Hot blast stove using natural draft, preheating stove heat preservation system and its regulation method

Abstract

The application provides a hot blast furnace, a preheating furnace heat preservation system and a regulation method thereof, and belongs to the technical field of blast furnace ironmaking equipment maintenance in the metallurgical industry. The system comprises a hot blast furnace body, a large-diameter flue valve, a first temperature sensor, a second temperature sensor and a controller. The flue of the hot blast furnace body is communicated with a chimney, and the upward branch pipeline of the hot blast pipeline is communicated with a backflow cooling valve. The large-diameter flue valve is arranged on the flue, and the flow area thereof is larger than that of the exhaust branch pipe. Cold air is driven into the flue by the chimney natural draft. The controller obtains the lower and upper temperatures, calculates the deviation and outputs the opening degree instruction for regulating the large-diameter flue valve through PID operation, so that the cold air flows through the lower low-temperature zone and the upper high-temperature zone in sequence and is discharged to the atmosphere, and the lower temperature is not higher than the upper limit, and the upper temperature is not lower than the lower limit. The application does not need external power, has good energy-saving effect, can cooperatively control the lower and upper temperatures of the hot blast furnace body and avoids equipment damage.

Description

Technical Field

[0001] This application belongs to the technical field of blast furnace ironmaking equipment maintenance in the metallurgical industry, specifically relating to a hot blast stove and preheating furnace insulation system utilizing natural suction and its control method. Background Technology

[0002] The blast furnace hot blast stove is a key heating device in the ironmaking system. Its main function is to heat the cold air delivered by the blower to above 1200°C before feeding it into the blast furnace. Currently, the upper part of large high-temperature hot blast stoves is generally constructed with silica bricks, which have good high-temperature volume stability and high thermal conductivity, while the lower part mostly uses ordinary high-alumina bricks and cast iron grates and support structures.

[0003] The silica bricks in the upper part of the blast furnace hot blast stove are prone to crystal transformation and cracking in the 200-600℃ range, requiring the dome temperature to be maintained at ≥700℃. The lower cast iron grate and support columns have a temperature resistance limit of only 350-400℃, and will melt and collapse if overheated. During long-term heat preservation, the latent heat in the upper part is conducted downwards, creating a technical contradiction that requires cooling in the lower part and heat preservation in the upper part.

[0004] To address the aforementioned contradictions, existing technologies employ a natural convection method using a fly-through pipe. This involves cutting a hole in the exhaust branch pipe of the hot blast stove to connect with the atmosphere, serving as a cold air inlet. The connection between the exhaust branch pipe and the main flue is then sealed. The natural draft of the chimney drives the cold air into the furnace through this opening, flowing through the lower part and exiting through a backflow valve at the top, achieving zero-energy cooling. While this method requires no external power, it has inherent drawbacks: First, it requires cutting the exhaust pipe and sealing the flue with blind flanges, a destructive physical modification that necessitates restoration upon resuming production, making the operation cumbersome. Second, the exhaust branch pipe diameter is typically only DN400-DN600, resulting in a small cross-sectional area and extremely low airflow under natural draft, leading to slow temperature control response and difficulty in handling emergency overheating at the lower part. Furthermore, existing technologies also employ forced ventilation using combustion fans, where a high-powered fan is used to force cold air into the cold air duct for forced cooling. This method is extremely energy-intensive, and the fan is prone to surge under backflow conditions, posing a significant safety hazard.

[0005] In summary, none of the above methods effectively resolved the contradiction between the need for cooling at the bottom and insulation at the top. Therefore, there is an urgent need for a hot blast stove insulation system and control method that does not rely on external power, does not damage the equipment structure, and can simultaneously achieve coordinated temperature control of both the top and bottom parts. Summary of the Invention

[0006] In a first aspect, embodiments of this application provide a hot air furnace insulation system utilizing natural draft, including a hot air furnace body, a large-diameter flue valve, a first temperature sensor, a second temperature sensor, and a controller; The interior of the hot blast stove body is divided into an upper high-temperature working zone and a lower low-temperature tolerance zone from top to bottom; The hot blast stove body is connected to a flue and a hot air pipe. The flue is connected to a chimney. The hot air pipe is connected to a backflow shut-off valve through an upward branch pipe. The backflow shut-off valve is located at the end of the branch pipe. A hot air valve is provided on the hot air pipe between the hot blast stove body and the branch pipe. A large-diameter flue valve is installed on the flue. The flow cross-sectional area of ​​the large-diameter flue valve is larger than the flow cross-sectional area of ​​the original exhaust gas branch pipe of the hot blast stove, so as to use the natural draft of the chimney to drive the cooling air into the flue. The first temperature sensor is located in the lower low-temperature tolerance zone and is used to detect the temperature of the lower part of the hot air furnace body; The second temperature sensor is located in the upper high-temperature working area and is used to detect the temperature of the upper part of the hot air furnace body. The controller is connected to the first temperature sensor, the second temperature sensor, and the large-diameter flue valve. The controller is configured as follows: The system acquires the temperatures of the lower and upper parts of the hot blast stove body, calculates the temperature deviations of the lower and upper parts, and then calculates the overall deviation. Based on the overall deviation, it outputs an opening command through PID calculation to adjust the opening of the large-diameter flue valve, thereby controlling the flow of cold air entering the flue. This allows the cold air to flow sequentially through the lower low-temperature tolerance zone and the upper high-temperature working zone before being discharged to the atmosphere through the hot air duct and the backflow shut-off valve. Ultimately, this ensures that the temperature of the lower part of the hot blast stove body does not exceed the preset upper temperature limit and the temperature of the upper part of the hot blast stove body does not fall below the preset lower temperature limit.

[0007] Furthermore, the nominal diameter of the large-diameter flue valve is DN≥2000mm, and the flow cross-sectional area of ​​the large-diameter flue valve is more than 20 times that of the original exhaust gas branch pipe of the hot blast stove. The first temperature sensor is located at the grate and support column at the bottom of the hot blast stove body, and the second temperature sensor is located at the silicon brick dome at the top of the hot blast stove body.

[0008] Furthermore, it also includes alarms; The alarm is connected to the controller; The controller also has an input terminal that connects to the status detection signal of the hot air valve and the backflow shut-off valve.

