WO2020056847A1

WO2020056847A1 - Multi-stage membrane assembly integrated with semiconductor heat pump and use thereof in membrane distillation

Info

Publication number: WO2020056847A1
Application number: PCT/CN2018/112108
Authority: WO
Inventors: 关国强; 姚成龙; 江燕斌
Original assignee: 华南理工大学
Priority date: 2018-09-21
Filing date: 2018-10-26
Publication date: 2020-03-26
Also published as: CN109012200A

Abstract

A multi-stage membrane assembly integrated with a semiconductor heat pump and use thereof in membrane distillation. The multi-stage membrane assembly integrated with the semiconductor heat pump mainly consists of an environment heat absorption unit (11), an environment heat dissipation unit (12) and a multi-stage membrane assembly; an in-situ heat transfer membrane separation unit (14) comprises a hydrophobic microporous membrane (21), a heating-side cavity (25), a cooling-side cavity (29) and a fluid inlet and outlet channel; the heating-side cavity (25) and the cooling-side cavity (29) are provided at two sides of the hydrophobic microporous membrane (21), respectively; a semiconductor heat pump assembly (13) is provided between two adjacent stages of membrane assemblies, a heat absorption surface of the semiconductor heat pump assembly (13) being attached to the cooling-side cavity (29) of the upper stage of membrane assembly, and a heat dissipation surface of the semiconductor heat pump assembly (13) being attached to the heating-side cavity (25) of the lower stage of membrane assembly; and the distance between the heat dissipation surface or the heat absorption surface of the semiconductor heat pump assembly (13) and the hydrophobic microporous membrane (21) is 1-5 mm. The heat required for separation is directly transferred to a region adjacent to the membrane, improving the membrane separation efficiency, reducing the energy consumption and cost of using the membrane distillation method for the evaporation and concentration process such as seawater desalination, sewage treatment and food concentration.

Description

Multi-stage membrane module with integrated semiconductor heat pump and application in membrane distillation

Technical field

The invention relates to a membrane distillation technology, in particular to a multi-stage membrane module integrated with a semiconductor heat pump and its application in membrane distillation. The multi-stage membrane module uses a semiconductor refrigeration sheet as a heat pump and is integrated in each stage of the membrane module. Multi-stage membrane separation unit; belongs to the technical field of energy conservation and environmental protection.

Background technique

Membrane distillation (MD) is an energy-saving membrane separation technology that uses steam pressure difference on both sides of a microporous hydrophobic membrane to drive steam penetration. It is widely used in the fields of seawater desalination, sewage treatment, and food concentration. Different from traditional thermal evaporation and concentration methods (such as multi-effect evaporation, multi-stage flash evaporation, etc.) and other membrane separation technologies (such as reverse osmosis, nanofiltration, electrodialysis, etc.), MD can be used under milder operating conditions (absolute pressure) (At 101 kPa, temperature below 80 ° C) while obtaining pure permeate (pure water) and concentrating the feed liquid to a saturated state, it has shown great potential in the fields of mineral salt recovery, high salinity industrial wastewater treatment, fruit juice and dairy product concentration, etc. Its application prospects have received extensive attention from the industry. At present, there are more than 1,300 public patents related to MD technology.

According to the capture method on the permeate side, MD can be generally divided into direct contact (MDD), air gap (MDG), gas sweeping (MDMD), and vacuum (SGMD) vacuum MD, VMD). Compared with other MD methods, DCMD is the most widely studied MD process because of the simplest process configuration.

