JP7540348B2 - 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 addition, it is currently becoming difficult to obtain ores with high nickel content and few impurities, and research and development is urgently needed to manufacture high-quality ferronickel to compensate for this. For this reason, it is necessary to efficiently process various ores and accumulate data, and highly accurate testing is required.

Specifically, when a small amount of pellets are loaded into a reduction furnace to cause a reduction reaction, and then removed after the reaction to investigate the condition of the pellets, it is necessary to reliably and quickly handle the high-temperature samples, which reach temperatures of 1000°C to 1500°C. When conducting the test, pellets are inserted into the furnace and removed from the furnace using a jig such as a ladle made of heat-resistant metal. However, conventional ladles have the disadvantage that they are prone to deformation, such as bending when exposed to high temperatures. If a deformed ladle is used, problems occur such as the ladle getting caught on the furnace wall during handling, which results in inaccurate sampling, affecting data accuracy and ultimately affecting actual operation.

As described above, there are still issues to be addressed in the technology of mixing nickel oxide ores, reducing them, and producing 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 using a sample lifting device installed at the top of the reduction furnace to load and unload the sample mixture 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 loaded into the reduction furnace from the top by a sample lifting device and reduced, and the reduced product obtained by the reduction process is removed from the reduction furnace by the sample lifting device.

(2) The second invention of the present invention is a method for smelting nickel oxide ore according to the first invention, in which the sample lifting device is equipped with a lifting chain, and the mixture contained in a sample container is loaded into or removed from the reduction furnace by engaging the sample container with the lifting chain.

(3) The third invention of the present invention is a method for smelting nickel oxide ore, in which the reduction furnace is a box furnace.

(4) The fourth invention of the present invention is a method for smelting nickel oxide ore, 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, 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 and reducing a treatment object, the reduction furnace being a box-type furnace, equipped with a sample lifting device composed of a lifting chain at the top of the furnace, a sample container containing the treatment object being engaged with the lifting chain, and the treatment object being loaded into or removed from the furnace by lowering or raising the lifting chain.

According to the present invention, the materials 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 showing an example of an internal configuration of a reduction furnace as viewed from the side. 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.

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, the smelting method according to this embodiment is characterized in that, during the reduction process in the reduction step, the mixture is loaded into the reduction furnace from the top using a sample lifting device, and after the reduction process, the reduced material obtained by the process is removed from the reduction furnace using the sample lifting device.

As will be described in more detail later, for example, the reduction furnace is a box-shaped furnace (box furnace) with a sample lifting device consisting of a lifting chain installed on the top (ceiling) of the furnace. During reduction processing, a sample container containing the mixture to be processed is attached to the lifting chain, and the mixture is loaded into or removed from the furnace by lowering or raising the lifting chain.

By carrying out the reduction treatment using a reduction furnace with such a configuration, it is possible to prevent poor treatment operation caused by deformation of the jig, which is the case in conventional operations using jigs such as ladles, and it is possible 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 high-quality ferronickel can be produced 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.

Here, in this embodiment, during the reduction process, the mixture is loaded into the reduction furnace from the top using a sample lifting device, and the reduced product obtained by the reduction process is removed from the reduction furnace using the sample lifting device.

(Configuration of reduction furnace)
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 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 may be any of gas fuels such as LPG, liquid fuels such as heavy oil, and solid fuels such as coal and coke, but LPG is preferable because of its excellent combustibility.

The reduction furnace 1 also includes a sample stage 13 that is disposed inside the box-shaped furnace body 11. The sample stage 13 is a stage on which the mixture to be reduced is placed. A sample container containing the mixture is placed on the sample stage 13. The reduction furnace 1 also includes an exhaust port 14, for example on its upper surface (ceiling surface), for exhausting gas from within the furnace.

The reduction furnace 1 also has a sample lifting device 15 at the top of the furnace. The sample lifting device 15 is provided at the top of the furnace so as to be located directly above (vertically at the top) the sample stage on which the mixture (sample) to be reduced is placed. This allows the mixture to be placed on the sample stage 13 by vertically lifting the sample lifting device 15, or the mixture can be lifted up from the sample stage 13 and removed from the furnace.

