JP7167565B2 - Method for smelting oxide ore - Google Patents

Description

TECHNICAL FIELD The present invention relates to a smelting method for oxide ore, and for example, to a smelting method for obtaining a reduced product by reducing oxide ore such as nickel oxide ore as a raw material with a carbonaceous reducing agent.

As a smelting method for nickel oxide ore called limonite or saprolite, which is a kind of oxide ore, a pyrometallurgical method that uses a smelting furnace to produce nickel matte, a rotary kiln or a moving hearth furnace that uses iron and nickel A hydrometallurgical method that produces ferronickel, which is an alloy of nickel, and a hydrometallurgical method that produces mixed sulfides (mixed sulfides) in which nickel and cobalt are mixed by acid leaching at high temperature and pressure using an autoclave are known. ing.

Among the various methods described above, when the nickel oxide ore is reduced and smelted using the pyrometallurgical method, the raw material nickel oxide ore is crushed to an appropriate size in order to proceed with the reaction. Agglomeration processing is performed as a pretreatment.

Specifically, when the nickel oxide ore is agglomerated, that is, when powdery or fine-grained ore is agglomerated, the nickel oxide ore and other components such as a binder and a reducing agent such as coke are mixed. After adjusting the moisture content, etc., the mixture is charged into a lump manufacturing machine, for example, a molded product (pellets, briquettes, etc.) having a side or a diameter of about 10 mm or more and 30 mm or less. Hereinafter, simply “pellets” It is common to assume that

Pellets obtained by agglomeration require a certain degree of air permeability in order to "fly off" the contained moisture. Furthermore, in the subsequent reduction treatment, if the reduction does not proceed uniformly within the pellet, the composition of the resulting reduced product becomes non-uniform, causing problems such as dispersion or uneven distribution of the metal. Therefore, it is important to uniformly mix the mixture when producing pellets, and to maintain as uniform a temperature as possible when reducing the obtained pellets.

For example, Patent Literature 1 discloses a method for producing ferronickel that can stably produce ferronickel with a high nickel content at high efficiency and at low cost. Specifically, when a mixture of a raw material containing nickel oxide and iron oxide and a carbonaceous reducing agent is pelletized by a granulator and then heat-reduced in a moving hearth furnace, the residence time of the pellets in the furnace is A method is disclosed for obtaining ferronickel with a high nickel content by adjusting the .

The reduction treatment of the pellets is performed using a reduction furnace or the like. For example, the pellets are charged into a reduction furnace heated to a predetermined reduction temperature and heated for reduction. In the reduction treatment, oxides on the surface of the pellet, on which the reduction reaction easily progresses, are first reduced and metallized to form a shell.

However, for example, when the oxide ore contains oxides (impurities) that are not to be reduced, the reduction of the oxides on the surface of the pellet does not proceed, and the formation of the shell may be hindered. If the oxide is reduced without forming a shell on the pellet surface, the carbonaceous reducing agent and the like contained in the pellet may leak out of the pellet during the heat reduction treatment. As a result, there has been a problem in that the reduction reaction varies throughout the pellet, making it difficult to efficiently produce a high-quality metal.

Japanese Patent Application Laid-Open No. 2004-156140

The present invention is a smelting method for producing metal by reducing a mixture containing oxide ore such as nickel oxide ore, which can increase the grade of the obtained metal and efficiently produce high-quality metal. An object of the present invention is to provide a method for smelting oxide ore.

The present inventors have found that a mixture containing oxide ore is extruded and cut at predetermined intervals to obtain moldings, and by subjecting the moldings to a reduction treatment, a shell can be effectively formed on the surface of the moldings. The present inventors have found that it is possible to solve the above problems, and have completed the present invention.

