric acid, and the sample is measured by ICP emission spectrometry. Similarly, the magnesium concentration (mass) in "alkaline earth metal-containing ore" can be determined by leaching 0.5 g of the ore in hydrochloric acid and measuring it using ICP atomic emission spectrometry.

[0041] (Elution improvement treatment process) As described above, the elution property improvement process S21 is a process for changing the crystal structure of the "high magnesium ore" which has a complex crystal structure and tends to make Mg difficult to elute, thereby improving the elution property of Mg from the "high magnesium ore" into a solution. The specific process for improving the elution property is not limited to a specific process, and any process method, whether known or not, can be used. As a conventionally known process for improving the elution property, as disclosed in JP-A-10-249153 and JP-T-2012-500718, a process for burning the "high magnesium ore" or a process for crushing the "high magnesium ore" into fine particles and then heating the same can be mentioned. In this way, the elution property of Mg from the "high magnesium ore" into a solution can be improved by changing the crystal structure of the "high magnesium ore" by dehydration or the like. It is preferable to use water as the above-mentioned solution used when 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 of the "elution property improvement treatment" is preferably 500° C. to 800° C. (furnace atmosphere temperature), more preferably 600° C. to 750° C., 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] In the "hydrometallurgical method for nickel oxide ore" of the present invention, the "high-magnesium ore" may be pulverized to a particle size of about 300 μm or less as a pretreatment before being charged into the elution property improvement treatment step S21, from the viewpoint of ease of handling. The "high-magnesium ore" may be pulverized by any common method, and specific examples include pulverization using a rod mill or a ball mill. However, the particle size of the "alkaline earth metal-containing ore" does not have a significant effect on the elution property of the alkaline earth metal.

[0044] Here, Table 1 below shows the results of a "magnesium elution test" conducted on nickel oxide ore (saprolite ore: particle size 150 μm to 300 μm) with a magnesium concentration of 6 mass% or more as a specific example of "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] This "magnesium elution test" was carried out by putting 5 g of the above "high magnesium ore (nickel oxide ore)" with different heating conditions during the above "elution improvement treatment" into 200 mL of solution (pure water at 60°C) and stirring for 2 hours at a rotation speed of 450 rpm while blowing CO2 gas (manufactured by Takamatsu Teisan Co., Ltd., concentration 99.995 vol.%) into the solution at a blowing rate of 0.1 L / min. The magnesium elution rate (%) in Table 1 was measured and calculated after the above 2 hours of stirring using the "Method for measuring the amount of eluted magnesium and the method for calculating the elution rate" described below. (Method of measuring amount of magnesium elution and method of calculating 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)) The magnesium concentrations were all measured by ICP emission spectrometry.

[0046] The results of this "magnesium elution test" showed that without the "elution improvement treatment" by firing, the magnesium elution rate was 1.8%. It was also found that the "elution improvement treatment" at a heating temperature of 600°C, which is above 500°C, could sufficiently improve the magnesium elution rate to 32.0%. It was also confirmed that at a heating temperature of 900°C, which exceeds 800°C, the magnesium elution rate drops to 2.0%. The reason why the magnesium elution rate drops when heated to 900°C is thought to be because magnesium silicate (Mg3Si2O5(OH)4), whose complex crystal structure is destroyed by heating, recrystallizes in the form of Mg2SiO4.

[0047] [Table 1]

[0048] Whether the complex crystal structure of the minerals contained in the "high magnesium ore" has been actually sufficiently broken down and made amorphous (i.e., whether the elution property has been improved) can be determined by confirming the peak of the (002) plane of lizardite (Mg3SiO5(OH)4) through XRD analysis. As an apparatus for performing XRD analysis, for example, an X-ray diffractometer "Empyrean (manufactured by Malvern Instruments)" can be suitably used.

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

[0050] The embodiment of the above-mentioned "mechanochemical treatment" is not limited to a specific treatment method, and can be carried out by 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. In addition, the above-mentioned "mechanochemical treatment" can also be carried out using various other known or unknown stirring or kneading devices that can exert the same action and effect as these.

[0051] Incidentally, the "mechanochemical treatment" is different from the general "pulverization treatment" in that it is not a treatment aimed at reducing particle size. Even when the "mechanochemical treatment" is carried out, the particle size of each particle may be reduced by the destruction of the ore to be treated during the treatment, but the purpose of the "mechanochemical treatment" is to make the ore amorphous by reducing the crystallinity (change (destruction) of the structure). Therefore, it is a new treatment method with a different purpose and effect from the pulverization treatment for particle size adjustment carried out to increase the specific surface area of ​​the object to be treated as a pretreatment preceding the conventional amorphization treatment that reduces the crystallinity by heat treatment. Figure 2 shows the change in particle size distribution of the "high magnesium ore" when the "mechanochemical treatment" is carried out, but since the particle size distribution shown in the figure has hardly changed, it can be understood that the "mechanochemical treatment" that can be a means for carrying out the elution improvement treatment step S21 in the present invention is a new treatment method different from the general "pulverization treatment" aimed at adjusting the particle size distribution.

