Process for producing a sulfide and process for smelting nickel

Abstract

Provided is a method for treating nickel oxide ore that enables efficient recovery of nickel as a recovery target. A method for producing a sulfide, which is a method for producing a sulfide from nickel oxide ore, includes: a mixing process in which nickel oxide ore and a reducing agent are mixed to obtain a mixture; a reduction process in which the mixture is charged into a reduction furnace and subjected to reduction treatment to obtain a reduction product including a metal that is a ferro-nickel and a slag that is an oxide; a separation process in which the metal and the slag are separated from the reduction product; and a sulfidation process in which a sulfidation agent is added to the metal obtained in the separation process to obtain a sulfide containing nickel.

Description

Technical Field

[0001] This invention relates to a method for producing sulfides from nickel oxide ores and a method for smelting nickel. Background Technology

[0002] Known methods for smelting nickel from nickel oxide ores known as limonite or sapropel include: dry smelting methods that produce nickel matte by sulfidation roasting with sulfur in a smelting furnace; dry smelting methods that produce iron-nickel alloys (hereinafter also referred to as "iron-nickel") by reduction using a rotary kiln or moving bed furnace and a reducing agent; and wet smelting methods that produce mixed sulfides by adding a sulfiding agent to the leachate obtained by leaching nickel and cobalt in an autoclave with sulfuric acid.

[0003] For example, Patent Document 1 describes a method for recovering valuables from metal sulfides containing precious metals. The method involves using sulfuric acid in a specified amount relative to nickel to oxidize metal sulfide matte with nickel and copper as the main components, selectively leaching nickel for separation, and concentrating the precious metals together with copper sulfides in the leaching residue.

[0004] Patent document 1 describes a method for recovering valuable materials that can effectively utilize existing copper smelting equipment to efficiently recover valuable components.

[0005] On the other hand, easily processed ores are becoming increasingly scarce, and the reduction in nickel grade and the increase in smelting costs due to high MgO content in ores are gradually reaching their limits in existing smelting technologies. Against this backdrop, there is a need for technologies to recover valuable metals such as nickel from ores that cannot be processed using existing technologies.

[0006] If valuable metals such as nickel are recovered from low-grade nickel oxide ores with high impurity content using existing technologies, the cost of recovering these valuable metals increases. For example, in dry smelting methods that use a smelting furnace to roast nickel matte with sulfur, if the Ni grade is less than a few percent, the melting energy of the slag becomes very high, and the sulfidation efficiency decreases, making it uneconomical. In smelting methods using rotary kilns, if the nickel grade in the ore is, for example, below 1.5% by mass, the proportion of slag becomes higher, and the corresponding heating energy becomes enormous, making it uneconomical. Furthermore, in the Elkem process using electric furnaces, if the Ni grade decreases, the energy required to melt the slag becomes correspondingly large, resulting in a cost mismatch. In wet processing using autoclaves, for example, if the MgO content in the ore exceeds 2% by mass, the cost of reagents such as sulfuric acid becomes enormous, making it unprofitable.

[0007] Therefore, there is a need for processing methods for nickel oxide ores that can efficiently recover valuable metals from low-grade oxide ores.

[0008] Existing technical documents

[0009] Patent documents

[0010] Patent document 1: Japanese Patent Application Publication No. 2009-97076. Summary of the Invention

[0011] The problem that the invention aims to solve

[0012] The purpose of this invention is to provide a method for efficiently recovering nickel oxide ore, which is the target of recovery.

[0013] Methods for solving problems

[0014] The inventors conducted in-depth research to solve the aforementioned problems. The results showed that by adding a sulfiding agent to a metal obtained through reduction treatment of a mixture containing oxide ore and a reducing agent to produce sulfides, the aforementioned problems could be solved, thus completing this invention.

[0015] The first invention is a method for manufacturing sulfides, which is a method for manufacturing sulfides from nickel oxide ore, comprising: a mixing process step of mixing nickel oxide ore and a reducing agent to obtain a mixture; a reduction process step of loading the mixture into a reduction furnace and performing reduction treatment on the mixture to obtain a reduced product containing a metal as an iron-nickel metal and slag as an oxide; a separation process step of separating the metal and the slag from the reduced product; and a sulfidation process step of adding a sulfiding agent to the metal obtained in the separation process to obtain a sulfide containing nickel.

[0016] The second invention is that in the sulfide manufacturing method of the first invention, in the aforementioned sulfidation process, the aforementioned metal is melted using a melting furnace with a burner, and a sulfiding agent is added to the molten metal, thereby forming a sulfide layer between the molten metal and the gas phase.

[0017] The third invention is that in the method for manufacturing sulfides of the first invention, in the aforementioned sulfidation process, an electric arc furnace is used to melt the aforementioned metal and a sulfiding agent is added to the molten metal.

[0018] The fourth invention is that in the method for manufacturing sulfides in the second invention, in the aforementioned sulfidation process, one or more fuels selected from charcoal, coke and natural gas are used as fuels for the aforementioned burner.

[0019] The fifth invention is that in the method for manufacturing a sulfide of any one of the first to third inventions, solid sulfur or sulfur gas is used as a sulfiding agent in the aforementioned sulfidation process.

[0020] The sixth invention is a method for manufacturing sulfides in any one of the first to third inventions, wherein in the aforementioned reduction step, the aforementioned mixture is loaded into a reduction furnace, the mixture is subjected to reduction treatment to obtain iron-nickel metal, and the iron-nickel metal is supplied to the aforementioned sulfidation step.

