A waste heat recovery system for a power plant

Abstract

The present invention provides a waste heat recovery system for a power plant, including a flue gas recovery device, which is connected to a heating device, which is connected to a steam recovery device, which includes a steam turbine, a low-pressure cylinder, and an intermediate-pressure cylinder, which is connected to a heat network heater, which is connected to the heating device; the steam turbine is connected to a condenser, which is connected to a cooling tower, and a circulating water supply pipe and a circulating water return pipe are provided between the cooling tower and the condenser, and the circulating water supply pipe is connected to the flue gas recovery device, wherein the condenser is also connected to a condensate recovery system; the present application recovers the waste heat of the steam turbine and the waste heat of the flue gas, which can reduce the heat loss of the cold end of the steam turbine to "zero", and recycle the waste heat for heating; recovering the waste heat of the slurry can increase the heating capacity of the unit during deep adjustment, and after the exhaust temperature is reduced, the emission of soluble salts to the atmosphere is reduced, thereby improving the air quality and further reducing the emission of pollutants such as smoke and dust.

Description

Technical Field

[0001] The present application relates to the field of waste heat recovery in power plants, and in particular to a waste heat recovery system in power plants. Background Art

[0002] In a power plant, high-pressure steam from the boiler is passed through a steam turbine to generate electricity. The steam exhausted by the turbine is called waste heat. It has a high pressure and temperature and is widely used. Exhaust steam is the main waste heat of the power plant, while other waste heat, such as flue gas, only accounts for a few percent. In the existing technology, most exhaust steam is utilized, but the utilization rate of flue gas is low. In actual production, the flue gas generated by power generation in power plants contains a large amount of sulfur dioxide. This flue gas is generally sprayed to remove sulfur dioxide through a limestone / gypsum wet flue gas desulfurization method. The flue gas obtained after this process still has a low temperature of 55-60°C. This part of the waste heat is discharged through the chimney, and often some tail plume phenomenon is generated, resulting in heat waste. There is no system in the existing technology that fully recovers the waste heat of power plants. The applicant conducted a detailed search of the existing technology before writing this paper, and the closest existing technology retrieved is as follows:

[0003] Prior art 1: Application number 201420453944.X is a low-temperature waste heat recovery device for power plants used for low-pressure heating extraction steam; it includes a high-temperature and high-pressure steam pipe, an extraction-condensing steam turbine, an industrial extraction steam pipeline, a heating extraction steam pipeline, a steam-water heat exchanger, a pressure matcher, an absorption heat pump, a primary network supply and return water pipe, a condenser and a circulating water pipe, the high-temperature and high-pressure steam pipe is connected to the extraction-condensing steam turbine, the extraction-condensing steam turbine is connected to the condenser, the extraction-condensing steam turbine is connected to the pressure matcher through the industrial extraction steam pipeline, the extraction-condensing steam turbine is respectively connected to the steam-water heat exchanger and the pressure matcher through the heating extraction steam pipeline, the pressure matcher is connected to the absorption heat pump through a pipeline, the absorption heat pump is connected to the steam-water heat exchanger through the primary network supply and return water pipe, and the absorption heat pump is connected to the condenser through the circulating water pipe. The present invention can efficiently recover low-temperature waste heat from power plants, and is particularly suitable for situations where the extraction steam pressure for heating in power plants is insufficient; this application utilizes exhaust steam, has a complex structure, and does not form a circulation system. Although both the application and the present application utilize waste heat from power plants, the concept is different from that of the present application.

[0004] In summary, a new technical solution needs to be provided to solve the above technical problems. Summary of the Invention

[0005] The present invention provides a waste heat recovery system for a power plant, comprising a flue gas recovery device, wherein the flue gas recovery device is connected to a heating device, and the heating device is further connected to a steam recovery device, wherein the steam recovery device comprises a low-pressure cylinder and a medium-pressure cylinder connected to a steam turbine, and the medium-pressure cylinder is connected to a heat network heater, and a heat network water supply pipe and a heat network return pipe are provided between the heat network heater and the heating equipment, and the heat network return pipe is connected to the flue gas recovery device, and a steam drain pipe is provided on the heat network heater; the steam turbine is connected to a condenser, and the condenser is connected to a cooling tower, and a circulating water supply pipe and a circulating water return pipe are provided between the cooling tower and the condenser, and the circulating water supply pipe is connected to the flue gas recovery device via a waste hot water supply pipe and a waste hot water return pipe, wherein the condenser is further connected to a condensate recovery system.

