A cooling method for furnace repair and shutdown of a super large blast furnace

Abstract

A cooling method for super-large blast furnaces during maintenance shutdowns involves intermittently spraying water from cross-shaped temperature measuring holes and tuyere water guns inserted into the tuyere outlets after the furnace is shut down. The water spraying method is monitored and controlled in stages to effectively cool the remaining coke surface in the hearth. Throughout the process, the water volume is rationally controlled based on a series of collected parameters, including gas temperature, gas concentration, and coke surface temperature. The installed water guns and tuyere water guns have atomizing spraying functions, working in conjunction with pre-set top water guns to spray water onto the coke surface in the center of the hearth for cooling. This invention implements intermittent water spraying cooling by collecting multiple parameters. This invention not only achieves coke cooling, creating safe working conditions for furnace construction, but also avoids damage to the carbon bricks caused by excessive water contact with the cooling water. Furthermore, it creates favorable conditions for cleaning broken coke from the hearth before furnace restart.

Description

Technical Field

[0001] This invention relates to the field of iron and steel metallurgical equipment repair and maintenance, and particularly to a system applicable to equipment with an effective volume of 5000m³. 3 Cooling methods for extra-large blast furnaces during mid-term maintenance shutdowns. Background Technology

[0002] Currently, in the production process of iron and steel metallurgy, certain complex maintenance tasks that cannot be handled during regular maintenance, such as repairing or replacing furnace linings / walls, replacing upper coolers, replacing material feeders, and replacing hoisting rope pulleys, are called intermediate maintenance. Intermediate maintenance is a necessary measure to restore and improve blast furnace production capacity, improve technical condition, and update main and auxiliary equipment.

[0003] Blast furnaces undergoing intermediate repairs require shutdown operations, especially those preparing to replace cooling walls or the furnace body. The first step is to shut down the blast furnace by lowering the burden line. However, after shutdown, the temperature of the residual coke inside the furnace exceeds 750°C, and the combustion of coke releases toxic carbon monoxide gas. At this time, personnel cannot carry out construction work to replace the cooling facilities of the blast furnace body. Therefore, temperature isolation or cooling treatment must be carried out first.

[0004] To protect the carbon bricks in the hearth and bottom of the blast furnace, the water-cooling method used during major overhaul shutdowns cannot be adopted during intermediate repairs. The main existing method is to spray a covering agent to isolate temperature and gas. The advantage of this method is that it can continuously keep the coke in the hearth at a red-hot state, but its disadvantages are also quite obvious, as follows:

[0005] 1. Although the temperature after isolation can meet the construction conditions, the gas concentration still exceeds 50 PPM, which affects the safety of the workers;

[0006] 2. When cleaning the covering agent, the partially exposed coke after partial cleaning will cause the ambient temperature to rise instantly, exceeding the normal temperature. Under the influence of the high concentration of escaping gas, it is very difficult to clean the covering agent and coke in the hearth before restarting the furnace. As a result, the covering agent cannot be completely cleaned and some seeps into the hearth, resulting in a high alumina content in the slag when the furnace is restarted, and the viscosity of the slag increases, affecting the fluidity of the slag.

[0007] 3. The red-hot coke is basically impossible to clean up. When the furnace is shut down, the remaining coke fragments will cover the entire area from the bottom of the hearth to the tuyeres. This makes it easy to block the taphole when slag and iron are discharged during the start-up process. At the same time, it affects the permeability of the hearth after the furnace is started up, reduces the activity of the hearth, and makes it easy to generate molten iron circulation, which leads to mechanical erosion of the hearth sidewalls by the molten iron.

[0008] Existing technologies have also made considerable efforts, such as the method for replacing the cooling wall of a blast furnace as disclosed in publication (announcement) number CN105420432A. This patent mainly describes a method for replacing the cooling wall without entering the blast furnace, which uses external cutting, replacement, and welding methods, but does not involve specific methods for cooling the furnace in extra-large blast furnaces.

