A multi-stage membrane concentration system based on dual-mode and shunt resistance reduction

Abstract

The application relates to the technical field of membrane concentration, and particularly discloses a multi-stage membrane concentration system based on a double mode and a shunt resistance reduction. The system has a normal circulation concentration and a cleaning and discharge double mode, and is provided with a shunt channel in parallel. The system evaluates a circulation period lengthening trend through a stall monitoring module to determine a mass transfer instability risk period; a feedback judgment module uses a hysteresis geometric feature of a phase space running track to judge an irreversible concentration difference polarization critical state; a critical analysis module extracts a failure prediction node and determines a track correction strength; a flow path reconstruction module adjusts a flow section of the shunt channel based on the strength, strengthens a tangential shear force, and peels off a polarization layer solute, so that a cleaning and discharge mode is triggered; and a recovery evaluation module tracks a track convergence trend and a flux recovery rate to determine a reset node to switch back to the normal mode. The application is beneficial to blocking concentration difference polarization deterioration and improving the stability of system operation by identifying a mass transfer collapse critical point and dynamically adjusting a flow path.

Description

Technical Field

[0001] This invention relates to the field of membrane concentration technology, and specifically to a multi-stage membrane concentration system based on dual-mode and shunt drag reduction. Background Technology

[0002] In multi-stage membrane concentration processes, when handling high-concentration fluids or operating under varying load conditions, solutes undergo continuous convective migration to the membrane surface as the separation process progresses. When the migration rate far exceeds the reverse diffusion rate, the polarization layer concentration on the membrane surface rises rapidly, increasing the apparent osmotic pressure of the fluid and reducing the net driving force for permeation, as well as causing a continuous decline in permeate flux. This decrease in flux leads to a reduction in crossflow velocity, exacerbating polarization layer adhesion. When the polarization phenomenon exceeds the system's steady-state boundary, it disrupts the fluid mass transfer equilibrium, causing phase transition crystallization of the high-concentration solute on the membrane surface. The system loses its autonomous reflux capability, triggering irreversible mass transfer instability.

[0003] Existing membrane concentration systems rely on fixed operating cycles or static physical thresholds as triggering mechanisms for fouling and cleaning when addressing mass transfer instability. In actual operation, fluctuations in fluid temperature and dynamic viscosity can mask the true changes in membrane surface permeation resistance, making it difficult for static warning mechanisms to identify geometric variations in hydraulic hysteresis characteristics. Intervention is often only passively triggered after irreversible adhesion to the polarization layer. Furthermore, conventional systems lack the ability to dynamically reconfigure the flow cross-section during the cleaning phase, failing to enhance the tangential shear force on the membrane surface in the main flow channel by adjusting the diversion channels while maintaining the overall feed water dynamic balance.

[0004] Therefore, the present invention provides a multi-stage membrane concentration system based on dual-mode and shunt drag reduction. Summary of the Invention

[0005] The purpose of this invention is to provide a multi-stage membrane concentration system based on dual-mode and shunt resistance reduction to solve the aforementioned background problems.

[0006] The objective of this invention can be achieved through the following technical solutions: A multi-stage membrane concentration system based on dual-mode and shunt drag reduction includes the following modules: Stall monitoring module: used to collect data on the permeate flux and the liquid level change of the concentrate accumulator under variable load conditions, perform flux decay analysis to obtain the flux decay rate, evaluate the extension trend of the cycle based on the flux decay rate, and determine whether the system has entered the mass transfer instability risk period. Feedback Judgment Module: If the system enters the mass transfer instability risk period, the operating state parameters are extracted and the dynamic operating trajectory of the system is constructed in the two-dimensional phase plane; the hysteresis geometric features of the phase plane trajectory within the reflux cycle are extracted and it is determined whether the system has entered the irreversible concentration polarization critical state. Critical Analysis Module: If the concentration polarization critical state is triggered, the dynamic operating trajectory and the boundary layer update capability of the system are cross-compared to obtain the failure prediction node of the loss of membrane mass transfer function; and combined with the current operating state parameters, the trajectory correction intensity of the breakthrough mass transfer collapse is determined. Flow path reconstruction module: Based on trajectory correction intensity, the flow cross section of the diversion channel is dynamically adjusted to enhance the tangential shear force on the membrane surface and extract the amount of solute stripped from the membrane surface during the physical flushing process; the cleaning and drainage mode of the control system is based on the amount of solute stripped from the membrane surface.

[0007] As a further technical solution of the present invention, the method for determining whether the system has entered a period of mass transfer instability risk is as follows: Read the performance specifications of the membrane module and the hydraulic parameters of the booster pump and pipeline. Based on the performance specifications and hydraulic parameters, perform flux tolerance analysis to obtain the flux tolerance threshold of the system. Extract the cycle delay of the system; Based on the cycle delay and flux tolerance threshold, the current operating conditions are logically graded and marked to identify whether the system has entered the mass transfer instability risk period and to establish a stall risk early warning mechanism.

[0008] As a further technical solution of the present invention, the method for extracting the cycle delay is as follows: Obtain the height difference between the preset full-load liquid level and the current liquid level, as well as the inner bottom area of ​​the accumulator; Multiply the height difference by the inner bottom area to obtain the target remaining volume; Obtain the current actual volumetric flow rate of the concentrate, divide the target remaining volume by the current actual volumetric flow rate of the concentrate, and obtain the predicted remaining filling time. The actual volume flow rate of the concentrate flowing in real time is obtained by a flow sensor installed on the accumulator inlet line, and the consumed filling time is read at the same time. Synchronously retrieve the theoretical charging time of the system under the baseline state, sum the consumed charging time with the predicted remaining charging time, and obtain the predicted total charging time. The cycle delay is obtained by subtracting the actual predicted total charging time from the theoretical charging time.

