JP2018150568A - Oxide ore smelting method, pellet and container - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an oxide ore smelting method, capable of inexpensively producing ferronickel of a high quality, having high productivity or efficiency, and excellent in handling ability, in a method of producing a metal or an alloy by reducing a mixture including an oxide ore.SOLUTION: An oxide ore smelting method is of producing a metal or an alloy by reducing a molded oxide ore. The oxide ore smelting method includes: a mixing treatment step S1 of mixing at least the oxide ore and a carbonaceous reducer; a mixture molding step S2 of molding the obtained mixture; and a reduction step S3 of heating the molded mixture in a reduction furnace at a prescribed reduction temperature. In the reduction step S3, the mixture molded to have a thickness t of 17 mm or more is put into the reduction furnace and heated.SELECTED DRAWING: Figure 3

Description

  The present invention smelts pellets and containers produced from a mixture of oxide ore such as nickel oxide ore and a reducing agent at a high temperature in a reduction furnace to obtain a reduced product such as ferronickel. The present invention relates to a smelting method and pellets and containers used therefor.

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

  In the above-described various smelting methods, when nickel oxide ore is smelted by reduction together with a carbon source, first, pretreatment for making the raw material ore into blocks or slurries is performed. Specifically, when nickel oxide ore is agglomerated, that is, when it is made into a lump from powder or fine particles, 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”).

  This pellet needs to have a certain level of air permeability in order to “fly off” the contained water. In addition, if the reduction does not proceed uniformly in the pellet, the composition of the resulting reduced product becomes non-uniform, resulting in inconveniences such as metal dispersion or uneven distribution. It is important to maintain a uniform temperature as much as possible when the reduction treatment is performed.

  In addition, it is a very important technique to coarsen the ferronickel produced by reduction. This is because, when the produced ferronickel has a fine size of, for example, several tens of μm to several hundreds of μm, it is difficult to separate from the slag produced at the same time, and the recovery rate (yield) as ferronickel is greatly reduced. It is because it will do. For this reason, the process which coarsens the ferronickel after reduction | restoration is needed.

  In addition, how to reduce the smelting cost is an important technical matter, and a continuous process that can be operated with a compact facility is desired.

  For example, in Patent Document 1, an agglomerate containing a metal oxide and a carbonaceous reducing agent is supplied to a hearth of a moving bed type reduction melting furnace and heated to reduce and melt the metal oxide. In the production method, when the relative value of the projected area ratio of the agglomerate to the hearth with respect to the maximum projected area ratio of the agglomerate to the hearth when the distance between the agglomerates is 0 is used as the bed density A method is disclosed in which an agglomerate having an average diameter of 19.5 mm or more and 32 mm or less is supplied onto a hearth so that the bed density is 0.5 or more and 0.8 or less and heated. In this method, it is described that the productivity of granular metallic iron can be enhanced by controlling the bed density and the average diameter of the agglomerates together.

  However, the method disclosed in Patent Document 1 is a technique for controlling a reaction occurring outside the agglomerate, and is a control of the reaction occurring inside the agglomerate, which is the most important factor in the reduction reaction. Is not focused on. On the other hand, by controlling the reaction that takes place inside the agglomerate, it has been demanded to obtain higher quality metals (metals, alloys) by increasing the reaction efficiency and promoting the reduction reaction more uniformly. .

  Moreover, since the method of using what has a specific diameter as an agglomerate like patent document 1 needs to remove what does not have a specific diameter, the yield at the time of producing an agglomerate is high. It was low. In addition, the method disclosed in Patent Document 1 is a method with low productivity because it is necessary to adjust the bed density of the agglomerates to 0.5 or more and 0.8 or less, and the agglomerates cannot be laminated. It was. For these reasons, the method in Patent Document 1 has a high manufacturing cost.

  As described above, the technique for producing a metal or alloy by mixing and reducing oxide ore has many problems in terms of increasing productivity, reducing manufacturing cost, and improving metal quality.

JP 2011-256414 A

  The present invention has been proposed in view of such circumstances, and in a method for producing a metal or alloy by reducing a mixture containing oxide ore, productivity and efficiency are high, and handling properties are excellent. And it aims at providing the smelting method of the oxide ore which can manufacture a high quality metal cheaply.

