JP2002129211A - Method for operating blast furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To keep the ventilation in a blast furnace good and to obtain a stable operation for injecting high blend of pulverized fine coal by reducing the pressure loss in the charged material layer at the upper part of the furnace, in the blast furnace operation performed by injecting the pulverized fine coal at >=180 kg par ton of molten iron. SOLUTION: In the blast furnace operation charging raw material by alternately charging coke and ore from the furnace top part and alternately stacking the coke layer and the ore layer, the coke and the ore are charged from the furnace top part so that each ratio [Lc/(Lc+Lo)] of a thickness Lc of the coke layer to a thickness (Lc+Lo) of the charged layer adding the thickness Lc of the coke and the thickness Lo of the ore layer, satisfies such condition at each zone in the radius direction of the furnace as (1) at the center part side range in the radius direction of the furnace, [Lc/(Lc+Lo)]>=0.9 in the average value, (2) at the intermediate range in the radius direction of the furnace, [Lc/(Lc+Lo)]>=0.4 in the average value and (3) bat the peripheral part side range in the radius direction of the furnace, [Lc/(Lc+Lo)]>=0.5 in the average value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of operating a blast furnace by blowing a large amount of pulverized coal into a furnace, and more particularly, to controlling a charge distribution in an upper part of a furnace in order to maintain good air permeability in the furnace. And a method of operating a blast furnace.

[0002]

2. Description of the Related Art Normally, in blast furnace operation, ore and coke are charged alternately from the top of a furnace, and coke is burned with hot air of about 1200 ° C. blown from a tuyere at the bottom of the furnace, and the ore is generated by the generated gas. It is to obtain hot metal by reduction. In recent blast furnace operations, pulverized coal has been blown from the tuyere instead of coke for the purpose of extending the life of the coke oven and reducing the cost of hot metal, etc. .

[0003] In a high pulverized coal injection operation in which pulverized coal is blown by 180 kg or more per ton of hot metal, the charged material layer is increased by increasing the ratio (O / C ratio) of the amount of ore charged to the amount of coke charged per ton of hot metal. In the upper part of the furnace due to a decrease in the porosity of the furnace, an increase in the furnace gas temperature due to a decrease in the ratio of the charge weight per ton of hot metal to the furnace gas amount (heat flow ratio), and an accompanying increase in the furnace gas flow velocity. It is known that this causes an increase in airflow resistance and pressure loss.

[0004] When such a state occurs, a blow-up phenomenon in which the blowing pressure rises remarkably and the charged material is blown up to the upper part of the furnace without being stably lowered is caused. As a result, the stable operation of the blast furnace is greatly impaired. , Operation elasticity is remarkably reduced. Therefore, in order to realize stable operation under high pulverized coal injection operation, it is important to improve the permeability of the charge in the upper part of the furnace.

On the other hand, as the charge distribution control method conventionally performed under the operation of high pulverized coal, materials of the 89th Ironmaking Subcommittee, “High PCI Operation of Kakogawa 1 Blast Furnace” (hereinafter referred to as Prior Art 1), Materials from the 84th Ironmaking Subcommittee, "Operation Test of Injecting Large Pulverized Coal in Kimitsu 3 Blast Furnace" (hereinafter referred to as Prior Art 2)
By increasing the ratio [Lo / Lc] of the layer thickness of the ore layer and the coke layer in the peripheral part (furnace wall side part) as described in the above, the gas flow velocity in the peripheral part (hereinafter referred to as peripheral flow) is increased. Curb,
On the other hand, there is a method of strengthening the gas flow velocity (hereinafter, referred to as the central flow) in the central part (furnace central side part).

FIG. 7 shows [Lo / Lo] in the furnace radial direction before and after the charge distribution control shown in Prior Art 1.
Lc]. According to the prior art 1, as shown in FIG.
[Lo / Lc] at the periphery with increasing to 0kg
As a result, the blast energy at the tuyere was reduced under high oxygen-enriched blast due to high pulverized coal injection, but the central flow was strengthened and the peripheral flow was reduced. It is said that the gas flow velocity distribution in the furnace is suppressed, and as a result, heat loss to the furnace wall can be maintained at a relatively low level, thereby enabling stable operation.

