JP6953835B2 - Oxidized ore smelting method - Google Patents

Description

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

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. There are known pyrometallurgical methods for producing ferrometallurgy, which is an alloy of the above, and wet smelting methods for producing mixed smelted using an ore.

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 the water content is adjusted, the mixture is charged into a lump manufacturing machine, and for example, a lump (pellet, briquette, etc.) having a side or a diameter of about 10 mm to 30 mm is simply referred to as "pellet". ) Is common.

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 producing 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 to 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.

Furthermore, how low the smelting cost can be kept is also an important technical issue, and continuous processing that can be operated with compact equipment is desired.

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

Here, Patent Document 1 describes that it is necessary to reduce the nickel oxide remaining in the reduction mixture in a 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 heat required for reduction can be 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 required for reduction in the melting furnace, Ni is metallized. Since the amount of heat required for the smelting is the same, it does not reduce the energy consumption as a whole, and therefore does not reduce the smelting cost.

Further, in Patent Document 1, the reduced agglomerate (reduction mixture) reduced in the mobile hearth furnace is usually about 1000 ° C. by a radiation type cooling plate or a refrigerant spraying device provided in the mobile hearth furnace. There is a description that it is discharged by the discharge device after being cooled down. However, if the reduced agglomerates are cooled to about 1000 ° C. or lower and then discharged from the mobile hearth furnace and recovered, the mobile hearth furnace will be cooled, and energy for raising the temperature again for reduction will occur. It costs money. In addition, repeated cooling and heating increase the thermal shock to the furnace, shortening the life of the equipment, which also causes an increase in cost.

In this way, when the raw material nickel oxide ore is mixed and the mixture is reduced to produce metal, there are many ways to improve productivity and produce high quality metal while suppressing the production cost. There was a problem.

Japanese Unexamined Patent Publication No. 2004-156140

The present invention has been proposed in view of such circumstances, and effectively reduces energy costs in a smelting method for producing metal by reducing a mixture containing oxide ore such as nickel oxide ore. It is an object of the present invention to provide a method capable of efficiently producing high quality metal with high productivity.

The present inventors have made extensive studies to solve the above-mentioned problems. As a result, the mixture containing the raw material of the metal oxide is subjected to a reduction treatment in which a drying step, a preheating step, a reduction step using a rotary hearth furnace, and a cooling step are sequentially executed, and in particular, the cooling step. In the above, it was found that an efficient smelting process can be performed by performing a specific cooling process divided into two stages, and the present invention has been completed.

(1) The first invention of the present invention includes a drying step of drying a mixture obtained by mixing an oxide ore and a carbonaceous reducing agent, a preheating step of preheating the dried mixture, and a hearth rotating. A reduction treatment step including a reduction step of reducing the preheated mixture and a cooling step of cooling the obtained reduced product by using a rotary hearth furnace is included, and the cooling step includes cooling of the reduced product. The treatment is divided into two stages, the reduced product is cooled stepwise, and the first stage cooling treatment is performed in the furnace of the rotary hearth furnace in which the reduction treatment in the reduction step is executed, and the second stage cooling is performed. This is a method for smelting oxide ore, in which the treatment is performed outside the rotary hearth furnace.

(2) The second invention of the present invention is, in the first invention, a method for smelting an oxidized ore in which the reduction temperature is reduced to 1200 ° C. or higher and 1450 ° C. or lower in the reduction step.

(3) In the third invention of the present invention, in the first or second invention, in the cooling step, the temperature of the reduced product is cooled to a range of 700 ° C. or higher and 1280 ° C. or lower in the first step cooling treatment. , A method of smelting oxide ore.

(4) In the fourth invention of the present invention, in any one of the first to third inventions, the temperature of the reduced product obtained through the second-step cooling treatment in the cooling step is 600 ° C. or higher. This is a method for smelting oxidized ore.

(5) In the fifth aspect of the present invention, in any one of the first to fourth inventions, the temperature holding of the reduced product obtained through the reduction step is maintained at a predetermined temperature in the rotary hearth furnace. A method for smelting an oxide ore, which further comprises a step, in which the reduced product is held for a predetermined time in the temperature holding step, and then the reduced product is supplied to the cooling step.

(6) In the sixth invention of the present invention, in the fifth invention, the treatment in the reduction step and the treatment in the temperature holding step are executed in the same rotary hearth furnace, and in the cooling step, the treatment is performed. This is a method for smelting oxide ore, in which a first-stage cooling treatment is performed on a reduced product held for a predetermined time in a rotary hearth furnace.

(7) The seventh invention of the present invention is the method for smelting oxide ore in the fifth or sixth invention, in which the reduced product is maintained at a temperature of 1300 ° C. or higher and 1500 ° C. or lower in the temperature holding step. be.

(8) In the eighth invention of the present invention, in any one of the first to seventh inventions, the treatment in the preheating step is executed in the same rotary hearth furnace in which the treatment in the reduction step is performed. This is a method for smelting oxidized ore.

(9) In the ninth aspect of the present invention, in any one of the first to eighth aspects, the mixture to be dried in the drying step is a mixture of at least an oxide ore and a carbonaceous reducing agent. It is a method for smelting oxide ore, which is obtained through a mixing treatment step of obtaining a mixture and a pretreatment step of agglomerating the obtained mixture or filling a predetermined container.

