Rapid recovery method for short-term blowing-down furnace condition of blast furnace

Abstract

The invention relates to the field of iron and steel metallurgy blast furnace ironmaking, in particular to a quick recovery method for short-term shutdown furnace conditions of a blast furnace. The rapid furnace condition recovery technology for short-term damping-down (less than or equal to 4 hours) of the blast furnace has the main technical characteristics that 1) coke adding and heat compensation for coke annealing load: the coke ratio is increased by 10-15 kg / t, and 2-3 t of coke (or 20-30% of coke in a coke batch) is added for heat compensation 3-4 hours and 1-2 hours earlier than the damping-down time; (3) during air supply, the ore returning batch is 80%-85% of the normal ore batch, the coke ratio is maintained to be 355-365 kg / t, discharging is carried out after material movement, air is added to 1500-1800 m < 3 > / min (the normal air volume is 40%-50%), coal injection and oxygen enrichment are started, the air volume is recovered to be normal within 1-2 h, and the oxygen enrichment is normal within 2-4 h, and (4) after the accumulated air volume reaches 150-200 thousand m < 3 > after air supply, first furnace iron is discharged.

Description

Technical Field

[0001] This invention relates to the field of blast furnace ironmaking in iron and steel metallurgy, and more particularly to a method for rapidly restoring the furnace condition during a short-term shutdown of a blast furnace. Background Technology

[0002] Blast furnace smelting, a crucial link in the long process of steelmaking, accounts for 60%-70% of costs and energy consumption. Its economic efficiency requires continuous improvement in production technology and economic indicators. Blast furnaces operate continuously for 24 hours under high temperature and pressure. During this time, temporary short-term (≤4h) shutdowns are inevitable due to production or equipment failures. The ability to quickly restore blast conditions after such shutdowns is a key indicator of the skill level of blast furnace operators and managers. Restoring blast after a short shutdown is difficult, primarily because the slag-iron temperature difference (molten iron temperature 1400-1450℃) after a shutdown hinders flow and requires extensive cleaning work in front of the furnace. This results in a slow recovery process, typically exceeding 8h, leading to significant losses in both output and quality.

[0003] Here, a rapid recovery technology for blast furnace conditions during short-term shutdowns (≤4 hours) is proposed. This patented technology enables safe, stable, and rapid recovery of blast furnace conditions during scheduled maintenance. Within 1-2 hours of blasting, the air volume, oxygen content, and top pressure are restored to normal production levels, and the coke load is restored to normal levels within 4 hours.

[0004] This method aims to provide a rapid recovery technology for blast furnace conditions during short-term shutdowns (≤4 hours) of scheduled maintenance. Through this patented technology, the furnace conditions during scheduled maintenance can be safely, stably, and rapidly recovered. Within 1-2 hours of blasting, the air volume, oxygen content, and top pressure can be restored to normal production levels, and the coke load can be restored to normal levels within 4 hours.

[0005] To reduce the loss of furnace condition recovery during short-term shutdowns, reduce the frequency of water injection at the furnace top, protect the furnace top and furnace body cooling equipment, achieve a reasonable gas flow distribution in the furnace as soon as possible, and promote the blast furnace to return to the normal production track of "safety, stability, economy and long service life". Summary of the Invention

[0006] The purpose of this invention is to address the above-mentioned problems by providing a method for rapidly restoring the furnace condition during a short-term shutdown of a blast furnace.

