A flue gas heat exchanger tube connecting structure capable of preventing heat stress from causing leakage

Abstract

The application discloses a flue gas heat exchanger pipe connecting structure capable of preventing heat stress from causing leakage. The structure comprises a heat exchange pipe, which is connected with a flue wall in a soft manner to eliminate the influence of heat stress between the heat exchange pipe and the flue wall. An expansion joint is arranged on the heat exchange pipe in the flue to provide a buffer space for the deformation of the heat exchange pipe caused by thermal expansion and contraction in the axial direction. The heat exchange pipe and the flue wall are connected in a soft manner by using a fixing nut, an elastic gasket and a fixing ring, and the gasket is made of polytetrafluoroethylene material. The axial and radial deformation of the heat exchange pipe caused by thermal expansion and contraction is effectively absorbed while the sealing is considered, so as to offset the influence of heat stress between the heat exchange pipe and the flue wall. The heat exchange pipe and the expansion joint are welded in the flue, and the expansion joint provides a buffer space for the deformation of the heat exchange pipe body caused by thermal expansion and contraction in the axial direction, so that the influence of heat stress on the connecting point of the flue gas heat exchanger and the flue wall can be further inhibited.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of flue gas heat exchanger, and particularly relates to a flue gas heat exchanger heat exchange pipe connecting structure capable of preventing heat stress from causing leakage. BACKGROUND

[0002] The flue gas heat exchanger is widely used as a waste heat recovery device, which can recover the waste heat in the flue gas to the steam system of the unit to improve the thermal economy of the power plant. The flue gas heat exchanger has excellent energy saving effect, but the problem of low-temperature corrosion is increasingly prominent. The corrosion problem of the heat exchange pipe at the tightly connected flue gas duct presents a concentrated outbreak, mainly because: first, the temperature of the heat exchange pipe is in a long-term change state due to the start-stop and daily load change of the unit, second, the thermal expansion coefficients of the heat exchange pipe material and the flue gas duct wall material are inconsistent, and the traditional heat exchange pipe and the flue gas duct wall are connected by welding, therefore, the welding points of the heat exchange pipe and the flue gas duct wall are greatly affected by the thermal stress caused by thermal expansion and contraction, and the welding points will be cracked and leaked in severe cases, resulting in water pipe leakage, which combines with SO3 in the flue gas to form acid liquid to further corrode the metal pipe wall.

[0003] At present, the technology for preventing the connection point between the flue gas heat exchanger and the flue gas duct wall from being cracked and leaked due to the influence of thermal stress has not been proposed, therefore, the present application discloses a flue gas heat exchanger capable of preventing heat stress from causing leakage, which has important guiding significance. SUMMARY

[0004] In order to solve the technical problems existing in the prior art, the purpose of the present application is to provide a flue gas heat exchanger heat exchange pipe connecting structure capable of preventing heat stress from causing leakage.

[0005] In order to achieve the above-mentioned purpose and achieve the above-mentioned technical effect, the technical solution adopted by the present application is as follows:

[0006] A flue gas heat exchanger heat exchange pipe connecting structure capable of preventing heat stress from causing leakage, comprising a heat exchange pipe, one end of the heat exchange pipe is provided with a heat exchange pipe water inlet, and the opposite end is provided with a heat exchange pipe water outlet, the heat exchange pipe is soft-connected with the flue gas duct wall to eliminate the influence of thermal stress between the heat exchange pipe and the flue gas duct wall, and an expansion joint is arranged on the heat exchange pipe located in the flue gas duct to provide a buffer space for the deformation of the heat exchange pipe caused by thermal expansion and contraction in the axial direction.

[0007] Further, a fixing nut, an elastic gasket and a fixing ring are arranged at the connection between the heat exchange pipe and the flue gas duct wall.

[0008] Further, the fixing nut, the elastic gasket and the fixing ring are sequentially sleeved on the heat exchange pipe.

[0009] Furthermore, the fixing nut is located outside the flue, the fixing ring is located inside the flue, a portion of the elastic gasket is outside the flue, and the remaining portion is inside the flue.

[0010] Furthermore, an external thread is provided on the outer wall of one end of the heat exchange tube located outside the flue and close to the water inlet of the heat exchange tube, and the fixing nut is sleeved on the external thread.

