Sea water desalination system driven by sea waves and sea water desalination method

Abstract

In the sea wave-driven sea water desalination system and sea water desalination method disclosed by the invention, primary fresh water prepared by the primary reverse osmosis unit is discharged into the sea surface fresh water tank, and fresh water in the water storage tank is conveyed from the sea surface fresh water tank by a group of sea wave fresh water pumps. The piston pump is close to the sea surface fresh water pool and far away from the reservoir, and when fresh water in the reservoir is sufficient, the piston pump is jointly driven by the fresh water in the reservoir and the fresh water directly pumped by the sea wave fresh water pump to pump seawater for the primary reverse osmosis unit. The working medium of the piston pump is buffered by the reservoir, and the pressure and flow are stable, so that the primary reverse osmosis unit can obtain stable seawater supply.

Description

Technical Field

[0001] The present application belongs to the technical field of seawater desalination, and specifically relates to a seawater desalination system and a seawater desalination method driven by ocean waves. Background Art

[0002] It is difficult for small islands or offshore platforms to be self-sufficient in fresh water. The desalination system driven by wave power generation is complex in structure and high in cost. The reverse osmosis desalination system driven directly by waves can only obtain a stable supply of seawater if more wave energy pumps are arranged on the sea surface, which is difficult to miniaturize.

[0003] Floating wave energy desalination equipment usually uses a two-way piston pump to draw seawater, and a pressure regulating valve is set upstream of the reverse osmosis membrane group to smooth the seawater pressure, such as the product of Canada's Oneka Company. In the seawater desalination system disclosed in patent CN115557573A, the pretreated seawater is pumped from the pretreatment reservoir to the buffer tank, and the multiple outlet pipes of the buffer tank are each connected to a reverse osmosis membrane group. The working number of the reverse osmosis membrane group can be dynamically adjusted according to the pressure change of the buffer tank. The above-mentioned smoother and buffer tank are high-pressure containers and are not suitable for large-scale.

[0004] The inventors believe that the wave-driven desalination system should be suitable for various project scales, require no external electricity, have fewer transmission mechanisms, have low construction costs, and be simple to use and maintain. Summary of the invention

[0005] The technical problem to be solved by this application is how to stabilize the working conditions of the primary reverse osmosis unit and promote the engineering application of the wave-driven seawater desalination system.

[0006] The "external fresh water" mentioned below refers to the fresh water that must be added when the seawater desalination system is started.

[0007] In a first aspect of the present application, a wave-driven seawater desalination system is disclosed. The seawater desalination system comprises: A surface freshwater tank located on the sea surface for receiving external freshwater and primary freshwater; A group of wave fresh water pumps, arranged below the sea surface fresh water pool, for receiving the kinetic energy of the wave fluctuations and conveying the fresh water in the sea surface fresh water pool; A water reservoir having a predetermined altitude and used for storing the fresh water delivered by the wave fresh water pump; a piston pump, located at an altitude close to the sea surface freshwater tank and away from the water reservoir, driven by the freshwater in the water reservoir and the freshwater directly pumped by the sea wave freshwater pump to extract seawater from the sea and pressurize the seawater to a predetermined pressure when the freshwater in the water reservoir is sufficient; and A primary reverse osmosis unit is adjacent to the piston pump and is used to process the seawater from the piston pump to produce the primary fresh water.

[0008] In some embodiments of the present application, the seawater desalination system may further include: another piston pump, when the fresh water in the water reservoir is sufficient, is driven by the fresh water in the water reservoir and the fresh water directly pumped by the wave fresh water pump to extract fresh water from the sea surface fresh water tank and pressurize fresh water to a predetermined pressure; and a secondary reverse osmosis unit for treating the fresh water from the other piston pump to produce secondary fresh water; Among them, all piston pumps have basically the same structure, but the pumping pressure is adapted to the respective downstream equipment.

[0009] In some embodiments of the present application, the seawater desalination system may further include: an energy recovery unit configured as another piston pump; Wherein, when the fresh water in the water reservoir is insufficient, the other piston pump is driven by the concentrated seawater discharged from the primary reverse osmosis unit to extract fresh water from the sea surface fresh water tank and transport the fresh water to the water reservoir; Among them, all piston pumps have basically the same structure, but the pumping pressure is adapted to the respective downstream equipment.

