JP2023176596A - Refining method for nickel oxide ore, and pellet production method - Google Patents

Abstract

To provide a refining method for nickel oxide ore capable of efficiently producing high-quality valuable metals in the refining method including production of valuable metals by reduction of pellets including the above ore, and to provide a production method for the pellets used in the above refining method.SOLUTION: A refining method for nickel oxide ore using pellets in this invention comprises: a mixture preparation process of preparing a mixture containing nickel oxide ore and a carbonaceous reducer; a mixture-molding process of molding pellets from the mixture; a reduction treatment process of obtaining a nickel-including valuable metal and a slag by heating reduction of the pellets obtained in the mixture-molding process; and a collection process of collecting the valuable metal by separating that metal obtained by the reduction treatment process from the slag. In the above processes, the solidus temperature of the pellet is controlled to 1,250°C or more but the heating reduction temperature in the reduction treatment process or less.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method for smelting nickel oxide ore and a method for producing pellets. More specifically, the present invention relates to a method for smelting nickel oxide ore using pellets and a method for producing pellets used in the method for smelting nickel oxide ore.

The nickel oxide ore called limonite or saprolite is smelted using a pyro-smelting method in which nickel matte is produced by sulfurization roasting with sulfur in a smelting furnace, or a carbonaceous material using a rotary kiln or mobile hearth furnace. A pyrometallurgical method that produces alloys containing nickel by reduction using a reducing agent, and mixed sulfides (mixed sulfides) by adding a sulfiding agent to the leachate obtained by leaching nickel and cobalt with sulfuric acid using an autoclave. A hydrometallurgical method for producing mixed sulfide (mixed sulfide) is known.

Among the various smelting methods mentioned above, when attempting to smelt nickel oxide ore by charging it into a kiln or furnace with a carbon source and subjecting it to reduction treatment (pyrometallurgy method), the nickel metal produced by reduction is is preferable from the viewpoint of productivity. This is because if the nickel metal has a small size of, for example, several tens of micrometers, it will be difficult to separate it from the slag that is generated at the same time, and the recovery rate (yield) of nickel will decrease significantly.
Processing high nickel grade ores is the easiest way to obtain coarse nickel metal. However, in recent years resource conditions have become severe worldwide, and it is not easy to obtain ore with high nickel grade.

Therefore, research is being conducted to obtain coarse nickel metal from low-grade ores (for example, ores with a nickel grade of 1.0% by mass or less). For example, Patent Document 1 discloses that when producing nickel metal (granular metal) by heating pellets containing a metal oxide and a carbonaceous reducing agent in a reduction melting furnace and reducing and melting the metal oxide, The average diameter of the supplied pellets is 19.5 mm or more and 32 mm or less, and the bed density calculated from the projected area ratio of the pellets to the hearth when heating the pellets on the hearth is 0.5 or more and 0.8 or less. A method of improving the productivity of nickel metal by controlling the nickel metal is disclosed.

Japanese Patent Application Publication No. 2011-256414

However, with the technology of Patent Document 1, the production of pellets is costly and the density of pellets in the furnace needs to be adjusted to a predetermined value, resulting in no improvement in productivity, so nickel metal A problem has arisen in that the manufacturing cost is high.

In view of the above circumstances, the present invention provides a smelting method for producing valuable metals by reducing pellets containing nickel oxide ores, which can efficiently produce high-quality (high-grade) valuable metals. The present invention aims to provide a smelting method and a method for producing pellets used in the smelting method.

As a result of intensive studies to solve the above-mentioned problems, the present inventor discovered that valuable metals can be efficiently obtained by controlling the solidus temperature of the pellets, and has completed the present invention.

The nickel oxide ore smelting method of the first invention is a nickel oxide ore smelting method using pellets, and includes a mixture preparation step of preparing a mixture containing nickel oxide ore and a carbonaceous reducing agent; A mixture forming step of forming pellets, a reduction treatment step of heating and reducing the pellets obtained in the mixture forming step to obtain a valuable metal containing nickel and slag, and a valuable metal and slag obtained in the reduction treatment step. and a recovery step of separating valuable metals and recovering valuable metals, and the solidus temperature of the pellets is 1250° C. or higher and lower than the heating reduction temperature in the reduction treatment step.
A method for smelting nickel oxide ore according to a second invention is characterized in that, in the first invention, the solidus temperature of the pellets is 1250°C or more and 1380°C or less.
The pellet manufacturing method of the third invention is a pellet manufacturing method used in a nickel oxide ore smelting method, and includes a mixture preparation step of preparing a mixture containing a nickel oxide ore and a carbonaceous reducing agent; and a mixture forming step of forming pellets from the smelting method, and is characterized in that the solidus temperature of the pellets is adjusted to be 1250° C. or higher and lower than the heating reduction temperature in the smelting method.
The method for producing pellets according to a fourth aspect of the invention is characterized in that, in the third aspect, the solidus temperature of the pellets is adjusted to be 1250° C. or more and 1380° C. or less.

