A seawater desalination device and a seawater desalination method

Abstract

The application relates to the technical field of seawater desalination, in particular to a seawater desalination device and a seawater desalination method, which comprise a permeation tank, a seawater inlet and a seawater concentrated liquid outlet are arranged on the permeation tank, a membrane element is arranged in the permeation tank, the inlet of the membrane element is connected with the outlet of a draw solution tank through a pipeline, the outlet of the membrane element is connected with the inlet of a separation tank through a pipeline, an ultrafiltration membrane is arranged in the separation tank, a liquid outlet and a water outlet are arranged on the separation tank, and the liquid outlet is connected with the inlet of the draw solution tank through a pipeline. The seawater desalination device adopts the combination of an immersed forward osmosis and ultrafiltration, is small and light, does not need to pretreat seawater, shortens the seawater desalination process, is high in efficiency and energy saving, does not need to add any chemical agent, the carbon quantum dot draw solution can be reused, operation cost is saved, the device is automatically operated, operation is simple, and management is convenient.

Description

Technical Field

[0001] This invention relates to the field of seawater desalination technology, and in particular to a seawater desalination device and a seawater desalination method. Background Technology

[0002] Compared with mainland areas at the same latitude, islands suffer from low rainfall, high evaporation, low available runoff, poor groundwater conditions, and difficulties in utilizing groundwater.

[0003] Seawater desalination is an effective way to solve the problem of freshwater scarcity. Currently, the most commonly used method for seawater desalination is the reverse osmosis membrane method. After extracting seawater, it undergoes preliminary treatment, and then a high-pressure pump is used to pressurize the seawater, forcing it into the reverse osmosis membrane. However, the reverse osmosis membrane method has high energy consumption and requires excessive operating pressure, leading to increased operating costs. Summary of the Invention

[0004] The purpose of this invention is to provide a seawater desalination device that is highly efficient and energy-saving, reducing the operating pressure of the seawater desalination device and saving operating costs; this invention also provides a seawater desalination method using this device.

[0005] This invention provides a seawater desalination device, including a permeation tank with a seawater inlet and a seawater concentrate outlet. A membrane element is installed inside the permeation tank. The inlet of the membrane element is connected to the outlet of a draw solution tank via a pipe, and the outlet of the membrane element is connected to the inlet of a separation tank via a pipe. An ultrafiltration membrane is installed inside the separation tank, and a liquid outlet and a water outlet are provided on the separation tank. The liquid outlet is connected to the inlet of the draw solution tank via a pipe.

[0006] Furthermore, the seawater inlet of the infiltration tank is connected to a submersible pump via a pipeline, and the submersible pump is connected to a PLC controller.

[0007] Furthermore, a circulation pump is provided on the pipeline between the inlet of the membrane element and the outlet of the draw liquid tank.

[0008] Furthermore, the circulating pump is connected to the PLC controller.

[0009] Furthermore, a booster pump is installed on the pipeline between the outlet of the membrane element and the inlet of the separation tank.

[0010] Furthermore, the booster pump is connected to the PLC controller.

[0011] Furthermore, the outlet of the separation tank is connected to the inlet of the ultraviolet sterilizer via a pipe, and the ultraviolet sterilizer is equipped with a product water outlet.

[0012] Furthermore, the ultraviolet sterilizer is connected to the PLC controller.

[0013] The present invention also provides a seawater desalination method, comprising the following steps:

[0014] S1. Seawater is transported into the permeation tank through the seawater inlet, so that the membrane element inside the permeation tank is immersed in seawater;

[0015] S2. The extractant in the extractant tank is transported to the interior of the membrane element. The seawater is separated by the osmotic pressure difference between the inside and outside of the membrane element, allowing water molecules in the seawater to enter the interior of the membrane element, diluting the extractant inside the membrane element to form a diluted solution. Other substances in the seawater are retained by the membrane element to form a concentrated seawater solution, which is discharged through the concentrated seawater outlet.

[0016] S3. The diluent inside the membrane element is transported to the separation tank, and fresh water and draw liquid are separated through the ultrafiltration membrane. The separated draw liquid is returned to the draw liquid tank through the outlet for reuse in seawater desalination.

