JP2017197813A - Pellet production method, and method of refining nickel oxide ore - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pellet production method capable of preventing a decrease in reaction efficiency or a fluctuation in compositions by generating a uniform metal shell on a pellet surface in a method of producing ferronickel by using the pellets from a nickel oxide ore.SOLUTION: The present invention is a pellet production method of producing pellets from a nickel oxide ore and includes a block-forming step S12 in which at least the nickel oxide ore and a carbonaceous reducing agent are mixed to form a block object into pellets. In the block-forming step S12, a mixture obtained by mixing at least the nickel oxide ore and the carbonaceous reducing agent is molded into a bar or a cylinder, and a compact thus obtained is cut into planar or disc-like pellets.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a method for producing a pellet from nickel oxide ore containing at least nickel oxide and iron oxide, and a method for smelting nickel oxide ore to smelt the pellet by reducing and heating it in a smelting furnace. About.

  As a smelting method of nickel oxide ore called limonite or saprolite, a dry smelting method in which smelting roasting with sulfur using a smelting furnace to produce nickel matte, carbon reduction using a rotary kiln or moving hearth furnace A dry smelting method that produces iron-nickel alloy (hereinafter also referred to as “ferronickel”) by reducing with an additive, and adding a sulfiding agent to the leachate obtained by leaching nickel or cobalt with sulfuric acid using an autoclave Thus, a hydrometallurgical method for producing mixed sulfide (mixed sulfide) is known.

  In the various smelting methods described above, when nickel oxide ore is smelted by reduction together with a carbon source, first, pretreatment for making the raw material ore into a lump or slurry is performed. Specifically, when nickel oxide ore is agglomerated, that is, when powdered or finely granulated, the nickel oxide ore is mixed with a binder, a reducing agent, etc., and further adjusted for moisture, etc. Generally, it is charged into a manufacturing machine to form, for example, a lump of about 10 mm to 30 mm (referred to as pellets, briquettes, etc., hereinafter simply referred to as “pellets”).

  For example, the pellet needs to have a certain degree of air permeability in order to remove moisture. Furthermore, if the reduction reaction does not occur uniformly in the pellets, the composition becomes non-uniform and the metal is dispersed and unevenly distributed, so that the smelting operation such as reduction heating is started after being charged into the smelting furnace. However, it is important to maintain the shape.

  What is particularly important is that shell-like metal is formed on the pellet surface in the early stage of reduction. If a uniform metal shell is not effectively formed on the pellet surface, the reducing agent component in the pellet (for example, carbon monoxide in the case of a carbonaceous reducing agent) is lost, and not only the reduction but also the reduction rate is not possible. It becomes difficult to control. In addition, the variation in the partial composition becomes large, and as a result, the intended ferronickel cannot be produced.

  In order to generate such a uniform metal shell, the shape of the pellet of the raw material mixture, its strength, and the like are very important. That is, if the shape is distorted, local metallization proceeds on the pellet surface, and a uniform metal shell is not generated. In addition, if the pellet strength is low, cracks may occur at the time of moving to the next process after molding, during drying, during reduction, and the like, which may cause cracks.

  Thus, in order to generate a uniform metal shell on the pellet surface, the shape and strength of the pellet are very important factors. Further, in metal smelting that not only merely generates a metal shell but also has high cost competition, there is a demand for a technology that enables high productivity and efficient agglomeration.

  For example, in Patent Document 1, as a pretreatment method for producing ferronickel using a moving hearth furnace, a mixture containing a raw material containing nickel oxide and iron oxide and a carbonaceous reducing agent is mixed. In the mixing step to be performed, a technique is disclosed in which the amount of surplus carbon in the mixture is adjusted to produce pellets, and the pellets are charged into a furnace to perform a reduction step.

  Specifically, in Patent Document 1, a raw material and a carbonaceous reducing agent may be mixed with a mixer, and the resulting mixture may be directly charged into a moving hearth furnace, but agglomerated with a granulator. It is described that the agglomeration reduces the amount of dust generated and improves the heat transfer efficiency inside the agglomerate (mixture) in the moving hearth furnace and increases the reduction rate. It is described that as a granulator used for agglomeration, an extrusion molding machine can be used in addition to a compression molding machine such as a briquette press and a rolling granulator such as a disk type pelletizer.

  However, when agglomerating (agglomerating), it is necessary to generate a metal shell only by using a general compression molding machine or rolling granulator. It is difficult to agglomerate well.

