JP2017020077A - Raw material charging method for blast furnace - Google Patents

Abstract

An object of the present invention is to suppress the eccentricity of a raw material in a vertical chute in a furnace top charging device and appropriately charge the raw material into a blast furnace.
When a raw material is charged from a furnace top bunker into a blast furnace through a collecting hopper, a vertical chute and a rotating chute, the raw material is charged into the blast furnace at a flow rate satisfying the following formula (1).
0.30 ≦ F / Fmax ≦ 0.49 (1)
However, F: the flow rate of the raw material, Fmax: the maximum flow rate of the raw material, and the maximum flow rate at the lower end of the vertical chute assuming that the raw material falling speed at the upper end of the vertical chute is zero.

Description

  The present invention relates to a method for charging a raw material from a furnace top bunker into a blast furnace through a collecting hopper, a vertical chute and a swivel chute.

  Conventionally, a bellless type furnace top charging apparatus is known as an apparatus for charging a raw material into a blast furnace. The furnace top charging device has a configuration in which a collecting hopper, a vertical chute, and a turning chute are arranged in this order below the furnace top bunker. Then, the raw material is discharged from the furnace top bunker to the turning chute via the collecting hopper and the vertical chute, and the raw material is charged into the blast furnace from the turning chute while rotating the turning chute.

  Here, in the so-called parallel bunker type furnace top charging apparatus in which the furnace top bunkers are arranged in parallel, each furnace top bunker is arranged eccentrically from the central axis of the vertical chute. In such a case, the raw material from the furnace top bunker is discharged with a horizontal velocity component when falling from the collecting hopper to the vertical chute, so the raw material is eccentric (diffused) in the vertical chute, and the swivel chute has a different position. Fall into. As a result, the time for the raw material to move on the swiveling chute, the falling speed of the raw material discharged from the swirling chute, the dropping trajectory, etc. fluctuate, and further, the deposition position of the raw material in the blast furnace fluctuates. Deviations may occur in the raw material distribution in the direction. And there exists a possibility that the stable blast furnace operation cannot be performed by the raw material distribution deviation of the circumferential direction.

  Generally, it is said that the eccentricity of the raw material in the vertical chute is suppressed as the raw material flow rate is increased. However, an increase in raw material flow rate leads to blockage of the vertical chute. When the vertical chute is blocked, it is necessary to cope with the wind, so the operation is usually performed with a small flow rate.

  Therefore, various methods have been proposed in the past in order to suppress the material eccentricity in the vertical chute even at a small flow rate.

  Patent Document 1 proposes a method of dispersing the raw material and suppressing the eccentricity of the raw material in the vertical chute by providing a flow dividing protrusion in the collecting hopper.

  Non-Patent Document 1 describes that by causing a vertical chute to protrude into the collecting hopper, the raw material can be retained in the collecting hopper and the eccentricity of the raw material in the vertical chute can be suppressed.

  Patent Documents 2 and 3 propose a method of suppressing the eccentricity of the raw material in the vertical chute by installing a movable device on the vertical chute and controlling the movable device.

Japanese Patent No. 3799987 Japanese Patent No. 2921777 Japanese Patent No. 3777654

Toshiro Sawada et al. “Operation of 3 parallel bunker type bell-less blast furnace and control of burden distribution” Iron and Steel Vol. 78 (1992) No. 8 P1337-1344 Japan Iron and Steel Association

  However, when the method described in Patent Document 1 is used, since the raw material is dispersed by the diverting projection, the raw material is accumulated in a large amount in the collecting hopper. Ancillary equipment such as a seal valve driving device and a vibration sensor for detecting the raw material flow is installed in the collecting hopper, and the accumulated raw material hinders the operation of the auxiliary equipment. Therefore, it is not preferable to accumulate raw materials in the collecting hopper. In addition, it is necessary to provide a separate diverting projection, which is troublesome and expensive.

  In addition, when the method described in Non-Patent Document 1 is used, it is necessary to once retain the raw material in the collecting hopper, which is not preferable because it causes the vertical chute to be blocked.

