JPH05255720A - Method for operating blast furnace - Google Patents

Abstract

PURPOSE:To avoid the reduction in productivity caused by the defective ventilation and the increase in a fuel ratio by recovering temp. without drastically increasing the fuel ratio when powders are accumulated in a coke layer (called as a furnace core) in the center at the lower part of a blast furnace and the flowing property of a molten material in the furnace center part is reduced and temp. in the furnace core is reduced and the molten material starts solidification. CONSTITUTION:A probe mounting a plasma torch is inserted from a space between tuyeres or by utilizing the opening part of one piece of the tuyere, and any one of nitrogen + gaseous carbon dioxide, nitrogen + steam, nitrogen + gaseous carbon dioxide + steam, nitrogen + oxygen oxygen at 1400-2000 deg.C is blown to heat and melt the molten material starting to solidify and also promote the consumption of the powders, and the furnace core starting the solidification is heated and melted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention maintains the temperature in the coke layer (referred to as the core) in the lower center of the blast furnace during the operation of blowing hot air or hot air and auxiliary fuel from the tuyere of the blast furnace. , Blast furnace operation method that maintains productivity and fuel ratio.

[0002]

2. Description of the Related Art In blast furnace operation, hot air or hot air and auxiliary fuel are blown from the tuyere to blow hot metal, but as a substitute for coke, it is inexpensive and has good flammability and high calorific value. Pulverized coal, petroleum, heavy oil, naphtha, etc.) are blown from the tuyere to reduce the hot metal production cost and improve the productivity, and the technique is disclosed in Japanese Examined Patent Publication No. 40-23763. In particular, the injection of pulverized coal has become the mainstream in recent years from the viewpoint of price, reducing the fuel ratio (cost reduction),
It greatly contributes to productivity improvement.

The auxiliary fuel blown in this way burns in the blast furnace instead of a part of the coke, and due to its good combustibility and high calorific value, it produces a large amount of reducing gas at high temperature and is efficient. A simple reduction reaction. Therefore, the iron ore charged from the top of the furnace is quickly reduced to a metallic state, and is melted to form high-temperature hot metal, so that the furnace heat of the blast furnace is high and the productivity is improved.

[0004]

By the way, in the conventional blast furnace operation, when the strength of the coke charged from the furnace top is lowered, powder is generated during swirl combustion by the hot air blown from the tuyere, The powder is trapped in a coke layer (referred to as a core) in the lower center of the blast furnace. When the trapped amount is large, the liquid permeability of the melt flowing down this portion is hindered, and further the gas permeability of this portion is hindered, so that the temperature inside the furnace core is lowered. If this state continues, the melt will begin to solidify and eventually solidify.

When a large amount of auxiliary fuel, especially pulverized coal, is blown in, the entire amount of pulverized coal blown in is not burned, and some unburned char is generated, and this unburned char is trapped in the furnace core. The temperature inside the furnace core decreases, leading to solidification of the melt. In either case, the blast furnace production will drop significantly. At this time, it is assumed that the blast pressure, which shows the air permeability of the entire blast furnace, increased and the core temperature decreased.

When it is assumed that the blast pressure rises and the temperature in the furnace core lowers, the value of the central portion of the ratio of iron ore and coke (abbreviated as O / C) charged from the furnace top is lowered. Instead, the O / C from the middle part to the peripheral part is increased, but when there is no margin for increasing the O / C from the middle part to the peripheral part, the total O / C is increased.
/ C is reduced. When the auxiliary fuel, especially pulverized coal, is blown, the blowing amount is reduced or cut, and instead, the overall O / C is lowered. In either case, the fuel ratio rises significantly and the production volume decreases.

In view of the above, the present invention aims to recover the temperature of the core without significantly increasing the fuel ratio when the temperature in the core decreases, and to avoid aeration failure and a decrease in production amount due to an increase in fuel ratio. And

[0008]

The blast furnace operating method of the present invention comprises:
In order to achieve that purpose, in a blast furnace operation in which iron ore and coke are charged in layers from the furnace top and hot air or hot air and auxiliary fuel are blown from the tuyere to produce hot metal, the core cools and solidifies. It is characterized in that a plasma torch is inserted at the beginning of the operation, and steam, carbon dioxide, or both of them are blown into the furnace core together with high-temperature nitrogen. Further, as a gas, oxygen is blown into the furnace core together with high-temperature nitrogen instead of this. Furthermore, it is characterized in that hot air or oxygen is blown into the furnace core in place of these gases.

