JP2020037727A - Smelting method for ore oxide - Google Patents

Abstract

To provide a smelting method for an ore oxide, by which high-quality metal can be efficiently produced by improving the quality of a metal in a smelting method of reducing a mixture containing ore oxide such as nickel ore oxide.SOLUTION: The smelting method for ore oxide includes a mixing step of mixing an ore oxide and a carbonaceous reducing agent to obtain a mixture, an extruding step of charging the mixture into an extruder and extruding the mixture, a molding step of cutting the extruded mixture at a predetermined interval and obtaining a molded product having a cut surface, and a reducing step of obtaining a reduced product containing a metal and slag by subjecting the obtained molded product to a reduction treatment.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for smelting an oxide ore, for example, a method for smelting an oxide ore such as a nickel oxide ore as a raw material with a carbonaceous reducing agent to obtain a reduced product.

  As a method for smelting nickel oxide ore called limonite or saprolite, which is a kind of oxide ore, a dry smelting method that uses a smelting furnace to produce nickel matte, and iron and nickel using a rotary kiln or a moving hearth furnace There are known a dry smelting method for producing ferronickel, which is an alloy of the present invention, and a wet smelting method for producing a mixed sulfide (mixed sulfide) containing nickel and cobalt at high temperature and pressure using an autoclave. ing.

  Among the various methods described above, particularly when reducing and smelting nickel oxide ore using a dry smelting method, the nickel oxide ore as a raw material is crushed to an appropriate size in order to advance the reaction. Agglomeration processing is performed as preprocessing.

  Specifically, when the nickel oxide ore is agglomerated, that is, when the powdered or fine ore is agglomerated, the nickel oxide ore is mixed with other components, for example, a reducing agent such as a binder or coke. The mixture is then adjusted for water content, and then charged into a lump manufacturing machine, for example, a molded product (pellet, briquette, or the like having a side or diameter of about 10 mm or more and 30 mm or less; hereinafter, simply referred to as “pellet”. It is common to say).

  The pellets obtained by agglomeration need to have a certain degree of air permeability in order to "blow off" the contained water. Further, if the reduction does not proceed uniformly in the pellets in the subsequent reduction treatment, the composition of the obtained reduced product becomes non-uniform, which causes inconveniences such as dispersion or uneven distribution of the metal. Therefore, it is important to uniformly mix the mixture when preparing pellets and to maintain the temperature as uniform as possible when reducing the obtained pellets.

  For example, Patent Literature 1 discloses a method for producing ferronickel that can stably produce ferronickel having a high nickel content at high efficiency and at low cost. Specifically, upon heating and reducing pellets obtained by pelletizing a mixture comprising a raw material containing nickel oxide and iron oxide and a carbonaceous reducing agent in a moving hearth furnace, the residence time of the pellets in the furnace A method for obtaining ferronickel with a high nickel content by adjusting the temperature of the ferro-nickel is disclosed.

  Now, the reduction treatment of the pellets is performed by using a reduction furnace or the like. For example, the pellets are charged into a reduction furnace heated to a predetermined reduction temperature and subjected to reduction heating. In the reduction treatment, first, the oxide on the pellet surface where the reduction reaction easily proceeds is reduced and metallized to form a shell.

  However, for example, when the oxide ore that is not the object of reduction is contained in the oxide ore, the reduction of the oxide on the pellet surface does not proceed, and the formation of the shell may be hindered. If the oxide is reduced in a state where no shell is formed on the surface of the pellet, the carbonaceous reducing agent and the like contained in the pellet may leak out of the pellet during the heat reduction treatment. For this reason, there has been a problem in that the reduction reaction varies in the entire pellet, and it is difficult to efficiently produce high-quality metal.

JP 2004-156140 A

  The present invention provides a smelting method for producing a metal by reducing a mixture containing an oxide ore such as a nickel oxide ore, which can improve the quality of the obtained metal and efficiently produce a high-quality metal. It is an object of the present invention to provide a method for smelting an oxide ore that can be performed.

