Intelligent control system and method for energy recovery of concentrated water of seawater desalination secondary low-pressure reverse osmosis

Abstract

The application discloses a seawater desalination secondary low-pressure reverse osmosis concentrated water energy recovery intelligent control system and method, wherein the system comprises a seawater pretreatment module, a primary reverse osmosis system module, a secondary reverse osmosis system module and an intelligent regulation and control module connected in sequence, and the method comprises the following steps: S1, real-time data acquisition; S2, pressure grading reservation and power generation; and S3, dynamic pressure compensation. Through optimization of the operation mode and control strategy of the hydraulic power generation device, the application realizes recovery and utilization of the low-pressure concentrated water residual pressure, does not need to rely on new hardware equipment, reduces system energy consumption, and improves system stability and economy.

Description

Technical Field

[0001] This invention relates to the field of seawater desalination and residual energy recovery technology, specifically to an intelligent control system and method for energy recovery of concentrate from secondary low-pressure reverse osmosis in seawater desalination. Background Technology

[0002] Seawater desalination plays a crucial role in addressing the global freshwater shortage, particularly in coastal areas. With dwindling freshwater resources and population growth, seawater desalination has become a key solution for ensuring a sustainable water supply. Currently, reverse osmosis (RO) technology is the primary method for seawater desalination. In the RO process, raw water passes through a semi-permeable membrane, where salt is retained, producing both freshwater and concentrate. To further improve recovery rates or water quality, secondary RO systems are frequently used. These systems treat the permeate from the primary RO system to produce higher-quality freshwater. Energy recovery units are essential components in reverse osmosis seawater desalination to recover energy, reducing energy consumption and environmental impact.

[0003] In existing seawater desalination systems, the energy recovery technology for first-stage reverse osmosis concentrate is relatively mature. Commonly used first-stage reverse osmosis energy recovery devices include pressure exchange type and hydraulic turbine type. Among them, the pressure exchange type can achieve an energy recovery rate of over 94%, which can significantly reduce the energy consumption per ton of desalinated water and the cost of water production. However, the energy recovery technology for second-stage reverse osmosis concentrate still has significant shortcomings. On the one hand, the pressure of second-stage reverse osmosis concentrate is relatively low, making recovery more difficult and resulting in energy waste. On the other hand, the equipment and processes for energy recovery of second-stage reverse osmosis concentrate are not yet perfect, lacking efficient, stable, and economically feasible solutions. In addition, seawater desalination systems under new energy systems face energy fluctuations, and energy recovery devices also need to adapt to changing demands and be suitable for complex operating conditions with frequent start-ups and shutdowns. Summary of the Invention

[0004] The present invention provides an intelligent control system and method for energy recovery of concentrated water from secondary low-pressure reverse osmosis in seawater desalination, which is more energy-efficient, more efficient and improves resource utilization, and can solve at least one of the above-mentioned technical problems.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: The intelligent control system for energy recovery of concentrate from secondary low-pressure reverse osmosis in seawater desalination includes a seawater pretreatment module, a primary reverse osmosis system module, a secondary reverse osmosis system module, and an intelligent control module connected in sequence. The seawater pretreatment module includes a screen filter and a security filter, which are used to pretreat the raw seawater through multiple filtration processes to obtain stable and clean influent. The primary reverse osmosis system module includes a primary high-pressure pump, a primary reverse osmosis membrane module, a primary booster pump, a pressure exchange energy recovery device, and a concentrate tank, used to treat high-salinity seawater in the feed water and produce industrial-grade freshwater. The secondary reverse osmosis system module includes a secondary high-pressure pump, a secondary reverse osmosis membrane module, a hydroelectric generator set, a product water tank, and an intelligent regulating valve, which is used to deeply purify industrial-grade freshwater, improve water quality to drinking standards, and meet refined needs. The intelligent control module has a built-in operation control algorithm, which is used to calculate and control the inlet flow of the hydroelectric generator while ensuring maximum power generation and optimal return pressure. This enables the hydroelectric generator set to respond within seconds when the inlet pressure of the high-pressure pump fluctuates, thus ensuring the stable operation of the first-stage high-pressure pump.

[0006] Furthermore, in the seawater pretreatment module: The screen filter is equipped with a seawater inlet for introducing raw seawater and initially filtering impurities in the raw seawater. The security filter is connected to the outlet of the screen filter to filter out fine impurities, and the outlet of the security filter is connected to the inlet of the primary high-pressure pump and the low-pressure inlet of the pressure exchange energy recovery device.

