JPS62270711A - Method for charging raw material to bell-less type blast furnace - Google Patents

Abstract

PURPOSE:To control the O/C distribution in a radial direction in a bell-less type blast furnace with good accuracy by successively increasing the tilting angle of a distributing chute at the time of charging an iron source and reducing agent into the blast furnace. CONSTITUTION:The tilting angle of the distributing chute 10 is controlled in order to charge the iron source 12 from the furnace wall toward the central part of the furnace in the stage of charging the iron source 12 at the the time of charging the iron source 12 and the reducing agent 11 into the bell-less type blast furnace 1. The tilting angle of the distributing chute 10 is so controlled as to charge the reducing agent 11 from the central part of the furnace toward the furnace wall in the stage of charging the reducing agent 11. At least one among the tilting angle of the distributing chute 10, the number of swivelings at respective angles and the opening degree of a lower gate valve 8 are controlled in such a manner that the heaping angle of a stock level 7 of the reducing agent 11 after the charging does not exceed 20 deg..

Description

[Detailed Description of the Invention] 3. Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a method for charging raw materials in a bellless blast furnace, and more specifically, to a method for charging raw materials into a bellless blast furnace. This invention relates to a raw material charging method aimed at improving the controllability of the weight ratio (hereinafter abbreviated as ro/CJ) distribution of a reducing agent.

(Prior art) 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.

A method of charging raw materials into a conventional bell-less blast furnace will be explained with reference to FIG. FIG. 4 shows a schematic diagram of the raw material charging device at the top of the furnace of a bellless type blast furnace. Once the charge in the blast furnace is unloaded and reaches a predetermined stock level 7 to be replenished, the lower gate valve 8 for adjusting the charge flow rate and the lower seal The valve 9 is opened and the raw material in the furnace top bunker 6 is charged into the furnace through the distribution chute 10.

(Problem to be solved by the invention) However, in the conventional raw material charging method, the O/C in the radial direction
Controllability of distribution was insufficient.

In other words, the O/C distribution in the radial direction is likely to fluctuate due to ■variations in the amount of mixed layer formed when charging the iron source, ■variations in the stacking angle of the raw material, ■variations in the time taken to feed into the furnace, etc. It will be done. Each of them will be explained in detail below.

■ Regarding fluctuations in the amount of mixed layer formed during iron source charging In the conventional material charging method, the tilting angle of the distribution chute (θ in Figure 4: the angle between the bottom of the distribution chute and the axis of the blast furnace) The raw material was charged into the furnace from the wall of the furnace to the center of the furnace by gradually decreasing the angle (angle) from a predetermined angle. Therefore,
In most cases, the surface shape of the raw material after charging was M-shaped or M-shaped as shown in FIG. 4, and in both cases, a slope was formed. For this reason, when the iron source is charged above the reducing agent layer, a part of the surface layer of the reducing agent layer near the iron source falling position is scraped off by the impact energy of the iron source and moves toward the center of the furnace. A mixed layer of iron source and reducing agent is formed in the center and deposited over a wide range of areas.

Regarding the formation of a mixed layer in the bellless charging method, one of the inventors has reported a study using a full-scale model (
"Tetsu to Hagane" Vol. 71, 1985, p. 175). An example of this mixed layer measurement is shown in FIG.

In this measurement example, sintered ore is used as the iron source and coke is used as the reducing agent. In the figure, the broken line shows the surface shape of the coke layer before charging the sintered ore, and the solid line shows the surface shape of the coke layer after charging the sintered ore.

In the vicinity of the center, the coke that was present near the sintered ore falling position on the furnace wall is moved, and a single coke layer and a mixed layer of sintered ore and coke are formed over a wide area. In this way, if the coke layer forms a slope, the surface shape of the coke layer changes when charging sintered ore, and the O/C in the radial direction changes.
The distribution is significantly different from the O/C distribution calculated from the surface shape of the raw material before and after charging the sintered ore. Furthermore, the amount of mixed layer formed is influenced by not only controllable factors such as the distribution chute tilt angle schedule and charging amount, but also disturbance factors such as changes in the particle size composition of the raw material and changes in the surface shape of the coke layer due to changes in the gas flow distribution in the furnace. receive. Therefore, the conventional bellless charging method of forming an inclined surface has insufficient controllability of the O/C distribution in the radial direction.

