Method for smelting nickel oxide ore

Abstract

Provided is a method for smelting an oxidized ore with which it is possible to improve the grade of the obtained metal and to efficiently produce a high-quality metal. This nickel oxide ore smelting method comprises: a mixing step in which a nickel oxide ore and a first reducing agent are mixed to obtain a mixture; and a reduction step in which the mixture is introduced into a reduction furnace, a second reducing agent is introduced into the reduction furnace, and the mixture is reduced.

Description

Technical Field

[0001] This invention relates to a smelting method for obtaining reduced products such as iron and nickel by smelting particles made from oxidized ores such as nickel oxide ore and reducing agents in a reduction furnace under high temperature conditions. Background Technology

[0002] As for smelting methods for nickel oxide ores known as limonite or sapropel, there are known dry smelting methods that use a smelting furnace to roast nickel with sulfur to produce nickel matte; dry smelting methods that use a rotary kiln or moving bed furnace to reduce with a carbonaceous reducing agent to produce iron-nickel alloys (hereinafter also referred to as "iron-nickel"); and wet smelting methods that use an autoclave to add a sulfiding agent to the leachate obtained by leaching nickel or cobalt with sulfuric acid to produce mixed sulfides.

[0003] In the various smelting methods described above, when smelting nickel oxide ore by reduction together with a carbon source, a pretreatment process is first performed to granulate or slurry the raw ore. Specifically, when granulating the nickel oxide ore, i.e., processing it from powder or particulate form into lumps, the nickel oxide ore is mixed with a binder or reducing agent, and after adjusting the moisture content, it is loaded into a lump-forming machine, generally processed into lumps (referring to particles, clumps, etc., hereinafter referred to as "particles") of approximately 10 mm to 30 mm.

[0004] In order for the moisture contained in the particles to "evaporate," a certain degree of aeration is required. In addition, if the reduction does not proceed uniformly within the particles, the composition of the resulting reduced product becomes uneven, resulting in undesirable conditions such as metal dispersion or uneven distribution. Therefore, it is crucial to mix the mixture uniformly and to maintain as uniform a temperature as possible during the reduction treatment of the particles.

[0005] Furthermore, coarsening the reduced iron-nickel is also an important technique. This is because when the generated iron-nickel is extremely small, for example, tens to hundreds of micrometers in size, it is difficult to separate it from the simultaneously generated slag, leading to a significant decrease in the iron-nickel recovery rate. Therefore, it is necessary to coarsen the reduced iron-nickel.

[0006] In addition, how to reduce smelting costs is also an important technical issue, and there is a desire to achieve continuous operation with compact equipment.

[0007] For example, Patent Document 1 discloses a method for manufacturing granular metal by feeding lumps containing carbonaceous reducing agents such as metal oxides, coal, or coke onto the furnace bed of a moving bed reduction melting furnace for heating, thereby reducing and melting the metal oxides. In this method, when the relative value of the projected area ratio of the lumps on the furnace bed relative to the maximum projected area ratio of the lumps on the furnace bed when the distance between the lumps is set to 0 is used as the packing density, lumps with an average diameter of 19.5 mm or more and 32 mm or less are fed onto the furnace bed at a packing density of 0.5 or more and 0.8 or less for heating. This method describes how the production rate of granular iron can be improved by simultaneously controlling the packing density and average diameter of the lumps.

[0008] However, the method disclosed in Patent Document 1 is a technique for controlling the reaction occurring on the outside of the block, and does not focus on controlling the most important factor in the reduction reaction, namely the reaction occurring inside the block. On the other hand, by controlling the reaction occurring inside the block, reaction efficiency can be improved, and the reduction reaction can be carried out more uniformly, thereby seeking to obtain a higher quality metal (metal, alloy).

[0009] Furthermore, as described in Patent Document 1, the method for using materials with a specific diameter as blocks requires the removal of materials without the specific diameter, resulting in a low yield when producing blocks. Additionally, the method in Patent Document 1 requires adjusting the block density to between 0.5 and 0.8, making it impossible to stack the blocks, thus resulting in low productivity. For these reasons, the method in Patent Document 1 has high manufacturing costs.

[0010] As mentioned above, in the technology of mixing and reducing oxidized ores to manufacture metals or alloys, there are many challenges in improving productivity, reducing manufacturing costs, and improving the quality of the metals.

[0011] Existing technical documents

[0012] Patent documents

[0013] Patent document 1: Japanese Patent Application Publication No. 2011-256414. Summary of the Invention

[0014] The problem that the invention aims to solve

[0015] The purpose of this invention is to provide a smelting method for oxide ores, which is a smelting method for producing metals by reducing a mixture of oxide ores including nickel oxide ores. This method can improve the grade of the obtained metals and can effectively produce high-quality metals.

[0016] Methods for solving problems

[0017] The inventors conducted in-depth research to solve the aforementioned problems. The results showed that by introducing a second reducing agent containing coal, and further containing at least one of charcoal and starch, into a reduction furnace to perform reduction treatment on the mixture, the aforementioned problems could be solved, thus completing this invention.

[0018] (1) The first invention of the present invention is a method for smelting nickel oxide ore, comprising: a mixing process of mixing nickel oxide ore and a first reducing agent to obtain a mixture; and a reduction process of loading the mixture into a reduction furnace, adding a second reducing agent into the reduction furnace, and performing a reduction process on the mixture, wherein the second reducing agent is a reducing agent containing at least one of coal, and further containing charcoal and starch.

[0019] (2) The second invention of the present invention is a method for smelting nickel oxide ore. In the first invention, in the reduction process, a reducing agent containing coal and charcoal is used as the second reducing agent.

[0020] (3) The third invention of the present invention is a method for smelting nickel oxide ore. In the first invention, in the reduction process, a reducing agent containing coal and starch is used as the second reducing agent.

[0021] (4) The fourth invention of the present invention is a method for smelting nickel oxide ore. In the first invention, in the reduction process, a reducing agent containing coal, starch and charcoal is used as the second reducing agent.

[0022] (5) The fifth invention of the present invention is a method for smelting nickel oxide ore. In any one of the first to fourth inventions, the reduction process includes: a first reduction process in which at least a portion of the second reducing agent is fed into the reduction furnace to reduce the mixture; and a second reduction process in which the remaining second reducing agent is fed into the reduction furnace to reduce the mixture.

[0023] (6) The sixth invention of the present invention is a method for smelting nickel oxide ore. In the fifth invention, in the first reduction step, a reducing agent containing coal is added to the reduction furnace to reduce the mixture. In the second reduction step, a reducing agent containing at least one of charcoal and starch is added to the reduction furnace to reduce the mixture.

