CN111981465A - A flue gas waste heat utilization system - Google Patents

Abstract

The invention discloses a flue gas waste heat utilization system, which belongs to the field of energy saving and emission reduction of thermal power units. The economizer of the flue gas waste heat utilization system is respectively connected to an air preheater and a bypass flue, and the outlet of the air preheater and the bypass flue are respectively connected. The end of the road flue is connected to the high temperature section flue gas heat exchanger; the feed water heater and the condensate water heater are arranged in series in the bypass flue, the feed water heater is connected in parallel with the high pressure heater pipeline, the condensate water heater and the high temperature section flue gas The heat exchanger is connected in parallel with the low-pressure heater pipeline; the low-temperature section flue gas heat exchanger is set between the high-temperature section flue gas heat exchanger and the flue gas treatment device, and the secondary air heater is set between the blower and the air preheater. A primary air heater is set between the primary fan and the air preheater, and a circulating water system is set between the low temperature section flue gas heat exchanger, the secondary air heater and the primary air heater. The flue gas waste heat utilization system realizes the cascade utilization of boiler flue gas waste heat, and avoids the disadvantage that the air preheater occupies an excessively large area and is difficult to arrange.

Description

A flue gas waste heat utilization system

technical field

The invention relates to the technical field of energy saving and emission reduction of thermal power units, in particular to a system for utilizing waste heat of flue gas.

Background technique

In my country's thermal power plants, 70% to 80% of the overall heat loss of the boiler is exhaust heat loss. When the exhaust gas temperature rises by 10℃～15℃, the boiler efficiency will decrease by 1%, and the annual average standard coal consumption will increase by 3～4g/(kW·h). With the increasingly strict energy conservation and emission reduction policies and rising energy prices, the importance of rational utilization of boiler flue gas waste heat is increasing.

The most common method of traditional flue gas waste heat utilization is to arrange a low-temperature economizer in the tail flue after the air preheater, and use the flue gas waste heat to heat the condensed water in the regenerative system to reduce the extraction steam of the regenerative system. The saved extraction steam enters the subsequent steam turbine to continue to expand and do work, and the total output of the steam turbine increases, thereby improving the economy of the entire unit.

The above-mentioned waste heat utilization scheme of flue gas mainly has the disadvantages that the waste heat of flue gas cannot be used in cascade, the utilization rate of waste heat is low, and the waste of energy is caused.

Therefore, there is an urgent need to propose a flue gas waste heat utilization system to solve the above technical problems existing in the prior art.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a flue gas waste heat utilization system, which can realize the cascade utilization of flue gas waste heat and has high energy utilization rate.

For achieving the above object, the technical scheme adopted in the present invention is:

A flue gas waste heat utilization system, in which an economizer and an air preheater are arranged in sequence in a boiler flue, and the flue gas waste heat utilization system further includes a feed water heater, a condensate water heater, a high temperature section flue gas heat exchanger, a low temperature Section flue gas heat exchanger, low pressure heater group, high pressure heater group, blower, primary fan, primary air heater, secondary air heater and flue gas treatment device;

The low-pressure heater group includes a plurality of low-pressure heaters, and the plurality of low-pressure heaters are connected in turn through a low-pressure heater pipeline; the high-pressure heater group includes a plurality of high-pressure heaters, and the plurality of the high-pressure heaters pass through The pipelines of the high-pressure heaters are connected in sequence; the condensed water passes through the plurality of the low-pressure heaters and the plurality of the high-pressure heaters in sequence and then enters the economizer;

The flue gas outlet of the economizer is respectively connected to the air preheater and the bypass flue of the air preheater, and the outlet of the air preheater and the end of the bypass flue are confluent and communicated To the flue gas inlet of the high temperature section flue gas heat exchanger;

The feed water heater and the condensate water heater are arranged in series in the bypass flue, the feed water heater is connected in parallel to the high-pressure heater pipeline, the condensate water heater and the high temperature section smoke The gas heat exchanger is connected in parallel in the pipeline of the low-pressure heater;

The low temperature section flue gas heat exchanger is arranged between the high temperature section flue gas heat exchanger and the flue gas treatment device, the blower and the primary fan are both communicated with the air preheater, the The secondary air heater is arranged between the blower and the air preheater, the primary air heater is arranged between the primary blower and the air preheater, and the flue gas in the low temperature section is arranged A circulating water system is arranged between the heat exchanger, the secondary air heater and the primary air heater.

