Self-driven seawater desalination system and method

Abstract

The self-driven seawater desalination system comprises a tide turbine pump, a water tank, a front-end filtering device, a back washing pump, a multi-stage capacitive deionization module and a voltage stabilizer or a current stabilizer, the tide turbine pump comprises a first impeller used for generating electricity and a second impeller used for pumping seawater, the water tank is connected with the tide turbine pump through a first pipeline, and the front-end filtering device is connected with the back washing pump through a second pipeline. The front-end filtering device is connected with the water tank through a second pipeline, the backwashing pump is connected with the water tank through a third pipeline and is connected with the front-end filtering device through a fourth pipeline, and the front-end filtering device is provided with a backwashing water discharge pipeline; the multi-stage capacitive deionization module is connected with the front-end filtering device through a desalting pipeline and a desorption concentrated water pipeline which are connected in parallel, the backwash pump and the voltage stabilizer or the current stabilizer are electrically connected with the tide turbine pump, and the multi-stage capacitive deionization module is electrically connected with the voltage stabilizer or the current stabilizer. The system is good in stability and reliability, does not need additional energy storage equipment, and overcomes the defects of high energy consumption, high cost and the like of the traditional seawater desalination technology.

Description

Technical Field

[0001] The present invention relates to the technical field of seawater desalination systems and methods, and particularly to a self-driven seawater desalination system and method. Background Art

[0002] With the rapid growth of the global population and the acceleration of the industrialization process, the contradiction between the supply and demand of fresh water resources has become increasingly prominent. Many countries and regions, especially arid and semi-arid regions, are facing serious water shortages. The ocean, as the largest water source on Earth, covers 71% of the Earth's surface and contains rich potential for fresh water resources. Therefore, the development of efficient seawater desalination technologies is of great significance for ensuring global water resource security.

[0003] Seawater desalination technology is one of the effective means to alleviate water shortages. The current main seawater desalination technologies include two categories: thermal distillation and membrane processes. Thermal distillation technologies such as multi-stage flash (MSF), multi-effect distillation (MED), and vapor compression (VC) can produce high-quality fresh water, but they have extremely high energy consumption and are difficult to promote on a large scale. For example, the total energy consumption of the multi-stage flash process is in the range of 50 - 100 kWh / m 3 , which makes it difficult to promote thermal distillation technologies on a large scale economically, especially in areas lacking cheap heat sources. Membrane processes such as reverse osmosis (RO) and electrodialysis (ED) are relatively energy-saving, with energy consumption of about 3 - 10 kWh / m 3 , but still require relatively high operating costs, including membrane replacement and maintenance costs. In addition, the reverse osmosis process has high requirements for pretreatment and is easily affected by pollutants in seawater, resulting in a decline in system performance. To overcome the high energy consumption and high cost problems of traditional seawater desalination technologies, researchers have begun to explore the possibility of combining seawater desalination technologies with renewable energy. Renewable energy sources such as solar energy, wind energy, and tidal energy have the advantages of being clean and sustainable, providing new power for seawater desalination. For example, a solar photovoltaic power generation system can convert solar energy into electrical energy to supply power to seawater desalination equipment; a wind power generation system utilizes the kinetic energy of sea breeze to generate electrical energy. However, the supply of these renewable energy sources is unstable and requires additional energy storage facilities to ensure the stable operation of the system, which increases the complexity and cost of the system.

[0004] The ocean is not only the largest water body reservoir on Earth but also an important source of renewable energy (such as tidal energy) and mineral resources. Tidal energy, as a clean and sustainable form of energy, is particularly abundant in coastal areas. However, despite being a very reliable energy source in theory, its development and utilization still face many challenges. Large-scale tidal energy power generation projects often require substantial investment and technical support, while the research on miniaturized comprehensive utilization is relatively insufficient, limiting its application in more scenarios. In addition, although tidal energy has strong periodic regularity and is predictable, its supply has intermittent characteristics, and reasonable energy management and control strategies are needed to ensure the stable operation of the system. At the same time, seawater is rich in various minerals, such as magnesium, potassium, lithium, uranium, etc., and these elements play important roles in the global industry and economy. However, the existing extraction technologies are inefficient and difficult to meet the growing demand. How to efficiently extract these mineral resources has become an urgent problem to be solved.

[0005] In summary, the comprehensive utilization of ocean resources, especially the efficient extraction of tidal energy, seawater desalination, and minerals in seawater, is an emerging technical field that humans have been exploring. However, there are still some major problems at present, including insufficient research on the miniaturized comprehensive utilization of tidal energy, and the difficulty in developing large-scale tidal energy projects; the high energy consumption of existing seawater desalination technologies, the immaturity of efficient desalination technologies, and the high operating costs, which limit their wide application; the rich mineral elements in seawater, and the low efficiency of existing mineral extraction technologies, unable to meet the market demand. It is urgent to develop more efficient and low-cost technical solutions to achieve the comprehensive utilization of ocean resources and promote the global transformation to a low-carbon economy. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide a self-driven seawater desalination system with good stability and reliability, without the need for additional energy storage devices, and overcoming the high energy consumption and high cost defects of traditional seawater desalination technologies.

[0007] The present invention further provides a desalination method for the above self-driven seawater desalination system.

