Salinity difference energy-turbine coupling energy recovery device for seawater desalination and working method of salinity difference energy-turbine coupling energy recovery device

Abstract

The invention belongs to the technical field of seawater resource utilization, and discloses a salinity gradient energy-turbine coupling energy recovery device for seawater desalination and a working method.The device is structurally divided into a first cavity, a second cavity, a third cavity, a fourth cavity and a fifth cavity; comprising a first cavity water inlet, a first cavity water outlet, a first cavity water inlet bearing, a first cavity impeller, a first cavity solid bearing, a second cavity impeller, a second cavity water inlet, a second cavity hollow bearing, a third cavity impeller, a third cavity water outlet, a third cavity solid bearing, a fourth cavity impeller and a fourth cavity water outlet bearing. The system comprises a first chamber water inlet, a second chamber water inlet, a third chamber water inlet, a fourth chamber water inlet, a fourth chamber water outlet, a fifth chamber raw seawater inlet, a fifth chamber forward osmosis membrane assembly and a fifth chamber water outlet. According to the technical scheme, gradient energy utilization of strong brine discharged by the reverse osmosis system can be realized, the utilization efficiency of salinity gradient energy is improved, and the comprehensive energy consumption of the reverse osmosis seawater desalination system is reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of seawater resource utilization, and in particular relates to a salinity difference energy-turbine coupled energy recovery device for seawater desalination and a working method. Background Art

[0002] Reverse osmosis (RO) technology is the most mature and widely used membrane separation technology for seawater desalination. Its core principle is to use a high-pressure pump to apply a working pressure of 4.0-8.5MPa to the raw seawater, allowing water molecules to overcome the osmotic pressure difference and pass through the semi-permeable membrane, thereby effectively separating fresh water from brine. This technology produces high-pressure brine during operation. The Energy Recovery Device (ERD), a key energy-saving component of the reverse osmosis system, mainly recovers the residual pressure energy in the brine through positive displacement or centrifugal working principles, which can reduce system energy consumption by 40%-50%, reducing energy consumption to 2.0-4.5kWh / m3 per ton of water. 3 .

[0003] In the field of renewable energy, salinity gradient energy (SGE) is a renewable energy source based on the chemical potential difference of solution, and its theoretical energy density can reach 0.8kWh / m 3 Among them, Pressure Retarded Osmosis (PRO) technology is the most promising way to utilize salinity difference energy. It drives the migration of water molecules through the osmotic pressure difference between solutions of different salinities (such as seawater and river water) on both sides of the semipermeable membrane, and can convert salinity difference energy into hydraulic energy. Studies have shown that in a typical seawater-river water system, the theoretical power density of PRO technology can reach 5-10W / m 2 However, the energy recovery device in the existing seawater desalination reverse osmosis system can only recover the residual pressure energy in the concentrated brine, but cannot utilize the salinity difference energy between the concentrated brine and the low-salinity water, resulting in significant energy waste.

[0004] Patent application publication number CN118183941A proposes a "dual-engine" seawater desalination and brine treatment system based on PRO+PRMD. This system utilizes pressure-delayed osmosis and pressure-delayed membrane distillation technologies to construct a "dual-engine" power drive system powered by salinity and temperature differential energy. The system transfers the salinity and temperature differential energies stored in the brine into normal temperature and pressure seawater in the form of mechanical energy, reducing its salinity and increasing its flow rate. This system achieves energy and resource utilization of high-salinity, high-temperature brine. Patent application publication number CN106379961A proposes a multi-stage reverse osmosis desalination coupled with salinity differential energy power generation system, comprising a multi-stage reverse osmosis unit, a raw seawater pipeline, a forward osmosis unit, an energy recovery unit, a turbine, a generator, and a discharge water pipeline. The raw seawater pipeline is divided into two routes: one route enters a multi-stage reverse osmosis unit for desalination and separation, while the other route enters a forward osmosis unit. The osmotic pressure between the seawater and the high-concentration discharge water from the multi-stage reverse osmosis unit causes some of the freshwater in the seawater to mix with the high-concentration discharge water through a semipermeable membrane, driving a turbine to generate power, thereby driving a generator. The remaining seawater is boosted by an energy recovery unit and then introduced into the multi-stage reverse osmosis unit. This technical solution offers low investment costs, stable operation, and strong practicality, facilitating the practical application of salinity gradient energy generation. Furthermore, the invention further leverages the advantages of the multi-stage reverse osmosis unit, namely, high water output and recovery rate, while reducing the environmental impact of its wastewater discharge.

[0005] In addition, the existing technology uses energy recovery devices and salt difference energy generation to achieve energy saving in the entire system. Figure 1 As shown in the figure, the process involves pressurizing seawater, desalinating it through a reverse osmosis membrane, and separating it into freshwater and high-pressure brine. The high-pressure brine is then recovered through a first energy recovery device, and then discharged as low-pressure brine. The low-pressure brine is then pressurized by a second energy recovery device to produce pressurized brine, which is then fed to a forward osmosis membrane. The pressurized brine is further pressurized by the forward osmosis membrane and then fed to a turbine generator for power generation. Using SGE power generation technology to reduce desalination energy consumption is a long process, resulting in a complex system and low energy conversion efficiency.

