JP2013095970A - Method for operating blast furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for operating a blast furnace, with which the amount of coke to be used can be reduced by improving reduction efficiency, in the blast furnace operation using an ore-coke mixture charging process.SOLUTION: At the upper part inside a furnace top bunker 11, a segregation control plate 12 which can adjust an inclination angle for changing the dropping direction of the raw materials charged into the furnace top bunker 11, is arranged. Then, during charging the mixed raw material (the raw material obtained by mixing the ore and the coke for forming the coke-mixed ore layer) into the furnace top bunker, the inclination angle of the segregation control plate 12 is changed from a first inclination angle where the dropping position of the mixed raw material becomes a position near the upper part of the discharging port of the furnace top bunker 11, to a second inclination angle where the dropping position thereof becomes a position away from the vicinity of the upper part of the discharging port in a horizontal direction. Thus, the mixing ratio of the coke in the mixed raw material discharged from the furnace top bunker 11 is gradually increased from the initial stage of the discharge to the latter stage of the discharge.

Description

  The present invention relates to a method of operating a blast furnace in which raw materials are charged from the top of the furnace to alternately form a coke layer and a coke mixed ore layer, and in particular, when forming a coke mixed ore layer, the ore and coke are mixed in advance. The present invention relates to a blast furnace operation method using an ore coke mixed charging method for charging mixed raw materials.

For efficient operation of the blast furnace, it is necessary to appropriately distribute the gas in the furnace in the radial direction. Therefore, in order to control the gas flow distribution in the furnace, the charging point of the coke has been adjusted to ensure mainly ventilation. Furthermore, since the furnace top charging equipment has been developed in recent years, it has become possible to charge ore and coke in a mixed manner, and to improve both aeration and reduction efficiency.
In blast furnace operation, ore and coke are usually charged from the top of the furnace so that they are alternately layered to form an ore layer and a coke layer. On the other hand, a method of improving the reducibility of the ore layer itself by previously mixing and charging coke in the ore layer is an ore coke mixing and charging method (see, for example, Patent Documents 1 and 2). ).

In a normal operation for forming an ore layer and a coke layer, air permeability deteriorates due to a decrease in the porosity of the ore layer in the cohesive zone, and there is little contact between the ore and the coke, and the reduction reaction is stagnant. On the other hand, in the ore coke mixing charging method, in the cohesive zone, the coke mixed with the ore suppresses the coarsening of the fused layer, so that a void is secured and the air permeability is improved. And the reduction of coke is increased.
In the technique described in Patent Document 1, in order to perform ore coke mixing charging using a bell-less charging apparatus, the ore and coke are cut out so as to be stacked on a belt conveyor, and then from the furnace top bunker into the blast furnace. The method of charging and forming a coke mixed ore layer is adopted.

Moreover, in the technique described in Patent Document 2, when a raw material is charged into a blast furnace using a bellless charging apparatus having a plurality of furnace top bunkers, ore and coke are charged into separate furnace top bunker. In addition, when discharging from the top bunker, a part of the ore and coke is simultaneously discharged and charged into the blast furnace to form a coke mixed ore layer.
These techniques are methods in which coke single charging and ore coke mixed charging are alternately performed. In the coke mixed ore layer in which coke and ore are mixed, the ore and coke are almost uniformly mixed.

JP-A-3-211210 JP 2004-107794 A

By the way, in recent years, from the viewpoint of environmental problems, development of a technology capable of reducing the amount of coke used in a blast furnace as much as possible has been demanded. Therefore, also in the ore coke mixing charging method, it is expected that the reduction efficiency is further improved and the amount of coke used in the blast furnace is reduced.
Then, this invention makes it a subject to provide the blast furnace operating method which can raise reduction efficiency and can reduce the usage-amount of coke in the blast furnace operation using the ore coke mixing charging method.

  In order to solve the above problems, a blast furnace operating method according to the present invention is a method of charging a raw material stored in a furnace top bunker from a furnace top through a turning chute installed below the furnace top bunker, And a coke layer, wherein the ore layer is a coke mixed ore layer formed by a mixed raw material of ore and coke stored in the furnace top bunker, and the top of the furnace In the upper part of the bunker, a segregation control plate capable of adjusting the inclination angle for changing the falling direction of the raw material charged into the furnace top bunker is provided, and during the charging of the mixed raw material into the furnace top bunker, The inclination angle of the segregation control plate is determined from a first inclination angle at which the mixed raw material falls at a position directly above the outlet of the furnace top bunker, and the mixed raw material falls from the position directly above the outlet in the horizontal direction. The side wall position is far away It is characterized in that switching to second inclined angle.

