JP4283814B2 - Blast furnace operation method - Google Patents

Description

  The present invention relates to a method of operating a blast furnace in which a large amount of high Al2 O3 ore is used and a blast furnace slag ratio is reduced, and more particularly to a stable operation of a blast furnace when a large amount of pulverized coal is injected.

In Australia and India, the iron ore has an Al2 O3 content of 2.0 mass% or more, and the Al2 O3 content is more than double that of low Al2 O3 ores such as Brazil. In blast furnace operation, the amount of Al2 O3 in the blast furnace slag is controlled to 14.0 to 15.5%, and it is not preferable that the amount of Al2 O3 in the ore increases. However, Japan is geographically close to Australia and India and is required to use more of the high Al2 O3 ore in these areas to reduce transportation costs.

  In addition, the technology to inject pulverized coal from the blast furnace tuyere to replace the coke charged to the blast furnace and reduce the hot metal cost is also important as a countermeasure for aging of the coke oven, and is adopted in almost all blast furnaces in Japan. An example in which the amount of pulverized coal injection is 150 kg / tp or more has been reported.

  For example, Non-Patent Document 1 includes the improvement of coke DI and high oxygen enrichment operation, the use of low Al2 O3 and highly reducible sintered ore, and a local high O / C (ore / coke ratio) part. It has been reported that an operation test with a pulverized coal ratio of 200 kg / tp for one week could be achieved by controlling the charge distribution not to occur. This is thought to be due to the suppression of the increase in the thickness of the melted body by reducing the Al2 O3 content of the charge.

  In Non-Patent Document 2, the slag ratio is reduced (320 → 280 kg / tp) to improve the ventilation and liquid permeability in the lower part of the furnace, and the high RI (reducible reduction) of agglomerated ore by using the entire surface of HPS ore. It has been reported that an operation result of 218 kg / tp per month of pulverized coal ratio was obtained. Since it is well known that the HPS ore is a low SiO2 and low Al2 O3 ore, it is considered that the increase in the cohesive zone thickness was suppressed by lowering the SiO2 and low Al2 O3 of the charge.

  In Patent Document 1, the basicity of sinter ore (C / S) is set to 2 or more in blast furnace operation, and the amount of increase from the target basicity of blast furnace slag is adjusted by charging SiO2 source auxiliary material in the blast furnace, and softening and melting are performed. A blast furnace operating method is described in which the Si concentration in the hot metal is lowered by lowering the landing level.

JP-A 61-56211 “Materials and Processes” 7 (1994), p126 “Materials and Processes” 8 (1995), p. 319

  Since high Al2 O3 ore is cheaper than Brazil's low Al2 O3 ore, the establishment of technology for using high Al2 O3 sintered ore will be one of the important issues in blast furnace operation. However, in blast furnace operation, it is necessary to keep the amount of Al2O3 in the blast furnace slag below the control value. When a large amount of high Al2O3 ore is added, the amount of melt produced decreases due to the melting point of the calcium ferrite melt increasing. Conventionally, it has been difficult to increase the blending amount of high Al2 O3 ore because the production yield of the ore is reduced and the quality (especially strength and RDI) deteriorates.

  For stable operation of the blast furnace, it is necessary to improve the air permeability and liquid permeability at the bottom of the blast furnace. Especially when pulverized coal is blown at 150 kg / tp or more from the blast furnace tuyere, the top of the furnace is increased by increasing the pulverized coal ratio. As the amount of coke charged from the inside decreases (reduction of coke slits), the O / C in the blast furnace increases, increasing the thickness of the cohesive zone and lowering the air permeability of the lower part of the furnace including the furnace core less than that It becomes. In order to improve the permeability of the lower part of the furnace, it is necessary to reduce the blast furnace slag ratio.

  Therefore, in order to reduce the blast furnace slag ratio, reduction of the SiO2 component of the sintered ore has been studied. However, in blast furnace operation, the amount of Al2 O3 in the blast furnace slag must be less than the control value for blast furnace operation. If a large amount of low SiO2 ore is added, the amount of Al2 O3 in the blast furnace slag will exceed the control value for blast furnace operation. Thus, the slag viscosity increases and the slag fluidity deteriorates.

