A control method for reducing silicon deviation in blast furnace smelting

Abstract

The present application relates to the technical field of blast furnace ironmaking, and specifically discloses a control method for reducing silicon deviation in blast furnace smelting; the present application is realized by constructing an integrated control system which is synergized with raw material pretreatment, real-time detection closed loop, accurate regulation of air supply parameters, optimization of slagging system and auxiliary stabilization of furnace conditions; the method comprises: controlling the particle size, homogenizing the composition and preheating and dewatering of the raw material entering the furnace; online detecting the silicon content of pig iron with a period of not more than 5 minutes, and generating an adjustment instruction based on a process parameter correlation model; dynamically adjusting the air temperature, air volume and oxygen enrichment rate according to the instruction; controlling the binary basicity of the slag at 1.15-1.25, and controlling the slag viscosity by adding flux; and stabilizing the furnace top pressure and the distribution system. The method can systematically reduce the silicon deviation of pig iron to below 0.1%, effectively improve the stability of molten iron quality and the smooth running rate of the blast furnace, and reduce the energy consumption per ton of iron.

Description

Technical Field

[0001] This invention belongs to the field of blast furnace ironmaking technology, specifically relating to a control method for reducing silicon deviation in blast furnace smelting. Background Technology

[0002] In blast furnace ironmaking, the silicon content in pig iron is a key indicator for measuring molten iron quality, smelting stability, and energy consumption. Its fluctuation range, or silicon deviation, directly affects the product quality, energy consumption, and production costs of subsequent steelmaking or casting processes. Excessive silicon deviation can lead to substandard pig iron grades, forcing additional processing in subsequent steps, increasing costs, and potentially causing fluctuations in blast furnace conditions, such as hearth accumulation and suspended charge, threatening production safety and continuity.

[0003] Currently, blast furnace silicon deviation control faces the following challenges: First, the composition and particle size of raw materials (sinter, pellets, coke, etc.) fluctuate significantly, leading to unstable metallurgical properties of the feed material, which is one of the root causes of silicon content fluctuations. Second, the adjustment of operating parameters, especially blast parameters (blast temperature, blast volume, oxygen enrichment rate), relies heavily on operator experience, lacking a precise, closed-loop control model driven by real-time silicon content data, resulting in lag and blind adjustments. Third, fluctuations in the slag-forming process affect the adsorption and reduction balance of silicon oxides (SiO2) in the slag, thus affecting the amount of silicon entering the pig iron. Fourth, traditional methods of manual sampling and offline analysis of silicon content are time-consuming (usually 1-2 hours) and have slow feedback, failing to meet the needs of real-time, dynamic control.

[0004] Several attempts to improve upon existing technologies have been made. For example, Chinese patent CN111383723B discloses a silicon content pre-control method based on fuzzy control and data modeling; Chinese patent CN108153146B discloses a hot metal quality control system based on model-free adaptive control. These technical solutions mostly focus on adjusting single or a few parameters (such as air supply parameters) through algorithmic models, which belongs to "local optimization." However, silicon deviation is the systematic result of the combined effects of multiple links such as raw materials, air supply, slag formation, and detection. Existing technologies lack an integrated control system that stabilizes from the source, intelligently links the process, and provides real-time feedback closed loops. Therefore, it is difficult to fundamentally and systematically stabilize silicon deviation at an extremely low level, resulting in limited control effects and failing to meet the stringent requirements of modern blast furnaces for efficient, stable, and low-consumption production. Summary of the Invention

