JPH09256017A - Production of metallic iron - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method, by which a metallic iron having extremely high metallization can efficiently be obtd. as solid metallic iron or molten metallic iron in a simple treatment even from iron ore, etc., having comparatively low iron component content, as a matter of course from iron oxide having high iron component content without developing the erosion of refractory. SOLUTION: In the method for producing the metallic iron by heating and reducing an iron oxide formed material 1 containing carbonaceous reducing agent, the metallic iron outer shell 1a is produced and grown by heating and reducing, and the reduction is progressed until the iron oxide does not exist substantially in the inner part. Then, coagulating material of the produced slag Sg is formed in the inner part, or the slag Sg produced in the inner part is flowed out to the outside of the metallic iron outer shell 1a by succeeding further heating, and the slag Sg is separated to obtain the metallic iron having high metallization.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for improving a method for obtaining metallic iron by heating and reducing iron oxide such as iron ore together with a carbonaceous reducing agent such as carbonaceous material, and more specifically, to a technique for improving iron ore and the like. When iron oxide is heated and reduced with a carbonaceous reducing agent such as carbonaceous material to obtain metallic iron, iron oxide is efficiently reduced to metallic iron, and as a gangue component etc. in the iron oxide source such as iron ore. The present invention relates to a method capable of efficiently melting and separating mixed slag components to efficiently produce high-purity metallic iron.

[0002]

2. Description of the Related Art As a direct iron making method of directly reducing iron oxide such as iron ore and iron oxide pellets with a carbon material or a reducing gas to obtain reduced iron, a shaft furnace method represented by the Midrex method has been conventionally used. Are known. This type of direct iron-making method is a method in which a reducing gas produced from natural gas or the like is blown from the tuyere at the bottom of a shaft furnace, and the reducing power is used to reduce iron oxide to obtain reduced iron. Further, recently, a reduced iron manufacturing process using a carbonaceous material such as coal as a reducing agent instead of natural gas has been attracting attention, and specifically, a fired pellet of iron ore or the like is heated and reduced in a rotary kiln together with coal powder, The so-called SL / RN method has already been put to practical use.

As another method for producing reduced iron, US Pat. No. 3,443,931 discloses a method in which carbonaceous material and powdered iron oxide are mixed and agglomerated, and reduced by heating on a rotary hearth to produce reduced iron. A process for doing so is disclosed. In this process, powdered ore and powdered coal are mixed and agglomerated, and this is heated and reduced in a high temperature atmosphere.

The reduced iron produced by these methods is used as an iron source by charging it into an electric furnace as it is or after forming it into a briquette shape or the like. In recent years, as the recycling of iron scrap has become more active, reduced iron obtained by the above method has attracted attention as a diluent for impurity elements mixed into the scrap.

However, in the reduced iron obtained by the conventional reduced iron manufacturing method, the iron oxide (iron ore etc.) used as a raw material is used.
SiO _2, Al ₂ O ₃ contained in or carbonaceous material (such as coal),
Since the slag component such as CaO is mixed in as it is, the iron quality (purity as metallic iron) of the product becomes low. In practical use, these slag components are separated and removed in the next refining process, but an increase in the amount of slag not only lowers the yield of the refining molten metal, but also has a large effect on the operating cost of the electric furnace. There is a demand for reduced iron with a high content of slag, but in order to meet these demands with the conventional method for producing reduced iron as described above, iron ore with high iron quality must be used as a raw material for producing reduced iron. Not only that, the range of practical ironmaking raw materials to be selected is significantly narrowed.

Furthermore, the conventional method as described above has the final purpose of obtaining a reduced solid product as an intermediate product, and in practical use, it is transported, stored, and stored before being sent to the scouring process which is the next process. A process such as briquetting or cooling is required, and there are disadvantages that a large energy loss occurs during this process, and extra energy or a special device is required for briquetting.

On the other hand, as a method of directly reducing iron oxide to obtain reduced iron, a smelting reduction method such as a DIOS method is also known.
In this method, iron oxide is preliminarily reduced to an iron purity of about 30 to 50%, and then reduced to metallic iron by direct reduction reaction with carbon in an iron bath. This method requires two steps of pre-reduction and final reduction in an iron bath, which not only complicates the operation, but also makes direct contact between the molten iron oxide (FeO) present in the iron bath and the refractory. Therefore, it is pointed out that the refractory is severely worn.

