A drain structure for a warm air heater to prevent fouling and blockage of an air preheater in winter

Abstract

The present invention provides a drain structure for a warm air heater to prevent fouling and blockage of an air preheater in winter, which is characterized in that: the main drain pipe of the primary air warm air heater is connected to the warm air heater drain tank through a pipeline and a valve. One end of the main drain pipe is connected to the warm air heater drain tank, and the other end is connected to an exhaust device through a drain pipe. A regulating valve group for draining the warm air heater to the exhaust device is provided on the main drain pipe; the main drain pipe of the primary air warm air heater is connected to a fixed drain expansion vessel I through a pipeline and an isolating valve, and the main drain pipe of the secondary air warm air heater is connected to a fixed drain expansion vessel II through a pipeline and an isolating valve. The present invention provides a drain structure for a warm air heater to prevent fouling and blockage of an air preheater in winter, which is safe and reliable in operation and avoids affecting other equipment and the entire unit.

Description

Technical Field

[0001] The present invention relates to a drain structure of a warm air heater for preventing fouling and blockage of an air preheater in winter. Background Art

[0002] At present, two sets of warm air heaters are installed on both sides of a power station boiler for the primary and secondary cold air systems respectively. The steam from a low-pressure auxiliary steam header is used to heat the primary and secondary cold air, so as to increase the metal wall temperature at the cold end of the air preheater, ensure that the comprehensive temperature at the cold end of the air preheater is higher than the acid dew point temperature, avoid low-temperature corrosion of the air preheater, and prevent the formation of ammonium bisulfate at the same time. The drain system of its warm air heater is as follows: 1. The inlet and exhaust device. After the primary and secondary cold air is collected in a main pipe, it enters the drain tank of the warm air heater. Through the frequency conversion control (liquid level) of the drain pump, the water in the drain tank is pumped into the exhaust device. The system involves many devices, with a large amount of maintenance work. Problems often occur with the drain pump and frequency converter, etc., resulting in the drain water being discharged to the regular drain expansion tank and wasted, and it may also cause poor drainage and freeze the warm air heater; 2. Enter the regular drain expansion tank. The drains of the four sets of warm air heaters on both sides of the boiler pass through the drainers of each set of warm air heaters respectively. After steam-water separation, the drain water enters the drain tank of the warm air heater through a centralized drain main pipe, and is pumped into the regular drain expansion tank through the drain pump, or directly through a pipeline to the regular drain expansion tank to discharge the drain water when the system is started or the drain water quality is unqualified.

[0003] The control of the warm air heater system is the regulation on the steam supply side. The regulation on the drain side only has a manual throttle drain manual valve. The outlet air temperature of the warm air heater is controlled by the steam supply regulating valve of each set of warm air heaters, and the heat exchange capacity of the warm air heater is controlled by the opening degree of the steam supply regulating valve. Occasionally, the manual valve on the drain side is throttled to control the drain water temperature and the outlet air temperature.

[0004] After the warm air heater system is put into operation, the drain valve frequently fails, resulting in poor drainage. There have been multiple cases where the heat exchange tubes of the warm air heater are frozen, cracked, leaking water and steam. After the maintenance personnel removed the drain valve, the situation was alleviated.

[0005] After the warm air heater system is put into operation, the drain pump of the warm air heater and the variable frequency drain control system frequently fail, resulting in the drain water being discharged to the regular drain expansion tank through the pipeline, and only a small part is recycled, causing a large amount of waste of working medium. An attempt is made to directly recycle the drain water to the exhaust device through the recycle pipe of the warm air heater drain pump, the outlet pipe of the drain pump to the exhaust device pipeline, basically realizing the recycling of the working medium.

[0006] After the initial transformation of the air preheater system, the system operates basically stably and reliably, and the outlet air temperature of the air preheater can meet the requirements. With the increase in the operation time of the system, the decrease in ambient temperature, and the increase in boiler load during the winter heating period, a larger steam inlet volume is required to increase the outlet air temperature of the air preheater, and the drain temperature gradually increases. When the primary air and secondary air preheaters ensure the outlet air temperature, due to different steam consumption, there is a large deviation in the drain temperature between the primary air preheater and the secondary air preheater, resulting in water hammer in the drain main pipe and frequent leakage problems in the main pipe. In addition, the drain of the plant heating device is discharged to the drain main pipe of the primary and secondary air preheaters through pipelines, further aggravating the imbalance of the three-party drain temperatures in the drain main pipe and intensifying the water hammer phenomenon of the air preheater drain main pipe. The packing and flange of the valves related to the drain main pipe frequently leak, and the drain main pipe leaks.