The second problem with the radial O/C distribution due to the formation of slopes is the variation in the radial O/C distribution due to the variation in the stacking angle of the charged material.
/C distribution is likely to fluctuate.

In other words, when a slope is formed, the surface shape of the raw material changes easily due to fluctuations in the gas flow distribution within the furnace.
Even if raw materials are charged into the furnace with the same tilting angle schedule of the distribution chute and the same charging amount, that is, the same charging conditions, the 0/C distribution in the radial direction is likely to fluctuate.

■Regarding variation in furnace charging time The third problem arises in the conventional charging method in which the distribution chute tilt angle is gradually decreased from large to small, regardless of whether or not a slope is formed. In other words, in the conventional charging method, the raw material is charged from the part where the raw material layer thickness increases per unit time is small, that is, the furnace wall, to the part where the raw material layer thickness increases per unit time, that is, the center part. is included.

For this reason, the outflow characteristics at the lower gate valve change due to changes in the moisture content of the raw material, changes in the particle size composition of the raw material, etc.
When the total charging time into the furnace varies, the layer thickness of the raw material at the center, which is the position at which the raw material is introduced into the furnace at the end of charging, becomes extremely variable.

In the conventional material charging method for bell-less blast furnaces, in which the tilting angle of the distribution chute is gradually decreased from large to small both when charging the iron source and when charging the reducing agent, the radial O/
Controllability of C distribution was insufficient.

The present invention aims to solve the above-mentioned problems and provide a method for charging materials into a bellless blast furnace, which can improve the controllability of the radial O/C distribution in the furnace.

(Means for Solving the Problems) The raw material charging method for a bellless blast furnace according to the present invention is such that when charging the iron source, one of the distribution chutes is charged so that the iron source is charged from the furnace wall toward the center of the furnace. In addition, when charging the reducing agent, the tilting angle of the distribution chute is controlled so that the reducing agent is charged from the center of the furnace toward the furnace wall. The gist 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 so that the angle does not exceed 20 degrees.

In the present invention, the following method was adopted to solve the above-mentioned problems.

That is, in order to prevent the variation in the amount of mixed layer formation, which is the first problem, the conditions under which the mixed layer itself is not formed,
In other words, the goal is to create conditions under which slopes will not form.

According to a research report using the above-mentioned full-scale model, it has been found that when coke is charged onto a sintered ore layer, a mixed layer is hardly formed because the impact energy possessed by the coke is small. Therefore, it can be seen that in order to suppress the formation of a mixed layer, the deposition angle of the surface of the reducing agent layer at the time of charging the iron source should be well controlled.

The present inventors manufactured a full-scale model outside the furnace, charged sinter with various coke layer deposition angles, and investigated the effect of the coke layer deposition angle on the amount of mixed layer formation.

The results are shown in FIG. The increase in the thickness of the coke layer in the center (increase in the thickness of the single coke layer + 172×increase in the thickness of the mixed layer) was used as a guideline for the amount of mixed layer formed. As is clear from the figure, the coke layer 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 the charging of sinter, but below that, it is practically ignored. It turned out to be Shiro. To summarize the above results, in order to prevent fluctuations in the amount of mixed layer formation, the deposition angle after charging the reducing agent must be
It can be seen that the temperature should not exceed 0 degrees.

In order to prevent fluctuations in the stacking angle of the raw material, which is the second problem, it is sufficient to prevent fluctuations in the gas flow distribution, but this is difficult in actual operation, and rather the gas flow distribution fluctuates. It is necessary to create conditions in which the stacking angle of the raw material does not change even when However, since the iron source has a high density and a small deposition angle in the furnace, it is not susceptible to fluctuations in the deposition angle due to changes in gas flow distribution, but the reducing agent has a low density and a large deposition angle in the furnace, so The deposition angle tends to change due to changes in gas flow distribution. Therefore, it is necessary to reduce the deposition angle after charging the reducing agent to prevent fluctuations in the deposition angle due to fluctuations in gas flow distribution.

