An extreme concentration reverse osmosis system based on osmotic pressure balance driving and a use method thereof

Abstract

The application discloses an extreme concentration reverse osmosis system based on osmotic pressure balance driving and a use method, relates to the field of high-salinity wastewater treatment, and comprises a reverse osmosis membrane assembly, a water inlet circuit, a water production side auxiliary flow circuit, an auxiliary flow regeneration unit, a crystallization risk monitoring unit, a pressure exchanger and a control unit. The reverse osmosis membrane assembly is a standard commercial membrane element, and the upper limit of the operation pressure of the reverse osmosis membrane assembly is 160 bar. Through the deep cooperation of the water inlet circuit, the water production side auxiliary flow circuit, the auxiliary flow regeneration unit, the crystallization risk monitoring unit, the pressure exchanger and the control unit, and relying on the real-time regulation and control capability of the osmotic pressure on both sides of the membrane and the precise matching mechanism of the auxiliary flow salinity of a dynamic net pressure difference self-adaptive algorithm, the extreme concentration of total dissolved solids up to 260,000 mg / L can be safely realized within the upper limit of the pressure resistance of a standard commercial reverse osmosis membrane without relying on special membrane elements with ultrahigh pressure or frequent chemical cleaning.

Description

Technical Field

[0001] This invention relates to high-salinity wastewater treatment technology, specifically to an extreme concentration reverse osmosis system driven by osmotic pressure balance and its usage method. Background Technology

[0002] With increasingly stringent environmental standards for industrial water treatment and the deepening of the "dual carbon" goal, enterprises have placed higher demands on the energy efficiency and economy of high-salinity wastewater treatment technologies. In scenarios such as coal chemical industry, power plant desulfurization, landfill leachate treatment, and industrial zero discharge, reverse osmosis (RO) technology, as the core membrane separation method, is widely used. However, when treating ultra-high salinity wastewater with a total dissolved solids (TDS) concentration exceeding 80,000–100,000 mg / L, traditional reverse osmosis processes face a fundamental bottleneck: the osmotic pressure on the feed side rises sharply, forcing the system to apply operating pressure far exceeding the pressure resistance limit of conventional commercial RO membrane elements (approximately 160 bar). This not only leads to a surge in energy consumption but also easily causes mechanical damage, compaction, or sealing failure of the membrane elements. As a result, existing RO systems can usually only concentrate wastewater to TDS < 120,000 mg / L, and subsequent zero discharge still requires expensive thermal evaporation methods (such as MVR), significantly increasing the overall treatment cost.

[0003] Currently, some improvement solutions attempt to alleviate pressure problems through multi-stage series or segmented concentration, but they are essentially still in the "high-pressure driven" mode, only dispersing but not eliminating risks. Other solutions focus on the development of special high-pressure resistant membranes, but are limited by high costs, low throughput and unstable supply chains, making it difficult to promote in engineering. More importantly, existing technologies generally lack the ability to perceive and actively intervene in the crystallization risk during the concentration process. They cannot adaptively adjust operating parameters according to the dynamic changes of influent TDS to approach the crystallization saturation limit (such as 260,000 mg / L), nor do they have an online monitoring and linkage control mechanism for key indicators such as concentrate turbidity and particulate matter concentration, making it difficult for the system to balance safety and concentration efficiency.

[0004] Traditional solutions rely excessively on fixed high-pressure strategies, failing to accurately match the optimal net driving pressure difference required for different concentration stages, resulting in energy waste and limited concentration ratios. Existing so-called "optimized" systems are mostly limited to the frequency conversion control of single devices (such as high-pressure pumps), failing to construct a closed-loop control system that integrates osmotic pressure balance, crystallization risk warning, energy recovery, and intelligent regeneration of auxiliary flow. In particular, they lack the dynamic synergistic function of automatically adjusting the salinity of auxiliary flow and circulation flow based on real-time water quality data, making it impossible to achieve safe, stable, and extreme concentration of ultra-high salinity wastewater within the pressure range of standard membrane elements. Thus, they fail to fundamentally solve the dual challenges of efficient resource recovery and reliable system operation.

[0005] To address these issues, the applicant proposes a limit concentration reverse osmosis system and its usage method based on osmotic pressure balance to solve the aforementioned problems. Summary of the Invention

[0006] The purpose of this invention is to provide an extreme concentration reverse osmosis system and its usage method based on osmotic pressure balance drive, in order to solve the problems of existing technologies that mostly adopt a fixed high-pressure operation mode, which makes it difficult to dynamically optimize the net pressure difference across the membrane as the concentration process progresses, resulting in high energy consumption and limited concentration capacity; even if some systems introduce frequency conversion control of equipment, they still lack an intelligent closed-loop mechanism that coordinates osmotic pressure balance regulation, real-time early warning of crystallization risk, pressure energy recovery and auxiliary flow regeneration, and cannot achieve safe and efficient extreme concentration of ultra-high salinity wastewater within the pressure range of standard reverse osmosis membrane elements.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a limit concentration reverse osmosis system based on osmotic pressure balance drive, comprising a reverse osmosis membrane module, a feed water circuit, a product water side auxiliary flow circuit, an auxiliary flow regeneration unit, a crystallization risk monitoring unit, a pressure exchanger, and a control unit;