[0006] As a preferred solution, the flue gas recovery device includes a desulfurization slurry cooling system, which is connected to the heat pump through circulating water pipe 1 and circulating water pipe 2. The heat pump is connected to the heat network return pipe through pipeline 1 and pipeline 2. The heat pump is connected to the waste hot water supply pipe and the waste hot water return pipe; the heat pump is connected to a steam drain pipe 1.

[0007] As a preferred solution, a water inlet pipe is provided between the heating network water supply pipe and the heating network return pipe, and a switch valve is provided on the water inlet pipe.

[0008] As a preferred solution, the heat pump is also connected to the pipeline between the medium-pressure cylinder and the heat network heater through pipeline three.

[0009] As a preferred embodiment, the steam turbine includes steam turbine 1 and steam turbine 2, wherein steam turbine 1 is connected to low-pressure cylinder 1 and intermediate-pressure cylinder 1, intermediate-pressure cylinder 1 is connected to heat network heater 1, heat network heater 1 is connected to heat network heater 2 through circulation pipeline 1 and circulation pipeline 2, heat network heater 2 is connected to intermediate-pressure cylinder 2, intermediate-pressure cylinder 2 is connected to low-pressure cylinder 2, and steam turbine 2 is connected to the condenser; both heat network heater 1 and heat network heater 2 are connected to steam drain pipes.

[0010] As a preferred solution, a one-way pipe is provided between the heating network water supply pipe and the heating network return pipe, and a valve is provided on the one-way pipe.

[0011] As a preferred solution, a one-way pipe 2 is provided between the circulation pipeline 1 and the circulation pipeline 2, and a valve 2 is provided on the one-way pipe 2.

[0012] The high-temperature and high-pressure steam generated in the boiler in this application enters the steam turbine 1 and the steam turbine 2 to perform work, and the low-temperature exhaust steam after the steam turbine 2 performs work enters the condenser to condense into water, and then enters the cooling tower through the circulating water supply pipe. The cooling tower cools it, and the cooled water is sent to the condenser through the circulating water return pipe. The condenser returns it to the boiler through the condensate recovery system for reheating; the water flow in the circulating water supply pipe has a certain temperature, enters the heat network return pipe through the waste hot water supply pipe, and then is heated by the heat network heater 1 and / or the heat network heater 2 to heat the heating equipment Hot water is circulated, and when the temperature reaches the required level, it can also directly enter the heating network water supply pipeline through the one-way pipe 1; the steam condensate and non-condensable gases such as air in the heating network heater 1 and the heating network heater 2 are discharged through the steam drain pipe; the gas phase in the desulfurization tower is cooled by the desulfurization slurry cooling system to form a liquid with a certain temperature, and the liquid enters the heat pump through the circulating water return pipe for heat exchange treatment, and after heat exchange, the water flows into the desulfurization slurry cooling system for circulation; the heating network heater uses the steam extracted by the steam turbine as a heat source to heat the circulating water in the heating network water supply pipeline, and heats the heating equipment through the circulating water.

