JP2953255B2 - Method and apparatus for injecting solid fuel into blast furnace - 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 and an apparatus for injecting solid fuel into a blast furnace, and more particularly to a blast furnace operation in which solid fuel such as pulverized coal is blown into a blast furnace from tuyeres. The present invention relates to a method and an apparatus for injecting solid fuel into a blast furnace, which can improve the diffusion efficiency without causing pressure loss of a blow pipe and without using a complicated apparatus.

[0002]

2. Description of the Related Art Coke, which is a main fuel of a blast furnace, is generally produced from coking coal. Coking coal has a limited production area and is more expensive than steam coal used as fuel for boilers and the like. For this reason, in the blast furnace operation, some alternative fuels of coking coal have been conventionally used, that is, liquid fuel such as heavy oil or gas fuel such as natural gas is used as auxiliary fuel, and these auxiliary fuels are introduced into the blast furnace from the tuyeres. Blowing,
The required coke was being reduced. In Japan, heavy oil was generally used as an auxiliary fuel because of the difficulty in obtaining natural gas.

However, in the 1980s, the use of heavy oil was no longer economical due to soaring oil prices.
Heavy oil injection has been discontinued. Instead, the steamed coal is reduced to a predetermined particle size, for example, 80%
, And pulverized coal is blown into the blast furnace directly from the tuyere as an auxiliary fuel. This method has been practiced for a long time in steelworks where coal is easily available, but since the 1980s, easily available steam coal can be used directly as part of blast furnace fuel, Due to the great economic effect, it has been implemented at many steelworks. In addition, the method using pulverized coal as an auxiliary fuel can simultaneously reduce the coke ratio, thereby reducing the load on the coke oven and, as a result, reducing environmental problems associated with the operation of the coke oven. Have been. From such a background, it is directed to inject more pulverized coal. For example, pulverized coal is injected at a rate of 150 kg or more per ton of pig iron. The present invention is a technique that enables a large amount of pulverized coal to be injected.

Generally, pulverized coal is injected into a blast furnace as shown in FIG.
As shown in FIG. 2, the injection is performed through a lance 3 inserted into the blow pipe 2 with the tip directed toward the tuyere 1. However, when a large amount of pulverized coal is to be blown, the ratio of pulverized coal to oxygen (kg
/ Nm ³ ) increases, and the flammability of pulverized coal decreases. Therefore, the rate at which a part of the coke charged into the blast furnace can be replaced with pulverized coal, that is, the replacement rate, decreases, and the pulverized coal blowing effect decreases. Obviously, increasing the oxygen concentration improves flammability, but generally the cost of producing oxygen is high, so this method is not economical. Also,
The pulverized coal is usually blown into hot air, passes through a combustion space called a raceway 4 at the tip of the tuyere 1, and enters the blast furnace. However, a large amount of coke is mixed into the raceway 4. However, the oxygen in the hot air decreases rapidly.

FIG. 10 shows the relationship between the distance from the tip of the tuyere 1 and the gas component composition. As shown in FIG. 10, the combustible space where oxygen exists is narrow. In addition, since the gas flow velocity in the tuyere 1 is generally extremely high at 200 m / sec, the time during which the injected pulverized coal is present in the combustible space is extremely small.
20 ms. The unburned pulverized coal that does not burn out in the combustion space is discharged without being used as a heat source in the blast furnace. Therefore, the amount of pulverized coal burned in a limited space, that is, how to increase the combustion rate is the key to the success or failure of this pulverized coal injection technology, and to improve the combustion rate of the pulverized coal injected. It is necessary for pulverized coal to instantaneously come into contact with oxygen in hot air and burn in this limited space. However, according to the general pulverized coal injection method shown in FIG. 9, the pulverized coal injected from one lance 3 does not instantaneously diffuse into the blow pipe 2, so that a large amount of pulverized coal is supplied. When the pulverized coal is blown, the pulverized coal consumes oxygen in the surrounding hot air at the tip of the lance 3, and becomes short of oxygen near the flow of the pulverized coal, so that combustion does not proceed promptly.

