CN115193262A - Flat plate type membrane assembly for directly cooling penetrating fluid and application of flat plate type membrane assembly in membrane distillation - Google Patents
Flat plate type membrane assembly for directly cooling penetrating fluid and application of flat plate type membrane assembly in membrane distillation Download PDFInfo
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- CN115193262A CN115193262A CN202210549108.0A CN202210549108A CN115193262A CN 115193262 A CN115193262 A CN 115193262A CN 202210549108 A CN202210549108 A CN 202210549108A CN 115193262 A CN115193262 A CN 115193262A
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D63/00—Apparatus in general for separation processes using semi-permeable membranes
- B01D63/08—Flat membrane modules
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- A—HUMAN NECESSITIES
- A23—FOODS OR FOODSTUFFS; TREATMENT THEREOF, NOT COVERED BY OTHER CLASSES
- A23P—SHAPING OR WORKING OF FOODSTUFFS, NOT FULLY COVERED BY A SINGLE OTHER SUBCLASS
- A23P30/00—Shaping or working of foodstuffs characterised by the process or apparatus
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- A—HUMAN NECESSITIES
- A23—FOODS OR FOODSTUFFS; TREATMENT THEREOF, NOT COVERED BY OTHER CLASSES
- A23P—SHAPING OR WORKING OF FOODSTUFFS, NOT FULLY COVERED BY A SINGLE OTHER SUBCLASS
- A23P30/00—Shaping or working of foodstuffs characterised by the process or apparatus
- A23P30/30—Puffing or expanding
- A23P30/38—Puffing or expanding by heating
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
- B01D61/36—Pervaporation; Membrane distillation; Liquid permeation
- B01D61/364—Membrane distillation
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
- B01D61/36—Pervaporation; Membrane distillation; Liquid permeation
- B01D61/366—Apparatus therefor
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
- B01D61/36—Pervaporation; Membrane distillation; Liquid permeation
- B01D61/368—Accessories; Auxiliary operations
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D63/00—Apparatus in general for separation processes using semi-permeable membranes
- B01D63/08—Flat membrane modules
- B01D63/087—Single membrane modules
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D65/00—Accessories or auxiliary operations, in general, for separation processes or apparatus using semi-permeable membranes
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/44—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis
- C02F1/447—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis by membrane distillation
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2103/00—Nature of the water, waste water, sewage or sludge to be treated
- C02F2103/08—Seawater, e.g. for desalination
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2209/00—Controlling or monitoring parameters in water treatment
- C02F2209/02—Temperature
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2303/00—Specific treatment goals
- C02F2303/10—Energy recovery
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
- Y02A20/00—Water conservation; Efficient water supply; Efficient water use
- Y02A20/124—Water desalination
Abstract
The invention belongs to the technical field of membrane distillation, and particularly relates to a flat-plate membrane module and a system for directly cooling penetrating fluid; the flat plate type membrane component mainly comprises: the device comprises a hydrophobic microporous membrane, a hot side cavity, a cold side cavity, a semiconductor heat pump assembly and an external heating unit; a hot side cavity and a cold side cavity are respectively arranged at two sides of the hydrophobic microporous membrane, and a feeding channel and a discharging channel are respectively arranged at two ends of the two side cavities; the heat absorbing surface of the semiconductor heat pump component is attached to the cold side cavity, and the heat radiating surface of the semiconductor heat pump is closely attached to the external heating unit; the distance between the heat absorbing surface of the semiconductor heat pump component and the hydrophobic microporous membrane is 1-5mm. The heat absorption unit of the semiconductor heat pump is integrated in the cold side cavity of the membrane component, so that the penetrating fluid is directly cooled and kept at a lower temperature to improve the average temperature difference of two sides of the membrane, and the energy consumption and the cost of the membrane distillation method in the evaporation concentration processes of seawater desalination, sewage treatment, food concentration and the like are reduced.
Description
Technical Field
The invention belongs to the technical field of membrane distillation, and particularly relates to a flat-plate membrane component for directly cooling penetrating fluid and application thereof in membrane distillation.
Background
Membrane Distillation (MD) is a novel membrane separation technology that drives steam permeation by steam pressure difference between two sides of a microporous hydrophobic membrane, and is widely applied to the fields of seawater desalination, sewage treatment, food concentration and the like. Compared with the traditional thermal method evaporation concentration method (such as multi-effect evaporation, multi-stage flash evaporation and the like) and other membrane separation technologies (such as reverse osmosis, nanofiltration, electrodialysis and the like), the membrane distillation has the advantages of high rejection rate, mild operation conditions, easiness in scale production and the like.