[0011] Furthermore, the elastic gasket is a polytetrafluoroethylene gasket.

[0012] Furthermore, the expansion joint is arranged between the water inlet and the water outlet of the heat exchange tube. The heat exchange tube and the expansion joint have the same thermal expansion coefficient, and the two are welded into an integral structure.

[0013] Furthermore, a heat absorption layer is provided on the inner wall of the heat exchange tube. The thickness of the heat absorption layer is 2-5 mm. The heat absorption layer is made of polyethylene, corundum powder, sodium polyacrylate, palygorskite powder and magnesium oxide.

[0014] Furthermore, the mass ratio of the polyethylene, corundum powder, sodium polyacrylate, palygorskite powder and magnesium oxide is 30-58:5-20:8-15:10-25:10-20.

[0015] The present invention also discloses a method for designing a heat exchange tube connection structure of a flue gas heat exchanger to prevent leakage caused by thermal stress, comprising the following steps:

[0016] Design an expansion joint, and then weld the opposite ends of the expansion joint to the heat exchange tubes;

[0017] Place the heat exchange tube in the flue, and extend one end of the heat exchange tube out of the flue wall so that the water inlet of the heat exchange tube is placed outside the flue. Use external threads, fixing nuts, elastic gaskets and fixing rings to make soft connections at the junction of the heat exchange tube and the flue wall to ensure good sealing and effectively absorb the axial and radial deformation of the heat exchange tube caused by thermal expansion and contraction.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] The application discloses a flue gas heat exchanger heat exchange pipe connecting structure and design method for preventing heat stress from causing leakage, which comprises a heat exchange pipe, a heat exchange pipe water inlet is arranged at one end of the heat exchange pipe, a heat exchange pipe water outlet is arranged at the opposite end of the heat exchange pipe, the heat exchange pipe is connected with a flue wall in a soft mode, heat stress influence between the heat exchange pipe and the flue wall is eliminated, an expansion joint is arranged on the heat exchange pipe in the flue, and a buffer space is provided for deformation of the heat exchange pipe caused by thermal expansion and cold contraction in the axial direction of the heat exchange pipe. The flue gas heat exchanger heat exchange pipe connecting structure and design method for preventing heat stress from causing leakage provided by the application adopts external threads, fixing nuts, elastic gaskets and fixing rings and the like to perform soft connection at the connecting position of the heat exchange pipe and the flue wall, and adopts a gasket made of polytetrafluoroethylene material, so that axial and radial deformation of the heat exchange pipe caused by thermal expansion and cold contraction is effectively absorbed while sealing is considered, the heat stress influence between the heat exchange pipe and the flue wall is offset, and meanwhile, the heat exchange pipe and the expansion joint are welded together in the flue, the expansion joint provides a buffer space for deformation of the heat exchange pipe body caused by thermal expansion and cold contraction in the axial direction of the heat exchange pipe, and the influence of heat stress on the connecting position of the flue gas heat exchanger and the flue wall is further inhibited. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 It is a structural schematic diagram of the application. DETAILED DESCRIPTION

[0021] The application will be described in detail below, so that the advantages and features of the application can be more easily understood by those skilled in the art, and the protection scope of the application can be more clearly and definitely defined.

[0022] The following presents a simplified summary of one or more aspects in order to provide a basic understanding of such aspects. This summary is not an extensive overview of all contemplated aspects, and is intended to neither identify key or critical elements of all aspects nor delineate the scope of any or all aspects. Its sole purpose is to present some concepts of one or more aspects in a simplified form as a prelude to the more detailed description that is presented later.

