Heat exchange tube and flue gas heat exchanger with same

Abstract

The utility model discloses a heat exchange tube and a flue gas heat exchanger with the heat exchange tube. The heat exchange pipe comprises a heat exchange main pipe and a heat exchange main pipe, the heat exchange main pipe is used for introducing gas for heat exchange, and the heat exchange main pipe is made of fluoroplastic; the multiple first fins are arranged on the peripheral wall of the heat exchange main pipe in a sleeving mode at intervals, and the first fins are made of Gr / PTFE composite materials; the second fins are arranged on the peripheral wall of the heat exchange main pipe in a sleeving mode at intervals, the second fins and the first fins are alternately arranged, and the second fins are made of Gr / PTFE composite rigid foam plastic. The heat exchanger can resist corrosion and strengthen heat exchange.

Description

Technical Field

[0001] The utility model relates to heat exchange equipment, and more particularly to a heat exchange tube and a flue gas heat exchanger having the heat exchange tube. Background Art

[0002] As the core equipment of the flue gas waste heat recovery system, the flue gas heat exchanger plays a decisive role in the performance of the waste heat recovery system. The heat exchange tubes in existing flue gas heat exchangers are generally metal heat exchange tubes, which are prone to low-temperature corrosion, scaling, and low waste heat recovery rates. Special alloy steel heat exchange tubes are expensive. Lining with hard materials will inevitably cause lining cracking and internal metal tube corrosion. Fluoroplastic heat exchange tubes can effectively solve the corrosion and scaling problems of flue gas heat exchangers, but fluoroplastic heat exchange tubes have poor heat transfer efficiency. Generally, thin tube walls and small tube diameters are used to improve the heat transfer coefficient. The resulting problem is that the thin tube wall shakes and deforms under the impact of flue gas, causing damage to the fluoroplastic tube, affecting the working effect of the heat exchanger and the overall layout of the fluoroplastic tube bundle. It can be seen from this that metal tubes have high heat transfer efficiency and high strength but are not corrosion-resistant, while fluoroplastic tubes are corrosion-resistant but have low heat transfer efficiency. Efficiency and corrosion resistance cannot be achieved at the same time.

[0003] Utility model CN201152715Y, "A Metal Heat Exchange Tube," relates to a heat exchange tube with fins spirally wrapped around the outside of the tube. The tube boasts improved heat transfer efficiency, resistance to thermal shock and mechanical vibration, and superior rigidity. While the fins enhance heat transfer, they offer poor corrosion resistance, making them unsuitable for use in environments with corrosive gases.

[0004] Invention CN108950311A "A protective coating for flue gas heat exchange tubes and its preparation method" provides a nickel-based protective coating for flue gas heat exchange tubes and its preparation method. The coating is composed of Cr, Mo, Fe, Ti, Co, Si, Al, Mn, C, W and Ni. ① This method melts and blends the components in proportion, then crushes and ball-mills the resulting alloy block into micron-sized particles, and uses plasma spraying technology to spray the coating material onto the surface of the heat exchange tube substrate. The preparation process is complex, the operation requirements are high, and the production cost is expensive. ② Although the spraying technology can effectively reduce the corrosion of the wall tube, it has very high requirements on the coating quality. It is difficult to ensure the long-term stable and safe operation of the heat exchanger in a highly corrosive acidic gas environment.

[0005] Patent CN102607299B, "Modular Fluoroplastic Tube Flue Gas Heat Exchanger," discloses a modular fluoroplastic tube flue gas heat exchanger. The heat exchange tubes consist of a U-shaped fluoroplastic heat exchange tube bundle, secured with parallel, spaced-apart positioning nets to prevent the flexible fluoroplastic tubes from vibrating and deforming under the impact of flue gas flow. However, the positioning nets are made of a rigid, high-temperature, and corrosion-resistant material. The specific material type is not specified in the document, and the corrosion resistance of this material remains to be demonstrated. Furthermore, high-temperature, corrosion-resistant materials are generally expensive, and the large amount of positioning nets used in the patented heat exchanger significantly increases the economic cost.

[0006] Therefore, designing wet heat exchange tubes that are suitable for different working conditions, corrosion-resistant, and cost-effective is of great significance for waste power plants to improve energy utilization efficiency, reduce operating costs, and achieve energy conservation and emission reduction. Utility Model Content

[0007] In order to solve the above problems, the utility model provides a heat exchange tube with high heat exchange efficiency and corrosion resistance and a flue gas heat exchanger having the heat exchange tube.

