JPH08100208A - Tuyere structure for blast furnace pulverized coal injection - Google Patents

Abstract

PURPOSE: To enhance combustion efficiency of pulverized coal in operation to blow the pulverized coal to a blast furnace. CONSTITUTION: This tuyere part structure is used at the time of inserting a pulverized coal blowing lance 3 into a blow pipe 2 connected to a small tuyere 1 and blowing the pulverized coal to the blast furnace. The bore of the blow pipe 2 of the part to blow the pulverized coal is specified to >=1.7 times the bore of the small tuyere 1. The section from the pulverized coal blowing part of the blow pipe 2 to the part connected to the small tuyere 1 is made into a water cooled structure 4. As a result, a coke ratio is lowered.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tuyere structure for blowing pulverized coal into a blast furnace, and more particularly to a tuyere structure capable of increasing the burning rate of pulverized coal.

[0002]

2. Description of the Related Art Conventionally, in order to reduce the coke ratio in the operation of a blast furnace, a pulverized coal blowing lance is inserted into a blow pipe connected to a blast furnace tuyere, and the inside of the blast furnace is fed from a small tuyere connected to the blow pipe. The operation of blowing pulverized coal into is being carried out.

In the pulverized coal blowing operation of the blast furnace as described above, the distance L from the tip of the small tuyere 21 to the pulverized coal blowing lance 22 shown in FIG. 4 and the burning rate of the pulverized coal (of C in pulverized coal) , The rate of gasification by combustion) is as shown in the graph of FIG. The reason why the combustion rate tends to be as shown in the graph of FIG. 5 is that basically there is no oxygen for burning pulverized coal in the blast furnace, and the pulverized coal injection lance 22 is brought close to the tip of the tuyere 21. The closer it is, the lower the combustion rate.

Therefore, when the distance L from the tip of the small tuyere 21 to the pulverized coal injection lance 22 is increased, the combustion rate of the pulverized coal is improved, and as shown in the graph of FIG. 6, the replacement rate {per 1 ton of hot metal] The coke amount (kg) per ton of hot metal, which decreases when 1 kg of pulverized coal is blown, is improved.

For this reason, conventionally, the tip end position of the lance must be arranged close to the tip end position of the blow pipe.

Another method for blowing pulverized coal is disclosed in Japanese Patent Laid-Open No. Hei 5
There is a method disclosed in Japanese Patent Laid-Open No. 112806. In this pulverized coal blowing method, as shown in FIG. 7, the pulverized coal blowing lance 33 is inserted into the blow pipe 32 connected to the blast tuyere 31 of the blast furnace, and the oxygen blowing lance 3 is inserted.
4 is inserted so as to face the pulverized coal injection lance 33, and the axes of the pulverized coal injection lance 33 and the oxygen injection lance 34 are perpendicular to the axis of the blow pipe 32.
After inclining each other by the same angle, pulverized coal and oxygen are blown from the respective lances 33 and 34,
A swirl flow is formed. Due to this swirling flow, the residence time of the pulverized coal in the blow pipe 32 can be lengthened without increasing the distance L from the tip of the small tuyere 21 to the pulverized coal injection lance 22. The combustion efficiency of pulverized coal is improved.

[0007]

However, when the distance L from the tip of the tuyere 21 to the pulverized coal blowing lance 22 is increased, there are the following problems. (1) Since pulverized coal rapidly burns in a narrow space and the amount of gas increases, the pressure loss in the blow pipe increases, and the blowing pressure to the blast furnace fluctuates. (2) Molten ash generated during combustion of pulverized coal adheres and grows on the inner surface of the blow pipe, and the tuyere is closed.

On the other hand, according to the method disclosed in the above-mentioned Japanese Patent Laid-Open No. 5-112806, even if the distance L is not increased,
Although this is a technique that can improve combustion efficiency, it is a method of blowing oxygen, so that there is a problem that equipment for supplying oxygen is required and the equipment cost is high.

The present invention has been made in order to solve the above-mentioned problems of the prior art, and it is possible to improve the combustion rate of pulverized coal, and thus the combustion efficiency, without requiring a high equipment cost. An object of the present invention is to provide a tuyere structure for blowing blast furnace pulverized coal.

[0010]

The tuyere structure for blast furnace pulverized coal injection according to the present invention blows pulverized coal into a blast furnace by inserting a pulverized coal injection lance into a blow pipe connected to a small tuyere. In the tuyere structure at the time, the inner diameter of the blow pipe of the portion where the pulverized coal is blown is 1.7 times or more the inner diameter of the small tuyere, and the portion where the pulverized coal blowing portion of the blow pipe is connected to the small tuyere The section up to is a water-cooled structure.

