Modularized multi-stage membrane distillation synchronous concentration device and method

Abstract

The invention belongs to the technical field of water treatment, and particularly relates to a modularized multi-stage membrane distillation synchronous concentration device and method. The device comprises one or two of a concentration module and a desalination module, the concentration module and the desalination module comprise the following devices which are stacked in sequence: a concentration piece, a porous membrane and a vacuum piece; each group of the sequentially stacked devices forms a membrane separation unit, and the number of the membrane separation units is one or more. The system adopts an innovative multi-stage modular expansion framework, and the core of the system is an inter-stage isolation structure based on gradient pressure balance. The whole process integration of front-end desalination and impurity removal, middle-end gradient concentration and tail-end pure water production is realized in the same set of plate and frame type assembly. According to the structure, the hydrophobic microporous membranes and the plate frame type assemblies are alternately stacked to form the concentration chamber and the desalination chamber, flexible expansion from a single stage to multiple stages is supported, and high concentration and desalination application scenes with different scales and treatment requirements are perfectly adapted.

Description

Technical Field

[0001] The present invention belongs to the technical field of water treatment, and in particular relates to a modular multi-stage membrane distillation synchronous concentration device and method. Background Art

[0002] Membrane distillation (MD), as a heat-driven membrane separation technology, has shown broad application prospects in recent years in fields such as seawater desalination (total dissolved solids (TDS)>35g / L), high-salt wastewater treatment (TDS>100g / L) and food concentration due to its ability to achieve high retention rate separation using low-grade heat sources (30-80℃).

[0003] However, the existing single-stage membrane distillation system still faces the following technical bottlenecks in industrial application:

[0004] Due to the attenuation of mass transfer driving force and the limitation of processing capacity, the water production flux of single-stage membrane distillation is mainly driven by the vapor pressure difference on both sides of the membrane. When treating high-concentration feed liquid (such as industrial wastewater with TDS>100g / L), the vapor pressure on the feed liquid side is significantly reduced, resulting in a decrease in the mass transfer driving force. Studies have shown that when the feed liquid TDS exceeds 150g / L, the water production flux attenuation rate can reach more than 60%. The traditional method of increasing the processing capacity by increasing the membrane area will aggravate the concentration polarization phenomenon due to the uneven distribution of the flow channel, resulting in a 30-50% increase in the solute concentration on the membrane surface, further reducing the mass transfer efficiency.

[0005] Thermal energy utilization is inefficient. Even with a multi-stage series structure (US20170349447A1), the inter-stage heat recovery rate is still less than 55%, making it difficult to meet the energy cost requirements for industrial-scale applications. Research has shown that combining solar energy (top heating) and waste heat (final stage heating) can achieve a synergistic "high-temperature-low-temperature" gradient, reducing reliance on a single heat source. Research has also shown that a multistage osmotically assisted reverse osmosis process for concentrating solutions using hollow fiber membrane modules, with 10 HF membrane modules connected in series, with the concentrate from the first stage used as the feed for the next stage and the same pressure applied to each stage (10–15 bar), can achieve a gradual increase in concentration.

[0006] Complex structure and difficult maintenance: Multi-stage membrane modules rely on external series equipment (e.g., CN201110428029.6) to achieve multi-stage design, which can meet most non-high-temperature and high-pressure operating conditions. Research has shown that (Optimal design of multi-stage vacuum membrane distillation and integration with supercritical water desalination for improved zero liquid discharge desalination) by designing temperature gradients between multi-stage VMD stages, the latent heat of condensation from the previous stage can be used to preheat the feed in the next stage, achieving heat recovery.

[0007] Membrane fouling control and system scalability are insufficient. When traditional flat-plate membrane modules process high-concentration feed solutions, local stagnant areas are easily formed in the flow channel, resulting in an accelerated solute crystallization rate. Experimental data show that when the feed solution TDS exceeds 80g / L, the incidence of membrane pore wetting increases by 2-3 times. Existing patents (such as CN113354013B) mostly limit the number of stages to a fixed number (such as 40 stages), and cannot dynamically adjust the flow channel parameters or stage configuration according to the feed liquid characteristics (salt concentration, viscosity). For example, when processing high-viscosity food solutions (viscosity ≥ 300mPa·s), customized equipment modification is required, and the module reuse rate is less than 20%. Studies have shown that (Application of vacuum membrane distillation for concentration) simulates a multi-stage effect through cyclic concentration (the feed solution refluxes through a single-stage module multiple times) to gradually increase the concentration.

[0008] In contrast, the optimized multi-stage assembly's S-shaped flow channel coupled with a diamond-shaped manifold array design can increase the salt content at the concentration endpoint by 1.6 times, while reducing back-end processing energy consumption by 38-50%. Furthermore, existing multi-stage systems often use a fixed series structure, which cannot flexibly adjust the number of stages or flow channel parameters based on the characteristics of the feed liquid (such as salt concentration and viscosity), limiting process adaptability. Existing membrane distillation technology for heavy water treatment faces core issues such as single functionality, low thermal energy utilization efficiency, complex components, insufficient adaptability, and poor system scalability and process adaptability.

[0009] In addition, membrane distillation technology faces many challenges in the process of concentration and desalination industrial applications. For example:

[0010] Membrane components have a single function: Traditional systems only support one-way operation (for example, patent CN113354013B only focuses on the concentration function), and cannot flexibly switch between concentration and desalination modes according to demand, resulting in low equipment utilization and limited application scenarios.

[0011] Poor system scalability and process adaptability: Existing multi-stage membrane components mostly adopt a fixed series structure (such as patent KR102020012258A), which cannot dynamically adjust the flow channel parameters (such as width, inclination) or stage configuration according to the characteristics of the feed liquid (salt concentration, viscosity). Faced with diverse application scenarios (such as high-viscosity food solutions and high-salt wastewater), customized equipment modification is required, resulting in the development cycle being extended by more than 50%, and the module reuse rate being less than 20%. Studies have shown (Chemical Engineering Research and Design doi: 10.1016 / j.cherd.2020.07.029) that after the number of stages exceeds 10, the viscosity of the concentrated water increases significantly, resulting in a sudden increase in mass transfer resistance and a drop in flux to 50% of the initial value.

[0012] Low thermal energy utilization efficiency: The latent heat recovery efficiency of steam is low, the multi-stage condensation process does not achieve cascaded thermal energy utilization (for example, the solar membrane distillation system relies on a single-stage condensation), the auxiliary heating equipment consumes a high proportion of energy, and the overall energy efficiency is insufficient. Existing research shows (the ITEWA team of Shanghai Jiaotong University published the results in Nature Communications (doi:10.1038 / s41467-024-51880-y)): The multi-stage solar membrane distillation system is heavily dependent on external heat sources (requiring 250W·m -2 Power is continuously input). The thermal pressurization mechanism causes the system maintenance cost to increase by more than 30%. Studies have shown that although the air gap reduces heat loss, it increases the water vapor diffusion resistance, which may require a higher flow rate to offset.

[0013] Complex structure and difficult maintenance: Multi-stage membrane modules rely on external tandem equipment (e.g., CN201110428029.6), resulting in bulky systems, low integration, and difficulty adapting to high-temperature and high-pressure operating conditions. Existing research (10.1016 / j.jclepro.2022.132189.) indicates that multi-stage SCWD requires a high-temperature heat source (>450°C), limiting the direct application of renewable energy sources such as solar energy. The integration of multi-stage VMD and SCWD requires precise thermal matching and pressure control, resulting in high equipment investment costs.