[0007] Furthermore, in the first-stage reverse osmosis system module: The inlet of the first-stage reverse osmosis membrane module is connected to the outlet of the first-stage high-pressure pump for pumping high-pressure seawater into the first-stage reverse osmosis membrane module. The concentrate outlet of the first-stage reverse osmosis membrane module is connected to the high-pressure inlet of the pressure exchange energy recovery device, for conveying the high-pressure concentrate output from the first-stage reverse osmosis membrane module to the high-pressure inlet of the pressure exchange energy recovery device. The freshwater outlet of the first-stage reverse osmosis membrane module is connected to the inlet of the second-stage high-pressure pump, for conveying the permeate output from the first-stage reverse osmosis membrane module to the second-stage high-pressure pump located before the second-stage reverse osmosis membrane module. The high-pressure outlet of the pressure exchange energy recovery device is connected to the inlet of the first-stage booster pump, and is used to transport the high-pressure seawater output from the high-pressure outlet of the pressure exchange energy recovery device to the first-stage booster pump for pressurization. The outlet of the first-stage booster pump is connected to the inlet of the first-stage reverse osmosis membrane module, and is used to transport high-pressure seawater pressurized by the first-stage booster pump to the first-stage reverse osmosis membrane module. The low-pressure outlet of the pressure exchange energy recovery device is connected to the concentrate tank, and is used to transport the first-stage reverse osmosis low-pressure concentrate output from the low-pressure outlet of the pressure exchange energy recovery device to the concentrate tank.

[0008] Furthermore, in the secondary reverse osmosis system module: The inlet of the secondary reverse osmosis membrane module is connected to the outlet of the secondary high-pressure pump for pumping high-pressure permeate into the secondary reverse osmosis membrane module; The concentrate outlet of the secondary reverse osmosis membrane module is connected to two pipes, which are respectively connected to the turbine inlet and turbine outlet of the hydroelectric generator set. These pipes are used to divide the pressurized concentrate output from the concentrate outlet of the secondary reverse osmosis membrane module into two streams. One stream is sent to the hydroelectric generator set for hydroelectric power generation, while the other stream maintains its original pressure and mixes with the stream after hydroelectric power generation. The intelligent regulating valve is located on the pipe connected to the turbine outlet and is used to dynamically regulate the flow rate of pressurized concentrate entering the turbine for hydropower generation, so as to ensure that the mixed concentrate formed by the low-pressure water flow after hydropower generation and the pressurized concentrate maintaining the original pressure can flow back to the inlet of the first-stage high-pressure pump. The freshwater outlet of the secondary reverse osmosis membrane module is connected to the product water tank, and is used to transport the freshwater output from the freshwater outlet of the secondary reverse osmosis membrane module to the product water tank for storage as the final product.

[0009] Furthermore, the intelligent control module is connected to the hydroelectric generator set and includes a controller and a pressure sensor. It uses a built-in operation control algorithm to regulate the backflow pressure of the mixed concentrate, ensuring that the backflow pressure can overcome the pipeline resistance, so as to achieve a second-level response to pressure fluctuations and ensure the stable operation of the first-stage high-pressure pump.

[0010] A smart control method for energy recovery of concentrate from secondary low-pressure reverse osmosis in seawater desalination, implemented using the aforementioned smart control system for energy recovery of concentrate from secondary low-pressure reverse osmosis in seawater desalination, includes the following steps: S1. Real-time data acquisition: Pressure sensors are placed at the turbine inlet, turbine outlet, and first-stage high-pressure pump inlet to collect the turbine inlet pressure P1, turbine outlet pressure P3, first-stage high-pressure pump inlet pressure P2, and mixed concentrate return pressure P4 in real time. S2. Pressure Classification and Power Generation: Using an intelligent regulating valve to limit the turbine inlet flow, the pressurized concentrate output from the second-stage reverse osmosis membrane module is divided into two streams. One stream, Q1, is delivered to the turbine of the hydroelectric generator unit, converting pressure energy into electrical energy for hydroelectric power generation. The pressure of this stream Q1 is the turbine outlet pressure P3. The other stream, Q2, maintains its original pressure and is discharged directly without entering the turbine. The pressure of this stream Q2 is the turbine inlet pressure P1. The two streams are mixed to form a mixed stream Q3, which flows back to the inlet of the first-stage high-pressure pump. The pressure P of the mixed stream Q3 is calculated. 4计算 ; S3. Dynamic pressure compensation: When the collected mixed concentrate return pressure P4 is less than the inlet pressure P2 of the first-stage high-pressure pump, the intelligent regulating valve adjusts the pressure until the mixed concentrate return pressure P4 is increased to the target value P2, ensuring that the concentrate overcomes the pipeline resistance and returns to the inlet of the first-stage high-pressure pump.

