JPH02205605A - Method and apparatus for charging raw material in bellless blast furnace - Google Patents

Abstract

PURPOSE:To control distribution of grain diameters of raw material in radius direction in a furnace at high accuracy by arranging plural raw material discharging holes at upper step and lower step bunkers, respectively and specifying the discharging conditions of the raw material from each bunker, respectively. CONSTITUTION:In the upper step bunker 5 and the lower step bunker 7, the raw material discharging holes (6-1)-(6-3), (8-1)-(8-3) and gate valves V1-V3 are arranged, respectively. In this constitution, according to average grain size of the raw material 3 charged into a blast furnace 1 from the lower step bunker 7, open/shut of each discharging hole (6-1)-(6-3) in the upper step bunker 5 is suitably selected and also the raw material discharging velocity is controlled with the gates V1-V3. Further, the raw material discharge from the lower bunker 7 is executed by opening each discharging hole (8-1)-(8-3) at the same time. By this method, the distribution of the grain diameters in the radius direction in the blast furnace 1 is controlled at high accuracy and the operation of the bellless blast furnace is stabilized and the iron-making cost is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to a material charging technology for a bell-less blast furnace, and more specifically to a bell-less blast furnace having two top bunkers perpendicular to the furnace axis (hereinafter referred to as vertical two-stage bunker). The present invention relates to a raw material charging method and apparatus for controlling the radial particle size distribution of raw materials in a furnace (referred to as a bellless blast furnace) with high precision.

Conventional technology Bell-less blast furnaces allow the introduction time of raw materials into the furnace to be more than 10 times that of bell-type blast furnaces, and the distribution chute angle can be arbitrarily controlled during charging of raw materials to control the position of raw materials introduced into the furnace. , it has better controllability of charge distribution in the radial direction than the bell type blast furnace. For this reason, bellless charging devices are often used in recent blast furnaces.

However, in the system where the furnace top bunkers are arranged in parallel, the raw material discharged from the bunker is not charged vertically into the distribution chute, but is charged in a specific circumferential direction. For example, research by Murai et al. (Steel Manufacturing Research No. 325@, 1987, p. 14) revealed that the falling position of the raw materials is different and the difference in the circumferential direction i of the raw materials in the furnace becomes large.

As a countermeasure, two furnace top bunkers are arranged vertically, and the raw material discharged from the lower bunker is allowed to fall vertically and charged into the distribution chute, thereby making the falling position of the raw material uniform in the circumferential direction and causing deviation in the circumferential direction. Methods to improve this are being adopted.

FIG. 5 is a schematic diagram showing an example of raw material charging equipment for a conventional vertical two-stage bunker type bellless blast furnace.

In other words, there is a charging belt conveyor (2) at the top of the blast furnace (1).
), the raw material (3) is transferred to the rotating chute (4).
) into the upper bunker (5). next,
Each gate valve (V+
) (V2) (■3) is opened and the raw material in the upper bunker (5) is charged into the lower bunker (7).

When the raw material in the blast furnace (1) descends and reaches a predetermined level, a discharge port (
Open the gate valve (V4) in step 8) to guide the raw material in the lower bunker to the distribution chute (9), and charge it into the furnace from the distribution chute.

However, in such a vertical two-stage bunker type bellless blast furnace, the following problems have occurred regarding control of radial particle size distribution.

The first problem is that the average particle size of the raw material charged into the furnace from the distribution chute changes significantly over time. The cause of this will be explained below.

When the gate valves installed at the respective discharge ports of the upper bunker (5) are used simultaneously, the raw materials in the bunker are discharged sequentially from the bottom, creating a so-called mass flow state. As a result, the deposition state of the raw material in the lower bunker (7) becomes almost the same as the deposition state in the upper bunker (5).

Therefore, the rotating chute (
When the raw material is charged to the periphery of the upper bunker in step 4), the raw material accumulation state in the upper bunker (5) becomes V-shaped, with coarse particles in the center of the bunker and coarse particles in the periphery of the bunker due to the classification action when charging the raw material. Fine grains are deposited on the surface. Even after the raw material is charged from the upper bunker (5) to the lower bunker (7), coarse grains are deposited in the center and fine grains are deposited in the periphery within the lower bunker (7).

When the lower bunker (sword discharge port (8)) is opened in this state of grain size segregation, the coarse grains in the center are discharged in order, and the fine grains in the peripheral region are discharged last, resulting in a so-called funnel flow. The lower bunker (
The time change in the particle size of the raw material discharged from 7) shows a pattern in which coarse particles are discharged at the beginning of discharge and fine particles are discharged at the end, as shown in FIG.

Therefore, in the blast furnace, coarse grains are segregated and deposited on the furnace wall and fine grains are segregated and deposited in the center, and the gas flow rate at the furnace wall becomes excessive, increasing the furnace wall heat load and increasing the fuel ratio. lead to deterioration.

