JPS62260010A - Charging method of mixed raw material for bell-less type blast furnace - Google Patents

Abstract

PURPOSE:To stabilize a blast furnace operation by controlling the ratio between an iron source and reducing agent in mixed raw materials to be charged and controlling the operation of a distributing chute, thereby controlling the charging direction and heaping angle of the mixed raw materials. CONSTITUTION:The mixed raw materials for iron source and reducing agent fed out of storage tanks 13, 14 are charged through a charging belt conveyor 2 and a furnace top bunker 6 into the bell-lens type blast furnace 1 via the distributing chute 10. The weight ratio of the iron source and reducing agent in the mixed raw materials is controlled to be constant or with lapse of time by adjusting feeding valves (not shown) of the tanks 13, 14, a lower gate valve 8 of the bunker 6, etc. The angle thetaof inclination of the distributing chute 10 is so controlled as to increase in an arrow direction so that the raw materials are charged in the furnace wall direction from the central part of the furnace. At least one of the angle of inclination of the distributing chute 10, the number of swiveling at the respective angles of inclination and the lower gate valve are controlled at the same instant to control the heaping angle of the mixed raw materials after charging in the furnace to <=20 deg., by which the mixed raw materials are uniformly mixed in the furnace.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a method for charging raw materials into a bellless blast furnace, and more specifically, the present invention relates to a method for charging raw materials into a bellless blast furnace. When charging, the deposition angle of the charging material in the furnace, the weight ratio of the iron source to the reducing agent in the radial direction (hereinafter referred to as ro/CJ)
The present invention relates to a method for charging mixed raw materials with the aim of improving the controllability of so-called charge distribution, such as distribution and radial particle size distribution.

(Prior art and its problems) In blast furnace operation, the O/
It is necessary to appropriately control the radial distribution of C1 grain size, etc., maintain the radial gas flow distribution and heat flow ratio distribution within the furnace within a predetermined range, and stably reduce and melt the ore.

By the way, in the conventional so-called layered charging method in which iron source and reducing agent are charged alternately into a furnace, the iron source softens and fuses in a high temperature range of 1000°C or higher, forming a so-called cohesive zone. It was important to maintain the cohesive zone shape within the proper range as the gas is redistributed radially through the coke layer. Since the cohesive zone shape is determined by the radial gas flow distribution and heat flow ratio distribution in the furnace, charge distribution control has been important as a means of controlling the cohesive zone shape.

However, in actual operation, it is difficult to properly and accurately control the cohesive zone shape using charge distribution control, and it is often the case that the cohesive zone is lower than necessary in the middle part or the cohesive zone is formed on the furnace wall. If the value of the blast furnace was lower than necessary, an abnormal unloading phenomenon (slip/hanging) of the raw material in the furnace occurred, and stable operation of the blast furnace could not be achieved.

In order to solve this problem, Kokubun et al.
No., 1984, p. 350, proposes a method in which the iron source and reducing agent are completely mixed and charged into the furnace. In this completely mixed charging, the heat transfer area of the iron source increases greatly, and the width of the cohesive zone is estimated to be about 1/100 of that of layered charging.
In fact, it can be considered that there is no cohesive zone. Therefore, the problem of worsening loading due to abnormal cohesive zone shape, which was a problem during layered charging, disappears when completely mixed charging is performed. Furthermore, there is also the advantage of improved air permeability during completely mixed charging. That is, although the air permeability in the shaft portion is not much different from that when charging in layers, the air permeability in the lower part of the furnace is greatly improved by improving the air permeability of the fusion layer. This improvement in the permeability of the cohesive layer during mixed charging is due to the fact that the slag whose main component is unreduced FeO in the iron source immediately undergoes a melt-reduction reaction with the adjacent coke, resulting in an increase in the hold up of the FeO-based slag. This is because the amount decreases. By improving air permeability, not only can the stable operation of the blast furnace be achieved, but also the amount of air that can be blown into the furnace increases, making it possible to increase the production volume of the blast furnace.

Although this method of completely mixing the iron source and reducing agent and charging the mixture into the furnace has many advantages, it has not been applied to actual operations due to the following problems.

The first problem is that completely mixed raw materials re-separate when entering the furnace, and are segregated and deposited inside the furnace.
/C distribution is not uniform.

