Low-energy consumption differential pressure reverse osmosis wastewater concentration system

Abstract

The utility model relates to wastewater concentration treatment technical field discloses a kind of low-energy consumption differential pressure reverse osmosis wastewater concentration systems, including first reverse osmosis section and second differential pressure reverse osmosis section, and first reverse osmosis section includes containing first reverse osmosis equipment, with an import and two exports, respectively as fresh water outlet and concentrated solution outlet;Second differential pressure reverse osmosis section includes the differential pressure reverse osmosis equipment with multiple layers of permeation membrane element, and permeation membrane unit includes sheet permeation membrane and filter plate, and flow channel is formed between sheet permeation membrane two sides and filter plate, and filter plate is opened with water inlet and water outlet, and water inlet, water outlet and flow channel are communicated and form independent first channel and second channel on the same side of sheet permeation membrane;Concentrated solution outlet is divided into two parts, respectively pressurized and normal pressure delivery to first channel and second channel;Solution at second channel export is delivered to the import of first reverse osmosis equipment.The utility model concentrates solution by differential pressure reverse osmosis equipment for second time, and effectively reduce system energy consumption.

Description

Technical Field

[0001] This utility model relates to the field of wastewater concentration and treatment technology, specifically to a low-energy differential pressure reverse osmosis wastewater concentration system. Background Technology

[0002] Concentration is a common step in wastewater treatment. By reducing the volume of wastewater, the amount of wastewater discharged can be effectively reduced, thus alleviating the pressure on the environment. At the same time, after wastewater is concentrated, it is easier to recover and reuse the valuable metals, chemicals or other substances contained in it.

[0003] Reverse osmosis systems are commonly used in wastewater treatment projects. Their main principle is that, under pressure, pure water passes through a membrane to the other side, obtaining clean pure water and thus increasing the concentration of the solution on the pressure side. This type of reverse osmosis system, based on spiral wound membranes, suffers from problems such as high osmotic pressure difference across the membrane, high operating pressure, and high energy consumption. Furthermore, the high pressure exceeds the capacity of the equipment and membrane materials themselves, creating a significant technical bottleneck: the concentration achievable by the reverse osmosis membrane concentration system is limited. Practical application data shows that even using the seawater desalination membrane system, which has the highest concentration tolerance, the maximum concentration achievable is only 7%-8%.

[0004] To achieve resource utilization of concentrated wastewater, further concentration via evaporation is typically required after reverse osmosis concentration. However, evaporation concentration consumes a significant amount of heat energy, resulting in high energy consumption throughout the entire wastewater concentration process. Simultaneously, the evaporation concentration process places extremely high demands on the high-temperature and corrosion resistance of equipment, leading to high equipment selection and maintenance costs. Furthermore, evaporation concentration under high concentration conditions is challenging, requiring strict control of various process parameters. This complex operation not only increases labor costs but also raises the risk of safety accidents due to improper operation. Ultimately, this significantly increases the overall cost of wastewater treatment projects, severely hindering the sustainable development and economic efficiency of the wastewater treatment industry. Utility Model Content

[0005] The present invention aims to provide a low-energy differential pressure reverse osmosis wastewater concentration system to solve the problems of high energy consumption and high investment cost in wastewater concentration treatment using traditional reverse osmosis membrane technology.

[0006] To achieve the above objectives, this utility model adopts the following technical solution: a low-energy differential pressure reverse osmosis wastewater concentration system, comprising a first reverse osmosis section and a second differential pressure reverse osmosis section. The first reverse osmosis section is used for primary osmosis concentration of wastewater and includes a first reverse osmosis device containing a spiral wound membrane. The first reverse osmosis device has one inlet and two outlets, namely a freshwater outlet and a concentrated solution outlet. The second differential pressure reverse osmosis section includes a differential pressure reverse osmosis device for secondary osmosis concentration of wastewater. The differential pressure reverse osmosis device includes multilayer membrane units and clamping components for clamping the membrane units. The membrane units include sheet-like membranes. The membrane and filter plate are located on both sides of the sheet-like permeation membrane and have inlet and outlet ports. Flow channels are provided on both sides of the sheet-like permeation membrane and the filter plate, through which a first solution and a second solution flow respectively. The inlet, outlet and flow channel on the same side of the sheet-like permeation membrane in each permeation membrane unit are connected to form an independent first channel and a second channel. The solution at the concentrated solution outlet of the first reverse osmosis section is divided into two parts. One part is pressurized and transported to the first channel of the second differential pressure reverse osmosis section, and the other part is transported to the second channel at normal pressure. The solution at the outlet of the second channel is circulated to the inlet of the first reverse osmosis equipment.

