A boiler flue gas waste heat recovery heat exchange system and method
Patent Information
- Application Number
- CN202610896685.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-06-22
- Publication Date
- 2026-10-09
AI Technical Summary
这种湿灰垢极难清除，且会不断增厚，导致换热管后期传热效率大幅下降，排烟温度升高，甚至堵塞烟气流道
本发明在预处理管内设置经弹簧片弹性连接的从动扰流板，正常运行时仅依靠烟气冲击即可使从动扰流板产生自然风致振动，附着在板面的松散灰尘因惯性自行脱落并落入堵灰箱，实现了无需外部动力的预除尘自清洁，有效减少进入换热箱的粉尘量。
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Figure CN122881084A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of boiler flue gas waste heat recovery technology, and specifically discloses a boiler flue gas waste heat recovery heat exchange system and method. Background Technology
[0002] Energy-saving boilers generate a large amount of high-temperature flue gas during operation, typically ranging from 150 to 250°C, containing considerable sensible heat and latent heat of steam. To reduce flue gas heat loss and improve energy efficiency, waste heat recovery heat exchangers are usually installed in the boiler's tail flue. These exchangers utilize cold water within the heat exchange tubes to absorb heat from the flue gas, heating the water for reuse in boiler feedwater or the heating system. These heat exchangers often employ finned tube or bare tube bundle structures, with the flue gas laterally scouring the tube bundle, and boiler feedwater or circulating water flowing through the tubes.
[0003] When dust-laden flue gas enters the heat exchanger and comes into contact with the surface of the heat exchange tubes, the dust in the flue gas gradually deposits on the tube walls, forming a layer of ash and increasing the heat transfer resistance. More seriously, cold water flows through the heat exchange tubes, resulting in a low tube wall temperature. Once hot flue gas enters the heat exchange box and comes into contact with the tubes, the water vapor in the flue gas quickly condenses on the tube wall surface, forming condensate. This condensate mixes with the deposited dust to form a thick, sticky ash deposit that adheres firmly to the surface of the heat exchange tubes. This ash deposit is extremely difficult to remove and continues to thicken, leading to a significant decrease in the heat transfer efficiency of the heat exchange tubes, an increase in exhaust gas temperature, and even blockage of the flue gas flow channels. Currently, the common solution is to install a scraping device on the surface of the heat exchange tubes for mechanical cleaning. However, for S-shaped bends, the scraping device cannot pass along the bend, creating significant cleaning dead zones. Furthermore, cleaning operations usually require manual entry into the box after the furnace has been shut down and cooled, which is not only time-consuming and labor-intensive but also causes production interruptions and economic losses. Summary of the Invention
[0004] The purpose of this invention is to solve the problems existing in the background art, and to propose a boiler flue gas waste heat recovery heat exchange system, including a heat exchange box, one end of which is connected to an air outlet box, and the other end of which is connected to an air inlet box. A heat exchange mechanism is connected inside the heat exchange box, and a drain outlet is opened at the lower end of the heat exchange box corresponding to the heat exchange mechanism. A water collection mechanism is connected at the lower end of the heat exchange box corresponding to the drain outlet. One end of the air intake box is connected to a connecting pipe, the inner wall of the connecting pipe is connected to a screen, and a pull-out opening is provided at the upper end of the connecting pipe corresponding to the screen. The upper end of the screen is located inside the pull-out opening. One end of the connecting pipe is connected to a pretreatment mechanism, which is used to clean the dust in the boiler flue gas. By setting up a heat exchange box and a water collection mechanism, the waste heat of flue gas is recovered and the condensate is centrally discharged. The pretreatment mechanism and the screen work together to effectively intercept large particles, reducing the burden on subsequent deep dust removal.
[0005] Preferably, the heat exchange mechanism includes a water inlet pipe, and heat exchange tubes are evenly connected to one side of the water inlet pipe. The number of heat exchange tubes is four, and the four heat exchange tubes are S-shaped. The middle of the four heat exchange tubes is located inside the heat exchange box, and one end of the four heat exchange tubes is connected to a water outlet pipe. Both the water inlet pipe and the water outlet pipe are located on one side of the heat exchange box.
