CN120817645A - A modular multi-stage membrane distillation simultaneous concentration device and method - Google Patents
A modular multi-stage membrane distillation simultaneous concentration device and methodInfo
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- CN120817645A CN120817645A CN202510959303.4A CN202510959303A CN120817645A CN 120817645 A CN120817645 A CN 120817645A CN 202510959303 A CN202510959303 A CN 202510959303A CN 120817645 A CN120817645 A CN 120817645A
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Abstract
本发明属于水处理技术领域，具体涉及一种模块化多级膜蒸馏同步浓缩装置和方法。所述装置包括：浓缩模块和淡化模块中的一种或两种；所述浓缩模块和所述淡化模块包括依次堆叠的以下器件：浓缩件、多孔膜、真空件；每组上述依次堆叠的器件形成一个膜分离单元，膜分离单元的数量均为一个或多个。本系统采用创新的多级模块化扩展架构，其核心在于基于梯度压力平衡的级间隔离结构。在同一套板框式组件中实现"前端淡化除杂‑中端梯度浓缩‑末端纯水产出"的全流程集成。该结构通过将疏水微孔膜与板框式组件交替堆叠形成浓缩室与淡化室，支持从单级到多级的灵活扩展，完美适配不同规模和处理要求的高浓缩和淡化应用场景。
The present invention belongs to the field of water treatment technology, and specifically relates to a modular multi-stage membrane distillation synchronous concentration device and method. The device includes: one or two of a concentration module and a desalination module; the concentration module and the desalination module include the following devices stacked in sequence: a concentration component, a porous membrane, and a vacuum component; each group of the above-mentioned devices stacked in sequence forms a membrane separation unit, and the number of membrane separation units is one or more. This system adopts an innovative multi-stage modular expansion architecture, the core of which lies in 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, and terminal pure water production" is realized in the same set of plate and frame components. The structure forms a concentration chamber and a desalination chamber by alternately stacking hydrophobic microporous membranes and plate and frame components, supports flexible expansion from single stage to multi-stage, and perfectly adapts to high concentration and desalination application scenarios of different scales and processing requirements.
Description
Technical Field
The invention belongs to the technical field of water treatment, and particularly relates to a modularized multistage membrane distillation synchronous concentration device and method.
Background
The membrane distillation (Membrane Distillation, MD) is used as a heat driven membrane separation technology, and has wide application prospect in the fields of sea water desalination (total dissolved solid substances (TDS) >35 g/L), high-salt wastewater treatment (TDS >100 g/L), food concentration and the like in recent years by utilizing the characteristic that low-grade heat sources (30-80 ℃) can be utilized to realize high-retention-rate separation.
However, existing single-stage membrane distillation systems still face the following technical bottlenecks in industrial applications:
Mass transfer driving force attenuation and processing capacity limitation, and the water production flux of single-stage membrane distillation is mainly driven by the vapor pressure difference at two sides of the membrane. When treating high concentration feed liquids (such as industrial wastewater with TDS >100 g/L), the vapor pressure on the feed side is significantly reduced, resulting in a reduction in the driving force for mass transfer. The research shows that when the TDS of the feed liquid exceeds 150g/L, the attenuation rate of the produced water flux can reach more than 60 percent. In the traditional mode of increasing the membrane area and improving the treatment capacity, concentration polarization phenomenon is aggravated due to uneven distribution of flow channels, so that the concentration of solute on the membrane surface is increased by 30-50%, and the mass transfer efficiency is further reduced.
The heat energy utilization efficiency is low, a multistage series structure (US 20170349447A 1) is adopted, the interstage heat recovery rate is still lower than 55%, and the requirement of industrial large-scale application on energy consumption cost is difficult to meet. Researches show that (Ultra-high freshwater production in multistage solar membrane distillation via waste heat injection to condenser), combines solar energy (top heating) and waste heat (final heating) to realize 'high temperature-low temperature' gradient synergy and reduce the dependence on a single heat source. Researches show that (Multistage osmotically assisted reverse osmosis process for concentrating solutions using hollow fiber membrane modules),10 stages of HF film modules are connected in series, the front stage concentrated water is used as the rear stage feed, and the concentration can be gradually increased by applying the same pressure (10-15 bar) to each stage.
The structure is complex and the maintenance is difficult, the multistage membrane assembly depends on external series equipment (such as CN 201110428029.6), realizes multistage, and can meet most of non-high-temperature high-pressure working conditions. Studies show that (Optimal design of multi-stage vacuum membrane distillation and integration with supercritical water desalination for improved zero liquid discharge desalination) utilizes the latent heat of condensation of the previous stage to preheat the feed of the next stage through the design of temperature gradient among the multistage VMD stages, so as to realize heat recovery.
The membrane pollution control and the system expansibility are insufficient, and when the traditional flat plate type membrane component is used for treating high-concentration feed liquid, a local stagnation area is easy to form in a flow channel, so that the solute crystallization rate is accelerated. Experimental data shows that when the feed liquid TDS exceeds 80g/L, the incidence of film Kong Runshi increases 2-3 times. The prior patent (such as CN 113354013B) has a plurality of fixed stages (such as 40 stages), and the flow channel parameters or stage arrangement can not be dynamically adjusted according to the characteristics (salt concentration and viscosity) of the feed liquid. For example, when high-viscosity food solutions (viscosity: 300 mPa.s or more) are processed, custom-made modification equipment is required, and the module multiplexing rate is lower than 20%. Studies show that (Application of vacuum membrane distillation for concentration) simulate a multi-stage effect by circulating concentration (feed liquid flows back through a single-stage module for multiple times), and the concentration is gradually increased.
In contrast, the optimized design of the S-shaped flow channel coupling diamond-shaped flow distribution plate array of the multi-stage component can improve the salt content of a concentration end point by 1.6 times, and meanwhile, the energy consumption of back-end treatment is reduced by 38-50%. In addition, the existing multistage system adopts a fixed serial structure, and the stage number or flow channel parameters cannot be flexibly adjusted according to the characteristics (such as salt concentration and viscosity) of the feed liquid, so that the process suitability is limited. The existing membrane distillation technology has the core problems of single function, low heat energy utilization efficiency, complex components, insufficient adaptability, poor system expansibility and process suitability and the like in heavy water treatment.
In addition, membrane distillation techniques present challenges in the course of concentrating and desalting industrial applications. Such as:
The membrane component has a single function, and the traditional system only supports one-way operation (such as a focusing concentration function of a patent CN 113354013B), and cannot flexibly switch a concentration or desalination mode according to requirements, so that the equipment utilization rate is low, and the application scene is limited.
