Device and method for preventing corrosion of cold end layer heat exchange element of air preheater

Abstract

The invention provides a device and method for preventing corrosion of a cold end layer heat exchange element of an air preheater, and belongs to the technical field of corrosion prevention and treatment of air preheaters. According to the device for preventing corrosion of the cold end layer heat exchange element of the air preheater, one end of an inlet flue is connected with an outlet flue of a power station boiler, the other end of the inlet flue is connected with the first inlet end of the air preheater, and a temperature transmitting device is arranged at the first outlet end of the air preheater. The cold primary air duct and the hot primary air duct are connected with the second inlet end and the second outlet end of the air preheater respectively. And the cold secondary air duct and the hot secondary air duct are respectively connected with a third inlet end and a third outlet end of the air preheater. The first inlet end of the air preheater, the second inlet end of the air preheater and the third inlet end of the air preheater are provided with vortex generating devices. And a guide plate is arranged in the vortex generating device. The problems that an anti-corrosion device in the prior art is complex in structure and high in operation cost are solved.

Description

Technical Field

[0001] The invention belongs to the technical field of air preheater corrosion prevention and treatment, and in particular relates to a device and method for preventing corrosion of a heat exchange element at a cold end layer of an air preheater. Background Art

[0002] An air preheater is a heat exchange device that uses the heat from the flue gas at the tail end of the boiler to heat the air required for combustion. Rotary air preheaters are widely used in large-scale, high-parameter power station boilers due to their compact structure, small size and low metal consumption.

[0003] With the access of a large number of renewable energy sources to the power grid, the intermittent and volatile characteristics of renewable energy require existing thermal power units to participate in peak-shaving operation, which is the main flexible adjustment means of the power grid.

[0004] Under the new situation, the type of coal burned by boilers is unstable. Moreover, in the operation mode of deep and frequent peak load regulation, low flue gas temperature and large fluctuations are more likely to cause corrosion of the heat exchange elements of the boiler rotary air preheater, especially the cold end (i.e. the flue gas outlet and air inlet) which is most susceptible to corrosion due to the influence of temperature and combustion conditions.

[0005] Low-temperature corrosion mainly occurs at the cold end of the air preheater. Since the flue gas contains water vapor and sulfuric acid vapor, when the flue gas temperature drops below the acid dew point, the sulfuric acid vapor will condense on the metal surface, causing corrosion. In addition, the condensation of water vapor on the heated surface can also cause oxygen corrosion. At present, the flue gas denitrification facilities added to coal-fired power plants are mainly based on selective catalytic reduction (SCR) technology. After adopting the SCR denitrification process, part of the SO in the flue gas 2 Will be oxidized to SO by the denitrification catalyst 3 , increasing the SO in flue gas 3 The volume concentration of ammonium bisulfate (NH 4 HSO 4 ) and other by-products are generated in large quantities, and the flue gas acid dew point temperature is increased, resulting in increased low-temperature corrosion.

[0006] Low-temperature corrosion of the cold-end heat exchanger elements of the rotary air preheater will pose a great hazard to the safe operation of the unit. Some power stations in China have been unable to solve or alleviate this problem, resulting in load limits on the units or even forced shutdowns. Therefore, it is urgent to find a low-cost and highly adaptable method and device to prevent corrosion of the cold-end heat exchanger elements of the air preheater, so as to extend the life of the air preheater heat exchanger elements and improve the safe and reliable operation of the unit.

[0007] For example, the patent document with authorization announcement number CN211739154U discloses a double-circulation hot air anti-blocking and acid dew point corrosion system for a rotary air preheater. Although the corrosion system can avoid ammonium bisulfate blockage and cold end low-temperature sulfuric acid corrosion, it requires the establishment of independent wind bins on the primary air side and the secondary air side. When the boiler is modified on site, it is necessary not only to modify the rotary air preheater body, which is complex and difficult to construct, but also to increase the high-temperature booster fan for pressurization, which makes the system complex.

[0008] For example, the patent application document with application publication number CN109163351A discloses an air preheater combination structure that solves the problem of blockage and corrosion. The air preheater includes a high temperature section and a medium temperature section, but does not include a low temperature section. Therefore, it is necessary to modify the heat exchange elements of the existing air preheater, which is a large project with high costs. In addition, a heat medium water smoke cooler needs to be set in the flue gas system, and a heat medium water heater needs to be set between the primary and secondary fans and the rotary air preheater, which adds a hot water circulation system and increases the complexity of the system. Summary of the invention

[0009] The object of the present invention is to provide a device and method for preventing corrosion of heat exchange elements at the cold end layer of an air preheater, so as to solve the problems of complex structure and high operating cost of the anti-corrosion device in the prior art.

