JPH0734108A - Operating method for blast furnace - Google Patents

Abstract

PURPOSE:To prevent the failure of tuyeres, Keuhlkastes, etc., in blast furnace operation for blowing pulverized coal from the tuyeres. CONSTITUTION:A nozzle for blowing the pulverized coal into a blow pipe successively connected to the blast tuyere of the blast furnace is formed of double pipes to enclose the pulverized coal injected from the inside pipe of the double pipes by steam injected from the outside pipe and to blow the pulverized coal into the furnace, by which the combustion rate of the pulverized coal is regulated and the combustion peak point of the pulverized coal is moved to a furnace core side and, therefore, the thermal influence exerted on the part near the tuyere is lessened and the failure of the tuyeres, Keuhlkastes, etc., is prevented even in the high pulverized coal ratio operation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for operating a blast furnace in which pulverized coal is blown into a blast furnace, by moving the combustion peak point of the pulverized coal to the core side of the blast furnace to prevent damage to the blast tuyere, dust, etc. The present invention relates to a method for operating a blast furnace to stabilize the

[0002]

2. Description of the Related Art In recent years, due to the development of blast furnace technology, heavy oil has been blown from the tuyere into the blast furnace as an auxiliary fuel, and further reflecting the energy situation thereafter, it is economical and economical to replace heavy oil. A method of blowing pulverized coal into a blast furnace has been put into practical use.

As a method of blowing pulverized coal into the furnace from the blast tuyere, as shown in FIG. 3, the pulverized coal is passed through the wall of the hot-air blowing blow pipe 3 connected to the blast tuyere 2 of the blast furnace 1. In general, the blowing nozzle 4 is projected into the blow pipe and blown into the furnace from the tuyere 2 together with the hot air flowing in the blow pipe 3.

A single pipe was generally used as the pulverized coal injection nozzle in this pulverized coal injection method, but in the case of a single pipe, the nozzle protruding into the blow pipe 3 is
While being heated by the high-temperature hot air that passes through the blow pipe, the progress of erosion becomes remarkable due to the heat of combustion of pulverized coal ejected from the nozzle and the radiant heat from the furnace,
Recently, a pulverized coal injection nozzle with a double-tube cooling structure has been adopted.

As shown in FIG. 4, the pulverized coal blowing nozzle having a double pipe structure injects pulverized coal from an inner pipe 4-1 and a cooling medium such as oxygen, air, nitrogen and carbon dioxide gas from an outer pipe 4-2. It is known that the structure is made to be (JP-A-58-171).
508, JP-A-62-142706, etc.). In the case of such a double-tube blowing nozzle, there is an advantage that the progress of melting loss of the nozzle is suppressed by the cooling effect of the cooling medium passing through the outer tube, and the life is extended as compared with the single tube.

[0006]

However, in the case of a blast furnace operating at a high pulverized coal ratio, the pulverized coal blown into the blow pipe burns regardless of whether the pulverized coal injection nozzle is a single pipe or a double pipe. As a result, the gas volume at the tuyere and the root of the raceway (combustion zone in front of the tuyere) increases, resulting in an increase in blast pressure, which reduces the raceway depth and enlarges the raceway root. Furthermore, the combustion of pulverized coal has a large surface area compared to coke, so the combustion speed is high, and the combustion peak point is closer to the furnace wall because it is burned from inside the blow pipe. Therefore, in a blast furnace with a high pulverized coal ratio operation, a large amount of pulverized coal combustion causes an increase in heat load on the tuyere 2 and the chiricus 5 portion, causing problems such as damage.

The present invention has been made in view of the above problems, and proposes a blast furnace operating method capable of burning a large amount of pulverized coal in the blast furnace and protecting the tuyere and the chiricus portion. It is what

[0008]

The present invention, in a blast furnace operating method for blowing pulverized coal using a double tube structure nozzle, injects pulverized coal from an inner tube of a pulverized coal injection nozzle and steam from an outer tube. The purpose of this is to move the combustion peak point of pulverized coal to the core side.

[0009]

[Function] In the pulverized coal injection nozzle having a double pipe structure, when pulverized coal is injected from the inner pipe and steam is injected from the outer pipe,
The pulverized coal injected from the inner pipe is blown into the furnace while being surrounded by the steam injected from the outer pipe. As a result, the combustion speed of the pulverized coal is suppressed by the steam, and the combustion peak point of the pulverized coal shifts toward the furnace core. This shift of the combustion peak point suppresses the enlargement of the root part of the raceway (combustion zone in front of the tuyere), increases the raceway depth, and reduces the heat load in the vicinity of the tuyere. Damage is prevented.