[0009] As a further technical solution of the present invention, the method for determining whether the system has entered the concentration polarization critical state is as follows: Obtain the area of ​​the closed region enclosed by the trajectory within the current cycle, and monitor the coordinate slippage state of the trajectory endpoint relative to the starting point; The average area of ​​the closed region of the reference hysteresis loop and the coordinate position of the starting point of the closure are extracted during the initial stable operation of the system and used as a comparison baseline. If, within M consecutive cycles, the area of ​​the closed region shows a continuous expansion trend, and the projection component of the displacement vector of the trajectory endpoint relative to the starting point on the normalized flux axis is negative, then the system is determined to have entered an irreversible concentration polarization critical state.

[0010] As a further technical solution of the present invention, the method for generating the running trajectory is as follows: Obtain standardized flux and net driving pressure; Establish a two-dimensional phase plane coordinate system with standardized flux as the vertical axis and net driving pressure as the horizontal axis; Establish data pairs between the real-time net driving pressure and the standardized flux; The data pairs are continuously projected into a two-dimensional phase plane coordinate system, and the trajectory of the phase space is generated by fitting.

[0011] As a further technical solution of the present invention, the method for obtaining the failure prediction node is as follows: Retrieve the pre-stored collapse limit area threshold in the system control unit, subtract the area of ​​the closed region in the most recent cycle from the collapse limit area threshold, and obtain the remaining tolerance margin of the trajectory area. The expansion increment of the closed region area between two adjacent cycle periods is obtained and evolutionary divergence analysis is performed to obtain the evolutionary divergence rate; Divide the remaining tolerance margin of the trajectory area by the evolution divergence rate to calculate the remaining survival time of the system before it loses its mass transfer function. The absolute timestamp of the current calculation cycle is read through the internal clock of the system's main control unit. The remaining survival time is used as the time offset and superimposed with the current absolute timestamp to obtain the target time coordinates at which the system is expected to reach the collapse limit area threshold, and this is used as the failure prediction node.

[0012] As a further technical solution of the present invention, the method for performing evolutionary divergence analysis is as follows: The duration of a single cycle is obtained, and the expansion increment is divided by the duration of a single cycle to obtain the evolution divergence rate of the current phase space trajectory.

[0013] As a further technical solution of the present invention: recovery evaluation module: track the convergence trend of the phase space trajectory and the recovery rate of the standardized flux in the purge and discharge mode, perform mass transfer recovery evaluation to obtain the mass transfer recovery index; perform node reset analysis based on the mass transfer recovery index to determine the reset node when the system switches back to the normal circulation concentration mode.

[0014] As a further technical solution of the present invention, the method for conducting the mass transfer recovery assessment is as follows: During the continuous execution of the sweeping and drainage mode, the area of ​​the closed region enclosed by the phase space trajectory within the current recovery cycle is calculated in real time. Retrieve the average area of ​​the closed region of the reference hysteresis loop extracted during the initial stable operation of the system; The trajectory convergence coefficient is calculated by dividing the average area of ​​the closed region of the baseline hysteresis loop by the area of ​​the closed region in the current recovery cycle. At the same time, extract the standardized flux increase increment within the currently set evaluation time window; Divide the increase in standardized flux by the time span of the evaluation window to obtain the recovery rate of standardized flux. Extract the system's preset baseline flux recovery rate; normalize the standardized flux recovery rate by dividing it by the baseline flux recovery rate to obtain the flux recovery score; multiply the trajectory convergence coefficient and the flux recovery score to obtain the dimensionless mass transfer recovery index.

[0015] As a further technical solution of the present invention, the method for determining the reset node is as follows: The preset recovery threshold in the system control unit is retrieved, and the real-time calculated mass transfer recovery index is continuously compared with the recovery threshold. If the mass transfer recovery index is continuously rising and reaches or exceeds the recovery qualification threshold, and the phase space trajectory coordinates within the current recovery cycle are simultaneously monitored to physically close again, then the membrane surface mass transfer performance is determined to be restored to within the safe operating boundary. The system's main control unit establishes the current absolute time coordinate that meets the judgment conditions as the reset node.

[0016] The beneficial effects of this invention are as follows: 1. By synchronously acquiring multi-stage permeate flow rate sequences and accumulator level height sequences, the system's operational trends under varying load conditions are identified. Using the residual between the collapse limit area threshold and the current trajectory area, combined with the divergence rate, the remaining survival time is calculated and marked as a failure prediction node, establishing a link between system lifespan loss and operating conditions. By calculating the collapse urgency index, the urgency of the time window is correlated with the system's self-rescue potential from excess flushing flow, which facilitates the graded matching of trajectory correction intensity output based on the degree of loss of membrane mass transfer function. Dynamic allocation of intervention resources enables subsequent flow path reconfiguration actions to adjust physical intensity according to risk level, delaying the process of membrane module performance entering the degradation phase.