[0011]

[Operation] By making the inner diameter of the blow pipe 1.7 times or more of the inner diameter of the small tuyere, the fluctuation of the blast pressure due to the sudden increase in the amount of gas generated during the combustion of pulverized coal can be kept within the allowable range for operation. Can be relaxed. In addition, the section from the pulverized coal blowing part of the blow pipe to the part connected to the small tuyere has a water-cooled structure, so even if the molten ash generated when the pulverized coal burns will adhere to the inner surface of the blow pipe, Is rapidly cooled, solidified and peeled off. Therefore, the distance from the pulverized coal blowing portion of the blow pipe to the portion connected to the tuyere can be increased, and the combustion rate can be improved.

[0012]

EXAMPLE A tuyere structure for blowing blast furnace pulverized coal, which is an example of the present invention, will be described with reference to FIG.

In this blast furnace pulverized coal blowing tuyere structure, the inner diameter D of the blow pipe 2 connected to the small tuyere 1 is 1.7 times or more the inner diameter d of the small tuyere 1, and the blow pipe 2 The part connected from the pulverized coal blowing lance 3 insertion part to the tuyere 1 is the water cooling part 4. Reference numeral 5 in FIG. 1 is a large tuyere.

FIG. 2 is a graph showing the relationship between the pulverized coal ratio {amount of pulverized coal per ton of hot metal (kg)} and burning rate.
The solid line indicates that the distance L from the tip of the conventional tuyere to the tip of the pulverized coal injection lance is 400 mm, and the dotted line indicates that the distance L from the tip of the small tuyere to the tip of the pulverized coal injection lance based on the present invention is 900 mm. is there. In each case, the combustion rate decreases as the pulverized coal ratio increases, but it can be seen that the reduction rate is smaller in the case of the present invention than in the conventional case.

FIG. 3 shows an internal volume 42 having 40 tuyeres.
When all the tuyere of the 88 m ³ blast furnace has the structure shown in FIG. 1 and is operated by blowing in pulverized coal at a rate of 200 kg / t, (a) is the coke ratio (kg / hot metal t), (b) is Is a graph showing time-series fluctuations of the blowing pressure (kg / cm ³ ) in comparison with the case where the conventional method is operated (∘ indicates the example of the present invention, ● indicates the conventional method).

As is apparent from this graph, when both the pulverized coal ratios were 200 kg / hot metal t, the conventional coke ratio was 340 kg / hot metal t, but in the embodiment of the present invention 320 kg / hot metal t. And 20 kg / hot metal t
Has been reduced. Further, the blast pressure also fluctuates with time in the conventional method, but hardly changes in the embodiment of the present invention.

Table 1 shows the effect after the present invention is carried out in comparison with the conventional method.

[0018]

[Table 1]

[0019]

EFFECTS OF THE INVENTION According to the present invention, the combustion efficiency of pulverized coal can be improved, and stable blowing can be performed in a high pulverized coal operation of 200 kg / molt t, so that the fuel ratio can be reduced and the manufacturing cost of molten pig iron can be reduced. be able to.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a tuyere structure for blowing blast furnace pulverized coal according to an embodiment of the present invention.

FIG. 2 is a graph showing a relationship between a pulverized coal ratio and a burning rate.

FIG. 3 is a graph showing a time-series variation of the operation results when the pulverized coal ratio is 200 kg / molt pig t, (a)
Indicates the coke ratio, and (b) indicates the blowing pressure.

FIG. 4 is an explanatory view showing a positional relationship between a small tuyere and a pulverized coal blowing lance.

FIG. 5 is a graph showing the relationship between the distance from the tip of the tuyere to the pulverized coal injection lance and the burning rate of the pulverized coal.

FIG. 6 is a graph showing a relationship between a combustion rate and a substitution rate of pulverized coal.

FIG. 7 is an explanatory view showing a conventional pulverized coal blowing method.

[Explanation of symbols]

 1 Small tuyere 2 Blow pipe 3 Pulverized coal injection lance 4 Water cooling part 5 Large tuyere

Claims (1)

[Claims] 1. A tuyere structure when a pulverized coal blowing lance is inserted into a blow pipe connected to a small tuyere to blow pulverized coal into a blast furnace. For blast furnace pulverized coal injection, characterized in that the inner diameter is 1.7 times or more the diameter of the small tuyere, and the section from the pulverized coal injection part of the blow pipe to the part connected to the small tuyere has a water cooling structure. Tuyere structure.