JP2006028538A - Method for operating blast furnace using sintered ore excellent in high temperature reducibility - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for operating a blast furnace with which the ventilation in the furnace is improved by using sintered ore excellent in a high temperature reducibility and a large quantity of pulverized fine coals can be injected. <P>SOLUTION: In the method for operating the blast furnace, in which the injecting quantity of the pulverized fine coals is ≥150 kg/p-t, the sintered ore having 5-10 vol% porosity exceeding 50μm pore diameter and 5-15 vol% porosity at less than 5μm pore diameter in ≥70 mass% of iron oxide charging material charged from the furnace top, is used. As the above sintered ore, the sintered ore having 3.8-4.6 mass% content of SiO<SB>2</SB>component and 5-9 mass% content of FeO component, is desirable to use and further, the sintered ore which is sintered by using a sintering raw material blended at 25-80 mass% high crystallization water ore having ≥4 mass% ratio of the crystallization water content, is desirable to use. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for producing pig iron using a blast furnace, and more particularly to a method for operating a large quantity of pulverized coal in a blast furnace using a sintered ore excellent in high temperature reducibility.

  The blast furnace is a vertical reactor of a packed bed type in which coke and iron source charge are alternately charged in layers, and the iron source charge is reduced and melted to produce pig iron. Here, as the iron source charge, iron oxide charges such as sintered ore, pellets and lump ore are usually used, but metal iron charges such as reduced iron and scrap may also be included. is there.

Usually, the sintered ore is made up of multiple brands of iron ore (raw ore), limestone, serpentine, dolomite, etc., so that the basicity (CaO / SiO ₂ ) and SiO ₂ content are within the target values. It is manufactured by blending auxiliary materials, mixing a blended raw material with coagulant such as coke and granulating with a drum mixer or disk pelletizer, and then firing it with a sintering machine. The sintered ore thus produced is charged into a blast furnace.

  In Patent Document 1, the pore size distribution of sintered ore is measured using a mercury porosimeter so that the average pore size of open pores of 300 μm or less is in the range of 0.05 to 0.15 μm. A method of operating a vertical furnace such as a blast furnace using a sintered ore having good high-temperature properties produced by adjusting conditions or components in the sintered ore is disclosed. However, the operation method disclosed here does not describe a specific method for producing sintered ore and a method for blending iron ore that increase the fine pores.

  Further, Patent Document 2 discloses an average when heated to 1200 ° C. or higher in a method for producing sintered ore obtained by mixing or granulating an iron-containing raw material, an auxiliary raw material, a carbonaceous material, and moisture, and then firing with a sintering machine. Contains iron ore containing 0.035 cc / g or more of fine pores with a pore size of 10 μm or less and iron ore containing less than 0.025 cc / g of fine pores with an average pore size of 10 μm or less when heated to 1200 ° C. or more. Thus, a method for producing a sintered ore with excellent high-temperature properties is disclosed.

  However, in this production method, it is necessary to measure the fine pore volume with an average pore diameter of 10 μm or less when heated to 1200 ° C. or higher for all iron ores used as a sintering raw material. Because it is inevitable that the quality of the components and particle sizes will vary and it is necessary to measure the fine pore volume every time iron ore arrives from the aspect of quality control of sintered ore, There is a problem that an increase in quality control costs is inevitable. In addition, these documents do not describe the range of the fine pore volume contained in the sintered ore to be solved by the present invention.

  In the blast furnace, the pulverized coal blowing operation in which about 100 kg of pulverized coal per tonne of brewing is blown into the furnace from the tuyere with hot air can be performed sufficiently stably by using a conventional sintered ore. However, if the amount of pulverized coal injection exceeds 150 kg per ton of tapping (hereinafter also referred to as “150 kg / pt”), the blast furnace may deteriorate due to deterioration of the blast furnace air permeability and abnormal lowering of the charge. Factors that impede operations increase, making it difficult to maintain stable operations.

In addition, when a large amount of pulverized coal is injected, char (unburned coal) is generated due to the deterioration of pulverized coal combustibility in the front tuyere, and the amount of char generated when the amount of pulverized coal injection exceeds 150 kg / pt. Is known to increase significantly. This char comes into contact with the droplet slag melt (FeO—CaO—SiO ₂ —Al ₂ O ₃ —MgO slag) containing the FeO component (wustite) jumping out from the raceway and is captured by the slag melt. At this time, the carbon contained in the char reacts with the FeO component contained in the droplet slag melt, the FeO component is reduced to Fe, the FeO component in the droplet slag melt decreases, and the produced FeO Is separated from the droplet slag melt to become metallic iron. The melting point of the droplet slag melt that has reacted with the char rises due to a decrease in the FeO component, and part of the solid phase is precipitated to increase the viscosity of the droplet slag melt. In addition, there is a char that is suspended in the droplet slag melt as a solid phase without reacting with the FeO component even if it is captured in contact with the droplet slag melt. Raise.

