Seawater desalination pool and method

Abstract

The invention relates to the field of water treatment, in particular to a seawater desalination pool and method.The seawater desalination pool comprises a waterfall pool, a waterfall platform is arranged on the waterfall pool, a water pump is arranged at the top of the waterfall platform and used for pumping seawater to the waterfall platform, a plurality of first air pumps are arranged on the waterfall platform, and the first air pumps are used for generating airflow acting on the top of the waterfall platform and flowing down the seawater; a water outlet of the waterfall pool is communicated with a desalting system, and the desalting system is used for reducing salt of flowing seawater to obtain desalted seawater; a water outlet of the desalination system is communicated with a reservoir, a gate is arranged at the communication position of the desalination system and the reservoir, an air suction port of the first air pump is communicated with the top of the reservoir, and the first air pump is used for reducing air pressure in the reservoir so that the dissolved oxygen content of desalted seawater in the reservoir can be reduced. With the adoption of the technical scheme, the seawater on the waterfall platform is subjected to oxygen exposure by pumping out the air of the water storage reservoir, so that the seawater is fully oxidized before salt desalination, and the steel bar corrosion of the concrete is subsequently delayed by reducing the salt and oxygen.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of water treatment, in particular to a seawater desalination tank and method. BACKGROUND

[0002] Concrete is the most commonly used building material in daily life, but it consumes a large amount of fresh water resources in mixing, curing and cleaning. The construction site of Yantai Changdao Beiwangcheng Island damaged island body repair project is located in Beiwangcheng Island of Changdao Comprehensive Experimental Zone, Beiwangcheng Island is located in the Bohai Strait, the junction of the Yellow Sea and the Bohai Sea, and is administratively subordinate to Beiwangcheng Township of Changdao Comprehensive Experimental Zone in Yantai City, Shandong Province, and faces Dalian Lushun District across the sea. On the one hand, the traffic is extremely inconvenient, and the transportation of materials on the island mainly depends on ships, which is low in efficiency and greatly affected by natural factors such as weather; on the other hand, the island is extremely short of fresh water resources, which seriously restricts the development of construction activities.

[0003] In the construction measures of the project, the construction of retaining wall and frame beam is a key link, and concrete is the core material of the entire construction measure, and its use runs through multiple construction processes. However, concrete needs to consume a large amount of fresh water resources in mixing, curing and cleaning. In view of the current situation of the scarcity of fresh water resources on the island, fresh water can only be transported into the island by ships, which not only consumes a lot of time and manpower, but also has high transportation cost, greatly increasing the project cost, and also has an adverse effect on the construction progress.

[0004] In recent years, the trend of seawater building material resourceization is becoming more and more obvious, and fresh water can be directly used for construction in the area near the coast to reduce fresh water resource consumption and facilitate resource allocation, but seawater contains a large amount of chloride and sulfate, which will affect the performance of concrete and seriously limit the application of seawater concrete.

[0005] In the prior art, seawater can be desalinated and then used for concrete preparation, wherein the desalination means includes extracting fresh water from seawater and separating chemical elements from seawater. Extracting fresh water from seawater can obtain fresh water with higher purity and quality, but usually through evaporation and distillation, etc., the yield is low and the cost is high. Reverse osmosis is the most popular seawater desalination technology, which uses a special semi-permeable membrane that only allows water molecules to pass through while blocking salt ions to desalinate and obtain desalinated seawater at low cost.

[0006] Desalinated seawater has a lower salt content, which significantly reduces corrosion of concrete and reinforcing steel. From another perspective, the corrosion of concrete and reinforcing steel by desalinated seawater is also related to oxygen content. The corrosion rate of reinforcing steel in dense concrete is significantly slower than that in conventional concrete because dense concrete has fewer pores, allowing less air to penetrate. Furthermore, in their study "Long-Term Durability Research of Marine Concrete," Wang Shengnian and Pan Deqiang exposed concrete specimens to a marine environment for ten years to study the long-term durability of marine concrete. Their results showed that the corrosion of reinforcing steel was most severe in the splash zone, while the concentration of chloride ions in the concrete decreased continuously with increasing seawater depth. This indicates that the penetration effect of seawater is actually less with increasing depth below the sea surface. This is likely because the dissolved oxygen content in seawater decreases with increasing depth, making it less likely to provide oxygen for corrosion and thus delaying the corrosion process. Therefore, in addition to improving the performance of concrete prepared with desalinated seawater by reducing salt content, a desalination tank and method are needed to reduce the oxygen content of treated seawater to improve concrete performance. Summary of the Invention

[0007] To address the aforementioned problems, this invention provides a seawater desalination pond and method, which aerates seawater on a waterfall platform by extracting air from a reservoir, thereby ensuring sufficient oxidation of the seawater before salinization and delaying steel corrosion of concrete by reducing salinity and oxygen levels.

