Whole-plant water resource coupling utilization system and process method for coastal power plant

Abstract

The invention discloses a whole coastal power plant water resource coupling utilization system and process method. The system comprises a seawater desalination system, a concentrated water electrolysis chlorine production system and a seawater desulfurization system, the seawater desalination system comprises an ultrafiltration system, a first-stage reverse osmosis membrane system, a second-stage reverse osmosis membrane system and an EDI system which are connected in sequence; the concentrated water electrolysis chlorine production system comprises a wastewater mixing pool and an electrolytic bath which are connected in sequence; an inlet of the wastewater mixing tank is divided into two paths, one path is used for introducing ammonia nitrogen wastewater, and the other path is connected with a concentrated water outlet of the primary reverse osmosis membrane system; the seawater desulfurization system comprises a neutralization tank, a desulfurization absorption tower and a seawater desulfurization aeration tank which are connected in sequence; an inlet of the neutralization tank is connected with a water outlet of the electrolytic tank, and external seawater is introduced into the inlet of the neutralization tank; the desulfurization absorption tower uses mixed seawater from the neutralization tank as an absorption liquid. When the subsystems operate independently, part of water paths between the subsystems are coupled, and the water resource utilization rate is greatly increased.

Description

Technical Field

[0001] The present invention relates to the technical field of water treatment, and in particular to a system and process method for coupling utilization of water resources in a coastal power plant. Background Art

[0002] Due to their geographical advantages, coastal thermal power plants can use seawater as their primary water source, replacing surface freshwater. This significantly reduces freshwater consumption. For example, coastal power plants can employ seawater direct cooling technology, directly extracting seawater without the need for a circulating cooling tower. This not only conserves freshwater resources but also significantly reduces infrastructure and chemical costs. Coastal power plants can also use seawater's alkalinity to absorb SO2, replacing traditional limestone-gypsum wet desulfurization technology. Boiler feed water and other industrial and domestic water within the plant can also be produced through seawater desalination technology. However, coastal power plants still face significant challenges in the comprehensive utilization of water resources throughout the plant. For example, the concentrated water produced by the seawater desalination system is much more difficult to treat than concentrated water from surface rivers. These issues hinder the promotion of comprehensive seawater utilization technology throughout coastal power plants.

[0003] Therefore, there is an urgent need for a plant-wide water resource coupling utilization system for coastal power plants to solve the above technical problems. Summary of the Invention

[0004] In order to solve the above technical problems existing in the prior art, the purpose of the present invention is to provide a system and process method for coupling utilization of water resources in the entire coastal power plant.

[0005] The technical solution adopted in the present invention is as follows: A plant-wide water resource coupling utilization system for a coastal power plant includes a seawater desalination system, a concentrated water electrolysis chlorine production system, a seawater circulating cooling water system, and a seawater desulfurization system. Each system maintains independent operating conditions, while some waterways between them are coupled to fully utilize seawater resources.

[0006] The seawater desalination system includes an ultrafiltration system, a primary reverse osmosis membrane system, a secondary reverse osmosis membrane system and an EDI system connected in sequence.

[0007] The concentrated water electrolysis chlorine production system includes a wastewater mixing tank and an electrolytic cell connected in sequence; the inlet of the wastewater mixing tank is divided into two routes, one route is fed with ammonia nitrogen wastewater, and the other route is connected to the concentrated water outlet of the first-level reverse osmosis membrane system.

[0008] The seawater desulfurization system includes a neutralization tank, a desulfurization absorption tower and a seawater desulfurization aeration tank connected in sequence.

[0009] The seawater circulating cooling water system includes a seawater circulating pump and a cooling system for power plant generator sets. The inlet of the seawater circulating pump is divided into two routes, one is connected to the water outlet of the electrolyzer, and the other is connected to external seawater. The mixed seawater at the outlet of the seawater circulating pump is passed into the cooling system of the power plant generator sets for heat exchange, and the seawater after heat exchange is then passed into the inlet of the neutralization tank.

[0010] The desulfurization absorption tower uses mixed seawater from the neutralization tank as an absorption liquid to absorb SO2-containing flue gas. The seawater desulfurization aeration tank is equipped with an aeration device. The inlet of the seawater desulfurization aeration tank is divided into three routes: the first is connected to the absorption tower, the second is connected to the outlet of the neutralization tank via a pipeline, and the third is connected to the concentrate outlet of the secondary reverse osmosis membrane system.

[0011] Furthermore, the electrolytic cell is equipped with a cathode electrode and an anode electrode. The material of the cathode electrode is pure titanium, and the material of the anode electrode is a titanium-based coating electrode. The coating composition includes a Ta2O5 intermediate layer and a RuO2 / TiO2 active coating sequentially coated on the surface of the titanium substrate. The molar ratio of Ru to Ti in the active coating is 1:2-3.