According to the method for smelting nickel oxide ore of the present invention, pellets having a solidus temperature within a predetermined range are used, so that a valuable metal with a large particle size can be obtained. Therefore, valuable metals can be efficiently produced.
According to the method for producing pellets of the present invention, by keeping the solidus temperature within a predetermined range, pellets can be produced that yield valuable metals with large particle sizes when used in a method for smelting nickel oxide ore. I can do it.

1 is a schematic flow diagram of a method for smelting nickel oxide ore according to the present embodiment.

The nickel oxide ore smelting method of the present embodiment is a pyrometallurgical method for obtaining valuable metals containing nickel, and by using pellets having a solidus temperature within a predetermined range, valuable metals having a large particle size can be obtained. It is characterized by being able to manufacture. Further, the method for producing pellets of the present invention is characterized in that pellets from which valuable metals having a large particle size can be obtained can be produced by using the method for smelting nickel oxide ore.

Hereinafter, a method for smelting nickel oxide ore according to the present embodiment will be explained based on the drawings.
As shown in FIG. 1, the method for smelting nickel oxide ore of the present embodiment (hereinafter referred to as the present smelting method) uses a mixture containing nickel oxide ore as a raw material ore and a carbonaceous reducing agent as a reducing agent. a mixture preparation step S1 of preparing a mixture, a mixture forming step S2 of forming pellets from the obtained mixture, a reduction treatment step S3 of heating and reducing the pellets at a predetermined reduction temperature in a reduction furnace, and reduction after the reduction treatment step. It includes a recovery step S4 of separating slag from objects and recovering valuable metals.
In addition, in the reduction treatment step S3, the temperature at which the pellets are heated and reduced at a predetermined reduction temperature in the reduction furnace corresponds to the "heat reduction temperature" in the claims. Hereinafter, this temperature may be simply referred to as the reduction temperature.

(Mixture preparation step S1)
The mixture preparation step S1 of the present smelting method is a step of preparing a mixture containing a nickel oxide ore, which is a raw material ore, and a carbonaceous reducing agent, which is a reducing agent.
For example, the mixture preparation step S1 is a step of preparing a mixture by mixing powdered nickel oxide ore and powdered carbonaceous reducing agent while adding an appropriate amount of water. Note that the mixture may contain powdered iron ore, a flux component, a binder, and the like as optional additives to be described later.

In addition, if the composition and mixing ratio of the nickel oxide ore, carbonaceous reducing agent, optional additives, etc. in the mixture are adjusted so that the solidus temperature of the pellets, which will be described later, is within a predetermined range, Not particularly limited.
For example, pellets are preliminarily prepared from the mixture, and the solidus temperature of the prepared pellets is measured using a thermogravimetric differential thermal analyzer (TG-TDA). Based on the measured values, the content, composition ratio, etc. of nickel oxide ore in the mixture can be adjusted. In addition, if it is necessary to adjust the solidus temperature based on the measurement, it can be adjusted using a component containing, for example, magnesium oxide (MgO), calcium oxide (CaO), silicon dioxide (SiO ₂ ), etc. It's okay. Particularly from an economic point of view, materials containing SiO ₂ are preferred because they are inexpensive.

In the mixture preparation step S1, the method of mixing the nickel oxide ore and the like is not particularly limited, and for example, a commercially available mixer can be used. Further, when mixing nickel oxide ore, etc., kneading may be performed at the same time to improve mixability, or kneading may be performed after mixing.
In the mixture preparation step S1, kneading can be carried out using a batch kneader such as a Brabender, a Banbury mixer, a Henschel mixer, a helical rotor, a roll, a single-screw kneader, a twin-screw kneader, or the like. By kneading the mixture, shearing force can be applied to the mixture, so that the carbonaceous reducing agent, powdered nickel oxide ore, etc. can be deagglomerated and mixed uniformly. Moreover, it is possible to improve the adhesion of each particle and to reduce voids.
Therefore, by performing the kneading operation in the mixture preparation step S1, the reduction reaction in the pellets formed from the mixture becomes more likely to occur in the reduction treatment step S3, and the reaction can proceed uniformly. Then, since the reaction time of the reduction reaction in the reduction treatment step S3 can be shortened, the operability can be improved.
Moreover, since the components within the pellet can be made homogeneous, it is possible to suppress variations in the quality of valuable metals after the recovery step S4.