[0024] The effects of the invention

[0025] The smelting method for oxide ores according to the present invention can effectively produce high-quality metals.

[0026] Brief description of the attached diagram

[0027] Figure 1 This is a process diagram illustrating an example of a smelting method for nickel oxide ore.

[0028] Figure 2 These are the TG / DTA results for starch.

[0029] Figure 3 These are the TG / DTA test results for charcoal.

[0030] Figure 4 These are the TG / DTA test results for coal.

[0031] Figure 5 This is a top view showing an example of the configuration of a reduction furnace (rotary hearth furnace). Detailed Implementation

[0032] The specific embodiments of the present invention will be described in detail below. It should be noted that the present invention is not limited to the following embodiments, and various modifications can be made without changing 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".

[0033] 1. Summary of the Invention

[0034] This invention relates to a smelting method for producing iron-nickel metal oxide ore as a reducing agent by reducing a mixture of nickel oxide ore and a reducing agent.

[0035] Moreover, the smelting method is characterized by feeding a reducing agent (a second reducing agent) containing coal, and further containing at least one of charcoal and starch into a reduction furnace to perform a reduction treatment on the mixture.

[0036] According to this method, a reducing agent (a second reducing agent) containing coal, and further containing at least one of charcoal and starch, is fed into a reduction furnace to reduce the mixture, thereby improving the grade of the obtained metal.

[0037] Figure 1 This is a diagram illustrating an example of a process for smelting nickel oxide ore. (See diagram for example.) Figure 1 As shown, the smelting method includes: a mixing process S1 in which nickel oxide ore is mixed with a first reducing agent to obtain a mixture; a block forming process S2 in which the obtained mixture is shaped into granules (blocks) in a predetermined shape; a drying process S3 in which the granules (mixture) are dried; a reduction process S4 in which the granules (mixture) are subjected to reduction treatment; and a recovery process S5 in which metal is recovered from the reduced product generated by reduction.

[0038] <2-1. Mixing Process>

[0039] The mixing process S1 is a process of mixing raw material powder containing nickel oxide ore to obtain a mixture. Specifically, a first reducing agent is added to nickel oxide ore, which is used as raw material ore, and the mixture is then mixed with powders of iron ore, fluxing agents, binders, etc., with a particle size of, for example, 0.2 mm or more and 0.8 mm or less, as an additive of any component, to obtain a mixture.

[0040] There are no particular restrictions on the nickel oxide ore used as raw material; limonite, sapropelite, etc., can be used. Typical components of nickel oxide ore include nickel oxide (NiO) and iron oxide (Fe2O3).

[0041] There are no particular limitations on the primary reducing agent; examples include carbonaceous reducing agents such as coal powder and coke powder. Furthermore, it can also consist partly or entirely of plant-derived components such as starch. If the carbonaceous reducing agent is a substance with the same particle size or particle size distribution as the nickel oxide ore used as the raw material, it is easier to mix uniformly and to carry out the reduction reaction uniformly, and is therefore preferred.

[0042] The amount of the first reducing agent is not particularly limited, but when the amount of reducing agent required to just completely reduce the nickel oxide and iron oxide constituting the nickel oxide ore is set to 100% by mass, it is preferably 25% by mass or more, more preferably 30% by mass or more, and even more preferably 35% by mass or more.

[0043] Furthermore, there is no particular upper limit to the mixing amount of the first reducing agent. When the total stoichiometric amount is set to 100%, it is preferably 300% by mass or less, more preferably 200% by mass or less, further preferably 100% by mass or less, and even more preferably 50% by weight or less. It should be noted that the amount of reducing agent required to just completely reduce nickel oxide and iron oxide can be defined as the total stoichiometric amount required to reduce the total amount of nickel oxide contained in the mixture to nickel metal and the total stoichiometric amount required to reduce the iron oxide contained in the mixture to iron metal (hereinafter, also referred to as the "total stoichiometric amount").

[0044] The iron ore added as an additive is not particularly limited; 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. Furthermore, as a binder, examples include bentonite, polysaccharides, resins, water glass, and dehydrated filter cake. Additionally, as a fluxing agent, examples 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] Raw materials [mass %] Ni <![CDATA[Fe2O3]]> C Nickel oxide ore 1～2 50～60 - carbonaceous reducing agent - - ≈85 iron ore - 80～95 -

[0048] In the mixing process S1, raw material powder containing nickel oxide ore can be mixed using a mixer or the like. Furthermore, when obtaining a mixture by mixing the raw material powder, a kneading process can be performed on the raw material powder to improve its inmiscibility. This applies shear force to the mixture, disperses agglomerates of reducing agents or raw material powder, allows for more uniform mixing, improves the adhesion of individual particles, and reduces voids. Therefore, uniform reduction processing can be easily performed, and the reaction time of the reduction reaction can be shortened. Furthermore, quality deviations can be suppressed.

[0049] Mixing can be performed using batch kneaders such as the Brabender, Banbury internal mixers, Henschel mixers, helical rotors, rollers, single-shaft mixers, and twin-shaft mixers. By applying shear force to the mixture during mixing, agglomerates of reducing agents or raw material powders are dispersed and uniformly mixed, improving the adhesion of individual particles and reducing voids. This facilitates reduction reactions in the mixture, ensuring uniform reaction and shortening the reaction time. Furthermore, it helps to suppress quality deviations.

[0050] Furthermore, the mixture can be extruded after mixing or after mixing and kneading. This applies pressure (shear force) to the mixture, dispersing any agglomerates of the reducing agent or raw material powder, resulting in a more uniformly mixed state. Furthermore, it reduces voids within the mixture. Therefore, in the reduction step S3 described later, the reduction reaction of the mixture occurs more readily and uniformly, improving the grade of the obtained metal and enabling the production of high-quality metal.

[0051] The extruder is preferably an extruder capable of mixing and shaping mixtures under high pressure and high shear force, and examples include single-screw extruders and twin-screw extruders. In particular, an extruder equipped with a twin-screw extruder is preferred. By mixing the mixture under high pressure and high shear, the agglomeration of the raw material powder mixture can be dispersed. In addition, effective mixing can improve the strength of the mixture. Furthermore, by using an extruder equipped with a twin-screw extruder, a mixture can be obtained while continuously maintaining high productivity.