[0008] The reverse osmosis membrane module is a standard commercial membrane element, and the maximum operating pressure of the reverse osmosis membrane module is 160 bar;

[0009] The water inlet circuit includes a raw water tank, a high-pressure pump, and a water inlet-side circulation pump. The outlet of the raw water tank is connected to the inlet of the high-pressure pump, the outlet of the high-pressure pump is connected to the inlet of the water inlet-side circulation pump, and the outlet of the water inlet-side circulation pump is connected to the water inlet of the reverse osmosis membrane module.

[0010] The product water side auxiliary flow loop includes an auxiliary flow storage tank, an auxiliary flow circulation pump, an online salinity detector, and an auxiliary flow regulating valve. The outlet of the auxiliary flow storage tank is connected to the inlet of the auxiliary flow circulation pump, and the outlet of the auxiliary flow circulation pump is connected to the product water side inlet of the reverse osmosis membrane module via the online salinity detector and the auxiliary flow regulating valve.

[0011] The inlet of the auxiliary flow regeneration unit is connected to the permeate outlet of the reverse osmosis membrane module, and the concentrate outlet of the auxiliary flow regeneration unit is connected to the inlet of the auxiliary flow storage tank.

[0012] The crystallization risk monitoring unit includes an online turbidity meter and a particle counter. The online turbidity meter and the particle counter are installed on the concentrate circulation pipeline on the feed water side of the reverse osmosis membrane module. The signal output terminals of the online turbidity meter and the particle counter are electrically connected to the control unit.

[0013] The high-pressure fluid inlet of the pressure exchanger is connected to the concentrate outlet on the feed side of the reverse osmosis membrane module, and the high-pressure fluid outlet of the pressure exchanger is connected to the inlet of the high-pressure pump.

[0014] The control unit is electrically connected to the high-pressure pump, the auxiliary flow regulating valve, the auxiliary flow regeneration unit, the crystallization risk monitoring unit, and the pressure exchanger, respectively. The control unit stores the execution instructions of the dynamic net pressure differential adaptive algorithm.

[0015] Furthermore, the inlet of the auxiliary flow storage tank is also connected to the outlet of the raw water tank, the fresh water outlet of the auxiliary flow regeneration unit, or the outlet of the industrial salt preparation device.

[0016] Furthermore, the auxiliary flow regeneration unit is a low-pressure reverse osmosis membrane module, an electrodialysis unit, or a nanofiltration membrane module.

[0017] A method for using an extreme concentration reverse osmosis system driven by osmotic pressure equilibrium includes the following steps:

[0018] S1. The high-salinity raw water to be treated is pressurized from the raw water tank by a high-pressure pump and an inlet-side circulation pump and then sent to the inlet side of the reverse osmosis membrane module. At the same time, the auxiliary flow is sent from the auxiliary flow storage tank by an auxiliary flow circulation pump, an online salinity detector and an auxiliary flow regulating valve and then sent to the product water side of the reverse osmosis membrane module.

[0019] S2. By executing a dynamic net pressure differential adaptive algorithm through the control unit, the auxiliary flow regulating valve and high-pressure pump are adjusted according to the stage of the total dissolved solids (TDS) concentration of the raw water on the inlet side, thereby controlling the salinity of the auxiliary flow and the system operating pressure.

[0020] S3. The turbidity and particulate matter concentration of the concentrate on the influent side are monitored in real time using the crystallization risk monitoring unit, and the monitoring signal is sent to the control unit.

[0021] S4. The auxiliary flow from the permeate side of the reverse osmosis membrane module is sent to the auxiliary flow regeneration unit for desalination, and the resulting concentrate is sent back to the auxiliary flow storage tank.

[0022] S5. The high-pressure concentrate discharged from the feed water side of the reverse osmosis membrane module is sent to the pressure exchanger to recover its pressure energy and transfer it to the raw water at the inlet of the high-pressure pump.

[0023] Further, in step S2, the dynamic net pressure differential adaptive algorithm divides the concentration process into a low-concentration stage, a medium-concentration stage, and a high-concentration stage, and executes the following control strategy: when the total dissolved solids concentration of the feed water is in the low-concentration stage (TDS < 120,000 mg / L), the auxiliary flow salinity is controlled at 50,000–100,000 mg / L, and the net driving pressure across the membrane is controlled at 3–5 bar; when in the medium-concentration stage (TDS > 120,000 mg / L and < 200,000 mg / L), the auxiliary flow salinity is controlled at 100,000–150,000 mg / L, and the net driving pressure across the membrane is controlled at 2–3 bar; when in the high-concentration stage (TDS > 200,000 mg / L), the auxiliary flow salinity is controlled at 150,000–200,000 mg / L, and the net driving pressure across the membrane is controlled at 0.5–2 bar.