[0008] To solve the above technical problems, the present invention adopts the following technical solutions:

[0009] A self-driven seawater desalination system, comprising a tidal turbine pump, a water tank, a front-end filtering device, a backwashing pump, a multi-stage capacitive deionization module, and a voltage stabilizer or current stabilizer. The tidal turbine pump includes a first impeller for power generation and a second impeller for pumping seawater. The water inlet of the water tank is connected to the tidal turbine pump through a first pipeline. The water inlet of the front-end filtering device is connected to the water outlet of the water tank through a second pipeline. The backwashing pump is connected to the water outlet of the water tank through a third pipeline and to the backwashing water inlet of the front-end filtering device through a fourth pipeline. The front-end filtering device is provided with a backwashing water discharge pipeline. The water inlet of the multi-stage capacitive deionization module is connected to the water outlet of the front-end filtering device through a parallel desalination pipeline and a desorption concentrated water pipeline. The backwashing pump and the voltage stabilizer or current stabilizer are both electrically connected to the tidal turbine pump. The multi-stage capacitive deionization module is electrically connected to the voltage stabilizer or current stabilizer.

[0010] As a further improvement of the above technical solution: The tidal turbine pump is equipped with a mechanical start switch and a mechanical power supply switch. The mechanical start switch is automatically started according to the change of tidal flow rate. The mechanical power supply switch supplies power to the backwashing pump within a set time after power generation, and then supplies power to the voltage stabilizer or current stabilizer.

[0011] As a further improvement of the above technical solution: The front-end filtering device includes a security filter. The security filter includes multi-stage filters, and the pore diameter of the filter element of each stage gradually decreases.

[0012] As a further improvement of the above technical solution: Each stage of the multi-stage capacitive deionization module includes multiple capacitive deionization modules. The number of capacitive deionization modules in the subsequent stage does not exceed that of the previous stage and the height is lower than that of the previous stage.

[0013] As a further improvement of the above technical solution: Each stage of the capacitive deionization module has an independent water inlet pipeline and concentrated water pipeline. A concentrated water tank is provided between adjacent two stages of capacitive deionization modules. An electric energy recovery device is integrated in each capacitive deionization module to capture the electric energy released after desorption and transfer the electric energy to the capacitive deionization module of the next level. A DC-DC converter is provided in the electric energy transfer path.

[0014] As a further improvement of the above technical solution: Electric valves are provided at the water inlet and concentrated water outlet of each stage of the capacitive deionization module.

[0015] As a further improvement of the above technical solution: The heights of the water tank, the front-end filtering device, and the multi-stage capacitive deionization module decrease in sequence.

[0016] As a further improvement of the above technical solution: The voltage regulator or current stabilizer includes a linear voltage regulator or a switching voltage regulator for converting the electric energy output by the tidal turbine pump generator into a stable DC voltage;

[0017] Alternatively, the voltage regulator or current stabilizer includes a constant current source circuit for converting the electric energy output by the tidal turbine pump generator into a stable DC current.

[0018] A seawater desalination method based on the above self-driven seawater desalination system includes the following stages,

[0019] Backwashing stage: During the peak period of tidal power generation, when the tidal current velocity is high, the mechanical start switch and mechanical power supply switch of the tidal turbine pump are turned on, seawater is pumped into the water tank through the first pipeline, and electricity is generated for the backwashing pump; the inlet of the third pipeline is opened, the backwashing pump takes water from the water tank as the backwashing water source, and backwashes the front-end filtering device, and the backwashing water is discharged from the backwashing water external discharge pipeline;

[0020] Electrode desorption stage: After the backwashing is completed, the water in the water tank flows into the front-end filtering device through the second pipeline, and then flows into the multi-stage capacitive deionization module through the desorption concentrated water pipeline. The tidal turbine pump supplies power to the voltage regulator or current stabilizer, so that the salt ions adsorbed on the surface of the electrode material of the multi-stage capacitive deionization module are desorbed, and the adsorption capacity of the electrode is restored. The electric energy released after desorption is transmitted to the subsequent capacitive deionization module for desorption, and the concentrated water generated flows into each stage of the concentrated water tank for desorption of the subsequent capacitive deionization module;

[0021] Seawater desalination stage: During the low peak period of tidal power generation, the mechanical start switch and mechanical power supply switch of the tidal turbine pump are turned off. The water in the water tank flows into the front-end filtering device through the second pipeline, and then flows into the multi-stage capacitive deionization module through the desalination pipeline. The multi-stage capacitive deionization module is short-circuited for seawater desalination. The cathode and anode of the capacitive deionization module respectively adsorb negative ions and positive ions in seawater, remove the salt in seawater, and produce treated fresh water.

[0022] As a further improvement of the above technical solution:

[0023] The duration of the backwashing stage is 0.2 to 1.5 hours, and the electrode desorption stage is carried out under a constant voltage of 0.4 to 2.0 V or a constant current of 0 to 100 mA; a priority control strategy is adopted, so that only one level of capacitive deionization module performs desorption each time, and the other levels continue to adsorb seawater.

