Safe and efficient blast furnace charge level lowering blowing-out process

Abstract

The invention discloses a safe and efficient blast furnace charge level lowering blowing-out process. Comprising the following steps: adding manganese ore and fluorite to wash a furnace 2 days before blowing out the furnace; 5-8 batches of materials before lowering the charge level are changed into full coke smelting; wet quenched coke accounting for 50-70% of the volume of the hearth is prepared, and the moisture of the wet quenched coke is 8-15%; the water yield of a high-pressure atomization water gun at the top of the furnace is 60-80 t / h, and the top temperature is controlled to be 200- The coal injection quantity of a hearth with a coal injection gun is 5-10 t / h, when a stockline continues to descend to enter a furnace bosh, the air quantity is reduced to 2400-2800 m < 3 > / min, the top pressure is reduced to 110 kPa, coal injection into the furnace is stopped, nitrogen is introduced into the coal injection gun, and the nitrogen quantity is 3000-6000 m < 3 > / h; rich oxygen is brought in from the blast, and 4000-8000m < 3 > / h. By the adoption of the charge level lowering blowing-out technology, in the charge level lowering process, the H2 content is always smaller than 6%, and the duration of the whole charge level lowering blowing-out process can be shortened by 10-15%.

Description

Technical Field

[0001] The invention belongs to the technical field of blast furnace smelting, and in particular relates to a safe and efficient blast furnace shutdown process for lowering the material level. Background Art

[0002] Blast furnace charge level reduction is a key part of blast furnace production and a necessary stage for medium and major repairs. During the process of stopping the furnace for charge level reduction, the temperature of the recovered gas is often greater than 300℃, which will burn the gas recovery equipment and gas purification equipment. Excessive gas temperature may even cause the gas recovery pipe network to explode. Therefore, we need to control the gas temperature at 200-300℃. We use a water pumping device installed on the top of the furnace to pump water to cool the recovered gas. When water is pumped to lower the gas temperature, the unevaporated water vapor will gather and drip down along the furnace wall. When it touches the hot coke, it will be reduced to H 2 and CO, which can cause fires. When the accumulated water meets iron-containing materials, explosions will occur, causing safety accidents. As the blast furnace material level drops, H 2 The content continued to increase, making the gas produced by the blast furnace within the explosion range and could only be released into the air, causing environmental accidents. The blast furnace was forced to shut down, and the material surface was only at the furnace body. The furnace contained a large amount of unreduced iron-containing materials and coke, causing great economic losses. It took a lot of time to arrange personnel to enter the blast furnace to clean up the unreduced iron and coke, and there were also safety hazards such as gas poisoning, burns, and falling from heights. Summary of the invention

[0003] In view of the technical problems existing in the existing blast furnace shutdown process by lowering the material level, the object of the present invention is to provide a safe and efficient blast furnace shutdown process by lowering the material level.

[0004] The present invention maintains a suitable theoretical combustion temperature by enriching oxygen and injecting pulverized coal, which not only increases the speed of material lowering but also maintains the reducing agent and heat required for reducing the iron-containing furnace charge. In the later stage, the coal injection gun is changed to inject nitrogen. The nitrogen injected into the coal gun at high pressure and uniformly can effectively dilute the H in the furnace gas. 2 and O 2 content, and can effectively absorb the temperature of the furnace atmosphere, reducing the probability of water gas reaction. The above method makes the H 2 The content is always less than 6%, and the gas composition is always within the safe recovery range. The gas can be fully recovered and the material surface can be lowered to the furnace tuyere zone.

[0005] Specifically, the method steps and control parameters of the furnace shutdown process for reducing the material level provided by the present invention are as follows: Step 1: Preparation for shutdown. Add manganese ore and fluorite to wash the furnace 2 days before shutdown. The manganese content of molten iron should be 0.40-0.60%, and the fluorite should be 8-10kg per ton of iron. Ensure the normal operation of the gas online monitoring device, the furnace top atomization water injection system, and all equipment. Prepare for wet quenching. Divide the wet quenching coke that occupies 50-70% of the furnace volume into 8 batches on average. Water it thoroughly with water before use to prepare for high-water-content wet quenching coke.