This increase in the viscosity of the droplet slag melt is one factor that deteriorates the air permeability of the blast furnace. Therefore, in a large-volume injection operation in which the amount of pulverized coal injection is 150 kg / pt or more, the droplet slag melt A technique for suppressing the increase in viscosity is required. For the improvement of the viscosity, the reducibility of the iron source charge is improved, the amount of FeO component when the droplet slag melt is dropped is reduced in advance, and the reaction with char occurs. A method for preventing the melting point of the droplet slag melt from increasing is proposed. In other words, by increasing the basicity of the sintered ore (hereinafter also referred to as “(CaO / SiO ₂ ) ratio”), the high-temperature reducibility of the sintered ore at a high temperature of 1000 ° C. or higher is improved, and it is not reduced to the bottom of the blast furnace This is a method of reducing the amount of FeO component that falls and remains, and suppresses deterioration of the air permeability of the blast furnace.

However, the total slag amount and the (CaO / SiO ₂ ) ratio in the bottom water pool of the blast furnace are limited, the total slag amount is 330 kg / pt or less, and the (CaO / SiO ₂ ) ratio is 1.3 or less. Constrained by Therefore, a sintered ore with a high content of (FeO + CaO + SiO ₂ + Al ₂ O ₃ + MgO) with an increase in the (CaO / SiO ₂ ) ratio of the sintered ore can achieve a total slag amount even if the reducibility is good. It is constrained that more than 70% by weight of the iron oxide charge source charged from the top of the furnace cannot be used. Also, as the (CaO / SiO ₂ ) ratio of the sintered ore increases, the (CaO / SiO ₂ ) ratio of the droplet slag melt also increases, so the viscosity of the droplet slag melt increases and the blast furnace interior There is also a problem of deteriorating air permeability.

  Here, the reduction reaction of the FeO component in the furnace of the blast furnace includes an indirect reduction reaction by CO gas and a direct reduction reaction by solid carbon (C), and the indirect reduction reaction is an exothermic reaction (+13930 kJ / mol). On the other hand, the direct reduction reaction is an endothermic reaction (−158490 kJ / mol). In other words, since the direct reduction reaction of the FeO component requires a large amount of heat energy, if this reaction occurs in a concentrated manner in the lower part of the blast furnace, the thermal balance in the blast furnace is lost, and the blast furnace operation becomes impossible. There is a risk of a cold accident. For this reason, in blast furnace operation where the amount of pulverized coal injection is 150 kg / pt or more, it is necessary to reduce in advance the FeO component that falls to the lower part of the furnace while remaining unreduced.

JP 11-43709 A (claims, paragraphs [0006] and [0013])

JP 2001-303142 A (claims, paragraphs [0010] to [0014])

  As described above, the following problems (a) and (b) remain in the prior art. That is, (a) in blast furnace operation where the amount of pulverized coal injection is 150 kg / pt or more, there is an increase in the amount of unburned char, and there is an endotherm of unreduced FeO component and carbon at the bottom of the blast furnace. Direct reduction reaction tends to occur, and the fluidity of slag deteriorates accordingly. Therefore, it is necessary to reduce the residual amount of the unreduced FeO component as compared with the time of operation with a small amount of pulverized coal injection. For this purpose, it is necessary to use a sintered ore that is more excellent in high temperature reducibility. (B) A method for improving the high temperature reducibility of sintered ore and reducing the residual amount of unreduced FeO component in the blast furnace to suppress the deterioration of air permeability in the blast furnace has been disclosed, but this is realized. The method for producing sintered ore with increased fine pores is not clear, and quality control is not easy.

  The present invention has been made in order to solve the above-mentioned problems, and its problem is to control the ratio of pores having a pore diameter exceeding 50 μm and the ratio of pores having a pore diameter of less than 5 μm contained in the sintered ore. A blast furnace operating method that improves the air permeability of the blast furnace by reducing the remaining FeO component that remains unreduced to the lower part of the blast furnace furnace by using sintered ore with excellent high temperature reducibility Is to provide.

  In order to solve the above-mentioned problems, the inventors of the present invention have a porosity ratio in which the pore diameter in the sintered ore exceeds 50 μm and a pore ratio in which the pore diameter is less than 5 μm are high temperature reducible, hot air permeability and cold. While investigating the effect on strength, the blast furnace operation using those sintered ores was performed, and the following findings (a) to (f) were obtained to complete the present invention.

  (A) By making the sintered ore excellent in high temperature reducibility 70 mass% or more of the iron oxide charge charged from the top of the blast furnace, in the dripping slag melt generated at the bottom of the blast furnace The content rate of a FeO component can be reduced and the ventilation | gas_flowing and liquid permeability in a furnace lower part can be improved.

  (B) If the pore ratio of the sintered ore with a pore diameter exceeding 50 μm is in the range of 5 to 10% by volume, the hot air permeability is improved, so that the productivity of the sintered ore can be ensured, Cold strength can also be secured by increasing the FeO component content in the ore.

(C) If the porosity of the sintered ore with a pore diameter of less than 5 μm is in the range of 5 to 15% by volume, the high temperature reducibility is improved, and the SiO ₂ component content in the sintered ore is improved. By increasing it, the cold strength can be secured.

(D) If the SiO ₂ component content in the sintered ore is in the range of 3.8 to 4.6% by mass, the amount of melt produced in the process of producing the sintered ore is secured and the cold strength is maintained. And since the increase in the amount of silicate slag formation is suppressed, high temperature reducibility is ensured and it is preferable.

