JP2021031705A - Smelting method of oxide ore - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the quality of the obtained metal in a smelting method for producing a metal by reducing a mixture containing an oxide ore such as a nickel oxide ore, and to efficiently produce a high quality metal. Provide a method for smelting oxidized ore that can be produced. SOLUTION: The reduction step comprises a mixing step of obtaining a mixture containing an oxide ore and a first reducing agent, and a reduction step of charging the obtained mixture into a reduction furnace and performing a reduction treatment. Then, it is a method of smelting an oxide ore in which a second reducing agent is added to the mixture at the time of reduction treatment. [Selection diagram] Fig. 1

Description

The present invention relates to a method for smelting oxidized ore.

As a method for smelting nickel oxide ore called limonite or saprolite, which is a type of oxide ore, a pyrometallurgical method for producing nickel matte using a smelting furnace, iron and nickel using a rotary kiln or a mobile hearth furnace. Pyrometallurgical smelting method for producing the alloy of iron and nickel (hereinafter, the alloy of iron and nickel is also referred to as "ferronickel"), acid leaching at high temperature and high pressure using an ore, and mixed sulfide mixed with nickel and cobalt (mixed sulfide). ) Is known as a wet smelting method.

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

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

The pellets obtained in the form of agglomerates need to have a certain degree of air permeability in order to "fly" the contained moisture. 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, causing inconveniences such as metal being dispersed or unevenly distributed. Therefore, it is important to mix the mixture uniformly when preparing the pellets and to maintain the temperature as uniform as possible when reducing the obtained pellets.

In addition, coarsening the metal (ferronickel) produced by the reduction treatment is also a very important technique. When the produced ferronickel has a fine size of, for example, several tens of μm or more and several hundreds of μm or less, it becomes difficult to separate it from the slag produced at the same time, and the recovery rate (yield) as ferronickel is greatly reduced. It ends up. Therefore, a treatment for coarsening the reduced ferronickel is required.

For example, Patent Document 1 is characterized in that pellets are placed in a mobile hearth furnace, and the pellets are continuously subjected to reduction heat treatment and reheat treatment using the mobile hearth furnace. The method for smelting the oxide ore is disclosed. According to Patent Document 1, this smelting method for oxidized ore can effectively proceed the smelting reaction (reduction reaction) to efficiently obtain an iron-nickel alloy having a high nickel grade.

JP-A-2017-52994

INDUSTRIAL APPLICABILITY The present invention can improve the quality of the obtained metal in a smelting method for producing a metal by reducing a mixture containing an oxide ore such as a nickel oxide ore, and efficiently produce a high quality metal. It is an object of the present invention to provide a method for smelting oxidized ore.

The present inventor has found that the above problems can be solved by adding a second reducing agent to the mixture and performing the reduction treatment at the time of the reduction treatment, and have completed the present invention.

(1) The first of the present invention is a mixing step of obtaining a mixture containing an oxide ore and a carbonaceous reducing agent which is a first reducing agent, and charging the obtained mixture into a reduction furnace for reduction treatment. The reduction step is a method for smelting an oxidized ore in which a second reducing agent is added to the mixture during the reduction treatment.

(2) The second aspect of the present invention is that in the first invention, the second reducing agent is a carbonaceous reducing agent, and in the reduction step, the coal throwing rate defined by the following formula is 0.1 or more and 0. This is a method for smelting an oxide ore in which the second reducing agent is added so as to be 0.3 or less.
Coking rate = mass of carbon contained in the second reducing agent (g) / mass of oxidized ore contained in the mixture (g)

(3) The third aspect of the present invention is, in the second invention, a method for smelting an oxidized ore in which the second reducing agent is added to the mixture twice or more in the reduction step.

(4) A fourth aspect of the present invention is that in the third invention, in the reduction step, the mixture is subjected to a reduction treatment by adding the second reducing agent for the first time, and 2 in the middle of the reduction treatment. This is a method for smelting oxidized ore in which the second reducing agent is added after the first time.