  This inventor repeated earnest examination in order to solve the subject mentioned above. As a result, by introducing the mixture containing oxide ore and carbonaceous reducing agent into the reduction furnace so that the thickness exceeds a predetermined value, it is possible to produce ferronickel with high efficiency of reduction reaction and less composition variation. The headline, the present invention has been reached. That is, the present invention provides the following.

  (1) A first invention of the present invention is a method for smelting an oxidized ore for producing a metal or an alloy by reducing the shaped oxidized ore, and at least the oxidized ore and a carbonaceous reducing agent are mixed. A mixing treatment step, a mixture forming step for forming the resulting mixture, and a reduction step in which the formed mixture is heated at a predetermined reduction temperature in a reduction furnace. In the reduction step, the thickness is It is a smelting method of oxide ore in which the mixture formed to be 17 mm or more is charged into the reduction furnace and heated.

  (2) The second invention of the present invention is the method of smelting ore oxide according to the first invention, wherein, in the mixture forming step, the mixture is formed into pellets having a thickness of 17 mm or more.

  (3) According to a third aspect of the present invention, in the first aspect, in the mixture molding step, the mixture is filled in a container so that the thickness of the mixture becomes 17 mm or more. Is the method.

  (4) A fourth invention of the present invention is the method of smelting ore oxide according to any one of the first to third inventions, wherein the reduction temperature in the reduction step is 1250 ° C. or higher and 1450 ° C. or lower.

  (5) According to a fifth aspect of the present invention, in any one of the first to fourth aspects, the method further includes a separation step of separating the slag from the mixture after the reduction step to obtain a metal or alloy. This is a method for smelting oxide ore.

  (6) A sixth invention of the present invention is a method for smelting an oxidized ore according to any one of the first to fifth inventions, wherein the oxidized ore is a nickel oxide ore.

  (7) A seventh invention of the present invention is the method of smelting ore oxide according to the sixth invention, wherein ferronickel is obtained as the alloy.

  (8) The eighth invention of the present invention is a pellet containing oxide ore and a carbonaceous reducing agent, has a thickness of 17 mm or more, and is charged in a reduction furnace and subjected to reduction heat treatment. It is a pellet.

  (9) A ninth invention of the present invention is a container in which a mixture containing oxide ore and a carbonaceous reducing agent is accommodated, wherein the mixture is accommodated so as to have a thickness of 17 mm or more. And a reductive heat treatment for the mixture.

  According to the present invention, in a method of producing a metal or alloy by reducing a mixture containing oxide ore, high productivity and efficiency, excellent handling properties, and high quality ferronickel are produced at low cost. It is possible to provide a method for smelting oxidized ore that can be used.

It is process drawing which shows an example of the flow of the smelting method of an oxide ore. It is a processing flowchart which shows an example of the flow of a process in a mixture shaping | molding process. It is the perspective view and side sectional drawing which show the example of a lump. It is the perspective view and side sectional drawing which show the example of a container.

  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 oxide ore≫
The method for smelting oxidized ore according to the present embodiment forms a mixture of raw materials containing oxidized ore, which is a raw material ore, and charges the formed product into a smelting furnace (reducing furnace) for reduction treatment. Thus, metal and slag are generated. More specifically, a mixture of at least nickel oxide ore and a carbonaceous reducing agent is formed to form a mixture contained in pellets or containers, and the mixture formed to have a thickness of 17 mm or more is a smelting furnace. (Reduction furnace) is charged and subjected to reduction treatment.

  Here, “pellet” means a massive shaped body (pellet, briquette, etc.) produced from a mixture of oxide ore and a carbonaceous reducing agent. And the shape of this pellet is not limited, The shape of a cube, a rectangular parallelepiped, a cylinder, or a sphere may be sufficient.

  As a mixture to be reduced and obtained by molding, pellets with a thickness of 17 mm or more can be used, or a container filled so that the thickness (height) from the bottom is 17 mm or more Can be used.

  In the following, by reducing nickel (nickel oxide) and iron (iron oxide) contained in nickel oxide ore which is an oxide ore which is a raw material ore, an iron-nickel alloy metal (reduced metal) is generated, A smelting method for producing ferronickel by separating the metal will be described as an example.

