JPS6143405B2 - - Google Patents

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a method for adjusting the thickness of a charge layer at the mouth of a blast furnace, which adjusts the thickness of ore and coke layers deposited at the mouth of a blast furnace. It is something.

(Prior art) Normally, ore and coke are alternately layered at the mouth of a blast furnace. (hereinafter referred to as O/C) is an extremely important factor closely related to the thermal efficiency of the furnace and the condition of the furnace.

If this O/C is too large, it will cause operational troubles such as poor descending condition of the charge and damage to the tuyere, but if it is too small, the amount of gas rising in the surrounding area will increase and As a result of increased heat diffusion from the walls, a problem arises in that thermal efficiency becomes extremely poor. For this reason, blast furnace operators adjust the O/C as appropriate by changing the setting position of the armor plate attached to the bell charging device or the distribution chute of the bellless charging device.

(Problems to be Solved by the Invention) The above-mentioned armor plate and distribution chute are primarily intended to adjust the thickness ratio of the ore layer and coke layer in the radial direction of the furnace, and can be adjusted by changing their inclination. However, since the tilt angle has to be set discontinuously in only a few steps, the O/C also changes only discontinuously. Further, although methods for correcting this discontinuous change have been studied, such problems have not yet been overcome.

Therefore, the present inventors investigated the radial distribution of the descending speed of the charge deposited at the furnace mouth using a 1/5 scale model of the blast furnace mouth equipped with a bell armor device and a bellless device. . This experimental device was equipped with a bottom plate to allow the sediment layer to descend, in order to successfully approximate the descending behavior of the sediment layer (including ore layer and coke layer, hereinafter the same) in a blast furnace. Then, the rate of descent of the surface of the sediment layer was determined by multiplying the ratio of the distance of descent of the surface of the sediment layer to the distance of descent of the bottom plate by the rate of descent of the bottom plate.

As a result of the experiment, the rate of descent of the surface of the deposited layer was found to be
0.9), the rate of descent was the same as that of the bottom plate, indicating a uniform descent, whereas the peripheral part (dimensionless radius 0.9
~1.0) region was found to be faster than other regions. Note that the dimensionless radius of 0.9 corresponds to the measuring position.

Furthermore, as a result of investigating the cause of the increased rate of descent in the peripheral area, we found that the rate of descent in the peripheral area, especially the furnace wall, depends on the surface inclination angle θ of the deposited layer, as shown in Figure 1. It became clear that there was. The horizontal axis in Figure 1 indicates the surface inclination angle θ of the deposited layer between the measuring position and the furnace wall. The case is shown as negative. Further, the vertical axis indicates the descending speed ratio Dw ^* , which is the ratio of the descending speed of the surface of the deposited layer at the furnace wall to the descending speed of the bottom plate. As is clear from the figure, the falling velocity ratio Dw ^* increases as the surface inclination angle θ increases for both ore and coke.

The present invention has been made in view of the above-mentioned conventional problems and experimental results, and its purpose is to provide a blast furnace that can accurately adjust the charge layer thickness ratio, that is, O/C, at the mouth wall of the blast furnace with an extremely simple operation. An object of the present invention is to provide a method for adjusting the thickness of the charge layer on the wall of the furnace mouth.

(Structure of the Invention) In order to achieve the above object, the present invention provides a method for increasing the size of the ore layer on the furnace wall when charging a charge into the mouth of a blast furnace having a bell armor device or a bellless device. , the descending distance of the ore is reduced to increase the descending distance of the coke, while when increasing the coke layer on the furnace wall, the descending distance of the coke is reduced and the descending distance of the ore is increased. .

(Example) Next, a method for adjusting the charge layer thickness of the blast furnace mouth wall according to the present invention will be described.

FIGS. 2 and 3 schematically show the state of an ore layer and a coke layer immediately after charging in the vicinity of the blast furnace mouth, and the meanings of each symbol in the figures are as follows.

θ _OD : Surface inclination angle between the measuring position of the ore layer immediately after charging and the furnace wall θ _CD : Surface inclination angle between the measuring position of the coke layer and the furnace wall immediately after charging θ _p : Surface inclination angle between the measuring position of the ore layer that has reached the charging start stock level and the furnace wall θ _c : Surface between the measuring position of the coke layer that has reached the charging starting stock level and the furnace wall Slope angle Lo′: Drop distance of the ore layer at the measuring position Lc′: Drop distance of the coke layer at the measuring position Lo: Thickness of the ore layer at the measuring position Lc: Drop distance of the coke layer at the measuring position Layer thickness Low: Thickness of the ore layer at the furnace wall that has reached the charging starting stock level Lcw: Layer thickness of the coke layer at the furnace wall that has reached the charging starting stock level SL: This is the charging starting stock level.

Therefore, the O/C ( (already mentioned) can be expressed by the following formula.

