JP2005220398A - Reduced metal molded body, and device and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reduced metal molded body which maintains a high metallization ratio, and whose reoxidization is prevented, and to provide a device and a method for producing the same. <P>SOLUTION: A powdery film forming substance 2 prepared in such a manner that whose melting point is controlled so as to be ≥1,100°C is stuck to the surface of a molded body 1 comprising iron oxide, carbon as a reducing agent, zinc oxide as impurity metal or the like. Thereafter, the molded body 1 is heated to reduce and evaporate the zinc oxide or the like, then, the film forming substance 2 is melted by further heating to cover the surface of the molded body 1 with the film forming substance 2, and the iron oxide is reduced with a reducing agent. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a reduced metal molded body, a manufacturing apparatus thereof, and a manufacturing method, for example, reduced iron molding having a function of preventing a reoxidation during storage, transportation and the like while maintaining a high metallization rate immediately after reduction. Can be applied as a body.

  The reduced metal molded body is obtained by mixing a metal oxide such as ore with a reducing agent such as coal to form a molded body having a predetermined shape and then heating it to a high temperature in a reduction furnace to reduce the metal oxide. It is a molded body. The shape of the molded body may be either a spherical pellet by a rolling granulation method, a briquette by a compression granulation method, or a cylindrical pellet by an extrusion granulation method.

  A conventional method for producing a reduced metal molded body will be described by taking reduced iron pellets as an example. First, iron ore powder as an iron source, coal powder as a reducing agent, and a binder are sufficiently mixed by a mixer. Next, the mixed powder is put into a granulator together with water so as to be easily granulated, granulated into a spherical molded body called a green ball (raw pellets), and then put into a dryer and dried. Further, the dried green ball is put into a rotary bed furnace type reduction furnace and maintained in a high temperature atmosphere of about 1300 ° C. heated by a burner for about 10 minutes to reduce iron oxide in iron ore by the action of coal. To produce reduced iron pellets.

  The reduced iron pellets produced in this way are put into a melting furnace, where they are separated into hot metal and slag, and are taken out and used as high-purity iron.

  If the reduced metal pellet manufactured by the above-described method is kept as it is, it is easily oxidized (reoxidized) by oxygen in the atmosphere during storage and transportation. When this reoxidized reduced metal pellet is melted, a slag containing a large amount of metal oxide is generated on the surface of the molten metal, and the yield of the resulting metal deteriorates, or the concentration of the reducing agent added to the melting furnace additionally. However, there is a problem that the metal oxide becomes unstable due to reduction of the metal oxide in the reduced metal or the metal oxide in the slag.

With respect to these problems, a technique for preventing reoxidation by forming a film containing an organic film substance or a CO ₂ generating substance on the surface of the reduced metal pellet after completion of the reduction (see, for example, Patent Document 1 below). ), And a technique for preventing reoxidation by forming a film composed of a hydrocarbon-based substance and a surfactant (see, for example, Patent Document 2 below).

JP-A-8-260172 JP 2002-363625 A

  However, the above-described reoxidation prevention technique is based on a coating process performed on reduced metal pellets cooled to a low temperature after the reduction is completed, and is an effective technique mainly for preventing reoxidation during long-term storage. is there. This is because the coating disappears due to heat even if the same treatment is performed on the reduced metal pellet in a high temperature state immediately after the reduction is completed.

  However, the reduced metal pellet is most easily reoxidized while being cooled from the high temperature state immediately after the reduction is completed to room temperature. Therefore, it is necessary to block the reduced metal pellet from the external atmosphere (oxygen) even in this high temperature state.

  In addition, in metal oxides such as iron ore and steel dust, impure metal oxides such as zinc oxide and lead oxide which are reduced and evaporate at a relatively low temperature are also included. If the impure metal can be evaporated at the same time as reducing the target metal, a reduced metal pellet with a higher content of the target metal can be produced. For this reason, measures such as pre-coating the surface of the green ball with a heat-resistant material before being put into the reduction furnace are not preferable. This is because the coated refractory material hinders the evaporation of impure metals.

  The present invention has been made in view of the above situation, and while maintaining a high metallization rate at the reduction temperature in the reduction furnace, for example, reduced metal molding having a function of preventing reoxidation during storage, transportation, etc. An object is to provide a body, a manufacturing apparatus thereof, and a manufacturing method.

The method for producing a reduced metal molded body according to the present invention that solves the above problems is as follows.
After attaching a powdery film-forming substance to the surface of the molded body containing a metal oxide and a reducing agent,
The molded body is heated to reduce the metal oxide with the reducing agent, and the film-forming substance is melted to coat the surface of the molded body with the film-forming substance.
It is a method for producing a reduced metal molded body obtained by cooling the molded body.

  By melting and coating with a film-forming substance already at the end of reduction, for example, not only re-oxidation during storage, transportation, etc., but also prevention of re-oxidation at the reduction temperature, the reduction temperature in the reduction furnace A reduced metal molded body that maintains a high metallization rate at the time is manufactured.

In the method for producing the reduced metal molded body,
The molded body contains an impure metal oxide,
The film forming substance is a method for producing a reduced metal molded body, wherein the impure metal oxide is reduced to an impure metal by the reducing agent and melted at a temperature higher than a temperature at which the impure metal evaporates.

  By selecting a substance that melts at a temperature higher than the temperature at which the impure metal evaporates as the film forming substance, a reduced metal molded body with a higher content of the target metal is produced without impeding the evaporation of the impure metal. Examples of the metal oxide include iron oxide and chromium oxide, and examples of the impure metal oxide include zinc oxide and lead oxide.

