JP2847995B2 - Raw material charging method for bellless blast furnace - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art In the operation of a blast furnace, it is a basic task in the operation to control the gas flow distribution in the furnace inner diameter direction to stably reduce and dissolve ore in the furnace.

[0003] The main means of controlling the gas flow distribution in the furnace in the blast furnace operation is the control of the distribution of the charge at the furnace top. More specifically, the distribution of the ore and coke in the inner diameter direction of the furnace (hereinafter referred to as "O / C distribution"). ") And the adjustment of the particle size distribution of each of the ore and coke.

[0004] The raw material charging apparatus in the bellless blast furnace can be roughly classified into a furnace top bunker for directly supplying a raw material into the furnace and a furnace top bunker. FIG. 1 shows an example of a bellless charging apparatus having a two-stage furnace top bunker. Raw materials (ore, sinter, coke) 1 are first stored in a furnace top bunker 3 by a belt conveyor 2, and then supplied to a lower bunker 4 which is depressurized. 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 charge flow rate are opened, and the raw material 8 in the lower bunker is opened. Is supplied onto the distribution chute 9, and the raw material is charged into the furnace 10 by adjusting the tilt angle and the number of turns of the distribution chute.

[0005] O / C distribution control in the bellless blast furnace is mainly performed by controlling the operation schedule of the distribution chute (specifically, setting the tilt angle of the chute and assigning the number of turns at the tilt angle). This is done by utilizing the change over time in the particle size of the raw material charged into the furnace. That is,
In normal bellless charging, the raw material is charged into the furnace by turning the distribution chute 10 times or more, and during this time, the tilting angle of the distribution chute is changed at least once to change the raw material drop position in the furnace. Takes form. At this time, if the particle diameter of the raw material supplied to the distribution chute changes with time in one dump, the effect appears in the particle diameter distribution in the inner diameter direction of the furnace.

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

Therefore, by controlling at least one of the above factors, it is possible to change the time-dependent change pattern of the particle size of the discharged raw material, and various devices have been conventionally devised from such a viewpoint. Regarding the factor (1), there is a method to prevent funnel flow by installing an obstruction (insert) just above the discharge port in the bunker. On the other hand, as for the method, a rebound box (stone box) is provided in the bunker, and the raw material charged in the bunker is scattered and dropped at a plurality of locations or concentric circles (Japanese Utility Model Publication No. 56-18597). Providing a swivel chute in a bunker to adjust its tilt angle (Japanese Patent Laid-Open No. 1-111)
No. 9612), or a method of controlling a material falling position by providing a repulsion plate and adjusting the angle thereof (Japanese Patent Publication No. 2-401). However, these methods are intended to control the position of the raw material to be dropped or the number of the falling points, and in each case, a work is provided in a bunker, so that maintenance is troublesome and the distribution of the charged material is increased. In particular, the effect of controlling the particle size distribution in the furnace is not always sufficient. Furthermore, with these methods,
Although the flow of the raw material is deviated from the vertical direction, the falling trajectory of the raw material that has undergone such a direction change is a parabola, and the radial drop 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 deposition layer also changes, and as a result, the raw material charged from the bunker into the furnace also has a time-dependent particle size. Change occurs. That is, in order to accurately control the time-dependent change in the particle size of the charged raw material in each of the above-described methods, some control is required according to the raw material supply amount to the bunker.

[0008]

SUMMARY OF THE INVENTION According to the present invention, a raw material is discharged from a bunker provided at the furnace top, and the change in the particle size of the raw material over time when the raw material is charged into the furnace through a chute is controlled. It is another object of the present invention to provide a method for adjusting a radial particle size distribution of a raw material in a furnace to a most appropriate pattern according to a furnace condition.

[0009]

The present invention provides the following (1) to
The summary of the method for charging raw materials for a bellless blast furnace, which is characterized by (3), is as follows.

(1) In a bellless blast furnace in which the raw material discharged from the lowermost storage tank in the raw material storage tank at the furnace top is charged into the furnace through a distribution chute, (2) the tilt angle of the distribution chute is controlled. (3) Calculate the raw material supply rate to the lowermost storage tank of the raw material storage group from the following formula. Based on the dimensionless number π to be used as a reference, if it is desired to increase the particle size of the raw material at the furnace wall, adjust π to be 5 × 10 ⁻³ or more, and if it is desired to increase the particle size of the raw material at the center of the furnace, π Is adjusted to be less than 5 × 10 ⁻³ .