[0052] <2-2. Block Forming Process>

[0053] The granulation process S2 is a process of shaping the mixture of raw material powders obtained in the mixing process S1 into granules. The granulation process is not strictly necessary, but shaping the mixture into a predetermined shape improves operability. The shape of the granules can be any shape that can be stacked on the hearth of the reduction furnace; for example, spherical, cuboid, cubic, or cylindrical shapes are preferred. Shaping the mixture into this shape facilitates molding and thus reduces molding costs. Furthermore, since the shaped form is not complex, it reduces the production of poorly formed granules and makes it easier to maintain granule strength.

[0054] Preferably, the particles are placed on the furnace bed in a high density, such as an elliptical or cylindrical shape. By placing the particles on the furnace bed of the reduction furnace at a high density and performing the reduction treatment, the proportion of unavoidable oxygen or water consumption can be reduced, thereby effectively maintaining the reducing environment.

[0055] In the granulation process S2, the mixture can be shaped using a pelletizing device, for example. The pelletizing device is not particularly limited, but a device capable of mixing and shaping 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 dispersed, and the mixing can be performed effectively, thereby increasing the strength of the resulting pellets.

[0056] <2-3. Drying treatment>

[0057] In drying step S3, the obtained particles are dried. This drying step is not essential; the particles obtained by clumping them into a blocky shape contain an excessive amount of moisture, for example, about 50% by mass. Therefore, if the particles containing excessive moisture are rapidly heated to the reduction temperature, the moisture vaporizes instantly, expands, and destroys the particles. Therefore, by drying the obtained particles, for example by reducing the solid content to about 70% by mass and the moisture content to about 30% by mass, particle disintegration during the reduction heating treatment in the subsequent reduction step S3 can be prevented. Furthermore, this prevents the particles from being difficult to remove from the reduction furnace. Moreover, since the particles often become sticky due to excessive moisture, drying makes them easier to handle.

[0058] There are no particular limitations on the method for drying the particles. Conventionally known methods can be used, such as maintaining the particles at a specified drying temperature (e.g., above 200°C and below 400°C) or blowing hot air at a specified drying temperature onto the mixture and drying it. Through this drying process, for example, the solid content of the particles becomes approximately 70% by mass, and the moisture content becomes approximately 30% by mass. It should be noted that the temperature of the mixture itself during this drying process is preferably less than 100°C, thereby preventing the mixture from breaking down due to factors such as violent boiling of moisture.

[0059] It should be noted that the drying process can be carried out outside the reduction furnace described later, or the particles can be loaded into the reduction furnace and the drying process can be carried out inside the reduction furnace.

[0060] In the case of particularly large particles, cracks or fractures may appear in the particles before and after drying. With large particle volumes, cracks or fractures are more likely to occur due to the shrinkage caused by melting during reduction. However, with large particle volumes, the increase in surface area resulting from cracks or fractures is minimal, making major problems less likely. Therefore, cracks or fractures can also be present in particles before reduction.

[0061] Furthermore, the drying process can be performed continuously in one step or in several steps. Performing the drying process in several steps more effectively suppresses the breakage of the mixture. It should be noted that when the drying process is performed in several steps, the drying temperature for subsequent steps is preferably 150°C or higher and 400°C or lower. Drying within this range allows for drying without a reduction reaction.

[0062] Table 2 below shows an example of the composition (parts by mass) of the solid components in the dried granules (mixture). It should be noted that the composition of the granules (mixture) is not limited to this.

[0063] [Table 2]

[0064]

[0065] <2-4. Reduction Process>

[0066] In reduction step S4, the particles dried in drying step S3 are subjected to reduction treatment. Specifically, the resulting lumps (particles) are placed on the hearth of a reduction furnace, and the mixture is subjected to heating reduction treatment in the reduction furnace. Through the heating reduction treatment in reduction step S4, a smelting reaction (reduction reaction) occurs based on the reducing agent (first reducing agent) in the mixture, and iron-nickel metal (hereinafter referred to as "metal") and iron-nickel slag (hereinafter referred to as "slag") are generated separately in the mixture. It should be noted that, for ease of explanation, the particles that are the object of reduction treatment will be referred to as the mixture below.

[0067] In the heat reduction process, for example, within a short period of about one minute, nickel oxide and iron oxide in the mixture are first reduced and metallized near the surface of the mixture, which is prone to reduction, to form nickel-iron iron, thus forming a shell. On the other hand, within the shell, the slag components gradually melt to form liquid slag. Thus, the metal and slag are generated separately in the mixture.

[0068] Furthermore, if the processing time exceeds approximately 10 minutes, the remaining reducing agent that did not participate in the reduction reaction is absorbed by the metal, lowering its melting point, and the metal also becomes a liquid phase. This allows for a stable increase in the grade of the obtained metal, resulting in high-quality metal.

[0069] The temperature used in the reduction process (reduction temperature) is not particularly limited, but it is preferably set in the range of 1200°C or higher and 1450°C or lower, more preferably in the range of 1300°C or higher and 1400°C or lower. Reduction within this temperature range allows the reduction reaction to occur uniformly, resulting in iron-nickel with suppressed quality deviations. Furthermore, reduction at a temperature in the range of 1300°C or higher and 1400°C or lower is more preferable, as this allows the desired reduction reaction to occur in a relatively short time.

[0070] The processing time (processing time) during the reduction treatment is set according to the temperature of the reduction furnace, but preferably 10 minutes or more, more preferably 15 minutes or more. On the other hand, regarding the upper limit of the reduction heating treatment time, from the viewpoint of suppressing the increase in manufacturing costs, it can be 50 minutes or less, or 40 minutes or less.

[0071] It should be noted that the value obtained by multiplying the reduction temperature (°C) by the reduction time (minutes) is the cumulative heat required for reduction, preferably in the range of 20,000 (°C × minutes) or higher and 40,000 (°C × minutes) or lower. By performing the reduction process with this heat, high-quality metals can be effectively manufactured.

[0072] In reduction step S4, the characteristic is that a reducing agent (second reducing agent) containing coal, and further containing at least one of charcoal and starch, is added to reduce the mixture. As a method for elucidating the behavior of the sample within the reduction furnace, one can cite the method of determining the TG curve or DTA curve using a TG / DTA (differential thermal / thermogravimetric analysis) device. TG / DTA is a device capable of simultaneously performing differential thermal analysis and thermogravimetric analysis, and can elucidate the behavior of the sample, such as decomposition or phase transfer, as indicated by the TG curve or DTA curve when a temperature change is applied to the sample. It should be noted that the TG curve represents the weight of the sample relative to temperature, and the DTA curve represents the temperature difference between the sample and the reference substance relative to temperature.

