Sulfide production method and nickel smelting method

Abstract

The present invention provides a method for treating nickel oxide ore, the method capable of efficiently recovering nickel that is intended to be recovered.　The present invention also provides a sulfide production method for producing sulfide from nickel oxide ore, the method comprising: a mixing treatment step for mixing nickel oxide ore with a reducing agent to obtain a mixture; a reducing step for charging the mixture into a reduction furnace and subjecting the mixture to a reduction process to obtain a reduced product containing a metal, which is ferro-nickel metal, and a slag, which is an oxide; a separation step for separating the metal and the slag from the reduced product; and a sulfurization step for adding a sulfurizing agent to the metal obtained in the separation step to obtain a sulfide containing nickel.

Description

Sulfide manufacturing method and nickel smelting method

[0001] The present invention relates to a method for producing sulfides from nickel oxide ore and a method for smelting nickel.

[0002] Known methods for smelting nickel to obtain nickel from nickel oxide ores called limonite or saprolite include a pyrometallurgical method in which nickel is sulfided and roasted together with sulfur using a smelting furnace to produce nickel matte, a pyrometallurgical method in which nickel is reduced with a reducing agent using a rotary kiln or a moving hearth furnace to produce an iron-nickel alloy (hereinafter also referred to as "ferronickel"), and a hydrometallurgical method in which nickel and cobalt are leached with sulfuric acid using an autoclave, and a sulfiding agent is added to the leachate to produce a mixed sulfide.

[0003] For example, Patent Document 1 describes a method for recovering valuables from precious metal-containing metal sulfides, in which a metal sulfide matte containing nickel and copper sulfides as main components is air-oxidized using sulfuric acid in a predetermined equivalent amount relative to the nickel, thereby selectively leaching and separating nickel, and concentrating the precious metal together with copper sulfide in the leaching residue.

[0004] Patent Document 1 describes that this valuable resource recovery method can efficiently recover valuable components by utilizing existing copper smelting facilities.

[0005] On the other hand, the amount of easily processable ore continues to decrease, and conventional smelting technology is reaching its limits due to factors such as a decline in the nickel grade in the ore and a high MgO content, which increases smelting costs. Against this background, there is a need for technology to recover valuable metals such as nickel from ores that cannot be processed using conventional technology.

[0006] When valuable metals such as nickel are recovered from such low-grade nickel oxide ores containing high impurities using conventional techniques, the cost of the recovered valuable metals increases. For example, in a dry smelting process in which nickel matte is produced by sulfurizing and roasting the ore with sulfur in a smelting furnace, if the Ni content is less than a few percent, the melting energy of the slag components becomes excessive, reducing the sulfurization efficiency and making the process unprofitable. In a rotary kiln smelting process, if the nickel content in the ore is, for example, 1.5% by mass or less, the proportion of slag components increases, requiring significant heating energy, making the process unprofitable. Similarly, in the Elkem process using an electric furnace, if the Ni content decreases, the energy required to melt the slag becomes excessive, making the process unprofitable. In a wet processing process using an autoclave, if the MgO content in the ore exceeds 2% by mass, the cost of chemicals such as sulfuric acid becomes excessive, making the process unprofitable.

[0007] Thus, there is a need for a method for processing nickel oxide ore that can efficiently recover valuable metals from low-grade oxide ore.

[0008] JP 2009-97076 A

[0009] An object of the present invention is to provide a method for treating nickel oxide ore that can efficiently recover nickel, which is the target of recovery.

[0010] The present inventors have conducted extensive research to solve the above-mentioned problems, and as a result have found that the above-mentioned problems can be solved by reducing a mixture containing an oxide ore and a reducing agent, obtaining a metal, and then adding a sulfiding agent to the resulting metal to produce a sulfide, thereby completing the present invention.

[0011] A first aspect of the present invention is a sulfide manufacturing method for manufacturing sulfides from nickel oxide ore, comprising: a mixing step of mixing the nickel oxide ore with a reducing agent to obtain a mixture, a reduction step of charging the mixture into a reduction furnace and subjecting the mixture to a reduction treatment to obtain a reduced product containing metal, which is ferronickel metal, and slag, which is an oxide, a separation step of separating the metal and the slag from the reduced product, and a sulfiding step of adding a sulfiding agent to the metal obtained in the separation step to obtain a sulfide containing nickel.

[0012] A second aspect of the present invention is a method for producing sulfides according to the first aspect of the present invention, wherein the sulfurization step involves melting the metal in a melting furnace using a burner and adding a sulfiding agent to the molten metal, thereby forming a sulfide layer between the molten metal and the gas phase.

[0013] A third aspect of the present invention is the method for producing a sulfide according to the first aspect of the present invention, wherein the sulfurizing step comprises melting the metal using an arc furnace and adding a sulfiding agent to the molten metal.

[0014] A fourth aspect of the present invention is the method for producing a sulfide according to the second aspect of the present invention, wherein the sulfurization step uses a fuel containing one or more selected from charcoal, coke, and natural gas as fuel for the burner.

[0015] A fifth aspect of the present invention is a method for producing a sulfide according to any one of the first to third aspects, wherein solid sulfur or sulfur gas is used as the sulfiding agent in the sulfiding step.

[0016] A sixth aspect of the present invention is the method for producing sulfides according to any one of the first to third aspects, wherein in the reduction step, the mixture is charged into a reduction furnace and subjected to a reduction treatment to obtain ferronickel metal, and the ferronickel metal is then subjected to the sulfurization step.

