Method and system for reducing influence of air leakage of cold end of air pre-heater on downstream low-temperature economizer
By setting up a fan-shaped air intake and a gas collection hood on the flue gas side of the air preheater, and using the air leakage flue and regulating valve to control the flue gas temperature, the corrosion and ash blockage problems of cold-end air leakage in the air preheater to the low-temperature economizer were solved, thereby improving the heat utilization rate and equipment life.
Patent Information
- Application Number
- CN202511704184.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-19
- Publication Date
- 2026-01-20
AI Technical Summary
Air leakage at the cold end of the air preheater reduces the heat transfer difference of the low-temperature economizer and reduces heat recovery. The flue gas temperature is lower than the acid dew point, which can easily lead to corrosion and ash blockage, affecting the service life of the low-temperature economizer.
A fan-shaped air intake and a gas collection hood are installed on the flue gas side outlet face of the air preheater. Low-temperature gas is guided to the downstream of the low-temperature economizer through the air leakage flue. The flue gas temperature is controlled by adjusting the isolation door and regulating door to ensure that the temperature of the low-temperature economizer is not lower than the outlet temperature and to reduce the impact of air leakage.
It effectively reduced the negative impact of cold-end air leakage of the air preheater on the low-temperature economizer, reduced the decrease in flue gas temperature, solved the problems of corrosion and ash blockage, extended the service life of the low-temperature economizer, and improved the heat utilization rate.
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Figure CN121363736A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The application relates to a method for reducing the influence of air preheater cold end air leakage on a downstream low-temperature economizer and a system thereof, and belongs to the technical field of air preheater sealing and flue gas waste heat utilization. BACKGROUND
[0002] Low-pressure water-coal heat exchangers are widely used in the industrial field, such as the field of coal-fired power generation. With the promotion of low-carbon and environmental protection policies in the power generation industry of China, the waste heat utilization technology of coal-fired boilers has developed rapidly, and the installation of low-temperature economizers after air preheaters is a specific type of the above waste heat utilization. The low-temperature economizer is composed of a plurality of tube bundles, the inside of the tube is water (cold medium), and the outside of the tube is flue gas (hot medium). The inlet water temperature in the low-temperature economizer is generally 60-90℃, and the inlet flue gas temperature outside the tube is generally 120-180℃, so that the heat of the flue gas outside the tube is transferred to the medium water inside the tube.
[0003] However, in the field of coal-fired power generation, the traditional low-temperature economizer is prone to problems such as corrosion leakage and ash accumulation. The reasons include at least the following two points: 1) After combustion, part of the sulfur in the coal is converted into sulfur trioxide (SO3), which reacts with water vapor (H2O) in the flue gas to generate sulfuric acid vapor (H2SO4). When the flue gas temperature is lower than the acid dew point (generally 95-160℃, which is closely related to the SO3 concentration in the flue gas), the sulfuric acid vapor will condense and adhere to the heat exchange tube wall of the low-pressure water-coal heat exchanger together with the fly ash; 2) In order to reduce NOx emissions, coal-fired boilers are generally equipped with denitrification equipment, which generally adopts the technical route of selective catalytic reduction (SCR) or selective non-catalytic reduction (SNCR) or SCR+SNCR combination. However, regardless of which technical route is adopted, it is necessary to spray a reducing agent (liquid ammonia, urea or ammonia water) into the flue gas upstream of the air preheater. The reducing agent and NOx do not react completely, resulting in the occurrence of ammonia (NH3) escape in the denitrification system. The escaped NH3 reacts with SO3 in the flue gas to generate ammonium bisulfate (NH4HSO4), which is in a molten state at a temperature of 146-207 ℃, and is extremely easy to adhere to the heat exchange tube wall of the air preheater and the downstream low-temperature economizer together with the fly ash.