  The method of Patent Document 1 improves the high-temperature properties of the sinter by improving the basicity, thereby improving the shrinkage rate and the ventilation resistance of the softened cohesive zone. However, if the basicity is increased, the amount of blast furnace slag increases. Therefore, it is difficult to apply it to a large amount of pulverized coal injection that requires improvement of the air permeability at the bottom of the furnace.

  The method of the present invention was made in order to solve the above-mentioned problems, and enables a large amount of high Al2 O3 ore to be used in a blast furnace, and particularly reduces the blast furnace slag ratio when a large amount of pulverized coal is blown to reduce the bottom of the furnace. It aims to provide blast furnace operation that can improve air permeability and liquid permeability.

In order to solve the above problems, the present invention has the following gist.
(1) High C / S sintered ore containing 3.9 to 4.9 mass% of SiO2, 0.5 to 1.2 mass% of MgO, and C / S of 2.0 to 2.8, and SiO2 Of 4.5 to 6.0 mass%, 1.3 to 2.5 mass% of MgO, and C / S of 0.5 to 1.2 to produce a low C / S sintered ore with a blast furnace slag ratio Is characterized in that the high C / S sintered ore and the low C / S sintered ore are mixed and charged into the blast furnace so as to be less than the operation control value of the blast furnace.

(2) In the blast furnace operation in which pulverized coal of 150 kg / tp or more is blown from the blast furnace tuyere, the operation described in the above (1) is performed.
Here, the blast furnace slag ratio indicates the amount of slag produced per 1 ton of pig iron, and C / S is the basicity expressed by CaO / SiO2. The blast furnace slag contains about 0.2% FeO and alkali components in addition to CaO, SiO2, Al2 O3 and MgO.

  As described above, even if the amount of pulverized coal injection was increased to 150 kg / tp or more, the blast furnace stable operation could be continued for a long time without increasing the total pressure loss value in the furnace by the method of the present invention. The method of the present invention makes it possible to use a large amount of high Al2 O3 sintered ore and reduce the amount of blast furnace slag, and in particular, to enable stable operation of the blast furnace when a large amount of pulverized coal is injected.

The present invention makes it possible to use a large amount of high Al2 O3 sintered ore, reduce the amount of blast furnace slag, and stabilize the blast furnace operation particularly in the operation with high pulverized coal ratio.
First, the method 1 of the present invention will be described below.
Conventionally, when the amount of Al2O3 in the sintered ore is 2.0 mass% or more, the amount of melt produced decreases, the coexistence structure of "hematite + columnar calcium ferrite" that tends to be reduced to powder increases, and high FeO produced during reduction However, since the melting point of the melt is lowered to make it easy to soften, there is a problem that strength of sintered ore, RDI (reducible powdering property), high temperature reduction / softening melt properties deteriorate.

  Therefore, as a result of various investigations on the blending conditions of the sintering raw material that can produce a sintered ore of excellent quality even if a large amount of high Al2 O3 ore is blended, the SiO2 in the sintered ore is 3.9 to 4.9 mass%. , High Al2 O3 ore and other ores and auxiliary materials are blended so that MgO is 0.5 to 1.2 mass% and Al2 O3 is 2.0 to 3.0 mass% to obtain a high Al2 O3 sintered ore. As a result, it has been found that a sintered ore having excellent strength, RDI (reducible powdering property), JIS-RI (reducible property), high temperature reduction / softening melting property can be obtained. Furthermore, the low Al2 O3 sintered ore having SiO2 of 4.5 to 6.0 mass%, MgO of 0.8 to 2.5 mass% and Al2 O3 of 1.0 to 1.7 mass% is referred to as the high Al2 O3 sintered ore. It was found that the amount of Al2 O3 in the blast furnace slag, which has a great influence on the viscosity of the blast furnace slag, can be easily adjusted below the control value of the blast furnace operation.

