JP6219266B2 - Blast furnace metallic raw material charging method - Google Patents

Description

  The present invention relates to a metallic raw material charging method for a blast furnace in which a metallic raw material is charged into a blast furnace (a vertical metallurgical furnace).

Conventionally, in a blast furnace (vertical metallurgical furnace), raw materials such as pellets, sintered ore, lump ore, coke and limestone and reducing materials are charged in layers from the top, and hot air is blown from the bottom to iron ore. A series of reactions, such as reduction and dissolution, are performed to produce pig iron. There exist some which are shown by patent documents 1-5 as a technique of operation of a blast furnace.
Patent Document 1 aims to ensure the ventilation and liquid permeability of the core coke and to maintain a high temperature without causing deterioration in gas utilization efficiency and excessive rise in the furnace top gas temperature. In this Patent Document 1, when operating a blast furnace by repeatedly charging coke and charging an iron source material, a part of the iron source material of each charge is changed from an iron oxide source to a metal iron source. Prior to both normal coke charging and iron source material charging or both, the central charge is charged at the center, and a portion of each charge charging coke is charged with normal coke charging or iron source material. Prior to the charging, or both of the above, the central portion of the coke is centrally charged, and the distance from the surface level of the top layer of the charge on the furnace center axis to the vertical downward direction is 1 m to 5 m. A hydrocarbon-based gas and / or liquid is blown into the layer.

  In Patent Document 2, the core coke temperature decreased by selecting an iron source material (metallic iron material) other than the iron oxide material charged in the high center part is recovered more quickly, stabilizing operation and production. The purpose is to ensure sex. In Patent Document 2, a part of the iron oxide raw material charged into the blast furnace is replaced with a metal iron raw material having a carbon content of 2.5% by weight or more, and this is replaced with a furnace prior to charging the remaining iron oxide raw material. The center of the furnace is charged and part of the coke to be charged is charged mainly in the center of the furnace.

  Patent Document 3 aims to quickly raise the lowered core coke temperature and recover the furnace condition in a short time. In Patent Document 3, a part of the iron source material charged in the blast furnace is replaced with iron-based scrap or / and reduced iron, and this is charged into the center of the furnace prior to charging the remaining iron source material. A part of the coke to be charged is charged mainly in the center of the furnace.

Patent Document 4 aims to suppress wear of the blast furnace bottom brick and extend the life of the furnace, and when coke and iron source material are alternately charged into the furnace from the top of the blast furnace furnace, coke charging is performed. Prior to charging the iron source material, coke or alternative lumps, or reduced iron or iron scrap is preferentially charged into the furnace center area.
In Patent Document 5, the present invention reduces the iron oxide in a rotary hearth type reduction furnace, and when the reduced iron pellets are supplied to a vertical furnace such as a blast furnace or a cupola, proper operation in these furnaces is performed. It is intended to be implemented. According to Patent Document 5, a powder compact including iron oxide and carbon is heat-treated in a rotary hearth type reduction furnace to produce reduced iron pellets having an iron metallization rate of 50 to 85%. As the properties of the reduced iron pellets, those having a porosity of 20 to 50% are manufactured. After classifying, etc., a reduced iron pellet having a reduced diameter of 5 to 20 mm and a ratio of 80% or more is charged into a vertical furnace such as an iron blast furnace or a cupola. Molten iron is produced by reducing and melting with reducing gas generated by the reaction between air blown from the tuyeres at the bottom of the furnace and coke or pulverized coal.

Japanese Patent Laid-Open No. 08-269508 Japanese Patent Laid-Open No. 08-253802 Japanese Patent Application Laid-Open No. 06-279818 Japanese Patent Laid-Open No. 09-78110 JP 2009-84688 A

In Patent Documents 1 to 3 described above, the pulverized coal blown from the tuyere is 100 kg / tp, and the preconditions are different from the operation of blowing auxiliary fuel from the tuyere at 150 kg / tp or more. “Kg / tp” refers to the mass of pulverized coal blown per ton of pig iron.
Further, in Patent Documents 1 to 3, although it is described that charging is mainly performed on the raw material, the composition of the raw material is not described in detail. In addition, the strength of the central charge coke charged to the blast furnace is not shown. Therefore, it is difficult to maintain air permeability in the center of the furnace under low coke operation while operating stably.

