JPH08157916A - Blowing of pulverized fine coal into blast furnace and lance for blowing pulverized fine coal - Google Patents

Abstract

PURPOSE: To improve the combustion efficiency of blown pulverized fine coal by arranging plural pieces of double pipe structural lances to the side wall of a blow pipe connected to a tuyere of a blast furnace and controlling air or mixed gas quantity blown from an inner pipe at a fixed value, when blowing the pulverized coal together with gas for carrying from a gap between an inner pipe and an outer pipe of the lance. CONSTITUTION: When blowing pulverized fine coal, the flow rate of air or oxygen or the mixed gas thereof blown from the inner pipe of the lance is made to be 2-5 times that of the pulverized fine coal and the carrier gas blown between the inner pipe and the outer pipe in the double pipe structural lance and the mixing efficiency of the pulverized fine coal and the oxygen during blasting is risen to improve the combustion efficiency. At this time, it is desirable that spiral-state blade is arranged in t inner pipe near the tip part of the using double pipe structural lance or the inner pipe is projected from the tip part of the outer pipe and the tip part of the inner pipe is closed, and also, slits are arranged to the tip part side wall of the inner pipe projected from the outer pipe.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for blowing pulverized coal from tuyere of a blast furnace and a lance for blowing pulverized coal.

[0002]

2. Description of the Related Art Blowing pulverized coal into a blast furnace is used in many blast furnaces because it has a great cost advantage due to a price difference with coke, and contributes greatly to improving the economical efficiency of blast furnace operation. In recent years, the importance of the extension of the life of a coke oven has been re-recognized, and technical development aiming for large-scale injection of the coke oven has been actively carried out.

As the amount of pulverized coal blown into the blast furnace increases, various problems become apparent, one of which is a problem caused by unburned char. That is, as the amount of pulverized coal injected increases, the oxygen excess coefficient decreases, so the combustion rate of pulverized coal decreases, and a large amount of unburned char that cannot be completely burned in the raceway is generated. This unburned char may be preferentially consumed due to the solution loss reaction in the cohesive zone or in the lower part of the blast furnace, but there is a limit value in the in-reactor consumption, so it exceeds the in-reactor limit. When char is generated, it is discharged from the furnace top as dust, causing a decrease in the replacement rate and an increase in the fuel ratio. Further, if char accumulates in the core of the furnace or the root of the cohesive zone, it may cause unstable furnace conditions and reduced productivity due to obstruction of ventilation and liquid permeability.

Therefore, in order to realize a stable blast operation of a large amount of pulverized coal, it is indispensable to keep the amount of unburned char generated below the in-furnace consumption limit. For that purpose, combustion of pulverized coal in the raceway section is required. It is necessary to further improve the rate.

In a normal pulverized coal blowing operation, it is common to inject a pulverized coal blowing single pipe lance tip into the blow pipe and blow pulverized coal from the opening of the lance tip. In this method, since the entire amount of pulverized coal is ejected from one lance, the concentration of pulverized coal immediately after being ejected from the lance is high, and the inertial force of hot air is also large, so that the pulverized coal is sufficiently diffused in the radial direction of the blow pipe. I can't. Therefore, the mixing efficiency of the pulverized coal and hot air and the contact efficiency of the pulverized coal and oxygen are lowered, the temperature rise of the pulverized coal is delayed, and it becomes difficult to achieve a high burning rate.

