JP2789995B2 - Blast furnace operation method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a blast furnace operating method capable of preventing the formation of a shell in a blast furnace and performing a stable operation.

[0002]

2. Description of the Related Art A blast furnace for steelmaking has a tuyere for heating and melting raw materials and auxiliary raw materials charged in the furnace and for blowing hot air into the furnace to reduce iron ore. Is provided. Tuyeres, the furnace wall around the blast furnace bottom, and provided with a plurality at predetermined intervals, hot air at a temperature of about 1200 ^O C is from 200 meters / s into the furnace from the tuyere at a rate of 250 meters / s It is blown. Blown hot air is charged into the furnace has been co - reacted with hex, 240 about 2000 ^O C
A reducing gas of ^O OC is generated. The iron ore charged in the furnace is reduced and melted by the high-temperature reducing gas. The iron in the reduced or molten iron ore becomes molten metal, and the gangue in the iron ore transfers to the slag-making agent to become molten slag. The molten metal and the molten slag generated in this manner gradually descend in the furnace and reach near the tuyere.

On the other hand, by blowing hot air from the tuyere into the blast furnace, a space in which a part of the coke charged in the furnace is swirled and burns in front of the tip of the tuyere in the furnace. -A sway is formed. In blast furnace operation, by adjusting the flow rate of hot air blown from tuyeres,
The size and shape of the sway are properly controlled to prevent molten metal and slag that have fallen in the furnace from entering the raceway, and to optimize the gas flow in the furnace. .

[0004]

However, since the movement of the coke below the raceway is extremely slow, fine particulate matter generated in the raceway is trapped in the periphery of the raceway. As a result, a dense shell composed of small-grain coke, slag, metal and the like is formed below the raceway and below the tuyere. In normal blast furnace operation, the formation of the dense shell cannot be prevented.

FIG. 3 is a partially schematic vertical sectional view of the lower part of the blast furnace showing the state of formation of the shell in the above-mentioned conventional blast furnace operation. FIG. 4 is a partially schematic horizontal view of the lower part of the blast furnace taken along the line BB in FIG. It is sectional drawing. As shown in FIG.
And the tuyere 2 supported by the large tuyere 3 is provided on the furnace wall. A raceway 4 is formed in front of the tip of the tuyere 2, and shells 5, 5 ′ are formed below the raceway 4.
Is formed. As can be seen from FIGS. 3 and 4, below the tuyere 2 and the tuyere 2 ', a shell 5 "is formed.

As described above, when a dense shell is formed in the periphery of the raceway, air permeability and liquid permeability in the periphery of the raceway are impaired, and stable airflow cannot be achieved. Accordingly, it takes a long time for the coke to disappear in the periphery of the raceway, and as a result, the coke renewal time is prolonged, and accordingly, the coke renewal time in the core of the lower part of the blast furnace is prolonged. Become. As a result, the air permeability and liquid permeability of the furnace core deteriorate, and the blast furnace operation becomes unstable.

Japanese Unexamined Patent Publication No. 1-96309 discloses a blast furnace operating method comprising the following. In order to efficiently reduce the silicon concentration in the hot metal from the blast furnace, an iron oxide blower that can move back and forth between tuyeres at the tuyere level is installed, and oxidizing gas is blown from the iron oxide blower. Is used as a carrier gas, and iron oxide is blown into a packed bed between adjacent raceways in a blast furnace (hereinafter referred to as prior art).

According to the prior art, iron oxide is transported to a low oxygen partial pressure region in a blast furnace by using an oxidizing gas as a carrier, so that a region around an outlet of an iron oxide blowing pipe is a high oxygen partial pressure region. In addition, it is possible to improve the desiliconization reaction efficiency of the hot metal by the reaction between the hot metal dropped around the outlet of the iron oxide blowing pipe and the iron oxide. However, the prior art
It is intended to improve the efficiency of the desiliconization reaction of hot metal,
It does not solve the above-mentioned problem caused by the formation of the shell around the raceway.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the above-mentioned problems and to prevent a dense shell from being formed below the tuyere of a blast furnace. It is an object of the present invention to provide a blast furnace operating method capable of shortening the renewal time of the furnace and improving the air permeability and liquid permeability of the blast furnace core.

[0010]

According to the blast furnace operating method of the present invention, at least one auxiliary air pipe is provided between each of a plurality of tuyeres provided at predetermined intervals in a circumferential direction of a lower part of the blast furnace. By blowing auxiliary fuel together with hot air into the blast furnace from the auxiliary blower tube, a dense shell is prevented from being formed below the tuyere.