[0006] Based on the above technical background, the development of a short-process, high-efficiency energy recovery device that can simultaneously recover the residual pressure energy and salinity difference energy in concentrated brine has important theoretical value and engineering significance for the seawater desalination industry. Summary of the Invention

[0007] In view of the problem that existing seawater desalination technology lacks efficient and quick utilization of salinity difference energy, the present invention proposes a short-process, high-efficiency salinity difference energy-turbine coupled energy recovery device and working method for seawater desalination.

[0008] A salt difference energy-turbine coupled energy recovery device for seawater desalination, the structure of which is divided into a first chamber, a second chamber, a third chamber, a fourth chamber, and a fifth chamber;

[0009] The first chamber, the second chamber, the third chamber, the fourth chamber, and the fifth chamber adopt an upper and lower split chamber structure, and the upper and lower chambers are mechanically sealed by flanges;

[0010] The first chamber, the second chamber, the third chamber, and the fourth chamber are arranged axially in sequence along the central axis, and the fifth chamber is located outside the third chamber and the fourth chamber;

[0011] The first chamber, the second chamber, the third chamber, and the fourth chamber are coaxially rotated and fluid-isolated through a central axis and a mechanical seal structure.

[0012] The first chamber is provided with a first water inlet, a second water outlet, a first water inlet bearing, a first chamber impeller, and a first chamber solid bearing. The first water inlet bearing is provided with a mechanical seal to ensure that the fluid in the first chamber does not leak;

[0013] The second chamber contains a second chamber impeller, a second chamber water inlet, and a second chamber hollow bearing;

[0014] The third chamber contains a third chamber impeller, a third chamber water outlet, and a third chamber solid bearing;

[0015] The fourth chamber is provided with a fourth chamber impeller, a fourth chamber water outlet bearing, a fourth chamber water inlet, and a fourth chamber water outlet. A mechanical seal is provided on the fourth chamber water outlet bearing to ensure that the fluid in the fourth chamber does not leak;

[0016] The fifth chamber is located outside the third chamber and the fourth chamber, forming an independent membrane separation unit, which is equipped with a fifth chamber raw seawater inlet, a fifth chamber forward osmosis membrane assembly, and a fifth chamber outlet;

[0017] The raw seawater inlet of the fifth chamber is connected to the pretreated raw seawater;

[0018] The fifth chamber forward osmosis membrane assembly is a core functional component and is installed in the form of a hollow fiber, spiral or tubular separation membrane. The key flow channel structure of the fifth chamber forward osmosis membrane assembly adopts a dual independent flow channel design for the raw seawater side flow channel and the draw liquid side flow channel. The raw seawater side flow channel and the draw liquid side flow channel are strictly isolated by a high-performance forward osmosis membrane. The membrane only allows water molecules to selectively permeate and blocks the migration of salt ions. The raw seawater side flow channel connects the raw seawater inlet and the fifth chamber outlet of the fifth chamber, circulating low-osmotic pressure raw seawater. The draw liquid side flow channel connects the third chamber outlet and the fourth chamber inlet, and is used to transport the draw liquid, that is, the low-pressure concentrated seawater from the third chamber.

[0019] The water outlet of the fifth chamber is used to discharge the medium-salinity seawater produced by the forward osmosis process, that is, the concentrated raw seawater;

[0020] The solid bearing of the first chamber connects the first chamber impeller and the second chamber impeller through an interference fit, and the shaft is sealed by a sealing ring to prevent fluid leakage between the chambers;

[0021] A guide groove is provided on the inner wall of the hollow structure of the second chamber hollow bearing, allowing concentrated seawater after depressurization in the second chamber to enter the third chamber impeller through the hollow internal flow channel of the shaft. The shaft is sealed with a sealing ring to prevent fluid leakage between the chambers. The second chamber impeller and the third chamber impeller are connected by a threaded shaft.

[0022] The third chamber solid bearing connects the third chamber impeller and the fourth chamber impeller through an interference fit, and the shaft is sealed by a sealing ring to prevent fluid leakage between the chambers;

[0023] The fifth chamber is connected to the third chamber in a copy forest form through the water outlet of the third chamber. There is a one-way valve in the water outlet of the third chamber, which only allows water to flow from the third chamber to the fifth chamber;

[0024] The fifth chamber is connected with the fourth chamber in a copy forest form through the water inlet of the fourth chamber.

[0025] An overrunning clutch is provided at the connection between the third chamber solid bearing and the third chamber impeller.

[0026] The working method of the above-mentioned salinity difference energy-turbine coupled energy recovery device is adopted, and its process route in seawater desalination is shown in the figure. The raw seawater passes through the security filter and the high-pressure pump and enters the water inlet of the first chamber. The water outlet of the first chamber is connected to the inlet of the reverse osmosis membrane assembly. The pressurized seawater exits the water outlet of the first chamber and enters the reverse osmosis membrane assembly. The outlet of the high-pressure concentrated seawater of the reverse osmosis membrane assembly is connected to the water inlet of the second chamber. The water outlet of the fifth chamber and the water outlet of the fourth chamber are used to discharge the salt water and brine of the salinity difference energy-turbine coupled energy recovery device respectively. The raw seawater inlet of the fifth chamber is connected to the inlet of the raw seawater branch pipeline after filtration by the security filter.

