JP2024010512A - Nickel oxide ore smelting method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique capable of effectively manufacturing high-quality ferronickel in a method with less CO₂ emission while suppressing a smelting cost, in a method of manufacturing ferronickel through reducing a mixture containing nickel oxide ore.

SOLUTION: A smelting method of nickel oxide ore reduces a mixture containing nickel oxide ore being raw material ore to manufacture ferronickel. The smelting method of nickel oxide ore mixes the nickel oxide ore and a carbonaceous reductant to obtain a massive mixture, charges the mixture into a reduction furnace 1 of an electric heating system that uses electricity as a heat source, and heats up to a prescribed reduction temperature inside the reduction furnace 1 to apply a reduction treatment. The reduction furnace 1 includes a reductant supply part 70 configured to supply a reduction gas RG to an input part 21 configured to input the mixture into an inside-furnace part 16 of the reduction furnace 1. At the reduction treatment, the reduction gas RG is supplied to the reductant supply part 70.

SELECTED DRAWING: Figure 2

COPYRIGHT: (C)2024,JPO&INPIT

Description

The present invention relates to a method for smelting nickel oxide ore.

As a smelting method for nickel oxide ore called limonite or saprolite, a pyro-smelting method uses a smelting furnace to produce nickel matte, and a pyro-smelting method uses a rotary kiln or mobile hearth furnace to produce ferronickel. , a hydrometallurgical method for producing mixed sulfide using an autoclave, etc. are known.

When smelting nickel oxide ore, the raw ore is first subjected to pretreatment to form it into lumps, slurry, and the like. Specifically, when nickel oxide ore is turned into agglomerates, that is, from powder or fine particles to lumps, it is mixed with components other than the nickel oxide ore, such as a binder and a reducing agent, to form a mixture, and further water adjustment etc. After that, it is generally charged into a lump making machine to produce lumps (referring to pellets, briquettes, etc., hereinafter also simply referred to as "pellets") of about 10 to 30 mm.

Pellets formed in this manner require a certain degree of air permeability in order to evaporate moisture. Furthermore, if the reduction is not performed uniformly within the pellet, the composition will become non-uniform, and the metal will be dispersed and unevenly distributed. For this reason, it is important to uniformly mix the raw materials to form a mixture and to treat the pellets at as uniform a temperature as possible when reducing the pellets.

In addition, it is also a very important technology to coarsen the metal (ferronickel) produced by reduction. This is because if the produced ferronickel has a size of, for example, several tens of micrometers or less, it will be difficult to separate it from the slag, and the yield of ferronickel will drop significantly. Therefore, it is important to coarsen the ferronickel produced by reduction to improve its separability from slag and improve the yield.

In addition, in recent years, ores with high nickel grades and ores that are difficult to mix with impurities when turned into metal have become scarce, and even more advanced smelting technology is required to produce high-quality ferronickel. . Furthermore, metal prices often fluctuate wildly, and a system must be in place to remain profitable even when prices drop, and an important issue is how to keep smelting costs low. There is.

As described above, many technical issues remain in the technology for smelting nickel from nickel oxide ore. On the other hand, in recent years, the demand for reducing environmental loads has increased significantly, and particularly in the smelting and refining field, the demand for reducing greenhouse gases, specifically CO ₂ , has become very strong. Regarding _CO2 reduction measures, various research and development efforts are underway in various fields. _As an example, in the steel smelting industry, which emits a large amount of _CO2 , papers such as Reference 1, "Estimating the potential for reducing _CO2 emissions from the global steel sector in 2050" have been published. It is estimated that this will increase by 6% to 12% compared to 2005.

Nickel pyrometallurgy also emits a large amount of _CO2 , and one reason for this is that in the reduction process, methods such as the Krupplen process, which uses a rotary kiln, and the Elkem process, which uses a rotary kiln for preliminary reduction, use coal as the fuel for the kiln. One point is that it uses .

Furthermore, these fossil fuels and gases such as LNG contain some moisture in the fuel itself, so steam is generated during combustion, and the generated steam is thermally decomposed and processed in the reduction process. It is also known that it re-oxidizes the reduced product and significantly reduces the reduction efficiency.

In this way, the technology of mixing and reducing nickel oxide ore to produce metals such as ferronickel has the potential to not only improve the quality of the metals produced, but also improve productivity, reduce smelting costs, and There are many important issues such as reducing CO ₂ emissions.

Proceedings of the Japan Society of Civil Engineers G (Environment), Vol.70, No.6 (Environmental System Research Papers Vol. 42), II_239-II_247, 2014

The present invention was proposed in view of the above circumstances, and is a method for producing ferronickel by reducing a mixture containing nickel oxide ore, which produces high-quality ferronickel while suppressing smelting costs. The purpose of the present invention is to provide a technology that enables effective production with a method that produces less CO ₂ emissions.

The inventors of the present invention have made extensive studies to solve the above-mentioned problems. As a result, by using electricity for energy when reducing a mixture containing nickel oxide ore, which is the raw material ore, and a carbonaceous reducing agent, it is possible to suppress the partial oxidation of the mixture that may occur during reduction. As a result, it was discovered that ferronickel with a high nickel metallization rate and high nickel content can be produced, and that CO ₂ emissions can be significantly reduced, leading to the present invention. That is, the present invention provides the following.