[0007] The principle and advantages of this scheme are:

[0008] This concentration system comprises a first reverse osmosis section and a second differential pressure reverse osmosis section. The first reverse osmosis section is used for primary wastewater concentration, and the second differential pressure reverse osmosis section is used for secondary wastewater concentration. Compared to traditional wastewater concentration, differential pressure reverse osmosis replaces evaporation concentration. Specifically, the principle of differential pressure reverse osmosis technology is to place solutions of the same solute but different concentrations on both sides of a osmotic membrane. Due to the difference in concentration between the solutions on both sides, there are different osmotic pressures on both sides of the osmotic membrane. At this point, the pressure required to allow the solvent in the concentrated solution to pass through the osmotic membrane into the dilute solution is exactly equal to the osmotic pressure difference between the concentrated and dilute solutions; that is, additional pressure needs to be applied to the concentrated solution. In this way, the concentrated solution obtained after the primary concentration undergoes secondary differential pressure reverse osmosis to achieve deep concentration. This invention includes the following technical effects:

[0009] 1. Reduced Overall Concentration Energy Consumption: In existing wastewater concentration technologies, traditional spiral wound reverse osmosis membrane concentration has a low concentration upper limit and relies on evaporation concentration for deep treatment. Evaporation concentration requires a continuous supply of high-grade heat energy and a high-temperature environment to ensure evaporation efficiency, resulting in extremely high energy costs. This wastewater concentration system replaces evaporation concentration with differential pressure reverse osmosis technology. After initial concentration in the first reverse osmosis section, the concentrated solution enters the second differential pressure reverse osmosis section. Utilizing the pressure difference between the solutions on both sides, the solvent permeates through the sheet-like reverse osmosis membrane without heating. This process mainly consumes the mechanical energy to maintain the pressure difference, which is more energy efficient than the heat energy consumed by evaporation concentration, thus fundamentally reducing system energy consumption. Moreover, after concentration treatment in the second reverse osmosis section, the concentration of the concentrate is significantly increased, meeting the requirements for deep treatment of most wastewater, resulting in a substantial reduction in the processing capacity of the evaporation concentration stage, or even eliminating the need for evaporation concentration altogether. From an overall system perspective, this not only avoids the large heat energy consumption of the evaporation concentration stage but also reduces the use of high-temperature and corrosion-resistant equipment, lowering energy consumption during equipment operation and maintenance.

[0010] 2. Segmented Concentration Enhances Concentration Efficiency and Concentration: The second differential pressure reverse osmosis section of this invention is a crucial link in deep concentration. Its differential pressure reverse osmosis equipment employs a multi-layer permeate membrane unit design, consisting of a sheet-like permeate membrane and filter plates on both sides. Through this structure, wastewater, after initial concentration in the first reverse osmosis section, enters the first channel of the second differential pressure reverse osmosis section. Since the sheet-like permeate membrane has the same solute solution on both sides, with one side being the high-pressure side connected to the first channel and the other the low-pressure side connected to the second channel, the solvent can permeate from the high-pressure side to the low-pressure side under the pressure difference, thereby further concentrating the wastewater. Compared to the traditional single spiral wound reverse osmosis membrane concentration method, segmented concentration can gradually increase the concentration of the concentrate, breaking through the limitation of existing technologies where the wastewater concentrate concentration can only reach 7%-8%, thus more closely approaching the requirements for deep wastewater treatment and reducing the necessity of subsequent evaporation and concentration, fundamentally solving the problem of insufficient concentration in existing technologies.

[0011] 3. Differential pressure reverse osmosis equipment has a simple structure, reducing investment costs: The independent first and second channels in the differential pressure reverse osmosis equipment not only make the flow path of wastewater within the system clear but also facilitate control and management. Each filter plate has an inlet and an outlet. The inlets, outlets, and flow channels on the same side of the sheet membrane in each membrane unit are connected to form independent first and second channels. This standardized and modular design not only facilitates equipment installation and maintenance, reducing equipment selection and maintenance costs, but also makes the operation process simpler and more intuitive. Compared with evaporation and concentration processes, which require strict control of various complex process parameters and are difficult to operate, this solution offers a more stable and controllable operation process, reducing reliance on the professional skills of operators, lowering labor costs, and reducing the risk of safety accidents caused by improper operation. This reduces the overall cost of the wastewater treatment project from multiple dimensions, improving the project's economic benefits and sustainability.