The system expansibility and the process suitability are poor, the existing multistage membrane component mostly adopts a fixed series structure (such as patent KR 102020012258A), and the flow channel parameters (such as width and dip angle) or series configuration cannot be dynamically adjusted according to the characteristics (salt concentration and viscosity) of the feed liquid. In the face of diversified application scenes (such as high-viscosity food solution and high-salt wastewater), equipment needs to be customized and modified, so that the development period is prolonged by more than 50%, and the module multiplexing rate is lower than 20%. Studies have shown (CHEMICAL ENGINEERING RESEARCHAND DESIGN doi:10.1016/j. Ward. 2020.07.029) that after a series limit of more than 10 stages, the concentrate viscosity increases significantly, resulting in a sudden increase in mass transfer resistance and a flux drop to 50% of the initial value.
The heat energy utilization efficiency is low, the latent heat recovery efficiency of steam is low, the heat energy cascade utilization is not realized in the multi-stage condensation process (for example, a solar membrane distillation system depends on single-stage condensation), the energy consumption of auxiliary heat equipment is high, and the overall energy efficiency is low. The prior research shows that (the achievements of the Saint Kong's ITEWA team at Nature Communications (doi: 10.1038/s 41467-024-51880-y)) the multistage solar membrane distillation system is severely dependent on an external heat source (250 W.m -2 power input is needed continuously). The thermal pressurization mechanism results in a 30% increase in system maintenance costs. Studies have shown that while the air gap reduces heat loss, it increases water vapor diffusion resistance and may require a higher flow rate to counteract
The structure is complex, the maintenance is difficult, the multistage membrane assembly depends on external series equipment (such as CN 201110428029.6), the system is large in size, the integration level is low, and the high-temperature and high-pressure working condition is difficult to adapt. Prior studies have shown (10.1016/j.jclepro.2022.132189.) that multistage SCWD requires a high temperature heat source (> 450 ℃) which limits the direct use of renewable energy sources such as solar energy. The integration of multi-stage VMDs with SCWD requires precise thermal matching and pressure control, and equipment investment costs are high.
The membrane pollution is serious and the maintenance cost is high, the traditional flat plate type flow channel has a flowing dead zone (the stagnation area accounts for 15 percent), the solute crystallization and the membrane Kong Runshi are accelerated (the membrane wetting risk is improved by 2-3 times when the TDS is more than 80 g/L), and frequent shutdown cleaning is needed (the period is 50-80 hours). The service life of the membrane is shortened to less than 1 year, the maintenance cost of equipment is increased by 30% -40%, and the continuous operation stability of the system is reduced due to frequent start and stop.
The structure complexity and the manufacturing cost are high, the prior patent (such as CN 113354013B) has a plurality of fixed series (such as 40 series) and cannot dynamically adjust the flow channel parameters or series configuration according to the characteristics (salt concentration and viscosity) of the feed liquid, the processing scale is flexibly increased and decreased, and the expansibility is insufficient. For example, when high-viscosity food solutions (viscosity: 300 mPa.s or more) are processed, custom-made modification equipment is required, and the module multiplexing rate is lower than 20%. The equipment occupies a large area, is difficult to adapt to the industrial site with limited space, and the initial investment cost hinders the technical popularization.
Poor adaptability and insufficient stability, namely, lack of intelligent regulation and control means, inability to dynamically regulate temperature, vacuum degree and flow rate according to the concentration of feed liquid (such as low concentration heavy water needs high differential pressure driving, high concentration needs pollution prevention strategy), and unstable treatment efficiency.
The technology integration is lack, the existing research is multi-focus and single-improvement (such as uniform distribution and pollution prevention), the system integration of multi-stage membrane components, heat energy recovery and intelligent regulation is lack, and the comprehensive requirements of high efficiency, flexibility and low energy consumption are difficult to meet.
The present application has been made to solve at least part of the above problems.
Disclosure of Invention
The application provides a modularized multistage membrane distillation synchronous concentration device, which comprises one or two of a concentration module and a desalination module;
The concentration module comprises a concentration piece, a porous membrane and a vacuum piece which are stacked in sequence;
each group of the devices stacked in sequence form a membrane separation unit, and the number of the 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 piece is provided with a concentrating flow channel on at least one surface in the stacking direction, and is provided with a concentrating piece liquid inlet and a concentrating piece liquid outlet which are communicated with the concentrating flow channel;
The porous membrane is stacked to a surface of a concentration flow path of the concentration member;
the vacuum member has a vacuum chamber facing the porous membrane for vaporizing a liquid portion in a concentrating flow path of the concentrating member through the porous membrane into the vacuum chamber and condensing;
The concentrated piece liquid outlet of the concentrated piece of the concentrated module is communicated with the concentrated piece liquid inlet of the concentrated piece of the next membrane separation unit so as to realize continuous concentration of liquid;
the condensate outlet of the vacuum bin of the membrane separation unit of the concentration module is used for discharging desalted liquid, or the concentrate liquid inlet of the concentrate communicated to the corresponding-stage membrane separation unit of the desalination module is used for desalinating the desalted liquid again;
The desalination module comprises a concentration piece, a porous membrane and a vacuum piece which are stacked in sequence;
each group of the devices stacked in sequence form a membrane separation unit, and the number of the membrane separation units is one or more in the concentration module and the desalination module;
in each membrane separation unit of the desalination module, the communication mode of each device is as follows:
the concentrating piece is provided with a concentrating flow channel on at least one surface in the stacking direction, and is provided with a concentrating piece liquid inlet and a concentrating piece liquid inlet which are communicated with the concentrating flow channel;
The porous membrane is stacked to a surface of a concentration flow path of the concentration member;
the vacuum member has a vacuum chamber facing the porous membrane for vaporizing a liquid portion in a concentrating flow path of the concentrating member through the porous membrane into the vacuum chamber and condensing;
The condensate outlet of the vacuum bin is communicated with the concentrate liquid inlet of the concentrate of the next membrane separation unit of the desalination module so as to realize continuous desalination of liquid;
The concentrate liquid outlet of the concentrate of the non-first membrane separation unit of the desalination module is used for discharging concentrate or the concentrate liquid inlet of the concentrate of the membrane separation unit of the corresponding stage of the concentration module is communicated to re-concentrate the liquid:
A concentrate liquid inlet of a concentrate of a first membrane separation unit of the desalination module is for receiving a liquid to be treated;
When the device comprises a concentration module and a desalination module, the concentration module and the desalination module are as follows:
the stacking sequence of all devices in the concentration module and the desalination module is opposite;
The concentrated piece liquid outlet of the concentrated piece of the first membrane separation unit of the desalination module is communicated with the concentrated piece liquid inlet of the first membrane separation unit of the concentration module, or the concentrated piece of the first membrane separation unit of the desalination module is provided with concentrated flow channels on two surfaces in the stacking direction, the concentrated piece liquid outlet of the concentrated piece of the first membrane separation unit of the desalination module is communicated with the inlet of the concentrated flow channel on the back of the concentrated piece, and at the moment, the concentrated module and the desalination module share the same concentrated piece at the abutting position of the two modules.