  The present inventors have found that a mixture containing oxide ore is extruded and cut at a predetermined interval to obtain a molded product, and by subjecting the molded product to a reduction treatment, a shell can be effectively formed on the surface of the molded product. The present inventors have found that the above-mentioned problems can be solved thereby, and have completed the present invention.

  (1) A first step of the present invention is a mixing step of mixing an oxide ore and a carbonaceous reducing agent to obtain a mixture, an extruding step of charging the mixture into an extruder and extruding the mixture, A method of smelting an oxide ore comprising: a forming step of obtaining a molded product having a cut surface by cutting at intervals; and a reducing step of performing a reduction treatment on the obtained molded product to obtain a reduced product containing metal and slag. It is.

  (2) In a second aspect of the present invention, in the first aspect, in the reduction step, a shell made of metal is formed on the surface of the molded article by contacting the surface of the obtained molded article with a reducing gas. An oxidized ore smelting method including a first reduction step and a second reduction step of heating a molded product having a shell formed thereon to a predetermined temperature to obtain a reduced product.

  (3) In a third aspect of the present invention, in the second aspect, at least a part of the atmospheric gas after the reduction treatment in the second reduction step is supplied to a processing space in the first reduction step, and the molded article is formed. A smelting method of an oxide ore used as the reducing gas to be contacted.

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

  (5) A fifth aspect of the present invention is the method for refining an oxide ore in which the oxide ore is a nickel oxide ore according to any one of the first to fourth inventions.

  ADVANTAGE OF THE INVENTION According to the smelting method of the oxide ore which concerns on this invention, a high quality metal can be manufactured efficiently.

It is a flowchart showing an example of a flow of a smelting method of nickel oxide ore.

  Hereinafter, specific embodiments of the present invention will be described in detail. Note that the present invention is not limited to the following embodiments, and various changes can be made without changing the gist of the present invention. 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 of oxide ore
In the method for smelting oxide ore according to the present embodiment, oxide ore (oxide) as a raw material ore is mixed with a carbonaceous reducing agent, and the mixture (pellet) is mixed in a smelting furnace (reduction furnace). By performing the reduction treatment, metal and slag are generated.

  For example, as the oxide ore, a nickel oxide ore containing nickel oxide, iron oxide, or the like is used as a raw material, and the nickel oxide ore and a carbonaceous reducing agent are mixed to form a molded product. There is a method of producing ferronickel, which is an alloy of iron and nickel, by reducing preferentially and partially reducing iron.

  In the method for smelting oxide ore according to the present embodiment, a mixture containing oxide ore is extruded and cut at a predetermined interval to obtain a molded product having a cut surface, and the molded product is subjected to reduction treatment. It is characterized by.

  According to such a method, by subjecting the molded product having the cut surface to the reduction treatment, the reduction reaction easily proceeds at the cut surface and the vicinity thereof, and the metal shell is formed well. Further, metal shells are formed on surfaces other than the cut surface with the metal shell formed on the cut surface as a starting point. By forming the metal shell on the surface of the molded product in this way, it is possible to prevent the carbonaceous reducing agent and the like contained in the molded product from leaking to the outside during the heat reduction treatment, and to reduce the reduction in the molded product. By making the reaction uniform, the quality of the obtained metal can be improved.

{2. Smelting method for producing ferronickel using nickel oxide ore.
In the following, the nickel (nickel oxide) and iron (iron oxide) contained in the nickel oxide ore, which is the raw material ore, are reduced to generate a metal of the iron-nickel alloy, and the metal is separated to separate the ferromagnetic alloy. A smelting method for producing nickel will be described as an example.

  Specifically, as shown in FIG. 1, the smelting method of nickel oxide ore according to the present embodiment includes a mixing step S1 of mixing nickel oxide ore and a carbonaceous reducing agent to obtain a mixture, and extruding the mixture. An extrusion step S2 of charging the mixture and extruding the mixture, a molding step S3 of cutting the extruded mixture at predetermined intervals to obtain a molded article having a cut surface, a drying step S4 of drying the molded article, and a molding step. A heat treatment step S5 for heating the product to a predetermined temperature, a reduction process S6 for performing a reduction process on the molded product to obtain a reduced product containing metal and slag, and a separation process S7 for 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 an optional additive such as iron ore, flux component, binder, etc. A powder having a diameter of about 0.2 mm to 0.8 mm is added and mixed to obtain a mixture.