[0024] Furthermore, in S3, when the monitored turbidity exceeds 2 NTU or the particulate matter concentration indicator solution saturation reaches 95%, the control unit sends a command to the auxiliary flow regulating valve to increase the salinity or circulation flow rate of the auxiliary flow.

[0025] Furthermore, in step S4, the fresh water generated by the auxiliary flow regeneration unit is transported to the recycled water network.

[0026] Furthermore, throughout the concentration process, the operating pressure of the reverse osmosis membrane module does not exceed 160 bar, and the total dissolved solids of the feed water are ultimately concentrated to 260,000 mg / L.

[0027] Compared with existing technologies, this invention provides an extreme concentration reverse osmosis system based on osmotic pressure balance drive. Through deep collaboration of the feed water loop, product water side auxiliary flow loop, auxiliary flow regeneration unit, crystallization risk monitoring unit, pressure exchanger, and control unit, and relying on the real-time control capability of dynamic net pressure difference adaptive algorithm for osmotic pressure on both sides of the membrane and the precise matching mechanism of auxiliary flow salinity, it can safely achieve extreme concentration of total dissolved solids (TDS) up to 260,000 mg / L within the pressure limit of standard commercial reverse osmosis membranes (160 bar) without relying on ultra-high pressure special membrane elements or frequent chemical cleaning. The system actively counteracts the continuously increasing osmotic pressure on the feed water side by injecting a controllable high-salt auxiliary flow on the product water side, reducing the effective driving pressure difference and fundamentally alleviating membrane fouling and scaling driving forces. At the same time, it combines an online turbidity meter and particle counter to monitor early crystallization. The signal is captured in milliseconds. Once the turbidity exceeds 2 NTU or the particle concentration indicator saturation reaches 95%, the control unit immediately adjusts the salinity of the auxiliary flow or the circulation flow rate to actively suppress the risk of crystallization. The auxiliary flow is recycled after regeneration through low-pressure reverse osmosis, electrodialysis, or nanofiltration, allowing for freshwater reuse. The pressure exchanger simultaneously recovers the pressure energy of the concentrate, significantly reducing the overall energy consumption of the system. The entire process is fully automated by the control unit, executing a closed-loop logic of "stage identification → differential pressure control → risk warning → flow response → energy recovery." This completely solves the technical bottlenecks faced by traditional high-pressure reverse osmosis or disc tube reverse osmosis (DTRO) in treating high-salinity wastewater, such as high equipment investment, high energy consumption, easy membrane fouling, and difficulty in overcoming the solubility limitations of low-soluble salts like sodium sulfate. It improves the volume reduction efficiency and resource utilization potential of high-salinity wastewater, combining engineering feasibility, operational stability, and economic and environmental benefits. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this invention. For those skilled in the art, other drawings can be obtained based on these drawings.

[0029] Figure 1 This is a schematic diagram of the overall process provided for an embodiment of the present invention;

[0030] Figure 2 This is a schematic diagram of the system structure provided in an embodiment of the present invention. Detailed Implementation

[0031] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings.

[0032] As attached Figure 1 To be continued Figure 2 As shown:

[0033] Example 1:

[0034] In this invention, the system operating pressure refers to the total hydraulic pressure on the inlet side of the reverse osmosis membrane module, which ranges from 30 to 160 bar (preferably ≤83 bar) and is provided by a high-pressure pump;

[0035] Net driving pressure refers to the effective pressure actually used to drive water molecules to permeate the membrane. The calculation formula is:

[0036] Net driving pressure = hydraulic pressure difference across the membrane - osmotic pressure difference across the membrane.

[0037] Winter extreme concentration scenario for high-salt wastewater from coal chemical industry

[0038] This invention provides a reverse osmosis system for extreme concentration driven by osmotic pressure balance, comprising a reverse osmosis membrane module, a feed water loop, a product water side auxiliary flow loop, an auxiliary flow regeneration unit, a crystallization risk monitoring unit, a pressure exchanger, and a control unit. The reverse osmosis membrane module uses standard commercial seawater desalination membrane elements with an operating pressure limit of 160 bar. The feed water loop is used to pressurize and send high-salinity raw water into the feed water side of the reverse osmosis membrane module. The product water side auxiliary flow loop injects an auxiliary flow with controllable salinity into the product water side of the reverse osmosis membrane module to adjust the net driving pressure difference across the membrane. The auxiliary flow regeneration unit desalinates the outflowing auxiliary flow, and the concentrate is returned to the auxiliary flow storage tank for recycling. The crystallization risk monitoring unit monitors the turbidity and particulate matter concentration of the concentrate on the feed water side in real time. The pressure exchanger recovers the pressure energy of the concentrate and feeds it back to the feed water end. The control unit executes a dynamic net pressure difference adaptive algorithm to coordinate and control the high-pressure pump, auxiliary flow regulating valve, and regeneration unit to ensure that the system achieves extreme concentration under safe pressure.

