JP3379360B2 - Hot metal production method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to powdered iron oxides such as iron ore, dust containing iron in iron mills, sludge, scales (hereinafter collectively referred to as powdered iron oxides), and powdered iron oxides. Solid reducing agent, for example, coal, charcoal, petroleum coke, coke, etc. (hereinafter collectively referred to as powdery solid reducing agent) is mixed, charged into a furnace heated in powdery state without agglomeration, Reduced at high temperature to produce reduced iron, charged with carbonaceous material from the upper part of the furnace, blown oxygen-containing gas from the tuyere, to the refining furnace with a packed bed of carbonaceous material in the furnace, the reduced iron at high temperature The present invention relates to a method for producing hot metal by charging from the upper part of a furnace and reducing and melting the reduced iron in the furnace.

[0002]

2. Description of the Related Art Conventionally, hot metal has been mainly manufactured by a blast furnace method. In the blast furnace method, massive coke and massive iron raw material are charged from the upper part of the furnace, hot air is blown from the tuyere installed at the lower part of the furnace to burn the coke, generate high-temperature reducing gas, and reduce iron oxide. , The process of dissolution.

Recently, a massive iron raw material is reduced in a shaft reduction furnace to produce reduced iron, and the reduced iron is charged into the carbonaceous material fluidized bed type melting furnace from the upper part of the furnace at a high temperature to reduce and melt it. , A method for producing hot metal has been developed, and commercial equipment has already been installed. In addition, various methods have been developed as a method for directly producing hot metal from powdered iron ore. For example, Japanese Patent Publication No. 3-60883 discloses the following method.

That is, fine iron ore and fine carbonaceous material are compacted into a nodule, and the compact is pre-reduced in a rotary hearth furnace as a pre-reduction furnace at a temperature of at least 1000 ° C.
Discharge from the furnace. On the other hand, a smelting furnace that has a molten metal bath in the furnace and introduces fine carbonaceous material below the bath surface and blows oxygen into the furnace is prepared, and the above-mentioned reduced iron is charged into this smelting furnace. Then, reduction and dissolution are performed. At this time, the exhaust gas from the smelting furnace is recovered and introduced into the rotary hearth furnace, which is a preliminary reduction furnace, as the fuel for preliminary reduction of the molded body.

[0005]

However, these conventional techniques have the following drawbacks. That is,
Although the blast furnace method is a very efficient process, it has the drawback of requiring bulk feedstock and fuel. Therefore, coal, which is both a major reducing agent and a fuel,
The coke is used in the form of lumps, which is obtained by dry distillation in a coke oven to form coke and sieving. Since it is necessary to use lump-shaped ores as well, it is unavoidable to use powdered ores as pellets or sintered ores, except when lump ores are used. Among them, regarding coal, in terms of resources, the production of strong coking coal for coke is unevenly distributed, and in addition to the huge investment burden at the time of coke oven replacement and pollution measures due to the coke oven, the blast furnace law It is a big issue. On the other hand, as for ores, the supply of lump ore is very tight and the price of pellets is expensive, so in Japan it is mainly used in the form of sinter, but there is no pollution. In addition to the problem, it has a problem that agglomeration is necessary.

[0006] Further, a lumpy iron raw material is reduced in a shaft reduction furnace to produce reduced iron, and this reduced iron is charged into a carbonaceous material fluidized bed type melting furnace at a high temperature to reduce and melt to produce hot metal. The method does not require coke, but uses a shaft furnace for the reduction furnace, and therefore requires a massive ore like the blast furnace.

On the other hand, the method disclosed in Japanese Examined Patent Publication No. 3-60883 is excellent, but after mixing the powdery iron oxide and the powdery solid reducing agent, it is formed into a nodule before charging into the reduction furnace. It has the disadvantage that it needs to be molded. Also, in agglomeration,
The generation of particles other than the predetermined size is unavoidable, and the undersize has to be returned to the mixing step as it is, and the oversize needs to be crushed and then returned to the mixing step. In addition, since the strength of the agglomerated product cannot withstand handling in the agglomerated state, it is necessary to dry the agglomerated product before charging it into the reduction furnace.Therefore, agglomeration equipment and drying equipment are required. In addition, since it requires operating and maintenance costs, it has a drawback of increasing the production cost of reduced iron. Moreover, it requires a relatively long agglomeration and drying time as compared with a short reduction time, and has a drawback of impairing the efficiency of the entire plant.

Further, when powdered iron oxide generated in an iron mill is used alone or mixed with iron ore, in order to agglomerate into pellets, the recovery form of these oxides discharged from the iron mill is “powder”. Lumps or mills in which solids are bound and solidified
Since it often has a "shape too large for pelletizing" like a scale (however, in this specification, these are referred to as "powdered iron raw material"). There is also a problem that it is necessary to pulverize it, and therefore a fine pulverization facility for oxides discharged from the ironworks is indispensable. Furthermore, in the conventional method, the surface of the agglomerate may be reoxidized during high temperature reduction, which has been a cause of hindering the improvement of the metallization rate of the product.

