JPH1060507A - Operation of blast furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for suitably controlling a fusing zone base level by stabilizing a gas flow distribution in a furnace. SOLUTION: At the time of alternately and repeatedly charging coke and ore layers layer by layer into a blast furnace having >=2500m<3> inner vol. in the furnace, a part of the ore is charged to a reduced iron source (reduced pellet, spherical scrap or cold pig), and the coke and the ore are dropped in the range of <=0.6 times of the furnace opening hole diameter in the radius directional distance from the axis of the furnace, and only the reduced iron source is dropped in the range of >=0.6 times of the furnace opening hole diameter in the radius directional distance from the axis of the furnace. Such method can be adopted that a part of the ore is beforehand changed into the reduced iron source and mixed and this dropping position is made to in the range of <=0.6 times of the furnace opening hole diameter in the radius directional distance from the axis of the furnace.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a method for operating a blast furnace,
Specifically, while stabilizing the gas flow distribution in the radial direction inside the furnace, and appropriately controlling the level at the furnace wall of the cohesive zone, the blast furnace that can secure operation stability while protecting the furnace body Regarding the operation method.

[0002]

2. Description of the Related Art In a blast furnace operation, an iron source material (hereinafter, referred to as an iron source material) is used.
Its basic mission is to smoothly reduce and dissolve "ore" to produce the required amount of pig iron. Of course, the stability of the operation depends on how smoothly the unloading of the charge and the falling down of the molten iron and slag are maintained for the reducing gas rising in the furnace. For this reason, in actual operation, the charge distribution in the furnace top radial direction is controlled to
It is a routine practice to adjust the distribution balance between solids and liquids.

[0003] Generally, in actual operation, means for measuring the gas state distribution in the radial direction using a temperature measuring and gas sampling sonde provided at the upper level of the shaft to grasp the distribution balance in the furnace in the radial direction is employed. I have. Therefore, in order to accurately control the distribution of the logistics in the radial direction, more specifically, the gas flow distribution estimated from the measured values of the sonde, it is necessary to ensure that the distribution of the charge at the furnace top is a stable and stable profile. It is important to stack the layers, especially in large blast furnaces having a large furnace diameter.

In controlling the gas flow distribution in a blast furnace, it is important to improve the gas permeability in the furnace and to reduce the fluctuation of the gas flow distribution. And for the former,
It has been conventionally known that the air permeability in the furnace can be improved by directing the distribution in which the gas flow rate at the furnace center is enhanced. As a method for surely forming such a gas flow distribution, there is a so-called "coke center charging method" disclosed in Japanese Patent Publication No. 64-9373. According to the law, a part of the charged coke is directly charged into the furnace center using a coke supply pipe with the tip facing the furnace center, thereby strengthening the gas flow in the section and installing the coke. It also has the effect of suppressing fluctuations in the distribution of incoming substances and stabilizing the gas flow.

On the other hand, regarding the latter method of reducing the fluctuation of the gas flow distribution, the distribution state of the charged material in the radial direction and the circumferential direction of the furnace depends on disturbance influence factors involved in the process of forming the charged material distribution other than the operable factors. To minimize fluctuations. The disturbance influence factors include, for example, a coke layer collapse caused by a drop impact when ore is charged on a coke layer stacked in a furnace.

The fluctuation of the gas flow distribution caused by such a disturbance is described in Japanese Patent Publication No. 64-9373 and Japanese Patent Application Laid-Open No.
According to the method disclosed in Japanese Patent Application Laid-Open No. 1-227109, in which the raw material is directly charged into the furnace center, the amount is reduced near the furnace center. However, there is no direct effect of reducing fluctuations around the furnace wall.

[0007] In the charging method using a bell-type or bell-less type charging apparatus, most of the charged materials are generally charged near the furnace wall, so that the charging position is finely adjusted. The charge distribution control around the furnace wall is performed. However, when looking at the actual operation, the charge distribution around the furnace wall fluctuates due to disturbance influence factors, so the fine adjustment at the charging position described above sufficiently reduces the fluctuation of the gas flow distribution around the furnace wall. It cannot be said that it has been done.

