JP4894989B2 - Blast furnace operation method - Google Patents

Description

  The present invention relates to a method for operating a blast furnace in which a large amount of inexpensive low-strength coke can be used.

  In the blast furnace where coke and iron oxide raw material are alternately charged and deposited from the upper part of the furnace in layers, and hot air is sent from the tuyere installed in the lower part of the furnace to produce pig iron, coke serves as a reducing agent, It also plays a role as a spacer (which secures a gap for allowing gas to pass through).

In order to fulfill this role, coke is required to have high strength, not easily pulverized, and to have an appropriate particle size (about 25 to 75 mm).
The reason is as follows. When coke with low strength is used, as the coke particles descend from the top of the furnace, they become finer due to the friction between the furnace walls or coke particles, filling the voids formed by the large particles, significantly impairing the air permeability, and reducing properties This prevents the gas from flowing from the bottom of the furnace to the top of the furnace. In such a case, the production amount of pig iron may be reduced, and in severe cases, so-called blow-through and slip phenomena may be induced, making it difficult to continue the operation.

Here, blow-through refers to a phenomenon in which the flow of reducing gas explosively resumes when the flow of reducing gas stops and the pressure in the furnace rises and reaches a certain pressure. In such a case, since the charge in the furnace moves along with the resumption of the gas flow, the distribution of the charge deposited in layers is disturbed.
Also, the slip phenomenon is a slightly light blow-through phenomenon, and in many cases, a stagnant portion of the flow of reducing gas occurs in a part of the radial direction, and only the distribution of the charge in one direction is disturbed (slips down) as the gas flow resumes. ) A phenomenon.
If either the blow-through or the slip phenomenon occurs, and the distribution of the charge is disturbed, the air permeability is further deteriorated and the reduction of iron oxide is caused. There is also a concern that mechanical damage to the blast furnace body may occur due to the rise in the temperature, and thermal adverse effects on various facilities due to the rapid ejection of high-temperature gas.

The occurrence of such blow-through or slip phenomenon has a great adverse effect. Therefore, in order to avoid the occurrence of these phenomena, the strength of coke used in the blast furnace is controlled very carefully.
As a strength management index, a so-called drum strength index (DI) is often used. This is an index indicating that the higher the value, the higher the strength.

As mentioned above, it is very important to use high strength coke for stable blast furnace operation.
However, in order to produce high-strength coke, expensive raw coal having caking properties is required as its raw material, and the cost required for this is enormous.

Therefore, in order to suppress the conventional cost increase, for example, in the method disclosed in Patent Document 1, when using low-strength coke, the amount of blown air is reduced and / or the amount of oxygen enriched in the blown air is reduced. The amount of gas in the blast furnace Bosch part should be reduced by increasing
Patent Document 2 discloses a technology that enables the use of low-strength coke by blowing oxygen from a blast furnace instead of hot air (normal temperature gas having an oxygen concentration of 40% or more).
JP 2004-263258 A Japanese Patent Publication No. 5-64201

As described above, in Patent Document 1, when low-strength coke is used, the amount of gas in the blast furnace bosch part is reduced by reducing the amount of air blown and / or the amount of oxygen enrichment into the air blown. I should do it.
However, if only the blown air is simply reduced in order to reduce the gas amount in the Bosch section, the production amount is proportional to the amount of oxygen charged into the blast furnace, so that there is a problem that the production amount is reduced.
Therefore, a method of increasing the oxygen enrichment amount and decreasing the blown air (that is, making the oxygen input amount to the blast furnace constant and reducing only nitrogen in the Bosch gas) can be adopted. When the coke combustion temperature rises, the tuyere melts, the heat removal through the tuyere cooling water increases, or some components of the slag evaporate and move to the top of the furnace, where it is cooled again. Various problems occur, such as the formation of deposits on the walls and the normal descent of the blast furnace charge.

Even if the method shown in Patent Document 2 in which oxygen (normal temperature gas having an oxygen concentration of 40% or more) is blown in instead of hot air to blow the blast furnace, the amount of oxygen used increases greatly, Construction of manufacturing equipment is required, which increases costs.
Also, in terms of equipment, if the oxygen enrichment exceeds 10% in the current blast furnace equipment, the method disclosed in Patent Document 2 is implemented, for example, the shaft center of the drive part of the blower is oxidized and becomes unusable. Therefore, various problems that are difficult to solve occur.