[0008]

As described above, the realization of the method for producing metallic iron having a small slag component content not only enhances the added value as the metallic iron product, but also the cost of ironmaking using an electric furnace. It becomes extremely important from the viewpoint of reduction of the amount of waste and flexibility of selection of raw materials used in the production of metallic iron.

The present invention has been made in view of such a situation, and its purpose is to obtain refractory materials from iron ore having a relatively low iron content as well as iron oxide having a high iron content. An object of the present invention is to provide a method by which metallic iron having an extremely high iron purity can be efficiently obtained as solid metallic iron or molten metallic iron by a simple treatment without causing melting loss or the like.

[0010]

The method for producing metallic iron according to the present invention, which has been able to solve the above-mentioned problems, is a method for producing metallic iron by heating and reducing an iron oxide molding containing a carbonaceous reducing agent. In the method, a metallic iron crust is produced and grown by heat reduction, the reduction is promoted until iron oxide is substantially absent inside, and an aggregate of generated slag is formed inside, and a metallic iron crust is caused by heat reduction. Generate and grow, and proceed with reduction until iron oxide is substantially absent inside,
Continue heating and let the slag generated inside flow out to the outside of the metallic iron crust, generate and grow the metallic iron crust by heat reduction, and proceed with reduction until iron oxide is substantially absent inside.
Further heating is continued to melt and separate metallic iron and slag, or metallic iron skin is generated and grown by heat reduction, and reduction is promoted until iron oxide is substantially absent inside, and the generated slag is internally generated. It is characterized by forming agglomerates and then separating the produced slag from metallic iron.

In carrying out the above method, a part of the metallic iron shell may be melted so that the molten slag in the inside flows out of the metallic iron shell. At this time, or in carrying out the above method, in order to melt a part or the whole of the metallic iron shell, advance the carburization by the carbonaceous reducing agent present in the metallic shell to lower the melting point of the metallic shell. You can do it easily.

Further, in carrying out the above inventions (1) to (4), the maximum heating temperature in the heat reduction step is controlled to a temperature not lower than the melting point of the produced slag and not higher than the melting point of the produced metallic iron shell, thereby producing the metallic iron producing reaction. In this reduction step, iron oxide can be reduced by solid-phase reduction, and further, iron oxide mainly composed of FeO can be reduced by liquid-phase reduction until substantially no iron oxide is obtained. It is possible to improve the quality of metallic iron more efficiently.

In the present invention, "reduction is carried out until iron oxide is substantially absent in the metallic iron shell".
As a preferable quantitative criterion of the above, in the heat reduction step,
"The content of iron oxide mainly composed of FeO is 5% by weight or less,
It is more preferable to proceed with the reduction until it becomes 2% by weight or less. ”From another viewpoint, the content of iron oxide mainly composed of FeO in the produced slag separated from metallic iron according to the present invention is It is desirable to proceed with the reduction until the amount becomes 5% by weight or less, more preferably 2% by weight or less.

The high-purity metallic iron and the produced slag obtained by the above method are melted by heating and separated by a difference in specific gravity, or cooled and solidified and then crushed, and only high-purity metallic iron is selectively recovered by magnetic separation. , Metallization rate is 9
It is possible to obtain very high-purity metallic iron of about 5% or more, and further 98% or more.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION As described above, according to the present invention, as a first characteristic point, a carbonaceous reducing agent such as coal and an iron oxide powder such as iron ore can be formed into an arbitrary shape such as granules or pellets. When heat-reducing the formed product, it is possible to generate and grow a metal iron crust by heat reduction, and proceed with the reduction until iron oxide is substantially absent inside.

