JP6273983B2 - Blast furnace operation method using reduced iron - Google Patents

Description

  The present invention relates to a blast furnace operation method using reduced iron. In particular, it relates to a blast furnace operating method using reduced iron derived from iron-based dust.

  Currently, most of the iron is produced by the blast furnace method. In the blast furnace, iron ore is reduced by a reducing material, and molten pig iron is produced. The raw material charged into the blast furnace is required to have a particle size that can maintain a certain level of strength and ensure air permeability in the furnace. For this reason, the carbon material used as the reducing material depends on coke obtained by blending a large amount of strongly caking coal and dry-distilled, and the iron raw material largely depends on the agglomerated sintered ore. Therefore, it is necessary to install ancillary equipment other than the blast furnace such as coke production equipment and sintering equipment, and the equipment cost is high. Moreover, since high quality is required for the blast furnace raw material, the raw material cost is also high. In addition, in recent years, the depletion of raw materials has progressed, and utilization of inferior raw materials has become a major issue. Furthermore, enormous amounts of energy and carbon materials are consumed inside the blast furnace to reduce iron ore, which is an oxide. As a result, the steel industry accounts for 15-20% of carbon dioxide emissions in Japan.

  Under these circumstances, it has been studied to promote the utilization of inferior raw materials in blast furnaces, reduce the ratio of reducing materials and reduce carbon dioxide emissions by producing reduced iron from relatively cheap ores and using it as blast furnace raw materials. . The production of reduced iron continues to expand against the background that the plant is inexpensive, easy to operate, and can be located even on a small scale.

  It has been disclosed that by introducing reduced iron containing 79% by mass of metallic iron into a blast furnace, the reducing material ratio in the blast furnace is reduced and productivity is improved (Non-Patent Document 1).

  As reduced iron, reduced iron produced from iron ore as a raw material (hereinafter referred to as reduced iron derived from iron ore) is generally used, but iron generated in blast furnaces, converters, electric furnaces, etc. There is also reduced iron (hereinafter referred to as reduced iron derived from iron-based dust) that is produced using the system dust as a raw material. From the viewpoint of using inexpensive inferior raw materials, it can be said that producing reduced iron from iron-based dust and utilizing it is an effective means. However, reduced iron derived from iron-based dust and reduced iron derived from iron ore are greatly different in properties, and it is considered that the effect of use on a blast furnace is different.

Use reduced iron powder obtained by reducing and roasting zinc-containing iron-based dust using a rotary hearth furnace or rotary kiln, then cold-molding, and then water immersion and stationary treatment to use the blast furnace The production of high-strength briquettes that can be performed has been proposed (Patent Document 1).
The iron-based dust-derived reduced iron described in the Examples of Patent Document 1 has a total iron content of 57.4% by mass and metal iron of 33.9% by mass. 1% by mass, SiO ₂ is 6.5% by mass, Al ₂ O ₃ is 2.9% by mass, and MgO is 3.3% by mass. (CaO + SiO ₂ + Al ₂ O ₃ + MgO) / T. The ratio of Fe (hereinafter referred to as gangue ratio) is 0.47, which is larger than the gangue ratio of reduced iron derived from iron ore. Moreover, since the dust generated in the steel making process is contained in the reduced iron raw material, the CaO concentration in the reduced iron is high, and the basicity (= CaO / SiO ₂ ) of the reduced iron to be generated is 2.17, which is general. It is a large value compared to sintered ore or block ore, which is a blast furnace raw material.

  As described above, reduced iron derived from iron-based dust having a high gangue ratio and extremely high basicity and reduced iron derived from iron ore have different effects in use in a blast furnace. There is a concern that reduced iron derived from iron-based dust significantly changes the properties of the slag to be produced and deteriorates the high-temperature air permeability at the bottom of the blast furnace.

The hot briquette iron produced by reducing iron oxide in a rotary hearth type reduction furnace and hot forming it is located within 2/3 in the radial direction from the center of the furnace inside the outer circle when the blast furnace is viewed from above. In addition, it has been proposed that 65% or more of reduced iron compacts be charged (Patent Document 2).
When a large amount of reduced iron compact is put on the outer peripheral side of the blast furnace, the reduced iron compact is reduced and melted faster than ore or the like, so that the rate of descent of the packing at the outer peripheral portion increases. As a result, there is a problem that the ore of the outer peripheral portion that is slow to reduce reaches the lower part of the furnace without being reduced and the lower part of the furnace is supercooled. On the other hand, if a large amount of reduced iron compact is supplied to the furnace center, reduced powdering of the reduced iron compact is suppressed, and gas pressure loss in the packing can be reduced. Moreover, the fall of a filling is accelerated | stimulated with the increase in the fall speed of a reduced iron molded object. Thereby, the gas flow in the center part is promoted, the amount of blown air can be increased, and pig iron productivity (production t / d) in the blast furnace can be improved.

