JP7533089B2 - 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 this type of smelting method, the processing temperature in the reduction furnace is so high that it exceeds 1000°C, so for example, loading pellets into the reduction furnace or removing them from it is not an easy task. In particular, when sampling or other such work is performed, operations are performed to load or remove pellets from the reduction furnace using a "ladle" made specifically for reduction processing and made from a metal that can withstand relatively high temperatures. However, because the processing temperature is high, the ladle can bend and deform, causing problems such as the ladle getting caught on the furnace wall when removing the pellets, making it difficult to remove them properly.

In addition, when a reduction reaction is carried out in a reduction furnace, if the atmosphere inside the furnace cannot be maintained with precision, it is difficult to stabilize the quality and also to efficiently proceed with the reduction reaction. On the other hand, when a reaction is carried out using a reduction furnace, it is essential to open the reduction furnace to supply raw materials to the high-temperature furnace, remove the reactants from the furnace, and take samples during the reaction. In such cases, the atmosphere outside the furnace, which is close to room temperature and contains oxygen, is connected, even if only temporarily, to the inside of the furnace, which is a high-temperature reducing atmosphere in which oxygen is virtually absent. This makes it unavoidable that unfavorable conditions occur during the smelting process, especially when sampling is carried out to check and control the condition, such as oxygen from outside the furnace entering the furnace and accelerating the oxidation of the metal, or the sudden temperature difference between the inside and outside of the furnace causing cracks in the removed reduced material.

JP 2018-178252 A

The present invention has been proposed in light of the above circumstances, and aims to provide a method for producing ferronickel by reducing a mixture containing nickel oxide ore, which can suppress deterioration in the quality of the resulting reduced product and produce ferronickel through efficient operations.

After extensive research, the inventors discovered that the above-mentioned problems could be solved by performing the reduction process using a reduction furnace connected to a cooling chamber through which a cooling gas flows, 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 of nickel oxide ore, which is a raw material, and a carbonaceous reducing agent, and includes a mixing process for mixing the nickel oxide ore and the carbonaceous reducing agent, and a reduction process for charging the mixture into a reduction furnace and heating the mixture to perform a reduction process, in which a reduction furnace connected to a cooling chamber through which a cooling gas flows is used as the reduction furnace in the reduction process.

(2) The second invention of the present invention is a method for smelting nickel oxide ore according to the first invention, in which the cooling chamber is configured to circulate an inert gas as the cooling gas and to be capable of replacing the gas inside with the inert gas.

(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 furnace is a box furnace.

(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 cooling chamber is connected to the reduction furnace via a partition plate that can be opened and closed from the side of the cooling chamber, and in the reduction furnace, the partition plate constitutes a sample loading/unloading port for loading or unloading the mixture.

(5) The fifth invention of the present invention is a method for smelting nickel oxide ore according to the fourth invention, in which, in the reduction step, the mixture is loaded into the reduction furnace through the cooling chamber, the partition plate is opened from inside the cooling chamber, and the mixture is loaded into a predetermined position in the reduction furnace through the sample loading/unloading opening formed by the partition plate.

(6) The sixth invention of the present invention is the method for smelting nickel oxide ore according to the fifth invention, in which, in the reduction step, after the reduction treatment is completed, the partition plate is opened from inside the cooling chamber, and the reduced material is removed from the reduction furnace through the sample loading/unloading port via the cooling chamber.

(7) The seventh invention of the present invention is a method for smelting nickel oxide ore according to the fifth or sixth invention, in which, in the reduction step, a sample ladle having a handle and a sample placement part connected to the end of the handle is used, and the mixture is placed on the sample placement part and then charged into the reduction furnace via the cooling chamber.

(8) The eighth aspect of the present invention is a method for smelting nickel oxide ore according to any one of the first to seventh aspects, 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.

(9) The ninth aspect of the present invention is a reduction furnace used to produce ferronickel by reducing a mixture of nickel oxide ore, which is a raw material ore, and a carbonaceous reducing agent, the reduction furnace being a box-shaped furnace, with a cooling chamber through which a cooling gas flows connected to a predetermined side of the box, the cooling chamber being connected to the reduction furnace via a partition plate that can be opened and closed from inside the cooling chamber, and the partition plate forming a sample loading and unloading port for loading or unloading the mixture.