[0010] In some embodiments of the present application, it can be selected that each of the piston pumps includes a four-way reversing valve and two working groups connected in parallel downstream of the four-way reversing valve and working alternately, and each of the working groups includes a first piston cylinder, a second piston cylinder and a piston connecting rod, one end of the piston connecting rod is fixedly connected to the piston of the first piston cylinder and the other end is fixedly connected to the piston of the second piston cylinder.

[0011] In some embodiments of the present application, the seawater desalination system may further include: A seawater pretreatment unit, including an ultrafiltration membrane group, is used for pretreating the seawater entering the piston pump.

[0012] In some embodiments of the present application, it can be selected that the primary reverse osmosis unit includes several reverse osmosis membrane groups with a working pressure of 5.0 to 6.5 MPa, the water reservoir is greater than 50 meters above sea level, and the primary reverse osmosis unit and the piston pump are 1 to 10 meters above sea level.

[0013] In a second aspect of the present application, a wave-driven seawater desalination method is disclosed. The seawater desalination method comprises: A fresh water filling step, if a fresh water tank located on the sea surface is insufficient in fresh water, injecting external fresh water into the fresh water tank; A fresh water allocation step, if a water reservoir with a predetermined altitude is insufficient in fresh water, waiting for a group of wave fresh water pumps to transport fresh water from the sea surface fresh water tank to the water reservoir; A seawater pumping step, if the fresh water in the water reservoir is sufficient, the fresh water in the water reservoir and the fresh water directly pumped by the wave fresh water pump drive a piston pump together to extract seawater from the sea, and pump the seawater to a primary reverse osmosis unit at a predetermined pressure; and a primary fresh water production step, controlling the primary reverse osmosis unit to process seawater, and discharging the produced primary fresh water into the sea surface fresh water pool; The primary reverse osmosis unit and the piston pump are adjacent to each other, and their altitude is close to the sea surface freshwater pool and far away from the water reservoir.

[0014] In some embodiments of the present application, the seawater desalination method may further include: a step of producing secondary fresh water, using another piston pump to extract fresh water from the sea surface fresh water pool and transport the fresh water to a secondary reverse osmosis unit, and controlling the secondary reverse osmosis unit to produce secondary fresh water; Wherein, when the fresh water in the water reservoir is sufficient, the other piston pump is driven by the fresh water in the water reservoir and the fresh water directly pumped by the wave fresh water pump; Among them, all piston pumps have basically the same structure, but the pumping pressure is adapted to the respective downstream equipment.

[0015] In some embodiments of the present application, the seawater desalination method may further include: an energy recovery step, using another piston pump, using concentrated seawater discharged from the primary reverse osmosis unit as a working medium, to extract fresh water from the sea surface fresh water tank and transport the fresh water to the water storage tank; Among them, all piston pumps have basically the same structure, but the pumping pressure is adapted to the respective downstream equipment.

[0016] In some embodiments of the present application, the seawater desalination method may further include: The seawater pretreatment step uses an ultrafiltration membrane group to pretreat the seawater entering the piston pump.

[0017] By implementing the technical solution of this application, the following beneficial effects can be obtained.

[0018] In the wave-driven desalination system and desalination method disclosed in the present application, the primary fresh water produced by the primary reverse osmosis unit is discharged into the sea surface fresh water tank, and the fresh water in the reservoir is transported from the sea surface fresh water tank by a group of wave fresh water pumps. Its piston pump is located at an altitude close to the sea surface fresh water tank and far away from the reservoir. When the reservoir has sufficient fresh water, it is driven by the fresh water in the reservoir and the fresh water directly pumped by the wave fresh water pump to pump sea water for the primary reverse osmosis unit. The working medium of the piston pump is buffered by the reservoir and the pressure and flow are stable, so that the primary reverse osmosis unit can obtain a stable supply of sea water. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The following drawings should be used in conjunction with the detailed description.

