A low-pressure boiler system using high-temperature flue gas heat exchange and working method

Abstract

The application discloses a low-pressure boiler system utilizing high-temperature flue gas heat exchange, which comprises a flue gas heating furnace wall, a liquid medium bin in the flue gas heating furnace wall, and heated liquid medium filled in the liquid medium bin; a plurality of flue gas heat exchange pipes are transversely arranged in the liquid medium bin and are parallel to each other and are uniformly distributed at intervals, the plurality of flue gas heat exchange pipes jointly form a flue gas heat exchange pipe array, and the flue gas heat exchange pipe array is immersed in the heated liquid medium in the liquid medium bin; the two ends of the liquid medium bin are respectively connected with a liquid medium leading-in pipe and a liquid medium leading-out pipe; in the flue gas heat exchange pipe array, any three flue gas heat exchange pipes adjacent to each other are recorded as a heat exchange pipe combination unit; the enclosed area between the three flue gas heat exchange pipes of any heat exchange pipe combination unit forms a liquid medium heat exchange enhancement tunnel extending along an axial direction; and a plurality of heat exchange enhancement cages are equidistantly arranged in each liquid medium heat exchange enhancement tunnel along the length extension direction. The output supply stability of the hot liquid medium is improved.

Description

Technical Field

[0001] This invention belongs to the field of flue gas heating. Background Technology

[0002] In industrial and residential heating sectors, traditional flue gas heat exchange boilers typically employ a structure where flue gas heat exchange tubes are immersed in a liquid medium. The heat from the flue gas is transferred to the surrounding liquid medium through the tube walls, thus heating the liquid medium. However, such boiler systems generally suffer from a slow initial heating phase. Due to the large volume and heat capacity of the liquid medium within the tank, even with sufficient heat exchange tube area, it takes a considerable amount of time for the liquid medium to reach the target temperature, resulting in slow system startup and an inability to meet rapid response requirements. Secondly, during actual operation, the flow rate and temperature of the flue gas often fluctuate, directly causing significant fluctuations in the temperature of the output hot liquid medium, making it difficult to achieve a stable and consistent heat supply. To maintain a stable output temperature, traditional solutions usually require the addition of large buffer tanks or complex bypass control systems, which not only increases equipment size and cost but also reduces system thermal efficiency. Summary of the Invention

[0003] Purpose of the invention: In order to overcome the shortcomings of the existing technology, the present invention provides a low-pressure boiler system and working method that utilizes high-temperature flue gas heat exchange, thereby improving the stability of the output supply of hot liquid medium.

[0004] Technical solution: To achieve the above objectives, the present invention provides a low-pressure boiler system that utilizes high-temperature flue gas for heat exchange, comprising a flue gas heating furnace wall, a liquid medium chamber inside the flue gas heating furnace wall, and the liquid medium chamber being filled with a heated liquid medium.

[0005] A number of parallel and evenly spaced flue gas heat exchange tubes are transversely distributed within the liquid medium chamber. These tubes together form a flue gas heat exchange tube array, which is immersed in the heated liquid medium within the liquid medium chamber. The two ends of the liquid medium chamber are connected to a liquid medium inlet pipe and a liquid medium outlet pipe, respectively. In the flue gas heat exchange tube array, any three adjacent flue gas heat exchange tubes are considered as a heat exchange tube combination unit. The enclosed area between the three flue gas heat exchange tubes in any combination unit forms a liquid medium heat exchange enhancement channel extending along the axial direction. In each liquid medium heat exchange enhancement channel, several heat exchange enhancement cages are equidistantly arranged along the length extension direction.

[0006] Furthermore, from the perspective of the axis, the line connecting the geometric centers of the three flue gas heat exchange tubes in any set of heat exchange tube combination units forms an equilateral triangle.

[0007] Furthermore, the heat exchange enhancement cage is made of thermally conductive metal and is immersed in the liquid medium in the liquid medium heat exchange enhancement tunnel.

[0008] Furthermore, liquid medium voids are formed between adjacent heat exchange enhancement cages in the liquid medium heat exchange enhancement tunnel.

[0009] Furthermore, the heat exchange enhancement cage is a cage cavity, and a variable cage cavity airbag is installed in the cage cavity, and the variable cage cavity airbag is an airbag cavity; the variable cage cavity airbags in any two adjacent heat exchange enhancement cages in the liquid medium heat exchange enhancement roadway are interconnected by a pressure transmission pipe; a pressure control air pump is installed outside the flue gas heating furnace wall, and the pressure output end of the pressure control air pump is connected to any pressure transmission pipe in the liquid medium heat exchange enhancement roadway.