[0004] The rotary air preheater is used to heat low-temperature air with high-temperature flue gas, and at least includes an air side and a flue gas side. Due to the dynamic and static sealing, air leakage to the flue gas side cannot be completely avoided. The air preheater cold end air leakage will cause the temperature of the flue gas entering the low-temperature economizer to decrease, which on the one hand reduces the heat transfer end difference, and the heat recovered by the low-temperature economizer becomes less; on the other hand, the flue gas temperature after flowing through the low-temperature economizer is more likely to be lower than the acid dew point temperature, which causes the low-temperature corrosion and ash plugging problems to be aggravated. SUMMARY
[0005] In order to reduce the negative influence of the air preheater cold end air leakage on the downstream low-temperature economizer in the prior art, the application provides a method and system for reducing the influence of air preheater cold end air leakage on the downstream low-temperature economizer.
[0006] To solve the above technical problems, the technical solutions adopted by the application are as follows: A method for reducing the influence of air preheater cold end air leakage on the downstream low-temperature economizer, a fan-shaped gas taking port is separated at the outlet end face of the air preheater flue gas side, the fan-shaped gas taking port is adjacent to the cold end fan-shaped plate and located at the starting end of the rotation into the flue gas side; the angle θ of the fan-shaped gas taking port is between 7.5-30°; A gas collecting hood is arranged below the fan-shaped gas taking port, and the low-temperature gas of the fan-shaped gas taking port is guided to the downstream of the low-temperature economizer through the newly added air leakage flue; an isolation door, a regulating door and an air leakage flue gas temperature measuring point are arranged on the air leakage flue; a low-province outlet flue gas temperature measuring point is arranged downstream of the low-temperature economizer; when the measured value T1 of the air leakage flue gas temperature measuring point is less than the measured value T2 of the low-province outlet flue gas temperature measuring point, the regulating door is gradually opened at a speed of 1% / s until T1 is not less than T2.
[0007] In order to improve the heat utilization rate and at the same time take into account the anti-blocking effect of the low-temperature economizer, when T1 is greater than T2 and the difference between T1 and T2 is greater than 5℃, the regulating door is gradually closed at a speed of 1% / s.
[0008] The opening degree of the regulating door is 0-100%, and 1% / s represents 1% adjustment per second.
[0009] In order to reduce the influence on the boiler exhaust gas temperature and at the same time improve the heat utilization rate, further preferably, when T1 is greater than T2 and the difference between T1 and T2 is greater than 20℃, the isolation door and the regulating door are closed.
[0010] In order to facilitate control and modification, and at the same time reduce the negative influence of the air preheater cold end air leakage on the downstream low-temperature economizer, the angle θ of the fan-shaped gas taking port is between 7.5-15°.
[0011] A system for reducing the influence of air preheater cold end air leakage on the downstream low-temperature economizer, comprising an air preheater and a low-temperature economizer located downstream of the air preheater, and further comprising a gas collecting hood, an air leakage flue, an isolation door, a regulating door, an air leakage flue gas temperature measuring point and a low-province outlet flue gas temperature measuring point; The outlet end face of the air preheater flue gas side is separated by a fan-shaped gas taking port, the fan-shaped gas taking port is adjacent to the cold end fan-shaped plate and located at the starting end of the rotation into the flue gas side; the angle θ of the fan-shaped gas taking port is between 7.5-30°; The gas collecting hood is arranged below the fan-shaped gas taking port and can cover the fan-shaped gas taking port, the side surface of the gas collecting hood is provided with a gas outlet, one end of the air leakage flue communicates with the gas outlet on the gas collecting hood, and the other end communicates with the downstream flue of the low-temperature economizer; the isolation door, the regulating door and the air leakage flue gas temperature measuring point are all arranged on the air leakage flue; The low-province outlet flue gas temperature measuring point is arranged at the outlet flue of the low-temperature economizer. When the measured value T1 of the air leakage flue gas temperature measuring point is less than the measured value T2 of the low-province outlet flue gas temperature measuring point, the damper is opened at a speed of 1% / s until T1 is not less than T2.