[0012] Furthermore, the coating amount of Ta2O5 intermediate layer on the titanium substrate surface is 0.5-2 mg / cm 2 The coating amount of RuO2 / TiO2 active coating on the surface of the intermediate layer is 4-8 mg / cm 2 .

[0013] The present invention also discloses a process for coupled utilization of water resources in a coastal power plant, which is carried out in the system of the present invention. The process comprises: S1: Seawater is processed by ultrafiltration, first-stage reverse osmosis membrane, and second-stage reverse osmosis membrane in sequence, and then desalinated by the EDI system to obtain desalinated water. S2: The primary concentrated water obtained from the primary reverse osmosis membrane treatment is passed into the wastewater mixing tank, and ammonia nitrogen wastewater is added for mixing. The mixed wastewater is passed into the electrolytic cell for electrolytic deammoniation and nitrogen removal to obtain deammoniation nitrogen wastewater; S3: The wastewater after ammonia and nitrogen removal in step S2 is mixed with external seawater in a neutralization tank. The mixed seawater in the neutralization tank is divided into two paths, one of which is sprayed down from the upper liquid inlet of the desulfurization absorption tower as an absorption liquid, and at the same time, SO2-containing flue gas is introduced from the lower air inlet of the desulfurization absorption tower. The SO2-removed flue gas is discharged from the top of the desulfurization absorption tower, and the SO2-absorbed seawater is discharged from the bottom of the tower; S4: The seawater desulfurization aeration tank receives the seawater after SO2 absorption discharged from step S3 and the second seawater from the front-end neutralization tank, and blows a large amount of air into it through the aeration device to mix the seawater in the seawater desulfurization aeration tank and further increase the pH value of the seawater. Finally, the seawater in the seawater desulfurization aeration tank meets the standards and is discharged into the sea.

[0014] Furthermore, in step S2, the ammonia nitrogen wastewater is the finely treated regeneration wastewater and / or urea wastewater of the power plant, and the wastewater after the ammonia nitrogen wastewater is mixed with the primary concentrated water has an ammonia nitrogen concentration of 100~200 mg / L, a pH of 8~9, and a chloride ion concentration of 30000~40000 mg / L.

[0015] Furthermore, the electrolysis in step S2 adopts a constant voltage mode with an operating voltage range of 70V~90V. After the electrolytic treatment, the ammonia nitrogen concentration in the deammonified wastewater is less than 1mg / L, the pH is 6~7.8, and the residual chlorine in the effluent is 400~600mg / L. The residual chlorine refers to the Cl element component in hypochlorous acid, hypochlorite ion and dissolved chlorine gas.

[0016] Furthermore, in step S3, the wastewater after deammonification and nitrogen removal is mixed with external seawater in a volume ratio of 1:25-45, preferably in a volume ratio of 1:30-35, and the obtained mixed seawater is passed into the cooling system of the power plant generator set for heat exchange to 22-37°C, and then passed into the neutralization tank.

[0017] Furthermore, the pH value of the seawater finally discharged in step S4 is above 7.

[0018] The present invention proposes a system and process method for coupled utilization of water resources in the entire coastal power plant. The system mainly includes four subsystems: a seawater desalination system, an electrolytic concentrated water chlorination system, a seawater circulating cooling water system, and a seawater desulfurization system, which can cover the production and domestic water of the entire coastal power plant. The raw water is taken from the surrounding seawater and is eventually discharged into the ocean in compliance with regulations. The water produced by the seawater desalination system can meet the boiler water replenishment needs. The electrolytic concentrated water chlorination system uses the concentrated water produced by the seawater desalination system to absorb the high ammonia nitrogen wastewater produced by the power plant. The seawater circulating cooling water system meets the heat exchange needs of the power plant generator cooling system. The seawater desulfurization system replaces the traditional limestone-gypsum desulfurization method to remove sulfur substances in the flue gas. The system proposed by the present invention has significant advantages such as high process maturity, stable operation and low pollutant emissions, and has good application prospects in the field of energy technology and other related industrial fields.

[0019] Compared with the prior art, the present invention has the following advantages: 1) This system fully utilizes the abundant seawater resources in coastal areas. It uses seawater as the system water source, centrally draws water and distributes it step by step within the system. It can meet major production needs such as boiler water replenishment, heat exchange in the cooling system of power plant generator sets, and flue gas desulfurization. While each subsystem operates independently, some waterways are coupled with each other, greatly improving water resource utilization.

