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

Abstract

The invention 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 invention belongs to the technical field of waste heat utilization and water treatment of waste heat boilers, and specifically relates to a new type of combined cycle unit flue gas waste heat utilization seawater desalination system. Background Art

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

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

[0004] According to the technical solution of the present invention, the present invention provides a new type of combined cycle unit flue gas waste heat utilization seawater desalination system, including a waste heat boiler hot water system, a material water supply system, a cooling water system, a brine system, a finished product water system, and a vacuum system; The waste heat boiler hot water system includes a waste heat boiler, a steam-water separator, an evaporator, and a condenser connected in sequence, wherein the steam output end of the steam-water separator is connected to the evaporator; the hot water output end of the steam-water 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 multiple-effect evaporator with eight effects in total, and the condensate output end of the first-effect evaporator of the evaporator is connected to the hot water return pipeline; The cooling water system includes a circulating cooling pipeline, and the condenser is arranged on the circulating cooling pipeline; The material water supply system includes a water supply pipeline led out from the circulating cooling pipeline, a seawater booster pump is arranged on the water supply pipeline, and 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 evaporator of the evaporator, and a brine heater is arranged on the first water supply pipeline; the second water supply pipeline is connected to the spray water device of the last three-effect evaporator of the evaporator; The brine system includes a primary brine discharge pipeline and a secondary brine discharge pipeline; the primary brine discharge pipeline sequentially 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 sequentially 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; The finished water system includes a finished water pipeline, which sequentially connects the fresh water output ends of the second effect to the 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; The vacuum system includes a vacuum pipeline, which connects the evaporators of each effect and the condenser of the evaporator in sequence, and a steam ejector is arranged on the vacuum pipeline.

[0005] Furthermore, the output end of the steam ejector is connected to a steam ejector condenser, and the steam ejector condenser is located on the first water supply pipeline at a position of a spray water device close to the first effect evaporator of the evaporator.

[0006] Furthermore, a first steam heat recovery heater is provided on the first water supply pipeline, and the first steam heat recovery heater is located in the third effect evaporator of the evaporator.

[0007] Furthermore, on the first water supply pipeline, the first steam heat recovery heater is located at the upstream side of the spray water device of the first effect and the second effect evaporator and the downstream side of the spray water device of the fourth effect evaporator.

[0008] Furthermore, a second steam heat recovery heater is provided on the second water supply pipeline, and the second steam heat recovery heater is located in the seventh effect evaporator of the evaporator.

[0009] Furthermore, on the second water supply pipeline, the second steam heat recovery heater is located on the upstream side of the spray water device of the sixth effect evaporator and the downstream side of the spray water device of the eighth effect evaporator.

[0010] Further, the primary brine discharge pipeline is connected to the upstream side of the secondary brine discharge pump of the secondary brine discharge pipeline.

[0011] Compared with the prior art, the beneficial technical effects of the present invention are as follows: The novel combined cycle unit flue gas waste heat utilization seawater desalination system of the present invention adds a rear heating surface on the basis of the original boiler, reduces the exhaust temperature of the waste heat boiler, increases the recovered heat, and increases the external hot water supply without affecting the original unit power generation output; the first effect condensate and the seawater desalination fresh water generated later are isolated and discharged. Considering that the first effect steam may contain pollution caused by boiler feed water treatment and dosing, it is separated from the seawater desalination product water to prevent the produced fresh water from being affected by pollutants; and it is preferred to use a full direct current horizontal tube falling film low-temperature multi-effect evaporator, and divide the evaporators of each effect at different positions, adopt different water supply methods, temperatures, etc., and adopt methods such as two-stage pressurized discharge of brine, so as to further realize heat recovery and increase the output efficiency and quality of finished fresh water. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is a structural schematic diagram according to an embodiment of the present invention.

[0013] Description of reference numerals in the accompanying drawings: 1. Evaporator; 2. Condenser; 3. Steam-water separator; 4. Seawater booster pump; 5. Finished water pump; 6. Steam 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. Secondary water supply pipeline; 15. Primary brine discharge pipeline; 16. Secondary brine discharge pipeline; 17. Finished water pipeline; 18. Vacuum pipeline; 19. Steam ejector condenser; 20. First steam heat recovery heater; 21. Secondary steam heat recovery heater. DETAILED DESCRIPTION

[0014] The present invention provides a novel combined cycle unit flue gas waste heat utilization seawater desalination system, which utilizes the waste heat at the tail of the waste heat boiler as the heat source for seawater desalination, thereby achieving the beneficial effects of lowering the exhaust temperature of the waste heat boiler, recovering the tail flue gas waste heat, improving the thermal efficiency of the combined cycle, and reducing the cost of seawater desalination water production.

