Device for testing interception performance of hollow fiber nanofiltration membrane

Abstract

The utility model provides a device for testing the interception performance of a hollow fiber nanofiltration membrane. The device comprises a produced water sampling flow path, a concentrated water sampling flow path, a centrifugal pump, a first water tank and a second water tank, the first water tank and the second water tank are connected with the water inlet end of the centrifugal pump. The centrifugal pump is connected with the water inlet end of the membrane component; the water inlet end of the produced water sampling flow path is used for being connected with an interception side outlet of a membrane assembly, the water inlet end of the concentrated water sampling flow path is used for being connected with a permeation outlet of the membrane assembly, the water outlet ends of the produced water sampling flow path and the concentrated water sampling flow path are connected together and then connected with a first water tank, and the produced water sampling flow path and the concentrated water sampling flow path are each provided with a branch. The branch is provided with an online monitoring unit, and the online monitoring unit is used for synchronously collecting multiple parameters. The system has the advantages of being capable of covering multi-parameter dynamic testing, automatic operation and high-precision monitoring.

Description

A Hollow Fiber Nanofiltration Membrane Retention Performance Testing Device Technical Field

[0001] This utility model relates to the technical field of water quality testing equipment, specifically to a hollow fiber nanofiltration membrane retention performance testing device. Background Technology

[0002] Hollow fiber ultrafiltration membranes are asymmetric semi-permeable membranes made from polymer materials using a special process. They are hollow capillary-shaped with densely packed micropores on the walls. The pore size of the hollow fiber ultrafiltration membrane is approximately in the range of 0.001-0.1 micrometers, and the molecular weight cutoff is approximately 1000-500000 Daltons. Under pressure, the feed solution flows inside or outside the membrane. Solvents or small molecules can permeate through the membrane and are collected as ultrafiltrate, while large molecules (proteins, various enzymes, nucleic acids, polysaccharides, etc.), colloidal particles (latex, microparticles), bacteria, etc., are retained outside the membrane and carried away by the circulating feed solution to become concentrate. This achieves the separation, concentration, and purification of substances.

[0003] Hollow fiber ultrafiltration membranes use high molecular polymers such as polysulfone, polyethersulfone, and polyvinylidene fluoride as the main raw materials; they have excellent acid and alkali resistance and good water permeability. They are composed of two very thin separation layers (inner and outer) and a porous sponge-like support layer, which can achieve low membrane deep fouling and high membrane cleaning and recovery efficiency.

[0004] Existing testing devices have the following shortcomings: First, traditional devices can only measure a single parameter (such as rejection rate or flux) and cannot simultaneously acquire comprehensive data on the combined effects of multiple parameters such as pressure, temperature, and flow rate on membrane performance, resulting in an inability to fully evaluate the performance of membrane modules under complex operating conditions.

[0005] Secondly, relying on manual adjustment of pressure, flow rate and solution concentration is cumbersome and prone to human error, and the single test cycle is long, making it difficult to meet the needs of high-throughput screening.

[0006] Third, it only supports static single solute testing and cannot simulate dynamic pressure fluctuations (such as pressure oscillations caused by industrial pumping) and multi-component solution environments in actual working conditions, resulting in significant deviations between test results and engineering application scenarios. Summary of the Invention

[0007] The purpose of this invention is to provide a hollow fiber nanofiltration membrane retention performance testing device, which has the advantages of being able to cover multi-parameter dynamic testing, automated operation and high-precision monitoring.

[0008] To solve the above-mentioned technical problems, the technical solution adopted by this utility model is as follows:

[0009] A hollow fiber nanofiltration membrane retention performance testing device includes a permeate sampling flow path, a concentrate sampling flow path, a centrifugal pump, a first water tank, and a second water tank.

[0010] The first and second water tanks are connected to the inlet of the centrifugal pump.

