Bypass air gap anticorrosion structure for condensing waste heat recovery flue

Abstract

The application provides a kind of anticorrosion structure for bypass air gap of condensing waste heat recovery flue, condensing heat exchanger for recovering flue gas waste heat is equipped in flue, and anticorrosion structure includes anticorrosion layer that is sleeved in the inside of flue downstream of condensing heat exchanger, anticorrosion layer is fixedly connected with the metal inner wall of flue by support, anticorrosion layer and the metal inner wall of flue form bypass channel, the inlet end of bypass channel is communicated with high-temperature flue gas upstream of condensing heat exchanger, the edge of the air inlet side of condensing heat exchanger is provided with throttling assembly at the junction with the inlet of bypass channel, throttling assembly controls the flow of high-temperature protective gas entering bypass channel, the inside bottom end of anticorrosion layer is communicated with hydrophobic assembly, hydrophobic assembly is closed and extends to outside through the side wall of bypass channel and flue, and outside is provided with U-shaped water sealing section for safely discharging acidic condensate generated in the inside of anticorrosion layer. The application can recover flue gas waste heat and prevent low-temperature corrosion of flue.

Description

Technical Field

[0001] This invention relates to the field of power plant waste heat recovery and energy conservation and emission reduction technology, specifically to a bypass air gap anti-corrosion structure for condensing waste heat recovery flues. Background Technology

[0002] In the operation of coal-fired or gas-fired power plants, the flue gas at the tail end of the boiler or gas turbine contains a large amount of low-grade heat energy. Currently, waste heat recovery heat exchangers are usually installed in the tail flue to recover this waste heat and improve the overall thermal economy of the plant. However, after the flue gas is cooled by the heat exchanger, its exhaust temperature often drops below the acid dew point of corrosive gases such as sulfides in the flue gas. This causes condensation to form on the metal walls of the flue downstream of the heat exchanger, forming a highly acidic condensate, which in turn leads to severe low-temperature corrosion.

[0003] Currently, the conventional method for treating low-temperature corrosion in tail flues mostly involves directly applying or pasting anti-corrosion materials onto the surface of the metal flue. However, conventional anti-corrosion coatings are prone to peeling and aging under prolonged and complex flue gas erosion and temperature fluctuations, while using all-special alloy materials would result in extremely high retrofit costs. In addition, if the acidic condensate generated after cooling and condensation cannot be safely and securely collected and discharged, it will also cause secondary corrosion and flue gas leakage hazards to the system.

[0004] Therefore, how to solve the low-temperature corrosion problem of the downstream flue gas duct of the heat exchanger at a lower engineering cost while deeply recovering the waste heat of the tail flue gas has become a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0005] To address the technical problem of low-temperature corrosion in existing flue gas waste heat recovery systems after deep cooling, this invention provides a bypass air gap anti-corrosion structure for condensing waste heat recovery flues, achieving dual protection of physical corrosion prevention and thermal isolation by high-temperature protective gas, effectively preventing low-temperature corrosion of the flue.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0007] A bypass air gap anti-corrosion structure for a condensing waste heat recovery flue gas duct, wherein a condensing heat exchanger for recovering waste heat from flue gas is installed inside the flue gas duct, and the anti-corrosion structure includes an anti-corrosion layer sleeved inside the flue gas duct downstream of the condensing heat exchanger. The anti-corrosion layer is fixedly connected to the metal inner wall of the flue gas duct by a support member. The anti-corrosion layer is suitable for physically isolating the main flue gas that undergoes condensation heat exchange after being cooled by the condensing heat exchanger. A bypass channel is formed between the anti-corrosion layer and the metal inner wall of the flue gas duct, and the inlet end of the bypass channel is connected to the high-temperature flue gas upstream of the condensing heat exchanger, so that part of the... High-temperature flue gas that has not been cooled is filled into the bypass channel as protective gas; a throttling component is provided at the junction of the air inlet edge of the condensing heat exchanger and the inlet of the bypass channel. The throttling component is used to control the flow rate of the high-temperature protective gas entering the bypass channel so as to maintain the metal wall temperature of the flue above the acid dew point of the flue gas; a hydrophobic component is connected to the bottom of the inner part of the anti-corrosion layer. The hydrophobic component extends to the outside through the bypass channel and the side wall of the flue, and a U-shaped water-sealing section is provided on the outside for safe discharge of acidic condensate generated inside the anti-corrosion layer.