  However, when reduced iron derived from iron-based dust having a high slag ratio and basicity described in Patent Document 1 is introduced into the blast furnace by the method disclosed in Patent Document 2, high-temperature ventilation is deteriorated near the center. Can be considered.

Using iron oxide as a raw material, a reduced iron pellet having high crushing strength is produced in a rotary hearth type reducing furnace, and a method for producing pig iron is provided in which this pellet is directly used in a blast furnace (Patent Documents 3 and 4).
In Patent Document 3, in order to dissolve and remove solid solution impurities such as slag products, sulfur, and phosphorus from the reduced iron pellets, it is desirable to mix with other blast furnace raw materials and use them in a steelmaking blast furnace. Yes. On the other hand, in patent document 4, the lump ore, the sintered ore, etc. are raised as a raw material to mix. This suppresses deterioration of gas ventilation inside the blast furnace when reducing iron particles having a relatively small particle size of 5 to 20 mm are introduced. That is, according to Patent Document 3 and Patent Document 4, there is a problem in using reduced iron alone or in a large amount in a blast furnace, and the problem is caused by using the reduced iron mixed with other raw materials in a blast furnace. It has been suggested that it can be mitigated.

  However, depending on the combination of raw materials to be mixed with reduced iron, it is conceivable that the high temperature air permeability in the blast furnace is deteriorated. For example, when reduced iron derived from iron-based dust described in Patent Document 1 is mixed with sintered ore and charged into a blast furnace, the slag ratio after mixing becomes larger than that when charged simply as a sintered ore. . Sintered ore is artificially designed with components such as basicity so that the properties in the blast furnace are optimized. Therefore, the mixture of reduced iron derived from iron-based dust and sintered ore, which has a large gangue ratio such as that targeted in Patent Document 1 and may affect the slag properties, is a high-temperature breathing property of the slag to be produced. There is a concern that the sinter is worsened than the sinter ore.

JP 2011-63835 A JP 2010-255075 A JP 2002-194410 A JP 2002-194212 A

Yutaka Ujisawa et al., CAMP-ISIJ, 22 (2009), p.282

Reduced iron produced by heating, reducing, and molding iron-based dust has a high gangue ratio ((CaO + SiO ₂ + Al ₂ O ₃ + MgO) / Fe), and also has a high basicity (CaO / SiO ₂ ). If this is used in a blast furnace as it is, there is a problem that the high temperature ventilation resistance is increased due to an increase in softening / fusion temperature and a decrease in fluidity of slag.

  An object of the present invention is to provide a blast furnace operating method using reduced iron that does not increase high-temperature ventilation resistance even when reduced iron derived from iron-based dust is used.

  The present inventor has obtained knowledge that blast furnace operation in which high-temperature ventilation resistance does not increase is possible by mixing reduced iron derived from iron-based dust and acidic block ore in advance and charging the blast furnace. The present invention is based on such knowledge.

The gist of the present invention is as follows.
(1) Reduced iron produced by heating, reducing and molding iron-based dust,
The reduced iron has an iron content of 50.0% by mass or more, a gangue ratio ((CaO + SiO ₂ + Al ₂ O ₃ + MgO) / Fe) of 0.30 to 0.60 in terms of mass ratio , basicity (CaO / SiO _2). ) Is 2.0 or more by mass ratio ,
The reduced iron and acidic lump ore are mixed, the iron content is 50.0% by mass or more, the gangue ratio ((CaO + SiO ₂ + Al ₂ O ₃ + MgO) / Fe) is 0.32 or less by mass ratio, and the basicity (CaO / SiO ₂ ) is prepared by adjusting the mass ratio to 1.0 or more and 2.0 or less,
A method for operating a blast furnace, comprising charging the mixture into a blast furnace.
(2) Cut out from each tank of reduced iron and acidic lump ore treated by static curing to the same transport belt, mix on the belt, put into the ore hopper, and mix the cured reduced iron and acidic lump ore The blast furnace operating method according to claim 1, wherein the blast furnace operating method is prepared.
(3) In stationary curing in the manufacturing process of reduced iron,
The acidic lump ore is loaded on the molded reduced iron after water immersion loaded on the transport belt and put into a stationary curing tank to create a mixture of reduced iron and acidic lump ore (1 ) Blast furnace operation method.
(4) wherein the acidic lump ore, high Romisao industry method according to, characterized in that a lobe River lump ore (1) to (3).

