A magnetic fluid assisted reverse osmosis membrane cleaning device and method

Abstract

The present application relates to a magnetic fluid-assisted reverse osmosis membrane cleaning device and method, belonging to the field of water treatment technology. The device includes: a frame, which is provided with multiple stations for installing reverse osmosis membrane components, and each station is arranged in an array around the central axis of the frame; a magnetic fluid reservoir, which is used to store two types of magnetic fluid products suitable for acidic and alkaline cleaning environments; a magnetic fluid deflector, which is used to inject magnetic fluids of corresponding properties into the reverse osmosis membrane; a core rod made of magnetic conductive material, which is arranged in the middle of each station along the horizontal direction of the frame; an electromagnetic coil, which is located on the outside of the frame, is coaxially connected to the core rod and can move along the axis, is connected to a variable AC power supply, and controls the magnetic field strength and direction by adjusting the current. By adjusting the current strength and movement direction of the electromagnetic coil, the device drives the magnetic fluid to vibrate and scrub rapidly inside the reverse osmosis membrane, thereby strengthening the membrane cleaning process, improving the membrane cleaning efficiency, reducing the use of chemical agents, and extending the service life of the reverse osmosis membrane.

Description

Technical Field

[0001] The present application relates to the field of water treatment, and in particular to a magnetic fluid-assisted reverse osmosis membrane cleaning device and method. Background Art

[0002] Reverse osmosis technology has been widely used in seawater desalination, wastewater treatment, and drinking water purification. A reverse osmosis membrane, a semipermeable membrane and the core component of membrane filtration technology, removes dissolved salts and other impurities from water, thereby producing high-quality pure water. A reverse osmosis membrane assembly consists of a number of reverse osmosis membrane elements and a pressure vessel, which in turn consists of two end caps and a central pressure-resistant membrane shell. However, reverse osmosis membranes are susceptible to contamination by microorganisms and inorganic matter. Over long-term use, this can lead to decreased filtration performance of the reverse osmosis membrane assembly, increased operating pressure in the reverse osmosis membrane system, and increased energy consumption in the desalination process.

[0003] In order to solve the problem of reverse osmosis membrane pollution, when the transmembrane pressure difference of the reverse osmosis membrane increases to a certain extent, a membrane cleaning method is needed to restore the water production performance of the reverse osmosis membrane. The traditional seawater desalination reverse osmosis membrane cleaning method mainly includes physical cleaning and chemical cleaning processes. Physical cleaning usually uses low-pressure water washing, but water washing alone has limited effect on removing stubborn dirt; chemical cleaning uses chemical reagents such as acid and alkali to clean the membrane. The conventional reverse osmosis membrane cleaning process is: (1) water washing, the washing time is based on the complete replacement of the concentrated water or chemical waste liquid in the membrane with product water; (2) acid washing, the acidic agent circulates in the reverse osmosis membrane for 10 hours, and the agent needs to be replenished when the agent concentration decreases; (3) water washing; (4) alkali washing, the alkaline agent circulates in the reverse osmosis membrane for 10 hours, and the agent needs to be replenished when the agent concentration decreases; (5) water washing; (6) alkali washing; (7) water washing; (8) acid washing; (9) water washing. It can be seen that due to the poor cleaning effect of low-pressure water flushing and chemical circulation flushing, the conventional seawater desalination reverse osmosis membrane cleaning process has problems such as long cleaning time, large chemical usage, and high energy consumption. In particular, during the long-term chemical immersion process, the chemical may cause permanent damage to the reverse osmosis membrane material, reducing the filtration performance of the reverse osmosis membrane. At the same time, due to the different levels of contamination of the front-end and back-end membrane elements of the reverse osmosis membrane assembly in actual operation, during membrane cleaning, contaminants in the front-end membrane elements of the reverse osmosis membrane assembly will be transported to the back-end membrane elements along with the flushing water and chemicals, causing contamination of the back-end membrane elements, increasing the difficulty of cleaning, and reducing cleaning efficiency. Therefore, it is necessary to develop a new auxiliary cleaning method to improve the cleaning efficiency of the reverse osmosis membrane assembly, reduce the amount of chemical used, and extend the service life of the reverse osmosis membrane.

[0004] Magnetic fluid is a liquid containing suspended magnetic nanoparticles. Under the influence of an external magnetic field, it can flow, rotate, and vibrate, thereby generating a mechanical force on the surface to be cleaned. By introducing magnetic fluid into the cleaning process of reverse osmosis membrane components, the distribution and motion of the magnetic fluid are controlled by an external magnetic field. By leveraging the rapid movement and vibration of the magnetic fluid within the reverse osmosis membrane, a front-to-back segmented cleaning method is employed to improve the cleaning efficiency of contaminants on the membrane surface. Compared to conventional membrane cleaning methods, the magnetic fluid-assisted membrane cleaning method reduces the amount of chemical cleaning agents used and the cleaning time of the reverse osmosis membrane, reduces damage to the reverse osmosis membrane material, extends the life of the membrane, and improves production efficiency. This is of great significance for energy conservation, consumption reduction, cost reduction, and efficiency improvement in seawater desalination plants.

[0005] Against the above background, the present application proposes a magnetic fluid-assisted reverse osmosis membrane cleaning device and method, which aims to drive the magnetic fluid to move and vibrate rapidly in the reverse osmosis membrane by adjusting the current and movement direction of the electromagnetic coil, thereby enhancing the cleaning process of the reverse osmosis membrane, improving the membrane cleaning efficiency, reducing the use of chemical agents, and extending the service life of the reverse osmosis membrane. Summary of the Invention

[0006] In order to solve the problems in the background technology, the present application provides a magnetic fluid assisted reverse osmosis membrane cleaning device and method.

[0007] The present application provides a magnetic fluid-assisted reverse osmosis membrane cleaning device, which adopts the following technical solution:

[0008] A magnetic fluid-assisted reverse osmosis membrane cleaning device comprises: a frame provided with a plurality of stations for installing reverse osmosis membrane components, wherein the stations are arranged in an array around a horizontal axis of the frame;

[0009] The magnetic fluid reservoir has two internal cavities for storing two types of finished magnetic fluids suitable for acidic and alkaline cleaning environments, respectively. The finished magnetic fluids are made from a mixture of magnetic fluid base particles and other materials used to condition the magnetic fluid. During cleaning, the reservoir port containing the magnetic fluid with the corresponding properties is opened, depending on the acidic or alkaline environment corresponding to the cleaning process.