[0010] Furthermore, the heat exchange enhancement cage has three concave arc surfaces and three convex arc surfaces arranged in a circumferential array. The three concave arc surfaces of the heat exchange enhancement cage are respectively heat-transferring and attached to the outer circumferential surfaces of the three flue gas heat exchange tubes, which can be achieved through heat transfer and bonding using a thermally conductive and heat-resistant adhesive. The three convex arc surfaces of the heat enhancement cage are all hollowed out with an array of circumferential cage holes that connect to the cage cavity. The front and rear ends of the heat enhancement cage are both hollowed out with an array of end cage holes that connect to the cage cavity.

[0011] Furthermore, a working method for a low-pressure boiler system utilizing high-temperature flue gas heat exchange:

[0012] S1. Before introducing the liquid medium into the liquid medium chamber inside the flue gas heating furnace wall, the pressure transmission pipe is pressurized by an external pressure control air pump so that the variable cage chamber airbags in all heat exchange enhancement cages are in an inflated state. Under the cage constraint of the heat exchange enhancement cage, the volume of the variable cage chamber airbags will not increase significantly and burst.

[0013] S2. Fill the liquid medium chamber inside the flue gas heating furnace wall with liquid medium, so that all the flue gas heat exchange tubes and heat exchange enhancement cages inside the furnace are immersed in the liquid medium.

[0014] S3. During the initial heating stage, high-temperature flue gas flows continuously through each flue gas heat exchange tube. Since most of the space in the cage cavity of each heat exchange enhancement cage is occupied by the hollow, bulging variable cage cavity airbag, the liquid medium completely submerges each heat exchange enhancement cage and each flue gas heat exchange tube. With the heating surface area remaining unchanged, the total volume of the liquid medium in the liquid medium chamber is at its minimum.

[0015] S4, after the liquid medium in the liquid medium chamber is rapidly heated to the target temperature, the liquid medium inlet pipe continuously injects a slightly cooler liquid medium into one end of the liquid medium chamber, while the liquid medium outlet pipe continuously discharges the hot liquid medium that has been heated to the target temperature from the liquid medium chamber; when the flue gas flow rate and flue gas temperature in each flue gas heat exchanger tube remain constant, the liquid medium outlet pipe can stably supply the hot liquid medium at the target temperature to the outside at a constant flow rate; the flow rates of the liquid medium inlet pipe and the liquid medium outlet pipe are relatively constant.

[0016] When the flue gas flow rate and temperature in each flue gas heat exchanger tube are high during a certain period, while maintaining a relatively constant flow rate of hot liquid medium discharged from the liquid medium outlet pipe, the flow rate of cold liquid medium injected into the liquid medium chamber through the liquid medium inlet pipe is increased. At the same time, an external pressure-controlled air pump evacuates the pressure transmission pipe, causing the variable cage air bladders in all heat exchange enhancement cages, which were originally inflated, to gradually deflate. This releases the cage space that was originally occupied in each heat exchange enhancement cage, and each heat exchange enhancement cage, like a sponge, continuously absorbs the liquid medium in the liquid medium chamber through the circumferential cage hole array and the end cage hole array. This forms a dynamic balance and offset in volume with the excess flow rate of cold liquid medium injected into the liquid medium chamber through the inlet pipe. At the same time, the excess flow rate of cold liquid medium injected into the liquid medium chamber through the inlet pipe offsets the high flue gas flow rate and high flue gas temperature in each flue gas heat exchanger tube in terms of thermal balance. This ensures that during this stage, the liquid medium outlet pipe can still supply hot liquid medium with relatively stable temperature and flow rate.

[0017] When the flue gas flow rate and temperature in each flue gas heat exchanger tube change from high to low during a certain period, while maintaining a relatively constant flow rate of hot liquid medium discharged from the liquid medium outlet pipe, the flow rate of cold liquid medium injected into the liquid medium chamber by the liquid medium inlet pipe is reduced. At the same time, the pressure transmission pipe is pressurized by an external pressure control air pump, causing the originally deflated variable cage cavity air bladders in all heat exchange enhancement cages to gradually expand outward. As a result, the hot liquid medium originally stored in the cage cavity of each heat exchange enhancement cage is squeezed out into the liquid medium chamber like a sponge through the circumferential cage cavity array and the end cage cavity array under the gradually enlarging variable cage cavity air bladders. This forms a dynamic balance and offset in volume with the missing flow rate of cold liquid medium injected into the liquid medium chamber by the inlet pipe. At the same time, the missing flow rate of cold liquid medium injected into the liquid medium chamber by the inlet pipe offsets the low flue gas flow rate and low flue gas temperature in each flue gas heat exchanger tube in terms of thermal balance. Ultimately, during this stage, the liquid medium outlet pipe can still supply hot liquid medium with relatively stable temperature and flow rate.