[0023] As Figure 1As shown, a flue gas heat exchanger heat pipe connection structure preventing heat stress from causing leakage, comprising a heat pipe 2, one end of the heat pipe 2 is provided with a heat pipe water inlet 1, and the opposite end is provided with a heat pipe water outlet 3, the heat pipe water inlet 1 is located outside the flue, and the heat pipe 2 adopts a soft connection mode of external threads 5, a fixing nut 6, a polyelastic gasket 7 and a fixing ring 8 in the connection with the flue wall surface 4, the fixing nut 6, the polytetrafluoroethylene gasket 7 and the fixing ring 8 are sequentially sleeved on the heat pipe 2, specifically, the outer wall of the end of the heat pipe 2 close to the heat pipe water inlet 1 located outside the flue is provided with external threads 5, the fixing nut 6 is sleeved on the external threads 5, the fixing nut 6 is located outside the flue, the elastic gasket 7 is arranged at the connection of the heat pipe 2 and the wall surface 4, part of which is outside the flue and part of which is inside the flue, and the fixing ring 8 is located inside the flue, in use, low-temperature water enters the heat pipe 2 of the flue gas heat exchanger through the heat pipe water inlet 1 and absorbs the high-temperature flue gas energy in the flue, and then flows out from the heat pipe water outlet 3, the material of the elastic gasket 7 is polytetrafluoroethylene, which has the advantages of high temperature resistance and high elasticity, and effectively absorbs the axial and radial deformation of the heat pipe 2 caused by thermal expansion and contraction while considering sealing, so as to offset the influence of thermal stress between the heat pipe 2 and the flue wall surface 4. At the same time, an expansion joint 9 is designed on the heat pipe 2 inside the flue, and the arrangement position is close to the wall surface, which provides a buffer space for the deformation of the heat pipe 2 in the axial direction caused by thermal expansion and contraction, further inhibits the influence of thermal stress at the connection point of the flue gas heat exchanger and the flue wall surface 4, and effectively prevents the connection point of the flue gas heat exchanger and the flue wall surface 4 from being affected by thermal stress to cause rupture and leakage.

[0024] In order to improve the heat absorption effect, the heat absorption layer with a thickness of 2-5mm is arranged on the inner wall of the heat pipe 2, and the sufficient thickness is helpful to fully play the heat absorption advantage of the heat absorption layer, improve the heat absorption performance, and the heat absorption layer is made of polyethylene, corundum powder, sodium polyacrylate, palygorskite powder and magnesium oxide with a mass ratio of 30-58:5-20:8-15:10-25:10-20, the polyethylene is used as the main body, the addition of the sodium polyacrylate and the palygorskite powder is helpful to improve the viscosity between the raw material components of the heat absorption layer, the corundum powder, the palygorskite powder and the magnesium oxide are all in the form of solid powder, the particle size can reach micrometer level or nanometer level, the magnesium ion in the magnesium oxide dissolved in water is easy to react with the sodium polyacrylate, and the combination and strength of the heat absorption layer are enhanced, and the heat absorption effect of the heat absorption layer is good. The preparation steps of the heat absorption layer include: the polyethylene, the corundum powder, the sodium polyacrylate and the magnesium oxide with a mass ratio of 30-58:5-20:8-15:10-20 are sent into a high-speed mixer to be uniformly stirred, the stirring speed is 10-55 revolutions / minute, the mixing time is 5-15 minutes, then the palygorskite powder is added, the stirring speed is 15-50 revolutions / minute, the mixing time is 3-8 minutes, then appropriate amount of water is added, the stirring speed is increased to 20-60 revolutions / minute, the mixing time is 5-15 minutes, and then the heat absorption layer can be directly arranged on the inner wall of the heat pipe 2 by spraying or other common ways.

[0025] The present invention also discloses a method for designing a heat exchange tube connection structure of a flue gas heat exchanger to prevent leakage caused by thermal stress, comprising the following steps:

[0026] Design an expansion joint 9, and then weld the opposite ends of the expansion joint 9 to the heat exchange tube 2 respectively;

[0027] The heat exchange tube 2 is placed in the flue, and one end of the heat exchange tube 2 is extended out of the flue wall 4, so that the heat exchange tube water inlet 1 of the heat exchange tube 2 is placed outside the flue. The external thread 5, fixing nut 6, elastic gasket 7 and fixing ring 8 are used to make a soft connection at the junction of the heat exchange tube 2 and the flue wall 4 to ensure a good seal and effectively absorb the axial and radial deformation of the heat exchange tube 2 caused by thermal expansion and contraction, thereby offsetting the influence of thermal stress between the heat exchange tube 2 and the flue wall 4.