  (E) If the FeO component (magnetite component) content in the sintered ore is 5% by mass or more, the amount of melt produced in the process of producing the sintered ore is secured to maintain the cold strength, and the hematite This is preferable because an increase in the mineral content can be suppressed and deterioration of the reduced powdering property can be prevented. Further, if the FeO component content is 9% by mass or less, it is preferable because it prevents the formation of excessive melt during the sintering process, thereby securing the amount of fine pores and improving the high temperature reducibility.

  (F) If the blending ratio of the high crystal water ore is 25 to 80% by mass, the fine pores contained in the sintered ore can be secured to improve the high temperature reducibility, and the cold strength is maintained. This is preferable.

  This invention is completed based on said knowledge, The summary exists in the operating method of the blast furnace shown to following (1)-(3).

  (1) A blast furnace operation method in which pulverized coal of 150 kg or more per ton of tuna is blown into the furnace together with hot air from the tuyere, to 70% by mass or more of the iron oxide charge charged from the top of the furnace, A method for operating a blast furnace using a sintered ore having a porosity of 5 to 10% by volume with a pore diameter exceeding 50 μm and a porosity of 5 to 15% by volume with a pore diameter of less than 5 μm (hereinafter referred to as “first invention”). ").

(2) The sintered ore having a SiO ₂ component content of 3.8 to 4.6% by mass and a FeO component content of 5 to 9% by mass as the sintered ore (1) ) Operation method (hereinafter also referred to as “second invention”).

  (3) (1) or (1) above, wherein the sintered ore is fired using a sintered raw material containing 25 to 80% by mass of a high crystal water ore having a crystal water content of 4% by mass or more as the sintered ore. A method of operating a blast furnace according to (2) (hereinafter also referred to as “third invention”).

In the present invention, the “FeO component” in the sintered ore means a magnetite component (FeO · Fe ₂ O ₃ ).

  “Porosity diameter” and “pore ratio” are the values of the pore diameter contained in the sintered ore and the volume ratio of the pores having the diameter to the volume of the sintered ore in percentage. The details are as described later.

  The “sintered raw material” refers to raw material ore and auxiliary raw materials.

  According to the method of the present invention, by using a sintered ore excellent in high temperature reducibility in which the pore size distribution is adjusted to 70% by mass or more of the iron oxide charge charged from the top of the blast furnace. In addition, since it is possible to prevent deterioration of the air permeability in the blast furnace with an increase in the amount of pulverized coal injection, it becomes possible to perform a large amount of pulverized coal injection of 150 kg / pt or more while maintaining stable operation of the blast furnace, A large quantity of pulverized coal can be achieved with a high output ratio and a low reducing material ratio.

  The present invention relates to a blast furnace operating method in which pulverized coal of 150 kg or more per ton of tuna is blown into a furnace together with hot air from a tuyere, and the amount of iron oxide charged from the top of the furnace is 70% by mass or more. The operation method of a blast furnace using a sintered ore having a pore ratio of 5 to 10% by volume with a pore diameter exceeding 50 μm and a pore ratio of 5 to 15% by volume with a pore diameter of less than 5 μm. The reason why the scope of the present invention is limited as described above and the preferred range will be described below.

(A) Charge ratio of sintered ore excellent in high temperature reducibility: 70 mass% or more In the present invention, sintered ore excellent in high temperature reducibility in the iron oxide charge charged from the furnace top The reason why the charging ratio is set to 70% by mass or more is to improve the in-furnace air permeability at the bottom of the blast furnace.

  FIG. 1 shows the relationship between the charging ratio of sintered ore excellent in high-temperature reducibility in the iron oxide charge charged from the top of the furnace, the amount of pulverized coal injection, and the lower blast furnace ventilation resistance. FIG. From the relationship shown in the figure, the sintering is excellent in high temperature reducibility in which the pore ratio is 5 to 10% by volume with a pore diameter exceeding 50 μm and the pore ratio is 5 to 15% by volume with a pore diameter of less than 5 μm. By making the blending ratio of the ore 70% by mass or more of the iron oxide charge, the content of the FeO component in the slag melt that is melted and dropped in the lower part of the blast furnace furnace can be reduced.

  Therefore, an increase in the slag viscosity due to an increase in the melting point of the slag due to the reaction of the FeO component in the slag melt with unburned char, and a temperature decrease due to endotherm based on a direct reduction reaction in the lower part of the furnace are prevented. Good air permeability can be secured.

(B) Pore ratio in which the pore diameter of the sintered ore exceeds 50 μm: 5 to 10% by volume
The pore ratio in which the pore diameter of the sintered ore exceeds 50 μm is in the range of 5 to 10% by volume because the hot air permeability of the sintered layer in the sinter production process is ensured and the sintered ore is cooled. This is to ensure the strength between the layers. The reason will be described in detail below.

  FIG. 2 is a diagram showing the relationship between the pore ratio of the sintered ore having a pore diameter exceeding 50 μm and the hot air permeability index (JPU) for various FeO component contents of the sintered ore. In the figure, the hot air permeability index (JPU) is an index representing the air permeability of the sintered layer in the sinter production process, and is a value calculated by the following equation (1).