According to the present invention, in a smelting method for producing ferronickel by reducing a mixture containing nickel oxide ore, it is possible to suppress deterioration in the quality of the resulting reduced product and produce ferronickel through efficient operations.

FIG. 1 is a process diagram showing the flow of a method for smelting nickel oxide ore. FIG. 2 is a diagram showing an example of the configuration of a reduction furnace. FIG. 2 is a diagram illustrating a reduction furnace when a surface on which a burner is installed is viewed from the front, and is a diagram for explaining a configuration of a cooling chamber connected to the reduction furnace. FIG. 2 is a diagram showing an example of the configuration of a sample ladle.

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.

At this time, the smelting method according to this embodiment is characterized in that a reduction furnace connected to a cooling chamber is used as the reduction furnace in the reduction step. Here, as will be described in detail later, the cooling chamber connected to the reduction furnace is configured with a structure that allows gas replacement with an inert gas inside. Also, for example, the reduction furnace is a box-shaped furnace (box furnace), and the reduction furnace and the cooling chamber are connected via a partition plate that can be opened and closed from inside the cooling chamber.

By carrying out the reduction process using a reduction furnace having such a configuration, it is possible to produce ferronickel through efficient operation while suppressing deterioration in the quality of the ferronickel metal, which is the reduction product obtained by the reduction process.

≪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 treatment 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.

Now, in this embodiment, a reduction furnace to which a cooling chamber through which a cooling gas flows is connected is used as the reduction furnace used in the reduction process.

Figure 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 and in contact with a specific surface of the box (the inner surface of the 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.

Figure 3 is a diagram showing the installation surface of the burner 12 of the reduction furnace 1 as seen from the front, and is a diagram for explaining the configuration of the cooling chamber connected to the reduction furnace 1.

As shown in FIG. 3, the reduction furnace 1 is connected to the cooling chamber 2. The cooling chamber 2 has a box shape like the reduction furnace 1, and is connected to a predetermined surface of the furnace body 11. Here, the predetermined surface of the reduction furnace 1 to which the cooling chamber 2 is connected is the surface with which the sample stage 13 installed inside the furnace body 11 of the reduction furnace 1 comes into contact with the inner surface. In other words, the cooling chamber 2 and the sample stage 13 are arranged in contact with the same surface of the furnace body 11 of the reduction furnace 1.

Cooling gas flows through the cooling chamber 2, which cools the reduced material obtained by the reduction process. As described above, the cooling chamber 2 is connected to the reduction furnace 1, so the reduced material after the reduction process can be cooled without being taken out of the furnace, in other words, without being exposed to the air. This prevents the reduced material from being oxidized by the air, and suppresses deterioration in the quality of the ferronickel metal produced.

More preferably, the cooling gas flowing through the cooling chamber 2 is an inert gas, and the cooling chamber 2 is constructed so that the inside of the cooling chamber 2 can be replaced with an inert gas. By using an inert gas as the cooling gas in this way, the inside of the cooling chamber 2 can be made into an inert atmosphere, and oxidation of the reduced product can be more effectively prevented. The inert gas is not particularly limited, but can be nitrogen, argon, etc., since they are relatively inexpensive and easily available, or carbon dioxide.

The structure of the cooling chamber 2 will be described in more detail. The cooling chamber 2 is provided with a partition plate 21 that can be opened and closed from the cooling chamber 2 side. The cooling chamber 2 and the reduction furnace 1 (furnace body 11) are connected via the partition plate 21. In other words, the cooling chamber 2 and the reduction furnace 1 are separated by the partition plate 21. The partition plate 21 constitutes a so-called openable/closable cover of the sample inlet through which the mixture is loaded from the cooling chamber 2 into the reduction furnace 1, and also constitutes a so-called openable/closable cover of the sample outlet through which the reduced product produced by reduction is removed from the inside of the reduction furnace 1 to the cooling chamber 2.

In this way, the sample inlet and sample outlet are the same thing, configured by the partition plate 21, and will be referred to below as the "sample inlet/outlet."