Preferably, the concentration module further comprises a desalination auxiliary heating element stacked on the back surface of the vacuum bin of the vacuum element;
the desalination module further comprises a desalination auxiliary heating element stacked on the back surface of the vacuum bin of the vacuum element;
the desalting auxiliary heat piece is provided with a condensate flow channel and a heat source for supplying heat to liquid in the condensate flow channel;
The condensate outlet of the vacuum bin is communicated with the condensate flow channel inlet of the desalting auxiliary heat piece, and the flow channel outlet of the desalting auxiliary heat piece is communicated with the concentrate liquid inlet of the concentrating piece of the next membrane separation unit of the desalting module or the concentrating module.
Preferably, a flow dividing plate is arranged between the concentrating piece and the porous membrane;
the splitter plate comprises a porous bottom plate and a lug which is positioned on the porous bottom plate;
And the diverter plate is configured such that the projection is embedded in the concentrate flow path of the concentrate. The porous bottom plate is attached to the surface of the concentrating flow passage of the concentrating piece.
Preferably, a projection is provided in the concentrating flow path of the concentrating piece. Thus, a porous bottom plate is not required.
Preferably, the porous membrane is a hydrophobic microporous membrane having a pore size of micro-or nano-scale.
Preferably, a sealing ring is arranged between the devices.
Preferably, the vacuum bin of the vacuum part is communicated with a vacuum pumping system;
a bevel cutting plate is also arranged in the vacuum bin of the vacuum part;
One side of the bevel board is higher than the other side, and the bevel board is provided with a pore canal so that condensed liquid in the vacuum bin flows into a liquid collecting tank positioned at the bottom of the vacuum bin through the pore canal.
Preferably, in the apparatus, the devices in the membrane separation units are stacked in order from a certain position to form the concentration module in the reverse order, and the devices in the membrane separation units are stacked in order from the certain position to form the desalination module in the reverse order.
A second aspect of the present application provides a modular multistage membrane distillation synchronous concentration method using the modular multistage membrane distillation synchronous concentration device according to any one of the first aspects;
the working method of the desalination module comprises the following steps:
the liquid to be treated enters from a concentrate liquid inlet of a concentrate of a first membrane separation unit of the desalination module and flows into a concentrate flow channel of the concentrate;
in the concentration flow channel, part of the liquid to be treated is vaporized under the action of negative pressure transmitted by the vacuum bin, passes through the porous membrane, enters the vacuum bin and is condensed;
the liquid obtained after condensation flows out from a condensate outlet of the vacuum bin and enters a concentrated piece liquid inlet of a concentrated piece of a next membrane separation unit of the desalination module to flow into a concentrated flow channel, and the steps are repeated to carry out multistage desalination;
the non-vaporized liquid in the concentration flow channel of the concentration piece is discharged from the concentration piece liquid inlet of the concentration piece to the desalination module, or is discharged into the concentration piece liquid inlet of the concentration piece of the membrane separation unit of the corresponding stage of the concentration module to be used for re-concentrating the liquid;
The working method of the concentration module comprises the following steps:
The liquid to be treated enters a concentration flow passage of a concentration piece of a first membrane separation unit of the concentration module, and part of the liquid to be treated is vaporized under the action of negative pressure transferred by the vacuum bin, passes through the porous membrane, enters the vacuum bin and is condensed in the concentration flow passage;
The liquid obtained after condensation flows out of the concentration module from a condensate outlet of the vacuum bin, or is discharged into a concentrate liquid inlet of a concentrate of a corresponding-stage membrane separation unit of the desalination module to be used for desalinating the desalinated liquid;
The liquid which is not vaporized flows out from the concentrate liquid inlet of the concentrate to the concentrate liquid inlet of the concentrate of the next membrane separation unit of the concentration module to enter the concentration flow channel, and the steps are repeated to perform multistage concentration.
When the device comprises a concentration module and a desalination module, the concentration module and the desalination module are as follows:
In the concentrating flow channel of the concentrating piece of the first membrane separation unit of the desalting module, liquid which is not gasified flows out from the concentrating piece liquid inlet of the concentrating piece and then enters the concentrating flow channel on the back surface of the concentrating piece or enters the concentrating flow channel of the concentrating piece of the first membrane separation unit of the concentrating module;
The liquid to be treated is at 30-80 ℃.
Preferably, the liquid obtained after condensation flows out from the condensate outlet of the vacuum bin before entering the concentrate liquid inlet from the concentrate of the next membrane separation unit of the desalination module:
and the condensed liquid flows out of a condensate outlet of the vacuum bin, enters the condensate flow channel through a condensate flow channel inlet of the desalting auxiliary heat element, is heated by the heat source in the condensate flow channel, and enters a concentrate liquid inlet of a concentrate of the next membrane separation unit of the desalting module from a condensate flow channel outlet of the desalting auxiliary heat element.
Compared with the prior art, the invention has the following beneficial effects:
1. The system adopts an innovative multistage modularized expansion architecture, and the core of the system is an interstage isolation structure based on gradient pressure balance. The whole process integration of front end desalination and impurity removal, middle end gradient concentration and end pure water output is realized in the same set of plate and frame assembly. The structure forms a concentration chamber and a desalination chamber by alternately stacking PTFE/PVDF/PP and other high-performance hydrophobic microporous membranes and plate-frame assemblies, supports flexible expansion from single stage to multi-stage, and is perfectly suitable for high concentration and desalination application scenes (such as industrial wastewater zero discharge, medicine extraction and purification, sea water desalination concentrate treatment, high-salt material concentration, azeotrope separation, radioactive wastewater treatment, fruit juice concentration, dairy product processing and the like) with different scales and treatment requirements.
2. The integrated flow integration of the multistage membrane component adopts the whole flow coupling design of the plate-frame membrane component, and the multistage treatment system with high integration can be constructed by isolating and connecting the concentration module and the desalination module in series through the interstage sealing structure without the recombination of an external switching valve group and a pipeline and can synchronously realize the gradient concentration of feed liquid and the production of pure water. The utilization rate of the equipment is improved to more than 95%, the number of pipeline connection nodes is reduced by 40%, and the leakage point risk and the control complexity are reduced.
3. And the efficient condensation recovery is realized by integrating the oblique cutting guide baffle plate and the cold wall condensation module in the vacuum bin, so that a three-stage treatment path of condensation, liquid accumulation and waste heat recovery is realized. The vacuum bin can simulate and optimize the inclined angle of the inclined plate and the heat exchange area of the cold wall through a three-dimensional flow field, and the steam phase change efficiency reaches more than 98%. Condensate is directly discharged to a liquid collecting tank at the bottom of the vacuum bin through 4-5 groups of flow guide through holes on the bevel cutting plate, the transmission path is shortened by 30%, and the latent heat recovery efficiency is improved by 25%.
