JP7540349B2 - Nickel oxide ore smelting method, reduction furnace - 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. Generally, the ore is first mixed with components other than nickel oxide ore, such as a binder and a reducing agent, to form a mixture, and the mixture is then fed into a lump-making machine after moisture adjustment, 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.

In order to obtain coarse ferronickel, it is important to examine the conditions through experiments. For example, a small amount of pellets are placed in a reduction furnace and reduction treatment tests are conducted to examine various characteristics.

However, even in experimental reduction furnaces, the processing temperature is high, at around 1000°C to 1500°C, and loading and unloading pellets from the furnace is no easy task.

Generally, pellets are loaded into and removed from a reduction furnace using a special ladle made of a metal that can withstand relatively high temperatures. However, the high heat can cause the ladle to bend, which can lead to problems such as the ladle getting caught on the furnace wall, making it difficult to remove the pellets accurately and efficiently. This can affect the quality of the metal obtained, making it impossible to conduct appropriate tests to thoroughly examine the conditions.

As described above, there are many problems remaining with the technology for producing metal by reducing a mixture containing nickel oxide ore, and a particularly important challenge is being able to perform various tests 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 using a reduction furnace with a specific configuration, and loading and unloading the sample mixture from the reduction furnace by pushing or pushing it in and out with a sample push rod, thus completing 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 step of mixing the nickel oxide ore with the carbonaceous reducing agent, and a reduction process step of charging the mixture into a reduction furnace and heating the mixture to perform a reduction process, the reduction furnace being a box furnace, and a sample inlet for charging the mixture as a sample and a sample outlet for removing the reduced product obtained by the reduction process being installed on opposing sides of the box furnace so that they are arranged on a straight line, and the mixture is charged into the reduction furnace by pushing it through the sample inlet using a sample extrusion rod, and the reduced product is removed from the reduction furnace by pushing it out to the sample outlet.

(2) The second invention of the present invention is a method for smelting nickel oxide ore according to the first invention, in which a sample stage for placing the mixture as a sample is provided in the reduction furnace so as to extend from the sample inlet to the sample outlet, and during the reduction treatment, the sample push-out rod is used to push the mixture from the sample inlet onto the sample stage so as to slide it and place it in a predetermined position, and after the reduction treatment is completed, the sample push-out rod is used to push the reduced product onto the sample stage so as to slide it to the sample outlet.

(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 a plate constituting the extrusion surface is connected perpendicularly to the axis to the tip of the sample extrusion rod, and the sample extrusion rod is inserted through the sample inlet and the extrusion surface of the sample extrusion rod is pressed against the mixture.

(4) The fourth invention of the present invention is a method for smelting nickel oxide ore according to any one of the first to third inventions, in which the reduction furnace is a burner furnace whose heating method is a burner.

(5) The fifth invention of the present invention is a method for smelting nickel oxide ore according to any one of the first to fourth inventions, 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.

(6) The sixth aspect of the present invention is a reduction furnace for heating an object to be treated and performing a reduction treatment, the reduction furnace being a box-type furnace, in which a sample inlet for loading the object to be treated and a sample outlet for removing the reduced product obtained by the reduction treatment are provided on opposing sides of the box-type furnace so as to be arranged on a straight line, the object to be treated is pushed into the reduction furnace through the sample inlet by a sample extrusion rod, and the reduced product produced by the reduction treatment is removed from the reduction furnace by being pushed out to the sample outlet.

(7) The seventh aspect of the present invention is the reduction furnace of the sixth aspect, which is provided with a sample stage for placing the object to be treated inside the reduction furnace, extending from the sample inlet to the sample outlet.

According to the present invention, the mixture to be treated can be accurately and efficiently loaded into and removed from the reduction furnace, preventing 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. FIG. 2 is a diagram (side view) showing an example of the configuration of a sample container for containing a mixture that is a sample. FIG. 2 is a diagram showing an example of the internal configuration of a reduction furnace, and is a diagram for explaining an operation of charging a mixture into the reduction furnace during reduction treatment, and an operation of removing a reduced product generated by the reduction treatment from the reduction furnace. FIG. 2 is a diagram showing an example of the configuration of a sample extrusion rod.

