JP2731829B2 - Blast furnace operation method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial application field) The present invention provides a method for improving productivity by using a coke that has increased reactivity in a blast furnace and an agglomerate in which a plurality of pellets having a particle size of 3 to 10 mm are combined. For blast furnace operation with improved quality.

(Prior art) In a normal blast furnace, iron ore and coke are charged in layers from a furnace section, and the iron ore is reduced in a furnace, then reduced and melted to a metal state to produce hot metal. ing.

At this time, in order to operate the blast furnace stably,
According to Japanese Patent No. 174403, in the blast furnace operating method in which iron raw material and coke are sequentially charged and refined in the blast furnace, when charging the coke into the blast furnace, an average of 15 to 25 mm around the furnace is constantly or intermittently charged. A method of operating a blast furnace characterized by charging small coke having a particle size of large coke having an average particle size of 35 to 70 mm in the center of the furnace and operating the same is disclosed.

Further, the present inventors have disclosed in Japanese Patent Application No. 62-193457
mm or less, the high-reactivity coke is mixed with ordinary coke or ore and charged into the blast furnace, thereby lowering the heat storage zone temperature of the blast furnace and increasing the reaction efficiency of the blast furnace. A blast furnace operation method to increase the blast furnace was proposed.

Further, the present inventors have disclosed in Japanese Patent Application Laid-Open No. 62-40322 an iron ore agglomerate characterized in that a void portion is provided inside an agglomerate in which a plurality of pellets having a particle size of 3 to 10 mm are combined. Proposed.

(Problems to be Solved by the Invention) However, in the blast furnace operation, large coke having an average particle size of 35 to 70 mm is provided in the center of the furnace, and small coke having an average particle size of 15 to 25 mm is provided in the periphery of the furnace. It is considered that the introduction of the core can ensure the liquid permeability of the furnace core in the central part of the furnace, thereby enabling stable operation. However, in the operation using ordinary coke, the reaction efficiency of the blast furnace cannot be improved.

On the other hand, in order to improve the reaction efficiency of the blast furnace, it is effective to use a small lump highly reactive coke mixed with ore or coke. Since the reactor is charged so as not to reach the center of the furnace, the reduction efficiency of the center of the furnace is not improved, and the reaction efficiency in the entire radial direction of the blast furnace is hardly improved. In addition, if the small reactive mass coke is charged into the center of the furnace by controlling the charge distribution, the reaction efficiency in the entire blast furnace radial direction can be improved, but there is a problem with the permeability of the core in the center of the furnace. It hinders stable operation.

Also, even when the reaction efficiency can be improved and low fuel ratio operation is possible, as is often seen during low fuel ratio operation,
When the gas flow becomes unbalanced and a region with a small gas flow is generated in the blast furnace shaft, a low-temperature heat preservation zone of 600 to 700 ° C is easily generated. As a result, poor ventilation of the blast furnace shaft occurs, resulting in delays in ore reduction and poor descent of the charged materials, which often hinders stable operation of the blast furnace.

The temperature distribution in the height direction in the blast furnace is measured by a vertical probe, as disclosed in JP-A-59-17917, and in JP-A-62-054006, the temperature distribution in the blast furnace top or A method of detecting the temperature distribution in the furnace by measuring the hydrogen gas utilization rate or the hydrogen gas utilization rate / CO gas utilization rate at the upper portion of the shaft is disclosed, but the amount of pellet used is adjusted using the information. Not yet.

Fig. 4 compares the reduced powdering index (hereinafter referred to as RDI) of low-reduced powdered sinter, pellets and ordinary sinter, and the indirect reduction rate when reduced under blast furnace conditions. , Low-reduced powdered sinter and pellets both have lower RDI than ordinary sinter and suppress the powder rate of the blast furnace shaft,
It is possible to eliminate poor ventilation, and stable operation is expected under low fuel ratio operation.

However, both low-reduced powdered sinters and pellets are inferior to ordinary sinters in terms of their reducibility, making it possible to make the most effective use of the fuel ratio reduction possible by using highly reactive coke. Absent.

Therefore, in the present invention, by increasing the reactivity of coke charged into the blast furnace, and separating and charging large coke and small coke, the heat storage zone temperature is reduced, and iron ore of the entire blast furnace is reduced. To reduce the in-furnace powder rate as much as possible,
Efficiently producing hot metal and suppressing the increase in the powder rate due to sinter reduction pulverization, which is likely to occur at low fuel ratio operations, stably establish a blast furnace with high reaction efficiency and high productivity. It is intended to operate.

