Membrane seawater desalination system for large temperature difference and control method

Abstract

The application provides a membrane seawater desalination system for large temperature difference and a control method, the membrane seawater desalination system for large temperature difference comprises a water supply module, a high-pressure module, a reverse osmosis desalination module, an energy recovery module and a PLC controller, the high-pressure module comprises M sets of high-pressure pump groups arranged in parallel, the high-pressure pump group comprises a booster high-pressure pump and a high-pressure pump arranged in series along the water flow direction; the energy recovery device has N sets of energy recovery devices corresponding to the reverse osmosis devices in the reverse osmosis desalination module one by one, wherein M < N; each set of energy recovery device is matched with one energy recovery booster pump and one second water supply pump simultaneously. The first water supply pump, the second water supply pump, the high-pressure pump, the booster high-pressure pump, the energy recovery booster pump and the low-pressure circuit and the high-pressure circuit are optimally combined, so that the number of high-pressure pumps and the use of high-power frequency converters are reduced, the investment cost is reduced, and the system operation efficiency and the safety redundancy are improved.

Description

Technical Field

[0001] This invention relates to the field of seawater desalination technology, and more specifically, to a membrane-based seawater desalination system and control method for large temperature differences. Background Technology

[0002] In the field of seawater desalination, traditional pumping systems typically employ a one-to-one three-pump combination: each reverse osmosis (RO) membrane system is equipped with a feed water pump (FP), a variable frequency high-pressure pump (HPP), and an energy recovery booster pump (BP). This traditional approach has significant drawbacks: the permeate flow rate of the RO membrane changes with temperature; a 1°C drop in temperature leads to a 2.5% to 2.7% decrease in permeate flow rate. To meet the permeate demand during low winter temperatures, the operating pressure of the HPP needs to be increased. Therefore, the high-pressure pump must be selected based on winter operating conditions, often with a head exceeding 700m. However, during the high summer temperatures, the HPP only requires a head of approximately 500m. Except for the coldest months of winter, the HPP operates at low frequencies for extended periods, resulting in high motor heat generation, deviation from the optimal efficiency point, energy waste, and operational risks. Furthermore, adding a high-power medium-voltage frequency converter increases costs and maintenance requirements, further increasing system investment and operating costs.

[0003] As the scale of seawater desalination plants continues to expand, the problems of "high investment, high energy consumption, and high operating costs" of traditional pumping systems are becoming increasingly prominent, creating an urgent need for a high-efficiency, energy-saving, and reliable membrane seawater desalination system for large temperature differences. Summary of the Invention

[0004] The present invention aims to provide a membrane-based seawater desalination system and control method for large temperature differences. By optimizing the coordination of five types of pumps, the system operating efficiency is improved, energy consumption and failure rate are reduced, and operating costs are decreased.

[0005] To achieve the above objectives, the present invention provides a membrane-based seawater desalination system for large temperature differences, comprising:

[0006] The water supply module has its outlet connected to a low-pressure circuit for water supply.

[0007] The high-pressure module has its inlet connected to the low-pressure circuit and its outlet connected to the high-pressure circuit. The high-pressure module includes M sets of high-pressure pump groups arranged in parallel. The high-pressure pump groups include booster high-pressure pumps and high-pressure pumps arranged in series along the water flow direction to provide power for seawater desalination.

[0008] A reverse osmosis desalination module, the inlet of which is connected to the high-pressure circuit, the reverse osmosis desalination module comprising N sets of reverse osmosis devices arranged in parallel;

[0009] An energy recovery module includes an energy recovery device, wherein there are N sets of energy recovery devices and each set corresponds to a reverse osmosis device in the reverse osmosis desalination module, where M < N;

[0010] Each of the energy recovery devices is also equipped with an energy recovery booster pump and a second water supply pump. The energy recovery booster pump is used to supplement the energy that is insufficient during the process of pressurizing low-pressure seawater in the energy recovery device, and the second water supply pump is used to supply seawater to the energy recovery device.

[0011] The PLC controller is connected to the water supply module, high pressure module, and reverse osmosis desalination module respectively.

[0012] Preferably, the second feed pump, the energy recovery device, and the energy recovery booster pump are connected in sequence to supply high-pressure seawater to the pipeline between the high-pressure circuit and the reverse osmosis device; the energy recovery device is connected to the concentrated seawater outlet of the reverse osmosis device to recover and reuse the pressure energy of the high-pressure concentrated seawater generated by the reverse osmosis device to boost the pressure of low-pressure seawater.