[0027] The drawn liquid inlet is connected to the water outlet of the third chamber, and the drawn liquid outlet is connected to the water inlet of the fourth chamber;

[0028] High-precision pressure sensors are provided at the water inlet of the second chamber and the water inlet of the fourth chamber;

[0029] An electromagnetic flow control valve is provided on the pipe connected to the water outlet of the fourth chamber;

[0030] The working method of the salt difference energy-turbine coupled energy recovery device is as follows:

[0031] The raw seawater pressurized by the high-pressure pump enters the salinity energy-turbine coupled energy recovery device through the first chamber water inlet, passes through the first chamber water inlet bearing, and the internal flow channel of the first chamber impeller, and enters the reverse osmosis membrane assembly from the first chamber water outlet. After being filtered by the reverse osmosis membrane assembly, the high-pressure concentrated seawater enters the second chamber through the second chamber water inlet. The high pressure drives the impeller to rotate, converting the residual pressure energy of the high-pressure concentrated seawater into mechanical energy for the rotation of the second chamber impeller. The second chamber impeller drives the first chamber impeller to rotate through the first chamber solid shaft, causing the first chamber impeller to pressurize the raw seawater entering the first chamber, thereby completing the first energy conversion process of the high-pressure concentrated seawater.

[0032] The concentrated seawater that has been decompressed in the second chamber enters the third chamber impeller through the flow channel in the second chamber hollow shaft, and then enters the fifth chamber through the flow channel arranged in the third chamber impeller through the third chamber outlet. The pretreated raw seawater enters the raw water side of the fifth chamber forward osmosis membrane assembly through the raw seawater inlet of the fifth chamber. The decompressed low-pressure concentrated seawater enters the draw liquid side of the fifth chamber forward osmosis membrane assembly through the third chamber outlet. In the forward osmosis membrane assembly, because the osmotic pressure of the low-pressure concentrated seawater is greater than that of the raw seawater, water molecules in the raw seawater migrate toward the low-pressure concentrated seawater side, causing the pressure on the low-pressure concentrated seawater side to increase, and the low-pressure concentrated seawater is pressurized to medium-pressure seawater. Under the action of salinity difference energy, the raw seawater becomes medium-salinity seawater. Due to the action of the one-way valve at the third chamber outlet, the medium-pressure seawater enters the fourth chamber through the fourth chamber inlet, and the medium-salinity seawater in the fifth chamber is discharged from the fifth chamber outlet. At this point, the salinity difference energy conversion is completed in the fifth chamber, converting the salinity difference energy of the low-pressure concentrated seawater into the hydraulic energy of the medium-pressure seawater.

[0033] The medium-pressure seawater carrying hydraulic energy enters the fourth chamber from the water inlet of the fourth chamber, driving the fourth chamber impeller to rotate. The fourth chamber impeller drives the first chamber impeller to rotate through the solid shaft of the third chamber, the hollow shaft of the second chamber, and the solid shaft of the first chamber, thereby secondary pressurizing the original seawater entering the first chamber, thereby completing the second energy conversion of the low-pressure concentrated seawater. The decompressed medium-pressure seawater passes through the fourth chamber impeller and the inside of the fourth chamber water outlet bearing, and flows out through the fourth chamber water outlet for discharge, thereby completing the recovery and utilization of the residual pressure energy and salinity difference energy of the high-pressure concentrated seawater.

[0034] The working principle of the fifth chamber forward osmosis membrane assembly:

[0035] In this technical solution, the draw fluid refers to the low-pressure concentrated seawater flowing out of the third chamber after undergoing primary residual pressure energy recovery and decompression. This concentrated seawater originates from the reverse osmosis desalination process and has a salinity (or solute concentration) much higher than the original seawater entering the fifth chamber, resulting in an extremely high osmotic pressure.

[0036] Flow process of raw seawater and draw liquid: Pretreated raw seawater (low osmotic pressure) enters the raw seawater side channel of the fifth chamber's forward osmosis membrane assembly through the raw seawater inlet of the fifth chamber. Depressurized low-pressure concentrated seawater (serving as the draw liquid with high osmotic pressure) enters the draw liquid side channel of the fifth chamber's forward osmosis membrane assembly through the third chamber's outlet (where a one-way valve ensures unidirectional flow).

[0037] The forward osmosis process, driven by salinity gradient energy, occurs due to the osmotic pressure differential across the forward osmosis membrane. The osmotic pressure on the draw fluid side is greater than that on the source seawater side. According to the principle of osmosis, water molecules spontaneously and selectively migrate through the forward osmosis membrane from the low-osmotic-pressure source seawater side to the high-osmotic-pressure draw fluid (concentrated seawater) side. This process occurs spontaneously, requiring no additional hydraulic pressure. Its driving force comes entirely from the salinity difference (i.e., salinity gradient energy) between the concentrated seawater (draw fluid) and the source seawater.

[0038] Energy conversion and solution state changes:

[0039] Original seawater side: As water molecules migrate out, the original seawater is concentrated, the salinity increases, and medium-salinity seawater is formed, which is eventually discharged through the outlet of the fifth chamber.

[0040] On the draw liquid side: As water molecules continue to migrate in, the originally low-pressure concentrated seawater is diluted, increasing its volume. Because this process occurs within a relatively closed flow channel (and subsequently connected to the fourth chamber), the dilution effect causes the pressure of the draw liquid solution to increase significantly. Therefore, the salinity differential energy (osmotic pressure differential) is directly converted into the hydraulic energy of medium-pressure seawater during this process. This diluted and pressurized medium-pressure seawater (the original draw liquid) then flows out of the draw liquid channel.