[0009] The announcement (publication number) CN106282450A describes an automatic control device and method for cooling water level in blast furnaces to protect carbon bricks in the furnace body. It adopts a combination of several water level monitoring devices and a controller. Its main purpose is to control the water level during blast furnace cooling. This scheme is not applicable to extra-large blast furnaces, nor does it belong to the specific methods for cooling blast furnaces during maintenance. Summary of the Invention

[0010] In summary, since water cooling of the hearth is not suitable for blast furnace overhauls, and the use of covering agents has many drawbacks, and existing technologies lack specific methods for cooling down extra-large blast furnaces during overhauls, this invention addresses these shortcomings by providing a cooling method for extra-large blast furnaces during overhaul shutdowns. The specific steps are as follows:

[0011] A method for cooling a blast furnace during maintenance shutdown of an extra-large blast furnace includes the blast furnace to be cooled and eight pre-installed water jets on the furnace top. The specific steps are as follows:

[0012] 1) Confirm the condition of the blast furnace to be cooled, including:

[0013] 1.1) When the material line is lowered to the tuyeres, the empty material line operation ends, the blast furnace stops blowing air, that is, the blast furnace stops production;

[0014] 1.2) Confirm the blast furnace status after shutdown as follows: Steam is introduced into the furnace throat, water pumping at the furnace top is stopped, the hot air vent valve and related valves of the gas cleaning system are closed to prevent gas from passing through, and the furnace top vent valve is fully open, and safety nitrogen continues to be introduced into the furnace.

[0015] 1.3) Conduct a thorough inspection of the furnace cooling wall to confirm whether there are any leaks. If so, shut off the water supply.

[0016] 1.4) Confirm that the furnace top thermal imaging device or the material surface detection camera is functioning normally. This detection camera function is used to monitor the open flame on the material surface inside the furnace and assist in controlling the amount and rhythm of water spraying during the subsequent furnace cooling process.

[0017] 2) Preparations before cooling the furnace by sprinkling water:

[0018] 2.1) CO < 30 mg / m³ was detected at the gas detection points of the furnace top riser pipe and gravity dust collector. 3 ;

[0019] 2.2) When the temperature of the gas at the furnace top is <200℃ and the furnace is under negative pressure, shut off the steam at the furnace top and control the flow rate of the safety nitrogen in the furnace to 5000m³. 3 / min, and open the large manhole on the top of the furnace;

[0020] 2.3) When the furnace is under negative pressure in step 2.2), disassemble the direct blow pipe and perform blind flange sealing. The blind flange sealing is performed from two opposing directions, and the number of tuyeres with blind flanges inserted at the same time is controlled to be 3 to 5.

[0021] 2.4) After the large manhole in step 2.2) above is opened, stop the nitrogen gas supply to the furnace body, and arrange 4 water spray guns at 90° intervals at the cross temperature measuring hole position. Among them, the 2 water spray guns arranged at 180° opposite each other form a group.

[0022] 2.5) After the direct blowing pipe is disassembled, the tuyeres are disassembled one by one, and the air intake of the tuyeres is increased. At intervals of 6 to 8 tuyeres, each tuyere is equipped with a water gun, which is inserted into the material surface inside the furnace.

[0023] It should be noted that the number of water guns at the air vents can be increased to 12 depending on the actual situation.

[0024] 2.6) Select the taphole and 2-4 tuyeres where water guns are not installed. Install the furnace cooling detection thermocouples at these locations. Insert the front end of the thermocouple into the top of the material surface inside the furnace and connect the thermocouple monitoring data to the computer in the control room for monitoring. This step tracks the change trend of the material surface temperature during the furnace cooling stage and accurately grasps the actual effect of the furnace cooling process.

