JP7563248B2 - Method for smelting nickel oxide ore - Google Patents

Description

The present invention relates to a method for smelting nickel oxide ore, which produces ferronickel by reducing a mixture of nickel oxide ore, which is a raw material, and a carbonaceous reducing agent.

Known methods for smelting nickel oxide ores called limonite or saprolite include the dry smelting method, which uses a smelting furnace to produce nickel matte, the dry smelting method, which uses a rotary kiln or a moving hearth furnace to produce ferronickel, and the wet smelting method, which uses an autoclave to produce mixed sulfides.

When smelting nickel oxide ore, the raw ore is first treated to form agglomerates, slurry, etc. (pretreatment prior to reduction treatment). Specifically, in pretreatment, nickel oxide ore is agglomerated, that is, converted from a powder or fine particle form into agglomerates, by first mixing it with components other than nickel oxide ore, such as a binder and a reducing agent, to form a mixture, which is then fed into a lump-making machine after adjusting the moisture content, etc., to form agglomerates (pellets, briquettes, etc., hereafter simply referred to as "pellets") of, for example, about 10 mm to 30 mm in size.

For example, pellets need to have a certain degree of breathability to allow moisture to evaporate. Also, if reduction is not performed uniformly within the pellet, the composition will be non-uniform, and the metals may become dispersed and unevenly distributed. For this reason, it is important to mix the mixture uniformly and to maintain as uniform a temperature as possible during pellet reduction.

In addition, it is also important to coarsen the ferronickel produced by reduction. If the ferronickel produced is, for example, a few tens of microns to a few hundreds of microns in size, 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.

For example, a small amount of pellets is loaded into a reduction furnace, a reduction test is performed, and the resulting reduced product is removed to examine various properties. However, the processing temperature is high, at 1000°C to 1500°C, and loading and removing pellets is not an easy task. Conventionally, pellets have been loaded into the furnace and the reduced product obtained by reduction removed using a special ladle made of metal that can withstand relatively high temperatures. However, due to the high processing temperature, the ladle can bend, causing problems such as getting caught on the inner wall of the furnace when removing the pellets, making it difficult to remove them smoothly.

As such, many challenges remain in the technology of mixing and reducing nickel oxide ore to produce metal, and a particularly important technical challenge is being able to carry out various experiments accurately and efficiently.

JP 2018-178252 A

The present invention has been proposed in light of these circumstances, and aims to provide a method for producing ferronickel by heating and reducing a mixture containing nickel oxide ore in a reduction furnace, which allows the mixture to be treated to be accurately and efficiently loaded into and removed from the reduction furnace, and prevents deterioration in the quality of the resulting metal.

After extensive research, the inventors discovered that the above-mentioned problems could be solved by carrying the mixture in a horizontal-hole type sample container with a through hole for reduction treatment, and then inserting a rod-shaped sample loading/unloading tool into the through hole of the horizontal-hole type sample container to carry the mixture when loading it into or unloading it from the reduction furnace, and thus completed the present invention.

(1) The first invention 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, and includes a mixing process for mixing the nickel oxide ore with the carbonaceous reducing agent, and a reduction process for loading the mixture into a reduction furnace and heating the mixture to perform a reduction process, in which the mixture is placed in a horizontal-hole type sample container with through holes formed on two opposing sides and reduced, and the operation of loading the mixture placed in the horizontal-hole type sample container into the reduction furnace and removing the reduced product obtained by the reduction process from the reduction furnace is performed by inserting rod-shaped sample loading/removal jigs into the through holes on the two sides of the horizontal-hole type sample container and carrying it.

(2) The second invention of the present invention is the method for smelting nickel oxide ore according to claim 1, in which the through hole formed in the side of the horizontal hole type sample container in the first invention is a circular hole, and the sample loading/unloading jig is a round bar with a circular cross section.

(3) The third invention of the present invention is a method for smelting nickel oxide ore according to the first or second invention, in which the reduction step involves carrying out reduction treatment in the reduction furnace at a reduction temperature of 1200°C or higher and 1500°C or lower.