Further, in the blast furnace operating method according to the present invention, the diameter (D _T ) of the tip of the auxiliary blower tube and the diameter of the auxiliary blower tube are controlled so that a raceway is not substantially formed at the tip of the auxiliary blower tube. It is characterized in that the gas flow velocity (U _O ) at the tip is determined, and the auxiliary fuel is blown together with the hot air under the conditions determined in this way.

[0012]

[Action] In the method of the present invention, the auxiliary air duct provided between the blast furnace tuyeres from 1000 ^O C 1200 ^O C
Auxiliary fuel is blown into the blast furnace together with hot air having a temperature of, and the injected auxiliary fuel burns to generate thermal energy, thereby forming a dense shell made of small coke, slag, metal, and the like. The temperature below the mouth rises. Therefore, the formation of the dense shell described above is prevented.

[0013] It is desirable that the auxiliary blower tube is provided with its axis positioned below the axis of the tuyere, and that the outlet of the auxiliary blower tube is positioned downward and forward with respect to the horizontal line. By arranging the blower tubes in this way, the hot air from the blower tubes or the auxiliary fuel and the hot air are efficiently injected downward between the tuyeres. Therefore, the temperature of this portion rises further, and the formation of a shell can be more effectively prevented.

When hot air or hot air and auxiliary fuel are blown from the auxiliary blower tube, a raceway is formed in front of the distal end of the auxiliary blower tube under the condition that the gas flow velocity at the distal end of the auxiliary blower tube is large. A dense shell may be formed in the lower part of the periphery. If such a raceway is formed in front of the tip of the auxiliary blower tube, the effect of preventing the formation of a shell below the tuyere, which is the object of the present invention, is significantly reduced. Therefore, it is desirable to blow hot air through the auxiliary blower tube under the following conditions where a substantial raceway is not formed in front of the tip of the auxiliary blower tube.

That is, the diameter (D _T ) of the tip of the auxiliary air duct and the diameter of the auxiliary air duct are set so that the raceway depth (D _R ) calculated by the following equation (1) is 0.01 m or less. It is desirable to determine the gas flow rate (U _O ) at the tip and to blow hot air from the auxiliary blower tube under the conditions thus determined. D _R = C ・ D _{T g} (ρ _g / p _C ) ^1/2・ U ₀ / (g ・ D _C ) ^1/2 ｝ ⁿ ─ (1) where D _R : formed at the tip of the auxiliary air duct Depth of raceway to be used (m) D _T : Diameter of tip of auxiliary air duct (m) U ₀ : Gas flow velocity at the tip of auxiliary air duct (m /
s) D _C: Co in feather preoral in the furnace - camphor particle diameter (m) ρ _C: Co in feather preoral in the furnace - box particle apparent density
(Kg / m ³ ) ρ _g : density of gas blown into the furnace from the auxiliary blower
(Kg / m ³⁾ g: gravitational acceleration (m / s ²⁾ C: constant (= 0.521) n: Constant (= 0.8)

As described above, the installation position of the auxiliary air duct,
By limiting the direction of the outlet of the auxiliary blower tube, the blowing substance from the auxiliary blower tube, or the blowing condition of hot air from the auxiliary blower tube, the shell formed around the raceway and the periphery of the raceway The remaining coke can be actively burned. Therefore, it is possible to stably blow hot air into the blast furnace, and as a result, the time required to eliminate coke around the raceway is reduced, and
The renewal time of the coke around the sway is reduced, and the air permeability and liquid permeability of the furnace core are also improved.

[0017]

Next, the method of the present invention will be described with reference to the drawings. FIG. 1 is a partial schematic horizontal sectional view of a blast furnace showing one embodiment of the method of the present invention, and FIG. 2 is a partial schematic vertical cross section of the blast furnace showing one embodiment of the method of the present invention. FIG.
As shown in FIG. 2 and FIG.
One auxiliary blower tube 6 is provided with its axis positioned below the axis of the tuyere 2, 2 '. Auxiliary air duct 6
Hot air outlet 6a is located closer to the furnace wall 1 side than the tip positions of the tuyeres 2 and 2 'and faces downward and forward from the horizontal. And the shell 5 which is likely to be formed near the furnace wall at a position lower than the tuyere 2 and the tuyere 2 '.

FIG. 1 shows three auxiliary blower tubes. An auxiliary blower tube 6 is provided between each of a plurality of tuyeres 2 provided in the circumferential direction over the entire circumference of the furnace wall 1. Is provided.
Pulverized coal was blown from each of the auxiliary blower tubes 6 together with hot air. The blowing conditions of the hot air and the pulverized coal from the auxiliary blower tubes 6 are the same for all the auxiliary blower tubes 6.