[0011] The centrifugal pump is used to connect to the inlet of the membrane module;

[0012] The inlet end of the permeate sampling flow path is used to connect to the outlet on the filtration side of the membrane module, and the inlet end of the concentrate sampling flow path is used to connect to the outlet of the membrane module. The outlet ends of the permeate sampling flow path and the concentrate sampling flow path are connected together and then connected to the first water tank. Both the permeate sampling flow path and the concentrate sampling flow path are equipped with branches, and the branches are equipped with online monitoring units for simultaneous acquisition of multiple parameters.

[0013] In one embodiment of the present invention, the permeate sampling flow path includes a first pipe, and a first pressure gauge, a first flow meter and a first shut-off valve installed on the first pipe. A branch is installed at the inlet end of the first shut-off valve. The inlet end of the first pipe is connected to the outlet of the membrane module on the interception side, and the other end is connected to the outlet end of the concentrate sampling flow path.

[0014] In one embodiment of this utility model, the concentrate sampling flow path includes a second pipe and a second pressure gauge, a second flow meter, and a second shut-off valve arranged sequentially on the second pipe. A branch is arranged at the inlet end of the second shut-off valve. One end of the second pipe is connected to the permeate outlet of the membrane module, and the other end is connected to the first pipe and then to the first water tank.

[0015] In one embodiment of this utility model, the branch includes a branch pipe and a first valve. The branch pipe is connected to the first pipe or the second pipe. The first valve is installed on the branch pipe, and the online monitoring unit is installed at the outlet end of the first valve.

[0016] In one embodiment of this utility model, a third pressure gauge is provided between the centrifugal pump and the membrane module.

[0017] In one embodiment of this utility model, a temperature control device is provided between the centrifugal pump and the membrane module. The temperature control device includes a temperature sensor, a heat exchanger, and a PID controller. The heat exchanger is located between the centrifugal pump and the membrane module. The temperature sensor is used to detect the temperature. The temperature sensor and the heat exchanger are connected to the PID controller.

[0018] In one embodiment of this utility model, a four-way valve is connected to the inlet end of the centrifugal pump, the first water tank and the second water tank are connected to the four-way valve, the four-way valve is also connected to a pure water pipeline, and ball valves are provided between the first water tank, the second water tank and the four-way valve; a three-way valve is provided between the pure water pipeline and the four-way valve, and the three-way valve is also connected to a drain pipe.

[0019] In one embodiment of this utility model, the concentrate sampling flow path further includes a product water ratio regulating valve, which is located on the outlet side of the second flow meter.

[0020] In one embodiment of this utility model, the heat exchanger is a plate heat exchanger.

[0021] In one embodiment of this utility model, the online monitoring unit includes a conductivity meter, a spectrophotometer, or a mass spectrometer.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] In practical applications, this invention is mainly used to test the retention performance of hollow fiber nanofiltration membranes. The membrane module is connected to a centrifugal pump and sampling paths for permeate and concentrate to form a testing system. The centrifugal pump drives the test solution from the first or second water tank through the membrane module. The solute concentration on the retention side (concentrate) and the permeate side (permeate) is monitored in real time by the online monitoring unit of the sampling path. A third pressure gauge, a first flow meter, and a second flow meter synchronously provide pressure and flow data. A thermostat controls the liquid temperature, enabling simultaneous acquisition of multiple parameters including pressure, temperature, flow rate, and concentration. This allows for the testing of the hollow fiber nanofiltration membrane's retention performance. This invention offers advantages such as the ability to cover dynamic testing of multiple parameters, automated operation, and high-precision monitoring. Attached Figure Description

[0024] To more clearly illustrate the technical solutions of the embodiments of this utility model, the drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this utility model and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained from these drawings without creative effort.

[0025] Figure 1 is a schematic diagram of the overall principle of this utility model.

[0026] Figure 2 is a schematic diagram of the overall structure of this utility model.

[0027] Figure 3 is an enlarged schematic diagram of the layout at point A in Figure 2 of this utility model.