  In Patent Document 4, the pulverized coal blown from the tuyere is 70 kg / tp, and the precondition is different from the operation of blowing auxiliary fuel from the tuyere at 150 kg / tp or more. In addition, in Patent Document 4, regarding the properties of the iron raw material to be charged centrally, the iron scrap may be commercial iron scrap, and the ironworks generated scrap not containing impurities such as Cu, Ni, Sn, etc. It describes what may be used. However, the strength of the central charge coke is not shown. Therefore, as in the case of the above-described patent document, it is difficult to maintain air permeability in the center of the furnace under low coke operation while stably operating.

Patent Document 5 is not an operation in which raw materials are mainly charged. Moreover, although the raw material to be charged is shown, the strength of the coke to be charged is not shown, and it is actually difficult to operate stably.
In recent years, the quality of coke has deteriorated, and the price has been rising. For this reason, the ratio of high-quality coke has been reduced, and on the other hand, the development of operations that use a large amount of auxiliary fuel such as pulverized coal (referred to as PC) (high-PC ratio operation) is being promoted. Also, from the viewpoint of CO ₂ reduction, the development of high PC ratio operation is being promoted.

In the conventional technology as described above, when a high PC ratio operation, that is, a low coke ratio operation is performed, the in-furnace gas permeability and the spacer coke amount decrease, and the in-furnace air permeability decreases and the operation becomes unstable. There is a fear. Moreover, at the time of operation with a low reducing material ratio, there is a risk of cooling due to lack of heat and unstable operation.
In view of the above problems, the present invention recovers high-temperature gas sensible heat while maintaining air permeability under a high PC ratio operation (low coke operation), and is stable at a low reducing material ratio (low coke ratio). It aims at providing the metallic raw material charging method of the blast furnace which can operate.

In order to achieve the above-described object, the present invention takes the following technical means.
The method for charging metallic raw material of a blast furnace according to the present invention is carried out when the central charging coke and metallic raw material are charged in the center of the furnace body and 150 kg / tp or more of auxiliary fuel is blown from the tuyere to operate the blast furnace. , Regarding the components of the metallic raw material, FeO is 1.0 mass% or less; Fe is 90.0% by mass or more, C is 1.0% by mass or more, and M.I. Fe + C is 93.0% by mass or more, the particle diameter DC of the central charging coke is 40 mm or more and 100 mm or less, the particle diameter DM of the metallic raw material is 5 mm or more and 30 mm or less, and the drum of the central charging coke The relationship between the strength index DIC (−) and the maximum value DM _MAX (mm) of the particle diameter DM (mm) of the metallic raw material satisfies the formula (1), and the particle diameter DC (mm) of the central charging coke is The relationship between the particle size DM (mm) of the metallic raw material and the mass ratio (mass%) of FeO contained in the metallic raw material satisfies the formula (2) in all numerical values, and the mass M1 of the metallic raw material and the central charging coke. The mass ratio indicating the ratio with respect to the mass M2 satisfies the formula (3), and the metallic raw material and the centrally charged coke are charged into the central portion having a relative radius of 0.20 or less. It is characterized by that.

DIC ≧ 84.0 + DM _MAX ³ / 100,000 (1)
DM / (DC / (1-FeO / 100) = 0.05 to 0.75 (2)
M1 / M2 = 1.0 to 3.0 (3)

According to the present invention, high temperature gas sensible heat can be recovered while maintaining air permeability under high PC ratio operation, and stable operation can be performed at a low reducing material ratio.

It is the schematic of a bell armor type raw material charging device. It is the figure which showed the pressure loss in a furnace at the time of charging only center charging coke in the center part, and drum strength index | exponent DIC. FIG. 5 is a diagram showing the relationship between the maximum value DM _MAX of the particle size DM of the metallic raw material and the drum strength index DIC of the central charging coke. In this invention, it is the schematic diagram which has arrange | positioned center charging coke and a metallic raw material in center part. As a comparison with FIG. 4, FIG. 5 is a schematic view in which a central charging coke and a metallic raw material are arranged in the center. It is a related figure of coke ratio and central liquid index in an example and a comparative example. It is a related figure of a reducing material ratio and a central liquid index in an example and a comparative example.