[0006] Step 2: Stop injecting pulverized coal, replace pulverized coal with wet quenching coke, and continue to add iron-containing materials; Step 3: After 5-8 batches of iron-containing materials are fed, the feeding is stopped and the furnace is stopped. The coal gun starts to spray a small amount of pulverized coal, and the coal injection rate is about 5-10t / h. At the same time, the oxygen enrichment valve is opened and the oxygen enrichment dosage is adjusted to 4000-8000m 3 / h.

[0007] Step 4: During the material level reduction period, strictly control the top temperature at 200-300℃; when the top temperature is greater than 300℃, turn on the furnace top water supply system, and the high-pressure atomizing water gun starts to spray water for cooling. The water spray flow rate of each high-pressure atomizing water gun is about 60-80t / h.

[0008] Step 5: Divide the furnace body into 8 sections according to the furnace body height, and use a mechanical probe to monitor the material line height. Add a batch of high-water-content wet-quenched coke every time the blast furnace material line drops by one section. When the high-water-content coke enters the blast furnace, a large amount of water evaporates and absorbs the heat of the recovered gas, so that the temperature of the recovered gas is always below 300°C, which will not burn the equipment.

[0009] In a specific embodiment of the present invention, 50-70% of the volume of the furnace (about 80-100t of net coke) of wet quenching is wetted and thoroughly soaked with a water pipe. The moisture content of the wet quenching coke after soaking is required to be 8-15%. We divide the wet quenching coke into 8 batches, each batch is about 8-10t. The 15m furnace height is divided into 8 parts, each part is about 1.8m. A batch of wetted wet quenching coke is added every 1.8m below the blast furnace charge line. When the charge line drops to the bottom of the furnace, a total of 8 batches of wet quenching coke are added.

[0010] Step 6: When the material line continues to descend into the furnace waist, reduce the air volume to 2400-2800m 3 / min, the top pressure is reduced to 110kPa, and coal injection into the furnace is stopped.

[0011] Step 7: Connect nitrogen to the coal injection gun and use the coal injection gun to evenly spray nitrogen into the furnace tuyere zone. The required pressure is > 220kPa and the nitrogen flow rate is 3000-6000m 3 / h, and at the same time reduce the supply air temperature to 1050℃.

[0012] Step 8: When H 2The content rises to 6.0%, and the air volume is further reduced to 2000-2200m 3 / min, and open the tapping hole at the same time.

[0013] Step 9: When the blast furnace tuyere turns black, it means that the material level has been lowered to the furnace tuyere. Open the furnace top to vent, stop recovering coal gas, and close the oxygen enrichment valve and coal gun nitrogen valve.

[0014] Step 10: Prepare to shut down the blast furnace, disconnect the hot blast furnace air supply, open the air valve to fully release the air, shut down the fan, and shut down the blast furnace.

[0015] The innovation of the present invention is: 1. The shutdown process combining oxygen enrichment and coal injection is adopted to balance the theoretical combustion temperature. This process can shorten the shutdown time due to material drop by 10-15% and save 10% of the coke used for shutdown.

[0016] 2. When the material surface enters the lower part of the furnace body and the furnace waist, H 2 The content starts to rise to 6%. At this time, the coal injection gun is changed to nitrogen injection, and the nitrogen pressure is adjusted to >220kPa and the nitrogen flow rate is 3000-6000m 3 / h, temperature 50-100℃, 24 coal guns spray nitrogen evenly at high pressure, which can effectively dilute the H in the furnace gas. 2 and O 2 content, and can effectively absorb the temperature of the gas in the furnace, reducing the probability of water-gas reaction, so that H 2 The content is always less than 6%, and the gas recovery is maintained.

[0017] 3. Through these adjustments, we make (1) in the process of lowering the material level, H 2 The content is always less than 6%, ensuring that the material surface can be lowered to the furnace tuyere zone while the gas can be safely recovered throughout the process, greatly reducing the workload of cleaning the furnace; (2) preventing the gas from being 2 The content exceeds the safe range and is released into the atmosphere, polluting the environment; (3) The entire process of lowering the material level and shutting down the furnace can be shortened by 10-15%. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 Schematic diagram of blast furnace; 1-furnace throat, 2-furnace body, 3-furnace waist, 4-furnace belly, 5-furnace hearth, 6-high-pressure atomizing water gun, 7-tuyere, 8-iron outlet, 9-coal gun, 10-air supply duct, 11-oxygen enrichment adding duct, 12-coal injection duct, 13-nitrogen injection duct, 14-hot blast valve. DETAILED DESCRIPTION

[0019] The present invention is further described in detail below in conjunction with embodiments: Tegang Steel Plant 1580m 3 Blast furnace, the furnace top is conventionally equipped with 8 high-pressure atomizing water guns, the furnace top water supply system is normal; 24 coal injection guns are evenly distributed in the furnace tuyere belt. The furnace body height is 15m; the furnace volume is 280 m 3 .

