Flue gas heat exchanger

Abstract

The application discloses a flue gas heat exchange device, which comprises a shell, an upper end plate, a heat exchange pipe bundle, a lower end plate and an expansion absorption assembly which are sequentially connected in the shell; the two ends of the shell are respectively a flue gas inlet end and a flue gas outlet end, and the shell is provided with a cold fluid inlet close to the flue gas outlet end and a cold fluid outlet close to the flue gas inlet end; the upper end plate is connected with the shell between the flue gas inlet end and the cold fluid outlet, so that the inside of the shell is divided into an inflow cavity and a heat exchange cavity; the two ends of the heat exchange pipe bundle are respectively connected with the inflow cavity and the expansion absorption assembly, and the other end of the expansion absorption assembly is sealingly connected with the shell of the flue gas outlet end; along the flue gas flowing direction, the lower end plate and the shell have a preset axial space, and in the heat exchange process, the heat exchange pipe bundle is heated and expanded to push the lower end plate to move and compress the expansion absorption assembly. In this way, a floating structure is formed from the lower part of the heat exchange pipe bundle to the expansion absorption assembly, the heat exchange pipe bundle expansion amount is absorbed by the expansion absorption assembly, and the service life of the device is ensured.

Description

Technical Field

[0001] This utility model relates to the field of heat exchanger technology, and in particular to a flue gas heat exchange device. Background Technology

[0002] In low-carbon metallurgical processes, the flue gas from the furnace top is characterized by large volume and high temperature. The waste heat can be used to recover heating process gas, which has a significant impact on the energy-saving and carbon-reduction effects of the entire low-carbon metallurgical process.

[0003] Currently, heat recovery from flue gas is achieved through traditional tubular heat exchangers. In low-carbon metallurgical processes, the conventional flue layout involves connecting shell-and-tube heat exchangers in series with the flue. The flue gas flows from top to bottom through the tubes of the heat exchanger, exchanging heat with the process gas inside the shell.

[0004] To meet process requirements, heat exchange devices are typically around 20 meters long and are nested within the vertical furnace flue as part of the flue. High-temperature flue gas can cause the equipment to expand, making it unable to meet stress calculation requirements and easily causing deformation of the connected flue, resulting in flue gas leakage. Since low-carbon metallurgy uses hydrogen-containing gases, leaked flue gas poses a risk of explosion.

[0005] Furthermore, in traditional shell-and-tube heat exchangers, the process gas enters the heat exchanger perpendicularly to the heat exchange tube bundle, which causes the process gas to continuously scour the heat exchange tube bundle near the tube opening, reducing its service life. In addition, the process gas tends to travel in the direction of less pressure drop, making the area far from the tube opening a heat exchange "dead zone". Utility Model Content

[0006] The purpose of this invention is to provide a flue gas heat exchange device that at least solves the problem of equipment expansion caused by high-temperature flue gas in the prior art.

[0007] The above-mentioned objectives of this utility model can be achieved by the following technical solutions:

[0008] This utility model provides a flue gas heat exchange device, including a shell and an upper end plate, a heat exchange tube bundle, a lower end plate, and an expansion absorption assembly disposed inside the shell and connected in sequence. The two ends of the shell are a flue gas inlet and a flue gas outlet, respectively. The shell is provided with a cold fluid inlet near the flue gas outlet and a cold fluid outlet near the flue gas inlet. The upper end plate is connected to the shell between the flue gas inlet and the cold fluid outlet, so that the interior of the shell is divided into an inflow chamber and a heat exchange chamber. The two ends of the heat exchange tube bundle are respectively connected to the inflow chamber and the expansion absorption assembly, and the other end of the expansion absorption assembly is sealed to the shell at the flue gas outlet. Along the flue gas flow direction, there is a preset axial space between the lower end plate and the shell. During the heat exchange process of the flue gas heat exchange device, the heat exchange tube bundle expands due to heat, pushing the lower end plate to move and compress the expansion absorption assembly.

[0009] Preferably, the preset axial space is greater than the axial thermal expansion generated when the heat exchange tube bundle is heated.

[0010] Preferably, the flue gas heat exchange device further includes a first flow equalization cylinder with its cylinder wall facing the cold fluid inlet and sleeved between the outer shell and the heat exchange tube bundle. The end of the first flow equalization cylinder near the cold fluid outlet is connected to the outer shell, so that the cold fluid flowing in through the cold fluid inlet flows through the free end of the first flow equalization cylinder.

