A system for eliminating safety hazards in operation of air preheater and a control method thereof

Abstract

The present application relates to a system for eliminating safety hazards in the operation of an air preheater and a control method thereof. The system for eliminating safety hazards in the operation of an air preheater includes setting a bypass flue between the boiler flue before the low-temperature superheater and the inlet of the SCR reactor, setting a flue gas regulating damper at the inlet of the bypass flue, setting a heat pipe heat exchanger on the flue connected to the flue gas outlet of the air preheater, and setting a heater at the inlet of the blower and the primary blower. The system for eliminating safety hazards in the operation of an air preheater can increase the flue gas temperature entering the flue gas inlet of the air preheater and the cold air temperature at the air inlet of the air preheater according to the operation needs of the unit, can prevent the generation of ammonium bisulfate on the air preheater, and effectively solve the problem of blockage of the air preheater that has already occurred, which is conducive to improving the safety of the operation of the air preheater and ensuring the safe, stable and efficient operation of the boiler unit.

Description

Technical Field

[0001] The present application relates to a system for eliminating potential safety hazards in the operation of an air preheater and a control method thereof, and belongs to the technical field of coal-fired boilers. Background Art

[0002] At present, domestic thermal power plants generally use SCR (selective catalytic reduction) to control NO X The emission of SCR is mostly high-temperature catalysts, and the reaction temperature range is 320-420℃. After the SCR is installed in the coal-fired power generation unit, the air preheater is often blocked. The main reason for the blockage of the air preheater is that with the continuous increase in the installed capacity of clean energy power generation, thermal power units are responsible for more and more peak-shaving tasks. Although most thermal power plants have carried out wide-load denitrification transformation in recent years to meet the temperature requirements of low-load SCR reactors, when the boiler load drops to about 30% of the unit load, the SCR reactor may still drop to about 300℃. With the decrease of the SCR inlet flue gas temperature, the activity of the reaction catalyst decreases, which is very likely to cause excessive ammonia injection, resulting in aggravated ammonia escape in the SCR device, and easy to generate ammonium bisulfate at the cold end of the air preheater. In addition, factors such as coal quality, comprehensive temperature of the cold end of the air preheater, catalyst activity, and low load can also cause air preheater blockage.

[0003] When the air preheater is blocked, the negative pressure fluctuation in the furnace will increase, the fan output will increase, and in severe cases, stall will occur, affecting the unit's load-bearing capacity and even the unit's operating safety, and will also lead to boiler load limitation and shutdown. At the same time, it will also cause problems such as increased exhaust gas temperature and increased air preheater leakage rate, which greatly reduces the boiler efficiency and has a great impact on the economy and safety of boiler operation.

[0004] In response to the operational risks and reduced furnace efficiency caused by air preheater blockage, major power plants have gradually explored some measures to improve air preheater blockage, such as: controlling the amount of SO3 generated at the air preheater inlet, controlling the ammonia escape concentration, controlling the coal quality entering the furnace, optimizing the air preheater soot blowing method, reducing the amount of NOx generated at the denitrification inlet, regularly performing high-pressure water flushing and air preheater transformation, etc. Although these methods can alleviate the frequency of air preheater blockage to a certain extent, they cannot completely eradicate the problem of air preheater blockage.

[0005] Regarding the problem of air preheater blockage, how to take preventive and control measures to keep it in good working condition is the basis for ensuring the safe and stable operation of the unit. Summary of the invention

[0006] In order to solve the above problems, the present application proposes a system for eliminating safety hazards in the operation of an air preheater and a control method thereof. The system for eliminating safety hazards in the operation of an air preheater can increase the flue gas temperature entering the flue gas inlet of the air preheater and the cold air temperature at the air inlet of the air preheater according to the operation needs of the unit, prevent the generation of ammonium bisulfate on the air preheater, and effectively solve the problem of blockage of the air preheater that has already occurred, which is conducive to improving the safety of the operation of the air preheater. At the same time, the exhaust gas temperature is regulated by a heat pipe heat exchanger, and the waste heat of the flue gas is recovered to ensure the safe, stable and efficient operation of the boiler unit.

[0007] According to one aspect of the present application, the present application provides the following technical solution:

[0008] A system for eliminating safety hazards in the operation of an air preheater, comprising a low-temperature superheater, an economizer, an SCR reactor and an air preheater arranged in sequence in a boiler flue, a bypass flue being arranged between the boiler flue before the low-temperature superheater and the inlet of the SCR reactor, a flue gas regulating damper being arranged at the inlet of the bypass flue, the flue gas regulating damper being used to regulate the flue gas temperature at the flue gas inlet of the air preheater; a heat pipe heat exchanger being arranged on the flue connected to the flue gas outlet of the air preheater, the heat pipe heat exchanger being used to regulate the flue gas temperature at the flue gas outlet of the air preheater;

[0009] It also includes an air supply fan and a primary fan connected to the air inlet of the air preheater. Air heaters are respectively arranged at the inlets of the air supply fan and the primary fan. The air heaters are used to adjust the cold air temperature at the air inlet of the air preheater.

