Plate-type air pre-heater system

Abstract

The utility model discloses a plate-type air pre-heater system, which belongs to the technical field of air pre-heaters, solves the problem that the service life and the safety are influenced by dry burning of an air duct, and adopts the technical scheme that the plate-type air pre-heater system mainly comprises an economizer, a high-temperature air pre-heater, a low-temperature air pre-heater, a main flue and the air duct. The main flue is provided with a high-temperature bypass flue, the front end of the high-temperature bypass flue is communicated with the main flue at the head end of the economizer, a plurality of bypass flue partition plates are arranged in the tail end of the high-temperature bypass flue, and the high-temperature bypass flue is divided into a plurality of sub-bypass flues by the bypass flue partition plates; a main flue partition plate is arranged in the side, close to the low-temperature air pre-heater, of the main flue to divide the main flue into a plurality of sub-flues, the sub-bypass flues correspond to the sub-flues one by one, the corresponding sub-bypass flues and the sub-flues are always in the state that one is opened and the other is closed, and the sub-bypass flues are opened or closed one by one. The utility model mainly improves the service life and safety of the air duct.

Description

Technical Field

[0001] The utility model relates to the technical field of air preheaters, in particular to a plate - type air preheater system. Background Art

[0002] As the country has increasingly strict control over the emission standards of air pollutants from coal - fired boilers, waste boilers or biomass boilers, when boilers use fuels with relatively high sulfur and nitrogen content, it is necessary to carry out denitrification treatment on the flue gas generated by fuel combustion in the boilers. The commonly used denitrification devices are SCR, SNCR or combined denitrification, and the denitrifying agent is generally ammonia water or urea solution.

[0003] After the boiler operates for a period of time, ash plugging occurs to varying degrees at the air preheater. The reason for ash plugging is usually that unreacted ammonia water or urea solution reacts with sulfur trioxide in the flue gas to form ammonium bisulfate; the melting point of ammonium bisulfate is 147 °C, that is, when the flue gas temperature is lower than 147 °C, ammonium bisulfate will crystallize, and during the crystallization process of ammonium bisulfate, it will also adhere to fly ash, resulting in blockage. After ash plugging, it will cause consequences such as a decrease in boiler efficiency, an increase in the long - term power consumption of the fan, corrosion in the air preheating area, an increase in boiler resistance, and a decrease in boiler output.

[0004] The prior art CN111102596A discloses a system for preventing ammonium bisulfate ash plugging in a boiler air preheater, which includes a plurality of isolation plates are arranged in each of two primary air preheaters and two secondary air preheaters. The plurality of isolation plates divide the heat exchange cavity into a plurality of sub - heat exchange cavities arranged side by side. The number of the first air pipes is the same as the number of the sub - heat exchange cavities in the primary air preheater, and the number of the second air pipes is the same as the number of the sub - heat exchange cavities in the secondary air preheater. Isolation components for blocking gas flow are arranged in both the first air pipe and the second air pipe, and the isolation components are electrically connected to a control system, solving the problem of ammonium bisulfate ash plugging in the existing boiler air preheater and the problem of cumbersome maintenance operations.

[0005] In the prior art, by closing the air duct, there is no air flow in the first air pipe and the second air pipe, and correspondingly, there is no air flow in the air duct, so that the flue gas in the sub - heat exchange cavity where the air duct is located cannot be cooled, and thus the temperature rises. The deposited ammonium bisulfate crystals sublimate and are discharged with the flue gas flow. At this time, the inner wall of the air duct is in a dry - burning state. The air duct repeatedly in a dry - burning state will have cracks, which will affect the service life and safety of the air duct. Summary of the Utility Model

[0006] The purpose to be achieved by the utility model is to provide a plate - type air preheater system, which solves the problem that the service life and safety are affected by the dry - burning of the air duct, and improves the service life and safety of the air duct.