[0011] Preferably, along the flue gas flow direction, the free end of the cylinder wall of the first flow equalization cylinder near the cold fluid inlet is not higher than the lowest point of the cold fluid inlet.

[0012] Preferably, a gap is left between the first flow equalization cylinder and the lower end plate, and the gap between the first flow equalization cylinder and the lower end plate is increased along the direction from the cylinder wall of the first flow equalization cylinder near the cold fluid inlet to the cylinder wall away from the cold fluid inlet.

[0013] Preferably, the flue gas heat exchange device further includes a second flow equalization cylinder with its cylinder wall facing the cold fluid outlet and sleeved between the outer shell and the heat exchange tube bundle. The end of the second flow equalization cylinder near the cold fluid inlet is connected to the outer shell, so that the cold fluid in the heat exchange cavity flows through the free end of the second flow equalization cylinder.

[0014] Preferably, along the flue gas flow direction, the free end of the second flow equalization cylinder wall on the side near the cold fluid outlet is not lower than the highest point of the cold fluid outlet.

[0015] Preferably, a gap is left between the second flow equalization cylinder and the upper end plate, and the gap between the second flow equalization cylinder and the upper end plate is increased along the direction from the cylinder wall of the second flow equalization cylinder near the cold fluid outlet to the cylinder wall away from the cold fluid outlet.

[0016] Preferably, the expansion absorption assembly includes a connecting cylinder and a corrugated compensator connected together. The other end of the connecting cylinder is connected to the lower end plate, and the other end of the corrugated compensator is sealed to the outer shell at the flue gas outlet end. Along the flue gas flow direction, the distance between the connecting cylinder and the outer shell is not less than the preset axial space.

[0017] Preferably, the flue gas heat exchange device further includes a plurality of baffles equally spaced within the outer casing, with adjacent baffles arranged alternately within the outer casing along the flue gas flow direction.

[0018] The features and advantages of this utility model are as follows: In the flue gas heat exchange device provided by this utility model, the lower part of the heat exchange tube bundle to the expansion absorption assembly forms a floating structure. During the heat exchange process, the downward stress generated by the thermal expansion of the heat exchange tube bundle is transmitted to the expansion absorption assembly through the lower end plate and absorbed by it, thereby reducing the equipment expansion stress caused by the heat exchange tubes being heated. This allows the heat exchange device in the use state to still meet the equipment stress calculation requirements, thereby ensuring its service life. Attached Figure Description

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

[0020] Figure 1 This is a schematic diagram of the structure of the flue gas heat exchange device provided in the embodiments of this utility model;

[0021] Figure 2 This is a schematic diagram showing the connection between the first flow equalization cylinder and the outer shell in the flue gas heat exchange device provided in this embodiment of the utility model.

[0022] Figure 3 This is a schematic diagram showing the connection between the second flow equalization cylinder and the outer shell in the flue gas heat exchange device provided in this embodiment of the present invention.

[0023] Explanation of icon numbers:

[0024] 1. Outer shell; 11. Flue gas inlet; 12. Flue gas outlet; 13. Cold fluid inlet; 14. Cold fluid outlet;

[0025] 2. Top plate;

[0026] 3. Heat exchanger tubes;

[0027] 4. Lower end plate;

[0028] 5. Expansion absorption assembly; 51. Connecting cylinder; 52. Bellows compensator;

[0029] 6. First flow equalization cylinder;

[0030] 7. Second flow equalization cylinder;

[0031] 8. Baffle plate;

[0032] 10. Inlet cavity; 20. Heat exchange cavity; 30. Preset axial space; 40. Heat exchange zone. Detailed Implementation

[0033] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0034] like Figures 1 to 3 As shown, this utility model provides a flue gas heat exchange device, including a shell 1 and an upper end plate 2, a heat exchange tube bundle, a lower end plate 4, and an expansion absorption assembly 5 arranged inside the shell 1 and connected in sequence. The two ends of the shell 1 are a flue gas inlet end 11 and a flue gas outlet end 12, respectively. The shell 1 is provided with a cold fluid inlet 13 near the flue gas outlet end 12 and a cold fluid outlet 14 near the flue gas inlet end 11. The upper end plate 2 is connected to the shell 1 between the flue gas inlet end 11 and the cold fluid outlet 14, so that the interior of the shell 1 is divided into an inlet chamber 10 and a heat exchange chamber 20. The two ends of the heat exchange tube bundle are respectively connected to the inlet chamber 10 and the expansion absorption assembly 5, and the other end of the expansion absorption assembly 5 is sealed to the shell 1 at the flue gas outlet end 12. Along the flue gas flow direction, there is a preset axial space 30 between the lower end plate 4 and the shell 1. During the heat exchange process of the flue gas heat exchange device, the heat exchange tube bundle is heated and expands, pushing the lower end plate 4 to move and compress the expansion absorption assembly 5. The heat exchange tube bundle includes multiple heat exchange tubes 3 arranged and connected between the upper end plate 2 and the lower end plate 4. The two ends of each heat exchange tube 3 are respectively connected to the inlet cavity 10 and the expansion absorption assembly 5.

