JPH09157709A - Operation of blast furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an operation method which can quickly improve an inactivity condition of temp. derease at a furnace bottom without aggravating the cost. SOLUTION: In this operation method of a blast furnace operated in high ore/coke ratio, at the time of lowering the furnace bottom temp., the operation is executed by lowering a stock line from the level of No.2' to that of No.2 in the figure in the range of 70-80% of a blow-off limit stock line level. By this method, the center gas flow is increased from the figure No.3' to the figure No.3 and the fused zone at the center part of the furnace is raised to the level of the figure No.5 and gas ventilation and liquid penetration at the lower part of the furnace are improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a so-called core inactive furnace in which a bottom temperature is lowered in a blast furnace operating at a high ore / coke amount (hereinafter referred to as "high ore / coke"). It relates to a blast furnace operating method for improving the situation.

[0002]

2. Description of the Related Art In a blast furnace operating at high ore / coke,
When the furnace bottom temperature decreases, the air permeability and liquid permeability in the lower part of the furnace deteriorate, the blowing pressure rises, and the amount of tapped iron cannot be secured.

When such a lowering of the bottom temperature (core inertness) occurs during blast furnace operation, conventionally, the amount of coke charged is increased to raise the furnace heat level, and the quality (DI, By increasing CSR, particle size, etc.), the ventilation and liquid permeability of the furnace core were improved.

However, in the method of increasing the furnace heat level by increasing the amount of coke charged, the effect of the effect, that is, the appearance of the effect is slow, and since the viscosity of the hot metal increases, it is impossible to ensure good discharge of the hot metal slag. There is. Further, the method of improving the quality of the injected coke to improve the air permeability has a problem that the cost is significantly deteriorated.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of such a situation, and in a blast furnace operating at a high ore / coke, it is possible to quickly deal with a situation where the furnace core temperature is lowered and the furnace core is inactive. In addition, it is an object of the present invention to establish an operation method that can be improved without causing deterioration of cost.

[0006]

The gist of the present invention resides in the following blast furnace operating method.

A method of operating a blast furnace operating at a high ore / coke, wherein the stock line level is blown through when the temperature of the bottom of the furnace decreases, and 70 to 80% of the limit stock line level.
The method of operating a blast furnace is characterized by lowering the operating range to

The stock line is the outline of the upper end of the charge formed by the upper end surface of the furnace interior charge, and the stock line level is 1 m below the lower end of the large bell opening as a reference (0 position). , The level of the stock line expressed by the distance (m) downward from the reference level.

The blow-through limit stock line level is a lower limit stock line level at which a constant air flow rate can be secured without causing blow-through, and is calculated from the amount of charge and air flow rate into the blast furnace. It is a level.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The blast furnace operating method of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic diagram schematically showing changes in the situation in the blast furnace when the stock line level is changed. In FIG. 1, 1 is a charge charged from the furnace top, 2 and 2'are stock lines of the charge 1, 4 is a core, and 5 and 5'are cohesive zones. Further, the arrow-shaped figures 3 and 3'represent gas rising in the furnace (central gas flow), and the size of this arrow represents the strength of the gas flow (size of flow rate). In FIG. 1, the stock line 2 ', the central gas flow 3', and the cohesive zone 5'indicated by broken lines represent the case where the furnace core is inactive under normal operation. is there.

In the operating method of the present invention, when the furnace bottom temperature decreases and the furnace core becomes inactive, the charging of raw materials into the furnace is controlled and the stock line is indicated by a broken line. The operation is performed from the 2'level to the 2 level indicated by the solid line. The level of 2 is a level within a predetermined range described later.

When the stock line is at the 2'level, the central gas flow is weak as shown by the dashed line 3'and the cohesive zone drops to the level also shown by the dashed line 5'in the center of the furnace, Although presenting a wick inert condition, lowering the stock line from the 2'level to the 2 level increases the central gas flow as shown by the solid line 3. This is because originally the ore / coke in the radial direction is the smallest in the central part of the furnace and the ventilation resistance in the central part is small, but by lowering the stock line, that phenomenon is further promoted and the central gas flow increases. It is a thing. as a result,
The cohesive zone at the center of the furnace rises to the level shown by the solid line 5, high-temperature hot metal is supplied to the furnace core 4, the ventilation and liquid permeability of the lower part of the furnace are improved, and the furnace bottom temperature rises. That is, activation of the furnace core can be achieved by lowering the stock line of the charging material 1 from the level 2'to the level 2.

