Low-temperature economizer and method for maintaining the same

Abstract

The application discloses a low-temperature economizer and a maintenance method thereof. The low-temperature economizer comprises a flue and at least two levels of heat exchange modules arranged in the flue in sequence along a first direction. Each level of heat exchange module comprises at least one mounting unit and at least one heat exchange unit detachably mounted on the mounting unit. The heat exchange unit has a first side and a second side which are symmetrically arranged with respect to the first direction, so that the heat exchange unit can be mounted on the mounting unit in at least two mounting orientations. The different mounting orientations correspond to the exchange of the orientations of the first side and the second side in the first direction. The mounting units and the heat exchange units in different levels of heat exchange modules are consistent in structure, so that any heat exchange unit can be mounted on the mounting unit of the original level of heat exchange module or the mounting unit of another different level of heat exchange module. The application realizes the conversion and utilization of the wear surface and the cyclic use of the heat exchange units in different levels, thereby prolonging the service life of the equipment.

Description

Technical Field

[0001] This invention relates to the field of flue gas waste heat recovery, and in particular to a low-temperature economizer and its maintenance method. Background Technology

[0002] Boiler flue gas waste heat recovery is a common technology in thermal power generation and industrial heat recovery. During the operation of coal-fired units, the flue gas discharged from the boiler retains a high temperature and carries a certain amount of heat after completing the main heat release process. To reduce flue gas heat loss and improve thermal energy utilization, heat exchange equipment is usually installed in the boiler tail flue to transfer the remaining heat in the flue gas to condensate or feedwater, thereby reducing boiler fuel consumption and improving the unit's operating economy. With increasingly stringent energy conservation and emission reduction requirements, the application of boiler tail flue gas waste heat recovery equipment in thermal power units is becoming increasingly common, especially in the flue gas area after the air preheater and before the electrostatic precipitator. Recovering flue gas heat by arranging low-temperature economizers has become a common technical approach in related devices.

[0003] In the aforementioned application scenarios, low-temperature economizers operate in dusty flue gas environments for extended periods, especially in the flue gas ducts before electrostatic precipitators (ESPs), where the flue gas typically contains a large amount of unseparated fly ash particles. These fly ash particles continuously scour the outer surface of the heat exchange tubes under the influence of flue gas flow, easily causing wear and thinning of the heating surface. Existing low-temperature economizers mostly employ a row-arranged heat exchange tube structure and are fixedly installed. Common heat exchange tube types include H-shaped finned tubes and integrally rolled spiral finned tubes. While these devices can perform waste heat recovery during operation, their location in high-ash flue gas areas and the long-term particle erosion of the heat exchange surface make them prone to localized wear, wall thinning, leakage, and shutdown during actual operation. For low-temperature economizers in the flue gas ducts before ESPs, leakage not only affects waste heat recovery but also increases the frequency of equipment maintenance and operating costs. Therefore, their service life has always been a crucial concern in the application of this type of equipment.

[0004] The main problem with the existing technology is that when the low-temperature economizer is running in the flue before the electrostatic precipitator, the wear of the heat exchange tubes after being scoured by fly ash usually occurs in the windward side where the scour is stronger. Under the existing structure, the worn surface of this part is difficult to continue to be effectively used after wear, which causes the equipment to face leakage and replacement after heavy wear in local parts, resulting in a short service life of the heat exchanger. Summary of the Invention

[0005] To address the issues of wear and thinning, leakage, short overall lifespan, and high maintenance costs in low-temperature economizers operating in dusty flue gas environments, the present invention addresses these problems by setting up at least two stages of heat exchange modules. These modules allow for disassembly, reversal, and inter-stage swapping of heat exchange units, enabling the conversion and utilization of worn surfaces and the cyclical use of different stages of heat exchange units, thereby extending the equipment's service life.

[0006] Based on this, in a first aspect of the present invention, a low-temperature economizer is provided, which includes a flue and at least two stages of heat exchange modules arranged sequentially in the flue along a first direction, each stage of the heat exchange module including at least one installation unit and at least one heat exchange unit detachably installed on the installation unit.

[0007] The heat exchange unit has a first side and a second side symmetrically arranged about a first direction, so that the heat exchange unit can be installed on the mounting unit in at least two mounting orientations, the different mounting orientations corresponding to the interchange of the orientation of the first side and the second side in the first direction;

[0008] The mounting units and heat exchange units in different levels of heat exchange modules have the same structure, so that any heat exchange unit can be installed in the mounting unit of its original level of heat exchange module or in the mounting unit of another different level of heat exchange module.

[0009] Preferably, the installation unit includes a support frame inserted into the flue along a third direction, and the support frame has an installation space for the heat exchange unit to be inserted therein along a third direction;

[0010] The flue is provided with a loading and unloading port that communicates with the installation space.

[0011] Preferably, the support frame includes a support member and a supporting member;

[0012] The support members are multiple and are inserted into the flue along a third direction, forming the installation space between the multiple support members;

[0013] The support is fixed to the top of the plurality of supports, and the outer periphery of the support is sealed to the loading and unloading port on the flue.

[0014] Preferably, the heat exchange unit includes a heat exchange tube assembly, an inlet water manifold and a return water manifold respectively connected to the heat exchange tube assembly;

[0015] The heat exchange tube assembly includes several heat exchange tubes and is inserted into the installation space;

[0016] The inlet water collector and the return water collector are respectively located on opposite sides of the upper part of the heat exchange tube group, and are symmetrically arranged about the first direction;

[0017] The inlet water tank is connected to an inlet pipe on the side opposite to the return water tank, and an inlet flange is provided at the open end of the inlet water pipe.

[0018] A return water pipe is connected to the side of the return water manifold away from the inlet water manifold, and a return water flange is provided at the open end of the return water pipe.

[0019] The inlet flange is used to connect to the return flange or the inlet flange of the adjacent heat exchange unit, so that the inlet pipe of the adjacent heat exchange unit is connected to the return pipe or the inlet pipe.

[0020] The return water flange is used to connect to the inlet flange or the return water flange of the adjacent heat exchange unit, so that the return water pipe of the adjacent heat exchange unit is connected to the inlet pipe or the return water pipe.

[0021] Preferably, the low-temperature economizer further includes a sealing unit connected to the mounting unit and the heat exchange unit;

[0022] The sealing unit includes a first sealing element, a second sealing element, and a third sealing element;

[0023] The first sealing element is an annular component, which is fixed to the top of the support and is sealed to the support.

[0024] The second sealing element is a plate-shaped component, and a plurality of the heat exchange tubes are inserted through the second sealing element in a third direction and are sealed to the second sealing element; the bottom of the second sealing element is sealed to the top of the first sealing element.

[0025] The third sealing element is an annular component and is disposed outside the second sealing element; the third sealing element has a first pressing part and a second pressing part, which respectively seal and abut against the first sealing element and the second sealing element.

[0026] Preferably, a first circumferential mating portion is provided between the first seal and the second seal;

[0027] A second circumferential mating portion is provided between the first sealing element and the third sealing element;

[0028] A third circumferential mating portion is provided between the third sealing element and the second sealing element;

[0029] At least one of the first circumferential mating portion, the second circumferential mating portion, and the third circumferential mating portion includes a groove and a sealing strip that fit together.

