Novel combined cycle unit flue gas waste heat utilization seawater desalination system

Abstract

The utility model discloses a novel combined cycle unit flue gas waste heat utilization seawater desalination system which comprises a waste heat boiler hot water system, a material water supply system, a cooling water system, a saline water system, a finished product water system and a vacuum system, the waste heat boiler hot water system comprises a waste heat boiler, a steam-water separator, an evaporator and a condenser which are connected in sequence, and the steam output end of the steam-water separator is connected with the evaporator; the hot water output end of the steam-water separator is connected with the waste heat boiler through a hot water return pipeline; a hot water booster pump is arranged on the hot water return pipeline; the evaporators are multi-effect evaporators and have eight effects, and the condensed water output end of the first-effect evaporator of the evaporators is connected with the hot water return pipeline. According to the scheme, the tail heating surface is additionally arranged on the basis of an original boiler, the exhaust gas temperature of the waste heat boiler is reduced, the recycled heat is increased, and the external hot water supply amount is increased under the condition that the power generation output of an original unit is not affected.

Description

Technical Field

[0001] The utility model belongs to the technical field of waste heat utilization and water treatment of waste heat boilers, and particularly relates to a seawater desalination system for waste heat utilization of flue gas of a new combined cycle unit. Background Art

[0002] At present, traditional waste heat utilization of flue gas, for example, obtains steam or hot water through a simple heat exchanger for production or domestic use, and its energy recovery efficiency and economy need to be improved. Some existing patents have studied the use of waste heat in flue gas for seawater desalination, but they have not fully considered various specific situations such as flue gas properties, and have not fully utilized waste heat to obtain better desalination efficiency without affecting the original unit. Summary of the Utility Model

[0003] The technical problem to be solved by the utility model is to provide a seawater desalination system for waste heat utilization of flue gas of a new combined cycle unit, solve the problems of poor heat recovery rate and fresh water output of the existing technical solutions, and achieve beneficial effects such as reducing the flue gas discharge temperature of the waste heat boiler and increasing the recovered heat.

[0004] According to the technical solution of the utility model, the utility model provides a seawater desalination system for waste heat utilization of flue gas of a new combined cycle unit, which includes a waste heat boiler hot water system, a material water supply system, a cooling water system, a brine system, a finished water system, and a vacuum system;

[0005] The waste heat boiler hot water system includes a waste heat boiler, a steam separator, an evaporator, and a condenser connected in sequence. Among them, the steam output end of the steam separator is connected to the evaporator; the hot water output end of the steam separator is connected to the waste heat boiler through a hot water return pipeline, and a hot water booster pump is provided on the hot water return pipeline; the evaporator is a multi-effect evaporator with a total of eight effects, and the condensate output end of the first-effect evaporator of the evaporator is connected to the hot water return pipeline;

[0006] The cooling water system includes a circulating cooling pipeline, and the condenser is arranged on the circulating cooling pipeline;

[0007] The material water supply system includes a water supply pipeline led out from the circulating cooling pipeline, and a seawater booster pump is provided on the water supply pipeline. The water supply pipeline includes a first water supply pipeline and a second water supply pipeline. The first water supply pipeline is connected to the spray water device of the first five-effect evaporators of the evaporator, and a brine heater is provided on the first water supply pipeline; the second water supply pipeline is connected to the spray water device of the last three-effect evaporators of the evaporator;

[0008] The brine system includes a primary brine discharge pipeline and a secondary brine discharge pipeline; the primary brine discharge pipeline successively connects the brine discharge ends of the first five-effect evaporators of the evaporator, and a primary brine discharge pump and a brine heater are provided on the primary brine discharge pipeline; the secondary brine discharge pipeline successively connects the brine discharge ends of the last three-effect evaporators of the evaporator, and a secondary brine discharge pump is provided on the secondary brine discharge pipeline;

[0009] The finished water system includes a finished water pipeline, and the finished water pipeline successively connects the fresh water output ends of the second to eighth-effect evaporators of the evaporator and the condensate output end of the condenser, and a finished water pump is provided on the finished water pipeline;

[0010] The vacuum system includes a vacuum pipeline, and the vacuum pipeline successively connects each effect evaporator of the evaporator and the condenser, and a steam jet air ejector is provided on the vacuum pipeline.