[0020] Figure 1 is a schematic diagram of a seawater desalination system in Example 1, wherein the hollow arrows in the figure indicate the flow direction of fresh water, the gray arrows indicate the flow direction of seawater, and the black arrows indicate the flow direction of concentrated seawater; Figure 2 is a flow chart of a seawater desalination method in Embodiment 2; Figure 3 It is a schematic diagram of a seawater desalination system in Embodiment 4. DETAILED DESCRIPTION

[0021] The embodiments are described below with reference to the accompanying drawings.

[0022] In this specification, unless otherwise specified, one embodiment, some embodiments and other embodiments are used to distinguish different embodiments and do not refer to all embodiments; the accompanying drawings are schematic diagrams, not proportional drawings; the directions / positions indicated by top, bottom, center, edge, inside, outside, far, near, length, width, vertical, horizontal, up, down, front, back, left, right, etc., based on the observation angle of the accompanying drawings, cannot be understood as the components / devices are located in specific positions and facing specific directions; ordinal words such as first, second, third, etc., do not have a sequential meaning when used to distinguish components / devices with the same function / name.

[0023] Embodiment 1 An ocean wave driven desalination system 100 is disclosed.

[0024] See also Figure 1 The seawater desalination system 100 is located at the coast or the edge of an offshore platform, and includes a support platform 10, a group of wave freshwater pumps 20, a sea surface freshwater tank 30, a reservoir 40, a first piston pump 50, a primary reverse osmosis unit 60, an energy recovery unit 70 and related pipelines.

[0025] The seawater desalination system 100 also includes a seawater pretreatment unit, various valves, various sensors, several signal lights, an electronic control unit and related circuits. The seawater pretreatment unit is located upstream of the seawater inlet of the first piston pump 50 and includes a quartz sand filter, an activated carbon filter and an ultrafiltration membrane group for removing suspended matter, organic matter, colloidal particles and some heavy metal ions. The equipment, devices and processes described in this paragraph are all conventional technical means. Figure 1 Not drawn in.

[0026] The cap 10 is fixed on the seabed or moored to the edge of the offshore platform, with the top surface exposed 3 to 10 meters above the sea level.

[0027] The sea surface freshwater tank 30 is fixed on the top surface of the support platform 10, and is used to receive and store external fresh water, and receive primary fresh water produced by the primary reverse osmosis unit 60. That is, the sea surface freshwater tank 30 is located at the sea surface and 3 to 10 meters above the sea surface.

[0028] All the wave freshwater pumps 20 are installed on the support 10 and are evenly distributed on the top surface of the support 10. The water inlet and outlet are located in the freshwater of the sea surface freshwater pool 30, and are used to receive the kinetic energy of the wave fluctuations and transport the freshwater of the sea surface freshwater pool 30. That is, all the wave freshwater pumps 20 are evenly distributed below the sea surface freshwater pool 30.

[0029] Each wave freshwater pump 20 includes an upright cylindrical cylinder, a small-diameter piston in the cylindrical cylinder, and a large-diameter float 21 that pushes and pulls the piston with the waves. The diameter of the float 21 is 1 / 4 of the minimum wave wavelength. The ratio of the piston diameter to the float 21 diameter can be calculated based on the altitude of the reservoir 40, and the piston stroke ≥ the highest wave height. The specific number and arrangement of the wave freshwater pump 20 are configured according to the wave conditions and the scale of freshwater preparation.

[0030] The water inlet of each wave fresh water pump 20 is used to absorb fresh water and is provided with a one-way valve. The water outlet of each wave fresh water pump 20 is connected to the fresh water pipe 81 and is also provided with a one-way valve. The cut-off pressure of these two one-way valves is greater than 2.5MPa. That is, the fresh water pumped by all the wave fresh water pumps 20 converges into the fresh water pipe 81.

[0031] One end of the fresh water pipe 81 is located in the sea surface fresh water tank 30 and is connected to the water outlet of each wave fresh water pump 20. The other end of the fresh water pipe 81 is connected to the water reservoir 40. A fresh water branch pipe 811 is led out from the middle of the fresh water pipe 81. The other end of the fresh water branch pipe 811 is connected to the first piston pump 50 to provide the first piston pump 50 with working medium.