  By blending reduced iron derived from iron-based dust and acidic lump ore in advance and charging it into the blast furnace, it is possible to operate the blast furnace without increasing the high-temperature ventilation resistance.

The figure which shows the blast furnace operating method (embodiment 1) using the reduced iron derived from an iron-type dust. The figure which shows the shaping | molding process of the reduced iron derived from an iron-type dust. The figure which shows the blast furnace operating method (embodiment 2) using the reduced iron derived from an iron-type dust.

(First embodiment)
FIG. 1 shows a blast furnace operating method (embodiment 1) using reduced iron derived from iron-based dust.
Reduced iron is produced by reducing reduced iron raw material 12 (iron-based dust, charcoal) in a reduction furnace 11 to produce reduced iron.
As iron-based dust, in addition to dust collected in a blast furnace and a steelmaking process, powder containing iron such as oxide scale and oxidized sludge is also included.
Examples of the reducing furnace 11 include a rotary kiln furnace and a rotary hearth type reducing furnace.
The reduced iron produced in the reduction furnace 11 is sieved by a sieve classification device 16 and classified into a sieved product and a sieved product. The coarse granular reduced iron 13 on the sieve is conveyed to the reduced iron tank 37.

  On the other hand, the powdered reduced iron 2 under the sieve is supplied to the mixer 18 and mixed with an additive 17 such as water or a binder, and then introduced into a double roll briquette molding machine 19 to mold the reduced iron briquette. .

  Examples of the inorganic binder include aging binders composed of fine powder mainly composed of blast furnace granulated slag and an alkali stimulant, Portland cement, alumina cement, blast furnace cement, bentonite, fly ash, clay, and the like. Moreover, metallic iron contained in iron-based dust also functions as a binder. Examples of the organic binder include starch, molasses, tar, pulp waste liquid, and plastic. However, there are concerns that the binder is expensive and that the components contained in the binder hinder blast furnace operation. Therefore, as described later, the strength of the reduced iron briquette should be improved by water immersion treatment and stationary curing treatment, and the amount of binder to be added should be reduced as much as possible. Preferably it is not added.

FIG. 2 shows a reduced iron briquette molding machine. A double roll briquette molding machine 19 is schematically shown. The double roll briquette molding machine 19 has a structure in which two cylindrical rolls 4 are disposed horizontally adjacent to each other. Of the rolls 4, the left forming roll in the figure rotates clockwise, and the right forming roll rotates counterclockwise, and there are many holes called pockets 5 on the outer peripheral surfaces of both rolls. The pocket 5 is arranged so as to be synchronized on the circumferential surface between both rolls. A raw material supply hopper 1 is installed above a portion where both rolls 4 are adjacent to each other, and the granular reduced iron 2 as a briquette raw material is supplied from the raw material supply hopper 1. The granular reduced iron 2 supplied between the rolls enters the pocket 5 and is compressed while receiving a strong shearing force due to a frictional force with the surface of the pocket 5. Inside the pocket 5, the reduced iron particles slide with each other, change positions, fill the gaps, and entangle with each other to produce a reduced structure iron briquette 6 a having a dense structure. Here, the reduced iron briquette refers to reduced iron molded by a molding machine, and is different from the coarse granular reduced iron 13 discharged from the reduction furnace 11.
Powdered reduced iron 2 is not simply supplied between the rolls by natural fall, but is forced into the interior of the pocket 5 by the screw 3 installed in the raw material supply hopper-1, thereby increasing the packing density. It is set as reduced iron briquette 6a having high strength.