[0010] Preferably, an air preheater inlet pressure sensor is provided at the flue gas inlet of the air preheater, and an air preheater outlet pressure sensor is provided at the flue gas outlet of the air preheater.

[0011] Preferably, an SCR reactor inlet smoke temperature sensor is provided at the inlet of the SCR reactor.

[0012] Preferably, a dust collector, an induced draft fan, a desulfurization tower and a chimney are sequentially arranged on the flue connected to the flue gas outlet of the air preheater;

[0013] The heat pipe heat exchanger is arranged between the air preheater and the dust collector;

[0014] Alternatively, the heat pipe heat exchanger is arranged between the dust collector and the induced draft fan;

[0015] Alternatively, the heat pipe heat exchanger is arranged between the induced draft fan and the desulfurization tower.

[0016] Preferably, the heat pipe heat exchanger comprises a smoke chamber and a hot water chamber, the smoke chamber and the hot water chamber are isolated from each other, at least one heat pipe connecting the smoke chamber and the hot water chamber is arranged in the smoke chamber and the hot water chamber, and the heat pipe is used to transfer the heat of the smoke chamber to the hot water chamber;

[0017] A main water inlet pipe and a main water outlet pipe are arranged on the outside of the hot water chamber. The water inlet of the hot water chamber is connected to the main water inlet pipe, and the water outlet of the hot water chamber is connected to the main water outlet pipe. The main water outlet pipe is used to transfer the heat in the hot water chamber to the boiler condensate pipe or the boiler feed water pipe.

[0018] Preferably, the smoke chamber and the hot water chamber are isolated by a bidirectional partition, and the bidirectional partitions are filled with heat-insulating and anti-corrosion materials.

[0019] Preferably, a hot water chamber inlet water temperature sensor is provided at the water inlet of the hot water chamber, and a hot water chamber outlet water temperature sensor is provided at the water outlet of the hot water chamber;

[0020] A smoke temperature sensor at an inlet of the smoke chamber is arranged at the smoke inlet of the smoke chamber, and a smoke temperature sensor at an outlet of the smoke chamber is arranged at the smoke outlet of the smoke chamber.

[0021] Preferably, a first electric regulating door is provided on the main water inlet pipe.

[0022] Preferably, a branch water outlet pipe is provided on the main water outlet pipe, and the branch water outlet pipe is connected to the water inlet of the air heater. A branch water inlet pipe is provided on the main water inlet pipe, and the branch water inlet pipe is connected to the water outlet of the air heater.

[0023] Preferably, a heater inlet air temperature sensor is provided at the air inlet of the heater, a heater outlet air temperature sensor is provided at the air outlet of the heater, and a second electric regulating door is provided on the branch water outlet pipe.

[0024] Preferably, an air preheater inlet pressure sensor is provided at the flue gas inlet of the air preheater, an air preheater outlet pressure sensor is provided at the flue gas outlet of the air preheater, and an SCR reactor inlet flue gas temperature sensor is provided at the inlet of the SCR reactor;

[0025] The flue gas damper, the air preheater inlet pressure sensor, the air preheater outlet pressure sensor and the SCR reactor inlet flue gas temperature sensor are all connected to the controller.

[0026] According to another aspect of the present application, the present application provides the following technical solutions:

[0027] A control method for eliminating a system for eliminating hidden dangers in the operation of an air preheater comprises the following steps:

[0028] When the differential pressure at the flue gas inlet and outlet of the air preheater is higher than a first differential pressure preset value, the system enters a first operation mode;

[0029] When the differential pressure at the flue gas inlet and outlet of the air preheater is lower than the first differential pressure preset value and higher than the second differential pressure preset value, the system enters the second operation mode;

[0030] When the differential pressure at the flue gas inlet and outlet of the air preheater is lower than the second differential pressure preset value, the system enters the third operation mode;

[0031] The step of operating the system in the first operating mode includes:

[0032] Increasing the opening of the flue gas damper until the flue gas temperature at the inlet of the SCR reactor rises to the maximum temperature allowed by the SCR reactor;

[0033] Increase the water flow rate to the hot water chamber of the heat pipe heat exchanger and increase the water flow rate to the heater;

