JP2007186759A - Method for operating blast furnace - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for operating a blast furnace with which, when performing the blast furnace operation using reduction material having high hydrogen content, the optimum management index can be set and a stable operation can be continued by using the index. <P>SOLUTION: In the blast furnace operation injecting the reduction material containing 20 mass% or more of H, the method for operating the blast furnace is used, in which the distribution of hydrogen concentration (vol%) in the radius direction of the furnace is measured at the upper part of a shaft part in the blast furnace, and the operational control is performed by using [each radius position in H<SB>2</SB>/furnace top H<SB>2</SB>] as an index dividing the hydrogen concentration in each radius position with the average hydrogen concentration (vol%) in the gas at the furnace top part. Then, it is desirable that the operational control is performed so that a value of [each radius position H<SB>2</SB>/furnace top H<SB>2</SB>] at the position having 0.95-1 non-dimensional radius does not exceeded 1.2. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method of operating a blast furnace in which a reducing material having a high hydrogen content is blown from a tuyere.

In recent years, global warming due to an increase in carbon dioxide emissions has become a problem, and the suppression of emitted CO ₂ is an important issue even in the steel industry. Blast furnaces mainly use coke and pulverized coal as reducing materials, and in order to achieve carbon dioxide emission suppression, measures to replace coke with reducing materials with a high hydrogen content are effective. As a technology to use reducing materials with high hydrogen content in the blast furnace, there is a low carbon dioxide emission steelmaking method that reduces the carbon dioxide emitted in the ironmaking process by blowing LNG (Liquefied Natural Gas) into the blast furnace from the tuyere. It is known (for example, refer to Patent Document 1).

On the other hand, it is known that the reduction reaction of iron oxide with hydrogen is a relatively large endothermic reaction. The reaction and heat of reaction during iron oxide reduction with CO gas and H ₂ gas are shown in the following (a) to (f) (for example, see Non-Patent Document 1).
3Fe ₂ O ₃ + CO → 2Fe ₃ O ₄ + CO ₂ (Reaction heat: +38 kcal / kgFe) (a)
Fe ₃ O ₄ + CO → 3FeO + CO ₂ (heat of reaction: −38 kcal / kg Fe) (b)
FeO + CO → Fe + CO ₂ (Reaction heat: +60 kcal / kgFe) (c)
3Fe ₂ O ₃ + H ₂ → 2Fe ₃ O ₄ + H ₂ O (heat of reaction: +5 kcal / kg Fe) (d)
Fe ₃ O ₄ + H ₂ → 3FeO + H ₂ O (heat of reaction: −96 kcal / kg Fe) (e)
FeO + H ₂ → Fe + H ₂ O (reaction heat: −116 kcal / kg Fe) (f)
In the above reaction formula, the amount of hydrogen input from the tuyere increases, and if the ratio of hydrogen reduction in the reduction of iron oxide increases, the temperature of the shaft portion may decrease and the low temperature region may expand. Suggests that. It has been pointed out that the expansion of the low temperature region of the shaft part deteriorates the air permeability and the charge lowering behavior through the expansion of the reduced powdered region of the sintered ore.

If it can be detected that a low temperature region has been formed, it is possible to cope with this. When the low-temperature region (low-temperature heat preservation zone) is expanded, the water gas shift reaction H ₂ O + CO → H ₂ + CO ₂ (g) shown in (g) below.
As the hydrogen utilization rate decreases, the gas component (CO, CO ₂ , H ₂ , H ₂ O, N ₂ ) in the radial direction of the furnace is measured at the top of the furnace or at the top of the shaft to obtain the hydrogen utilization rate. Thus, there is known a technique for detecting the temperature distribution in the furnace height direction at each radial position and estimating the generation state of the low-temperature heat storage zone (see, for example, Patent Document 2).

However, H ₂ O is not measured by ordinary gas analysis, and the hydrogen utilization rate cannot be calculated directly. In Patent Document 2, when H ₂ O cannot be measured, the H ₂ O concentration is calculated from the Bosch gas component and furnace gas component measurement results obtained by calculation. Therefore, it is difficult to reliably detect the formation of the low temperature region.

