JP2001279308A - Method for operating blast furnace using metallic iron- based raw material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a stable and efficient operation method for a blast furnace by which the shortage of a reduction efficiency and the deterioration of the furnace condition at the lower part of the furnace with high ore/coke and the extreme raising of a gas utilizing ratio caused by the high ore/coke can be avoided without raising the fuel ratio when the high ore/coke charging operation aimed at a low fuel ratio and a high productivity, is performed. SOLUTION: In the blast furnace operation method for charging the coke and the iron oxide-based raw material, the gas utilizing ratio in the radium direction at the furnace top part in the blast furnace, is measured and a part or the whole of the iron oxide-based raw material in a zone where the gas utilizing ratio is higher than a preset prescribed value, is replaced with the metallic iron raw material and charged.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of operating a blast furnace, and more particularly to a method of operating a blast furnace using a metal iron-based material together with an iron oxide-based material.

[0002]

2. Description of the Related Art In a normal blast furnace operation, iron-based raw materials and coke are charged alternately from the furnace top, and they are deposited in layers in the furnace. Hot air and heavy oil, pulverized coal, etc. are discharged from the tuyeres. Inject auxiliary fuel. Hot air blown from the tuyere
The reaction with coke in the furnace and the auxiliary fuel blown from the tuyere generates reducing gas (CO, H ₂ ) and its reaction heat. The charged iron-based raw material is reduced and heated by the sensible heat of the reducing gas or hot air while falling in the furnace, forming a softening and melting zone. Hot metal is discharged from the mouth.

Here, as the iron-based raw material charged from the top of the blast furnace, an iron oxide-based raw material containing iron oxide as a main component, such as sinter, iron ore, and pellets, is usually used. These iron oxides are gradually reduced (indirectly reduced) and softened and melted by a reducing gas (CO, H ₂ ) rising from the lower part of the shaft while descending in the furnace to form a cohesive zone. In a high temperature region (above 1000 ° C.) from the lower part to the tuyere level, the molten iron oxide is directly reacted with coke and reduced (direct reduction).

Normally, in the operation of a blast furnace, in order to smoothly reduce and melt iron oxide-based raw materials to obtain hot metal of a stable quality and quantity, the mole fraction of the gas in the furnace is used as an index of the indirect reduction efficiency in the furnace. The gas utilization rate defined by the following equation based on the following equation is used. Gas utilization rate (%) = 100 × (CO ₂ + H ₂ O) / (CO + CO ₂ + H ₂ + H ₂ O) (1)

The gas utilization rate obtained by the above equation (1) is:
It indicates the rate at which the reducing gas (CO, H ₂ ) in the furnace is converted into the oxidizing gas (CO ₂ ) and H ₂ O by an indirect reaction with the iron oxide-based raw material. Therefore, increasing the gas utilization rate means that the gas is converted into a larger amount of oxidizing gas. Can reduce the fuel ratio.

A conventional method for increasing the gas utilization rate is to increase the amount of iron oxide in contact with a predetermined reducing gas (CO, H ₂ ) to promote the reaction efficiency, thereby reducing the reducing gas (CO, H ₂ ). Generally, a method of converting ₂ ) into CO ₂ and H ₂ O more, that is, a method of increasing the amount of oxygen to be reduced brought by the oxidizing raw material per reducing gas is generally used. Specifically, by charging coke and an oxidizing raw material so as to increase the ore weight per coke weight (hereinafter referred to as Ore / Coke) in the blast furnace radius as a whole, the fuel in the blast furnace cross section is averaged. In this method, the amount of iron oxide-based raw material per (total of coke and auxiliary fuel) is increased so that heat balance can be achieved with a lower fuel ratio.

[0007] In addition, the high Ore /
In order to perform stable operation in the Coke charging operation, Japanese Patent Publication No. 64-9373 and the like disclose increasing the amount of coke charged into the central region of the furnace radius by increasing the amount of coke charged.
/ Coke to improve the air permeability (improve the center flow) and to reduce the Ore /
Blast furnace operations that increase Coke to improve gas utilization are also known.

Further, in the central flow operation in which the Ore / Coke is lowered in the center region of the furnace as disclosed in Japanese Patent Publication No. 64-9373, etc., a part of the iron oxide-based raw material in the center region of the furnace radius is further scrapped or reduced iron. Etc.
Japanese Patent Application Laid-Open No. 6-279818 discloses a conventional method of suppressing coke powdering by reaction with CO ₂ gas generated by reduction of iron oxide and reducing the heat load to enhance the central flow.