4. Preferably, the condensate flow channel on the surface of the desalting auxiliary heat piece is an S-shaped flow channel, the other surface of the desalting auxiliary heat piece is provided with an S-shaped auxiliary heat liquid flow channel, and a heat source is arranged in the S-shaped auxiliary heat liquid flow channel and is used for heating liquid in the condensate flow channel. The front S-shaped condensate flow channel and the back S-shaped auxiliary hot liquid flow channel are integrated aiming at the double-sided composite flow channel plate of the desalination auxiliary hot piece, so that direct heat exchange is realized, and energy consumption is reduced. The CFD simulation optimization can realize the reverse heat energy coupling of cold and hot fluid. The design is simplified by 60% of pipeline system, the device volume is reduced by 40%, the manufacturing cost is reduced by 35%, and the gradient utilization rate of heat energy is up to 85%. In addition, S-shaped flow channels with different functions are respectively arranged on the concentrating piece and the desalting auxiliary heating piece, CFD simulation optimization can be utilized, the angle and the heat exchange area of the flow channels are further refined, and heat loss is reduced.
5. Membrane contamination control, eliminating flow dead zones, preferably the bumps on the diverter plate are diamond shaped. Through the optimization of the convection field, the diamond blocks of the regularized array type are connected with each other at an included angle of 60-120 degrees, so that the dead zone of the fluid is eliminated (the stagnation area accounts for < 5%), the shearing rate of the membrane surface is improved by 30%, and the concentration polarization is inhibited (delta C/C 0 is less than or equal to 15%). The structural design can guide fluid to flow according to a preset track, and solves the problems of concentration polarization and turbulence degree.
Preferably, the bump surface on the shunt plate may be coated with a hydrophilic coating. After hydrophilic coating treatment (contact angle <60 °), the contaminant attachment rate was reduced by 65% and the film cleaning cycle was extended to 2.5 times that of conventional devices.
Drawings
FIG. 1 is an exploded view of a multistage membrane distillation synchronous concentration desalination device of the present application.
Fig. 2 is a schematic diagram of a concentrate structure.
Fig. 3 is a schematic diagram of the front structure of the desalination auxiliary heating unit.
Fig. 4 is a schematic view of the back structure of the desalination auxiliary heating member.
Fig. 5 is a schematic view of the structure of the vacuum member.
FIG. 6 is a diagram of a diamond shaped splitter plate.
FIG. 7 is a schematic diagram of the location of the concentrating flow channels of the diamond-shaped splitter plate and concentrating element.
Fig. 8 is a flow field velocity cloud for a non-diamond flow splitter plate in a concentrate flow channel.
FIG. 9 is a flow field velocity cloud of a diamond-shaped splitter plate added to a concentrate flow channel.
List of reference numerals:
1. 1-1 parts of concentrated piece, 1-2 parts of concentrated piece liquid inlet, 1-3 parts of concentrated piece sealing ring clamping groove, 1-4 parts of concentrated runner, 1-5 parts of concentrated piece liquid outlet and 1-5 parts of concentrated runner outlet;
2. A porous membrane;
3. 3-1 parts of vacuum parts, 3-2 parts of vacuumizing channels, 3-3 parts of vacuumizing through holes, 3-3 parts of condensation wall surfaces, 3-4 parts of bevel board through holes, 3-5 parts of bevel boards, 3-6 parts of condensate outlets, 3-7 parts of sealing ring clamping grooves of the vacuum parts;
4. the device comprises a desalination auxiliary heat piece, 4-1 parts, a condensate flow channel outlet, 4-2 parts, a desalination side sealing ring clamping groove, 4-3 parts, a condensate flow channel inlet, 4-4 parts, a condensate flow channel, 4-5 parts, an auxiliary heat inlet, 4-6 parts and an auxiliary heat side sealing ring clamping groove, 4-7 parts, an auxiliary heat outlet, 4-8 parts and an auxiliary heat liquid flow channel, wherein the desalination side sealing ring clamping groove is a hollow structure;
5. a diamond-shaped flow dividing plate, 5-1, diamond-shaped blocks, 5-2 and a flow channel turbulence area of the diamond-shaped flow dividing plate;
6. And (3) sealing rings.
Detailed Description
The present application will be described in further detail with reference to examples.
It will be appreciated by those skilled in the art that the following examples are illustrative of the present application and should not be construed as limiting the scope of the application. The specific techniques or conditions are not identified in the examples and are performed according to techniques or conditions described in the literature in this field or according to the product specifications. The materials or equipment used are conventional products available from commercial sources, not identified to the manufacturer.
As used herein, the singular forms "a", "an", "the" and "the" are intended to include the plural forms as well, unless expressly stated otherwise, as understood by those skilled in the art. In the description of the present application, unless otherwise indicated, the meaning of "a plurality" is two or more. It will be further understood that the terms "comprises" and/or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. It will be understood that when an element is referred to as being "connected" to another element, it can be directly connected to the other element or intervening elements may also be present. Further, "connected" as used herein may include wireless connections.
In the description of the present application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings are merely for convenience in describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a specific orientation, be configured and operated in a specific orientation, and thus should not be construed as limiting the present application.
Furthermore, the terms "first," "second," and the like, are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include one or more such feature. In the description of the present application, the meaning of "a plurality" is two or more, unless explicitly defined otherwise.
In the present application, unless explicitly specified and limited otherwise, the terms "mounted," "connected," "secured," and the like are to be construed broadly, and may be, for example, connected, detachably connected, or integrally formed, mechanically connected, electrically connected, directly connected, indirectly connected via an intervening medium, or in communication between two elements or in an interaction relationship between two elements. The specific meaning of the above terms in the present application can be understood by those of ordinary skill in the art according to the specific circumstances.
In the present application, unless expressly stated or limited otherwise, a first feature "above" or "below" a second feature may include both the first and second features being in direct contact, as well as the first and second features not being in direct contact but being in contact with each other through additional features therebetween. Moreover, a first feature being "above," "over" and "on" a second feature includes the first feature being directly above and obliquely above the second feature, or simply indicating that the first feature is higher in level than the second feature. The first feature being "under", "below" and "beneath" the second feature includes the first feature being directly under and obliquely below the second feature, or simply means that the first feature is less level than the second feature.
In the description of the present specification, a description referring to terms "one embodiment," "some embodiments," "examples," "specific examples," or "some examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present application. In this specification, schematic representations of the above terms should not be understood as necessarily being directed to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, one skilled in the art can combine and combine the different embodiments or examples described in this specification.