According to the present invention, in a technology for producing ferronickel by heating and reducing a mixture containing nickel oxide ore in a reduction furnace, a method can be provided that allows the mixture to be accurately and efficiently charged into and removed from the reduction furnace, and prevents deterioration in the quality of the resulting metal.

FIG. 1 is a process diagram showing an example of the flow of a method for smelting nickel oxide ore. FIG. 2 is a schematic diagram showing an example of the configuration of a reduction furnace. 1A and 1B are diagrams showing the configuration of a sample container, in which (A) is a perspective view and (B) is a side view showing the side of the container. FIG. 13 is a diagram showing an example of the configuration of a sample loading/unloading jig. 1 is a diagram showing the state when a sample loading/unloading jig is inserted into a through hole of a horizontal-hole type sample container. FIG. FIG. 2 is a diagram showing the schematic configuration of a sample container (A) provided with a handle and a ladle (B) used in a comparative example.

A specific embodiment of the present invention (hereinafter referred to as "the present embodiment") will be described in detail below. Note that the present invention is not limited to the following embodiment, and various modifications are possible without departing from the gist of the present invention. In addition, in this specification, the expression "X to Y" (X and Y are arbitrary numbers) means "X or more and Y or less."

≪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) to produce ferronickel metal and slag.

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

In this case, in the smelting method according to the present embodiment, in the reduction step, the mixture to be reduced is placed in a horizontal-hole type sample container with through holes formed on two opposing sides, and the reduction process is carried out. The operation of loading the mixture placed in the horizontal-hole type sample container into the reduction furnace, and removing the reduced product obtained by the reduction process from the reduction furnace, is characterized in that the horizontal-hole type sample container is carried by inserting rod-shaped sample loading/removal jigs into the through holes on the two sides.

This method allows the mixture to be reduced and the reduced product to be charged and removed stably and smoothly, and prevents the deterioration of workability caused by, for example, the deformation of the ladle as in the past. As a result, it is possible to effectively suppress deterioration in the quality of the reduced product due to oxidation, etc.

≪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 of an iron-nickel alloy (ferronickel).Ferronickel can be obtained by separating the metal from the reduction product obtained by the reduction process (separating the metal from the slag).

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

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

In the mixing process S1, kneading may be performed to improve mixability. For example, by kneading the mixture with a twin-screw kneader or the like, shear force is applied to the mixture, which breaks down aggregates of the carbonaceous reducing agent, raw material powder, etc., and allows for more uniform mixing. In addition, the adhesion of each particle can be increased, making it easier to perform a uniform reduction process on the resulting mixture.

The nickel oxide ore as the raw material ore is not particularly limited, and may be limonite ore, saprolite ore, etc. Nickel oxide ore contains nickel oxide (NiO) and iron oxide (Fe ₂ O ₃ ) as constituents.

As described above, in the mixing process S1, a specific amount of carbonaceous reducing agent is added to the nickel oxide ore and mixed to form a mixture. The carbonaceous reducing agent is not particularly limited, but examples 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. If the particle sizes of the carbonaceous reducing agent and the nickel oxide ore are the same, they can be easily mixed uniformly, and as a result, the reduction reaction can occur uniformly, which is preferable.

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 reduce the nickel oxide and iron oxide constituting the nickel oxide ore without excess or deficiency is taken as 100%. Here, the amount of the carbonaceous reducing agent required to reduce the nickel oxide and iron oxide without excess or deficiency can be rephrased as the total value of the chemical equivalent required to reduce the entire amount of 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 value of chemical equivalents"). In this way, by setting the amount of the carbonaceous reducing agent to a ratio of 50.0% or less when the total value of the chemical equivalents is taken as 100%, the reduction reaction can be efficiently promoted. 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 value of the chemical equivalents is taken as 100%.

In addition to nickel oxide ore and carbonaceous reducing agent, the iron ore added as an optional component is not particularly limited, but examples include iron ore with an iron content of about 50% or more, and hematite obtained by wet smelting 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.

Table 1 below shows an example of the composition (weight %) of some of the raw material powders mixed in the mixing process S1. Note that the composition of the raw material powders is not limited to this.

