A method for preventing a collapse of a blast furnace

Abstract

The present application relates to the technical field of blast furnace smelting operation, and a method for preventing collapse of a blast furnace. The method is aimed at determining the possibility of collapse of the blast furnace by accurately predicting the change trend of the operation parameters of the blast furnace. On this basis, the collapse mechanism of the blast furnace is scientifically utilized, the existing conditions of the blast furnace are reasonably utilized, the best operation opportunity is grasped, the coke is reasonably placed at a reasonable position, the possibility of central collapse is eliminated, the air volume is timely controlled, the air flow distribution is adjusted, the energy distribution is optimized, the edge stagnation space is digested, the fast and slow changes of the material speed are waited, the central coke amount is timely adjusted, and then the air is added, so as to fundamentally eliminate the collapse. The use of the method can greatly reduce the smelting cost, eliminate the adverse effects of the collapse on the furnace body and the air supply system (especially the tuyere), avoid other derivative adverse effects caused by the suspended material after the collapse, and avoid the influence of the collapse on the production capacity and product quality.

Description

Technical Field

[0001] This invention relates to the field of blast furnace smelting operation technology, and in particular to a method for preventing blast furnace collapse. Background Technology

[0002] The primary goal of blast furnace smelting is stable and smooth operation; only on this basis can low-cost smelting be carried out. Therefore, stable and smooth operation of the blast furnace is a prerequisite for normal blast furnace smelting.

[0003] Blast charge collapse is an abnormal smelting process in a blast furnace, a phenomenon characterized by a sudden acceleration in the charging of materials into the blast furnace.

[0004] If a blast furnace experiences a collapse, it will have a significant impact on the safe operation of the blast furnace.

[0005] 1. A sudden drop in the furnace charge will disrupt the gas flow in the blast furnace, significantly reducing the gas utilization rate. In order to prevent the heat from dropping too much, a large amount of coke will often be added, which will inevitably lead to a significant increase in the fuel ratio and increase the smelting cost.

[0006] 2. A sudden drop in a large amount of furnace charge can generate tremendous impact force, potentially causing the furnace body to tear; it can also damage the blast system (large, medium, and small tuyere sleeves). The collapsing charge can block the central airflow, causing increased air pressure and potentially leading to charge suspension, which is a more dangerous and difficult-to-handle process in blast furnace smelting.

[0007] 3. After a collapse, the blast furnace will reduce air and oxygen to deal with the collapse, which will result in a significant reduction in output.

[0008] 4. After a collapse, the furnace temperature will drop significantly immediately. If the amount of coke added after the collapse is not appropriate, the furnace temperature will rise significantly. Therefore, collapses are often accompanied by significant fluctuations in furnace temperature and loss of molten iron quality.

[0009] The purpose of this invention is to take timely measures in advance to prevent blast furnace collapse by making timely predictions in the early stage of collapse, so as to take measures that have the least impact on the blast furnace and avoid a series of adverse consequences after the collapse, so that the blast furnace smelting can proceed smoothly. Summary of the Invention

[0010] The purpose of this invention is to address the above-mentioned problems by providing a method for preventing blast furnace collapse.

[0011] The purpose of this invention is achieved as follows: a method for preventing blast furnace collapse, comprising the following steps: Step 1: Prediction of collapse: the judgment criteria are as follows: (1) the hourly air-oxygen ratio has not changed significantly from the previous hour's air-oxygen ratio, the air volume fluctuation range is ±20 m³ / min, and the oxygen fluctuation range is ±200 m³ / h; (2) the hourly equivalent material rate decreases by 0.5 batches / hour or more in 20 min; (3) the air pressure decreases by more than 5 kPa in 20 min; (4) the gas utilization rate decreases by more than 1% in 20 min; (5) (6) The top temperature rises over 20 minutes and the rise is greater than 5°C; (7) The edge heat load shows a downward trend over 20 minutes; Step 2: After determining the collapse, the first measure to be taken is to replenish enough central coke to occupy the space already generated in the center; Step 3: After replenishing coke in the center, it is necessary to reduce the airflow to suppress the development of the central airflow. The reduction range is controlled within the range of 50-100 m³ / min; Step 4: After waiting for the material speed to return to normal, adjust the material system to suppress the central airflow: reduce the central coke by 0.2 to 0.3 cycles; Step 5: Increase the airflow to the normal level to ensure the smooth operation of the blast furnace.