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

  Although it does not specifically limit as a carbonaceous reducing agent, For example, coal powder, coke powder, etc. are mentioned. It is preferable that the carbonaceous reducing agent has a particle size and a particle size distribution equivalent to that of the nickel oxide ore, which is a raw material ore, because it is easy to mix uniformly and the reduction reaction easily proceeds uniformly.

  As the content of the carbonaceous reducing agent (the content of the carbonaceous reducing agent contained in the mixture), the chemical equivalent required to reduce the total amount of nickel oxide constituting the nickel oxide ore to nickel metal and the iron oxide ( 50.0% by mass when the total value of the chemical equivalents required to reduce ferric oxide to metallic iron (also referred to as “the sum of the chemical equivalents” for convenience) is 100% by mass. The ratio is preferably set to the following ratio, more preferably 40.0% by mass or less. The amount of iron reduction can be suppressed, the nickel quality can be increased, and high quality ferronickel can be manufactured.

  The mixing amount of the carbonaceous reducing agent is preferably not less than 10.0% by mass, and more preferably not less than 15.0% by mass, when the total value of the chemical equivalents is 100% by mass. More preferred. The reduction of nickel can proceed efficiently and productivity can be improved.

  As the iron ore as 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, or the like can be used.

  Examples of the flux component include calcium oxide, calcium hydroxide, calcium carbonate, and silicon dioxide. Examples of the binder include bentonite, polysaccharide, resin, water glass, dehydrated cake, and the like.

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

  Further, the obtained mixture may be kneaded. By kneading the mixture containing the raw material powder, a pressure (shear force) can be applied to the mixture at the time of the kneading, and the carbonaceous reducing agent, the raw material powder, etc. are disaggregated and the mixture is more uniformly mixed. State. Further, by kneading, it is possible to reduce voids formed between particles of the mixture.

  The kneading can be performed using a batch type kneader such as Brabender, a Banbury mixer, a Henschel mixer, a helical rotor, a roll, a single-screw kneader, a 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, a mixture containing the nickel oxide ore and the carbonaceous reducing agent obtained in the mixing step S1 is charged into an extruder, and the mixture is extruded. As a result, a pressure (shearing force) is applied to the mixture, and the aggregation of the carbonaceous reducing agent, the raw material powder, and the like is released, and the mixture can be more uniformly mixed. Furthermore, voids in the mixture can be reduced. From these facts, the reduction reaction of the molded product easily occurs uniformly in the reduction step described later, the quality of the obtained metal can be improved, and a high-quality metal can be manufactured.

  The extruder that can be used in the extrusion step S2 is preferably one capable of kneading and molding the mixture under high pressure and high shearing force, and examples thereof include a single screw extruder and a twin screw extruder. In particular, it is preferable to provide a twin-screw extruder. By kneading the mixture at high pressure and high shear, the mixture of the raw material powders can be deagglomerated, can be effectively kneaded, and the strength of the obtained molded product can be increased. Moreover, by using the one provided with the twin-screw extruder, it is possible to continuously obtain a molded product 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 a molded article having a cut surface.

  Here, in a reduction step S6 to be described later, by performing a reduction treatment on the molded article, first, a reduction reaction proceeds from the surface of the molded article to form a shell. However, if the shell is not formed properly, the internal carbonaceous reducing agent may leak.

  Therefore, a molded product having a cut surface is used as a molded product to be subjected to the reduction step S6 described below. By performing a reduction treatment on a molded product having a cut surface, a reduction reaction easily proceeds on the cut surface and in the vicinity thereof, and a metal shell can be favorably formed. Further, a metal shell is formed on a surface other than the cut surface with the metal shell as a starting point. As described above, 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, whereby the carbonaceous reducing agent or the like contained in the molded product during the heat reduction treatment is obtained. Can be suppressed from leaking to the outside.

