Method for smelting nickel oxide ore

Abstract

To provide a method for smelting nickel oxide ore that can efficiently produce high-quality metal.SOLUTION: A method for smelting nickel oxide ore includes a mixing step for mixing nickel oxide ore with a carbonaceous reductant to obtain a mixture, a molding step for molding the mixture to obtain briquette, and a reduction step for reducing the briquette. The nickel oxide ore includes nickel oxide ore with an average particle size of 75 μm or more and 800 μm or less.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a smelting method for producing a briquette from nickel oxide ore and a reducing agent by reducing and heating it at high temperatures in a reduction furnace to obtain a reduced product such as ferronickel. [Background technology]

[0002] Known methods for smelting nickel oxide ore called limonite or saprolite include a dry smelting method in which nickel matte is produced by roasting together with sulfur using a smelting furnace, a dry smelting method in which nickel matte is produced by reducing the ore with a carbonaceous reducing agent using a rotary kiln or a moving hearth furnace, and an autoclave in which a sulfurizing agent is added to the leachate obtained by leaching nickel and cobalt with sulfuric acid to produce a mixed sulfide.

[0003] Among the various smelting methods described above, when nickel oxide ore is smelted by reduction together with a carbon source, first, a pretreatment is performed to agglomerate the raw material ore, form a slurry, etc. Specifically, when agglomerating nickel oxide ore, that is, when converting a powder or fine particle form into an agglomerate, the nickel oxide ore is generally mixed with a binder, a reducing agent, etc., and then subjected to moisture adjustment, etc., before being charged into an agglomeration machine to form agglomerates (referring to pellets, briquettes, etc., hereinafter simply referred to as "briquettes") of about 10 mm to 30 mm in size.

[0004] The briquette needs to have a certain degree of breathability to "evaporate" the moisture contained therein. Also, if the reduction does not proceed uniformly within the briquette, the composition of the resulting reduced product will be non-uniform, resulting in problems such as metal dispersion or uneven distribution. Therefore, it is important to mix the mixture uniformly and to maintain as uniform a temperature as possible during the reduction process of the briquette.

[0005] In addition, it is also important to coarsen the ferronickel produced by reduction. This is because if the produced ferronickel has a fine size of, for example, several tens of μm to several hundreds of μm, it becomes difficult to separate it from the slag produced at the same time, and the recovery rate (yield) of ferronickel is significantly reduced. For this reason, a process for coarsening the ferronickel after reduction is also necessary.

[0006] Furthermore, from an industrial point of view, it is also important to keep smelting costs as low as possible, and there is a demand for continuous processing that can be operated in compact facilities.

[0007] For example, Patent Document 1 discloses a method for producing granular metals in which agglomerates containing a metal oxide and a carbonaceous reducing agent are supplied onto the hearth of a moving-bed type reducing melting furnace, heated, and the metal oxide is reduced and melted, in which agglomerates having an average diameter of 19.5 mm to 32 mm are supplied onto the hearth and heated so as to have a laying density of 0.5 to 0.8, where the laying density is the relative value of the projected area ratio of the agglomerates onto the hearth to the maximum projected area ratio of the agglomerates onto the hearth when the distance between the agglomerates is 0. In this method, it is described that the productivity of granular metallic iron can be increased by controlling both the laying density and the average diameter of the agglomerates.

[0008] However, the method disclosed in Patent Document 1 is a technique for controlling the reaction occurring outside the agglomerates, and does not focus on controlling the reaction occurring inside the agglomerates, which is the most important factor in the reduction reaction. On the other hand, there has been a demand for obtaining higher quality metal (metal, alloy) by controlling the reaction occurring inside the agglomerates to increase the reaction efficiency and promote the reduction reaction more uniformly.