Therefore, in order to improve the burning rate of pulverized coal, JP-A-2-213406 and JP-A-6-100.
In Japanese Patent No. 912, the lance has a concentric double pipe structure, pulverized coal is blown from the inside of the inner pipe, and air or oxygen or a mixed gas thereof is flowed through a gap between the inner pipe and the outer pipe.
A method for improving the contact efficiency between pulverized coal and oxygen has been proposed. Further, in Japanese Patent Laid-Open No. 1-92304, a lance is
As a heavy pipe structure, pulverized coal is blown from the inner pipe, the gap in the outermost shell is water-cooled, and a plurality of nozzles are provided in the gap in the inner shell so as to surround the inner pipe, and oxygen is discharged from the nozzle. A method of ejecting is disclosed. Furthermore, the technical document “Iron and Steel” [vol. 80 (1994) P28
8] proposes a so-called double lance method in which two single tube lances are installed at each tuyere. In this method, since there are two pulverized coal ejection points, it is possible to disperse the pulverized coal relatively uniformly in a wider space immediately after injection, and the contact efficiency between the pulverized coal and hot air and oxygen in hot air Will increase. Therefore, the temperature rise and the thermal decomposition of the volatile matter are accelerated, the volatile matter is quickly burned, and the pulverized coal receives the heat of combustion of the volatile matter to accelerate the thermal decomposition of the volatile matter. It is possible to proceed to achieve a high pulverized coal burning rate.

[0007]

[Patent Document 1] Japanese Unexamined Patent Application Publication No.
In the methods described in JP-A-213406 and JP-A-6-100912, the pulverized coal is easily cooled by the introduction of a large amount of cold gas, and when a large amount of pulverized coal is blown, the flow rate of the pulverized coal is increased, so that ignition occurs. There may be a delay. In addition, since the gas diffuses more easily than solids, the oxygen blown near the pulverized coal is immediately mixed with the hot air, so the effect of increasing the oxygen concentration near the pulverized coal particles is expected only at a short distance immediately after the lance ejection. Can not. Therefore, the burning rate of the pulverized coal becomes significantly lower than the value expected from the initial oxygen excess coefficient in the vicinity of the pulverized coal, and in some cases, the effect of introducing oxygen may not appear at all.

In the method described in Japanese Patent Application Laid-Open No. 1-92304, the oxygen outside the pulverized coal diffuses and is not effectively used for combustion, and the temperature rise of the pulverized coal is delayed.
There are similar problems to the above method.

The technical document "Iron and Steel" [vol. 80 (19
94) P288], a relatively high pulverized coal combustion rate can be achieved, but since a single pipe lance is used, there is a limit to the diffusion of pulverized coal in the radial direction of the blow pipe immediately after the lance ejection. Therefore, there is a limit to improving the combustion rate.

The present invention has been made to solve the above problems, and improves the dispersibility of pulverized coal blown from a lance, improves the mixing efficiency of the pulverized coal and hot air, and at the same time makes oxygen blown in effective. It is an object of the present invention to provide a pulverized coal blowing method and a pulverized coal blowing lance capable of further improving the burning rate of pulverized coal by utilizing the above.

[0011]

SUMMARY OF THE INVENTION The above problem is that a plurality of lances having a concentric double pipe structure are provided on the side wall of a blow pipe connected to each tuyere of a blast furnace, and the lance is provided between an inner pipe and an outer pipe. Pulverized coal is blown together with the pulverized coal transporting gas from a certain gap, and air or oxygen or a mixed gas of these is flowed in the inner pipe so as to have a flow rate not less than 2 times and not more than 5 times the flow rate of the pulverized coal carrying gas. This is solved by a method of blowing pulverized coal into a blast furnace, which is characterized in that

Further, as a lance having a concentric double pipe structure provided on the side wall of the blow pipe connected to each tuyere of the blast furnace,
A lance with spiral wings provided in the inner tube near the tip, or the tip of the inner tube that projects from the tip of the outer tube to close the tip of the inner tube and projects from the outer tube If a lance provided with a slit on the side wall of the portion is used, the burning rate of pulverized coal can be further improved.

