CN115200005A - A flue gas waste heat utilization system based on the boiler system itself - Google Patents

Abstract

The invention belongs to the technical field of boilers, and in particular relates to a flue gas waste heat utilization system based on the boiler system itself. The technical scheme is as follows: a flue gas waste heat utilization system based on the boiler system itself, comprising a boiler main body, an inlet flue is connected to the tail of the boiler, an air preheater is connected to the inlet flue, and the other end of the air preheater is connected to a The outlet flue also includes a primary air duct and a secondary air duct. Both the primary air duct and the secondary air duct pass through the air preheater. The primary air duct is connected to the coal mill, and the outlet end of the coal mill is connected to the main body of the boiler through pipes. connection, the secondary air duct is connected to the main body of the boiler; a bypass heating system is connected between the inlet flue and the outlet flue, and the bypass heating system is connected to the pipeline between the coal mill and the boiler main body. The invention provides a flue gas waste heat utilization system that absorbs the waste heat of flue gas by the boiler system itself to improve the taste of energy utilization.

Description

A flue gas waste heat utilization system based on the boiler system itself

technical field

The invention belongs to the technical field of boilers, and particularly relates to a flue gas waste heat utilization system based on the boiler system itself.

Background technique

The exhaust gas temperature of large power station boilers is generally controlled at around 120 °C, which is difficult to further reduce due to various factors. Driven by the national policy of energy conservation and emission reduction, flue gas waste heat utilization technologies emerge in an endless stream. The flue gas waste heat utilization system can be classified into three forms: 1) flue gas cooler (low temperature economizer); 2) cold air heater + flue gas cooler; 3) cold air heater + air preheater bypass system.

1) Figure 2 is a schematic diagram of the system of the flue gas cooler (low temperature economizer). The heating surface of the flue gas cooler is arranged in the flue from the outlet of the air preheater to the inlet of the dust collector to absorb the waste heat of the flue gas at the tail of the boiler. This part of the absorbed heat is used to displace the extraction steam from the low-pressure condensate system of the turbine, and the displaced extraction steam continues to enter the downstream of the turbine to do work, thereby achieving the purpose of improving the efficiency of the unit.

2) Figure 3 is a schematic diagram of the system of cold air heater + flue gas cooler, the system consists of two systems of cold air heater and flue gas cooler. The cold air heater increases the inlet cold air temperature of the air preheater, and the exhaust gas temperature at the air preheater outlet also increases accordingly. The flue gas cooler is arranged in the flue between the outlet of the air preheater and the flue gas temperature reduction section of the cold air heater, and utilizes the waste heat of the flue gas whose temperature has been raised. The cold air heater improves the quality of the waste heat of the tail flue gas. Compared with the single flue gas cooler system, the efficiency of the unit is improved by a higher degree.

3) Fig. 4 is a system schematic diagram of a cold air heater + air preheater bypass system. The system consists of a cold air heater and an air preheater bypass system. The function of the cold air heater is to increase the temperature of the cold air at the inlet of the air preheater, while keeping the temperature at the outlet of the air preheater unchanged, correspondingly increasing the cold end metal Wall temperature to prevent corrosion and clogging problems at the cold end of the air preheater. The air preheater flue gas bypass consists of two-stage high-pressure and low-pressure flue gas coolers arranged in the air preheater bypass flue. Extraction steam; the low-pressure flue gas cooler uses the absorbed flue gas waste heat to heat part of the low-pressure condensate water, thereby displacing the extraction steam from the low-pressure cylinder of the turbine. Because the bypass flue gas temperature is higher, the waste heat grade is higher, and the exhaust steam of the high-pressure cylinder is squeezed out, it is better than the above-mentioned two flue gas waste heat utilization methods in improving the efficiency of the unit.

It can be seen from the above analysis that although the system configurations of the three flue gas waste heat utilization systems are different and the energy-saving effects are different, they have one thing in common: the flue gas waste heat acts on the turbine regenerative system, which is used to displace the steam extraction of the turbine, and its energy utilization of relatively low quality.