(1) The first aspect of the present invention includes a mixing step of mixing an oxide ore and a carbonaceous reducing agent to obtain a mixture, an extrusion step of charging the mixture into an extruder and extruding it, and extruding the extruded mixture into a predetermined A method of smelting an oxide ore, comprising a forming step of cutting at intervals to obtain a molded product having a cut surface, and a reducing step of subjecting the obtained molded product to a reduction treatment to obtain a reduced product containing metal and slag. is.

(2) In the second aspect of the present invention, in the first aspect, in the reduction step, the surface of the molded product obtained is brought into contact with a reducing gas to form a shell made of metal on the surface of the molded product. A method for smelting an oxide ore, comprising a first reduction step and a second reduction step for obtaining a reduced product by heating a molding having a shell formed thereon to a predetermined temperature.

(3) In the third aspect of the present invention, in the second aspect, at least part of the atmosphere gas after the reduction treatment in the second reduction step is supplied to the treatment space in the first reduction step, and the molded product is It is a method of smelting oxide ore used as the reducing gas to be brought into contact.

(4) In the fourth aspect of the present invention, in the second or third aspect, in the first reduction step, the molded product is maintained at a temperature of 900 ° C. or more and less than 1200 ° C., and in the second reduction step, the A method for smelting an oxide ore in which a molding is maintained at a temperature of 1200°C or higher and 1450°C or lower.

(5) A fifth aspect of the present invention is the method for smelting an oxide ore according to any one of the first to fourth aspects, wherein the oxide ore is a nickel oxide ore.

According to the method for smelting oxide ore according to the present invention, high-quality metal can be efficiently produced.

BRIEF DESCRIPTION OF THE DRAWINGS It is process drawing which shows an example of the flow of the smelting method of a nickel oxide ore.

Specific embodiments of the present invention will be described in detail below. In addition, the present invention is not limited to the following embodiments, and various modifications are possible without changing the gist of the present invention. Further, in this specification, the notation "X to Y" (X and Y are arbitrary numerical values) means "X or more and Y or less".

≪1. Outline of smelting method for oxide ore≫
In the method for smelting oxide ore according to the present embodiment, oxide ore (oxide), which is a raw material ore, is mixed with a carbonaceous reducing agent, and the mixture (pellets) is placed in a smelting furnace (reducing furnace). Metal and slag are generated by performing a reduction treatment.

For example, as the oxide ore, nickel oxide ore containing nickel oxide, iron oxide, etc. is used as a raw material, the nickel oxide ore and a carbonaceous reducing agent are mixed to form a molded product, and nickel contained in the molded product is removed. A method of producing ferronickel, which is an alloy of iron and nickel, by preferential reduction and partial reduction of iron.

In the method for smelting oxide ore according to the present embodiment, a mixture containing oxide ore is extruded and cut at predetermined intervals to obtain moldings having cut surfaces, and the moldings are subjected to a reduction treatment. is characterized by

According to such a method, by subjecting the molding having the cut surface to the reduction treatment, the reduction reaction is facilitated to progress at and near the cut surface, and the metal shell is formed satisfactorily. Also, starting from the metal shell formed on the cut surface, the metal shell is formed on surfaces other than the cut surface. By forming a metal shell on the surface of the molded article in this way, the carbonaceous reducing agent contained in the molded article is suppressed from leaking to the outside during the heat reduction treatment, and the reduction inside the molded article is suppressed. It is possible to make the reaction uniform and improve the quality of the metal obtained.

≪2. Smelting method for producing ferronickel using nickel oxide ore>>
In the following, nickel (nickel oxide) and iron (iron oxide) contained in nickel oxide ore, which is the raw material ore, are reduced to produce iron-nickel alloy metals, and then the metals are separated into ferromagnetic A smelting method for producing nickel will be described as an example.

Specifically, as shown in FIG. 1, the nickel oxide ore smelting method according to the present embodiment includes a mixing step S1 in which a nickel oxide ore and a carbonaceous reducing agent are mixed to obtain a mixture; Extrusion step S2 of charging the machine and extruding the mixture, molding step S3 of cutting the extruded mixture at predetermined intervals to obtain a molded product having a cut surface, drying step S4 of drying the molded product, and molding A heat treatment step S5 of heating the object to a predetermined temperature, a reduction step S6 of subjecting the molding to a reduction treatment to obtain a reduced product containing metal and slag, and a separation step S7 of separating the metal and slag from the reduced product. ,including.