[0014] Severe membrane fouling and high maintenance costs: Traditional flat-plate flow channels have dead zones (>15% stagnation), which accelerate solute crystallization and membrane pore wetting (the risk of membrane wetting increases 2-3 times when TDS > 80 g / L). Frequent system downtime for cleaning (50-80 hours) shortens membrane life to less than one year, increases equipment maintenance costs by 30%-40%, and reduces system stability during continuous operation due to frequent starts and stops.

[0015] Structural complexity and high manufacturing costs: Existing patents (such as CN113354013B) often limit the number of stages to a fixed number (such as 40). They cannot dynamically adjust the flow channel parameters or the number of stages according to the characteristics of the feed liquid (salt concentration, viscosity), and the processing scale cannot be flexibly increased or decreased, resulting in insufficient scalability. For example, when processing high-viscosity food solutions (viscosity ≥ 300mPa·s), customized equipment must be modified, and the module reuse rate is less than 20%. The equipment occupies a large area, making it difficult to adapt to industrial sites with limited space, and the initial investment cost hinders the promotion of the technology.

[0016] Poor adaptability and insufficient stability: Lack of intelligent control means, unable to dynamically adjust the temperature, vacuum degree and flow rate according to the concentration of the feed liquid (for example, low-concentration heavy water requires high pressure difference drive, and high concentration requires anti-pollution strategy), resulting in unstable treatment efficiency.

[0017] Lack of technical integration: Existing research focuses on single improvements (such as uniform distribution to prevent pollution), lacks system integration of multi-stage membrane components, heat recovery and intelligent regulation, and is unable to meet the comprehensive needs of high efficiency, flexibility and low energy consumption.

[0018] In order to solve at least part of the above problems, this application is proposed. Summary of the Invention

[0019] The present application provides a modular multi-stage membrane distillation simultaneous concentration device, the device comprising: one or both of a concentration module and a desalination module;

[0020] The concentration module includes the following components stacked in sequence: a concentration component, a porous membrane, and a vacuum component;

[0021] Each group of the devices stacked in sequence forms a membrane separation unit, and the number of membrane separation units in the concentration module is one or more;

[0022] In each membrane separation unit of the concentration module, the communication mode of each device is as follows:

[0023] The concentrating element has a concentrating flow channel on at least one surface in the stacking direction, and the concentrating element has a concentrating element liquid inlet and a concentrating element liquid outlet communicated with the concentrating flow channel;

[0024] The porous membrane is stacked on the surface of the concentrating flow channel of the concentrating element;

[0025] The vacuum component has a vacuum chamber facing the porous membrane, which is used to allow the liquid in the concentration flow channel of the concentration component to partially vaporize, pass through the porous membrane, enter the vacuum chamber, and condense;

[0026] The concentrated liquid outlet of the concentrated element of the concentration module is connected to the concentrated liquid inlet of the concentrated element of the next membrane separation unit to achieve continuous concentration of the liquid;

[0027] The condensate outlet of the vacuum chamber of the membrane separation unit of the concentration module is used to discharge the desalinated liquid, or is connected to the concentrate liquid inlet of the concentrate of the corresponding membrane separation unit of the desalination module for further desalination of the desalinated liquid;

[0028] The desalination module includes the following components stacked in sequence: a concentrating component, a porous membrane, and a vacuum component;

[0029] Each group of the devices stacked in sequence forms a membrane separation unit, and the number of membrane separation units in the concentration module and the desalination module is one or more;

[0030] In each membrane separation unit of the desalination module, the connection mode of each device is as follows:

[0031] The concentrating element has a concentrating flow channel on at least one surface in the stacking direction, and the concentrating element has a concentrating element liquid inlet and a concentrating element liquid inlet communicating with the concentrating flow channel;

[0032] The porous membrane is stacked on the surface of the concentrating flow channel of the concentrating element;

[0033] The vacuum component has a vacuum chamber facing the porous membrane, which is used to allow the liquid in the concentration flow channel of the concentration component to partially vaporize, pass through the porous membrane, enter the vacuum chamber, and condense;

[0034] The condensate outlet of the vacuum chamber is connected to the concentrate liquid inlet of the concentrate of the next membrane separation unit of the desalination module to achieve continuous desalination of the liquid;

[0035] The concentrate liquid outlet of the concentrate of the non-first membrane separation unit of the desalination module is used to discharge the concentrate, or is connected to the concentrate liquid inlet of the concentrate of the membrane separation unit of the corresponding stage of the concentration module for further concentrating the liquid.

[0036] The concentrate liquid inlet of the concentrate of the first membrane separation unit of the desalination module is used to receive the liquid to be treated;

[0037] When the device comprises a concentration module and a desalination module:

[0038] The stacking order of the components in the concentration module and the desalination module is opposite;

[0039] The concentrating element liquid outlet of the concentrating element of the first membrane separation unit of the desalination module is connected to the concentrating element liquid inlet of the first membrane separation unit of the concentrating module; or, the concentrating element of the first membrane separation unit of the desalination module has concentrating flow channels on both surfaces in the stacking direction, and the concentrating element liquid outlet of the concentrating element of the first membrane separation unit of the desalination module is connected to the inlet of the concentrating flow channel on the back side of the concentrating element. In this case, the concentrating module and the desalination module share the same concentrating element at the junction of the two modules.

[0040] Preferably, the concentration module further comprises: a desalination auxiliary heating element stacked on the back of the vacuum chamber of the vacuum element;

[0041] The desalination module further comprises: a desalination auxiliary heating element stacked on the back of the vacuum chamber of the vacuum element;

[0042] The desalination auxiliary heating element comprises a condensate flow channel and a heat source for heating the liquid in the condensate flow channel;

[0043] The condensate outlet of the vacuum chamber is connected to the condensate flow channel inlet of the desalination auxiliary heating component, and the flow channel outlet of the desalination auxiliary heating component is connected to the concentrate liquid inlet of the concentrate component of the next membrane separation unit of the desalination module or the concentration module.

[0044] Preferably, a diverter plate is provided between the concentrating element and the porous membrane;

[0045] The diverter plate includes: a porous bottom plate and a protrusion located on the porous bottom plate;

[0046] The diverter plate is configured such that the protrusions are embedded in the concentrating flow channel of the concentrating element. The porous bottom plate is attached to the surface of the concentrating flow channel of the concentrating element.

[0047] Preferably, a protrusion is provided in the concentrating flow channel of the concentrating element, so that a porous bottom plate is not required.

[0048] Preferably, the porous membrane is a hydrophobic microporous membrane, and the pore size thereof is in the micrometer or nanometer scale.

[0049] Preferably, a sealing ring is provided between the components.

[0050] Preferably, the vacuum chamber of the vacuum component is connected to a vacuum pumping system;

[0051] A bevel plate is also provided in the vacuum chamber of the vacuum component;

[0052] One side of the beveled plate is higher than the other side, and the beveled plate is provided with a hole so that the condensed liquid in the vacuum chamber flows into the liquid collecting tank at the bottom of the vacuum chamber through the hole.

[0053] Preferably, in the device, from a certain position forward, the devices in the membrane separation unit are stacked in sequence in the above reverse order to form the concentration module, and from the certain position backward, the devices in the membrane separation unit are stacked in sequence in the above order to form the desalination module.