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

The shape of the agglomerates (also called pellets) obtained by molding the mixture can be rectangular, cylindrical, spherical, etc. Such shapes make it easy to mold the mixture and reduce molding costs. Furthermore, these shapes are not complicated, so there are almost no defective products and the yield rate of molding is extremely high. Furthermore, rectangular, cylindrical, and spherical shapes make it easy to stack them in the reduction furnace, making it possible to increase the amount of material to be processed during reduction. Furthermore, the amount of material to be processed during reduction can be increased without making each pellet huge, and they are easy to handle. In addition, they do not collapse when loaded into the reduction furnace, making it less likely to cause defects.

The volume of the pellets of the molded (agglomerated) mixture is not particularly limited, and can be, for example, 8000 ^mm3 or more. If the volume of the pellets is too small, the molding cost will be high, and it may be troublesome to charge the pellets into a reduction furnace. Furthermore, if the volume of the pellets is small, the ratio of the surface area to the entire pellet will be high, so that the difference in reduction between the surface and the inside is likely to appear, and this may affect the quality of ferronickel. By setting the volume of the pellets of the mixture to 8000 ^mm3 or more, molding costs can be suppressed and handling is easy, which is preferable. Furthermore, high quality ferronickel can be produced.

After the mixture has been molded, it may be subjected to a drying process. Depending on the moisture in the mixture, the rapid temperature rise during the reduction process may cause the moisture in the mixture to evaporate and expand all at once, causing the mixture to break into pieces. For this reason, a drying process may be provided after the mixture molding process to dry the mixture. For example, in the drying process, a drying process may be performed so that the solid content of the mixture is about 70% by weight and the moisture content is about 30% by weight.

There are no particular limitations on the method of drying the mixture, and for example, hot air at 150°C to 400°C can be blown onto the lumps to dry them. If the mixture is in relatively large lumps, it is acceptable for the mixture to have cracks or fissures before and after drying. If the lumps are large, the effect is minimal even if the surface area increases due to cracks, etc.

Table 2 below shows an example of the composition (parts by weight) of the solid content in the mixture (after drying). Note that the composition of the mixture is not limited to this.

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

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 this range, the reduction reaction can proceed efficiently and reliably, and ferronickel with the desired characteristics can be obtained.

During the reduction process, the slag in the mixture becomes semi-molten and the liquid and solid phases coexist, but the metal and slag that have already separated do not mix together, and subsequent cooling results in a mixture of metal solid and slag solid phases that coexist as separate phases. The volume of this mixture has shrunk to about 50% to 60% of the volume of the mixture to be charged.

In this embodiment, the mixture to be reduced is placed in a horizontal-hole type sample container with through holes formed on two opposing sides, and then the reduction process is carried out. The operation of loading the mixture placed in the horizontal-hole type sample container into a reduction furnace, and removing the reduced product obtained by the reduction process from the reduction furnace, is characterized in that the horizontal-hole type sample container is carried by inserting rod-shaped sample loading/removal tools into the through holes on the two sides.

First, we will explain the configuration of the reduction furnace used in the reduction process S3. Figure 2 is a schematic diagram showing an example of the configuration of the reduction furnace.

As shown in FIG. 2, the reduction furnace 1 can be a box furnace in which the furnace body 11 has a box shape (rectangular parallelepiped shape). The reduction furnace 1 can be a burner furnace in which a burner 12 is provided at a predetermined position and the reduction process is performed by heating with the burner, although this is not particularly limited. By adopting burner heating (burner furnace) as the heating method for the reduction furnace 1, the inside of the furnace can be heated with excellent combustibility, which is preferable. The fuel for the burner is not particularly limited and can be any of gas fuel such as LPG, liquid fuel such as heavy oil, and solid fuel such as coal or coke, but LPG is preferable because of its excellent combustibility.

The reduction furnace 1 is also equipped with a sample stage 13 inside the box-shaped furnace body 11. The sample stage 13 is a stage on which the mixture to be reduced is placed. A reducing agent such as a carbonaceous reducing agent may be laid on the upper surface of the sample stage 13.

