JP2002146415A - Method for operating blast furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for operating a blast furnace, by which the remaining iron slag quantities can be reduced by changing the operational factor of the blast furnace and making a simple ingenious plan for a part of a facility without raising the cost of a molten iron. SOLUTION: In the method for operating the blast furnace, by which coke and iron ores are charged from a furnace top to form the deposited layer of charged materials at the upper part in the furnace and a furnace core coke layer at the lower part in the furnace, the coke are burned with the blast blown from a tuyere to generate the high temperature reducing gas, and the molten iron and slag produced by melting and reducing the iron ores are made flow down and retained on the furnace hearth part and are properly discharged from a molten iron tapping hole, the slag quantity retained in the furnace during operation is calculated, and the operational factor contributing to the float-up of the furnace core coke layer is changed when the calculated value exceeds the reference value for stable operation. In this case, it is preferable that the operational factors are defined as one or more kinds selected among the ratio of the charged iron ore kinds to the coke, the distribution in the radius direction of the charged materials in the blast furnace and the blast volume.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a blast furnace operating method, and more particularly, to a method for reducing the amount of residual iron slag in a furnace as much as possible.
The technology relates to maintaining stable operation at all times.

[0002]

2. Description of the Related Art In a blast furnace, raw materials (iron ores and coke) are charged and deposited in layers, and high-temperature air is blown from a lower part of the furnace to burn coke in the furnace and to reduce high-temperature reducibility. Gas is generated, and while this high-temperature reducing gas rises in the furnace, the temperature of the raw material deposited in the furnace is raised, and the ore is reduced and melted, and molten iron and slag flow down to the hearth. I have. As described above, ores are melted and disappear at the lower part of the furnace,
The lower part of the furnace forms a packed bed of coke.

[0003] Hot metal and slag flowing down to the hearth are discharged out of the furnace by opening a tap hole provided in the hearth. In large blast furnaces constructed in recent years, this tap hole has 2 to 4 taps.
An operation is performed in which the hot metal and the slag flowing down to the furnace bottom are constantly discharged outside the furnace by appropriately opening and closing these tap holes.

FIG. 2 schematically shows a state in the furnace immediately after one of the tap holes is closed and the other is opened. As shown in FIG. 2, in the closed tap hole 1 on the right side, the liquid level positions 2 and 3 (hereinafter, referred to as levels) of the hot metal and the slag are the tap holes 1.
Has decreased to almost the height inside the furnace. This is because the taphole 1 was closed after the hot metal and slag were discharged until the gas in the furnace was ejected. On the other hand, in the tap hole 4 on the left side, which has just been opened, the slag level 3 is at a position considerably higher than the inside height of the tap hole 4 in the furnace. This means that the slag that has accumulated near the taphole on the left side does not flow much to the taphole side on the right side that was opened during the previous tapping. This is because there was resistance of the coke packed bed 5 and it was difficult for hot metal or slag to pass through the coke packed bed 5 from near the taphole on the left side to near the taphole on the right side. After the opening of the left tap hole 4, the hot metal or slag is gradually discharged from the left tap hole 4 to the outside of the furnace, and the levels 2 and 3 of the hot metal or slag decrease. However, since the blast furnace operation is continuous, new hot metal or slag is constantly generated and flows down to the hearth 6, so that newly generated hot metal or slag is near the right taphole on the opposite side. Accumulate and their level increases. As described above, the levels 2 and 3 of the hot metal and slag in the hearth 6 of the blast furnace alternately rise and fall near each tap hole according to the tapping time. In fact, in addition to the flow of hot metal and slag inside the furnace, the balance between the amount of their production and the amount of discharge outside the furnace,
Levels 2 and 3 of the hot metal and slag in the furnace are determined.

In the blast furnace, the tuyere 7 shown in FIG.
Hot air is supplied into the furnace from the furnace to burn the coke and the pulverized coal simultaneously blown from the tuyere 7, and the iron ore charged separately from the furnace top using the generated CO gas;
Reduces and melts slag-forming agents, etc. to produce hot metal and slag. At this time, if the level 3 of the slag in the furnace rises and reaches the installation position of the tuyere 7, the slag undesirably causes tuyere melting. Even if the slag level 3 is not so high, if it is relatively high, the slag level will affect the flow of gas rising in the furnace, and the operation will often be unstable. Therefore, the level of molten iron or slag (usually referred to as residual iron slag in the furnace) at levels 2 and 3
Is preferably as low as possible. That is,
For stable operation of the blast furnace, it is important to reduce the amount of residual iron slag in the furnace.