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 one of ordinary skill in the art to which this application belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the prior art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.
The application provides a modularized multistage membrane distillation concentration device and a modularized multistage membrane distillation concentration method.
The device comprises one or two of a concentration module and a desalination module.
The concentration module comprises a concentration piece 1, a porous membrane 2 and a vacuum piece 3 which are stacked in sequence;
each group of the devices stacked in turn form a membrane separation unit, and the number of the 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:
at least one surface of the concentrating piece 1 in the stacking direction is provided with a concentrating runner 1-3, and the concentrating piece 1 is provided with a concentrating piece liquid inlet 1-1 and a concentrating piece liquid outlet 1-4 which are communicated with the concentrating runner 1-3;
the concentrating runner 1-3, the concentrating runner outlet 1-5 and the concentrating piece liquid outlet 1-4 are communicated in sequence;
the porous membrane 2 is stacked on the surface of the concentration flow channel 1-3 of the concentration member 1;
The vacuum member 3 has a vacuum chamber facing the porous membrane 2 for vaporizing the liquid portion in the concentration flow path 1-3 of the concentration member 1 through the porous membrane 2 into the vacuum chamber and condensing;
the concentrate liquid outlet 1-4 of the concentrate 1 of the concentration module is communicated to the concentrate liquid inlet 1-1 of the concentrate 1 of the next membrane separation unit to achieve continuous concentration of the liquid;
The condensate outlet 3-6 of the vacuum bin of the membrane separation unit of the concentration module is used for discharging desalted liquid, or the concentrate liquid inlet 1-1 communicated to the concentrate 1 of the corresponding-stage membrane separation unit of the desalination module is used for carrying out desalination on the desalted liquid again.
The desalination module comprises a concentration piece 1, a porous membrane 2 and a vacuum piece 3 which are stacked in sequence, wherein in each membrane separation unit of the desalination module, the communication modes of the devices are as follows:
each group of the devices stacked in sequence form a membrane separation unit, and the number of the membrane separation units is one or more in the concentration module and the desalination module;
The concentrating piece 1 is provided with a concentrating runner on at least one surface in the stacking direction, and the concentrating piece 1 is provided with a concentrating piece liquid inlet 1-1 and a concentrating piece liquid outlet 1-4 which are communicated with the concentrating runner 1-3;
the porous membrane 2 is stacked on the surface of the concentration flow channel 1-3 of the concentration member 1;
The vacuum member 3 has a vacuum chamber facing the porous membrane 2 for vaporizing the liquid portion in the concentration flow path 1-3 of the concentration member 1 through the porous membrane 2 into the vacuum chamber and condensing;
the condensate outlet 3-6 of the vacuum bin is communicated with the concentrate liquid inlet 1-1 of the concentrate 1 of the next membrane separation unit of the desalination module so as to realize continuous desalination of liquid;
The concentrate outlet 1-4 of the concentrate 1 of the non-first membrane separation unit of the desalination module is used for discharging concentrate or the concentrate inlet 1-1 of the concentrate 1 of the membrane separation unit of the corresponding stage of the concentration module is used for re-concentrating the liquid:
a concentrate liquid inlet 1-1 of a concentrate of a first membrane separation unit of the desalination module is used for receiving liquid to be treated;
When the device comprises a concentration module and a desalination module, the concentration module and the desalination module are as follows:
the stacking sequence of all devices in the concentration module and the desalination module is opposite;
The concentrated piece liquid inlet 1-1 of the concentrated piece 1 of the first membrane separation unit of the desalination module is communicated with the concentrated piece liquid inlet 1-1 of the first membrane separation unit of the concentration module, or the concentrated piece 1 of the first membrane separation unit of the desalination module is provided with concentrated flow channels 1-3 on two surfaces in the stacking direction, the concentrated piece liquid inlet 1-1 of the concentrated piece 1 of the first membrane separation unit of the desalination module is communicated with the inlet of the concentrated flow channel 1-3 on the back surface of the concentrated piece 1, and at the moment, the concentration module and the desalination module share the same concentrated piece at the joint of the two modules.
Preferably, the concentration module further comprises a desalination auxiliary heating element 4 which is stacked on the surface of the vacuum element 3 in reverse order;
the desalination module further comprises a desalination auxiliary heating element 4 sequentially stacked on the surface of the vacuum element 3;
The desalination auxiliary heating element 4 is provided with a condensate flow channel 4-4 and a heat source for supplying heat to liquid in the condensate flow channel 4-4;
the condensate outlet 3-6 of the vacuum bin is communicated with the condensate flow channel inlet 4-3 of the desalination auxiliary heat element 4, and the condensate flow channel outlet 4-1 of the desalination auxiliary heat element 4 is communicated with the concentrate liquid inlet 1-1 of the concentrate 1 of the next membrane separation unit of the desalination module or the concentration module.
The porous membrane 2 is preferably a hydrophobic microporous membrane.
In a preferred embodiment:
The details of the thickening element 1 are as follows, the thickening element 1 having a thickening chamber. The concentration chamber of the first membrane separation unit of the desalination module serves as a first-stage feeding chamber, and S-shaped concentration flow channels 1-3 are arranged in the concentration chamber. Diamond-shaped flow splitter plates 5 are stacked into the S-shaped concentrating flow channels. The membrane surface concentration polarization is reduced by enhancing turbulence. The feed liquid enters the S-shaped concentrating flow passage 1-3 from the liquid inlet 1-1 of the concentrating piece, and the flow is turbulent through the diamond-shaped flow dividing plate 5 in the S-shaped concentrating flow passage 1-3, so that dead zones are reduced. Wherein, the diamond-shaped splitter plate 5 is provided with diamond-shaped blocks 5-1. The spaces between the different diamond-shaped blocks 5-1 form diamond-shaped flow channel turbulent regions 5-2 of the flow distribution plate. The diamond-shaped flow dividing plate 5 and the S-shaped concentration flow passage 1-3 are stacked to enhance the fluid dynamic characteristics of the assembly, the vacuum membrane distillation process is facilitated to occur under the action of the porous membrane 2 and the vacuum piece 3, and part of vapor enters the vacuum bin through the hydrophobic microporous membrane to be condensed into first-stage desalted water.
FIG. 6 is a diagram of a diamond shaped splitter plate. The holes in the perforated bottom plate are not shown.