[0013] Preferably, an automatic regulating valve is installed between the high-pressure circuit and the reverse osmosis unit. The outlet of the booster pump is connected to the pipeline between the automatic regulating valve and the reverse osmosis unit. The automatic regulating valve is electrically connected to the PLC controller. Preferably, the value of M ranges from 3 to 6 sets, and the value of N ranges from 7 to 14 sets. Preferably, the ratio of M to N ranges from 1 to 2 to 3.

[0014] Preferably, the membrane seawater desalination system for large temperature differences includes a sensor group, which includes a water temperature sensor, a TDS sensor, and a pressure transmitter, all electrically connected to the PLC controller.

[0015] Preferably, the water temperature sensor and TDS sensor are installed in the low-pressure loop to detect the raw seawater temperature and the inlet TDS value. There are three pressure transmitters, which are respectively installed in the low-pressure loop, the high-pressure loop and the inlet end of each reverse osmosis unit. They are respectively used to detect the pressure of the low-pressure pipeline to control the operation of the feed water module, detect the pressure of the high-pressure pipeline to control the operation of the booster high-pressure pump, and detect the pressure difference ΔP between the inlet water and the transmembrane of the reverse osmosis unit.

[0016] Preferably, the sensor group further includes a flow meter for detecting the influent flow rate of the reverse osmosis unit.

[0017] The present invention also provides a control method for a membrane-based seawater desalination system with a large temperature difference, comprising:

[0018] S1. Real-time data collection of raw seawater temperature T, influent TDS value C, and transmembrane pressure difference ΔP is achieved through a sensor array;

[0019] S2. Calculate the compensation value ΔP for deviation from the normal operating pressure P3. b =K1×(T−T0)+K2×(C−C0)+

[0020] K3×(ΔP−ΔP0), where T0 is the reference water temperature, C0 is the reference TDS value, ΔP0 is the reference transmembrane pressure difference, and K1, K2, and K3 are coefficients obtained by fitting based on the characteristics of the reverse osmosis desalination module.

[0021] S3 and PLC controllers adjust the speed of the booster pump based on calculation results to provide the corresponding boost pressure value; at the same time, the high-pressure pump maintains power frequency operation and can dynamically adjust the operating parameters of the booster pump according to the system status.

[0022] S4. Adjust the opening of the automatic regulating valve in real time according to the flow meter reading to ensure that the influent flow of N sets of reverse osmosis units set in parallel is the same.

[0023] Preferably, in step S2, the reference operating pressure P3 is determined by the required pressure of the reverse osmosis desalination module under the design conditions, and the compensated target pressure P3' = P3 + ΔPb.

[0024] Preferably, in step S3, the PLC controller adjusts the frequency of the first water supply pump group based on the sensor group to achieve constant pressure water supply, and at the same time adjusts the frequency of the booster high-pressure pump to maintain constant pressure in the high-pressure circuit.

[0025] Preferably, the rated output power of the high-pressure pump HPP is P. HPP额 Then the output P of the booster high-pressure pump DHP DHP实时 =P2-P HPP- P1 = P3' * X1 - P HPP- P1, where the value of X1 ranges from 1.03 to 1.08.

[0026] Preferably, the target pressure P1 of the water supply module is preset according to the water temperature range: when the water temperature is 3-10℃, P1 is 6.5-7.5 bar; when the water temperature is 10-20℃, P1 is 4.5-5.5 bar; when the water temperature is 20-30℃, P1 is 2.5-3.5 bar. Preferably, the target pressure P1 of the water supply module is preset according to the water temperature range: when the water temperature is 3-10℃, P1 is 7.0 bar; when the water temperature is 10-20℃, P1 is 5.0 bar; when the water temperature is 20-30℃, P1 is 3.0 bar.