(1) A first aspect of the present invention is a nickel oxide ore smelting method for producing ferronickel by reducing a mixture containing nickel oxide ore as a raw material ore, the nickel oxide ore and carbon and a solid reducing agent to form a lumpy mixture, the mixture is charged into an electrically heated reduction furnace that uses electricity as a heat source, and is heated to a predetermined reduction temperature in the reduction furnace for reduction treatment. and the reducing furnace includes a reducing agent supply section that supplies reducing gas to an input section that introduces the mixture into the inside of the reduction furnace, and during the reduction process, the reducing furnace is provided with a reducing agent supply section that supplies the reducing gas to the reducing furnace. This is a method of smelting nickel oxide ore that supplies gas.

(2) A second invention of the present invention is the method for smelting nickel oxide ore according to the first invention, wherein the reducing gas is one or more of hydrogen and carbon monoxide.

(3) A third invention of the present invention is the method for smelting nickel oxide ore according to the first or second invention, wherein the reduction temperature of the reduction treatment is 1200°C or more and 1500°C or less.

(4) A fourth aspect of the present invention is the method for smelting nickel oxide ore according to the first or second aspect, wherein the reduction furnace is a rotary hearth furnace.

According to the present invention, in a method for producing ferronickel by reducing a mixture containing nickel oxide ore, high quality ferronickel can be effectively produced with low _CO2 emissions while suppressing smelting costs. We can provide technology that enables production.

It is a process diagram showing an example of the flow of a nickel oxide ore smelting method. FIG. 1 is a perspective view showing an example of a reduction furnace according to an embodiment. FIG. 3 is a plan view showing the reduction furnace of FIG. 2 with some parts omitted. 3 is a sectional view taken along line AA in FIG. 2. FIG. 5 is a sectional view taken along line BB in FIG. 4. FIG. 3 is a sectional view taken along line CC in FIG. 2. FIG.

Hereinafter, embodiments (hereinafter also simply referred to as "embodiments") of the present invention will be described in detail. Note that the present invention is not limited to the following embodiments, and various changes can be made without changing the gist of the present invention. Furthermore, in this specification, the expression "X to Y" (X and Y are arbitrary numerical values) means "more than or equal to X and less than or equal to Y."
≪Method for smelting nickel oxide ore≫

The method for smelting nickel oxide ore according to the present embodiment includes mixing nickel oxide ore, which is a raw material ore, with a carbonaceous reducing agent, etc., and subjecting the mixture to a reduction treatment in a smelting furnace (reduction furnace). This produces metal and slag. In this smelting method, at least a nickel oxide ore and a carbonaceous reducing agent are mixed to form a lumpy mixture.

The smelting method according to the present embodiment is characterized in that an electrically heated reduction furnace using electricity as a heat source is used to reduce the mixture. In this way, by performing the reduction treatment in an electrically heated reduction furnace, the influence of oxidation due to oxygen can be effectively reduced, and high quality fernickel can be produced. Reducing gas (reducing gas) is then supplied to the point where the mixture is introduced into the furnace, and by reacting with the oxygen that is inevitably brought in when the mixture is introduced into the furnace, the oxygen concentration in the furnace is further increased. It can be lowered further. Furthermore, compared to the case where fossil fuels such as coal, coke, LNG, and LPG are used as heating fuel for the reduction furnace, in principle, electric power can be used not only for thermal power generation but also for hydroelectric power generation, solar power generation, and wind power generation. Since it can also be obtained from renewable energy such as, the total amount of CO ₂ emissions can be reduced.

In the following, we will generate an iron-nickel alloy (ferronickel) metal by reducing nickel (nickel oxide) and iron (iron oxide) contained in nickel oxide ore, which is the raw material ore, and then separate the metals. A more specific explanation will be given by taking as an example a smelting method for producing ferronickel.

As shown in FIG. 1, the method for smelting nickel oxide ore according to the present embodiment includes a mixing step S1 of mixing raw materials containing nickel oxide ore, and a mixture forming step of forming the obtained mixture into a predetermined shape. The method includes a step S2 and a reduction step S3 in which the molded mixture is charged into a reduction furnace and subjected to reduction treatment at a predetermined reduction temperature. Furthermore, there is a separation step S4 in which metal (ferronickel metal) is recovered by separating the metal and slag that have been generated and grown by the reduction treatment.

[Mixing process]
The mixing process S1 is a process of mixing raw material powders containing nickel oxide ore to obtain a mixture. Specifically, a carbonaceous reducing agent is added and mixed with nickel oxide ore, which is a raw material ore, and optional additives such as iron ore, a flux component, a binder, etc., for example, with a particle size of 0.1 mm are mixed. A mixture is obtained by mixing powders of about 0.8 mm. Note that the mixing process can be performed using a mixer or the like.

