Air preheater blockage cleaning system

Abstract

The utility model discloses a kind of air preheater unblocking systems, including rotary air preheater, inlet flue, outlet flue, primary fan and connected primary air inlet air duct, primary air outlet air duct, secondary fan and connected secondary air inlet air duct, secondary air outlet air duct;Its characterized in that: secondary air inlet air duct and secondary air outlet air duct are connected by secondary air bypass air duct, and damper adjusting baffle and pressure transmitter are equipped on secondary air bypass air duct;The utility model controls the metal wall temperature of air preheater by adjusting the secondary air volume entering air preheater, can completely solve the problem of ammonium bisulfate blockage, and greatly reduce the maintenance workload of unit and additional energy consumption, with the advantage of good economy.

Description

Technical Field

[0001] This utility model relates to an air preheater unblocking system, and more particularly to an air preheater unblocking system for boilers equipped with denitrification devices. Background Technology

[0002] For large coal-fired boilers, a rotary air preheater is usually installed after the denitrification device to heat the boiler's air supply, thereby reducing the boiler's flue gas temperature and improving boiler efficiency.

[0003] However, for boilers equipped with denitrification devices, the ammonia injection rate is usually relatively large to meet current requirements for ultra-clean emissions and flexible operation. Ammonia gas that has not reacted with NOx reacts with SO3 in the flue gas to form ammonium bisulfate. Ammonium bisulfate is a highly viscous liquid between 147℃ and 207℃, and is the main culprit for preheater blockage. Because the rotary air preheater is located below the denitrification unit, under ultra-low emission requirements, especially at low loads, the ammonia injection rate is excessive to ensure emission standards are met, resulting in ammonia escape far exceeding 3 ppm. The actual flue gas temperature during boiler operation is generally 120–140℃. The cold-end elements of the rotary preheater inevitably fall within the liquid phase temperature range of ammonium bisulfate. Due to its high viscosity, ammonium bisulfate adheres to the surface of the preheater elements and adsorbs ash, causing blockages, reduced heat exchange capacity, and increased cold-end corrosion. Furthermore, at low loads, the air preheater flue gas temperature is low, and the metal wall temperature decreases, causing the ammonium bisulfate deposit zone to shift upwards. When this deposit zone reaches the stratification point of the air preheater elements, it becomes difficult to remove, significantly increasing the air preheater's operating resistance, which is also difficult to recover.

[0004] To mitigate the risks of cold-end corrosion and ammonium bisulfate blockage, current methods primarily involve optimizing component plate design, increasing the height of cold-end components, and installing air heaters at the preheater inlet to raise the overall cold-end temperature of the preheater. Alternatively, adding a fan or a separate flue gas circulation compartment or duct circulation compartment can be implemented. However, adding air heaters or fans reduces the unit's operational economy and increases auxiliary equipment and maintenance workload. Based on actual operating conditions in most power plants, these solutions have some effect on delaying the blockage cycle, but they cannot completely solve the problem of cold-end ammonium bisulfate blockage, especially for boilers burning high-sulfur coal and units with high ammonia escape, where ammonium bisulfate deposition and blockage are particularly severe. Summary of the Invention

[0005] The purpose of this invention is to address the aforementioned shortcomings of the existing technology by providing an air preheater unblocking system. This system controls the metal wall temperature of the air preheater by adjusting the secondary air volume entering the air preheater, which can completely solve the problem of ammonium bisulfate blockage and significantly reduce the unit's maintenance workload and additional energy consumption, thus offering the advantage of good economic efficiency.

[0006] To achieve the above objectives, this utility model provides an air preheater unblocking system, comprising a rotary air preheater, an inlet flue, an outlet flue, a primary air fan and connected primary air inlet duct, a primary air outlet duct, a secondary air fan and connected secondary air inlet duct, and a secondary air outlet duct; characterized in that: the secondary air inlet duct and the secondary air outlet duct are connected through a secondary air bypass duct, and the secondary air bypass duct is equipped with a damper regulating baffle and a pressure transmitter.

[0007] When cold-end blockage occurs in the air preheater, the damper regulating plate is opened, allowing some cold secondary air to directly enter the secondary air outlet duct through the secondary air bypass duct, mix with the hot secondary air, and then enter the boiler. This reduction in the amount of cold secondary air entering the air preheater increases the metal wall temperature, causing the ammonium bisulfate to be heated and evaporated, thus completely resolving the ammonium bisulfate blockage problem. Furthermore, by utilizing the output of the secondary air fan, no additional equipment or system energy consumption is required, significantly reducing unit maintenance workload and additional energy consumption, offering excellent economic advantages. The pressure transmitter monitors the resistance of the cold secondary air in the secondary air bypass duct, thereby determining and adjusting the amount of cold secondary air passing through the bypass, improving the timeliness of clearing the blockage. After clearing the blockage, the damper regulating plate is closed, without affecting the unit's normal load-bearing and operation.

[0008] As a further improvement of this utility model, a temperature transmitter is provided in the secondary air outlet duct behind the connection between the secondary air outlet duct and the secondary air bypass duct; it is used to monitor the temperature of the mixed hot air so as to adjust the opening of the damper regulating baffle and ensure that the furnace can maintain a stable combustion state.