[0005] This invention aims to overcome the shortcomings of existing technologies and provide a control method for reducing silicon deviation in blast furnace smelting. This method achieves precise and stable control of the silicon content in pig iron by constructing an integrated control system covering "raw material pretreatment - blast optimization - slag stabilization - closed-loop detection," thereby significantly reducing silicon deviation, stabilizing blast furnace conditions, and lowering production costs.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a method for controlling silicon deviation in blast furnace smelting, comprising the following steps: S1. Raw material pretreatment and homogenization control: Particle size control and homogenization treatment are carried out on the iron-containing raw materials and coke entering the furnace to stabilize the physicochemical properties of the raw materials entering the furnace. S2. Real-time detection and closed-loop feedback control: An online detection device is installed at the blast furnace taphole to acquire the silicon content data of pig iron in real time at a cycle of no more than 5 minutes; based on the deviation between the silicon content data and the target value, and the established process parameter correlation model, adjustment instructions are generated and executed; and the silicon deviation is calculated periodically, with whether the silicon deviation is greater than 0.1% as the criterion for triggering the re-optimization of control parameters. S3. Precise control of air supply parameters: Based on the adjustment instructions generated by S2, dynamically adjust at least one of the following parameters of the blast furnace: air temperature, air volume and oxygen enrichment rate. S4. Slag Formation Optimization and Control: Based on the adjustment instructions generated in S2 and / or the preset optimization targets, control the slag basicity within the range of 1.15-1.25, and control the slag viscosity by adding flux. S5. Auxiliary Stability Control of Blast Furnace Condition: By stabilizing the top pressure of the furnace and optimizing the charging system, external conditions are provided for the smooth operation of the blast furnace.

[0007] Preferably, S1 includes: S1.1 Particle Size Control: Sieve the sinter, pellets, and lump ore to control the content of powder with a particle size ≤5mm to not exceed 3%; control the proportion of 10-30mm particles in sinter to be ≥75%, the proportion of 10-20mm particles in pellets to be ≥75%, and the proportion of 10-25mm particles in lump ore to be ≥75%, and the upper limit difference in particle size of the three raw materials to be no greater than 10mm; control the proportion of 30-50mm particles in coke to be ≥70%; S1.2, Composition Homogenization: The raw materials are homogenized to ensure that the total iron content of the homogenized sinter fluctuates within ±0.5%, the silica content fluctuates within ±0.3%, the fixed carbon content of the coke fluctuates within ±0.8%, and the raw material mixing uniformity is ≥90%. S1.3 Preheating and dehydration: Before the raw materials are put into the furnace, they are preheated to 100-150℃ and their moisture content is controlled to be ≤0.5%.

[0008] Preferably, in step S2, the process parameter correlation model is a correlation model between the air supply parameters and the silicon content of pig iron established using a multiple linear regression method based on historical blast furnace production data, and the coefficient of determination R² of the model is ≥0.9.

[0009] Preferably, S3 specifically includes: When the silicon content of pig iron detected in real time is higher than the target value, perform at least one of the following operations: reduce the air temperature by 10-20℃, increase the air volume by 50-100m³ / min, increase the oxygen enrichment rate by 0.3%-0.5%; and set the air supply parameter adjustment cycle to 20-30 minutes. When the silicon content of pig iron detected in real time is lower than the target value, perform at least one of the following operations: increase the air temperature by 10-20℃, reduce the air volume by 50-100m³ / min, reduce the oxygen enrichment rate by 0.3%-0.5%; and set the air supply parameter adjustment cycle to 30-40 minutes.

[0010] Preferably, step S3 further includes controlling the uniformity of air supply in the circumferential direction of the blast furnace to ensure that the air supply deviation between each tuyer is ≤5%.

[0011] Preferably, S4 includes: S4.1 By adjusting the amount of limestone and / or dolomite added, the binary basicity of the slag is controlled at 1.15-1.25, and its fluctuation is controlled to not exceed ±0.05. S4.2 Add flux accounting for 0.6%-1.0% of the total mass of raw materials entering the furnace, wherein the flux is fluorite or manganese oxide, so that the viscosity of the slag at 1500℃ is controlled at 0.5-1.0 Pa·s; S4.3. Sample and test the composition and fluidity of slag every 15-20 minutes, and adjust the amount of auxiliary materials added in S4.1 and S4.2 in real time according to the test results.

[0012] Preferably, in S4.2, when the slag fluidity is lower than expected, fluorite is preferred as a flux; when it is necessary to reduce the erosion of the blast furnace lining, manganese oxide is preferred as a flux.

[0013] Preferably, S5 includes: controlling the blast furnace top pressure at 0.18-0.22 MPa, with fluctuations ≤ ±0.01 MPa; and / or using a uniform material distribution method to control the flatness deviation of the material surface to ≤100 mm.