Large-scale power station boilers use a medium-speed grinding and cooling primary air pulverizing system. The hot primary air at the outlet of the air preheater enters the pulverizer to dry the pulverized coal, and forms a mixture of pulverized coal from the pulverized coal pipe at the outlet of the pulverizer and enters the boiler for combustion. In recent years, the generalized regenerative theory has been developed rapidly, and the technology of using the extraction steam of the steam turbine as the heat source to heat the primary air powder at the outlet of the coal mill has appeared. That is, there is a technology of directly heating the primary air powder by using the steam extraction of a steam turbine, and there is also a technology of indirect heating through a heat transfer medium. But the heat source is from the recuperation of the steam turbine.

The above three waste heat utilization methods of flue gas and primary air powder heating technology all have the coupling of boiler and steam turbine, the operation control is complicated, and the efficiency improvement of the unit is limited.

SUMMARY OF THE INVENTION

In order to solve the above problems existing in the prior art, the purpose of the present invention is to provide a flue gas waste heat utilization system that absorbs the flue gas waste heat by the boiler system itself to improve the quality of the utilization energy.

The technical scheme adopted in the present invention is:

A flue gas waste heat utilization system based on the boiler system itself, including a boiler main body, an inlet flue is connected to the tail of the boiler, an air preheater is connected to the inlet flue, and the other end of the air preheater is connected to an outlet flue, and Including the primary air duct and the secondary air duct, both the primary air duct and the secondary air duct pass through the air preheater, the primary air duct is connected to the coal mill, the outlet end of the coal mill is connected to the main body of the boiler through pipes, and the secondary air The duct is connected to the boiler main body; a bypass heating system is connected between the inlet flue and the outlet flue, and the bypass heating system is connected to the pipeline between the coal mill and the boiler main body.

In the present invention, the waste heat of flue gas is recovered to the air-powder mixture at the outlet of the coal mill, and the waste heat enters the boiler system, which is equivalent to directly reducing the exhaust gas temperature, effectively improving the efficiency of the boiler, the heat grade is high, and the energy saving effect is remarkable. After the temperature of the air-powder mixture is increased, the ignition heat is reduced, and the stable combustion ability is improved; the effect on burning low-volatile coal is better. The temperature of the air-powder mixture is increased, the ignition is advanced, and the combustion efficiency is improved; the effect of burning low-volatile coal is better.

As a preferred solution of the present invention, the bypass heating system includes a bypass flue, the bypass flue is connected between the inlet flue and the outlet flue, and a flue gas heat conduction medium heat exchanger is connected to the bypass flue. A heat-conducting medium air-powder mixture heater is connected to the pipeline between the coal machine and the boiler main body, and a heat-conducting medium circulating pipeline is connected between the flue gas heat-conducting medium heat exchanger and the heat-conducting medium air-powder mixture heater. The heat-conducting medium absorbs the heat of the flue gas in the heat-conducting medium heat exchanger of the flue gas, the temperature of the heat-conducting medium rises, the temperature of the flue gas decreases, and the low-temperature flue gas returns to the outlet flue of the air preheater. The heat-conducting medium heats the air-powder mixture at the outlet of the coal mill in the heat-conducting medium air-powder mixture heat exchanger, the temperature of the heat-conducting medium drops, and the air-powder mixture rises.

As a preferred solution of the present invention, a regulating oil tank and a pressurizing pump are connected to the heat transfer medium circulating pipeline. The pressurizing pump can adjust the circulation rate of the heat transfer medium, and the adjusting oil tank can supplement the heat transfer medium to the adjusting heat transfer medium circulation pipeline.