However, in such an operation method,
The gas utilization rate in the high Ore / Coke charging area is Ore / C
Oke increases to a certain level with increasing, but gradually
Gas utilization rate will decrease and Ore / Coke rise
Overheating, the upper 100
The reducing gas (CO, H
_Two ) Increases the amount of iron oxide-based raw materials that cannot be reduced (reduction delay).
The iron oxide-based raw material is transferred from the upper part of the shaft to the blast furnace.
High temperature area of 1000 ° C or higher at the lower part of the tuyere (direct return
Direct reduction reaction that reacts directly with coke in the
Or dripping on the hearth.

[0010] Since the direct reduction reaction is an endothermic reaction, the amount of heat required for reducing iron oxide is much larger than that of the indirect reduction reaction, which is disadvantageous in terms of heat. The balance will be lost and the stable operation of the blast furnace will be hindered. As a result, iron oxide in an unreduced state drops on the hearth, causing a drop in hot metal temperature, variations in components, and fluctuations in wind pressure, and in the worst case, cooling down of the lower part of the furnace.

In particular, high Ore / Co with a low fuel ratio
In the ke charging operation, the Ore / Co is extremely increased in the furnace radial direction due to a slight variation in the charging distribution in the furnace radial direction.
A region where the ke is high occurs, and a local reduction delay due to the region is likely to occur. To avoid this, conventionally, the average Ore / Coke in the furnace radial direction was reduced to increase the fuel ratio. I had to return to operation.

[0012]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and has been made in view of the above-mentioned problems.
During the re / Coke charging operation, if there is a region where the gas utilization rate in the furnace radial direction is extremely high and a reduction delay is likely to occur due to a variation in the charging distribution or the like, the reactor caused by the reduction delay without increasing the low fuel ratio. An object of the present invention is to provide a stable and efficient method of operating a blast furnace while avoiding adverse effects of the lower part.

[0013]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems of the prior art. In a blast furnace operating method for charging coke and an iron oxide-based raw material, the present invention relates to a method for operating a gas at a furnace radius at the top of a blast furnace. A blast furnace operation characterized in that the utilization rate is measured, and a part or all of the iron oxide-based raw material in a region where the gas utilization rate is higher than a predetermined value is replaced with a metallic iron-based raw material and charged. Is the way.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Generally, in a blast furnace, gas in the furnace is sampled at a plurality of locations in the radial direction of the furnace at least at the top of the furnace, and components such as CO, CO ₂ , H ₂ , and H ₂ O in the gas are measured. Thereafter, a device for immediately calculating the gas utilization rate defined by the above equation (1) is provided.

The present inventors have found that, in the furnace radial direction at the time of a high Ore / Coke charging operation aimed at a low fuel ratio or a high production, a region where the gas utilization rate is relatively high indicates that the reducing capacity at the upper part of the furnace is low. It was found that there was a shortage and there was a high tendency to deteriorate the furnace condition at the bottom of the furnace. The present invention has been made based on this finding, and measures the gas utilization rate at the furnace radius at the top of the blast furnace, and detects the iron oxide-based raw material in a region where the gas utilization rate in the furnace radial direction is higher than a predetermined value. Is replaced with metallic iron-based raw material, and this reduces the reduction load on the upper part of the furnace in areas where the gas utilization rate is high, eliminates the reduction capacity shortage, and thus solves the deterioration of the furnace condition at the lower part of the furnace Is what you do.

Here, the iron oxide-based raw material is an iron-based raw material containing iron oxide as a main component, such as sintered ore, iron ore, pellets, and the like, and the metallic iron-based raw material is scrap, reduced iron, granular iron, or the like. It is an iron-based raw material containing metallic iron as a main component.

According to the study of the present inventors, the gas utilization rate measured at the top of the blast furnace furnace is such that the carbon contained in the auxiliary fuel blown from the tuyere and the coke charged from the furnace top is oxygen and combustion.
It depends on how the reducing gas (CO, H ₂ ) generated by the reaction comes in contact with the iron ore charged from the furnace top and undergoes a reducing reaction. It was found that the ratio of the direct reduction reaction of iron oxide in the lower part of the furnace (direct reduction ratio) tended to increase due to an increase in the amount of iron oxide that was not reduced due to insufficient reducing ability.
In this case, since the direct reduction reaction is an endothermic reaction, when the gas utilization rate exceeds a predetermined value, the heat balance in the furnace deteriorates, and the furnace condition particularly deteriorates due to a decrease in temperature in the lower part of the furnace and a decrease in air permeability. It turned out to be.

