Supercritical CFB boiler deep peak regulation working condition smoke temperature optimization control system

Abstract

The invention belongs to the technical field of supercritical CFB (circulating fluid bed) boilers, and particularly relates to a supercritical CFB boiler deep peak regulation working condition smoke temperature optimization control system which comprises a sensing monitoring module, an intelligent control module and a regulation execution module. The primary air bypass air duct is introduced from a primary cold air duct of the supercritical CFB boiler and is divided into two paths which are respectively connected into a primary hot air duct and a secondary hot air duct; according to the requirements of boiler load and smoke exhaust temperature, the air volume of primary cold air passing through the primary air bypass air duct can be effectively adjusted by adjusting the electric adjusting air door, so that effective control over the volume of the primary cold air flowing into the air preheater is achieved, heat loss in smoke is reduced, and the energy consumption is reduced. Therefore, the temperature reduction amplitude when the flue gas passes through the air preheater is reduced, and the problem of bag pasting caused by too low temperature when the flue gas passes through a bag-type dust collector is avoided.

Description

Technical Field

[0001] This invention belongs to the field of supercritical CFB boiler technology, specifically a supercritical CFB boiler deep peak-shaving flue gas temperature optimization control system. Background Technology

[0002] With the expansion of grid connection of new energy power generation, coal-fired units need to frequently participate in deep peak shaving operations, and the load often drops below 30% of the rated load. Under low load conditions, the flue gas temperature of CFB boilers drops significantly, especially in winter, it can be as low as about 80°C, close to or even below the flue gas acid dew point temperature (about 85°C), which can easily lead to problems such as bag filter clogging, increased power consumption of induced draft fans, and unstable system operation.

[0003] Currently, common methods for increasing flue gas temperature include flue gas bypass and air bypass. However, flue gas bypass has drawbacks such as high flue gas temperature, high dust content, easy ash accumulation and wear, and high cost. This invention addresses the high proportion of primary air in deep peak-shaving operations of CFB boilers by proposing a primary air bypass optimization system to solve the aforementioned problems. Summary of the Invention

[0004] To overcome the shortcomings of existing technologies and solve the aforementioned technical problems, this invention proposes a flue gas temperature optimization control system for deep peak shaving conditions in supercritical CFB boilers.

[0005] The technical solution adopted by the present invention to solve its technical problem is as follows: The present invention proposes a flue gas temperature optimization control system for deep peak shaving operation of supercritical CFB boiler, including a sensing and monitoring module, an intelligent control module and an adjustment and execution module. The sensing and monitoring module is used to monitor the flue gas temperature entering the flue and exiting the flue on both sides of the air preheater. The adjustment execution module includes a primary air bypass duct. The primary air bypass duct is introduced from the primary cold air duct of the supercritical CFB boiler and divided into two paths, namely a primary air branch pipe and a secondary air branch pipe, which are finally connected to the primary hot air duct and the secondary hot air duct, respectively. The preheating pipe inside the air preheater is connected to the primary cold air duct and has a continuously curved structure.

[0006] Preferably, the primary air distribution pipe and the secondary air distribution pipe are equipped with electrically adjustable dampers, and the junction of the primary air bypass duct and the primary cold air duct is equipped with an electrically shut-off damper, an air volume measuring device and an expansion joint.

[0007] Preferably, protective tubes are evenly arranged on the vertical part of the preheating pipe. The protective tubes include a pipe body, which is evenly distributed along the vertically extending preheating pipe. An installation groove is provided at the bottom of the pipe body. An elastic insulating heat strip is fixedly connected inside the installation groove. The insulating heat strip has a ring structure and is folded inside the installation groove. The bottom of the insulating heat strip is fixedly connected to a closed ring provided at the bottom opening of the installation groove. The closed ring is connected to a telescopic device installed at the bottom of the air preheater through a connecting rod.