[0039] Component parameters and compatibility requirements: The reverse osmosis membrane module uses standard 8-inch seawater desalination membrane elements, with a maximum pressure resistance of 160 bar per element; the feed circuit is equipped with a plunger-type high-pressure pump (rated pressure 160 bar, flow rate 50 m³ / h). 3 / h) and centrifugal inlet circulating pump; auxiliary flow storage tank with a volume of 20m³ in the product water side auxiliary flow circuit. 3 The auxiliary flow circulation pump has a flow rate of 30m³ / h. 3 The online salinity analyzer measures 0–250,000 mg / L with an accuracy of ±1%, and the auxiliary flow regulating valve has a response time of ≤2 seconds. The auxiliary flow regeneration unit uses a low-pressure reverse osmosis membrane module, achieving a desalination rate of ≥95% for the auxiliary flow. The crystallization risk monitoring unit is equipped with an online turbidity meter (range 0–10 NTU, accuracy ±0.1 NTU) and a laser particle counter (detection particle size 1–100 μm). The pressure exchanger is a PX type pressure exchanger with an efficiency of ≥95%. The control unit has a built-in PLC and a dynamic net pressure differential adaptive algorithm module, with a sampling frequency of 1 Hz.

[0040] Before system startup, the auxiliary flow tank is injected with initial auxiliary solution (TDS 80000 mg / L, prepared with industrial salt), and the reverse osmosis membrane module undergoes low-pressure flushing. The control unit inputs the basic parameters of the feed water: TDS 100000 mg / L, temperature 8℃, pH 7.2, and sets the concentration target to 260000 mg / L. The crystallization risk warning threshold is turbidity 2 NTU or particulate matter concentration corresponding to saturation of 95%. The dynamic net pressure differential adaptive algorithm divides the control strategy into three stages: in the low concentration stage (TDS < 120000 mg / L), the auxiliary flow salinity is set to 80000 mg / L, and the net pressure differential is 4 bar; in the medium concentration stage (120000 ≤ TDS < 200000 mg / L), the auxiliary flow salinity is increased to 130000 mg / L, and the net pressure differential is 2.5 bar; in the high concentration stage (TDS ≥ 200000 mg / L), the auxiliary flow salinity is adjusted to 180000 mg / L, and the net pressure differential is 1.2 bar.

[0041] During winter operation, 100,000 mg / L TDS raw water is pressurized to 65 bar by a high-pressure pump and enters the feed water side of the reverse osmosis membrane module. Simultaneously, an auxiliary flow with a salinity of 80,000 mg / L is injected into the permeate side. The system's net drive pressure differential is maintained at 4 bar, and the initial concentrate TDS rises rapidly. When the concentrate TDS reaches 125,000 mg / L, the control unit automatically increases the auxiliary flow salinity to 130,000 mg / L, the system pressure is fine-tuned to 70 bar, the net pressure differential drops to 2.5 bar, and the concentration rate stabilizes. When the TDS rises to 205... The system entered the high-concentration stage with a concentration of 000 mg / L. The salinity of the auxiliary flow increased to 180,000 mg / L, and the system pressure stabilized at 78 bar (below the upper limit of 160 bar), with the net pressure difference maintained at 1.2 bar. The crystallization risk monitoring unit continuously monitored the system. When the TDS reached 250,000 mg / L, the turbidity rose to 1.8 NTU, and the particle count showed a saturation of 92%. The system did not trigger an alarm. Finally, the concentrate TDS stabilized at 260,000 mg / L, and the product water TDS < 500 mg / L was reused at the freshwater outlet of the auxiliary flow regeneration unit.

[0042] The auxiliary flow regeneration unit desalinates the auxiliary flow (TDS approximately 185,000 mg / L) from the permeate side to below 10,000 mg / L, with the freshwater being incorporated into the recycled water network. The concentrate (TDS approximately 220,000 mg / L) is returned to the auxiliary flow storage tank to replenish salinity. The pressure exchanger efficiently transmits the 78 bar concentrate pressure to the high-pressure pump inlet, reducing the overall system energy consumption by 35%. When a sudden increase in turbidity to 2.1 NTU (TDS 258,000 mg / L) is detected, the control unit immediately instructs the auxiliary flow regulating valve to increase the circulation flow rate by 10%, and the turbidity quickly drops back to 1.7 NTU, effectively suppressing the risk of crystallization.