[0009] In addition, the method of using a specific diameter as the agglomerates as described in Patent Document 1 has the problem of low metal recovery rate when producing agglomerates because it is necessary to remove those that do not have the specific diameter. Furthermore, in the method of Patent Document 1, the laying density of the agglomerates needs to be adjusted to 0.5 to 0.8, and the agglomerates cannot be stacked, which also causes a problem of low productivity. For these reasons, the method of Patent Document 1 also has the problem of high manufacturing costs.

[0010] As described above, the technology of producing metals and alloys by mixing and reducing oxide ores has many problems in terms of increasing productivity, reducing production costs, and improving metal quality. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] JP 2011-256414 A Summary of the Invention [Problem to be solved by the invention]

[0012] The present invention has been proposed in view of the above circumstances, and has an object to provide a method for smelting nickel oxide ore that can efficiently produce high-quality metal. [Means for solving the problem]

[0013] As a result of extensive research, the inventors have found that the above-mentioned problems can be solved by mixing nickel oxide ore having a predetermined average particle size with a carbonaceous reducing agent to obtain a mixture, and then subjecting briquettes of the mixture to a reduction treatment, thereby completing the present invention.

[0014] (1) A first aspect of the present invention is a method for smelting nickel oxide ore, the method comprising: a mixing step of mixing a nickel oxide ore with a carbonaceous reducing agent to obtain a mixture; a molding step of molding the mixture to obtain briquettes; and a reduction step of subjecting the briquettes to a reduction treatment, wherein the nickel oxide ore contains nickel oxide ore having an average particle size in the range of 75 μm or more and 800 μm or less.

[0015] (2) A second aspect of the present invention is a method for smelting nickel oxide ore according to the first aspect of the present invention, wherein the carbonaceous reducing agent has an average particle size of 30 μm or more and 500 μm or less. Effect of the Invention

[0016] According to the present invention, a method for smelting nickel oxide ore capable of efficiently producing high-quality metal can be provided. [Brief description of the drawings]

[0017] [Figure 1] FIG. 1 is a process diagram showing an example of a flow of a method for smelting nickel oxide ore. [Diagram 2] FIG. 1 is a schematic diagram showing an example of a configuration of a reduction furnace, and is a diagram for explaining the state of reduction treatment in the reduction furnace. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] Hereinafter, the embodiments of the present invention will be described in detail, but 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 numbers) means "X or more and Y or less."

[0019] 1. Overview of the Invention The present invention relates to a method for smelting nickel oxide ore, which uses nickel oxide ore as a raw material, and produces a metal as a reduction product by mixing the nickel oxide ore with a reducing agent and reducing the resulting mixture.

[0020] Specifically, the method for smelting an oxide ore according to the present invention is characterized in that nickel oxide ore having an average particle size in the range of 75 μm to 800 μm is mixed with a carbonaceous reducing agent to obtain a mixture, and briquettes of the mixture are subjected to a reduction treatment.

[0021] According to this method, by subjecting briquettes that have both strength and moldability to reduction treatment, it is possible to improve the nickel recovery rate and also to stably apply reduction treatment to the briquettes, thereby improving the quality of the obtained metal.

[0022] 2. Nickel oxide ore smelting method Hereinafter, as a specific embodiment of the present invention (hereinafter referred to as "the present embodiment"), a smelting method will be described as an example in which nickel oxide ore is used as a raw ore, and the nickel (nickel oxide) and iron (iron oxide) contained in the nickel oxide ore are metallized by reducing the nickel oxide ore to produce an iron-nickel alloy (ferronickel).

[0023] Specifically, as shown in FIG. 1, the method for smelting nickel oxide ore according to the present embodiment includes a mixing step S1 of mixing nickel oxide ore with a reducing agent to obtain a mixture, a molding step S2 of molding the obtained mixture into a predetermined shape to obtain briquettes, a drying step S3 of drying the obtained briquettes, a reduction step S4 of reducing the briquettes, and a recovery step S5 of recovering metal from the obtained reduced product.