Moreover, the manufacturing method of the other reduced metal molding which solves the said subject is as follows.
The molded body containing a metal oxide, a reducing agent, and an impure metal oxide is heated to reduce the impure metal oxide to an impure metal by the reducing agent and evaporate the impure metal, and then the molded body. A powdery film-forming substance is attached to the surface of
The metal oxide is reduced by the reducing agent, and the film forming substance is melted to coat the surface of the molded body with the film forming substance,
It is a method for producing a reduced metal molded body obtained by cooling the molded body.

  In the method in which the film-forming substance is attached to the molded body in advance, a film-forming substance that does not inhibit the evaporation of the impure metal that occurs at a relatively low temperature must be selected. However, the impure metal is almost completely evaporated from the molded body. Later, by attaching a film-forming substance, the degree of freedom in selecting the film-forming substance is increased. For example, it is not necessary to increase the particle size of the powdery film-forming substance for the impurity metal evaporation, and the melting point may be lower than the evaporation temperature of the impurity metal.

In the method for producing the reduced metal molded body,
The method of attaching a powdery film-forming substance to the surface of the molded body,
A method of spraying the powdery film-forming substance (for example, by rolling and rotating), a method of spraying a liquid in which the powdery film-forming substance is dispersed or dissolved, or a method of immersing the molded body in the liquid A method for producing a reduced metal molded body, which is any one of the methods.

In the method for producing the reduced metal molded body,
The metal oxide is iron oxide, and the impure metal oxide is zinc oxide or lead oxide.

  In this manufacturing method, a reduced iron molded body can be manufactured. In addition, when manufacturing a reduced chromium molding, chromium ore containing chromium oxide is used as a raw material.

In the method for producing the reduced metal molded body,
The reducing agent is a carbonaceous material containing fixed carbon.

In the method for producing the reduced metal molded body,
The molded body is either a spherical pellet by a rolling granulation method, a briquette by a compression granulation method, or a cylindrical pellet by an extrusion granulation method, and has a short side of 5 mm to 15 mm and a long side of 40 mm or less. It is a manufacturing method of the reduced metal molded object characterized by being.

In the method for producing the reduced metal molded body,
The powdery film-forming substance has a particle diameter of 10 μm or more, and is a method for producing a reduced metal molded body.

  When the short side is smaller than 5 mm, the size of the molded body is difficult and unrealistic to handle, and when the short side is larger than 15 mm or the long side is larger than 40 mm, it takes time to reduce the inside of the molded body. Becomes worse. On the other hand, if the particle size of the powdery film-forming substance is smaller than 10 μm, the powder is too densely attached to the surface of the molded body, which may impede the evaporation of impure metals.

In the method for producing the reduced metal molded body,
The film-forming substance is a compound containing silicon oxide, calcium oxide, and aluminum oxide.

  In the case of a single compound such as silicon oxide, calcium oxide or aluminum oxide, the melting point is too high, so that it cannot be melted by heating in the reduction step to cover the surface of the molded body as a coating. Therefore, by using mainly a compound in which these are mixed (mixed at the molecular level), the melting point can be controlled at a low temperature, and the film forming material is optimal for the production of the reduced metal molded body. In particular, it is an optimum film-forming substance when producing a reduced iron molding.

In the method for producing the reduced metal molded body,
The film forming substance has a melting point of 1100 ° C. or higher, and is a method for producing a reduced metal molded body.

  When producing a reduced iron molded body, impure metal oxides such as zinc oxide contained in iron ore start to be reduced at about 800 ° C. or more, and the reduced zinc metal evaporates. Therefore, the melting point is preferably 1100 ° C. or higher as a film-forming substance that does not inhibit evaporation of impure metals such as zinc. On the other hand, even if the melting point is too high, it does not melt at the temperature of the reduction step, so the melting point is preferably 1200 to 1300 ° C.

In the method for producing the reduced metal molded body,
The film-forming substance comprises 20% to 40% by weight of silicon oxide, 20% to 40% by weight of calcium oxide, and 1% to 20% by weight of aluminum oxide. It is a manufacturing method. However, the total of all the components is 100% or less.

  By setting each component of the film-forming substance to the above-described content ratio, the film-forming substance is optimal for the production of the reduced metal molded body.

The reduced metal molded body according to the present invention for solving the above problems is
In a reduced metal molding containing a reduced metal,
The reduced metal molded body is characterized in that the surface of the reduced metal molded body is coated with a film forming substance.

  In addition to preventing re-oxidation during storage and transportation, re-oxidation at the reduction temperature is prevented, and a reduced metal molded body maintaining a high metallization rate at the reduction temperature in the reduction furnace is obtained.

In the reduced metal molded body,
The reduced metal molding is characterized in that the metal is iron.

In the reduced metal molded body,
The film-forming substance is a reduced metal molding characterized in that it is a compound containing silicon oxide, calcium oxide, and aluminum oxide.

  By using a compound mainly mixed with silicon oxide, calcium oxide and aluminum oxide (mixed at the molecular level), it becomes possible to control the melting point to a low temperature, and an optimum film-forming substance for the production of the reduced metal molded body To do. In particular, it is an optimum film-forming substance when producing a reduced iron molding.

In the reduced metal molded body,
The film forming substance has a melting point of 1100 ° C. or higher, and is a reduced metal molding.