  The cutting of the mixture can be performed using a cutting machine. The cutting of the mixture is preferably performed by a continuous operation following the extrusion in the extrusion step S2. Specifically, an extruder provided with a cutter at an outlet is used, the mixture is put into the extruder, and the extruded mixture is cut at the outlet by the cutter. As described above, by manufacturing a molded product by continuous processing, productivity can be increased, and variation in quality between molded products can be reduced.

  The cutting interval of the extruded mixture may be appropriately set according to the desired size of the molded product. The shape of the molded product (molded product having a cut surface) is not particularly limited, and examples thereof include a flat plate shape and a disk shape.

  Also, the ratio of the area of the cut surface to the surface area of the molded product is not particularly limited. For example, the ratio of the area of the cut surface / the surface area of the molded product is preferably 0.1 or more, and more preferably about 0.2 or more. More preferably, it is more preferably 0.3 or more. By preparing a molded product having a cut surface such that the area of the cut surface / the surface area of the molded product is 0.1 or more, reduction reactivity can be increased over the entire surface of the molded product, and the surface of the molded product can be reduced. Thus, a metal shell can be formed more uniformly. The upper limit is preferably about 0.9 or less. By setting the ratio of the area of the cut surface / the surface area of the molded product in the above range, the molded product can be formed into a shape that can be easily charged into the reduction furnace, and the molded product can be relatively easily handled. .

<2-4. Drying process>
The drying step S4 is a step of drying the molded product obtained in the molding step S3. Here, the molded product may contain an excessive amount of water, for example, about 50% by mass. Therefore, when the temperature of the molded article containing excessive moisture is rapidly increased to the reduction temperature, the moisture is vaporized at a stretch, and the molded article may be broken by expansion.

  Therefore, by subjecting the obtained molded product to a drying treatment, for example, by setting the solid content of the molded product to about 70% by mass and the water content to about 30% by mass, the reduction heating in the subsequent reduction step is performed. The treatment can prevent the molded product from collapsing. Further, the molded product is often in a sticky state due to excessive moisture, and can be easily handled by performing a drying treatment.

  Specifically, the drying process on the molded product in the drying step S4 is not particularly limited. For example, hot air of 300 ° C. or more and 400 ° C. or less is blown on the molded product to be dried. In addition, it is preferable that the temperature of the molded product during the drying treatment is less than 100 ° C. because the molded product is less likely to be broken.

  Note that the drying process in the drying step S4 can be omitted as long as no destruction occurs during handling such as charging into a reduction furnace or during reduction heating treatment.

  Table 2 below shows an example of the composition (parts by mass) in the solid content of the molded product after the drying treatment. The composition of the molded product is not limited to this.

<2-5. Heating process>
A heat treatment step S5 for heating the molded product obtained in the drying step S4 to a predetermined temperature may be provided. In the present embodiment, it is not an essential aspect to include the heat treatment step S5, but a heat treatment (preliminary heat treatment) is performed on the molded product before the reduction treatment in the reduction step S6 described below. By this, in the reduction treatment under high temperature conditions, components such as nickel oxide ore and carbonaceous reducing agent contained in the molded product are prevented from rapidly expanding thermally, and the bursting of the molded product is more effectively suppressed. it can.

  Specifically, a heat treatment for heating the molded product to a temperature of 350 ° C. or more and 600 ° C. or less is performed. Further, it is preferable to heat to a temperature of 400 ° C. or more and 550 ° C. or less.

  The heat treatment time is not particularly limited, and may be appropriately adjusted depending on the size of the molded product. However, if the molded product has a normal size of about 10 mm or more and 30 mm or less, it is 15 times. The processing time can be reduced to about 30 minutes or less.

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

[Reduction processing]
In the reduction treatment, the nickel oxide contained in the nickel 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 partially reduced. So-called partial reduction is performed to obtain ferronickel of high nickel quality.

  In addition, the slag in the molded product melts into a liquid phase, but the metal and slag that have already been separated by reduction do not mix with each other. It becomes a mixture mixed as another phase. The volume of this mixture has shrunk to a volume of about 50% or more and 60% or less as compared with the mixture to be charged.