Further, in the mixing process, kneading may be performed to improve mixability. For example, by kneading the mixture using a twin-screw kneader, shearing force is applied to the mixture, and the carbon reducing agent and raw material powder can be deagglomerated and mixed more uniformly, and the adhesion of each particle can be improved. By increasing the amount, it is possible to easily perform a uniform reduction process in the reduction step S3.

The nickel oxide ore that is the raw material ore is not particularly limited, but limonite ore, saprolite ore, etc. can be used. Note that the nickel oxide ore contains nickel oxide (NiO) and iron oxide (Fe ₂ O ₃ ) as constituent components.

In this embodiment, a specific amount of carbonaceous reducing agent is mixed with nickel oxide ore to form a mixture. Examples of the carbonaceous reducing agent include, but are not limited to, coal powder, coke powder, and the like. In addition, it is preferable that the carbonaceous reducing agent has a particle size equivalent to that of the nickel oxide ore that is the above-mentioned raw material ore. It is preferable to mix using a carbonaceous reducing agent that has the same particle size and particle size distribution as the nickel oxide ore, because it facilitates uniform mixing and allows the reduction reaction to occur uniformly.

The mixed amount of the carbonaceous reducing agent is 50.0 mass% when the amount of the carbonaceous reducing agent necessary to reduce the nickel oxide and iron oxide that constitute the nickel oxide ore is 100% by mass. % or less, more preferably 40.0% by mass or less. The amount of carbonaceous reducing agent required to reduce nickel oxide and iron oxide in just the right amount is the chemical equivalent required to reduce the entire amount of nickel oxide to nickel metal, and the amount of carbonaceous reducing agent required to reduce the total amount of nickel oxide to nickel metal. It can be expressed as the total value of the chemical equivalents required to reduce the chemical equivalents to (hereinafter also referred to as the "total value of chemical equivalents").

In this way, by setting the mixed amount of the carbonaceous reducing agent to a ratio of 50.0% by mass or less when the total value of chemical equivalent is 100% by mass, the reduction reaction can proceed efficiently. .

The lower limit of the mixing amount of the carbonaceous reducing agent is not particularly limited, but it is preferably 10.0% by mass or more, and 15.0% by mass, based on 100% by mass of the total chemical equivalent. % or more is more preferable.

Further, as described above, in addition to the nickel oxide ore and the carbonaceous reducing agent, additives such as iron ore, a flux component, and a binder can be added and mixed as optional components.

As the iron ore, for example, iron ore having an iron grade of about 50% by mass or more, hematite (Fe ₂ O ₃ ) obtained by hydrometallurgy of nickel oxide ore, etc. can be used. Further, examples of the binder include bentonite, polysaccharide, resin, water glass, dehydrated cake, and the like. Furthermore, examples of the flux component include calcium oxide, calcium hydroxide, calcium carbonate, and silicon dioxide.

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

[Mixture forming process]
The mixture forming step S2 is a step of forming the mixture obtained in the mixing treatment step S1. That is, a mixture obtained by mixing raw material powders is made into a lump of a certain size (hereinafter also referred to as "pellet"). The mixture, in the form of a lump obtained by molding, is subjected to a reduction treatment in the next step, reduction step S3, and charged into a reduction furnace.

The shape of the pellets obtained by agglomerating the mixture can be various shapes such as a rectangular parallelepiped, a cylinder, and a sphere, and is not particularly limited. Among these, by forming the mixture into a shape that is easy to mold, the cost of molding can be suppressed. Moreover, by simplifying the shape, there are almost no defective products, and the yield in molding can be increased.

The volume of the molded (agglomerated) mixture (volume of pellets) is not particularly limited, but may be 8000 mm ³ or more. If the volume of the pellets is too small, the molding cost will be high and it may take time and effort to charge the pellets into the reduction furnace. Furthermore, if the volume of the pellet is small, the ratio of the surface area to the entire pellet increases, so when reduction treatment is performed, a difference in reduction tends to appear between the surface and the inside, making it difficult to obtain high quality ferronickel. Sometimes there isn't. On this point, by molding the pellets so that the volume is 8000 mm ³ or more, not only can molding costs be reduced and handling becomes easier, but it is also possible to manufacture high quality fernickel. .

Alternatively, after being molded into a predetermined shape, the molded mixture (lump) may be subjected to a drying process to form pellets. By performing a drying process before reduction, it is possible to prevent problems such as pellets being rapidly heated and bursting during the reduction process. In the drying process, the drying temperature is preferably about 150°C to 400°C. By drying in such a temperature range, it becomes possible to effectively dry the mixture without proceeding with the reduction reaction within the mixture.

Table 2 below shows an example of the solid content composition (mass %) of the mixture (pellet) after the drying process. Note that the composition of the mixture is not limited to this.

[Reduction process]
In the reduction step S3, the mixture (pellets) obtained in the mixture forming step S2 is charged into a reduction furnace, heated to a predetermined reduction temperature, and subjected to reduction treatment. Through such reduction treatment, a smelting reaction (reduction reaction) progresses, and metal (ferronickel metal) and slag are generated.

