JPH051311A - Belleless blast furnace raw material charging method - Google Patents

Abstract

(57) [Summary] [Purpose] When the raw material is charged into the bellless blast furnace by the internal distribution charging method, the raw material particle size distribution in the radial direction of the furnace is arbitrarily controlled. [Structure] Based on the dimensionless exponent π calculated from the equation, the charge of raw material into the lowermost storage tank of the furnace top raw material storage tank is used as a reference, and π is 5 when the raw material particle size on the furnace wall is to be increased. × adjusted to 10 ^-3 or more, if you want to increase the raw material particle size of the furnace center portion is charged adjusted to π is less than 5 × 10 ^-3. Where v: raw material charging speed (kg / sec), g: gravity acceleration (m
/ sec ² ), ρ: Raw material bulk density (kg / m ³ ), D: Bunker diameter
(m), H: Charge drop (m) [Effect] For example, if the raw material charge speed v is adjusted as shown in (a) to (c) and π is set to 5 × 10 ^-3 or more, as shown in the figure. It is possible to charge coarse-grain raw material into the center of the furnace.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a raw material charging method in a so-called bellless blast furnace which uses a raw material storage tank (hereinafter referred to as a "top bunker" or simply "bunker") provided at the top of a blast furnace and a distribution chute. Then, by operating the tilt angle of the distribution chute, the raw material is charged from the furnace wall to the center of the furnace, the particle size of the raw material charged into the furnace by the so-called internal distribution charging method. The present invention relates to a raw material charging method capable of controlling a change over time.

[0002]

2. Description of the Related Art In blast furnace operation, controlling the gas flow distribution in the inner diameter direction of the furnace to stably reduce or dissolve the ore in the furnace is a basic operation problem.

The main control means of the gas flow distribution in the furnace in the operation of the blast furnace is the distribution control of the charge at the furnace top, and more specifically, the deposit weight ratio distribution of ore and coke in the furnace inner diameter direction (hereinafter referred to as "O / C distribution"). ") And the ore and coke particle size distribution adjustment.

The raw material charging device in the bellless blast furnace can be broadly classified into one having a top bunker for directly supplying the raw material into the furnace and one having a plurality of bunkers. FIG. 1 shows an example of a bellless charging device having a two-stage furnace top bunker in series. A raw material (ore, sinter, coke) 1 is first stored in a furnace top bunker 3 by a belt conveyor 2 and is supplied to a lower bunker 4 whose pressure is exhausted from here. Then, when the charge in the furnace is unloaded and reaches a predetermined stock line 5 to be replenished, the gate valve 6 and the seal valve 7 for adjusting the flow rate of the charge are operated to open, and the raw material 8 in the lower bunker is opened. Is supplied onto the distribution chute 9, the tilt angle and the number of turns of the distribution chute are adjusted, and the raw material is charged into the furnace 10.

The O / C distribution control in the bellless blast furnace is mainly carried out by controlling the operation schedule of the distribution chute (specifically, setting the tilt angle of the chute and assigning the number of turns at that tilt angle), and the particle size distribution is controlled. On the other hand, it is done by utilizing the change with time of the particle size of the raw material charged in the furnace. That is,
In normal bellless charging, the distribution chute is rotated 10 times or more to load the raw material into the furnace, and during that time, the tilt angle of the distribution chute is changed once or more to change the falling position of the raw material in the furnace. It takes a form. At this time, when the particle size of the raw material supplied to the distribution chute changes with time in one dump, the influence appears in the particle size distribution in the inner diameter direction of the furnace.

[0006] There have been many reports about the time-dependent change in the particle size of the raw material discharged from the top bunker, but the main factor is that the raw material in the top bunker has a particle size distribution in the radial direction. , And when the raw material is discharged from the bottom of the bunker, the center of the bunker is discharged first, which is a so-called funnel flow type distribution that occurs in the bunker (Iron and Steel 74 (1988) P.978).