[0054] A second aspect of the present application provides a modular multi-stage membrane distillation simultaneous concentration method, the method using the modular multi-stage membrane distillation simultaneous concentration device according to any one of the first aspects;

[0055] The working method of the desalination module comprises the following steps:

[0056] The liquid to be treated enters from the concentration unit liquid inlet of the concentration unit of the first membrane separation unit of the desalination module and flows into the concentration flow channel of the concentration unit;

[0057] In the concentration flow channel, part of the liquid to be treated is vaporized under the negative pressure transmitted from the vacuum chamber and passes through the porous membrane into the vacuum chamber and condenses;

[0058] The liquid obtained after condensation flows out from the condensate outlet of the vacuum chamber and enters the concentrate liquid inlet of the concentrate of the next membrane separation unit of the desalination module to flow into the concentrate flow channel, and the above steps are repeated to perform multi-stage desalination;

[0059] The unvaporized liquid in the concentrating flow channel of the concentrating element is discharged from the desalination module through the concentrating element liquid inlet of the concentrating element, or is discharged into the concentrating element liquid inlet of the concentrating element of the membrane separation unit of the corresponding stage of the concentrating module for further concentration of the liquid;

[0060] The working method of the enrichment module comprises the following steps:

[0061] The liquid to be treated enters the concentration flow channel of the concentration element of the first membrane separation unit of the concentration module. In the concentration flow channel, part of the liquid to be treated is vaporized under the action of the negative pressure transmitted by the vacuum chamber and passes through the porous membrane into the vacuum chamber and condenses.

[0062] The liquid obtained after condensation flows out of the concentration module from the condensate outlet of the vacuum chamber, or is discharged into the concentration unit liquid inlet of the concentration unit of the corresponding stage membrane separation unit of the desalination module for further desalination of the desalinated liquid;

[0063] The unvaporized liquid flows out from the liquid inlet of the concentrating element to the liquid inlet of the concentrating element of the next membrane separation unit of the concentrating module to enter the concentrating flow channel, and the above steps are repeated to perform multi-stage concentration.

[0064] When the device comprises a concentration module and a desalination module:

[0065] In the concentrating flow channel of the concentrating element of the first membrane separation unit of the desalination module, the liquid that has not been vaporized flows out from the concentrating element liquid inlet of the concentrating element and then enters the concentrating flow channel on the back of the concentrating element or enters the concentrating flow channel of the concentrating element of the first membrane separation unit of the concentrating module;

[0066] The liquid to be treated is at a temperature of 30-80 degrees Celsius.

[0067] Preferably, before the liquid obtained after condensation flows out from the condensate outlet of the vacuum chamber and enters the concentrate liquid inlet of the concentrate of the next membrane separation unit of the desalination module:

[0068] The liquid obtained after condensation flows out from the condensate outlet of the vacuum chamber, enters the condensate flow channel through the condensate flow channel inlet of the desalination auxiliary heating component, is heated by the heat source in the condensate flow channel, and then enters the concentrated component liquid inlet of the next membrane separation unit of the desalination module from the condensate flow channel outlet of the desalination auxiliary heating component.

[0069] Compared with the prior art, the present invention has the following beneficial effects:

[0070] 1. Multi-stage modular expansion: This system adopts an innovative multi-stage modular expansion architecture, the core of which is the inter-stage isolation structure based on gradient pressure balance. The full process integration of "front-end desalination and impurity removal - mid-end gradient concentration - end-end pure water output" is achieved in the same set of plate-and-frame components. This structure forms concentration chambers and desalination chambers by alternately stacking high-performance hydrophobic microporous membranes such as PTFE / PVDF / PP with plate-and-frame components. It supports flexible expansion from single to multi-stage and is perfectly adapted to high-concentration and desalination application scenarios of different scales and treatment requirements (such as zero discharge of industrial wastewater, drug extraction and purification, desalination concentrate treatment, high-salt material concentration, azeotropic separation, radioactive wastewater treatment, juice concentration, dairy processing, etc.).

[0071] 2. Multi-stage membrane module integrated process integration: Utilizing a fully coupled plate-and-frame membrane module design, the concentration and desalination modules are isolated and connected in series via interstage sealing structures. This eliminates the need for external switching valves and pipeline reconfiguration, enabling simultaneous gradient concentration of feed liquid and pure water production, creating a highly integrated multi-stage treatment system. This increases equipment utilization to over 95%, reduces pipeline connection nodes by 40%, and reduces leak risk and control complexity.

[0072] 3. Efficient Condensate Recovery: The vacuum chamber integrates beveled guide baffles and a cold wall condensation module, achieving a three-stage process: condensation, liquid accumulation, and waste heat recovery. Three-dimensional flow field simulation optimizes the beveled plate angle and cold wall heat exchange area, achieving a vapor phase change efficiency exceeding 98%. Condensate is discharged directly into the sump at the bottom of the vacuum chamber through four or five sets of guide holes in the beveled plates, shortening the transfer path by 30% and increasing latent heat recovery efficiency by 25%.

[0073] 4. Adopting a multi-functional S-shaped flow channel integrated design - compact flow channel design: Preferably, the condensate flow channel on the surface of the desalination auxiliary heating component of the present application is an S-shaped flow channel, and the other surface of the desalination auxiliary heating component has an S-shaped auxiliary heating liquid flow channel. There is a heat source in the S-shaped auxiliary heating liquid flow channel, which is used to heat the liquid in the condensate flow channel. The double-sided composite flow channel plate of the desalination auxiliary heating component integrates the front S-shaped condensate flow channel and the back S-shaped auxiliary heating liquid flow channel to achieve direct heat exchange and reduce energy consumption. The above can be optimized through CFD simulation to achieve reverse thermal energy coupling of hot and cold fluids. This design simplifies the piping system by 60%, reduces the device volume by 40%, reduces the manufacturing cost by 35%, and the thermal energy step utilization rate reaches 85%. In addition, the condenser and desalination auxiliary heating component are both arranged with S-shaped flow channels with different functions. CFD simulation optimization can be used to further refine the flow channel angle and heat exchange area to reduce heat loss.

[0074] 5. Membrane fouling control and elimination of flow dead zones: Preferably, the bumps on the manifold are diamond-shaped. By optimizing the flow field and forming a regular array of diamond blocks, the diamond blocks are connected at angles of 60°-120° to each other, eliminating fluid dead zones (stagnation zones account for less than 5%), increasing membrane shear rate by 30%, and suppressing concentration polarization (ΔC / C0 ≤ 15%). This structural design guides the fluid to flow along a preset trajectory, resolving concentration polarization and turbulence issues.

[0075] Preferably, the surface of the bumps on the diverter plate can be coated with a hydrophilic coating. After the hydrophilic coating is treated (contact angle < 60°), the pollutant attachment rate is reduced by 65%, and the membrane cleaning cycle is extended to 2.5 times that of traditional devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0076] Figure 1 This is an exploded diagram of the multi-stage membrane distillation simultaneous concentration and desalination device of this application.

[0077] Figure 2 Schematic diagram of the concentrated component structure.

[0078] Figure 3 This is a schematic diagram of the front structure of the desalination auxiliary heating component.

[0079] Figure 4 It is a schematic diagram of the back structure of the desalination auxiliary heating component.

[0080] Figure 5 Schematic diagram of the vacuum component structure.

[0081] Figure 6 This is the structural diagram of the diamond-shaped manifold.

[0082] Figure 7 Schematic diagram of the position of the diamond-shaped manifold and the concentrating flow channel of the concentrator.

[0083] Figure 8 This is the velocity cloud diagram of the flow field without diamond-shaped diverter plates in the concentration channel.

[0084] Figure 9 This is the velocity cloud diagram of the flow field with a diamond-shaped diverter plate in the concentration channel.