[0020] 2) This system utilizes an electrochemical process to mix two difficult-to-treat wastewater streams, seawater reverse osmosis concentrate and power plant high-ammonia nitrogen wastewater, and then electrolyzes them using an applied voltage. This not only absorbs the ammonia nitrogen components in the wastewater, but also allows the residual chlorine in the electrolyte to be incorporated into the seawater circulating cooling water system for sterilization, effectively saving the addition of reagents.

[0021] 3) The seawater desulfurization process has stringent requirements on the temperature of seawater. This system uses the effluent from the seawater circulating cooling water system as the inlet water for the desulfurization system, effectively saving the energy consumption required to heat the desulfurized seawater and reducing the ecological impact caused by the direct discharge of the effluent into the ocean after heat exchange. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a structural schematic diagram of a water resource coupling utilization system for a coastal power plant according to the present invention.

[0023] Figure 2 This is the process flow chart for coupling the concentrated water electrolysis chlorine production system and the seawater desulfurization system.

[0024] Figure 3 The inlet and outlet seawater temperatures of the seawater circulation system when a 1000MW unit of a coastal power plant is performing heat exchange under full load conditions in different months.

[0025] Figure 4 The test results for the comparison of seawater desulfurization efficiency before and after heat exchange (summer conditions).

[0026] Figure 5 The amount of flue gas generated by coal combustion in a 1000MW unit of a coastal power plant under full load conditions in different months.

[0027] Figure 6 The flue gas generated by coal combustion in a 1000MW unit of a coastal power plant under full load conditions in different months, and the SO2 concentration and removal rate in the inlet and outlet flue gas entering the desulfurization absorption tower.

[0028] Figure 7 The flue gas generated by coal combustion in a 1000MW unit of a coastal power plant under full load conditions in different months is treated with seawater for desulfurization by passing through the desulfurization absorption tower. The alkalinity of the seawater at the inlet and outlet of the desulfurization absorption tower is shown in the figure.

[0029] Figure 8 The flue gas generated by coal combustion in a 1000MW unit of a coastal power plant under full load conditions in different months is treated with seawater for desulfurization by passing through the desulfurization absorption tower. The salt concentration of seawater at the inlet and outlet of the desulfurization absorption tower is shown.

[0030] Figure 9 The flue gas generated by coal combustion in a 1000MW unit of a coastal power plant under full load conditions in different months is treated with seawater for desulfurization by passing through the desulfurization absorption tower. The pH value of the seawater at the inlet and outlet of the desulfurization absorption tower is shown in the figure.

[0031] The following are the descriptions of the reference numerals: 1. Water intake grille; 2. Seawater lift pump; 3. High-density sedimentation tank; 4. Sedimentation tank water pump; 5. Sand filter; 6. Ultrafiltration feed pump; 7. Ultrafiltration safety filter; 8. Ultrafiltration membrane assembly; 9. Ultrafiltration water tank; 10. Ultrafiltration water pump; 11. Seawater reverse osmosis safety filter; 12. Seawater reverse osmosis high-pressure pump; 13. First-stage reverse osmosis membrane assembly; 14. Seawater reverse osmosis water tank; 15. Freshwater reverse osmosis feed pump; 16. Desalinated water safety filter; 17. Desalination Water high-pressure pump; 18. Secondary reverse osmosis membrane assembly; 19. Pre-desulphurization water tank; 20. EDI system; 21. Wastewater mixing tank; 22. Mixed liquid lifting pump; 23. Precision filter; 24. Electrolyzer; 241. Pickling tank; 242. Pickling pump; 25. Outlet water storage tank; 26. Seawater circulation pump; 27. Neutralization tank; 28. Desulfurization seawater booster pump forebay; 29. ​​Desulfurization seawater booster pump; 30. Desulfurization absorption tower; 31. Seawater desulfurization aeration tank; 32. Industrial water pump. DETAILED DESCRIPTION

[0032] The following is a more detailed description of the present invention in conjunction with the accompanying drawings and reference numerals, so that those skilled in the art can implement the invention after studying the present invention. It should be understood that the specific embodiments described herein are for illustration only.