[0008] Preferably, the bottom end of the closed ring has a conical structure and is in contact with the outer surface of the preheating pipe, and both the pipe body and the insulating heat strip are made of non-metallic high-temperature resistant material.

[0009] Preferably, the vertically distributed tubes are connected by connecting rods, the bottom of which is fixed to the inner wall of the bottom of the preheating tube to support and stabilize the vertical part of the preheating tube.

[0010] Preferably, the connecting rod is a tubular structure, and the top of the connecting rod communicates with the purification air chamber provided in the inner wall of the top of the air preheater. The purification air chamber is connected to the air outlet of the purification fan provided on the outside. The connecting rod vertically penetrates the flushing chamber located on the upper side of the mounting groove inside each tube, and the connecting rod communicates with the flushing chamber. The inner wall of the flushing chamber is provided with flushing holes.

[0011] Preferably, the flushing hole is a conical hole, and the flushing hole communicates with the gap between the insulating tape and the outer surface of the preheating pipe. The insulating tape is woven from high-temperature resistant wire.

[0012] Preferably, the connecting rod slides through the closed ring, and an annular cleaning block is provided on the inner surface of the closed ring. The end of the cleaning block is tapered and contacts the outer surface of the preheating pipe.

[0013] Preferably, the conical end of the closed ring is provided with a guide groove, which extends vertically through each cleaning block and communicates with the gap area between the insulation tape and the preheating pipe.

[0014] Preferably, the air preheater has a collection trough at the bottom, a protective net at the top of the collection trough, and an interception net inside the collection trough located above the telescopic device. The air inlet of the purification fan is connected to the area below the interception net.

[0015] The beneficial effects of this invention are as follows: The present invention discloses a flue gas temperature optimization control system for deep peak shaving conditions in a supercritical CFB boiler. Based on the boiler load and flue gas temperature requirements, the system can effectively adjust the air volume of primary cold air passing through the primary air bypass duct by adjusting the electric regulating damper. This achieves effective control of the primary cold air volume flowing into the air preheater, reduces heat loss in the flue gas, and thus reduces the temperature drop of the flue gas when passing through the air preheater, preventing the bag filter from clogging due to excessively low temperature when the flue gas passes through it. Attached Figure Description

[0016] The invention will now be further described with reference to the accompanying drawings.

[0017] Figure 1 This is a schematic diagram of the present invention; Figure 2 This is a cross-sectional view of the air preheater in this invention; Figure 3 yes Figure 2 A magnified view of a section at point A in the middle; Figure 4 yes Figure 2 A magnified view of a section at point B in the middle; Figure 5 yes Figure 4 A magnified view of a section at point C; Figure 6 This is a perspective view of the protective tube in this invention; Figure 7 This is a perspective view of the protective tube in this invention from another angle; Figure 8 This is a three-dimensional view of the preheating pipe in this invention.

[0018] In the diagram: 1. Air preheater; 11. Preheating pipe; 12. Protective pipe; 121. Pipe body; 122. Mounting groove; 123. Insulation strip; 124. Connecting rod; 125. Flushing chamber; 126. Flushing hole; 13. Sealing ring; 131. Cleaning block; 132. Guide groove; 14. Telescopic device; 15. Purified air chamber; 16. Collection groove; 161. Interception net; 2. Primary air bypass duct; 21. Primary air branch pipe; 22. Secondary air branch pipe; 3. Primary cold air duct; 4. Primary hot air duct; 5. Secondary hot air duct; 6. Flue gas enters the flue; 7. Flue gas exits the flue. Detailed Implementation