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

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

[0054] From Figure 3, it was confirmed that the peak of the (002) plane of lizardite (Mg3Si2O5(OH)4) in each sample (ore) was reduced by the mechanochemical treatment. This indicates that the crystallinity of the ore sample was changed.

[0055] Furthermore, Table 2 below shows the results of a "dissolution promotion 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 amorphous treatment under the following (Test Condition 2), 5 g of each "ore sample" after the treatment was placed in 200 mL of solution (pure water at 60°C), and while stirring at a rotation speed of 450 rpm, CO2 gas (manufactured by Takamatsu Teisan Co., Ltd., concentration 99.995% by volume) was blown into the solution at a rate of 0.1 L / min, and the elution rate of Mg or Ca into the solution was measured and calculated according to the "Method for measuring the amount of elution 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 each of the "ore samples," 50 g of each "ore sample" and 300 g of zirconia balls (diameter 10 mm) as grinding media were placed in the same planetary ball mill as in the above "amorphization treatment test," and mechanochemical amorphization treatment was performed. However, the table rotation speed of the planetary ball mill was 300 rpm, and the treatment time was the treatment time shown in Table 2 below. (Method of measuring the amount of eluted alkaline earth metal (Mg) and method of 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)) The magnesium concentrations were all measured by ICP emission spectrometry.

[0056] [Table 2]

[0057] From the above, it was confirmed that the dissolution of Mg from magnesium silicate in the ore was improved by carrying out the mechanochemical amorphization treatment as described above. The effect of the mechanochemical amorphization treatment is due to a uniquely discovered new method, but it is believed that the effect is due to the fact that the crystal structure of the alkaline earth metal-containing mineral in the alkaline earth metal-containing ore is changed by the mechanical stress applied from the outside, making it easier for the alkaline earth metal to dissolve into the solution. Therefore, the effect of the mechanochemical treatment is not limited to stirring or kneading by a ball mill, but is also considered to be an effect that is expressed when similar treatment is carried out 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 inventors.

[0059] (Carbonate generation process) The carbonate production process S22 is a process in which Mg is sufficiently dissolved into solution from the "high-magnesium ore" whose elution ability into solution has been improved through the elution improvement treatment process S21, CO2 gas is blown into the solution, and MgCO3 is precipitated and produced by reacting the dissolved Mg with the CO2 blown in as gas in the solution (hereinafter also referred to as the "carbonate production process").

[0060] The ratio of "high magnesium ore" to the solution from 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 "high magnesium ore" in the solution 2% by mass or more, high precipitation efficiency of MgCO3 can be achieved. In addition, by making the amount (mass ratio) 30% by mass or less, the viscosity of the above-mentioned solution that becomes a slurry can be appropriately maintained, and the handleability of the slurry material is improved.

[0061] The method of blowing CO2 gas into the solution is not particularly limited, but as an example, it can be performed by blowing CO2 gas using a disk-type diffuser, a cylindrical diffuser, or the like. The CO2 concentration of the CO2 gas blown into the solution may be 10% or more. However, by using a higher concentration of CO2 gas exceeding 10%, the production of MgCO3 can be promoted more efficiently.

[0062] Incidentally, the source and method of supplying the CO2 used in the carbonate production process S22 are not particularly limited. However, in the neutralization process S13 of the first process S1, CO2 gas generated in a neutralization process using a neutralizing agent derived from fossil fuels or carbonates can be used, which can contribute to reducing the total amount of CO2 gas emissions from the nickel smelting plant.

[0063] (Carbonate recovery process) The carbonate recovery step S23 is a process for recovering the MgCO3 generated in the carbonate generation step S22 from the solution. The specific method for recovering this MgCO3 is not particularly limited, but as an example, it may be a method of recovering the MgCO3 by separating the liquid using a filter such as a filter press, or a method of recovering the MgCO3 by volatilizing the water in the solution.

[0064] [Other processes] In the "hydrometallurgical method for nickel oxide ore" of the present invention, in addition to the above-mentioned 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 (elution property improvement treatment step S21, carbonate formation step S22, and carbonate recovery step S23), an embodiment may be implemented in which an ore sieving step is performed as a step upstream of the leaching step S11 and the elution property improvement treatment step S21. In addition, it is preferable to further perform a final neutralization step as a step downstream of the sulfurization step S14 in the first step S1. Each of these steps is not necessarily an essential step in the "hydrometallurgical method for nickel oxide ore" of the present invention. Regardless of whether or not each of these steps is performed, or regardless of the embodiment of each of these steps, any smelting process that performs the above-mentioned 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 screening process) When using a raw ore consisting of a mixture of multiple types of nickel oxide ores with different magnesium concentrations, it is preferable to carry out an ore screening process in which the raw ore is screened into coarse ore and fine ore prior to the second process S2. When the ore screening process is carried out, the coarse ore screened into the coarse part is regarded as "high magnesium ore" and charged into the second process S2, and the subsequent processes are carried out. On the other hand, the fine ore screened into the fine part in this ore screening process can be charged into the leaching process S11 without passing through the second process S2.