FIG. 7 shows a schematic diagram of a material charging device for a bellless blast furnace intended to be used for conventional complete mixed charging. The mixed raw material 3 conveyed to the top of the blast furnace 1 by the belt conveyor 2 is temporarily stored in the top bunker 6 through the upper gate valve 4 and the upper seal valve 5, and the charge in the blast furnace is unloaded. When the predetermined stock level 7 to be replenished is reached, the lower gate valve 8 and the lower seal valve 9 for adjusting the charge flow rate are opened, and the mixed raw material 3 in the furnace top bunker 6 is passed through the distribution chute 10. It is charged into the furnace.

However, as shown in Figure 7, the tilting angle (θ) of the distribution chute is large at the beginning of charging the mixed raw material and small at the end of charging, so that the mixed raw material is directed from the furnace wall toward the center of the furnace. In order to charge, the mixed raw material this time is charged onto the slope formed by the mixed raw material that was previously loaded into the furnace, and the iron source and reducing agent are separated on the slope, as shown schematically in Figure 7. As shown, the reducing agent 11 is unevenly distributed in the furnace center and the furnace wall, and the O/C of the furnace center and the furnace wall inevitably decreases.
It is not possible to obtain a uniform O/C distribution in the radial direction.

The second problem is that fine adjustment of the radial O/C distribution is difficult. In other words, in the conventional fully mixed charging method, the raw material supplied to the distribution chute is completely mixed with the iron source and reducing agent in advance, and the gas flow distribution and unloading rate distribution in the furnace are constant. If so, the radial O/C in the furnace
There can only be one distribution. However, in actual operation, in order to prevent the wear and tear of the furnace wall bricks, there are cases where it is desired to reduce the O/C distribution to reduce the furnace wall heat load, that is, to make the O/C slightly higher than the average value at the furnace wall. In some cases, it is desired to lower the ○/C in the center from the average value in order to ensure gas flow in the center. In such cases, it is difficult to fine-tune the 070 distribution in the radial direction using the conventional complete charging method in which the iron source and reducing agent are completely mixed and charged into the bunker in a uniform state.

As detailed above, in the conventional method of charging mixed raw materials into a bell-less blast furnace, the raw materials in the furnace form slopes, resulting in uneven radial 0/C distribution and radial 0/C distribution.
There was a problem in that fine adjustment of the /C distribution was difficult.

The present invention was made in order to solve all of the above-mentioned problems regarding the conventional complete mixing charging method, and the first problem is that the radial zero 0.
In order to eliminate the non-uniformity of /C distribution, the tilting angle of the distribution chute is controlled to charge the mixed raw material from the center of the furnace toward the furnace wall, and the tilting angle of the distribution chute and each tilting angle are The second problem is to control at least one of the number of revolutions in the furnace and the opening degree of the lower gate valve so that the deposition angle of the raw material in the furnace after charging does not exceed 20 degrees. In order to overcome the difficulty in fine-tuning the radial O/C distribution, the O
The purpose is to control /C over time.

(Means for Solving the Problems) The present invention provides a method for charging a mixed raw material of an iron source and a reducing agent into a bellless blast furnace, in which the weight ratio of the iron source and reducing agent in the mixed raw material is kept constant or over time. and the tilting angle of the distribution chute to charge the mixed raw material from the center of the furnace toward the furnace wall, and the deposition angle of the mixed raw material after production in the furnace does not exceed 20 degrees. This is a mixed raw material charging method for a bellless blast furnace, the gist of which is to control at least one of the tilting angle of the distribution chute, the number of turns at each tilting angle, and the opening degree of the lower gate valve.

The configuration of the present invention will be explained based on FIG. The raw material is conveyed to the top of the furnace by a belt conveyor 2, and the upper gate valve 4
, the charge is temporarily stored in the top bunker 6 through the upper seal valve 5, and when the level of the charge in the blast furnace reaches a predetermined stock level 7, the lower gate valve 8 and the lower seal valve 9 are opened and the charge is distributed. The flow of charging raw materials into the furnace through the chute 10 is the same as in the conventional invention.

The feature of the present invention is that the tilting angle of the distribution chute is gradually increased from small to large as shown by the arrow in FIG. Set a schedule, charge the mixed raw materials from the center of the furnace toward the furnace wall, and during charging, at least the following: the tilting angle of the distribution chute, the number of turns at each tilting angle, and the opening degree of the lower gate valve. One is to control. The reason why the stacking angle of the raw material after charging is set to 20 degrees or less is that if it is 20 degrees or less, the rolling of the raw material during charging can be practically ignored, and it is considered that no slope will be formed in practice. , this value of 20 degrees or less was obtained through experiments by the inventors.

