Nickel oxide ore smelting method

Abstract

To provide a smelting method for manufacturing ferronickel by reducing a mixture containing nickel oxide ore that can suppress quality degradation of a resultant reduced product and manufacture ferronickel through efficient operations.SOLUTION: A smelting method for manufacturing ferronickel by reducing a mixture containing nickel oxide ore and a carbonaceous reducer includes a step for mixing the nickel oxide ore and the carbonaceous reducer and a step for loading the mixture into a reduction furnace and reducing the mixture by heating. In the reduction step, the reduction furnace 1 is equipped with a heat treatment unit 11 for reduction treatment and a coal-loading unit 21 connected to the heat treatment unit 11. At the halfway stage of the reduction treatment, the mixture is transferred from the heat treatment unit 11 to the coal-loading unit 21 and supplied with the carbonaceous reducer in addition in the coal-loading unit 21 and the mixture supplied with the carbonaceous reducer is then transferred to the heat treatment unit 11 for additional reduction treatment.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a method for smelting nickel oxide ore, in which ferronickel is produced by reducing a mixture of nickel oxide ore as a raw material ore and a carbonaceous reducing agent. [Background technology]

[0002] Known methods for smelting nickel oxide ores called limonite or saprolite include a pyrometallurgical method for producing nickel matte using a smelting furnace, a pyrometallurgical method for producing ferronickel using a rotary kiln or a moving hearth furnace, and a hydrometallurgical method for producing mixed sulfide using an autoclave.

[0003] When smelting nickel oxide ore, the raw material ore is first subjected to a process ("pretreatment" prior to reduction treatment) for agglomerating, slurriing, etc. Specifically, in the pretreatment, nickel oxide ore is agglomerated, that is, converted from a powder or fine particle form into agglomerates, by first mixing the nickel oxide ore with components other than the nickel oxide ore, such as a binder and a reducing agent, to form a mixture, which is then subjected to moisture adjustment and the like, and then charged into an agglomeration machine to form agglomerates (which refer to pellets, briquettes, etc.; hereinafter simply referred to as "pellets") of, for example, about 10 mm to 30 mm in size.

[0004] Pellets require a certain degree of breathability, for example, to allow moisture to evaporate. Furthermore, if reduction is not uniform within the pellet, the composition may become uneven, resulting in metal dispersion and uneven distribution. Therefore, it is important to mix the mixture uniformly and maintain as uniform a temperature as possible during pellet reduction.

[0005] In addition, it is also important to coarsen the ferronickel produced by reduction. If the produced ferronickel has a size of, for example, about several tens of μm to several hundreds of μm, it becomes difficult to separate it from the slag, and the yield of ferronickel drops significantly. For this reason, a technology is needed to effectively coarsen the ferronickel produced after reduction.

[0006] In addition, in recent years, ores with high nickel grade and few impurities have become scarce, and in order to produce high-quality ferronickel, it is necessary to efficiently process a variety of ores and accumulate data.

[0007] For example, a small amount of pellets may be charged into a reduction furnace, reduction treatment performed, and the resulting reduced product removed to examine various properties. However, the treatment temperature is high, around 1000°C to 1500°C, making it difficult to charge and remove pellets. Conventionally, in such operations, pellets were charged into the furnace and the resulting reduced product removed using a special dipper made of a metal that can withstand relatively high temperatures. However, due to the high temperature, the dipper would bend, causing problems such as getting caught on the inner wall of the furnace during removal, which required more time than necessary and made it difficult to obtain accurate findings.

[0008] In particular, in a small reduction furnace used for testing, it is preferable to make the opening to the outside of the furnace used for putting in and taking out samples as small as possible to avoid the influence of outside air, and such a small opening can make it difficult to remove the ladle because it is likely to get caught on the furnace wall when removing it.If the ladle cannot be removed smoothly, accurate data on the reduction status inside the furnace cannot be obtained, and it becomes difficult to reflect this data in operations.

[0009] Furthermore, in small furnaces, it is generally not easy to stably adjust and maintain the degree of reduction in the reduction furnace, which is in a high-temperature state. For example, if a burner or the like is used to heat the reduction furnace, a large amount of air is used for fuel combustion, and oxygen contamination is unavoidable. On the other hand, if coal or LNG is used as the heating fuel, the fuel contains moisture and water is generated during combustion, which can accelerate the oxidation of the ferro-nickel metal produced.

[0010] As described above, in order to efficiently obtain ferronickel metal by mixing nickel oxide ore with a carbonaceous reducing agent and reducing it, it was necessary to be able to carry out experiments accurately and efficiently. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] Japanese Patent Application Publication No. 2018-178252 Summary of the Invention [Problem to be solved by the invention]

[0012] The present invention has been proposed in view of the above-mentioned circumstances, and has an object to provide a smelting method for producing ferronickel by reducing a mixture containing nickel oxide ore, which can suppress deterioration in the quality of the reduced product obtained and produce ferronickel through an efficient operation. [Means for solving the problem]

[0013] As a result of extensive research, the inventors discovered that the above-mentioned problems could be solved by using a reduction furnace equipped with a heat treatment section in which the mixture is heated and subjected to a reduction treatment, and a coal throwing section connected to the heat treatment section, and by moving the mixture from the heat treatment section to the coal throwing section during the reduction treatment and supplying additional carbonaceous reducing agent to the mixture, thereby completing the present invention.