  An object of the present invention is to provide a blast furnace operating method capable of suppressing the occurrence of blow-through and slip phenomenon even when such low-cost low-strength coke that cannot be achieved by the conventional technology is used.

The inventors for solving such problems first examined coke pulverization behavior in a blast furnace.
The gasification reaction of coke with CO ₂ or H ₂ O can be expressed by equations (1) and (2).
C + CO ₂ = 2CO (1)
C + H ₂ O = CO + H ₂ (2)
The above reaction rate is very slow at 900 ° C. or less and is practically negligible, but it is known that the reaction rate becomes active at high temperatures. If the reaction rate is sufficiently high in a high-temperature atmosphere and the reaction proceeds on the surface of the coke mass, the strength of the coke does not deteriorate. However, since the reaction rate is still slow at temperatures of about 900 to 1100 ° C., gas diffusion occurs inside the coke particles, and a gasification reaction also occurs inside the particles.
As a result, the vicinity of the surface layer of the coke becomes brittle and easily pulverizes. Therefore, if the coke gasification reaction of (1) or (2) at 900 ° C. to 1100 ° C. is suppressed, the amount of coke pulverization can be suppressed.

Next, CO ₂ gas or H ₂ O gas causing the reaction (1) or (2) was examined.
Oxygen and water vapor blown from the tuyere react with the auxiliary reducing material blown together with coke and blast at the tip of the tuyere, but in a high-temperature atmosphere where carbon is present excessively and over a few hundred degrees Celsius (1) The reaction of (2) proceeds to the right very quickly and becomes a strong reducing atmosphere. For this reason, CO ₂ and H ₂ O are not included in the gas at the bottom of the furnace (so-called Bosch gas), which is a high-temperature atmosphere exceeding a few hundred degrees Celsius, and all exist in the form of CO and H _2. Yes. These strong reducing gases come into contact with iron oxide at the shaft part of the blast furnace.
FeO + CO = Fe + CO ₂ (3)
FeO + H ₂ = Fe + H ₂ O (4)
As a result of this reduction reaction, CO ₂ and H ₂ O are produced, which degrades coke when the reactions (1) and (2) occur under relatively low temperature conditions of about 900 to 1100 ° C. , Will promote powdering.

The equilibrium gas composition of the reactions (3) and (4) is calculated from thermodynamic data (for example, edited by the Japan Institute of Metals, Steel Smelting, Maruzen Co., Ltd., published on March 20, 2000, pages 36-38). can do. The calculation results are shown in FIG. In FIG. 4, the vertical axis indicates the value of H ₂ O / (H ₂ + H ₂ O) or CO ₂ / (CO + CO ₂ ), and the horizontal axis indicates the temperature. As shown in FIG. 4, both cross at about 890 ° C., but the value of CO ₂ / (CO + CO ₂ ) is H ₂ O at a temperature higher than 890 ° C. where the reaction of (1) and (2) occurs. It can be seen that the value is larger than the value of / (H ₂ + H ₂ O). This indicates that in this temperature range, the production of CO ₂ by the reaction (3) is relatively larger than the production of H ₂ O by the reaction (4). In other words, the amount of H ₂ O produced by the reaction (4) is relatively smaller than the amount of CO ₂ produced by the reaction (3) with respect to the unit amount of FeO. To do. Therefore, reduction by the reaction of (4) with less generation of oxidizing gas with respect to the unit amount of FeO reduces the amount of oxidizing gas and reduces coke by the reaction of (1) and (2). Powdering can be suppressed.
For this purpose, the amount of hydrogen input into the blast furnace is increased to increase the hydrogen partial pressure in the Bosch gas, thereby increasing the reduction reaction of iron oxide by hydrogen.
In this way, even when low strength coke is used, pulverization can be suppressed, and harmful effects due to pulverization can be prevented.

  The inventor further investigated the above and found that in order to reduce the amount of coke powder generated by the coke gasification reaction, the amount of hydrogen charged into the blast furnace should be 12 kg / tp or more. (kg / t-p is a unit indicating mass kg per ton of hot metal). The reason why the amount of hydrogen to be charged is 12 kg / tp or more is based on experimental data on the relationship between the amount of hydrogen input and the reducing material ratio for coke having various drum strengths, as described in the following embodiments. Is.