As a preferred solution of the present invention, a heat medium water system is also connected to the outlet flue, the heat medium water system is connected to the primary air duct and the secondary air duct respectively, and the heat medium water system is located on the outlet flue. The bypass heating system is far away from the air side of the preheater. The heat medium water system reduces the exhaust gas temperature, increases the inlet air temperature of the conventional air preheater, and accordingly increases the metal wall temperature of the cold end, which can effectively prevent the corrosion and blockage of the cold end. The heat of the heated air is recovered by the boiler system, which further improves the thermal efficiency of the boiler.

As a preferred solution of the present invention, the heat medium water system includes a flue gas cooler, the flue gas cooler is connected to the outlet flue, the flue gas cooler is connected with a water circulation pipeline, and the water circulation pipeline is connected in parallel with a primary heater and For the secondary air heater, the primary air heater is connected to the primary air duct, and the secondary air heater is connected to the secondary air duct. The heat medium water absorbs the heat of the flue gas in the flue gas cooler, the temperature of the heat medium water rises, and the temperature of the flue gas decreases. The heat medium water heats the cold primary air and the cold secondary air in the primary air heater and the secondary air heater respectively, the temperature of the heat medium water decreases and the temperature of the cold air increases.

As a preferred solution of the present invention, an organic unit condensate water system is also connected in parallel with the water circulation pipeline. The heat medium water system is also connected and coupled with the condensate water system of the unit. When the boiler's own waste heat recovery capacity is insufficient due to coal types, environmental reasons and operating load reasons, it can be adjusted through the condensate water system. When the residual heat of the flue gas is abundant, the condensed water can be heated through the connection system to transfer the residual heat of the flue gas to the condensed water system; when the ambient temperature is low or the load is low, the heat of the condensed water can be used to heat the cold air through the connecting system, Avoid the effect of low exhaust gas temperature on the air preheater and dust collector.

As a preferred solution of the present invention, a dust collector is connected to the end of the outlet flue. The dust collector can remove dust from the flue gas to ensure that the flue gas meets the emission standards.

As a preferred solution of the present invention, a temperature-adjusting air duct is connected to the primary air duct, one end of the temperature-adjusting air duct is connected to a section before the primary air duct enters the air preheater, and the other end of the temperature-adjusting air duct is connected to the primary air duct The duct extends beyond the air preheater. The temperature-adjusting air duct adjusts the temperature of the primary air entering the coal mill by controlling the proportion of the primary air entering the air preheater.

As a preferred solution of the present invention, an adjustment baffle is arranged on the bypass flue. Adjusting the baffle can adjust the amount of flue gas entering the bypass flue, and then adjust the waste heat utilization of the bypass heating system.

As a preferred solution of the present invention, a primary fan is connected to the primary air duct, and a secondary fan is connected to the secondary air duct.

The beneficial effects of the present invention are:

1. In the present invention, the waste heat of flue gas is recovered to the air-powder mixture at the outlet of the coal mill, and the waste heat enters the boiler system, which is equivalent to directly reducing the exhaust gas temperature, effectively improving the efficiency of the boiler, the heat grade is high, and the energy saving effect is remarkable.

2. The heat medium water heats the cold primary air and the cold secondary air in the primary air heater and the secondary air heater respectively, the temperature of the heat medium water drops, and the temperature of the cold air rises. The heat of the heated air is recovered by the boiler system, so that the heat of the flue gas is further recycled by the boiler itself, and the thermal efficiency of the boiler is further improved.

3. The heat medium water system reduces the exhaust gas temperature, increases the inlet air temperature of the conventional air preheater, and correspondingly increases the metal wall temperature of the cold end, which can effectively prevent the corrosion and blockage of the cold end.

4. After the temperature of the air-powder mixture is increased, the ignition heat is reduced, and the stable combustion ability is improved; the effect of burning low-volatile coal is better. The temperature of the air-powder mixture is increased, the ignition is advanced, and the combustion efficiency is improved; the effect of burning low-volatile coal is better.