[0008] This invention is achieved through the following technical solution: a seawater desalination pool, including a waterfall pool, a waterfall platform on the waterfall pool, a water pump on the top of the waterfall platform, the water pump being used to pump seawater onto the waterfall platform, a plurality of first air pumps being provided on the waterfall platform, the first air pumps being used to generate airflow acting on the seawater flowing down the top of the waterfall platform, and a grid being provided on the waterfall platform, the grid being located where the airflow acts on the seawater. The outlet of the waterfall pool is connected to a desalination system, which is used to reduce the salinity of the incoming seawater to desalinate it. The outlet of the desalination system is connected to a water storage reservoir. A gate is installed at the connection between the desalination system and the water storage reservoir. The air intake of the first air pump is connected to the top of the water storage reservoir. The first air pump is used to reduce the air pressure in the water storage reservoir, thereby reducing the dissolved oxygen content of the desalinated seawater in the water storage reservoir.

[0009] Furthermore, the air intake of the first air pump is connected to a three-way pipe. One end of the three-way pipe is connected to the top of the reservoir, and the other end of the three-way pipe is left unconnected. A first one-way valve is installed at the connection between the three-way pipe and the reservoir, and a pressure relief valve is installed at the unconnected part of the three-way pipe.

[0010] Furthermore, the desalination system includes a reverse osmosis unit, which includes a booster pump and a reverse osmosis membrane.

[0011] Further, the desalination system further comprises a pretreatment tank, and an automatic feeder is arranged on the pretreatment tank and used to add lime milk and sodium metaaluminate into the pretreatment tank.

[0012] Further, one side of the pretreatment tank is provided with a motor, and an output shaft of the motor is fixedly connected with a stirring paddle.

[0013] Further, the stirring paddle comprises a main shaft, a plurality of frame bodies are fixedly arranged on the main shaft in a circumferential direction, and a mesh body is fixedly connected in each frame body.

[0014] Further, one side of the frame body close to the main shaft is provided with a collection box, one side of the collection box close to the mesh body is provided with an opening, an elastic member is connected with a sealing plate at the opening of the collection box, a driving member is fixedly connected on the frame body, and an output end of the driving member is fixedly connected with a scraper.

[0015] Further, a pressure sensor is arranged on the frame body, and the pressure sensor is used to determine whether the frame body is away from seawater. A second one-way valve is arranged on one side of the collection box close to the main shaft, the second one-way valve is communicated with the collection box, an intercepting net is arranged at the communication position of the second one-way valve and the collection box, and a second air pump is arranged on one side of the collection box away from the main shaft. A weight sensor is arranged on one side of the collection box close to the main shaft, and the weight sensor is used to detect the weight of the sediment in the collection box. The driving member is used to send the impurities on the mesh body into the collection box after the weight sensor detects the weight of the sediment. The automatic feeder is used to obtain the detection data of the weight sensor, and the automatic feeder is used to determine whether the increased sediment is Ca4Al2O6Cl2·10H2O or Ca2Al(OH)6Cl·2H2O according to the increment of the feeding amount and the increased weight of the sediment.

[0016] Further, the outlet of the pretreatment tank is communicated with a filter tank, a plurality of filter screens are arranged in the filter tank, and the outlet of the filter tank is communicated with the reverse osmosis unit.

[0017] A seawater desalination method based on the seawater desalination tank is provided, and the method comprises the following steps. In step one, seawater is pumped to the waterfall platform, the waterfall platform forms a water waterfall to make the seawater fully contact with oxygen, oxidize the reducing substances in the seawater, and generate an air flow by the first air pump to make the water waterfall fully act on the air flow. Step two, desalination of seawater through a desalination system to obtain desalinated seawater; Step three, the desalinated seawater is stored in the water storage, and the first air pump is used to remove the gas in the water storage to make the water storage in a low pressure state, thereby reducing the dissolved oxygen content of the desalinated seawater in the water storage; Step four, the desalinated seawater in the water storage is extracted for concrete preparation and pouring in a ready-to-use manner.