[0025] 3) After completing the preparatory work in step 2), begin the furnace cooling process by spraying water. The total amount of water required is determined based on the latent heat of the residual coke in the furnace hearth, and the calculation formula is as follows:

[0026]

[0027] In the formula: c coke V coke γ coke These represent the specific heat capacity, volume, and specific gravity of coke, respectively; t w This represents the water temperature;

[0028] In this step, water spraying is intermittent, and nitrogen gas is introduced into the furnace during the spraying process to control the water flow rate and timing. Specifically, it is divided into three stages: initial spraying, middle spraying, and later spraying. The control standards for the water spraying volume in each stage are determined by controlling the composition of the gas at the furnace top and the thermocouple temperature on the material surface.

[0029] Initial watering stage: H2 < 6%, O2 < 0.6%; Mid-watering stage: H2 around 30%, O2 < 0.4%; Late watering stage: H2 < 4%, O2 < 0.6%.

[0030] It should be noted that in this step, it is necessary to ensure that the water sprayed into the furnace reaches the center of the furnace hearth for cooling and rapid steam evaporation, to prevent water from seeping in from the edge of the furnace hearth and damaging the furnace hearth refractory.

[0031] 4) Determine whether the water spraying cooling furnace cooling process is complete. Specifically, if the temperature of the thermocouple installed at the taphole drops to less than 60°C for 3-4 consecutive hours, and the material surface temperature is about 50°C, then stop the cooling furnace cooling process if the conditions are met. If the conditions are not met, continue the water spraying process until the conditions are met.

[0032] According to the present invention, a cooling method for a super-large blast furnace during maintenance and shutdown is characterized in that, in step 2.1), the furnace is maintained at full flow of safety nitrogen for purging and dilution cooling for 1 hour, and when the hydrogen content in the furnace top gas is <2%, the tuyere sight glass valve and the tuyere cover are gradually opened to ensure air intake at the tuyere.

[0033] According to a method for cooling a blast furnace during maintenance and shutdown of an extra-large blast furnace, the present invention is characterized in that, in step 2.5), in order to increase the air intake at the tuyeres and enhance the effect of tuyer exhaust cooling to displace the furnace heat from the burden surface during the cooling stage, 18 to 20 axial flow fans are installed in the tuyeres area to cool the furnace as natural ventilation.

[0034] According to the present invention, a cooling method for a super-large blast furnace during maintenance and shutdown is characterized in that the specific operation of the initial water spraying in step 3) is as follows:

[0035] First, activate one set of two water spray guns (arranged 180° opposite each other) from the four water spray guns installed at the cross temperature measuring hole in step 2.4) to spray water in a rain-like pattern to cool the highest temperature area on the upper part of the central pile tip. After spraying for 5 minutes, pause and wait for another 5 minutes. When confirming that the hydrogen content in the furnace top gas is <3%, activate the other set of two water spray guns (also arranged 180° opposite each other). Repeat this process, cyclically activating these two pairs of water spray guns. In other words, by switching between the two sets of water spray guns, the water cooling covers the upper 360° circumference of the central pile tip. The initial water volume required in this step accounts for approximately 12-15% of the total water volume. Throughout the initial water spraying process, it is necessary to constantly monitor the changes in the hydrogen content in the furnace top gas and the changes in the material surface temperature, controlling H2 <6% and O2 <0.6%.

[0036] According to the present invention, a cooling method for a super-large blast furnace during maintenance and shutdown is characterized in that the specific operation of the water spraying in step 3) is as follows:

[0037] After the initial cooling process of water spraying, once the thermocouple temperature on the material surface drops below 100℃, the middle stage of water spraying begins. In this stage, in addition to the water spray guns installed with cross-shaped temperature measuring holes, eight furnace top water spray guns, evenly spaced in four directions and pre-installed on the furnace top, are also needed. First, two furnace top water spray guns in one direction are used for spraying for 5 minutes, then pause for 5 minutes, and then the other two furnace top water spray guns in the other direction are used, and so on in a cyclical manner. The water volume required in the middle stage of water spraying accounts for about 70-75% of the total water volume. The duration of water spraying is measured by whether there is obvious steam coming out of the tuyeres and tapholes, whether the dynamic changes in hydrogen content on the furnace top are safe, and the temperature of the material surface. Specifically, if steam is coming out of the tapholes or the thermocouple temperature on the material surface is <75℃, the amount of water sprayed and the spraying rhythm need to be reduced to prevent excessive water from seeping into the carbon bricks of the hearth before it can evaporate.