As the preferred technical solution of the above-mentioned flue gas waste heat utilization system, the flue gas waste heat utilization system also includes:

The bypass flue regulating valve is arranged in the bypass flue and is used to adjust the amount of flue gas in the bypass flue.

As the preferred technical solution of the above-mentioned flue gas waste heat utilization system, the flue gas waste heat utilization system also includes:

Condensate water inlet pipeline, the water inlet end of the condensate water inlet pipeline is connected with the low pressure heater pipeline, and the water outlet end of the condensate water inlet pipeline is respectively connected with the condensate water heater and the high temperature section The flue gas heat exchanger is connected;

The condensate water inlet regulating valve is arranged in the condensate water inlet pipeline.

As the preferred technical solution of the above-mentioned flue gas waste heat utilization system, the flue gas waste heat utilization system also includes:

a condensate variable frequency circulating pump, arranged in the condensate water inlet pipeline, and the condensate at the outlet of the condensate variable frequency circulating pump respectively flows into the condensate heater and the high temperature section flue gas heat exchanger;

The condensate parallel regulating valve is arranged in the pipeline between the condensate variable frequency circulating pump and the condensate heater, or between the condensate variable frequency circulating pump and the high temperature section flue gas heat exchanger in the pipeline between.

As the preferred technical solution of the above-mentioned flue gas waste heat utilization system, the flue gas waste heat utilization system also includes:

a water supply water inlet pipeline, the water inlet end of the water supply water inlet pipeline is in communication with the high pressure heater pipeline, and the water outlet end of the water supply water inlet pipeline is in communication with the water supply heater;

The water supply water inlet regulating valve is arranged in the water supply water inlet pipeline.

As the preferred technical solution of the above-mentioned flue gas waste heat utilization system, the flue gas waste heat utilization system also includes:

A deaerator is arranged between the low pressure heater group and the high pressure heater group.

As a preferred technical solution of the above-mentioned flue gas waste heat utilization system, the flue gas temperature at the outlet of the high temperature section flue gas heat exchanger is 90°C-100°C, and the flue gas resistance is 100Pa-800Pa.

As a preferred technical solution of the above-mentioned flue gas waste heat utilization system, the flue gas temperature at the outlet of the low temperature section flue gas heat exchanger is 75°C-85°C, and the flue gas resistance is 100Pa-800Pa.

As a preferred technical solution of the above-mentioned flue gas waste heat utilization system, the outlet air temperature of the primary air heater and the secondary air heater is 50°C-90°C, and the air resistance is 100Pa-800Pa.

As a preferred technical solution of the above-mentioned flue gas waste heat utilization system, the amount of flue gas in the bypass flue is 10%-30% of the total amount of flue gas at the outlet of the air preheater.

Compared with the prior art, the beneficial effects of the present invention are:

The flue gas waste heat utilization system proposed by the present invention efficiently recovers and utilizes the heat of the flue gas by coordinating the water supply, condensate water and the heater system. The thermal efficiency is improved, and the efficient utilization of energy is realized; at the same time, the waste heat utilization system of the flue gas can also avoid the disadvantage that the air preheater occupies an excessively large area and is difficult to arrange when the conventional smoke recovery and exhaust system heats the hot air.

Description of drawings

FIG. 1 is a schematic diagram of a flue gas waste heat utilization system provided by a specific embodiment of the present invention.

In the picture:

1. Economizer; 2. Air preheater; 3. Feed water heater; 4. Condensate heater; 5. Flue gas heat exchanger at high temperature; 6. Flue gas heat exchanger at low temperature; 7. Blower; 8. Primary fan; 9. Primary air heater; 10. Secondary air heater; 11. Flue gas treatment device; 12. Bypass flue control valve; 13. Condensate water inlet control valve; 14. Condensation Water frequency conversion circulating pump; 15. Condensate parallel regulating valve; 16. Feed water inlet regulating valve; 17. Deaerator; 18. First low-pressure heater; 19. Second low-pressure heater; 20. Third low-pressure heater 21, the fourth low pressure heater; 22, the first high pressure heater; 23, the second high pressure heater; 24, the third high pressure heater; 25, the booster pump; valve; 27, electrostatic precipitator; 28, induced draft fan.

Detailed ways

In order to make the technical problems solved by the present invention, the technical solutions adopted and the technical effects achieved more clearly, the technical solutions of the present invention are further described below with reference to the accompanying drawings and through specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention, but not to limit the present invention. In addition, it should be noted that, for the convenience of description, the accompanying drawings only show some but not all of the parts related to the present invention.