[0012] 4. In this scheme, the outlet solution obtained from the second channel of the differential pressure reverse osmosis equipment is circulated to the first reverse osmosis equipment for initial concentration, which not only further recovers valuable substances in the wastewater, but also avoids the additional energy consumption required for separate treatment.

[0013] Furthermore, both sides of the filter plate are engraved with folded channels, with a depth of 3-5 mm. This folded channel design ensures a more uniform solution distribution on both sides of the sheet-like permeable membrane, enabling sufficient differential pressure reverse osmosis and preventing insufficient permeation concentration due to excessively rapid flow, thus guaranteeing wastewater concentration efficiency and quality. Additionally, limiting the channel depth within this range ensures sufficient permeation of the solution on both sides of the sheet-like permeable membrane. If the channel is too deep, the portion of the solution far from the sheet-like permeable membrane cannot participate in the permeation concentration process, reducing concentration efficiency. Conversely, if the channel is too shallow, the solution will flow too quickly and not have enough time to participate in the concentration permeation, affecting the concentration effect.

[0014] Furthermore, the solutions on both sides of the sheet-like permeate membrane flow in the same direction. This symmetrical flow of the two solutions on both sides of the membrane maintains a relatively stable concentration difference, reducing fluctuations in membrane permeability caused by unstable concentration differences and ensuring wastewater concentration efficiency and quality. Simultaneously, it also reduces damage to the sheet-like permeate membrane and the overall equipment, improving equipment reliability and stability.

[0015] Furthermore, the initial concentration difference of the solutions in the first and second channels is no greater than 0.1 mol / L. The differential pressure reverse osmosis process relies on reducing the concentration difference of the solutions on both sides of the sheet-like osmotic membrane, thereby reducing the osmotic pressure difference. This causes the solvent to migrate from the high concentration (high pressure) side to the low concentration (low pressure) side under relatively low applied pressure. Setting the initial concentration difference to no greater than 0.1 mol / L ensures a small osmotic pressure difference in the system and reduces system energy consumption.

[0016] Furthermore, a grid for supporting the folded flow channel is provided between the filter plate and the sheet-like permeable membrane. A clamping bolt is installed at the outlet of the filter plate, and the matching clamping nut fixes the sheet-like permeable membrane and the grid, thereby separating the first and second channels.

[0017] Furthermore, the clamping assembly includes plate frames located on both sides of the permeation membrane unit, and the plate frames have clearance grooves to avoid the clamping bolts.

[0018] This utility model also provides a technical solution: a low-energy differential pressure reverse osmosis wastewater concentration process, which achieves wastewater concentration based on the above-mentioned concentration system, including the following steps:

[0019] Step 1: The pre-softened wastewater is pumped to the first reverse osmosis section for initial osmosis concentration to obtain fresh water and concentrated solution.

[0020] Step 2: The concentrated solution is divided into two parts. One part is pressurized by a high-pressure pump to form a high-pressure concentrated solution and is transported to the first channel. The other part is a normal-pressure concentrated solution and is directly transported to the second channel.

[0021] Step 3: The high-pressure concentrated solution and the atmospheric pressure concentrated solution are subjected to differential pressure osmosis in a differential pressure reverse osmosis device to obtain a concentrated solution and a dilute solution, respectively. The concentrated solution is the final concentrated product.

[0022] Step 4: The diluted solution and untreated wastewater are combined and transported together to the first reverse osmosis unit for initial concentration.

[0023] Furthermore, in step 2, the high-pressure concentrated solution and the atmospheric-pressure concentrated solution have the same volume.

[0024] The beneficial effects of this plan are:

[0025] 1. Deep concentration is achieved through the synergistic effect of segmented concentration and differential pressure drive:

[0026] This concentration process begins with initial permeation concentration in step 1, utilizing a traditional spiral-wound membrane to achieve preliminary solvent separation and solute enrichment, laying the foundation for subsequent deep concentration. In steps 2 and 3, the concentrated solution is divided into a high-pressure concentrated solution and an atmospheric-pressure concentrated solution, which are then transported to the first and second channels of a differential pressure reverse osmosis unit, respectively, for secondary permeation concentration using the pressure difference across the sheet-like membrane. This combination of segmented concentration and differential pressure drive achieves a higher degree of concentration compared to single reverse osmosis concentration.