[0006]

In order to keep the level of slag and hot metal from being too high during operation, it is conceivable to improve the flow of hot metal and slag passing through the coke packed bed 5 in the furnace. . Specifically, it is a method of increasing the particle size of the coke to be filled to widen the flow path or reducing the viscosity of the hot metal and slag. In addition, when decreasing the viscosity, the molten iron has a much lower viscosity than the slag, so it is effective to lower the viscosity of the larger slag.

However, among these methods, it is easy to increase the coke particle size by increasing the size of the coke sieve, but the coke having a small particle size that cannot be used in a blast furnace is increased. It is not preferable to increase the cost per unit amount of hot metal. As another method, Japanese Patent Application Laid-Open No. 5-70813 discloses a lower central portion of a coke packed bed of a blast furnace (usually, it has an upward cone shape and is called a deadman or a core coke layer 5).
A technique is disclosed in which a lance that blows oxygen or air is inserted into the furnace to directly burn small-diameter coke with air or the like to increase the particle size of coke existing in the core coke layer 5. However, this technique requires maintaining the lance in a high-temperature furnace for a long period of time, or requires frequent replacement of the lance, and is not considered to be practical. Furthermore, Japanese Patent Publication No. Hei 6-37649 discloses that the quality of a part of coke which is charged from the furnace top to the furnace center and is considered to form the core coke layer 5 is improved and the core coke layer 5 is formed. A technique for increasing the particle size of coke is disclosed. However, this technique also requires an additional special charging device, and it takes more than one week for the core coke layer to be replaced, so that it is insufficient as a control means.
Furthermore, cost is also required to improve coke quality, and an increase in hot metal cost is inevitable. In addition, in the method of reducing the viscosity of the slag, a large amount of a slag-making agent for changing the composition of the generated slag must be used, and this method also increases the cost of hot metal.

The present invention has been made in view of the above circumstances, and has been made to change the operating factor of blast furnace operation without increasing the cost of hot metal,
It is an object of the present invention to provide a blast furnace operating method capable of reducing the amount of residual iron slag in a furnace by simply devising a part of the equipment.

[0009]

The inventor of the present invention considers that in order to achieve the above object, it is necessary to clarify the factors that determine the amount of residue in the hearth. We tried to find out the relationship between this and the amount of residual iron slag in the furnace by model experiments.

First, a half-cylindrical model hearth as shown in FIG. 3 was manufactured. This model is a 1/25 scale of a blast furnace having a hearth diameter of 10 m, and the front surface is formed of a transparent acrylic resin plate so that the inside corresponding to the hearth can be observed. Into the model hearth 8, plastic beads having a diameter of 6 mm were charged as pseudo coke to form a packed layer. The bead filling layer 9 supports the lower portion with a wire mesh 20 to stabilize the shape of the filling layer,
The packed bed itself can be moved up and down. The reason why the whole of the bead packed layer 9 can be moved up and down is that in the actual blast furnace, the specific gravity of the coke is smaller than that of the hot metal. Floating on
This is because it is said that there is a region 10 where the coke packed layer 5 does not exist (hereinafter, referred to as a free space 10).

In the model experiment, the specific gravity was 1.8 as pseudo hot metal.
Liquid freon 11 and oil 12 having a specific gravity of 0.8 as a pseudo slag are supplied from the upper part of the model to a pseudo coke packed layer (also referred to as a bead filled layer 9), and pseudo tap holes provided on the lower left and right walls. From No. 13 was carried out by discharging. Air 14 at a pressure of 30 kPa was supplied into the model during liquid supply by imitating gas in the furnace. Simulated taphole 1
The timing of switching between opening and closing of No. 3 was based on blowing gas (in this case, air 14) as in the actual blast furnace. That is, the liquid Freon 11 and the oil 12 are discharged from the pseudo tap hole 13, and when the upper surface 21 of the oil 12 falls to the level of the pseudo tap hole 13, the air 14 is discharged from the pseudo tap hole 13. Therefore, the opening and closing of the pseudo tap hole 13 were switched at the timing when this phenomenon occurred.

FIGS. 4A and 4B show examples of the experimental results. This is because, as shown in FIG. 4B, the bead-filled layer 9 in the hearth is gradually lifted and the upper end position of the free space 10, that is, the boundary position between the bead-filled layer 9 and the furnace wall is variously changed. Next, the results of an investigation on the amount of residue (slag) in the simulated hearth will be described. The boundary position was changed by setting the center line position 13a of the pseudo tap hole 13 to 0 and moving the entire bead-filled layer 9 up and down. The residue ratio was determined as 0% when no pseudo slag was accumulated above the taphole level, and 100% when pseudo slag was accumulated up to 40 mm above the pseudo taphole 13. 4A, when the upper end position of the free space 10 is low (H = −40 mm), the amount of residue is large, but the lower end of the furnace wall of the bead packed layer 9 is lifted to above the pseudo tap hole 13, When the upper end position of the free space 10 is raised (H = + 20, +40, +80 mm), a new finding is obtained that the amount of residue decreases.