[0027] Compared with existing technologies, the membrane seawater desalination system and control method for large temperature differences described in this invention have the following beneficial effects: 1) By optimizing the combination of the first feed water pump, the second feed water pump, the high-pressure pump, the booster high-pressure pump, the energy return booster pump, and the low-pressure and high-pressure circuits, the traditional one-to-one correspondence three-pump combination is replaced, reducing the number of high-pressure pumps and the use of high-power frequency converters, lowering investment costs, and improving system operating efficiency and safety redundancy; 2) The operating status of the pumps is dynamically adjusted based on water temperature, influent TDS, and transmembrane pressure difference, further improving the system's adaptability and energy-saving effect; 3) Compared with the previous method, the number of equipment is reduced, the system fault tolerance is increased, the safety margin is significantly improved, the overall investment cost is reduced by about 5.03%, the workshop floor space is reduced by about 9.23%, the energy consumption per ton of water is reduced by about 0.09 kWh, and the comprehensive operating cost is reduced by about 0.063 yuan / ton of water. Attached Figure Description

[0028] The accompanying drawings, which constitute a part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0029] Figure 1 This is a schematic diagram showing the main equipment setup and connection of the integrated power system for membrane-based seawater desalination in an embodiment of the present invention.

[0030] Explanation of reference numerals in the attached figures:

[0031] FP1 - First feed water pump, FP2 - Second feed water pump, LPLOOP - Low-pressure loop, DHP - Booster high-pressure pump, HHP - High-pressure pump, HPLOOP - High-pressure loop, CV - Automatic regulating valve, RO - Reverse osmosis unit, ERD - Energy recovery unit, BP - Energy recovery booster pump, TT01 - Temperature transmitter, PT01 - Low-pressure loop pressure transmitter, CT01 - TDS detector, PT02 - High-pressure loop pressure transmitter, PT03 - RO inlet pressure transmitter, FI01 - Flow meter. Detailed Implementation

[0032] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Without conflict, the technical features of the embodiments of the present invention can be combined with each other.

[0033] Example 1

[0034] like Figure 1 As shown, a membrane-based seawater desalination system for large temperature differences includes:

[0035] The water supply module has its outlet connected to the low-pressure circuit LPLOOP for water supply.

[0036] The high-pressure module has its inlet connected to the low-pressure circuit LPLOOP and its outlet connected to the high-pressure circuit HPLOOP. The high-pressure module includes M sets of high-pressure pumps arranged in parallel. The high-pressure pumps include a booster high-pressure pump DHP and a high-pressure pump HHP arranged in series along the water flow direction to provide power for seawater desalination.

[0037] The reverse osmosis desalination module has its inlet connected to the high-pressure loop HPLOOP, and the reverse osmosis desalination module includes N sets of reverse osmosis units RO arranged in parallel.

[0038] An energy recovery module includes an energy recovery device ERD, wherein there are N sets of energy recovery devices ERD and each ERD corresponds to a reverse osmosis device RO in the reverse osmosis desalination module, where M < N;

[0039] Each set of the energy recovery device ERD is simultaneously matched with an energy recovery booster pump BP and a second water supply pump FP2. The energy recovery booster pump BP is used to supplement the energy that is insufficient during the process of boosting low-pressure seawater in the energy recovery device ERD, and the second water supply pump FP2 is used to supply seawater to the energy recovery device ERD.

[0040] Specifically, the second feed water pump FP2, the energy recovery device ERD, and the energy return booster pump BP are connected in sequence to supply high-pressure seawater to the pipeline between the high-pressure loop HPLOOP and the reverse osmosis unit RO; the energy recovery device ERD is connected to the concentrated seawater outlet of the reverse osmosis unit RO to recover and reuse the pressure energy of the high-pressure concentrated seawater generated by the reverse osmosis unit RO to boost the pressure of low-pressure seawater; an automatic regulating valve CV is installed between the high-pressure loop HPLOOP and the reverse osmosis unit RO, and the energy return booster pump BP and the automatic regulating valve CV are connected in parallel, and the automatic regulating valve CV is electrically connected to the PLC controller;

[0041] The PLC controller is connected to the water supply module, high pressure module, and reverse osmosis desalination module respectively.

[0042] As a preferred example of the present invention, the membrane seawater desalination system for large temperature differences includes a sensor group, which includes a water temperature sensor, a TDS sensor, a pressure transmitter, and a flow meter, all electrically connected to the PLC controller. The water temperature sensor and TDS sensor are located in the low-pressure loop and are used to detect the raw seawater temperature and the inlet TDS value. There are three pressure transmitters, which are respectively located in the low-pressure loop, the high-pressure loop, and the inlet end of each reverse osmosis unit. They are used to detect the pressure P1 of the low-pressure pipeline to control the operation of the feed water module, detect the pressure P2 of the high-pressure pipeline to control the operation of the booster high-pressure pump, and detect the inlet water pressure P3 and the transmembrane pressure difference ΔP of the reverse osmosis unit. The flow meter is used to detect the inlet water flow rate of the reverse osmosis unit.