FIG. 8 is shown in prior art 2.
It shows a change in gas utilization distribution in the furnace radial direction when charge distribution control is performed. Here, the smaller the value of the gas utilization rate, the higher the gas flow rate at that site. According to the prior art 2, as the pulverized coal injection ratio was increased from 118 kg to 203 kg per ton of hot metal, the charging mode of coke was set to the furnace center side, and the charging mode of ore was set to the furnace wall side. As a result of changing the charge distribution control so that [Lo / Lc] on the furnace wall side becomes higher, as shown in FIG. 8, the peripheral flow is suppressed and the central flow is strengthened. It is said that the flow velocity distribution was obtained, and a stable gas flow was maintained even in the upper part of the furnace.

[0008]

By using the charge distribution control method as described in the above prior arts 1 and 2,
By suppressing the increase in heat load on the furnace wall in the lower part of the furnace, which is conspicuous when high-pulverized coal is injected, or by forming the shape of the cohesive zone in an inverted V-shape, The pressure loss in the furnace can be reduced. However, these prior arts 1 and 2 have the following problems.

That is, when the above-mentioned prior art method is used in the case of using blast furnace raw materials (sinter ore, coke, etc.) that have a bad influence on air permeability, the peripheral flow is extremely reduced. As a result, phenomena such as a decrease in furnace heat due to ore reduction stagnation in the peripheral portion and a decrease in the actual volume in the furnace due to the formation of a stagnant layer on the furnace wall and a decrease in the actual volume inside the furnace become remarkable. Here, in the charge distribution control methods of the prior arts 1 and 2, the shape of the cohesive zone is inverted V-shaped,
The effect of reducing the pressure loss at this part is expected, but the permeability in the cohesive zone is not limited to its shape, but also the ore burn-through behavior, the thickness of the cohesive layer, and the thickness of the coke slit. Since it is greatly influenced by factors such as the number, a sufficient effect may not be obtained in some cases. Therefore, even with the prior arts 1 and 2, the deterioration of the in-furnace air permeability due to the above-described factors could not be sufficiently improved, and it was very difficult to stably perform the operation of injecting high pulverized coal. .

Therefore, an object of the present invention is to maintain good air permeability in a furnace by reducing pressure loss in a charge layer at the upper part of a furnace in a blast furnace operation in which pulverized coal is blown at 180 kg or more per ton of hot metal. It is an object of the present invention to provide a method of operating a blast furnace that enables stable high-pulverized coal injection operation.

[0011]

In order to achieve the above object, a method of operating a blast furnace according to the present invention comprises the steps of: providing a coke layer thickness Lc, a coke layer thickness Lc, and an ore layer thickness at the uppermost part of the furnace interior layer.
The ratio [Lc / (Lc + L) to the charging layer thickness (Lc + Lo) with Lo
o)] is to control the charge distribution so that the distribution in the furnace radial direction is large on the furnace center side and the furnace wall side and small on the middle part between them. The features are as follows.

[1] Coke and ore are charged alternately from the furnace top, and raw materials for alternately laminating a coke layer and an ore layer are charged, and pulverized coal is charged into the furnace at a rate of 180 kg per ton of hot metal.
In the blast furnace operation performed by blowing as described above, the ratio [Lc / (Lc) of the charged layer thickness (Lc + Lo) obtained by adding the coke layer thickness Lc and the coke layer thickness Lc and the ore layer thickness Lo at the top of the furnace interior layer
+ Lo)] in each area in the furnace radial direction.
A method of operating a blast furnace, comprising charging coke and ore from the furnace top so as to satisfy the following conditions. (1) Furnace center side area in the furnace radial direction: [Lc
/(Lc+Lo)]≧0.9 (2) Middle area in the furnace radial direction: [Lc / (L
c + Lo)] ≤ 0.4 (3) Furnace peripheral side area in the furnace radial direction: [Lc
/(Lc+Lo)]≧0.5