<2-1. Mixing process>
The mixing step S1 is a step of mixing a nickel oxide ore and a carbonaceous reducing agent to obtain a mixture. Specifically, in the mixing step S1, a carbonaceous reducing agent is added to and mixed with nickel oxide ore, which is a raw material ore, and optional additives such as iron ore, flux components, binders, etc., such as grains Powder having a diameter of about 0.2 mm or more and 0.8 mm or less is added and mixed to obtain a mixture.

The nickel oxide ore, which is the raw material ore, is not particularly limited, but limonite ore, saprolite ore, and the like can be used. The nickel oxide ore contains at least nickel oxide (NiO) and iron oxide (Fe ₂ O ₃ ).

Examples of the carbonaceous reducing agent include, but are not particularly limited to, coal powder, coke powder, and the like. It is preferable that the carbonaceous reducing agent has the same particle size and particle size distribution as the nickel oxide ore, which is the raw material ore, because it is easily mixed uniformly and the reduction reaction proceeds uniformly.

The content of the carbonaceous reducing agent (the content of the carbonaceous reducing agent contained in the mixture) includes the chemical equivalent required to reduce the total amount of nickel oxide constituting the nickel oxide ore to nickel metal, and iron oxide ( 50.0% by mass when the total value of both chemical equivalents (also referred to as “total chemical equivalents” for convenience) is 100% by mass The following ratio is preferable, and the ratio of 40.0% by mass or less is more preferable. The amount of iron to be reduced can be suppressed, the nickel grade can be improved, and high-quality ferronickel can be produced.

The amount of the carbonaceous reducing agent mixed is preferably 10.0% by mass or more, and more preferably 15.0% by mass or more, when the total chemical equivalent is 100% by mass. more preferred. Nickel reduction can be efficiently advanced, and productivity is improved.

As the iron ore, which is an optional additive, for example, iron ore having an iron grade of about 50.0% by mass or more, hematite obtained by hydrometallurgy of nickel oxide ore, and the like can be used.

Examples of flux components include calcium oxide, calcium hydroxide, calcium carbonate, and silicon dioxide. Examples of binders include bentonite, polysaccharides, resins, water glass, and dehydrated cakes.

Table 1 below shows an example of the composition (% by mass) of some of the raw material powders mixed in the mixing step S1, but the composition of the raw material powder is not limited to this.

Moreover, you may knead with respect to the obtained mixture. By kneading the mixture containing the raw material powder, it is possible to apply pressure (shear force) to the mixture during the kneading, deagglomerate the carbonaceous reducing agent, raw material powder, etc., and mix the mixture more uniformly. state. In addition, kneading can reduce voids formed between particles of the mixture.

Kneading can be performed using a batch type kneader such as Brabender, Banbury mixer, Henschel mixer, helical rotor, roll, single-screw kneader, twin-screw kneader, or the like.

<2-2. Extrusion process>
The extrusion step S2 is a step of charging the mixture into an extruder and extruding the mixture. Specifically, the mixture containing the nickel oxide ore and the carbonaceous reducing agent obtained in the mixing step S1 is charged into an extruder to extrude the mixture. As a result, pressure (shearing force) is applied to the mixture, and the aggregation of the carbonaceous reducing agent, the raw material powder, etc. is released, and the mixture can be mixed more uniformly. Additionally, voids within the mixture can be reduced. For these reasons, the reduction reaction of the molded product is more likely to occur uniformly in the reduction step, which will be described later, and the quality of the obtained metal can be improved, making it possible to manufacture high-quality metal.