JPU = (9.807 × h / ΔP) ^0.6 × Q / A (1)
Here, h is the layer thickness (m) of the sintered layer, ΔP is the suction negative pressure (kPa) of the exhaust fan, Q is the suction air volume (m ³ / min), and A is the effective suction area (m ² ). To express.

  In addition, said hot air permeability index | exponent shows that the gas air permeability in a sintered layer is so favorable that the value is large.

  In addition, the porosimetry of pores having a pore diameter exceeding 50 μm and pore ratios having a pore diameter of less than 5 μm included in the sintered ore used in FIG. 3 and FIGS. It calculated | required as follows with the measuring method of pore diameter distribution.

  That is, a sintered ore having a particle diameter of 15 to 19 mm is collected, one of the grains is placed in a press-fitted sealed container, and after the mercury is filled in the sealed container, the mercury is gradually pressurized. The relationship between the press-in pressure and the pore size at which mercury can enter at that pressure is determined in advance, and the pore size corresponding to the press-in pressure and the pores based on the measured value of the intrusion amount of mercury injected at a certain press-in pressure The volume was determined. The pore volume having the predetermined pore diameter determined in this way was divided by the volume of the sintered ore and displayed as a percentage (%) to obtain the pore ratio of the pores having the predetermined pore diameter. This measuring method is a method generally used as a pore diameter distribution measuring method of sintered ore. In the investigation in the present invention, the pore size distribution was obtained by performing eight measurements for each sintered ore sample.

  According to the results of FIG. 2, as the pore ratio exceeding 50 μm increases, the hot air permeability index increases as the FeO component content in the sintered ore decreases, and the sintered layer The air permeability becomes better. Accordingly, pores having a pore diameter exceeding 50 μm are indispensable for the formation of a ventilation network in the sinter production process, and in order to ensure the hot air permeability of the sintered layer and improve the productivity, the pore diameter is small. It was found that the pore ratio exceeding 50 μm needs to be 5% by volume or more.

  FIG. 3 is a graph showing the relationship between the porosity ratio of pores contained in the sintered ore with a pore diameter exceeding 50 μm and the cold strength index (TI) for various FeO component contents of the sintered ore. In the figure, the cold strength index is expressed by using the cold rotational strength TI (+5 mm) of the sintered ore specified in JIS M 8712.

  According to the result of FIG. 3, the cold strength index decreases as the pore ratio with a pore diameter exceeding 50 μm increases and as the FeO component content in the sintered ore decreases. The pores having a pore diameter exceeding 50 μm is one of the factors that reduce the cold strength of the sintered ore. When the pore ratio exceeding 50 μm is 10% by volume or less, the FeO component content of the sintered ore is 10% by volume or less. Although the cold strength can be ensured by setting the content to 5% by mass or more, if the pore ratio of the pore diameter exceeding 50 μm exceeds 10% by volume, the FeO component content of the sintered ore is increased to 5% by mass or more. Even if the amount of the sintered melt produced in the sinter production process is increased, it is difficult to ensure the cold strength. Sintered ore with low cold strength is significantly reduced in grain size due to mechanical stresses such as impact during charging into the blast furnace and wear caused by the fall of the charge in the furnace. Deteriorates the air permeability in the furnace. Therefore, the pore ratio with a pore diameter exceeding 50 μm needs to be 10% by volume or less.

  As described above, from the viewpoint of ensuring the productivity at the time of manufacturing the sintered ore and ensuring the cold strength of the sintered ore, the appropriate range of the pore ratio with a pore diameter exceeding 50 μm is set to 5 to 10% by volume. .

(C) Porosity ratio of sintered ore having a pore diameter of less than 5 μm: 5 to 10% by volume
The reason why the porosity of the sintered ore having a pore diameter of less than 5 μm is in the range of 5 to 15% by volume is to improve the high temperature reducibility and increase the SiO ₂ component content in the sintered ore. This is because the cold strength can be secured. The reason will be described below.

FIG. 4 is a graph showing the relationship between the ratio of pores having a pore diameter of less than 5 μm contained in the sintered ore and the high-temperature reducible index for various SiO ₂ component contents of the sintered ore. In the figure, the high temperature reducibility index is as follows. 500 g of sintered ore having a particle diameter of 19 to 21 mm is charged into a stainless steel reaction tube having an inner diameter of 75 mm, and a mixed gas of CO: 30% and N ₂ : 70% is reduced gas The flow rate was 15 NL / min, and the reduction rate at 1100 ° C. for 6 hours was used to indicate the ultimate reduction rate (reduced oxygen mass actual value / total reduced oxygen mass theoretical value × 100%).