[0018] The above process is completed with the cooperation of temperature and flow sensors, so that even when the flue gas flow rate and flue gas temperature fluctuate, the liquid medium outlet pipe can still supply a hot liquid medium with relatively stable temperature and flow rate.

[0019] Beneficial effects: This invention arranges the flue gas heat exchange tubes in an equilateral triangle, naturally forming a liquid medium heat exchange enhancement channel between the tubes, and sets heat exchange enhancement cages made of thermally conductive metal at equal intervals in the channel. The concave arc surface of the heat exchange enhancement cage is closely attached to the three flue gas heat exchange tubes, which not only greatly expands the heat exchange area, but also constructs a cage cavity structure that can accommodate a variable cage cavity airbag.

[0020] All the variable cage chamber airbags in the heat exchange enhancement cage are interconnected through pressure transmission pipes and uniformly regulated by an external pressure control pump, realizing the synchronous linkage of airbag expansion and contraction.

[0021] During startup, the airbag remains inflated, occupying space within the cage cavity and minimizing the amount of liquid medium inside the tank. This significantly reduces the total heat required for heating while maintaining the same heat exchange area, thereby shortening the time to reach the target temperature and achieving rapid startup. During operation, when fluctuations occur in flue gas flow or temperature, the liquid medium inlet flow rate and airbag volume are adjusted synchronously. Utilizing the volume offset mechanism—cold liquid being drawn into the cage cavity when the airbag contracts and hot liquid being expelled when the airbag expands—a dynamic balance is formed with the increase or decrease in the inlet flow rate. This simultaneously achieves heat offset compensation, keeping the temperature and flow rate of the liquid medium at the output end relatively constant.

[0022] This system integrates heat exchange enhancement, rapid start-up, and fluctuation suppression into one unit, eliminating the need for external buffers and improving the system's adaptability to fluctuating heat sources and energy supply stability. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the boiler as a whole.

[0024] Figure 2 for Figure 1 The cross-sectional view along direction A, in which the heat exchange enhancement cage is omitted;

[0025] Figure 3 This is a schematic diagram of the structure of any local area of ​​the flue gas heat exchange tube array, consisting of seven flue gas heat exchange tubes.

[0026] Figure 4 This is a schematic diagram of the combination structure of three flue gas heat exchange tubes and heat exchange enhancement cage for any set of heat exchange tube combination units. Detailed Implementation

[0027] The invention will now be further described with reference to the accompanying drawings.

[0028] like Figures 1 to 4 The diagram shows a low-pressure boiler system that utilizes high-temperature flue gas for heat exchange, including a flue gas heating furnace wall 1, with a liquid medium chamber 4 inside the flue gas heating furnace wall 1, and the liquid medium chamber 4 filled with the liquid medium to be heated; the flue gas heating furnace wall 1 is made of high-temperature resistant and pressure-resistant metal material, and its internal space forms a closed liquid medium chamber 4 for containing the liquid medium to be heated.

[0029] Several parallel and evenly spaced flue gas heat exchange tubes 3 are transversely distributed within the liquid medium chamber 4. These flue gas heat exchange tubes 3 together form a flue gas heat exchange tube array, which is immersed in the heated liquid medium within the liquid medium chamber 4. The flue gas heat exchange tubes 3 are made of metal materials with high thermal conductivity, such as stainless steel or copper alloy. High-temperature flue gas is introduced into the tubes as a heat source, and the outer wall of the tubes is in direct contact with the liquid medium, efficiently transferring the heat of the flue gas to the liquid medium through the tube wall.

[0030] The two ends of the liquid medium tank 4 are connected to a liquid medium inlet pipe and a liquid medium outlet pipe, respectively. The liquid medium inlet pipe is used to replenish the cold liquid medium to be heated into the liquid medium tank 4, and the liquid medium outlet pipe is used to transport the heated hot liquid medium outward. By controlling the flow balance between the inlet and outlet, the system can achieve continuous and stable operation.