The reduction furnace 1 also has an exhaust port 14, for example on its upper surface (ceiling surface), for exhausting gas from within the furnace.

A sample loading/unloading port 15 is provided on a specific side of the reduction furnace 1 for loading a sample mixture into the reduction furnace and for removing the reduced product obtained by reduction treatment from the reduction furnace. The height position of the sample loading/unloading port 15 corresponds approximately to the height of the mounting surface of the sample stage 13 inside the furnace body 11. Therefore, when a mixture is loaded from the sample loading/unloading port 15, it can be appropriately placed on the mounting surface of the sample stage 13. Furthermore, when removing the reduced product, it can be easily removed from the sample loading/unloading port 15, which is provided at the same height as the sample stage 13.

Although not shown, the sample loading/unloading port 15 is provided with an opening/closing door, which can be opened when loading the mixture or unloading the reduced product, and closed when performing the reduction process. This allows the inside of the reduction furnace 1 to be an airtight space during the reduction process.

Next, we will explain the horizontal-hole type sample container that contains the mixture to be reduced. Figure 3 shows the structure of the horizontal-hole type sample container, where (A) is a perspective view and (B) is a side view showing the side of the container.

As shown in FIG. 3, the horizontal-hole sample container 2 is, for example, a box-shaped container having sides 21 to 24 on all four sides. The mixture is contained inside the horizontal-hole sample container 2, and in this state, it is loaded into the reduction furnace 1 and subjected to reduction treatment. The horizontal-hole sample container 2 has an open ceiling at the top, and the reduced material is placed inside the container from above.

As shown in FIG. 3, the horizontal-hole sample container 2 has through holes 21h, 23h formed on two opposing side surfaces 21, 23. The two through holes 21h, 23h are formed at approximately the same height position from the bottom of the container on each side surface 21, 23. In other words, they are arranged in a straight line at the same height position. As will be described in detail later, a rod-shaped sample loading and unloading jig 3 (see FIG. 4) is inserted into the through holes 21h, 23h from one through hole 21h to the other through hole 23h. The horizontal-hole sample container 2 is then carried in a lifted state like a balance, whereby the horizontal-hole sample container 2 containing the mixture is loaded into and unloaded from the reduction furnace 1.

The through holes 21h and 23h are preferably circular holes, although there is no particular limitation to such holes. In addition, it is preferable that the diameter of the holes is sufficiently larger than the cross-sectional diameter of the rod-shaped sample loading/unloading jig 3 that is inserted into the through holes.

The through holes are not limited to being formed on only two side surfaces of the horizontal-hole sample container 2, but may be formed on all four side surfaces, for example. Even in this case, it is preferable that the height positions of each through hole from the bottom of the container are approximately the same.

Next, we will explain the sample loading and unloading jig. Figure 4 is a side view showing an example of the configuration of the sample loading and unloading jig.

The sample loading/unloading jig 3 is a jig used for loading the mixture into the reduction furnace 1 and for unloading the reduced material obtained by the reduction process from the reduction furnace 1. As shown in Figure 4, the sample loading/unloading jig 3 is made of a long rod-shaped body.

The sample loading/removal jig 3 is preferably shaped so that its tip is slightly sharper than the central portion. This makes it easier to insert into the through holes 21h, 23h of the horizontal-hole type sample container 2. The size of the sample loading/removal jig 3 is smaller than the size of the through holes 21h, 23h of the horizontal-hole type sample container 2. It is preferable to set the size appropriately, taking into account thermal expansion and distortion of the horizontal-hole type sample container 2.

When loading and unloading a mixture, the sample loading/unloading jig 3 is inserted into the through holes 21h, 23h formed in the side surfaces 21, 23 of the horizontal-hole sample container 2. Specifically, for example, from the outside of the horizontal-hole sample container 2, the tip of the sample loading/unloading jig 3 is inserted into the through hole 21h formed in the side surface 21, and then passed through the inside of the horizontal-hole sample container 2 and inserted into the through hole 23h formed in the opposing side surface 23.