[0038] According to the present invention, a method for cooling a super-large blast furnace during maintenance and shutdown is characterized in that the specific operation in the later stage of water spraying in step 3) is as follows:

[0039] After the mid-stage cooling process, once the steam volume decreases and the coke surface thermocouple temperature remains below 65°C for 5 hours, the late stage of water spraying begins. In this step, the water spray guns used in the early and mid-stages of water spraying, as well as the furnace top water spray guns used in the mid-stage, are turned off. Instead, the tuyere water spray guns configured in step 2.5) are used for water spraying and cooling. After turning them on for 5 minutes, they are paused. When the coke surface temperature rises again to ≥65°C, the water spray guns configured with cross-shaped temperature measuring holes and the furnace top water spray guns are switched back to water spraying and cooling. This process is repeated in a cycle until step 4) is met. The water volume required in the late stage of water spraying in this step accounts for approximately 10-15% of the total water volume.

[0040] The present invention provides a furnace cooling method for shutdown during overhaul of an extra-large blast furnace, the main idea of ​​which can be summarized as follows:

[0041] After the shutdown of the extra-large blast furnace, water is intermittently sprayed / sprayed through the water guns installed at the cross-shaped temperature measuring holes and the water guns inserted from the tuyere, and the water spraying method is monitored and controlled in stages to effectively cool the surface of the remaining coke in the hearth. Throughout the process, the water volume is reasonably controlled based on a series of collected parameters such as gas temperature, gas composition concentration, and surface temperature. The installed water guns and tuyere water guns have atomizing water spraying function, which, together with the preset furnace top water guns, spray / spray water to cool the coke surface in the center of the hearth.

[0042] The following beneficial effects were obtained by using the furnace cooling method of the present invention for shutdown and repair during the maintenance of an extra-large blast furnace:

[0043] 1. A method for cooling a super-large blast furnace during maintenance shutdown, which involves intermittent water spraying for cooling by collecting multiple parameters;

[0044] 2. The present invention provides a cooling method for a super-large blast furnace during maintenance and shutdown. This method can not only cool the coke and create working conditions for safe furnace construction, but also avoid damage to the carbon bricks caused by excessive water contact between the cooling water and the carbon bricks in the hearth. Furthermore, it can create favorable conditions for cleaning the broken coke in the hearth before starting the furnace. Attached Figure Description

[0045] Figure 1 This is a schematic diagram of the furnace top water spray gun of the present invention, which is used in a furnace cooling method for shutdown during maintenance of an extra-large blast furnace.

[0046] Figure 2 This is a schematic diagram of a water spray gun with a cross-shaped temperature measuring hole, which is used in a cooling method for a super-large blast furnace during maintenance and shutdown according to the present invention. Detailed Implementation

[0047] The following description, in conjunction with the accompanying drawings and embodiments, further describes the technical means, creative features, objectives, and effects of a cooling method for a super-large blast furnace during maintenance and shutdown.

[0048] Example

[0049] A method for cooling a blast furnace during maintenance shutdown of an extra-large blast furnace includes the blast furnace to be cooled and eight pre-installed water jets on the furnace top (such as...). Figure 1 As shown in the figure, the specific steps are as follows:

[0050] 1) Confirm the condition of the blast furnace to be cooled, including:

[0051] 1.1) When the material line is lowered to the tuyeres, the empty material line operation ends, the blast furnace stops blowing air, that is, the blast furnace stops production;

[0052] 1.2) Confirm the blast furnace status after shutdown as follows: Steam is introduced into the furnace throat, water pumping at the furnace top is stopped, the hot air vent valve and related valves of the gas cleaning system are closed to prevent gas from passing through, and the furnace top vent valve is fully open, and safety nitrogen continues to be introduced into the furnace.

