Method for eliminating tuyere fire after damping down of high-pressure-difference large blast furnace

Abstract

The invention discloses a method for eliminating tuyere fire after damping down of a high-pressure-difference large blast furnace, which comprises the following steps of: (1) quickly reducing air at the earlier stage of damping down of the blast furnace, stopping coal and oxygen in time, and reducing the pressure in the furnace; (2) furnace top pressure control: rapidly reducing the furnace top pressure in the early damping-down stage of the blast furnace; (3) stock line control: in order to increase the air permeability of stock columns in the furnace, controlling the stock line to be 2.5-3.0 m after damping down; and (4) reducing the pressure in the furnace, gradually increasing damaged pipes on the cooling wall of the furnace body in the later period of furnace service, maintaining a part of the damaged pipes by medium-pressure nitrogen, and stopping the maintenance nitrogen in time to reduce the pressure in the furnace after damping down. The invention aims to quickly, safely and effectively eliminate the tuyere fire phenomenon, reduce the equipment loss, reduce the safety risk, particularly shorten the tuyere replacement time, improve the blast furnace productivity and reduce the environmental pollution through scientific and reasonable operation procedures and technical means. And a good condition is created for reblowing after damping down of the blast furnace.

Description

Technical Field

[0001] This invention belongs to the field of high-pressure differential large blast furnace shutdown technology in the metallurgical industry, and particularly relates to a method for eliminating fire at the tuyeres after a high-pressure differential large blast furnace has shut down. Background Technology

[0002] In the production process of large blast furnaces, shutdown is a necessary operation. However, after shutdown, large blast furnaces with high pressure differentials often experience tuyere flames after unloading the tuyere pipes due to poor permeability, internal pressure changes, uneven temperature distribution, and residual combustible materials. This tuyere flame not only threatens the safe operation of the blast furnace, potentially causing fires or explosions, but also leads to significant heat loss and increased energy consumption. Furthermore, the flames and smoke generated by the flames prolong tuyere replacement time and pollute the environment, failing to meet environmental protection requirements. Current solutions are often ineffective, failing to completely eliminate tuyere flames, or are complex and costly, hindering widespread application. Therefore, a more effective, convenient, and economical method is needed to eliminate the problem of tuyere flames after shutdown in large blast furnaces.

[0003] Currently, both blast furnaces are in the late stages of their service life. Damaged cooling walls and water-cooled columns are undergoing maintenance (through water or nitrogen). After the tuyeres were damaged, water leakage into the furnace increased, resulting in persistently high pressure differentials and poor charge permeability after shutdowns. After removing the tuyeres, flame ejection from the tuyeres and their intermediate sections became significant. In severe cases, sealing plates had to be used to block the intermediate sections before tuyer replacement could proceed, thus prolonging the shutdown period. This situation has several serious consequences: First, the prolonged shutdown time leads to increased production losses; second, the large amount of dense smoke and gas ejected after the tuyeres are removed poses a risk of carbon monoxide poisoning to personnel at the tuyeres platform and pollutes the iron tapping area. Summary of the Invention

[0004] The purpose of this invention is to provide a method for eliminating tuyere flames after a high-pressure differential large blast furnace shutdown. Through a scientific and reasonable operating procedure and technical means, the method can quickly, safely, and effectively eliminate tuyere flames, reduce equipment wear and tear, minimize safety risks, and especially shorten tuyere replacement time, thereby increasing blast furnace productivity and reducing environmental pollution. It also creates favorable conditions for blast furnace restart after shutdown.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0006] This invention provides a method for eliminating tuyeres flameout after shutdown of a large blast furnace with high pressure differential, comprising:

[0007] (1) Rapidly reduce blast during the early stage of blast furnace shutdown, promptly stop coal and oxygen production, and reduce furnace pressure.

[0008] In the early stage of blast furnace shutdown and blast reduction, rapid blast reduction and timely shutdown of coal and oxygen can quickly reduce the blast volume in the blast furnace, thereby reducing the intensity of the combustion reaction.

