JP2000336409A - Operation of blast furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for providing the operational method of a blast furnace, with which the gas ventilating resistance can efficiently be reduced. SOLUTION: (1) When the gas ventilating resistance in the blast furnace is raised, the operational method of the blast furnace is executed by changing over raw material containing iron oxide into raw material containing metallic iron to lower the ventilating resistance. At this time, the raw material containing the metallic iron is charged into the blast furnace so that a ratio (Dri/Ds) of a grain diameter Dri (mm) in the raw material containing the metallic iron and a grain diameter Ds (mm) in the raw material containing the iron oxide satisfies the undermentioned formula I and a ratio (Lri/Dri) of a layer thickness Lri (mm) of the raw material containing the metallic iron in the blast furnace and the grain diameter Dri (mm) of the raw material containing metallic iron satisfies the undermentioned formula II. Formula I: (Dri/Ds) >=1.5 Formula II: (Lri/Pri)>=5. (2) The raw material containing the metallic iron is charged into the blast furnace so that a ratio (Sri/Sb) of a charging cross sectional area Sb (m2) in the blast furnace and the charging area Sri (m2) possessed with the raw material containing the metallic iron satisfies the undermentioned formula III. Formula III: (Sri/Sb)>=0.05.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for operating a blast furnace, which can effectively reduce the ventilation resistance in the blast furnace.

[0002]

2. Description of the Related Art In a blast furnace, an upper portion (hereinafter, referred to as a cohesive zone) and a lower portion (hereinafter, referred to as a cohesive zone) are separated from a region (hereinafter, referred to as a cohesive zone) in which an iron oxide-containing raw material is softened and dissolved by heating. In this case, the state is greatly different.

[0003] In the massive zone, the iron oxide-containing raw material exists in a solid state together with coke, and is reduced by a reducing gas that rises through the voids while descending downward, and is heated.

On the other hand, in the dropping zone, the reduced and heated iron oxide-containing raw material dissolves, and is dropped downward through the voids in the coke packed bed together with the molten iron slag generated during the melting.

[0005] The gas blown from the tuyere rises toward the center of the furnace through a gap in the coke packed bed, and most of the coke in the drip zone moves toward the tuyere combustion zone. And disappear. However, a part of the coke stays in the central portion of the furnace where the material flow is extremely slow, and forms a dead zone called a "core".

[0006] In the massive zone, the magnitude of the airflow resistance largely depends on the particle size of the iron oxide-containing raw material and the coke.

[0007] In the cohesive zone, the magnitude of the airflow resistance largely depends on the high-temperature properties of the iron oxide-containing raw material (the burn-through property in the cohesive zone region).

In the dropping zone, the magnitude of the airflow resistance largely depends on the porosity of the coke packed layer (determined from the powder rate of the coke packed layer and the amount of molten iron slag) and the air permeability of the core coke.

In Japanese Patent Application Laid-Open No. 06-256819, iron-based scrap or reduced iron (hereinafter referred to as a metal-iron-containing raw material) is charged into the center of a furnace to prevent deterioration of the permeability of the core coke. A method is disclosed.

[0010]

However, the above-mentioned invention can prevent the deterioration of the permeability of the furnace core coke in the dropping zone, but lowers the ventilation resistance in the massive zone and the cohesive zone. There is a problem that you can not. In addition, there has been a problem that a quantitative study has not been made on the particle size, layer thickness, and the like of the metallic iron-containing raw material, so that the airflow resistance cannot be reduced efficiently.

An object of the present invention is to provide a method for operating a blast furnace, which can reduce the ventilation resistance efficiently.