[0011] Further, the output end of the steam jet air ejector is connected with a steam jet air ejector condenser, and the steam jet air ejector condenser is located at a position on the first water supply pipeline close to the spray water device of the first-effect evaporator of the evaporator.

[0012] Further, a first steam regenerative heater is also provided on the first water supply pipeline, and the first steam regenerative heater is located in the third-effect evaporator of the evaporator.

[0013] Further, on the first water supply pipeline, the first steam regenerative heater is located on the upstream side of the spray water devices of the first-effect and second-effect evaporators and on the downstream side of the spray water device of the fourth-effect evaporator.

[0014] Further, a second steam regenerative heater is provided on the second water supply pipeline, and the second steam regenerative heater is located in the seventh-effect evaporator of the evaporator.

[0015] Further, on the second water supply pipeline, the second steam regenerative heater is located on the upstream side of the spray water device of the sixth-effect evaporator and on the downstream side of the spray water device of the eighth-effect evaporator.

[0016] Further, the primary brine discharge pipeline is connected to the upstream side of the secondary brine discharge pump of the secondary brine discharge pipeline.

[0017] Compared with the prior art, the beneficial technical effects of the present utility model are as follows:

[0018] The flue gas waste heat utilization seawater desalination system of the new combined cycle unit of the present utility model adds a tail heating surface on the basis of the original boiler, reduces the flue gas discharge temperature of the waste heat boiler, increases the recovered heat, and increases the external supply of hot water without affecting the power generation output of the original unit; the first-effect condensate and the seawater desalinated fresh water generated later are isolated and discharged from the equipment. Considering that the first-effect steam may contain pollution caused by the addition of boiler feed water treatment chemicals, separating it from the seawater desalination product water can prevent the produced fresh water from being affected by pollutants; and preferably, a fully direct-current horizontal tube falling film low-temperature multi-effect evaporator is adopted, and the evaporators of each effect at different positions are divided, and different water supply methods, temperatures, etc. are adopted, as well as methods such as two-stage pressurized discharge of brine, etc., to further realize the recovery and utilization of heat, increase the output efficiency and quality of finished fresh water. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is a schematic structural diagram according to an embodiment of the present utility model.

[0020] Explanation of the reference numerals in the drawings:

[0021] 1. Evaporator; 2. Condenser; 3. Steam-water separator; 4. Seawater booster pump; 5. Product water pump; 6. Steam jet air ejector; 7. Brine heater; 8. Primary brine discharge pump; 9. Secondary brine discharge pump; 10. Hot water booster pump; 11. Hot water return pipeline; 12. Circulating cooling pipeline; 13. First water supply pipeline; 14. Second water supply pipeline; 15. Primary brine discharge pipeline; 16. Secondary brine discharge pipeline; 17. Product water pipeline; 18. Vacuum pipeline; 19. Condenser of steam jet air ejector; 20. First steam regenerative heater; 21. Second steam regenerative heater. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0022] The present utility model provides a flue gas waste heat utilization seawater desalination system for a new combined cycle unit, which utilizes the waste heat at the tail of the waste heat boiler as the heat source for seawater desalination, achieving beneficial effects such as reducing the flue gas discharge temperature of the waste heat boiler, recovering the waste heat of the tail flue gas, improving the combined cycle thermal efficiency, and reducing the cost of seawater desalination for water production.

[0023] Please refer to Figure 1 , a flue gas waste heat utilization seawater desalination system for a new combined cycle unit according to an embodiment of the present utility model, including a waste heat boiler hot water system, a material water supply system, a cooling water system, a brine system, a product water system, and a vacuum system.

[0024] The waste heat boiler hot water system includes a waste heat boiler, a steam-water separator 3, an evaporator 1, and a condenser 2 that are connected in sequence. Among them, the steam output end of the steam-water separator 3 is connected to the evaporator 1; the hot water output end of the steam-water separator 3 is connected to the waste heat boiler through a hot water return pipeline 11, and a hot water booster pump 10 is provided on the hot water return pipeline 11. The evaporator 1 is a multi-effect evaporator with a total of eight effects, and the condensate output end of the first-effect evaporator of the evaporator 1 is connected to the hot water return pipeline 11.