[0009] Secondly, this application also provides a preheating furnace insulation system that utilizes natural draft, including a preheating furnace body, a preheating furnace large-diameter flue valve, a third temperature sensor, a fourth temperature sensor, a hot air furnace body, and a controller. The hot air furnace body is connected to hot air ducts and air ducts; The hot air duct is connected to a backflow shut-off valve via an upward branch duct, and the backflow shut-off valve is located at the end of the branch duct; a hot air valve is provided on the hot air duct between the hot air furnace body and the branch duct. The preheating furnace body is divided into an upper high-temperature working zone and a lower low-temperature tolerance zone from top to bottom. The preheating furnace body is connected to the preheating furnace flue and the preheating furnace hot air duct. The preheating furnace flue is connected to the chimney. The preheating furnace hot air duct is detachably connected to the air duct, and the air duct is equipped with a preheating furnace hot air valve. The large-diameter flue valve of the preheating furnace is installed on the flue of the preheating furnace, and the flow cross-sectional area of ​​the large-diameter flue valve of the preheating furnace is larger than the flow cross-sectional area of ​​the original exhaust gas branch pipe of the preheating furnace. The third temperature sensor is located in the low-temperature tolerance zone at the bottom of the preheating furnace body and is used to detect the temperature at the bottom of the preheating furnace body. The fourth temperature sensor is located in the high-temperature working zone at the top of the preheating furnace body and is used to detect the temperature at the top of the preheating furnace body. The controller is connected to the third temperature sensor, the fourth temperature sensor, and the large-diameter flue valve. The controller is configured as follows: The system acquires the temperature of the lower part of the preheating furnace body and the temperature of the upper part of the hot blast stove body, calculates the temperature deviation of the lower part and the temperature deviation of the upper part, and then calculates the comprehensive deviation. Based on the comprehensive deviation, it outputs an opening command through PID calculation to adjust the opening of the large-diameter flue valve of the preheating furnace, thereby controlling the flow rate of cold air entering the flue of the preheating furnace. The cold air flows sequentially through the lower low-temperature tolerance zone and the upper high-temperature working zone, and then exits through the air duct, and finally through the hot air duct of the hot blast stove body and the backflow shut-off valve to the atmosphere. Ultimately, the temperature of the lower part of the preheating furnace hot blast stove body does not exceed the preset upper temperature limit and the temperature of the upper part of the preheating furnace body does not fall below the preset lower temperature limit.

[0010] Thirdly, embodiments of this application also provide a method for controlling the heat preservation of a hot blast stove using the system described in the first aspect, comprising the following steps: S1. Close the combustion air valve, gas valve, cold air valve and exhaust gas valve of the hot blast stove body, and lock the conventional combustion and air supply passages; S2. Open the hot air valve on the hot air duct and the backflow shut-off valve on the branch duct, and then open the large-diameter flue valve on the flue to establish a reverse non-powered thermal circulation path that passes through the flue, the hot air furnace body, the hot air duct, and the backflow shut-off valve to the atmosphere. S3. The controller acquires the temperature of the lower part of the hot air furnace body detected by the first temperature sensor and the temperature of the upper part of the hot air furnace body detected by the second temperature sensor in real time, calculates the temperature deviation of the lower part and the temperature deviation of the upper part, and then calculates the comprehensive deviation. Based on the comprehensive deviation, the controller outputs the opening command through PID calculation to adjust the opening of the large-diameter flue valve. S4. When the temperature of the lower part of the hot blast stove body is not higher than the preset upper temperature limit and the temperature of the upper part of the hot blast stove body is not lower than the preset lower temperature limit, the controller locks the current opening of the large-diameter flue valve in a PID self-optimization mode to maintain the dynamic balance of the hot blast stove body.

[0011] Furthermore, the specific steps of step S2 are as follows: S21. Maintain the connection between the flue and the chimney; S22. Open the hot air valve on the hot air duct and the backflow shut-off valve on the branch duct; S23. After the backflow shut-off valve and hot air valve are fully opened, open the large-diameter flue valve on the flue at the preset rate, so that the ambient cold air flows through the flue, the hot air furnace body and the hot air pipe in sequence under the natural draft of the chimney and is discharged to the atmosphere through the backflow shut-off valve.

[0012] Furthermore, the specific steps of step S3 are as follows: S31. Preset the upper limit of the temperature of the lower part of the hot air furnace body. Lower limit of temperature at the upper part of the hot blast stove body ; S32. The controller acquires the measured temperature of the lower part detected by the first temperature sensor. The measured temperature at the top, detected by the second temperature sensor ; S33. Calculate the lower temperature deviation Calculate the upper temperature deviation ; S34. Based on lower temperature deviation Temperature deviation from the upper part Calculate the overall deviation : ; in, , The weighting coefficients are preset and pre-calibrated based on the volume of the hot blast stove; S35. Based on comprehensive deviation The PID algorithm is used to calculate the change in opening degree during the current control cycle. :

[0013] in, , , These are the preset PID parameters. To control the cycle; S36. Based on the change in opening degree Calculate the target opening:

[0014] in, This indicates the target opening degree for the current control cycle. This indicates the actual opening degree in the previous control cycle; S37. Calculate the target opening degree for the current control cycle. It serves as the actuator for outputting opening commands to large-diameter flue valves.

[0015] Furthermore, step S3 also includes the following multi-mode automatic switching steps: S301. The controller identifies the measured temperature at the bottom of the hot air furnace body. and the measured temperature at the top The current state; when Proceed to step S302; when and Proceed to step S303; when Proceed to step S304; in, The preset rapid cooling trigger temperature difference, The preset lower low-temperature hysteresis temperature difference, The preset upper low temperature warning temperature difference; S302. The controller automatically switches to rapid cooling mode and forces the output to the target opening degree. The corresponding opening command, where, The preset maximum opening threshold; S303. The controller automatically switches to the fine insulation mode, and performs PID control according to steps S31 to S37 to maintain the opening degree. to Between, among them, , These are the upper and lower limits of the preset medium opening range; S304. The controller automatically switches to low-temperature protection mode and forces the output to the target opening degree. The opening command, where, This is the preset small opening threshold.

[0016] Furthermore, it also includes the following safety interlocking steps: S51. The controller monitors the temperature of the lower part of the hot air furnace body, the status signal of the hot air valve, and the status signal of the backflow shut-off valve in real time. The controller will forcibly lock the large-diameter flue valve to prevent it from closing and trigger the alarm when any of the following conditions are met: The lower part temperature is greater than or equal to the preset danger temperature threshold. ; A signal indicating that the hot air valve is not fully open has been received. When a signal indicating that the backflow damper is not fully open is received; S52. When the controller detects that the hot air furnace body has unexpectedly resumed the air supply signal, it automatically cuts off the heat preservation path and fully closes the large-diameter flue valve.

[0017] Furthermore, it also includes the following independent heat preservation steps for the preheating furnace: S61. Locking the conventional combustion and air supply passage of the preheater furnace; S62. Open the large-diameter flue valve, hot air valve of the preheating furnace, and air pipe shut-off valve connecting the preheating furnace and the hot air furnace, and confirm that the hot air valve and backflow shut-off valve on the hot air furnace side are in the open state. S63. Establish an extended reverse non-powered passage from ambient cold air through the preheating furnace flue, preheating furnace body, preheating furnace hot air duct, hot air furnace air duct, hot air furnace body, hot air duct, and backflow shut-off valve before being discharged into the atmosphere. S64. By adjusting the opening of the large-diameter flue valve of the preheating furnace, the flow rate of cold air flowing through the preheating furnace can be independently controlled to achieve zoned and coordinated temperature control of the preheating furnace.