Membrane distillation can be generally classified into Direct Contact Membrane Distillation (DCMD), air gap distillation (AGMD), sweep Gas Membrane Distillation (SGMD), and Vacuum Membrane Distillation (VMD) according to the collection method on the permeate side. Compared to other MD methods, DCMD is a widely studied MD process because the process configuration is the simplest.
Typical DCMD systems require both feed solution heating and permeate cooling, so system operation requires both hot and cold trap actuation. The heat source required by heating can generally utilize waste heat resources (such as low-temperature steam, hot water and the like) in the process industry, and feed liquid enters the hot side of the membrane module after being heated by external heat exchange equipment; and the penetrating fluid enters the cold side of the membrane component after being cooled by the cold trap. Due to evaporation of the feed liquid at the hot side of the membrane module and heat dissipation loss, the temperature at the hot side of the membrane module will decrease along the flow direction of the feed liquid, while the temperature at the cold side will increase along the flow direction of the permeate liquid, thereby causing the average temperature difference (effective driving force for membrane separation) at the membrane surface to be less than the inlet temperature difference (i.e., driving force for process system increase) at both sides of the cold and hot membrane modules. Thus, the separation efficiency of the DCMD membrane module is low; meanwhile, polarization (boundary layer phenomenon) exists on both the cold side and the hot side of the membrane component, so that the fluid temperature on the surface of the hot side membrane is lower than that of the main stream, while the fluid temperature on the surface of the cold side membrane is higher than that of the main stream, and the unavoidable polarization further reduces the DCMD separation efficiency.
At present, in order to improve the separation efficiency of the DCMD, methods such as countercurrent operation, improvement of fluid flow rate on two sides of a membrane module, enhancement of fluid disturbance in a flow channel and the like are mainly adopted to improve the average temperature difference of the membrane surface and relieve polarization. However, these methods increase membrane separation efficiency at the expense of increased power consumption for fluid transport, and thus it is difficult to significantly increase the overall energy efficiency of a DCMD system. In addition, cold traps commonly used in the process industry are typically implemented by refrigeration cycles, which include compression, throttling, and heat exchange processes, which are complex and costly to implement.
Therefore, in order to reduce the energy consumption of the DCMD system process, MD integrated systems using heat pumps have appeared in recent years. The heat pump is a device for transferring heat energy from a low-temperature material system to a heating object, and can remarkably improve the comprehensive energy efficiency of the MD system by realizing high-efficiency energy conversion of refrigeration and heating at the same time. The Chinese patent application CN108622983b discloses a membrane distillation device and a method adopting a heat pump, wherein the traditional heat pump is circularly integrated in a DCMD membrane component, and the refrigeration of penetrating fluid and the heating of feed liquid are simultaneously realized by utilizing the heat pump principle. Further, the membrane distillation method using a heat pump further includes: a heat pump integrated double-effect membrane distillation system (CN 105709601A), a DCMD system (CN 105749752A) integrated with solar energy preheating and heat pump cooling, a method (CN 106582292A) for improving the heat efficiency of the heat pump membrane distillation system by optimizing a hollow fiber membrane, and the like.
Compared with the traditional compression heat pump (comprising a compressor, a throttle valve and other devices) adopting steam as a working medium, the semiconductor refrigeration piece adopting the thermoelectric refrigeration technology has the advantages of small volume, low cost and easy realization of system miniaturization, and has higher simplicity and convenience in the aspect of energy conversion of heating and refrigeration. The semiconductor heat pump utilizes the Peltier effect to move heat from a low-temperature heat absorption surface to a high-temperature heat radiation surface by the action of current. Chinese patent CN113716785A discloses a membrane module that uses thermoelectric refrigeration technology to realize VMD, but in this technology, the heat dissipation surface of the semiconductor refrigeration sheet needs to be adapted to the large-area metal heat dissipation fins, thereby increasing the material cost of the equipment, and making it difficult to further reduce the size of the membrane module; meanwhile, the patented technology needs an additional heating device to provide heat required by system operation, which also increases implementation cost of the scheme.
In summary, in order to promote the application of membrane distillation technology in the fields of seawater desalination, sewage treatment, food concentration, etc., the following problems are urgently needed to be solved at present: (1) The complexity and the cost of system configuration of a high-efficiency heat and cold source utilization method like a heat pump membrane distillation system are reduced; (2) The membrane module design is optimized to mitigate polarization, enhance the heat and mass transfer process, and improve energy utilization in the membrane module.