[0025] When the waste heat boiler hot water system is working, the hot water supplied from the waste heat boiler first enters the steam-water separator to separate steam, which is used as the heating steam for the low-temperature multi-effect seawater desalination device. The first-effect heating steam is successively evaporated and condensed to produce seawater desalinated water. The system preferably adopts a fully direct-flow horizontal tube falling film low-temperature multi-effect evaporator. Preferably, a steam jet air ejector condenser 19 is provided at a position on the first water supply pipeline 13 close to the spray water device of the first-effect evaporator of the evaporator 1; the hot water separated by the steam-water separator and the first-effect condensate are directly pressurized by the hot water booster pump and returned to the waste heat boiler. In this solution, the first-effect condensate and the seawater desalinated fresh water generated later are discharged separately from the MED (multi-effect distillation) device. This is mainly considered that the first-effect steam may contain pollution caused by boiler feed water treatment chemicals, and separating it from the seawater desalination product water can prevent the produced fresh water from being affected by pollutants.

[0026] The cooling water system includes a circulating cooling pipeline 12, and the condenser 2 is provided on the circulating cooling pipeline 12.

[0027] The material water supply system includes a water supply pipeline led out from the circulating cooling pipeline 12. A seawater booster pump 4 is provided on the water supply pipeline. The water supply pipeline includes a first water supply pipeline 13 and a second water supply pipeline 14. The first water supply pipeline 13 is connected to the spray water devices of the first five-effect evaporators of the evaporator 1, and a brine heater 7 is provided on the first water supply pipeline 13; the second water supply pipeline 14 is connected to the spray water devices of the last three-effect evaporators of the evaporator 1.

[0028] The material water supply system adopts a primary boosting and two-way water supply scheme. The water supply is provided from the cooling water drainage behind the condenser through a seawater booster pump. One-way water supply is adopted for the last three effects of the 6th, 7th, and 8th effects; and preferably, a second steam regenerative heater 21 is provided on the second water supply pipeline 14. The second steam regenerative heater 21 is located in the seventh effect evaporator of the evaporator 1. More specifically, on the second water supply pipeline 14, the second steam regenerative heater 21 is located on the upstream side of the spray water device of the sixth effect evaporator and on the downstream side of the spray water device of the eighth effect evaporator. Thus, setting the regenerative heater in the 7th effect can increase the inlet water temperature of the 6th and 7th effects, while reducing the amount of condensed steam in the 8th effect and the condenser, and improving the thermal efficiency. One-way seawater supply is adopted for the first five effects, and the discharged circulating cooling water of the condenser is also used as the water source; and preferably, a first steam regenerative heater 20 is further provided on the first water supply pipeline 13. The first steam regenerative heater 20 is located in the third effect evaporator of the evaporator 1. More specifically, on the first water supply pipeline 13, the first steam regenerative heater 20 is located on the upstream side of the spray water devices of the first and second effect evaporators and on the downstream side of the spray water device of the fourth effect evaporator. Thus, this one-way water supply first exchanges heat with the brine heater for the discharged brine of the 5th effect to increase the seawater supply temperature, and then the steam regenerative heater provided in the 3rd effect reheats and raises the temperature of the seawater for the first three effects. Further, finally, through the steam jet condenser 19, the seawater of the first effect is used as the cooling water of the steam jet vacuum system condenser to recover heat and further increase the seawater temperature of the first effect. The cooling water system is the same as that of traditional low-temperature multi-effect seawater desalination equipment, adopting seawater once-through cooling water supply, and the discharged circulating cooling water is used as the water source for seawater desalination.

[0029] The brine system includes a primary brine discharge pipeline 15 and a secondary brine discharge pipeline 16. The primary brine discharge pipeline 15 sequentially connects the brine discharge ends of the first five effect evaporators of the evaporator 1. A primary brine discharge pump 8 and a brine heater 7 are provided on the primary brine discharge pipeline 15. The secondary brine discharge pipeline 16 sequentially connects the brine discharge ends of the last three effect evaporators of the evaporator 1. A secondary brine discharge pump 9 is provided on the secondary brine discharge pipeline 16.

