JPH03291314A - Method for operating blast furnace - Google Patents

Abstract

PURPOSE:To maintain production and Si content in molten iron to the constants by regulating the total quantity of iron ore and powdery iron source so that furnace heat is stabilized in the operational method where the powdery iron source is blown from tuyere part and the iron ore and coke are alternately charged from the furnace top. CONSTITUTION:The powdery iron source is blown into the blast furnace from the tuyere part and the iron ore and the coke are alternately charged from the furnace top. In this operational method, at the time of executing the operation, the iron ore charged from the furnace top is reduced, after this iron ore reaches to the tuyere part the powdery iron source quantity corresponding to this iron ore is blown into the blast furnace from the tuyere part. By this method, when dropping delay and stagnation of charged material and the development of stuck material without accompanying lowering of the furnace temp. in the blast furnace occur, the fixed production and the fixed Si content in the molten iron can be maintained without raising coke ratio in order to eliminate or prevent the above. Therefore, the molten iron can be stably supplied.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention aims to reduce the total amount of iron ore charged from the top of the furnace and powdered iron source injected from the siding so that the furnace heat of the blast furnace is stabilized. This article relates to a blast furnace operating method that stabilizes productivity through adjustment.

(Prior Art) In recent blast furnace operations, low-silicon operations are being pursued from the viewpoint of improving quality in the subsequent steel manufacturing process and from the viewpoint of economic efficiency. A typical method of this type of operation is to inject a powdered iron source such as oxidized iron powder or reduced iron powder together with pulverized coal from the tuyere.
It is disclosed in Publication No. 402.

Powdered iron sources such as iron oxide powder and reduced iron powder that are injected in this way undergo a reduction reaction in the blast furnace and are reduced to a metallic state. F
The reaction of SiOy (SiOy) lowers the silicon in the hot metal.

When blast furnace operation is stable, the amount of iron ore charged from the top of the blast furnace can be reduced by the amount of powdered iron source injected from the tuyere.

Normally, the iron ore that is charged from the top of the furnace is agglomerated in order to maintain ventilation inside the furnace, so it is a cheaper alternative to iron ore that requires preliminary treatment. Using a powdered iron source is also highly effective in improving the economic efficiency of blast furnace operation.

(Problems to be Solved by the Invention) In conventional blast furnace operations, there are cases in which the amount of iron ore charged from the top of the blast furnace is reduced for reasons other than a decrease in the furnace heat of the blast furnace. This occurs when there is poor ventilation or abnormality in the descent of the burden due to delays in the descent of the burden, stagnation, or the formation of deposits on the furnace wall from the bottom of the shaft of the blast furnace to the belly of the furnace and the morning glory. If symptoms are observed, the ratio of ore to coke (hereinafter abbreviated as 0/C) in the furnace wall is reduced, and the O/C in the central part is increased. If it is not possible to increase the O/C from the middle to the center,
Reduce the O/C of the furnace wall and reduce the overall O/C. This strengthens the gas flow at the furnace wall and eliminates or prevents delays in lowering the charge, stagnation, and the formation of deposits.

When a delay in the descent of the charge, stagnation, or the formation of deposits on the furnace wall occurs, it is often not accompanied by a decrease in the furnace heat of the blast furnace.Reducing the overall O/C will increase the coke ratio and reduce the production volume. This is unfavorable for blast furnace operation as it causes a decrease in silicon content and an increase in silicon content in the hot metal. It often takes 3 to 10 days to eliminate or prevent the delay in lowering the charge, stagnation, and the formation of deposits, during which time production continues to decrease and silicon levels in the hot metal continue to increase. Even when powdered iron source is injected through the tuyeres, the amount of powdered iron source is often left unchanged or cut for fear of poor ventilation.

As described above, conventional blast furnace operations have been forced to reduce production by 3 to 10 days and increase the amount of silicon in the hot metal.

Therefore, the present invention aims to eliminate or prevent the slow descent of the charge, stagnation, and the formation of deposits without decreasing the furnace heat of the blast furnace, without increasing the coke ratio. The aim is to maintain the production volume and silicon in the hot metal constant.

(Means and effects for solving the problem) In order to achieve the object, the blast furnace operating method of the present invention injects a powdered iron source into the blast furnace from the tuyere part, and iron ore and coke from the top of the furnace. In an operation method in which iron ore is alternately charged, when an operation is performed to reduce the amount of iron ore charged from the top of the furnace, after the iron ore reaches the tuyere, an amount of powdered iron source corresponding to the iron ore is is blown into the inside of the blast furnace from the tuyere.

If poor ventilation or an abnormality in the descent of the burden occurs due to delays in the descent of the burden, stagnation, or the formation of deposits on the furnace wall from the bottom of the shaft of the blast furnace to the belly of the furnace and the morning glory, or if there are any signs of such occurrence. If this occurs, it is often not accompanied by a decrease in the furnace heat of the blast furnace (that is, the raceway section is in a stable reaction heat transfer state), so there is no need to change the air blowing conditions at the tuyere section.