FIG. 1 shows the relationship between the gas utilization rate in the furnace and the direct reduction rate or the amount of residual heat in the furnace per iron ore. Here, the furnace residual heat amount is the heat balance in the furnace,
Sensible heat of hot air blown from tuyeres, heat removal / radiation from raw materials and furnace body, reduction gasification reaction of auxiliary fuel and coke,
The difference between the amount of heat input into the furnace and the amount of heat output in the reaction heat (exothermic or endothermic) in the reduction reaction of iron ore is calculated. As shown in FIG. 1, the rate of the direct reduction reaction (direct reduction rate) increases as the gas utilization rate in the furnace increases, and the heat balance in the furnace (surplus heat) decreases due to the increase in the endothermic reaction.

In the present invention, the in-furnace gas utilization rate and the direct reduction rate as shown in FIG. 1, which are determined by the conditions such as the injection amount of auxiliary fuel, the charging amount of coke, the charging amount of iron ore, and Ore / Coke, are shown. From the relationship with the heat balance in the furnace (excess heat), the measured value of the gas utilization rate in the furnace at the top of the blast furnace in the radial direction of the furnace indicates that the furnace condition deteriorated due to lower temperature and lower air permeability in the lower part of the furnace. Part or all of the iron oxide-based raw material at a position corresponding to a region higher than the upper limit of the gas utilization rate is replaced with a metallic iron-based raw material and charged.

The upper limit of the gas utilization rate at which the deterioration of the furnace condition due to the lowering of the temperature and the permeability of the lower part of the furnace becomes remarkable is directly related to the gas utilization rate in the furnace as shown in FIG. In the relation diagram with the reduction rate or the heat balance in the furnace (surplus heat), for example, it can be determined by using the furnace gas utilization rate at which the surplus heat amount becomes zero.

As a result, the amount of oxygen to be reduced by the iron oxide per amount of the reducing gas supplied to the upper region of the furnace where the reducing capacity is insufficient is reduced, so that the reduction load in the upper region of the furnace is reduced. You. In this case, the gas utilization rate in the area where the iron oxide-based raw material is replaced with the metal iron-based raw material tends to decrease, but the reduction load of the gas utilization rate is small because the reduction load is originally high and the reduction capacity is insufficient. In addition, since the iron source in the region can be maintained, the fuel ratio can be reduced while maintaining the amount of pig iron generated in the region.

In recent years, in blast furnace operation, the Ore / Coke has been increased in order to achieve a low fuel ratio, and further, a large amount of auxiliary fuel (such as pulverized coal) has been used in order to achieve high production. There is a tendency to reduce coke entering. Under such an operating condition where the Ore / Coke is high, there is a region in which the Ore / Coke becomes extremely high in the radial direction of the furnace due to a slight variation in the charging distribution. Furnace conditions are likely to deteriorate. In such a case, conventionally, in order to avoid the deterioration of the furnace condition in the lower part of the furnace due to the local reduction delay, the Ore / Co in the entire radial direction of the furnace is known, knowing that the fuel ratio increases.
Blast furnace operation with reduced ke had to be performed.

On the other hand, according to the present invention, based on the measurement result of the gas utilization rate at the furnace top, it is possible to identify the region of the furnace upper part where the reducing capacity is insufficient in the radial direction of the furnace, and only the region has the iron oxide type raw material. By partially or entirely replacing the metal iron and charging, it is possible to effectively eliminate the reduction delay in the region without lowering the fuel ratio and consequently improve the furnace condition in the lower part of the furnace.

A method of replacing a predetermined amount of the iron oxide-based raw material in the entire radial direction of the furnace including the region with the insufficient reducing capacity with a metallic iron-based material can be considered. By replacing with, the reduction of the gas utilization rate is increased and the reduction efficiency is reduced. In addition, since it is disadvantageous from the viewpoint of economy when the amount of the metal iron-based material to be replaced is increased,
It is not preferable to avoid deterioration of the furnace condition at the lower part of the furnace due to the reduction.

