JP2001294921A - Method for producing granular metallic iron - Google Patents

Abstract

PROBLEM TO BE SOLVED: To establish a method for stably and efficiently producing granular iron by forming of raw material body, drying, heat-reducing, melting and agglomerating, solving such problems caused by using the large diameter body as the non-uniform forming and drying the low strength, and the shortage of heat- transfer at the heating, and reducing time, when a metallic iron is produced by heating and reducing the mixture containing iron oxide and carbonaceous reducing agent. SOLUTION: The raw material body with the small agglomerate desirably about 3-7 mm diameter, is used. The bodies are charged into a heating and reducing furnace so as to mutually stack at the thickness having 10-30 mm. After performing the solid-reduction of the bodies, the granular metallic iron is produced by further heating, melting and agglomerating.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a technique for obtaining granular metallic iron by heating and reducing iron oxide such as iron ore with a carbonaceous reducing agent such as coke or the like. The iron oxide contained is efficiently reduced to metallic iron by a simple treatment, and the slag forming components contained as gangue components are efficiently separated from the metallic iron as slag to produce highly pure granular metallic iron with good productivity. It relates to an improved method so that it can be manufactured.

[0002]

2. Description of the Related Art As methods for producing metallic iron or reduced iron similar to the present invention, many methods are known as follows.

JP-A-11-337264 discloses that reduced iron is produced by forming a raw material powder containing an iron oxide source such as iron ore and coke into pellets, and heating and reducing the raw pellets. A method is disclosed. However, the reduced iron obtained by this method contains a large amount of slag components mixed as gangue components in the raw iron ore, etc., so that the Fe purity is low, and the slag components are removed by refining in the next step. Is weighted as an essential step. Moreover,
The reduced iron obtained by this method is spongy and easily broken, and thus lacks in handleability when commercialized as an iron source. Therefore, in order to remedy these drawbacks, sponge-like reduced iron must be processed into a briquette-like compression molded body,
Extra equipment is required.

This publication also discloses that a raw material powder containing an iron oxide source and coke is formed, and the obtained raw material compact is charged in an undried state into a heating reduction furnace, and drying and heating reduction are subsequently performed. A method is disclosed. Although this method has the advantage of omitting the equipment and time required for drying the raw material molded body, it requires a pre-tropical zone that also serves as drying before the heat reduction zone, so the entire furnace must be large. I can't get it. Moreover, in order to prevent the flow of the high-temperature gas from the heating reduction zone in the pre-tropical direction, for example, a shielding member such as a curtain wall must be provided, which causes a problem that the structure of the furnace becomes complicated and the equipment cost increases. .

Japanese Patent Laid-Open Publication No. Hei 10-30106 discloses a method in which the surface of a raw material layer charged on a hearth is shaped like a ridge and the surface area of the raw material layer is increased to increase the heating efficiency. Have been. However, the raw material pellets disclosed in this publication have medium to large diameters of 10 to 20 mm in diameter, have a low rate of heat transfer to the inside of the pellets for burner heating and radiant heat, and form ridges. Also,
The pellets are stacked in several layers, and a sufficient heat transfer effect cannot always be obtained. This publication also recommends that the ridge be plowed in the middle of the heat reduction to increase the heating efficiency, but plowing the laminated portion of the medium to large particle size pellets may damage the pellets. To lower the Fe yield.

JP-A-10-306304: This publication discloses a method of supplying raw material powder while forming irregularities on a hearth. However, according to this method, the maximum deposition thickness of the raw material is very thick, 120 mm, and the raw material powder is only a mixture of the iron oxide source and the carbonaceous material. The heat property and the heat reduction reactivity are considerably inferior to the case where a molded article is used.

Further, Japanese Patent Application Laid-Open No. 10-30106 and
Each of the methods disclosed in Japanese Patent Application No. 0-306304 is a method for producing reduced iron, which is distinguished from a method for producing granular metallic iron by further heating and melting the reduced iron. On the other hand, Japanese Patent Application Laid-Open No. 9-256017 discloses a method of melting metallic iron formed following heat reduction and aggregating the molten metallic iron while separating it from by-product slag components to obtain granular metallic iron. Have been. However, even in this publication, sufficient consideration has not always been made on how to efficiently produce granular metallic iron in consideration of the size of the raw material molded body and the like.

In any case, in a known method including the above-described technique, the raw material mixture is formed into a compact having a size of about 10 to 20 mm in diameter, and the compact is supplied to the hearth of a heating and reducing furnace. A method of reducing by heating is adopted. However, when such a large-diameter raw material compact is exposed to a high temperature of about 1400 ° C. or more at which a high-level reduction reaction is ensured, moisture and volatile components contained therein are reduced. In many cases, a method of preliminarily drying a raw material molded body and then charging the raw material molded body into a heating reduction furnace is adopted because the molded body is easily ruptured due to the influence of the above.