[0024] <2-1. Mixing process> In the mixing step S1, nickel oxide ore and a carbonaceous reducing agent are mixed to obtain a mixture. Specifically, in the mixing step S1, first, a carbonaceous reducing agent is added to nickel oxide ore, which is a raw material ore, and mixed, and then powders of iron ore, flux components, binders, etc., as optional additives, are added and mixed to obtain a mixture. The mixing process can be performed using a mixer, etc.

[0025] The nickel oxide ore as the raw material ore is not particularly limited, but may be limonite ore, saprolite ore, etc. The nickel oxide ore contains at least nickel oxide (NiO) and iron oxide (Fe2O3).

[0026] Here, the mixing step S1 is characterized in that a nickel oxide ore containing a nickel oxide ore having an average particle size in the range of 75 μm or more and 800 μm or less and a carbonaceous reducing agent containing a carbonaceous reducing agent having an average particle size of 30 μm or more and 500 μm or less are mixed to obtain a mixture.

[0027] In the smelting of nickel oxide ore, a mixture containing nickel oxide ore and a carbonaceous reducing agent is formed into a predetermined shape and the briquette is subjected to a reduction treatment. However, even if nickel oxide ore having a large average particle size is mixed with a carbonaceous reducing agent and the like to obtain a mixture and then formed into a briquette, the strength of the briquette is low. When a reduction treatment is performed on a briquette with low strength, the briquette may burst during the reduction treatment. This causes the briquette to burst and generate briquettes of different shapes and sizes and their fragments, which reduces the nickel recovery rate and further makes it difficult to stably perform a reduction treatment on the briquettes, resulting in a decrease in the quality of the obtained metal.

[0028] On the other hand, even if nickel oxide ore having a small average particle size is mixed with a carbonaceous reducing agent or the like to obtain a mixture and molded into a briquette, the strength of the briquette is improved, but the moldability of the briquette is reduced. As a result, the obtained briquette is cracked or chipped, and cannot be used as a briquette to be subjected to reduction treatment. Even if the briquette can be used as a briquette, the briquette stuck to the die becomes a loss, and the recovery rate of nickel is reduced. Furthermore, the moldability of the briquette is reduced, and a briquette of a desired shape cannot be obtained, and it becomes difficult to stably perform reduction treatment on the briquette, and the quality of the obtained metal is reduced. In this way, it is difficult to achieve both strength and moldability of the briquette by controlling only the average particle size of the nickel oxide ore.

[0029] Therefore, the inventors have found through their research that it is possible to obtain a briquette with both strength and moldability by mixing a nickel oxide ore containing nickel oxide ore having an average particle size in the range of 75 μm to 800 μm with a mixture, obtaining a mixture, and molding the mixture into a briquette. By subjecting such a briquette to a reduction treatment, it is possible to improve the nickel recovery rate, and it is also possible to stably apply the reduction treatment to the briquette, thereby improving the quality of the obtained metal.

[0030] The average particle size of the nickel oxide ore is preferably 100 μm or more and 500 μm or less.

[0031] The nickel oxide ore may further contain nickel oxide ores having different particle sizes, so long as the nickel oxide ore contains nickel oxide ores having an average particle size in the range of 75 μm to 800 μm. The nickel oxide ores having an average particle size in the range of 75 μm to 800 μm preferably account for 50 mass% or more of the total amount of nickel oxide ores contained in the mixture, more preferably 70 mass% or more, even more preferably 90 mass% or more, and most preferably 100 mass%.

[0032] The method for obtaining nickel oxide ore or carbonaceous reductant having a predetermined average particle size may be a method of crushing the nickel oxide ore or carbonaceous reductant using a crushing device to obtain the desired average particle size, or a method of sieving the crushed nickel oxide ore or carbonaceous reductant using a sieve having a predetermined diameter.