[0043] Preferably, the target pressure P1 of the water supply module is preset according to the water temperature range: when the water temperature is 3-10℃, P1 is 6.5-7.5 bar; when the water temperature is 10-20℃, P1 is 4.5-5.5 bar; and when the water temperature is 20-30℃, P1 is 2.5-3.5 bar. Preferably, the target pressure P1 of the water supply module is preset according to the water temperature range: when the water temperature is 3-10℃, P1 is 7.0 bar; when the water temperature is 10-20℃, P1 is 5.0 bar; and when the water temperature is 20-30℃, P1 is 3.0 bar.

[0044] The present invention also provides a control method for a membrane-based seawater desalination system with a large temperature difference, comprising:

[0045] S1. Real-time data collection of raw seawater temperature T, influent TDS value C, and transmembrane pressure difference ΔP is achieved through a sensor array;

[0046] S2. Calculate the compensation value ΔP for deviation from the normal operating pressure P3. b =K1×(T−T0)+K2×(C−C0)+

[0047] K3×(ΔP−ΔP0), where T0 is the reference water temperature (°C), C0 is the reference TDS value (mg / L), ΔP0 is the reference transmembrane pressure difference (bar), and K1, K2, and K3 are coefficients obtained by fitting based on the characteristics of the reverse osmosis desalination module. Then, the compensated target pressure P3'=P3+ΔPb.

[0048] S3 and PLC controllers adjust the speed of the booster pump based on calculation results to provide the corresponding boost pressure value; at the same time, the high-pressure pump maintains power frequency operation and can dynamically adjust the operating parameters of the booster pump according to the system status.

[0049] Preferably, the rated output power of the high-pressure pump HPP is P. HPP Then the output P of the booster high-pressure pump DHP DHP实时 =P2-P HPP- P1 = P3' * X1 - P HPP- P1 = (P3 + △Pb) * X1 - P HPP- P1. The value of X1 ranges from 1.03 to 1.08.

[0050] S4. Adjust the opening of the automatic regulating valve in real time according to the flow meter reading to ensure that the inlet flow of N sets of reverse osmosis units set in parallel is the same, and avoid the occurrence of flow deviation. Adjust the frequency of the first feed water pump group based on the sensor group to achieve constant pressure water supply, and at the same time adjust the frequency of the booster high pressure pump to maintain the constant pressure of the high pressure circuit.

[0051] Example 2

[0052] Taking a membrane-based seawater desalination plant with a capacity of 200,000 tons / day as an example, it includes:

[0053] Reverse osmosis (RO) units: 10 units, each producing Q water. 产水 =1000m³ / h, total influent 2500m³ / h, production rate 40%; winter operating temperature 3℃, summer maximum temperature 30℃, constant production rate throughout the year. Calculations show that at the lowest temperature and after membrane aging, the required head is approximately 650m, and at the highest summer temperature, it is 520m. Adjustments are made according to temperature, TDS value, etc. in other seasons.

[0054] Energy recovery unit (ERD): 10 units, single unit flow rate Q 过 =1500m³ / h.

[0055] First water supply pump FP1: 5 units, specifications Q=2000m³ / h, H=70m, P=500kW, frequency conversion.

[0056] Second water supply pump FP2: 10 units, specifications Q=1500m³ / h, H=25m, P=130kW, power frequency.

[0057] High-pressure pumps (HHP): 5 units, specifications Q=2000m³ / h, H=470m, P=3000kW, power frequency.

[0058] 5 units of booster high-pressure pump DHP, specifications Q=2000m³ / h, H=110m, P=800kW, frequency conversion.

[0059] BP booster pumps: 10 units, specifications Q=1500m³ / h, H=35m, P=180kW, frequency conversion.

[0060] Based on the characteristics and historical operating data of the reverse osmosis unit of the seawater desalination plant, the parameters in the control formula were obtained through fitting as follows:

[0061] Reference water temperature T0 = 20℃. Reference TDS value C0 = 34000 mg / L, reference transmembrane pressure difference ΔP0 = 1 bar, reference operating pressure P3 = 55 bar, water temperature influence coefficient K1 = -0.25, TDS influence coefficient K2 = 0.0005, transmembrane pressure difference influence coefficient K3 = 1;

[0062] The P1 value is preset according to the temperature range: when the TT01 value is 3-10℃, the P1 value is 7 bar; when the TT01 value is 10-20℃, the P1 value is 5 bar; when the TT01 value is 20-30℃, the P1 value is 3 bar.