[0017] A seventh aspect of the present invention is a method for smelting nickel, comprising: a mixing step of mixing a nickel oxide ore with a reducing agent to obtain a mixture; a reduction step of charging the mixture into a reduction furnace and subjecting the mixture to a reduction treatment to obtain a reduced product containing a metal that is ferronickel metal and a slag that is an oxide; a separation step of separating the metal and the slag from the reduced product; a sulfiding step of adding a sulfiding agent to the metal obtained in the separation step to obtain a sulfide; and a wet process of obtaining a leachate from the sulfide obtained in the sulfiding step.

[0018] According to the method for producing sulfide of the present invention, nickel can be recovered efficiently.

[0019] 1 is a process diagram showing an example of the flow of a method for producing sulfide. FIG. 2 is a diagram (plan view) showing an example of the configuration of a reduction furnace (rotary hearth furnace).

[0020] Specific embodiments of the present invention will be described in detail below. Note that the present invention is not limited to the following embodiments, and various modifications are possible within the scope of the present invention. In addition, in this specification, the expression "X to Y" (X and Y are arbitrary numerical values) means "X or more and Y or less."

[0021] 1. Overview of the Invention The method for producing a sulfide of the present invention is characterized by comprising: a mixing step of mixing a nickel oxide ore with a reducing agent to obtain a mixture; a reduction step of charging the mixture into a reduction furnace and subjecting the mixture to a reduction treatment; and a sulfurization step of adding a sulfiding agent to the metal obtained in the reduction step to obtain a sulfide.

[0022] In this way, valuable metals can be efficiently recovered by mixing oxide ore with a reducing agent to obtain a mixture, and then subjecting the mixture to a reduction treatment to obtain metals, which are then sulfidized to obtain sulfides.

[0023] Furthermore, in the sulfurization step of sulfurizing the metal obtained by the reduction treatment, the metal may be melted using a melting furnace with a burner, and a sulfurizing agent may be added to the molten metal. By melting the metal using a melting furnace with a burner and adding a sulfurizing agent to the molten metal, it becomes possible to separate metals containing metals other than nickel, such as iron, and to recover nickel more efficiently.

[0024] In addition, in the sulfurization step of sulfurizing the metal obtained by the reduction treatment, the metal may be melted in an arc furnace and a sulfurizing agent may be added to the molten metal. By melting the metal in an arc furnace and adding a sulfurizing agent to the molten metal, it becomes possible to separate metals containing metals other than nickel, such as iron, and to recover valuable metals more efficiently.

[0025] The nickel to be recovered contained in the sulfide can be recovered, for example, by subjecting the sulfide to a wet process.

[0026] 2. Method for Producing Sulfide Hereinafter, as a specific embodiment of the present invention (hereinafter referred to as "the present embodiment"), a method for producing sulfide from nickel oxide ore, using nickel oxide ore as a raw material ore, will be described as an example.

[0027] Specifically, as shown in FIG. 1 , the method for producing sulfides according to 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 form pellets (lumps), a reduction process S3 in which the mixture is charged into a reduction furnace and subjected to a reduction process, a separation process S4 in which slag is separated from the obtained reduced product to obtain an iron-nickel alloy (ferronickel metal), and a sulfiding process S5 in which a sulfiding agent is added to the ferronickel metal to obtain a sulfide.

[0028] <2-1. Mixing Step> In the mixing step S1, raw material powders containing nickel oxide ore are mixed to obtain a mixture. Specifically, in this mixing step S1, a reducing agent, for example, a carbonaceous reducing agent such as coal or coke, is added to and mixed with the nickel oxide ore, which is the raw material ore, and powders of iron ore, flux components, binders, etc., having a particle size of, for example, about 0.2 mm to 0.8 mm, are also mixed as optional additives to obtain a mixture. Here, the raw material powders containing nickel oxide ore can be mixed using a mixer or the like.

[0029] The nickel oxide ore as the raw material ore is not particularly limited, but limonite ore, saprolite ore, etc. can be used. For example, the nickel content in the ore may be 1 mass % or less, and the MgO content may be 2 mass % or more. The nickel oxide ore contains nickel oxide (NiO) and iron oxide (FeO) as its constituents. ２ O ３ ) and contains.

[0030] In this embodiment, a mixture is obtained by mixing a specific amount of reducing agent with the raw ore. It is preferable that this reducing agent has the same particle size and particle size distribution as the nickel oxide ore, which is the raw ore described above. The same particle size and particle size distribution are preferable because this makes it easier to mix uniformly and the reduction reaction also occurs uniformly.

[0031] The amount of the reducing agent mixed, i.e., the amount of the reducing agent contained in the pellets after molding, is preferably 50.0% by mass or less, and more preferably 40.0% by mass or less, when the amount of the reducing agent necessary to exactly reduce the nickel oxide and iron oxide that constitute the nickel oxide ore is taken as 100% by mass. Note that the amount of the reducing agent necessary to exactly reduce the nickel oxide and iron oxide can be rephrased as the sum of the chemical equivalent necessary to reduce all of the nickel oxide contained in the pellets to nickel metal and the chemical equivalent necessary to reduce the iron oxide contained in the pellets to iron metal (hereinafter also referred to as the "total value of chemical equivalents").

[0032] In this way, by setting the amount of reducing agent contained in the mixture (mixed amount of reducing agent) to a ratio of 50.0 mass% or less when the total value of chemical equivalents is 100 mass%, the reduction reaction can be efficiently progressed.

[0033] The lower limit of the amount of reducing agent mixed is not particularly limited, but is preferably 20.0% by mass or more, and more preferably 23.0% by mass or more, when the total value of the chemical equivalents is 100% by mass. In this way, by making the amount of reducing agent mixed 20.0% by mass or more, it becomes easier to produce an iron-nickel alloy with a high nickel quality.