Therefore, by controlling at least one of the above factors and (1), it is possible to change the temporal change pattern of the particle size of the discharged raw material, and various ideas have been hitherto made from such a viewpoint. Regarding the factor of, there is a method to suppress the funnel flow by installing an obstacle (insert) just above the discharge port in the bunker. On the other hand, as for the method, a repulsion box (stone box) is provided in the bunker to scatter and drop the raw materials to be charged into the bunker at multiple points or in concentric circles (Act No. Sho 56-18597), or the furnace top. A turning chute is provided in the bunker to adjust its tilting angle (Japanese Patent Laid-Open No. 1-11
No. 9612) or by adjusting the angle by providing a repulsion plate (Japanese Patent Publication No. 2-401), there has been proposed a method of controlling the material dropping position. However, these methods are intended to control the falling position of the raw material or the number of the falling points, and both of them require the work to be carried out in the bunker, and therefore the maintenance of the work is complicated, and moreover, the distribution of the charged materials is not sufficient. Especially, the effect of controlling the particle size distribution in the furnace is not always sufficient. In addition, these methods
Although the flow of the raw material deviates from the vertical direction, the falling trajectory of the raw material subjected to such a direction change is a parabola, and therefore the radial falling position changes depending on the level of the falling point. This means that when the total amount of raw material supplied to the bunker changes, the radial particle size distribution of the entire bunker sedimentary layer also changes, and as a result, the particle size of the raw material charged into the furnace from the bunker changes with time. Changes occur. That is, in order to accurately control the time-dependent change in the particle size of the charging raw material by each of the above methods, some control is required according to the amount of raw material supplied to the bunker.

[0008]

DISCLOSURE OF THE INVENTION The present invention controls the change with time of the raw material particle diameter when a raw material is discharged from a bunker provided at the top of a furnace and is charged into the furnace through a chute. The present invention aims to provide a method for adjusting the radial particle size distribution of a raw material in a furnace to the most suitable pattern according to the furnace conditions.

[0009]

The present invention includes the following (1) to
The gist is the method of charging the raw material for the bellless blast furnace, which is characterized in (3).

(1) In a bellless blast furnace in which the raw material discharged from the lowermost storage tank of the raw material storage tank at the top of the furnace is charged into the furnace via a distribution chute, (2) the tilt angle of the distribution chute is controlled. In doing so-called internal distribution charging, in which the raw material is charged from the furnace wall to the center of the furnace, (3) Calculate the raw material supply rate to the lowermost storage tank of the raw material storage tank group from the following formula. Based on the dimensionless number π, the π is adjusted to 5 × 10 ^-3 or more when the raw material particle size of the furnace wall is to be increased, and π is required when the raw material particle size of the furnace center is to be increased. Is adjusted to be less than 5 × 10 ^-3 .

[0011]

[Equation 2]

Here, v: raw material charging rate (kg / sec), g:
Gravity acceleration (m / sec ² ) ρ: Raw material bulk density (kg / m ³ ), D: Bunker diameter (m) H: Charge head (m) To change the above dimensionless number π, It is most practical to change the charging rate (v).

As a method of charging raw materials such as sinter and coke into a furnace through a distribution chute, the raw materials are sequentially fed from the furnace wall to the center of the furnace by operating the tilt angle of the distribution chute. The charging method, that is, internal distribution charging is adopted. The present invention is premised on this internal distribution charging.

It is empirically known that in order to secure the stability of the furnace condition during the operation of the blast furnace, it is necessary to make the gas flow in the central part of the furnace have a stronger distribution than in other regions.

To obtain such a radial gas flow distribution,
It is necessary to keep the central part of the furnace more air permeable than the wall side of the furnace. Therefore, the O / C in the central part of the furnace must be low and the deposited particle size must be large. However, for example, when deposits are generated on the inner wall of the furnace and it is desired to strengthen the gas flow in the region near the furnace wall in order to remove it, the air permeability on the furnace wall side must be higher than that on the furnace center. I have to. In that case, a charging method is required in which coarse-grained raw material is deposited on the furnace wall side. The method of the present invention is a raw material charging method capable of promptly and appropriately responding to the need to change the particle size distribution of the raw material in the radial direction in the furnace according to the furnace conditions.

[0016]

The radial particle size distribution in the bunker is finally determined by the particle size segregation process on the deposition slope in addition to the position and number of the raw material dropping points described above. The present invention utilizes this latter process to change the particle size distribution in the inner diameter direction of the bunker, and thereby to control the change over time in the particle size of the raw material discharged from the bunker and charged into the furnace. is there.

The most significant feature of the method of the present invention is that the control is performed on the basis of the dimensionless number π calculated from the above equation.

