JPH06256828A - Method for charging raw material into bell-less blast furnace - Google Patents

Abstract

PURPOSE:To charge finer grains at the initial stage and coarser grains at the end stage in the secular change pattern of grain diameters of the raw material discharged from a furnace top bunker, in a bell-less blast furnace having a single port type bunker in series. CONSTITUTION:In a method for charging the raw material into the blast furnace having the single port type center feed system bell-less charging device, while the raw material is charged from the furnace top bunker of a preceding step to the furnace top bunker 11 of the lowermost step, gas is blown into the bunker from plural directions at the bottom part of the side wall in the furnace top bunker 11 of the lowermost step. By this gas, the fine grains having a tendency to flow near the furnace top bunker wall are blown off in the center axial direction, and the coarse grains are piled on the bunker wall and the fine grains are piled around the center axis.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a raw material storage tank (hereinafter referred to as "top bunker") having one raw material receiving port and one raw material discharging port arranged in series at the top of a blast furnace, and a furnace interior The present invention relates to a raw material charging method in a so-called single-port center-feed type bellless blast furnace equipped with a distribution chute.

[0002]

2. Description of the Related Art In blast furnace operation, it is a basic operational task to control the gas flow distribution in the radial direction of the furnace to stably reduce and dissolve the ore in the furnace. The main control means of the in-furnace gas flow distribution in the blast furnace operation is the control of the charge distribution at the top of the furnace. More specifically, the deposition weight ratio distribution of ore and coke in the in-furnace radial direction "hereinafter," O / C distribution " And)
To adjust the particle size distribution of each ore and coke.

By the way, the raw material charging device in the bellless blast furnace can be roughly classified into one having a furnace top bunker for directly supplying the raw material into the furnace (series type) and a plurality of furnace top bunkers (parallel type). FIG. 4 shows an example of a bellless charging device having a two-stage furnace top bunker in series, in which a raw material (ore, sinter ore, coke) 1 is conveyed by a belt conveyor 2 to the upper bunker 3 at the top. And is supplied to the lower top bunker 4 discharged from here.

When the charge in the furnace is unloaded and reaches a predetermined stock line 5 to be replenished, a gate valve 6 and a seal valve 7 for adjusting the flow rate of the charge in the lower bunker 4 of the furnace top. Is operated to supply the raw material 8 in the lower top bunker 4 onto the distribution chute 9, and the tilt angle and the number of turns of the distribution chute 9 are adjusted to bring the raw material 8 into the furnace 1.
Charge 0.

Therefore, the 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 distribution chute and allocation of the number of turns in this tilt angle). The particle size distribution is controlled by utilizing the change over time in the particle size of the raw material charged into the furnace.

That is, normally, in the bellless charging, the distribution chute is rotated 10 times or more to charge the raw material into the furnace, and during that time, the tilt angle of the distribution chute is changed once or more to drop the raw material in the furnace. It takes the form of charging that changes its position one after another. 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 radial direction in the furnace.

[0007] 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 cause 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 raw material in 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).

By the way, the bellless charging device includes one having a series-type top bunker as shown in FIG. 4 and one having a plurality of bunker tops in parallel as shown in FIG. is there.

In a parallel type charging device having two furnace top bunker as shown in FIG. 5, the raw material 1 supplied from the belt conveyor 2 is alternately supplied to two (or more) furnace top bunker 4. The method of storing and then charging into the furnace 10 is adopted.

Regarding these two types of charging systems, the series type and the parallel type, there are differences in the characteristics of the distribution control of the contents inside the furnace in some respects. One of the major differences among them is as follows. Top bunker directly connected to the distribution chute (in the case of the series two-stage type as shown in Fig. 4, this is the bottom bunker in the lower stage, and in the parallel type as shown in Fig. 5, the tops are arranged in parallel. There is a difference in the charging time of raw materials into the bunker.

That is, in the parallel type, while one furnace top bunker is carrying out the furnace interior filling, the other furnace top bunker can receive the raw material from the belt conveyor,
If the pressure in the bunker at the top of the furnace is equalized when the receiving is completed, the next charging can be carried out immediately.