[0008] The utility model adopts the following technical solutions:

[0009] A heat exchange tube, comprising:

[0010] A heat exchange main pipe is used to pass gas for heat exchange, and the heat exchange main pipe is made of fluoroplastic;

[0011] Also includes:

[0012] A plurality of first fins are spaced and sleeved on the peripheral wall of the heat exchange main pipe, wherein the first fins are made of Gr / PTFE composite material;

[0013] A plurality of second fins are sleeved at intervals on the peripheral wall of the heat exchange main pipe and are arranged alternately with the plurality of first fins. The second fins are made of Gr / PTFE composite hard foam plastic.

[0014] Furthermore, the cross section of the first fin is trapezoidal, and the end thereof close to the main heat exchange pipe is wider than the end thereof away from the main heat exchange pipe.

[0015] Furthermore, the cross section of the second fin is trapezoidal, and the end close to the heat exchange main pipe is wider than the end away from the heat exchange main pipe; the cross section height of the second fin is lower than the cross section of the first fin, and the width of the second fin is greater than the width of the first fin.

[0016] Furthermore, a metal mesh is provided inside the first fin.

[0017] Furthermore, metal ribs are provided inside the first fins.

[0018] Furthermore, a plurality of openings are provided on the surface of the second fin, and the apertures are 0.8 mm to 2 mm.

[0019] The utility model also provides a flue gas heat exchanger, comprising the above-mentioned heat exchange tube. Beneficial effects

[0020] Compared with the prior art, the beneficial effects of the present invention are:

[0021] The main heat exchange tubes are made of corrosion-resistant fluoroplastic. The fins on the tubes are constructed of different materials and structures, with alternating fin layers. The first layer of fins utilizes a Gr / PTFE composite material, which exhibits excellent wear resistance, compression creep, chemical resistance, and high-temperature resistance. Graphite has thermal conductivity comparable to metal, and graphite-modified fluoroplastics have a thermal conductivity up to five times that of pure fluoroplastics. The second layer of fins utilizes a Gr / PTFE composite rigid foam, which combines excellent corrosion resistance, high-temperature resistance, and thermal conductivity with superior sound-absorbing properties. Multiple small holes are provided in the second layer of fins to further enhance the sound-absorbing effect.

[0022] The utility model provides fluoroplastic heat exchange tubes of a gas-to-gas heat exchange tube wet heat exchanger suitable for different working conditions and recovery of waste heat from highly corrosive flue gas, which avoids corrosion and scaling problems, has a good sound-absorbing effect, and solves the problem of high overall replacement and maintenance costs caused by easy damage of thin tube walls and small tube diameters. It provides guarantees for the long-term stable and safe operation of garbage power plants with complex flue gas components and the recovery of flue gas waste heat to achieve energy saving. At the same time, it ensures the exhaust and lifting power of the flue gas and reduces the adverse effects on the surrounding environment of the power plant. That is, under the premise of ensuring the anti-corrosion effect and the sound-absorbing effect, the heat exchange efficiency of the heat exchanger is greatly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a cross-sectional view of the first fin of the heat exchange tube according to an embodiment of the present invention.

[0024] Figure 2 This is a cross-sectional view of the second fin of the heat exchange tube according to an embodiment of the present invention.

[0025] Figure 3 This is a side cross-sectional view of a heat exchange tube according to an embodiment of the present invention.

[0026] In the figure: 1. Heat exchange main pipe; 2. First fin; 3. Second fin; 4. Metal mesh; 5. Opening. DETAILED DESCRIPTION

[0027] The present invention will be further described below in conjunction with specific embodiments and accompanying drawings.

[0028] See Figures 1 to 3The embodiment of the present invention provides a flue gas heat exchanger, including a heat exchange tube. Other components of the flue gas heat exchanger can adopt common industry designs.

[0029] Heat exchange tubes, including:

[0030] The heat exchange main pipe 1 is used to pass gas for heat exchange, and the heat exchange main pipe 1 is made of fluoroplastic;

[0031] A plurality of first fins 2 are spaced and sleeved on the peripheral wall of the heat exchange main pipe 1, wherein the first fins 2 are made of Gr / PTFE composite material;

[0032] A plurality of second fins 3 are sleeved on the peripheral wall of the main heat exchange pipe 1 at intervals and arranged alternately with the plurality of first fins 2 . The second fins 3 are made of Gr / PTFE composite hard foam plastic.