The extruder that can be used in the extrusion step S2 is preferably one capable of kneading and molding the mixture at high pressure and high shear force, and examples thereof include a single-screw extruder and a twin-screw extruder. In particular, it is preferable to have a twin-screw extruder. By kneading the mixture under high pressure and high shear, the agglomeration of the mixture of the raw material powders can be released, the kneading can be effectively performed, and the strength of the molded product obtained can be increased. Further, by using a machine equipped with a twin-screw extruder, it is possible to continuously obtain molded products while maintaining high productivity.

<2-3. Molding process>
The molding step S3 is a step of cutting the extruded mixture at predetermined intervals to obtain moldings having cut surfaces.

Here, in the reduction step S6, which will be described later, the molding is subjected to a reduction treatment, so that the reduction reaction first progresses from the surface of the molding to form a shell. However, if the shell is not properly formed, the carbonaceous reducing agent inside may leak out.

Therefore, a molded article having a cut surface is used as the molded article to be subjected to the reduction step S6, which will be described later. By subjecting the molding having the cut surface to the reduction treatment, the reduction reaction proceeds more easily at and near the cut surface, and the metal shell is formed satisfactorily. Moreover, the metal shell is formed on the surface other than the cut surface with the metal shell as a starting point. In this way, the molded product having the cut surface is subjected to the reduction treatment, and the metal shell is favorably formed on the surface of the molded product. can be suppressed from leaking to the outside.

A cutting machine can be used to cut the mixture. The cutting treatment of the mixture is preferably carried out in a continuous operation subsequent to the extrusion treatment in the extrusion step S2. Specifically, an extruder provided with a cutter at the outlet is used, the mixture is fed into the extruder, and the extruded mixture is cut by the cutter at the outlet. In this way, by manufacturing moldings in a continuous process, it is possible to increase productivity and reduce variations in quality between moldings.

The cutting interval of the extruded mixture may be appropriately set according to the desired size of the molding. The shape of the molded article (molded article having a cut surface) is not particularly limited, but may be, for example, a plate-like shape or a disk-like shape.

Also, the ratio of the area of the cut surface to the surface area of the molded product is not particularly limited. is more preferably 0.3 or more. By preparing a molded article having a cut surface such that the ratio of cut surface area/surface area of molded article is 0.1 or more, reduction reactivity can be enhanced over the entire surface of the molded article. A metal shell can be uniformly formed by this. In addition, as an upper limit, it is preferable to set it as about 0.9 or less. By setting the ratio of the area of the cut surface to the surface area of the molded article within the above range, it is possible to mold into a shape that is easy to charge into the reducing furnace, and it is further preferable in that the handling of the molded article becomes relatively easy. .

<2-4. Drying process>
The drying step S4 is a step of drying the molding obtained in the molding step S3. Here, the molded article may contain an excessive amount of moisture, for example, about 50% by mass. Therefore, if the temperature of a molded product containing excessive moisture is rapidly raised to the reducing temperature, the moisture will evaporate all at once, and the molded product will swell and break.

Therefore, the obtained molded product is subjected to a drying treatment, for example, so that the solid content of the molded product is about 70% by mass and the moisture content is about 30% by mass, so that the reduction heating in the next reduction step is performed. The treatment can prevent the molding from collapsing. In addition, moldings are often in a sticky state due to excessive moisture, and can be easily handled by applying a drying treatment.

Specifically, the drying process for the molded article in the drying step S4 is not particularly limited, but for example, the molded article is dried by blowing hot air at 300° C. or higher and 400° C. or lower. The temperature of the molded article during this drying treatment is preferably less than 100° C. because the molded article is less likely to be destroyed.

The drying process in the drying step S4 can be omitted if the material is in a manner that does not cause breakage during handling such as loading into the reduction furnace or during the reduction heat treatment.

Table 2 below shows an example of the solid content composition (parts by mass) of the molded product after drying. In addition, the composition of the molding is not limited to this.