[0010] A magnetic fluid deflector is provided at least two times at each station position of the frame, each of the magnetic fluid deflectors is connected to the magnetic fluid reservoir, and each of the magnetic fluid deflectors can be connected to the reverse osmosis membrane assembly installed at the corresponding station position of the frame. The two magnetic fluid deflectors provided at the same station position of the frame can respectively inject magnetic fluid into the reverse osmosis membrane assembly from both ends thereof;

[0011] The core rod is arranged at the middle position of each work station of the frame, and the length direction of the core rod is arranged along the horizontal axis direction of the frame. The core rod is made of magnetic conductive material;

[0012] The electromagnetic coil is arranged outside each station of the frame corresponding to itself. The central axis of the electromagnetic coil can be arranged collinearly with the length direction of the core rod. The electromagnetic coil is also connected to a variable AC power supply. Changing the current of the variable AC power supply can adjust the strength of the magnetic field generated by the electromagnetic coil. Changing the current direction of the variable AC power supply can adjust the direction of the magnetic field generated by the electromagnetic coil. The electromagnetic coil is movably connected to the frame. The electromagnetic coil can move along the horizontal axis of the frame. The movement of the electromagnetic coil can drive the magnetic fluid in the reverse osmosis membrane assembly of each station of the frame to move accordingly. The variable AC power supply adjusts the current to adjust the vibration amplitude and vibration frequency of the magnetic fluid in the electromagnetic coil. By adopting the above technical solution, the magnetic fluid can achieve precise movement and vibration in the reverse osmosis membrane under the action of the magnetic field generated by the electromagnetic coil, thereby effectively removing pollutants attached to the membrane surface and improving cleaning efficiency.

[0013] Preferably, each pressure-resistant membrane shell at each workstation position of the rack is provided with two relatively arranged pressure-resistant membrane shell end covers, and any two relatively arranged pressure-resistant membrane shell end covers are arranged as a pressure-resistant membrane shell end cover group, and each of the pressure-resistant membrane shell end cover groups can jointly seal the reverse osmosis membrane assembly setting of the corresponding workstation of the rack with the pressure-resistant membrane shell, and when performing magnetic fluid-assisted cleaning, each pressure-resistant membrane shell end cover group and the pressure-resistant membrane shell seal the corresponding reverse osmosis membrane element setting.

[0014] Preferably, the magnetic fluid configuration process used in the magnetic fluid reservoir under the pickling cleaning environment is as follows:

[0015] Fe3+ and Fe2+ are prepared into a solution in a molar ratio of 1:1.5-2, and concentrated ammonia water is added thereto until a black precipitate is completely formed, thereby obtaining a first black precipitate solution;

[0016] The obtained first black precipitate solution is rapidly heated to 80-100° C., and oleic acid and a low-carbon alkane are added thereto, and stirred until the solution is clearly separated into layers. A magnetic fluid liquid is obtained by magnetic decantation, and the magnetic fluid liquid is centrifuged, washed with deionized water, flocculated with an organic solvent, and then dried in a low-temperature vacuum to obtain a single-layer coated magnetic powder.

[0017] Weigh the single-layer coated magnetic powder obtained in step 1, add the single-layer coated magnetic powder to the base liquid at room temperature, stir and disperse until there is no precipitation, and then centrifuge. The liquid poured out after centrifugation is the magnetic fluid.

[0018] Preferably, the magnetic fluid configuration process used in the magnetic fluid reservoir under the alkaline cleaning environment is:

[0019] Fe3+ and Fe2+ are prepared into a solution in a molar ratio of 1:1.5-2, and concentrated ammonia water is added thereto until a black precipitate is completely formed, thereby obtaining a first black precipitate solution;

[0020] The obtained first black precipitate solution is rapidly heated to 80-100° C., and oleic acid and a low-carbon alkane are added thereto, and stirred until the solution is clearly separated into layers. A magnetic fluid liquid is obtained by magnetic decantation, and the magnetic fluid liquid is centrifuged, washed with deionized water, flocculated with an organic solvent, and then dried in a low-temperature vacuum to obtain a single-layer coated magnetic powder.

[0021] Weigh the resulting single-layer coated magnetic powder and disperse it in an intermediate solution at room temperature with stirring to obtain a second intermediate solution. The second intermediate solution is then quickly heated to 140-170°C. Polyisobutylene succinimide and a base carrier liquid are then added and stirred until the intermediate solution is completely evaporated. The solution is then cooled to room temperature and centrifuged. The resulting liquid is the magnetic fluid. Magnetic fluids with specific properties can be customized to enhance cleaning effectiveness based on actual cleaning needs.

[0022] Preferably, the recovery device is used to recover the magnetic fluid after auxiliary cleaning. The recovery device includes a recovery pipeline, each recovery pipeline can be connected to the concentrated brine discharge port of each pressure-resistant membrane shell, and each recovery pipeline is provided with a closed valve at one end close to the pressure-resistant membrane shell end cover, and each closed valve can close the corresponding recovery pipeline setting; a recovery bin is provided, and each recovery pipeline is provided with a plurality of electromagnet rings at the position corresponding to its own recovery bin. The electromagnet rings are coated on the outer side of the corresponding recovery bin along the length direction of the recovery bin. The cleaning waste liquid of the reverse osmosis membrane is discharged into the recovery pipeline along the concentrated brine discharge port, and the magnetic fluid base particles therein are adsorbed on the inner wall of the recovery bin under the action of the electromagnet rings, thereby achieving separation from other cleaning waste liquids, thereby achieving separation from other cleaning liquids. Pressure-resistant membrane shell end cover Pressure-resistant membrane shell end cover Pressure-resistant membrane shell end cover The pressure-resistant membrane shell end cover realizes the recycling of resources. By setting up the recovery device, the magnetic fluid after cleaning can be recycled and reused, reducing resource consumption and cost.

[0023] Preferably, it also includes a leak detection device, which is used to detect whether the reverse osmosis membrane assembly has structural damage, specifically to detect whether there is magnetic fluid in the cleaning liquid discharged from the water outlet of the reverse osmosis membrane assembly after cleaning. It includes multiple leak detection pipelines, each of which can be connected to the water outlet of the reverse osmosis membrane assembly installed at each station of the frame, and each leak detection pipeline is connected to the corresponding pressure-resistant membrane shell end cover. Each leak detection pipeline is connected to a closed valve near the pressure-resistant membrane shell end cover, and each closed valve can close the corresponding leak detection pipeline. A magnetic flux sensor is provided in each leak detection pipeline. If the magnetic flux of the magnetic flux sensor changes when the cleaning liquid passes through the leak detection pipeline, it means that there is magnetic fluid mixed therein, thereby judging that structural damage has occurred inside the reverse osmosis membrane assembly and preventing the magnetic fluid from flowing out with the cleaning liquid. By adding a leak detection device, the integrity of the reverse osmosis membrane can be monitored in real time during the cleaning process, structural damage problems can be discovered and dealt with in a timely manner, and the safe operation of the equipment can be ensured.