[0034] In addition to the nickel oxide ore and the reducing agent, the iron ore that is an optional additive is not particularly limited, and examples that can be used include iron ore with an iron content of about 50 mass % or more and hematite obtained by hydrometallurgy of nickel oxide ore.

[0035] Examples of binders include bentonite, polysaccharides, resins, water glass, dehydrated cake, etc. Examples of flux components include calcium oxide, calcium hydroxide, calcium carbonate, silicon dioxide, etc.

[0036] The following Table 1 shows an example of the composition (mass %) of some of the raw material powders mixed in the mixing process S1. Note that the composition of the raw material powders is not limited to this.

[0037]

[0038] When the raw material powders are mixed to obtain a mixture, the raw material powders may be kneaded to improve mixability. This applies shear force to the mixture, breaks down agglomerations of the carbon reducing agent, raw material powder, etc., allowing for more uniform mixing, and also increases the adhesion between the particles, making it easier to perform a uniform reduction treatment.

[0039] <2-2. Mixture Forming Step> In the mixture forming step S2, the mixture of raw material powders obtained in the mixing step S1 is formed and dried as necessary to obtain pellets. The mixture forming step S2 may include an agglomeration step S21 in which the raw material mixture containing nickel oxide ore is formed into agglomerates, and a drying step S22 in which the obtained agglomerates are dried.

[0040] (1) Agglomeration Step In the agglomeration step S21, the mixture of raw materials containing nickel oxide ore obtained in the mixing step S1 is formed into agglomerates of a predetermined shape and size.

[0041] The shape of the mixture to be molded, i.e., the shape of the pellets, may be any shape that can be stacked on the hearth of a reducing furnace, but is preferably an elliptical, cubic, rectangular, cylindrical, or spherical shape. Molding the mixture into such a shape makes it easier to mold the mixture, thereby reducing molding costs. Furthermore, since the molded shape is not complicated, the occurrence of defectively molded pellets can be reduced.

[0042] In the agglomeration step S21, the mixture can be molded using, for example, a pellet molding device. The pellet molding device is not particularly limited, but is preferably one that can knead and mold the mixture under high pressure and high shear force. Kneading the mixture under high pressure and high shear can break up agglomerations in the raw material powder mixture, enable effective kneading, and increase the strength of the resulting pellets.

[0043] It is also possible to form the powder using a briquette press. The appropriate equipment can be selected taking into consideration the equipment, pellet strength, yield, etc.

[0044] (2) Drying Step The drying step S22 is a step of drying the pellets obtained in the agglomeration step S21. The pellets obtained by the agglomeration step contain an excessive amount of moisture, for example, about 50% by mass. Therefore, if the temperature of pellets containing excessive moisture is suddenly raised to the reduction temperature, the moisture will suddenly evaporate, causing expansion and destruction of the pellets.

[0045] Therefore, by subjecting the obtained pellets to a drying treatment so that the solid content of the pellets is, for example, about 70% by mass and the moisture content is about 30% by mass, the pellets can be prevented from collapsing during the reduction heat treatment in the next reduction step S3, which makes it difficult to remove the pellets from the reduction furnace. Furthermore, since the pellets are often sticky due to excess moisture, drying the pellets makes them easier to handle.

[0046] Specifically, the drying treatment for the pellets in the drying treatment step S22 is not particularly limited, but for example, the lumps are dried by blowing hot air at 200° C. to 400° C. It is preferable that the temperature of the lumps during this drying treatment is less than 100° C., as this makes it difficult for the pellets to be broken.

[0047] Here, when drying pellets having a particularly large volume, it is acceptable for the lumps to have cracks or breaks before or after drying. When the pellets have a large volume, they melt and shrink during reduction, which often results in cracks or breaks. However, when the pellets have a large volume, the effects of cracks or breaks, such as an increase in surface area, are minimal, and therefore, no major problems are likely to occur. Therefore, it is acceptable for the pellets to have cracks or breaks before reduction.

[0048] If the pellets are designed so that they are not broken when handled in the reduction furnace to form a pellet stack or during the reduction heat treatment, the drying treatment in the drying treatment step S22 may be omitted.

[0049] An example of the composition (mass %) of the solid content in the pellets after drying is shown in Table 2 below. However, the composition of the pellets is not limited to this.

[0050]

[0051] <2-3. Reduction Step> In the reduction step S3, the pellets obtained in the mixture forming step S2 are loaded into a reduction furnace and heated for reduction to a predetermined reduction temperature. Specifically, the obtained pellets (mixture) are placed on the hearth of the reduction furnace, and the mixture is subjected to a heat reduction treatment in the reduction furnace. The heat reduction treatment in the reduction step S3 causes a smelting reaction (reduction reaction) to proceed based on the reducing agent in the mixture, and ferronickel metal (hereinafter simply referred to as "metal") and ferronickel slag (hereinafter simply referred to as "slag") are produced separately in the mixture. Note that, hereinafter, the pellets to be subjected to the reduction treatment will be referred to as the mixture for convenience.

[0052] The present invention is not limited to the embodiment in which pellets are formed in advance outside the reduction furnace and then charged into the reduction furnace for treatment. The mixtures may be charged into the reduction furnace one by one, and pellets may be formed inside the reduction furnace.

[0053] In the reduction heat treatment of the heat treatment, first, in a short time of, for example, about one minute, the nickel oxide and iron oxide contained in the pellet are reduced and metallized near the surface of the pellet where the reduction reaction is most likely to occur, becoming an iron-nickel alloy and forming a shell (hereinafter also referred to as the "shell"). Meanwhile, within the shell, as the shell forms, the slag components in the pellet gradually melt, producing liquid slag. As a result, within a single pellet, metal (hereinafter simply referred to as the "metal") made of alloys or metals such as ferronickel, and slag (hereinafter simply referred to as the "slag") made of oxides are produced separately.