[0024] Compared with the prior art, the advantages of the present invention are:

[0025] The present invention does not require the setting of additional energy storage devices. It directly drives the operation of the system by utilizing the periodic regularity of tidal energy and realizes the self-control of the system, so as to overcome the defects of high energy consumption, high cost and unstable supply of renewable energy in traditional seawater desalination technologies, reduce the dependence on additional energy storage devices, improve the long-term stability of the system, and provide concentrated brine for further extraction of mineral resources in seawater.

[0026] Other features and advantages of the present invention will be described in detail in the following specific implementation section. Brief Description of the Drawings

[0027] Figure 1 It is a schematic structural diagram of the backwashing pipeline and the desorption concentrated water pipeline involved in the present invention.

[0028] Figure 2 It is a schematic structural diagram of the desalination pipeline involved in the present invention.

[0029] Figure 3 It is a schematic structural diagram of the power supply line involved in the present invention.

[0030] Figure 4 It is a schematic flow diagram of the seawater desalination method involved in the present invention.

[0031] Each label in the figure represents:

[0032] 1. Tidal turbine pump; 10. Mechanical power supply switch; 12. First pipeline; 2. Water tank; 20. Water outlet switch; 21. Second pipeline; 22. Third pipeline; 3. Front-end filtration device; 4. Backwashing pump; 41. Fourth pipeline; 42. Backwashing water external discharge pipeline; 5. Multi-stage capacitive deionization module; 51. Desalination pipeline; 52. Desorption concentrated water pipeline; 6. Voltage stabilizer or current stabilizer; 7. Concentrated water tank. Specific Implementation Manner

[0033] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present invention.

[0034] In addition, the terms "first" and "second" are for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present invention, "a plurality of" means two or more unless otherwise specifically defined.

[0035] In the present invention, unless otherwise clearly specified and defined, terms such as "assembled", "connected", "joined", "fixed", etc. shall be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or integrated; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium, and it may be the communication inside two components or the interaction relationship between two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0036] The present invention will be further described in detail below in conjunction with the accompanying drawings of the specification and specific embodiments.

[0037] Embodiment 1

[0038] Figures 1 to 3 An embodiment of the self-driven seawater desalination system of the present invention is shown. The self-driven seawater desalination system of this embodiment includes a tidal turbine pump 1, a water tank 2, a front-end filtration device 3, a backwash pump 4, a multi-stage capacitive deionization module 5, and a voltage regulator or current stabilizer 6. A first pipeline 12 is connected between the tidal turbine pump 1 and the water tank 2. The outlet of the water tank 2 is connected with a water outlet switch 20. The water outlet switch 20 is connected with a second pipeline 21 and a third pipeline 22. The second pipeline 21 is connected with the water inlet of the front-end filtration device 3. The third pipeline 22 is connected with the backwash pump 4. A fourth pipeline 41 is connected between the backwash pump 4 and the backwash water inlet of the front-end filtration device 3. A backwash water discharge pipeline 42 is provided at the upper outlet of the front-end filtration device 3. A desalination pipeline 51 and a desorption concentrated water pipeline 52 are connected between the front-end filtration device 3 and the multi-stage capacitive deionization module 5. The desalination pipeline 51 and the desorption concentrated water pipeline 52 are in a parallel structure. The backwash pump 4 is electrically connected with the tidal turbine pump 1. The voltage regulator or current stabilizer 6 is electrically connected with the tidal turbine pump 1. The multi-stage capacitive deionization module 5 is electrically connected with the voltage regulator or current stabilizer 6.

[0039] In this embodiment, the tidal turbine pump 1 adopts a double-impeller design. One impeller is used for power generation, and the other impeller is used for pumping seawater. The tidal turbine pump 1 can simultaneously generate electricity and pump seawater when the tidal flow rate is relatively high, improving the energy utilization efficiency. With this structure, the tidal turbine pump 1 can not only provide power for the system, but also pump seawater into the water tank 2 at a high position to ensure the continuous operation of the system.

[0040] In this embodiment, the tidal turbine pump 1 includes a mechanical start switch (not shown in the figure) and a mechanical power supply switch 10. The mechanical start switch is automatically started according to the change of the tidal flow rate. When the tidal flow rate reaches the set value, the mechanical start switch will automatically turn on to start the tidal turbine pump 1. The mechanical power supply switch 10 supplies power to the backwash pump 4 at a set time after power generation, and then supplies power to the voltage stabilizer or current stabilizer 6, realizing the automatic control of the system operation according to the change of the tidal flow rate, reducing manual intervention, and improving the automation degree and reliability of the system.

[0041] In this embodiment, the water tank 2 is arranged at a position higher than the front-end filtering device 3, and the water naturally flows into the front-end filtering device 3 by gravity, reducing the need for additional pumping equipment, reducing the energy consumption of the system. By the action of gravity, the water in the water tank 2 at a high position can flow smoothly into the front-end filtering device 3, ensuring the uniform distribution of the water flow and improving the filtering effect.

[0042] In this embodiment, when the tidal turbine pump 1 supplies power to the backwash pump 4, the water outlet switch 20 opens the inlet of the third pipeline 22, and opens the inlet of the second pipeline 21 at other times, ensuring that during the backwash stage, the water flow can smoothly enter the backwash pump 4, and during the seawater desalination stage and the electrode desorption stage, the water flow can smoothly enter the front-end filtering device 3. This not only ensures the backwash effect but also does not affect the normal desalination process.

