JPH11222614A - Method for deciding fitting position of lance for injecting pulverized fine coal in blast furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the stickiness of an ash component drerived from pulverized fine coal to a refractory ring fitted on the inner surface of a tuyere and the tip part of a lance by adjusting the fitting position of the lances in a pulverized fine coal injection blast furnace provided with a plurality of injection lances. SOLUTION: The fitting positions of the plurality of lances whose tip parts are projectingly arranged in the tuyere hole fitted with the refractory ring 4 in the inner part, in the blast furnace, and adjusted so that the interval of mutual tip parts of the lances is >=250 mm in the longitudinal range of the ring and both tip parts of the lances are away at the distance satisfying the following inequality from the inner peripheral surface of the ring. X>=L.tanθ. Wherein, X is the shortest distance from the axial center of the lance tip part to the inner peripheral surface of the ring, L is the distance from the tuyere tip part to the lance tip part and θ is the widening angle of the pulverized fine coal injected from the lance 3. Therefore even if the refractory ring 4 is used in the pulverized fine coal injection blast furnace, such long service life is obtd. in this tuyere as to equal to the case which does not execute the injection of the pulverized fine coal and such problem as the clogging of the pulverized fine coal in the lance 3 caused by the stickiness of the ash content, can be dissolved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of injecting pulverized coal from tuyeres of a blast furnace, and more particularly to a method of injecting pulverized coal by adjusting a mounting position of a pulverized coal injection lance (or PC lance). The present invention relates to a blast furnace pulverized coal injection lance installation position determining method for preventing ash from adhering to a refractory ring.

[0002]

2. Description of the Related Art In recent blast furnace operations, a method of injecting pulverized coal powder fuel into a blast furnace has been put to practical use in order to reduce the unit fuel consumption and stabilize the furnace condition. FIG. 4 is a schematic view showing an example of a conventional technique relating to a pulverized coal fuel injection method having a plurality of lances. Pulverized coal fuel is supplied as carrier gas (mainly air) from two blowing lances 3 penetrating the wall of the blow pipe 2 connected to the tuyere 1 and inserted into the tuyere.
And blow into the blast furnace. A heat-insulating refractory ring 4 is mounted on the inner surface of the tuyere for the purpose of suppressing a decrease in the blowing temperature and adjusting the wind speed of the tuyere.

However, in the method of injecting pulverized coal fuel by such a method, ash derived from pulverized coal is melted by combustion heat in a high temperature atmosphere of 1000 to 1300 ° C., and heat insulation and tuyere wind speed adjustment are performed. The refractory ring has a composition similar to that of ash in pulverized coal, which causes the ash to adhere to and melt on the inner peripheral surface of the refractory ring in the state of the melt 5, which significantly increases the life of the refractory ring. Had been lowered. Occasionally, it was often observed that the blast furnace had to be operated without the ring installation effect, with the ring broken before the scheduled breeze before repairs, which would be performed every few months of continuous operation of the blast furnace. For this reason, the tuyere insulation effect by the refractory ring is not obtained and not only a large energy loss occurs, but also the adjustment of the tuyere wind speed collapses and an imbalance occurs in the furnace circumferential direction,
As a result, there have been problems such as deterioration of the furnace condition.

In the case where a plurality of lances are provided, when one of the lances is arranged so as to be burned by the pulverized coal injected from the other lance, the lance tip is melted or the lance tip is damaged. There was also a problem that ash was adhered to the portion and clogged with pulverized coal in the lance.

As a measure for preventing ash from adhering to the refractory ring (or the inner peripheral surface of the tuyere), only a precedent in the case where one lance is provided can be found. . (1) JP-A-58-171509 discloses a method in which the position of the tip of a lance is adjusted so as to reduce the pulverized coal combustion rate from the blowing lance to the tip of the tuyere.
Japanese Patent Application Laid-Open No. 4-268002 discloses a method in which high pressure gas is blown onto the inner surface of a tuyere to prevent ash adhesion. (3) In Japanese Patent Application Laid-Open No. 4-268002, the tip of a lance is bent in parallel to the longitudinal direction of the blow pipe. And the like, in which the flow of pulverized coal blown by being set at a position corresponding to the axis of the hot air so as to follow the flow at the center of the hot air have been proposed.

On the other hand, there is no precedent clarifying the lower limit value of the distance between the plurality of lance tip portions so as not to cause erosion or ash adhesion.