(5) The fifth aspect of the present invention is that in the third or fourth invention, when the second reducing agent is added from the second time onward, the coal throwing rate is 0.03 or more and 0.1 or less. It is a method of smelting oxidized ore.

(6) A sixth aspect of the present invention is that in any one of the first to fifth aspects, the oxide ore is a nickel oxide ore, and the smelting of the oxide ore that reduces the nickel oxide ore to produce ferronickel. The method.

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

It is a process drawing which shows an example of the flow of the smelting method of nickel oxide ore.

Hereinafter, specific embodiments of the present invention will be described in detail. The present invention is not limited to the following embodiments, and various modifications can be made without changing the gist of the present invention. Further, in the present 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 oxidized ore ≫
In the method for smelting an oxidized ore according to the present embodiment, an oxide ore (oxide) which is a raw material ore is mixed with a first reducing agent, and the mixture (pellets) is smelted in a smelting furnace (reduction furnace). The metal and slag are produced by performing the reduction treatment in.

For example, as the oxide ore, nickel oxide ore containing nickel oxide, iron oxide, etc. is used as a raw material, and the nickel oxide ore is mixed with the first reducing agent to obtain a mixture, and the nickel contained in the mixture is given priority. There is a method of producing ferronickel, which is an alloy of iron and nickel, by reducing the amount of iron to iron and partially reducing iron.

Then, in the method for smelting the oxidized ore according to the present embodiment, when the mixture of the oxidized ore and the carbonaceous reducing agent as the first reducing agent is subjected to the reduction treatment, the mixture is subjected to the second reduction treatment. It is characterized in that it is treated by adding a reducing agent separately as a reducing agent.

According to such a method, for example, the metal oxidized by oxygen remaining in the reduction furnace can be re-reduced, and the quality of the obtained metal can be improved. As a result, high-quality metal can be efficiently produced.

≪2. Smelting method for producing ferronickel using nickel oxide ore ≫
In the following, a metal of an iron-nickel alloy is generated by reducing nickel (nickel oxide) and iron (iron oxide) contained in nickel oxide ore, which is a raw material ore, and further, by separating the metal, ferro A smelting method for producing nickel will be described as an example.

Specifically, as shown in FIG. 1, the method for smelting the nickel oxide ore according to the present embodiment is obtained in the mixing step S1 of mixing the nickel oxide ore and the carbonaceous reducing agent to obtain a mixture. It includes a reduction step S2 in which the mixture is reduced and a recovery step S3 in which the metal is recovered from the obtained reduced product.

<2-1. Mixing process>
The mixing step S1 is a step of mixing the nickel oxide ore and the carbonaceous reducing agent which is the first reducing agent to obtain a mixture. Here, the carbonaceous reducing agent that is mixed with the nickel oxide ore in the mixing step S1 to form a mixture is referred to as a "first reducing agent", and is a reducing agent (second reducing agent) that is separately used in the reduction step S2 described later. ) Is distinguished.

Specifically, in the mixing step S1, first, a carbonaceous reducing agent, which is a first reducing agent, is added to and mixed with nickel oxide ore, which is a raw material ore, and iron ore and flux are used as additives of arbitrary components. Powders such as components and binders having a particle size of 0.2 mm or more and 0.8 mm or less are added and mixed to obtain a mixture. The mixing process can be performed using a mixer or the like.

The nickel oxide ore as a 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).

The carbonaceous reducing agent, which is the first reducing agent, is not particularly limited, and examples thereof include coal powder and coke powder. It is preferable that this carbonaceous reducing agent has a size equivalent to the particle size and particle size distribution of nickel oxide ore, which is a raw material ore, because it is easy to mix uniformly and the reduction reaction is likely to proceed uniformly.