[0018] As can be seen from the above technical solutions, this application has the following advantages: The hot blast stove and preheating furnace insulation system and its control method provided in this application utilize the natural draft of the chimney to drive the circulation of cold air, eliminating the need to turn on external power equipment such as combustion fans, thus reducing energy consumption during maintenance or insulation. By establishing a reverse non-powered thermal circulation path, heat can be removed from the lower low-temperature tolerance zone to prevent the cast iron grate from overheating and melting, while the residual heat of the upper high-temperature working zone can be used to heat the cold air to prevent the silicon brick dome from cracking due to excessively low crystal transformation. The PID automatic adjustment of the large-diameter flue valve opening can dynamically adjust the cold air flow according to the temperature difference between the upper and lower parts, achieving coordinated temperature control and avoiding the lag and instability of manual operation. By setting up a multi-mode automatic switching and safety interlock mechanism, an alarm can be automatically triggered and the passage can be cut off when the valve status is abnormal or unexpected air is supplied, ensuring production safety. Attached Figure Description

[0019] To more clearly illustrate the technical solution of this application, the accompanying drawings used in the description will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of the hot air furnace insulation system utilizing natural draft, as described in this invention.

[0021] Figure 2 This is a schematic diagram of the control system of the hot air furnace insulation system utilizing natural draft, as described in this invention.

[0022] Figure 3 This is a schematic diagram of the preheating furnace insulation system utilizing natural draft, as described in this invention.

[0023] Figure 4 This is a schematic flowchart of the hot air furnace heat preservation and control method of the present invention.

[0024] Among them, 1-Hot blast furnace body; 2-Large diameter flue valve; 3-First temperature sensor; 4-Second temperature sensor; 5-Controller; 6-Flue; 7-Hot air duct; 8-Chimney; 9-Backflow shut-off valve; 10-Hot air valve; 11-Heat exchanger; 12-Preheat furnace body; 13-Preheat furnace large diameter flue valve; 14-Third temperature sensor; 15-Fourth temperature sensor; 16-Air duct; 17-Preheat furnace flue; 18-Preheat furnace hot air duct; 19-Preheat furnace hot air valve; 20-Alarm. Detailed Implementation

[0025] The various embodiments of this disclosure will be described more fully in the following detailed description of a hot blast stove insulation system utilizing natural draft. This disclosure may have various embodiments, and adjustments and changes may be made therein. However, it should be understood that there is no intention to limit the various embodiments of this disclosure to the specific embodiments disclosed herein, but rather this disclosure should be understood to cover all adjustments, equivalents, and / or alternatives falling within the spirit and scope of the various embodiments of this disclosure.

[0026] For example, the blast furnace hot blast stove is a key piece of equipment in ironmaking, and large furnace bodies generally adopt a structure of silica brick dome (upper part) and cast iron grate (lower part). During long-term heat preservation and maintenance, there is a serious contradiction in the temperature control of the upper and lower parts. The upper silica brick needs to be maintained at ≥700℃ to prevent crystal transformation and cracking, while the lower cast iron structure has a temperature resistance limit of only 350-400℃ and needs to be prevented from overheating and melting.

[0027] Existing methods of opening exhaust ducts compromise equipment integrity and are limited by small diameters (DN400-DN600), resulting in low natural convection flow and slow temperature control response. Existing forced ventilation methods using combustion fans are extremely energy-intensive and pose a risk of fan surge, creating significant safety hazards. Existing methods using manholes in cold air ducts have uncontrollable air intake, poor temperature control accuracy, and cannot achieve coordinated control between upper and lower sections.

[0028] Therefore, there is an urgent need to develop a new type of insulation system and method that requires no external power, does not damage the equipment structure, and can coordinate the temperature of the upper and lower parts in order to solve the above-mentioned technical bottlenecks.

[0029] To address the aforementioned issues, this embodiment provides a hot air furnace insulation system that utilizes natural draft to drive cold air, achieving energy savings without requiring power and coordinating the control of the upper and lower temperatures of the hot air furnace.

[0030] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] Please see Figure 1 and Figure 2 The diagram shown is a schematic of a hot air furnace insulation system utilizing natural draft in a specific embodiment. The system includes a hot air furnace body 1, a large-diameter flue valve 2, a first temperature sensor 3, a second temperature sensor 4, and a controller 5. The hot air furnace body 1 has an upper high-temperature working zone and a lower low-temperature tolerance zone arranged from top to bottom. The hot air furnace body 1 is connected to a flue 6 and a hot air pipe 7. The flue 6 is connected to a chimney 8. The hot air pipe 7 is connected to a backflow shut-off valve 9 through an upward branch pipe. The backflow shut-off valve 9 is located at the end of the branch pipe. A hot air valve 10 is provided on the hot air pipe 7 between the hot air furnace body 1 and the branch pipe. It should be noted that the hot blast stove body 1 has an upper high-temperature zone and a lower low-temperature zone inside, which meets the actual working conditions of the hot blast stove and provides a basis for zoned temperature control. A large-diameter flue valve 2 is installed on the flue 6. The flow cross-sectional area of ​​the large-diameter flue valve 2 is larger than the flow cross-sectional area of ​​the original exhaust gas branch pipe of the hot blast stove, so as to use the natural draft of the chimney 8 to drive the cooling air into the flue 6. It should be noted that this application directly utilizes the existing large-diameter flue valve with a nominal diameter of not less than DN2000 on the flue 6 of the hot air furnace body 1 as the cold air inlet control control. There is no need to cut, open or block the exhaust gas branch pipe, nor is there any need to add any pipes. The switching between the heat preservation mode and the normal production mode is completed only by the valve logic control, without the need for physical modification, thus avoiding equipment structure damage and subsequent restoration work. The flow cross-sectional area of ​​the large-diameter flue valve 2 is much larger than that of the original exhaust gas branch pipe. A large amount of cold air can be driven by the natural draft of the chimney 8 without the need for external power, which is energy-saving and has a large flow rate. A heat exchanger 11 is also installed between the large-diameter flue valve 2 on the flue 6 and the chimney 8. Heat exchanger 11 is an existing waste heat recovery device for the hot blast stove, located on the flue 6, between the large-diameter flue valve 2 and the chimney 8. Under insulation conditions, heat exchanger 11 does not participate in active heat exchange; there is no medium circulation inside or the medium is in a static state, serving only as a passage for cold air. Since the large-diameter flue valve 2 of this application results in a large flow rate and low temperature of cold air, the influence of heat exchanger 11 on the system's natural draft is negligible. Under normal production conditions, heat exchanger 11 is used to recover waste heat from exhaust gas and is not directly related to the core function of this insulation system. The first temperature sensor 3 is located in the lower low-temperature tolerance zone and is used to detect the temperature of the lower part of the hot blast stove body. It should be noted that the first temperature sensor 3 is located in the lower low-temperature tolerance zone (i.e., at the grate) to monitor the temperature of key cast iron components in real time and prevent them from being damaged due to overheating (e.g., >350-400℃). The second temperature sensor 4 is set in the upper high-temperature working area to detect the temperature of the upper part of the hot air furnace body. It should be noted that the second temperature sensor 4 is set in the upper high-temperature working area to monitor the temperature of the silica brick in real time and ensure that it is maintained at a safe temperature (such as >700℃) to prevent crystal transformation cracking. The controller 5 is connected to the first temperature sensor 3, the second temperature sensor 4, and the large-diameter flue valve 2. Controller 5 is configured as follows: The lower temperature and upper temperature of the hot blast stove body 1 are obtained, the temperature deviation of the lower part and the temperature deviation of the upper part are calculated, and the comprehensive deviation is calculated. Based on the comprehensive deviation, the opening command is output through PID calculation to adjust the opening of the large-diameter flue valve 2 to control the flow of cold air entering the flue 6. The cold air flows through the lower low temperature tolerance zone and the upper high temperature working zone in sequence, and then is discharged to the atmosphere from the hot air duct 7 and the backflow shut-off valve 9. Finally, the lower temperature of the hot blast stove body 1 is not higher than the preset upper temperature limit and the upper temperature of the hot blast stove body 1 is not lower than the preset lower temperature limit. It should be noted that controller 5 performs PID calculations based on the temperature deviation between the upper and lower parts, and automatically adjusts the valve opening, realizing coordinated control of cooling and heat preservation, and solving the problem of poor accuracy of manual adjustment.