[0006] Preferably, the water collection mechanism includes a water collection tank, the upper end of which is connected to the lower end of the heat exchange box, the upper two sides of which are inclined, and a drain pipe is connected to the middle of the lower end of the water collection tank.
[0007] Preferably, the pretreatment mechanism includes a pretreatment pipe, one end of which is connected to one side of a connecting pipe. A ash discharge port is provided in the middle of the lower end of the pretreatment pipe. A ash-blocking box is connected to the lower end of the pretreatment pipe corresponding to the ash discharge port. The two sides of the ash-blocking box are connected to the lower end of the pretreatment pipe through mounting plates. The two mounting plates are connected to the lower end of the pretreatment pipe through mounting bolts.
[0008] Preferably, three spring plates are evenly connected to the upper end of the inner wall of the pretreatment tube. The lower ends of the three spring plates are connected to driven baffles. The cross-sectional shape of the driven baffles is wavy. The three driven baffles are evenly provided with first vent holes on one side. The wave-shaped driven spoiler increases the contact area with the flue gas, improving the efficiency of dust impact and settling. The semi-circular design of the spring plate allows the spoiler to swing elastically, generating natural vibration under the action of wind, thus achieving passive self-cleaning.
[0009] Preferably, the upper end of the pretreatment tube is connected to a housing, and an opening is provided at the upper end of the pretreatment tube corresponding to the housing. An electric telescopic rod is connected to one side of the housing, and the output end of the electric telescopic rod extends through into the interior of the housing. A first moving rod is connected to the output end of the electric telescopic rod, a fixed rod is connected to one side of the first moving rod, and a second moving rod is connected to one end of the fixed rod. The lower ends of both the first and second moving rods are located inside the pretreatment tube. A connecting block is connected to the lower end of both the first and second moving rods, and a movable spoiler is connected to the lower end of the two connecting blocks. Elastic impact blocks are connected to the lower parts of both sides of the two movable spoilers. The electric telescopic pole drives two moving spoilers to move synchronously through a connecting rod. It has a compact structure, low energy consumption, and elastic impact blocks that buffer and reduce shocks during impact, reducing metal wear and enhancing the vibration cleaning effect.
[0010] Preferably, the cross-sectional shape of the movable spoiler is wavy, and a second vent is provided on one side of each of the two movable spoilers. The two movable spoilers and the three driven spoilers are alternately arranged along the flue gas flow direction.
[0011] A method for recovering waste heat from boiler flue gas includes the following steps: S1: Boiler flue gas enters the pretreatment pipe and passes through the alternating turbulence zones of three driven baffles and two movable baffles. Under normal operating conditions, the electric telescopic rod is stationary, and the flue gas impact causes the driven baffles to vibrate due to wind. Dust falls off and into the bottom ash-blocking box, which has a small volume and only temporarily stores a small amount of dust. When deep cleaning is required, the boiler air supply is stopped, so that there is no flue gas flow in the pretreatment pipe. The electric telescopic rod is started to drive the movable baffles to move back and forth. The elastic impact blocks on both sides of the movable baffles alternately impact the adjacent driven baffles, generating buffered forced vibration to forcibly shake off the accumulated ash. At the same time, the ash-blocking box is removed and the ash discharge is opened. After pretreatment, the flue gas enters the air inlet box through the connecting pipe. S2: The pretreated clean flue gas enters the heat exchange box and comes into contact with the outer wall of the S-shaped heat exchange tube; cold water flows in from the inlet pipe, absorbs heat from the flue gas as it flows through the heat exchange tube, and becomes hot water that flows out from the outlet pipe; during the flue gas cooling process, when the tube wall temperature is lower than the dew point, water vapor condenses into water droplets, slides down the tube wall to the drain outlet, enters the water collection tank, and is discharged through the drain pipe. S3: The low-temperature flue gas after heat exchange is discharged into the subsequent treatment equipment through the exhaust box.
[0012] Compared with the prior art, the present invention has the following beneficial effects: This invention features a driven baffle plate elastically connected by spring sheets inside the pretreatment tube. During normal operation, the driven baffle plate can generate natural wind-induced vibration simply by the impact of flue gas. Loose dust adhering to the plate surface falls off by inertia and into the dust-blocking box, achieving pre-dust removal and self-cleaning without external power, effectively reducing the amount of dust entering the heat exchange box.