[0012]

The present inventors have obtained the following findings. (A) The air permeability in the massive band largely depends on the particle size of the charged particles. The porosity increases as the particle size increases,
The ventilation resistance of the charging layer (hereinafter also referred to as a packed layer) in the blast furnace is reduced. In a system in which the charged particles are not a single particle but a mixture of particles having a plurality of types of particle diameters, the porosity is smaller than in a system in which each particle is present alone, resulting in poor air permeability. (Ironmaking handbook, p183, Jinjinshokan,
(Issued December 10, 1979) In order to improve the air permeability of a lump belt, it is better to insert single particles of a uniform particle size without mixing particles having multiple particle sizes. It is effective for

(B) The permeability in the cohesive zone largely depends on the high-temperature properties (burn-through property) of the iron oxide-containing raw material and / or metallic iron-containing raw material (hereinafter also referred to as iron raw material).

References (iron and steel (Vol. 72 (198)
6), P1855), a mixture using sinter as an iron oxide-containing raw material and reduced iron as a metallic iron-containing raw material was subjected to a high-temperature property test (melting of the iron raw material in the cohesive zone). Drop test).

In the following tests, all tests were performed using sintered ore as a raw material containing iron oxide and reduced iron as a raw material containing metallic iron.

FIG. 1 is a graph showing the relationship between the mixing ratio of reduced iron in the sinter and the high-temperature properties. The high-temperature property on the vertical axis is an index indicating that the smaller the value, the better the burn-through property of the iron raw material and the smaller the airflow resistance.

As shown in FIG. 1, the higher the mixing ratio of reduced iron in the sintered ore, the better the burn-through property and the lower the airflow resistance in the cohesive zone.

On the other hand, most of the reduced iron has already been reduced to metallic iron, so that the amount of CO ₂ , H ₂ O gas and the like generated during the reduction is reduced. As a result, generated CO ₂ , H ₂
Since the reaction between the O gas or the like and C in the coke is suppressed, powdering of the coke can be prevented, and good permeability of the coke in the dropping zone can be maintained.

(C) In order to quantitatively examine the effect of reducing the ventilation resistance due to the charging of reduced iron having various particle diameters, the test was performed and evaluated under the conditions shown in Tables 1 to 3 using a test blast furnace.

Table 1 shows the specifications of the test blast furnace. Table 2
The operating conditions of the test blast furnace are shown below. Table 3 shows each test No.
And the conditions such as the reduced iron particle diameter Dri and the reduced iron layer thickness Lri. Sri / Sb shown in the table indicates the ratio of the charged area Sri of the reduced iron to the charged cross-sectional area Sb in the furnace. Indicates that reduced iron is present in the entire region.

[0021]

[Table 1]

[0022]

[Table 2]

[0023]

[Table 3]

FIG. 2 is a conceptual diagram showing a method of charging each raw material into the blast furnace by layer. Normally, the sintered ore 3 is charged into the upper layer of the coke 1, but as shown in FIG.
In this test, the reduced iron 2 having a constant particle diameter Dri was fixed to a certain layer thickness L
The coke 1 is charged into the upper layer with ri, then the sinter 3 is charged, and the coke 1 is charged thereon again, and each raw material is repeatedly charged.

FIG. 3 shows the test results under the above conditions.
The ratio (Lri / D) between the reduced iron particle diameter Dri and the reduced iron layer thickness Lri
6 is a graph showing the relationship between the pressure loss in the furnace and the ratio (Dri / Ds) of the particle diameter Ds of the sintered ore and the particle diameter Dri of the reduced iron, using ri) as a parameter.

It should be noted that the dotted line in the figure indicates the total amount of sintered ore (particle size:
15 mm) indicates the value of the pressure loss during use.

As shown in the figure, the pressure drop in the furnace was reduced under the condition that the ratio (Dri / Ds) was 1.5 or more and the ratio (Lri / Dri) was 5 or more.

(D) The lower limit of the ratio (Sri / Sb) of the charged area Sri of reduced iron to the charged cross-sectional area Sb in the furnace was examined.

FIG. 4 is a schematic view of a packed bed for test for measuring pressure loss, which is a packed bed having a diameter of 2 m and a height of 2 m.