[0032] This embodiment utilizes the natural draft of the chimney to drive the circulation of cold air, eliminating the need for external power and resulting in significant energy savings. Simultaneously, it coordinates the temperature control of the upper and lower parts, resolving the technical contradiction of needing to cool the lower part while keeping the upper part warm, thus preventing equipment damage.

[0033] Furthermore, as a refinement and extension of the specific implementation of the above embodiments, in order to fully illustrate the specific implementation process in this embodiment, another hot air furnace insulation system utilizing natural draft is provided. The system includes a hot air furnace body 1, a large-diameter flue valve 2, a first temperature sensor 3, a second temperature sensor 4, and a controller 5. The hot air furnace body 1 has an upper high-temperature working zone and a lower low-temperature tolerance zone arranged from top to bottom. The hot air furnace body 1 is connected to a flue 6 and a hot air pipe 7. The flue 6 is connected to a chimney 8. The end of the hot air pipe 7 is connected to a backflow shut-off valve 9 through an upward branch pipe. The backflow shut-off valve 9 is located at the end of the branch pipe. A hot air valve 10 is provided on the hot air pipe 7 between the hot air furnace body 1 and the branch pipe. A large-diameter flue valve 2 is installed on the flue 6. The flow cross-sectional area of ​​the large-diameter flue valve 2 is larger than the flow cross-sectional area of ​​the original exhaust gas branch pipe of the hot blast stove, so as to use the natural draft of the chimney 8 to drive the cooling air into the flue 6. The nominal diameter of the large-diameter flue valve 2 is DN≥2000mm, and the flow cross-sectional area of ​​the large-diameter flue valve 2 is more than 20 times that of the original exhaust gas branch pipe of the hot blast stove. The large-diameter flue valve 2 in this application refers to the existing valve installed on the main channel of the flue 6 connected to the hot blast furnace body, with a nominal diameter ≥ DN2000. Under the condition of heat preservation, the exhaust valve on the original exhaust branch pipe is in the closed state, and the exhaust branch pipe does not participate in the airflow. This application does not replace or remove the exhaust branch pipe, but directly uses the existing large-diameter flue valve 2 on the flue 6, which has a diameter much larger than that of the exhaust branch pipe, as the inlet control of cold air, without the need to cut, block or add any new pipes to the existing pipeline. Traditional exhaust gas branch pipes (e.g., using DN400-DN600) generate low flow velocities and high resistance losses under natural draft, making it difficult to form sufficient airflow through the furnace body. By using large-diameter flue valves (i.e., DN≥2000mm) with a flow cross-sectional area at least 20 times that of the exhaust gas branch pipe, the pressure difference generated by the natural draft of the chimney 8 can effectively overcome the flow resistance inside the furnace and pipes, achieving a stable flow velocity of 2-5m / s, thereby ensuring the cooling effect on the lower grate area. A heat exchanger 11 is also installed between the large-diameter flue valve 2 on the flue 6 and the chimney 8. The first temperature sensor 3 is located in the lower low-temperature tolerance zone and is used to detect the temperature of the lower part of the hot air furnace body 1. The second temperature sensor 4 is installed in the upper high-temperature working area and is used to detect the temperature of the upper part of the hot air furnace body 1. The first temperature sensor 3 is located at the grate and support column at the lower part of the hot blast stove body 1, and the second temperature sensor 4 is located at the silicon brick dome at the upper part of the hot blast stove body 1. The controller 5 is connected to the first temperature sensor 3, the second temperature sensor 4, and the large-diameter flue valve 2. Controller 5 is configured as follows: The lower temperature and upper temperature of the hot blast stove body 1 are obtained, the temperature deviation of the lower part and the temperature deviation of the upper part are calculated, and the comprehensive deviation is calculated. Based on the comprehensive deviation, the opening command is output through PID calculation to adjust the opening of the large-diameter flue valve 2 to control the flow of cold air entering the flue 6. The cold air flows through the lower low temperature tolerance zone and the upper high temperature working zone in sequence, and then is discharged to the atmosphere from the hot air duct 7 and the backflow shut-off valve 9. Finally, the lower temperature of the hot blast stove body 1 is not higher than the preset upper temperature limit and the upper temperature of the hot blast stove body 1 is not lower than the preset lower temperature limit. It also includes alarm 20; Alarm 20 is connected to controller 5; The controller 5 is also provided with an input terminal that is connected to the status detection terminal signal of the hot air valve 10 and the backflow shut-off valve 9.