5. The heat medium water system is also connected and coupled with the condensate water system of the unit. When the boiler's own waste heat recovery capacity is insufficient due to coal types, environmental reasons and operating load reasons, it can be adjusted through the condensate water system. When the residual heat of the flue gas is abundant, the condensed water can be heated through the connection system to transfer the residual heat of the flue gas to the condensed water system; when the ambient temperature is low or the load is low, the heat of the condensed water can be used to heat the cold air through the connecting system, Avoid the effect of low exhaust gas temperature on the air preheater and dust collector.

Description of drawings

Fig. 1 is the structural representation of the present invention;

Fig. 2 is the system schematic diagram of flue gas cooler (low temperature economizer);

Fig. 3 is the system schematic diagram of cold air heater + flue gas cooler;

Figure 4 is a system schematic diagram of a cold air heater + air preheater bypass system.

In the figure: 1- boiler body; 2- air preheater; 3- flue gas heat transfer medium heat exchanger; 4- heat transfer medium air-powder mixture heater; 5- pressurization pump; 6- regulating oil tank; 7- valve group ; 8- coal mill; 9- flue gas cooler; 10- secondary air heater; 11- primary air heater; 12- unit condensate system; 13- secondary fan; 14- primary fan; 15 - Dust collector; 16-inlet flue; 17-bypass flue; 18-exit flue; 19-secondary air duct; 20-primary air duct; 21-tempering air duct; 22-heat medium water system; 23-Heat conduction medium circulation pipeline; 24-Water circulation pipeline; 25-Bypass heating system.

Detailed ways

In order to make the purposes, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments These are some embodiments of the present invention, but not all embodiments. The components of the embodiments of the invention generally described and illustrated in the drawings herein may be arranged and designed in a variety of different configurations.

Thus, the following detailed description of the embodiments of the invention provided in the accompanying drawings are not intended to limit the scope of the invention as claimed, but are merely representative of selected embodiments of the invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention. It should be noted that the embodiments of the present invention and the features of the embodiments may be combined with each other under the condition of no conflict.

As shown in FIG. 1 , the flue gas waste heat utilization system based on the boiler system itself in this embodiment includes a boiler main body 1 , an inlet flue 16 is connected to the tail of the boiler, and an air preheater 2 is connected to the inlet flue 16 . The other end of the heater 2 is connected with an outlet flue 18, and also includes a primary air duct 20 and a secondary air duct 19. Both the primary air duct and the secondary air duct 19 pass through the air preheater 2, and the primary air duct 20 is connected to the mill. The coal mill 8, the outlet end of the coal mill 8 is connected to the boiler main body 1 through pipes, and the secondary air duct 19 is connected to the boiler main body 1; a bypass heating system 25 is connected between the inlet flue 16 and the outlet flue 18, The bypass heating system 25 is connected to the pipeline between the coal mill 8 and the boiler body 1; the primary air duct 20 is connected to the primary fan 14, and the secondary air duct 19 is connected to the secondary fan 13; the outlet A dust collector 15 is connected to the end of the flue 18 . The dust collector 15 can dedust the flue gas to ensure that the flue gas meets the emission standard.

In the present invention, the waste heat of the flue gas is recovered to the air-powder mixture at the outlet of the coal mill 8, and the waste heat enters the boiler system, which is equivalent to directly reducing the exhaust gas temperature, effectively improving the efficiency of the boiler, the heat grade is high, and the energy saving effect is remarkable. After the temperature of the air-powder mixture is increased, the ignition heat is reduced, and the stable combustion ability is improved; the effect on burning low-volatile coal is better. The temperature of the air-powder mixture is increased, the ignition is advanced, and the combustion efficiency is improved; the effect of burning low-volatile coal is better.