[0014] (1) A first aspect of the present invention is a method for smelting nickel oxide ore, which produces ferronickel by reducing a mixture containing nickel oxide ore as a raw material ore and a carbonaceous reducing agent, the method comprising: a mixing step of mixing the nickel oxide ore with the carbonaceous reducing agent; and a reduction step of charging the mixture into a reduction furnace and heating the mixture to subject it to a reduction treatment. In the reduction step, the reduction furnace is equipped with a heat treatment section that heats the mixture to a reduction treatment and a coal throwing section connected to the heat treatment section, and during a stage of the reduction treatment, the mixture is moved from the heat treatment section to the coal throwing section, and additional carbonaceous reducing agent is supplied to the mixture in the coal throwing section, and then the mixture to which the carbonaceous reducing agent has been additionally supplied is moved again to the heat treatment section to be subjected to a reduction treatment.

[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, after completion of the reduction treatment, the resulting reduced material is moved to the coal throwing section and cooled in the coal throwing section.

[0016] (3) A third aspect of the present invention is a method for smelting nickel oxide ore according to the second aspect of the present invention, wherein a carbonaceous reducing agent is laid on the floor of the coal throwing section, and the reduced material is cooled in the coal throwing section.

[0017] (4) A fourth aspect of the present invention is the method for smelting nickel oxide ore according to any one of the first to third aspects, wherein the coal throwing section in the reduction furnace has a structure that allows gas replacement.

[0018] (5) A fifth aspect of the present invention is a method for smelting nickel oxide ore according to any one of the first to fourth aspects of the present invention, wherein in the reduction step, a sample ladle having a handle and a sample mounting part connected to the tip of the handle is used, the mixture is placed on the sample mounting part and then reduced in a heat treatment part of the reduction furnace, and the mixture is moved between the heat treatment part and the coal throwing part in the reduction furnace by moving the sample ladle.

[0019] (6) A sixth aspect of the present invention is a method for smelting nickel oxide ore according to any one of the first to fifth aspects, wherein the reduction step comprises carrying out a reduction treatment at a reduction temperature of 1200°C or higher and 1500°C or lower. [Effects of the Invention]

[0020] According to the present invention, in a smelting method for producing ferronickel by reducing a mixture containing nickel oxide ore, it is possible to suppress deterioration in the quality of the obtained reduced product and produce ferronickel through an efficient operation. [Brief explanation of the drawings]

[0021] [Figure 1] FIG. 1 is a process diagram showing the flow of a method for smelting nickel oxide ore. [Figure 2] FIG. 1 is a diagram showing an example of the configuration of a reducing furnace, and is a diagram for explaining the configuration of a heat treatment unit that serves as a main body of the reducing furnace. [Figure 3] FIG. 2 is a diagram showing an example of the configuration of a reduction furnace, illustrating the configuration of a coal throwing unit connected to a heat treatment unit of the reduction furnace. [Figure 4] FIG. 2 is a diagram showing an example of the configuration of a sample ladle. DETAILED DESCRIPTION OF THE INVENTION

[0022] Specific embodiments of the present invention (hereinafter referred to as "present embodiments") will be described in detail below. Note that the present invention is not limited to the following embodiments, and various modifications are possible within the scope of the present invention. In addition, in this specification, the expression "X to Y" (X and Y are arbitrary numerical values) means "X or more and Y or less."

[0023] ≪1. Nickel oxide ore smelting method≫ In the method for smelting nickel oxide ore according to the present embodiment, nickel oxide ore, which is a raw material ore, is mixed with a carbonaceous reducing agent, and the mixture is subjected to a reduction treatment in a smelting furnace (reduction furnace), thereby producing ferronickel metal and slag.

[0024] Specifically, the method for smelting nickel oxide ore includes at least a mixing step of mixing nickel oxide ore with a carbonaceous reducing agent, and a reduction step of charging the resulting mixture into a reduction furnace and heating the mixture to perform a reduction treatment.

[0025] In this case, in the smelting method according to the present embodiment, the reduction furnace is a furnace equipped with a heat treatment section for heating the mixture to perform the reduction treatment and a coal throwing section connected to the heat treatment section, and during the reduction treatment, the mixture is moved from the heat treatment section of the reduction furnace to the coal throwing section, and a carbonaceous reducing agent is additionally supplied to the coal throwing section. The mixture to which the carbonaceous reducing agent has been additionally supplied is then moved again to the heat treatment section and subjected to the reduction treatment.

[0026] According to such a method, for example, metal that has been partially oxidized by oxygen or moisture during reduction treatment can be reduced again, and ferronickel metal with improved quality and properties can be produced through an efficient operation.

[0027] Furthermore, as will be described in detail later, preferably, a sample ladle having a handle and a sample mounting portion connected to the tip of the handle is used, and the reduction treatment is carried out in the heat treatment portion of the reducing furnace with the mixture placed on the sample mounting portion, and the movement of the mixture between the heat treatment portion and the coal feeding portion in the reducing furnace is carried out by moving the sample ladle. According to this method, the mixture can be appropriately moved with a simple operation to supply additional carbonaceous reducing agent, and can be returned to the heat treatment portion to continue the reduction treatment. This makes it possible to efficiently produce ferronickel while suppressing deterioration in quality.

[0028] ≪2. About the smelting process≫ As described above, the method for smelting nickel oxide ore involves heating a mixture of nickel oxide ore, which is a raw material ore, and a carbonaceous reducing agent in a reduction furnace to reduce nickel (nickel oxide) and iron (iron oxide), thereby producing metal iron-nickel alloy (ferronickel).Ferronickel can be obtained by separating the metal from the reduction product obtained by the reduction treatment (separating the metal from the slag).

[0029] Specifically, as shown in FIG. 1 , the method for smelting nickel oxide ore according to the present embodiment includes a mixing step S1 in which a raw material containing nickel oxide ore is mixed with a carbonaceous reducing agent, a mixture forming step S2 in which the resulting mixture is formed into a predetermined shape, a reduction step S3 in which the formed mixture is reduced and heated in a reduction furnace at a predetermined reduction temperature, and a recovery step S4 in which the metal and slag produced in the reduction step S3 are separated and the metal is recovered.