(Means and Actions for Solving the Problems) The blast furnace operation method of the present invention has the following features.
In a blast furnace in which coke is separated into large and small lumps, high-reactivity coke is separated into large and small lump, large lump high-reactivity coke is placed in the center of the furnace, and small lump highly reactive coke is placed in the furnace. At the time of charging from the middle part to the furnace peripheral part, it is necessary to charge agglomerate ore (hereinafter, referred to as new agglomerate ore) in which a plurality of pellets having a particle size of 3 to 10 mm are combined together with the highly reactive coke. In addition, when operating with high-reactivity coke charged into the blast furnace, the temperature distribution in the height direction inside the blast furnace or the hydrogen gas utilization rate distribution in the radial direction inside the blast furnace was measured, and the measured temperature or hydrogen gas utilization was measured. When the difference between the rate and the reference value reaches a preset value, the entire amount of the normal ore is replaced with the new agglomerate.

 First, highly reactive coke will be described.

The highly reactive coke used in the present invention is JISK2151-1977.
It is desirable that the JIS reactivity measured by the reactivity test method described above is 30% or more. If that value is less than 30%,
There is almost no decrease in the heat storage zone temperature described below. Further, it is necessary to maintain high strength even for highly reactive coke, and it is desirable to maintain the same strength as normal coke.

As a method for preparing highly reactive coke having high strength,
There is a method of adding an alkaline aqueous solution to high-strength ordinary coke, or a method of forming and drying a common coal.

The high-reactivity coke is replaced with a part or all of the coke usually charged from the furnace top, and the high-reactivity coke is separated into large and small lumps, and the large lumps are mixed with normal coke, or The iron ore is charged separately and layered into the center of the furnace alone. The lumps are charged from the middle of the furnace to the periphery of the furnace in a mixture with iron ore and / or ordinary coke, or are separately charged separately and layered with iron ore.

In the present invention, the furnace center is defined as the furnace opening radius of the blast furnace at 20 mm.
%, For example, if the furnace opening radius is 5 m, the area within 1 m radius is called the furnace center. The outside of the furnace wall excluding the furnace center is referred to as the furnace middle to the furnace periphery.

It is desirable that the particle size of iron ore and / or highly reactive coke mixed and used with ordinary coke to be charged from the middle part of the furnace to the periphery of the furnace is 15 mm or less. If the particle size is 15 mm or less, the surface area per unit weight of coke increases, and the proportion contributing to the reaction increases.

Since this highly reactive coke has high reactivity, the interfacial reaction in which CO ₂ in the furnace comes into contact with CO on the coke surface is smoothly performed. Further, as a result, the reaction that the CO gas generated in the furnace effectively reacts with the iron ore to reduce to a lower oxide or a metal state is promoted.

The gasification reaction of coke of C + CO ₂ = 2CO is an endothermic reaction, and can lower the temperature of the heat storage zone in the blast furnace shaft. For example, 1000 ℃
The use of highly reactive coke makes it possible to reduce the temperature of the heat storage zone to 900-950 ° C., while the degree of heat storage zone is produced and its value hardly changes. As a result, since the reduction equilibrium reaching point has a margin, the reduction proceeds more, and the shaft efficiency, the indirect reduction rate, and the CO gas utilization rate are improved, and the coke ratio can be reduced.

In addition, by introducing high-reactivity coke with a particle size of 35 to 70 mm as large lump high-reactivity coke into the center of the furnace, the permeability of the furnace core at the center of the furnace is ensured, and stable operation is possible. In addition, since the reduction of the iron ore charged in the center of the furnace is promoted, the reduction efficiency in the entire blast furnace radial direction can be improved.

In addition, as shown in Fig. 1, the new agglomerate ore has a lower reducible pulverizability index (RDI) and better reducibility than ordinary sintered ore, so the use of the new agglomerate This is effective in lowering the fuel efficiency, and also contributes to the improvement of the reduction efficiency in the blast furnace, which is an effective means for reducing the fuel ratio.

 Next, the reduction powdering phenomenon of the sintered ore will be described.

The use of highly reactive coke improves the reduction efficiency, but promotes the reduction at low temperatures, which promotes the reduction and pulverization of the sinter, increases the amount of powder generated, and increases the air permeability in the blast furnace. If the measures for suppressing the deterioration are not implemented, the effect of high-reactivity coke cannot be maximized, and high productivity cannot be secured. When air permeability deteriorates, a low-temperature heat storage zone of 600 to 700 ° C is generated in the temperature distribution in the height direction inside the blast furnace,
Due to the progress of the water gas shift reaction in the low-temperature heat storage zone at 600 to 700 ° C., the hydrogen gas utilization rate decreases.