[0034] The steps of operating the system in the second operating mode include:

[0035] Increase the feed water flow rate into the air heater to determine the required flue gas temperature at the flue gas inlet of the air preheater;

[0036] Increase the flue gas flow rate entering the bypass flue so that the flue gas temperature at the flue gas inlet of the air preheater reaches the required flue gas temperature at the flue gas inlet of the air preheater determined above;

[0037] Increase the water flow rate of the hot water chamber of the heat pipe heat exchanger to maintain the appropriate temperature of the smoke at the smoke outlet of the smoke chamber of the heat pipe heat exchanger;

[0038] The steps of operating the system in the third operating mode include:

[0039] Determine the minimum flue gas temperature required at the flue gas outlet of the heat pipe heat exchanger;

[0040] When the smoke temperature at the inlet of the SCR reactor is lower than its minimum reaction temperature, the smoke regulating damper is opened to make the smoke temperature at the inlet of the SCR reactor higher than its minimum reaction temperature;

[0041] Determine the required heating temperature of the air inlet of the air preheater, and adjust the water flow entering the heater to achieve the required heating temperature of the air inlet of the air preheater.

[0042] The beneficial effects of this application include but are not limited to:

[0043] 1. The air preheater operation safety hazard elimination system provided in the present application has a flue gas regulating damper for adjusting the flue gas flow entering the bypass flue, thereby realizing operational regulation of the flue gas temperature at the air preheater inlet; the heat pipe heat exchanger provided can realize operational regulation of the flue gas temperature at the flue gas outlet of the air preheater; the heater provided can realize regulation of the cold air temperature at the air inlet of the air preheater; the air preheater operation safety hazard elimination system under wide load denitrification conditions can increase the flue gas temperature entering the flue gas inlet of the air preheater and the cold air temperature at the air inlet of the air preheater according to the operation needs of the unit, can prevent the generation of ammonium bisulfate in the air preheater, and effectively solve the problem of air preheater blockage that has already occurred, which is beneficial to improving the operating safety of the air preheater. At the same time, the exhaust gas temperature is regulated by the heat pipe heat exchanger to recover the flue gas waste heat, thereby ensuring the safe, stable and efficient operation of the boiler unit.

[0044] 2. The air preheater operation safety hazard elimination system provided in this application, by setting up a heat pipe heat exchanger, is conducive to the recovery and utilization of flue gas waste heat, reducing the exhaust temperature, saving energy, and improving the safe and economical operation of the boiler unit.

[0045] 3. The air preheater operation safety hazard elimination system provided in the present application, by setting a heater, regulates the temperature of the cold air entering the air preheater inlet, thereby further increasing the comprehensive temperature of the cold end of the air preheater, reducing the risk of air preheater blockage, increasing the hot air temperature, and improving the boiler efficiency.

[0046] 4. The control method of the air preheater operation safety hazard elimination system provided in the present application can realize the intelligent automatic control of the air preheater operation safety hazard elimination system. Compared with the existing technology, it can realize the safe, stable, reliable and efficient operation of the boiler air preheater system under full load denitrification conditions, while ensuring the economy of the boiler unit operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0048] Figure 1 This is a structural schematic diagram of a system for eliminating safety hazards in the operation of an air preheater according to an embodiment of the present application.

[0049] List of parts and reference numerals:

[0050] 1. Boiler; 2. Low-temperature superheater; 3. Economizer; 4. SCR reactor; 5. Air preheater; 6. Tail flue; 7. Dust collector; 8. Draft fan; 9. Desulfurization tower; 10. Chimney; 11. Bypass flue; 12. Flue gas damper; 13. Heat pipe heat exchanger; 14. Air heater; 131. Flue gas chamber; 132. Hot water chamber; 133. Main water inlet pipe; 134. Main water outlet pipe; 135. Boiler condensate pipe or boiler feed water pipe; 136. First electric regulating door; 141. Branch water outlet pipe; 142. Branch water inlet pipe; 143. Second electric regulating door. DETAILED DESCRIPTION

[0051] In order to more clearly illustrate the overall concept of the present application, a detailed description is given below in an illustrative manner in conjunction with the accompanying drawings.

[0052] In order to more clearly understand the above-mentioned purposes, features and advantages of the present application, the present application is further described in detail below in conjunction with the accompanying drawings and specific implementation methods. It should be noted that the embodiments of the present application and the features in the embodiments can be combined with each other without conflict.

[0053] In the following description, many specific details are set forth to facilitate a full understanding of the present application. However, the present application may also be implemented in other ways different from those described herein. Therefore, the scope of protection of the present application is not limited to the specific embodiments disclosed below.