[0010] In order to achieve the above object, the present invention adopts the following technical solution: In a first aspect, the present invention provides a device for preventing corrosion of heat exchange elements at a cold end layer of an air preheater, comprising a power station boiler, an air preheater, a cold primary air duct, a hot primary air duct, a cold secondary air duct, a hot secondary air duct and an inlet flue; One end of the inlet flue is connected to the outlet flue of the power station boiler, and the other end of the inlet flue is connected to the first inlet end of the air preheater. The first outlet end of the air preheater is provided with a temperature transmitter for monitoring the exhaust gas temperature. The cold primary air duct and the hot primary air duct are respectively connected to the second inlet end and the second outlet end of the air preheater; The cold secondary air duct and the hot secondary air duct are respectively connected to the third inlet end and the third outlet end of the air preheater; The first inlet end of the air preheater, the second inlet end of the air preheater and the third inlet end of the air preheater are provided with vortex generating devices, and guide plates are provided inside the vortex generating devices.

[0011] A further improvement of the present invention is that the air preheater is a rotary air preheater.

[0012] A further improvement of the present invention is that the rotary air preheater is specifically a two-compartment rotary air preheater, a three-compartment rotary air preheater or a four-compartment rotary air preheater.

[0013] A further improvement of the present invention is that the vortex generating device is a double-wing symmetrical structure.

[0014] A further improvement of the present invention is that the guide plate is a variable-angle guide plate.

[0015] A further improvement of the present invention is that the first outlet end of the air preheater is also connected to a dust collector for purifying flue gas.

[0016] A further improvement of the present invention is that it also includes a hot air recirculation duct, which is connected to the inlet duct of the fan.

[0017] In a second aspect, the present invention provides a method for preventing corrosion of a heat exchange element at a cold end layer of an air preheater, using the device for preventing corrosion of a heat exchange element at a cold end layer of an air preheater introduced above, comprising the following steps: Adjust the angle of the guide plate in the vortex generating device so that the flue gas and air entering the air preheater through the inlet flue, the cold primary air duct and the cold secondary air duct form a vortex; The temperature transmitter is used to monitor the exhaust gas temperature at the first outlet of the air preheater in real time; The angle of the guide plate in the vortex generating device is adjusted according to the exhaust gas temperature monitored in real time by the first outlet end of the temperature transmitter.

[0018] A further improvement of the present invention is that the vortex generating device is a double-wing symmetrical structure.

[0019] Compared with the prior art, the present invention has the following beneficial effects: The present invention belongs to an improved invention. Compared with the existing device for preventing the corrosion of the heat exchange element at the cold end layer of the air preheater, the present invention designs a power station boiler, an air preheater, a cold primary air duct, a hot primary air duct, a cold secondary air duct, a hot secondary air duct and an inlet flue. The first inlet end of the air preheater, the second inlet end of the air preheater and the third inlet end of the air preheater are provided with a vortex generating device, and a guide plate is provided inside the vortex generating device. On the one hand, the present invention can enhance the disturbance of the airflow through the guide plate inside the vortex generating device and the guide plate in the vortex generating device, so that the flue gas and air entering the air preheater through the inlet flue, the cold primary air duct and the cold secondary air duct flow to the part of the air preheater that is easy to corrode the heat exchange element at the cold end, mix with the low-temperature flue gas and air of the heat exchange element at the cold end, increase the metal wall temperature of the heat exchange element at the cold end, and thus prevent the heat exchange element at the cold end layer of the air preheater from corroding. On the other hand, the anti-corrosion device of the present invention has a simple structure. It increases the metal wall temperature of the cold end heat exchange element by changing the fluid flow field. It does not require an additional high-temperature boost fan to increase the pressure, nor does it require the heat exchange element of the existing air preheater to be modified, thereby effectively solving the problems of complex structure and high operating cost of the anti-corrosion device in the prior art.

[0020] Furthermore, the present invention also discloses that the vortex generating device is a double-wing symmetrical structure. The double-wing symmetrical structure can not only generate vortices efficiently, but the airfoil itself is relatively light and thin, and occupies a small space, which is conducive to effective control of airflow under limited space conditions.