[0019] 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. Example

[0020] As shown in the attached diagram of the instruction manual. Figures 1-8 As shown, this application proposes a flue gas temperature optimization control system for deep peak shaving operation of a supercritical CFB boiler, including a sensing and monitoring module, an intelligent control module, and an adjustment and execution module. The sensing and monitoring module includes various monitoring devices such as temperature monitoring sensors and air volume measuring devices, which are used to monitor relevant data such as flue gas temperature and air volume in the flue gas entering the flue duct 6 and the flue gas flowing out of the flue duct 7 on both sides of the air preheater 1. The intelligent control module can be selected from the intelligent control system configured in the CFB boiler, which controls the automatic operation of each part of this application through the intelligent controller; the adjustment and execution module includes a primary air bypass duct 2, which is introduced from the primary cold air duct 3 of the supercritical CFB boiler and divided into two paths, namely primary air branch pipe 21 and secondary air branch pipe 22, which are finally connected to the primary hot air duct 4 and secondary hot air duct 5 respectively. The primary air bypass duct 2 is mainly fixed to the boiler steel frame by a suspension structure, and the support beam is connected to the boiler column; the intelligent control system can use the flue gas temperature as the adjustment target and automatically adjust the air volume of the primary air bypass duct 2 according to the load and flue gas temperature; The preheating pipe 11 inside the air preheater 1 is connected to the primary cold air duct 3 and has a continuous curved structure, leading to the primary hot air duct 4. Specifically, the part of the preheating pipe 11 inside the air preheater 1 that comes into contact with the flue gas is mainly a continuous vertical part, and adjacent vertical parts are connected by bends. The primary air branch pipe 21 and the secondary air branch pipe 22 are equipped with electrically adjustable dampers. The junction of the primary air bypass duct 2 and the primary cold air duct 3 is equipped with an electrically shut-off damper, an air volume measuring device and an expansion joint. The electrically adjustable damper and the electrically shut-off damper are all controlled by an intelligent controller. Specific workflow: When the CFB boiler is working normally, the flue gas discharged from the tail end of the boiler is generally passed through the flue gas inlet duct 6 and the flue gas outlet duct 7 through the air preheater 1, so that the heat in the flue gas can be transferred to the primary cold air and secondary cold air that also pass through the preheating tube 11 inside the air preheater 1, forming primary hot air and secondary hot air, realizing the heat recovery of "exhaust gas heat release - cold air heat absorption". This can both increase the inlet air temperature to enhance combustion and reduce the exhaust gas temperature to improve boiler efficiency. However, under deep peak shaving and low load conditions, the boiler combustion intensity decreases and the heat of the exhaust flue gas itself is greatly reduced. At this time, the proportion of primary air is still relatively high, and a large amount of cold air still needs to absorb heat through the air preheater 1, resulting in excessive extraction of exhaust gas heat. Finally, the exhaust gas temperature drops to close to or below the acid dew point, which can easily cause the bag filter to clog. Therefore, this application proposes a flue gas temperature optimization control system for deep peak shaving conditions in a supercritical CFB boiler, which effectively solves the above-mentioned problems. Specifically, a primary air bypass duct 2 is set on the primary cold air duct 3. The primary air bypass duct 2 can bypass the air preheater 1 and is divided into a primary air branch pipe 21 and a secondary air branch pipe 22, which are respectively connected to the primary hot air duct 4 and the secondary hot air duct 5. During the operation of the CFB boiler, when the sensing and monitoring module detects that the temperature of the discharged flue gas is low, the electric shut-off damper at the interface of the primary air bypass duct 2 can be opened to allow the primary air to reach the desired temperature. Bypass duct 2 is connected to primary cold air duct 3. In this way, some of the primary cold air will flow along the primary air bypass duct 2 to primary hot air duct 4 or secondary hot air duct 5 before being sent into air preheater 1. This reduces the amount of primary cold air passing through air preheater 1. When the flue gas passes through the interior of air preheater 1, the heat transferred from the flue gas to the primary cold air is also reduced due to the reduced flow of primary cold air. This reduces the heat loss in the flue gas and thus reduces the temperature drop when the flue gas passes through air preheater 1. This avoids the problem of bag clogging caused by the flue gas being too cold when passing through the bag filter. Regarding how to control the reduction in flue gas temperature during the above process, the mathematical relationship between the flue gas temperature and the primary air volume can be determined through multiple pre-experiments. Based on the corresponding mathematical relationship, the air volume of the primary air bypass duct 2 can be adjusted. This can be achieved by setting an electric regulating damper to adjust the air volume flowing inside the primary air branch pipe 21 and the secondary air branch pipe 22. This can effectively adjust the air volume of the primary air passing through the primary air bypass duct 2, thereby achieving effective control of the primary air volume flowing into the air preheater 1. Furthermore, it can effectively control the flue gas temperature of the boiler according to the boiler load, ensuring the safe and normal operation of the boiler. Example

