JP6926993B2 - Pellet manufacturing method, nickel oxide smelting method - Google Patents

Description

The present invention is a method for producing pellets obtained by mixing an oxide ore such as nickel oxide ore and a carbonaceous reducing agent to form pellets, and nickel for producing metal by reducing the pellets. Regarding the smelting method of oxide ore.

As a method for smelting nickel oxide ore called limonite or saprolite, a dry smelting method for producing nickel matte using a smelting furnace, ferronickel which is an alloy of iron and nickel using a rotary kiln or a mobile hearth furnace. Pyrometallurgical smelting method for producing mixed smelting using an autoclave, and wet smelting method for producing mixed smelted using an autoclave are known.

Among the various methods described above, especially when reducing and smelting nickel oxide ore using a pyrometallurgical method, the raw material nickel oxide ore is crushed to an appropriate size in order to proceed with the reaction, and the crushing is performed. After the product is mixed with other raw material components, a pretreatment for pelletizing or smelting the mixture is performed (for example, Patent Document 1).

Specifically, when the nickel oxide ore is pelletized, that is, when the pellet is produced, the nickel oxide ore is mixed with other components, for example, a reducing agent such as binder or coke to form a mixture, and the water content is further adjusted. After performing the above, it is generally charged into a lump product manufacturing machine to form a lump product having a size of, for example, about 10 mm to 30 mm (referring to pellets, briquettes, etc., hereinafter simply referred to as “pellet”).

Conventionally, it has been necessary to add an appropriate amount of water to produce pellets in order to provide strength to the extent that the pellets are not damaged when the pellets are transported or transported. However, when the obtained pellets are charged into a furnace and subjected to a reduction treatment, there is a problem that the pellets are damaged after the reduction treatment and the metal cannot be sufficiently recovered. Further, there is a demand for a technique for producing a higher quality metal by increasing the reduction rate of the metal by the reduction treatment using the pellets.

Japanese Unexamined Patent Publication No. 2016-20533

The present invention has been proposed in view of such circumstances, and is subjected to a reduction treatment in a smelting method using pellets obtained by mixing an oxide ore such as nickel oxide ore and a carbonaceous reducing agent. An object of the present invention is to provide a method capable of efficiently recovering the metal obtained by reduction by preventing damage to pellets and further increasing the reduction rate in the reduction treatment to produce high-quality metal. And.

The present inventor has made extensive studies to solve the above-mentioned problems. As a result, when producing pellets, bentonite is mixed as a binder to prepare a mixture, and the prepared mixture is press-molded to form pellets, thereby preventing the pellets from being damaged in the reduction treatment using the pellets. Further, they have found that a high-quality metal can be produced by increasing the reduction rate, and have completed the present invention.

(1) The first invention of the present invention includes a mixing treatment step of mixing an oxide ore and a carbonaceous reducing agent to form a mixture, and a mixture forming step of molding the obtained mixture into pellets. In the mixing treatment step, bentonite is mixed as a binder to prepare a mixture, and in the mixture molding step, the mixture is press-molded at a molding pressure of ^{50 kg / cm 2} or more and less than 500 kg / cm ^{2 to form pellets.} This is a method for producing pellets.

(2) In the second invention of the present invention, in the first invention, in the mixing treatment step, the bentonite is mixed in the mixture so as to have a ratio of 0.5% by mass or more and 10% by mass or less. It is a manufacturing method of.

(3) The third invention of the present invention is a pellet manufacturing process for producing pellets containing nickel oxide ore and a carbonaceous reducing agent, and the obtained pellets are charged into a reduction furnace and heated at a predetermined reduction temperature. It has a reduction step of smelting and a recovery step of recovering the metal from the mixture of the metal and the slag obtained in the reduction step. In the pellet manufacturing step, bentonite is mixed as a binder to prepare a mixture. This is a method for smelting nickel oxide ore, in which the mixture is ^{press-molded at a molding pressure of 50 kg / cm 2} or more and less than 500 kg / cm ^{2 to form pellets.}

(4) The fourth invention of the present invention further includes, in the third invention, a drying step of drying the pellets obtained in the pellet manufacturing step, and in the drying step, the temperature is 100 ° C. to 120 ° C. This is a method for smelting nickel oxide ore, in which the pellets are dried in.