[0035] For example, such as Figure 1 As shown, the flue gas heat exchange device includes a shell 1 extending longitudinally along the axial direction. One end of the shell 1 is a flue gas inlet 11 for high-temperature flue gas to flow in, and the other end is a flue gas outlet 12 for flue gas to flow out after heat exchange and cooling. A flue gas flow space is formed inside the inlet cavity 10, multiple heat exchange tubes 3, and expansion absorption assembly 5. A cold fluid flow space is formed between the heat exchange tube bundle, expansion absorption assembly 5, and shell 1. The area inside the shell 1 where the heat exchange tube bundle is located forms a heat exchange area 40. The flue gas flow direction is as follows: Figure 1As shown by the hollow arrow, the direction of cold fluid flow is as follows: Figure 1 As indicated by the solid arrow in the center. The upper end plate 2 is fixedly connected inside the outer casing 1 between the flue gas inlet end 11 and the cold fluid outlet 14, providing installation space for multiple heat exchange tubes 3 and enabling sufficient heat exchange between the cold fluid and the flue gas. The lower end plate 4, connected between the heat exchange tube bundle and the expansion absorption assembly 5, is a floating end plate, meaning it is not connected to the outer casing 1. This allows the lower end plate 4 to move axially along with the heat exchange tubes 3, forming a floating structure from the lower part of the heat exchange tube bundle to the expansion absorption assembly 5. During heat exchange, the downward stress generated by the thermal expansion of the heat exchange tube bundle is transmitted through the lower end plate 4 to the expansion absorption assembly 5 and absorbed by it, thereby reducing the equipment expansion stress caused by the heat exchange tubes 3 being heated. This ensures that the heat exchange device can still meet the equipment stress calculation requirements under operating conditions, thus guaranteeing its service life. In this embodiment, the cold fluid is preferably process gas.

[0036] As a preferred implementation method, such as Figure 1 As shown, along the flue gas flow direction, the diameter of the shell section 1 between the flue gas inlet end 11 and the upper end plate 2 is increased to ensure that the high-temperature flue gas is fully dispersed in the inlet cavity 10, ensuring that the high-temperature flue gas flows evenly into each heat exchange tube 3; the diameter of the shell section 1 between the lower end plate 4 and the flue gas outlet end 12 is reduced to collect the flue gas flowing out of each heat exchange tube 3 after heat exchange and cooling. Furthermore, the cold fluid inlet 13 and the cold fluid outlet 14 are respectively arranged on opposite sides of the shell 1 to obtain better structural stability and heat exchange effect.

[0037] According to one embodiment of this utility model, the axial space 30 is preset to be greater than the axial thermal expansion generated when the heat exchange tube bundle is heated. This is to prevent the lower end plate 4 from contacting and jamming with the outer shell 1 during the heat exchange process, which would limit the compression of the expansion absorption assembly 5 and prevent the axial expansion generated by the heat exchange tube bundle from being fully absorbed and compensated by the expansion absorption assembly 5. This application, through the above-mentioned setting, ensures that the axial expansion generated by the heat exchange tube bundle is fully absorbed and compensated by the expansion absorption assembly 5, thereby avoiding the risk of bending deformation due to thermal expansion of the heat exchange tube bundle.