[0012] In step two, the amount of additional center coke to ensure sufficient center coke quantity is 1.5 ± 0.5 tons.

[0013] The beneficial effects of this invention are: 1. Preventing material collapse can prevent a significant increase in the blast furnace fuel ratio. By taking measures in advance, turbulent gas flow in the blast furnace can be prevented, large amounts of coke replenishment can be eliminated, and a significant increase in the fuel ratio caused by material collapse can be avoided, thereby reducing smelting costs.

[0014] 2. Ensured the safety of the furnace body and the air supply system. Eliminating material collapse also eliminated the huge impact force generated by the collapse, thus avoiding tearing of the furnace body and damage to the air supply system (large, medium, and small tuyeres).

[0015] 3. It avoids the possibility of material hanging. Material hanging is a very dangerous and extremely difficult smelting process to handle.

[0016] 4. It avoids the production loss caused by the blast furnace significantly reducing air and oxygen after the material collapses.

[0017] 5. It avoids fluctuations in molten iron quality. Eliminating material breakage also eliminates large fluctuations in furnace temperature after breakage, thus avoiding fluctuations in molten iron quality. Detailed Implementation

[0018] The purpose of this invention is to solve a common adverse process in blast furnaces—bursting. The specific solution is as follows: 1. Prediction of Bursting. Blast furnace smelting is carried out under a certain air-oxygen ratio. This air-oxygen ratio generates a certain amount of charging space through combustion and other means. This charging space provides space for charging at the top of the blast furnace. This continuous generation of new space and the continuous influx of new material from the top of the blast furnace allows for continuous smelting. However, in actual production, it often happens that while the air-oxygen ratio remains constant, the charging speed gradually slows down, the air pressure gradually decreases, the gas utilization rate gradually decreases, and the top temperature gradually increases, leading to a bursting phenomenon. Specific judgment criteria are as follows: 1) The hourly air-oxygen ratio does not change significantly from the previous hour, with air volume fluctuations within ±20 m³ / min and oxygen fluctuations within ±200 m³ / h. 2) The hourly equivalent material rate decreases by 0.5 batches / hour or more over 20 minutes. 3) A downward trend in air pressure forms over 20 minutes, and the decrease is greater than 5 kPa. 4) A downward trend in gas utilization rate is formed within 20 minutes, with a decrease of more than 1%. 5) An upward trend in top temperature is formed within 20 minutes, with an increase of more than 5℃. 6) A downward trend in edge heat load is formed within 20 minutes.

[0019] 2. Once a potential collapse is confirmed, the first measure is to replenish sufficient central coke to occupy the space already created in the center. After the initial assessment, we can confirm the possibility of a collapse. The immediate action required is to replenish the central coke. Based on the practical experience of Taiyuan Iron & Steel Plant's 1800m³ blast furnace with a blast volume of 3730±30m³ / min and an oxygen content of 12000±500m³ / h, it is recommended to add 1.5±0.5 tons of central coke. This is because, under such a confirmed collapse trend, the central airflow will inevitably develop, resulting in a large amount of space being created in the center of the blast furnace. Meanwhile, the charging speed at the edges slows down, creating a positional difference between the edge and center material surfaces. If this difference is too large, it will cause the edge material to suddenly collapse towards the center, leading to a collapse. Therefore, to prevent the material from collapsing towards the center, it is essential to first replenish the center with coke to occupy space, reduce the positional difference between the edge and center, and thus prevent a collapse.

[0020] 3. Appropriately reduce airflow to control the downward trend of air pressure. After center coking, it is necessary to reduce airflow to suppress the development of central airflow. The reduction should be controlled within the range of 50-100 m³ / min. While reducing airflow suppresses the development of central airflow, it also promotes peripheral airflow. This ensures sufficient heat at the edges, allowing the root of the remelting zone to obtain more energy.

[0021] 4. Wait for the material speed to increase. After the edge airflow develops relatively, the edge feeding space that was previously insufficient due to insufficient heat is released, and the edge feeding speed improves. Therefore, the material speed will show an increasing trend at this time.

[0022] 5. Wait for the material rate to return to normal, i.e., 6.5 batches / h, matching the current air-oxygen ratio. In point 4, because the previously accumulated space is released in a relatively short period of time, the material rate will appear to be faster. Once the accumulated space is filled, the material rate will return to a level that matches the current air-oxygen ratio.

