Dual flow direction synergistic reverse osmosis membrane detection process

Abstract

The application discloses a double-flow-direction cooperative reverse osmosis membrane detection process, which comprises the following steps: S1. membrane element installation; S2. bidirectional pulse type low-pressure pure water preflushing operation; S3. gradient pressure lifting adjustment; S4. working condition stabilizing; and S5. core performance detection. After forward flushing, reverse flushing is performed, reverse hydraulic impact is formed by relying on the reverse change of the fluid flow direction, the internal flow field distribution of the membrane element is changed, the flow inertia formed by the single flow direction water flow is broken, the diffusion rate of the solute molecules of the pure water after temperature rising can be accelerated, the fluid viscosity of the viscous protective liquid is reduced, the periodic hydraulic pulsation effect is formed by cooperating with the periodic pulse pressurization, the alternating shear force is generated by means of the transient pressure difference, the peeling effect of the fluid on the attachments on the inner wall of the gap is strengthened, the forced exchange of the media in the deep gap is realized by relying on the pulsating water flow, the overall preflushing time length is effectively compressed under the premise that the flushing cleanliness meets the standard, and the overall operation time of the reverse osmosis membrane complete set performance detection is effectively shortened.

Description

Technical Field

[0001] This invention belongs to the field of membrane performance testing technology, and particularly relates to a dual-flow synergistic reverse osmosis membrane testing process. Background Technology

[0002] As a core separation element in the water treatment field, reverse osmosis membranes are widely used in pure water preparation, seawater desalination, industrial wastewater treatment and many other fields due to their excellent screening and retention performance. Before leaving the factory, membrane elements must undergo standardized performance testing to accurately measure key indicators such as permeate flux, desalination rate and operating pressure difference, so as to determine whether the product quality meets the standards and ensure stable and consistent performance in actual use.

[0003] In the current reverse osmosis membrane element factory performance testing and offline retesting, the pre-rinsing process is a key preliminary process for removing the protective liquid inside the membrane and completing the hydration and wetting of the membrane. At present, the industry generally adopts a single forward ambient temperature constant pressure uniform speed rinsing method to carry out the operation, relying on extending the continuous rinsing time to improve the cleaning effect. This makes the entire pre-rinsing process time-consuming, which greatly prolongs the overall operation cycle of the entire membrane performance testing and is not conducive to the efficient carrying out of centralized testing of large batches of membrane elements. Summary of the Invention

[0004] To address the problems in the prior art, the present invention proposes the following technical solution: The dual-flow synergistic reverse osmosis membrane testing process includes the following steps: S1. Membrane element installation: Select membrane elements that are in good condition, without damage, delamination, or deformation, and install them into the test pressure vessel after verifying the water flow direction markings; S2. Bidirectional Pulsed Low-Pressure Pure Water Pre-rinsing Operation: First, pure water is introduced at a high flow rate for 4-7 minutes to purge air from the equipment pipelines and membrane elements. Then, a forward rinse is performed steadily for 5-8 minutes at a pressure of 0.2-0.3 MPa and a room temperature of 25°C to fully wet the membrane elements. Switch to the reverse rinsing channel, raise the water temperature to 30-35°C, and perform a reverse rinse for 3-5 minutes at a pressure of 0.15-0.2 MPa. During this process, the pressure is adjusted from the reference value to 0.25-0.30 MPa at a frequency of 20 seconds per cycle, and the water flow rate is increased simultaneously to carry out pulsed rinsing. Alternate forward and reverse rinsing multiple times until the conductivity of the product water is close to that of the pure water, thus removing residual protective fluid from the membrane. S3. Gradient pressure increase adjustment: Switch to the sodium chloride test solution pipeline and adopt a segmented gradient pressure increase adjustment method. Stabilize the pressure at 0.3MPa and 0.8MPa for 5 minutes respectively, and continue to stabilize the pressure for 10 minutes after reaching the standard test pressure. Control the pressure increase rate to not exceed 0.2MPa per minute throughout the process to keep the system operating pressure stable. S4. Stable operation: Prepare a standard test solution of sodium chloride with a concentration of 1500 mg / L, keep the water temperature constant at 25℃, adjust the pipeline flow rate to maintain the recovery rate, and run the system in a cycle for 30 minutes. After the pressure, flow rate and conductivity parameters have no fluctuation for 5 minutes, the test operation is considered to have reached a stable state. S5. Core Performance Testing: Under stable operating conditions, perform multiple performance tests, collect permeate data to calculate the permeate flux of the membrane element; collect feed water and permeate water samples, test conductivity or TDS values ​​and calculate desalination rate; read feed water pressure and concentrate pressure, calculate operating pressure difference and complete all data recording.