In the reduction treatment, pellets containing nickel oxide ore are placed on the hearth of a reduction furnace, and the pellets are heated. The heating is carried out so that the reduction temperature is, for example, 1200°C or more and 1500°C or less, preferably 1250°C or more and 1400°C or less.

Through such reduction treatment, in a short period of time, for example, about 1 minute, the nickel oxide and iron oxide contained in the pellet are first reduced and metalized near the pellet surface where the reduction reaction easily proceeds, forming an iron-nickel alloy, and the shell ( (hereinafter also referred to as a "shell"). On the other hand, inside the shell, as the shell is formed, the slag component in the pellet gradually melts, producing liquid slag. As a result, ferronickel metal (hereinafter also simply referred to as "metal") and slag made of oxide (hereinafter simply referred to as "slag") are separated and generated in one pellet. Then, when the treatment time of the reduction treatment by heating has elapsed for about 10 minutes, the excess carbon component of the carbonaceous reducing agent that does not participate in the reduction reaction is incorporated into the iron-nickel alloy, lowering the melting point. As a result, the iron-nickel alloy dissolves into a liquid phase.

Here, the smelting method according to the present embodiment is characterized in that the reduction process is performed using an electrically heated reduction furnace that uses electricity as a heat source.

Conventionally, reduction processing has mainly been performed using a burner furnace (burner heating type reduction furnace) using fossil fuels such as coal, coke, LNG, and LPG as heating fuel. However, when solids such as coal or liquids such as heavy oil are used as fuel, it is difficult to achieve 100% combustion, and it is necessary to introduce excess air (oxygen) for combustion and heating. Furthermore, since gas such as LNG contains hydrogen, a large amount of water is generated during combustion. Therefore, in the reduction process using these fossil fuels as a heat source, large amounts of oxygen and water inevitably exist in the furnace, which prevents the reduction reaction from proceeding, and even if reduction is possible, the produced metals Problems such as partial oxidation (reoxidation) may occur, and as a result, high quality ferronickel may not be obtained.

Therefore, in the smelting method according to the present embodiment, the reduction process is performed using an electrically heated reduction furnace that uses electricity as a heat source. By the reduction treatment, it is possible to eliminate the mixing of oxygen into the furnace and the generation of water, and it is possible to suppress the oxidation of the mixture that inevitably oxidizes as much as possible. This makes it possible to improve the metallization rate and the nickel content in the metal, and to produce high quality ferronickel.

Specifically, in an electrically heated reduction furnace, the reduction process is performed by heating the furnace to a predetermined temperature using electrical energy while keeping the inside of the furnace at positive pressure (1 atmosphere or more) while flowing inert gas. conduct. In such an electrically heated reduction furnace, it is possible to maintain a state in which substantially no oxygen exists in the furnace, and it is also possible to realize a state in which no water is generated. With such an atmosphere in the furnace, the reduction treatment progresses uniformly on the mixture, and there is no fear that the produced metal will be re-oxidized, so that high quality ferronickel can be obtained.

Note that when the mixture is introduced into the reduction furnace, air (oxygen) is inevitably brought into the mixture. Oxygen brought into the furnace together with this mixture may cause variations in the reduction reaction or reoxidation of the metal.

Therefore, in the present invention, a method of supplying reducing gas to the place where the mixture is introduced into the furnace is also used. Since the oxygen brought into the furnace by the supply of the reducing gas reacts with the supplied reducing gas and is consumed, there is no possibility of adverse effects on the properties of the pellets such as oxidation. As the reducing gas to be supplied, one or more of hydrogen and carbon monoxide can be used. An appropriate one may be selected in consideration of the amount of oxygen brought into the furnace, the reactivity of reducing gas, cost, etc.

Further, since the smelting method according to the present embodiment uses electricity for heating, carbon dioxide (CO ₂ ) is not generated during heating. Therefore, compared to the case where coal, heavy oil, LNG, etc. are used as the heating fuel, it is possible to effectively reduce CO ₂ emissions, especially in the smelter. Furthermore, compared to a heating method using a burner, the amount of exhaust gas is much smaller, so the amount of thermal energy carried away with the exhaust gas is also extremely small. Specifically, when using electricity, energy consumption can be reduced by several tens to 50% compared to using burners such as coal or LNG (liquefied natural gas), making it extremely efficient. It becomes possible to carry out smelting operations.

In addition, since the amount of exhaust gas is small, the generation of dust can be greatly suppressed. Therefore, costs and equipment costs for exhaust gas treatment and dust collection can be effectively reduced.

Furthermore, electrical heating has the advantage that temperature can be easily and accurately controlled. For this reason, it is particularly suitable to use a mobile hearth furnace (electrically heated mobile hearth furnace) that continuously performs a series of heating and cooling treatments as the reduction furnace.

The mobile hearth furnace is not particularly limited, and for example, a rotary hearth furnace that is circular and divided into a plurality of processing areas can be used. A rotary hearth furnace rotates in a predetermined direction while performing different treatments in each region. In a rotary hearth furnace, the processing temperature and processing time in each region can be adjusted by controlling the time taken to pass through each region (travel time, rotation time). Each rotation smelts the mixture. Further, as the mobile hearth furnace, a roller hearth kiln or the like may be used.