[0007] The purpose of this invention is achieved as follows: A method for rapid recovery of blast furnace conditions during short-term shutdowns includes the following aspects: (1) Coke load reduction and coke replenishment: 1) When the furnace condition is stable, the ore batch can be maintained, and 300-400 kg of coke batch can be added to reduce the load and increase the coke ratio by 10-15 kg / t, increasing the coke ratio to 355-365 kg / t, controlling the coal ratio to not exceed 170 kg / t, increasing the heat to a silicon content of 0.5-0.6, and reducing the slag basicity to 1.15-1.20; 2) 3-5 hours and 1-2 hours before shutdown, 2-3 t of coke or 20%-30% of the coke batch can be added, and 1-2 t of silica can be added to balance the slag basicity to 1.1. 5-1.20, during the process of reducing air volume, add 1-2t of central coke or 20%-30% of coke in the coke batch; (2) Increase furnace temperature and reduce basicity: 6-8 hours before shutting down the blast furnace, reduce the slag basicity by 0.02-0.04, and 2-4 hours before shutting down the blast furnace, increase the furnace temperature to pig iron [Si]=0.55~0.60, and measure the temperature of molten iron at 1480-1520℃; (3) Increase pulverized coal injection: 1-2 hours before shutting down the blast furnace, increase the pulverized coal injection rate by 2-3t / h; (4) Iron tapping and air reduction arrangement: 1) Before shutting down the blast furnace, ensure that the tap hole of the two furnaces is open, and calculate whether there is a loss of iron and the slag discharge situation. According to the calculation of the theoretical slag and iron volume generated by the top material of the furnace, the deviation between the actual slag and iron volume discharged is within 50m 3 Within; 2) When shutting down the air, open the first tap for 30-40 minutes, then open the other tap and tap out iron at the same time; 3) Reduce air: When the tap blows to the skimmer, start reducing air, and control the air shutdown time to 50-60 minutes; 4) Observe the front end of the tuyeres during the air shutdown process. If the front end of the tuyeres is bright and active and there is no slag, prevent the tuyeres from being filled; (5) Material line during shutdown: shut down the air with the normal material line, and the material line ≯2.0m; (6) Clean the tuyeres: 1) If a tuyer is found to have slag during the shutdown process, organize the furnace front to clean it; 2) Before the air is supplied, the furnace front should pry open the mud blocking the tuyeres before replacement and see the red coke; (7) Restore air supply: When supplying air, reduce the ore batch to 80%-85% of the normal ore batch, i.e., 50t-52t, maintain the coke ratio of 355-365kg / t, release the material after the material moves, and increase the air supply to 1500-1800m. 3 Coal injection and oxygen enrichment begin at a rate of / min, and the air volume returns to normal (3600-3800 m³ / min) within 1-2 hours. 3 / min, normal oxygen enrichment level over 2-4 hours is 12000-16000m 3 / h; (8) Timing of the first furnace of iron: when the cumulative air volume after the air supply reaches 150,000-200,000 m³ / h; 3 , the first furnace of iron was produced.

[0008] The beneficial effects of this invention are as follows: The No. 3 blast furnace (1800m³) of Taiyuan Iron & Steel Plant was put into operation on July 31, 2007. After 2023, the rapid recovery technology for short-term shutdowns (≤4 hours) of the blast furnace, combined with the furnace design and the characteristics of the full cooling wall structure, was implemented. Through comprehensive adjustments, the overall gas flow was stabilized, the gas utilization rate was improved, and the furnace body heat load was steadily reduced, thereby achieving a stable and rapid recovery of the furnace condition.

[0009] After nearly two years of production practice and adjustments, this invention has been developed. According to this technology, blast furnace operators can quickly increase air volume, enrich oxygen, and inject pulverized coal during the furnace condition recovery process. Based on the changes in the gas flow inside the furnace, they can promptly adjust the upper and lower operating parameters to achieve rapid furnace condition recovery.

[0010] Using this blast furnace short-term shutdown (≤4 hours) scheduled maintenance rapid furnace condition recovery technology, the furnace condition can be quickly restored. Within 1-2 hours of blasting, the air, oxygen and top pressure return to normal, within 3-4 hours the coke load returns to normal, and within 4-6 hours the furnace temperature and alkalinity return to normal levels. During the furnace condition recovery process, the loss of production, technical and economic indicators is minimal.