[0043] This concentration process was completed entirely within the pressure resistance range of standard membrane elements, without the need for special high-pressure equipment. It achieved safe, stable, and extreme concentration of TDS from 100,000 mg / L to 260,000 mg / L. The system is highly automated and has low energy consumption. It successfully avoids the risks of membrane damage and scaling under ultra-high salinity conditions of traditional high-pressure RO, providing an efficient and reliable core concentration solution for zero discharge of high-salt wastewater from coal chemical industry.

[0044] Example 2:

[0045] Landfill leachate nanofiltration concentrate summer high organic load extreme concentration scenario

[0046] This invention provides an extreme concentration reverse osmosis system based on osmotic pressure balance drive, comprising a reverse osmosis membrane module, a feed water loop, a product water side auxiliary flow loop, an auxiliary flow regeneration unit, a crystallization risk monitoring unit, a pressure exchanger, and a control unit. The reverse osmosis membrane module adopts a standard commercially available antifouling seawater desalination membrane element with an upper operating pressure limit of 160 bar. The feed water loop pressurizes pretreated high-salinity, high-organic concentrate and sends it to the feed water side of the membrane module. The product water side auxiliary flow loop injects an adjustable salinity auxiliary flow into the product water side of the membrane module to dynamically maintain the optimal net driving pressure difference. The auxiliary flow regeneration unit performs desalination regeneration on the outflow auxiliary flow. The crystallization risk monitoring unit senses the tendency of concentrate scaling in real time. The pressure exchanger recovers the pressure energy of the concentrate. The control unit executes a dynamic net pressure difference adaptive algorithm to achieve closed-loop control under all operating conditions.

[0047] Component parameters and compatibility requirements: The reverse osmosis membrane module uses an 8-inch anti-fouling seawater membrane, with a maximum pressure resistance of 160 bar per unit and an anti-organic fouling coating; the feed circuit is equipped with a variable frequency high-pressure pump (rated 160 bar, flow rate 40 m³ / h). 3 / h) and circulating pump; auxiliary flow storage tank with a volume of 15m³ in the product water side auxiliary flow circuit; 3 The auxiliary flow circulation pump has a flow rate of 25m³ / h. 3 / h, the online salinity analyzer has a range of 0–250000 mg / L (accuracy ±1%), the auxiliary flow regulating valve is a pneumatic V-type ball valve with a response time ≤1.5 seconds; the auxiliary flow regeneration unit uses an electrodialysis unit with a desalination rate ≥90%; the crystallization risk monitoring unit integrates an online turbidity meter (0–20 NTU, accuracy ±0.2 NTU) and a particle counter (1–200 μm); the pressure exchanger is a turbine pressure exchanger with an efficiency ≥92%; the control unit has a built-in dynamic net pressure difference adaptive algorithm, a sampling frequency of 2 Hz, and organic matter interference compensation logic.

[0048] Before system startup, the auxiliary flow storage tank is injected with initial auxiliary solution (TDS 70000 mg / L, diluted and prepared from the raw water tank), and the membrane module completes alkaline washing pretreatment. The control unit enters the summer influent water quality: TDS 50000 mg / L, COD 800 mg / L, temperature 32℃, pH 6.8, and sets the concentration target to 260000 mg / L. The crystallization warning threshold is turbidity 3 NTU or particle saturation 95%. The dynamic net pressure difference strategy is set as follows: low concentration stage (TDS < 120000 mg / L) auxiliary flow salinity 70000 mg / L, net pressure difference 4.5 bar; medium concentration stage (120000 ≤ TDS < 200000 mg / L) auxiliary flow salinity 120000 mg / L, net pressure difference 2.2 bar; high concentration stage (TDS ≥ 200000 mg / L) auxiliary flow salinity 170000 mg / L, net pressure difference 1.0 bar.

[0049] During summer operation, 50,000 mg / L LDS leachate concentrate is pressurized to 60 bar by a high-pressure pump and enters the influent side of the membrane module. The auxiliary flow is injected into the permeate side at 70,000 mg / L, with a net pressure difference of 4.5 bar and stable initial flux. When TDS rises to 130,000 mg / L, the control unit automatically increases the salinity of the auxiliary flow to 120,000 mg / L, adjusts the system pressure to 72 bar, and reduces the net pressure difference to 2.2 bar, effectively inhibiting the deposition of organic matter on the membrane surface. When TDS reaches 210,000 mg / L, the salinity of the auxiliary flow increases to 170,000 mg / L, the system pressure stabilizes at 81 bar (below the upper limit of 160 bar), and the net pressure difference is 1.0 bar. At this time, the turbidity monitoring value is 2.6 NTU, and the particle count shows a saturation of 93%, close to the warning line.