[0007] To achieve the above object, the utility model adopts the following technical solution: A plate-type air preheater system includes an economizer, a high-temperature air preheater communicated with the tail end of the economizer, a main flue sequentially communicating the high-temperature air preheater and the low-temperature air preheater, and an air duct through which cold air passes. The air in the air duct flows through the low-temperature air preheater and the high-temperature air preheater in sequence. The main flue is provided with a high-temperature bypass flue. The front end of the high-temperature bypass flue is communicated with the main flue at the head end of the economizer. A plurality of bypass flue partitions are arranged in the tail end of the high-temperature bypass flue. The plurality of bypass flue partitions divide the high-temperature bypass flue into a plurality of sub-bypass flues. A main flue partition is arranged inside the main flue on one side close to the head end of the low-temperature air preheater to divide the main flue into a plurality of sub-flues. The sub-bypass flues correspond to the sub-flues one by one, and the corresponding sub-bypass flue and sub-flue are always in a state where one is open and the other is closed. The plurality of sub-bypass flues are opened or closed one by one.

[0008] After adopting the above technical solution, the utility model has the following advantages: When the flue gas passes through the low-temperature air preheater and the ammonium bisulfate solidifies and blocks the low-temperature air preheater due to the low temperature in the low-temperature air preheater, the sub-bypass flue at the tail end of the high-temperature bypass flue is opened, and the sub-flue corresponding to the opened sub-bypass flue is closed, so that the high-temperature flue gas enters the low-temperature air preheater from the opened sub-bypass flue, causing the crystallized ammonium bisulfate to sublime and be discharged from the low-temperature air preheater with the flue gas. When other sub-bypass flues are opened one by one, the corresponding sub-flues are closed, and the solid ammonium bisulfate is sublimated one by one, thereby avoiding the solidification of ammonium bisulfate at a low temperature and attaching to the inside of the low-temperature air preheater, resulting in the blockage of the low-temperature air preheater; The plurality of bypass flue partitions divide the high-temperature bypass flue into a plurality of sub-bypass flues, and the plurality of sub-bypass flues are opened one by one, avoiding the simultaneous opening of the sub-bypass flues, which may cause all the sub-flues to be closed, resulting in the shutdown of the low-temperature air preheater and affecting the stable operation of the low-temperature air preheater; The plurality of main flue partitions divide the main flue into a plurality of sub-flues. After the sub-flues correspond to the sub-bypass flues one by one, the low-temperature air preheater is divided into a plurality of regions. The sub-bypass flues are opened one by one to clean the ammonium bisulfate deposited in a single region, and the remaining regions operate normally to preheat the cold air, avoiding the complete blockage of the low-temperature air preheater and the need for shutdown cleaning, ensuring the long-term stable operation of the low-temperature air preheater. The temperature of the flue gas discharged after the high-temperature flue gas introduced into a single sub-bypass flue is mixed with the low-temperature flue gas in the remaining sub-flues is within the allowable temperature range, with high safety.

[0009] Further, each of the plurality of sub-bypass flues is respectively provided with a first electric switch valve, and each of the plurality of sub-flues is respectively provided with a second electric switch valve. The first electric switch valve in the corresponding sub-bypass flue and sub-flue is opened and the second electric switch valve is closed, or the second electric switch valve is opened and the first electric switch valve is closed.

[0010] With the foregoing technical solution, the sub-bypass flue is controlled to open and close by the first electric switch valve, which facilitates the opening or closing of the sub-bypass flue. Moreover, each sub-bypass flue is controlled to open and close by a separate first electric switch valve, and each sub-flue is also controlled to open and close by a separate second electric switch valve, reducing the difficulty of opening and closing the sub-bypass flue and the sub-flue.

[0011] Furthermore, it further includes a control system. A plurality of first electric switch valves and a plurality of second electric switch valves are all electrically connected to the control system, and the control system controls the opening and closing of the first electric switch valves and the second electric switch valves.