[0015] See also Figure 1 A novel combined cycle unit flue gas waste heat utilization seawater desalination system according to one embodiment of the present invention 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.

[0016] The waste heat boiler hot water system includes a waste heat boiler, a steam-water separator 3, an evaporator 1, and a condenser 2 which are connected in sequence, wherein 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 multiple-effect evaporator with eight effects in total, and the condensate output end of the first-effect evaporator of the evaporator 1 is connected to the hot water return pipeline 11.

[0017] 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, and the steam is separated as the heating steam for the low-temperature multi-effect seawater desalination device. The first-effect heating steam is condensed effect by effect to produce seawater desalination water. The system preferably uses a full direct current horizontal tube falling film low-temperature multi-effect evaporator. Preferably, a steam ejector condenser 19 is provided at the position of the spray water device of the first-effect evaporator close to the evaporator 1 on the first water supply pipeline 13; the hot water separated by the steam-water separator and the first-effect condensed water are directly pressurized and returned to the waste heat boiler through a hot water booster pump. In this scheme, the first-effect condensed water and the seawater desalination fresh water produced later are isolated and discharged from the MED (multiple-effect distillation) equipment. This is mainly because the first-effect steam may contain pollution caused by the addition of chemicals in the boiler feed water treatment. Separating it from the seawater desalination product water can prevent the produced fresh water from being affected by pollutants.

[0018] The cooling water system includes a circulating cooling pipeline 12 , and the condenser 2 is arranged on the circulating cooling pipeline 12 .

[0019] 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 arranged 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 device of the front five-effect evaporator of the evaporator 1, and a brine heater 7 is arranged on the first water supply pipeline 13; the second water supply pipeline 14 is connected to the spray water device of the rear three-effect evaporator of the evaporator 1.

[0020] The material water supply system adopts a one-stage boosting and two-way water supply scheme. The water supply is supplied from the cooling water drainage after the condenser through a seawater booster pump, and the three effects after 6, 7, and 8 adopt one way of water supply; and preferably, a second steam heat recovery heater 21 is provided on the second water supply pipeline 14, and the second steam heat recovery 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 heat recovery heater 21 is located on the upstream side of the spray water device of the sixth effect evaporator and the downstream side of the spray water device of the eighth effect evaporator, so that the heat recovery heater is set in the 7th effect to increase the inlet water temperature of the 6th and 7th effects, while reducing the condensation amount of the 8th effect and the condenser, thereby improving the thermal efficiency. The first five effects use one seawater supply, and the condenser discharge circulating cooling water is also used as the water source; and preferably, the first water supply pipeline 13 is also provided with a first steam heat recovery heater 20, and the first steam heat recovery 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 heat recovery heater 20 is located on the upstream side of the spray water device of the first and second effect evaporators and the downstream side of the spray water device of the fourth effect evaporator. Thus, this water supply first exchanges heat with the 5-effect discharge salt water heater to increase the seawater supply temperature, and then the steam heat recovery heater set in the 3rd effect heats the first three effects of seawater again. Further, finally, through the steam ejector condenser 19, the first effect seawater is used as the cooling water of the steam ejector vacuum system condenser, and the heat is recovered to further increase the seawater temperature of the first effect. The cooling water system is the same as the traditional low-temperature multi-effect seawater desalination equipment, using seawater direct cooling water supply and circulating cooling water drainage as the water source for seawater desalination.

[0021] 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, 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 sequentially connects the brine discharge ends of the last three-effect evaporators of the evaporator 1, and a secondary brine discharge pump 9 is provided on the secondary brine discharge pipeline 16.

[0022] The brine is discharged by 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 first five-effect brine is pressurized by the primary brine discharge pump, and the seawater is heated by the brine heater. The brine temperature is reduced to a temperature close to the last-effect temperature, and then pressurized by the last-effect brine pump and discharged from the evaporator system; the last three-effect brine is directly discharged after being pressurized by the secondary brine discharge pump.

[0023] The finished water system includes a finished water pipeline 17 , which 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 .

[0024] The finished water (i.e. the obtained fresh water) is discharged from the evaporator effect by effect. After reaching the last effect, it is mixed with the condensed water from the condenser and then discharged from the system after being pressurized by the finished water pump.

[0025] The vacuum system comprises a vacuum pipeline 18 , which connects the evaporators of each effect of the evaporator 1 and the condenser 2 in sequence, and a steam ejector 6 is provided on the vacuum pipeline 18 .