[0027] Traditional spiral wound reverse osmosis membranes can only achieve a maximum concentration of 7% to 8% after concentration. However, this process, through segmented treatment, allows the differential pressure reverse osmosis equipment to further separate the solvent under the pressure difference, thereby increasing the concentration of the concentrate to a higher level. This effectively breaks through the concentration bottleneck of traditional technologies, meets the requirements for deep wastewater treatment, reduces the need for subsequent high-energy-consuming evaporation and concentration processes, and lowers the overall system energy consumption.

[0028] 2. Material recycling improves resource utilization efficiency and reduces energy consumption:

[0029] Step 4 involves combining the dilute solution produced by the differential pressure reverse osmosis unit with the untreated wastewater and sending them together to the first reverse osmosis unit for initial concentration. This material recycling design has multiple advantages. On the one hand, the dilute solution still contains a certain amount of recyclable resources. By mixing it with the wastewater for reprocessing, the maximum recycling of resources is achieved, improving the overall system's efficiency in extracting valuable substances from the wastewater.

[0030] On the other hand, from an energy consumption perspective, reusing the dilute solution avoids the additional energy consumption required for its separate treatment. If the dilute solution is treated separately, whether for further concentration or for compliance treatment before discharge, energy is required; however, by mixing it with wastewater and utilizing the treatment process of the first reverse osmosis section, the dilute solution can be reprocessed without increasing energy consumption, thereby reducing the overall energy consumption of the system and improving energy utilization efficiency.

[0031] 3. Parameter optimization ensures stable and efficient process operation:

[0032] The precise control of the volume ratio of high-pressure and atmospheric-pressure concentrated solutions in the process ensures that their volumes are identical. This allows for accurate control of the pressure difference across the sheet-like membrane in the differential pressure reverse osmosis unit, which is crucial for ensuring stable and efficient operation. A stable and appropriate pressure difference is fundamental to the efficient operation of the differential pressure osmosis process. This setting ensures a stable solvent permeation rate across the membrane, making the concentration process more uniform and efficient. It reduces energy waste and inconsistent treatment results caused by pressure fluctuations, further enhancing the stability and reliability of the entire process and lowering operating and management costs. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the overall system structure of an embodiment of the present utility model. Figure 1 .

[0034] Figure 2 This is a schematic diagram of the overall system structure of an embodiment of the present utility model. Figure 2 .

[0035] Figure 3This is a schematic diagram of the differential pressure reverse osmosis device according to an embodiment of the present invention.

[0036] Figure 4 This is a schematic diagram of the filter plate structure according to an embodiment of the present utility model. Detailed Implementation

[0037] The following detailed description illustrates the specific implementation method:

[0038] The reference numerals in the accompanying drawings include: 1. First reverse osmosis section, 1-1. Inlet, 1-2. Freshwater outlet, 1-3. Concentrated solution outlet, 1-3. Second differential pressure reverse osmosis section, 2. Differential pressure reverse osmosis equipment, 3. Plate and frame, 4. End plate, 5. Permeation membrane unit, 6. Filter plate, 7. Inlet, 8. Outlet, 9. Sheet-shaped permeation membrane, 10. Grid, 11. Screw, 12. Folded flow channel, 13. First solution inlet, 14. First solution concentrate outlet, 15. Second solution inlet, 16. Second solution dilution outlet, 17. First channel, 18. Second channel, 19. Clamping bolt, 20. Clearance groove, 21. High-pressure pump, 22.

[0039] Example 1

[0040] A low-energy differential pressure reverse osmosis wastewater concentration system, such as Figure 1 , Figure 2 As shown, it includes a first reverse osmosis section 1 and a second differential pressure reverse osmosis section 2. The first reverse osmosis section 1 is used for the initial osmosis concentration of wastewater and includes a first reverse osmosis device containing a spiral wound osmosis membrane. The first reverse osmosis device has one inlet 1-1 and two outlets, namely a freshwater outlet 1-2 and a concentrated solution outlet 1-3. The first reverse osmosis device is a conventional reverse osmosis device, which belongs to the prior art and will not be described in detail here.