(10) In the tenth aspect of the present invention, in any one of the first to ninth inventions, the reduced product cooled to a predetermined temperature in the cooling step in the reduction treatment step is separated into metal and slag. This is a method for smelting oxide ore, which has a separation step of recovering the slag.

(11) The eleventh invention of the present invention is a method for smelting an oxide ore, which is a nickel oxide ore in any one of the first to tenth inventions.

(12) The twelfth invention of the present invention is the method for smelting an oxide ore in which the reduced product contains ferronickel in any one of the first to eleventh inventions.

According to the present invention, in a smelting method for producing metal by reducing a mixture containing oxide ore, energy cost is effectively reduced, and high quality metal is efficiently produced with high productivity. be able to.

It is a process drawing which shows an example of the flow of the smelting method of nickel oxide ore. It is a process drawing which shows the process process executed in the reduction process process. It is a block diagram which shows an example of the structure of the rotary hearth furnace.

Hereinafter, a specific embodiment of the present invention (hereinafter, referred to as “the present embodiment”) 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 the present invention ≫
In the method for smelting an oxidized ore according to the present invention, an oxidized ore is used as a raw material, the oxide ore and a carbonaceous reducing agent are mixed to form a mixture, and the obtained mixture is subjected to a reduction treatment at a high temperature to reduce the product. It is a method of manufacturing the metal. For example, as an 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 a carbonaceous reducing agent to preferentially reduce nickel contained in the mixture at a high temperature. Further, there is a method of producing ferronickel, which is an alloy of iron and nickel, by partially reducing iron.

Specifically, the method for smelting an oxide ore according to the present invention includes a drying step of drying a mixture obtained by mixing an oxide ore and a carbonaceous reducing agent, and a preheating step of preheating the dried mixture. It includes a reduction treatment step including a reduction step of reducing the preheated mixture using a rotary hearth furnace in which the hearth rotates, and a cooling step of cooling the obtained reduced product. Then, in the cooling step of cooling the reduced product, the cooling treatment for the reduced product was divided into two stages to cool the reduced product in stages, and the first stage cooling treatment was executed in the reduction step. It is characterized in that it is performed inside the rotary hearth furnace and the second stage cooling process is performed outside the rotary hearth furnace.

According to such a smelting method, the reduced product obtained through the reduction treatment is divided into two stages and cooled in stages, so that the cooling temperature in the first stage is set relatively high. be able to. In particular, in this cooling step, since the first-stage cooling treatment is performed in the furnace of the rotary hearth furnace that has been subjected to the reduction treatment, the furnace of the rotary hearth furnace that has executed the cooling treatment. The temperature of the floor can be maintained high, and even when the hearth returns to the preheating step or the reduction step, the energy for heating to the appropriate temperature for the treatment in each step can be reduced.

As a result, the temperature difference in the rotary hearth furnace can be reduced, and as a result, the thermal stress applied to the hearth and the furnace wall can be reduced, and the life of the furnace can be extended. In addition, defects during operation can be effectively reduced.

Furthermore, since the second stage cooling process is performed outside the rotary hearth furnace, the target temperature of the second stage cooling process is set independently of the appropriate temperature of the rotary hearth furnace. be able to. Therefore, it can be appropriately adjusted according to the purpose without affecting the processing time of the preheating step and the reducing step.

Furthermore, by cooling the reduced product stepwise over two stages and setting the temperature relatively high in the first stage cooling treatment, the metal components generated in the reduced product are sufficiently precipitated and coarse. Can be made. As a result, in the separation step S4 described later, the target ferronickel metal can be easily separated and efficiently recovered.

Hereinafter, as a specific embodiment of the present invention (hereinafter, referred to as “the present embodiment”), a method for smelting nickel oxide ore will be described as an example. As described above, the nickel oxide ore as a smelting raw material contains at least nickel oxide (NiO) and iron oxide (Fe ₂ O ₃ ), and the nickel oxide ore is reduced as a smelting raw material. By doing so, an iron-nickel alloy (ferronickel) can be produced as a metal.

The present invention is not limited to the nickel oxide ore as the oxide ore, and the smelting method is not limited to the method of producing ferronickel from the nickel oxide ore containing nickel oxide or the like.

≪2. Nickel oxide ore 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 raw material for smelting, with a carbonaceous reducing agent or the like to prepare a mixture, and to reduce the mixture. , A method of producing ferronickel, which is a metal, and slag. Ferronickel, which is a metal, can be recovered by separating the metal from a mixture containing the metal and slag obtained through the reduction treatment.

FIG. 1 is a process diagram showing an example of a flow of a method for smelting nickel oxide ore. As shown in FIG. 1, this method for smelting nickel oxide ore includes a mixing treatment step S1 in which a nickel oxide ore and a material such as a carbonaceous reducing agent are mixed to obtain a mixture, and the obtained mixture is agglomerated or agglomerated. The metal is separated from the mixture containing the metal and slag produced by the reduction treatment, the reduction injection pretreatment step S2 for filling a predetermined container, the reduction treatment step S3 for reducing the mixture at a predetermined temperature (reduction temperature), and the reduction treatment. It has a separation step S4 for collecting.