[0053] 1.3) Conduct a thorough inspection of the furnace cooling wall to confirm whether there are any leaks. If so, shut off the water supply.

[0054] 1.4) Confirm that the furnace top thermal imaging device or the material surface detection camera is functioning normally. This detection camera function is used to monitor the open flame on the material surface inside the furnace and assist in controlling the amount and rhythm of water spraying during the subsequent furnace cooling process.

[0055] 2) Preparations before cooling the furnace by sprinkling water:

[0056] 2.1) CO < 30 mg / m³ was detected at the gas detection points of the furnace top riser pipe and gravity dust collector. 3 ;

[0057] 2.2) When the temperature of the gas at the furnace top is <200℃ and the furnace is under negative pressure, shut off the steam at the furnace top and control the flow rate of the safety nitrogen in the furnace to 5000m³. 3 / min, and open the large manhole on the top of the furnace;

[0058] 2.3) When the furnace is under negative pressure in step 2.2), disassemble the direct blow pipe and perform blind flange sealing. The blind flange sealing is performed from two opposing directions, and the number of tuyeres with blind flanges inserted at the same time is controlled to be 3 to 5.

[0059] 2.4) After the large manhole in step 2.2) above is opened, stop the nitrogen gas supply to the furnace body, and arrange 4 water spray guns at 90° intervals at the cross temperature measuring hole position. Among them, the 2 water spray guns arranged at 180° opposite each other form a group.

[0060] 2.5) After the direct blowing pipe is disassembled, the tuyeres are disassembled one by one, and the air intake of the tuyeres is increased. At intervals of 6 to 8 tuyeres, each tuyere is equipped with a water gun, which is inserted into the material surface inside the furnace.

[0061] 2.6) Select the taphole and 2-4 tuyeres where water guns are not installed. Install the furnace cooling detection thermocouples at these locations. Insert the front end of the thermocouple into the top of the material surface inside the furnace and connect the thermocouple monitoring data to the computer in the control room for monitoring. This step tracks the change trend of the material surface temperature during the furnace cooling stage and accurately grasps the actual effect of the furnace cooling process.

[0062] 3) After completing the preparatory work in step 2), begin the furnace cooling process by spraying water. The total amount of water required is determined based on the latent heat of the residual coke in the furnace hearth, and the calculation formula is as follows:

[0063]

[0064] In the formula: c coke V coke γ coke These represent the specific heat capacity, volume, and specific gravity of coke, respectively; t w This represents the water temperature;

[0065] In this step, water spraying is intermittent, and nitrogen gas is introduced into the furnace during the spraying process to control the water flow rate and timing. Specifically, it is divided into three stages: initial spraying, middle spraying, and later spraying. The control standards for the water spraying volume in each stage are determined by controlling the composition of the gas at the furnace top and the thermocouple temperature on the material surface.

[0066] Initial watering stage: H2 < 6%, O2 < 0.6%; Mid-watering stage: H2 around 30%, O2 < 0.4%; Late watering stage: H2 < 4%, O2 < 0.6%.

[0067] 4) Determine whether the water spraying cooling furnace cooling process is complete. Specifically, if the temperature of the thermocouple installed at the taphole drops to less than 60°C for 3-4 consecutive hours, and the material surface temperature is about 50°C, then stop the cooling furnace cooling process if the conditions are met. If the conditions are not met, continue the water spraying process until the conditions are met.

[0068] In step 2.1), the furnace is purged and diluted with full flow of safety nitrogen for 1 hour. When the hydrogen content in the gas at the top of the furnace is less than 2%, the tuyere sight glass valve and the tuyere cover are gradually opened to ensure air intake at the tuyere.