As a result, as shown in FIG. 5, the sample loading/removal jig 3 is attached from through-hole 21h to through-hole 23h. In other words, the horizontal-hole type sample container 2 is held in a hooked state on the sample loading/removal jig 3. In this state, for example, an operator can grasp the end of the sample loading/removal jig 3 and hold it up like a balance, allowing the horizontal-hole type sample container 2 to be carried.

In this embodiment, the rod-shaped sample loading/unloading tool 3 is inserted into the through holes 21h, 23h on the two side surfaces 21, 23 of the horizontal-hole type sample container 2 and carried around, so that the mixture contained in the horizontal-hole type sample container 2 can be loaded into the reduction furnace 1, and the reduced product obtained by the reduction process can be unloaded from the reduction furnace 1.

More specifically, we will explain the operation of loading the sample mixture into reduction furnace 1 during the reduction process, and the operation of removing the reduced material obtained by the process from reduction furnace 1.

First, the mixture, which is the sample to be subjected to the reduction treatment, is placed inside the horizontal-hole type sample container 2. Next, the sample loading/removal jig 3 is prepared, and the sample loading/removal jig is inserted tip-first into the through-hole 21h formed in the side surface 21 of the horizontal-hole type sample container 2 containing the mixture, and after passing through the inside of the container, the tip is brought out through the through-hole 23h formed in the opposing side surface 23. This results in the horizontal-hole type sample container 2 being hooked and held by the sample loading/removal jig 3 from the through-hole 21h to the through-hole 23h (see FIG. 5). In this state, the operator can grasp and lift the end of the rod-shaped sample loading/removal jig 3 to carry the horizontal-hole type sample container 2 containing the mixture.

Next, with the horizontal-hole sample container 2 held by the sample loading/unloading jig 3, the door of the sample loading/unloading port 15 on the side of the reduction furnace 1 is opened, and an operator grasps the end of the sample loading/unloading jig 3 and loads the horizontal-hole sample container 2 into the reduction furnace 1 through the sample loading/unloading port 15. Then, still holding the end of the sample loading/unloading jig 3, the operator moves the horizontal-hole sample container 2 close to the sample stage 13 provided in the furnace body 11 and gently places it on the sample stage 13.

Then, the sample loading/unloading jig 3 is removed from the through holes 21h, 23h of the horizontal-hole sample container 2, and only the sample loading/unloading jig 3 is taken out of the reduction furnace 1 through the sample loading/unloading port 15. Then, the door at the sample loading/unloading port 15 is closed, heating of the reduction furnace 1 by the burner 12 is started, and the reduction process is carried out on the mixture in the horizontal-hole sample container 2 placed on the sample stage 13. At this time, the sample loading/unloading jig 3 used to load the mixture has been removed from the reduction furnace 1, so it is outside the furnace during the reduction process, and the load from high temperature heat can be avoided.

After the reduction process is completed, the mixture is heated and reduced inside the horizontal-hole sample container 3 placed on the sample stage 13 of the reduction furnace 1 to produce a reduced product. The operation of removing the reduced product from the reduction furnace 1 is performed in the reverse order of the operation of loading. That is, the door of the sample loading/unloading port 15 on the reduction furnace 1 is opened, the sample loading/unloading jig 3 is inserted into the through holes 21h and 23h of the horizontal-hole sample container 2 placed on the sample stage 13, and the horizontal-hole sample container 2 is held by the sample loading/unloading jig 3 in the same state as when it was loaded into the reduction furnace 1 (see Figure 5).

In this state, the end of the sample loading/unloading jig 3 can be grasped and pulled out, allowing the horizontal-hole sample container 2 containing the reduced material to be easily removed from the reduction furnace 1.

When starting the reduction process, the sample loading/unloading jig 3 may not be taken out of the furnace. That is, after the horizontal-hole type sample container 2 held by the sample loading/unloading jig 3 is loaded into the reduction furnace 1 and placed on the sample stage 13, the opening/closing door provided at the sample loading/unloading port 15 may be closed and heating of the reduction furnace 1 may be started with the sample loading/unloading jig 3 still inserted into the through holes 21h and 23h of the horizontal-hole type sample container 2. Even in this case, since the sample loading/unloading jig 3 is inserted into the horizontal-hole type sample container 2 through the through holes 21h and 23h, even if the sample loading/unloading jig 3 is deformed by high-temperature heat, the horizontal-hole type sample container 2 can be smoothly removed out of the reduction furnace 1 by grasping the end of the sample loading/unloading jig 3 after the reduction process is completed.