[0073] Figure 2 These are the TG and DTA curves of "starch" measured using TG / DTA. The TG curve of starch shows a sharp weight loss around 240°C upon heating from room temperature, while the DTA curve shows a significant maximum around 600°C. This indicates that the decomposition temperature of starch is relatively low compared to that of coal. Therefore, it can be inferred that starch is a substance capable of undergoing a rapid reduction reaction at relatively low temperatures. This is believed to be because starch is a polymer composed of carbon, hydrogen, and oxygen. Upon heating, the bonds between these hydrogen and carbon atoms break, producing H2 gas, resulting in a porous structure. The bonds between the carbon atoms constituting starch are weak.

[0074] Figure 3 These are the TG and DTA curves of "charcoal" measured using TG / DTA. The TG curve of charcoal shows an immediate weight loss upon heating from room temperature, while the DTA curve shows a significant maximum near 600°C. This indicates that the decomposition temperature of charcoal is relatively low compared to that of coal. Therefore, it can be inferred that charcoal is a substance capable of undergoing a reduction reaction at a relatively low temperature with a fast reaction rate. This is believed to be because charcoal is produced by burning wood, causing the moisture in the wood to evaporate, thus creating a porous structure with weak bonds between the carbon atoms that make up the charcoal.

[0075] on the other hand, Figure 4These are the TG and DTA curves of "coal" measured using TG / DTA. The TG curve of coal shows that, compared to charcoal, its weight hardly changes even when heated from room temperature, and the curve is almost flat. The weight reduction near 420°C is attributed to the volatilization of volatile organic compounds (Volatile Matter). This indicates that the decomposition temperature of coal is relatively high compared to that of charcoal. Therefore, it can be inferred that coal is a substance capable of undergoing reduction reactions over a long period at relatively high temperatures. This is believed to be because coal is a fossil fuel formed by the long-term metamorphism (coalification) of plants or oxides under geothermal or geostatic pressure. The carbon atoms from the plants are concentrated, resulting in strong bonds between the carbon atoms that make up coal.

[0076] In the smelting method of this embodiment, a second reducing agent is introduced into a reduction furnace, containing at least one of charcoal and starch, which have relatively low decomposition temperatures and are substantially free of oxides and other components, and coal, which has relatively high decomposition temperatures and may contain oxides, to perform reduction treatment on the mixture. Therefore, even if a portion of the obtained metal is re-oxidized due to oxygen inevitably mixed in from the reductant recovery port, the mixture loading port, the second reducing agent input port, or oxygen supplied through the burner, or water generated from fuel combustion in the burner, it can be reduced again by the second reducing agent containing starch and coal. This further suppresses the oxidation of the obtained metal and thus improves the grade of the obtained metal.

[0077] Furthermore, in the smelting method of this embodiment, a reducing agent containing coal and charcoal can also be used as the second reducing agent. This prevents a portion of the obtained metal from oxidizing, thereby improving the grade of the obtained metal.

[0078] Furthermore, in the smelting method of this embodiment, a reducing agent containing coal and starch can also be used as the second reducing agent. This prevents a portion of the obtained metal from oxidizing, thereby improving the grade of the obtained metal.

[0079] Furthermore, in the smelting method of this embodiment, a reducing agent containing coal, starch, and charcoal can also be used as the second reducing agent. This suppresses the oxidation of a portion of the obtained metal, thereby improving the grade of the obtained metal.

[0080] Regarding the method of adding the second reducing agent to the reduction furnace, one example is adding it through a designated inlet of the reduction furnace. There are no particular restrictions on the location of addition; it can be near the mixture, near a heat source (e.g., a burner flame), or between the mixture and a heat source (e.g., a burner flame). In particular, the location of addition is preferably near the mixture.

[0081] The second reducing agent can be added to the reduction furnace at any time. For example, it can be added before the reduction process, during the process of heating to the set reduction temperature, when the set reduction temperature is reached, when the reduction reaction has progressed to a certain extent after the reduction temperature is reached (or when the set reduction temperature is maintained), or when the reduction reaction ends.

[0082] The amount of the second reducing agent added to the reduction furnace is not particularly limited. When the amount of reducing agent required to just completely reduce the iron oxide and nickel oxide contained in the nickel oxide ore constituting the mixture is set to 100% by mass, it is preferably set to a ratio in the range of 3% by mass or more and 100% by mass, more preferably in the range of 4% by mass or more and 70% by mass, and even more preferably in the range of 5% by mass or more and 50% by mass. By setting the amount of the second reducing agent to 3% by mass or more, the re-oxidation of the generated metal can be more effectively suppressed. Furthermore, by setting the amount of the second reducing agent to 100% by mass or less, the possibility of over-reduction can be reduced, and the decrease in the nickel grade in the metal can be suppressed.

[0083] The second reducing agent is not particularly limited. For example, it can be a carbonaceous reducing agent such as coal or coke, or an organic reducing agent derived from plants such as charcoal, bamboo charcoal, or starch.

[0084] When using organic reducing agents derived from plants as a second reducing agent, these agents may combust during the heating reduction process. Therefore, it is preferable to set the reduction furnace to a low-oxygen concentration environment for the reduction treatment of the mixture. A low-oxygen concentration environment means, for example, preferably performing the reduction treatment in an environment with an oxygen concentration of 3.0 vol% or less, and more preferably in an environment with an oxygen concentration of 1.0 vol% or less. Furthermore, the reduction treatment can also be performed in an inert gas environment such as nitrogen or argon.

[0085] As a second reducing agent, when using a reducing agent containing coal and charcoal, the amount of coal added in the second reducing agent is not particularly limited. However, when the amount of reducing agent required to just completely reduce the nickel oxide and iron oxide constituting the nickel oxide ore is set to 100% by mass, it is preferably 1% by mass or more and 15% by mass or less, more preferably 3% by mass or more and 12% by mass or less, and even more preferably 6% by mass or more and 11% by mass or less.

[0086] As a second reducing agent, when using a reducing agent containing coal and charcoal, the amount of charcoal added to the second reducing agent is not particularly limited. However, when the amount of reducing agent required to just completely reduce the nickel oxide and iron oxide constituting the nickel oxide ore is set to 100% by mass, it is preferably 1.0% by mass or more and 10.0% by mass or less, more preferably 1.3% by mass or more and 7.0% by mass or less, and even more preferably 1.5% by mass or more and 4.5% by mass or less.