[0021] Based on Example 1, as shown in the appendix to the specification. Figure 2 As shown, protective pipes 12 are evenly arranged on the vertical part of the preheating pipe 11, and on the attached... Figure 2The schematic diagram shows the arrangement of a single preheating pipe 11 inside the air preheater 1. This is for illustrative purposes only and does not imply that the air preheater 1 of this application has only one preheating pipe 11 inside. The protective pipe 12 includes a pipe body 121, which is evenly distributed along the vertically extending preheating pipe 11. The bottom of the pipe body 121 is provided with an installation groove 122. An elastic insulating heat strip 123 is fixedly connected inside the installation groove 122. The insulating heat strip 123 has a ring structure and is folded inside the installation groove 122. The bottom of the insulating heat strip 123 is fixedly connected to a closed ring 13 provided at the bottom opening of the installation groove 122. The closed ring 13 is connected to the telescopic device 14 installed at the bottom of the air preheater 1 via a connecting rod. The bottom end of the closed ring 13 has a conical structure and contacts the outer surface of the preheating pipe 11. Both the pipe body 121 and the insulating heat strip 123 are made of non-metallic high-temperature resistant material.

[0022] Specific workflow: Based on the specific workflow in Embodiment 1, in order to further control the heat exchange efficiency between the primary cold air and the flue gas inside the air preheater 1, thereby effectively controlling the final exhaust temperature, in addition to adjusting the amount of primary cold air entering the preheating tube 11 through the primary air bypass duct 2, this embodiment also provides an implementation scheme to control the exhaust temperature by adjusting the effective heat exchange area on the surface of the preheating tube 11. Specifically, when the flue gas temperature flowing into the air preheater 1 is too low, in order to reduce the heat loss of the flue gas, the telescopic device 14 can be activated to pull the protective pipe 12 on the vertical part of the preheating pipe 11, causing the closed ring 13 at the bottom of the protective pipe 12 to move downward, and pulling the insulating tape 123 located inside the mounting groove 122 downward. The insulating tape 123 is an elastic continuous bending structure, so when the insulating tape 123 is subjected to downward tension, it can be straightened and deformed, increasing its vertical dimension and expanding the coverage area of ​​the preheating pipe 11; and because Both the tube body 121 and the insulating heat strip 123 are made of high-temperature resistant, heat-insulating non-metallic material. Therefore, the shielded part of the preheating tube 11 is difficult to contact with the horizontally flowing flue gas. Moreover, the heat-insulating material properties can prevent the flue gas from transferring heat to the primary cold air in the preheating tube 11. In this way, only the exposed area between the protective tubes 12, located outside the insulating heat strip 123, serves as the effective heat exchange area and directly contacts the flue gas. This reduces the efficiency of the flue gas transferring heat to the primary cold air inside the preheating tube 11, thereby effectively improving the final exhaust gas temperature. Based on the control requirements of flue gas temperature, the shielding range of the gap area between each protective pipe 12 can be adjusted by pre-adjusting the telescopic length of the telescopic device 14. When it is necessary to reduce the transfer of flue gas heat to the primary cold air, the extension length of the insulating tape 123 can be increased, reducing the area of ​​normal contact between the preheating pipe 11 located between the protective pipes 12 and the flue gas, thereby reducing the heat loss of the flue gas; conversely, the extension length of the insulating tape 123 can be reduced, increasing the area of ​​normal contact between the preheating pipe 11 located between the protective pipes 12 and the flue gas, thereby increasing the heat loss of the flue gas. Thus, by adjusting the size of the effective heat exchange area on the preheating tube 11, and coordinating with the adjustment of the amount of primary cold air entering through the primary air bypass duct 2, the heat loss of the flue gas can be effectively controlled, thereby better controlling the boiler's exhaust temperature. Furthermore, considering that particulate impurities mixed in the flue gas easily adhere to the surface of the preheating tube 11 during contact with it, forming a fouling layer that affects the heat transfer efficiency between the inside and outside of the preheating tube 11, it becomes difficult to accurately calculate the mathematical correspondence between the effective heat exchange area on the preheating tube 11 and the exhaust gas temperature, which can easily lead to increased errors in the control of the exhaust gas temperature. Therefore, the end of the closed ring 13 is designed with a conical structure and contacts the outer surface of the preheating tube 11. This allows the closed ring 13 to effectively scrape away the particulate impurities adhering to the outer surface of the preheating tube 11 during its vertical sliding process, eliminating the fouling layer on the outer surface of the preheating tube 11. This ensures that the effective heat exchange area of ​​the preheating tube 11 exposed outside the protective tube 12 and the insulating heat exchanger 123 can maintain a stable and normal heat exchange efficiency, guaranteeing the heating efficiency of the primary and secondary cold air during normal preheating. It can also effectively reduce the control error of the boiler exhaust gas temperature when it is necessary to adjust the boiler exhaust gas temperature. Example