[0063] The value of P2 is set to 1.05 times that of P3, that is, P2 = 1.05 × P3.

[0064] A) Under winter operating conditions:

[0065] Water temperature T=8℃, influent TDS=34000mg / L, transmembrane pressure difference ΔP=2bar, calculate ΔP. b △P b =-0.25×(8-20)+0.0005×(34000-34000)+1×(2-1)=3+0+1=4bar

[0066] Therefore, P3 = 55 + 4 = 59 bar, P2 = 1.05 × 59 = 61.95 bar, and P1 is 7 bar corresponding to a water temperature of 8℃.

[0067] The first feed pump FP1 needs to output a pressure of 7 bar (70 m head); the outlet pressure of the high-pressure pump HHP should be P2=61.95 bar (619.5 m), and the high-pressure pump HHP itself outputs a pressure of 47 bar (470 m head). Therefore, the booster high-pressure pump DHP needs to supplement the pressure with 7.95 bar, which is approximately 619.5-470-70=79.5 m head.

[0068] B) Under summer operating conditions:

[0069] Water temperature T=28℃, influent TDS=35000mg / L, transmembrane pressure difference ΔP=1bar, calculate ΔP. b :

[0070] △P b =-0.25×(28-20)+0.0005×(35000-34000)+1×(1-1)=-2+0.5+0=-1.5bar

[0071] Therefore, P3 = 55 - 1.5 = 53.5 bar, P2 = 1.05 × 53.5 = 56.175 bar, and P1 is 3 bar corresponding to a water temperature of 28℃.

[0072] The first feedwater pump FP1 needs to output a pressure of 3 bar (30 m head); the outlet pressure of the high-pressure pump HHP should be 56.175 bar (561.75 m), and the pump body output pressure of high-pressure pump HHP is 47 bar (470 m head). Therefore, the booster high-pressure pump DHP needs to supplement the pressure by 6.175 bar, which is approximately 561.75 - 470 - 30 = 61.75 m head.

[0073] After the system initially establishes its operating flow, it begins to perform calculations and adjustments based on online instrument readings:

[0074] Based on the reading of pressure transmitter PT01, adjust the frequency of the first feed water pump FP1 so that the pressure of the low-pressure circuit LPLOOP reaches the set value P1, achieving dynamic constant pressure.

[0075] Based on the reading of pressure transmitter PT02, adjust the frequency of booster high-pressure pump DHP to make the pressure of high-pressure circuit HPLOOP reach the set value P2, achieving dynamic constant pressure.

[0076] Based on the reading of pressure transmitter PT03, adjust the frequency of the booster pump BP to make the inlet pressure of the reverse osmosis unit (RO) reach the set value P3, achieving dynamic constant pressure.

[0077] The second feedwater pump FP2 and the high-pressure pump HHP operate at industrial frequency and will run normally after startup. The second feedwater pump FP2 is turned on according to the number of energy recovery devices (ERDs) put into operation.

[0078] Based on the reading of flow meter FI01, the opening of the automatic regulating valve CV on the inlet pipe of each RO unit is adjusted in real time to ensure that the inlet flow of multiple RO units operating in parallel is consistent.

[0079] Compared with the previous version, the membrane desalination plant in this embodiment saves about 5.03% in equipment investment, reduces the workshop floor space by about 9.23%, and reduces energy consumption per ton of water by about 0.09 kWh. Based on an electricity price of 0.53 yuan / kWh, it can save about 3.2 million yuan per year and reduce the overall operating cost by about 0.063 yuan / ton of water.

[0080] While the present invention has been disclosed above, it is not limited thereto. Any person skilled in the art can make various modifications and alterations without departing from the spirit and scope of the invention; therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.

Claims

1. A membrane-based seawater desalination system for large temperature differences, characterized in that, include: The water supply module has its outlet connected to a low-pressure circuit for water supply. The high-pressure module has its inlet connected to the low-pressure circuit and its outlet connected to the high-pressure circuit. The high-pressure module includes M sets of high-pressure pump groups arranged in parallel. The high-pressure pump groups include booster high-pressure pumps and high-pressure pumps arranged in series along the water flow direction to provide power for seawater desalination. A reverse osmosis desalination module, the inlet of which is connected to the high-pressure circuit, the reverse osmosis desalination module comprising N sets of reverse osmosis devices arranged in parallel; An energy recovery module includes an energy recovery device, wherein there are N sets of energy recovery devices and each set corresponds to a reverse osmosis device in the reverse osmosis desalination module, where M < N; Each of the energy recovery devices is also equipped with an energy recovery booster pump and a second water supply pump. The energy recovery booster pump is used to supplement the energy that is insufficient during the process of pressurizing low-pressure seawater in the energy recovery device, and the second water supply pump is used to supply seawater to the energy recovery device. The PLC controller is connected to the water supply module, high pressure module, and reverse osmosis desalination module respectively.