[0017] 2. Based on the dynamic driving ratio adjustment of the flow diversion channel driven by trajectory correction intensity, the fluid is forced to flow into the main concentration channel by increasing the liquid resistance of the branch, thereby increasing the tangential shear force on the membrane surface while maintaining the overall feed water balance. By obtaining the total amount of solute stripping, a one-time replacement of the high salinity fluid is performed through the drain pipe, realizing the physical renewal of the liquid inside the system, and reducing the salinity accumulation that hinders the production water from the perspective of mass balance.

[0018] 3. By utilizing the convergence trend of the phase space trajectory and the recovery rate of standardized flux, a system mass transfer recovery index was constructed to achieve closed-loop verification of membrane repair effectiveness. By calculating the trajectory convergence coefficient and monitoring the geometric regression state of the operating trajectory to the baseline hysteresis loop, the evaluation mechanism combines the static resistance recovery space with the dynamic flux recovery acceleration to assess the degree of membrane surface functional repair. Determining the reset node facilitates ensuring that the system switches from the purge and discharge mode back to the normal circulation concentration mode within the steady-state boundary of mass transfer performance. This reset decision, based on the trajectory self-convergence characteristics, reduces the risk of secondary polarization due to incomplete flushing and shortens non-productive operating time, improving the overall water production efficiency and logical stability of cross-mode switching in the long-term operation of the multi-stage concentration process. Attached Figure Description

[0019] The invention will now be further described with reference to the accompanying drawings.

[0020] Figure 1 This is a functional block diagram of a multi-stage membrane concentration system based on dual-mode and shunt drag reduction according to the present invention; Figure 2 This is a flowchart of the logical hierarchical marking of the currently monitored operating conditions in this invention; Figure 3 This is a flowchart of a multi-stage membrane concentration method based on dual-mode and shunt drag reduction in this invention. Detailed Implementation

[0021] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below in conjunction with specific embodiments.

[0022] Example 1: A multi-stage membrane concentration system based on dual-mode and shunt resistance reduction, the system has a normal circulation concentration mode and a purge discharge mode that can be switched between each other, and a shunt channel is configured in parallel in the system pipeline; In normal circulation concentration mode, the diversion channel is in a preset opening state to divert part of the inlet water to reduce the overall fluid pressure drop in the main channel of the membrane module, thereby achieving diversion and resistance reduction and system energy saving. When the system triggers an irreversible concentration polarization critical state, the system switches from normal circulation concentration mode to purge and discharge mode, dynamically shrinking the diversion channel to increase the main flow velocity and performing forced sewage replacement. like Figure 1 As shown, the system includes the following modules: Stall monitoring module: used to collect data on permeate flux and concentrate accumulator level changes under variable load conditions, perform flux decay analysis to obtain flux decay rate, assess the extension trend of cycle period based on flux decay rate, and determine whether the system has entered the mass transfer instability risk period. The method for collecting data on permeate flux and concentrate accumulator level changes under variable load conditions, and then performing flux decay analysis to obtain the flux decay rate, is as follows: In some embodiments, flow sensors installed on each level of the product water pipeline are used to obtain the product water volume flow rate sequence under variable load conditions in real time. At the same time, the liquid level height sequence of the storage tank during the pressure accumulation process is synchronously collected by the liquid level transmitter installed inside the low-pressure accumulator. From the product water volumetric flow rate sequence, the decrease variable of flow rate within a unit time window is extracted and divided by the time interval to obtain the current flux decay rate; The method for assessing the trend of increasing cycle length is as follows: Obtain baseline cycle parameters for a multi-stage membrane system at rated feed concentration and standard pressure; It should be noted that the reference cycle period parameter refers to the theoretical charging time required for the low-pressure accumulator to reach the preset full-load liquid level that triggers the reflux pipeline to open from the emptied state. The calibration basis of the preset full-load liquid level is: based on the physical geometric dimensions of the low-pressure accumulator, the absolute elevation of the reflux overflow port is extracted, and the buffer dead zone height reserved by the system pipeline to cope with the water hammer effect is deducted. It is used to ensure sufficient physical safety margin for the system pressure building and depressurization process. Extract the current liquid level from the liquid level height sequence, read the consumed charging time from the system, and obtain the real-time actual volume flow rate of the concentrate flowing in through the flow sensor installed on the accumulator inlet pipe; Calculate the height difference between the preset full-load liquid level and the current liquid level, and multiply the height difference by the inner bottom area of ​​the accumulator to obtain the target remaining volume; Divide the target remaining volume by the current actual volumetric flow rate of the concentrate to obtain the predicted remaining filling time; The total predicted charging time is obtained by summing the consumed charging time with the predicted remaining charging time. The difference between the actual predicted total filling time and the theoretical filling time is processed to obtain the cycle delay, which is used to characterize the extension trend of the return cycle. The method for determining whether the system has entered a period of mass transfer instability risk is as follows: S101. Read the performance specifications of the membrane module and the hydraulic parameters of the booster pump and pipeline. Based on the performance specifications and hydraulic parameters, perform flux tolerance analysis to obtain the system's flux tolerance threshold. Preferably, the method for performing flux tolerance analysis is as follows: The flow rate required to maintain the minimum surface crossflow velocity is extracted from the membrane module parameters and used as the minimum flow rate of the first concentrate. Obtain the minimum pressure required to overcome the resistance of the reflux pipeline and the resistance coefficient. Based on the principle that pressure is proportional to the square of flow rate, calculate the minimum flow rate of the second concentrate to meet the pressure build-up requirements. The maximum value between the minimum flow rate of the first concentrate and the minimum flow rate of the second concentrate is selected as the critical concentrate flow rate of the system. The instantaneous influent volumetric flow rate is obtained by a flow sensor, and the critical concentrate flow rate is subtracted, then divided by the total membrane area of ​​the system, and finally multiplied by a preset safety margin factor to obtain the flux tolerance threshold. For example, the safety margin factor is preset in the following way: based on the current number of operating hours of the membrane module, the corresponding performance degradation ratio is extracted as the safety margin factor by referring to the flux degradation curve in the membrane module specification. S102. Based on the cycle delay and flux tolerance threshold, the current monitored operating conditions are logically graded and labeled to identify whether the system has entered a period of mass transfer instability risk and to establish a stall risk early warning mechanism: Preferred, such as Figure 2 As shown, the logical hierarchical marking process is as follows: obtain the standard deviation of the charging time of the system for N consecutive complete cycles under standard operating conditions, and set three times the standard deviation as the time fluctuation margin. If the cycle delay is less than or equal to the time fluctuation margin, and the flux decay rate is within the preset smooth range, the system is determined to be in a stable operating state. If the cycle delay is less than or equal to the time fluctuation margin, but the flux decay rate exceeds the preset smooth range, the system is determined to be in a latent decay warning state. If the cycle delay is greater than the time fluctuation margin, but the current instantaneous water production flux is still greater than the flux tolerance threshold, the system is determined to be in a state of mild sluggishness. If the cycle delay is greater than the time fluctuation margin, and the current instantaneous permeable flux is less than or equal to the flux tolerance threshold, the system is determined to have entered the mass transfer instability risk period. If it is determined that the system is in a period of mass transfer instability risk, the system generates an activation command to start the feedback judgment module. The feedback judgment module further extracts the hysteresis geometric features of the phase plane trajectory within the reflux cycle to determine whether the irreversible critical state of the surface mass transfer structure is triggered. It should be noted that the predetermined smooth interval is defined as follows: during the initial stable operation phase after pure water commissioning or deep chemical cleaning, the natural flux decay rate caused by the inherent pressure drop of the system is extracted over several consecutive reference cycles; the statistical average of the natural flux decay rate is multiplied by a predetermined tolerance coefficient (e.g., 1.1 to 1.2, preferably 1.15) to calculate the upper limit critical value of the smooth interval, while the lower limit critical value is zero. When the measured flux decay rate falls into the corresponding interval, it indicates that the current slight decrease in the system flux falls within the allowable normal hydraulic fluctuations or the reversible initial deposition range of the polarization layer.

