Method for operating active hearth through blast furnace

Abstract

The invention relates to the field of iron and steel metallurgy blast furnace ironmaking, in particular to a method for activating a hearth through blast furnace operation, which comprises the following steps of: establishing a reasonable lower air supply system and an upper charging system, balancing edge and middle airflow distribution, stabilizing a heat system and a slagging system, implementing low-silicon smelting, improving stokehole operation and the like. The temperature of the furnace bottom and the temperature of each layer of the side wall of the hearth are stable, uniform and controllable. A blast furnace operator operates the blast furnace by implementing the technology, the effect of activating the hearth can be achieved, long-term stable and smooth operation of the furnace condition is promoted, and safe, economical, efficient and long-life production of the blast furnace with the stable upper part and the active hearth is achieved.

Description

Technical Field

[0001] The present invention relates to the field of blast furnace ironmaking in steel metallurgy, and in particular to a method for activating a hearth through blast furnace operation. Background Art

[0002] The hearth is the source of pig iron in a blast furnace, providing gas and heat for the smelting process. The initial distribution of the gas flow within the hearth not only determines the heat and temperature distribution across the hearth's cross-section but also the overall height of the blast furnace. Therefore, the operating condition of the hearth is crucial to achieving "high efficiency, high quality, low energy consumption, and longevity" in blast furnace smelting.

[0003] The working condition of the hearth is a key factor directly affecting blast furnace performance. Blast furnace hearths have large diameters (9.0 to 14.0 meters). Changes in raw material quality, equipment operating conditions, airflow distribution, and slag and iron heat can all lead to changes in the hearth's working condition, making it prone to inactivity. Hearth inactivity can lead to significant losses in the technical and economic indicators of blast furnace production.

[0004] This invention aims to provide a method for maintaining a blast furnace hearth. It proposes establishing a rational air supply and charging system, achieving a reasonable gas flow distribution within the furnace, stabilizing the thermal and slagging systems, implementing low-silicon smelting, and improving furnace operations. This method ensures stable and active blast furnace operation, with stable and uniformly controlled blast furnace sidewall and bottom temperatures. This maintains the blast furnace hearth's optimal activity, promoting efficient, safe, stable, and long-lasting blast furnace operation. Summary of the Invention

[0005] The object of the present invention is to solve the above problems and provide a method for activating the hearth through blast furnace operation.

[0006] The object of the present invention is achieved as follows: A method for activating the hearth of a blast furnace by operating the blast furnace comprises the following aspects: (1) a reasonable air supply system to ensure that the primary gas flow distribution is reasonable and stable: the working area of the stable air outlet is 0.260 to 0.270 m 2 , use air volume of 3700-3800m³ / min, adjust the output by adjusting the oxygen enrichment volume to 13000-18000m³ / min, and stabilize the humidity at 10-15g / m 3The operating air temperature is 1200-1240℃, the monthly average air temperature is 1190-1230℃, the theoretical combustion temperature is 2200-2350℃, the control standard wind speed is 235-250m / s, the actual wind speed is 260-275m / s, and the blast kinetic energy is 11500-12500kg.m / s. (2) Adjust the charging system to balance the distribution of air flow at the edge and middle: After stabilizing the air supply system, optimize the upper charging system: stabilize the central coke ratio at 26%-28.1%, adjust the edge coke load to 1.20-1.27, and stabilize the gas utilization rate at 49%-50%; (3) Stabilize the thermal system and slag making system, and implement low-silicon smelting: the target molten iron silicon content is 0.43±0.05%, the slag basicity is 1.20±0.03, the pig iron sulfur content is 0.030±0.005%, the molten iron temperature is 1490±15℃, ≮1470℃, and the molten iron temperature is not allowed to be lower than 1470℃ for three consecutive furnaces; (4) Improve the operation in front of the furnace: maintain the normal iron tapping of two or three iron mouths, adjust the mud discharge amount to 40-60kg / time according to the iron mouth condition, stabilize the iron mouth depth, and stabilize the iron mouth area temperature at 200-450℃.

[0007] (4) Medium stable iron mouth depth, specifically, the controlled iron mouth depth of medium-sized blast furnaces is 2.7-3.0m, and the controlled iron mouth depth of large blast furnaces is 3.6-4.0m. The basic drill bit diameter of medium-sized blast furnaces is 47-50mm, and the basic drill bit diameter of large blast furnaces is 55-60mm.