[0007]

However, the above method has the following problems. The application conditions of the above (1) are that the inner diameter of the blowpipe is 130 to 180 mm, the inner diameter of the blowpipe and the tuyere are The lance tip is set 100 to 350 mm upstream from the boundary position of, and the problem has not been solved when a ring is attached for the purpose of adjusting the tuyere wind speed in addition to suppressing the blast temperature. For example, the inner diameter of a tuyere connected to a blow pipe of 180 mm
When a significant step is generated by squeezing to the maximum, a stagnant area of the airflow is generated at the step, so that ash adhesion cannot be suppressed so much. In the case of (2), since a separate adhesion preventing means is employed, a pressure loss occurs in the blow pipe and a protruding portion is worn, which is rather a problem. In the case of (3), when the lance is once closed due to clogging of the pulverized coal, the lance cannot be pulled out and replaced, so that there is a major drawback that a normal state cannot be restored unless the tuyere is removed by cooling down.
The present invention solves the above-mentioned problems of the prior art, prevents the adhesion of ash, and provides a heat-insulating refractory on the inner surface of the tuyere of a pulverized coal-injected blast furnace for the purpose of suppressing a decrease in blast temperature and adjusting the tuyere wind speed. An object of the present invention is to provide a method for determining a lance installation position for injecting blast furnace pulverized coal into which a ring can be mounted. In addition, the present invention also provides a method for determining a lance mounting position for preventing the lances from adhering to each other when a plurality of lances are provided.

[0008]

According to the present invention, a blow pipe is connected to a blow tuyere of a blast furnace provided with a refractory ring, and a tip of the blow pipe is provided inside the blow pipe. A plurality of lances are inserted so as to face each other, and pulverized coal powder is blown with a carrier gas from the lances. Characterized in that the distance between the tips of the lances is not less than 25 mm, and the respective tips of the lances are separated from the inner peripheral surface of the ring by a distance satisfying the condition of the following formula (1). The present invention relates to a method of determining a lance installation position for coal injection. X ≧ L · tanθ (1) where X is the shortest distance (mm) from the axis of the pulverized coal injection lance tip to the inner peripheral surface of the refractory ring, and L is the distance from the tuyere tip to the lance tip. The distance (mm) and θ are the spread angles (°) of the pulverized coal ejected from the lance.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Pulverized coal injected from a lance is accelerated by the flow of blast gas, and is gradually diffused in the cross-sectional direction as it flies in the longitudinal direction of the tuyere. FIG. 1 schematically shows the flow of pulverized coal injected from two lances and the state of diffusion. Here, the spread angle θ of the pulverized coal ejected from the lance is important,
This value can be confirmed, for example, by examining the state of adhesion of ash to the refractory ring under various conditions where the mounting position of the lance is changed for the actual tuyere of the blast furnace. Further, in the pulverized coal injection method having a plurality of lances, the mutual distance W [that is, the center distance of each lance, which should be secured at least so as not to cause the phenomenon of erosion or ash adhesion at the ends of the lances. There is also a lower limit for the shortest distance between the shafts, and the same applies to the tuyere of the blast furnace, and by investigating the state of erosion and ash adhesion at the tip of the lance under various conditions where the lance is mounted at various positions. You can check.

Therefore, all the lances are adjusted so that the tips thereof are positioned within the longitudinal direction of the refractory ring in which no abnormal flow occurs in the blast gas flow, and the lance tips of the lances are mutually adjusted. The distance W between each other, which does not cause the phenomenon of erosion and ash adhesion, and the spread angle θ of the pulverized coal ejected from the lance is considered,
If the distance X between the tip of the lance and the inner peripheral surface of the refractory ring is sufficiently set, even in the pulverized coal-blown blast furnace, a heat-insulating refractory for the purpose of suppressing a decrease in blast temperature and adjusting the tuyere wind speed. The ring can be worn with confidence.

[0011]

EXAMPLES In the following, the mutual distance W to be minimum secured between two lances on the basis of the test results intended for the blast furnace tuyeres ten internal volume 2650M ^3, the pulverized coal injected from the lance Investigation of the spread angle θ, when the condition of no erosion or ash adhesion at the tip of each lance was obtained from the former result, and the condition of no ash adhesion to the refractory ring was obtained from the latter result. Will be described. The average blowing conditions and pulverized coal injection conditions during the test period of this blast furnace are as follows. <Blowing conditions> Blowing volume: 3900 Nm ³ / min Blasting temperature: 1160 ° C Tuyere wind speed: 230 m / s Flowhife Inner diameter: 180 mm Ring inner diameter: 110 mm <Pulverized coal injection condition> Pulverized coal injection flow rate: 41 t / h (PC ratio) : 165kg /
t) Pulverized coal particle size: 70% by weight or more with a particle size of 200 mesh or less Lance insertion angle: 11 ° By the way, each blast furnace manufacturer has to adjust the lance insertion angle for the purpose of preventing ash from adhering to the tuyere inner surface or tuyere ring inner surface. Measures have been taken to reduce the size of the lance and extend the tip of the lance to the inside of the furnace.However, due to design limitations, the lance angle for general blast furnaces is almost the same as 10 to 12 °. There is no difference between blast furnace manufacturers. Most of the blast furnaces in Japan also have an average of 210 blasts of hot air inside the tuyeres.
Adjustment is made within the range of ~ 245 m / s on the high flow velocity side, and the difference in tuyere wind speed between blast furnaces is not so large. Therefore, the investigation of the effects of the above two variables on the spread angle θ of pulverized coal was omitted, and was fixed in the actual furnace test.
In addition, each of the plurality of lances needs to avoid the risk of pulverized coal blown from the upstream lance being attached to the downstream lance, and when using two lances as in the actual furnace test, The center axis of the lance tip was arranged to be axially symmetric with respect to the center axis of the tuyere ring, and the distance from the tuyere tip was the same. The mutual distance W is 2
This corresponds to the shortest distance connecting the center axes of the lance tips.