Hereinafter, an embodiment of a metallic raw material charging method for a blast furnace according to the present invention will be described with reference to the drawings.
In the blast furnace (vertical metallurgical furnace), raw materials such as pellets, sintered ore, lump ore, coke, limestone and reducing materials are charged in layers from the top, and hot air is blown from the bottom to reduce iron ore, A series of reactions such as dissolution is performed to produce pig iron.
In the present invention, even in a high PC ratio operation using a large amount of auxiliary fuel such as pulverized coal, as described later, high temperature gas sensible heat is recovered while maintaining air permeability, and stable at a low reducing material ratio. Can perform operations.

Hereinafter, the present invention, that is, the raw material charging method of the blast furnace will be described.
First, in the PC ratio operation of the present invention, it is assumed that 150 kg / tp or more of auxiliary fuel (pulverized coal, PC) is blown from the tuyere. The domestic average of the amount of pulverized coal injected is currently 120 to 130 kg / tp, and in this operation, the amount of pulverized coal injected is greater than the national average. “Kg / tp” refers to the mass of pulverized coal blown per ton of pig iron.

The raw material charging method into the blast furnace can be broadly classified as shown in "Lecture / Modern Metallurgy Sophistication Volume 1 Steel Refining, Japan Institute of Metals, (1979), p120". There are two types: bell armor type and bellless type (turning chute type). In this embodiment, the bell armor type is adopted as the raw material charging method.
FIG. 1 is a schematic view of a bell armor type raw material charging apparatus.

  As shown in FIG. 1, the raw material charging apparatus includes a bell 2 that is positioned above the blast furnace (furnace body) and that can move up and down, an armor (repulsion plate) 3 that repels the raw material and charges it into the furnace, A supply device (not shown) for supplying the raw material toward the bell cup and a center charging chute 4 are provided. The center charging chute 4 has a tip directed toward the center, as shown in “R & D Kobe Steel Engineering Reports, Vol. 55, No. 2, (2005), p9-17”. The raw material can be supplied toward the section.

  According to this raw material charging device, when a predetermined raw material is supplied from the supply device to the bell cup and the bell 2 is lowered, the raw material is discharged from the bell cup, and the raw material discharged from the bell cup is the armor 3 It is repelled and is inserted into the furnace. Specifically, using a bell 2, ores such as pellets, sintered ore, ore and coke are alternately charged in layers. In addition, in the present invention, the “coke center charging” is performed in which the coke is charged toward the center using the center charging chute 4. The coke center charging is described in a document “Feramu, Vol. 9 (2004) No. 10, p721-728”.

When the “coke center charging method” is implemented, O / C (ore mass / coke mass) in the center can be easily controlled, ensuring a central gas flow, forming an inverted V-type cohesive zone, and core Activation and liquid permeability can be improved. On the other hand, in the coke center charging method, if the amount of coke charged toward the center (referred to as center charging coke) is too large, the CO gas utilization rate will decrease and the exhaust gas sensible heat will increase. It is necessary to increase the material (reducing material ratio). For example, the gas temperature of the charge layer in the central region is as high as about 1000 ° C., and a large amount of high-temperature gas sensible heat is discharged. The center charging coke rises to about 1200 ° C. in just one hour after charging, and sensible heat is wasted because heat exchange in the furnace is not sufficient. As a result, when the coke center charging is simply performed, while the reducing material ratio is increased, stable operation is performed with priority given to air permeability.

Therefore, in the present invention, not only the central charging coke but also the metallic raw material is charged into the central portion, thereby suppressing an increase in the reducing material ratio and performing stable operation. That is, as shown in FIG. 1, the metallic raw material and the central charging coke are charged into the central portion having a relative radius (relative radius = distance from the center of the furnace body / furnace port radius) of 0.20 or less. Yes.
The metallic raw material is a general term for reduced iron (DRI, HBI), cast iron, scrap (crushed iron), etc., whose main component is metallic iron (M.Fe).