[0041] Transportation and utilization of medium-pressure seawater: The medium-pressure seawater flowing out from the liquid side of the forward osmosis membrane module, carrying the hydraulic energy converted from salinity difference energy, enters the fourth chamber through the water inlet of the fourth chamber, drives the impeller of the fourth chamber to rotate, and realizes the mechanical energy recovery of salinity difference energy (i.e., the second energy conversion).

[0042] During operation, an external PLC compares the pressure sensor readings at the second and fourth chamber inlets, automatically adjusting the opening of the electromagnetic flow control valve in the pipe connecting the fourth chamber's outlet to ensure that the medium-pressure seawater flow matches the impeller speed, avoiding overload or energy waste. If the salt differential energy boost in the fifth chamber is insufficient, the overrunning clutch automatically disconnects the drive connection between the third and fourth chamber impellers, preventing the fourth chamber impeller from obstructing the third chamber's rotation and ensuring that residual pressure energy recovery takes priority. When the salt differential energy boost reaches the target, the overrunning clutch reengages, achieving dual-energy coupled drive.

[0043] In the working method of the above-mentioned salinity difference energy-turbine coupled energy recovery device, seawater is first pressurized, and the pressurized seawater is desalinated through a reverse osmosis membrane assembly to generate fresh water and high-pressure concentrated seawater. The high-pressure concentrated seawater first completes the first-level residual pressure energy recovery and is converted into low-pressure concentrated seawater in the salinity difference energy-turbine coupled energy recovery device. Under the action of the forward osmosis separation membrane, the low-pressure concentrated seawater and the original seawater undergo osmotic pressure transfer to form medium-pressure seawater. The medium-pressure seawater directly drives the impeller to rotate, completing the second-level salinity difference energy recovery. The seawater is discharged after the residual pressure energy and salinity difference energy are recovered. The entire process is shortened, the system is simpler and more efficient, and since the salinity difference energy is directly converted into mechanical energy, the conversion efficiency is higher.

[0044] This technical solution proposes a salinity-energy-turbine coupled energy recovery device and its operating method. This device utilizes the salinity difference between raw seawater and concentrated seawater to recover low-pressure concentrated seawater salinity energy. Coupled with hydraulic turbine-type excess pressure energy recovery technology, this device achieves gradient recovery of concentrated seawater energy. This technical solution not only enables cascaded energy utilization of concentrated brine discharged from reverse osmosis systems but also improves the efficiency of salinity energy utilization. The application of this dual energy recovery technology is expected to further reduce the overall energy consumption of reverse osmosis desalination systems. This technical solution promotes the development of seawater desalination technology towards higher efficiency and environmental friendliness, and is of great strategic significance for achieving sustainable water resource utilization. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] The accompanying drawings, as part of this disclosure, are intended to provide a further understanding of the disclosure. The exemplary embodiments of the disclosure and their descriptions are intended to explain the disclosure and do not constitute undue limitations thereon. Obviously, the drawings described below are merely examples, and those skilled in the art can derive other drawings based on these drawings without inventive effort.

[0046] Figure 1 It is the process roadmap of existing seawater desalination salinity difference energy power generation technology;

[0047] Figure 2 This is the process roadmap of the salt difference energy-turbine coupled energy recovery device of the present invention technology;

[0048] Figure 3 This is a cross-sectional view of the salt difference energy-turbine coupled energy recovery device of the present invention;

[0049] Figure 4 This is a rotor structure diagram of the salt difference energy-turbine coupled energy recovery device of the present invention;

[0050] Figure 5 This is an appearance diagram of the salt difference energy-turbine coupled energy recovery device of the present invention;

[0051] Figure 6 1 is a comparison table of experimental data of the embodiments of the present invention.

[0052] In the picture:

[0053] 1. First chamber, wherein: 1-1 is the first chamber water inlet, 1-2 is the first chamber water outlet, 1-3 is the first chamber water inlet bearing, 1-4 is the first chamber impeller, and 1-5 is the first chamber solid bearing;

[0054] 2. The second chamber, wherein: 2-1 is the second chamber impeller, 2-2 is the second chamber water inlet, and 2-3 is the second chamber hollow bearing;

[0055] 3. The third chamber, wherein: 3-1 is the third chamber impeller, 3-2 is the third chamber water outlet, and 3-3 is the third chamber solid bearing;

[0056] 4. The fourth chamber, wherein: 4-1 is the fourth chamber impeller, 4-2 is the fourth chamber water outlet bearing, 4-3 is the fourth chamber water inlet, and 4-4 is the fourth chamber water outlet;

[0057] 5. The fifth chamber, wherein: 5-1 is the raw seawater inlet of the fifth chamber, 5-2 is the forward osmosis membrane assembly of the fifth chamber, and 5-3 is the water outlet of the fifth chamber.

[0058] It should be noted that these drawings and textual descriptions are not intended to limit the conceptual scope of the present invention in any way, but rather to illustrate the concept of the present invention for those skilled in the art by referring to specific embodiments. DETAILED DESCRIPTION

[0059] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. The following embodiments are used to illustrate the present invention but are not used to limit the scope of the present invention.

[0060] Example: Figures 3 to 5 As shown, a salt difference energy-turbine coupled energy recovery device for seawater desalination, the structure of which is divided into a first chamber 1, a second chamber 2, a third chamber 3, a fourth chamber 4, and a fifth chamber 5;

[0061] The first chamber 1, the second chamber 2, the third chamber 3, the fourth chamber 4, and the fifth chamber 5 adopt an upper and lower split cavity structure, and the upper and lower cavities are mechanically sealed by flanges;

[0062] The first chamber 1, the second chamber 2, the third chamber 3, and the fourth chamber 4 are arranged axially in sequence along the central axis, and the fifth chamber 5 is located outside the third chamber 3 and the fourth chamber 4;

[0063] The first chamber 1, the second chamber 2, the third chamber 3, and the fourth chamber 4 are coaxially rotated and fluidically isolated through a central axis and a mechanical seal structure.