[0008] Furthermore, the anti-corrosion layer has a cylindrical structure and is made of an organic anti-corrosion material that can withstand temperatures of not less than 150°C.

[0009] Furthermore, the width of the bypass channel is 5-10mm.

[0010] Furthermore, the throttling component is a rotating baffle gate with adjustable opening.

[0011] Furthermore, the U-shaped water-sealing section utilizes the gravity of the collected acidic condensate to form a liquid seal, preventing the main flue gas from condensing and exchanging heat inside the anti-corrosion layer from leaking outward, thus achieving safe and environmentally friendly discharge of the condensate.

[0012] Compared with the prior art, the bypass air gap anti-corrosion structure for condensing waste heat recovery flue gas ducts provided by the present invention has the following beneficial effects:

[0013] 1) This invention utilizes the system's own high-temperature flue gas, introducing a small portion of the uncooled high-temperature flue gas as a protective gas through an adjustable throttling component via a bypass upstream of the condensing heat exchanger, forming a thermal isolation layer between the flue inner wall and the anti-corrosion layer. This not only ensures that the flue metal wall temperature remains above the flue gas acid dew point, preventing condensation corrosion of the metal shell, but also allows for flexible adjustment of the bypass flow rate according to the unit load, ensuring that the overall plant thermal economy is not significantly affected.

[0014] 2) The anti-corrosion layer inside the flue physically isolates the cooled and condensed main flue gas, serving as the primary condensation surface. Because the anti-corrosion layer is made of organic anti-corrosion material that can withstand temperatures not lower than 150℃, it can resist the erosion of acidic condensate. Attached Figure Description

[0015] Figure 1 This is a cross-sectional schematic diagram of the bypass air gap anti-corrosion structure for a condensing waste heat recovery flue provided by the present invention.

[0016] Figure 2 yes Figure 1 A schematic diagram of the cross-section along the AA direction.

[0017] In the diagram, 1 is the flue; 2 is the condensing heat exchanger; 3 is the anti-corrosion layer; 4 is the support component; 5 is the bypass channel; 6 is the throttling component; and 7 is the drainage component. Detailed Implementation

[0018] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below with reference to specific illustrations.

[0019] In the description of this invention, it should be understood that the terms "longitudinal," "radial," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientation or positional relationships, are based on the orientation or positional relationships shown in the accompanying drawings and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0020] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0021] Please refer to Figure 1 and Figure 2As shown, this invention provides a bypass air gap anti-corrosion structure for a condensing waste heat recovery flue, mainly applied to the tail flue of a power plant boiler or the tail of a gas turbine waste heat boiler. The flue 1 contains a condensing heat exchanger 2 for recovering waste heat from the flue gas. The anti-corrosion structure includes an anti-corrosion layer 3 fitted inside the flue downstream of the condensing heat exchanger 2. The anti-corrosion layer 3 is fixedly connected to the metal inner wall of the flue 1 via a support member 4. The anti-corrosion layer 3 is suitable for physically isolating the main flue gas that undergoes condensation heat exchange after being cooled by the condensing heat exchanger 2. The support member 4 is suitable for maintaining the gap width of the bypass channel 5. A bypass channel 5 is formed between the anti-corrosion layer 3 and the metal inner wall of the flue 1. The inlet end of the bypass channel 5 is connected to the high-temperature flue gas upstream of the condensing heat exchanger 2, allowing some of the uncooled high-temperature flue gas to fill the bypass channel 5 as protective gas. A throttling component 6 is provided at the junction of the air inlet edge of the condensing heat exchanger 2 and the inlet of the bypass channel 5. The throttling component 6 is used to control the flow rate of the high-temperature protective gas entering the bypass channel 5, so as to maintain the metal wall temperature of the flue 1 above the acid dew point of the flue gas. The bottom of the anti-corrosion layer 3 is connected to a hydrophobic component 7. The hydrophobic component 7 extends to the outside through the bypass channel 5 and the side wall of the flue 1, and the outside is provided with a U-shaped water seal section for the safe discharge of acidic condensate generated inside the anti-corrosion layer 3.

