JP5534118B2 - Raw material charging method to blast furnace - Google Patents

Description

  The present invention relates to a raw material charging method for a blast furnace in which a raw material is charged into the furnace with a turning chute.

  In a blast furnace, generally, ore raw materials such as sintered ore, pellets and massive ore and coke are charged in layers from the top of the furnace, and combustion gas flows from the tuyere to obtain pig iron. The coke and ore raw material, which are the charged raw materials for the blast furnace, descend from the top of the furnace to the lower part of the furnace, and ore reduction and raw material temperature rise occur. The ore raw material layer is gradually deformed while filling the gaps between the ore raw materials due to the temperature rise and the load from above, and the lower part of the shaft part of the blast furnace has a very high resistance to gas and almost no gas flows. Form a layer.

Conventionally, raw material charging into a blast furnace is performed by alternately charging ore raw materials and coke, and in the furnace, ore raw material layers and coke layers are alternately layered. Further, in the lower part of the blast furnace, there is a region called a cohesive zone where an ore raw material layer having a large ventilation resistance softened and fused with ore and a coke slit having a relatively small ventilation resistance derived from coke are mixed.
The air permeability of this cohesive zone has a great influence on the air permeability of the entire blast furnace, and the productivity in the blast furnace is limited. When performing a low coke operation, it is considered that the coke slit becomes very thin because the amount of coke used is reduced.

In order to improve the cohesive zone ventilation resistance, it is known that mixing coke into the ore raw material layer is effective, and many studies have been reported to obtain an appropriate mixing state. .
For example, in Patent Document 1, in a bell-less blast furnace, coke is charged into the ore hopper on the downstream side of the ore hopper, the coke is stacked on the ore on a conveyor, charged into the furnace top bunker, and the ore And coke are charged into the blast furnace through a turning chute.

  In Patent Document 2, ore and coke are separately stored in a bunker at the top of the furnace, and coke and ore are mixed and charged at the same time. And three batches for mixing and charging are performed simultaneously.

  Furthermore, in Patent Document 3, in order to prevent the instability of the cohesive zone shape in the blast furnace operation and the decrease in the gas utilization rate near the center, and to improve the safe operation and thermal efficiency, the raw material charging method in the blast furnace is In addition, all ore and all coke are thoroughly mixed and then charged into the furnace.

JP-A-3-211210 JP 2004-107794 A Japanese Patent Publication No.59-10402

In order to improve the ventilation resistance of the cohesive zone, it is known that it is effective to mix coke into the ore layer as in the conventional example described in Patent Document 3 described above.
Therefore, the inventors tried to enter the furnace interior as a mixed layer in which coke equivalent to the coke layer, which had been alternately charged as the ore raw material layer and the coke layer, was completely mixed in the ore raw material layer. It was.
As a result, it has been found that when the ore raw material and coke are charged only as a mixed layer of both, good air permeability may not always be obtained.

  The present invention was developed in view of the above-mentioned present situation, and a raw material charging method into a blast furnace that advantageously eliminates the deterioration of air permeability, which is a concern when ore raw materials and coke are mixed into a furnace as a mixed layer. The purpose is to provide.

That is, the gist configuration of the present invention is as follows.
1. In the blast furnace operation method of charging ore raw materials such as sintered ore, pellets, massive ore and blast furnace charging raw materials of coke into the blast furnace using a rotating chute,
In charging the blast furnace charging material into the blast furnace, 60 to 75% by mass of the total amount of coke charged in the furnace is charged as a mixed layer with the ore raw material, while the remaining 25 to 40%. A raw material charging method for a blast furnace, characterized in that the amount of coke in mass% is left as coke slits.