[0009] As a further improvement of this utility model, the damper adjustment baffle is an electric damper adjustment baffle. The flue gas chamber of the rotary air preheater is equipped with a flue gas pressure transmitter. Both the electric damper adjustment baffle and the flue gas pressure transmitter are connected to the DCS controller. The flue gas pressure transmitter can detect the blockage status of ash accumulation or ammonium bisulfate, and the DCS controller can automatically open the electric damper adjustment baffle to realize automatic control of clearing blockage.

[0010] As a further improvement of this utility model, the cross-sectional area of ​​the secondary air bypass duct is smaller than the cross-sectional area of ​​the secondary air inlet duct; the air volume of cold secondary air flowing through the secondary air bypass duct can be controlled to be less than that of hot secondary air.

[0011] In summary, this invention controls the metal wall temperature of the air preheater by adjusting the secondary air volume entering the air preheater, which can completely solve the problem of ammonium bisulfate blockage and significantly reduce the unit's maintenance workload and additional energy consumption, thus having the advantage of good economic efficiency. Attached Figure Description

[0012] Figure 1 This is a simplified structural diagram of an embodiment of the present utility model. Detailed Implementation

[0013] The present invention will be further described below with reference to the accompanying drawings.

[0014] like Figure 1 As shown, an air preheater unblocking system of this embodiment includes a rotary air preheater 1, an inlet flue 2, an outlet flue 3, a primary air fan 4 and connected primary air inlet duct 5, primary air outlet duct 6, a secondary air fan 7 and connected secondary air inlet duct 8, and secondary air outlet duct 9. A flue gas pressure transmitter 14 is installed in the flue gas chamber of the rotary air preheater 1. The secondary air inlet duct 8 and the secondary air outlet duct 9 are connected through a secondary air bypass duct 10. The cross-sectional area of ​​the secondary air bypass duct 10 is smaller than that of the secondary air inlet duct 8. An electric damper regulating baffle 11 and a pressure transmitter 12 are installed on the secondary air bypass duct 10. A temperature transmitter 13 is installed in the secondary air outlet duct 9 behind the connection between the secondary air outlet duct 9 and the secondary air bypass duct 10. The electric damper regulating baffle 11, the pressure transmitter 12, the flue gas pressure transmitter 14, and the temperature transmitter 13 are all connected to a DCS controller (not shown).

[0015] When this invention is used, if cold-end blockage occurs in the air preheater 1, and the flue gas resistance pressure transmitter 14 detects that the flue gas resistance exceeds the set value, it indicates that there is ash accumulation or ammonium bisulfate blockage in the air preheater 1. The DCS controller commands the electric damper regulating baffle 11 to open, and most of the cold secondary air directly enters the secondary air outlet duct 9 through the secondary air bypass duct 10, mixes with the hot secondary air, and then enters the boiler. The amount of cold secondary air entering the air preheater 1 is reduced, while the amount of flue gas entering the air preheater through the inlet flue duct 2 remains unchanged. This can increase the metal wall temperature of the air preheater, allowing the ammonium bisulfate to be heated and evaporated, thus completely solving the problem of ammonium bisulfate blockage. Furthermore, it utilizes existing secondary air preheater technology. The output of the secondary air fan does not require additional equipment or increase system energy consumption, significantly reducing unit maintenance workload and additional energy consumption, thus offering economic advantages. It also enables automatic control of unblocking. The pressure transmitter 12 can monitor the resistance of the cold secondary air in the secondary air bypass duct 10, thereby judging and adjusting the volume of cold secondary air passing through the bypass, improving the heating rate of the metal wall temperature and the timeliness of unblocking. The temperature transmitter 13 is used to monitor the temperature of the mixed hot air to adjust the opening of the electric damper 11, ensuring that the furnace can maintain a stable combustion state. After unblocking, closing the electric damper 11 does not affect the normal load-bearing and normal operation of the unit.

[0016] The above embodiments have been used to illustrate the invention, but it should be understood that the above embodiments are for illustrative purposes only and are not intended to limit the invention to the scope of the described embodiments.

Claims

1. An air preheater unblocking system, comprising a rotary air preheater, an inlet flue, an outlet flue, a primary air fan and connected primary air inlet duct, a primary air outlet duct, a secondary air fan and connected secondary air inlet duct, and a secondary air outlet duct; characterized in that: The secondary air inlet duct and the secondary air outlet duct are connected by a secondary air bypass duct, which is equipped with a damper and a pressure transmitter.

2. The air preheater unclogging system as described in claim 1, characterized in that: A temperature transmitter is installed in the secondary air outlet duct behind the connection between the secondary air outlet duct and the secondary air bypass duct.

3. The air preheater unclogging system as described in claim 1 or 2, characterized in that: The damper adjustment baffle is an electric damper adjustment baffle. The flue gas chamber of the rotary air preheater is equipped with a flue gas pressure transmitter. Both the electric damper adjustment baffle and the flue gas pressure transmitter are connected to the DCS controller.

4. The air preheater unclogging system as described in claim 3, characterized in that: The cross-sectional area of ​​the secondary air bypass duct is smaller than that of the secondary air inlet duct.

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