[0033] Examples of the carbonaceous reducing agent mixed with the nickel oxide ore include fossil fuels such as coal and coke. The average particle size of the carbonaceous reducing agent is not particularly limited, but is preferably 30 μm or more and 500 μm or less, and more preferably 30 μm or more and 150 μm or less. By setting the average particle size of the carbonaceous reducing agent to 30 μm or more and 500 μm or less, it becomes possible to uniformly mix the carbonaceous reducing agent with nickel oxide ore having an average particle size in a predetermined range, improving uniformity during reduction treatment and enabling the production of higher quality ferronickel.

[0034] The amount of the carbonaceous reducing agent mixed is preferably 50% by mass or less, and more preferably 40% by mass or less, when the amount of the carbonaceous reducing agent necessary to reduce the nickel oxide and iron oxide constituting the nickel oxide ore without excess or deficiency is taken as 100% by mass. The lower limit of the amount of the carbonaceous reducing agent mixed is not particularly limited, but is preferably 10% by mass or more, and more preferably 15% by mass or more, relative to the total value of the chemical equivalents, 100% by mass.

[0035] The amount of carbonaceous reducing agent necessary to reduce nickel oxide and iron oxide without excess or deficiency can be rephrased as the total value of the chemical equivalent necessary to reduce all of the nickel oxide to nickel metal and the chemical equivalent necessary to reduce the iron oxide to iron metal (hereinafter also referred to as the "total value of chemical equivalents").

[0036] The iron ore, which is an optional additive, is not particularly limited, but for example, iron ore with an iron content of about 50 mass % or more, hematite obtained by hydrometallurgy of nickel oxide ore, etc. can be used.

[0037] The ore and the carbonaceous reducing agent may be mixed and then formed into pellets or briquettes. In this case, examples of the binder include bentonite, polysaccharides, resins, water glass, dehydrated cake, etc. Examples of the flux component include calcium oxide, calcium hydroxide, calcium carbonate, silicon dioxide, etc.

[0038] Table 1 below shows an example of the composition (wt %) of some of the raw material powders mixed in the mixing step S1, but the composition of the raw material powders is not limited to this.

[0039] [Table 1]

[0040] <2-2. Molding process> In the molding step S2, the mixture is molded into a predetermined shape to form a briquette (pellet). In this embodiment, nickel oxide ore having a predetermined average particle size is mixed to form a mixture, and the mixture is molded to obtain a briquette, so that the strength of the briquette can be increased and moldability can be improved.

[0041] The shape of the briquettes (pellets) may be any shape that allows them to be stacked on the hearth of the reduction furnace, and is preferably, for example, a spherical, rectangular, cuboidal, cylindrical, or other shape. By forming the mixture into such a shape, the mixture can be easily formed, and the cost of forming can be reduced. In addition, since the shape to be formed is not complicated, the occurrence of pellets with molding defects can be reduced.

[0042] In the molding step S2, for example, the mixture can be molded using a briquette (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. By kneading the mixture under high pressure and high shear, it is possible to break up the agglomerations of the raw material powder mixture, to effectively knead the mixture, and to increase the strength of the resulting briquettes (pellets).

[0043] It is also possible to form the powder using a briquette press. The appropriate equipment can be selected in consideration of the equipment, pellet strength, recovery rate, etc.

[0044] <2-3. Drying process> In the drying step S3, the briquettes obtained in the molding step S2 are dried. Although the drying step is not essential, when the mixture is mixed with a large amount of water in the kneading in the mixing step S1 or the molding step S2 or in the molding of the briquettes, the amount of moisture contained in the atmospheric gas in the reduction furnace can be reduced by subjecting the briquettes to a drying treatment. In addition, by drying the briquettes obtained in the molding step S2, the strength of the briquettes can be further improved. In addition, the amount of moisture contained in the atmospheric gas in the reduction furnace can be more effectively reduced, and the oxidation of the metal contained in the briquettes can be more effectively suppressed.