Generally, the particle size segregation (a phenomenon in which the particle size of the deposited particles differs depending on the deposition position) that occurs on the deposition slope when the particles having a particle size configuration are deposited may change depending on the supply conditions of the particles. Known (Iron and Steel 74 (1
988) P. 978). However, its quantitative relationship has not been found, and therefore, this phenomenon is used to control the change over time in the particle size of the raw material discharged from the bunker, and thus to control the radial particle size distribution of the raw material supplied into the furnace. I can't find the idea.

The inventors of the present invention investigated the same phenomenon by experiments using a sinter used in an actual furnace for a raw material storage bunker in a blast furnace. Experiments are full-scale model and 1/10
It was carried out using a scale model, and was carried out over a wider range, including the conditions equivalent to the conventional charging method. Table 1 shows the experimental conditions.

[0020]

[Table 1]

FIG. 2 shows the results of comparing the degree of particle size segregation in the bunker with various combinations of the raw material charging conditions (charging speed, charging drop) shown in Table 1. Here, as a measure of the degree of particle size segregation in the bunker, the gradient (dD _P / dr) when the particle size distribution in the radial direction in the bunker is approximated by a linear function of the starting point of the raw material drop point is taken. As a raw material charging condition index, the dimensionless number (π) shown in the above equation was taken.

The dimensionless number π is the ratio of the force exerted on the amount of the falling raw material deposited in the bunker and the repulsive force from the raw material in the bunker. By taking such an index, the experimental data under various conditions can be organized as shown in FIG.

What should be noted here is the fact that the change gradient of the particle size distribution in the radial direction is reversed at the boundary where the dimensionless number π becomes approximately 5 × 10 ^-3 . By using this phenomenon together with the above-described funnel flow type physical distribution that occurs in the bunker at the time of discharging the raw material, it becomes possible to freely adjust the particle size change pattern of the raw material discharged from the bunker. In other words, in the internal distribution charging method, if the π is 5 × 10 ⁻³ or more, the raw material of the coarse particles is charged into the furnace wall side first, and the furnace central part is charged with a delay. The raw material of is a fine grain. On the contrary, under the condition that π is smaller than 5 × 10 ^-3 , the raw material deposited in the central portion becomes coarse grains.

The value of the dimensionless number π can be controlled by changing one or more of each factor in the above equation, but the bulk density (ρ) of the raw material is almost constant, and the bunker diameter (D). The charging head (H) is a value determined by the equipment. Therefore,
In normal operation, π is controlled by controlling the raw material charging rate (v).
Is most practical to adjust. The control of v can be performed, for example, by adjusting the opening degree of the gate valve 6 of the bunker 3 in FIG.

By adjusting the dimensionless number π as described above, a desired bunker discharge particle size pattern required in accordance with the furnace conditions, that is, a desired radial particle size distribution of the raw material in the furnace is obtained. You can get it.

[0026]

Example 1 Similar to the above-mentioned full-scale model experiment,
First, a test for increasing the raw material particle size of the furnace wall was conducted. The test conditions are as follows.

Charge rate of raw material into bunker (v): (a) 0.08 ton / sec ・ ・ ・ at this time π = 1 × 10 ^-4 (b) 0.40 ton / sec ・ ・ ・ at this time π = 5 × 10 ^-4 (C) 2.4 ton / sec ・ ・ ・ at this time π = 3 × 10 ^-3 Insertion difference (H): 4 m Bunker diameter: 7 m Raw material (sintered ore) Particle size: as shown in Table 1 The survey results are shown in Fig. 3. Note that FIG. 3 and FIGS.
The “dimensionless particle size” on the vertical axis of 6 is the amount obtained by dividing the particle size at each time point or each position by the average particle size of the charging material.

In order to increase the gas flow velocity in the furnace wall without changing the O / C of the raw material, the grain size of the deposited raw material in that portion may be made coarse.
In order to achieve this by the internal distribution charging method, the coarse-grain raw material may be charged in the initial stage of the raw material charging into the furnace, and the fine-grain raw material in the final stage.

FIG. 3 shows changes with time in the particle size of the raw material discharged from the bunker when the raw material is charged into the bunker at the respective charging speeds (a), (b) and (c). Is.

FIG. 4 is a diagram showing the particle size distribution of the raw material discharged from the bunker and charged into the furnace in the furnace inner diameter direction. At the charging rates of (a), (b), and (c), π is all less than 5 × 10 ^-3, so the raw materials discharged from the bunker are coarse particles in the initial stage and fine particles in the final stage, as shown in Fig. 3. Therefore, in the furnace, the coarse-grained raw material was deposited on the furnace wall side as shown in FIG.