[0022] For a specific embodiment, please refer to Figure 2 As shown, the anti-corrosion layer 3 has a cylindrical structure and is made of organic anti-corrosion materials such as polytetrafluoroethylene that can withstand temperatures of not less than 150°C. This ensures that the anti-corrosion layer has strong chemical stability and low surface tension, which not only resists the corrosion of high-concentration acidic condensate for a long time without aging, but also effectively prevents fly ash in flue gas from adhering and scaling on the surface.

[0023] As a specific embodiment, the width of the bypass channel 5 is 5-10mm, which can form a stable and uniform high-temperature protective gas film between the metal inner wall of the flue and the anti-corrosion layer. This can ensure that the temperature of the metal wall surface is consistently higher than the acid dew point of the flue gas, and limit the total bypass flow of the uncooled high-temperature flue gas, thus avoiding excessive heat loss.

[0024] As a specific embodiment, the throttling component 6 is a rotary damper with adjustable opening. The operator or control system can dynamically adjust the opening of the rotary damper according to the real-time flue gas temperature, thereby adjusting the flow rate of the high-temperature protective gas filling the bypass channel 5, so as to maintain the metal wall temperature of the flue 1 above the acid dew point of the flue gas.

[0025] For a specific embodiment, please refer to Figure 2 As shown, the U-shaped water sealing section uses the gravity of the collected acidic condensate to form a liquid seal, preventing the main flue gas from condensing and exchanging heat inside the anti-corrosion layer 3 from leaking out, thus achieving safe and environmentally friendly discharge of the condensate.

[0026] To better understand the bypass air gap corrosion protection structure for condensing waste heat recovery flue provided by this invention, its working principle is explained below.

[0027] When the system is running normally, the original high-temperature flue gas with a temperature of about 90-120℃ enters the system from the front end of flue 1. When it flows through the condenser heat exchanger 2, the flue gas flow is divided into two parts: the main flue gas flow and the bypass protection gas flow.

[0028] Most of the main flue gas passes through the condensing heat exchanger 2 for condensation and heat exchange. After heat exchange and cooling, the temperature of the main flue gas drops to approximately 40-50℃, which is below the acid dew point of the flue gas. This portion of the low-temperature, high-humidity main flue gas enters the internal core channel wrapped by the anti-corrosion layer 3. The anti-corrosion layer 3 is made of organic anti-corrosion material that can withstand temperatures of not less than 150℃, thus effectively resisting the corrosion of acidic substances generated by the condensation of the main flue gas during cooling.

[0029] A small portion of the high-temperature flue gas that does not pass through the condenser heat exchanger 2 is guided and its flow controlled by the throttling component 6, entering the 5-10mm wide bypass channel 5 maintained by the support member 4. This throttling component 6 can be a rotary damper, whose opening can be dynamically adjusted by the operator or control system based on the real-time exhaust gas temperature. This portion of high-temperature protective gas flows in the bypass channel 5, continuously heating the inner metal wall of the flue 1, ensuring that the metal wall temperature is higher than the flue gas acid dew point, thus eliminating the conditions for condensation to form on the metal wall and preventing corrosion of the outer shell of the flue 1.