[0011] Furthermore, in S2, the expression for calculating the volumetric flow rate of the mixed water flow Q3 is: Q3=Q1+Q2=A1v1+A2v2(1) Where Q1 and Q2 are the volumetric flow rates of the two water streams, A1 and A2 are the cross-sectional areas of the pipes for the two water streams, and v1 and v2 are the flow velocities of the water streams in the pipes. Considering the steady-state flow of water within a controlled pipeline, the change in momentum equals the resultant force of pressure and momentum flow, which can be formally expressed as: P1A1+P3A2+ρ(A1v1 2 +A2v2 2 )=P 4计算 A+ρ(Av 2 (2) Among them, P 4计算 Let Q3 be the pressure of the mixed water flow, A be the cross-sectional area of ​​the pipe after mixing, v = Q / A be the velocity of the two water flows after mixing, and ρ be the density of water. Substituting v=Q / A into the momentum conservation equation and rearranging, we obtain the pressure P of the mixed water flow Q3. 4计算 for: P 4计算 = (3) Considering the viscous loss during fluid mixing, the above momentum conservation equation needs to be modified. After deducting the pressure loss caused by viscous loss, the modified momentum conservation equation is as follows: ΔP loss = (4) P 4计算 = (5) Where K is the local loss coefficient, ΔP loss This refers to the pressure loss caused by viscosity loss during the mixing of two water streams.

[0012] Furthermore, in S3, based on the real-time detection value of the pressure of the mixed water flow Q3 during actual operation, let P... 4计算 =P4, substitute into the original momentum conservation equation (1), and calculate the pressure loss ΔP caused by the viscous loss in the current system. loss The calculated pressure loss ΔP lossSubstitute this into the modified momentum conservation equation (5) and input the modified momentum conservation equation into the intelligent control system. When a fluctuation in the inlet pressure P2 of the first-stage high-pressure pump is detected, P2=P4=P 4计算 To achieve this goal, the concentrate flow rate allocated to the secondary reverse osmosis system module is updated and adjusted in a timely manner.

[0013] Furthermore, in S3, the power generation E gen If the goal is to maximize the momentum, then the flow of water Q1 used for hydroelectric power generation needs to be maximized. According to the modified momentum conservation equation (5), when P 4计算 =P2 calculates the other water flow Q2 at this time, and allocates the flow rates of the two water flows output by the secondary reverse osmosis membrane module according to the calculation results.

[0014] Furthermore, the water flow Q1 delivered to the hydroelectric generator unit drives a synchronous generator via a water turbine, with the output frequency synchronized with the power grid. The generated electrical energy is connected to the power transmission network through a step-up transformer, thus completing energy recovery.

[0015] The beneficial effects of this invention are reflected in: In a two-stage reverse osmosis system, this invention improves energy utilization efficiency by recovering pressure energy from a portion of the concentrate through a hydroelectric turbine, directly converting it into electrical energy. The low-pressure concentrate from the turbine outlet is mixed with another portion of the direct-discharge concentrate, and this mixed flow is returned to the inlet of the first-stage reverse osmosis high-pressure pump. This helps improve the overall energy utilization efficiency of the seawater desalination system, making the desalination process more energy-efficient. Simultaneously, an intelligent control algorithm is used to precisely regulate the return pressure, ensuring it can overcome pipeline resistance and achieve a second-level response to pressure fluctuations, thereby guaranteeing the stable operation of the first-stage reverse osmosis high-pressure pump. This technology can also be applied to freshwater reverse osmosis systems for the efficient recovery of energy from low-pressure concentrate. Attached Figure Description

[0016] The accompanying drawings, which are provided to further illustrate this application and form part of this application, illustrate exemplary embodiments of this application and are used to explain this application, but do not constitute an undue limitation of this application.

[0017] Figure 1 This is a schematic diagram of the overall structure of the intelligent control system according to an embodiment of the present invention.

[0018] Figure 2 This is a schematic diagram of the overall process of the intelligent control method according to an embodiment of the present invention.

[0019] Figure 3 This is a schematic diagram of the specific operation and control process of the intelligent control method according to an embodiment of the present invention.

[0020] Figure 4This is a structural block diagram of a computer device according to an embodiment of the present invention.