JP 2004-156140 A

  The present invention has been proposed in view of such circumstances, and in a method for producing ferronickel using pellets from nickel oxide ore, a uniform metal shell is stably generated on the pellet surface, and reaction efficiency is improved. It is an object of the present invention to provide a method for producing pellets and a method for smelting the nickel oxide ore that can prevent the decrease in composition and the occurrence of variation in composition and have good productivity and efficiency.

  This inventor repeated earnest examination in order to solve the subject mentioned above. As a result, according to pellets obtained by forming a mixture obtained by mixing at least a nickele ore and a carbonaceous reducing agent into a rod shape or a columnar shape and cutting the molded product into a flat plate shape or a disk shape. For example, the present inventors have found that a uniform metal shell can be effectively generated on the pellet surface, the efficiency of the reduction reaction is high, and ferronickel with little composition variation can be produced, and the present invention has been achieved. That is, the present invention provides the following.

  (1) A first invention of the present invention is a pellet manufacturing method for manufacturing pellets from nickel oxide ore, wherein at least the nickel oxide ore and a carbonaceous reducing agent are mixed to form a lump and pellets In the agglomeration treatment step, a mixture obtained by mixing at least the nickel oxide ore and the carbonaceous reducing agent is formed into a rod shape or a columnar shape, and obtained by molding. It is the manufacturing method of a pellet which cut | disconnects the molded object which was cut, and is set as a flat plate-shaped or disk-shaped pellet.

  (2) The second invention of the present invention is the method for producing a pellet according to the first invention, wherein the pellet has an aspect ratio of 0.3 or more and 2.0 or less.

  (3) According to a third aspect of the present invention, in the first or second aspect, the nickel oxide ore and a carbonaceous reducing agent are mixed, and the resulting mixture is molded and formed. It is the manufacturing method of a pellet which performs the process which cuts | disconnects continuously.

  (4) The fourth invention of the present invention is the pellet according to any one of the first to third inventions, wherein the plate-shaped or disk-shaped pellet is subjected to a heat treatment for heating to a temperature of 350 ° C. to 600 ° C. It is a manufacturing method.

  (5) A fifth invention of the present invention is a nickel oxide ore smelting method for producing ferronickel by forming pellets from nickel oxide ore and reducing the pellets, wherein the pellets are formed from the nickel oxide ore. A pellet manufacturing process for manufacturing the obtained pellets, and a reduction process for heating the obtained pellets at a predetermined reduction temperature in a reduction furnace, and in the pellet manufacturing process, at least the nickel oxide ore and the carbonaceous reducing agent. This is a method for smelting nickel oxide ore, in which the mixture is formed into a rod-like or columnar shape, and the mixture obtained by molding is cut into a plate-like or disc-like pellet.

  (6) According to a sixth aspect of the present invention, in the fifth aspect, in the reduction step, a moving hearth furnace is used as the reducing furnace, and the plate-shaped or disk-shaped pellets are mounted on the moving hearth furnace. This is a method for smelting nickel oxide ore that is reduced and heated.

  According to the present invention, in a method for producing ferronickel using pellets from nickel oxide ore, a metal shell can be uniformly formed on the pellet surface, and a reduction in reaction efficiency and occurrence of composition variation can be prevented. It is possible to provide a method for producing pellets with good productivity and efficiency, and a method for refining the nickel oxide ore.

It is process drawing which shows an example of the flow of the smelting method of nickel oxide ore. It is a processing flowchart which shows an example of the flow of a process in a pellet manufacturing process. It is a processing flowchart which shows the flow of the process in a lump processing process. It is a figure which shows typically a disk-shaped lump (pellet).

  Hereinafter, a specific embodiment of the present invention (hereinafter referred to as “the present embodiment”) will be described in detail. In addition, this invention is not limited to the following embodiment, A various change is possible in the range which does not change the summary of this invention. In this specification, the notation “X to Y” (X and Y are arbitrary numerical values) means “X or more and Y or less”.

≪Smelting method of nickel oxide ore≫
The nickel oxide ore smelting method according to the present embodiment uses nickel oxide ore pellets that are raw material ores, and the pellets are charged into a smelting furnace (reduction furnace) and subjected to a reduction treatment to obtain a metal. And slag.

  Below, the nickel oxide ore, which is the raw ore, is pelletized, and nickel (nickel oxide) and iron (iron oxide) in the pellet are reduced to produce an iron-nickel alloy metal. A smelting method for producing ferronickel by separation will be described as an example.