<2-5. Heat treatment process>
A heat treatment step S5 may be provided for heating the molding obtained in the drying step S4 to a predetermined temperature. In the present embodiment, the inclusion of the heat treatment step S5 is not an essential aspect, but prior to the reduction treatment in the reduction step S6 described later, the molded product is previously subjected to heat treatment (preliminary heat treatment). As a result, rapid thermal expansion of components such as nickel oxide ore and carbonaceous reducing agent contained in the molding can be suppressed in reduction treatment under high-temperature conditions, and bursting of the molding can be suppressed more effectively. can.

Specifically, heat treatment is performed to heat the molding to a temperature of 350° C. or higher and 600° C. or lower. Moreover, it is preferably heated to a temperature of 400° C. or higher and 550° C. or lower.

The heat treatment time is not particularly limited, and may be appropriately adjusted according to the size of the molded product. The processing time can be set to about 30 minutes or less.

<2-6. Reduction process>
The reduction step S6 is a step in which a molding having a cut surface is charged into a reduction furnace and heated at a predetermined reduction temperature to perform a reduction treatment. Due to the reduction treatment in the reduction step S6, the smelting reaction (reduction reaction) proceeds, and in the molding, ferronickel metal (hereinafter simply referred to as "metal") and ferronickel slag (hereinafter simply referred to as "slag") ) and generate separately.

[About reduction treatment]
In the reduction treatment, the nickel oxide contained in the nickel oxide ore, which is the raw material ore, is reduced as completely and preferentially as possible, while the iron oxide contained in the nickel oxide ore is only partially reduced to obtain the desired product. A so-called partial reduction is performed to obtain ferronickel with a high nickel grade of .

In addition, the slag in the molding melts and becomes a liquid phase, but the metal and slag that have already been separated and formed by reduction do not mix, and the metal solid phase and the slag solid phase do not mix by subsequent cooling. It becomes a mixture mixed as a separate phase. The volume of this mixture has shrunk to about 50% or more and 60% or less of the volume of the charged mixture.

Specifically, in the reduction treatment, the molded article is placed in a reducing furnace and then heated to a reduction temperature of about 1200° C. or higher and 1450° C. or lower to cause a reduction reaction.

In this reduction treatment, carbon monoxide (reducing gas) derived from the carbonaceous reducing agent contained in the molding is generated, and the inside of the reduction furnace is made into a reducing atmosphere. The contact between the molding and the reducing gas first promotes the reduction reaction on the surface of the molding. Thereby, a metal shell is formed on the surface of the molding.

As for the reducing gas, as described above, carbon monoxide derived from the carbonaceous reducing agent is generated in the reducing furnace. Therefore, it is not necessary to supply the reducing gas separately from the outside, but from the viewpoint of making the reduction reaction on the surface of the molding proceed more efficiently, the reducing gas may be supplied separately. The reducing gas is not particularly limited as long as it is a gas capable of reducing an oxide to a metal, and examples thereof include hydrogen gas (H ₂ ), carbon monoxide (CO), and hydrogen sulfide (H ₂ S). , sulfur dioxide (SO ₂ ), nitrous oxide (N ₂ O), and the like. In addition, an oxidizing gas such as oxygen may be contained as long as it does not inhibit the formation of a metal shell on the surface of the molding.

In this way, when the reduction reaction proceeds on the surface of the molding and a metal shell is formed on the surface, the reduction reaction proceeds inside the molding to generate metal.

The reducing furnace is not particularly limited, but even if a single furnace is used, a furnace such as a moving hearth furnace that can rotate and move the hearth to continuously perform treatments at different treatment temperatures is used. may Among them, by using a moving hearth furnace as the reducing furnace, the reduction reaction can be progressed continuously and the reaction can be completed in one facility. In addition, if separate furnaces are used for each process, the temperature may drop and heat loss may occur when moving between furnaces. and may not be able to react immediately when the furnace is recharged. In this regard, by using a moving hearth furnace to perform each process in one facility, heat loss can be reduced and the atmosphere inside the furnace can be controlled accurately, so the reaction can proceed more effectively. can be done.

