JP2961071B2 - Pulverized coal injection method to blast furnace and pulverized coal injection burner - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for injecting pulverized coal into a blast furnace and an improvement in a burner for injecting pulverized coal, and more particularly to blowing a large amount of pulverized coal of at least 148 kg or more per ton of pig iron. The present invention relates to a method for injecting pulverized coal into a blast furnace and a burner for injecting pulverized coal into a blast furnace, which make it possible to surely burn it even if it is injected.

[0002]

2. Description of the Related Art In response to a sharp rise in the price of petroleum, blast furnace operation has shifted to all-coke operation in which heavy oil injected as auxiliary fuel is completely stopped. Since then, pulverized coal injection, which has a high economic effect, has attracted attention as a stabilization of blast furnace operation and a substitute for coke, and is now used in most blast furnaces in Japan. However, pulverized coal or other pulverized fuel has the disadvantage of poorer flammability than heavy oil, and has the drawback of containing ash and thus impairing air permeability in the blast furnace. In doing so, it is necessary to take various measures. Under these circumstances, the applicant of the present application has been intensively researching and developing in order to establish an effective method of injecting pulverized fuel such as pulverized coal, and for example, Japanese Patent Publication No. 60-53081 described later. Gazette, Japanese Patent Publication No. 63-32842, or Japanese Patent Publication No.
Japanese Patent Laid-Open No. 29846/1989 proposes a pulverized coal injection technique.

First, Japanese Patent Publication No. Sho 60-53081 discloses a method for satisfying both of the two requirements of improving the combustion rate of pulverized fuel such as pulverized coal and preventing ash from adhering to a blow pipe. The blowing position is shifted upstream of the blow pipe section. Also, JP-B 63-32
No. 842 and Japanese Patent Publication No. 01-29846,
Even in the case of using a low-temperature hot air having a temperature lower than 1050 ° C., in order to sufficiently enhance the combustion of pulverized coal or other pulverized fuel, easily combustible gas such as coke oven gas or natural gas is converted into calorie from the outer periphery of pulverized coal. Combustion of 2% or more or oxygen-enriched combustion in hot air with an oxygen concentration of 23% by volume or more is performed.

Further, Japanese Patent Publication No. 04-2642 discloses a method in which the tip position of a pulverized coal injection burner is changed in accordance with the condition of the air ratio.
In Japanese Patent No. 40908 and Japanese Patent Publication No. 06-94565, a plurality of pulverized coal injection burners are used, and the position of blowing auxiliary fuel having good combustibility is set higher than the position of blowing auxiliary fuel having poor combustion. It proposes something that blows on the side.

[0005]

Any of the above pulverized coal blowing methods is useful as such. However, as described above, in addition to pulverized coal, not only fuel such as coke oven gas, natural gas, and heavy oil is required, but also depending on conditions, it is necessary to change the tip position of the pulverized coal injection burner. There is a problem that complicated operation is required or equipment cost is increased due to the complicated structure of the pulverized coal injection burner. That is, it is preferable to blow as much pulverized coal as possible into the blast furnace with a pulverized coal injection burner having a simple structure. However, if the amount of pulverized coal injected is excessive with respect to the amount of hot air, the air-fuel ratio will be insufficient and the pulverized coal will not be completely burned, and the unburned pulverized coal will increase the furnace pressure loss in the blast furnace or will cause combustion. This is not desirable for the stable operation of the blast furnace because of the lack of heat.

Accordingly, it is an object of the present invention to provide a method and a method for injecting pulverized coal into a blast furnace which makes it possible to inject and burn a larger amount of pulverized coal with equipment having a structure as simple as possible. The purpose is to provide a burner.

[0007]

DISCLOSURE OF THE INVENTION The present invention has been studied as to how the pulverized coal can be more effectively burned with a minimum equipment change, and as a result, the pulverized coal has a different particle size. It has been found that the flammability is completely different, and the finer the pulverized coal, the higher the burning rate.

[0008] Therefore, in order to solve the above-mentioned problem, the method adopted by the method of injecting pulverized coal into a blast furnace according to claim 1 of the present invention is characterized in that it is connected to a blast furnace tuyere or a blast furnace tuyere. In this case, pulverized coal separated into fine particles and coarse particles in advance is blown into the blowpipe for blowing hot air.