[0021] Furthermore, the present invention also discloses that the guide plate is a variable angle guide plate. It can be seen that the present invention can guide the flue gas and air entering the air preheater to flow more evenly to the cold end heat exchange element part which is prone to corrosion by adjusting the angle of the guide plate, thereby reducing the eddy current blind angle and eddy current intensity fluctuation, thereby improving the uniformity of the overall eddy current. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The schematic diagram of the structure of the device for preventing the corrosion of the heat exchange element of the cold end layer of the air preheater according to the present invention is that the rotary air preheater is a three-compartment type with three layers of heat exchange elements; Figure 2 Another structural schematic diagram of the device for preventing corrosion of the heat exchange element at the cold end layer of the air preheater according to the present invention, the rotary air preheater is a three-compartment type with two layers of heat exchange elements; Figure 3 Another structural schematic diagram of the device for preventing corrosion of the heat exchange element at the cold end layer of the air preheater according to the present invention, the rotary air preheater is a two-compartment type with three layers of heat exchange elements; Figure 4Another structural schematic diagram of the device for preventing corrosion of the heat exchange element at the cold end layer of the air preheater according to the present invention, the rotary air preheater is a four-compartment type with three layers of heat exchange elements; Figure 5 is a structural diagram of a vortex generating device; In the figure: 1. Power station boiler; 2. Air preheater; 21. Hot end heat exchange element; 22. Medium temperature section heat exchange element; 23. Cold end heat exchange element; 3. Vortex generating device; 31. Guide plate; 4. Cold primary air duct; 41. Cold air duct; 5. Hot primary air duct; 51. Hot air duct; 6. Primary fan; 7. Secondary fan; 71. Blower; 8. Warmer; 9. Cold secondary air duct; 10. Hot secondary air duct; 11. Inlet flue; 12 Hot air recirculation duct; 13. Temperature transmitter; 14. Dust collector; 15. Single wing structure. DETAILED DESCRIPTION

[0023] In order to further understand the content of the present invention, the present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the embodiments are only for explaining the present invention and are not intended to limit it.

[0024] The present invention proposes a device for preventing corrosion of heat exchange elements at the cold end layer of an air preheater, comprising a power station boiler, an air preheater, a cold primary air duct, a hot primary air duct, a cold secondary air duct, a hot secondary air duct and an inlet flue. A vortex generating device is provided at the first inlet end of the air preheater, the second inlet end of the air preheater and the third inlet end of the air preheater, and a guide plate is provided inside the vortex generating device. Compared with the prior art, the present invention effectively solves the problems of complex structure and high operating cost of the anti-corrosion device in the prior art.

[0025] Embodiment 1: This embodiment discloses a device for preventing corrosion of heat exchange elements at the cold end layer of an air preheater. The technical solution of this embodiment is specifically described as follows: The device for preventing corrosion of the heat exchange elements at the cold end layer of the air preheater in this embodiment includes a power station boiler 1, an air preheater 2 (the air preheater 2 includes a hot end heat exchange element 21, a medium temperature section heat exchange element 22 and a cold end heat exchange element 23), a cold primary air duct 4, a hot primary air duct 5, a cold secondary air duct 9, a hot secondary air duct 10 and an inlet flue 11.

[0026] One end of the inlet flue 11 is connected to the outlet flue of the power plant boiler 1, and the other end of the inlet flue 11 is connected to the first inlet end of the air preheater 2. The first outlet end of the air preheater 2 is provided with a temperature transmitter 13 for monitoring the exhaust gas temperature.

[0027] The cold primary air duct 4 and the hot primary air duct 5 are connected to the second inlet end and the second outlet end of the air preheater 2 respectively.

[0028] The cold secondary air duct 9 and the hot secondary air duct 10 are connected to the third inlet end and the third outlet end of the air preheater 2 respectively.

[0029] The first inlet end of the air preheater 2, the second inlet end of the air preheater 2 and the third inlet end of the air preheater 2 are provided with a vortex generating device 3, and a guide plate 31 is provided inside the vortex generating device 3. The guide plate 31 of this embodiment is a variable angle guide plate. In this embodiment, the flue gas and air entering the air preheater can be guided to flow more evenly to the cold end heat exchange element part that is easy to corrode by adjusting the angle of the guide plate, thereby reducing the vortex dead angle and the vortex intensity fluctuation, thereby improving the uniformity of the overall vortex.