Using the packed bed of FIG.
By changing the ratio (Sri / Sb) of the charged area 5 (Sri) of the reduced iron to (Sb), air 6 at a constant pressure is flowed from the lower end, the pressure at the upper end is measured, and the pressure loss ( k
g / cm ² ).

Table 4 shows the test conditions when the influence of the ratio of the charged area Sri of the reduced iron to the charged cross-sectional area Sb (Sri / Sb) was investigated.

[0032]

[Table 4]

FIG. 5 shows the cross-sectional area Sb of the packed bed under the above conditions.
4 is a graph showing the relationship between the ratio of the charged area Sri of reduced iron (Sri / Sb) and the pressure loss of gas.

As shown in the figure, when the area ratio of reduced iron (Sri / Sb) exceeds 0.05, the gas pressure loss (kg / cm ² ) decreases, that is, the gas flow resistance decreases. I understand.

The present invention has been made based on the above findings, and the gist is as follows.

(1) When the ventilation resistance in the blast furnace increases,
In a blast furnace operating method in which an iron oxide-containing raw material is switched to a metal iron-containing raw material in order to reduce the ventilation resistance, the particle diameter Dri (mm) of the metal iron-containing raw material and the particle size Ds (m
m) and (Dri / Ds) satisfy the following expression (1),
The metal-iron-containing material is mixed such that the ratio (Lri / Dri) of the layer thickness Lri (mm) of the metal-iron-containing material in the blast furnace to the particle diameter Dri (mm) of the metal-iron-containing material satisfies the following formula (2). A method for operating a blast furnace, wherein the blast furnace is charged into the blast furnace.

(Dri / Ds) ≧ 1.5 (1) (Lri / Dri) ≧ 5 (2) (2) The charging cross-sectional area Sb (m ² ) in the blast furnace and the charging area occupied by the material containing metallic iron Ratio to Sri (m ² ) (Sri / Sb)
The method for operating a blast furnace according to the above (1), wherein the metal-iron-containing raw material is charged into the blast furnace so that the following formula (3) is satisfied.

(Sri / Sb) ≧ 0.05 (3)

[0039]

BEST MODE FOR CARRYING OUT THE INVENTION When the ventilation resistance in a blast furnace increases, the iron oxide-containing raw material which is a blast furnace charging material is switched to a metal iron-containing raw material in order to reduce the ventilation resistance.

The iron oxide-containing raw material used in the present invention is, for example, sintered ore, iron ore or raw pellets, and the metallic iron-containing raw material is iron-based scrap or reduced iron.

The reduced iron is a metal-iron-containing raw material that has been reduced in advance in a process other than the blast furnace.

Iron-based scrap or reduced iron particle diameter Dri (m
m) and the particle diameter Ds (mm) of the iron oxide-containing raw material (Dri /
Ds) may be 1.5 or more, but is preferably 2 or more.

Under the above conditions, the layer thickness Lri (mm) of the metallic iron-containing raw material and the particle diameter Dri (mm) of the metallic iron-containing raw material in the blast furnace
The ratio (Lri / Dri) may be 5 or more, but is preferably 7 or more.

The ratio (Sri / Sb) of the charging cross-sectional area (Sb) in the blast furnace to the charging area (Sri) of the metallic iron-containing raw material
Is 0.05 or more, but is preferably 0.08 or more. The upper limits of the above three indices may be appropriately selected from the viewpoint of manufacturing costs.

[0045]

EXAMPLES The following examples were carried out under the operating conditions shown in Table 5 using a blast furnace having a furnace volume of 2700 m ³ and a hearth diameter of 11 m.

[0046]

[Table 5]

A bell-less charging device was used for controlling the charging area. Table 6 shows the test conditions.