[0028] Example 1

[0029] like Figure 1 As shown, a heat exchange tube connection structure of a flue gas heat exchanger that prevents leakage caused by thermal stress includes a heat exchange tube 2, a heat exchange tube water inlet 1 is provided at one end of the heat exchange tube 2, and a heat exchange tube water outlet 3 is provided at the other end opposite thereto. The heat exchange tube water inlet 1 is located outside the flue, and the heat exchange tube 2 is connected to the flue wall 4 by adopting a soft connection method of external thread 5, fixing nut 6, polyelastic gasket 7 and fixing ring 8. The fixing nut 6, polytetrafluoroethylene gasket 7 and fixing ring 8 are sequentially sleeved on the heat exchange tube 2. Specifically, the outer wall of one end of the heat exchange tube 2 located outside the flue and close to the heat exchange tube water inlet 1 is provided with an external thread 5, and the fixing nut 6 is sleeved on the external thread On the groove 5, the fixing nut 6 is located outside the flue, and the elastic gasket 7 is arranged at the connection between the heat exchange tube 2 and the wall 4, part of which is outside the flue and part of which is inside the flue. The fixing ring 8 is located inside the flue. When in use, low-temperature water enters the heat exchange tube 2 of the flue gas heat exchanger through the water inlet 1 of the heat exchange tube, and absorbs the high-temperature flue gas energy in the flue, and then flows out from the water outlet 3 of the heat exchange tube. The material of the elastic gasket 7 is polytetrafluoroethylene, which has the advantages of high temperature resistance and high elasticity. While taking into account sealing, it effectively absorbs the axial and radial deformation of the heat exchange tube 2 caused by thermal expansion and contraction, thereby offsetting the influence of thermal stress between the heat exchange tube 2 and the flue wall 4. At the same time, an O-shaped expansion joint 9 is designed on the heat exchange tube 2 inside the flue, and is arranged close to the wall to provide a buffer space for the deformation of the heat exchange tube 2 in its axial direction due to thermal expansion and contraction, further suppressing the influence of thermal stress at the connection point between the flue gas heat exchanger and the flue wall 4, and effectively preventing the connection point between the flue gas heat exchanger and the flue wall 4 from being affected by thermal stress and causing rupture and leakage.

[0030] A heat-absorbing layer with a thickness of 2 mm is provided on the inner wall of the heat exchange tube 2. Sufficient thickness helps to give full play to the heat absorption advantage of the heat-absorbing layer and improve the heat absorption performance. The heat-absorbing layer is made of polyethylene, corundum powder, sodium polyacrylate, palygorskite powder, and magnesium oxide in a mass ratio of 30:20:15:25:20. The heat-absorbing layer is mainly composed of polyethylene. The addition of sodium polyacrylate and palygorskite powder helps to improve the viscosity between the raw material components of the heat-absorbing layer. Corundum powder, palygorskite powder, and magnesium oxide are all solid powders with a particle size of micron or nanometer. After magnesium oxide is dissolved in water, the magnesium ions in it easily react with sodium polyacrylate, thereby enhancing the bonding force and strength of the heat-absorbing layer, and the heat-absorbing layer has a good heat absorption effect. The preparation steps of the heat absorption layer include: adding polyethylene, corundum powder, sodium polyacrylate, and magnesium oxide in a mass ratio of 30:20:15:20 into a high-speed mixer and stirring evenly at a stirring speed of 30 rpm for 5 minutes, then adding all the palygorskite powder, stirring at a speed of 40 rpm, mixing for 5 minutes, then adding an appropriate amount of water, increasing the stirring speed to 60 rpm, and mixing for 10 minutes. Later, it can be directly arranged on the inner wall of the heat exchange tube 2 by spraying or other common methods.

[0031] A method for designing a heat exchange tube connection structure of a flue gas heat exchanger to prevent leakage caused by thermal stress comprises the following steps:

[0032] Design an expansion joint 9, and then weld the opposite ends of the expansion joint 9 to the heat exchange tube 2 respectively;

[0033] The heat exchange tube 2 is placed in the flue, and one end of the heat exchange tube 2 is extended out of the flue wall 4, so that the heat exchange tube water inlet 1 of the heat exchange tube 2 is placed outside the flue. The external thread 5, fixing nut 6, elastic gasket 7 and fixing ring 8 are used to make a soft connection at the junction of the heat exchange tube 2 and the flue wall 4 to ensure a good seal and effectively absorb the axial and radial deformation of the heat exchange tube 2 caused by thermal expansion and contraction, thereby offsetting the influence of thermal stress between the heat exchange tube 2 and the flue wall 4.