On the other hand, in the case of the in-line type, while the lower bunker is carrying in the furnace interior, the raw material can be received from the belt conveyor to the upper bunker at the upper stage in parallel, but In order to complete the preparation for charging, after this, the pressure in the upper bunker on the lower stage is discharged, the raw material from the bunker on the upper stage is charged into this, and the pressure in the lower bunker on the lower stage is made equal to the pressure inside the furnace. I have to equalize the pressure as much as possible,
As a result, the margin of the charging sequence is reduced.

This is an important problem under the operation of high output ratio where the feed pitch of the raw material becomes fast, and in the case of the serial type, the raw material charging from the upper bunker to the lower bunker is as follows. In this type of blast furnace, it is usually necessary to carry out the process in the shortest time possible, so in this type of blast furnace, the actual raw material from the top bunker of the upper stage to the bunker of the lower stage (that is, the bunker directly connected to the distribution chute) is used. The charging time is approximately 10 to 30 seconds.

On the other hand, since the raw material charging time from the belt conveyor is about 2 minutes, the raw material charging time in the case of the parallel type is about 5 times or longer than that of the series type. There is.

The difference in the charging time of the raw material into the furnace top bunker directly connected to the distribution chute as described above has an effect on the particle size aging pattern when the raw material is charged into the furnace interior. That is, the charging time of the raw material into the furnace top bunker, in other words, the raw material charging speed, changes the radial particle size distribution of the raw material inside the furnace top bunker, and when the material is discharged from this furnace bunker ( It affects the particle size aging pattern (when the raw material is charged into the blast furnace), that is, the particle size aging pattern of the raw material charged into the furnace.

In general, when a granular material having a particle size constitution such as a raw material used in a blast furnace is deposited, the particle size distribution which appears in the radial direction of the deposited layer, that is, the particle size segregation phenomenon changes depending on the supply condition of the granular material. It is qualitatively known to do so (for example, Iron and Steel 74 (1988) P.978).

As described above, in the bellless charging, the charging angle is changed by sequentially changing the tilt angle of the distribution chute to change the dropping position of the raw material in the furnace when the raw material is charged into the furnace one time. , At this time, the charging method of charging the raw material by the distribution chute from the center of the furnace toward the furnace wall (hereinafter, referred to as “external distribution method”), conversely, charging the raw material to the furnace wall side first, There is a charging method (hereinafter referred to as "internal distribution method") in which charging is sequentially performed toward the center.

Of these, the internal swing distribution method is generally the mainstream from the viewpoint of reducing the load on the distribution chute drive device. However, in the internal swing distribution method, as described above, the internal swing distribution method is used. The raw materials are deposited on the furnace wall side, and the raw materials at the final stage of charging are deposited from the center of the furnace.

In general, it is empirically known that in order to secure the stability of the furnace condition, it is necessary to make the gas flow in the center of the furnace stronger than in other regions. Therefore, it is indispensable to keep the air permeability in the furnace central part good by controlling the distribution of the charge, and specifically, the deposited particle size in the furnace central part must be increased.

By the way, the particle size distribution of the raw material in the furnace necessary for stable operation of the furnace, that is, the state in which the fine-grained raw material is deposited on the furnace wall and the coarse-grained raw material is deposited on the central part of the furnace, is determined by the above-mentioned internal distribution method. In order to obtain it, it is necessary to charge the fine-grained raw material in the initial stage of the raw material charging and the coarse-grained raw material in the final stage.
For that purpose, the particle size of the raw material discharged from the furnace bunker at the bottom must also be fine in the initial stage and coarse in the final stage.

In order to obtain such a particle size change pattern of the discharged raw material, the particle size distribution in the lowermost furnace bunker must be adjusted to a shape suitable for this.