In addition, large-diameter raw material compacts are generally difficult to granulate, which increases not only the costs required for granulating equipment and drying equipment, but also increases manufacturing costs. Also, a binder is used to maintain the shape after drying stably, but if the blending amount of the binder is too large, the uniform dispersion of the iron oxide source and the carbon material in the formed body tends to be hindered, and heating is performed. There is a risk that the efficiency of the reduction reaction may be adversely affected. As described above, in some cases, drying may be omitted and the raw pellets may be supplied to the heating and reducing furnace in a raw pellet state. However, the raw pellets are not only low in strength, but also adhere to each other and adhere to a hopper of a supply device. Therefore, it is not a method suitable for practical use on an industrial scale because clogging is likely to occur and handling is poor.

As described above, when producing a reduced iron or metallic iron by heating and reducing a raw material compact containing an iron oxide source and a carbonaceous reducing agent, various processes are required because the compact has a large diameter. Although there is a problem, most of the known methods use a raw material molded body having a diameter of 10 to 30 mm, and list the difficulties due to the large diameter as described above, and try to solve the problem. No active research has been done.

[0011]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to heat and reduce a raw material compact containing an iron oxide source and a carbonaceous reducing agent. When manufacturing granular metallic iron, particularly the above-mentioned difficulties derived from the size of the raw material molded body, particularly the problem of molding or drying due to the large diameter, the problem of the strength of the molded body, The problem of reduction efficiency due to lack of heat transfer is solved at once, and the raw material compact is formed, dried, reduced by heating and melted.
An object of the present invention is to establish a method capable of stably and efficiently performing granulation by aggregation.

[0012]

In order to solve the above-mentioned problems, a method for producing granular metallic iron according to the present invention is to form a raw material mixture containing a carbonaceous reducing agent and a substance containing iron oxide into a small compacted compact. The compacted compact is heated in a reduction melting furnace to solid-reduce the iron oxide in the compacted compact, melt the metallic iron generated by the solid reduction, and melt the molten metallic iron in the compacted compact. The gist lies in obtaining granular metallic iron by separating and aggregating the contained gangue components.

[0013] The above compact agglomerates have a particle size of 3 to 7 mm.
Preferably, when heat reduction is performed using such a compacted compact as a raw material, the compacted compact has a thickness of about 10 to 30 mm (about 10 to 30 mm) on a hearth of a reduction melting furnace. It is preferable to charge them so that they are overlapped with each other (about 3 to 10 layers) because the productivity of granular metallic iron can be further increased.
Also, if the small ingot layer is formed on the hearth so that peaks and valleys are formed on the surface of the small-lumped adult layer so as to be uneven, the heat transfer efficiency is increased by increasing the effective heat transfer surface area, and the lower layer portion of the laminate is formed. It is preferable because the heating rate of the compacted compact can be increased, and the whole solid reduction and melting can be more efficiently advanced.

In carrying out the method of the present invention, the powdered carbonaceous material is laid on the hearth and then the small compacted material is charged, or the carbonaceous powder is adhered to the surface of the small compacted material. If the method of charging on the hearth is adopted, the carbonaceous material is carburized into the metallic iron generated by the solid reduction to lower the melting point, so that the melting of the metallic iron can be advanced more efficiently. In addition, the adhesion of the molten metal iron generated by melting to the hearth surface is also suppressed, and the granulation due to the aggregation of the molten metal iron can be promoted.Furthermore, in particular, small compacted compacts are stacked and mounted on the hearth. It is preferable because melting of the hearth refractory due to FeO-rich molten slag, which is likely to occur due to insufficient reduction in the lowermost layer, can be suppressed.

Further, if a method is adopted in which at least the surface of the compacted compact is dried and then placed on the hearth, the compacted compact in the hopper or the like when the compacted compact is loaded into the furnace is adopted. It is recommended because it can further suppress the supply failure due to adhesion and the crushing of compacted iron due to the lamination load after loading.

[0016]

DETAILED DESCRIPTION OF THE INVENTION As described above, in the present invention, an iron oxide source such as iron ore or iron oxide or a partially reduced product thereof (hereinafter sometimes referred to as iron ore or the like) and a carbonaceous material such as coke or coal are used. When reducing and melting a raw material compact containing a reducing agent (hereinafter sometimes referred to as a carbon material) to produce granular metallic iron, granulation is facilitated, particularly by using small agglomerates as the raw material compact. In addition to reducing the cost of granulation equipment, it is possible to improve the granulation yield and shorten the granulation time,
Furthermore, by using a compact compact, a number of advantages as described below can be enjoyed.

