JP4149531B2 - Metallic iron manufacturing method and manufacturing equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an improvement in a technique for obtaining metallic iron by heating and reducing iron oxide such as iron ore together with a carbonaceous reducing agent such as a carbonaceous material, and efficiently reducing iron oxide to metallic iron, and in an iron oxide source. The present invention relates to a method and equipment capable of successfully melting and separating a slag component mixed as a gangue component or the like and efficiently producing high-purity metallic iron as molten iron.
[0002]
[Prior art]
As a direct iron manufacturing method for obtaining reduced iron by directly reducing iron oxide such as iron ore and iron oxide pellets with a carbonaceous material or a reducing gas, a shaft furnace method represented by the Midrex method has been known. This type of direct iron manufacturing method is a method in which reducing gas produced from natural gas or the like is blown from the tuyere at the bottom of the shaft furnace, and the reducing power is used to reduce iron oxide to obtain reduced iron. Recently, a reduced iron production process using a carbonaceous material such as coal as a reducing agent in place of natural gas has attracted attention. The so-called SL / RN method has already been put into practical use.
[0003]
As another method for producing reduced iron, U.S. Pat. No. 3,443,931 discloses a process for producing reduced iron by mixing a carbonaceous material and powdered iron oxide and agglomerating and reducing heat on a rotary hearth. It is disclosed. In this process, pulverized ore and pulverized coal are mixed and agglomerated, and this is heated and reduced in a high-temperature atmosphere.
[0004]
Reduced iron produced by these methods is used as an iron source after being formed into a briquette or the like as it is and then charged into an electric furnace. In recent years, as iron scrap recycling has become active, reduced iron obtained by the above method has attracted attention as a diluent for impurity elements mixed in scrap.
[0005]
However, in the reduced iron obtained by the conventional reduced iron manufacturing method, slag components such as SiO ₂ , Al ₂ O ₃ , and CaO contained in iron oxide (iron ore etc.) and carbonaceous materials (coal etc.) used as raw materials are intact. Since it mixes, the iron quality (purity as metallic iron) of a product will become low.
[0006]
In practical use, these slag components are separated and removed in the next refining process. However, in order to meet these demands with the conventional methods for producing reduced iron as described above, high-quality iron ore must be used as a raw material for producing reduced iron. In other words, the range of practical steelmaking raw materials will be greatly reduced.
[0007]
Further, the conventional method as described above has the final purpose of obtaining a reduced solid product as an intermediate product. For practical use, it is transported, stored, briquetted or sent to the next scouring step. There is a disadvantage that a process such as cooling is necessary, and a large energy loss occurs during this period, and extra energy and special equipment are required for briquetting.
[0008]
On the other hand, a smelting reduction method such as the DIOS method is also known as a method for obtaining reduced iron by directly reducing iron oxide. In this method, iron oxide is preliminarily reduced to about 30 to 50% in terms of iron purity, and then reduced to metallic iron by direct reduction reaction with carbon in an iron bath. In this method, two steps of preliminary reduction and final reduction in an iron bath are indispensable, so the work is not only complicated, but the molten iron oxide (FeO) present in the iron bath is in direct contact with the refractory. Therefore, the problem that the wear of the refractory is severe is also pointed out.
[0009]
Furthermore, Japanese Patent Publication No. 56-19366 discloses heating and reducing agglomerates of a metal oxide, a solid carbonaceous material, and a slag forming material, and maintaining the shape of the agglomerates while reducing the metal produced by the reduction. A method is disclosed in which the state of wrapping with a shell is formed, and then the slag shell is melted to separate the metal and slag. However, in this method, in order to prevent reoxidation of metallic iron generated by reduction, it is necessary to generate an amount of slag sufficient to completely enclose the metallic iron, and it is necessary to increase the amount of the slag forming material. is there. In addition, this method easily generates slag having a high FeO concentration, and causes a serious problem in practical use in that the refractory lining the equipment is significantly damaged.