[0013] When deep cleaning is required, the electric telescopic rod drives the moving spoiler to move back and forth. The elastic impact blocks on both sides alternately impact the adjacent driven spoilers, generating forced vibration and forcibly shaking off the long-term adhered dust. At the same time, the dust blocking box is removed and opened to discharge dust, ensuring that the pretreatment mechanism is unobstructed for a long time and with low energy consumption.
[0014] The wave-shaped driven baffle and the moving baffle generate strong turbulence on the flue gas inside the pretreatment tube, which not only effectively settles dust, but also makes the flue gas velocity distribution more uniform and increases the turbulence intensity. This is beneficial for the flue gas to more fully scour the outer wall of the S-shaped heat exchange tube after entering the heat exchange box. At the same time, the S-shaped heat exchange tube itself extends the water flow path. The two work together to transfer heat from the flue gas side to the water side more efficiently, significantly improving the overall heat exchange efficiency. Attached Figure Description
[0015] Figure 1 This is a schematic diagram of the overall structure of the device of the present invention; Figure 2This is an overall cross-sectional view of the device of the present invention; Figure 3 This is a schematic diagram of the internal structure of the heat exchanger box of the present invention; Figure 4 This is a schematic diagram of the connection structure of the ash-blocking box of the present invention; Figure 5 This is a schematic diagram of the installation structure of the driven spoiler of the present invention; Figure 6 This is a schematic diagram of the internal structure of the pretreatment tube of the present invention; Figure 7 This is a schematic diagram of the structure of the three driven spoilers and two movable spoilers of the present invention.
[0016] In the diagram: 1. Heat exchanger box; 2. Air outlet box; 3. Air inlet box; 4. Water inlet pipe; 5. Heat exchanger tube; 6. Water outlet pipe; 7. Drain outlet; 8. Water collection box; 9. Drain pipe; 10. Connecting pipe; 11. Screen; 12. Pull-out port; 13. Pretreatment pipe; 14. Ash discharge port; 15. Ash blocking box; 16. Spring plate; 17. Driven baffle; 18. First vent; 19. Shell; 20. Opening; 21. Electric telescopic rod; 22. First moving rod; 23. Fixed rod; 24. Second moving rod; 25. Connecting block; 26. Moving baffle; 27. Second vent; 28. Elastic impact block. Detailed Implementation
[0017] To better understand the above-mentioned objectives, features, and advantages of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.
[0018] Numerous specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and therefore the invention is not limited to the specific embodiments disclosed below.
[0019] like Figures 1-7 The boiler flue gas waste heat recovery heat exchange system shown includes a heat exchange box 1, an outlet box 2 connected to one end of the heat exchange box 1, an inlet box 3 connected to the other end of the heat exchange box 1, a heat exchange mechanism connected inside the heat exchange box 1, a drain outlet 7 opened at the lower end of the heat exchange box 1 corresponding to the heat exchange mechanism, and a water collection mechanism connected at the lower end of the heat exchange box 1 corresponding to the drain outlet 7. One end of the air intake box 3 is connected to a connecting pipe 10, and a screen 11 is connected to the inner wall of the connecting pipe 10. A pull-out port 12 is opened at the upper end of the connecting pipe 10 corresponding to the screen 11, and the upper end of the screen 11 is located inside the pull-out port 12. One end of the connecting pipe 10 is connected to a pretreatment mechanism, which is used to clean the dust in the boiler flue gas. In actual operation, the high-temperature dusty flue gas discharged from the boiler first enters the pretreatment mechanism. After the coarse particles are initially intercepted, the flue gas enters the air inlet box 3 through the connecting pipe 10, and then the waste heat is recovered through the heat exchange mechanism in the heat exchange box 1. The screen 11 can intercept the dust in the flue gas and can be pulled out for cleaning through the pull-out port 12. The drain outlet 7 at the bottom of the heat exchange box 1 discharges the condensate into the water collection mechanism to achieve gas-liquid separation.