[0041] The second differential pressure reverse osmosis section 2 includes a differential pressure reverse osmosis device 3, used for secondary osmosis concentration of wastewater, such as... Figure 3 , Figure 4 As shown, the differential pressure reverse osmosis device 3 includes multiple coaxially arranged permeate membrane units 6, and a clamping assembly for clamping the permeate membrane units 6, a sheet-like permeate membrane 10, and filter plates 7 located on both sides of the sheet-like permeate membrane 10. The clamping assembly includes a plate frame 4 located on both sides of the permeate membrane unit 6. The filter plate 7 and the plate frame 4 are provided with corresponding mounting holes, and screws 12 are installed in the mounting holes. The screws 12 connect the filter plate 7 and the plate frame 4 into a whole to achieve axial through support.

[0042] The sheet-like permeation membrane 10 forms a flow channel between itself and the filter plates 7 on both sides. Each filter plate 7 has an inlet 8 and an outlet 9. The inlets 8 and outlets 9 of the two filter plates 7 in the permeation membrane unit 6 are staggered on the circumferential plane. The inlets 8 and outlets 9 on the same side of the sheet-like permeation membrane 10 in each permeation membrane unit 6 are connected to form an independent first channel 18 and a second channel 19. A first solution and a second solution flow in the first channel 18, respectively. The pressure in the first channel 18 is greater than that in the second channel 19, and the concentration of the first solution is not less than that of the second solution.

[0043] The solution at the concentrated solution outlet 1-3 of the first reverse osmosis section 1 is divided into two parts. One part is pressurized by the high-pressure pump 22 and sent to the first channel 18 of the second differential pressure reverse osmosis section 2, and the other part is sent to the second channel 19 at normal pressure. The outlet of the second channel 19 in the second differential pressure reverse osmosis section 2, namely the second solution dilution outlet 17, is connected to the inlet 1-1 of the first reverse osmosis section 1 through a pipeline. This is used to send the obtained dilution to the untreated wastewater for concentration treatment, thereby realizing system circulation.

[0044] A grid 11 for supporting the folded flow channel 13 is provided between the filter plate 7 and the sheet-like permeable membrane 10. A clamping bolt 20 is installed at the outlet 9 of the filter plate 7, and its matching clamping nut fixes the sheet-like permeable membrane 10 and the grid 11, thus separating the first and second channels 19. The plate frame 4 has a relief groove 21 at the corresponding position of the clamping bolt 20 to prevent interference between the plate frame 4 and the clamping bolt 20, and also to ensure that the two plate frames 4 can press and fix the middle permeable membrane unit 6 to ensure airtightness.

[0045] The plate frames 4 at both ends are end plates 5, each with an interface. One end's interface is the first solution inlet 14 and the second solution diluent outlet 17, while the other end's interface is the first solution concentrate outlet 15 and the second solution inlet 16. The flow directions of the first and second solutions on both sides of the sheet-like permeable membrane 10 are the same, thereby maintaining a relatively stable concentration difference across the sheet-like permeable membrane 10, reducing fluctuations in the permeability performance of the sheet-like permeable membrane 10 caused by unstable concentration differences, and ensuring wastewater concentration efficiency and quality. Figure 3 The diagram illustrates the flow paths of the first and second solutions within the device. Solid arrows represent the flow path of the first solution, while hollow arrows represent the flow path of the second solution.

[0046] The filter plate 7 is engraved with folded channels 13, which are three-channel flows with a depth of 3-5 mm. The folded channel 13 design ensures a more uniform solution distribution on both sides of the sheet-like permeable membrane 10, enabling sufficient differential pressure reverse osmosis and preventing insufficient permeation concentration due to excessively fast flow, thus guaranteeing wastewater concentration efficiency and quality. Furthermore, limiting the channel depth within this range ensures sufficient permeation of the solution on both sides of the sheet-like permeable membrane 10. If the channel is too deep, the solution far from the sheet-like permeable membrane 10 cannot participate in the permeation concentration process, reducing concentration efficiency. Conversely, if the channel is too shallow, the solution will flow too quickly and not have enough time to participate in the concentration permeation, affecting the concentration effect.