In order to suppress the third problem, radial O/C distribution fluctuations due to fluctuations in the furnace loading time, it is necessary to The raw material may be charged toward a portion where the increase in material layer thickness is small, that is, toward the furnace wall. In particular, the moisture content of the reducing agent fluctuates more than the iron source, and the discharge time from the furnace top bunker, that is, the time it takes to enter the furnace, fluctuates significantly. Therefore, the reducing agent is charged from the center toward the furnace wall. It is necessary to do it.

Based on the above considerations, in the present invention, when charging the reducing agent, (1) charging from the center of the furnace toward the furnace wall;
(2) By setting the deposition angle on the surface of the raw material after charging to be 20 degrees or less, the above-mentioned problems of the conventional method are solved. Of course, if similar measures are taken when charging the iron source, the effect will be even better, but even if it is applied only to the reducing agent as in the present invention, the effect is sufficient as described below.

The configuration of the present invention will be explained based on FIG. In addition, the first
In the figure, the same numbers as in FIG. 4 indicate the same or corresponding parts, and the explanation will be omitted. The raw material is conveyed to the top of the furnace by the belt conveyor 2, passes through the upper gate valve 4 and the upper seal valve 5, and is temporarily stored in the furnace top bunker 6. When the stock level 7 is reached, the lower gate valve 8 and the lower seal valve 9 are opened, and the flow of charging into the furnace via the distribution shoe 1-10 is the same as in the conventional method.

First, in order to achieve the first condition of charging from the center of the furnace toward the wall of the furnace, a schedule is set in which the tilt angle of the distribution chute is gradually increased from small to large.

The arrows shown in FIG. 1 indicate the movement of the distribution chute tilt angle. Next, the second condition, the pile angle after charging, is set to 2
In order to achieve 0 degrees or less, 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 can be arbitrarily set.

By doing so, the deposition angle of the reducing agent 11 in the furnace can be kept at 20 degrees or less, as shown in FIG.

On the other hand, as in the conventional method, the iron source 12 is charged from the furnace wall toward the center by decreasing the tilt angle of the distribution chute 10 from large to small, as shown in FIG. The surface shape is M-shaped, and therefore the O/C distribution in the radial direction is such that the O/C at the furnace center is low and the O/C at the furnace wall is high.

In normal blast furnace operation, a radial O/C distribution with a reduced O/C in the center is aimed at in order to ensure a central gas flow, and the present invention satisfies that purpose. In addition, in order to prevent the formation of an inert zone on the furnace wall and to ensure an appropriate gas flow on the furnace wall, the distribution chute tilt angle should be adjusted so that the surface shape of the iron source is M-shaped. At least one of the number of turns in the tilting angle and the opening degree of the lower gate valve may be controlled.

In the present invention, the deposition angle of the reducing agent layer before charging the iron source is 2.
Since the temperature is 0 degrees or less, it is much easier to control the surface shape after charging the iron source than in the conventional method.

In addition, in order to fully demonstrate the effects of the present invention, the stacking angle of the raw material after charging is actually measured using a profile meter 13 normally installed at the top of the blast furnace, and if the desired stacking angle has not been changed, the distribution At least one of the tilting angle of the chute, the number of turns at each tilting angle, and the opening degree of the lower gate valve is controlled, and measurement is performed using the profile meter 13, and while confirming the effect, the desired deposition angle of the raw material is obtained. It can also be controlled within the range of . Furthermore, in order to improve the controllability of the raw material charging time into the furnace, the amount of raw material deposited in the furnace top bunker may be measured by sounding 14, and the raw material charging time may be measured by an acoustic method, etc. Needless to say.

By the way, although the method of the present invention employs a method of gradually increasing the tilting angle of the distribution chute, this method 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. In contrast, 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 3, 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.

(Function) When charging an iron source and a reducing agent to a bell-less blast furnace, the present invention is designed to charge the iron source from the furnace wall toward the center of the furnace (tilting angle of the distribution chute). control and also
When charging the reducing agent, charge it from the center of the furnace toward the furnace wall (control the tilt angle of the distribution chute and make sure that the angle of accumulation on the surface of the reducing agent after charging does not exceed 20 degrees). Since 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 is controlled, the 070 distribution in the radial direction in the furnace can be controlled with high precision.