[0020] like Figures 1-2 As shown: The heat exchange mechanism includes an inlet pipe 4, and heat exchange pipes 5 are evenly connected to one side of the inlet pipe 4. There are four heat exchange pipes 5, and the four heat exchange pipes 5 are S-shaped. The middle of the four heat exchange pipes 5 is located inside the heat exchange box 1. One end of the four heat exchange pipes 5 is connected to an outlet pipe 6. Both the inlet pipe 4 and the outlet pipe 6 are located on one side of the heat exchange box 1. Cold water enters through the inlet pipe 4 and is distributed into four S-shaped heat exchange tubes 5. Inside the heat exchange box 1, it exchanges heat with the high-temperature flue gas. The S-shaped design increases the length of the flow channel inside the tube, allowing the water to contact the flue gas for a longer time and the heat exchange to be more complete. The hot water that has absorbed the heat flows out through the outlet pipe 6 for use.
[0021] The water collection mechanism includes a water collection tank 8, the upper end of which is connected to the lower end of the heat exchange box 1. The upper two sides of the water collection tank 8 are inclined, and a drain pipe 9 is connected to the middle of the lower end of the water collection tank 8. When the flue gas condenses into water droplets on the outer wall of the heat exchange tube 5, the water droplets slide down the inner wall of the heat exchange tube 5 and the heat exchange box 1 to the bottom, and enter the water collection box 8 through the drain outlet 7. The inclined design on both sides of the upper end of the water collection box 8 allows the condensate to flow quickly to the middle, avoiding local accumulation, and then it is discharged through the drain pipe 9.
[0022] like Figures 4-7 As shown: The pretreatment mechanism includes a pretreatment pipe 13. One end of the pretreatment pipe 13 is connected to one side of the connecting pipe 10. A ash discharge port 14 is opened in the middle of the lower end of the pretreatment pipe 13. A ash blocking box 15 is connected to the lower end of the pretreatment pipe 13 corresponding to the ash discharge port 14. The two sides of the ash blocking box 15 are connected to the lower end of the pretreatment pipe 13 through mounting plates. The two mounting plates are connected to the lower end of the pretreatment pipe 13 through mounting bolts. After the dust-laden flue gas is discharged from the boiler, it directly enters the pretreatment pipe 13. Under the action of the driven baffle 17 and the moving baffle 26 inside the pipe, the dust is impacted and settled, and falls into the ash-blocking box 15 through the ash discharge port 14. The ash-blocking box 15 is fixed to the lower end of the pretreatment pipe 13 by mounting bolts and can be disassembled and cleaned periodically.
[0023] Spring plates 16 are evenly connected to the upper end of the inner wall of the pretreatment pipe 13. There are three spring plates 16. The lower ends of the three spring plates 16 are connected to driven spoilers 17. The cross-sectional shape of the driven spoilers 17 is wavy. The three driven spoilers 17 are evenly provided with first vent holes 18 on one side. During normal operation, when the flue gas flows through the driven spoiler 17, the wavy surface increases the turbulence effect. At the same time, the first vent 18 allows some flue gas to pass through, reducing resistance. The impact of the flue gas causes the driven spoiler 17 to vibrate naturally around the spring plate 16. The dust attached to the plate surface falls off due to inertia and is discharged through the ash discharge port 14.
[0024] The upper end of the pretreatment tube 13 is connected to the housing 19. An opening 20 is provided at the upper end of the pretreatment tube 13 corresponding to the housing 19. An electric telescopic rod 21 is connected to one side of the housing 19. The output end of the electric telescopic rod 21 extends through into the interior of the housing 19. The output end of the electric telescopic rod 21 is connected to a first moving rod 22. A fixed rod 23 is connected to one side of the first moving rod 22. A second moving rod 24 is connected to one end of the fixed rod 23. The lower ends of the first moving rod 22 and the second moving rod 24 are both located inside the pretreatment tube 13. A connecting block 25 is connected to the lower ends of the first moving rod 22 and the second moving rod 24. A movable spoiler 26 is connected to the lower ends of the two connecting blocks 25. An elastic impact block 28 is connected to the lower part of both sides of the two movable spoilers 26. When deep cleaning is required, the boiler air supply is stopped, so that there is no flue gas flow in the pretreatment pipe 13. The electric telescopic rod 21 is activated, pushing the first moving rod 22 and the second moving rod 24 to reciprocate. Through the connecting block 25, the two moving baffles 26 are moved along the flue gas flow direction. The elastic impact blocks 28 on both sides of the moving baffles 26 alternately impact the adjacent driven baffles 17, causing them to generate forced vibration, which forcibly shakes off the long-term adhered ash. The elastic impact blocks 28 are made of high temperature and corrosion resistant rubber, which can buffer the impact and reduce noise.
