JPH0680165B2 - Blast furnace operation method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for operating a blast furnace having an internal volume of more than 4000 m ³ .

(Prior Art) Generally, in the operation of a blast furnace, the adjustment of the distribution of the charged material occupies an important position in the operation action as a means for controlling the gas flow distribution in the furnace.

In recent years, especially with the introduction of a bellless charging device and a continuous drive type movable armor, the degree of freedom with respect to the distribution of the charging is improved, and coke and ore can be charged at any charging position in the furnace radial direction. It became possible to create a different charge deposit shape than before.

In addition, by using a μ-wave profile meter, layer thickness gauge, etc., it becomes possible to easily obtain detailed information on the deposition shape of the charge, and to understand the deposition shape corresponding to changes in the gas flow in the furnace. Is coming.

From these technical backgrounds, in the blast furnace operation, it became possible to maintain a stable blast furnace operation by comparing the operation state and the charge deposition shape.

As an example based on such an idea, Japanese Patent Application Laid-Open No. 59-50102 discloses a deposit layer in the furnace in the radial direction of the furnace, in which the distance from the inner wall of the furnace to the mountain portion is L, and the furnace center side. Where the deposition angle of the charging layer deposition slope is θ ₁ and the deposition angle of the charging layer deposition surface on the furnace wall side is θ ₂ , L: 0.5 to 1.5 m and coke layer θ ₁ : 25 ° to Θ ₂ at 35 °: Within ± 10 °, θ ₁ : 2 of ore layer
There is a disclosure that it is possible to maintain the in-reactor deposition shape having the target gas flow distribution by controlling so that θ _{2 is} within ± 10 ° at 0 ° to 30 °.

On the other hand, it is a well-known operating method to divide the charging raw material by the particle size and charging the fine particle raw material to the peripheral portion of the furnace, for example, JP-A-55-62106 and JP-A-57-134503. The publication proposes a method of improving the gas utilization rate or producing low [Si] pig iron by dividing the charged raw material into particles according to the particle size and charging the fine particle raw material into the periphery of the furnace.

(Problems to be Solved by the Invention) In the above-mentioned Japanese Patent Laid-Open No. 59-50102, it is necessary to control the deposition shape of the raw material for the furnace interior within a predetermined range, and particularly to set the distance L from the inner wall of the furnace to the crest portion to 0.5. Although it is said that stable blast furnace operation can be maintained by controlling within a range of ~ 1.5 m, the present inventors conducted experiments focusing on the coke deposition shape, and disclosed in JP-A-59-50102. It was found that there is no region within the disclosed range where stable operation of the blast furnace is possible.

That is, as shown in FIG. 7, when L is in the range of 0.5 to 1.5 m,
We found that the inclination angle θ ₁ of the coke became 35 ° or more and the coke accumulation state became unstable, and the finger scale fluctuation occurred.

On the other hand, in the blast furnace operation in which the fine-grain raw material is charged into the periphery of the blast furnace, the state of deposition of the fine-grain raw material is not stable, and when the fine-grain raw material flows into the center of the furnace, the central gas flow is extremely deteriorated. To cause aeration blockage, or when fine-grained raw material is deposited in one place, unreduced or unmelted ore drops to the lower part of the furnace,
May cause operational fluctuations. Therefore, it is desirable that the fine-grain raw material is widely and thinly charged into the peripheral portion of the furnace, but the conventional method has no knowledge that the deposition shape required to form such a charge shape is presented.