[0016] That is, the inventors of the present invention have aimed for the development of a new metallic iron production technique which replaces the indirect iron production method represented by the iron production method using a blast furnace and the direct iron production method represented by the SL / RN method. As we proceeded with various researches, as described above, when the carbonaceous reducing agent and iron oxide powder particles were molded into an arbitrary shape such as granules or pellets and heated in a non-oxidizing atmosphere, I found out that such a phenomenon occurs. That is, when the molded product is heated, iron oxide is reduced by the carbonaceous reducing agent contained in the molded product to produce metallic iron, but the reduction proceeds from the outer peripheral side of the molded product, and the initial heat reduction is performed. The metallic iron generated in the process is diffusion bonded on the surface of the molded product to form a metallic iron outer cover on the outer peripheral side of the molded product. Then, after that, the reduction of iron oxide by the carbonaceous reducing agent efficiently proceeds in the outer skin, and the iron oxide remaining inside is promptly until substantially no iron oxide is present in a very short time thereafter. The metal iron that is reduced and produced successively adheres and grows on the inner surface side of the outer skin, while it is derived from the gangue component contained in the iron oxide source such as iron ore or contained in the carbonaceous reducing agent. Most of the slag that is produced as a by-product from ash is aggregated (aggregated) in the metallic iron shell, and it is possible to efficiently separate it into high-purity metallic iron that constitutes the shell and the slag that is aggregated inside. I stopped.

The phenomenon that occurs during this reduction will be explained by showing actual photographs in the examples described later, but it is considered that the following process is followed. That is, FIG. 1 is a schematic sectional view conceptually showing a phenomenon occurring when the present invention is carried out.
For example, when a molded product 1 made of a mixture of a carbonaceous reducing agent and iron oxide having a shape as shown in FIG. 1 (A) is heated to, for example, about 1450 to 1500 ° C. in a non-oxidizing atmosphere, the molded product 1 The reduction of iron oxide by the carbonaceous reducing agent proceeds from the outside, and the produced metallic irons are diffusion-bonded to each other and the metallic iron skin 1
a is formed [FIG. 1 (B)]. When heating is further continued thereafter, as shown in FIG. 1 (C), the iron oxide in the outer skin 1a is produced by the reducing action of the carbonaceous reducing agent present inside and further by the reaction of the carbonaceous reducing agent and iron oxide. The metallic iron Fe that is rapidly reduced by the reducing action of CO that is produced and is successively deposited and grown on the inner surface side of the outer cover 1A, and most of the slag Sg that is a by-product derived from the gangue component, etc. While mutually adhering and growing, they gather in the cavity formed in the outer skin 1a as shown in FIG. 1 (D).

The heat reduction reaction occurring during this period is as shown in the following formula: FeO _x + xC → Fe + xCO (1) FeO _x + (x / 2) C → Fe + (x / 2) CO ₂ (2) Y = y ₁ + y ₂ (3) However, Y: Chemical equivalent amount of carbon required for reduction (mol) y ₁ : Carbon amount required for reaction of formula (1) (mol) y ₂ : Required for reaction of formula (2) Amount of carbon (mol) By adjusting the blending ratio of the two so that the blending amount of the carbonaceous reducing agent with respect to the iron oxide in the production of the molded product is equal to or more than the theoretical equivalent represented by the above formula (3), It is possible to efficiently proceed the heating reduction reaction.

As described above, in the present invention, the metallic iron outer skin 1a is formed on the outer peripheral side of the molded product in the initial stage of the heat reduction, and the outer skin 1a is formed.
By further advancing the reduction reaction inside the
The reduction efficiency can be dramatically increased. More preferably, the maximum attainable temperature of the heat reduction is set to be lower than the melting temperature of the metallic iron shell 1a to be generated and higher than the melting temperature of the slag to be generated. When the maximum temperature reaches or exceeds the melting temperature of the metal shell 1a, the generated metal irons are immediately melted and fused to each other, the metal iron skin 1a as described above is not formed, and the subsequent reduction reaction is efficient. It will not progress. Also, when unreduced iron oxide inside melts and flows out,
The risk of damaging the refractory is also increased. When the highest temperature above is higher than the melting temperature of the generated slag, the slag produced as a by-product of the heat reduction is melted and the fusion / aggregation of the slags proceeds,
Diffusion bonding between metallic irons is also promoted and the results are shown in FIGS. 1 (C) and (D).
This is because the growth of the metallic iron outer skin 1a and the separation of the slag Sg proceed as shown in FIG.