[2] In the operation method of the above [1], the furnace center side region, the middle region region, and the furnace peripheral side region in the furnace radial direction are respectively set to the following regions, and coke and ore are set from the furnace top. A method for operating a blast furnace, comprising charging a blast furnace. (a) Furnace center side region in the furnace radial direction: r / Rt ≦ 0.
Region 1 (b) Middle region in the furnace radial direction: 0.1 <r / Rt ≦
Area of 0.6 (c) Area around the furnace periphery in the furnace radial direction: 0.6 <r /
Rt region where r: distance from furnace center in furnace radius direction (m) Rt: furnace radius at furnace port (m)

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a graph showing a state of a charge accumulation in a furnace radial direction at an upper portion of a furnace (uppermost portion of an inner layer of a furnace) and a ratio of [Lc / (Lc + Lo)] when the method of the present invention is carried out. It is explanatory drawing which shows a distribution. Here, Lc: the coke layer thickness at the upper part of the furnace,
Lo: The ore layer thickness at the top of the furnace, and therefore (Lc +
Lo) is the bed thickness of the combined coke and ore layers at the furnace top. In FIG. 1, 1 is an ore layer,
2 is a coke layer and 3 is a lower layer.

In the method of the present invention, coke and ore are charged alternately from the furnace top and raw material charging for alternately laminating a coke layer and an ore layer is performed. Inserted layer thickness (Lc + Lo) with layer thickness Lo
The coke and the ore are charged so that the ratio [Lc / (Lc + Lo)] satisfies the following conditions (1) to (3) in each region in the furnace radial direction. (1) Furnace center side area in the furnace radial direction: [Lc
/(Lc+Lo)]≧0.9 (2) Middle area in the furnace radial direction: [Lc / (L
c + Lo)] ≤ 0.4 (3) Furnace peripheral side area in the furnace radial direction: [Lc
/(Lc+Lo)]≧0.5 Here, as shown in FIG. 1, [Lc / (Lc + Lo)] is an average value in each region on the furnace center side, the middle part, and the furnace peripheral side in the furnace radial direction. It suffices if the above conditions (1) to (3) are satisfied.

By adopting the above charge distribution form, the pressure loss in the charge layer at the upper part of the furnace is effectively reduced,
Good air permeability in the furnace can be maintained. This is because, in the charging distribution mode as described above, a solid packed bed with small airflow resistance is formed in the furnace peripheral side region in the furnace radial direction, but a fixed gas amount is formed in the cylindrical solid packed bed. When gas is passed through the furnace peripheral area, a gas-permeable layer is formed in the furnace peripheral area where the cross-sectional area is larger than the furnace intermediate area (intermediate area in the furnace radial direction). This is because, as a result, the pressure loss of the entire solid packed bed is reduced as a result of the flow with preferentially low pressure loss.

Further, in the above charging distribution mode, a packed bed mainly composed of coke and having a very small ore ratio is formed in the furnace central area in the furnace radial direction. Is formed, a reduction reaction (FeO + CO) by CO gas from the tuyere
= Fe + CO ₂ ) does not occur much, so that the amount of generated CO ₂ gas is reduced. Thus CO ₂ solution loss reaction (C + CO 2 = _2CO) hardly occurs due to this result the deterioration of the coke is suppressed, coke in this region is supplied to the left lower part of the furnace of the healthy state. Since coke existing in this region is replaced with most of the coke in the lower part of the furnace, sounder coke is supplied to the lower part of the furnace, and the gas permeability and liquid permeability of the lower part of the furnace are greatly improved. Will be done.

Here, the value of [Lo / (Lo + Lc)] in the region (1) (furnace center side region in the furnace radial direction) is as close as possible to 1.0 (state in which no ore is present). Is more desirable. This is because, as described above, if there is little ore in the furnace central area, the amount of CO ₂ gas generated by the reduction reaction is small, and thus the deterioration of coke due to the solution loss reaction is suppressed, and the coke in this area is sound. This is because, as a result of being supplied to the lower part of the furnace as it is, the gas permeability and liquid permeability of the lower part of the furnace are effectively improved.