[0038] According to one embodiment of the present invention, such as Figure 1 and Figure 2As shown, the expansion absorption assembly 5 includes a connecting cylinder 51 and a corrugated compensator 52 connected together. The other end of the connecting cylinder 51 is connected to the lower end plate 4, and the other end of the corrugated compensator 52 is sealed to the outer shell 1 of the flue gas outlet end 12. Along the flue gas flow direction, the distance between the connecting cylinder 51 and the outer shell 1 is not less than a preset axial space 30, ensuring that when the heat exchange tube bundle is heated and the lower end plate 4 moves, the connecting cylinder 51 will not jam against the outer shell 1, ensuring that the axial movement space of the lower end plate 4 is available. This ensures that the axial expansion generated by the heat exchange tube bundle is completely absorbed and compensated by the corrugated compensator 52. The corrugated compensator 52 is preferably an alloy steel corrugated pipe, which facilitates a sealed connection between the connecting cylinder 51 and the outer shell 1 of the flue gas outlet end 12 via welding, avoiding hydrogen embrittlement and ensuring its service life in hot environments. In this embodiment, the corrugated compensator 52 is in a pre-stretched state during installation to achieve a better expansion absorption and compensation effect.

[0039] According to one embodiment of the present invention, such as Figure 1 and Figure 2 As shown, the flue gas heat exchange device also includes a first flow equalization cylinder 6, whose cylinder wall is positioned directly opposite the cold fluid inlet 13 and fitted between the outer shell 1 and the heat exchange tube bundle. One end of the first flow equalization cylinder 6 near the cold fluid outlet 14 is connected to the outer shell 1, allowing the cold fluid flowing in through the cold fluid inlet 13 to pass through the free end of the first flow equalization cylinder 6. By setting the first flow equalization cylinder 6, the cold fluid flowing in from the cold fluid inlet 13 is guided through the annular space between the first flow equalization cylinder 6 and the outer shell 1, flowing from below the first flow equalization cylinder 6 into the heat exchange area 40. This avoids the cold fluid from perpendicularly contacting the lower part of the heat exchange tube bundle, solving the problem that when the cold fluid enters the heat exchange device perpendicularly to the heat exchange tube bundle, it causes the cold fluid to continuously scour the lower part of several heat exchange tubes 3 near the cold fluid inlet 13, reducing the service life of these heat exchange tubes 3.

[0040] According to one embodiment of the present invention, such as Figure 1 and Figure 2 As shown, along the flue gas flow direction, the free end of the cylinder wall of the first flow equalization cylinder 6 near the cold fluid inlet 13 is not higher than the lowest point of the cold fluid inlet 13. This completely prevents the cold fluid from entering the heat exchanger perpendicularly to the heat exchange tube bundle, ensuring the long-term availability of the lower part of the heat exchange tube bundle.

[0041] According to one embodiment of the present invention, such as Figure 1 and Figure 2As shown, there is a gap between the first flow equalization cylinder 6 and the lower end plate 4. Along the direction from the cylinder wall of the first flow equalization cylinder 6 near the cold fluid inlet 13 to the cylinder wall away from the cold fluid inlet 13, the gap between the first flow equalization cylinder 6 and the lower end plate 4 is increased to make the cold fluid flow through the lower part of the heat exchange area 40 as evenly as possible, and to avoid the cold fluid flowing into the heat exchange area 40 along the path of least resistance, which would cause the heat exchange area 40 to have a heat exchange "dead corner" away from the cold fluid inlet 13.

[0042] In a preferred embodiment, when the heat exchange tube 3 is not heated, an annular groove is formed on the inner wall of the outer shell 1 facing the lower end plate 4. A sealing ring is provided in the annular groove to prevent a large amount of cold fluid entering from the cold fluid inlet 13 from entering the space where the lower expansion absorption assembly 5 is located, so that the cold fluid can flow more evenly from the lower end of the first flow equalization cylinder 6 into the heat exchange area 40.

[0043] According to one embodiment of the present invention, such as Figure 1 and Figure 3 As shown, the flue gas heat exchange device also includes a second flow equalization cylinder 7, which is positioned with its wall facing the cold fluid outlet 14 and is fitted between the outer shell 1 and the heat exchange tube bundle. The end of the second flow equalization cylinder 7 near the cold fluid inlet 13 is connected to the outer shell 1, allowing the cold fluid in the heat exchange chamber 20 to flow through the free end of the second flow equalization cylinder 7. By setting the second flow equalization cylinder 7, the cold fluid is guided to flow out of the heat exchange area 40 from above the second flow equalization cylinder 7 and flow to the cold fluid outlet 14 through the annular space between the second flow equalization cylinder 7 and the outer shell 1. This avoids the cold fluid from making vertical contact with the upper part of the heat exchange tube bundle, solving the problem that when the cold fluid flows out of the heat exchange device perpendicularly to the heat exchange tube bundle, it causes the cold fluid to continuously scour several heat exchange tubes 3 near the cold fluid outlet 14, reducing the service life of these heat exchange tubes 3.