[0009]

[Operation] As an example of applying the plasma torch to the blast furnace,
As disclosed in JP-A-57-51207, when a large amount of water is generated in a blast furnace and a hearth (a region existing below the core described in the present specification) is cooled and solidified, There is a technique of injecting heat into the hearth with a plasma torch, but this is only an emergency means, and the insertion area is different, and is not intended for stable blast furnace operation as in the present invention.

The method of inserting the plasma torch into the furnace core in the present invention is shown in FIGS. 1 to 3. FIG. 1 shows an elevation view when a shutoff valve is installed near the tuyere center level of the blast furnace, the shutoff valve is opened and a water cooling probe is inserted into the blast furnace, and a plasma torch is connected through the probe. Figure 1
1, 1 is a blast furnace iron skin, 2 is a brick, 3 is a tuyere, 4 is a blast branch pipe, 5 is a shutoff valve, 6 is a water cooling probe, 7 is a furnace core,
8 is a plasma torch and 9 is a raceway. FIG. 2 is a plan view showing a case where a probe equipped with a plasma torch is inserted between tuyere and tuyere. Fig. 3 shows tuyere 1
The top view at the time of inserting a probe equipped with a plasma torch using a hole part of a book is shown.

When the coke or powder derived from pulverized coal (mainly carbon) is trapped and accumulated in the furnace core and the molten material dripping into the furnace core begins to solidify near the tuyere center level, a plasma torch The temperature inside the furnace core can be raised by introducing a high-temperature gas heated by means of the probe into the furnace core and heating and melting the melt that has started to solidify.
At the same time, the injected carbon dioxide and water vapor are
The carbon-based powder can be consumed by the gasification reaction of Chemical formula 2. When the gas is nitrogen + oxygen, air, or oxygen, the powder can be consumed by the gasification reaction of Chemical formula 3 and Chemical formula 4.

[0012]

[Chemical 1]

[Chemical 2]

[Chemical 3]

[Chemical 4] Since a high temperature gas is used, the powder is consumed in a short time by heating and melting and the gasification reaction, and the effect is very large. By consuming the powder and heating and melting the melt, the liquid permeability of the melt is secured, the gas permeability in the core is improved, and the temperature inside the core can be recovered.

The type of gas heated by the plasma torch used in FIGS. 1 to 3 can be nitrogen + carbon dioxide, nitrogen + steam, nitrogen + carbon dioxide + steam, nitrogen + oxygen, air, oxygen. .. Further, the temperature of the gas is 120 because the solidification of the melt occurs from 1200 ° C.
Since it is necessary to set the temperature to 0 ° C. or higher, and the reactions of Chemical formulas 5 and 6 are endothermic reactions, it is necessary to compensate for the heat. Considering the above, 1400 ° C to 2000 ° C is used.

[0014]

[Chemical 5]

[Chemical 6] The furnace core here means the raceway depth L (1600 m in the blast furnace center direction from the brick working surface as shown in FIG.
m) shows the area of the circle toward the center of the blast furnace. The insertion of the plasma torch into the furnace core in the present invention can be performed not only when the blast furnace is in a quiescent state, but also during operation, and can be arbitrarily performed during operation, which is highly effective.

Whether or not the temperature inside the furnace core has dropped may be judged by an increase in the blowing pressure, or it can be detected from the temperature drop by installing a thermometer inside the furnace core. It is also possible to insert a gold rod from the tuyere to determine whether or not the melt is solidified. In any case, the conventional method for detecting the temperature decrease in the core can be adopted.

[0016]

EXAMPLES The features of the present invention will be specifically described with reference to the following examples. Table 1 shows the operation results in each example.

[Table 1] Example 1 From a state where the blast pressure was normally 3.5 ± 0.05 kg / square centimeter, the operation was 3.85 ± 0.08.
Since it increased to kg / square centimeter, as shown in Fig. 2, the shutoff valve between the tuyere installed near the tuyere center level of the blast furnace was opened, and the water-cooled probe equipped with the plasma torch was installed inside the blast furnace core. Insert from 1400 degrees C to 160
A mixture of 0 ° C nitrogen: carbon dioxide gas = 7 to 8: 3 to 2 was fed at 12000 standard cubic meters / hour for 15
When stopped after a lapse of time, the blast pressure is normally 3.55 ± 0.
This is an example of an operation that returned to 04 kg / square centimeter.

Example 2 From a state in which the blast pressure was usually 3.5 ± 0.05 kg / square centimeter, it was 3.95 ± 0.07.
Since it increased to kg / square centimeter, as shown in Fig. 3, the shutoff valve attached using the opening of one tuyere of the blast furnace was opened, and the water-cooled probe equipped with the plasma torch was inserted into the blast furnace core. Then, a mixed gas of 1600 ° C to 1800 ° C nitrogen: steam = 9 to 8: 1 to 2 is mixed with 1000
This is an operation example in which the air pressure was returned to the normal 3.45 ± 0.05 kg / square centimeter after 0 standard state cubic meters / hour feeding and stopping after 19 hours.