2. The membrane seawater desalination system for large temperature differences according to claim 1, characterized in that, The second feed water pump, energy recovery device, and energy recovery booster pump are connected in sequence to supply high-pressure seawater to the pipeline between the high-pressure circuit and the reverse osmosis device; the energy recovery device is connected to the concentrated seawater outlet of the reverse osmosis device to recover and reuse the pressure energy of the high-pressure concentrated seawater generated by the reverse osmosis device to boost the pressure of low-pressure seawater.

3. The membrane seawater desalination system for large temperature differences according to claim 2, characterized in that, An automatic regulating valve is installed between the high-pressure circuit and the reverse osmosis device. The outlet of the booster pump is connected to the pipeline between the automatic regulating valve and the reverse osmosis device. The automatic regulating valve is electrically connected to the PLC controller.

4. The membrane seawater desalination system for large temperature differences according to claim 1, characterized in that, The membrane seawater desalination system for large temperature differences includes a sensor group, which includes a water temperature sensor, a TDS sensor, and a pressure transmitter, all of which are electrically connected to the PLC controller.

5. The membrane seawater desalination system for large temperature differences according to claim 4, characterized in that, The water temperature sensor and TDS sensor are installed in the low-pressure loop to detect the raw seawater temperature and the inlet TDS value. There are three pressure transmitters, which are respectively installed in the low-pressure loop, the high-pressure loop and the inlet end of each reverse osmosis unit. They are used to detect the pressure of the low-pressure pipeline to control the operation of the feed water module, detect the pressure of the high-pressure pipeline to control the operation of the booster high-pressure pump, and detect the pressure difference ΔP between the inlet water and the transmembrane pressure of the reverse osmosis unit.

6. The membrane seawater desalination system for large temperature differences according to claim 4, characterized in that, The sensor group also includes a flow meter for detecting the inlet flow rate of the reverse osmosis unit.

7. A control method for a membrane-based seawater desalination system with a large temperature difference, based on any one of claims 1 to 6, characterized in that, Includes the following steps: S1. Real-time data collection of raw seawater temperature T, influent TDS value C, and transmembrane pressure difference ΔP is achieved through a sensor array; S2. Calculate the compensation value ΔP for deviation from the normal operating pressure P3. b =K1×(T−T0)+K2×(C−C0)+K3×(ΔP−ΔP0), where T0 is the reference water temperature, C0 is the reference TDS value, ΔP0 is the reference transmembrane pressure difference, and K1, K2, and K3 are coefficients obtained by fitting based on the characteristics of the reverse osmosis desalination module. S3 and PLC controllers adjust the speed of the booster pump based on calculation results to provide the corresponding boost pressure value; at the same time, the high-pressure pump maintains power frequency operation and can dynamically adjust the operating parameters of the booster pump according to the system status. S4. Adjust the opening of the automatic regulating valve in real time according to the flow meter reading to ensure that the influent flow of N sets of reverse osmosis units set in parallel is the same.

8. The control method according to claim 7, characterized in that, In step S2, the reference operating pressure P3 is determined by the required pressure of the reverse osmosis desalination module under the design conditions, and the compensated target pressure P3' = P3 + ΔPb.

9. The control method according to claim 7, characterized in that, In step S3, the PLC controller adjusts the frequency of the first water supply pump group based on the sensor group to achieve constant pressure water supply, and at the same time adjusts the frequency of the booster high-pressure pump to maintain constant pressure in the high-pressure circuit.

10. The control method according to claim 7, characterized in that, The target pressure P1 of the water supply module is preset according to the water temperature range: when the water temperature is 3 to 10℃, P1 is 6.5 to 7.5 bar; when the water temperature is 10 to 20℃, P1 is 4.5 to 5.5 bar; when the water temperature is 20 to 30℃, P1 is 2.5 to 3.5 bar.

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