[0030] Preferably, the low-temperature economizer includes an outlet section heat exchange module, an intermediate section heat exchange module, and an inlet section heat exchange module arranged sequentially along a first direction;

[0031] Each heat exchange module includes three heat exchange units arranged at intervals along the second direction;

[0032] The outside of the flue is provided with a main water inlet tank that is connected to the heat exchange module of the inlet section and a main water return tank that is connected to the heat exchange module of the outlet section.

[0033] In a second aspect of the invention, a maintenance method for a low-temperature economizer is provided, which is applied to the aforementioned low-temperature economizer, comprising the following steps:

[0034] Wear testing is performed on each heat exchange unit in at least two stages of heat exchange modules;

[0035] Heat exchange units that have reached a predetermined wear level are extracted from their installation units along a third direction.

[0036] The extracted heat exchange unit is rotated and reinstalled into the original installation unit so that the orientation of the original first side and the second side in the first direction is interchanged.

[0037] And / or the extracted heat exchange unit can be installed in a different stage heat exchange module installation unit for continued use.

[0038] Preferably, the wear detection includes detecting the windward and leeward sides of the heat exchange unit along the first direction;

[0039] When the wear on the windward side is greater than the wear on the leeward side and the predetermined rotation conditions are met, the heat exchange unit is rotated and installed.

[0040] When the heat exchange unit in the front heat exchange module meets the predetermined interchange conditions, it is interchanged with the heat exchange unit in the rear heat exchange module.

[0041] Preferably, the maintenance method includes the following rotation process:

[0042] Prioritize rotating the heat exchange units in the heat exchange module of the outlet section;

[0043] After the outlet section heat exchange unit reaches the predetermined wear condition again after being rotated and installed, it is interchanged with the heat exchange unit in the intermediate section heat exchange module or the heat exchange unit in the inlet section heat exchange module.

[0044] The heat exchange units, after being swapped and installed, continue to operate and are rotated and installed again after reaching the predetermined wear conditions, in order to cyclically extend the service life of the low-temperature economizer.

[0045] Compared with the above-mentioned background technology, the technical solution provided by the present invention has at least the following technical effects:

[0046] First, this invention enables the reuse of worn surfaces of heat exchange units, thereby extending the service life of individual heat exchange units. In existing technologies, low-temperature economizers are constantly exposed to dusty flue gas environments before electrostatic precipitators. Fly ash particles continuously scour the heat exchange surfaces under the influence of flue gas flow, and wear typically concentrates on the windward side, while wear on the leeward side is relatively lighter. When conventional heat exchangers use a fixed installation structure, once the windward side is worn down to near failure, the heat exchange unit becomes unusable, resulting in the entire heat exchange unit losing its usability due to localized surface wear alone. In this invention, the heat exchange unit has a first side and a second side symmetrically arranged about a first direction, and can be installed on the mounting unit in at least two installation orientations. Thus, after heavy wear occurs on the side originally facing the incoming flue gas, the heat exchange unit can be removed and the installation orientation changed, so that the side originally facing away from the incoming flue gas turns towards it. Since the original leeward side experienced less wear during previous operation, its remaining wall thickness and load-bearing capacity are typically higher than those of the worn windward side. Therefore, after rotation, it can serve as a new erosion-resistant surface to continue performing heat exchange tasks. Thus, this invention does not simply achieve the disassembly and assembly of heat exchange units, but rather, through the combination of a symmetrical structure and reversing installation conditions, enables the reuse of previously unusable leeward side surfaces, thereby extending the service life of individual heat exchange units.

[0047] Secondly, this invention enables the reconfiguration of heat exchange units with varying degrees of wear between different stages of heat exchange modules, thereby delaying premature failure of the entire unit due to localized wear in the preceding stages. In existing technologies, cryogenic economizers are typically arranged in rows along the flue gas flow direction. The intensity of fly ash scouring varies at different locations, with the side closer to the upstream flow usually experiencing stronger particle scouring earlier, while the scouring intensity in the heat exchange parts at later stages is relatively lower. Therefore, there are differences in service environment and wear levels between different stages. Under traditional fixed structures, even if the wear of the later-stage heat exchange parts is relatively light, it is difficult to relocate them to the preceding stage to continue to bear the high scouring conditions. As a result, the lifespan of the entire unit is often limited by the localized location that fails first. In this invention, the installation units and heat exchange units in different stages of heat exchange modules have the same structure, allowing any heat exchange unit to be installed back in its original stage or in an installation unit in a different stage. When a preceding heat exchange unit reaches a high level of wear while a subsequent heat exchange unit still has a significant lifespan reserve, the subsequent heat exchange unit can be moved to a preceding position for continued use, while the used preceding heat exchange unit can be transferred to a location with less scouring conditions to continue service. In this way, the originally fixed wear distribution is transformed into an adjustable lifespan resource distribution, thus freeing the entire machine from being entirely dependent on the premature wear and failure of a single preceding local heat exchange unit.

[0048] Furthermore, this invention improves the overall lifespan utilization of the cryogenic economizer. In existing fixed cryogenic economizers, the heat exchanger lifespan is typically determined by the first point of wear and leakage, rather than by the uniform depletion of all heat exchange surfaces. In other words, traditional structures suffer from uneven lifespan utilization, with some areas failing first while others retain usable lifespan. This invention addresses this by, on one hand, rotating the heat exchange units to release the underutilized lifespan on the other side of the same heat exchange unit. On the other hand, it releases the underutilized lifespan between heat exchange units in different locations through interchangeable installations between different stages. The combined effect means that the usable lifespan of the cryogenic economizer is no longer determined solely by the localized area on the windward side of the front stage, but rather depends more on the overall lifespan consumption of all heat exchange units and surfaces throughout the entire equipment. Therefore, this invention improves the overall lifespan utilization of the equipment and delays downtime or replacement due to failure of the weakest point in a localized area.

[0049] Furthermore, this invention reduces the frequency of maintenance and replacement needs caused by localized wear and tear. In existing low-temperature economizers, once localized thinning and leakage occur in the heat exchange surface, it not only affects waste heat recovery but also increases maintenance frequency and operating costs. The root cause of this is the lack of a reuse path after localized wear in the existing structure; the only options are shutdown or complete replacement after failure. In this invention, as long as the wear has not progressed to a point where safe use is no longer possible, the heat exchange unit can still be used. Therefore, maintenance can be shifted from traditional replacement after failure to disassembly, rotation, reassembly, or inter-stage swapping after a predetermined level of wear has been reached. Thus, equipment maintenance shifts from passive replacement to proactive rotation, thereby reducing the need for premature replacement of the entire unit due to localized wear.