In the reduction process in the reduction step S3, first, the lid 22 of the cooling chamber 2 is opened, the mixture is placed in the cooling chamber 2, and the lid 22 is closed. In the cooling chamber 2, an inert gas is constantly flowing so that it is filled with inert gas. The lid 22 of the cooling chamber 2 can be made of the same material and structure as the partition plate 21. The lid 22 may also be made of processed bricks, and may further be configured to be plugged with a heat insulating material. When putting the mixture in or taking it out of the cooling chamber 2, the lid 22 must be removed once, and after putting the mixture in or taking it out, the lid 22 must be replaced. This ensures that the inside of the cooling chamber 2 is always filled with inert gas. Below, the removal of the lid 22 is omitted as it is of course done.

Next, when loading the mixture to be treated into the reduction furnace 1, the partition plate 21 is opened from inside the cooling chamber 2 to open the sample loading/unloading port. The mixture is then passed through the cooling chamber 2 and placed on the sample stage 13 installed inside the reduction furnace 1 through the sample loading/unloading port.

After the mixture to be treated is placed in the reduction furnace 1, the partition plate 21 is closed to close the sample loading/unloading port. This creates an airtight space inside the reduction furnace 1, and heating with a burner is started to carry out the reduction process. In this way, since the cooling chamber 2 and the reduction furnace 1 are connected by the openable and closable partition plate 21, each space can be made into an airtight space by the simple operation of opening and closing the partition plate 21, and for example, a drop in temperature inside the reduction furnace 1 and a rise in temperature inside the cooling chamber 2 can be prevented.

After the reduction process is completed, the partition plate 21 is opened from inside the cooling chamber 2 to open the sample loading/unloading port, and the reduced product obtained by the reduction process is removed from the sample loading/unloading port via the cooling chamber 2. Since the reduced product passes through the cooling chamber 2 at this time, it is possible to rapidly and efficiently cool the reduced product that has been kept at a high temperature. In addition, in the cooling chamber 1, it is preferable to circulate an inert gas as the cooling gas, thereby preventing the oxidation of the reduced product, etc.

The partition plate 21 can be made of, for example, a plate-shaped insulating board or bricks. Alternatively, it may be made of insulating wool in the form of a plate.

The mixture to be treated can be loaded into the reduction furnace 1 and the reduced material can be removed from the reduction furnace 1 using a sample ladle.

Figure 4 shows an example of the structure of a sample ladle. As shown in Figure 4, the sample ladle 3 has a handle 31 and a sample placement part 32 connected to the tip of the handle 31. In the sample ladle 3, the handle 31 is a part that an operator holds by hand or machine, and is composed of a rod-shaped body. The sample placement part 32 is connected to the tip of the handle 31, and is a part on whose upper surface (placement surface 32a) the sample, i.e., the mixture to be reduced, is placed. Note that Figure 4 shows an example in which the sample placement part 32 is composed of a rectangular parallelepiped, but this is not limited thereto, and it may be composed of, for example, a container in which the placement surface for the mixture, which is the sample, forms a recess, walls are provided on all four sides, and the top is open.

In the reduction process, the sample mixture is placed on the sample placement portion 32 of the sample ladle 3, and in this state, the handle 31 is grasped by hand or by machine and inserted into the cooling chamber 2. Then, as described above, the partition plate 21 is opened from inside the cooling chamber 2 to open the sample loading/unloading port, and the handle 31 of the sample ladle 3 is pushed in to place the sample placement portion 32 into the reduction furnace 1.

At this time, the sample ladle 3 placed inside the reduction furnace 1 is moved to near the center of the sample stage 13, the mixture placed on the top surface of the sample placement section 32 is transferred to the sample stage 13, the sample ladle 3 is pulled out of the reduction furnace 1, and the reduction process can be started.

Alternatively, the sample ladle 3 placed in the reduction furnace 1 may be moved to near the center of the sample stage 13, and the sample ladle 3 itself may be placed on the sample stage 13, and the reduction process may be started in this state (with the mixture on the sample ladle 3 still placed on it), which is a more preferred embodiment. In other words, during the reduction process, heating is started while the sample ladle 3 is left in the reduction furnace 1.

