JP3764939B2 - Method for determining lance installation position for blast furnace pulverized coal injection - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a method for injecting pulverized coal from a tuyere of a blast furnace, and in particular, by adjusting the mounting position of a pulverized coal injecting lance (or PC lance), ash derived from the pulverized coal is added to the refractory ring. The present invention relates to a method for determining a lance mounting position for injecting blast furnace pulverized coal to prevent adhesion.
[0002]
[Prior art]
In recent blast furnace operations, a method of blowing pulverized coal powder fuel into a blast furnace has been put into practical use in order to reduce the fuel consumption rate and stabilize the furnace conditions. FIG. 6 is a schematic view showing an example of a conventional method for injecting pulverized coal fuel. From the injecting lance 3 inserted into the tuyere through the wall of the blow pipe 2 connected to the tuyere 1, A method of injecting charcoal fuel into a blast furnace together with a carrier gas (mainly air) is common. A heat-insulating refractory ring 4 is attached to the inner surface of the tuyere for the purpose of suppressing a decrease in the blowing temperature and adjusting the tuyere wind speed.
[0003]
However, in the method of injecting pulverized coal fuel by such a method, the ash derived from pulverized coal is melted by combustion heat in a high temperature atmosphere of 1000 to 1300 ° C., and the refractory for heat insulation and tuyere wind speed adjustment Based on the fact that the ring has a composition similar to that of ash in pulverized coal, there is a phenomenon that the ash adheres to the inner surface of the refractory ring in the state of the melt 5, and the life of the refractory ring is significantly increased. It was decreasing. Occasionally, it was often found that the ring was damaged before the scheduled rest days for repairs that were carried out every few months for continuous operation of the blast furnace, and the blast furnace had to be operated without the effect of ring attachment. For this reason, the tuyere heat insulation effect due to the refractory ring is not obtained, resulting in a large energy loss, and the adjustment of the tuyere wind speed collapses, causing an imbalance in the circumferential direction of the furnace, resulting in deterioration of the furnace condition. There were problems such as mixing.
[0004]
In order to prevent the ash from adhering to the refractory ring (or tuyere inner peripheral surface), the following conventional techniques have been proposed as countermeasures. (1) In Japanese Patent Laid-Open No. 58-171509, the position of the tip of the lance is adjusted so as to reduce the pulverized coal combustion rate from the blowing lance to the tip of the tuyere, (2) Japanese Patent Laid-Open No. 1-259110 In the publication No. 4, the high pressure gas is blown to the inner peripheral surface of the tuyere to prevent ash from adhering. (3) In Japanese Patent Laid-Open No. 4-26802, the tip of the lance is bent parallel to the longitudinal direction of the blow pipe, There has been proposed a method in which the flow of pulverized coal set in a position coincident with the axial center of the gas is aligned with the flow at the center of the hot air.
[0005]
[Problems to be solved by the invention]
However, the above method has the following problems. The application condition of (1) is that the inner diameter of the blow pipe and the tuyere is the same and there is no step and the inner diameter of the blow pipe is 130 to 180 mm and the tuyere and blow The tip of the lance is set 100 to 350 mm upstream from the pipe boundary, and the problem cannot be solved when a ring is attached for the purpose of adjusting the tuyere wind speed in addition to the suppression of the air temperature drop. For example, when the inner diameter of a tuyere connected to a blow pipe with an inner diameter of 180 mm that is suitable for low-pressure loss is reduced to 110 mm by attaching a ring, a stagnant area of airflow occurs at the step, causing ash adhesion. It has not been suppressed so much.
In (2), since a separate adhesion preventing means is employed, pressure loss occurs in the blow pipe, and wear occurs in the raised portions, which is rather problematic. In (3), once clogged by pulverized coal in the lance, the lance cannot be pulled out and replaced. Therefore, there is a major disadvantage that the normal state cannot be recovered unless the wind is stopped and the tuyere is removed.