  Specifically, in the method for smelting oxidized ore according to the present embodiment, as shown in FIG. 1, a mixing treatment step S <b> 1 for mixing raw materials containing the oxidized ore and the resulting mixture is formed into a predetermined shape. A mixture forming step S2, a reduction step S3 in which the formed mixture is heated at a predetermined reduction temperature in a reduction furnace, and a separation step S4 in which the metal and slag generated in the reduction step S3 are separated to recover the metal. Have

<1. Mixing process>
The mixing process step S1 is a step of obtaining a mixture by mixing raw material powders containing nickel oxide ore. Specifically, in this mixing treatment step S1, a carbonaceous reducing agent is added to and mixed with nickel oxide ore as a raw material ore, and as optional additives, iron ore, flux components, binders, For example, powder having a particle size of about 0.2 mm to 0.8 mm is mixed to obtain a mixture. Here, mixing of the raw material powder containing nickel oxide ore can be performed using a mixer or the like.

Although it does not specifically limit as a nickel oxide ore which is a raw material ore, Limonite ore, 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, a specific amount of carbonaceous reducing agent is mixed with the raw material ore to obtain a mixture. 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 a thing equivalent to the particle size and particle size distribution of the nickel oxide ore which is the raw material ore mentioned 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 will be included in the mixture in the pellets and containers after molding, 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 50.0% or less, more preferably 40.0% or less. The amount of carbonaceous reducing agent necessary to reduce nickel oxide and iron oxide without excess or shortage is the chemical necessary to reduce the total amount of nickel oxide contained in pellets or containers to nickel metal. In other words, it can be paraphrased as the total value of the equivalent and the chemical equivalent required to reduce the iron oxide contained in the pellet or container to iron metal (hereinafter also referred to as “total value of chemical equivalent”).

  Thus, the amount of carbonaceous reducing agent contained in the mixture (mixed amount of carbonaceous reducing agent) is reduced to a ratio of 50.0% or less when the total value of chemical equivalents is 100%. The reaction can proceed efficiently.

  The lower limit of the mixing amount of the carbonaceous reducing agent is not particularly limited, but preferably 10.0% or more when the total value of chemical equivalents is 100%. It is more preferable to set it as the above ratio. Thus, an iron-nickel alloy having a high nickel quality can be easily manufactured by setting the mixing amount of the carbonaceous reducing agent to 10.0% 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. For example, iron ore having an iron grade of about 50% or more, or 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 S1. The composition of the raw material powder is not limited to this.

  When the raw material powder is mixed to obtain a mixture, the raw material powder may be kneaded in order to improve the mixing property. As a result, a shearing force is applied to the mixture, and agglomeration of the carbon reducing agent, raw material powder, etc. can be dissolved and mixing can be performed more uniformly, and the adhesion of each particle is increased, so that uniform reduction treatment can be easily performed. it can.

<2. Mixture molding process>
The mixture forming step S2 is a step of forming a mixture of the raw material powder obtained in the mixing process step S1 and drying it as necessary to obtain a molded product such as a pellet. FIG. 2 is a process flow diagram showing a process flow in the mixture forming step S2.

  As shown in FIG. 2, the mixture forming step S2 includes an agglomeration treatment step S21 for forming a mixture of raw materials containing oxide ore into a lump, and a drying treatment step S22 for drying the obtained lump. Or it has the container filling process S26 which fills the container of the raw material containing an oxide ore into the container for predetermined reduction, and the drying process S22 which dries the obtained lump.

(1) Agglomeration treatment step The agglomeration treatment step S21 is a step of forming the mixture of raw materials containing oxide ore obtained in the mixing treatment step S1 into an agglomerate having a predetermined shape and size.

  FIG. 3A is a perspective view and FIG. 3B is a side view showing an example of the shape of a lump. In the agglomeration treatment step S21, the agglomerate 1 obtained by molding the mixture is preferably molded (agglomerated) so that the thickness (height) t of the agglomerate is 17 mm or more, and has a part that is 30 mm or more. Thus, it is more preferable to form (agglomerate). By increasing the thickness t of the lump 1, more ferronickel metal settles in the lower part, so that larger ferronickel can be easily manufactured. In addition, since the ratio of the surface area to the volume of the lump 1 is reduced, the difference in reduction rate between the surface and the inside of the lump 1 can be reduced, and the composition uniformity is very high, producing high quality ferronickel. Can be made easier. In addition, by increasing the thickness t of the lump 1, the throughput can be increased by increasing the throughput in one reduction process, and the handling property is improved. Extraction can be easily performed.

  There is no specific upper limit for the thickness t of the lump 1 after molding, and it may be set to such a size that it can be charged into the reduction furnace by actual operation and the heat heated during the reduction is sufficiently transmitted.