According to this operating method, the reduction process can be carried out simply by placing the mixture to be treated on the sample ladle 3 and then moving the sample ladle 3 into and out of the reduction furnace 1 via the cooling chamber 2. This prevents erroneous operation, such as the sample mixture falling off the sample stage 13 when transferring it from the sample ladle 3 to the sample stage 13, and prevents problems such as uneven heating by the burner.

When the sample ladle 3 is left inside the reduction furnace 1 in this way, the handle 31 of the sample ladle 3 is located inside the cooling chamber 2. For example, by forming a semicircle at the lower end of the partition plate 21 provided in the cooling chamber 2 so that the handle 31 of the sample ladle 3 passes through, the partition plate 21 can ensure the airtightness of the reduction furnace 1 even when the partition plate 21 is closed with the sample ladle 3 left inside the reduction furnace 1.

By leaving the sample ladle 3 in the reduction furnace 1 and starting the reduction process with the handle 31 positioned inside the cooling chamber 2, it is possible to prevent the sample ladle 3 from being thermally deformed by the heat of the reduction process. The reduction process is carried out under high temperature conditions, for example, at about 1200°C to 1500°C, and the sample ladle 3 may be deformed and bent due to the heat. In this regard, by keeping the handle 31 positioned inside the cooling chamber 2, it is possible to prevent thermal deformation.

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

After the reduction process in the reduction furnace 1 is completed, as described above, the reduced material obtained by the reduction process is removed from the sample loading/unloading port via the cooling chamber 2. At this time, since it passes through the cooling chamber 2, the reduced material that has been kept at a high temperature can be cooled rapidly and efficiently.

The reduced material is cooled in the cooling chamber 2 with the partition plate 21 closed from inside the cooling chamber 2 and the sample loading/unloading port closed. This prevents high-temperature heat from the reduction furnace 1 from entering, allowing for efficient cooling. The reduced material is then cooled in the cooling chamber 2 until its temperature drops to a certain level. There is no particular limit to the cooling time, but it is preferably cooled for 10 minutes or more. By cooling for 10 minutes or more, the temperature of the reduced material can be lowered to 1000°C or less, and even if the reduced material is subsequently removed from the cooling chamber 2, oxidation of the generated metal can be suppressed.

As described above, the reduction furnace 1 is configured to be connected to the cooling chamber 2, so the reduced material obtained by the reduction process can be cooled without being released into the atmosphere. If the reduced material heated to a high temperature is directly released into the atmosphere, the oxidation of the generated metal progresses rapidly, the metal properties deteriorate, and the metal recovery rate drops significantly. In this regard, by performing the reduction process using the reduction furnace 1 connected to the cooling chamber 2, the cooling operation of the high-temperature reduced material can be efficiently performed in the cooling chamber 2, and the oxidation of the metal can be effectively prevented.

In addition, by using an inert gas as the cooling gas flowing through the cooling chamber 2 and replacing the atmospheric gas with the inert gas, oxidation and other problems within the cooling chamber 2 can be effectively prevented.

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 material ore, iron ore, silica sand and limestone as flux components, a binder, and a carbonaceous reducing agent (coal powder, carbon content: 75% by weight, average particle size: about 75 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 required to reduce nickel oxide and iron oxide (Fe ₂ O ₃ ) contained in the nickel oxide ore as raw material 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±0.5 mm. Thereafter, the sample was dried by blowing hot air at 170°C to 250°C onto it before reduction so that the solid content was about 70% by weight and the moisture content was about 30% by weight. The solid content composition (excluding carbon) of the sample after drying is shown in Table 3 below.

(Reduction process)
Next, the sieved sample (mixture sample) was divided into 14 pieces (Examples 1 to 11, Comparative Examples 1 to 3), and each was heated in a reduction furnace (burner furnace) to undergo reduction treatment.

In this embodiment, a reduction furnace connected to a cooling chamber as shown in the schematic diagrams of Figures 2 and 3 was used. Specifically, a box-shaped burner furnace was used as the reduction furnace, and a cooling chamber through which a cooling gas was circulated was connected. The cooling chamber and the reduction furnace were connected via a partition plate made of a plate-shaped insulating board, and the partition plate could be opened and closed from inside the cooling chamber. The reduction furnace was equipped with a burner, and pulverized coal, LPG, heavy oil, and coke were used as fuel.