The moving hearth furnace is not particularly limited, and for example, a circular rotary hearth furnace divided into a plurality of processing areas can be used. In a rotary hearth furnace, each process is performed in each zone while rotating in a predetermined direction. In this rotary hearth furnace, by controlling the time (moving time, rotation time) when passing through each region, the processing temperature in each region can be adjusted, and the rotary hearth furnace rotates once. The mixture is smelted every time. A roller hearth kiln or the like may be used as the moving hearth furnace.

In the reduction step S6, when the molding is charged into the reducing furnace, a reducing agent (hereinafter also referred to as a “hearth reducing agent”) is spread over the hearth of the reducing furnace in advance, and the spread hearth is reduced. A molding may be placed on the agent. A bedding material containing an oxide as a main component may be laid on the hearth and the molding may be placed thereon.

[Regarding reduction treatment target (molding with cut surface)]
Now, in the nickel oxide ore smelting method according to the present embodiment, a molding having a cut surface is obtained in the above-described molding step S4. Then, in the reduction step S6, the reduction treatment is performed on the molding having the cut surface as the object to be treated.

By subjecting the molding having such a cut surface to a reduction treatment, a metal shell can be formed satisfactorily at or near the cut surface. In addition, starting from the metal shell formed on the cut surface, a metal shell is formed on the surface of the molded product other than the cut surface, and the metal shell is formed on the entire surface of the molded product. This is because the cut surface formed on the molding is relatively rough compared to the other surfaces, and the contact area with the atmospheric gas (reducing gas) containing carbon monoxide is large. , the reduction reaction is likely to proceed at the cut surface.

By effectively forming a metal shell on the surface of the molding in this way, leakage of the carbonaceous reducing agent and the like contained in the molding during the heat reduction treatment to the outside can be effectively suppressed. As a result, it is possible to uniformly cause a reduction reaction in the molding, and to improve the grade of the obtained metal.

[Other Embodiments of Reduction Treatment]
Here, as the reduction step S6, the first reduction step and the second reduction step may be separately processed. Specifically, the reduction step S6 includes a first reduction step of heating at a predetermined temperature to form a metal shell on the surface of the molding having the cut surface, and a reduction of the molding having the metal shell formed on the surface. and a second reduction step of obtaining a reduced product by heating to a temperature higher than the treatment temperature in the first step. According to such an embodiment, the metal shell can be more reliably formed on the surface of the molding, and leakage of the carbonaceous reducing agent contained in the molding to the outside can be more effectively suppressed. , can produce high-quality metal. Each step will be described in more detail below. For convenience of explanation, the first reduction step is referred to as "S61", and the second reduction step is referred to as "S62".

(Reduction first step)
In the first reduction step S61, a metal shell is formed on the surface of the molded article having the cut surface by contacting the molded article with a reducing gas. This forms a metal shell on the surface, including the cut surface, in contact with the reducing gas. In particular, the cut surface has high reactivity with the reducing gas, and a uniform metal shell can be formed on the surface of the molding starting from the metal shell formed on the cut surface.

In the first reduction step S61, it is preferable to efficiently form a metal shell on the surface of the molded article without reacting the carbonaceous reducing agent in the molded article. For this purpose, it is preferable to keep the molded product below the reaction temperature at which the carbonaceous reducing agent reacts with the metal oxide. Moreover, in the first reduction step S61, it is preferable to keep the molding at a temperature of 900° C. or higher. By maintaining the molded product at a temperature of 900° C. or more and less than 1200° C. in this way, the reduction reaction inside the molded product can be suppressed while reducing the surface of the molded product to metal and effectively forming a metal shell. can be done.