[0032] The water reservoir 40 is located on a high ground, a bracket or a navigation lighthouse at an altitude of 75 to 125 meters, and is used to store fresh water from the sea surface fresh water tank 30 delivered by the wave fresh water pump 20. The first piston pump 50 is located on a coast (or an offshore platform) at an altitude of 1 to 10 meters. Its altitude is close to the sea surface freshwater tank 30 and far away from the water reservoir 40 .

[0033] The first piston pump 50 uses the fresh water in the water reservoir 40 and the fresh water directly pumped by the sea wave fresh water pump 20 as working medium. When the fresh water in the water reservoir 40 is sufficient, the fresh water in the water reservoir 40 and the fresh water directly pumped by the sea wave fresh water pump 20 jointly drive the first piston pump 50, so that the first piston pump 50 extracts seawater from the sea and pressurizes the seawater to above 5MPa.

[0034] The fresh water pumped by the wave fresh water pump 20 can supply the first piston pump 50 and flow into the reservoir 40. The reservoir 40 accumulates the potential energy of fresh water, which is convenient for the use of fresh water, such as irrigation and supplying the secondary desalination system. The fresh water in the reservoir 40 also participates in driving the first piston pump 50, which can stabilize the input pressure and flow of the working medium, thereby becoming a working medium buffer container for the first piston pump 50.

[0035] The first piston pump 50 includes a four-way reversing valve 51 and two working groups connected in parallel downstream of the four-way reversing valve 51 and working alternately. Each working group of the first piston pump 50 includes a first piston cylinder 52, a second piston cylinder 54 and a piston connecting rod 53. The piston connecting rod 53 is configured as a horizontally extending straight bar, one end of which is fixedly connected to the piston of the second piston cylinder 54, and the other end of which is fixedly connected to the piston of the first piston cylinder 52. The inner diameter of the first piston cylinder 52 is approximately three times the inner diameter of the second piston cylinder 54. Figure 1 The size relationship is only indicated and not drawn to scale. The four-way reversing valve 51 is a solenoid valve, one interface is connected to the fresh water branch pipe 811, one interface is connected to the fresh water recovery pipe 82, and the remaining two interfaces are respectively connected to the two first piston cylinders 52. The two second piston cylinders 54 draw seawater from the sea through the seawater pipe 88. The fresh water as the working medium flows back to the sea surface freshwater tank 30 through the fresh water recovery pipe 82.

[0036] For other aspects of the first piston pump 50, reference may be made to the description of the "water pump part" in patent CN108397340A / 2018, or to commercially available concrete pumps.

[0037] The primary reverse osmosis unit 60 is adjacent to the first piston pump 50 and has the same altitude as the first piston pump 50 . It is used for primary desalination of seawater and includes a plurality of reverse osmosis membrane groups with a working pressure of 5.0-6.5 MPa.

[0038] The primary fresh water produced by the primary reverse osmosis unit 60 is discharged into the sea surface fresh water tank 30 through the primary fresh water pipe 83 , and participates in the working medium circulation between the sea surface fresh water tank 30 and the water storage tank 40 .

[0039] The concentrated seawater produced by the primary reverse osmosis unit 60 enters the energy recovery unit 70, where its high-pressure kinetic energy is recycled and the pressure is reduced to normal pressure. After being harmlessly treated, the concentrated seawater can be discharged into the sea through the wastewater pipe 89, and can be used for salt drying or as the draw liquid of the forward osmosis sewage treatment system.

[0040] The energy recovery unit 70 includes a hydro-turbine generator and storage unit to supply power to the above-mentioned electronic control unit.

[0041] During the use of the seawater desalination system 100, the water levels of the seawater desalination tank 30 and the water reservoir 40, as well as the working pressure of each pipeline and equipment should be monitored. If the water level of the seawater desalination tank 30 or the water reservoir 40 is lower than the minimum water level, the four-way reversing valve 51 must be operated to cut off the fresh water supply of the fresh water branch pipe 811, so that the first piston pump 50 and the primary reverse osmosis unit 60 stop working. Add external fresh water to the sea surface desalination tank 30, and allocate fresh water to the water reservoir 40, so that the water levels of the seawater desalination tank 30 and the water reservoir 40 are both higher than the minimum water level. When stopping work and allocating fresh water, a working group of the first piston pump 50 and the primary reverse osmosis unit 60 should maintain a certain standby pressure.