[0050] It should also be noted that this invention provides a basis for the implementation of subsequent maintenance methods. These maintenance methods require the ability to extract, rotate, and interchange heat exchange units that have reached a predetermined level of wear. These operations are only possible when the device body has detachable installation conditions, i.e., symmetrical reversal conditions and inter-stage structural compatibility conditions. This invention provides a corresponding basis for subsequent maintenance actions through several features: at least two stages of detachable heat exchange units with symmetrical first and second sides about a first direction, and consistent installation units and heat exchange unit structures across different stages. Attached Figure Description

[0051] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0052] Figure 1 This is an isometric view of the low-temperature economizer provided in an embodiment of the present invention;

[0053] Figure 2 This is a top view of the cryogenic economizer provided in an embodiment of the present invention;

[0054] Figure 3 This is a front view of the cryogenic economizer provided in an embodiment of the present invention;

[0055] Figure 4 This is a front view of the internal structure of the cryogenic economizer provided in an embodiment of the present invention;

[0056] Figure 5 This is a schematic diagram showing the combined state of the heat exchange unit and the installation unit provided in an embodiment of the present invention;

[0057] Figure 6 This is a schematic diagram showing the separated state of the heat exchange unit and the installation unit provided in an embodiment of the present invention;

[0058] Figure 7 This is an isometric view of the sealing unit provided in an embodiment of the present invention;

[0059] Figure 8 This is a top view of the sealing unit provided in an embodiment of the present invention;

[0060] Figure 9 for Figure 8 Schematic diagram of the cross section at point AA;

[0061] Figure 10 This is a top view of the first seal provided in an embodiment of the present invention;

[0062] Figure 11 for Figure 10 Schematic diagram of the cross section at point BB;

[0063] Figure 12 This is a top view of the third seal provided in an embodiment of the present invention;

[0064] Figure 13 for Figure 12 A schematic diagram of the cross-section at point CC.

[0065] Explanation of reference numerals in the attached figures:

[0066] 1. Flue; 2. Heat exchange module; 21. Heat exchange tube assembly; 22. Inlet water header; 221. Inlet water pipe; 222. Inlet water flange; 23. Return water header; 231. Return water pipe; 232. Return water flange; 24. Mounting unit; 241. Support component; 242. Support component; 25. Sealing unit; 251. First sealing component; 2511. First sealing groove; 2512. Second sealing groove; 252. Second sealing component; 2521. First sealing strip; 253. Third sealing component; 2531. First crimping part; 2532. Second crimping part; 2533. Second sealing strip; 26. Support column; 27. Support plate; 3. Main inlet water tank; 31. Outlet water control valve; 4. Main return water tank; 41. Inlet water control valve. Detailed Implementation

[0067] The present invention will be further described below with reference to the accompanying drawings. It should be understood that the following embodiments are only for illustrating the technical content of the present invention and are not intended to limit the scope of protection of the present invention. For those skilled in the art, equivalent substitutions and conventional changes made to the quantity, shape, connection relationship, installation sequence, detection method, and replacement path of the components without departing from the concept of the present invention should all fall within the scope of protection of the present invention.

[0068] In the specification, the first direction indicates the main flow direction of flue gas within the flue, the second direction indicates the direction in which multiple heat exchange units are arranged side-by-side laterally along the flue, and the third direction indicates the direction in which the heat exchange units are inserted into or extracted from the installation unit. In one embodiment, the third direction is vertical, with the heat exchange units inserted into the installation unit from top to bottom and extracted from bottom to top along the third direction. It should be noted that the terms "first" and "second" are used only to distinguish different components and do not indicate any sequential, primary, or unique correspondence between these components.

[0069] See Figures 1 to 13 In this embodiment, the low-temperature economizer includes a flue 1, heat exchange modules 2, a main inlet tank 3, and a main return tank 4. The flue 1 forms the flow space for the boiler tail gas. The heat exchange modules 2 are located within the flue 1 and are used to recover waste heat from the flue gas. The main inlet tank 3 distributes the heating medium to the heat exchange modules 2. The main return tank 4 collects the heated medium flowing out of each heat exchange module 2. In this embodiment, the flue gas flows sequentially through the outlet section heat exchange module, the intermediate section heat exchange module, and the inlet section heat exchange module in a first direction. The medium enters the inlet section heat exchange module from the main inlet tank 3, then flows in the opposite direction to the flue gas flow through the intermediate section heat exchange module and the outlet section heat exchange module, finally entering the main return tank 4, thus forming a counter-current heat exchange path. This arrangement can improve the heat exchange efficiency of the low-temperature economizer.

[0070] Specifically, the heat exchange module 2 is provided in at least two stages along the first direction. Each stage of the heat exchange module 2 includes at least one mounting unit 24 and at least one heat exchange unit detachably mounted on the mounting unit 24. The mounting unit 24 is used to form a support interface, a positioning interface, and a sealing interface, and the heat exchange unit is used to form a removable heat exchange component. The heat exchange unit has a first side and a second side disposed opposite to each other along the first direction, and the first side and the second side are symmetrical about the symmetrical interface located between them.

[0071] In one embodiment, the symmetrical interface extends along a second direction and a third direction, so that after the heat exchange unit is rotated and installed, the orientation of the first side and the second side in the first direction is interchanged. Thus, if the first side facing the incoming flue gas wears down during the initial operation, the heat exchange unit can be removed from the mounting unit 24, repositioned, and reinstalled, so that the second side, which was originally facing away from the incoming flue gas, now faces it and continues to operate. Because the two sides of the heat exchange unit maintain a corresponding relationship in shape and mounting interface, reassembly can be completed without changing the structure of the mounting unit 24 after reversing the orientation.

[0072] Furthermore, the mounting units 24 and heat exchange units in different stages of heat exchange modules 2 have identical structures. This identical structure includes at least identical outer dimensions, identical mating interfaces with mounting units 24, identical mating interfaces with sealing units 25, and identical connection positions with external pipelines. Therefore, any heat exchange unit can be installed in the mounting unit 24 of its original stage of heat exchange module 2, or in the mounting unit 24 of another different stage of heat exchange module 2, thus creating inter-stage interchangeability. In other words, after the heat exchange units in the outlet section heat exchange module reach a predetermined wear level, the less worn downstream heat exchange units can be moved to the upstream position to continue service, or the upstream heat exchange units can be transferred to the intermediate or inlet section to continue service, thereby releasing the underutilized life reserve between heat exchange units in different positions.

[0073] In this embodiment, the cryogenic economizer adopts a three-stage heat exchange structure. Specifically, the cryogenic economizer includes an outlet section heat exchange module, an intermediate section heat exchange module, and an inlet section heat exchange module arranged sequentially along a first direction. Each heat exchange module 2 includes three heat exchange units arranged at intervals along a second direction, corresponding to the left flow channel, the middle flow channel, and the right flow channel, respectively. The main inlet tank 3 is connected to the inlet section heat exchange module, and the main return tank 4 is connected to the outlet section heat exchange module. The inlet section heat exchange unit, the intermediate section heat exchange unit, and the outlet section heat exchange unit located at the same position in the second direction are connected sequentially, thereby forming three parallel medium flow branches. The medium in each branch first enters the inlet section heat exchange unit, then enters the corresponding intermediate section heat exchange unit, and then enters the corresponding outlet section heat exchange unit, finally flowing into the main return tank 4. Through the above-mentioned series-parallel connection method, the total heat exchange area can be guaranteed while also taking into account flow distribution and maintenance convenience.

[0074] In some implementations, the heat exchange module 2 can have two, four or more stages, and the number of heat exchange units in each stage can be one, two, four or more, as long as the installation units 24 and heat exchange units between different stages are interchangeable.