[0021] The components in the attached diagram are labeled as follows: 1. Seawater pretreatment module; 2. First-stage reverse osmosis system module; 3. Second-stage reverse osmosis system module; 4. Screen filter; 5. Security filter; 6. First-stage high-pressure pump; 7. First-stage reverse osmosis membrane module; 8. First-stage booster pump; 9. Pressure exchange energy recovery device; 10. Concentrate tank; 11. Second-stage high-pressure pump; 12. Second-stage reverse osmosis membrane module; 13. Hydroelectric generator set; 14. Product water tank; 15. Intelligent regulating valve; 16. Smart control module. Detailed Implementation

[0022] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Unless otherwise specified, the embodiments and features in the embodiments of this application can be combined with each other. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] It should be noted that the technical solutions of the various embodiments can be combined with each other, but only if they are based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0024] See Figure 1 The present invention provides an intelligent control system for energy recovery of concentrate from secondary low-pressure reverse osmosis in seawater desalination, comprising a seawater pretreatment module 1, a primary reverse osmosis system module 2, a secondary reverse osmosis system module 3, and an intelligent control module 16 connected in sequence. The seawater pretreatment module 1 includes a screen filter 4 and a security filter 5, which are used to pretreat the raw seawater through multiple filtration processes to obtain stable and clean influent. The first-stage reverse osmosis system module 2 includes a first-stage high-pressure pump 6, a first-stage reverse osmosis membrane module 7, a first-stage booster pump 8, a pressure exchange energy recovery device 9, and a concentrate tank 10, which are used to treat high-salinity seawater in the feed water and produce industrial-grade freshwater. The secondary reverse osmosis system module 3 includes a secondary high-pressure pump 11, a secondary reverse osmosis membrane module 12, a hydroelectric generator set 13, a product water tank 14, and an intelligent regulating valve 15, which are used to deeply purify industrial-grade freshwater, improve water quality to drinking standards, and meet refined needs. The intelligent control module 16 has a built-in operation control algorithm, which is used to calculate and control the inlet flow of the hydroelectric generator while ensuring maximum power generation and optimal return pressure. This enables the hydroelectric generator set to respond within 13 seconds when the inlet pressure of the high-pressure pump fluctuates, thus ensuring the stable operation of the first-stage high-pressure pump 6.

[0025] In this embodiment, in the seawater pretreatment module 1: The screen filter 4 is equipped with a seawater inlet for introducing raw seawater and initially filtering impurities in the raw seawater. The security filter 5 is connected to the outlet of the screen filter 4 to filter out fine impurities, and the outlet of the security filter 5 is connected to the inlet of the primary high-pressure pump 6 and the low-pressure inlet of the pressure exchange energy recovery device 9.

[0026] The seawater pretreatment module 1 intercepts a large amount of suspended solids and colloidal particles such as silt, plankton, and organic matter in the seawater, providing stable and clean feed water conditions for the subsequent reverse osmosis membrane, thereby ensuring efficient system operation and extending equipment life.

[0027] In this embodiment, in the first-stage reverse osmosis system module 2: The inlet of the first-stage reverse osmosis membrane module 7 is connected to the outlet of the first-stage high-pressure pump 6 for pumping high-pressure seawater into the first-stage reverse osmosis membrane module 7. The concentrate outlet of the first-stage reverse osmosis membrane module 7 is connected to the high-pressure inlet of the pressure exchange energy recovery device 9, for conveying the high-pressure concentrate output by the first-stage reverse osmosis membrane module 7 to the high-pressure inlet of the pressure exchange energy recovery device 9. The freshwater outlet of the first-stage reverse osmosis membrane module 7 is connected to the inlet of the second-stage high-pressure pump 11, for conveying the permeate output from the first-stage reverse osmosis membrane module 7 to the second-stage high-pressure pump 11 located before the second-stage reverse osmosis membrane module 12. The high-pressure outlet of the pressure exchange energy recovery device 9 is connected to the inlet of the first-stage booster pump 8, and is used to transport the high-pressure seawater output from the high-pressure outlet of the pressure exchange energy recovery device 9 to the first-stage booster pump 8 for pressurization. The outlet of the first-stage booster pump 8 is connected to the inlet of the first-stage reverse osmosis membrane module 7, and is used to transport the high-pressure seawater boosted by the first-stage booster pump 8 to the first-stage reverse osmosis membrane module 7. The low-pressure outlet of the pressure exchange energy recovery device 9 is connected to the concentrate tank 10, and is used to transport the first-stage reverse osmosis low-pressure concentrate output from the low-pressure outlet of the pressure exchange energy recovery device 9 to the concentrate tank 10.