  Further, when the methods described in Patent Document 2 and Patent Document 3 are used, the cost of the separate movable device itself becomes high. In addition, since the vertical chute length is required to some extent for installation of the movable equipment, it is necessary to install the furnace top charging device itself at a high position, and the equipment cost of the blast furnace itself is high.

  This invention is made | formed in view of this point, and it aims at suppressing the eccentricity of the raw material in the vertical chute in a furnace top charging apparatus, and charging a raw material into a blast furnace appropriately.

  As described above, conventionally, the eccentricity of the raw material in the vertical chute has been monotonously decreased as the raw material flow rate is increased. In this regard, the present inventors investigated the flow behavior of the raw material in the collecting hopper and the vertical chute and the discharging behavior of the raw material from the collecting hopper and the vertical chute by the discrete element method, and the eccentricity of the raw material in the vertical chute Were investigated in more detail. As a result, it was found that the material eccentricity in the vertical chute takes a minimum value at a predetermined material flow rate.

The present inventors have arrived at the present invention based on such knowledge. That is, the present invention is a method of charging a raw material into a blast furnace from a furnace top bunker through a collecting hopper, a vertical chute, and a turning chute, and charging the raw material into the blast furnace at a flow rate satisfying the following formula (1). It is characterized by. The basis for these upper limit value and lower limit value will be described in detail in an embodiment described later.
0.30 ≦ F / Fmax ≦ 0.49 (1)
Where F is the flow rate of the raw material, Fmax is the maximum flow rate of the raw material, and the maximum flow rate at the lower end of the vertical chute when it is assumed that the material falling speed at the upper end of the vertical chute is zero.

  In the raw material charging method for the blast furnace, it is preferable that the inclination angle of the bottom surface of the collecting hopper is equal to or smaller than the repose angle of the raw material.

  According to the present invention, by adjusting the raw material flow rate, the eccentricity of the raw material in the vertical chute can be suppressed and the raw material can be appropriately charged into the blast furnace. This enables stable blast furnace operation. In addition, in order to suppress the eccentricity of the raw material in the vertical chute, it is not necessary to provide a separate device for the furnace top charging device as in the prior art. That is, no new capital investment is required.

It is explanatory drawing which shows typically the outline of a structure of the furnace top charging apparatus used by this Embodiment. It is explanatory drawing which shows the outline of a structure of a collection hopper and a vertical chute. It is explanatory drawing which shows the outline of a structure of a turning chute. It is explanatory drawing which shows the behavior of the raw material in a collection hopper and a vertical chute when changing a raw material flow rate. It is a graph which shows the relationship between a raw material flow volume and a raw material mainstream position. It is a graph which shows the relationship between an azimuth | direction and a fall locus | trajectory mainstream position. It is a graph which shows the relationship between a dimensionless flow volume and the maximum deviation of a falling flow.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the present specification and drawings, components having substantially the same functional configuration are denoted by the same reference numerals, and redundant description is omitted.

<1. Furnace top charging equipment>
First, the furnace top charging apparatus used in the present embodiment will be described. FIG. 1 is an explanatory view schematically showing the outline of the configuration of the furnace top charging apparatus. The furnace top charging apparatus 10 is a parallel bunker type furnace top charging apparatus, and charges the blast furnace 20 with raw materials.

  The furnace top charging device 10 includes a plurality of, for example, two furnace top bunkers 11 a and 11 b, a collecting hopper 12, a vertical chute 13, and a turning chute 14. The furnace top bunkers 11a and 11b, the collecting hopper 12, the vertical chute 13, and the turning chute 14 are arranged in this order from the upper side to the lower side.