As described above, the present invention utilizes "the formation of the metallic iron shell and the efficient progress of the reduction reaction therein" which has never been adopted in the conventional indirect iron manufacturing method or direct iron manufacturing method. It has the greatest feature in dramatically increasing the heating and reduction reaction. The formation of the metallic iron skin 1a proceeds by the reduction reaction by the carbonaceous reducing agent contained in the molded product, and after the formation of the metallic iron skin 1a. Is promoted by the reduction by the carbonaceous reducing agent and the generated CO in the outer skin 1a, it is not necessary to make the heating reducing atmosphere a reducing atmosphere,
For example, a non-oxidizing gas atmosphere such as nitrogen gas may be used, which is a significant difference from the conventional method.

The above-mentioned heat reduction reaction basically proceeds by solid-phase reduction in which the metallic iron shell 1a does not melt, but as is clear from the above description, the inside of the metallic iron shell 1a contains a carbonaceous reducing agent and It is considered that the presence of CO produced by the reduction reaction maintains a highly reducing atmosphere, which leads to a dramatic increase in reduction efficiency.
The metallic iron generated inside is carburized in such a highly reducing internal atmosphere, and the melting point gradually decreases. Therefore, it is conceivable that a part of the raw material is melted in the final stage or the latter half of the reduction reaction and the final reduction of iron oxide is progressed by the liquid phase reduction. If the reduction temperature is set lower, it is possible to proceed with everything by solid-state reduction, but the reduction reaction rate increases as the temperature increases, so in order to complete the reduction reaction in a shorter time, increase the reaction temperature. It is more advantageous to set to, and if so, it can be said that it is desirable to complete the reduction reaction by liquid phase reduction at the end of the reduction reaction as described above.

As a simple confirmation method for confirming whether or not the reduction reaction is completed, a method for confirming the CO or CO ₂ concentration in the heating reducing atmosphere gas is exemplified. That is, in the heating reduction step, the reduction reaction by the carbonaceous reducing agent itself and the reduction reaction by the CO gas generated by the reaction between the reducing agent and iron oxide proceed as described above, and after all the iron oxide is reduced, Since CO and CO ₂ are no longer produced, it is possible to know that the reduction reaction has been completed when the produced gas in the reduction reaction furnace is sequentially withdrawn and CO and CO ₂ gas are no longer produced.

However, in practical use, it is not necessary to carry out the reaction until CO or CO ₂ gas is completely released, and the inventors of the present invention have confirmed that the space volume of the reaction furnace, etc. C in the gas in the furnace, depending on
When the O and CO ₂ gas concentrations were reduced to about 2% by volume or less, 95% by weight or more of the iron oxide was reduced, and when the concentration of the gas was reduced to about 1% by volume or less, 98% of the iron oxide was reduced. It is confirmed that more than weight% is reduced.

In the state shown in FIG. 1 (D), substantially all of the iron oxide mainly composed of FeO in the molded product is reduced to metallic iron (usually, the iron oxide content is 5%). weight%
In the following, it was confirmed by experiment that the iron oxide was reduced to 2% by weight or less, or 1% by weight or less), and most of the iron oxide was FeO mainly dissolved in the molten slag Sg aggregated inside. The throat is reduced (usually, the content of iron oxide mainly composed of FeO in the slag is 5% by weight or less, 2% by weight or less, or 1% by weight or less as confirmed by experiments). Therefore, by cooling and taking out in this state, crushing the metallic iron outer shell 1a with a crusher, etc., and selecting and taking out only metallic iron by magnetic separation, etc., all of the aggregated slag components are removed, and high-purity metallic iron is obtained. Can be obtained efficiently. Further, a method of separating the generated slag from the metallic iron by melting a part or all of the metallic iron outer shell 1a as shown below by further maintaining the same temperature and continuing heating, or further raising the temperature and further continuing heating. It is also preferable to adopt.