[0021] The seventh invention is a nickel smelting method comprising: a mixing process of mixing nickel oxide ore and a reducing agent to obtain a mixture; a reduction process of charging the mixture into a reduction furnace and subjecting the mixture to reduction treatment to obtain a reduced product containing a metal as an iron-nickel metal and slag as an oxide; a separation process of separating the metal and the slag from the reduced product; a sulfidation process of adding a sulfiding agent to the metal obtained in the separation process to obtain a sulfide; and a wet process of obtaining a leachate from the sulfide obtained in the sulfidation process.

[0022] Invention Effects

[0023] According to the method for manufacturing sulfides of the present invention, nickel can be recovered efficiently. Attached Figure Description

[0024] Figure 1 This is a process diagram illustrating an example of a method for manufacturing sulfides.

[0025] Figure 2 This is a top view showing an example of the configuration of a reduction furnace (rotary hearth furnace). Detailed Implementation

[0026] The specific embodiments of the present invention will now be described in detail. It should be noted that the present invention is not limited to the following embodiments, and various modifications can be made without altering the spirit of the invention. Furthermore, in this specification, the expression "X~Y" (where X and Y are arbitrary values) means "X or more and Y or less".

[0027] 1. Summary of the Invention

[0028] The method for manufacturing sulfides according to the present invention is characterized by comprising: a mixing process in which nickel oxide ore and a reducing agent are mixed to obtain a mixture; a reduction process in which the mixture is loaded into a reduction furnace and subjected to reduction treatment; and a sulfidation process in which a sulfiding agent is added to the metal obtained in the reduction process to obtain a sulfide.

[0029] In this way, by mixing oxide ore and reducing agent to obtain a mixture, and by reducing the mixture to obtain metal, sulfide is obtained to obtain sulfide, thereby enabling the efficient recovery of valuable metals.

[0030] Furthermore, in the sulfidation process of sulfiding the metal obtained through reduction treatment, a molten furnace utilizing a burner can be used to melt the metal, and a sulfiding agent can be added to the molten metal. By using a molten furnace utilizing a burner to melt the metal and adding a sulfiding agent to the molten metal, metals containing different metals from nickel, such as iron, can be separated, enabling more efficient nickel recovery.

[0031] Furthermore, in the sulfidation process of sulfiding the metal obtained through reduction treatment, an electric arc furnace can be used to melt the aforementioned metal, and a sulfiding agent can be added to the molten metal. By using an electric arc furnace to melt the metal and adding a sulfiding agent to the molten metal, metals containing different metals from nickel, such as iron, can be separated, enabling more efficient recovery of valuable metals.

[0032] It should be noted that the nickel contained in the sulfide, which is the object of recycling, can be recovered, for example, by feeding the sulfide into a wet process.

[0033] 2. Methods for manufacturing sulfides

[0034] Hereinafter, as a specific embodiment of the present invention (hereinafter referred to as "this embodiment"), a method for manufacturing sulfides by using nickel oxide ore as raw material ore and producing sulfides from nickel oxide ore will be described as an example.

[0035] Specifically, such as Figure 1 As shown, the method for manufacturing sulfides in this embodiment includes: a mixing process S1, in which nickel oxide ore and a reducing agent are mixed to obtain a mixture; a mixture forming process S2, in which the obtained mixture is formed into a predetermined shape to produce granules (blocks); a reduction process S3, in which the mixture is loaded into a reduction furnace and subjected to reduction treatment; a separation process S4, in which slag is separated from the obtained reduced product to obtain an iron-nickel alloy (iron-nickel metal); and a sulfidation process S5, in which a sulfiding agent is added to the iron-nickel metal to obtain sulfides.

[0036] <2-1. Mixing Process>

[0037] In the mixing process S1, raw material powder containing nickel oxide ore is mixed to obtain a mixture. Specifically, in this mixing process S1, a reducing agent, such as a carbonaceous reducing agent like coal or coke, is added to the nickel oxide ore, which is the raw material ore, and the mixture is then mixed. Additionally, as an additive, powders such as iron ore, fluxing agents, and binders with a particle size of approximately 0.2 mm to 0.8 mm are mixed to obtain the mixture. Here, the mixing of the raw material powder containing nickel oxide ore can be performed using a mixer or similar device.

[0038] There are no particular restrictions on the nickel oxide ore used as raw material; limonite, sapropelite, etc., can be used. For example, the nickel grade in the ore can be less than 1% by mass, and the MgO content can be more than 2% by mass. It should be noted that this nickel oxide ore contains nickel oxide (NiO) and iron oxide (Fe2O3) as constituent components.

[0039] In this embodiment, a mixture is obtained by mixing a specific amount of reducing agent into the raw ore. It should be noted that the reducing agent is preferably of the same particle size and particle size distribution as the nickel oxide ore used as the raw ore. By ensuring that the particle size and particle size distribution are similar, uniform mixing is easily achieved, and the reduction reaction occurs uniformly, which is therefore preferable.

[0040] The amount of reducing agent mixed in, i.e., the amount of reducing agent contained in the particles through molding, is preferably 50.0% by mass or less, more preferably 40.0% by mass or less, when the amount of reducing agent required to just reduce the nickel oxide and iron oxide constituting the nickel oxide ore is set to 100% by mass. It should be noted that the amount of reducing agent required to just reduce the nickel oxide and iron oxide can be expressed in other words as the total chemical equivalent required to reduce the total amount of nickel oxide contained in the particles to nickel metal and the total chemical equivalent required to reduce the iron oxide contained in the particles to iron metal (hereinafter also referred to as the "total chemical equivalent").

[0041] Thus, when the total chemical equivalent is set to 100% by mass, the amount of reducing agent contained in the mixture (the amount of reducing agent mixed) is set to a proportion of 50.0% by mass or less, thereby enabling the reduction reaction to proceed efficiently.