[0043] In this embodiment, the front-end filtering device 3 is arranged at a position higher than the multi-stage capacitive deionization module 5, and the water naturally flows into the multi-stage capacitive deionization module 5 by gravity. Further, the front-end filtering device 3 includes a security filter, and the security filter includes multi-stage filters, and the pore diameter of the filter element of each stage gradually decreases. The materials of the filter element include but are not limited to polypropylene meltblown filter elements, fiber filter elements, etc., which can effectively remove larger impurities and suspended matters in seawater, protect the subsequent multi-stage capacitive deionization module 5, extend its service life, and improve the desalination efficiency.

[0044] In this embodiment, when the voltage stabilizer or current stabilizer 6 supplies power to the multi-stage capacitive deionization module 5 for desorption (or when the previous-stage capacitive deionization module supplies power to the subsequent-stage capacitive deionization module for desorption), the desorption concentrated water pipeline 52 is opened, and the desalination pipeline 51 is opened during the rest of the adsorption time, realizing the automatic switching of the water flow path according to the operation mode of the system, ensuring that during the electrode desorption stage, the concentrated water can be smoothly discharged, and during the normal seawater desalination stage, the treated fresh water can flow out smoothly. This not only ensures the regeneration effect of the electrode but also improves the output of fresh water.

[0045] In this embodiment, the multi-stage capacitive deionization module 5 is modularly designed. Each stage contains multiple capacitive deionization modules. The number of modules in the subsequent stage is less than or equal to that in the previous stage and the height is lower than that in the previous stage. An electric energy recovery device and a concentrated water tank 7 are provided between the capacitive deionization modules. The desorption time of the previous stage is earlier than that of the subsequent stage. After the desorption of the previous stage is completed, the module transfers electric energy to the next-stage module, and the concentrated water generated by desorption flows into the next-stage module through the concentrated water tank 7 for desorption. Further, the capacitive deionization module includes a cathode and an anode. The surface of the cathode material is positively charged and spontaneously adsorbs anions, including but not limited to activated carbon, carbon aerogel, graphene, carbon nanotube, porous carbon and other materials with positive charge groups such as amino group (-NH2) introduced on the surface, or positive charge polymers such as polydimethyldiallylammonium chloride (PDADMAC) grafted on the surface, or positive charge metal oxides such as alumina loaded on the surface. The surface of the anode material is negatively charged and spontaneously adsorbs cations, including but not limited to activated carbon, carbon aerogel, graphene, carbon nanotube, porous carbon and other materials with negative charge groups such as carboxyl group (-COOH) and sulfonic acid group (-SO3H) introduced on the surface, or negative charge polymers such as polyacrylic acid (PAA) grafted on the surface, or negative charge metal oxides such as titanium dioxide loaded on the surface. Preferably, a membrane material can be added between the cathode and the anode for separation. The membrane material includes but not limited to ion exchange membrane, nanofiltration membrane or reverse osmosis membrane. This enables the cathode and anode materials to efficiently adsorb anions and cations in seawater, achieving an efficient desalination effect. At the same time, the use of the membrane material can further improve the desalination efficiency and prevent cross-contamination of anions and cations.

[0046] In this embodiment, there is a voltage regulator or a current regulator 6. The voltage regulator includes a linear voltage regulator or a switching voltage regulator, which is used to convert the electric energy output by the tidal turbine pump generator into a stable DC voltage. The current regulator includes a constant current source circuit, such as a current feedback amplifier or a constant current diode, which is used to convert the electric energy output by the tidal turbine pump generator into a stable DC current. Ensure that the multi-stage capacitive deionization module 5 can obtain a stable power supply under different working conditions, so as to ensure the stable and reliable adsorption and desorption processes of the electrodes, and improve the overall performance and service life of the system.

[0047] During the low tide period of tidal power generation, the seawater desalination stage is entered. During the high tide period of tidal power generation, the backwashing stage and the electrode desorption stage are entered in sequence.

[0048] Seawater desalination stage: During the low tide period of tidal power generation, the mechanical start switch and the mechanical power supply switch 10 of the tidal turbine pump 1 are closed. The water in the water tank 2 at a high position flows into the front-end filtering device 3 by gravity, and then flows into the multi-stage capacitive deionization module 5 through the desalination pipeline 51. The multi-stage capacitive deionization module 5 is short-circuited for seawater desalination. The cathode and the anode respectively adsorb negative ions and positive ions in the water, removing the salt in the seawater and generating treated fresh water.

[0049] Backwashing stage: During the peak period of tidal power generation, the high tidal current velocity turns on the mechanical start switch and the mechanical power supply switch 10 of the tidal turbine pump 1, pumps seawater into the water tank 2 at a high position through the first pipeline 12, and generates electricity for the backwashing pump 4 to use. The water outlet switch 20 opens the inlet of the third pipeline 22. The backwashing pump 4 takes in water from the water tank 2 at a high position as the backwashing water source to backwash the front-end filtering device 3, and the backwashing water is discharged through the backwashing water external discharge pipeline 42.