  Specifically, in the method for smelting nickel oxide ore according to the present embodiment, as shown in FIG. 1, a pellet manufacturing step S1 for manufacturing pellets from nickel oxide ore and the obtained pellets at a predetermined reduction temperature. It has reduction process S2 which carries out reduction heating, and separation process S3 which isolate | separates the metal and slag which were produced | generated in reduction process S2, and collect | recovers metals.

<1. Pellet manufacturing process>
In the pellet manufacturing step S1, pellets are manufactured from nickel oxide ore which is a raw material ore. FIG. 2 is a process flow diagram showing a process flow in the pellet manufacturing process S1. As shown in FIG. 2, the pellet manufacturing step S1 includes a mixing treatment step S11 for mixing raw materials containing nickel oxide ore, and an agglomeration treatment step S12 for forming (granulating) the obtained mixture into a lump. A drying treatment step S13 for drying the obtained lump.

(1) Mixing treatment step The mixing treatment step S11 is a step of obtaining a mixture by mixing raw material powders containing nickel oxide ore. Specifically, in this mixing process step S11, a carbonaceous reducing agent is added and mixed together with nickel oxide ore which is a raw material ore, and as an optional additive, iron ore, a flux component, a binder, For example, powder having a particle size of about 0.2 mm to 0.8 mm is mixed to obtain a mixture.

Although it does not specifically limit as a nickel oxide ore which is a raw material ore, Limonite ore, a saprolite ore, etc. can be used. This nickel oxide ore contains nickel oxide (NiO) and iron oxide (Fe ₂ O ₃ ) as constituent components.

  In the present embodiment, when producing pellets, a specific amount of carbonaceous reducing agent is mixed to form a mixture, and the mixture is formed into pellets. Although it does not specifically limit as a carbonaceous reducing agent, For example, coal powder, coke powder, etc. are mentioned. In addition, it is preferable that this carbonaceous reducing agent is equivalent to the particle size and particle size distribution of the nickel oxide ore which is the raw material ore described above. When the particle size and particle size distribution are the same, it is easy to mix uniformly, and a reduction reaction is also generated uniformly, which is preferable.

  The amount of carbonaceous reductant mixed, that is, the amount of carbonaceous reductant that forms a lump and is present inside the pellet, reduces nickel oxide and iron oxide that constitute nickel oxide ore without excess or deficiency. When the amount of the carbonaceous reducing agent necessary for the treatment is 100%, the proportion is preferably 40.0% or less, more preferably 35.0% or less. The amount of carbonaceous reducing agent necessary to reduce nickel oxide and iron oxide without excess or deficiency is the chemical necessary to reduce the total amount of nickel oxide contained in the formed pellets to nickel metal. In other words, it can be paraphrased as the sum of the equivalent and the chemical equivalent required to reduce the iron oxide contained in the pellets to iron metal (hereinafter also referred to as “total chemical equivalent”).

  Thus, by setting the amount of carbonaceous reducing agent present in the pellet (mixed amount of carbonaceous reducing agent) to a ratio of 40.0% or less when the total value of chemical equivalents is 100%, More effectively, a metal shell can be uniformly formed on the surface of the pellet. In addition, if the reduction reaction proceeds too much and the amount of iron produced increases, the nickel quality in the iron-nickel alloy may decrease, but the amount of carbonaceous reducing agent inside the pellet is 40.0% or less. By doing so, a decrease in nickel quality can be suppressed.

  The lower limit of the mixing amount of the carbonaceous reducing agent is not particularly limited. However, when the total value of chemical equivalents is 100%, the ratio is preferably 8.0% or more, and 12.0% It is more preferable to set it as the above ratio. Thus, it becomes easy to manufacture an iron-nickel alloy with high nickel quality by setting the mixing amount of the carbonaceous reducing agent to 8.0% or more.

  In addition to nickel oxide ore and carbonaceous reducing agent, iron ore which is an additive added as an optional component is not particularly limited, but for example, iron ore having an iron grade of about 50% or more, hydrometallurgy of nickel oxide ore Can be used.

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

  Table 1 below shows an example of the composition (% by weight) of some raw material powders to be mixed in the mixing process step S11. The composition of the raw material powder is not limited to this.

(2) Agglomeration treatment step The agglomeration treatment step S12 is a step of forming (granulating) the mixture of the raw material powders obtained in the mixing treatment step S11 into a lump.