2. The top of the blast furnace is provided with at least two top bunker, and one or two of the top bunker is provided with the ore raw material or the ore raw material and the coke, and the coke amount is 30% of the total coke amount. Either or both of the mixed raw materials mixed so as to be less than or equal to mass% are respectively stored, the coke is stored in one of the remaining furnace top bunkers, and the raw materials discharged from each furnace top bunker are temporarily collected into a collecting hopper And when charging the blast furnace charging raw material into the blast furnace by supplying to the swivel chute,
(1) First, a coke slit is formed by discharging coke from a top bunker charged with only coke.
(2) Next, coke and ore materials and / or mixed materials are discharged from each furnace top bunker at the same time, mixed in a collecting hopper, and then supplied to the swivel chute, so that the ores are placed on the coke slit. Forming a mixed layer of raw material and coke,
(3) Repeat (1) and (2) above,
(4) The amount of coke forming the coke slit is set to 25 to 40% by mass of the total amount of coke charged in the furnace, and the amount of coke forming the mixed layer of the ore raw material and coke is set in the furnace. 2. The raw material charging method to the blast furnace as described in 1 above, wherein the amount is 60 to 75% by mass of the total amount of coke charged therein.

3. 3. The raw material charging method to the blast furnace according to 1 or 2 above, wherein a central coke layer is formed in the axial center portion of the blast furnace when charging the blast furnace raw material into the blast furnace.

  According to the present invention, the gas flow in the blast furnace can be controlled by leaving some coke slits, and good blast furnace air permeability can be maintained, so that stable blast furnace operation is possible.

It is a schematic diagram which shows one Embodiment of the raw material charging method to the blast furnace of this invention. It is explanatory drawing which shows the raw material discharge | emission order from a furnace top bunker. It is a schematic diagram which shows the state which mixed coke little by little in the ore raw material layer, and was finally set as the complete mixed layer. It is a graph which shows the relationship between mixed coke amount and air permeability. It is a schematic block diagram which shows the experimental apparatus which measures the high temperature property of an ore raw material. 6 is a graph showing the maximum pressure loss when coke is divided into mixed coke and slit coke under a coke ratio of 350 kg / t. It is a schematic diagram which shows the raw material charging state containing a furnace top bunker.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a diagram schematically showing an embodiment of a method for charging a raw material into a blast furnace according to the present invention.
In the figure, reference numeral 1 denotes an ore raw material hopper for storing an ore raw material 2 composed of at least one of sintered ore, pellets and massive ore, and 3 denotes a coke hopper for storing coke 4. The ore raw material 2 and the coke 4 cut out from the ore raw material hopper 1 and the coke hopper 3 at a predetermined ratio are conveyed upward by the ore conveyor 5, and the ore raw material 2 and the coke 4 are mixed with the reserve hopper 6. It is stored as a blast furnace charging raw material 7. The blast furnace charging raw material 7 cut out from the reserve hopper 6 is transferred to the furnace top of the blast furnace 10 by the charging conveyor 8, and one of a plurality of, for example, three furnace top bunkers 12 a to 12 c through the receiving chute 11, for example. It is thrown into 12b and stored. In addition, the ore raw material and the mixed raw material of coke stored in the furnace top bunker 12b are adjusted so that the amount of coke becomes 30% by mass or less of the total amount of coke.

Here, the reason for adjusting the coke amount to 30% by mass or less of the total coke amount is as follows. The ore raw material 2 and the coke 4 cut out from the ore raw material hopper 1 and the coke hopper 3 are put into the reserve hopper 6 in a state where the coke 4 is laminated on the ore raw material 2 by the ore conveyor 5. By this, the ore raw material 2 and the coke 4 are mixed by this reserve hopper 6 and become a mixed raw material. However, since there is a difference in specific gravity and particle size between the coke 4 and the ore raw material 2, while the mixed raw material stored in the reserve hopper 6 is conveyed to the receiving chute 11 by the charging conveyor 8, the charging conveyor 8 may be segregated, and may also be segregated when thrown into the furnace top bunker 12b via the receiving chute 11.
At this time, if the amount of coke to be mixed is 30% by mass or less of the total amount of coke, no large segregation occurs between the coke and the ore raw material when stored in the furnace top bunker 12b. The mixing rate of the mixed layer of the ore raw material and coke formed can be made substantially uniform.