The content of the carbonaceous reducing agent (content of the carbonaceous reducing agent contained in the mixture) is the chemical equivalent required to reduce the total amount of nickel oxide constituting the nickel oxide ore to nickel metal and iron oxide (the content of iron oxide (content of the carbonaceous reducing agent). When the total value of both the chemical equivalent required to reduce ferric oxide) to metallic iron (also referred to as "total chemical equivalent" for convenience) is 100% by mass, it is 50% by mass or less. The ratio is preferably 40% by mass or less, and more preferably 40% by mass or less. The amount of iron reduced can be suppressed, the nickel grade can be improved, and high-quality ferronickel can be produced. The mixing amount of the carbonaceous reducing agent is preferably 10% by mass or more, and more preferably 15% by mass or more, when the total value of chemical equivalents is 100% by mass. The reduction of nickel can proceed efficiently and productivity is improved.

As the iron ore as an additive of an optional component, for example, iron ore having an iron grade of about 50% by mass or more, hematite obtained by hydrometallurgy of nickel oxide ore, or the like can be used. Moreover, as a flux component, for example, calcium oxide, calcium hydroxide, calcium carbonate, silicon dioxide and the like can be mentioned. Examples of the binder include bentonite, polysaccharides, resins, water glasses, dehydrated cakes and the like.

In the mixing step S1, a mixture is obtained by uniformly mixing the raw material powder containing nickel oxide ore. Table 1 below shows an example of the composition (mass%) of some of the raw material powders to be mixed in the mixing step S1, but the composition of the raw material powders is not limited to this.

At the time of mixing, kneading may be performed at the same time in order to improve the mixing property, or kneading may be performed after mixing. Kneading can be performed using a batch type kneader such as lavender, a Banbury mixer, a Henschel mixer, a helical rotor, a roll, a uniaxial kneader, a biaxial kneader or the like. By kneading the mixture, a shearing force is applied to the mixture to disaggregate the carbonaceous reducing agent, the raw material powder, etc., and the mixture can be uniformly mixed, and the adhesion of each particle is improved and the voids are reduced. Can be done. As a result, the reduction reaction is likely to occur in the mixture, and the reaction can be carried out uniformly, and the reaction time of the reduction reaction can be shortened. Moreover, the variation in quality can be suppressed.

Further, after mixing, or after mixing and kneading, the extrusion may be performed using an extruder. As a result, pressure (shearing force) is applied to the mixture to disaggregate the carbonaceous reducing agent, the raw material powder, and the like, and the mixture can be mixed more uniformly. In addition, voids in the mixture can be reduced. From these facts, in the reduction step S2 described later, the reduction reaction of the mixture is likely to occur uniformly, the quality of the obtained metal can be improved, and a high quality metal can be produced.

The extruder is preferably one that can be formed by kneading the mixture with high pressure and high shearing force, and examples thereof include a single-screw extruder and a twin-screw extruder. In particular, it is preferably equipped with a twin-screw extruder. By kneading the mixture under high pressure and high shear, it is possible to disaggregate the mixture of the raw material powders, effectively knead the mixture, and increase the strength of the mixture. Further, by using an extruder equipped with a twin-screw extruder, a mixture can be continuously obtained while maintaining high productivity.

Further, the mixture may be molded into a molded product (pellet) having a predetermined shape. The shape of the molded product may be, for example, spherical, rectangular parallelepiped, cubic, cylindrical or the like. Since such a shape is a simple shape and not complicated, it is possible to suppress the occurrence of defective products while suppressing the molding cost, the quality of the obtained molded product is uniform, and the decrease in yield is suppressed. can do.

The shape of the molded product is particularly preferably spherical. Since it is a spherical molded product, the reduction treatment is uniformly applied, and smelting with little variation and high productivity can be performed. When the shape of the molded product is spherical, it can be molded so that the diameter is about 10 mm or more and 30 mm or less. Further, in the case of a rectangular parallelepiped shape, a cube shape, a columnar shape, or the like, it can be molded so that the vertical and horizontal internal dimensions are approximately 500 mm or less.

The size of the molded product is not particularly limited, but the volume of the molded product ^{is preferably 8000 mm 3} or more. When the volume of the molded product is 8000 mm ³ or more, the molding cost is suppressed, and the ratio of the surface area to the entire molded product is low, so that the reduction treatment is uniformly applied, the variation is small, and the productivity is high. High smelting can be performed.