[0034] Example 2

[0035] like Figure 1As shown, a flue gas heat exchanger heat pipe connection structure preventing heat stress from causing leakage, comprising a heat pipe 2, one end of the heat pipe 2 is provided with a heat pipe water inlet 1, and the opposite end is provided with a heat pipe water outlet 3, the heat pipe water inlet 1 is located outside the flue, and the heat pipe 2 adopts a soft connection mode of external threads 5, a fixing nut 6, a polyelastic gasket 7 and a fixing ring 8 in the connection with the flue wall surface 4, the fixing nut 6, the polytetrafluoroethylene gasket 7 and the fixing ring 8 are sequentially sleeved on the heat pipe 2, specifically, the outer wall of the end of the heat pipe 2 close to the heat pipe water inlet 1 located outside the flue is provided with external threads 5, the fixing nut 6 is sleeved on the external threads 5, the fixing nut 6 is located outside the flue, the elastic gasket 7 is arranged at the connection of the heat pipe 2 and the wall surface 4, part of which is outside the flue and part of which is inside the flue, and the fixing ring 8 is located inside the flue, in use, low-temperature water enters the heat pipe 2 of the flue gas heat exchanger through the heat pipe water inlet 1 and absorbs the high-temperature flue gas energy in the flue, and then flows out from the heat pipe water outlet 3, the material of the elastic gasket 7 is polytetrafluoroethylene, which has the advantages of high temperature resistance and high elasticity, and effectively absorbs the axial and radial deformation of the heat pipe 2 caused by thermal expansion and contraction while considering sealing, so as to offset the influence of thermal stress between the heat pipe 2 and the flue wall surface 4. At the same time, an expansion joint 9 is designed on the heat pipe 2 inside the flue, and the arrangement position is close to the wall surface, which provides a buffer space for the deformation of the heat pipe 2 in the axial direction caused by thermal expansion and contraction, further inhibits the influence of thermal stress at the connection point of the flue gas heat exchanger and the flue wall surface 4, and effectively prevents the connection point of the flue gas heat exchanger and the flue wall surface 4 from being affected by thermal stress to cause rupture and leakage.

[0036] In order to improve the heat absorption effect, the heat absorption layer with a thickness of 2-5mm is arranged on the inner wall of the heat pipe 2, and the sufficient thickness is helpful to fully play the heat absorption advantage of the heat absorption layer, improve the heat absorption performance, and the heat absorption layer is made of polyethylene, corundum powder, sodium polyacrylate, palygorskite powder and magnesium oxide with a mass ratio of 58:5:8:10:10, the polyethylene is used as the main body, the addition of the sodium polyacrylate and the palygorskite powder is helpful to improve the viscosity among the raw material components of the heat absorption layer, the corundum powder, the palygorskite powder and the magnesium oxide are all in the form of solid powder, the particle size can reach micron level or nanometer level, the magnesium ion in the magnesium oxide dissolved in water is easy to react with the sodium polyacrylate, and the combination and the strength of the heat absorption layer are enhanced, and the heat absorption effect of the heat absorption layer is good. The preparation steps of the heat absorption layer include: the polyethylene, the corundum powder, the sodium polyacrylate and the magnesium oxide with a mass ratio of 58:5:8:10 are sent into a high-speed mixer to be uniformly stirred, the stirring speed is 10 revolutions per minute, the mixing time is 15 minutes, then the palygorskite powder is added, the stirring speed is 50 revolutions per minute, the mixing time is 8 minutes, then appropriate amount of water is added, the stirring speed is increased to 60 revolutions per minute, the mixing time is 15 minutes, and then the heat absorption layer can be directly arranged on the inner wall of the heat pipe 2 by spraying or other common ways.

[0037] A design method of a flue gas heat exchanger pipe connection structure capable of preventing heat stress from causing leakage, comprising the following steps:

[0038] An expansion joint 9 is designed, and then the opposite ends of the expansion joint 9 are respectively welded with the heat exchange pipes 2;

[0039] The heat exchange pipes 2 are arranged in the flue, and one end of the heat exchange pipes 2 extends out of the flue wall 4, so that the heat exchange pipe water inlet 1 of the heat exchange pipes 2 is arranged outside the flue, and the outer thread 5, the fixing nut 6, the elastic gasket 7 and the fixing ring 8 are used for soft connection at the joint of the heat exchange pipes 2 and the flue wall 4, so as to ensure good sealing and effectively absorb the axial and radial deformation of the heat exchange pipes 2 caused by thermal expansion and contraction, thereby offsetting the influence of heat stress between the heat exchange pipes 2 and the flue wall 4.

