JPH04268001A - Method for operating blast furnace - Google Patents

Abstract

PURPOSE:To secure the fluidity of a slag and to avoid inferior permeability when the fluidity of the bosh slag is deteriorated in the change of the kind of fine powdered coal (composition of ash) blown from a tuyere part, Al2O3 in iron ore charged from a furnace top or basicity (CaO/SiO2). CONSTITUTION:At the time of blowing CaF2-based flux (fluorite) together with fine powdered coal from the tuyere part, the mixed rate is adjusted so that CaF2 concn. in both slag becomes 2-10%. As the fluidity of both slag can be secured, the permeability on an operation in a blast furnace can be stabilized and molten iron can stably be supplied.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention stabilizes productivity by ensuring the fluidity of Bosch slag produced from iron ore and coke charged from the top of the furnace and pulverized coal injected from the tuyere. Regarding blast furnace operation method.

0002

[Prior art] In blast furnace operation, cheap, combustible, high calorific fuel (pulverized coal, petroleum, heavy oil, naphtha, etc.) is injected from the tuyeres as a substitute for coke, reducing hot metal production costs. , and has been working to improve productivity.
The technique is disclosed in Japanese Patent No.-23763. Particularly recently, pulverized coal injection has become mainstream due to price considerations, and it greatly contributes to reducing the fuel ratio (cost reduction) and improving productivity.

The pulverized coal injected in this way burns in place of some of the coke in the blast furnace, and because of its good combustibility and high calorific value, it generates a large amount of reducing gas at high temperatures and is efficient. Performs a reduction reaction. Therefore, the iron ore charged from the top of the furnace is quickly reduced to a metallic state and melts into high-temperature molten pig iron, which increases the furnace heat of the blast furnace and improves productivity.

0004

[Problems to be Solved by the Invention] In conventional blast furnace operation, the pulverized coal injected from the tuyere maintains a constant value determined by the operating conditions set based on the supply and demand situation at that time. It is only a matter of fine adjustment according to fluctuations in furnace heat. However, depending on the type of pulverized coal (ash composition) injected, the slag flowing into the raceway (
When the fluidity of the blast furnace (called Bosch slag) changes and the fluidity deteriorates, the ventilation of the blast furnace becomes poor, and the amount of air blown cannot be maintained constant, resulting in a decrease in production. Also, the Al2O3 and basicity (CaO/SiO2) in the iron ore charged from the top of the furnace are
) increases, the fluidity of Bosch slag deteriorates and the ventilation of the blast furnace becomes poor. At this time, in order to eliminate poor ventilation, the ratio of iron ore to coke charged from the top of the furnace (hereinafter abbreviated as O/C) should be reduced, or the amount of pulverized coal injected from the tuyere should be reduced. In order to increase the amount of coke charged from the top of the furnace, the fuel ratio (coke ratio)
increases, resulting in a further decline in production.

[0005] As described above, the conventional blast furnace operation has poor stability, and the productivity cannot be improved and the fuel ratio cannot be lowered.

Therefore, the present invention aims to improve the type of pulverized coal (ash composition) injected from the tuyere, or the Al2O3 and basicity (CaO/SiO2) in iron ore charged from the top of the furnace.
), the purpose is to ensure the fluidity of Bosch slag, avoid poor ventilation, and stabilize blast furnace operation.

[0007]

[Means and effects for solving the problems] In order to achieve the object, the blast furnace operating method of the present invention injects pulverized coal into the inside of the blast furnace from the tuyere, and alternately injects iron ore and coke from the top of the furnace. In the operation method for charging the blast furnace, CaF2-based flux is injected into the blast furnace from the tuyere along with the pulverized coal to ensure the fluidity of Bosch slag produced from pulverized coal, coke, iron ore, etc. shall be.

[0008] Here, Bosch slag refers to iron ore charged from the top of the furnace, gangue in flux, coke charged from the top of the furnace, air blown from the tuyere, O2
, ash in coke consumed by steam, ash in pulverized coal injected from the tuyere, flux (CaF
2) Refers to the slag generated from the gangue in the system.

In the steel industry, CaF2-based flux (fluorite) is generally used in converter furnaces for the purpose of improving dephosphorization efficiency. It's not a thing.

In the present invention, in order to ensure the fluidity of Bosch slag, CaF2-based flux is mixed in advance with pulverized coal and blown into the tuyere. CaF2
The mixing amount of the system flux is the C occupied in Bosch slag.
The concentration of aF2 is adjusted to 2 to 10%. When the concentration of CaF2 is less than 2%, the concentration is too low to have any effect of improving fluidity. When the concentration of CaF2 is 2% or more, the higher the concentration, the better the fluidity is, but it is limited to 10% or less for the following reason. That is, when the concentration exceeds 10%, the temperature of the combustion gas at the tuyere decreases due to the decomposition heat of the injected CaF2, and the temperature of the Bosch slag decreases, resulting in poor fluidity. When the concentration of CaF2 is 2 to 10%, the fluidity of Bosch slag is good, and the generated Bosch slag smoothly descends around the raceway and is not held in the coke layer, making it suitable for blast furnace operation. There will be no problem with poor ventilation.

In the present invention, a CaF2-based flux (fluorite) is used to ensure the fluidity of Bosch slag, but any other flux that can ensure fluidity may be used.

0012

[Examples] The features of the present invention will be explained in detail with reference to Examples below. As shown in Table 1, in Example 1, when the pulverized coal was being injected, CaF2-based flux was mixed in advance into the pulverized coal so that the concentration of CaF2 in the Bosch slag was 2 to 4%. This is an example of operation using

[0013] In Example 2, when blowing pulverized coal,
This is an example of an operation in which CaF2-based flux was mixed in advance into pulverized coal and injected so that the concentration of CaF2 in Bosch slag was 4 to 6%.

In Example 3, when blowing pulverized coal,
This is an example of operation in which CaF2-based flux was mixed in advance into pulverized coal and injected so that the concentration of CaF2 in Bosch slag was 6 to 8%.

In Example 4, when blowing pulverized coal,
The concentration of CaF2 in Bosch slag is 8-10%
This is an example of operation in which CaF2-based flux was mixed in advance into pulverized coal and blown into it.

In either case, as a result of ensuring the fluidity of the Bosch slag, compared to the comparative example, the blowing pressure is lower, the amount of pig iron tapped is larger, and the fuel ratio is lower.

[0017] The comparative example is a case where only pulverized coal is injected and no other fluxes are injected, and compared to Examples 1 to 4, the blowing pressure is higher, the amount of pig iron tapped is smaller, and the fuel ratio is lower. expensive.

[0018]

[Table 1]

[0019]

As explained above, in the present invention, the fluidity of the iron ore charged from the top of the furnace, the coke, the pulverized coal injected from the tuyere, and the Bosch slag generated from the CaF2-based flux is ensured. By doing so, poor ventilation during blast furnace operation can be avoided and productivity can be stabilized, so production volume can be maintained constant and hot metal can be supplied stably.

Claims (1)

[Claims] Claim 1: In an operating method in which pulverized coal is injected into the blast furnace from the tuyere and iron ore and coke are alternately charged from the top of the furnace, Bosch slag produced from pulverized coal, coke, iron ore, etc. A blast furnace operating method characterized by injecting CaF2-based flux together with pulverized coal into the blast furnace through the tuyere to ensure fluidity.