[0087] As a second reducing agent, when using a reducing agent containing coal and charcoal, the total content of charcoal and coal in the second reducing agent is preferably 50% by mass or more, more preferably 70% by mass or more, even more preferably 90% by mass or more, and most preferably the second reducing agent consists only of charcoal and coal (i.e., the total content of charcoal and coal is 100% by mass in the total reducing agent).

[0088] As a second reducing agent, when using a reducing agent containing coal and starch, the amount of coal added in the second reducing agent is not particularly limited. When the amount of reducing agent required to just completely reduce the nickel oxide and iron oxide constituting the nickel oxide ore is set to 100% by mass, it is preferably 0.01% by mass or more and 15% by mass or less, more preferably 0.03% by mass or more and 12% by mass or less, and even more preferably 0.05% by mass or more and 11% by mass or less.

[0089] As a second reducing agent, when using a reducing agent containing coal and starch, the amount of starch added in the second reducing agent is not particularly limited. When the amount of reducing agent required to just completely reduce the nickel oxide and iron oxide constituting the nickel oxide ore is set to 100% by mass, it is preferably 0.01% by mass or more and 15% by mass or less, more preferably 0.03% by mass or more and 10% by mass or less, and even more preferably 0.05% by mass or more and 6% by mass or less.

[0090] As a second reducing agent, when using a reducing agent containing coal and starch, the total content of starch and coal in the second reducing agent is preferably 50% by mass or more, more preferably 70% by mass or more, even more preferably 90% by mass or more, and most preferably the second reducing agent consists only of starch and coal (i.e., the total content of starch and coal in the total reducing agent is 100% by mass).

[0091] As a second reducing agent, when using a reducing agent containing coal, charcoal, and starch, the total amount of starch and charcoal added in the second reducing agent is not particularly limited. When the amount of reducing agent required to just completely reduce the nickel oxide and iron oxide constituting the nickel oxide ore is set to 100% by mass, it is preferably 0.01% by mass or more and 15% by mass or less, more preferably 0.03% by mass or more and 10% by mass or less, and even more preferably 0.05% by mass or more and 6% by mass or less.

[0092] As a second reducing agent, when using a reducing agent containing coal, charcoal, and starch, the ratio of starch and charcoal in the second reducing agent is not particularly limited, but the mixing ratio of the stoichiometric amount of starch mixed with nickel oxide ore and the stoichiometric amount of charcoal mixed with nickel oxide ore is preferably in the range of 30:70 to 70:30, more preferably in the range of 40:60 to 60:40, and even more preferably in the range of 45:55 to 55:45.

[0093] As a second reducing agent, when using a reducing agent containing coal, charcoal, and starch, the total content of starch, coal, and charcoal in the second reducing agent is preferably 50% by mass or more, more preferably 70% by mass or more, further preferably 90% by mass or more, and most preferably the second reducing agent consists only of starch, coal, and charcoal (i.e., the total content of starch, coal, and charcoal in the total reducing agent is 100% by mass).

[0094] Furthermore, the introduction of the second reducing agent into the reduction furnace can be carried out in two or more stages. Specifically, the reduction process can be divided into two stages, making it a reduction process that includes a first reduction stage and a second reduction stage. In the first reduction stage, in the early stage of the reduction treatment, at least a portion of the second reducing agent is introduced into the reduction furnace to reduce the mixture. In the second reduction stage, in the later stage of the reduction treatment, the remaining second reducing agent is introduced into the reduction furnace to reduce the mixture. At this time, the second reducing agent can be introduced into the reduction furnace from one inlet or from multiple inlets of the reduction furnace.

[0095] When the reduction process is configured to include a first reduction process and a second reduction process, the amount of the second reducing agent added in the first reduction process is not particularly limited. However, when the amount of reducing agent required to just completely reduce the nickel oxide and iron oxide constituting the nickel oxide ore is set to 100% by mass, it is preferably 1% by mass or more and 10% by mass or less, and more preferably 1% by mass or more and 5% by mass or less.

[0096] When the reduction process is configured to include a first reduction process and a second reduction process, the amount of the second reducing agent added in the second reduction process is not particularly limited. When the amount of reducing agent required to just completely reduce the nickel oxide and iron oxide constituting the nickel oxide ore is set to 100% by mass, it is preferably 1% by mass or more and 7% by mass or less, and more preferably 1% by mass or more and 4% by mass or less.

[0097] Furthermore, as described above, in the case of a reduction process comprising a first reduction step and a second reduction step, a reducing agent containing coal can be added to the reduction furnace in the first reduction step, which is the initial stage of the reduction treatment, to reduce the mixture. In the second reduction step, which is the later stage of the reduction treatment, a reducing agent containing at least one of charcoal and starch can be added to the reduction furnace to reduce the mixture. The decomposition temperature of coal is relatively high compared to that of charcoal. Therefore, by adding relatively difficult-to-decompose coal to the reduction furnace in the first reduction step, which is the initial stage of the reduction treatment, a reducing environment can be maintained for a longer period. Moreover, by adding at least one of relatively easily decomposed charcoal and starch, which can undergo a rapid reduction reaction, to the reduction furnace in the second reduction step, which is the later stage of the reduction treatment, the re-oxidized metal can be effectively re-reduced.

[0098] At this point, a "reducing agent containing coal" and a "reducing agent containing at least one of charcoal and starch" can also be added from the same inlet. Alternatively, multiple inlets can be provided in the reduction furnace, with the "reducing agent containing at least one of charcoal and starch" added from one inlet and the "reducing agent containing coal" added from the other inlet.

[0099] In the case where the reduction process includes a first reduction step and a second reduction step, the first and second reduction steps can be implemented in stages at different temperatures. For example, the temperature in the processing chamber can be controlled by implementing the reduction treatment of the first reduction step at a reduction temperature in the range of 1150°C to 1350°C, and the temperature in the other processing chambers can be controlled by implementing the reduction treatment of the second reduction step at a reduction temperature in the range of 1350°C to 1450°C. In this way, by implementing the heating treatment in stages at different temperatures, coal that is more difficult to decompose is fed into the reduction furnace at a relatively low temperature range in the first reduction step, thereby maintaining a reduction environment for a long time, carrying out the reduction reaction uniformly, and effectively generating metal. Furthermore, by feeding a reducing agent containing at least one of charcoal and starch, which are more easily decomposed and can undergo a fast reduction reaction, into the reduction furnace at a relatively high temperature range in the second reduction step, the re-oxidation of the metal that has been re-oxidized can be effectively inhibited in a short time.