<2-1. Mixing process>
The mixing treatment step S1 is a step of mixing the raw material powder containing nickel oxide ore to obtain a mixture. Specifically, in the mixing treatment step S1, the raw material ore, nickel oxide ore, carbonaceous reducing agent, and, if necessary, iron ore, flux component, binder, etc., for example, have a particle size of 0.2 mm to 0. A mixture is obtained by mixing with a raw material powder of about 0.8 mm at a predetermined ratio.

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

The mixing amount of the carbonaceous reducing agent is the chemical equivalent required to reduce the total amount of nickel oxide constituting the nickel oxide ore to nickel metal, and the chemical equivalent required to reduce iron oxide (ferrous oxide) to metallic iron. When the total value of both chemical equivalents (also referred to as "total value of chemical equivalents" for convenience) is 100% by mass, the ratio of carbon content of 5% by mass or more and 60% by mass or less is preferable, and more preferably. The ratio of the carbon content can be adjusted to be 10% by mass or more and 40% by mass or less. In this way, by setting the mixing amount of the carbonaceous reducing agent to a ratio of 5% by mass or more with respect to the total value of 100% by mass of chemical equivalents, the reduction of nickel can be efficiently promoted and the productivity can be improved. improves. On the other hand, by setting the ratio to 60% by mass or less with respect to the total value of 100% by mass of chemical equivalents, it is possible to suppress the reduction amount of iron, prevent deterioration of nickel grade, and produce high quality ferronickel. can. As described above, preferably, the mixing amount of the carbonaceous reducing agent is set to the ratio of the carbon amount of 5% by mass or more and 60% by mass or less with respect to the total value of 100% by mass of the chemical equivalents, so that the metal component is formed on the surface of the mixture. It is preferable that the shell (metal shell) produced by the above method can be uniformly produced to improve the productivity, and high-quality ferronickel having a high nickel grade can be obtained.

Further, as the iron ore as an additive of an arbitrary component, for example, iron ore having an iron grade of about 50% 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 treatment step S1, a mixture is obtained by uniformly mixing the raw material powder containing the nickel oxide ore as described above. At the time of this mixing, kneading may be performed at the same time in order to improve the mixing property, or kneading may be performed after mixing. Specifically, kneading can be performed using, for example, a twin-screw kneader, and by kneading the mixture, a shearing force is applied to the mixture to disaggregate the carbonaceous reducing agent, the raw material powder, and the like, and the mixture is uniform. It is possible to improve the adhesion of each particle and reduce the voids. As a result, the reduction reaction is likely to occur and the reaction can be made uniform, and the reaction time of the reduction reaction can be shortened. Moreover, the variation in quality can be suppressed. As a result, highly productive treatment can be performed and high quality ferronickel can be produced.

Further, after kneading, it may be extruded using an extruder. By extruding with an extruder in this way, a higher kneading effect can be obtained.

Table 1 below shows an example of the composition (mass%) of the nickel oxide ore, which is the raw material ore, and the iron ore, which are mixed in the mixing treatment step S1. The composition of the raw material is not limited to this.

<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 the container. That is, in the reduction injection pretreatment step S2, the mixture obtained by mixing the raw material powders can be easily charged into the furnace used in the reduction treatment step S3 described later, and the reduction reaction can be efficiently generated. Mold.

[Agglomeration of mixture]
When the obtained mixture is agglomerated, the mixture is formed (granulated) into a agglomerate. Specifically, a predetermined amount of water required for agglomeration is added to the obtained mixture, and for example, it is also referred to as a agglomerate manufacturing apparatus (rolling granulator, compression molding machine, extrusion molding machine, etc., or pelletizer). ) To form pellets of a predetermined shape.

The shape of the agglomerate (pellet) obtained by molding the mixture is not particularly limited, and may be, for example, a rectangular parallelepiped shape, a columnar shape, a spherical shape, or the like. Among them, the spherical pellet is preferable because the reduction reaction can proceed relatively uniformly. Further, in the treatment in the reduction treatment step S3 of the next step, it is preferable that the pellets can be treated in a laminated state, and in that respect as well, if the pellets are rectangular parallelepiped, columnar, spherical or the like, they are laminated in the reduction furnace. It is easy to place it on the surface, and the amount of processing to be applied to the reduction treatment can be increased. Further, by laminating in this way and subjecting it to the reduction treatment, it is possible to increase the processing amount at the time of reduction without enlarging one pellet, so that it is easy to handle and it may collapse during movement or the like. It is possible to suppress the occurrence of defects and the like.

The size of the pellets is not particularly limited, but is installed in a furnace used for performing a reduction treatment (reduction step S33) through, for example, a drying treatment (drying step S31) and a preheat treatment (preheating step S32). The size of the pellets to be inserted (diameter in the case of spherical pellets) can be about 10 mm to 30 mm.

The volume of the pellet is not particularly limited, but is preferably ^{8000 mm 3 or more.} If the volume of the pellet is too small, the molding cost becomes high and it takes time and effort to put it into the reduction furnace. In addition, if the volume of the pellet is small, the ratio of the surface area to the entire pellet is large, so that the difference in the degree of reduction between the surface and the inside of the pellet is likely to appear, and it may be difficult to proceed with the reduction uniformly. This makes it difficult to produce high quality ferronickel. On the other hand, if the volume of the pellet made of the mixture is 8000 mm ³ or more, the molding cost can be effectively suppressed and the handling becomes easy. Moreover, high quality fernickel can be stably obtained.