In general, variations in raw material quality (e.g. cold strength) cause variations in the particle size composition of the raw material, which in turn causes variations in the amount of coarse particles deposited on the furnace walls, which in turn causes fluctuations in the amount of gas flowing through the furnace walls. It makes blast furnace operation unstable.

The second problem is that it is not possible to control the radial particle size distribution because there is no means to control the temporal change in the particle size of the raw material discharged from the lower bunker.

That is, for example, in order to reduce the amount of gas at the furnace wall, the particle size of the raw material discharged from the lower bunker (7) is reduced in the early stage of discharge to deposit fine particles on the furnace wall, and at the end of discharge, the raw material with a large particle size is reduced. Since the coarse particles cannot be discharged and deposited in the center, it has not been possible to control the gas flow distribution in the radial direction with high precision.

Problems to be Solved by the Invention As mentioned above, the raw material charging system in the conventional two-stage vertical bunker type bellless blast furnace suffers from the fact that the average particle size of the raw material charged into the furnace from the distribution chute changes greatly over time. In the furnace, coarse particles are segregated and deposited on the furnace wall and fine particles are segregated and deposited in the center, and the gas flow rate at the furnace wall becomes excessive, increasing the furnace wall heat load and deteriorating the fuel ratio. radial particle size distribution control cannot be implemented, and radial gas flow distribution control cannot be performed at high speed. This method has the problem of not being able to be implemented accurately.

Therefore, this invention solves the problems of these conventional techniques,
This paper attempts to propose a raw material charging method and charging device that can improve the controllability of radial particle size distribution in the bellless blast furnace, in order to achieve stable operation of a vertical two-stage bunker type bellless blast furnace and reduce pig iron costs. It is.

Means for Solving the Problems This invention aims to improve the controllability of the radial particle size distribution in a raw material charging method for a vertical two-stage bunker type bellless blast furnace, that is, to improve the controllability of the particle size distribution of the raw material discharged from the lower bunker over time. In order to control the change with high precision, the following measures were taken.

(2) A plurality of raw material discharge ports are provided in the lower bunker as well as the upper bunker, and the raw material flow in the lower bunker is massed when the raw material is discharged from the lower bunker.

■ Control the opening/closing state of each discharge port of the upper bunker and/or the raw material discharge speed in order to control the time change in the particle size of the raw material discharged from the upper bunker.

■ When discharging raw materials in the lower bunker, open each outlet of the bunker at the same time.

In addition, as a raw material charging device for carrying out the above method,
The gist of this invention is to provide a plurality of raw material discharge ports in the lower bunker of the vertical two-stage bunker, and to arrange one of the discharge ports in the center of the bunker.

Operation: When discharging raw materials from the upper bunker, all raw material discharge ports of the bunker are opened, and the raw material discharge speed of each discharge port is controlled so that the raw material discharge time of each discharge port is approximately the same,
When discharging raw materials from the lower bunker, all raw material discharge ports of the bunker are opened, and the raw material discharge speed of each discharge port is controlled so that the raw material discharge time of each discharge port is approximately the same. The raw materials are discharged in the order in which they were charged into the bunker, and even if a particle size distribution occurs within the bunker, the average particle size of the raw materials charged into the furnace can be maintained approximately constant.

At the beginning of raw material discharge from the upper bunker, only the outlet in the vicinity where fine particles are accumulated is opened, and the others are closed to charge the lower bunker, and when discharging raw material from the lower bunker, By opening all the raw material discharge ports of the bunker and controlling the discharge speed so that the raw material discharge time of each discharge port is almost the same, the particle size of the raw material discharged from the bunker is reduced only in the initial stage of discharge. can.

At the beginning of raw material discharge from the upper bunker, only the discharge port in the center where coarse particles are accumulated is opened, and the others are closed to charge the raw material into the lower bunker. Open all the outlets of the bunker,
In addition, by controlling the discharge speed so that the raw material discharge time of each discharge port is approximately the same, the particle size of the raw material discharged from the bunker can be increased only in the initial stage of discharge.

Example FIG. 1 is a schematic diagram showing an embodiment of the present invention.

Here, an example will be explained in which three raw material discharge ports are provided in both the upper bunker and the lower bunker.

That is, in this invention, the lower bunker (7) also has raw material discharge ports (8-1) (8-2) in the same way as the upper bunker (5).
(8-3) and gate valve (V+ > (V2) (V3
> is provided.

In this case, a collection chute (0) is connected to the lower part of each discharge port to collect the raw materials in one place, and a distribution chute (9) is connected to this collection chute.

The raw material discharge ports of the upper bunker (5) and lower bunker (7) are arranged on the diameter line as shown in Figure 2, and the discharge ports (6-1) and (8-1) are located at the center of the bottom of the bunker. The exits (6-2), (6-3), (8-2), and (8-3) are located on concentric circles, respectively.