[0023] Feedback Judgment Module: If the system enters the mass transfer instability risk period, the operating state parameters are extracted and the dynamic operating trajectory of the system is constructed in the two-dimensional phase plane; the hysteresis geometric features of the phase plane trajectory within the reflux cycle are extracted and it is determined whether the system has entered the irreversible concentration polarization critical state. If the system enters a period of mass transfer instability risk, the method for extracting operating state parameters and constructing the system's dynamic operating trajectory in a two-dimensional phase plane is as follows: The system synchronously acquires the instantaneous operating temperature of the fluid through a temperature sensor installed on the main inlet pipe, and acquires the instantaneous measured flow rate through a flow sensor installed on the product water pipeline; Based on the preset correction relationship between fluid viscosity and temperature, the current instantaneous measured flux is uniformly mathematically converted into the equivalent permeable flux at the reference temperature, which is defined as the standardized flux, to reduce the interference of temperature fluctuations on the permeability performance assessment. The apparent salinity of the feed water and the apparent salinity of the product water are collected in real time by online water quality sensors (such as conductivity meters or salinity meters) configured on the feed water main and product water pipelines of the membrane module, respectively. The apparent salinity difference across the membrane is calculated by subtracting the apparent salinity of the product water from the apparent salinity of the influent. The pressure difference between the inlet and outlet water on both sides of the membrane module is acquired synchronously. Combined with the fluid operating temperature, the apparent salinity difference is converted into apparent osmotic pressure difference by calling the existing van der Hoff osmotic pressure formula. Instantaneous measured flux, fluid operating temperature, pressure difference between inlet and outlet water of the membrane module, and apparent salinity difference are used as operating parameters; Subtract the apparent osmotic pressure difference from the inlet and outlet water pressure difference to obtain the net driving pressure; Establish a two-dimensional phase plane coordinate system with standardized flux as the vertical axis and net driving pressure as the horizontal axis; During each reflux cycle of system operation, the real-time net driving pressure and standardized flux are used to establish a data pair. The data pairs are continuously projected into a two-dimensional phase plane coordinate system, and the trajectory of the phase space within a single cycle is generated by fitting. It should be noted that, due to the inherent hydraulic response hysteresis and solute diffusion time difference in the pressurization and depressurization process of the membrane system, under stable operating conditions, the operating trajectory of a single cycle is closed at both ends in the phase plane, forming a reference hysteresis loop with a stable internal mapping area. The method for determining whether the system has entered an irreversible concentration polarization critical state by extracting the hysteresis geometric features of the phase plane trajectory within the reflux cycle is as follows: The area of ​​the closed region enclosed by the trajectory, the coordinates of the starting point of the trajectory, and the displacement vector of the ending point of the trajectory relative to the starting point are used as hysteresis geometric features. Calculate the area of ​​the closed region enclosed by the trajectory within the current cycle in real time, and monitor the coordinate slippage of the trajectory endpoint relative to the starting point; The average area of ​​the closed region of the reference hysteresis loop and the coordinate position of the starting point of the closure are extracted during the initial stable operation of the system and used as the comparison baseline for subsequent judgments. It should be noted that the average area of ​​the closed region of the benchmark hysteresis loop and the coordinate position of the starting point of the closure are obtained as follows: In the initial stage of stable water production after the system is first put into operation or after deep chemical cleaning, the main control unit of the system starts a self-learning program to continuously collect the phase plane running trajectory for N standard reflux cycle cycles (e.g., N=30); after removing abnormal trajectories that deviate from the normal distribution, the geometric area of ​​the remaining trajectory and the starting point coordinates are calculated by arithmetic mean. This is used as a personalized comparison baseline to characterize the membrane module in a pure and healthy state. If, within M consecutive cycles, the area of ​​the closed region shows a continuous expansion trend, and the projection component of the displacement vector of the trajectory endpoint relative to the starting point on the normalized flux axis is negative; Among them, the trajectory feature indicates that the standardized flux value at the end of a single cycle is lower than the value at the beginning of the cycle, indicating that the system has entered an irreversible concentration polarization critical state. Preferably, M=20.