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

The shape of the mixture to be filled in the container is not particularly limited, but is preferably a rectangular parallelepiped, a cube, a cylinder, or the like. Further, the size thereof is not particularly limited, but for example, in the case of a rectangular parallelepiped shape or a cube shape, it is preferable that the vertical and horizontal internal dimensions are generally 500 mm or less. With 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 agglomerated or filled in the container in the reduction charging pretreatment 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 and metal and slag are produced.

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

Here, the treatment in the reduction step S33 is performed using a rotary hearth furnace in which the hearth rotates, and for example, the reduction treatment is performed with the reduction temperature set to 1200 ° C. or higher and 1450 ° C. or lower. Further, when the temperature holding step S34 for holding the reduced product obtained by the reduction treatment in a predetermined temperature range is executed, at least the treatment in the reduction step S33 and the treatment in the temperature holding step S34 are performed in the rotary hearth furnace. And execute.

In this way, by performing these treatments in the same rotary hearth furnace, the temperature inside the rotary hearth furnace can be maintained at a high temperature, so that the temperature is raised each time the treatment is performed in each process. There is no need to lower or lower it, and the energy cost can be significantly reduced. Further, according to the treatment using the rotary hearth furnace, the temperature can be easily controlled and controlled. From these facts, it is possible to continuously and stably produce high quality ferronickel with high productivity.

Then, in the present embodiment, the cooling treatment in the cooling step S35 for cooling the reduced product is divided into two stages, and the reduced product is cooled in stages, and the first stage cooling treatment is performed by the reduction treatment. It is characterized in that it is performed inside the executed rotary hearth furnace and the second stage cooling process is performed outside the rotary hearth furnace.

According to such a method, the reduced product can be cooled in a continuous operation, and efficient treatment can be performed, and the hearth of the rotary hearth furnace in which the first-stage cooling treatment is executed is performed. The temperature can be maintained high, and even when the hearth returns to the preheating step or the reduction step, the energy for heating to the appropriate temperature for the treatment in each step can be reduced. As a result, the temperature difference in the rotary hearth furnace can be reduced, and as a result, the thermal stress applied to the hearth and the furnace wall can be reduced, and the life of the furnace can be extended. In addition, defects during operation can be effectively reduced.

Furthermore, by cooling the reduced product stepwise over two stages and setting the temperature relatively high in the first stage cooling treatment, the metal components generated in the reduced product are sufficiently precipitated and coarsened. Can be made to. As a result, in the separation step S4 described later, the target ferronickel metal can be easily separated and efficiently recovered.

(1) Drying Step In the drying step S31, a drying treatment is performed on the mixture obtained by mixing the raw material powders. The purpose of this drying step S31 is mainly to remove water and water of crystallization in the mixture.

The mixture obtained in the mixing treatment step S1 contains a large amount of water and the like, and when the mixture is rapidly heated to a high reduction temperature during the reduction treatment in such a state, the water vaporizes and expands at once, and the mixture is agglomerated. Will crack or burst into pieces in some cases, making it difficult to perform a uniform reduction treatment. Therefore, prior to the reduction treatment, the mixture is dried to remove water and prevent destruction of pellets and the like.

The drying process in the drying step S31 is preferably performed in a form connected to a rotary hearth furnace. It is conceivable to provide an area (drying area) for drying treatment in the rotary hearth furnace, but in such a case, the drying treatment in the drying area becomes rate-determining, and the treatment and temperature in the reduction step S33 It may affect the processing in the holding step S34.

Therefore, it is preferable that the drying process in the drying step S31 is performed in a drying chamber provided outside the rotary hearth furnace and connected to the rotary hearth furnace. Although details will be described later, FIG. 3 shows a configuration example of the rotary hearth furnace 1 and the drying chamber 20 connected to the rotary hearth furnace 1. In this way, by providing the drying chamber 20 outside the rotary hearth furnace 1, the drying chamber can be designed completely separately from the steps such as preheating, reduction, and cooling described later, and the desired drying treatment, preheat treatment, and reduction treatment can be performed. It becomes easier to execute each cooling process. For example, if a large amount of water remains in the mixture depending on the raw material, the drying process takes time, so the total length of the drying chamber 20 may be designed to be longer, or the mixture in the drying chamber 20 may be designed longer. It may be designed so that the transport speed becomes slow.

As the drying treatment in the drying chamber 20, for example, the solid content in the mixture is about 70% by mass and the water content is about 30% by mass. The drying method is not particularly limited, but it can be performed by blowing hot air onto the mixture conveyed in the drying chamber 20. The drying temperature is also not particularly limited, but is preferably 500 ° C. or lower, and is preferably uniformly dried at a temperature of 500 ° C. or lower, from the viewpoint of preventing the reduction reaction from starting.

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

(2) Preheating Step In the preheating step S32, the mixture after removing water by the drying treatment in the drying step S31 is preheated (preheated).

If the mixture is charged into a rotary hearth furnace and suddenly raised to a high reduction temperature, the mixture may crack or become powdery due to thermal stress. In addition, the temperature of the mixture may not rise uniformly, the reduction reaction may vary, and the quality of the produced metal may vary. Therefore, it is preferable to preheat the mixture to a predetermined temperature after the mixture has been dried, which can suppress the destruction of the mixture and the variation in the reduction reaction.