The rest feed liquid which is not gasified flows through the S-shaped concentrating flow passage 1-3 and finally flows out through the S-shaped concentrating flow passage 1-3, flows into the first-stage concentrating chamber of the concentrating module through the concentrating piece liquid inlet 1-2 of the first membrane separating unit of the concentrating module, and then is subjected to the membrane distillation process under the action of the porous membrane 2 and the vacuum piece 3 to finish the first concentrating process, and the liquid which is not gasified is used as first-stage concentrated water. The first-stage concentrated water enters the second stage of the concentration module, the vacuum membrane distillation process is repeated through the stacking of the porous membrane 2 and the vacuum piece 3, partial liquid is vaporized and enters the vacuum bin through the hydrophobic microporous membrane to become second-stage desalted water, the rest feed liquid which is not vaporized flows through the S-shaped flow channel 2-2 to flow out and enters the second-stage concentration chamber of the concentration piece of the second membrane separation unit of the concentration module, and the vacuum membrane distillation process is repeated through the stacking of the porous membrane 2 and the vacuum piece 3 to realize second-stage concentration. And the like, the multistage membrane distillation concentration process can be realized in an expanding way.
The periphery of the S-shaped concentrated runner 1-3 of the concentrated piece is provided with a concentrated piece sealing ring clamping groove 1-2, and a sealing ring 6 is arranged in the clamping groove to seal the S-shaped concentrated runner 1-3 of the concentrated piece. Each stage of membrane separation unit is formed by stacking parts such as a concentration piece 1, a sealing ring 6, a diamond-shaped flow dividing plate 5, a porous membrane 2, a vacuum piece 3 and the like.
The pore size of the hydrophobic microporous separation membrane may be micro-scale or nano-scale. For example, the pore diameter is 0.1 to 0.5 μm. The hydrophobic microporous separation membrane is made of PTFE or PP or PVDF. The surface of the hydrophobic microporous membrane is attached to the diamond-shaped splitter plate 5, and the process realizes the gradual concentration or desalination process.
The vacuum part 3 has the structure that a vacuum bin is arranged in the vacuum part 3. Only the side of the vacuum chamber facing the porous membrane 2 is open. The vacuum bin is internally provided with a bevel board 3-5, and the bevel board 3-5 is provided with a bevel board through hole 3-4. The vacuum part 3 is internally provided with a vacuum-pumping channel 3-1 communicated with the outside. The top wall of the vacuum bin is provided with three vacuumizing through holes 3-2 which are communicated with the cavity of the vacuum bin and the vacuumizing channel 3-1 and are used for vacuumizing the vacuum bin. The steam enters the vacuum bin and contacts the wall of the vacuum bin, namely the condensing wall surface 3-3 for liquefaction, flows into the bottom of the vacuum bin along the condensing wall surface 3-3 through the bevel plate through holes 3-4 on the bevel plate 3-5, finally flows into the primary desalting chamber through the condensate outlet 3-6 of the vacuum bin in a converging way, and the primary desalting process is completed. The first-stage desalted water enters the second stage, the module stack of single-stage vacuum membrane distillation is adopted, the vacuum membrane distillation process is repeated, part of liquid enters the vacuum chamber through the hydrophobic microporous membrane to become second-stage desalted water, the rest of feed liquid flows out through the S-shaped flow channel to enter the second-stage concentration chamber, the second-stage desalination is realized, and the like, and the multistage membrane distillation desalination process can be realized in an expanding manner.
The periphery of the vacuum bin of the vacuum part 3 is also provided with a vacuum part sealing ring clamping groove 3-7 for arranging a sealing ring 6 to seal the vacuum bin.
The working process of the desalination auxiliary heat piece 4 is that primary desalination condensate collected by the vacuum piece 3 flows into the condensate flow channel 4-4 of the desalination auxiliary heat piece 4 from the condensate flow channel inlet 4-3, meanwhile, the back of the desalination auxiliary heat piece 4 is an S-shaped auxiliary heat liquid flow channel 4-8, the liquid in the condensate flow channel 4-4 is heated by the S-shaped auxiliary heat liquid flow channel 4-8 of the auxiliary heat chamber 4 to enable the primary desalination condensate to reach the feeding temperature, and enters the concentration flow channel 1-3 of the concentration piece 1 of the next-stage membrane separation unit of the desalination module from the condensate flow channel outlet 4-1, the membrane distillation process occurs, and part of vapor enters the vacuum bin through the hydrophobic microporous membrane to be condensed into secondary desalination water, so that secondary desalination is realized. The multi-stage desalination process is completed by such pushing.
The heating medium in the auxiliary hot fluid flow path 4-8 enters the auxiliary hot fluid flow path 4-8 from the auxiliary hot inlet 4-5 and then is discharged through the auxiliary hot outlet 4-7. The periphery of the condensate flow channel 4-4 of the desalination auxiliary heating element 4 is provided with auxiliary heating side sealing ring clamping grooves 4-6 for arranging sealing rings 6.
The periphery of the condensate flow channel 4-4 is provided with a desalination side sealing ring clamping groove 4-2 for arranging a sealing ring 6.
The technical scheme provided by the application has the technical effects that:
1. high-efficiency concentration effect, turbulence strengthening and concentration polarization inhibition. The S-shaped flow channel in the concentrating piece and the flow dividing plate are stacked to cooperate, so that the hydrodynamic characteristics are improved, the supporting effect of the traditional separation net on the membrane surface is broken, the Reynolds number of the fluid is increased by 3-5 times by prolonging the flow path and generating secondary vortex, the shearing rate of the boundary layer reaches more than 100S -1, and the concentration polarization layer of the membrane surface is effectively destroyed. By combining the salt resistance of the hydrophobic microporous membrane (with the pore diameter of 0.1-0.5 mu m), the salting-out crystallization risk of the membrane surface is reduced by more than 70%, and the service life of the membrane is obviously prolonged. The single-stage concentration chamber realizes the concentration ratio of the feed liquid to be 1.5-2 times by vacuum membrane distillation, the unevaporated high-concentration liquid flows into the next stage, and the total concentration ratio can reach more than 10 times after the inside of the multi-stage membrane separation units are connected in series (the concentrated liquid TDS is more than 200g/L when the 6 stages are connected in series). The modularized design supports increasing and decreasing the number of stages according to the needs, and flexibly adapts to different concentration target requirements.
2. The multi-stage membrane assembly has the advantages that a modularized lamination structure is adopted, and the concentrating piece, the porous membrane, the vacuum piece and the desalting auxiliary heat piece are alternately arranged in multiple stages, so that the concentrating and desalting functions are realized at the same time. By means of the selective permeability of the hydrophobic microporous membrane material, the vapor directional transmission channel is constructed, and meanwhile effective separation between liquid phases is achieved. The multistage cooperative operation mode can synchronously complete efficient concentration of solute and directional recovery of solvent in the same system, and the comprehensive recovery rate of the system breaks through 60% by depending on the gradient separation efficiency of multistage membrane modules, so that an efficient membrane treatment system integrating separation, concentration and recovery is formed, and the resource recycling efficiency is remarkably improved.
