JPH1112613A - Lance for pulverized coal injection of blast furnace - Google Patents

Abstract

(57) [Problem] To provide a blast furnace pulverized coal injection lance which prevents ignition delay of pulverized coal and obtains a high combustion rate. SOLUTION: In a pulverized coal injection lance 1 through which a pulverized coal and oxygen or oxygen-enriched air are simultaneously blown through a wall of a blow pipe 13 connected to a blast furnace tuyere, a central pulverized coal injection pipe 2 is provided. A lance for blowing pulverized coal of a blast furnace in which a plurality of small-diameter pipes 4 for blowing oxygen or oxygen-enriched air are provided so as to surround the periphery.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a pulverized coal injection lance for simultaneously injecting pulverized coal and oxygen or oxygen-enriched air into a blast furnace.

[0002]

2. Description of the Related Art Pulverized coal injection is used in many blast furnaces because of its great cost advantage based on the price difference with coke, and it greatly contributes to improvement of economic efficiency. In recent years, its importance has been recognized again from the viewpoint of extending the life of coke ovens, and a large amount of pulverized coal has been increasingly injected.

[0003] As the amount of pulverized coal injected into the blast furnace increases,
Various problems become apparent, and one of them is a problem caused by emission of unburned char. That is, as the pulverized coal injection amount increases, the excess oxygen coefficient decreases, so that the combustion amount (burning rate) of the pulverized coal decreases, and unburned char that cannot be completely burned in the raceway is discharged into the furnace. This unburned char may be preferentially consumed by the solution loss reaction in the lower part of the furnace, but there is naturally a limit value in the furnace consumption. It is discharged from the furnace top and causes a decrease in the replacement rate and an increase in the fuel ratio. In addition, if this accumulates in the furnace core and the cohesive zone root, it causes unstable furnace conditions and reduced productivity due to impaired ventilation and liquid permeability.

[0004] Therefore, in order to realize a stable pulverized coal injection operation, it is indispensable to keep the amount of unburned char below the consumption limit in the furnace. It is necessary to further improve the combustion rate.

In a normal pulverized coal injection operation, a single pipe lance tip for pulverized coal injection is projected into a blow pipe,
A method of blowing from a hole at the tip of the lance is generally used. In this method, since the entire amount of pulverized coal is ejected from one lance, the solid concentration immediately after ejection from the lance is high, and the inertia of the hot air is large, so that it cannot be diffused much in the radial direction. Therefore, the mixing efficiency of the pulverized coal and the hot air and the contact efficiency with the oxygen are low, and the temperature rise of the solid is delayed. In addition, as combustion proceeds, oxygen around pulverized coal is rapidly consumed, and oxygen around pulverized coal is in a state of lack of oxygen, but there is a disadvantage that oxygen in hot air cannot be easily diffused and a rise in combustion rate cannot be expected. .

As a means for solving such a problem, a method of improving the contact efficiency between oxygen and pulverized coal by using a lance with a double pipe structure has been developed. For example, Japanese Unexamined Patent Publication
In the method described in JP-A-213406 and JP-A-6-100912, pulverized coal is provided inside a concentric double tube lance, and oxygen or a mixture of oxygen and air (oxygen-enriched air) is provided outside.
To increase the oxygen concentration around the pulverized coal to improve the combustion rate and eliminate the problem of oxygen deficiency. In the method described in Japanese Patent Application Laid-Open No. 1-92304, in order to increase the efficiency of introducing oxygen, a lance is formed as a triple pipe structure, cooling water is flowed to the outermost pipe, pulverized coal is flowed to the innermost pipe, Discloses a method in which oxygen is ejected toward pulverized coal from a plurality of nozzles arranged so as to surround the pulverized coal.

[0007]

However, in the methods described in JP-A-2-213406 and JP-A-6-100912, a gas (oxygen or a mixture of oxygen and air) is caused to flow around the pulverized coal. However, even if high-concentration oxygen and pulverized coal come into contact near the lance outlet, combustion does not always start immediately. This is because at the lance outlet, there is basically a mixture of cooled substances, and the pulverized coal needs to be heated at least up to the ignition point. For this purpose, the temperature must be raised by radiant heat from the blow pipe wall surface or hot air, and a certain moving distance is required. Therefore, in some cases, high-concentration oxygen introduced during the temperature rise of the pulverized coal is rapidly mixed or diffused with the surrounding hot air and lost, and the effect of increasing the combustion rate may be reduced by half.