[0030] The cold primary air duct 4, the hot primary air duct 5, the cold secondary air duct 9, the hot secondary air duct 10 and the inlet flue duct 11 are described in detail below: The flue gas entering the air preheater 2 through the inlet flue 11 passes through the disturbance guide of the guide plate 31 in the vortex generating device 3, and enters the hot end heat exchange element 21, the medium temperature section heat exchange element 22 and the cold end heat exchange element 23 (the cold end heat exchange element is also called the cold end layer heat exchange element) in sequence for heat exchange, and then is connected to the dust collector 14 after heat exchange.

[0031] The outlet cold air of the primary fan 6 enters the air preheater 2 through the cold primary air duct 4. The cold air passes through the disturbance guide of the guide plate 31 in the vortex generating device 3, and enters the cold end heat exchange element 23, the medium temperature section heat exchange element 22 and the hot end heat exchange element 21 in turn for heat exchange. After heat exchange, it is connected to the hot primary air duct 5 to meet the boiler combustion needs.

[0032] The cold air at the outlet of the secondary fan 7 enters the heater 8 and then enters the air preheater 2 through the cold secondary air duct 9. The cold air passes through the disturbance guide of the guide plate 31 in the vortex generating device 3, and enters the cold end heat exchange element 23, the medium temperature section heat exchange element 22 and the hot end heat exchange element 21 in turn for heat exchange. After heat exchange, it is connected to the hot secondary air duct 10 to meet the boiler combustion needs.

[0033] The air preheater 2 in this embodiment is a rotary air preheater. The air preheater 2 is described in detail below: The air preheater 2 is a heat exchanger that utilizes the heat of the flue gas at the tail end of the power plant boiler 1 to heat the air required for fuel combustion, so as to improve the thermal efficiency of the power plant boiler 1 .

[0034] The working principle of air preheater 2 is described as follows: Hot flue gas and cold air flow alternately through the heating surface. When the flue gas flows through, the heat of the flue gas is transferred to the metal heat exchange element of the heating surface and stored, the flue gas temperature drops, and the energy utilization of the flue gas is improved. When the air flows through later, the metal releases the stored heat to heat the air, increasing the temperature of the air entering the furnace for combustion, thereby meeting the combustion needs of the boiler.

[0035] According to the setting of primary and secondary air on the air side, the rotary air preheater can be divided into three-compartment rotary air preheater (such as Figure 1 and Figure 2 As shown), two-chamber rotary air preheater (as shown Figure 3 As shown, Figure 3 Intercooler air duct 41 is equivalent to Figure 1 , Figure 2 and Figure 4 Intercooler primary air duct 4; Figure 3 Medium hot air duct 51 is equivalent to Figure 1 , Figure 2 and Figure 4 Medium heat primary air duct 5) or four compartment rotary air preheater (such as Figure 4 as shown).

[0036] The three-compartment rotary air preheater is divided into a flue gas compartment, a primary air compartment and a secondary air compartment. The structural difference between the two-compartment rotary air preheater and the four-compartment rotary air preheater is mainly the number of compartments, and the other structural parts are basically the same. Modern large-capacity boilers generally use rotary air preheaters.

[0037] The vortex generating device 3 of this embodiment is a double-wing symmetrical structure. In this embodiment, the single-wing structure 15 is inverted upside down to obtain a double-wing symmetrical structure. The structure of the vortex generating device 3 is as follows: Figure 5 The double-wing symmetrical structure can not only generate vortices efficiently, but the airfoil itself is relatively light and thin, and occupies little space, which is conducive to effective control of airflow in limited space.

[0038] In the device for preventing corrosion of heat exchange elements at the cold end layer of an air preheater in this embodiment, the first outlet end of the air preheater 2 is also connected to a dust collector 14 for purifying flue gas.

[0039] The device for preventing corrosion of the heat exchange elements at the cold end layer of the air preheater in this embodiment further comprises a hot air recirculation duct 12, and the hot air recirculation duct 12 is connected to the inlet duct of the fan (the fan in this embodiment is the secondary fan 7 or the air supply fan 71).

[0040] The specific working principle of the device for preventing corrosion of the heat exchange element at the cold end layer of the air preheater in this embodiment is described as follows: When the power station boiler 1 is in operation, a vortex generating device 3 is provided at the first inlet end of the air preheater 2, the second inlet end of the air preheater 2 and the third inlet end of the air preheater 2. The disturbance of the airflow is enhanced by the guide plate 31 in the vortex generating device 3, so that the flue gas and air entering the air preheater 2 through the inlet flue 11, the cold primary air duct 4 and the cold secondary air duct 9 flow to the part of the air preheater that is easy to corrode the cold end heat exchange element 23, and mix with the low-temperature flue gas and air of the cold end heat exchange element 23, thereby increasing the metal wall temperature of the cold end heat exchange element 23, thereby preventing the corrosion of the heat exchange element of the cold end layer of the air preheater.