When the bead packed layer 9 exists inside the furnace of the pseudo tap hole 13 (see FIG. 5A),
Before the pseudo slag was sufficiently discharged, gas was blown out, and it was necessary to switch the left and right of the pseudo tap hole 13. This is because the resistance of the bead filling layer 9 was large, and the pseudo slag (arrow C) did not easily flow through the inside. On the other hand, when the free space 10 exists inside the furnace of the pseudo tap hole 13 (see FIG. 5B), a phenomenon in which the pseudo slag in the furnace is significantly reduced was confirmed. This is a pseudo taphole 1
Since an annular flow (arrow D) of pseudo slag which selectively flows through the free space 10 inside the furnace of No. 3 is generated, the pseudo slag flows radially (arrow E) from the inside of the bead packed layer 9 to the return flow. It is. In other words, it is considered that the pseudo slag flows easily in the bead-filled layer 9 because the flow of the pseudo slag is dispersed and the linear velocity decreases, thereby reducing the resistance.

Next, the inventor conducted an experiment to clarify the size (size) of the free space 10 for improving the waste property. First, as shown in FIG. 6, one of the two pseudo tapholes 13A and 13B on the left and right is completely covered with the bead-filled layer 9, and the degree of the covering is represented by an angle θ from the center of the model. did. Then, the residue ratio was measured with the angle θ changed variously, and the results are shown in FIG. From FIG. 7, it has been clarified that the pseudo tap hole 13A having the free space 10 inside the furnace has less residue than the pseudo tap hole 13B covered with the bead-filled layer 9 at all times. On the other hand, even when the size of the bead-filled layer 9 covering the pseudo taphole 13B is still small, that is, θ = 10 °
By the tailings are getting worse. Further, in the pseudo tap hole 13A having the free space 10 in front of the tap hole furnace, when the size of the free space 10 becomes small (θ is 170 ° or more), the residue ratio sharply increases. From the above results, when a region in which the bead-filled layer 9 does not exist is formed in front of the pseudo tap hole 13 on the inside of the furnace, the free space 10 is placed at another location (near the furnace wall where the tap hole is not installed). It was found that the formation of the residue was more effective in reducing the amount of residue. FIG. 1 shows the relationship between the filling state of the beads in front of the pseudo taphole and the shapes of the respective upper surfaces of the oil and liquid fluorocarbon in the experimental apparatus. This shape is the shape at the timing when the air is mixed with the oil and liquid Freon discharged from the pseudo taphole and discharged.

Since the pseudo slag has a high viscosity, when passing through the bead-filled layer 9, the shape of the upper surface 21 is
It is inclined toward the pseudo taphole 13 (see FIG. 1A). Since this inclination becomes larger as approaching the pseudo taphole 13, even if only a small area around the taphole is covered with the bead-filled layer 9, the cross-sectional shape of the pseudo-slag is entirely the bead-filled layer. 9 is almost the same as the above case (see FIG. 1B). On the other hand, under the condition of θ = 0 °, that is, when there is the free space 10, since no inclination is formed on the slag surface, almost all the pseudo slag is discharged (see FIG. 1 (c)). According to the above experimental results, the free space 10 does not necessarily need to be present in the entire front of the inside of the taphole furnace. It was confirmed that the residue could be stabilized at a low level.

When the results of these model experiments are summarized,
In order to reduce the amount of residual iron slag in the blast furnace, it is effective to positively form a free space state where there is no coke packed bed around the opening inside the tap hole during tapping It can be said. Therefore, the inventor has sought a method for embodying such a free space and came up with the following method.

That is, according to the present invention, coke and iron ore are charged from the furnace top, a deposited layer of the charged materials is formed in the upper part of the furnace, and a core coke layer is formed in the lower part of the furnace. After burning the coke by blowing air from it to generate high-temperature reducing gas, melting and reducing the iron ores, the hot metal and slag generated by flowing down to the hearth are allowed to stay, and then from the tap hole as appropriate. In the blast furnace operating method to be discharged, the amount of slag remaining in the furnace during operation is calculated, and when the calculated value exceeds the reference value for stable operation, a change operation of an operation factor contributing to the ascent of the core coke layer is performed. This is a method for operating a blast furnace. In this case, it is preferable that the operation factor is one or two or more selected from the ratio of iron ore and coke to be charged, the radial distribution of the charged material, and the amount of air blown.