The reason why the charge distribution controllability at the periphery of the furnace wall is as important as that at the center of the furnace is that the periphery of the furnace wall occupies most of the furnace cross-sectional area, and In order to adjust the gas flow balance, it is required to increase the control accuracy and reduce the fluctuation. Furthermore, considering that the current charge distribution control is radial control, it can be said that reducing the charge distribution fluctuation in the circumferential direction (particularly, around the furnace wall) is also important.

However, in the bell-type blast furnace, the repulsion of the charged material is different between the inner plate and the outer plate of the movable armor, which causes a difference in the falling locus. In addition, when the raw material is dropped to the vicinity of the furnace wall and its position is to be controlled, there is a control region in which the charged raw material only partially repels the armature plate. In addition to the structural fluctuation factors described above, uneven wear of the armor plate and the large bell and the like also become disturbance fluctuation factors, resulting in a distribution deviation of the furnace interior contents.

On the other hand, the bellless blast furnace has a charging mode in which the blast furnace is relatively widely distributed from the furnace wall toward the center of the furnace. However, since the charging is performed while the distribution chute is swung, a deviation in the amount of deposition occurs in the circumferential direction depending on the charging start and charging end timings, or the material falling trajectory from the distribution chute due to the fluctuation of the charged material particle diameter ( In other words, the position at which the raw material falls in the furnace varies. They are,
It becomes a factor of disturbance fluctuation of the bellless blast furnace, and causes a distribution deviation of the furnace interior contents.

There are many cases in which the fluctuation in the charge distribution around the furnace wall as described above causes a fluctuation in the gas flow distribution, leading to a fluctuation in the furnace condition.

In view of this, one of the inventors of the present invention first set the falling position of coke and ore in the radial direction from the furnace center line when charging raw materials for medium to large blast furnaces having an inner volume of 2500 m ³ or more. In order to reduce fluctuations in the charge distribution not only in the center of the furnace but also in the periphery of the furnace wall by controlling the furnace radius to within 0.6 times the furnace opening radius, an operation method to stabilize the gas flow distribution in the furnace Proposed (Japanese Patent Application No. Hei 7-261173,
Hereinafter, this is referred to as “first application”).

This makes it possible to control the gas flow distribution in the furnace and maintain a stable operation of the blast furnace. However, in blast furnace operation, in addition to ensuring stable operation,
Protecting the furnace body is also an important issue.

Usually, when considering the state distribution in the furnace radial direction, the shape of the cohesive zone, that is, the shape of the area where the ore charged in the furnace is heated and softened, fused and melted, is one index. However, in order to protect the furnace body, the level of the cohesive zone at the furnace wall (hereinafter referred to as “cohesive zone root level”) is an important index. If the cohesive zone root level rises abnormally, the thermal load on the furnace wall will increase, leading to breakage of the staves and even the steel shell. It has been empirically known that the reactor condition may be deteriorated due to unloading irregularities or unreduced or undissolved ore flowing into the tuyere. In particular, when the latter is deactivated, it is difficult to normalize by normal gas flow distribution control, and rebuilding is performed by low load operation by increasing the coke ratio (fuel ratio). It is necessary to do.

[0015]

SUMMARY OF THE INVENTION An object of the present invention is to reduce the cohesive zone root level based on the blast furnace operating method of the prior application from the viewpoint of securing the stability of operation and protecting the furnace body. An object of the present invention is to provide a method that can be controlled quickly.

[0016]

The gist of the present invention resides in the following (1) and (2) blast furnace operating methods.