  Here, FIG. 3 is a process flow diagram showing a process flow in the agglomeration process S12. As shown in FIG. 3, the agglomeration treatment step S12 is obtained by shaping a mixture obtained by mixing at least nickel oxide ore and a carbonaceous reducing agent into a rod-like or columnar shape and a shaping step S31. And a cutting step S32 for cutting the obtained mixture into a flat plate shape or a disk shape.

  As described above, in the present embodiment, the raw material powder mixture is formed into a rod-like or columnar shape, and then the molded product is cut into a plate-like or disk-like lump, A plate-shaped or disk-shaped pellet is produced from the obtained lump. According to such flat plate or disc shaped pellets, the variation in shape is very small and stable, so that stable quality is obtained, and like pellets granulated with a bread granulator There is no unevenness on the surface, and it can be finished smoothly. Also, by reducing and heat-treating plate-like or disk-like pellets in a reduction furnace, a metal shell can be uniformly formed on the surface, reducing the efficiency of the reduction reaction and generating ferronickel composition variations. Can be effectively prevented.

[Molding process]
The forming step S31 is a step of forming the raw material powder mixture (at least a mixture obtained by mixing nickel oxide ore and a carbonaceous reducing agent) obtained in the mixing treatment step S11. Specifically, in the forming step S31, the mixture is formed into a rod shape or a cylindrical shape.

  In the molding step S31, for example, the mixture can be molded using a pellet molding apparatus. The pellet forming apparatus is not particularly limited, but is preferably one that can knead and form the mixture with high pressure and high shear force, and particularly equipped with a twin screw type kneader (biaxial kneader). It is preferable that By kneading the mixture at high pressure and high shear, the agglomeration of the mixture of raw material powders can be released, and the mixture can be effectively kneaded and the strength of the resulting pellets can be increased. In addition, by using a machine equipped with a twin-screw kneader, pellets can be produced while maintaining high productivity continuously as well as kneading with high pressure and high shear, which is particularly preferable.

  Although it is possible to mold using a briquette press, high shear cannot be applied, and the strength of the pellet may not be sufficiently improved, thereby causing cracks during processing, It tends to collapse, and the shape also varies, resulting in a wide particle size distribution. In addition, when a briquette press is used, a part that protrudes from the molded pellets (a part that protrudes from the mold, so-called "ear") is created, and a decrease in quality and yield is avoided. It becomes difficult.

  Moreover, in order to continuously perform the operation of cutting the formed mixture in the cutting step S32 described later, it is more preferable to use the one provided with a cutting machine at the discharge port in the pellet forming apparatus to be used. By using such a pellet molding apparatus, it is possible to cut into a desired shape with high accuracy, and to produce pellets with no variation in shape while maintaining high productivity in continuous operation. it can. Moreover, by manufacturing by such a continuous process, the dispersion | variation in the quality of the pellets obtained can be made small.

[Cutting process]
The cutting step S32 is a step of cutting a rod-like or columnar mixture (molded product) obtained by molding. Specifically, in the cutting step S32, the rod-shaped or columnar shaped product is cut into a flat plate shape or a disk shape. Here, the shape of a flat plate shape or a disk shape is also expressed as “disk shape”.

  FIG. 4 is a diagram schematically showing a disk-like lump obtained by cutting the molded product in the cutting step S32, (A) is an external perspective view, and (B) is a top view and side views. FIG. The disc-shaped lump shown in FIG. 4 is referred to as “lump 1”. In addition, in pellet manufacturing process S1, since a pellet can be manufactured by drying the disk-shaped lump obtained in this way, the shape of the pellet is also shown in the schematic diagram of FIG. It is the same, and becomes a disk-shaped pellet (also referred to as “pellet 1”).

Although it does not specifically limit as a magnitude | size of the disk-shaped lump (pellet) 1, It is preferable that the diameter (D) is about 5-30 mm. Further, the aspect ratio (formula (1) below) which is the ratio of the diameter (D) to the height (H) is preferably in the range of 0.3 to 2.0, More preferably, it is 1.5 or less.
Aspect ratio = D / H (1)

  As shown in FIG. 4, the diameter (D) means the diameter of the disk surface when viewed from the upper surface with one of the disk surfaces down, and the height (H) is the disk surface. Means the height from the disk surface, which is the bottom surface when placed with one side down.

  Thus, the pellet manufactured by setting it as the disk-shaped pellet 1 from which the aspect-ratio becomes like this. Preferably it is the range of 0.3-2.0, More preferably, it is the range of 0.5-1.5. Can be effectively prevented, thereby generating a uniform metal shell on the surface of the pellet and causing a desired reduction reaction.