[0085] List of reference numerals:

[0086] 1. Concentrator, 1-1, Concentrator liquid inlet, 1-2, Concentrator sealing ring groove, 1-3, Concentrator flow channel, 1-4, Concentrator liquid outlet, 1-5, Concentrator flow channel outlet;

[0087] 2. Porous membrane;

[0088] 3. Vacuum component, 3-1. Vacuum channel, 3-2. Vacuum through hole, 3-3. Condensation wall, 3-4. Bevel plate through hole, 3-5. Bevel plate, 3-6. Condensate outlet, 3-7. Vacuum component sealing ring slot;

[0089] 4. Desalination auxiliary heating element, 4-1. Condensate flow channel outlet, 4-2. Desalination side sealing ring slot, 4-3. Condensate flow channel inlet, 4-4. Condensate flow channel, 4-5. Auxiliary heating inlet, 4-6. Auxiliary heating side sealing ring slot; 4-7. Auxiliary heating outlet, 4-8. Auxiliary heating liquid flow channel;

[0090] 5. Diamond-shaped manifold, 5-1. Diamond-shaped block, 5-2. Turbulent flow area of ​​diamond-shaped manifold;

[0091] 6. Sealing ring. DETAILED DESCRIPTION

[0092] The present application is further described in detail below with reference to the embodiments.

[0093] Those skilled in the art will understand that the following examples are intended to illustrate the present invention only and should not be construed as limiting the scope of the present invention. Where specific techniques or conditions are not specified in the examples, the techniques or conditions described in the literature in the art or in the product specifications were used. Materials or equipment used without manufacturer identification are conventional products that can be purchased.

[0094] Those skilled in the art will appreciate that, unless expressly stated otherwise, the singular forms "one", "an", "said" and "the" used herein may also include plural forms. In the description of this application, unless otherwise stated, "a plurality" means two or more. It should be further understood that the term "comprising" used in the specification of this application refers to the presence of the features, integers, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or groups thereof. It should be understood that when we refer to an element as being "connected" to another element, it may be directly connected to the other element, or there may be intermediate elements. In addition, the "connection" used here may include wireless connections.

[0095] In the description of this application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like to indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on this application.

[0096] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. Throughout the description of this application, "plurality" means two or more, unless otherwise specifically defined.

[0097] In this application, unless otherwise expressly specified or limited, terms such as "mounted," "connected," "connect," and "fixed" should be understood broadly. For example, they may refer to connection, detachable connection, or integration; mechanical connection or electrical connection; direct connection or indirect connection through an intermediate medium; and internal communication between two components or interaction between two components. Those skilled in the art will understand the specific meanings of the above terms in this application based on specific circumstances.

[0098] In this application, unless otherwise expressly specified or limited, a first feature being "above" or "below" a second feature may include the first and second features being in direct contact, or may include the first and second features being in contact not directly but through another feature between them. Moreover, a first feature being "above," "above," and "above" a second feature may include the first feature being directly above or obliquely above the second feature, or may simply mean that the first feature is higher in level than the second feature. A first feature being "below," "below," and "below" a second feature may include the first feature being directly below or obliquely below the second feature, or may simply mean that the first feature is lower in level than the second feature.

[0099] In the description of this specification, the reference terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic expressions of the above terms should not be understood as necessarily referring to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification.

[0100] It will be understood by those skilled in the art that, unless otherwise defined, all terms used herein, including technical and scientific terms, have the same meaning as commonly understood by those skilled in the art to which this application belongs. It should also be understood that terms such as those defined in common dictionaries should be understood to have meanings consistent with their meanings in the context of the prior art and, unless defined as such, will not be interpreted in an idealized or overly formal sense.

[0101] The present application provides a modular multi-stage membrane distillation concentration device and method.

[0102] The device comprises: one or both of a concentration module and a desalination module.

[0103] The concentration module comprises the following components stacked in sequence: a concentration component 1, a porous membrane 2, and a vacuum component 3;

[0104] Each group of the devices stacked in sequence forms a membrane separation unit. In the concentration module, the number of the membrane separation units is one or more.

[0105] In each membrane separation unit of the concentration module, the communication mode of each device is as follows:

[0106] The concentrating element 1 has a concentrating flow channel 1-3 on at least one surface in the stacking direction, and the concentrating element 1 has a concentrating element liquid inlet 1-1 and a concentrating element liquid outlet 1-4 communicating with the concentrating flow channel 1-3;

[0107] The concentration flow channel 1-3, the concentration flow channel outlet 1-5, and the concentration element liquid outlet 1-4 are connected in sequence;

[0108] The porous membrane 2 is stacked on the surface of the concentrating flow channels 1-3 of the concentrating element 1;

[0109] The vacuum component 3 has a vacuum chamber facing the porous membrane 2, which is used to allow the liquid in the concentrating flow channel 1-3 of the concentrating component 1 to partially vaporize, pass through the porous membrane 2, enter the vacuum chamber, and condense;

[0110] The concentrated liquid outlet 1-4 of the concentrated element 1 of the concentration module is connected to the concentrated liquid inlet 1-1 of the concentrated element 1 of the next membrane separation unit to achieve continuous concentration of the liquid;

[0111] The condensate outlets 3-6 of the vacuum chamber of the membrane separation unit of the concentration module are used to discharge the desalinated liquid, or are connected to the concentrate liquid inlet 1-1 of the concentrate 1 of the corresponding membrane separation unit of the desalination module for further desalination of the desalinated liquid.

[0112] The desalination module includes the following components stacked in sequence: a concentration component 1, a porous membrane 2, and a vacuum component 3. In each membrane separation unit of the desalination module, the components are connected in the following manner:

[0113] Each group of the devices stacked in sequence forms a membrane separation unit, and the number of membrane separation units in the concentration module and the desalination module is one or more;

[0114] The concentrating element 1 has a concentrating flow channel on at least one surface in the stacking direction, and the concentrating element 1 has a concentrating element liquid inlet 1-1 and a concentrating element liquid outlet 1-4 communicating with the concentrating flow channel 1-3;

[0115] The porous membrane 2 is stacked on the surface of the concentrating flow channels 1-3 of the concentrating element 1;

[0116] The vacuum component 3 has a vacuum chamber facing the porous membrane 2, which is used to allow the liquid in the concentrating flow channel 1-3 of the concentrating component 1 to partially vaporize, pass through the porous membrane 2, enter the vacuum chamber, and condense;

[0117] The condensate outlet 3-6 of the vacuum chamber is connected to the concentrate liquid inlet 1-1 of the concentrate 1 of the next membrane separation unit of the desalination module to achieve continuous desalination of the liquid;

[0118] The concentrate liquid outlets 1-4 of the concentrate 1 of the non-first membrane separation unit of the desalination module are used to discharge the concentrate, or are connected to the concentrate liquid inlet 1-1 of the concentrate 1 of the membrane separation unit of the corresponding stage of the concentration module for further concentrating the liquid:

[0119] The concentrate liquid inlet 1-1 of the concentrate of the first membrane separation unit of the desalination module is used to receive the liquid to be treated;

[0120] When the device comprises a concentration module and a desalination module:

[0121] The stacking order of the components in the concentration module and the desalination module is opposite;

[0122] The concentrating element liquid inlet 1-1 of the concentrating element 1 of the first membrane separation unit of the desalination module is connected to the concentrating element liquid inlet 1-1 of the first membrane separation unit of the concentrating module; or, the concentrating element 1 of the first membrane separation unit of the desalination module has concentrating flow channels 1-3 on both surfaces in the stacking direction, and the concentrating element liquid inlet 1-1 of the concentrating element 1 of the first membrane separation unit of the desalination module is connected to the inlet of the concentrating flow channel 1-3 on the back side of the concentrating element 1. In this case, the concentrating module and the desalination module share the same concentrating element at the junction of the two modules.