[0042] The above-mentioned external fresh water can be taken from an existing seawater desalination system and added to the sea surface freshwater tank when starting a new seawater desalination system. After the new seawater desalination system starts to operate, the fresh water in the reservoir gradually increases and can be used after exceeding a certain water level.

[0043] The seawater desalination system 100 is used to prepare primary fresh water. The primary fresh water can be desalinated in a secondary manner using a similar seawater desalination system. In the secondary desalination system, a second piston pump draws primary fresh water from a sea surface fresh water tank 30, the primary fresh water is treated by a secondary reverse osmosis unit, and the secondary fresh water obtained is fed into the secondary fresh water tank.

[0044] In summary, the fresh water produced by the primary reverse osmosis unit 60 is discharged into the sea surface fresh water tank 30, and the fresh water in the reservoir 40 is transported from the sea surface fresh water tank 30 by a group of sea wave fresh water pumps 20; the first piston pump 50 is located at an altitude close to the sea surface fresh water tank 30 and far away from the reservoir 40. When the reservoir 40 has sufficient fresh water, it is driven by the fresh water in the reservoir 40 and the fresh water directly pumped by the sea wave fresh water pump 20 to pump sea water for the primary reverse osmosis unit 60; the working medium (fresh water) of the first piston pump 50 is buffered by the reservoir 40 and the input pressure and flow are stable, so that the primary reverse osmosis unit 60 can obtain a stable supply of seawater.

[0045] Specifically, (1) the floating body 21 that rises and falls with the waves pushes the piston of the wave freshwater pump 20, and the fresh water in the sea surface freshwater tank 30 is transported to the reservoir 40, converting part of the wave energy into freshwater potential energy; (2) the fresh water pumped by the wave freshwater pump 20 can supply the first piston pump 50 and flow into the reservoir 40, and the fresh water in the reservoir 40 can be used and participate in driving the first piston pump 50. Therefore, the first piston pump 50 can obtain the working medium fresh water with stable pressure and flow.

[0046] Assuming that the reservoir 40 is built on a mountain top at an altitude of 100m, the potential energy of fresh water is approximately equal to the kinetic energy of fresh water at a pressure of 1MPa; the water inlet pressure of the primary reverse osmosis unit 60 should be 5.0~6.5MPa, and the first piston pump 50 needs to pressurize seawater above 5.0MPa, so the flow ratio of the working medium to seawater should be greater than 5. For the first piston pump 50, if the energy efficiency is 100%, the ratio of the piston diameters of the first piston cylinder 52 and the second piston cylinder 54 should be greater than 2.45; if the energy efficiency is 60%, the above ratio should be greater than 2.89.

[0047] The seawater desalination system 100 can be provided with a water reservoir 40 according to the specific environment, and the water reservoir 40 is used as a buffer container for a stable seawater supply. A high-pressure buffer container is not used, and the number and distribution of the wave desalination pumps 20 are not limited, so the design scale can be large or small.

[0048] In other embodiments, there are multiple sea surface freshwater tanks 30, water reservoirs 40 and first piston pumps 40, one of which is a spare.

[0049] In other embodiments, the energy recovery unit 70 may be eliminated to allow the high-pressure concentrated seawater to be discharged directly; an independent wind turbine or photovoltaic unit may be used to power the above-mentioned electronic control unit.

[0050] In other embodiments, a forward osmosis unit is added upstream of the primary reverse osmosis unit 60 , and seawater is used as the draw liquid to concentrate the freshwater sewage, so that the seawater is diluted to reduce the working pressure of the primary reverse osmosis unit 60 .

[0051] Embodiment 2 A wave-driven seawater desalination method is disclosed.

[0052] The seawater desalination method can be implemented using the seawater desalination system 100 of the first embodiment.

[0053] See also Figure 2 , the seawater desalination method includes the following steps.

[0054] S11. Fresh water filling step: If a fresh water pool located on the sea surface is insufficient in fresh water, inject external fresh water into the fresh water pool.