In the above apparatus, for example, when charging so that the average particle size of the raw material discharged from the lower bunker (7) is maintained constant, all discharge ports (6-1) of the upper bunker (5) (
6-2) CB-3>(D each gate valve (Vt>(V2
) (v3) and control the opening degree of each gate valve so that the time for discharging the raw material from each discharge port is constant, and the raw material in the upper bunker (5) is transferred to the lower bunker (7). Charge.

When the raw material in the blast furnace (1) descends and reaches a predetermined level, all gate valves (Vt) (Vz) (V3) installed at the three discharge ports of the lower bunker (7) are opened, and each The raw material in the lower bunker (7) is discharged by controlling the opening degree of each gate valve so that the raw material discharge time from the discharge port is constant, and the raw material in the lower bunker (7) is merged at the tip of each discharge port. The collected waste is guided to the distribution chute (9) through the collecting chute (9), and charged into the blast furnace from the distribution chute.

In addition, if you want to slightly reduce the particle size of the raw material discharged from the lower bunker ('7) only in the early stage of discharge, it is possible to Open only the gate valve (V2 > (V3), close the gate valve (■1) of the other discharge port, and after the desired time has elapsed, open the closed gate valve (Vt) to prevent further discharge. The raw material is charged into the lower bunker (7) while maintaining the particle size of the raw material constant.

When the raw material is discharged from the lower bunker (7), the gate valves of all the discharge ports are opened to convert the raw material in the lower bunker (7) into a mass flow.

In addition, if you want to slightly increase the particle size of the raw material discharged from the lower bunker (7) only at the initial stage of discharge,
), open only the gate valve (■1) of the central discharge port (6-1) where coarse particles are deposited, and close the gate valves (V2) and (V3) of the other discharge ports. Ok,
After a desired period of time has elapsed, the gate valves (2) and (3) are also opened, and the particle size of the discharged raw material is kept constant from then on, and the raw material is charged into the lower bunker (7).

When the raw material is discharged from the lower bunker (7), the beteno discharge ronocate valve (Vt > (V2) (V3)) is opened to convert the raw material in the lower bunker ('7) into a mass flow.

In addition, the number of raw material discharge ports in the bunker is, for example, 4 or 5.
If you want to increase the number of outlets, as shown in Figure 3, taking the upper bunker (5) as an example, if there are four outlets, three outlets ( 6-4) may be arranged on concentric circles. Similarly, when there are five outlets, there are four outlets (6-1) around the central outlet (6-1).
5) should be arranged on concentric circles.

Next, the results of investigating changes in the particle size of the raw material discharged from the lower bunker using the full-scale charging device model shown in FIG. 1 installed outside the furnace will be described.

Sintered ore and coke used in an actual furnace were used in the test. Test conditions are shown in Table 1.

In the conventional technology, the opening degree of the three gate valves in the upper bunker was set at 80°.
% constant, and the opening degree of one gate valve in the lower bunker was set to 9.
Figure 6 shows the change over time in the particle size of the raw material discharged from the lower bunker, assuming that the particle size is constant at 0%.

The present invention is an example of control that eliminates temporal changes in the particle size of the raw material discharged from the lower bunker.

In other words, in order to realize mass distribution of raw materials in the upper bunker, the opening degree of the gate valve of the discharge port installed in the center of the upper bunker is reduced to 50%, and the raw material is discharged from each discharge port of the upper bunker. The time was fixed.

The opening degree of the gate valve of each discharge port in the lower bunker was set so that the raw material discharge time from each discharge port was constant, and the mass flow of raw materials in the lower bunker was promoted.

Figure 4 shows the change in particle size of the raw material discharged from the lower bunker over time.

From Figure 4, compared to the results shown in Figure 6 for the conventional technology, the time change in the particle size of the discharged raw material is significantly reduced, and the particle size of the raw material discharged from the practical upper and lower bunkers can be maintained constant. There was found.

The present invention (2) is an example in which the particle size of the raw material discharged from the lower bunker is controlled to be slightly coarse only in the early stage of discharge, and to be constant after the middle stage of discharge.

In other words, at the beginning of raw material discharge from the upper bunker, the opening degree of the gate valve at the outlet in the center where coarse particles are accumulated is slightly increased, and the opening degree of the gate valve at the outlet in the peripheral area where fine particles are accumulated is increased slightly. The opening degree of the gate valve of each discharge port was made the same as that of the present invention after the middle stage of raw material discharge.

The raw materials were discharged from the lower bunker in the same manner as in Invention I, and the results are also shown in FIG.

From Figure 4, compared to the conventional technology, the increase in particle size at the beginning of raw material discharge is slight, and the particle size after the middle stage of raw material discharge remains almost constant, and the radial particle size distribution in the blast furnace is It was shown that high precision control is possible.