The level 2 in FIG. 1 (referred to as the "changed stock line level") is set to 70 to 80% of the blow-through limit stock line level. The stock line level is represented by the distance (m) from the level to the lower side of the large bell opening 1 m below the lower end of the large bell opening as described above. Taking the case where the blow-through limit stock line level is 6 m as an example, the range of 70 to 80% of the blow-through limit stock line level is a range of 4.2 to 4.8 m downward from the reference level.

When the changed stock line level is higher than 80% of the blow-through limit stock line level, that is, when it exceeds 4.8 m in the above example, the blast pressure due to defective tapping during blast furnace operation Rises to cause blow-through, which causes deterioration of furnace conditions such as rapid decrease of furnace heat (hot metal temperature). Also, if the changed stock line level is less than 70% of the blow-through limit stock line level (when it is less than 4.2 m in the above example), the central gas flow cannot be strengthened and the furnace bottom temperature rises. I can't let you do it.

The normal stock line level in this example is about 1.5 m. As the stock line is lowered, the shaft efficiency (indirect reduction (exothermic reaction) rate between the cohesive zone and the upper part of the bed) deteriorates, and the fuel ratio deteriorates accordingly, so operation is performed at the above level. .

As described above, the operating method of the present invention has a high ore.
This method can be applied to a blast furnace operating at / coke. This is because core inactivity is unlikely to occur in low ore / coke operation such as all coke operation.

As described above, the operating method of the present invention is a method of operating by lowering the stock line level to a predetermined level when the furnace bottom temperature decreases and the furnace core becomes inactive. As shown in the examples described later, the effect appears early. Since it is not necessary to improve the quality of input coke, the cost does not deteriorate.

[0019]

[Example] Blast furnace operating at high ore / coke (internal volume 1
At 850 m ³ ), when the furnace bottom temperature decreases, the furnace bottom temperature, the central gas flow index (Y1 value), the blast pressure and the furnace heat (in the case of changing the stock line level by applying the operation method of the present invention) ( The change in hot metal temperature) was measured.

Table 1 shows operational specifications. The blow-through limit stock line level at this time was 6 m.

FIG. 2 shows the transition of the measurement items when the stock line level is changed.

The horizontal axis of FIG. 2 shows the time after the start of measurement.

As shown in this figure, the stock line level before the change (1.5 m) is 70 to 80% of the blow-through limit stock line level (6 m), that is, 4.2 to 4.2.
By lowering to the range of 4.8m (in Fig. 2,
After 22 to 24 hours), the blast pressure decreased, the central gas flow index (Y1) increased, and several hours later, the furnace bottom temperature began to increase. At this time, there was no fluctuation in furnace heat (hot metal temperature),
Moreover, after the furnace bottom temperature increased, the blast pressure decreased even when the stock line level was returned to the original 1.5m.
It can be seen that the ventilation and liquid permeability of the furnace bottom are improved.

[0024]

[Table 1]

[0025]

EFFECTS OF THE INVENTION In a blast furnace operating at a high ore / coke, when the furnace bottom temperature is lowered and the furnace core is inactive, the operation method of the present invention is applied to strengthen the central gas flow. It is possible to improve the air permeability to the furnace core and to raise the temperature of the furnace bottom and the temperature of the hot metal dropped on the furnace bottom to activate the furnace core. This method is a practical method in which the effect appears quickly and the cost does not deteriorate.

[Brief description of the drawings]

FIG. 1 is a schematic diagram schematically showing changes in the situation in a blast furnace when the stock line level is changed.

FIG. 2 is a diagram showing changes in furnace bottom temperature, central gas flow index (Y1 value), blast pressure and furnace heat (hot metal temperature) when the stock line level is changed.

[Explanation of symbols]

 1: Charge 2, 2 ': Stock line 3, 3': Central gas flow 4: Furnace core 5, 5 ': Cohesive zone

Claims (1)

[Claims] 1. A method of operating a blast furnace operating with a high ore / coke amount (high ore / coke), which blows through the stock line level when the temperature of the bottom of the furnace drops and the limit stock line level is 70-80. A method of operating a blast furnace, which is characterized by lowering the operation rate to the range of%.