[0018] The technical scheme of the present application has at least the following beneficial effects: Cl - in seawater can cause corrosion of steel bars in concrete, and the principle is that Cl - catalyzes iron to produce Fe(OH)2, and Fe(OH)2 is further oxidized to produce rust, so if seawater is used for concrete preparation, the amount of Cl - in seawater needs to be reduced.

[0019] The composition of seawater is complex, in addition to high concentration of salt, it also contains a large amount of silt, colloid, organic matter, metal ions, etc. Although the reverse osmosis unit in the desalination system can intercept other impurities, due to the large amount of impurities, it is easy to block the reverse osmosis unit, so the impurities need to be pretreated before being treated by the reverse osmosis unit to reduce the pressure of the reverse osmosis unit.

[0020] The pretreatment is treated by super-high lime-aluminum method, which can effectively produce sediment and adsorb other impurities by electric neutralization. The seawater can be aerated before pretreatment, which can increase the oxygen content of the seawater, so that the reducing substances in the seawater are oxidized, which is convenient for sedimentation and subsequent treatment, and reduces the pollution and corrosion risk of the subsequent reverse osmosis unit. The grid net is arranged at the water fall and gas flow action position, so that the water fall can be cut into small water flows by the grid net, and the gas can fully wrap the cut water fall, and the aeration oxidation effect is stronger.

[0021] The desalinated seawater treated by the reverse osmosis unit will flow into the water storage for storage, and the water storage can be closed by the gate to form a closed environment, and the first air pump can extract the gas in the water storage for aeration assistance, and the gas flow can enhance the mixing of seawater and air, and the low pressure environment is formed in the water storage, the oxygen saturation of the desalinated seawater is reduced, and the oxygen content in the desalinated seawater is gradually reduced and stored in a low oxygen content state.

[0022] In the subsequent concrete preparation process using desalinated seawater, the salt and oxygen content in the desalinated seawater are further reduced, so that Cl - , SO4 2-The number of ions for catalysis is less, and the corrosion process of the reinforcing steel is not easy to be promoted by catalysis, and the oxygen content in the desalinated seawater is further reduced by treatment, so that the oxygen content in the slurry contacted by the reinforcing steel is further reduced, and the corrosion process of the reinforcing steel under the catalysis of Cl - , SO4 2- , and other ions is more difficult. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 It is a whole schematic diagram of the seawater desalination pool embodiment of the present application; Figure 2 It is a water cascade schematic diagram of the seawater desalination pool embodiment of the present application; Figure 3 It is a three-way pipe schematic diagram of the seawater desalination pool embodiment of the present application; Figure 4 It is a stirring paddle schematic diagram of the seawater desalination pool embodiment of the present application; Figure 5 It is an enlarged schematic diagram of part A in the collecting box; Figure 4 Figure 6 It is an internal structure schematic diagram of the collecting box; Figure 7 It is a treatment process schematic diagram of the seawater desalination pool and method embodiment of the present application; Figure 8 It is a step schematic diagram of the seawater desalination pool method embodiment of the present application; Figure 9 It is a gate schematic diagram of the seawater desalination pool embodiment of the present application.

[0024] Reference signs: 1, cascade pool; 2, cascade platform; 3, water pump; 4, first air pump; 5, desalination system; 6, water storage; 7, gate; 8, three-way pipe; 9, first one-way valve; 10, pressure relief valve; 11, grid; 501, reverse osmosis unit; 50101, reverse osmosis membrane; 50102, booster pump; 502, pretreatment pool; 503, automatic feeder; 504, motor; 505, stirring paddle; 50501, frame body; 50502, net body; 50503, collecting box; 50504, sealing plate; 50505, driving piece; 50506, scraper; 50507, pressure sensor; 50508, second one-way valve; 50509, intercepting net; 50510, second air pump; 50511, weight sensor; 506, filter pool; 507, filter screen. DETAILED DESCRIPTION

[0025] ​The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0027] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0028] The following detailed description illustrates the specific implementation method: Example 1 As attached Figures 1-9 As shown, a seawater desalination pool includes a waterfall pool 1, a waterfall platform 2 on the waterfall pool 1, a water pump 3 on the top of the waterfall platform 2, the water pump 3 being used to pump seawater onto the waterfall platform 2, a plurality of first air pumps 4 on the waterfall platform 2, the first air pumps 4 being used to generate airflow acting on the seawater flowing down the top of the waterfall platform 2, and a grid 11 on the waterfall platform 2, the grid 11 being located where the airflow acts on the seawater.