(Example) In order to confirm the effects of the present invention, a charge distribution test was conducted using the above-mentioned full-scale model outside the furnace. The iron source used in the test was sintered ore used in actual blast furnaces, and the reducing agent was coke. In addition, the charging conditions for raw materials in the test were the same as those in an actual blast furnace, except that there was no unloading and no air blowing. It was solidified, taken out of the device, and measured.

By applying the present invention, the radial O/C distribution can be controlled with high precision. For example, the conventional charging method was changed to C (112233445
56677), O(11223344556677)
It is written as. 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 is set. The number of turns was 14.

On the other hand, the charging method of the present invention for obtaining the same radial 0/C distribution as the charging method described above uses C(1010998876543
211), O(11112222333345).

The moisture content of the coke used under these conditions is 1.
A charging test was carried out by increasing the amount from 5% by weight to 6.5% by weight.

In the conventional charging method, charging was performed using the same distribution chute tilting angle schedule and lower gate valve opening, so charging was not completed in 14 turns and took about 6 seconds longer. Therefore, at the final tilt angle of 7 of the distribution chute, extra coke was charged from the center to the center of the furnace, and the thickness of the coke layer in the center increased. In addition, the amount of increase in the thickness of the coke layer in the center due to the formation of a mixed layer after charging the sintered ore decreased slightly. As a comprehensive result, as shown in the table below, the O/C at the center of the furnace decreased from 1.2 to 0.9.

On the other hand, in the charging method according to the present invention, an increase in the amount of charged coke deposited due to an increase in coke moisture content is detected by a sounding device installed in the furnace top bunker, and the same O/C ratio as before the increase in coke moisture is detected. The opening of the lower gate valve was increased by 5% to obtain the distribution. As a result, the coke charging time can be maintained almost the same at 106 seconds, the surface deposition angle after coke charging can be maintained at 20 degrees or less, and the coke layer in the center can be maintained due to the formation of a mixed layer when charging the sintered ore. The layer thickness increase was extremely suppressed to 10 fi, the same as before the increase in coke water content. As a result, the O/C in the center could be maintained at 1.1, which is almost the same as before changing the coke water content, confirming the effectiveness of the present invention.

As described above, the present invention is used to control the tilting angle of the distribution chute from small to large when charging the reducing agent, and to distribute the distribution so that the deposition angle on the surface after charging the reducing agent is 20 degrees or less. Controllability of the radial O/C distribution in the furnace can be improved by controlling at least one of the tilting angle of the chute, the number of turns at each tilting angle, and the opening degree of the lower gate valve.

(Effects of the Invention) As explained above, the present invention has the advantage that when charging an iron source and a reducing agent into a bellless blast furnace, the iron source is charged from the furnace wall toward the center of the furnace. The tilting angle of the distribution chute is controlled so that the reducing agent is charged from the center of the furnace toward the furnace wall when charging the reducing agent. the tilting angle of the distribution chute so that the deposition angle on the agent surface does not exceed 20 degrees;
Since it controls only one of the number of rotations at each tilting angle and the opening degree of the lower gate valve, the radial O/C distribution in the furnace can be controlled with precision, which is very important for stable operation of the blast furnace. It has a certain effect.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of the method of the present invention, and FIG. 2 is a diagram of the relationship between the deposition angle of the coke layer and the amount of increase in the thickness of the coke layer in the center of the furnace.
FIG. 3 is a diagram showing the relationship between the tilting angle of the distribution chute and the motor shaft torque, FIG. 4 is an explanatory diagram of the conventional method, and FIG. 5 is an explanatory diagram of the state of formation of the mixed layer in the conventional method. 1 is the blast furnace, 7 is the stock level, 8 is the lower gate valve, 1
0 is a distribution chute, 11 is a reducing agent, and 12 is an iron source.

Claims (1)

[Claims] (1) When charging the iron source and reducing agent into a bell-less blast furnace, the tilt angle of the distribution chute is controlled so that the iron source is charged from the furnace wall toward the center of the furnace. When charging the reducing agent, the tilting angle of the distribution chute is controlled so that the reducing agent is charged from the center of the furnace toward the furnace wall, and
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 is controlled so that the deposition angle on the surface of the reducing agent after charging does not exceed 20 degrees. A method for charging raw materials into a bellless blast furnace.