[0044] According to one embodiment of the present invention, such as Figure 1 and Figure 3 As shown, along the flue gas flow direction, the free end of the second flow equalization cylinder 7 on the side near the cold fluid outlet 14 is not lower than the highest point of the cold fluid outlet 14. This completely prevents the cold fluid from flowing out of the heat exchanger perpendicularly to the heat exchange tube bundle, ensuring the long-term availability of the upper part of the heat exchange tube bundle.

[0045] According to one embodiment of the present invention, such as Figure 1 and Figure 3 As shown, there is a gap between the second flow equalization cylinder 7 and the upper end plate 2. Along the direction from the cylinder wall of the second flow equalization cylinder 7 near the cold fluid outlet 14 to the cylinder wall away from the cold fluid outlet 14, the gap between the second flow equalization cylinder 7 and the upper end plate 2 is increased so that the cold fluid flows through the upper part of the heat exchange area 40 as evenly as possible, and avoids the cold fluid from flowing out of the heat exchange area 40 along the path of least resistance, which would cause the heat exchange area 40 to have a heat exchange "dead zone" away from the cold fluid outlet 14.

[0046] It should be noted that the gap between the first flow equalization cylinder 6 and the lower end plate 4 is increased along the direction from the cylinder wall near the cold fluid inlet 13 to the cylinder wall away from the cold fluid inlet 13. This gap increase can be continuous, such as the lower end of the first flow equalization cylinder 6 being set as a beveled opening, or it can be discontinuous, such as the lower end of the first flow equalization cylinder 6 being set as a stepped opening. Similarly, the upper end of the second flow equalization cylinder 7 can also be set as a stepped opening or a stepped opening. This application does not impose any restrictions on this.

[0047] According to one embodiment of this utility model, in order to enhance the heat transfer coefficient of the heat exchange region 40, such as... Figure 1 As shown, the flue gas heat exchange device also includes multiple baffles 8 evenly spaced within the outer shell 1. Adjacent baffles 8 are staggered within the outer shell 1 along the flue gas flow direction. For example, each baffle 8 is a meniscus with multiple holes spaced apart for multiple heat exchange tubes 3 to pass through. Adjacent baffles 8 are fixedly connected to opposite sides of the shell, allowing the cold fluid to flow along an S-shaped path within the heat exchange zone 40. This extends the flow path length of the shell-side medium, thereby increasing the heat exchange time between the cold fluid and the high-temperature flue gas within the heat exchange tubes 3, further improving the heat transfer effect. Simultaneously, the baffles 8 increase the turbulence intensity of the cold fluid, achieving the goal of improving the heat transfer effect.

[0048] Based on the above description, the flue gas heat exchange device provided in this embodiment of the present invention has the following beneficial effects:

[0049] In the flue gas heat exchange device provided in this embodiment, the lower part of the heat exchange tube bundle to the expansion absorption assembly 5 forms a floating structure. During the heat exchange process, the downward stress generated by the thermal expansion of the heat exchange tube bundle is transmitted through the lower end plate 4 to the expansion absorption assembly 5 and absorbed by it, thereby reducing the equipment expansion stress caused by the heat exchange tube 3 being heated. This ensures that the heat exchange device can still meet the equipment stress calculation requirements under operating conditions, thus guaranteeing its service life. Furthermore, the preset axial space 30 for the movement of the lower end plate 4 is designed to be greater than the axial thermal expansion generated when the heat exchange tube bundle is heated, ensuring that the axial expansion generated by the heat exchange tube bundle being heated can be completely absorbed and compensated by the expansion absorption assembly 5, thereby avoiding the risk of bending deformation of the heat exchange tube bundle due to thermal expansion. By setting up the first flow equalization cylinder 6 and the second flow equalization cylinder 7, the cold fluid is prevented from contacting the heat exchange tube bundle perpendicularly when entering and exiting the heat exchange device. This solves the problem that when the cold fluid enters and exits the heat exchange device perpendicularly to the heat exchange tube bundle, it will cause the cold fluid to continuously scour several heat exchange tubes 3 near the cold fluid inlet 13 and the cold fluid outlet 14, reducing the service life of these heat exchange tubes 3. Through the gap design between the first flow equalization cylinder 6 and the lower end plate 4 and the gap design between the second flow equalization cylinder 7 and the upper end plate 2, the cold fluid flows through the lower and upper parts of the heat exchange area 40 as evenly as possible, avoiding the cold fluid from entering and exiting the heat exchange area 40 along the path of least resistance, which would cause the heat exchange area 40 to have heat exchange "dead corners" far away from the cold fluid inlet 13 and the cold fluid outlet 14.