Further, the iron bath type smelting furnace used in the process of Japanese Patent Publication No. 3-60883 has a problem that the refractory of the furnace has a short life, and the high-temperature exhaust gas is emitted, so that the thermal efficiency is poor. There is a problem that the S concentration in the hot metal is higher than that in the blast furnace hot metal because of the disadvantages and the reducing atmosphere in the furnace is lower than that in the blast furnace. Thus, an object of the present invention is to develop a technique for treating powdered iron oxide by an efficient and simple means and utilizing it as a useful iron resource.

[0010]

In order to solve such a problem, the present inventor has noticed that one of the drawbacks of the prior art is the agglomeration process and the drying process of the raw fuel. Conventionally, it has been considered that such a step is essential for the preliminary reduction of the raw material. Therefore, in order to avoid the increase in the manufacturing cost of the conventional method due to the need for such an agglomeration step and a drying step, the present inventor charges a furnace heated in a mixed state without agglomeration. Then, it was thought that iron oxide could be reduced in the bed state by forming a bed of almost uniform thickness on the hearth. That is, after mixing powdery iron oxide and a powdery solid reducing agent, a basic experiment was carried out in which this was charged into a furnace heated to 1200 ° C. or higher to perform reduction, and agglomerates were formed. The present inventors have completed the present invention, knowing that a result comparable to that in the case of reduction can be obtained.

That is, according to the present invention, in reducing powdery iron oxide at a high temperature, powdery iron oxide and a powdery solid reducing agent are mixed in advance, and the obtained mixture is agglomerated. It is charged into a furnace that is heated in a powdery state without being used, and a bed with a substantially uniform thickness is formed on the hearth, or the mixture is molded into a plate shape and placed on the hearth, and fuel is fed into the furnace. By blowing in an oxygen-containing gas, this fuel, volatile matter (VM) generated from the solid reducing agent, and CO generated by reducing iron oxide
By burning gas and maintaining the temperature inside the furnace at 1100 ° C or higher, powdered iron oxide is reduced to produce reduced iron.

On the other hand, the smelting furnace used for melting reduced iron has a packed bed of carbonaceous material in the furnace and is charged with lump-grained carbonaceous material from the upper part of the furnace through tuyeres installed in the lower part of the furnace. Use a vertical furnace that blows oxygen-containing gas to burn the carbonaceous material in front of the tuyere to generate high-temperature reducing gas.The reduced iron is charged at high temperature from the upper part of this vertical furnace to remove the hot metal. It is manufactured.
The produced gas from this refining furnace may be recovered and at least a part thereof may be used as the fuel for preliminary reduction.

The type of the pre-reduction furnace used in the present invention is not particularly limited, but it is recommended to use the rotary hearth type furnace described above. Regarding the temperature in the furnace, the reduction proceeds even at 900 to 1100 ° C, but the reduction rate is slow, so the temperature was set to 1100 ° C or higher in the present invention.

In the present invention, it is easy to mix the powdery iron oxide and the powdery solid reducing agent, and it is easy to form a bed or a plate-shaped molded product of a mixture having a substantially uniform thickness on the hearth. , And for the purpose of preventing the scattering of fine powder from the surface of the mixture in such a form, when producing a mixture of powdery iron oxide and a powdery solid reducing agent, water, binder (bentonite, lime, organic One or both of these may be added in small amounts. In addition, in order to adjust the basicity of the slag component contained in the reduced iron, lime
(Quick lime, limestone, etc.) may be added.

In the present invention, the temperature of the molded product is kept lower than the temperature in the furnace during the reduction of iron oxide due to the endothermic reaction. Therefore, in order to obtain a sufficiently high reduction rate, the temperature in the furnace should be 12
It is desirable to maintain the temperature above 00-1400 ℃.

Furthermore, in the present invention, in order to prevent reoxidation of reduced iron during high temperature reduction, a bed of a mixture of powdered iron oxide and powdered solid reducing agent having a substantially uniform thickness is provided on the hearth. A method of thinly coating the bed surface with a powdery solid reducing agent after forming it may be adopted.

When the mixture is formed into a bed having a substantially uniform thickness, a compression roller or the like is used to prevent the mixture from scattering by the combustion gas and to promote heat transfer and reduction in the bed. May be filled to increase the apparent density of the mixture. Further, in order to positively prevent the mixture from being scattered by the combustion gas, it is also effective to spray the cement aqueous solution or the like onto the bed after forming the bed or after the pressure is applied.