[0064] The first chamber 1 has a first water inlet 1-1, a second water outlet 1-2, a first water inlet bearing 1-3, a first chamber impeller 1-4, and a first chamber solid bearing 1-5. The first water inlet bearing 1-3 is provided with a mechanical seal to ensure that the fluid in the first chamber 1 does not leak;

[0065] The second chamber 2 contains a second chamber impeller 2-1, a second chamber water inlet 2-2, and a second chamber hollow bearing 2-3;

[0066] The third chamber 3 contains a third chamber impeller 3-1, a third chamber water outlet 3-2, and a third chamber solid bearing 3-3;

[0067] The fourth chamber 4 contains a fourth chamber impeller 4-1, a fourth chamber water outlet bearing 4-2, a fourth chamber water inlet 4-3, and a fourth chamber water outlet 4-4. A mechanical seal is provided on the fourth chamber water outlet bearing 4-2 to ensure that the fluid in the fourth chamber 4 does not leak.

[0068] The fifth chamber 5 is located outside the third chamber 3 and the fourth chamber 4, forming an independent membrane separation unit, which is provided with a fifth chamber raw seawater inlet 5-1, a fifth chamber forward osmosis membrane assembly 5-2, and a fifth chamber outlet 5-3;

[0069] The raw seawater inlet 5-1 of the fifth chamber is connected to the pre-treated raw seawater;

[0070] The fifth chamber forward osmosis membrane assembly 5-2 is a core functional component and is installed in the form of a hollow fiber, spiral or tubular separation membrane. The key flow channel structure of the fifth chamber forward osmosis membrane assembly 5-2 adopts a dual independent flow channel design for the raw seawater side channel and the draw liquid side channel. The raw seawater side channel and the draw liquid side channel are strictly isolated by a high-performance forward osmosis membrane. This membrane only allows water molecules to selectively permeate, blocking the migration of salt ions. The raw seawater side channel connects the raw seawater inlet 5-1 of the fifth chamber and the fifth chamber outlet 5-3, circulating low-osmotic pressure raw seawater. The draw liquid side channel connects the third chamber outlet 3-2 and the fourth chamber inlet 4-3, used to transport the draw liquid, i.e., the low-pressure concentrated seawater from the third chamber 3.

[0071] The fifth chamber outlet 5-3 is used to discharge the medium-salinity seawater produced by the forward osmosis process, that is, the concentrated raw seawater;

[0072] The first chamber solid bearing 1-5 connects the first chamber impeller 1-4 and the second chamber impeller 2-1 through an interference fit, and the shaft is sealed by a sealing ring to prevent fluid leakage between the chambers;

[0073] A guide groove is provided on the inner wall of the hollow structure of the second chamber hollow bearing 2-3, allowing the concentrated seawater after depressurization of the second chamber 2 to enter the third chamber impeller 3-1 through the hollow internal flow channel of the shaft. The shaft is sealed with a sealing ring to prevent fluid leakage between the chambers. The second chamber impeller 2-1 and the third chamber impeller 3-1 are connected by a threaded shaft.

[0074] The third chamber solid bearing 3-3 connects the third chamber impeller 3-1 and the fourth chamber impeller 4-1 through interference fit, and the shaft is sealed by a sealing ring to prevent fluid leakage between the chambers;

[0075] The fifth chamber 5 is connected to the third chamber 3 in a copy forest form through the third chamber outlet 3-2. The third chamber outlet 3-2 has a one-way valve that only allows water to flow from the third chamber 3 to the fifth chamber 5.

[0076] The fifth chamber 5 is connected to the fourth chamber 4 in a copy forest form through the fourth chamber water inlet 4-3.

[0077] An overrunning clutch is provided at the connection between the third chamber solid bearing 3 - 3 and the third chamber impeller 3 - 1 .

[0078] The working method of the above-mentioned salt difference energy-turbine coupled energy recovery device is adopted, and its process route in seawater desalination is as follows: Figure 2 As shown, raw seawater passes through the security filter and the high-pressure pump and enters the first chamber water inlet 1-1. The first chamber water outlet 1-2 is connected to the inlet of the reverse osmosis membrane assembly. The pressurized seawater exits the first chamber water outlet 1-2 and enters the reverse osmosis membrane assembly. The outlet of the high-pressure concentrated seawater of the reverse osmosis membrane assembly is connected to the second chamber water inlet 2-2. The fifth chamber water outlet 5-3 and the fourth chamber water outlet 4-4 are used to discharge salt water 1 and salt water 2 of the salt difference energy-turbine coupling energy recovery device, respectively. The fifth chamber raw seawater inlet 5-1 is connected to the inlet of the raw seawater branch pipeline after filtration by the security filter.