[0123] Preferably, the concentration module further comprises: a desalination auxiliary heating element 4 stacked in reverse order on the surface of the vacuum element 3;

[0124] The desalination module further comprises: desalination auxiliary heating elements 4 sequentially stacked on the surface of the vacuum element 3;

[0125] The desalination auxiliary heating element 4 has a condensate flow channel 4-4 and a heat source for heating the liquid in the condensate flow channel 4-4;

[0126] The condensate outlet 3-6 of the vacuum chamber is connected to the condensate flow channel inlet 4-3 of the desalination auxiliary heating component 4, and the condensate flow channel outlet 4-1 of the desalination auxiliary heating component 4 is connected to the concentrate liquid inlet 1-1 of the concentrate 1 of the next membrane separation unit of the desalination module or the concentration module.

[0127] The porous membrane 2 is preferably a hydrophobic microporous membrane.

[0128] In a preferred embodiment:

[0129] The details of the concentrating element 1 are as follows: the concentrating element 1 has a concentrating chamber. The concentrating chamber of the first membrane separation unit of the desalination module acts as the first-stage feed chamber, and is equipped with an S-shaped concentrating flow channel 1-3. The diamond diverter plate 5 is stacked in the S-shaped concentrating flow channel. The concentration polarization on the membrane surface is reduced by enhancing turbulence. The feed liquid enters the S-shaped concentrating flow channel 1-3 from the liquid inlet 1-1 of the concentrating element, and passes through the diamond diverter plate 5 in the S-shaped concentrating flow channel 1-3 to make the fluid turbulent and reduce the dead zone. Among them, the diamond diverter plate 5 has diamond blocks 5-1. The space between different diamond blocks 5-1 forms a diamond diverter plate flow turbulence zone 5-2. The diamond diverter plate 5 and the S-shaped concentrating flow channel 1-3 stack enhance the fluid dynamics characteristics in the assembly. Under the action of the porous membrane 2 and the vacuum element 3, it is conducive to the vacuum membrane distillation process. Part of the gas passes through the hydrophobic microporous membrane into the vacuum chamber and is condensed into primary desalinated water.

[0130] Figure 6 This is a diagram of the diamond-shaped manifold structure. The holes on the porous bottom plate are not shown.

[0131] The remaining feed liquid that has not been vaporized flows through the S-shaped concentration flow channel 1-3, and finally flows out through the S-shaped concentration flow channel 1-3, flows into the first concentration chamber of the concentration module through the concentration component liquid inlet 1-2 of the first membrane separation unit of the concentration module, and then under the action of the porous membrane 2 and the vacuum component 3, the above-mentioned membrane distillation process occurs, completing a concentration process, and the liquid that has not been vaporized is used as the first-level concentrated water. The first-level concentrated water enters the second stage of the concentration module, and through the stacking of the porous membrane 2 and the vacuum component 3, the vacuum membrane distillation process is repeated. Part of the liquid vaporizes and passes through the hydrophobic microporous membrane into the vacuum chamber to become secondary desalinated water. The remaining feed liquid that has not been vaporized flows through the S-shaped flow channel 2-2 and flows out into the secondary concentration chamber of the concentration component of the second membrane separation unit of the concentration module, and through the stacking of the porous membrane 2 and the vacuum component 3, the vacuum membrane distillation process is repeated to achieve secondary concentration. By analogy, the multi-stage membrane distillation concentration process can be expanded.

[0132] The outer periphery of the S-shaped concentrating flow channel 1-3 of the concentrating element is provided with a concentrating element sealing ring groove 1-2, which is equipped with a sealing ring 6 to seal the S-shaped concentrating flow channel 1-3 of the concentrating element. Each membrane separation unit is composed of a stack of components such as the concentrating element 1, the sealing ring 6, the diamond-shaped diverter plate 5, the porous membrane 2, and the vacuum element 3.

[0133] The pore size of the hydrophobic microporous separation membrane can be micrometer- or nanometer-sized. For example, the pore size is 0.1 to 0.5 μm. The hydrophobic microporous separation membrane is made of PTFE, PP, or PVDF. The surface of the hydrophobic microporous membrane is bonded to the diamond-shaped diverter plate 5, achieving a step-by-step concentration or desalination process.

[0134] The structure of the vacuum component 3 is as follows: the vacuum component 3 contains a vacuum chamber. The vacuum chamber is open only on the side facing the porous membrane 2. A bevel plate 3-5 is built into the vacuum chamber, and a bevel plate through hole 3-4 is provided on the bevel plate 3-5. The vacuum component 3 has a vacuum channel 3-1 connected to the outside world. The top wall of the vacuum chamber is provided with three vacuum through holes 3-2 connecting the vacuum chamber cavity and the vacuum channel 3-1, which are used to vacuum the vacuum chamber. After entering the vacuum chamber, the steam contacts the vacuum chamber wall, i.e., the condensation wall 3-3, and liquefies. It flows along the condensation wall 3-3 through the bevel plate through holes 3-4 on the bevel plate 3-5 to the bottom of the vacuum chamber, and finally gathers and flows into the primary desalination chamber through the condensate outlet 3-6 of the vacuum chamber, completing a desalination process. The first-stage desalinated water enters the second stage, and through the stacking of single-stage vacuum membrane distillation modules, the vacuum membrane distillation process is repeated. Part of the liquid passes through the hydrophobic microporous membrane into the vacuum chamber to become secondary desalinated water, and the remaining feed liquid flows through the S-shaped flow channel and flows out into the secondary concentration chamber to achieve secondary desalination. By analogy, the multi-stage membrane distillation desalination process can be expanded to achieve.

[0135] The outer periphery of the vacuum chamber of the vacuum component 3 is also provided with a vacuum component sealing ring groove 3-7 for setting a sealing ring 6 to seal the vacuum chamber.

[0136] The desalination auxiliary heating element 4 operates as follows: the primary desalinated condensate collected by the vacuum element 3 flows from the condensate flow channel inlet 4-3 into the condensate flow channel 4-4 of the desalination auxiliary heating element 4. Simultaneously, the back of the desalination auxiliary heating element 4 is provided with an S-shaped auxiliary heating flow channel 4-8. This S-shaped auxiliary heating flow channel 4-8 of the auxiliary heating chamber 4 heats the liquid in the condensate flow channel 4-4 to the feed temperature. The primary desalinated condensate then flows from the condensate flow channel outlet 4-1 into the concentrating flow channel 1-3 of the concentrating element 1 of the next membrane separation unit in the desalination module, where membrane distillation occurs. Part of the vapor passes through the hydrophobic microporous membrane and enters the vacuum chamber, condensing into secondary desalinated water, thus achieving secondary desalination. This multi-stage desalination process is completed in this manner.

[0137] The heating medium in the auxiliary heat liquid flow channel 4-8 enters the auxiliary heat liquid flow channel 4-8 from the auxiliary heat inlet 4-5 and is then discharged through the auxiliary heat outlet 4-7. The condensate flow channel 4-4 of the desalination auxiliary heat element 4 is surrounded by auxiliary heat side sealing ring grooves 4-6 for setting sealing rings 6.

[0138] The condensate flow channel 4 - 4 is surrounded by a desalination side sealing ring groove 4 - 2 for arranging a sealing ring 6 .

[0139] The technical effects brought about by the technical solution provided by this application are:

[0140] 1. High-efficiency concentration effect, turbulence enhancement and concentration polarization suppression. The S-shaped flow channel in the concentrator and the stacked diverter plates work together to improve fluid dynamics, breaking the traditional support function of the separator on the membrane surface. By extending the flow path and generating secondary vortices, the fluid Reynolds number is increased by 3-5 times, and the boundary layer shear rate reaches >100s -1 , effectively destroying the concentration polarization layer on the membrane surface. Combined with the salt-blocking properties of the hydrophobic microporous membrane (pore size 0.1-0.5μm), the risk of salt precipitation crystallization on the membrane surface is reduced by more than 70%, significantly extending the membrane life. The single-stage concentration chamber achieves a feed liquid concentration ratio of 1.5-2 times through vacuum membrane distillation, and the unevaporated high-concentration liquid flows into the next stage. After the multi-stage membrane separation unit is connected in series, the total concentration ratio can reach more than 10 times (the concentrated liquid TDS is > 200g / L when 6 stages are connected in series). The modular design supports the increase or decrease of the number of stages as needed, and flexibly adapts to different concentration target requirements.