[0007] There are many problems in the existing air preheater drain system: the drain valve fails, and the steam-water separation function cannot be realized. Only a small amount of drain passes through the drain valve, and the drain of the air preheater cannot be discharged in time, resulting in a large amount of the heating medium (auxiliary steam) of the air preheater not entering, directly leading to a decrease in the heat exchange capacity of the air preheater and a small increase in the air temperature. Due to the limited drain discharge capacity, the flow capacity of the entire system is greatly weakened, and the entire air preheater system cannot operate normally. If the drain of the air preheater cannot be discharged in time, a large amount of drain will accumulate in the air preheater. The air preheater itself can no longer heat the air further. When the ambient temperature drops, ice may form inside the air preheater, causing the heat exchange pipes of the air preheater to freeze and crack, resulting in leakage, causing ash accumulation in the air preheater and at the cold end of the air preheater, increasing the resistance of the air preheater and the preheater, and causing the fan to surge, affecting the normal and safe operation of the air preheater. Currently, the drain of the air preheater is directly connected to the exhaust device side through pipelines, and the existing drain valve has been removed. Uncondensed steam may appear and be discharged into the exhaust device, which will affect the back pressure of the unit and thus affect the safe operation of the unit. There are many devices in the entire drain system (including pipeline flanges, gate valves, regulating valves, etc.). Water hammer in the drain main pipe occurs frequently. If a certain device is not tightly sealed and leaks, it will also have a great impact on the back pressure of the exhaust device, and even affect the safe and economic operation of the entire unit. Summary of the Invention

[0008] The technical problem to be solved by the present invention is that the existing drain system of the air preheater can no longer meet the requirements for the safe and reliable operation of the entire air preheater system.

[0009] To solve the above technical problems, the technical solution of the present invention is to provide a drain structure for a warm air heater to prevent fouling and blockage of an air preheater in winter, which includes a first warm air heater and a second warm air heater on both sides of a boiler in a primary cold air system, and a third warm air heater and a fourth warm air heater on both sides of the boiler in a secondary cold air system. Drain pipes are respectively provided on the first warm air heater, the second warm air heater, the third warm air heater and the fourth warm air heater. The drain pipes of the first warm air heater and the second warm air heater are connected to a common primary air warm air heater drain main pipe, and the drain pipes of the third warm air heater and the fourth warm air heater are connected to a common secondary air warm air heater drain main pipe. It is characterized in that: the primary air warm air heater drain main pipe is connected to a warm air heater drain tank through a pipe and a valve. One end of the main drain pipe is connected to the warm air heater drain tank, and the other end is connected to an exhaust device through a drain pipe. A regulating valve group for draining the warm air heater to the exhaust device is provided on the main drain pipe; the primary air warm air heater drain main pipe is connected to a constant drainage expansion vessel 1 through a pipe and an isolation valve, and the secondary air warm air heater drain main pipe is connected to a constant drainage expansion vessel 2 through a pipe and an isolation valve.

[0010] Preferably, the regulating valve group for draining the warm air heater to the exhaust device includes an electric control valve, an electric stop valve, a manual stop valve and a bypass manual valve.

[0011] Preferably, there is an isolation manual valve before the drain pipe enters the exhaust device.

[0012] Preferably, a third set of warm air heater drain stop valves is provided on the drain pipe connecting the third warm air heater and the secondary air warm air heater drain main pipe; a fourth set of warm air heater drain stop valves is provided on the drain pipe connecting the fourth warm air heater and the secondary air warm air heater drain main pipe; before the third set of warm air heater drain stop valves and the fourth set of warm air heater drain stop valves, there is a pipe valve connected to the primary air warm air heater drain main pipe respectively.

[0013] Preferably, a safety valve is provided at the top of the warm air heater drain tank.

[0014] Preferably, a local pressure gauge is provided at the top of the warm air heater drain tank.

[0015] Preferably, a remote transmission liquid level gauge and a local liquid level gauge are provided on the warm air heater drain tank.

[0016] Preferably, a drain sampling valve is provided at the lower part of the warm air heater drain tank.

[0017] Preferably, remote transmission thermometers are respectively provided on the drain pipes connecting the first warm air heater and the primary air warm air heater drain main pipe, the drain pipes connecting the second warm air heater and the primary air warm air heater drain main pipe, the drain pipes connecting the third warm air heater and the secondary air warm air heater drain main pipe, and the drain pipes connecting the fourth warm air heater and the secondary air warm air heater drain main pipe.

[0018] Preferably, a first set of air heater stop valves and a second set of air heater stop valves are respectively provided on the drain pipe connecting the first air heater to the drain main pipe of the primary air preheater and on the drain pipe connecting the second air heater to the drain main pipe of the primary air preheater.