Figure 3 shows the internal configuration of the reduction furnace 1 as viewed from the side, and is a diagram for explaining the configuration of the sample lifting device 15 in more detail.

As shown in FIG. 3, the sample lifting device 15 provided at the top of the reduction furnace 1 is composed of a lifting chain 51. The configuration of the lifting chain 51 is not particularly limited, and for example, as shown in FIG. 3, it can have a chain 51a and a sprocket 51b. The lifting chain 51 is composed by wrapping one end of the chain 51a around the sprocket 51b, folding it back upward, and then wrapping it around the sprocket 51b and folding it back downward. The other end of the chain 51a folded back downward by the sprocket 51b is connected to the sample container 20 that contains the mixture to be treated. The sprocket 51b is a gear for transmitting the rotation of a rotating shaft (not shown) to the chain 51a.

In addition, the sample lifting device 15 is preferably configured to be surrounded to form a sealed space as shown in FIG. 3. In addition, it is preferable to provide an opening and closing door (not shown) at the connection point between the sample lifting device 15 and the ceiling of the reduction furnace 1, so that the opening and closing door can be opened when the mixture is loaded or removed using the lifting chain 51, and closed during the reduction process after the mixture is loaded. In this way, it is preferable to make the sample lifting device 15 a structure that can form a sealed space, and further provide an opening and closing door between the reduction furnace 1 and the sample lifting device 15 so that the movement of gas between the reduction furnace 1 and the sample lifting device 15 can be blocked during the reduction process. This prevents the inflow of air from outside the reduction furnace 1, and suppresses the oxidation of the metal generated by the reduction process. In addition, the reducing gas generated by the reduction process can be confined in the furnace to maintain a reducing atmosphere, allowing the reduction reaction to proceed more efficiently.

Figures 4 (A) and (B) are side views of a sample container for containing a mixture as a sample. 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 provided to span the opposing wall surface. The handle portion 20b of the sample container 20 is a portion to which the end of the lifting chain 51 of the sample lifting device 15 is engaged and connected, and the mixture contained inside the container body 20a of the sample container 20 is lifted or lowered by the lifting operation of the lifting chain 51.

In addition, 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.

(Operation of loading/unloading mixture using sample lifting device)
More specifically, the following describes the loading of the mixture into the reduction furnace 1 using the sample lifting device 15 and the removal of the mixture (reduced material obtained by the reduction treatment) from the furnace during the reduction treatment in the reduction furnace 1. As described above, when the mixture is subjected to the reduction treatment, the mixture is loaded into the furnace from the top of the reduction furnace 1 using the sample lifting device 15, and after the reduction treatment is completed, the reduced material obtained is removed from the furnace using the sample lifting device 15.

Loading the mixture into the reduction furnace First, the mixture, which is a sample, is placed and accommodated in the container body 20a of the sample container 20. Next, an end of the lifting chain 51 (chain 51a) constituting the sample lifting device 15 installed at the top of the reduction furnace 1 is connected to the handle 20b of the sample container 20 containing the mixture. Then, the sprocket 51b of the lifting chain 51 is rotated to gradually lower the chain 51a, thereby placing the sample container 20 connected to the chain 51a on the sample stage 13 installed inside the reduction furnace 1 below the sample lifting device 15.

After placing the sample container 20 on the sample stage 13, the connection between the lifting chain 51 and the handle portion 20b of the sample container 20 may be released and the lifting chain 51 may be wound up and stored in the sample lifting device 15, or the connection may be maintained, i.e., the lifting chain 10 may be held in the reduction furnace 1 from the sample lifting device 15.

Once the mixture has been placed on the sample stage 13, the temperature inside the reduction furnace 1 is raised to a predetermined reduction temperature and the reduction process begins.