The invention content is as follows:
the invention aims to provide a flat plate type membrane component for directly cooling penetrating fluid and application thereof in membrane distillation, which can improve the membrane distillation separation efficiency and reduce the cost of a DCMD method, and realize the obvious reduction of energy consumption and cost in the evaporation concentration processes of seawater desalination, sewage treatment, food concentration and the like.
The semiconductor refrigeration piece is adopted to replace the traditional heat pump circulating system, so that the system configuration complexity and the cost of the cold and heat source utilization method are reduced; compared with the prior technical scheme that the heat absorption surface of the semiconductor refrigeration sheet absorbs heat from the air gap at the permeation side through the metal partition wall, the invention adopts a mode of directly cooling the penetrating fluid, improves the heat transfer efficiency by utilizing the characteristic that the heat conductivity coefficient of liquid is obviously higher than that of gas, effectively increases the average temperature difference at two sides of the membrane and obviously improves the membrane separation efficiency.
The purpose of the invention is realized by the following technical scheme:
a flat-plate membrane module for directly cooling penetrating fluid mainly comprises a membrane separation unit, a semiconductor heat pump assembly and an external heating unit;
the membrane separation unit comprises a hydrophobic microporous membrane, a hot side cavity and a cold side cavity; a hot side cavity and a cold side cavity are respectively arranged on two sides of the hydrophobic microporous membrane; the heat absorbing surface of the semiconductor heat pump assembly is attached to the cold side cavity of the membrane separation unit, and the heat radiating surface of the semiconductor heat pump assembly is tightly attached to the external heating unit;
preferably, at least one feed liquid inlet channel and at least one feed liquid outlet channel are respectively arranged at two ends of the hot side cavity, and the axes of any feed liquid inlet channel and any feed liquid outlet channel are not collinear.
Preferably, at least one permeate inlet channel and at least one permeate outlet channel are respectively arranged at two ends of the cold side accommodating cavity, and the axis of any one permeate inlet channel is not collinear with the axis of any one permeate outlet channel.
The distance between the heat absorbing surface of the semiconductor heat pump and the hydrophobic microporous membrane is 1-5mm.
Preferably, the semiconductor heat pump assembly comprises a mounting frame and a semiconductor cooling plate, more preferably, the semiconductor cooling plate is selected from a model TEC2-19006, has a size of 40x 6.3mm, and is embedded in the heat-resistant epoxy resin mounting frame.
Preferably, the hydrophobic microporous membrane is a polyvinylidene fluoride planar membrane, the average pore diameter is 0.22um, and the average membrane thickness is 0.012mm.
Preferably, the external heating element is made of a highly heat conductive material, with dimensions 40x 7mm, provided with both inlet and outlet channels at one end, the internal configuration being an M-shaped flow channel. More preferably, the high heat conduction material is aluminum material, copper material, aluminum alloy or copper alloy.
A direct contact type membrane distillation system comprises a feed liquid storage tank, a feed liquid circulating pump, a flat plate type membrane module for directly cooling penetrating fluid, a penetrating fluid storage tank and a penetrating fluid circulating pump;
the feed liquid storage tank is connected with a feed liquid circulating pump through a pipeline, the feed liquid circulating pump is connected with an inlet channel of an external heating unit of the flat-plate membrane component for directly cooling the penetrating fluid through a pipeline, an outlet channel of the external heating unit is respectively connected with a feed liquid inlet channel of a hot-side accommodating cavity of the flat-plate membrane component for directly cooling the penetrating fluid through a pipeline, and a feed liquid outlet channel of the hot-side accommodating cavity of the flat-plate membrane component for directly cooling the penetrating fluid is connected with the feed liquid storage tank through a pipeline; the penetrating fluid storage tank is connected with a penetrating fluid circulating pump through a pipeline, the penetrating fluid circulating pump is respectively connected with a penetrating fluid inlet channel of the cold side cavity of the flat-plate type membrane assembly for directly cooling the penetrating fluid through the pipeline, and a penetrating fluid outlet channel of the cold side cavity of the flat-plate type membrane assembly for directly cooling the penetrating fluid is connected with the penetrating fluid storage tank through the pipeline.