The lower limit of [Lo / (Lo + Lc)] in the area (2) (intermediate area in the furnace radial direction) is as follows:
Preferably, the average value is 0.2. When the average value of [Lo / (Lo + Lc)] in this region (2) is less than 0.2, the amount of ore to be reduced is excessive with respect to the amount of gas supplied from below, and the reduction of ore is delayed. Becomes remarkable,
Undesirably, the furnace heat decreases due to an increase in the amount of direct reduction, and stable operation is impaired.

The upper limit of [Lo / (Lo + Lc)] in the area (3) (furnace peripheral area in the furnace radial direction) is preferably 0.7 on average. If the average value of [Lo / (Lo + Lc)] exceeds 0.7 in the region (3), the amount of gas passing near the furnace wall increases, and the heat load on the furnace wall increases. It is not preferable because adverse effects such as damage to the furnace body and an increase in fuel cost become significant.

Further, in the above-mentioned regions (1) to (3) in the furnace radial direction, the distance from the furnace center in the furnace radial direction is r (m), and the furnace radius at the furnace opening is Rt (m). In this case, it is preferable to set the following regions. (a) Furnace center side region in the furnace radial direction: r / Rt ≦ 0.
Region 1 (b) Middle region in the furnace radial direction: 0.1 <r / Rt ≦
Area of 0.6 (c) Area around the furnace periphery in the furnace radial direction: 0.6 <r /
Rt area

Hereinafter, a preferred raw material charging method for realizing the above charged material distribution mode will be described. FIG.
(A) and (b) are bell-type furnace top charging devices (devices in FIG. 2 (a)) and bell-less type furnace top charging devices (devices in FIG. 2 (b)) used for carrying out the method of the present invention. FIG. 2 is a schematic explanatory view of FIG.
In FIG. 2A, reference numeral 4 denotes a shaft shell, 5 denotes a bell, 6 denotes a dedicated charging chute, 7 denotes an auxiliary dispensing device, 8 denotes a raw material charge layer surface, and in FIG. Iron skin, 6 is a dedicated charging chute, 8 is the surface of the raw material charge layer, 9
Is a turning chute.

In carrying out the method of the present invention, the locus of coke falling from the dedicated chute 6 and the state of accumulation at the center of the coke are investigated in advance, and the charged raw material is accurately dropped and accumulated at the center of the coke. The equipment conditions such as the height and angle of the dedicated chute 6 are determined so as to be able to perform the operation. Similarly, in the case of the bell-less furnace top charging device of FIG. 2B, the length of the swirling chute 9 and the length of the turning chute 9 in FIG. 2A are set so that the charged material forms a desired raw material charge distribution. In the case of a bell furnace top charging device, equipment conditions such as the angle of the auxiliary distribution device 7 and the length of the arm are determined.

In the method of the present invention, when charging coke on the surface of the lower layer (ore layer), the bell-type furnace top charging shown in FIG. In the apparatus, the distance from the furnace wall to the position of the tip of the auxiliary distributor 7 is adjusted, and in the bellless type furnace top charging apparatus in FIG. Here, coke is charged using the dedicated charging chute 6 at the center, but in the bellless type furnace top charging apparatus of FIG. 2B, the turning chute 9 is set so as to be parallel to the vertical direction. The coke may be charged at an angle.

Next, the ore is charged on the coke layer charged as described above, and the condition (1) to (3) is satisfied with the ore charged. The charging conditions such as the amount of ore charged per batch and the position of the auxiliary distribution device 7 are adjusted. For example, in the case of FIG. 2A, the position of the auxiliary distribution device 7 is set closer to the center of the furnace than the furnace wall in order to increase the ratio of ore in the intermediate region in the furnace radial direction. At least 70 mass% of the ore charge is charged to the intermediate region in the furnace radial direction. As a result, the ore accumulation form (layer cross section) at the furnace upper part after ore charging
Has an M-shape with a peak at a position closer to the center of the furnace about 1.5 to 2 m from the furnace wall in the radial direction of the furnace, and the coke charged into the furnace is located on the furnace wall side (furnace peripheral side region). Yield becomes easier. As a result, the [Lo /
(Lo + Lc)] can be easily maintained at 0.5 or more.