  The reduced iron briquette manufactured by the double roll briquette molding machine 19 is classified into reduced iron briquettes on the sieve and granular reduced iron 6b under the sieve by the sieve classification device 20 shown in FIG. The sieving and classifying device 20 is a cylindrical part that is provided with a mesh for classifying the sieved and unsieved articles on the outer peripheral part, and is rotated at a constant speed with the shafts slightly inclined from the horizontal with the centers at both ends as axes. It is desirable to employ a trommel type sieve classifier equipped with By placing the reduced iron briquette in the cylinder of this classifier, the granular reduced iron 6b under the sieve passes through the meshes (screen), so that the reduced iron briquette and the granular reduced iron 6b can be separated. . At this time, the reduced iron briquette rolls in a rotating trommel type sieve classifier, and burrs on the outer periphery of the briquette are removed. Since the burr causes wear of the belt of the belt conveyor when the briquette is transported to the blast furnace, the use of this trommel type sieving classifier is also effective from the viewpoint of maintenance management of the conveyor belt conveyor. The sieved granular reduced iron 6 b is returned to the mixer 18.

  The reduced iron briquette on the sieve of the sieve classification device 20 is subjected to a water immersion treatment in which water is arranged on the entire surface of the briquette with the briquette water immersion treatment device 21 and then subjected to a stationary treatment with the briquette stationary treatment device 22. By water immersion and standing treatment, the oxidized iron of the metallic iron contained in the reduced iron briquette progresses and develops strength, and a high-strength briquette that can be used in a blast furnace with little or no binder can be obtained. The reduced iron briquette 6 (6a, 6c) subjected to the stationary treatment is returned to the sieve classifier 16 and classified into the reduced iron briquette 6a and the granular reduced iron 6c. The reduced iron briquette 6a is combined with the coarse reduced iron 13 It is conveyed to the reduced iron tank 37.

  As a briquetting method of reduced iron, there is a method (Japanese Patent No. 5059379, Japanese Patent Laid-Open No. 2000-204419) in which reduced iron discharged from the reduction furnace 11 is hot molded at a high temperature. In this case, the briquette water immersion treatment device 21 and the briquette stationary treatment device 22 are unnecessary.

On the other hand, the acidic massive ore 25 is conveyed to the acidic massive ore tank 38. Reduced iron (13, 6a) and acidic lump ore 25 are cut out from each tank into the same transport belt 24 and mixed on the belt. The reduced iron (13, 6a) and the acidic block ore 25 are mixed uniformly and driven into the ore surge hopper 29.
In addition, sintered ore and other iron ores cut out from the sintered ore and other iron ore tanks 39 are also driven into the ore surge hopper 29. Other iron ores refer to iron ores that are not mixed with reduced iron. The coke cut out from the coke tank 40 is driven into the coke surge hopper 30.
The mixture of reduced iron and acidic lump ore, sintered ore, other iron ores, and coke that have been driven into each surge hopper are charged into the blast furnace 15 via a storage hopper 33, a collecting hopper 34, and a swivel chute 35. The

The charging method to the blast furnace is described.
As for the charging method of the bell-less blast furnace, for example, coke (hereinafter referred to as C) is charged in two batches of C ₁ and C ₂ , and ore (hereinafter referred to as O) is It is charged in two batches of O ₁ and O ₂ . The charging of C ₁ , C ₂ , O ₁ and O ₂ is referred to as 1 charge.
In the first embodiment, one batch of one charge is a mixture of reduced iron and acidic block ore, whereas one batch of conventional methods of using reduced iron includes reduced iron and sintered ore, etc. It is different in that it is a mixture.

In the conventional charging method, reduced iron and sintered ore are mixed and charged into at least one of O ₁ and O ₂ batches. In this case, even if the reduced iron particles and the sintered ore particles having greatly different gangue ratio and basicity are close to each other, the gangue ratio and basicity between the particles are not adjusted. In contrast, in the first embodiment, since reduced iron and acidic lump ore are mixed and charged as one batch, the gangue ratio and base between the particles of reduced iron and acidic lump ore that are in contact with each other The degree is adjusted and the effects of the present invention are achieved.
In the case of the conventional method in which 10% of the reduced raw material is charged into the blast furnace, reduced iron and sintered ore are charged for each charge. On the other hand, in the first embodiment, for example, when reducing iron and acidic lump ore are mixed at a ratio of 5/5, the batch of reduced iron and acidic lump ore is charged at a rate of once per 5 charges. Entered.