  Thus, when charging the mixed material into the furnace top bunker, first the segregation control plate as the first inclination angle, the position where the mixed material falls is the position near the upper outlet of the furnace top bunker, The segregation control plate is switched to the second inclination angle, and the dropping position of the mixed raw material is set to a position far from the discharge port. Thereby, the coke in the mixed raw material can be segregated and deposited at a position far from the discharge port in the furnace top bunker. Furthermore, at this time, it is possible to suppress the coke in the mixed raw material from being excessively concentrated at a position far from the discharge port in the furnace top bunker.

Since the mixed raw material deposited in the furnace bunker is discharged from directly above the outlet, when the mixed raw material deposited as described above is discharged from the outlet of the furnace top bunker, the coke mixing ratio of the mixed raw material is discharged. It will gradually increase from the initial stage to the late stage of discharge. Therefore, when the mixed raw material discharged from the furnace top bunker is sequentially charged from the lower layer to the upper layer in the furnace through the swivel chute, the upper part of the coke can be segregated in the coke mixed ore layer formed in the furnace. .
As a result, in the furnace, the reducing gas from the coke layer can be used for the reduction of the ore below the coke mixed ore layer, and the reducing gas generated from the coke mixed in the coke mixed ore layer above. The reducing gas can be used efficiently.

Further, in the above, the amount of the mixed raw material charged into the furnace top bunker with the inclination angle of the segregation control plate as the first inclination angle is 60 mass% of the total charged amount of the mixed raw material into the furnace top bunker. It is characterized by being 95 mass% or less.
Thereby, the coke mixing ratio of the mixed raw material discharged from the furnace top bunker can be reliably increased from the initial discharge stage to the late discharge stage while preventing the coke mixing ratio from rapidly increasing at the end of discharge.

Furthermore, in the above, one charge of charging the mixed raw material to form a coke mixed ore layer into the blast furnace is charged to the furnace center and from the furnace center to the furnace peripheral part on the furnace wall side. The segregation control plate tilt angle during the charging of the mixed raw material, which is divided into at least two batches of the charging batch and charged into the blast furnace in the charging batch to the periphery of the furnace, into the furnace bunker Is controlled to switch from the first tilt angle to the second tilt angle.
Thereby, coke can be segregated in the upper part in the coke mixed ore layer formed in the furnace peripheral part, and the reducing gas in the furnace peripheral part can be used efficiently. Thus, the reduction efficiency of the entire blast furnace can be effectively improved by improving the reduction efficiency of the furnace peripheral part, which generally tends to have a relatively low gas utilization rate.

Further, in the above, the furnace peripheral portion is in a region where the dimensionless radius r / R of the blast furnace is 0.7 or more and 1 or less when the radius of the blast furnace is R and the position in the radial direction from the center of the blast furnace is r. It is characterized by setting in.
Thus, by setting the furnace peripheral portion within the region of 0.7 ≦ r / R ≦ 1, the reduction efficiency of the entire blast furnace can be improved more effectively.

According to the present invention, since coke can be segregated in the upper part in the coke mixed ore layer, the reduction efficiency of the ore can be increased and the operation of the blast furnace can be performed efficiently. Further, since the amount of coke used can be reduced by improving the reduction efficiency of the ore, the operation that contributes to the global environment can be achieved by reducing the generation of CO ₂ .

It is a schematic diagram of a uniformly mixed coke mixed ore layer. It is a schematic diagram of the coke mixed ore layer which segregated the coke upper part. It is a figure which shows the measurement result of the average reduction rate of an ore. It is side surface sectional drawing which shows an example of an ore layer and a coke layer typically. It is a figure which shows the difference in the deposition condition of the mixed raw material by the difference in the inclination angle of a segregation control board. It is a figure which shows the deposition condition of the mixed raw material in the furnace top bunker in this embodiment. It is a figure which shows the change of the coke mixing rate in the mixed raw material discharged | emitted from a furnace top bunker. FIG. 5 is a diagram showing a deposition state of mixed raw materials in a furnace top bunker when the inclination angle of the segregation control plate is charged by switching from the first inclination angle to the second inclination angle when the charged amount of the mixed raw material exceeds 95 mass%. is there. It is a measurement result of the reduction rate distribution in a coke mixed ore layer. It is a figure which shows the measurement result of the average reduction rate of an ore. It is a figure which shows schematic structure of a bell-less charging device.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
In order to investigate the effect of the upper segregation of coke in the coke mixed ore layer in which coke is mixed in the ore layer, the present inventors conducted a test using a load softening test apparatus.
The load softening test device reproduces the temperature, atmosphere, and load that the raw material receives in the blast furnace. The raw material charged in a graphite crucible having a diameter of 100 mm is heated to a predetermined temperature in a reducing gas atmosphere and tested. It was.