The components of the metallic raw material are FeO 1.0% by mass or less, M.I. Fe is 90.0 mass% or more, C is 1.0 mass% or more, M.I. Fe + C is 93.0% by mass or more. In addition to the components described above, MgO, Al ₂ O ₃ , SiO ₂ and inevitable impurities are included. Note that FeO, M.I. The component of Fe can be obtained by a titration method shown in JISM8213. Further, the component of C can be obtained by a combustion-infrared absorption method shown in JISM8217.

When FeO is 1.0% by mass or less, even if both the centrally charged coke and the metallic raw material are charged, the centrally charged coke is deteriorated by reaction (FeO + C = Fe + CO) due to FeO contained in the metallic raw material. Without this, coke can be sufficiently supplied into the furnace.
M.M. When Fe is 90.0% or more, flooding can be suppressed in the high gas flow rate region at the furnace center, and the air permeability and the central gas flow at the center are not affected.

  Carbon content (C) is a component carburized into metallic iron. That is, it is not carburized C but a component caused by entrainment of precipitation C or solid C. In this case, the melting point (melting-off temperature) of the metallic raw material is lower than that of pure iron, and melts in the range from the upper surface temperature of the cohesive zone to the lower surface temperature. When C is 1.0% by mass or more, the centrally charged coke can be supplied to the lower part of the furnace with almost no reaction deterioration due to the carburization reaction.

M.M. When Fe + C is 93.0% or more, M.I. There is no influence due to the supply of Fe and the influence of the supply of C, and healthy coke can be supplied to the lower part of the furnace, and flooding can be suppressed in the high gas flow rate region at the furnace center.
Now, the particle diameter DC of the central charging coke charged in the furnace center is 40 mm or more and 100 mm or less. Specifically, the coke before charging in a furnace is sieved to prepare coke having a particle size DC of 40 to 100 mm, and the coke is charged toward the center (center charging coke) and To do. By setting the particle size DC of the central charging coke to be in the range of 40 to 100 mm, the porosity of the central coke layer is improved and the central flow is strengthened. As a result, an inverted V-type cohesive zone can be formed, pressure loss can be reduced, and heat loss can be reduced. In particular, in order to improve the air permeability, the average particle size of the centrally charged coke is not increased, but those having a small particle size DC are reduced (powder reduction, undercut), while the particle size DC is large to some extent. It is effective to use a large mass and further narrow the particle size distribution width. As described above, by setting the particle size DC of the centrally charged coke to 40 to 100 mm, it is possible to improve air permeability and the like. it can.

In addition, when the particle diameter DC of the central charging coke is less than 40 mm, the central charging coke fills the gaps in the packed bed, so that the porosity becomes small. Further, when the particle size DC of the central charging coke is larger than 100 mm, the particle size distribution width becomes wide and the porosity becomes small.
Moreover, the coke dry-distilled with the chamber furnace type coke oven has many large and small cracks, and has an indefinite shape. It is known that coke is extruded from a coke oven and then destroyed by a drop impact or the like in the course of passing through a transportation process, and the particle size distribution determined as a result thereof is generally a normal distribution. In the present invention, the particle size is determined just before the coke is charged, that is, after the coke is produced and transported, and when the coke is charged into the feeding device.

The particle size DM of the metallic raw material is 5 mm or more and 30 mm or less. Specifically, the metallic raw material before charging is passed through a sieve in a furnace to prepare a metallic raw material having a particle size of 5 to 30 mm, and the metallic raw material is charged toward the center.
When the particle size of the metallic raw material is 5 mm or more, even if the metallic raw material is charged into the high flow velocity region in the central portion, it is not fluidized and can be prevented from scattering. On the other hand, when the particle size of the metallic raw material is less than 5 mm, fluidization occurs. In addition, since the metallic raw material is carburized, it is heated immediately after charging and melts down (melts at a low melting point), so even if the particle size is the lower limit (5 mm) and small particle size, There was no decrease in air permeability.

The upper limit of the particle size of the metallic raw material was comprehensively determined from the following three points.
First, when the particle size of the metallic raw material is too large, the metallic raw material does not enter the gap of the coke packed layer, that is, cannot be deposited in the gap. That is, the volume of the packed bed in the central portion becomes large, and the central gas flow region becomes too wide. As a result, the central flow becomes too strong and the CO gas utilization rate decreases. Therefore, even if the metallic raw material is charged, it is impossible to suppress an increase in the reducing material ratio.