[0079] The drawn liquid inlet is connected to the third chamber outlet 3-2, and the drawn liquid outlet is connected to the fourth chamber inlet 4-3;

[0080] High-precision pressure sensors are installed at the second chamber water inlet 2-2 and the fourth chamber water inlet 4-3;

[0081] The pipe connected to the water outlet 4-4 of the fourth chamber is provided with an electromagnetic flow control valve;

[0082] The working method of the salt difference energy-turbine coupled energy recovery device is as follows:

[0083] The raw seawater pressurized by the high-pressure pump enters the salinity difference energy-turbine coupled energy recovery device through the first chamber water inlet 1-1, passes through the first chamber water inlet bearing 1-3 and the internal flow channel of the first chamber impeller 1-4, and enters the reverse osmosis membrane assembly from the first chamber water outlet 1-2. After being filtered by the reverse osmosis membrane assembly, the high-pressure concentrated seawater enters the second chamber 2 through the second chamber water inlet 2-2. The high pressure drives the impeller to rotate, converting the residual pressure energy of the high-pressure concentrated seawater into mechanical energy for the rotation of the second chamber impeller 2-1. The second chamber impeller 2-1 drives the first chamber impeller 1-4 to rotate through the first chamber solid shaft 1-5, causing the first chamber impeller 1-4 to pressurize the raw seawater entering the first chamber 1, thereby completing the first energy conversion process of the high-pressure concentrated seawater.

[0084] The concentrated seawater that has completed pressure relief in the second chamber 2 enters the third chamber impeller 3-1 through the flow channel in the second chamber hollow shaft 2-3, and enters the fifth chamber 5 through the flow channel arranged in the third chamber impeller 3-1 through the third chamber outlet 3-2; the pretreated raw seawater enters the raw water side of the fifth chamber forward osmosis membrane assembly 5-2 through the fifth chamber raw seawater inlet 5-1, and the low-pressure concentrated seawater that has been pressure relieved enters the draw liquid side of the fifth chamber forward osmosis membrane assembly 5-2 through the third chamber outlet 3-2. In the forward osmosis membrane assembly, due to the low-pressure concentrated seawater The osmotic pressure is greater than the osmotic pressure of the original seawater. The water molecules in the original seawater migrate to the low-pressure concentrated seawater side, resulting in an increase in the pressure on the low-pressure concentrated seawater side. The low-pressure concentrated seawater is pressurized to medium-pressure seawater. The original seawater forms medium-salinity seawater under the action of salinity difference energy. Under the action of the one-way valve at the water outlet 3-2 of the third chamber, the medium-pressure seawater enters the fourth chamber 4 from the water inlet 4-3 of the fourth chamber, and the medium-salinity seawater in the fifth chamber 5 is discharged from the water outlet 5-3 of the fifth chamber. At this point, the salinity difference energy conversion is completed in the fifth chamber, and the salinity difference energy of the low-pressure concentrated seawater is converted into the hydraulic energy of the medium-pressure seawater.

[0085] The medium-pressure seawater carrying hydraulic energy enters the fourth chamber 4 from the fourth chamber water inlet 4-3, driving the fourth chamber impeller 4-1 to rotate. The fourth chamber impeller 4-1 drives the first chamber impeller 1-4 to rotate through the third chamber solid shaft 3-3, the second chamber hollow shaft 2-3, and the first chamber solid shaft 1-5, thereby secondary pressurizing the original seawater entering the first chamber 1, thereby completing the second energy conversion of the low-pressure concentrated seawater. The decompressed medium-pressure seawater passes through the fourth chamber impeller 4-1 and the interior of the fourth chamber water outlet bearing 4-2, and flows out through the fourth chamber water outlet 4-4 for discharge, thus completing the recovery and utilization of the residual pressure energy and salinity difference energy of the high-pressure concentrated seawater.

[0086] Working principle of the fifth chamber forward osmosis membrane assembly 5-2:

[0087] In this embodiment, the draw fluid refers to the low-pressure concentrated seawater flowing out of the third chamber 3 after undergoing primary residual pressure energy recovery and decompression. This concentrated seawater originates from the reverse osmosis desalination process and has a salinity (or solute concentration) much higher than the original seawater entering the fifth chamber 5, resulting in an extremely high osmotic pressure.

[0088] Flow process of raw seawater and draw liquid: Pretreated raw seawater (low osmotic pressure) enters the raw seawater side channel of the fifth chamber forward osmosis membrane assembly 5-2 through the fifth chamber raw seawater inlet 5-1. Depressurized low-pressure concentrated seawater (serving as the draw liquid with high osmotic pressure) enters the draw liquid side channel of the fifth chamber forward osmosis membrane assembly 5-2 through the third chamber outlet 3-2 (with a one-way valve ensuring unidirectional flow).

[0089] The forward osmosis process, driven by salinity gradient energy, occurs due to the osmotic pressure differential across the forward osmosis membrane. The osmotic pressure on the draw fluid side is greater than that on the source seawater side. According to the principle of osmosis, water molecules spontaneously and selectively migrate through the forward osmosis membrane from the low-osmotic-pressure source seawater side to the high-osmotic-pressure draw fluid (concentrated seawater) side. This process occurs spontaneously, requiring no additional hydraulic pressure. Its driving force comes entirely from the salinity difference (i.e., salinity gradient energy) between the concentrated seawater (draw fluid) and the source seawater.

[0090] Energy conversion and solution state changes:

[0091] Original seawater side: As water molecules migrate out, the original seawater is concentrated, the salinity increases, and medium-salinity seawater is formed, which is finally discharged through the outlet 5-3 of the fifth chamber.