In the reduced metal molded body,
The film-forming substance is a reduced metal molded body characterized in that silicon oxide is 20 wt% to 40 wt%, calcium oxide is 20 wt% to 40 wt%, and aluminum oxide is 1 wt% to 20 wt%. is there. However, the total of all the components is 100% or less.

An apparatus for producing a reduced metal molded body according to the present invention that solves the above problems is as follows.
An attachment means for attaching a powdery film-forming substance to the surface of a molded body containing a metal oxide and a reducing agent;
It is installed at the subsequent stage of the adhering means, and heats the molded body to reduce the metal oxide with the reducing agent and melts the film-forming substance to coat the surface of the molded body with the film-forming substance. An apparatus for producing a reduced metal molded body comprising a reduction furnace.

Moreover, the manufacturing apparatus of the other reduced metal molding which solves the said subject is as follows.
A reduction furnace that heats a molded body containing a metal oxide, a reducing agent, and an impure metal oxide, reduces the impure metal oxide to an impure metal by the reducing agent, and evaporates the impure metal;
An attachment means for attaching a powdery film-forming substance to the surface of the molded body after the impure metal has evaporated,
The reducing furnace further reduces the metal oxide with the reducing agent, melts the film forming material, and coats the surface of the molded body with the film forming material. It is a manufacturing apparatus.

  In a reduction furnace that reduces the compact by moving the hearth, select the installation position where the impure metal will evaporate (the compact will be heated to the evaporation temperature of the impure metal) and adhere to the middle of the move Install means. In the batch type reduction furnace, the timing of depositing the film forming substance is determined in consideration of the heating temperature (time), and the deposition means is operated.

Moreover, in the manufacturing apparatus of the reduced metal molded body,
Furthermore, it is a manufacturing apparatus for a reduced metal molded body, characterized by having means for crushing an aggregate of reduced metal molded bodies that are brought into close contact with each other by melting the film forming substance.

  Since the film-forming substance is melted to cover the surface of the molded body, the reduced metal molded body is brought into close contact with each other when cooled as it is. In a later step, when there is a problem in handling such as poor handling in the aggregate, the aggregate is crushed by applying a vibration to the aggregate or applying a mixer by means of crushing.

According to the method for producing a reduced metal molded body according to the present invention,
After attaching a powdery film-forming substance to the surface of the molded body containing a metal oxide and a reducing agent,
The molded body is heated to reduce the metal oxide with the reducing agent, and the film-forming substance is melted to coat the surface of the molded body with the film-forming substance.
Since it was decided to cool the molded body,
By melting and coating the reduced metal molded body in a high temperature state immediately after the reduction process with a film-forming substance, for example, not only re-oxidation during storage, transportation, etc., but also the highest temperature at which there is a risk of re-oxidation. It is possible to produce a reduced metal molded body that prevents oxidation during the cooling process from the state and maintains a high metallization rate at the reduction temperature in the reduction furnace.

Further, the molded body contains an impure metal oxide,
Since the film-forming substance is melted at a temperature higher than the temperature at which the impure metal oxide is reduced to the impure metal by the reducing agent and the impure metal evaporates,
By selecting a material that melts at a temperature higher than the temperature at which the impure metal evaporates as the film forming material, a reduced metal molded body with a higher content of the target metal is produced without impeding the evaporation of the impure metal. Can do.

According to another method for producing a reduced metal molded body according to the present invention,
The molded body containing a metal oxide, a reducing agent, and an impure metal oxide is heated to reduce the impure metal oxide to an impure metal by the reducing agent and evaporate the impure metal, and then the molded body. A powdery film-forming substance is attached to the surface of
The metal oxide is reduced by the reducing agent, and the film forming substance is melted to coat the surface of the molded body with the film forming substance,
Since it was decided to cool the molded body,
In the method in which the film-forming substance is attached to the molded body in advance, a film-forming substance that does not inhibit the evaporation of the impure metal that occurs at a relatively low temperature must be selected. However, the impure metal is almost completely evaporated from the molded body. Later, by attaching a film-forming substance, the degree of freedom in selecting the film-forming substance can be increased.

Further, the method of attaching a powdery film-forming substance to the surface of the molded body,
A method of spraying the powdery film-forming substance (for example, by rolling and rotating), a method of spraying a liquid in which the powdery film-forming substance is dispersed or dissolved, or a method of immersing the molded body in the liquid Since it was decided to be one of the methods
The film-forming substance can be effectively attached to the surface of the molded body.

In addition, since the metal oxide is iron oxide and the impure metal oxide is zinc oxide or lead oxide,
A reduced iron molding can be manufactured.

Also, since the reducing agent contains carbon,
Metal oxide can be effectively reduced.

The molded body is either a spherical pellet by a rolling granulation method, a briquette by a compression granulation method, or a cylindrical pellet by an extrusion granulation method, and has a short side of 5 mm to 15 mm and a long side. Because it was 40mm or less,
The molded body can be optimized from the aspects of handling and reduction efficiency.

Further, since the powdery film-forming substance has a particle size of 10 μm or more,
The powdery film-forming substance can be optimized from the viewpoint of evaporation of impure metals.

In addition, since the film-forming substance is a compound containing silicon oxide, calcium oxide, and aluminum oxide,
It is possible to obtain a film forming material that is most suitable for the production of a reduced metal molded body, particularly reduced iron molded body.