[0025] The cross-sectional shape of the movable spoiler 26 is wavy. Each of the two movable spoilers 26 has a second vent 27 on one side. The two movable spoilers 26 and the three driven spoilers 17 are alternately arranged along the flue gas flow direction. Two movable spoilers 26 and three driven spoilers 17 are arranged alternately, that is, the flue gas first passes through the first driven spoiler 17, then through the first movable spoiler 26, then through the second driven spoiler 17, and so on. This alternating arrangement makes the flue gas form an S-shaped flow path, effectively prolonging the residence time and increasing the probability of dust being intercepted by impact. The second vent 27 on the movable spoiler 26 and the first vent 18 on the driven spoiler 17 work together to keep the airflow smooth and prevent excessive resistance. The wavy plate surface increases the surface area and enhances the turbulence and dust adhesion effect.
[0026] A method for recovering waste heat from boiler flue gas includes the following steps: S1: Boiler flue gas enters the pretreatment pipe 13 and passes through the alternating turbulence zones of three driven baffles 17 and two movable baffles 26 in sequence. Under normal operating conditions, the electric telescopic rod 21 is stationary, and the flue gas impact causes the driven baffles 17 to vibrate due to wind. Dust falls off and into the bottom ash-blocking box 15. The ash-blocking box 15 has a small volume and only temporarily stores a small amount of dust. When deep cleaning is required, the boiler air supply is stopped, so that there is no flue gas flow in the pretreatment pipe 13. The electric telescopic rod 21 is started to drive the movable baffles 26 to move back and forth. The elastic impact blocks 28 on both sides of the movable baffles 26 alternately impact the adjacent driven baffles 17, generating buffered forced vibration, forcibly shaking off the accumulated ash, and removing the ash-blocking box 15 to open the ash discharge. After pretreatment, the flue gas enters the air inlet box 3 through the connecting pipe 10. S2: The pretreated clean flue gas enters the heat exchange box 1 and comes into contact with the outer wall of the S-shaped heat exchange tube 5; cold water flows in from the inlet pipe 4, absorbs the heat of the flue gas as it flows through the heat exchange tube 5, and becomes hot water that flows out from the outlet pipe 6; during the flue gas cooling process, when the tube wall temperature is lower than the dew point, water vapor condenses into water droplets, slides down the tube wall to the drain outlet 7, enters the water collection box 8, and is discharged through the drain pipe 9. S3: The low-temperature flue gas after heat exchange is discharged into the subsequent treatment equipment through the exhaust box 2.
[0027] Working principle: The high-temperature dust-laden flue gas discharged from the boiler first enters the pretreatment pipe 13. Three driven baffles 17 and two movable baffles 26 are alternately arranged in the pretreatment pipe 13 along the flue gas flow direction.
[0028] During most of the operating time, the electric telescopic rod 21 is stationary, the movable spoiler 26 does not move actively, and when the flue gas flows through the driven spoiler 17, the wavy surface of the plate causes the flue gas to turbulent, and the dust settles due to the inertial impact on the plate surface; at the same time, the impact force of the flue gas causes the driven spoiler 17 to vibrate naturally around the spring plate 16, which loosens and falls off the dust attached to the plate surface. The fallen dust falls into the ash box 15 through the bottom ash discharge port 14 for temporary storage. Due to the presence of the first vent 18 and the second vent 27, the flue gas flow resistance remains at a low level.
[0029] When the running time reaches the preset cycle, the electric telescopic rod 21 is activated. The electric telescopic rod 21 pushes the first moving rod 22 and the second moving rod 24 to reciprocate. Through the connecting block 25, it drives the two moving baffles 26 to move back and forth in a straight line along the flue gas flow direction.