[0050] Electrode desorption stage: After the backwashing is completed, the tidal turbine pump 1 supplies power to the voltage stabilizer or current stabilizer 6. The water outlet switch 20 opens the inlet of the second pipeline 21. The water in the water tank 2 at a high position flows into the front-end filtering device 3 by gravity, and then flows into the multi-stage capacitive deionization module 5 through the desorption concentrated water pipeline 52. The voltage stabilizer or current stabilizer 6 provides a stable DC voltage or current for the multi-stage capacitive deionization module 5, so that the salt ions adsorbed on the surface of the electrode material on the multi-stage capacitive deionization module 5 are desorbed, and the adsorption capacity of the electrode is restored. The electric energy released after desorption is transmitted to the subsequent capacitive deionization module for desorption, and the generated concentrated water flows into the respective concentrated water tanks 7 for the desorption of the subsequent capacitive deionization module. The concentrated water generated by the last-stage capacitive deionization module is used for enrichment treatment.

[0051] The self-driven seawater desalination system of this embodiment uses the periodic regularity of tidal energy to perform seawater desalination, backwashing and electrode desorption without additional energy storage equipment. The tidal turbine pump 1 with a double-impeller design has one impeller for power generation and the other for pumping seawater, ensuring automatic startup when the tidal current velocity is high, pumping seawater into the water tank 2 at a high position and generating electricity for the system to use, so as to achieve efficient energy utilization during the tidal peak period. The water tank 2 is arranged at a position higher than the front-end filtering device 3, and the water flows into the front-end filtering device 3 naturally by gravity, reducing the dependence on pumping equipment and lowering the energy consumption. The front-end filtering device 3 is further arranged at a position higher than the multi-stage capacitive deionization module 5, and the water also flows into the multi-stage capacitive deionization module 5 naturally by gravity, ensuring smooth water flow and stable operation of the system. The backwashing pump 4 is controlled by the mechanical power supply switch 10 of the tidal turbine pump 1, and backwashing is performed in the first half of the tidal power generation peak period, avoiding the conflict between the backwashing and electrode desorption processes and improving the operation efficiency of the system. The use of the voltage stabilizer or current stabilizer 6 ensures that the multi-stage capacitive deionization module 5 can obtain a stable DC voltage or current during the tidal power generation peak period, guaranteeing the smooth progress of the electrode desorption process. The modular design of the multi-stage capacitive deionization module 5 is convenient for production and installation, and the tidal energy is fully utilized through the electric energy transmission between each stage. The design of the entire system fully considers the periodic regularity of tidal energy, and through reasonable energy management and control strategies, ensures the efficient and reliable operation of the system, improving the long-term stability and sustainability of the system.

[0052] Embodiment 2

[0053] Figure 4 An embodiment of the self-driven seawater desalination method of the present invention is shown, which is carried out by using the above-mentioned self-driven seawater desalination system, including a backwashing stage, an electrode desorption stage, and a seawater desalination stage. The tidal power generation is monitored in real time to ensure that the system can automatically adjust its operating state according to the change of tidal flow velocity. When it is detected that the tidal power generation reaches a preset value, the system determines whether to enter the backwashing stage.

[0054] If it is decided to enter the backwashing stage, during the peak period of tidal power generation, the high tidal flow velocity turns on the mechanical start switch and the mechanical power supply switch 10 of the tidal turbine pump 1, pumps seawater into the water tank 2 at a high position through the first pipeline 12, and generates electricity for the backwashing pump 4 to use. The water outlet switch 20 opens the inlet of the third pipeline 22. The backwashing pump 4 takes water from the water tank 2 as the backwashing water source to backwash the front-end filtering device 3 to remove accumulated impurities and pollutants, ensuring the smooth progress of the subsequent treatment process. The backwashing water is discharged from the backwashing water external discharge pipeline 42.

[0055] After the backwashing is completed, the system will decide whether to enter the electrode desorption stage or directly start the seawater desalination process according to the current tidal conditions and the internal state of the system. In the electrode desorption stage, the tidal turbine pump 1 supplies power to the voltage stabilizer or current stabilizer 6. The water outlet switch 20 opens the inlet of the second pipeline 21. The water in the water tank 2 flows into the front-end filtering device 3 by gravity, and then flows into the multi-stage capacitive deionization module 5 through the desorption concentrated water pipeline 52. The voltage stabilizer or current stabilizer 6 provides a stable DC voltage or current for the multi-stage capacitive deionization module 5, so that the salt ions adsorbed on the surface of the electrode material in the capacitive deionization module are desorbed, and the adsorption capacity of the electrode is restored. The concentrated water generated during the desorption process flows into the concentrated water pools 7 at all levels as the desorption inlet water for the subsequent stage of the capacitive deionization module. Finally, the concentrated water generated by the last stage of the capacitive deionization module can be used for the extraction of mineral resources; at the same time, the electric energy released after desorption is transmitted to the subsequent stage of the capacitive deionization module for desorption.