That is, if the temperature is raised slightly from the state shown in FIG. 1D and the heating is continued, for example, as shown in FIG.
As shown in (E), a part of the metallic iron outer skin 1a is melted and the generated slag Sg inside flows out of the outer skin 1a, so that the subsequent separation can be further facilitated. Alternatively, if the heating is further continued thereafter, for example, as shown in FIG. 1 (F), the entire metallic iron shell is melted and aggregated, and separated from the slag Sg that was previously melted and aggregated. Therefore, if it is cooled and solidified in such a state and then taken out and put on a crusher etc., only the fragile slag is crushed and the metallic iron remains as a lump,
If this is passed through a screen of moderate sieve or magnetically selected,
High-purity metallic iron can be easily selected. As another method of separating the metallic iron and the generated slag, it is of course possible to separate the metallic iron and the slag that have been heated and melted in the molten state by the difference in specific gravity as described above.

In the above, the heating and melting of the metallic iron shell can be performed by further raising the heating temperature after completion of the reduction reaction, but at the final stage of reduction within the metallic iron shell, as described above, Since the reduced iron undergoes carburization due to the strong reducing atmosphere and its melting point drops considerably, it is possible to melt the metallic iron shell by the melting point drop as the carburization progresses, just by continuing heating at the reducing temperature. is there.

As the carbonaceous reducing agent used when carrying out the present invention, coal powder that has just been subjected to treatments such as crushing and sieving after mining, and coke that has been subjected to heat treatment such as carbonization is crushed. It does not matter what kind of material is used, such as petroleum coke and petroleum coke, and of course, for example, blast furnace dust or the like recovered as waste containing carbonaceous matter. However, the carbonaceous reducing agent used in the present invention is selected to have a carbon content of 70% by weight or more, more preferably 80% by weight or more, in order to efficiently proceed the heat reduction reaction, and to increase the specific surface area, It is desirable to use a powdery material having a diameter of 2 mm or less, preferably 1 mm or less. Further, iron oxide such as iron ore is also preferably used in the form of powder having a particle size of 2 mm or less, preferably 1 mm or less in order to similarly increase the specific surface area and enhance the reduction reaction efficiency.

In the present invention, these carbonaceous reducing agents and iron oxide are uniformly mixed and, if necessary, a suitable binder is used in combination to form an arbitrary shape such as a lump, a granule, a briquette, a pellet or a rod. It is subjected to the above-mentioned heat reduction, and the amount of the carbonaceous reducing agent blended at this time is as shown in the above formulas (1) to (3) depending on the amount of oxygen in the iron oxide used in combination. It is preferable to add a stoichiometric amount or more necessary for the reduction reaction, preferably a slightly excessive amount in consideration of the carburizing amount necessary for lowering the melting point of the metallic iron shell.

As described above, it is desirable to set the maximum temperature at the time of heat reduction to be not less than the melting point of the produced slag and not more than the melting point of the metallic iron shell, but the temperature of the produced slag is It changes depending on the mixing of gangue components and iron oxide contained in iron oxide sources such as stones, and the melting point of the reduced iron crust also changes considerably depending on the carburizing amount. Not necessarily appropriate. However, a standard suitable reduction temperature is 1400 to 1540 ° C, more preferably 143
The range of 0 to 1500 ° C. is recommended. By adopting such temperature conditions, the metallization rate is at least 95% by weight or more, usually 98% by weight or more, and further 99% by weight or more, which is an extremely high purity metal. It becomes possible to obtain iron.

As for the slag produced as a by-product, as described above, the content of iron oxide mainly composed of FeO is 5% by weight or less, usually 2% by weight or less. If it is controlled, it can be reduced to 1% by weight or less, which is extremely advantageous for preventing melting damage of the refractory wall of the processing furnace. That is, in the conventional reduction iron making method as described above, when iron oxide such as iron ore is heated and reduced by the carbonaceous material, or when the metallic iron produced by the reduction is separated from the produced slag,
Iron oxide mainly composed of FeO is mixed in a non-reduced state in the slag, which causes a problem of melting and destroying the refractory material of the processing furnace. In the present invention, however, FeO in the slag is removed as described above. Almost all of the iron oxide, which is the main component, is reduced, and there is almost no iron oxide in the slag, and even if it remains, the amount is very small, so the reduction process and subsequent Even in the slag separation step, problems such as melting damage of the refractory of the processing furnace will not occur.