(1) When a solid reducing agent (coke) and ore are repeatedly and alternately charged into a blast furnace having a furnace internal volume of 2500 m ³ or more in layers, a part of the ore is replaced with a reduced iron source and the furnace shaft is Drop coke and ore within a range of 0.6 times or less of the furnace opening radius at a radial distance from the core, and within a range of 0.6 times or more of the furnace opening radius at a radial distance from the furnace axis. A method of operating a blast furnace, wherein only the reduced iron source is dropped.

(2) When charging coke and ore alternately and repeatedly into a blast furnace having a furnace internal volume of 2500 m ³ or more in a layered manner, part of the ore is previously mixed with the ore instead of the reduced iron source. A method for operating the blast furnace, wherein the coke and the ore are dropped within a range of 0.6 times or less of a furnace opening radius in a radial distance from a furnace axis.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention (the inventions of the above (1) and (2), and these inventions are also referred to as the method of the present invention) will be described in detail below.

According to the invention of (1), as described above, when coke and ore are alternately and repeatedly charged into a blast furnace having a furnace internal volume of 2500 m ³ or more in a layered manner, part of the ore is converted into a reduced iron source. Instead, the radius of the furnace port is 0.6
The coke and the ore are dropped within a range of less than twice, and the reduced iron source is 0.6 mm of the furnace opening radius at a radial distance from the furnace axis.
It is a method of dropping within a range of more than double. In addition, as a reduced iron source, reduced pellets, spherical scrap, or cold iron can be used.

In this method, the drop position of the charged materials (coke and ore) is 0.6 times the furnace opening radius (0.6R ₀ , where R ₀ is the furnace opening radius) as a radial distance from the furnace axis. ) Within the following range, as explained in the earlier application,
This is for the following reason. That is, when the raw material falling position and 0.6R ₀ within the range, the raw material deposition layer includes, from the furnace middle portion or the furnace center portion in the furnace wall portion forms a slope with a descending slope. And the above-mentioned coke layer collapse occurs near the center of the furnace corresponding to the ore drop position, but since the layered coke flows toward the periphery of the furnace wall having a large area, the coke layer collapse due to the coke layer collapse This is because the amount of rise in the coke layer thickness is small, and on the other hand, since the amount of the broken coke flowing into the center of the furnace is originally small, the amount of rise in the coke layer thickness in the center of the furnace is also small. Thus, it is possible to reduce the variation of the charge distribution not only in the central portion of the furnace but also in the peripheral portion of the furnace wall, and to stabilize the gas flow distribution in the furnace.

The blast furnace in which this method is carried out has a furnace internal volume of 250.
A blast furnace of 0 m ³ or more is used because, as described in the same application, the effect of reducing the fluctuation of the charge distribution around the furnace wall is 250 m.
This is because it is clearly recognized in a blast furnace having a furnace internal volume of 0 m ³ or more.

The charging of coke and ore into the blast furnace is performed alternately and repeatedly so as to form a layer. A part of the ore charged in the layer is replaced with a source of reduced iron in the usual unreduced state. The purpose is to reduce the thermal load required for reducing and dissolving the ore, and to raise the temperature distribution in the height direction to raise the level of the cohesive zone root.

In order to effectively carry out this, it is necessary to deposit the above-mentioned reduced iron source near the furnace wall. As a method for that, a method of dropping and charging the reduced iron source directly near the furnace wall, and using a reduced iron source having a particle shape with a small deposition angle, that is, a shape close to a sphere, A method of rolling the slope to flow into the vicinity of the furnace wall and depositing it is conceivable.However, in a method depending only on the former method, the problem solved by the above-mentioned prior application invention, that is, most of the charged materials are Since the gas is charged near the wall, the charge distribution around the furnace wall fluctuates due to disturbance influence factors, causing a problem that the fluctuation of the gas flow distribution around the furnace wall is not sufficiently reduced. There is danger. Therefore, it is desirable to mainly consider the latter method.