  Here, SiO2 in the high Al2 O3 sintered ore is defined as 3.9 to 4.9 mass% and MgO in the range of 0.5 to 1.2 mass%. The amount of Al2 O3 is 2.0 to 3. When the mass is as high as 0 mass%, SiO2 is reduced to 4.9 mass% or less and MgO is reduced to 1.2 mass% or less simultaneously, thereby reducing the amount of MgO that adversely affects the strength of the sintered ore while maintaining the strength. The total amount of slag can be reduced. In addition, since the amount of heat in the sintered layer is constant, if the amount of slag is reduced, the temperature of the sintered layer rises and magnetite increases, the porosity increases and the reducibility is improved. The RDI (reducible powdering property), JIS-RI (reducible property), high temperature reduction / softening melt properties of the ore can be improved. However, if SiO2 is reduced to less than 3.9 mass% and MgO to less than 0.5 mass%, the strength and RDI of the sintered ore are deteriorated, which is not preferable. In this case, since the amount of Al2 O3 is higher than that of the ordinary sinter, the RDI is improved when the coke blending ratio is increased as compared with the case of the ordinary sinter. Does not increase significantly.

  In order to keep the viscosity of the blast furnace slag constant, the amount of Al2 O3 in the slag must be controlled to 14.0 to 15.5%. Therefore, when a large amount of the above high Al2 O3 sintered ore is charged into the blast furnace, the Al2 O3 is mixed with the low Al2 O3 sintered ore specified to 1.0 to 1.7 mass% and charged into the blast furnace. The amount of Al2O3 in the blast furnace slag is adjusted below the operation control value. Further, the high Al2 O3 sintered ore is charged in order to regulate the SiO2 in the low Al2 O3 sintered ore to 4.5 to 6.0 mass% and MgO to 0.8 to 2.5 mass%. This is to adjust the amount of SiO2 and MgO in the slag.

The quality of the low Al2 O3 sintered ore is stable, and there is no problem in terms of the quality of the sintered ore even if SiO2 and MgO are regulated to the above values. In this case, since Al2 O3 is at a low level of 1.0 to 1.7 mass%, the coke blending ratio can be made lower than that in the case of ordinary sintered ore.
As a method of mixing the high Al2 O3 sintered ore and the low Al2 O3 sintered ore, a method of cutting out on the transport belt at a set ratio of each sintered ore from separate ore tanks may be the simplest.

  Next, a method for stabilizing the operation by reducing the amount of blast furnace slag in Method 2 of the present invention will be described below. Conventionally, when SiO2 in sintered ore is 4.9% or less, there is a problem that strength and RDI (reducible powdering property) deteriorate. Accordingly, as a result of various investigations on the blending conditions of the sintering raw material capable of producing a low-quality SiO2 sintered ore with excellent quality, 3.9 to 4.9 mass% of the SiO2 component and 0.5 to 1. Excellent RDI (reducible powdering property), JIS- by blending ores and auxiliary materials so as to be 2 mass%, C / S 2.0 to 2.8 to make high C / S sintered ore It has been found that sintered ore with RI (reducibility), high temperature reduction / softening melt properties can be obtained. Furthermore, a low C / S sintered ore with SiO2 of 4.5 to 6.0 mass%, MgO of 1.3 to 2.5 mass% and C / S of 0.5 to 1.2 is manufactured, and blast furnace slag is produced. If the high C / S sintered ore and low C / S sintered ore are mixed and charged into the blast furnace so that the ratio is less than the operation control value of the blast furnace, the blast furnace slag amount is reduced and the air permeability of the lower part of the furnace is reduced. -It has been found that liquid permeability can be improved, and the present invention has been achieved.

  Here, MgO in the sintered ore was defined in the range of 0.5 to 1.2 mass% and C / S in the range of 2.0 to 2.8 because the SiO2 in the sintered ore was 3.9 to 4 When it is as low as 9 mass%, MgO is reduced to 1.2 mass% or less, and C / S is increased to 2.0 or more, so that RDI (reducible powdering property) of sinter, JIS-RI (covered) Reducing property), high temperature reduction / softening melt properties can be improved. However, when MgO is less than 0.5 mass% and C / S exceeds 2.8, the quality of sintered ore is deteriorated, which is not preferable.