[0075] In other embodiments, the multiple heat exchange units along the second direction can be arranged with equal or unequal spacing depending on the cross-sectional shape of the flue. For example, when the flow velocity is higher in the middle of the flue and lower on both sides, the spacing of the heat exchange units in the middle can be appropriately reduced to improve the heat exchange coverage in the middle region. Furthermore, in the case of local flue velocity deviation, multiple heat exchange units along the second direction within the same stage can also be interchanged laterally to make the wear degree at different lateral positions more even.

[0076] Specifically, refer to Figures 4 to 6 The installation unit 24 includes a support frame inserted into the flue 1 along a third direction, and an installation space is formed in the support frame for inserting the heat exchange unit into it along the third direction. The flue 1 is provided with a loading / unloading port communicating with the installation space, through which the heat exchange unit is inserted and removed. The lateral contour of the installation space can match the outer contour of the heat exchange unit, and an assembly gap is maintained between the installation space and the outer contour of the heat exchange unit to avoid interference between the heat exchange unit and the inner wall of the flue during insertion.

[0077] In one embodiment, the loading and unloading port is located on the top wall of the flue 1, and the heat exchange unit falls from top to bottom into the installation space and is positioned by its own weight. In other embodiments, the loading and unloading port may also be located on the side wall or bottom wall of the flue 1, and the heat exchange unit enters the installation space in a horizontal or inclined direction, as long as subsequent flipping installation and interstage interchange are not affected.

[0078] In one specific embodiment, the support frame includes support members 241 and support members 242. Four support members 241 are arranged along a third direction in the flue 1, forming a rectangular installation space. The support members 242 are fixed to the top of the four support members 241, and their outer periphery is sealed to the loading / unloading port on the flue 1. The support members 241 bear the weight of the heat exchange unit, flow impact, and lifting force during loading and unloading. The support members 242 receive the sealing unit 25 and serve as the upper support interface for the heat exchange unit.

[0079] In this embodiment, the support member 241 can be a steel profile, a plate, or a combination thereof. The inner side of the support member 241 may be provided with a guide surface, guide strip, or limiting shoulder to guide and initially limit the heat exchange unit during insertion. The support member 242 can be a circumferentially continuous ring or formed by several supporting beams. To adapt to the high-temperature environment of the flue 1, the support member 242 and the flue 1 can be connected by welding or by flange connection with a sealing gasket.

[0080] Furthermore, the top of the support member 242 is provided with a positioning structure. The positioning structure can be a positioning pin, a positioning post, a limiting boss, a positioning block, or a combination thereof. Correspondingly, the bottom of the first sealing member 251 is provided with a positioning hole, a positioning groove, or a clearance opening that cooperates with the positioning structure.

[0081] In this embodiment, the top of the support member 242 is provided with multiple circumferentially distributed positioning pins, and the bottom of the first seal member 251 is provided with multiple positioning holes at corresponding positions. When the first seal member 251 is placed on the support member 242, the positioning pins are inserted into the positioning holes to limit the first seal member 251 laterally and circumferentially. With this structure, the first seal member 251 can still return to the predetermined position after repeated disassembly and assembly, which is beneficial to maintaining the mating state of the second seal member 252 and the third seal member 253. In other embodiments, the positioning structure can also be set as a positioning rib and positioning groove extending circumferentially, or as a mutually cooperating conical guide part, so as to automatically complete the centering during the insertion of the heat exchange unit.

[0082] In some embodiments, the installation unit 24 may further include an auxiliary stabilizing component disposed at the lower part of the support frame. The auxiliary stabilizing component may be a lower limit frame, a lower support strip, a lower guide sleeve, or a lower guide block, used to limit the swaying of the lower part of the heat exchange unit under flue gas impact. After the heat exchange unit is inserted into the installation space from top to bottom, the lower end of the lower support plate 27 or the heat exchange tube assembly 21 may form a clearance fit or a contact fit with the auxiliary stabilizing component, thereby ensuring the overall stability of the heat exchange unit under the condition that the upper part is supported by the support component 242 and the lower part is limited by the auxiliary stabilizing component. Furthermore, a lifting beam, slide rail, hoisting device, or lifting lug may be provided on the outside of the flue duct 1 to facilitate unitized lifting during heat exchange unit maintenance.

[0083] Specifically, the heat exchange unit includes a heat exchange tube assembly 21, an inlet water header 22, and a return water header 23. The heat exchange tube assembly 21 forms the main heat exchange interface between the flue gas and the medium. The inlet water header 22 distributes the medium to be heated to the heat exchange tube assembly 21. The return water header 23 collects the medium after heat exchange. The heat exchange tube assembly 21 includes several heat exchange tubes that extend along a third direction and are inserted into the installation space. The inlet water header 22 and the return water header 23 are located on opposite sides of the upper part of the heat exchange tube assembly 21 and are symmetrically arranged about the first direction. An inlet water pipe 221 is connected to the side of the inlet water header 22 away from the return water header 23, and an inlet flange 222 is provided at the open end of the inlet water pipe 221. A return water pipe 231 is connected to the side of the return water header 23 away from the inlet water header 22, and a return water flange 232 is provided at the open end of the return water pipe 231. Since the inlet water header 22 and the return water header 23 are symmetrically positioned relative to each other at the center of the heat exchange unit, the inlet water flange 222 and the return water flange 232 can still be reconnected to the corresponding external branches after the heat exchange unit is rotated.

[0084] Furthermore, to ensure that both the inlet water header 22 and the return water header 23 are located above the heat exchange tube assembly 21, the heat exchange tube assembly 21 can employ various internal flow channel structures. In one embodiment, the heat exchange tube assembly 21 consists of multiple U-shaped heat exchange tubes, with each U-shaped heat exchange tube having two openings connected to the inlet water header 22 and the return water header 23, respectively. The U-shaped bend is located at the lower part of the heat exchange tube assembly 21. After entering from the inlet water header 22, the medium flows downward along one side of the U-shaped heat exchange tube, then turns back through the lower bend and flows upward along the other side to the return water header 23.

[0085] In another embodiment, the heat exchange tube assembly 21 can also be composed of multiple straight tubes and connecting elbows located at the bottom. The lower ends of the multiple straight tubes are connected in pairs through connecting elbows or lower flow collectors, thereby forming a reciprocating flow path similar to that of a U-shaped heat exchange tube. In a further embodiment, the heat exchange tube assembly 21 can also adopt a sleeve-type, heat pipe-type, or two-pass baffled structure, as long as the inlet water header 22 and the return water header 23 can be located on the upper part of the heat exchange tube assembly 21 and maintain their corresponding relationship with the external interface after being flipped up and installed.

[0086] In this embodiment, the heat exchange tubes in the heat exchange tube group 21 can be bare tubes, H-shaped finned tubes, spiral finned tubes, heat exchange tubes with reinforcing fins, or other heat exchange tubes suitable for flue gas waste heat recovery. If H-shaped finned tubes or spiral finned tubes are used, it is preferable to keep the heat exchange tube type, fin parameters, number of rows, and outer dimensions consistent in each heat exchange unit to enhance versatility when installing on flip-top and interchangeable between stages.

[0087] In some embodiments, the heat exchange tube bundles 21 may be arranged in a straight line to reduce resistance and facilitate ash removal. In other embodiments, the heat exchange tube bundles 21 may be arranged in a staggered manner to increase flue gas turbulence and improve heat transfer intensity.