[0009] (2) Furnace top pressure control

[0010] In the early stage of blast furnace shutdown, the pressure at the top of the furnace is reduced rapidly to effectively alleviate the overall pressure level inside the furnace and avoid high gas pressure differential caused by excessive pressure. At the same time, it creates safe and stable conditions for subsequent shutdown operations and ensures that the shutdown process proceeds smoothly and orderly.

[0011] (3) Material line control

[0012] To increase the air permeability of the charge column inside the furnace, the charge height should be controlled at 2.5m-3.0m after the furnace is shut down.

[0013] (4) Reduce furnace pressure

[0014] In the later stages of furnace operation, the number of damaged tubes on the furnace cooling wall gradually increases. Some of the damaged tubes are maintained with medium-pressure nitrogen. After the furnace is shut down, the maintenance nitrogen is turned off in time to reduce the pressure inside the furnace.

[0015] Furthermore, starting with reducing the airflow, within 15 minutes, the airflow should be reduced to 68-72% of the full air volume, with an air volume of 4400-4600 m³ / h. 3 / min.

[0016] Furthermore, within 10 minutes of reducing the airflow, the air volume is reduced to 4800-5200 m³ / h. 3 / min, coal and oxygen supply stopped.

[0017] Furthermore, the top pressure is required to be reduced to 20% of the full top pressure within 30 minutes.

[0018] Furthermore, within 35 minutes of reducing the airflow, the air volume is reduced to 2500-2700 m³ / h. 3 / min, change to normal pressure.

[0019] Furthermore, the material feeding line is controlled at 2.5m.

[0020] Furthermore, the material feed line is controlled at 2.8m.

[0021] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0022] Blast Furnace #8 underwent a short-term shutdown on September 12, 2024. No flames were observed at the tuyeres. Replacing the three tuyeres took 42 minutes, saving 16 minutes compared to the shutdown on August 29, 2024. Based on 5 batches of feed per hour, 16 minutes affected 1.5 batches, resulting in a production of 116 tons. Assuming a profit of 500 yuan per ton of iron, this translates to a cost saving of 58,000 yuan. If each blast furnace undergoes a shutdown for tuyeres replacement once a month on average, with an estimated 24 shutdowns per year, the cost reduction could reach 1.392 million yuan. Attached Figure Description

[0023] The present invention will be further described below with reference to the accompanying drawings.

[0024] Figure 1 The extent of blast furnace shutdown and blast reduction;

[0025] Figure 2 The reduction in top pressure during blast furnace shutdown;

[0026] Figure 3 A trend chart of blast furnace shutdown air volume;

[0027] Figure 4 This is a graph showing the trend of hot blast pressure during blast furnace shutdown. Detailed Implementation

[0028] A method for eliminating fire at the tuyeres after shutdown of a large blast furnace with high pressure differential:

[0029] (1) Initial reduction in airflow and control of hot air pressure

[0030] In the initial stage of blast furnace shutdown and blast reduction, rapid blast reduction and timely cessation of coal and oxygen supply are crucial. Rapid blast reduction quickly decreases the blast volume within the blast furnace, thereby reducing the intensity of the combustion reaction. This alters the combustion environment of the pulverized coal, allowing for a rapid cessation of pulverized coal injection. Simultaneously, the reduced blast volume correspondingly decreases the oxygen supply, further aiding in the timely cessation of oxidation reactions within the furnace. Reduced blast volume decreases the gas flow rate within the blast furnace, lowering flow resistance and effectively reducing furnace pressure. This is critical for shutdown operations; rapidly reducing furnace pressure through blast reduction creates safe conditions for subsequent shutdown procedures, ensuring a smooth shutdown process.