However, by reducing the amount of iron ore charged from the top of the furnace (that is, reducing the overall O/C), when the O/C charge that descended to the tuyere reached the raceway after 5 to 6 hours, part of the furnace becomes overheated. In the present invention, after the iron ore charged from the top of the furnace reaches the tuyere section, 5 hours after the iron ore is charged from the top of the furnace.
~6 hours have passed. At this time, the raceway section is maintained in a stable reaction heat transfer state by injecting from the tuyeres an amount of powdered iron source equivalent to the reduced amount of iron ore charged from the top of the furnace. . This does not lead to poor air permeability.

In principle, the amount of powdered iron source equivalent to the reduced amount of iron ore charged from the top of the furnace will have a constant iron content, but depending on whether it is oxidized iron powder or reduced iron powder, the reduction part Adjust the amount accordingly. When pulverized coal is injected at the same time as the pulverized iron source, the amount of pulverized iron source can be increased by increasing the amount of pulverized coal. Table 1 shows the relationship between the reduction rate of the powdered iron source and the corresponding amount, and the relationship between the increased amount of pulverized coal.

Part 1 table (Example) The features of the present invention will be specifically explained below with reference to Examples.

As shown in Table 2, in the all-coke operation in Example 1, the average value in the circumferential direction of the thermometer installed on the furnace wall brick at the bottom of the shaft deviated from the normal value of 120°C ± 20°C to 95°C. Therefore, the amount of ore charged from the top of the furnace was reduced from 75 tons/time to It/time, and after 5 hours, the particle size of the ore injected from the tuyere was 1. Amount of iron oxide powder (reduction rate 0%) below Oam 4
080 Kg/hr, and the production amount and silicon in the hot metal are almost constant compared to the standard operation 1, which is an all-coke operation.

In Comparative Example 1, during all-coke operation, the average value in the circumferential direction of the thermometer installed on the furnace wall brick at the bottom of the shaft deviated from the normal 120°C ± 20°C and reached 95°C. This is a case where the amount of ore inputted is reduced by 75t/time to It/time and the operation is continued as it is, and the production volume decreases and the silicon content in the hot metal increases significantly compared to the standard operation 1 of all coke operation.

As shown in Table 3, in Example 2, during the pulverized coal injection operation, the average value in the circumferential direction of the thermometer embedded in the stave in the furnace belly deviated from the normal 100°C ± 15°C to 80°C.
Therefore, the amount of ore charged from the top of the furnace (90t/time) was reduced by 1.5t/time, and the amount of iron oxide powder with a particle size of 0.51 or less (30% reduction rate) injected from the siding after 6 hours was reduced. 815
0 Kg/hr, and the amount of pulverized coal was increased to I 000
Kg/hr is increased, and the production amount and silicon in the hot metal are almost constant compared to the standard operation 2 of the pulverized coal injection operation.

In Example 3, during the pulverized coal injection operation, the average value in the circumferential direction of the thermometer embedded in the stave of the morning glory section was 15
As the temperature exceeded 0℃±25℃ and reached 120℃, the amount of ore charged from the top of the furnace (90t/time) was reduced by 1.5t/time, and after 6 hours, the amount of ore charged from the tuyere with a grain size of 0.75am or less was reduced. The amount of iron oxide powder (reduction rate 60%) was 9270 Kg/hr.
This is a case where the amount of pulverized coal is increased by 500 kg/hr, and the production amount and silicon in the hot metal are almost constant compared to the standard operation 2 of the pulverized coal injection operation.

In Example 4, during the pulverized coal injection operation, the average value in the circumferential direction of the thermometer embedded in the stave of the morning glory section was 15
Since the temperature was deviated from 0℃±25℃ and became 120℃, the amount of ore charged from the top of the furnace, 90t/time, was reduced by 1.5t/time, and after 6 hours, the amount of ore charged from the tuyere was reduced to 0.25g+g+ or less. The amount of iron oxide powder (reduction rate 100%) was 186301[
g/hr is increased, and the production amount increases and the silicon content in the hot metal decreases compared to the standard operation 2 of the pulverized coal injection operation.

In Comparative Example 2, during pulverized coal injection operation, the average value in the circumferential direction of the thermometer embedded in the furnace stave was 100%, which is the normal value.
Since the temperature was 80℃, which was outside of ±15℃, the amount of ore charged from the top of the furnace, which was 90t/time, was reduced by 1.5t/time.
This is the case where the operation continues as it is, and the production volume decreases and the silicon in the hot metal increases significantly compared to the standard operation 2 of pulverized coal injection operation.

(Effects of the Invention) As explained above, the present invention adjusts the total amount of iron ore charged from the top of the furnace and powdered iron source injected from the tuyere so that the furnace heat of the blast furnace is stabilized. By doing so, production volume and silicon content in hot metal can be maintained constant, and a stable supply of hot metal can be achieved.

Out wish Man Nippon Steel Corporation

Claims (1)

[Claims] (1) In an operating method in which powdered iron source is injected into the blast furnace from the tuyere and iron ore and coke are alternately charged from the top of the furnace, an operation was performed to reduce the amount of iron ore charged from the top of the furnace. When,
A blast furnace operating method characterized in that after the iron ore reaches the tuyere, a powdered iron source in an amount equivalent to the iron ore is injected into the blast furnace from the tuyere.