On the other hand, when the amount of coke exceeds 30% by mass of the total amount of coke, segregation due to difference in specific gravity and particle size is likely to occur, and segregation between coke and ore raw material when stored in the furnace top bunker 12b. As a result, a region in which only the ore raw material or only coke exists locally is generated.
Moreover, as shown in FIG. 2, the discharging order when discharging the mixed raw material from the furnace top bunker 12b is sequentially moved upward from a position close to the discharge port 12g close to the central axis of the blast furnace, and thereafter from the central axis of the blast furnace. It moves in the direction away from the outside, and finally the upper end side of the inclined side wall 12h is discharged.

For this reason, when only the ore raw material or only the coke exists directly above the discharge port 12g or the upper end side of the inclined side wall 12h, only the ore raw material or only the coke is discharged. Even in such a case, the collecting hopper 14 described later is mixed with the coke and ore raw materials discharged from the other top bunker 12a and 12c, but the ratio of the ore raw material or the coke is As a result, the mixing rate of the mixed layer of the ore raw material and the coke formed by the turning chute 16 becomes non-uniform.
The amount of coke to be mixed is equal to or less than 30% by mass of the total amount of coke, which corresponds to 7% by mass or less in the ratio of (coke amount / ore raw material amount).

  In addition, even when the particle size difference between the ore raw material and the coke is large, and depending on the particle size distribution of the ore raw material and the coke, segregation may occur when they are mixed.

Accordingly, the inventors have conventionally mixed the coke that has been separately charged as the ore raw material layer and the coke layer into the ore raw material layer little by little as shown in FIG. 3 (a). Finally, as shown in FIG. 3B, the air permeability in the furnace when it was formed in the furnace as a complete mixed layer was investigated. In the figure, reference numeral 17 is a central coke layer, 18 is a coke slit, and 19 is a mixed layer.
The experiment was performed by placing 50 kg as the central coke layer under the condition of coke ratio: 400 kg / t and gradually mixing the remaining coke: 350 kg into the mixed layer. Air permeability was evaluated by logK. Here, K is a ventilation resistance index, and is obtained by the following equation.
K = (P _B ² −P _T ² ) / μ ^0.3 ρ ^0.7 V _B ^1.7
Where P _B is the blowing pressure (absolute pressure), P _T is the furnace top pressure (absolute pressure), μ is the viscosity of the Bosch gas in the standard state, ρ is the density of the Bosch gas in the standard state, and V _B is the standard state Bosch gas amount.

As a result, as shown by the broken line in FIG. 4, the ventilation resistance gradually decreased for 7 charges out of 10 charges, and good air permeability as expected was obtained. As shown by the solid line, the ventilation resistance showed a minimum value before coke was completely mixed, and thereafter the ventilation resistance increased. That is, the air permeability may be deteriorated.
As described above, this cause is considered to be related to segregation generated during storage in the furnace top bunker, particle size difference and particle size distribution of the charged raw materials.

However, as shown by the solid line in FIG. 4, even if the ventilation resistance finally increases due to segregation of raw materials, the ventilation resistance gradually decreases to a minimum value until a certain mixing amount. Reach.
Therefore, if the coke is mixed into the ore raw material up to the minimum value to form a mixed layer and the remaining coke is left as it is as a coke slit, good air permeability can be obtained.