[0023] Based on Embodiment 2, the vertically distributed tubes 121 are connected by connecting rods 124. The bottom of the connecting rods 124 is fixed to the inner wall of the bottom of the air preheating tube 11 to support and stabilize the vertical part of the preheating tube 11. The connecting rod 124 is a tubular structure, and the top of the connecting rod 124 communicates with the purification air chamber 15 provided in the inner wall of the top of the air preheater 1. The purification air chamber 15 communicates with the air outlet of the purification fan provided on the outside. The connecting rod 124 vertically penetrates the flushing chamber 125 located on the upper side of the mounting groove 122 inside each tube 121, and the connecting rod 124 communicates with the flushing chamber 125. The inner wall of the flushing chamber 125 is provided with flushing holes 126. The flushing hole 126 is a conical hole, and the flushing hole 126 is connected to the gap between the insulating heat pack 123 and the outer surface of the preheating pipe 11. The insulating heat pack 123 is woven from high temperature resistant material wire, such as asbestos cloth. Regarding the elasticity of the folded structure, a continuously bent elastic metal skeleton structure can be set inside the insulating heat pack 123 to maintain the shape and elastic deformation of the insulating heat pack 123. The air preheater 1 has a collection trough 16 at the bottom, a protective net at the top of the collection trough 16, and an interception net 161 inside the collection trough 16 located on the upper side of the telescopic device 14. The air inlet of the purification fan is connected to the lower area of ​​the interception net 161. Specific workflow: Based on the specific workflow in Embodiment 2, the soot and impurities adhering to the inner wall of the air preheater 1 and the surface of the preheating tube 11 are generally cleaned by blowing purified airflow into the interior through an external purification fan. In order to improve the utilization efficiency of the purified airflow, when cleaning the preheating tube 11 inside the air preheater 1, the entry of flue gas is first closed, and the purification fan is started to send the purified airflow into the flushing chamber 125. Then, part of the purified airflow enters the air preheater 1 from the nozzle set at the bottom of the flushing chamber 125, forming a vertical downward airflow to flush the surface of the preheating tube 11, so that the soot and impurities fall off and enter the collection chamber at the bottom. Because the protective mesh at the opening of the collection chamber has a large aperture, while the internal interceptor mesh 161 has a small aperture, the soot and impurities enter the area above the interceptor mesh 161 in the collection chamber, and the airflow penetrates the interceptor mesh 161 and enters the air inlet of the purification fan, realizing the airflow recycling. Meanwhile, part of the airflow inside the flushing chamber 125 flows downward along the connecting rod 124 of the tubular structure, causing the purified airflow to flow into the flushing chamber 125 in each tube 121 along the connecting rod 124. Then, it enters the mounting groove 122 through the flushing hole 126 on the side wall of the flushing chamber 125, flushing the soot and impurities adhering to the surface of the insulating heat line 123 inside the mounting groove 122, causing the soot and impurities to detach from the insulating heat line 123. Furthermore, because the flushing hole 126 is connected to the gap area between the insulating tape 123 and the preheating pipe 11, the purified airflow entering the gap area increases the air pressure in the gap area. This causes the purified airflow to permeate downwards from the gap between the sealing ring 13 and the preheating pipe 11, improving the cleaning effect of the sealing ring 13 on the surface of the preheating pipe 11 and promptly removing the dust and impurities cleaned from the inner wall of the sealing ring 13, thus reducing scratches on the surface of the preheating pipe 11. On the other hand, because the insulating tape 123 is woven and has a uniformly distributed porous structure on its surface, the purified airflow in the gap area permeates upwards from the woven holes on the surface of the insulating tape 123, removing any dust and impurities that may adhere to the outer surface of the insulating tape 123, thereby improving the cleaning efficiency of the insulating tape 123 and ensuring its normal operation. This also improves the utilization efficiency of the purified airflow. Example