  Specifically, in the reduction treatment, after the molded article is charged into a reduction furnace, the molded article is heated to a reduction temperature of about 1200 ° C. to 1450 ° C. to cause a reduction reaction.

  In this reduction treatment, carbon monoxide (reducing gas) derived from the carbonaceous reducing agent contained in the molded product is generated, and the inside of the reduction furnace is set to a reducing atmosphere. Then, the contact between the molded article and the reducing gas promotes the reduction reaction on the surface of the molded article. As a result, a metal shell is formed on the surface of the molded product.

As for the reducing gas, as described above, carbon monoxide derived from the carbonaceous reducing agent is generated in the reduction furnace. Therefore, it is not necessary to separately supply the gas from the outside, but a reducing gas may be separately supplied from the viewpoint of more efficiently performing the reduction reaction on the surface of the molded product. Note that the reducing gas is not particularly limited as long as it is a gas that can reduce an oxide to a metal. For example, 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. Further, an oxidizing gas such as oxygen may be contained as long as the formation of the metal shell on the surface of the molded product is not hindered.

  As described above, when the reduction reaction on the surface of the molded product proceeds to form a metal shell on the surface, the reduction reaction inside the molded product proceeds to generate metal.

  As the reduction furnace, although not particularly limited, even if a single furnace is used, a furnace such as a moving hearth furnace is used in which the hearth can be rotated and moved, for example, to continuously perform processing at different processing temperatures. You may. Among them, by using a moving hearth furnace as the reduction furnace, the reduction reaction can proceed continuously and the reaction can be completed with one facility. In addition, if operation is performed using a separate furnace for each processing step, when moving between furnaces, the temperature may decrease and heat loss may occur. May not be able to occur immediately when the furnace is recharged. In this regard, using a moving hearth furnace to perform each process in a single facility reduces heat loss and enables accurate control of the furnace atmosphere, allowing the reaction to proceed more effectively. Can be.

  The moving hearth furnace is not particularly limited. For example, a rotary hearth furnace having a circular shape and divided into a plurality of processing regions can be used. In a rotary hearth furnace, each process is performed in each region while rotating in a predetermined direction. In this rotary hearth furnace, the processing temperature in each area can be adjusted by controlling the time (moving time, rotation time) when passing through each area, and the rotary hearth furnace makes one rotation. Each time the mixture is smelted. The moving hearth furnace may be a roller hearth kiln or the like.

  In the reduction step S6, when the molded product is charged into the reduction furnace, a reducing agent (hereinafter, also referred to as "hearth reducing agent") is spread on the hearth in the reduction furnace in advance, and the spread hearth reduction is performed. The molded product may be placed on the agent. Further, a floor covering material mainly composed of an oxide may be laid on the hearth, and a molded product may be placed thereon.

[Reduction target (molded product with cut surface)]
By the way, in the method for smelting nickel oxide ore according to the present embodiment, a molded product having a cut surface is obtained in the above-described molding step S4. In the reduction step S6, a reduction process is performed on a molded product having the cut surface as a processing target.

  By performing a reduction treatment on a molded product having such a cut surface, a metal shell can be favorably formed at or near the cut surface. Further, starting from the metal shell formed on the cut surface, the metal shell is formed also 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 means that the cut surface formed on the molded product is relatively rough as compared with the other surfaces, and the contact area with the atmospheric gas (reducing gas) containing carbon monoxide is increased. It is considered that the reduction reaction easily proceeds on the cut surface.

  By effectively forming the metal shell on the surface of the molded product, it is possible to effectively prevent the carbonaceous reducing agent and the like contained in the molded product from leaking to the outside during the heat reduction treatment. As a result, the reduction reaction in the molded product can be uniformly generated, and the quality of the obtained metal can be improved.

[Other Embodiments of Reduction Treatment]
Here, the reduction step S6 may be a mode in which the first reduction step and the second reduction step are performed separately. Specifically, as the reduction step S6, a reduction first step of forming a metal shell on the surface of a molded product having a cut surface by heating at a predetermined temperature, and reducing the molded product having the metal shell formed on the surface. A second step of obtaining a reduced product by heating to a temperature higher than the processing temperature in the first step. According to such an embodiment, the metal shell can be more reliably formed on the surface of the molded article, and the leakage of the carbonaceous reducing agent contained in the molded article to the outside can be more effectively suppressed. , High quality metal can be manufactured. Hereinafter, each step will be described more specifically. For convenience of explanation, the first reduction step is “S61” and the second reduction step is “S62”.