(Means for Solving the Problem) The present invention considers that the relationship between the charge deposition shape and the gas flow distribution differs depending on the size of the furnace volume, and quantitatively evaluates the gas flow distribution in the blast furnace, Stable operation of the blast furnace by clarifying the relationship between it and the corresponding charge deposition shape,
In other words, to give a deposition shape that can achieve the target gas flow distribution, and to give a deposition shape of the charge that can stably deposit the fine-grained raw material in the periphery of the furnace to enable stable blast furnace operation. (1) In a method of operating a blast furnace while controlling the gas flow in the blast furnace with an internal volume of more than 4000 m ³ , the state of coke deposition in the blast furnace is measured from the center of the furnace wall to the furnace wall. Toward the furnace wall from the vicinity where the inclination angle of the volume surface becomes less than 15 degrees toward the terrace, with the shoulder of the intersection of the extension line of the slope on the furnace center side of the terrace and the extension line of the deposition area of the terrace, When the distance from the furnace wall to the shoulder is R, the blast furnace operation method is characterized by managing R so that it exceeds 1.5 m. (2) Managing the gas flow in the blast furnace with an internal volume of more than 4000 m ^3. However, in the method of operating the blast furnace, Regarding the state of coke and ore deposits in the furnace, the slope extends from the center of the furnace toward the furnace wall to the furnace wall, where the slope of the volume surface is less than 15 degrees from the furnace center to the furnace wall. Let the shoulder be the intersection of the line and the extension of the accumulated area of the terrace, and let the distance from the furnace wall to the shoulder be R, manage R so that it exceeds 1.5 m, and divide the ore by grain size. The blast furnace operating method is characterized by charging fine grained ore into the periphery of the furnace.

The present invention will be described in detail below with reference to the drawings.

Generally, blast furnace operation is governed by gas flow distribution in the furnace, and maintaining operation at the optimum point leads to long-term stable operation.

As a means to know the gas flow in the furnace radial direction, there is a device that measures the radial gas component by a shaft sonde, etc., and the reduction rate distribution in the furnace radial direction can be calculated from the measurement data, and each point in the furnace can be calculated. The gas flow velocity distribution can be calculated.

The gas flows flowing through each part divided by concentric circles divided in three in the radial direction of the furnace are the central gas flow distribution, the intermediate gas flow distribution, and the peripheral gas flow distribution, and the data of the blast furnace with different internal volumes are shown in FIG. As a result of arranging in a triangular diagram like this, the stable gas flow distribution in blast furnace operation is
~ 35%, intermediate gas flow distribution is 30 ± 2%, peripheral gas flow distribution is
It was found to be in the range of 35-45%.

Among these, the stable range of the intermediate gas flow distribution is particularly narrow, and achieving this is an absolute condition for stabilizing the operation. That is, the shortage of the intermediate gas flow indicates that the ventilation resistance in the middle part of the blast furnace is large and the reduction and temperature rise of the raw material are poor. It causes bloat, deteriorates ventilation, and disturbs dropping of charge. On the contrary, an excessive amount of the intermediate gas flow inevitably causes a shortage of the gas flow in the central portion and the peripheral portion, which causes a trouble such as a decrease in the core temperature or an inactive state in the lower part of the furnace.

Next, in order to compare the charge deposition shape with the gas flow distribution, as shown in Fig. 2, from the center of the furnace to the furnace wall, the slope of the surface of the deposit is less than 15 ° to the furnace wall. Is called "terrace" and its length is defined. That is, when the extension line of the slope on the furnace center side of the terrace is a and the extension line of the deposition surface of the terrace is b, the distance between the intersection of a and b and the furnace wall was defined as the terrace length R. Further, the angle between the line a and the horizontal line is defined as the inclination angle θ.

Figure 3 shows the relationship between the coke terrace length and the intermediate gas flow distribution in the blast furnace with an internal volume of more than 4000 m ³ . As shown in the figure, as the terrace length increases, the distribution of the intermediate gas flow increases.However, as the terrace length increases, the coke inclination angle decreases and the coke deposit shape stabilizes. This is because the amount of coke breakage due to is reduced, and as a result, Ore / Coke in the middle portion is reduced.

From Fig. 3, it was found that a coke deposit shape with a coke terrace length of more than 1.5 m is necessary to secure 30% of the intermediate flow.