[0029] The outlet of the waterfall pool 1 is connected to a desalination system 5. In this embodiment, the waterfall pool 1 overflows, so the desalination system 5 is located at the bottom of the waterfall pool 1 to receive the overflowing water. The desalination system 5 includes a reverse osmosis unit 501, which includes a booster pump 50102 and a reverse osmosis membrane 50101. The desalination system 5 is used to reduce the salinity of the incoming seawater to obtain desalinated seawater.

[0030] The water outlet of the desalination system 5 is communicated with a water storage 6, a gate 7 is arranged at the communication position of the desalination system 5 and the water storage 6, the suction port of the first air pump 4 is communicated with a three-way pipe 8, one end of the three-way pipe 8 is communicated with the top of the water storage 6, the other end of the three-way pipe 8 is connected with the atmosphere, a first one-way valve 9 is arranged at the communication position of the three-way pipe 8 and the water storage 6, and a pressure relief valve 10 is arranged at the atmosphere connection position of the three-way pipe 8. The first air pump 4 is used to reduce the air pressure in the water storage 6, so as to reduce the dissolved oxygen content of the desalinated seawater in the water storage 6.

[0031] A seawater desalination method based on the above seawater desalination tank, comprising: Step one, the seawater is pumped to the waterfall platform 2, the waterfall platform 2 forms a water waterfall to make the seawater fully contact with oxygen, oxidizes the reducing substances in the seawater, and generates an air flow through the first air pump 4 to make the water waterfall fully act on the air flow.

[0032] Step two, the seawater is desalinated through the desalination system 5 to obtain desalinated seawater.

[0033] Step three, the desalinated seawater is stored in the water storage 6, and the first air pump 4 pumps the gas in the water storage 6 away, so that the water storage 6 is in a low-pressure state, and the dissolved oxygen content of the desalinated seawater in the water storage 6 is reduced.

[0034] Step four, the desalinated seawater in the water storage 6 is pumped out for concrete preparation and pouring in a just-mixing mode.

[0035] Cl - in seawater can cause corrosion of steel bars in concrete, and the corrosion process is as follows: Anode reaction: Fe→Fe 2+ +2e - , Fe 2+ +2OH - →Fe(OH)2, Cathode reaction: O2+2H2O+4e - →4OH - , Chloride ion catalytic reaction: Fe 2+ +2Cl - +4H2O→FeCl2·4H2O, FeCl2·4H2O→Fe(OH)2+2Cl - +2H + +2H2O.

[0036] Fe(OH)2 is further oxidized to produce rust, so if seawater is used for concrete preparation, the amount of Cl - in seawater needs to be reduced, and the steel bars need to be prevented from contacting oxygen as much as possible.

[0037] The fundamental role of the reverse osmosis membrane 50101 is to allow water molecules to pass through under the driving force of an applied pressure, while intercepting most of the dissolved salts, organic matter, bacteria, viruses, colloids and other impurities in the water. The reverse osmosis unit 501 in the desalination system 5 can drive seawater through the reverse osmosis membrane 50101 by the booster pump 50102, and intercept various impurities.

[0038] Before the reverse osmosis membrane 50101, the seawater can be aerated to increase the oxygen content of the seawater, so that the reducing substances in the seawater are oxidized, which facilitates the generation of precipitates by pretreatment and subsequent treatment, and reduces the pollution and corrosion risk of the subsequent reverse osmosis unit 501. The grid net 11 is arranged at the action position of the waterfalls and the gas flow, and the grid net 11 can be fixed on the side wall of the seawater treatment site, so that the waterfalls can be cut into small streams by the grid net 11, and the gas can fully wrap the cut waterfalls, further enhancing the aeration oxidation effect. Since there may be floating objects in the seawater, the grid net 11 needs to be cleaned regularly to ensure that the holes of the grid net 11 are not blocked.