On the other hand, in order to shorten the reduction time of iron oxide, it is desirable to quickly raise the temperature of the mixture to an appropriate reduction temperature. For that purpose, when heating the mixture, the solid reducing agent in the mixture is reduced. It is also possible to adopt a method in which an oxygen-containing gas is supplied to the bed surface until the generation of the VM generated from the above is almost finished, the VM is burned on the bed surface, and the temperature rising rate of the bed is increased. After the generation of VM is completed, it is desirable to keep the temperature inside the furnace at 1100 ° C or higher.
It may be heated to 1200 to 1400 ° C or higher.

Further, in the present invention, in order to prevent the reduced iron from sticking to the hearth in the preliminary reduction furnace, a thin solid reducing agent is first laid thinly on the hearth of the preliminary reduction furnace, and then the thin reducing agent is laid on top of it. To form a bed of a mixture of powdery iron oxide and powdery solid reducing agent with a substantially uniform thickness, or place the plate-shaped molding on a thinly spread powdery solid reducing agent Technology may be adopted.

First, in the present invention, as a smelting furnace, a vertical furnace having a carbonaceous material-filled layer in the furnace is adopted from the viewpoint of ensuring the life of the refractory and ensuring high thermal efficiency and the quality of the hot metal. However, as a result, the life of the refractory becomes longer than that of the smelting furnace adopted in the method of Japanese Patent Publication No. 3-60883 mentioned above.
The thermal efficiency is improved and the S concentration in the hot metal is also reduced. Even when coke is used as the carbonaceous material, the reduced iron obtained by reduction in the preliminary reduction furnace is charged and used at a high temperature, so the coke consumption can be smaller than in the case of the blast furnace.
Furthermore, in order to significantly reduce the amount used, blowing carbon-containing material from the tuyere, and blowing oxygen-containing gas from the furnace side wall above the tuyere of the vertical furnace, CO, H ₂ gas in the furnace It may be burned and the heat of combustion may be used to dissolve the reduced iron.

Further, in the present invention, in order to use the dust generated from the vertical furnace in the system, a method of blowing it from the tuyere of the vertical furnace and a method of using it as a part of the raw material of the preliminary reduction furnace are adopted. Good.

Thus, in the present invention, the agglomeration step and agglomerate drying step employed in the conventional method are omitted,
It is characterized by using a powdery mixture without agglomeration, and because agglomeration equipment and agglomerate drying equipment are not required, it is possible to reduce equipment costs, operating costs and improve thermal efficiency. And is effective in reducing the reduced iron production cost.

Further, in the present invention, reduction of powdery iron oxide is rapidly progressed in the preliminary reduction furnace to produce reduced iron, and in the vertical furnace, high thermal efficiency is achieved without damage to refractory material. The excellent effect of being able to dissolve reduced iron and producing good quality hot metal having a low S concentration is exhibited.

[0024]

As described above, the present invention employs, as basic steps, a mixing step of powdered iron oxide and a solid oxide, and an agglomeration and drying step, as shown in FIG. Without charging, the charging process of charging into the pre-reduction furnace, the pre-reduction process of performing pre-reduction, its discharge process, the pre-reduction of iron
It consists of a melting process and a gas recovery process. Hereinafter, each of these steps will be sequentially described in detail with reference to FIG.

Mixing Step Before reducing the powdery iron oxide, that is, reducing the powdery iron oxide at a high temperature, the powdery iron oxide and the powdery solid reducing agent are mixed in advance. However, depending on the conditions such as the iron oxide to be used and the water content originally contained in the solid reducing agent, when mixing the powdery iron oxide and the powdery solid reducing agent, some water, or one of the binders or Addition of both facilitates uniform and rapid mixing, facilitates formation of a bed of a mixture having a substantially uniform thickness on the rotary hearth, and facilitates molding of plate-shaped moldings It was found that it is effective in preventing the scattering of fine powder from the surface of the mixture.

In FIG. 1, a powdered ore 12, a powdery reducing agent 14, and a binder 16 from a raw material receiving hopper 10 are mixed by a mixer 18. In addition, in order to adjust the basicity of the slag component contained in the obtained reduced iron, lime is added to the mixture.
By adding (quick lime, limestone, etc.), the S concentration contained in the exhaust gas of the preliminary reduction furnace can be reduced. Further, when limestone is used, the decomposition during calcination of limestone is an endothermic reaction, and therefore burning in a preliminary reduction furnace improves the fuel consumption rate in the smelting furnace.

Further, when powdered iron oxide is used, it is not necessary to agglomerate, so that the scale or the like can be used only by coarsely pulverizing, and fine pulverizing is not necessary. Also, Zn
When dust containing such as is used as a raw material, Zn remains in the reduced iron of the product, and there is a concern that the product value will decrease, but in the present invention, a low boiling point metal such as Zn due to the high temperature in the furnace. Evaporates and is discharged out of the furnace together with the exhaust gas, so the residual amount of these low-boiling-point metals in the product reduced iron can be reduced, the product quality can be improved, and it can be collected by the dust collection facility. Since these low-boiling-point metals are concentrated in the dust, it is possible to collect and use them.