According to the result of FIG. 4, when the pore ratio with a pore diameter of less than 5 μm increases, the high temperature reducibility of the sintered ore is improved, and the high temperature reducibility index increases. However, if the pore ratio is less than 5% by volume with a pore diameter of less than 5 μm, the high temperature reducibility index is 90% or more unless the SiO ₂ component content of the sintered ore is reduced excessively to less than 3.8% by mass. The improvement effect sufficient to obtain If the SiO ₂ component content is excessively reduced to less than 3.8% by mass, it is difficult to prevent a decrease in cold strength (TI) as described later, which is not preferable. Here, according to the results of in-furnace investigation by blast furnace dismantling and the like, if the high temperature reducible index is 86% or more, preferably 90%, FeO component (wustite component) remaining unreduced in the lower portion of the blast furnace furnace The increase in the viscosity of the slag melt and the increase in the melting point at the lower part of the blast furnace are also reduced, and good air permeability in the furnace can be secured.

  Therefore, in order to reduce the FeO component remaining unreduced to the lower part of the blast furnace and improve the in-furnace air permeability of the lower part of the blast furnace, the porosity of the sintered ore with a pore diameter of less than 5 μm is set to 5% by volume or more. It is necessary to.

FIG. 5 is a graph showing the relationship between the porosity ratio of pores with a pore diameter of less than 5 μm and cold strength index (TI) contained in the sintered ore for various SiO ₂ component contents of the sintered ore. According to the results shown in the figure, the cold strength decreases as the pore ratio with a pore diameter of less than 5 μm increases.

  Since pores having a pore diameter of less than 5 μm are fine, the influence of the pore ratio on the cold strength is small compared to pores having a pore diameter of more than 50 μm, but if the pore ratio of less than 5 μm increases excessively, The interstitial strength index decreases, and the particle size of the sintered ore decreases due to mechanical stress in the blast furnace and when charged in the blast furnace, and the air permeability of the blast furnace deteriorates. Therefore, in order to ensure the cold strength of the sintered ore, the ratio of pores having a pore diameter of less than 5 μm needs to be 15% by volume or less.

  For the above reasons, from the viewpoint of improving the high temperature reducibility of the sintered ore and ensuring the cold strength, the pore ratio with a pore diameter of less than 5 μm is set in the range of 5 to 15% by volume.

(D) Preferred range of SiO ₂ component content of sintered ore: 3.8 to 4.6% by mass
When the SiO ₂ component content of the sintered ore is 3.8% by mass or more, as shown in FIG. 5, the cold strength index (TI) due to the decrease in the amount of sintered melt produced in the manufacturing process of the sintered ore is obtained. Decline can be prevented. Therefore, the impact during charging of the sintered ore into the blast furnace furnace and the decrease in the particle size of the sintered ore due to mechanical stress in the furnace are suppressed, and deterioration of air permeability in the blast furnace is prevented, which is preferable. .

Also, if the SiO ₂ component content of less 4.6 wt%, as shown in FIG. 4, the increase in the amount of silicate slag is irreducible is suppressed, deterioration of the high-temperature reducibility is Is prevented. Therefore, it is preferable because the increase in the remaining FeO component that remains unreduced down to the lower part of the blast furnace is suppressed, and deterioration of the air permeability in the furnace at the lower part of the blast furnace is prevented. Therefore, the preferable range of the SiO ₂ component content of the sintered ore is set to 3.8 to 4.6% by mass.

(E) Preferred range of FeO component content of sintered ore: 5-9% by mass
When the FeO component content of the sintered ore is 5% by mass or more, as shown in FIG. 3, the amount of sintered melt produced in the process of producing the sintered ore is secured, and the cold strength index (TI) is high. Easy to maintain. Further, it is possible to prevent an increase in the hematite-based mineral structure having inferior reduced powdering property and to prevent an increase (that is, deterioration) of the reduced powdering index (RDI) of the sintered ore defined in JIS M 8720. Therefore, the mechanical stress in the blast furnace furnace and the mechanical stress in the furnace, as well as the reduction in the grain size of the sintered ore due to reduced powdering in the blast furnace furnace, are suppressed, and the air permeability of the blast furnace is reduced. Since it can prevent, it is preferable.

Further, when the FeO component content of the sintered ore is 9% by mass or less, as shown in FIG. 2, an excessive sintered melt is not generated in the manufacturing process of the sintered ore, so that fine pores are sufficiently formed. Since high temperature reducibility is ensured, the air permeability in the lower part of the blast furnace is improved, which is preferable. Therefore, the preferable range of the FeO component content of the sintered ore is set to 5 to 9% by mass.
(F) Preferred blending ratio of high crystal water ore having a crystal water content of 4% by mass or more: 25 to 80% by mass
In the manufacturing process of sintered ore, pores and the like are formed after the crystal water is decomposed and vaporized. Therefore, in order to produce fine pores with a pore diameter of less than 5 μm, the content of crystal water in the high crystal water ore is included. The rate is preferably 4% or more. When the blending ratio of the high crystal water ore in the entire sintered raw material is 25% by mass or more, the amount of fine pores contained in the sintered ore can be sufficiently ensured, so that high temperature reducibility is ensured. . Therefore, an increase in the FeO component remaining unreduced up to the lower part of the blast furnace can be prevented, and air permeability in the furnace at the lower part of the blast furnace can be secured, which is preferable.
Moreover, if the blending ratio of the high crystal water ore in the entire sintered raw material is 80% by mass or less, the amount of pores contained in the sintered ore will not be excessive, and the cold strength index (TI) is maintained. be able to. Therefore, it is preferable because it is possible to suppress the deterioration of the air permeability in the furnace due to the particle size of the sintered ore being reduced due to the impact at the time of charging into the blast furnace furnace and the mechanical stress in the furnace.