[0012] In order to improve the accuracy of control, the low-province outlet flue gas temperature measuring point is arranged at the upstream of the communication between the air leakage flue and the downstream flue of the low-temperature economizer.
[0013] The above-mentioned isolation door, damper and air leakage flue gas temperature measuring point are arranged at one end of the air leakage flue close to the hood.
[0014] In order to facilitate control, the isolation door, damper and air leakage flue gas temperature measuring point are arranged in sequence from upstream to downstream.
[0015] The upstream-to-downstream direction of the present application is consistent with the flow direction of the gas or material.
[0016] In order to facilitate modification and arrangement, the hood is a horizontal triangular pyramid structure; the triangular surface at the top of the hood is an open structure as an air inlet, and is identical in shape and size to the fan-shaped air inlet and opposite to each other (referring to the position that the air preheater can be rotated to the fan-shaped air inlet and the air inlet of the hood).
[0017] Further preferably, the angle θ of the above-mentioned fan-shaped air inlet is between 7.5-15°.
[0018] The technologies not mentioned in the present application refer to the prior art.
[0019] The method and system for reducing the influence of air preheater cold end air leakage on downstream low-temperature economizer can effectively reduce the negative influence of air preheater cold end air leakage on downstream low-temperature economizer in the prior art, reduce the temperature of flue gas entering the low-temperature economizer due to air preheater cold end air leakage, solve the problems of low-temperature economizer corrosion and ash deposition, and prolong the service life of the low-temperature economizer; it is simple, easy to control, and has remarkable effect, and is easy to popularize. BRIEF DESCRIPTION OF DRAWINGS
[0020] Figure 1 The structure diagram of the system for reducing the influence of air preheater cold end air leakage on downstream low-temperature economizer.
[0021] In the figure, 1 is an air preheater, 11 is an air side, 12 is a flue gas side, 13 is a fan-shaped air inlet, 2 is a hood, 3 is an air leakage flue, 4 is an isolation door, 5 is a damper, 6 is an air leakage flue gas temperature measuring point, 7 is a low-temperature economizer, 8 is a low-province outlet flue gas temperature measuring point. DETAILED DESCRIPTION
[0022] In order to better understand the present application, the content of the present application is further illustrated below in conjunction with examples, but the content of the present application is not limited only to the following examples.
[0023] Example 1
[0024] A method for reducing the influence of air preheater cold end air leakage on downstream low-temperature economizer, a fan-shaped gas taking port is separated at the outlet end face of the air preheater flue gas side, the fan-shaped gas taking port is adjacent to the cold end fan-shaped plate and located at the starting end of the rotation into the flue gas side; the angle θ of the fan-shaped gas taking port is 15°; A gas collecting hood is arranged below the fan-shaped gas taking port, and the low-temperature gas of the fan-shaped gas taking port is guided to the downstream of the low-temperature economizer through the newly added air leakage flue; an isolation door, a regulating door and an air leakage flue temperature measuring point are arranged on the air leakage flue; a low-province outlet flue gas temperature measuring point is arranged downstream of the low-temperature economizer; when the measured value T1 of the air leakage flue temperature measuring point is less than the measured value T2 of the low-province outlet flue gas temperature measuring point, gradually open the regulating door at a speed of 1% / s until T1 is not less than T2.
[0025] In order to improve the heat utilization rate and at the same time take into account the anti-blocking effect of the low-temperature economizer, when T1 is greater than T2 and the difference between T1 and T2 is greater than 5℃, gradually close the regulating door at a speed of 1% / s. When T1 is greater than T2 and the difference between T1 and T2 is greater than 20℃, the isolation door and the regulating door are closed.