In such a load softening test device, when a layer of only ore is laminated on the coke layer (no mixing), a coke mixed ore layer in which coke and ore are uniformly mixed is formed as the ore layer. Experiments were carried out using the case of stacking (uniform mixing) and the case of stacking a coke mixed ore layer in which coke was segregated as an ore layer (upper segregation), and the average reduction rate of ore in each case was measured. .
Here, as a sample, a block coke having an average particle diameter of 15 to 25 mm is used as a raw material for forming a coke layer, and an ore having an average particle diameter of 8 to 10 mm and an average particle diameter are used as a raw material for forming a coke mixed ore layer. A coke of 8 mm to 10 mm was used.

FIG. 1 is a schematic view of a uniformly mixed coke mixed ore layer, in which reference numeral 1 is ore and reference numeral 2 is coke. The average coke mixing ratio of the uniformly mixed coke mixed ore layer was 120 kg / tp equivalent. Here, kg / tp is a unit indicating the amount of coke per ton of hot metal.
FIG. 2 is a schematic diagram of an upper segregated coke mixed ore layer. The average coke mixing rate of the upper segregation coke mixed ore layer is equivalent to 120 kg / tp, which is the same as the above homogeneously mixed coke mixed ore layer, and the average coke mixing rate in the upper 50% by volume is 170 kg / tp. Correspondingly, the average coke mixing ratio in the lower 50 volume% was set to 70 kg / tp equivalent. That is, in this example of upper segregation, about 70 mass% of coke mixed in the coke mixed ore layer was mixed in the upper half (upper 50% by volume) of the coke mixed ore layer.

FIG. 3 is a diagram showing the measurement results of the average reduction rate of ore. As shown in FIG. 3, by performing mixed charging of coke and ore, the reduction rate is improved as compared to charging ore alone, and by further segregating the coke to the top, the reduction rate is further increased. It has improved. Thus, it turned out that there exists an effect which improves reduction efficiency by making an ore layer into a coke mixed ore layer, and also making a coke upper-segregate within this coke mixed ore layer.
When a coke mixed ore layer of uniform mixing is applied, in the furnace where the coke layer and the coke mixed ore layer overlap each other, macroscopically, at the boundary between the coke layer and the coke mixed ore layer stacked on top of it, The amount of reducing gas is excessive relative to the amount of ore near the coke layer. Therefore, reduction efficiency will fall.

On the other hand, when the upper segregated coke mixed ore layer was applied, the reducing gas from the coke layer was mixed in the furnace below the coke mixed ore layer and mixed with the coke mixed ore layer above. The reducing gas generated from the coke can be used for ore reduction. Therefore, it is considered that the reducing gas can be used efficiently and the total reduction efficiency is improved.
Therefore, in this embodiment, the ore layer is a coke mixed ore layer in which coke is segregated in the upper part, the coke mixed ore layer is in a dense state, and the lower part is in a coarse coke state.

  In this case, the upper part in the coke mixed ore layer is preferably in a state where the coke density is higher. In the upper half of the coke mixed ore layer (upper 50% by volume), 60 mass of coke mixed in the coke mixed ore layer. % Or more are preferably mixed. More preferably, 70 mass% or more of coke mixed in the coke mixed ore layer is mixed in the upper half (upper 50% by volume) of the coke mixed ore layer.

  The surface of the coke mixed ore layer actually formed in the blast furnace is not horizontal but has a height distribution. That is, the upper surface height position differs depending on the in-furnace radius position. In the above, the upper 50 volume% which is the upper half of the coke mixed ore layer is 50% of the vertical thickness of the coke mixed ore layer from the upper surface of the coke mixed ore layer in an arbitrary range of the coke mixed ore layer. When a curved surface formed by connecting points vertically downward by a distance corresponding to is imagined, it means the volume of the coke mixed ore layer located above the curved surface.