A feature of the means adopted by the method for injecting pulverized coal into a blast furnace according to the second aspect of the present invention is that a method for blowing hot air into a blast furnace tuyere or a blow pipe connected to the blast furnace tuyere is provided. While injecting coarse pulverized coal of the pulverized coal previously separated into fine and coarse particles, and surrounding the finely pulverized coal to be blown, It is where the fine pulverized coal is injected.

According to a third aspect of the present invention, there is provided a method for injecting pulverized coal into a blast furnace according to claim 3 of the present invention.
The particle size of the fine pulverized coal is set to 20 μm or less.

A feature of the means adopted by the pulverized coal blowing burner into the blast furnace according to claim 4 of the present invention is that the hot air blowing blow pipe connected to the blast furnace tuyere or the blast furnace tuyere is provided. In a pulverized coal injection burner for injecting pulverized coal, the pulverized coal injection burner is provided between an inner cylinder member for injecting coarse pulverized coal, and an outer casing provided on the inner cylinder member, and an outer periphery of the inner cylinder member. And an outer cylinder member for injecting fine pulverized coal from an outer blowing portion formed at the outer cylindrical portion.

[0012]

According to the method for injecting pulverized coal into a blast furnace according to the first aspect of the present invention, fine and coarse particles are previously introduced into a blast furnace tuyere or a blow pipe for hot air blowing connected to the blast furnace tuyere. The fine pulverized coal is blown in a state similar to the coal dust explosion because the pulverized coal separated is blown in a separated state, while the coarse pulverized coal explodes in the fine pulverized coal. Dispersed by typical combustion.

According to the method of injecting pulverized coal into a blast furnace according to claim 2 of the present invention, coarse pulverized coal is introduced into a blast furnace tuyere or a blow pipe for hot air injection connected to the blast furnace tuyere. Since the pulverized coal is blown in a state surrounded by the fine pulverized coal, the fine pulverized coal is explosively exploded by the same phenomenon as the coal dust explosion, similarly to the method of injecting pulverized coal into the blast furnace according to claim 1. While burning,
Coarse pulverized coal is promoted in the explosive combustion region of fine pulverized coal and combustion is remarkably promoted.

According to the method of injecting pulverized coal into a blast furnace according to claim 3 of the present invention, fine pulverized coal having a particle size of 20 μm or less is blown together with coarse pulverized coal, and the fine powder having a fine particle size of 20 μm or less is injected Charcoal burns explosively.

According to the pulverized coal injection burner into the blast furnace according to the fourth aspect of the present invention, the coarse particles from the inner cylindrical member are introduced into the blast furnace tuyere or the blow pipe for hot air blowing connected to the blast furnace tuyere. Pulverized coal can be blown, and fine pulverized coal can be blown from the outer blowing portion formed between the outer periphery of the inner cylinder member and the inner periphery of the outer cylinder member. While pulverized coal can be explosively burned, coarse pulverized coal can be promoted to disperse in the explosive combustion region of fine pulverized coal, and combustion can be significantly promoted.

As described above, according to the first to fourth aspects of the present invention, the same pulverized coal is separated into fine particles and coarse particles as compared with the case where the pulverized coal is injected alone. Blowing can increase the combustion rate. In addition, if the combustion rate is the same, finer and coarser particles can be blown and burned in a larger amount.

[0017]

FIG. 1 is a sectional view of an injection burner for realizing a pulverized coal injection method according to an embodiment of the present invention.
FIG. 2 showing the relationship between the combustion rate of pulverized coal and the ratio of fine pulverized coal to the total amount of pulverized coal injected, and the description of a separation pipe for separating pulverized coal into fine particles and coarse particles. FIG. 3 (a),
This will be described with reference to FIG.

First, the configuration of a pulverized coal injection burner used for injecting pulverized coal into a blast furnace according to the present invention will be described with reference to FIG. 1. An outer cylinder member 3 is provided concentrically with the inner cylinder member 2 and has an outer cylinder member 2 having an inner blowing section 2a for blowing. A fine-grain inflow pipe 4 for blowing fine pulverized coal into an outer blowing portion 3a formed between the inner cylindrical member 2 and the outer cylindrical member 3 is joined to the outer cylindrical member 3 in an inclined state. Have been. In addition,
Reference numerals 5 and 6 denote flanges for connecting pipe ends of branch pipes to be described later, and reference symbol A denotes fine-grain pulverized coal,
Symbol B is coarse pulverized coal.

As shown in FIG. 3A, a pipe end of a separation pipe 10 for separating pulverized coal into fine grains and coarse grains as shown in FIG. I have. This separation line 10
Is composed of a horizontal main conduit 11 communicating with the inner cylinder member 2 and a branch conduit 12 branched from the main conduit 11 and communicating with the fine-grain inflow pipe 4.