[0054] After about 10 minutes of the reduction heat treatment, the carbon component of the excess carbonaceous reducing agent that is not involved in the reduction reaction is absorbed into the iron-nickel alloy, lowering its melting point, and as a result, the iron-nickel alloy melts and becomes liquid.

[0055] In this embodiment, the reduction product after the reduction heat treatment is a mixture of large lumps of metal and slag. The metal and slag that have already been separated do not mix, and subsequent cooling results in a mixture of separate phases, namely, a metal solid phase and a slag solid phase. This makes it possible to easily separate the nickel-containing metal to be recovered from the slag that is substantially free of nickel. Therefore, even when a low-grade nickel oxide ore is used as the smelting target, it is possible to obtain a metal with a relatively high nickel concentration.

[0056] The volume of the inclusions has shrunk to about 50% to 60% by volume compared to the pellets before the reduction heat treatment.

[0057] The reduction furnace used in the reduction heat treatment is not particularly limited, but it is preferable to use a moving hearth furnace. By using a moving hearth furnace as the reduction furnace, the mixture can be efficiently treated in the reduction furnace. Furthermore, by using a moving hearth furnace, the reduction reaction proceeds continuously and can be completed in a single facility, allowing for more accurate control of the treatment temperature than when treating each step using separate furnaces. Furthermore, heat loss between each treatment is reduced, enabling more efficient operation. In other words, when reactions are performed using separate furnaces, the temperature drops when the pellet stack is moved between furnaces, resulting in heat loss and a change in the reaction atmosphere, preventing the reaction from proceeding immediately when the pellets are recharged into the furnace. In contrast, by using a moving hearth furnace to perform each treatment in a single facility, heat loss is reduced and the furnace atmosphere can be accurately controlled, allowing the reaction to proceed more effectively. As a result, iron-nickel alloys with a high nickel content can be obtained more effectively.

[0058] The moving hearth furnace is not particularly limited, and for example, a circular rotary hearth furnace 2 divided into multiple treatment chambers 20a to 20d, as shown in FIG. 2, can be used. The rotary hearth furnace 2 rotates in a predetermined direction, performing each treatment in each zone. In this rotary hearth furnace, the treatment temperature in each zone can be adjusted by controlling the time it takes to pass through each zone (travel time, rotation time), and the mixture constituting the pellet stack 1 is smelted with each rotation of the rotary hearth furnace. Here, the rotary hearth furnace 2 may be provided with a preheating chamber 21 outside the furnace, and the pellet stack 1 is moved to the preheating chamber 21 and preheated, and the preheated pellet stack 1 may be sequentially transferred into the rotary hearth furnace 2. The rotary hearth furnace 2 may also be provided with a cooling chamber 40 outside the furnace, and the reduced material obtained through the treatment chambers 20a to 20d may be cooled in the cooling chamber 40. The moving hearth furnace may also be a roller hearth kiln or the like.

[0059] The heating means for the reducing furnace is not particularly limited, and may be a burner or a device using electricity, etc. A burner is preferable because it can effectively subject the mixture to a heating and reduction treatment in a short period of time. When a reducing furnace having a burner is used, for example, LPG, LNG, coal, coke, pulverized coal, etc. are used as fuel. The cost of these fuels is very low, and the equipment costs and maintenance costs can be kept significantly lower than those of an electric furnace, etc.

[0060] The temperature in the reduction treatment (reduction temperature) is not particularly limited, but is preferably in the range of 1250°C or higher and 1450°C or lower, and more preferably in the range of 1300°C or higher and 1400°C or lower. By carrying out reduction within such a temperature range, the reduction reaction can be caused to occur uniformly, and ferronickel metal with reduced quality variation can be produced. Furthermore, by carrying out reduction at a reduction temperature more preferably in the range of 1300°C or higher and 1400°C or lower, the desired reduction reaction can be caused to occur in a relatively short time.

[0061] The time for the reduction treatment (treatment time) is set depending on the temperature of the reduction furnace, but is preferably 10 minutes or more, more preferably 15 minutes or more. On the other hand, the upper limit of the time for the reduction heat treatment may be set to 50 minutes or less, or 40 minutes or less, from the viewpoint of suppressing an increase in production costs.

[0062] The cumulative heat required for reduction, calculated by multiplying the reduction temperature (°C) by the reduction time (minutes), is preferably in the range of 20,000 (°C x min) to 40,000 (°C x min). By carrying out reduction treatment with this heat amount, high-quality metal can be efficiently produced.

[0063] <2-4. Separation Step> In the separation step S4, the metal and slag produced in the reduction step S3 are separated and the metal is recovered. Specifically, the metal phase is separated and recovered from the mixture containing the metal phase (metal solid phase) and the slag phase (slag solid phase) obtained by the reduction heat treatment of the pellets.

[0064] Before the separation step of separating the metal and slag from the reduced product, the molten reduced product may be cooled to a viscosity range that does not interfere with the separation of the metal and slag, and the cooled reduced product may be subjected to the separation step. The cooling of the reduced product may be performed by allowing the reduced product to cool naturally.

[0065] As a method for separating the metal phase and the slag phase from the mixture of the metal phase and the slag phase obtained as a solid, in addition to removing unnecessary substances by sieving, methods such as separation by specific gravity or separation by magnetic force can be used.

[0066] Furthermore, the resulting metal phase and slag phase can be easily separated due to their poor wettability. For example, by subjecting the large inclusions obtained by the reduction step S3 to an impact, such as by dropping them over a predetermined drop or by applying a predetermined vibration during sieving, the metal phase and slag phase can be easily separated from the inclusions.