[0028] Figure label:

[0029] 101 Permeate sampling flow path, 102 Concentrate sampling flow path, 103 Centrifugal pump, 104 First water tank, 105 Second water tank, 106 Membrane module, 107 Branch line, 108 Online monitoring unit, 109 First pipeline, 110 First pressure gauge, 111 First flow meter, 112 First shut-off valve, 113 Second pipeline, 114 Second pressure gauge, 115 Second flow meter, 116 Second shut-off valve, 117 Branch pipeline, 118 First valve, 119 Third pressure gauge, 120 Thermostat, 121 Heat exchanger, 122 Four-way valve, 123 Ball valve, 124 Three-way valve, 125 Sewage pipe, 126 Permeate proportional regulating valve, 127 Pure water pipeline, 128 Frame, 129 Spring clamp, 130 Base, 131 First slider, 132 Second slider, 133 Tension spring. Detailed Implementation

[0030] In the following description, only certain exemplary embodiments are briefly described. As those skilled in the art will recognize, the described embodiments can be modified in various ways without departing from the spirit or scope of the present invention. Therefore, the drawings and description are considered to be exemplary in nature and not restrictive.

[0031] In the description of the embodiments of this utility model, it should be understood that the terms "length", "vertical", "horizontal", "top", "bottom", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings. They are only for the convenience of describing the embodiments of this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this utility model.

[0032] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the embodiments of this utility model, "a plurality of" means two or more, unless otherwise explicitly specified.

[0033] In this embodiment of the invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a communication connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this embodiment of the invention according to the specific circumstances.

[0034] In this embodiment of the invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0035] The following disclosure provides many different implementations or examples for different structures of the embodiments of the present invention. To simplify the disclosure of the embodiments of the present invention, specific examples of components and arrangements are described below. Of course, these are merely examples and are not intended to limit the embodiments of the present invention. Furthermore, reference numerals and / or reference letters may be repeated in different examples of the embodiments of the present invention; such repetition is for simplification and clarity and does not in itself indicate a relationship between the various implementations and / or arrangements discussed.

[0036] The embodiments of this utility model will now be described in detail with reference to the accompanying drawings.

[0037] Referring to Figures 1-3, this embodiment discloses a hollow fiber nanofiltration membrane retention performance testing device, including a permeate sampling flow path 101, a concentrate sampling flow path 102, a centrifugal pump 103, a first water tank 104, and a second water tank 105;

[0038] The first water tank 104 and the second water tank 105 are connected to the inlet end of the centrifugal pump 103.

[0039] Centrifugal pump 103 is used to connect to the inlet end of membrane module 106;

[0040] The inlet end of the permeate sampling flow path 101 is used to connect to the filtration side outlet of the membrane module 106, and the inlet end of the concentrate sampling flow path 102 is used to connect to the permeate outlet of the membrane module 106. The outlet ends of the permeate sampling flow path 101 and the concentrate sampling flow path 102 are connected together and then connected to the first water tank 104. Both the permeate sampling flow path 101 and the concentrate sampling flow path 102 are provided with branch paths 107. The branch paths 107 are provided with online monitoring units 108, which are used for simultaneous acquisition of multiple parameters.

[0041] In one embodiment of the present invention, the permeate sampling flow path 101 includes a first pipe 109, and a first pressure gauge 110, a first flow meter 111 and a first shut-off valve 112 disposed on the first pipe 109. A branch is disposed at the inlet end of the first shut-off valve 112. The inlet end of the first pipe 109 is connected to the outlet of the membrane module 106 on the interception side, and the other end is connected to the outlet end of the concentrate sampling flow path 102.

[0042] In one embodiment of the present invention, the concentrate sampling flow path 102 includes a second pipe 113 and a second pressure gauge 114, a second flow meter 115, and a second shut-off valve 116 sequentially arranged on the second pipe 113. A branch is arranged at the inlet end of the second shut-off valve 116. One end of the second pipe 113 is connected to the permeate outlet of the membrane module 106, and the other end is connected to the first pipe 109 and then to the first water tank 104.

[0043] In one embodiment of the present invention, the branch 107 includes a branch pipe 117 and a first valve 118. The branch pipe 117 is connected to the first pipe 109 or the second pipe 113. The first valve 118 is installed on the branch pipe 117. The online monitoring unit 108 is installed at the outlet end of the first valve 118.