[0019] The present invention provides a drain structure for a winter air preheater anti-fouling and anti-blocking device that is safe and reliable in operation and avoids affecting other equipment and the entire unit, and has the following advantages:

[0020] 1) Reducing the defects of the drain main pipe of the air heater caused by water hammer in the pipeline;

[0021] 2) Reducing the power consumption and maintenance costs of the drain pump and frequency converter;

[0022] 3) Ensuring that most of the defects occurring in the winter air heater drain can be eliminated without shutting down the air heater operation, ensuring that the inlet air temperature of the air preheater is not lower than 20 °C, thereby reducing the risks of air preheater blockage and low-temperature corrosion of the air preheater;

[0023] 4) Simple structure, convenient operation and control, and low transformation cost, ensuring the normal and safe operation of the air heater system and avoiding affecting the safe and stable operation of equipment such as the air preheater, fan and exhaust device. Description of the Drawings

[0024] Figure 1 is the system diagram before the transformation of the present invention;

[0025] In the figure: 1. First air heater; 2. Second air heater; 3. Third air heater; 4. Fourth air heater; 5. Fixed drainage expansion vessel (from the drain main pipe 6 of the air heater); 6. Drain main pipe of the air heater; 7. Drain pump of the air heater drainage tank; 8. Liquid level gauge of the air heater drainage tank; 9. Air heater drainage tank; 10. Pipe for draining air heater water to the exhaust device; 11. Recirculation pipe of the air heater drain pump; 12. Regulation valve group (for draining air heater water to the exhaust device); 13. Pipe for draining factory area heating water to the drain main pipe of the air heater.

[0026] Figure 2 is the system diagram after the transformation of the present invention;

[0027] In the figure: 1. First air heater; 2. Second air heater; 3. Third air heater; 4. Fourth air heater; 17. Regular blowdown flash tank (from the drain main pipe 14 of the secondary air heater); 18. Drain main pipe of the primary air heater; 7. Drain pump of the air heater drain tank; 8. Level gauge of the air heater drain tank; 9. Air heater drain tank; 10. Pipe for draining air heater water to the exhaust device; 11. Recirculation pipe of the air heater drain pump; 12. Control valve group for draining air heater water to the exhaust device; 19. Pipe for draining plant heating water to the air heater drain tank; 14. Drain main pipe of the secondary air heater; 15. Drain valve group of the secondary air heater, with the front drain connected to the drain main pipe 18 of the primary air heater; 16. Regular blowdown flash tank (from the drain main pipe 18 of the primary air heater). Detailed implementation mode

[0028] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of this application.

[0029] Embodiment 1

[0030] A drain structure for an air heater to prevent fouling and blockage in winter air preheaters, including the first air heater 1 and the second air heater 2 on both sides of the primary cold air system of the boiler, and the third air heater 3 and the fourth air heater 4 on both sides of the secondary cold air system of the boiler. The first air heater 1, the second air heater 2, the third air heater 3, and the fourth air heater 4 are respectively provided with drain pipes. The first and second air heaters share a common drain main pipe 18 of the primary air heater, and the drains of the third and fourth air heaters share a common drain main pipe 14 of the secondary air heater. The drain main pipe 18 of the primary air heater is connected to the air heater drain tank 9 through a pipe and a valve. A main drain pipe is connected below the air heater drain tank 9. An electric control valve, an electric stop valve, a manual stop valve, and a bypass manual valve are provided on the main drain pipe, that is, the control valve group 12 for draining air heater water to the exhaust device. The main drain pipe is connected to the exhaust device through a drain pipe. There is an isolation manual valve before the drain pipe enters the exhaust device. The drain main pipe 18 of the primary air heater is connected to the regular blowdown flash tank 16 through a pipe and an isolation valve. The drain main pipe 14 of the secondary air heater is connected to the regular blowdown flash tank 17 through a pipe and an isolation valve. Before the drain stop valves of the third and fourth sets of air heaters, there is a pipe valve connected to the drain main pipe 15 of the primary air heater respectively.

[0031] Embodiment 2

[0032] For the heater drain structure for preventing fouling and blockage of the winter air preheater according to Embodiment 1, there is no drain valve in the drain systems of the first heater 1, the second heater 2, the third heater 3, and the fourth heater 4. By throttling the heater drain valve group and the steam supply regulating valve of the heater, the drain temperature and the primary and secondary air temperatures at the inlet of the air preheater are controlled within the qualified range.

[0033] Embodiment 3

[0034] For the heater drain structure for preventing fouling and blockage of the winter air preheater according to Embodiment 1 or 2, the drains of the first heater 1 and the second heater 2 are collected in the same primary air heater drain main pipe 18, and the drains of the third heater 3 and the fourth heater 4 are collected in the same secondary air heater drain main pipe 14. They enter the heater drain tank 9 through pipeline valves respectively. This avoids a large deviation between the drain temperature of the primary air heater and the drain temperature of the secondary air, and prevents the formation of a gas-liquid two-phase flow and water hammer phenomenon.

