JPH06330114A - Method for blowing powder to blast furnace - Google Patents

Abstract

PURPOSE:To prevent the accumulation of undissolved powder ore and to improve productivity by mixing an optimum ratio of CaO flux with reduced iron-contg. powder having SiO2 and Al2O3 as main impurities and blowing this mixture together with a specific ratio of pulverized coal into a blast furnace from tuyeres. CONSTITUTION:The iron-contg powder having the SiO2 and the Al2O3 as >=60% of the impurity content and >=60% reduction ratio is blown together with the pulverized coal into the blast furnace to improve a tapping rate and to reduce a fuel rate. A flux is mixed and blown with an into the iron-contg. powder described above. In the above-mentioned blast furnace operation method. The flux contg. >=70% CaO and CaCo3 is used as a slag forming agent at this time. The mixing ratio of the flux at which the m.p. of the mixture composed of the SiO2, Al2O3 and CaO in the iron-contg. powder and the CaO and CaCo3 in the flux is min. is determined from the state diagram of a ternary system at this time, The flux is mixed within this optimum point + or -20%. This powder mixture is blown at 50 to 300kg/t molten iron together with pulverized coal at 50 to 250kg/t molten iron into the furnace from the tuyeres at 0.2 to 1.2 weight ratio of the powder and the pulverized coal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of operating a blast furnace in which powder is blown from tuyere.

[0002]

2. Description of the Related Art In a blast furnace operation, from tuyere to CaO, M
Blowing powder such as gO flux and iron ore,
It is performed to control the reaction in the furnace and adjust the components such as reducing the concentration of Si and S in the hot metal. For example, Japanese Patent Laid-Open No. 61-261408 discloses that the basicity (CaO / SiO ₂ ) and Al of molten slag and Al for the purpose of lowering the concentration of Si and S in the hot metal during blast furnace operation with a low sinter ratio.
_A method is disclosed in which powdered limestone or serpentine is blown from the tuyere so as to adjust the ratio of ₂ O ₃ to a specific range.

In Japanese Patent Laid-Open No. 3-19109, C is used for the purpose of preventing clogging and wear of the flux blowing pipe.
A method of mixing and blowing aO, MgO based flux and pulverized coal is disclosed.

Further, for the purpose of improving the tap ratio and reducing the fuel ratio per blast furnace, iron-containing powder having a reduction rate of 60% or more such as pre-reduced iron ore is blown into the blast furnace together with pulverized coal from the tuyere. The method is described in, for example, Japanese Patent Application No. 04-350221 filed by the applicant of the present application.

[0005]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
The method of 1408 is to blow flux from the tuyere in order to adjust the composition of the hot metal in the normal blast furnace operating method in which almost all of the iron source is charged by lump ore or sinter that is charged from the furnace top of the blast furnace. Yes, and JP-A-3-19
The method of 1009 is a similar blast furnace operation method in which pulverized coal is mixed with flux and blown from the tuyere for the purpose of preventing clogging and wear of the pipe, and therefore a considerable amount of iron source is fed from the tuyere. There is a problem that it is not intended to be put inside. On the other hand, the method of Japanese Patent Application No. 04-350221 is a method of injecting iron-containing powder having a reduction rate of 60% or more together with pulverized coal into the blast furnace from the tuyere for the purpose of improving the tap ratio and reducing the fuel ratio per blast furnace. That is, it is intended to put a considerable amount of iron source into the furnace through the tuyere,
Fine ore with a reduction rate of 60% or more is a mixture of Fe, FeO, and gangue that contains a considerable amount of solid iron powder. Since this powder has a low reduction ratio, that is, it has a low melting point, that is, Fe and has a higher melting point than an oxide-based ore, it does not easily dissolve when blown from the tuyere and scatters in powder form. , It may adversely affect the operation by invading the furnace core.

The present invention prevents the accumulation of undissolved powdered ore in the core of a furnace in the operation of putting a considerable amount of iron source into the furnace from the tuyere in order to improve the tap ratio and reduce the fuel ratio. An object of the present invention is to provide a method for injecting powder into a blast furnace that improves productivity.