[0034] Please see Figure 3 The diagram shown is a schematic of a preheating furnace insulation system utilizing natural draft in a specific embodiment. The system includes a preheating furnace body 12, a preheating furnace large-diameter flue valve 13, a third temperature sensor 14, a fourth temperature sensor 15, a hot air furnace body 1, and a controller 5. The hot air furnace body 1 is connected to a hot air duct 7 and an air duct 16; The hot air duct 7 is connected to a backflow shut-off valve 9 via an upward branch duct, and the backflow shut-off valve 9 is located at the end of the branch duct; a hot air valve 10 is provided on the hot air duct 7 between the hot air furnace body 1 and the branch duct. The preheating furnace body 12 has an upper high-temperature working zone and a lower low-temperature tolerance zone arranged from top to bottom. The preheating furnace body 12 is connected to the preheating furnace flue 17 and the preheating furnace hot air pipe 18. The preheating furnace flue 17 is connected to the chimney 8. The preheating furnace hot air pipe 18 is detachably connected to the air pipe 16, and the air pipe 16 is equipped with a preheating furnace hot air valve 19. The large-diameter flue valve 13 of the preheating furnace is installed on the flue 17 of the preheating furnace, and the flow cross-sectional area of ​​the large-diameter flue valve 13 of the preheating furnace is larger than the flow cross-sectional area of ​​the original exhaust gas branch pipe of the preheating furnace. A heat exchanger 11 is also installed between the large-diameter flue valve 13 of the preheating furnace and the chimney 8 on the preheating furnace flue 17. The third temperature sensor 14 is located in the lower low-temperature tolerance zone of the preheating furnace body 12 and is used to detect the temperature of the lower part of the preheating furnace body 12. The fourth temperature sensor 15 is located in the upper high-temperature working area of ​​the preheating furnace body 12 and is used to detect the upper temperature of the preheating furnace body 12. The controller 5 is connected to the third temperature sensor 14, the fourth temperature sensor 15, and the large-diameter flue valve 13. Controller 5 is configured as follows: The lower temperature of the preheating furnace body 12 and the upper temperature of the hot blast stove body 12 are obtained. The temperature deviations of the lower and upper parts are calculated, and the comprehensive deviation is calculated. Based on the comprehensive deviation, the opening command is output through PID calculation to adjust the opening of the large-diameter flue valve 13 of the preheating furnace, so as to control the flow rate of cold air entering the flue 17 of the preheating furnace. The cold air flows through the lower low-temperature tolerance zone and the upper high-temperature working zone in sequence, and then flows out through the air pipe 16, and finally through the hot air pipe 7 and the backflow shut-off valve 9 of the hot blast stove body 1 to the atmosphere. Ultimately, the lower temperature of the preheating furnace hot blast stove body 1 is not higher than the preset upper temperature limit and the upper temperature of the preheating furnace body 1 is not lower than the preset lower temperature limit.

[0035] like Figure 4 As shown, the following are embodiments of the hot blast stove heat preservation and control method provided in this disclosure. This method belongs to the same inventive concept as the hot blast stove heat preservation system utilizing natural suction in the above embodiments. For details not described in detail in the embodiments of the hot blast stove heat preservation and control method, please refer to the embodiments of the hot blast stove heat preservation system utilizing natural suction described above.

[0036] The method includes the following steps: S1. Close the combustion air valve, gas valve, cold air valve and exhaust gas valve of the hot blast stove body, and lock the conventional combustion and air supply passages; It should be noted that this step cuts off the combustion air, coal gas, cold air and exhaust gas passages, physically isolating the hot air furnace from the production system to ensure that a closed and controllable thermal circulation environment is formed inside the furnace during the heat preservation period, preventing gas cross-contamination and potential danger. S2. Open the hot air valve on the hot air duct and the backflow shut-off valve on the branch duct, and then open the large-diameter flue valve on the flue to establish a reverse non-powered thermal circulation path that passes through the flue, the hot air furnace body, the hot air duct, and the backflow shut-off valve to the atmosphere. It should be noted that this step utilizes the chimney's suction to draw in cold air, which flows through the furnace body, carrying away the heat from the lower part and being heated by the residual heat from the upper part before finally being discharged. S3. The controller acquires the temperature of the lower part of the hot air furnace body detected by the first temperature sensor and the temperature of the upper part of the hot air furnace body detected by the second temperature sensor in real time, calculates the temperature deviation of the lower part and the temperature deviation of the upper part, and then calculates the comprehensive deviation. Based on the comprehensive deviation, the controller outputs the opening command through PID calculation to adjust the opening of the large-diameter flue valve. It should be noted that this step calculates the weighted average value of the temperature deviation between the upper and lower parts, and uses a PID algorithm to dynamically adjust the opening of the large-diameter flue valve. S4. When the temperature of the lower part of the hot blast stove body is not higher than the preset upper temperature limit and the temperature of the upper part of the hot blast stove body is not lower than the preset lower temperature limit, the controller locks the current opening of the large-diameter flue valve in a PID self-optimization mode to maintain the dynamic balance of the hot blast stove body. It should be noted that this step automatically locks the current valve opening when the temperature is within the ideal range, allowing the hot air furnace to enter a stable dynamic equilibrium state, which maintains the necessary cooling effect while retaining the heat at the furnace top to the maximum extent, achieving the best heat preservation effect.

[0037] This embodiment utilizes the natural draft of the chimney to drive cold air into the flue, and uses a large-diameter flue valve with a flow cross-sectional area larger than the exhaust gas branch pipe as the sole flow regulating component, achieving zero-energy insulation without the need for external power. Simultaneously, the controller performs PID self-optimization calculations based on the weighted deviation between the lower and upper temperatures, dynamically adjusting the valve opening so that the cold air first cools the lower low-temperature zone, then passes through the upper high-temperature zone before being discharged into the atmosphere, forming a synergistic temperature control effect. This resolves the contradiction of excessive temperature at the bottom and insufficient temperature at the top during the hot blast furnace insulation period, and eliminates the need for any modifications to the flue, such as opening or sealing, thus improving the safety and economy of the insulation operation.