[0011] Using this technology, each short-term shutdown requires 20 tons less coke. With a coke price of 1,750 yuan / ton and assuming 10 short-term shutdowns per blast furnace per year, the economic benefit is: 20 * 10 * 1,750 = 350,000 yuan / year. Detailed Implementation

[0012] The basic technical concept of this invention is as follows: 1. Coke loading and coke supplementation: 1) Based on the stability of the furnace condition, when the furnace condition is stable, the ore batch can be maintained, and 300-400 kg of coke batch or 2 tons of ore batch (or 4%-8% of the ore amount of the ore batch) can be added, the load can be reduced by 10-15 kg / t, the coke ratio can be reduced to 355-365 kg / t, the coal ratio can be controlled to not exceed 170 kg / t, the heat can be increased to a silicon content of 0.5-0.6, the slag basicity can be reduced by 1.15-1.20, and the iron temperature can be controlled at 1480-1520℃. 2) Based on the blast shutdown time and smelting cycle, 3 tons of coke (or 20%-30% of the coke amount of the coke batch) can be added 4 hours and 2 hours before the blast shutdown, and 2 tons of silica can be added to balance the slag basicity. During the blast reduction process, 2 tons of center coke (or 20%-30% of the coke amount of the coke batch) can be added. Five typical characteristics of stable blast furnace conditions: 1. Stable blast pressure: The blast pressure fluctuates within 10-15 kPa per day. 2. Top cross temperature measurement: The temperature distribution at the cross measurement points falls within the following ranges: The center temperature can be maintained at 500-600℃ (with a change of 60-100℃ before and after charging). The sub-center temperature is 250-300℃, with smooth and stable airflow in the center. The temperature at the four edge points is 70-110℃. 3. Top temperature: The average temperature at the four points on the top is 160-200℃, and the temperature deviation at the four points is less than 30℃. 4. Throat brick temperature is 100-140℃, showing small, regular fluctuations before and after charging. 5. Top water injection: 4-8 times / day.

[0013] 2. Increase furnace temperature and reduce basicity: 8 hours before shutting down the blast furnace, reduce the slag basicity by 0.02, and 4 hours before shutting down the blast furnace, increase the furnace temperature to pig iron [Si] = 0.55~0.60, and measure the temperature of molten iron at 1480-1520℃.

[0014] 3. Increase pulverized coal injection: Increase the pulverized coal injection rate by 2-3 t / h 2 hours before the ventilation shutdown, taking into account the relationship between material feeding and pressure.

[0015] 4. Iron tapping and blast reduction arrangements: 1) Before shutting down the furnace, ensure the tapholes of the two furnaces are open and calculate whether there is a shortage of iron and the slag discharge situation. 2) During the shutdown, after opening the first taphole for 30-40 minutes, open the other taphole and tap iron simultaneously. 3) Blast reduction: Keep the tapholes open in front of the furnace. When the blast reaches the slag skimmer, start reducing the blast. The shutdown time should be controlled at 50-60 minutes. 4) During the blast reduction process, notify the water watcher to observe the situation at the front of the tuyeres, i.e., the front of the tuyeres should be noticeably active and there should be no slag inflow to prevent blast from entering the tuyeres.

[0016] 5. Material line during ventilation shutdown: When shutting down ventilation, the material line should be ≤2.0m.

[0017] 6. Air supply recovery: During air supply, reduce the ore batch size to 80%-85% of the normal batch size, maintain a coke ratio of 355-365 kg / t, discharge the material after it starts moving, and increase the air supply to 1500 m³ / t. 3Coal injection and oxygen enrichment begin at 1 / min (40%-50% of normal air volume). Air volume returns to normal within 1-2 hours, and oxygen enrichment returns to normal within 2-4 hours.

[0018] 7. Timing for tapping the first furnace of iron: When the cumulative air volume after blasting reaches 150,000-200,000 m³ / h. 3 , the first furnace of iron was produced.

[0019] The specific technical solution of this invention is as follows: Taiyuan Iron & Steel Group's No. 3 blast furnace is scheduled to shut down for 2.5 hours at 19:30 on February 13th to replace tuyeres No. 16 and No. 20. The following plan is formulated for reheating, furnace condition adjustment, and recovery before the shutdown: 1. Reheating and Coking: 1) On the 13th, maintain an ore batch of 51t. At 14:00, add 300kg of coking coal to reduce the load to a coke ratio of 365kg / t, controlling the coal ratio to not exceed 170kg / t, and raising the heat to a silicon content of 0.5-0.6 and a slag basicity of 1.15-1.20. 2) Based on the 19:30 shutdown and smelting cycle, add 3t of coking coal at 15:00 and 17:00 each time, and add 2t of silica to balance the basicity. During the blast reduction process, add another 2t of center coke.