I) Since the heat transfer to the inside can be enhanced, the solid reduction and the subsequent melting can be efficiently advanced in a shorter time, and the productivity of granular metallic iron can be increased. Ii) Small compacted iron By doing so, it is possible to reduce the compounding amount of the binder, thereby promoting the uniform dispersion of the iron oxide source and the carbonaceous material in the agglomerate, which also effectively improves the reduction rate and the melting rate. Iii) By using small compacted iron, individual crushing strength can be increased as compared with large compacted iron, and particularly, collapse and powdering of compacted iron at the time of solid reduction can be suppressed. The yield can be improved. In addition, since the thickness of the stack charged into the hearth can be increased, this also contributes to an improvement in productivity.

In order to effectively exert the above-mentioned effects by using the compacted compact, the particle size of the compacted compact is 7 mm.
Below, more preferably, it is desirable to be 6 mm or less, and if there are a large number of large-diameter agglomerates, it is difficult to effectively exert the above-mentioned effects. However, in the case of small-diameter compacted iron having a particle diameter of 2 mm or less, particularly 1 mm or less, clogging is likely to occur due to selection using a sieve or the like, and not only the handleability is deteriorated, but also the finally obtained granular metallic iron has a small diameter. And the subsequent handling becomes complicated, so that it is preferably 3 mm or more, and more preferably 4 mm or more.
It is desirable to make the above. However, in practicing the present invention, not all agglomerates need to be within the above-mentioned preferred particle size range. Even if a small amount of compacted compact or large-diameter compacted steel (preferably about 20% or less in mass ratio) is contained, the above-described effects can be effectively exhibited as a whole.

The small agglomerates referred to in the present invention are a general term for agglomerates of a mixture containing an iron oxide source and a carbonaceous reducing agent, pellets, briquettes, etc., regardless of their names. In addition, not only a simple substance thereof, but also a mixture thereof, or a small amount of debris or powder broken in a transfer step or the like may be contained. There is also no particular limitation on the method of producing compact agglomerates, and bread-type granulators, disk-type granulators,
A normal molding method using a drum type granulator or the like may be employed.

The iron oxide source used as a raw material for the compacted compact is
It is a broad concept including iron ore, mill scale, etc.
For example, it is of course possible to include blast furnace dust, electric furnace dust, steelmaking dust, and the like. The type of the carbonaceous reducing agent is not particularly limited, and charcoal powder and the like can be used in addition to the most common coal powder and coke powder. Examples of the binder that may be added as necessary include bentonite and starch, but of course there is no reason to be limited to these. Furthermore, if an appropriate amount of CaO source (quick lime, slaked lime, calcium carbonate, etc.) is contained in the raw material mixture for adjusting the basicity of the slag forming component, these act as desulfurizing agents, and S contained in the raw material mixture is reduced. CaS
Is fixed to the slag side to obtain a granular metallic iron having a low S content.

When such a compact compact is used, not only can it be charged in the form of a single layer on the hearth of a reduction melting furnace, and solid reduction and melting / agglomeration can be efficiently carried out according to a conventional method,
By taking advantage of the excellent crushing strength characteristics, it is possible to increase the productivity per unit hearth area by stacking multiple layers on the hearth. The lamination thickness at this time is preferably in the range of 3 to 10 laminations in the number of small agglomerates, and in the range of 10 to 30 mm in thickness, and if less than 3 laminations, the effect of improving productivity by laminating is somewhat insufficient. If the lamination charging thickness is excessively increased beyond 10 layers, the small compacted body on the lower layer side of the lamination will be insufficiently heated, and the efficiency of solid reduction and melt aggregation will tend to deteriorate.

A special method is not always adopted for supplying small-sized compacts to the hearth surface. For example, cutting is performed by a hopper, a vibration feeder, a drum feeder, or the like, and a gutter, a pipe, or an inclined plate for guiding is used. It is sufficient to adopt a method of supplying by feeding.

When the compacted compact is charged in a multi-layered state, peaks and valleys of an arbitrary shape are formed in the laminating surface in the vertical and / or horizontal direction to form irregularities, thereby increasing the surface area. Accordingly, it is desirable to increase the heating efficiency by burner heating from above or radiant heat. It is effective to form irregularities on the surface of the laminate, since the heat transfer efficiency of the lower layer of the laminate to the compacted compact can be increased. The preferred shape, size, pitch and the like of the irregularities cannot be uniformly defined because they vary depending on the lamination thickness, but are preferably 5 to 30 mm in height (interval between the top and the bottom), It is more preferably in the range of 10 to 30 mm, and the preferred pitch (width between adjacent peaks) is in the range of 10 to 100 mm, more preferably 10 to 70 mm. There is no particular limitation on the method of forming the irregularities, for example, a method of changing the charging amount from a plurality of supply ports in a width direction of the hearth, a charging method, a method of charging from an irregular hopper extending in the furnace width direction. A method in which the thickness is changed and a method in which the unevenness is formed by tracing with a surface shaping member having the unevenness after being substantially horizontally inserted can be arbitrarily selected and applied.