[0031]

Example 2 Next, a test was conducted to increase the grain size of the raw material in the center of the furnace. In the same manner as in Example 1, the following (d)
As shown in (e), the test was conducted by increasing the charging rate of the raw material into the bunker. The other test conditions are the same as in Example 1.

Rate of charging raw material into bunker (v): (d) 6.4 ton / sec ... π = 8 × 10 ^-3 (e) 16.1 ton / sec ... π = 2 at this time Contrary to Example 1, in order to increase the raw material particle size in the central part of the furnace by the × 10 ⁻² internal distribution charging method, the fine-grain raw material was coarse in the initial stage of the raw material charging into the furnace and was coarse in the final stage. It suffices that the granular raw material is charged.

FIGS. 5 and 6 are views similar to FIGS. 3 and 4, respectively. As shown in FIG.
(D) When the raw materials are charged into the bunker at the respective charging speeds of (e), π is 5 × 10 ⁻³ or more in any case, so the particle size of the raw material discharged therefrom is large at the initial stage, It becomes smaller in the final stage. Therefore, as shown in FIG. 6, the particle size distribution of the raw material charged in the furnace in the furnace inner diameter direction was coarse particles in the furnace center and fine particles in the furnace wall side.

In FIG. 6, the dimensionless particle size at the position 3 in the furnace is the minimum, but this is due to the operation schedule of the distribution chute. That is, in this example, an operation schedule was adopted in which the raw material forms a terrace (flat portion) from the furnace wall to the vicinity of the position 3. In this case, the change over time in the particle size of the charging raw material appears faithfully in the terrace portion.
However, as it goes from there to the center of the furnace, a slope is formed on the surface of the raw material that descends toward the center of the furnace, and along this slope there is a reclassification phenomenon in which the coarse-grained raw material drops and accumulates in the center of the furnace. As a result, the particle size distribution of the raw material in the furnace is
It takes a form as shown in FIG.

As is clear from Examples 1 and 2, by adjusting the dimensionless number π when charging the raw material into the bunker, it is possible to control the time-dependent pattern of the raw material particle diameter discharged from the bunker. it can. Therefore, it is possible to arbitrarily adjust the radial particle size distribution of the raw material charged into the furnace from the bunker.

[0036]

According to the method of the present invention, when the raw material is charged into the bellless blast furnace, the radial particle size distribution of the raw material charged into the interior of the furnace can be controlled to the most desirable pattern according to the operating conditions of the furnace. . This method does not require special equipment,
For example, it can be carried out only by changing the charging rate of the raw material into the lowermost bunker.

[Brief description of drawings]

FIG. 1 is a schematic explanatory view of a raw material charging mode in a bellless blast furnace.

FIG. 2 is a diagram showing a relationship between a dimensionless number π and a particle size change gradient in a radial direction in a bunker.

FIG. 3 is a diagram showing a relationship between a dimensionless discharge time and a dimensionless particle diameter in one example of the present invention.

FIG. 4 is a diagram showing a relationship between a radial position in the blast furnace and a non-dimensional grain size.

FIG. 5 is a diagram showing a relationship between a dimensionless discharge time and a dimensionless particle diameter in another example of the present invention.

FIG. 6 is a diagram showing a relationship between a radial position in the blast furnace and a dimensionless particle size.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Yoshimasa Kajiwara             4-53 Kitahama, Chuo-ku, Osaka City, Osaka Prefecture             Sumitomo Metal Industries, Ltd.

Claims (2)

[Claims] 1. A method for charging a bellless blast furnace in which a raw material discharged from a lowermost storage tank of a raw material storage tank is charged into a furnace through a distribution chute by an internal distribution method, to a lowermost storage tank. Based on the dimensionless number π calculated from the following formula, the raw material charging condition of is adjusted so that π becomes 5 × 10 ^-3 or more when increasing the raw material particle size of the furnace wall, A method for charging a raw material for a bellless blast furnace, characterized in that π is adjusted to be less than 5 × 10 ^-3 when it is desired to increase the raw material particle diameter in the central portion. [Equation 1] Where v: raw material charging speed (kg / sec), g: gravity acceleration (m
/ sec ² ) ρ: Raw material bulk density (kg / m ³ ), D: Bunker diameter (m) H: Charge head (m) 2. The dimensionless number π is adjusted by controlling a raw material supply rate (v) to the lowermost storage tank of the raw material storage tank group.
Raw material charging method.