According to the present invention, in smelting using pellets obtained by mixing an oxide ore such as nickel oxide ore and a carbonaceous reducing agent, the metal obtained by reduction is prevented from being damaged by the pellets to be subjected to the reduction treatment. Can be efficiently recovered.

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

Hereinafter, specific embodiments of the present invention will be described in detail. The present invention is not limited to the following embodiments, and various modifications can be made without changing the gist of the present invention. Further, in the present specification, the notation "X to Y" (X and Y are arbitrary integers) means "X or more and Y or less".

≪1. Outline of the present invention ≫
The method for producing pellets according to the present invention is, for example, a method for producing pellets containing at least an oxide ore, a carbonaceous reducing agent, and a binder, which is used in a method for producing nickel oxide ore. The method for producing pellets includes a mixing treatment step of mixing an oxide ore, a carbonaceous reducing agent and a binder to form a mixture, and a mixture molding step of molding the obtained mixture into pellets.

The method for producing pellets is characterized in that, in the mixing treatment step, bentonite is mixed as a binder to prepare a mixture, and in the mixture molding step, the mixture is press-molded to form pellets. The mixed amount of bentonite, which is the binder, is preferably in the range of 0.5% by mass to 10% by mass, more preferably 1% by mass to 5% by mass, and particularly preferably 2.5% by mass or more and 3.5% by mass. It shall be mass% or less.

According to such a method, bentonite is mixed as a binder at a predetermined ratio to prepare a mixture, and the mixture is press-molded to form pellets. Therefore, the strength of the obtained pellets can be effectively increased. Even when the pellets are subjected to a reduction treatment at a predetermined reduction temperature, damage can be prevented, metal can be effectively generated, and the produced metal can be efficiently recovered. Further, by using pellets containing bentonite, it is possible to effectively increase the reduction rate of valuable metals such as nickel contained in nickel oxide ore, and it is possible to improve the quality and produce high quality metal. ..

In the following, as a specific embodiment of the present invention (hereinafter, referred to as “the present embodiment”), a method for smelting nickel oxide ore is taken as an example, and the pellets used in the treatment are explained while explaining the flow of the smelting method. The manufacturing method of the above will be described. The nickel oxide ore, which is a raw material for smelting, _{contains at least nickel oxide (NiO) and iron oxide (Fe 2} O ₃ ), and by reducing the nickel oxide ore as a raw material for smelting, iron as a metal. -A nickel alloy (ferronickel) can be produced.

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

≪2. Nickel oxide ore smelting method ≫
In the method for smelting nickel oxide ore according to the present embodiment, nickel oxide ore is mixed with a carbonaceous reducing agent and a binder to form a mixture, and the mixture is subjected to a reduction treatment to obtain a metal (reduced product). Ferronickel, which is an alloy of iron and nickel) and slag are produced. Ferronickel, which is a metal, can be recovered by separating the metal from a mixture containing the metal and slag obtained through the reduction treatment.

FIG. 1 is a process diagram showing an example of the flow of a nickel oxide smelting method. As shown in FIG. 1, in this smelting method, a pellet manufacturing step S1 for producing pellets by mixing raw materials containing nickel oxide ore, a drying step S2 for drying the obtained pellets, and a predetermined reduction of pellets are performed. It has a reduction step S3 of reducing and heating at a temperature, and a recovery step S4 of separating the metal and slag produced in the reduction step S3 and recovering the metal.

<2-1. Pellet manufacturing process>
The pellet manufacturing step S1 is a step of mixing raw material powders containing nickel oxide ore to form a mixture, and molding the mixture into pellets. Specifically, the pellet manufacturing step S1 includes at least a mixing treatment step S11 in which nickel oxide ore, a carbonaceous reducing agent and a binder are mixed to form a mixture, and a mixture molding step S12 in which the obtained mixture is molded and pelletized. , Have.

(1) Mixing Treatment Step In the mixing treatment step S11, at least a nickel oxide ore, a carbonaceous reducing agent and a binder are mixed to obtain a mixture composed of a raw material powder. Specifically, a carbonaceous reducing agent is added to and mixed with nickel oxide ore, which is a raw material ore, and as an additive of an optional component, iron ore, a flux component, etc., for example, having a particle size of 0.1 mm to 0 Add powder of about 0.8 mm and mix to make a mixture.