[0050] The above descriptions are merely a few embodiments of this utility model. Those skilled in the art can make various modifications or variations to the embodiments of this utility model based on the content disclosed in the application documents without departing from the spirit and scope of this utility model.

Claims

1. A flue gas heat exchange device, characterized in that, It includes an outer shell and an upper end plate, a heat exchange tube bundle, a lower end plate, and an expansion absorption assembly disposed inside the outer shell and connected in sequence. The outer casing has a flue gas inlet and a flue gas outlet at its two ends, respectively. A cold fluid inlet and a cold fluid outlet are located near the flue gas outlet. An upper end plate is connected to the outer casing between the flue gas inlet and the cold fluid outlet, thus dividing the interior of the outer casing into an inflow chamber and a heat exchange chamber. Both ends of the heat exchange tube bundle are connected to the inflow chamber and the expansion absorption assembly, respectively. The other end of the expansion absorption assembly is sealed to the outer casing at the flue gas outlet. Along the flue gas flow direction, there is a preset axial space between the lower end plate and the outer shell. During the heat exchange process of the flue gas heat exchange device, the heat exchange tube bundle expands due to heat, pushing the lower end plate to move and compress the expansion absorption assembly.

2. The flue gas heat exchange device according to claim 1, characterized in that, The preset axial space is greater than the axial thermal expansion generated when the heat exchange tube bundle is heated.

3. The flue gas heat exchange device according to claim 2, characterized in that, The flue gas heat exchange device further includes a first flow equalization cylinder with its cylinder wall facing the cold fluid inlet and sleeved between the outer shell and the heat exchange tube bundle. The end of the first flow equalization cylinder near the cold fluid outlet is connected to the outer shell, so that the cold fluid flowing in through the cold fluid inlet flows through the free end of the first flow equalization cylinder.

4. The flue gas heat exchange device according to claim 3, characterized in that, Along the flue gas flow direction, the free end of the cylinder wall of the first flow equalization cylinder near the cold fluid inlet is not higher than the lowest point of the cold fluid inlet.

5. The flue gas heat exchange device according to claim 4, characterized in that, A gap is left between the first flow equalization cylinder and the lower end plate. The gap between the first flow equalization cylinder and the lower end plate is increased along the cylinder wall of the first flow equalization cylinder from the cylinder wall near the cold fluid inlet to the cylinder wall away from the cold fluid inlet.

6. The flue gas heat exchange device according to claim 1 or 5, characterized in that, The flue gas heat exchange device further includes a second flow equalization cylinder with its cylinder wall facing the cold fluid outlet and sleeved between the outer shell and the heat exchange tube bundle. The end of the second flow equalization cylinder near the cold fluid inlet is connected to the outer shell, so that the cold fluid in the heat exchange cavity flows through the free end of the second flow equalization cylinder.

7. The flue gas heat exchange device according to claim 6, characterized in that, Along the flue gas flow direction, the free end of the second flow equalization cylinder wall on the side near the cold fluid outlet is not lower than the highest point of the cold fluid outlet.

8. The flue gas heat exchange device according to claim 7, characterized in that, A gap is left between the second flow equalization cylinder and the upper end plate. The gap between the second flow equalization cylinder and the upper end plate is increased along the direction from the cylinder wall of the second flow equalization cylinder near the cold fluid outlet to the cylinder wall away from the cold fluid outlet.

9. The flue gas heat exchange device according to claim 1 or 2, characterized in that, The expansion absorption assembly includes a connecting cylinder and a corrugated compensator connected together. The other end of the connecting cylinder is connected to the lower end plate, and the other end of the corrugated compensator is sealed to the outer shell at the flue gas outlet end. Along the flue gas flow direction, the distance between the connecting cylinder and the outer shell is not less than the preset axial space.

10. The flue gas heat exchanger according to claim 1, characterized in that, The flue gas heat exchange device also includes multiple baffles that are equally spaced inside the outer shell, with adjacent baffles arranged alternately inside the outer shell along the flue gas flow direction.

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