  The target reduced iron exhibits a greater effect when mixed with a porous high crystal water ore containing 3% or more of crystal water, such as lobe river block ore. Porous high crystal hydroacid ore is inexpensive and can be drastically reduced in pig iron cost when used in large quantities. However, there is a concern that porous high crystal hydroacid ore has a large amount of pulverization at the blast furnace shaft portion, which causes poor ventilation and prevents stable operation.

On the other hand, reduced iron is a raw material that is difficult to powder in the blast furnace shaft portion. Since it has already been reduced, the content of Fe ₂ O ₃ is extremely small, and reduction powdering that occurs when Fe ₂ O ₃ is reduced to Fe ₃ O ₄ does not occur. Moreover, since metal iron is firmly bonded in the briquette, thermal cracking does not occur. Therefore, when mixed with porous high-crystal water acidic ore and put into the blast furnace, even if the porous high-crystal water ore is pulverized in the blast furnace shaft, the reduced iron maintains its shape and becomes an aggregate, Maintain the gas flow in the shaft. That is, even when using porous high crystal water ore that is pulverized at the blast furnace shaft, such as lobe river lump ore, reducing gas can be maintained by arranging reduced iron around it. it can. The uneven flow of the reducing gas is also suppressed, and the reduction of the ore proceeds in a nearly uniform state.

In addition, the size of the reduced iron briquette 6a is extremely important from the viewpoint of promoting the mixing of the reduced iron (6a, 13) and the acidic block ore 25. In general, a raw material with a higher density and a smaller particle size is more likely to accumulate in the lower layer of the mixture. Therefore, the apparent density and particle size of the reduced iron briquette 6a should be determined in consideration of the apparent density and particle size of the acidic massive ore 25 to be mixed. However, it is difficult to adjust the apparent density. This is because the blast furnace raw material needs strength, and in order to produce high strength reduced iron briquette 6a, it is essential to use briquette with a large apparent density. That is, the apparent density of the reduced iron briquette 6a needs to be increased as much as possible. Then, the particle size of the reduced iron briquette 6a is determined so that the mixing with the acidic massive ore 25 is promoted. The particle diameter of the reduced iron briquette 6a can be easily controlled by adjusting the size and shape of the pocket 5 of the briquette machine shown in FIG. The average particle diameter Db of the reduced iron briquette 6a is preferably determined from the following equation (1). Here, ρb is the apparent density of the reduced iron briquette 6 a, ρo is the apparent density of the acidic massive ore, and Do is the average particle size of the acidic massive ore 25.
Db = Do × (0.21 × ρb / ρo + 0.76) (1)

Actually, the size and shape of the pocket 5 of the double roll briquette molding machine shown in FIG. 2 are adjusted so that the average particle diameter is in the range of plus or minus 20% of the average particle diameter Db obtained by this formula. . Therefore, it is realistic to adjust so that Db / Do is in a range satisfying the expression (2).
(0.17 × ρb / ρo + 0.61) ≦ Db / Do ≦ (0.25 × ρb / ρo + 0.91) (2)

As the reduction furnace 11, there are a rotary kiln and a rotary hearth type reduction furnace, but most of the reduced iron discharged from the reduction furnace 11 such as a rotary kiln is granular. For this reason, most of the reduced iron is transported to the blast furnace after determining an appropriate particle size based on the formula (2) and briquetting. Some of the reduced iron is discharged from the rotary kiln as coarse granular reduced iron 13, but it is difficult to adjust the apparent density and particle size. However, if the amount discharged as the coarse granular reduced iron 13 is reduced, the influence on the mixing is small, and there is no problem. The coarse granular reduced iron 13 can be pulverized, briquetted, and conveyed to the blast furnace 15 as reduced iron briquette 6a.
In a rotary hearth type reduction furnace, dust raw materials are agglomerated in advance into pellets, briquettes, etc., and put into a rotary hearth type reduction furnace to produce reduced iron pellets and reduced iron briquettes with high crushing strength. In this case, reduced iron pellets or reduced iron briquettes are discharged as coarse granular reduced iron 13. Adjust the particle size of pellets and briquettes to be fed into the rotary hearth reducing furnace so that the average particle size of the reduced iron pellets and reduced iron briquettes discharged from the rotary hearth reducing furnace satisfies the formula (2). And mixing with the acidic massive ore 25 is promoted. Further, in the rotary hearth type reducing furnace, powdered reduced iron is also discharged, and the particle size of the reduced iron briquette produced therefrom can be determined based on the equation (2).