The nickel oxide ore is not particularly limited, but limonite ore, saprolite ore and the like can be used. Nickel oxide ore contains at least nickel oxide (NiO) and iron oxide (Fe ₂ O _3). The content ratio of the water content (adhered water content adhering to the surface of the ore) contained in the nickel oxide ore is usually about 1% by mass to 12% by mass.

The carbonaceous reducing agent is not particularly limited, and examples thereof include coal powder and coke powder. When this carbonaceous reducing agent has a size equivalent to the particle size and particle size distribution of nickel oxide ore, which is a raw material ore, it is easy to mix uniformly, and the reduction reaction in the reduction step S3 described later is also easy to proceed uniformly. Therefore, it is preferable.

The mixed amount of the carbonaceous reducing agent is the chemical equivalent required to reduce the total amount of nickel oxide constituting the nickel oxide ore to nickel metal, and the chemical equivalent required to reduce iron oxide (ferrous oxide) to metallic iron. When the total value of both chemical equivalents (also referred to as "total value of chemical equivalents" for convenience) is 100% by mass, the ratio of carbon content of 5% by mass or more and 60% by mass or less is preferable, and more preferably. It can be adjusted so that the ratio of the amount of carbon is 10% by mass or more and 40% by mass or less. In this way, by setting the mixing amount of the carbonaceous reducing agent to a ratio of 5% by mass or more with respect to the total value of 100% by mass of chemical equivalents, the reduction of nickel can be efficiently promoted and the productivity can be improved. improves. On the other hand, by setting the ratio to 60% by mass or less with respect to the total value of 100% by mass of chemical equivalents, it is possible to suppress the reduction amount of iron, prevent deterioration of nickel grade, and produce high quality ferronickel. can. From the viewpoint of producing pellets from the mixture obtained by mixing the carbonaceous reducing agent and preventing oxidation due to mixing of oxygen into the reduction furnace when the pellets are subjected to the reduction treatment (reduction step S3). Therefore, an excess amount may be mixed as the mixing amount of the carbonaceous reducing agent in the preparation of the mixture. Also at that time, the amount is appropriately adjusted so that the reduction of iron can be suppressed.

Further, as the iron ore as an additive of an arbitrary component, for example, iron ore having an iron grade of about 50% by mass or more, hematite obtained by hydrometallurgy of nickel oxide ore, or the like can be used.

Moreover, as a flux component, for example, calcium oxide, calcium hydroxide, calcium carbonate, silicon dioxide and the like can be mentioned.

Here, the present embodiment is characterized in that, in the mixing treatment step S11, bentonite is mixed as a binder together with nickel oxide ore and a carbonaceous reducing agent to prepare a mixture. As described above, bentonite is mixed as a binder to form a mixture, and the mixture is press-molded in the next mixture molding step S12 to produce pellets having good moldability and high strength. Further, according to the pellets obtained by mixing bentonite in a predetermined ratio in this way, the reduction rate of nickel contained in the raw material ore can be improved, and the quality of the metal obtained by the reduction treatment of the pellets is improved. be able to.

Bentonite is a clay mineral whose main component is montmorillonite. Sodium-type bentonite in which the main cation in the layers of montmorillonite is sodium ion, calcium-type bentonite in which cation is calcium ion, and potassium in which cation is potassium. Examples include type bentonite.

As the bentonite, it is preferable to use a powdery one, the average particle size thereof is preferably 75 μm or less, and more preferably 50 μm or less. The average particle size can be measured using, for example, a laser diffraction type particle size analyzer. Further, for example, it is preferable to use a mesh that has passed through the mesh by sieving with a mesh having an opening of 46 μm.