[0030] [Mixing process] The mixing step S1 is a step of mixing raw material powders containing nickel oxide ore to obtain a mixture. Specifically, the raw material ore, nickel oxide ore, is mixed with a carbonaceous reducing agent, and optional additives such as iron ore, flux components, binders, and the like, each having a particle size of about 0.2 mm to 0.8 mm, are mixed to obtain a mixture. The mixing process can be performed using a mixer or the like.

[0031] In the mixing step S1, kneading may be performed to improve mixability. For example, by kneading the mixture using a twin-screw kneader or the like, shear force is applied to the mixture, which breaks down agglomerations of the carbonaceous reducing agent, raw material powder, etc., and allows for more uniform mixing. This also increases the adhesion of each particle, making it easier to perform a uniform reduction treatment on the resulting mixture.

[0032] The nickel oxide ore that is the raw material ore is not particularly limited, and limonite ore, saprolite ore, etc. Nickel oxide ore contains nickel oxide (NiO) and iron oxide (Fe2O3) as constituent components.

[0033] As described above, in the mixing process S1, a specific amount of carbonaceous reducing agent is added to nickel oxide ore and mixed to form a mixture. The carbonaceous reducing agent is not particularly limited, but examples thereof include coal powder and coke powder. It is preferable that the carbonaceous reducing agent has the same particle size as the nickel oxide ore, which is the raw material ore. It is preferable that the particle sizes of the carbonaceous reducing agent and the nickel oxide ore are the same, as this facilitates uniform mixing and results in a uniform reduction reaction.

[0034] The amount of the carbonaceous reducing agent is not particularly limited, but is preferably 50.0% or less, and more preferably 40.0% or less, when the amount of the carbonaceous reducing agent required to properly reduce the nickel oxide and iron oxide constituting the nickel oxide ore is taken as 100%. Here, the amount of the carbonaceous reducing agent required to properly reduce the nickel oxide and iron oxide can be rephrased as the sum of the chemical equivalent required to reduce all of the nickel oxide to nickel metal and the chemical equivalent required to reduce the iron oxide to iron metal (hereinafter also referred to as the "total chemical equivalents"). In this way, by setting the amount of the carbonaceous reducing agent to 50.0% or less, when the total chemical equivalents are taken as 100%, the reduction reaction can be efficiently promoted. Note that the lower limit of the amount of the carbonaceous reducing agent is not particularly limited, but is preferably 10.0% or more, and more preferably 15.0% or more, when the total chemical equivalents are taken as 100%.

[0035] In addition to the nickel oxide ore and carbonaceous reducing agent, the iron ore added as an optional component is not particularly limited, and examples thereof include iron ore with an iron content of about 50% or more and hematite obtained by hydrometallurgy of nickel oxide ore. Examples of binders include bentonite, polysaccharides, resins, water glass, and dehydrated cake. Examples of flux components include calcium oxide, calcium hydroxide, calcium carbonate, and silicon dioxide.

[0036] The following Table 1 shows an example of the composition (wt %) of some of the raw material powders mixed in the mixing treatment step S1, but the composition of the raw material powder is not limited to this.

[0037] [Table 1]

[0038] [Mixture forming process] The mixture forming step S2 is a step of forming the mixture obtained in the mixing treatment step S1. Specifically, the mixture obtained by mixing the raw material powders is formed into lumps of a certain size or larger so that the mixture can be loaded, for example, in a stacked form, into a reduction furnace during the reduction treatment in the next reduction step S3.

[0039] The shape of the agglomerates (also called pellets) obtained by molding the mixture can be rectangular, cylindrical, spherical, or the like. Such shapes make it easy to mold the mixture and reduce molding costs. Furthermore, because these shapes are not complex, there are almost no defective products and the yield in molding is extremely high. Furthermore, rectangular, cylindrical, or spherical shapes make it easy to stack the materials in a reduction furnace, making it possible to increase the amount of material processed during reduction. Furthermore, the amount of material processed during reduction can be increased without making each pellet large, and they are easy to handle. Furthermore, they do not collapse when being charged into a reduction furnace, making it less likely that defects will occur.

[0040] The volume of the pellets of the molded (agglomerated) mixture is not particularly limited, and may be, for example, 8000 mm 3 If the volume of the pellets is too small, the molding cost will be high and it may take time and effort to load them into the reduction furnace. Furthermore, if the volume of the pellets is small, the proportion of the surface area in the entire pellet will be high, which may result in a difference in reduction between the surface and the interior, which may affect the quality of the ferronickel. If the volume of the pellets of the mixture is 8000 mm 3By doing so, molding costs can be reduced, handling is easy, and it is preferable. Furthermore, high-quality ferric nickel can be produced.

[0041] After the mixture is molded, it may be subjected to a drying treatment. Depending on the moisture content of the mixture, the rapid temperature rise during the reduction treatment may cause the moisture in the mixture to evaporate and expand all at once, causing the mixture to break into pieces. Therefore, a drying step may be provided after the mixture molding step to dry the mixture. For example, in the drying step, the mixture may be dried so that the solid content is about 70% by weight and the moisture content is about 30% by weight.

[0042] The method for drying the mixture is not particularly limited, and for example, hot air at 150°C to 400°C can be blown onto the lumps to dry them. In the case of a mixture in the form of relatively large lumps, the mixture may have cracks or fractures before or after drying. In the case of large lumps, even if the surface area increases due to cracks or the like, the impact is minimal.

[0043] An example of the composition (parts by weight) of the solid content in the mixture (after drying treatment) is shown in the following Table 2. However, the composition of the mixture is not limited to this.