  In addition, the disk-shaped pellet 1 is thus placed on the hearth of the reduction furnace so that the disk surface faces down, thereby preventing the pellet from moving or rolling in the reduction furnace. Therefore, the reduction reaction can be caused stably, and variation in composition can be suppressed. Further, by using the disk-shaped pellet, the ferronickel metallized in the pellet is uniformly settled, the separation of the metal is facilitated, and the recovery rate can be improved.

  As described above, it is preferable that the cutting process of the mixture in the cutting process S32 is performed by a continuous operation following the molding process in the molding process S31. Specifically, using a pellet forming apparatus provided with a cutting machine at the discharge port, the mixture is put into the pellet forming apparatus and formed into a rod shape or a cylindrical shape, and then the discharged molded product is used as the discharge port. Then cut it into discs with a cutting machine. Thus, productivity can be made high by manufacturing a lump by a continuous process, and the dispersion | variation in the quality of pellets can be made small.

(3) Drying process process Drying process process S13 is a process of drying the disk-shaped lump obtained in lump processing process S12. Here, the mass obtained by the agglomeration treatment contains an excessive amount of water, for example, about 50% by weight. Therefore, when the pellet containing excess moisture is rapidly heated to the reduction temperature, the moisture may be vaporized at once, and may expand and break the pellet.

  Therefore, the obtained disk-shaped lump is subjected to a drying treatment, for example, the solid content of the lump is about 70% by weight, and the water content is about 30% by weight. The reduction heat treatment in S2 can prevent the pellet from collapsing. Further, the lump is often sticky due to excessive moisture, and handling can be facilitated by performing a drying treatment.

  Specifically, the drying process for the lump in the drying step S13 is not particularly limited. For example, hot air of 300 ° C. to 400 ° C. is blown against the lump to be dried. In addition, it is preferable that the temperature of the lump at the time of the drying treatment is less than 100 ° C. because the pellets are not easily broken.

  It should be noted that the drying process in the drying process step S13 can be omitted as long as it does not cause destruction during handling such as charging into a reduction furnace or during reduction heat treatment.

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

(4) Heat treatment (pre-heat treatment) step In the pellet manufacturing step S1, there is provided a heat treatment step for heating the pellet, which is a lump subjected to the drying treatment in the above-described drying treatment step S13, to a predetermined temperature. Good. This heat treatment is a heat treatment prior to heating at a predetermined reduction temperature in the subsequent reduction step S2, and can also be referred to as “pre-heat treatment”. Hereinafter, this process is also referred to as a pre-heat treatment process.

  The pellets to be manufactured are disk-shaped, for example, having a diameter of 5 mm to 30 mm and an aspect ratio of 0.3 to 2.0. The pellet is preferably a pellet having such a strength that the shape can be maintained, for example, a strength at which the proportion of the pellet that is broken even when dropped from a height of 1 m is about 1% or less. Such a pellet can withstand an impact such as a drop at the time of charging in the reduction step S2 and can maintain its shape. A gap is formed, and the reduction reaction in the reduction step S2 proceeds effectively and efficiently.

  In this regard, the pellets are produced by performing a heat treatment (pre-heat treatment) after the drying treatment, and thus in the reduction step S2, even when the pellets are reduced and heated at a high temperature of about 1400 ° C., for example, due to heat shock. It is possible to effectively prevent the cracking (breakage, collapse) of the pellet. For example, the proportion of the collapsing pellets out of all the pellets charged in the reduction furnace can be made a small proportion, and the shape of the pellets can be more effectively maintained.

  Specifically, in the pre-heat treatment step, a heat treatment for heating the pellets after the drying treatment to a temperature of 350 ° C. to 600 ° C. is performed. Moreover, it heats to the temperature of 400 to 550 degreeC preferably. Thus, by heating to a temperature of 350 ° C. to 600 ° C., preferably 400 ° C. to 550 ° C., the water of crystallization contained in the nickel oxide ore constituting the pellet can be reduced, for example, a reduction of about 1400 ° C. Even when the temperature is rapidly increased by charging the furnace, it is possible to suppress the collapse of the pellet due to the detachment of the crystal water.

  In addition, prior to the reduction heat treatment in the reduction step S2, the nickel oxide ore constituting the pellet, the carbonaceous reducing agent, the iron oxide to be arbitrarily added, the binder, the flux component, etc. are formed by performing the heat treatment in advance. The thermal expansion of the particles proceeds slowly in two stages, whereby the disintegration of the pellets due to the difference in particle expansion can be suppressed.