The mixed amount of bentonite is preferably 0.5% by mass or more and 10% by mass or less, more preferably 1.0% by mass or more and 6.0% by mass or less, as a mass ratio in the mixture. It is particularly preferable that it is 5% by mass or more and 3.5% by mass or less. If the mixed amount of bentonite is less than 0.5% by mass, it is not possible to impart appropriate strength to the obtained pellets, and the reduction treatment may cause damage. In addition, the effect of improving the nickel reduction rate in the reduction treatment using the pellets is also reduced. On the other hand, when the mixed amount of bentonite exceeds 10% by mass, the amount of water brought in from the binder composed of the bentonite increases, and the content of adhering water in the pellet increases. Then, the strength of the obtained pellets is decreased, and the reduction treatment may cause damage. In addition, the load of the drying heat treatment performed prior to the reduction treatment for reducing the water content such as adhering water increases, which leads to an increase in the treatment cost and makes it impossible to perform an efficient smelting method.

The mixing treatment of the raw material powder is preferably carried out so that the raw material powder is uniformly mixed, and can be carried out by a known method using a mixer or the like. Further, in this mixing treatment, kneading may be carried out at the same time in order to improve the mixing property, or kneading may be carried out after the mixing treatment. Specifically, kneading can be performed using, for example, a twin-screw kneader, and by kneading the mixture, a shearing force is applied to the mixture to disaggregate the carbonaceous reducing agent, the raw material powder, and the like to make them uniform. As well as mixing, the adhesion of each particle can be improved and the voids can be reduced. As a result, a reduction reaction with respect to the pellets formed based on the obtained mixture is likely to occur, the reaction can be uniformly generated, and the reaction time of the reduction reaction can be shortened. In addition, it is possible to suppress variations in quality, and it is possible to stably produce high-quality ferronickel with high productivity.

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

(2) Mixture molding step In the mixture molding step S12, the mixture prepared and obtained in the mixing treatment step S11 is molded into lumps (lumps, hereinafter referred to as “pellets”) having a certain size or larger. The pellets obtained in the mixture molding step S12 are subject to the reduction treatment (reduction heat treatment) at a predetermined temperature in the reduction step S3.

Here, the pellets produced in the pellet production step S1 are charged into the reduction furnace in the reduction step S3 and heat-treated at a high temperature of about 1200 ° C. to 1450 ° C. Therefore, if the strength of the pellets is low, damage may occur during charging into the reduction furnace or during the reduction reaction, and it may not be possible to produce high-quality metal.

Therefore, the present embodiment is characterized in that pellets are produced by mixing bentonite as a binder as described above to prepare a mixture, and press-molding the mixture by applying a predetermined pressure in the molding process. It is said. By press-molding the mixture mixed with bentonite into pellets in this way, the moldability can be enhanced and appropriate strength can be imparted to the pellets.

Further, by press-molding the mixture into pellets, it is possible to remove the water contained in the mixture in the process of applying a predetermined pressure to the mixture, and the load of the drying treatment on the pellets obtained by molding can be applied. Can be reduced.

On the other hand, in press molding, it is important to appropriately control the pressure (surface pressure) of the mixture by the press machine. The surface pressure refers to the load per unit area when the pressure applied to the press surface is divided by the contact area with respect to the mixture, and is also simply referred to as “molding pressure”. Specifically, the surface pressure for the mixture containing bentonite is 50 kg / cm ² or more and less than 500 kg / cm ^2. Further, it is preferably 100 kg / cm ² or more and 300 kg / cm ² or less. According to the research of the present inventor, the strength of the obtained pellets can be increased by press-molding the mixture mixed with bentonite, but the reason is not clear, but the surface pressure of the press-molding at that time is It was found that if it is too large, on the contrary, the strength is lowered and the reduction treatment causes damage.

As described above, in the present embodiment, bentonite is mixed as a binder to prepare a mixture, and pellets are produced by press molding the ^{mixture at a molding pressure of 50 kg / cm 2} or more and less than 500 kg / cm ^2. do. As a result, the strength of the obtained pellets can be made appropriate, and even when the reduction treatment is performed at a high reduction temperature, the pellets can be effectively prevented from being damaged, and the metal can be efficiently recovered. be able to.

If the molding pressure in press molding is ^{less than 50 kg / cm 2} , sufficient strength is not imparted to the obtained pellets, and the pellets are damaged by the reduction treatment. On the other hand, even when the molding pressure is 500 kg / cm ² or more, on the contrary, the strength is lowered and the damage is caused.