[0035] Embodiment 4

[0036] According to Embodiment 1 Figure 2 , for the heater drain structure for preventing fouling and blockage of the winter air preheater, when there is a leak in the secondary air heater drain main pipe 14 of the third heater 3 and the fourth heater 4 and it needs to be taken out for maintenance, it can be connected to the primary air heater drain main pipe 18 through the secondary air heater drain valve group 15 to ensure that the secondary air heater does not stop operating, ensure the cold air temperature at the inlet of the air preheater, and achieve the purpose of overhauling the main pipe.

[0037] Embodiment 5

[0038] For the heater drain structure for preventing fouling and blockage of the winter air preheater according to Embodiment 1, the main drain pipe at the outlet of the heater drain tank 9 directly discharges the heater drain to the exhaust device. The liquid level of the heater drain tank 9 controls the exhaust device to prevent vacuum leakage, not affect the back pressure, and ensure the safe operation of the unit.

Claims

1. A warm air heater drain structure for preventing fouling and blockage of an air preheater in winter, comprising a first warm air heater and a second warm air heater on both sides of a boiler in a primary cold air system, and a third warm air heater and a fourth warm air heater on both sides of the boiler in a secondary cold air system. The first warm air heater, the second warm air heater, the third warm air heater and the fourth warm air heater are respectively provided with drain pipes. The drain pipes of the first warm air heater and the second warm air heater are connected to a common primary air warm air heater drain main pipe, and the drain pipes of the third warm air heater and the fourth warm air heater are connected to a common secondary air warm air heater drain main pipe. It is characterized in that: The drain main pipe of the primary air preheater is connected to the preheater drain tank through pipelines and valves. One end of the main drain pipeline is connected to the preheater drain tank, and the other end is connected to the exhaust device through a drain pipeline. An adjusting valve group for draining the preheater to the exhaust device is provided on the main drain pipeline; the drain main pipe of the primary air preheater is connected to the fixed drainage expansion vessel 1 through a pipeline and an isolating valve, and the drain main pipe of the secondary air preheater is connected to the fixed drainage expansion vessel 2 through a pipeline and an isolating valve; A third set of preheater drain stop valves is provided on the drain pipeline connecting the third preheater and the drain main pipe of the secondary air preheater; a fourth set of preheater drain stop valves is provided on the drain pipeline connecting the fourth preheater and the drain main pipe of the secondary air preheater; in front of the third set of preheater drain stop valves and the fourth set of preheater drain stop valves, there is a pipeline valve connected to the drain main pipe of the primary air preheater respectively; There is no drain valve in the drain systems of the first preheater, the second preheater, the third preheater and the fourth preheater. The drain temperature and the primary and secondary air temperatures at the inlet of the air preheater are controlled within the qualified range by throttling through the preheater drain valve group and the steam supply regulating valve of the preheater.

2. The drain structure of the warm air heater for preventing fouling and blockage of the air preheater in winter according to claim 1, characterized in that, The adjusting valve group for draining the preheater to the exhaust device includes an electric regulating valve, an electric stop valve, a manual stop valve and a bypass manual valve.

3. The drain structure of the warm air heater for preventing fouling and blockage of the air preheater in winter according to claim 1, characterized in that, There is an isolating manual valve before the drain pipeline enters the exhaust device.

4. The drain structure of the warm air heater for preventing fouling and blockage of the air preheater in winter according to claim 1, characterized in that, A safety valve is provided at the top of the preheater drain tank.

5. The drain structure of the warm air heater for preventing fouling and blockage of the air preheater in winter according to claim 1, characterized in that, A local pressure gauge is provided at the top of the preheater drain tank.

6. The drain structure of the warm air heater for preventing fouling and blockage of the air preheater in winter according to claim 1, characterized in that, A remote transmission liquid level gauge and a local liquid level gauge are provided on the preheater drain tank.

7. The drain structure of the warm air heater for preventing fouling and blockage of the air preheater in winter according to claim 1, characterized in that, A drain sampling valve is provided at the lower part of the preheater drain tank.

8. The drain structure of the warm air heater for preventing fouling and blockage of the air preheater in winter according to claim 1, characterized in that, Remote transmission thermometers are respectively provided on the drain pipelines connecting the first preheater and the drain main pipe of the primary air preheater, the second preheater and the drain main pipe of the primary air preheater, the third preheater and the drain main pipe of the secondary air preheater, and the fourth preheater and the drain main pipe of the secondary air preheater.

9. The drain structure of the warm air heater for preventing fouling and blockage of the air preheater in winter according to claim 1, characterized in that, A first set of preheater stop valves and a second set of preheater stop valves are respectively provided on the drain pipelines connecting the first preheater and the drain main pipe of the primary air preheater, and the second preheater and the drain main pipe of the primary air preheater.

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