As the reducing gas, a gas containing carbon monoxide (CO) or the like can be used as described above. Here, in the second reduction step S62, which will be described later, carbon monoxide (CO) derived from the carbonaceous reducing agent is generated by subjecting the molding to a reduction treatment. Therefore, at least part of the atmosphere gas after the reduction treatment in the second reduction step S62 may be supplied to the treatment space in the first reduction step S61 and used as the reducing gas. In this case, since the atmosphere gas after the reduction treatment is usually at a high temperature (for example, about 1200° C. to 1450° C.), the temperature of the gas is 1200° C. when the gas is supplied to the treatment space in the first reduction step S61. Adjustments may be made by standing to cool, etc., so as to achieve the following.

(Second reduction step)
The second reduction step S62 is a step of obtaining a reduced product by heating the molding having the metal shell formed on its surface to a predetermined temperature. Specifically, the molding having the shell formed thereon is subjected to heat reduction treatment in a reduction furnace heated to a temperature (reduction temperature) higher than the treatment temperature in the first reduction step S61. As a result, the carbonaceous reducing agent in the compact is reacted to reduce the oxide in the compact to obtain a reduced product containing metal and slag.

Here, as described above, the molding to be subjected to the heat reduction treatment has undergone the treatment in the first reduction step S61, and since a metal shell is formed on the surface thereof, the carbonaceous reducing agent leaks to the outside. is suppressed, it is possible to cause an appropriate reduction reaction based on the carbonaceous reducing agent, and it is possible to efficiently produce high-quality metal.

In order to react the carbonaceous reducing agent in the molded article to reduce the oxide, it is preferable to heat the molded article to a temperature higher than the reaction temperature at which the carbonaceous reducing agent reacts with the oxide. It is preferable to keep the temperature at 1200° C. or higher. The upper limit of the reduction temperature is preferably 1450° C. or less. As a result, the oxide can be subjected to the reduction treatment with high accuracy.

<2-7. Separation process>
The separation step S7 is a step of separating metal and slag from the reduced product obtained from the reduction step S6. Specifically, the metal phase is separated and recovered from the mixture (mixture) containing the metal phase and the slag phase obtained by the reduction heat treatment of the mixture filled in the container.

Methods for separating the metal phase and the slag phase from the mixture of the metal phase and the slag phase obtained as a solid include, for example, in addition to removing unnecessary substances by sieving, separation by specific gravity, separation by magnetic force, etc. method can be used.

In addition, the obtained metal phase and slag phase can be easily separated due to their poor wettability. The metal phase and the slag phase can be easily separated from the inclusions by dropping them with a force or applying an impact such as giving a predetermined vibration during sieving.

By separating the metal phase and the slag phase in this way, the metal is recovered.

In the nickel oxide ore smelting method according to the present embodiment, a metal shell is formed on the surface of the molding to suppress the leakage of the carbonaceous reducing agent contained in the molding to the outside, so that the entire molding can be Since the reduction treatment can be performed uniformly, the quality of the obtained metal can be improved, and a high-quality metal can be manufactured.

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples and comparative examples, but the present invention is not limited to the following examples.

<Example 1, Comparative Example 1>
Nickel oxide ore as a raw material ore, iron ore, silica sand and limestone as flux components, a binder, and a carbonaceous reducing agent (coal powder, carbon content: 85% by mass, average particle size: about 200 μm) are mixed in appropriate amounts. of water was added and mixed using a mixer to obtain a mixture. The amount of the carbonaceous reducing agent (coal powder) is 100% by mass, which is the amount necessary to reduce nickel oxide and iron oxide (Fe ₂ O ₃ ) contained in the nickel oxide ore, which is the raw material ore, in just the right amount. was added in an amount of 24.0% by mass according to the samples (mixtures) of Examples 1-6 and Comparative Examples 1-3.

Next, the obtained samples (mixtures) of Examples 1 to 6 were continuously charged into a twin-screw kneading extruder (model name: HYPERKTX, manufactured by Kobe Steel, Ltd.) and extruded. Then, the extruded mixture was cut by a cutter attached to the tip of the extrusion port of the twin-screw kneading extruder to obtain a molding having a cut surface.