[0054] refer to Figure 1The present invention illustrates an air preheater operation safety hazard elimination system, comprising a boiler 1, a low-temperature superheater 2, an economizer 3, an SCR reactor 4, an air preheater 5, a tail flue 6, a dust collector 7, an induced draft fan 8, a desulfurization tower 9 and a chimney 10 which are arranged in sequence. Along the flue gas flow direction, the low-temperature superheater 2, the economizer 3, the SCR reactor 4 and the air preheater 5 are arranged in sequence in the boiler flue gas duct, the flue gas outlet of the air preheater 5 is connected to the tail flue 6, and the tail flue 6 The outlet is connected with the flue gas inlet of the dust collector 7, a bypass flue 11 is arranged on the boiler flue, the inlet of the bypass flue 11 is located in the boiler flue before the low-temperature superheater 2, the outlet of the bypass flue 11 is directly connected to the inlet of the SCR reactor 4, and a flue gas regulating damper 12 is arranged at the inlet of the bypass flue 11, and the flue gas regulating damper 12 is used to adjust the flue gas flow rate entering the bypass flue 11 from the boiler flue, so as to realize the operation regulation of the flue gas temperature at the inlet of the air preheater 5. By setting the bypass flue 11, when the load is low, by adjusting the flue gas regulating damper 12, the high-temperature flue gas does not need to pass through the low-temperature superheater 2 and the economizer 3 for heat exchange, and directly enters the SCR reactor, thereby increasing the flue gas temperature at the inlet of the SCR reactor; when the air preheater 5 is blocked due to load, coal quality and other problems, the flue gas regulating damper 12 can be properly opened to increase the flue gas temperature at the inlet of the SCR reactor 4 while ensuring that the flue gas temperature at the inlet of the SCR reactor meets the reaction conditions. At this time, the flue gas temperature at the flue gas inlet of the air preheater 5 is also increased, which can further increase the cold end comprehensive temperature of the air preheater 5. The increase in the cold end comprehensive temperature can effectively inhibit the generation of ammonium bisulfate at the cold end of the air preheater 5, reduce the risk of blockage of the air preheater 5, and is conducive to preventing the blockage of the air preheater 5; and by increasing the flue gas temperature entering the inlet of the SCR reactor 4, the ammonium bisulfate generated on the air preheater 5 can be gasified, which can effectively solve the problem of blockage of the air preheater 5 that has already occurred, and ensure the safe, stable and efficient operation of the boiler unit. A heat pipe heat exchanger 13 is arranged on the flue connected to the flue gas outlet of the air preheater 5, and the heat pipe heat exchanger 13 is used to adjust the flue gas temperature at the flue gas outlet of the air preheater 5; it also includes a blower and a primary fan connected to the air inlet of the air preheater 5, and a heater 14 is respectively arranged at the inlet of the blower and the primary fan. The heater 14 is used to adjust the cold air temperature at the air inlet of the air preheater 5. By arranging the heater, the cold air that will enter the boiler can be heated, so that the air temperature at the inlet of the air preheater 5 is increased, which is beneficial to increase the comprehensive temperature of the cold end of the air preheater 5, thereby reducing the blockage risk of the air preheater 5, increasing the hot air temperature, and improving the efficiency of the boiler.

[0055] As an implementation method, in order to better monitor whether the air preheater 5 is blocked, an air preheater inlet pressure sensor is set at the flue gas inlet of the air preheater 5, and an air preheater outlet pressure sensor is set at the flue gas outlet of the air preheater 5. By setting the air preheater inlet pressure sensor and the air preheater outlet pressure sensor, the inlet and outlet pressure difference of the air preheater can be monitored. When the inlet and outlet pressure difference of the air preheater increases to a certain value, it means that the air preheater 5 is blocked. The flue gas regulating damper 12 can be opened when the boiler is under high load to greatly increase the flue gas temperature at the inlet of the SCR reactor 4. At this time, the flue gas temperature at the flue gas inlet of the air preheater 5 also increases. Since the gasification temperature of ammonium bisulfate is 150℃-230℃, a higher flue gas temperature is conducive to the gasification of ammonium bisulfate generated on the air preheater 5, which can effectively solve the problem of air preheater blockage that has occurred. In order to better monitor the flue gas temperature entering the inlet of the SCR reactor, an SCR reactor inlet flue gas temperature sensor is set at the inlet of the SCR reactor 5. The flue gas regulating damper 12, the air preheater inlet pressure sensor, the air preheater outlet pressure sensor and the SCR reactor inlet flue gas temperature sensor are all connected to the controller.