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 this embodiment, a box-shaped furnace is used as the reduction furnace for the reduction treatment in the reduction step, and a sample inlet for loading the sample mixture and a sample outlet for removing the reduced product obtained by the reduction treatment are provided on opposing sides of the box-shaped furnace so that they are arranged in a straight line. The method is characterized in that a sample push rod is used to push the mixture through the sample inlet into the reduction furnace, and the resulting reduced product is removed from the reduction furnace by pushing it out through the sample outlet.

By carrying out the reduction treatment in this manner, it is possible to prevent operational problems caused by deformation of the tool, as occurs in conventional operations using a jig such as a ladle, and to efficiently and accurately charge or remove the mixture. This also makes it possible to prevent deterioration in the quality of the ferronickel metal, which is the reduction product obtained by the reduction treatment, and allows for the production of high-quality ferronickel through efficient operations.

In this embodiment, a method is shown in which nickel oxide ore is used as the raw material ore and a mixture with a carbonaceous reducing agent (processing target) is subjected to a reduction process to produce ferronickel, an iron-nickel alloy, but the present invention can be widely applied to methods in which other raw materials are used and the processing target is heated in a reduction furnace for reduction processing.

≪2. About the smelting process≫
As described above, the method for smelting nickel oxide ore involves charging a mixture containing nickel oxide ore as a raw material ore and a carbonaceous reducing agent into a reduction furnace, heating the mixture in the reduction furnace to reduce nickel (nickel oxide) and iron (iron oxide), thereby producing metal of an iron-nickel alloy (ferronickel). Note that 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 heated at a predetermined reduction temperature in a reduction furnace for reduction, and a recovery process S4 in which the metal and slag generated by the reduction process 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 charged, for example, in a stacked manner into a reduction furnace during the reduction treatment in the next reduction step S3. As will be described later, the mixture is contained in a sample container and charged into the reduction furnace.

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. In addition, because these shapes are not complicated, there are almost no defective products and the yield rate of molding is extremely high.

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 S2 to dry the mixture. For example, in the drying process, the mixture may be dried so that the solid content 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 obtained in the mixture forming step S2 is heated to a predetermined reduction temperature in a reduction furnace and reduced. By such reduction treatment, a reduction reaction of the mixture containing nickel oxide ore progresses, and metal and slag are generated as reduction products.

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.

(Configuration of reduction furnace)
In this embodiment, the reduction furnace used is a box-type furnace in which a sample inlet for introducing a mixture, which is a sample (a material to be treated in the reduction treatment), and a sample outlet for removing a reduced product obtained by the reduction treatment are provided on opposing sides of the box-type furnace so as to be arranged on a straight line. Fig. 2 is a schematic diagram showing an example of the configuration of a reduction furnace.

As shown in FIG. 2, the reduction furnace 1 is a box furnace in which the furnace body 11 has a box shape (rectangular parallelepiped shape). The reduction furnace 1 is not particularly limited, but may be a burner furnace equipped with a burner 12 at a predetermined position and performing reduction processing by heating with the burner. 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 may 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 equipped with a sample inlet 13 for loading a sample mixture, and a sample outlet (sample recovery port) 14 for removing the reduced product obtained by reduction treatment in the furnace. The sample inlet 13 and the sample outlet 14 are provided on opposing surfaces of the box-shaped reduction furnace 1 (for example, surfaces 11a and 11b of the furnace wall in FIG. 2), and are arranged on a line connecting each other with a straight line. For example, as shown in FIG. 2, the sample inlet 13 is provided in the center of surface 11a of the furnace wall, and the sample outlet 14 is provided in the center of surface 11b opposite surface 11a. The sample inlet 13 and the sample outlet 14 are at approximately the same height from the bottom of the furnace, and are arranged on a straight line (see also FIG. 3).

The sample inlet 13 and the sample outlet 14 are provided with lids (doors) that can be opened and closed from outside the reduction furnace 1, and the lids can be closed during reduction processing to prevent air and the like from entering the reduction furnace 1. Also, as long as the sample inlet 13 and the sample outlet 14 are arranged on a straight line, they do not have to be a horizontal line. For example, the height of the sample outlet 14 may be lower than the height of the sample inlet 13, and the sample inlet 14 may be arranged on a straight line that slopes from the sample inlet 13 to the sample outlet 14.