[0013] This application recovers the waste heat of the steam turbine and the flue gas, which can reduce the heat loss at the cold end of the steam turbine to "zero" and recycle the waste heat for heating; recovering the waste heat of the slurry can increase the heating capacity of the unit during deep adjustment, reduce the emission of soluble salts to the atmosphere after the exhaust temperature is reduced, improve the air quality, and further reduce the emission of pollutants such as smoke dust (including soluble salts, etc.); under the designed operating conditions, water vapor emissions are reduced, and the diffusion effect of pollutants is significantly improved. By recovering the waste heat of the circulating water in the slurry cooling device, a maximum annual heat recovery of 2.622 million GJ can be achieved. , it can save 88,000 tons of standard coal per year, reduce the evaporation of circulating water by 5,600 tons per day, and more than 800,000 tons of water in the whole heating season, and reduce carbon dioxide emissions by 223,000 tons per year, dust by 209 tons per year, sulfur dioxide by 748 tons per year, and nitrogen oxides by 651 tons per year; the desulfurization slurry cooling system reduces the flue gas temperature from 55°C to 45-48°C, and the overall particulate matter emission reduction is about 96.21 tons per year, of which smoke dust emissions are reduced by 4.01 tons per year and soluble particulate matter emissions are reduced by 92.2 tons per year, with obvious pollution reduction and carbon reduction effects. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is a working principle diagram of Example 2 of the present application;

[0015] Figure 2 This is a working principle diagram of Example 3 of the present application;

[0016] Reference numerals:

[0017] 1. Heating equipment 2. Steam turbine 3. Low-pressure cylinder 4. Medium-pressure cylinder

[0018] 5. Heating steam extraction pipeline 6. Heating network heater 7. Heating network water supply pipeline

[0019] 8. Heat network return pipe 9. Condenser 10. Cooling tower

[0020] 11. Circulating water supply pipeline 12. Circulating water return pipeline

[0021] 13. Waste hot water supply pipe 14. Waste hot water return pipe

[0022] 15. Condensate recovery system 16. Desulfurization slurry cooling system

[0023] 17. Circulating water pipeline 1 18. Circulating water pipeline 2 19. Heat pump

[0024] 20. Pipeline 1 21. Pipeline 2 22. Steam drain pipe 1

[0025] 23. Pipeline 3 24. Steam Turbine 1 25. Steam Turbine 2

[0026] 26. Low pressure cylinder 1 27. Medium pressure cylinder 1 28. Heating network heater 1

[0027] 29. Circulation line 1 30. Circulation line 2 31. Heating network heater 2

[0028] 32. Medium-pressure cylinder 2 33. Low-pressure cylinder 2 34. Steam drain pipe

[0029] 35. One-way pipe 1 36. Valve 1 37. One-way pipe 2

[0030] 38. Valve 2 39. Water inlet pipe 40. Switch valve DETAILED DESCRIPTION

[0031] The following is a detailed description of the specific embodiments of the present invention in conjunction with the accompanying drawings. It should be noted that the specific embodiments described herein are only used to illustrate and explain the present invention and are not intended to limit the present invention.

[0032] Example 1:

[0033] The present embodiment provides a waste heat recovery system for a power plant, including a flue gas recovery device, which is connected to a heating device 1. The heat recovered by the flue gas recovery device is used to heat the circulating water in the heating device 1. The heating device 1 is also connected to a steam recovery device. The heat recovered by the steam recovery device is also used to heat the circulating water in the heating device 1. The heating device 1 can use the water heating equipment in the prior art. The steam recovery device includes a low-pressure cylinder 3 and a medium-pressure cylinder 4 connected to the steam turbine 2. The medium-pressure cylinder 4 is connected to the heat network through a heating steam extraction pipe 5. The heater 6 is connected to the heating network heater 6, which is connected to the steam drain pipe 34. A heating network water supply pipe 7 and a heating network return pipe 8 are provided between the heating network heater 6 and the heating equipment 1. The heating network return pipe 8 is connected to the flue gas recovery device; an inlet pipe 39 is provided between the heating network water supply pipe 7 and the heating network return pipe 8, and a switch valve 40 is provided on the inlet pipe 39. The water flow in the flue gas recovery device can be directly used as the circulating water of the heating equipment 1 without being heated by the heating network heater 6; the heating network heater 6 uses the steam extracted by the steam turbine 2 to heat the circulating water in the heating network water supply pipe 7 Water is heated by circulating water to heat the heating equipment 1; the steam turbine 2 is connected to the condenser 9, the condenser 9 is connected to the cooling tower 10, and a circulating water supply pipe 11 and a circulating water return pipe 12 are provided between the cooling tower 10 and the condenser 9. The circulating water supply pipe 11 is connected to the flue gas recovery device through the waste hot water supply pipe 13 and the waste hot water return pipe 14, wherein the condenser 9 is also connected to a condensate recovery system 15; the high-temperature and high-pressure steam generated in the boiler enters the steam turbine 2 to perform work, and the low-temperature exhaust steam after the steam turbine 2 performs work enters the condenser 9 to condense into water , and then enters the cooling tower 10 through the circulating water supply pipe 11. The cooling tower 10 cools the water. The cooled water is sent to the condenser 9 through the circulating water return pipe 12. The condenser 9 returns it to the boiler through the condensate recovery system 15 for reheating; the water flow in the circulating water supply pipe 11 has a certain temperature, and provides heat to the flue gas recovery device through the waste hot water supply pipe 13. The high-temperature water after heat exchange enters the heat network return pipe 8, and then is heated by the heat network heater 6 to circulate hot water to the heating equipment 1 for heating.