  The furnace top bunkers 11 a and 11 b are arranged to face each other in parallel, and the discharge ports of the furnace top bunkers 11 a and 11 b are arranged eccentrically from the central axis of the vertical chute 13. Flow rate adjusting gates 15a and 15b for adjusting the flow rate of the raw material are provided at the outlets of the furnace top bunkers 11a and 11b. In each furnace top bunker 11a, 11b, raw material Ma, Mb for one charge is temporarily stored. While the raw material Ma in one furnace top bunker 11a is charged into the furnace, the other furnace top bunker 11b receives the raw material Mb. By repeating this alternately, the time required for receiving and charging the raw materials is shortened. The raw material Ma is, for example, ore, and the raw material Mb is, for example, coke. In the following description, the raw materials Ma and Mb may be collectively referred to as the raw material M.

  The collecting hopper 12 collects the raw material M discharged from the furnace top bunkers 11 a and 11 b and flows it to the vertical chute 13.

  The vertical chute 13 has a tapered portion 16 and a vertical portion 17 as shown in FIG. The tapered portion 16 is connected to the lower end of the collecting hopper 12, and the vertical portion 17 extends downward from the tapered portion 16. The tapered portion 16 has an upper end diameter Da larger than a lower end diameter Db, and has a substantially truncated cone shape. The vertical portion 17 has a substantially cylindrical shape with a constant diameter Db.

  As shown in FIG. 3, the upper surface of the turning chute 14 is opened, receives the raw material M discharged from the vertical chute 13, and charges the raw material M into the blast furnace 20 from its tip. The turning chute 14 is configured to be rotatable in the circumferential direction of the blast furnace 20 around the vertical chute 13 by a drive mechanism (not shown). The turning chute 14 is configured to be rotatable (tilted) in the vertical direction about the vertical chute 13, and the rotation radius of the turning chute 14 can be arbitrarily changed.

  In the furnace top charging device 10, the raw material M in the furnace top bunkers 11 a and 11 b is adjusted in flow rate by the flow rate adjusting gates 15 a and 15 b and discharged to the collecting hopper 12. The raw material M collected by the collecting hopper 12 falls on the turning chute 14 through the vertical chute 13 and is charged into the blast furnace 20 from the tip of the turning chute 14.

<2. Evaluation at the bottom of the vertical chute>
The present inventors investigated the flow behavior of the raw material M in the collecting hopper 12 and the vertical chute 13 and the discharge behavior of the raw material M from the collecting hopper 12 and the vertical chute 13 by the discrete element method. The eccentricity of the raw material M was investigated. As a result, it has been found that the eccentricity of the raw material M in the vertical chute 13 takes a minimum value at a predetermined raw material flow rate as described below.

  The dimensions of the vertical chute 13 to be investigated are as follows. As shown in FIG. 2, the upper end diameter Da of the tapered portion 16 is 870 mm, the lower end diameter Db of the tapered portion 16 (vertical portion 17) is 600 mm, the vertical length La of the tapered portion 16 is 1470 mm, and the vertical direction of the tapered portion 16 The length Lb is 2070 mm. Further, the inclination angle θ1 from the vertical direction of the tapered portion 16 is about 5 degrees.

  And the raw material M was discharged | emitted from the furnace top bunker 11a, and the behavior was investigated. At this time, as shown in FIG. 4, the raw material flow rate is changed to 8 t / min, 16 t / min, 24 t / min, 32 t / min, 40 t / min, 48 t / min, and the raw material with respect to the eccentricity of the raw material in the vertical chute 13 is obtained. The effect of flow rate was investigated.

  The survey results are shown in FIG. In FIG. 4, the upper part shows the flow rate distribution of the raw material M when the collecting hopper 12 and the vertical chute 13 are viewed from the side, and the lower part shows the flow rate distribution of the raw material M in the lower end cross section of the vertical chute 13.