[0040] The same as in Embodiment 1.

[0041] Embodiment 3

[0042] As shown in the drawings, Figure 1 A flue gas heat exchanger pipe connection structure capable of preventing heat stress from causing leakage, comprising heat exchange pipes 2, one end of the heat exchange pipes 2 is provided with a heat exchange pipe water inlet 1, the opposite end is provided with a heat exchange pipe water outlet 3, the heat exchange pipe water inlet 1 is located outside the flue, and the heat exchange pipes 2 adopt a soft connection mode of outer thread 5, fixing nut 6, polytetrafluoroethylene gasket 7 and fixing ring 8 in the connection with the flue wall 4, the fixing nut 6, the polytetrafluoroethylene gasket 7 and the fixing ring 8 are sequentially sleeved on the heat exchange pipes 2, specifically, the outer wall of one end of the heat exchange pipes 2 close to the heat exchange pipe water inlet 1 located outside the flue is provided with the outer thread 5, the fixing nut 6 is sleeved on the outer thread 5, the fixing nut 6 is located outside the flue, the elastic gasket 7 is arranged at the joint of the heat exchange pipes 2 and the wall 4, part of which is outside the flue and part of which is inside the flue, the fixing ring 8 is located inside the flue, in use, low-temperature water enters the heat exchange pipes 2 of the flue gas heat exchanger through the heat exchange pipe water inlet 1 and absorbs the energy of high-temperature flue gas in the flue, and then flows out from the heat exchange pipe water outlet 3, the material of the elastic gasket 7 is polytetrafluoroethylene, which has the advantages of high temperature resistance and high elasticity, and effectively absorbs the axial and radial deformation of the heat exchange pipes 2 caused by thermal expansion and contraction, thereby offsetting the influence of heat stress between the heat exchange pipes 2 and the flue wall 4. At the same time, the expansion joint 9 is designed on the heat exchange pipes 2 inside the flue, and the arrangement position is close to the wall, which provides a buffer space for the deformation of the heat exchange pipes 2 in the axial direction caused by thermal expansion and contraction, further inhibits the influence of heat stress at the connection point of the flue gas heat exchanger and the flue wall 4, and effectively prevents the connection point of the flue gas heat exchanger and the flue wall 4 from being affected by heat stress to cause rupture and leakage.

[0043] In order to improve the heat absorption effect, the heat absorption layer with the thickness of 2-5mm is arranged on the inner wall of the heat exchange pipe 2, and the sufficient thickness is helpful to fully play the heat absorption advantage of the heat absorption layer, improve the heat absorption performance, and the heat absorption layer is made of polyethylene, corundum powder, sodium polyacrylate, palygorskite powder and magnesium oxide with the mass ratio of 40:8:10:15:15, the polyethylene is used as the main body, the sodium polyacrylate and the palygorskite powder are added to improve the viscosity between the raw material components of the heat absorption layer, the corundum powder, the palygorskite powder and the magnesium oxide are all in the form of solid powder, the particle size can reach micron level or nanometer level, the magnesium ion in the magnesium oxide dissolved in water is easy to react with the sodium polyacrylate, so that the bonding force and the strength of the heat absorption layer are enhanced, and the heat absorption effect of the heat absorption layer is good. The preparation steps of the heat absorption layer include: the polyethylene, the corundum powder, the sodium polyacrylate and the magnesium oxide with the mass ratio of 40:8:10:15 are sent into a high-speed mixer to be uniformly stirred, the stirring speed is 45 revolutions / minute, the mixing time is 8 minutes, then the palygorskite powder is added, the stirring speed is 40 revolutions / minute, the mixing time is 8 minutes, then the appropriate amount of water is added, the stirring speed is increased to 60 revolutions / minute, the mixing time is 5 minutes, and then the heat absorption layer can be directly arranged on the inner wall of the heat exchange pipe 2 by spraying or other common ways.