[0013]

[Function] When a lance having a concentric double pipe structure is used, pulverized coal is blown from the gap between the inner pipe and the outer pipe, and air or oxygen or a mixed gas of these is flowed from the inner pipe to blow pulverized coal. , The density of the pulverized coal main flow immediately after being ejected from the lance should be significantly reduced compared to the conventional method of ejecting the entire amount of pulverized coal from the inner pipe, which is performed with a single pipe lance or a double or triple pipe lance. You can This means that the distance between the pulverized coal particles increases, the sensible heat of hot air and the absolute amount of oxygen that can effectively use a unit weight of pulverized coal increase, and the increase in the temperature rising rate of pulverized coal and eventually combustion This will lead to an increase in speed and improve the burning rate of pulverized coal. In addition to the above method, when a plurality of lances are provided on the side wall of the blow pipe for blowing pulverized coal, the starting point of pulverized coal injection increases, and the dispersibility of the pulverized coal in the blow pipe is significantly improved. Further improves the burning rate. As described above, there has been conventionally proposed a method of improving the burning rate of pulverized coal by using a single tube lance with a double lance. However, pulverized coal is injected by the method of the present invention using a lance having a concentric double tube structure. When,
The effect is remarkably large as compared with the conventional method. Furthermore, in addition to the above method, the flow rate of air or oxygen or a mixed gas thereof flowing in the inner tube of the lance is set to the flow rate of the carrier gas flowing for blowing the pulverized coal from the gap between the inner tube and the outer tube of the lance. When pulverized coal is blown into the pulverized coal at a ratio of 2 times or more and 5 times or less, the pulverized coal main flow can be diffused to the outside without causing a large temperature drop of the pulverized coal particles, so that the dispersibility of the pulverized coal is further improved. A higher burning rate of pulverized coal can be achieved as compared with the conventional method. When the gas flow rate ratio is less than 2 times, the effect of diffusing the pulverized coal main flow outward is not so great, and when it exceeds 5 times, the temperature of the pulverized coal particles is lowered.

In the lance having the concentric double pipe structure used in the above method, spiral wings are provided in the inner pipe near the tip of the lance, or the inner pipe is protruded from the front end of the outer pipe, Use of a lance with a slit on the side wall of the tip of the inner tube that blocks the tip and protrudes from the outer tube significantly promotes the diffusion of the pulverized coal main flow to the outside, further improving the dispersibility of the pulverized coal. Therefore, the combustion rate can be further increased.

[0015]

【Example】

(Example 1) A pulverized coal combustion experiment was conducted using the pulverized coal combustion furnace shown in FIG. In FIG. 1, 1 is a lance for blowing pulverized coal, 2 is a blow pipe, 3 is a coke packed layer, 4 is a tuyere, 5 is a lance guide pipe, 6 is a sampling probe guide pipe, 7 is a pulverized coal cutting hopper, and 8 is Pulverized coal supply pipe, 9 is a gas supply pipe for lance inner pipe. The pulverized coal combustion furnace is composed of a coke packed bed 3 and a blow pipe 2 having an inner diameter of 90φ connected to a tuyere 4 having an inner diameter of 65φ. At the rear end of the blow pipe 2, two lances 1 are provided obliquely via a lance guide pipe 5 symmetrically with respect to the axis of the blow pipe 2. The distance from the tip of the lance 1 to the tip of the tuyere 4 is 1200 mm.

FIG. 2 shows a cross-sectional view of a lance used in this experiment, which is one embodiment of the present invention. In FIG. 2, 10 is an inner pipe,
Reference numeral 11 is an outer tube, and 12 is a spiral wing.

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

Pseudo air adjusted to have an oxygen concentration of 21% by mixing oxygen into the combustion gas of LPG was blown into the blow pipe 2 at 350 Nm ³ , and the temperature at the tip of the tuyere 4 was adjusted to 12%.
The temperature was raised to 00 ° C. When the temperature is stable at 1200 ° C, the pulverized coal cutting hopper 7 cuts the pulverized coal at 65 kg / h, and nitrogen gas of 12 Nm ³ / h is used as a carrier gas, and two lances are provided via the pulverized coal supply pipe 8. It was blown in through the gap between the inner tube and the outer tube of No. 1. At the same time, cold air was supplied to the inner pipes of the two lances 1 through the lance inner pipe gas supply pipe 9 at 40 Nm ³ / h. The flow velocity of pulverized coal / transporting gas ejected from the tip of the outer pipe was 16 Nm / s calculated from the area of the flow passage, and the gas flow velocity at the end of the inner pipe was 48 Nm / s. The oxygen excess coefficient under these conditions was calculated to be 0.78, which corresponds to 200 kg / t in terms of the pulverized coal blowing rate of the actual blast furnace. Insert the sampling probe from the sampling probe guide pipe 6 during the combustion of pulverized coal, and insert 300, 600, 9 from the tip of the lance 1.
Pulverized coal dust was sampled at each position of 00 mm. Then, the burning rate of pulverized coal was obtained by chemical analysis.