In the direct contact membrane distillation system, feed liquid to be concentrated in a feed liquid storage tank is sent to an external heating unit of a flat plate type membrane component for directly cooling penetrating fluid through a feed liquid circulating pump, and then the feed liquid is heated and enters a hot side cavity of a membrane separation unit component; the penetrating fluid in the penetrating fluid storage tank is sent to a cold side cavity of the flat plate type membrane component for directly cooling the penetrating fluid through a penetrating fluid circulating pump to be cooled; in the membrane separation unit of the flat membrane component for directly cooling the penetrating fluid, under the driving of fluid temperature difference on two sides of the membrane, water vapor migrates from a hot side to a cold side through the membrane under the driving of steam pressure difference on two sides of the membrane, thereby realizing the concentration of feed liquid and the enrichment of the penetrating fluid.
The heating and cooling process of the feed liquid and the penetrating fluid in the flat plate type membrane component for directly cooling the penetrating fluid is specifically described as follows: the penetrating fluid in the cold side cavity is directly cooled by the semiconductor heat pump assembly, the absorbed heat is transferred to the external heating unit to heat the feed liquid, and then the feed liquid enters the hot side cavity in the membrane separation unit and transfers heat to the penetrating side.
Compared with the prior art, the invention has the following advantages and effects:
(1) The invention uses the economic semiconductor refrigeration piece to replace the traditional heat pump refrigeration to develop the heat pump membrane distillation system with lower cost.
(2) After high-temperature feed liquid and low-temperature penetrating liquid in MD respectively enter the membrane units, the temperature difference formed on two sides of the membrane is the driving force in the membrane distillation process, and because the feed liquid on the hot side of the membrane component is evaporated and transferred, the temperature of the hot side of the membrane component is reduced along the membrane surface, and the temperature of the cold side is increased along the membrane surface, the membrane separation efficiency is reduced accordingly. According to the invention, the heat absorption surface of the semiconductor heat pump is integrated in the cold side cavity of the membrane separation unit, so that heat transferred from the hot side across the membrane can be removed in time, the effective temperature difference of the cold side and the hot side of the fluid on the membrane surface is increased, and the thermal efficiency of the DCMD process is effectively improved.
(3) The heat absorption surface of the semiconductor heat pump component is directly contacted with the penetrating fluid, so that high heat transfer resistance generated by air gap heat transfer is avoided, and the effective temperature difference of the cold side and the hot side of the fluid on the membrane surface is increased.
(4) The two side cavities of the membrane separation unit in the invention comprise internal components such as external heating units with the thickness not exceeding 10mm and not containing metal fins, thereby not only effectively reducing the size of the membrane module, but also completely adopting light materials such as plastics to manufacture the membrane module, realizing the compactness and the light weight of a DCMD system and obviously reducing the configuration cost of the MD system.
(5) According to the invention, by optimizing the runners on two sides of the membrane, the phenomena of short circuit, dead zone and the like are effectively avoided without remarkably increasing the energy consumption of the runners, and the separation efficiency of the membrane component is further improved.
Drawings
FIG. 1 is a schematic structural view of a flat-plate membrane module for direct cooling of permeate in accordance with the present invention;
FIG. 2 is a schematic structural view of two side cavities in a membrane separation unit in a flat-plate membrane module for directly cooling permeate;
FIG. 3 is a schematic diagram of the construction of an external heating unit in a flat-plate membrane module for direct cooling of permeate;
FIG. 4 is a schematic structural view of a flat-plate membrane module directly cooling permeate as described in the examples;
FIG. 5 is a schematic diagram of the structure of a DCMD system constructed by the flat-plate membrane module using direct cooling of permeate in the embodiment;
FIG. 6 is a schematic diagram of a DCMD system employing a single cold and heat source;
fig. 7 is a schematic structural diagram of a DCMD system in which a semiconductor heat pump is disposed outside a membrane module.
Detailed Description
For a better understanding of the present invention, reference is made to the following description taken in conjunction with the accompanying drawings and examples.
As shown in fig. 1, the flat plate type membrane module for directly cooling the permeate consists of a membrane separation unit, a semiconductor heat pump assembly 6 and an external heating unit 12, wherein the membrane separation unit comprises a hydrophobic microporous membrane 1, a hot side containing cavity 7, a cold side containing cavity 10, a feed liquid inlet channel 8, a feed liquid outlet channel 2, a permeate inlet channel 9 and a permeate outlet channel 3.
A hot side cavity 7 and a cold side cavity 10 are respectively arranged on two sides 1 of the hydrophobic microporous membrane; one end of the hot side cavity 7 is provided with a feed liquid inlet channel 8, and the other end is provided with a feed liquid outlet channel 2; one end of the cold side cavity 10 is provided with a penetrating fluid inlet channel 9, and the other end is provided with a penetrating fluid outlet channel 3.