[0024] Example 2: Please refer to Figure 1 As shown, a multi-stage membrane concentration system based on dual-mode and shunt drag reduction also includes the following modules: Critical Analysis Module: If the concentration polarization critical state is triggered, the dynamic operating trajectory and the boundary layer update capability of the system are cross-compared to obtain the failure prediction node of the loss of membrane mass transfer function; and combined with the current operating state parameters, the trajectory correction intensity of the breakthrough mass transfer collapse is determined. If the concentration polarization critical state is triggered, the dynamic trajectory and the system's boundary layer update capability are cross-compared to obtain the failure prediction node for the loss of membrane mass transfer function. The implementation method is as follows: The system extracts the area sequence of the closed region enclosed by the phase space trajectory within M consecutive reflux cycles; The expansion increment of the closed region area between two adjacent cycle periods is calculated, and the expansion increment is divided by the duration of a single cycle period to obtain the evolution divergence rate of the current phase space trajectory, which is used to characterize the dynamic acceleration of the thickness of the polarization layer on the film surface. Synchronously read the maximum safe crossflow rate allowed in the membrane module specifications and obtain the current instantaneous measured flux; Subtract the current instantaneous concentrated liquid volume flow rate from the maximum safe crossflow flow rate to obtain the surplus flushing flow rate that the system can currently call upon. It should be noted that the excess flushing flow characterization system removes the physical margin of the polarization layer by increasing the flow velocity, which represents the boundary layer renewal capability of the system. Retrieve the pre-stored collapse limit area threshold in the system control unit, subtract the area of ​​the closed region in the most recent cycle from the collapse limit area threshold, and obtain the remaining tolerance margin of the trajectory area. It should be noted that the collapse limit area threshold in the system is set based on the following: extracting the maximum withstand pressure drop parameter of the membrane surface provided in the membrane module manufacturer's specification sheet, and combining it with the saturated crystallization concentration of the target treated fluid, and calculating the critical area of ​​the phase trajectory just before irreversible flow channel fouling occurs, which is used as the collapse limit area threshold of this type of membrane module under the current operating conditions. Divide the remaining tolerance margin of the trajectory area by the evolution divergence rate to calculate the remaining survival time of the system before it loses its mass transfer function. The absolute timestamp of the current calculation cycle is read through the internal clock of the system's main control unit. The remaining survival time is used as the time offset and superimposed with the current absolute timestamp to obtain the target time coordinate of the system's expected collapse limit area threshold. Use the target time coordinate as the failure prediction node; The method for determining the trajectory correction intensity to overcome mass transfer collapse, based on the current operating parameters, is as follows: After obtaining the failure prediction node, extract the time difference between the failure prediction node and the current actual running time; The time difference and excess flushing flow rate are used as two-dimensional input parameters and input into the intervention intensity fuzzy control matrix built into the system control unit. Based on the built-in optimization rules of the intervention intensity fuzzy control matrix, the corresponding trajectory correction intensity is output. It should be noted that the intervention intensity fuzzy control matrix follows the following response logic: when the time difference is large and the excess flushing flow representing the boundary layer update capability is sufficient, a lower trajectory correction intensity is output; when the time difference is extremely small, or the excess flushing flow falls below the system maintenance limit, the highest trajectory correction intensity is output, thereby achieving the matching of intervention intensity under different levels of urgency.