[0033] The heat exchange main pipe 1 is provided with first fins 2 and second fins 3, and a highly heat-conductive material is added to the first fin 2. Therefore, the wall thickness of the designed fluoroplastic heat exchange main pipe 1 is thicker than that of ordinary fluoroplastic pipes, which can prevent the heat exchange main pipe 1 from shaking, deforming and being damaged during the heat exchange process, reduce equipment losses and maintenance costs, and improve economic benefits.

[0034] The Gr / PTFE composite material and Gr / PTFE composite rigid foam plastic used in this application are existing materials, and their descriptions are as follows:

[0035] Gr / PTFE composites are graphite-modified polytetrafluoroethylene (PTFE) composites. Gr / PTFE composites are composed of graphite (Gr) and polytetrafluoroethylene (PTFE). Gr / PTFE composites exhibit excellent wear resistance, compression creep, chemical resistance, and high-temperature resistance. Graphite has thermal conductivity comparable to metals, and the thermal conductivity of graphite-modified fluoroplastics can reach up to five times that of pure fluoroplastics. The typical ratio of Gr / PTFE composites ranges from 5% to 40% graphite to 60% to 95% PTFE matrix, typically adjusted based on specific application requirements. The manufacturing process for Gr / PTFE composites generally includes: mixing: uniformly mixing graphite powder and PTFE powder; molding: forming by pressing or extrusion; and sintering: heating and sintering to enhance the overall performance of the material.

[0036] The Gr / PTFE composite material used in this application has no specific requirements for its ratio, and a conventional ratio can be used.

[0037] Gr / PTFE composite rigid foam plastic has excellent corrosion resistance, high temperature resistance, good thermal conductivity and good sound insulation performance.

[0038] Gr / PTFE composite rigid foam is a composite foam that combines graphite and polytetrafluoroethylene (PTFE) materials, with excellent mechanical properties, thermal properties and chemical stability. Its ingredients include:

[0039] Polytetrafluoroethylene (PTFE):

[0040] Function: As a base material, PTFE provides excellent chemical stability, heat resistance and low friction properties.

[0041] Proportion: PTFE is usually the majority component of the composite and may range from 60% to 90%, depending on the formulation and application.

[0042] Graphite (Gr):

[0043] Function: Graphite is used to improve the electrical conductivity, thermal conductivity and lubricity of materials, and to enhance the strength and wear resistance of materials.

[0044] Proportion: The addition amount of graphite can be between 10% and 40%, and the specific ratio depends on the required performance.

[0045] Foaming agent:

[0046] Function: Used to create foam structures, reduce material density, and improve shock absorption performance. Commonly used foaming agents include physical foaming agents and chemical foaming agents.

[0047] Filling (optional):

[0048] Such as microbeads (glass microbeads, polystyrene microbeads, etc.), etc., are used to further improve the performance of the foam.

[0049] Reinforcement material (optional):

[0050] For example, fiber-reinforced materials (such as carbon fiber, glass fiber, etc.) can increase the mechanical strength and toughness of the material.

[0051] Mixing: Evenly mix PTFE powder, graphite and other additives (such as foaming agent, filler, etc.).

[0052] Molding: Using a mold to press or adopt other molding processes.

[0053] Foaming: The foaming agent is activated under heat conditions to form a foam structure.

[0054] Curing or sintering: Thermal treatment (e.g. sintering) is used to increase the mechanical strength and stability of composite materials.

[0055] There is no specific requirement for the ratio of the Gr / PTFE composite rigid foam plastic used in this application, and a conventional ratio can be used.

[0056] Furthermore, the cross section of the first fin 2 is trapezoidal, and the end thereof close to the main heat exchange pipe 1 is wider than the end thereof away from the main heat exchange pipe 1 .

[0057] The first fin 2 is a trapezoidal structure, which is narrow at the top and wide at the bottom and surrounds the main pipe. It is stable and increases the heat exchange area, effectively prevents tearing, and improves airflow separation and vortex phenomenon in the leeward area.

[0058] Furthermore, the cross-section of the second fin 3 is trapezoidal, and the end close to the heat exchange main pipe 1 is wider than the end away from the heat exchange main pipe 1; the cross-sectional height of the second fin 3 is lower than the cross-sectional height of the first fin 2, and the width of the second fin 3 is greater than the width of the first fin 2.