[0010]
[Problems to be solved by the invention]
On the other hand, the realization of a method for producing high-purity metallic iron with a low slag component content not only increases the added value as product metallic iron, but also reduces the cost of iron making using an electric furnace, and further produces metallic iron. It is extremely important because it increases the flexibility of selection of the raw materials used. In addition, since slag containing a large amount of iron oxide melts the refractory, it is this type of iron making that suppresses refractory damage by reducing the iron oxide content in the slag by-produced by heating and reduction as much as possible. It is extremely important to make the law feasible on an industrial scale.
[0011]
The inventors pay attention to such a situation, and not only iron oxide with a high iron component content but also iron ore with a relatively low iron component content, the iron purity is extremely high without causing refractory melting or the like. We have been working on the development of technology that can efficiently obtain metallic iron as molten iron with a simple process. As a result of this research, we developed the following method and filed a patent application first ( Japanese Patent Application No. 8-59801).
[0012]
This prior application invention, when producing iron metal by heat reduction of a molded body of iron oxide containing a carbonaceous reducing agent,
(1) A metallic iron skin is generated and grown by heat reduction, and the reduction is advanced until iron oxide is substantially absent, and an aggregate of generated slag is formed inside.
(2) Generate and grow metallic iron skin by heat reduction, proceed reduction until iron oxide is substantially absent, and continue heating to allow the slag produced inside to flow out to the outside of the metallic iron skin.
(3) Produces and grows a metallic iron shell by heat reduction, proceeds reduction until iron oxide is substantially absent, and further heats to melt and separate metallic iron and slag.
Or (4) heat reduction to produce and grow metallic iron skin, proceed reduction until iron oxide is substantially absent, form aggregates of produced slag, and then separate the produced slag from metallic iron It has a feature.
[0013]
In carrying out the method (2), the molten slag inside the metal iron shell may be allowed to flow out of the metal iron shell by melting a part of the metal iron shell. In order to melt part or all of the metal iron shell, the carburization with a carbonaceous reducing agent present in the metal shell is advanced to lower the melting point of the metal shell.
[0014]
In carrying out the above inventions (1) to (4), the maximum heating temperature in the heat reduction process is controlled to a temperature not less than the melting point of the produced slag and not more than the melting point of the produced metal iron shell. The iron production reaction can proceed more efficiently. In this reduction step, if iron oxide is reduced by solid-phase reduction and further reduced by liquid phase reduction until iron oxide mainly composed of FeO is substantially absent. Thus, the quality of the obtained metallic iron can be improved more efficiently.
[0015]
In order to successfully proceed with the reduction of iron oxide in the solid phase, it is necessary that the slag produced in the reduction process melts at a lower temperature than the metallic iron produced by the reduction. If necessary, adjust the composition of the slag-generating component contained in the iron oxide, carbonaceous reducing agent, etc., in advance so that the melting point of the generated slag is lower than the melting point of the reduced iron. It is desirable to additionally adjust Al ₂ O ₃ , SiO ₂ , CaO or the like.
[0016]
In the prior application invention, as a preferable quantitative standard for “progressing reduction until iron oxide is substantially absent inside the metallic iron shell”, in the heating reduction step, “of iron oxide mainly composed of FeO” It is preferable to proceed the reduction until the content is 5% by weight or less, more preferably 2% by weight or less. From another viewpoint, FeO in the produced slag separated from the metallic iron produced by the reduction reaction is reduced. It is desirable to proceed the reduction until the content of the main iron oxide is 5% by weight or less, more preferably 2% by weight or less.
[0017]
The high-purity metallic iron and produced slag obtained by this method can be separated by a specific gravity difference in a state where both are heated and melted. In addition, according to the invention of the prior application, the iron oxide content in the generated slag can be reduced as much as possible. It does not happen and it is expected to be put into practical use as a highly practical technology from the viewpoint of equipment maintenance.
[0018]
An object of the present invention is to provide a manufacturing method and a manufacturing facility that can utilize the basic technical idea of the invention of the prior application and can efficiently implement this on an industrial scale.
[0019]
[Means for Solving the Problems]
The method for producing metallic iron according to the present invention is to produce metallic iron by heating and reducing a granular or massive shaped body of iron oxide in which a carbonaceous reducing agent is present (hereinafter sometimes simply referred to as a shaped body). by heating reduced while transferring the molded body in a horizontal direction, inside the product slag with advancing reduced to content of definitive iron oxide therein generated and grown metallic iron skin is 5 wt% or less The gist is to form agglomerates and discharge them from the transfer end, and then heat them to melt them, and then separate them into molten slag and molten iron.