[0024] Preferably, each station is equipped with a fixture for securing the reverse osmosis membrane assembly. The fixture is detachably connected to the frame and is made of a non-metallic material. Using a fixture made of a non-metallic material to secure the reverse osmosis membrane can effectively prevent unnecessary damage to the reverse osmosis membrane during the cleaning process.

[0025] Preferably, it also includes a detection component for detecting the content of the agent in the reverse osmosis membrane component during the cleaning process, including:

[0026] The sampling tubes are arranged one by one at the end caps of the pressure-resistant membrane shells, and each sampling tube can be connected to the corresponding reverse osmosis membrane assembly;

[0027] A plurality of probes are provided, each of the probes being correspondingly provided at the rear end of each of the sampling tubes (92). During detection, the sampling tubes (92) are opened, and the outflow liquid of the sampling tubes is detected by the probes to measure the pH value and conductivity of the liquid in the reverse osmosis membrane assembly;

[0028] The detection control module is electrically connected to each of the probes. The detection control module determines the concentration of the liquid medicine according to the changes in the pH value and conductivity of the liquid medicine in each reverse osmosis membrane assembly, and further determines whether the liquid medicine needs to be replenished.

[0029] Preferably, a control system is further included, wherein the control system is used to control the cleaning process of the reverse osmosis membrane assembly to realize automation, and the control system includes:

[0030] The controller sends a signal to control the start of cleaning. The electromagnetic coil is electrically connected to the controller, and the controller can control the movement of the electromagnetic coil; the variable AC power supply is also electrically connected to the controller, and the controller can control the current magnitude and direction of the variable AC power supply; the magnetic fluid deflector is also electrically connected to the controller, and the controller controls the magnetic fluid in the magnetic fluid reservoir to be injected into the reverse osmosis membrane assembly at the corresponding station;

[0031] The time relay is connected to the controller and is used to measure the execution time of each step.

[0032] A magnetic fluid-assisted reverse osmosis membrane cleaning device and method, applicable to the above-mentioned reverse osmosis membrane cleaning device, comprising:

[0033] S1: Install the reverse osmosis membrane assembly at each station position of the frame (1), fix it with a clamp (11), inject raw water into it through the raw water inlet, filter it through the reverse osmosis membrane assembly, and then discharge the pure water through the water outlet through the leak detection pipeline, and discharge the concentrated brine through the concentrated brine outlet of the reverse osmosis membrane assembly through the recovery pipeline. After a fixed operation period, shut down the machine for cleaning;

[0034] S2: Inject produced water into the reverse osmosis membrane assembly to replace the concentrated brine remaining in the reverse osmosis membrane assembly with produced water;

[0035] S3: drain the cleaning water and inject cleaning liquid into the reverse osmosis membrane assembly to pre-treat the pollutants therein, soaking for a period of time to soften the pollutants;

[0036] S4: injecting magnetic fluid into the front end of the reverse osmosis membrane assembly through the magnetic fluid deflector;

[0037] S5: Control the electromagnetic coil to move repeatedly within the range of the first three membranes of the reverse osmosis membrane assembly along the length direction of the reverse osmosis membrane assembly, and repeatedly change the current direction and magnitude of the variable AC power supply during this process. When the electromagnetic coil moves close to the third membrane of the reverse osmosis membrane assembly, magnetic fluid is injected into the rear end of the reverse osmosis membrane assembly through the magnetic fluid guide, and this part of the magnetic fluid is driven by another electromagnetic coil to move toward the fourth membrane of the reverse osmosis membrane assembly, so that a certain distance is always maintained between the two electromagnetic coils. The reciprocating movement of the two electromagnetic coils drives the magnetic fluid to scrape the inside of the reverse osmosis membrane assembly.

[0038] S6: Open the closed valve in the recovery pipeline connected to the front end of each reverse osmosis membrane module, and discharge the cleaning liquid and magnetic fluid used to clean the first three membranes of each reverse osmosis membrane module from the concentrated brine outlet at the front end of the reverse osmosis membrane module. The magnetic fluid and cleaning liquid located in the last four membranes inside the reverse osmosis membrane module are discharged into the recovery pipeline from the concentrated brine outlet at the end of the reverse osmosis membrane module.

[0039] S7: clean water is injected from the water inlet of each reverse osmosis membrane assembly through the reverse osmosis membrane assembly self-cleaning system to flush the residual chemical solution and magnetic fluid in each reverse osmosis membrane assembly to the outside of the reverse osmosis membrane assembly;

[0040] S8: Recover the magnetic fluid base particles stored in the recovery bin installed in the recovery pipeline. The recovered magnetic fluid base particles and other substances used to prepare the magnetic fluid are re-mixed into magnetic fluid products with corresponding properties and placed in the magnetic fluid storage container for use in the next membrane cleaning.

[0041] In summary, this application includes at least one of the following beneficial technical effects:

[0042] 1. By combining magnetic fluid technology and reverse osmosis technology, this application provides an efficient and non-destructive reverse osmosis membrane cleaning device, which achieves efficient removal of pollutants while avoiding damage to the membrane structure caused by traditional cleaning methods;

[0043] 2. By setting up the preferred solutions such as the pressure-resistant membrane shell end cover group, recovery device and leak detection device, the equipment's safety and maintenance convenience are further improved, and the chemical consumption and membrane cleaning costs are reduced;

[0044] 3. The magnetic fluid-assisted reverse osmosis membrane cleaning equipment of this application has broad application prospects and can be widely used in water treatment, seawater desalination, wastewater recycling and other fields, contributing to technological progress and energy conservation and emission reduction in related industries. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 2 is a schematic structural diagram of a magnetic fluid-assisted reverse osmosis membrane cleaning device according to an embodiment of the present application;

[0046] Figure 2 This is a schematic structural diagram of a recovery device according to an embodiment of the present application;

[0047] Figure 3 is a schematic side view of a magnetic fluid-assisted reverse osmosis membrane cleaning device according to an embodiment of the present application;

[0048] Figure 4 is a cross-sectional view of a detection device provided in an embodiment of the present application;

[0049] Figure 5 It is a cross-sectional view of a magnetic fluid-assisted reverse osmosis membrane cleaning device provided in an embodiment of the present application.