Further, according to the present invention, coke and iron ore are charged from the furnace top, a deposited layer of the charged materials is formed in the upper part of the furnace, and a core coke layer is formed in the lower part of the furnace. After burning the coke by blowing air from it to generate high-temperature reducing gas, melting and reducing the iron ores, the hot metal and slag generated by flowing down to the hearth are allowed to stay, and then from the tap hole as appropriate. In the blast furnace operating method for discharging, a blast furnace operating method is characterized in that the blowing condition of a tuyere installed immediately above a taphole is controlled independently of a tuyere installed at another position. At this time, it is preferable that the air blowing conditions are one or more selected from the air blowing amount, the enriched oxygen amount and the diameter of the tuyere.

Further, according to the present invention, coke and iron ore are charged from the furnace top, a deposited layer of the charged materials is formed in the upper part of the furnace, and a core coke layer is formed in the lower part of the furnace. After burning the coke by blowing air from it to generate high-temperature reducing gas, melting and reducing the iron ores, the hot metal and slag generated by flowing down to the hearth are allowed to stay, and then from the tap hole as appropriate. In the blast furnace operating method to discharge, calculate the amount of slag remaining in the furnace during operation, and when the calculated value exceeds the standard value for stable operation, when closing the tap hole after tapping, the mud material A blast furnace operating method characterized in that the filling amount is reduced from that in normal operation.

According to the present invention, when it becomes necessary to reduce the amount of residual iron slag in the blast furnace, the core coke layer is floated, and the coke bed is not present on the furnace floor in front of the taphole furnace. To form As a result, the slag at the time of tapping becomes smooth, the amount of the remaining slag is reduced, and the stable operation of the blast furnace can be maintained. Further, in the present invention, the blowing condition to the tuyere installed immediately above the taphole is made different from that of the tuyere installed at another position, the raceway depth is increased, and the front of the taphole inside the furnace is increased. The same effect can be achieved because a condition without a coke packed bed is formed in the hearth portion of (1). In addition, as a highly responsive measure, reducing the filling amount of mud material after tapping and making the taphole depth shallower,
Tapping slag can be performed smoothly.

[0021]

Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1) The average lower end position of the core coke layer 5 when the coke packed layer 5 (hereinafter referred to as the core coke layer 5) shown in FIG. The sum of the weight of the coke layer 5 and the load applied to the core coke layer 5 from above,
It is thought that it is determined by the balance with the buoyancy generated by being buried in the slag.

Of these, an increase in buoyancy is equivalent to an increase in the amount of residual iron slag in the furnace, and is an operation incompatible with a reduction in the amount of residual iron slag in the furnace. Further, changing the dead weight of the core coke layer 5, that is, changing the specific gravity of the coke or the coke filling rate requires a long time before the change effect is exerted. Cannot be adopted as a factor. In this regard, there is no problem in reducing the load applied to the core coke layer 5.

Usually, ore and coke are charged into the blast furnace from the furnace top in a layered manner at a predetermined ratio, and a part of this weight acts as a load applied to the furnace core coke layer 5 from above. I have. The reason why the weight of the whole charge does not fall on the furnace core coke layer 5 is that the furnace body is directly loaded by the friction with the furnace wall, the bosh section of the furnace body or the like, or is blown from the tuyere 7. This is because, as the in-furnace gas rises toward the furnace top, the ore and coke as the charge are lifted from below. Therefore, in order to float the core coke layer 5, it is considered effective to reduce the weight of the entire charge or to enhance the force of the furnace gas to lift the charge.

To reduce the weight of the entire charge, the weight ratio of the amount of ore to the amount of coke in the charge (commonly referred to as OR by
(Referred to as coke, which is represented by O / C).
Since the bulk specific gravity of the ore is about four times as large as that of coke, reducing the O / C reduces heavy ore,
Since light coke is increased, the weight of the whole charge can be relatively reduced.

In order to increase the power of the furnace gas to lift the charge, there is a method of increasing the ventilation resistance of the charge layer (including not only coke but also the ore layer). In order to increase the ventilation resistance of the charge layer, first, it is conceivable to reduce the particle size of the charge. However, this takes a long time in handling the charged material, and is difficult to employ as an operation to be taken immediately when the amount of residual iron slag increases. The inventor, as a simple method, controls the distribution of the charge at the furnace top, increases the amount of ore charged into the furnace center, and changes the gas flow distribution in the furnace from the furnace wall to the furnace center. We decided to adopt a flattening method. Normally, in the blast furnace operation, a large amount of coke with a large diameter is charged into the center of the furnace to secure a strong central flow, thereby reducing the ventilation resistance in the shaft of the blast furnace. Thus, the ventilation resistance of the shaft portion is increased, and as a result, the load applied from above to the furnace core coke layer 5 in the hearth 6 is reduced.