[0033] Example: Figure 1 This is a schematic diagram of the structure of a water resource coupling utilization system for a coastal power plant according to the present invention. The system mainly includes a water intake grid 1, a seawater lifting pump 2, a high-density sedimentation tank 3, a sedimentation tank water pump 4, a sand filter 5, an ultrafiltration water inlet pump 6, an ultrafiltration safety filter 7, an ultrafiltration membrane assembly 8, an ultrafiltration water tank 9, an ultrafiltration water pump 10, a seawater reverse osmosis safety filter 11, a seawater reverse osmosis high-pressure pump 12, a first-stage reverse osmosis membrane assembly 13, a seawater reverse osmosis water tank 14, and a freshwater reverse osmosis inlet. Water pump 15, desalinated water security filter 16, desalinated water high-pressure pump 17, secondary reverse osmosis membrane assembly 18, pre-desalting water tank 19, EDI system 20, wastewater mixing tank 21, mixed liquor lift pump 22, precision filter 23, electrolytic cell 24, pickling tank 241, pickling pump 242, effluent storage tank 25, seawater circulation pump 26, neutralization tank 27, desulfurization seawater booster pump forebay 28, desulfurization seawater booster pump 29, desulfurization absorption tower 30, seawater desulfurization aeration tank 31, industrial water pump 32.

[0034] Figure 2 This is a process flow chart of the coupled concentrated water electrolysis chlorine production system and the seawater desulfurization system of the present invention.

[0035] Throughout the present invention, during the desalination treatment of seawater by each system, the system recovery rate is equal to the volume ratio of the freshwater produced after desalination to the saltwater volume before desalination, and the system desalination rate is equal to (salt concentration before desalination - salt concentration of freshwater produced) / salt concentration before desalination * 100%.

[0036] See also Figure 1-Figure 2 The seawater desalination system, concentrated water electrolysis chlorine production system, seawater circulating cooling water system and seawater desulfurization system of the present invention work in the following manner: First, seawater desalination system: The water source for the plant's coupled water resource utilization system is seawater from the nearby sea. Its COD value is approximately 4 mg / L, its pH is between 8.0 and 8.3, its ammonia nitrogen content is below 0.1 mg / L, and its total salt content is between 32,000 and 35,000 mg / L. The seawater first passes through the water intake screen 1, which initially intercepts larger debris. The screen pitch is 50 to 100 mm. It is then pressurized by the seawater lift pump 2 and delivered to the high-density sedimentation tank 3, where flocculants are added at concentrations ranging from 0.2 to 0.5 mg / L, with a total hydraulic retention time of 30 to 50 minutes. The sedimentation tank's output water pump 4 then delivers it to the sand filter 5 for filtration. The sand filter's output water is then pressurized by the ultrafiltration inlet pump 6 and delivered to the ultrafiltration safety filter 7, which intercepts larger particulate matter. The filter element has a pore size range of 5 to 20 µm. Subsequently, macromolecular substances such as proteins and colloids are further filtered out through the ultrafiltration membrane assembly 8, and the concentrations of ammonia nitrogen and salt remain basically unchanged. The ultrafiltration membrane assembly 8 uses a hollow fiber membrane element, which is made of polyvinylidene fluoride or polyethersulfone. The pore size of the membrane surface of the ultrafiltration membrane assembly 8 for retaining particulate matter is: the inner diameter range is 0.5mm~2.0mm, and the outer diameter range is 1.0mm~3.0mm.

[0037] The water produced by the ultrafiltration membrane assembly 8 enters the ultrafiltration water tank 9. The water in the ultrafiltration water tank is then pressurized by the ultrafiltration water pump 10 and delivered to the seawater reverse osmosis safety filter, which has a pore size range of 1 to 5 µm. It then passes through the primary reverse osmosis membrane assembly 13 for desalination, achieving a system recovery rate of 35% to 50% and a system desalination rate of 99.0% to 99.5%. The total salt concentration of the concentrated water after treatment by the primary reverse osmosis membrane is 50,000 to 65,000 mg / L, while the total salt concentration of the fresh water is 100 to 300 mg / L. The fresh water produced by the primary reverse osmosis membrane assembly 13 enters the seawater reverse osmosis water tank 14. The effluent from the seawater reverse osmosis water tank 14 is split into two streams: one stream is delivered to various industrial water users within the plant, while the other stream is pressurized by the freshwater reverse osmosis inlet pump 15 and delivered to the desalinated water safety filter 16, which has a pore size range of 1 to 5 µm.

[0038] The water produced by the desalinated water safety filter 16 is pressurized by the desalinated water high-pressure pump 17 and then enters the secondary reverse osmosis membrane assembly 18 for further desalination. The system recovery rate ranges from 75% to 90% (the system recovery rate is the ratio of the system's freshwater output to the system's incoming water volume), and the system desalination rate ranges from 93% to 99%. The produced freshwater enters the pre-desalinated water tank 19 and then undergoes deep desalination via electrolysis in the EDI system 20. The EDI system recovery rate ranges from 92% to 95%, and the EDI system desalination rate ranges from 98.5% to 99.5%. The produced water enters the desalinated water tank. The produced water can be directly used as boiler feed water.