[0020]
By allowing the carbonaceous reducing agent to be present in the molded body, the reduction proceeds in the molded body itself to produce metallic iron (outer skin) and slag (inside). Then, by heating and melting, metallic iron and slag can be separated by the specific gravity difference.
[0021]
The amount of the carbonaceous reducing agent present in the molded body is at least an amount necessary for the reduction of the raw iron oxide. Further, it is preferable that a carbonaceous reducing agent in an amount necessary for carburizing the reduced iron is present, so that carburization can be performed as reduced iron (metallic iron) is generated. In addition, the solid state (unmelted) reduced iron forming the outer skin is porous and easily reoxidized. However, the above-mentioned “amount necessary for reducing raw iron oxide + required for carburizing reduced iron” If a larger amount of carbonaceous reducing agent is present in the molded body in addition to the “quantity”, CO gas is generated from the molded body, and this CO gas creates a non-oxidizing atmosphere around the molded body. Reoxidation can be prevented. That is, the most preferable amount of the carbonaceous reducing agent is “amount required for reduction of raw iron oxide + amount required for carburization of reduced iron + amount of oxidation loss”.
[0022]
Moreover, in this invention, it is preferable to transfer the said molded object to the horizontal direction by mounting this molded object on the hearth in a heating reduction apparatus.
In addition, in the present invention, it is preferable to perform the heat reduction while replenishing the carbonaceous reductant when the molded body is heated and reduced while being transferred in the horizontal direction.
In the above, it was proposed that a carbonaceous reducing agent of “amount necessary for carburization of reduced iron + amount of oxidation loss” was previously present in the molded body. The amount of carbonaceous reductant of “required iron carburizing amount + oxidation loss amount” may be replenished from the outside during heat reduction, “Amount necessary for reduction of raw iron oxide + amount required for carburization of reduced iron” may be included, and an “oxidation loss amount” of carbonaceous reducing agent may be replenished from the outside during heating reduction. In this way, it is good to supply the shortage as necessary. In these cases, it is needless to say that the metal skin and the internal slag are satisfactorily produced by the “required amount of the raw iron oxide” for the carbonaceous reducing agent.
[0023]
In addition, if a powdery carbonaceous reducing agent is used and this powder is adhered to the surface of the molded body, it becomes a large block by sintering adhesion between the molded bodies, or a molded body on the furnace wall. Can be prevented from being sintered and the handleability is improved.
[0024]
In addition, when melting metallic iron (reduced iron), a carbonaceous reducing agent of “amount necessary for carburizing reduced iron” or “oxidation loss amount” may be replenished. Carburization proceeds, and the periphery of the molded body is kept in a non-oxidizing atmosphere by the CO gas from the carbonaceous reducing agent, so that reoxidation of metallic iron can be prevented.
Furthermore, in the production method of the present invention, by adjusting the composition of the slag generating component in the molded body in advance, the melting temperature of the slag generated by the reduction is made lower than the melting temperature of the metallic iron generated by the reduction. It is preferable.
[0025]
The metal iron production facility according to the present invention realizes the above production method, and is a facility for producing metal iron by heating and reducing a granular or massive shaped body of iron oxide in which a carbonaceous reducing agent is present. And a heating member provided with a transfer member for transferring the molded body in the horizontal direction, a heating reduction device for heating the molded body, and a discharge end portion of the transfer member in the heating reduction apparatus, which is discharged rearward. The gist of the invention is that it comprises a melting device provided with a heating and melting mechanism for heating and melting the molded body , and a separation device arranged behind the melting device and separated into molten slag and molten iron. .
If the manufacturing equipment of the present invention is used, molten iron can be continuously manufactured from a compact.
[0026]
Furthermore, in this invention, it is preferable that the transfer member which transfers the said molded object to a horizontal direction is provided with the hearth on which the said molded object is mounted. Furthermore, the transfer member is preferably an endless belt type.
