WO2018147146A1

WO2018147146A1 - Metal oxide smelting method

Info

Publication number: WO2018147146A1
Application number: PCT/JP2018/003274
Authority: WO
Inventors: 井関　隆士; 幸弘合田; 純一小林; 岡田　修二
Original assignee: 住友金属鉱山株式会社
Priority date: 2017-02-09
Filing date: 2018-01-31
Publication date: 2018-08-16
Also published as: US20200010925A1; JP2018127695A; AU2018218644B2; JP6900696B2; AU2018218644A1; PH12019501858A1

Abstract

Provided is a smelting method in which, for example, a metal oxide such as a nickel oxide ore including nickel oxide is used as a source material and is reduced with a carbonaceous reducing agent to obtain a reduced product, with which method efficient processing can be achieved. This metal oxide smelting method is, for example, a nickel oxide ore smelting method. Specifically, the method includes a reduction process step that has: a drying step in which a mixture that was obtained by mixing a metal oxide and a carbonaceous reducing agent is dried; a preheating step in which the dried mixture is preheated; a reduction step in which the preheated mixture is reduced using a rotary hearth furnace, said rotary hearth having a hearth that rotates and not having a partition structure in an interior; and a cooling step in which the obtained reduced product is cooled.

Description

Metal oxide smelting method

The present invention relates to a metal oxide smelting method, for example, a smelting method of obtaining a reduced product by reducing nickel oxide ore or the like with a carbonaceous reducing agent as a raw material.

As a smelting method of nickel oxide ore called limonite or saprolite, a dry smelting method for producing nickel matte using a smelting furnace, a dry smelting method for producing ferronickel using a rotary kiln or moving hearth furnace In addition, an HPAL process, which is a hydrometallurgical method for obtaining a nickel cobalt mixed sulfide (mixed sulfide) by adding a high-pressure acid leaching sulfiding agent using an autoclave, is known.

Among the various methods described above, particularly when the nickel oxide ore is reduced and smelted using a dry smelting method, the raw material nickel oxide ore is crushed into an appropriate size, etc. Alternatively, a slurry process or the like is performed as a pretreatment.

Specifically, when a nickel oxide ore is agglomerated, that is, when it is made into a lump from powder or fine particles, the nickel oxide ore and other components, for example, a reducing agent such as a binder or coke are mixed to form a mixture. Further, after performing moisture adjustment and the like, it is inserted into a lump manufacturing machine, for example, a lump or a lump called a pellet or briquette with a diameter of about 10 mm to 30 mm (hereinafter collectively referred to as “pellet”). ).

Now, the pellet needs to have a certain degree of air permeability in order to “fly” the contained moisture. In addition, if the reduction does not proceed uniformly in the pellet, the composition of the resulting reduced product becomes non-uniform, resulting in inconveniences such as metal dispersion or uneven distribution. It is important to maintain a uniform temperature as much as possible when the reduction treatment is performed.

In addition, it is a very important technique to coarsen the ferronickel produced by reduction. This is because when the produced ferronickel has a fine size of, for example, several tens of μm to several hundreds of μm, it becomes difficult to separate from the slag produced at the same time, and the recovery rate (yield) as ferronickel is greatly reduced. It is because it will do. For this reason, the process which coarsens the ferronickel after reduction | restoration is needed.

Also, how to keep the smelting cost low is an important technical matter, and continuous processing that can be operated with compact equipment is desired.

For example, Patent Document 1 discloses a technique related to a method for producing ferronickel, and particularly discloses a method for producing ferronickel or a ferronickel refining raw material with high efficiency from low-grade nickel oxide ore. Specifically, a mixing step in which a raw material containing nickel oxide and iron oxide and a carbonaceous reducing material are mixed to form a mixture, and the mixture is heated and reduced in a moving hearth furnace to obtain a reduced mixture. A method comprising a step and a melting step of melting a reducing mixture in a melting furnace to obtain ferronickel is disclosed.

Here, in Patent Document 1, it is necessary to reduce nickel oxide remaining in the reduction mixture in the melting furnace by setting the metallization rate of Ni in the reduction mixture to 40% or more, preferably 85% or more. There is a description that the required heat for reduction is reduced and the energy consumption in the melting furnace can be reduced. However, even if the metallization rate of Ni in the reduction mixture (hereinafter also referred to as “metalation rate”) is increased to reduce the heat required for reduction in the melting furnace, Ni can be metallized. Since the amount of heat required for the same is the same, the overall energy consumption is not reduced, and therefore the smelting cost is not reduced.

Patent Document 1 discloses that a reduced agglomerate (reduced mixture) reduced in a moving hearth furnace is usually about 1000 ° C. by a radiant cooling plate or a refrigerant spraying device provided in the moving hearth furnace. There is a description that it is discharged by a discharge device after being cooled. However, if the reduced agglomerate is cooled to about 1000 ° C. or lower and then discharged and recovered from the moving hearth furnace, the moving hearth furnace cools down, and the energy for raising the temperature again for reduction. Cost and cost. In addition, repeated cooling and heating increase the thermal shock to the furnace and shorten the life of the apparatus, which also increases the cost.

As described above, there are many problems in obtaining ferronickel by mixing and reducing nickel oxide ore and continuously refining at low cost.