[0050] 1. Frame; 11. Clamp; 12. Pressure-resistant membrane shell; 2. Magnetic fluid reservoir; 3. Magnetic fluid deflector; 4. Core rod; 5. Electromagnetic coil; 6. Pressure-resistant membrane shell end cover; 7. Recovery device; 71. Recovery pipeline; 72. Recovery bin; 73. Electromagnetic iron ring; 8. Leak detection device; 81. Leak detection pipeline; 82. Closing valve; 83. Magnetic flux sensor; 9. Detection device; 91. Probe; 92. Sampling tube. DETAILED DESCRIPTION

[0051] Example

[0052] The magnetic fluid assisted reverse osmosis membrane cleaning device provided in the embodiment of the present application is as follows: Figure 1 and Figure 2 As shown, the apparatus comprises key components such as a frame 1, a magnetic fluid reservoir 2, a magnetic fluid deflector 3, a core rod 4, and an electromagnetic coil 5. The frame 1, serving as the supporting structure for the entire apparatus, is specially designed with multiple workstations specifically for installing reverse osmosis membranes. These workstations are cleverly arranged circumferentially around the central axis of the frame 1, saving space and facilitating operation.

[0053] The magnetic fluid reservoir 2, which stores and prepares the magnetic fluid, contains magnetic particles, a base liquid, and a surfactant. This design allows the reservoir 2 to flexibly prepare the appropriate magnetic fluid base liquid based on the actual contaminated environment to be cleaned, thereby ensuring cleaning effectiveness and efficiency.

[0054] The magnetic fluid deflectors 3 are responsible for precisely injecting the magnetic fluid from the magnetic fluid reservoir 2 into the reverse osmosis membranes installed at each station in the frame 1. To this end, each magnetic fluid deflector 3 is connected to the frame 1 via fasteners and is positioned correspondingly to each station in the frame 1. Furthermore, each magnetic fluid deflector 3 maintains communication with the magnetic fluid reservoir 2, ensuring a smooth supply of magnetic fluid.

[0055] The core rod 4 is an important component located in the middle of each station of the frame 1 and is made of a magnetic material. This design allows the core rod 4 to effectively guide and control the direction and path of the magnetic fluid in the reverse osmosis membrane under the influence of the magnetic field generated by the electromagnetic coil 5.

[0056] Electromagnetic coils 5 are positioned around the outside of each station of frame 1 and connected to a variable AC power supply. By varying the current and direction of the variable AC power supply, the strength and direction of the magnetic field generated by the electromagnetic coils 5 can be flexibly adjusted. Furthermore, the electromagnetic coils 5 are designed to move along their own central axis. This feature enables the electromagnetic coils 5 to move the magnetic fluid within the reverse osmosis membranes at each station of frame 1, thereby achieving a more comprehensive and thorough cleaning effect.

[0057] The implementation principle of Example 1 is as follows: First, according to the actual reverse osmosis membrane assembly cleaning process, a suitable magnetic fluid base liquid is prepared in the magnetic fluid reservoir 2. Then, the prepared magnetic fluid is accurately injected into the reverse osmosis membrane installed at each station of the frame 1 through the magnetic fluid deflector 3. Next, the electromagnetic coil 5 is started and the intensity and direction of the magnetic field generated by it are adjusted, while the electromagnetic coil 5 is controlled to move along its own central axis. Under the action of the magnetic field, the magnetic fluid moves accurately in the reverse osmosis membrane and removes pollutants attached to the membrane. Finally, the electromagnetic coil 5 is turned off and the cleaned magnetic fluid is recovered to complete the entire cleaning process.

[0058] After the reverse osmosis membrane is installed at the station of the frame 1, a magnetic fluid is first injected into the reverse osmosis membrane through an injector, and then a magnetic field generator generates a magnetic field. The magnetic field generator moves along the axial direction of the reverse osmosis membrane, so that the magnetic fluid shuttles and cleans the membrane, and the attachments on the inner surface of each layer of the reverse osmosis membrane are vibrated and scraped, thereby removing the pollutants in the membrane. After cleaning is completed, a flushing liquid is injected through the flusher to flush out the cleaned magnetic fluid and pollutants together. The whole process is simple to operate and has high cleaning efficiency. Compared with traditional cleaning liquid cleaning, it can more effectively remove pollutants attached to the inner surface of the reverse osmosis membrane, reduce the use of cleaning liquid, reduce resource waste and improve the cleaning effect.

[0059] Example

[0060] Based on Example 1, this embodiment further refines the equipment's sealing and recovery functions. Specifically, each station on the rack is equipped with two opposing end caps 6 for the pressure-resistant membrane housing 12, forming six sets of pressure-resistant membrane housing 12 end caps that seal the reverse osmosis membrane's water inlet, brine outlet, and product outlet. This design ensures that key interfaces of the reverse osmosis membrane are tightly sealed during the cleaning process, preventing magnetic fluid leakage and maintaining a sealed cleaning environment, thereby improving cleaning efficiency and effectiveness.

[0061] In addition, Example 2 also includes a recovery device 7, which is connected to the brine outlet of each workstation via multiple recovery pipes 71 to recover the cleaned magnetic fluid. Each recovery pipe 71 is equipped with an electromagnet ring 73, which uses a magnetic field to attract the magnetic fluid, ensuring its efficient recovery and reducing resource waste.

[0062] In terms of implementation principle, Example 2, by adding six sets of end caps to the pressure-resistant membrane housing 12 and a recovery device 7, not only improves the airtightness and efficiency of the cleaning process but also enables the recycling of the magnetic fluid, reducing operating costs and embodying environmental protection. During the cleaning process, driven by the electromagnetic coil 5, the magnetic fluid precisely removes contaminants from the reverse osmosis membrane and is then effectively recovered by the recovery device 7, making the entire process efficient, environmentally friendly, and economical.

[0063] Example

[0064] The present invention provides a method for configuring a magnetic fluid in a magnetic fluid-assisted reverse osmosis membrane cleaning device. Specifically, the method includes the following steps:

[0065] Step 1: Prepare a solution of Fe₃+ and Fe₂+ at a molar ratio of 1:1.5-2, and add concentrated ammonia until a black precipitate is completely formed, obtaining the first black precipitate solution. This step is crucial in preparing the magnetic base particles. By controlling the ratio of Fe₃+ to Fe₂+ and the amount of concentrated ammonia added, base particles with excellent magnetic properties can be produced.