[0031] In the flue gas heat exchanger tube array, any three adjacent flue gas heat exchanger tubes 3 are denoted as a group of heat exchanger tube combination units 26. From the axial perspective, the line connecting the geometric centers of the three flue gas heat exchanger tubes 3 in any group of heat exchanger tube combination units 26 forms an equilateral triangle 23. This makes the enclosed area between the three flue gas heat exchanger tubes 3 form a geometrically symmetrical flow channel structure, providing uniform spatial conditions for the subsequent installation of heat exchange enhancement elements, and also facilitating the formation of a uniform temperature field and flow field between the tubes by the liquid medium.

[0032] The enclosed area between the three flue gas heat exchange tubes 3 of any set of heat exchange tube combination unit 26 forms a liquid medium heat exchange enhancement channel 27 extending along the axial direction; the liquid medium heat exchange enhancement channel 27 is an axial channel naturally formed between the three adjacent flue gas heat exchange tubes 3, and is the core area for liquid medium flow and heat exchange. Adding heat exchange elements in the channel can significantly improve the heat exchange efficiency of this area.

[0033] Each liquid medium heat exchange enhancement tunnel 27 is provided with several heat exchange enhancement cages 6 at equal intervals along its length extension direction. The heat exchange enhancement cages 6 are made of thermally conductive metal and are immersed in the liquid medium in the liquid medium heat exchange enhancement tunnel 27. The heat exchange enhancement cages 6 are made of high thermal conductivity metals such as copper, aluminum or stainless steel. Their function is to further expand the heat exchange surface area based on the flue gas heat exchange tube 3, and at the same time, they serve as the constraint carrier of the variable cage cavity air bag 14, realizing the dual functions of heat exchange and dynamic adjustment.

[0034] In the liquid medium heat exchange enhancement roadway 27, a liquid medium gap 12 is formed between each of two adjacent heat exchange enhancement cages 6; the liquid medium gap 12 serves as a channel for the axial flow of the liquid medium in the roadway, ensuring that the liquid medium can flow smoothly along the roadway direction and achieve continuous heat exchange between each heat exchange enhancement cage 6.

[0035] The heat exchange enhancement cage 6 contains a cage cavity 15, and a variable cage cavity airbag 14 is installed in the cage cavity 15. The variable cage cavity airbag 14 contains an airbag cavity 13. Any two adjacent variable cage cavity airbags 14 in the liquid medium heat exchange enhancement tunnel 27 are interconnected by a pressure transmission pipe 8. A pressure control air pump is installed outside the flue gas heating furnace wall 1. The pressure output end of the pressure control air pump is connected to any one of the pressure transmission pipes 8 in the liquid medium heat exchange enhancement tunnel 27, thereby achieving the purpose of controlling the air pressure in each airbag cavity 13. By pressurizing or evacuating the pressure transmission pipe 8 through the pressure control air pump, the expansion degree of all variable cage cavity airbags 14 can be adjusted synchronously. Since each airbag cavity 13 is interconnected through the pressure transmission pipe 8, the air pressure of all airbag cavities 13 in the entire system remains consistent, thereby achieving synchronous linkage adjustment of the airbag volume in all heat exchange enhancement cages 6.

[0036] The variable-cavity airbag 14 is made of fiber-reinforced fluororubber. Fluororubber has excellent high-temperature resistance and can be used for a long time at 250°C. It also has excellent resistance to boiling water and high-temperature steam. The addition of the fiber reinforcement layer significantly improves the mechanical strength of the airbag, enabling it to maintain its shape stability without rupture when subjected to internal pressure. At the same time, it gives the airbag good elastic recovery ability, ensuring that it expands uniformly when pressurized and contracts uniformly when depressurized.

[0037] The heat exchange enhancement cage 6 has three concave arc surfaces 10 and three convex arc surfaces 11 arranged in a circumferential array. The three concave arc surfaces 10 of the heat exchange enhancement cage 6 respectively heat transfer and adhere to the outer circumferential surfaces of the three flue gas heat exchange tubes 3, which can be achieved through heat transfer and fit using a thermally conductive and heat-resistant adhesive. The radius of curvature of the concave arc surface 10 matches the outer diameter of the flue gas heat exchange tube 3, ensuring that the two form a surface contact rather than a point contact, thereby minimizing the contact thermal resistance. A thermally conductive and heat-resistant adhesive, such as thermally conductive silicone or metal-based thermally conductive adhesive, further fills the micro-gap, forming an efficient heat conduction path between the heat exchange enhancement cage 6 and the flue gas heat exchange tubes 3, allowing the heat from the flue gas heat exchange tubes 3 to be quickly transferred to the entire heat exchange enhancement cage 6.