[0042] It should be noted that there is no particular limitation on the lower limit of the mixing amount of the reducing agent. When the total stoichiometric amount is set to 100% by mass, it is preferable to set it to a proportion of 20.0% by mass or more, and more preferably to a proportion of 23.0% by mass or more. In this way, by setting the mixing amount of the reducing agent to 20.0% by mass or more, it is easy to manufacture iron-nickel alloys with high nickel content.

[0043] Besides nickel oxide ore and reducing agent, iron ore can be added as an additive as any component without any particular restrictions. For example, iron ore with an iron content of about 50% by mass or more, or hematite obtained by wet smelting of nickel oxide ore can be used.

[0044] In addition, examples of binders include bentonite, polysaccharides, resins, water glass, and dehydrated filter cake. Examples of fluxing agents include calcium oxide, calcium hydroxide, calcium carbonate, and silicon dioxide.

[0045] Table 1 below shows an example of the composition (mass %) of a portion of the raw material powder mixed in the mixing process S1. It should be noted that the composition of the raw material powder is not limited to this.

[0046] [Table 1]

[0047] When mixing raw material powders to obtain a mixture, the raw material powders can be kneaded to improve mixability. This applies shear force to the mixture, breaking down the agglomeration of the carbon reducing agent, raw material powders, etc., allowing for more uniform mixing. Furthermore, the density of individual particles is improved, thus facilitating uniform reduction processing.

[0048] <2-2. Mixture Forming Process>

[0049] In the mixture forming step S2, the mixture of raw material powders obtained in the mixing process S1 is formed and dried as needed to obtain granules. The mixture forming step S2 may include: a block forming process S21 that forms the mixture of raw materials containing nickel oxide ore into blocks; and a drying process S22 that dries the obtained blocks.

[0050] (1) Block forming process

[0051] In the block forming process S21, the mixture of raw materials containing nickel oxide ore obtained in the mixing process S1 is formed into blocks of a specified shape and size.

[0052] The shape of the mixture, i.e., the shape of the particles, can be any shape that can be stacked on the hearth of the reduction furnace, preferably elliptical, cubic, cuboid, cylindrical, or spherical. By shaping the mixture into such a shape, the molding process becomes easier, thus reducing molding costs. Furthermore, since the molded shape is not complex, the occurrence of poorly molded particles can be reduced.

[0053] In the block forming process S21, for example, a pelletizing device can be used to form the mixture. The pelletizing device is not particularly limited, but a device capable of mixing and forming the mixture under high pressure and high shear force is preferred. By mixing the mixture under high pressure and high shear, the agglomeration of the raw material powder mixture can be de-agglomerated, and the mixing can be carried out effectively, thereby improving the strength of the resulting granules.

[0054] Alternatively, a briquetting machine can be used for molding. The appropriate equipment should be selected based on factors such as the type of equipment, particle strength, and yield.

[0055] (2) Drying process

[0056] The drying process S22 is a process of drying the particles obtained in the granulation process S21. Here, the particles obtained by the granulation process contain an excess of, for example, about 50% by mass of moisture. Therefore, if the particles containing excess moisture are rapidly heated to the reduction temperature, the moisture may vaporize and expand at once, thus destroying the particles.

[0057] Therefore, by drying the obtained particles, for example, reducing the solid content to approximately 70% by mass and the moisture content to approximately 30% by mass, particle disintegration can be prevented during the reduction heating treatment in the subsequent reduction step S3, thus preventing difficulty in removing them from the reduction furnace. Furthermore, since the particles are often sticky due to excess moisture, drying them makes processing easier.

[0058] Specifically, the drying process for particles in drying step S22 is not particularly limited; for example, hot air at 200°C to 400°C is blown onto the block to dry it. It should be noted that the particles are difficult to break down when the temperature of the block during this drying process is below 100°C, so this is preferred.

[0059] Here, especially when drying large particles, cracks and fractures can occur in the lumps before and after drying. When the particles are large, they melt and shrink during reduction, thus increasing the likelihood of cracks and fractures. However, the increase in surface area due to cracks and fractures is minimal when the particles are large, making it difficult to cause significant problems. Therefore, particles can have cracks and fractures before reduction.

[0060] It should be noted that, in the process of forming particle stacks in the reduction furnace and in the reduction heating process, as long as the particles are not damaged, the drying process in the drying process S22 can be omitted.

[0061] Table 2 below shows an example of the composition (mass %) of the solids in the dried particles. It should be noted that the composition of the particles is not limited to this.

[0062] [Table 2]

[0063] <2-3. Reduction Process>

[0064] In reduction step S3, the particles obtained in mixture forming step S2 are loaded into a reduction furnace and heated to a specified reduction temperature. Specifically, the obtained particles (mixture) are placed on the hearth of the reduction furnace, and the mixture is subjected to heating and reduction treatment using the reduction furnace. Through the heating and reduction treatment in reduction step S3, a smelting reaction (reduction reaction) occurs based on the reducing agent in the mixture, and iron-nickel metal (hereinafter referred to as "metal") and iron-nickel slag (hereinafter referred to as "slag") are separately generated in the mixture. It should be noted that, for convenience, the particles that are the object of reduction treatment will be referred to as the mixture below.

[0065] It should be noted that, in addition to the method of pre-forming particles outside the reduction furnace and then loading the particles into the reduction furnace for processing, the mixture can also be loaded one by one into the reduction furnace so that the particles are formed inside the reduction furnace.

[0066] In reduction heating processes during heat treatment, for example, within a short period of about one minute, the nickel oxide and iron oxide contained in the particles, which are prone to reduction, are first reduced and metallized near the surface of the particles, becoming an iron-nickel alloy and forming a shell (hereinafter also referred to as "shell"). On the other hand, within the shell, as the shell forms, the slag components in the particles gradually melt to generate liquid-phase slag. Thus, within a single particle, a metal composed of alloys or metals such as iron and nickel (hereinafter referred to as "metal") and slag composed of oxides (hereinafter referred to as "slag") are separately generated.