A typical DCMD system requires both heating of the feed liquid and cooling of the permeate, so the system requires both a heat source and a cold trap to operate. The heat source required for heating can generally use the waste heat resources in the process industry (such as low-temperature steam, hot water, etc.), and heat the feed liquid through an external heat exchange device and enter the hot side of the membrane module; and after the permeate is cooled by the cold trap, Enter the cold side of the membrane module. Due to the evaporation and heat transfer of the liquid material on the hot side of the membrane module and the heat loss, the temperature of the hot side of the membrane module will decrease along the flow direction of the material liquid, while the temperature of the cold side will increase along the direction of the permeate flow, thereby causing two sides of the membrane surface. The temperature difference distribution is not uniform, and the average temperature difference on the membrane surface (that is, the effective driving force for membrane separation) is smaller than the inlet temperature difference between the cold and hot sides of the membrane module (that is, the driving force provided by the process system). As a result, the separation efficiency of DCMD membrane modules is low; at the same time, polarization exists on both the cold and hot sides of the membrane module (that is, the boundary layer phenomenon), which makes the temperature of the fluid on the hot-side membrane surface lower than the mainstream, and the fluid on the cold-side surface of the membrane The temperature is higher than the mainstream. This unavoidable polarization will further reduce the separation efficiency of DCMD membrane modules. In order to improve the separation efficiency of DCMD, methods such as countercurrent operation, increasing the fluid flow rate on both sides of the membrane module, and enhancing fluid disturbance in the flow channel are currently used to increase the average temperature difference of the membrane surface and alleviate the polarization effect. However, although these methods improve the membrane separation efficiency, they all significantly increase the power consumption of fluid transportation, and it is difficult to significantly improve the overall energy efficiency of the DCMD system. In addition, cold traps commonly used in the process industry are generally implemented through refrigeration cycles, which include processes such as compression, throttling (or expansion), and heat exchange, and the equipment cost is relatively high.

Since the DCMD system requires both a heat source and a cold trap drive, an MD integrated system using a heat pump has appeared in recent years. A heat pump is a device that transfers heat energy from a low-temperature system to a heating object. By simultaneously achieving efficient energy conversion between cooling and heating, the overall energy efficiency of the MD system can be significantly improved.

Chinese invention patent application CN105709601A discloses a two-effect membrane distillation device and method using a heat pump. The two-effect DCMD membrane module is integrated in a traditional heat pump cycle, and the permeate-side refrigeration and the material-liquid-side heating are realized simultaneously using the heat pump principle. Similar membrane distillation methods using heat pumps include: a DCMD system (CN206652392U) that integrates a heat pump cycle and a heat storage process, a DCMD system (CN205461826U) that integrates a single membrane module into a heat pump cycle, a DCMD system that integrates solar heating and heat pump cooling ( CN105749752A) and a method for improving the thermal efficiency of a heat pump membrane distillation system by optimizing a hollow fiber membrane (CN106582292A) and the like. Compared with the traditional heat pump cycle (including compressors, throttles and other equipment), the semiconductor refrigeration chip using thermoelectric refrigeration has the advantages of small size, low cost, and easy realization of system miniaturization. The semiconductor refrigeration chip uses the Peltier effect, and the current is applied to the semiconductor element to move the heat from the low-temperature heat absorption to the high-temperature heat radiation surface. Chinese utility model patent CN203155103U discloses a membrane module for realizing multi-stage AGMD using thermoelectric refrigeration and a method for purifying water using solar energy. Because of the air gap between the permeate side and the cold surface in AGMD, the transmission resistance of permeate steam to the condensing surface is large, so the water production efficiency of AGMD is usually lower than DCMD, SGMD, and VMD [Guan Yang, Yang X, Wang R, et al .Journal of Membrane Distillation, 2014,464: 127-139]; In addition, this method requires 3 chambers (cold, hot working fluid and air gap) for each stage of the membrane unit, in which the cold working fluid contains a large area. Metal cooling fins, which not only makes it difficult to further reduce the size of the membrane module, but also increases the material cost; at the same time, the patented technology requires an additional solar heat collection system to provide the heat required for system operation, which will also increase the method implementation cost.

In short, in order to promote the application of membrane distillation technology in the fields of seawater desalination, sewage treatment and food concentration, it is urgent to solve the following problems: 1) Reduce the system configuration complexity of efficient heat and cold source utilization methods such as heat pump integrated membrane distillation systems And cost; 2) Optimize the design of the membrane module to alleviate the polarization effect and uneven flow field, improve the energy utilization efficiency in the membrane module, and strengthen the heat and mass transfer.

Summary of the Invention

The purpose of the present invention is to provide a multi-stage membrane module of an integrated semiconductor heat pump capable of significantly improving membrane separation efficiency while reducing the cost of adopting the DCMD method and its application in membrane distillation, so as to realize evaporation and concentration processes such as seawater desalination, sewage treatment, and food concentration. Energy consumption and costs are significantly reduced.