[0027]
Further, in the present invention, it is preferable that the furnace floor is provided with an isolation member for preventing mutual adhesion of the molded bodies at an arbitrary pitch, and the isolation member is a plate made of refractory or the like. Illustrated. As a result, the compacts can be prevented from sintering and adhering to a large lump, and the handleability is improved.
[0028]
Further, it is more preferable that the separating member is formed of a desulfurizing agent. In this case, the separating member (desulfurizing agent) is easily detached from the hearth, and the desulfurizing agent is melted together with the reduced molded body. By putting it in the apparatus, desulfurization can be carried out in the melting apparatus as it is. Examples of the separating member include a plate-like member and a powdery member.
[0029]
In addition, a powder desulfurizing agent may be used so that the powder adheres to the surface of the molded body. In addition to preventing mass formation due to sintering adhesion between the molded bodies, Sintering adhesion of the molded body can be prevented, and further, the desulfurization agent is put into the melting apparatus together with the molded body reduced as described above, so that desulfurization can be performed in the melting apparatus as it is. Examples of the desulfurizing agent include limestone.
[0030]
In addition, in the present invention, it is preferable that a reducing burner is provided as the heating and reducing mechanism, and a melting burner is provided as the heating and melting mechanism.
Moreover, in this invention, it is preferable that it is comprised so that it may isolate | separate into molten slag and molten iron behind the said heating-melting mechanism.
[0031]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the manufacturing method and the manufacturing equipment according to the present invention will be described in detail with reference to the drawings showing an embodiment. However, the present invention is not limited to the illustrated examples, and the purpose described above and below is intended. It is also possible to carry out with appropriate modifications within a range that can be adapted, and all of them are included in the technical scope of the present invention.
[0032]
FIG. 1 is a schematic cross-sectional view showing an embodiment of a metal iron production facility according to the present invention.
The production facility includes a heating reduction device 23, a melting device 12, and a separation device 13. The heating reduction device 23 moves a hearth 46 on which the molded body 4 is placed as a transfer member and the hearth 46 horizontally. A roller 47 is provided. This transfer member has a structure in which a pallet type hearth 46 is attached to a belt conveyor, is an endless belt type, and the roller 47 is rotated by external power (not shown). Further, the heating reduction device 23 is provided with a reduction burner 48 as a heating reduction mechanism, and adjusts the inside of the heating reduction furnace 50 surrounded by the refractory furnace wall 5 to a desired heating temperature. The hearth 46 passes through the inside of the heat reduction furnace 50, and the molded body 4 is placed on the hearth 46 and transferred in the horizontal direction. In addition, the heating reduction furnace 50 of the example shown in FIG. 1 is divided into three chambers, and can be adjusted to a desired temperature according to the reduction stage.
[0033]
The melting device 12 is continued to the transfer terminal (downstream side) of the hearth 46 (transfer member) of the heating and reducing device 23, and the melting device 12 is provided with a melting burner 61 as a heating and melting mechanism, The inside of the melting apparatus 12 surrounded by the furnace wall 6 is adjusted to a desired heating temperature. The melting device 12 is provided with an inclined bed 51 so as to guide the molded body 4 to the rear side (separation device 13). A weir 52 is provided at the boundary between the melting device 12 and the separation device 13 provided behind the melting device 12. The separation device 13 is configured to accumulate molten iron 54 and molten slag 53, and is provided with a slag outlet 55 and a molten iron outlet 56.
The heating and reducing furnace 50 and the melting device 12 are provided with exhaust gas discharge ports 49 and 57.
[0034]
Next, the manufacturing process of metallic iron will be described with reference to FIG. A granular material of a carbonaceous reducing agent such as coal and iron oxide such as iron ore is formed into a small sphere, for example, to produce a compact. The molded body has a carbonaceous reductant in "amount + oxidation loss required for carburizing quantity + reduced iron required for the reduction of the raw material iron oxide".
[0035]
The molded body 4 is placed on the hearth 46 from the entrance side (left side shown in FIG. 1) of the heating and reducing device 23 and sequentially moves in the heating and reducing furnace 50 (moves to the right side in FIG. 1). The temperature in the heating and reducing furnace 50 is adjusted by adjusting the heating power of the reducing burner 48 so that the temperature is lower than the melting temperature of the generated metal iron shell and higher than the melting temperature of the generated slag. Reduced.