[0066] In step two, the resulting first black precipitate solution is rapidly heated to 80-100°C, oleic acid and a low-carbon alkane are added, and the mixture is stirred until the solution clearly separates into layers. Magnetic decantation is then used to obtain a magnetic fluid. This step involves heating and adding specific chemicals to form a stable magnetic fluid between the magnetic base particles and the base liquid.

[0067] Step 3: Centrifuge the magnetic fluid, rinse with deionized water, flocculate with an organic solvent, and then dry it in a low-temperature vacuum oven to obtain a single-layer coated magnetic powder. This step further purifies and dries the magnetic fluid to obtain high-quality magnetic particles.

[0068] In step 4, the resulting single-layer coated magnetic powder is weighed and added to a base liquid at room temperature. Stir and disperse until no precipitation occurs, then centrifuge. The resulting liquid is the desired magnetic fluid. This step involves mixing the purified magnetic base particles with the base liquid to form the magnetic fluid used to clean the reverse osmosis membrane. In step 1, the concentration of the aqueous ammonia is 25% to 28%; based on the molar amount of Fe₃⁺, the amount of aqueous ammonia added is 400 to 700 ml / mol Fe₃⁺. The low-carbon alkane is kerosene. For a single flocculation, the volume of the organic solvent is 2 to 4 times the volume of the magnetic fluid. Acetone is used for flocculation. The amount of the intermediate liquid added is 3 to 6 times the weight of the weighed single-layer coated magnetic powder. The intermediate liquid is a low-boiling hydrocarbon. The intermediate liquid is a C₄ to C₁₀ hydrocarbon. The intermediate liquid is one or more of hexane and heptane. The base liquid is a low-carbon oil; based on the weight of the single-layer coated magnetic powder, the volume of base liquid added is 0.8 mL / g to 2 mL / g of the single-layer coated magnetic powder. The low-carbon oil is one or more of kerosene and diesel. The amount of polyisobutylene succinimide added is 20% to 50% of the weight of the single-layer coated magnetic powder. The base carrier liquid is one or more of a diester-based carrier liquid, hydraulic oil, total-loss system oil, and pump oil. Based on the weight of the single-layer coated magnetic powder, the volume of base carrier liquid added is 0.4 mL / g to 2 mL / g of the single-layer coated magnetic powder.

[0069] In the present invention, magnetic powder is first prepared by chemical coprecipitation. A solution containing Fe₂+ and Fe₃+ in a ratio of 1:1.5 to 2 is heated to 25-60°C and concentrated ammonia is added until a black precipitate is completely formed, thereby obtaining a first black precipitate solution. Furthermore, the ammonia concentration is 25%-28%, and the amount added is 400-700 ml / mol Fe₃+.

[0070] Next, the magnetic powder is coated with a single layer: the resulting black precipitate is rapidly heated to 80°C–100°C, and appropriate amounts of oleic acid and a low-carbon, small-molecule alkane (such as kerosene) are added with accelerated stirring. After 3–8 minutes, the seal is removed (in the case of kerosene, a liquid seal forms before stirring, which is broken after stirring, effectively removing the seal). Stirring is continued until the mixed solution clearly separates into layers. A strong magnetic separation is then performed, and the supernatant is discarded to initially obtain magnetic fluid A. This magnetic fluid A is then centrifuged, repeatedly washed with deionized water, and repeatedly coagulated with acetone. Finally, it is vacuum-dried at low temperature to obtain the single-layer coated magnetic powder. Furthermore, the amount of oleic acid used is 40–110 ml / mol Fe₃⁺, calculated as Fe₃⁺, and the volume of acetone is 2–4 times the volume of magnetic fluid A.

[0071] Finally, for the low-carbon base liquid magnetic fluid, the prepared monolayer-coated magnetic powder is weighed and dispersed in the base liquid at room temperature, stirring until no precipitation occurs. The mixture is then centrifuged and the liquid is decanted to obtain the magnetic fluid. The base liquid can be a low-carbon oil such as kerosene or diesel, and the volume added should be between 0.8 mL / g and 2 mL / g of the magnetic powder weight. This method yields a magnetic fluid coated with the first surfactant (oleic acid).

[0072] For esters with high carbon content, hydraulic oil, pump oil, etc., weigh the prepared monolayer-coated magnetic powder, stir and disperse it in an intermediate liquid at room temperature. The temperature is then rapidly raised to 140-170°C. A uniform mixture of T154A and a base carrier liquid is added and rapidly stirred. After 20-30 minutes, the intermediate liquid is completely evaporated. The mixture is then cooled to room temperature and centrifuged at high speed to obtain a uniform magnetic fluid. The intermediate liquid can be a low-boiling hydrocarbon such as (n-) heptane or (n-) hexane. The mass of T154A should be 20%-50% of the weight of the magnetic powder. The base carrier liquid can be a diester, hydraulic oil, total-loss system oil, pump oil, etc., and the volume added should be 0.4mL / g-2mL / g of the magnetic powder weight. This method produces a magnetic fluid coated with the first surfactant (oleic acid) and the second surfactant (T154A).

[0073] In hydrocarbon-based magnetic fluids, the amount of surfactant used to coat the magnetic particles must be appropriate. Too little is insufficient to form a complete coating, while too much results in multiple layers of adsorption, which in turn reduces stability and magnetic properties. While ensuring that the first coating layer, or chemical adsorption layer, completely covers the magnetic particles, the present invention incorporates a step of repeated washing of the modified nanoparticles to minimize the removal of the unstable physical adsorption layer. This added step eliminates the need for precise requirements for the amount of surface modifier added initially; a slight excess of surfactant is sufficient to ensure that the chemical coating layer completely covers the magnetic particles. This added step not only simplifies the control of the added surfactant dosage but also minimizes the removal of the unstable surfactant (physical adsorption layer), resulting in a single-layer coating on the magnetic particle surface.

[0074] For magnetic fluids requiring secondary modification, such as diesters and pump oils, the present invention uses polyisobutylene succinimide (T154A) to disperse the oil. This dispersant is harmless to both humans and the environment, making it an environmentally friendly product. Experimental measurements have shown that the magnetic fluid prepared using polyisobutylene succinimide exhibits excellent oil dispersibility and superior magnetic fluid performance. The saturation magnetization intensity of the present invention is comparable to similar products on the market, demonstrating promising application prospects.

[0075] Example

[0076] This embodiment discloses a magnetic fluid-assisted reverse osmosis membrane cleaning method, which is applicable to the reverse osmosis membrane cleaning equipment described in any of the above embodiments. The method includes the following steps:

[0077] S1: Install the reverse osmosis membrane assembly to each station position of the frame 1 and fix it with the clamp 11;

[0078] S2: Raw water is injected into the machine through the raw water inlet, filtered through the reverse osmosis membrane module, and the pure water is discharged through the water outlet and the leak detection pipeline. The concentrated brine is discharged through the concentrated brine outlet of the reverse osmosis membrane module and the recovery pipeline. After a fixed operation period, the machine is shut down for cleaning.