Since the compacted compact used in the present invention has a small diameter as described above, the crushing strength of each compacted article is relatively strong, and the compacted compact is less likely to be crushed by the laminating pressure even when charged in a laminate. In addition, because heat transfer is fast, it is quickly dried by initial heating, so it is possible to supply it on the hearth in an undried state, but damage due to impact at the time of charging and lamination load is more. In order to surely prevent, it is preferable to charge at least the surface layer side of the small compacted body before drying,
This is preferable because clogging in a charging hopper or the like due to the attachment of the compacted compact can be prevented.

Further, in carrying out the present invention, the powdered carbonaceous material is laid on the hearth and then the compacted iron is charged, or the carbonaceous material is adhered to the surface of the compacted iron and then placed on the hearth. If the charging method is adopted, for example, a) the carbonaceous substance enhances the degree of reduction of the atmospheric gas near the small compacted body during the solid reduction to promote the solid reduction more efficiently. Carburizing metal iron after solid reduction to lower its melting point and promote melting and agglomeration; c) the carbonaceous substance suppresses adhesion of molten metal iron to the hearth surface and promotes granulation; D) Insufficient reduction in the lower layer, which tends to occur when small compacted compacts are stacked and charged, is supplemented by the carbonaceous substance to increase the overall solid reduction rate. E) FeO, which is likely to be generated due to insufficient reduction in the lower layer To reduce this quickly, The formation of FeO-containing molten slag, which significantly damages the fire, is also suppressed, and the life of the hearth is extended. F) If the carbonaceous material is adhered to the surface of the small agglomerate, the mutual adhesion will occur. It is also possible to prevent the small compacted body from being charged in an undried state, since it is prevented from adhering to the hopper and the charging hopper.

As the carbonaceous substance used here, coal powder, coke powder, charcoal powder and the like are arbitrarily selected and used. The preferred particle size for more effectively exhibiting the above-described effects as a powdery carbonaceous material spread on the upper surface of the hearth is an average particle size of 2 mm or less, more preferably 1.5 mm or less. When the carbonaceous material is to be adhered to the surface of the compacted compact, a method of attaching a material having an average particle size of about 0.3 mm or less so as to cover the surface is performed by dispersing the carbonaceous material in a dispersion medium such as water. A method of spray attachment may be employed.

Next, a specific apparatus for producing granular metallic iron by performing solid reduction, melting and agglomeration using the above compacted compact as a raw material will be briefly described.

FIGS. 1 to 3 are schematic illustrations showing an example of a moving bed type reduction melting furnace developed by the present inventors to which the present invention is applied, and which has a dome-shaped structure having a donut-shaped rotating moving bed. FIG. 1 is a schematic view, FIG. 2 is a cross-sectional view taken along the line AA in FIG. 1, and FIG. 3 is developed in the direction of rotation of the rotary moving floor in FIG. FIG. 1 is a schematic cross-sectional explanatory view, in which 1 is a rotary hearth, 2 is a furnace body that covers the rotary hearth, and the rotary hearth 1 is configured to be rotatable at an appropriate speed by a driving device (not shown). Have been.

A plurality of combustion burners 3 are provided at appropriate places on the wall of the furnace body 2.
The combustion heat of the combustion burner 3 and the radiant heat thereof are transmitted to the compacted compact on the rotary hearth 1,
Heat reduction of the agglomerates is performed. Furnace body 2 the illustrated shows a preferred example, the furnace body 2 inside is partitioned into the reduction melting zone Z ₁ and the cooling zone Z ₂ in one partition wall K,
The raw material and auxiliary raw material charging means 4 are arranged on the most upstream side in the rotational direction of the furnace body 2 facing the rotary hearth 1, and the most downstream side in the rotational direction (because of the rotating structure, charging is actually performed). Means 4
The discharge means 6 is provided immediately upstream of the discharge means.

As a heat source of the heating reduction melting furnace, a burner heating using gas, heavy oil, pulverized coal, waste plastic, or the like as a fuel, or oxygen or air is supplied by effectively using a combustible gas generated in the furnace. Type that burns this,
Furthermore, it is also possible to use a regenerative furnace. Further, for discharging the generated granular metallic iron, an arbitrary discharging device such as a screw or a scraper, or a method of discharging by using gas blowing or suction can be adopted.

In operating this reduction melting furnace,
The rotary hearth 1 is rotated at a predetermined speed, and the compacted compact as the main raw material is supplied onto the rotary hearth 1 from the charging device 4 by using a vibration feeder 5 or the like so as to have an appropriate thickness. I will do it. When charging the compacted compact, the compacted compact can be charged into a single layer, but as described above, preferably 3 to 10 layers, more preferably 3 to 6 layers, 10-30mm, more preferably 20-30m
It is preferable to charge the raw materials in the range of m since the amount of raw materials charged per unit hearth area can be increased, thereby increasing productivity.