[0039] The desalinated seawater treated by the reverse osmosis unit 501 will flow into the water storage 6 for storage, and the water storage 6 can be closed by the gate 7 to build a closed environment, and the first air pump 4 can exhaust the gas in the water storage 6 for aeration assistance, and the gas flow is used to enhance the mixing of seawater and air. The water storage 6 is a low-pressure environment, because the water body's oxygen dissolving capacity is related to the gas pressure value, the smaller the gas pressure, the lower the oxygen saturation, and the upper limit of the oxygen saturation of the desalinated seawater will decrease after the gas pressure decreases, so that the oxygen content in the desalinated seawater gradually decreases, and the desalinated seawater is stored in a low-oxygen state.

[0040] As the air extraction of the first air pump 4 continues, the negative pressure in the water storage 6 will become higher and higher, making it difficult for the first air pump 4 to extract gas, and it is difficult to provide sufficient gas flow to increase the aeration process. Therefore, the three-way pipe 8 is provided, which can communicate the water storage 6 and the outside (empty connection). Since the port of the three-way pipe 8 connected to the water storage 6 is provided with the first one-way valve 9, the water storage 6 will not be depressurized to the outside through the three-way pipe 8. The port of the three-way pipe 8 connected to the outside is provided with a pressure relief valve 10, which will be opened when the pressure difference between the outside and the three-way pipe 8 reaches the threshold value of the pressure relief valve 10. The first air pump 4 will directly extract outside air through the three-way pipe 8 for aeration assistance to maintain stable gas flow.

[0041] In subsequent use, the desalinated seawater in a low oxygen content state is directly mixed in the concrete. Although the desalinated seawater will still dissolve oxygen after being pumped out, the amount of dissolved oxygen will increase as the exposure time increases. However, when mixed with the concrete, the steel bars are wrapped by the concrete, only the outside of the concrete contacts oxygen, and the steel bars are inside the concrete. Through the ready-to-use method, the moisture content of the steel bar contact surface slurry is less, and it is less likely to corrode with salt, thereby improving the performance of the seawater mixed concrete and delaying the corrosion time.

[0042] Embodiment 2 The desalination system 5 further comprises a pretreatment tank 502, and an automatic feeder 503 is arranged on the pretreatment tank 502. The automatic feeder 503 is used for adding lime milk and sodium metaaluminate into the pretreatment tank 502. One side of the pretreatment tank 502 is provided with a motor 504, and a stirring paddle 505 is bolted on the output shaft of the motor 504. The stirring paddle 505 comprises a main shaft, a plurality of frame bodies 50501 are bolted on the main shaft in the circumferential direction, and a net body 50502 is fixedly bonded in each frame body 50501. The net body 50502 is a mesh net.

[0043] The seawater is complex in composition, and contains a large amount of silt, colloid, organic matter, metal ions and the like in addition to high-concentration salt. However, due to the large amount of impurities, the reverse osmosis unit 501 is easily blocked, so the impurities need to be pretreated before being treated by the reverse osmosis unit 501 to reduce the pressure of the reverse osmosis unit 501.

[0044] The pretreatment tank 502 can coagulate and flocculate and precipitate the seawater before reverse osmosis treatment. Coagulation and flocculation are carried out by adding lime milk and sodium metaaluminate. Coagulation and flocculation can remove part of the chloride ions, and at the same time, precipitate other metal ions. The motor 504 can drive the stirring paddle 505 to rotate, so that the frame body 50501 drives the net body 50502 to stir the pretreatment tank 502 while coagulating and flocculating the precipitate, so as to prevent the precipitate from reaching the reverse osmosis unit 501 and blocking the reverse osmosis unit 501.

[0045] Embodiment 3 The frame body 50501 is provided with a collection box 50503 on the side close to the main shaft. The net body 50502 is a straight net that is taut. The collection box 50503 is provided with an opening on the side close to the net body 50502. An elastic member is connected to the opening of the collection box 50503. A driving member 50505 is bolted on the frame body 50501. The driving member 50505 is an electric screw. A scraper 50506 is bolted on the output end of the driving member 50505. The driving member 50505 is used for driving the scraper 50506 to scrape off the impurities attached to the net body 50502, and the scraper 50506 is used for extruding the sealing plate 50504 to send the impurities into the collection box 50503.