That is, when pulverized coal comprising a mixture of fine particles and coarse particles is transported by air flow to the separation pipe 10, as shown in FIG. From the relation, coarse pulverized coal mainly passes under the main pipeline 11,
Since the fine pulverized coal mainly passes above the main pipeline 11,
Although a part of the fine pulverized coal passes through the main pipe 11 as it is, most of it flows into the branch pipe 12. The separation pipe 10 is employed in the case of high-concentration airflow transportation in which the solid-gas ratio (the ratio of the weight of pulverized coal to the transported gas) is 20 or more. In addition, the ratio of the fine pulverized coal can be controlled by the inner diameter ratio of the main pipeline 11 and the branch pipeline 12.

By the way, since the flow velocity of the transport gas is high,
When the solid-gas ratio is low, the main pipe 21 of the separation pipe 20 can be vertically oriented as shown in FIG. In other words, the coarse pulverized coal B travels straight by inertia and is mainly transported upwardly of the main pipe 21, but the fine pulverized coal A is carried over by the gas as it is extracted from the branch pipe 22, It is selectively separated by a branch line 22. It should be noted that, similarly to the case of the separation line 10, the main line 2
1 may be horizontal.

Therefore, according to the method of injecting pulverized coal into the blast furnace by the pulverized coal injection burner according to the present invention, the pulverized coal consisting of a mixture of fine particles and coarse particles transported by air flow is separated in the separation line 10. The fine coal pulverized coal A is separated into fine pulverized coal A and coarse pulverized coal B, and the fine pulverized coal A is divided into the branch line 12, the fine grain inflow pipe 4,
The coarse pulverized coal B is blown through the main pipeline 11 and the inside blow portion 2a while being blown through the outer blow portion 3a. In this way, when the fine pulverized coal A is blown from the outer blowing section 3a and the coarse pulverized coal B is blown from the inner blowing section 2a, the fine pulverized coal A with respect to the total amount of pulverized coal is blown. The combustion rate of the entire pulverized coal is improved as shown in FIG.

That is, pulverized coal consisting of 75% of 75 μm or less, 27% of 20 μm or less, 15% of 10 μm or less,
In a conventional blowing method in which fine particles and coarse particles are blown in a mixed state without being separated, the burning rate of pulverized coal is about 52%.

However, as shown by the broken line in FIG. 2, in parallel with the blowing of the coarse pulverized coal B from the inner blowing portion 2a, 10% or less of 8% or more of the total blowing amount of the pulverized coal. When the fine pulverized coal A is blown from the outer blowing section 3a, the burning rate of the entire pulverized coal sharply increases, and when the fine coal pulverized coal A is 12% or more, the rate of increase slows down. The burning rate of the whole pulverized coal is gradually increasing. As shown by the solid line in FIG. 2, when the fine-grained pulverized coal A is 20 μm or less, about 15% or more is supplied to the outer blowing portion 3.
a, the combustion rate of the entire pulverized coal rises sharply,
%, The rate of increase slows down, and thereafter the combustion rate gradually increases as the blow rate increases. On the other hand, as shown by the one-dot chain line in FIG. 2, when the fine-grain pulverized coal A is 30 μm or less, slight combustion occurs with an increase in the ratio of the fine-grained pulverized coal A blown from the outer blowing portion 3a. However, the effect of the present invention that the combustion rate of the entire pulverized coal is improved cannot be obtained. In other words, the fine coal A is 20μ
m or less suggests that it is effective in improving the combustion rate of the entire pulverized coal.

In this case, the total amount of pulverized coal injected is 250 kg per ton of pig iron, and the measurement position of the combustion rate of pulverized coal (definition; the ratio of the amount of combustion to the amount of pulverized coal injected) is not shown in the drawing. This position is within the raceway 0.8 m from the tip of the mouth. The hot air temperature is 1200
° C and the combustion enrichment condition with an air-fuel ratio of 0.6.

According to the conventional method for injecting pulverized coal into a blast furnace, when the amount of pulverized coal is 148 kg or more per ton of pig iron, the air-fuel ratio becomes 1.0 or less, and the amount of pulverized coal injected further decreases. When the air-fuel ratio exceeds 250 kg, the air-fuel ratio becomes about 0.6 and there is a significant shortage of air. Therefore, the combustion rate of pulverized coal has to be reduced. However, according to this embodiment, it is possible to effectively burn a larger amount of pulverized coal than before without increasing the amount of air or the oxygen content.