[0100] For example, when a reducing agent containing coal and charcoal is used as the second reducing agent in the reduction furnace, the temperature in the processing chamber can be controlled in such a way that the reduction treatment of the first reduction step is carried out at a reduction temperature in the range of 1250°C to 1350°C, and the temperature in other processing chambers can be controlled in such a way that the reduction treatment of the second reduction step is carried out at a reduction temperature in the range of 1350°C to 1450°C.

[0101] For example, when a reducing agent containing coal and starch is used as the second reducing agent to be fed into the reduction furnace, the temperature in the processing chamber can be controlled, for example, by performing the reduction treatment of the first reduction step at a reduction temperature in the range of 1150°C to 1250°C, and the temperature in other processing chambers can be controlled, for example, by performing the reduction treatment of the second reduction step at a reduction temperature in the range of 1350°C to 1450°C.

[0102] For example, when a reducing agent containing coal, charcoal, and starch is used as the second reducing agent in the reduction furnace, the temperature in the processing chamber can be controlled, for example, by performing the reduction treatment of the first reduction step at a reduction temperature in the range of 1150°C to 1350°C, and the temperature in other processing chambers can be controlled, for example, by performing the reduction treatment of the second reduction step at a reduction temperature in the range of 1350°C to 1450°C.

[0103] There are no particular limitations on the reduction furnace used for reduction heating treatment. For example, a fixed furnace bed or a moving furnace bed can be used, but a moving furnace bed is preferred. By using a moving bed furnace as such a reduction furnace, the mixture can be processed more efficiently. Furthermore, by continuously carrying out the reduction reaction with a moving bed furnace, the reaction can be completed in one unit, and the processing temperature can be accurately controlled compared to processing in different steps using various furnaces. Furthermore, heat loss between different processes is reduced, enabling more efficient operation. The following is an example of a moving bed furnace. Figure 4 Explain the composition of the rotary hearth furnace.

[0104] Figure 4 This is a top view illustrating an example of the configuration of a rotary hearth furnace with a rotating hearth. (See diagram below.) Figure 4 As shown, a rotary hearth furnace 2, which is circular and divided into multiple processing chambers 20a to 20d, is used. The furnace rotates in a predetermined direction, and processing is performed in each zone simultaneously. 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 furnace smelts the processed mixture 1. The rotary hearth furnace 2 may also have a preheating chamber outside the furnace. Furthermore, a cooling chamber may be provided outside the furnace. It should be noted that, as a moving bed furnace, a roller hearth furnace (or similar device) can also be used.

[0105] When using a rotary hearth furnace for reduction processing, heating can be carried out in stages at different temperatures. In a reduction process comprising a first reduction step and a second reduction step, a rotary hearth furnace is preferably used. In the first reduction step, a reducing agent containing at least one of charcoal and starch is introduced into the furnace to reduce the mixture. In the second reduction step, a reducing agent containing coal is introduced into the furnace to reduce the mixture. Specifically, the temperature in one processing chamber is controlled such that the reduction process in the first reduction step is carried out at a reduction temperature ranging from 1150°C to 1350°C, and the temperatures in other processing chambers are controlled such that the reduction process in the second reduction step is carried out at a reduction temperature ranging from 1350°C to 1450°C. By introducing relatively difficult-to-decompose coal into processing chambers controlled at a temperature ranging from 1150°C to 1350°C, a reducing environment can be maintained for a long time, the reduction reaction can proceed uniformly, and metals can be effectively generated. Furthermore, by introducing at least one of charcoal and starch, which are relatively easy to decompose and can undergo reduction reactions at a fast reaction rate, into a treatment chamber controlled within a range of 1350°C to 1450°C, the re-oxidation of re-oxidized metals can be effectively suppressed in a short time.

[0106] For example, when a reducing agent containing coal and charcoal is used as the second reducing agent in the reduction furnace, the temperature in one processing chamber can be controlled by performing the reduction treatment in the first reduction step at a reduction temperature in the range of 1250°C to 1350°C, and the temperature in other processing chambers can be controlled by performing the reduction treatment in the second reduction step at a reduction temperature in the range of 1350°C to 1450°C.

[0107] For example, when a reducing agent containing coal and starch is used as the second reducing agent to be fed into the reduction furnace, the temperature in one processing chamber can be controlled by performing the reduction treatment in the first reduction step at a reduction temperature in the range of 1150°C to 1250°C, and the temperature in other processing chambers can be controlled by performing the reduction treatment in the second reduction step at a reduction temperature in the range of 1350°C to 1450°C.

[0108] For example, when a reducing agent containing coal, charcoal, and starch is used as the second reducing agent in the reduction furnace, the temperature in one processing chamber can be controlled by performing the reduction treatment in the first reduction step at a reduction temperature in the range of 1150°C to 1350°C, and the temperature in other processing chambers can be controlled by performing the reduction treatment in the second reduction step at a reduction temperature in the range of 1350°C to 1450°C.

[0109] At this point, it is preferable to provide multiple inlets for each processing chamber of the reduction furnace, in a manner that allows the introduction of a reducing agent containing charcoal and a reducing agent containing coal into different processing chambers, and to introduce a reducing agent containing at least one of charcoal and starch and a reducing agent containing coal into each inlet. Alternatively, a reducing agent containing starch and a reducing agent containing charcoal can be introduced from the same inlet, or from different inlets.

[0110] The heating mechanism of the reduction furnace is not particularly limited, but can be a burner or an electric mechanism. From the viewpoint of being able to effectively perform heating and reduction treatment on the mixture in a short time, a burner is preferred. Furthermore, in the case of a reduction furnace with a burner, fuels such as LPG (liquefied petroleum gas), LNG (liquefied natural gas), coal, coke, and finely pulverized charcoal can be used. These fuels are very inexpensive, and equipment and maintenance costs can be significantly reduced compared to electric furnaces.

[0111] <2-5. Recycling Process>

[0112] In the recycling step S5, metal is recovered from the reduced product obtained in the reduction step S4. Specifically, the reduced product (mixture) containing the metal phase and the slag phase obtained by the heating reduction treatment is cooled, crushed and pulverized as needed, and the metal (metal powder particles) is separated and recovered.

[0113] As a method for separating the metal phase and slag phase from inclusions obtained as solids, in addition to removing unwanted substances by sieving, methods such as gravity-based separation or magnetic force-based separation can be used.

[0114] Furthermore, the resulting metallic phase and slag phase can be easily separated due to their poor wettability. For large inclusions obtained through the aforementioned reduction process S4, by setting a predetermined drop or applying a predetermined vibration or other impact during screening, the metallic phase and slag phase can be easily separated from the inclusions.

[0115] This process is repeated to separate the metallic phase and the slag phase, thereby recovering the metallic phase.