[0005] As a preferred embodiment of the above technical solution, it also includes S6. Post-treatment rinsing: After all performance testing is completed, the pressure is slowly released in stages at a rate not exceeding 0.1 MPa per minute to prevent damage to the membrane element; after the pressure is released, pure water is introduced and the membrane element and the entire test pipeline are rinsed at a low pressure of 0.2~0.3 MPa for 20 minutes to remove residual salt solution from the pipeline and membrane.

[0006] As a preferred embodiment of the above technical solution, the method further includes S7. Data judgment and archiving: integrating and organizing all measured process parameters and performance data, judging whether the product performance is qualified by referring to national standard testing standards and the nominal parameters of the membrane element; filling in the test record form in a standardized manner, marking various optimized process parameters, and uniformly organizing and archiving all test data to complete the entire test process.

[0007] As a preferred embodiment of the above technical solution, in step S2, the duration of a single pulse flush during backwashing is 5-8 seconds, after which the pressure returns to the reference pressure range of 0.15~0.2MPa for backwashing.

[0008] As a preferred embodiment of the above technical solution, in step S2, the number of cycles for forward and reverse rinsing is 2 to 3, and the reverse pulse rinsing is switched immediately after each round of forward rinsing is completed.

[0009] As a preferred embodiment of the above technical solution, in step S2, the difference between the conductivity of the produced water and the conductivity of the pure water is less than 5 μS / cm.

[0010] As a preferred embodiment of the above technical solution, in step S5, the timed collection period for permeable flow detection is not less than 10 minutes, the average value of three sets of water sample data is taken for desalination rate detection, and the average value is calculated after three synchronous recordings of operating pressure difference to accurately detect data.

[0011] The beneficial effects of this invention are as follows: 1. After forward rinsing, reverse rinsing is performed. Reverse rinsing is achieved by changing the direction of fluid flow to create a reverse hydraulic impact, which alters the internal flow field distribution of the membrane element, breaks the flow inertia formed by a single flow direction, and the heated pure water can accelerate the diffusion rate of solute molecules in the protective solution, reduce the viscosity of the viscous protective solution, and improve the compatibility and dissolution efficiency between the cleaning pure water and the protective solution. This allows poorly soluble and retained substances to be more easily removed with the water flow. Combined with periodic pulse pressurization, a periodic hydraulic pulsation effect is formed. The alternating shear force generated by the transient pressure difference is used to enhance the stripping effect of fluid on the inner wall of the gap. The forced exchange of media deep in the gap is achieved by relying on the pulsating water flow. Under the premise of not damaging the physical structure of the membrane substrate and the mechanical properties of the surface functional layer, the ability to remove deep dirt is enhanced. Under the premise of ensuring that the rinsing cleanliness meets the standards, the overall pre-rinsing time is effectively reduced, and the overall operation time of the entire reverse osmosis membrane performance test is effectively reduced. 2. Short-duration high-pressure pulse flushing is gentle and controllable, and will not cause long-term pressure and water flow impact damage to weak structures such as membranes and adhesive seals. At the same time, it effectively avoids the problems such as membrane deformation and loosening of adhesive layer that are easily caused by normal high-pressure flushing. The operation mode of short-term pressurization and intermittent return to the reference pressure can also create a pulsating turbulence effect in the water flow, enhance the medium exchange effect, further improve the efficiency of dirt removal, and achieve a deep cleaning effect. Attached Figure Description

[0012] Figure 1 The diagram shown is a process flow chart of an embodiment. Detailed Implementation

[0013] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments and the accompanying drawings.

[0014] Figure 1 The dual-flow synergistic reverse osmosis membrane testing process includes the following steps: S1. Membrane element installation: Select membrane elements that are in good condition, without damage, delamination, or deformation, and install them into the test pressure vessel after verifying the water flow direction markings.