[0031] Analysis revealed that the slow reduction in airflow at the tuyeres during the shutdown process, particularly the slow initial reduction, led to delayed shutdown of pulverized coal and oxygen, ultimately resulting in a high pressure differential within the furnace. From the start of airflow reduction, it is required to reduce the airflow to 70% of the total air volume within 15 minutes (airflow to 4500 m³ / h). 3 / min); within 10 minutes of reducing the airflow, the air volume reaches 5000m³ / min. 3 / min, coal and oxygen shutdown; blast furnace shutdown and blast reduction magnitude and blast volume trend chart as shown in the figure. Figure 1 and 3 As shown.

[0032] (2) Furnace top pressure control

[0033] The pressure requirement is to reduce the airflow to 20% (50 kPa) of the full pressure within 30 minutes, and to reduce the airflow to 2600 m³ / h within 35 minutes. 3 At approximately / min, switch to atmospheric pressure. The graph showing the decrease and trend of hot blast pressure during blast furnace shutdown is as follows. Figure 2 and 4 As shown.

[0034] (3) Material line control

[0035] To increase the air permeability of the material column inside the furnace, the material line should be controlled at 2.5m-3.0m after the ventilation is stopped.

[0036] (4) Reduce the amount of nitrogen used for cooling wall maintenance and lower the furnace pressure.

[0037] In the later stages of furnace operation, the number of damaged tubes on the furnace cooling wall gradually increases. Some of the damaged tubes are maintained with medium-pressure nitrogen. After the furnace is shut down, the maintenance nitrogen is turned off in time to reduce the pressure inside the furnace.

[0038] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for eliminating tuyeres flameout after shutdown of a large blast furnace with high pressure differential, characterized in that, include: (1) Rapidly reduce blast during the early stage of blast furnace shutdown, promptly stop coal and oxygen production, and reduce furnace pressure. In the early stage of blast furnace shutdown and blast reduction, rapid blast reduction and timely shutdown of coal and oxygen can quickly reduce the blast volume in the blast furnace, thereby reducing the intensity of the combustion reaction. (2) Furnace top pressure control In the early stage of blast furnace shutdown, the pressure at the top of the furnace is reduced rapidly to effectively alleviate the overall pressure level inside the furnace and avoid high gas pressure differential caused by excessive pressure. At the same time, it creates safe and stable conditions for subsequent shutdown operations and ensures that the shutdown process proceeds smoothly and orderly. (3) Material line control To increase the air permeability of the charge column inside the furnace, the charge height should be controlled at 2.5m-3.0m after the furnace is shut down. (4) Reduce furnace pressure In the later stages of furnace operation, the number of damaged tubes on the furnace cooling wall gradually increases. Some of the damaged tubes are maintained with medium-pressure nitrogen. After the furnace is shut down, the maintenance nitrogen is turned off in time to reduce the pressure inside the furnace.

2. The method for eliminating tuyeres fire after shutdown of a large blast furnace with high pressure differential, as described in claim 1, is characterized in that... Starting from the reduction of airflow, within 15 minutes, the airflow should be reduced to 68-72% of the full airflow, with an air volume of 4400-4600 m³ / h. 3 / min.

3. The method for eliminating tuyeres fire after shutdown of a large high-pressure differential blast furnace according to claim 1, characterized in that, Within 10 minutes of reducing the airflow, the air volume reached 4800-5200 m³ / h. 3 / min, stop coal and oxygen.

4. The method for eliminating tuyeres fire after shutdown of a large blast furnace with high pressure differential, as described in claim 1, is characterized in that... The top pressure should be reduced to 20% of the full top pressure within 30 minutes.

5. The method for eliminating tuyeres fire after shutdown of a large high-pressure differential blast furnace according to claim 1, characterized in that, Within 35 minutes of reducing the airflow, the air volume reaches 2500-2700 m³ / h. 3 / min, change to normal pressure.

6. The method for eliminating tuyeres fire after shutdown of a large high-pressure differential blast furnace according to claim 1, characterized in that, The material conveyor line is controlled at 2.5m.

7. The method for eliminating tuyeres fire after shutdown of a large high-pressure differential blast furnace according to claim 1, characterized in that, The material conveyor line is controlled at 2.8m.

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