In Japanese Patent Application Laid-Open No. 1-92304, oxygen can be introduced into pulverized coal relatively efficiently because oxygen is ejected toward pulverized coal, but oxygen is cooled by cooling water flowing through the outermost pipe. Therefore, there is a problem that the temperature rise of the pulverized coal is further delayed due to the cooling effect of the introduced oxygen itself.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a blast furnace pulverized coal injection lance which can prevent ignition delay of pulverized coal and obtain a high combustion rate.

[0010]

SUMMARY OF THE INVENTION The object of the present invention is to provide a pulverized coal injection lance for simultaneously blowing pulverized coal and oxygen or oxygen-enriched air through a wall of a blow pipe connected to a blast furnace tuyere. A plurality of small-diameter pipes for oxygen or oxygen-enriched air injection, which are arranged so as to surround the center pulverized coal injection pipe and are exposed to the hot air of a blowpipe, Achieved by Lance.

[0011] Since a plurality of small-diameter pipes for blowing oxygen or oxygen-enriched air are arranged so as to surround the pulverized coal injection pipe at the center of "action", the outer circumference of each small-diameter pipe is a blow pipe. Contact with hot air. Therefore, the heat transfer area from the hot air to oxygen or the like is much larger than that of the conventional double-tube lance, and the preheating of oxygen or the like by the hot air is sufficiently performed. Further, since the outer periphery of the pulverized coal blowing pipe comes into contact with the hot air of the blow pipe, preheating of the pulverized coal is also performed.

Therefore, the mixing temperature of pulverized coal and oxygen at the outlet of the lance can be increased, so that a delay in temperature rise of the pulverized coal can be prevented. As a result, oxygen or the like can be mixed with the surrounding hot air or diffused into the hot air and ignited before the concentration of the oxygen or the like decreases, so that the introduced oxygen can be effectively used for pulverized coal combustion. it can.

[0013]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a longitudinal sectional view of a pulverized coal injection lance of the present invention. FIG. 2 is a sectional view taken along line AA of FIG. The rear part of the pulverized coal injection lance 1 is composed of a double pipe composed of an inner pipe 2 and an outer pipe 3 concentric with the inner pipe 2, and the front part is formed by the inner pipe 2 and the outer periphery of the inner pipe 2. Inner tube 2 at a certain distance
And a plurality of small-diameter pipes 4 arranged at equal angular intervals around the inner pipe 2 and concentrically therearound. The front end opening of the outer tube 3 at the rear of the lance is closed by an annular end plate 3a. The rear end of the small-diameter pipe 4 penetrates the end plate 3 a and communicates with a space between the inner pipe 2 and the outer pipe 3. End plate 3a
From the front to the front, the length of the small diameter pipe 4 and the length of the inner pipe 2 are substantially the same.

In the pulverized coal injection lance 1, pulverized coal and carrier gas flow forward in the inner pipe 2 and are discharged from the tip. In addition, oxygen or oxygen-enriched air flows forward through a plurality of small-diameter tubes 4 via a space between the inner tube 2 and the outer tube 3 and is discharged from the distal end.

Since the front part of the inner pipe 2 and the small diameter pipe 4 are located in the hot air of the blow pipe, the pulverized coal is preheated by the hot air while flowing through the inner pipe 2, and oxygen and the like are heated by the hot air while flowing through the small diameter pipe 4. Preheated.

If the ignition is too fast, the lance tip may possibly be damaged, but this can be dealt with by adjusting the oxygen concentration or adjusting the blowing amount of oxygen-enriched air. . In addition, the number of small diameter tubes, the position of the tip of the small diameter tube, the material, etc.
It is necessary to determine the value appropriately according to the oxygen concentration and the amount of oxygen-enriched air blown. Further, it is desirable that the length of the small diameter pipe exposed to the flow path in the blow pipe be 500 mm or more. The small diameter pipe is not limited to a straight pipe, and may be spirally wound around the pulverized coal blowing inner pipe. Further, two or more lances may be attached to the same blow pipe.

[0018]

EXAMPLE A pulverized coal combustion experiment using the pulverized coal injection lance of the present invention was performed using a pulverized coal combustion furnace. FIG. 3 is a schematic diagram of the pulverized coal combustion furnace used in the experiment. 10 is a pulverized coal combustion furnace, 11 is coke filled in the pulverized coal combustion furnace 10, 12 is a tuyere (inner diameter 65 mm) attached to the lower part of the pulverized coal combustion furnace 10, and 13 is a blow pipe connected to the tuyere 12 (90 mm inner diameter). 15 is blow pipe 1
3 is a lance guide tube attached to the rear part. The lance guide tube 15 is attached to the blow pipe at an inclination angle of 10 °. The pulverized coal blowing lance 1 is inserted into the lance guide tube 15, and is attached so that a front portion thereof protrudes into the hot air flow passage 13 a of the blow pipe 13. 14
Is a sampling probe insertion tube, and a blow pipe 13
Are provided between the tip of the lance guide tube and the lance guide tube. 1
6 is a pulverized coal hopper, 17 is a supply pipe of pulverized coal, and 18 is a supply pipe of oxygen or oxygen-enriched air.