[0017] Furthermore, the extractant is a carbon quantum dot extractant.

[0018] The beneficial effects of this invention are:

[0019] The technical solution of this invention combines submerged forward osmosis and ultrafiltration, which shortens the seawater desalination process, is highly efficient and energy-saving, reduces the operating pressure of the device, and saves operating costs. Attached Figure Description

[0020] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0021] Figure 1 This is a schematic diagram of the seawater desalination device in an embodiment of the present invention.

[0022] Explanation of reference numerals in the attached figures:

[0023] 1-Submersible pump, 2-Osmosis tank, 3-Membrane element, 4-Circulation pump, 5-Draw liquid tank, 6-Boost pump, 7-Separation tank, 8-Ultrafiltration membrane, 9-Ultraviolet sterilizer. Detailed Implementation

[0024] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. 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.

[0025] In the description of this invention, it should be understood that the terms "inner" and "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing this invention and 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, and therefore should not be construed as a limitation of this invention.

[0026] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the stated features. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified. Furthermore, the terms "installed," "connected," and "linked" should be interpreted broadly; for example, they may refer to a fixed connection, a detachable connection, or an integral connection; they may refer to a mechanical connection or an electrical connection; they may refer to a direct connection or an indirect connection through an intermediate medium; and they may 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.

[0027] Example

[0028] A seawater desalination device, such as Figure 1 As shown, it includes a permeation tank 2, which is equipped with a seawater inlet and a seawater concentrate outlet. The seawater inlet is connected to a submersible pump 1 through a pipe. The pipe between the seawater inlet and the submersible pump 1 is preferably a coiled flexible hose, which has the advantages of corrosion resistance, fatigue resistance, and wear resistance, and can be used for a long time. The submersible pump 1 is connected to a PLC controller. The PLC controller controls the submersible pump 1 to extract seawater and deliver the seawater to the permeation tank 2. It operates automatically, is simple to operate, and is convenient to manage.

[0029] The infiltration tank 2 contains a membrane element 3, which is submerged in seawater. The inlet of the membrane element 3 is connected to the extract tank 5 via a pipe. The extract tank 5 contains carbon quantum dot extract. A circulation pump 4 is installed on the pipe between the inlet of the membrane element 3 and the extract tank 5. The circulation pump 4 is connected to a PLC controller and delivers the carbon quantum dot extract from the extract tank 5 to the inside of the membrane element 3. The seawater is separated by the osmotic pressure difference between the inside and outside of the membrane element 3, allowing only water molecules to enter the inside of the membrane element 3, diluting the carbon quantum dot extract inside the membrane element 3 to form a diluent. Salt, heavy metals and other pollutants in the seawater are retained by the membrane element 3, forming a seawater concentrate, which is discharged through the seawater concentrate outlet. By using the osmotic pressure difference to separate the seawater, there is less concentration polarization and a high rejection rate. No chemical reagents need to be added, and no pretreatment of the seawater is required, thus shortening the seawater desalination process.

[0030] The outlet of membrane element 3 is connected to the inlet of separation tank 7 via a pipeline. A booster pump 6 is installed on the pipeline between the outlet of membrane element 3 and the inlet of separation tank 7. The booster pump 6 is connected to a PLC controller and delivers the diluent inside membrane element 3 to separation tank 7. There are four separation tanks 7, each equipped with an ultrafiltration membrane 8. Each separation tank 7 has an outlet, which is connected to the inlet of the draw solution tank 5 via a pipeline. The ultrafiltration membrane 8 separates the water in the diluent, continuously concentrating the carbon quantum dot draw solution until the carbon quantum dots are fully absorbed. The extract is concentrated to 90% and returned to the extract tank 5 for reuse in seawater separation. An ultrafiltration membrane 8 is used to separate the diluted solution, resulting in lower energy consumption and reduced operating pressure. Simultaneous separation in four separation tanks 7 increases the desalination rate and saves operating costs. Each separation tank 7 has an outlet connected to the inlet of an ultraviolet (UV) sterilizer 9 via a pipe. The UV sterilizer 9 sterilizes and disinfects the freshwater to meet drinking water standards. The UV sterilizer 9 has a product water outlet for the discharged freshwater. In this embodiment, a deep UV sterilizer is used for sterilization and disinfection.

