US-12624404-B2 - Method for operating blast furnace

US12624404B2US 12624404 B2US12624404 B2US 12624404B2US-12624404-B2

Abstract

A method for operating a blast furnace with which, even in the case where there is an increase in the powder ratio of coke to be charged into the blast furnace, it is possible to achieve the stabilization of blast furnace operation. The method includes blowing air through a tuyere disposed in a lower part of the blast furnace, successively measuring a particle size distribution of coke transported to the blast furnace, and adjusting at least one of a blast volume and a coke ratio in accordance with an index derived from the particle size distribution.

Inventors

Yoshifumi KOBASHI
Naoshi Yamahira
Toshiki Tsuboi

Assignees

JFE STEEL CORPORATION

Dates

Publication Date: 20260512
Application Date: 20201019
Priority Date: 20191031

Claims (2)

1 . A method for operating a blast furnace, the method comprising: transporting coke to the blast furnace; blowing air through a tuyere disposed in a lower part of the blast furnace; successively measuring a particle size distribution of the coke transported to the blast furnace; determining a powder ratio of the coke from the particle size distribution, the powder ratio of the coke being a ratio of a mass of coke powder in the coke having a particle diameter of 5 mm or less to a total mass of the coke; determining whether an actual variation in the powder ratio within a length of time is equal to or more than a first threshold value and less than a second threshold value; determining whether the actual variation in the powder ratio within the length of time is equal to or more than the second threshold value, wherein: the first threshold value is a first predetermined variation in the powder ratio within the length of time that is set in advance, and the second threshold value is a second predetermined variation in the powder ratio within the length of time that is set in advance, the second threshold value having an absolute value that is more than an absolute value of the first threshold value; decreasing a blast volume of the air blown through the tuyere without changing the coke ratio, the coke ratio being a weight of coke used to produce one ton of pig iron, when determining that the actual variation in the powder ratio within the length of time is equal to or more than the first threshold value and less than the second threshold value; and increasing the coke ratio based on the powder ratio when determining that the actual variation in the powder ratio within the length of time is equal to or more than the second threshold value.
2 . A method for operating a blast furnace, the method comprising: transporting coke to the blast furnace; blowing air through a tuyere disposed in a lower part of the blast furnace; successively measuring a particle size distribution of the coke transported to the blast furnace; determining a void fraction of a coke-packed layer in the blast furnace from the particle size distribution; decreasing a blast volume of the air blown through the tuyere when an actual variation in the void fraction within a length of time is equal to or less than a first threshold value and more than a second threshold value, wherein: the first threshold value is a first predetermined variation in the void fraction within the length of time that is set in advance, and the second threshold value is a second predetermined variation in the void fraction within the length of time that is set is advance, the second threshold value having an absolute value that is more than an absolute value of the first threshold value; and increasing the coke ratio based on the void fraction, the coke ratio being a weight of coke used to produce one ton of pig iron, when the actual variation in the void fraction within the length of time is equal to or less than the second threshold value.

Description

TECHNICAL FIELD This application relates to a method for operating a blast furnace in which a blast volume blown through a tuyere in a lower part of the furnace is controlled in accordance with a variation in the powder ratio of coke to be charged into the blast furnace. BACKGROUND In a blast furnace, pig iron is manufactured by alternately charging an iron oxide-based iron raw material and coke from the furnace top, by burning the coke with hot air blown through a tuyere in the lower part of the furnace to generate CO, and by reducing the iron oxides contained in sintered ore and lump ore with a reducing gas containing the generated CO. In such a blast furnace operation, gas permeability in the blast furnace has a significant effect on stable blast furnace operation. To maintain satisfactory gas permeability in a blast furnace, maintaining satisfactory voids formed between coke particles is important. In the case where small lumps and powder are contained in the raw material, since the voids are filled with such small lumps and powder, there is a deterioration in gas permeability in the furnace, which results in unstable blast furnace operation. Therefore, generally, raw materials to be charged into a blast furnace are sieved to control the particle size of coke to be 25 mm to 35 mm or more and the particle size of sintered ore and iron ore to be 5 mm to 25 mm or more before being charged into the blast furnace. However, in the case of a common sieving method, it is difficult to completely remove powder adhering to coke. Powder adhering to coke is separated from the coke in the furnace, which results in a deterioration in gas permeability in the furnace. Therefore, in the case where it is possible to timely assess the amount of powder charged into a blast furnace, it is possible to operate the blast furnace in accordance with the assessed amount of powder. Patent Literature 1 and Patent Literature 2 disclose powder fraction-measuring devices with which it is possible to measure the powder ratio adhering to coke transported on a conveyer. In the case of the powder fraction-measuring devices disclosed in Patent Literature 1 and Patent Literature 2, by conducting an advance survey on the relationship between the powder ratio adhering to lump coke and an average luminance in image data obtained by taking an image of lump coke, the powder ratio adhering to lump coke is determined online on the basis of an average luminance in image data obtained by taking the image of the lump coke transported on a conveyer to a blast furnace. Patent Literature 3 discloses a powder ratio estimating method in which the powder fraction of a raw material for a blast furnace is estimated on the basis of the slope angle of a piled raw material in the furnace top bunker of a blast furnace. In the case of the powder fraction estimating method disclosed in Patent Literature 3, the powder fraction of a raw material for a blast furnace is estimated on the basis of the slope angle of a piled raw material in the furnace top bunker and the correlation between the slope angle of a piled raw material and the powder fraction. CITATION LIST Patent Literature PTL 1: International Publication No. WO2018/101287PTL 2: International Publication No. WO2018/181942PTL 3: Japanese Unexamined Patent Application Publication No. 2015-196888 Non Patent Literature NPL 1: Yamada, et al., “Distribution of Burden Materials and Gas Permeability in a Large Volume Blast Furnace”, KAWASAKI STEEL GIHO Vol. 6 (1974) No. 1, pp. 16-37 SUMMARY Technical Problem Patent Literature 1 discloses only a powder fraction-measuring device and a powder fraction-measuring system with which it is possible to measure the powder fraction of lump coke to be charged into a blast furnace, and there is no mention of a specific method for operating a blast furnace on the basis of the measured powder fraction. Although Patent Literature 2 discloses a device for measuring the void fraction in a blast furnace on the basis of a powder fraction, there is no mention of a method for operating a blast furnace. Patent Literature 3 discloses a method for operating a blast furnace on the basis of a fixed threshold value for the powder fraction of a raw material for a blast furnace which is estimated on the basis of the slope angle of a piled raw material in the furnace top bunker of the blast furnace. However, in the case of control on the basis of the fixed threshold value, it is not possible to prevent a deterioration in the operation state of the blast furnace caused by a variation in powder fraction. An object of the disclosed embodiments is to provide a method for operating a blast furnace with which, even in the case where there is a variation in the particle size distribution of coke to be charged into the blast furnace, it is possible to realize the stabilization of blast furnace operation by measuring the particle size distribution and by adjusting at least one of a blast volume blown throu