[0023] 6. Adjust the material preparation and appropriately suppress the central airflow. After the aforementioned five steps, the space in the early stage of the blast furnace has been filled, and the possibility of material collapse has been eliminated. However, the cause of this mismatch between space and material feeding is the development of the central airflow. Therefore, to address the root cause, it is necessary to adjust the central airflow to form a long-term stable situation. According to the conventional operation of Taiyuan Iron & Steel's 1800m³ blast furnace, the central coke volume is reduced by 0.2 to 0.3 turns to fine-tune the central airflow.

[0024] 7. Increase the air volume to the normal level of 3730 m³ / min to ensure smooth operation of the blast furnace. After taking the above measures, the possibility of material collapse was eliminated, and measures were taken at the root to suppress its occurrence, allowing the furnace condition to quickly return to normal. Example

[0025] On July 17, 2025, from 7:00 to 8:00, the air volume was 3713 m³ / min, the oxygen content was 13002 m³ / h, the ore batch was 52 t, the coke batch was 10.3 t, the coke briquettes were 0.8 t / batch, the coke ring count was 14.6 rings, the air pressure was 373 kPa, the gas utilization rate was 47.64%, the top temperature was 167℃, and the heat load was 8.6 MJ / h. No abnormalities were observed in the furnace condition. By 8:20, the air volume was 3710 m³ / min, and the oxygen content was 13000 m³ / h. The air volume and oxygen content did not change significantly. However, the 20-minute equivalent hourly material rate was 0.6 batches / h lower than the normal material rate. Furthermore, the 20-minute gas utilization rate showed a downward trend, reaching 46.60%, which was a significant decrease. The top temperature showed an upward trend, reaching 173℃, while the heat load showed a slow downward trend. Based on these data, the possibility of a material collapse could be determined. Immediately, 1.0t of central coke was added to the center of the furnace. After the central coke was indeed added to the center of the furnace charge from the top, the airflow was reduced by 50 m³ / min, controlling the air volume at 3660 m³ / min. With the possibility of a central collapse and excessive central airflow under control, the next step was to wait for the charge velocity to increase. From 8:20 to 8:50, the charge velocity showed a characteristic of initially being fast and then returning to normal, indicating that the previously accumulated pressure had been released normally. Next, the charge system needed to be adjusted (because this abnormal furnace condition was caused by excessive central airflow, the root cause of the abnormal furnace condition must be eliminated before increasing the airflow to restore normal volume). Therefore, at 8:50, the number of coke rings was reduced from 14.6 to 14.4, and at 8:57, airflow was increased to restore the normal volume of 3710 m³ / min. The furnace condition returned to normal, and a collapse was avoided.

[0026] 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 those skilled in the art within the scope of the present invention are covered by the patent scope of the present invention.

Claims

1. A method for preventing blast furnace collapse, characterized in that: Includes the following steps: Step 1: Prediction of material collapse: The judgment criteria are as follows: (1) The hourly air oxygen content has not changed significantly from the previous hour's air oxygen content, the air volume fluctuation range is ±20m³ / min, and the oxygen content fluctuation range is ±200m³ / h; (2) The material rate converted to an hourly rate in 20 minutes decreases by 0.5 batches / hour or more; (3) The air pressure decreases in 20 minutes and the decrease is greater than 5kPa; (4) The gas utilization rate decreases in 20 minutes and the decrease is greater than 1%; (5) The top temperature increases in 20 minutes and the top temperature increases by more than 5℃; (6) The edge heat load shows a decreasing trend in 20 minutes. Step 2: After determining the possibility of material collapse, the first measure to be taken is to replenish sufficient central coke to occupy the space already generated in the center; Step 3: After center coking, it is necessary to reduce the wind to suppress the development of the central airflow. The wind reduction should be controlled within the range of 50-100 m³ / min. Step 4: After the material speed returns to normal, adjust the material preparation to suppress the central airflow: reduce the amount of central coke by 0.2 to 0.3 revolutions; Step 5: Increase the air supply to the normal level to ensure smooth operation of the blast furnace.

2. The method for preventing blast furnace collapse according to claim 1, characterized in that: In step two, the amount of central coke replenished is 1.5 ± 0.5 tons.