[0067] Furthermore, if the reduction heat treatment in the heat treatment lasts for about 10 minutes, the carbon components of the remaining carbonaceous reducing agent that do not participate in the reduction reaction are absorbed by the iron-nickel alloy, thus lowering its melting point. As a result, the iron-nickel alloy melts and becomes a liquid phase.

[0068] In this embodiment, the reduced product after the reduction heating treatment becomes a mixture of bulk metal and slag. The separated metal and slag do not mix together; through subsequent cooling, they become a mixture existing as different phases—the metal solid phase and the slag solid phase. Therefore, it is possible to easily separate the metal containing nickel for recovery from the slag that does not substantially contain nickel. Thus, for example, even when using low-grade nickel oxide ore as the smelting target, it is possible to obtain metal with a relatively high nickel concentration.

[0069] It should be noted that the volume of the mixture shrinks to about 50% to 60% of the volume of the particles before the reduction and heating treatment.

[0070] There are no particular limitations on the reduction furnace used in the reduction heating process, but a moving bed furnace is preferred. Using a moving bed furnace as the reduction furnace allows for efficient processing of the mixture. Furthermore, by using a moving bed furnace, the reduction reaction can be carried out continuously, allowing the reaction to be completed in one unit. Compared to using different furnaces for each step, the processing temperature can be reliably controlled. Furthermore, heat loss between processes can be reduced, resulting in more efficient operation. That is, when reacting in different furnaces, the temperature drops and heat loss occurs when the particle stack is moved between furnaces, and the reaction environment changes, so the reaction does not proceed immediately upon reloading. In contrast, by using a moving bed furnace to perform each process in one unit, heat loss can be reduced, and the furnace environment can be reliably controlled, thus allowing for more efficient reaction. Through these advantages, iron-nickel alloys with a high nickel content can be obtained more efficiently.

[0071] As a mobile bed furnace, there are no particular limitations; for example, it can use... Figure 2 The rotary hearth furnace 2 shown is circular and divided into multiple processing chambers 20a to 20d. Within the rotary hearth furnace 2, the furnace rotates in a predetermined direction while processing occurs in each of its respective zones. By controlling the time taken to pass through each zone (movement time, rotation time), the processing temperature in each zone can be adjusted. Each rotation of the rotary hearth furnace smelts the mixture constituting the granular laminate 1. Alternatively, a preheating chamber 21 can be provided outside the rotary hearth furnace 2. The granular laminate 1 moves to the preheating chamber 21 for preheating treatment, and the preheated granular laminate 1 is then sequentially transferred into the rotary hearth furnace 2. Furthermore, a cooling chamber 40 can be provided outside the rotary hearth furnace 2, where the reduced product obtained after passing through processing chambers 20a to 20d is cooled. It should be noted that a moving bed furnace or a roller furnace, etc., can also be used.

[0072] There are no particular restrictions on the heating mechanism of the reduction furnace; it can be a burner or a heating mechanism using electricity, etc. Since a burner can effectively perform heating and reduction treatment on the mixture in a short time, it is preferred. Furthermore, when using a reduction furnace with a burner, fuels such as LPG, LNG, coal, coke, and pulverized coal can be used. These fuels are very inexpensive, and equipment and maintenance costs are significantly lower compared to electric furnaces.

[0073] The temperature used in the reduction process (reduction temperature) is not particularly limited, but it is preferably set to a range of 1250°C or higher and 1450°C or lower, and more preferably to a range of 1300°C or higher and 1400°C or lower. Reduction within this temperature range allows for a uniform reduction reaction, resulting in iron-nickel metal with suppressed quality deviations. Furthermore, it is even more preferable to perform reduction at a temperature within the range of 1300°C or higher and 1400°C, as this allows for a more rapid reduction reaction.

[0074] The processing time (processing time) during the reduction process is set according to the temperature of the reduction furnace, preferably 10 minutes or more, and more preferably 15 minutes or more. On the other hand, from the viewpoint of suppressing the increase in manufacturing costs, the upper limit of the reduction heating process time can be set to 50 minutes or less, or 40 minutes or less.

[0075] It should be noted that the cumulative heat required for reduction, obtained by multiplying the reduction temperature (°C) and reduction time (minutes), is preferably in the range of 20,000 (°C × minutes) or more and 40,000 (°C × minutes) or less. By performing reduction treatment with this heat, high-quality metals can be manufactured efficiently.

[0076] <2-4. Separation Process>

[0077] In separation step S4, the metal and slag generated in reduction step S3 are separated to recover the metal. Specifically, the metal phase is recovered by separating it from a mixture containing a metal phase (metal solid phase) and a slag phase (slag solid phase) obtained by reducing and heating the particles.

[0078] Before proceeding with the separation process of separating the metal and slag from the reducing agent, the molten reducing agent can be cooled within a viscosity range that does not impede the separation of the metal and slag, and the cooled reducing agent is then supplied to the separation process. Cooling of the reducing agent can be achieved by allowing it to cool naturally.

[0079] As a method for separating the metal phase and the slag phase from a mixture of metal phase and slag phase obtained as a solid, in addition to removing unwanted substances by sieving, methods such as gravity-based separation and magnetic force-based separation can be used.

[0080] Furthermore, the resulting metal phase and slag phase have poor wettability and can be easily separated. For the large mixture obtained through the reduction process S3, for example, by setting a specified drop to make it fall, or by applying a specified vibration during screening, the metal phase and slag phase can be easily separated from the mixture.