When the compacted compacts are charged in a laminated state, if the surface of the laminated body is formed with irregularities of an arbitrary size, the heat transfer effective area of the laminated surface is enlarged and the compacted compact is charged. This is preferable because the heating efficiency for small compacted iron can be further increased, and the heating efficiency for small compacted iron on the lower layer side can be increased. As described above, for example, as described above, the charging method is performed by changing the charging amount from a plurality of supply ports in the furnace floor width direction, and the charging thickness is changed from the uneven hopper provided extending in the furnace width direction. And a method of forming the concavities and convexities by tracing with a surface shaping member having concavities and convexities after being substantially horizontally inserted.

The compacted compact charged on the hearth 1 receives combustion heat and radiant heat from the combustion burner 3 in the process of moving through the reduction melting zone Z ₁ , and the iron oxide and carbonaceous material contained in the compacted compact are received. Iron oxide is reduced by carbon monoxide generated by the reaction with the reducing agent, and the generated metallic iron is further heated in a carbon-rich atmosphere to be carburized and melted, and aggregated while being separated from by-product slag. after a molten metallic iron particulate Te is cooled in any cooling means C in the cooling zone Z ₂ is solidified, sequentially scraped out by the discharging means 6 provided on the downstream side. At this time, slag by-produced is also discharged at the same time. After passing through the hopper H, the slag is separated from granular metallic iron and slag by an arbitrary separating means (a sieve or a magnetic separation device, etc.), and finally the iron content is reduced. Purity can be obtained as granular metallic iron having a purity of about 95% or more, more preferably about 98% or more, and extremely low slag content.

In the above-mentioned reduction / melting step, if the ambient temperature during the reduction (solid reduction period) is too high, specifically, during a certain period of the reduction process, the ambient temperature is changed to the gangue component or the unreduced oxidized material in the raw material. When the temperature of the slag is higher than the melting point of the slag composition composed of iron or the like, the slag having a low melting point melts and reacts with the refractory constituting the moving hearth to be melted, so that a smooth hearth cannot be maintained. Further, when heat more than required for the reduction of iron oxide is applied during the solid reduction period, FeO, which is an iron oxide in small compacted iron, is melted before being reduced, and the molten FeO is contained in the carbonaceous material. So-called smelting reduction (a phenomenon in which reduction proceeds in a molten state, which is different from solid state reduction) that reacts with carbon (C) proceeds rapidly. Although metallic iron is also generated by the smelting reduction, when the smelting reduction occurs, the highly fluid FeO-containing slag remarkably dissolves the hearth refractory, making continuous operation as a practical furnace difficult.

Such a phenomenon varies depending on the iron ore and the carbonaceous material constituting the small agglomerate or the composition of the slag forming component contained in the binder, etc., but the ambient temperature during the solid reduction exceeds about 1400 ° C. As described above, the low-melting point slag oozes out and the hearth refractory is eroded. If the temperature exceeds 1500 ° C., regardless of the brand of the raw material iron ore, the undesired smelting reduction reaction proceeds and the furnace Since the erosion of floor refractories becomes remarkable, the temperature during the solid reduction period is 15
It is desirable to suppress the temperature to 00 ° C. or lower, more preferably to about 1450 ° C. or lower. If the temperature during the solid reduction period is too low, it is difficult for the solid reduction to proceed efficiently.
It is desirable that the temperature be 200 ° C. or higher, more preferably 1300 ° C. or higher.

After the solid reduction, the ambient temperature is preferably raised to about 50 to 200 ° C. to 1350 to 1
The temperature is raised to 500 ° C., the metallic iron generated by the solid reduction is melted, and the molten metallic iron is aggregated. At this time, the molten metallic irons are mutually aggregated and coarsened, but during this time, the molten metallic slag is eliminated while being agglomerated, so that the aggregated metallic iron has a high Fe purity containing almost no slag. After cooling and solidifying this, the granular metallic iron and the slag are separated by a sieve, magnetic separation, or the like, whereby a granular metallic iron with high Fe purity can be obtained.

The melting of the metallic iron produced by the solid reduction proceeds by raising the ambient temperature to a temperature higher than the melting point of the metallic iron. However, C and CO are present near the metallic iron at the start of the melting. This is preferable because the metal iron is carburized to cause a decrease in melting point, and the melting of the metal iron can be performed at a lower temperature and in a shorter time. That is, in order to accelerate this melting, it is preferable to leave a sufficient amount of carbon for the carburization in the particles after the solid reduction, and this residual carbon amount is used to produce a small compact as a raw material. What is necessary is just to adjust according to the mixing ratio of the iron ore and the carbon material at the time. The present inventors have confirmed through experiments that the final reduction rate in the solid reduction phase is almost 100%.
%, Ie, when the metallization ratio has reached 100%, the initial carbon material blending amount such that the amount of residual carbon (that is, the amount of excess carbon) in the solid reduced product becomes 1.5% or more. It has been confirmed that if the temperature is maintained, the reduced iron can be rapidly carburized to lower the melting point, and can be quickly melted in a temperature range of 1300 to 1500 ° C. If the residual carbon content is less than 1.5%, the melting point of the reduced iron does not drop sufficiently due to a shortage of carbon due to carburization, and the temperature for heating and melting is reduced to 1%.
The temperature must be raised to 500 ° C. or higher.