In this way, according to this embodiment, the mixture is stored in a horizontal-hole type sample container 2 with through holes 21h, 23h formed on two opposing side surfaces 21, 23, and when the mixture is loaded into the reduction furnace 1 and the reduced product obtained by the reduction process is removed from the reduction furnace 1, the rod-shaped sample loading/removal jig 3 is inserted into the through holes 21h, 23h of the horizontal-hole type sample container 2 and is carried in a hooked state, so that transportation can be performed stably and smoothly. In addition, it is possible to prevent deterioration of workability due to deformation of the ladle as in the conventional case. As a result, it is possible to effectively suppress deterioration in quality of the reduced product due to oxidation, etc.

In addition, for example, when samples of various compositions are charged and used for testing to find effective reaction conditions for a specified reaction time, it is also important to consider the position (inside the furnace) at which the mixture is placed in the reduction furnace 1. In this regard, by charging the mixture using the above-mentioned operations, the mixture can be accurately placed in the reduction furnace, making it possible to more effectively perform testing to find reaction conditions.

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

[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 (mixture) 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.

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

The obtained metal phase and slag phase can be easily separated due to their poor wettability. For example, by dropping the large mixture obtained by the treatment in the reduction step S3 described above over a predetermined drop or by applying a certain amount of vibration during sieving, the metal phase and slag phase can be easily separated from the mixture.

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

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

[Examples and Comparative Examples]
A method for smelting nickel oxide ore was carried out to produce ferronickel by reducing a mixture of nickel oxide ore, which is a raw material ore, and a carbonaceous reductant under the conditions shown below.

(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, carbon content: 80% by weight, average particle size: about 85 μm) using a mixer while adding an appropriate amount of water. The carbonaceous reducing agent was contained in an amount that was 37.0% when the amount required to reduce nickel oxide and iron oxide (Fe ₂ O ₃ ) contained in the nickel oxide ore as raw ore without excess or deficiency was taken as 100%.

(Mixture molding process)
The resulting mixture was then granulated using a pan-type granulator and sieved to a size of φ15.0±0.8 mm. Thereafter, the sample was dried by blowing hot air at 170°C to 250°C onto it so that the solid content was about 70% by weight and the moisture content was about 30% by weight before reduction. Table 3 below shows the solid content composition (excluding carbon) of the sample after drying.

(Reduction process)
Next, the sieved sample (mixture sample) was divided into 12 pieces (Examples 1 to 9, Comparative Examples 1 to 3), and each was heated in a reduction furnace (burner furnace) to undergo reduction treatment.

In this embodiment, a horizontal-hole type sample container as shown in the schematic diagram of Fig. 3 was used, and the mixture was placed in the container and subjected to reduction treatment. The mixture was charged into the reduction furnace and the resulting reduced product was removed from the reduction furnace using a sample loading/removal tool as shown in Fig. 4, which was inserted into through holes formed on two side surfaces of the horizontal-hole type sample container and carried as shown in Fig. 5. Ash (mainly _SiO2 with small amounts of oxides such as _Al2O3 and MgO as other components) was spread over the top surface of the horizontal- _hole type sample container on which the sample was placed, and the mixture sample was placed on top of it.

The reduction furnace used was a box-shaped burner furnace with an internal sample stage and a sample loading/unloading port on a specific side at a position equivalent to the height of the sample stage's mounting surface (see Figure 2). The reduction furnace was equipped with a burner, and pulverized coal, LPG, heavy oil, and coke were used as fuel.

Specifically, in the examples, when loading the mixture into the reduction furnace, a sample loading/unloading jig was inserted into the through holes formed on two sides of the horizontal-hole type sample container containing the mixture, and the end of the sample loading/unloading jig was grasped and lifted, and the sample was loaded through the sample loading/unloading port provided on the side of the reduction furnace. The horizontal-hole type sample container was inserted near the top of the sample stage provided in the reduction furnace, and gently placed on the sample stage.