The preheat treatment in the preheating step S32 is preferably performed in a rotary hearth furnace for executing the reduction treatment in the reduction step S33, and one of the processing chambers divided in the rotating hearth is used as a preheating chamber. Is preferable. FIG. 3 shows a configuration example of the rotary hearth furnace 1, which is a place where the drying chamber 20 outside the furnace is connected, and the mixture transferred through the drying chamber 20 is charged into the rotary hearth furnace. The first processing chamber can be configured as a preheating chamber 10a.

The preheat treatment in the preheating chamber 10a is not particularly limited, but the preheating temperature is preferably 600 ° C. or higher, and the preheating temperature is more preferably 700 ° C. or higher and 1280 ° C. or lower. By treating at a preheating temperature in such a range, the energy required for reheating to the reduction temperature in the subsequent reduction treatment can be significantly reduced.

The preheat treatment may be performed in a processing chamber (preheating chamber) provided outside the rotary hearth furnace in the same manner as the drying treatment described above. In that case, the preheating chamber can be configured to be provided outside the rotary hearth furnace 1 and continuously provided with the drying chamber 20 for performing the drying treatment.

(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 treatment in the reduction step S33 is performed in the rotary hearth furnace 1 in which the hearth rotates. In this way, by performing the reduction treatment using the rotary hearth furnace, the temperature inside the furnace can be maintained in a high temperature range, there is no need to raise or lower the temperature, and the energy cost is significantly reduced. can do. In addition, temperature control and control become easy, and high-quality ferronickel can be stably produced.

(Composition 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 the region 10 is divided into four, each of which constitutes a processing chamber (10a, 10b, 10c, 10d). There is.

Specifically, in the rotary hearth furnace 1, for example, among the four processing chambers of reference numerals “10a” to “10d”, the processing chamber 10a connected to the drying chamber 20 outside the furnace is referred to as a “preheating chamber (preheating area)”. ) ”. When the temperature holding step S34, which will be described later, is executed after the reduction step S33, for example, the treatment chamber 10b is designated as a "reduction chamber (reduction area)", and the treatment chamber 10c is treated in the temperature holding step S34. It can be a room (holding area).

Then, in the present embodiment, the reduced product obtained by the reduction treatment in the reducing step S33 or the reduced product after the reduced product is held at a predetermined temperature in the temperature holding step S34 is cooled. The stage cooling process is performed in the rotary hearth furnace 1. Specifically, the processing chamber 10d in the rotary hearth furnace 1 is designated as a “first stage cooling chamber (cooling area)”, and the reduced product is cooled to a predetermined temperature range. In this way, by performing the first-stage cooling process in the rotary hearth furnace 1, operations including cooling can be continuously performed, and productivity can be improved.

The rotary hearth furnace 1 is directly connected to the processing chamber 10d, and the processing chamber (second stage cooling chamber) 30 is connected to the outside of the furnace. A second-stage cooling process is performed to further cool the reduced product that has undergone the first-stage cooling process.

In the rotary hearth furnace 1, it is preferable that each process, that is, between each processing chamber, has a structure partitioned by a partition wall in order to strictly control the reaction temperature and suppress energy loss. As described above, according to the rotary hearth furnace having a structure capable of partitioning between each process, the same rotary hearth furnace can be used while suppressing energy loss between each processing chamber. .. However, if the partition wall is a fixed type, it may be difficult to carry it between processes, and in particular, it may be difficult to charge and discharge it into the rotary hearth furnace. It is preferable to have a structure that can be opened and closed to the extent that it does not interfere with the above.

Here, the rotary hearth furnace 1 is composed of, for example, a metal hearth base (hereinafter, also simply referred to as “hearth base”) and a hearth formed on the hearth base. The material of the hearth is not particularly limited, but may be made of graphite, for example. By constructing the hearth with graphite, the reaction between the hearth and the mixture placed on the hearth can be suppressed. The reduced product (mixture of metal and slag) obtained by the reduction treatment has poor wettability with carbon constituting graphite and is difficult to react. Therefore, by providing the hearth made of graphite, the reaction with the mixture can be effectively suppressed.

As described above, the rotary hearth furnace 1 is provided with a hearth that rotates and moves on a flat surface, and the hearth on which the mixture is placed rotates and moves at a predetermined speed, so that each processing chamber (10a, 10a, It passes through 10b, 10c, 10d), and processing is performed at the time of passing. The arrow on the rotary hearth furnace 1 in FIG. 3 indicates the rotation direction of the hearth and the moving direction of the processed product (mixture).

Further, as described above, the rotary hearth furnace 1 is connected to a drying chamber 20 provided outside the furnace, and after the mixture is dried in the drying chamber 20, the dried mixture rotates. It is moved to the preheating chamber 10a in the hearth furnace 1 and preheated, and then the inside of the furnace is sequentially moved. Further, the rotary hearth furnace 1 is connected to a second stage cooling chamber 30 provided outside the furnace, and a reduced product obtained through the first stage cooling chamber 10d in the rotary hearth furnace 1. Is further cooled in the second stage cooling chamber 30.

The number of processing chambers formed by dividing the region 10 in which the hearth rotates is not limited to the four illustrated in FIG. Further, the number of reduction chambers and the like is not limited to the above-mentioned example, and can be appropriately set according to the processing time and the like.