In addition, since the melting point of the film forming material is 1100 ° C. or higher,
It is possible to obtain a film forming material that is most suitable for the production of a reduced metal molded body, particularly reduced iron molded body.

In addition, since the film-forming substance is 20% to 40% by weight of silicon oxide, 20% to 40% by weight of calcium oxide, and 1% to 20% by weight of aluminum oxide,
When the low boiling point impure metal is evaporated, it is not melted to prevent the impure metal from being evaporated, and the iron content of the formed reduced iron molded body can be improved.

Moreover, according to the reduced metal molded body according to the present invention,
In a reduced metal molding containing a reduced metal,
Because the surface of the reduced metal molding was coated with a film-forming substance,
For example, it is possible to prevent reoxidation during storage and transportation.

Since the metal is iron,
It can be applied to reduced iron moldings.

In addition, since the film-forming substance is a compound containing silicon oxide, calcium oxide, and aluminum oxide,
The present invention can be applied to the above-described manufacturing method for preventing oxidation in the cooling process from a high temperature state where there is a risk of reoxidation.

In addition, since the melting point of the film forming material is 1100 ° C. or higher,
The above-described method for producing a reduced metal molded body, particularly reduced iron molded body, which prevents oxidation in the cooling process from a high temperature state where there is a risk of reoxidation, and improves the target metal content by evaporation of impure metals. It can be applied to the manufacturing method.

In addition, the film-forming substance is 20 wt% to 40 wt% silicon oxide, 20 wt% to 40 wt% calcium oxide, and 1 wt% to 20 wt% aluminum oxide.
The above-described method for producing a reduced metal molded body, particularly a reduced iron molded body, which prevents oxidation in the cooling process from a high temperature state where there is a risk of reoxidation and improves the target metal content by evaporation of impure metals. It can be applied to the manufacturing method.

Moreover, according to the apparatus for producing a reduced metal molded body according to the present invention,
An attachment means for attaching a powdery film-forming substance to the surface of a molded body containing a metal oxide and a reducing agent;
It is installed at the subsequent stage of the adhering means, and heats the molded body to reduce the metal oxide with the reducing agent and melts the film-forming substance to coat the surface of the molded body with the film-forming substance. Since it was decided to have a reduction furnace,
By melting and coating the reduced iron molding in a high temperature state immediately after the reduction process with a film-forming substance, for example, not only re-oxidation during storage, transportation, etc., but also the highest temperature at which there is a risk of re-oxidation. It is possible to produce a reduced metal molded body that prevents oxidation during the cooling process from the state and maintains a high metallization rate at the reduction temperature in the reduction furnace.

In addition, according to another reduced metal molded body manufacturing apparatus according to the present invention,
A reduction furnace that heats a molded body containing a metal oxide, a reducing agent, and an impure metal oxide, reduces the impure metal oxide to an impure metal by the reducing agent, and evaporates the impure metal;
An attachment means for attaching a powdery film-forming substance to the surface of the molded body after the impure metal has evaporated,
Since the reduction furnace further reduces the metal oxide with the reducing agent and melts the film forming substance to coat the surface of the molded body with the film forming substance.
In an apparatus configuration in which a film-forming substance is attached to a molded body in advance, a film-forming substance that does not inhibit the evaporation of impure metals that occurs at a relatively low temperature must be selected, but the impure metal is almost completely evaporated from the molded body. After that, by adopting an apparatus configuration for attaching the film forming substance, the degree of freedom in selecting the film forming substance can be increased.

Furthermore, since it has means for pulverizing the aggregate of the reduced metal molded body that is closely adhered by melting the film-forming substance,
A loose reduced metal molded body can be obtained, and handling in a subsequent process can be improved.

<First Embodiment>
FIG. 1 is a schematic configuration diagram of a reduced iron pellet manufacturing apparatus (rotary hearth type) for carrying out the reduced iron pellet manufacturing method according to the first embodiment when a molded body is formed into pellets. Based on the same figure, the manufacturing process by the reduced iron pellet manufacturing apparatus 10 is demonstrated easily.

  As shown in the figure, first, iron ore powder (iron raw material), coal powder (reducing agent), and limestone powder, which are raw materials for pellets, are supplied from hoppers 11, 12, and 13, respectively. It is mixed in the mixer 15 together with the supplied binder. Next, the mixed powder is granulated into green balls (raw pellets) GB having a diameter of 10 to 20 mm by the pelletizer 16, put into a dryer 17, and dried by exhaust gas from a reduction furnace 19 described later.

  The dried green ball GB is supplied to the reduction furnace 19 by the conveyor 18. Here, the conveyor 18 is provided with an attachment device (attachment means) for applying a powdery film-forming substance on the surface of the green ball GB. The green ball GB to which the film forming substance is attached and supplied to the reduction furnace 19 is heated to a high temperature inside the furnace by the radiant heat of the high temperature gas when moving in the reduction furnace 19, and the iron oxide in the iron ore is converted by coal. Reduced iron pellets are produced by reduction.

  The temperature and rotation speed in the furnace are set so that the reduction process of the green ball GB is completed in the process of rotating the annular hearth once, and the reduced iron pellets formed after the reduction process is used for pellet discharge It is discharged from the reduction furnace 19 by the screw 28 and accommodated in the container 20.

  As shown in FIG. 1, the operation of the reduction furnace 19 in the reduced iron manufacturing apparatus 10 is as follows. In the reduction furnace 19, the hearth is rotated in the direction of arrow T by a drive device at a predetermined speed. While the inside of the reducing furnace 19 is heated to form a high temperature atmosphere, the gas inside the reducing furnace 19 flows in the direction of arrow G and is discharged from the exhaust duct 27.