Table 1 shows an example of the composition (% by mass) of the raw materials used for preparing the mixture. Note that the compositions shown in the table are merely examples, and the nickel oxide ore may contain a composition other than the composition shown in the table.

(nickel oxide ore)
The nickel oxide ore is not particularly limited as long as it contains nickel as nickel oxide (NiO). For example, limonite ore, saprolite ore, etc. can be used. Note that the nickel oxide ore contains iron oxide (Fe ₂ O ₃ ) as a typical component.

Note that the notation "~" means "more than or equal to", and for example, 1% to 2% by mass of nickel in the nickel oxide ore in Table 1 means 1% to 2% by mass of Ni in the nickel oxide ore. % or less.

(Carbonaceous reducing agent)
Examples of the carbonaceous reducing agent include coal powder, coke powder, and the like. Note that part or all of it may be composed of plant-derived components, such as starch.
It is preferable to use a carbonaceous reducing agent having a particle size and particle size distribution equivalent to that of the nickel oxide ore, which is the raw material ore. With such a size, it is easy to mix uniformly when mixing, and the reduction reaction also tends to proceed uniformly.

In addition, the mixing ratio of the carbonaceous reducing agent in the mixture preparation step S1 is determined based on the amount of the carbonaceous reducing agent necessary to reduce the nickel oxide, cobalt oxide, and iron oxide that constitute the nickel oxide ore in just the right amount. When taken as 100%, it is preferable to mix it so that it is 50% or less, more preferably 40% or less. On the other hand, the lower limit of the mixing amount of the carbonaceous reducing agent is not particularly limited, but for example, when the total value of chemical equivalents explained below is 100%, it is preferably 20% or more, more preferably 23% or more.
In other words, in the mixture preparation step S1, the ratio of mixing the carbonaceous reducing agent (mixing ratio) is the amount of the carbonaceous reducing agent contained in the pellets (mixed amount of the carbonaceous reducing agent), the total value of chemical equivalents being 100 %, if it is 20% or more and 50% or less, the reduction reaction in the reduction treatment step S3 described below can proceed efficiently, so that valuable metal with high nickel grade (mass%) can be efficiently produced. can do.

Note that the unit of the mixing ratio (%) of the carbonaceous reducing agent may be a molar ratio or a mass ratio. That is, the mixing ratio (%) of the carbonaceous reducing agent may be within the above range in terms of molar ratio or mass ratio.
In addition, the amount of carbonaceous reducing agent necessary to reduce nickel oxide, cobalt oxide, and iron oxide in just the right amount is the amount of carbonaceous reducing agent contained in the pellets obtained by molding the mixture in the reduction treatment step S3. The total value of the chemical equivalent required to reduce the entire amount of nickel oxide to nickel metal and the chemical equivalent required to reduce the iron oxide contained in the pellet to iron metal (hereinafter referred to as "total value of chemical equivalent") (also called).

(Other ingredients)
In addition, the mixture may contain iron ore, a flux component, and a binder in addition to the above-mentioned nickel oxide ore and carbonaceous reducing agent.
As the iron ore, for example, iron ore having an iron grade of about 50% by mass or more, hematite obtained by hydrometallurgy of nickel oxide ore, etc. can be used.
Examples of the flux component include calcium oxide (CaO), calcium hydroxide (Ca(OH) ₂ ), calcium carbonate (CaCO ₃ ), and silicon dioxide (SiO ₂ ).
Examples of the binder include bentonite, polysaccharide, resin, water glass, and dehydrated cake.

Further, the size of the nickel oxide ore, iron ore, flux component, etc. contained in the mixture is not particularly limited as long as it does not affect the shaping of the mixture. For example, the particle size is preferably 0.01 mm to 20 mm, more preferably 0.01 mm to 10 mm, and even more preferably 0.2 mm to 0.8 mm.

The particle size of the nickel oxide ore, etc. may be that of a single particle, or may be that of an aggregated particle formed by agglomerating single particles. For example, if pulverized nickel oxide ore is passed through a sieve (opening 0.1 mm), it is possible to obtain powdered nickel oxide ore (particles with a major diameter of approximately 0.03 mm to 0.3 mm) that pass through the sieve. can.

(Mixture forming process S2)
The mixture prepared in the mixture preparation step S1 is subjected to the next step, the mixture forming step S2.
The mixture forming step S2 of the present smelting method is a step of forming pellets by forming the supplied mixture.