As a result of further investigations, the inventors have found that the blast furnace reducing material ratio significantly increases when the hydrogen input exceeds 31 kg / tp. This is due to the following reason.
The reaction (3) is an exothermic reaction of 18.56 kJ per mol, and the reaction (4) is an endothermic reaction of 22.6 kJ per mol. For this reason, as the amount of hydrogen input increases, the reduction of iron ore with hydrogen gas proceeds, the temperature in the blast furnace decreases, and finally the temperature required for the reduction cannot be maintained. For this reason, the operation becomes unstable because unreduced iron oxide falls to the lower part of the furnace, and for this reason, the amount of reducing material must be increased to balance.

Next, the hydrogen source to be input was examined. As the hydrogen source, hydrogen in the hydrocarbon (general formula CnHm) in the auxiliary reducing material and H ₂ O can be considered.
About H ₂ O, it is thrown into the furnace as water vapor added to the blown air in the humidity control air blow that is indispensable for preventing the furnace cooling accident.
Once furnace cooling occurs in a large blast furnace and the melt in the furnace is not discharged, it takes a long time to recover. For this reason, when signs of furnace cooling appear, it is necessary to quickly raise the temperature in the furnace. Although there is a method of increasing the amount of coke used in this furnace temperature raising method, for example, the coke charged from the top of the furnace requires several hours until it is burned at the tuyere and generates heat, and is not immediately effective. Therefore, H ₂ O is intentionally introduced into the furnace as an immediate effective method for raising the temperature in the furnace, and the amount of H ₂ O input is reduced when signs of furnace cooling are detected (in equation (2)) Reducing the endothermic reaction represented).

Decreasing humidity conditioning steam by 10g per 1Nm ³ of blown air has the same effect as increasing the coke ratio by 7kg / tp. To prevent furnace cooling accidents, the amount of humidity conditioning steam should be converted to at least the coke ratio. 10kg / tp is necessary, and 50kg / tp is considered sufficient. This is an amount equivalent to 1.5 to 7.6 kg / tp in terms of the input hydrogen amount.
By the way, H ₂ O of the hydrogen source causes the reaction shown by the formula (2). This is a large endothermic reaction of 131.3 kJ per mol, so it is necessary to set an upper limit for the amount of H ₂ O input. It is believed that there is.
From the above, as the amount of H ₂ O as a hydrogen source of the input hydrogen amount, it is preferable that the amount to be input as humidity control steam for preventing furnace cooling is the minimum required amount and the upper limit is the upper limit. . That is, the amount of H ₂ O as a hydrogen source of the input hydrogen is preferably 1.5 to 7.6 kg / tp necessary for humidity control steam.

In this way, hydrogen of 1.5 to 7.6 kg / tp is introduced by H ₂ O introduced to prevent furnace cooling, but it is preferable to set this amount as the upper limit. The remaining hydrogen for securing tp or more is preferably introduced from the hydrocarbon of the auxiliary reducing material.
However, since hydrogen in pulverized coal is at most 5 mass%, it is not optimal as a hydrogen source. Hydrogen in plastics and heavy oil is about 10 mass%, and natural gas (methane) is up to 25 mass%. Therefore, in order to secure the amount of hydrogen input with the auxiliary reducing material, plastic, heavy oil, or natural gas is desirable rather than single pulverized coal injection, or it is desirable to inject these in combination with pulverized coal.

As described above, even if the amount of input hydrogen is secured by the auxiliary reducing material, there is a certain limitation on the blowing of the auxiliary reducing material. That is, it is usually not preferable that the temperature in the combustion zone before the tuyere of the blast furnace becomes too high. The reason for this is that, as described above as a problem of Patent Document 1, if the pre-combustion zone becomes hot, the tuyere melts, the amount of heat removed through the cooling water of the tuyere increases, or This is because a part of the slag vaporizes and moves to the upper part of the furnace, and when it is cooled again, deposits are formed on the furnace wall, thereby causing various problems such as preventing normal descent of the blast furnace charge.
Therefore, there is an upper limit to the temperature of the combustion zone before the tuyere. And it is known that the pre-tuyere combustion zone temperature is highly dependent on the blowing temperature and the oxygen concentration during blowing.

By the way, when a gas reducing material such as natural gas or a liquid reducing material such as heavy oil is blown from the blast furnace tuyere, thermal decomposition occurs, but this reaction is an endothermic reaction. Therefore, these gas reducing materials and liquid reducing materials have a function of lowering the pre-tuyere combustion zone temperature, and when these reducing materials are blown, the oxygen concentration during blowing can be increased. When the oxygen concentration during blowing is increased under the condition that the production amount is constant, the blowing air can be reduced and the amount of nitrogen is reduced, so that the gas volume is reduced. When the gas volume decreases in the same blast furnace, the gas flow rate decreases, so the pressure loss in the packed bed decreases.
For the above reasons, it is considered desirable to blow at least a gas reducing material and / or a liquid reducing material as the auxiliary reducing material blown from the tuyere.