[0055] S12. Fresh water allocation step: If a reservoir with a predetermined altitude is short of fresh water, wait for a group of wave fresh water pumps to transport fresh water from the sea surface fresh water tank to the reservoir.

[0056] S20. Seawater pumping step: If the fresh water in the water reservoir is sufficient, the fresh water in the water reservoir and the fresh water directly pumped by the wave fresh water pump jointly drive a piston pump to extract seawater from the sea and pump the seawater to a primary reverse osmosis unit at a predetermined pressure.

[0057] S30. Fresh water preparation step: controlling the primary reverse osmosis unit to process seawater, and discharging the prepared fresh water into the sea surface fresh water pool.

[0058] S40. Energy recovery step: controlling the concentrated seawater produced by the primary reverse osmosis unit to flow through the hydro-turbine generator storage unit to recover the high-pressure kinetic energy of the concentrated seawater.

[0059] During the initial activation of the seawater desalination system 100, the above steps are performed in sequence to debug the relevant equipment in turn. After the seawater desalination system 100 is in a stable operating state, a water flow cycle is formed, and step S11 does not need to be performed. The remaining steps are performed synchronously without a time sequence.

[0060] In the above steps, the primary reverse osmosis unit includes several reverse osmosis membrane groups with a working pressure of 5.0~6.5MPa, the water reservoir is 75~125 meters above sea level, and the primary reverse osmosis unit and the first piston pump are 1~10 meters above sea level; before entering the piston pump 50, the seawater flows through the quartz sand filter, the activated carbon filter and the ultrafiltration membrane group in sequence to remove suspended matter, organic matter, colloidal particles and some metal ions.

[0061] The above-mentioned external fresh water can be taken from an existing desalination system and added to the sea surface fresh water tank when starting a new desalination system. After the new desalination system starts to operate, the fresh water in the reservoir gradually increases and can be used after exceeding a certain water level.

[0062] This desalination method is used to prepare primary fresh water. Primary fresh water can be desalinated in a secondary manner using a similar desalination method. In the secondary desalination method, another piston pump is used to draw primary fresh water from the sea surface fresh water tank, the primary fresh water is treated by a secondary reverse osmosis unit, and the secondary fresh water produced is collected in the secondary fresh water tank.

[0063] The seawater desalination system using this seawater desalination method can set up a reservoir 40 according to the specific environment, use the reservoir 40 as a buffer container for a stable seawater supply, do not use a high-pressure buffer container, and do not limit the number and distribution of the wave freshwater pumps 20, so that the design scale can be large or small.

[0064] For other aspects of the seawater desalination method, please refer to the description of Example 1.

[0065] In other embodiments, step S40 may be omitted and the high-pressure concentrated seawater may be directly discharged.

[0066] In other embodiments, before the seawater enters the primary reverse osmosis unit 60 , it enters a forward osmosis unit as a draw liquid and is diluted when the freshwater sewage is concentrated, thereby reducing the working pressure of the primary reverse osmosis unit 60 .

[0067] Embodiment 3 Another wave-driven desalination system is disclosed.

[0068] The seawater desalination system can perform two-stage reverse osmosis desalination treatment on seawater.

[0069] The seawater desalination system is based on the seawater desalination system 100 of the first embodiment, and is improved as follows.

[0070] A second piston pump, a second reverse osmosis unit, a second fresh water tank and a second concentrated water tank are added.

[0071] The second piston pump has a substantially identical structure to the first piston pump 50, but its pumping pressure is adapted to the working pressure of the secondary reverse osmosis unit. When the fresh water in the water reservoir 40 is sufficient, the second piston pump is driven by the fresh water in the water reservoir 40 and the fresh water directly pumped by the wave fresh water pump 20, extracts fresh water from the sea surface fresh water tank 30 and pressurizes fresh water to a predetermined pressure, and supplies primary fresh water to the secondary reverse osmosis unit.

[0072] The secondary reverse osmosis unit is used to treat the fresh water from the second piston pump. The secondary fresh water is discharged into the secondary fresh water tank, and the secondary concentrated water is discharged into the secondary concentrated water tank. After necessary treatment, the secondary fresh water can be used for drinking, irrigation, and electrolytic hydrogen production.