[0020] The original metallurgical industry blast furnace shutdown process for lowering the material level: 1. Add manganese ore to wash the furnace 2 days before shutdown. The manganese content of molten iron is planned to be 0.40-0.60% (25kg manganese ore per ton of iron).

[0021] 2. Gradually change the smelting from pulverized coal injection to full coke smelting 12 hours in advance, stop coal injection and stop oxygen enrichment.

[0022] 3. During the period of lowering the material level, the cover coke covers about 100% of the volume of the furnace.

[0023] 4. H 2 If the content is greater than 6%, stop recovering gas and shut down the furnace.

[0024] The original special steel ironmaking plant adopted the industry's material level reduction shutdown process to shut down the 9# and 10# blast furnaces.

[0025] A total of 330 tons of coke was used in the 9# blast furnace. The material level dropped to 14m, only dropping to the lower part of the furnace body, and the gas was recovered for 4.5 hours.

[0026] A total of 350 tons of coke was used in the 10# blast furnace, and the material level dropped to 14.5m, only dropping to the lower part of the furnace body, and the gas was recovered for 4.7 hours.

[0027] On October 31, 2023, the 8# blast furnace adopted the blast furnace lowering material level shutdown process of the present invention: Before shutting down the furnace, ensure that the gas online monitoring device, the furnace top atomization water injection system, and all equipment are operating normally; add manganese ore and fluorite to wash the furnace 2 days before shutting down the furnace. The manganese content of the molten iron is 0.40-0.60%, and the fluorite is 8-10kg per ton of iron.

[0028] Prepare wet quenched coke with high water content: Divide 100t of wet quenched coke (about 50-70% of the furnace volume) into 8 batches and wet them thoroughly with a water pipe. The moisture content of the wet quenched coke after watering is required to be 8-15%.

[0029] Shutdown process: Stop injecting pulverized coal, replace pulverized coal with wet quenching coke, and continue to add iron-containing materials; After 8 batches of iron-containing materials were fed, the feeding was stopped, and the wet quenching coke with high water content was fed to cover the surface. The furnace entered the state of material level reduction and shutdown. The coal gun began to spray a small amount of pulverized coal, and the coal injection rate was about 10t / h. At the same time, the oxygen enrichment valve was opened and the oxygen enrichment dosage was adjusted to 8000m 3 / h.

[0030] During the period of lowering the material level, the top temperature is strictly controlled at 200-300℃; when the top temperature is greater than 300℃, the furnace top water supply system is turned on and atomization water spraying begins. The water spraying flow rate of each high-pressure atomization water gun is about 60-80t / h.

[0031] The 15m furnace body height is divided into 8 sections, each section is about 1.8m, and a batch of wet-quenched coke with high water content is added every 1.8m the blast furnace charge line goes down. When the charge line drops to the bottom of the furnace body, a total of 8 batches of wet-quenched coke are added.

[0032] When the material line continues to descend into the furnace waist, reduce the air volume to 2800m 3 / min, the top pressure is reduced to 110kPa, and coal injection into the furnace is stopped. Connect nitrogen to the coal injection gun, and use the coal injection gun to evenly spray nitrogen into the furnace tuyere zone, requiring pressure>220kPa, nitrogen flow rate 6000m 3 / h, and at the same time reduce the supply air temperature to 1050℃.

[0033] When H 2 The content rises to 6.0%, and the air volume of the blower is further reduced to 2000-2200m 3 / min, and at the same time open the iron mouth to discharge slag and iron. Observe that the blast furnace tuyere turns black, indicating that the material level has dropped to the furnace tuyere. At this time, open the furnace top to vent, stop recovering coal gas, close the oxygen enrichment valve and the coal gun nitrogen valve. Disconnect the hot blast furnace supply, open the vent valve to fully vent, stop the fan, and stop the blast furnace.