[0012] With the foregoing technical solution, the opening and closing of the first electric switch valve and the second electric switch valve are controlled by the control system, reducing the difficulty of opening and closing the first electric switch valve and the second electric switch valve. Moreover, by controlling the opening and closing sequence of the first electric switch valve and the second electric switch valve through the control system, the disorder of the opening and closing sequence of the first electric switch valve and the second electric switch valve is avoided.

[0013] Furthermore, a first differential pressure transmitter is provided at the tail end of the high-temperature air preheater, and a second differential pressure transmitter is provided at the tail end of the low-temperature air preheater. The first differential pressure transmitter and the second differential pressure transmitter are electrically connected to the control system. The control system is provided with a preset value of the pressure difference between the high-temperature air preheater and the low-temperature air preheater. When the pressure difference between the first differential pressure transmitter and the second differential pressure transmitter is higher than the preset value, the control system controls the first electric switch valves to open one by one and the second electric switch valves to close one by one.

[0014] With the foregoing technical solution, the first differential pressure transmitter detects the flue gas pressure at the tail end of the high-temperature air preheater, and the second differential pressure transmitter detects the flue gas pressure at the tail end of the low-temperature air preheater. When the low-temperature air preheater is blocked, resulting in less flue gas discharged from the low-temperature air preheater, so that the pressure at the tail end of the low-temperature air preheater decreases. When the pressure difference between the first differential pressure transmitter and the second differential pressure transmitter is higher than the preset value set in the control system, the control system controls the first electric switch valves to open one by one, and the second electric switch valves close one by one as the first electric switch valves open. The pressure detection of the first differential pressure transmitter and the second differential pressure transmitter is electrically connected to the control system, and the control system opens and closes the first electric switch valves and the second electric switch valves through the detected pressure difference, avoiding the complete blockage of the low-temperature air preheater.

[0015] Furthermore, the low-temperature air preheater includes a plurality of plate heat exchange fins. A gap for the flue gas to flow through is formed between two adjacent plate heat exchange fins. The plate heat exchange fin has a low-temperature chamber for the cold air to pass through, and the low-temperature chamber is communicated with the air duct.

[0016] With the foregoing technical solution, the air duct located in the low-temperature air preheater is arranged as a plate heat exchange fin, expanding the flow area of the cold air in the low-temperature chamber, increasing the contact area when the flue gas exchanges heat with the cold air, and improving the heat exchange efficiency between the flue gas and the cold air.

[0017] Further, both outer sides of the plate heat exchanger fins protrude outward to increase the contact area between the outer sides of the plate heat exchanger fins and the flue gas.

[0018] With the foregoing technical solution, both outer sides of the plate heat exchanger fins protrude outward, thereby increasing the area of the outer sides of the plate heat exchanger fins, expanding the contact range between the flue gas and the outer sides of the plate heat exchanger fins, and improving the heat exchange efficiency between the flue gas and the cold air.

[0019] Further, the outer sides of the plate heat exchanger fins are corrugated.

[0020] With the foregoing technical solution, after the outer sides of the plate heat exchanger fins protrude outward, they are corrugated, making the outer sides of the plate heat exchanger fins smooth curved surfaces, and avoiding the accumulation of a large amount of ammonium bisulfate due to the presence of edges and corners on the outer side walls of the plate heat exchanger fins.

[0021] Further, the plate heat exchanger fins are stably arranged in the low-temperature air preheater through stabilizing members.

[0022] With the foregoing technical solution, the plate heat exchanger fins are stably installed in the low-temperature air preheater through stabilizing members, preventing the high-temperature flue gas in the bypass flue from entering the low-temperature air preheater, and thus avoiding the possibility of deformation of the plate heat exchanger fins under differential pressure.

[0023] Further, a plurality of air inlet partition plates are provided at the air inlet end of the air duct. The air inlet partition plates divide the air duct into a plurality of sub-air ducts, and a wind-side electric switch valve is provided in each sub-air duct.