[0008] The beneficial effects of this invention are as follows: 1. The third blast furnace (1,800 m³) at the Taiyuan Iron and Steel Plant, commissioned on July 31, 2007, has always prioritized maintaining a healthy hearth through blast furnace operation. After years of operation, the invention of this technical method allows blast furnace operators to promptly adjust blast furnace operating procedures and parameters based on changes in hearth conditions, maintaining optimal hearth performance. As of May 2025, the plant had accumulated 18 years of production and production, with a cumulative iron output per unit capacity of 15,900 tons / m³, reaching the leading level for long-life blast furnaces in China. The furnace has been operating for 18 years without maintenance, and the hearth brick lining temperature is consistently controlled, ensuring safe, long-lasting, efficient, and stable blast furnace operation.

[0009] 2. Starting from 2023, the utilization coefficient of the three blast furnaces will be increased to 2.9. By operating the blast furnaces to activate the hearth, the smelting air supply ratio will be increased to 2.11. There will be no abnormal erosion of the hearth refractory materials, and the temperature of the furnace bottom and hearth side walls will be stable and controlled. DETAILED DESCRIPTION

[0010] In blast furnace smelting, especially with larger blast furnaces, the diameter of the hearth continues to increase. The activity of the hearth, therefore, impacts the long-term safe and stable operation of the blast furnace. Furthermore, as the furnace ages, hearth inactivity can lead to abnormal erosion of the furnace bottom and sidewalls, causing the bottom and hearth temperatures to reach high values. This erosion requires furnace protection, impacting the achievement of technical and economic indicators. In severe cases, the blast furnace may need to be shut down for overhaul. To reduce abnormal hearth erosion, blast furnace operations that maintain an active hearth are necessary, ensuring stable hearth temperature control and long-term safe and stable blast furnace operation. Taiyuan Iron and Steel's No. 3 blast furnace (1,800 m³) was put into operation on July 31, 2007. As of May 2025, it had accumulated 18 years of production and produced 27.9 million tons of iron. The No. 3 blast furnace design ensures a 15-year lifespan without maintenance. Over the years, adjustments to the upper and lower operating systems and parameters of the blast furnace have achieved long-term stable furnace conditions and maintained a healthy hearth.

[0011] The present invention adopts a basic technical concept: the operating status of the blast furnace hearth can be reflected in the blast furnace's slag and iron discharge capacity, the blast furnace's air volume, and the degree of furnace condition. By operating an active hearth in the blast furnace, the uniformity and stability of the furnace bottom temperature and the hearth side wall temperature can be reflected. The furnace bottom temperature represents the state of coke and dead coke accumulation in the hearth, and the uniformity of the hearth side wall temperature effectively represents the discharge, infiltration, and circulation of molten iron in the hearth. In daily production, by operating an active hearth, the long-term stable and smooth operation of the blast furnace can be achieved, and long-term production can be achieved.

[0012] The specific technical solutions of the present invention are as follows: 1. Reasonable air supply system ensures that the primary gas flow distribution is reasonable and stable: the working area of the stable air outlet is 0.2640m 2 , stabilize the air volume, use the air volume to 3700 ~ 3800m³ / min, mainly use stable air, adjust the output by adjusting the oxygen enrichment volume to 13000 ~ 18000m³ / min, stabilize the humidity to 10 ~ 15g / m 3 The daily operating air temperature reaches 1200-1240℃, and the monthly average air temperature reaches above 1200℃, thereby controlling the standard wind speed to 240m / s and above, the actual wind speed reaches 267m / s, the theoretical combustion temperature is 2300℃, and the blast kinetic energy is 12500kg.m / s, which improves the initial coal gas flow distribution in the furnace, activates the center of the furnace, and increases the furnace bottom temperature.

[0013] 2. Adjust the charging system to balance the distribution of side and middle airflow: After stabilizing the air supply system, optimize the upper charging system, basically stabilize the center coke ratio at 25%-28%, adjust the edge coke load at 1.10-1.20, loosen the edge appropriately, balance the side and middle airflow, stabilize the gas utilization rate at 48%-50%, and achieve good furnace stability. (1) During daily production, according to the material rate, furnace top temperature, heat load of each section and gas utilization rate change trend, center airflow stability, timely adjust the center coke ratio by 2% / time, and maintain a reasonable distribution of side and middle airflow. (2) Pay attention to the pressure difference: if the pressure difference is low, the permeability index is as high as 15.0 or above, the material is slowly depleted, the top temperature continues to rise, the heat load and gas utilization rate decrease, and the air flow must be reduced to prevent material collapse.