(Solidus temperature of pellet)
The composition and mixing ratio of the mixture are adjusted so that the solidus temperature of the formed pellets falls within a predetermined range. Specifically, the solidus temperature of the pellets is adjusted to be 1250° C. or higher.
If the solidus temperature of the pellets is less than 1250°C, the liquid phase ratio will become too high during the reduction treatment in the reduction treatment step S3, which will be described later, and the pellets will melt and react with the hearth, resulting in extremely shortened furnace life. , the recovery rate of valuable metals may decrease.
On the other hand, if the solidus temperature of the pellet becomes too high, the reduction reaction may not proceed sufficiently during the reduction treatment in reduction treatment step S3, which will be described later, or the liquid phase ratio of the pellet will become low, causing the valuable metal to become coarse. Sometimes there isn't. Therefore, the upper limit of the solidus temperature of the pellet is preferably adjusted to be equal to or lower than the temperature during the reduction treatment in the reduction treatment step S3 (that is, the reduction temperature). For example, when the reduction temperature is 1400°C, the upper limit of the solidus temperature of the pellet is preferably 1400°C or lower, more preferably 1380°C or lower, even more preferably 1350°C or lower, even more preferably 1330°C or lower. below ℃.

Therefore, the pellets prepared in the mixture forming step S2 are prepared so that the solidus temperature is 1250° C. or higher and lower than the reduction temperature during the reduction treatment in the reduction treatment step S3. For example, when the reduction temperature is 1400°C, the solidus temperature of the pellet is preferably adjusted to 1250°C or more and 1400°C or less, more preferably 1250°C or more and 1380°C or less, More preferably, the temperature is 1250°C or more and 1350°C or less, and even more preferably 1250°C or more and 1330°C or less.

The solidus temperature of the pellet can be measured using a thermogravimetric differential thermal analyzer (TG-DTA) described in Examples below.

Note that the solidus temperature refers to the temperature at which the pellet stably exists in a solid state at a temperature below this temperature, and at which a liquid phase is mixed or becomes a liquid state at a temperature higher than this temperature.

The shape of the pellets is not particularly limited as long as it can be stacked on the hearth of the reduction furnace.
For example, the shape may be an ellipse, a cube, a rectangular parallelepiped, a cylinder, or a sphere. Since such a shape is a simple shape and is not complicated, the molding cost can be suppressed. Moreover, the production of defective products can be suppressed, and the quality of the obtained molded products can be made uniform, so that a decrease in yield can be suppressed. Furthermore, it becomes easier to maintain strength.
In particular, the pellet shape is preferably spherical. Since the pellets are spherical, reduction treatment can be performed uniformly, and smelting can be performed with little variation and high productivity. When the shape of the pellet is spherical, it can be formed so that the diameter is about 10 mm or more and 30 mm or less. Further, when forming the shape into a rectangular parallelepiped, a cube, a cylinder, etc., it can be formed so that the inner dimensions in the vertical and horizontal directions are approximately 500 mm or less.

The size of the pellets is not particularly limited. For example, it is preferable that the volume of the pellet is 8000 mm ³ or more. By having a pellet volume of 8,000 ^mm3 or more, molding costs are suppressed, and the ratio of the surface area to the whole pellet is low, so reduction treatment is uniformly applied, resulting in less variation and high productivity. Can perform training.

In the mixture molding step S2, the means is not particularly limited as long as pellets can be molded from the mixture.
For example, a molded article can be formed from the mixture using a molding device such as a briquette machine, a pelletizer, or an extruder. As the molding device, for example, a device capable of kneading and molding the mixture under high pressure and high shear force is preferable. By kneading the mixture under high pressure and high shear, the mixture can be deagglomerated and kneaded effectively, and the strength of the resulting molded product can be increased.
It is also possible to mold using a briquette press. Apparatus may be selected as appropriate, taking into consideration the equipment, strength of the molded product, yield, etc.

(Drying treatment of pellets)
Note that the mixture molding step S2 may include a drying step of drying the molded pellets.
Generally, pellets may contain an excessive amount of water, for example about 50% by mass. If the pellets contain excessive moisture in this way, if they are heated rapidly, the moisture inside will vaporize at once, causing them to expand and break.
Therefore, the formed pellets are supplied to a drying process and dried. As for the drying conditions, the pellets are dried so that the solid content of the pellets is about 60% by mass and the moisture content is about 40% by mass or less. Note that it is preferable to dry the pellets so that the moisture content is about 30% by mass or less. That is, the pellets are dried so that the solid content of the pellets is about 70% by mass and the moisture content is about 30% by mass.