  The shape of the lump 1 after molding is a shape in which the thickness t is within a predetermined range, and can be charged into the reduction furnace so that the thickness t becomes a height from the mounting surface of the reduction furnace. Any shape is acceptable. Among these, it is preferable that the magnitude | size except thickness direction (height direction) is not less than 17 mm, and it is more preferable that it is not less than 30 mm. By preventing the size other than the thickness direction (height direction) from falling below a predetermined range, it is possible to easily achieve the effect when the thickness of the lump 1 is increased.

  Examples of the shape of the lump 1 include a cube, a rectangular parallelepiped, a cylinder, or a sphere. In particular, by forming the mixture into the shape of a cube, a rectangular parallelepiped, a cylinder, or a sphere, the mixture can be easily formed, so that the cost for forming can be suppressed. Moreover, since the shape to shape | mold is not complicated, generation | occurrence | production of the pellet of a molding defect can be reduced.

  In the agglomeration treatment step S21, moisture necessary for agglomeration is added to the mixture as necessary, and the mixture is converted into an agglomerate using, for example, an agglomerate manufacturing apparatus (compression molding machine, extrusion molding machine, etc.). Can be molded. Although it does not specifically limit as a lump manufacturing apparatus, It is preferable that it is what can knead | mix and shape | mold a mixture with a high pressure and a high shear force, and was equipped with the twin-screw type kneader (biaxial kneader) especially. It is preferable. 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 kneaded effectively, and the strength of the resulting mass can be increased. In addition, by using a machine equipped with a biaxial kneader, not only can kneading be performed under high pressure and high shear, but a lump can be produced while maintaining high productivity continuously, which is particularly preferable.

(2) Container Filling Step On the other hand, the container filling step S26 is a step of filling the predetermined reduction container with the mixture obtained in the mixing treatment step S1. Specifically, the obtained mixture is filled by supplying it to a container using an apparatus such as an extruder. Here, when filling the container with the mixture, the container filling step S26 may be performed after the mixture is dried, and the dried mixture may be filled into the container.

  FIG. 4A is a perspective view and FIG. 4B is a side view showing an example of the shape of the container. The container 2 filled with the mixture 21 in the container filling step S26 has a hollow portion for holding the mixture 21, as shown in FIG. The container is filled with the mixture 21 such that the thickness (height) t ′ of the mixture 21 is 17 mm or more, preferably 30 mm or more. The thickness of the mixture 21 refers to the thickness (height) from the bottom of the container filled with the mixture. By increasing the thickness t ′ of the mixture 21, more ferronickel metal settles in the lower portion, so that larger ferronickel can be easily manufactured. Moreover, since the ratio of the surface area to the volume of the mixture 21 is reduced, the difference in reduction rate between the surface and the inside of the mixture 21 can be reduced. Therefore, the uniformity of the composition is very high and high-quality ferronickel can be easily manufactured. be able to. In addition, by increasing the thickness t ′ of the mixture 21, the throughput can be increased by increasing the amount of treatment in one reduction process, and the handling property is improved. Extraction can be easily performed.

  There is no specific upper limit for the thickness t ′ of the mixture 21 filled in the container 2, and it may be set to a size that can be charged into the reduction furnace in actual operation and that the heat heated during the reduction is sufficiently transmitted.

  The shape of the hollow portion of the container 2 is not particularly limited as long as the mixture 21 can be held so that the thickness t ′ is not less than a predetermined value. Among them, it is preferable that the mixture 21 can be filled so that the size other than the thickness direction (height direction) is equal to or greater than the thickness t ′. By making the size of the cavity portion other than the thickness direction equal to or greater than the thickness t ′, the effect when the thickness t ′ of the mixture 21 is increased can be easily achieved.

  As an example of the shape of the hollow part of the container 2, the thing in which the shape of a cube, a rectangular parallelepiped, or a cylinder is comprised by the plane and inner wall surface containing the opening of a container can be mentioned. In particular, as shown in FIGS. 4A and 4B, a container 2 having a cylindrical shape constituted by a plane including the opening 25 and the inner wall surface 22 can be used.

  Moreover, the material of the container main body 23 of the container 2 is not particularly limited, but the material that does not adversely affect the mixture 21 accommodated in the container main body 23 during the reduction treatment and can efficiently advance the reduction reaction. It is preferable to use what consists of. Specifically, graphite crucibles, ceramics or metals can be used.