In addition, the obtained mixture may be filled in a predetermined reduction container. By performing the reduction treatment while the mixture filled in the container is still filled in the container, the metal reduced in the separation step S4 described later can be easily separated and recovered by a treatment such as magnetic separation, resulting in loss. It can be suppressed.

In the mixing step S1, the obtained mixture may be subjected to a drying treatment. The mixture is mixed with a large amount of water in kneading, molding of a molded product, or the like. Although it is not an essential aspect to carry out the odor drying treatment in the present embodiment, by carrying out the drying treatment on the mixture containing a large amount of water, it is possible to prevent the mixture from expanding due to the vaporization of water in the reduction treatment described later. ..

Further, by subjecting the mixture to a drying treatment, it is possible to suppress water contamination caused by the mixture in the reduction furnace. As a result, the amount of water contained in the atmospheric gas in the reduction furnace can be reduced more effectively, and the oxidation of the metal contained in the reduced product can be suppressed more effectively.

The method for drying the mixture is not particularly limited, and a method for holding the mixture at a predetermined drying temperature (for example, 150 ° C. or higher and 400 ° C. or lower), a method for blowing hot air at a predetermined drying temperature onto the mixture, and the like are used. , Conventionally known means can be used. By such a drying treatment, for example, the solid content of the mixture is about 70% by mass and the water content is about 30% by mass. The temperature of the mixture itself during this drying treatment is preferably less than 100 ° C., which can prevent the mixture from bursting due to the sudden boiling of water or the like.

Further, the drying treatment may be continuously performed at one time or may be performed in a plurality of times. By performing the drying treatment in a plurality of times, the rupture of the mixture can be suppressed more effectively. When the drying treatment is performed in a plurality of times, the drying temperature for the second and subsequent times is preferably 150 ° C. or higher and 400 ° C. or lower. By drying in this range, it becomes possible to dry without proceeding with the reduction reaction.

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

<2-2. Reduction process>
The reduction step S2 is a step of subjecting the obtained mixture to a reduction treatment. Specifically, the mixture is charged into a reduction furnace, and the mixture is subjected to a heat reduction treatment. In the reduction treatment, a smelting reaction (reduction reaction) proceeds based on the first reducing agent in the mixture, and in the mixture, ferronickel metal (hereinafter, simply referred to as “metal”) and ferronickel slag (hereinafter, simply referred to as “metal”) and ferronickel slag (hereinafter, referred to as “metal”). , Simply called "slag") and are generated separately.

In the reduction treatment, for example, in a short time of about 1 minute, the nickel oxide ore and iron oxide in the mixture are first reduced and metallized to become ferronickel in the vicinity of the surface of the mixture in which the reduction reaction easily proceeds, and the shell is formed. Form. On the other hand, in the shell, the slag component gradually melts with the formation of the shell to generate liquid phase slag. As a result, the metal and the slag are separately produced in the mixture. When the treatment time elapses for about 10 minutes, the excess carbonaceous reducing agent that is not involved in the reduction reaction is incorporated into the metal to lower the melting point, and the metal also becomes a liquid phase.

Here, a part of the generated metal may be oxidized by oxygen remaining in the reduction furnace, and there is a problem that the quality of the obtained metal is deteriorated. In particular, when a reduction furnace having a burner is used when performing the heat reduction treatment, more oxygen remains in the reduction furnace due to the combustion gas being mixed in the reduction furnace, so that a part of the metal is left. The problem of being more easily oxidized becomes relatively large.

Therefore, in the method for smelting nickel oxide ore according to the present embodiment, when the mixture of the nickel oxide ore and the carbonaceous reducing agent which is the first reducing agent is subjected to the reduction treatment, the mixture is subjected to the first reduction treatment. It is characterized in that a reducing agent is separately added (charred) as the reducing agent of No. 2 for treatment. According to such a method, the oxygen remaining in the treatment space can suppress the oxidation of the metal produced by the reduction, and can re-reduce a part of the oxidized metal. This makes it possible to produce high quality metal.