[0030] The elastic impact blocks 28 fixed on the lower part of both sides of the movable spoiler 26 alternately impact the adjacent driven spoiler 17 during the movement, causing the driven spoiler 17 to generate forced vibration, which can force off the long-term adhered or hardened dust. The elastic impact blocks 28 also play a buffering role to avoid damage caused by direct metal collision.
[0031] During deep cleaning, the dust-blocking box 15 is removed, and the shaken-off dust is discharged directly. After cleaning, the electric telescopic rod 21 is reset and the dust-blocking box 15 is installed.
[0032] The pretreated clean flue gas enters the air inlet box 3 through the connecting pipe 10. The connecting pipe 10 is also equipped with a screen 11 to intercept residual dust in the flue gas, and can be pulled out for cleaning through the pull-out port 12.
[0033] Clean flue gas enters the heat exchanger 1 from the air inlet box 3 and comes into contact with the outer wall of the four S-shaped heat exchange tubes 5. At the same time, cold water enters from the water inlet pipe 4 and flows into the four S-shaped heat exchange tubes 5.
[0034] The S-shaped heat exchange tube 5 increases the length of the flow channel inside the tube, allowing for a longer contact time between the water and the flue gas, resulting in more thorough heat exchange. The flue gas flows laterally outside the tube, and its heat is transferred to the cold water inside the tube through the tube wall. After being heated, the cold water flows out from the outlet pipe 6 for industrial or heating use.
[0035] Since the flue gas has been pretreated and dust removed, there is almost no dust accumulation on the outer wall of the heat exchange tube 5. Therefore, the heat exchange efficiency remains stable for a long time and there is no need for frequent dust removal.
[0036] During the heat exchange process, the flue gas temperature gradually decreases. When the temperature of the outer wall of the heat exchange tube 5 is lower than the dew point of the water vapor in the flue gas, the water vapor condenses into tiny water droplets on the surface of the tube wall. As the water droplets grow larger, under the combined action of gravity and flue gas flow, the water droplets slide down the outer wall of the S-shaped heat exchange tube 5 and eventually flow to the drain outlet 7 at the bottom of the heat exchange box 1.
[0037] Condensate enters the water collection tank 8 through the drain outlet 7. The upper two sides of the water collection tank 8 are inclined to guide the condensate to quickly flow into the middle, and then be discharged through the bottom drain pipe 9.
[0038] 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 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 claimed invention.
Claims
1. A boiler flue gas waste heat recovery heat exchange system, comprising a heat exchange box (1), characterized in that: One end of the heat exchange box (1) is connected to an air outlet box (2), and the other end of the heat exchange box (1) is connected to an air inlet box (3). A heat exchange mechanism is connected inside the heat exchange box (1). A drain outlet (7) is opened at the lower end of the heat exchange box (1) corresponding to the heat exchange mechanism. A water collection mechanism is connected at the lower end of the heat exchange box (1) corresponding to the drain outlet (7). One end of the air intake box (3) is connected to a connecting pipe (10), and a screen (11) is connected to the inner wall of the connecting pipe (10). A pull-out port (12) is opened at the upper end of the connecting pipe (10) corresponding to the screen (11), and the upper end of the screen (11) is located inside the pull-out port (12). One end of the connecting pipe (10) is connected to a pretreatment mechanism, which is used to clean the dust in the boiler flue gas.
2. The boiler flue gas waste heat recovery and heat exchange system according to claim 1, characterized in that: The heat exchange mechanism includes an inlet pipe (4), and heat exchange tubes (5) are evenly connected to one side of the inlet pipe (4). There are four heat exchange tubes (5), and the four heat exchange tubes (5) are S-shaped. The middle of the four heat exchange tubes (5) is located inside the heat exchange box (1). One end of the four heat exchange tubes (5) is connected to an outlet pipe (6). Both the inlet pipe (4) and the outlet pipe (6) are located on one side of the heat exchange box (1).
3. The boiler flue gas waste heat recovery heat exchange system according to claim 2, characterized in that: The water collection mechanism includes a water collection tank (8), the upper end of which is connected to the lower end of the heat exchange box (1). The upper sides of the water collection tank (8) are inclined, and a drain pipe (9) is connected to the middle of the lower end of the water collection tank (8).