[0038] Furthermore, as a refinement and extension of the specific implementation of the above embodiments, in order to fully illustrate the specific implementation process in this embodiment, another method for controlling the heat preservation of a hot blast stove is provided, which includes the following steps: S1. Close the combustion air valve, gas valve, cold air valve and exhaust gas valve of the hot blast stove body, and lock the conventional combustion and air supply passages; S2. Open the hot air valve on the hot air duct and the backflow shut-off valve on the branch duct, and then open the large-diameter flue valve on the flue to establish a reverse non-powered thermal circulation path that passes through the flue, the hot air furnace body, the hot air duct, and the backflow shut-off valve to the atmosphere. The specific steps of step S2 are as follows: S21. Maintain the connection between the flue and the chimney; S22. Open the hot air valve on the hot air duct and the backflow shut-off valve on the branch duct; S23. After the backflow shut-off valve and hot air valve are fully opened, open the large-diameter flue valve on the flue at the preset rate, so that the ambient cold air flows through the flue, hot air furnace body and hot air pipe in sequence under the natural draft of the chimney and is discharged to the atmosphere through the backflow shut-off valve. S3. The controller acquires the temperature of the lower part of the hot air furnace body detected by the first temperature sensor and the temperature of the upper part of the hot air furnace body detected by the second temperature sensor in real time, calculates the temperature deviation of the lower part and the temperature deviation of the upper part, and then calculates the comprehensive deviation. Based on the comprehensive deviation, the controller outputs the opening command through PID calculation to adjust the opening of the large-diameter flue valve. The specific steps of step S3 are as follows: S31. Preset the upper limit of the temperature of the lower part of the hot air furnace body. (e.g., 400-450℃), the lower limit of the temperature at the top of the hot blast stove body. (e.g., 700-800℃); S32. The controller acquires the measured temperature of the lower part detected by the first temperature sensor. The measured temperature at the top, detected by the second temperature sensor ; S33. Calculate the lower temperature deviation Calculate the upper temperature deviation ; S34. Based on lower temperature deviation Temperature deviation from the upper part Calculate the overall deviation : ; in, , The weighting coefficients are preset and pre-calibrated based on the volume of the hot blast stove; S35. Based on comprehensive deviation The PID algorithm is used to calculate the change in opening degree during the current control cycle. :

[0039] in, , , These are the preset PID parameters. To control the cycle; S36. Based on the change in opening degree Calculate the target opening:

[0040] in, This indicates the target opening degree for the current control cycle. This indicates the actual opening degree in the previous control cycle; S37. Calculate the target opening degree for the current control cycle. As an actuator that outputs opening commands to large-diameter flue valves; It should be noted that single PID control may have problems such as slow response or over-adjustment across the entire temperature range. Therefore, based on the degree of deviation between the upper and lower part temperatures and the set value, three working modes are preset: rapid cooling mode (i.e., to prevent the lower part from overheating and deteriorating), fine heat preservation mode (i.e., normal PID control), and low temperature protection mode (i.e., to prevent the upper part from underheating). The three modes switch automatically, taking into account both emergency response and steady-state regulation. It should be noted that the control logic of this application is as follows: the controller calculates the comprehensive deviation in real time. This drives the PID control; The comprehensive deviation The formula achieves bidirectional deviation fusion; under the actual measured temperature at the lower part Exceeding its upper limit At that time, the temperature deviation in the lower part Positive, overall deviation Increasing the PID output will result in a positive change in the opening degree. The increased opening of the large-diameter flue valve leads to a greater flow of cold air, which enhances the cooling of the lower grate and support columns, resulting in a higher measured temperature in the lower part. It has fallen back below the upper limit; when the lower part of the temperature is within a safe range but the upper part of the temperature... Below its lower limit At that time, the upper temperature deviation It is positive because of the temperature deviation at the top. The preceding sign is negative, indicating a comprehensive deviation. Decrease the negative opening change in the PID output. The valve opening decreases, reducing the flow of cold air and slowing down heat loss from the upper part, thus lowering the measured temperature at the upper part. It rebounded to above the lower limit; Preset weighting coefficients This reflects the sensitivity of valve adjustment to the risk of overheating in the lower part. It reflects the degree to which the risk of undertemperature at the upper part suppresses valve regulation; through field calibration, the system can respond quickly when facing overtemperature at the lower part, thereby opening the valve wider, and close the valve in advance when the upper part is close to undertemperature, thus achieving bidirectional control of the same valve; Furthermore, the multi-mode switching mechanism further safeguards boundary conditions: when the actual measured temperature at the bottom... In case of severe overheating, a rapid cooling mode is forcibly activated, with valves fully opened to prioritize the protection of the lower cast iron structure; when the measured temperature of the upper part... When the temperature approaches the minimum, the system forcibly switches to low-temperature protection mode, closing the valve slightly to prioritize maintaining the temperature of the upper silica bricks. These two modes both constrain and coordinate, working together to ensure... and ; Through the above control logic, this application achieves a dynamic balance between the two contradictory objectives of cooling the lower part and keeping the upper part warm by utilizing the physical process of the same cold air flowing through the lower low-temperature zone and the upper high-temperature zone in sequence without the need for external power. Step S3 also includes the following multi-mode automatic switching steps: S301. The controller identifies the measured temperature at the bottom of the hot air furnace body. and the measured temperature at the top The current state; when Proceed to step S302; when and Proceed to step S303; when Proceed to step S304; in, The preset rapid cooling trigger temperature difference, The preset lower low-temperature hysteresis temperature difference, The preset upper low temperature warning temperature difference; S302. The controller automatically switches to rapid cooling mode and forces the output to the target opening degree. The corresponding opening command, where, The preset maximum opening threshold; S303. The controller automatically switches to the fine insulation mode, and performs PID control according to steps S31 to S37 to maintain the opening degree. to Between, among them, , These are the upper and lower limits of the preset medium opening range; S304. The controller automatically switches to low-temperature protection mode and forces the output to the target opening degree. The opening command, where, This is the preset small opening threshold; This application also includes the following extreme operating condition where both the upper and lower parts simultaneously approach the threshold, i.e., when the controller recognizes... and When this occurs, it indicates that the system is simultaneously facing the risk of overheating at the bottom and underheating at the top. In this case, if the above method is still used for comprehensive deviation PID control, the two control objectives may cancel each other out, and the valve may remain stationary or make only minor movements. To resolve this issue, this application employs a lower-priority arbitration strategy: First, assess the urgency of the lower section overheating. The temperature limit of the cast iron grate is 350-400℃; exceeding this temperature may cause irreversible melting and collapse, which is a critical safety threshold. While the upper silica bricks may experience increased risk of crystal transformation when briefly below 700℃, the damage is not instantaneous. Therefore, when the lower section temperature reaches a dangerous threshold (e.g., ...), ... ≥450 In case C), the system prioritizes cooling, forcibly increasing the opening of the flue valve to lower the lower temperature; after the lower temperature returns to a safe range, the valve is adjusted according to the upper temperature to restore upper insulation. Specifically, the system dynamically adjusts the weighting coefficients in the comprehensive deviation formula according to the following rules. , : when and At that time, temporarily Increase to 1.5 times the default value, and at the same time... Reduced to 0.5 times the default value, thus reducing the overall deviation. Primarily governed by the lower deviation, the lower cooling section is prioritized when the output opening command is executed; when and When (i.e., the lower part is safe, but the upper part is still cold), Restore to default values, and at the same time Reduced to 0.3 times the default value, so that the control prioritizes meeting the upper insulation requirements; when and At that time, restore the default weight coefficient. , It then enters normal collaborative PID control; Through the priority arbitration mechanism, under extreme working conditions where the temperature difference between the upper and lower parts is extremely large and the control objectives conflict, the safety of the equipment can be prioritized, that is, the lower part can be prevented from melting, while the insulation requirements of the upper part can be taken into account, and the dynamic satisfaction of the two constraints can be achieved. S4. When the temperature of the lower part of the hot blast stove body is not higher than the preset upper temperature limit and the temperature of the upper part of the hot blast stove body is not lower than the preset lower temperature limit, the controller locks the current opening of the large-diameter flue valve in a PID self-optimization mode to maintain the dynamic balance of the hot blast stove body.