  The amount of coke to be mixed in the coke mixed ore layer is preferably large. When the coke is mixed into the coke mixed ore layer with respect to the total coke amount charged from the top of the furnace, it is 10 mass% or more, particularly preferably 30 mass% or more. The effect of improving the reduction efficiency is high. On the other hand, if the amount of coke mixed into the coke mixed ore layer is too large, the coke layer becomes thin, and the coke slit becomes thin in the cohesive zone, so the air permeability at the lower part of the furnace deteriorates. Therefore, the coke mixed in the coke mixed ore layer is preferably 50 mass% or less with respect to the total amount of coke charged from the top of the furnace.

FIG. 4 is a side cross-sectional view schematically showing an ore layer and a coke layer formed by using the blast furnace operating method according to the present invention.
In FIG. 4 (a), r / R is a dimensionless radius of the blast furnace when R is the radius of the blast furnace and r is a radial position from the center of the blast furnace, and r / R = 0 is the blast furnace radius. The center position, r / R = 1, indicates the furnace wall position.

  When forming the coke layer, the coke for one charge forming the coke layer is divided into two batches, charged from the top of the furnace, the coke layer 3a is formed in the first batch, and the coke is formed in the second batch. Layer 3b was formed. Moreover, when forming an ore layer, 1 charge of the charging of the raw material for forming the ore layer is charged into the furnace batch on the furnace wall side from the furnace center and the charging batch to the furnace center. In the first batch, the ore layer 4a in the center of the furnace was formed, and in the second batch, the ore layer 4b in the periphery of the furnace was formed. In addition, the furnace peripheral part was made into the area | region whose r / R is 0.7-1.0.

Here, the ore layers 4a and 4b are coke mixed ore layers in which ore and coke are mixed. In the present embodiment, the ore layer 4a is a uniformly mixed coke mixed ore layer, and the ore layer 4b is an upper segregation coke mixed ore layer.
When the raw material discharged from the furnace top bunker is swirled into the furnace using the swirl chute of the bellless charging device, for example, in the case of the ore layer 4b, as shown in FIG. The mixed raw material is sequentially deposited from the lower layer to the upper layer, and the mixed raw material at the later stage of charging is sequentially deposited from the lower layer to the upper layer.
Therefore, in order to segregate the coke in the ore layer 4b, coke mixing ratio of the mixed raw material for forming the ore layer 4b discharged from the furnace top bunker (= coke amount / (ore amount + coke amount)) May be increased from the initial discharge to the late discharge. Hereinafter, a method of causing the upper segregation of coke in the ore layer will be described.

  By the way, as a method of uniformly mixing the coke into the ore layer, a bell-less charging device having a furnace top bunker and a swivel chute is used, and the ore and coke are cut out to be stacked on a belt conveyor, and the furnace top bunker is received. Sometimes mixed and then charged into the blast furnace to form a coke mixed ore layer, or when discharging from the top bunker, a portion of the ore and coke are discharged simultaneously and charged into the blast furnace. A method of forming a mixed ore layer is known.

  In order to segregate coke into the ore layer, for example, in the above, when the mixing amount of coke is changed at the time of cutting, or when a portion of ore and coke is discharged simultaneously from a plurality of furnace top bunkers, the top bunker This can be done by adjusting the discharge rate and discharge rate of the coke using a flow rate adjustment gate and changing the mixing ratio of the coke. However, in such a method, the raw material charging process becomes complicated, and there is a possibility that the operation becomes inefficient. Moreover, it may be difficult to cope with equipment that does not have a flow rate adjustment gate.

Therefore, in the present embodiment, as a method of making the upper segregation easier and more effective, as shown in FIG. 5, the dropping direction of the raw material charged into the furnace top bunker 11 is changed to the upper part in the furnace top bunker 11. A segregation control plate 12 that can be tilted is provided, and a method using the segregation control plate 12 is employed.
That is, by changing the inclination angle of the segregation control plate 12 during the charging of the raw material into the furnace top bunker 11, the falling position of the mixed raw material is changed between the initial charging stage and the late charging stage. In this way, the mixed raw material is deposited on the top bunker 11 while forming a raw material distribution in which the coke mixing ratio of the mixed raw material discharged from the furnace top bunker 11 gradually increases from the initial discharge to the late discharge. Let Hereinafter, this method will be specifically described.