[0116] Example

[0117] The following describes embodiments of the present invention in more detail, but the present invention is not limited to the following embodiments.

[0118] (First Implementation)

[0119] [Mixed Processing Step]

[0120] For each sample, a mixture was prepared by mixing nickel oxide ore (as raw material), iron ore, silica sand and limestone (as fluxing agents), a binder, and a first reducing agent with an appropriate amount of water using a mixer. It should be noted that coal was used as the reducing agent, containing 30–45% by mass of nickel oxide and iron oxide (Fe₂O₃) contained in the nickel oxide ore (as raw material) relative to the required stoichiometric 100% by mass.

[0121] [Blocking Process]

[0122] Next, appropriate moisture was added to the mixture obtained in the mixing process to obtain spherical blocks (samples) with a diameter of 15±0.2 mm, which were formed by a granulator.

[0123] [Drying Process]

[0124] Next, the lumps obtained in the lumping process were dried by blowing hot air at 200°C to 250°C, with a solid content of approximately 70% by mass and a moisture content of approximately 30% by mass. The solid composition (excluding carbon) of the dried lumps (samples) is shown in Table 3 below.

[0125] [Table 3]

[0126] Ni <![CDATA[Fe2O3]]> <![CDATA[SiO2]]> CaO <![CDATA[Al2O3]]> MgO other 1.4 52.5 14.3 5.5 3.1 5.7 Adhesives, reducing agents, etc.

[0127] [Restoration Process]

[0128] Next, the lumps (samples) obtained in the drying process are placed into a reduction furnace set in a nitrogen environment that is substantially free of oxygen. It should be noted that the temperature conditions when placing the samples into the reduction furnace are set at 500±20℃.

[0129] Next, the reduction temperature was set to 1380°C and the reduction time to 50 minutes, and the particles of the mixture were subjected to reduction heating treatment. Ten minutes after the start of reduction, coal was added to the reduction furnace from one side of the furnace as a second reducing agent (first reduction step). Forty minutes after the start of reduction, charcoal was added to the reduction furnace from the other side of the furnace as a second reducing agent (second reduction step). It should be noted that by purging the reduction furnace with nitrogen, a nitrogen environment substantially free of oxygen was created, preventing oxygen from the outside air from entering the furnace through the inlet. The amount of the second reducing agent added is shown in Table 4 below. It should be noted that for Comparative Examples 1-1 to 1-3, the second reducing agent was not added to the reduction furnace. After the reduction treatment, the samples were rapidly cooled to room temperature in a nitrogen environment and then exposed to the atmosphere.

[0130] [Recycling Process]

[0131] For each reduced product (sample) after reduction heat treatment, the metal was recovered by magnetic sorting after being pulverized using a wet process. Then, the nickel metallization rate and the nickel content in the metal were analyzed and calculated using an ICP-based luminescence spectrophotometer (SHIMAZU S-8100).

[0132] Nickel metallization rate, nickel content in metal, and nickel metal recovery rate are calculated using the following formulas (1), (2), and (3).

[0133] Nickel metallization rate = (mass of nickel in the metal / (mass of all nickel in the reduced product)) × 100 (%) ... (1)

[0134] Nickel content in metal = (mass of nickel in metal / (total mass of nickel and iron in metal)) × 100 (%) ... (2)

[0135] Nickel metal recovery rate = Amount of recovered nickel / (Amount of ore input × Nickel content in ore) × 100……(3)

[0136] Table 4 below shows the nickel metallization rate, nickel content in the metal, and nickel metal recovery rate for each sample.

[0137] [Table 4]

[0138]

[0139] As shown in Table 4, in Examples 1-1 to 1-5, in which a second reducing agent was added to the reduction furnace and the mixture was reduced, good results were obtained in terms of nickel metallization rate and nickel content in the metal.

[0140] In Examples 1-3 to 1-5, where a reducing agent containing coal and charcoal was used as the second reducing agent, better results were obtained in terms of nickel metallization rate and nickel content in the metal compared to Examples 1-1 and 1-2.

[0141] On the other hand, in Comparative Examples 1-1 to 1-3, in which the mixture was reduced without adding a second reducing agent to the reduction furnace, the Ni metallization rate, Ni content, and metal recovery rate were all lower than those of the Examples, and the effects of the present invention were not achieved.

[0142] (Second Implementation)

[0143] [Mixed Processing Step]

[0144] For each sample, a mixture was prepared by mixing nickel oxide ore (as raw material), iron ore, silica sand and limestone (as fluxing agents), a binder, and a first reducing agent with an appropriate amount of water using a mixer. It should be noted that coal was used as the reducing agent, containing 30–45% by mass of nickel oxide and iron oxide (Fe₂O₃) contained in the nickel oxide ore (as raw material) relative to the required stoichiometric 100% by mass.

[0145] [Blocking Process]

[0146] Next, appropriate moisture was added to the mixture obtained in the mixing process to obtain spherical blocks (samples) with a diameter of 15±0.2 mm, which were formed by a granulator.

[0147] [Drying Process]

[0148] Next, the lumps obtained in the lumping process were dried by blowing hot air at 200°C to 250°C, with a solid content of approximately 70% by mass and a moisture content of approximately 30% by mass. The solid composition (excluding carbon) of the dried lumps (samples) is shown in Table 5 below.

[0149] [Table 5]

[0150] Ni <![CDATA[Fe2O3]]> <![CDATA[SiO2]]> CaO <![CDATA[Al2O3]]> MgO other 1.4 52.5 14.3 5.5 3.1 5.7 Adhesives, reducing agents, etc.

[0151] [Restoration Process]

[0152] Next, the lumps (samples) obtained in the drying process are placed into a reduction furnace set in a nitrogen environment that is substantially free of oxygen. It should be noted that the temperature conditions when placing the samples into the reduction furnace are set at 500±20℃.

[0153] Next, the reduction temperature was set to 1380°C and the reduction time was set to 50 minutes, and the particles of the mixture were subjected to reduction heating treatment. Ten minutes after the start of reduction, coal was added to the reduction furnace from one side of the furnace as a second reducing agent (first reduction step). Furthermore, 40 minutes after the start of reduction, starch was added to the reduction furnace from the other side of the furnace as a second reducing agent (second reduction step). It should be noted that the reduction furnace was purged with nitrogen to create a nitrogen environment that was substantially oxygen-free, thus preventing oxygen from the outside air from entering the furnace through the inlet. The amount of the second reducing agent added is shown in Table 6 below. For Examples 2-1 to 2-5, starch was added to the reduction furnace, and after 10 minutes, it was rapidly cooled to room temperature inside the furnace before the sample was exposed to the atmosphere. It should be noted that, on the other hand, for Comparative Examples 1 to 4, the second reducing agent was not added to the reduction furnace.