Another method for increasing the power of the furnace gas to lift the charge is to increase the gas volume in the furnace. This is effective when the high-temperature air supplied to the blast furnace is enriched with oxygen, and reduces the amount of enriched oxygen and increases the amount of air blown to match the amount of oxygen. As a result, the gas volume in the furnace can be increased without changing the amount of coke burned in front of the tuyere (without changing the amount of heat input into the furnace), and the power of lifting the charge in the shaft can be enhanced. . That is, the load applied to the core coke layer 5 in the hearth 6 from above is reduced accordingly.

In the first embodiment described above, the amount of hot metal and slag calculated from the amount of raw material charged into the furnace per unit time in normal blast furnace operation and the amount of molten iron and slag discharged from the taphole are calculated. When the amount of residual iron slag in the furnace is on the increase, the slag liquid level is temporarily avoided and the slag liquid level is close to the tuyere position. This is an operation that is performed so as not to ascend. At this time, as the operation, only one type selected from the above-mentioned O / C, the radial distribution of the blast furnace charge, and the air flow rate may be changed, or two or more types may be changed. This is because both cases are effective. In addition, as a result of performing the operation of the first embodiment, if a decrease in the slag liquid level and a decrease in the amount of residual iron slag can be confirmed, an operation of returning to the original operating conditions may be performed.

(Embodiment 2) In order to reduce the amount of residual iron slag in the furnace, as described above, it is sufficient that the vicinity of the front of the tap hole inside the furnace is in a free space state. It is considered that the lower end of the core coke layer 5 should be raised only in the vicinity of the front of the pigtail inside the furnace.

As described above, the lower end position 15 of the core coke layer 5 in the hearth 6 is determined by the balance between the load applied to the core coke layer 5 from above and the buoyancy of its own weight. There is a movement of the coke consumed by the tuyere 7 to the tuyere 7 in the vicinity of the furnace wall having the wall, and this movement of the coke also affects the lower end position of the core coke layer 5 around the furnace wall. . In other words, the tuyere 7
Space formed in front of the car (referred to as race way 16)
Has the wall formed of coke filled in the furnace, and the coke separated from the wall
It burns while turning inside. Peeled coke supplied from the upper surface or side surface of the raceway 16 wall corresponds to coke existing above the tuyere position. On the other hand, the coke supplied from the lower wall of the race way 16 is considered to be rising from below the race way 16. The coke forming the core coke layer 5 in the hearth moves toward the tuyere 7 above in the vicinity of the furnace wall, and the lower end position 15 of the core coke layer 5 in the hearth described above.
Is relatively low at the center of the furnace, high at the furnace wall, and is convex downward (see FIG. 8). The amount of upward movement of the coke on the furnace wall is determined by the amount of coke consumed in the race way 16 located in front of the tuyere 7 inside the furnace, so that the tuyere provided immediately above the taphole is provided. When the amount of air blown and the amount of oxygen enriched in the air blowing conditions to the nozzle 7 are controlled independently of the tuyere 7 provided at other positions and are selectively increased, the core around the taphole is increased. It is considered that the lower end position of the coke layer 5 can be raised. This is a balance between the rising speed of the lower end of the core coke layer and the lowering speed of the slag liquid level in front of the tap hole inside the furnace. This means that free space can be secured in front of the inside.
Here, the tuyere 7 provided immediately above the taphole is defined as two to four tuyeres on the left and right sides of the taphole 1, 4 on the vertical plane including the central axis. Say

Further, as described above, the lower end of the core coke layer near the front of the taphole inside the furnace is located above the new coke which supplements the combustion consumption of the coke in the race way 16 above the taphole position. Therefore, the greater the depth of the race way 16, the greater the amount of coke moved, and the higher the area of the lower end of the coke layer toward the center of the furnace ahead of the taphole inside the furnace, that is, the larger the free space -Space 10 can be formed. Race Way 1
This is because, if the depth of No. 6 is deep and the depth is large, coke is consumed deeply and deeply toward the furnace center, and the coke below it is urged to rise (see FIG. 9).

In the present invention, by utilizing this phenomenon, the depth of the race way 16 formed by the tuyere immediately above the taphole is increased, so that the free space near the front of the taphole inside the furnace is increased. 10 should be increased and maintained. For that purpose, tuyere 7 provided just above tapholes 1 and 4
The diameter of the air flow blown into the furnace from the nozzle may be larger than the diameter of the air flow blown from tuyeres provided at other positions. Specifically, the diameter of the tuyere provided immediately above the tap holes 1 and 4 is larger than the diameter of the tuyere provided at other positions, or a tuyere whose side wall is freely expandable and contractible is used. In addition,
In the present invention, the diameter of the air flow is also included in one of the blowing conditions, like the blowing amount and the oxygen enrichment amount.