The present invention eliminates the problems of the prior art, prevents the adhesion of ash, and on the inner surface of the tuyeres of a pulverized coal blowing blast furnace, is a heat-insulating refractory for the purpose of suppressing a decrease in blowing temperature and adjusting the tuyere wind speed. The present invention provides a lance mounting position determination method for blowing blast furnace pulverized coal to which a ring can be attached.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides a mounting position of a pulverized coal blowing lance provided with a tip protruding from a blast furnace tuyere hole with a refractory ring installed, and the tip of the lance is within the range of the ring longitudinal direction. And the position of the ring inner peripheral surface separated by a distance satisfying the condition of the following formula (1), and the spread of pulverized coal ejected from the lance according to the volatile content of various pulverized coal brands The angle θ is calculated from the following equation (2), and the mounting position of the pulverized coal blowing lance can be strictly adjusted based on the obtained calculated value.
X ≧ L · tan θ (1)
X: shortest distance (mm) between the axis of the tip of the lance for injecting pulverized coal 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 the lance (°)
θ = [ Spread angle of pulverized coal when volatile content is 35% by weight ] −0.233 × [ % VM ] + 0.00667 × [ % VM ] ² (2)
However, [ % VM ] : The volatile content (% by weight) of pulverized coal, and the range is from 20% to 45% by weight.
[0008]
Embodiment
The pulverized coal blown from the lance is accelerated by the flow of the blown gas, and gradually diffuses in the cross-sectional direction as it flies in the longitudinal direction of the tuyere in a follow-up manner. FIG. 1 schematically shows the pulverized coal flow blown from the lance and the state of diffusion. Here, the spread angle θ of the pulverized coal ejected from the lance is important, but this value is for example the actual tuyere of the blast furnace, and the ash content to the refractory ring under various conditions of changing the mounting position of the lance. This can be confirmed by examining the adhesion status.
[0009]
Therefore, the lance mounting is adjusted so that the tip of the lance is positioned within the longitudinal range of the refractory ring where no abnormal flow occurs in the blast gas flow, and the spread angle of the pulverized coal ejected from the lance is taken into account. If a sufficient distance between the tip of the lance and the inner peripheral surface of the refractory ring is taken, a heat-insulating refractory aimed at suppressing a decrease in the blowing temperature and adjusting the tuyere wind speed even in a pulverized coal blowing blast furnace It becomes possible to attach the ring with peace of mind.
[0010]
【Example】
Below, the spread angle θ of pulverized coal ejected from the lance is investigated based on the test results for 10 blast furnace tuyere with an internal volume of 2650 m ³ , and the conditions under which ash does not adhere to the refractory ring are obtained. The contents of the case will be described.
The average blowing conditions and pulverized coal blowing conditions during the blast furnace test period are as follows.
<Blower condition>
Air flow: 3900 Nm ³ / min
Air temperature: 1160 ° C
Tuyere wind speed: 230m / s
Flow height inner diameter: 180mm
Ring inner diameter: 110mm
<Pulverized coal blowing conditions>
Pulverized coal injection flow rate: 41 t / h (PC ratio: 165 kg / 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 taken measures such as reducing the lance insertion angle and extending the tip of the lance further to the inside of the furnace for the purpose of measures against ash adhesion to the inner surface of the tuyere or tuyere ring, Due to design limitations, the lance angle for a typical blast furnace is almost the same as 10-12 °, and there is no difference between domestic blast furnace manufacturers. In most blast furnaces in Japan, the average wind speed of hot air in the tuyere is adjusted within the range of 210 to 245 m / s, which is on the high flow rate side, and there is not much difference in the tuyere wind speed between blast furnaces.
Therefore, the investigation of the effect of the above two variables on the spread angle θ of pulverized coal was omitted, and it was assumed to be constant in this actual furnace test.
[0011]
In the actual furnace test, lances with an outer diameter of 19.4 mm were attached to 10 tuyere so that the relationship between the lance attachment conditions X and L (see FIG. 1) was different. The state of ash adhesion to the refractory ring was confirmed by visual observation from a viewing window provided at one end of the furnace outside in the longitudinal direction of the blowpipe or by a tuyere camera attached to the viewing window in order to observe the situation inside the tuyere. FIG. 2 summarizes the obtained results. The pulverized coal used here is a representative brand most frequently used, and the components are volatile matter = 35% by weight and ash content = 9% by weight. From the results in the figure, it can be seen that the result of the presence or absence of ash adhesion may be stratified by a boundary line where the spread angle θ of pulverized coal is 5 °.
However, in exceptional cases, ash deposits were observed under all conditions at a position upstream of one end of the refractory ring outside the furnace.