In an actual furnace test, the relationship between X and L, which are lance mounting conditions, and the value of W for ten tuyeres [see FIG. 1]
However, a lance having an outer diameter of 19.4 mm was attached so that each lance was different. The state of ash adhesion to the refractory ring and the tip of the lance was checked by viewing from the viewing window provided at one end of the furnace outside in the longitudinal direction of the blowpipe, or using a tuyere camera attached to the viewing window to observe the inside of the tuyere. Confirmation was made. FIG. 2 shows X
This is the result of stratifying the presence / absence of ash attachment to the ring for each arbitrary positional relationship between L and L and sorting them out with XX. The pulverized coal used is the most frequently used and representative brand, and its components are volatile matter = 35% by weight and ash content = 9% by weight. From the results in the figure, the result of the presence or absence of ash adhesion was
It can be understood that stratification may be performed at a boundary line of = 5 °. However, exceptionally, at the position upstream of one end of the refractory ring outside the furnace, phenomena of ash deposition were observed under all conditions. Table 1 shows the results of arranging the state of the presence or absence of erosion and ash adhesion at the tip of the lance for each distance W between the tips of the two lances. From the table, the lower limit value of the minimum distance between the two lances was 25 mm in order not to cause erosion or ash adhesion between the two lances.

[0013]

[Table 1]

FIG. 3 shows a case where the tip of the lance is in the conventional position,
FIG. 4 shows the average life of the refractory ring when the lance mounting condition is satisfied and when pulverized coal is not injected. From the figure, it can be seen that the average life of the ring when the lance tip is at the conventional position is about 45 days, but when the mounting conditions of the present invention are satisfied, it is extended to 300 days or more. It can be seen that a long life comparable to the case where no embedding is performed is obtained.

[0015]

As described above, according to the method of the present invention, the distance between the tip of the lance and the inner peripheral surface of the refractory ring is sufficiently increased by considering the spread angle of the pulverized coal ejected from the lance. Therefore, even in the pulverized coal-injected blast furnace, it is possible to install a heat-insulating refractory ring for the purpose of suppressing the lowering of the blast temperature and adjusting the tuyere wind speed with confidence, which is comparable to the case without pulverized coal injection. The service life can be extended.
In addition, even when a plurality of lances are provided, erosion and ash adhesion at the tip of the lance can be avoided, and the problem of clogging of pulverized coal in the lance due to ash adhesion has been eliminated.

[Brief description of the drawings]

FIG. 1 is a diagram schematically showing the flow of pulverized coal injected from two lances and the state of diffusion.

FIG. 2 is a diagram showing test results obtained by examining whether or not ash adheres to the inner peripheral surface of a refractory ring at various lance attachment positions when pulverized coal having a volatile content of 35% by weight is used.

FIG. 3 is a diagram showing an average life of a refractory ring.

FIG. 4 is a schematic view showing an example of a conventional pulverized coal powder fuel injection method having two lances.

[Explanation of symbols]

1: tuyere 2: blow pipe 3: pulverized coal injection lance 4: refractory ring 5: deposits derived from ash in pulverized coal
6: Furnace wall X: The shortest distance from the axis of the lance tip for pulverized coal injection to the inner peripheral surface of the refractory ring L: The distance from the tuyere tip to the lance tip θ: Spread of pulverized coal ejected from the lance Angle W: Distance between two lance tips

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kazuhiko Matsuyama 11-1, Showa-cho, Kure-shi, Hiroshima Nisshin Steel Co., Ltd. Kure Works (72) Inventor Yukio Tomita 111-1 Showa-cho, Kure-shi, Hiroshima Inside Kure Ironworks Co., Ltd. (72) Inventor Eiji Inohara 11-1 Showacho, Kure City, Hiroshima Prefecture Inside Kure Ironworks Co., Ltd.

Claims (1)

[Claims] 1. A blowpipe is connected to a blow tuyere of a blast furnace having a refractory ring therein, and a plurality of lances are inserted into the blowpipe such that tips are directed to the tuyere side. A method of injecting fine coal powder with gas,
The mounting position of the lance is set such that both ends of the lance are within the longitudinal direction of the refractory ring, the distance between the ends of the lances is 25 mm or more, and the ends of the lances are defined as follows from the inner peripheral surface of the ring. A method for determining a lance installation position for blast furnace pulverized coal injection, wherein the lance is installed at a position separated by a distance that satisfies the condition of the expression (1). X ≧ L · tan θ (1) where X: shortest distance (mm) from the axis of the pulverized coal blowing lance tip to the inner peripheral surface of the refractory ring L: distance from the tuyere tip to the lance tip ( mm) θ: Spread angle of pulverized coal ejected from lance (°)