A technique for solving the above problem is 2n.
d. European Ironmaking Congress 15-18, Sept., 1991, (G
lasgow), p247. In this technique, as shown in FIGS. 11 and 12, two lances 5 are inserted symmetrically into a blow pipe 2 with their tips facing the tuyere 1 direction. The central axis intersects the central axis of the blow pipe 2 at one point. Thus, it is expected that the pulverized coal quickly spreads in the blow pipe 2. Hereinafter, this technique is referred to as Conventional Technique 1.

[0007] Japanese Patent Application Laid-Open No. 64-28312 discloses a technique for improving the mixing efficiency of pulverized coal and oxygen by providing a swirl vane on the inner surface of a blow pipe to generate a swirl flow in the flow inside the blow pipe. Is disclosed. Hereinafter, this technology is referred to as Conventional Technology 2.
That.

In Japanese Patent Application Laid-Open No. 62-192509, two or more lances for blowing pulverized coal are inserted into a blowpipe, the distance from the tuyere of the lance is changed, and pulverized coal, oxygen and It is disclosed that the mixing ratio is changed and that a wind direction deflecting device such as a windmill is provided at the tip of the lance. Hereinafter, this technique is referred to as Conventional Technique 3.

[0009]

However, the above-mentioned prior art has the following problems.

In the prior art 1, since the pulverized coal injection lances are provided symmetrically, the flows from the two lances collide with each other. As a result, a vortex is generated in the flow direction, and the pulverized coal blown into the vortex is entrained, so that the pulverized coal is hardly diffused throughout the blow pipe.

In the prior art 2, the mixing efficiency of the pulverized coal and oxygen is promoted by the swirling flow. However, the swirling blade protruding from the inner surface of the blow pipe obstructs the flow of hot air, and the pressure loss of the blow pipe is reduced. It is unfavorable for blast furnace operation.

The prior art 3 requires a control device for changing the amount of pulverized coal for each lance, so that the equipment becomes complicated and the load of maintenance work is increased. Further, if a wind direction deflecting device is attached to the tip of the lance, the pressure loss of pulverized coal transportation increases, the power used increases, and the pulverized coal is likely to be clogged.

Accordingly, an object of the present invention is to provide a blast furnace operation in which a solid fuel such as pulverized coal is blown into a blast furnace from a tuyere.
Provided is a method of injecting solid fuel into a blast furnace, which can easily improve the diffusion efficiency of solid fuel in a blow pipe without causing pressure loss of the blow pipe and without using a complicated device. Is to do.

[0014]

SUMMARY OF THE INVENTION The present invention relates to a plurality of lances for injecting a plurality of solid fuels, each of which is inserted into a blow pipe connected to a blowing tuyere of a blast furnace so that a tip thereof faces the tuyere side. Wherein the solid fuel is blown into the blowpipe by a carrier gas from the blast furnace. In the method for blowing solid fuel into a blast furnace, each of the plurality of lances has a center axis at least at a distal end of the lance, and a center axis of the blowpipe. And the carrier gas does not cross
At least one of gas , air, CO and CO ₂ gas
It is characterized in that it consists of

[0015]

According to the present invention, a plurality of lances for injecting solid fuel are provided in a blow pipe at a position where the center axis of the lance does not intersect with the center axis of the blow pipe, and are mutually aligned with respect to the center axis of the blow pipe. By disposing them at symmetric positions, the diffusion efficiency of solid fuel such as pulverized coal is improved.

[0016]

Next, an embodiment of a method for injecting solid fuel into a blast furnace according to the present invention will be described with reference to the drawings.

FIG. 1 is a cross-sectional view showing one embodiment of the method for injecting solid fuel into a blast furnace according to the present invention, and FIG. 2 is a right side view of FIG.