[0036]
In this heat reduction step, first, heat reduction proceeds on the outer peripheral side of the molded body 4 to form a skin made of metallic iron, and then the carbonaceous reducing agent itself and the monoxide generated by thermal decomposition thereof inside the skin. Due to the reducing action of carbon, the reduction reaction of iron oxide in the outer skin proceeds efficiently, and the produced metallic irons adhere to each other and gather to grow the outer skin, and the produced slag also melts together to gather. As a result, the metallization rate in this heat reduction process is remarkably increased, and the amount of iron oxide mixed in the generated slag is remarkably reduced.
[0037]
This reduction is performed until iron oxide is substantially not present in the molded body 4, and the moving speed of the hearth 46 is adjusted according to the time required for this reduction. Since the amount of iron oxide mixed in the slag can be reduced by sufficiently reducing in this way, a refractory (furnace wall) made of iron oxide is used when the molded body 4 is melted in the next melting apparatus 12. Damage can be suppressed. The length of the heating and reducing furnace 50 to which the hearth 46 moves may be determined according to the required reduction time and moving speed.
[0038]
During the reduction in the heating and reducing furnace 50, as described above, the produced reduced iron is carburized by the carbonaceous reducing agent contained in the molded body 4, and the periphery of the molded body is generated by the CO gas generated from the molded body. Becomes a non-oxidizing atmosphere, and reoxidation of the produced reduced iron is prevented.
[0039]
The molded body 4 in which the reduction is substantially finished and has a structure of a metallic iron shell and an internal slag agglomerate is discharged from its terminal portion by a moving hearth 46 while at least the shell remains in a solid state, and is melted. 12 leads to. The melting device 12 rolls or slides on the inclined bed 51 and moves toward the rear side (the separation device 13 side) while being heated and melted. The temperature in the melting device 12 is a temperature at which not only the generated slag but also the generated metallic iron skin is melted.
[0040]
Even if a small amount of unreduced portion remains in the molded body 4 introduced into the melting apparatus 12 (reduction proceeds until the iron oxide substantially does not exist inside the metal iron outer shell in the heating reduction furnace 50, 5 wt. % Or 2% by weight or less of iron oxide may be included), and the reduction proceeds by heating at the time of melting and the reduction is completed. At this time, the melting device 12 may be supplemented with a carbonaceous reducing agent.
The molded body 4 in the process of being melted is stopped by the weir 52, and the melted liquid that has been melted falls over the weir 52 and is stored in the separation device 13.
[0041]
Since the molten slag 53 and the molten iron 54 have different specific gravities, the slag is separated into the upper layer and the molten iron is separated into the lower layer in the separation device 13. Only the separated slag 53 is taken out from the slag outlet 55 and only the molten iron 54 is taken out from the molten iron outlet 56, respectively.
[0042]
In this way, highly reduced metallic iron can be efficiently obtained as molten iron. This metallization rate reaches a high level of 95% or more, and further 98% or more. In addition, as a result of the advanced reduction of iron oxide in the heat reduction process, the amount of iron oxide mixed into the molten slag as a by-product is extremely reduced, and refractory damage due to iron oxide contamination is also possible. Can be suppressed.
[0043]
If the separator 13 is provided with burner heating or electric heating equipment, and the molten slag 53 and the molten iron 54 are heated to a higher temperature to improve their fluidity, the slag and molten iron are separated and discharged. Is preferable because it can be made easier.
[0044]
The exhaust gas discharged from the exhaust gas outlets 49 and 57 may be released as it is, but since the exhaust gas is high temperature and has a strong reducing power, it is effectively used as fuel gas supplied to the burners 48 and 61. It may also be used for drying or preheating the molded body 4 or preheating fuel or fuel air.