[0015] S2. Bidirectional Pulse-Type Low-Pressure Pure Water Pre-rinsing Operation: First, pure water is introduced at a high flow rate for 4-7 minutes to purge air from the equipment pipelines and membrane elements; then, a forward rinse is performed steadily for 5-8 minutes at a pressure of 0.2-0.3 MPa and a normal temperature of 25°C to fully wet the membrane elements; switch to the reverse rinse channel, raise the water temperature to 30-35°C, and perform a reverse rinse for 3-5 minutes at a pressure of 0.15-0.2 MPa. During this process, the pressure is adjusted from the reference value to 0.2 MPa at a frequency of 20 seconds per cycle. Increase the water flow rate synchronously to 5~0.30MPa and carry out pulse flushing. The duration of a single pulse flush in reverse flushing is 5-8s, and then return to the reference pressure range of 0.15~0.2MPa for reverse flushing. Alternate forward and reverse flushing multiple times, with 2~3 cycles of forward and reverse flushing. Immediately switch to reverse pulse flushing after each round of forward flushing. The end standard is when the conductivity of the product water is close to that of the pure water. The difference between the conductivity of the product water and the conductivity of the pure water is less than 5μS / cm. Remove the residual protective fluid in the membrane.

[0016] High-pressure pulse flushing is gentle and controllable, and will not cause long-term pressure and water flow impact damage to weak structures such as membranes and adhesive seals. At the same time, it effectively avoids the problems such as membrane deformation and loosening of adhesive layer that are easily caused by normal high-pressure flushing. The operation mode of short-term pressurization and intermittent return to the reference pressure can also create a pulsating turbulence effect in the water flow, enhance the medium exchange effect, further improve the efficiency of dirt removal, and achieve a deep cleaning effect.

[0017] S3. Gradient pressure increase adjustment: Switch to the sodium chloride test solution pipeline and adopt a segmented gradient pressure increase adjustment method. Stabilize the pressure at 0.3MPa and 0.8MPa for 5 minutes respectively, and continue to stabilize the pressure for 10 minutes after reaching the standard test pressure. Control the pressure increase rate to not exceed 0.2MPa per minute throughout the process to keep the system operating pressure stable.

[0018] S4. Stable Operation: Prepare a standard test solution of sodium chloride with a concentration of 1500 mg / L, keep the water temperature constant at 25℃, adjust the pipeline flow rate to maintain a fixed recovery rate, and run the system in a cycle for 30 minutes. Once the pressure, flow rate, and conductivity parameters remain stable for 5 minutes, the test operation is considered to have reached a stable state.

[0019] S5. Core Performance Testing: Under stable operating conditions, perform multiple performance tests, collect permeate data to calculate the permeate flux of the membrane element; collect feed water and permeate water samples, test conductivity or TDS values ​​and calculate desalination rate; read feed water pressure and concentrate pressure, calculate operating pressure difference and complete all data recording.

[0020] The timed collection period for permeate flux detection is no less than 10 minutes. For desalination rate detection, three sets of water sample data are collected continuously and the average value is taken. The operating pressure difference is recorded synchronously three times and the average value is calculated to obtain accurate detection data.

[0021] It also includes S6. Post-treatment rinsing: After all performance testing is completed, slowly release the pressure in stages at a rate not exceeding 0.1 MPa per minute to prevent damage to the membrane element; after the pressure is released, pure water is introduced and the membrane element and the entire test pipeline are rinsed at a low pressure of 0.2~0.3 MPa for 20 minutes to remove residual salt solution in the pipeline and membrane. During this process, the forward and reverse rinsing methods in step S2 can be used to shorten the rinsing time.

[0022] The process also includes S7. Data Judgment and Archiving: Integrate and organize all measured process parameters and performance data, and determine whether the product performance is qualified by referring to national standard testing standards and the nominal parameters of the membrane element; fill in the test record form in a standardized manner, mark all optimized process parameters, organize and archive all test data in a unified manner, and complete the entire test process.

[0023] After forward rinsing, reverse rinsing is performed. This reverse flow creates a reverse hydraulic impact, altering the internal flow field distribution of the membrane element through fluid turbulence. This breaks the flow inertia caused by a single-direction water flow, prompting the protective fluid medium and solid impurities deep within the membrane structure's gaps to detach from the adhesion interface, significantly improving the overall cleanliness of the pre-rinse. Furthermore, during reverse rinsing, simultaneous heating and periodic pulsed pressurization are performed. The heated pure water accelerates the diffusion rate of solute molecules in the protective fluid, reduces the viscosity of the viscous protective fluid, and enhances the cleaning effect of the pure water on the protective fluid. The improved compatibility and solubility between the protective fluids allows poorly soluble and retained substances to be more easily removed by the water flow. Combined with periodic pulse pressurization, this creates a periodic hydraulic pulsation effect. The transient pressure difference generates alternating shear force, which enhances the stripping effect of the fluid on the inner wall of the gaps. The pulsating water flow enables forced exchange of media deep within the gaps. Without damaging the physical structure of the membrane substrate or the mechanical properties of the surface functional layer, it enhances the ability to remove deep-seated contaminants. While ensuring that the rinsing cleanliness meets the standards, it effectively reduces the overall pre-rinse time and the overall operation time for testing the entire reverse osmosis membrane performance.