[0050] When the TDS rose to 255,000 mg / L and the turbidity suddenly increased to 3.2 NTU, the control unit immediately determined that the risk of crystallization had increased and instructed the auxiliary flow regulating valve to increase the circulation flow by 15% while slightly increasing the auxiliary flow salinity to 175,000 mg / L. Within 5 minutes, the turbidity dropped back to 2.4 NTU, successfully avoiding scaling. Finally, the concentrate TDS reached 260,000 mg / L, and the product water TDS was <800 mg / L (meeting the reuse standard).

[0051] The auxiliary flow regeneration unit (electrodialysis unit) desalinates the outflowing auxiliary flow (TDS approximately 178,000 mg / L) to 15,000 mg / L. The freshwater is then incorporated into the plant's recycled water network, while the concentrate (TDS approximately 210,000 mg / L) is returned to the auxiliary flow storage tank. The pressure exchanger feeds back 81 bar of concentrated water energy to the high-pressure pump inlet, reducing the system's energy consumption per ton of water by 40% compared to traditional DTRO. The overall membrane flux decay rate is <8%, eliminating the need for chemical cleaning.

[0052] This concentration operation successfully increased the concentration of landfill leachate nanofiltration concentrate from 50,000 mg / L to 260,000 mg / L under high summer temperatures and high organic load conditions. This breakthrough exceeded the application limits of standard membrane elements. The system operates fully automatically, effectively solving the membrane fouling and concentration bottlenecks of traditional processes in the context of high organic matter, reducing the subsequent evaporation and crystallization load, and providing a highly efficient, low-consumption, and highly reliable core concentration path for zero discharge of landfill leachate.

[0053] Example 3:

[0054] Winter Low-Temperature Extreme Concentration and Anti-Crystallization Control Scenario for High Sodium Sulfate Wastewater from Lithium Battery Materials

[0055] This invention provides a reverse osmosis system for extreme concentration driven by osmotic pressure balance, comprising a reverse osmosis membrane module, a feed water loop, a product water-side auxiliary flow loop, an auxiliary flow regeneration unit, a crystallization risk monitoring unit, a pressure exchanger, and a control unit. The reverse osmosis membrane module uses standard commercially available anti-fouling seawater desalination membrane elements with an operating pressure limit of 160 bar. The feed water loop is used to transport raw water with a high sodium sulfate content. The product water-side auxiliary flow loop precisely controls the net driving pressure difference across the membrane by dynamically adjusting the auxiliary flow salinity, thus inhibiting supersaturation crystallization on the feed water side. The auxiliary flow regeneration unit regenerates and circulates the auxiliary flow. The crystallization risk monitoring unit captures early nucleation signals in real time. The pressure exchanger recovers the pressure energy of the concentrate. The control unit executes a dynamic net pressure difference adaptive algorithm and integrates sodium sulfate phase diagram compensation logic to achieve safe extreme concentration of the low-temperature, high-salinity system.

[0056] Component parameters and compatibility requirements: The reverse osmosis membrane module uses an 8-inch anti-fouling seawater membrane with a maximum pressure resistance of 160 bar per unit and a hydrophilic modified surface; the feed circuit is equipped with a high-pressure pump (rated 160 bar, flow rate 35 m³ / h). 3 / h) and circulating pump; auxiliary flow storage tank with a volume of 18m³ in the product water side auxiliary flow circuit; 3 The auxiliary flow circulation pump has a flow rate of 28m³ / h. 3 The online salinity analyzer has a range of 0–250,000 mg / L (accuracy ±0.8%), and the auxiliary flow regulating valve is a high-precision electric regulating valve with a response time ≤1 second. The auxiliary flow regeneration unit uses a nanofiltration membrane module (retaining >95% of divalent ions) to retain sulfate and remove monovalent salts. The crystallization risk monitoring unit is equipped with a high-sensitivity online turbidity meter (0–5 NTU, accuracy ±0.05 NTU) and a submicron particle counter (0.5–50 μm) to identify early crystal nucleation. The pressure exchanger is a PX pressure exchanger with an efficiency ≥96%. The control unit has a built-in dynamic net pressure differential adaptive algorithm and a sodium sulfate low-temperature solubility database, with a sampling frequency of 2 Hz.

[0057] Before system startup, the auxiliary flow storage tank is injected with initial auxiliary solution (TDS 90000 mg / L, mainly containing a mixed salt of NaCl / Na2SO4, prepared from industrial salt), and the membrane module undergoes acid washing and passivation; the control unit records the winter influent water quality: TDS 95,000 mg / L (of which SO42-) 2- The concentration targets were set at 68,000 mg / L, 6°C, and pH 7.0, with a TDS target of 260,000 mg / L (corresponding to approximately 182,000 mg / L of Na2SO4, close to its low-temperature solubility limit). The crystallization warning threshold was set at 1.5 NTU of turbidity or a sudden increase of 50% in the number of particles. The dynamic net pressure differential strategy was optimized as follows: in the low concentration stage (TDS < 120,000 mg / L), the auxiliary flow salinity was 90,000 mg / L, and the net pressure differential was 4 bar; in the medium concentration stage (120,000 ≤ TDS < 200,000 mg / L), the auxiliary flow salinity was 140,000 mg / L, and the net pressure differential was 2.0 bar; in the high concentration stage (TDS ≥ 200,000 mg / L), the auxiliary flow salinity was 190,000 mg / L, and the net pressure differential was 0.8 bar (further reducing the driving force to inhibit nucleation).