[0048]

[Table 6]

FIG. 6 shows the test results. The ratio (Lri / Dri) between the particle diameter Dri of reduced iron and the layer thickness Lri of reduced iron, the charging cross-sectional area (Sb), and the charging area of reduced iron ( With the ratio (Sri / Sb) to the pressure drop ratio in the furnace, the ratio (Dr) between the particle size Ds of the sintered ore and the particle size Dri of the reduced iron,
ri / Ds). The pressure loss ratio is a ratio obtained by dividing the value of the pressure loss by the value of the pressure loss when the total amount of sintered ore (particle diameter: 15 mm) is used, and is 1.0 as shown by the dotted line in the figure. The value indicates that the pressure loss is equivalent to the value obtained when the entire amount of sintered ore is used, and a value smaller than 1.0 indicates a smaller pressure loss.

As shown in the figure, the particle diameter Dri (m
m) and the particle diameter Ds (mm) of the sintered ore (Dri / Ds) is 1.5 or more, and the layer thickness Lri (mm) of the reduced iron and the particle diameter Dri (mm) of the reduced iron If the ratio (Lri / Ds) is 5 or more, the pressure loss could be reduced.

Further, the ratio (Sri / Sb) of the charging area Sri (m ² ) of the reduced iron to the charging cross-sectional area Sb (m ² ) is 0.05.
If it was above, the effect of reducing the pressure loss could be exhibited.

[0052]

According to the method of the present invention, the ventilation resistance in the blast furnace can be reduced efficiently. This makes it easy to maintain stable operation, and has a significant economic effect.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the mixing ratio of reduced iron in sinter and high-temperature properties.

FIG. 2 is a conceptual diagram showing a method of charging each raw material into a blast furnace furnace for each layer.

FIG. 3 shows the pressure loss in the furnace, the particle diameter Ds of the sintered ore, the particle diameter Dri of the reduced iron, and the ratio of the particle diameter Dri of the reduced iron to the layer thickness Lri of the reduced iron (Lri / Dri). Ratio (Dri /
Ds).

FIG. 4 is a schematic view of a test packed bed for measuring pressure loss.

FIG. 5 shows the area S charged with reduced iron in the cross-sectional area Sb of the packed bed.
5 is a graph showing the relationship between the ratio of ri (Sri / Sb) and the pressure loss of gas.

FIG. 6 shows the ratio (Sri / Sb) between the reduced iron particle diameter Dri and the reduced iron layer thickness Lri (Lri / Dri) and the charged cross-sectional area (Sb) and the reduced iron charged area (Sri). ) Is a graph showing the relationship between the pressure loss in the furnace and the ratio (Dri / Ds) between the particle diameter Ds of the sintered ore and the particle diameter Dri of the reduced iron, using as parameters.

[Explanation of symbols]

 1: coke, 2: reduced iron, 3: sinter, 4: charging cross section, 5: area of reduced iron, 6: air.

Claims (2)

[Claims] 1. A method for operating a blast furnace in which the iron oxide-containing raw material is switched to a metal iron-containing raw material in order to reduce the airflow resistance when the airflow resistance in the blast furnace is increased, the method comprising the steps of: ) And the particle diameter Ds (mm) of the iron oxide-containing material (Dri / Ds) satisfy the following formula (1), and the layer thickness Lri (mm) of the metal-iron-containing material in the blast furnace and the metal iron-containing material The ratio (Lri / Dri) to the particle diameter Dri (mm) of the raw material is as follows (2)
A method for operating a blast furnace, comprising charging a raw material containing metallic iron into a blast furnace so as to satisfy the formula. (Dri / Ds) ≧ 1.5 (1) (Lri / Dri) ≧ 5 (2) ^2. The ratio (Sri) between the charging sectional area Sb (m ² ) in the blast furnace and the charging area Sri (m ² ) occupied by the metallic iron-containing raw material.
The method for operating a blast furnace according to claim 1, wherein the metallic iron-containing raw material is charged into the blast furnace so that / Sb) satisfies the following expression (3). (Sri / Sb) ≧ 0.05 (3)