[0067] In this way, the metal phase is separated from the slag phase, and the metal phase is recovered. Note that slag may accompany the metal. It is not necessary to completely separate the metal and slag in the recovery process; for example, a few percent of slag may accompany the metal, as long as it does not reduce the metal recovery rate.

[0068] <2-5. Sulfurization Step> In the sulfurization step S5, a nickel-containing metal to be recovered is sulfurized to obtain a nickel-containing sulfide.

[0069] By performing the sulfurization process, it is possible to obtain sulfides with a relatively high nickel concentration, even when low-grade nickel oxide ore is used as the smelting target. The sulfurization reaction of metal is a reversible reaction, and when a certain amount or more of a sulfurizing agent is present in the molten metal, the sulfurization reaction from metal to sulfide becomes dominant. In this case, nickel is sulfurized first, and after the nickel is sulfurized, other metals such as iron are sulfurized. This separates the nickel sulfide from the metal, allowing the nickel sulfide to be separated from metal containing metals other than nickel, such as iron. By recovering this nickel sulfide, it is possible to obtain sulfides with a relatively high nickel concentration.

[0070] In addition, when a sulfurizing agent is added to a metal at 1600°C or less, the sulfurization reaction from metal to sulfide can be made to proceed quickly by controlling the atmosphere in the furnace to a sulfur partial pressure of 0.01 atmospheres or more, more preferably 0.1 atmospheres or more.

[0071] The sulfurizing agent is not particularly limited, and examples thereof include solid sulfur and sulfur gas. Among these, it is preferable to use sulfur gas as the sulfurizing agent. By using sulfur gas as the sulfurizing 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 the sulfurizing agent. Nickel sulfide containing 0.67 or more sulfur atoms per nickel atom is preferable, and examples thereof include NiS and Ni. ９ S ８ , NiS ２ Compounds such as:

[0072] In this case, it is preferable to melt the obtained metal and supply a sulfiding agent to the molten metal. By causing a sulfiding reaction to proceed with the molten metal, nickel sulfides float up from the molten metal and form a sulfide layer on top of the molten metal, making it possible to easily separate metals containing metals other than nickel, such as iron.

[0073] As a method for melting the obtained metal, a method of melting ferronickel metal using a melting furnace with a burner can be mentioned. By melting ferronickel metal using a melting furnace with a burner and sulfiding the metal by supplying a sulfiding agent to the molten metal, nickel sulfide separates and floats from the molten metal, forming a sulfide layer on top of the molten metal, and metal containing other metals such as iron can be separated. By recovering this nickel-containing sulfide layer, it is possible to obtain sulfides with a relatively high nickel concentration.

[0074] In this case, by using a melting furnace with a burner, it is possible to easily heat and melt the metal. Furthermore, burner furnaces are very easy to maintain, and continuous operation can be effectively carried out, thereby improving operational efficiency. Furthermore, compared to the electric furnace used in the Elkem process, burner furnaces have a simpler structure and require less auxiliary equipment, which reduces operating costs and regular maintenance costs. Furthermore, burner furnaces allow for simplified power generation equipment, making them more suitable for on-site smelting where smelting is carried out near the mine. Furthermore, while the Elkem process uses a lot of electricity, which makes heating very expensive, burners require cheaper fuel, making it possible to produce sulfides inexpensively.

[0075] The fuel for the burner is not particularly limited and may be one or more fuels selected from coal, charcoal, coke, and natural gas. Natural gas is preferred because it has good combustibility and is easy to control the temperature.

[0076] When sulfurizing metal using a melting furnace with a burner, it is desirable to form a sulfide layer on top of the molten metal during the sulfurization process. When the sulfide layer is on top of the molten metal, the sulfide layer is located between the metal and the gas phase, making it difficult for the molten metal before the reaction to come into contact with oxygen (unburned combustion air, etc.). Furthermore, the sulfide layer after the sulfurization reaction produces sulfur gas and sulfur dioxide, which repel oxygen, making the sulfide layer itself less susceptible to oxidation. Therefore, throughout the sulfurization process, nickel (nickel metal) contained in the molten metal before the reaction and nickel (nickel sulfide) contained in the sulfide after the sulfurization reaction can be effectively prevented from being replaced by nickel oxide, making it possible to recover nickel as nickel sulfide at a high yield.

[0077] By controlling the amount of sulfiding agent added so as to correspond to the amount of molten metal, a sulfide layer can be formed between the molten metal and the gas phase. To obtain a large amount of sulfide containing a high concentration of nickel sulfide, the sulfur content supplied from the sulfiding agent should be adjusted so that the S / Ni molar ratio (S [mol] / Ni [mol]) is 1.0 or more and 3.0 or less, preferably 1.0 or more and less than 1.5.

[0078] Furthermore, if contact of the metal in the melting furnace with oxygen is unavoidable, iron oxide may form when the upper layer of the metal comes into contact with oxygen. In this case, it is desirable to add a flux to the iron oxide as needed to melt it. This allows the molten iron oxide to be removed efficiently by removing it from the tap as slag.

[0079] Furthermore, as a method for melting the obtained metal, a method of melting ferronickel metal using an arc furnace can be mentioned. An arc furnace is a furnace that heats by utilizing the heat generated when an electric current flows between electrodes, and such an arc furnace is an excellent furnace for raising the temperature of metal to a high temperature, melting it, and causing it to react quickly with sulfur. Because an arc furnace does not require oxygen or air as a heat source, oxidation of metals containing nickel can be avoided, and sulfides can be obtained in a high yield.