[0092] On the draw liquid side: As water molecules continue to migrate in, the originally low-pressure concentrated seawater is diluted, increasing its volume. Because this process occurs within a relatively closed flow channel (and subsequently connected to the fourth chamber 4), the dilution effect causes the pressure of the draw liquid solution to increase significantly. Therefore, the salinity difference (osmotic pressure difference) is directly converted into the hydraulic energy of the medium-pressure seawater during this process. This diluted and pressurized medium-pressure seawater (i.e., the original draw liquid) flows out of the draw liquid channel.

[0093] Transportation and utilization of medium-pressure seawater: The medium-pressure seawater flowing out from the liquid side of the forward osmosis membrane assembly, carrying the hydraulic energy converted from the salinity difference energy, enters the fourth chamber 4 through the fourth chamber water inlet 4-4, drives the impeller of the fourth chamber 4 to rotate, and realizes the mechanical energy recovery of the salinity difference energy (i.e., the second energy conversion).

[0094] During operation, an external PLC compares the pressure sensor readings at the second chamber's water inlet 2-2 and the fourth chamber's water inlet 4-3, automatically adjusting the opening of the electromagnetic flow control valve in the pipe connecting the fourth chamber's water outlet 4-4 to ensure that the medium-pressure seawater flow matches the impeller speed, avoiding overload and energy waste. If the salt differential energy boost in the fifth chamber 5 is insufficient, the overrunning clutch automatically disconnects the transmission connection between the third chamber's impeller 3-1 and the fourth chamber's impeller 4-1, preventing the fourth chamber's impeller 4-1 from obstructing the third chamber's rotation and ensuring that excess pressure energy recovery takes priority. When the salt differential energy boost reaches the target, the overrunning clutch reengages, achieving dual-energy coupled drive.

[0095] In the working method of the above-mentioned salinity difference energy-turbine coupled energy recovery device, seawater is first pressurized, and the pressurized seawater is desalinated through a reverse osmosis membrane assembly to generate fresh water and high-pressure concentrated seawater. The high-pressure concentrated seawater first completes the first-level residual pressure energy recovery and is converted into low-pressure concentrated seawater in the salinity difference energy-turbine coupled energy recovery device. Under the action of the forward osmosis separation membrane, the low-pressure concentrated seawater and the original seawater undergo osmotic pressure transfer to form medium-pressure seawater. The medium-pressure seawater directly drives the impeller to rotate, completing the second-level salinity difference energy recovery. The seawater is discharged after the residual pressure energy and salinity difference energy are recovered. The entire process is shortened, the system is simpler and more efficient, and since the salinity difference energy is directly converted into mechanical energy, the conversion efficiency is higher.

[0096] The experimental data comparison table of the embodiment of the present invention is as follows Figure 6 As shown, three solutions are compared under the same water inlet conditions:

[0097] Option 1: Use only high-pressure pump;

[0098] Option 2: Use a high-pressure pump and turbine energy recovery device;

[0099] Option 3: Use a high-pressure pump and a salt difference energy-turbine coupled energy recovery device;

[0100] It can be seen that the energy consumption and energy consumption per ton of water of the three high-pressure system solutions are:

[0101] The energy consumption of Option 1 is 316.7kW, and the energy consumption per ton of water is 4.59kW·h;

[0102] The energy consumption of Option 2 is 187kW, and the energy consumption per ton of water is 2.71kW·h;

[0103] The energy consumption of option three is 163.4kW, and the energy consumption per ton of water is 2.37kW·h;

[0104] Looking at total energy consumption or energy consumption per ton of water, Scheme 3 reduces energy consumption by 48% compared to Scheme 1 and 12.6% compared to Scheme 2. This embodiment not only enables cascaded energy utilization of concentrated brine discharged from the reverse osmosis system, but also increases salinity energy utilization efficiency by 15%-20%. The application of this dual energy recovery technology is expected to further reduce the overall energy consumption of reverse osmosis desalination systems by 10%-15%.

[0105] In this embodiment, the salinity-energy-turbine coupled energy recovery device utilizes the salinity difference between raw seawater and concentrated seawater to recover the salinity-energy difference of low-pressure concentrated seawater. Coupled with the hydraulic turbine-type excess pressure energy recovery technology, this device achieves a gradient recovery of concentrated seawater energy, achieving dual energy savings. Promoting the development of seawater desalination technology towards higher efficiency and greater environmental friendliness is of strategic importance for achieving sustainable water resource utilization.

[0106] In the description provided herein, numerous specific details are described. However, it is understood that embodiments of the present invention may be practiced without these specific details. In some instances, well-known methods, structures, and techniques are not shown in detail so as not to obscure the understanding of this description.

[0107] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed as above in terms of a preferred embodiment, it is not intended to limit the present invention. Any technician familiar with this patent can make slight changes or modifications to equivalent embodiments using the above technical content without departing from the scope of the technical solution of the present invention. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the solution of the present invention.