[0079] S3: Before starting cleaning, prepare the appropriate magnetic fluid according to the cleaning needs, and inject clean water into each reverse osmosis membrane component to flush and replace the concentrated brine in the membrane;

[0080] S4: injecting cleaning solution into the reverse osmosis membrane assembly to soak and pre-treat the pollutants therein for 300 minutes;

[0081] S5: Controlling the electromagnetic coil 5 to repeatedly move along the length direction of the reverse osmosis membrane assembly within the range of the first three membranes of the reverse osmosis membrane assembly, repeatedly changing the direction and magnitude of the current of the variable AC power supply during this process. When the electromagnetic coil 5 moves close to the third membrane of the reverse osmosis membrane assembly, magnetic fluid is injected into the rear end of the reverse osmosis membrane assembly through the magnetic fluid deflector 3, and this magnetic fluid is driven by another electromagnetic coil 5 to move toward the fourth membrane of the reverse osmosis membrane assembly, so that a certain distance is always maintained between the two electromagnetic coils 5. The reciprocating movement of the two electromagnetic coils 5 drives the magnetic fluid to vibrate and scrape the inside of the reverse osmosis membrane assembly;

[0082] S6: Based on the pH value of the drug solution in the outflow of the sampling tube measured by the probe, it is determined whether the drug solution needs to be added. If the pH value measured by the probe deviates too much from the set value, the drug solution suitable for the current cleaning process is added to the reverse osmosis membrane assembly through the drug washing pipeline provided by the reverse osmosis membrane assembly;

[0083] S7: After S5 is executed for a fixed time, the closed valve 82 in the recovery pipe 71 connected to the front end of each reverse osmosis membrane module is opened, and the cleaning liquid and magnetic fluid used to clean the first three membranes of each reverse osmosis membrane module are discharged from the concentrated brine outlet at the front end of the reverse osmosis membrane module. The magnetic fluid and cleaning liquid located in the last four membranes inside the reverse osmosis membrane module are discharged from the concentrated brine outlet at the end of the reverse osmosis membrane module into the recovery pipe 71;

[0084] S8: Recovering the magnetic fluid base particles stored in the recovery bin 72 installed in the recovery pipeline 71;

[0085] S9: Inject clean water from the water inlet of each reverse osmosis membrane assembly through the reverse osmosis membrane assembly self-cleaning system to flush the residual chemical solution and magnetic fluid in each reverse osmosis membrane assembly to the outside of the reverse osmosis membrane assembly;

[0086] S10: During the execution of S9, observe whether the magnetic flux sensor 83 of the leak detection pipeline 81 has any changes in magnetic flux. If changes occur, it is necessary to stop the machine and check the location of structural damage to the reverse osmosis membrane assembly; if there are no changes, re-execute step S2 until the next regular cleaning.

[0087] The principle behind Example 4 is that by combining magnetic fluid technology with electromagnetic field control technology, this method enables efficient cleaning of reverse osmosis membranes. First, a pretreatment step softens or dissolves contaminants that are difficult to remove directly. Then, the intense shear, impact, and vibration forces of the magnetic fluid under the influence of the electromagnetic field remove contaminants adhering to the membrane surface. Finally, a subsequent cleaning step ensures thorough cleaning of the reverse osmosis membrane. This method not only improves cleaning efficiency and quality, but also simplifies the operational process and reduces operational difficulty.

[0088] Example

[0089] This embodiment provides an automated control system for a magnetic fluid-assisted reverse osmosis membrane cleaning device, which is integrated into the device to achieve automated control of the reverse osmosis membrane cleaning process. The automated control system includes two core components: a controller and a time relay.

[0090] The controller is responsible for receiving and processing various command signals and controlling the various components of the equipment to work according to the preset process. Specifically, the controller is electrically connected to the electromagnetic coil 5 and can control the power on and off of the electromagnetic coil 5, thereby controlling the strength and direction of the magnetic field generated by it. At the same time, the controller is also electrically connected to the variable AC power supply and can adjust the current size and direction of the variable AC power supply output, thereby achieving refined control of the magnetic field generated by the electromagnetic coil 5. A pressure-resistant membrane shell 12 end cover 6 is also provided to ensure that the various ports of the reverse osmosis membrane can be effectively closed during the cleaning process to prevent leakage of magnetic fluid. Finally, the controller is also electrically connected to the magnetic fluid deflector 3 and can control the magnetic fluid deflector 3 to inject the magnetic fluid in the magnetic fluid reservoir 2 into the reverse osmosis membrane of the corresponding station to start the cleaning operation. The system also includes a detection assembly for detecting the concentration of the chemical within the reverse osmosis membrane assembly during the cleaning process. The assembly comprises multiple probes 91, each corresponding to the rear end of a sampling tube 92. During testing, the sampling tubes 92 are opened, and the effluent from the sampling tubes 92 is detected by the probes 91 to measure the pH and conductivity of the chemical solution within the reverse osmosis membrane assembly. A detection control module is also included. Each probe 91 is electrically connected to the detection control module. The detection control module determines the chemical concentration based on the pH changes within each reverse osmosis membrane assembly and further determines whether chemical addition is necessary. If the pH value measured by the probe deviates significantly from the set value, the detection control module sends a signal to the controller, which controls the chemical cleaning pipeline of the reverse osmosis membrane assembly to add the appropriate chemical solution for the current cleaning process. When the detection control module detects that the pH value of the chemical solution within the reverse osmosis membrane has stopped changing, the membrane cleaning process is concluded. A time relay measures the duration of each cleaning step. The time relay is connected to the controller and sends a signal to the controller after a preset time has elapsed, prompting the controller to proceed to the next step. For example, during the cleaning process, the time relay can set the residence time of the magnetic fluid in the reverse osmosis membrane to ensure that the magnetic fluid can fully act on the contaminants on the reverse osmosis membrane. When the set time is reached, the time relay will send a signal to the controller, which will then control the electromagnetic coil 5 to de-energize and complete the entire cleaning process.

[0091] Through the coordinated action of the controller and time relay, the automated control system provided in this embodiment can achieve comprehensive automated control of the reverse osmosis membrane cleaning process. This not only significantly improves cleaning efficiency and quality, reduces manual operation costs, but also ensures the stability and reliability of the cleaning process, providing a strong guarantee for the long-term and efficient operation of the reverse osmosis membrane.