Charging Step The mixture thus obtained is charged into the rotary hearth furnace 20 which is heated in the powder state without being agglomerated. 2 to 4 each show a case where the mixture is charged into the rotary hearth furnace 20, respectively. As shown in FIGS. 2 and 3, is it possible to form a bed having a substantially uniform thickness on the hearth? Alternatively, as shown in FIG. 4, the mixture may be formed into a plate shape by a pair of rolls and then placed on the hearth and charged.

Preliminary Reduction Step After charging, as shown in FIG.
The fuel and oxygen-containing gas were blown into the furnace by 22 and this fuel and the volatile matter (VM) generated from the solid reducing agent,
CO gas generated by reducing iron oxide is burned to maintain the temperature in the furnace at 1100 ° C. or higher, and powdered iron oxide is reduced to produce reduced iron.

At this time, as shown in FIG. 2, the floor furnace 22 of the rotary furnace 20 rotates at a constant speed on the rails provided on the lower side by the wheels 26 which are appropriately driven by the driving device 24. The top and bottom of the furnace are sealed with sealing water 28.

Further, in order to prevent reoxidation of the reduced iron during the high temperature reduction, a bed having a substantially uniform thickness of the mixture of the powdery iron oxide and the powdery solid reducing agent was formed on the hearth. It was later confirmed that the bed surface was thinly coated with a powdery solid reducing agent, which was effective in preventing reoxidation of the reduced iron surface observed by the conventional method.

On the other hand, if the bed of the mixture is simply formed, there are many voids in the bed depending on the bed formation conditions, and therefore the bed surface, which is the heat receiving surface from the high temperature atmosphere in the furnace, moves from the bed surface to the deep part (bottom part) of the bed. It was observed that the heat transfer in the bed was delayed and, as a result, the reduction in the deep bed was delayed. Also, combustion gas scatters fine powder on the bed surface,
Some phenomena were also taken out of the furnace with the combustion exhaust gas. To improve this phenomenon, as shown in FIG. 3,
When charging the mixture 30 charged from the charging port 33 onto the trolley 44 forming the hearth in the form of a bed having a substantially uniform thickness,
Using the level 31 which is installed between the over La 32 and spout, divide Hama bed 35 using Hama圧roller 32 and the like, found that increasing the apparent density of the mixture 30 are valid Shi
It was

Further, in order to prevent scattering of fine particles, it is also effective to spray cement milk, which is an aqueous solution of cement, from the nozzle 34 onto the bed surface. FIG. 4 shows another charging mode of the mixture 30 into the rotary hearth furnace 20. The mixture 30 of powdered iron oxide and the solid reducing agent is formed into a plate-shaped product by a roller pair 40 provided in the furnace. The rotary hearth also rotates as the carriage 44 placed in the rotary hearth furnace 20 advances, and the plate-shaped moldings 42 are continuously supplied accordingly. Reference numeral 46 is a heat shield plate,
Reference numeral 48 indicates a support roller.

FIG. 5 shows the shape of the plate-shaped molding 42 at this time. In order to maximize the surface area, in the illustrated example, the surface, that is, the surface opposite to the surface in contact with the hearth. In flute 50
An example of those provided with is shown. Numbers in the figure indicate dimensions (mm).

On the other hand, as another method, in order to increase the rate of temperature rise in the bed and accelerate the rate of reduction, in the present invention, VM generated from the solid reducing agent in the mixture is treated with an oxygen-containing gas as described above. A means of burning and heating on the surface of the mixture was also adopted. When a solid reducing agent such as coal is heated, VM is generated in a gas state, but it is more advantageous to heat the mixture on the bed surface, which is the heat receiving surface, than on burning it after diffusing into the space in the furnace. Is considered to be.

Then, the present inventor confirmed that it is extremely effective to raise the temperature of the mixture by blowing an oxygen-containing gas such as air onto the surface of the mixture after forming the bed or the plate-shaped molding and burning VM on the surface of the mixture. did. The components combusted by the blown oxygen-containing gas include not only VM generated from the solid reducing agent but also CO gas generated when iron oxide is reduced by the solid reducing agent. When the oxygen-containing gas is sprayed on the surface of the mixture, reoxidation of the reduced iron oxide may occur, but in order to prevent this, the oxygen-containing gas is sprayed on the bed surface only during the VM generation period. did. That is, from solid reducing agent to VM
Since the surface of the mixture is covered with VM during the generation of oxygen, oxygen in the blown oxygen-containing gas is preferentially V 2
Since M is consumed for combustion, reoxidation can be prevented. As such an oxygen-containing gas, air or a gas having an oxygen concentration adjusted to be equal to or slightly richer or poorer than the air composition is used.

Further, such an oxygen-containing gas is basically supplied immediately after the formation of the bed or the plate-shaped molded product, but it may be supplied after the occurrence of the VM or the like. Of course, in order to improve the temperature rising rate of the mixture,
It is perfectly acceptable to use the oxygen-containing gas and the fuel at the same time after securing the amount of oxygen required for combustion.