[0025] Flow path reconstruction module: Based on trajectory correction intensity, dynamically adjust the flow cross section of the diversion channel to enhance the tangential shear force on the membrane surface and extract the amount of solute stripped from the membrane surface during the physical flushing process; based on the amount of solute stripped from the membrane surface, dynamically control the cleaning and drainage mode of the system. The method of dynamically adjusting the flow cross-section of the diversion channel based on trajectory correction intensity to enhance the tangential shear force on the membrane surface and extracting the amount of solute stripped from the membrane surface during physical rinsing is as follows: Retrieve the pre-built mapping relationship between intervention intensity and channel resistance, and generate the corresponding valve adjustment command based on the current trajectory correction intensity; The valve adjustment command is sent to the electric proportional control valve installed on the diversion channel. By reducing the opening angle of the electric proportional control valve, the actual flow cross-section of the diversion channel is physically reduced, thereby increasing the liquid resistance of the diversion branch. It should be noted that, under the condition that the total influent flow rate of the system is kept in dynamic equilibrium, the increase in the liquid resistance of the branch flow path forces a larger proportion of the fluid to flow into the main concentration channel of the membrane module, thereby multiplying the tangential flow velocity on the membrane surface to maximize the physical tangential shear force of the fluid on the polarization layer of the membrane surface. During the physical flushing process that enhances tangential shear force, the system synchronously and continuously collects the initial apparent salinity of the flushing fluid at the inlet of the membrane module and the apparent salinity carrying salt at the outlet of the concentrate. Subtracting the initial apparent salinity of the rinsing fluid from the apparent salinity of the salt-carrying fluid yields the instantaneous concentration increment caused by polarization layer stripping. Real-time flushing volume flow rate is obtained by a flow sensor installed at the end of the concentration channel; The instantaneous solute stripping mass rate per unit time is obtained by multiplying the instantaneous concentration increment with the flushing volume flow rate. Within the duration window of the physical rinsing action, the instantaneous solute stripping mass rate is discretely accumulated and summed with a fixed calculation step size to obtain the total cumulative amount of solute stripping from the membrane surface during the entire physical rinsing process. The cleaning and venting mode based on the dynamic control system for solute stripping on the membrane surface is as follows: Extract the preset cleaning and sewage discharge target threshold and the stripping stagnation and decay baseline within the system control unit; The cumulative total amount of solute stripped from the membrane surface calculated in real time is compared with the target threshold for clean discharge in real time, and the decay trend of the instantaneous solute stripping mass rate is monitored simultaneously. If the total amount of solute stripped from the membrane surface is detected to be higher than or equal to the target threshold for clean discharge, or if the instantaneous solute stripping mass rate is detected to be continuously decreasing and below the stripping stagnation and decay baseline, then it is determined that the high concentration of polarization layer on the membrane surface has been stripped and is suspended inside the system pipeline. It should be noted that the clean discharge target threshold is obtained by mass balance calculation based on the total mass of solute retained by the system in a single concentration cycle, combined with the preset clean recovery target percentage (e.g., 85% to 90%); the stripping stagnation attenuation baseline is set at 5% to 8% of the peak instantaneous solute stripping mass rate monitored at the beginning of physical flushing, which is used to characterize the hydraulic inflection point where the membrane polarization layer has been basically stripped away and there is no obvious desalination benefit from continued energy-consuming flushing; The system's main control unit then generates a mode switching command, triggering the cleaning and draining mode in the dual-mode system; It should be noted that the mode switching command is used to control the valve array on the system pipeline, forcibly lock the circulation backflow path of the concentrate inside the system, and simultaneously open the discharge pipeline leading to the external drain or energy recovery unit. The high-salinity fluid rich in stripping solutes is replaced and discharged from the main body of the system in one go through the drain pipe, thus completing the renewal of the internal liquid of the system.

[0026] Example 3: Please refer to Figure 1 As shown, a multi-stage membrane concentration system based on dual-mode and shunt drag reduction also includes the following modules: Recovery assessment module: Tracks the convergence trend of the phase space trajectory and the recovery rate of the standardized flux within the purge and discharge mode, performs mass transfer recovery assessment to obtain the mass transfer recovery index; performs node reset analysis based on the mass transfer recovery index to determine the reset node for the system to switch back to the normal circulation concentration mode; The method for obtaining the mass transfer recovery index by tracking the convergence trend of the phase space trajectory and the recovery rate of the standardized flux within the purge discharge mode is as follows: During the continuous execution of the purging and drainage mode, the system main control unit continuously and synchronously acquires the instantaneous measured flux and instantaneous operating temperature of the fluid; Based on the pre-defined correction relationship between fluid viscosity and temperature, the instantaneous measured flux is mathematically converted into the equivalent permeable flux at the reference temperature to obtain the standardized flux used to assess the recovery state. The inlet and outlet water pressure difference of the membrane module and the apparent osmotic pressure difference calculated based on the apparent salinity difference are acquired simultaneously. The apparent osmotic pressure difference is subtracted from the inlet and outlet water pressure difference to obtain the real-time net driving pressure. During the continuous execution of the sweeping and discharge mode, the system main control unit periodically opens and closes the control valve on the discharge pipeline at a preset pulse frequency to construct a short-term diagnostic hydraulic circulation cycle for performance verification. The real-time net driving pressure and standardized flux are paired and continuously projected into a two-dimensional phase plane coordinate system to generate the phase space trajectory within a single diagnostic cycle in real time. Calculate in real time the area of ​​the closed region enclosed by the phase space trajectory within the current diagnostic loop; Retrieve the average area of ​​the closed region of the reference hysteresis loop extracted during the initial stable operation of the system; The average area of ​​the closed region of the benchmark hysteresis loop is divided by the area of ​​the closed region in the current recovery cycle to calculate the trajectory convergence coefficient, which characterizes the phase space trajectory as it approaches a healthy state. At the same time, extract the standardized flux increase increment within the currently set evaluation time window; Divide the increase in standardized flux by the time span of the evaluation window to obtain the recovery rate of standardized flux. Extract the system's preset baseline flux recovery rate; normalize the standardized flux recovery rate by dividing it by the baseline flux recovery rate to obtain the flux recovery score; multiply the trajectory convergence coefficient with the flux recovery score to obtain the dimensionless mass transfer recovery index. It should be noted that the baseline flux recovery rate refers to the maximum flux increase rate obtained by testing a brand-new membrane module of the same model under standard purge and discharge conditions, which is recorded as the theoretical optimal solution in the control unit; the recovery qualification threshold is a dimensionless control constant, usually set between 0.85 and 0.95, which indicates that the current comprehensive mass transfer performance of the system has recovered to 85% to 95% of the brand-new ideal state, proving that the system has the conditions to safely restart the normal concentration mode; Among them, the method for determining the reset node to switch the system back to normal circulation concentration mode based on node reset analysis using the mass transfer recovery index is as follows: Retrieve the preset recovery qualification threshold in the system control unit; The mass transfer recovery index calculated in real time is continuously compared with the recovery qualification threshold. If the mass transfer recovery index is continuously rising and reaches or exceeds the recovery qualification threshold, and the phase space trajectory coordinates within the current recovery cycle are simultaneously monitored to physically close again, i.e. the trajectory endpoint coincides with the trajectory starting point; Then it is determined that the high concentration of polarization layer on the membrane surface has been removed and the mass transfer performance of the membrane surface has been restored to within the safe operating boundary; The system's main control unit establishes the current absolute time coordinate that meets the judgment conditions as the reset node; Based on the reset node, the system main control unit immediately generates a mode reset command; It should be noted that the mode reset command is used to drive the valve actuator on the system pipeline, forcibly lock the drain pipeline pointing to the external drain outlet, and reconnect the diversion channel and the circulation return path of the concentrate in the system, thereby controlling the system to smoothly switch back from the cleaning drain mode to the normal circulation concentration mode.