[0044] [Table 2]

[0045] [Reduction process] (Regarding reduction treatment) In the reduction step S3, the mixture (molded product) obtained in the mixture molding step S2 is heated to a predetermined reduction temperature in a reduction furnace for reduction. This reduction treatment causes a smelting reaction (reduction reaction) of the mixture containing nickel oxide ore to proceed, producing metal and slag.

[0046] The temperature of the reduction treatment (reduction temperature) is preferably 1200° C. or higher and 1500° C. or lower, and more preferably 1250° C. or higher and 1450° C. or lower. By setting the reduction temperature within such a range, the reduction reaction can be progressed efficiently and reliably, and ferronickel having the desired properties can be obtained.

[0047] During the reduction process, the slag in the mixture becomes semi-molten and a mixture of liquid and solid phases is formed, but the metal and slag that have already separated do not mix, and after cooling, the mixture becomes a mixture of separate phases, the metal solid phase and the slag solid phase. The volume of this mixture shrinks to about 50% to 60% of the volume of the mixture that was charged.

[0048] (About the reduction furnace) In the present embodiment, a reduction furnace used in the reduction treatment is characterized in that it includes a heat treatment section that heats the mixture to perform the reduction treatment, and a coal throwing section that is connected to the heat treatment section.

[0049] FIG. 2 is a perspective view of a reducing furnace, illustrating the configuration of a heat treatment section that serves as the main body of the reducing furnace. As shown in FIG. 2, the reducing furnace 1 can be a box-shaped furnace. Inside the box-shaped furnace main body, a reduction treatment is performed in which the mixture to be treated is heated and reduced. That is, the reducing furnace 1 constitutes a heat treatment section 11.

[0050] The reduction furnace 1 is not particularly limited, but may be a burner furnace in which a burner 12 is provided at a predetermined position and reduction treatment is performed by heating with the burner. By employing burner heating (burner furnace) as the heating method for the reduction furnace 1, the interior of the heat treatment unit 11 can be heated with excellent combustibility, which is preferable. The fuel for the burner may be any of gaseous fuel such as LPG, liquid fuel such as heavy oil, and solid fuel such as coal or coke, but among these, LPG is preferable because of its superior combustibility.

[0051] The heat treatment unit 11 is provided with a sample stage 13 that is placed in contact with a predetermined surface of the box (the inner surface of the furnace). The sample stage 13 is a stage on which the mixture to be treated is placed and the reduction treatment is performed. A reducing agent such as a carbonaceous reducing agent may be laid on the upper surface of the sample stage 13. As will be described in detail later, the reduction treatment is performed using a sample ladle 3 having a handle 31 and a sample placement portion 32 connected to the tip of the handle 31, with the mixture to be treated placed on the sample placement portion 32 (see FIG. 3). Therefore, the sample ladle 3 with the mixture placed thereon is placed on the sample stage 13.

[0052] A partition plate 11a is provided on the side of the heat treatment section 11 to separate the inside from the outside. The partition plate 11a has a door-like structure that can be opened and closed. In the heat treatment section 11, the mixture to be treated is loaded through the partition plate 11a, and the mixture and the reduced product obtained after treatment are removed through the partition plate 11a. The partition plate 11a can be made of a plate-shaped insulating board, brick, insulating wool, or the like. In the heat treatment section 11, after the mixture to be treated is loaded inside, the partition plate 11a is closed and the reduction treatment is performed. In this way, by the simple operation of closing the partition plate 11a, the internal space of the heat treatment section 11 can be made into an airtight space, and a drop in temperature within the heat treatment section 11 can be prevented.

[0053] The reduction furnace 1 is also provided with an exhaust port 14 for exhausting gas from inside the furnace (inside the heat treatment section 11) on, for example, its upper surface (ceiling surface).

[0054] 3 is a side view of the reducing furnace 1, and is a diagram for explaining the configuration of a coal throwing unit 21 connected to the heat treatment unit 11 of the reducing furnace 1. As shown in FIG. 3, in the reducing furnace 1, the coal throwing unit 21 is connected to the heat treatment unit 11. The coal throwing unit 21 has, for example, a box shape similar to the heat treatment unit 11, and is connected to a predetermined surface of the heat treatment unit 11.

[0055] The heat treatment section 11 and the coal throwing section 21 are connected via the partition plate 11a in the heat treatment section 11 and the partition plate 21a on the heat treatment section 11 side in the coal throwing section 21. The partition plate 21a in the coal throwing section 21 has a door-like structure that can be opened and closed, similar to the partition plate 11a in the treatment section 11. Therefore, the mixture to be treated is charged into the coal throwing section 21, and then charged into the heat treatment section 11 through the door-like partition plates 21a, 11a.

[0056] The partition plate 21a can also be made of a plate-shaped insulating board, brick, insulating wool, etc. The partition plate 11a of the heat treatment section 11 and the partition plate 21a of the coal throwing section 21 can also be made to have a common structure.

[0057] In the coal throwing section 21, a carbonaceous reducing agent is supplied to the mixture to be treated. More specifically, during the reduction treatment, the mixture is moved from the heat treatment section 11 to the coal throwing section 21, and then the carbonaceous reducing agent is additionally supplied to the mixture in the coal throwing section 21. The procedure for additionally supplying the carbonaceous reducing agent will be described in detail later. Furthermore, in the coal throwing section 21, prior to the start of the reduction treatment, the carbonaceous reducing agent may be supplied to the mixture being charged into the heat treatment section 11 via the coal throwing section 21, or to the periphery of the mixture (the sample placement portion of the sample ladle). In this way, the coal throwing section 21 functions as a reducing agent supply chamber for the mixture.

[0058] The coal throwing section 21 also functions as a cooling chamber for cooling the reduced material obtained after reduction treatment in the heat treatment section 11. After reduction treatment in the heat treatment section 11, the reduced material obtained is moved to the coal throwing section 21 via door-like partition plates 11a, 21a, and cooled to a predetermined temperature in the coal throwing section 21.