[0026] The function of the vacuum system is mainly to establish vacuum at startup, and to extract the non-condensable gas of the equipment in time during operation to maintain the operating vacuum of the system. The non-condensable gas is discharged effect by effect, and finally discharged to the condenser, and then discharged out of the system through the vacuum pumping device and discharged into the atmosphere. More specifically, the jet steam vacuum pump 6 has a steam input end, an air input end and an output end. The steam input end of the jet steam vacuum pump 6 is connected to the steam pipeline of the steam turbine, that is, the steam input to the jet steam vacuum pump 6 comes from the steam extraction of the steam turbine; the steam enters the jet steam vacuum pump 6, and is ejected at high speed through the nozzle in the jet steam vacuum pump 6, generating low pressure, thereby sucking in the gas in the vacuum pipeline 18; the output end of the jet steam vacuum pump 6 is connected to the jet steam vacuum pump condenser 19, and the jet steam vacuum pump 6 sucks the steam and the vacuum into the steam pipeline 18. The gases in the empty pipeline 18 are mixed and output to the steam ejector condenser 19. The steam ejector condenser 19 is located on the first water supply pipeline 13 at the position of the spray water device of the first effect evaporator close to the evaporator 1, so that the first effect seawater is used as the cooling water for the condenser of the steam ejector system, and the heat is recovered by heat exchange to further increase the seawater temperature of the first effect; at the same time, the mixed gas output by the steam ejector 6 is condensed, and the hot water is returned to the waste heat boiler through the hot water return pipeline 11, and the non-condensable gas is discharged into the atmosphere.

[0027] In summary, the novel combined cycle unit flue gas waste heat utilization seawater desalination system of the present invention adds a tail heating surface on the basis of the original boiler, reduces the exhaust temperature of the waste heat boiler, increases the recovered heat, and increases the external hot water supply without affecting the power generation output of the original unit; the first effect condensate and the seawater desalination fresh water isolation and discharge equipment produced later, considering that the first effect steam may contain pollution caused by boiler feed water treatment and dosing, and separating it from the seawater desalination product water can prevent the produced fresh water from being affected by pollutants; and preferably adopts a full direct current horizontal tube falling film low-temperature multi-effect evaporator, and divides each effect evaporator at different positions, adopts different water supply methods, temperatures, etc., and adopts two-stage pressurized discharge of brine, etc., to further realize heat recovery and increase the output efficiency and quality of finished fresh water. It should be noted that the specific structure of each basic component in the technical solution of the present invention can adopt the existing technology, and can realize the corresponding required functions, and the setting of the pump and valve system can be adjusted in each pipeline as needed, etc., which is easy to achieve based on the existing technology and is not the focus of the improvement of the present invention, so it will not be repeated.

Claims

1. A new type of combined cycle unit flue gas waste heat utilization seawater desalination system, characterized in that: Including waste heat boiler hot water system, material water supply system, cooling water system, brine system, finished product water system, vacuum system; The waste heat boiler hot water system comprises a waste heat boiler, a steam-water separator (3), an evaporator (1), and a condenser (2) which are connected in sequence, wherein 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 via 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 multiple-effect evaporator having eight effects in total, 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 comprises a circulating cooling pipeline (12), and the condenser (2) is arranged on the circulating cooling pipeline (12); The material water supply system comprises a water supply pipeline led out from a circulating cooling pipeline (12), a seawater booster pump (4) is provided on the water supply pipeline, the water supply pipeline comprises a first water supply pipeline (13) and a second water supply pipeline (14), the first water supply pipeline (13) is connected to a spray water device of a front five-effect evaporator of the evaporator (1), and a salt water heater (7) is provided on the first water supply pipeline (13); the second water supply pipeline (14) is connected to a spray water device of a rear three-effect evaporator of the evaporator (1); The brine system comprises 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), 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) sequentially connects the brine discharge ends of the last three-effect evaporators of the evaporator (1), and a secondary brine discharge pump (9) is provided on the secondary brine discharge pipeline (16); The finished water system comprises a finished water pipeline (17), the finished water pipeline (17) sequentially connecting the fresh water output ends of the second effect to the eighth effect evaporators of the evaporator (1) and the condensate output end of the condenser (2), and a finished water pump (5) is provided on the finished water pipeline (17); The vacuum system comprises a vacuum pipeline (18), the vacuum pipeline (18) sequentially connecting the evaporators of each effect of the evaporator (1) and the condenser (2), and a steam 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 is characterized in that: The output end of the steam ejector (6) is connected to a steam ejector condenser (19), and the steam ejector condenser (19) is located on the first water supply pipeline (13) at a position 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 heat recovery heater (20) is also provided on the first water supply pipeline (13), and the first steam heat recovery 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 is characterized in that: On the first water supply pipeline (13), the first steam heat recovery heater (20) is located on the upstream side of the spray water device 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 is characterized in that: A second steam heat recovery heater (21) is provided on the second water supply pipeline (14), and the second steam heat recovery 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 is characterized in that: On the second water supply pipeline (14), the second steam heat recovery 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 is 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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