[0028] In this embodiment, in the secondary reverse osmosis system module 3: The inlet of the secondary reverse osmosis membrane module 12 is connected to the outlet of the secondary high-pressure pump 11 for pumping high-pressure permeate into the secondary reverse osmosis membrane module 12; The concentrate outlet of the secondary reverse osmosis membrane module 12 is connected to two pipes, which are respectively connected to the turbine inlet and turbine outlet of the hydro-generator set 13. These pipes are used to divide the pressurized concentrate output from the concentrate outlet of the secondary reverse osmosis membrane module 12 into two streams. One stream is sent to the hydro-generator set 13 for hydro-power generation, while the other stream maintains its original pressure and mixes with the stream after hydro-power generation. The intelligent regulating valve 15 is located on the pipe connected to the outlet of the water turbine and is used to dynamically regulate the flow rate of pressurized concentrated water entering the water turbine for hydropower generation, so as to ensure that the mixed concentrated water formed after the low-pressure water flow after hydropower generation and the pressurized concentrated water maintaining the original pressure can flow back to the inlet of the first-stage high-pressure pump 6. The freshwater outlet of the secondary reverse osmosis membrane module 12 is connected to the product water tank 14, and is used to transport the freshwater output from the freshwater outlet of the secondary reverse osmosis membrane module 12 to the product water tank 14 for storage as the final product.

[0029] It should be noted that, in this invention, the primary reverse osmosis membrane module 7 and the secondary reverse osmosis membrane module 12 can be combinations of various types of membranes or multi-stage membrane modules, and the turbine in the hydroelectric generator set 13 can be various types of turbines such as cross-flow turbines, mixed-flow turbines, axial-flow turbines, and oblique-flow turbines, and is equipped with a generator.

[0030] In this embodiment, the intelligent control module 16 is connected to the hydroelectric generator set 13 and includes a controller and a pressure sensor. It uses a built-in operation control algorithm to regulate the backflow pressure of the mixed concentrate, ensuring that the backflow pressure can overcome the pipeline resistance, so as to achieve a second-level response to pressure fluctuations and ensure the stable operation of the first-stage high-pressure pump 6.

[0031] See Figures 2-3 This invention also provides an intelligent control method for energy recovery of concentrate from secondary low-pressure reverse osmosis in seawater desalination, implemented using the aforementioned intelligent control system for energy recovery of concentrate from secondary low-pressure reverse osmosis in seawater desalination, comprising the following steps: S1. Real-time data acquisition: Pressure sensors are placed at the turbine inlet, turbine outlet, and first-stage high-pressure pump 6 inlet to collect the turbine inlet pressure P1, turbine outlet pressure P3, first-stage high-pressure pump 6 inlet pressure P2, and mixed concentrate return pressure P4 in real time. S2. Pressure Classification and Power Generation: Using intelligent regulating valve 15 to limit the turbine inlet flow, the pressurized concentrate output from the secondary reverse osmosis membrane module 12 is divided into two streams. One stream, Q1, is sent to the turbine of the hydroelectric generator set 13 to convert pressure energy into electrical energy for hydroelectric power generation. The pressure of this stream Q1 is the turbine outlet pressure P3. The other stream, Q2, maintains its original pressure and is discharged directly without entering the turbine. The pressure of this stream Q2 is the turbine inlet pressure P1. The two streams are mixed to form a mixed stream Q3, which flows back to the inlet of the primary high-pressure pump 6. The pressure P of the mixed stream Q3 is calculated. 4计算 ; S3. Dynamic pressure compensation: When the collected mixed concentrate return pressure P4 is less than the inlet pressure P2 of the first-stage high-pressure pump 6, the intelligent regulating valve 15 adjusts the mixed concentrate return pressure P4 until it reaches the target value P2, ensuring that the concentrate overcomes the pipeline resistance and returns to the inlet of the first-stage high-pressure pump 6.

[0032] In this embodiment, the expression for calculating the volumetric flow rate of the mixed water flow Q3 in step S2 is: Q3=Q1+Q2=A1v1+A2v2(1) Where Q1 and Q2 are the volumetric flow rates of the two water streams, A1 and A2 are the cross-sectional areas of the pipes for the two water streams, and v1 and v2 are the flow velocities of the water streams in the pipes. Since the physical parameters such as velocity, flow rate, and pressure at any cross-section within the pipe do not change with time, considering the steady-state flow of water within the pipe, the change in momentum equals the resultant force of pressure and momentum flow, which can be expressed as: P1A1+P3A2+ρ(A1v1 2 +A2v2 2 )=P 4计算 A+ρ(Av 2 (2) Among them, P 4计算 Let Q3 be the pressure of the mixed water flow, A be the cross-sectional area of ​​the pipe after mixing, v = Q / A be the velocity of the two water flows after mixing, and ρ be the density of water. Substituting v=Q / A into the momentum conservation equation and rearranging, we obtain the pressure P of the mixed water flow Q3. 4计算 for: P 4计算 = (3) In fluid mechanics, viscous loss refers to the irreversible dissipation of mechanical energy during fluid flow due to intermolecular friction (internal friction) and friction between the fluid and solid walls. Therefore, considering the viscous loss during fluid mixing, the above momentum conservation equation needs to be modified by subtracting the pressure loss caused by viscous loss. The modified momentum conservation equation is shown below: ΔP loss = (4) P 4计算 = (5) Where K is the local loss coefficient, ΔP loss This refers to the pressure loss caused by viscosity loss during the mixing of two water streams.