[0047] The initial concentration difference of the solution entering the first channel 18 and the second channel 19 is no greater than 0.1 mol / L, which can effectively reduce the osmotic pressure difference caused by the concentration difference of the solution on both sides of the sheet-like permeation membrane 10, reduce the operating pressure acting on the concentration, and make water permeate through the sheet-like permeation membrane 10 more quickly and effectively under the same operating pressure conditions. This results in a lower solute content in the dilute solution in the second channel 19 and a higher solute concentration in the concentrate in the first channel 18, thereby reducing the overall system energy consumption.

[0048] Preferably, the solutions entering the first channel 18 and the second channel 19 are solutions of the same concentration. The smaller the concentration difference of the solutions on both sides of the sheet-like permeation membrane 10, the smaller the osmotic pressure difference between the two solutions. This results in a smaller pressure that needs to be overcome to achieve differential pressure reverse osmosis, a reduction in additional pressure, lower energy consumption for concentration, and greater energy efficiency and environmental friendliness.

[0049] This embodiment uses a wastewater concentration example for specific illustration:

[0050] The actual amount of wastewater that needs to be treated is 10m³. 3 / h, the first reverse osmosis section 1 is designed to process 16m³ / h. 3 / h, the design capacity of the second differential pressure reverse osmosis section 2 is 4m³ / h. 3 / h, based on the energy consumption of 3.53 kWh / m³ for seawater desalination in the first reverse osmosis section 1. 3 (With energy recovery, it is 2.5 kWh / m³) 3 Based on estimates, the energy required to concentrate seawater to a concentration of 14% using a differential pressure reverse osmosis system is 7.06 kWh / m³. 3 (5 kWh / m³ when energy recovery is available) 3 ).

[0051] Traditional concentration processes often employ high-pressure reverse osmosis combined with MVR (Mechanical Vapor Recompression). Still using 10m³... 3Based on a wastewater concentration of 10% by reverse osmosis, the mass is reduced to 3.5 tons. Further concentration to 14% by MVR requires evaporation of 1 ton of water. The energy consumption for MVR evaporation is 64 kWh / m³. 3 The calculated comprehensive energy consumption is 9.93 kWh / m³. 3 (With energy recovery device, it is 8.9 kWh / m³) 3 Therefore, compared with the traditional membrane concentration + MVR process, using a differential pressure reverse osmosis system for brine concentration can reduce energy consumption by more than 30%.

[0052] Example 2

[0053] Based on the above concentration system, this embodiment provides a low-energy differential pressure reverse osmosis wastewater concentration process, including the following steps:

[0054] Step 1: The pre-softened wastewater is pumped to the first reverse osmosis section 1 via high-pressure pump 22 for initial osmosis concentration to obtain fresh water and concentrated solution. Pre-softening treatment prevents scaling during wastewater concentration, which would reduce the permeation efficiency of the osmosis membrane and ensure concentration efficiency and quality.

[0055] Step 2: The concentrated solution is divided into two parts. One part is pressurized by the high-pressure pump 22 to form a high-pressure concentrated solution and is transported to the first channel 18. The other part is a normal-pressure concentrated solution and is directly transported to the second channel 19.

[0056] Step 3: The high-pressure concentrated solution and the atmospheric pressure concentrated solution are subjected to differential pressure osmosis in the differential pressure reverse osmosis equipment 3 to obtain concentrated solution and dilute solution respectively. The concentrated solution is the final concentrated product.

[0057] Step 4: The diluted solution and untreated wastewater are combined and transported together to the first reverse osmosis unit for initial concentration, and the above steps are repeated. In this way, on the one hand, the diluted solution still contains a certain amount of recyclable resources. By mixing it with the wastewater for reprocessing, the maximum recycling of resources is achieved, improving the overall system's efficiency in extracting valuable substances from the wastewater. On the other hand, from an energy consumption perspective, reusing the diluted solution avoids the additional energy consumption required for its separate treatment, reducing the overall energy consumption of the system's concentration and achieving energy conservation and environmental protection.