Specifically, the bypass heating system 25 includes a bypass flue 17 , the bypass flue 17 is connected between the inlet flue 16 and the outlet flue 18 , and the bypass flue 17 is connected with a flue gas heat transfer medium for heat exchange 3, the pipeline between the coal mill 8 and the boiler main body 1 is connected with a heat-conducting medium air-powder mixture heater 4, and a heat-conducting medium is connected between the flue gas heat-conducting medium heat exchanger 3 and the heat-conducting medium air-powder mixture heater 4 Circulation line 23. The heat-conducting medium absorbs the heat of the flue gas in the heat-conducting medium heat exchanger 3 of the flue gas, the temperature of the heat-conducting medium rises, the temperature of the flue gas decreases, and the low-temperature flue gas returns to the outlet flue 18 of the air preheater 2 . The heat-conducting medium heats the air-powder mixture at the outlet of the coal mill 8 in the heat-conducting medium air-powder mixture heat exchanger, the temperature of the heat-conducting medium drops, and the air-powder mixture rises.

A regulating oil tank 6 , a pressurizing pump 5 and a valve group 7 are connected to the heat transfer medium circulating pipeline 23 . The pressurizing pump 5 can adjust the circulation rate of the heat-conducting medium, and the adjusting oil tank 6 can supplement the heat-conducting medium to the adjusting heat-conducting medium circulating pipeline 23 .

In order to further utilize the heat of the flue gas in the outlet flue 18, a heat medium water system 22 is also connected to the outlet flue 18, and the heat medium water system 22 is respectively connected to the primary air duct 20 and the secondary air duct 19. The water system 22 is located on the side of the outlet flue 18 away from the air preheater 2 by the bypass heating system 25 . The heat medium water system 22 reduces the exhaust gas temperature, increases the inlet air temperature of the conventional air preheater 2, and correspondingly increases the metal wall temperature of the cold end, which can effectively prevent the corrosion and blockage of the cold end. The heat of the heated air is recovered by the boiler system, which further improves the thermal efficiency of the boiler.

Specifically, the heat medium water system 22 includes a flue gas cooler 9, the flue gas cooler 9 is connected to the outlet flue 18, the flue gas cooler 9 is connected with a water circulation pipeline 24, and the water circulation pipeline 24 is connected in parallel with For the primary air heater 11 and the secondary air heater 10 , the primary air heater 11 is connected to the primary air duct 20 , and the secondary air heater 10 is connected to the secondary air duct 19 . The heat medium water absorbs the heat of the flue gas in the flue gas cooler 9, the temperature of the heat medium water rises, and the temperature of the flue gas decreases. The heat medium water heats the cold primary air and the cold secondary air in the primary air heater 11 and the secondary air heater 10 respectively, the temperature of the heat medium water decreases, and the temperature of the cold air increases.

Furthermore, the unit condensate water system 12 is connected in parallel with the water circulation pipeline 24 . The heat medium water system 22 is also connected and coupled with the condensate water system 12 of the unit. When the boiler's own waste heat recovery capacity is insufficient due to coal type reasons, environmental reasons and operating load reasons, it can be adjusted through the condensate water system. When the residual heat of the flue gas is abundant, the condensed water can be heated through the connection system to transfer the residual heat of the flue gas to the condensed water system; when the ambient temperature is low or the load is low, the heat of the condensed water can be used to heat the cold air through the connecting system, Avoid the influence of too low exhaust gas temperature on the air preheater 2 and the dust collector 15 .

In order to adjust the temperature of the hot primary air, the primary air duct 20 is connected with a temperature-adjusting air duct 21, and one end of the temperature-adjusting air duct 21 is connected to a section before the primary air duct 20 enters the air preheater 2. The temperature-adjusting air duct 21 The other end of the air duct 20 is connected to a section after the primary air duct 20 extends out of the air preheater 2 . The temperature-adjusting air duct 21 adjusts the temperature of the primary air entering the coal mill 8 by controlling the ratio of the primary air entering the air preheater 2 .