[0014] Preferably, in S4, when nodules are detected on the blast furnace wall, an enhanced furnace cleaning operation is performed. The operation includes: increasing the binary basicity of the slag to 1.25-1.30, increasing the amount of flux fluorite added to 0.8%-1.0% of the total mass of the raw materials fed into the furnace, and increasing the blast temperature by 10-20°C.

[0015] The technical effects and advantages of this invention are as follows: 1. This invention breaks through the limitations of existing technologies that only perform local optimization on a single parameter. It innovatively integrates five key aspects—raw material pretreatment, air supply regulation, slag formation optimization, real-time monitoring, and furnace condition stabilization—into an intelligent, interconnected, and closed-loop feedback collaborative control system. This system, starting from stabilizing the raw material source and driving precise process control with real-time data, forms a complete control chain, fundamentally and systematically solving the problem of excessive silicon deviation. 2. By establishing a high-precision (R²≥0.9) air supply parameter correlation model, a shift from experience-based operation to data-driven decision-making was achieved, making parameter adjustments more reliable, precise, and effective. Simultaneously, innovatively differentiated flux selection based on different operating conditions (improving fluidity or protecting the furnace lining), coupled with a strict slagging system, strengthened the stable control of silicon migration. The introduction of minute-level online real-time monitoring completely solved the problem of lag in traditional manual testing, providing immediate data support for closed-loop control. 3. The method of this invention can stably reduce the fluctuation range of silicon content in pig iron (silicon deviation) from the conventional above 0.25% to below 0.1%, a reduction of 68%-75%, while reducing energy consumption per ton of pig iron by approximately 4.17%. This method significantly improves the stability of pig iron quality and the smooth operation rate of blast furnaces. Moreover, the core modification only requires the addition of an online detection and control system, without large-scale alterations to the main equipment. The modification cost is low, the operation is highly operable, and it is easy to promote and apply widely in the industry. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the overall process flow of the present invention. Detailed Implementation

[0017] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] Example 1: This invention provides, for example Figure 1 The method for spraying cement mortar lining of ductile iron pipes is shown in this embodiment. This embodiment is applied to a 450m³ blast furnace, whose designed target silicon content in pig iron is 0.3%-0.45%. The specific process steps are as follows: Step S1, Raw Material Pretreatment and Homogenization Control: The sinter, pellets, and lump ore fed into the furnace are screened, controlling the content of powder with a particle size ≤5mm to ≤3%. Specifically, the proportion of 10-30mm particles in the sinter is controlled to be ≥75%, the proportion of 10-20mm particles in the pellets to be ≥75%, and the proportion of 10-25mm particles in the lump ore to be ≥75%, with the upper limit difference in particle size among the three raw materials ≤10mm; the proportion of 30-50mm particles in the coke is controlled to be ≥70%. The raw materials are homogenized to ensure that the total iron (TFe) content of the homogenized sinter fluctuates ≤±0.5%, the silicon dioxide (SiO2) content fluctuates ≤±0.3%, the fixed carbon content of the coke fluctuates ≤±0.8%, and the raw material mixing uniformity reaches 93%. Before feeding the raw materials into the furnace, they are preheated to 120℃, and the moisture content is controlled to be 0.3%. Step S2, Real-time Detection and Closed-Loop Feedback Control: An online infrared detection device is installed at the blast furnace taphole to detect the silicon content of pig iron in real time at a 5-minute interval, with a detection accuracy of ±0.03%. Based on historical blast furnace production data, a correlation model between blast furnace parameters and pig iron silicon content is established using a multiple linear regression method. The coefficient of determination (R²) of this model is 0.92. The control system calculates the silicon deviation (i.e., the difference between the maximum and minimum detected values) every hour. Step S3, Precise Control of Air Supply Parameters: When the silicon content of pig iron is detected to be 0.26% in real time (below the lower limit of the target value), adjustment instructions are generated based on the correlation model: the air temperature is increased by 20℃ from 1160℃ to 1180℃, the air volume is decreased by 30m³ / min from 1250m³ / min to 1220m³ / min, and the oxygen enrichment rate is decreased by 0.5% from 3.5% to 3.0%. The subsequent air supply parameter adjustment cycle is set to 35 minutes. Through the annular air distribution device, the air supply deviation between each tuyeres in the blast furnace circumference is controlled to ≤5%. Step S4, Slag Formulation Optimization and Control: The target for the binary basicity of the slag (CaO / SiO2) is set at 1.20, and its fluctuation is controlled to ≤ ±0.05 by adjusting the amount of limestone added. Fluorite is selected as the flux and added at 0.6% of the total mass of the raw materials fed into the furnace, and the slag viscosity at 1500℃ is controlled at 0.8 Pa·s. The slag composition and fluidity are sampled and tested every 16 minutes, and the amount of auxiliary materials added is adjusted in real time according to the results. Step S5, Auxiliary Stability Control of Blast Furnace Condition: Maintain the blast furnace top pressure at a stable level of 0.135 MPa, with fluctuations ≤ ±0.01 MPa. Adopt a uniform charge distribution method, controlling the flatness deviation of the charge surface to ≤90 mm. Regularly inspect and maintain the blast furnace body, and promptly clean any nodules on the furnace wall. Specific implementation results: After 90 days of continuous operation using the method in this embodiment, the silicon content of the pig iron in the blast furnace stabilized between 0.31% and 0.45%, and the average silicon deviation decreased from 0.25% before implementation to 0.08%, a reduction of 68%; at the same time, the incidence of furnace accidents decreased by 52%.