  The exhaust gas discharged from the exhaust duct 27 is cooled by the water spray type primary cooler 21 and then sent to the heat exchanger 22, where heat exchange is performed with the air sent by the blower fan 23, It cools again with the spray type secondary cooler 24. In addition, the air heated with the heat exchanger 22 is sent to the reduction furnace 19, and is supplied in a furnace with a fuel. On the other hand, the exhaust gas cooled by the secondary cooler 24 is sent to the dryer 17 by the fan 25 and becomes the drying gas of the green ball GB as described above. A hot air generating furnace or the like may be used as a gas source for drying the green ball GB.

FIG. 2 is a diagram for explaining the production process of reduced iron pellets according to the present embodiment together with the change due to the reduction treatment of the green ball GB when the molded body is pellets. FIG. 2A shows the green ball GB (molded body 1) supplied to the reduction furnace 19. As shown in the figure, the molded body 1 is mainly a mixed molding of iron oxide (Fe ₂ O ₃ ), which is a metal oxide, carbon (C), which is an oxidizing agent, and zinc oxide (ZnO), which is an impure metal oxide. Is the body. Further, a compound 2 containing mainly a silicon oxide (SiO ₂ ), calcium oxide (CaO), and aluminum oxide (Al ₂ O ₃ ), which is a powdery film-forming substance, is coated on and adhered to the surface. ing.

  The particle size of the molded body 1 is 12 mm. About this particle size, 5 mm-15 mm are suitable, and handling and reduction | restoration efficiency will be a problem in particle size other than this. The particle size of the powdery film-forming substance 2 is about 20 μm. If the particle size is smaller than 10 μm, it will adhere too closely to the surface of the molded body 1, which may hinder the evaporation of impure metals, which will be described later.

Further, the content ratio of silicon oxide (SiO ₂ ), calcium oxide (CaO) and aluminum oxide (Al ₂ O ₃ ) in the film-forming substance 2 is 34% by weight for silicon oxide, 32% by weight for calcium oxide, and oxidized. Aluminum is 2% by weight.

  The content ratio is preferably 20% to 40% by weight of silicon oxide, 20% to 40% by weight of calcium oxide, and 1% to 20% by weight of aluminum oxide. The melting point of 2 is 1050 ° C to 1400 ° C. More preferable content ratios are 30% to 40% by weight of silicon oxide, 30% to 40% by weight of calcium oxide, and 1% to 5% by weight of aluminum oxide. The melting point of 2 is 1050 ° C to 1250 ° C. Since the melting point of the compound 2 varies depending on the content ratio of each component, the composition in which the compound 2 has an appropriate melting point described later is an appropriate content ratio.

  The green ball GB shown in FIG. 2A is supplied to the reduction furnace 19 and heated to 800 to 1100 ° C. At this time, as shown in FIG. 5B, after the zinc oxide, which is an impure metal oxide contained in the green ball GB, is reduced to carbon zinc (impure metal) by carbon as a reducing agent, The zinc evaporates at an in-furnace temperature of 907 ° C. or higher, and is exhausted outside the reduction furnace 19 as exhaust gas. Also, other low boiling point metals are evaporated and exhausted. As a result, the reduced iron content in the finally obtained reduced iron pellet can be increased. In addition, as a low boiling point impure metal contained in the green ball GB, lead and the like are listed in addition to zinc.

  Here, the film-forming substance 2 adhering to the surface of the molded body 1 has a melting point of 1100 ° C. or higher by adjusting the constituent components described above. Therefore, at the temperature at which impure metals such as zinc evaporate (about 910 ° C.), the film-forming substance 2 does not melt and become a film, and the evaporation of zinc or the like is not hindered.

  Further, in the green ball GB heated to 1100 ° C. or higher while moving in the reduction furnace 19, the iron oxide is reduced by carbon to become reduced iron as shown in FIG. On the other hand, the film-forming substance 2 melts because the furnace temperature exceeds the melting point, and becomes a film 3 on the surface of the molded body 1. Since the molded body 1 with the coating 3 formed in this manner does not enter oxygen from the outside, it is not re-oxidized in the process of cooling as shown in FIG. The reduced iron pellets 4 manufactured in this way are discharged from the reduction furnace 19 by the pellet discharge screw 28 and stored in the container 20.

  In addition, since the film forming material 2 melted in the reducing furnace 19 brings the reduced iron pellets 4 into close contact with each other, the aggregate of the reduced iron pellets 4 closely attached to the discharge portion of the reducing furnace 19 is crushed. Providing means for improving the handling in the subsequent process can be improved.

  A series of steps shown in FIGS. 2A to 2D is performed while the green ball GB moves in the reduction furnace 19. Therefore, the temperature in the reduction furnace 19, the moving speed of the hearth, the output of each burner 26, etc. are adjusted so that each process is performed appropriately.

  According to the present embodiment, the reduced iron pellets in a high temperature state immediately after the reduction step can be subjected to a film treatment with a film forming substance, and therefore in a cooling process from a high temperature state that is most likely to be reoxidized. Oxidation can be prevented and the iron content of the produced reduced iron pellets can be maintained in a high state. Furthermore, since the composition of the film-forming substance is adjusted so that it does not melt when the low boiling point impure metal is evaporated, it does not hinder the evaporation of the impure metal and improves the iron content of the produced reduced iron pellets. Can do.