3. And optimizing vacuum condensing efficiency. The vacuum bin adopts a bevel cutting plate and a distributed vacuumizing system (3 phi 6mm vacuumizing interfaces), so that the working pressure is stabilized at 5-15kPa (abs), the steam transmission resistance is reduced by 35%, and the condensing efficiency is improved by 40%. The wall of the vacuum bin forms a gradient cooling cold wall (top 40 ℃ to bottom 25 ℃) and combines with a diversion port design, so that the steam is rapidly liquefied, and the single-stage fresh water recovery rate is more than 20%.
4. The energy efficiency and stability are superior, the final condensation heat is used for preheating the feed liquid, the auxiliary hot liquid flow channel and the S-shaped flow channel are coupled, the interstage heat energy cascade utilization is realized, and the energy consumption is reduced by 30-40% compared with the traditional membrane distillation. The fluororubber/EPDM sealing ring 6 and the stainless steel diamond splitter plate 5 are structured to ensure no leakage risk (withstand voltage >0.3 MPa) under long-term operation. The multi-stage membrane distillation process can be achieved using a single-stage membrane distillation modular stack.
5. The method has the advantages of wide applicability, can treat high-salt wastewater (TDS >100 g/L), desalinate seawater and concentrate high-value substances (such as lithium salt and antibiotics) at low temperature, has the operating temperature of 40-80 ℃ and is suitable for complex working conditions. CFD simulation is adopted to optimize the geometric structure of the runner (such as the layout of an S-shaped runner and a diamond-shaped splitter plate), so that the turbulence intensity of a near-membrane interface can be enhanced. Experiments show that the arrangement of the 45-degree diamond splitter plate in the flow channel can improve the flux of vacuum membrane distillation (VMD membrane) by 20 percent, and the along-path pressure drop is only increased by 8 percent.
6. The modularized multi-stage membrane distillation assembly synchronously realizes high-efficiency concentration and high-quality desalination through structural innovation and flow optimization, and has the characteristics of low energy consumption, high recovery rate and strong pollution resistance. The method is applicable to the field of zero emission of industrial wastewater, can realize deep reduction of solid content of concentrated solution which is more than or equal to 20 percent aiming at high-salt and high-COD wastewater in petrochemical industry, coal chemical industry, electroplating industry and the like, can reduce total energy consumption by 30 percent when matched with an MVR evaporation system, is applicable to the field of water resource purification, is applicable to desalination of seawater (35000 ppm) and brackish water (less than 10000 ppm), and the quality of produced water meets the water standard of GB/T19923-2005 industrial boilers, is especially applicable to islands, ships and emergency water supply scenes, is applicable to the field of azeotropic system separation, can realize efficient separation of substance systems with boiling point difference of less than 5 ℃ by utilizing the gas-liquid balance difference of membrane distillation processes, can realize efficient separation of substance systems with boiling point difference of more than 99.9 percent, and is applicable to special separation scenes, and can realize molecular level precise migration and orientation of solutes by gradient membrane group configuration with aperture of 0.1-10 mu m in the fields of biological medicine (concentration of antibiotics, purification of vaccines) and new energy (concentration of plant extracts) and lithium battery electrolyte). Has remarkable application value in the above fields.
According to the application, through innovatively designing the integrated end plate structure of stacking coupling of the concentrating piece 1, the diamond-shaped flow dividing plate 5, the porous membrane 2, the vacuum piece 3 and the desalination auxiliary heating piece 4, the high-efficiency compactness of the membrane assembly is realized by integrating the S-shaped flow channel and the multi-stage stacking technology. The detachable concentration/desalination functional film frame is internally provided with a diamond-shaped flow dividing plate 5,S type flow channel to separate a concentration chamber and a desalination chamber, so that the application mode (the concentration mode TDS is more than 300g/L and the desalination mode TDS is less than 10 mg/L) can be rapidly switched according to the requirement. The system has the characteristics of high recovery rate, low energy consumption and strong pollution resistance, can flexibly adapt to the multi-scene requirements of zero emission of industrial wastewater, high-salt seawater desalination, low-temperature concentration of high-value substances and the like, and breaks through the technical bottlenecks of complex maintenance and single function of the traditional membrane distillation assembly.
The application has the synergistic innovation of the transmembrane separation technology. In practical application, the application process not only covers membrane distillation (including direct contact membrane distillation, blowing membrane distillation, vacuum membrane distillation and air gap membrane distillation), but also can be expanded to Forward Osmosis (FO), reverse Osmosis (RO), ultrafiltration (UF), nanofiltration (NF) and other processes to form a multi-cascade system. For example, a three-stage combined system of nanofiltration, reverse osmosis and membrane distillation is adopted. Porous membrane materials used in the experiments include, but are not limited to, polypropylene (PP), polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polyvinyl chloride (PVC), polyethylene (PE) or modified materials thereof, and the pore size range of the membrane is 0.1 μm to 10 μm.
The materials of the vacuum part 3, the concentrating part 1, the desalination auxiliary heating part 4 and the like can be PP, PET, PE, PVC, PS, PP, metals and the like.
The diamond-shaped splitter plate 5 material can be PTFE, PVC, FRP, alumina ceramics, metal materials and the like. In addition, the employed flow dividing plate is not limited to a diamond shape, but may be rectangular, square, polygonal, or the like. The flow channels in the concentrating piece and the desalting auxiliary heating piece are not just S-shaped, and the modes of snakelike, rectangular, multi-flow channel coupling, geometric topological structure optimization and the like are also applicable.
The design of the vacuum is not limited to the design of the bevel board, the angle and the position of the openings can be varied. The connecting structure among the vacuum part, the concentrating part, the desalination auxiliary heating part, the porous membrane 2 and the flow dividing plate 5 comprises a mechanical sealing structure, a non-contact sealing structure, a liquid film/gas film sealing structure and a rigid connecting structure, wherein the mechanical sealing structure adopts any one or combination of an O-shaped ring, a rectangular ring, a polytetrafluoroethylene gasket and an asbestos gasket, the non-contact sealing structure comprises a labyrinth boss and a stepped matching surface which are arranged on a sealing surface, medium blocking is realized through a micro gap of 0.1 mm-0.5 mm and a multistage baffling path, the liquid film/gas film sealing structure forms a pressure barrier by arranging an annular flow passage on the sealing surface and introducing sealing liquid (water and oil) or sealing gas (nitrogen), and the rigid connecting structure comprises any one or combination of welding, riveting, flange connection and press-fit type fastener-free connection.
Any simple deduction, structural imitation or module replacement made by a person skilled in the art without departing from the core idea of the invention shall be considered as falling within the protection scope of the invention.
The application is further illustrated by the following examples.