[0039] The above-mentioned seawater desalination system belongs to the existing conventional technology.

[0040] Second, electrolysis concentrated water chlorine production system: High-concentration ammonia nitrogen wastewater from power plants consists of two types: polished regeneration wastewater (large volume) and urea wastewater (small volume). The former has an ammonia nitrogen concentration of approximately 800-1200 mg / L, while the latter has an ammonia nitrogen concentration of approximately 3000 mg / L. Both wastewaters have relatively high salinity. In actual operation, this application mixes polished regeneration wastewater with urea wastewater, resulting in a high-concentration ammonia nitrogen wastewater with a combined ammonia nitrogen concentration of approximately 1100 mg / L.

[0041] The concentrated water after treatment by the first-stage reverse osmosis membrane assembly 13 enters the wastewater mixing tank and is mixed with the high-concentration ammonia nitrogen wastewater prepared above in the wastewater mixing tank. The volume ratio of the concentrated water of the first-stage reverse osmosis and the high-concentration ammonia nitrogen wastewater is approximately 3-7:1. The ammonia nitrogen concentration of the mixed wastewater is controlled to be approximately 100~200 mg / L, the pH is 8~9, the chloride ion is 30000~40000 mg / L, and the total salt concentration of the wastewater is 57000~75000 mg / L.

[0042] The thoroughly mixed wastewater is pumped by mixed liquor lift pump 22 to precision filter 23 to remove suspended particulate matter. The wastewater then enters electrolytic cell 24 for electrolysis. The electrolytic cell uses a titanium-coated anode and a pure titanium cathode. It operates in constant voltage mode within a range of 70V to 90V. After constant voltage electrolysis, the ammonia nitrogen concentration in the mixed wastewater is less than 1mg / L, the pH is 6 to 7.8, and the residual chlorine content in the effluent is 400 to 600mg / L. The deammonified wastewater enters effluent storage tank 25.

[0043] comparison Figure 1-Figure 2The electrolytic cell 24 is also equipped with an acid cleaning pump 242 and an acid cleaning tank 241, which contains an acid cleaning solution. As the electrolytic cell 24 continues to operate, the anode electrode plates will scale, reducing electrolysis efficiency. Therefore, the anode electrode plates must be acid-cleaned at regular intervals. During the acid cleaning process, the electrolytic cell is drained of wastewater and filled with clean water. Dilute hydrochloric acid or dilute sulfuric acid is added to the acid cleaning tank and circulated through the acid cleaning pump 242 to clean the electrode plates.

[0044] The present invention specifically adopts 1% by mass HCl solution for pickling, and the immersion time of each pickling is 10-15 minutes.

[0045] Third, seawater circulating cooling water system: After passing through the water intake grille, the seawater reaches the seawater lifting pump and is discharged in two ways. A small part enters the high-density sedimentation tank, and most of it enters the seawater circulating cooling water system.

[0046] The deammonified wastewater in the effluent storage tank 25 is mixed with the external seawater by the seawater circulation pump 26. The mixed seawater at the outlet of the seawater circulation pump 26 is introduced into the cooling system of the power plant generator set for heat exchange. The seawater after heat exchange is then introduced into the inlet of the neutralization tank 27.

[0047] Fourth, seawater desulfurization system: After heat exchange in the seawater circulating cooling water system, the seawater enters the neutralization tank. After heat exchange, the water temperature reaches approximately 37°C in summer and 22°C in winter, which coincides with the optimal temperature range for seawater desulfurization process water. Most of the water in the neutralization tank enters the forebay of the desulfurization seawater booster pump, where it is then pressurized by the desulfurization seawater booster pump and transported to the desulfurization absorption tower. Here, seawater is sprayed from top to bottom, while the flue gas flows from bottom to top. During this two-phase contact process, the flue gas comes into contact with the slightly alkaline seawater over a large area, dissolving the sulfur dioxide in the flue gas into the water and thus reducing its sulfur dioxide content. The pH value of the seawater after SO2 absorption discharged from the bottom of the desulfurization absorption tower is about 6.3. The seawater after SO2 absorption flows into the seawater desulfurization aeration tank by gravity. At the same time, the seawater from the front neutralization tank is fully mixed with the seawater after SO2 absorption in the aeration tank. The pH value of the mixed seawater is increased to about 6.5, and a large amount of air is blown into the aeration device. On the one hand, it can effectively mix the two water sources, and on the other hand, it can increase the dissolved oxygen in the seawater and oxidize the sulfite into stable sulfate. Aeration can also release a large amount of CO2 from the seawater, while consuming more hydrogen ions in the seawater, so that the pH value of the seawater is further increased to above 7, and finally meets the Class IV seawater discharge standard and is discharged back to the sea.