In the present invention, the temperature in the furnace is set to 1100 ° C. or higher, but this temperature is a property that should change depending on the progress of reduction, the properties of the iron oxide and solid reducing agent used, the mixing ratio, and the like. That is, it is advantageous to promote the reduction by keeping the temperature inside the furnace at a high temperature and raising the temperature of the mixture for a short period of time immediately after the raw material is introduced into the furnace, because the temperature of the mixture is low. Since the melting points of the raw ore gangue and coal ash components change, the furnace temperature should be controlled accordingly to prevent melting and flowing out during the reduction process. However, the formation of an appropriate amount of melt in the mixture gives good results in terms of both heat transfer and reaction promotion, so it should be actively utilized.

In the case of using the pellets of the conventional method, when the melt is formed, the pellet strength is lowered, and the plastic deformation is large enough to withstand the handling. It is also one of the advantages of the present invention that there is no need to worry about the deformation.

On the other hand, when reducing a bed-like or plate-like mixture at high temperature, there is a concern that reduced iron may stick to the refractory hearth, but on the hearth of the preliminary reduction furnace,
First, a powdery solid reducing agent is spread thinly, and a bed or plate-shaped molded product of a mixture of powdery iron oxide and powdery solid reducing agent with a substantially uniform thickness is formed on the thin solid reducing agent to fix the solidified reducing agent. Can be prevented.

Discharging Step As described above, when reduction of iron oxide proceeds in the furnace and reduced iron having a predetermined metallization rate can be produced, it is discharged to the outside of the furnace. If the temperature is 1170 ° C or higher, melt may be present in the bed, which may hinder the discharge work.Therefore, the temperature in the bed should be 1170 ° C or lower before discharging to the outside of the furnace. It is desirable to stop the heating.

As a method for keeping the temperature inside the bed at 1170 ° C. or lower in a short time, “a method of spraying a reducing gas at room temperature or an inert gas such as nitrogen on the bed surface”, or a water cooling plate is installed so as to come to the bed surface. A method or the like can be considered, and a method that is easy to carry out may be adopted depending on the type of furnace.

According to the present invention, in the pre-reduction furnace approximately 1100
The reduced iron obtained by reducing at a temperature of ℃ or more is then discharged in a high temperature state and sent to the reduction melting step, but as shown in FIG. 1, this is the exhaust gas provided in the rotary hearth furnace 20. Exit 50
Is continuously discharged from the. If the distance to the vertical furnace 60 is long, it is transported in a closed container (not shown) filled with an inert gas such as nitrogen, but normally,
Since the vertical furnace 60 is installed adjacent to the rotary hearth furnace 20 that is a preliminary reduction furnace, it is shielded from the outside air and filled with an inert gas such as nitrogen or a reducing gas such as exhaust gas from the vertical furnace. The inside of the carrying path is loaded into the vertical furnace by a bucket conveyor or the like.

When the reduced iron is recovered, not only the method of using the plate-shaped molded product but also the method of forming the bed, it is already sintered into a plate-like shape at the end of the preliminary reduction. Therefore, it is possible to lightly roughly crush and then load it into the vertical furnace.

Reduction / Smelting Step As shown in FIG. 1, a smelting furnace used for melting reduced iron has a carbon material packed bed (not shown) in the furnace, and a lump-shaped carbon material from the upper part of the furnace. (Coke, coal, etc.) 62 and limestone 64 are charged, and an oxygen-containing gas is blown from the tuyere 66 installed at the bottom of the furnace to burn the carbonaceous material in front of the tuyere and generate a high-temperature reducing gas. By using No. 60, the above-mentioned reduced iron is charged at a high temperature from the upper part of the furnace to produce hot metal.

As described above, the smelting furnace used in the present invention is the vertical furnace 60 having the carbonaceous material-filled layer in the furnace, and like the blast furnace, the periphery of the combustion zone in front of the tuyere is surrounded by the carbonaceous material. Because
It is possible to prevent the refractory from being directly exposed to high-temperature gas to be melted and damaged, while the smelting furnace adopted in the method of Japanese Patent Publication No. 3-60883 stirs the basin, while the present invention is concerned. In the above smelting furnace, since there is no stirring of the pool, it is extremely effective in extending the life of the refractory.

Further, since the carbonaceous material-filled layer is formed in the furnace, the reducing atmosphere is as strong as that in the blast furnace, so that S in the hot metal can be kept low and high quality hot metal can be produced, and FeO in the slag can be produced. Since the concentration can be maintained as low as that of a blast furnace, it is extremely effective in suppressing the wear of refractory materials. Also in terms of thermal efficiency, since carbonaceous material and reduced iron are charged from the upper part of the furnace, countercurrent heat exchange is performed between gas and solid as in the blast furnace, and high thermal efficiency can be secured. Furthermore, when using coke as a carbonaceous material, blow a carbon-containing substance from the tuyere, and blow an oxygen-containing gas from the side wall of the furnace above the tuyere to burn CO and H ₂ gas in the furnace and burn it. The amount of coke used can be reduced by utilizing the heat to dissolve the reduced iron.