[0007]

According to the present invention, the reduction rate is 60%.
By blowing iron-containing powder such as the above powdered ore or dust from the tuyere of the blast furnace together with the flux whose mixing ratio is controlled according to the composition of impurities such as gangue, the melting point of the mixed powder is lowered and the inside of the blast furnace is reduced. It is characterized by promoting dissolution after being blown into. That is, the gist of the present invention is that iron-containing powder having a reduction rate of 60% or more, in which 60% or more of the impurity components other than iron or iron oxide are composed of SiO ₂ and Al ₂ O _3, is combined with pulverized coal in a blast furnace. In the operating method of blowing into the
Using slacks containing 70% or more of CO ₃ , CaO
From the state diagram of -SiO ₂ -Al ₂ O _{3 3} elemental oxides of,
The mixing ratio of the flux having the lowest melting point of the mixture of SiO ₂ , Al ₂ O ₃ and CaO in the iron-containing powder and CaO and CaCO _{3 in} the flux was found, The mixed powder 50 to 300 kg / t hot metal mixed at a ratio within the optimum point ± 20% by weight is used together with the pulverized coal 50 to 250 kg / t hot metal, and the weight ratio of the powder to the pulverized coal is 0.2 to 1.2. To blow into the furnace from the tuyere of the blast furnace.

[0008]

[Function] The iron-containing powder blown from the tuyere of the blast furnace flows into the furnace core through the raceway. When the reduction rate of the iron-containing powder is low, the solid Fe is small and most of the iron components are present in the form of FeO or Fe ₂ O ₃ , and these oxides are usually the main components of impurities such as SiO ₂ and Al ₂ O _3. It is easy to form compounds with low melting points such as oxides. On the other hand, when the iron-containing powder is powdered ore or dust having a reduction rate of 60% or more, the powder is a mixture of solid Fe, FeO and impurities. When this powder is blown into the furnace from the tuyere of the blast furnace,
It may not be easily dissolved and may be scattered in the form of powder and enter the furnace core, which may adversely affect the operation. However, CaO
Or, if a flux containing 70% or more of CaCO ₃ is mixed with iron-containing powder having a reduction rate of 60% or more and blown from the tuyere of the blast furnace, impurities and flux in the iron-containing powder form a compound with a low melting point. Therefore, it is possible to prevent the powder from easily melting in the furnace and staying in the core of the furnace in a powder state. CaCO ₃ can be converted to CaO because it releases Ca ₂ into CaO in the furnace.

Since the proportion and composition of impurities in the iron-containing powder differ depending on the raw material, the component analysis value of the iron-containing powder and, for example, "PHASE DIAGRRAMS FOR CERAM"
ISTS "(THE AMERICAN CERAMI
C SOCIETY, INC. 1964) P .; 21
Using the phase diagram of the CaO—SiO ₂ —Al ₂ O ₃ ternary oxide described in No. 9, find the mixing ratio of the powder and the flux such that the melting point becomes the lowest in the phase diagram. By blending with the powder so that it becomes close to this mixing ratio, a large amount of the iron-containing powder and the pulverized coal can be blown while avoiding an adverse effect on the operation such as intrusion of the powder into the furnace core.

[0010] Normally MgO in the iron-containing powder, the impurity components other than SiO ₂ and Al ₂ O ₃ such as TiO ₂ is contained, SiO ₂ and Al ₂ O ₃ is accounted for more than 60% of the impurity if, other impurities acts in a direction to lower the melting point of the oxide compound, melting point was determined from the phase diagram of _{CaO-SiO 2 -Al 2 O 3} 3 -way systems, be used without large error the composition giving the lowest You can In addition, Ca in the flux
O, The same applies if the component is included in addition to CaCO _3, in order to keep the reliability of the composition having a melting point determined from the phase diagram of _{CaO-SiO 2 -Al 2 O 3} 3 -way system becomes minimum,
A flux having CaO and CaCO ₃ content of 70% or more is used as the flux.

The mixing ratio of the flux may be deviated from the optimum point due to equipment restrictions, adjustment of the composition of the hot metal to be produced and the composition of the slag, but the fluctuation range is ± 20% from the viewpoint of keeping the melting point of the compound low. To do. When the reduction rate of the iron-containing powder is less than 60%, the main component in the iron-containing powder is iron oxide, that is, FeO or Fe ₂ O ₃ , so the reduction rate is 60% when blown into the blast furnace from the tuyere. Compared to the iron-containing powders described above, more heat is required to reduce the iron oxide, and the amount that can be blown is smaller than the iron-containing powders with a reduction rate of 60% or more due to the problem of thermal load. In addition, there is a small amount of Fe in the powder and FeO,
Since the amount of Fe ₂ O ₃ is large, the melting point of the oxide compound itself is low, and the problem of accumulation of undissolved powder in the furnace core is small,
It is not necessary to blow CaO-based flux to lower the melting point of the oxide-based compound.