[0056] Each level of the capacitive deionization module has independent inlet and concentrate water pipelines to ensure that the operations at different levels do not interfere with each other. Electric valves are set at the inlet and concentrate water outlet of each level of the capacitive deionization module, which are automatically opened or closed according to the control signal. A priority control strategy is adopted to ensure that only one level of the capacitive deionization module undergoes desorption at a time, and the other levels continue to adsorb seawater. Different desorption time intervals are set according to the adsorption capacity and desorption requirements of each level to ensure that the desorption of each level is carried out sequentially. An energy recovery device is integrated into each capacitive deionization module to capture the electric energy released during desorption and transfer it to the capacitive deionization module of the next level. A high-efficiency DC-DC converter is added to the electric energy transfer path to ensure the effective transfer of electric energy between different voltage levels. Based on the number and capacitive characteristics of the capacitive deionization modules at each level, the electric energy required for each level is calculated, and the electric energy transfer amount is adjusted accordingly. According to the real-time monitored data (such as voltage, current, capacitance status, etc.), the electric energy transfer amount is dynamically adjusted to ensure that the electric energy transferred to the next level exactly meets its requirements.

[0057] Assume the system has Figure 1 three levels of capacitive deionization modules (Level 1, Level 2, Level 3) as shown. Each level contains multiple capacitive deionization modules, and the number of modules in the lower level is less than that in the upper level.

[0058] Level 1 desorption: The tidal turbine pump (1) powers the voltage regulator or current regulator (6), which provides electric energy for all the capacitive deionization blocks in Level 1. The capacitive deionization modules in Level 1 start desorption. The desalination pipeline of Level 1 is closed, and the concentrate water pipeline of Level 1 is opened to discharge the concentrate water into the first-level concentrate water tank. After desorption is completed, the energy recovery device in Level 1 transfers the remaining electric energy to Level 2, the desalination pipeline of Level 1 is opened, and the concentrate water pipeline of Level 1 is closed.

[0059] Level 2 desorption: After receiving the electric energy transferred from Level 1, the capacitive deionization modules in Level 2 start desorption. The desalination pipeline of Level 2 is closed, and the concentrate water pipeline of Level 2 is opened and fed with water from the first-level concentrate water tank to discharge the further concentrated concentrate water into the second-level concentrate water tank. After desorption is completed, the energy recovery device in Level 2 transfers the remaining electric energy to Level 3, the desalination pipeline of Level 2 is opened, and the concentrate water pipeline of Level 2 is closed.

[0060] Level 3 desorption: After receiving the electrical energy transmitted by Level 2, the capacitive deionization module of Level 3 starts desorption. The desalination pipeline of Level 3 is closed, and the concentrated water pipeline of Level 3 is opened and filled with water from the second-stage concentrated water tank. The further enriched concentrated water is discharged for subsequent concentrated water treatment. After desorption, the remaining electrical energy can be used for other purposes or stored.

[0061] Assume that the power consumption for desorption of the capacitive deionization module at the i-th level is E desorb,i :

[0062] E desorb,i = f(V desorb,i , I desorb,i , t desorb,i , T, C electrolyte , m)

[0063] Among them, V desorb,i , I desorb,i and t desorb,i are respectively the voltage, current, and desorption time during the desorption stage of the capacitive deionization module at the i-th level, T is the temperature, C electrolyte is the electrolyte concentration, and m is the influence coefficient of the material and structure of the capacitive deionization module.

[0064] Among them, the desorption charge of the capacitive deionization module at the first level is:

[0065] E desorb,1 = (E total - E flush ) × η transfer,0

[0066] Among them, η transfer,0 is the transfer efficiency of tidal electrical energy to the capacitive deionization module at the first level.

[0067] Assume that the electrical energy transferred from the capacitive deionization module at the i-th level to the next level is E transfer,i :

[0068] E transfer,i = η transfer,i × E desorb,i

[0069] Among them, η transfer,i is the electrical energy transfer efficiency of each level.

[0070] η transfer,i = f(C i , R i , R line , η conv )

[0071] Among them, C i is the capacitance value of the capacitive deionization module of each level, Ri is the internal resistance of the capacitive deionization module, R line is the resistance of the transmission line connecting the capacitive deionization modules at all levels, η conv is the efficiency of the energy conversion device (such as a DC-DC converter) that may be involved in the process of transferring electrical energy from one level to the next.

[0072] In addition, the sum of the duration of the backwashing stage and the desorption time of the first-stage capacitive deionization module does not exceed the tidal power generation time, i.e.: t flush +t desorb,1 ≤t tide .

[0073] After the desorption of the last-stage capacitive deionization module is completed, or during the low peak period of tidal power generation, the system enters the seawater desalination stage. The mechanical start switch and mechanical power supply switch 10 of the tidal turbine pump 1 are closed. The water in the water tank 2 at a high position flows into the front-end filtering device 3 by gravity, and then flows into the multi-stage capacitive deionization module 5 through the desalination pipeline 51. The multi-stage capacitive deionization module 5 is short-circuited for seawater desalination. The cathode and anode respectively adsorb negative and positive ions in the water to remove the salt in the seawater and produce treated fresh water;

[0074] The adsorption time of each level is dynamically adjusted according to the tidal cycle and energy demand. The adsorption time of each capacitive deionization module can be determined according to the seawater treatment volume and adsorption efficiency. Suppose there are n levels of capacitive deionization modules, and the adsorption time of the i-th capacitive deionization module is t adsorb,i , then:

[0075]

[0076] Among them, V seawater is the volume of seawater entering the system, V flush is the volume of backwashing water, V desorb,i is the volume of desorbed water of the i-th capacitive deionization module, Q flow,i is the water flow rate of the i-th capacitive deionization module.