Secondly, when the particle size of the metallic raw material is too large, the individual weight (mass per one) of the metallic raw material becomes large, and there is a possibility that the coke may be destroyed by a drop impact at the time of central charging. As a result, the central flow decreases.
Thirdly, when the particle size of the metallic raw material is too large, the temperature rise is delayed (heat transfer delay in the particles). As a result, the effect of recovering the sensible heat of the hot gas is reduced. In view of the above, as a result of various verifications, the upper limit of the particle size of the metallic raw material was set to 30 mm.

Now, when the central charging coke and the metallic raw material are charged, if the strength of the central charging coke is small, the central charging coke may be broken by the impact of the drop and the air permeability may be lowered.
Therefore, in the present invention, the relationship between the drum strength index DIC of the central charging coke and the maximum value DM _MAX of the particle size DM of the metallic raw material satisfies the formula (1).

DIC ≧ 84.0 + DM _MAX ³ / 100,000 (1)
Here, the drum strength index DIC is obtained according to JISK2151, and is the mass ratio of coke having a particle size of 15 mm or more after 150 revolutions using a drum tester.
FIG. 2 shows an in-furnace pressure loss (kPa) when the metallic raw material is not charged in an actual blast furnace (internal volume = 4500 m ³ ), that is, an in-furnace pressure loss when only the central charging coke is charged at the center. FIG. 6 is a diagram showing a drum strength index DIC. As shown in FIG. 2, when the drum strength index DIC is 84.0 or more, the pressure loss in the furnace is 180 kPa or less, and in the actual operation, the ventilation and liquid permeability are improved, and the stable operation can be performed. . On the other hand, when the drum strength index DIC of the central charging coke is smaller than 84.0, the pressure loss in the furnace becomes larger than 180 kPa, slipping or blow-through occurs, and stable operation may not be continued. Therefore, the lower limit of the drum strength index DIC necessary for stable operation when no metallic raw material is charged is 84.0.

  When the metallic raw material is charged into the center portion in addition to the central charging coke, if the metallic raw material is large, the coke is destroyed due to a drop impact during the central charging. Therefore, in the present invention, in order to prevent the coke from being destroyed, it is necessary to increase the drum strength index DIC of the central charging coke according to the particle size DM of the metallic raw material so that the central charging coke is not destroyed.

  The drum strength index DIC required for the central charging coke was determined by a laboratory experiment. In the laboratory experiment, a metallic raw material was dropped from a height (12 m) simulating an actual blast furnace in a coke packed bed, and it was observed whether the coke was destroyed. The blast furnace of our company is "Bell armor type and center charging method combined, 12m from the bottom surface of the central charging hopper to the charging line that is the standard of charging. Other blast furnaces are" Bell armor type " And “Bellless type”, both types are within 12 m from the lower surface of the hopper or the lower surface of the bell cup to the charging line. Therefore, the test was carried out at 12 m, which is the highest drop height and the highest drop impact force.

In the laboratory experiment, the core charging coke having different drum strength index DIC was used. Metallic raw materials having different particle diameters were used.
FIG. 3 and Table 1 show the relationship between the maximum value DM _MAX of the particle size DM of the metallic raw material and the drum strength index DIC of the central charging coke.

When a metallic raw material having a predetermined size (maximum value DM _MAX = 7, 12, 18, 23, 27, 32 mm) is charged, the center charging coke has a low drum strength index DIC, as indicated by a cross in FIG. Then, the central charging coke is broken in two and destroyed. As indicated by a circle in FIG. 3, when the drum strength index DIC is high, the central charging coke is not broken and is not destroyed.
Here, in order to physically investigate the fracture behavior of coke due to the drop impact at the time of charging the metallic raw material, the boundary line where the central charging coke is cracked and not cracked was obtained from this result.
The drop impact force of the metallic material is obtained from the following relationship.