Removal of the mixture (reduced product) from the reduction furnace Next, when the reduction treatment of the mixture is completed and the reduced product (the reduced product obtained by the reduction treatment of the mixture) is to be removed from the reduction furnace 1, an operation is performed to gradually raise the lifting chain 51 connected to the handle 20b of the sample container 20. If the connection between the sample container 20 and the lifting chain 51 has been released during the reduction treatment, the lifting chain 51 is lowered again from the sample lifting device 15 to connect it to the sample container 20, and then an operation is performed to lift up the reduced product.

The sample lifting device 15 is located directly above the sample stage 13, so the reduced material can be easily and accurately removed from the reduction furnace 1 by vertically raising the lifting chain 51.

In this way, by using the sample lifting device 15 to load the sample mixture into the reduction furnace 1 from the top and to remove the mixture (reduced material) after the reduction process, it is possible to prevent operational problems caused by deformation of the tool due to high heat, as occurs in conventional operations using a jig such as a ladle. In addition, because operational problems can be prevented, loading and unloading can be performed in a short time, and oxidation of the metal generated by reduction can be suppressed, preventing deterioration in 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 35.0% when the amount required to reduce nickel oxide and iron oxide (Fe ₂ O ₃ ) contained in the nickel oxide ore as raw ore 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 reduction furnace equipped with a sample lifting device at the top, as shown in the schematic diagrams of Figures 2 and 3, was used. The sample lifting device is composed of a lifting chain as shown in Figure 3, and the mixture to be treated is placed in a sample container (see Figure 4), with one end of the lifting chain connected to the handle of the sample container. The surface of the sample container was covered with ash (mainly _SiO2 , with small amounts of oxides such as _Al2O3 and _MgO as other components), and the mixture was placed on top of it.

When the mixture was loaded into the reduction furnace, the lifting chain was lowered to gradually lower the sample container containing the mixture, and the sample was loaded onto the sample stage installed in the reduction furnace. After the mixture was loaded 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 inside of the sample lifting device was purged with nitrogen to prevent air from entering the reduction furnace and to cool the sample lifting device.

After the specified reduction time had elapsed, the sample container containing the mixture (reduced material) was removed from the reduction furnace. When removing the reduced material, the lifting chain of the sample lifting device was connected to the handle of the sample container, and the lifting chain was raised to gradually raise the sample container and remove it from the reduction furnace.

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 in the example, i.e., a simple box-type burner furnace without a sample lifting device. When loading the mixture into the reduction furnace, a heat-resistant iron ladle was used to push the mixture into the reduction furnace through a sample loading/unloading port located on the side of the reduction furnace. The reduced product obtained by the reduction treatment was removed by pulling it out using the same ladle. The sample loading/unloading port was covered with insulating wool except when the mixture was 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, in which the sample lifting device was used to load the mixture into the reduction furnace and remove the reduced product from the furnace, the loading and unloading operations could be carried out efficiently without any problems, and both the nickel metallization rate and metal content were good results. This is thought to be because the sample lifting device allowed the loading and unloading of the mixture to be carried out smoothly, accurately and precisely, and as a result, oxidation of the generated metals could be 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 stage 14 exhaust port 15 sample lifting device 51 lifting chain 51a chain 51b sprocket 20 sample container 20a container body 20b handle

Claims (5)

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 reduction furnace and heating the mixture to subject it to a reduction treatment;
having
In the reduction step, the mixture is loaded into the reduction furnace from an upper portion thereof by a sample lifting device, and a reduction treatment is performed therein. A reduced product obtained by the reduction treatment is removed from the reduction furnace by the sample lifting device.
The sample lifting device includes a lifting chain,
the mixture contained in a sample container is loaded into or removed from the reducing furnace by engaging the sample container with the lifting chain;
A method for smelting nickel oxide ores. The reduction furnace is a box furnace.
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;
The method for smelting nickel oxide ore according to claim 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 the smelting of nickel oxide ore, for heating and reducing a treatment object containing nickel oxide ore, comprising:
It is a box furnace,
A sample lifting device consisting of a lifting chain is installed at the top of the furnace.
A sample container containing the object to be treated is engaged with the lifting chain, and the object to be treated is loaded into or unloaded from the furnace by lowering or raising the lifting chain.
Reduction furnace.

Images