Claims

1. A salt difference energy-turbine coupled energy recovery device for seawater desalination, characterized in that: Its structure is divided into a first chamber (1), a second chamber (2), a third chamber (3), a fourth chamber (4), and a fifth chamber (5); The first chamber (1), the second chamber (2), the third chamber (3), the fourth chamber (4), and the fifth chamber (5) adopt an upper and lower split chamber structure, and the upper and lower chambers are mechanically sealed by flanges; The first chamber (1), the second chamber (2), the third chamber (3), and the fourth chamber (4) are arranged axially in sequence along the central axis, and the fifth chamber (5) is located outside the third chamber (3) and the fourth chamber (4); The first chamber (1), the second chamber (2), the third chamber (3), and the fourth chamber (4) are coaxially rotated and fluidically isolated through a central axis and a mechanical sealing structure. The first chamber (1) contains a first water inlet (1-1), a second water outlet (1-2), a first water inlet bearing (1-3), a first chamber impeller (1-4), and a first chamber solid bearing (1-5); the first water inlet bearing (1-3) is provided with a mechanical seal; The second chamber (2) contains a second chamber impeller (2-1), a second chamber water inlet (2-2), and a second chamber hollow bearing (2-3); The third chamber (3) contains a third chamber impeller (3-1), a third chamber water outlet (3-2), and a third chamber solid bearing (3-3); The fourth chamber (4) contains a fourth chamber impeller (4-1), a fourth chamber water outlet bearing (4-2), a fourth chamber water inlet (4-3), and a fourth chamber water outlet (4-4), and a mechanical seal is provided on the fourth chamber water outlet bearing (4-2); The fifth chamber (5) is located outside the third chamber (3) and the fourth chamber (4), forming an independent membrane separation unit, and is provided with a fifth chamber raw seawater inlet (5-1), a fifth chamber forward osmosis membrane assembly (5-2), and a fifth chamber outlet (5-3); The raw seawater inlet (5-1) of the fifth chamber is connected to the pre-treated raw seawater; The fifth chamber forward osmosis membrane assembly (5-2) is installed in the form of a hollow fiber, roll or tubular separation membrane; The key flow channel structure of the fifth chamber forward osmosis membrane assembly (5-2) adopts a dual independent flow channel design of a raw seawater side flow channel and an extraction liquid side flow channel. The two flow channels are strictly isolated by a high-performance forward osmosis membrane. The raw seawater side flow channel is connected to the raw seawater inlet (5-1) of the fifth chamber and the water outlet (5-3) of the fifth chamber, and the extraction liquid side flow channel is connected to the water outlet (3-2) of the third chamber and the water inlet (4-3) of the fourth chamber. The fifth chamber water outlet (5-3) is used to discharge the medium-salinity seawater produced by the forward osmosis process; The first chamber solid bearing (1-5) is connected to the first chamber impeller (1-4) and the second chamber impeller (2-1) through interference fit, and the shaft is sealed by a sealing ring to prevent fluid leakage between the chambers; A guide groove is provided on the inner wall of the hollow structure of the second chamber hollow bearing (2-3), allowing concentrated seawater after pressure relief in the second chamber (2) to enter the third chamber impeller (3-1) through the hollow internal flow channel of the shaft. The shaft is provided with a sealing ring to prevent fluid leakage between the chambers. The second chamber impeller (2-1) and the third chamber impeller (3-1) are connected via a threaded connection of the shaft. The third chamber solid bearing (3-3) is connected to the third chamber impeller (3-1) and the fourth chamber impeller (4-1) through interference fit, and the shaft is sealed by a sealing ring to prevent fluid leakage between the chambers; The fifth chamber (5) is connected to the third chamber (3) in a copy forest form through the third chamber water outlet (3-2), and a one-way valve is provided in the third chamber water outlet (3-2); The fifth chamber (5) is connected to the fourth chamber (4) in a copy forest form through the fourth chamber water inlet (4-3); An overrunning clutch is provided at the connection between the third chamber solid bearing (3-3) and the third chamber impeller (3-1).

2. The operating method of the salinity difference energy-turbine coupled energy recovery device for seawater desalination according to claim 1, characterized in that: The raw seawater passed through the security filter and the high-pressure pump enters the first chamber water inlet (1-1), the first chamber water outlet (1-2) is connected to the inlet of the reverse osmosis membrane assembly, the pressurized seawater exits the first chamber water outlet (1-2) and enters the reverse osmosis membrane assembly, the outlet of the high-pressure concentrated seawater of the reverse osmosis membrane assembly is connected to the second chamber water inlet (2-2), the fifth chamber water outlet (5-3) and the fourth chamber water outlet (4-4) are respectively used to discharge the brine of the salt difference energy-turbine coupling energy recovery device, and the fifth chamber raw seawater inlet (5-1) is connected to the inlet of the raw seawater branch pipeline after being filtered by the security filter; The drawn liquid inlet is connected to the third chamber outlet (3-2), and the drawn liquid outlet is connected to the fourth chamber inlet (4-3); High-precision pressure sensors are provided at the second chamber water inlet (2-2) and the fourth chamber water inlet (4-3); The pipeline connected to the water outlet (4-4) of the fourth chamber is provided with an electromagnetic flow control valve.

3. The operating method of the salinity difference energy-turbine coupled energy recovery device for seawater desalination according to claim 2, characterized in that: During operation, the pressure sensor values of the second chamber water inlet (2-2) and the fourth chamber water inlet (4-3) are compared by an external control PLC, and the opening of the electromagnetic flow control valve provided in the connecting pipe of the fourth chamber water outlet (4-4) is automatically adjusted.

4. The operating method of the salinity difference energy-turbine coupled energy recovery device for seawater desalination according to claim 2, characterized in that: When the salt difference energy boosting of the fifth chamber (5) is insufficient, the overrunning clutch automatically disconnects the transmission connection between the third chamber impeller (3-1) and the fourth chamber impeller (4-1); when the salt difference energy boosting reaches the standard, the overrunning clutch re-engages.

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