[0056] As an implementation method, a heat pipe heat exchanger 13 may be provided between the air preheater 5 and the dust collector 7; or, a heat pipe heat exchanger 13 may be provided between the dust collector 7 and the induced draft fan 8; or, a heat pipe heat exchanger may be provided between the induced draft fan 8 and the desulfurization tower 9. In order to better recover the waste heat of the flue gas, the heat pipe heat exchanger 13 is preferably provided between the air preheater 5 and the dust collector 7. The heat pipe heat exchanger 13 includes a flue gas chamber 131 and a hot water chamber 132. In order to prevent the flue gas chamber 131 from being connected to the hot water chamber 132, a bidirectional partition may be provided between the flue gas chamber 131 and the hot water chamber 132, and the bidirectional partition may be filled with heat-insulating and anti-corrosive materials. At least one heat pipe is arranged, so that a part of the heat pipe is in the smoke chamber 131 and the other part is in the hot water chamber 132. By arranging the working medium in the heat pipe, heat is taken from the smoke chamber 131 to reduce the exhaust temperature of the smoke chamber 131, and then the heat is released in the hot water chamber 132 to complete the transfer of heat in the smoke chamber 131 to the hot water chamber 132. By arranging the heat pipe heat exchanger 13, the acid dew point corrosion problem of the wall surface of the low-temperature heating surface at the tail of the boiler can be solved. First, the starting temperature of the heat pipe heat exchanger 13 can be set according to actual needs, so that the starting temperature is higher than the acid dew point temperature of the boiler flue gas; second, the surface of the heat pipe part exposed in the smoke chamber 131 is painted with corrosion-resistant materials, such as plastic steel, fluoroplastics, glass-lined materials, etc. In order to better utilize the heat in the hot water chamber 132, a main water inlet pipe 133 and a main water outlet pipe 134 are arranged outside the hot water chamber 132. The water inlet of the hot water chamber 132 is connected to the main water inlet pipe 133, and the water outlet of the hot water chamber 132 is connected to the main water outlet pipe 134. The main water outlet pipe 134 is used to transfer the heat in the hot water chamber 132 to the boiler condensate pipe or the boiler feed water pipe 135, so as to heat the boiler condensate or the boiler feed water. The boiler condensate or the boiler feed water is then directly merged into the deaerator, which greatly reduces the difficulty of boiler operation adjustment.

[0057] In order to make the boiler run more reasonably, a smoke temperature sensor at the smoke inlet of the smoke chamber 131 is set, and a smoke temperature sensor at the smoke outlet of the smoke chamber 131 is set; a water temperature sensor at the water inlet of the hot water chamber 132 is set, and a water temperature sensor at the water outlet of the hot water chamber 132 is set; a first electric regulating door 136 is set on the main water inlet pipe 133; the smoke temperature sensor at the smoke inlet of the smoke chamber, the smoke temperature sensor at the smoke outlet of the smoke chamber, the water temperature sensor at the hot water chamber inlet, the water temperature sensor at the hot water chamber outlet and the first electric regulating door 136 are all connected to the controller. By setting the first electric regulating door 136, the water inlet flow of the hot water chamber 132 can be automatically adjusted according to the smoke temperature collected by the smoke temperature sensor at the smoke inlet of the smoke chamber 131, so as to adjust the exhaust temperature of the smoke outlet of the smoke chamber 131 to achieve a constant effect.

[0058] As an implementation method, in order to allow the heating heat source of the heater 14 to come from part of the high-temperature hot water produced in the hot water chamber 132 of the heat pipe heat exchanger 13, a branch water outlet pipe 141 is provided on the main water outlet pipe 134, and the branch water outlet pipe 141 is connected to the water inlet of the heater 14; a branch water inlet pipe 142 is provided on the main water inlet pipe 133, and the branch water inlet pipe 142 is connected to the water outlet of the heater 14; after the hot water in the branch water outlet pipe 141 completes heating the cold air, it flows into the main water inlet pipe 133 through the branch water inlet pipe 142. In order to automatically adjust the hot water flow entering the heater from the branch water outlet pipe 141 according to the ambient temperature and the differential pressure between the inlet and outlet of the air preheater 5, so as to achieve the effect of adjusting the air heating temperature at the air outlet of the heater 14, a second electric regulating door 143 is arranged on the branch water outlet pipe 141, a heater inlet air temperature sensor is arranged at the air inlet of the heater 14, and a heater outlet air temperature sensor is arranged at the air outlet of the heater 14. The second electric regulating door 143, the heater inlet air temperature sensor and the heater outlet air temperature sensor are all connected to the controller.