[0011]

(Equation 2)

Here, v: raw material charging speed (kg / sec), g:
Gravitational acceleration (m / sec ² ) ρ: bulk density of raw material (kg / m ³ ), D: bunker diameter (m) H: head drop (m) To change the value of the above dimensionless number π, It is most practical to change the charging speed (v).

As a method of charging a raw material such as sinter or coke into a furnace through a distribution chute, usually, the raw material is sequentially fed from the furnace wall toward the furnace center by operating the tilt angle of the distribution chute. The method of charging, ie, the internal distribution charging, is employed. The present invention presupposes this swing distribution charging.

Now, it is empirically known that in order to secure the stability of the furnace conditions during the operation of the blast furnace, it is necessary to make the gas flow in the center of the furnace more intensely distributed than in other regions.

In order to obtain such a radial gas flow distribution,
It is necessary to keep the center of the furnace more permeable than the furnace wall side. For this purpose, the O / C in the center of the furnace must be lowered and the particle size of the sediment must be increased. However, for example, when deposits are generated on the inner wall of the furnace and it is desired to increase the gas flow in the vicinity of the furnace wall in order to remove the deposits, the gas permeability on the furnace wall side must be higher than that in the center of the furnace. Must. In that case, a charging method is required such that 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 accurately responding to the need to change the radial particle size distribution of the raw material in the furnace according to the furnace conditions.

[0016]

The particle size distribution in the radial direction in the bunker is finally determined through the process of particle size segregation on the deposition slope, in addition to the position and number of the material falling points described above. The present invention intends to change the particle size distribution in the inner diameter direction of the bunker by utilizing this latter process, thereby controlling the temporal change of 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 control is performed based on the dimensionless number π calculated from the above equation.

In general, particle size segregation (a phenomenon in which the particle size of a deposited granular material differs depending on the deposition position) that occurs on a deposition slope when the granular material having a particle size structure is deposited may vary depending on the supply condition of the granular material. Known (iron and steel 74 (1
988) p. 978). However, the quantitative relationship has not been found, and therefore, this phenomenon is used for controlling the time-dependent change in the particle diameter of the raw material discharged from the bunker and, consequently, the radial particle size distribution of the raw material supplied into the furnace. I do not find the idea.

The present inventors conducted an experiment to investigate the same phenomenon using a sintered ore used in an actual furnace for a raw material storage bunker in a blast furnace. The experiment was a full-scale model and 1/10
It was carried out using a scale model and carried out over a wider range, including 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 by variously combining the raw material charging conditions (charging speed and charging head) in Table 1. Here, as a measure of the degree of particle size segregation in the bunker, the gradient (dD _P / dr) when the radial particle size distribution in the bunker is approximated by a linear function of the distance from the starting point of the raw material drop point is taken. The dimensionless number (π) shown in the above equation was taken as an index of the raw material charging conditions.

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

What should be noted here is the fact that the change gradient of the radial particle size distribution is reversed at the point where the dimensionless number π is approximately 5 × 10 ⁻³ . If this phenomenon is used in combination with the above-described funnel flow type distribution generated in the bunker at the time of material discharge, it is possible to freely adjust the time-dependent change pattern of the particle diameter of the material discharged from the bunker. In other words, in the inner distribution charging method, if the condition that π is 5 × 10 ⁻³ or more, the coarse material is first charged into the furnace wall side, and the furnace The raw material is fine-grained. If π is less than 5 × 10 ⁻³ , the material deposited at the center becomes coarser.

The value of the dimensionless number π can be controlled by changing at least one of the factors in the above equation. However, the bulk density (ρ) of the raw material is almost constant, and the bunker diameter (D) And the charging head (H) are values determined by the equipment. Therefore,
In normal operation, π is controlled by controlling the material charging speed (v).
It is most practical to adjust The control of v can be performed, for example, by adjusting the opening of the gate valve 6 of the bunker 3 in FIG.

As described above, by adjusting the dimensionless number π, it is possible to obtain a desirable particle diameter distribution pattern from the bunker required according to the furnace condition, that is, a desirable radial particle diameter distribution of the raw material in the furnace. You can get it.

[0026]

[Example 1] In the same manner as the above-described full-scale model experiment,
First, a test was performed for increasing the particle size of the raw material in the furnace wall. The test conditions are as follows.