[0081] This process separates the metallic phase from the slag phase, thereby recovering the metallic phase. It should be noted that slag may be present alongside the metal. Perfect separation of the metal and slag is not required in the recovery process; for example, a few percent of slag may be present without reducing the metal recovery rate.

[0082] <2-5. Vulcanization Process>

[0083] The sulfidation process S5 obtains a nickel-containing sulfide by sulfiding a metal containing nickel, which is to be recycled.

[0084] By performing a sulfidation process, even when using low-grade nickel oxide ore as the smelting material, it is possible to obtain sulfides with a relatively high nickel concentration. The sulfidation reaction of metals is a reversible reaction; with the presence of a specified amount or more of a sulfiding agent in the molten metal, the sulfidation reaction from metal to sulfide becomes dominant. In this process, nickel is sulfided first, followed by the sulfidation of other metals such as iron. Thus, the nickel sulfide is separated from the metal, allowing it to be separated from metals containing iron or other metals different from nickel. By recovering this nickel sulfide, sulfides with a relatively high nickel concentration can be obtained.

[0085] It should be noted that the sulfidation reaction from metal to sulfide, for example, when a sulfiding agent is added to a metal below 1600°C, can be carried out rapidly by controlling the furnace environment to a pressure of 0.01 atmospheres or more, preferably 0.1 atmospheres or more, in terms of sulfur partial pressure.

[0086] There are no particular limitations on the sulfiding agent; solid sulfur and sulfur gas can be used. Sulfur gas is preferred as the sulfiding agent. By using sulfur gas as the sulfiding agent, sulfur can be efficiently supplied to the metal and reacted. In addition, sodium sulfide, sodium hydrosulfide, and nickel sulfide can also be used as sulfiding agents. Nickel sulfide preferably contains 0.67 or more sulfur atoms per nickel atom; for example, compounds such as NiS, Ni9S8, and NiS2 can be used.

[0087] At this point, it is preferable to melt the obtained metal and supply a sulfiding agent to the molten metal. By subjecting the molten metal to a sulfidation reaction, nickel sulfides float to the surface of the molten metal, forming a sulfide layer on top of the molten metal. This allows for the easy separation of metals containing iron or other metals different from nickel.

[0088] One method for melting the obtained metal is to use a furnace with a burner to melt iron-nickel metal. In this method, a sulfiding agent is supplied to the molten metal to sulfide it, causing nickel sulfides to separate from the molten metal and float to the surface, forming a sulfide layer on top. This allows the separation of other metals, such as iron, from the molten metal. By recovering this nickel-containing sulfide layer, a sulfide with a high nickel concentration can be obtained.

[0089] At this point, by using a burner-equipped smelting furnace, metal can be easily heated and melted. Furthermore, burner furnaces are very easy to maintain and can operate continuously and efficiently, improving operational efficiency. In addition, compared to the electric furnaces of the Elken process, they have a simpler structure and fewer auxiliary equipment, thus reducing operating costs and regular maintenance costs. Furthermore, burner furnaces simplify power generation equipment, making them more suitable for on-site smelting near the mine. Also, in the Elken process, the large amount of electricity used results in high heating costs, while burner furnaces use cheaper fuel, allowing for the inexpensive production of sulfides.

[0090] The fuel for the burner is not particularly limited and can be one or more fuels selected from coal, charcoal, coke, and natural gas. Natural gas is preferred because of its good combustibility and ease of temperature control.

[0091] When using a furnace with a burner to sulfidate metal, it is preferable to form a sulfide layer on top of the molten metal during the sulfidation process. If the sulfide layer is located on top of the molten metal, it lies between the molten metal and the gas phase. Therefore, the molten metal before the reaction is unlikely to come into contact with oxygen (unburned gases remaining in combustion air, etc.), and sulfur gas and sulfur dioxide are generated from the sulfide layer after the sulfidation reaction, displacing oxygen. Thus, the sulfide layer itself is also difficult to oxidize. Therefore, throughout the sulfidation process, the nickel (nickel metal) contained in the molten metal before the reaction and the nickel (nickel sulfide) contained in the sulfide after the sulfidation reaction can be effectively suppressed and replaced with nickel oxide, enabling high-yield recovery of nickel as nickel sulfide.

[0092] It should be noted that by controlling the amount of sulfiding agent added in a manner that matches the amount of molten metal, a sulfide layer can be formed between the molten metal and the gas phase. In order to obtain a large amount of nickel sulfide-rich sulfide, the sulfur content supplied from the sulfiding agent is 1.0 or more and 3.0 or less in terms of the S / Ni molar ratio (S[mol] / Ni[mol]), preferably 1.0 or more and less than 1.5.

[0093] Furthermore, when contact between metal and oxygen within the furnace cannot be avoided, iron oxide may sometimes form due to contact between the upper layer of metal and oxygen. In such cases, it is preferable to add flux to the iron oxide as needed to melt it. The iron oxide is then discharged as slag from the slag outlet, thereby efficiently removing the molten iron oxide.

[0094] Another method for melting the obtained metal is to use an electric arc furnace to melt iron-nickel metal. An electric arc furnace is a furnace that uses the heat generated when an electric current flows between electrodes for heating. Such furnaces are excellent at melting metals at high temperatures and reacting them rapidly with sulfur. Because an electric arc furnace does not require oxygen or air as a heat source, oxidation of nickel-containing metals can be avoided, and sulfides can be obtained in high yields.

[0095] As electric arc furnaces, there are furnaces that utilize direct electric arc heating (direct electric arc furnaces) and furnaces that utilize indirect electric arc heating (indirect electric arc furnaces), with direct electric arc furnaces being preferred. When a direct electric arc furnace is used, the electrodes are in direct contact with the metal, thus making it easier to raise the metal to a high temperature, and temperature control is also easier.