In the description of the present invention, unless otherwise expressly specified and limited, the terms "connected", "connected" and "fixed" should be understood in a broad sense, for example, it may be a fixed connection, a detachable connection, or an integrated ; It can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, and it can be the internal connection of two elements or the interaction relationship between the two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood in specific situations.

In the present invention, unless otherwise expressly specified and limited, a first feature "on" or "under" a second feature may include the first and second features in direct contact, or may include the first and second features Not directly but through additional features between them. Also, the first feature being "above", "over" and "above" the second feature includes the first feature being directly above and obliquely above the second feature, or simply means that the first feature is level higher than the second feature. The first feature is "below", "below" and "below" the second feature includes the first feature being directly below and diagonally below the second feature, or simply means that the first feature has a lower level than the second feature.

In the description of this embodiment, the terms "up", "down", "left", "right" and other azimuth or positional relationships are based on the azimuth or positional relationship shown in the drawings, which are only for convenience of description and simplification of operations, rather than indicating Or imply that the device or element referred to must have a particular orientation, be constructed and operate in a particular orientation, and therefore should not be construed as limiting the invention. In addition, the terms "first" and "second" are only used for distinction in description, and have no special meaning.

This embodiment discloses a flue gas waste heat utilization system for coordinating water supply, condensate water and air heater systems. Compared with conventional power station boiler systems, the cascade effective utilization of boiler flue gas waste heat can be achieved, and the coal-fired generating set can be effectively reduced. Coal consumption and improve boiler efficiency to achieve efficient use of energy. At the same time, the waste heat utilization system of flue gas can also avoid the disadvantage that the air preheater 2 occupies an excessively large area and is difficult to arrange when the conventional smoke recovery and exhaust system heats hot air.

As shown in Figure 1, the flue gas waste heat utilization system mainly includes an economizer 1, an air preheater 2, a feed water heater 3, a condensate water heater 4, a high temperature section flue gas heat exchanger 5, and a low temperature section flue gas exchange Heater 6 , low pressure heater group, high pressure heater group, blower 7 , primary fan 8 , primary air heater 9 , secondary air heater 10 and flue gas treatment device 11 .

The economizer 1 and the air preheater 2 are arranged in sequence in the boiler flue of the flue gas waste heat utilization system, and the flue gas outlet of the economizer 1 is connected to the air preheater 2 and the bypass flue of the air preheater 2 respectively. , a feed water heater 3 and a condensate water heater 4 are arranged in series in the bypass flue, a part of the flue gas enters the air preheater 2 to heat the air, and the other part of the flue gas enters the bypass flue and flows through the feed water heater 3 and the condensate in turn The water heater 4 heats feed water and condensate water, respectively. The outlet of the air preheater 2 and the end of the bypass flue are confluent and connected to the flue gas inlet of the flue gas heat exchanger 5 in the high temperature section. Optionally, the bypass flue is provided with a bypass flue regulating valve 12 for adjusting the amount of flue gas in the bypass flue, thereby adjusting the proportion of flue gas entering the air preheater 2 and the bypass flue. Preferably, the amount of flue gas in the bypass flue in this embodiment is 10%-30% of the total amount of flue gas at the outlet of the air preheater 2 .

The low-pressure heater group includes a plurality of low-pressure heaters, and the plurality of low-pressure heaters are sequentially communicated through the low-pressure heater pipeline. The water inlet end of the low pressure heater pipeline (shown as A in Figure 1) is connected to an external condensate water source (not shown in the figure), and the water outlet end of the low pressure heater pipeline is connected to the high pressure heater group. Optionally, along the direction from the water inlet end to the water outlet end of the low pressure heater pipeline, the low pressure heater group includes four low pressure heaters, which are the first low pressure heater 18, the second low pressure heater 19, and the third low pressure heater. The inlet of the first low-pressure heater 18 communicates with the condensed water source, and the outlet of the fourth low-pressure heater 21 communicates with the high-pressure heater group. It can be understood that the number of low-pressure heaters included in the low-pressure heater group can be designed according to actual working conditions.