[0058] The wastewater concentration process described above first involves initial permeation concentration in step 1, using a traditional spiral wound membrane to achieve preliminary solvent separation and solute enrichment, laying the foundation for subsequent deep concentration. Then, in steps 2-3, the concentrated solution is divided into a high-pressure concentrated solution and an atmospheric-pressure concentrated solution, which are respectively transported to the first channel 18 and the second channel 19 of the differential pressure reverse osmosis unit 3. Secondary permeation concentration is then performed using the pressure difference across the sheet-like membrane 10. This combination of segmented concentration and differential pressure drive achieves a higher concentration effect compared to single reverse osmosis concentration. While the concentration of the concentrated solution after concentration using a traditional spiral wound reverse osmosis membrane is only 7%-8%, this process, through segmented treatment, allows the differential pressure reverse osmosis unit 3 to further separate the solvent under pressure difference, increasing the concentration of the concentrated solution to a higher level. This effectively breaks through the concentration bottleneck of traditional technologies, achieving a maximum concentration of 14%, meeting the requirements for deep wastewater treatment, reducing the need for subsequent high-energy-consuming evaporation concentration processes, and lowering overall system energy consumption.

[0059] Example 3

[0060] The difference between this embodiment and Embodiment 1 is that the inlet 8 and outlet 9 on the filter plate 7 are not arranged axially, but radially. Connecting pipes are installed on the outside of the filter plate 7 to connect the corresponding inlet 8 / outlet 9 in adjacent membrane units 6, making the first channel 18 and the second channel 19 independent and unobstructed. Compared to Embodiment 1, the radial arrangement of the inlet and outlet 9 on the filter plate 7 improves the sealing between the filter plate 7 and the sheet-like permeate membrane 10 in the membrane unit 6. However, this increases the thickness of the filter plate 7, and the external connecting pipes increase the overall space required for the equipment. Therefore, in practical applications, the arrangement of the inlet and outlet 9 on the filter plate 7 can be selected according to specific process requirements.

[0061] The above descriptions are merely embodiments of this utility model. Commonly known technical solutions and / or characteristics are not described in detail here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the technical solution of this utility model. These modifications and improvements should also be considered within the scope of protection of this utility model, and will not affect the effectiveness of the implementation of this utility model or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A low-energy differential pressure reverse osmosis wastewater concentration system, characterized in that: The system includes a first reverse osmosis section and a second differential pressure reverse osmosis section. The first reverse osmosis section is used for the initial permeation and concentration of wastewater and includes a first reverse osmosis device containing a spiral wound membrane. The first reverse osmosis device has one inlet and two outlets, namely a freshwater outlet and a concentrated solution outlet. The second differential pressure reverse osmosis section includes a differential pressure reverse osmosis device for the secondary permeation and concentration of wastewater. The differential pressure reverse osmosis device includes multi-layer membrane units and clamping components for clamping the membrane units. The membrane units include sheet-like membranes and filter plates. The filter plates are located on both sides of the sheet-like membranes and have inlets and outlets. Flow channels are provided on both sides of the sheet-like membranes and the filter plates, through which first and second solutions flow respectively. The inlets, outlets, and flow channels on the same side of the sheet-like membranes in each membrane unit are connected to form independent first and second channels. The concentrated solution outlet of the first reverse osmosis section is divided into two parts. One part is pressurized and transported to the first channel of the second differential pressure reverse osmosis section, and the other part is transported to the second channel at atmospheric pressure. The solution at the outlet of the second channel is circulated back to the inlet of the first reverse osmosis device.

2. The low-energy differential pressure reverse osmosis wastewater concentration system according to claim 1, characterized in that: The filter plate is engraved with folded flow channels, the depth of which is 3-5mm.

3. The low-energy differential pressure reverse osmosis wastewater concentration system according to claim 2, characterized in that: The flow direction of the solution on both sides of the sheet-like permeable membrane is the same.

4. A low-energy differential pressure reverse osmosis wastewater concentration system according to any one of claims 1-3, characterized in that: The initial concentration difference of the solution in the first channel and the second channel is no greater than 0.1 mol / L.

5. A low-energy differential pressure reverse osmosis wastewater concentration system according to claim 4, characterized in that: A grid for supporting the folded flow channel is provided between the filter plate and the sheet-like permeable membrane. A clamping bolt is installed at the outlet of the filter plate, and the matching clamping nut fixes the sheet-like permeable membrane and the grid, thereby separating the first and second channels.

6. A low-energy differential pressure reverse osmosis wastewater concentration system according to claim 5, characterized in that: The clamping assembly includes a plate frame located on both sides of the permeation membrane unit, and the plate frame has a clearance groove to avoid the clamping bolt.

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