[0069] In step 2.5), in order to increase the air intake at the tuyeres and enhance the effect of tuyer exhaust cooling to displace the furnace heat on the material surface during the cooling stage, 18 to 20 axial flow fans are installed in the tuyer area to cool the furnace through natural ventilation.

[0070] The specific operation for the initial watering in step 3) is as follows:

[0071] First, activate one set of two water spray guns (arranged 180° opposite each other) from the four water spray guns installed at the cross temperature measuring hole in step 2.4) to spray water in a rain-like pattern to cool the highest temperature area on the upper part of the central pile tip. After spraying for 5 minutes, pause and wait for another 5 minutes. When confirming that the hydrogen content in the furnace top gas is <3%, activate the other set of two water spray guns (also arranged 180° opposite each other). Repeat this process, cyclically activating these two pairs of water spray guns. In other words, by switching between the two sets of water spray guns, the water cooling covers the upper 360° circumference of the central pile tip. The initial water volume required in this step accounts for approximately 12-15% of the total water volume. Throughout the initial water spraying process, it is necessary to constantly monitor the changes in the hydrogen content in the furnace top gas and the changes in the material surface temperature, controlling H2 <6% and O2 <0.6%.

[0072] The specific operations during the middle stage of watering in step 3) are as follows:

[0073] After the initial cooling process of water spraying, once the thermocouple temperature on the material surface drops below 100℃, the middle stage of water spraying begins. In this stage, in addition to the water spray guns installed with cross-shaped temperature measuring holes, eight furnace top water spray guns, evenly spaced in four directions and pre-installed on the furnace top, are also needed. First, two furnace top water spray guns in one direction are used for spraying for 5 minutes, then pause for 5 minutes, and then the other two furnace top water spray guns in the other direction are used, and so on in a cyclical manner. The water volume required in the middle stage of water spraying accounts for about 70-75% of the total water volume. The duration of water spraying is measured by whether there is obvious steam coming out of the tuyeres and tapholes, whether the dynamic changes in hydrogen content on the furnace top are safe, and the temperature of the material surface. Specifically, if steam is coming out of the tapholes or the thermocouple temperature on the material surface is <75℃, the amount of water sprayed and the spraying rhythm need to be reduced to prevent excessive water from seeping into the carbon bricks of the hearth before it can evaporate.

[0074] The specific operations in the later stage of watering in step 3) are as follows:

[0075] After the mid-stage cooling with water spraying, once the steam volume decreases and the thermocouple temperature on the coke surface remains below 65°C for 5 hours, the late stage of water spraying begins. In this step, the water spraying guns used in the early and mid-stages of water spraying, as well as the furnace top water spraying guns used in the mid-stages, are turned off. Instead, the water spraying guns configured at the tuyere in step 2.5) are used for water spraying and cooling. After turning them on for 5 minutes, they are paused. When the coke surface temperature rises again to ≥65°C, the water spraying guns configured with the cross-shaped temperature measuring holes and the furnace top water spraying guns are switched back to water spraying and cooling. This process is repeated until the conditions for ending the water spraying and cooling furnace in step 4) are met. The water volume required in the late stage of water spraying in this step accounts for approximately 10-15% of the total water volume.

[0076] This invention discloses a cooling method for a super-large blast furnace during maintenance and shutdown. This method involves intermittent water spraying for cooling by collecting multiple parameters. Furthermore, this method not only cools the coke, creating safe working conditions for furnace construction, but also prevents damage to the carbon bricks caused by excessive water flow due to contact between the cooling water and the hearth. Additionally, it creates favorable conditions for cleaning broken coke from the hearth before furnace restart.

[0077] The present invention provides a furnace cooling method for shutdown and repair of extra-large blast furnaces, applicable to the field of blast furnace maintenance in iron and steel metallurgical equipment.

[0078] Furthermore, those skilled in the art should recognize that the above embodiments are merely illustrative of this application and are not intended to limit this application. Any variations or modifications to the above embodiments that fall within the scope of the essential spirit of this application will fall within the scope of the claims of this application.