[0012]
In recent years, there has been a problem in terms of hardware that it is inevitable to use multiple types of coal for the purpose of eliminating fluctuations in supply and demand for each pulverized coal. Therefore, it is necessary to cope with the use of pulverized coal containing a high volatile content other than the above representative brands. In particular, when pulverized coal having a high volatile content is used, the dispersion in the tuyere cross-sectional direction becomes larger than that of the low volatile content pulverized coal due to a rapid release of the volatile content near the tip of the lance.
With respect to the spread angle θ of the pulverized coal, an actual furnace test was also conducted for two representative brands of low volatile content and high volatile content. The volatile content of each coal type is 20% by weight and 45% by weight, and the actual furnace test results are shown in FIG. 3 and FIG. Based on this figure, the spread angle θ of the pulverized coal was found to be 3 ° for the former and 8 ° for the latter. Moreover, if the results of the spread angle θ obtained by combining the test results of pulverized coal with various other volatile contents are arranged, θ is expressed by the relationship of the following equation as a function of the volatile content VM. The
θ = [Spread angle of pulverized coal when volatile content is 35% by weight] −0.233 × [% VM] + 0.00667 × [% VM] ²
[0013]
FIG. 5 shows the average life of the refractory ring when the tip of the lance is at a conventional position, when it is a position that satisfies the lance mounting conditions of the present invention, and when pulverized coal is not blown. From the figure, the ring average life when the tip of the lance is at the conventional position is about 45 days, whereas it is extended to more than 300 days when the installation conditions of the present invention are satisfied, It can be seen that a long life comparable to that obtained when the process is not performed is obtained.
[0014]
【The invention's effect】
As described above, according to the method of the present invention, a sufficient distance between the tip of the lance and the inner peripheral surface of the refractory ring is taken in consideration of the spread angle of the pulverized coal ejected from the lance, and various brands of pulverized coal. In order to adjust the lance installation position based on the spread angle of the pulverized coal calculated according to the volatile content of the pulverized coal, heat insulation for the purpose of suppressing air temperature drop and adjusting the tuyere wind speed even in the pulverized coal blowing blast furnace The refractory ring can be installed with peace of mind, and the life can be extended to the same level as when pulverized coal is not injected.
[Brief description of the drawings]
FIG. 1 is a diagram schematically showing a pulverized coal flow blown from a lance and a state of diffusion.
FIG. 2 is a diagram of test results for investigating the presence or absence of ash adhesion at various lance attachment positions when pulverized coal with a volatile content of 35% by weight is used.
FIG. 3 is a diagram of test results for examining the presence or absence of ash adhesion at various lance attachment positions when pulverized coal having a volatile content of 20% by weight is used.
FIG. 4 is a diagram of test results for examining the presence or absence of ash adhesion at various lance mounting positions when pulverized coal with a volatile content of 45% by weight is used.
FIG. 5 is a diagram showing the average life of a refractory ring.
FIG. 6 is a schematic view showing an example of a conventional method for injecting pulverized coal powder fuel.
[Explanation of symbols]
1: tuyere 2: blow pipe 3: pulverized coal blowing lance 4: refractory ring 5: deposit X derived from ash in pulverized coal X: refractory ring inner peripheral surface from the shaft core of the lance for pulverized coal blowing Shortest distance L: Distance from tuyere tip to lance tip θ: Spread angle of pulverized coal ejected from lance

Claims (1)

The mounting position of the pulverized coal injecting lance provided in the blast furnace tuyeres with the refractory ring inside is set so that the tip of the lance is in the range in the longitudinal direction of the ring, and the following (1 ) The distance of the distance satisfying the condition of the formula is calculated, and the spread angle θ of the pulverized coal ejected from the lance is calculated from the following formula (2) according to the volatile content of various pulverized coal brands. A lance attachment position determination method for blast furnace pulverized coal injection, characterized in that the attachment position of a pulverized coal injection lance is adjusted based on the calculated value obtained.
X ≧ L · tan θ (1)
X: shortest distance (mm) between the axis of the tip of the lance for injecting pulverized coal 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 the lance (°)
θ = [ Spread angle of pulverized coal when volatile content is 35% by weight ] -0.233x [ % VM ] + 0.00667x [ % VM ] ²     ... (2)
However, [ % VM ] : The volatile content (% by weight) of pulverized coal, and the range is from 20% to 45% by weight.

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