[0048] This seawater desulfurization technology utilizes the alkalinity of natural seawater (primarily composed of bicarbonates and carbonates) to absorb and neutralize sulfur dioxide in flue gas. SO2 in the flue gas dissolves upon contact with seawater, forming sulfurous acid. The bicarbonates and carbonates in the seawater neutralize the hydrogen ions produced by the ionization. The dissolved sulfite is oxidized by dissolved oxygen in the seawater to sulfate (the primary component of seawater), which is then discharged into the sea. The total salt concentration of the discharged seawater is limited to a maximum of 10%.

[0049] Example 1: The third phase of a coastal power plant, based on this system and process, utilizes a seawater desalination system, a concentrated water electrolysis chlorine production system, a seawater circulating cooling water system, and a seawater desulfurization system. The power plant utilizes a 1000MW coal-fired unit for power generation. The SO2-containing flue gas generated by coal combustion is treated by the seawater desulfurization system. The seawater circulating cooling water system also provides heat exchange for the 1000MW unit.

[0050] When the seawater desalination system is used for seawater desalination, the average output of the total reverse osmosis system is 250m3 during the operation of the first-stage reverse osmosis membrane assembly 13 and the second-stage reverse osmosis membrane assembly 18. 3 / h (i.e. the fresh water flow rate obtained), the system average recovery rate is 45.8%, and the average desalination rate is 99.5%. In addition, the average water output of the EDI system is 235m 3 / h, the system average recovery rate is 94%, and the average desalination rate is 99.3%.

[0051] During the operation of the electrolytic concentrated water chlorination system, the high-concentration wastewater and concentrated water are mixed, and the ammonia nitrogen content of the influent is 100~200mg / L, the pH is 8~9, and the chloride ion content of the influent is 30000~40000mg / L. The electrolytic cell is equipped with anode materials and cathode materials. The anode material is a titanium-based coated electrode (first coat the titanium substrate with a Ta2O5 intermediate layer with an intermediate coating of 1mg / cm 2 Then, the RuO2 / TiO2 active coating is applied on the surface of the intermediate layer, where the molar ratio of Ru to Ti is 3:7 and the active coating coating amount is 6 mg / cm 2 ), the cathode material is pure titanium, and the operating voltage range is 70V. The electrolytic water produced ammonia nitrogen of less than 1mg / L, with a pH of 6-7.8 and effluent residual chlorine of 400-600mg / L. According to the above-mentioned electrolytic concentrated water chlorine production system operation process, the electrolysis reaction continued for 9 months. During the electrolysis operation, the electrolysis was carried out every 20-40 days. The pickling interval was adjusted according to the scaling of the anode material. Each pickling was performed by immersing the anode in a 1% by mass HCl solution for 10-15 minutes. (After pickling, the surface structure of the electrolytic plate was scraped and polished to better remove scaling.) The average results of the electrolysis operation for 1 month, 6 months, and 9 months according to the time operation mode are shown in Table 1.

[0052] Table 1 .

[0053] The experimental results numbered 1, 2, and 3 in Table 1 correspond to the average results of the electrolysis operation for 1 month, 6 months, and 9 months, respectively. As the electrolysis operation continues, the current at constant voltage will slowly decrease.

[0054] The seawater desulfurization system uses only mixed seawater from the 1000MW unit after heat exchange. This mixed seawater is a mixture of external seawater and electrolytically denitrified wastewater, with a volume ratio of approximately 100:3. Depending on local climate conditions, the amount of mixed seawater required for heat exchange in the 1000MW unit and the amount of seawater used for desulfurization are both subject to seasonal fluctuations. The design quantities for "mixed seawater required for heat exchange in the 1000MW unit" and "seawater used for desulfurization" for the system are shown in Table 2.

[0055] Table 2 .

[0056] The power plant utilizes a 1000MW unit to generate electricity through coal combustion. The sulfur content of the coal is closely related to the SO2 content in the flue gas. The coal sulfur content in Table 2 represents the sulfur content of the raw coal used for power generation. The seawater desulfurization water consumption in Table 2 represents the amount of seawater used to remove SO2-containing coal flue gas in the desulfurization absorption tower. The seawater circulating cooling water system water consumption in Table 2 refers to the amount of mixed seawater required for heat exchange in the 1000MW unit.

[0057] As shown in Table 2, the amount of mixed seawater required for heat exchange of the 1000MW unit is always higher than the total water consumption of the seawater desulfurization design. The water that does not meet the desulfurization demand is directly sent to the seawater desulfurization aeration tank, mixed with the seawater after SO2 absorption in the seawater desulfurization aeration tank to increase the overall pH. After aeration treatment, it is discharged back to the ocean to meet the standards.