By reducing the moisture content of the pellets, it is possible to prevent the pellets from collapsing in the reduction treatment in the next reduction treatment step S3, making it easier to take out the pellets from the reduction furnace. Note that the reduction treatment in the reduction treatment step S3 may also be referred to as reduction heat treatment.
Further, since pellets are often sticky due to excess moisture, drying treatment makes them easier to handle.
Furthermore, in the next reduction treatment step S3, it is possible to suppress moisture contamination caused by the pellets in the reduction furnace. Thereby, the amount of water contained in the atmospheric gas in the reduction furnace can be more effectively reduced, and the oxidation of the metal contained in the reduced product can be more effectively suppressed.

The drying treatment in the drying step is not particularly limited as long as it can be treated so that the moisture content of the pellets falls within the above range.
For example, as a drying treatment in the drying step, hot air at 70° C. to 400° C. can be blown onto the pellets to dry them.
In particular, if the temperature of the pellets during the drying treatment is maintained at less than 100° C., it is possible to appropriately prevent the pellets from being destroyed during the drying treatment.

In addition, when drying large-volume pellets, cracks or cracks may appear before or after drying. If the volume of the pellet is large, it will melt and shrink during reduction, which will often cause cracks and cracks, but since the effects such as increase in surface area caused by cracks and cracks are small, no major problems will occur. On the other hand, it goes without saying that the drying process may be omitted if the pellets are not destroyed.

The drying treatment of the pellets may be performed continuously at once, or may be performed in multiple steps. By performing the drying process in multiple steps, bursting of the pellets can be more effectively suppressed. Note that when the drying process is performed in multiple steps, the drying temperature for the second and subsequent times is preferably 150° C. or higher and 400° C. or lower. By drying within this range, it becomes possible to dry without proceeding with the reduction reaction.

Table 2 shows an example of the solid content composition (excluding carbon) of the pellets after drying treatment. In addition, the composition shown in the table is only an example, and the pellets may contain a composition other than the composition shown in the table.
The solid content composition can be measured using an ICP emission spectrometer (SHIMAZU S-8100 model).

(Reduction processing step S3)
In the reduction treatment step S3 of the present smelting method, the pellets obtained in the mixture forming step S2 are charged into a reduction furnace (smelting furnace), heated to a predetermined temperature, and subjected to reduction treatment (reduction heat treatment). ). Through this reduction heat treatment, a reduced product containing slag and a valuable metal, which is a nickel-based alloy containing nickel, can be obtained.

In the reduction treatment step S3, the method of heating the pellets charged into the reduction furnace is not particularly limited. For example, pellets containing nickel oxide ore or the like are stacked on a hearth covered with bedding material of a reduction furnace, and the stack of pellets is heated. In addition, in order to suppress the reaction between the pellets and the hearth, the pellets may be placed on the hearth with alumina grains or the like spread thereon.

The heating temperature in the reduction treatment step S3 is not particularly limited. For example, the temperature can be about 1250°C to 1450°C, more preferably about 1300°C to 1400°C.

The time for the reduction heat treatment (treatment time) is not particularly limited.
For example, it can be set according to the temperature of the reduction furnace. For example, it is preferably 10 minutes or more, more preferably 15 minutes or more. On the other hand, the upper limit of the treatment time is preferably 50 minutes or less, more preferably 40 minutes or less, from the viewpoint of suppressing an increase in manufacturing costs.

In addition, in the reduction treatment step S3, the pellet stack subjected to the reduction heat treatment becomes a mixture (reduced product) of large chunks of metal and slag. By performing reduction heat treatment on pellets with a large apparent volume, large chunks of metal are likely to be formed. Therefore, it is possible to reduce the labor involved in recovering metal from the reduction furnace, and therefore it is possible to effectively suppress a decrease in the metal recovery rate. Note that the volume of the resulting mixture shrinks to about 50% to 60% by volume when compared to the pellet stack to be charged.

Further, in the reduction treatment step S3, a carbonaceous reducing agent as a reducing agent may be additionally added. The ratio of this additionally added carbonaceous reducing agent is not particularly limited.
For example, when the carbonaceous reducing agent contained in the pellets to be subjected to reduction treatment is 100% by mass, it is preferably in the range of 1% by mass or more and 30% by mass or less. By adding additionally within such a range, oxidation can be efficiently suppressed and over-reduction can also be prevented.

Further, the reduction furnace used in the reduction treatment step S3 is not particularly limited as long as it has the above function. For example, a rotary hearth furnace, a moving hearth furnace, or the like can be used as the reduction furnace.