[0045]
In carrying out the present invention, in order to facilitate the reduction of iron oxide in the solid phase, as described above, the slag produced in the heating reduction process must be melted at a lower temperature than the metallic iron produced by the reduction. For this purpose, the composition of the slag generating component in the molded body (the iron ore generally used as the iron oxide source and the gangue component mixed in the carbonaceous reducing agent) is adjusted in advance. Therefore, it is necessary to control the melting point of the generated slag so as to be lower than the melting point of reduced iron or its carburized material. Therefore, depending on the composition of the gangue component, it is desirable to replenish Al ₂ O ₃ , SiO ₂ , CaO or the like as necessary in the molding process of the molded body to generate slag having a low melting temperature.
[0046]
【The invention's effect】
The present invention is configured as described above, and makes it possible to efficiently implement the new metallic iron manufacturing technology proposed in the invention of the prior application on a practical scale, and not only high iron content but also low iron content. Even from an iron source such as iron ore, extremely high purity metallic iron having a metallization rate of 95% or more, and further 98% or more can be produced in a very short time with high productivity. In addition, if this method and equipment are used, the amount of iron oxide mixed into the slag produced as a by-product in the heat reduction process will be significantly reduced, so melting to the lining refractories such as heat reduction equipment, melting equipment, separation equipment It is also possible to suppress melting damage due to iron oxide as much as possible.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view showing an embodiment of an apparatus for producing metallic iron according to the present invention.
[Explanation of symbols]
4 Molded bodies 5 and 6 Furnace wall 12 Melting device 13 Separating device 23 Heating and reducing device 46 Furnace floor 47 Roller 48 Reduction burners 49 and 57 Exhaust gas outlet 50 Heating and reducing furnace 51 Inclined bed 52 Weir 53 Molten slag 54 Molten iron 55 Slag Outlet 56 molten iron outlet 60 melting furnace 61 melting burner

Claims (11)

In producing metallic iron by heating and reducing a granular or massive shaped body of iron oxide containing a carbonaceous reducing agent,
By heating reduced while transferring the molded body in a horizontal direction, inside the product slag with advancing reduced to content of definitive iron oxide therein generated and grown metallic iron skin is 5 wt% or less Agglomerates are formed,
A method for producing metallic iron, characterized in that after being discharged from the transfer terminal portion, it is further heated to melt it, and then separated into molten slag and molten iron.   The method for producing metallic iron according to claim 1, wherein the forming body is transferred in the horizontal direction by placing the forming body on a hearth in a heating and reducing device.   The method for producing metallic iron according to claim 1 or 2, wherein the heat reduction is performed while replenishing a carbonaceous reductant when the compact is heated and reduced while being transported in the horizontal direction.   The slag generation component in the molded body is adjusted in advance so that the melting temperature of the slag generated by the reduction is lower than the melting temperature of the metallic iron generated by the reduction. The manufacturing method of metallic iron as described in any one of.   The method for producing metallic iron according to any one of claims 1 to 4, wherein the temperature of the heat reduction is lower than the melting temperature of the generated metallic iron skin and equal to or higher than the melting temperature of the generated slag. It is the equipment which performs the manufacturing method of metallic iron in any one of Claims 1-5,
It is a facility for producing metallic iron by heat reduction of a granular or massive shaped body of iron oxide containing a carbonaceous reducing agent,
A heating / reduction apparatus provided with a transfer member for transferring the molded body in the horizontal direction and a heating reduction mechanism for heating the molded body;
A melting apparatus disposed with a heating and melting mechanism that heats and melts the discharged molded body behind the transfer terminal portion of the transfer member in the heating and reducing apparatus;
An apparatus for producing metallic iron, comprising: a separation device disposed behind the melting device and separated into molten slag and molten iron.   The metal iron manufacturing facility according to claim 6, wherein the transfer member that transfers the formed body in a horizontal direction includes a hearth on which the formed body is placed.   The metal iron manufacturing facility according to claim 7, wherein the hearth is provided with separation members at arbitrary pitches to prevent the compacts from adhering to each other.   The metal iron manufacturing facility according to claim 8, wherein the isolation member is formed of a desulfurizing agent. A reduction burner is provided as the heating reduction mechanism,
The facility for producing metallic iron according to any one of claims 6 to 9, wherein a melting burner is provided as the heating and melting mechanism.   The facility for producing metallic iron according to any one of claims 6 to 10, wherein the facility is configured to separate into molten slag and molten iron behind the heating and melting mechanism.

Images