The high-pressure heater group includes a plurality of high-pressure heaters, and the plurality of high-pressure heaters are sequentially connected through the high-pressure heater pipeline. The water inlet end of the high pressure heater pipeline is connected to the water outlet end of the low pressure heater pipeline, and the water outlet end of the high pressure heater pipeline is connected to the economizer 1 . Optionally, along the direction from the water inlet end to the water outlet end of the high pressure heater pipeline, the high pressure heater group includes three high pressure heaters, namely the first high pressure heater 22, the second high pressure heater 23 and the third high pressure heater. The inlet of the first high-pressure heater 22 communicates with the outlet end of the low-pressure heater pipeline, and the outlet of the third high-pressure heater 24 communicates with the economizer 1 . It can be understood that the number of high-pressure heaters included in the high-pressure heater group can be designed according to actual working conditions.

Preferably, a deaerator 17 is provided between the low pressure heater group and the high pressure heater group. The low-pressure heater group, the high-pressure heater group and the deaerator 17 together constitute the heat recovery system of the flue gas waste heat utilization system.

The feedwater heater 3 is connected in parallel to the water inlet and outlet ends of the high-pressure heater pipeline through the water supply water inlet pipeline and the water supply water outlet pipeline. water outlet. Preferably, a feed water inlet regulating valve 16 is provided in the feed water inlet pipeline to adjust the flow rate of the feed water flowing into the feed water heater 3 to ensure that the return water temperature of the feed water meets the outlet water temperature requirement of the third high pressure heater 24 .

The condensate heater 4 and the high temperature section flue gas heat exchanger 5 are connected in parallel in the low pressure heater pipeline, part of the condensate water flows through the condensate water heater 4 to absorb heat and then returns to the low pressure heater pipeline, and the other part of the condensate water flows through the high temperature section The flue gas heat exchanger 5 returns to the low-pressure heater pipeline after absorbing heat.

Specifically, the flue gas waste heat utilization system further includes a condensate water inlet pipeline and a condensate water return pipeline. Wherein, the water inlet end of the condensate water inlet pipeline is connected with the low pressure heater pipeline, and the water outlet end of the condensate water inlet pipeline is connected with the condensate heater 4 and the high temperature section flue gas heat exchanger 5 respectively. More specifically, the condensate water inlet pipeline includes two water inlet branches, namely a first water inlet branch and a second water inlet branch, wherein the first water inlet branch is connected to the first low pressure heater 18 . At the inlet pipe, the second water inlet branch is connected to the outlet pipe of the second low-pressure heater 19. Under this structure, two different temperatures of condensed water are mixed into the condensed water inlet pipe to ensure the water temperature of the mixed condensed water. Meet the inlet water temperature requirements of the condensate heater 4, and ensure that the tube wall of the flue gas heat exchanger 5 in the high temperature section does not undergo low-temperature corrosion. It can be understood that the number of water inlet branches and the communication positions on the low-pressure heater pipeline can be designed according to actual working conditions. The outlet end of the condensate water return pipeline is communicated with the outlet pipeline of the third low-pressure heater 20 .

In order to prevent the low temperature corrosion of the condensate heater 4 and the high temperature section flue gas heat exchanger 5, the flue gas waste heat utilization system also includes a condensate water inlet regulating valve 13, and the condensate water inlet regulating valve 13 is arranged on the first water inlet branch. road or the second inlet branch. By adjusting the opening of the condensate water inlet regulating valve 13, the proportional adjustment of the condensate water flow in the first water inlet branch and the condensate water flow in the second water inlet branch is realized, so as to realize the adjustment of the condensate water heater 4 and the condensate water inlet. Automatic control of condensate water temperature of flue gas heat exchanger 5 in high temperature section. Optionally, the temperature of the condensed water is designed to be 65°C-80°C. The condensate water inlet regulating valve 13 in this embodiment is preferably arranged in the first water inlet branch.

In order to prevent insufficient circulation power caused by insufficient pressure head of the condensate pump (not shown in the figure), the flue gas waste heat utilization system also includes a condensate water variable frequency circulating pump 14, which is arranged in the condensate water inlet pipeline to condense water. The water variable frequency circulating pump 14 provides power for the entire condensate system. The condensate water at the outlet of the condensate variable frequency circulating pump 14 is divided into two paths, one path enters the condensate water heater 4 to absorb the high-quality heat of the flue gas, and the other way enters the high-temperature section flue gas heat exchanger 5 to absorb the waste heat of the flue gas, and the condensate water of the two flows back to the outlet. The water is returned to the outlet pipe of the third low pressure heater 20 through the condensate water return pipe.