[0024] With the foregoing technical solution, under normal operating conditions, each sub-air duct is opened, so that cold air enters each sub-air duct. When there are special operating requirements, the number of opened sub-air ducts can be determined according to actual needs to control the amount of cold air entering. When the amount of air is relatively small and the temperature of the flue gas is constant, the temperature of the preheated air is relatively high. A wind-side electric switch valve is provided in the sub-air duct, and the opening of the sub-air duct is controlled by the wind-side electric switch valve, which is convenient for controlling the opening and closing of the sub-air duct.

[0025] Further, the plurality of air inlet partition plates correspond to a plurality of main flue partition plates one by one, so that the sub-air ducts correspond to the sub-flue ducts one by one.

[0026] With the foregoing technical solution, the sub-air ducts correspond to the sub-flue ducts one by one, so that the heat exchange between the cold air and the flue gas in each sub-air duct can be carried out separately, and the preheating effect of the cold air is prevented from being affected by the cold air in the sub-air ducts contacting the flue gas in multiple sub-flue ducts at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The following further describes the present invention with reference to the accompanying drawings:

[0028] Figure 1Schematic diagram of a plate - type air pre - heater system of the present utility model;

[0029] Figure 2 Schematic diagram of the structure of the sub - bypass flue and the sub - flue of the present utility model;

[0030] Figure 3 Schematic diagram of the structure of the air inlet partition and the air inlet end of the air duct of the present utility model;

[0031] Figure 4 Of the present utility model Figure 3 Enlarged view at position A. Specific embodiments

[0032] To make the objectives, technical solutions, and advantages of the embodiments of the present utility model clearer, the technical solutions in the embodiments of the present utility model will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present utility model. Obviously, the described embodiments are only a part of the embodiments of the present utility model, rather than all of the embodiments.

[0033] The terms "first", "second", etc. (if any) in the description and claims of the present utility model are used to distinguish similar objects, rather than to describe a specific order or sequence. Even if "second" is used to distinguish a certain technical feature, it does not necessarily imply the existence of "first". It should be understood that in the present utility model, "including" and "having" and any of their variations are intended to cover non - exclusive inclusion. It should be understood that in the present utility model, "a plurality of" means two or more. "And / or" is merely a description of the association relationship of associated objects, indicating that three relationships can exist. For example, X and / or Y can represent: X exists alone, X and Y exist simultaneously, and Y exists alone. The character " / " generally represents an "or" relationship between the associated objects before and after. "Including X, Y, and Z", "including X, Y, Z" means that all of X, Y, and Z are included, "including X, Y, or Z" means that one of X, Y, and Z is included, and "including X, Y, and / or Z" means that any one or any two or all three of X, Y, and Z are included.

[0034] The technical solutions of the present utility model will be described in detail below with specific embodiments. These specific embodiments can be combined or replaced according to the actual situation. For the same or similar concepts or processes, they may not be repeated in some embodiments.

[0035] Such as Figure 1As shown in the figure, the utility model provides a plate type air preheater system, which includes an economizer 1, a high-temperature air preheater 2 connected to the tail end of the economizer 1, a low-temperature air preheater 3 connected to the tail end of the high-temperature air preheater 2, a main flue 4 connecting the high-temperature air preheater 2 and the low-temperature air preheater 3 in sequence, and an air duct 6 through which cold air passes. The air in the air duct 6 flows through the low-temperature air preheater 3 and the high-temperature air preheater 2 in sequence.

[0036] The temperature of the flue gas in the high-temperature air preheater 2 is usually between 300 - 450 °C. It exchanges heat with the air in the air duct 6 in the high-temperature air preheater 2, and then enters the low-temperature air preheater 3 through the main flue 4. After the flue gas reaches the low-temperature air preheater 3, the temperature of the flue gas is usually between 140 - 230 °C. The melting point of ammonium bisulfate is relatively low. After the flue gas reaches the low-temperature air preheater 3 and exchanges heat with the cold air in the air duct 6, the temperature is relatively low, resulting in ammonium bisulfate being prone to condense and adhere to the outer wall of the air duct 6 and the inner wall of the low-temperature air preheater 3.