[0026] The above method can effectively reduce the negative influence of air preheater cold end air leakage on downstream low-temperature economizer in the prior art, reduce the temperature reduction of flue gas entering the low-temperature economizer due to air preheater cold end air leakage, solve the problems of low-temperature economizer corrosion and ash blocking, and prolong the service life of the low-temperature economizer.
[0027] Example 2
[0028] As shown in Figure 1 A system for reducing the influence of air preheater cold end air leakage on downstream low-temperature economizer, comprising an air preheater and a low-temperature economizer located downstream of the air preheater, further comprising a gas collecting hood, an air leakage flue, an isolation door, a regulating door, an air leakage flue temperature measuring point and a low-province outlet flue gas temperature measuring point; A fan-shaped gas taking port is separated at the outlet end face of the air preheater flue gas side, the fan-shaped gas taking port is adjacent to the cold end fan-shaped plate and located at the starting end of the rotation into the flue gas side; the angle θ of the fan-shaped gas taking port is between 7.5-30°; The gas collecting hood is arranged below the fan-shaped gas taking port and can cover the fan-shaped gas taking port, the side surface of the gas collecting hood is provided with a gas outlet, one end of the air leakage flue communicates with the gas outlet on the gas collecting hood and the other end communicates with the flue downstream of the low-temperature economizer; the isolation door, the regulating door and the air leakage flue temperature measuring point are all arranged on the air leakage flue; The low-province outlet flue gas temperature measuring point is arranged at the outlet flue of the low-temperature economizer; When the measured value T1 of the flue gas temperature measuring point in the leaking flue is less than the measured value T2 of the flue gas temperature measuring point at the low-temperature outlet, the regulating valve is gradually opened at a rate of 1% / s until T1 is not less than T2.
[0029] Example 3
[0030] Based on Example 2, the following improvements were made: To improve control accuracy, the low-temperature economizer outlet flue gas temperature measuring point is located upstream of the connection between the leaking flue and the downstream flue of the low-temperature economizer. The isolation door, regulating door, and leaking flue gas temperature measuring point are all located on the leaking flue near the gas collection hood, and are arranged sequentially from upstream to downstream.
[0031] Example 4
[0032] Based on Example 3, the following improvements were further made: Figure 1 As shown, for ease of modification and layout, the gas collecting hood is a horizontal triangular pyramid structure; the triangular face at the top of the hood is an open structure serving as an air inlet, and is identical in shape and size to the fan-shaped air intake, and is vertically opposite (meaning the air preheater can rotate to a position where the fan-shaped air intake and the air inlet of the gas collecting hood are vertically opposite). In this example, the angle θ of the aforementioned fan-shaped air intake is 7.5°. Simultaneously, when T1 is greater than T2, and the difference between T1 and T2 is greater than 5°C, the regulating valve is gradually closed at a rate of 1% / s. When T1 is greater than T2, and the difference between T1 and T2 is greater than 20°C, the isolation door and regulating valve are closed. After six consecutive months of trial operation, this scheme has been verified to effectively overcome the corrosion and ash blockage effects caused by cold-end air leakage from the air preheater on the downstream low-temperature economizer.
[0033] Before the modification (without the addition of fan-shaped air intakes, gas collection hoods, leaky flues, isolation doors, regulating valves, and flue gas temperature measuring points in the leaky flues and at the low-temperature economizer outlet), air leakage at the cold end of the air preheater had a significant negative impact on the downstream low-temperature economizer. Corrosion and ash blockage in the heat exchanger tube boxes were severe, resulting in an approximately 2 kPa deviation in flue gas-side resistance. This led to substantial power and heat losses, and prevented the coal-fired power generating unit from operating at full load. However, the modification using the scheme described in this example completely overcomes these problems.