Fig. 2 shows the relationship between the length of the low-temperature heat storage zone at 600-700 ° C and the increase in the in-furnace powder rate. I do.

FIG. 3 shows the relationship between the utilization rate of the hydrogen gas at the furnace top and the increase in the in-furnace powder rate. When the utilization rate of the hydrogen gas decreases, the reduction and sintering rate of the sinter increases.

The absolute value of the amount of increase in the reduction ratio is usually different depending on the RDI of the sintered ore. For example, when a low-temperature heat storage zone of about 4 m is detected in FIG. 2, about 10% of hydrogen is detected in FIG. When a decrease in the gas utilization rate is detected, it is determined that the in-furnace powder rate has increased by 5% compared to the reference value during normal stable operation.

As shown in Fig. 1, the new agglomerate has a lower reduced degradability index (RDI) than ordinary sinter. By replacing with ore, it is possible to suppress an increase in the in-furnace powder rate, and it is possible to eliminate operation fluctuations due to deterioration of air permeability in the blast furnace. Also, since the reducibility is good, the use of the new agglomerate can contribute to the improvement of the reduction efficiency in the blast furnace. In the process of generating the low-temperature heat storage zone,
The criterion for determining the total replacement of sinter ore with new agglomerate depends on the RDI of sinter ore, but it is assumed that the in-furnace powder rate has increased by 5% compared to the standard value during normal stable operation.

In the present invention, usually all the sinter is replaced with new agglomerate,
Charge with highly reactive coke. Or, usually, ordinary sinter is charged, and while detecting the presence or absence of a low-temperature heat storage zone of 600 to 700 ° C, when the low-temperature heat storage zone is generated, charging of the normal sinter is usually performed. By stopping and charging the entire amount of new agglomerate ore, the amount of reduced pulverization can be suppressed, the low-temperature heat preservation zone and / or the poor ventilation zone can be eliminated, and stable blast furnace operation can be performed.

The measurement and detection of the low-temperature heat storage zone at 600 to 700 ° C. can be detected by measuring the temperature using a vertical sonde or measuring the hydrogen gas utilization rate in the radial direction of the furnace top or shaft top using a horizontal sonde. The RDI is sample (15
To 20 mm, 500 g) the reducing gas _{(CO30% -N 2 70%,} 15Nl / min)
And then reduced at 550 ° C. for 30 minutes, and then indicated by a weight ratio of −3 mm after 900 rotations (30 rpm × 30 minutes) on a rotation tester.

(Examples) Hereinafter, features of the present invention will be specifically described with reference to examples.

Table 1 shows the blast furnace operation using the agglomerate ore in which a plurality of highly reactive coke and pellets having a particle size of 3 to 10 mm are combined as compared with the conventional method.

Subject blast furnace is a medium-sized blast furnace having an inner volume of 3000 m ^3, the conventional method was charged with iron ore and ordinary coke in a ratio of O / C = 3.2 from the furnace top at a weight ratio, 2270 ° C. wings preoral flame temperature (hot air temperature
Hot metal was manufactured using ordinary sintered ore having an RDI of 40% while maintaining the temperature at 1100 ° C., the added humidity of 35 g / Nm ³ , and pulverized coal was not injected (Comparative Example).

In Example 1, the total amount of normal coke was high reaction coke (JI
(S reactivity 50%), where the weight ratio is 20% for particle size 50mm or more, 80% for particle size less than 50mm, the total amount of ordinary sintered ore with RDI 40%, multiple pellets with particle size 3-10mm This is an operation example when replacing with individually formed agglomerate ores (referred to as new agglomerate ore). In Example 1, the operation results when normal sinter was charged were added (operation example before use of new agglomerate ore), and the operation results when the entire new ore was charged and A comparison is shown (example of operation after using new agglomerate ore).

The production of new agglomerate is about 94.0% of raw material composition Fe ₂ O ₃ by weight ratio,
SiO ₂ 2.0%, and granulating the only CaO2.5% of fine iron ore 4~6mm
The raw pellets are made, mixed with coke breeze so that the maximum firing temperature is 1300 ° C, fired in a sintering machine, and then crushed.
mm ore. The properties of the new agglomerate used in Examples 2 to 4 are the same.

In Example 2, 50% of normal coke was replaced by high-reactivity coke (JIS reactivity 50%) in weight ratio, and 1% in weight ratio was replaced.
RDI 40%, with 70% over 5mm and 30% under 15mm
This is an operation example in which 685 kg / pig-t of new agglomerate (T.Fe 66%) equivalent to 50% in terms of T.Fe is replaced from 1615 kg / pig-t of ordinary sinter ore. In Example 2, the operation results at the time of using the normal sinter are added (examples of operation before using the new agglomerate),
The results are shown in comparison with the operation results when new agglomerate was charged (example of operation after use of the new agglomerate).