Therefore, in the invention of (1), a reduced iron source having a shape close to a sphere is used, and its charging position is not limited to the vicinity of the furnace wall, and the distance in the radial direction from the furnace axis is not limited. At the furnace wall side that is at least 0.6 times (0.6R ₀ ) the furnace opening radius. As a result, as shown in the examples described later, the yield of the reduced iron source on the furnace wall can be improved, and the root level of the cohesive zone can be appropriately and promptly controlled.

The substitution ratio of the reduced iron source to the charged ore is not particularly limited, but is preferably 2 to 10% by weight. If the content is less than 2% by weight, a clear effect is not recognized. If the content is more than 10% by weight, the operation specifications are greatly affected, or the root level of the cohesive zone is excessively increased.

No special measures are required for the alternative charging of the reduced iron source. For example, in a bellless blast furnace, when charging while swirling the distribution chute, the above-described alternative ratio may be set by appropriately interposing the swirl charging of the reduced iron source.

As the above-mentioned reduced iron source, reduced pellets, spherical scraps or cold iron are used as described above. This is because these iron sources have a shape close to a sphere, and are suitable for rolling on a slope to flow in and deposit near the furnace wall.

The invention of the above (2) is characterized in that the furnace internal volume is 2500 m
When charging coke and ore alternately and repeatedly into ^three or more blast furnaces and charging them in layers, a part of the ore is replaced with a reduced iron source and mixed with the ore in advance, and the drop position of these coke and ore is determined. This is a method in which the radial distance from the furnace axis is within 0.6 times (0.6R ₀ ) or less of the furnace opening radius.

This method is based on the charging mode in the prior application, and the coke and ore drop position is 0.6 times the furnace opening radius (0. 0) as the radial distance from the furnace axis. 6R ₀ ) or less, as described above, it is possible to reduce the fluctuation of the charge distribution not only in the furnace center part but also in the peripheral part of the furnace wall.

As the reduced iron source, as in the case of the invention (1), reduced pellets, spherical scrap or cold iron is used. If such a shape close to a sphere is used, when the ore is dropped (charged) into the furnace, the reduced iron source mixed with the ore is more likely to roll on the slope, so the reduced iron The source can flow and deposit near the furnace wall.
That is, the reduced iron source is selectively deposited near the furnace wall by the classification effect due to the difference in shape from the ordinary unreduced ore, and as a result, as in the case of the invention of (1), the cohesive zone The root level can be properly controlled.

The amount of the reduced iron source previously mixed with the ore is preferably 2 to 10% by weight as in the case of the invention (1).

[0033]

【Example】

(Example 1) One actual furnace corresponding to a furnace inner volume of 5050 m ³
A model experiment was performed using a bellless model furnace reduced to / 20.

Table 1 shows the experimental conditions. The charging conditions were set on the assumption that the Froude number and the geometric similarity ratio were matched.

In Table 1, the charged O / C ratio is a weight ratio of ore (O) to charged coke (C).
The reduced iron source ratio is the weight ratio of the reduced iron source (in the experiment, a reduced pellet is used) to the total iron source charge. The numbers 1 to 9 shown in the column of the material falling position are the tilt notches No. of the bellless distribution chute. Represents the raw material drop position shown in Table 2, respectively. That is, the tilt notch No. Nos. 6 to 9 correspond to a radial distance from the furnace axis within a range of 0.6 times (0.6R ₀ ) or less (furnace center side) the furnace opening radius. 1 to 5 correspond to the range (0.6R ₀ ) or more of the furnace opening radius (0.6R ₀ ) or more (furnace wall peripheral side). As shown, the number of charging turns was 10 for both coke and ore, and 3 for the reduced iron source.

[0036]

[Table 1]

[0037]

[Table 2]

The experiment was performed three times for each charging condition (cases A to D), and the ratio of the reduced iron source to the total deposited iron source at the furnace wall (ratio of the reduced iron source) was measured.