[0034] Example 2:

[0035] This embodiment defines the flue gas recovery device, specifically:

[0036] The flue gas recovery device includes a desulfurization slurry cooling system 16. The desulfurization slurry cooling system 16 can adopt the desulfurization slurry cooling system in the prior art. This application does not make any improvements to it and will not be described in detail here. The desulfurization slurry cooling system 16 is connected to the heat pump 19 through a circulating water pipe 17 and a circulating water pipe 2 18. The heat pump 19 is connected to the heat network return pipe 8 through a pipeline 1 20 and a pipeline 2 21. The desulfurization slurry cooling system 16 reduces the flue gas temperature from 55°C to 45-48°C and condenses it into liquid. The liquid is heated by the circulating water pipe 17 to supply heat to the heat pump. The low-temperature liquid after heat exchange is returned to the desulfurization slurry cooling system 16 through the circulating water pipe 18 for the next cycle. The high-temperature liquid after heat exchange enters the heat network return pipe 8 through pipeline 1 20 and / or pipeline 2 21, circulates in the heating equipment 1, and provides heat to the heating equipment 1; the heat pump 19 is connected to the waste hot water supply pipe 13 and the waste hot water return pipe 14; the water flow in the circulating water supply pipe 11 exchanges heat with the heat pump 19 through the waste hot water supply pipe 13, and the low-temperature liquid after heat exchange flows back to the circulating water supply pipe 11 through the waste hot water return pipe 14, and then flows into the cooling tower 10; the heat pump 19 is connected to a steam drain pipe 12, and the steam condensate and non-condensable gases such as air in the heat pump 19 are discharged through the steam drain pipe 121 to prevent blockage and the like, thereby improving the service life of the equipment.

[0037] Preferably, the heat pump 19 is also connected to the heating steam extraction pipeline 5 between the medium-pressure cylinder 4 and the heat network heater 6 through pipeline three 23. The steam formed after heat exchange can directly enter the heat network heater 6 through pipeline three 23 and the heating steam extraction pipeline 5, and be used as a heat source for the circulating water in the heating equipment 1.

[0038] Example 3:

[0039] This embodiment improves practicality and saves energy to the greatest extent. Specifically:

[0040] The steam turbine 2 includes a steam turbine 1 24 and a steam turbine 2 25, wherein the steam turbine 1 24 is connected to a low-pressure cylinder 1 26 and an intermediate-pressure cylinder 1 27, the intermediate-pressure cylinder 1 27 is connected to a hot network heater 1 28, the hot network heater 1 28 is connected to a hot network heater 2 31 through a circulation pipeline 1 29 and a circulation pipeline 2 30, the hot network heater 2 31 is connected to an intermediate-pressure cylinder 2 32, the intermediate-pressure cylinder 2 32 is connected to a low-pressure cylinder 2 33, and the steam turbine 2 25 is connected to the condenser 9; the hot network heater 1 28 and the hot network heater 2 29 are both connected to a steam drain pipe 34, and the steam condensate and non-condensable gases such as air in the hot network heater 1 28 and the hot network heater 2 31 are discharged through the steam drain pipe 34 to prevent blockage and the like, thereby improving the service life of the equipment.