Here, as shown in FIG. 5, a case will be described in which the discharge port 13 of the furnace top bunker 11 is provided at a position closer to one side from the center as viewed from above the furnace top bunker 11.
FIG. 5A shows a case where the angle of the segregation control plate 12 in the furnace top bunker 11 is set to be inclined toward the discharge port 13 (hereinafter referred to as the bunker center side). At this time, if the inclination angle of the segregation control plate 12 is set to an angle (first inclination angle) at which the mixed raw material charged into the furnace top bunker 11 falls to a position immediately above the discharge port 13 as indicated by an arrow A, The ore 1 is deposited near the center of the bunker, but the coke 2 having a particle size larger than that of the ore 1 flows toward the bunker outer periphery.

  On the other hand, in FIG. 5B, the angle of the segregation control plate 12 in the furnace top bunker 11 is inclined in the horizontal direction to the side opposite to the discharge port 13 side (hereinafter referred to as the bunker outer periphery side). This is the case. At this time, the angle of the segregation control plate 12 is set such that the mixed raw material charged into the furnace top bunker 11 falls to the side wall position that is horizontally separated from the position immediately above the discharge port 13 as indicated by the arrow B (second When the inclination angle is set, the ore 1 accumulates near the bunker periphery, but the coke 2 having a particle size larger than that of the ore 1 flows toward the bunker center.

  The mixed raw material deposited on the furnace top bunker 11 is discharged immediately above the discharge port 13. Therefore, in the case of FIG. 5 (a), since the coke in the mixed raw material is concentrated near the bunker outer periphery, the coke mixing ratio of the mixed raw material discharged from the furnace top bunker 11 increases in the late stage of discharge, It will increase rapidly at the end of discharge. That is, an ideal result in which the coke mixing ratio increases almost uniformly from the initial discharge to the late discharge cannot be obtained. On the other hand, in the case of FIG.5 (b), the coke mixing rate of the mixed raw material discharged | emitted from the furnace top bunker 11 does not increase in the discharge | emission late stage.

In the present embodiment, when the mixed raw material is charged into the furnace top bunker 11, the mixed raw material charged into the furnace top bunker 11 is dropped toward the center of the bunker at the initial charging stage as shown in FIG. Then, at the end of charging, as shown in FIG. 5B, the mixed raw material charged into the furnace top bunker 11 is dropped toward the outer periphery of the bunker.
As a result, as shown in FIG. 6, the coke 2 is deposited near the bunker periphery in the furnace top bunker, and a part 2 a thereof is deposited near the bunker center. That is, the concentration of coke near the outer periphery of the bunker is suppressed. As a result, the coke mixing ratio of the mixed raw material discharged from the furnace top bunker 11 is gradually increased from the initial discharge to the late discharge without rapidly increasing at the end of discharge.

FIG. 7 is a diagram showing a change in the coke mixing ratio in the mixed raw material due to the difference in the angle of the segregation control plate 12 during the raw material charging. FIG. 7 shows the results of the model test. The average particle size of the ore was 1.5 mm, and the average particle size of coke was 2.0 mm.
As Comparative Example 1, the segregation control plate 12 is placed in the furnace top bunker 11 so that the mixed raw material is dropped toward the outer periphery of the bunker as shown in FIG. 5B during the entire period from the initial charging period to the late charging period. The mixed raw materials were charged and tested.

Further, as Comparative Example 2, the segregation control plate 12 is dropped over the bunker center as shown in FIG. 5 (a) in the entire period from the initial charging stage to the late charging stage. 11 was charged with the mixed raw material and tested.
As Example 1, the segregation control plate 12 is set in the furnace top bunker 11 at the initial charging stage with the first inclination angle shown in FIG. 5A and at the second charging stage with the second inclination angle shown in FIG. 5B. The mixed raw materials were charged and tested. In Example 1, of the mixed raw materials charged into the furnace top bunker 11, 80 mass% was charged at the first inclination angle and the remaining 20 mass% was charged at the second inclination angle.

Further, as the second embodiment, the segregation control plate 12 has a first inclination angle shown in FIG. 5A at the initial stage of charging and a second inclination angle shown in FIG. The mixed raw materials were charged into the inside and tested. In Example 2, among the mixed raw materials charged in the furnace top bunker 11, 60 mass% was charged at the first inclination angle and the remaining 40 mass% was charged at the second inclination angle.
Referring to FIG. 7, in Comparative Example 1, there is no significant change in the coke mixing ratio from the initial discharge stage to the late discharge stage. Thus, the coke mixed ore layer formed from the mixed raw material discharged from the furnace top bunker 11 is as follows. It turns out that it becomes uniform mixing.