[0020] 2. Increase furnace temperature and reduce basicity: 8 hours before shutting down the blast furnace, reduce the slag basicity by 0.02, and 4 hours before shutting down the blast furnace, increase the furnace temperature to pig iron [Si] = 0.55~0.60, and measure the temperature of molten iron ≥1490℃.

[0021] 3. Increase pulverized coal injection: Increase the pulverized coal injection rate by 2t / h 2 hours before the ventilation shutdown, taking into account the relationship between material feeding and pressure.

[0022] 4. Iron tapping and blast reduction arrangements: 1) Confirm that the dry slag pit is ready for slag discharge, and dump dry slag from the south side of the furnace before shutting down the blast furnace; 2) Ensure the tapholes of the two furnaces are open before shutting down the blast furnace, and calculate whether there is a shortage of iron and the status of slag discharge; 3) When shutting down the blast furnace, open the north side for about 30 minutes, then open the south side and tap iron simultaneously. After the north side starts blowing air, plug the taphole; 4) Blast reduction: Reduce blast as soon as the blowing air reaches the skimmer, and control the shutdown time within 60 minutes.

[0023] 5. During the air reduction process, notify the water monitoring system to simultaneously control the cooling water volume of No. 16 and No. 20 to reduce water leakage into the furnace.

[0024] 6. Calculation of coal loss during ventilation shutdown: Based on the coal ratio at the time and the corresponding cumulative air and oxygen content (the cumulative air volume is reset to zero when coal is stopped), calculate the coal loss during the coal shutdown period.

[0025] 7. Material line during ventilation shutdown: When shutting down ventilation, the material line should be ≤2.0m.

[0026] 8. Cleaning the tuyeres: 1) If slag is found in the tuyeres during the shutdown process, organize the furnace front to clean them. 2) Before the air is supplied, the furnace front should remove the sludge blocking the tuyeres to the point of revealing red coke.

[0027] 9. Air supply recovery: During air supply, reduce the ore batch to 45t, maintain the coke ratio at 365kg / t, discharge the material after it starts moving, and increase the air supply to 1500m³. 3 / min coal injection, oxygen enrichment. Target: air volume returns to normal in 2-3 hours, oxygen enrichment returns to normal in 4-6 hours.

[0028] 10. When the air and oxygen levels reach 90% of normal, increase to full air and full oxygen based on the heat of slag and iron and emissions.

[0029] By implementing this method, the No. 3 blast furnace (1800m³) of Taiyuan Iron & Steel Group Co., Ltd. 3 After a short-term shutdown from 2023 to September 2025, the furnace condition was able to be stabilized and quickly restored within 1-2 hours. Example 1

[0030] On February 13, 2025, a production example was planned to have the ventilation system shut down for 2-3 hours to replace the air outlets.

[0031] 1. Pre-shutdown furnace condition adjustment: 1) This shutdown is a short-term shutdown (≤4 hours), no shutdown material needs to be added, and the normal material line will be shut down. 2) Before the shutdown, maintain the ore batch at 51t, reduce the load of the 52nd furnace to a coke ratio of 366kg / t, control the coal ratio to not exceed 170kg / t, increase the heat to a silicon content of 0.5-0.6, and the slag basicity to 1.15-1.20. Add 3t of coke to the 98th and 110th furnaces respectively, and add 2t of silica to balance the basicity. Add another 2t of center coke during the blast reduction process.