  Filling the container 2 with the mixture 21 can be performed by supplying the mixture 21 to the container body 23 of the container 2 using an extruder or the like, as described above. At the time of filling, it is preferable to fill the mixture 21 at a high filling rate so that there are no gaps or spaces in the container 2. Moreover, after filling, it is preferable to press and harden the mixture 21. In this way, the mixture 21 is pressed and solidified and packed in the container body 23, so that the filling rate of the mixture 21 in the container 2 can be increased, and more uniform ferronickel with less variation in quality can be obtained. It can be manufactured efficiently.

  The mixture 21 filled in the container 2 in the container filling step S <b> 26 is subjected to a reduction process, which will be described later, in a state where the container 2 is filled. As described above, the mixture 21 is filled in the container 2 and the reduction treatment (the treatment in the reduction step S3) is performed in this state, so that the portion close to the surface of the mixture 21 filled in the container 2, that is, the container 2 A metal shell is formed near the inner wall surface 22 and the lid 24, and then metal is generated inside the metal shell. As a result, in the metal shell, a larger amount of ferronickel metal precipitates and is generated in the lower part, so that the metal can be easily separated and recovered by a process such as magnetic separation in the subsequent separation step S4. Ferronickel can be recovered in a recovery rate.

  At this time, as shown in FIGS. 4 (a) and 4 (b), the container 2 in a state in which the container body 23 filled with the mixture 21 is covered with the lid 24 is charged into a reduction furnace and subjected to reduction treatment. preferable. In this way, by performing the reduction heat treatment on the container 2 covered with the lid 24, the reduction reaction proceeds more efficiently, and nickel metallization can be promoted. The lid 24 is preferably made of the same material as the container body 23.

(3) Drying process process Drying process process S22 is a process of drying the lump obtained in lump forming process S21, and the mixture after being filled with the container. Here, the mass obtained by the agglomeration treatment contains an excessive amount of water, for example, about 50% by weight. Therefore, when the lump containing excessive moisture is rapidly heated to the reduction temperature, the moisture may vaporize and expand all at once, destroying the lump and the container holding the mixture.

  Therefore, the obtained mixture or lump is subjected to a drying treatment, for example, the solid content in the mixture or lump is about 70% by weight, and the water content is about 30% by weight. In the reduction heat treatment in step S3, it is possible to prevent the pellets made of a lump and the container holding the mixture from collapsing, thereby preventing difficulty in taking out from the reduction furnace. Moreover, since the lump and the mixture are often in a state where they are sticky due to excessive moisture, handling can be facilitated by subjecting them to a drying treatment.

  Specifically, although it does not specifically limit as a drying process with respect to a lump and a mixture in drying process process S22, For example, 300 degreeC-400 degreeC hot air is sprayed with respect to a lump or a mixture, and is dried.

  Here, particularly when a large volume lump or mixture is dried, the lump or mixture before or after drying may be cracked or cracked. When the volume of a lump or mixture is large, the lump or mixture melts and contracts during reduction, and thus cracks and cracks often occur. However, when the volume of the lump or mixture is large, the effect of an increase in the surface area caused by cracks or cracks is small, so that a big problem is unlikely to occur. Therefore, the lump or mixture before reduction may be cracked or cracked.

  Note that the drying process in the drying process step S22 may be omitted as long as the pellets and the container do not break during handling of the pellets in the reduction furnace or during the reduction heat treatment.

  Table 2 below shows an example of the composition (parts by weight) in the solid content in pellets made of a lump after the drying treatment and in the mixture after the drying treatment. In addition, as a composition of a pellet or a mixture, it is not limited to this.

<3. Reduction process>
In the reduction step S3, the pellets obtained in the mixture molding step S2 and the container filled with the mixture are charged into a reduction furnace and reduced to a predetermined reduction temperature. Thus, by heat-processing the mixture which comprises a pellet, and the mixture with which the container was filled, a smelting reaction (reduction reaction) advances and a metal and slag are produced | generated.

  In the present embodiment, the reduction heat treatment is performed on the pellets formed so as to have a thickness of 17 mm or more and the container filled with the mixture so that the thickness becomes 17 mm or more. Thus, it can be made easy to manufacture larger ferronickel by performing reduction heat processing with respect to the mixture which became more than predetermined thickness. In addition, by reducing the ratio of the surface area to the volume of the mixture, the difference in reduction rate between the surface and the inside of the mixture can be reduced, so the composition uniformity is very high and high quality ferronickel can be easily manufactured. Can do.