(First reduction step)
In the first reduction step S61, a metal shell is formed on the surface of a molded product having a cut surface by bringing the molded product into contact with a reducing gas. As a result, a metal shell is formed on the surface including the cut surface in contact with the reducing gas. In particular, on the cut surface, the reactivity with the reducing gas is high, and a uniform metal shell can be formed on the surface of the molded product starting from the metal shell formed on the cut surface.

  In the first reduction step S61, it is preferable that the metal shell is efficiently formed on the surface of the molded article without reacting the carbonaceous reducing agent in the molded article. For this purpose, the molded product is preferably kept at a temperature lower than the reaction temperature at which the carbonaceous reducing agent reacts with the metal oxide. For example, the molded product is preferably kept at a temperature of less than 1200 ° C. In the first reduction step S61, it is preferable to maintain the molded product at a temperature of 900 ° C. or higher. As described above, by maintaining the molded product at a temperature of 900 ° C. or more and less than 1200 ° C., it is possible to reduce the surface of the molded product to metal and effectively form a metal shell while suppressing the reduction reaction inside the molded product. Can be.

  As described above, a gas containing carbon monoxide (CO) or the like can be used as the reducing gas. Here, in a second reduction step S62 described below, carbon monoxide (CO) derived from the carbonaceous reducing agent is generated by performing a reduction treatment on the molded product. Therefore, at least a part of the atmospheric gas after the reduction process in the second reduction step S62 may be supplied to the processing space in the first reduction step S61 and used as a reducing gas. In this case, since the atmospheric gas after the reduction treatment is usually at a high temperature (for example, about 1200 ° C. to 1450 ° C.), when the gas is supplied to the processing space in the first reduction step S61, the temperature of the gas is 1200 ° C. The temperature may be adjusted by cooling or the like as described below.

(Reduction second step)
The second reduction step S62 is a step of obtaining a reduced product by heating a molded product having a metal shell formed on its surface to a predetermined temperature. Specifically, the molded article on which the shell is formed is subjected to a heat reduction treatment in a reduction furnace heated to a temperature (reduction temperature) higher than the processing temperature in the first reduction step S61. Thereby, the carbonaceous reducing agent in the molded product is reacted to reduce the oxide in the molded product, and a reduced product containing metal and slag is obtained.

  Here, as described above, since the metal shell is formed on the surface of the molded product subjected to the heat reduction treatment through the treatment in the first reduction step S61, the carbonaceous reducing agent leaks to the outside. Is suppressed, an appropriate reduction reaction can be caused based on the carbonaceous reducing agent, and a high-quality metal can be efficiently produced.

  In order to react the carbonaceous reducing agent in the molded product to reduce the oxide, the molded product is preferably heated to a reaction temperature or higher at which the carbonaceous reducing agent reacts with the oxide. It is preferable to keep the temperature at 1200 ° C. or higher. Note that the upper limit of the reduction temperature is preferably 1450 ° C. or lower. Thereby, the reduction treatment can be performed on the oxide with high accuracy.

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

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

  Further, the obtained metal phase and slag phase can be easily separated from each other due to poor wettability. For example, a predetermined head is provided for the large inclusion obtained in the treatment in the reduction step S6. By applying an impact such as applying predetermined vibration during sieving, the metal phase and the slag phase can be easily separated from the mixture.

  The metal is recovered by separating the metal phase and the slag phase in this way.

  In the method for smelting nickel oxide ore according to the present embodiment, a metal shell is formed on the surface of a molded product to suppress the carbonaceous reducing agent contained in the molded product from leaking to the outside, and the entire molded product is reduced. 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.