[0092] The implementation principle of Example 5 is as follows: By integrating automated control components such as a controller and a time relay, this example constructs an efficient and intelligent reverse osmosis membrane cleaning control system. This system automatically controls the operation of various equipment components according to a preset process, achieving full automation of the cleaning process.

Claims

1. A magnetic fluid assisted reverse osmosis membrane cleaning device, characterized in that: include: The frame (1) is provided with a plurality of workstations for installing reverse osmosis membrane components, and the workstations are arranged in an array around the horizontal axis of the frame (1); The magnetic fluid storage device (2) has two cavities formed therein for storing two magnetic fluid products suitable for acidic and alkaline cleaning environments, respectively. The magnetic fluid products are prepared by mixing magnetic fluid base particles and other substances for mixing magnetic fluid. During cleaning, the storage port storing the magnetic fluid of corresponding properties is opened according to the acidic or alkaline environment corresponding to the cleaning process. The frame (1) is provided with at least two magnetic fluid deflectors (3) corresponding to each workstation position thereof, each of the magnetic fluid deflectors (3) is connected to the magnetic fluid reservoir (2), and each of the magnetic fluid deflectors (3) can be connected to the reverse osmosis membrane assembly installed at the corresponding workstation of the frame, and the two magnetic fluid deflectors (3) provided at the same workstation position of the frame can respectively inject magnetic fluid into the reverse osmosis membrane assembly from both ends thereof; A core rod (4) is arranged at a middle position of each workstation of the frame (1), the length direction of the core rod (4) is arranged along the horizontal axis direction of the frame (1), and the core rod (4) is made of a magnetic conductive material; The electromagnetic coil (5) is arranged outside each station of the frame (1) corresponding to the electromagnetic coil (5). The central axis of the electromagnetic coil (5) can be arranged in a colinear manner with the length direction of the core rod (4). The electromagnetic coil (5) is also connected to a variable AC power supply. By changing the current of the variable AC power supply, the intensity of the magnetic field generated by the electromagnetic coil (5) can be adjusted. By changing the current direction of the variable AC power supply, the direction of the magnetic field generated by the electromagnetic coil (5) can be adjusted. The electromagnetic coil (5) is movably connected to the frame (1). The electromagnetic coil (5) can move along the horizontal axis of the frame (1). The movement of the electromagnetic coil (5) can drive the magnetic fluid in the reverse osmosis membrane assembly of each station of the frame (1) to move accordingly. The variable AC power supply can adjust the current to adjust the vibration amplitude and vibration frequency of the magnetic fluid in the electromagnetic coil (5). Each pressure-resistant membrane shell (12) at each station position of the frame is provided with two relatively arranged pressure-resistant membrane shell end covers (6), and any two relatively arranged pressure-resistant membrane shell end covers (6) are provided as a pressure-resistant membrane shell end cover (6) group, and each of the pressure-resistant membrane shell end cover (6) groups can jointly seal the reverse osmosis membrane assembly setting of the corresponding station of the frame with the pressure-resistant membrane shell (12), and when magnetic fluid-assisted cleaning is performed, each pressure-resistant membrane shell end cover (6) group and the pressure-resistant membrane shell (12) seal the corresponding reverse osmosis membrane element setting; The invention also includes a recovery device (7), which is used to recover the magnetic fluid after auxiliary cleaning. The recovery device (7) includes a recovery pipeline (71), each recovery pipeline (71) can be connected to the concentrated brine discharge outlet of each pressure-resistant membrane shell (12), and each recovery pipeline (71) is provided with a closing valve (82) at one end close to the pressure-resistant membrane shell end cover (6), and each closing valve (82) can close the corresponding recovery pipeline (71); a recovery bin (72) is provided, and each recovery pipeline (71) is provided with a plurality of electromagnet rings (73) at the position corresponding to its own recovery bin (72), and the electromagnet rings (73) are coated on the outer side of the corresponding recovery bin (72) along the length direction of the recovery bin (72), and the cleaning waste liquid of the reverse osmosis membrane is discharged into the recovery pipeline (71) along the concentrated brine discharge outlet, and the magnetic fluid base particles therein are adsorbed on the inner wall of the recovery bin (72) under the action of the electromagnet rings (73), so as to achieve separation from other cleaning waste liquids; The invention also includes a leak detection device (8), which is used to detect whether the reverse osmosis membrane assembly has structural damage, specifically to detect whether magnetic fluid appears in the cleaning liquid discharged from the water outlet of the reverse osmosis membrane assembly after cleaning. The leak detection device (8) includes a plurality of leak detection pipelines (81), each of which can be connected to the water outlet of the reverse osmosis membrane assembly installed at each station of the frame (1) in a one-to-one correspondence. Each leak detection pipeline (81) is connected to the corresponding pressure-resistant membrane shell end cover (6). The leakage pipeline (81) is connected to a closing valve (82) near the pressure-resistant membrane shell end cover (6). Each of the closing valves (82) can close the corresponding leakage detection pipeline (81). A magnetic flux sensor (83) is provided in each of the leakage detection pipelines (81). If the magnetic flux of the magnetic flux sensor (83) changes when the cleaning fluid passes through the leakage detection pipeline (81), it means that magnetic fluid is mixed therein, thereby judging that structural damage occurs inside the reverse osmosis membrane assembly and preventing the magnetic fluid from flowing out with the cleaning fluid.

2. The magnetic fluid assisted reverse osmosis membrane cleaning equipment according to claim 1, characterized in that: The magnetic fluid configuration process used in the magnetic fluid storage (2) under the pickling cleaning environment is as follows: Fe3+ and Fe2+ are prepared into a solution in a molar ratio of 1:1.5-2, and concentrated ammonia water is added thereto until a black precipitate is completely formed, thereby obtaining a first black precipitate solution; The obtained first black precipitate solution is rapidly heated to 80-100° C., and oleic acid and a low-carbon alkane are added thereto, and stirred until the solution is clearly separated into layers. A magnetic fluid liquid is obtained by magnetic decantation, and the magnetic fluid liquid is centrifuged, washed with deionized water, flocculated with an organic solvent, and then dried in a low-temperature vacuum to obtain a single-layer coated magnetic powder. Weigh the single-layer coated magnetic powder obtained in the step, add the single-layer coated magnetic powder to the base liquid at room temperature, stir and disperse until there is no precipitation, and then centrifuge. The liquid poured out after centrifugation is the magnetic fluid.