That is, the present inventors manufactured a full-scale model outside the furnace, changed the deposition angle of the coke layer variously, charged ore, and measured the amount of mixed layer formation and the radial particle size distribution. Examples of the results are shown in FIGS. 2 and 3. Figure 2 shows the deposition angle of the coke layer and the increase in the thickness of the coke layer in the center (
Increase in thickness of single coke layer + 172 x increase in thickness of mixed layer)
As is clear from the figure, the coke deposition angle reaches a boundary of 20 degrees, and when it exceeds this, the thickness of the coke layer in the center increases significantly due to ore charging.
It turns out that anything less than that can be ignored in practice. That is, in order to improve the controllability of O/C distribution in the radial direction, it is necessary to set the stacking angle of the raw material after charging to 20 degrees or less.

FIG. 3 is a diagram showing the relationship between the deposition angle of the coke layer and the grain size of the ore in the center (the test was carried out using all sintered ore). The coke deposition angle has a boundary of 20 degrees, and when this is exceeded, the ore grain size in the center increases significantly due to reclassification on the slope, but below this, the ore grain size does not increase in practical terms. It is clear that it is so small that it can be ignored. The reason is,
This is thought to be because the stacking angle of the slope is sufficiently small, and even if a pile of charge material corresponding to the swirl is formed during charging, the raw material does not move along the slope. That is, in order to improve the controllability of the particle size distribution in the radial direction, it is necessary to set the stacking angle of the raw material after charging to 20 degrees or less.

As described above, in order to significantly improve the control of the radial O/C distribution and the radial particle size distribution, the deposition angle on the surface of the raw material after charging needs to be 20 degrees or less.

Incidentally, the deposition angle of the raw material is actually measured, and whether or not the deposition angle is 20 degrees or less can be confirmed using a profile meter normally installed at the top of the blast furnace. Profile meters can be of the contact type, in which a heavy cone attached to the tip of a wire is lowered onto the surface of the deposited raw material, or the profile meter can be a contact type, in which a heavy cone attached to the tip of a wire is lowered to the surface of the deposited material, or a profile meter is a contact type, in which a heavy cone attached to the tip of a wire is lowered to the surface of the deposited material. It may also be a non-contact method that receives and measures the reflected waves oscillated from an oscillator and reflected on the raw material deposition surface.

If the stacking angle of the raw material after charging is likely to exceed 20 degrees, control at least one of the tilting angle of the distribution chute, the number of turns at each tilting angle, and the opening degree of the lower gate valve, The deposition angle is controlled to be maintained at 20 degrees or less while measuring the profile using the profile meter and confirming its effectiveness.

Further, in the method of the present invention, the tilting angle of the distribution chute is gradually increased, but this cannot be easily invented even by a person skilled in the art.

That is, by gradually decreasing the tilting angle of the distribution chute (in the conventional method, the direction of the moment caused by the distribution chute load and the material load on the distribution chute,
Since the distribution chutes are tilted in the same direction, the shaft torque applied to the tilting motor is small and therefore within the allowable rated torque range of the motor. On the other hand, in the method of the present invention in which the tilting angle of the distribution chute is gradually increased, the direction of the moment generated by the distribution chute load and the load of the raw material on the distribution chute is opposite to the direction of the tilting of the distribution chute. Therefore, since the shaft torque applied to the tilting motor is large and expected to exceed the rated torque of the motor, an invention such as the present invention in which the tilting angle of the distribution chute is gradually increased has not been made.

However, in carrying out the present invention, we actually measured the required torque of the motor shaft when the tilting angle of the distribution chute was gradually increased, and as shown in Figure 4, it was found that if the capacity of the conventional motor was increased by about 20%, it could be used regularly. It has been found that the tilting angle of the distribution chute can be gradually increased within the distribution chute tilting angle range.

Therefore, the present invention in which the tilting angle of the distribution chute is gradually increased can be implemented with a small investment.

The second feature of the present invention is to control over time the ○/C of the mixed raw material of iron source and reducing agent supplied to the distribution chute. The following means are suitable as the control means.