When the amount of carburizing is zero, that is, the melting temperature of pure iron is 1537 ° C., the reduced iron can be melted by heating to a temperature higher than this temperature. It is desirable to keep the operating temperature as low as possible in order to reduce the thermal load on the slag.
It is desirable to keep the temperature below about ° C.

Then, the raw material compacted in the furnace is
In order to efficiently promote the reduction rate without causing partial melting of the slag component contained in the agglomerate while maintaining the solid state, the furnace temperature is set to 1200 to 1500 ° C, more preferably 1200 to 1400 ° C. Solid reduction is performed while keeping the temperature within the range, and subsequently, the furnace temperature is set to 1350 to 1500 ° C.
It is desirable to adopt a two-stage heating method for reducing the remaining iron oxide and melting and aggregating the generated metallic iron, and by setting these conditions, the granular metallic iron can be stably and efficiently used. Can be manufactured, usually 10
The solid reduction, melting, and aggregation of the iron oxide can be completed in about 13 minutes to about 13 minutes.

By the way, in the reduction melting furnace used for carrying out the present invention, burner heating is often used for heating the compacted raw material compact. In this case, in the solid reduction period, a large amount of CO gas is generated by the reaction between the iron oxide source and the carbon material in the small compacted iron charged in the furnace, so that the vicinity of the raw compacted iron is released from itself. A sufficient reducing atmosphere is maintained by the shielding effect of the CO gas.

However, from the latter half of the solid reduction period to the end of the solid reduction period, the amount of generated CO gas is rapidly reduced, so that the self-shielding effect is reduced, and the combustion exhaust gas (oxidation of CO ₂ , H ₂ O, etc.) generated by burner heating is reduced. ), And the reduced metallic iron is susceptible to re-oxidation. Further, after completion of the solid reduction, melting and agglomeration of the fine reduced iron proceed due to the melting point drop due to the carburization of the reduced iron due to the residual carbon in the small agglomerate, but the self-shielding action is poor even at this stage. Are susceptible to re-oxidation.

Therefore, in order to efficiently promote the melting and agglomeration after the solid reduction while suppressing such reoxidation as much as possible, it is desirable to appropriately control the atmosphere gas composition in the melting region. As a preferable means for this, as described above, prior to charging the compacted compact as a raw material on the hearth, a powdery carbonaceous substance is charged on the hearth, or the carbonaceous material is previously placed on the surface of the compacted compact. There is a method of keeping the powder adhered. That is, the powdery carbonaceous material is charged into the furnace floor in this way,
Alternatively, if carbonaceous substances are adhered to the surface of small agglomerates, they immediately react with oxidizing gas (CO ₂ or H ₂ O) generated by burner combustion at the beginning of melting after solid reduction is completed. Since these gases are converted into reducing gases such as CO and H ₂ , the vicinity of the agglomerates subjected to solid reduction can be kept in a highly reducing atmosphere, and reoxidation of metallic iron can be prevented as much as possible. . In addition, these carbonaceous reducing agents are preferable because they serve as a carburizing source for the produced metallic iron, and also exhibit the effect of further reducing the time required for carburizing and melting the metallic iron.

In order to effectively exert the function and effect of the carbonaceous substance, the powdery carbonaceous substance previously charged on the hearth has a particle size of 3 mm or less, more preferably 2 mm or less, and particularly preferably 0 mm or less. It is preferable to use a finely divided material in the range of 3 to 1.5 mm, which is preferably charged to a thickness of about 2 to 7 mm, more preferably about 3 to 6 mm. When it is attached to the surface, it is desirable to set the amount of attachment to 1 to 10% by mass, more preferably 3 to 7% by mass, based on the compacted compact.

The granular metallic iron obtained by the above method is
It is agglomerated while excluding slag by-produced and contains very little slag components and has a very high Fe purity. This metallic iron is sent to existing steelmaking facilities such as electric furnaces and converters to send iron sources. However, in order to use these as steelmaking raw materials, it is desirable to reduce the content of sulfur [S] as much as possible. Therefore, in the manufacturing process of the metallic iron,
Research was conducted to obtain low [S] metallic iron by removing as much as possible the S component contained in iron ore and carbonaceous material. In doing this, a CaO source (including slaked lime and calcium carbonate, etc., in addition to quick lime) is positively blended into the raw material, and the raw material lumps in which slag forming components such as gangue components contained in iron ore and the like are added. The basicity (ie, CaO / S) of all slag forming components contained in the adult
iO ₂ ratio) is 0.6 to 1.8, more preferably 0.9 to 1.8.
It has been confirmed that by adjusting the components so as to be in the range of 1.5, the S content in the finally obtained metallic iron can be reduced to 0.10% or less, and further to about 0.05% or less. Was.