  In Comparative Example 2, it can be seen that, compared with Comparative Example 1, the coke mixing ratio increases from the initial discharge to the late discharge from the furnace top bunker 11. In particular, when most of the coke in the mixed raw material is deposited near the outer periphery of the bunker by the charging shown in FIG. 5 (a) in the entire period from the initial charging stage to the late charging stage, the raw material discharged from the furnace top bunker It can be seen that the coke mixing ratio increases rapidly at the end of discharge. Thereby, it turns out that the coke mixed ore layer formed with the mixed raw material discharged | emitted from the furnace top bunker on the conditions of the comparative example 2 becomes the upper segregation with which the coke was densely packed in the uppermost layer part.

  On the other hand, as in Examples 1 and 2, when the mixed raw material was dropped toward the bunker center at the first inclination angle in the initial charging stage, and the mixed raw material was dropped toward the bunker outer periphery at the second inclination angle in the late discharge stage, The coke mixing ratio of the mixed raw material discharged from the top bunker 11 increases from the initial discharge to the late discharge, but does not increase rapidly at the end of discharge as in Comparative Example 2. It was also found that if the ratio of the mixed raw material dropped toward the center of the bunker is 60 mass% or more of the charged amount, the coke mixing ratio of the mixed raw material discharged from the furnace top bunker 11 can be increased toward the latter stage of discharge.

Further, comparing Example 1 and Example 2, in Example 1, the ratio of the mixed raw material dropped toward the center of the bunker is as large as 80 mass%, so the ratio of the mixed raw material dropped toward the center of the bunker is 60 mass%. It can be seen that the ratio at which the coke mixing ratio of the mixed raw material discharged from the furnace top bunker 11 increases at the end of discharge is larger than that in Example 2.
However, if the ratio of the mixed raw material dropped toward the center of the bunker is too large, coke flows from the bunker outer periphery toward the bunker center in the furnace top bunker 11 even if the mixed raw material dropping position is changed to the bunker outer periphery. Since the effect cannot be obtained, the coke mixing ratio of the mixed raw material increases rapidly at the end of discharge, which is not preferable.

  FIG. 8 shows the furnace top bunker 11 when the segregation control plate 12 is switched from the first inclination angle to the second inclination angle after the charged amount of the mixed raw material charged into the furnace top bunker 11 exceeds 95 mass%. It is a figure which shows the deposition condition of the inside mixed material. Thus, the coke 2a in the mixed raw material charged near the bunker outer periphery cannot flow toward the bunker center but accumulates near the bunker outer periphery. Therefore, when the mixed raw material deposited as shown in FIG. 8 is discharged, the coke mixing ratio increases rapidly at the end of discharge.

  Therefore, in the present embodiment, the amount of the mixed raw material charged closer to the center of the bunker is set to 60 mass% to 95 mass% of the total charged amount of the mixed raw material charged into the furnace top bunker 11. Thereby, the coke mixing ratio of the mixed raw material discharged from the furnace top bunker 11 is gradually increased from the initial discharge stage to the late discharge stage. Then, in the coke mixed ore layer formed in the furnace, the coke is segregated in the upper part so that the coke gradually becomes dense from the lower layer part to the upper layer part.

Next, about the comparative example 1, comparative example 2, Example 1, and Example 2 mentioned above, the reduction rate distribution in the coke mixed ore layer by a load softening test was measured, respectively. The result is shown in FIG.
Referring to FIG. 9, it can be seen that, in Comparative Example 1 of uniform mixing, the reduction rate decreases as the height of the coke mixed ore layer increases (upper layer). On the other hand, it can be seen that in the upper segregation comparative example 2 in which the coke mixing ratio increases abruptly at the end of discharge, the reduction ratio at the uppermost portion where the coke mixing ratio is high is greatly improved. On the other hand, it can be seen that in the upper segregation example 1 and example 2 where the coke mixing ratio increases overall in the late discharge period, the reduction rate is improved overall in the upper layer part.

Furthermore, when the average reduction rate of the ore was measured for Comparative Example 1, Comparative Example 2, Example 1 and Example 2 described above, the results shown in FIG. 10 were obtained.
Referring to FIG. 10, it can be seen that the upper average segregation ratio is improved in the upper segregation comparative example 2 as compared with the uniform mixing comparative example 1. However, in Example 1 and Example 2, the average reduction rate is further improved compared to Comparative Example 2.