FIG. 3 shows the unit length in the height direction of the charged raw material layer when the raw material is charged by the above-described prior art method and when the raw material is charged by the method of the present invention. It shows the pressure loss per unit in comparison. This result was obtained from a charge distribution test using a 1/10 scale test device of an actual blast furnace. This test equipment uses the upper part of the actual blast furnace (furnace part and furnace top charging equipment part) as 1 /
The apparatus is scaled down to 10, and it is possible to blow air from the lower part, and it is possible to faithfully reproduce the charge distribution shape at the upper part of the actual blast furnace. In this test, raw ore and coke having a size of 1/10 of the raw ore and coke used in the actual blast furnace were used as the raw ore and coke. Decided.

Table 1 shows the raw material charging conditions. In the case of the method of the prior art, an auxiliary dispensing device for charging ore (FIG. 2 (a)
The position of the auxiliary distribution device 7) was set on the furnace wall side, and the value of [Lo / (Lo + Lc)] in the region on the furnace peripheral side side was adjusted to be 0.5 or less. Similarly, the amount of CFC input was reduced so that the value of [Lo / (Lo + Lc)] in the central region of the furnace was adjusted to 0.9 or less.

[0028]

[Table 1]

According to FIG. 3, when the raw material is charged by the method of the present invention, the gas flow rate in the middle area in the furnace radial direction decreases, and the gas flow rate in the furnace peripheral area having a large surface area increases. Therefore, it can be seen that the pressure loss of the charge layer as a whole is reduced as compared with the prior art. The blast furnace operating method according to the present invention described above is particularly effective for a high pulverized coal injection operation in which pulverized coal is blown in at least 230 kg per ton of hot metal.

[0030]

EXAMPLE In accordance with the method of the present invention, a high-pulverized coal injection operation with a pulverized coal ratio of 180 kg / hot metal ton or more was carried out in a blast furnace equipped with a bell-type furnace top charging device. Table 2 shows the raw material charge, the position of the auxiliary distribution device (MA), and the central coke input (CFC input) during operation according to the present invention and before operation of the present method. In this blast furnace operation, a method of alternately charging two batches of coke and three batches of ore was adopted. In the practice of the present invention, one of the ore batches was used.
The value of [Lc / (Lc + Lo)] in the furnace radial direction was adjusted by adjusting the MA position and the charging amounts of the three batches.

[0031]

[Table 2]

FIG. 4 is a graph showing the distribution of the charge and [Lc / (Lc) during the operation according to the method of the present invention and before the operation of the present invention.
+ Lo)]. The distribution shape of the charge and the [Lo / (Lo + Lc)] distribution are measured by measuring the surface shape in the furnace radial direction every time one batch is charged by the microwave distance measuring device installed on the furnace top. It was obtained by adjusting each surface shape level to match the volume of the charge. According to the figure, in the operation of the method of the present invention, [Lc / (Lc + Lo)] at the upper part of the furnace
It is set under the conditions of (1) to (3).

FIG. 5 shows the change of the operation data for about three months before and after the method of the present invention is carried out. According to this, even if the pulverized coal injection ratio is increased from 180 kg to 250 kg per ton of hot metal as a result of applying the charge distribution form according to the present invention as shown in FIG. Almost no water was found, and stable high pulverized coal injection operation was continued.

FIG. 6 shows the relationship between the pulverized coal injection ratio and the ventilation resistance index Ku at the upper part of the furnace before and after performing the method of the present invention. The permeability of the container layer has been significantly improved,
It is considered that this led to an improvement in the ventilation resistance of the entire furnace as shown in FIG.