Using the experimental apparatus shown in FIG. 5, the change in the ventilation resistance was examined by simulating the raw material reduction and the temperature rising process in the blast furnace.
In this experimental apparatus, a furnace core tube 32 is disposed on the inner peripheral surface of a cylindrical furnace body 31, and a cylindrical heating heater 33 is disposed outside the furnace core tube 32. A graphite crucible 35 is disposed at the upper end of a cylindrical body 34 made of a refractory inside the furnace core tube 32, and a charging raw material 36 is charged into the crucible 35. A load is applied to the charged raw material 36 from above by a load loading device 38 connected via a punch bar 37 so as to be in the same level as the fused layer at the bottom of the blast furnace. A drop sampling device 39 is provided below the cylindrical body 34.

The gas adjusted by the gas mixing device 40 is sent to the crucible 35 through the lower cylindrical body 34, and the gas that has passed through the charging material 36 in the crucible 35 is analyzed by the gas analyzer 41. The heating heater 33 is provided with a thermocouple 42 for controlling the heating temperature, and the crucible 35 is set to 1200 to 1500 by controlling the heater 33 with a control device (not shown) while measuring the temperature with the thermocouple 42. Heat to ° C.
Here, as the charging raw material 36, a sample obtained by mixing coke at various ratios with ore raw materials obtained by mixing sintered ore and iron ore at a predetermined ratio, and the maximum pressure under a coke ratio of 350 kg / t is used. An experiment was conducted to determine the loss.

FIG. 6 is a graph showing the maximum pressure loss when the coke used in the experiment is divided into mixed coke and slit coke under the coke ratio of 350 kg / t.
In the range of 60 to 75% by mass of the amount of coke charged in the furnace, the ventilation resistance becomes the lowest, and in order to obtain the effect of improving the ventilation of the ore layer by coke mixing, the amount of coke charged in the furnace is 60 to 60%. It can be seen that a range of 75% by weight is suitable. On the other hand, when the mixed coke amount is 75% by mass or more, that is, when the coke amount for the coke slit is 25% by mass or less, the coke slit is thin and there is a portion where the fused ore layer and the coke layer are integrated. As a result, the function of maintaining the air permeability of the coke layer was impaired, and the air resistance was increased.
From the above examination, about 60 to 75 mass% of the coke amount charged in the furnace is charged as a mixed layer with the ore raw material, while the remaining coke amount of 25 to 40 mass% is directly used as the coke slit. As a result, it was found that an advantageous improvement in air permeability was achieved by remaining as the above, and the present invention was completed.

Next, a specific charging procedure for charging the ore material and coke into the blast furnace will be described with reference to FIG.
In this example, the ore raw material and coke mixed raw material are stored in the furnace top bunker 12b, only the coke is stored in the furnace top bunker 12a, and only the ore raw material is stored in the furnace top bunker 12c. Yes.
Further, the turning chute 16 is rotated about the shaft center of the blast furnace 10 and at the same time is reversely tilted to tilt toward the furnace wall side from the shaft center portion of the blast furnace 10. The case of performing will be described.

The raw material charging sequence from the furnace top bunker is as follows. First, the swivel chute 16 is gradually tilted from the furnace wall side toward the furnace center or from the furnace center toward the furnace wall, and only the coke is stored. Coke is discharged to the bunker 12 a to form a coke layer (coke slit) 18. As described above, the amount of coke used to form the coke slit 18 is 25 to 40% by mass of the amount of coke charged into the furnace per charge.
Next, the central charging coke layer 17 is formed in the axial center part of the blast furnace by discharging only the coke from the furnace top bunker 12a in which only the coke is charged with the raw material charging destination of the turning chute 16 as the axial center part of the blast furnace. To do.
That is, in a state where the turning chute 16 is tilted in a substantially vertical state, the flow rate adjustment gates 13 of the furnace top bunkers 12b and 12c are closed, the flow rate adjustment gate 13 of only the furnace top bunker 12a is opened, and the furnace top bunker 12a By supplying only the stored coke to the turning chute 16, as shown in FIG. 5, the central coke layer 17 is formed in the axial center portion.