  In other words, rather than charging near the center of the bunker for the entire period from the initial charging period to the late charging period, it is more likely that the charging is performed closer to the bunker center in the initial discharge period and the outer bunker area is charged in the later discharging period. It was found that the average reduction rate of can be improved. Moreover, it turned out that the average reduction rate is improved in Example 1 in which the charging near the bunker center is 80 mass% than in Example 2 in which the charging near the bunker center is 60 mass%. .

(Example)
Hereinafter, the effect of the present invention will be specifically described with reference to examples.
Here, in a large blast furnace having an internal volume of more than 5000 m ³ , a coke layer, a coke, and a dimensionless radius r / R of a blast furnace that tends to have a relatively low gas utilization rate within a range of 0.7 to 1.0. The operation was carried out to alternately deposit coke mixed ore layers mixed with ore. The raw materials for forming the coke layer and the coke mixed ore layer were charged into the blast furnace 20 by the bell-less charging device 10 shown in FIG.

As shown in FIG. 11, the bellless charging apparatus 10 includes a furnace top bunker 11 in which a mixed raw material obtained by mixing ore and coke is stored, and a furnace top bunker 14 in which only coke is stored. Then, the mixed raw material in the furnace top bunker 11 or the coke in the furnace top bunker 14 charged into the collective hopper 17 by opening and closing the gates 15 and 16 provided in the lower part of the furnace top bunkers 11 and 14 is swirled. 18 is inserted into the blast furnace 20.
When the mixed raw material was stored in the furnace top bunker 11, the ore and coke were cut out so as to be stacked on a belt conveyor and charged into the furnace top bunker 11 via a surge hopper. At this time, the gate 15 was controlled to be closed by the raw material charging control unit 30.

Further, the furnace top bunker 11 is provided with a mass meter 31 configured by, for example, a load cell for measuring the mass of the mixed raw material charged into the furnace top bunker 11, and the raw material charging control unit 30 includes: According to the mass change of the furnace top bunker 11 measured by the mass meter 31 (corresponding to the amount of the mixed raw material charged), the inclination angle of the segregation control plate 12 installed in the upper part of the furnace top bunker 11 is set to the falling position of the mixed raw material Was controlled to be closer to the center or outer periphery.
Further, the mixed raw material for forming the coke mixed ore layer in the blast furnace was divided into two batches and charged into the blast furnace 20. At this time, the first batch was charged in the center to the middle part of the blast furnace 20, and the second batch was charged in the peripheral part (r / R = 0.7) of the blast furnace 20.

Here, as a comparative example, when the mixed raw material was charged into the furnace top bunker 11, 100 mass% was charged at the second inclination angle in both the first batch and the second batch. That is, in both the first batch and the second batch, the segregation control plate 12 is maintained at the second inclination angle shown in FIG. 5B by the raw material charging control unit 30 for the entire period from the initial charging stage to the late charging stage, The mixed raw material was charged.
Then, when charging the mixed raw material from the furnace top bunker 11 to the blast furnace 20, the swivel chute 18 was reversely tilted (tilted from the furnace center toward the furnace wall) in both the first and second batches. In this way, a coke mixed ore layer in which coke was distributed almost uniformly was formed and operated.

On the other hand, as an example, when charging the mixed raw material into the furnace top bunker 11, the first batch was charged with 100 mass% at the second inclination angle, and the second batch was charged with 80 mass% at the first inclination angle. , 20 mass% was charged at the second inclination angle. That is, in the first batch, the segregation control plate 12 is maintained at the second inclination angle shown in FIG. 5 (b) by the raw material charging control unit 30 for the entire period from the initial charging time to the late charging time. I entered.
In the second batch, until the mixed raw material is charged 80 mass%, the segregation control plate 12 is set to the first inclination angle shown in FIG. When it was detected that 80 mass% of the raw material was charged, the segregation control plate 12 was switched to the second inclination angle shown in FIG. 5B by the raw material charging control unit 30, and the mixed raw material was charged. As a result, the coke mixing ratio of the mixed raw material in the second batch was gradually increased as the discharge was late, as shown in Example 1 of FIG.