  In addition, it does not specifically limit as heat processing time in a preheat process, What is necessary is just to adjust suitably according to the magnitude | size of the lump containing a nickel oxide ore, but the magnitude | size of the pellet obtained will be about 10 mm-30 mm. If it is a lump of a normal magnitude | size, it can be set as the processing time of about 15 minutes-30 minutes.

<2. Reduction process>
In the reduction step S2, the disk-like pellets obtained in the pellet manufacturing step S1 are reduced and heated to a predetermined reduction temperature. By the reduction heat treatment of the pellets in the reduction step S2, a smelting reaction (reduction reaction) proceeds, and metal and slag are generated.

  The reduction heat treatment in the reduction step S2 is performed using a reduction furnace or the like. Specifically, reduction heating is performed by charging a pellet containing nickel oxide ore into a reduction furnace heated to a temperature of about 1400 ° C., for example.

  In the reduction heat treatment in the reduction step S2, nickel oxide and iron oxide in the pellet are first reduced and metalized in the vicinity of the surface of the pellet where the reduction reaction easily proceeds in a short time of about 1 minute, for example, to become an iron-nickel alloy. , To form a shell (hereinafter also referred to as “shell”). On the other hand, in the shell, as the shell is formed, the slag component in the pellet is gradually melted to form a liquid phase slag. Thereby, in one pellet, ferronickel metal (hereinafter simply referred to as “metal”) and slag made of oxide (hereinafter simply referred to as “slag”) are generated separately.

  And the carbon component of the surplus carbonaceous reducing agent not involved in the reduction reaction is taken into the iron-nickel alloy to lower the melting point by further extending the reduction heat treatment time in the reduction step S2 to about 10 minutes. . As a result, the iron-nickel alloy dissolves into a liquid phase.

  Specifically, in the present embodiment, a disk-shaped pellet is manufactured, and the pellet is reduced and heated in a reduction furnace, so that a metal shell can be stably generated on the surface of the pellet. As a result, the reduction reaction proceeds stably and efficiently, and ferronickel without variation in composition can be efficiently produced with high productivity.

  As described above, the slag in the pellet is melted to form a liquid phase, but the metal and slag that have already been separated and produced do not mix with each other. It becomes a mixture mixed as a separate phase. The volume of this mixture has shrunk to a volume of about 50% to 60% as compared with the pellets to be charged.

  When the reduction reaction described above proceeds most ideally, it can be obtained as a mixture of one metal solid phase and one slag solid phase for each charged pellet. It becomes a solid in the shape of Here, the “daruma shape” is a shape in which a metal solid phase and a slag solid phase are joined. In the case of a mixture having such a “dharma” shape, the mixture has the largest particle size, and therefore, when recovering from the reduction furnace, there is less time for recovery and the reduction in the metal recovery rate is suppressed. can do.

  In addition, in the reduction step S2, when charging the obtained pellets into the reduction furnace, a carbonaceous reducing agent (hereinafter also referred to as “hearth carbonaceous reducing agent”) is spread on the hearth of the reduction furnace in advance. The pellets may be placed on the spread hearth carbonaceous reducing agent. Further, the pellet placed on the hearth carbonaceous reducing agent can be further covered with the carbonaceous reducing agent. In this way, the pellets are charged into the reduction furnace in which the carbonaceous reducing agent is spread on the hearth, and further subjected to reduction heat treatment in a state surrounded by the carbonaceous reducing agent so as to cover the pellets, thereby the pellets The smelting reaction can be effectively advanced while maintaining the strength of the steel more effectively and suppressing the collapse.

  The reduction furnace used for the reduction heat treatment is not particularly limited, but a moving hearth furnace is preferably used. By using a moving hearth furnace as the reduction furnace, the reduction reaction proceeds continuously and the reaction can be completed with one facility, and the processing temperature is higher than when each process is performed using separate furnaces. Can be accurately controlled. In addition, heat loss between processes can be reduced, and more efficient operation can be performed. In other words, when a reaction is performed using separate furnaces, when the pellets are moved between the furnaces, the temperature decreases, heat loss occurs, and the reaction atmosphere changes, causing the furnaces to change. It is not possible to cause an immediate reaction when reinserted into On the other hand, by performing each treatment with one facility using a moving hearth furnace, heat loss is reduced and the atmosphere in the furnace can be controlled accurately, so that the reaction can proceed more effectively. it can. By these things, an iron-nickel alloy with high nickel quality can be obtained more effectively.