Specifically, in the molding process, the prepared mixture is filled in a mold of a press machine, and a predetermined pressure, that is, a pressure of 50 kg / cm ² or more and less than 500 kg / cm ² is applied to the press machine. By forming the mixture into pellets.

When press-molding with a press machine, the filling height of the mixture in the die of the press machine depends on the size of the pellets to be manufactured, but it also affects the pressure applied to the press machine, so adjust it appropriately. Is preferable. Specifically, the filling height is preferably 10 mm or more, and more preferably 15 mm or more. The filling height is preferably 60 mm or less, more preferably 50 mm or less. As described above, by setting the filling height of the mixture in the press machine in the range of 10 mm or more and 60 mm or less, the pressure by the press machine can be uniformly applied and the moldability can be improved.

Further, it is preferable that the mold of the press machine is filled with the mixture, and then the filled portion is vibrated by using ultrasonic waves or the like to discharge the air existing around the mixture. If the air can be efficiently discharged by applying vibration, the process is not limited to the above-mentioned processing using ultrasonic waves.

The shape of the pellet obtained by molding the mixture can be, for example, a rectangular parallelepiped shape, a columnar shape, a spherical shape, or the like. With such a shape, the mixture can be easily molded and the cost required for molding can be suppressed. Further, since the above-mentioned shape is a simple shape and is not complicated, it is possible to prevent the occurrence of defective products and to make the quality of the obtained pellets uniform. If the shape of the pellet is a rectangular parallelepiped, a columnar shape, or the like, the pellet can be laminated and placed in the reduction furnace in the reduction step S3, and the amount of treatment to be subjected to the reduction treatment can be increased. ..

<2-2. Drying process>
The drying step S2 is a step of drying the pellets produced in the pellet manufacturing step S1 and evaporating and removing the water (adhered water) contained in the pellets. Although it is not an essential aspect, by subjecting the produced pellets to a drying treatment in this way, the water content inside the pellets expands at once due to a rapid temperature rise during the reduction treatment in the reduction step S3 of the next step. It is possible to prevent the situation where it is broken into pieces.

The drying step S2 can also be positioned as a processing step included in the pellet manufacturing step S1 described above. That is, the pellet to be subjected to the reduction treatment in the reduction step S3 can be produced by subjecting the pellets, which are the molded products obtained in the mixture molding step S12, to a drying treatment.

The drying treatment is not particularly limited, but can be performed, for example, by blowing hot air heated to a predetermined temperature onto the pellets. Further, the drying treatment may be performed by holding the pellets in a heating atmosphere heated to a predetermined temperature.

Here, the present embodiment is characterized in that the mixture obtained by mixing the raw material powders is press-molded into pellets. Therefore, the water content in the mixture is removed in the process of press molding, and the water content in the obtained pellets becomes extremely small. Therefore, when such pellets are subjected to a drying treatment (drying step S2), the drying temperature for evaporating water can be set low, and the load of the drying treatment can be effectively reduced. Specifically, the temperature of the hot air and the ambient temperature for drying can be set to relatively low temperatures of about 100 ° C. to 120 ° C.

Further, for example, depending on the conditions of press molding, the drying process can be omitted, and the smelting process can be executed more efficiently.

<2-3. Reduction process>
The reduction step S3 is a step of charging the produced pellets into a reduction furnace and reducing and heating them at a predetermined reduction temperature. By the reduction treatment in the reduction step S3, the smelting reaction (reduction reaction) proceeds, and metal and slag, which are reduced products, are produced.

In the reduction treatment, the nickel oxide contained in the nickel oxide ore in the pellet is reduced as completely preferentially as possible, while the iron oxide contained in the nickel oxide ore is partially reduced for the purpose. So-called partial reduction is performed to obtain ferronickel with high nickel grade. Then, the slag in the pellet is melted into a liquid phase by this reduction heat treatment, but the metal and the slag that have already been separated and produced by the reduction treatment do not mix with each other, and the metal is cooled by the subsequent cooling. It is a mixture in which the solid phase and the slag solid phase are mixed as separate phases. The volume of the pellet at this time is reduced to about 50% to 60% of the volume of the pellet when it is charged into the reduction furnace.