Then, when charging the mixed raw material from the furnace top bunker 11 to the blast furnace 20, the swivel chute 18 was reversely tilted (tilted from the furnace center toward the furnace wall) in both the first and second batches. Thus, in the first batch, a coke mixed ore layer of uniform mixing is formed in the center to the middle part of the furnace, and in the second batch, the coke is in the range of about 0.7 to 1.0 in the dimensionless radius of the blast furnace. The upper segregated coke mixed ore layer was segregated and was operated.
Here, the average particle diameter of the ore and the average particle diameter of the mixed coke were set to 15 mm and 25 mm in both the comparative example and the example, respectively. Table 1 shows operating conditions and operating results.

In addition, the ventilation resistance index in Table 1 is an index obtained by indexing the ventilation resistance in the blast furnace shaft portion, and was calculated from the following equation (1).
Ventilation resistance index = ((A ² −B ² ) / C) × (1 / D ^1.7 ) × (273 / E) (1)
However,
A = ((BP / 98.0665) +1.033) × 10000,
B = ((TP / 98.0665) +1.033) × 10000,
C = 1.033 × 10000 × LST,
D = BGV / SAVE,
E = ((SGT + 273) / 2) +273
BP is the blowing pressure [kPa], TP is the furnace top pressure [kPa], LST is the distance from the stock line to the tuyere [m], BGV is the Bosch gas flow rate [Nm ³ / min], and SAVE is the blast furnace shaft The average horizontal sectional area [m ² ] of the part, SGT is the representative gas temperature (fixed at 1000 ° C.) of the blast furnace shaft part.

Further, gas utilization ratio in Table 1 is the ratio of CO ₂ to the total amount of CO and CO ₂ in the top gas.
When the operations of the comparative example and the example are compared in Table 1, by using the upper segregation, the gas utilization rate rises due to the effect of the reduction efficiency being improved despite the fact that the ventilation resistance index is the same. It can be seen that the material ratio (coke ratio + pulverized coal ratio) decreases. Moreover, it turns out that coke ratio falls.
From the above results, it was confirmed that the present invention is effective as a technology for improving the reduction efficiency of a blast furnace and further effective as a technology for operating a low coke ratio.

  DESCRIPTION OF SYMBOLS 1 ... Ore, 2 ... Coke, 3a, 3b ... Coke layer, 4a, 4b ... Ore layer, 10 ... Bellless charging device, 11 ... Furnace top bunker, 12 ... Segregation control board, 13 ... Discharge port, 14 ... Top of furnace Bunker, 15, 16 ... Gate, 17 ... Collecting hopper, 18 ... Turning chute, 20 ... Blast furnace, 30 ... Raw material charging control unit, 31 ... Mass meter

Claims (4)

A raw material stored in a furnace top bunker is charged from the furnace top through a swivel chute installed below the furnace top bunker, and a blast furnace operation method for alternately forming an ore layer and a coke layer,
The ore layer is a coke mixed ore layer formed by a mixed raw material of ore and coke stored in the furnace top bunker,
A segregation control plate capable of adjusting an inclination angle for changing a falling direction of the raw material charged into the furnace top bunker is provided at an upper portion in the furnace top bunker, and the mixed raw material is charged into the furnace top bunker. The inclination angle of the segregation control plate is determined from the first inclination angle at which the mixed raw material drop position is directly above the furnace top bunker outlet, and the mixed raw material drop position is immediately above the outlet. A blast furnace operating method characterized by switching to a second inclination angle that becomes a side wall position separated from the horizontal direction.   The amount of the mixed raw material charged into the furnace top bunker with the inclination angle of the segregation control plate as the first inclination angle is 60 mass% or more and 95 mass% or less of the total charged amount of the mixed raw material into the furnace top bunker. The blast furnace operating method according to claim 1, wherein: One charge for charging the mixed raw material into the blast furnace to form the coke mixed ore layer, a charging batch to the furnace center, and a charging batch from the furnace center to the furnace periphery on the furnace wall side Divided into at least two batches of
During the charging of the mixed raw material charged into the blast furnace in the charging batch to the furnace peripheral portion into the furnace top bunker, the inclination angle of the segregation control plate is changed from the first inclination angle to the second inclination angle. The blast furnace operating method according to claim 1, wherein switching control is performed. The periphery of the furnace is set within a region where a dimensionless radius r / R of the blast furnace is 0.7 or more and 1 or less, where R is a radius of the blast furnace and r is a radial position from the center of the blast furnace. The blast furnace operating method according to claim 3, wherein

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