[0019]

[Table 1]

FIG. 4 shows the relationship between the distance from the lance tip and the burning rate of pulverized coal. A high burning rate of 50% was obtained at a position of 300 mm from the lance tip, and a high burning rate of 80% was obtained at a position of 900 mm, and an increase in the burning rate can be confirmed.

The combustion rate can be further increased by increasing the number of lances to three or four, but the diameter of the blow pipe of this device is 90φ.
Considering the above, it is presumed that the effect will be saturated even if it is increased more.

(Embodiment 2) FIG. 3 shows a sectional view of a lance which is another embodiment of the present invention. In FIG. 3, 10 is an inner pipe,
Reference numeral 11 is an outer tube, and 13 is a slit. This lance has an inner tube 1
The tip of No. 0 is closed so as to project 10 mm from the tip of the outer tube 11, and a slit 13 is provided on the circumference at a position 3 mm from the tip of the inner tube.

Two similar lances were provided on the side wall of the blow pipe of the pulverized coal combustion furnace shown in FIG. 1 symmetrically with respect to the axis of the blow pipe, and the same experiment as in Example 1 was conducted. In addition, the width of the slit 13 is set so that the amount of pulverized coal carrying nitrogen gas to flow to the outer pipe and the amount of cold air gas to flow to the inner pipe and the gas flow velocity at the tips of the outer pipe and the inner pipe are the same as those in the first embodiment. It was adjusted.

The results are shown in FIG. In this case as well, a high combustion rate and a high combustion speed similar to those of the first embodiment can be obtained.

The projection length of the tip of the inner tube 10 with respect to the tip of the outer tube 11 is 1 m because it is necessary to provide the slit 13.
It is necessary to be at least m, and if the protruding length is too long, the tip may melt due to the radiant heat of pulverized coal combustion, so it is desirable to be 20 mm or less.

(Comparative Example 1) A single tube lance was provided on the side wall of the blow pipe of the pulverized coal combustion furnace shown in FIG. The lance diameter was adjusted so that the tip gas flow rate was the same as in Example 1.

The results are shown in FIG. 300 from the tip of the lance
At a position of mm, only a low burning rate of 25% is obtained, and at a position of 900 mm, the burning rate is improved to about 45% at most. It is considered that this is because the dispersibility immediately after blowing pulverized coal is poor and the contact efficiency with hot air is low.

(Comparative Example 2) Two single pipe lances were provided symmetrically with respect to the axis of the blow pipe on the side wall of the blow pipe of the pulverized coal combustion furnace shown in FIG. 1, and the same experiment as in Example 1 was conducted. . The lance diameter was adjusted so that the tip gas flow rate was the same as in Example 1.

The results are shown in FIG. 300 from the tip of the lance
40% at mm position and 7 at 900 mm position
Although a relatively high burning rate of 5% is obtained, it does not reach the burning rate according to the method of the present invention shown in Examples 1 and 2. This indicates that the use of multiple pulverized coal blowing starting points significantly enhances the dispersibility of the pulverized coal into the space, but the single pipe lance also has a limit.

Comparative Example 3 An experiment similar to that of Example 1 was carried out by providing one concentric double tube lance shown in FIG. 2 on the side wall of the blow pipe of the pulverized coal combustion furnace shown in FIG.