According to the study of the inventors, the degree of the diameter increase of the air flow is preferably 1.05 to 1.4 times. If the enlargement ratio is less than 1.05 times, the error is about the same as the error of the air volume of each tuyere, and it is not possible to make a relative distinction from tuyeres provided at other positions. Further, when the tuyere diameter is increased by more than 1.4 times, the area of the enlarged tuyere becomes two times that of the tuyere provided at another position.
This is unfavorable because the airflow balance in the circumferential direction of the entire blast furnace is lost. Demonstrate the effect,
In order to stably maintain the air volume balance in the circumferential direction of the entire blast furnace, an enlargement ratio of about 1.1 to 1.3 times is more preferable.

The tuyere 7 provided just above the taphole
Enlarging the diameter of the tuyere at other positions does not affect the stability of the blast furnace operation, that is, changing the production volume and the air volume and air temperature as operating conditions This is a very effective means because it increases the raceway depth of the tuyere located just above the taphole.

(Embodiment 3) In the above two embodiments, the lower end position 15 of the furnace core coke layer 5 is
4 is raised near the front of the inside of the furnace to form a coke-free region 10 therein, and an operation for changing operating factors such as the blowing conditions of the blast furnace is performed. These operations are certain in terms of effectiveness. However, it is necessary to actually raise the lower end position of the furnace core coke layer 5, and it may take a long time until the effect appears.

Therefore, the inventor studied a quicker coping method and found the following means.

Normally, the lower end position 15 of the core coke layer 5 in the hearth is higher at the periphery of the furnace wall than at the center of the furnace, as described above. That is, in the periphery of the furnace wall, the area 1 where the core coke layer 5 does not exist as a normal state
0, that is, free space. Therefore, it is considered that if a situation where the opening position inside the taphole furnace is in the area 10 without coke around the furnace wall is formed, a reduction in the amount of residual iron slag in the furnace can be achieved.

As shown schematically in FIG. 9, the tap hole is provided in front of the tap holes 1 and 4 formed of tap hole bricks 18 inside the furnace, and the mud material used for closing the tap hole is used. 17 is sticking out. When the protruding mud material 17 reaches the lower end position 15 of the core coke layer 5, even if the mud material 17 is opened, the opening position is always in the core coke layer 5, The goal cannot be achieved. Then, the inventor decided to reduce the amount of protrusion of the mud material 17 so that the opening inside the furnace of the tap hole is below the lower end position 15 of the furnace core coke layer 5, and this is the present invention. It was added. That is, the lower end position 1 of the furnace core coke layer 5
Even if the tap hole 5 was not changed, the free space 10 without the core coke layer 5 was formed in front of the tap hole inside the furnace by reducing the depth of the tap hole.

The present invention is extremely effective when the amount of residual iron slag in the furnace tends to increase during operation. Specifically, tapping is performed immediately after such a situation occurs, and the filling amount of the mud material 17 is reduced from a normal control value (for example, about 200 kg / time) so as to close the taphole. As a result, in the next tapping, very smooth tapping can be performed, and the amount of residual tapping in the furnace can be reduced. According to the study of the inventor, the reduction amount of the mud material 17 is as follows.
It is better to reduce by 10 to 40% than the normal management value.

Since the mud material 17 is pushed from the tap holes 1 and 4 and spreads around the inside of the furnace of the tap hole and solidifies, the filling amount of the mud material 17 and the protrusion amount of the mud material in the furnace are not necessarily proportional. . Therefore, even if the mud material 17 is reduced by less than 10% from the control value, a remarkable effect may not be obtained. Further, if the mud material 17 is reduced by more than 40%, the holes of the tap holes 1, 4 worn by tapping slag may not be filled and repaired with the amount of the mud material. Therefore, in the present invention, it is preferable that the reduction amount of the mud material 17 is set to 10 to 40% from the normal management value. In order to obtain a certain effect and to surely avoid defects due to wear of the taphole, it is more preferable to reduce the amount of the mud material 17 to about 20 to 30%.

[0041]

EXAMPLES Example 1 A] when deterioration of tapping slag in 5100M ³ grade large blast furnaces, performs an operation of floating the deadman coke layer and stabilize the operation. In this blast furnace, a so-called “hole clogging phenomenon of the tap hole” has frequently occurred, in which the tap hole is clogged in the tap hole during tapping and the tapping is stopped. In addition, the tapping time was as short as about 3 hours, and the slag in the hearth could not be sufficiently discharged. Frequent clogging of holes
It is considered that there is a core coke packed layer in front of the taphole inside the furnace, and the aim was to float the core coke layer.
A method for increasing the ventilation resistance of the packed bed by controlling the charge distribution according to the present invention was implemented.