<Second Embodiment>
FIG. 3 is a diagram for explaining the manufacturing process of reduced iron pellets according to the second embodiment together with the change due to the reduction process of the green ball GB when the molded body is pellets. The characteristics of the present embodiment will be described in comparison with the first embodiment. In this embodiment, the film forming substance is not attached to the molded body before being supplied into the reduction furnace. It is supposed to be done in the middle of the movement. Accordingly, the physical properties (melting point) of the film forming substance are also different from those of the first embodiment.

  The reduced iron pellet manufacturing apparatus for carrying out the present embodiment will be described with reference to FIG. 1, which is basically the same as the manufacturing apparatus shown in FIG. 1, but the conveyor 18 is provided with an attachment device (attachment means). In addition, an attachment device is provided in the middle of the rotational direction of the annular reduction furnace 19 to cover the green ball GB in the reduction furnace 19 with a film-forming substance. Except for this, the configuration of the manufacturing apparatus according to the first embodiment is the same.

FIG. 3A shows the green ball GB (molded body 1) supplied to the reduction furnace. As shown in the figure, the molded body 1 is mainly a mixed molding of iron oxide (Fe ₂ O ₃ ) which is a metal oxide, carbon (C) which is an oxidizing agent, and zinc oxide (ZnO) which is an impure metal oxide. Is the body. In this embodiment, the film forming substance is not attached to the molded body 1 when supplied to the reduction furnace.

  The green ball GB shown in FIG. 3A is supplied to a reduction furnace and heated to 800 to 1100 ° C. At this time, as shown in FIG. 5B, after the zinc oxide, which is an impure metal oxide contained in the green ball GB, is reduced to carbon zinc (impure metal) by carbon as a reducing agent, The zinc evaporates at a furnace temperature of 907 ° C. or higher, and is exhausted outside the reduction furnace as exhaust gas. Also, other low boiling point metals are evaporated and exhausted. As a result, the reduced iron content in the finally obtained reduced iron pellet can be increased.

  The conditions under which the impure metal evaporates almost completely depend on the impure metal content, the temperature in the reduction furnace, and the heating time. Therefore, the content of impure metals contained in the green ball GB is sampled and measured in advance, the temperature and heating time in the reduction furnace are determined, and the rotation speed of the hearth of the reduction furnace is adjusted to When the GB has been rotated to a predetermined position in the reduction furnace, it can be adjusted so that the evaporation of the impure metal has already ended.

In the present embodiment, a film forming substance deposition apparatus is provided at a position in the reduction furnace where it is calculated that evaporation of the impure metal has been completed. As shown in FIG. 3 (c), the adhesion apparatus thus provided mainly forms silicon oxide (SiO ₂ ) and calcium oxide (CaO), which are powdery film-forming substances, on the surface of the molded body 1. And a compound 2 containing aluminum oxide (Al ₂ O ₃ ) is applied.

  As an example of the deposition apparatus in the present embodiment, a film forming substance is supplied from the deposition apparatus to the green ball GB moving in the reduction furnace, and the hearth of the reduction furnace in the vicinity where the deposition apparatus is installed An apparatus configuration that is adapted to vibrate is mentioned. By the vibration of the hearth, the surface of the green ball GB can be uniformly coated with the film forming substance.

  After the film forming substance 2 is adhered, the green ball GB heated to 1100 ° C. or higher while rotating in the reduction furnace is reduced by reducing the iron oxide with carbon as shown in FIG. Become iron. On the other hand, the film-forming substance 2 melts because the furnace temperature exceeds the melting point, and becomes a film 3 on the surface of the molded body 1. Since the molded body 1 with the coating 3 formed in this way does not enter oxygen from the outside, it is not re-oxidized in the cooling process thereafter as shown in FIG. The reduced iron pellet 4 manufactured in this way is discharged from the reduction furnace by the pellet discharging screw and accommodated in a container.

  In the above description, the component and composition ratio of the film forming material 2 have been described as the film forming material having the same melting point in the same manner as in the first embodiment, but as one of the advantageous effects of the second embodiment. The film forming substance 2 has an effect that the melting point, the constituent component (material), and the composition ratio can be given freedom.

  In the first embodiment, the timing of forming a film is controlled by adjusting the melting point of the film-forming substance. In the second embodiment, the timing of film formation is determined by the position of the deposition apparatus in the reduction furnace. Can be controlled. That is, the impure metal evaporation stage in which the coating 3 is not preferably formed and the reduced iron re-oxidation stage in which the coating 3 needs to be formed are defined by the hearth movement position of the reduction furnace, What is necessary is just to install an adhesion apparatus in between.

  As a result, for example, even if the film-forming substance is a substance having a melting point that is equal to or lower than the boiling point of the impure metal, it can be used. However, since it is necessary to supply the film forming material so as to be applied to the green ball GB from the adhesion device, if the melting point is too low, the film may not be uniformly coated.

<Third Embodiment>
FIG. 5 is a schematic internal perspective view of a reduced iron pellet manufacturing apparatus (circular grate type) that implements the reduced iron pellet manufacturing method according to the third embodiment when the molded body is pellets. These are the figures which expand | deployed planarly the cross-section of the cyclic | annular reduction furnace.