The semiconductor heat pump assembly 6 comprises a mounting frame and a semiconductor refrigerating plate, wherein the semiconductor refrigerating plate is selected from TEC2-19006, is 40x 6.3mm in size, and is embedded in the heat-resistant epoxy resin mounting frame. The heat absorption surface 4 of the semiconductor heat pump assembly 6 is tightly attached to the cold side containing cavity 10 of the membrane separation unit, and the heat dissipation surface 5 of the semiconductor heat pump assembly 6 is tightly attached to the external heating unit 12; the distance between the heat absorbing surface 4 of the semiconductor heat pump assembly 6 and the hydrophobic microporous membrane 1 is 1-5mm.
In order to alleviate the influence of 'dead zone', 'short circuit' and the like caused when the material flows enter and exit from the cavity and realize the optimization of the flow channel, as shown in fig. 2, preferably, a plurality of material liquid inlet channels 8 and material liquid outlet channels 2 are respectively arranged at two ends of a hot side cavity 7, and the axes of any material liquid inlet channel 8 and any material liquid outlet channel 2 are not collinear; a plurality of permeate inlet channels 9 and permeate outlet channels 3 are respectively arranged at two ends of the cold side containing cavity 10, and the axes of any permeate inlet channel 9 and any permeate outlet channel 3 are not collinear.
In order to enhance the heat transfer performance of the external heating unit 12, the external heating unit 12 is made of a high heat conductive material, and has a size of 40 × 10mm, as shown in fig. 3, an inlet passage 111 and an outlet passage 112 are provided at one end of the external heating unit 12, and are configured as an M-shaped flow passage inside.
When the flat-plate membrane module directly cooling penetrating fluid operates, feed liquid enters the external heating unit 12 through the inlet channel 11, is heated and heated, then leaves the external heating unit through the outlet channel 112, and enters the hot side cavity 7 through the feed liquid inlet channel 8; permeate enters the cold side receiving volume 10 through permeate inlet channel 9 and is cooled directly by the semiconductor heat pump assembly 6. Temperature difference is formed on two sides of the hydrophobic microporous membrane 1, namely the water vapor pressure of the feed liquid is higher than that of the permeation side, and the water vapor in the membrane pores is driven by the steam pressure difference to migrate from the feed liquid side to the permeation side, so that evaporation concentration on the feed liquid side and water enrichment on the permeation side are realized.
Example 1
A flat-plate membrane module for direct cooling of permeate as shown in fig. 4 was constructed according to the fig. 1-3 construction, comprising: an epoxy resin frame 13, a plexiglass cover plate 14, a membrane separation unit 15, a semiconductor heat pump assembly 16, and an external heating unit 17. Wherein the organic glass cover plate 14 is 80 x 3mm in size and is fixed by the epoxy resin frame 13 which is 80 x 4mm in size.
The membrane separation unit 15 is made of plexiglass, wherein the hot side cavity and the cold side cavity are both 40x5mm in size, and the effective volume is 8ml. In order to improve the problems of flowing dead zones and short circuits when fluid enters and exits the cavity, 3 feeding channels with the diameter of 4mm are uniformly distributed on the feeding side surface of the hot side cavity, 3 discharging channels with the diameter of 4mm are uniformly distributed on the discharging side surface, and any inlet channel is not overlapped with the axis of the outlet channel; 3 feeding channels with the diameter of 4mm are uniformly distributed on the feeding side surface of the cold cavity, 3 discharging channels with the diameter of 4mm are uniformly distributed on the discharging side surface, and any inlet channel is not overlapped with the axis of the outlet channel; in order to better observe the membrane separation state, PT100 thermal resistance temperature sensors connected with a computer acquisition system are arranged in the hot side cavity and the cold side cavity; the hydrophobic microporous membrane was a Millipore PVDF flat membrane having an effective size of 40x40mm after cutting, an average pore diameter of 0.22um and an average membrane thickness of 0.012mm.
The semiconductor heat pump assembly 16 comprises a mounting frame and a semiconductor cooling plate, wherein the semiconductor cooling plate is selected from a type TEC2-19006, has a size of 40x 6.3mm, and is embedded in a heat-resistant epoxy resin frame with a size of 80 x4 mm.