Assuming that the metallic raw material is spherical and the particle diameter DM of the metallic raw material is a diameter, the mass (individual weight) of the metallic raw material is proportional to the cube of the radius. That is, since the drop impact force of the metallic material is proportional to the mass, it is considered that the drop impact force of the metallic material is proportional to the cube of the radius. Therefore, the boundary line is a function of the cube of the particle size DM of the metallic raw material. Since coke is most susceptible to cracking when the heaviest metallic raw material collides, let us consider the maximum value DM _MAX of the particle size DM of the metallic raw material. Note that a sphere of volume = 4πr ^3/3 (radius r, number weight = volume × density). Since the boundary line depends on the particle size DM of the metallic raw material, the coefficient was found to be “1 / 100,000” based on the experimental results. As shown in FIG. 3, when the coefficient is set to “1/200000” or “1/50000”, an appropriate boundary line cannot be obtained.

  Therefore, the drum strength index DIC of the central charging coke can satisfy the formula (1) to prevent the central charging coke from cracking even when both the central charging coke and the metallic raw material are charged. As a result, the pressure loss in the furnace can be maintained at 180 kPa or less. The coke having a very high drum strength index DIC of the central charging coke is a high-quality and expensive coke. Therefore, it is possible to operate at low cost by applying the central charging coke that can satisfy the lower limit value of the equation (1).

Now, it is conceivable that the centrally charged coke (coke) is subjected to reaction deterioration by FeO and the particle size is reduced. The center charging coke needs to have a predetermined size even after reaction deterioration.
Therefore, in the present invention, the relationship among the particle diameter DC of the central charging coke, the particle diameter DM of the metallic raw material, and FeO contained in the metallic raw material satisfies the formula (2).
DM / (DC / (1-FeO / 100) = 0.05 to 0.75 (2)
Since the degree of reaction deterioration is proportional to FeO (%), the particle diameter DC (particle diameter after reaction deterioration) of the centrally charged coke considering the influence of reaction deterioration due to FeO is DM / (DC / (1-FeO / 100).

  As shown in FIG. 4, when the central charge coke particle size DC considering reaction deterioration satisfies the formula (2), the metallic raw material can be arranged in the voids in the packed layer of the central charge coke. Further, as shown in FIG. 4, since the metallic raw material melts immediately after charging with a low melting point, the deterioration of the air flow due to the metallic raw material particle size DM being less than 5 mm is not observed, and the metallic raw material melts down. Sometimes the filling structure of the central charging coke does not change. That is, the filling layer does not shrink due to the molten dripping of the metallic raw material, and the ventilation (center flow) is not disturbed by the charging of the metallic raw material.

On the other hand, when the metallic raw material is as large as the central charging coke, when it is larger than the upper limit (0.75) of the formula (2), the metallic raw material cannot be deposited in the gap of the packed bed.
As shown in FIG. 5, in the solid state before melting of the metallic raw material, there is air permeability and the central gas flow region is too wide, but when it is charged in the high temperature region of the central part, the temperature rises and melts down directly. The center filling structure will change. For example, a mixed layer of centrally charged coke and ore is formed, and the aeration deteriorates or the gas flow changes.

Now, it is desirable that the metallic raw material is charged in an amount capable of reducing the reducing material ratio within a range in which the central flow in the central portion is maintained and the air permeability is not lowered. For this reason, in the present invention, the ratio (mass ratio) between the mass M1 of the metallic raw material and the mass M2 of the central charging coke satisfies the formula (3).
M1 / M2 (mass ratio) = 1.0 to 3.0 (3)
When the mass M1 of the metallic raw material to be charged is small and smaller than the lower limit (1.0) of the formula (3), the reducing material ratio, that is, the coke ratio reducing effect is small (the central high temperature gas sensible heat recovery effect is small). ). When the mass M1 of the metallic raw material to be charged is large and is larger than the upper limit (3.0) of the formula (3), there is a possibility that the molten metal hold-up may impede aeration, and the central gas flow is weak. Therefore, blast furnace operation may become unstable. In this case, since the stable blast furnace operation cannot be performed unless the reducing material ratio is increased, the reducing material cannot be reduced by charging the metallic raw material.