[0041] In some embodiments, unlike the embodiments described above, the following safety interlocking steps are also included: S51. The controller monitors the temperature of the lower part of the hot air furnace body, the status signal of the hot air valve, and the status signal of the backflow shut-off valve in real time. The controller will forcibly lock the large-diameter flue valve to prevent it from closing and trigger the alarm when any of the following conditions are met: The lower part temperature is greater than or equal to the preset danger temperature threshold. ; A signal indicating that the hot air valve is not fully open has been received. When a signal indicating that the backflow damper is not fully open is received; It should be noted that when the lower temperature is detected to be ≥500℃ or the critical valves (i.e., hot air valve and backflow shut-off valve) are not fully open, the controller will forcibly lock the large-diameter flue valve to prevent it from closing. This is to prevent the interruption of cold air from causing the lower temperature to get out of control. At the same time, an alarm will be triggered to remind the operator to intervene. If the valve is allowed to close at this time, the cooling capacity will be lost, which may cause a serious equipment accident such as the grate melting. S52. When the controller detects that the hot air furnace body has unexpectedly resumed the air supply signal, it automatically cuts off the heat preservation path and fully closes the large-diameter flue valve.

[0042] In some embodiments, unlike the embodiments described above, the following independent heat preservation step for the preheating furnace is also included: S61. Locking the conventional combustion and air supply passage of the preheater furnace; S62. Open the large-diameter flue valve, hot air valve of the preheating furnace, and air pipe shut-off valve connecting the preheating furnace and the hot air furnace, and confirm that the hot air valve and backflow shut-off valve on the hot air furnace side are in the open state. S63. Establish an extended reverse non-powered passage from ambient cold air through the preheating furnace flue, preheating furnace body, preheating furnace hot air duct, hot air furnace air duct, hot air furnace body, hot air duct, and backflow shut-off valve before being discharged into the atmosphere. S64. By adjusting the opening of the large-diameter flue valve of the preheating furnace, the flow rate of cold air flowing through the preheating furnace can be independently controlled to achieve zoned and coordinated temperature control of the preheating furnace. It should be noted that the above-mentioned independent insulation method for the preheating furnace utilizes the inherent air duct connection between the preheating furnace and the hot blast stove, eliminating the need for additional pipeline laying. When the hot blast stove body needs to be shut off for maintenance, the preheating furnace can still independently establish a reverse non-powered thermal circulation path, enabling zoned maintenance without interference, thus improving the flexibility of overall blast furnace system maintenance.

[0043] It should be understood that the sequence number of each step in the above embodiments does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

[0044] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A hot air furnace insulation system utilizing natural draft, characterized in that, Includes the hot air furnace body, large-diameter flue valve, first temperature sensor, second temperature sensor and controller; The interior of the hot blast stove body is divided into an upper high-temperature working zone and a lower low-temperature tolerance zone from top to bottom; The hot blast stove body is connected to a flue and a hot air pipe. The flue is connected to a chimney. The hot air pipe is connected to a backflow shut-off valve through an upward branch pipe. The backflow shut-off valve is located at the end of the branch pipe. A hot air valve is provided on the hot air pipe between the hot blast stove body and the branch pipe. A large-diameter flue valve is installed on the flue. The flow cross-sectional area of ​​the large-diameter flue valve is larger than the flow cross-sectional area of ​​the original exhaust gas branch pipe of the hot blast stove, so as to use the natural draft of the chimney to drive the cooling air into the flue. The first temperature sensor is located in the lower low-temperature tolerance zone and is used to detect the temperature of the lower part of the hot air furnace body; The second temperature sensor is located in the upper high-temperature working area and is used to detect the temperature of the upper part of the hot air furnace body. The controller is connected to the first temperature sensor, the second temperature sensor, and the large-diameter flue valve. The controller is configured as follows: The system acquires the temperatures of the lower and upper parts of the hot blast stove body, calculates the temperature deviations of the lower and upper parts, and then calculates the overall deviation. Based on the overall deviation, it outputs an opening command through PID calculation to adjust the opening of the large-diameter flue valve, thereby controlling the flow of cold air entering the flue. This allows the cold air to flow sequentially through the lower low-temperature tolerance zone and the upper high-temperature working zone before being discharged to the atmosphere through the hot air duct and the backflow shut-off valve. Ultimately, this ensures that the temperature of the lower part of the hot blast stove body does not exceed the preset upper temperature limit and the temperature of the upper part of the hot blast stove body does not fall below the preset lower temperature limit.

2. The hot air furnace insulation system utilizing natural draft as described in claim 1, characterized in that, The nominal diameter of the large-diameter flue valve is DN≥2000mm, and the flow cross-sectional area of ​​the large-diameter flue valve is more than 20 times that of the original exhaust gas branch pipe of the hot blast stove. The first temperature sensor is located at the grate and support column at the bottom of the hot blast stove body, and the second temperature sensor is located at the silicon brick dome at the top of the hot blast stove body.

3. The hot air furnace insulation system utilizing natural draft as described in claim 1, characterized in that, It also includes alarms; The alarm is connected to the controller; The controller also has an input terminal that connects to the status detection signal of the hot air valve and the backflow shut-off valve.