The sample mixture was charged into the reduction furnace using a sample ladle as shown in the schematic diagram of Figure 4. The sample ladle has a handle and a sample mounting part at the tip of the handle, and ash (mainly _SiO2 with small amounts of oxides such as _Al2O3 and _MgO as other components) was spread on the upper surface of the sample mounting part, and the mixture sample was placed on top of it.

When loading the mixture sample into the reduction furnace, the lid of the cooling chamber was opened and the mixture sample placed on the sample ladle was loaded inside. Next, the partition plate was opened from the cooling chamber side to open the sample loading/unloading port formed by the partition plate, and the mixture sample was loaded into the reduction furnace and placed on the sample stage. The sample was left on the sample stage while still placed on the sample ladle. After that, the partition plate was closed, the reduction furnace was made into an airtight space, and heating with a burner was started to carry out the reduction process.

After the specified reduction time had elapsed, the partition was opened from inside the cooling chamber, and the sample ladle with the mixture (reduced product) placed on it was removed from the reduction furnace. At this time, the reduced product was cooled for a specified time in the cooling chamber without being released into the atmosphere. In the cooling chamber, cooling gas (see Table 4 below) was continuously circulated at a flow rate of 20 L/min, and the mixture was cooled for 15 minutes.

After the cooling process was completed, the reduced material was removed from the cooling chamber and 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 process was carried out using a reduction furnace different from that of the embodiment, i.e., a simple box-type burner furnace without a cooling chamber. After the reduction process was completed, the reduced material obtained by the reduction process was taken out of the reduction furnace into the atmosphere and cooled (natural cooling).

[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 metallization rate = amount of metallized Ni in the mixture ÷ (total amount of Ni in the mixture) × 100 (%) ... [1] Metal nickel content = amount of metallized Ni in the mixture ÷ (total amount of metallized Ni and Fe in the mixture) × 100 (%) ... [2]

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 11, in which reduction treatment was performed using a reduction furnace connected to a cooling chamber, both the nickel metallization rate and the nickel content in the metal were good. This is believed to be because the reduced product obtained by the reduction treatment could be instantly and efficiently cooled in the cooling chamber without being released into the atmosphere, effectively suppressing the oxidation of the generated metal. In addition, treatment using such a reduction furnace could be performed efficiently with simple operations without complex procedures.

On the other hand, in Comparative Examples 1 to 3, in which the reduction process was carried out using a reduction furnace that was not connected to a cooling chamber and the resulting reduced material was taken out into the air and allowed to cool naturally, both the nickel metallization rate and metal content were lower than in the Example.

REFERENCE SIGNS LIST 1 reduction furnace 11 furnace body 12 burner 13 sample stage 14 exhaust port 2 cooling chamber 21 partition plate 22 (cooling chamber) lid 3 sample ladle 31 handle 32 sample placement section

Claims (4)

A method for smelting nickel oxide ore, comprising the steps of: producing ferro-nickel by reducing a mixture of nickel oxide ore as a raw material ore and a carbonaceous reductant, the method comprising the steps of:
a mixing step of mixing the nickel oxide ore with a 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, a reduction furnace having a cooling chamber through which a cooling gas, which is an inert gas , flows and a structure capable of gas replacement with an inert gas is used as the reduction furnace,
the cooling chamber is connected to the reducing furnace via a partition plate that can be opened and closed from the cooling chamber side,
In the reduction furnace, the partition plate constitutes a sample loading/unloading port for loading or unloading the mixture,
In the reduction step,
When the mixture is charged into the reducing furnace, the mixture passes through the cooling chamber, the partition plate is opened from inside the cooling chamber, and the mixture is charged into a predetermined position in the reducing furnace through the sample charging/discharging opening formed by the partition plate;
After the reduction treatment is completed, the partition plate is opened from inside the cooling chamber, and the reduced material is taken out from the inside of the reduction furnace through the sample loading/unloading port via the cooling chamber.
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 . In the reduction step,
using a sample ladle having a handle and a sample placement part connected to the tip of the handle, the mixture is placed on the sample placement part, and the mixture is charged into the reduction furnace through the cooling chamber;
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 .

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