  Therefore, the preferable blending ratio of the high crystal water ore having a crystal water content of 4% by mass or more in the sintering raw material is set to 25 to 80% by mass.

In order to confirm the effect of the operation method of the blast furnace of the present invention, as described below, a sintered ore is produced by performing a test operation of a sintering machine, and this is charged into a blast furnace having a furnace internal volume of 2150 m ^3. The test operation was conducted and the results were evaluated.

  The production conditions and sinter properties of the sinter, the blast furnace operation conditions and the operation results are summarized in Table 1.

  In the same table, the ratio of sintered ore indicates the ratio of the charged mass of the test sintered ore to the charged mass of the iron oxide charged charged from the top of the blast furnace. The reducing material ratio is the sum of the amount of coke charged (kg) per ton of tapping and the amount of auxiliary fuel blown in (kg) such as pulverized coal.

  Test Nos. 1 to 8 are tests for examples of the present invention that satisfy the range specified by the present invention, and Test Nos. 9 to 11 are for comparative examples that do not satisfy at least one of the conditions specified by the present invention. It is a test.

Test No. 9 has a SiO ₂ component content of 5.4% by mass, an Al ₂ O ₃ component content of 1.6% by mass, a MgO content of 1.0% by mass, (CaO / SiO ₂ ) The ratio is 1.9, the FeO component content is 10.0% by mass, the sintered ore ratio is 70% by mass, the amount of pulverized coal injection is 138 kg / pt, and the reducing material ratio is 513 kg / pt. As a result, the operation was carried out at an output ratio of 1.84 p-t / d / m ³ . As for the pore size distribution of the sintered ore at this time, the proportion of pores having a pore diameter exceeding 50 μm was 4% by volume, and the proportion of pores having a pore diameter of less than 5 μm was 10% by volume.

The sintered ore used in the blast furnace operation of Test No. 9 has a lower pore ratio with a pore diameter exceeding 50 μm as compared with the examples of the present invention, and further has a high SiO ₂ component content and FeO content. For this reason, although the cold strength index (TI) was good, the hot air permeability index (JPU) was 9, which was below the appropriate range, and the high temperature reducibility index was also below the control lower limit. In blast furnace operation using this sinter, despite the sinter ratio being 70% by mass, the amount of FeO component that remains unreduced down to the bottom of the blast furnace furnace cannot be reduced, The air permeability of the blast furnace remained in a poor state. As a result, although it was directed to increase the pulverized coal injection amount, it could be increased only to 138 kg / pt, and the reducing material ratio and the output ratio were not good.

Test No. 10 has an SiO ₂ component content of 5.4% by mass, an Al ₂ O ₃ component content of 1.8% by mass, an MgO content of 1.1% by mass, (CaO / SiO ₂ ) The ratio is 2.0, the FeO component content is 9.8% by mass, the sintered ore ratio is 70% by mass, the pulverized coal injection amount is 136 kg / pt, and the reducing material ratio is 524 kg / pt. As a result, the operation was carried out at an output ratio of 1.84 p-t / d / m ³ . The pore size distribution of the sintered ore at this time was 5% by volume of pores having a pore size exceeding 50 μm, and 4% by volume of pores having a pore size of less than 5 μm.

The sintered ore used in the blast furnace operation of test number 10 has a lower pore ratio with a pore diameter of less than 5 μm, and a higher SiO ₂ component content and FeO content than the examples of the present invention. In blast furnace operation using this sinter, despite the sinter ratio being 70% by mass, the amount of FeO component that remains unreduced down to the bottom of the blast furnace furnace cannot be reduced, The air permeability of the blast furnace remained in a poor state. As a result, the increase in the amount of pulverized coal injection was directed, but it could only be increased up to 136 kg / pt, and both the reducing material ratio and the output ratio were not good.

Test No. 11 includes 5% by volume of pores having a pore diameter of more than 50 μm, 5% by volume of pores having a pore diameter of less than 5 μm, 3.8% by mass of SiO ₂ component, _{The 2} O ₃ component content is 1.8% by mass, the MgO component content is 1.2% by mass, the (CaO / SiO ₂ ) ratio is 2.1, and the FeO component content is 9.0% by mass. This is an example of blast furnace operation with a mining ratio of 66% by mass. Sintered ore with good high temperature reducibility, with a high temperature reducibility index of 90% by mass, after controlling the hot air permeability index (JPU) and the cold strength index (TI) within the proper operation range of the sintering operation Could be manufactured. Although this sinter was charged into the blast furnace, the ratio of the sinter was as low as 66% by mass. Therefore, the sinter was derived from the iron oxide charge other than the sinter and descended to the lower part of the blast furnace without reduction. The increase in the FeO component could not be suppressed, and the operation was poor in furnace air permeability. As a result, although it was directed to increase the pulverized coal injection amount, it could only be increased up to 140 kg / pt, and the reducing material ratio and the output ratio were not good.