[0038] The heat-enhancing cage 6 has three convex arc surfaces 11 on its circumference, each with a circumferential cage hole array 7 connecting to the cage cavity 15. The heat-enhancing cage 6 also has end cage hole arrays 9 at both its front and rear ends, connecting to the cage cavity 15. The circumferential cage hole array 7 and the end cage hole array 9 together form a communication channel between the cage cavity 15 and the external liquid medium. When the airbag inflates or contracts, the liquid medium can freely enter and exit the cage cavity 15 through these holes, achieving the intake and discharge of the liquid medium within the cage cavity. The dense arrangement of the holes ensures smooth flow of the liquid medium while avoiding the risk of affecting the airbag's operation due to localized blockages.

[0039] Work methods:

[0040] S1, before introducing the liquid medium into the liquid medium chamber 4 inside the flue gas heating furnace wall 1, the pressure transmission pipe 8 is pressurized by an external pressure control air pump, so that all the variable cage chamber airbags 14 in the heat exchange enhancement cage 6 are in an inflated state. Because reinforcing fibers are added to the fluororubber material of the variable cage chamber airbags 14, when the pressure inside the variable cage chamber airbags 14 rises to a certain level, the heat enhancement cage 6 imposes a cage-like constraint on the variable cage chamber airbags 14, preventing the volume of the variable cage chamber airbags 14 from increasing significantly and bursting. At its maximum volume, the variable cage chamber airbags 14 are tangent to the inner wall of the heat exchange enhancement cage 6 and cannot increase further. Figure 4 As shown, this arrangement ensures that most of the space in the cage cavity 15 of each heat exchange enhancement cage 6 is occupied by the hollow, inflated variable cage cavity airbag 14, thus avoiding affecting the heating area of ​​the heat exchange enhancement cage 6 for the inner liquid medium. In this state, the metal skeleton of the heat exchange enhancement cage 6 still maintains heat transfer contact with the flue gas heat exchange tube 3, and only a very small amount of liquid medium remains in the cage cavity 15. The outer surface of the heat exchange enhancement cage 6 is still completely immersed in the liquid medium in the liquid medium chamber 4. Therefore, the heat exchange area is not reduced due to the inflation of the airbag.

[0041] S2. Fill the liquid medium chamber 4 inside the flue gas heating furnace wall 1 with liquid medium; thereby immersing all the flue gas heat exchange tubes 3 and heat exchange enhancement cages 6 in the liquid medium.

[0042] S3. In the initial heating stage, high-temperature flue gas continuously flows through each flue gas heat exchange tube 3, causing each flue gas heat exchange tube 3 to enter a continuous heating state. Under the action of heat conduction, the heat exchange enhancement cage 6, which is surrounded by three flue gas heat exchange tubes 3 and cooperates with heat transfer, is also in a continuous heating state. With the support of multiple arrayed heat exchange enhancement cages 6, the heat exchange area of ​​the flue gas heat exchange tubes 3 is significantly enhanced, thereby causing the liquid medium in the liquid medium chamber 4 inside the flue gas heating furnace wall 1 to heat up rapidly. At the same time, because most of the space of the cage cavity 15 in each heat exchange enhancement cage 6 is filled with a hollow, inflated variable cage cavity air bladder... The 14-position spacer ensures that the liquid medium completely submerges each heat exchange enhancement cage 6 and each flue gas heat exchange tube 3, maintaining a constant heating surface area while minimizing the total volume of the liquid medium in the liquid medium chamber 4. Because the total volume of the liquid medium in the liquid medium chamber 4 is at its minimum, while the heat conduction area remains constant, the liquid medium in the liquid medium chamber 4 can rapidly heat up to the target temperature. This significantly shortens the time required for the liquid medium to reach the target temperature during the initial heating phase. Under a fixed heating power, the heat required for the liquid medium to heat up is proportional to the total mass of the liquid. When the air bladder inflates and occupies the space, the amount of liquid medium inside the tank is minimized, resulting in a faster temperature rise after absorbing the same amount of heat. This significantly shortens the time from cold start to operating temperature, achieving a rapid start-up function.