[0024] Based on Embodiment 3, the connecting rod 124 slides through the closed ring 13, and an annular cleaning block 131 is provided on the inner surface of the closed ring 13. The end of the cleaning block 131 is tapered and contacts the outer surface of the preheating pipe 11. The tapered end of the closed ring 13 is provided with a guide groove 132, which extends vertically through each cleaning block 131 and communicates with the gap area between the insulating heat strip 123 and the preheating pipe 11. Specific workflow: Based on the specific workflow in Embodiment 3, by uniformly arranging multiple rings of cleaning blocks 131 on the surface of the closed ring 13, the friction between the closed ring 13 and the surface of the preheating tube 11 is improved. This allows for more efficient cleaning and scraping of soot and impurities adhering to the surface of the preheating tube 11 when the closed ring 13 slides vertically along the surface of the preheating tube 11. Furthermore, when the purified airflow released from the flushing hole 126 enters the gap area between the cleaning blocks 131 along the guide groove 132, it can carry away the soot and impurities scraped off by the cleaning blocks 131, allowing them to leave the gap area surrounded by the closed ring 13 under the flushing of the airflow, thus improving the cleaning efficiency of the surface of the preheating tube 11. In addition, the purified airflow in the gap area between the closed ring 13 and the preheating tube 11 can also reduce the occurrence of soot and impurities getting stuck in the gap area between the inner wall of the closed ring 13 and the preheating tube 11 and sliding downwards, causing scratches on the surface of the preheating tube 11. This ensures effective cleaning of the preheating tube 11 while maintaining the surface quality of the preheating tube 11.

[0025] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A supercritical CFB boiler deep peak shaving condition flue gas temperature optimization control system, comprising a sensing and monitoring module, an intelligent control module and an adjustment and execution module, characterized in that: The perception monitoring module is used to monitor the flue gas temperature of the flue gas entering the flue (6) and the flue gas flowing out of the flue (7) on both sides of the air preheater (1); The adjustment execution module comprises a primary air bypass air duct (2) which is introduced from a primary cold air duct (3) of the supercritical CFB boiler and is divided into two paths, namely a primary air branch (21) and a secondary air branch (22), and finally connected to a primary hot air duct (4) and a secondary hot air duct (5), respectively; The preheating pipe (11) inside the air preheater (1) is communicated with the primary cold air duct (3) and presents a continuous curved structure.