[0096] In addition, among electric arc furnaces, there are DC electric arc furnaces (DC) that utilize an electric arc generated based on direct current and AC electric arc furnaces (AC electric arc furnaces) that utilize an electric arc generated between each electrode and the object being heated using alternating current. AC electric arc furnaces with three-phase electrodes that correspond to three-phase alternating current are particularly preferred.

[0097] When melting iron and nickel in a furnace or electric arc furnace using a burner, oxygen can be blown into the molten metal. This oxidizes the iron contained in the molten metal and makes it easy to control the temperature of the molten metal. Furthermore, by oxidizing the iron contained in the molten metal through blowing oxygen, the nickel content in the resulting sulfide can be adjusted. It should be noted that the nickel content in the sulfide can be adjusted by controlling the amount of sulfiding agent added (supply rate), or by combining these methods.

[0098] The sulfides of molten metal that have undergone sulfidation treatment can be discharged from the slag outlet and cooled to obtain sulfides.

[0099] 3. Processing Methods for Nickel Oxide Ores

[0100] The aforementioned method for producing sulfides can also be defined as a method for processing nickel oxide ore. In this way, an oxide ore is mixed with a reducing agent to obtain a mixture, the mixture is subjected to reduction treatment, and the obtained metal is sulfided to obtain a sulfide, thereby obtaining a sulfide with a high nickel concentration. Therefore, if nickel is recovered from the sulfides processed by the nickel oxide ore processing method of this embodiment, even if the nickel oxide ore is low-grade, nickel can be efficiently recovered in the form of sulfides.

[0101] 4. Nickel Smelting Methods

[0102] The nickel smelting method of this embodiment includes a wet process for producing sulfides using the above-described sulfide manufacturing method and obtaining a leachate from the obtained sulfides. This wet process allows for further separation from impurities.

[0103] As an example of a wet process, the chlorination process can be cited, which uses nickel-containing sulfides obtained in the sulfidation process as raw materials and uses chlorine gas to leach metals such as nickel into an aqueous solution to generate an aqueous solution of nickel chloride as the chlorination leachate.

[0104] Alternatively, the nickel-containing sulfide obtained in the sulfidation process S5 can be supplied together with the displacement precipitation residue generated in the displacement precipitation process to the wet process (chlorine leaching process), which removes impurities, namely copper ions, contained in the copper-containing nickel chloride aqueous solution in the wet smelting process of nickel.

[0105] In the chlorine leaching process, when the sulfide is fed into the solution, the metallic components such as nickel sulfide (NiS) contained in the sulfide are oxidized and leached out. This produces an aqueous solution of nickel chloride, which serves as the chlorine leaching solution.

[0106] It should be noted that although the chlorine leaching process, in which nickel and other metals are leached from the nickel-containing sulfide obtained in the sulfidation process S5 using chlorine gas, is described as an example of a wet process, it is not limited to chlorine gas. A leachate can be obtained by using an acid to leach metals such as nickel.

[0107] Example

[0108] The following describes embodiments of the present invention in more detail, but the present invention is not limited to any of the following embodiments.

[0109] Example 1

[0110] [Mixing of raw material powders]

[0111] For each sample, a mixture was prepared by adding an appropriate amount of water to nickel oxide ore (nickel grade = 0.91% by mass, MgO content = 15.3% by mass) as raw material ore, silica sand and limestone as fluxing agent, binder, and reducing agent (coal powder, carbon content: 41% by mass, average particle size: approximately 130 μm) in a mixer.

[0112] For ores with low nickel grade and high MgO content, there are technical difficulties or commercial cost mismatches, making them unsuitable for processing using existing smelting methods. The reducing agent used is pulverized coal, containing 35% of the amount required to precisely reduce the nickel oxide and iron oxide (Fe2O3) contained in the nickel oxide ore used as raw material to 100%.

[0113] [Forming of the mixture]

[0114] Next, the mixtures obtained from each sample were granulated into granules using a granulator. Then, the granules were sieved to obtain particles with a diameter of 15±0.4 mm, which were used for testing.

[0115] Next, each sample was dried by blowing hot air at 200°C to 250°C with a solid content of approximately 70% by weight and a moisture content of approximately 30% by weight. The solid composition (excluding carbon) of the dried mixture (particles) is shown in Table 3 below.

[0116] [Table 3]

[0117] [Reduction heating treatment of particles]

[0118] The dried sample particles were individually loaded into a reduction furnace in a nitrogen environment that was essentially free of oxygen. It should be noted that the temperature conditions inside the reduction furnace were set at 500±20℃.

[0119] Next, the particles of the mixture were subjected to reduction heating treatment at the temperatures and times shown in Table 4. After reduction treatment, the samples were rapidly cooled to room temperature in a nitrogen environment and then exposed to the atmosphere.

[0120] Here, the particles are fed into the reduction furnace by first spreading ash (mainly SiO2, with small amounts of oxides such as Al2O3 and MgO as other components) on the furnace bed of the reduction furnace, and then placing the particles on it.

[0121] For each sample after reduction and heat treatment, the nickel metallization rate and the nickel content in the metal were calculated by analyzing it using an ICP emission spectrophotometer (SHIMAZU S-8100).

[0122] The nickel metallization rate and the nickel content in the metal are calculated using the following formula.

[0123] Nickel metallization rate =

[0124] Metallized Ni amount ÷ (Total Ni amount in the mixture) × 100 (%)

[0125] Nickel content in metal =

[0126] Metallized Ni amount ÷ (total amount of metallized Ni and Fe) × 100 (%)

[0127] In addition, for each sample after reduction and heat treatment, wet processing was used to pulverize the sample, and then magnetic separation was used to recover the metal. Then, the nickel metal recovery rate was calculated based on the content of nickel oxide ore in the particle stack loaded into the reduction furnace, the nickel content in the nickel oxide ore, and the amount of nickel recovered.