The external heating unit 17 is made of aluminum alloy, the size is 40x 11mm, the internal part is an M-shaped flow channel, and a feeding channel and a discharging channel are arranged on the bottom surface.
The energy consumption determination experiment was performed according to the DCMD system shown in fig. 5, using the present invention.
As shown in FIG. 5, the DCMD system specifically includes a feed reservoir 18 having a volume of 250mL and made of polypropylene, a set of Masterflex L/S feed circulation pumps 19 from Cole-Parmer, USA, a set of flat membrane modules 21 (the specific structure is shown in FIG. 4) for directly cooling the permeate, a permeate reservoir 24 having a volume of 250mL and made of polypropylene with an overflow outlet, and a set of Masterflex L/S permeate circulation pumps 23 from Cole-Parmer, USA; in addition, a DC adjustable power supply 20 with a rated power of 300W, a set of computers 22 for data acquisition and monitoring and an analytical balance 25 for measuring the seepage overflow are included.
The specific operation method and process parameters of the DCMD system are as follows:
at room temperature, adding sufficient normal-temperature pure water into a feed liquid storage tank 18 and a penetrating fluid storage tank 24 respectively, inputting the feed liquid into an external heating unit through a hot-side circulating pump 19 for heating, then inputting the feed liquid into a hot-side containing cavity of a flat membrane assembly 21 for directly cooling the penetrating fluid, inputting the penetrating fluid into a cold-side containing cavity of the flat membrane assembly 21 for directly cooling the penetrating fluid through a cold-side circulating pump 23, setting the output power of a direct-current adjustable power supply 20 driven by a semiconductor heat pump assembly to be 23.63W, setting the flow rates of the feed liquid circulating pump 19 and the penetrating fluid circulating pump 23 to be 2.5kg/h, collecting and recording the temperatures of the cold and hot-side containing cavities of the flat membrane assembly for directly cooling the penetrating fluid through a computer 22 (a computer temperature collecting module is connected with each stage of thermal resistors of the membrane assembly), evaporating the feed liquid at the hot-side on the membrane surface of the membrane assembly under the driving of the steam pressure difference of the hot side and the cold side, transferring heat and mass to the penetrating fluid, so that the penetrating fluid is increased, the generated penetrating fluid flows out through an overflow pipe of the feed liquid storage tank 24, and the generated amount of the penetrating fluid is measured by a balance 25 in unit time.
Comparative example 1
To better illustrate the performance differences between the present invention and conventional DCMD systems, a DCMD system using a single cold and heat source was constructed as shown in fig. 6.
The conventional DCMD system specifically includes a feed liquid reservoir 35 of 250mL volume and made of polypropylene, a Masterflex L/S feed circulation pump 27 of Cole-Parmer, usa, a 50W electric heating system 28, a DCMD membrane module 34, a permeate reservoir 33 of 250mL volume and made of polypropylene with an overflow outlet, a permeate circulation pump 31 of Masterflex L/S, cole-Parmer, usa, a heat pump refrigeration cycle system 30, a computer 36 for data acquisition and monitoring, and an analytical balance 32 for permeate overflow flow measurement. The traditional DCMD membrane component is made of colorless and transparent organic glass and comprises a hot side cavity 3411 and a cold side cavity 3412, wherein the sizes of the hot side cavity 3411 and the cold side cavity 3412 are 40x40x 5mm; the hydrophobic microporous membrane adopts a Millipore PVDF planar membrane, the effective size is 40x40mm, the average membrane thickness is 0.012mm, and the average pore diameter is 0.22um; both the hot and cold side plenums are provided with fluid outlet passages 3414 and fluid inlet passages 3415.
The energy consumption determination experiment was performed using the conventional DCMD system shown in fig. 6, and the specific operation method and process parameters were as follows:
at room temperature, sufficient normal-temperature pure water is respectively added into the feed liquid storage tank 35 and the penetrating fluid storage tank 33, and the feed liquid is fed into the electric heating system 28 through the feed liquid circulating pump 27 and is heated and then is input into a hot side accommodating cavity of the membrane component 34; the pure water in the penetrating fluid storage tank 33 is sent to the heat pump refrigeration cycle system 30 through the penetrating fluid circulating pump 31, and is input into the cold side cavity of the membrane module 34 after being cooled. The flow rates of the feed liquid circulating pump 27 and the penetrating fluid circulating pump 31 are both set to be 2.5kg/h, the input power of the electric heater 28 is set to be 11.55W, and the input power of the heat pump refrigeration cycle is set to be 23.63W. The inlet and outlet temperatures of the membrane modules 34 are recorded by a computer 36. In the membrane separation unit, under the driving of the steam pressure difference between the hot side and the cold side, feed liquid is evaporated on the membrane surface of the cavity at the hot side and transfers heat and mass to the cold side, so that the penetrating fluid is increased, the generated penetrating fluid flows out through an overflow pipe of a penetrating fluid storage tank 33, and the generated amount of the penetrating fluid per unit time is measured by a balance 32.