[0080] There are two types of arc furnaces: direct arc furnaces, which use direct arc heating, and indirect arc furnaces, which use indirect arc heating. Direct arc furnaces are preferred because the electrodes and metal are in direct contact with each other, making it easier to heat the metal to high temperatures and facilitating temperature control.

[0081] Arc furnaces include direct current arc furnaces (DC), which utilize arcs generated based on direct current, and alternating current arc furnaces (AC arc furnaces), which utilize arcs generated between each electrode and the object to be heated using alternating current. It is particularly preferable to use a three-phase electrode AC arc furnace equipped with three electrodes compatible with three-phase AC current.

[0082] When melting ferronickel in a melting furnace using a burner or an arc furnace, oxygen may be blown into the molten metal. This oxidizes the iron contained in the molten metal and makes it easier to control the temperature of the molten metal. Furthermore, blowing oxygen into the molten metal oxidizes the iron contained in the molten metal, making it possible to adjust the nickel content in the resulting sulfide. The nickel content in the sulfide may be adjusted by controlling the amount (supply amount) of the sulfiding agent added, or by a combination of these.

[0083] The sulfide of the sulfurized molten metal can be obtained by removing it from the tap and cooling it.

[0084] 3. Nickel Oxide Ore Treatment Method The above-described sulfide production method can also be defined as a nickel oxide ore treatment method. As described above, an oxide ore and a reducing agent are mixed to obtain a mixture, and the mixture is subjected to a reduction treatment to obtain a metal, which is then sulfidized to obtain a sulfide, thereby making it possible to obtain a sulfide with a high nickel concentration. Therefore, by recovering nickel from the sulfide treated by the nickel oxide ore treatment method according to this embodiment, it becomes possible to efficiently recover nickel in the form of sulfide, even if the nickel oxide ore is a low-grade nickel oxide ore.

[0085] 4. Nickel Smelting Method The nickel smelting method according to this embodiment includes a wet process for producing sulfide by the sulfide production method described above and obtaining a leachate from the obtained sulfide. By passing through the wet process, it becomes possible to further separate the sulfide from impurities.

[0086] An example of the wet process is a chlorine leaching process in which metals such as nickel are leached into an aqueous solution using chlorine gas from the nickel-containing sulfide obtained in the sulfurization process as a raw material, to produce a nickel chloride aqueous solution as a chlorine leachate.

[0087] Furthermore, together with the nickel-containing sulfide obtained in the sulfiding step S5, a cementation residue generated in a cementation step for removing copper ions, which are impurities contained in a copper-containing nickel chloride aqueous solution in a nickel hydrometallurgical process, may be subjected to this wet step (chlorine leaching step).

[0088] In the chlorine leaching step, when the sulfide is pumped, metal components contained in the sulfide, such as nickel sulfide (NiS), are oxidized and leached, thereby producing an aqueous nickel chloride solution, which is a chlorine leaching solution.

[0089] The chlorine leaching step in which metals such as nickel are leached from the nickel-containing sulfide obtained in the sulfurization step S5 using chlorine gas has been described as an example of a wet process, but the leachate may also be obtained by a process in which metals such as nickel are leached using an acid other than chlorine gas.

[0090] The present invention will be explained in more detail below by showing examples thereof, but the present invention is not limited to the following examples in any way.

[0091] <<Example 1>> [Mixing of Raw Powders] For each sample, nickel oxide ore (nickel grade = 0.91 mass %, MgO content = 15.3 mass %) as the raw ore, silica sand and limestone as flux components, a binder, and a reducing agent (coal powder, carbon content: 41 wt %, average particle size: approximately 130 μm) were mixed using a mixer while adding an appropriate amount of water to obtain a mixture.

[0092] Such ores with low nickel grades and high MgO contents cannot be processed by existing smelting methods due to technical difficulties or commercial costs. Pulverized coal is used as a reducing agent to remove nickel oxide and iron oxide (FeO) contained in the raw material nickel oxide ore. ２ O ３ ) was contained in an amount of 35%, assuming that the amount necessary for reducing them exactly was 100%.

[0093] [Molding of Mixture] Next, the mixture obtained for each sample was molded into pellets using a pelletizer, and the obtained pellets were then sieved to obtain pellets with a diameter of 15±0.4 mm, which were used for the test.

[0094] Next, each sample was dried by blowing hot air at 200 to 250°C onto it so that the solid content was approximately 70% by weight and the moisture content was approximately 30% by weight. Table 3 below shows the solid composition (excluding carbon) of the mixture (pellet) after drying.

[0095]

[0096] [Reducing Heat Treatment of Pellets] The dried sample pellets were each charged into a reducing furnace with a nitrogen atmosphere substantially free of oxygen. The temperature condition during charging into the reducing furnace was 500±20°C.

[0097] Next, the mixture pellets were subjected to a reduction heat treatment at the temperature and for the time shown in Table 4. After the reduction treatment, the samples were quickly cooled to room temperature in a nitrogen atmosphere and then taken out into the air.

[0098] Here, the pellets are charged into the reduction furnace by preliminarily adding ash (mainly composed of SiO ２ and other components include Al ２ O ３ The pellets were placed on a layer of silica gel (containing a small amount of oxides such as MgO) and then placed on the layer.

[0099] For each sample after the reduction heat treatment, the nickel metallization rate and the nickel content in the metal were analyzed and calculated using an ICP emission spectrometer (Shimaz Model S-8100).

[0100] The nickel metallization rate and the nickel content in the metal were calculated using the following formula.