The exhaust dust generated from the vertical furnace 60 may be used in the system. In the illustrated example, it is used as a method of blowing from the tuyere of the vertical furnace 60 and as a part of the raw material of the preliminary reduction furnace. Adopted the method of doing. As a result, it is possible to prevent the generation of dust, sludge, etc. from the process, improve the efficiency of use of raw fuel, and eliminate the need to dispose of dust, etc., which is advantageous in terms of cost and environment.

The exhaust gas 68 generated from the vertical furnace 60 in the gas recovery step may be sent to the lower step as it is, or may be separately used for power generation, but as shown in FIG. It may be used for combustion of the hearth furnace 20. In particular, when introduced for combustion in the rotary hearth furnace 20, the heat utilization rate in the system can be further increased.

As described above, in the present invention, reduction of powdery iron oxide is rapidly progressed in the preliminary reduction furnace to produce reduced iron, and in the vertical furnace, the refractory is damaged. It is possible to produce reduced-quality hot metal by melting reduced iron with high thermal efficiency.

[0051]

EXAMPLES Iron ore, pulverized coal, coke and bentonite having the components and particle size constitutions shown in Tables 1 to 4 were mixed in the ratio shown in Table 5 to prepare a mixed state. next,
As the test equipment, the small test equipment shown in FIG. 1 was used.

That is, the rotary hearth furnace 20 is used as a preliminary reduction furnace.
A vertical furnace 60 is used as a smelting furnace, and is composed of a raw material receiving hopper 10, a mixer 18, a waste heat recovery facility 70, and the like.
The powdered ore 12, the powdery reducing agent 14, which is pulverized coal, and the binder 16, which have been received by the raw material receiving hopper 10, are cut out from the respective hoppers 10 by a predetermined amount and charged into the mixer 18. A small amount of water is added to the mixer 18 to sufficiently mix the raw materials. The mixture is then discharged from the mixer 18 and charged into the rotary hearth furnace 20.

Regarding the method of placing the mixture 30 on the hearth of the rotary hearth furnace 20, a method of forming a bed as shown in FIG. 3 and a method of forming a plate with a pair of rollers as shown in FIG. I tested how to put it afterwards.

In the case of the method of FIG. 3, the mixture 30 is charged into the rotary hearth furnace 20 without agglomeration and the leveler 31
After forming into a bed having a height of about 35 mm, the pressure was applied by the pressure roller 32 until the height became 20 mm. In any case, after the mixture 30 was placed on the hearth, volatile matter in the coal was generated for about 2 minutes, so air was blown onto the bed surface through the burner to accelerate the temperature rise of the bed. The air used in the burner exchanged heat with the exhaust gas from the rotary hearth furnace 20 to preheat the combustion air to about 600 ° C before use. For the temperature in the furnace,
After the generation of VM, the average gas temperature in the inner space of the furnace is about 1300
℃ was made. The target value for the metallization rate of reduced iron was set to 92%.

As shown in FIG. 5, the dimensions when formed into a shape with a large number of vertical grooves were as shown in FIG. The reduced iron reduced in the rotary hearth furnace is discharged at about 1150 ° C, and when it is charged into a bed, it is left as it is, and in the case of a plate-shaped molded product, it is roughly coarsely crushed and then transferred to a vertical furnace. Charged from the top. Coke was charged with limestone from the upper part of the vertical furnace. The amount of limestone was set so that the basicity of slag became 1.25.

In addition to the case of blowing air and oxygen from the tuyere, the case of blowing pulverized coal to reduce the consumption of expensive coke as compared with pulverized coal was also examined. The hot metal is discharged from the tap hole together with the molten slag. Part of the exhaust gas from the vertical furnace was used as fuel for the pre-reduction furnace, and the rest was recovered as fuel for other equipment.

The following 11 cases were set as test cases. Case 1 is an example of using dry pellets containing a conventional powdery solid reducing agent.
Is an example according to the present invention. The results are summarized in Table 6.
First, the reduction time in the preliminary reduction furnace in the test using the conventional dry pellets of Case 1 was 10 minutes.

Next, in Case 2, if the reduction time is about 18 minutes without agglomeration (pelletization), the metallization rate is 92%.
It has been confirmed that it is possible to achieve%. This reduction time can be extremely short compared with the reduction time of about 8 to 10 hours in the shaft furnace type direct reduction method using the reducing gas obtained by reforming ordinary natural gas. Is shown.

Case 3 is an example in which the bed of the raw material mixture was pressed to increase the density. The reduction time was shortened to 15 minutes by this density increasing treatment, and it was confirmed that the pressing effect was great. it can.