Further, by adding the second reducing agent and performing the reduction treatment, it becomes possible to carry out the reduction treatment on the mixture while maintaining the high temperature for a long period of time, so that the agglomeration of the obtained metal is promoted. The metal can be coarsened. As a result, it is not necessary to finely crush the reduced product obtained in the recovery step S3 described later, and the cost required for crushing can be significantly reduced. Further, since the metal is coarsened, the metal can be reliably magnetized in the recovery step S3 described later, for example, when the metal is recovered by magnetic separation or the like, and the handling property of the magnetization and the metal recovery rate can be obtained. Can be improved.

The second reducing agent is not particularly limited as long as the mixture can be subjected to a reduction treatment, and examples thereof include powders and particles of a carbonaceous reducing agent such as coal powder and coke powder. it can.

The method of adding (charcoaling) the second reducing agent to the mixture is, for example, a carbonaceous reducing agent from a predetermined charging port of the reducing furnace so that the mixture placed in the reducing furnace and the carbonaceous reducing agent come into contact with each other. A method of adding and adding powder or particles of the above can be mentioned.

Further, the addition (charcoal injection) of the mixture may be performed, for example, at the timing when the set reduction temperature is reached, at the timing when the reduction reaction proceeds to some extent after reaching the reduction temperature, or at the timing when the reduction reaction is completed.

Regarding the amount of the second reducing agent added, it is preferable to add the second reducing agent so that the coal throwing rate defined by the following formula is 0.1 or more and 0.3 or less.
Coking rate = mass of carbon contained in the second reducing agent (g) / mass of oxidized ore contained in the mixture (g)

By adding the second reducing agent so that the coal casting rate is 0.1 or more, the oxidation of the metal by the oxygen remaining in the treatment space can be suppressed more effectively. Further, by adding the second reducing agent so that the coal casting rate is 0.3 or less, the reduction amount of iron can be suppressed and the nickel grade can be further improved. As will be described later, when the second reducing agent is added twice or more, the addition of the second reducing agent at the first time is such that the coal throwing rate is 0.1 or more and 0.3 or less. Add so that

Here, the second reducing agent may be added once during the reduction treatment, or may be added twice or more. Specifically, for example, when the second reducing agent is added twice or more, the first second reducing agent is added and the reduction treatment is performed, and the second and subsequent reduction treatments are performed in the middle of the reduction treatment. Add the reducing agent of 2. The term "in the middle of the reduction treatment" means, for example, the timing at which the first second reducing agent is added to the mixture to perform the reduction treatment and the reduction reaction is generally completed (for example, the set reduction). It means that the second reducing agent is added for the second time around 15 to 30 minutes after reaching the temperature). When the reduction reaction is almost completed, it means that the reduction reaction has reached an equilibrium state.

By adding the second reducing agent more than once in this way, it is possible to more effectively suppress the oxidation of the metal due to oxygen or the like remaining in the reduction furnace, and the oxidized metal can be regenerated. Reduction can also be promoted. In addition, it is possible to compensate for the insufficient reduction of nickel contained in nickel oxide ore, and it is possible to further improve the quality of metal.

When the second reducing agent is added two or more times, the amount of the second reducing agent added after the second reduction is 0.03 or more and 0.1 or less in the coal throwing rate defined by the above formula. It is preferable to add it so as to be.

When the coal injection rate of the second reducing agent after the second time is 0.03 or more, the oxidation of the metal can be suppressed more effectively. Further, when the coal throwing rate of the second reducing agent after the second time is 0.1 or less, the reduction amount of iron can be suppressed and the nickel grade can be further improved.