[0059] The present invention also illustrates a control method for a system for eliminating safety hazards in the operation of an air preheater, comprising the following steps:

[0060] When the differential pressure at the flue gas inlet and outlet of the air preheater 5 is higher than the first differential pressure preset value, the system enters the first operation mode;

[0061] When the differential pressure at the flue gas inlet and outlet of the air preheater 5 is lower than the first differential pressure preset value and higher than the second differential pressure preset value, the system enters the second operation mode;

[0062] When the differential pressure at the flue gas inlet and outlet of the air preheater 5 is lower than the second differential pressure preset value, the system enters the third operation mode;

[0063] The steps of operating the system in the first operating mode include:

[0064] Increase the opening of the flue gas damper 12 until the flue gas temperature at the inlet of the SCR reactor 4 rises to the maximum temperature allowed by the system;

[0065] The water flow rate of the hot water chamber 132 of the heat pipe heat exchanger 13 is increased, and the water flow rate entering the heater 14 is increased.

[0066] The first operation mode is also called the operation mode for handling air preheater blockage. The specific principle is as follows:

[0067] When the system detects that the flue gas inlet and outlet differential pressure of the air preheater 5 is greater than a certain value (such as 2.5 kPa, which may vary depending on the capacity of the specific boiler unit and the condition of the air preheater equipment), it is considered that the air preheater 5 is blocked, and the flue gas regulating damper 12 is slowly opened to closely monitor the inlet temperature of the SCR reactor 4 until the flue gas temperature at the inlet of the SCR reactor 4 is increased to the maximum allowable temperature of the denitrification system (such as 400°C). After the high-temperature flue gas enters the air preheater 5, the high temperature of the flue gas will promote the gasification of ammonium bisulfate generated on the heat exchange element of the air preheater 5, and the blockage of the air preheater 5 will be gradually alleviated under the flushing of the high-temperature flue gas, and the flue gas inlet and outlet differential pressure of the air preheater 5 will decrease accordingly. When the inlet and outlet differential pressure of the air preheater 5 is lower than a certain value (such as 1.5 kPa), it is considered that the blockage of the air preheater is resolved, and the system switches to other modes of operation.

[0068] In the operation mode for handling air preheater blockage, due to the substantial increase in the inlet flue gas temperature of the SCR reactor 4, the exhaust gas temperature at the flue gas outlet of the air preheater 5 also substantially increases. To ensure that the boiler efficiency is not reduced, the flue gas cooling effect of the heat pipe heat exchanger 13 must be ensured. Therefore, it is necessary to open the valve of the first electric regulating door 136 as wide as possible to increase the water feed flow rate of the hot water chamber 132 of the heat pipe heat exchanger 13 and maximize the heat exchange effect of the heat pipe heat exchanger 13. To promote the gasification of ammonium bisulfate generated on the heat exchange elements of the air preheater 5, it is necessary to increase the cold end comprehensive temperature of the air preheater 5 as much as possible. Therefore, the valve opening of the second electric regulating door 143 is opened as wide as possible to improve the warming effect of the heater 14.

[0069] The steps of operating the system in the second operating mode include:

[0070] Increase the water flow rate entering the air heater 14 to determine the required flue gas temperature at the flue gas inlet of the air preheater 5;

[0071] Increasing the flue gas flow rate entering the bypass flue 11 so that the flue gas temperature at the flue gas inlet of the air preheater 5 reaches the required flue gas temperature at the flue gas inlet of the air preheater 5 determined above;

[0072] The water supply flow rate of the hot water chamber 132 of the heat pipe heat exchanger 13 is increased to maintain the smoke temperature at the smoke outlet of the smoke chamber 131 of the heat pipe heat exchanger 13 at an appropriate temperature.

[0073] The second operation mode is also called the operation mode for preventing the air preheater 5 from being blocked, and the specific principle is as follows:

[0074] When the system detects that the differential pressure between the flue gas inlet and outlet of the air preheater 5 is less than a certain value (such as 2.5 kPa, which may vary depending on the capacity of the specific boiler unit and the condition of the air preheater equipment), it is considered that the air preheater 5 has not been blocked. If the system considers improving the operational safety and preventing the formation of ammonium bisulfate on the heat exchange element of the air preheater 5 after ammonia escapes, the system may be selected to enter the air preheater blockage prevention operation mode.