(reduction furnace)
The reduction furnace used in the present invention will be described in detail below. FIG. 2 is a perspective view showing an example of the reduction furnace according to the embodiment. FIG. 3 is a plan view of the reduction furnace of FIG. 2. FIG. 4 is a cross-sectional view taken along line AA in FIG. 2. FIG. 5 is a sectional view taken along line BB in FIG. 4. FIG. 6 is a sectional view taken along line CC in FIG. 2.

As shown in FIGS. 2 to 4, the reduction furnace 1 according to the embodiment is a rotary hearth furnace 10, which is a type of mobile hearth furnace. Specifically, the rotary hearth furnace 10 (reduction furnace 1) includes a cylindrical or cylindrical hearth furnace main body 11 in which a reduction treatment of a mixture P formed into pellets or the like is performed, and a rotary hearth furnace body 11 in which a mixture P is transferred into a rotary hearth. Reducing gas RG is supplied to the input section 21 that inputs into the furnace interior 16 of the furnace 10 (reduction furnace 1), the recovery section 25 that recovers the product obtained after the mixture P is reduced, and the input section 21. A reducing agent supply section 70 is provided.

Here, the furnace interior 16 means the inside of the rotary hearth furnace 10, which is the reduction furnace 1. Note that the inside of the hearth furnace body 11 is referred to as a main body interior 36, the interior of the input section 21 is referred to as an input section interior 26, and the interior of the recovery section 25 is referred to as a recovery section interior 27. The inside of the furnace 16 is the sum of the inside of the main body 36, the inside of the input section 26, and the inside of the recovery section 27. Note that the internal space of the reducing agent supply section 70 is not included in the furnace interior 16.

As shown in FIG. 4, a rotary hearth 12 is provided inside the main body 36 of the hearth furnace main body 11 and is capable of rotating the placed mixture P in the direction of an arrow M. Inside the input section 26 of the input section 21, a conveyance section 321 capable of conveying the mixture P introduced in the direction of the arrow _IP onto the rotary hearth 12 is provided. Inside the recovery unit 27 of the recovery unit 25, there is a transportable conveyor for receiving the product obtained after the reduction treatment of the mixture P from the rotary hearth 12, discharging it in the direction of the arrow _OS , and recovering it. A section 325 is provided. In the rotary hearth furnace 10, the mixture P introduced into the input section 21 is reduced on the rotary hearth 12 of the hearth furnace main body 11, and the product obtained after the reduction treatment of the mixture P is carried out in the recovery section. It can be collected at 25.

As shown in FIG. 5, the hearth furnace body 11 of the rotary hearth furnace 10 includes a body bottom portion 31, a body first side surface portion 33 which is the inner side surface of the body side surface portions 32, and A main body interior 36 is formed by being surrounded by a main body second side surface portion 34, which is an outer side surface of the main body, and a main body top portion 35.

In the hearth furnace body 11, the body bottom portion 31, the body first side surface portion 33, the body second side surface portion 34, and the body top portion 35 each have an outer surface member 41 disposed on the outside, and an outer surface member 41 is disposed on the body inside 36 side. A heat insulating material 42 is disposed at.

As shown in FIG. 5, in the hearth furnace main body 11, an electric heater 50 is provided on the surface of the heat insulating material 42 inside the main body 36 at the main body side parts 32 (33, 34) and the main body top part 35. That is, in the reduction furnace 1, an electric heater 50 is provided inside the main body 36 at the main body side parts 32 (33, 34) and the main body top part 35.

Specifically, the hearth furnace main body 11 is provided with a first side electric heater 53 as the electric heater 50 in the main body interior 36 of the main body first side surface portion 33 of the main body side portion 32 . Further, in the hearth furnace main body 11 , a second side electric heater 54 as an electric heater 50 is provided inside the main body 36 of the main body second side surface portion 34 of the main body side portion 32 . Further, the hearth furnace body 11 is provided with a top electric heater 55 as an electric heater 50 inside the body 36 at the top 35 of the body.

The structure of the electric heaters 50, such as the first side electric heater 53, the second side electric heater 54, and the top electric heater 55, is not particularly limited. In FIG. 5, a rod-shaped heating element 58 is formed into a substantially rectangular shape as a whole along the vertical direction of the page of FIG. 5 by repeating U-shaped bending multiple times on the front and back sides of the page of FIG. An electric heater 50 having a similar structure is shown. In FIGS. 2 to 4, the electric heater 50 disposed inside the main body 36 is shown as a broken line rectangle or a solid line rectangle. A heater 50 is shown.

As the heating element 58 constituting the electric heater 50, for example, a silicon carbide SiC heating element, a molybdenum disilicide MoSiO ₂ heating element, a graphite heating element, etc. are used. Among these, the silicon carbide SiC heating element and the molybdenum disilicide MoSiO ₂ heating element are less likely to affect the reduction treatment of the mixture P, are easy to handle, have high durability, and are relatively inexpensive. Therefore, it is preferable.