Raw material charging speed into the 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 π at this time = 3 × 10 ^-3 Charge head (H): 4 m Bunker diameter: 7 m Raw material (sinter ore) particle size: described in Table 1 As shown in Figure 3. FIG. 3 and FIGS.
The “dimension-free particle size” on the vertical axis of 6 is the amount obtained by dividing the particle size at each time or each position by the average particle size of the charge.

In order to increase the gas flow rate in the furnace wall without changing the O / C of the raw material, the particle size of the raw material in the furnace wall may be increased.
In order to realize this by the internal distribution charging method, the coarse raw material may be charged in the initial stage of the raw material charging into the furnace, and the fine granular raw material may be charged in the final stage.

FIG. 3 shows the change over time in the particle size of the raw material discharged from the bunker when the raw material is charged into the bunker at the charging speeds (a), (b) and (c) described above. It 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 speeds of (a), (b) and (c), since π is all smaller than 5 × 10 ^-3 , the raw material discharged from the bunker is coarse at the beginning and fine at the end as shown in Fig. 3. Therefore, in the furnace, the coarse material was deposited on the furnace wall side as shown in FIG.

[0031]

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

Raw material charging speed into the bunker (v): (d) 6.4 ton / sec... Π = 8 × 10 ⁻³ (e) 16.1 ton / sec .pi. = 2 In order to increase the particle size of the raw material at the center of the furnace by the × 10 ^-2 inner distribution method, contrary to the first embodiment, the fine raw material is coarse at the initial stage of charging the raw material into the furnace and coarse at the final stage. What is necessary is just to charge a granular raw material.

FIGS. 5 and 6 are views similar to FIGS. 3 and 4, respectively. As shown in FIG.
(D) When the raw material is charged into the bunker at each charging speed of (e), since π is 5 × 10 ^-3 or more, the particle diameter of the raw material discharged therefrom is initially large, It gets smaller at the end. Therefore, as shown in FIG. 6, the particle size distribution of the raw material charged into the furnace in the furnace inner diameter direction was coarse at the furnace center and fine at the furnace wall side.

In FIG. 6, the dimensionless particle size at the position 3 in the furnace is minimum, but this depends on the operation schedule of the distribution chute. That is, in this example, an operation schedule was adopted in which a terrace (flat portion) was formed in the raw material up to the position near the position 3 from the furnace wall. In this case, the temporal change of the particle diameter of the charged raw material appears faithfully in the terrace portion.
However, there is a slope down toward the center of the furnace from the material deposition surface toward the center of the furnace from there, and along this slope, a re-classification phenomenon occurs in which the coarse-grained material drops and accumulates at the center of the furnace. Due to the influence, the particle size distribution of the raw material in the furnace,
This is the form shown in FIG.

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

[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 in 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 implemented only by changing the raw material charging speed to the lowermost bunker.

[Brief description of the 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 gradient of a particle diameter change in a radial direction in a bunker.

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

FIG. 4 is a diagram showing a relationship between a radial position in a blast furnace and a dimensionless particle size.

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

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

────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Yoshimasa Kajiwara 4-5-33 Kitahama, Chuo-ku, Osaka-shi, Osaka Sumitomo Metal Industries, Ltd. (58) Field surveyed (Int. Cl. ⁶ , DB name) C21B 5/00-5 / 06,7 / 20

Claims (2)

(57) [Claims] In a method for charging a bellless blast furnace, a raw material discharged from a lowermost storage tank in a raw material storage tank is charged into a furnace by a swing distribution method via a distribution chute. The raw material charging conditions are based on the dimensionless number π calculated from the following equation, and when the raw material particle diameter of the furnace wall is to be increased, the furnace is adjusted so that π is 5 × 10 ⁻³ or more. A method for charging a raw material for a bellless blast furnace, characterized in that, when it is desired to increase the raw material particle diameter at the center, π is adjusted to be less than 5 × 10 ⁻³ . (Equation 1) Here, v: raw material charging speed (kg / sec), g: gravitational acceleration (m
/ sec ² ) ρ: Raw material bulk density (kg / m ³ ), D: Bunker diameter (m) H: Charge head (m) 2. The method according to claim 1, wherein the dimensionless number π is adjusted by controlling a material supply speed (v) to a lowermost storage tank of the raw material storage tank group.
Raw material charging method.