[0046] The pressure sensor 50507 is fixed on the frame 50501 by screws, and is used to determine whether the frame 50501 is away from seawater. The second one-way valve 50508 is arranged on the side of the collection box 50503 close to the main shaft, and is in communication with the collection box 50503. The second one-way valve 50508 is provided with the interception net 50509 at the communication position with the collection box 50503. The second air pump 50510 is arranged on the side of the collection box 50503 away from the main shaft. The air inlet of the second air pump 50510 is provided with a waterproof air-permeable film to prevent seawater from entering. The second air pump 50510 is used to inject air into the collection box 50503 to discharge seawater in the collection box 50503 from the second one-way valve 50508 after the frame 50501 is away from seawater. The weight sensor 50511 is arranged on the side of the collection box 50503 close to the main shaft. The weight sensor 50511 is a tension sensor. The interception net 50509 is adhesively fixed on the detection end of the weight sensor 50511. The weight sensor 50511 is used to detect the weight of the sediment in the collection box 50503. The driving member 50505 is used to send the impurities into the collection box 50503 after the weight sensor 50511 detects the weight of the sediment. The automatic feeder 503 is used to obtain the detection data of the weight sensor 50511. The automatic feeder 503 is used to determine whether the increased sediment is Ca4Al2O6Cl2·10H2O or Ca2Al(OH)6Cl·2H2O according to the feeding amount increment and the increased weight of the sediment. If the increased sediment is Ca4Al2O6Cl2·10H2O or Ca2Al(OH)6Cl·2H2O, the feeding amount is increased. If the increased sediment is not Ca4Al2O6Cl2·10H2O or Ca2Al(OH)6Cl·2H2O, the feeding amount is reduced.

[0047] The filter tank 506 is in communication with the outlet of the pretreatment tank 502. The filter tank 506 is provided with a plurality of filter screens 507. The outlet of the filter tank 506 is in communication with the reverse osmosis unit 501.

[0048] The net body 50502 can salvage the sediment. However, as the salvaged sediment increases, the net body 50502 will be blocked or fully loaded. Therefore, the optimized net body 50502 is a straight net that is taut. In this way, the sediment will be attached to the same plane. The driving member 50505 on the frame 50501 can drive the scraper 50506 to scrape the sediment on the net body 50502.

[0049] The collecting box 50503 can serve as a storage for impurities. An opening of the collecting box 50503 is provided with a sealing plate 50504. The sealing plate 50504 is connected to the opening of the collecting box 50503 by an elastic member. Without external intervention, the sealing plate 50504 will close the opening of the collecting box 50503, so that the collecting box 50503 will not be filled with water even when the water surface of the pretreatment pool 502 is below the collecting box 50503. The sealing plate 50504 will be pushed away by the scraper 50506 driven by the driving member 50505, so as to send the scraped precipitate into the collecting box 50503.

[0050] The pressure sensor 50507 can detect pressure. When the frame 50501 is inserted into the filter pool 506, the pressure sensor 50507 can determine whether the frame 50501 is immersed in seawater or not according to the water pressure.

[0051] After the lime milk and sodium metaaluminate are added, the lime milk and sodium metaaluminate will react with metal ions to produce hydroxide precipitate. In addition, the lime milk and sodium metaaluminate will also directly react with chloride ions to produce Ca4Al2O6Cl2·10H2O or Ca2Al(OH)6Cl·2H2O precipitate. The precipitate can fix chloride ions, thereby reducing the content of chloride in seawater. However, the amount of Ca4Al2O6Cl2·10H2O or Ca2Al(OH)6Cl·2H2O produced by the reaction increases first and then decreases with the addition of lime milk and sodium metaaluminate. When the ratio of lime milk, sodium metaaluminate and chloride ions is 3:2:1, the efficiency is optimal. However, if the amount of lime milk and sodium metaaluminate continues to increase, the following reaction will occur: 3Ca4Al2O6Cl2·10H2O + 2Al(OH)4 - + 4OH - = 4Ca3Al2(OH) 12 + 6Cl - + 12H2O The reaction will cause the release of chloride ions originally fixed in the precipitate, and the precipitate will be converted into Ca3Al2(OH) 12 . Therefore, it is necessary to control the amount of lime milk and sodium metaaluminate added to achieve the effect of fixing chloride ions.