[0058] In the initial stage of operation, 95,000 mg / L TDS raw water is pressurized to 62 bar by a high-pressure pump and enters the membrane module. The auxiliary flow is injected into the permeate side at 90,000 mg / L, with a net pressure difference of 4 bar and stable concentration. When TDS reaches 125,000 mg / L, the system automatically switches to a medium concentration strategy, the auxiliary flow salinity increases to 140,000 mg / L, the pressure is adjusted to 74 bar, and the net pressure difference is 2.0 bar. When entering the high concentration stage (TDS 205,000 mg / L), the auxiliary flow salinity increases to 190,000 mg / L, the system pressure stabilizes at 82 bar (below the upper limit of 160 bar), and the net pressure difference is only 0.8 bar, reducing local supersaturation on the membrane surface.

[0059] When the TDS rose to 250,000 mg / L, the particle counter detected a sudden 40% increase in the number of 0.8–2 μm particles, and the turbidity rose from 0.9 NTU to 1.4 NTU. The control unit immediately determined that sodium sulfate crystal nuclei were forming and triggered the anti-crystallization protocol: it instructed the auxiliary flow regulating valve to instantly increase the auxiliary flow salinity to 195,000 mg / L and increase the circulation flow rate by 12%, so that the effective supersaturation on the feed side decreased, the particle count dropped within 3 minutes, and the turbidity stabilized at 1.1 NTU; finally, the concentrate TDS reached 260,000 mg / L, no visible crystals occurred, and the product water TDS < 600 mg / L.

[0060] The auxiliary flow regeneration unit (nanofiltration) partially desalinates the effluent auxiliary flow (TDS approximately 198,000 mg / L), recycles the freshwater (TDS < 10,000 mg / L), and concentrates the solution (enriched with SO4). 2-The return flow to the auxiliary flow storage tank maintains a high-salt environment; the pressure exchanger efficiently recovers the energy of the 82 bar concentrate, reducing the system's energy consumption per ton of water by 38% compared to conventional high-pressure RO; the concentrate is directly sent to the cryogenic crystallization unit, successfully precipitating high-purity sodium sulfate decahydrate with a recovery rate of >90%.

[0061] This operation, conducted at a low temperature of 6℃ and under high sodium sulfate conditions, successfully broke through the solubility limit of sodium sulfate, achieving a safe concentration limit of 260,000 mg / LTDS. The entire process was free of membrane scaling and required no downtime for cleaning. The system precisely suppressed the risk of crystallization through a closed-loop "sensing-decision-adjustment" mechanism, providing a key technical path for the resource utilization of high-salt wastewater in the lithium battery industry that is both safe and economical and engineerable.

[0062] The foregoing has only described certain exemplary embodiments of the present invention by way of illustration. Undoubtedly, those skilled in the art can modify the described embodiments in various ways without departing from the spirit and scope of the present invention. Therefore, the foregoing drawings and descriptions are illustrative in nature and should not be construed as limiting the scope of protection of the claims of the present invention.

Claims

1. A limit concentration reverse osmosis system based on osmotic pressure balance driven by osmotic pressure balance, characterized in that, Includes reverse osmosis membrane modules, feed water circuit, product water side auxiliary flow circuit, auxiliary flow regeneration unit, crystallization risk monitoring unit, pressure exchanger and control unit; The reverse osmosis membrane module is a standard commercial membrane element, and the maximum operating pressure of the reverse osmosis membrane module is 160 bar; The water inlet circuit includes a raw water tank, a high-pressure pump, and a water inlet-side circulation pump. The outlet of the raw water tank is connected to the inlet of the high-pressure pump, the outlet of the high-pressure pump is connected to the inlet of the water inlet-side circulation pump, and the outlet of the water inlet-side circulation pump is connected to the water inlet of the reverse osmosis membrane module. The product water side auxiliary flow loop includes an auxiliary flow storage tank, an auxiliary flow circulation pump, an online salinity detector, and an auxiliary flow regulating valve. The outlet of the auxiliary flow storage tank is connected to the inlet of the auxiliary flow circulation pump, and the outlet of the auxiliary flow circulation pump is connected to the product water side inlet of the reverse osmosis membrane module via the online salinity detector and the auxiliary flow regulating valve. The inlet of the auxiliary flow regeneration unit is connected to the permeate outlet of the reverse osmosis membrane module, and the concentrate outlet of the auxiliary flow regeneration unit is connected to the inlet of the auxiliary flow storage tank. The crystallization risk monitoring unit includes an online turbidity meter and a particle counter. The online turbidity meter and the particle counter are installed on the concentrate circulation pipeline on the feed water side of the reverse osmosis membrane module. The signal output terminals of the online turbidity meter and the particle counter are electrically connected to the control unit. The high-pressure fluid inlet of the pressure exchanger is connected to the concentrate outlet on the feed side of the reverse osmosis membrane module, and the high-pressure fluid outlet of the pressure exchanger is connected to the inlet of the high-pressure pump. The control unit is electrically connected to the high-pressure pump, the auxiliary flow regulating valve, the auxiliary flow regeneration unit, the crystallization risk monitoring unit, and the pressure exchanger, respectively. The control unit stores the execution instructions of the dynamic net pressure differential adaptive algorithm.