However, as described above, the physical distribution in the top bunker 4 at the time of discharging the raw material is the funnel flow,
The raw material 8 is discharged from the inside of the furnace top bunker 4 in the order shown by to in FIG. Therefore, in order to obtain the above-mentioned particle size change pattern, it is necessary to deposit fine particles near the central axis of the furnace top bunker and coarse particles around the furnace top bunker wall.

In a bell-less charging system having a parallel bunker, the rate of charging the raw material into the furnace top bunker is relatively slow, so that fine particles are present at the material dropping point (that is, near the central axis of the furnace top bunker). The raw material is deposited, and the coarse-grained raw material is deposited near the wall of the furnace top bunker that is farthest from the dropping point.
Therefore, in the parallel type bunker, a desired particle size distribution can be naturally obtained, and the gas flow distribution in the blast furnace to be targeted can be relatively easily obtained.

[0024]

However, in the bellless charging system having the in-line type bunker, as described above, the charging rate of the raw material into the bottom-top bunker is very high, and conversely, the bunker center The distribution is such that relatively coarse material is deposited near the axis and fine material is deposited near the furnace top bunker wall. That is, in the series bunker, it is not easy to properly control the gas flow distribution pattern in the blast furnace.

Several methods have been proposed for controlling the particle size aging pattern of the discharged raw material in the bell-less bunker, but if roughly classified, a workpiece is installed in the bunker and the shape and A method for adjusting the position (Japanese Patent Publication No. 2-401, Japanese Patent Publication No. 3772, etc.),
There is a method (Japanese Patent Application No. 3-47552, Japanese Patent Application No. 3-57589, Japanese Patent Application No. 3-58509, Japanese Patent Application No. 4-1408) of adjusting raw material charging conditions into the furnace bunker.

However, the former method has a problem in maintenance because the raw material always collides with the workpiece, and the latter method has a risk of conflicting with the charging sequence.

In view of the above situation, the present invention provides a bellless blast furnace having a single-port series bunker,
Provide a method in which the temporal change pattern of the particle size of the raw material discharged from the furnace top bunker can be made into fine particles in the initial stage and coarse particles in the final stage, and there is no problem with facility maintenance and charging sequence. Is intended.

[0028]

In order to achieve the above-mentioned object, a method for charging a raw material for a bellless blast furnace according to the present invention is a single port type center feed type bellless charging device in which a raw material bunker is arranged in series on the furnace top. In the method of charging the raw material into the blast furnace that has, while charging the raw material from the top bunker of the previous stage to the bottom bunker of the lowermost stage of this blast furnace, from inside the bunker from multiple directions of the side wall bottom of the bottom bunker of the lowermost stage The gas is blown into the bunker wall at the top of the furnace by this gas to blow away fine particles in the central axis direction to deposit coarse particles on the bunker wall and fine particles around the central axis. That is, the change pattern of the particle size of the raw material discharged from the furnace bunker at the bottom is changed to a desired shape.

[0029]

Next, the action of the action of "injecting gas into the vicinity of the bunker wall to form a gas flow when the raw material is charged into the lowermost furnace bunker" which is a constituent feature of the present invention will be described.

Generally, when a particle is placed in an air stream, the particle tries to move by receiving a force from the air stream. At this time, it is known that the magnitude of the force that the particles receive from the air flow is proportional to the square of the flow velocity of the air flow and the projected area of the particles with respect to the air flow. If this force exceeds the gravity acting on the particles. , Particles can be carried away by the air flow.

That is, as the particle size of the fine-grained raw material to be removed at least from the furnace wall of the furnace top bunker, the particle size of the sintered ore is about 5 mm or less, the coke is about 30 mm or less, and the particle size is 10 mm or more and 40 mm or more, respectively. Assuming that the minimum amount of sedimentation is allowed, the flow velocity of the air flow to be formed on the furnace wall of the furnace bunker is 15 to 2 for the sinter.
The optimum value is 0 m / sec and 22 to 27 m / sec for coke.