  When the raw material flow rate is extremely small (8 t / min), the raw material M is eccentric to the side opposite to the furnace top bunker 11a (right side in the figure) and falls onto the vertical chute 13. When the raw material flow rate is increased to about 24 t / min, the flow of the raw material M is pushed back to the left in the drawing in the vertical chute 13, so that the raw material M passes through the center at the lower end of the vertical chute 13. When the raw material flow rate further increases and exceeds 32 t / min, the flow of the raw material M is excessively pushed back and eccentric to the furnace top bunker 11a side (left side in the figure). When the raw material flow rate exceeds 48 t / min, the raw material M falls once after staying in the collecting hopper 12, so that the eccentricity of the raw material is eliminated. However, this case is not suitable because there is a possibility that the collecting hopper 12 is blocked.

  FIG. 5 is a graph of the investigation result (FIG. 4), and shows the influence of the raw material flow rate on the mainstream position of the raw material M in the vertical chute 13 (hereinafter referred to as raw material mainstream position). Here, when the raw material mainstream position takes a positive value, the raw material M drifts to the right side of FIG. 4, and when the raw material mainstream position takes a negative value, the raw material M is eccentric to the left side of FIG. Indicates. Therefore, when the raw material mainstream position becomes 0 (zero), the raw material M is not decentered and passes through the lower end center of the vertical chute 13.

  As described above, with reference to FIGS. 4 and 5, it was found that when evaluated at the lower end of the vertical chute 13, the raw material flow rate of about 24 t / min is optimal with little eccentricity. The raw material flow rate 24 t / min derived here varies depending on the size of the blast furnace, and its absolute value itself is not important. It is important that the eccentricity of the raw material M in the vertical chute 13 takes a minimum value at a predetermined raw material flow rate, which is a new finding in the present invention.

<3. Evaluation in furnace interior entrance>
When the raw material is charged into the blast furnace 20, the charging position of the raw material M is assigned to the step width called “notch” and controlled. Here, when the position of the raw material M that jumps out of the turning chute 14 is called a drop locus, if the circumferential deviation of the drop locus is larger than the notch step width, the drop position of the raw material M cannot be controlled, and the blast furnace 20 It can be said that the impact on The number of notches varies depending on the blast furnace, but is generally about 10-20. Since the diameter of the large blast furnace currently in operation is about 10 m (radius is 5 m), the step width for one notch is 25 to 50 cm. Therefore, for the stable operation of the blast furnace 20, it is necessary to suppress the circumferential deviation of the falling locus within 25 cm.

  The material eccentricity in the vertical chute 13 causes a deviation in the circumferential direction of the dropping trajectory when the material M is charged into the blast furnace 20. Therefore, the above <2. In the investigation conducted in the evaluation at the lower end of the vertical chute>, the mainstream position on the entrance surface of the furnace interior of the dropping locus was further investigated. As an example, FIG. 6 shows the mainstream position on the furnace interior entrance surface of the drop trajectory with a raw material flow rate of 8 t / min where the circumferential deviation of the drop trajectory is the largest. The horizontal axis in FIG. 6 indicates the circumferential direction from the reference position. Referring to FIG. 6, it can be seen that the position of the fall trajectory differs by about 50 cm depending on the orientation, which adversely affects the stable operation of the blast furnace 20.

In the present invention, the following parameters are used to derive the range of the raw material flow rate for suppressing the circumferential deviation of the fall trajectory within 25 cm. That is, when evaluating the circumferential deviation of the fall trajectory, the difference between the maximum value and the minimum value in the circumferential direction of the distance from the center of the blast furnace 20 to the fall trace is the maximum deviation of the falling flow of the raw material M. Define and use. Moreover, since the raw material flow rate (F [m ³ / s]) varies greatly depending on the size of the blast furnace, it is expressed by F / Fmax, which is a ratio with the maximum volume flow rate (Fmax [m ³ / s]) of the raw material M. And Fmax is the maximum flow rate of the raw material M at the lower end of the vertical chute 13 when it is assumed that the falling speed of the raw material M at the upper end of the vertical chute 13 is 0 (zero), and is expressed by the following formula (2).
However, g: gravitational constant ^{(= 9.8 [m / s 2} ]), A: a vertical chute lower end cross sectional area ^{(= πDb 2/4 [M} 2])