[0031] A seawater desalination method includes the following steps:

[0032] S1. Seawater is extracted using a submersible pump 1 and transported to the permeation tank 2 through a coiled hose, so that the membrane element 3 inside the permeation tank 2 is immersed in seawater;

[0033] S2. A circulating pump 4 is used to transport the carbon quantum dot extract from the extract tank 5 to the inside of the membrane element 3. The seawater is separated by the osmotic pressure difference between the inside and outside of the membrane element 3, so that only water molecules in the seawater enter the inside of the membrane element 3, diluting the carbon quantum dot extract inside the membrane element 3 to form a diluent. Salt, heavy metals and other pollutants in the seawater are retained by the membrane element 3 to form a seawater concentrate, which is discharged through the seawater concentrate outlet.

[0034] S3. A booster pump 6 is used to transport the diluent inside the membrane element 3 to each separation tank 7. The water in the diluent is separated by the ultrafiltration membrane 8, which continuously concentrates the carbon quantum dot absorbent until it is concentrated to 90%. Then, it is returned to the absorbent tank 5 through the outlet and transported back to the membrane element 3 for seawater separation. The separated fresh water is transported to the ultraviolet sterilizer 9 through the outlet for sterilization and disinfection, so that the fresh water meets the drinking water standard and is discharged through the product water outlet.

[0035] In this embodiment, the carbon quantum dot extraction liquid inside the extraction tank 5 is prepared using the following method:

[0036] (1) Citric acid pyrolysis

[0037] Weigh 5g of Na2SO4 and 100g of anhydrous citric acid and add them to a 500mL beaker. Mix well, cover the beaker with a petri dish, and place it in an oven. Keep it at 200℃ for 200min to obtain a brownish-black solid through pyrolysis.

[0038] (2) Neutralization

[0039] Dissolve the brownish-black solid from step (1) in an appropriate amount of water, then add 10 mol / L NaOH solution dropwise to adjust the pH to 7, and obtain a mixed solution;

[0040] (3) Refined

[0041] Add ethanol to the mixed solution, stir and mix, let stand, remove the supernatant, keep the lower black viscous liquid, add an equal volume of water to the black viscous liquid to dilute, then add ethanol and stir to mix. Repeat this process 3-5 times to obtain a black viscous liquid.

[0042] A black, viscous liquid was added dropwise to methanol to form a brown precipitate. The brown precipitate was filtered and then washed with methanol. The filtration was repeated 2-3 times. The resulting solid was dried under vacuum at 40°C for 12 hours to obtain carbon quantum dot nanomaterials.

[0043] (4) Preparation

[0044] Dissolve the carbon quantum dot nanomaterials from step (3) in water and prepare a carbon quantum dot extraction solution of the appropriate concentration as needed.

[0045] By scanning the TEM image of the carbon quantum dot nanomaterial in step (3) above, it can be seen that the carbon quantum dots are uniformly dispersed and have a particle size of 30-50 nm.

[0046] The ultrafiltration membrane 8 in the separation tank 7 of this invention is made of one of the following materials: polysulfone, polyethersulfone, polyacrylonitrile, or PVDF, with a molecular weight cutoff of 100,000-180,000 and a pore size of 30-50 nm.

[0047] The membrane element 3 in the permeate tank 2 is a submerged forward osmosis membrane module with a pore size of about 0.5 nm. After the ultrafiltration membrane 8 separates the diluted carbon quantum dot draw solution, fresh water is produced. The concentrated draw solution flows into the draw solution tank 5. The carbon quantum dot draw solution in the draw solution tank 5 enters the interior of the submerged forward osmosis membrane in the permeate tank 2 and draws water molecules from seawater through the forward osmosis membrane.