The operating conditions in this embodiment will be described below. Blast furnace inner volume: 4900 m ³ , Number of blast furnace tuyeres: 40, Distance between blast furnace tuyere axis lines: 1.1 m, Number of auxiliary blower tubes installed: 40, Height of auxiliary blower tubes installed: From tuyere axis Downward 0.04 m, Horizontal installation position of auxiliary air duct: Position of 1/2 of tuyere axis, Distance of auxiliary air duct tip from tuyere tip: 0.20 m to furnace wall side, auxiliary air duct tip caliber: 0.015 m, hot air flow rate in the auxiliary air duct tip: 10 m / s, the density of the hot air blown from the auxiliary air duct into the furnace: 1.295 Kg / m ^3, an average particle diameter of the pulverized coal: 8.4 × 10 ^-5 m, Pulverized coal blowing rate: 0.26 Kg / s / piece, particle size of coke in front of tuyere in furnace: 0.35 m, apparent density of coke particles in front of tuyere in furnace: 1000 Kg / m ^3.

As a result of operating the blast furnace under the conditions described above, the formation of a dense shell below the tuyere is prevented,
As a result, the renewal time of coke in the core of the lower part of the blast furnace was shortened, and the permeability and liquid permeability of the core of the blast furnace were improved, and the operation of the blast furnace was stabilized.

[0021]

As described above, according to the present invention,
The formation of a dense shell below the tuyere of the blast furnace is prevented, thereby reducing the renewal time of coke in the core of the lower part of the blast furnace, and improving the air permeability and the permeability of the core of the blast furnace. The industrially useful effect that liquid permeability is improved and stable operation of the blast furnace is achieved is brought.

[Brief description of the drawings]

FIG. 1 is a partial schematic horizontal sectional view of a blast furnace, showing one embodiment of the method of the present invention.

2 is a partial schematic vertical sectional view of a lower part of a blast furnace taken along a line AA in FIG. 1;

FIG. 3 is a partial schematic vertical sectional view of a lower part of a blast furnace, showing one embodiment of a conventional method.

FIG. 4 is a partial schematic horizontal sectional view of a lower part of a blast furnace taken along a line BB in FIG. 3;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Blast furnace wall 2, 2 'tuyere 3 Large tuyere 4 Raceway 5 Shell 5' shell 5 "shell 6 Auxiliary air pipe 6a Tip of auxiliary air pipe 7 Pipe

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Naoya Yokoyama 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Inside Nippon Kokan Co., Ltd. (56) References JP-A-55-21555 (JP, A) Japanese Patent Publication No. 37 -15203 (JP, B1) (58) Fields investigated (Int. Cl. ⁶ , DB name) C21B 5/00 C21B 7/00

Claims (2)

(57) [Claims] At least one auxiliary blower tube is provided between each of a plurality of tuyeres provided at predetermined intervals in a circumferential direction of a lower portion of a blast furnace, and hot air is supplied from the auxiliary blower tube to a lower portion of the blast furnace inside. A method of operating a blast furnace, characterized by preventing formation of a shell below between each of the tuyeres by blowing auxiliary fuel. 2. An auxiliary blower tube is formed at a tip portion of the auxiliary blower tube.
The raceway depth (D calculated by the following equation (1)
_R ) is determined so that the diameter (D _T ) of the tip of the auxiliary blower tube and the gas flow rate (U _O ) at the tip of the auxiliary blower tube are set so that _R ) is 0.01 m or less. 2. The blast furnace operating method according to claim 1, wherein auxiliary fuel is blown into the lower part of the blast furnace together with hot air from the auxiliary blower tube depending on conditions. D _R = C ・ D _{T g} (ρ _g / p _C ) ^1/2・ U ₀ / (g ・ D _C ) ^1/2 ｝ ⁿ ─ (1) where D _R : formed at the tip of the auxiliary air duct Depth of raceway to be used (m) D _T : Diameter of tip of auxiliary air duct (m) U ₀ : Gas flow velocity at the tip of auxiliary air duct (m /
s) D _C: Co in feather preoral in the furnace - camphor particle diameter (m) ρ _C: Co in feather preoral in the furnace - box particle apparent density
(Kg / m ³ ) ρ _g : density of gas blown into the furnace from the auxiliary blower
(Kg / m ³⁾ g: gravitational acceleration (m / s ²⁾ C: Constant n: Constant