  The moving hearth furnace is not particularly limited, and for example, a rotary hearth furnace 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. In this rotary hearth furnace, the processing temperature in each area can be adjusted by controlling the time (movement time, rotation time) when passing through each area, and the rotary hearth furnace rotates once. Every time the pellets are smelted. The moving hearth furnace may be a roller hearth kiln or the like.

<3. Separation process>
In the separation step S3, the metal and slag generated in the reduction step S2 are separated and the metal is recovered. Specifically, the metal phase is separated and recovered from the mixture containing the metal phase (metal solid phase) and the slag phase (slag solid phase) obtained by the reduction heat treatment on the pellets.

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

  Further, the obtained metal phase and slag phase can be easily separated because of poor wettability, and the above-mentioned “dharma” mixture is dropped, for example, with a predetermined drop, or The metal phase and the slag phase can be easily separated from the “dharma” mixture by applying an impact such as applying a predetermined vibration during sieving.

  In this way, the metal phase is recovered by separating the metal phase and the slag phase.

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

[Manufacture of pellets]
Mix nickel oxide ore as raw ore, iron ore, silica sand and limestone as flux components, binder, and carbonaceous reducing agent (coal powder, carbon content: 85% by weight, average particle size: about 200 μm). To obtain a mixture. The carbonaceous reducing agent is 20% when the amount necessary for reducing nickel oxide and iron oxide (Fe ₂ O ₃ ) contained in nickel oxide ore as raw material ore without excess or deficiency is 100%. It contained in the quantity used as a ratio.

  Next, the obtained mixture was referred to as Sample No. 1-No. No. 12, of which no. 1-No. Nine 9 mixture samples were formed into a cylindrical shape using a pellet forming apparatus in which a cutting machine was attached to the sample discharge port of a twin screw type kneader. Moreover, in the cutting machine, the cylindrical molded product was cut so as to be a disk having a circular cross-sectional shape.

About the obtained lump, the pellet yield after granulation was computed using following (2) Formula based on the weight of the sample thrown into the pellet shaping | molding apparatus, and the weight of the obtained disk-like lump.
Pellet yield after granulation (%) = disc-shaped lump weight ÷ input sample weight × 100
... (2) formula

  On the other hand, no. 10-No. Twelve three mixture samples were granulated using a bread granulator. Specifically, the sample 10 has a mixture of samples 10 to 13 mm in diameter, and the sample 11 has a mixture of samples 12 to have a diameter of 15 mm to 18 mm. The mixture was granulated while adjusting the number of revolutions of the granulator, the amount of sample input, and the like so as to form a spherical lump having a diameter of 20 mm to 23 mm. In addition, after granulation, it classified so that it might become only a spherical pellet of diameter 10mm-13mm, 15mm-18mm, 20mm-23mm, respectively.

About the obtained lump, the pellet yield after granulation was computed using the following (3) formula based on the weight of the sample thrown into the bread-type granulator, and the weight of the obtained spherical lump. .
Pellet yield after granulation (%) = Spherical lump weight after classification ÷ Input sample weight × 100
... (3) formula

  Next, drying was performed by blowing hot air at 300 ° C. to 400 ° C. on the lump so that the solid content of the lump was about 70% by weight and the water content was about 30% by weight. Twelve sample pellets of No. 12 were produced, and Table 3 below shows the solids composition (excluding carbon) of the pellets after the drying treatment.

  In this example, No. 1-No. The treatment using the pellet sample (disk shape) of No. 9 was designated as Examples 1 to 9, and 10-No. The treatment using 12 pellet samples (spherical) was defined as Comparative Examples 1 to 3.

[Reduction heating treatment for pellets]
The manufactured pellets were charged into a reduction furnace and subjected to reduction heat treatment. Specifically, ash (the main component is SiO ₂ and contains a small amount of oxides such as Al ₂ O ₃ and MgO as other components) is preliminarily placed on the hearth of the reduction furnace, and pellets are formed thereon. 1000 samples were placed. In addition, No. 1-No. The disk-shaped pellet of No. 9 was placed stably with its circular surface (disk surface) facing down so that the circular surface and the hearth surface were parallel.

  Thereafter, the atmosphere was substantially nitrogen-free and the pellets were charged into a reduction furnace. The temperature condition at the time of charging was 500 ± 20 ° C.