4. The boiler flue gas waste heat recovery heat exchange system according to claim 3, characterized in that: The pretreatment mechanism includes a pretreatment pipe (13), one end of which is connected to one side of the connecting pipe (10). A ash discharge port (14) is provided in the middle of the lower end of the pretreatment pipe (13). A ash blocking box (15) is connected to the lower end of the pretreatment pipe (13) corresponding to the ash discharge port (14). The two sides of the ash blocking box (15) are connected to the lower end of the pretreatment pipe (13) through mounting plates. The two mounting plates are connected to the lower end of the pretreatment pipe (13) through mounting bolts.
5. A boiler flue gas waste heat recovery and heat exchange system according to claim 4, characterized in that: The upper end of the inner wall of the pretreatment tube (13) is uniformly connected with spring plates (16), and there are three spring plates (16). The lower ends of the three spring plates (16) are connected with driven spoilers (17). The cross-sectional shape of the driven spoilers (17) is wavy, and the three driven spoilers (17) are uniformly provided with first vent holes (18) on one side.
6. A boiler flue gas waste heat recovery and heat exchange system according to claim 5, characterized in that: The upper end of the pretreatment tube (13) is connected to a housing (19). An opening (20) is provided at the upper end of the pretreatment tube (13) corresponding to the housing (19). An electric telescopic rod (21) is connected to one side of the housing (19). The output end of the electric telescopic rod (21) extends through into the interior of the housing (19). The output end of the electric telescopic rod (21) is connected to a first moving rod (22). A fixed rod (23) is connected to one side of the first moving rod (22). A second moving rod (24) is connected to one end of the fixed rod (23). The lower ends of the first moving rod (22) and the second moving rod (24) are both located inside the pretreatment tube (13). A connecting block (25) is connected to the lower ends of the first moving rod (22) and the second moving rod (24). A moving spoiler (26) is connected to the lower ends of the two connecting blocks (25). An elastic impact block (28) is connected to the lower sides of the two moving spoilers (26).
7. A boiler flue gas waste heat recovery and heat exchange system according to claim 6, characterized in that: The cross-sectional shape of the movable spoiler (26) is wavy. A second vent (27) is provided on one side of each of the two movable spoilers (26). The two movable spoilers (26) and the three driven spoilers (17) are alternately arranged along the flue gas flow direction.
8. A method for recovering waste heat from boiler flue gas, using a boiler flue gas waste heat recovery and heat exchange system as described in any one of claims 1-7, characterized in that, The following usage steps are included: S1: Boiler flue gas enters the pretreatment pipe (13) and passes through the alternating turbulence areas of three driven baffles (17) and two moving baffles (26) in sequence. Under normal operating conditions, the electric telescopic rod (21) is stationary, and the flue gas impact causes the driven baffles (17) to generate wind-induced vibration. The dust falls off and into the bottom ash-blocking box (15). The ash-blocking box (15) has a small volume and only temporarily stores a small amount of dust. When deep cleaning is required, the boiler air supply is stopped so that there is no flue gas flow in the pretreatment pipe (13). The electric telescopic rod (21) is started to drive the moving baffles (26) to move back and forth. The elastic impact blocks (28) on both sides of the moving baffles (26) alternately impact the adjacent driven baffles (17), generating buffered forced vibration, forcibly shaking off the accumulated ash. At the same time, the ash-blocking box (15) is removed and the ash discharge is opened. After pretreatment, the flue gas enters the air inlet box (3) through the connecting pipe (10). S2: The pretreated clean flue gas enters the heat exchange box (1) and comes into contact with the outer wall of the S-shaped heat exchange tube (5); cold water flows in from the inlet pipe (4), absorbs the heat of the flue gas when it flows through the heat exchange tube (5), and becomes hot water that flows out from the outlet pipe (6); during the flue gas cooling process, when the temperature of the tube wall is lower than the dew point, the water vapor condenses into water droplets, slides down the tube wall to the drain outlet (7), enters the water collection box (8), and is discharged through the drain pipe (9); S3: The low-temperature flue gas after heat exchange is discharged into the subsequent treatment equipment through the exhaust box (2).