The "shortening of the reduction time by pressing the bed" means that the particles of the powder raw material are brought into close contact with each other by the pressing and heat transfer in the bed is promoted, so that the temperature rising rate in the bed is increased. As a result, it is considered that the reduction rate increased. Further, the dust loss ratio was 0.2%, which was lower than the 0.5% in case 2, confirming that the roller packing pressure is also effective in suppressing the scattering of the raw materials.

Case 4 is an example in which an aqueous cement solution was sprayed on the bed surface of the raw material mixture and then subjected to high temperature reduction. In this case, since the temperature rise of the bed is delayed due to the influence of water in comparison with Case 2, the reduction time is as long as 20 minutes, but the ratio of the amount of dust contained in the exhaust gas to the amount charged into the furnace. (Dust loss rate) was 0.5% in Case 2 but decreased to 0.1% in Case 4, confirming that spraying the cement aqueous solution is effective in suppressing the scattering of raw materials.

In Case 5, the surface of the raw material mixture bed was thinly coated with powdery coal and then the high temperature reduction was carried out. As a result, the reduction time was the same as in Case 2. The metallization rate has improved by about 1%,
It was confirmed that the coating with pulverized coal had the effect of preventing reoxidation of the bed surface.

In case 6, after the bed of the raw material mixture was pressed by the pressing roller (compressing roller), air was supplied to the bed surface for about 2 minutes in the furnace, and the flammable volatile components generated from coal were discharged from the bed. Burned on the surface.

As a result, the reduction time was 10 minutes, which was shorter than 15 minutes in Case 3 by 5 minutes, and the combustible volatile components generated from the bed were heated and heated while burning the bed surface. We were able to confirm the advantages of the method.
Further, this result is comparable to the conventional method, Case 1, and the effect can be sufficiently exhibited even if the agglomeration step and the drying step of the conventional method are omitted in the present invention. It is clear that

In case 7, the mixture was molded into a plate and reduced at a high temperature, but since the density is higher than in the case of simply forming a bed, the reduction time is about 15 minutes and case 2 for the same reason as in case 3. It was shortened by 3 minutes compared to.

In Case 8, the test was carried out under the condition that the plate-shaped molded product was placed on the furnace body on which the powdery solid reducing agent was thinly laid, but in other cases, some reduced iron adhered to the furnace floor. However, in Case 8, there was nothing, and the effect of this method was confirmed.

In Case 9, the metallization rate and reduction time are almost the same as those in Case 7 by making the upper surface of the plate-shaped molded product uneven, but the raw material loading amount per unit area of the hearth is about 1.9. Since it doubled, it was confirmed that the productivity could be improved about 1.9 times. This is because even if the raw material loading amount per unit area of the hearth is about 1.9 times, "the heat receiving area increased due to the unevenness on the upper surface of the plate-shaped molded product" It is believed that this is the result of the "improved speed."

In Cases 1 to 9 above, the air was blown at room temperature, the pulverized coal was not blown from the tuyere, and the theoretical combustion temperature before tuyere was 2500 ° C. Charged with reduced iron in a vertical furnace, carbon 4.6
%, And good quality hot metal containing 0.02% of sulfur could be produced. On the other hand, in Cases 10 and 11, the theoretical combustion temperature before the tuyere is 2500
The effects of blast temperature and pulverized coal injection from tuyere were investigated under constant conditions of ℃.

That is, in case 10, the air was heated to about 600 ° C. and blown in the refining furnace. As a result, the oxygen consumption was reduced by 57 Nm ³ / pt compared to Case 7, and
The fuel ratio of the vertical reactor also decreased, and its effect was confirmed. Next, in Case 11, a test was conducted in which pulverized coal was blown from the tuyere. As a result, the fuel ratio slightly increased, but the coke ratio was 107 kg / pt, which was about 1/3 that of other cases, and the effect was confirmed.

[0070]

[Table 1]

[0071]

[Table 2]

[0072]

[Table 4]

[0073]

[Table 6]

[0074]

As described above, according to the present invention, the powdered iron oxide and the powdered solid reducing agent are mixed and then charged into the preliminary reduction furnace without being agglomerated into the pre-reduction furnace. Was manufactured, and the reduced iron was charged into a vertical furnace at a high temperature so that high quality hot metal could be manufactured.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a hot metal production test facility according to the present invention.

FIG. 2 is a cross-sectional view of an example of a rotary hearth furnace used in the present invention.

FIG. 3 is a cross-sectional view of another example of a rotary hearth furnace used in the present invention.

FIG. 4 is a cross-sectional view of still another example of the rotary hearth furnace adopted in the present invention.

FIG. 5 is a perspective view showing an example of the shape of a plate-shaped molded product supplied to the rotary hearth furnace of FIG.