[0059] Here, in the coal throwing section 21, which functions as a cooling chamber, a carbonaceous reducing agent may be laid, for example, on its floor. Preferably, the carbonaceous reducing agent is laid in the coal throwing section 21, and the reduced material obtained by the reduction process is moved to the coal throwing section 21 in this state and cooled. This causes the carbonaceous reducing agent laid on the floor to heat and react with oxygen that is inevitably mixed in, consuming the oxygen, thereby more effectively preventing oxidation of the reduced material that has been cooled. The amount of carbonaceous reducing agent (amount laid on the floor) is not particularly limited as long as it can create a reducing atmosphere in the coal throwing section 21 and prevent oxidation of the reduced material, but it is preferable that the amount be such that the carbonaceous reducing agent is laid on the floor.

[0060] Furthermore, the coal throwing section 21 preferably has a structure that can replace the atmospheric gas. The gas to be replaced is preferably an inert gas. By flowing an inert gas to replace the atmosphere, it is possible to prevent the generated metal from being oxidized even when a carbonaceous reducing agent is additionally supplied to the mixture in the coal throwing section 21 during the reduction treatment, as will be described in detail later. Furthermore, when the obtained reduced material is cooled in the coal throwing section 21, the circulating inert gas acts as a cooling gas to promote cooling. Furthermore, during the cooling, the inert gas allows the obtained reduced material to be cooled even when the inert gas is used. thing The inert gas is not particularly limited, but may be nitrogen, argon, or the like, which are relatively inexpensive and readily available, or may be carbon dioxide.

[0061] The coal throwing section 21 is provided with a loading / unloading port 21b opposite the partition plate 21a for loading the mixture to be treated and for unloading the reduced material obtained by the reduction treatment. The loading / unloading port 21b is a lid and, like the partition plate 21a, has an openable door-like structure. The loading / unloading port 21b is preferably a double-door structure to minimize air intrusion. The loading / unloading port 21b is opened when the mixture is loaded into the coal throwing section 21, and the loading / unloading port 21b is closed when performing the reduction treatment in the heat treatment section 11, when supplying the reducing agent in the coal throwing section 21, and when cooling in the coal throwing section 21.

[0062] (Regarding the reduction process) In the reduction treatment using the reduction furnace 1 having the above-described configuration, first, the loading / unloading port 21b of the coal-feeding section 21 is opened and the material is loaded inside, and then the partition plates 11a, 21a are opened and the material is loaded into the heat treatment section 11 connected to the coal-feeding section 21, and then the material is placed on the sample stage 13.

[0063] In the reduction treatment, a sample ladle is used to load and unload the mixture sample to be treated. FIG. 4 shows an example of the configuration of a sample ladle 3. The sample ladle 3 includes a handle 31 and a sample placement part 32 connected to the tip of the handle 31. In the sample ladle 3, the handle 31 is a rod-shaped part that is held by an operator's hand or by a machine. The sample placement part 32 is connected to the tip of the handle 31, and the sample, i.e., the mixture to be treated, is placed on its upper surface (placement surface 32a). Note that FIG. 4 shows an example in which the sample placement part 32 is configured as a rectangular parallelepiped, but is not limited to this. For example, the sample placement part 32 may be configured as a container-like structure in which the placement surface for the mixture to be treated forms a recess, walls are provided on all four sides, and the top surface is open.

[0064] In the reduction treatment, the sample mixture is placed on the sample placement portion 32 of the sample ladle 3, and in that state, the handle 31 is grasped by hand or by machine and inserted into the coal-throwing portion 21. Then, the partition plates 11a and 21a are opened from inside the coal-throwing portion 21, and the handle 31 of the sample ladle 3 is pushed in, so that the sample placement portion 32 is inserted into the heat treatment portion 11.

[0065] At this time, the sample ladle 3 placed in the heat treatment unit 11 is moved to near the center of the sample stage 13, and then the sample ladle 3 itself is placed on the sample stage 13, and the reduction treatment is started in this state (with the sample ladle 3 containing the mixture still placed there). That is, during the reduction treatment, heating is started while the sample ladle 3 remains in the heat treatment unit 11. According to this method, the reduction treatment can be carried out simply by placing the mixture to be treated on the sample ladle 3 and then moving the sample ladle 3 into and out of the heat treatment unit 11 via the coal injection unit 21. This prevents, for example, erroneous operation, such as the mixture falling off the sample stage 13 when transferring the mixture from the sample ladle 3 onto the sample stage 13. It also prevents problems such as uneven heating by the burner.

[0066] In this case, ash or a carbonaceous reducing agent may be placed on the sample placement portion 32 of the sample ladle 3. This can prevent the mixture from fusing on the placement surface of the sample placement portion 32.

[0067] Furthermore, when the sample ladle 3 is left in the heat treatment section 11, the main part of the handle 31 of the sample ladle 3 is located in the coal throwing section 21 (see FIG. 3). By starting the reduction treatment with the handle 31 of the sample ladle 3 located in the coal throwing section 21, it is possible to prevent the handle 31 of the sample ladle 3 from being thermally deformed by the heat of the reduction treatment. Because the reduction treatment is performed under high-temperature conditions, for example, at approximately 1200°C to 1500°C, the handle 31 of the sample ladle 3 may be thermally deformed and bent. In this regard, by keeping the handle 31 located in the coal throwing section 21, it is possible to prevent thermal deformation.

[0068] Furthermore, for example, by forming a semicircular hole, for example, at the lower end of the partition plates 11a, 21a separating the coal-throwing section 21 and the heat-treatment section 11, so that the handle 31 of the sample ladle 3 can pass through, the partition plates 11a, 21a can ensure airtightness within the heat-treatment section 11 even when the sample ladle 3 is left inside the heat-treatment section 11 and the partition plates 11a, 21a are closed.