[0077] This seawater desalination method realizes the autonomous and efficient operation of three stages: seawater desalination, backwashing, and electrode desorption by reasonably utilizing the periodic regularity of tidal energy. During the low peak period of tidal power generation, the water in the water tank 2 at a high position flows into the front-end filtration device 3 by gravity, and then enters the multi-stage capacitive deionization module 5 for short-circuit desalination. The cathode and anode respectively adsorb negative ions and positive ions in the water to remove the salt in the seawater and produce treated fresh water. During the high peak period of tidal power generation, the high tidal current velocity turns on the mechanical start switch and mechanical power supply switch 10 of the tidal turbine pump 1, pumps seawater into the water tank 2 and generates electricity for the backwashing pump 4. The water outlet switch 20 opens the inlet of the third pipeline 22. The backwashing pump 4 takes water from the water tank 2 as the backwashing water source to backwash the front-end filtration device 3, and the backwashing water is discharged from the backwashing water external discharge pipeline 42. After the backwashing is completed, the tidal turbine pump 1 supplies power to the voltage stabilizer or current stabilizer 6. The water outlet switch 20 opens the inlet of the second pipeline 21. The water in the water tank 2 at a high position flows into the front-end filtration device 3 by gravity, and then enters the multi-stage capacitive deionization module 5. The voltage stabilizer or current stabilizer 6 provides a stable DC voltage or current for the multi-stage capacitive deionization module 5 to desorb the salt ions adsorbed on the surface of the electrode material and restore the adsorption capacity of the electrode. This seawater desalination method ensures the efficient and reliable operation of the system through reasonable energy management and control strategies, improves the long-term stability and sustainability of the system, and overcomes the problems of high energy consumption and high cost of traditional seawater desalination technologies, as well as the problem of unstable supply of renewable energy.

[0078] In this embodiment, the duration of the backwashing stage is fixed at 0.2 - 1.5 h.

[0079] In this embodiment, the electrode desorption stage is carried out under a constant voltage of about 0.4 - 2.0 V or a constant current of 0 - 100 mA.

[0080] During the low peak period of tidal power generation, the water stored in the water tank 2 at a high position naturally flows into the front-end filtration device 3 by gravity, and after multi-stage filtration, it enters the multi-stage capacitive deionization module 5. The multi-stage capacitive deionization module 5 utilizes the charge characteristics of the cathode and anode to respectively adsorb negative ions and positive ions in the water, thereby realizing the desalination of seawater. Since no additional power is required in this stage, the system can efficiently utilize the water in the water tank 2 for desalination, reducing energy consumption. This makes full use of the water in the water tank 2, reduces the dependence on pumping equipment, and lowers the energy consumption. At the same time, due to the gravity effect, the water flow is stable and uniform, improving the desalination efficiency. In addition, the short-circuit operation simplifies the operation of the multi-stage capacitive deionization module 5 and reduces the complexity of the system.

[0081] During the peak period of tidal power generation, the tidal turbine pump 1 automatically starts, pumping seawater into the water tank 2 and generating electricity. At this time, the backwash pump 4 uses the electric energy generated by the tidal turbine pump 1 to pump water from the water tank 2 for backwashing, removing impurities in the front-end filtering device 3 and maintaining the filtering effect. By utilizing the high flow rate during the peak period of tidal power generation, the system can automatically generate the required electricity to power the backwash pump 4. This not only reduces the dependence on external power sources, but also ensures the cleanliness of the front-end filtering device 3, extends its service life, and improves the overall operating efficiency of the system.

[0082] In the electrode desorption stage, the voltage regulator or current stabilizer 6 provides a stable DC voltage or current to the multi-stage capacitive deionization module 5, causing the salt ions adsorbed on the surface of the electrode material to desorb and restoring the adsorption capacity of the electrode. The previous-stage capacitive deionization module transfers electric energy to the next-stage capacitive deionization module, further saving energy consumption. The concentrated water is enriched through multi-stage desorption and can ultimately be used for subsequent resource utilization such as mineral extraction. This not only ensures the long-term performance of the electrode, but also improves the reliability and stability of the system, as well as the resource utilization efficiency.

[0083] Although the present invention has been disclosed above with preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make many possible changes and modifications to the technical solution of the present invention by using the above-disclosed technical content, or modify it into an equivalent embodiment with equivalent changes. Therefore, any simple modification, equivalent change, and modification made to the above embodiments based on the technical essence of the present invention without departing from the technical solution of the present invention shall fall within the scope of protection of the technical solution of the present invention.