[0030] The brine is discharged under two-stage pressurization. More specifically, the primary brine discharge pipeline 15 is connected to the upstream side of the secondary brine discharge pump 9 of the secondary brine discharge pipeline 16. The brine of the first five effects is boosted by the primary brine discharge pump, heated by the brine heater to heat the seawater, and the brine temperature is reduced to be close to the temperature of the last effect, and then discharged from the evaporator system after being boosted by the last effect brine pump; the brine of the last three effects is directly discharged after being boosted by the secondary brine discharge pump.

[0031] The finished water system includes a finished water pipeline 17. The finished water pipeline 17 sequentially connects the fresh water output ends of the second to eighth effect evaporators of the evaporator 1 and the condensate output end of the condenser 2. A finished water pump 5 is provided on the finished water pipeline 17.

[0032] The finished water (i.e., the obtained fresh water) is discharged from the evaporator in a sequential flashing manner. After reaching the last effect, it is mixed with the condensate of the condenser and then discharged from this system after being pressurized by the finished water pump.

[0033] The vacuum system includes a vacuum pipeline 18, which sequentially connects each effect evaporator of the evaporator 1 and the condenser 2. A steam jet air ejector 6 is provided on the vacuum pipeline 18.

[0034] The main function of the vacuum system is to establish a vacuum during startup and timely extract the non-condensable gases of the equipment during operation to maintain the operating vacuum degree of the system. The non-condensable gases are discharged in a sequential manner and finally discharged to the condenser, and then discharged from the system through the vacuum extraction device and into the atmosphere. More specifically, the steam jet air ejector 6 has a steam input end, an air input end, and an output end. The steam input end of the steam jet air ejector 6 is connected to the steam pipeline of the steam turbine, that is, the steam input into the steam jet air ejector 6 comes from the extraction steam of the steam turbine; the steam enters the steam jet air ejector 6 and is ejected at high speed through a nozzle inside the steam jet air ejector 6, generating a low pressure, thereby sucking the gas in the vacuum pipeline 18; the output end of the steam jet air ejector 6 is connected to a steam jet air ejector condenser 19. The steam jet air ejector 6 mixes the steam and the gas in the vacuum pipeline 18 and then outputs them to the steam jet air ejector condenser 19. The steam jet air ejector condenser 19 is located at a position on the first water supply pipeline 13 close to the spray water device of the first effect evaporator of the evaporator 1, so as to realize that the first effect seawater is used as the cooling water of the condenser of the steam jet air ejector system, and the heat is recovered through heat exchange to further increase the seawater temperature of the first effect; at the same time, the mixed gas output by the steam jet air ejector 6 is condensed, the hot water returns to the waste heat boiler through the hot water return pipeline 11, and the non-condensable gas is discharged into the atmosphere.

[0035] In summary, the flue gas waste heat utilization seawater desalination system of the novel combined cycle unit of the present utility model adds a tail heating surface on the basis of the original boiler, reduces the flue gas discharge temperature of the waste heat boiler, increases the recovered heat, and increases the external supply of hot water without affecting the power generation output of the original unit; the first effect condensate and the seawater desalinated fresh water generated later are discharged from the equipment separately. Considering that the first effect steam may contain pollution caused by the addition of boiler feed water treatment chemicals, separating it from the seawater desalination product water can prevent the produced fresh water from being affected by pollutants; and preferably, a fully direct current horizontal tube falling film low-temperature multi-effect evaporator is adopted, and the evaporators of each effect at different positions are divided, and different water supply methods, temperatures, etc. are adopted, as well as methods such as two-stage pressurized discharge of brine, etc., to further realize the recovery and utilization of heat, increase the production efficiency and quality of the finished fresh water. It should be noted that the specific structures of the various basic components in the technical solution of the present utility model can all adopt the existing technologies as long as they can achieve the corresponding required functions, and the settings of the pump valve system can be adjusted in each pipeline according to needs, which is easy to achieve based on the existing technologies and is not the focus of the improvement of the present utility model, so no further elaboration is made here.