Comparative example 2
To better illustrate the performance differences between the present invention and a DCMD system with a semiconductor heat pump disposed outside the membrane module, an integrated heat pump DCMD system with a heat pump disposed outside the membrane module as shown in fig. 7 was created.
The DCMD system with the semiconductor heat pump arranged outside the membrane module specifically comprises a feed liquid storage tank 37 with the volume of 250mL and made of polypropylene, a Masterflex L/S feed liquid circulating pump 45 of American Cole-Parmer company, an external semiconductor heat pump module 42, a DCMD membrane module 38, a permeate storage tank 46 with the volume of 250mL and made of polypropylene and provided with an overflow outlet, a permeate circulating pump 40 of Masterflex L/S of American Cole-Parmer company, a direct current adjustable power supply 47 with the rated power of 300W, a computer 43 for data acquisition and monitoring and an analysis balance 39 for measuring the overflow of permeate. Wherein, the DCMD membrane module 38 is made of colorless transparent organic glass, and includes a hot side cavity and a cold side cavity (same as in comparative example 1) which are both 40 × 5mm in size; the hydrophobic microporous membrane was a Millipore PVDF flat membrane with an effective size of 40X40mm, an average membrane thickness of 0.012mm and an average pore diameter of 0.22um. In addition, the external semiconductor heat pump assembly comprises a mounting frame and a semiconductor cooling plate, wherein the semiconductor cooling plate is selected from a heat-resistant epoxy resin frame with the model of TEC2-19006, the size of 40x 6.3mm and embedded in the size of 80 x 4mm, an external cooling unit 41 is attached to the heat absorbing surface of the semiconductor cooling plate, and an external heating unit 44 is attached to the heat radiating surface of the semiconductor cooling plate; the external heating unit and the external cooling unit are both made of aluminum alloy, the size is 40x 7mm, the internal part is an M-shaped flow channel, and a feeding channel and a discharging channel are arranged on the bottom surface.
The DCMD system with the semiconductor heat pump outside the membrane module shown in fig. 7 is used for energy consumption determination experiments, and the specific operation method and process parameters are as follows:
at room temperature, adding sufficient normal-temperature pure water into the feed liquid storage tank 37 and the penetrating fluid storage tank 46 respectively, feeding the feed liquid into an external heating unit 44 of a semiconductor heat pump assembly 42 through a feed liquid circulating pump 45, heating and then inputting the feed liquid into a hot side containing cavity of the membrane assembly 38; pure water placed in the permeate storage tank 46 is sent to an external cooling unit of the semiconductor heat pump assembly 42 through the permeate circulation pump 40 to be cooled and then is input to the cold side receiving chamber of the membrane module 38. The flow rates of the feed liquid 45 and the penetrating fluid circulating pump 40 are both set to be 2.5kg/h, and the input power of the direct current power supply is set to be 23.63W. The inlet and outlet temperatures of the membrane modules are collected and recorded by the computer 43. Under the driving of the steam pressure difference between the hot side and the cold side, the feed liquid is evaporated on the membrane surface of the cavity at the hot side and transfers heat and mass to the cold side, so that the penetrating fluid is increased, the generated penetrating fluid flows out through an overflow pipe of the penetrating fluid storage tank 46, and the generated amount of the penetrating fluid per unit time is measured by the balance 39.
TABLE 1 comparison of DCMD System Performance of DCMD System with Single Cold and Heat Source, DCMD System with external semiconductor Heat Pump, and DCMD System with Flat Membrane Module with direct Cooling of permeate
The performance of the example (the flat sheet membrane module DCMD system using the direct cooling permeate), the comparative example 1 (the DCMD system using the single cold heat source) and the comparative example 2 (the DCMD system of the external semiconductor heat pump) were compared under the same operating conditions, and the results are shown in table 1, and it can be seen that: (1) The unit energy consumption of the DCMD system can be effectively reduced by adopting a thermoelectric refrigeration technology, and the unit energy consumption of the comparative example 2 and the unit energy consumption of the embodiment are respectively reduced by 34 percent and 55 percent compared with that of the comparative example 1; (2) Compared with the comparative example 2, the invention has higher membrane separation efficiency, the water yield is improved by 47 percent, and the unit energy consumption is reduced by 32 percent, because the heat absorbing surface of the semiconductor heat pump is attached to the cold side cavity of the membrane separation unit to directly cool the penetrating fluid, the lower temperature of the penetrating fluid is kept, the effective temperature difference of the cold side and the hot side of the fluid on the membrane surface is increased, in addition, the design scheme of an optimized flow channel is applied in the flat plate type membrane component, and the heat and mass transfer process in the membrane distillation process is improved.