In addition, it is desirable that the metallic raw material and the central charging coke are uniformly (uniformly) dispersed in a solid state (between charging and before melting) in the furnace. If the relationship of Formula (3) is satisfied for each charging batch, Formula (3) can be satisfied even in the furnace. In addition, the mass ratio shown by Formula (3) is a ratio of the total mass for every batch.
As mentioned above, according to the metallic raw material charging method of the blast furnace of the present invention, the metallic raw material and the central charging coke are charged into the central portion (portion having a relative radius of 0.20 or less). Regarding the components of the metallic raw material, FeO is 1.0 mass% or less, M.I. Fe is 90.0 mass% or more, C is 1.0 mass% or more, M.I. Fe + C is 93.0% by mass or more. The particle diameter DC of the central charging coke is 40 mm or more and 100 mm or less, and the particle diameter DM of the metallic raw material is 5 mm or more and 30 mm or less. The relationship between the drum strength index DIC of the central charging coke and the maximum value DM _MAX of the particle size DM of the metallic raw material satisfies the formula (1). The relationship between the particle diameter DC of the central charging coke, the particle diameter DM of the metallic raw material, and FeO contained in the metallic raw material satisfies the formula (2). The mass ratio indicating the ratio between the mass M1 of the metallic raw material and the mass M2 of the central charging coke satisfies the formula (3).

  Tables 2 to 5 show examples in which the operation was performed by the metallic raw material charging method for the blast furnace of the present invention and comparative examples in which the operation was performed by a method different from the present invention.

First, implementation conditions in Examples and Comparative Examples will be described.
As the blast furnace, a bell armor type blast furnace having an internal volume of 4500 m ³ was used. The output ratio was 1.8 t / m ³ / day. The output ratio is a value obtained by dividing the amount of output (t) per day (day) by the blast furnace volume (m ³ ). In the operation of the blast furnace, the auxiliary fuel was blown at 150 kg / tp or more. In addition, centrally charged coke and metallic raw materials were charged in the center. The test period of the example and the comparative example was one week, and the cumulative amount of output during that period was 56700 tons (4500 × 1.8 × 7 tons). The reducing material ratio (kg / tp) is the mass (kg) of the reducing material (coke, PC, heavy oil, etc.) required when producing 1 ton of pig iron. The coke ratio (kg / tp) is the mass (kg) of coke necessary for producing 1 ton of pig iron.

The evaluation of Examples and Comparative Examples was performed using the central liquid index. The central liquid index can be obtained by “central liquid index (−) = furnace bottom central brick temperature (TRC, ° C.) / Furnace bottom side wall brick temperature (TRW, ° C.)”.
In Examples 1-30, FeO is 1.0 mass% or less regarding the component of a metallic raw material, M.I. Fe is 90.0 mass% or more, C is 1.0 mass% or more, M.I. Fe + C is 93.0% by mass or more (column of metallic raw material). The particle diameter DC of the central charging coke is 40 mm or more and 100 mm or less, and the particle diameter DM of the metallic raw material is 5 mm or more and 30 mm or less (particle diameter column).

Furthermore, in Examples 1 to 30, the relationship between the drum strength index DIC of the central charging coke and the maximum value DM _MAX of the particle size DM of the metallic raw material satisfies the formula (1), and the particle size DC of the central charging coke. And the particle size DM of the metallic raw material and the FeO contained in the metallic raw material satisfy the formula (2) (column of the correlation equation between the coke shape and the metallic raw material shape). Further, the metallic raw material and the central charging coke are charged in the central portion (the portion having a relative radius of 0.20 or less) (center charging column).

On the other hand, in Comparative Example 1, although the charging is performed toward the central charging of the coke, the central charging is not performed on the metallic raw material. In Comparative Examples 2 and 3, FeO exceeds 1.0 mass%, and in Comparative Examples 4 and 5, M.I. Fe exceeds 90.0% by mass, in Comparative Examples 6 and 7, C exceeds 1.0% by mass, and in Comparative Examples 5, 7 and 8, M. Fe + C exceeds 93.0% by mass. In Comparative Examples 9, 10, and 13, the particle diameter DC of the central charging coke is less than 40 mm, and in Comparative Examples 11 to 13, the particle diameter DC of the central charging coke exceeds 100 mm. In Comparative Examples 14 and 15, the particle size DM of the metallic raw material exceeds 5 mm, and in Comparative Examples 16 to 19, the particle size DM of the metallic raw material exceeds 30 mm. In Comparative Examples 19 and 20, the relationship between the drum strength index DIC of the central charging coke and the maximum value DM _MAX of the particle size DM of the metallic raw material does not satisfy the formula (1). In Comparative Examples 9, 10, and 13 to 19, the relationship between the particle diameter DC of the central charging coke, the particle diameter DM of the metallic raw material, and FeO contained in the metallic raw material does not satisfy the formula (2). In Comparative Example 21, the central charging coke and the metallic raw material are charged at a position where the range of the central charging exceeds 0.20 in relative radius. In Comparative Examples 22 to 24, the mass ratio indicating the ratio between the mass M1 of the metallic raw material and the mass M2 of the central charging coke does not satisfy the formula (3).