[0128] Nickel metal recovery rate is calculated using the following formula.

[0129] Nickel metal recovery rate =

[0130] The amount of Ni recovered ÷ (the amount of oxide ore loaded × the Ni content in the oxide ore) × 100 (%)

[0131] Table 4 below shows the nickel metallization rate, nickel content in the metal, and nickel metal recovery rate for each sample.

[0132] [Table 4]

[0133] As can be seen from the table above, by reducing a mixture containing oxide ore and reducing agent, metals with relatively high nickel concentration (i.e., high nickel grade) can be obtained even when using low-grade nickel oxide ore.

[0134] [Vulcanization process]

[0135] The metal obtained in the reduction process described above is melted in a furnace using a burner. Sulfur gas, acting as a sulfiding agent, is supplied to the molten metal, resulting in sulfides. The sulfur gas supply is controlled to maintain a sulfur partial pressure of 1 atmosphere within the furnace. Coal, charcoal, coke, and natural gas are used as fuels for heating the furnace. Natural gas burns most stably and its temperature is easily controlled. The sulfidation process ends when the ratio of the amount of sulfur consumed (atomic number) to the amount of nickel present in the furnace reaches 1:1.

[0136] The obtained sulfides were analyzed using an ICP-based spectrophotometer (SHIMAZU S-8100) to calculate the nickel grade (Ni content). The nickel grade in the sulfides was 63–66%, and the sulfur content was 21–24%. It can be seen that by feeding the metal obtained in the reduction process to the sulfidation process, metals such as iron, which are different from the target metals, can be separated, thereby obtaining sulfides with high nickel concentrations. Furthermore, it is speculated that by using a wet process that contacts the sulfides with an acid solution, even if the oxide ore being processed is of low grade, nickel, the target metal, can be recovered efficiently.

[0137] Example 2

[0138] [Mixing of raw material powders]

[0139] For each sample, a mixture was prepared by adding an appropriate amount of water to nickel oxide ore (nickel grade = 0.91% by mass, MgO content = 15.3% by mass) as raw material ore, silica sand and limestone as fluxing agent, binder, and carbonaceous reducing agent (coal powder, carbon content: 41% by mass, average particle size: approximately 130 μm) in a mixer.

[0140] For ores with low nickel grade and high MgO content, there are technical difficulties or commercial cost mismatches, making them unsuitable for processing using existing smelting methods. A carbonaceous reducing agent using pulverized coal is employed, and when the amount of nickel oxide and iron oxide (Fe2O3) contained in the nickel oxide ore used as raw material is set to exactly 100%, the content is 35%.

[0141] [Forming of the mixture]

[0142] Next, the mixtures obtained from each sample were granulated into granules using a granulator. Then, the granules were sieved to obtain particles with a diameter of 15±0.4 mm, which were used for testing.

[0143] Next, each sample was dried by blowing hot air at 200°C to 250°C with a solid content of approximately 70% by weight and a moisture content of approximately 30% by weight. The solid composition (excluding carbon) of the dried mixture (particles) is shown in Table 5 below.

[0144] [Table 5]

[0145] [Reduction heating treatment of particles]

[0146] The dried sample particles were individually loaded into a reduction furnace in a nitrogen environment that was essentially free of oxygen. It should be noted that the temperature conditions inside the reduction furnace were set at 500±20℃.

[0147] Next, the particles of the mixture were subjected to reduction heating treatment at the temperatures and times shown in Table 6. After reduction treatment, the samples were rapidly cooled to room temperature in a nitrogen environment and then exposed to the atmosphere.

[0148] Here, the particles are fed into the reduction furnace by first spreading ash (mainly SiO2, with small amounts of oxides such as Al2O3 and MgO as other components) on the furnace bed of the reduction furnace, and then placing the particles on it.

[0149] For each sample after reduction and heat treatment, the nickel metallization rate and nickel content in the metal were calculated by analyzing it using an ICP emission spectrophotometer (SHIMAZU S-8100).

[0150] [Table 6]

[0151] As can be seen from the table above, by reducing a mixture containing oxide ore and reducing agent, metals with relatively high nickel concentration (i.e., high nickel grade) can be obtained even when using low-grade nickel oxide ore.

[0152] [Vulcanization process]

[0153] The metal obtained in the above reduction process is melted in an electric arc furnace. Sulfur gas, used as a sulfiding agent, is supplied to the molten metal to perform sulfidation, resulting in sulfides. The sulfur gas supply is controlled to maintain a sulfur partial pressure of 1 atmosphere within the furnace. The sulfidation process ends when the ratio of the amount of sulfur consumed (atomic number) to the amount of nickel present in the furnace reaches 1:1.

[0154] The obtained sulfide was analyzed using an ICP-based spectrophotometer (SHIMAZU S-8100) to calculate the nickel grade (Ni content). The nickel grade in the sulfide was 67%, and the sulfur grade was 24%. It can be seen that by feeding the metal obtained in the reduction process into the sulfidation process, metals such as iron, which are different from the target metals, can be separated, resulting in sulfides with a relatively high nickel concentration. Furthermore, it is speculated that by using a wet process that contacts the sulfide with an acid solution, even if the oxide ore being processed is of low grade, the nickel target metals can be recovered efficiently.