The invention uses a semiconductor refrigeration chip to replace the traditional heat pump circulation system, reduces the system configuration complexity and cost of the heat and cold source utilization method, and improves the film through "in-situ heat transfer" and optimized flow channel design for heat transfer near the film surface. The average temperature difference between the two sides and the mitigation of polarization can reduce the cost of the DCMD system and increase the efficiency of separation and heat transfer. The "in-situ heat transfer" of the present invention is to reduce the space-time interval of energy transfer, so that the energy of the input system is more efficiently transferred to the hot side of the membrane surface required for separation, and the heat on the cold side of the membrane surface is absorbed faster. Hot surface removal system.

The semiconductor refrigerating sheet of the present invention utilizes the Peltier effect to transfer heat from the low-temperature heat absorption of the refrigerating sheet to the high-temperature exothermic surface through the action of current. Compared with the existing technical solution that uses semiconductor refrigeration fins to absorb heat from the air gap on the permeate side through the metal partition wall, the present invention adopts a method of directly cooling the permeate and utilizes the characteristic of the liquid thermal conductivity significantly higher than that of the gas, which effectively improves the heat transfer efficiency.

The purpose of the present invention is achieved through the following technical solutions:

A multi-stage membrane module integrated with a semiconductor heat pump is mainly composed of an environmental heat absorption unit, an environmental heat dissipation unit and a multi-stage membrane module. Each stage membrane module includes a semiconductor heat pump module and an in-situ heat transfer membrane separation unit;

The in-situ heat transfer membrane separation unit includes a hydrophobic microporous membrane, a hot-side volume, a cold-side volume, a material liquid inlet channel, a material liquid outlet channel, a permeate liquid inlet channel, and a permeate liquid outlet channel. A hot-side volume and a cold-side volume are provided on both sides; one end of the hot-side volume is provided with a material-liquid inlet channel, and the other end is provided with a volume-liquid outlet channel; There are permeate outlet channels;

There is a semiconductor heat pump module between the adjacent two-stage membrane modules. The heat-absorbing surface of the semiconductor heat pump module is attached to the cold-side volume of the upper-stage membrane module, and the heat-dissipating surface of the semiconductor heat pump module is attached to the hot-side of the next-stage membrane module. On the cavity; the distance from the heat dissipation surface of the semiconductor heat pump component to the hydrophobic microporous membrane is 1 to 5 mm on the hot side cavity; the distance from the heat absorption surface of the semiconductor heat pump component to the hydrophobic microporous membrane is 1 ~ 5mm; the environmental heat absorption unit is close to the heat absorption surface of the semiconductor heat pump module on the hot side cavity of the first-stage membrane module, and the heat dissipation surface of the semiconductor heat pump module is connected to the heat side cavity of the first-stage membrane module; The unit is closely attached to the heat radiation surface of the semiconductor heat pump component on the cold side cavity of the last stage membrane module, and the heat absorption surface of the semiconductor heat pump component is connected to the cold side cavity of the last stage membrane module.

In order to further achieve the objective of the present invention, preferably, a plurality of material liquid inlet channels and material liquid outlet channels are respectively provided at both ends of the hot side cavity, and any material liquid inlet channel does not share an axis with any material liquid outlet channel. line.

Preferably, a plurality of permeate inlet channels and permeate outlet channels are respectively provided at both ends of the cold-side volume, and any of the permeate inlet channels and the axis of any of the permeate outlet channels are not aligned.

Preferably, the environmental heat absorption unit adopts a natural convection air heat exchanger, and the environmental heat dissipation unit adopts a forced convection air radiator.

Preferably, the natural convection air heat exchanger uses a natural flow fin-type refrigeration heat exchanger; and the forced convection air radiator uses an aluminum fin fan cooler.

Preferably, the semiconductor heat pump assembly includes a mounting frame and a semiconductor cooling sheet, wherein the semiconductor cooling sheet is selected as TEC1-19006 with a size of 40x40x4mm, and is embedded in a heat-resistant epoxy resin mounting frame.