[0037] In this embodiment, as Figure 1 and Figure 2 shown, multiple main flue partitions 41 are provided inside one end of the main flue 4 close to the low-temperature air preheater 3. The multiple main flue partitions 41 divide the main flue 4 into multiple sub-flues 42. The main flue 4 is provided with a high-temperature bypass flue 5. The front end of the high-temperature bypass flue 5 is connected to the main flue 4 at the head end of the economizer 1. Multiple bypass flue partitions 51 are provided inside the other end of the high-temperature bypass flue 5. The multiple bypass flue partitions 51 divide the tail end of the high-temperature bypass flue 5 into multiple sub-bypass flues 52. The multiple sub-bypass flues 52 correspond to the sub-flues 42 one by one, and the corresponding sub-bypass flue 52 and sub-flue 42 are not opened simultaneously, that is, when the sub-bypass flue 52 is opened, the corresponding sub-flue 42 is closed; when the sub-flue 42 is opened, the corresponding sub-bypass flue 52 is in a closed state.

[0038] In this embodiment, as Figure 1 and Figure 2 shown, the plate type air preheater system further includes a control system. The control system is provided with a preset value of the pressure difference between the high-temperature air preheater 2 and the low-temperature air preheater 3. A first differential pressure transmitter 71 is provided at the tail end of the low-temperature air preheater 3, and a second differential pressure transmitter 72 is provided at the tail end of the high-temperature air preheater 2. Both the first differential pressure transmitter 71 and the second differential pressure transmitter 72 are electrically connected to the control system. When the pressure difference between the first differential pressure transmitter 71 and the second differential pressure transmitter 72 is greater than the preset value, at this time, the low-temperature air preheater 3 is blocked by solid ammonium bisulfate, resulting in a decrease in the pressure value at the tail end of the low-temperature air preheater 3; the control system controls the sub-bypass flues 52 to be opened in sequence, so that high-temperature flue gas enters the low-temperature air preheater 3, and the ammonium bisulfate adhering to the inner wall of the low-temperature air preheater 3 is discharged from the lower port of the low-temperature air preheater 3 along with the flue gas under the action of the high-temperature flue gas.

[0039] Specifically, as Figure 2As shown in the figure, each of the multiple sub-bypass flues 52 is respectively provided with a first electric switch valve 53, and each of the multiple sub-flues 42 is respectively provided with a second electric switch valve 43. The multiple first electric switch valves 53 and the multiple second electric switch valves 43 are all electrically connected to the control system. When the pressure difference between the first differential pressure transmitter 71 and the second differential pressure transmitter 72 is greater than the preset value, the control system controls the multiple first electric switch valves 53 to be opened one by one, and at the same time controls the multiple second electric switch valves 43 to be closed one by one, so that the first electric switch valve 53 and the second electric switch valve 43 in the corresponding sub-bypass flue 52 and sub-flue 42 are in a state of one open and one closed. After the first electric switch valve 53 is opened, the high-temperature flue gas enters the regenerative air preheater 3 from the sub-bypass flue 52, so that the ammonium bisulfate adhering to the inner wall of the low-temperature regenerative air preheater 3 corresponding to the opened sub-bypass flue 52 becomes liquid at high temperature, and then flows to the tail end of the low-temperature regenerative air preheater 3 with the flue gas and is discharged from the low-temperature regenerative air preheater 3, avoiding the possibility of being blocked due to the solid phase of ammonium bisulfate in the low-temperature regenerative air preheater 3. The multiple first electric switch valves 53 are opened in sequence. On the one hand, the high-temperature flue gas entering the low-temperature regenerative air preheater 3 is less, and a small amount of high-temperature flue gas is discharged from the low-temperature regenerative air preheater 3 together with the remaining low-temperature flue gas, so that the temperature of the discharged flue gas is within the allowable temperature range, and the safety is high; on the other hand, during the process of the high-temperature flue gas passing through the sub-bypass flue 52, the other sub-bypass flues 52 are open, and the sub-flue 42 continuously supplies flue gas to the low-temperature regenerative air preheater 3, so that the low-temperature regenerative air preheater 3 is still in operation, and thus there is no need to stop the machine to remove the solid-phase ammonium bisulfate.