[0043] S4, after the liquid medium in the liquid medium chamber 4 rapidly heats up to the target temperature, the liquid medium inlet pipe continuously injects a slightly cooler liquid medium into one end of the liquid medium chamber 4, while the liquid medium outlet pipe continuously discharges the heated liquid medium from the liquid medium chamber 4 to the outside. When the flue gas flow rate and flue gas temperature in each flue gas heat exchanger pipe 3 remain constant, the liquid medium outlet pipe can stably supply the hot liquid medium at the target temperature at a constant flow rate. The flow rates of the liquid medium inlet pipe and the liquid medium outlet pipe are relatively constant. However, in reality, both the flue gas flow rate and flue gas temperature fluctuate, causing the temperature of the hot liquid medium continuously supplied by the liquid medium outlet pipe to also fluctuate drastically. Furthermore, flue gas with excessive temperature fluctuations cannot fully utilize its energy, which does not meet the goals of stable supply and energy saving. This solution suppresses this problem through the following strategies:

[0044] When the flue gas flow rate and temperature in each flue gas heat exchanger tube 3 are high during a certain period, while maintaining a relatively constant flow rate of hot liquid medium discharged from the liquid medium outlet pipe, the flow rate of cold liquid medium injected into the liquid medium chamber 4 through the liquid medium inlet pipe is increased. At the same time, an external pressure-controlled air pump evacuates the pressure transmission pipe 8, causing the variable cage cavity air bladders 14 in all heat exchange enhancement cages 6, which were originally inflated, to gradually deflate. This releases the space of the cage cavity 15 that was originally occupied in each heat exchange enhancement cage 6, and each heat exchange enhancement cage 6 functions as if... Like a sponge, the liquid medium in the liquid medium chamber 4 is continuously absorbed through the circumferential cage array 7 and the end cage array 9. This creates a dynamic balance and counterbalance in volume with the excess flow of cold liquid medium injected into the liquid medium chamber 4 through the inlet pipe. Simultaneously, the excess flow of cold liquid medium injected into the liquid medium chamber 4 through the inlet pipe counterbalances the higher flue gas flow rate and temperature in each flue gas heat exchanger tube 3 in terms of heat balance. Ultimately, this ensures that the liquid medium outlet pipe can still supply hot liquid medium with relatively stable temperature and flow rate during this stage. When the flue gas input power increases, maintaining the original liquid inlet flow rate would inevitably lead to an increase in outlet temperature. This solution absorbs excess heat by simultaneously increasing the cold liquid inlet flow rate, while simultaneously drawing in some cold liquid through the airbag evacuation chamber 15. This balances the increase in inlet flow rate in volume and ensures that excess heat is absorbed by the cold liquid drawn into the chamber 15 in terms of heat balance, thereby maintaining a stable temperature of the liquid medium at the outlet pipe.

[0045] When the flue gas flow rate and temperature in each flue gas heat exchanger tube 3 change from high to low during a certain period, while maintaining a relatively constant flow rate of hot liquid medium discharged from the liquid medium outlet pipe, the flow rate of cold liquid medium injected into the liquid medium tank 4 through the liquid medium inlet pipe is reduced. At the same time, the pressure transmission pipe 8 is pressurized by an external pressure control air pump, causing the originally deflated variable cage cavity air bladders 14 in all heat exchange enhancement cages 6 to gradually inflate outward again. This allows the hot liquid medium originally stored in the cage cavity 15 in each heat exchange enhancement cage 6 to be dispersed like a sponge under the gradually enlarging variable cage cavity air bladders 14. The liquid medium is extruded into the liquid medium chamber 4 through the circumferential cage array 7 and the end cage array 9. This creates a dynamic balance and offset in volume with the missing flow rate of the cold liquid medium injected into the liquid medium chamber 4 through the inlet pipe. At the same time, the missing flow rate of the cold liquid medium injected into the liquid medium chamber 4 through the inlet pipe offsets the low flue gas flow rate and low flue gas temperature in each flue gas heat exchange tube 3 in terms of thermal balance. Ultimately, this ensures that the liquid medium outlet pipe can still supply hot liquid medium with relatively stable temperature and flow rate during this stage. When the flue gas input power decreases, if the original liquid inlet flow rate is maintained, the outlet temperature will inevitably decrease. This scheme reduces the total amount of liquid that needs to be heated by simultaneously reducing the cold liquid inlet flow rate. At the same time, the hot liquid stored in the cage cavity 15 is extruded by pressurizing the air bladder, which compensates for the reduction in inlet flow rate in terms of volume. In terms of thermal balance, the extruded hot liquid replenishes the heat insufficient due to the decrease in input power, thereby maintaining the stable temperature of the liquid medium at the outlet pipe.