[0088] Furthermore, the wall thickness of the heat exchange tube can be selected appropriately while meeting pressure and life requirements. The outer surface of the heat exchange tube can also be provided with a wear-resistant layer, an anti-corrosion layer, or easily replaceable sheath components to adapt to different ash contents and corrosive conditions. These additional components are preferably arranged symmetrically along the first and second sides to avoid affecting flipping installation and interstage interchangeability.

[0089] Furthermore, the heat exchange unit may also include a frame component, a lifting component, and an identification component surrounding the heat exchange tube assembly 21. The frame component connects the inlet manifold 22, the return manifold 23, the second seal 252, the support column 26, and the support plate 27 into a single unit to maintain overall rigidity during lifting and rotation. The lifting component can be a lifting lug, lifting plate, lifting hole, or lifting beam, used to cooperate with lifting equipment when the heat exchange unit is extracted, flipped, or moved. The identification component marks the stage, lateral position, installation orientation, number of rotations, and maintenance batch of the heat exchange unit for life management during subsequent maintenance. The frame component and lifting component are preferably arranged in a position that does not interfere with the installation space and sealing interface, and preferably maintain a symmetrical relationship with the first and second sides.

[0090] Specifically, four support columns 26 are provided on the outer side of the heat exchange tube assembly 21, and a support plate 27 is provided on the lower side of the second seal 252. The heat exchange tubes in the heat exchange tube assembly 21 pass through the support plate 27 and are fixedly connected to the support plate 27. The four support columns 26 are respectively fixedly connected to the four end corners of the second seal 252 and the support plate 27 to form a stable spatial frame. The support plate 27 is used to fix the lower part of the heat exchange tube assembly 21 in groups and to provide support for the lower U-shaped bend section or the lower connecting member. The support columns 26 are used to maintain the relative positional relationship between the second seal 252 and the support plate 27 to prevent deformation of the heat exchange unit during extraction, rotation, hoisting, and reinstallation.

[0091] In some embodiments, the number of support columns 26 can be two, six, eight, or more, and they can be cylindrical, square, channel-shaped, or plate-shaped columns with reinforcing ribs. The support plate 27 can be a single plate, a grid plate, a frame plate, or a split plate. The support plate 27 can also be provided with reinforcing ribs, guide holes, ash discharge holes, or inspection holes to improve overall rigidity and adapt to different flue gas conditions.

[0092] Specifically, the low-temperature economizer also includes a sealing unit 25 disposed between the installation unit 24 and the heat exchange unit. The sealing unit 25 is used to prevent flue gas in the flue 1 from leaking out through the periphery of the loading and unloading port or the gap between the heat exchange unit and the installation unit 24, and also to prevent external air from being drawn into the flue 1 from the periphery of the loading and unloading port.

[0093] Reference Figure 7 The sealing unit 25 includes a first sealing element 251, a second sealing element 252 and a third sealing element 253.

[0094] Reference Figures 9 to 11 The first sealing element 251 is an annular component, which is fixed to the top of the support 242 and is sealed to the support 242.

[0095] Reference Figure 8 and Figure 9 The second sealing element 252 is a plate-shaped component, and several heat exchange tubes are inserted through the second sealing element 252 along a third direction and are sealed to the second sealing element 252. The bottom of the second sealing element 252 is sealed to the top of the first sealing element 251.

[0096] Reference Figure 9 , Figure 12 and Figure 13The third seal 253 is an annular member surrounding the outside of the second seal 252. The third seal 253 has a first pressing portion 2531 and a second pressing portion 2532, which respectively seal against the first seal 251 and the second seal 252. The first seal 251 forms a reference seal on the support interface, the second seal 252 forms an upper seal that moves synchronously with the heat exchange unit, and the third seal 253 forms an additional pressing seal on the outside of both, thereby forming multiple sealing paths after assembly.

[0097] Furthermore, the first sealing element 251 can be an annular plate, a square annular plate, or a frame-shaped element formed by splicing multiple components. The lower surface of the first sealing element 251 can be directly attached to the support element 242, or a padding element, a flexible sealing layer, or a heat-resistant sealing rope can be provided between the two. The first sealing element 251 and the support element 242 can be fixed by welding, pressure plate, groove, or screw connection.

[0098] Considering that the flue 1 is in a high-temperature and ash-containing environment, in some embodiments, the first seal 251 is preferably provided as a replaceable component on the support 242, and can be replaced individually when it is worn or aged. The outer contour of the first seal 251 preferably matches the support 242, and its inner contour preferably matches the outer contour of the second seal 252, so as to form a continuous circumferential sealing interface after the second seal 252 is pressed into place.

[0099] Furthermore, the second sealing element 252 can be a single-plate sealing plate or a composite plate formed by splicing several sub-plates. Several heat exchange tubes pass through the second sealing element 252 and are sealed to the perforated edges of the second sealing element 252. The sealing connection can be welded, expanded, brazed, pressed, or connected with a sealing sleeve. The second sealing element 252 not only serves a sealing function but also acts as part of the upper frame of the heat exchange unit, connecting to the support column 26, thereby improving the overall rigidity of the heat exchange unit.

[0100] In some embodiments, the upper surface of the second seal 252 may also be provided with reinforcing ribs, lifting holes, or clearance holes for connection to external pipelines. In other embodiments, a transition bracket may be provided between the second seal 252 and the inlet manifold 22 and the return manifold 23 to share the load when the weight of the manifold is large.

[0101] Furthermore, referring to Figure 9 and Figure 13The cross-section of the third seal 253 can be L-shaped, thus simultaneously forming a first crimping portion 2531 and a second crimping portion 2532 extending in different directions. The first crimping portion 2531 is used to form a crimping relationship with the first seal 251, and the second crimping portion 2532 is used to form a crimping relationship with the second seal 252. The inner surface of the third seal 253 can also abut against the outer surface of the second seal 252 to further improve the sealing effect.

[0102] In one embodiment, the third seal 253 is an integral annular component, which is integrally fitted onto the outside of the second seal 252. In another embodiment, the third seal 253 is a square annular component spliced ​​from four strip components. The ends of the four strip components can be joined by beveling, overlapping, tongue and groove, or interlocking to improve the sealing continuity at the splice. Furthermore, the third seal 253 can be held in a predetermined position by gravity pressing, pressure plate limiting, groove limiting, or elastic pre-tightening. If the third seal 253 adopts a detachable structure, when the heat exchange unit is removed for maintenance, the third seal 253 can be removed first before the heat exchange unit is lifted out to reduce lifting interference.

[0103] Specifically, a first circumferential mating portion is provided between the first sealing member 251 and the second sealing member 252, a second circumferential mating portion is provided between the first sealing member 251 and the third sealing member 253, and a third circumferential mating portion is provided between the third sealing member 253 and the second sealing member 252.

[0104] At least one of the first circumferential mating part, the second circumferential mating part, and the third circumferential mating part includes mutually fitting grooves and sealing strips.