[0052] The collecting box 50503 can collect solid precipitate and impurities. Therefore, the current amount of addition can be evaluated by detecting the change in the mass of the solid product. When the scraper scrapes off the impurities, seawater on the net body 50502 will also be brought in. Therefore, the seawater in the collecting box 50503 needs to be further removed in order to measure the weight of the solid precipitate.

[0053] When the frame 50501 leaves the seawater, the second air pump 50510 is started to inject air flow into the collection box 50503, which will increase the pressure in the collection box 50503 and force the seawater out of the collection box 50503. During this process, the air flow will press the solid precipitate and the seawater through the second one-way valve 50508, wherein the solid precipitate will be intercepted by the interception net 50509 and thus remain in the collection box 50503, and the seawater will be discharged through the second one-way valve 50508. After the seawater is discharged, the second air pump 50510 can be closed, and the second one-way valve 50508 will continue to discharge air to restore the normal pressure of the collection box 50503, so as to avoid the influence of the pressure of the air flow on the subsequent weighing.

[0054] The weight sensor 50511 can weigh the solid precipitate on the interception net 50509, and the weight of the solid precipitate can be obtained by excluding the weight of the interception net 50509. In order to ensure the accuracy of the weighing result, the rotation speed of the motor 504 needs to be set to be slow to reduce the interference caused by the centrifugal force, and the time node of the measurement is selected as when the collection box 50503 rotates to the water surface and is perpendicular to the horizontal line.

[0055] The content of chloride ions in seawater varies with regions. The automatic feeder 503 obtains the detection data of the weight sensor 50511, and takes the weight of the precipitate generated when the conventional lime milk and sodium metaaluminate are put as background data. When the amount of lime milk and sodium metaaluminate is increased, if the weight increase of the precipitate generated is within the weight range of Ca4Al2O6Cl2·10H2O or Ca2Al(OH)6Cl·2H2O precipitate, it indicates that the current amount of lime milk and sodium metaaluminate has not reached the optimal dosage for removing chloride ions, and the amount of lime milk and sodium metaaluminate needs to be further increased. When the amount of lime milk and sodium metaaluminate is increased, if the weight increase of the precipitate generated is within the weight range of Ca3Al2(OH) 12 , it indicates that the current amount of lime milk and sodium metaaluminate is too much, which causes the chloride ion removal efficiency to decrease, and the amount of lime milk and sodium metaaluminate should be reduced.

[0056] The driving member 50505 is used to drive the scraper 50506 to send the impurities into the collection box 50503. Since the weighing is preferably performed when the collection box 50503 rotates to the water surface and is perpendicular to the horizontal line, in order to ensure better seawater removal efficiency, the impurities on the net body 50502 are sent after the weighing.

[0057] The seawater treated by the pretreatment tank 502 will flow into the filter tank 506, which will filter the remaining particles in the seawater, further reducing the filtration pressure of the reverse osmosis unit 501, so as to avoid the reverse osmosis unit 501 from being blocked too fast.

[0058] Obviously, the above embodiments are merely example for clearly illustrating but not limitation to the embodiments. Based on the above description, other different forms of changes or variations can be made by those skilled in the art. Here, all the embodiments need not and can not be enumerated. The obvious changes or variations derived from the above description are still within the protection scope of the present application.

Claims

1. A seawater desalination tank, characterized in that, It includes a waterfall pool (1), a waterfall platform (2) on the waterfall pool (1), a water pump (3) on the top of the waterfall platform (2), the water pump (3) is used to pump seawater to the waterfall platform (2), a number of first air pumps (4) are provided on the waterfall platform (2), the first air pumps (4) are used to generate airflow that acts on the top of the waterfall platform (2) and the waterfall platform (2) is provided with a grid (11), the grid (11) is located where the airflow acts on the seawater; The outlet of the waterfall pool (1) is connected to a desalination system (5), which is used to reduce the salt content of the seawater flowing in to obtain desalinated seawater; The outlet of the desalination system (5) is connected to the reservoir (6). A gate (7) is provided at the connection between the desalination system (5) and the reservoir (6). The air intake of the first air pump (4) is connected to the top of the reservoir (6). The first air pump (4) is used to reduce the air pressure in the reservoir (6) so as to reduce the dissolved oxygen content of the desalinated seawater in the reservoir (6).