(Reduction treatment in a rotary hearth furnace)
In the reduction treatment using the rotary hearth furnace 1, the nickel contained in the mixture is preferentially and completely reduced as much as possible, while the iron contained in the mixture is partially reduced to achieve the purpose. It is preferable to obtain a nickel-grade ferronickel.

Specifically, the reduction temperature is not particularly limited, but is preferably in the range of 1200 ° C. or higher and 1450 ° C. or lower, and more preferably in the range of 1300 ° C. or higher and 1400 ° C. or lower. By reducing in such a temperature range, a uniform reduction reaction can be generated, and a metal (ferronickel metal) in which quality variation is suppressed can be produced. Further, more preferably, by reducing at a reduction temperature in the range of 1300 ° C. or higher and 1400 ° C. or lower, a desired reduction reaction can be generated in a relatively short time.

In the reduction treatment, the internal temperature of the reduction chamber 10b in the rotary hearth furnace 1 is raised until the reduction temperature reaches the above-mentioned range, and the temperature is maintained after the temperature rise.

(4) Temperature Holding Step Although it is not an essential aspect, even if the temperature holding step S34 for holding the reduced product obtained through the reduction step S33 under a predetermined high temperature condition in the rotary hearth furnace 1 is performed. good. As described above, by holding the reduced product obtained by the reduction treatment at the predetermined reduction temperature in the reduction step S33 in a high temperature atmosphere instead of immediately cooling it, the metal component produced in the reduced product can be obtained. It can be settled and coarsened.

If the metal component in the reduced product is small in the state obtained by the reduction treatment, for example, if it is a bulk metal of about 200 μm or less, the metal and the slag are separated in the subsequent separation step S4. Becomes difficult. Therefore, if necessary, the reduced product is kept at a high temperature for a certain period of time even after the reduction reaction is completed, so that the metal having a higher specific density than the slag in the reduced product is precipitated and aggregated to form the metal. Make it coarse.

When the metal is coarsened to a level where there is no problem in manufacturing by the reduction treatment in the reduction step S33, it is not necessary to provide the temperature holding step S34 in particular.

Specifically, the holding temperature of the reduced product in the temperature holding step S34 is preferably in a high temperature range of, for example, 1300 ° C. or higher and 1500 ° C. or lower. 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 obtain a coarse metal. If the holding temperature is less than 1300 ° C., most of the reduced product becomes a solid phase, so that the metal component does not settle, or even if it does settle, it 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 may proceed, and the reduced product may not be recovered, and the furnace may be damaged. ..

The treatment in the temperature holding step S34 is continuously performed in the rotary hearth furnace 1 used in the reduction step S33 following the reduction treatment. That is, as described with reference to FIG. 3, in the rotary hearth furnace 1, the processing chamber 10a is used as a preheating chamber, the processing chamber 10b is used as a reduction chamber, and the processing chamber 10c is used as a temperature holding chamber for performing the treatment in the temperature holding step S34. As a result, the reduced product obtained through the reduction chamber 10b is kept in a predetermined temperature range in the temperature holding chamber (10d).

In this way, the treatment of holding the reduced product obtained through the reduction treatment at a predetermined temperature is continuously performed using the rotary hearth furnace 1, so that the metal component in the reduced product is efficiently settled. Can be coarsened. Moreover, by continuously performing the treatment in the reduction step S33 and the treatment in the temperature holding step S34 using the rotary hearth furnace 1 instead of separate furnaces, heat loss between each treatment is reduced and it is efficient. Enables operations.

(5) Cooling Step In the cooling step S35, the reduced product obtained through the reducing step S33 or the reduced 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 to a temperature that allows.

In the present embodiment, the cooling treatment for the reduced product is divided into two stages to cool the reduced product in stages. Further, the first-stage cooling treatment is performed in the furnace of the rotary hearth furnace 1 that has executed the reduction treatment in the reduction step, and the second-stage cooling treatment is performed outside the rotary hearth furnace 1. It is characterized by doing.

Specifically, as described with reference to FIG. 3, in the rotary hearth furnace 1, the processing chamber 10d is used as the first-stage cooling chamber, and the reduced product or the reduced product that has undergone the reduction treatment is maintained at a predetermined temperature. The first-step cooling treatment for the reduced product is carried out. Further, in the second-stage cooling chamber 30 connected to the outside of the rotary hearth furnace 1, the second-stage cooling treatment for the reduced product after the first-stage cooling treatment is performed is executed.

Here, the temperature in the cooling step S35 (hereinafter, also referred to as “recovery temperature”) is preferably a temperature at which the reduced product can be treated as a substantially solid, and is as high as possible. In this respect, by performing the cooling treatment in two stages, it is possible to gradually cool the cooling in stages, and the temperature of the first stage cooling treatment, that is, one stage in the rotary hearth furnace 1. The temperature in the eye cooling chamber 10d can be as high as possible. As a result, even when the hearth returns to the processing chamber 10a for executing the preheating step, the energy for reheating to the appropriate temperature for the preheat treatment can be reduced, and nickel smelting can be performed at low cost. be able to. In addition, the recovery temperature can be set as high as possible, for example, 600 ° C. or higher.