For example, when a mobile hearth furnace is used as the reduction furnace, pellets can be processed more efficiently in the reduction furnace. In addition, by using a mobile hearth furnace, the reduction reaction proceeds continuously and the reaction can be completed in one piece of equipment. Control can be performed accurately.
Furthermore, when a mobile hearth furnace is used, heat loss during each treatment is reduced, allowing more efficient operation. In other words, if separate furnaces are used for the reaction, the temperature will drop and heat loss will occur when the pellet stack is moved between the furnaces, and the reaction atmosphere will change. Therefore, the reaction does not proceed immediately when it is reloaded into the furnace. On the other hand, when a mobile hearth furnace is used, each treatment can be performed with one piece of equipment, so that heat loss is reduced and the atmosphere inside the furnace can be controlled accurately. Therefore, since the reduction reaction can proceed more effectively, a valuable metal with a high nickel grade can be obtained more effectively.

(Collection process S4)
The recovery step S4 of the present smelting method is a step of separating the valuable metal and slag produced in the reduction treatment step S3 and recovering the valuable metal. Specifically, the valuable metal phase is separated from the inclusion (reduced product) containing a valuable metal phase (valuable metal solid phase) and a slag phase (slag solid phase) obtained by reducing heat treatment of pellets. to recover.

In the recovery step S4, the recovery method is not particularly limited as long as the valuable metal can be separated and recovered from the reduced product.
For example, methods for separating a valuable metal phase and a slag phase from a mixture of valuable metal phases and slag phases obtained as a solid include, in addition to removing unnecessary materials by sieving, separation by specific gravity and magnetic force. Methods such as separation can be used.
In particular, with this smelting method, valuable metals with a large average particle size can be obtained, and the valuable metal phase and slag phase can be easily separated by applying impact to the reduced product. .
Moreover, the obtained valuable metal phase and slag phase have poor wettability, so they can be easily separated. As such a method of applying vibration, for example, a method of providing a predetermined head to allow the reduced product to fall, or applying a predetermined vibration during sieving can be adopted.

As described above, in this smelting method, by using pellets whose solidus temperature is adjusted to be within a predetermined range, the liquid phase within the pellets is brought into an appropriate state in the reduction treatment step S3. It becomes possible to proceed with the reduction reaction appropriately. In other words, liquid phase slag and liquid phase valuable metal can appropriately coexist in the pellet in the reduction treatment step S3, so if the temperature is lowered, coarse valuable metal with a large average particle size can be formed. . Moreover, since coarse valuable metal can be formed, the separability from slag can be improved, and the recovery rate of valuable metal can be improved. Therefore, by using the present smelting method, productivity of valuable metals containing nickel can be improved.

Here, in the smelting method of nickel oxide ore using a general pyrometallurgical method, it is said that the average particle size of nickel metal cannot be made larger than a certain size (for example, 50 μm or more). However, if this smelting method is used, valuable metals having an average particle size of 50 μm or more can be appropriately produced. Note that the average particle size of the valuable metal is measured by the method described in Examples described later.

An outline of the generation mechanism of coarse valuable metals in this smelting method will be explained.
When the reduction treatment is performed in the reduction treatment step S3 of the present smelting method, the reduction reaction of nickel oxide (nickel oxide) and the reduction reaction of iron oxide (iron oxide) proceed in the surface layer portion of the pellet. Then, in a treatment time of only one to several minutes from the start of the reaction, the nickel oxide and some iron oxide contained in the pellet are reduced and metallization progresses on the surface layer of the pellet, resulting in nickel metal or an alloy of iron and nickel. A shell (hereinafter also referred to as "shell") is formed.
On the other hand, inside the pellet (in other words, inside the shell), as the shell is formed, the solidus temperature of the pellet is below the reduction temperature (below the heating reduction temperature), so the slag components in the pellet are gradually reduced. It melts to produce liquid phase slag. As a result, valuable metals of iron and nickel (for example, iron-nickel alloy) and liquid phase slag (hereinafter simply referred to as "slag") consisting of oxides are separated and produced in one pellet. Then, for example, after about 10 minutes have passed from the start of the reaction, 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 melts into a liquid phase. That is, in the reduction treatment step S3, the liquid phase slag and the liquid phase valuable metal can appropriately coexist in the shell of the pellet.
Therefore, in this production method, by using pellets whose solidus temperature has been appropriately adjusted in the reduction processing step S3, there is a large A valuable metal having a particle size can be formed.