In FIGS. 1 and 2, reference numeral 6A denotes two lances for injecting solid fuel inserted into a blow pipe 2 connected to the tuyere 1. The lance 6A has its tip directed toward the tuyere 1 so that the center axis (l) of each lance 6A does not cross the center axis (L) of the blow pipe 2 and
The blow pipe 2 is disposed so as to be axially symmetric with respect to the center axis (O).

Pulverized coal is blown from the two lances 6A together with the carrier gas at a flow rate of about 15 m / sec.
However, since the ends of the two lances 6A do not face each other on the same straight line and are arranged at axially symmetric positions, the pulverized coal is blown into the blow pipe 2 without interference with each other. , Quickly diffuses in the blow pipe 2. Therefore, the combustion efficiency of pulverized coal is improved. Carrier gas, nitrogen, air, CO, consists of at least one of a CO2 gas.

As shown in FIG. 3, two lances 6B having only the tip portions bent outward are provided such that the center axis of only the tip portions does not intersect with the center axis of the blow pipe, and They may be arranged so as to be axially symmetric with respect to the axis. The number of lances may be two or more. FIG. 4 shows an example in which three lances 6C are arranged at 120 ° intervals at axially symmetric positions with respect to the center axis of the blow pipe. Note that the lances do not necessarily need to be arranged at axially symmetric positions with respect to the center axis of the blow pipe as long as the center axis of the lances does not intersect with the center axis of the blow pipe.

Next, a test for verifying the effect of the present invention was conducted. Hereinafter, the test method and test results will be described with reference to the drawings.

FIG. 5 is a sectional view showing a reactor for a pulverized coal combustion test simulating the vicinity of a tuyere of a blast furnace, wherein 7 is a reactor main body, and 8 is a tuyere provided on the reactor main body 7. , 9 is a blowpipe connected to the tuyere 8, 10 is a pulverized coal injection lance inserted into the blowpipe 9, 11 is coke filled in the reactor body 7, 12 is a blowpipe Three pulverized coal sampling probe holes formed in the pipe 9;
They are provided at positions of 200 mm, 300 mm, and 400 mm from the tip of 10, respectively. Reference numeral 13 denotes hot air blown into the reactor main body 7 from the blow pipe 9, 14 denotes a raceway formed at the tip of the tuyere 8, and 15 denotes exhaust gas from the reactor main body 7.

Hot air was blown into the coke 11 filled in the reactor body 7 as described above. This hot air burns LPG with air from the upstream side of the blow pipe 9,
It had the same oxygen concentration as in the blast furnace, obtained by mixing oxygen. Then, pulverized coal was blown into the blow pipe 9 by the pulverized coal blowing method using three types of lances A, B, and C shown in FIG. The lance format will be described later. Then, the pulverized coal sampling probe is inserted into each of the three pulverized coal sampling probe holes 12 to sample and analyze the pulverized coal during the combustion process, and the combustion rate of the pulverized coal is determined for each pulverized coal injection method. I checked. The definition of the combustion rate was calculated as the consumption rate of combustibles as shown in the following equation (1). The test conditions at this time are shown in Table 1, and the specifications of the test equipment are shown in Table 2.

[0024]

(Equation 1)

[0025]

[Table 1]

[0026]

[Table 2]

In FIG. 6, the lance type A indicates the blow method of the present invention, and the lance types B and C indicate the comparative blow method. The lance type A is the same as that shown in FIGS. 1 and 2, the lance type B uses one blow pipe, and the lance type C uses the conventional lance shown in FIGS. 11 and 12. It was the same as in Technology 1. FIG. 6 also shows the arrangement dimensions of the lances in each lance type.

FIG. 7 shows the results of the combustion test performed in this manner. The amount of pulverized coal injected under these test conditions is equivalent to 200 kg / t in an actual blast furnace. As is clear from FIG. 7, it was found that according to the blowing method of the present invention, higher combustion efficiency can be obtained than in any of the comparative blowing methods.