[0044] In one embodiment of the present invention, a third pressure gauge 119 is provided between the centrifugal pump 103 and the membrane module 106.

[0045] In one embodiment of the present invention, a temperature control device 120 is provided between the centrifugal pump 103 and the membrane module 106. The temperature control device 120 includes a temperature sensor, a heat exchanger 121 and a PID controller. The heat exchanger 121 is provided between the centrifugal pump 103 and the membrane module 106. The temperature sensor is used to detect the temperature. The temperature sensor and the heat exchanger 121 are connected to the PID controller.

[0046] In one embodiment of this utility model, a four-way valve 122 is connected to the water inlet of the centrifugal pump 103. The first water tank 104 and the second water tank 105 are connected to the four-way valve 122. The four-way valve 122 is also connected to a pure water pipe 127. A ball valve 123 is provided between the first water tank 104, the second water tank 105 and the four-way valve. A three-way valve 124 is provided between the pure water pipe 127 and the four-way valve. The three-way valve 124 is also connected to a drain pipe 125.

[0047] In one embodiment of the present invention, the concentrate sampling flow path 102 further includes a product water ratio regulating valve 126, which is located on the outlet side of the second flow meter 115.

[0048] In one embodiment of the present invention, the heat exchanger 121 is a plate heat exchanger 121.

[0049] In one embodiment of this utility model, the online monitoring unit 108 includes a conductivity meter, a spectrophotometer, or a mass spectrometer.

[0050] In practical applications, this invention is mainly used to test the retention performance of hollow fiber nanofiltration membranes. The membrane module 106 is connected to a centrifugal pump 103 and permeate sampling flow path 101 and concentrate sampling flow path 102 to form a testing system. The centrifugal pump 103 drives the test liquid from the first water tank 104 or the second water tank 105 through the membrane module 106. The solute concentration on the retention side (concentrate) and the permeate side (permeate) is detected in real time by the online monitoring unit 108 of the sampling flow path. The third pressure gauge 119, the first flow meter 111, and the second flow meter 115 synchronously feed back pressure and flow data. The constant temperature device 120 controls the liquid temperature, achieving synchronous acquisition of multiple parameters such as pressure, temperature, flow rate, and concentration, thereby enabling the testing of the retention performance of the hollow fiber nanofiltration membrane. This invention has the advantages of covering multi-parameter dynamic testing, automated operation, and high-precision monitoring.

[0051] To facilitate a better understanding of this invention by those skilled in the art, the following detailed description is provided in conjunction with specific implementation examples.

[0052] The testing device mainly includes a product water sampling flow path 101, a concentrate sampling flow path 102, a centrifugal pump 103, a first water tank 104, and a second water tank 105.

[0053] In actual use, it also includes a frame 128, a product water sampling flow path 101, a concentrate sampling flow path 102, a centrifugal pump 103, a first water tank 104, and a second water tank 105, all mounted on the frame 128.

[0054] The specific structure is as follows:

[0055] The inlet of the centrifugal pump 103 is connected to the first water tank 104, the second water tank 105 and the pure water pipe 127 via a four-way valve 122. The pure water pipe 127 is connected to the drain pipe 125 via a three-way valve 124. A ball valve 123 is installed between the first water tank 104, the second water tank 105 and the four-way valve 122 to switch the test liquid type and realize single-component, multi-component solution or cleaning liquid.

[0056] The outlet of centrifugal pump 103 is connected in sequence to the third pressure gauge 119, the constant temperature device 120 and the membrane module 106 to form the test liquid input flow path; the outlet of the membrane module 106 on the intercept side is connected to the permeate sampling flow path 101 and the outlet on the permeate side is connected to the concentrate sampling flow path 102. The outlets of the two flow paths converge and return to the first water tank 104 to form a closed loop.

[0057] The product water sampling flow path 101 includes a first pipe 109, on which a first pressure gauge 110, a first flow meter 111, and a first shut-off valve 112 are sequentially installed. A branch 107 is set at the inlet end of the first shut-off valve 112, and a first valve 118 is installed on the branch pipe 117. An online monitoring unit 108 (conductivity meter, spectrophotometer, or mass spectrometer) is set at the outlet end of the first valve 118 for real-time detection of the concentration of the intercepted solution.