In the present invention, the fluid blown from the outer tube of the double-tube nozzle is limited to water vapor, even if the cooling effect of the nozzle itself is obtained with a cooling medium other than water vapor, such as oxygen or air. Since the combustion peak point of pulverized coal cannot be moved to the core side because the combustion speed of pulverized coal blown from the nozzle cannot be suppressed, in the case of steam, the combustion velocity suppression effect of pulverized coal and nozzle This is because the cooling effect can be obtained at the same time.

[0011]

FIG. 1 is a schematic view showing an example of the construction of an apparatus for carrying out the method of the present invention. 6 is a pulverized coal hopper, 7 is a steam supply system, 8 is a flow meter, 9 is a flow control valve, and 10 is shut off. valve,
11 is a blast furnace instrument room, C is pulverized coal, and S is steam.

That is, the pulverized coal C stored in the pulverized coal hopper 6 is gas-transported by the carrier gas, and passes through the side surface of the blow pipe 3 from the pulverized coal injection nozzle 4 of the double pipe structure which is installed obliquely. It is blown into the blow pipe 3 and blown into the furnace. On the other hand, S is introduced into the outer tube of the pulverized coal blowing nozzle 4 from the steam supply system 7 through the flow meter 8, the flow rate control valve 9 and the shutoff valve 10, and S is ejected from the nozzle tip and at the same time the inner tube of the nozzle is injected. It is blown into the furnace while surrounding the pulverized coal C to be sprayed. The flow meter 8, the flow rate control valve 9 and the shutoff valve 10 are operated in the blast furnace instrument chamber 11 so that the flow rate of steam with respect to the pulverized coal injection amount is controlled to a predetermined value and supplied to the pulverized coal injection nozzle 4. Has become.

As described above, since the pulverized coal C blown from the pulverized coal blowing nozzle 4 having the double pipe structure is jetted into the blow pipe 3 and at the same time it is blown into the furnace while being surrounded by the steam S, the steam S As a result, the combustion speed of the pulverized coal is suppressed and the combustion peak point of the pulverized coal moves to the core side. The movement of this combustion peak point toward the core side increases the raceway depth, reduces the heat load in the vicinity of the tuyere 2, and prevents damage to the tuyere 2 and the equipment near the tuyere 5 and the like.

Example 1 The method of the present invention was applied to a blast furnace having an internal volume of 1850 m ³ .
Comparison of the tuyere damage situation and changes in the pulverized coal ratio when pulverized coal (ash content 11.7%) was blown together with steam under the operating conditions shown in Table 1 compared with the conventional method using N ₂ as a cooling medium. As shown in FIG. As is clear from the results of FIG. 2, in the conventional method using N ₂ as the cooling medium, the tuyere was often damaged at the time of operation with a high pulverized coal ratio, and the chip was also damaged. Even in the pulverized coal ratio operation, it was possible to completely prevent damage to the tuyere and the dust.

[0015]

[Table 1]

[0016]

As described above, according to the present invention, since the combustion peak point of pulverized coal can be moved to the core side, it is possible to inject the pulverized coal into the tuyere, the dust and the like near the tuyere. The effect of heat is greatly reduced, and the tuyere and the cuts can be prevented from being damaged, resulting in a great effect on the stable operation of the blast furnace.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an example of a device configuration for carrying out the method of the present invention.

FIG. 2 is a diagram showing the state of damage to the tuyere of the blast furnace and the change in the pulverized coal ratio in Example 1 of the present invention in comparison with the conventional method.

FIG. 3 is a schematic view showing a conventional pulverized coal blowing method.

FIG. 4 is an enlarged side view showing an example of a pulverized coal blowing nozzle having a double pipe structure with a part thereof cut away.

[Explanation of symbols] 1 Blast furnace 2 Blast tuyere 3 Blow pipe 4 Pulverized coal injection nozzle 4-1 Inner pipe 4-2 Outer pipe 5 Kirikasu 6 Pulverized coal hopper 7 Steam supply system 8 Flowmeter 9 Flow control valve 10 Shutoff valve 11 Blast furnace instrument room C Pulverized coal S S Steam.

Claims (1)

[Claims] 1. A blast furnace operating method in which pulverized coal is blown together with hot air from a blowing tuyere, a double pipe is used as a nozzle for blowing pulverized coal into a blow pipe, and pulverized coal is injected from an inner pipe and steam is ejected from an outer pipe. The blast furnace operating method is characterized in that the combustion peak point of pulverized coal is moved to the core side by doing so.