JP 2004-156140 A

The present invention has been proposed in view of such circumstances. For example, a metal oxide such as nickel oxide ore containing nickel oxide or the like is used as a raw material and reduced with a carbonaceous reducing agent to obtain a reduced product. Provided is a method capable of efficiently treating a smelting method.

The present inventors have made extensive studies to solve the above-described problems. As a result, a reduction process that sequentially performs a drying process, a preheating process, a reduction process using a rotary hearth furnace that does not have a partition structure inside, and a cooling process on a mixture containing metal oxide raw materials. By performing the treatment, it was found that an efficient smelting treatment can be performed, and the present invention has been completed.

(1) The first invention of the present invention comprises a drying step of drying a mixture obtained by mixing a metal oxide and a carbonaceous reducing agent, a preheating step of preheating the dried mixture, and a hearth Using a rotary hearth furnace that rotates and does not have a partition structure inside, and includes a reduction process step of reducing the preheated mixture and a cooling step of cooling the resulting reduction product, This is a method for smelting metal oxides.

(2) According to a second aspect of the present invention, in the first aspect, the reduced product obtained through the reduction step is subjected to a temperature maintaining step of maintaining a predetermined temperature in the rotary hearth furnace, In this method, the reduced product is supplied to the cooling step after being held for a predetermined time.

(3) The third invention of the present invention is the metal oxide according to the first invention, wherein the treatment in the reduction step and the treatment in the temperature holding step are performed using the same rotary hearth furnace. It is a smelting method.

(4) According to a fourth aspect of the present invention, in the second or third aspect, in the temperature maintaining step, the reduced product is maintained at a temperature of 1300 ° C. or higher and 1500 ° C. or lower. It is.

(5) A fifth invention of the present invention is a metal oxide smelting method according to any one of the first to fourth inventions, wherein in the reduction step, the reduction temperature is reduced to 1200 ° C. or higher and 1500 ° C. or lower. is there.

(6) According to a sixth aspect of the present invention, in the fifth aspect, in the reduction step, the mixture is reduced at a two-stage reduction temperature, and the first-stage reduction temperature is 1200 ° C. or higher and 1450 ° C. or lower. Yes, the second stage reduction temperature is 1300 ° C. or higher and 1500 ° C. or lower.

(7) According to a seventh aspect of the present invention, in the sixth aspect, the rotary hearth furnace includes a plurality of heating sources, and the rotation by controlling the amount of energy supplied to each heating source. A metal oxide smelting method in which a temperature distribution in a hearth furnace is controlled.

(8) According to an eighth aspect of the present invention, in any one of the first to seventh aspects, the mixture to be dried in the drying step includes at least a metal oxide and a carbonaceous reducing agent. A metal oxide smelting method obtained through a mixing treatment step for obtaining a mixture and a pretreatment step for performing a treatment for agglomerating the obtained mixture or a treatment for filling a predetermined container. is there.

(9) According to a ninth aspect of the present invention, in any one of the first to eighth aspects, the reduced product cooled in the cooling step in the reduction treatment step is separated and recovered into metal and slag. It is a smelting method of a metal oxide which has a separation process.

(10) A tenth aspect of the present invention is a method for smelting a metal oxide according to any one of the first to ninth aspects, wherein the metal oxide is nickel oxide ore.

(11) The eleventh invention of the present invention is a metal oxide smelting method according to any one of the first to tenth inventions, wherein the reduced product contains ferronickel.

According to the present invention, for example, a method capable of efficiently treating a smelting method using a metal oxide such as nickel oxide ore containing nickel oxide or the like as a raw material to obtain a reduced product by reduction with a carbonaceous reducing agent. Can be provided.

It is process drawing which shows an example of the flow of the refining method of nickel oxide ore. It is a process which shows the process process performed in a reduction process process. It is a figure (plan view) which shows the example of composition of the rotary hearth furnace which a hearth rotates and does not have a partition structure inside.

<< 1. Outline of the present invention >>
The metal oxide smelting method according to the present invention is a smelting method in which a metal oxide is used as a raw material to perform a reduction treatment at a high temperature with a carbonaceous reducing agent to obtain a reduced product. For example, a method for producing ferronickel by using nickel oxide ore containing nickel oxide or iron oxide as a metal oxide as a raw material, and reducing the smelting raw material at a high temperature using a carbonaceous reducing agent Is mentioned.

Specifically, the metal oxide smelting method according to the present invention includes a drying step of drying a mixture obtained by mixing a metal oxide and a carbonaceous reducing agent, and a preheating step of preheating the dried mixture. And a reduction process step comprising: a reduction step in which the hearth rotates and a reduction step is performed using a rotary hearth furnace having no partition structure; and a cooling step in which the obtained reduction product is cooled. It is a feature.

As described above, according to the present invention, the mixture including the metal oxide as a raw material is subjected to the treatment in each step described above, and the hearth in the reduction step rotates, and the rotary hearth does not have a partition structure inside. By performing using a furnace, the metal contained in a metal oxide can be effectively metallized, and an efficient smelting process can be performed.

Hereinafter, as a specific embodiment of the present invention (hereinafter referred to as “the present embodiment”), a nickel oxide ore smelting method will be described as an example. Nickel oxide ore, which is a smelting raw material, contains at least nickel oxide. In this nickel oxide ore smelting method, ferronickel (iron-nickel alloy) is reduced by reducing nickel oxide and the like contained in the raw material. Can be manufactured.