2. The supercritical CFB boiler deep peak shaving operating condition flue gas temperature optimization control system according to claim 1, characterized in that: The primary air branch (21) and the secondary air branch (22) are provided with electrically adjustable dampers inside, and the combination part of the primary air bypass air duct (2) and the primary cold air duct (3) is provided with an electrically closed damper, a wind volume measuring device and an expansion joint.

3. The supercritical CFB boiler deep peak shaving operating condition flue gas temperature optimization control system according to claim 1, characterized in that: The vertical part of the preheating pipe (11) is uniformly provided with a protection pipe (12), and the protection pipe (12) comprises a pipe body (121) which is uniformly distributed along the vertically extending preheating pipe (11); The bottom of the pipe body (121) is provided with a mounting groove (122), and a resilient heat insulation belt (123) is fixedly connected inside the mounting groove (122), the heat insulation belt (123) is in an annular structure, and the part of the heat insulation belt (123) inside the mounting groove (122) presents a folded shape, and the bottom of the heat insulation belt (123) is fixedly connected with a closed ring (13) which is provided with an opening at the bottom of the mounting groove (122), and the closed ring (13) is connected with a telescopic device (14) mounted at the bottom of the air preheater (1) through a connecting rod.

4. The supercritical CFB boiler deep peak shaving operating condition flue gas temperature optimization control system according to claim 3, characterized in that: The bottom end of the closed ring (13) is in a conical structure and in contact with the outer surface of the preheating pipe (11), and the pipe body (121) and the heat insulation belt (123) are made of non-metallic high-temperature resistant material.

5. The supercritical CFB boiler deep peak shaving operating condition flue gas temperature optimization control system according to claim 4, characterized in that: The vertically distributed pipe bodies (121) are connected through connecting rods (124), and the bottom of the connecting rod (124) is fixedly connected with the inner wall of the bottom of the preheating pipe (11) to support and stabilize the vertical part of the preheating pipe (11).

6. The supercritical CFB boiler deep peak shaving operating condition flue gas temperature optimization control system according to claim 5, characterized in that: The connecting rod (124) is in a tubular structure, and the top of the connecting rod (124) is communicated with a purification gas cavity (15) provided in the inner wall of the top of the air preheater (1), and the purification gas cavity (15) is communicated with the outlet end of the purification fan provided outside; the connecting rod (124) vertically penetrates the flushing cavity (125) inside each pipe body (121) located on the upper side of the mounting groove (122), and the connecting rod (124) is communicated with the flushing cavity (125), and the inner wall of the flushing cavity (125) is provided with a flushing hole (126).

7. The supercritical CFB boiler deep peak shaving operating condition flue gas temperature optimization control system according to claim 6, characterized in that: The flushing hole (126) is a conical hole, and the flushing hole (126) is communicated with the gap between the heat insulation belt (123) and the outer surface of the preheating pipe (11), and the heat insulation belt (123) is obtained by weaving a wire made of high-temperature resistant material.

8. The supercritical CFB boiler deep peak shaving operating condition flue gas temperature optimization control system according to claim 7, characterized in that: The connecting rod (124) slides through the closed ring (13), and the inner surface of the closed ring (13) is provided with an annular cleaning block (131), and the end of the cleaning block (131) is conical and in contact with the outer surface of the preheating pipe (11).

9. The supercritical CFB boiler deep peak shaving operating condition flue gas temperature optimization control system according to claim 8, characterized in that: The tapered end of the closed ring (13) is provided with a flow guide groove (132) vertically extending through each cleaning block (131) and communicating with the gap area between the heat insulation belt (123) and the preheating pipe (11).

10. The supercritical CFB boiler deep peak shaving operating condition flue gas temperature optimization control system according to claim 9, characterized in that: The bottom of the air preheater (1) is provided with a collection groove (16), the top of which is provided with a protective net, and the inside of the collection groove (16) is provided with an intercepting net (161) at the position on the upper side of the telescopic device (14), and the air inlet end of the purification fan communicates with the lower side area of the intercepting net (161).

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