JPH0565515A - Method for operating blast furnace - Google Patents

Abstract

(57) [Summary] [Purpose] In the operation of blowing a large amount of pulverized coal from the tuyere of the blast furnace, when unburned char is deposited on the core of the furnace, it is removed to ensure stable blast furnace operation. [Composition] In a method of operating a blast furnace in which pulverized coal is blown together with hot air from the blast tuyere of a blast furnace, a gas containing O ₂ is mixed with iron oxide powder, and a tube inserted from outside the furnace is used to center the furnace from the raceway tip. At the side and at the level area from the tuyere to the furnace side. Specifically, an opening is provided in the furnace side of the blast furnace, a lance is inserted, and a gas containing O ₂ is blown together with the iron oxide powder from the lance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention aims to secure stable blast furnace operation by blowing out a large amount of pulverized coal from tuyere of a blast furnace when unburned char is deposited on the core of the furnace. It is what

[0002]

2. Description of the Related Art In blast furnace operation, a technique of blowing fuel from tuyere to replace coke charged from the top of the furnace was developed (Japanese Patent Publication No. 40-23763) to reduce hot metal production costs and improve productivity. ing. Pulverized coal, petroleum, heavy oil, naphtha and the like are used as the fuel, but recently, pulverized coal injection is mainly used in terms of price.

The pulverized coal blown from the tuyere burns in the area near the tuyere in the raceway, the carbon content becomes CO ₂ , and H ₂ O is also generated due to the organic matter partially contained.
Further, when oxygen disappears in the area outside the raceway, CO and H ₂ are formed by reaction with coke, and these are supplied as reducing gas into the furnace.

That is, the carbon content in the pulverized coal is once completely oxidized to CO ₂ and CO is produced by the solution reaction. That is, the amount of oxygen required to finally form CO gas is required in the course of the reaction, and the amount of air required for complete combustion of the pulverized coal, that is, the air ratio needs to be 1 or more. Therefore, if the blowing of the pulverized coal increases, the combustion efficiency of the pulverized coal decreases as the air ratio decreases. Then, when the air ratio falls below the vicinity of 1, the amount of unburned char generated in the raceway increases rapidly. Blast furnace fuel ratio is 500
The blowing amount of the pulverized coal that gives an air ratio of 1 at kg / t-pig is about 170 kg / t-pig, which is the limit of the blowing amount.

[0005]

Since it is cost effective to replace coke with pulverized coal as much as possible, attempts have been made to increase the amount of pulverized coal blown. However, if a large amount of the charcoal is blown in beyond the above-mentioned limit, the unburned char generated will be deposited on the core of the furnace, impairing air permeability and liquid permeability. For this reason, the amount of tapped iron is reduced, which is not profitable.
The present invention is intended to solve the above problems and eliminate the adverse effect of the accumulation of the above-mentioned unburned char on the core portion of the furnace, thereby making it possible to blow a large amount of pulverized coal.

[0006]

Means for Solving the Problems The present invention is to solve the above problems, and in a method for operating a blast furnace, in which pulverized coal is blown together with hot air from a blast furnace tuyere, a gas containing O ₂ is used as an iron oxide. It is characterized in that the powder is blown together with the powder from the outside of the furnace into a region from the tuyere to the furnace belly on the furnace center side from the tip of the raceway. Further, as this means, an opening is provided in the blast furnace belly, a lance is inserted, and a gas containing O ₂ is blown together with the iron oxide powder.

[0007]

The present invention significantly increases the pulverized coal ratio to 200 kg /
The operation is performed with a blowing amount of t-pig or more, but this can be dealt with by blowing a gas containing O ₂ together with the iron oxide powder into the furnace through a tube inserted from outside the furnace.

As a means for introducing O ₂ into the furnace of a blast furnace, there is a method of supplying oxygen-enriched air. This makes it possible to reduce the air ratio while maintaining the same amount of blown air, and to suppress the generation of unburned char. However, this method may cause a problem in the stable operation of the blast furnace because the combustion temperature before the tuyere rises. There is also a problem that the amount of generated SiO increases and the amount of Si in the hot metal increases.

Therefore, in the present invention, the gas containing O ₂ is blown into the region of the level from the tuyere to the front of the furnace on the furnace center side from the tip of the raceway by the pipe inserted from the outside of the furnace. O ₂
In addition to pure O _{2, the} gas containing is air or oxygen-enriched air. It is not pure O ₂ but rather N like air enriched with oxygen.
_It is preferable that _{2 and the} like are mixed because of the durability of the blow-in pipe, and the cost of gas is low. It is in the level area from the tuyere to the core of the raceway tip to the core of the furnace that the unburned char tends to accumulate during the operation of the pulverized coal. O ₂ is blown directly into this area to react with the unburned char. Let it disappear. This reaction is an exothermic reaction as shown in the following formula.

O ₂ + 2C = 2CO + 58.8 (kcal / mol)

Therefore, the temperature rises due to the blowing of the gas. Since excessive local temperature rise is not preferable for stable operation of the blast furnace as described above, iron oxide powder is blown together with a gas containing O ₂ as a temperature adjusting means. Iron oxide absorbs heat while reacting with carbon itself to remove unburned char as shown in the following formula.