[0048] Test case

[0049] A carbon quantum dot extracting solution with a concentration of 45000 mg / L-55000 mg / L was prepared, and the seawater was desalinated using the seawater desalination device and method described in the examples. The desalinated seawater showed a salt removal rate of >99%.

[0050] The above test results show that the seawater desalination device and method described in the examples have a good effect on removing salt from seawater, and the water quality after desalination can meet or exceed the "Standards for Drinking Water Quality" (GB5749-2006).

[0051] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method of desalination of sea water, characterized in that, The seawater desalination device is used, and the seawater desalination device comprises a permeation tank (2), a seawater inlet and a seawater concentrate outlet are arranged on the permeation tank (2), a membrane element (3) is arranged in the permeation tank (2), the inlet of the membrane element (3) is connected with the outlet of a draw solution tank (5) through a pipeline, the outlet of the membrane element (3) is connected with the inlet of a separation tank (7) through a pipeline, an ultrafiltration membrane (8) is arranged in the separation tank (7), a liquid outlet and a water outlet are arranged on the separation tank (7), the liquid outlet is connected with the inlet of the draw solution tank (5) through a pipeline; The seawater inlet of the permeation tank (2) is connected with a submersible pump (1) through a pipeline, and the submersible pump (1) is connected with a PLC controller; A circulating pump (4) is arranged on the pipeline between the inlet of the membrane element (3) and the outlet of the draw solution tank (5); and the circulating pump (4) is connected with the PLC controller; A booster pump (6) is arranged on the pipeline between the outlet of the membrane element (3) and the inlet of the separation tank (7); and the booster pump (6) is connected with the PLC controller; The water outlet of the separation tank (7) is connected with the inlet of an ultraviolet sterilizer (9) through a pipeline, and a product water outlet is arranged on the ultraviolet sterilizer (9); and the ultraviolet sterilizer (9) is connected with the PLC controller; The method comprises the following steps: S1. The seawater is conveyed into the permeation tank (2) through the seawater inlet, so that the membrane element (3) in the permeation tank (2) is immersed in the seawater; S2. The draw solution in the draw solution tank (5) is conveyed into the membrane element (3), the seawater is separated by the osmotic pressure difference between the inside and outside of the membrane element (3), so that the water molecules in the seawater enter the inside of the membrane element (3), the draw solution in the inside of the membrane element (3) is diluted to form diluted solution, and other substances in the seawater are intercepted by the membrane element (3) to form seawater concentrate, which is discharged through the seawater concentrate outlet; S3. The diluted solution in the inside of the membrane element (3) is conveyed into the separation tank (7), and fresh water and draw solution are separated through the ultrafiltration membrane (8), and the separated draw solution is returned to the draw solution tank (5) through the liquid outlet to be used for seawater desalination again; The draw solution is a carbon quantum dot draw solution; and the carbon quantum dot draw solution is prepared by the following method: (1) Citric acid pyrolysis 5g of Na2SO4 and 100g of anhydrous citric acid are weighed into a 500mL beaker, mixed uniformly, a culture dish is covered on the beaker, and the beaker is placed in an oven at 200℃ for 200min to obtain brown-black solid by pyrolysis; (2) Neutralization The brown-black solid in step (1) is dissolved in an appropriate amount of water, then 10mol / L NaOH solution is added dropwise, and the pH value is adjusted to 7 to obtain a mixed solution; (3) Refining Ethanol is added to the mixed solution, stirred and mixed, the supernatant is removed, and the black viscous liquid is retained. The black viscous liquid is diluted with one volume of water, and then stirred and mixed with ethanol. This process is repeated 3-5 times to obtain a black viscous liquid. The black viscous liquid is dropped into methanol to form a brown precipitate, the brown precipitate is subjected to suction filtration and then washed with methanol, the suction filtration is repeated for 2-3 times, and the obtained solid is vacuum dried at 40 DEG C for 12 h to obtain the carbon quantum dot nanomaterial; (4) preparation The carbon quantum dot nanomaterial in step (3) is dissolved into water, and a carbon quantum dot drawing solution with a corresponding concentration is prepared according to requirements.

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