[0019] Example 2: This invention provides, for example Figure 1 The method for spraying cement mortar lining of ductile iron pipes is shown in this embodiment. This embodiment is applied to a 2000m³ blast furnace, with a target silicon content of 0.25%-0.40% in the pig iron. The specific process steps are as follows: Step S1, Raw Material Pretreatment and Homogenization Control: The raw materials fed into the furnace are screened to control the powder content to ≤3%. The proportion of 10-30mm particles in sinter is controlled to be ≥78%, the proportion of 10-20mm particles in pellets to be ≥80%, and the proportion of 10-25mm particles in lump ore to be ≥78%, with the upper limit difference in particle size between the three types of raw materials ≤8mm; the proportion of 30-50mm particles in coke is controlled to be ≥72%. After homogenization, the total iron (TFe) content of sinter fluctuates ≤±0.4%, the silicon dioxide (SiO2) content fluctuates ≤±0.25%, the fixed carbon content of coke fluctuates ≤±0.7%, and the raw material mixing uniformity is 95%. The raw materials are preheated to 130℃ before entering the furnace, with a moisture content ≤0.4%. Step S2, Real-time Detection and Closed-Loop Feedback Control: An online detection device is set up with a detection cycle of 4 minutes and a detection accuracy of ±0.025%. The coefficient of determination (R²) of the established correlation model between air supply parameters and silicon content is 0.93. The system statistically analyzes and evaluates silicon deviation every hour. Step S3, Precise Control of Air Supply Parameters: When the silicon content of pig iron is detected to be 0.42% (higher than the upper limit of the target value), the adjustment instructions are as follows: reduce the air temperature by 15℃, increase the air volume by 80m³ / min, increase the oxygen enrichment rate by 0.4%, and set the air supply parameter adjustment cycle to 25 minutes. Control the circumferential air supply deviation to ≤5%; Step S4, Slag Formulation Optimization and Control: The target for slag binary basicity is set at 1.22, with fluctuations controlled to ≤ ±0.05. To reduce furnace lining erosion, manganese oxide is selected as a flux, added at 0.7% of the total mass of the raw materials fed into the furnace. The slag viscosity at 1500℃ is controlled at 0.7 Pa·s. Slag parameters are checked every 15 minutes and adjusted accordingly. Step S5, Auxiliary Furnace Condition Stabilization Control: Control the furnace top pressure to 0.19 MPa, with fluctuations ≤ ±0.01 MPa. Use uniform material distribution, controlling the flatness deviation of the material surface to ≤ 80 mm. Regularly clean furnace wall nodules.

[0020] Specific implementation results: After 120 days of continuous operation using the method in this embodiment, the silicon content of the pig iron in the blast furnace stabilized between 0.26% and 0.39%, the average silicon deviation dropped to 0.07%, a reduction of 72% compared to before the modification; and the furnace operation smoothness rate increased to 98%.