In the first place, in the conventional normal blast furnace operation, the low temperature region was hardly formed. Although there are cases where the amount of hydrogen input to the blast furnace increases due to high pulverized coal ratio operation, generally the coke replacement rate of pulverized coal is normally around 0.9, which is high enough to exceed the injection basic unit of 150 kg / t. In the case of the pulverized coal ratio, the substitution rate further decreases. Therefore, in the case of operation that increases the pulverized coal ratio, the ratio of reducing material increases with the increase in the amount of input hydrogen, and the furnace top temperature generally rises, and the low temperature region is hardly formed. On the other hand, in the method in which LNG is blown from the tuyere as in the method described in Patent Document 1, the coke replacement ratio of natural gas is about 1.1 to 1.2 (see, for example, Non-Patent Document 2). As the natural gas blowing rate increases, the reducing material ratio decreases, so the formation of a low temperature region is actually a problem.
JP-A-3-240906 JP 59-226109 A “Seikan Handbook” Jinjinshokan 1979, p. 78 “Materials and Process 18” Japan Steel Association 2005, p. 984

  As mentioned above, there is a concern that the temperature at the top of the furnace may decrease due to the increase in hydrogen input to the blast furnace. Operation using a reducing material with a high hydrogen content, such as natural gas, and directing a reduction in the reducing material ratio. There is a problem that the operation management in the pulverized coal blowing operation that has been reported and implemented so far cannot be handled.

  Therefore, when using a reducing material having a high hydrogen content and performing an operation aimed at reducing the reducing material ratio, it is necessary to perform operation management from a viewpoint different from the conventional one. The object of the present invention is to solve such problems of the prior art, set an optimum management index when performing blast furnace operation using a reducing material having a high hydrogen content, and use this to maintain stable operation. It is to provide a blast furnace operation method.

The features of the present invention for solving such problems are as follows.
(1) In a blast furnace operation in which a reducing material containing 20% by mass or more of H is blown from the tuyere, the hydrogen concentration (volume%) distribution in the radial direction of the furnace is measured at the upper part of the shaft of the blast furnace, and at each radial position. Blast furnace operation method, characterized in that operation management is performed using "each radial position H ₂ / furnace top H ₂ ", which is an index obtained by dividing the hydrogen concentration of the gas by the average hydrogen concentration (volume%) in the gas at the top of the furnace .
(2) Operation management is performed so that the value of “each radial position H ₂ / furnace top H ₂ ” at the position of dimensionless radius 0.95 to 1 does not exceed 1.2 (1) The blast furnace operating method described in 1.

  According to the present invention, appropriate operation management can be performed even in a blast furnace operation in which a reducing material having a high hydrogen content is blown, and a stable operation is possible.

  The present invention provides a technique for simply estimating the expansion of the low temperature region in the upper part of the furnace, which is a concern when a reducing material having a high hydrogen content is blown, and achieving stable operation. The present invention is an operation in which a reducing material having a high hydrogen content is blown from the tuyere of the blast furnace, and the results of the investigation are led to be described as follows. In the present invention, the reducing material having a high hydrogen content is a substance containing 20% or more of H as a mass ratio and acting as an iron reducing material in a blast furnace, and specifically, LNG (H content of about 23 mass). %), COG (coke oven gas generated when coke is produced: H content: about 25% by mass), and the like. In the present invention, the effect is exhibited when a reducing material having a high hydrogen content is blown, but it is particularly effective when the reducing material is blown into a blast furnace at 10 kg / t-pig or more.

When a reducing material with a high hydrogen content is blown from the tuyere of the blast furnace and the low temperature region expands at a certain radial position and the reaction of the above formula (g) proceeds, the generation of H ₂ and CO ₂ causes the H ₂ Concentration increases. The present invention utilizes this phenomenon and detects the expansion of the low temperature region by measuring the hydrogen concentration distribution in the radial direction of the furnace by gas analysis in the radial direction of the upper portion of the shaft portion. At that time, the degree of excess hydrogen concentration is determined using an index obtained by dividing the hydrogen concentration (volume%) at each radial position by the average hydrogen concentration (volume%) in the gas at the top of the furnace, and the operation action is determined. By taking this measure, the expansion of the low temperature region at a specific location in the radial direction is prevented.

For stable operation, measure the hydrogen concentration at each radial position in the upper part of the shaft of the blast furnace, and the value of “hydrogen concentration at the upper part of the shaft / average hydrogen concentration in the gas at the top of the furnace” is locally high. It is important to operate so that it does not become. The upper portion of the shaft portion is located above the furnace body of the blast furnace and indicates a portion above half of the portion that spreads downward from the upper portion to the lower portion. The analysis of the hydrogen concentration at each radial position in the upper portion of the shaft portion can be performed by fixing or inserting a horizontal sonde in the furnace. The gas at the top of the furnace is blast furnace gas (BFG) discharged from the top of the blast furnace. Hereinafter, “the hydrogen concentration at the upper portion of the shaft at each radial position / the average hydrogen concentration in the gas at the top of the furnace” is referred to as “each radial position H ₂ / furnace top H ₂ ”.