[0027] Example 4: Please refer to Figure 3 As shown, a multi-stage membrane concentration method based on dual-mode and shunt drag reduction includes the following steps: S10. Collect data on the permeate flux and the liquid level change of the concentrate accumulator under variable load conditions, perform flux decay analysis to obtain the flux decay rate, and based on the flux decay rate, assess the trend of the cycle extension and determine whether the system has entered the mass transfer instability risk period. S20. If the system enters the period of mass transfer instability risk, extract the operating state parameters and construct the dynamic operating trajectory of the system in the two-dimensional phase plane; extract the hysteresis geometric features of the phase plane trajectory within the reflux cycle, and determine whether the system has entered the irreversible concentration polarization critical state. S30. If the concentration polarization critical state is triggered, the dynamic running trajectory and the boundary layer update capability of the system are cross-compared to obtain the failure prediction node of the loss of membrane mass transfer function; and combined with the current running state parameters, the trajectory correction intensity of the breakthrough mass transfer collapse is determined. S40. The flow cross-section of the diversion channel is dynamically adjusted based on the trajectory correction intensity to enhance the tangential shear force on the membrane surface and extract the amount of solute stripped from the membrane surface during the physical flushing process; the cleaning and venting mode is based on the dynamic control system of the amount of solute stripped from the membrane surface. S50. Track the convergence trend of the phase space trajectory and the recovery rate of the standardized flux within the sweeping and venting mode, and conduct a mass transfer recovery assessment to obtain the mass transfer recovery index; based on the mass transfer recovery index, perform node reset analysis to determine the reset node for the system to switch back to the normal circulation concentration mode.

[0028] The foregoing has provided a detailed description of one embodiment of the present invention, but this description is merely a preferred embodiment and should not be construed as limiting the scope of the invention. All equivalent variations and modifications made within the scope of the present invention should still fall within the scope of the present invention.

Claims

1. A multi-stage membrane concentration system based on dual-mode and shunt drag reduction, characterized in that, Includes the following modules: Stall monitoring module: used to collect data on the permeate flux and the liquid level change of the concentrate accumulator under variable load conditions, perform flux decay analysis to obtain the flux decay rate, evaluate the extension trend of the cycle based on the flux decay rate, and determine whether the system has entered the mass transfer instability risk period. Feedback Judgment Module: If the system enters the mass transfer instability risk period, the operating state parameters are extracted and the dynamic operating trajectory of the system is constructed in the two-dimensional phase plane; the hysteresis geometric features of the phase plane trajectory within the reflux cycle are extracted and it is determined whether the system has entered the irreversible concentration polarization critical state. Critical Analysis Module: If the concentration polarization critical state is triggered, the dynamic operating trajectory and the boundary layer update capability of the system are cross-compared to obtain the failure prediction node of the loss of membrane mass transfer function; and combined with the current operating state parameters, the trajectory correction intensity of the breakthrough mass transfer collapse is determined. Flow path reconstruction module: Based on trajectory correction intensity, the flow cross section of the diversion channel is dynamically adjusted to enhance the tangential shear force on the membrane surface and extract the amount of solute stripped from the membrane surface during the physical flushing process; the cleaning and drainage mode of the control system is based on the amount of solute stripped from the membrane surface.

2. The multi-stage membrane concentration system based on dual-mode and shunt drag reduction according to claim 1, characterized in that: The method to determine whether the system has entered the period of mass transfer instability risk is as follows: Read the performance specifications of the membrane module and the hydraulic parameters of the booster pump and pipeline. Based on the performance specifications and hydraulic parameters, perform flux tolerance analysis to obtain the flux tolerance threshold of the system. Extract the cycle delay of the system; Based on the cycle delay and flux tolerance threshold, the current operating conditions are logically graded and marked to identify whether the system has entered the mass transfer instability risk period and to establish a stall risk early warning mechanism.