Incidentally, coke and coal, which are most commonly used as carbonaceous reducing agents, usually contain 0.2 to 1.0%
To the extent that most of these [S] are incorporated into metallic iron. On the other hand, when the basicity is not adjusted by the active addition of the CaO source, the basicity calculated from the slag-forming component contained in the raw material agglomeration is usually 0, although there are considerable differences depending on the brand of iron ore. .
In such a low basicity slag, incorporation (vulcanization) of S into metallic iron during solid reduction or subsequent melting / aggregation process is unavoidable, and the total amount of [ About 85% of [S] is taken into metallic iron. As a result, the [S] amount of metallic iron is 0.1 to 0.5.
A very high value of 2% impairs the quality as granular metallic iron.

However, if the composition of the slag-forming component is adjusted so that the basicity is in the range of 0.6 to 1.8 by the active addition of a CaO source during the production stage of the raw material compact as described above, the solid reduction [S] is fixed in slag by-produced during carburization, melting, and agglomeration, and as a result, the [S] amount of granular metallic iron can be significantly reduced to, for example, a 0.050 to 0.080% level. . The mechanism for lowering S is that [S] contained in the raw material compacted reacts with CaO (CaO + S =
It is considered that CaS) is fixed as CaS.

[0047]

EXAMPLES Hereinafter, the structure, operation, and effects of the present invention will be described in detail with reference to examples. However, the present invention is not limited to the following examples, and can be adapted to the above and following points. The present invention can be implemented by appropriately changing the scope, and all of them are included in the technical scope of the present invention.

Example 1 Iron ore as iron source (main component: T.Fe; 69.2)
_{%, Al 2 O 3; 0.51} %, SiO 2; 1.81%),
Coal powder as carbonaceous reducing agent (major component: fixed carbon; 7
1.6%, ash content: 8.8%, volatile content: 19.6%), and quicklime was used as a binder.
After mixing uniformly at a mass ratio of 20.46: 1.00, the mixture was stirred for about 15 minutes while sprinkling water with a mixer to form pseudo-agglomerated small agglomerates (water content: 12.9%).
I got After drying this small agglomerate to a water content of about 6%, it is sieved to 1.0 mm or less, 1.0 to 3.35 m.
m, 3.35 to 5.6 mm and 5.6 to 6.7 mm.

After the pseudo carbon material particles obtained above were spread on the bottom of a refractory flat plate, each of the small agglomerates sieved as described above was laminated to a height of about 12 mm. The mixture was placed in a small electric furnace, and heated at 1440 ° C. for 12 minutes (15 minutes when a particle having a particle size of less than 1 mm was used) while flowing 100% nitrogen gas to reduce and melt the particles. An experiment on the production of metallic iron was performed. The average value of the apparent density of the obtained granular metallic iron and the Fe yield of the granular metallic iron having a particle size of 3 mm or more were as follows. For comparison, the results of the production of granular metallic iron in the same manner as described above except that the average particle size of the compacted iron was changed to 18.5 mm and the heating conditions were changed to 1430 ° C. for 12 minutes are also shown. Small compacted irons granularity apparent density of less than Fe yield 1.0mm metallic iron nuggets ^{7.56g / cm 3 73.8% 1.0~3.35mm 6.87g} / cm 3 83.0% 3.35~5.6mm 7.37g / cm 3 87.2% 5.6~6.7mm 7.35g / cm ³ 87.4% 18.5mm 7.38g / cm ³ 89.7%

In the case of producing granular metallic iron by heating and reducing a compact containing an iron oxide source and a carbonaceous reducing agent, in general, the larger the size of the raw material compact, the larger the granular metallic iron obtained. Is believed to be. In fact, even in the above experiment, it is recognized that the larger the particle size of the raw material compacted iron, the larger the particle size of the obtained granular metallic iron. However, the tendency is very slight, and even when a small compacted compact having a particle size of about 3 to 7 mm, which is preferably used in the present invention, is used as a raw material, the particle size of the obtained granular iron is about 18 mm, which is a general particle size. Hardly any difference from the particle size of the granular iron obtained when using the molded body of the above. Therefore, according to the present invention, it can be seen that the above-mentioned advantages of using the compacted compact can be effectively enjoyed with almost no deterioration in the quality of the granular metallic iron.