At this time, the coke dropping position at the height of the raw material stock line is preferably 0 or more and 0.3 or less in the dimensionless radius of the blast furnace where the blast furnace shaft center part is 0 and the furnace wall part is 1. The reason for this is that by collecting a part of the coke in the core part of the furnace, the air permeability in the shaft part and thus the air permeability of the entire blast furnace can be effectively improved.
The amount of coke charged to form the central coke layer is preferably about 5 to 30% by mass of the amount of coke charged per charge. This is because if the amount of coke charged to the shaft center portion is less than 5% by mass, the air permeability around the shaft center portion is not sufficiently improved, while more than 30% by mass of coke is concentrated on the shaft center portion. In this case, not only the amount of coke for use in the mixed layer is reduced, but also the amount of heat removed from the furnace body is increased due to excessive gas flow in the axial center. Preferably it is 10-20 mass%.
As described above, the amount of coke used to form the coke slit 18 and the amount of coke that forms the center coke layer 17 are 25 to 40% by mass of the total coke amount charged in the furnace, as described above. It is distributed for forming 18 and for forming the central coke layer 17. The charge amount per charge may be as long as the coke layer thickness is 100 mm or more, preferably 150 mm or more for forming the coke layer (coke slit) 18. Since it forms only with coke, the layer which can maintain ventilation | gas_flowing as a coke slit is formed.

Next, or subsequent to the formation of the central coke layer described above, coke and ore raw materials and / or mixed raw materials are simultaneously discharged from each furnace top bunker, mixed with the collecting hopper 14, and then supplied to the turning chute 16. By doing so, a mixed layer 19 of the ore raw material and coke is formed outside the central coke layer 17 and on the upper surface of the coke slit 18.
That is, in this case, not only the furnace top bunker 12a but also the flow rate adjusting gates 13 of the remaining two furnace top bunkers 12b and 12c are opened at a predetermined opening, and coke discharged from the furnace top bunker 12a, The mixed raw material discharged from the top bunker 12b and the ore raw material discharged from the furnace top bunker 12c are simultaneously supplied to the collecting hopper 14, and the coke and the ore raw material are completely mixed in the collecting hopper 14. Supply to the turning chute 16. As a result, a mixed layer 19 is formed on the upper surface of the coke slit 18 outside the central coke layer 17 in the blast furnace 10 so that the coke and the ore raw material have a substantially uniform mixing ratio.
In addition, the ratio of the coke in the mixed layer 19 shall be 60-75 mass% of the amount of coke per charge.

Here, the size of the ore raw material and the coke will be described. The ore raw material is not so large in particle size difference and is usually about 5 to 25 mm. In contrast, coke has a large particle size difference and a width of 10 to 60 mm. Usually, those having a particle size of about 30 to 60 mm are called lump coke, and those having a particle size of about 10 to 30 mm are called small and medium lump coke.
Therefore, in order to prevent segregation of the raw material, it is desirable to adjust the size of the used coke according to the size of the ore raw material used, and it is also preferable to adjust the particle size distribution of the used coke.
Here, in order to avoid deterioration of the air permeability in the furnace due to the particle size of the ore raw material and the coke, the particle size of the ore raw material is preferably 10 to 30 mm and the particle size of the coke is preferably 30 to 55 mm. Furthermore, it is preferable that the particle size ratio (coke particle size / ore material particle size) is about 1.0 to 5.5.

  However, as in the present invention, not all of the coke is mixed in the mixed layer, but if a part of the coke is left as a coke slit, there is no need to particularly adjust the size of the ore material to be used or the coke. Good furnace air permeability can be obtained.

  Further, the ratio of coke in the mixed layer suitable for improving air permeability, that is, the ratio of (coke amount / ore raw material amount) is about 7 to 25%, more preferably 10 to 15% in terms of mass ratio. . When the ratio of (coke amount / ore raw material amount) is less than 7% by mass, the effect of improving the air permeability by coke mixing is not sufficiently obtained, and the air permeability of the ore layer is poor, while (coke amount / ore raw material amount) When the ratio is more than 25% by mass, the amount of coke existing as coke slits is insufficient and the air permeability of the coke layer is deteriorated.