In Example 3, 35% of normal coke was replaced by high-reactivity coke (JIS reactivity 45%) in weight ratio, and 1% in weight ratio was replaced.
In this example, 50% is over 5mm and 50% is 15mm or less.
Since the low-temperature heat preservation zone of 00 ° C was detected (operation example before use of new agglomerate), the operation state when the entire sintered ore was replaced with the new agglomerate ore and operated was shown (new agglomerate ore). Example of operation after use).

In Example 4, 50% of normal coke was replaced by high-reactivity coke (JIS reactivity 50%) in weight ratio, and 1% in weight ratio was replaced.
In this example, 70% is over 5mm and 30% is 15mm or less. Using a horizontal sonde, the hydrogen gas utilization rate in the blast furnace in the radial direction (= H ₂ O /
(H ₂ + H ₂ O)) In the operation that detected the distribution, it was detected that the hydrogen gas utilization at 1 m from the furnace wall of the blast furnace dropped by 10% from the standard value (hydrogen gas utilization 50%). (Example of operation before use of new agglomerate), shows the operation state when the entire sintered ore is replaced with new agglomerate ore (example of operation after use of a new agglomerate).

As for the charging method, in the case of Example 1, a large lump of highly reactive coke was charged into the center and a small lump was charged from the middle of the furnace to the periphery, and charged alternately with the sinter. In the case of Examples 2, 3, and 4, large lump highly reactive coke was mixed with normal coke and charged into the furnace center, and small lump coke was mixed with normal coke and new agglomerate by 1/2.
Each was mixed and charged into the peripheral part from the furnace middle part.

In the examples shown in Table 1, the gas utilization rate was improved and the coke ratio was reduced as compared with the comparative example, and the fuel ratio was able to be reduced. In addition, the operation result before use of the new agglomerate in Examples 1 to 4 is smaller than the operation result after the use of the new agglomerate ore, in which the degree of decrease in the coke ratio is small, and the blast furnace operation is not efficient. .

(Effect of the Invention) As described above, in the present invention, high-reactivity coke is separated into large lumps and small lumps. By charging the furnace core from the middle of the furnace to the periphery of the furnace, ventilation permeability of the core in the center of the furnace can be ensured, and the temperature of the heat preservation zone can be reduced, so shaft efficiency can be increased. As a result, the gas utilization efficiency of the entire blast furnace can be increased, and the blast furnace can be operated with a small coke ratio. Even during the low-temperature heat preservation zone near 600 to 700 ° C, which is easy to generate when the fuel ratio is low, the agglomeration ore formed by combining a plurality of pellets with a particle size of 3 to 10 mm is charged to increase the aeration due to the increase in the fineness. Defects can be suppressed, and stable operation can be performed for a long period of time.

Thus, according to the present invention, the productivity of the blast furnace operation can be improved.

[Brief description of the drawings]

FIG. 1 is a diagram showing a comparison between the RDI of agglomerate ore and a normally sintered ore obtained by combining a plurality of pellets having a particle size of 3 to 10 mm and an indirect reduction rate when reduced under blast furnace conditions, and FIG. 600 ~ 700 ℃
Fig. 3 shows the relationship between the length of the low-temperature heat storage zone and the increase in the in-furnace powder ratio, Fig. 3 shows the relationship between the furnace top hydrogen gas utilization rate and the increase in the in-furnace powder ratio, and Fig. It is a figure which shows the RDI of a reduced powdering sinter, a pellet, and a normal sinter, and the comparison with the indirect reduction rate at the time of reducing under blast furnace conditions.

Claims (2)

(57) [Claims] In a blast furnace in which coke is separated into large lumps and small lumps and charged, high-reactivity coke is separated into large lumps and small lumps, and large lumps and high-reactivity coke are placed at the center of the furnace. A blast furnace operating method characterized in that, when reactive coke is charged from a furnace intermediate portion to a furnace peripheral portion, agglomerate ore obtained by combining a plurality of pellets having a particle size of 3 to 10 mm together with the highly reactive coke is charged. . 2. A high-reactivity coke is charged into a blast furnace to perform an operation, and a temperature distribution in a height direction in the blast furnace or a hydrogen gas utilization distribution in a radial direction in the blast furnace is measured, and the measured temperature or hydrogen gas is measured. A blast furnace operating method characterized in that when the difference between the utilization rate and the reference value reaches a preset value, the entire amount of the normally sintered ore is replaced by agglomerate ore obtained by combining a plurality of pellets having a particle size of 3 to 10 mm. .