  The present invention has been made on the basis of the above studies, and specifically has the following configuration.

(1) The blast furnace operating method according to the present invention is the blast furnace operating method in which the auxiliary reducing material is blown from the tuyere together with the blown air, and the amount of hydrogen input to the blast furnace (water or iron ore attached to the coke charged from the top of the furnace) except water adhering to equal, the strength of the coke DI (drum strength) 150/15 77 or 85 for use with a hydrogen partial) to be introduced into the blast furnace in the range of 12 to 31 kg / tp in addition to this, the Of the amount of hydrogen input to the blast furnace, the amount supplied as H ₂ O from the tuyere is 1.5 to 7.6 kg / tp .

The amount of hydrogen input here is determined as the amount that becomes hydrogen inside the blast furnace and contributes to the reduction of the iron oxide of the formula (4) and causes the reaction of the formula (2).
Therefore, the moisture adhering to the coke charged from the top of the furnace and the moisture adhering to the iron ore and the like are excluded from the amount of hydrogen input here. These are vaporized when the temperature is raised to the boiling point after charging, but because of the low temperature, the reaction of the formula (2) does not occur and is discharged as steam from the blast furnace.
Other than this, the total amount of hydrogen charged into the blast furnace, that is, steam added from the tuyere, hydrogen in the auxiliary reducing material blown from the tuyere and its adhering water, hydrogen in coke charged from the top of the furnace, etc. Is defined as the hydrogen input.

The coke strength DI (drum strength) 150/15 in the above (1) is an index indicating the strength of the coke. After a predetermined amount of coke is put into a predetermined drum test apparatus and the drum is rotated 150 times, 15 mm is obtained. It represents the weight fraction of the above coke. A method for measuring the drum strength is defined in JIS K 2151.
In addition to the drum strength index described above, the coke strength test method may be the same drum strength index, the number of revolutions may be different, the screen may be different, or a tumbler test instead of a drum tester There are various variations such as when using a machine. However, even if the coke strength is tested by these different test methods, it can be finally reduced to the drum strength index mentioned here by using various conversion formulas.
Even if there is no conversion formula, the coke strength can be specified by measuring the drum strength by this test method.

( 2 ) Further, in the above (1), at least a gas reducing material and / or a liquid reducing material is blown as the auxiliary reducing material blown from the tuyere.

( 3 ) Further, in the above ( 2 ), the gas reducing material is at least one of natural gas, city gas, coke oven gas, and coal gasification gas, and the liquid reducing material is heavy oil, tar. Of these, at least one of them is used.

( 4 ) Further, in the above (1) to ( 3 ), pulverized coal and / or synthetic resin is used as an auxiliary reducing material blown from the tuyere.

In the present invention, the amount of hydrogen input to the blast furnace (excluding the water adhering to the coke charged from the top of the furnace and the water adhering to iron ore, etc., the hydrogen content input to the blast furnace other than this) is 12 to 31 kg / The coke strength DI (drum strength) 150/15 used in the tp range is 77 to 85, and the amount of hydrogen supplied to the blast furnace as H ₂ O from the tuyere is 1.5 to 7.6. Because it is kg / tp , even when inexpensive low-strength coke is used, it is possible to operate the blast furnace while suppressing the occurrence of blow-through and slip phenomenon.

The blast furnace 1 used in the blast furnace operating method according to the present embodiment has an internal volume of 3223 m ³ and, as shown in FIG. 1, penetrates the blow pipe 2 and blows a solid reducing material blowing lance 3 and a liquid reducing material blowing. A lance 4 and a gas reducing material blowing lance 5 are provided.
Further, in the embodiment of the present invention, raw materials including coke and iron source are alternately charged from the upper part of the blast furnace 1 and hot air is blown through the blower pipe 2 to reduce and melt iron oxide. We made pig iron.
Further, pulverized coal alone or a mixture of pulverized coal and plastic was injected as a solid reducing material. The liquid reducing material was heavy oil, and the gas reducing material was methane gas. The analysis values of the used coke are shown in Table 1, and the analysis values of pulverized coal, synthetic resin material, and gas reducing material are shown in Table 2.