In an operation in which pulverized coal is blown from the tuyere, the pulverized coal is burned near the raceway. Due to this thermal combustion, a considerable amount of iron-containing powder with a high reduction rate that requires less energy for reduction is blown simultaneously. However, if a considerable amount of flux is mixed and blown in advance in accordance with this, the melting of impurities in the iron-containing powder in the furnace will be promoted and it will be easy to operate with a large amount of iron-containing powder. The body can be blown into the furnace. In this case, the blowing amount of the mixture of iron-containing powder and flux can be increased according to the blowing amount of pulverized coal, and the blowing amount can be increased as the reduction rate of the iron-containing powder is higher. The amount of pulverized coal and mixed powder to be blown is 50 to 250 kg / t of molten pig iron as an operable range in consideration of the thermal load in the lower part of the blast furnace while achieving improvement in productivity and reduction in fuel ratio. Mixed powder 50
~ 300 kg / t hot metal, mixed powder / pulverized coal ratio 0.2 ~
Set to 1.2. However, it is preferable that the reduction rate of the iron-containing powder is higher as the blowing amount of the mixed powder is larger. For example, in a blast furnace in which pulverized coal of 200 kg / t molten pig iron is blown, 100,200,300 kg / In order to inject t hot metal, the reduction rates are 60, 80 and 90, respectively.
% Or more is desirable.

[0013]

EXAMPLE An iron-containing powder having a composition shown in Table 1 obtained by pre-reducing iron ore powder with a circulating fluidized bed (reduction ratio 85
% Of pre-reduced ore; hereinafter referred to as powder F) was blown into the blast furnace, and the amount of flux calculated by the method of the present invention was mixed as described below and further blown together with the pulverized coal from the tuyere of the blast furnace. That is, in the powder F, SiO
The ratio of SiO _{2 to} the total of ₂ and Al ₂ O ₃ is 67.
The ratio of 8% and Al ₂ O ₃ is 32.2%. SiO _{2
67.8%, Al 2 O 3 32.2} % of the mixture corresponds to point B in the phase diagram of _{CaO-SiO 2 -Al 2 O 3} 3 elemental oxides of shown in FIG. If CaO is mixed while maintaining SiO ₂ and Al ₂ O ₃ at this ratio, the mixture will be CaO.
The line segment AB is moved in the state diagram of FIG. Point A corresponds to 100% CaO.

[0014]

[Table 1]

From this state diagram, the melting point of the mixture on the line AB can be drawn as shown in FIG. In this graph, the lowest melting point is at point P, the composition is A38.4%, B
61.6%. This composition is powder F in weight ratio.
CaO is 7.33 with respect to 100, but since 0.17 CaO is also contained in the powder F, C in the flux is
The optimum value of aO is 7.16. Although the melting point of this mixture is about 1270, the powder F actually contains MgO, Fe.
Since components such as O are also included, the melting point of the mixture of the powder F and the flux is further lowered if this is taken into consideration. Further, when the mixing ratio of the flux is within the range of the optimum value ± 20%, the point between the points Q and R in FIG. 2 corresponds. Based on the result of this calculation, the powder F and the flux containing CaO as the main components were mixed so that the powder F: CaO = 14: 1, and the powder F equivalent to 100 kg / t molten pig iron was mixed with the pulverized coal 20.
It was blown into the furnace from the tuyere of the blast furnace together with 0 kg / t hot metal. By this blowing, it is possible to operate smoothly without causing adverse effects such as inertness in the lower part of the furnace, and as a result of the blowing of the reducing ore, 8% of the tapping amount per unit time is compared with the case where the blowing of the powder F and the flux is not performed. Could be achieved.

[0016]

The present invention has the following effects.
(1) Since the melting point of impurities in iron-containing powder such as pre-reduced ore or dust having a high reduction rate is lowered by flux mixing, it is easily melted in the blast furnace after being blown from the tuyere and is in a liquid state flag. As a result, the fluidity of the flag is improved, the air permeability and liquid permeability of the furnace core are maintained, and the heat transfer is performed well. (2)
In blast furnace operation in which pulverized coal is blown from the tuyere, a large amount of iron-containing powder with a high reduction rate is blown from the blast furnace tuyere without adversely affecting the operation, such as accumulation of solid powder in the lower part of the furnace. Can be improved.

[Brief description of drawings]

[1] _{CaO-SiO 2 -Al 2 O 3} 3 ternary phase diagram

FIG. 2 is a diagram showing a melting point of a mixture on a line segment AB in the state diagram of FIG.