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

<Example 1, Comparative Example 1>
Appropriate amount of nickel oxide ore, iron ore, silica sand and limestone as flux components, binder, and carbonaceous reducing agent (coal powder, carbon content: 85% by mass, average particle size: about 200 μm) as raw material ores While adding water, mixing was performed using a mixer to obtain a mixture. The amount of the carbonaceous reducing agent (coal powder) required to reduce nickel oxide and iron oxide (Fe ₂ O ₃ ) contained in the nickel ore, which is the raw material ore, is 100 mass%. Was contained in an amount of 24.0% by mass according to the samples (mixtures) of Examples 1 to 6 and Comparative Examples 1 to 3.

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

  On the other hand, for the sample of Comparative Example 1, a sample (molded product) was manufactured by filling the extruded mixture in a container as it was without cutting the mixture extruded by the twin-screw kneading extruder with a cutter. did. Further, for the sample of Comparative Example 2, a sample (mixture) was cut out by a cutting machine, and a briquette (molded product) was manufactured using a commercially available briquetting apparatus without extruding the sample using a twin-screw kneading extruder. In addition, for the sample of Comparative Example 3, the sample (mixture) was cut out by a cutting machine, and was granulated by using a pan-type granulator without being extruded by a twin-screw kneading extruder. It was classified into a size of 5 mm.

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

Next, each of the molded products after the drying treatment was placed in a reduction furnace in a nitrogen atmosphere containing no oxygen. A hearth protecting agent (main component is SiO ₂ and a small amount of oxides such as Al ₂ O ₃ and MgO as other components) is spread over the hearth of the reduction furnace in advance, and a molded product (sample) ). 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 portion having the highest temperature (reduction temperature) on the surface of the molded article charged in the furnace reaches 1400 ° C., and the molded article is subjected to reduction heating treatment. did. The processing time by the reduction heat treatment was 15 minutes. After the reduction treatment, the sample was immediately cooled to room temperature in a nitrogen atmosphere, and the sample was taken out to 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).

The Ni metallization ratio and the Ni content in the metal were calculated by the following equations 1.2.
Ni metallization ratio = mass of Ni in metal ÷ (mass of all Ni in reduced product) × 100 (%) Formula (1) Ni content in metal = mass of Ni in metal ÷ (metal Total mass of Ni and Fe in) × 100 (%) (2)

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

  As can be seen from the results in Table 4, in Examples 1 to 6 in which a mixture containing an oxide ore was extruded to obtain a molded product having a cut surface, and the molded product was subjected to a reduction treatment, compared with Comparative Examples 1 to 3 As a result, both the Ni metallization ratio and the Ni content in the metal were increased. This means that by performing a reduction treatment on a molded product having a cut surface, a metal shell can be favorably formed on the surface of the molded product, whereby the carbonaceous reducing agent and the like contained in the molded product can be reduced. It is considered that the reduction reaction was able to proceed appropriately by suppressing leakage to the outside.

Claims (5)

A mixing step of mixing the oxide ore and the carbonaceous reducing agent to obtain a mixture,
An extrusion step in which the mixture is charged into an extruder and extruded,
A molding step of cutting the extruded mixture at predetermined intervals to obtain a molded article having a cut surface,
A reduction step of performing a reduction treatment on the obtained molded product to obtain a reduced product containing metal and slag,
For smelting oxide ores containing In the reduction step,
A reduction first step of forming a metal shell on the surface of the molded article by contacting the surface of the molded article with a reducing gas;
A reduction second step of obtaining a reduced product by heating the molded product on which the shell is formed to a predetermined temperature;
The method for smelting oxide ore according to claim 1. The oxide ore according to claim 2, wherein at least a part of the atmosphere gas after the reduction treatment in the second reduction step is supplied to the processing space in the first reduction step and used as the reducing gas to be brought into contact with the molded product. Smelting method. In the first reduction step, the molded product is maintained at a temperature of 900 ° C or more and less than 1200 ° C,
The method for smelting oxide ore according to claim 2 or 3, wherein in the second reduction step, the molded product is maintained at a temperature of 1200 ° C or more and 1450 ° C or less. The smelting method of an oxide ore according to any one of claims 1 to 4, wherein the oxide ore is a nickel oxide ore.

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