The present invention is not limited to nickel oxide ore as a metal oxide, and the smelting method is not limited to a method for producing ferronickel from nickel oxide ore containing nickel oxide or the like. Various changes can be made without departing from the scope of the present invention.

≪2. Nickel Oxide Smelting Method >>
The method for smelting nickel oxide ore according to the present embodiment is to mix and knead nickel oxide ore, which is a smelting raw material, with a carbonaceous reducing agent, etc., to make a mixture, and to perform a reduction treatment on the mixture In this method, ferronickel and slag, which are metals, are generated. In addition, the ferronickel which is a metal can be collect | recovered by isolate | separating the metal from the mixture containing the metal and slag obtained through the reduction process.

FIG. 1 is a process diagram showing an example of the flow of a nickel oxide ore smelting method. As shown in FIG. 1, this nickel oxide ore smelting method comprises mixing treatment step S1 in which nickel oxide ore and a material such as a carbonaceous reducing agent are mixed to obtain a mixture, and the resulting mixture is agglomerated or A metal is separated from a mixture including a reduction charging pre-treatment step S2 for filling a predetermined container, a reduction treatment step S3 for reducing the mixture at a predetermined temperature (reduction temperature), and a mixture including metal and slag generated by the reduction treatment. And a separation step S4 to be recovered.

<2-1. Mixing process>
The mixing process step S1 is a step of obtaining a mixture by mixing raw material powders containing nickel oxide ore. Specifically, in the mixing treatment step S1, raw material powder having a particle size of about 0.2 mm to 0.8 mm, such as nickel oxide ore as a smelting raw material, iron ore, a flux component, a binder, a carbonaceous reducing agent, etc. Are mixed at a predetermined ratio to obtain a mixture.

The nickel oxide ore, which is a smelting raw ore, is not particularly limited, but limonite or saprolite ore can be used.

As the iron ore, for example, iron ore having an iron grade of about 50% or more, hematite obtained by wet refining of nickel oxide ore, and the like can be used.

Table 1 below shows an example of the composition (wt%) of nickel oxide ore and iron ore as raw materials. In addition, as a composition of a raw material, it is not limited to this.

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

Although it does not specifically limit as a carbonaceous reducing agent, For example, coal powder, coke, etc. are mentioned. In addition, it is preferable that this carbonaceous reducing agent has a magnitude | size equivalent to the particle size of the nickel oxide ore of a raw material ore. In addition, as the mixing amount of the carbonaceous reducing agent, for example, the chemical equivalent required to reduce the total amount of nickel oxide contained in the formed mixture to nickel metal and the ferric oxide contained in the pellets as metal When the total value of both chemical equivalents required for reduction to iron (also referred to as “total value of chemical equivalents” for the sake of convenience) is 100%, the carbon content is 5% or more and 60% or less. Can be adjusted as follows.

In the mixing treatment step S1, a mixture is obtained by uniformly mixing the raw material powder containing nickel oxide ore as described above. In this mixing, kneading may be performed at the same time, or kneading may be performed on a mixed word. Thus, by mixing and kneading the raw material powder, the contact area between the raw materials is increased and the voids are reduced, so that a reduction reaction is easily caused and a uniform reaction can be achieved. Thereby, the reaction time of the reduction reaction can be shortened, and quality variation is eliminated. As a result, it is possible to process with high productivity and to manufacture high quality ferronickel.

Further, after the raw material powder is kneaded, it may be extruded using an extruder. Thus, by extruding with an extruder, a much higher kneading effect can be obtained, the contact area between the raw material powders can be increased, and the voids can be reduced. Thereby, high quality ferronickel can be produced efficiently.

<2-2. Reduction input pretreatment process (pretreatment process)>
The reduction charging pretreatment step S2 is a step of agglomerating the mixture obtained in the mixing treatment step S1 into a lump or filling a container. That is, in this pre-reduction charging treatment step S2, the mixture obtained by mixing the raw material powders can be easily put into a furnace used in the reduction treatment step S3 described later, and the reduction reaction can be efficiently performed. Mold.

(Agglomeration of the mixture)
When the obtained mixture is agglomerated, the mixture is formed (granulated) into a lump. Specifically, a predetermined amount of water necessary for agglomeration is added to the obtained mixture, and for example, using an agglomerate production apparatus (rolling granulator, compression molding machine, extrusion molding machine, etc.), etc. It is formed into a lump (hereinafter also referred to as “pellet”).

The shape of the pellet is not particularly limited, and may be spherical, for example. Spherical pellets are preferable because the reduction reaction can proceed relatively uniformly. In addition, the size of the lump to be pelletized is not particularly limited. For example, in order to perform the reduction process (reduction process S33) through the drying process (drying process S31) and the preheating process (preheating process S32). The size of the pellets charged into the smelting furnace to be used (diameter in the case of spherical pellets) can be about 10 mm to 30 mm. Details of the reduction step will be described later.

(Filling the mixture into the container)
When filling the obtained mixture into a container, the mixture can be filled into a predetermined container while kneading the mixture with an extruder or the like. As described above, after filling the container, the reduction treatment may be performed in the next reduction treatment step S3 as it is, but it is preferable to press and harden the mixture filled in the container by a press or the like. By pressing and compacting the mixture in the container, the density of the mixture can be increased, the density can be made uniform, the reduction reaction can proceed more uniformly, and ferronickel with less quality variation can be produced. .