4. A preheating furnace insulation system utilizing natural draft, characterized in that, Includes the preheating furnace body, the preheating furnace large-diameter flue valve, the third temperature sensor, the fourth temperature sensor, the hot air furnace body and controller; The hot air furnace body is connected to hot air ducts and air ducts; The hot air duct is connected to a backflow shut-off valve via an upward branch duct, and the backflow shut-off valve is located at the end of the branch duct; a hot air valve is provided on the hot air duct between the hot air furnace body and the branch duct. The preheating furnace body is divided into an upper high-temperature working zone and a lower low-temperature tolerance zone from top to bottom. The preheating furnace body is connected to the preheating furnace flue and the preheating furnace hot air duct. The preheating furnace flue is connected to the chimney. The preheating furnace hot air duct is detachably connected to the air duct, and the air duct is equipped with a preheating furnace hot air valve. The large-diameter flue valve of the preheating furnace is installed on the flue of the preheating furnace, and the flow cross-sectional area of ​​the large-diameter flue valve of the preheating furnace is larger than the flow cross-sectional area of ​​the original exhaust gas branch pipe of the preheating furnace. The third temperature sensor is located in the low-temperature tolerance zone at the bottom of the preheating furnace body and is used to detect the temperature at the bottom of the preheating furnace body. The fourth temperature sensor is located in the high-temperature working zone at the top of the preheating furnace body and is used to detect the temperature at the top of the preheating furnace body. The controller is connected to the third temperature sensor, the fourth temperature sensor, and the large-diameter flue valve of the preheating furnace. The controller is configured as follows: The system acquires the temperatures of the lower and upper parts of the preheating furnace body, calculates the temperature deviations of the lower and upper parts, and then calculates the overall deviation. Based on the overall deviation, it outputs an opening command through PID calculation to adjust the opening of the large-diameter flue valve of the preheating furnace. This controls the flow rate of cold air entering the preheating furnace flue, allowing the cold air to flow sequentially through the lower low-temperature tolerance zone and the upper high-temperature working zone before exiting through the air duct and finally through the hot air duct of the hot air furnace body and the backflow shut-off valve to the atmosphere. Ultimately, this ensures that the temperature of the lower part of the preheating furnace body does not exceed the preset upper temperature limit and the temperature of the upper part of the preheating furnace body does not fall below the preset lower temperature limit.

5. A method for heat preservation and control of a hot blast stove using the system described in any one of claims 1 to 3, characterized in that, Includes the following steps: S1. Close the combustion air valve, gas valve, cold air valve and exhaust gas valve of the hot blast stove body, and lock the conventional combustion and air supply passages; S2. Open the hot air valve on the hot air duct and the backflow shut-off valve on the branch duct, and then open the large-diameter flue valve on the flue to establish a reverse non-powered thermal circulation path that passes through the flue, the hot air furnace body, the hot air duct, and the backflow shut-off valve to the atmosphere. S3. The controller acquires the temperature of the lower part of the hot air furnace body detected by the first temperature sensor and the temperature of the upper part of the hot air furnace body detected by the second temperature sensor in real time, calculates the temperature deviation of the lower part and the temperature deviation of the upper part, and then calculates the comprehensive deviation. Based on the comprehensive deviation, the controller outputs the opening command through PID calculation to adjust the opening of the large-diameter flue valve. S4. When the temperature of the lower part of the hot blast stove body is not higher than the preset upper temperature limit and the temperature of the upper part of the hot blast stove body is not lower than the preset lower temperature limit, the controller locks the current opening of the large-diameter flue valve in a PID self-optimization mode to maintain the dynamic balance of the hot blast stove body.

6. The hot blast stove heat preservation and control method according to claim 5, characterized in that, The specific steps of step S2 are as follows: S21. Maintain the connection between the flue and the chimney; S22. Open the hot air valve on the hot air duct and the backflow shut-off valve on the branch duct; S23. After the backflow shut-off valve and hot air valve are fully opened, open the large-diameter flue valve on the flue at the preset rate, so that the ambient cold air flows through the flue, hot air furnace body and hot air pipe in sequence under the natural draft of the chimney and is discharged to the atmosphere through the backflow shut-off valve.

7. The hot blast stove heat preservation and control method according to claim 5, characterized in that, The specific steps of step S3 are as follows: S31. Preset the upper limit of the temperature of the lower part of the hot air furnace body. Lower limit of temperature at the upper part of the hot blast stove body ; S32. The controller acquires the measured temperature of the lower part detected by the first temperature sensor. The measured temperature at the top, detected by the second temperature sensor ; S33. Calculate the lower temperature deviation Calculate the upper temperature deviation ; S34. Based on lower temperature deviation Temperature deviation from the upper part Calculate the overall deviation : ； in, , The weighting coefficients are preset and pre-calibrated based on the volume of the hot blast stove; S35. Based on comprehensive deviation The PID algorithm is used to calculate the change in opening degree during the current control cycle. : in, , , These are the preset PID parameters. To control the cycle; S36. Based on the change in opening degree Calculate the target opening: in, This indicates the target opening degree for the current control cycle. This indicates the actual opening degree in the previous control cycle; S37. Calculate the target opening degree for the current control cycle. It serves as the actuator for outputting opening commands to large-diameter flue valves.

8. The hot blast stove heat preservation and control method according to claim 7, characterized in that, Step S3 also includes the following multi-mode automatic switching steps: S301. The controller identifies the measured temperature at the bottom of the hot air furnace body. and the measured temperature at the top The current state; when Proceed to step S302; when and Proceed to step S303; when Proceed to step S304; in, The preset rapid cooling trigger temperature difference, The preset lower low-temperature hysteresis temperature difference, The preset upper low temperature warning temperature difference; S302. The controller automatically switches to rapid cooling mode and forces the output to the target opening degree. The corresponding opening command, where, The preset maximum opening threshold; S303. The controller automatically switches to the fine insulation mode, and performs PID control according to steps S31 to S37 to maintain the opening degree. to Between, among them, , These are the upper and lower limits of the preset medium opening range; S304. The controller automatically switches to low-temperature protection mode and forces the output to the target opening degree. The opening command, where, This is the preset small opening threshold.

9. The hot blast stove heat preservation and control method according to claim 5, characterized in that, It also includes the following safety interlocking steps: S51. The controller monitors the temperature of the lower part of the hot air furnace body, the status signal of the hot air valve, and the status signal of the backflow shut-off valve in real time. The controller will forcibly lock the large-diameter flue valve to prevent it from closing and trigger the alarm when any of the following conditions are met: The lower part temperature is greater than or equal to the preset danger temperature threshold. ; A signal indicating that the hot air valve is not fully open has been received. When a signal indicating that the backflow damper is not fully open is received; S52. When the controller detects that the hot air furnace body has unexpectedly resumed the air supply signal, it automatically cuts off the heat preservation path and fully closes the large-diameter flue valve.

10. The hot blast stove heat preservation and control method according to claim 5, characterized in that, It also includes the following independent insulation steps for the preheating furnace: S61. Locking the conventional combustion and air supply passage of the preheater furnace; S62. Open the large-diameter flue valve, hot air valve of the preheating furnace, and air pipe shut-off valve connecting the preheating furnace and the hot air furnace, and confirm that the hot air valve and backflow shut-off valve on the hot air furnace side are in the open state. S63. Establish an extended reverse non-powered passage from ambient cold air through the preheating furnace flue, preheating furnace body, preheating furnace hot air duct, hot air furnace air duct, hot air furnace body, hot air duct, and backflow shut-off valve before being discharged into the atmosphere. S64. By adjusting the opening of the large-diameter flue valve of the preheating furnace, the flow rate of cold air flowing through the preheating furnace can be independently controlled to achieve zoned and coordinated temperature control of the preheating furnace.

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