3. The magnetic fluid assisted reverse osmosis membrane cleaning equipment according to claim 2, characterized in that: The configuration process of the magnetic fluid used in the magnetic fluid storage (2) under the alkaline cleaning environment is as follows: Fe3+ and Fe2+ are prepared into a solution in a molar ratio of 1:1.5-2, and concentrated ammonia water is added thereto until a black precipitate is completely formed, thereby obtaining a first black precipitate solution; The obtained first black precipitate solution is rapidly heated to 80-100° C., and oleic acid and a low-carbon alkane are added thereto, and stirred until the solution is clearly separated into layers. A magnetic fluid liquid is obtained by magnetic decantation, and the magnetic fluid liquid is centrifuged, washed with deionized water, flocculated with an organic solvent, and then dried in a low-temperature vacuum to obtain a single-layer coated magnetic powder. The obtained single-layer coated magnetic powder is weighed and stirred and dispersed in an intermediate liquid at room temperature to obtain a second intermediate solution. The second intermediate solution is quickly heated to 140-170°C, and polyisobutylene succinimide and a base carrier liquid are added thereto. The mixture is stirred and mixed until the intermediate liquid is completely evaporated, cooled to room temperature, and then centrifuged. The liquid poured out after centrifugation is the magnetic fluid.

4. The magnetic fluid assisted reverse osmosis membrane cleaning equipment according to claim 3, characterized in that: Each workstation is provided with a clamp (11) for fixing the reverse osmosis membrane assembly. The clamp (11) is detachably connected to the frame (1), and the clamp (11) is made of non-metallic material.

5. The magnetic fluid assisted reverse osmosis membrane cleaning equipment according to claim 4, characterized in that: It also includes a detection component for detecting the concentration of the reagent in the reverse osmosis membrane component during the cleaning process, including: Sampling tubes (92) are provided on each pressure-resistant membrane shell end cover (6) in a one-to-one correspondence, and each sampling tube (92) can be connected to the corresponding reverse osmosis membrane assembly; A plurality of probes (91) are provided, each of the probes (91) being correspondingly provided at the rear end of each of the sampling tubes (92). During detection, the sampling tubes (92) are opened, and the outflow liquid of the sampling tubes (92) is detected by the probes (91) to measure the pH value and conductivity of the liquid in the reverse osmosis membrane assembly; A detection control module, wherein each of the probes (91) is electrically connected to the detection control module, and the detection control module determines the concentration of the liquid medicine according to the changes in the pH value and conductivity of the liquid medicine in each reverse osmosis membrane assembly, and further determines whether the liquid medicine needs to be replenished.

6. The magnetic fluid assisted reverse osmosis membrane cleaning equipment according to claim 5, characterized in that: It also includes a control system, which is used to control the cleaning process of the reverse osmosis membrane assembly to achieve automation. The control system includes: The controller sends a signal to start cleaning. The electromagnetic coil (5) is electrically connected to the controller, and the controller can control the movement of the electromagnetic coil (5). The variable AC power supply is also electrically connected to the controller, and the controller can control the current size and direction of the variable AC power supply. The magnetic fluid deflector (3) is also electrically connected to the controller, and the controller controls the magnetic fluid in the magnetic fluid reservoir (2) to be injected into the reverse osmosis membrane assembly of the corresponding station. The time relay is connected to the controller and is used to measure the execution time of each step.

7. A method for cleaning a reverse osmosis membrane, applicable to the magnetic fluid-assisted reverse osmosis membrane cleaning apparatus according to claim 6, characterized in that: include, S1: Install the reverse osmosis membrane assembly at each station position of the frame (1) and fix it with a clamp (11); S2: Raw water is injected into the machine through the raw water inlet, filtered through the reverse osmosis membrane module, and the pure water is discharged through the water outlet and the leak detection pipeline. The concentrated brine is discharged through the concentrated brine outlet of the reverse osmosis membrane module and the recovery pipeline. After a fixed operation period, the machine is shut down for cleaning. S3: Before starting cleaning, prepare the appropriate magnetic fluid according to the cleaning needs, and inject clean water into each reverse osmosis membrane component to flush and replace the concentrated brine in the membrane; S4: injecting cleaning solution into the reverse osmosis membrane assembly to soak and pre-treat the pollutants therein for 300 minutes; S5: Control the electromagnetic coil (5) to repeatedly move within the first three membranes of the reverse osmosis membrane assembly along the length direction of the reverse osmosis membrane assembly, repeatedly changing the current direction and magnitude of the variable AC power supply during this process. When the electromagnetic coil (5) moves close to the third membrane of the reverse osmosis membrane assembly, a magnetic fluid is injected into the rear end of the reverse osmosis membrane assembly through the magnetic fluid deflector (3), and this magnetic fluid is driven by another electromagnetic coil (5) to move toward the fourth membrane of the reverse osmosis membrane assembly, so that a certain distance is always maintained between the two electromagnetic coils (5). The two electromagnetic coils (5) move back and forth to drive the magnetic fluid to vibrate and scrape the inside of the reverse osmosis membrane assembly; S6: Based on the pH value of the drug solution in the outflow of the sampling tube measured by the probe, it is determined whether the drug solution needs to be added. If the pH value measured by the probe deviates too much from the set value, the drug solution suitable for the current cleaning process is added to the reverse osmosis membrane assembly through the drug washing pipeline provided by the reverse osmosis membrane assembly; S7: After S5 is executed for a fixed time, the closed valve (82) in the recovery pipeline (71) connected to the front end of each reverse osmosis membrane assembly is opened, and the cleaning liquid and magnetic fluid used to clean the first three membranes of each reverse osmosis membrane assembly are discharged from the concentrated brine outlet at the front end of the reverse osmosis membrane assembly, and the magnetic fluid and cleaning liquid of the last four membranes inside the reverse osmosis membrane assembly are discharged from the concentrated brine outlet at the end of the reverse osmosis membrane assembly into the recovery pipeline (71); S8: Recovering the magnetic fluid base particles stored in the recovery bin (72) installed in the recovery pipeline (71); S9: Inject clean water from the water inlet of each reverse osmosis membrane assembly through the reverse osmosis membrane assembly self-cleaning system to flush the residual chemical solution and magnetic fluid in each reverse osmosis membrane assembly to the outside of the reverse osmosis membrane assembly; S10: During the execution of S9, observe whether the magnetic flux sensor (83) of the leak detection pipeline (81) has any change in magnetic flux. If there is a change, it is necessary to stop the machine and check the location of structural damage to the reverse osmosis membrane assembly; if there is no change, re-execute step S2 until the next regular cleaning.

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