[0105] In this embodiment, a first sealing groove 2511 is formed on the inner side of the upper end face of the first sealing member 251, and a second sealing groove 2512 is formed on the outer side of the upper end face of the first sealing member 251. A first sealing strip 2521 that mates with the first sealing groove 2511 is provided on the lower end face of the second sealing member 252, and a second sealing strip 2533 that mates with the second sealing groove 2512 is provided on the lower end face of the third sealing member 253. When the heat exchange unit is inserted into the installation unit 24 in a third direction, the first sealing strip 2521 enters the first sealing groove 2511 and forms a first circumferential fit, and the second sealing strip 2533 enters the second sealing groove 2512 and forms a second circumferential fit, thereby forming an additional labyrinthine sealing path outside the pressing interface.

[0106] In other embodiments, the positions of the groove and the sealing strip can be interchanged. For example, the first sealing strip 2521 can be disposed on the first sealing element 251, while the first sealing groove 2511 can be disposed on the second sealing element 252. Alternatively, a third sealing groove and a third sealing strip can be further disposed between the third sealing element 253 and the second sealing element 252 to form another interlocking seal on the outside. The sealing strip can be a flexible graphite strip, a metal-coated sealing strip, a ceramic fiber sealing strip, a high-temperature resistant rubber sealing strip, or other high-temperature resistant sealing elements suitable for flue gas waste heat recovery. The cross-section of the sealing groove can be rectangular, dovetail-shaped, wedge-shaped, semi-circular, or stepped. Using a dovetail-shaped or stepped sealing groove helps maintain the stability of the sealing strip's position after repeated disassembly and assembly. Using a semi-circular sealing groove helps reduce local stress concentration.

[0107] Furthermore, when assembled, the sealing unit 25 can form a multi-layered sealing relationship that progresses sequentially from the inside out. First, the bottom surface of the second sealing element 252 forms a surface contact pressure seal with the top surface of the first sealing element 251. Second, the first sealing strip 2521 forms a circumferential fitting seal with the first sealing groove 2511. Third, the third sealing element 253 forms an outer pressure seal with the first sealing element 251. Fourth, the third sealing element 253 forms a further pressure or fitting seal with the second sealing element 252. Thus, if flue gas attempts to leak from the inside to the outside, it needs to pass through the surface contact interface, the fitting interface, and the outer pressure interface in sequence. Its leakage path is prolonged and its flow direction is changed multiple times, which is not conducive to continuous crossflow. Especially when the heat exchange unit presses against the sealing unit 25 by its own weight, the weight of the heat exchange unit is converted into a clamping force, which helps to maintain the fit of each sealing interface.

[0108] In some implementations, to prevent the seal from loosening after prolonged high temperatures, a compensating pre-tightening element, such as an elastic pressure plate, a corrugated gasket, or an adjustable limiting element, can be provided on the third seal 253 or the support 242 to maintain the compression amount after the seal wears out.

[0109] In one embodiment, the heat exchange unit is positioned and secured primarily by its own weight after insertion, eliminating the need for a large number of fasteners to be installed in the high-temperature, ash-containing area for extended periods. This reduces disassembly difficulties caused by high-temperature oxidation and ash accumulation. In other embodiments, a small number of auxiliary limiting components, such as detachable pressure plates, limiting pins, locking blocks, or vibration damping clips, can be installed after the heat exchange unit is in place to prevent the heat exchange unit from floating upwards or moving laterally under the influence of flue gas pulsation or equipment vibration. These auxiliary limiting components are preferably located in external positions that facilitate maintenance and are preferably easily releasable before the heat exchange unit is removed.

[0110] Specifically, the main inlet water tank 3 is located outside the flue 1 and connected to the inlet section heat exchange module, while the main return water tank 4 is located outside the flue 1 and connected to the outlet section heat exchange module. In this embodiment, the main inlet water tank 3 is equipped with three outlet branch pipes, each with an outlet control valve 31, and each outlet branch pipe has a branch connection flange at its end that connects to the inlet flange 222 on the corresponding heat exchange unit of the inlet section heat exchange module. The main return water tank 4 is equipped with three inlet branch pipes, each with an inlet control valve 41, and each inlet branch pipe has a branch connection flange at its end that connects to the return flange 232 on the corresponding heat exchange unit of the outlet section heat exchange module. Thus, the media in the three parallel flow channels enter from the main inlet water tank 3 and ultimately flow into the main return water tank 4. Since each branch is equipped with a control valve, when a heat exchange unit needs to be repaired separately, the corresponding branch can be shut off without affecting the continued operation of the other branches.

[0111] In some embodiments, adjacent heat exchange units located in the same second direction can be connected in series via connecting short sections. Specifically, the return flange 232 of the inlet heat exchange unit can be connected to the inlet flange 222 of the intermediate heat exchange unit via a first connecting short section, and the return flange 232 of the intermediate heat exchange unit can be connected to the inlet flange 222 of the outlet heat exchange unit via a second connecting short section. The connecting short section can be a rigid flange short pipe, a detachable elbow, a metal hose, or a corrugated connector with compensation capability. Using a rigid flange short pipe helps maintain stable medium flow resistance. Using a connector with compensation capability provides space for the removal and installation of the heat exchange unit. Furthermore, branch control valves, drain valves, air vents, or temperature and pressure measurement interfaces can also be installed on each connecting short section to facilitate operation monitoring and unit-level maintenance.

[0112] In some embodiments, baffles, flow equalization orifice plates, guide plates, or throttling devices may be installed inside the main inlet tank 3 and the main return tank 4 to improve the flow distribution among the three parallel branches. Insulation layers, inspection ports, supports, and temperature measuring points may also be installed on the outer shells of the main inlet tank 3 and the main return tank 4. The outlet control valve 31 and inlet control valve 41 on each branch can be manual valves, electric valves, pneumatic valves, or regulating valves with position feedback. By setting independently controllable branch valves and detachable connecting sections, the isolation, extraction, flipping, reassembly, and interstage relocation of individual heat exchange units can be completed without disassembling the entire cryogenic economizer.

[0113] In this embodiment, the heat exchange units preferably maintain a standardized structure. Specifically, the outer dimensions of each heat exchange unit, the mating interface between the first seal 251 and the second seal 252, the fitting interface of the third seal 253, the relative positions of the inlet manifold 22 and the return manifold 23, the interface dimensions of the inlet flange 222 and the return flange 232, the positions of the lifting components, and the connection relationship between the support column 26 and the support plate 27 are all consistent. Through the above-mentioned standardized structure, any heat exchange unit in different stages of the heat exchange module can be extracted and transferred to the target stage for reinstallation without requiring additional modifications to the installation unit 24, the sealing unit 25, and the external piping. Furthermore, to facilitate identification by maintenance personnel, highly readable stage markings and installation orientation markings can be provided on the outer surface of the heat exchange unit.

[0114] In some embodiments, to further adapt to the flue gas scouring environment, anti-wear component mounting positions can be reserved on both the first and second sides of the heat exchange unit. The anti-wear components can be guide plates, anti-wear plates, scouring shields, wear-resistant strips, or sacrificial layer components. Preferably, the anti-wear components are installed in a detachable manner so that they can be used or replaced before and after flipping the heat exchange unit. If the same mounting positions are reserved on both the first and second sides, the anti-wear components can be transferred to the new windward side without changing the structure of the heat exchange unit itself after flipping it. Furthermore, the windward side of the heat exchange unit can also be equipped with wear detection reference points, thickness gauges, or color-coded marking layers for quickly determining the degree of wear during shutdown maintenance. Preferably, the above-mentioned additional components do not affect the insertion relationship between the heat exchange unit and the mounting unit 24, or the mating relationship with the sealing unit 25.