Claims

1. A method for cooling a blast furnace during maintenance shutdown of an extra-large blast furnace, comprising the blast furnace to be cooled and eight pre-installed water jets on the furnace top, the specific steps of which are as follows: 1) Confirm the condition of the blast furnace to be cooled, including: (1.1) When the material line is lowered to the tuyere, the empty material line operation ends, the blast furnace stops blowing air, that is, the blast furnace stops production; (1.2) Confirm the blast furnace status after shutdown as follows: steam is introduced into the furnace throat, water pumping at the furnace top is stopped, the hot air vent valve and related valves of the gas cleaning system are closed to prevent gas from passing through, the furnace top vent valve is fully open, and safety nitrogen continues to be introduced into the furnace. (1.3) Conduct a thorough inspection of the furnace cooling wall to confirm whether there is any water leakage. If so, cut off the water supply. (1.4) Confirm that the furnace top thermal imager or the material surface detection camera function is normal. This detection camera function is used to monitor the open flame on the material surface inside the furnace and assist in the control of the amount and rhythm of water spraying during the subsequent furnace cooling process. 2) Preparations before cooling the furnace by sprinkling water: (2.1) CO < 30 mg / m³ was detected at the gas detection points of the furnace top riser pipe and gravity dust collector. 3 ; (2.2) When the temperature of the gas at the top of the furnace is <200℃ and the furnace is under negative pressure, shut off the steam at the top of the furnace and control the flow rate of the safety nitrogen in the furnace to 5000m³. 3 / min, and open the large manhole on the top of the furnace; (2.3) When the furnace is under negative pressure in step 2.2), the direct blow pipe is disassembled and the blind plate is sealed. The blind plate sealing operation is carried out from two opposing directions, and the number of tuyeres with blind plates inserted at the same time is controlled to be 3 to 5. (2.4) After the large manhole in step 2.2) above is opened, stop the nitrogen gas supply to the furnace body, and arrange 4 water spray guns at 90° intervals at the cross temperature measuring hole position. Among them, the 2 water spray guns arranged at 180° opposite each other form a group. (2.5) After the direct blowing pipe is disassembled, the tuyeres are disassembled one by one, and the air intake of the tuyeres is increased. At intervals of 6 to 8 tuyeres, each tuyere is equipped with a water gun, which is inserted into the material surface inside the furnace. (2.6) Select the taphole and 2 to 4 tuyeres where water guns are not installed. Install the furnace cooling detection thermocouples at these locations. Insert the front end of the thermocouple into the top of the material surface inside the furnace and connect the thermocouple monitoring data to the computer in the control room for monitoring. This step tracks the trend of the material surface temperature drop during the furnace cooling stage and accurately grasps the actual effect of the furnace cooling process. 3) After completing the preparatory work in step 2), begin the water spraying and cooling process. The total amount of water required is determined based on the latent heat of the residual coke in the hearth, and the calculation formula is as follows: In the formula: c coke V coke γ coke These represent the specific heat capacity, volume, and specific gravity of coke, respectively; t w This represents the water temperature; In this step, water spraying is intermittent, and nitrogen gas is introduced into the furnace during the spraying process to control the water flow rate and timing. Specifically, it is divided into three stages: initial spraying, middle spraying, and later spraying. The control standards for the water spraying volume in each stage are determined by controlling the composition of the gas at the furnace top and the thermocouple temperature on the material surface. Initial watering stage: H2 < 6%, O2 < 0.6%; Mid-watering stage: H2 around 30%, O2 < 0.4%; Late watering stage: H2 < 4%, O2 < 0.6%. 4) Determine whether the water spraying cooling furnace cooling process is complete. Specifically, if the temperature of the thermocouple installed at the taphole drops to less than 60°C for 3-4 consecutive hours, and the material surface temperature is about 50°C, then stop the cooling furnace cooling process if the conditions are met. If the conditions are not met, continue the water spraying process until the conditions are met.