  In order to make the slag ratio of the blast furnace below the operation control value, it is usually necessary to manage MgO in the slag at 6.0 to 8.0% and C / S at 1.2 to 1.3. Therefore, when a large amount of the above high C / S sintered ore is charged into a blast furnace, the low C / S sintered ore having C / S defined as 0.5 to 1.2 and the above high C / S sintered ore. Is mixed and charged into the blast furnace, C / S in the blast furnace slag can be adjusted to the operation control value range. In the case of a low C / S sintered ore having a C / S of 0.5 to 1.2, it is preferable that the amount of SiO2 and MgO is high, SiO2 is 4.5 to 6.0 mass%, and MgO is 1.3 to 2.5 mass% is appropriate. Here, when SiO2 exceeds 6.0 mass%, JIS-RI and high-temperature reduction / softening melt properties deteriorate, and when MgO exceeds 2.5 mass%, the strength decreases. In this case, the coke mixing ratio of the sintered ore may be an ordinary sinter ore mixing ratio.

Next, the method 3 of the present invention will be described.
When aiming for operation using a large amount of low-cost raw fuel, when blowing pulverized coal of 150 kg / tp or more from the blast furnace tuyere, the improvement of the air permeability and liquid permeability at the bottom of the blast furnace is increased due to the increase in the powder rate. As a result, the management of slag components and the quality of sintered ore that have a great influence on the air permeability of the lower part of the furnace have become particularly important.

  If the pulverized coal ratio increases to 150 kg / tp (coke ratio is 350 kg / tp) on the assumption that the fuel ratio is 500 kg / tp, the ore / coke ratio (O / C) rises to 4.5 level. To do. When the pulverized coal ratio reaches 200 kg / tp (the coke ratio is 300 kg / tp), the O / C increases to 5.5. Since O / C of normal operation is less than 4.0, if the pulverized coal ratio is 150 kg / tp or more, the ore layer thickness will be greatly increased, and the cohesive zone shape will be enlarged.

  FIG. 1 shows changes in the shape of the in-furnace cohesive zone based on the simulation results in the pulverized coal ratio of 60 and 200 kg / tp blowing operation. It can be seen that the cohesive zone is enlarged as the pulverized coal ratio increases. If the enlargement of the cohesive zone can be suppressed, the air permeability in the furnace can be improved.

  The combination of the method of the present invention method 1 and the pulverized coal large quantity injection technology can greatly improve the high temperature reduction and softening properties of sintered ore even if a large amount of inexpensive high Al2O3 ore is used. Stable operation can be realized by suppressing the enlargement of hot metal, and the effect of reducing hot metal production cost is great. Further, in combination with the method 2 of the present invention, the effect of reducing the blast furnace slag ratio is particularly great, and it can contribute to the reduction of the hot metal production cost.

During normal operation with a small amount of pulverized coal injection, the “high Al2 O3 sintered ore and low Al2 O3 sintered ore” or “high C / S sintered ore and low C / S sintered ore” of the present invention is mixed. As shown in periods D and E of Table 3, there was no problem in blast furnace operation even when compared with the conventional method (Comparative Example 3), and an effect of reducing the slag ratio was observed. Since the method of the present invention is particularly effective in the case of a large amount of pulverized coal blowing operation, the following example will be described with an example of pulverized coal large amount blowing.
Example 1
First, the sinter quality of the high Al2 O3 sintered ore and low Al2 O3 sintered ore according to Method 1 of the present invention will be described. The sintered ore was produced with a 450 m @ 2 sintering machine. The conventional method and the sintered ore of Example 1 are compared, the components of the sintered ore and the measurement results of RDI and JIS-RI are shown in Table 1, and the high temperature reduction / softening melt property measurement results are shown in FIG. It can be seen that the sintered ore used in the method of the present invention is greatly improved in high temperature reducing property and softening and melting property in addition to RDI and JIS-RI. In the method 1 of the present invention, two kinds of sintered ores of high Al2 O3 iron ore (low SiO2, low MgO) and low Al2 O3 iron ore (high SiO2, high MgO) are produced, and these are produced as Al2 in blast furnace slag. A large amount of high Al2 O3 sintered ore is used (by the ratio of sintered ore) by mixing it so that the O3 component is 15.5% or less and the MgO component is 6.0% or more. 40%) is possible. As a method for producing these sinters, either a method of separately making a plurality of sintering machines or a method of separately making a time zone using the same sintering machine can be selected.