(Second embodiment)
FIG. 3 shows a blast furnace operating method (embodiment 2) using reduced iron derived from iron-based dust.
In the present embodiment, in the stationary curing in the production process of reduced iron, the acidic lump ore 25 is loaded on the shaped reduced iron after the water immersion process loaded on the transport belt 24 and is put into the briquette stationary treatment apparatus 22. And a mixture of reduced iron and acidic lump ore cured in the briquette stationary treatment apparatus 22.

In the first embodiment, after the briquette is formed cold by the double roll briquette molding machine 19, the briquette is immersed in water by the briquette water immersion treatment device 21 and cured by the briquette stationary treatment device 22. To express. That is, the reduced iron briquette 6a manufactured in the cold state does not have sufficient strength in that state, but the reduced iron briquette between the reduced iron briquettes constituting the reduced iron briquette by performing a water immersion treatment and a stationary treatment. Strengthens the bond, resulting in a strong briquette.
The briquette stationary treatment device 22 is preferably a hopper because the installation space can be reduced. A briquette packed bed is formed in a wet state in the hopper, and oxygen and carbon dioxide gas such as factory exhaust gas and air are formed from the bottom of the hopper. Blowing in a gas containing, to develop strength.

However, inside the briquette stationary processing apparatus 22, there is a problem that the reduced iron briquettes 6a adhere to each other and become a large lump (metal iron is fixed when oxidized). Water is disposed on the surface of the reduced iron briquette 6a, and when a long time has passed in this state, iron hydroxide is formed at the contact point of the briquette. As a result, briquettes are bonded together, and further dehydration and oxidation proceed, thereby strengthening the bonding. Eventually, a plurality of briquettes adhere to form a large lump. If a large lump is formed in the inside of the briquette stationary processing apparatus 22, it will become an obstacle in cutting out from the briquette stationary processing apparatus 22 and transporting to the blast furnace.
Therefore, in the second embodiment, reduced iron briquette and acidic lump ore are mixed and cured in the briquette stationary treatment apparatus 22 from the viewpoint of sticking suppression. In short, by reducing the contact between the reduced iron briquettes as much as possible, sticking in the briquette stationary processing apparatus 22 can be suppressed. By simultaneously charging the briquette stationary treatment apparatus 22, a mixed state of the acidic block ore 25 and the reduced iron briquette 6a is created.

  Inside the briquette stationary treatment apparatus 22, a mixture of the acidic block ore 25 and the reduced iron briquette 6a forms a packed bed. From the bottom of the packed bed, air, factory combustion exhaust gas, etc. necessary for developing the strength of the reduced iron briquette 6a. Is supplied. As the strength expression of the reduced iron briquette 6a progresses, the reduced iron briquette 6a and the acidic block ore 25 move to the lower part and are finally discharged from the lower part of the briquette stationary treatment apparatus 22.

Specifically, the acidic lump ore 25 cut out from the acidic lump ore tank 38 is placed on the reduced iron briquette 6a transported by the transport belt 24, and the reduced iron briquette 6a and the acidic lump ore 25 are placed. Blend and feed into the briquette stationary processing device 22. The control of the mixing ratio of the reduced iron briquette 6a and the acidic lump ore 25 corresponds to the mass of the reduced iron briquette 6a weighed by the weighing machine (belt scale) 41 installed on the transport belt of the reduced iron briquette 6a. The mass of the acidic massive ore 25 cut out from 38 is controlled. The cured reduced iron briquette 6a and the acidic lump ore 25 discharged from the briquette stationary processing device 22 are further mixed with the coarse granular reduced iron 13 and driven into the ore surge hopper 29.
Through the above operation, the reduced iron briquettes can be charged into the blast furnace without sticking.

(Manufacture of reduced iron)
A reduced iron powder obtained by subjecting a raw material obtained by mixing carbonaceous material to granular iron-based dust containing about 6.0% by mass of a zinc component to reduction roasting treatment in a rotary kiln and cooling to room temperature was used. . After this reduced iron powder was briquetted at room temperature, a crushing strength per briquette was set to 1470 N or more by performing a water immersion treatment and a stationary treatment as described in Patent Document 1.
Table 1 shows the component analysis values of the produced reduced iron briquettes. 32.6% by mass of metallic iron is contained. Further, the gangue ratio ((CaO + SiO ₂ + Al ₂ O ₃ + MgO) / Fe) was 0.472, and the basicity (CaO / SiO ₂ ) was 2.9.