FIG. 1 shows the results. Case A shown in the figure
caseD corresponds to cases A to D in Table 1, respectively. ca
seA (case A in Table 1) is a conventional example based on a charging mode in which most of the charged materials are charged near the furnace wall, and cases B to D are used.
(Cases B to D in Table 1) are examples of the present invention, and cases B and C
The case D corresponds to the invention example of the above (1), and case D corresponds to the invention example of the above (2) in which the reduced iron source is mixed with ordinary unreduced ore and charged.

From these results, in each of the examples of the present invention (cases B to D), the ratio of the reduced iron source in the furnace wall was high, and the yield of the reduced iron source in the furnace wall was good.
In addition, there was little variation in each experiment.

(Example 2) Actual furnace (volume inside the furnace: 5050 m)
^{In 3} ), the present invention (the invention of the above (1)) was applied, and a test was conducted on the controllability of the cohesive zone root level.

Table 3 shows the test conditions. In Table 3, the meanings of the charged O / C ratio and the reduced iron source ratio are the same as in Table 1. In addition, 1 shown in the column of the material drop position
The meanings of the numbers from 1 to 9 are the same as those in Table 1, and represent the raw material falling positions shown in Table 2 above. Although not shown, the particle diameters of coke and ore were determined in Example 1.
5 mm and 4 mm, respectively.

[0043]

[Table 3]

The movement of the cohesive zone at the root level in the furnace was verified by measuring the temperature distribution in the height direction using a vertical sonde (a vertical gas sampling sonde) inserted in the furnace wall.
And the stave temperature of the lower wall of the furnace was measured.

The results are shown in FIG. 2 and FIG. FIG. 2 shows the results of the stave temperature measurement by a thermometer installed in the furnace body. B1 to B3 are the staves corresponding to the Berry-Bosch portion, and S1 to S4 are the staves corresponding to the lower stage of the shaft. After applying the method of the present invention (indicated by ● in the figure) compared to before applying the method of the invention (indicated by ○ in the figure)
Indicates that the stave temperature has increased. FIG. 3 shows the furnace temperature distribution in the height direction measured by a vertical sonde inserted into the furnace wall, and the furnace temperature in a portion corresponding to the Berry-Bosch section also increases. These results indicate that the cohesive zone root level has moved upward.

[0046]

According to the method of the present invention, the gas flow distribution in the furnace can be stabilized and the cohesive zone root level can be properly controlled. Thereby, it is possible to greatly contribute to protection of the furnace body and improvement of operation stability in a blast furnace having a large furnace volume.

[Brief description of the drawings]

FIG. 1 is a diagram showing a relationship between a furnace wall yield of a reduced iron source and a method of charging raw materials.

FIG. 2 is a diagram showing temperature control results of a stave before and after application of the method of the present invention, showing the controllability of the cohesive zone root level by the method of the present invention.

FIG. 3 is a graph showing the controllability of the root level of the cohesive zone according to the method of the present invention, based on the measurement results of the temperature in the furnace by a vertical sonde inserted into the furnace wall.

Claims (2)

[Claims] When a solid reducing agent and an iron source material are alternately and repeatedly charged into a blast furnace having a furnace internal volume of 2500 m ³ or more in layers, a part of the iron source material is replaced with a reduced iron source, Drop the solid reducing agent and the iron source material within a range of 0.6 times or less the furnace radius at a radial distance from the core, and at least 0.6 times the furnace radius at a radial distance from the furnace axis. A method for operating a blast furnace, wherein only the reduced iron source is dropped within the range. 2. When a solid reducing agent and an iron source material are alternately and repeatedly charged into a blast furnace having a furnace internal volume of 2500 m ³ or more in a layered manner, a part of the iron source material is replaced with a reduced reduced iron source beforehand. A method for operating a blast furnace, comprising: mixing a solid reducing agent and an iron source material within a range of 0.6 times or less the radius of the furnace opening at a radial distance from the furnace axis in a state of being mixed with the source material.