The reduction treatment in the reduction step S2 is performed using a reduction furnace. The heating means of the reduction furnace may be a burner or electricity, but a burner is preferable because the mixture can be effectively heat-reduced in a short time. When a reduction furnace having a burner is used, for example, LPG gas, LNG gas, coal, coke, pulverized coal or the like is used as the fuel. The cost of these fuels is very low, and the equipment cost and maintenance cost can be kept much lower than those of an electric furnace or the like. On the other hand, in a reducing furnace having a burner, a part of the obtained metal is relatively easily oxidized by the combustion gas mixed in the reducing furnace, but the method for smelting nickel oxide ore according to the present embodiment can be used. For example, since the mixture is treated by adding (charcoalizing) a reducing agent separately as a second reducing agent, it is possible to effectively suppress the oxidation of a part of the obtained metal. It is possible, and high quality metal can be produced as in the case of using an electric furnace.

When a reduction furnace having a burner is used, a mixture containing nickel oxide ore is used, and a burner fueled by fossil fuel such as coal, heavy oil, or hydrocarbon gas is used, and the reduction temperature is 1300 ° C. or higher, preferably 1300 ° C. or higher, 1450. The reduction treatment is performed by charging the coal into a reduction furnace heated to a temperature of ° C. or lower.

The time (treatment time) in the reduction treatment is set according to the temperature of the reduction furnace, but is preferably 10 minutes or more, and more preferably 15 minutes or more.

The amount of heat required for reduction by multiplying the value of the reduction temperature (° C.) and the reduction time (minutes) is preferably in the range of 20000 (° C. × min) or more and 40,000 (° C. × min) or less. High quality metal can be produced efficiently.

The reduction furnace is not particularly limited, but a single furnace may be used, or a furnace such as a mobile hearth furnace or the like in which the hearth can be continuously processed by rotational movement or the like may be used. By using a mobile hearth furnace to perform processing in each process in different processing spaces in one facility, heat loss can be reduced and the atmosphere inside the furnace can be controlled accurately, so the reaction proceeds more effectively. Can be made to.

The mobile hearth furnace is not particularly limited, and for example, a rotary hearth furnace which has a circular shape and is divided into a plurality of processing regions can be used. In the 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 region can be adjusted by controlling the time (movement time, rotation time) when passing through each region, and the rotary hearth furnace makes one rotation. The mixture is smelted each time. Further, the mobile hearth furnace may be a roller hearth kiln or the like.

<2-3. Recovery process>
The recovery step S3 is a step of recovering the metal from the reduced product obtained in the reduction step S2. 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 in the state of being filled in the container.

As a method for 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, etc. Method can be used.

In the nickel oxide ore smelting method according to the present embodiment, since the agglutination of the obtained metal is promoted and the metal is coarsened, it is not necessary to crush the obtained reduced product into small pieces, and a predetermined head is provided. Separation is also easy by giving an impact such as dropping the metal or giving a predetermined vibration.

Further, since the metal is coarsened, the metal can be reliably magnetized, and the handleability of the magnetism and the metal recovery rate can be improved.

Hereinafter, examples of the present invention will be described in more detail, but the present invention is not limited to the following examples.

<Examples and comparative examples>
An appropriate amount of nickel oxide ore as a raw material ore, iron ore, flux components such as silica sand and limestone, a binder, and a carbonaceous reducing agent (coal powder, carbon content: 83% by mass, average particle size: about 75 μm). The mixture was obtained by mixing using a mixer while adding the water of. _{When 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 oxide ore, which is the raw material ore, in just proportion is 100% by mass. Was contained in an amount of 29% by mass.

Next, 12 (Examples 1 to 8, Comparative Examples) of a mixture (sample) having a diameter of 15.0 ± 0.5 mm, which was formed into a spherical shape by appropriately adding water to the obtained mixture by a pan-type granulator. 1-4) Obtained. Next, each sample was dried by blowing hot air at 200 ° C. to 250 ° C. so that the solid content was about 70% by weight and the water content was about 30% by weight. Table 3 below shows the solid content composition (excluding carbon) of the sample after the drying treatment.

Next, the mixtures (samples) of Examples 1 to 8 and Comparative Examples 1 to 4 were charged into a rotary hearth furnace, and reduction was carried out under the conditions shown in Table 4, respectively.