In the present invention, as means for charging a metal iron-based raw material by replacing the iron oxide-based raw material with an iron oxide-based raw material in a region where the gas utilization rate in the furnace radial direction is higher than a predetermined value and the reducing ability is insufficient, In a blast furnace equipped with a bellless charging device,
The metal-iron-based raw material may be charged at the timing of being discharged into the furnace by setting the chute angle or the notch so that the gas utilization rate becomes a predetermined position above a predetermined value. In a bell-type blast furnace, similar control is possible using movable armor.

The amount of the metal-based material to be replaced with the iron-oxide-based material greatly varies depending on the operating conditions when the action is taken. However, when 1% is replaced by iron in normal operation, the gas utilization rate is reduced by about 1 point. Has the effect of doing Therefore, in actual operation, it is preferable to take an action based on this as a guide and then perform an operation of increasing or decreasing the charged amount of the metal-based raw material based on the result.

[0027]

Embodiments of the present invention will be described below. Table 1 shows the operating conditions and results of the blast furnace with an inner volume of 4400 cubic meters of the present invention and Comparative Examples 1 and 2.

[0028]

[Table 1]

In Comparative Example 1, the low coke ratio (= 512 (k)
g / t)), high Ore / Coke (= 4.42 (−))
During this operation, the gas utilization rate in the furnace top in the furnace radial direction at the furnace top became excessively high at 61%, and as a result, the furnace condition at the bottom of the furnace deteriorated (hot metal temperature, hot metal (Si component and blast pressure fluctuate, causing slip)
did.

As a countermeasure against the deterioration of the furnace condition in the lower part of the furnace in Comparative Example 1, as Comparative Example 2, a raw material charging method for adjusting the Ore / Coke of the entire charged raw material, which is a conventional operation action,
In addition, as an example of the present invention, a method of charging a predetermined amount of a metallic iron raw material by substituting the iron oxide-based raw material in a region where the in-furnace gas utilization rate is high in the furnace radial direction was performed.

In Comparative Example 2, the average Ore in the furnace radial direction was
As a result of operating with / Coke reduced from 4.42 of Comparative Example 1 to 4.26 (reduction amount: 0.16), the maximum gas utilization rate in the radial direction in the furnace in Comparative Example 1 was 61 (%). The gas utilization rate in the region where the gas flow was reduced could be reduced to 55%. However, in Comparative Example 2, the fuel ratio increased to 526 (Kg / t) (512 (Kg / t) in Comparative Example 1) due to the increase in the average Ore / Coke.

On the other hand, in the example of the present invention, in the operation of Comparative Example 1, the oxide-based material corresponding to the intermediate portion in the furnace radial direction where the gas utilization rate at the furnace top reached 61% was replaced with the metallic iron-based material. In order to do so, the metallic iron-based raw material is 60 to 70 kg /
As a result of charging in the range of t, the gas utilization rate in that region is 55
%. The fuel ratio at this time was 492 (kg / t), and the fuel ratio of Comparative Example 1 was 5: 5.
It was possible to keep it lower than 12 (kg / t).

From the above embodiment, the present invention is applied to increase the fuel ratio without deteriorating the furnace condition in the lower part of the furnace due to the region where the gas utilization rate in the furnace is high (the molten iron temperature, the Si content in the molten iron, the blowing pressure vary, Was generated).

[0034]

As described above, according to the present invention, an extremely high gas utilization rate and a reduction in the reduction capacity generated due to a variation in the charging distribution during a high Ore / Coke charging operation for low fuel ratio or high production. Thus, it is possible to efficiently avoid the deterioration of the furnace condition at the lower part of the furnace without increasing the fuel ratio, thereby achieving a stable and efficient blast furnace operating method.

[Brief description of the drawings]

FIG. 1 is a graph showing the gas utilization rate in a furnace and the direct reduction rate, or
It is a figure which shows the relationship with the heat balance in a furnace (surplus heat).

Claims (1)

[Claims] In a blast furnace operating method in which coke and an iron oxide-based raw material are charged, a gas utilization rate at a furnace radius of a blast furnace top is measured, and the gas utilization rate is in a region higher than a predetermined value. A method for operating a blast furnace, wherein a part or all of an iron oxide-based material is replaced with a metal-iron-based material and charged.