Taking a conventional 660MW ultra-supercritical boiler as an example, the inlet smoke temperature of air preheater 2 in this project is 370°C, the exhaust gas temperature is 120°C, the hot primary air temperature (after mixing) is 300°C, and the hot secondary air temperature is 345°C. The difference between the hot ends of the air preheater 2 is 25°C, and it is difficult to further reduce the exhaust gas temperature. The calculated value of boiler efficiency is 94.5%, which is a relatively advanced level at this stage. 85℃～90℃ is the temperature range with higher dust removal efficiency of dust collector 15, so 90℃ is selected as the inlet smoke temperature of dust collector 15. Therefore, the heat released when the flue gas is reduced from 120°C (the temperature of the flue gas at the outlet of the air preheater 2) to 90°C (the temperature of the flue gas at the inlet of the dust collector 15) is the waste heat of the flue gas. If the existing flue gas waste heat utilization system (including flue gas cooler 9 (low temperature economizer), cold air heater + flue gas cooler 9, cold air heater + air preheater 2 bypass system) is used to utilize this part The waste heat and flue gas waste heat are all introduced into the turbine regenerative system, which is used to expel the steam extraction of the turbine.

In this scheme, a bypass flue 17 is set, the proportion of flue gas in the bypass flue 17 is 13.5%, the bypass flue gas is reduced from 370 ℃ to 130 ℃, and the heat exchange is 23.3MW; 3, absorb the heat of the flue gas, heat the air-powder mixture in the heat-conducting medium air-powder mixture heater 4, and the air-powder mixture is heated from 75 ℃ to 185 ℃, and the heat absorption is 23.3MW. The amount of flue gas in the air preheater 2 is only 86.5%, the calculated inlet cold air is 80°C, and the calculated exhaust gas temperature is 130°C. The outlet temperatures of the air preheater 2 and the bypass flue 17 are equivalent, both being 130°C. The heat medium water-type air preheater 2 realizes the first heat exchange between flue gas and air, and the cold air is heated from 25°C to 80°C in the primary air heater 11 and the secondary air heater 10 . The flue gas is reduced from 130°C to 90°C in the smoke cooler.

All the heat of the flue gas in this system is recovered by the boiler system, which is equivalent to the reduction of the exhaust gas temperature from 120 to 90 °C, and the reduction range reaches 30 °C. The gain of this part of the waste heat of the flue gas can be fully included in the calculation of the thermal efficiency of the boiler, and the thermal efficiency of the boiler is increased by about 1.5 %, which greatly improves the efficiency of the unit.

When the temperature of the air-powder mixture is increased from 75℃ to 185℃, the ignition heat is reduced, the stable combustion ability is improved, and the combustion efficiency is improved after the ignition is advanced.

Table 1 is the calculation table of filtration efficiency:

In particular, the outlet temperature of the pulverized coal heater is set to 185°C in the above-mentioned embodiment. If the temperature is lower than 185°C due to the influence of coal quality, the heat absorbed by the air-pulverized mixture will decrease. Under the condition of the same waste heat, the heat recovered by the air-powder mixture is reduced, and the excess heat will be transferred to the unit condensate system 12 through the heat medium water system 22, and part of the flue gas waste heat will be recovered through the unit condensate water system 12.

In particular, when the ambient temperature is low or under low load conditions, when the flue gas temperature at the inlet of the dust collector 15 is lower than 90°C, the condensate water system is used to preheat the air through the connection between the heat medium water system 22 and the condensate water system. , to avoid the influence of the low exhaust gas temperature on the air preheater 2 and the dust collector 15 . At this time, it is equivalent to recovering the exhaust heat of the steam turbine as the heat input of the boiler, which improves the thermal energy grade and improves the efficiency of the unit.

Specially, the bypass flue 17 is provided with an adjustment baffle, and the amount of flue gas entering the bypass flue 17 can be adjusted by adjusting the baffle, and then the waste heat utilization of the bypass heating system 25 can be adjusted.