(Method for manufacturing pellets of this embodiment)
Further, the method for manufacturing pellets of this embodiment is similar to the method for manufacturing pellets used in the present smelting method. That is, the pellet manufacturing method of the present embodiment is a method including the mixture preparation step S1 and the mixture forming step S2 of the present smelting method. Since the pellets produced by the pellet production method of the present embodiment are adjusted so that the solidus temperature is within a predetermined range as described above, when used in the nickel oxide ore smelting method, You can obtain coarse valuable metals.
Note that a detailed explanation of each step is omitted because it is described in the section related to the present smelting method.

In addition, the valuable metal produced by this smelting method can be separated and recovered into highly pure valuable metal by performing a wet treatment to separate impurities in a post-process. Examples of wet treatments for separating impurities include neutralization by dissolving in acid, solvent extraction, and electrowinning.

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

<Mixture preparation process>
For each sample (samples 1 to 6), nickel oxide ore as raw material ore, iron ore, silica sand (main component is SiO ₂ ) and limestone (main component is CaCO ₃ ) as flux components, binder, and carbonaceous reduction A mixture was prepared by mixing the agent with a mixer while adding an appropriate amount of water.

The nickel oxide ore used had an average particle size of 0.085 mm and a nickel grade of 1±0.1% by mass.
Note that a laser diffraction particle size distribution measuring device was used to measure the average particle size of the nickel oxide ore.

The iron ore used had an average particle size of 0.75 mm.
Note that the same device as used for nickel oxide ore was used to measure the average particle size of iron ore.

Coal powder (carbon content: 52% by mass) with an average particle size of about 145 μm was used as the carbonaceous reducing agent.
The average particle size of the carbonaceous reducing agent was measured using the same device as used for nickel oxide ore.

(Mixing ratio of carbonaceous reducing agent)
The carbonaceous reducing agent is the amount necessary to reduce nickel oxide (NiO) and iron oxide (Fe ₂ O ₃ ) contained in the nickel oxide ore, which is the raw material ore, in an amount equal to 100%. They were mixed at a ratio of 34%.

<Mixture forming process>
The prepared mixture was subjected to a mixture molding step to mold cylindrical pellets.
A pelletizer was used for molding. The obtained pellets were subjected to sieving treatment to prepare pellets with a diameter of 16±2 mm.

The prepared pellets were dried by blowing hot nitrogen air at 150° C. to 200° C. so that the solid content was about 70% by mass and the water content was about 25% by mass.

A typical example of the solid content composition (excluding carbon) of the pellets after drying treatment is shown in Table 3 below.
An ICP emission spectrometer (SHIMAZU S-8100 model) was used to measure the solid content composition.

(Solidus temperature of pellet)
Table 3 shows the solidus temperature of each sample (Samples 1 to 6).
The solidus temperature of the pellet was measured using a thermogravimetric differential thermal analyzer (TG-TDA, manufactured by Rigaku Co., Ltd., model number: Thermo plus EVO2 TG-DTA8122).
The measurement conditions were as follows: sample amount: 0.20 g, temperature: room temperature to 1500°C, atmosphere: argon gas.

Comparative examples were prepared so that the solidus temperature of the pellets was higher than the reduction temperature in the reduction treatment step (for example, in the solid content composition of the pellets, silicon dioxide (SiO ₂ ) was 25% by mass, calcium oxide ( The content of aluminum oxide (Al 2 O ₃ ) was 3% by mass, the content of aluminum oxide (Al ₂ O 3 ) was 3% by mass, and the content of magnesium oxide (MgO) was 30% by mass.

<Reduction process>
The prepared pellets were subjected to a reduction treatment step.
The pellets after the drying treatment were charged into a reduction furnace containing a nitrogen atmosphere substantially free of oxygen. The temperature at the time of charging into the reduction furnace was 500±20°C.
Next, the hearth was spread with alumina grains, and the pellets were placed on top of the alumina grains. By spreading the alumina grains, the reaction between the pellets and the hearth can be suppressed.

The reduction treatment of the pellets was performed at the temperature (reduction temperature in Table 3) and time (reduction time in Table 3) shown in Table 3 below. After the reduction treatment, the sample was quickly cooled to room temperature in a nitrogen atmosphere and taken out from the furnace into the atmosphere.

(Nickel metalization rate)
The nickel metalization rate of the reduced product taken out from the furnace was measured using an ICP emission spectrometer (SHIMAZU S-8100 model) and calculated using the following formula (1).

Nickel metallization rate (%) = (amount of metalized Ni in the pellet/total amount of Ni in the pellet) x 100 (1)

(Ni content in metal)
The nickel quality of the metalized valuable metal in the pellet was measured using an ICP emission spectrometer (SHIMAZU S-8100 model) and calculated using the following formula (2).