[0045] The method for drying the lumps is not particularly limited, and any conventionally known method can be used, such as a method of keeping the briquettes at a predetermined drying temperature (e.g., 200°C to 400°C) or a method of blowing hot air at a predetermined drying temperature (e.g., 200°C to 400°C) onto the briquettes to dry them. By such a drying process, for example, the solid content of the briquettes is adjusted to about 70% by mass and the moisture content to about 30% by mass. Note that the temperature of the briquettes themselves during this drying process is preferably less than 100°C, which can prevent the briquettes from bursting due to bumping of moisture or the like.

[0046] This drying step may be carried out outside a reduction furnace, which will be described later, or the lumps may be placed in a reduction furnace, which will be described later, and the drying process may be carried out in the reduction furnace.

[0047] Here, when drying briquettes having a particularly large volume, cracks or cracks may be present in the briquettes before and after drying. When the volume of the briquettes is large, the briquettes melt and shrink during reduction, which often results in cracks or cracks. However, when the volume of the briquettes is large, the effects of the increase in surface area caused by the cracks or cracks are small, and therefore no major problems are likely to occur. Therefore, cracks or cracks may be present in the briquettes before reduction.

[0048] The drying process may be carried out continuously at one time or in multiple steps. By carrying out the drying process in multiple steps, the bursting of the briquettes can be more effectively suppressed. When the drying process is carried out in multiple steps, the drying temperature from the second step onwards is preferably 150°C or higher and 400°C or lower. Drying within this range makes it possible to dry without the reduction reaction proceeding.

[0049] An example of the composition (parts by mass) of the solid content in the aggregates (mixture) after drying treatment is shown in the following Table 2. Note that the composition of the aggregates (mixture) is not limited to this.

[0050] [Table 2]

[0051] <2-4. Reduction process> In the reduction step S4, the briquettes that have been through the drying step are subjected to a reduction treatment. Specifically, the briquettes are loaded into a reduction furnace, and the briquettes are subjected to a heat reduction treatment. The heat reduction treatment in the reduction step S4 causes a smelting reaction (reduction reaction) to proceed based on the carbonaceous reducing agent in the mixture, and ferronickel metal (hereinafter simply referred to as "metal") and ferronickel slag (hereinafter simply referred to as "slag") are generated separately in the mixture (briquette).

[0052] In this embodiment, nickel oxide ores having a predetermined average particle size are mixed to prepare a mixture, and the mixture is molded into briquettes, so that briquettes having both strength and moldability can be obtained. By subjecting such briquettes to a reduction treatment, the nickel recovery rate can be improved, and the briquettes can be stably reduced, thereby improving the quality of the obtained metal.

[0053] The temperature in the reduction treatment (reduction temperature) is not particularly limited, but is preferably in the range of 1200°C to 1450°C, and more preferably in the range of 1300°C to 1400°C. By carrying out reduction within such a temperature range, the reduction reaction can be caused to occur uniformly, and ferronickel with reduced quality variation can be produced. Moreover, by carrying out reduction at a reduction temperature more preferably in the range of 1300°C to 1400°C, the desired reduction reaction can be caused to occur in a relatively short time.

[0054] The time for which the reducing heat treatment is performed in the reducing furnace is set according to the temperature of the reducing furnace, but is preferably 10 minutes or more, and more preferably 15 minutes or more. On the other hand, the upper limit of the time for which the reducing heat treatment is performed may be 50 minutes or less, or may be 40 minutes or less, from the viewpoint of suppressing an increase in production costs.

[0055] The heat required for reduction, calculated by multiplying the reduction temperature (°C) by the reduction time (min), is preferably in the range of 20,000 (°C x min) to 40,000 (°C x min). This allows efficient production of high-quality metal.