Claims

1. A novel combined cycle unit flue gas waste heat utilization seawater desalination system, characterized in that It includes a waste heat boiler hot water system, a material water supply system, a cooling water system, a brine system, a finished water system, and a vacuum system; The waste heat boiler hot water system includes a waste heat boiler, a steam-water separator (3), an evaporator (1), and a condenser (2) that are connected in sequence. Among them, the steam output end of the steam-water separator (3) is connected to the evaporator (1); the hot water output end of the steam-water separator (3) is connected to the waste heat boiler through a hot water return pipeline (11), and a hot water booster pump (10) is provided on the hot water return pipeline (11); the evaporator (1) is a multi-effect evaporator with a total of eight effects, and the condensate output end of the first-effect evaporator of the evaporator (1) is connected to the hot water return pipeline (11); The cooling water system includes a circulating cooling pipeline (12), and the condenser (2) is arranged on the circulating cooling pipeline (12); The material water supply system includes a water supply pipeline led out from the circulating cooling pipeline (12), and a seawater booster pump (4) is provided on the water supply pipeline. The water supply pipeline includes a first water supply pipeline (13) and a second water supply pipeline (14). The first water supply pipeline (13) is connected to the spray water devices of the first five-effect evaporators of the evaporator (1), and a brine heater (7) is provided on the first water supply pipeline (13); the second water supply pipeline (14) is connected to the spray water devices of the last three-effect evaporators of the evaporator (1); The brine system includes a primary brine discharge pipeline (15) and a secondary brine discharge pipeline (16); the primary brine discharge pipeline (15) connects the brine discharge ends of the first five-effect evaporators of the evaporator (1) in sequence, and a primary brine discharge pump (8) and a brine heater (7) are provided on the primary brine discharge pipeline (15); the secondary brine discharge pipeline (16) connects the brine discharge ends of the last three-effect evaporators of the evaporator (1) in sequence, and a secondary brine discharge pump (9) is provided on the secondary brine discharge pipeline (16); The finished water system includes a finished water pipeline (17), and the finished water pipeline (17) connects the fresh water output ends of the second to eighth-effect evaporators of the evaporator (1) and the condensate output end of the condenser (2) in sequence, and a finished water pump (5) is provided on the finished water pipeline (17); The vacuum system includes a vacuum pipeline (18), and the vacuum pipeline (18) connects the various-effect evaporators of the evaporator (1) and the condenser (2) in sequence, and a steam jet air ejector (6) is provided on the vacuum pipeline (18).

2. The novel combined cycle unit flue gas waste heat utilization seawater desalination system according to claim 1, wherein The output end of the steam jet air ejector (6) is connected to a steam jet air ejector condenser (19), and the steam jet air ejector condenser (19) is located at a position on the first water supply pipeline (13) close to the spray water device of the first-effect evaporator of the evaporator (1).

3. The novel combined cycle unit flue gas waste heat utilization seawater desalination system according to claim 1 or 2, characterized in that, A first steam regenerative heater (20) is also provided on the first water supply pipeline (13), and the first steam regenerative heater (20) is located in the third-effect evaporator of the evaporator (1).

4. The novel combined cycle unit flue gas waste heat utilization seawater desalination system according to claim 3, characterized in that, On the first water supply pipeline (13), the first steam regenerative heater (20) is located on the upstream side of the spray water devices of the first-effect and second-effect evaporators and on the downstream side of the spray water device of the fourth-effect evaporator.

5. The novel combined cycle unit flue gas waste heat utilization seawater desalination system according to claim 1, wherein A second water supply pipeline (14) is provided with a second steam regenerative heater (21), and the second steam regenerative heater (21) is located in the seventh-effect evaporator of the evaporator (1).

6. The novel combined cycle unit flue gas waste heat utilization seawater desalination system according to claim 5, characterized in that, On the second water supply pipeline (14), the second steam regenerative heater (21) is located on the upstream side of the spray water device of the sixth-effect evaporator and on the downstream side of the spray water device of the eighth-effect evaporator.

7. The novel combined cycle unit flue gas waste heat utilization seawater desalination system according to claim 1, characterized in that The primary brine discharge pipeline (15) is connected to the upstream side of the secondary brine discharge pump (9) of the secondary brine discharge pipeline (16).

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