On the other hand, the second-stage cooling process is performed in the second-stage cooling chamber 30 connected to the outside of the rotary hearth furnace 1, so that the cooling end temperature in the cooling chamber 30 is reached. Can be set independently of the optimum temperature distribution of the processing in each step in the rotary hearth furnace 1. Therefore, it does not affect the processing time and the like in the steps such as preheating, reduction, and cooling in the rotary hearth furnace 1, and can be individually adjusted according to the purpose.

Further, by performing a two-step cooling process and reducing the temperature difference in the rotary hearth furnace 1, the thermal stress applied to the hearth, the furnace wall, etc. of the rotary hearth furnace 1 can be reduced, and the rotation The life of the hearth furnace 1 can be greatly extended. In addition, defects during operation can be significantly reduced, enabling stable operation.

Further, by cooling the reduced product stepwise over two steps in this way and setting the temperature relatively high in the first step cooling treatment, the metal component generated in the reduced product is sufficiently precipitated. Can be coarsened. As a result, in the separation step S4, the target ferronickel metal can be easily separated and efficiently recovered.

It is more efficient that the second-stage cooling chamber 30 has a structure that can receive the reduced product (reduced product that has undergone the first-stage cooling treatment) discharged from the rotary hearth furnace 1 and continuously cool it as it is. Therefore, it is preferable to have a structure capable of transporting on a straight line such as a belt conveyor.

In the first-step cooling treatment, it is preferable to cool the reduced product so that the temperature is in the range of 700 ° C. or higher and 1280 ° C. or lower. Within such a range, the above-mentioned effects will be more prominent, which is preferable.

Further, in the second-stage cooling treatment, the reduced product is further cooled, but it is preferable that the temperature of the reduced product discharged from the second-stage cooling chamber 30 is maintained at 600 ° C. or higher. The temperature of this reduced product is the recovery temperature.

<2-4. Separation process>
In the separation step S4, the metal (ferronickel metal) is separated and recovered from the reduced product produced in the reduction treatment step S3. Specifically, in the separation step S4, the metal phase is obtained from the mixture (reduced product) containing the metal phase (metal solid phase) and the slag phase (slag solid phase) obtained by reducing and heating the mixture. 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 substances by sieving, separation by specific gravity, separation by magnetic force, etc. Method can be used. Further, the obtained metal phase and slag phase can be easily separated due to their poor wettability, and are dropped on a large mixture, for example, with a predetermined head, or when sieving. The metal phase and the slag phase can be easily separated from the mixture by giving an impact such as giving a predetermined vibration.

By separating the metal phase and the slag phase in this way, the metal phase can be recovered and a ferronickel product can be obtained.

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

<< Examples 1 to 17 >>
[Mixing process]
An appropriate amount of nickel oxide ore as a raw material ore, iron ore, silica sand and limestone as flux components, a binder, and a carbonaceous reducing agent (coal powder, carbon content: 85% by mass, average particle size: about 190 μm). The mixture was obtained by mixing using a mixer while adding the water of the above. The carbonaceous reducing agent has a total value of 100% by mass, which is the total amount required to reduce _{nickel oxide (NiO) and iron oxide (Fe 2} O ₃ ) contained in the raw material ore, nickel oxide ore, in just proportion. When it was added, it was contained in an amount of 32%. Then, the raw materials mixed by the mixer were kneaded by the twin-screw kneader.

[Mixture molding process]
Next, the obtained mixture was granulated using a pan-type granulator to obtain spherical pellets having a diameter of 18 ± 1.5 mm.

[Reduction process]

Next, using the reduction furnace bed furnace 1 as illustrated in FIG. 3, the reduction treatment was performed by changing the treatment conditions. As shown in FIG. 3, the rotary hearth furnace 1 is divided into four processing chambers 10a to 10d, and outside the furnace, a drying chamber 20 for drying pellets and a drying chamber 20 for reducing products are provided. The one connected to the second-stage cooling chamber 30 that executes the second-stage cooling treatment was used. In the rotary hearth furnace 1, the processing chamber 10a is a preheating chamber, the processing chamber 10b is a reduction chamber, the processing chamber 10c is a temperature holding chamber, and the processing chamber 10d is a first-stage cooling chamber.

The hearth of the rotary hearth furnace 1 has ash (main component is ash) from the viewpoint of suppressing the reaction between the hearth and the sample in order to prevent the hearth and the sample from reacting with each other and becoming unrecoverable. SiO ₂ and other components containing a small amount of oxides such _{as Al 2} O _{3 and Mg O) were spread.}

First, pellets are charged into a drying chamber 20 connected to the outside of the rotary hearth furnace 1, and hot air at 250 ° C. to 350 ° C. is provided so that the solid content is about 70% by mass and the water content is about 30% by mass. Was sprayed onto the mixture and dried. The drying treatment was carried out in a nitrogen atmosphere containing substantially no oxygen. 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 the preheating chamber (treatment chamber 10a) of the rotary hearth furnace 1, the temperature in the preheating chamber is maintained in the range of 700 ° C. or higher and 1280 ° C. or lower, and the pellets are preheated. went.

Subsequently, by rotating the hearth, the pellets after the preheat treatment were sequentially transferred to the reduction chamber (treatment chamber 10b) and the temperature holding chamber (treatment chamber 10c), and the reduction treatment and the temperature holding treatment were performed. In the embodiment in which the reduced product was not kept at a high temperature, it was only passed through the temperature holding chamber (the temperature holding temperature is indicated as 0 ° C. in Table 4 below).