The metallic iron thus obtained has a high iron purity as described above and contains no slag component, so that it can be used as it is without any problem as long as it is used as a diluent or the like during steelmaking. Since the metallic iron contains a considerable amount of S, P, etc. as impurity elements, if these impurities interfere, refining treatment is performed as necessary to reduce these impurity elements. Of course, it is also possible to adjust the amount of carbon.

In practicing the present invention, a method of aggregating the molten slag without melting the grown metal iron shell may be adopted, and a method of separating and removing the slag without melting the metal iron may be adopted thereafter. For example, S in the obtained metallic iron
It is preferable because the amount of P and P can be suppressed as low as possible. That is, when the metallic iron is melted together with the slag after reduction,
There is a possibility that a part of S and P taken into the molten slag will dissolve into the molten metallic iron and cause a phenomenon similar to re-sulfurization / re-phosphorus, but the metallic iron will be solidified in the reduction step and the subsequent steps. If a method is adopted in which only the produced slag is melted and separated by melting, the S and P mixed in the carbonaceous reducing agent such as coal are dissolved in the molten slag and separated and removed together with the produced slag to form metallic iron. The reason for this is that the contamination of is suppressed as much as possible.

[0033]

EXAMPLES Next, the present invention will be described in more detail with reference to specific examples, but the present invention is not limited by the following examples, and is within a range applicable to the spirit of the preceding and following. It is needless to say that appropriate modifications can be implemented, and all of them are included in the technical scope of the present invention.

Example Table 1 shows a carbonaceous reducing agent (coal powder) and iron oxide (iron ore) having the composition shown in Table 1 and bentonite as a binder (all having an average particle size of 45 μm or less). After mixing in a ratio, preform it into a substantially spherical pellet, and put it in a non-oxidizing atmosphere (nitrogen gas atmosphere) 140
After heating and reducing at 0 ° C., 1450 ° C. and 1500 ° C. for 20 minutes and then cooling, the cross-sectional state of the pellet was observed. A typical cross-sectional photograph is shown in FIG.

[0035]

[Table 1]

As is clear from these figures, 14
In the case of heat reduction at 00 ° C and 1450 ° C, it was observed that the metallic iron crust was formed on the pellet surface, metallic iron adhered and grew inside, and the generated slag was separated in the state of being solidified in the internal space. To be done. Again 1500
In the case of heat reduction at ℃, it is thought that the metallic iron shell once formed melted after the reduction reaction and solidified in a state where it separated from the molten slag, and metallic iron showing a metallic luster and black glass The slag is separated into pieces (the photograph shows only the metallic iron that has been selected by removing the slag after crushing). The chemical composition of the reduced pellets at this time is shown in Table 2,
Table 3 shows the chemical composition of the glassy slag.

[0037]

[Table 2]

[0038]

[Table 3]

From Table 2, when the reduction temperature was raised to 1500 ° C., the metallic iron having an elliptical solidified metallic luster (see FIG. 2) contained almost no slag component,
It can be seen that metallic iron having a metallization rate of 99% by weight or more produced by the reduction can be almost completely separated from the slag. on the other hand,
When the reduction temperature was set to 1400 ° C or 1450 ° C, the metallic iron crust still remained, and the reduction of iron oxide appeared to be slightly insufficient when looking at the chemical composition of the pellets after reduction, but it can also be confirmed by Fig. 2. Similarly, inside the pellets, the metallic iron forming the outer skin and the slag aggregated inside have already been separated. Therefore, this is crushed and selected by magnetic separation, or the temperature is raised and heating is continued to melt a part of the metallic iron shell to let the slag flow out of the metallic iron shell, or to melt the entire metallic iron shell. It can be seen that when the metallic iron and the slag are aggregated and then separated, high-purity granular metallic iron is obtained.

Next, FIG. 3 shows the appearance change of the pellets observed when the heat reduction temperature was set to 1500 ° C. and the treatment time was changed from 3 minutes to 15 minutes, and the chemical composition of the pellets after the reduction is shown in FIG. Is shown in Table 4, and the metallization rate, slag component content, iron oxide content, and carbon content at each treatment time are shown in FIGS. 4 to 7, respectively.