In the pulverized coal injection lance of the present invention used in the experiment, the inner diameter of the inner pipe is 16 mm, and the inner diameter of the small diameter pipe is 4 mm. The length of the lance inserted into the hot air flow path in the blow pipe was about 260 mm. At this time, the distance from the tip of the lance to the tuyere tip was 1200 mm.

Table 1 shows the industrial analysis values of the pulverized coal used in the combustion experiment. The particle size of the pulverized coal is 80% at −74 μm.

[0021]

[Table 1]

In the experiment, first, LPG was
Was blown with 350 Nm ³ / h of pseudo air adjusted to have an oxygen concentration of 21% by mixing oxygen into the combustion gas of No. ¹ , and the tuyere temperature was raised to 1200 ° C. Tuyere temperature is 1200 ℃
When the coal became stable, pulverized coal was cut out from the pulverized coal hopper 16 at 65 kg / h, and nitrogen gas of 12 Nm ³ / h was supplied as a carrier gas to the inner pipe 2 of the lance 1 via the supply pipe 17, and at the same time, 14 Nm ^3. / H oxygen supply pipe 1
The oxygen was supplied to the flow path between the outer pipe 3 and the inner pipe 2 of the lance 1 through 8, and the oxygen in the flow path was branched into eight small-diameter pipes 4. At this time, the oxygen enrichment rate is 3%, and the oxygen excess coefficient is 0.78. In addition, 65 kg / h is equivalent to 200 kg / t in terms of pulverized coal injection amount of a real blast furnace.

During the combustion of the pulverized coal, a sampling probe was inserted from the sampling probe insertion pipe 14, and sampling of the pulverized coal dust was performed at 300 mm, 600 mm, and 900 mm from the tip of the lance. The resulting dust was chemically analyzed to determine the combustion rate. Also, using a conventional double-pipe lance which does not branch off the flow path between the outer pipe and the inner pipe, the pulverized coal injection amount is reduced to 6 in the same manner as in the lance of the present invention.
The experiment was performed at 5 kg / h.

FIG. 4 is a graph showing the change in the combustion rate of the lance of the present invention and the conventional lance depending on the distance from the tip of the lance. In the conventional lance, the combustion rate was 52% at a position 300 mm from the tip of the lance, and 62% at a position 900 mm from the tip of the lance. On the other hand, in the lance of the present invention, the ratio was 65% at a position 300 mm from the tip of the lance, and 75% at a position of 900 mm from the lance tip. At any position, the lance of the present invention has a 13% higher combustion rate than the conventional lance. This is because heat exchange between hot air and oxygen is sufficiently performed through the surface of the small-diameter pipe, heat exchange between hot air and pulverized coal is performed through the surface of the inner pipe, and oxygen and pulverized coal are preheated. Distance to ignition after discharge from lance (or
Time was shortened.

[0025]

According to the present invention, since oxygen or oxygen-enriched air can be preheated by hot air through a small-diameter pipe, a delay in temperature rise after mixing of pulverized coal and oxygen-enriched air can be prevented. The ignition can be made remarkably faster than the conventional lance. In addition, since the ignition of the pulverized coal is fast, the final burning rate of the pulverized coal can be greatly improved as compared with the conventional lance.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a pulverized coal injection lance of the present invention.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is a schematic diagram of a pulverized coal combustion furnace used in a pulverized coal combustion experiment.

FIG. 4 is a graph showing a relationship between a distance from a lance tip and a combustion rate of pulverized coal.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 pulverized coal blowing lance 2 inner pipe 3 outer pipe 3a end plate 4 small diameter pipe 10 pulverized coal combustion furnace 12 tuyere 13 blow pipe 14 sampling probe insertion pipe 15 lance guide pipe

Claims (1)

[Claims] 1. A pulverized coal injection lance for simultaneously blowing pulverized coal and oxygen or oxygen-enriched air through a wall of a blow pipe connected to a blast furnace tuyere, comprising a plurality of oxygen or oxygen-enriched lances. A pulverized coal blowing lance for a blast furnace, wherein a small-diameter pipe for air blowing is disposed so as to surround the center of the pulverized coal blowing pipe and to be exposed to the hot air of the blowpipe.