Subsequently, by rotating the hearth, the reduced product was transferred to the first-stage cooling chamber (treatment chamber 10d), and the first-stage cooling treatment was performed. In the first stage cooling treatment, the temperature of the reduced product was set to be in the range of 700 ° C. or higher and 1280 ° C. or lower.

Then, the reduced product that has undergone the first-stage cooling treatment is transferred to the second-stage cooling chamber 30 connected to the rotary hearth furnace 1, and the second-stage cooling treatment is performed while flowing nitrogen to the atmosphere. I took it out. The temperature of the reduced product after the second stage cooling treatment was defined as the temperature at the time of recovery (temperature at the time of recovery).

≪Evaluation≫
For the recovered sample, the nickel metal ratio and the nickel content in the metal were analyzed and calculated by an ICP emission spectrophotometer (SHIMAZU S-8100 type). Each of the recovered samples was crushed by a wet treatment, and then the metal was recovered by magnetic force sorting.

Here, the nickel metallization rate was determined by the following formula (1), and the nickel content in the metal was determined by the following formula (2).
Nickel metallization rate = Amount of metallized Ni in the mixture ÷ (All Ni in the pellet) x 100 (%) ... (1) Nickel content in the metal = Metallicized Ni in the mixture Amount ÷ (total amount of metallized Ni and Fe in pellets) × 100 (%) ・ ・ ・ Eq. (2)

In addition, the Ni metal recovery rate was calculated from the input amount of nickel oxide ore, the Ni content ratio in the nickel oxide ore, and the recovered Ni amount. The Ni metal recovery rate was calculated by the following formula (3).
Ni metal recovery rate = amount of recovered Ni ÷ (amount of ore input x Ni content ratio in ore) x 100 ... Equation (3)

As shown in the results of Table 4, in Examples 1 to 17 in which the reduced product obtained through the reduction treatment was cooled in a stepwise manner over two steps, the nickel metallization rate and the nickel content in the metal were contained. Both the amount and the metal recovery rate were high, and good results were obtained. Further, the recovery temperature was maintained at 610 ° C. or higher, the entire rotary hearth furnace 1 was maintained at a high temperature, the energy required for reheating was suppressed, and efficient nickel smelting was possible.

1 Rotating hearth furnace 10 area 10a, 10b, 10c, 10d Processing room 20 Drying room 30 Second stage cooling room

Claims (9)

A drying step of drying the mixture obtained by mixing nickel oxide ore and a carbonaceous reducing agent, and
A preheating step to preheat the dried mixture and
A reduction process that reduces the preheated mixture using a rotary hearth furnace with a rotating hearth.
A cooling step for cooling the obtained reduced product containing ferronickel, and
Including a reduction treatment step having
In the cooling step, the cooling treatment for the reduced product is divided into two stages, the reduced product is cooled stepwise, and the first stage cooling treatment is the furnace of the rotary hearth furnace in which the reduction treatment in the reduction step is executed. The second stage cooling process is performed inside the rotary hearth furnace, and at the same time, it is performed outside the furnace .
After further having a temperature holding step of holding the reduced product obtained through the reduction step at a predetermined temperature in the rotary hearth furnace, and holding the reduced product at a predetermined time in the temperature holding step, the reduced product is held. A method for smelting an oxide ore that supplies the reduced product to the cooling step. The method for smelting an oxidized ore according to claim 1, wherein in the reduction step, the reduction temperature is set to 1200 ° C. or higher and 1450 ° C. or lower. The method for smelting an oxidized ore according to claim 1 or 2, wherein in the cooling step, the temperature of the reduced product is cooled to a range of 700 ° C. or higher and 1280 ° C. or lower in the first-step cooling treatment. The method for smelting an oxidized ore according to any one of claims 1 to 3, wherein the temperature of the reduced product obtained through the second-step cooling treatment in the cooling step is maintained at 600 ° C. or higher and becomes the recovery temperature. The treatment in the reduction step and the treatment in the temperature holding step are executed in the same rotary hearth furnace, and in the cooling step, the reduced product held in the rotary hearth furnace for a predetermined time is subjected to. The method for smelting an oxide ore according to any one of claims 1 to 4, wherein the first-stage cooling treatment is performed. The method for smelting an oxidized ore according to any one of claims 1 to 5, wherein in the temperature holding step, the reduced product is held at a temperature of 1300 ° C. or higher and 1500 ° C. or lower. The method for smelting oxidized ore according to any one of claims 1 to 6 , wherein the treatment in the preheating step is carried out in the same rotary hearth furnace in which the treatment in the reduction step is performed. The mixture to be dried in the drying step is
at least,
A mixing treatment step of mixing an oxide ore and a carbonaceous reducing agent to obtain a mixture, and
A pretreatment step of agglomerating the obtained mixture or filling a predetermined container, and
The method for smelting an oxidized ore according to any one of claims 1 to 7, which is obtained through the above. The smelting of the oxide ore according to any one of claims 1 to 8 , further comprising a separation step of separating and recovering the reduced product cooled to a predetermined temperature in the cooling step of the reduction treatment step into metal and slag. Method.

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