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[Procedure amendment]

[Submission date] August 18, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0012

[Correction method] Change

[Correction content]

In the operation in which the pulverized coal is blown from the tuyere, the pulverized coal burns near the raceway.
Due to the heat of combustion , it is possible to simultaneously inject a considerable amount of iron-containing powder with a high reduction rate, which requires less energy for reduction. By promoting the melting of the impurities in the furnace, a large amount of iron-containing powder can be easily blown into the furnace without any problems in the operation. In this case, the blowing amount of the mixture of iron-containing powder and flux can be increased according to the blowing amount of pulverized coal, and the blowing amount can be increased as the reduction rate of the iron-containing powder is higher. The amount of pulverized coal and mixed powder to be blown is 50 to 250 kg / t of molten pig iron as an operable range in consideration of the thermal load in the lower part of the blast furnace while achieving improvement in productivity and reduction in fuel ratio. Mixed powder 50
~ 300 kg / t hot metal, mixed powder / pulverized coal ratio 0.2 ~
Set to 1.2. However, it is preferable that the reduction rate of the iron-containing powder is higher as the blowing amount of the mixed powder is larger. For example, in a blast furnace in which pulverized coal of 200 kg / t molten pig iron is blown, 100,200,300 kg / In order to inject t hot metal, the reduction rates are 60, 80 and 90, respectively.
% Or more is desirable.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be corrected] 0015

[Correction method] Change

[Correction content]

From this state diagram, the melting point of the mixture on the line AB can be drawn as shown in FIG. In this graph, the lowest melting point is at point P, the composition is A38.4%, B
61.6%. This composition is powder F in weight ratio.
CaO is 7.33 with respect to 100, but since 0.17 CaO is also contained in the powder F, C in the flux is
The optimum value of aO is 7.16. Although the melting point of this mixture is about 1270 ° C. , the powder F actually contains MgO, F
Since a component such as eO is also included, the melting point of the mixture of the powder F and the flux is further lowered if this is taken into consideration. Further, when the mixing ratio of the flux is within the range of the optimum value ± 20%, the point between the points Q and R in FIG. 2 corresponds. Based on the result of this calculation, the powder F and the flux containing CaO as the main components were mixed so that the powder F: CaO = 14: 1, and the powder F equivalent to 100 kg / t molten pig iron was mixed with the pulverized coal 20.
It was blown into the furnace from the tuyere of the blast furnace together with 0 kg / t hot metal. By this blowing, it is possible to operate smoothly without causing adverse effects such as inertness in the lower part of the furnace, and as a result of the blowing of the reducing ore, 8% of the tapping amount per unit time is compared with the case where the blowing of the powder F and the flux is not performed. Could be achieved.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0016

[Correction method] Change

[Correction content]

[0016]

The present invention has the following effects.
(1) Since the melting point of impurities in iron-containing powder such as pre-reduced ore and dust having a high reduction rate is lowered by flux mixing, it is easily melted in a blast furnace after being blown from the tuyere and becomes a liquid state . becomes lug, slag fluidity is maintained ventilation, liquid permeability in the furnace core with improved heat transfer is performed satisfactorily. (2)
In blast furnace operation in which pulverized coal is blown from the tuyere, a large amount of iron-containing powder with a high reduction rate is blown from the blast furnace tuyere without adversely affecting the operation, such as accumulation of solid powder in the lower part of the furnace. Can be improved.

Claims (1)

[Claims] 1. An operating method of blowing iron-containing powder having a reduction rate of 60% or more, which comprises 60% or more of SiO ₂ and Al ₂ O ₃ out of impurity components other than iron or iron oxide, into a blast furnace together with pulverized coal, CaO and Ca as slag forming agents
CaO is used with a flux containing 70% or more of CO _3.
From the state diagram of -SiO ₂ -Al ₂ O _{3 3} elemental oxides of,
The mixing ratio of the flux having the lowest melting point of the mixture of SiO ₂ , Al ₂ O ₃ and CaO in the iron-containing powder and CaO and CaCO _{3 in} the flux was found, The mixed powder 50 to 300 kg / t hot metal mixed at a ratio within the optimum point ± 20% by weight is used together with the pulverized coal 50 to 250 kg / t hot metal, and the weight ratio of the powder to the pulverized coal is 0.2 to 1.2. The method for injecting powder into a blast furnace is characterized in that the powder is blown into the furnace from the tuyere of the blast furnace.