2. The ultimate concentration reverse osmosis system based on osmotic pressure balance driven according to claim 1, characterized in that, The inlet of the auxiliary flow storage tank is also connected to the outlet of the raw water tank, the fresh water outlet of the auxiliary flow regeneration unit, or the outlet of the industrial salt preparation device.

3. The ultimate concentration reverse osmosis system based on osmotic pressure balance driven according to claim 1, characterized in that, The auxiliary flow regeneration unit is a low-pressure reverse osmosis membrane module, an electrodialysis unit, or a nanofiltration membrane module.

4. A method of using a limit concentration reverse osmosis system based on osmotic pressure balance driven according to any one of claims 1 to 3, characterized in that, Includes the following steps: S1. The high-salinity raw water to be treated is pressurized from the raw water tank by a high-pressure pump and an inlet-side circulation pump and then sent to the inlet side of the reverse osmosis membrane module. At the same time, the auxiliary flow is sent from the auxiliary flow storage tank by an auxiliary flow circulation pump, an online salinity detector and an auxiliary flow regulating valve and then sent to the product water side of the reverse osmosis membrane module. S2. By executing a dynamic net pressure differential adaptive algorithm through the control unit, the auxiliary flow regulating valve and high-pressure pump are adjusted according to the stage of the total dissolved solids (TDS) concentration of the raw water on the inlet side, thereby controlling the salinity of the auxiliary flow and the system operating pressure. S3. The turbidity and particulate matter concentration of the concentrate on the influent side are monitored in real time using the crystallization risk monitoring unit, and the monitoring signal is sent to the control unit. S4. The auxiliary flow from the permeate side of the reverse osmosis membrane module is sent to the auxiliary flow regeneration unit for desalination, and the resulting concentrate is sent back to the auxiliary flow storage tank. S5. The high-pressure concentrate discharged from the feed water side of the reverse osmosis membrane module is sent to the pressure exchanger to recover its pressure energy and transfer it to the raw water at the inlet of the high-pressure pump.

5. The method of using a limit concentration reverse osmosis system based on osmotic pressure balance drive according to claim 4, characterized in that, In step S2, the dynamic net pressure differential adaptive algorithm divides the concentration process into low-concentration, medium-concentration, and high-concentration stages, and executes the following control strategies: When the total dissolved solids concentration (TDS) of the feed water is in the low-concentration stage (TDS < 120,000 mg / L), the auxiliary flow salinity is controlled at 50,000–100,000 mg / L, and the net driving pressure across the membrane is controlled at 3–5 bar; when in the medium-concentration stage (TDS > 120,000 mg / L and < 200,000 mg / L), the auxiliary flow salinity is controlled at 100,000–150,000 mg / L, and the net driving pressure across the membrane is controlled at 2–3 bar; when in the high-concentration stage (TDS > 200,000 mg / L), the auxiliary flow salinity is controlled at 150,000–200,000 mg / L, and the net driving pressure across the membrane is controlled at 0.5–2 bar.

6. The method of using a limit concentration reverse osmosis system based on osmotic pressure balance drive according to claim 4, characterized in that, In step S3, when the monitored turbidity exceeds 2 NTU or the particulate matter concentration indicator solution saturation reaches 95%, the control unit sends a command to the auxiliary flow regulating valve to increase the salinity or circulation flow rate of the auxiliary flow.

7. The method of using a limit concentration reverse osmosis system based on osmotic pressure balance drive according to claim 4, characterized in that, In step S4, the fresh water generated by the auxiliary flow regeneration unit is transported to the recycled water pipeline network.

8. The method of using a limit concentration reverse osmosis system based on osmotic pressure balance drive according to claim 4, characterized in that, Throughout the concentration process, the operating pressure of the reverse osmosis membrane module does not exceed 160 bar, and the total dissolved solids of the feed water are ultimately concentrated to 260,000 mg / L.

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