The present invention is not limited to the above-mentioned optional embodiments, and anyone can draw other various forms of products under the inspiration of the present invention, but no matter what changes are made in its shape or structure, all fall within the definition of the claims of the present invention. The technical solutions within the scope all fall within the protection scope of the present invention.

Claims (10)

1. A flue gas waste heat utilization system based on the boiler system itself, comprising a boiler main body (1), an inlet flue (16) is connected to the tail of the boiler, and an air preheater (2) is connected to the inlet flue (16), The other end of the air preheater (2) is connected with an outlet flue (18), and also includes a primary air duct (20) and a secondary air duct (19), both of which pass through the air The preheater (2), the primary air duct (20) is connected to the coal pulverizer (8), the outlet end of the coal pulverizer (8) is connected to the boiler main body (1) through pipes, and the secondary air duct (19) is connected to A boiler main body (1); characterized in that a bypass heating system (25) is connected between the inlet flue (16) and the outlet flue (18), and the bypass heating system (25) is connected to a coal mill (8). ) and the main body of the boiler (1). 2. A flue gas waste heat utilization system based on the boiler system itself according to claim 1, characterized in that: the bypass heating system (25) comprises a bypass flue (17), a bypass flue (17) ) is connected between the inlet flue (16) and the outlet flue (18), the bypass flue (17) is connected with a flue gas heat transfer medium heat exchanger (3), the coal mill (8) and the boiler main body ( A heat-conducting medium air-powder mixture heater (4) is connected to the pipeline between 1), and a heat-conducting medium circulating pipeline is connected between the flue gas heat-conducting medium heat exchanger (3) and the heat-conducting medium air-powder mixture heater (4). (twenty three). 3. A flue gas waste heat utilization system based on the boiler system itself according to claim 2, characterized in that: a regulating oil tank (6) and a pressurizing pump (5) are connected to the heat transfer medium circulation pipeline (23) ). 4. A flue gas waste heat utilization system based on the boiler system itself according to claim 1, characterized in that: the outlet flue (18) is also connected with a heat medium water system (22), the heat medium water system (22) are respectively connected to the primary air duct (20) and the secondary air duct (19). 5. A flue gas waste heat utilization system based on the boiler system itself according to claim 5, characterized in that: the heat medium water system (22) comprises a flue gas cooler (9), a flue gas cooler (9) ) is connected to the outlet flue (18), the flue gas cooler (9) is connected with a water circulation pipeline (24), and the water circulation pipeline (24) is connected in parallel with a primary air heater (11) and a secondary air heater (10), the primary air heater (11) is connected to the primary air duct (20), and the secondary air heater (10) is connected to the secondary air duct (19). 6 . The flue gas waste heat utilization system based on the boiler system itself according to claim 5 , characterized in that: the water circulation pipeline ( 24 ) is also connected in parallel with an organic unit condensate water system ( 12 ). 7 . 7 . The waste heat utilization system of flue gas based on the boiler system itself according to claim 1 , wherein a dust collector ( 15 ) is connected to the end of the outlet flue ( 18 ). 8 . 8. A flue gas waste heat utilization system based on the boiler system itself according to claim 1, characterized in that: the primary air duct (20) is connected with a temperature-adjusting air duct (21), and the temperature-adjusting air duct ( One end of 21) is connected to a section before the primary air duct (20) enters the air preheater (2), and the other end of the temperature-adjusting air duct (21) is connected to the primary air duct (20) extending out of the air preheater (2). ) after the paragraph. 9 . The waste heat utilization system of flue gas based on the boiler system itself according to claim 1 , wherein a regulating baffle is arranged on the bypass flue ( 17 ). 10 . The flue gas waste heat utilization system based on the boiler system itself according to any one of claims 1 to 9, characterized in that: a primary fan (14) is connected to the primary air duct (20), and a secondary fan (14) is connected to the primary air duct (20). A secondary fan (13) is connected to the air duct (19).

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