[0014] 3. Stabilize the thermal and slag-making systems and implement low-silicon smelting: (1) Target hot metal silicon content: 0.43±0.05, slag basicity: 1.20±0.03, pig iron sulfur content: 0.030±0.005, hot metal temperature: 1490±15℃, ≮1470℃, and no more than three consecutive furnaces below 1470℃. (2) Pay attention to changes in the quality of sintered ore, such as FeO, basicity, and particle size, adjust the fuel ratio, and control the furnace temperature and basicity limit. This will maintain long-term stable and active furnace hearth and increase furnace bottom temperature.

[0015] 4. Improve furnace operations: Maintain the slag and iron trenches and main trenches, ensuring that two or three tapholes are tapping in rotation. Adjust the amount of mud pumping according to taphole conditions to stabilize the taphole depth. The taphole depth for medium-sized blast furnaces should be 2.7-3.0m, and for large blast furnaces, 3.6-4.0m. The basic drill bit diameter should be 47-50mm (for medium-sized blast furnaces) or 55-60mm (for large blast furnaces). The drill bit size can be temporarily adjusted based on slag delivery time and discharge to stabilize the taphole area temperature.

[0016] By implementing these technical methods, the temperatures at the furnace bottom and hearth of Taiyuan Iron and Steel's No. 3 blast furnace remain under control after 18 years of operation: 1) The furnace bottom temperature remains stable at 180-230°C. 2) The galvanic temperature of each hearth layer at elevations of 8.116m, 9.276m, 9.856m, and 10.436m remains below 350°C. Residual thickness calculations indicate the presence of slag and iron condensation layers of varying thicknesses. Further corrosion of the hearth refractory material has not progressed, ensuring continued safe and stable production. Example 1

[0017] This invention has been applied to the third blast furnace (1800m³) of the Taiyuan Iron and Steel Plant. Taking the actual production from 2023 to May 2025 as an example, the specific implementation plan is as follows: 1. A reasonable air supply system ensures a reasonable and stable distribution of primary coal gas flow: the working area of the stable tuyere of the third blast furnace is 0.2640m 2, use air volume to 3700 ~ 3800m³ / min, mainly use stable air, adjust the output by adjusting the oxygen enrichment volume to 13000 ~ 18000m³ / min, and stabilize the humidity to 10 ~ 15g / m 3 The daily operating air temperature reaches 1200-1240℃, and the monthly average air temperature reaches above 1200℃, thereby controlling the standard wind speed to 240m / s and above, the actual wind speed reaches 270m / s, and the blast kinetic energy is above 12500kJ / s, which improves the initial gas flow distribution in the furnace, activates the center of the furnace, and increases the temperature of the furnace bottom.

[0018] 2. Adjust the charging system to balance the distribution of side and middle airflow: After stabilizing the air supply system, optimize the upper charging system, basically stabilize the center coke ratio at 26%-28.1%, adjust the edge coke load at 1.20-1.27, appropriately loosen the edge, balance the side and middle airflow, stabilize the gas utilization rate at 49%-50%, and the furnace condition is relatively stable. (1) During daily production, according to the material rate, furnace top temperature, each section heat load and gas utilization rate change trend, center airflow stability, timely adjust the number of coke batches by 0.3 turns / time, and maintain a reasonable distribution of side and middle airflow. (2) Pay attention to the pressure difference: if the pressure difference is low and the permeability index is as high as 15.0 or above, the material is slowly depleted, the top temperature continues to rise, the heat load and gas utilization rate decrease, and the air flow must be reduced to prevent the collapse of the material.

[0019] 3. Stabilize the thermal and slag-making systems and implement low-silicon smelting: (1) Target hot metal silicon content: 0.43±0.05, slag basicity: 1.20±0.03, pig iron sulfur content: 0.030±0.005, hot metal temperature: 1490±15℃, ≮1470℃, and no more than three consecutive furnaces below 1470℃. (2) Pay attention to changes in the quality of sintered ore, such as FeO, basicity, and particle size, adjust the fuel ratio, and control the furnace temperature and basicity limit. This will maintain long-term stable and active furnace hearth and increase furnace bottom temperature.

[0020] 4. Improve furnace operations: Maintain the slag and iron trenches and main trenches, ensuring normal tapping at the two tapholes, one in the south and one in the north. Adjust the amount of mud pumping according to the taphole conditions, maintaining a stable taphole depth of 2.6 to 3.0 meters. The basic drill bit diameter is 47.5 mm. The drill bit size can be temporarily adjusted according to the slag inflow time and discharge to stabilize the taphole area temperature.