The electric heater 50 consists of a heating element 58 that is generally rectangular in shape, has a generally small thickness, and can control temperature with very high precision. For this reason, according to the rotary hearth furnace 10 in which the electric heater 50 is provided in the main body side part 32 and the main body top part 35, a wide soaking zone is provided inside the main body 36, which allows temperature control with very high precision. It is easy to do. Therefore, according to the rotary hearth furnace 10 in which the electric heater 50 is provided on the main body side part 32 and the main body top part 35, it is easy to carry out an efficient reduction reaction of the mixture P compared to the external size.

On the other hand, in a conventional rotary hearth furnace using a burner, a large soaking auxiliary area is required to form a soaking zone around the mixture P on the hearth, and the soaking zone is formed with high precision. It is also difficult to control the temperature. For example, in conventional rotary hearth furnaces using burners, it is necessary to create a steady flow of heated gas to create a soaking zone around the mixture P on the hearth. For this reason, in a conventional rotary hearth furnace using a burner, an air supply section that supplies air to the inside of the hearth furnace body and an exhaust section that exhausts air from the inside of the main body are usually operated to remove large amounts of air from the mixture P. formed to have a distance. That is, in a conventional rotary hearth furnace using a burner, a large soaking area is usually required between the mixture P and the air supply part of the hearth furnace body, and a large area between the mixture P and the hearth furnace body is required. A large heat equalization auxiliary area is required between the exhaust section and the exhaust section.

In addition, in conventional rotary hearth furnaces that use LNG burners, auxiliary equipment such as LNG supply equipment and exhaust equipment are usually installed around the hearth furnace body of the rotary hearth furnace, so the entire rotary hearth furnace is Become larger. Furthermore, in conventional rotary hearth furnaces that use pulverized coal burners, in addition to auxiliary equipment such as exhaust equipment, auxiliary equipment such as coal charging equipment is installed on the inner peripheral side of the hearth furnace body of the rotary hearth furnace. The entire rotary hearth furnace becomes even larger. As described above, it is difficult for the conventional rotary hearth furnace using a burner to perform an efficient reduction reaction of the mixture P compared to the size of the rotary hearth furnace.

Note that in the burner furnace, a soaking zone is formed using a flow of heated gas. However, in the electric furnace using the electric heater 50, a soaking zone is formed near the electric heater 50 because a flow of heating gas is not used. For this reason, if the electric heater 50 is provided only on one of the main body side part 32 and the main body top part 35 in the rotary hearth furnace 10, it is likely to be difficult to widen the soaking zone inside the main body 36.

On the other hand, according to the rotary hearth furnace 10 in which the electric heater 50 is provided on the main body side part 32 and the main body top part 35, it is easy to widen the soaking zone inside the main body 36, and the burner heating type Compared to traditional rotary hearth furnaces, more ore can be processed with the same size furnace. According to the electric heating type rotary hearth furnace 10, temperature control is possible with very high precision, and ferronickel with high characteristics and small quality variations can be manufactured.

In addition, in the rotary hearth furnace 10, an example is shown in which the electric heater 50 is provided on the surface of the heat insulating material 42 inside the main body 36 at the main body side parts 32 (33, 34) and the main body top part 35. However, as a modified example of the rotary hearth furnace 10, there is a rotary hearth furnace in which an electric heater 50 is further provided on the main body bottom 31, or only one of the main body first side surface 33 and the main body second side surface 34 of the main body side surface 32 is provided. It may also be a rotary hearth furnace in which an electric heater 50 is provided.

Further, in the rotary hearth furnace 10, an example is shown in which 12 first side electric heaters 53, 20 second side electric heaters 54, and 12 top electric heaters 55 are provided. However, as a modification of the rotary hearth furnace 10, a rotary hearth furnace may be used in which the numbers of the first side electric heater 53, the second side electric heater 54, and the top electric heater 55 are changed as appropriate.

Furthermore, in the rotary hearth furnace 10, an example is shown in which the electric heater 50 is provided only in the hearth furnace main body 11. However, as a modification of the rotary hearth furnace 10, it may be a rotary hearth furnace in which one or more of the input section 21 and the recovery section 25 are provided with an electric heater 50.

<Processing zone>
The rotary hearth furnace 10, which is the reduction furnace 1, is a mobile hearth furnace 10 that has a plurality of treatment zones 60 in the furnace interior 16 that are controllably partitioned to have different reaction temperatures. Specifically, as shown in FIGS. 3 and 4, the rotary hearth furnace 10 has a plurality of processing zones 60 in the furnace interior 16, including a charging zone 61, a temperature raising zone 62, a temperature holding zone 63, and a cooling zone. zone 64 and recovery zone 65.

More specifically, as shown in FIGS. 3 and 4, the rotary hearth furnace 10 includes a charging zone 61 provided in the charging section 21, a temperature increasing zone 62 provided in the hearth furnace main body 11, and a temperature increasing zone 62 provided in the hearth furnace main body 11. It includes a holding zone 63, a cooling zone 64, and a recovery zone 65 provided in the recovery section 25.