[0041]

[Table 4]

As seen from FIG. 3, no extreme change in appearance is observed 3 minutes after the start of heating, but as is clear from Table 4, the reduction of iron oxide in the pellets has already progressed considerably, and the start of heating has started. 5 minutes after, the pellet surface has a clear metallic luster and a metallic iron skin is formed.
Moreover, at that time, the T. The amount of Fe exceeds 90% by weight, and the T. It can be seen that Fe has been increased to 98% by weight or more.

At this point, a part of the metallic iron crust was melted and the outflow of slag was observed outside the crust, and after 9 minutes, almost all of the metallic iron crust was melted and agglomerated to form a fried egg. The metallic iron hardens at the position corresponding to the yolk, and the glass-like slag is aggregated on the outside corresponding to the white. After this point, the shapes of metallic iron and slag change slightly,
As can be confirmed from Table 4, the T. The increase in the Fe concentration has hardly progressed any more, and therefore, the reduction reaction of iron oxide in the pellets is observed until the metallic iron crust is formed and after the crust is formed. Under the enhanced reducing conditions, the reaction proceeds rapidly and almost completely, and thereafter, the separation of metallic iron and slag progresses over time. Further, as can be seen from Table 4 and FIGS. 4 to 7,
Six minutes after the start of heat reduction, the slag content and FeO content contained in the produced metallic iron are reduced to a very low level, and a very high-quality metallic iron having a metallization rate of 99% or more can be obtained. I understand.

As is clear from the above results, when a molded product obtained by mixing a carbonaceous reducing agent in an equivalent ratio or more with iron oxide, which is an iron raw material, and molding is heated at a temperature of about 1400 ° C. or more, A metallic iron crust is formed on the outer peripheral side of the object at an initial stage, and thereafter, iron oxide is rapidly reduced in the metallic iron crust, and the generated slag component is separated from the metallic iron in a molten state. Then, when the treatment temperature is raised to 1500 ° C., the reduction reaction and the separation of metallic iron and the generated slag proceed in a very short time, and metallic iron having a very high iron content purity can be obtained in a high yield.

FIG. 8 shows a typical flow chart for carrying out the present invention. Raw iron oxide powder particles are mixed with a carbonaceous reducing agent powder and a binder, and then pelletized. After being formed into a shape, it is charged into a heating reduction furnace, and heating reduction is performed at a temperature of 1400 ° C. or higher. In the reduction step, after the metallic iron crust is formed in the initial stage, the reduction reaction proceeds inside the crust, and the generated slag component aggregates inside the crust in a molten state. When selecting iron from this, once it is cooled and solidified, it is crushed and crushed and only metallic iron is collected by magnetic separation, or further heating is continued until the temperature rises to a temperature above the melting point of metallic iron and the difference in specific gravity Only metallic iron needs to be collected. If necessary, the collected metallic iron may be refined to remove impurities such as S and P and further adjust the carbon content.

[0046]

As described above, according to the present invention, a molded product of iron oxide containing a carbonaceous reducing agent is heated and reduced to form a metallic iron crust at an initial stage, and strengthening formed in the crust. The reduction reaction of iron oxide can be carried out extremely efficiently and rapidly by promoting the reduction of iron oxide under the specified reducing conditions, and the metallization rate is 95% by weight or even 98% by weight or more. High-purity metallic iron that cannot be obtained can be efficiently produced by heating and reducing for an extremely short time. The obtained high-grade metallic iron can be easily separated from the slag by cooling and crushing and then magnetic separation or the like or by melting and then the specific gravity difference.

Further, according to the present invention, since the iron oxide content in the produced slag can be reduced as much as possible, the melting loss of the refractory of the processing furnace due to the iron oxide does not occur and the viewpoint of equipment maintenance It can be said that this technology is extremely highly practical.

[Brief description of drawings]

FIG. 1 is a cross-sectional explanatory diagram schematically showing the progress of a reduction reaction when carrying out the present invention.

FIG. 2 is a drawing-substituting photograph showing a cross-sectional shape of reduced pellets when heated and reduced at different temperatures according to the present invention.

FIG. 3 is a drawing-substituting photograph showing the appearance change of a reducing pellet when the heating reduction temperature is set to 1500 ° C. and the holding time at the same temperature is changed.

FIG. 4 is a graph showing changes in metallization rate of reducing pellets when the heating and reducing temperature is set to 1500 ° C. and the holding time at the same temperature is changed.