[0073] Embodiment 4 An ocean wave driven desalination system 200 is disclosed.

[0074] The seawater desalination system 200 is based on the seawater desalination system 100 of the first embodiment, and is improved as follows.

[0075] The seawater desalination system 200 can perform two-stage reverse osmosis desalination treatment on seawater.

[0076] See also Figure 3 The water reservoir 40' is located on a mountain top near the coast at an altitude of 1000 meters, and its fresh water potential energy is equivalent to 10MPa fresh water kinetic energy; the wave fresh water pump 20' replaces the wave fresh water pump 20 to adapt to the altitude of the water reservoir 40'; the third piston pump 50' replaces the first piston pump 50, and a fourth piston pump 50", a secondary reverse osmosis unit 60', a secondary fresh water tank 91 and a secondary concentrated water tank 92 are added.

[0077] The structures of the third piston pump 50' and the fourth piston pump 50" are basically the same as the first piston pump 50. The pumping pressure of the third piston pump 50' needs to adapt to the primary reverse osmosis unit 60, and the pumping pressure of the fourth piston pump 50" needs to adapt to the secondary reverse osmosis unit 60', so the piston diameter ratio of the first piston cylinder 52 to the second piston cylinder 54 of the two is less than 1 but inconsistent. Figure 3 The above piston diameter size relationship is only shown schematically and is not drawn to scale.

[0078] When the fresh water in the water reservoir 40 ′ is sufficient, the third piston pump 50 ′ is driven by the fresh water in the water reservoir 40 ′ and the fresh water directly pumped by the wave fresh water pump 20 , extracts seawater from the sea and pressurizes the seawater to a predetermined pressure, and supplies the seawater to the primary reverse osmosis unit 60 .

[0079] When the fresh water in the water reservoir 40' is sufficient, the fourth piston pump 50' is driven by the fresh water in the water reservoir 40' and the fresh water directly pumped by the wave fresh water pump 20, extracts fresh water from the sea surface fresh water tank 30 and pressurizes fresh water to a predetermined pressure, and supplies primary fresh water to the secondary reverse osmosis unit 60'.

[0080] The secondary reverse osmosis unit 60' is used to process the primary fresh water from the fourth piston pump 50", and the secondary fresh water produced is discharged into the secondary fresh water tank 91, and the secondary concentrated water is discharged into the secondary concentrated water tank 92. The secondary fresh water can be used for drinking, irrigation, electrolysis and hydrogen production after necessary treatment.

[0081] Embodiment 5 Another wave-driven desalination system is disclosed.

[0082] The seawater desalination system is based on the seawater desalination system 100 of the first embodiment, and is improved as follows.

[0083] A fifth piston pump is added to replace the energy recovery unit 70 .

[0084] The fifth piston pump has a substantially identical structure to the first piston pump 50, but the pumping pressure needs to adapt to the altitude of the water reservoir 40. The fifth piston pump uses concentrated seawater discharged from the primary reverse osmosis unit 60 as a working medium, and can pump fresh water from the sea surface fresh water tank 30 to the water reservoir 40. That is, the fifth piston pump is also used to pump fresh water from the sea surface fresh water tank 30 to the water reservoir 40 and the first piston pump 50.

[0085] The above embodiments, application examples and technical analysis are intended to introduce the technical concept and features of the present application so that those skilled in the art can implement the technical solution of the present application, and do not constitute a limitation on the scope of protection claimed. Simple modifications and equivalent transformations of the embodiments are within the scope of protection.

Claims

1. A wave-driven seawater desalination system, characterized in that include: A surface freshwater tank located on the sea surface for receiving external freshwater and primary freshwater; A group of wave fresh water pumps, arranged below the sea surface fresh water pool, for receiving the kinetic energy of the wave fluctuations and conveying the fresh water in the sea surface fresh water pool; A water reservoir having a predetermined altitude and used for storing the fresh water delivered by the wave fresh water pump; a piston pump, located at an altitude close to the sea surface freshwater tank and away from the water reservoir, driven by the freshwater in the water reservoir and the freshwater directly pumped by the sea wave freshwater pump to extract seawater from the sea and pressurize the seawater to a predetermined pressure when the freshwater in the water reservoir is sufficient; and A primary reverse osmosis unit is adjacent to the piston pump and is used to process the seawater from the piston pump to produce the primary fresh water.