The shape of the mixture filled in the container is not particularly limited, but is preferably a rectangular parallelepiped, a cube, a cylinder, or the like. Moreover, although the size is not particularly limited, for example, in the case of a rectangular parallelepiped shape or a cubic shape, it is generally preferable that the vertical and horizontal inner dimensions are 500 mm or less. By adopting such a shape and size, smelting with small quality variation and high productivity can be performed.

<2-3. Reduction process>
In the reduction treatment step S3, the raw material powder is mixed in the mixing treatment step S1, and the mixture that has been agglomerated or filled in the container in the reduction pre-treatment step S2 is reduced and heated to a predetermined reduction temperature. By the reduction heat treatment of the mixture in the reduction treatment step S3, the smelting reaction proceeds to produce metal and slag.

FIG. 2 is a process diagram showing the process executed in the reduction process S3. As shown in FIG. 2, the reduction treatment step S3 in the present embodiment is obtained by a drying step S31 for drying the mixture, a preheating step S32 for preheating the dried mixture, and a reduction step S33 for reducing the mixture. Cooling step S35 for cooling the reduced product. Moreover, it preferably has a temperature holding step S34 for holding the reduced product obtained through the reduction step S33 in a predetermined temperature range.

Here, the process in the reduction step S33 is performed using a rotary hearth furnace in which the hearth rotates. The rotary hearth furnace does not have a partition structure inside. Furthermore, when performing the temperature holding process S34 which hold | maintains a reduced product in a predetermined temperature range, at least the process in the reduction process S33 and the process in the temperature holding process S34 are performed in a rotary hearth furnace.

In this way, by performing these treatments in the rotary hearth furnace, the temperature in the rotary hearth furnace can be maintained at a high temperature. Therefore, the temperature is increased or decreased at each process in each process. The energy cost can be significantly reduced. Moreover, according to the process using a rotary hearth furnace, control and management of temperature become easy. For these reasons, it is possible to continuously and stably produce ferronickel with good quality with high productivity.

Furthermore, by using a rotary hearth furnace that does not have a partition structure inside, the maintenance cost of the rotary hearth furnace can be reduced, enabling efficient processing and reducing the temperature in the furnace. Even more uniform control is possible.

(1) Drying process In drying process S31, a drying process is performed with respect to the mixture obtained by mixing raw material powder. The purpose of this drying step S31 is mainly to remove water and crystal water in the mixture.

The mixture obtained in the mixing treatment step S1 contains a lot of moisture and the like, and when rapidly heated to a high temperature such as the reduction temperature during the reduction treatment, the moisture is vaporized, expanded and agglomerated at once. The mixture breaks or breaks up to break up in some cases, making it difficult to perform a uniform reduction treatment. Therefore, prior to the reduction treatment, the mixture is subjected to a drying treatment to remove moisture, thereby preventing the destruction of pellets and the like.

It is preferable that the drying process in drying process S31 is performed in the form connected to a rotary hearth furnace. Although it is conceivable to provide an area (drying area) for performing a drying process in the rotary hearth furnace, in such a case, the drying process in the drying area becomes rate-limiting, and the process and temperature in the reduction step S33 are performed. There is a possibility of affecting the processing in the holding step S34.

Therefore, the drying process in the drying step S31 is preferably performed in a drying chamber provided outside the rotary hearth furnace and connected to the rotary hearth furnace. In addition, although mentioned later in detail, FIG. 3 shows a configuration example of the rotary hearth furnace 1 and the drying chamber 20 connected to the rotary hearth furnace 1. Thus, by providing the drying chamber 20 outside the rotary hearth furnace 1, the drying chamber can be designed completely different from the steps such as preheating, reduction, and cooling described later, and desirable drying treatment, preheat treatment, reduction treatment, It becomes easy to perform each cooling process. For example, when a lot of moisture remains in the mixture depending on the raw material, the drying process takes time. Therefore, the drying chamber 20 may be designed to have a long overall length, or the mixture in the drying chamber 20 What is necessary is just to design so that a conveyance speed may become slow.

As the drying treatment in the drying chamber 20, for example, the solid content in the mixture can be about 70% by weight and the water content can be about 30% by weight. Further, the drying method is not particularly limited, but can be performed by blowing hot air on the mixture conveyed in the drying chamber 20. Also, the drying temperature is not particularly limited, but from the viewpoint of preventing the reduction reaction from starting, it is preferably 500 ° C. or lower, and it is preferable to uniformly dry at the temperature of 500 ° C. or lower.

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

(2) Preheating process In preheating process S32, the mixture after water | moisture content was removed by the drying process in drying process S31 is preheated (preheating).

If the mixture is charged into the rotary hearth furnace and raised to a high reduction temperature, the mixture may break or become powdery due to thermal stress. In addition, the temperature of the mixture may not rise uniformly, causing variations in the reduction reaction, and the quality of the metal produced may vary. For this reason, it is preferable to preheat the mixture to a predetermined temperature after the drying treatment, whereby the destruction of the mixture and variations in the reduction reaction can be suppressed.