[0044] A design method of a flue gas heat exchanger heat exchange pipe connection structure capable of preventing heat stress from causing leakage, comprising the following steps:

[0045] An expansion joint 9 is designed, and then the opposite ends of the expansion joint 9 are respectively welded with the heat exchange pipe 2 to form the heat exchange pipe connection structure;

[0046] The heat exchange pipe 2 is arranged in the flue, and one end of the heat exchange pipe 2 extends out of the flue wall surface 4, so that the heat exchange pipe water inlet 1 of the heat exchange pipe 2 is arranged outside the flue, and the outer thread 5, the fixing nut 6, the elastic gasket 7 and the fixing ring 8 are used for soft connection at the joint of the heat exchange pipe 2 and the flue wall surface 4, so as to ensure good sealing and effectively absorb the axial and radial deformation of the heat exchange pipe 2 caused by thermal expansion and contraction, thereby offsetting the influence of the thermal stress between the heat exchange pipe 2 and the flue wall surface 4.

[0047] The remainder is the same as in example 1.

[0048] The parts or structures not specifically described in the present application can adopt the prior art or existing products, and will not be described here.

[0049] The above is only an embodiment of the present application, and does not limit the patent range of the present application, and any equivalent structure or equivalent process transformation using the content of the present application specification, or direct or indirect application in other related technical fields, are also included in the patent protection range of the present application.

Claims

1. A flue gas heat exchanger tube connection structure for preventing leakage caused by thermal stress, comprising a heat exchange tube, one end of which is provided with a heat exchange tube water inlet, and the opposite end of which is provided with a heat exchange tube water outlet, characterized in that, The heat exchange pipe is connected with the flue wall in a soft manner, which is used to eliminate the influence of thermal stress between the heat exchange pipe and the flue wall, and an expansion joint is arranged on the heat exchange pipe inside the flue, which is used to provide a buffer space for the deformation of the heat exchange pipe in the axial direction caused by thermal expansion and contraction; The connecting position of the heat exchange pipe and the flue wall is provided with a fixing nut, an elastic gasket and a fixing ring; The fixing nut is located outside the flue, the fixing ring is located inside the flue, the elastic gasket is made of polytetrafluoroethylene gasket, and a part of the elastic gasket is located outside the flue and the remaining part is located inside the flue; An outer thread is arranged on the outer wall of the end of the heat exchange pipe close to the water inlet of the heat exchange pipe outside the flue, and the fixing nut is sleeved on the outer thread; The expansion joint is arranged between the water inlet and the water outlet of the heat exchange pipe, the heat expansion coefficient of the heat exchange pipe and the expansion joint is the same, and the heat exchange pipe and the expansion joint are welded into an integral structure.

2. A flue gas heat exchanger tube connection structure according to claim 1, wherein The fixing nut, the elastic gasket and the fixing ring are sequentially sleeved on the heat exchange pipe.

3. A connection structure of a flue gas heat exchanger tube which prevents leakage due to thermal stress according to claim 1, characterized in that, An endothermic layer is arranged on the inner wall of the heat exchange pipe, the thickness of the endothermic layer is 2-5mm, and the endothermic layer is made of polyethylene, corundum powder, sodium polyacrylate, palygorskite powder and magnesium oxide.

4. A flue gas heat exchanger tube connection structure according to claim 3, wherein The mass ratio of the polyethylene, the corundum powder, the sodium polyacrylate, the palygorskite powder and the magnesium oxide is 30-58:5-20:8-15:10-25:10-20.

5. The method of designing a connection of heat exchange tubes of a flue gas heat exchanger against leakage due to thermal stresses according to any of claims 1 to 4, characterized in that, The method comprises the following steps: Designing the expansion joint, and then welding the opposite ends of the expansion joint with the heat exchange pipe; Placing the heat exchange pipe in the flue, and extending one end of the heat exchange pipe out of the flue wall, so that the water inlet of the heat exchange pipe is located outside the flue, and the connecting position of the heat exchange pipe and the flue wall is connected in a soft manner by using the outer thread, the fixing nut, the elastic gasket and the fixing ring, so as to ensure good sealing and effectively absorb the axial and radial deformation of the heat exchange pipe caused by thermal expansion and contraction.

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