[0024] Example 1

[0025] This embodiment uses the above-described dual-flow synergistic reverse osmosis membrane testing process to perform performance testing on the 8-inch commercial polyamide reverse osmosis membrane element under test. The specific operation steps are as follows: S1. Membrane element installation Qualified reverse osmosis membrane elements with intact appearance, no cracks, no delamination, and no extrusion deformation are manually selected. The flow direction markings of the inlet and concentrate ends of the membrane are confirmed to be correct. The membrane is then steadily and vertically installed into the matching test pressure vessel to complete the basic assembly and positioning.

[0026] S2. Two-way pulse-type low-pressure pure water pre-rinsing operation Turn on the pure water supply valve and let pure water flow in at a high flow rate for 5 minutes to completely purge the air accumulated inside the entire test pipeline and membrane element; adjust the pipeline pressure to 0.25MPa, maintain the water temperature at 25℃, and perform a forward and stable flush for 6 minutes to complete the full hydration and wetting of the membrane. Switch the pipeline to the backwash channel, raise the pure water temperature to 32℃, set the backwash reference pressure to 0.18MPa, and set the overall backwash duration to 4min. The pressure is periodically increased from 0.18MPa to 0.27MPa at a frequency of 20 seconds per pulse, while the water flow rate in the pipeline is increased simultaneously for pulse flushing. Each pulse lasts for 6 seconds, and the pressure immediately drops back to the reference pressure of 0.18MPa after the pulse ends. After completing one round of forward and reverse rinsing, another round of circulation is performed. The conductivity of the product water is monitored in real time throughout the process. When the difference between the conductivity of the product water and the conductivity of the pure water is less than 5 μS / cm, the low-pressure pre-rinsing process is terminated to thoroughly remove the glycerol protective solution and residual impurities from the membrane.

[0027] S3. Gradient pressure increase adjustment Shut down the pure water circuit and switch to the sodium chloride standard test solution pipeline; start the high-pressure pump to perform gradient pressure increase and adjustment, first stabilize the pressure at 0.3MPa for 5 minutes, then increase the pressure to 0.8MPa and stabilize for 5 minutes, and finally increase to the industry-standard test pressure of 1.5MPa and stabilize for 10 minutes. The pressure increase rate is strictly controlled at 0.15MPa / min throughout the process to ensure that the system pressure does not fluctuate or impact.

[0028] S4 stable operation A 1500 mg / L sodium chloride test solution was prepared using electronic precision weighing. The solution temperature was stabilized at 25°C using a constant temperature unit. The opening of the concentrate valve was adjusted to fix the system recovery rate at 18%. The test solution was circulated in the system for 30 minutes until the system operating pressure, pipeline flow rate, and inlet water conductivity remained stable for 5 consecutive minutes, indicating that the test conditions were completely stable.

[0029] S5 Core Performance Detection After the operating conditions stabilize, data collection begins. The permeate from the membrane element is collected continuously for 12 minutes. The actual permeate flux is calculated based on the effective filtration area of ​​the membrane. Samples are taken simultaneously at the inlet and outlet, and the values ​​are measured using a calibrated conductivity meter. The actual desalination rate of the membrane element is then calculated using the formula. The system inlet pressure and concentrate side pressure are read separately, and the operating pressure difference is calculated. Each set of parameters is recorded three times and the average value is taken to complete the recording of all performance data.

[0030] S6. Post-treatment rinsing After all tests are completed, the pressure is slowly released in stages at a rate of 0.08 MPa / min to avoid damage to the membrane structure from sudden pressure changes. After the pressure is released, room temperature pure water is introduced and flushed continuously at a low pressure of 0.25 MPa for 20 minutes to clean the membrane element flow channels and test pipelines of any residual salt solutes and to prevent salt scale from adhering and accumulating.