The results were evaluated at the bottom wall temperature of the blast furnace,
As shown in FIG. The temperature of the bottom wall of the blast furnace increased due to the fact that the hot metal flowed to the vicinity of the side wall due to the free space formed by the rise of the core coke layer. It was reduced to about 1/3 in comparison. This decrease in clogging of holes is considered to be due to the fact that the core coke layer did not exist at least near the tip of the taphole, and free space was created. Also, the time required for tapping is 5 to
It was extended to 6 hours, and the slag was sufficiently discharged.

[0043] In large blast furnaces Example 2] 5100m ³ primary, (in this case, change of the oxygen-enriched rate) blowing conditions of the tuyere provided in the taphole just above the vicinity of the present invention other tuyeres An example in which the amount of tapping slag has been improved by changing it to be different from that shown in FIG.

First, the rate of coke consumption by blowing air is determined from the amount of oxygen charged into the blast furnace.

[0045]

(Equation 1)

Here, it is calculated by using BV: blown air amount, O ₂ : oxygen concentration in blown air, and C: C concentration in coke.
BV = 7100 (Nm ² / min), oxygen concentration during blowing:
Calculating with O ₂ : 25% and C = 88%, the coke consumption rate is 45 × 10 ⁻³ (m ³ / sec). Further, assuming that the hearth diameter is 15 m and the depth of the raceway is 1.0 m, the coke consumption area around the hearth is 15 × 1.
Since it can be approximated by 0 × π = 47.1 (m ² ), the height variation of the coke layer due to coke consumption is 0.95 mm /
sec. Since it is considered that most of this height fluctuation is used for lowering the furnace top charging surface, the moving speed of the furnace core coke layer is estimated to be a fraction of this value.

On the other hand, the rate of drop of the liquid level due to the tapping slag is such that the tapping amount is 7500 t / day and the slag ratio is 300 k.
Assuming g / t, it is 0.124 mm / sec. The tapping slag speed gradually increased after the start of tapping, and at the end of the period, became 2 to 3 times this value. Therefore, it was estimated that the tapping slag speed exceeded the rising speed of the core coke layer.

Therefore, oxygen was enriched in the air through the pulverized coal injection lance for the four tuyeres immediately above the taphole during tapping, and their oxygen concentration was increased to 40% by volume. The operation results are shown in FIG. 11 evaluated by the slag index. During the period of oxygen enrichment, the slag index (slag time / slag time) is large. This is because the slag is improved by the free space at the front of the tap hole inside the furnace, but the mud material injected at the time of tapping stop is not in the coke packed bed, so it becomes massive upwards in the hot metal. It is presumed that the taphole has become shorter and the depth of the taphole has become shorter. This is to raise the coke consumption rate of the tuyere near the taphole just above the tuyere provided at other positions,
This suggests that tapping slag is improved.

[0049] In Example ^3] 4500m 3-class large-scale blast furnaces, in the operation to deepen the race way of depth, shows an example of improved Dezukukasu.

The inner diameter of the four tuyeres provided immediately above the taphole was increased by 20 mm from the 140 mmφ of the tuyeres provided at other positions, thereby enlarging the race way. The results were evaluated using the slag index and the furnace bottom side wall temperature.
(A) and (b). In the operation after the tuyere diameter expansion work, it is clear that the temperature of the side wall around the taphole rises, the inside of the furnace inside the taphole becomes free space, and the hot metal circulates there. In addition, the free space improved the slag index and facilitated the discharge of slag in the furnace.

[0051]

As described above, according to the present invention, it is possible to effectively reduce the amount of residual iron slag in the furnace without a particular increase in cost. As a result, it has become possible to stabilize blast furnace operation.

[Brief description of the drawings]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view for explaining an effect when a free space is formed in front of a taphole inside a furnace; FIG. 1 (a) shows an angle θ = 180 ° at which a coke layer covers a taphole; θ = 15
° and (c) are for θ = 0 °.

FIG. 2 is a schematic view showing a lower part of a blast furnace.

FIG. 3 is a view showing a half-cut cylindrical model of a hearth portion.

4A and 4B are diagrams showing the results of a model experiment, wherein FIG. 4A is an explanatory diagram of the experimental results, and FIG.

FIGS. 5A and 5B are plan views for explaining the reduction of the amount of residue due to the generation of an annular flow of pseudo slag, where FIG. 5A is a case where the front of the pseudo tap hole is completely covered with coke, and FIG. Is a case where a free space is formed in front of.