Further, the flue gas waste heat utilization system also includes a condensate parallel regulating valve 15, and the condensate parallel regulating valve 15 is arranged in the pipeline between the condensate variable frequency circulating pump 14 and the condensate heater 4, or the condensate variable frequency circulation In the pipeline between the pump 14 and the flue gas heat exchanger 5 in the high temperature section. This embodiment is preferably the former.

Through the condensate parallel regulating valve 15 and the condensate variable frequency circulating pump 14, the flow into the condensate heater 4 and the high temperature section flue gas heat exchanger 5 is jointly adjusted, on the one hand, to ensure that the condensate return water temperature meets the outlet of the third low pressure heater 20 On the other hand, it ensures that the outlet flue gas temperature of the flue gas heat exchanger 5 in the high temperature section meets the operating requirements, so as to prevent the exhaust gas temperature from rising in summer or under high load conditions, causing the flue gas heat exchanger 6 in the low temperature section to recover a large amount of The residual heat of the flue gas causes the outlet air temperature of the primary air heater 9 and the secondary air heater 10 to be overheated.

Specifically, a low temperature section flue gas heat exchanger 6 is arranged between the high temperature section flue gas heat exchanger 5 and the flue gas treatment device 11, the blower 7 and the primary blower 8 are both communicated with the air preheater 2, and the blower 7 and the air A secondary air heater 10 is arranged between the preheaters 2, a primary air heater 9 is arranged between the primary fan 8 and the air preheater 2, a low temperature section flue gas heat exchanger 6, and a secondary air heater A circulating water system is set between the air heater 10 and the primary air heater 9 to achieve the purpose of heating the air with the heat of the flue gas, increase the temperature of the cold air entering the air preheater 2, and reduce the high quality of the original heater system in the power plant. The steam extraction volume of the unit can be reduced, thereby reducing the coal consumption of the unit for power generation. Optionally, the circulating water system is provided with a booster pump 25 and a parallel regulating valve 26 of the low temperature section flue gas heat exchanger, the power of the circulating water is provided by the booster pump 25, and the low temperature section flue gas heat exchanger parallel regulating valve 26 is used. It is used to adjust the amount of water entering the primary air heater 9 and the secondary air heater 10 .

The flue gas treatment device 11 in this embodiment is a desulfurization tower, and an electrostatic precipitator 27 and an induced draft fan 28 are further provided between the flue gas outlet of the high temperature section flue gas heat exchanger 5 and the desulfurization tower. The gas heat exchanger 6 is arranged in the flue between the induced draft fan 28 and the desulfurization tower.

It should be noted that the structures of the economizer 1, the air preheater 2, the electrostatic precipitator 27 and the desulfurization tower in this embodiment are all conventional structures in the prior art, and the specific structures and working principles of this embodiment are Do not make specific statements.

In this embodiment, the flue gas heat exchanger 5 in the high temperature section is a fin-and-tube steam-water heat exchanger arranged in a countercurrent flow. The outlet flue gas temperature of the flue gas heat exchanger 5 in the high temperature section is designed to be 90°C-100°C, and the flue gas resistance is designed to be 100Pa-800Pa.

The flue gas heat exchanger 6 in the low temperature section is a fluoroplastic or PPS plastic alloy tubular heat exchanger arranged in a countercurrent. The flue gas temperature at the outlet of the flue gas heat exchanger 6 in the low temperature section is designed to be 75°C-85°C, and the flue gas resistance is designed to be 100pa-800Pa.

Both the primary air heater 9 and the secondary air heater 10 are spiral fin-and-tube heat exchangers arranged in countercurrent flow. The outlet air temperature of the primary air heater 9 and the secondary air heater 10 is designed to be 50°C-90°C, and the air resistance is designed to be 100Pa-800Pa.

The above embodiments only illustrate the basic principles and characteristics of the present invention. The present invention is not limited by the above embodiments. Without departing from the spirit and scope of the present invention, the present invention also has various changes and changes. These changes and changes are all fall within the scope of the claimed invention. The claimed scope of the present invention is defined by the appended claims and their equivalents.