[0141] 2. Advantages of multi-stage membrane modules: A modular stacked architecture is used to alternately arrange the concentration components, porous membranes, vacuum components, and desalination auxiliary heating components in multiple stages to achieve both concentration and desalination functions. Through the selective permeability of the hydrophobic microporous membrane material, a directional steam transmission channel is constructed while effectively isolating the liquid phase. This multi-stage collaborative operation mode can simultaneously achieve efficient solute concentration and directional solvent recovery within the same system. Relying on the gradient separation efficiency of the multi-stage membrane module, the system's comprehensive recovery rate exceeds 60%, forming a high-efficiency membrane treatment system that integrates separation, concentration, and recovery, significantly improving resource recycling efficiency.

[0142] 3. Optimized vacuum condensation efficiency. The vacuum chamber utilizes beveled plates and a distributed vacuum system (three Φ6mm vacuum ports) to stabilize the operating pressure at 5-15kPa (abs), reducing steam transmission resistance by 35% and increasing condensation efficiency by 40%. The vacuum chamber's walls form a gradient cooling wall (40°C top → 25°C bottom), combined with a diversion port design, to achieve rapid steam liquefaction, resulting in a single-stage fresh water recovery rate exceeding 20%.

[0143] 4. Energy efficiency and stability advantages: The final stage condensation heat is used to preheat the feed liquid. The auxiliary hot liquid flow channel is coupled with the S-shaped flow channel to achieve cascaded utilization of interstage heat energy, reducing energy consumption by 30-40% compared to traditional membrane distillation. The fluororubber / EPDM seal 6 and stainless steel diamond-shaped manifold 5 structure ensure no leakage risk during long-term operation (pressure resistance > 0.3 MPa). Multi-stage membrane distillation processes can be achieved by modularly stacking single-stage membrane distillation systems.

[0144] 5. Broad applicability: Suitable for treating high-salinity wastewater (TDS>100g / L), seawater desalination, and low-temperature concentration of high-value substances (such as lithium salts and antibiotics). Operating in a temperature range of 40-80°C, it adapts to complex operating conditions. CFD simulations optimize flow channel geometry (such as S-shaped flow channels and diamond-shaped manifold layouts) to enhance turbulence near the membrane interface. Experimental results show that the placement of 45° diamond-shaped manifolds in the flow channel can increase vacuum membrane distillation (VMD) membrane flux by 20%, while increasing pressure drop by only 8%.

[0145] 6. The modular multi-stage membrane distillation component of the present invention achieves efficient concentration and high-quality desalination simultaneously through structural innovation and process optimization, and has low energy consumption, high recovery rate and strong anti-pollution characteristics. Application areas include: in the field of zero discharge of industrial wastewater, for high-salt and high-COD wastewater in petrochemical, coal chemical, electroplating and other industries, it can achieve a deep reduction of the solid content of the concentrated liquid by ≥20%, and the total energy consumption is reduced by 30% when equipped with an MVR evaporation system; in the field of water resource purification, it is suitable for the desalination of seawater (35000ppm) and brackish water (below 10000ppm), and the water quality of the produced water meets the GB / T19923-2005 industrial boiler water standard, which is particularly suitable for islands, ships and emergency water supply scenarios; in the field of azeotropic system separation, for Azeotropic systems such as ethanol-water and methanol-acetone can overcome the azeotropic limitations of traditional distillation by leveraging the differences in gas-liquid equilibrium during membrane distillation, achieving efficient separation of systems with boiling point differences less than 5°C, with purities exceeding 99.9%. In specialty separation scenarios, in biomedicine (antibiotic concentration, vaccine purification), food and beverage (juice concentration, plant extract refining), and new energy (lithium battery electrolyte recovery, rare earth element enrichment), gradient membrane groups with pore sizes of 0.1-10μm can achieve molecular-level precision screening and directional solute migration. This has significant application value in these areas.

[0146] This application realizes efficient and compact membrane assembly through the innovative design of an integrated end plate structure with stacked coupling of a concentration component 1, a diamond-shaped diverter plate 5, a porous membrane 2, a vacuum component 3, and a desalination auxiliary heating component 4, integrating S-shaped flow channels and multi-stage stacking technology. The detachable concentration / desalination functional membrane frame has a built-in diamond-shaped diverter plate 5, and the S-shaped flow channel separates the concentration chamber and the desalination chamber, supporting rapid switching of application modes on demand (TDS>300g / L in concentration mode, TDS<10mg / L in desalination mode). The system has high recovery rate, low energy consumption and strong anti-pollution characteristics, and can flexibly adapt to multiple scenarios such as zero discharge of industrial wastewater, desalination of high-salt seawater and low-temperature concentration of high-value substances, breaking through the technical bottleneck of complex maintenance and single function of traditional membrane distillation components.

[0147] This application has a collaborative innovation of transmembrane separation technology. In practical applications, its applicable process not only covers membrane distillation (including direct contact membrane distillation, sweep membrane distillation, vacuum membrane distillation, air gap membrane distillation), but can be expanded to forward osmosis (FO), reverse osmosis (RO), ultrafiltration (UF), nanofiltration (NF) and other processes to form a multi-stage combined system. For example, a "nanofiltration-reverse osmosis-membrane distillation" three-stage combined system is adopted. The porous membrane materials used in the experiment include but are not limited to polypropylene (PP), polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polyvinyl chloride (PVC), polyethylene (PE) or its modified materials, and the membrane pore size range is 0.1μm to 10μm.

[0148] The materials of the vacuum component 3, the concentration component 1, the desalination auxiliary heating component 4 and the like can be various options such as PP, PET, PE, PVC, PS, PP, metal and the like.

[0149] The diamond-shaped manifold 5 can be made of a variety of materials, including PTFE, PVC, FRP, alumina ceramics, and metal. Furthermore, the manifold is not limited to diamonds; rectangular, square, or polygonal shapes are also possible. The flow channels in the concentrator and desalination auxiliary heating elements are not limited to S-shaped; serpentine, rectangular, multi-channel coupling, and optimized geometric topology are also applicable.

[0150] In the design of vacuum parts, the styles, angles and opening positions of the beveled plates are not limited to being different. The connection structures between the vacuum parts, the concentration parts, the desalination auxiliary heating parts, the porous membrane 2 and the diverter plate 5 include: a mechanical sealing structure, which uses any one or a combination of O-rings, rectangular rings, polytetrafluoroethylene gaskets and asbestos gaskets; a non-contact sealing structure, which includes setting a labyrinth boss and a stepped mating surface on the sealing surface, and achieving medium isolation through a small gap of 0.1mm to 0.5mm and a multi-stage deflection path; a liquid film / air film sealing structure, which forms a pressure barrier by opening an annular flow channel on the sealing surface and introducing a sealing liquid (water, oil) or a sealing gas (nitrogen); a rigid connection structure, which includes any one or a combination of welding, riveting, flange connection and press-fit connection without fasteners.

[0151] For ordinary technicians in the technical field to which the present invention belongs, any simple deduction, structural imitation or module replacement made without departing from the core concept of the present invention should be deemed to fall within the protection scope of the present invention.

[0152] Several specific examples are provided below to further illustrate the present application.