Nickel content (%) in valuable metals = (amount of metalized Ni in pellets/total amount of metalized Ni and Fe in pellets) x 100 (2)

(Valuable metal recovery process)
The reduced product contains valuable metals and slag. Therefore, in order to separate and sort and recover valuable metals from the reduced product, the reduced product was subjected to a valuable metal recovery process.
In this recovery process, the reduced product was subjected to a pulverization process using a wet process, and the obtained pulverized product was pulverized, and metals were recovered by magnetic separation. In magnetic separation, the crushed materials fed at a feed rate of 4.5 kg/min are subjected to magnetic separation at 3000 G, with slag containing iron etc. as the magnetic material, and valuable metals containing valuable components such as nickel as the non-magnetic material. They were sorted and collected.

The valuable metal recovery rate was calculated from the amount of raw material in the pellet stack charged into the reduction furnace, the Ni content in the raw material, and the amount of valuable metal recovered using the following formula (3).

Valuable metal recovery rate (%) = {Amount of valuable metal recovered / (Amount of charged raw material x Valuable metal content in oxide ore) } x 100 (%) ... (3)

(Average particle size of valuable metal)
The average particle size of the recovered valuable metals was measured using X-ray CT (manufactured by Rigaku Co., Ltd.).

(Experimental result)
Table 4 shows the pellet solidus temperature (°C), reduction temperature (°C) in the reduction process, reduction time (minutes), and average particle size of valuable metals for each sample (samples 1 to 6) and comparative example. (μm), nickel metalization rate (%), nickel content in valuable metal (%), and recovery rate of valuable metal (%).

As shown in the results in Table 4, sample No. 1, which is an example, 1~No. In No. 6, it was confirmed that by using pellets with a solidus temperature of 1250°C or higher and 1380°C or lower (reduction temperature of 1400°C or lower), the average particle size of the valuable metal produced was larger compared to the comparative example. Ta. Moreover, the average particle size of all of them is 50 μm or more, and it is possible to produce a valuable metal larger than the conventional smelting method of nickel oxide ore, which is difficult to produce nickel metal with an average particle size of 50 μm or more. It was confirmed that it can be done.
Furthermore, it was confirmed that the Ni metalization rate, the nickel content in valuable metals, and the recovery rate of valuable nickel metals were also improved compared to the comparative example.
Moreover, from the results in Table 4, it was confirmed that as the difference between the solidus temperature of the pellet and the reduction temperature increases, the average particle size of the valuable metal tends to increase. Furthermore, it was confirmed that as the difference between the solidus temperature of the pellet and the reduction temperature became larger, the nickel metalization rate also improved.
On the other hand, in the comparative example (sample No. 7) prepared so that the solidus temperature of the pellet was higher than the reduction temperature, the values were lower than those of the example in all items, especially for valuable metals. It was confirmed that the average particle size of the sample was about 1/3 that of the example.

The method for smelting nickel oxide ore of the present invention is suitable as a method for producing valuable metals from nickel oxide ore. Further, the method for producing pellets of the present invention is suitable as a method for producing pellets used in a method for producing valuable metals from nickel oxide ore.

S1 Mixture preparation process S2 Mixture forming process S3 Reduction process S4 Recovery process

Claims (4)

A method for smelting nickel oxide ore using pellets,
A mixture preparation step of preparing a mixture containing a nickel oxide ore and a carbonaceous reducing agent;
a mixture molding step of molding pellets from the mixture;
a reduction treatment step of heating and reducing the pellets obtained in the mixture forming step to obtain a valuable metal containing nickel and slag;
A recovery step of separating the valuable metal and slag obtained in the reduction treatment step and recovering the valuable metal,
A method for smelting nickel oxide ore, characterized in that the solidus temperature of the pellets is 1250° C. or higher and lower than the heating reduction temperature in the reduction treatment step. The method for smelting nickel oxide ore according to claim 1, wherein the solidus temperature of the pellets is 1250°C or more and 1380°C or less. A method for producing pellets used in a smelting method for nickel oxide ore,
A mixture preparation step of preparing a mixture containing a nickel oxide ore and a carbonaceous reducing agent;
a mixture forming step of forming pellets from the mixture,
A method for producing pellets, characterized in that the solidus temperature of the pellets is adjusted to be 1250° C. or higher and lower than the heating reduction temperature in the smelting method. 4. The method for producing pellets according to claim 3, wherein the solidus temperature of the pellets is adjusted to be 1250° C. or more and 1380° C. or less.

Images