■Method of controlling when discharging from the furnace top banger.

The iron source and the reducing agent are stored in separate furnace top bunkers 6, and when the level of the charge in the blast furnace reaches a predetermined stock level 7, the iron source and the reducing agent are stored in the lower part of each of the furnace top bunkers 6. The iron source and the reducing agent are simultaneously cut out by opening the gate valve 8 and the lower seal valve 9, and are supplied to the distribution chute 10 in a mixed state.

At this time, if the opening degree of the lower gate valve 8 is controlled over time,
The O/C in the mixed raw material supplied to the distribution chute 10 can be controlled from time to time. Further, in order to completely mix the iron source and the reducing agent in the mixed raw material supplied to the distribution chute 10, a mixing device 12 may be installed at the position shown in FIG.

Note that the type of mixing device does not matter as long as it has this function.

(2) Method for controlling the time of cutting from the storage tank Each raw material is simultaneously cut out from the storage tanks 13 and 14 in which the iron source and the reducing agent 11 are stored, and conveyed to the top of the furnace by the charging belt conveyor 2. At this time, if the opening degree of each gate valve of the storage tanks 13 and 14 is controlled over time, the O/C in the mixed raw material supplied to the distribution chute 10 via the furnace top bunker 6 can be controlled over time. can do. However, in this case, since the iron source and reducing agent are not completely mixed on the charging belt conveyor 2, a stone box 15' or the like is installed in the furnace top bunker 6 to supply the iron source to the furnace top bunker 6. During the passage of the raw materials, the raw materials collide once to promote mixing of the iron source and the reducing agent. Of course, if it is a mixing device, the type is not specified. Next, a funnel flow occurs when the raw material is discharged from the furnace top bunker 6, and the O/C change over time of the mixed raw material when it is charged into the furnace top bunker 6, and the mixture discharged from the furnace top bunker 6. It is expected that the O/C changes over time in the raw materials will not match. Therefore, it is necessary to take measures such that the materials are discharged from the furnace top bunker 6 in the order in which they are charged into the furnace top bunker 6. FIG. 1 shows an example in which a cone 16 is installed for this purpose. Of course, it goes without saying that other means of mass flow may also be used. Furthermore, there is also a method of separately measuring the O/C change over time at the time of discharge, and feedback controlling the change over time of O/C at the time of cutting out from the storage tank.

(Function) The present invention provides a method for charging a mixed raw material of an iron source and a reducing agent into a Hellless blast furnace, in which the weight ratio of the iron source and reducing agent in the mixed raw material is controlled at a constant rate or over time, and The tilting angle of the distribution chute is controlled so that the mixed raw material is charged from the center of the furnace toward the wall, and the tilting angle of the distribution chute is controlled so that the deposition angle of the mixed raw material after charging into the furnace does not exceed 20 degrees. , the number of rotations at each tilt angle, and the opening degree of the lower gate valve, so it controls the stacking angle of the charging material in the furnace, the 070 distribution in the radial direction, the particle size distribution in the radial direction, etc. The so-called charge distribution can be controlled with precision.

(Example) In order to confirm the effects of the present invention, a full-scale model was manufactured outside the furnace and a charge distribution test was conducted.

The charging raw material used in the test was the same as that used in an actual blast furnace. In addition, the raw material charging conditions in the test were the same as those in an actual blast furnace, except that there was no unloading and no air blowing. Also, 0 in the radial direction
70 distribution was measured by solidifying the raw material after the charging test with epoxy resin and taking it out of the apparatus.

■Uniform radial 0/C distribution example The schedule for the tilting angle of the distribution chute in the conventional mixed charging method is (1, ■, 2.2.3.3.4.4.5.
5.6.6.7.7).

The numbers in parentheses indicate the magnitude and order of the tilting angle of the distribution chute, and the smaller the number, the larger the tilting angle of the distribution chute. The number of turns is 14. On the other hand, in the present invention, in order to keep the deposition angle of raw materials in the furnace to 20 degrees or less, the distribution chute tilting angle schedule is (10, 9, 9, 8, 7, 6, 5, 4, 3, 2, 2,1
, 1, 1). As a result, the deposition angle of the raw materials after charging was 16 degrees at the center and 0 to 5 degrees from the middle to the furnace wall, which was the almost desired deposition angle.