[0034] No. 8 blast furnace shutdown due to material reduction: (1) The material surface dropped to 21m and reached the furnace tuyere zone, which was nearly 7m lower than the original process material surface.

[0035] (2) The entire furnace was shut down for 9 hours to recover gas, recovering more than 810,000 m3 of gas 3 .

[0036] (3) Only 100 tons of coke was used in the entire process of stopping the furnace to reduce the material level, which is more than 200 tons less than the 9# and 10# furnaces using the industry's material level reduction process, directly reducing costs by more than 460,000 yuan.

[0037] (4) It only takes 4 hours to reduce the material level to 14m, which is 0.4h less than the industry material level reduction process used for 9# and 10#, or about 10%.

[0038] It should be noted that the operations not particularly described in the present invention are conventional operations of shutting down a blast furnace by lowering the charge level.

[0039] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical solutions and concepts of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

[0040] The present invention is not limited to the following specific embodiments. A person skilled in the art can implement the present invention in various other specific embodiments according to the contents disclosed in the present invention, or any simple changes or modifications made to the design structure and ideas of the present invention fall within the protection scope of the present invention. It should be noted that the embodiments and features in the embodiments of the present invention can be combined with each other without conflict.

Claims

1. A process for stopping the furnace by lowering the material level, characterized in that: Includes the following steps and parameter controls: Step 1: Preparation for shutdown: add manganese ore and fluorite to wash the furnace 2 days before shutdown. The manganese content of molten iron is 0.40-0.60%, and the fluorite is 8-10kg per ton of iron. Before shutdown, ensure that the gas online monitoring device, the furnace top atomization water system, and all equipment are operating normally; Prepare wet quenching coke, divide the wet quenching coke that accounts for 50-70% of the furnace volume into 8 batches, and soak them with water before use to prepare high-water content wet quenching coke for standby use; Step 2: Stop injecting pulverized coal, replace pulverized coal with wet quenching coke, and continue to add iron-containing materials; Step 3: After 5-8 batches of iron-containing materials are fed, the feeding is stopped and the furnace is stopped to lower the material level; the coal gun is opened to spray pulverized coal and the oxygen-enriched valve is opened at the same time; Step 4: During the material level reduction period, strictly control the top temperature at 200-300℃; when the top temperature is greater than 300℃, open the furnace top water supply system and use a high-pressure atomizing water gun to spray water to reduce the temperature; Step 5: Divide the furnace body into 8 sections according to the furnace body height, monitor the material line height with a mechanical probe, and add a batch of high-water-content wet-quenched coke every time the blast furnace material line drops by one section; Step 6: When the material line continues to descend and enters the furnace waist, reduce the air supply volume and stop coal injection; Step 7: Connect nitrogen to the coal injection gun and use the coal injection gun to evenly spray nitrogen into the furnace tuyere zone. The required pressure is > 220kPa and the nitrogen flow rate is 3000-6000m 3 / h, and at the same time reduce the air supply temperature to 1050℃; Step 8: When the H2 content rises to 6.0%, further reduce the air volume and open the taphole at the same time; Step 9: When the material surface drops to the furnace tuyere, open the furnace top to vent, stop recovering gas, and close the oxygen enrichment valve and coal gun nitrogen valve; Step 10: Prepare to shut down the blast furnace, disconnect the hot blast furnace air supply, open the air valve to fully release the air, shut down the fan, and shut down the blast furnace.

2. The process for stopping the furnace by lowering the material level according to claim 1, characterized in that: The moisture content requirement for high-moisture wet quenching is 8-15%.

3. The process for stopping the furnace by lowering the material level according to claim 1, characterized in that: In step 3, the coal injection rate of the coal injection gun is 5-10t / h.

4. The process for stopping the furnace by lowering the material level according to claim 1, characterized in that: In step 3, the amount of oxygen enrichment is 4000-8000m 3 / h.

5. The process for stopping the furnace by lowering the material level according to claim 1, characterized in that: In step 4, the water spray flow rate of each high-pressure atomizing water gun is 60-80t / h.

6. The process for stopping the furnace by lowering the material level according to claim 1, characterized in that: In step 6, reduce the air volume to 2400-2800m 3 / min, the top pressure is reduced to 110kPa.

7. The process for stopping the furnace by lowering the material level according to claim 1, characterized in that: In step 8, the air volume is further reduced to 2000-2200m 3 / min.

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