[Explanation of symbols]

18: Mixer, 20: Rotary hearth furnace, 22: Burner 30: Mixture, 42: Plate-shaped molding, 50: Discharge port 60: Vertical furnace

Claims (10)

(57) [Claims] 1. A mixing step of (a) mixing powdery iron oxide and a powdery solid reducing agent to obtain a mixture, and (b) the mixture being in a powdery state without agglomeration,
A charging step of charging into a heated pre-reduction furnace to form a bed having a substantially uniform thickness on the hearth floor, and (c) blowing fuel and oxygen-containing gas into the furnace, Combustible flammable volatile components generated from the solid reducing agent and CO gas generated by reducing iron oxide are maintained so that the temperature in the furnace is 1100 ° C or higher, and the powdered iron oxide is maintained. A preliminary reduction step of reducing the carbon dioxide, (d) a discharge step of discharging the reduced iron obtained in the preliminary reduction step from the preliminary reduction furnace at a temperature of 500 ° C. or higher, and (e) a carbonaceous material in the furnace. It has a packed bed and is charged with lump-grained carbonaceous material from the upper part of the furnace and blows oxygen-containing gas from the tuyere installed at the lower part of the furnace to burn the carbonaceous material in front of the tuyere to generate high-temperature reducing gas. The reduced iron from the discharging process is charged into the vertical furnace from the top of the furnace at a high temperature to reduce and melt the molten iron and the molten iron. A reduction / melting step of extracting from the tap hole at the lower part of the furnace, and (f) a gas recovery step of recovering the product gas of the vertical furnace and introducing a part of it into the preliminary reducing furnace as fuel for preliminary reducing A method for producing hot metal from powdered iron oxide, comprising: 2. A mixing step of (a) mixing powdery iron oxide and a powdery solid reducing agent to obtain a mixture, and (b) the mixture being in a powdery state without agglomeration,
A charging step of forming a plate-shaped molded product on the hearth of the heated pre-reduction furnace, and (c) blowing the fuel and the oxygen-containing gas into the furnace, and then the fuel and the solid reduction. Combustible flammable volatile components generated from the agent and CO gas generated by reducing iron oxide, maintain the temperature in the furnace at 1100 ° C or higher, and reduce the powdered iron oxide. A preliminary reduction step, (d) a discharging step of discharging the reduced iron obtained in the preliminary reduction step from the preliminary reduction furnace at a temperature of 500 ° C. or higher, and (e) a packed bed of carbonaceous material in the furnace. A vertical type that has a lump-shaped carbonaceous material charged from the top of the furnace and blows oxygen-containing gas from the tuyere installed at the bottom of the furnace to burn the carbonaceous material in front of the tuyere to generate high-temperature reducing gas. The reduced iron from the discharging process was charged into the furnace from the upper part of the furnace at high temperature, reduced and melted, and the molten pig iron and slag were tapped at the bottom of the furnace. And a gas recovery step of (f) recovering the product gas of the vertical furnace and introducing a part of it into the preliminary reduction furnace as a fuel for preliminary reduction. A method for producing hot metal from powdered iron oxide. 3. The method for producing hot metal according to claim 1, wherein the surface of the mixture is thinly coated with a powdery solid reducing agent after charging into the preliminary reduction furnace. 4. After forming a bed of the mixture having a substantially uniform thickness on the hearth of the preliminary reduction furnace, or after thinly coating the surface of the bed with a powdery solid reducing agent, the bed is formed. 2. The method for producing hot metal according to claim 1, wherein the apparent density of the mixture is increased by compressing. 5. The hot metal according to claim 4, wherein the bed is formed by adjusting the thickness of the raw material on the hearth before filling with a leveler, and the bed is filled with a pressure roller located downstream of the leveler. Production method. 6. The method for producing hot metal according to claim 2, wherein the surface of the plate-shaped molded article opposite to the surface in contact with the hearth is provided with irregularities. 7. The molding according to claim 2, wherein the surface of the plate-shaped molded product opposite to the surface in contact with the hearth is coated with a powdery solid reducing agent mixed with a binder. Hot metal manufacturing method. 8. A bed of a mixture of powdery iron oxide and a powdery solid reducing agent having a substantially uniform thickness is formed on the hearth of the preliminary reduction furnace, or the bed surface is powdered. 2. The cement aqueous solution or the like is sprayed onto the bed after being thinly coated with the solid reducing agent or after the bed is pressed using a packing roller or the like to increase the apparent density of the mixture. The method for producing hot metal according to 1. 9. When the mixture is heated in the preliminary reduction furnace, an oxygen-containing gas is supplied to the bed surface until the generation of combustible volatile components generated from the solid reducing agent in the mixture is almost completed, and the mixture is combustible. The method for producing hot metal according to claim 1 or 2, wherein the volatile component is burned on the surface, and after the generation of the combustible volatile component is finished, the temperature in the furnace is reduced to 1100 ° C or higher by heating. . 10. The method for producing hot metal according to claim 1, wherein a thin powdery solid reducing agent is first laid on the hearth of the preliminary reduction furnace.