[0056] In the thermal reduction process, for example, in a short time of about one minute, the nickel oxide and iron oxide in the mixture are first reduced near the surface of the mixture where the reduction reaction is likely to proceed, and are converted into metal and ferronickel, forming a shell. Meanwhile, within the shell, the slag components gradually melt as the shell forms, producing liquid slag. After about 10 minutes of processing, the excess reducing agent that is not involved in the reduction reaction is absorbed into the metal, lowering its melting point, and the metal also becomes liquid.

[0057] The metal and slag do not mix, and become a mixture of separate phases of metal solid and slag solid by subsequent cooling. The volume of these mixtures shrinks to about 50% to 60% of the volume of the briquette before it is inserted into the reduction furnace.

[0058] The reduction furnace may be a fixed hearth, but it is preferable to use a moving hearth furnace. By using a moving hearth furnace as such a reduction furnace, the briquettes can be processed more efficiently. In addition, by using a moving hearth furnace, the reduction reaction proceeds continuously and the reaction can be completed in one facility, and the processing temperature can be controlled more accurately than when the processing in each step is performed using separate furnaces. Furthermore, the heat loss between each process is reduced, making it possible to operate more efficiently. Below, the configuration of a rotary hearth furnace as an example of a moving hearth furnace is described with reference to FIG. 2.

[0059] FIG. 2 is a diagram (plan view) showing a configuration example of a rotary hearth furnace with a rotating hearth. As shown in FIG. 2, a rotary hearth furnace 2 that is circular and divided into a plurality of processing chambers 20a to 20d can be used. In the rotary hearth furnace 2, each processing is performed in each region while rotating in a predetermined direction. In this rotary hearth furnace, the processing temperature in each region can be adjusted by controlling the time (moving time, rotating time) when passing through each region, and the briquettes 1 are smelted every time the rotary hearth furnace rotates once. Here, the rotary hearth furnace 2 may be provided with a preheating chamber outside the furnace. In addition, the rotary hearth furnace 2 may be provided with a cooling chamber outside the furnace. The moving hearth furnace may be a roller hearth kiln or the like.

[0060] The heating means of the reduction furnace is not particularly limited, and may be a burner or may be one using electricity or the like. A burner is preferable because it can effectively perform a heating and reducing treatment on the mixture in a short time. When a reduction furnace having a burner is used, for example, LPG, LNG, coal, coke, pulverized coal, or the like is used as the 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 or the like.

[0061] <2-5. Recovery process> In the recovery step S5, the metal is recovered from the reduction product obtained in the reduction step S4. Specifically, the reduction product containing a metal phase and a slag phase obtained by the thermal reduction treatment is cooled, and if necessary, pulverized to form a powder, and the metal (metal powder particles) is separated and recovered.

[0062] Methods for separating the metal phase and the slag phase from the mixture of the metal phase and the slag phase obtained as a solid include, for example, sieving to remove unnecessary materials, as well as separation by specific gravity or magnetic force.

[0063] Furthermore, the obtained metal phase and slag phase have poor wettability and can be easily separated. For example, by dropping the large mixture obtained by the reduction step S4 described above from a predetermined drop or by applying a predetermined vibration during sieving, the metal phase and slag phase can be easily separated from the mixture.

[0064] By separating the metal phase from the slag phase in this manner, the metal phase is recovered. EXAMPLES

[0065] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples in any way.

[0066] [Mixing process] For each sample, nickel oxide ore as raw ore, iron ore, silica sand and limestone as flux components, binder, and carbonaceous reductant (pulverized coal) were mixed using a mixer while adding an appropriate amount of water to obtain a mixture. For each sample, nickel oxide ore was used by mixing two types of nickel oxide ore with different particle sizes (first nickel oxide ore and second nickel oxide ore). The pulverized coal was included in an amount that was 28.0 mass% when the amount required to reduce nickel oxide and iron oxide (Fe2O3) contained in the nickel oxide ore as raw ore was taken as 100 mass%. The average particle size and mixing ratio of the nickel oxide ore and pulverized coal (carbonaceous reductant) used for each sample are shown in Table 4.