The preheating process in the preheating step S32 is preferably performed in a processing chamber provided outside the rotary hearth furnace, similarly to the drying process, and is performed in a preheating chamber connected to the rotary hearth furnace. It is preferable to do so. In addition, although the structural example of the preheating chamber 30 connected to the rotary hearth furnace 1 is shown in FIG. 3, this preheating chamber 30 is provided outside the furnace of the rotary hearth furnace 1, and the drying chamber which performs a drying process 20 are continuously provided. Thus, by performing the pre-heat treatment in the pre-heating chamber 30 provided outside the rotary hearth furnace 1, the temperature in the rotary hearth furnace 1 for performing the reduction process can be maintained at a high temperature, and heating is performed. The energy required can be saved significantly.

The preheat treatment in the preheating chamber 30 is not particularly limited, but is preferably performed at a preheating temperature of 600 ° C or higher, and more preferably at a preheating temperature of 700 ° C or higher and 1280 ° C or lower. By processing at the preheating temperature in such a range, the energy required for reheating to the reduction temperature in the subsequent reduction process can be greatly reduced.

(3) Reduction step In the reduction step S33, the mixture preheated in the preheating step S32 is reduced at a predetermined reduction temperature. Specifically, the reduction process in the reduction step S33 is performed using a rotary hearth furnace in which the hearth rotates. Furthermore, the rotary hearth furnace does not have a partition structure in the furnace, that is, does not have a structure such as a partition or a sill.

In this way, by performing reduction treatment using a rotary hearth furnace, the temperature inside the furnace can be maintained in a high temperature range, and there is no need to raise or lower the temperature, greatly reducing energy costs. can do. Moreover, temperature control and management become easy, and high quality ferronickel can be produced stably. Furthermore, by using a rotary hearth furnace that does not have a partition structure in the furnace, the temperature in the furnace can be more uniformly controlled. Moreover, the initial cost and maintenance cost for the partition structure can be reduced, and more efficient processing can be performed.

[Configuration of rotary hearth furnace]
Here, FIG. 3 is a diagram (plan view) showing a configuration example of a rotary hearth furnace in which the hearth rotates. As shown in FIG. 3, the rotary hearth furnace 1 has a region 10 in which the hearth rotates, and this region 10 does not have a partition structure such as a partition or a sill.

For example, as a rotary hearth furnace, it is conceivable to arbitrarily divide a rotating hearth area into a plurality of sections and to configure a plurality of divided processing chambers. In the plurality of processing chambers, the reaction temperatures can be adjusted and controlled to perform different processes. And at this time, it can be set as the structure divided by providing a partition wall between each process chamber, ie, between each process, and, thereby, arbitrary temperature settings etc. can be performed in each process chamber. Can also reduce energy loss.

However, in the rotary hearth furnace, if the partition structure as described above is provided and divided into a plurality of processing chambers, the structure of the rotary hearth furnace becomes complicated and not only the initial cost is increased, but also the maintenance cost is increased. Moreover, it is considered that by having such a partition structure, it is difficult to set a uniform temperature in the furnace, the reduction reaction does not proceed sufficiently, and becomes inefficient.

Therefore, in this embodiment, a rotary hearth furnace having no partition structure is used. By using such a rotary hearth furnace, the temperature in the furnace can be controlled more uniformly, and the initial cost and maintenance cost for the partition structure can be reduced, so that efficient processing is possible. It can be performed.

As described above, the rotary hearth furnace 1 includes a hearth that rotates and moves on a plane. Therefore, in the rotary hearth furnace 1, the hearth on which the mixture is placed rotates at a predetermined speed, so that the reduction process is performed while the mixture is being transferred. In addition, while the arrow on the rotary hearth furnace 1 in FIG. 3 shows the rotation direction of a hearth, it shows the moving direction of a processed material (mixture).

Further, the rotary hearth furnace 1 is connected to a drying chamber 20 provided outside the furnace and a preheating chamber 30, and as described above, after the drying treatment is performed on the mixture in the drying chamber 20. The dried mixture moves to the preheating chamber 30 and is preheated, and the preheated mixture is sequentially transferred into the rotary hearth furnace 1. Further, the rotary hearth furnace 1 is connected to a cooling chamber 40 provided outside the furnace, and a reduction product obtained by performing a reduction process is transferred to the cooling chamber 40 and subjected to a cooling process ( Cooling step S35) which will be described later.

In the rotary hearth furnace 1, a plurality of heating sources are provided, and the temperature distribution in the rotary hearth furnace 1 is controlled by controlling the amount of energy supplied to each heating source. Can do. For example, in the reduction process using the rotary hearth furnace 1, the mixture is reduced at a two-stage reduction temperature, and at this time, the first heating for adjusting a predetermined position in the furnace to the first-stage reduction temperature. And a second heating source for adjusting a predetermined position in the furnace to the reduction temperature of the second stage. Then, by controlling the amount of energy supplied to each heating source, the temperature distribution inside the rotary hearth furnace 1 is controlled to cause an appropriate reduction reaction.

Thus, by providing a plurality of heating sources in the rotary hearth furnace 1 used in the reduction treatment, and controlling the temperature distribution in the furnace by controlling the amount of energy supplied to each heating source, A treatment according to the degree of reduction can be performed, and a reduction reaction can be effectively generated to increase the recovery rate of nickel to ferronickel metal.