On the other hand, for the sample of Comparative Example 1, the mixture extruded by the twin-screw kneading extruder was filled into a container as it was extruded without being cut by a cutting machine to produce a sample (molded product). did. Also, for the sample of Comparative Example 2, the sample (mixture) was cut out by a cutter and not extruded by a twin-screw kneading extruder, but a commercially available briquette machine was used to produce a briquette (molded product). Further, for the sample of Comparative Example 3, the sample (mixture) was cut out with a cutter, granulated with a pan-type granulator without being extruded with a twin-screw kneading extruder, and then φ15±1. It was classified to a size of 5 mm.

Subsequently, the samples (molded products) of Examples 1 to 6 and Comparative Examples 1 to 3 were subjected to drying treatment. Table 3 below shows the solid content composition (excluding carbon) of the molded product after drying.

Next, the dried moldings were put into a reducing furnace in a nitrogen atmosphere containing no oxygen. The hearth of the reducing furnace was previously covered with a hearth protective agent (mainly composed of SiO ₂ and containing a small amount of oxides such as Al ₂ O ₃ and MgO as other components), and a molding (sample ) was placed. The temperature condition during charging was 500±20°C.

Then, the temperature of the reduction furnace is raised until the temperature (reduction temperature) of the part where the temperature is the highest on the surface of the molding charged into the furnace reaches 1400° C., and the reduction heat treatment is applied to the molding. did. The treatment time for the reduction heat treatment was 15 minutes. After the reduction treatment, the sample was quickly cooled to room temperature in a nitrogen atmosphere and taken out into the atmosphere.

For each sample after the reduction heat treatment, the nickel metallization ratio and the nickel content in the metal were analyzed and calculated using an ICP emission spectrometer (SHIMAZU S-8100 type).

The Ni metallization rate and the Ni content rate in the metal were calculated by the following formulas 1 and 2.
Ni metallization ratio = mass of Ni in metal ÷ (mass of all Ni in reduced product) × 100 (%) (1) formula Ni content in metal = mass of Ni in metal ÷ (metal Total mass of Ni and Fe in) × 100 (%) (2) formula

Table 4 below shows the Ni metallization rate and the Ni content in the metal for each sample.

As can be seen from the results in Table 4, in Examples 1 to 6 in which a mixture containing oxide ore was extruded to obtain a molded product having a cut surface, and the molded product was subjected to reduction treatment, compared to Comparative Examples 1 to 3, As a result, both the Ni metallization rate and the Ni content in the metal increased. This is because by subjecting a molding having a cut surface to reduction treatment, a metal shell can be formed satisfactorily on the surface of the molding. This is probably because the reduction reaction was able to proceed appropriately by suppressing leakage to the outside.

Claims (2)

a mixing step of mixing nickel oxide ore and a carbonaceous reducing agent to obtain a mixture;
an extrusion step of charging the mixture into an extruder and extruding it;
a molding step of cutting the extruded mixture at predetermined intervals to obtain a molding having a cut surface;
a reduction step of subjecting the molded product obtained to a reduction treatment to obtain a reduced product containing metal and slag;
including
In the reduction step,
The obtained molding is charged into the first treatment space, the molding is maintained at a temperature of 900° C. or more and less than 1200° C., and the surface of the molding is brought into contact with a reducing gas to obtain the molding. A reduction first step of forming a shell made of metal on the surface of
The molded product having the shell formed thereon is charged into a second processing space different from the first processing space, and the molded product is maintained at a temperature of 1200° C. or higher and 1450° C. or lower to obtain a reduced product. a second step;
including
A method for smelting nickel oxide ore. At least a part of the atmosphere gas in the second processing space after the reduction treatment in the second reduction step is supplied to the first processing space in the first reduction step, and is used as the reducing gas to be brought into contact with the molded article. The method for smelting nickel oxide ore according to claim 1 .

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