Claims

1. A self-driven seawater desalination system, characterized in that: It includes a tidal turbine pump (1), a water tank (2), a front-end filtering device (3), a backwash pump (4), a multi-stage capacitive deionization module (5), and a voltage regulator or current stabilizer (6). The tidal turbine pump (1) includes a first impeller for power generation and a second impeller for pumping seawater. The water inlet of the water tank (2) is connected to the tidal turbine pump (1) through a first pipeline (12). The water inlet of the front-end filtering device (3) is connected to the water outlet of the water tank (2) through a second pipeline (21). The backwash pump (4) is connected to the water outlet of the water tank (2) through a third pipeline (22) and is connected to the backwash water inlet of the front-end filtering device (3) through a fourth pipeline (41). The front-end filtering device (3) is provided with a backwash water discharge pipeline (42). The water inlet of the multi-stage capacitive deionization module (5) is connected to the water outlet of the front-end filtering device (3) through a desalination pipeline (51) and a desorption concentrated water pipeline (52) connected in parallel. The backwash pump (4) and the voltage regulator or current stabilizer (6) are both electrically connected to the tidal turbine pump (1). The multi-stage capacitive deionization module (5) is electrically connected to the voltage regulator or current stabilizer (6).

2. The self-driven seawater desalination system according to claim 1, wherein: The tidal turbine pump (1) is equipped with a mechanical start switch and a mechanical power supply switch (10). The mechanical start switch is automatically started according to the change of tidal flow rate. The mechanical power supply switch (10) supplies power to the backwash pump (4) within a set time after power generation and then supplies power to the voltage regulator or current stabilizer (6).

3. The self-driven seawater desalination system according to claim 1, wherein: The front-end filtering device (3) includes a security filter. The security filter includes a multi-stage filter, and the pore diameter of the filter element of each stage gradually decreases.

4. The self-driven seawater desalination system according to claim 1, wherein: Each stage of the multi-stage capacitive deionization module (5) includes a plurality of capacitive deionization blocks. The number of capacitive deionization blocks in the subsequent stage does not exceed that of the previous stage and the height is lower than that of the previous stage.

5. The self-driven seawater desalination system according to claim 4, wherein: Each stage of capacitive deionization blocks has an independent water inlet pipeline and concentrated water pipeline. A concentrated water tank (7) is provided between adjacent two stages of capacitive deionization blocks. An electric energy recovery device is integrated in each capacitive deionization block to capture the electric energy released after desorption and transfer the electric energy to the capacitive deionization blocks of the next level. A DC-DC converter is provided in the electric energy transfer path.

6. The self-driven seawater desalination system according to claim 5, wherein: Electric valves are provided at the water inlet and concentrated water outlet of each stage of capacitive deionization blocks.

7. The self-driven seawater desalination system according to claim 1, wherein: The heights of the water tank (2), the front-end filtering device (3), and the multi-stage capacitive deionization module (5) decrease in sequence.

8. The self-driven seawater desalination system according to any one of claims 1 to 7, characterized in that: The voltage regulator or current stabilizer (6) includes a linear voltage regulator or a switching voltage regulator for converting the electric energy output by the generator of the tidal turbine pump (1) into a stable DC voltage; Alternatively, the voltage regulator or current stabilizer (6) includes a constant current source circuit for converting the electric energy output by the generator of the tidal turbine pump (1) into a stable DC current.

9. A self-driven seawater desalination method based on the self-driven seawater desalination system according to any one of claims 1 to 8, characterized in that: It includes the following stages, Backwashing stage: During the peak period of tidal power generation, the high tidal current velocity turns on the mechanical start switch and mechanical power supply switch (10) of the tidal turbine pump (1), pumps seawater into the water tank (2) through the first pipeline (12), and generates electricity for the backwashing pump (4); the inlet of the third pipeline (22) is opened, and the backwashing pump (4) takes water from the water tank (2) as the backwashing water source to backwash the front-end filtering device (3), and the backwashing water is discharged through the backwashing water external discharge pipeline (42). Electrode desorption stage: After the backwashing is completed, the water in the water tank (2) flows into the front-end filtering device (3) through the second pipeline (21), and then flows into the multi-stage capacitive deionization module (5) through the desorption concentrated water pipeline (52). The tidal turbine pump (1) supplies power to the voltage stabilizer or current stabilizer (6), so that the salt ions adsorbed on the surface of the electrode material of the multi-stage capacitive deionization module (5) are desorbed, and the adsorption capacity of the electrode is restored. The electric energy released after desorption is transmitted to the subsequent capacitive deionization module for desorption, and the generated concentrated water flows into the concentrated water tanks (7) at all levels for desorption of the subsequent capacitive deionization module. Seawater desalination stage: During the low peak period of tidal power generation, the mechanical start switch and mechanical power supply switch (10) of the tidal turbine pump (1) are closed. The water in the water tank (2) flows into the front-end filtering device (3) through the second pipeline (21), and then flows into the multi-stage capacitive deionization module (5) through the desalination pipeline (51). The multi-stage capacitive deionization module (5) is short-circuited for seawater desalination. The cathode and anode of the capacitive deionization module respectively adsorb negative ions and positive ions in seawater to remove the salt in seawater and produce treated fresh water.

10. The self-driven seawater desalination method according to claim 9, characterized in that: The duration of the backwashing stage is 0.2 - 1.5 hours, and the electrode desorption stage is carried out under a constant voltage of 0.4 - 2.0V or a constant current of 0 - 100mA; a priority control strategy is adopted to ensure that only one level of capacitive deionization module undergoes desorption each time, and the remaining levels continue to adsorb seawater.

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