Test No. 1 is 5% by volume of pores having a pore diameter exceeding 50 μm, 10% by volume of pores having a pore diameter of less than 5 μm, 4.2% by mass of SiO ₂ component, Al _{The 2} O ₃ component content is 1.8% by mass, the MgO component content is 1.2% by mass, the (CaO / SiO ₂ ) ratio is 2.0, and the FeO component content is 8.6% by mass. This is an example in which the blast furnace operation was performed with the ore ratio as 70% by mass. The hot breathability index (JPU) of the sinter is controlled within the proper operating range of the sintering operation, and the cold strength index (TI) is controlled above the lower limit determined from the blast furnace operation. Was 90 mass%. The furnace air permeability of the blast furnace charged with this sintered ore remained good, and the amount of pulverized coal injection could be increased to 156 kg / pt, resulting in a reducing material ratio of 500 kg / pt. It was possible to reduce to less than.

Test No. 2 has 10% by volume of pores having a pore diameter of more than 50 μm, 10% by volume of pores having a pore diameter of less than 5 μm, 4.2% by mass of SiO ₂ component, Al _{The 2} O ₃ component content is 1.8% by mass, the MgO component content is 1.2% by mass, the (CaO / SiO ₂ ) ratio is 2.0, and the FeO component content is 5.4% by mass. This is an example in which the blast furnace operation was performed with the ore ratio set to 70% by mass. While the hot air permeability index (JPU) and the cold strength index (TI) could be managed within the proper operating range, the high temperature reducible index could be 92% by mass. When this sinter was charged into a blast furnace, the air permeability of the blast furnace was excellent, and the amount of pulverized coal injection could be increased to a high level of 154 kg / pt. As a result, the reducing material ratio in blast furnace operation could be reduced to less than 500 kg / pt.

Test No. 3 has a porosity of 7.5% by volume with a pore diameter exceeding 50 μm, 5% by volume with a pore diameter of less than 5 μm, and 4.2% by mass of SiO ₂ component. The Al ₂ O ₃ component content is 1.8% by mass, the MgO component content is 1.2% by mass, the (CaO / SiO ₂ ) ratio is 2.0, and the FeO component content is 7.3% by mass. This is an example in which blast furnace operation was performed with a sintered ore ratio of 80% by mass. While the hot air permeability index (JPU) and the cold strength index (TI) could be managed within the proper operation range, the high temperature reducible index could be 88% by mass. When this sinter was charged into a blast furnace, the air permeability of the blast furnace was good, and the amount of pulverized coal injection could be increased to a high level of 155 kg / pt. As a result, the reducing material ratio in blast furnace operation could be reduced to less than 500 kg / pt.

Test No. 4 has a porosity of 7.5% by volume with a pore diameter exceeding 50 μm, 15% by volume with a pore diameter of less than 5 μm, and a SiO ₂ component content of 4.2% by mass. The Al ₂ O ₃ component content is 1.8% by mass, the MgO component content is 1.2% by mass, the (CaO / SiO ₂ ) ratio is 2.0, and the FeO component content is 6.8% by mass. This is an example in which blast furnace operation was performed with a sintered ore ratio of 80% by mass. While the hot air permeability index (JPU) and the cold strength index (TI) could be managed within the proper operating range, the high temperature reducible index could be 92% by mass. When this sinter was charged into a blast furnace, the air permeability of the blast furnace was good, and the amount of pulverized coal injection could be increased to a high level of 162 kg / pt. As a result, the reducing material ratio in blast furnace operation could be reduced to less than 500 kg / pt.

Test No. 5 is 7.5% by volume of pores having a pore diameter exceeding 50 μm, 12% by volume of pores having a pore diameter of less than 5 μm, and 3.6% by mass of SiO ₂ component. , Al ₂ O ₃ component content of 1.6 wt%, the MgO component content of 1.2 mass%, the (CaO / SiO ₂₎ ratio of 2.1, and a FeO component content and 8.9 wt% This is an example in which blast furnace operation was performed with a sintered ore ratio of 70 mass%. While the hot air permeability index (JPU) and the cold strength index (TI) could be managed within the proper operating range, the high temperature reducible index could be 94% by mass. When this sinter was charged into the blast furnace, the in-furnace air permeability of the blast furnace was excellent, and the amount of pulverized coal injection could be increased to a high level of 152 kg / pt. As a result, the reducing material ratio in blast furnace operation was able to secure a low level of about 500 kg / pt.

Test No. 6 has a porosity of 7.5% by volume with a pore diameter exceeding 50 μm, 12% by volume with a pore diameter of less than 5 μm, and a SiO ₂ component content of 4.8% by mass. The Al ₂ O ₃ component content is 1.7% by mass, the MgO component content is 1.4% by mass, the (CaO / SiO ₂ ) ratio is 2.0, and the FeO component content is 7.8% by mass. This is an example in which blast furnace operation was performed with a sintered ore ratio of 70 mass%. While the hot air permeability index (JPU) and the cold strength index (TI) could be managed within the proper operating range, the high temperature reducible index could be 86% by mass. When this sinter was charged into a blast furnace, the air permeability of the blast furnace was excellent, and the amount of pulverized coal injection could be increased to a high level of 151 kg / pt. As a result, the reducing material ratio in blast furnace operation was able to secure a low level of about 500 kg / pt.