Example 1 (synchronous concentrated light mode)
The concentration module of the device is used for treating nuclear wastewater containing 0.015wt% of water. The number of membrane separation units in the concentration module is 5, forming a 5-stage process.
The porous membrane is specifically pp hydrophobic flat membrane, the membrane thickness is 0.2-0.3mm, and the membrane pores are 0.1-0.3 μm.
The treatment process has the parameters of 25L/h feed liquid flow rate, 80 deg.c feeding temperature, 0.07MPa vacuum degree and 10 deg.c cooling bath temperature.
After 5-level concentration, the concentration of the heavy water concentrated solution is 0.0183wt% (0.0033 wt% improvement), the deuterium content of the penetrating fluid is 0.00675wt%, the deuterium removal rate is 55% (the deuterium removal rate=1- (the deuterium content after treatment/the initial deuterium content) ×100%), the energy consumption is reduced by 35% compared with the traditional system (calculated by 800kWh compared with the water consumption of 1 ton evaporation), and the concentration rate is 22% (the concentration rate=the concentration of the concentrated solution/the feeding concentration-1).
Example 2 (high salt wastewater Recycling treatment mode)
The desalting module of the device is used for treating chemical high-salt wastewater containing 15wt% of sodium chloride, 0.5wt% of sodium sulfate and trace heavy metal ions, and the COD (chemical oxygen demand) concentration is 800mg/L and the high-salt wastewater at 35 ℃.
Module configuration and process parameters:
The number of the membrane separation units in the desalination module is 3, so that 3-stage treatment is formed.
In the first-stage membrane separation unit, the porous membrane is a Nanofiltration (NF) membrane. Nanofiltration (NF) membrane operating pressure is 1.8MPa. The feed temperature was 40 ℃. The porous membrane entraps sodium sulfate, and the divalent ion entraps rate is more than 99%. The vacuum piece functions as a pressure bearing seal (vacuum degree 0 bar).
In the secondary membrane separation unit, a polyamide reverse osmosis membrane (RO), sodium chloride is concentrated, the pressure is 4.0MPa, the feeding temperature is 50 ℃, and the NaCl interception rate is more than 99.5 percent. The vacuum piece functions as a pressure bearing seal (vacuum degree 0 bar).
In the three-stage membrane separation unit, PTFE hydrophobic microporous membrane (VMD), deep desalting/pure water production, feeding temperature of 65 ℃, vacuum degree of 0.08MPa and membrane flux of 12L/(m 2. H).
After three-stage treatment, liquid at a condensate outlet of a vacuum bin of a third-stage membrane separation unit is taken for detection:
the salt concentration of the third-stage fresh water effluent is reduced to be less than 100mg/L, the industrial reuse water standard is met, and the COD removal rate is more than 95 percent (COD removal rate= (COD concentration of sewage before treatment-COD concentration of sewage after treatment)/COD concentration of sewage before treatment multiplied by 100 percent).
The purity of Na2SO 4 is more than 98%, and the anhydrous sodium sulfate can be recovered by evaporation and crystallization.
The concentration of NaCl in the second-stage concentrated solution is more than 18wt%, and industrial salt (purity is more than 96%) can be recovered and prepared by evaporation and crystallization.
And the third-stage concentrated solution is heavy metal solution (the total amount is less than 5 wt%) containing trace NaCl, and can be used for dangerous waste solidification treatment.
Mass fraction (wt%) =mass concentration (mg/L)/(10,000) (solution density ≡1 g/mL).
Example 3 (organic-Water separation mode) desalination Module
The pharmaceutical wastewater (methanol/water azeotropic system) containing 5% of methanol is treated by using the desalting module of the device.
Module configuration and process parameters:
The flow rate of the feed liquid is 30L/h, the vacuum degree of the vacuum bin is 0.65bar, and the temperature of the membrane distillation assembly is 65 ℃ on the feed side/25 ℃ on the permeate side. The membrane material is a polypropylene (PP) sintered microporous membrane with the pore diameter of 0.8 mu m.
Module configuration and process parameters:
In the primary membrane separation unit, PP hydrophobic microporous membrane (VMD) is used for breaking azeotropic preseparation, the feeding temperature is 65 ℃, the vacuum degree is 0.065MPa, and the aperture is 0.8 mu m. The retention rate of methanol is more than 99.8 percent (original more than 99.6 percent), and the methanol of effluent is less than 0.02 percent. Retention= [1- (200/50,000) ]x100% = 99.6%.
In the secondary membrane separation unit, a PP hydrophobic microporous membrane (VMD), methanol is deeply trapped at the feeding temperature of 60 ℃ and the vacuum degree of 0.07MPa (gradient pressurization), and the water recovery rate reaches 78 percent. Rectifying to 8.2kWh/t. VMD is 3.7kWh/t, and the energy consumption is reduced by 55% compared with the rectification method.
In the three-stage membrane separation unit, a PP hydrophobic microporous membrane (VMD) is adopted, the feeding temperature of high-purity aquatic water is 55 ℃, the vacuum degree is 0.075MPa, and the condensation is 25 ℃.
The module occupies 20% of the area of the rectifying tower, and the compactness is improved by 80%.
Example 4 (salt lake brine lithium magnesium separation mode) concentration Module
The concentration module of the device is used for treating salt lake brine with high magnesium-lithium ratio and 1.2 percent of Li +、8％wt Mg2+ by weight.
Module configuration and process parameters:
The feed flow rate was 18L/h and the feed temperature was 25 ℃. Nanofiltration membrane assembly pressure is 1.5MPa, porous membrane selective block copolymer nanofiltration membrane, and the membrane has a separation coefficient=c >50 for Li +/Mg2+. α Li/Mg = 24.035/0.15=160.23 >50.
The primary membrane separation unit is Li + selective nanofiltration membrane (NF), mg 2+ is pre-trapped, the pressure is 1.5MPa, the temperature is 25 ℃, the Li/Mg separation coefficient is more than 50, and the vacuum piece is in pressure-bearing sealing (vacuum degree is 0 bar).
And a secondary membrane separation unit, namely a PTFE hydrophobic membrane (VMD), wherein Li + is deeply concentrated, the feeding temperature is 40 ℃, the vacuum degree is 0.08MPa, and the membrane flux is 8L/(m 2.h).
After nanofiltration of the primary membrane separation unit, the concentration of Li + is 11.4g/L, the concentration of Mg 2+ is 0.474g/L, the alpha Li/Mg =11.4/0.474=24.05, and the high-efficiency separation of magnesium and the improvement of the Li/Mg ratio by 160 times are realized.
After the secondary membrane separation unit VMD, the concentration of Li + is 16.29g/L, the concentration of Mg 2+ is 0.677g/L, and the concentration of lithium is further concentrated to prepare for extracting lithium.
Claims (9)
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