The reduction furnace 1 also includes a sample stage 15 arranged inside the box-shaped furnace body 11. The sample stage 15 is a stage on which a mixture, which is a sample, is placed. In the reduction furnace 1, as shown in FIG. 2, the sample stage 15 is arranged to extend from the sample inlet 13 to the sample outlet 14. That is, the sample stage 15 has, for example, a rectangular parallelepiped shape, with one end of the sample inlet 13 in contact with the surface 11a of the furnace wall on which the sample inlet 13 is provided and the other end of the sample stage 15 in contact with the surface 11b of the furnace wall on which the sample outlet 14 is provided, and extends from the sample inlet 13 to the sample outlet 14.

As a result, the mixture can be placed on the sample stage 15 immediately after being loaded into the reduction furnace 1 through the sample loading port 13, and as described in detail below, the mixture can be moved in the direction of the sample removal port 14 by sliding it on the sample stage 15 using the sample push-out rod 30. In addition, when removing the reduced product obtained by the reduction process, the reduced product can be removed from the sample removal port 14 by the simple operation of pushing it out by sliding it on the sample stage 15 using the sample push-out rod 30.

In addition, the reduction furnace 1 is provided with an exhaust port 16, for example on its upper surface (ceiling surface), for exhausting gas from within the furnace.

Although not particularly limited, in the reduction furnace 1, the mixture to be treated in the reduction process may be placed as is on the sample stage 15 and treated, but it is preferable to place the mixture in a sample container and place the sample container on the sample stage 15 to treat it.

Figures 3 (A) and (B) are side views of a sample container for containing a mixture that is a sample (substance to be processed). The sample container 20 is composed of a container body 20a, for example, in which the surface for placing the mixture forms a recess, walls are erected on all four sides, and the top is open, and a handle portion 20b that is provided so as to span the opposing wall surface. The handle portion 20b of the sample container 20 is, for example, a part that is grasped by an operator, and improves the workability of processing tests, etc.

Ash or a carbonaceous reducing agent may be laid on the mounting surface of the container body 20a of the sample container 20. This can prevent the mixture from fusing on the mounting surface during the reduction process.

In this way, preferably, the mixture is contained in the sample container 20, and the sample container 20 containing the mixture is placed on the sample stage 15 in the reduction furnace 1 to perform a reduction process on the mixture. As a result, as will be described in detail later, the sample container 20 can be moved smoothly by operating the sample extrusion rod, making it possible to efficiently load the mixture into the reduction furnace 1 and remove the generated reduced product from the reduction furnace 1.

(Mixture loading/unloading operations)
4 is a diagram for explaining the operation of charging the mixture into the reduction furnace 1 during the reduction treatment, and the operation of removing the reduced product produced by the reduction treatment from the reduction furnace 1. The figure shows the state when the mixture contained in the sample container 20 is charged into the reduction furnace 1.

As described above, the reduction furnace 1, which is a box-shaped furnace, has a sample inlet 13 for inserting the sample mixture and a sample outlet 14 for removing the reduced product obtained by the reduction process, which are provided on opposing surfaces 11a and 11b so that they are arranged in a straight line. In addition, inside the reduction furnace 1, a sample stage 15 for placing the mixture is provided so as to span from the sample inlet 13 to the sample outlet 14.

The mixture is loaded into the reduction furnace 1 and the mixture (reduced material) is removed from the reduction furnace 1 using a sample extrusion rod.

Here, Figures 5 (A) and (B) show an example of the configuration of a sample extrusion rod. The sample extrusion rod 30 has a rod-shaped handle 31 that is the part that the operator holds, and a plate body 32 that is connected to the tip of the handle 31 perpendicular to the axis. The plate body 32 forms the extrusion surface that is pressed against the sample mixture by operating the sample extrusion rod 30. The size of the sample extrusion rod 30 is not particularly limited, and can be set according to the size of the reduction furnace 1, the size of the sample insertion port 13, or the size of the sample container 20 that contains the mixture.

Regarding loading the mixture into the reduction furnace During the reduction process in the reduction furnace 1, when loading the mixture, which is the sample to be treated, into the reduction furnace 1, the sample container 20 containing the mixture is pushed in through the sample loading port 13 using the sample extrusion rod 30.

For example, as shown in the schematic diagram of Figure 4, after the sample container 20 containing the mixture is set in the sample inlet 13, the sample extrusion rod 30 is inserted into the sample inlet 13 from outside the reduction furnace 1, and the plate 32, which is the extrusion surface 32a of the sample extrusion rod 30, is pressed against the sample container 20, thereby loading it into the reduction furnace 1.