[0021] Example 3: This invention provides, for example Figure 1 The method for spraying cement mortar lining of ductile iron pipes is shown in this embodiment. This embodiment is applied to a 3200m³ blast furnace, with the target silicon content of pig iron controlled at 0.20%-0.35%. The specific process steps are as follows: Step S1, Raw Material Pretreatment and Homogenization Control: The raw materials fed into the furnace are screened to control the powder content ≤2.5%. The proportion of 10-30mm particles in sinter is controlled to be ≥80%, the proportion of 10-20mm particles in pellets to be ≥82%, and the proportion of 10-25mm particles in lump ore to be ≥80%, with the upper limit difference in particle size between the three types of raw materials ≤7mm; the proportion of 30-50mm particles in coke is controlled to be ≥75%. After homogenization, the total iron (TFe) content of sinter fluctuates ≤±0.35%, the silicon dioxide (SiO2) content fluctuates ≤±0.2%, the fixed carbon content of coke fluctuates ≤±0.6%, and the raw material mixing uniformity is 96%. The raw materials are preheated to 140℃ before entering the furnace, with a moisture content ≤0.35%. Step S2, Real-time Detection and Closed-Loop Feedback Control: An online detection device is set up with a detection cycle of 3 minutes and a detection accuracy of ±0.02%. The established correlation model has a coefficient of determination R² of 0.94. The closed-loop feedback system can adjust the control parameters of each link in conjunction with real-time data. Step S3, Precise Control of Air Supply Parameters: When the silicon content of pig iron is detected to be 0.38% (higher than the target value), the adjustment instructions are as follows: reduce the air temperature by 20℃, increase the air volume by 100m³ / min, increase the oxygen enrichment rate by 0.5%, and set the air supply parameter adjustment cycle to 20 minutes. Control the circumferential air supply deviation to ≤5%; Step S4, Slag Formation Optimization and Control: Set the slag binary basicity control target to 1.24, controlling its fluctuation ≤ ±0.05. Add 0.9% fluorite as a flux, accounting for 0.9% of the total mass of the raw materials fed into the furnace, and control the slag viscosity at 1500℃ to 0.6 Pa·s. Detect slag indicators every 18 minutes. If a tendency for thickening of the furnace wall is detected during operation, perform an enhanced furnace cleaning operation: temporarily increase the slag basicity to 1.28, increase the amount of flux fluorite added to 1.0%, and simultaneously increase the blast temperature by 15℃. After the thickening is removed, restore normal parameters. Step S5, Auxiliary Stability Control of Furnace Condition: Control the furnace top pressure to 0.21 MPa, with fluctuations ≤ ±0.01 MPa. Use uniform material distribution, controlling the flatness deviation of the material surface to ≤ 70 mm. Conduct monthly inspection and maintenance of the furnace body. Specific implementation results: After 180 days of continuous operation using the method of this embodiment, the silicon content of the pig iron in the blast furnace stabilized between 0.21% and 0.34%, and the average silicon deviation dropped to 0.065%, a 75% reduction compared to before the modification (0.26%); the energy consumption per ton of iron decreased from 192 kgce to 184 kgce, a reduction of 4.17%.

[0022] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for controlling silicon deviation in blast furnace smelting, characterized in that, Includes the following steps: S1. Raw material pretreatment and homogenization control: Particle size control and homogenization treatment are carried out on the iron-containing raw materials and coke entering the furnace to stabilize the physicochemical properties of the raw materials entering the furnace. S2. Real-time detection and closed-loop feedback control: An online detection device is installed at the blast furnace taphole to acquire the silicon content data of pig iron in real time at a cycle of no more than 5 minutes; based on the deviation between the silicon content data and the target value, and the established process parameter correlation model, adjustment instructions are generated and executed; and the silicon deviation is calculated periodically, with whether the silicon deviation is greater than 0.1% as the criterion for triggering the re-optimization of control parameters. S3. Precise control of air supply parameters: Based on the adjustment instructions generated by S2, dynamically adjust at least one of the following parameters of the blast furnace: air temperature, air volume and oxygen enrichment rate. S4. Slag Formation Optimization and Control: Based on the adjustment instructions generated in S2 and / or the preset optimization targets, control the slag basicity within the range of 1.15-1.25, and control the slag viscosity by adding flux. S5. Auxiliary Stability Control of Blast Furnace Condition: By stabilizing the top pressure of the furnace and optimizing the charging system, external conditions are provided for the smooth operation of the blast furnace.