[0059] The first fin 2 is roughly annular, with its thickness gradually decreasing from its inner circle toward the outer circle. Therefore, the cross-section of the first fin 2 is two trapezoids. The shape of the second fin 3 is the same as that of the first fin 2, except for its size. The outer diameter of the second fin 3 is smaller than that of the first fin 2. The thickness of the second fin 3 is greater than that of the first fin 2. In other words, the upper base length of the trapezoidal cross-section of the second fin 3 is greater than the upper base length of the trapezoidal cross-section of the first fin 2; and the lower base length of the trapezoidal cross-section of the second fin 3 is greater than the lower base length of the trapezoidal cross-section of the first fin 2.

[0060] The height of the first fin 2 and the second fin 3 are both 0.5-3 cm.

[0061] The above structure can increase the noise reduction effect and ensure the stability of fins 2 and 3. The use of trapezoidal fin heat exchange tubes has good stability, enhances the turbulence outside the tube, increases the heat exchange area, enhances the strength of the heat exchange tube, is not easy to vibrate, and plays a certain role in noise reduction.

[0062] Furthermore, a metal mesh 4 is provided inside the first fin 2 .

[0063] Furthermore, metal ribs are provided inside the first fin 2 .

[0064] The metal mesh 4 / metal ribs can further increase the strength and heat transfer capacity, and are applicable even in harsh working conditions.

[0065] Furthermore, a plurality of openings 5 ​​are provided on the surface of the second fin 3 , and the apertures are 0.8 mm to 2 mm.

[0066] The opening 5 has a good sound-absorbing effect. The aperture is in the range of 0.8 mm to 2 mm. If the aperture is too large, the noise will not be able to pass through the hole and will be reflected back, resulting in poor sound absorption effect. If the aperture is too small, friction noise will increase and the sound absorption effect will also deteriorate.

[0067] This heat exchange tube design combines corrosion resistance, enhanced heat transfer, and noise absorption, making it suitable for a wide range of operating conditions. Fins 2 and 3 on the outer wall of the main heat exchange tube 1 continuously redirect the fluid, achieving low Reynolds number flow, enhancing heat mixing and turbulence, and significantly improving the gas heat transfer coefficient. The first fin 2 is constructed of a graphite-modified fluoroplastic composite material and features an internal metal mesh 4 (metal ribs) to further increase the heat transfer coefficient and enhance tube strength, making it suitable for use even in challenging operating conditions. The second fin 3 utilizes microporous Gr / PTFE composite rigid foam fins, ensuring excellent thermal conductivity while enhancing sound absorption through both material and structural design.

[0068] The heat exchange tubes designed in this application offer excellent corrosion resistance and noise reduction, increased heat exchange velocity, high heat exchange efficiency and lifespan, and are suitable for diverse operating conditions. By improving the design of the heat exchanger tubes (by adding fins and modifying fin shape, material, structure, and internal components), they are suitable for waste heat recovery under various operating conditions, maximizing energy efficiency and improving operational economics.

[0069] The examples described in the present invention are merely descriptions of the preferred implementation methods of the present invention, and are not intended to limit the concept and scope of the present invention. Without departing from the design concept of the present invention, various modifications and improvements made to the technical solutions of the present invention by engineers and technicians in this field should fall within the scope of protection of the present invention.

Claims

1. A heat exchange tube, comprising: A heat exchange main pipe is used to pass gas for heat exchange, and the heat exchange main pipe is made of fluoroplastic; It is characterized by further comprising: A plurality of first fins are spaced and sleeved on the peripheral wall of the heat exchange main pipe, wherein the first fins are made of Gr / PTFE composite material; A plurality of second fins are sleeved at intervals on the peripheral wall of the heat exchange main pipe and are arranged alternately with the plurality of first fins. The second fins are made of Gr / PTFE composite hard foam plastic.

2. The heat exchange tube according to claim 1, characterized in that The cross section of the first fin is trapezoidal, and the end of the first fin close to the heat exchange main pipe is wider than the end away from the heat exchange main pipe.

3. The heat exchange tube according to claim 2, characterized in that: The cross section of the second fin is trapezoidal, and the end close to the heat exchange main pipe is wider than the end away from the heat exchange main pipe; the cross section height of the second fin is lower than the cross section of the first fin, and the width of the second fin is greater than the width of the first fin.

4. The heat exchange tube according to claim 1, characterized in that A metal mesh is provided inside the first fin.

5. The heat exchange tube according to claim 1, characterized in that Metal ribs are provided inside the first fin.

6. The heat exchange tube according to claim 1, characterized in that The surface of the second fin is provided with a plurality of openings, and the apertures are 0.8 mm to 2 mm.

7. A flue gas heat exchanger, characterized in that: The heat exchange tube comprises the heat exchange tube according to any one of claims 1 to 6.

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