[0075] In the operation mode for preventing the air preheater 5 from being blocked, the appropriate cold end comprehensive temperature of the air preheater 5 is calculated and determined according to the actual situation of the boiler unit, and the second electric regulating door 143 is opened first to increase the temperature of the air inlet of the air preheater 5, so as to determine the required inlet flue gas temperature of the air preheater 5 (the cold end comprehensive temperature of the air preheater is the sum of the inlet air temperature and the outlet flue gas temperature). Under different loads of the unit, the inlet flue gas temperature of the air preheater 5 is adjusted by adjusting the flue gas regulating damper 12 until The inlet flue gas temperature of the air preheater 5 reaches the above-mentioned determined value. To ensure that the boiler efficiency is not reduced, the flue gas cooling effect of the heat pipe heat exchanger 13 must be ensured. By adjusting the opening of the first electric regulating door 136 and the water feed flow rate of the hot water chamber 132 of the heat pipe heat exchanger 13, the flue gas temperature at the flue gas outlet of the flue gas chamber 131 of the heat pipe heat exchanger 13 is maintained within a safe and economical range (such as 110-125°C, which should be set according to the specific load size of the boiler unit and the coal quality).

[0076] The steps of the system operating in the third operating mode include:

[0077] Determine the minimum flue gas temperature required at the flue gas outlet of the heat pipe heat exchanger 13;

[0078] When the smoke temperature at the inlet of the SCR reactor 4 is lower than its minimum reaction temperature, the smoke regulating damper is opened to make the smoke temperature at the inlet of the SCR reactor 4 higher than its minimum reaction temperature;

[0079] The required heating temperature of the air inlet of the air preheater 5 is determined, and the required heating temperature of the air inlet of the air preheater 5 is achieved by adjusting the water flow rate entering the heater 14 .

[0080] The third operation mode is also called the economic operation mode. The specific principles are as follows:

[0081] When the system detects that the flue gas inlet and outlet differential pressure of the air preheater 5 is less than a certain value (such as 1.5 kPa, which may vary depending on the capacity of the specific boiler unit and the condition of the air preheater equipment), it is considered that the risk of blockage of the air preheater 5 is low. If the economic efficiency of the unit operation is to be improved and the boiler efficiency is to be maximized, the system may be selected to enter the economic operation mode.

[0082] In this economic operation mode, the lowest controllable temperature of the flue gas temperature at the flue gas outlet of the flue gas chamber 131 of the heat pipe heat exchanger 13 is first determined (e.g., 105°C, adjusted according to the actual coal quality of the unit). The flue gas regulating damper 12 is only opened when the inlet flue gas temperature of the SCR reactor 4 does not reach the minimum safe temperature of the catalyst reaction (e.g., it can be set at 310°C), and is gradually adjusted to the inlet flue gas temperature of the SCR reactor 4 to meet the catalyst reaction requirements. The hot water chamber 131 of the heat pipe heat exchanger 13 operates under the economic circulation water volume of the water pump. The required heating temperature of the cold air at the air inlet of the air preheater 5 can be determined by the above fixed parameters, and is achieved by dynamically adjusting the second electric regulating door 143.

[0083] Each embodiment in this specification is described in a progressive manner, and the same or similar parts between the embodiments can be referred to each other, and each embodiment focuses on the differences from other embodiments. In particular, for the system embodiment, since it is basically similar to the method embodiment, the description is relatively simple, and the relevant parts can be referred to the partial description of the method embodiment.

[0084] The above is only an embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various changes and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the scope of the claims of the present application.

Claims

1. A system for eliminating hidden dangers of air preheater operation safety, characterized in that: The invention comprises a low-temperature superheater, an economizer, an SCR reactor and an air preheater which are sequentially arranged in the boiler flue, a bypass flue is arranged between the boiler flue before the low-temperature superheater and the inlet of the SCR reactor, a flue gas regulating damper is arranged at the inlet of the bypass flue, and the flue gas regulating damper is used to adjust the flue gas temperature at the flue gas inlet of the air preheater; A heat pipe heat exchanger is arranged on the flue connected to the flue gas outlet of the air preheater, the heat pipe heat exchanger comprises a flue gas chamber and a hot water chamber, and the heat pipe heat exchanger is used to control the flue gas temperature at the flue gas outlet of the air preheater; It also includes a blower and a primary blower connected to the air inlet of the air preheater, and a heater is respectively arranged at the inlet of the blower and the primary blower, and the heater is used to adjust the cold air temperature at the air inlet of the air preheater; A main water inlet pipe and a main water outlet pipe are arranged outside the hot water chamber and connected to each other; a branch water outlet pipe is arranged on the main water outlet pipe; An air preheater inlet pressure sensor is arranged at the flue gas inlet of the air preheater, and an air preheater outlet pressure sensor is arranged at the flue gas outlet of the air preheater; An SCR reactor inlet smoke temperature sensor is arranged at the inlet of the SCR reactor; a hot water chamber inlet water temperature sensor is arranged at the water inlet of the hot water chamber, and a hot water chamber outlet water temperature sensor is arranged at the water outlet of the hot water chamber; A smoke temperature sensor for the smoke chamber inlet is arranged at the smoke inlet of the smoke chamber, and a smoke temperature sensor for the smoke chamber outlet is arranged at the smoke outlet of the smoke chamber; A first electric regulating door is arranged on the main water inlet pipe; A heater inlet air temperature sensor is provided at the air inlet of the heater, a heater outlet air temperature sensor is provided at the air outlet of the heater, and a second electric regulating door is provided on the branch water outlet pipe; The smoke temperature sensor at the smoke chamber inlet, the smoke temperature sensor at the smoke chamber outlet, the water temperature sensor at the hot water chamber inlet, the water temperature sensor at the hot water chamber outlet, the air temperature sensor at the heater inlet, the air temperature sensor at the heater outlet, the first electric regulating door and the second electric regulating door are all connected to the controller.