Low/Lcw={Rx(tazθ _OD −tanθ _CD )−Lc′(1
−Dwc ^* )Lo′×(1−Dwo ^* )＋Lo}/{Rx
(tanθ _CD −tanθ _OD )−Lo′(1−Dwo ^* )+
Lc′ (1−Dwc ^* ) + Lc} …(1) where, Dwo ^* : Falling speed ratio of ore (-, i.e., dimensionless) Dwc ^* : Falling speed ratio of coke layer (-), and other symbols are Same as above, the unit is
Low, Lcw, Rx, Lc, Lo, Lc _× Lo′ is (m),
θ _OD and θ _CD are (°). By the way, the above 1st
In the figure, Dw ^* on the vertical axis includes Dwo ^* and Dwc ^* , and θ on the horizontal axis includes θo and θc.

Note that the first term in the denominator and numerator of equation (1) is ore, which depends on the difference in inclination angle between coke and ore immediately after charging.
The thickness of the furnace wall of each coke layer is shown, the second term shows the thickness of the furnace wall of each of ore and coke considering the descent distance, and the third term is the thickness of the furnace wall of each of coke and ore considering the descent speed. Indicates the partial layer thickness.

Next, by substituting the relational expression Dwo ^* =0.0043θ _OD +1.0355 …(2) Dwc ^* =0.0043θ _CD +1.0355 …(3) found from Figure 1 into equation (1), we get Low/Lcw={ R×(tanθ _OD −tanθ _CD )−Lc′(−
0.0043θ _CD −0.0355)−Lo′(−0.0043θ _OD −
0.0355) + Lo} / {Rx (tanθ _CD −tanθ _OD )
Lo′(−0.0043θ _OD −0.0355)+Lc′(−0.0043θ _CD
−0.0355)+Lc} …(4).

Therefore, we measured the measuring position of the deposited layer immediately after charging and the depth at the furnace wall, and from these measurements we calculated Lo, Lc.
In addition to calculating θ _OD and θ _CD , the descending distance of the ore layer and coke layer at the measuring position is calculated.
By measuring Lo′ and Lc′ and substituting each value into equation (4), we get
Since Rx is constant, O/C (=Low/Lcw) can be determined.

Therefore, as an example, Rx=0.4m, Lo=Lc=
Under the conditions of 0.5m, θ _CD = 20°, the relationship between Lc′ and O/C is expressed as θ _OD = 10°, 20°, 30° using equation (4).
When we investigated the case of 20°, we obtained the results shown in Fig. 4. As shown in the figure, as the charging start stock level of the coke layer is increased and the descending distance Lc' of the coke layer is lengthened, the sum of the descending distances of the ore layer and the coke layer must remain constant. (in this example, Lo′+Lc′=
1.0m), O/C gradually increases as the descending distance Lc′ of the ore layer becomes shorter, and by changing these values (Lo′, Lc′) appropriately, O/C can be effectively controlled. You can see that it can be adjusted.

Furthermore, we estimated O/C from equation (4) by variously changing the descent distance Lc', and compared this estimated value with O/C measured in an actual blast furnace, as shown in Figure 5. We were able to obtain results with good approximation accuracy.

Here, the horizontal axis in FIG. 5 shows the O/C estimated by the method according to the present invention, that is, the equation (4), and the vertical axis shows the O/C measured in an actual blast furnace.

In addition, although the above-mentioned example shows the case where ore and coke are charged alternately every time, the present invention is not limited to this, and in addition to this, each of the above-mentioned charges may be divided into multiple times. It was also confirmed that it could be fully applied even when charged.

(Effects of the Invention) As is clear from the above description, according to the present invention, O/C is appropriately adjusted by changing the descending distance between the ore layer and the coke layer.

Therefore, the O/C can be adjusted with high precision by extremely simple operation and by obtaining the above estimation formula, and it has the effect that a stable blast furnace condition can be maintained.

[Brief explanation of the drawing]

Figure 1 shows the experimental results on the relationship between the surface inclination angle of the deposited layer (ore and coke) and the descent rate ratio. Figures 2 and 3 show the ore layer and coke in the vicinity of the blast furnace mouth. Partial sectional view showing the state immediately after charging the layer (solid line) and the state when the charging start stock level is reached (dashed line), No. 4
The figure shows the relationship between the descending distance of coke or ore and the layer thickness ratio O/C at the furnace wall, and Figure 5 shows the relationship between the estimated O/C results and the actual measurement results. θ _OD , θ _CD ... Surface inclination angle of ore layer and coke layer immediately after charging, θo, θc ... Surface inclination angle of ore layer and coke layer when charging start stock level is reached, Lo', Lc'... Inspection Descending distance of the ore layer and coke layer at the scale position, Lo, Lc...thickness of the ore layer and coke layer at the measuring position, Low, Lcw...furnace of the ore layer and coke layer that have reached the charging start stock level Layer thickness at the wall, θo′, θc′…surface inclination angle of the ore layer and coke layer that have reached the charging start stock level,
SL...Charging start stock level, O/C...Layer thickness ratio (Low/Lcw).

Claims (1)

[Claims] 1 When charging the charge into the mouth of a blast furnace where the bell armor device has a bellless device, if the ore layer on the furnace wall is to be enlarged, the descending distance of the ore should be shortened to increase the descending distance of the coke. On the other hand,
A method for adjusting the thickness of the charge layer at the mouth wall of a blast furnace, characterized in that when increasing the coke layer at the furnace wall, the descending distance of the coke is reduced and the descending distance of the ore is increased.