[0046] The above process is completed with the cooperation of temperature and flow sensors, ensuring that even when flue gas flow and temperature fluctuate, the liquid medium outlet pipe can still supply a relatively stable hot liquid medium in terms of temperature and flow. The temperature sensor monitors the outlet temperature of the liquid medium outlet pipe in real time, and the flow sensor monitors the flow rates of the inlet and outlet pipes. The control system dynamically adjusts the pressure control pump's pressurization or extraction action, as well as the flow rate of the liquid medium inlet pump, based on flue gas fluctuations, forming a closed-loop control system to ensure the dual stability of the output medium's temperature and flow rate.

[0047] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A low-pressure boiler system utilizing high-temperature flue gas heat exchange, characterized in that: It includes a flue gas heating furnace wall (1), and inside the flue gas heating furnace wall (1) is a liquid medium chamber (4), which is filled with the heated liquid medium; The liquid medium chamber (4) has several parallel and evenly spaced flue gas heat exchange tubes (3) passing through it laterally. The flue gas heat exchange tubes (3) together form a flue gas heat exchange tube array. The flue gas heat exchange tube array is immersed in the heated liquid medium in the liquid medium chamber (4). The two ends of the liquid medium chamber (4) are respectively connected to the liquid medium inlet pipe and the liquid medium outlet pipe. In the flue gas heat exchange tube array, any three adjacent flue gas heat exchange tubes (3) are denoted as a heat exchange tube combination unit (26). The enclosed area between the three flue gas heat exchange tubes (3) of any set of heat exchange tube combination units (26) forms a liquid medium heat exchange enhancement tunnel (27) extending along the axial direction; each liquid medium heat exchange enhancement tunnel (27) is provided with several heat exchange enhancement cages (6) at equal intervals along the length extension direction.

2. The low-pressure boiler system utilizing high-temperature flue gas heat exchange according to claim 1, characterized in that: From the perspective of the axis, the line connecting the geometric centers of the three flue gas heat exchange tubes (3) of any heat exchange tube combination unit (26) forms an equilateral triangle (23).

3. A low-pressure boiler system utilizing high-temperature flue gas heat exchange according to claim 1, characterized in that: The heat exchange enhancement cage (6) is made of thermally conductive metal and is immersed in the liquid medium in the liquid medium heat exchange enhancement tunnel (27).

4. A low-pressure boiler system utilizing high-temperature flue gas heat exchange according to claim 3, characterized in that: In the liquid medium heat exchange enhancement tunnel (27), liquid medium voids (12) are formed between two adjacent heat exchange enhancement cages (6).

5. A low-pressure boiler system utilizing high-temperature flue gas heat exchange according to claim 4, characterized in that: The heat exchange enhancement cage (6) has a cage cavity (15) inside, and a variable cage cavity airbag (14) is installed in the cage cavity (15). The variable cage cavity airbag (14) has an airbag cavity (13) inside. The variable cage cavity airbags (14) in any two adjacent heat exchange enhancement cages (6) in the liquid medium heat exchange enhancement roadway (27) are connected to each other through a pressure transmission pipe (8). A pressure control air pump is installed outside the flue gas heating furnace wall (1). The pressure output end of the pressure control air pump is connected to any one of the pressure transmission pipes (8) in the liquid medium heat exchange enhancement roadway (27).

6. A low-pressure boiler system utilizing high-temperature flue gas heat exchange according to claim 5, characterized in that: The heat exchange enhancement cage (6) has three concave arc surfaces (10) and three convex arc surfaces (11) arranged in a circular array around its circumference. The three concave arc surfaces (10) of the heat exchange enhancement cage (6) are respectively heat-transferring and attached to the outer circumference of the three flue gas heat exchange tubes (3), which can be specifically matched by heat transfer through a heat-conducting and heat-resistant adhesive. The three convex arc surfaces (11) of the heat enhancement cage (6) are all hollowed out with a circumferential cage hole array (7) that connects to the cage cavity (15). The front and rear ends of the heat enhancement cage (6) are hollowed out with an end cage hole array (9) that connects to the cage cavity (15).