[0115] In other embodiments, an auxiliary guide member may be provided between the heat exchange unit and the mounting unit 24. The auxiliary guide member may be an inclined guide surface located inside the support member 241, or a guide protrusion located outside the second seal member 252 or the support plate 27. When the heat exchange unit is inserted into the mounting space, the guide protrusion and the inclined guide surface cooperate to automatically move the heat exchange unit towards a predetermined center position as it approaches the mounting position.

[0116] Furthermore, the auxiliary guide components can also be used in conjunction with the positioning structure on the support 242 to simultaneously complete guidance and positioning at the end of assembly. If the cross-section of the flue 1 is large and the weight of the heat exchange unit is large, roller guide components or sliding supports can also be set around the loading and unloading port to reduce hoisting friction and sway.

[0117] In this embodiment, during operation of the low-temperature economizer, flue gas enters from one end of the flue duct 1 and sequentially washes the outer surface of the heat exchange tube assemblies 21 of the outlet section heat exchange module, the intermediate section heat exchange module, and the inlet section heat exchange module along a first direction. Because the flue gas carries fly ash particles, the windward side of the heat exchange unit closest to the incoming flow direction typically experiences stronger scouring, especially the heat exchange unit located in the outlet section heat exchange module, which is more prone to windward side wear first. On the other hand, the medium enters the inlet section heat exchange module from the main inlet tank 3, then flows through the intermediate section heat exchange module into the outlet section heat exchange module, and finally enters the main return tank 4, thus forming a flow path on the medium side opposite to the flue gas flow direction. As operating time increases, differentiated wear states gradually form between the windward and leeward sides, between the preceding and following stages, and between the middle and sides of the same stage. This invention utilizes the detachable, reversible, and interchangeable features of the heat exchange units to prevent these differentiated wear states from directly causing premature failure of the entire equipment. Instead, the remaining lifespan can be redistributed through maintenance procedures.

[0118] This embodiment also proposes a maintenance method for the aforementioned low-temperature economizer. Specifically, the maintenance method includes the following steps:

[0119] First, wear testing is performed on each heat exchange unit in at least two stages of the heat exchange module. Wear testing can be conducted during shutdown maintenance or in conjunction with online monitoring data. The testing targets include representative areas of the heat exchange unit along the first direction: the windward side, the leeward side, the region near the middle of the flue, and the region near the sidewall of the flue. Testing methods can include ultrasonic thickness measurement, endoscopic observation, sample comparison, observation of wear marks, or indirect judgment based on pressure difference and changes in heat transfer capacity. The test results can be used to create a wear profile for each heat exchange unit to determine whether predetermined rotation conditions or predetermined replacement conditions have been met.

[0120] Furthermore, when a heat exchange unit reaches the predetermined processing conditions, first close the outlet control valve 31 and inlet control valve 41 corresponding to that heat exchange unit, and close or remove the valves on the connecting short sections between adjacent stages. Then, drain the medium from the heat exchange unit and disconnect the connection between the inlet flange 222 and the return flange 232 and the external pipeline. Subsequently, lift the entire heat exchange unit out from the loading / unloading port along a third direction. After the heat exchange unit is lifted out, simultaneously check whether the first seal 251, second seal 252, third seal 253, first sealing groove 2511, second sealing groove 2512, first sealing strip 2521, second sealing strip 2533, and the positioning structure on the support 242 are worn, dusty, or damaged, and clean, replace, or repair them as needed. Afterward, determine whether the heat exchange unit should be reassembled by flipping over or interchanged between stages based on the wear detection results.

[0121] Specifically, when the wear on the windward side is greater than that on the leeward side and a predetermined rotation condition is met, the heat exchange unit is rotated. This rotation can be achieved by rotating the heat exchange unit 180° around a third direction, or by rotating it 180° around an axis parallel to the second direction, as long as the rotation allows the orientation of the original first and second sides in the first direction to be interchanged.

[0122] In this embodiment, it is preferable to rotate the heat exchange unit 180° around a third direction to complete the conversion between the windward and leeward sides while keeping the inlet water header 22 and the return water header 23 at the top. After rotation, the heat exchange unit is re-aligned with the original installation space of the installation unit 24, inserted along the third direction, and the second seal 252 is re-pressed against the first seal 251, the first sealing strip 2521 is re-fitted against the first sealing groove 2511, and the third seal 253 is re-pressed against the second seal 252 and the first seal 251. Then, the corresponding flanges and valves are reconnected to put the heat exchange unit back into operation.

[0123] Furthermore, when a heat exchange unit in the preceding heat exchange module reaches a predetermined interchangeability condition, it is interchanged with a heat exchange unit in the following heat exchange module. The predetermined interchangeability condition can be that the preceding heat exchange unit has completed at least one flip-over installation and reaches a set wear level again, or that the remaining wall thickness of the preceding heat exchange unit is lower than a preset value while the corresponding following heat exchange unit still retains a significant lifespan reserve. In a three-stage heat exchange structure, it is preferable to process the heat exchange units in the outlet section heat exchange module first. When a heat exchange unit in the outlet section heat exchange module reaches the rotation condition for the first time, it is rotated. When the rotated heat exchange unit reaches the predetermined wear condition again, it is then interchanged with the corresponding heat exchange unit in the intermediate section heat exchange module or the inlet section heat exchange module. The interchanged heat exchange unit continues to operate, and when it reaches the predetermined wear condition again, it can be flipped over again. Through this cyclical maintenance path of rotation, interchange, and rotation, the lifespan on both sides of the same heat exchange unit and the lifespan reserve between different stages can be gradually released.

[0124] In some implementations, the maintenance method may also include a lateral interchange step within the same stage. When it is detected that the heat exchange unit near the middle of the flue is worn faster than the heat exchange unit near the sidewall in the same stage heat exchange module, the two can be interchanged along the second direction within the same stage to balance the differences in flue gas scour at different lateral positions. Furthermore, lifespan grades can be established for each heat exchange unit based on its operating time, number of flipping operations, number of inter-stage interchanges, and thickness measurement results. Heat exchange units with higher lifespan grades are preferentially placed in positions with stronger flue gas scour, while heat exchange units with lower lifespan grades but still safe to use are placed in positions with weaker scour. This makes the service life of the entire equipment more balanced.

[0125] In other embodiments, the maintenance method may also include a reassembly verification step. This verification step includes at least flange connection verification, sealing crimp verification, valve opening / closing status verification, and water leakage testing verification. If necessary, airtightness checks, static pressure checks, and partial purging before restarting may also be performed. If an assembly deviation is found between a heat exchange unit and the installation unit 24 after reassembly, it can be corrected using adjusting shims, adjustable limit blocks, or replaceable guides on the support 242. Furthermore, maintenance personnel can record the installation orientation, stage position, lateral position, and corresponding thickness measurement results of the heat exchange unit after each disassembly and reassembly to form continuous historical management data.