(High temperature load softening dripping experiment)
In order to grasp the high-temperature air permeability in the blast furnace, a mixture of acidic block ore and reduced iron briquette was filled into a reaction tube as a sample, and a high temperature load softening dripping experiment was conducted.
This reduced iron briquette was mixed with a lobe river (acidic block ore) or sintered ore in a reaction tube having an inner diameter of 70 mm, and a load softening test was performed. The particle sizes of the reduced iron briquette, lobe river and sintered ore were 15 to 19 mm. Table 1 shows the component analysis values of the robbribber and the sintered ore. The gangue ratio ((CaO + SiO ₂ + Al ₂ O ₃ + MgO) / Fe) of the low bribber is 0.108, which is smaller than that of the reduced iron briquette. The basicity is 0.02 acidic lump ore. The crystal water contained in the lobe river lump used was 9% by mass. On the other hand, the gangue ratio of the sintered ore was 0.272, and the basicity was 1.7. These do not contain metallic iron.

The reaction tube filled with the sample was set in an electric furnace and heated up until the sample temperature reached 1873K. The heating rate was 5 K / min from normal temperature to 993 K, 3.5 K / min from 993 to 1323 K, and 4 K / min from 1323 to 1873 K. Meanwhile, a constant load of 1 kg / cm ² was applied to the sample from the top, and the pressure loss in the packed bed was continuously measured. Further, during the temperature increase of the sample, a reducing gas was supplied from the bottom of the packed bed. The reducing gas was a mixed gas of CO, CO ₂ and N ₂ , and each flow rate was changed depending on the sample temperature. When the sample temperature was from room temperature to 573 K, only N ₂ gas was flowed at 5 NL / min. In the range of 573 to 973K, a mixed gas of 8 NL / min for CO gas, 5 NL / min for CO ₂ gas, and 17 NL / min for N ₂ gas was circulated.
In the range from 973 to 1173K, the mixed gas was 10 NL / min for CO gas, 3 NL / min for CO ₂ gas, and 17 NL / min for N ₂ gas. In the range of 1173 to 1473K, a mixed gas of 12 NL / min for CO gas, 1 NL / min for CO ₂ gas, and 17 NL / min for N 2 gas was used. In the range of 1473 to 1873K, a mixed gas of 13 NL / min for CO gas, 0 NL / min for CO ₂ gas, and 17 NL / min for N ₂ gas was used. This condition was the same in any experiment where the mixing ratio of the sample was changed.

In the high temperature load softening dripping experiment, displacement due to softening shrinkage of the packed bed and pressure loss were continuously measured, and a high temperature ventilation resistance index KS from 573K to 1873K was calculated and evaluated. The high-temperature ventilation resistance index KS is a value obtained by integrating the high-temperature ventilation resistance per packed bed height with temperature, and is expressed by the following formula (3). The higher this value, the worse the air permeability. To do. In equation (3), ΔP is the pressure loss (N / m ² ) in the packed bed, H is the packed bed height (m), ρg is the gas density (kg / m ³ ), and μg is the gas viscosity (kg / M / sec), ug is the gas flow rate (m / s).

(Test results)
The test results are summarized in Table 2.
<Comparative Example 1>
The comparative example 1 shows the test result in the sinter simple. The test sample had a gangue ratio of 0.272, a basicity of 1.7, and a high temperature ventilation resistance index KS value of 1967 × 10 ⁵ .
<Comparative example 2>
Comparative Example 2 shows the results of testing with reduced iron briquette. The test sample had a gangue ratio of 0.472 and a basicity of 2.9. Although 32.6 mass% of metallic iron was contained, the KS value at this time was 4,483 × 10 ⁵ , which was larger than the value of the sintered ore alone. This is due to the extremely high gangue ratio and basicity compared to sintered ore.

<Comparative Example 3>
Comparative Example 3 shows the results of testing with a simple lobe river. The gangue ratio of the test sample was 0.108, but the high temperature ventilation resistance index KS value was 6,172 × 10 ⁵ , which was a higher value than the value for the sintered ore. This is because the basicity is as extremely low as 0.02 and the viscosity of the molten slag to be produced is high.