In this reduction treatment, a carbonaceous reducing agent (coal powder, carbon content: 83% by mass, average particle size: about 75 μm) as a second reducing agent is brought into contact with the mixture placed in the reduction furnace. Addition was added.

Here, regarding the addition of the second reducing agent, in Examples 1 to 4, the coal injection rate (the second reducing agent added during the reduction treatment) is performed at the timing 10 minutes after the set reduction temperature is reached. The carbon mass (g) contained in the mixture / the mass (g) of the oxidized ore contained in the mixture) was added (coal-throwing) so as to be 0.20 (in Table 4, the "second reducing agent" was "Yes". (1 time) ".).

In Examples 5 to 8, a second reducing agent is added (charcoal thrown) in the same manner as in Examples 1 to 4 at a timing 10 minutes after the set reduction temperature is reached, and the set reduction temperature is reached. A second reducing agent was further added (coal-thrown) so that the coal-throwing rate became 0.07 30 minutes after that (in Table 4, "2nd-reducing agent" was "Yes" twice. ) ”. ).

On the other hand, for the samples of Comparative Examples 1 to 4, the second reducing agent was not added to the mixture during the reduction treatment (in Table 4, "second reducing agent" is described as "none").

In the reduction treatment, a hearth protective agent (main component is SiO ₂ and contains a small amount of oxides such _{as Al 2} O ₃ and Mg O as other components) is spread in advance on the hearth of the reduction furnace. A sample was placed on the sample and subjected to a reduction treatment.

After such reduction treatment, the obtained samples of Examples 1 to 8 and Comparative Examples 1 to 4 after cooling of the reduced product were pulverized, and then the metal was recovered by magnetic force sorting.

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

The nickel metallization rate, the nickel content in the metal, and the nickel metal recovery rate were calculated by the following formulas (1), (2), and (3).
Nickel metallization rate = mass of nickel in metal / (mass of all nickel in reduced product) × 100 (%) ・ ・ ・ Equation (1) Nickel content in metal = mass of nickel in metal / (metal Total mass of nickel and iron in it) x 100 (%) ... (2) Nickel metal recovery rate = amount of recovered nickel / (amount of input ore x nickel content in ore) x 100 ・・ ・ Equation (3)

Table 4 below shows the reduction time after the reduction temperature during the heat reduction treatment, the nickel metallization rate, the nickel content in the metal, and the nickel metal recovery rate in each sample.

As can be seen from the results in Table 4, in Examples 1 to 8 in which the second reducing agent was added to the mixture during the reduction treatment and the reduction treatment was performed, the nickel metallization rate was compared with that in Comparative Examples 1 to 4. , Nickel content in metal and nickel recovery rate were both high.

Claims (6)

A mixing step of obtaining a mixture containing an oxide ore and a carbonaceous reducing agent as a first reducing agent, and
It has a reduction step of charging the obtained mixture into a reduction furnace and performing a reduction treatment.
In the reduction step, a method for smelting an oxidized ore in which a second reducing agent is added to the mixture during the reduction treatment. The second reducing agent is a carbonaceous reducing agent.
The method for smelting oxidized ore according to claim 1, wherein in the reduction step, the second reducing agent is added so that the coal throwing rate defined by the following formula is 0.1 or more and 0.3 or less.
Coking rate = mass of carbon contained in the second reducing agent (g) / mass of oxidized ore contained in the mixture (g) The method for smelting an oxidized ore according to claim 2, wherein in the reduction step, the second reducing agent is added to the mixture twice or more. In the reduction step, the mixture is subjected to the reduction treatment by adding the second reducing agent for the first time, and the second and subsequent reducing agents are added in the middle of the reduction treatment. The method for smelting oxidized ore described in. The method for smelting oxidized ore according to claim 3 or 4, wherein the second reducing agent is added so that the coal casting rate is 0.03 or more and 0.1 or less in the second and subsequent additions. The method for smelting an oxide ore according to any one of claims 1 to 5, wherein the oxide ore is a nickel oxide ore, and the nickel oxide ore is reduced to produce ferronickel.

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