Adjacent processing zones 60 are separated by a partition member 120 in order to allow the processing zones 60 to be controlled at different reaction temperatures. Specifically, in the hearth furnace body 11, the temperature raising zone 62, the temperature holding zone 63, and the cooling zone 64, which are provided adjacent to each other, are partitioned by partition members 122, 123, and 124, respectively. More specifically, in the hearth furnace body 11, the temperature raising zone 62 and the temperature holding zone 63 are partitioned by a partition member 122, and the temperature holding zone 63 and the cooling zone 64 are partitioned by a partition member 123. The cooling zone 64 and the temperature increasing zone 62 are separated by a partition member 124.

Furthermore, in the rotary hearth furnace 10 , a charging zone 61 provided in the charging section 21 and a temperature rising zone 62 provided in the hearth furnace main body 11 are partitioned off by a partition member 121 . The provided cooling zone 64 and the recovery zone 65 provided in the recovery section 25 are partitioned off by a partition member 125.

FIG. 5 shows the partition member 122, and FIG. 6 shows the partition member 121. Note that both the partition member 122 shown in FIG. 5 and the partition member 121 shown in FIG. 6 are arranged further back than the mixture P in the paper plane. 5 and 6 show the surfaces of the partitioning member 122 and the partitioning member 121, which are arranged on the back side of the paper plane than the mixture P.

Although the shape of the partition member 120 is not particularly limited, for example, a plate-shaped body is used. The material of the partition member 120 is not particularly limited as long as it has sufficient heat resistance, but for example, fireproof ceramics such as SiC, firebricks or fireproof boards whose main components are alumina, silica, magnesia, etc., and high-temperature metals may be used. It will be done.

The output of each electric heater 50 can be individually controlled to allow the treatment zone 60 to be controlled to different reaction temperatures. Note that the output of the electric heaters 50 may be controlled to the same value for one or more of the electric heaters 50, if necessary. The output of the electric heater 50 is controlled based on, for example, a value measured with a thermometer (not shown). Each processing zone 60 can be controlled to a different reaction temperature by controlling the output of the partition member 120 and each electric heater 50.

In the rotary hearth furnace 10, the processing zone 60 includes an input zone 61, a temperature raising zone 62, a temperature holding zone 63, a cooling zone 64, and a recovery zone 65. However, as a modification of the rotary hearth furnace 10, it may be a rotary hearth furnace that does not include one or more of these processing zones 60 or that further includes a processing zone 60 other than those described above.

<Reducing agent supply section>
As shown in FIGS. 2 and 6, the rotary hearth furnace 10 includes a reducing agent supply section 70 that supplies a reducing gas RG to an input section 21 that inputs the mixture P into the furnace interior 16. The reducing agent supply section 70 includes a reducing agent introduction section 75 that supplies the reducing gas RG into the input section 21 from above the outer surface member 221 that constitutes the input section 21 .

By disposing the reducing agent introduction part 75 above the outer surface member 221, the reducing gas RG supplied from the reducing agent introduction part 75 into the input part 21 is supplied toward the mixture P below. ing. As a result, the reducing gas RG supplied from the reducing agent introducing section 75 into the charging section 21 is sufficiently supplied to the charging section interior 26 of the charging section 21, particularly to the portion including the periphery of the mixture P. There is. In the rotary hearth furnace 10, the reducing gas RG is supplied to the reducing agent supply section 70 during the reduction process. In the reducing agent supply section 70, the oxygen concentration in the furnace interior 16 is reduced by causing the oxygen that is inevitably brought in when charging the mixture P into the furnace interior 16 to react with the reducing gas RG supplied into the charging section 21. Now it can be lowered even further.

[Separation process]
In the separation step S4, slag is separated from the reduced product produced in the reduction step S3, and metal (ferronickel) is recovered. Specifically, the metal phase is recovered from a mixture (reduced product) containing a metal phase (metal solid phase) and a slag phase (slag solid phase) obtained by reducing the pellets.

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

In addition, the obtained metal phase and slag phase can be easily separated because of their poor wettability, and the large inclusions obtained in the above-mentioned reduction step S3 can be separated, for example, by a predetermined head. The metal phase and the slag phase can be easily separated from the mixed materials by providing a filter and dropping it, or by applying a shock such as a predetermined vibration during sieving.

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

[Mixing process]
Appropriate amounts of nickel oxide ore as raw material ore, iron ore, silica sand and limestone as flux components, binder, and carbonaceous reducing agent (coal powder, carbon content: 76% by weight, average particle size: approximately 63 μm) A mixture was obtained by mixing using a mixer while adding water. The carbonaceous reducing agent is used in an amount that is 31% by mass relative to 100% by mass, which is the amount necessary to reduce nickel oxide and iron oxide (Fe ₂ O ₃ ) contained in the nickel oxide ore. Contained.

[Mixture forming process]
Next, the obtained mixture was granulated into pellets using a pan-type granulator, and the pellets were sieved to a size of φ16.0±0.7 mm. Thereafter, the sieved pellet sample was divided into three parts, and each sample was subjected to the next reduction step.