From the examination results of the operation test shown below, it is understood that the value of the “each radial position H ₂ / top H ₂ ” index preferably does not exceed 1.2 at each radial position other than the furnace center. It was. In particular, at the dimensionless radius position 0.95-1 of the blast furnace, the operation management is performed so that the above-mentioned “each radial position H ₂ / furnace top H ₂ ” index is 1.2 or less for stable operation. It was found to be important. In order to set the value of the above index to 1.2 or less, it is possible to control the distribution of furnace interior inclusions or to change the air blowing conditions.

Hereinafter, the operation test conducted for the present invention will be described in detail. An operation test was conducted in a blast furnace having a bell-less charging device having a furnace volume of 5000 m ³ . The operation condition (base) as a standard is to carry out pulverized coal injection, and test operation 1 and test operation 2 in which LNG tuyere is injected in addition to pulverized coal were conducted as test operations. Table 1 shows the operation test conditions.

As shown in FIG. 1, the gas composition in the radial direction at the upper part of the shaft portion of the blast furnace 1 is analyzed using the horizontal sonde 2, and the excessive hydrogen concentration at the radial position is determined from the gas analysis result in the radial direction and the top gas analysis value. Was judged. FIG. 2 shows “each radial position H ₂ / furnace top H ₂ ” at each radial position (dimensionless radius: r / R) in the base and test operations 1 and 2. In the period of “Test Operation 1” in which LNG was blown against the base, the air flow fluctuation was remarkable in the shaft portion, and the operation was not stable. On the other hand, the charge that adjusts the tilt pattern of the bellless chute when charging the main raw material such as sintered ore or iron ore into the blast furnace so that more main raw material is deposited in the periphery of the furnace. When distribution control was performed and the gas distribution was changed to the “test operation 2”, the gas permeability was stable. In “Test operation 2”, “Hydrogen concentration in the center (dimensionless radius 0) / top H ₂ ” is almost the same as “Test operation 1”, but “peripheral (near dimensionless radius 1.0)” ) In “Hydrogen concentration / top H ₂ ” is lower than “Test operation 1”. This is presumably because the region that affects the air flow fluctuation is the peripheral portion having a large cross-sectional area. Repeatedly such operational performance, especially in the furnace peripheral portion "each radial position H ₂ / furnace top H _2" result of performing control of, "the radial position H ₂ / furnace top H _2" furnace peripheral portion only of the Control is sufficient, and the control standard for the radial hydrogen concentration when reducing material having a high hydrogen content such as LNG is blown is defined as “each radial position H ₂ / furnace top” in dimensionless radial positions 0.95 to 1. It has been found that a value of “H ₂ ” of 1.2 or less is desirable for stable operation.

The present invention was applied to various hydrogen-containing reducing material blowing operations in a blast furnace having an internal volume of 5000 m ³ . Using LNG and COG as the hydrogen-containing reducing material, the operation conditions were changed, and operations a to c were performed. Table 2 shows the operation conditions for each operation.

Under each operating condition, the hydrogen concentration was measured using a horizontal sonde at the upper part of the shaft portion, and the operation was performed while monitoring the “each radial position H ₂ / furnace top H ₂ ” index. In each region of dimensionless radial position (r / R) 0.95-1, “each radial position H ₂ / furnace top H ₂ ” may exceed 1.2 and fluctuations in ventilation were observed. The tilt pattern of the bellless chute is adjusted so that more sintered ore or iron ore, which is the main raw material, is deposited in the periphery of the furnace, and the above index becomes the dimensionless radius position (r / R) as shown in FIG. ) When adjusted to 1.2 or less in the range of 0.95 to 1, the air permeability was stable in any operation.

Schematic which shows the gas sampling method of a blast furnace radial direction. Graph showing the furnace radial distribution of "each radial position H ₂ / furnace top H _2" in operation test. Graph showing the furnace radial distribution of "each radial position H ₂ / furnace top H _2" at the time of stable operation.

Explanation of symbols

1 Blast furnace 2 Horizontal sonde

Claims (2)

In the blast furnace operation in which a reducing material containing 20% by mass or more of H is blown from the tuyere, the hydrogen concentration (volume%) distribution in the radial direction of the furnace is measured at the upper part of the shaft portion of the blast furnace, and the hydrogen concentration at each radial position A blast furnace operation method characterized in that operation management is performed using “each radial position H ₂ / furnace top H ₂ ” which is an index obtained by dividing the above by the average hydrogen concentration (volume%) in the gas at the top of the furnace. The operation management is performed so that the value of “each radial position H ₂ / furnace top H ₂ ” at a position of dimensionless radius 0.95 to 1 does not exceed 1.2. Blast furnace operation method.

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