Further, such an aspect is particularly effective when performing a high-temperature holding step S34 described later. That is, by providing a plurality of heating sources in the rotary hearth furnace 1 and controlling the temperature distribution inside the furnace by controlling the amount of energy supplied to each heating source, for example, the rotary hearth furnace 1 is heated by the first heating source. In the first processing region, reduction processing (reduction step S33) is performed, and in the second processing region heated by the second heating source, temperature holding processing (temperature holding step S34) is performed. Thereby, after performing the reduction process with respect to a mixture effectively in a 1st process area | region and producing | generating the reduced product which consists of a mixture of a metal and slag, holding a reduced product at a high temperature in a 2nd process area | region. Thus, it is possible to efficiently perform the process of effectively coarsening the metal. The processing in the high temperature holding step S34 (high temperature holding processing) will be described in detail later.

[Reduction treatment in rotary hearth furnace]
In the reduction treatment using the rotary hearth furnace 1, nickel oxide, which is a metal oxide contained in nickel oxide ore, is reduced as completely as possible, while iron ore mixed as raw material powder with nickel oxide ore, etc. It is preferable that only a part of the iron oxide derived from is reduced so that the desired nickel-grade ferronickel is obtained.

Specifically, the reduction temperature is not particularly limited, but is preferably in the range of 1200 ° C to 1500 ° C, and more preferably in the range of 1300 ° C to 1400 ° C. By reducing in such a temperature range, a reduction reaction can be caused uniformly and a metal (ferronickel metal) with suppressed quality variation can be generated. More preferably, by performing reduction at a reduction temperature in the range of 1300 ° C. or higher and 1400 ° C. or lower, a desired reduction reaction can be caused in a relatively short time.

In the reduction treatment, the mixture may be reduced at a two-stage reduction temperature. For example, the first stage reduction temperature is set to 1200 ° C. or higher and 1450 ° C. or lower, and the second stage reduction temperature is set to 1300 ° C. or higher and 1500 ° C. or lower, and the mixture placed on the hearth of the rotary hearth furnace 1 is transferred. A reduction process is performed on the surface. In this way, by performing the reduction treatment on the mixture at the two-stage reduction temperature, first, the reduction reaction on the mixture proceeds in the first stage, and then the metal in the reduced product generated in the second stage is precipitated. However, it can be made coarse.

In the reduction treatment, the internal temperature of the reduction chamber in the rotary hearth furnace 1 is raised until the reduction temperature is in the above-described range, and the temperature is maintained after the temperature rise. Further, as described above, when a plurality of heating sources are provided in the rotary hearth furnace 1, the temperature distribution in the furnace can be controlled by controlling the amount of energy supplied to each heating source.

Further, in the reduction treatment, a reaction inhibitor such as ash is placed on the hearth of the rotary hearth furnace 1 to be used in order to prevent the hearth and the mixture sample from reacting and becoming difficult to recover. The mixture sample may be placed on the reaction suppressing material. For example, as the ash as a reaction inhibitor, a ash having a main component of SiO ₂ and a small amount of oxides such as Al ₂ O ₃ and MgO can be used as the other components.

(4) Temperature holding process Although it is not an indispensable aspect, you may make it perform the temperature holding process S34 which hold | maintains the reduced material obtained through reduction process S33 on a predetermined high temperature condition in a rotary hearth furnace. . In this way, the reduced product obtained by the reduction treatment at the predetermined reduction temperature in the reduction step S33 is not immediately cooled, but is held in a high-temperature atmosphere, so that the metal component generated in the reduced product is retained. It can be coarsened by sedimentation.

When the metal component in the reduced product is small in the state obtained by the reduction treatment, for example, when it is a bulk metal of about 200 μm or less, the metal and slag are separated in the subsequent separation step S4. Will become difficult. For this reason, if necessary, the reduced product is kept at a high temperature for a certain period of time after the reduction reaction is completed, so that the metal having a higher specific gravity than the slag in the reduced product is settled and aggregated. Make it coarse.

In addition, when the metal is coarsened to a level at which there is no problem in manufacturing due to the reduction process in the reduction step S33, it is not particularly necessary to provide the temperature holding step S34.

Specifically, the reduced product holding temperature in the temperature holding step S34 is preferably in the high temperature range of 1300 ° C to 1500 ° C. By holding the reduced product at a high temperature in such a range, the metal component in the reduced product can be efficiently precipitated to form a coarse metal. Note that if the holding temperature is lower than 1300 ° C., a large part of the reduced product becomes a solid phase, so that the metal component does not settle or even takes time, which is not preferable. On the other hand, if the holding temperature exceeds 1500 ° C., the reaction between the obtained reduced product and the hearth material proceeds, and the reduced product may not be recovered, and the furnace may be damaged. .

Here, it is preferable that the treatment in the temperature holding step S34 is performed continuously following the reduction treatment in the rotary hearth furnace 1 used in the reduction step S33. Thus, the metal component in the reduction product is efficiently settled by continuously performing the process of maintaining the reduction product obtained through the reduction treatment at a predetermined temperature using the rotary hearth furnace 1. Can be coarsened. In addition, the process in the reduction process S33 and the process in the temperature holding process S34 are continuously performed using the rotary hearth furnace 1 instead of separate furnaces, so that heat loss between the processes is reduced and efficient. Enable operation.

Specifically, when the reduction process and the temperature holding process are performed in the same rotary hearth furnace 1, a plurality of heating sources are provided in the rotary hearth furnace 1, and the amount of energy supplied to each heating source is set. By controlling, the temperature distribution inside the furnace can be controlled. That is, the temperature in the reduction step S33 (reduction temperature) and the temperature in the temperature holding step S34 (holding temperature) are controlled by different heating sources. Thereby, even if it is the rotary hearth furnace 1 which does not have a partition structure inside, temperature can be controlled exactly and an efficient process can be performed.