[0041] Embodiment 2: This embodiment discloses a method for preventing corrosion of a heat exchange element at a cold end layer of an air preheater, using the device for preventing corrosion of a heat exchange element at a cold end layer of an air preheater introduced above, comprising the following steps: Adjust the angle of the guide plate 31 in the vortex generating device 3 so that the flue gas and air entering the air preheater 2 through the inlet flue 11, the cold primary air duct 4 and the cold secondary air duct 9 form a vortex, thereby guiding the flue gas and air entering the air preheater 2 to flow to the part of the cold end heat exchange element that is easily corroded; The temperature transmitter 13 is used to monitor the exhaust gas temperature at the first outlet of the air preheater 2 in real time; According to the exhaust gas temperature monitored in real time by the first outlet end of the temperature transmitter 13 , the angle of the guide plate 31 in the vortex generating device 3 is adjusted.

[0042] The device for preventing corrosion of the heat exchange elements at the cold end layer of the air preheater in this embodiment includes a power station boiler 1, an air preheater 2 (the air preheater 2 includes a hot end heat exchange element 21, a medium temperature section heat exchange element 22 and a cold end heat exchange element 23), a cold primary air duct 4, a hot primary air duct 5, a cold secondary air duct 9, a hot secondary air duct 10 and an inlet flue 11.

[0043] One end of the inlet flue 11 is connected to the outlet flue of the power plant boiler 1, and the other end of the inlet flue 11 is connected to the first inlet end of the air preheater 2. The first outlet end of the air preheater 2 is provided with a temperature transmitter 13 for monitoring the exhaust gas temperature.

[0044] The cold primary air duct 4 and the hot primary air duct 5 are connected to the second inlet end and the second outlet end of the air preheater 2 respectively.

[0045] The cold secondary air duct 9 and the hot secondary air duct 10 are connected to the third inlet end and the third outlet end of the air preheater 2 respectively.

[0046] The first inlet end of the air preheater 2, the second inlet end of the air preheater 2 and the third inlet end of the air preheater 2 are provided with a vortex generating device 3, and a guide plate 31 is provided inside the vortex generating device 3. The guide plate 31 of this embodiment is a variable angle guide plate. In this embodiment, the flue gas and air entering the air preheater can be guided to flow more evenly to the cold end heat exchange element part that is easy to corrode by adjusting the angle of the guide plate, thereby reducing the vortex dead angle and the vortex intensity fluctuation, thereby improving the uniformity of the overall vortex.

[0047] The cold primary air duct 4, the hot primary air duct 5, the cold secondary air duct 9, the hot secondary air duct 10 and the inlet flue duct 11 are described in detail below: The flue gas entering the air preheater 2 through the inlet flue 11 passes through the disturbance guide of the guide plate 31 in the vortex generating device 3, and enters the hot end heat exchange element 21, the medium temperature section heat exchange element 22 and the cold end heat exchange element 23 (the cold end heat exchange element is also called the cold end layer heat exchange element) in sequence for heat exchange, and then is connected to the dust collector 14 after heat exchange.

[0048] The outlet cold air of the primary fan 6 enters the air preheater 2 through the cold primary air duct 4. The cold air passes through the disturbance guide of the guide plate 31 in the vortex generating device 3, and enters the cold end heat exchange element 23, the medium temperature section heat exchange element 22 and the hot end heat exchange element 21 in turn for heat exchange. After heat exchange, it is connected to the hot primary air duct 5 to meet the boiler combustion needs.

[0049] The cold air at the outlet of the secondary fan 7 enters the heater 8 and then enters the air preheater 2 through the cold secondary air duct 9. The cold air passes through the disturbance guide of the guide plate 31 in the vortex generating device 3, and enters the cold end heat exchange element 23, the medium temperature section heat exchange element 22 and the hot end heat exchange element 21 in turn for heat exchange. After heat exchange, it is connected to the hot secondary air duct 10 to meet the boiler combustion needs.

[0050] The air preheater 2 of this embodiment is a rotary air preheater. According to the setting of the primary and secondary air on the air side, the rotary air preheater can be divided into three compartment rotary air preheaters (such as Figure 1 and Figure 2 As shown), two-chamber rotary air preheater (as shown Figure 3 As shown, Figure 3 Intercooler air duct 41 is equivalent to Figure 1 , Figure 2 and Figure 4 Intercooler primary air duct 4; Figure 3 Medium hot air duct 51 is equivalent to Figure 1 , Figure 2 and Figure 4 Medium heat primary air duct 5) or four compartment rotary air preheater (such as Figure 4 as shown).