It should be understood by those skilled in the art that the present invention is not limited to the embodiments. All changes, equivalents and modifications which come within the spirit and scope of the invention are desired to be protected.
Claims (6)
1. A flat-plate membrane module for direct cooling of permeate, comprising: mainly comprises a membrane separation unit, a semiconductor heat pump assembly and an external heating unit;
the membrane separation unit comprises a hydrophobic microporous membrane, a hot side cavity and a cold side cavity; a hot side cavity and a cold side cavity are respectively arranged on two sides of the hydrophobic microporous membrane; the heat absorbing surface of the semiconductor heat pump assembly is attached to the cold side containing cavity of the membrane separation unit, and the heat radiating surface of the semiconductor heat pump assembly is tightly attached to the external heating unit.
2. The flat-plate membrane module according to claim 1, wherein:
two ends of the hot side cavity are respectively provided with at least one feed liquid inlet channel and at least one feed liquid outlet channel, and the axes of any feed liquid inlet channel and any feed liquid outlet channel are not collinear;
at least one permeate inlet channel and at least one permeate outlet channel are respectively arranged at two ends of the cold side containing cavity, and the axes of any permeate inlet channel and any permeate outlet channel are not collinear.
3. The flat-plate membrane module according to claim 1, wherein: the distance from the heat absorbing surface of the semiconductor heat pump to the hydrophobic microporous membrane is 1-5mm; the semiconductor heat pump assembly comprises a mounting frame and semiconductor refrigeration sheets.
4. The flat-plate membrane module according to claim 1, wherein: the microporous hydrophobic membrane is a PVDF microporous hydrophobic membrane, the average pore diameter is 0.22um, and the average membrane thickness is 0.012mm;
the semiconductor refrigeration piece is selected from a type TEC2-19006, has a size of 40x 6.3mm, and is embedded in the heat-resistant epoxy resin mounting frame.
5. The flat-plate membrane module according to claim 1, wherein:
the external heating unit is made of high heat conduction materials, the size of the external heating unit is 40x 7mm, an inlet channel and an outlet channel are arranged at one end of the external heating unit at the same time, and the internal structure of the external heating unit is an M-shaped flow channel.
6. A direct contact membrane distillation system characterized by: comprises a feed liquid storage tank, a feed liquid circulating pump, a flat-plate membrane component for directly cooling penetrating fluid, a penetrating fluid storage tank and a penetrating fluid circulating pump;
the feed liquid storage tank is connected with a feed liquid circulating pump through a pipeline, the feed liquid circulating pump is connected with an inlet channel of an external heating unit of the flat-plate membrane component for directly cooling the penetrating fluid through a pipeline, an outlet channel of the external heating unit is respectively connected with a feed liquid inlet channel of a hot-side accommodating cavity of the flat-plate membrane component for directly cooling the penetrating fluid through a pipeline, and a feed liquid outlet channel of the hot-side accommodating cavity of the flat-plate membrane component for directly cooling the penetrating fluid is connected with the feed liquid storage tank through a pipeline; the penetrating fluid storage tank is connected with a penetrating fluid circulating pump through a pipeline, the penetrating fluid circulating pump is respectively connected with a penetrating fluid inlet channel of the cold side cavity of the flat-plate type membrane assembly for directly cooling the penetrating fluid through the pipeline, and a penetrating fluid outlet channel of the cold side cavity of the flat-plate type membrane assembly for directly cooling the penetrating fluid is connected with the penetrating fluid storage tank through the pipeline.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| TWI815787B (en) * | 2023-05-19 | 2023-09-11 | 上品綜合工業股份有限公司 | Replaceable membrane distillation module and a membrane distillation plate thereof |
| US11969691B1 (en) | 2024-01-10 | 2024-04-30 | King Faisal University | Clean water production with enhanced electricity |
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