[0058] When the 1000MW unit of the power plant performs heat exchange under full load conditions in different months, the seawater temperature at the inlet and outlet of the seawater circulation system (i.e. the temperature of the mixed seawater before and after heat exchange) is as follows: Figure 3 As shown in the figure, due to climatic factors, the seawater temperature in summer is quite different from that in winter, so the inlet and outlet temperatures of the heat exchange show seasonal fluctuations throughout the year. Taking summer as an example, the desulfurization efficiency of seawater before and after heat exchange was compared on the pilot test equipment. After 48 hours of continuous operation, the desulfurization efficiency of seawater before and after heat exchange was compared. Figure 4 As shown, the SO2 removal rate before heat exchange is about 95.9%, and the SO2 removal rate after heat exchange is about 98.1%. The absorption and removal rate of SO2 by seawater after heat exchange is significantly higher than that before heat exchange. Figure 4In the embodiment, the temperature of the mixed seawater before heat exchange corresponds to approximately 27-28°C, and the temperature of the mixed seawater before heat exchange corresponds to approximately 34-35°C.

[0059] The seawater desulfurization system was tested for full-year operation. The data only included the full-load operation of the 1000MW unit. Affected by factors such as season and coal quality, the amount of flue gas generated by coal-fired power generation under full-load conditions in different months of the power plant's 1000MW unit is as follows: Figure 5 As shown, the average converted flue gas volume is about 3200000Nm 3 / h. According to Figure 5 The flue gas volume in Table 2 and the sulfur content in the coal are used to design the water consumption for seawater desulfurization in Table 2. The flue gas generated by coal combustion in the 1000MW power plant unit under full load conditions in different months enters the desulfurization absorption tower for SO2 removal. The SO2 concentration and removal rate of the flue gas at the inlet and outlet of the desulfurization absorption tower are as follows: Figure 6 As shown, the average SO2 concentration of the flue gas at the desulfurization tower inlet is 1094 mg / Nm 3 The average SO2 concentration of the outlet flue gas is 15.2 mg / Nm 3 (Control value is ≤35mg / Nm 3 ), with an average removal rate of 98.6%. When the flue gas generated by coal combustion in a 1000MW power plant under full load conditions in different months is treated by a desulfurization absorption tower, the alkalinity of the seawater inlet and outlet of the desulfurization absorption tower is as follows: Figure 7 As shown in the figure, the average alkalinity of seawater at the inlet of the desulfurization absorption tower is 2.27mmol / L, and the average alkalinity of seawater at the outlet of the desulfurization absorption tower is 0.66mmol / L; the salt concentration of seawater at the inlet and outlet of the desulfurization absorption tower is as follows: Figure 8 As shown in the figure, the average salt concentration of seawater at the desulfurization tower inlet is 31734 mg / L, and the average salt concentration of seawater at the desulfurization tower outlet is 34152 mg / L; the pH of seawater at the inlet and outlet of the desulfurization absorption tower is as follows: Figure 9 As shown in the figure, the average pH of seawater at the desulfurization tower inlet is 8.12, and the average pH of seawater at the desulfurization tower outlet is 6.29.

[0060] according to Figure 6 The desulfurization effect is Figure 7-Figure 9 The system is operating smoothly with no major defects found, and all parameters meet design values ​​and operating limits, demonstrating the system's rationality and reliability, and its potential for widespread application within the industry.

Claims

1. A coupled water resource utilization system for a coastal power plant, characterized by Including seawater desalination system, concentrated water electrolysis chlorine production system and seawater desulfurization system; The seawater desalination system includes an ultrafiltration system, a primary reverse osmosis membrane system, a secondary reverse osmosis membrane system and an EDI system connected in sequence; The concentrated water electrolysis chlorine production system comprises a wastewater mixing tank and an electrolytic cell connected in sequence; the inlet of the wastewater mixing tank is divided into two routes, one of which is fed with ammonia nitrogen wastewater, and the other is connected to the concentrated water outlet of the first-level reverse osmosis membrane system; The seawater desulfurization system includes a neutralization tank, a desulfurization absorption tower and a seawater desulfurization aeration tank connected in sequence; the inlet of the neutralization tank is connected to the water outlet of the electrolytic cell, and the inlet of the neutralization tank also allows external seawater to enter; the desulfurization absorption tower uses mixed seawater from the neutralization tank as an absorption liquid to absorb and treat SO2-containing flue gas, and an aeration device is provided in the seawater desulfurization aeration tank.