Preferably, the hydrophobic microporous membrane is a surface-modified super-hydrophobic polyvinylidene fluoride planar membrane, and the average membrane thickness is 0.018 mm.

The application of the multi-stage membrane module with integrated semiconductor heat pump in a direct contact membrane distillation system. The multi-stage membrane module with integrated semiconductor heat pump and accessories form a direct contact membrane distillation system. The direct contact membrane distillation system is mainly composed of Material liquid storage tank, hot-side circulation pump, multi-stage membrane module with integrated semiconductor heat pump, permeate storage tank, and permeate circulation; material liquid storage tank is connected to the hot-side circulation pump through a pipeline, and the hot-side circulation pump is connected to The material-liquid inlet channels of the multiple hot-side cavities of the integrated multistage membrane module of the semiconductor heat pump are connected, and the material-liquid outlet channels of the multiple hot-side cavities of the integrated multistage membrane module of the semiconductor heat pump are connected to the material-liquid storage tank through pipes. ; The permeate storage tank is connected to the permeate circulation pump through a pipeline, and the permeate circulation pump is connected to the permeate inlet channels of multiple cold-side cavities of a multi-stage membrane module integrated with a semiconductor heat pump through a pipeline; The permeate outlet channels of the multiple cold-side receptacles of the multi-stage membrane module are connected to the permeate storage tank through pipes, respectively.

Preferably, seawater, sewage or liquid food to be concentrated is added to the feed liquid storage tank; ultrapure water is added to the feed liquid storage tank to realize seawater desalination, sewage treatment or food concentration.

Preferably, the liquid food to be concentrated is milk.

In the direct contact membrane distillation system of the present invention, the material liquid to be concentrated in the material liquid storage tank is sent to the hot-side volume chambers of the multistage membrane module integrated with the semiconductor heat pump through the material liquid circulation pump for heating; The permeate is sent to the cold side cavity in the multi-stage membrane module of the integrated semiconductor heat pump through the permeate circulation pump. In the multi-stage membrane module of the integrated semiconductor heat pump, the permeate vapor is driven by the temperature difference between the two sides of the membrane. Driven by the vapor pressure difference between the two sides of the membrane, the membrane migrates from the hot side to the cold side through the membrane, thereby achieving the evaporation and concentration of the feed liquid and the condensation and enrichment of the permeate.

The heating and cooling processes of the feed liquid and permeate in the multi-stage membrane module of the present invention are described in detail as follows: the heat is absorbed by the first-stage semiconductor heat pump module from the ambient heat absorption unit and transferred to the first-stage in-situ heat transfer membrane separation unit; The side volume cavity transfers heat to heat the material liquid in the hot side volume cavity; the permeate in the cold side volume cavity is cooled by the next-stage semiconductor heat pump assembly, and the heat absorbed by it is transferred to the next-stage in-situ heat transfer membrane separation unit Heat-side cavity transfer; by analogy, the semiconductor heat pump components of each level absorb heat from the cold-side volume of the in-situ heat transfer membrane separation unit at the previous level and release heat to the heat-side volume of the in-situ heat transfer membrane separation unit at that level ; The heat of the cold side cavity of the last-stage in-situ heat transfer membrane separation unit transfers heat to the environmental heat-dissipating unit through the last-stage semiconductor heat pump assembly, thereby realizing heating and infiltration on the material and liquid side of the in-situ heat transfer membrane separation unit at all levels Side cooling.

Compared with the prior art, the present invention has the following advantages and effects:

1) The energy transfer required for the membrane separation of the conventional DCMD system is completed by a heater and a cooler outside the membrane module, and there is a large space-time interval between the supply and use of energy. The present invention finds that in the hot-side cavity, the distance from the heat-radiating surface of the semiconductor heat pump component to the hydrophobic microporous membrane is 1 to 5 mm; in the cold-side cavity, the heat-absorbing surface of the semiconductor heat pump component is controlled to the hydrophobic microporous membrane. The distance is 1 to 5 mm; the two adjacent membrane modules are spaced apart; the heat absorption surface of the upper membrane module and the heat radiation surface of the lower membrane module are spaced 1 to 5 mm; the distance between the heat transfer surface and the membrane surface should be less than The width of the temperature boundary layer can achieve "in-situ heat transfer" and effectively improve the thermal efficiency of the DCMD process.