In the reduction step S3, when the mixture was charged into the reduction furnace, a carbonaceous reducing agent (hereinafter, also referred to as “hearth carbonaceous reducing agent”) was spread in advance on the hearth of the reduction furnace, and the mixture was spread. The pellets may be placed on the hearth carbonaceous reducing agent for treatment. Alternatively, a flooring material such as alumina, zirconia, or magnesia may be laid on the hearth, and pellets may be placed on the flooring material for treatment. As the floor covering material, a material containing an oxide as a main component can be used. In this way, by laying a carbonaceous reducing agent, bedding material, etc. on the hearth of the reduction furnace and placing pellets on it to perform reduction treatment, the direct reaction between the hearth and the pellets can be suppressed. This can prevent fusion to the hearth and extend the life of the hearth.

The reduction furnace is not particularly limited, but for example, a rotary kiln or a mobile hearth furnace can be used. For example, by using a mobile hearth furnace as a reduction furnace, the reduction reaction can proceed continuously and the reaction can be completed with one facility, rather than performing the processing in each process using separate furnaces. The processing temperature can be controlled accurately. Further, by using a mobile hearth furnace, heat loss (heat loss) between each treatment can be reduced, and more efficient operation becomes possible. In other words, when the reaction is performed using separate furnaces, the temperature of the container containing the mixture is temporarily lowered by exposing it to the outside air or a state close to it when moving between the furnaces. As a result, heat loss occurs and the reaction atmosphere changes. As a result, the reaction does not start immediately when the furnace is recharged in order to perform the next processing. On the other hand, by using a mobile hearth furnace and performing each treatment in one facility, heat loss can be reduced and the atmosphere inside the furnace can be controlled accurately, so that the reaction can proceed more effectively. ..

As the mobile hearth furnace, for example, a rotary hearth furnace which has a circular shape and is divided into a plurality of processing regions can be used. In the rotary hearth furnace, each process is performed in each region while rotating in a predetermined direction. The mobile hearth furnace may be a roller hearth kiln or the like.

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

Here, in the present embodiment, the pellets to be subjected to the reduction treatment are obtained by mixing bentonite as a binder and press-molding the ^{mixture with a molding pressure of 50 kg / cm 2} or more and less than 500 kg / cm ^2. Is used. From this, even when the reduction treatment is performed at a high reduction temperature in the range of 1200 ° C. or higher and 1450 ° C. or lower, damage to the pellets can be effectively prevented. Then, the metal can be efficiently recovered in the recovery step S4 of the next step. Further, in such pellets, since bentonite is contained, the reduction rate of nickel can be increased, and a high-quality metal having improved nickel quality can be obtained.

In the reduction treatment, the internal temperature of the reduction furnace is raised by a burner or the like until the reduction temperature reaches the above-mentioned range, and the temperature is maintained after the temperature rise.

<2-4. Recovery process>
In the recovery step S4, the metal and slag produced in the reduction step S3 are separated and the metal is recovered. Specifically, the metal phase is separated and recovered from the mixture (mixture) containing the metal phase (metal solid phase) and the slag phase (slag solid phase) obtained by the reduction heat treatment of the mixture.

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

Further, the obtained metal phase and slag phase can be easily separated due to poor wettability, and for example, a predetermined head can be separated from the large mixture obtained by the treatment in the reduction step S3 described above. The metal phase and the slag phase can be easily separated from the mixture by providing an impact such as dropping the metal phase or giving a predetermined vibration at the time of sieving.

By separating the metal phase and the slag phase in this way, the metal phase is recovered.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples of the present invention, but the present invention is not limited to the following Examples.

<< Examples, Comparative Examples >>
Pellets used for ferronickel smelting were produced as follows.

[Mixing process]
Nickel oxide ore as a raw material ore (containing about 10% by mass of water), iron ore, silica sand and limestone as flux components, carbonaceous reducing agent (coal powder, carbon content: 85% by mass, average) Particle size: about 90 μm) and bentonite as a binder were mixed using a mixer to obtain a mixture.

The carbonaceous reducing agent has a total value of 100% by mass, which is the total amount required to reduce _{nickel oxide (NiO) and iron oxide (Fe 2} O ₃ ) contained in the raw material ore, nickel oxide ore, in just proportion. When it was added, it was contained in an amount of 20% by mass.