FIG. 6 shows the relationship between the coke ratio and the central liquid index in Examples and Comparative Examples. As shown in FIG. 6, when the comparative example 1 in which the metallic raw material is not charged in the furnace center is used as a boundary, in the example, the central liquid index can be increased as compared with the comparative example even if the coke ratio is low. It was.
FIG. 7 shows the relationship between the reducing agent ratio and the central liquid index in Examples and Comparative Examples. As shown in FIG. 7, when Comparative Example 1 was used as the boundary, in the Examples, the central liquid index could be increased as compared with the Comparative Example even when the reducing material ratio was low.

  In other words, in general, even in blast furnace operation, the operation is stable under a condition where the central liquid index is large. However, if the metallic raw material is simply charged for such general blast furnace operation, the central liquid index decreases. Operation becomes unstable. On the other hand, in the present invention, regarding the metallic raw material to be charged, the relationship between the composition of the metallic raw material, the size of the metallic raw material (particle size), and the size of the central charging coke (particle size) is specified. Even under the reduced material ratio / low coke condition, the central liquid index can be equal to or higher than that of the conventional technology (when the metallic raw material is not charged). That is, a low reductant ratio / low coke operation is possible while maintaining a stable operation.

  In the examples and comparative examples, the central gas index was also measured for reference. The center gas index can be obtained by “center gas index (−) = furnace top center gas temperature (TGC, ° C.) / Furnace top gas temperature (TG, ° C.)”. In the case of the blast furnace operation method, it is said that the operation becomes stable as the central gas index increases. In this embodiment, since the central gas sensible heat is recovered, the central gas index is small, but the blast furnace operation can be stabilized as indicated by the central liquid index.

  In the embodiment disclosed herein, matters not explicitly disclosed, for example, operating conditions, various parameters, dimensions, weights, volumes, etc. of the components do not deviate from the range normally practiced by those skilled in the art. However, matters that can be easily assumed by those skilled in the art are employed.

2 bells 3 armor
4 Central charging chute

Claims (1)

When operating the blast furnace by charging the central charging coke and metallic raw material into the center of the furnace body and blowing auxiliary fuel of 150 kg / tp or more from the tuyere,
Regarding the components of the metallic raw material, FeO is 1.0 mass% or less, M.I. Fe is 90.0% by mass or more, C is 1.0% by mass or more, and M.I. Fe + C is 93.0% by mass or more,
The central charge coke has a particle diameter DC of 40 mm to 100 mm, and the metallic raw material has a particle diameter DM of 5 mm to 30 mm.
The relationship between the drum strength index DIC (−) of the central charging coke and the maximum value DM _MAX (mm) of the particle size DM (mm) of the metallic raw material satisfies the formula (1),
The relationship between the particle diameter DC (mm) of the central charge coke, the particle diameter DM (mm) of the metallic raw material, and the mass ratio (mass%) of FeO contained in the metallic raw material is expressed by Equation (2) in all numerical values. Meet,
The mass ratio indicating the ratio between the mass M1 of the metallic raw material and the mass M2 of the central charging coke satisfies the formula (3),
The metallic raw material charging method for a blast furnace, comprising charging the metallic raw material and the central charging coke into the central portion having a relative radius of 0.20 or less.
DIC ≧ 84.0 + DM _MAX ³ / 100,000 (1)
DM / (DC / (1-FeO / 100) = 0.05 to 0.75 (2)
M1 / M2 = 1.0 to 3.0 (3)