2. The seawater desalination system according to claim 1, characterized in that Also includes: another piston pump, when the fresh water in the water reservoir is sufficient, is driven by the fresh water in the water reservoir and the fresh water directly pumped by the wave fresh water pump to extract fresh water from the sea surface fresh water tank and pressurize fresh water to a predetermined pressure; as well as a secondary reverse osmosis unit for treating the fresh water from the other piston pump to produce secondary fresh water; Among them, all piston pumps have basically the same structure, but the pumping pressure is adapted to the respective downstream equipment.

3. The seawater desalination system according to claim 1, characterized in that Also includes: an energy recovery unit configured as another piston pump; Wherein, when the fresh water in the water reservoir is insufficient, the other piston pump is driven by the concentrated seawater discharged from the primary reverse osmosis unit to extract fresh water from the sea surface fresh water tank and transport the fresh water to the water reservoir; Among them, all piston pumps have basically the same structure, but the pumping pressure is adapted to the respective downstream equipment.

4. The seawater desalination system according to claim 1, 2 or 3, characterized in that: Each of the piston pumps includes a four-way reversing valve and two working groups connected in parallel downstream of the four-way reversing valve and working alternately. Each of the working groups includes a first piston cylinder, a second piston cylinder and a piston connecting rod, one end of the piston connecting rod is fixedly connected to the piston of the first piston cylinder and the other end is fixedly connected to the piston of the second piston cylinder.

5. The seawater desalination system according to claim 1, characterized in that Also includes: A seawater pretreatment unit, comprising an ultrafiltration membrane group, is used for pretreating the seawater entering the piston pump.

6. The seawater desalination system according to claim 1, characterized in that: The primary reverse osmosis unit includes several reverse osmosis membrane groups with a working pressure of 5.0 to 6.5 MPa. The water reservoir is at an altitude of more than 50 meters. The primary reverse osmosis unit and the piston pump are at an altitude of 1 to 10 meters.

7. A wave-driven seawater desalination method, characterized in that include: A fresh water filling step, if a fresh water tank located on the sea surface is insufficient in fresh water, injecting external fresh water into the fresh water tank; A fresh water allocation step, if a water reservoir with a predetermined altitude is insufficient in fresh water, waiting for a group of wave fresh water pumps to transport fresh water from the sea surface fresh water tank to the water reservoir; A seawater pumping step, if the fresh water in the water reservoir is sufficient, the fresh water in the water reservoir and the fresh water directly pumped by the wave fresh water pump drive a piston pump together to extract seawater from the sea, and pump the seawater to a primary reverse osmosis unit at a predetermined pressure; as well as a primary fresh water production step, controlling the primary reverse osmosis unit to process seawater, and discharging the produced primary fresh water into the sea surface fresh water pool; The primary reverse osmosis unit and the piston pump are adjacent to each other, and their altitude is close to the sea surface freshwater pool and far away from the water reservoir.

8. The seawater desalination method according to claim 7, characterized in that Also includes: a step of producing secondary fresh water, using another piston pump to extract fresh water from the sea surface fresh water pool and transport the fresh water to a secondary reverse osmosis unit, and controlling the secondary reverse osmosis unit to produce secondary fresh water; Wherein, when the fresh water in the water reservoir is sufficient, the other piston pump is driven by the fresh water in the water reservoir and the fresh water directly pumped by the wave fresh water pump; Among them, all piston pumps have basically the same structure, but the pumping pressure is adapted to the respective downstream equipment.

9. The seawater desalination method according to claim 7, characterized in that Also includes: an energy recovery step, using another piston pump, using concentrated seawater discharged from the primary reverse osmosis unit as a working medium, to extract fresh water from the sea surface fresh water tank and transport the fresh water to the water storage tank; Among them, all piston pumps have basically the same structure, but the pumping pressure is adapted to the respective downstream equipment.

10. The seawater desalination method according to claim 7, characterized in that Also includes: The seawater pretreatment step uses an ultrafiltration membrane group to pretreat the seawater entering the piston pump.

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