[0154] [Recycling Process]

[0155] For each reduced product (sample) after reduction heat treatment, the metal was recovered by magnetic sorting after being pulverized by wet processing. Then, the nickel metallization rate, nickel content in the metal, and nickel metal recovery rate were measured in the same manner as in the first embodiment described above.

[0156] Table 6 below shows the nickel metallization rate, nickel content in the metal, and nickel metal recovery rate for each sample.

[0157] [Table 6]

[0158]

[0159] As shown in Table 6, in Examples 2-1 to 2-5, in which a second reducing agent containing coal and starch was added to the reduction furnace and the mixture was subjected to reduction treatment, good results were obtained in terms of nickel metallization rate and nickel content in the metal.

[0160] On the other hand, in Comparative Examples 2-1 to 2-4, in which the mixture was reduced without adding a second reducing agent to the reduction furnace, the Ni metallization rate, Ni content, and metal recovery rate were all lower than those of the Examples, and the effects of the present invention were not achieved.

[0161] (Third Implementation)

[0162] [Mixed Processing Step]

[0163] For each sample, a mixture was prepared by mixing nickel oxide ore (as raw material), iron ore, silica sand and limestone (as fluxing agents), a binder, and a first reducing agent with an appropriate amount of water using a mixer. It should be noted that coal was used as the reducing agent, containing 30–45% by mass of nickel oxide and iron oxide (Fe₂O₃) contained in the nickel oxide ore (as raw material) relative to the required stoichiometric 100% by mass.

[0164] [Blocking Process]

[0165] Next, appropriate moisture was added to the mixture obtained in the mixing process to obtain spherical blocks (samples) with a diameter of 15±0.2 mm, which were formed by a granulator.

[0166] [Drying Process]

[0167] Next, the lumps obtained in the lumping process were dried by blowing hot air at 200°C to 250°C, with a solid content of approximately 70% by mass and a moisture content of approximately 30% by mass. The solid composition (excluding carbon) of the dried lumps (samples) is shown in Table 7 below.

[0168] [Table 7]

[0169] Ni <![CDATA[Fe2O3]]> <![CDATA[SiO2]]> CaO <![CDATA[Al2O3]]> MgO other 1.4 52.5 14.3 5.5 3.1 5.7 Adhesives, reducing agents, etc.

[0170] [Restoration Process]

[0171] Next, the lumps (samples) obtained in the drying process are placed into a reduction furnace set in a nitrogen environment that is substantially free of oxygen. It should be noted that the temperature conditions when placing the samples into the reduction furnace are set at 500±20℃.

[0172] Next, the reduction temperature was set to 1380°C and the reduction time to 50 minutes, and the particles of the mixture were subjected to reduction heating treatment. Ten minutes after the start of reduction, coal was added to the reduction furnace from one side of the furnace as a second reducing agent (first reduction step). Furthermore, 40 minutes after the start of reduction, starch and charcoal were added to the reduction furnace from the other side of the furnace as a second reducing agent (second reduction step). The starch and charcoal used as reducing agents were in a 1:1 weight ratio. It should be noted that nitrogen purging was performed into the reduction furnace to create a nitrogen environment that was substantially oxygen-free, thus preventing oxygen from the outside air from entering the furnace through the inlet. The amount of the second reducing agent added is shown in Table 8 below. For Examples 3-1 to 3-5, starch and charcoal were added to the reduction furnace, and after 10 minutes, the samples were rapidly cooled to room temperature inside the furnace before being exposed to the atmosphere. It should be noted that for Comparative Examples 3-1 to 3-4, the second reducing agent was not added to the reduction furnace.

[0173] [Recycling Process]

[0174] For each reduced product (sample) after reduction heat treatment, the metal was recovered by magnetic sorting after being pulverized based on wet processing. Then, the nickel metallization rate, nickel content in the metal, and nickel metal recovery rate were measured in the same manner as in the first embodiment described above.

[0175] Table 8 below shows the nickel metallization rate, nickel content in the metal, and nickel metal recovery rate for each sample.

[0176] [Table 8]

[0177]

[0178] As shown in Table 8, in Examples 3-1 to 3-5, in which a second reducing agent containing starch and charcoal was added to the reduction furnace to reduce the mixture, good results were obtained in terms of nickel metallization rate and nickel content in the metal.

[0179] On the other hand, in Comparative Examples 3-1 to 3-4, in which the mixture was reduced without adding a second reducing agent to the reduction furnace, the Ni metallization rate, Ni content, and metal recovery rate were all lower than those of the Examples, and the effects of the present invention were not achieved.

[0180] Explanation of reference numerals in the attached figures

[0181] 1. Entrance

[0182] 2 Rotary Hearth Furnace

[0183] 20a~20d processing room

[0184] 21 Preheating Chamber

[0185] 22 Cooling chamber.

Claims

1. A method for smelting nickel oxide ore, wherein, include: A mixing process in which nickel oxide ore and a first reducing agent are mixed to obtain a mixture; as well as The mixture is loaded into a reduction furnace, a second reducing agent is added to the furnace, and a reduction process is performed to reduce the mixture. In the reduction process, a reducing agent containing coal, and further containing at least one of charcoal and starch, is used as the second reducing agent.

2. The smelting method for nickel oxide ore according to claim 1, wherein, In the reduction process, a reducing agent containing coal and charcoal is used as the second reducing agent.

3. The smelting method for nickel oxide ore according to claim 1, wherein, In the reduction process, a reducing agent containing coal and starch is used as the second reducing agent.

4. The smelting method for nickel oxide ore according to claim 1, wherein, In the reduction process, a reducing agent containing coal, starch, and charcoal is used as the second reducing agent.

5. The smelting method for nickel oxide ore according to any one of claims 1 to 4, wherein, The reduction process includes: The first reduction step involves introducing at least a portion of the second reducing agent into the reduction furnace to perform a reduction treatment on the mixture; and The second reduction step involves adding the remaining second reducing agent to the reduction furnace to reduce the mixture.

6. The smelting method for nickel oxide ore according to claim 5, wherein, In the first reduction step, a reducing agent containing coal is added to the reduction furnace to reduce the mixture. In the second reduction step, a reducing agent containing at least one of charcoal and starch is introduced into the reduction furnace to perform a reduction treatment on the mixture.

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