  Next, the reduction temperature was set to 1400 ° C., and the pellet was reduced and heated in a reduction furnace. The treatment time was set to 15 minutes so that a metal shell was generated on the surface of the pellet and the reduction in the pellet as a mixture proceeded efficiently. After the reduction treatment, the sample was quickly cooled to room temperature in a nitrogen atmosphere, and the sample was taken out into the atmosphere.

  No. 1-No. After 12 samples of 12 spherical pellets were subjected to the same reduction heat treatment, in each pellet, “cracking”, “collapse”, “more than a quarter of the pellet volume”, “clearance 1 mm or more” The presence or absence of “occurrence of large cracks” was judged, and any pellet sample in which one or more defects occurred was judged as “bad”. On the other hand, a pellet sample that did not have such a defective portion and was subjected to a clean reduction treatment was judged to be “good”. The number of non-defective products was divided by the number of input (1000), and the yield (%) after the reduction treatment was calculated.

  Moreover, in each pellet, the nickel metal rate and the nickel content rate in the metal were analyzed and calculated using an ICP emission spectroscopic analyzer (S-8100, manufactured by Shimadzu Corporation).

In addition, the nickel metal rate and the nickel content rate in the metal were calculated by the following equations.
Nickel metal ratio =
Amount of Ni metalized in pellets / (total amount of Ni in pellets) × 100 (%)
Nickel content in metal =
Amount of metalized Ni in the pellet ÷ (total amount of metalized Ni and Fe in the pellet)
× 100 (%)

  Table 4 below shows the aspect ratio, spherical pellet diameter, pellet yield after granulation and reduction treatment in each pellet sample. Moreover, the measurement result measured by ICP analysis is shown.

  As shown in the results of Table 4, by producing a disk-shaped pellet and subjecting the pellet to reduction heat treatment, nickel in the pellet can be metalized well, and the nickel content is 19 It was found that high-quality ferronickel of 0.0% to 21.4% can be produced (Examples 1 to 9). Further, such disk-shaped pellets were stable without rolling even when vibrations occurred in the reduction furnace during the reduction heat treatment.

  As described above, the reason why the ferronickel can be manufactured as a good ferronickel is that a disk shell is used to uniformly and stably generate a metal shell, thereby preventing the reducing agent from escaping in the metal shell. In addition, it is considered that the reduction reaction occurred uniformly and stably.

  On the other hand, as shown in the results of Comparative Examples 1 to 3, in the case of spherical pellets, the nickel metallization rate is lower on average than the disk-shaped pellet samples used in the examples. Thus, the nickel content in the metal was also 17.4% to 18.8%, which was a low value for ferronickel.

1 Disc-shaped pellet D Diameter of the circular surface of the disc-shaped pellet H Height of the disc-shaped pellet

Claims (6)

A method for producing a pellet for producing a pellet from nickel oxide ore,
At least the nickel oxide ore and the carbonaceous reducing agent are mixed, and includes a lump processing step for forming a lump and forming pellets.
In the agglomeration treatment step, a mixture obtained by mixing at least the nickel oxide ore and the carbonaceous reducing agent is molded into a rod shape or a columnar shape, and the molded product obtained by molding is cut into a flat plate. A method for producing pellets in the form of pellets or discs. The pellet manufacturing method according to claim 1, wherein the pellet has an aspect ratio of 0.3 to 2.0. The method for producing pellets according to claim 1 or 2, wherein the nickel oxide ore and a carbonaceous reducing agent are mixed, the resulting mixture is molded, and the treatment obtained by forming and cutting the mixture is continuously performed. . The manufacturing method of the pellet of any one of Claims 1 thru | or 3 which performs the heat processing which heat the said flat plate-shaped or disk-shaped pellet to the temperature of 350 to 600 degreeC. A nickel oxide ore smelting method for producing ferronickel by forming pellets from nickel oxide ore and reducing the pellets,
A pellet manufacturing process for manufacturing pellets from the nickel oxide ore;
A reduction step of heating the obtained pellets at a predetermined reduction temperature in a reduction furnace,
In the pellet manufacturing step, at least the nickel oxide ore and a carbonaceous reducing agent are mixed, the mixture is formed into a rod shape or a column shape, the mixture obtained by molding is cut into a plate shape or a disk shape pellet and Yes Nickel oxide ore smelting method. The smelting of nickel oxide ore according to claim 5, wherein in the reduction step, a moving hearth furnace is used as the reduction furnace, and the plate-shaped or disk-shaped pellets are charged into the moving hearth furnace for reduction heating. Method.

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