[0069] In the method according to the present embodiment, during the reduction treatment, the mixture being reduced is moved from the heat treatment section 11 to the coal throwing section 21, and a carbonaceous reducing agent is additionally supplied to the mixture in the coal throwing section 21. Thereafter, the mixture to which the carbonaceous reducing agent has been additionally supplied is moved again to the heat treatment section 11, and the reduction treatment is continued.

[0070] In this way, by supplying additional carbonaceous reducing agent during the reduction process, it is possible to reduce again the metal that was partially oxidized by the oxygen and moisture contained in the combustion gas during the reduction process, thereby improving the quality and characteristics. Furthermore, when the mixture sample is heated again, the presence of the reducing agent on the surface of the mixture sample can suppress oxidation.

[0071] As described above, the coal throwing section 21 is connected continuously to the heat treatment section 11. Therefore, even when a carbonaceous reducing agent is replenished to the mixture during the reduction treatment, the mixture can be replenished without being taken out into the atmosphere, and oxidation of the produced metal can be prevented.

[0072] Here, the mixture is moved between the heat treatment section 11 and the coal throwing section 21 in the reduction furnace 1 by moving the sample ladle 3.

[0073] As described above, in the reduction treatment, the mixture to be treated is placed on the sample placement portion 32 of the sample ladle 3, and the reduction treatment is carried out in the heat treatment portion 11. When the mixture is to be moved from the heat treatment portion 11 to the coal throwing portion 21 during the reduction treatment, the partition plates 11a, 21a are opened, and then the handle 31 of the sample ladle 3 is grasped and the sample ladle 3 is pulled out from the coal throwing portion 21 side, thereby moving the portion of the sample placement portion 32 on which the mixture is placed into the coal throwing portion 21. Thereafter, in the coal throwing portion 21, a carbonaceous reducing agent is added to the mixture placed on the sample placement portion 32.

[0074] When the mixture replenished with the carbonaceous reducing agent is again moved to the heat treatment section 11, the handle 31 of the sample ladle 3 is grasped and the sample ladle 3 is pushed out from the coal throwing section 21 side, so that the portion of the sample placement section 32 on which the mixture is placed is moved into the heat treatment section 11. Thereafter, the reduction treatment is continued in the heat treatment section 11.

[0075] In this way, the mixture can be moved between the heat treatment section 11 and the coal throwing section 21 by moving the sample ladle 3, which allows for smooth and reliable operation.

[0076] After the reduction treatment is completed, the partition plates 11a and 21a are opened from inside the coal throwing section 21, and the reduced material obtained by the reduction treatment is taken out from the heat treatment section 11 via the coal throwing section 21.

[0077] When the reduced material is removed, it is cooled in the coal throwing section 21. As described above, the coal throwing section 21 has a structure that allows gas replacement by circulating an inert gas. Therefore, the circulating inert gas acts as a cooling gas, and the reduced material can be efficiently and quickly cooled to a predetermined temperature. Furthermore, in the environment inside the coal throwing section 21 filled with inert gas, oxidation of the metal in the obtained reduced material can be suppressed, and deterioration in quality can be prevented.

[0078] The reduced material is cooled in the coal throwing section 21 with the partition plates 11a, 21a closed from inside the coal throwing section 21. This prevents high-temperature heat from the heat treatment section 11 from entering the coal throwing section 21, allowing for efficient cooling. The cooling time is not particularly limited as long as it can cool the reduced material to a predetermined temperature, but is preferably 10 minutes or more. By cooling for 10 minutes or more, the temperature of the reduced material can be lowered to 1000°C or less, and even if the reduced material is subsequently removed from the coal throwing section 212, oxidation of the generated metal can be suppressed.

[0079] Furthermore, because the coal throwing section 21 is connected continuously to the heat treatment section 11, the reduced material obtained by the reduction treatment in the heat treatment section 11 can be cooled without being taken out into the atmosphere. If the reduced material heated to a high temperature is taken out into the atmosphere as is, oxidation of the generated metal will proceed rapidly, resulting in a deterioration in the metal properties and a significant drop in the metal recovery rate. In this regard, by performing the reduction treatment using a reduction furnace 1 in which the coal throwing section 21 is connected to the heat treatment section 11, the cooling operation of the high-temperature reduced material can be efficiently performed in the coal throwing section 21, and oxidation of the metal can be effectively prevented.

[0080] Furthermore, it is preferable to lay a carbonaceous reducing agent in advance on the floor of the coal throwing section 21, which functions as a cooling chamber, and then move the reduced material to the coal throwing section 21 in this state to cool it. As a result, the carbonaceous reducing agent laid on the floor is heated and reacts with oxygen that is inevitably mixed in, consuming the oxygen, thereby more effectively preventing oxidation of the reduced material that has been cooled.

[0081] By carrying out the reduction treatment in the reduction step S3 as described above, ferronickel can be produced accurately, reliably, and efficiently.

[0082] [Recovery process] In the recovery step S4, the metal and slag produced in the reduction step S3 are separated and the metal is recovered. Specifically, the metal phase is separated and recovered from a mixture (inclusion) containing a metal phase (metal solid phase) and a slag phase (slag solid phase) obtained by subjecting the mixture filled in a container to a reduction heat treatment.

[0083] As a method for separating the metal phase and the slag phase from the mixture of the metal phase and the slag phase obtained as a solid, in addition to removing unnecessary substances by sieving, methods such as separation by specific gravity or separation by magnetic force can be used.

[0084] Furthermore, the resulting metal phase and slag phase can be easily separated due to their poor wettability. For example, by subjecting the large inclusions obtained by the reduction step S3 to an impact, such as by dropping them over a predetermined drop or by applying a predetermined vibration during sieving, the metal phase and slag phase can be easily separated from the inclusions.