(5) Cooling step In the cooling step S35, the reduction product obtained through the reduction step S33 or the reduction product after being held at a high temperature for a predetermined time in the temperature holding step S34 is separated and recovered in the subsequent separation step S4. Cool down to a temperature where you can.

Since the cooling step S35 is a step of cooling the reduction product obtained as described above, it is preferably performed in a cooling chamber connected to the outside of the rotary hearth furnace 1. FIG. 3 shows a configuration example of the cooling chamber 40 connected to the rotary hearth furnace 1. The cooling chamber 40 is provided outside the rotary hearth furnace 1. Thus, by performing the cooling process in the cooling chamber 40 provided outside the rotary hearth furnace 1, a decrease in the internal temperature of the rotary hearth furnace 1 can be prevented and energy loss can be suppressed. it can. This enables efficient production of ferronickel.

The temperature in the cooling step S35 (hereinafter also referred to as “recovery temperature”) is a temperature at which the reduced product can be handled substantially as a solid, and is preferably as high as possible. By making the temperature at the time of recovery as high as possible, energy loss can be reduced even when the hearth of the rotary hearth furnace 1 that rotates and moves back to the connection point with the preheating chamber 30 that executes the preheating step S32, and reheating is possible. The required energy can be further saved.

Specifically, the recovery temperature is preferably 600 ° C. or higher. Thus, by making the temperature at the time of recovery high, the energy required for reheating can be greatly reduced, and efficient smelting treatment can be performed at low cost. Moreover, by reducing the temperature difference in the rotary hearth furnace 1, the thermal stress applied to the hearth, the furnace wall, etc. can be reduced, and the life of the rotary hearth furnace 1 can be greatly extended. In addition, problems during operation can be greatly reduced.

<2-4. Separation process>
Separation process S4 isolate | separates and collect | recovers a metal (ferronickel metal) from the reduced material produced | generated in reduction process process S3. Specifically, in the separation step S4, a metal phase is obtained from a mixture (reduced product) including a metal phase (metal solid phase) and a slag phase (slag solid phase) obtained by subjecting the mixture to reduction heat treatment. Separate and collect.

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 materials by sieving, separation by specific gravity, separation by magnetic force, etc. Can be used. In addition, the obtained metal phase and slag phase can be easily separated because of poor wettability, and for example, when a large mixture is dropped with a predetermined drop, or when sieving By giving an impact such as giving a predetermined vibration, the metal phase and the slag phase can be easily separated from the mixture.

Thus, by separating the metal phase and the slag phase, the metal phase can be recovered and made into a ferronickel product.

Hereinafter, although an example of the present invention is shown and explained more concretely, the present invention is not limited to the following example at all.

(Mixing process)
Nickel oxide ore as raw material ore, iron ore, silica sand and limestone as flux components, binder, and coal powder as carbonaceous reducing agent (carbon content: 85% by weight, average particle size: about 190 μm) Were mixed using a mixer while adding an appropriate amount of water to obtain a mixture. The carbonaceous reducing agent is 33% in terms of carbon when the total value of chemical equivalents required to reduce nickel oxide and iron oxide (Fe ₂ O ₃ ) to metal without excess or deficiency is 100%. In an amount corresponding to.

The mixture obtained by mixing with a mixer was kneaded with a twin-screw kneader.

(Reduction input pretreatment process)
Next, the mixture obtained by kneading was classified into nine, and each sample of the mixture was formed into spherical pellets of φ19 ± 1.5 mm using a bread granulator.

(Reduction treatment process)
Next, using the reduction hearth furnace 1 illustrated in FIG. 3, reduction treatment was performed by changing the treatment conditions using each of the nine mixture samples. As the rotary hearth furnace 1, as shown in FIG. 3, the one in which the hearth rotates and does not have a partition structure inside was used. Further, the rotary hearth furnace 1 includes a drying chamber 20 for drying pellets, a preheating chamber 30 provided continuously to the drying chamber 20, and a reduction obtained by reduction treatment in the furnace. A cooling chamber 40 for cooling the object was connected.

Specifically, nine pellet samples were placed in the drying chamber 20 connected to the outside of the reduction hearth furnace 1 and dried. In the drying process, hot air of 250 ° C. to 350 ° C. is blown onto the pellets in a nitrogen atmosphere that does not substantially contain oxygen so that the pellets have a solid content of about 70% by weight and water content of about 30% by weight. Went by. Table 3 below shows the solid content composition (excluding carbon) of the pellets after the drying treatment.

Subsequently, the pellets after the drying treatment are transferred to a preheating chamber 30 continuously provided in the drying chamber 20, and the temperature in the preheating chamber 30 is maintained in a range of 700 ° C. or higher and 1280 ° C. or lower, so Heat treatment was performed.

Subsequently, the pellets after the pre-heat treatment were transferred into the rotary hearth furnace 1 and subjected to reduction treatment and temperature holding treatment. Specifically, as the rotary hearth furnace 1, two heating sources are provided, and the amount of energy supplied to each heating source is controlled, so that the temperature of the reduction treatment and the temperature of the high temperature holding treatment are different. I did it.