[0032] 2. Shutdown Process: 1) On the 13th, due to the excessively long tapping time of batch 69051, the expected shutdown time was postponed from 19:30 to the actual 20:35. However, the slag and iron discharge was good, laying a good foundation for the subsequent shutdown process. 2) Before the shutdown, the furnace conditions were good and the furnace temperature was stable. The slag and iron heat was abundant. For batches 69050 and 69051, the slag and iron temperatures before the shutdown were 1502°C and 1488°C, respectively. The Si content of the molten iron was 0.53% and 0.45%, and the slag basicity was 1.18% and 1.17%, respectively. 3) Dual tapping was organized. The tapholes were opened at 18:03 in the north and 18:33 in the south. After a large blow at the north taphole at 19:09, the blast was reduced. During this period, the blowers cooperated with the blast reduction, and the top pressure was continuously adjusted according to the blast volume. At 19:15, the north gate ventilation was reduced to 2830 m³ / min, oxygen to 1000 m³ / h, coal to 30 t / h, and top pressure to 170 kPa. 4) During the subsequent ventilation shutdown while awaiting the south gate's large-scale ventilation, the top pressure gradually recovered to 190 kPa. There were no signs of a short-term large-scale ventilation in the south gate. At 20:10, the north gate was reopened, and after large-scale ventilation in both gates, ventilation was shut down according to the normal shutdown procedure. From 19:15 to 20:10, the ventilation was maintained at 2800 m³ / min. The slow ventilation period was too long, but fortunately, it had little impact on the subsequent ventilation shutdown and supply process. 5) At 20:22, coal and oxygen were stopped. At 20:25, nitrogen was introduced into the furnace throat and downcomer. At 20:30, exhaust was started. At 20:35, ventilation was shut down. The shutdown material line was 1.85 m on the north foot and 1.83 m on the south foot.

[0033] 3. Air Supply Process: 1) The air supply process went smoothly. During air supply, the ore batch was reduced to 45t (normal production ore batch is 50-52t), maintaining a coke ratio of 365kg / t. After receiving the air supply notification at 22:00, air supply was carried out according to the normal procedure. At 22:09, the air volume was restored to 500m³ / min, at 22:12 it was restored to 800m³ / min, and at 22:18 it was restored to 1200m³ / min. 2) At 22:26, ​​the probe was used to check the material surface, with a north probe reading of 2.83m and a south probe reading of 2.87m. At 22:40, the material line reached a north probe reading of 3.04m and a south probe reading of 3.02m, and the first batch of material was placed (air volume 1800m³ / min). 3) At 23:23, the cumulative air volume reached 140kJ / min, and the taphole was opened. Subsequently, based on the airflow in the furnace, the heat of the slag and iron in front of the furnace, and the discharge situation, the air supply was gradually increased to expand the ore batch and increase the load.

[0034] 4. Results: The shutdown period was expected to be 2.5 hours from 20:35 to 22:25, but it actually lasted 1 hour and 50 minutes. During the ventilation, the ore batch was reduced to 45t, and the coke ratio was maintained at 365kg / t. The ventilation recovery took 2-3 hours, and the furnace condition was restored smoothly. Example 2

[0035] The No. 3 blast furnace is scheduled to shut down for 2-3 hours from 18:30 to 21:30 on November 18, 2025, to replace the sealing rings of tuyeres No. 6 and No. 20, and the tie rods of hot blast stove No. 4. The following plan is formulated for reheating, furnace condition adjustment and recovery before the shutdown.

[0036] 1. Reheating and Coking: 1) At 15:00 on the 18th, the current ore batch is 52t, with a coke ratio of 345kg / t. At 18:00, add 300kg of coke to reduce the coke ratio to 355kg / t, increase the heat to a silicon content of 0.5-0.6, lower the slag basicity to 1.15-1.21, and measure the molten iron temperature to ≥1490℃. 2) Based on the 19:00 shutdown and smelting cycle, add 3t of coke and 2t of silica at 15:40 and 17:00 respectively.

[0037] 2. Furnace temperature: 3 hours before shutting down the furnace, raise the furnace temperature to pig iron [Si] = 0.50~0.70, and the temperature of molten iron ≥ 1490℃.

[0038] 3. Increase pulverized coal injection: Increase the pulverized coal injection rate by 2t / h 2 hours before the ventilation shutdown, taking into account the relationship between material feeding and pressure.

[0039] 4. Iron tapping and blast reduction arrangements: 1) Iron tapping in both the south and north sections will be suspended, with dry slag being discharged from the south section. 2) Before blast suspension, ensure the taphole is clear and calculate whether there is a loss of iron and the slag discharge situation. 3) Blast reduction: Blast reduction can begin as soon as the blown iron reaches the A cover at the taphole in the north section.

[0040] 5. During the air reduction process, notify the water monitoring department to simultaneously control the cooling water volume of air outlets #7 and #20 to reduce water leakage.