  Note that during blast furnace operation, the shaft pressure is closely monitored, and when the blast furnace charging according to the present invention is continuously performed, if an abnormality is detected in the shaft pressure, the raw material charging method is changed to the normal charging method. It is advantageous to switch to a method in which the ore raw material layer and the coke slit are formed separately, and then after switching to the charging method according to the present invention, once the shaft pressure abnormality is resolved, it is advantageous to operate. .

As shown in Table 1, blast furnace operation was performed under various conditions in which the ratio of coke used for forming coke slits and the ratio of coke used for forming mixed layers in all cokes were varied.
The results of examining the gas utilization rate, the pressure loss ΔP / V of the packed bed, and the pressure fluctuation σΔP / V of the packed bed when implemented under each operating condition are shown in comparison with Table 1.
In addition, σΔP / V indicates a standard deviation when ΔP / V is measured every minute and measured for 30 minutes, and the smaller this value is, the more stable the gas flow in the furnace is. .

  As shown in the table, according to the present invention, when coke of 35% by mass (Example 1) and 25% by mass (Example 2) in the total coke amount was used for forming the coke slit, the coke ratio was Despite the reduction, the gas utilization rate is improved, and the pressure loss ΔP / V of the packed bed and the pressure fluctuation σΔP / V of the packed bed are both reduced.

DESCRIPTION OF SYMBOLS 1 Ore powder hopper 2 Ore raw material 3 Coke hopper 4 Coke 5 Ore conveyor 6 Reserving hopper 7 Blast furnace charge raw material 8 Charge conveyor 10 Blast furnace 11 Receiving chute 12a-12c Furnace top bunker 13 Flow control gate 14 Collecting hopper 15 Bellless Type charging device 16 turning chute 17 central coke layer 18 coke slit 19 mixed layer

Claims (3)

In the blast furnace operation method of charging ore raw materials such as sintered ore, pellets, massive ore and blast furnace charging raw materials of coke into the blast furnace using a rotating chute,
When charging the blast furnace raw material into the blast furnace, about 60 to 75 mass% of the amount of coke charged into the furnace per charge is charged as a mixed layer with the ore raw material, while the remaining 25 A method of charging raw materials into a blast furnace, wherein a coke amount of ˜40 mass% is left as coke slits. The top of the blast furnace is provided with at least two top bunker, and one or two of the top bunker is provided with the ore raw material or the ore raw material and the coke, and the coke amount is 30% of the total coke amount. Either or both of the mixed raw materials mixed so as to be less than or equal to mass% are respectively stored, the coke is stored in one of the remaining furnace top bunkers, and the raw materials discharged from each furnace top bunker are temporarily collected into a collecting hopper And when charging the blast furnace charging raw material into the blast furnace by supplying to the swivel chute,
(1) First, a coke slit is formed by discharging coke from a top bunker charged with only coke.
(2) Next, coke and ore materials and / or mixed materials are discharged from each furnace top bunker at the same time, mixed in a collecting hopper, and then supplied to the swivel chute, so that the ores are placed on the coke slit. Forming a mixed layer of raw material and coke,
(3) Repeat (1) and (2) above,
(4) The amount of coke forming the coke slit is set to 25 to 40% by mass of the total amount of coke charged in the furnace, and the amount of coke forming the mixed layer of the ore raw material and coke is set in the furnace. It is set as 60 to 75 mass% of the total amount of coke charged in, The raw material charging method to the blast furnace of Claim 1 characterized by the above-mentioned.   3. The method of charging a blast furnace with a raw material according to claim 1 or 2, wherein a central coke layer is formed at the axial center of the blast furnace when the blast furnace charging material is charged into the blast furnace.

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