As the bentonite, a sodium-type bentonite that had passed through the mesh by sieving with a mesh having an opening of 46 μm was used. Table 1 below shows the mixed amount (addition ratio) of bentonite in each test example.

[Mixture molding process]
Next, the obtained mixture was press-molded to produce pellets. Specifically, the mixture was filled in a die of a press machine so that the height of the molded product was about 14 mm to 15 mm. Then, press molding was performed by applying the pressure (surface pressure) shown in Table 1 below to the mixture.

[Drying process]
Next, the pellets obtained by press molding were dried in a temperature atmosphere of about 105 ° C. to 110 ° C.

[Reduction process]
Next, the dried pellets were placed in a reduction furnace in which the temperature inside the furnace was heated to 1300 ° C. Then, the reduction treatment was carried out for 30 minutes while maintaining the reduction temperature.

≪Evaluation≫
After the completion of the reduction treatment, the reduced product produced in the furnace was collected and observed to see if it was damaged. In Table 1 below, the case where the damage occurred was evaluated as “with” the damage, and the case where the damage did not occur was evaluated as “without”.

Further, for the recovered sample, the nickel metal ratio and the nickel content in the metal were analyzed and calculated by an ICP emission spectrophotometer (SHIMAZU S-8100 type). Each of the recovered samples was crushed by a wet treatment, and then the metal was recovered by magnetic force sorting. Here, the nickel metallization rate was determined by the following formula (1), and the nickel content in the metal was determined by the following formula (2).
Nickel metallization rate = Amount of metallized Ni in pellets ÷ (All amount of Ni in pellets) x 100 (%) ・ ・ ・ (1) Equation (1) Nickel content in metal = Metallicized Ni in pellets Amount ÷ (total amount of metallized Ni and Fe in pellets) × 100 (%) ・ ・ ・ Eq. (2)

As shown in the results of Table 1, in Examples 1 to 4 in which the mixture mixed with bentonite was press-molded at a predetermined molding pressure, no damage occurred even if the reduction treatment was performed at a high temperature, and the mixture was efficient. I was able to recover the metal. In addition, nickel in pellets could be effectively reduced, and high-quality metal could be produced.

On the other hand, although bentonite was mixed, in ^{Comparative Example 1 in which the molding pressure was 1000 kg / cm 2 and Comparative Example 2 in} which the molding pressure was 500 kg / cm ² , damage was caused in the reduction treatment probably because the molding pressure was high. It has happened. Damage occurred in the reduction furnace, making recovery work difficult. Further, in Comparative Example 3 in which bentonite was not mixed, although no damage occurred in the reduction treatment, the nickel metallization rate was lowered and the nickel content in the metal was also lowered as compared with Examples.

Claims (3)

A mixing process in which nickel oxide, a carbonaceous reducing agent, and bentonite as a binder are mixed to form a mixture.
A mixture molding step of molding the obtained mixture into pellets, and
Have,
Wherein in the mixing step, a mixture of base bentonite so that the proportion of 6 wt% or less 3 wt% or more in the mixture, and the mixture was prepared,
In the mixture molding step, a method for producing pellets in which the mixture is press-molded at a molding pressure of 150 kg / cm ² or more and less than 250 kg / cm ^2. A pellet manufacturing process for producing pellets containing nickel oxide ore, a carbonaceous reducing agent, and bentonite as a binder.
A reduction step in which the obtained pellets are placed in a reduction furnace and heated at a predetermined reduction temperature,
A recovery step of recovering metal from a mixture of metal and slag obtained in the reduction step, and a recovery step.
Have,
In the pellet manufacturing process,
And mixed to base bentonite so that the proportion of 3 mass% or more 6 wt% or less in the mixture, and the mixture was prepared, the mixture is 0.99 kg / cm ² or more 250 kg / cm ² less than the molding pressure A method of smelting nickel oxide ore that is pelletized by press molding. It further has a drying step of drying the pellets obtained in the pellet manufacturing step.
The method for smelting nickel oxide ore according to claim 2 , wherein in the drying step, the pellets are dried at a temperature of 100 ° C. to 120 ° C.

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