FIG. 5 is a graph showing changes in the slag content in the reducing pellet when the heating and reducing temperature is set to 1500 ° C. and the holding time at the same temperature is changed.

FIG. 6 is a graph showing changes in the FeO content in the reducing pellet when the heating and reducing temperature is set to 1500 ° C. and the holding time at the same temperature is changed.

FIG. 7 is a graph showing changes in the amount of carbon in the reducing pellet when the heating reduction temperature is set to 1500 ° C. and the holding time at the same temperature is changed.

FIG. 8 is a schematic flow diagram of a reduced iron manufacturing process showing an example of the present invention.

Front page continuation (72) Inventor Toshihide Matsumura 1 Kanazawa-machi, Kakogawa, Hyogo Prefecture Kamido Steel Works, Ltd. Kakogawa Works (72) Inventor Yoshimichi Takenaka 1, Kanazawa-machi, Kakogawa City, Hyogo Kamido Steel Works, Ltd. Kakogawa Steel Works (72) Inventor Masaken Shimizu 1 Kanazawa-machi, Kakogawa City, Hyogo Prefecture Kado Steel Works, Ltd. Kakogawa Steel Works (72) Inventor Shinichi Inaba 1 Kanazawa-machi, Kakogawa City, Hyogo Prefecture Kakogawa Steel Works Co., Ltd. Inside the steel mill

Claims (13)

[Claims] 1. A method for producing metallic iron by heating and reducing an iron oxide molding containing a carbonaceous reducing agent, wherein a metallic iron crust is produced and grown by thermal reduction, and iron oxide is substantially present inside. And proceed with the reduction until it no longer exists,
A method for producing metallic iron, characterized in that an aggregate of generated slag is formed inside. 2. A method for producing metallic iron by heating and reducing an iron oxide molding containing a carbonaceous reducing agent, wherein a metallic iron crust is produced and grown by the heating reduction, and iron oxide is substantially present inside. A process for producing metallic iron, characterized in that the reduction is advanced until it no longer exists in the metallic iron, and further heating is continued to allow the slag generated inside to flow out to the outside of the metallic iron crust. 3. The method according to claim 2, wherein a part of the metallic iron shell is melted to separate the metallic iron and the molten slag. 4. The method according to claim 3, wherein the melting point of the metallic iron crust is lowered by carburization to melt a part of the metallic iron crust. 5. A method for producing metallic iron by heating and reducing an iron oxide molding containing a carbonaceous reducing agent, wherein a metallic iron crust is produced and grown by heating and iron oxide is substantially present inside. A process for producing metallic iron, characterized in that the reduction is advanced until it no longer exists, and heating is further continued to melt and separate metallic iron and slag. 6. The method according to claim 5, wherein the melting point of the metallic iron shell is lowered by carburization, and the metallic iron shell is melted and separated from the slag by melting. 7. A method for producing metallic iron by heating and reducing an iron oxide molding containing a carbonaceous reducing agent, wherein a metallic iron crust is produced and grown by the heating reduction, and iron oxide is substantially present inside. And proceed with the reduction until it no longer exists,
A method for producing metallic iron, which comprises forming an aggregate of the produced slag inside and then separating the produced slag from the metallic iron. 8. The production method according to claim 1, wherein the maximum heating temperature in the heat reduction step is not less than the melting point of the produced slag and not more than the melting point of the produced metallic iron shell. 9. The method according to claim 1, wherein iron oxide is reduced by solid phase reduction in the heating reduction step, and further iron oxide mainly composed of FeO is reduced by liquid phase reduction until substantially no iron oxide is present. The manufacturing method described. 10. The production method according to claim 1, wherein in the heating reduction step, reduction is performed until the content of iron oxide mainly composed of FeO becomes 5% by weight or less. 11. The method according to claim 10, wherein in the heating reduction step, reduction is performed until the content of iron oxide mainly composed of FeO becomes 2% by weight or less. 12. The method according to claim 1, wherein the content of iron oxide mainly composed of FeO in the produced slag is 5% by weight or less. 13. The method according to claim 12, wherein the content of iron oxide mainly composed of FeO in the produced slag is 2% by weight or less.