  In the reduced iron pellet manufacturing apparatus according to the first and second embodiments, as shown in FIG. 1, a plurality of burners 26 provided in the reduction furnace 19 are used as means for heating the reduction furnace 19. The green ball GB in the reduction furnace 19 was heated using radiation heating. For this reason, the green ball GB supplied into the reduction furnace can be stacked only up to a single layer or about two layers on the hearth. In order to improve the productivity of reduced iron pellets, It was necessary to enlarge the device.

  On the other hand, the reduced iron pellet manufacturing apparatus according to the third embodiment is a net-like great having eyes that do not drop the green ball GB as a member corresponding to the hearth as shown in FIGS. 31 is employed, the upper surface of the reduction furnace 19 ′ is covered with a hood 30, and combustion air 32 is supplied from a combustion air supply port 33 provided below the great 31.

  In the manufacturing apparatus according to the present embodiment, the combustion air 32 passes through the gap between the green balls GB and heats the green balls GB without using the radiant heating by the burner. Therefore, a reduction process can be performed by stacking a plurality of green balls GB on the grate 31 as the hearth.

  The exhaust gas 34 exhausted by heating the green ball GB is exhausted from a plurality of exhaust holes provided in the hood 30. Further, as shown in FIG. 1, the exhaust gas may flow in one direction in the reduction furnace 19 and be exhausted from the exhaust duct.

  This embodiment is an embodiment in which the heating means in the first and second embodiments is modified, and the timing at which the film forming material is attached to the film forming material and the green pellet GB is the first and second embodiments. Can be done as well.

  In the case where the attachment apparatus is installed in the middle of the reduction furnace (see the second embodiment), the green balls GB are stacked in a plurality of stages in the third embodiment. It is necessary to devise a method for uniformly attaching the film forming substance to all the green balls GB by a method such as making the vibration stronger.

  Moreover, since the aggregate formed by close contact between the reduced iron pellets after the reduction step is coarser than in the first and second embodiments, the means for crushing the aggregate is more powerful. You may need to

  Further, in the circular great reduction furnace employed in the present embodiment, in contrast to the advantage that the green balls GB can be reduced by stacking a plurality of stages, reduction is sequentially performed in the stacking direction of the green balls GB stacked in a plurality of stages. As the process proceeds, there is a problem in that the green ball GB that has undergone the reduction process is re-oxidized.

  That is, among the stacked green balls GB, the green ball GB of the layer close to the Great 31 finishes the reduction process early, while the green ball GB stacked on the upper layer starts the reduction process after the lower layer reduction ends. For this reason, there is a problem that if the upper green ball GB is completely reduced, the lower green ball GB is reoxidized. On the other hand, in the present embodiment, as shown in the first and second embodiments, the film processing is performed by the film forming material so that re-oxidation at a high temperature does not occur, so the problem of the circular great type is solved. In addition, the improvement in productivity, which is an advantage, can be maintained.

  The green ball GB tends to reduce its particle size as the reduction reaction proceeds. This is because the moisture, the reducing agent and the like originally contained are evaporated and consumed. Therefore, the initial green ball GB does not pass through the size of the mesh constituting the great 31, but the reduction step ends by setting the size so that the green ball GB (reduced iron pellets) after the reduction step passes. At the same time, the reduced iron pellets can be automatically taken out, and problems caused by being exposed to the combustion air for a long time after the reduction process can be further prevented.

<Implementation results according to the first to third embodiments>
About embodiment mentioned above, the metallization rate (Degree of Metallization) of the reduced iron pellet obtained was measured. As an experimental method, green pellets with the following composition are used as raw materials, and a ceramic glaze (a glass-based antioxidant mainly composed of silica, calcia, and alumina), which is a kind of antioxidant, is used as a film-forming substance. Then, the heating conditions in the reduction furnace were 1200 ° C. and the reduction furnace was 10 minutes round.

The pellets used were Quebec iron ore (Fe ₂ O ₃ 60%, ZnO 5%, remaining SiO ₂ , Al ₂ O ₃ etc.) with an average particle size of 67 μm (75% particle size 200 μm), average particle size 20 μm. Pinnacle coal (80% particle size is 54 μm) has a composition of 19.5% and bentonite as a binder is 0.33%. 1% water was added to this, and a green ball having a particle diameter of 12 mm was formed with a pelletizer. The component composition of the ceramic glaze is as described in each embodiment.

  The metallization rate after the reduction process was compared between when the ceramic glaze was attached to the green ball produced as described above and when it was not attached. As a result, the metallization rate was 64% when not treated with the ceramic glaze, but when the ceramic glaze was adhered, the metallization rate was 84%, indicating that the metallization rate was improved.

<Other embodiments>
In the embodiment described above, an example in which the reduced metal molded body is applied to a reduced iron molded body has been described. However, the present invention is not limited to this, and can be applied to chromium.

It is a schematic block diagram of the manufacturing apparatus of the reduced iron pellet which enforces the manufacturing method of the reduced iron pellet concerning 1st Embodiment. It is the figure explaining the manufacturing process of the reduced iron pellet concerning 1st Embodiment with the change by the reduction process of the green ball GB. It is the figure explaining the manufacturing process of the reduced iron pellet concerning 2nd Embodiment with the change by the reduction process of the green ball GB. It is the figure which expand | deployed planarly the cross-section of the cyclic | annular reduction furnace regarding the manufacturing apparatus of the reduced iron pellet which implements the manufacturing method of the reduced iron pellet concerning 3rd Embodiment. It is a general | schematic internal perspective view of the manufacturing apparatus of the reduced iron pellet which enforces the manufacturing method of the reduced iron pellet concerning 3rd Embodiment.