There are various methods for blowing the reducing material. For example, two or three of a solid reducing material, a liquid reducing material, and a gas reducing material are simultaneously blown by a concentric multi-tube lance, A plurality of methods such as a method of mixing and blowing seeds or three kinds in a single tube may be considered.
However, since the hydrocarbons introduced into the furnace are pyrolyzed and finally become all hydrogen, the dependence on the shape and type of the blowing lance is low.
Therefore, in the present invention, any structure or blowing method of the blowing lance may be used.

For each coke shown in Table 1, the blast furnace operation was carried out with various amounts of hydrogen input, and the ratio of reducing materials at that time was investigated. The result is shown in the graph of FIG. In the graph of FIG. 2, the vertical axis represents the reducing material ratio (kg / tp), and the horizontal axis represents the hydrogen input (kg / tp).
When high-strength coke (DI = 85) was used, the reducing material ratio could be kept low regardless of the amount of hydrogen input, and good blast furnace operation could be continued.

With DI = 77 coke, when the hydrogen input was less than 12 kg / tp, the amount of coke pulverization increased, air permeability deteriorated, and blow-through and slip phenomenon occurred. Therefore, measures were taken to improve the air permeability by increasing the amount of coke charged. For this reason, the reducing material ratio increased.
When the amount of hydrogen input was in the range of 12 to 31 kg / tp, good air permeability was secured and the reducing material ratio could be kept low.
When the amount of hydrogen input exceeds 31 kg / tp, the reduction of iron ore, which is an endothermic reaction, with hydrogen gas increases, and there is a tendency for heat shortage. Therefore, it was necessary to increase the reducing material ratio and compensate for heat.

In the case of DI = 76 coke, when the hydrogen input was less than 12 kg / tp, the amount of coke pulverization increased, the air permeability deteriorated, and blow-through and slip phenomenon occurred. For this reason, measures were taken to improve the air permeability by further increasing the amount of coke charged than DI = 77.
When the hydrogen input is in the range of 12 to 31 kg / tp, the amount of coke charged is smaller than when the hydrogen input is less than 12 kg / tp. This is probably because the amount of hydrogen input was larger than that of normal operation, and the coke surface layer was weakened. However, compared to DI = 77 coke, the amount of coke charged is large and the ratio of reducing material is high. This is because the coke strength itself is low, so that a lot of powder from a healthy tissue that is not weakened is generated, and an increase in pressure loss is unavoidable, and as a result, the reducing material ratio has to be increased.
When the amount of hydrogen input exceeded 31 kg / tp, the ratio of reducing material increased because the amount of coke charged was increased due to the need for heat compensation as in the case of DI = 77 coke.

From the above considerations, the drum strength (DI) of coke is preferably 77 or more, and the amount of hydrogen input at that time is preferably in the range of 12 to 31 kg / tp.
In addition, even if the drum strength of coke exceeds 85, there will be no problem in operation. However, as shown in FIG. 3 which graphs the relationship between the coke production cost index and the coke drum strength, the coke production cost index increases as the coke drum strength increases. This is because it is necessary to use high-grade coal for producing high-strength coke, which leads to an increase in cost. As shown in FIG. 3, if the drum strength is up to 85, the cost increase is moderate, but if it exceeds that, the cost increases rapidly. Therefore, considering the cost, the upper limit of the actual coke strength is the drum index. 85.

Table 3 shows typical blast furnace operations shown in FIG.

Example 1 shows a case where high strength coke with a drum strength of 85 is used and the amount of hydrogen input is 19.4 kg / tp. The amount of hydrogen input as H ₂ O is 2.4 kg / tp. The drum strength of coke, the amount of hydrogen input, and the amount of hydrogen input as H ₂ O are within the scope of the present invention, and correspond to an example of the implementation of the present invention.
In this example, the number of slips was 0 / day, and blast furnace operation was extremely smooth.

Example 2 shows a case where coke B having a drum strength of 77 is used and the amount of hydrogen input is 14.9 kg / tp. The input hydrogen as H ₂ O is 3.6 kg / tp. The drum strength of coke, the amount of hydrogen input, and the amount of hydrogen input as H ₂ O are within the scope of the present invention and, like Example 1, correspond to one example of the implementation of the present invention.
Also in this example, the number of slips was 0 times / day, and the blast furnace operation was very smooth as in Example 1.