[0066] When the ore sieving step is performed, specifically, the sieving is preferably performed in such a manner that the portion in which the ratio of particles having a particle diameter of less than 45 μm is 40 mass% or less in the solid content is sieved to the coarse particle portion side, and the remaining portion is sieved to the fine particle portion side. By treating the portion sieved to the coarse particle portion side in this way as coarse particle ore and as "high magnesium ore", a portion containing relatively high Mg concentration is separated from the raw ore in which multiple types of nickel oxide ores with different magnesium concentrations are mixed, and charged into the second step S2, the effect of the "hydrometallurgical method for nickel oxide ore" of the present invention can be enjoyed.

[0067] (Final neutralization step) The final neutralization step is a step of performing a neutralization process (detoxification process) on the poor liquid containing impurity elements such as Fe, Mg, and Mn discharged in the sulfurization step S14 to adjust the pH to a predetermined range that meets the discharge standard. The method of detoxification process in the final neutralization step, i.e., the method of adjusting the pH, is not particularly limited, but for example, a calcium carbonate (limestone) slurry, a calcium hydroxide (slaked lime) slurry, or, as described above, MgCO3 separated and recovered in the second step S2 can be added as a neutralizing agent to adjust the pH to a predetermined range. In addition, although not shown, this final neutralization step can also be performed using MgCO3 as a neutralizing agent, similar to the neutralization step S13 in the present invention. This process is also one of the neutralization steps in that it is a process of separating neutralized precipitate to obtain a neutralized final liquid. Therefore, an embodiment in which MgCO3 generated in the carbonate generation step S22 is used as the neutralizing agent used in this final neutralization step is naturally within the technical scope of the present invention.

[0068] [Characteristics of the overall process] The overall process of the "hydrometallurgical method for nickel oxide ore" consisting of the above steps is characterized in that, first, MgCO3 generated in the carbonate generation step S22 of the second step S2 is utilized as a neutralizing agent used in the neutralization step S13 of the first step S1. As a second characteristic, in the "hydrometallurgical method for nickel oxide ore", CO2 gas generated in the smelting plant can be utilized as CO2 used to generate MgCO3 in the carbonate generation step S22 of the second step S2. Furthermore, as a third characteristic, in the "hydrometallurgical method for nickel oxide ore", nickel oxide ore slurry, which is the residue (of "high magnesium ore") after MgCO3 is recovered in the carbonate recovery step S23 of the second step S2, can be charged as a raw material that has been treated to reduce the magnesium concentration in the leaching step S11 of the first step S1. The "nickel oxide ore hydrometallurgy method" is a composite process in which the first step S1 and the second step S2 are performed in parallel, making it possible to effectively utilize "high magnesium ore," which was difficult to utilize in conventional hydrometallurgy processes. In addition to being able to effectively utilize ore that was previously unused, it is also possible to enjoy the additional effects of reducing the amount of neutralizing agent used and reducing CO2 emissions throughout the process. Furthermore, the magnesium carbonate production process carried out in the "nickel oxide ore hydrometallurgy method" of the present invention is also an excellent technology as a method for fixing CO2 in minerals. In other words, the "nickel oxide ore hydrometallurgy method" of the present invention is also a suitable process for specifically implementing the "mineral carbonation technology," which is one of the "carbon sequestration and utilization technologies (CCSU)." [Explanation of symbols]

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

Claims

1. a leaching step of leaching the nickel oxide ore with a mineral acid to obtain a leach slurry; a solid-liquid separation step of separating the leaching slurry into a leachate and a leach residue; a neutralization step of separating a neutralized precipitate from the leaching solution to obtain a neutralization end solution; A first step in which a leaching improvement treatment step for improving the leaching of magnesium by changing the crystal structure of a magnesium-containing ore having a magnesium concentration of more than 5% by mass; a carbonate production step in which the magnesium-containing ore that has been subjected to the elution improvement treatment step is put into a solution, and the magnesium eluted into the solution is reacted with carbon dioxide to produce magnesium carbonate; A second step in which having 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. A hydrometallurgical process for nickel oxide ores.

2. 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.

2. The method for hydrometallurgy of nickel oxide ore according to claim 1.

3. A sulfurizing agent is added to the neutralization end solution obtained in the neutralization step of the hydrometallurgical method for producing nickel oxide ore according to claim 1 or 2 to generate nickel-containing sulfide. A method for producing nickel-containing sulfides.

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

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