[0155] Example 3

[0156] [Mixing of raw material powders]

[0157] For each sample, a mixture was prepared by adding an appropriate amount of water to nickel oxide ore (nickel grade = 0.90% by mass, MgO content = 15.5% by mass) as raw material ore, silica sand and limestone as fluxing agent, binder, and carbonaceous reducing agent (coal powder, carbon content: 41% by mass, average particle size: approximately 130 μm) in a mixer.

[0158] For ores with low nickel grade and high MgO content, there are technical difficulties or commercial cost mismatches, making them unsuitable for processing using existing smelting methods. A carbonaceous reducing agent using pulverized coal is employed, and when the amount of nickel oxide and iron oxide (Fe2O3) contained in the nickel oxide ore used as raw material is set to exactly 100%, the content is 35%.

[0159] [Forming of the mixture]

[0160] Next, the mixtures obtained from each sample were granulated into granules using a granulator. Then, the granules were sieved to obtain particles with a diameter of 15±0.4 mm, which were used for testing.

[0161] Next, each sample was dried by blowing hot air at 200°C to 250°C with a solid content of approximately 70% by weight and a moisture content of approximately 30% by weight. The solid composition (excluding carbon) of the dried mixture (particles) is shown in Table 7 below.

[0162] [Table 7]

[0163] [Reduction heating treatment of particles]

[0164] The dried sample particles were individually loaded into a reduction furnace in a nitrogen environment that was essentially free of oxygen. It should be noted that the temperature conditions inside the reduction furnace were set at 500±20℃.

[0165] Next, the particles of the mixture were subjected to reduction heating treatment at the temperatures and times shown in Table 8. After reduction treatment, the samples were rapidly cooled to room temperature in a nitrogen environment and then exposed to the atmosphere.

[0166] Here, the particles are fed into the reduction furnace by first spreading ash (mainly SiO2, with small amounts of oxides such as Al2O3 and MgO as other components) on the furnace bed of the reduction furnace, and then placing the particles on it.

[0167] For each sample after reduction and heat treatment, the nickel metallization rate and the nickel content in the metal were calculated by analyzing it using an ICP emission spectrophotometer (SHIMAZU S-8100).

[0168] Table 8 below shows the nickel metallization rate, nickel content in the metal, and nickel metal recovery rate for each sample.

[0169] [Table 8]

[0170] As can be seen from the table above, by reducing a mixture containing oxide ore and reducing agent, metals with relatively high nickel concentration (i.e., high nickel grade) can be obtained even when using low-grade nickel oxide ore.

[0171] [Vulcanization process]

[0172] The metal obtained in the above reduction process is melted in an electric arc furnace, and a sulfiding agent is supplied to the molten metal to obtain a sulfide. Solid sulfur and sulfur gas are used as sulfiding agents. The substance using solid sulfur as a sulfiding agent is designated as sulfide 1, and the substance using sulfur gas as a sulfiding agent is designated as sulfide 2.

[0173] At this point, the sulfur partial pressure inside the furnace is controlled to be 1 atmosphere, and the sulfiding agent is supplied. The amount of sulfiding agent used to obtain sulfide 2 is approximately 90% of the amount used to obtain sulfide 1. Both sulfide 1 and sulfide 2 have a nickel grade of 64-66% and a sulfur grade of 22-24%. It can be seen that by feeding the metal obtained in the reduction process to the sulfidation process, metals such as iron that are different from the target metal can be separated, resulting in sulfides with high nickel concentrations. Furthermore, it is speculated that by using a wet process that contacts the sulfide with an acid solution, even if the oxide ore being processed is of low grade, nickel, the target metal, can be recovered efficiently.

[0174] Explanation of reference numerals in the attached figures

[0175] 1 particle.

[0176] 2. Rotary hearth furnace.

[0177] Processing room 20a~20d.

[0178] 21. Preheating chamber.

[0179] 40 Cooling chamber.

Claims

1. A method for manufacturing sulfides, wherein the sulfide is produced from nickel oxide ore, wherein... have: A mixing process in which nickel oxide ore and a reducing agent are mixed to obtain a mixture; The mixture is loaded into a reduction furnace and subjected to reduction treatment to obtain a reduction process containing a metal as an iron-nickel metal and slag as an oxide. The separation process of separating the metal and the slag from the reduced product; and A sulfiding agent is added to the metal obtained in the separation process to obtain a sulfidation process containing nickel sulfide.

2. The method for manufacturing sulfides according to claim 1, wherein, In the vulcanization process, the metal is melted using a furnace with a burner, and a vulcanizing agent is added to the molten metal to form a sulfide layer between the molten metal and the gas phase.

3. The method for manufacturing sulfides according to claim 1, wherein, In the vulcanization process, an electric arc furnace is used to melt the metal, and a vulcanizing agent is added to the molten metal.

4. The method for manufacturing sulfides according to claim 2, wherein, In the vulcanization process, one or more fuels selected from charcoal, coke, and natural gas are used as fuel for the burner.

5. The method for producing a sulfide according to any one of claims 1 to 3, wherein, In the vulcanization process, solid or sulfur gas is used as the vulcanizing agent.

6. The method for producing a sulfide according to any one of claims 1 to 3, wherein, In the reduction process, the mixture is loaded into a reduction furnace and subjected to reduction treatment to obtain iron-nickel metal, which is then supplied to the sulfidation process.

7. A method for smelting nickel, wherein, have: A mixing process in which nickel oxide ore and a reducing agent are mixed to obtain a mixture; The mixture is loaded into a reduction furnace and subjected to reduction treatment to obtain a reduction process containing a metal as an iron-nickel metal and slag as an oxide. The separation process of separating the metal and the slag from the reduced product; A sulfidation process in which a sulfiding agent is added to the metal obtained in the separation process to obtain a sulfide; and A wet process for obtaining leachate from the sulfide obtained in the vulcanization process.

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