7. The operating method of a low-pressure boiler system utilizing high-temperature flue gas heat exchange according to claim 6, characterized in that: S1, before introducing liquid medium into the liquid medium chamber (4) inside the flue gas heating furnace wall (1), pressurize the pressure transmission pipe (8) through an external pressure control air pump so that the variable cage cavity airbags (14) in all heat exchange enhancement cages (6) are in an inflated state. Under the cage constraint of the heat exchange enhancement cage (6), the volume of the variable cage cavity airbags (14) will not increase significantly and burst. S2. Fill the liquid medium chamber (4) inside the flue gas heating furnace wall (1) with liquid medium; thereby immersing all the flue gas heat exchange tubes (3) and heat exchange enhancement cages (6) in the furnace in the liquid medium; S3. During the initial heating stage, high-temperature flue gas flows continuously through each flue gas heat exchange tube (3). Since most of the space in the cage cavity (15) of each heat exchange enhancement cage (6) is occupied by the hollow, bulging variable cage cavity airbag (14), the liquid medium completely submerges each heat exchange enhancement cage (6) and each flue gas heat exchange tube (3). On the basis of keeping the heating surface area unchanged, the total volume of the liquid medium in the liquid medium tank (4) is at its minimum. S4, when the liquid medium in the liquid medium chamber (4) is rapidly heated to the target temperature, the liquid medium inlet pipe continuously injects a slightly cool liquid medium into one end of the liquid medium chamber (4), while the liquid medium outlet pipe continuously discharges the hot liquid medium that has been heated to the target temperature from the liquid medium chamber (4); when the flue gas flow rate and flue gas temperature in each flue gas heat exchanger pipe (3) remain constant, the liquid medium outlet pipe can stably supply the hot liquid medium at the target temperature to the outside at a constant flow rate; the flow rates of the liquid medium inlet pipe and the liquid medium outlet pipe are relatively constant.

8. The operating method of a low-pressure boiler system utilizing high-temperature flue gas heat exchange according to claim 7, characterized in that: When the flue gas flow rate and flue gas temperature in each flue gas heat exchanger tube (3) are high during a certain period, while keeping the flow rate of hot liquid medium discharged from the liquid medium outlet tube relatively constant, the flow rate of cold liquid medium injected into the liquid medium tank (4) by the liquid medium inlet tube is increased. At the same time, the pressure transmission tube (8) is evacuated by an external pressure control air pump, so that the variable cage cavity air bladder (14) in all heat exchange enhancement cages (6) that were originally inflated gradually deflates, thereby releasing the space of the cage cavity (15) that was originally occupied in each heat exchange enhancement cage (6), and each heat exchange enhancement cage ( 6) Like a sponge, it continuously absorbs the liquid medium in the liquid medium tank (4) through the circumferential cage array (7) and the end cage array (9), forming a dynamic balance and offset in volume with the excess flow of cold liquid medium injected into the liquid medium tank (4) by the inlet pipe. At the same time, the excess flow of cold liquid medium injected into the liquid medium tank (4) by the inlet pipe forms an offset in thermal balance with the high flue gas flow and high flue gas temperature in each flue gas heat exchange tube (3), so that during this stage, the liquid medium outlet pipe can still supply hot liquid medium with relatively stable temperature and flow. When the flue gas flow rate and flue gas temperature in each flue gas heat exchanger tube (3) change from high to low during a certain period, while keeping the flow rate of hot liquid medium discharged from the liquid medium outlet tube relatively constant, the flow rate of cold liquid medium injected into the liquid medium tank (4) by the liquid medium inlet tube is reduced. At the same time, the pressure transmission tube (8) is pressurized by an external pressure control air pump, so that the originally deflated variable cage cavity air bladders (14) in all heat exchange enhancement cages (6) gradually expand outward again, so that the hot liquid medium originally stored in the cage cavity (15) in each heat exchange enhancement cage (6) gradually expands in the variable cavity. Under the occupation of the cage airbag (14), like a sponge, it is squeezed into the liquid medium chamber (4) through the circumferential cage hole array (7) and the end cage hole array (9). It forms a dynamic balance and offset in volume with the missing flow rate of the cold liquid medium injected into the liquid medium chamber (4) by the inlet pipe. At the same time, the missing flow rate of the cold liquid medium injected into the liquid medium chamber (4) by the inlet pipe forms an offset in thermal balance with the low flue gas flow rate and low flue gas temperature in each flue gas heat exchange tube (3). Thus, in this stage, the liquid medium outlet pipe can still supply hot liquid medium with relatively stable temperature and flow rate.

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