[0085] In this way, the metal phase and the slag phase are separated, and the metal phase, i.e., ferronickel, is recovered. [Example]

[0086] The present invention will be explained in more detail below by showing examples, but the present invention is not limited to the following examples in any way.

[0087] <1. Ferronickel Production> A nickel oxide ore smelting method was carried out to produce ferronickel by reducing a mixture of nickel oxide ore as a raw material ore and a carbonaceous reducing agent under the conditions shown below.

[0088] (Mixing process) A mixture was obtained by mixing nickel oxide ore as raw ore, iron ore, silica sand and limestone as flux components, a binder, and a carbonaceous reducing agent (coal powder (pulverized coal): carbon content 76% by weight, average particle size approximately 75 μm) using a mixer while adding an appropriate amount of water. The carbonaceous reducing agent was added in an amount that would result in a ratio of 32.0% when the amount necessary to properly reduce the nickel oxide and iron oxide (Fe2O3) contained in the nickel oxide ore as raw ore was taken as 100%.

[0089] (Mixture forming process) The resulting mixture was then granulated using a pan granulator and sieved to a size of φ15.0±0.7 mm. The sample was then dried by blowing hot air at 170°C to 250°C onto it to achieve a solid content of approximately 70% by weight and a moisture content of approximately 30% by weight before reduction. Table 3 below shows the solid composition (excluding carbon) of the sample after drying.

[0090] [Table 3]

[0091] (Reduction process) Next, the sieved sample (mixture sample) was divided into 14 pieces (Examples 1 to 11, Comparative Examples 1 to 3), and was subjected to a reduction treatment by heating in a reduction furnace (burner furnace).

[0092] In this example, a reduction furnace 1 connected to a coal-throwing unit 21 as shown in the schematic diagrams of FIGS. 2 and 3 was used as the reduction furnace. Specifically, the reduction furnace 1 was a box-shaped burner furnace equipped with a heat treatment unit 11 that heats a mixture sample to perform a reduction treatment, and a coal-throwing unit 21 connected to the heat treatment unit 11. The coal-throwing unit 21 had a structure that allowed gas replacement with an inert gas. In the reduction furnace 1, the coal-throwing unit 21 and the heat treatment unit 11 were connected via partition plates 21a, 11a made of plate-shaped insulation boards, and the partition plates 21a, 11a were openable and closable from inside the coal-throwing unit 21. The reduction furnace was equipped with a burner, and pulverized coal, LPG, heavy oil, and coke were used as fuels.

[0093] The sample mixture was charged into the reduction furnace 1 using a sample ladle 3 as shown in the schematic diagram of Fig. 4. The sample ladle 3 has a handle 31 and a sample mounting portion 32 at the tip of the handle 31. Ash (mainly composed of SiO2, with small amounts of oxides such as Al2O3 and MgO as other components) was spread on the upper surface of the sample mounting portion 32, and the mixture sample was placed on top of it.

[0094] When charging the mixture sample into the reduction furnace 1, the mixture sample placed on the sample ladle 3 was first charged into the coal-charging section 21 by opening the lid (charging / removal port 21b) of the coal-charging section 21, and then the partition plates 21a, 11a were opened from the coal-charging section 21 side, so that the mixture sample was charged into the heat-treating section 11 and placed on the sample stage 13. The sample ladle 3 containing the mixture was placed on the sample stage 13 as it was. Thereafter, the partition plates 11a, 21a were closed, and the heat-treating section 11 was made into an airtight space, and heating with a burner was started to carry out the reduction treatment.

[0095] In the example, during the reduction treatment, specifically 8 minutes before the end of the reduction time, the mixture sample was returned from the heat treatment unit 11 to the coal feeding unit 21, and a carbonaceous reducing agent (pulverized coal) was additionally supplied from above the mixture sample. The amount of pulverized coal supplied was 30% when the amount of pulverized coal mixed in the mixture was taken as 100%. After the pulverized coal was supplied, the mixture was again moved to the heat treatment unit 11, and the reduction treatment was continued.

[0096] After the specified reduction time had elapsed, the partition plates 21a and 11a were opened from inside the coal throwing section 21, and the sample ladle 3 containing the obtained reduced product was removed. At this time, the reduced product was cooled within the coal throwing section 21 without being released into the atmosphere. In the coal throwing section 21, an inert gas (nitrogen) was continuously circulated at a flow rate of 20 L / min, and the reduced product was cooled for 15 minutes using the inert gas as a cooling gas.

[0097] After cooling was completed, the reduced product was taken out from the coal throwing section 21 and the nickel metallization rate and nickel content in the metal were measured as shown below.

[0098] On the other hand, in the comparative example, the same reduction furnace 1 as in the example was used, but the carbonaceous reducing agent was not replenished during the reduction treatment. After the reduction treatment was completed, the reduced material was cooled and recovered in the coal throwing section 21.

[0099] [evaluation] After cooling each sample, the nickel metallization rate and nickel content in the metal, defined by the following formula, were analyzed and calculated using an ICP emission spectrometer (SHIMAZU S-8100). Nickel metal ratio = amount of metalized nickel in the mixture ÷ (total amount of nickel in the mixture) × 100 (%)... [1] Nickel content in metal = amount of metalized Ni in the mixture ÷ (total amount of metalized Ni and Fe in the mixture) × 100 (%)... [2]

[0100] Table 4 below shows the conditions of the reduction treatment, the calculated results of the nickel metal ratio and the nickel content in the metal.

[0101] [Table 4]

[0102] As shown in Table 4, in Examples 1 to 11, in which the reduction treatment was carried out by additionally supplying a carbonaceous reducing agent during the reduction treatment, both the nickel metallization rate and the metal content were good. This is thought to be because the additional supply of the carbonaceous reducing agent allowed the metal that had been partially oxidized during the reduction treatment to be reduced again, allowing for a more sufficiently uniform reduction treatment.