[0040] In another embodiment, as Figure 1 and Figure 3 shown, the low-temperature regenerative air preheater 3 includes a plurality of plate heat exchange fins 64. A gap for the flue gas to flow through is formed between two adjacent plate heat exchange fins 64. The inside of the plate heat exchange fin 64 has a low-temperature chamber 641 for the cold air to pass through and exchange heat with the flue gas in the low-temperature regenerative air preheater 3. The low-temperature chamber 641 is communicated with the air duct 6. The cold air entering from the air inlet of the air duct 6 enters the low-temperature chamber 641 of the plate heat exchange fin 64. After the flue gas enters the low-temperature regenerative air preheater 3, it contacts the outer wall of the plate heat exchange fin 64 in the gap between two adjacent plate heat exchange fins 64, and then exchanges heat with the cold air in the low-temperature chamber 641.

[0041] In this embodiment, in order to improve the heat exchange effect, the two outer side surfaces of the plate heat exchange fin 64 protrude toward the outside of the low-temperature chamber 641, thereby increasing the contact area between the outer side surface of the plate heat exchange fin 64 and the flue gas. After the contact area is increased, the heat exchange efficiency between the flue gas and the air in the low-temperature chamber 641 is improved.

[0042] To avoid the outer side surface of the plate heat exchange fin 64 having inward depressions to form sharp corners, making it difficult to remove the solid-phase ammonium bisulfate, as Figure 4As shown in the figure, the outer side of the plate heat exchanger fin 64 protrudes outward, making the outer side surface of the plate heat exchanger fin 64 corrugated and the outer side wall of the plate heat exchanger fin 64 a smooth curved surface, avoiding the sharp corners on the outer side surface of the plate heat exchanger fin 64 that are recessed into the low-temperature chamber 641, so that it is difficult to remove the ammonium bisulfate accumulated at the tips of the sharp corners.

[0043] To improve the stability of the plate heat exchanger fin 64, as Figure 3 shown in the figure, the plate heat exchanger fin 64 is stably arranged in the low-temperature air preheater 3 through the stabilizer 31. In this embodiment, the stabilizer 31 can be a screw; the plate heat exchanger fin 64 is stabilized through the stabilizer 31 to avoid the possibility of the plate heat exchanger fin 64 being bent after the high-temperature flue gas passes through. In the above situation, due to the different pressures of the high-temperature flue gas and the lower-temperature flue gas, when the high-temperature flue gas is introduced to remove the ammonium bisulfate, the pressure on the side where the high-temperature flue gas is not introduced is different from that on the side where the high-temperature flue gas passes through, resulting in different forces on both sides of the plate heat exchanger fin 64. After the plate heat exchanger fin 64 is stably installed through the stabilizer 31, the plate heat exchanger fin 64 is prevented from being bent due to different forces on both sides.

[0044] In another embodiment, as Figure 3 shown in the figure, a plurality of inlet partition plates 61 are provided at the inlet end of the air duct 6. The inlet partition plates 61 divide the inlet end of the air duct 6 into a plurality of sub-air ducts 62. The inlet partition plates 61 correspond to the main flue partition plates 41, so that the plurality of sub-air ducts 62 correspond to the plurality of sub-flues 42 one by one. A wind-side electric switch valve 63 is provided in each sub-air duct 62. In the use state, all the wind-side electric switch valves 63 are opened, or the corresponding wind-side electric switch valves 63 can also be opened or some wind-side electric switch valves 63 can be closed according to special use requirements, so that the air intake volume of the air duct 6 can be adjusted according to actual needs. The sub-flues 42 correspond to the sub-air ducts 62 one by one. When the high-temperature flue gas in the sub-bypass flue 52 enters the low-temperature air preheater 3, it contacts the cold air in the corresponding sub-air duct 62, avoiding some cold air contacting the flue gas on both sides, while some flue gas contacts a smaller part of the flue gas, thereby affecting the cold air preheating effect.