2) In the present invention, since the energy supply position (that is, the heat transfer surface) and the energy use position (that is, the film surface) are sufficiently close to each other, the heat transfer distance is very small, and there is no need to provide enhanced heat transfer measures such as fins between the heat transfer surface and the film surface. This significantly reduces the structural complexity and cost of the membrane module.

3) The heat absorption surface of the semiconductor heat pump assembly of the present invention is in direct contact with the permeate, which avoids high heat transfer resistance caused by air gap heat transfer, and improves the effective temperature difference between the hot and cold sides of the film surface fluid.

4) The heat absorbing surface and the heat radiating surface of the semiconductor heat pump module of the present invention perform heat exchange through the heat radiating surface and the heat absorbing surface of the adjacent semiconductor heat pump module, respectively, which shortens the space distance for energy supply and use, and avoids the need for external installation. The energy loss caused by the two fluid transport links from the heat exchange equipment to the membrane module and from the membrane module inlet to the membrane surface also slows down the effect of polarization.

5) The present invention uses economical semiconductor refrigeration chips to replace the traditional heat pump cycle, which can conveniently develop a multi-stage DCMD system at a lower cost. Compared with existing methods (such as the patent CN203155103), membrane separation units at all levels have only two cold and hot sides with a thickness not exceeding 5mm, and there are no internal components such as metal fins in the cavity. Effectively reduce the size of the membrane module, and can completely use lightweight materials such as plastic to manufacture membrane units at all levels, achieving compactness and lightness of the DCMD system, and significantly reducing the configuration cost of the MD system.

6) By optimizing the flow channels on both sides of the membrane, the present invention effectively avoids the "dead zone" and "short circuit" phenomena without significantly increasing the flow energy consumption, and further improves the separation efficiency of the membrane module.

BRIEF DESCRIPTION OF THE DRAWINGS

1 is a schematic structural diagram of a multi-stage membrane module with an integrated semiconductor heat pump according to the present invention;

2 is a schematic structural diagram of a combination of an in-situ heat transfer membrane separation unit and a semiconductor heat pump assembly;

3 is a schematic structural diagram of a membrane distillation system established by applying a multi-stage membrane module of an integrated semiconductor heat pump of the present invention;

4 is a schematic structural diagram of a conventional two-stage parallel DCMD system and membrane separation units at each stage in Comparative Examples 1, 2 and 3;

5 is a schematic structural diagram of a two-stage membrane module of an integrated semiconductor heat pump described in Examples 1, 2 and 3;

FIG. 6 is a schematic structural diagram of a membrane distillation system established by using an integrated semiconductor heat pump secondary membrane module in Examples 1, 2 and 3;

FIG. 7 is a curve of the concentration rate with time of Comparative Example 1 and Example 1; FIG.

8 is a change curve of the sewage treatment amount with time in Comparative Example 2 and Example 2;

FIG. 9 is a curve of the concentration rate with time of Comparative Example 3 and Example 3. FIG.

detailed description

To better understand the present invention, the following further describes the present invention with reference to the accompanying drawings and embodiments, but the embodiments of the present invention are not limited thereto.

As shown in FIG. 1, a multi-stage membrane module integrated with a semiconductor heat pump is composed of an environmental heat absorption unit 11, an environmental heat dissipation unit 12, and a multi-stage membrane module.

The multi-stage membrane module includes a plurality of in-situ heat transfer membrane separation units 14 separated by a semiconductor heat pump module 13. The structure of each in-situ heat transfer membrane separation unit 14 is shown in FIG. 2. The in situ heat transfer membrane separation unit 14 includes a hydrophobic microporous membrane 21, a hot-side volume 25, a cold-side volume 29, a material liquid inlet channel 22, a material liquid outlet channel 26, a permeate liquid inlet channel 23, and a permeate liquid outlet channel 27. .