[0103] On the other hand, in Comparative Examples 1 to 3 in which reduction treatment was carried out without additionally supplying a carbonaceous reducing agent, both the nickel metallization rate and the metal content were lower than those in the Examples.

[0104] <2. Verification of the effect of laying a reducing agent on the coal-throwing area during cooling> In the following Examples 12 to 25, when the reduced material obtained after the reduction treatment was cooled in the coal throwing section 21, a carbonaceous reducing agent was laid in advance on the floor surface of the coal throwing section 21, and the effect of cooling was verified when the reduced material was cooled there.

[0105] Specifically, in Examples 12 to 22, similarly to Examples 1 to 11 described above, the mixture sample was returned from the heat treatment section 11 to the coal feeding section 21 during the reduction treatment (8 minutes before the end of the reduction time), and additional carbonaceous reducing agent (pulverized coal) was supplied onto the mixture sample. After the pulverized coal was replenished, the mixture sample was again moved to the heat treatment section 11, and the reduction treatment was continued. After the predetermined reduction time had elapsed, the partition plates 21a and 11a were opened from inside the coal feeding section 21, and the sample ladle 3 containing the obtained reduced product was removed. The reduced product was then cooled in the coal feeding section 21.

[0106] In the coal throwing section 21, a carbonaceous reducing agent (pulverized coal) was spread on the floor in advance, and the sample ladle 3 containing the reduced material was moved thereto. In the coal throwing section 21, an inert gas (nitrogen) was continuously circulated at a flow rate of 20 L / min, and the reduced material was cooled for a cooling time of 10 minutes.

[0107] On the other hand, in Examples 23 to 25, the reduction treatment was carried out while replenishment of pulverized coal in the coal feeding section 21, but when the obtained reduced material was cooled, no carbonaceous reducing agent was laid on the floor surface of the coal feeding section 21. Note that other than that, the treatment was carried out in the same manner as in Examples 12 to 22.

[0108] As in Examples 1 to 11, each sample was cooled, and then the nickel metallization rate and nickel content in the metal were analyzed and calculated using an ICP optical emission spectrometer (SHIMAZU S-8100). Table 5 below shows the reduction treatment conditions, cooling conditions (presence or absence of a reducing agent bedding), and the calculation results for the nickel metallization rate and nickel content in the metal.

[0109] [Table 5]

[0110] As shown in Table 5, in Examples 12 to 22, in which the reduced material was cooled in the coal throwing section 21, the floor of which was covered with a carbonaceous reducing agent, both the nickel metallization rate and the metal content were good. This is thought to be because, not only was the reduction treatment performed by additionally supplying a carbonaceous reducing agent, but the resulting reduced material was also cooled in the coal throwing section 21, which was covered with a carbonaceous reducing agent. This caused the carbonaceous reducing agent to consume oxygen that inevitably became mixed into the coal throwing section 21, thereby suppressing oxidation of the resulting reduced material.

[0111] On the other hand, in Examples 23 to 25, in which the obtained reduced material was cooled in a coal throwing section 21 where no carbonaceous reducing agent was laid, the reduction treatment was carried out by additionally supplying a carbonaceous reducing agent, and thus the results were good, but the results were slightly inferior to those of Examples 12 to 22. This is thought to be because the obtained reduced material was partially oxidized by oxygen that inevitably got mixed in, since the cooling was carried out without laying a carbonaceous reducing agent in the coal throwing section 21. [Explanation of symbols]

[0112] 1. Reduction furnace 11 Heat treatment section 12 burners 13 Sample stage 14 Exhaust port 21 Coal dumping department 11a, 21a Partition 21b Loading / unloading port 3. Sample ladle 31 patterns 32 Sample placement section

Claims

1. A method for smelting nickel oxide ore to produce ferronickel by reducing a mixture containing nickel oxide ore as a raw material ore and a carbonaceous reducing agent, comprising: a mixing step of mixing the nickel oxide ore with the carbonaceous reducing agent; a reduction step of charging the mixture into a reduction furnace and heating the mixture to perform a reduction treatment; Including, In the reduction step, The reduction furnace is a furnace including a heat treatment section for heating the mixture to perform a reduction treatment, and a coal throwing section connected to the heat treatment section, During the reduction treatment, the mixture is moved from the heat treatment section to the coal throwing section, and a carbonaceous reducing agent is additionally supplied to the mixture in the coal throwing section; Thereafter, the mixture to which the carbonaceous reducing agent has been additionally supplied is again moved to the heat treatment section and subjected to reduction treatment. A method for smelting nickel oxide ore.

2. After the reduction treatment is completed, the obtained reduced material is moved to the coal throwing section and cooled in the coal throwing section. The method for smelting nickel oxide ore according to claim 1.

3. A carbonaceous reducing agent is laid on the floor of the coal throwing section, and the reduced material is cooled in the coal throwing section. The method for smelting nickel oxide ore according to claim 2.

4. The coal throwing section in the reduction furnace has a structure capable of gas replacement.

4. The method for smelting nickel oxide ore according to claim 1.

5. In the reduction step, using a sample ladle having a handle and a sample placement portion connected to the tip of the handle, and carrying out a reduction treatment in a heat treatment portion of the reduction furnace while the mixture is placed on the sample placement portion; The mixture is moved between the heat treatment section and the coal throwing section in the reduction furnace by moving the sample ladle.

5. The method for smelting nickel oxide ore according to claim 1.

6. In the reduction step, A reduction treatment is carried out at a reduction temperature of 1200°C or higher and 1500°C or lower.

6. The method for smelting nickel oxide ore according to claim 1.

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