[0101] Nickel metallization rate = amount of metallized Ni ÷ (total amount of Ni in the mixture) × 100 (%)

[0102] Nickel content in metal = amount of metalized Ni ÷ (total amount of metalized Ni and Fe) × 100 (%)

[0103] After the reduction heat treatment, each sample was crushed by wet processing, and then the metal was recovered by magnetic separation. The nickel metal recovery rate was calculated from the content of nickel oxide ore in the pellet stack charged into the reduction furnace, the nickel content in the nickel oxide ore, and the amount of recovered nickel.

[0104] The nickel metal recovery rate was calculated by the following formula: Nickel metal recovery rate = recovered Ni amount / (charged oxide ore amount x Ni content in oxide ore) x 100 (%)

[0105] Table 4 below shows the nickel metallization rate, nickel content in the metal, and nickel metal recovery rate for each sample.

[0106]

[0107] As can be seen from the above table, by subjecting a mixture containing an oxide ore and a reducing agent to a reduction treatment to obtain a metal, it is possible to obtain a metal with a relatively high nickel concentration (i.e., a high nickel grade) even when a low-grade nickel oxide ore is used.

[0108] [Sulfurization Process] The metal obtained in the reduction process was melted in a melting furnace using a burner, and sulfur gas was supplied as a sulfurizing agent to the molten metal to obtain sulfides. The sulfur gas was supplied while controlling the sulfur partial pressure in the furnace to 1 atmosphere. Coal, charcoal, coke, and natural gas were used as heating fuels for the melting furnace. Natural gas burned most stably and was easy to control the temperature. The sulfurization process was terminated when the amount of sulfur consumed and the amount of nickel present in the furnace reached a 1:1 atomic ratio.

[0109] The nickel grade (Ni content) of the obtained sulfide was calculated by analyzing it using an ICP optical emission spectrometer (SHIMAZU S-8100 model). The nickel grade in the sulfide was 63-66%, and the sulfur grade was 21-24%. As described above, it can be seen that by subjecting the metal obtained in the reduction step to the sulfurization step, it is possible to separate metals other than the target of recovery, such as iron, and obtain sulfide with a high nickel concentration. It is then speculated that by subjecting this sulfide to a wet process in which it is brought into contact with an acid solution, it is possible to efficiently recover the target nickel, even if the target oxide ore to be treated is of low grade.

[0110] <<Example 2>> [Mixing of Raw Powders] For each sample, nickel oxide ore (nickel grade = 0.91 mass %, MgO content = 15.3 mass %) as the raw ore, silica sand and limestone as flux components, a binder, and a carbonaceous reducing agent (coal powder, carbon content: 41 wt %, average particle size: approximately 130 μm) were mixed using a mixer while adding an appropriate amount of water to obtain a mixture.

[0111] Such ores with low nickel grade and high MgO content cannot be processed by existing smelting methods due to technical difficulties or commercial unreasonable costs. Pulverized coal is used as a carbonaceous reducing agent to remove nickel oxide and iron oxide (Fe) contained in the raw ore, which is nickel oxide ore. ２ O ３ ) was contained in an amount of 35%, assuming that the amount necessary for reducing them exactly was 100%.

[0112] [Molding of Mixture] Next, the mixture obtained for each sample was molded into pellets using a pelletizer, and the obtained pellets were then sieved to obtain pellets with a diameter of 15±0.4 mm, which were used for the test.

[0113] Next, each sample was dried by blowing hot air at 200 to 250°C onto it so that the solid content was about 70% by weight and the moisture content was about 30% by weight. Table 5 below shows the solid composition (excluding carbon) of the mixture (pellet) after drying.

[0114]

[0115] [Reducing Heat Treatment of Pellets] The dried sample pellets were each charged into a reducing furnace with a nitrogen atmosphere substantially free of oxygen. The temperature condition during charging into the reducing furnace was 500±20°C.

[0116] Next, the pellets of the mixture were subjected to a reduction heat treatment at the temperature and for the time shown in Table 6. After the reduction treatment, the pellets were quickly cooled to room temperature in a nitrogen atmosphere, and then taken out into the air.

[0117] Here, the pellets are charged into the reduction furnace by preliminarily adding ash (mainly composed of SiO ２ and other components include Al ２ O ３ The pellets were placed on a layer of silica gel (containing a small amount of oxides such as MgO) and then placed on the layer.

[0118] For each sample after the reduction heat treatment, the nickel metallization rate and the nickel content in the metal were analyzed and calculated using an ICP emission spectrometer (Shimaz Model S-8100).

[0119]

[0120] As can be seen from the above table, by subjecting a mixture containing an oxide ore and a reducing agent to a reduction treatment to obtain a metal, it is possible to obtain a metal with a relatively high nickel concentration (i.e., a high nickel grade) even when a low-grade nickel oxide ore is used.

[0121] [Sulfurization step] The metal obtained in the reduction step was melted in an arc furnace, and sulfur gas was supplied as a sulfurizing agent to the molten metal in the molten state to sulfurize it, thereby obtaining a sulfide. At this time, the sulfur gas was supplied while controlling the sulfur partial pressure in the furnace to 1 atmosphere. The sulfurization step was terminated when the amount of consumed sulfur and the amount of nickel present in the furnace reached a ratio of 1:1 in atomic number.

[0122] The nickel grade (Ni content) of the obtained sulfide was calculated by analyzing it using an ICP optical emission spectrometer (SHIMAZU S-8100 model). The nickel grade in the sulfide was 67%, and the sulfur grade was 24%. As described above, it can be seen that by subjecting the metal obtained in the reduction step to the sulfurization step, metals other than the target to be recovered, such as iron, can be separated, and a sulfide with a relatively high nickel concentration can be obtained. It is then speculated that by subjecting this sulfide to a wet process in which it is brought into contact with an acid solution, it is possible to efficiently recover the target nickel, even if the target oxide ore to be treated is of low grade.