[0021] The three blast furnaces were put into operation on July 31, 2007, and as of May 2025, they had been in operation for 18 years (the design of the three blast furnaces ensures a 15-year lifespan without maintenance). After 18 years of operation, as of May 2025, the temperatures at the bottom and hearth of the three blast furnaces remain under control: 1) The current bottom and hearth temperature is 206°C, with a historical high of 228°C. 2) The galvanic temperatures at the four hearth levels at different elevations (8.116m, 9.276m, 9.856m, and 10.436m) are below 350°C. Residual thickness calculations indicate the presence of slag and iron condensation layers of varying thickness, and hearth erosion has not progressed further. Example 2

[0022] On May 3, 2023, Taigang No. 3 (1800m 3 ) The temperature of the blast furnace hearth at an elevation of 9.276m at point 189° (below the iron mouth in the north field) rose rapidly, reaching 290°C at 1:46, and continued to rise during the period, reaching 455°C at 19:18, an increase of 165°C. The corresponding skin-coupling temperature increased from 43°C to 62°C. During the same period, the cooling wall coupling temperature also increased from 125°C at 7:40 to 178°C, an increase of 53°C (historical high 161°C). In response to the continued rise in the temperature at this point in the furnace hearth, measures were taken starting at 16:00 on May 3: 1) The Si content of pig iron was increased from 0.40-0.50 to 0.50-0.60, and the binary basicity of the slag was increased from 1.16-1.20 to 1.20-1.24; 2) The inlet water temperature of the furnace cooling water softening system was reduced from 38°C to 36°C; 3) The tapping operation at the iron mouth in front of the furnace was adjusted from "one south and one north" to "two south and one north", and the amount of mud removed from the iron mouth was adjusted to stabilize the iron mouth depth to 2.8m, the basic drill bit diameter was 47.5mm, and stable slag and iron discharge was maintained. 4) Normal air oxygen volume was used stably, with an air volume of 3800m 3 / min, oxygen enrichment 17000m 3 / h, maintain wind speed at 266m / s, blast energy at 12,000kg.m / s, theoretical combustion temperature at 2280°C, keep initial furnace gas flow stable, and do not control output. 5) Strengthen management and continuously monitor furnace temperature trends, recording the temperature at this point every two hours to observe trends.

[0023] After taking the above measures, the effect was obvious. By 9:00 on May 4, the temperature at this point and the corresponding cooling wall temperature dropped to 306°C and 133°C respectively. By 9:00 on May 5, they dropped to 255°C and 125°C respectively, which were reduced to the temperature level during normal production.

[0024] The above description is only a specific embodiment of the present invention, but the structural features protected by the present invention are not limited thereto. Any changes or modifications made by any technician in this field within the scope of the present invention are included in the patent scope of the present invention.

Claims

1. A method for operating an active hearth in a blast furnace, characterized in that: It includes the following aspects: (1) Reasonable air supply system to ensure the reasonable and stable distribution of primary gas flow: the working area of the stable air outlet is 0.260~0.270m 2 , use air volume of 3700-3800m³ / min, adjust the output by adjusting the oxygen enrichment volume to 13000-18000m³ / min, and stabilize the humidity at 10-15g / m 3 , operating air temperature is 1200~1240℃, monthly average air temperature is 1190~1230℃, theoretical combustion temperature is 2200~2350℃, control standard wind speed is 235~250m / s, actual wind speed is 260~275m / s, blast kinetic energy is 11500~12500kg.m / s; (2) Adjust the charging system to balance the airflow distribution at the edge and middle: After stabilizing the air supply system, optimize the upper charging system: stabilize the center coke ratio at 26%-28.1%, adjust the edge coke load to 1.20-1.27, and stabilize the gas utilization rate at 49%-50%; (3) Stabilize the thermal and slag-making systems and implement low-silicon smelting: the target silicon content of molten iron is 0.43±0.05%, the slag basicity is 1.20±0.03, the sulfur content of pig iron is 0.030±0.005%, the molten iron temperature is 1490±15℃, ≮1470℃, and the molten iron temperature is not allowed to be lower than 1470℃ for three consecutive furnaces; (4) Improve the operation in front of the furnace: keep 2 or 3 tapping holes in normal rotation, adjust the mud injection amount to 40-60 kg / time according to the tapping hole condition, stabilize the tapping hole depth, and stabilize the tapping hole area temperature at 200-450℃.

2. A method for operating an active hearth in a blast furnace according to claim 1, characterized in that: (4) Medium stable iron mouth depth, specifically, the controlled iron mouth depth of medium-sized blast furnaces is 2.7-3.0m, and the controlled iron mouth depth of large blast furnaces is 3.6-4.0m. The basic drill bit diameter of medium-sized blast furnaces is 47-50mm, and the basic drill bit diameter of large blast furnaces is 55-60mm.