The results are shown in FIG. The burning rate at each position shows an intermediate value between Comparative Examples 1 and 2. Higher than Comparative Example 1 is
Injecting pulverized coal by the method of the present invention using the concentric double tube lance of the present invention improves the dispersibility of the pulverized coal in the space more than the conventional method using a single tube lance. Is shown. However, compared with the case of Comparative Example 2 in which two single tube lances are used, the dispersibility thereof is not reached.

(Embodiment 3) Two concentric double pipe lances shown in FIG. 2 are provided on the side wall of the blow pipe of the pulverized coal combustion furnace shown in FIG. 1 symmetrically with respect to the axis of the blow pipe, and inside the lance inner pipe. The amount of gas to flow is 0, 12, 24, 36, 48, 60, 7
The effect on the combustion rate was investigated by changing the value to 2,84 Nm ³ / h. In this case, the cross-sectional area of the gas flow path is the same for both the outer pipe and the inner pipe, and the gas flow velocity at the tip of the outer pipe is 16 Nm / s.
Met. Then, after combustion is stabilized, 3 from the tip of the lance.
Sampling was performed at a position of 00 mm, and the burning rate of pulverized coal was determined by chemical analysis. The conditions other than the amount of gas flowing into the lance inner tube and the sampling position are the same as in the first embodiment.

FIG. 5 shows the amount of gas flowing into the inner pipe (hereinafter referred to as the inner pipe gas amount) and the amount of pulverized coal carrying gas flowing from the gap between the inner pipe and the outer pipe (hereinafter referred to as the outer pipe gas amount). ) And the burning rate of pulverized coal. When the ratio of the inner pipe gas amount to the outer pipe gas amount is 2 or more and 5 or less, the improvement of the burning rate is recognized. Particularly, the effect is remarkable when it is 3 or more and 5 or less. When the gas flow rate ratio is within this range, it is considered that the pulverized coal main flow can be diffused further outward without causing a large temperature drop of the pulverized coal particles, and therefore the dispersibility of the pulverized coal is improved.

[0034]

EFFECTS OF THE INVENTION Since the present invention is constituted as described above, the dispersibility of pulverized coal blown from a lance is improved, the mixing efficiency of pulverized coal and hot air is improved, and the oxygen blown at the same time is made effective. By utilizing this, it is possible to provide a pulverized coal blowing method and a pulverized coal blowing lance that can further improve the burning rate of the pulverized coal.

[Brief description of drawings]

FIG. 1 is a diagram showing a pulverized coal combustion furnace.

FIG. 2 is a cross-sectional view of a lance that is an embodiment of the present invention.

FIG. 3 is a sectional view of a lance that is another embodiment of the present invention.

FIG. 4 is a diagram showing the relationship between the distance from the tip of the lance and the burning rate of pulverized coal.

FIG. 5 is a diagram showing a relationship between a ratio of an inner pipe gas amount and an outer pipe gas amount and a burning rate of pulverized coal.

[Explanation of symbols] 1 Lance 2 Blow pipe 4 Tuyere 10 Inner tube 11 Outer tube 12 Spiral blade 13 Slit

Claims (3)

[Claims] 1. A plurality of lances having a concentric double pipe structure are provided on a side wall of a blow pipe connected to each tuyere of a blast furnace, and pulverized coal is pulverized coal from a gap between an inner pipe and an outer pipe of the lance. A blast furnace characterized by being blown together with a carrier gas and flowing air or oxygen or a mixed gas thereof into the inner pipe so as to have a flow rate which is 2 times or more and 5 times or less the flow rate of the pulverized coal carrying gas. Pulverized coal blowing method. 2. A lance having a concentric double pipe structure provided on a side wall of a blow pipe connected to each tuyere of a blast furnace,
A lance for blowing pulverized coal, characterized in that a spiral blade is provided in the inner pipe near the tip thereof. 3. A lance having a concentric double pipe structure provided on a side wall of a blow pipe connected to each tuyere of a blast furnace,
A lance for blowing pulverized coal, characterized in that the inner tube is projected from the tip of the outer tube to close the tip of the inner tube, and a slit is provided on the side wall of the tip of the inner tube protruding from the outer tube.