[0033] In this embodiment, in step S3, based on the real-time detected value of the pressure of the mixed water flow Q3 during actual operation, P is set to... 4计算 =P4, substitute into the original momentum conservation equation (1), and calculate the pressure loss ΔP caused by the viscous loss in the current system. loss The calculated pressure loss ΔP loss Substituting this into the modified momentum conservation equation (5), and inputting this modified momentum conservation equation into the intelligent control system, when a fluctuation in the inlet pressure P2 of the first-stage high-pressure pump 6 is detected, P2=P4=P 4计算 To achieve this goal, the concentrate flow rate allocated to module 3 of the secondary reverse osmosis system is updated and adjusted in a timely manner.

[0034] In this embodiment, in step S3, the power generation E gen If the goal is to maximize the momentum, then the flow of water Q1 used for hydroelectric power generation needs to be maximized. According to the modified momentum conservation equation (5), when P 4计算 =P2 calculates the other water flow Q2 at this time, and distributes the flow rates of the two water flows output by the secondary reverse osmosis membrane module 12 according to the calculation results.

[0035] In this embodiment, the water flow Q1 delivered to the hydroelectric generator set 13 drives a synchronous generator through a water turbine, and the output frequency is synchronized with the power grid, typically 50 / 60 Hz. The generated electrical energy is connected to the power transmission network through a step-up transformer to complete energy recovery.

[0036] To verify the superiority and feasibility of this invention, the intelligent control method will be further illustrated below with a specific simulation case: The simulation case study uses typical water quality from the high seas of the Pacific Ocean as a benchmark: total dissolved solids (TDS) of 40,000 mg / L and temperature of 28℃. AquaGRID software is used to simulate a 10,000-ton-scale reverse osmosis (RO) system. The designed permeable volume of the single-stage seawater reverse osmosis (SWRO)-brackish water reverse osmosis (BWRO) integrated unit is 56,250 m³. 3 / d (equivalent to 2,344 m) 3 / h).

[0037] Simulation results of system operating parameters and energy recovery mechanism show that: BWRO concentrate characteristics: The treated concentrate flow rate is 260.33 m³ / s.3 / h, pressure 8.32 bar, TDS 3,011.13 mg / L.

[0038] Energy recovery path: Concentrate diversion Q1: 200.16 m 3 / h (76.9%) enters the hydraulic energy recovery device (such as a turbine), inlet pressure P1 = 8.32 bar; the remaining diversion Q2: 60.17 m 3 / h (accounting for 23.1%) maintain the original pressure (8.32 bar).

[0039] Mixing control strategy: After energy recovery, the water flow Q1 (0.01 bar) is mixed with the remaining diverted flow Q2 (8.32 bar), with a target mixing pressure P4 = 2 bar, and the water flows back to the inlet of the first-stage high-pressure pump to overcome pipeline resistance.

[0040] Energy efficiency optimization effect: Power generation: The BWRO concentrate recovers energy through a hydroelectric power generation device, with a theoretical power generation of 39.27 kWh (calculated based on an equipment efficiency of 85%).

[0041] Reduced system energy consumption: After the introduction of the energy recovery device, the overall energy consumption of the reverse osmosis system decreased by 0.6%.

[0042] Economic benefits: Based on 300 days of operation per year and a normal electricity cost of 0.55 yuan / kWh, introducing a single reverse osmosis system with hydropower generation can save 155,509 yuan in electricity costs per year.

[0043] Dynamic response control: When the inlet pressure of the first-stage high-pressure pump fluctuates, the concentrate-to-water ratio (200.16 m³) is adjusted in real time. 3 / h vs 60.17 m 3 ( / h) to achieve rapid and stable control of system pressure, ensuring that the mixing pressure constantly meets the reflux requirements.

[0044] Table 1 Comparison of energy consumption calculations using AquaGRID software

[0045] This invention also provides a computer-readable storage medium storing a computer program, which, when executed by a processor, causes the processor to perform the steps of the intelligent control method for energy recovery of concentrate from secondary low-pressure reverse osmosis in seawater desalination as described above.