Therefore, unlike the prior art, fuels such as coke oven gas, natural gas, and heavy oil other than pulverized coal are not required.
In addition, it is not necessary to change the tip position of the pulverized coal injection burner depending on the conditions, so that the structure can be simplified and an increase in equipment cost can be avoided, and the blast furnace can be stabilized by improving the pulverized coal combustion rate. Operation becomes possible.

As described above, the combustion rate of pulverized coal is improved by separating and pulverizing pulverized coal into fine particles and coarse flow in advance. Combustion, the dispersion of coarse pulverized coal is promoted in the high temperature range due to the explosive combustion of such fine pulverized coal, so that the whole amount of pulverized coal to be blown effectively burns Can be understood.

In the above, in order to separate fine particles and coarse particles before pulverized coal is blown, the separation pipe 1 having the above-described structure is used.
Although the example using 0, 20 was explained, pulverized coal, for example,
Since the separation can be performed by a separation device such as a cyclone, the means for separating fine and coarse particles of pulverized coal is not limited at all. In the above description, the case where fine pulverized coal is blown in a state surrounding the coarse pulverized coal has been described as an example.For example, the cylindrical member of the pulverized coal blowing burner is partitioned by a plate member, and fine powder is burned from one side. A configuration in which coarse pulverized coal is blown in from the other while pulverized pulverized coal is blown from the other side has an effect of improving the combustion rate of the pulverized coal.

[0030]

As described above, when pulverized coal previously separated into fine particles and coarse particles is blown together in a separated state, the fine-particle pulverized coal explodes in the same manner as a coal dust explosion. Burning,
As a result, coarse pulverized coal is dispersed and combustion is promoted, so that even if a larger amount of pulverized coal is blown than in the past, the entire amount can be effectively burned. Therefore, unlike the conventional pulverized coal, there is no need to use fuel such as coke oven gas, natural gas, or heavy oil, and it is not necessary to change the tip position of the pulverized coal injection burner depending on the conditions. Even if the pulverized coal injection amount is increased, the unburned pulverized coal does not flow out of the raceway, so the pressure loss in the blast furnace does not increase. In spite of the fact, there is a great effect that stable operation of the blast furnace becomes possible.

[Brief description of the drawings]

FIG. 1 is a sectional view of an injection burner for realizing a pulverized coal injection method according to the present invention.

FIG. 2 is a graph illustrating the relationship between the combustion rate of pulverized coal and the ratio of fine pulverized coal to the total amount of pulverized coal injected according to the present invention.

3 (a) and 3 (b) are explanatory views of a separation pipe for separating pulverized coal into fine particles and coarse particles according to the present invention.

[Explanation of symbols]

 A: Fine-grained pulverized coal B: Coarse-grained pulverized coal 1 ... Pulverized coal blowing burner 2 ... Inner cylinder member, 2a ... Inner blowing section 3: Outer cylinder member, 3a ... Outer blowing section Pipe 5 ... Flange 6 ... Flange 10 ... Separation pipeline 11 ... Main pipeline 12 ... Branch pipeline 20 ... Separation pipeline 21 ... Main pipeline 22 ... Branch pipeline

Claims (4)

(57) [Claims] The present invention is characterized in that pulverized coal separated into fine particles and coarse particles in a separated state is blown into a blast furnace tuyere or a blowpipe for hot air blowing connected to the blast furnace tuyere. Pulverized coal injection method to blast furnace. 2. A method for injecting coarse-grain pulverized coal among fine-pulverized coal previously divided into fine and coarse particles into a blast furnace tuyere or a blowpipe for hot air blowing connected to the blast furnace tuyere. A method of injecting pulverized coal into a blast furnace, characterized by injecting fine pulverized coal of the separated pulverized coal while surrounding the coarse pulverized coal to be injected. 3. The method for injecting pulverized coal into a blast furnace according to claim 1, wherein the particle size of the finely divided pulverized coal is 20 μm or less. 4. A pulverized coal blowing burner for blowing pulverized coal into a blast furnace tuyere or a blowpipe for hot air blowing connected to the blast furnace tuyere, wherein the pulverized coal blowing burner comprises coarse pulverized coal. An inner cylinder member that blows in, and is externally mounted on the inner cylinder member,
A pulverized coal blowing burner, comprising: an outer cylinder member for injecting fine pulverized coal from an outer blowing portion formed between the inner cylinder member and the outer periphery thereof.