Fe ₂ O ₃ + 3C = 2Fe + 3CO-11
5.4 (kcal / mol)

Therefore, when pure O ₂ and pure Fe ₂ O ₃ are used, the molar ratio is about 2 to 1, and thermal balance is achieved. In practice, the proportion of O ₂ may be increased and the amount of heat generated may be adjusted according to the furnace conditions. Since iron oxide is less reactive than O ₂ , it reacts preferentially with unburned char, which is more reactive than coke, and it is advantageous that unburned char can be selectively removed. As iron oxides, iron ore powder, converter dust, blast furnace dust, sintered dust and the like can be used.

As a gas blowing means, a blowing lance is inserted from a tuyere, a tuyere, on a tuyere, a furnace belly, etc. in a region from the tip of the raceway to the furnace center side from the tuyere to the furnace belly level. .. FIG. 1 is a sectional view of a part of the blast furnace 1 showing this situation. In recent years, a technique for inserting a sonde from a tuyere or the like has been developed, but as shown in FIG. 1, the present invention inserts a water-cooling blow-in lance 6 from an opening provided in advance by the same means as this. It is to blow.

Of these, when the blowing lance 6 is inserted from the tuyere 2, the lance is inserted through the high temperature portion of the raceway, so the blowing time is restricted by the durability of the lance, but existing equipment can be used. There is an advantage that there is no need to newly provide an opening. Further, a method (not shown) in which openings are provided between the tuyere is preferable because the high temperature portion of the raceway can be avoided. However, the space between the tuyere is the thickest part of the iron shell of the blast furnace due to strength problems, and there is the problem that it is quite difficult to provide openings. For this reason, there is also a method (not shown) of providing an opening on the upper part of the tuyere, but this part has an annular pipe 7 and a blower branch pipe 8 for blowing the tuyere, which may be an obstacle, and thus the blowing lance There is a case where it is difficult to have equipment.

From these points, it is most preferable to provide an opening in the furnace belly 3. As shown in FIG. 1, a blowing lance 6 is inserted obliquely downward from the furnace belly 3. According to this method, by adjusting the insertion angle and the depth, the blast furnace can be blown to any location from the core 4 to the portion close to the tuyere in the radial direction and from the tuyere level to the belly level in the vertical direction. .. In addition, the lance can reach the furnace core without passing through the high temperature part on the way, which is preferable in terms of durability of the lance and can be continued for a long time.

[0017]

EXAMPLES Examples will be described below with reference to Table 1.

[Table 1]

In a blast furnace having an internal volume of 3900 cubic meters, the amount of pulverized coal blown was changed to test the effect of blowing iron oxide powder and a gas containing oxygen into the blast furnace by a lance. Converter dust was used as the iron oxide powder, and oxygen-enriched air with a gas-acid ratio of 50% was used as the gas containing oxygen. The gas was blown at room temperature without heating. Blowing was performed during operation by providing an opening in the furnace belly 3 and inserting the lance 6 as shown in FIG. The blowing position is shown in Figure 1.
As shown in (4), it is a range centered on the surface layer portion of the furnace core 4 at a level slightly above the tuyere. The blowing time was once for 15 minutes, and the locations were sequentially changed at six locations around the blast furnace. The gas is blown into one place once a day.

Comparative Example 1 is a standard condition, in which the pulverized coal is blown in at a rate of 150 kg / t-pig, and is a normal operation in which no gas is blown into the furnace core. In Examples 1 and 2, the amount of pulverized coal blown was increased to 200 kg / t-pig, and the unburned char in the furnace core was removed by blowing iron oxide powder and oxygen-enriched air. The second embodiment has a larger blowing amount than the first embodiment. In these examples, the replacement ratio of coke by pulverized coal does not change, the fuel ratio does not increase, and the amount of tapped metal is also good.

On the other hand, the amount of pulverized coal injected is 200 kg / t-
However, in Comparative Example 2 in which gas was not blown into the furnace core, the fuel ratio tended to increase and the amount of tapped metal tended to decrease.

Further, the amount of pulverized coal blown is 250 kg /
Although it was increased to t-pig, when the iron oxide powder and oxygen-enriched air were blown in as seen in Examples 3 and 4, the increase in fuel ratio was almost the same as in Examples 1 and 2. And the amount of tapping is good. The amount of air blown in Example 4 is larger than that in Example 3, but the effect can be seen to some extent. On the other hand, in Comparative Example 3, the amount of pulverized coal blown was increased to 230 kg / t, but unburned char was accumulated because gas was not blown into the core, which impaired air permeability and liquid permeability of the core. As a result, the fuel ratio increases and the amount of tapping metal decreases.

[0022]

In the operation of the blast furnace, unburned char accumulated on the core of the furnace when the amount of pulverized coal blown from the tuyere is increased can be removed by the method of the present invention during the operation. As a result, the amount of pulverized coal injected can be increased without deteriorating the furnace condition, the amount of coke used can be reduced, and the cost can be reduced.

[Brief description of drawings]

FIG. 1 is a diagram illustrating a gas and powder blowing method of the present invention.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Tsutomu Okada 5-3 Tokai-cho, Tokai-shi, Aichi Nippon Steel Co., Ltd. Nagoya Steel Works

Claims (2)

[Claims] 1. A method of operating a blast furnace, in which pulverized coal is blown together with hot air from a blast furnace tuyere, in a furnace center side from a raceway tip end by a pipe in which a gas containing O ₂ is inserted from outside the furnace together with iron oxide powder. The method of operating a blast furnace is characterized by blowing into the area from the tuyere to the side of the furnace. 2. The method for operating a blast furnace according to claim 1, wherein an opening is provided in the blast furnace belly, a lance is inserted, and a gas containing O ₂ is blown together with the iron oxide powder.