2. A coupled water resource utilization system for a coastal power plant as claimed in claim 1, characterized in that The inlet of the seawater desulfurization aeration tank is divided into three routes, the first route is connected to the absorption tower, the second route is connected to the outlet of the neutralization tank through a pipeline, and the third route is connected to the concentrated water outlet of the secondary reverse osmosis membrane system.

3. A coupled water resource utilization system for a coastal power plant as claimed in claim 1, characterized in that The electrolytic cell is equipped with a cathode electrode and an anode electrode. The cathode electrode is made of pure titanium, and the anode electrode is made of a titanium-based coating electrode. The coating composition includes a Ta2O5 intermediate layer and a RuO2 / TiO2 active coating sequentially coated on the surface of the titanium substrate. The molar ratio of Ru to Ti in the active coating is 1:2-3.

4. A coupled water resource utilization system for a coastal power plant as claimed in claim 3, characterized in that The coating amount of Ta2O5 intermediate layer on the titanium substrate surface is 0.5-2 mg / cm 2 The coating amount of RuO2 / TiO2 active coating on the surface of the intermediate layer is 4-8 mg / cm 2 .

5. A coupled water resource utilization system for a coastal power plant as claimed in claim 1, characterized in that A seawater circulating cooling water system is also included between the electrolysis concentrated water chlorination system and the seawater desulfurization system. The seawater circulating cooling water system includes a seawater circulating pump and a power plant generator set cooling system. The seawater circulating pump inlet is divided into two paths, one is connected to the water outlet of the electrolytic cell, and the other is connected to external seawater. The mixed seawater at the seawater circulating pump outlet is passed into the power plant generator set cooling system for heat exchange, and the seawater after heat exchange is then passed into the inlet of the neutralization tank.

6. A process for coupled utilization of water resources in a coastal power plant, characterized in that: The method is carried out in the system according to any one of claims 1 to 5, and the method comprises: S1: Seawater is processed by ultrafiltration, first-stage reverse osmosis membrane, and second-stage reverse osmosis membrane in sequence, and then desalinated by the EDI system to obtain desalinated water. S2: The primary concentrated water obtained from the primary reverse osmosis membrane treatment is passed into the wastewater mixing tank, and ammonia nitrogen wastewater is added for mixing. The mixed wastewater is passed into the electrolytic cell for electrolytic deammoniation and nitrogen removal to obtain deammoniation nitrogen wastewater; S3: The wastewater after ammonia and nitrogen removal in step S2 is mixed with external seawater in a neutralization tank. The mixed seawater in the neutralization tank is divided into two paths, one of which is sprayed down from the upper liquid inlet of the desulfurization absorption tower as an absorption liquid, and at the same time, SO2-containing flue gas is introduced from the lower air inlet of the desulfurization absorption tower. The SO2-removed flue gas is discharged from the top of the desulfurization absorption tower, and the SO2-absorbed seawater is discharged from the bottom of the tower; S4: The seawater desulfurization aeration tank receives the seawater after SO2 absorption discharged from step S3 and the second seawater from the front-end neutralization tank, and blows a large amount of air into it through the aeration device to mix the seawater in the seawater desulfurization aeration tank and further increase the pH value of the seawater. Finally, the seawater in the seawater desulfurization aeration tank meets the standards and is discharged into the sea.

7. A process for coupled utilization of water resources in a coastal power plant as claimed in claim 6, characterized in that: In step S2, the ammonia nitrogen wastewater is the finely treated regeneration wastewater and / or urea wastewater of the power plant. The ammonia nitrogen concentration in the wastewater after the ammonia nitrogen wastewater is mixed with the primary concentrated water is 100-200 mg / L and the pH is 8-9.

8. A process for coupled utilization of water resources in a coastal power plant as claimed in claim 7, characterized in that: The electrolysis in step S2 adopts a constant voltage mode with an operating voltage range of 70V~90V. After the electrolysis treatment, the ammonia nitrogen concentration in the deammonification wastewater is less than 1mg / L, the pH is 6~7.8, and the residual chlorine in the effluent is 400~600mg / L.

9. A process for coupled utilization of water resources in a coastal power plant as claimed in claim 6, characterized in that: The pH value of the seawater discharged in step S4 is finally above 7.

10. A process for coupled utilization of water resources in a coastal power plant as claimed in claim 6, characterized in that: In step S3, the wastewater after deammonification and nitrogen removal is mixed with external seawater in a volume ratio of 1:25-45, and the obtained mixed seawater is passed into the cooling system of the power plant generator set for heat exchange to 22-37°C, and then passed into the neutralization tank.

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