2. The air preheater operation safety hazard elimination system according to claim 1 is characterized in that: A dust collector, an induced draft fan, a desulfurization tower and a chimney are sequentially arranged on a flue connected to the flue gas outlet of the air preheater; The heat pipe heat exchanger is arranged between the air preheater and the dust collector; Alternatively, the heat pipe heat exchanger is arranged between the dust collector and the induced draft fan; Alternatively, the heat pipe heat exchanger is arranged between the induced draft fan and the desulfurization tower.

3. The air preheater operation safety hazard elimination system according to claim 1 is characterized in that: The smoke chamber and the hot water chamber are isolated from each other, and at least one heat pipe connecting the smoke chamber and the hot water chamber is arranged in the smoke chamber and the hot water chamber, and the heat pipe is used to transfer the heat of the smoke chamber to the hot water chamber; The water inlet of the hot water chamber is connected to the main water inlet pipe, and the water outlet of the hot water chamber is connected to the main water outlet pipe. The main water outlet pipe is used to transfer the heat in the hot water chamber to the boiler condensate pipe or the boiler feed water pipe.

4. The air preheater operation safety hazard elimination system according to claim 3 is characterized in that: The smoke chamber and the hot water chamber are isolated by a bidirectional partition, and the bidirectional partitions are filled with heat-insulating and anti-corrosion materials.

5. The air preheater operation safety hidden danger elimination system according to claim 1 is characterized in that: The branch water outlet pipe is connected to the water inlet of the air heater, and a branch water inlet pipe is arranged on the main water inlet pipe, and the branch water inlet pipe is connected to the water outlet of the air heater.

6. A control method for eliminating a system for eliminating hidden dangers in the operation of an air preheater according to any one of claims 1 to 5, characterized in that: The following steps are involved: When the differential pressure at the flue gas inlet and outlet of the air preheater is higher than a first differential pressure preset value, the system enters a first operation mode; When the differential pressure at the flue gas inlet and outlet of the air preheater is lower than the first differential pressure preset value and higher than the second differential pressure preset value, the system enters the second operation mode; When the differential pressure at the flue gas inlet and outlet of the air preheater is lower than the second differential pressure preset value, the system enters the third operation mode; The step of operating the system in the first operating mode includes: Increasing the opening of the flue gas damper until the flue gas temperature at the inlet of the SCR reactor rises to the maximum temperature allowed by the SCR reactor; Adjust the opening of the first electric regulating door to increase the water flow rate of the hot water chamber of the heat pipe heat exchanger, and adjust the opening of the second electric regulating door to increase the water flow rate entering the heater; The steps of operating the system in the second operating mode include: Adjust the opening of the second electric regulating door to increase the water flow rate entering the heater to determine the required flue gas temperature at the flue gas inlet of the air preheater; Increase the flue gas flow rate entering the bypass flue so that the flue gas temperature at the flue gas inlet of the air preheater reaches the required flue gas temperature at the flue gas inlet of the air preheater determined above; Adjust the opening of the first electric regulating door to increase the water supply flow rate of the hot water chamber of the heat pipe heat exchanger so that the smoke temperature at the smoke outlet of the smoke chamber of the heat pipe heat exchanger is maintained at a suitable temperature; The steps of operating the system in the third operating mode include: Determine the minimum flue gas temperature required at the flue gas outlet of the heat pipe heat exchanger; When the smoke temperature at the inlet of the SCR reactor is lower than its minimum reaction temperature, the smoke regulating damper is opened to make the smoke temperature at the inlet of the SCR reactor higher than its minimum reaction temperature; The required heating temperature of the air inlet of the air preheater is determined, and the water feed flow entering the heater is adjusted through the second electric regulating door to achieve the required heating temperature of the air inlet of the air preheater.

Images