[0123] <<Example 3>> [Mixing of Raw Powders] For each sample, nickel oxide ore (nickel grade = 0.90 mass %, MgO content = 15.5 mass %) as the raw ore, silica sand and limestone as flux components, a binder, and a carbonaceous reducing agent (coal powder, carbon content: 41 wt %, average particle size: approximately 130 μm) were mixed using a mixer while adding an appropriate amount of water to obtain a mixture.

[0124] Such ores with low nickel grade and high MgO content cannot be processed by existing smelting methods due to technical difficulties or commercial unreasonable costs. Pulverized coal is used as a carbonaceous reducing agent to remove nickel oxide and iron oxide (Fe) contained in the raw ore, which is nickel oxide ore. ２ O３ ) was contained in an amount of 35%, assuming that the amount necessary for reducing them exactly was 100%.

[0125] [Molding of Mixture] Next, the mixture obtained for each sample was molded into pellets using a pelletizer, and the obtained pellets were then sieved to obtain pellets with a diameter of 15±0.4 mm, which were used for the test.

[0126] Next, each sample was dried by blowing hot air at 200 to 250°C onto it so that the solid content was approximately 70% by weight and the moisture content was approximately 30% by weight. Table 7 below shows the solid composition (excluding carbon) of the mixture (pellet) after drying.

[0127]

[0128] [Reducing Heat Treatment of Pellets] The dried sample pellets were each charged into a reducing furnace with a nitrogen atmosphere substantially free of oxygen. The temperature condition during charging into the reducing furnace was 500±20°C.

[0129] Next, the pellets of the mixture were subjected to a reduction heat treatment at the temperature and for the time shown in Table 8. After the reduction treatment, the pellets were quickly cooled to room temperature in a nitrogen atmosphere, and then taken out into the air.

[0130] Here, the pellets are charged into the reduction furnace by preliminarily adding ash (mainly composed of SiO ２ and other components include Al ２ O ３ The pellets were placed on a layer of silica gel (containing a small amount of oxides such as MgO) and then placed on the layer.

[0131] For each sample after the reduction heat treatment, the nickel metallization rate and the nickel content in the metal were analyzed and calculated using an ICP emission spectrometer (Shimaz Model S-8100).

[0132] Table 8 below shows the nickel metallization rate, nickel content in the metal, and nickel metal recovery rate for each sample.

[0133]

[0134] As can be seen from the above table, by subjecting a mixture containing an oxide ore and a reducing agent to a reduction treatment to obtain a metal, it is possible to obtain a metal with a relatively high nickel concentration (i.e., a high nickel grade) even when a low-grade nickel oxide ore is used.

[0135] [Sulfurization Step] The metal obtained in the reduction step was melted in an arc furnace, and a sulfiding agent was supplied to the molten metal in a molten state to obtain a sulfide. Solid sulfur and sulfur gas were used as the sulfiding agent. The sulfide 1 was obtained by using solid sulfur as the sulfiding agent, and the sulfide 2 was obtained by using sulfur gas as the sulfiding agent.

[0136] At this time, the sulfurizing agent was supplied while controlling the sulfur partial pressure in the furnace to 1 atmosphere. The amount of sulfurizing agent used to obtain sulfide 2 was approximately 90% of the amount used to obtain sulfide 1. The nickel grade of both sulfide 1 and sulfide 2 was 64-66%, and the sulfur content was 22-24%. As described above, it can be seen that by subjecting the metal obtained in the reduction step to the sulfurization step, metals other than the target to be recovered, such as iron, can be separated and a sulfide with a high nickel concentration can be obtained. It is then speculated that by subjecting this sulfide to a wet process in which it is brought into contact with an acid solution, the target to be recovered, nickel can be efficiently recovered even if the target oxide ore to be treated is of low grade.

[0137] 1 Pellets 2 Rotary hearth furnace 20a to 20d Treatment chamber 21 Preheating chamber 40 Cooling chamber

Claims

1. A method for producing sulfide by producing sulfide 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 charging the mixture into a reduction furnace and subjecting the mixture to a reduction treatment to obtain a reduced product containing a metal which is ferronickel metal and a slag which is 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 step to obtain a sulfide containing nickel. A method for producing sulfide.

2. The method for producing sulfide according to claim 1, wherein in the sulfidation process step, the metal is melted using a melting furnace using a burner, and a sulfide layer is formed between the molten metal and the gas phase part by adding a sulfiding agent to the molten metal.

3. The method for producing sulfide according to claim 1, wherein in the sulfidation process step, the metal is melted using an arc furnace, and a sulfiding agent is added to the molten metal.

4. The method for producing sulfide according to claim 2, wherein in the sulfidation process step, a fuel containing one or more selected from charcoal, coke, and natural gas is used as the fuel of the burner.

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

6. The method for producing sulfide according to any one of claims 1 to 3, wherein in the reduction process step, the mixture is charged into a reduction furnace, and a reduction treatment is performed on the mixture to obtain ferronickel metal, and the ferronickel metal is supplied to the sulfidation process step.

7. A nickel smelting method, comprising: a mixing process step of mixing nickel oxide ore and a reducing agent to obtain a mixture; a reduction process step of charging the mixture into a reduction furnace and subjecting the mixture to a reduction treatment to obtain a reduced product containing a metal which is ferronickel metal and a slag which is an oxide; a separation process step of separating the metal and the slag from the reduced product; a sulfidation process step of adding a sulfiding agent to the metal obtained in the separation process step to obtain a sulfide; and a wet process step of obtaining a leachate from the sulfide obtained in the sulfidation process step.

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