2. The seawater desalination tank according to claim 1, characterized in that, The air inlet of the first air pump (4) is connected to a three-way pipe (8). One end of the three-way pipe (8) is connected to the top of the reservoir (6), and the other end of the three-way pipe (8) is unconnected. A first one-way valve (9) is provided at the connection between the three-way pipe (8) and the reservoir (6), and a pressure relief valve (10) is provided at the unconnected part of the three-way pipe (8).

3. The seawater desalination tank according to claim 1, characterized in that, The desalination system (5) includes a reverse osmosis unit (501), which includes a booster pump (50102) and a reverse osmosis membrane (50101).

4. The seawater desalination tank according to claim 3, characterized in that, The desalination system (5) also includes a pretreatment tank (502), which is equipped with an automatic feeder (503) for adding lime slurry and sodium aluminate to the pretreatment tank (502).

5. The seawater desalination tank according to claim 4, characterized in that, A motor (504) is provided on one side of the pretreatment tank (502), and an agitator (505) is fixedly connected to the output shaft of the motor (504).

6. The seawater desalination tank according to claim 5, characterized in that, The stirring paddle (505) includes a main shaft, and several frames (50501) are fixed circumferentially on the main shaft. Each frame (50501) is fixedly connected to a mesh (50502).

7. The seawater desalination tank according to claim 6, characterized in that, A collection box (50503) is provided on the side of the frame (50501) near the main shaft. The collection box (50503) has an opening on the side near the mesh (50502). A sealing plate (50504) is connected to the opening of the collection box (50503) through an elastic element. A driving element (50505) is fixedly connected to the frame (50501). A scraper (50506) is fixedly connected to the output end of the driving element (50505). The driving element (50505) is used to drive the scraper (50506) to scrape off the impurities attached to the mesh (50502) and make the scraper (50506) squeeze the sealing plate (50504) to send the impurities into the collection box (50503).

8. The seawater desalination tank according to claim 7, characterized in that, A pressure sensor (50507) is installed on the frame (50501). The pressure sensor (50507) is used to determine whether the frame (50501) is out of the seawater. A second one-way valve (50508) is provided on the side of the collection box (50503) near the main shaft. The second one-way valve (50508) is connected to the collection box (50503). An intercepting net (50509) is provided at the connection between the second one-way valve (50508) and the collection box (50503). A second air pump (50510) is provided on the side of the collection box (50503) away from the main shaft. The second air pump (50510) is used to inject air into the collection box (50503) after the frame (50501) leaves the seawater, so that the seawater in the collection box (50503) is discharged from the second one-way valve (50508). A weight sensor (50511) is provided on one side of the collection box (50503) near the main shaft. The weight sensor (50511) is used to detect the weight of the sediment in the collection box (50503). The drive unit (50505) is used to send the impurities on the mesh (50502) into the collection box (50503) after the weight sensor (50511) detects the weight of the sediment; The automatic feeder (503) is used to acquire the detection data of the weight sensor (50511). The automatic feeder (503) is used to determine whether the increased precipitate is Ca4Al2O6Cl2·10H2O or Ca2Al(OH)6Cl·2H2O based on the increase in the amount of feed and the increase in the weight of the precipitate. If it is Ca4Al2O6Cl2·10H2O or Ca2Al(OH)6Cl·2H2O, the amount of feed is increased. If it is not Ca4Al2O6Cl2·10H2O or Ca2Al(OH)6Cl·2H2O, the amount of feed is reduced.

9. The seawater desalination tank according to claim 8, characterized in that, The outlet of the pretreatment tank (502) is connected to the filter tank (506), which is equipped with several filter screens (507). The outlet of the filter tank (506) is connected to the reverse osmosis unit (501).

10. A seawater desalination method based on the seawater desalination tank of claim 1, characterized in that, include: Step 1: The seawater is pumped to the waterfall platform (2). The waterfall platform (2) will form a waterfall so that the seawater can fully contact with oxygen, oxidize the reducing substances in the seawater, and generate airflow through the first air pump (4) so ​​that the waterfall and airflow can fully interact. Step 2: Desalinate the seawater through the desalination system (5) to obtain desalinated seawater; Step 3: The desalinated seawater is placed in the reservoir (6) and the first air pump (4) extracts the gas from the reservoir (6) to make the reservoir (6) a low-pressure state, thereby reducing the dissolved oxygen content of the desalinated seawater in the reservoir (6). Step 4: The desalinated seawater in the reservoir (6) is extracted and poured into concrete using an on-demand method.

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