2. The method for controlling silicon deviation in blast furnace smelting according to claim 1, characterized in that, S1 includes: S1.1 Particle Size Control: Sieve the sinter, pellets, and lump ore to control the content of powder with a particle size ≤5mm to not exceed 3%; control the proportion of 10-30mm particles in sinter to be ≥75%, the proportion of 10-20mm particles in pellets to be ≥75%, and the proportion of 10-25mm particles in lump ore to be ≥75%, and the upper limit difference in particle size of the three raw materials to be no greater than 10mm; control the proportion of 30-50mm particles in coke to be ≥70%; S1.2, Composition Homogenization: The raw materials are homogenized to ensure that the total iron content of the homogenized sinter fluctuates within ±0.5%, the silica content fluctuates within ±0.3%, the fixed carbon content of the coke fluctuates within ±0.8%, and the raw material mixing uniformity is ≥90%. S1.3 Preheating and dehydration: Before the raw materials are put into the furnace, they are preheated to 100-150℃ and their moisture content is controlled to be ≤0.5%.

3. The method for controlling silicon deviation in blast furnace smelting according to claim 1, characterized in that, In S2, the process parameter correlation model is a correlation model between air supply parameters and silicon content of pig iron established using a multiple linear regression method based on historical blast furnace production data, and the coefficient of determination R² of the model is ≥0.

9.

4. A method for controlling silicon deviation in blast furnace smelting according to claim 1 or 3, characterized in that, Specifically, S3 is: When the silicon content of pig iron detected in real time is higher than the target value, perform at least one of the following operations: reduce the air temperature by 10-20℃, increase the air volume by 50-100m³ / min, increase the oxygen enrichment rate by 0.3%-0.5%; and set the air supply parameter adjustment cycle to 20-30 minutes. When the silicon content of pig iron detected in real time is lower than the target value, perform at least one of the following operations: increase the air temperature by 10-20℃, reduce the air volume by 50-100m³ / min, reduce the oxygen enrichment rate by 0.3%-0.5%; and set the air supply parameter adjustment cycle to 30-40 minutes.

5. The method for controlling silicon deviation in blast furnace smelting according to claim 1, characterized in that, The S3 also includes controlling the uniformity of air supply in the circumferential direction of the blast furnace to ensure that the air supply deviation between each tuyer is ≤5%.

6. The method for controlling silicon deviation in blast furnace smelting according to claim 1, characterized in that, S4 includes: S4.1 By adjusting the amount of limestone and / or dolomite added, the binary basicity of the slag is controlled at 1.15-1.25, and its fluctuation is controlled to not exceed ±0.

05. S4.2 Add flux accounting for 0.6%-1.0% of the total mass of raw materials entering the furnace, wherein the flux is fluorite or manganese oxide, so that the viscosity of the slag at 1500℃ is controlled at 0.5-1.0 Pa·s; S4.

3. Sample and test the composition and fluidity of slag every 15-20 minutes, and adjust the amount of auxiliary materials added in S4.1 and S4.2 in real time according to the test results.

7. The method for controlling silicon deviation in blast furnace smelting according to claim 6, characterized in that, In S4.2, fluorite is preferred as a flux when the slag fluidity is lower than expected; manganese oxide is preferred as a flux when it is necessary to reduce the erosion of the blast furnace lining.

8. The method for controlling silicon deviation in blast furnace smelting according to claim 1, characterized in that, S5 includes: controlling the blast furnace top pressure at 0.18-0.22 MPa, with fluctuations ≤ ±0.01 MPa; and / or using a uniform material distribution method to control the flatness deviation of the material surface ≤ 100 mm.

9. The method for controlling silicon deviation in blast furnace smelting according to claim 1, characterized in that, In S4, when nodules are detected on the blast furnace wall, an enhanced furnace cleaning operation is performed. The operation includes: increasing the binary basicity of the slag to 1.25-1.30, increasing the amount of flux fluorite added to 0.8%-1.0% of the total mass of the raw materials fed into the furnace, and increasing the blast temperature by 10-20°C.

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