  The reduction heat treatment in the reduction step S3 is performed using a reduction furnace or the like. Specifically, the mixture containing nickel oxide ore is reduced and heated by charging it into a reduction furnace heated to a reduction temperature of, for example, 1250 to 1450 ° C., more specifically to a reduction temperature of about 1300 to 1400 ° C. Note that the “reduction temperature” in the present embodiment means the temperature at the highest temperature in the furnace. For example, in the case of a moving hearth furnace, it is the temperature at a location that is substantially centered in the width direction (the direction that intersects at right angles to the hearth moving direction and is in the plane where the pellets and containers are placed). . In particular, in the case of a rotary hearth furnace such as a rotary hearth furnace, the temperature near the center in the width direction (the radial direction from the central axis of the rotary hearth and in the plane where the pellets and containers are placed). It is.

  In the reduction heat treatment in the reduction step S3, nickel oxide and iron oxide are reduced and metallized in the vicinity of the surface of the pellet or mixture, for example, in a short time of about 1 minute. (Ferronickel) to form a shell (hereinafter also referred to as “shell”). On the other hand, in the shell, with the formation of the shell, the slag component in the mixture gradually melts to form liquid phase slag. As a result, in one pellet or container, a metal composed of an alloy or metal such as ferronickel (hereinafter simply referred to as “metal”) and a slag composed of oxide (hereinafter simply referred to as “slag”). Generate separately.

  And when the processing time of the reduction heat treatment in the reduction step S3 elapses for about 10 minutes, the excess carbon component of the carbonaceous reducing agent not involved in the reduction reaction is taken into the iron-nickel alloy to lower the melting point. As a result, the iron-nickel alloy dissolves into a liquid phase.

  The time for performing the reduction heat treatment in the reduction furnace is set according to the temperature of the reduction furnace, but is preferably 10 minutes or more, and more preferably 15 minutes or more. On the other hand, the upper limit of the time for performing the reduction heat treatment may be 50 minutes or less or 40 minutes or less from the viewpoint of suppressing an increase in manufacturing cost.

  In the present embodiment, when the reduction reaction progresses ideally, the mixture after the reduction heat treatment, that is, the mixture filled in the pellets or the container, becomes a composite of a large lump of metal and slag. Become. At this time, by forming a large lump of metal, it is possible to reduce the time and effort required for recovery from the reduction furnace, and it is possible to suppress a decrease in the metal recovery rate.

  As described above, the slag formed inside the pellet and the container is melted into a liquid phase by the reduction heat treatment, but the metal and the slag that have already been separated and mixed do not mix, As a result of cooling, the mixture becomes a mixed phase as a separate phase between the metal solid phase and the slag solid phase. The volume of the mixture is contracted to a volume of about 50% to 60% as compared with the mixture to be charged.

  Here, particularly when the pellets are charged into the reduction furnace, in the reduction step S3, a carbonaceous reducing agent (hereinafter also referred to as “furnace carbonaceous reducing agent”) is preliminarily spread on the hearth of the reduction furnace, A container filled with pellets or a mixture may be placed on the hearth carbonaceous reducing agent laid down. Moreover, after placing a container filled with pellets or a mixture on the hearth carbonaceous reducing agent, the container can be covered with the carbonaceous reducing agent. In this way, reduction heating is performed in a state in which pellets or the like are charged into a reduction furnace in which a carbonaceous reducing agent is laid on the hearth or surrounded by a carbonaceous reducing agent so as to further cover the charged pellets or the like. By performing the treatment, the smelting reaction can be advanced more quickly while suppressing the collapse of the pellets and the container.

  In particular, in a mode in which pellets are charged into a reduction furnace, a pellet laminate may be formed by charging two or more layers of pellets molded to a thickness of 17 mm or more. By laminating the pellets in two or more stages, it is possible to increase the amount of pellets that are reduced by a single reduction heat treatment while improving the handleability when the pellets are installed in a reduction furnace. In addition, a larger metal can be generated.