[0046] See Figure 4 The present invention also provides a computer device, including a memory and a processor. The memory stores a computer program. When the computer program is executed by the processor, the processor performs the steps of the intelligent control method for energy recovery of concentrate from secondary low-pressure reverse osmosis in seawater desalination as described above.

[0047] This invention also provides a computer program product containing instructions that, when run on a computer, cause the computer to perform the steps of the intelligent control method for energy recovery of concentrate from secondary low-pressure reverse osmosis in seawater desalination as described above.

[0048] It is understood that the systems, devices and storage media provided in the embodiments of the present invention correspond to the methods provided in the embodiments of the present invention, and the explanations, examples and beneficial effects of the relevant contents can be referred to the corresponding parts of the above-mentioned intelligent control method for energy recovery of concentrated water in secondary low-pressure reverse osmosis of seawater desalination.

[0049] It should be noted that those skilled in the art will understand that all or part of the steps implemented in the embodiments of the present invention can be implemented entirely or partially by software, hardware, firmware, or any combination thereof. When implemented in hardware, it can be implemented entirely or partially by purchasing standard parts or modifications. When implemented in software, it can be implemented entirely or partially in the form of a computer program product. The computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, all or part of the processes or functions described in the embodiments of this application are generated. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions can be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another. For example, the computer instructions can be transmitted from one website, computer, server, or data center to another website, computer, server, or data center via wired (e.g., coaxial cable, fiber optic, digital subscriber line (DSL)) or wireless (e.g., infrared, wireless, microwave, etc.) means. The computer-readable storage medium can be any available medium that a computer can access or a data storage device such as a server or data center that integrates one or more available media. The available media may be magnetic media (e.g., floppy disks, hard disks, magnetic tapes), optical media (e.g., DVDs), or semiconductor media (e.g., solid state disks (SSDs)).

[0050] In summary, to address the two main problems of existing seawater desalination systems: first, the secondary reverse osmosis concentrate in seawater desalination systems needs to be depressurized and discharged through a back pressure valve, consuming additional energy and potentially requiring the addition of anti-siphon devices, increasing system complexity and leading to potential energy waste; second, in the context of renewable energy sources, how can the secondary reverse osmosis energy recovery device adapt to the fluctuations in the pressure required for reflux? This invention proposes an intelligent control system and method for energy recovery of low-pressure reverse osmosis concentrate from the secondary stage of seawater desalination.

[0051] Specifically, regarding the first question, the technical solution provided by this invention is based on maximizing power generation and optimizing the pressure of the return concentrate. Through optimized design calculations, the concentrate from the second-stage reverse osmosis is divided into two streams. One stream directly enters the hydropower generation device, which can adapt to the characteristics of low-pressure concentrate and convert the pressure energy of the concentrate into electrical energy, thus achieving energy recovery. The slightly positive pressure water stream after power generation mixes with the other low-pressure concentrate stream that did not enter the hydropower generation device and flows back to the inlet of the high-pressure pump of the first-stage reverse osmosis.

[0052] Regarding the second problem, the solution provided by this invention is as follows: In order to ensure that the concentrated water after mixing can overcome the pipeline resistance and flow back smoothly, a system intelligent operation control method is provided. With the goal of maximizing power generation and optimizing the pressure of the returned concentrated water, the inlet flow rate of the hydraulic generator set is calculated to achieve a second-level response of the hydraulic generator set when the inlet pressure of the high-pressure pump fluctuates, thus ensuring the stable operation of the first-stage reverse osmosis high-pressure pump.

[0053] It should be understood that the examples and embodiments described herein are for illustrative purposes only and are not intended to limit the invention. Those skilled in the art can make various modifications or changes based on them. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the invention should be included within the protection scope of the invention.