[0153] Example 1: (Synchronous Condensed Dilute Mode)

[0154] The concentration module of the device is used to treat nuclear wastewater containing 0.015 wt% heavy water. The number of membrane separation units in the concentration module is 5, forming a 5-stage treatment.

[0155] The porous membrane is specifically a PP hydrophobic flat membrane with a membrane thickness of 0.2-0.3 mm and a membrane pore size of 0.1-0.3 μm.

[0156] The processing parameters are as follows: feed liquid flow rate 25L / h, feed temperature 80°C, vacuum degree of vacuum chamber 0.07Mpa, cooling bath temperature 10°C.

[0157] After five stages of concentration, the concentration of the heavy water concentrate is 0.0183 wt% (an increase of 0.0033 wt%), the deuterium content of the permeate is 0.00675 wt%, and the deuterium removal efficiency reaches 55% (deuterium removal efficiency = 1 - (deuterium content after treatment / initial deuterium content) × 100%). Energy consumption is reduced by 35% compared to traditional systems (calculated based on 800 kWh of electricity consumed to evaporate 1 ton of water), and the concentration rate is 22% (concentration rate = concentrate concentration / feed concentration - 1).

[0158] Example 2 (High-salt wastewater resource treatment mode)

[0159] The desalination module of the device is used to treat chemical high-salt wastewater containing 15wt% sodium chloride, 0.5wt% sodium sulfate and trace heavy metal ions, COD (chemical oxygen demand) concentration of 800mg / L, and high-salt wastewater at 35°C.

[0160] Module configuration and process parameters:

[0161] The number of membrane separation units in the desalination module is 3, forming a 3-stage treatment.

[0162] In the primary membrane separation unit, the porous membrane is a nanofiltration (NF) membrane. The NF membrane operates at a pressure of 1.8 MPa and a feed temperature of 40°C. The porous membrane retains sodium sulfate, with a divalent ion rejection rate of >99%. The vacuum component functions as a pressure-bearing seal (vacuum level 0 bar).

[0163] In the secondary membrane separation unit: polyamide reverse osmosis membrane (RO), sodium chloride concentration, pressure 4.0MPa, feed temperature 50°C, NaCl rejection rate >99.5%. Vacuum component function: pressure-bearing seal (vacuum degree 0 bar).

[0164] In the three-stage membrane separation unit: PTFE hydrophobic microporous membrane (VMD), deep desalination / pure water production, feed temperature 65 ° C, vacuum degree 0.08 MPa, membrane flux 12 L / (m 2 ·h).

[0165] After three-stage treatment, the liquid at the condensate outlet of the vacuum chamber of the third-stage membrane separation unit is taken for testing:

[0166] The salt concentration of the tertiary freshwater effluent is reduced to <100 mg / L, meeting the industrial reuse water standard, and the COD removal rate is >95% (COD removal rate = (COD concentration of sewage before treatment - COD concentration of sewage after treatment) / COD concentration of sewage before treatment × 100%).

[0167] First-stage concentrated solution: Na2SO4 purity>98%, evaporation and crystallization can be recycled to prepare sodium sulfate.

[0168] Secondary concentrated liquid: NaCl concentration>18wt%, evaporation and crystallization can be recycled to prepare industrial salt (purity>96%).

[0169] Level 3 concentrated liquid: heavy metal liquid containing trace amounts of NaCl (total amount <5wt%), which can be used for hazardous waste solidification treatment.

[0170] Mass fraction (wt%) = mass concentration (mg / L) ÷ 10,000 (solution density ≈ 1 g / mL).

[0171] Example 3 (Organic Matter-Water Separation Mode) Desalination Module

[0172] The desalination module of the device is used to treat pharmaceutical wastewater containing 5% methanol (methanol / water azeotropic system).

[0173] Module configuration and process parameters:

[0174] Feed flow rate: 30 L / h, vacuum chamber vacuum: 0.65 bar, membrane distillation module temperature: 65°C (feed side) / 25°C (permeate side). Membrane material: Polypropylene (PP) sintered microporous membrane, pore size 0.8 μm.

[0175] Module configuration and process parameters:

[0176] In the primary membrane separation unit, a PP hydrophobic microporous membrane (VMD) was used to eliminate azeotropic pre-separation. The feed temperature was 65°C, the vacuum was 0.065 MPa, and the pore size was 0.8 μm. A methanol rejection rate of >99.8% (previously >99.6%) was achieved, with a methanol content of <0.02% in the effluent. Retention rate = [1 - (200 / 50,000)] × 100% = 99.6%.

[0177] The secondary membrane separation unit uses a PP hydrophobic microporous membrane (VMD) with a deep methanol rejection rate. The feed temperature is 60°C, and the vacuum level is 0.07 MPa (gradient pressure increase). Water recovery reaches 78%. Distillation efficiency is 8.2 kWh / t, and VMD efficiency is 3.7 kWh / t, reducing energy consumption by 55% compared to distillation.

[0178] In the three-stage membrane separation unit: PP hydrophobic microporous membrane (VMD), high-purity water production: feed temperature 55°C, vacuum degree 0.075MPa, condensation 25°C.

[0179] The module occupies 20% of the distillation tower's floor space, making it 80% more compact.

[0180] Example 4 (Salt Lake Brine Lithium-Magnesium Separation Mode) Concentration Module

[0181] The concentration module of the present device is used to treat 1.2% wt Li + 、8%wt Mg 2+ High magnesium-lithium ratio salt lake brine.

[0182] Module configuration and process parameters:

[0183] Feed flow rate: 18L / h, feed temperature: 25℃. Nanofiltration membrane assembly pressure: 1.5MPa, porous membrane selective block copolymer nanofiltration membrane, the membrane is Li + / Mg 2+ Separation coefficient = C > 50. α Li / Mg =24.035 / 0.15=160.23>50.

[0184] Primary membrane separation unit: Li + Selective nanofiltration membrane (NF), Mg 2+ Pre-retention, pressure 1.5MPa, 25℃, Li / Mg separation coefficient>50, vacuum component function: pressure-bearing seal (vacuum degree 0bar).

[0185] Secondary membrane separation unit: PTFE hydrophobic membrane (VMD), Li + Deep concentration, feed 40℃, vacuum 0.08MPa, membrane flux 8L / (m 2 ·h).

[0186] After nanofiltration of the first-stage membrane separation unit: Li + Concentration: 11.4g / L, Mg 2+ Concentration: 0.474g / L, α Li / Mg =11.4 / 0.474=24.05, achieving efficient separation of magnesium and increasing the Li / Mg ratio by 160 times.

[0187] After the secondary membrane separation unit VMD: Li + Concentration: 16.29g / L, Mg 2+ Concentration: 0.677g / L, the lithium concentration is further concentrated in preparation for lithium extraction.