  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. Furthermore, heat loss between each process is reduced, and more efficient operation is possible. In other words, when a reaction is performed using separate furnaces, when the pellets or containers are moved between the furnaces, the temperature decreases and heat loss occurs, and the reaction atmosphere changes. As a result, the reaction does not proceed immediately when the furnace is recharged. 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 a rotary hearth furnace, a roller hearth kiln, or the like can be used. Among these, as the rotary hearth furnace, for example, a rotary hearth furnace (rotary hearth furnace) that is circular and divided into a plurality of processing regions can be used. In this rotary hearth furnace, each process is performed in each region while rotating in a predetermined direction. At this time, by controlling the time (movement time, rotation time) when passing through each region, the processing temperature in each region can be adjusted, and the mixture is produced every time the rotary hearth rotates once. Smelted.

<4. Separation process>
In the separation step S4, the metal and slag generated in the reduction step S3 are separated and the metal is recovered. Specifically, the metal phase is separated from the mixture contained in the container and the mixture including the metal phase (metal solid phase) and the slag phase (slag solid phase) obtained by reduction heat treatment on the pellets. And collect.

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

  Further, the obtained metal phase and slag phase can be easily separated because of poor wettability, and the large mixture obtained by the reduction step S3 described above is dropped with a predetermined drop, for example. By applying an impact such as applying a predetermined vibration during sieving, the metal phase and the slag phase can be easily separated from the mixture.

  In particular, in the present embodiment, in the reduction step S3, the reduction or heat treatment is performed on the mixture of oxidized ores formed to have a thickness greater than or equal to a predetermined thickness, so that the metal obtained by reduction passes through the containers and pellets. By settling, larger ferronickel metal is produced. Therefore, ferronickel metal can be easily separated by a process such as magnetic separation while suppressing loss in terms of manufacturing efficiency, and the metal can be recovered at a high recovery rate.

  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.

[Mixing raw material powder]
Nickel oxide ore as raw material ore, iron ore, silica sand and limestone as flux components, binder, and carbonaceous reducing agent (coal powder, carbon content: 85% by weight, average particle size: about 200 μm), appropriate amount The mixture was mixed using a mixer while adding water. The carbonaceous reducing agent is 28.0 when the amount necessary for reducing nickel oxide and iron oxide (Fe ₂ O ₃ ) contained in the nickel oxide ore as raw material ore without excess or deficiency is 100%. %.

[Molding the mixture]
Next, 28 samples were separated from the obtained mixture and formed into the shapes shown in Table 4. Specifically, the mixture was molded into a pellet using a compression molding machine so as to have a predetermined thickness. In addition, about the sample of Examples 21-24, the vibration was intentionally given to the mixture and the surface of the mixture was cracked and cracked.

  Next, hot air of 300 ° C. to 400 ° C. is blown to each of the samples of Examples 1 to 28 and Comparative Examples 1 to 4 so that the solid content is about 70% by weight and the moisture is about 30% by weight. And dried. Table 3 below shows the solid composition (excluding carbon) of the mixture after the drying treatment.

[Reduction heat treatment of the mixture]
After the drying treatment, the pellets formed with the mixture and the container filled with the mixture were respectively charged into a reduction furnace having a nitrogen atmosphere substantially free of oxygen. The temperature condition at the time of charging into the reduction furnace was 500 ± 20 ° C.

  Next, the reducing heat treatment was performed on the mixture (pellet) at the temperature and time shown in Table 4. After the reduction treatment, it was quickly cooled to room temperature in a nitrogen atmosphere and taken out into the atmosphere.

Here, the charging of the pellets into the reduction furnace is performed in advance in the hearth of the reduction furnace with a small amount of ash (main component is SiO ₂ and other components such as Al ₂ O ₃ and MgO). ) Was spread and the pellets were placed thereon.

  In this example, the treatment in which a mixture having a thickness (height) of 17 mm or more was charged into a reduction furnace was referred to as Examples 1 to 24, and the mixture having a thickness (height) of less than 17 mm was loaded in the reduction furnace. The entered treatments were designated as Comparative Examples 1 to 4.

  About each sample which performed the reduction heat processing, the mixture after reduction | restoration was embedded in resin, the metal deposited on the surface was observed with the metal microscope, and the average particle diameter of the metal was measured. Here, the average particle diameter was the average value of the maximum cross-section lengths for any 100 metal particles deposited on each sample.

  Moreover, about each sample after reduction heat processing, the nickel metalization rate and the nickel content rate in a metal were analyzed and calculated by the ICP emission-spectral-analyzer (SHIMAZU S-8100 type | mold).