Figure 5 (a) shows the O of the mixed raw material charged into the furnace top bunker.
(B) shows the change in O/C of the mixed raw material supplied to the distribution chute over time, and (C) shows the radial O/C distribution of the mixed raw material in the device. In the conventional method, since the slope is formed, the iron source and reducing agent are separated during charging and O/
C decreases in the center and the furnace wall. On the other hand, in the present invention, since the stacking angle of the raw materials in the furnace could be maintained at 20 degrees or less, the mixed raw materials did not separate during charging, and the angle of 070 degrees in the radial direction
The distribution was almost uniform, demonstrating the effectiveness of the present invention.

In addition, in the mixed raw material preparation method of this example, the iron source and the reducing agent were mixed at the time of cutting from the storage tank, and a stone box and a cone were installed in the furnace top bunker.

■Example in which O/C decreases only in the center area In the conventional mixed charging method, O/C decreases in both the center area and the furnace wall, as shown by the broken line in Figure 5 (C), and only in the center area. On the other hand, in the present invention, as shown in Fig. 6, the O/C of the mixed raw material charged into the furnace top bunker was reduced only at the initial stage of charging ( As a result of lowering the O/C initially supplied to the distribution chute ((b) in the same figure), the O/C is reduced only in the center where raw materials initially accumulate in the equipment. I was able to do it (
Same figure (c)). Note that the schedule for the distribution shoe HtQ movement angle was the same as in (2) above.

(Effects of the Invention) As explained above, the present invention provides a method for charging a mixed raw material of an iron source and a reducing agent into a Hellless blast furnace.
Controlling the weight ratio of the iron source and reducing agent in the mixed raw material at a constant rate or over time, and controlling the tilting angle of the distribution chute to charge the mixed raw material from the center of the furnace toward the furnace wall, The furnace controls at least one of the tilting angle of the distribution chute, the number of turns at each tilting angle, and the opening degree of the lower gate valve so that the deposition angle of the mixed raw material after entering the furnace does not exceed 20 degrees. The so-called charge distribution, such as the stacking angle of the charge material, the O/C distribution, and the radial particle size distribution, can be controlled with high precision.

That is, according to the present invention, separation of the mixed raw material during charging is prevented, and by changing ○/C in the mixed raw material supplied to the distribution chute over time, The 070 distribution in the radial direction within the furnace can be finely adjusted, and this has a great effect on the operation of the blast furnace.

[Brief explanation of drawings]

Figure 1 is a schematic explanatory diagram of the mixed raw material charging method for a bellless blast furnace according to the present invention, Figure 2 is a relationship between the coke layer deposition angle and the coke layer thickness at the center of the furnace, and Figure 3 is a diagram showing the relationship between the coke layer deposition angle and the coke layer thickness at the center of the furnace. Figure 4 is a diagram showing the relationship between the deposition angle and the ore grain size at the center of the furnace, Figure 4 is a diagram showing the relationship between the tilting angle of the distribution chute and the motor shaft torque, and Figures 5 (A) to (C) are the diagrams showing the relationship between the tilting angle of the distribution chute and the ore grain size in the central part of the furnace. A diagram showing the test results of a method of charging mixed raw materials that makes the /C distribution uniform,
FIGS. 6(A) to 6(C) are diagrams showing the test results of the mixed raw material charging method that reduces only the 0/C in the center according to the present invention,
FIG. 7 is a schematic explanatory diagram of a conventional method for charging mixed raw materials into a bellless blast furnace. 1 is a blast furnace, 3 is a mixed raw material, 6 is a furnace top bunker, 8 is a lower gate valve, 10 is a distribution chute, 11 is a reducing agent, and 12 is a mixing device. Patent Applicant: Sumitomo Metal Industries, Ltd. Figure 1 1.1 11 Izu Publishing

Claims (1)

[Claims] (1) In a method of charging a mixed raw material of an iron source and a reducing agent into a bell-less blast furnace, the weight ratio of the iron source and reducing agent in the mixed raw material is controlled at a constant rate or over time, and the distribution chute is tilted. The mixed raw material is charged from the center of the furnace toward the furnace wall by controlling the angle, and the tilting angle of the distribution chute is adjusted at each tilting angle so that the deposition angle of the mixed raw material after loading into the furnace does not exceed 20 degrees. A method for charging a mixed raw material into a bellless blast furnace, characterized by controlling at least one of the number of rotations and the opening degree of a lower gate valve.