[0030] The acidic condensate that is released from the main flue gas as it cools inside the anti-corrosion layer 3 is collected at the bottom of the anti-corrosion layer 3 under the action of gravity. It then flows into the U-shaped water seal section outside the hydrophobic component 7 through the inlet of the hydrophobic component 7 and accumulates there. The static pressure head of the liquid column forms a liquid seal to prevent the main flue gas that has been condensed and heat exchanged inside the anti-corrosion layer 3 from leaking outward, thus achieving safe and environmentally friendly discharge of the condensate.

[0031] Compared with the prior art, the bypass air gap anti-corrosion structure for condensing waste heat recovery flue gas ducts provided by the present invention has the following beneficial effects:

[0032] 1) This invention utilizes the system's own high-temperature flue gas, introducing a small portion of the uncooled high-temperature flue gas as a protective gas through an adjustable throttling component via a bypass upstream of the condensing heat exchanger, forming a thermal isolation layer between the flue inner wall and the anti-corrosion layer. This not only ensures that the flue metal wall temperature remains above the flue gas acid dew point, preventing condensation corrosion of the metal shell, but also allows for flexible adjustment of the bypass flow rate according to the unit load, ensuring that the overall plant thermal economy is not significantly affected.

[0033] 2) The anti-corrosion layer inside the flue physically isolates the cooled and condensed main flue gas, serving as the primary condensation surface. Because the anti-corrosion layer is made of organic anti-corrosion material that can withstand temperatures not lower than 150℃, it can resist the erosion of acidic condensate.

[0034] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A bypass air gap anti-corrosion structure for a condensing waste heat recovery flue, wherein a condensing heat exchanger for recovering waste heat from flue gas is installed inside the flue, characterized in that, The anti-corrosion structure includes an anti-corrosion layer fitted inside the downstream flue of the condensing heat exchanger. The anti-corrosion layer is fixedly connected to the metal inner wall of the flue via a support member. The anti-corrosion layer is suitable for physically isolating the main flue gas that undergoes condensation heat exchange after being cooled by the condensing heat exchanger. A bypass channel is formed between the anti-corrosion layer and the metal inner wall of the flue. The inlet end of the bypass channel is connected to the high-temperature flue gas upstream of the condensing heat exchanger, allowing some of the uncooled high-temperature flue gas to fill the bypass channel as protective gas. A throttling component is provided at the junction of the air inlet edge of the condensing heat exchanger and the inlet of the bypass channel. The throttling component is used to control the flow rate of the high-temperature protective gas entering the bypass channel to maintain the metal wall temperature of the flue above the acid dew point of the flue gas. A hydrophobic component is connected to the bottom of the inner part of the anti-corrosion layer. The hydrophobic component extends to the outside through the bypass channel and the side wall of the flue, and a U-shaped water-sealing section is provided on the outside for the safe discharge of acidic condensate generated inside the anti-corrosion layer.

2. The bypass air gap anti-corrosion structure for a condensing waste heat recovery flue gas duct according to claim 1, characterized in that, The anti-corrosion layer has a cylindrical structure and is made of organic anti-corrosion material that can withstand temperatures of not less than 150°C.

3. The bypass air gap anti-corrosion structure for a condensing waste heat recovery flue gas duct according to claim 1, characterized in that, The width of the bypass channel is 5-10mm.

4. The bypass air gap anti-corrosion structure for a condensing waste heat recovery flue according to claim 1, characterized in that, The throttling component is a rotating baffle door with adjustable opening.

5. The bypass air gap anti-corrosion structure for a condensing waste heat recovery flue according to claim 1, characterized in that, The U-shaped water-sealing section utilizes the gravity of the collected acidic condensate to form a liquid seal, preventing the main flue gas from condensing and exchanging heat inside the anti-corrosion layer from leaking outward, thus achieving safe and environmentally friendly discharge of the condensate.

Images