In each of the above experiments, coke powder was laid on the floor, so that all of the granular metallic iron produced was agglomerated on the surface of the coke powder, and almost no erosion was observed on the bottom of the dish. Only slight erosion was noted.

Further, the heat reduction was carried out under the same conditions as above except that the raw material used was an iron oxide source and a carbonaceous reducing agent having the same composition as described above, and a dry powder not subjected to any agglomeration treatment was used. As a result, it was confirmed that even when the heating temperature was increased to 1480 ° C., the formation of molten metallic iron did not occur.
This is presumably because the iron oxide source and the carbonaceous reducing agent were not in close contact with each other, so that solid reduction hardly proceeded, and the metal oxide was not reduced to metallic iron at the 1440 ° C level.

Example 2 Iron ore (same as in Example 1) was used as an iron source, and coal powder (same as in Example 1) was used as a carbonaceous reducing agent.
After uniformly mixing at a ratio of 3: 20.7% (% by mass),
10% of water was added thereto, and the mixture was granulated by a bread granulator to produce a compact compact having a particle size of 3 to 5 mm. This compacted compact is placed on a refractory plate without drying for about 3
Filled to a thickness of 0 mm, on the surface of which are formed three ridges 20 mm or 30 mm in height at intervals of about 30 mm in width,
This is charged into a box-type electric furnace and heated at 1425 ° C. for 12 minutes to perform solid reduction and melting / aggregation, and compare the production state of granular metallic iron (yield of granular metallic iron with a diameter of 3.35 mm or more). did. The results are shown below. Ridge height Yield of granular metallic iron with a diameter of 3.35mm or more 20mm 93.0% 30mm 94.7%

In the above experiment, when the flow state of the molten metal iron generated by the heating after the solid reduction was observed through a viewing window, the molten metal iron generated at the ridge portion flowed down along the valley.
The phenomenon of agglomeration and granulation at the bottom of the valley was observed, and it was confirmed that as the ridge height was increased, the particle size of the granular metallic iron obtained increased. However, if the ridge spacing is too wide, it becomes difficult to effectively exert the above-described aggregation effect. Then, it was confirmed that when the ridge interval was set to about 10 mm, granular metallic iron having a particle size of about 3 mm or more could be efficiently produced.

[0055]

The present invention is constituted as described above. When a mixture containing an iron oxide source and a carbonaceous reducing agent is formed and reduced by heating to produce granular metallic iron, it is used as a compact. By using small compacted irons, preferably small compacted irons having a particle size of about 3 to 7 mm, the above-mentioned disadvantages derived from the size of the raw material compacted irons, especially molding or drying due to the large diameter. Problem, strength of molded body, problem of insufficient heat transfer at the time of heat reduction, etc., and stabilize a series of processes from molding of raw material agglomerate to drying, heat reduction and granulation by melting and agglomeration. It was able to perform efficiently.

[Brief description of the drawings]

FIG. 1 is an explanatory view illustrating a reduction melting facility used in the present invention.

FIG. 2 is a sectional view corresponding to the line AA in FIG.

FIG. 3 is an explanatory cross-sectional view showing FIG. 1 developed in a rotation direction of a rotary hearth.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Rotary hearth 2 Furnace 3 Combustion burner 4 Raw material and auxiliary raw material charging means 5 Vibration feeder 6 Discharge means K Partition wall C Cooling zone H Hopper

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Osamu Tsuchiya 4-3-1 Bingocho, Chuo-ku, Osaka-shi Kobe Steel, Ltd. Osaka branch office F term (reference) 4K001 AA10 BA02 CA18 CA20 CA21 CA23 GA12 HA01 4K012 DE03 DE06

Claims (7)

[Claims] 1. A raw material mixture containing a carbonaceous reducing agent and an iron oxide-containing substance is formed into a compacted compact, and the compacted compact is heated in a reduction melting furnace to reduce the iron oxide in the compacted compact into a solid. And melting the metallic iron generated by the solid reduction, and aggregating the molten metallic iron while separating the slag component contained in the small compacted iron to obtain granular metallic iron. Manufacturing method of metallic iron. 2. The method according to claim 1, wherein the compacted compact mainly has a particle size of 3 to 7 mm. 3. The method according to claim 3, wherein the compacted compact is 10 to 3 pieces on the hearth.
3. The method according to claim 1, wherein the parts are charged so as to overlap each other at a thickness of 0 mm. 4. The method according to claim 3, wherein peaks and valleys are formed on the surface of the compacted adult layer charged on the hearth. 5. The method according to claim 1, wherein the powdered carbonaceous material is laid on the hearth and the compacted compact is charged. 6. The method according to claim 1, wherein a carbonaceous powder is attached to a surface of the compacted compact and charged on the hearth. 7. The method according to claim 1, wherein at least the surface of the compacted compact is dried and then charged on the hearth.