[0045] In addition to the above preferred embodiments, the present utility model has other implementation manners. Based on the embodiments in the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection requested by the present utility model.

Claims

1. A plate type air preheater system, comprising an economizer, a high-temperature air preheater connected to the tail end of the economizer, a low-temperature air preheater connected to the tail end of the high-temperature air preheater, a main flue sequentially connecting the high-temperature air preheater and the low-temperature air preheater, and an air duct through which cold air passes. The air in the air duct flows through the low-temperature air preheater and the high-temperature air preheater in sequence, and is characterized in that The main flue is provided with a high-temperature bypass flue. The front end of the high-temperature bypass flue is communicated with the main flue at the first end of the economizer. The tail end of the high-temperature bypass flue is provided with a plurality of bypass flue partition plates, and the plurality of bypass flue partition plates divide the high-temperature bypass flue into a plurality of sub-bypass flues. A main flue partition plate is arranged inside one side of the main flue close to the first end of the low-temperature air preheater to divide the main flue into a plurality of sub-flues. The sub-bypass flues correspond to the sub-flues one by one, and the corresponding sub-bypass flue and sub-flue are always in a state where one is open and the other is closed, and the plurality of sub-bypass flues are opened or closed one by one.

2. The plate type air preheater system according to claim 1, characterized in that, A first electric switch valve is respectively arranged on each of the plurality of sub-bypass flues, and a second electric switch valve is respectively arranged on each of the plurality of sub-flues. The first electric switch valve in the corresponding sub-bypass flue and sub-flue is open and the second electric switch valve is closed, or the second electric switch valve is open and the first electric switch valve is closed.

3. The plate type air preheater system according to claim 2, wherein It further includes a control system. The plurality of first electric switch valves and the plurality of second electric switch valves are all electrically connected to the control system, and the control system controls the opening and closing of the first electric switch valves and the second electric switch valves.

4. The plate type air preheater system according to claim 3, characterized in that, A first differential pressure transmitter is arranged at the tail end of the high-temperature air preheater, and a second differential pressure transmitter is arranged at the tail end of the low-temperature air preheater. The first differential pressure transmitter and the second differential pressure transmitter are electrically connected to the control system. The control system is provided with a preset value of the pressure difference between the high-temperature air preheater and the low-temperature air preheater. When the pressure difference between the first differential pressure transmitter and the second differential pressure transmitter is higher than the preset value, the control system controls the first electric switch valves to be opened one by one and the second electric switch valves to be closed one by one.

5. The plate type air preheater system according to claim 1, wherein, The low-temperature air preheater includes a plurality of plate heat exchange fins. A gap for the flue gas to flow through is formed between two adjacent plate heat exchange fins. The plate heat exchange fin has a low-temperature chamber for the cold air to pass through, and the low-temperature chamber is communicated with the air duct.

6. The plate type air preheater system according to claim 5, characterized in that, Two outer side surfaces of the plate heat exchange fin protrude outwards to increase the contact area between the outer side surface of the plate heat exchange fin and the flue gas.

7. The plate-type air preheater system according to claim 6, characterized in that, The outer side surface of the plate heat exchange fin is corrugated.

8. The plate type air preheater system according to claim 5, characterized in that, The plate heat exchange fin is stably arranged in the low-temperature air preheater through a stabilizing member.

9. The plate type air preheater system according to claim 1, wherein, A plurality of inlet partition plates are arranged at the air inlet end of the air duct. The inlet partition plates divide the air duct into a plurality of sub-air ducts, and a wind-side electric switch valve is arranged in each sub-air duct.

10. The plate-type air preheater system according to claim 9, characterized in that, The plurality of inlet partition plates correspond to the plurality of main flue partition plates one by one, so that the sub-air ducts correspond to the sub-flues one by one.

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