As described above, the reduction furnace 1 is provided with a sample stage 15 on which the mixture is placed, spanning from the sample inlet 13 to the sample outlet 14. By pushing the sample container 20 in with the sample push rod 30, the sample container 20 slides from the sample inlet 13 onto the sample stage 15. When the sample container 20 is moved to a predetermined position (mixture installation position) on the sample stage 15, the sample push rod 30 is removed from the sample inlet 13. The reduction process in the reduction furnace 1 then begins.

Removal of the mixture (reduced product) from the reduction furnace Next, when completing the reduction treatment of the mixture and removing the reduced product (the reduced product obtained by the reduction treatment of the mixture) from the reduction furnace 1, the sample extrusion rod 30 is used to push the sample container 20 containing the reduced product out toward the sample removal port 14 to remove it.

For example, as shown in the schematic diagram of FIG. 4, a sample extrusion rod 30 is inserted from the outside of the reduction furnace 1 through the sample insertion port 13, and the plate 32, which is the extrusion surface 32a of the sample extrusion rod 30, is pressed against the sample container 20 containing the generated reduced product, thereby moving the sample extrusion rod 30 from the predetermined position where the reduction process was performed.

The sample stage 15 in the reduction furnace 1 is provided from the sample insertion port 13 to the sample removal port 14, so that the sample container 20 is pushed out by the sample push rod 30, causing it to slide along the sample stage 15 in the direction of the sample removal port 14. When the sample container 20 is then moved to the sample removal port 14 connected to the end of the sample stage 15, the sample container 20 containing the reduced product is collected from the sample removal port 14.

When loading and unloading mixtures into and from a reduction furnace using tools such as ladles, the handle of the ladle becomes heated by the high heat inside the furnace, and when heated to temperatures of, for example, 1200°C or higher, it becomes soft and bent, resulting in deformation. This causes problems, particularly when removing the reduced material, as the deformed ladle gets caught on the inner wall of the furnace, making it difficult to remove. Such problems are more likely to occur the higher the reduction temperature. Furthermore, if such problems cause the reduced material to take a long time to be removed, the metal (ferronickel) contained in the reduced material will oxidize, reducing its quality.

In contrast, according to the method of this embodiment, the reduction furnace 1 of the above-mentioned configuration is used, and the sample extrusion rod 30 is inserted into the furnace only when the mixture is to be charged into the reduction furnace 1 or when the reduced material is to be removed from the reduction furnace 1. The mixture is charged by pushing it in through the sample inlet 13, and the reduced material is removed by pushing it out through the sample outlet 14, making it possible to smoothly charge and remove the mixture. This also makes it possible to perform the operation in a short time, which makes it possible to suppress the oxidation of the metals contained in the reduced material, and effectively prevents deterioration of quality.

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 36.0% when the amount necessary 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±1.0 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 was heated in a reduction furnace (burner furnace) to perform reduction treatment. Pulverized coal, heavy oil, and coke were used as fuel for the burner.

In this embodiment, a box-shaped reduction furnace as shown in the schematic diagrams of Fig. 2 and Fig. 4 was used as the reduction furnace. In the reduction furnace, a sample inlet for charging the mixture to be treated and a sample outlet for taking out the reduced product obtained by the reduction treatment are provided on opposing sides of the box-shaped furnace so as to be arranged in a straight line. In addition, a sample stage is provided inside the reduction furnace, extending from the sample inlet to the sample outlet, on which the mixture is placed and reduced. The mixture to be treated was placed in a sample container (see Fig. 3) and loaded into the reduction furnace in this state, and the reduction treatment was performed. The loading surface of the sample container was covered with ash (mainly SiO ₂ , with small amounts of oxides such as Al ₂ O ₃ and MgO as other components), and the mixture was placed on top of it.

When loading the mixture into the reduction furnace, a sample push rod as shown in the schematic diagram of Figure 5 was used to push the mixture contained in the sample container through the sample inlet of the reduction furnace by sliding it over the sample stage, and the mixture was placed in a specified location on the sample stage. After loading the mixture into the reduction furnace, the reduction furnace was made into an airtight space and heating with a burner was started to carry out the reduction process. The sample inlet and sample outlet were covered to prevent air from entering the reduction furnace.

After the specified reduction time had elapsed, the sample container containing the mixture (reduced material) was removed from the reduction furnace. The reduced material was removed by using the same sample push rod to push it out over the sample stage and into the sample outlet.

