BR-112024018530-B1 - METHOD FOR DETERMINING SLAG LEVEL IN BLAST FURNACE, METHOD FOR OPERATING BLAST FURNACE AND CONTROL UNIT

Abstract

METHOD FOR DETERMINING SLAG LEVEL OF BLAST FURNACE, METHOD FOR OPERATING BLAST FURNACE AND CONTROL UNIT. The method for determining the slag level of a blast furnace includes acquiring an image of a raceway (5) inside the blast furnace, the image being captured through a tuyere (2) by a camera (7) installed in front of the tuyere (2), the tuyere (2) being installed in a furnace wall (1) of the blast furnace, calculating an average brightness of the image, calculating a degree of raw ore fall, which contributes to a reduction in the brightness of the image, based on the image, calculating a corrected average brightness correcting the average brightness based on the degree of raw ore fall and determining the slag level based on the corrected average brightness.

Inventors

• Satoki YASUHARA
• Tetsuya Yamamoto
• Ryotaro Matsunaga

Assignees

• JFE STEEL CORPORATION

Dates

Publication Date

20260310

Application Date

20230213

Priority Date

20220328

Claims (5)

1. 1. Method for determining a blast furnace slag level comprising: acquiring an image of a raceway (5) inside the blast furnace, the image being captured through a tuyere (2) by a camera (7) installed in front of the tuyere (2), the tuyere (2) being installed in a furnace wall (1) of the blast furnace; calculating an average brightness of the image; the method CHARACTERIZED by the fact of calculating a raw ore drop degree based on the image; calculating a corrected average brightness correcting the average brightness based on the raw ore drop degree; and determining the slag level based on the corrected average brightness.
2. 2. A method for determining the slag level of a blast furnace, according to claim 1, characterized in that determining the slag level includes determining the slag level based on a negative correlation between the corrected mean brightness and the slag level.
3. 3. Method for determining a blast furnace slag level, according to claim 1 or 2, CHARACTERIZED in that the calculation of the raw ore drop degree includes calculating the raw ore drop degree by taking the homogeneity of the image as an index.
4. 4. Method for operating a blast furnace CHARACTERIZED in that the method comprises performing an overlay tapping or a process for reducing the volume of air blown from the tuyere (2) to the blast furnace in a case where the corrected mean brightness calculated using the method to determine a slag level, as defined in any of claims 1 to 3, is less than a predetermined limit.
5. 5. Control unit (10) for determining a blast furnace slag level, the control unit (10) comprising: a controller (11) configured to acquire an image of a raceway (5) within the blast furnace, the image being captured through a tuyere (2) by a camera (7) installed in front of the tuyere (2), the tuyere (2) being installed in a furnace wall (1) of the blast furnace, calculating an average brightness of the image; the control unit (10) CHARACTERIZED in that it calculates a raw ore drop degree based on the image, calculates a corrected average brightness by correcting the average brightness based on the raw ore drop degree, and determines the slag level based on the corrected average brightness.

Description

TECHNICAL FIELD [001] This disclosure relates to a method for determining the slag level of a blast furnace, a method for operating a blast furnace and a control unit. BACKGROUND OF THE INVENTION [002] A blast furnace is a piece of equipment located upstream in the steelmaking process. Blast furnaces produce pig iron from raw materials such as iron ore, coke, and limestone. Raw materials such as iron ore, coke, and limestone are charged into the blast furnace from the top of the furnace. Approximately 40 tuyeres are installed around the bottom of the blast furnace. In a blast furnace, a jet of heat at approximately 1,000 °C blown through the tuyeres causes the iron ore to react with the coke and be reduced to produce liquid pig iron. [003] During pig iron production, impurities combine with limestone to form slag. If the slag level, which is the height of the slag surface, rises and reaches the tuyere, it can cause explosions in the lower part of the blast furnace. An explosion is a phenomenon in which the jet of heat blown into the blast furnace from the tuyere flows locally in a circumferential direction within the blast furnace. When an explosion occurs, the upper part of the blast furnace can be damaged. [004] When the slag level exceeds a predetermined limit, conventional measures taken to prevent explosions include overlapping taps, in which two tap holes are opened at the same time to lower the slag level, and reducing the pressure in the furnace by reducing the volume of air blown out. [005] Known methods for measuring slag level include the mass balance method, the taphole nitrogen injection method, the electrical resistance method, and the furnace body deformation measurement method. [006] The mass balance method is a method for estimating the slag level based on the difference between the amount of material fed into the blast furnace and the amount discharged. The nitrogen injection method in the tap hole is a method for injecting nitrogen through the tap hole and calculating the slag level from the nitrogen pressure. The electrical resistance method is a method for determining the slag level by measuring the electrical resistance when an alternating current is applied to electrodes fixed inside the blast furnace iron layer. The furnace body strain measurement method is a method for determining the slag level by calculating the strain using a strain measuring instrument fixed to the surface of the blast furnace iron layer. [007] Patent Literature (PTL) 1 discloses a method for determining the slag level by detecting the amount of change in radiant heat from the slag surface using a thermometer embedded in the tuyere. PTL 2 discloses a method for determining the slag level by measuring the electromotive force generated, as the liquid pig iron level changes, by electrodes welded to the surface of the iron lining of a blast furnace. LIST OF QUOTES Patent Literature PTL 1: JP H1-198412 A PTL 2: JP 2000-192123 A SUMMARY (Technical problem) [008] The mass balance method requires information such as the instantaneous rate of pig iron and slag production, the coke void ratio, and the wear conditions of the furnace bricks. However, these pieces of information are difficult to measure. The nitrogen injection method into the tap hole is not suitable for regular use because it requires loading a lance through the tap hole. The electrical resistance method has low accuracy because the electrical resistance fluctuates with the furnace heat level. The furnace body strain measurement method requires the installation of strain measuring instruments throughout the blast furnace, which is expensive. [009] The method disclosed in PTL 1 is also problematic because as the raw ore drop increases, the temperature embedded in the tuyere decreases and cannot be accurately measured. The method disclosed in PTL 2 requires opening the iron lining to place the electrodes in contact with the carbon bricks. However, opening the iron lining ends up damaging the furnace body. [010] The conventionally known methods for measuring slag levels therefore have room for improvement. [011] It is an objective of the present disclosure to provide a method for determining the slag level of a blast furnace, a method for operating a blast furnace and a control unit that can improve methods for measuring the slag level. (Solution to the problem) [012] A method for determining the slag level of a blast furnace according to an embodiment of the present disclosure includes acquiring an image of a raceway inside the blast furnace, the image being captured through a tuyere by a camera installed in front of the tuyere, the tuyere being installed in a furnace wall of the blast furnace; calculating an average brightness of the image; calculating the degree of raw ore fall based on the image; calculating a corrected average brightness by correcting the average brightness based on the degree of raw ore fall; and determining the slag level based on the c