Claims (10)

1. A flue gas waste heat utilization system, in which an economizer (1) and an air preheater (2) are arranged successively in the boiler flue, it is characterized in that, the flue gas waste heat utilization system also comprises a feed water heater (3) , condensate heater (4), high temperature section flue gas heat exchanger (5), low temperature section flue gas heat exchanger (6), low pressure heater group, high pressure heater group, blower (7), primary fan (8) ), a primary air heater (9), a secondary air heater (10) and a flue gas treatment device (11); The low-pressure heater group includes a plurality of low-pressure heaters, and the plurality of low-pressure heaters are connected in turn through a low-pressure heater pipeline; the high-pressure heater group includes a plurality of high-pressure heaters, and the plurality of the high-pressure heaters pass through The high-pressure heater pipelines are connected in sequence; the condensed water passes through the plurality of the low-pressure heaters and the plurality of the high-pressure heaters in sequence and then enters the economizer (1); The flue gas outlet of the economizer (1) is respectively connected to the air preheater (2) and the bypass flue of the air preheater (2). The outlet and the end of the bypass flue are confluent and connected to the flue gas inlet of the high temperature section flue gas heat exchanger (5); The feed water heater (3) and the condensate water heater (4) are arranged in series in the bypass flue, and the feed water heater (3) is connected in parallel to the high-pressure heater pipeline, and the condensate water heater (3) is connected in parallel in the pipeline of the high-pressure heater. A water heater (4) and the high temperature section flue gas heat exchanger (5) are connected in parallel in the low pressure heater pipeline; The low temperature section flue gas heat exchanger (6) is arranged between the high temperature section flue gas heat exchanger (5) and the flue gas treatment device (11), the blower (7) and the primary fan (8) are all communicated with the air preheater (2), and the secondary air heater (10) is arranged between the blower (7) and the air preheater (2). The primary air heater (9) is arranged between the primary fan (8) and the air preheater (2), the low temperature section flue gas heat exchanger (6), the secondary air heater A circulating water system is arranged between the heater (10) and the primary air heater (9). 2. The flue gas waste heat utilization system according to claim 1, wherein the flue gas waste heat utilization system further comprises: A bypass flue regulating valve (12) is arranged in the bypass flue and is used to adjust the amount of flue gas in the bypass flue. 3. The flue gas waste heat utilization system according to claim 1, wherein the flue gas waste heat utilization system further comprises: Condensate water inlet pipeline, the water inlet end of the condensate water inlet pipeline is communicated with the low pressure heater pipeline, and the water outlet end of the condensate water inlet pipeline is respectively connected with the condensate water heater (4) and the low pressure heater pipeline. The high temperature section flue gas heat exchanger (5) is communicated; A condensate water inlet regulating valve (13) is arranged in the condensate water inlet pipeline. 4. The flue gas waste heat utilization system according to claim 3, wherein the flue gas waste heat utilization system further comprises: A condensed water variable frequency circulating pump (14), which is arranged in the condensed water inlet pipeline, and the condensed water at the outlet of the condensed water variable frequency circulating pump (14) flows into the condensed water heater (4) and the condensed water heater (4) and the condensed water respectively. High temperature section flue gas heat exchanger (5); A condensate parallel regulating valve (15), which is arranged in the pipeline between the condensate variable frequency circulating pump (14) and the condensate heater (4), or is arranged in the condensate variable frequency circulating pump (14) ) and the pipeline between the high temperature section flue gas heat exchanger (5). 5. The flue gas waste heat utilization system according to claim 1, wherein the flue gas waste heat utilization system further comprises: a water supply water inlet pipeline, the water inlet end of the water supply water inlet pipeline is connected with the high pressure heater pipeline, and the water outlet end of the water supply water inlet pipeline is connected with the water supply heater (3); The feed water inlet regulating valve (16) is arranged in the feed water inlet pipeline. 6. The flue gas waste heat utilization system according to claim 1, wherein the flue gas waste heat utilization system further comprises: A deaerator (17) is arranged between the low pressure heater group and the high pressure heater group. 7. The flue gas waste heat utilization system according to claim 1, wherein, The flue gas temperature at the outlet of the high temperature section flue gas heat exchanger (5) is 90°C-100°C, and the flue gas resistance is 100Pa-800Pa. 8. The flue gas waste heat utilization system according to claim 1, wherein, The flue gas temperature at the outlet of the low temperature section flue gas heat exchanger (6) is 75°C-85°C, and the flue gas resistance is 100Pa-800Pa. 9. The flue gas waste heat utilization system according to claim 1, characterized in that, The outlet air temperature of the primary air heater (9) and the secondary air heater (10) is 50°C-90°C, and the air resistance is 100Pa-800Pa. 10. The flue gas waste heat utilization system according to claim 1, wherein, The flue gas volume in the bypass flue is 10%-30% of the total flue gas volume at the outlet of the air preheater (2).

Images