After the reduced material was removed from the reduction furnace and cooled, the nickel metallization rate and nickel content in the metal were measured, as shown below.

On the other hand, in the comparative example, the reduction treatment was carried out using a reduction furnace different from that used in the example, i.e., a simple box-type burner furnace that has been conventionally used. When loading the mixture into the reduction furnace, a heat-resistant iron ladle was used to push the mixture into the furnace through a sample loading/unloading port located on the side of the furnace, and the reduction treatment was carried out while the ladle was still inside the reduction furnace. When removing the reduced product obtained by the reduction treatment, the same ladle was used to pull it out. The sample loading/unloading port was covered with insulating wool except when the mixture was being loaded or unloaded.

[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]

In addition, the workability of loading the sample mixture into the reduction furnace and removing the reduced material from the furnace was evaluated. Specifically, the case where loading and removing the sample could be performed without any problems was evaluated as "○", the case where a malfunction occurred in the work due to deformation of the jig or the like, which required more than one minute of work time was evaluated as "△", and the case where the work could not be performed due to the mixture or reduced material getting stuck in the furnace was evaluated as "×".

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

As shown in Table 4, in Examples 1 to 9, the charging and unloading operations could be carried out efficiently without any problems, and both the nickel metallization rate and metal content rate were good. This is thought to be because the charging and unloading of the mixture could be carried out smoothly, accurately, and with high precision, which resulted in the oxidation of the generated metal being effectively suppressed.

On the other hand, in Comparative Examples 1 to 3, where the mixture was charged and removed using a ladle as in the past, problems arose, particularly when removing the reduced product, such as the ladle being significantly bent and deformed by the high heat, and getting caught in the furnace. This caused the work to take a long time, which in turn caused the oxidation of the generated metal to progress, resulting in both a lower nickel metallization rate and metal content rate compared to the Examples (Comparative Example 1). Note that in Comparative Examples 2 and 3, removal at all was not possible.

REFERENCE SIGNS LIST 1 reduction furnace 11 furnace body 12 burner 13 sample inlet 14 sample outlet 15 sample stage 16 exhaust port 20 sample container 20a container body 20b handle 30 sample extrusion rod 31 handle 32 plate 32a extrusion surface

Claims (6)

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 loading the mixture contained in a sample container into a reduction furnace and heating the mixture to perform a reduction treatment;
having
the reduction furnace is a box-type furnace, and a sample inlet for introducing the mixture as a sample and a sample outlet for extracting a reduced product obtained by the reduction treatment are provided on opposing sides of the box-type furnace so as to be arranged on a straight line;
A sample extrusion rod having a plate at its tip that forms an extrusion surface and that is connected perpendicularly to its axis is used, and the plate, which is the extrusion surface of the sample extrusion rod, is pressed against a sample container that contains the mixture from the sample inlet to push the mixture into the reduction furnace, and the plate, which is the extrusion surface of the sample extrusion rod, is pressed against a sample container that contains the reduced product to push the reduced product out of the reduction furnace.
A method for smelting nickel oxide ores. a sample stage for placing the mixture as a sample thereon is provided in the reduction furnace so as to extend from the sample inlet to the sample outlet;
During the reduction treatment, the sample extrusion rod is used to push the mixture through the sample insertion port onto the sample stage in a sliding manner, and the mixture is placed at a predetermined location;
After the reduction treatment is completed, the sample extrusion rod is used to push the reduced material out toward the sample outlet so as to slide the reduced material on the sample stage.
2. The method for smelting nickel oxide ore according to claim 1. The reduction furnace is a burner furnace whose heating method is a burner;
3. A method for smelting nickel oxide ore according to claim 1 or 2 . 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.
A method for smelting nickel oxide ore according to any one of claims 1 to 3 . A reduction furnace used in smelting nickel oxide ore, for heating and reducing a treatment object containing nickel oxide ore, comprising:
It is a box furnace,
a sample inlet for introducing a material to be treated and a sample outlet for extracting a reduced material obtained by the reduction treatment are provided on opposing surfaces of the box furnace so as to be arranged on a straight line;
The object to be treated is pushed into the reduction furnace through the sample inlet by a sample push-out rod, and the reduced product produced in the reduction treatment is pushed out to the sample outlet and removed from the reduction furnace.
Reduction furnace. A sample stage for placing a processing object thereon is provided so as to extend from the sample inlet to the sample outlet.
The reduction furnace according to claim 5 .

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