[0041] As a preferred solution, a one-way pipe 35 is provided between the heating network water supply pipe 7 and the heating network return pipe 8, and a valve 36 is provided on the one-way pipe 35; the liquid that does not need to be heated directly flows into the heating equipment 1 through the one-way pipe 35 for heating and heat exchange, saving heat energy; as a preferred solution, a one-way pipe 37 is provided between the circulation pipeline 1 29 and the circulation pipeline 2 30, and a valve 38 is provided on the one-way pipe 37. The liquid that only needs to pass through one heating network heater for heating enters the heating network water supply pipe 7 through the one-way pipe 37, is heated by the heating network heater 28, and then enters the heating equipment 1 for heating and heat exchange, which can also achieve the effect of saving heat energy.

[0042] The working principle of the present invention is as follows: the high-temperature and high-pressure steam generated in the boiler enters the steam turbine 1 24 and the steam turbine 2 25 to perform work, and the low-temperature exhaust steam after the steam turbine 2 25 performs work enters the condenser 9 to condense into water, and then enters the cooling tower 10 through the circulating water supply pipe 11, and the cooling tower 10 cools it. The cooled water is sent to the condenser 9 through the circulating water return pipe 12, and the condenser 9 returns it to the boiler through the condensate recovery system 15 for reheating; the water flow in the circulating water supply pipe 11 has a certain temperature, enters the heat network return pipe 8 through the waste hot water supply pipe 13, and is then heated by the heat network heater 1 28 and / or the heat network heater 2 31, and circulates hot water to the heating equipment 1. When the temperature reaches the required level, It can also directly enter the heating network water supply pipe 7 through the one-way pipe 35; the steam condensate and non-condensable gases such as air in the heating network heater 1 28 and the heating network heater 2 31 are discharged through the steam drain pipe 34; the gas phase in the desulfurization tower is cooled by the desulfurization slurry cooling system 16 to form a liquid with a certain temperature. The liquid enters the heat pump 19 through the circulating water pipe 17 for heat exchange treatment. After the heat exchange, the high-temperature water flows into the heating network return pipe 8 for circulation, and the low-temperature water flows into the desulfurization slurry cooling system 16 for circulation after the heat exchange; the heating network heater 1 28 and the heating network heater 2 31 respectively use the steam extracted from the steam turbine 1 24 and the steam turbine 2 25 as heat sources to heat the circulating water in the heating network water supply pipe 7, and heat the heating equipment 1 through the circulating water.

[0043] This application can provide circulating water of suitable temperature for heating equipment 1 through the cooperation of heating equipment 1, flue gas recovery device and steam recovery device, thereby saving energy to the greatest extent; in summary, due to the adoption of the above technical scheme, this application recovers the waste heat of turbine and flue gas, which can reduce the heat loss of the cold end of the turbine to "zero", and recycle the waste heat for heating; recovering the waste heat of slurry can increase the heating capacity of the unit during deep adjustment, and after the exhaust gas temperature is lowered, the emission of soluble salts to the atmosphere is reduced, the air quality is improved, and the emission of pollutants such as smoke dust (including soluble salts, etc.) is further reduced; under the design conditions, water vapor emissions are reduced and the pollutant diffusion effect is obvious. Significant improvement has been achieved. By recovering the waste heat from the steam turbine and the flue gas, a maximum of 2.622 million GJ of heat can be recovered annually, saving 88,000 tons of standard coal per year, reducing the evaporation of circulating water by 5,600 tons per day, and more than 800,000 tons of water in the entire heating season. Carbon dioxide emissions can be reduced by 223,000 tons per year, dust by 209 tons per year, sulfur dioxide by 748 tons per year, and nitrogen oxides by 651 tons per year. The desulfurization slurry cooling system reduces the flue gas temperature from 55°C to 45-48°C, and the overall particulate matter emission reduction is about 96.21 tons per year, of which dust emissions are reduced by 4.01 tons per year and soluble particulate matter emissions are reduced by 92.2 tons per year. The pollution reduction and carbon reduction effects are obvious.