Example 3 shows a case where coke B having a drum strength of 77 is used and the input hydrogen amount is 28.8 kg / tp. The input hydrogen as H ₂ O is 3.5 kg / tp. This example also includes the drum strength of coke, the amount of hydrogen input, and the amount of hydrogen input as H ₂ O within the scope of the present invention, and corresponds to one example of implementation of the present invention as in Example 1.
In this example, as in Examples 1 and 2, the blast furnace operation was extremely smooth with the number of slips being 0 times / day.

Comparative Example 1 shows a case where coke C having a drum strength of 76 is used and the input hydrogen amount is 24.0 kg / tp. The input hydrogen as H ₂ O was 2.3 kg / tp. Although the amount of hydrogen input and the amount of H ₂ O input are within the range of the present invention, the drum strength of coke is an example lower than the range of the present invention.
In this example, the number of slips was 9 times / day, the blast furnace operation became unstable, and the coke ratio had to be increased to ensure air permeability. As a result, the hot metal production cost increased. This phenomenon is presumed to be due to the fact that the coke strength was insufficient and the generation of powder increased, which deteriorated the air permeability of the blast furnace.

Comparative Example 2 shows the case where coke B having a drum strength of 77 is used and the input hydrogen amount is 7.5 kg / tp. The amount of hydrogen input as H ₂ O was 2.3 kg / tp. The drum strength of coke and the amount of hydrogen input as H ₂ O are within the scope of the present invention, but the amount of hydrogen input is less than the range of the present invention.
In this example, the number of slips was 12 times / day, and the blast furnace operation became unstable. Therefore, in order to continue the blast furnace operation, the reducing material cost had to be increased.
In the case of this example, since the amount of hydrogen input is small, it is presumed that the weakness of the coke surface layer due to carbon dioxide could not be suppressed and the air permeability deteriorated.

Comparative Example 3 shows a case where coke A having a drum strength of 85 is used and the input hydrogen amount is 34.6 kg / tp. The input hydrogen as H ₂ O was 3.3 kg / tp. Although the drum strength of coke and the amount of hydrogen input as H ₂ O are within the scope of the present invention, this is an example in which the amount of hydrogen input is greater than the range of the present invention.
In this example, as the amount of input hydrogen becomes excessive, the endothermic reaction of the equation (4) increases and the furnace heat tends to decrease. Therefore, it is necessary to increase the reducing material ratio and perform heat compensation.

Comparative Example 4 shows a case where coke A having a drum strength of 85 is used and the input hydrogen amount is 16.4 kg / tp. The input hydrogen as H ₂ O was 8.3 kg / tp. The drum strength and input hydrogen amount of coke are within the scope of the present invention, but the input hydrogen amount as H ₂ O is larger than the present invention range.
In this example, as the amount of H ₂ O input becomes excessive, the endothermic reaction of equation (2) increases and the furnace heat tends to decrease. Therefore, it is necessary to increase the reducing material ratio and perform heat compensation. It was.

  As described above, as shown in the examples of the present invention, it has been demonstrated that the blast furnace operation method of the present invention enables stable blast furnace operation using inexpensive low-strength coke.

It is explanatory drawing of the blast furnace used for the blast furnace operating method which concerns on one Embodiment of this invention. It is a graph which shows the verification result of one Embodiment of this invention. It is a graph which shows the relationship between a coke manufacturing cost index | exponent and drum strength. It is a graph which shows the equilibrium gas composition of a reductive reaction. It is fu.

Explanation of symbols

    1 Blast furnace, 2 air duct, 3 solid reducing material blowing lance, 4 liquid reducing material blowing lance, 5 gas reducing material blowing lance.

Claims (4)

In the blast furnace operation method in which the auxiliary reducing material is blown from the tuyere together with the blown air, the amount of hydrogen input to the blast furnace (except for the water adhering to the coke charged from the top of the furnace and the water adhering to the iron ore, etc.) The coke strength DI (drum strength) 150/15 is 77 to 85 and the amount of hydrogen input to the blast furnace is from the tuyere. A method for operating a blast furnace, characterized in that the amount supplied as H ₂ O is 1.5 to 7.6 kg / tp .   The blast furnace operating method according to claim 1, wherein at least a gas reducing material and / or a liquid reducing material is blown as the auxiliary reducing material blown from the tuyere.   The gas reducing material uses at least one of natural gas, city gas, coke oven gas, and coal gasification gas, and uses at least one of heavy oil and tar as the liquid reducing material. The blast furnace operating method according to 2. The blast furnace operating method according to any one of claims 1 to 3, wherein pulverized coal and / or synthetic resin is used as the auxiliary reducing material blown from the tuyere.

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