Claims

1. An intelligent control system for energy recovery of concentrate from secondary low-pressure reverse osmosis seawater desalination, characterized in that: It includes a seawater pretreatment module (1), a primary reverse osmosis system module (2), a secondary reverse osmosis system module (3), and a smart control module (16) connected in sequence. The seawater pretreatment module (1) includes a screen filter (4) and a security filter (5), which are used to pretreat the raw seawater through multiple filtration processes to obtain stable and clean influent. The first-stage reverse osmosis system module (2) includes a first-stage high-pressure pump (6), a first-stage reverse osmosis membrane module (7), a first-stage booster pump (8), a pressure exchange energy recovery device (9), and a concentrate tank (10), which is used to treat the high-salt seawater in the feed water and produce industrial-grade fresh water; The secondary reverse osmosis system module (3) includes a secondary high-pressure pump (11), a secondary reverse osmosis membrane module (12), a hydroelectric generator set (13), a product water tank (14), and an intelligent regulating valve (15), which are used to deeply purify industrial-grade freshwater, improve water quality to drinking standards, and meet refined needs; The intelligent control module (16) has a built-in operation control algorithm, which is used to calculate and control the inlet flow of the hydroelectric generator on the basis of maximizing power generation and optimizing return pressure, so as to realize the second-level response of the hydroelectric generator set (13) when the inlet pressure of the high-pressure pump fluctuates, and ensure the stable operation of the first-stage high-pressure pump (6). In the secondary reverse osmosis system module (3): The inlet of the secondary reverse osmosis membrane module (12) is connected to the outlet of the secondary high-pressure pump (11) for pumping high-pressure permeate into the secondary reverse osmosis membrane module (12); The concentrate outlet of the secondary reverse osmosis membrane module (12) is connected to two pipes, which are respectively connected to the turbine inlet and turbine outlet of the hydro-generator set (13) to divide the pressurized concentrate output from the concentrate outlet of the secondary reverse osmosis membrane module (12) into two streams. One stream is sent to the hydro-generator set (13) for hydro-power generation, and the other stream is kept at the original pressure and mixed with the stream after hydro-power generation. The intelligent regulating valve (15) is located on the pipe connected to the outlet of the water turbine and is used to dynamically regulate the flow rate of pressurized concentrated water entering the water turbine for hydropower generation, so as to ensure that the mixed concentrated water formed after the low-pressure water flow after hydropower generation and the pressurized concentrated water that maintains the original pressure can flow back to the inlet of the first-stage high-pressure pump (6). The intelligent control module (16) is connected to the hydroelectric generator set (13) and includes a controller and a pressure sensor. It uses the built-in operation control algorithm to regulate the backflow pressure of the mixed concentrate, ensuring that the backflow pressure can overcome the pipeline resistance, so as to achieve a second-level response to pressure fluctuations and ensure the stable operation of the first-stage high-pressure pump (6).

2. The intelligent control system for energy recovery of concentrated water from secondary low-pressure reverse osmosis in seawater desalination as described in claim 1, characterized in that, In the seawater pretreatment module (1): The screen filter (4) is provided with a seawater inlet for introducing raw seawater and initially filtering impurities in the raw seawater. The security filter (5) is connected to the outlet of the screen filter (4) to filter out fine impurities, and the outlet of the security filter (5) is connected to the inlet of the primary high-pressure pump (6) and the low-pressure inlet of the pressure exchange energy recovery device (9).

3. The intelligent control system for energy recovery of concentrated water from secondary low-pressure reverse osmosis in seawater desalination as described in claim 1, characterized in that, In the first-stage reverse osmosis system module (2): The inlet of the first-stage reverse osmosis membrane module (7) is connected to the outlet of the first-stage high-pressure pump (6) for pumping high-pressure seawater into the first-stage reverse osmosis membrane module (7); The concentrate outlet of the first-stage reverse osmosis membrane module (7) is connected to the high-pressure inlet of the pressure exchange energy recovery device (9) for conveying the high-pressure concentrate output by the first-stage reverse osmosis membrane module (7) to the high-pressure inlet of the pressure exchange energy recovery device (9). The freshwater outlet of the primary reverse osmosis membrane module (7) is connected to the inlet of the secondary high-pressure pump (11) for conveying the permeate output by the primary reverse osmosis membrane module (7) to the secondary high-pressure pump (11) located before the secondary reverse osmosis membrane module (12). The high-pressure outlet of the pressure exchange energy recovery device (9) is connected to the inlet of the first-stage booster pump (8) to transport the high-pressure seawater output from the high-pressure outlet of the pressure exchange energy recovery device (9) to the first-stage booster pump (8) for pressurization. The outlet of the first-stage booster pump (8) is connected to the inlet of the first-stage reverse osmosis membrane module (7) for conveying high-pressure seawater pressurized by the first-stage booster pump (8) to the first-stage reverse osmosis membrane module (7). The low-pressure outlet of the pressure exchange energy recovery device (9) is connected to the concentrate tank (10) to transport the first-stage reverse osmosis low-pressure concentrate output from the low-pressure outlet of the pressure exchange energy recovery device (9) to the concentrate tank (10).

4. The intelligent control system for energy recovery of concentrated water from secondary low-pressure reverse osmosis in seawater desalination as described in claim 1, characterized in that, The freshwater outlet of the secondary reverse osmosis membrane module (12) is connected to the product water tank (14) to transport the freshwater output from the freshwater outlet of the secondary reverse osmosis membrane module (12) to the product water tank (14) for storage as the final product.

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