[0044] The structures and connection relationships described in detail in the present invention are all prior art, and the present invention will not go into details here; the connection relationship between the above-mentioned components is preferably fixed by a well-known method in the prior art such as pipeline connection.

[0045] The preferred embodiment of the present application is described in detail above in conjunction with the accompanying drawings. However, the present application is not limited to the specific details in the above-mentioned embodiments. Within the technical concept of the present application, various simple modifications can be made to the technical solution of the present application, and these simple modifications all fall within the scope of protection of the present application.

[0046] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any appropriate manner unless there is any contradiction. In order to avoid unnecessary repetition, the various possible combinations of this application will not be described separately.

[0047] In addition, the various implementation methods of the present application can be arbitrarily combined, as long as they do not violate the concept of the present application, and they should also be regarded as the contents disclosed in the present application.

Claims

1. A waste heat recovery system for a power plant, comprising a flue gas recovery device, characterized in that: The flue gas recovery device is connected to the heating equipment (1), and the heating equipment (1) is also connected to a steam recovery device. The steam recovery device includes a low-pressure cylinder (3) and a medium-pressure cylinder (4) connected to the steam turbine (2). The medium-pressure cylinder (4) is connected to the heat network heater (6). A heat network water supply pipe (7) and a heat network return pipe (8) are provided between the heat network heater (6) and the heating equipment (1). The heat network return pipe (8) is connected to the flue gas recovery device. A steam drain pipe (34) is provided; the steam turbine (2) is connected to the condenser (9), the condenser (9) is connected to the cooling tower (10), a circulating water supply pipe (11) and a circulating water return pipe (12) are provided between the cooling tower (10) and the condenser (9), the circulating water supply pipe (11) is connected to the flue gas recovery device through the waste hot water supply pipe (13) and the waste hot water return pipe (14), wherein the condenser (9) is also connected to a condensate recovery system (15); The flue gas recovery device includes a desulfurization slurry cooling system (16), the desulfurization slurry cooling system (16) is connected to a heat pump (19) through a circulating water pipe 1 (17) and a circulating water pipe 2 (18), the heat pump (19) is connected to a heat network return pipe (8) through a pipeline 1 (20) and a pipeline 2 (21), and the heat pump (19) is connected to the waste hot water supply pipe (13) and the waste hot water return pipe (14); the heat pump (19) is connected to a steam drain pipe 1 (22), and the heat pump (19) is also connected to a heating steam extraction pipe (5) between a medium pressure cylinder (4) and a heat network heater (6) through a pipeline 3 (23); the steam turbine (2) includes The invention comprises a steam turbine 1 (24) and a steam turbine 2 (25), wherein the steam turbine 1 (24) is connected to a low-pressure cylinder 1 (26) and an intermediate-pressure cylinder 1 (27), the intermediate-pressure cylinder 1 (27) is connected to a heat network heater 1 (28), the heat network heater 1 (28) is connected to a heat network heater 2 (31) through a circulation pipeline 1 (29) and a circulation pipeline 2 (30), the heat network heater 2 (31) is connected to an intermediate-pressure cylinder 2 (32), the intermediate-pressure cylinder 2 (32) is connected to a low-pressure cylinder 2 (33), and the steam turbine 2 (25) is connected to the condenser (9); the heat network heater 1 (28) and the heat network heater 2 (31) are both connected to a steam drain pipe (34).

2. A power plant waste heat recovery system according to claim 1, characterized in that: A water inlet pipe (39) is provided between the heating network water supply pipe (7) and the heating network return water pipe (8), and a switch valve (40) is provided on the water inlet pipe (39).

3. The power plant waste heat recovery system according to claim 1, characterized in that: A one-way pipe (35) is provided between the heating network water supply pipe (7) and the heating network return pipe (8), and a valve (36) is provided on the one-way pipe (35).

4. The power plant waste heat recovery system according to claim 1, characterized in that: A one-way pipe 2 (37) is provided between the circulation pipeline 1 (29) and the circulation pipeline 2 (30), and a valve 2 (38) is provided on the one-way pipe 2 (37).

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