In addition, the hearth of the rotary hearth furnace 1 is prevented in advance from the viewpoint of suppressing the reaction between the hearth and the sample as much as possible in order to prevent the hearth and the sample from reacting and becoming difficult to recover. Ash was spread on the hearth (the main component is SiO ₂ and other components contain a small amount of oxides such as Al ₂ O ₃ and MgO).

In addition, in the embodiment in which the treatment for holding the reduced product at a high temperature is not performed, the temperature of the high temperature holding treatment is set to 0 ° C. Moreover, about the reduction | restoration thing obtained through the reduction process or a reduction process and a temperature maintenance process, it transfers to the cooling chamber connected to the rotary hearth furnace 1, and it cools to room temperature rapidly, flowing nitrogen, and air | atmosphere. Removed inside. The reductant was collected from the rotary hearth furnace in a form in which the reductant was transferred to the cooling chamber 40, and the reductant was collected along a guide installed in the cooling chamber 40.

Table 4 below shows the conditions of the reduction treatment and the temperature holding treatment in the reduction treatment step.

Further, the nickel quality of the sample taken out was analyzed by an ICP emission spectroscopic analyzer (SHIMAZU S-8100 type), and the nickel metal ratio and the nickel content in the metal were calculated. The nickel metal ratio was calculated by the following formula (i), and the nickel content in the metal was calculated by the following formula (ii).
Nickel metal ratio = amount of Ni metalized in pellets / (total amount of Ni in pellets) × 100 (%) (i)
Nickel content in metal = amount of Ni metalized in pellet / (total amount of metalized Ni and Fe in pellet) × 100 (%) (ii)

Moreover, the collect | recovered sample collect | recovered the metal (ferronickel metal) by the magnetic selection after the grinding | pulverization by wet processing. Then, the Ni metal recovery rate was calculated from the Ni content and the input amount of the input nickel oxide ore and the recovered Ni amount. The Ni metal recovery rate was calculated by the following formula (iii).
Ni metal recovery rate = recovered Ni amount ÷ (amount of ore charged × Ni content ratio in ore) × 100 (iii) formula

As can be seen from Table 4, with respect to the mixture containing raw material ore, the drying step, the preheating step, the reduction step of reducing using a rotary hearth furnace in which the hearth rotates, and the obtained reduction product are cooled. By performing a reduction treatment step having at least a cooling step, ferronickel with high nickel quality could be obtained, and nickel could be recovered with a high recovery rate of 90% or more.

In addition, reduction processing, or reduction processing and temperature holding processing are performed using a rotary hearth furnace, so that the internal temperature of the rotary hearth furnace can be held at a high temperature, and energy required for reheating. Was suppressed, and an efficient smelting process could be performed.

Furthermore, by using a rotary hearth furnace that does not have a partition structure inside, the internal temperature can be kept uniform, and the initial cost and maintenance cost can be effectively reduced.

1 rotary hearth furnace 10 area 20 drying room 30 preheating room 40 cooling room

Claims

A drying step of drying the mixture obtained by mixing the metal oxide and the carbonaceous reducing agent;
A preheating step for preheating the dried mixture;
A reduction step of reducing the preheated mixture using a rotary hearth furnace in which the hearth rotates and does not have a partition structure inside;
A cooling step for cooling the obtained reduced product,
A method for smelting a metal oxide, comprising a reduction treatment step comprising:
The reduced product obtained through the reduction step is subjected to a temperature holding step for holding the reduced product at a predetermined temperature in the rotary hearth furnace. After holding the reduced product for a predetermined time, the reduced product is supplied to the cooling step. The method for smelting a metal oxide according to claim 1.
The metal oxide smelting method according to claim 2, wherein the treatment in the reduction step and the treatment in the temperature holding step are performed using the same rotary hearth furnace.
The metal oxide smelting method according to claim 2 or 3, wherein in the temperature holding step, the reduced product is held at a temperature of 1300 ° C or higher and 1500 ° C or lower.
5. The method for smelting a metal oxide according to claim 1, wherein the reduction is performed at a reduction temperature of 1200 ° C. to 1500 ° C. 5.
In the reduction step, the mixture is reduced at a two-stage reduction temperature,
The reduction temperature in the first stage is 1200 ° C. or higher and 1450 ° C. or lower,
The metal oxide smelting method according to claim 5, wherein the reduction temperature in the second stage is 1300 ° C. or higher and 1500 ° C. or lower.
The temperature distribution in the rotary hearth furnace is controlled by controlling the amount of energy supplied to each of the heating sources, and the rotary hearth furnace includes a plurality of heating sources. A method for smelting metal oxides.
The mixture to be dried in the drying step is
At least a mixing treatment step of mixing a metal oxide and a carbonaceous reducing agent to obtain a mixture;
A pretreatment step of performing a process of agglomerating the obtained mixture or a process of filling a predetermined container;
The method for smelting a metal oxide according to any one of claims 1 to 7, wherein the metal oxide is smelted through the process.
The metal oxide smelting method according to any one of claims 1 to 8, further comprising a separation step of separating and recovering the reduced product cooled in the cooling step in the reduction treatment step into metal and slag. .
The metal oxide smelting method according to any one of claims 1 to 9, wherein the metal oxide is nickel oxide ore.
The metal oxide smelting method according to any one of claims 1 to 10, wherein the reduced product contains ferronickel.