<2. FIG. 7 shows the relationship between the maximum deviation of the falling flow and the dimensionless flow rate (F / Fmax) of the raw material in the investigation conducted in the evaluation performed at the lower end of the vertical chute. According to FIG. 7, in order to make the maximum deviation of the falling flow within 25 cm, the dimensionless flow rate (F / Fmax) of the raw material is within the range of 0.30 to 0.49 as shown in the equation (1). There is a need to. In other words, if the dimensionless flow rate (F / Fmax) of the raw material is adjusted to 0.30 to 0.49, the raw material is transferred from the furnace top charging device 10 to the blast furnace 20 without providing a separate device as in the prior art. M can be charged appropriately.
0.30 ≦ F / Fmax ≦ 0.49 (1)

  In the present embodiment, when the inclination angle θ1 of the tapered portion 16 is about 5 degrees, the range of the dimensionless flow rate (F / Fmax) of the raw material, that is, the equation (1) is derived. However, the inclination angle θ1 is not limited to this, and may be adjusted so as to satisfy Expression (1). As a result of intensive studies by the present inventors, it is preferable to set the inclination angle θ1 to 3 to 5 degrees.

<4. Inclination angle of the collective hopper>
In order to suppress the eccentricity of the raw material M in the vertical chute 13, it is preferable to control the behavior of the raw material M entering the vertical chute 13 from the collecting hopper 12 in addition to the adjustment of the raw material flow rate described above. For this purpose, the inclination angle θ2 of the bottom surface of the collecting hopper 12 shown in FIG. 2 is defined.

  When the inclination angle θ2 of the collecting hopper 12 is larger than the repose angle of the raw material M, it is difficult to control the position where the raw material M flowing from the collecting hopper 12 collides with the vertical chute 13. As a result, it may be difficult to control the material eccentricity in the vertical chute 13.

  Therefore, it is preferable that the inclination angle θ2 of the collecting hopper 12 is equal to or less than the repose angle of the raw material M. That is, when different raw materials Ma and Mb are used as in the present embodiment, the inclination angle θ2 is equal to or smaller than the smaller one of the repose angles of the raw materials Ma and Mb, and is, for example, 0 degrees to 25 degrees.

  In this case, since the raw material M is temporarily retained in the collecting hopper 12, even if the raw material M discharged from the furnace top bunkers 11a and 11b falls to various positions of the collecting hopper 12, the collecting hopper 12 is concerned. The raw material M is stably discharged into the vertical chute 13. Therefore, the eccentricity of the raw material M in the vertical chute 13 can be more reliably suppressed.

  The preferred embodiments of the present invention have been described above with reference to the accompanying drawings, but the present invention is not limited to such examples. It is obvious for those skilled in the art that various modifications or modifications can be conceived within the scope of the idea described in the claims, and these naturally belong to the technical scope of the present invention. It is understood.

  The present invention is useful when charging a raw material into a blast furnace from a parallel bunker type furnace top charging apparatus.

DESCRIPTION OF SYMBOLS 10 Furnace top charging apparatus 11a, 11b Furnace top bunker 12 Collective hopper 13 Vertical chute 14 Turning chute 15a, 15b Flow control gate 16 Taper part 17 Vertical part 20 Blast furnace M (Ma, Bb) Raw material

Claims (2)

A method of charging raw materials from a furnace top bunker into a blast furnace through a collecting hopper, a vertical chute and a swivel chute,
A raw material charging method for a blast furnace, wherein the raw material is charged into the blast furnace at a flow rate satisfying the following formula (1).
0.30 ≦ F / Fmax ≦ 0.49 (1)
Where F is the flow rate of the raw material, Fmax is the maximum flow rate of the raw material, and the maximum flow rate at the lower end of the vertical chute when it is assumed that the material falling speed at the upper end of the vertical chute is zero. The blast furnace raw material charging method according to claim 1, wherein an inclination angle of a bottom surface of the collecting hopper is equal to or less than a repose angle of the raw material.