However, since the deviation of the particle size distribution in the radial direction in the bunker in the furnace top remarkably appears in the case of charging the sintered ore in reality, the method of the present invention is applied only when charging the sintered ore. Even if only applied, a sufficient effect can be obtained to improve the controllability of the gas flow distribution in the furnace.

[0033]

EXAMPLE In order to verify the effect of the method of the present invention,
Experiments were conducted using a 10-scale scale model. Table 1 shows the experimental conditions, and FIG. 1 shows a schematic view of the gas blowing device for carrying out the method of the present invention.

In FIG. 1, reference numeral 11 denotes a lowermost furnace top bunker, and an appropriate number (eight in this embodiment) of gas blowing ports 12 are provided in a plurality of orientations at the bottom of the side wall of the furnace top bunker 11. From the outside, for example, an inert gas supply pipe 13, through the gas blowing port 12, a furnace top bunker 11
A gas having a required flow rate adapted to the above-mentioned charge can be blown into the inside. In addition, 14 in FIG.
Is a flow rate adjusting valve provided in the middle of the supply pipe 13, and 15 is a raw material discharge port.

In the model test, sinter ore was used as an experimental material, and 3 mm or less was regarded as a fine-grain raw material, and the amount of gas blown was a dimensionless radius of 0.9 to 1.
An amount capable of forming an air flow for excluding the fine-grain raw material is set in the region of 0, and the raw material charging time is determined based on the condition of Froude number matching.

FIG. 2 shows a particle size distribution made dimensionless by the charged average particle size of the deposited raw material in the inner diameter direction of the furnace top bunker after the charging is completed.
FIG. 3 shows change patterns of the dimensionless particle size of the raw material discharged from the furnace top bunker.

[0037]

[Table 1]

2 and 3, according to the method of the present invention,
By blowing gas, fine particles accumulated near the bunker wall at the top of the furnace are removed from the same part, so the average particle size increases, while the average particle size around the central part of the bunker decreases. It is clear that

As a result, the particle size variation pattern of the raw material discharged from the furnace top bunker changes from the shape of coarse particles in the initial stage to the shape of fine particles in the final stage to the shape of fine particles in the initial stage and coarse particles in the final stage. It is possible to obtain an easy pattern to secure the gas flow in the central part of the furnace.

[0040]

As described above, according to the method of the present invention,
At the time of charging the raw material into the top bunker at the bottom, gas is blown into the bunker from the bottom of the side wall of the bunker, which prevents the deposition of fine-grained raw material near the bunker wall. The change in particle size with time when the raw material is discharged from the bunker can be made into a pattern in which fine particles are obtained in the early period of discharge and coarse particles are obtained in the late period of discharge. Therefore, in the single-port center-feed type bellless blast furnace, basic gas flow distribution control for ensuring the gas flow velocity in the center of the furnace can be easily performed.

[Brief description of drawings]

FIG. 1 is a diagram showing an installation example of gas blowing equipment for carrying out the method of the present invention, (a) is a vertical sectional view, and (b) is a view taken along the line bb in FIG.

FIG. 2 is a diagram showing an example of a particle size distribution in a furnace bunker.

FIG. 3 is a drawing showing changes over time in the particle size of raw materials discharged from a furnace bunker.

FIG. 4 is a schematic view of an in-line bunker / bellless charging system.

FIG. 5 is a schematic view of a parallel bunker / bellless charging system.

FIG. 6 is an explanatory diagram of a discharge order of raw materials in a furnace bunker.

[Explanation of Codes] 11 Top Bunker 12 Gas Injection Port 13 Gas Supply Pipe 14 Flow Control Valve

Claims (1)

[Claims] 1. A method for charging a raw material bunker into a blast furnace having a single-port center-feed type bellless charging device in which the raw material bunker is arranged in series at the top of the blast furnace, wherein the bunker at the bottom of the blast furnace is provided with a furnace at the front stage. A method for charging a raw material for a bellless blast furnace, characterized in that gas is blown into the bunker from multiple directions at the bottom of the side wall of the furnace top bunker at the lowest stage while charging the raw material from the top bunker.