[0051] The three-compartment rotary air preheater is divided into a flue gas compartment, a primary air compartment and a secondary air compartment. The structural difference between the two-compartment rotary air preheater and the four-compartment rotary air preheater is mainly the number of compartments, and the other structural parts are basically the same. Modern large-capacity boilers generally use rotary air preheaters.

[0052] The vortex generating device 3 of this embodiment is a double-wing symmetrical structure. In this embodiment, the single-wing structure 15 is inverted upside down to obtain a double-wing symmetrical structure. The structure of the vortex generating device 3 is as follows: Figure 5 The double-wing symmetrical structure can not only generate vortices efficiently, but the airfoil itself is relatively light and thin, and occupies little space, which is conducive to effective control of airflow in limited space.

[0053] For other details of this embodiment, please refer to Embodiment 1.

[0054] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A device for preventing corrosion of heat exchange elements at the cold end layer of an air preheater, characterized in that: It comprises a power station boiler (1), an air preheater (2), a cold primary air duct (4), a hot primary air duct (5), a cold secondary air duct (9), a hot secondary air duct (10) and an inlet flue (11); One end of the inlet flue (11) is connected to the outlet flue of the power station boiler (1), and the other end of the inlet flue (11) is connected to the first inlet end of the air preheater (2). The first outlet end of the air preheater (2) is provided with a temperature transmitter (13) for monitoring the exhaust gas temperature; The cold primary air duct (4) and the hot primary air duct (5) are respectively connected to the second inlet end and the second outlet end of the air preheater (2); The cold secondary air duct (9) and the hot secondary air duct (10) are respectively connected to the third inlet end and the third outlet end of the air preheater (2); A vortex generating device (3) is provided at the first inlet end of the air preheater (2), the second inlet end of the air preheater (2), and the third inlet end of the air preheater (2), and a guide plate (31) is provided inside the vortex generating device (3).

2. The device for preventing corrosion of heat exchange elements at the cold end layer of an air preheater according to claim 1 is characterized in that: The air preheater (2) is a rotary air preheater.

3. The device for preventing corrosion of heat exchange elements at the cold end layer of an air preheater according to claim 2 is characterized in that: The rotary air preheater is specifically a two-compartment rotary air preheater, a three-compartment rotary air preheater or a four-compartment rotary air preheater.

4. The device for preventing corrosion of heat exchange elements at the cold end layer of an air preheater according to claim 1 is characterized in that: The vortex generating device (3) is a double-wing symmetrical structure.

5. The device for preventing corrosion of heat exchange elements at the cold end layer of an air preheater according to claim 1, characterized in that: The guide plate (31) is a variable-angle guide plate.

6. The device for preventing corrosion of heat exchange elements at the cold end layer of an air preheater according to claim 1, characterized in that: The first outlet end of the air preheater (2) is also connected to a dust collector (14) for purifying flue gas.

7. The device for preventing corrosion of heat exchange elements at the cold end layer of an air preheater according to claim 1 is characterized in that: It also comprises a hot air recirculation duct (12), wherein the hot air recirculation duct (12) is connected to an inlet duct of the fan.

8. A method for preventing corrosion of heat exchange elements at the cold end layer of an air preheater, characterized in that: The device for preventing corrosion of the heat exchange element at the cold end layer of the air preheater according to any one of claims 1 to 7 comprises the following steps: Adjusting the angle of the guide plate (31) in the vortex generating device (3) so that the flue gas and air entering the air preheater (2) through the inlet flue (11), the cold primary air duct (4) and the cold secondary air duct (9) form a vortex; Using a temperature transmitter (13) to monitor in real time the exhaust gas temperature at the first outlet end of the air preheater (2); The angle of the guide plate (31) in the vortex generating device (3) is adjusted according to the exhaust gas temperature monitored in real time by the first outlet end of the temperature transmitter (13).

9. The method for preventing corrosion of heat exchange elements at the cold end layer of an air preheater according to claim 8, characterized in that: The vortex generating device (3) is a double-wing symmetrical structure.

10. The method for preventing corrosion of heat exchange elements at the cold end layer of an air preheater according to claim 8, characterized in that: The guide plate (31) is a variable-angle guide plate.

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