(Example 2)
Next, the quality of the sintered ore of the high C / S sintered ore and the low C / S sintered ore of the method 2 of the present invention will be described. As in Example 1, the sintered ore was produced on a 450 m @ 2 sintering machine. The conventional method and the sintered ore of Example 2 are compared, the components of the sintered ore and the measurement results of RDI and JIS-RI are shown in Table 1, and the high temperature reduction / softening melt property measurement results are shown in FIG. It can be seen that the sintered ore used in Example 2 also has greatly improved high-temperature reducing properties and softening and melting properties in addition to RDI and JIS-RI.
In Example 2, two types of sintered ores of high C / S iron ore (low SiO 2, low MgO) and low C / S iron ore (high SiO 2, high MgO) are produced and mixed to produce a blast furnace. The blast furnace slag ratio is reduced to 280 kg / tp or less while adjusting the Al2 O3 component in the blast furnace slag to 15.5% or less and the MgO component to 6.0% or more. It became possible. As in Example 1, the method for producing these sintered ores can be selected from either a method in which a plurality of sintering machines are used or a method in which a time zone is divided using the same sintering machine. .

(Example 3)
An example in the A blast furnace (internal volume 3800 m @ 3) in which the amount of pulverized coal injection was increased to 180 kg / tp using the sintered ore of Example 1 or 2 will be described. The method of the present invention was compared with the conventional method in the periods B to C in Table 2.
In the conventional method, the ventilation resistance increases in the process of using a large amount from the operation level (comparative example 1) of the pulverized coal ratio 130 kg / tp to the pulverized coal ratio 180 kg / tp operation (period A, comparative example 2), Slip frequency increased and furnace body heat dissipation increased. This is because O / C increased due to an increase in the pulverized coal ratio, and the total pressure loss in the furnace increased, and this tendency was particularly remarkable at 170 kg / tp or more.

  On the other hand, when switching to methods 1 and 2 of the present invention where a plurality of sintered ores are mixed and used at the same time, even if the amount of pulverized coal injection is 180 kg / tp, the total pressure loss value in the furnace and the amount of heat dissipated in the furnace Fell and the number of slips dropped dramatically. In addition to improving the air permeability at the top of the furnace due to a decrease in the RDI value, the reducibility at the shaft is improved, and the enlargement of the root of the cohesive zone that is concerned about worsening the air resistance is prevented by improving the high temperature properties This is because there was no abnormality at the bottom of the furnace.

Simulation of cohesive zone in blast furnace Result of high temperature property measurement of sintered ore by the method of the present invention

Claims (2)

High C / S sintered ore containing 3.9 to 4.9 mass% of SiO2, 0.5 to 1.2 mass% of MgO, and C / S of 2.0 to 2.8, and SiO2 of 4. A low C / S sintered ore containing 5-6.0 mass%, MgO 1.3-2.5 mass% and C / S 0.5-1.2 is manufactured, and the blast furnace slag ratio is the blast furnace A method for operating a blast furnace, comprising mixing the high C / S sintered ore and the low C / S sintered ore so as to be equal to or less than an operation control value and charging the blast furnace. In the blast furnace operation which inject | pours 150 kg / tp or more pulverized coal from a blast furnace tuyere, the operation of Claim 1 is performed, The blast furnace operation method characterized by the above-mentioned.