Example 3 Since the thermometer installed in the core of the furnace decreased to 1200 ± 80 ° C from the state where the thermometer was normally operated at about 1400 ± 50 ° C, as shown in FIG. Open the shut-off valve installed using the opening of one tuyere, insert the water-cooled probe equipped with the plasma torch into the blast furnace core, and from 1800 to 2000 degrees C nitrogen: carbon dioxide: water vapor = 6 8: 2
This is an example of operation in which the mixed gas of 1: 2 to 1 was sent at 16000 standard state cubic meters / hour and stopped after 22 hours, the temperature inside the furnace core returned to the normal 1400 ± 60 ° C.

Example 4 From a state in which the blast pressure was normally 3.5 ± 0.05 kg / square centimeter, the operation was 3.9 ± 0.08 k
It was confirmed that the melt solidified when the pressure was increased to g / square centimeter and the gold rod was inserted from the tuyere, so as shown in Fig. 2, the tuyere installed near the tuyere center level of the blast furnace Open the shutoff valve between the tuyere, insert the water-cooled probe equipped with the plasma torch into the blast furnace core,
To 1900 degree C nitrogen: oxygen = 6 to 7: 4 to 3 mixed gas at 9000 standard state cubic meters / hour, 2
If stopped after 0 hours, the blast pressure will be normal 3.45 ±
This is an operation example in which the solidification of the melt is eliminated when the pressure is returned to 0.05 kg / cm 2 and the gold rod is inserted from the tuyere.

Example 5 From the state in which the blast pressure was normally 3.5 ± 0.05 kg / square centimeter, the operation was 3.75 ± 0.08.
Since it was confirmed that the melt solidified when the pressure was increased to kg / square centimeter and the gold rod was inserted from the tuyere, as shown in Fig. 3, the opening of one tuyere of the blast furnace was used. Open the shut-off valve installed in the blast furnace and insert the water-cooled probe equipped with the plasma torch into the blast furnace core.
When 0 degree C air is sent 8000 standard state cubic meters / hour and stopped after 15 hours, the blast pressure is normal 3.4.
This is an operation example in which the solidification of the melt is eliminated when the gold rod is inserted from the tuyere after returning to 5 ± 0.05 kg / cm 2.

Comparative Example From a state in which the blast pressure was normally 3.5 ± 0.05 kg / square centimeter, it was 3.8 ± 0.08 k.
O / C at the center because it increased to g / cm2
Is an example of an operation in which the overall O / C has been reduced. Compared to Examples 1 to 6, the amount of tapped iron is small and the fuel ratio is high.

[0022]

As described above, according to the present invention,
When powder accumulates in the furnace core and the temperature of the melt that drops in the center of the furnace decreases and the melt solidifies and the temperature inside the furnace begins to decrease, a high temperature gas is generated using the plasma torch. By sending it to the core and heating and melting the melt that is about to solidify promptly, by consuming the powder and recovering the temperature inside the furnace core, avoiding defective ventilation, improving productivity, measuring the fuel ratio, A stable hot metal supply is possible.

[Brief description of drawings]

FIG. 1 is an elevational view of inserting a water-cooled probe equipped with a plasma torch into a furnace core used in the blast furnace operation method of the present invention.

FIG. 2 is a plan view when the water-cooled probe is inserted between the tuyere and the tuyere.

FIG. 3 is a plan view of the case where a water-cooled probe is inserted using the opening portion of one tuyere.

[Procedure amendment]

[Submission date] May 28, 1991

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Claim 3

[Correction method] Change

[Correction content]

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Kenji Tamura Kenji Tamura 1-1-1 Edamitsu, Hachimanto-ku, Kitakyushu-shi, Fukuoka Inside Nippon Steel Co., Ltd.

Claims (3)

[Claims] 1. In a blast furnace operation in which iron ore and coke are charged in layers from the furnace top and hot air or hot air and auxiliary fuel are blown from the tuyere to blow hot metal, the core begins to cool and solidify. A blast furnace operating method characterized in that a plasma torch is sometimes inserted and either or both of steam and carbon dioxide gas are blown into the core together with high-temperature nitrogen. 2. Oxygen is blown into the core together with high-temperature nitrogen instead of blowing either or both of steam and carbon dioxide into the core together with high-temperature nitrogen.
The blast furnace operating method according to claim 1. 3. A method of blowing hot air or carbon dioxide into the furnace core instead of blowing steam, carbon dioxide, or both together with hot nitrogen into the furnace core. 1. The blast furnace operation method described in 1.