[0058] The concentrate sampling flow path 102 includes a second pipe 113, on which a second pressure gauge 114, a second flow meter 115, and a second shut-off valve 116 are sequentially installed. A branch 107 is installed at the inlet end of the second shut-off valve 116. The structure is symmetrical to the product water sampling flow path 101 and is used to monitor the concentration of the solution on the permeate side. A product water ratio regulating valve 126 is installed at the outlet side of the second pipe 113 to control the flow ratio of concentrate to product water.

[0059] The third pressure gauge 119 is installed between the centrifugal pump 103 and the membrane module 106 to monitor the pressure at the inlet of the membrane module 106 in real time. Together with the first pressure gauge 110 on the product water side and the second pressure gauge 114 on the concentrate side, it calculates the transmembrane pressure difference.

[0060] The constant temperature device 120 includes a temperature sensor, a plate heat exchanger 121 and a PID controller. The heat exchanger 121 is installed on the pipeline between the centrifugal pump 103 and the membrane module 106. The temperature sensor provides real-time feedback of the liquid temperature, and the PID controller automatically adjusts the power of the heat exchanger 121 according to the set value to control the temperature of the test liquid between 20-80℃ with a fluctuation accuracy of ±1℃.

[0061] Furthermore, in actual use, the first pressure gauge 110, the first flow meter 111, the first shut-off valve 112, the second pressure gauge 114, the second flow meter 115, the second shut-off valve 116, the third pressure gauge 119, the thermostat 120, the four-way valve 122, and the product water proportioning valve 126 are connected to a PLC or microcontroller. In actual use, the PLC or microcontroller synchronously collects pressure (first pressure gauge 110, second pressure gauge 114, third pressure gauge 119), flow (first flow meter 111, second flow meter 115), temperature (temperature sensor), and concentration (online monitoring unit 108) data, and uses a built-in data fitting algorithm to generate a rejection rate-flux relationship curve.

[0062] Start centrifugal pump 103. After the system stabilizes (about 5 minutes), PLC controls the first valve 118 to open branch 107. The conductivity meter collects the conductivity data of permeate and concentrate in real time and automatically calculates the rejection rate. The formula is: rejection rate = (1 - permeate conductivity / concentrate conductivity) × 100%, generating a real-time rejection rate-flux curve.

[0063] Furthermore, in actual use, the membrane module 106 is connected using a standard flange or quick-connect interface to achieve the purpose of quickly replacing the membrane module 106.

[0064] The specific working principle of this utility model is as follows:

[0065] Centrifugal pump 103 drives the test liquid to flow from the first water tank 104 and the second water tank 105 through the membrane module 106. The solute concentration is detected in real time by the online monitoring unit 108 of the sampling flow path on the intercept side (concentrate) and the permeate side (product water). The pressure gauge 119, the first flow meter 111, and the second flow meter 115 synchronously feed back pressure and flow data. The constant temperature device 120 controls the liquid temperature, realizing the synchronous acquisition of multiple parameters such as pressure, temperature, flow rate, and concentration.

[0066] By controlling the speed of centrifugal pump 103 and the PID controller through PLC programming, the pressure fluctuates periodically within the range of ±10% of the set value. At the same time, the product water ratio regulating valve 126 is adjusted to simulate different recovery rates. With the multi-tank switching function, the retention rate of solutes with different molecular weights in the mixed solution can be tested.

[0067] In actual use, a fixing device is provided on the frame 128 to quickly fix the membrane module 106; the fixing device is a spring clamp 129, which fixes the membrane module 106 by clamping; an anti-slip pad is provided on the side of the spring clamp 129 that contacts the membrane module 106, and the anti-slip pad is provided with anti-slip texture.

[0068] Furthermore, in actual use, there are multiple anti-slip pads, which are stacked together in a snap-fit ​​manner; in actual use, the number of anti-slip pads can be increased or decreased to meet the clamping and fixing of different models of membrane modules 106.