3. A multi-stage membrane concentration system based on dual-mode and shunt drag reduction according to claim 2, characterized in that: The method for extracting the cycle delay is as follows: Obtain the height difference between the preset full-load liquid level and the current liquid level, as well as the inner bottom area of ​​the accumulator; Multiply the height difference by the inner bottom area to obtain the target remaining volume; Obtain the current actual volumetric flow rate of the concentrate, divide the target remaining volume by the current actual volumetric flow rate of the concentrate, and obtain the predicted remaining filling time. The actual volume flow rate of the concentrate flowing in real time is obtained by a flow sensor installed on the accumulator inlet line, and the consumed filling time is read at the same time. Synchronously retrieve the theoretical charging time of the system under the baseline state, sum the consumed charging time with the predicted remaining charging time, and obtain the predicted total charging time. The cycle delay is obtained by subtracting the actual predicted total charging time from the theoretical charging time.

4. A multi-stage membrane concentration system based on dual-mode and shunt drag reduction according to claim 1, characterized in that: The method for determining whether a system has entered the concentration polarization critical state is as follows: Obtain the area of ​​the closed region enclosed by the trajectory within the current cycle, and monitor the coordinate slippage state of the trajectory endpoint relative to the starting point; The average area of ​​the closed region of the reference hysteresis loop and the coordinate position of the starting point of the closure are extracted during the initial stable operation of the system and used as a comparison baseline. If, within M consecutive cycles, the area of ​​the closed region shows a continuous expansion trend, and the projection component of the displacement vector of the trajectory endpoint relative to the starting point on the normalized flux axis is negative, then the system is determined to have entered an irreversible concentration polarization critical state.

5. A multi-stage membrane concentration system based on dual-mode and shunt drag reduction according to claim 4, characterized in that: The method for generating the running trajectory is as follows: Obtain standardized flux and net driving pressure; Establish a two-dimensional phase plane coordinate system with standardized flux as the vertical axis and net driving pressure as the horizontal axis; Establish data pairs between the real-time net driving pressure and the standardized flux; The data pairs are continuously projected into a two-dimensional phase plane coordinate system, and the trajectory of the phase space is generated by fitting.

6. A multi-stage membrane concentration system based on dual-mode and shunt drag reduction according to claim 1, characterized in that: The method for obtaining the failure prediction node is as follows: Retrieve the pre-stored collapse limit area threshold in the system control unit, subtract the area of ​​the closed region in the most recent cycle from the collapse limit area threshold, and obtain the remaining tolerance margin of the trajectory area. The expansion increment of the closed region area between two adjacent cycle periods is obtained and evolutionary divergence analysis is performed to obtain the evolutionary divergence rate; Divide the remaining tolerance margin of the trajectory area by the evolution divergence rate to calculate the remaining survival time of the system before it loses its mass transfer function. The absolute timestamp of the current calculation cycle is read through the internal clock of the system's main control unit. The remaining survival time is used as the time offset and superimposed with the current absolute timestamp to obtain the target time coordinates at which the system is expected to reach the collapse limit area threshold, and this is used as the failure prediction node.

7. A multi-stage membrane concentration system based on dual-mode and shunt drag reduction according to claim 6, characterized in that: The method for performing evolutionary divergence analysis is as follows: The duration of a single cycle is obtained, and the expansion increment is divided by the duration of a single cycle to obtain the evolution divergence rate of the current phase space trajectory.

8. A multi-stage membrane concentration system based on dual-mode and shunt drag reduction according to claim 1, characterized in that: Recovery assessment module: Track the convergence trend of the phase space trajectory and the recovery rate of the standardized flux within the purge and discharge mode, perform mass transfer recovery assessment to obtain the mass transfer recovery index; based on the mass transfer recovery index, perform node reset analysis to determine the reset node for the system to switch back to the normal circulation concentration mode.

9. A multi-stage membrane concentration system based on dual-mode and shunt drag reduction according to claim 8, characterized in that: The method for conducting the mass transfer recovery assessment is as follows: During the continuous execution of the sweeping and drainage mode, the area of ​​the closed region enclosed by the phase space trajectory within the current recovery cycle is calculated in real time. Retrieve the average area of ​​the closed region of the reference hysteresis loop extracted during the initial stable operation of the system; The trajectory convergence coefficient is calculated by dividing the average area of ​​the closed region of the baseline hysteresis loop by the area of ​​the closed region in the current recovery cycle. At the same time, extract the standardized flux increase increment within the currently set evaluation time window; Divide the increase in standardized flux by the time span of the evaluation window to obtain the recovery rate of standardized flux. Extract the system's preset baseline flux recovery rate; normalize the standardized flux recovery rate by dividing it by the baseline flux recovery rate to obtain the flux recovery score; multiply the trajectory convergence coefficient and the flux recovery score to obtain the dimensionless mass transfer recovery index.

10. A multi-stage membrane concentration system based on dual-mode and shunt drag reduction according to claim 8, characterized in that, The method for determining the reset node is as follows: The preset recovery threshold in the system control unit is retrieved, and the real-time calculated mass transfer recovery index is continuously compared with the recovery threshold. If the mass transfer recovery index is continuously rising and reaches or exceeds the recovery qualification threshold, and the phase space trajectory coordinates within the current recovery cycle are simultaneously monitored to physically close again, then the membrane surface mass transfer performance is determined to be restored to within the safe operating boundary. The system's main control unit establishes the current absolute time coordinate that meets the judgment conditions as the reset node.

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