The nickel metal conversion rate and the nickel content rate in the metal were calculated by the following equations.
Nickel metal conversion rate =
Metalized amount of Ni in the mixture / (total amount of Ni in the mixture) × 100 (%)
Nickel content in metal =
Amount of metallized Ni in the mixture ÷ (total amount of metalized Ni and Fe in the mixture)
× 100 (%)

  Moreover, about each sample after a reduction heat processing, the metal was collect | recovered by the magnetic selection after the grinding | pulverization by wet processing. And the nickel metal recovery rate was computed from the content of nickel oxide ore in the pellet laminated body charged into the reduction furnace, the nickel content rate in nickel oxide ore, and the amount of recovered nickel.

The nickel metal recovery rate was calculated by the following formula.
Nickel metal recovery rate =
Recovered Ni amount ÷ (Amount of charged ore charged x Ni content in oxidized ore)
× 100 (%)

  Table 4 below shows the average particle diameter of nickel metal, the nickel metal conversion rate, the nickel content in the metal, and the nickel metal recovery rate in each sample.

  As shown in the results of Table 4, the nickel metalization rate is 96.9% by charging the mixture into a reduction furnace and performing a reduction treatment so that the thickness (height) of the mixture becomes 17 mm or more. It was found that high quality ferronickel with high nickel content in the metal and 18.8% or more can be produced (Examples 1 to 24). In these examples, it was found that the metal recovery rate from the mixture was as high as 91.0% or more. Moreover, regarding the average particle diameter of the metal, it has been found that as the thickness of the mixture increases (the height increases), the particles grow and become larger.

  As described above, the reason why the high-quality ferronickel could be manufactured is that by increasing the thickness of the mixture to a predetermined thickness or more, more metal is generated, It is conceivable that the metal easily aggregated and large metal particles were obtained. As a result, it is considered that a high value can be obtained for the metal recovery rate.

  Moreover, since the favorable result was obtained also about the samples 21-24 which made the surface crack and a crack formed, although it thinks according to a grade, even if a crack and a crack generate | occur | produce in the pellet before reduction to some extent, The effect on the quality of ferronickel and the metal recovery rate is considered to be small.

  On the other hand, as shown in the results of Comparative Examples 1 to 4, when the mixture was charged into a reduction furnace so that the thickness (height) of the mixture was less than 17 mm, the reduction treatment was performed. The nickel metalization rate is 90.3% at the highest, the nickel content in the metal is 16.3% at the highest, and the metal recovery rate is 81.5% at the highest. It was a low value compared with the example.

DESCRIPTION OF SYMBOLS 1 Thick thing t Thickness of chunk 2 Container 21 Mixture 22 Inner wall surface 23 Container body 24 Lid 25 Opening t 'Thickness of mixture

Claims (9)

A method for smelting an oxide ore that produces a metal or alloy by reducing the formed oxide ore,
A mixing treatment step of mixing at least the oxide ore and a carbonaceous reducing agent;
A mixture molding step for molding the resulting mixture;
A reduction step of heating the molded mixture at a predetermined reduction temperature in a reduction furnace,
In the reduction step, the mixture formed so as to have a thickness of 17 mm or more is charged into the reduction furnace and heated. The method for refining oxide ore according to claim 1, wherein, in the mixture forming step, the mixture is formed into pellets having a thickness of 17 mm or more. The method for refining oxide ore according to claim 1, wherein in the mixture forming step, the container is filled with the mixture such that the thickness of the mixture becomes 17 mm or more. 4. The method for smelting oxidized ore according to claim 1, wherein a reduction temperature in the reduction step is 1250 ° C. or higher and 1450 ° C. or lower. 5. The method for smelting ore oxide according to any one of claims 1 to 4, further comprising a separation step of separating the slag from the mixture after the reduction step to obtain a metal or an alloy. The method for smelting an oxide ore according to any one of claims 1 to 5, wherein the oxide ore is a nickel oxide ore. The method for refining oxide ore according to claim 6, wherein ferronickel is obtained as the alloy. A pellet containing oxide ore and a carbonaceous reducing agent,
Having a thickness of 17 mm or more,
Pellet that is subjected to reduction heat treatment charged in a reduction furnace. A container containing a mixture containing an oxide ore and a carbonaceous reducing agent,
The mixture is accommodated to a thickness of 17 mm or more,
A container charged in a reduction furnace and subjected to reduction heat treatment for the mixture.

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