[Reduction process]
Each sample was charged into the reduction furnace 1 (rotary hearth furnace 10) shown in FIG. 2, and subjected to reduction treatment under the conditions shown in Table 3 below.
For the reduction treatment, electrically heated reduction furnaces of the same size were used, the reduction temperature was 1380°C, and the reduction time (that is, the holding time at 1380°C) was 25 minutes. Inside the reduction furnace, ash (mainly composed of SiO ₂ , containing small amounts of oxides such as Al ₂ O ₃ and MgO as other components) is spread on the hearth, and pellets are placed on top of it. did.

More specifically, in Examples 1 and 2, the reducing gas shown in Table 3 was supplied to the reducing agent supply section 70 at the point where the mixture was introduced into the furnace (input section 21). The amount of reducing gas supplied was set to 3% when the amount necessary to reduce the nickel oxide and iron oxide (Fe ₂ O ₃ ) contained in the nickel oxide ore, which is the raw material ore, to 100%. .

Further, in Comparative Example 1, the same electrically heated reducing furnace as in the example was used, but no reducing gas was supplied to the reducing agent supply section 70 at the place where the mixture was introduced (input section 21).

The nickel (Ni) metal ratio and the nickel (Ni) content in the metal of the reduced product obtained by performing the reduction treatment in this way were analyzed and calculated using an ICP emission spectrometer (SHIMAZU S-8100). . Table 3 below shows the values calculated from the analysis results.
The nickel metal ratio was calculated by formula [1], and the nickel content in metal was calculated by formula [2].
Ni metal ratio = amount of metalized Ni in the pellet ÷ (amount of all Ni in the pellet) x 100 (%) ... Formula [1] Ni content rate in metal = amount of metalized Ni in the pellet ÷ (Total amount of metalized Ni and Fe in the pellet) x 100 (%) ... Formula [2]

Further, the obtained reduced product was pulverized by wet processing, and then the metal was recovered by magnetic separation. Then, the nickel (Ni) metal recovery rate was calculated from the nickel content of the nickel oxide ore, the amount of nickel, and the amount of nickel recovered. Note that the recovery rate of nickel metal is as shown in equation [3].
Ni metal recovery rate = Amount of Ni recovered ÷ (Amount of ore input x Ni content ratio in ore) x 100 ... Formula [3]

As shown in Table 3, good results were obtained in Examples 1 and 2 in which the reduction treatment was performed using an electrically heated reduction furnace. That is, the nickel metalization rate was 96% or more, the nickel content in the metal was 17% or more, and the metal recovery rate was 96% or more. On the other hand, in Comparative Example 1, in which reduction treatment was performed without supplying reducing gas to the inlet to the reduction furnace, results were worse than in Examples.

The reason for this result is that in Examples 1 and 2, the reduction process was carried out using an electrically heated reduction furnace, which not only allowed the temperature to be controlled with high precision, but also substantially reduced the amount of oxygen and water. This is thought to be because the process could be carried out in a free atmosphere, which allowed the reduction reaction to occur uniformly and the produced metal to not be reoxidized. Furthermore, since it is an electrically heated reduction furnace, there is no CO ₂ emission around the furnace, and compared to burner heating using pulverized coal or LNG, CO ₂ emissions can be significantly reduced.

1 Reduction furnace 10 Rotary hearth furnace (mobile hearth furnace)
11 Hearth furnace body 12 Rotary hearth (hearth)
16 Inside of Furnace 21 Input Part 22 Temperature Raising Part 23 Temperature Holding Part 24 Cooling Part 25 Recovery Part 26 Inside Input Part 27 Inside Recovery Part 32 Bottom of Main Body 33 First Side of Main Body (Inner Side)
34 Main body second side surface (outer side surface)
35 Top of main body 36 Inside of main body 41 External member 42 Insulating material 50 Electric heater 53 First side electric heater 54 Second side electric heater 55 Top electric heater 58 Heating element 60 Processing zone 61 Input zone 62 Temperature raising zone 63 Temperature holding zone 64 Cooling Zone 65 Recovery zone 70 Reducing agent supply section 75 Reducing agent introduction section 120, 121, 122, 123, 124, 125 Partition member 221, 225 External member 321, 325 Conveyance section P Pellet (mixture)
RG reducing gas

Claims (4)

A nickel oxide ore smelting method for producing ferronickel by reducing a mixture containing nickel oxide ore as a raw material ore, the method comprising:
Mixing the nickel oxide ore and a carbonaceous reducing agent to form a lumpy mixture,
The mixture is charged into an electrically heated reduction furnace that uses electricity as a heat source, and is heated to a predetermined reduction temperature in the reduction furnace to perform a reduction treatment,
The reduction furnace includes a reducing agent supply unit that supplies reducing gas to an input unit that inputs the mixture into the inside of the reduction furnace,
supplying the reducing gas to the reducing agent supply section during the reduction process;
Method for smelting nickel oxide ore. The reducing gas is one or more of hydrogen and carbon monoxide,
The method for smelting nickel oxide ore according to claim 1. The reduction temperature of the reduction treatment is 1200°C or more and 1500°C or less,
The method for smelting nickel oxide ore according to claim 1 or 2. The reduction furnace is a rotary hearth furnace,
The method for smelting nickel oxide ore according to claim 1 or 2.

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