Explanation of symbols

1 Molded body (green ball)
2 SiO ₂ / CaO / Al ₂ O ₃ compound (film-forming substance)
DESCRIPTION OF SYMBOLS 3 Coating 4 Reduced iron pellet 10 Reduced iron pellet manufacturing apparatus 11-14 Hopper 15 Mixer 16 Pelletizer 17 Dryer 18 Conveyor (with adhesion device)
DESCRIPTION OF SYMBOLS 19 Reduction furnace 20 Container 21 Primary cooler 22 Heat exchanger 23 Blower fan 24 Secondary cooler 25 Fan 26 Burner 27 Exhaust duct 28 Pellet discharge screw 30 Hood 31 Great 32 Combustion air 33 Combustion air supply port 34 Exhaust gas

Claims (19)

After attaching a powdery film-forming substance to the surface of the molded body containing a metal oxide and a reducing agent,
The molded body is heated to reduce the metal oxide with the reducing agent, and the film-forming substance is melted to coat the surface of the molded body with the film-forming substance.
A method for producing a reduced metal molded body obtained by cooling the molded body. In the manufacturing method of the reduced metal molding as described in claim 1,
The molded body contains an impure metal oxide,
The method for producing a reduced metal molding, wherein the film-forming substance is melted at a temperature higher than a temperature at which the impure metal oxide is reduced to an impure metal by the reducing agent and the impure metal evaporates. The molded body containing a metal oxide, a reducing agent, and an impure metal oxide is heated to reduce the impure metal oxide to an impure metal by the reducing agent and evaporate the impure metal, and then the molded body. A powdery film-forming substance is attached to the surface of
The metal oxide is reduced by the reducing agent, and the film forming substance is melted to coat the surface of the molded body with the film forming substance,
A method for producing a reduced metal molded body obtained by cooling the molded body. The method for producing a reduced metal molded body according to any one of claims 1 to 3, wherein a powdery film-forming substance is attached to the surface of the molded body.
It is one of a method of spraying the powdery film-forming substance, a method of spraying a liquid in which the powdery film-forming substance is dispersed or dissolved, or a method of immersing the molded body in the liquid. A method for producing a reduced metal molded body.   5. The method for producing a reduced metal molded body according to claim 1, wherein the metal oxide is iron oxide, and the impure metal oxide is zinc oxide or lead oxide. A method for producing a molded body.   6. The method for producing a reduced metal molded body according to claim 1, wherein the reducing agent is a carbonaceous material containing fixed carbon.   The method for producing a reduced metal molded body according to any one of claims 1 to 6, wherein the molded body is a spherical pellet by a rolling granulation method, a briquette by a compression granulation method, or a cylindrical shape by an extrusion granulation method. A method for producing a reduced metal molded body, which is one of pellets, wherein a short side is 5 mm to 15 mm and a long side is 40 mm or less.   The method for producing a reduced metal molded body according to any one of claims 1 to 7, wherein the powdery film-forming substance has a particle diameter of 10 µm or more.   The method for producing a reduced metal molded body according to any one of claims 1 to 8, wherein the film-forming substance is a compound containing silicon oxide, calcium oxide, and aluminum oxide. Production method. In the manufacturing method of the reduced metal molding according to claim 9,
The film forming substance has a melting point of 1100 ° C. or higher, and a method for producing a reduced metal molding. In the manufacturing method of the reduced metal molding according to claim 9,
The film-forming substance comprises 20% to 40% by weight of silicon oxide, 20% to 40% by weight of calcium oxide, and 1% to 20% by weight of aluminum oxide. Production method. However, the total of all the components is 100% or less. In a reduced metal molding containing a reduced metal,
A reduced metal molded body, wherein the surface of the reduced metal molded body is coated with a film forming substance. In the reduced metal molding according to claim 12,
The reduced metal molded body, wherein the metal is iron. In the reduced metal molding according to claim 12 or 13,
The reduced metal molded body, wherein the film forming substance is a compound containing silicon oxide, calcium oxide, and aluminum oxide. In the reduced metal molding according to claim 14,
The film forming material has a melting point of 1100 ° C. or higher. In the reduced metal molding according to claim 14,
The reduced-metal molded body, wherein the film-forming substance is 20% to 40% by weight of silicon oxide, 20% to 40% by weight of calcium oxide, and 1% to 20% by weight of aluminum oxide. However, the total of all the components is 100% or less. An attachment means for attaching a powdery film-forming substance to the surface of a molded body containing a metal oxide and a reducing agent;
It is installed at the subsequent stage of the adhering means, and heats the molded body to reduce the metal oxide with the reducing agent and melts the film-forming substance to coat the surface of the molded body with the film-forming substance. An apparatus for producing a reduced metal molded body comprising a reduction furnace. A reduction furnace that heats a molded body containing a metal oxide, a reducing agent, and an impure metal oxide, reduces the impure metal oxide to an impure metal by the reducing agent, and evaporates the impure metal;
An attachment means for attaching a powdery film-forming substance to the surface of the molded body after the impure metal has evaporated,
The reducing furnace further reduces the metal oxide with the reducing agent, melts the film forming material, and coats the surface of the molded body with the film forming material. Manufacturing equipment. In the manufacturing apparatus of the reduced metal molding according to claim 17 or 18,
The apparatus for producing a reduced metal molded body further comprises means for pulverizing an aggregate of the reduced metal molded bodies that are brought into close contact with each other by melting the film forming substance.

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