[0067] [Molding process] Each sample was molded into a shape of 25 mm wide x 35 mm long x 15 mm high (the corners were rounded and curved to prevent cracks and chips) using a briquette molding machine. After molding, briquettes without cracks or chips were considered to be good products and the recovery rate was calculated. The results are shown in Table 5 (referred to as "briquette recovery rate" in Table 5).

[0068] [Drying process] Next, each sample was dried by blowing hot air at 200°C to 250°C onto it so that the solid content was about 70% by weight and the moisture content was about 10% by weight. Table 3 below shows the solid content composition (excluding carbon) of the briquettes after drying.

[0069] [Table 3]

[0070] [Reduction process] The dried sample briquettes were then charged into a reduction furnace with a nitrogen atmosphere substantially free of oxygen, at a temperature of 500±20°C. Next, the mixture briquettes were subjected to a reduction heat treatment at the temperature and for the time shown in Table 5. After the reduction treatment, the samples were quickly cooled to room temperature in a nitrogen atmosphere and taken out into the air.

[0071] 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 (SHIMAZU S-8100 type).

[0072] The nickel metallization rate and the nickel content in the metal were calculated by the following formula. Nickel metallization rate = amount of metallized Ni in the mixture ÷ (total amount of Ni in the mixture) × 100 (%) Nickel content in metal = amount of metalized Ni in the mixture ÷ (total amount of metalized Ni and Fe in the mixture) × 100 (%)

[0073] After the reduction heat treatment, each sample was crushed by wet processing, and the metal was recovered by magnetic separation. The nickel metal recovery rate was calculated from the content of nickel oxide ore in the briquette charged in the reduction furnace, the nickel content in the nickel oxide ore, and the amount of recovered nickel. The nickel metal recovery rate was calculated by the following formula. Nickel metal recovery rate = Amount of Ni recovered ÷ (Amount of oxide ore charged × Ni content in oxide ore) × 100 (%)

[0074] Table 4 below shows the average particle size of nickel metal, nickel metallization rate, nickel content in the metal, and nickel metal recovery rate for each sample.

[0075] [Table 4]

[0076] As can be seen from Table 4, in Examples 1 to 12 in which nickel oxide ore containing nickel oxide ore having an average particle size in the range of 75 μm to 800 μm was mixed with a carbonaceous reducing agent to obtain a mixture, and the briquettes of the mixture were subjected to a reduction treatment, the briquette recovery rate was high.

[0077] Furthermore, good results were obtained in the nickel metallization rate and the nickel content in the metal in Examples 1 to 12. From this, it is understood that the method for smelting nickel oxide ore according to the present invention can improve the nickel recovery rate by achieving both strength and moldability of the briquette, and can also improve the quality of the obtained metal by stably applying a reduction treatment to the briquette.

[0078] On the other hand, in Comparative Examples 1 to 6 in which the average particle size of the nickel oxide ore was less than 75 μm and more than 800 μm, the briquette recovery rate was low, and the briquette strength and moldability could not be compatible, so that high-quality metal could not be efficiently produced. [Explanation of symbols]

[0079] 1 briquette 2 Rotary hearth furnace 20a~20d Processing chamber 21 Preheating Room 40 Cooling room

Claims

[Claim 1] a mixing step of mixing nickel oxide ore and a carbonaceous reductant to obtain a mixture; a molding step of molding the mixture to obtain briquettes; A reduction step of subjecting the briquettes to a reduction treatment, The nickel oxide ore contains nickel oxide ore having an average particle size in the range of 125 μm or more and 800 μm or less, The carbonaceous reducing agent contains a carbonaceous reducing agent having an average particle size of 30 μm or more and 117 μm or less, The average particle diameter of the nickel oxide ore and the carbonaceous reducing agent is a median diameter based on the sieve diameter of particles passing through a sieve. A method for smelting nickel oxide ores.

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