In addition, in the method of charging fine grain raw material into the peripheral portion of the blast furnace,
As shown in FIG. 4, by changing the amount of the fine-grained raw material used, the peripheral gas flow distribution can be adjusted without changing the peripheral coke and the raw material layer thickness. It turned out to be an effective means of maintenance.

In addition, the average particle size difference ΔDp between the coarse particles and the fine particles as shown in Table 1.
When a fine-grain raw material having a diameter of 4 to 15 mm is used, as shown in FIG. 5, the amount of the charge per one time including the fine-grain raw material is When it is less than 16%, it becomes a stable operation area.

Also, when using a fine grain raw material by the above method,
1.5m for stable deposition of fine-grained material on the periphery
It was also found that a terrace length of ore (coarse-grained raw material) exceeding 10 is necessary.

(Example) Example 6 of the present invention in a large blast furnace having an internal volume of 4063 m ³
Shown in the figure.

As shown in the figure, changing the terrace length of coke and ore (coarse grain raw material) changes the number of finger scale disturbances.
The coke terrace had a marked decrease in the number of finger scale disturbances when the length exceeded 1.5 m, enabling stable operation to continue. When the terrace length of coke and ore (raw material) is further extended, the terrace length is 2.5 m for coke,
Ore (coarse-grained raw material) could continue stable operation until it reached 2.8 m.

In addition, from the B period when the ore terrace exceeds 1.5 m, 16% of the total amount of raw material charged was charged into the peripheral area of the furnace, but it was stably deposited on the ore (coarse-grained material) terrace. I confirmed that.

(Effect of the Invention) According to the present invention, stable operation can be continued by creating a charge deposit shape in which the coke terrace exceeds 1.5 m.

Furthermore, by extending the ore (coarse-grained raw material) terrace, fine-grained raw material was stably deposited around the furnace, enabling stable operation to continue.

[Brief description of drawings]

FIG. 1 is a triangular diagram of gas flow distribution in a furnace according to the present invention, FIG. 2 is a definition diagram of in-reactor deposition shape according to the present invention, and FIG. 3 is a diagram showing a relationship between in-reactor deposition shape and in-reactor gas flow distribution. FIG. 4 is a diagram showing the relationship between the amount of fine grain raw material used and the distribution of the surrounding gas flow, FIG. 5 is a diagram showing the relation between the percentage of fine grain raw material used and the fuel ratio, and FIG. 6 is an embodiment of the present invention. FIG. 7 is a diagram showing the relationship between the distance L from the furnace inner wall to the mountain portion and the coke inclination angle.

Claims (2)

[Claims] Claim: What is claimed is: 1. In a method of operating a blast furnace while controlling a gas flow in the blast furnace having an internal volume of more than 4000 m ³ , the state of coke deposition in the blast furnace is measured from the center of the furnace toward the wall of the furnace. The terrace from the vicinity of the inclination angle of less than 15 degrees to the furnace wall is the shoulder, and the intersection of the extension line of the slope on the furnace center side of the terrace and the extension line of the deposition area of the terrace is the shoulder, and from the furnace wall to the shoulder A blast furnace operating method characterized in that when the distance is R, R is controlled to exceed 1.5 m. 2. A method of operating a blast furnace while controlling a gas flow in the blast furnace having an internal volume of more than 4000 m ³ , wherein the state of deposition of coke and ore in the blast furnace is measured from the center of the furnace toward the wall of the furnace. The terrace extends from the area where the surface inclination angle is less than 15 degrees to the furnace wall, and the intersection between the extension line of the slope on the furnace center side of the terrace and the extension line of the terrace accumulation area is the shoulder, and the furnace wall to the shoulder When the distance between them is R, R is 1.5m
The blast furnace operation method is characterized in that the ore is managed to exceed the above, and the ore is divided according to the grain size and the fine ore is charged into the peripheral area of the furnace.