[0041] 6. Calculation of coal loss during ventilation shutdown: Based on the coal ratio at the time and the corresponding cumulative air and oxygen content (the cumulative air volume is reset to zero when coal is stopped), calculate the coal loss during the coal shutdown period.

[0042] 7. Material line during ventilation shutdown: When shutting down ventilation, the material line should be ≤2.0m.

[0043] 8. Cleaning the tuyeres: 1) If slag is found in the tuyeres during the shutdown process, organize the furnace front to clean them. 2) Before the air is supplied, the furnace front should remove the sludge blocking the tuyeres to the point of revealing red coke.

[0044] 9. Air supply recovery: When supplying air, reduce the ore batch to 49t, coke ratio to 355kg / t, discharge the material after it moves, and increase the air supply to 1500-1800m. 3 / min coal injection, oxygen enrichment. Target: air volume returns to normal within 2-3 hours, oxygen enrichment returns to normal within 3-5 hours.

[0045] After operating according to the above plan, the No. 3 blast furnace will recover to the normal air volume of 3600-3700 m3 / min and oxygen enrichment of 11000-13000 m3 / h within 3-4 hours, and the furnace condition will return to normal.

[0046] 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 rapidly restoring the furnace condition after a short-term shutdown of a blast furnace, characterized in that: Including the following aspects: (1) Coke loading and reheating: 1) When the furnace condition is stable, maintain the ore batch and add 300-400 kg of coke batch to reduce the load and increase the coke ratio by 10-15 kg / t, increasing the coke ratio to 355-365 kg / t. Control the coal ratio to not exceed 170 kg / t, increase the heat to a silicon content of 0.5-0.6, and reduce the slag basicity to 1.15-1.20; 2) Add 2-3 t of coke or 20%-30% of the coke batch 3-5 hours and 1-2 hours before the blast shutdown, and add 1-2 t of silica to balance the slag basicity to 1.15-1.

20. During the blast reduction process, add another 1-2 t of central coke or 20%-30% of the coke batch. (2) Increase furnace temperature and reduce basicity: 6-8 hours before shutting down the blast furnace, reduce the basicity of the slag by 0.02-0.04, and 2-4 hours before shutting down the blast furnace, increase the furnace temperature to pig iron [Si]=0.55~0.60, and measure the temperature of molten iron at 1480-1520℃; (3) Increase pulverized coal injection: Increase the pulverized coal injection rate by 2-3 t / h 1-2 hours before the ventilation shutdown; (4) Iron tapping and blast reduction arrangements: 1) Before shutting down the blast furnace, ensure the tapholes of the two furnaces are open and calculate whether there is a shortage of iron and the slag discharge situation. According to the calculation of the theoretical slag and iron volume generated based on the top charge, the deviation between the actual slag and iron volume discharged should be within 50m³. 3 Within; 2) When shutting down the air supply, open the first tap for 30-40 minutes, then open the other tap and tap out iron at the same time; 3) Reduce the air supply: when the tap blows to the skimmer, start reducing the air supply and control the shutdown time to 50-60 minutes; 4) During the reduction of air supply, observe the water and the front end of the tuyeres. If the front end of the tuyeres is bright and active and there is no slag rushing in, prevent the tuyeres from being filled with slag. (5) Material line during ventilation shutdown: When the ventilation is shut down, the material line should be ≤2.0m. (6) Cleaning the tuyere: 1) If slag is found in the tuyere during the shutdown process, organize the furnace front to clean it; 2) Before the air is supplied, the furnace front should remove the mud blocking the tuyere before it is replaced to see the red coke. (7) Air supply recovery: When supplying air, reduce the ore batch to 80%-85% of the normal ore batch, i.e., 50t-52t, maintain the coke ratio at 355-365kg / t, release the material after it moves, and increase the air supply to 1500-1800m. 3 Coal injection and oxygen enrichment begin at a rate of / min, and the air volume returns to normal (3600-3800 m³ / min) within 1-2 hours. 3 / min, normal oxygen enrichment level over 2-4 hours is 12000-16000m 3 / h; (8) Timing of tapping the first furnace of iron: When the cumulative air volume after blasting reaches 150,000-200,000 m³ / h 3 , the first furnace of iron was produced.