Fig. 6 Free sizes of various sizes in front of the taphole inside the furnace
It is a schematic diagram illustrating an experiment to form a space,
(A) is a side surface, (b) is a plane.

FIG. 7 is a diagram showing the relationship between the size of a free space existing in front of the taphole inside the furnace and the amount of residue.

FIG. 8 is a schematic diagram for explaining a relationship between a sedimentation speed of a furnace core coke layer and a coke consumption speed at a tuyere tip.

FIG. 9 is a schematic diagram illustrating the formation of a free space near a furnace wall.

FIG. 10 is a diagram showing the effect of the operation of floating the core coke layer.

FIG. 11 is a diagram showing an example in which the amount of tapping slag is improved by increasing the coke consumption rate in the tuyere immediately above the taphole, (a) is a slag index, and (b) is a plot of taphole depth. Daily change.

FIG. 12 is a diagram showing an example of improvement in tapping slag by increasing the size of a raceway, where (a) shows the daily change of the slag index, and (b) shows the relationship between the furnace bottom wall temperature and the furnace bottom plate temperature. FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Right tap hole 2 Hot metal liquid level position (level) 3 Slag liquid level position (level) 4 Left tap hole 5 Coke packed bed (core coke layer) 6 Furnace floor 7 Tuyere 8 Model furnace Floor 9 Bead-filled layer (beads) 10 Area where coke-packed layer does not exist (free space) 11 Liquid Freon (pseudo hot metal) 12 Oil (pseudo slag) 13 Pseudo tap 13a Tap tap centerline position 14 Air 15 Lower end position 16 Race way 17 Mud material 18 Taphole brick 20 Wire mesh (lower end of bead packed layer) 21 Upper surface of oil 22 Upper surface of liquid Freon

 ──────────────────────────────────────────────────の Continuing from the front page (72) Inventor Shiro Watanabe 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Prefecture Inside the Technical Research Institute of Kawasaki Steel Corporation (72) Inventor Yoshitaka Sawa Yoshikawa 1-cho, Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Kawasaki Steel Engineering Laboratory (72) Inventor Hideo Oide 1 Kawasaki-cho, Chuo-ku, Chiba City, Chiba Prefecture Kawasaki Steel Engineering Laboratory F-term (reference) 4K012 BC01 BC03 BC04 BC06 BC07 BD01 BD02 BD04

Claims (5)

[Claims] 1. An air blower in which coke and iron ore are charged from the furnace top, a deposited layer of the charged materials is formed in an upper part of the furnace, a core coke layer is formed in a lower part of the furnace, and the tuyere is blown from a tuyere. Combustion of coke to generate high-temperature reducing gas,
Calculate the amount of slag retained in the furnace during operation in the blast furnace operating method, in which molten iron and slag generated by melting and reducing iron ores are allowed to flow down to the hearth and stagnate, and then appropriately discharged from the taphole. When the calculated value exceeds a reference value for stable operation, a blast furnace operation method is performed, wherein an operation factor that contributes to the ascent of the core coke layer is changed. 2. The method according to claim 1, wherein the operating factor is at least one selected from the ratio of iron ore and coke to be charged, the radial distribution of the charged material, and the amount of air blown. Item 2. A blast furnace operating method according to Item 1. 3. A blower in which coke and iron ore are charged from the furnace top, a deposit layer of the charged materials is formed in an upper part of the furnace, and a core coke layer is formed in a lower part of the furnace, and blown from tuyeres. Combustion of coke to generate high-temperature reducing gas,
In a blast furnace operating method in which molten iron and slag generated by melting and reducing iron ores are allowed to flow down and stay in the hearth, and then appropriately discharged from the taphole, the tuyere installed near the taphole A method for operating a blast furnace, characterized in that blowing conditions are controlled independently of tuyeres installed at other positions. 4. The blast furnace operating method according to claim 3, wherein the air blowing conditions are one or more selected from air blowing amount, enriched oxygen amount and tuyere diameter. 5. A blower in which coke and iron ore are charged from the furnace top, a deposited layer of the charged material is formed in an upper part of the furnace, and a core coke layer is formed in a lower part of the furnace, and blown from tuyeres. Combustion of coke to generate high-temperature reducing gas,
Calculate the amount of slag retained in the furnace during operation in the blast furnace operating method, in which molten iron and slag generated by melting and reducing iron ores are allowed to flow down to the hearth and stagnate, and then appropriately discharged from the taphole. And a method for operating the blast furnace, characterized in that when the calculated value exceeds the standard value for stable operation, the filling amount of the mud material is reduced from that in the normal operation when closing the tap hole after tapping.