[0035]

As described above, according to the method of the present invention, in a blast furnace operation in which pulverized coal is blown in at least 180 kg per ton of hot metal, pressure loss in the charge layer at the upper part of the furnace is reduced to reduce the pressure inside the furnace. The air permeability can be significantly improved. For this reason, stable high pulverized coal injection operation can be performed.

[Brief description of the drawings]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory diagram showing a charge deposition form and [Lc / (Lc + Lo)] distribution in a furnace radial direction in a furnace upper part when a method of the present invention is carried out.

FIG. 2 shows a bell-type furnace top charging device (FIG. 2 (a)) and a bell-less type furnace top charging device (FIG. 2) used for carrying out the method of the present invention.
Explanatory drawing showing the outline of (b))

FIG. 3 shows the pressure loss per unit length in the height direction of the charged raw material layer when the raw material is charged by the method of the prior art and when the raw material is charged by the method of the present invention. Graph

FIG. 4 is a graph showing a comparison between a charge distribution shape and a distribution of [Lc / (Lc + Lo)] during operation according to the present invention and before operation according to the present invention.

FIG. 5 is a graph showing changes in operating parameters before and after the method of the present invention is performed.

FIG. 6 is a graph showing the relationship between the pulverized coal injection ratio and the upper furnace airflow resistance index Ku before and after the method of the present invention is performed.

FIG. 7 is a graph showing the distribution of the ratio of the ore layer thickness Lo / coke layer thickness Lc in the furnace radial direction before and after the charge distribution control of Prior Art 1 is performed.

FIG. 8 is a graph showing a change in gas utilization distribution in the furnace radial direction when the charge distribution control of Prior Art 2 is performed.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Ore layer, 2 ... Coke layer, 3 ... Lower layer, 4 ... Steel shell, 5 ... Bell, 6 ... Dedicated charging chute, 7 ... Auxiliary distribution device, 8 ... Raw material charge layer surface, 9 ... Swirl chute

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Shinji Matsubara 1-1-2 Marunouchi, Chiyoda-ku, Tokyo Inside Nihon Kokan Co., Ltd. (72) Inventor Shokazu Hayasaka 1-1-2 Marunouchi, Chiyoda-ku, Tokyo Inside Nippon Kokan Co., Ltd. (72) Michitaka Sato, 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Japan Inside Nippon Kokan Co., Ltd. (72) Ryota Murai, 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Sun F-term in Honko Co., Ltd. (Reference) 4K012 BC03 BC04 BC06 BC07 BE01 BE06

Claims (2)

[Claims] Clay and ore are charged alternately from the furnace top, and raw materials for alternately laminating a coke layer and an ore layer are charged, and pulverized coal is blown into the furnace at a rate of 180 kg or more per ton of hot metal. In the blast furnace operation, the ratio [Lc / (Lc + Lo)] of the charged layer thickness (Lc + Lo), which is the sum of the coke layer thickness Lc and the coke layer thickness Lc and the ore layer thickness Lo, at the top of the furnace interior layer is determined by the furnace radius. A method for operating a blast furnace, comprising charging coke and ore from a furnace top so as to satisfy the following conditions (1) to (3) in each region in a direction. (1) Furnace center side area in the furnace radial direction: [Lc
/(Lc+Lo)]≧0.9 (2) Middle area in the furnace radial direction: [Lc / (L
c + Lo)] ≤ 0.4 (3) Furnace peripheral side area in the furnace radial direction: [Lc
/(Lc+Lo)]≧0.5 2. The furnace central part area, the intermediate part area and the furnace peripheral part area in the furnace radial direction are respectively set to the following areas, and coke and ore are charged from the furnace top. Item 2. A method for operating a blast furnace according to Item 1. (a) Furnace center side region in the furnace radial direction: r / Rt ≦ 0.
Region 1 (b) Middle region in the furnace radial direction: 0.1 <r / Rt ≦
Area of 0.6 (c) Area around the furnace periphery in the furnace radial direction: 0.6 <r /
Rt region where r: distance from furnace center in furnace radius direction (m) Rt: furnace radius at furnace port (m)