Claims
1. A method for reducing the influence of air preheater cold end air leakage on a downstream low-temperature economizer, characterized in that: A fan-shaped gas taking port is separated at the outlet end face of the flue gas side of the air preheater, the fan-shaped gas taking port is adjacent to the cold end fan-shaped plate and is located at the starting end of the rotation into the flue gas side; the angle θ of the fan-shaped gas taking port is between 7.5-30°; A gas collecting cover is arranged below the fan-shaped gas taking port, and the low-temperature gas of the fan-shaped gas taking port is guided to the downstream of the low-temperature economizer through the newly added air leakage flue; an isolation door, a regulating door and an air leakage flue temperature measuring point are arranged on the air leakage flue; a low-economizer outlet flue gas temperature measuring point is arranged downstream of the low-temperature economizer; when the measured value T1 of the air leakage flue temperature measuring point is less than the measured value T2 of the low-economizer outlet flue gas temperature measuring point, the regulating door is opened at a speed of 1% / s until T1 is not less than T2.
2. The method of claim 1, wherein the method further comprises: When T1 is greater than T2, and the difference between T1 and T2 is greater than 5℃, the regulating door is closed at a speed of 1% / s.
3. The method of claim 1 or 2, wherein the method is characterized in that: When T1 is greater than T2, and the difference between T1 and T2 is greater than 20℃, the isolation door and the regulating door are closed.
4. The method of claim 1 or 2, wherein the method is characterized in that: The angle θ of the fan-shaped gas taking port is between 7.5-15°.
5. A system for reducing the impact of air preheater cold end air leakage on a downstream low temperature economizer, comprising an air preheater and a low temperature economizer located downstream of the air preheater, characterized by: It also includes a gas collecting cover, an air leakage flue, an isolation door, a regulating door, an air leakage flue temperature measuring point and a low-economizer outlet flue gas temperature measuring point; A fan-shaped gas taking port is separated at the outlet end face of the flue gas side of the air preheater, the fan-shaped gas taking port is adjacent to the cold end fan-shaped plate and is located at the starting end of the rotation into the flue gas side; the angle θ of the fan-shaped gas taking port is between 7.5-30°; The gas collecting cover is arranged below the fan-shaped gas taking port and can cover the fan-shaped gas taking port, the side of the gas collecting cover is provided with a gas outlet, one end of the air leakage flue communicates with the gas outlet on the gas collecting cover, and the other end communicates with the flue downstream of the low-temperature economizer; the isolation door, the regulating door and the air leakage flue temperature measuring point are all arranged on the air leakage flue; The low-economizer outlet flue gas temperature measuring point is arranged at the flue downstream of the low-temperature economizer; When the measured value T1 of the air leakage flue temperature measuring point is less than the measured value T2 of the low-economizer outlet flue gas temperature measuring point, the regulating door is opened at a speed of 1% / s until T1 is not less than T2.
6. The system of claim 5, wherein the system further comprises a bypass damper. The low-economizer outlet flue gas temperature measuring point is located upstream of the communication between the air leakage flue and the flue downstream of the low-temperature economizer.
7. The system for reducing the impact of air preheater cold end air leakage on a downstream low-temperature economizer of claim 5 or 6, wherein: The isolation door, the regulating door and the air leakage flue temperature measuring point are all arranged on one end of the air leakage flue close to the gas collecting cover.
8. The system for reducing the impact of air preheater cold end air leakage on a downstream low-temperature economizer of claim 5 or 6, wherein: The isolation door, the regulating door and the air leakage flue temperature measuring point are sequentially arranged in the direction from upstream to downstream.
9. The system for reducing the impact of air preheater cold end air leakage on a downstream low-temperature economizer of claim 5 or 6, wherein: The gas collecting cover is a horizontal triangular pyramid structure; the triangular surface at the top of the gas collecting cover is an open structure as a gas inlet, and is the same shape and size as the fan-shaped gas taking port and is opposite to the fan-shaped gas taking port.
10. The system for reducing the impact of air preheater cold end air leakage on a downstream low-temperature economizer of claim 5 or 6, wherein: The angle θ of the fan-shaped gas taking port is between 7.5-15°.