[0126] In some implementations, to further improve maintenance convenience, the flange interface positions of the main inlet tank 3, the main return tank 4, and each connecting section can be standardized. This allows different heat exchange units to be reconnected to the system simply by changing the direction of the section or adjusting the valve opening / closing status after being flipped over or interchanged between stages. In other implementations, electronic tags or mechanical coding plates can be installed on the heat exchange units to correspond one-to-one with maintenance records. If used in conjunction with an online monitoring system, wear risks can be predicted based on flue gas temperature distribution, branch pressure difference changes, outlet medium temperature changes, and local vibration conditions, allowing for priority treatment of higher-risk heat exchange units during planned maintenance.

[0127] It should be noted that although the above embodiment is illustrated using a three-stage heat exchange module, three heat exchange units per stage, and a series-parallel connection of a main inlet tank 3 and a main return tank 4 as an example, the present invention is not limited thereto. Without changing the detachable, reversible installation, and interchangeability of the heat exchange units between different stages, the heat exchange module 2 can be configured as two-stage, four-stage, or more stages. The number of heat exchange units per stage can be adjusted according to the flue cross-section, and the inter-stage connection relationship can be selected according to the medium flow rate and system resistance, choosing a suitable series, parallel, or series-parallel combination method. The specific forms of the installation unit 24, sealing unit 25, main inlet tank 3, main return tank 4, connecting short sections, branch valves, and additional guide components and wear-resistant components can also be adaptively adjusted according to actual working conditions.

[0128] It should also be noted that the technical features of the specific embodiments described in this specification can be combined with each other where there is no contradiction. All technical contents that employ the detachable heat exchange unit structure, symmetrical reversing installation relationship, inter-stage interchangeable relationship, cartridge installation relationship, and multi-seal relationship disclosed in this invention, and thereby achieve heat exchange unit flipping reuse and inter-stage interchangeability reuse, should be understood to fall within the protection scope of this invention.

Claims

1. A low-temperature economizer, characterized in that, It includes a flue and at least two stages of heat exchange modules sequentially arranged in the flue along a first direction. Each stage of the heat exchange module includes at least one installation unit and at least one heat exchange unit detachably installed on the installation unit. The heat exchange unit has a first side and a second side symmetrically arranged about a first direction, so that the heat exchange unit can be installed on the mounting unit in at least two mounting orientations, the different mounting orientations corresponding to the interchange of the orientation of the first side and the second side in the first direction; The mounting units and heat exchange units in different levels of heat exchange modules have the same structure, so that any heat exchange unit can be installed in the mounting unit of its original level of heat exchange module or in the mounting unit of another different level of heat exchange module.

2. The low-temperature economizer according to claim 1, characterized in that, The installation unit includes a support frame inserted into the flue along a third direction, and the support frame has an installation space for the heat exchange unit to be inserted therein along a third direction. The flue is provided with a loading and unloading port that communicates with the installation space.

3. The low-temperature economizer according to claim 2, characterized in that, The support frame includes support components and supporting components; The support members are multiple and are inserted into the flue along a third direction, forming the installation space between the multiple support members; The support is fixed to the top of the plurality of supports, and the outer periphery of the support is sealed to the loading and unloading port on the flue.

4. The low-temperature economizer according to claim 3, characterized in that, The heat exchange unit includes a heat exchange tube assembly, an inlet water manifold and a return water manifold, which are respectively connected to the heat exchange tube assembly. The heat exchange tube assembly includes several heat exchange tubes and is inserted into the installation space; The inlet water collector and the return water collector are respectively located on opposite sides of the upper part of the heat exchange tube group, and are symmetrically arranged about the first direction; The inlet water tank is connected to an inlet pipe on the side opposite to the return water tank, and an inlet flange is provided at the open end of the inlet water pipe. A return water pipe is connected to the side of the return water manifold away from the inlet water manifold, and a return water flange is provided at the open end of the return water pipe. The inlet flange is used to connect to the return flange or the inlet flange of the adjacent heat exchange unit, so that the inlet pipe of the adjacent heat exchange unit is connected to the return pipe or the inlet pipe. The return water flange is used to connect to the inlet flange or the return water flange of the adjacent heat exchange unit, so that the return water pipe of the adjacent heat exchange unit is connected to the inlet pipe or the return water pipe.

5. The low-temperature economizer according to claim 4, characterized in that, The low-temperature economizer also includes a sealing unit connected to the mounting unit and the heat exchange unit; The sealing unit includes a first sealing element, a second sealing element, and a third sealing element; The first sealing element is an annular component, which is fixed to the top of the support and is sealed to the support. The second sealing element is a plate-shaped component, and a plurality of the heat exchange tubes are inserted through the second sealing element in a third direction and are sealed to the second sealing element; the bottom of the second sealing element is sealed to the top of the first sealing element. The third sealing element is an annular component and is disposed outside the second sealing element; the third sealing element has a first pressing part and a second pressing part, which respectively seal and abut against the first sealing element and the second sealing element.

6. The low-temperature economizer according to claim 5, characterized in that, A first circumferential mating portion is provided between the first sealing element and the second sealing element; A second circumferential mating portion is provided between the first sealing element and the third sealing element; A third circumferential mating portion is provided between the third sealing element and the second sealing element; At least one of the first circumferential mating portion, the second circumferential mating portion, and the third circumferential mating portion includes a groove and a sealing strip that fit together.

7. The cryogenic economizer according to any one of claims 1 to 6, characterized in that, The low-temperature economizer includes an outlet section heat exchange module, an intermediate section heat exchange module, and an inlet section heat exchange module arranged sequentially along a first direction. Each heat exchange module includes three heat exchange units arranged at intervals along the second direction; The outside of the flue is provided with a main water inlet tank that is connected to the heat exchange module of the inlet section and a main water return tank that is connected to the heat exchange module of the outlet section.

8. A maintenance method for a low-temperature economizer, characterized in that, The cryogenic economizer applied to any one of claims 1 to 7 comprises the following steps: Wear testing is performed on each heat exchange unit in at least two stages of heat exchange modules; Heat exchange units that have reached a predetermined wear level are extracted from their installation units along a third direction. The extracted heat exchange unit is rotated and reinstalled in the original mounting unit so that the orientation of the original first side and the second side in the first direction is interchanged; and / or the extracted heat exchange unit is installed in the mounting unit of another heat exchange module of a different stage for continued use.

9. The maintenance method according to claim 8, characterized in that, The wear detection includes detecting the windward and leeward sides of the heat exchange unit along the first direction respectively; When the wear on the windward side is greater than the wear on the leeward side and the predetermined rotation conditions are met, the heat exchange unit is rotated and installed. When the heat exchange unit in the front heat exchange module meets the predetermined interchange conditions, it is interchanged with the heat exchange unit in the rear heat exchange module.

10. The maintenance method according to claim 8 or 9, characterized in that, The maintenance method includes the following rotation process: Prioritize rotating the heat exchange units in the heat exchange module of the outlet section; After the outlet section heat exchange unit reaches the predetermined wear condition again after being rotated and installed, it is interchanged with the heat exchange unit in the intermediate section heat exchange module or the heat exchange unit in the inlet section heat exchange module. The heat exchange units, after being swapped and installed, continue to operate and are rotated and installed again after reaching the predetermined wear conditions, in order to cyclically extend the service life of the low-temperature economizer.

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