<Example 1>
Example 1 is a case in which lobe river and reduced iron briquette are mixed so that the weight ratio is 3/1. The gangue ratio at this time is 0.201, which is larger than that of the lobe river, but the high-temperature ventilation resistance index KS is 1,959 × 10 ^5, and the conventional blast furnace raw material lobe river and sintered ore are tested in plain It was lower than when I did it. This is because the viscosity of the molten slag produced when the basicity after mixing becomes 1.0 is lowered.

<Example 2>
Example 2 is a case in which lobe river and reduced iron briquette are mixed at a weight ratio of 1/1. The gangue ratio at this time is 0.293, but the basicity after mixing is 1.7, so the viscosity of the molten slag to be generated is lowered. Furthermore, metallic iron may increase to 16.3% by mass, and the high temperature ventilation resistance index KS decreased to 1,116 × 10 ⁵ .

<Comparative Example 4>
Reduced iron briquettes were mixed with sintered ore. The basicity of the mixed sample is 1.9 and the gangue ratio is 0.313. The high-temperature ventilation resistance index KS value was 2,051 × 10 ⁵ , which was slightly increased as compared with the case of testing with a simple sinter ore.

<Summary>
In the case of simple use of reduced iron derived from iron-based dust (Comparative Example 2) and acidic block ore (Comparative Example 3), the high temperature ventilation resistance index (KS value) is very large. Reduced iron derived from iron-based dust and acidic lump ore are mixed, and the gangue ratio is adjusted to 0.32 or less, and the basicity (CaO / SiO ₂ ) is adjusted to 1.0 or more and 2.0 or less, thereby providing a high temperature ventilation resistance index. (KS value) was greatly reduced.
In this case, the high-temperature ventilation resistance index (KS value) is lower than in the case of simple use of sinter (Comparative Example 1) and in the case of mixing of sinter and reduced iron derived from iron-based dust (Comparative Example 4). did.

  Even if reduced iron derived from iron-based dust is used, it can be used for blast furnace operation using reduced iron that does not increase the high-temperature ventilation resistance.

  1: Raw material supply hopper, 2: Powdered reduced iron, 3: Screw, 4: Roll, 5: Pocket, 6a: Reduced iron briquette, 6b: Powdered reduced iron (after briquetting), 6c: Powdered reduced iron ( After standing), 11: reducing furnace, 12: reducing furnace raw material, 13: coarse granular reduced iron, 15: blast furnace, 16: sieve classification device, 17: additive (water, binder), 18: mixer, 19: Double roll type briquette molding machine, 20: sieve classification device, 21: briquette immersion treatment device (water tank), 22: briquette stationary treatment device, 24: transport belt, 25: acidic block ore, 29: ore surge hopper 30: Coke surge hopper, 33: Storage hopper, 34: Collecting hopper, 35: Swivel chute, 37: Reduced iron tank, 38: Acid lump ore tank, 39: Sintered or other iron ore tank, 40: Co Box bath, 41: weighing device (belt scale).

Claims (4)

Reduced iron manufactured by heating, reducing and molding iron-based dust,
The reduced iron has an iron content of 50.0% by mass or more, a gangue ratio ((CaO + SiO ₂ + Al ₂ O ₃ + MgO) / Fe) of 0.30 to 0.60 in terms of mass ratio , basicity (CaO / SiO _2). ) Is 2.0 or more by mass ratio ,
The reduced iron and acidic lump ore are mixed, the iron content is 50.0% by mass or more, the gangue ratio ((CaO + SiO ₂ + Al ₂ O ₃ + MgO) / Fe) is 0.32 or less by mass ratio, and the basicity (CaO / SiO ₂ ) is prepared by adjusting the mass ratio to 1.0 or more and 2.0 or less,
A method for operating a blast furnace, comprising charging the mixture into a blast furnace.   Cut out from each tank of reduced-cured iron and acidic lump ore after static curing to the same transport belt, mix on the belt, and put into ore hopper to make a mixture of cured reduced iron and acidic lump ore The blast furnace operating method according to claim 1, wherein: In static curing in the manufacturing process of reduced iron,
The acidic lump ore is loaded on the reduced iron after water immersion treatment loaded on a transport belt, and is put into a stationary curing tank to create a mixture of reduced iron and acidic lump ore. The blast furnace operating method according to 1.   The blast furnace operating method according to any one of claims 1 to 3, wherein the acidic block ore is a lobe river block ore.

Images