Then, the sample loading/removal jig inserted into the through hole of the horizontal-hole sample container was removed, and only the sample loading/removal jig was removed from the sample loading/removal port. The door at the sample loading/removal port was closed, and heating of the reduction furnace was started with a burner, and the reduction process was carried out on the mixture inside the horizontal-hole sample container placed on the sample stage.

Next, after the reduction process was completed, the door of the sample loading/unloading port installed in the reduction furnace was opened, and the sample loading/unloading jig was inserted close to where the horizontal-hole type sample container was placed. The sample loading/unloading jig was then inserted into the through hole of the horizontal-hole type sample container, and in that state, the end of the sample loading/unloading jig was grasped and lifted up, thereby removing the reduced material contained in the horizontal-hole type sample container from the reduction furnace.

After cooling the extracted reduced material, the nickel metallization rate and nickel content in the metal were measured as shown below.

On the other hand, in the comparative example, a sample container with a handle as shown in the side view of Figure 6 (A) and a ladle as shown in Figure 6 (B) were used, and the mixture sample was placed in the sample container, and the ladle was hooked onto the handle of the sample container to load it into the reduction furnace. After the reduction process was completed, the ladle was similarly hooked onto the handle of the sample container to remove it from the reduction furnace. Note that the door to the sample loading/unloading port was closed during the reduction process.

[evaluation]
After cooling each sample, the nickel metallization rate and the 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 Ni in the mixture ÷ (total amount of Ni in the mixture) × 100 (%) ... [1] Metal nickel content = amount of metalized Ni in the mixture ÷ (total amount of metalized Ni and Fe in the mixture) × 100 (%) ... [2]

The removal of the reduced material from the reduction furnace was also evaluated. In other words, the case where the removal was performed without any problems was rated as "○", and the case where the sample container was tilted or shifted and the removal took more than 30 seconds was rated as "△".

Table 4 below shows the reduction treatment conditions and the calculation results for the ease of removal, nickel metal ratio, and nickel content in metal.

As shown in Table 4, in Examples 1 to 9, the workability of sample removal was excellent, and both the nickel metallization rate and metal content were good. This is thought to be because the mixture was placed in a horizontal-hole sample container and then loaded into and removed from the reduction furnace, allowing for stable and smooth operation.

On the other hand, in Comparative Examples 1 to 3, the stability of the work was reduced, and tilting and shifting occurred, which required more work time, and as a result, the quality of the reduced material obtained was also reduced.

REFERENCE SIGNS LIST 1 reduction furnace 11 furnace body 12 burner 13 sample stage 14 exhaust port 15 sample loading/unloading port 2 horizontal hole type sample container 21-24 side surface 21h, 23h through hole 3 sample loading/unloading jig

Claims (3)

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 reductant, comprising the steps of:
a mixing step of mixing the nickel oxide ore with the carbonaceous reductant;
a reduction step of charging the mixture into a box-shaped reduction furnace and heating the mixture to perform a reduction treatment;
having
In the reduction step, the mixture is placed in a horizontal-hole type sample container having through holes formed on two opposing side surfaces, and the reduction treatment is performed thereon;
In the operation of loading the mixture contained in the side-hole type sample container into the reduction furnace and removing the reduced product obtained by the reduction treatment from the reduction furnace, the side-hole type sample container is carried by inserting a rod-shaped sample loading/removal jig into the through holes on the two side surfaces of the side-hole type sample container, and the side-hole type sample container is loaded into and removed from the reduction furnace through a sample loading/removal port provided on the side surface of the reduction furnace .
A method for smelting nickel oxide ores. The through hole formed in the side surface of the horizontal-hole-type container for specimen is a circular hole,
The sample loading/unloading jig is a round bar having a circular cross section.
2. The method for smelting nickel oxide ore according to claim 1. In the reduction step,
In the reduction furnace, a reduction treatment is performed at a reduction temperature of 1200° C. or more and 1500° C. or less.
3. A method for smelting nickel oxide ore according to claim 1 or 2.

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