Test No. 7 has a porosity of 7.5% by volume with a pore diameter exceeding 50 μm, 10% by volume with a pore diameter of less than 5 μm, and 4.2% by mass of SiO ₂ component. The Al ₂ O ₃ component content is 1.9% by mass, the MgO component content is 0.9% by mass, the (CaO / SiO ₂ ) ratio is 2.0, and the FeO component content is 10.0% by mass. This is an example in which blast furnace operation was performed with a sintered ore ratio of 70 mass%. While the hot air permeability index (JPU) and the cold strength index (TI) could be managed within the proper operating range, the high temperature reducible index could be 89% by mass. When this sinter was charged into a blast furnace, the air permeability of the blast furnace was excellent, and the amount of pulverized coal injection could be increased to a high level of 153 kg / pt. As a result, the reducing material ratio in blast furnace operation was able to secure a low level of about 500 kg / pt.

Test No. 8 has a porosity of 7.5% by volume with a pore diameter exceeding 50 μm, 10% by volume with a pore diameter of less than 5 μm, and 4.2% by mass of SiO ₂ component. , Al ₂ O ₃ component content of 1.6 wt%, the MgO component content of 1.2 mass%, the (CaO / SiO ₂₎ ratio of 2.0, and a FeO component content and 7.7 wt% This is an example in which blast furnace operation was performed with a sintered ore ratio of 70 mass%. While the hot air permeability index (JPU) and the cold strength index (TI) could be managed within the proper operating range, the high temperature reducible index could be 86% by mass. When this sinter was charged into the blast furnace, the in-furnace air permeability of the blast furnace was excellent, and the amount of pulverized coal injection could be increased to a high level of 152 kg / pt. As a result, the reducing material ratio in blast furnace operation was able to secure a low level of about 500 kg / pt.

From the above results, in a large quantity injection operation where the amount of pulverized coal injection is 150 kg / pt or more, the ratio of pores with a pore diameter exceeding 50 μm is added to 70% by mass or more of the iron oxide charge to be charged. By using a sintered ore containing 5 to 10% by volume and having a pore ratio of 5 to 15% by volume with a pore diameter of less than 5 μm, a blast furnace having a high iron ratio and a low reducing material ratio is used. It has been found that operation is possible. Also, sintered ore composition of that time, with the range of FeO component content in sintered ore of 5-9 wt%, and the range of the SiO ₂ component content of 3.8 to 4.6 mass% It is preferable to do.

  According to the method of the present invention, by using a sintered ore excellent in high temperature reducibility in which the pore size distribution is adjusted to 70% by mass or more of the iron oxide charge charged from the top of the blast furnace. Since the deterioration of air permeability in the blast furnace due to the increase in the amount of pulverized coal injection can be prevented, a large amount of pulverized coal injection of 150 kg / pt or more can be achieved while maintaining stable operation of the blast furnace. A large amount of pulverized coal can be achieved. Therefore, the blast furnace operation method of the present invention can be widely applied in the field of blast furnace high-injection pulverized coal aiming to reduce productivity and pig iron cost while reducing the load on the coke oven.

It is the figure which showed the relationship between the charging ratio of the sintered ore excellent in the high temperature reducibility in the iron oxide charge with which it charges from a furnace top, the amount of pulverized coal injection, and the ventilation resistance of the lower part of a blast furnace . It is the figure which showed the relationship between the porosity which the pore diameter contained in a sintered ore exceeds 50 micrometers, and a hot air permeability index (JPU) about the various FeO component content rate of a sintered ore. It is the figure which showed the relationship between the pore ratio in which the pore diameter contained in a sintered ore exceeds 50 micrometers, and a cold strength index | exponent (TI) about the various FeO component content rate of a sintered ore. The relationship between the pore diameter contained in sintered ore is the pore rate and the high-temperature reducibility index of less than 5 [mu] m, is a diagram showing the various SiO ₂ component content of sinter. The relationship between the porosity ratio and the cold strength index of less than the pore diameter contained in sintered ore is 5 [mu] m (TI), a diagram showing the various SiO ₂ component content of sinter.

Claims (3)

  A blast furnace operating method in which pulverized coal of 150 kg or more per ton of tuna is blown into the furnace together with hot air from the tuyere, and the pore diameter is over 70% by mass of the iron oxide charge charged from the top of the furnace. A method for operating a blast furnace, comprising using a sintered ore having a pore ratio of more than 50 μm and a pore ratio of 5 to 15% by volume with a pore diameter of less than 5 μm. A sintered ore having a SiO ₂ component content of 3.8 to 4.6% by mass and a FeO component content of 5 to 9% by mass is used as the sintered ore. Item 2. A method for operating a blast furnace according to Item 1. 2. The sintered ore used as the sintered ore is a sintered ore fired using a sintering raw material containing 25 to 80% by mass of high crystal water ore having a crystal water content of 4% by mass or more. Or the operating method of the blast furnace of 2 or 2.

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