[0069] The spring clamp 129 includes a base 130 and a first slider 131 and a second slider 132 that are slidably disposed on the base 130. The first slider 131 and the second slider 132 are disposed opposite to each other, forming a clamping area between the first slider 131 and the second slider 132. The first slider 131 and the second slider 132 are connected by a tension spring 133. Anti-slip pads are disposed on the first slider 131 and the second slider 132, thus enabling the rapid clamping and fixing of the multi-specification membrane assembly 106.

[0070] Although preferred embodiments of the present invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of the present invention.

[0071] The above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. It should be noted that any modifications, equivalent substitutions and improvements made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A device for testing the retention performance of hollow fiber nanofiltration membranes, characterized in that: It includes a permeate sampling flow path, a concentrate sampling flow path, a centrifugal pump, a first water tank, and a second water tank. The first and second water tanks are connected to the inlet of the centrifugal pump. The centrifugal pump is used to connect to the inlet of the membrane module. The inlet of the permeate sampling flow path is used to connect to the filtration outlet of the membrane module, and the inlet of the concentrate sampling flow path is used to connect to the permeate outlet of the membrane module. The outlets of the permeate and concentrate sampling flow paths are connected together and then connected to the first water tank. Both the permeate and concentrate sampling flow paths are equipped with branches, and each branch is equipped with an online monitoring unit for simultaneous acquisition of multiple parameters.

2. The hollow fiber nanofiltration membrane retention performance testing device according to claim 1, characterized in that: The permeate sampling flow path includes a first pipe, and a first pressure gauge, a first flow meter and a first shut-off valve installed on the first pipe. A branch is installed at the inlet end of the first shut-off valve. The inlet end of the first pipe is connected to the outlet of the membrane module on the interception side, and the other end is connected to the outlet end of the concentrate sampling flow path.

3. The hollow fiber nanofiltration membrane retention performance testing device according to claim 2, characterized in that: The concentrate sampling flow path includes a second pipe and a second pressure gauge, a second flow meter, and a second shut-off valve arranged sequentially on the second pipe. A branch is located at the inlet end of the second shut-off valve. One end of the second pipe is connected to the permeate outlet of the membrane module, and the other end is connected to the first pipe and then to the first water tank.

4. The hollow fiber nanofiltration membrane retention performance testing device according to claim 3, characterized in that: A branch line includes a branch line pipe and a first valve. The branch line pipe is connected to the first or second pipe. The first valve is installed on the branch line pipe, and the online monitoring unit is installed at the outlet end of the first valve.

5. The hollow fiber nanofiltration membrane retention performance testing device according to claim 1, characterized in that: A third pressure gauge is installed between the centrifugal pump and the membrane module.

6. The hollow fiber nanofiltration membrane retention performance testing device according to claim 1, characterized in that: A temperature control device is installed between the centrifugal pump and the membrane module. The temperature control device includes a temperature sensor, a heat exchanger, and a PID controller. The heat exchanger is installed between the centrifugal pump and the membrane module. The temperature sensor is used to detect the temperature. The temperature sensor and the heat exchanger are connected to the PID controller.

7. The hollow fiber nanofiltration membrane retention performance testing device according to claim 1, characterized in that: The centrifugal pump inlet is connected to a four-way valve. The first and second water tanks are connected to the four-way valve. The four-way valve is also connected to a pure water pipeline. Ball valves are installed between the first and second water tanks and the four-way valve. A three-way valve is installed between the pure water pipeline and the four-way valve. The three-way valve is also connected to a drain pipe.

8. The hollow fiber nanofiltration membrane retention performance testing device according to claim 1, characterized in that: The concentrate sampling flow path also includes a product water proportioning valve, which is located on the outlet side of the second flow meter.

9. The hollow fiber nanofiltration membrane retention performance testing device according to claim 6, characterized in that: The heat exchanger is a plate heat exchanger.

10. A hollow fiber nanofiltration membrane retention performance testing device according to any one of claims 1-9, characterized in that: The online monitoring unit includes a conductivity meter, spectrophotometer, or mass spectrometer.

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