2. The furnace cooling method for shutdown during overhaul of an extra-large blast furnace as described in claim 1, characterized in that, In step 2.1), the furnace is purged and diluted with full flow of safety nitrogen for 1 hour, and when the hydrogen content in the furnace top gas is <2%, the tuyere sight glass valve and tuyere cover are gradually opened to ensure air intake.

3. The furnace cooling method for shutdown during overhaul of an extra-large blast furnace as described in claim 1, characterized in that, In step 2.5), in order to increase the air intake of the tuyere and enhance the effect of tuyere exhaust cooling to displace the furnace heat of the material surface during the cooling stage, 18 to 20 axial flow fans are set in the tuyere area to cool the furnace through natural ventilation.

4. The furnace cooling method for shutdown during overhaul of an extra-large blast furnace as described in claim 1, characterized in that, The specific operation of the initial watering stage in step 3) is as follows: First, activate one set of two water spray guns (arranged 180° opposite each other) from the four water spray guns installed at the cross temperature measuring hole in step 2.4) to spray water in a rain-like pattern to cool the highest temperature area on the upper part of the central pile tip. After spraying for 5 minutes, pause and wait for another 5 minutes. When confirming that the hydrogen content in the furnace top gas is <3%, activate the other set of two water spray guns (also arranged 180° opposite each other). Repeat this process, cyclically activating these two pairs of water spray guns. In other words, by switching between the two sets of water spray guns, the water cooling covers the upper 360° circumference of the central pile tip. The initial water volume required in this step accounts for approximately 12-15% of the total water volume. Throughout the initial water spraying process, it is necessary to constantly monitor the changes in the hydrogen content in the furnace top gas and the changes in the material surface temperature, controlling H2 <6% and O2 <0.6%.

5. The method for cooling a blast furnace during maintenance shutdown of an extra-large blast furnace as described in claim 1, characterized in that, The specific operation during the watering process in step 3) is as follows: After the initial cooling process of water spraying, once the thermocouple temperature on the material surface drops below 100℃, the middle stage of water spraying begins. In this stage, in addition to the water spray guns installed with cross-shaped temperature measuring holes, eight furnace top water spray guns, evenly spaced in four directions and pre-installed on the furnace top, are also needed. First, two furnace top water spray guns in one direction are used for spraying for 5 minutes, then pause for 5 minutes, and then the other two furnace top water spray guns in the other direction are used, and so on in a cyclical manner. The water volume required in the middle stage of water spraying accounts for about 70-75% of the total water volume. The duration of water spraying is measured by whether there is obvious steam coming out of the tuyeres and tapholes, whether the dynamic changes in hydrogen content on the furnace top are safe, and the temperature of the material surface. Specifically, if steam is coming out of the tapholes or the thermocouple temperature on the material surface is <75℃, the amount of water sprayed and the spraying rhythm need to be reduced to prevent excessive water from seeping into the carbon bricks of the hearth before it can evaporate.

6. The furnace cooling method for shutdown during overhaul of an extra-large blast furnace as described in claim 1, characterized in that, The specific operations in the later stage of watering in step 3) are as follows: After the mid-stage cooling with water spraying, once the steam volume decreases and the thermocouple temperature on the coke surface remains below 65°C for 5 hours, the late stage of water spraying begins. In this step, the water spraying guns used in the early and mid-stages of water spraying, as well as the furnace top water spraying guns used in the mid-stages, are turned off. Instead, the water spraying guns configured at the tuyere in step 2.5) are used for water spraying and cooling. After turning them on for 5 minutes, they are paused. When the coke surface temperature rises again to ≥65°C, the water spraying guns configured with the cross-shaped temperature measuring holes and the furnace top water spraying guns are switched back to water spraying and cooling. This process is repeated until the conditions for ending the water spraying and cooling furnace in step 4) are met. The water volume required in the late stage of water spraying in this step accounts for approximately 10-15% of the total water volume.

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