Invention (2) is an example in which the particle size of the raw material discharged from the lower bunker is controlled to be slightly fine only in the early stage of discharge, and the particle size from the middle stage onwards to be constant.

In other words, at the beginning of raw material discharge from the upper bunker, the opening degree of the gate valve at the outlet in the peripheral area where fine particles are accumulated is slightly increased, and the opening degree of the gate valve at the central outlet is slightly decreased. After the middle stage of discharge, the opening degree of the gate valve of each discharge port was the same as that of the present invention (2).

The raw materials were discharged from the lower bunker in the same manner as in the present invention.

The results are also shown in FIG. 4.

It has been found that in contrast to the prior art in which it was not possible to reduce the particle size of the raw material at the initial stage of discharge, in the present invention (2), the particle size of the raw material could be reduced only at the early stage of discharge.

The above is an application example in which the bunker has three discharge ports for both the upper and lower bunkers, but it goes without saying that the same effect can be obtained when the number of discharge ports is increased as shown in FIG.

In addition, here, we have shown a case in which a rotating chute is installed in the upper bunker and raw materials are charged to the periphery of the upper bunker. When the surface shape of the raw material deposited in the upper bunker takes on an inverted V-shape, fine grains are deposited in the center of the upper bunker and coarse grains are deposited in the periphery due to the classification action during raw material charging. can also be applied.

For example, in order to make the particle size of the raw material discharged from the lower bunker only yellow or coarse in the early stage of discharge, and to keep the particle size constant after the middle stage of discharge, as in the present invention (2), the raw material discharged from the upper bunker Initially, the opening degree of the gate valve at the outlet in the peripheral area where coarse particles are accumulated may be made slightly larger, and the opening degree of the gate valve at the outlet in the central area where fine particles are accumulated may be made smaller.

As explained in detail below, the present invention makes it possible to completely eliminate temporal changes in the particle size of the raw material discharged from the upper bunker in a vertical two-stage bunker type bellless blast furnace. The particle size of the raw material discharged can be maintained constant.

In addition, it is possible to control the particle size of the raw material discharged from the lower bunker so that it is slightly coarse only in the early stage of discharge and remains constant after the middle stage of discharge. It is possible to control the particle size to be slightly finer only in the early stage of discharge, and to keep the particle size constant after the middle stage of discharge.

Therefore, it becomes possible to control the radial particle size distribution in the blast furnace with high precision, which greatly contributes to maintaining stable operation of the bellless blast furnace and reducing ironmaking costs.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram showing a device according to an embodiment of the present invention, Fig. 2 is a schematic diagram showing raw material discharge ports of a bunker in the same device, and Fig. 3 (A> shows the arrangement when there are four raw material discharge ports). For example, Figure 4 (B) is a schematic diagram showing an example of the arrangement when there are five raw material discharge ports, and Figure 4 is a diagram showing the raw material discharge time from the lower bunker and the average sintered ore charging in the embodiment of this invention. A diagram showing the relationship between grain sizes, Figure 5 is a schematic diagram showing an example of raw material charging equipment for a conventional two-stage vertical bunker type bellless blast furnace, and Figure 6 shows the raw material discharge time from the lower bunker and sintered ore in the same equipment. It is a diagram showing the relationship between charging average particle diameter. 1... Blast furnace 3... Raw material 4... Rotating chute 5... Upper bunker 6-1. 6-2
．． 6-3... Upper bunker discharge port 8-1. 8-
2. 8-3... Lower bunker discharge port 9... Distribution chute 10... Collection chute Applicant Sumitomo Metal Industries Co., Ltd. Agent Patent attorney Yoshihisa Oshida 1r] Figure 1

Claims (1)

[Scope of Claims] 1. A raw material charging method for a bellless blast furnace in which two top bunkers are provided vertically on the furnace axis, and raw materials discharged from the lower bunker are charged into the furnace via a distribution chute. In a bellless raw material charging device in which a plurality of raw material discharge ports are provided in a bunker and a lower bunker, and one of the discharge ports is provided in the center of the bottom of the bunker, the opening/closing state of the upper bunker discharge port and/or the raw material discharge A raw material for a bellless blast furnace characterized in that the particle size distribution of the raw material in the lower bunker is controlled by controlling the speed, and that each discharge port of the bunker is opened simultaneously when discharging the raw material in the lower bunker. How to charge. 2. In a raw material charging device for a bellless blast furnace, in which two top bunkers are provided vertically on the furnace axis, and the raw material discharged from the lower bunker is charged into the furnace via a distribution chute, the upper bunker and the lower bunker are A raw material charging device for a bellless blast furnace, characterized in that a bunker is provided with a plurality of raw material discharge ports, and one of the discharge ports is arranged at the center of the bottom of the bunker.