Further, in order to examine the influence of the brand of pulverized coal, similar combustion tests were performed on other pulverized coals b and c shown in Table 3. FIG. 8 shows the results of the combustion rate at a position 400 mm from the tip of the lance. As is clear from FIG.
It was found that regardless of the type of pulverized coal, according to the blowing method of the present invention, it is possible to obtain higher combustion efficiency than any of the comparative blowing methods.

[0030]

[Table 3]

[0031]

As described above, according to the present invention, the pulverized coal does not interfere with each other unlike the prior art 1, so that the mixing of the pulverized coal and oxygen is promoted, and the conventional art 2 As described above, there is no need to provide swirling vanes, so that the pressure loss of the blow pipe is significantly reduced. As a result, the combustion rate of pulverized coal can be significantly increased as compared with the prior art. Therefore, it is possible to inject a large amount of pulverized coal of about 200 kg / t, which has been difficult in the past. Moreover, since the arrangement of the lance is merely changed, a useful effect such as no need for a complicated device is provided.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing one embodiment of a method for blowing solid fuel into a blast furnace according to the present invention.

FIG. 2 is a right side view of FIG.

FIG. 3 is a sectional view showing another embodiment of the method for injecting solid fuel into a blast furnace according to the present invention.

FIG. 4 is a sectional view showing still another embodiment of the method for injecting solid fuel into a blast furnace according to the present invention.

FIG. 5 is a sectional view of a reactor main body used for a combustion test of the present invention.

FIG. 6 is a diagram showing a lance type used in the combustion test of the present invention.

FIG. 7 is a graph showing a relationship between a distance from a lance tip and a combustion rate.

FIG. 8 is a graph showing a relationship between coals b and c and a combustion rate.

FIG. 9 is a cross-sectional view showing a conventional solid fuel injection method.

FIG. 10 is a graph showing a relationship between a distance from a tuyere tip and a gas composition.

FIG. 11 is a partial front view showing Conventional Technique 1.

FIG. 12 is a right side view of FIG. 11;

[Explanation of symbols]

 1: Tuyere, 2: Blowpipe, 3: Lance for pulverized coal injection, 4: Raceway, 5: Lance for pulverized coal injection, 6, 6A, 6B, 6C: Lance for pulverized coal injection, 7: 8: Tuyere, 9: Blow pipe, 10: Lance for pulverized coal injection, 11: Coke, 12: Hole for pulverized coal sampling probe, 13: Hot air, 14: Raceway, 15: Exhaust gas.

Continuation of the front page (72) Inventor Yuichi Yamakawa 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Inside Nippon Kokan Co., Ltd. (72) Inventor Takao Tsuboi 2722-5 Kurihara, Zama City, Kanagawa Prefecture (56) References JP Akira 64-28312 (JP, A) JP-A-5-112806 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C21B 5/00, 7/00

Claims (2)

(57) [Claims] 1. A solid fuel is injected into a blow pipe connected to a blow tuyere of a blast furnace by a carrier gas from a plurality of solid fuel injection lances, each of which is inserted so that a tip thereof faces the tuyere side. Injecting into the blowpipe, in the method of injecting solid fuel into the blast furnace, each of the plurality of lances, disposed at a position at least the center axis of the tip of the lance does not intersect the center axis of the blowpipe, A method for injecting a solid fuel into a blast furnace, wherein at least one of nitrogen, air, CO and CO2 gas is used as the carrier gas. 2. A blow pie connected to a blowing tuyere of a blast furnace.
Key inserted into the pump so that the tip faces the tuyere side.
Carrier gas to blow solid fuel into the blowpipe.
Equipped with multiple solid fuel injection lances
Further, in the solid fuel injection device into the blast furnace, each of the plurality of lances is at least one of the lances
The center axis of the tip crosses the center axis of the blow pipe
And the carrier gas is nitrogen,
Consisting of at least one of gas, CO and CO2 gas
Characterized in that solid fuel is injected into the blast furnace.
Place. "