[0031] S7. Data Determination and Archiving The measured permeate flux, desalination rate, operating pressure difference, and process parameters such as pre-flush stage heating temperature, pulse pressure regulation frequency, and pressure range are summarized and compared with the GB / T 32373-2025 testing standard and the factory nominal parameters of the membrane element model to determine its performance compliance; the paper test record form is filled out truthfully and simultaneously entered into the electronic ledger to complete the classification and archiving, thus completing the entire testing process.

[0032] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it.

Claims

1. A dual-flow synergistic reverse osmosis membrane detection process, characterized in that, Includes the following steps: S1. Membrane element installation: Select membrane elements that are in good condition, without damage, delamination, or deformation, and install them into the test pressure vessel after verifying the water flow direction markings; S2. Bidirectional Pulsed Low-Pressure Pure Water Pre-rinsing Operation: First, pure water is introduced at a high flow rate for 4-7 minutes to purge air from the equipment pipelines and membrane elements. Then, a forward rinse is performed steadily for 5-8 minutes at a pressure of 0.2-0.3 MPa and a room temperature of 25°C to fully wet the membrane elements. Switch to the reverse rinsing channel, raise the water temperature to 30-35°C, and perform a reverse rinse for 3-5 minutes at a pressure of 0.15-0.2 MPa. During this process, the pressure is adjusted from the reference value to 0.25-0.30 MPa at a frequency of 20 seconds per cycle, and the water flow rate is increased simultaneously to carry out pulsed rinsing. Alternate forward and reverse rinsing multiple times until the conductivity of the product water is close to that of the pure water, thus removing residual protective fluid from the membrane. S3. Gradient pressure increase adjustment: Switch to the sodium chloride test solution pipeline and adopt a segmented gradient pressure increase adjustment method. Stabilize the pressure at 0.3MPa and 0.8MPa for 5 minutes respectively, and continue to stabilize the pressure for 10 minutes after reaching the standard test pressure. Control the pressure increase rate to not exceed 0.2MPa per minute throughout the process to keep the system operating pressure stable. S4. Stable Operation: Prepare a standard test solution of sodium chloride with a concentration of 1500 mg / L, keep the water temperature constant at 25℃, adjust the pipeline flow rate to maintain the recovery rate, and run the system in a cycle for 30 minutes. After the pressure, flow rate and conductivity parameters have no fluctuation for 5 minutes, the test operation is considered to have reached a stable state. S5. Core Performance Testing: Under stable operating conditions, perform multiple performance tests, collect permeate data to calculate the permeate flux of the membrane element; collect feed water and permeate water samples, test conductivity or TDS values ​​and calculate desalination rate; read feed water pressure and concentrate pressure, calculate operating pressure difference and complete all data recording.

2. The dual-flow synergistic reverse osmosis membrane detection process according to claim 1, characterized in that, It also includes S6. Post-treatment rinsing: After all performance testing is completed, the pressure is slowly released in stages at a rate not exceeding 0.1 MPa per minute to prevent damage to the membrane element; after the pressure is released, pure water is introduced and the membrane element and the entire test pipeline are rinsed at a low pressure of 0.2~0.3 MPa for 20 minutes to remove residual salt solution from the pipeline and membrane.

3. The dual-flow synergistic reverse osmosis membrane detection process according to claim 2, characterized in that, The process also includes S7. Data Judgment and Archiving: Integrate and organize all measured process parameters and performance data, and determine whether the product performance is qualified by referring to national standard testing standards and the nominal parameters of the membrane element; fill in the test record form in a standardized manner, mark all optimized process parameters, organize and archive all test data in a unified manner, and complete the entire test process.

4. The dual-flow synergistic reverse osmosis membrane detection process according to claim 1, characterized in that, In step S2, the duration of a single pulse flush during backwashing is 5-8 seconds, after which the pressure returns to the reference range of 0.15~0.2MPa for backwashing.

5. The dual-flow synergistic reverse osmosis membrane detection process according to claim 4, characterized in that, In step S2, the number of cycles for forward and reverse rinsing is 2 to 3, and the reverse pulse rinsing is switched immediately after each round of forward rinsing.

6. The dual-flow synergistic reverse osmosis membrane detection process according to claim 1, characterized in that, In step S2, the difference between the conductivity of the produced water and the conductivity of the pure water is less than 5 μS / cm.

7. The dual-flow synergistic reverse osmosis membrane detection process according to claim 1, characterized in that, In step S5, the timed collection period for permeate flux detection is no less than 10 minutes, the average value of three sets of water sample data is taken for desalination rate detection, and the average value is calculated after three synchronous recordings of operating pressure difference to accurately detect data.

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