Claims

1. A modular multi-stage membrane distillation simultaneous concentration device, characterized in that: The device comprises: one or both of a concentration module and a desalination module; The concentration module includes the following components stacked in sequence: a concentration component, a porous membrane, and a vacuum component; Each group of the devices stacked in sequence forms a membrane separation unit, and the number of membrane separation units in the concentration module is one or more; In each membrane separation unit of the concentration module, the communication mode of each device is as follows: The concentrating element has a concentrating flow channel on at least one surface in the stacking direction, and the concentrating element has a concentrating element liquid inlet and a concentrating element liquid outlet communicated with the concentrating flow channel; The porous membrane is stacked on the surface of the concentrating flow channel of the concentrating element; The vacuum component has a vacuum chamber facing the porous membrane, which is used to allow the liquid in the concentration flow channel of the concentration component to partially vaporize, pass through the porous membrane, enter the vacuum chamber, and condense; The concentrated liquid outlet of the concentrated element of the concentration module is connected to the concentrated liquid inlet of the concentrated element of the next membrane separation unit to achieve continuous concentration of the liquid; The condensate outlet of the vacuum chamber of the membrane separation unit of the concentration module is used to discharge the desalinated liquid, or is connected to the concentrate liquid inlet of the concentrate of the corresponding membrane separation unit of the desalination module for further desalination of the desalinated liquid; The desalination module includes the following components stacked in sequence: a concentrating component, a porous membrane, and a vacuum component; Each group of the devices stacked in sequence forms a membrane separation unit, and the number of membrane separation units in the concentration module and the desalination module is one or more; In each membrane separation unit of the desalination module, the connection mode of each device is as follows: The concentrating element has a concentrating flow channel on at least one surface in the stacking direction, and the concentrating element has a concentrating element liquid inlet and a concentrating element liquid inlet communicating with the concentrating flow channel; The porous membrane is stacked on the surface of the concentrating flow channel of the concentrating element; The vacuum component has a vacuum chamber facing the porous membrane, which is used to allow the liquid in the concentration flow channel of the concentration component to partially vaporize, pass through the porous membrane, enter the vacuum chamber, and condense; The condensate outlet of the vacuum chamber is connected to the concentrate liquid inlet of the concentrate of the next membrane separation unit of the desalination module to achieve continuous desalination of the liquid; The concentrate liquid outlet of the concentrate of the non-first membrane separation unit of the desalination module is used to discharge the concentrate, or is connected to the concentrate liquid inlet of the concentrate of the membrane separation unit of the corresponding stage of the concentration module for further concentrating the liquid. The concentrate liquid inlet of the concentrate of the first membrane separation unit of the desalination module is used to receive the liquid to be treated; When the device comprises a concentration module and a desalination module: The stacking order of the components in the concentration module and the desalination module is opposite; The concentrating element liquid outlet of the concentrating element of the first membrane separation unit of the desalination module is connected to the concentrating element liquid inlet of the first membrane separation unit of the concentrating module; or, the concentrating element of the first membrane separation unit of the desalination module has concentrating flow channels on both surfaces in the stacking direction, and the concentrating element liquid outlet of the concentrating element of the first membrane separation unit of the desalination module is connected to the inlet of the concentrating flow channel on the back side of the concentrating element. In this case, the concentrating module and the desalination module share the same concentrating element at the junction of the two modules.

2. The modular multi-stage membrane distillation simultaneous concentration device according to claim 1, characterized in that: The concentration module further comprises: a desalination auxiliary heating element stacked on the back of the vacuum chamber of the vacuum element; The desalination module further comprises: a desalination auxiliary heating element stacked on the back surface of the vacuum chamber of the vacuum element; The desalination auxiliary heating element comprises a condensate flow channel and a heat source for heating the liquid in the condensate flow channel; The condensate outlet of the vacuum chamber is connected to the condensate flow channel inlet of the desalination auxiliary heating component, and the condensate flow channel outlet of the desalination auxiliary heating component is connected to the concentrate liquid inlet of the concentrate component of the next membrane separation unit of the desalination module or the concentration module.

3. The modular multi-stage membrane distillation simultaneous concentration device according to claim 1, characterized in that: A diverter plate is provided between the concentrating element and the porous membrane; The diverter plate includes: a porous bottom plate and a protrusion located on the porous bottom plate; The diverter plate is configured such that: the protrusion is embedded in the concentrating flow channel of the concentrating element; Alternatively, a protrusion is provided in the concentrating flow channel of the concentrating element.

4. The modular multi-stage membrane distillation simultaneous concentration device according to claim 1, characterized in that: The porous membrane is a hydrophobic microporous membrane, and the pore size thereof is in the micrometer or nanometer level.

5. The modular multi-stage membrane distillation simultaneous concentration device according to claim 1, characterized in that: A sealing ring is provided between the components.

6. The modular multi-stage membrane distillation simultaneous concentration device according to claim 1, characterized in that: The vacuum chamber of the vacuum component is connected to a vacuum pumping system; A bevel plate is also provided in the vacuum chamber of the vacuum component; One side of the beveled plate is higher than the other side, and the beveled plate is provided with a hole so that the condensed liquid in the vacuum chamber flows into the liquid collecting tank at the bottom of the vacuum chamber through the hole.

7. The modular multi-stage membrane distillation simultaneous concentration device according to claim 1, characterized in that: In the device, from a certain position forward, the devices in the membrane separation unit are stacked in sequence in the above reverse order to form the concentration module, and from the certain position backward, the devices in the membrane separation unit are stacked in sequence in the above order to form the desalination module.

8. A modular multi-stage membrane distillation simultaneous concentration method, characterized in that: The method uses the modular multi-stage membrane distillation simultaneous concentration device according to any one of claims 1 and 3-7; The working method of the desalination module comprises the following steps: The liquid to be treated enters from the concentration unit liquid inlet of the concentration unit of the first membrane separation unit of the desalination module and flows into the concentration flow channel of the concentration unit; In the concentration flow channel, part of the liquid to be treated is vaporized under the negative pressure transmitted from the vacuum chamber and passes through the porous membrane into the vacuum chamber and condenses; The liquid obtained after condensation flows out from the condensate outlet of the vacuum chamber and enters the concentrate liquid inlet of the concentrate of the next membrane separation unit of the desalination module to flow into the concentrate flow channel, and the above steps are repeated to perform multi-stage desalination; The unvaporized liquid in the concentrating flow channel of the concentrating element is discharged from the desalination module through the concentrating element liquid inlet of the concentrating element, or is discharged into the concentrating element liquid inlet of the concentrating element of the membrane separation unit of the corresponding stage of the concentrating module for further concentration of the liquid; The working method of the enrichment module comprises the following steps: The liquid to be treated enters the concentration flow channel of the concentration element of the first membrane separation unit of the concentration module. In the concentration flow channel, part of the liquid to be treated is vaporized under the action of the negative pressure transmitted by the vacuum chamber and passes through the porous membrane into the vacuum chamber and condenses. The liquid obtained after condensation flows out of the concentration module from the condensate outlet of the vacuum chamber, or is discharged into the concentration unit liquid inlet of the concentration unit of the corresponding stage membrane separation unit of the desalination module for further desalination of the desalinated liquid; The unvaporized liquid flows out from the liquid inlet of the concentrating element to the liquid inlet of the concentrating element of the next membrane separation unit of the concentrating module to enter the concentrating flow channel, and the above steps are repeated to perform multi-stage concentration; When the device comprises a concentration module and a desalination module: In the concentrating flow channel of the concentrating element of the first membrane separation unit of the desalination module, the liquid that has not been vaporized flows out from the concentrating element liquid inlet of the concentrating element and then enters the concentrating flow channel on the back of the concentrating element or enters the concentrating flow channel of the concentrating element of the first membrane separation unit of the concentrating module; The liquid to be treated is at a temperature of 30-80 degrees Celsius.

9. The modular multi-stage membrane distillation simultaneous concentration method according to claim 8, characterized in that: The method uses the modular multi-stage membrane distillation simultaneous concentration device according to claim 2; Before the condensed liquid flows out from the condensate outlet of the vacuum chamber and enters the concentrate liquid inlet of the concentrate of the next membrane separation unit of the desalination module: The liquid obtained after condensation flows out from the condensate outlet of the vacuum chamber, enters the condensate flow channel through the condensate flow channel inlet of the desalination auxiliary heating component, is heated by the heat source in the condensate flow channel, and then enters the concentrated component liquid inlet of the next membrane separation unit of the desalination module from the condensate flow channel outlet of the desalination auxiliary heating component.

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