On both sides of the hydrophobic microporous membrane 21, a hot-side volume 25 and a cold-side volume 29 are respectively provided; the hot-side volume 25 is provided with a material liquid inlet channel 22 at one end and a material-liquid outlet channel 26 at the other end; the cold-side volume 29 One end is provided with a permeate inlet channel 23 and the other end is provided with a permeate outlet channel 27. A semiconductor heat pump module 13 is arranged between two adjacent membrane modules, and the heat absorption surface of the semiconductor heat pump module 13 is closely attached to the first stage membrane module. On the cold side cavity 29, the heat dissipation surface of the semiconductor heat pump module 13 is closely adjacent to the heat side cavity 25 of the next-stage membrane module. In the hot side volume 25, the distance from the heat dissipation surface 24 of the semiconductor heat pump module to the hydrophobic microporous membrane 21 is 1 to 5 mm; the distance from the heat-absorbing surface 28 of the semiconductor heat pump module to the hydrophobic microporous membrane 21 is 1 to 5 mm in the cold-side chamber 29; the environmental heat absorption unit 11 is close to the hot-side chamber of the first-stage membrane module The heat absorption surface of the semiconductor heat pump module 13 and the heat radiation surface of the semiconductor heat pump module 13 are connected to the first-stage membrane module hot-side volume 25; the ambient heat-dissipating unit 12 is close to the semiconductor heat pump of the last-stage membrane module cold-side volume. The heat radiation surface of the module 13 and the heat absorption surface of the semiconductor heat pump module 13 The cold-side volume 19 of the latter-stage membrane module is connected.

In order to improve the heat transfer of material liquid heating and permeate cooling, the present invention uses "in-situ heat transfer" to directly transfer heat near the membrane, that is, the heat dissipation surface 24 and heat absorption surface 28 of the semiconductor heat pump module 13 to the hydrophobic microporous membrane The distances of 21 are 1 to 5 mm, respectively, so that the heated and cooled fluid directly contacts the heat dissipation surface and the heat absorption surface, and by reducing the space-time distance of energy transmission and conversion, the average temperature difference between the two sides of the hydrophobic microporous membrane 21 is increased. It also relieves the polarization effect, thereby improving heat transfer and separation efficiency.

The environmental heat absorption unit of the present invention may use a natural convection air heat exchanger, and the environmental heat dissipation unit may use a forced convection air radiator. The natural convection air heat exchanger preferably adopts a natural flow fin-type refrigeration heat exchanger, and the fin size is 60x10x1.5mm. The forced convection air radiator adopts aluminum fin fan cooler. The cooling fan comes with a standard 5V power management function, and the maximum cooling power is 360W.

Each of the semiconductor heat pump components 13 includes a mounting frame and a semiconductor refrigerating sheet. The semiconductor refrigerating sheet uses a model number of TEC1-19006 with a size of 40x40x4mm and is embedded in a heat-resistant epoxy resin mounting frame. The semiconductor heat pump module 13 uses a thermoelectric effect (Peltier effect) to transfer heat from a low-temperature heat absorption surface 28 to a high-temperature heat radiation surface 24.

In order to mitigate the effects of "dead zone" and "short circuit" caused by the flow of material into and out of the cavity, and to optimize the flow path, as shown in FIG. 2, preferably, multiple material liquid inlets are provided at both ends of the hot side cavity 25, respectively. Channel 22 and material liquid outlet channel 26, the axis of any material liquid inlet channel 22 and any material liquid outlet channel 26 are not collinear; a plurality of permeate liquid inlet channels 23 are respectively provided at both ends of the cold-side volume cavity 29 And the permeate outlet channel 27, the axis of any of the permeate inlet channel 23 and the axis of any of the permeate outlet channel 27 are not collinear.

When the multi-stage membrane module integrated with a semiconductor heat pump of the present invention runs, the material liquid enters the hot-side volume cavity 25 through the material-liquid inlet channel 22, and is heated and heated by the semiconductor heat pump component 13; the permeate enters the cold-side volume through the permeate inlet channel 23. The cavity 29 is cooled by the heat absorption of the semiconductor heat pump module 13. A temperature difference is formed on both sides of the hydrophobic microporous membrane 21, that is, the water vapor pressure on the material liquid side is higher than that on the permeate side, and the water vapor in the membrane pores is moved from the material liquid side to the permeation side by the vapor pressure difference, thereby realizing the material The liquid-side evaporation is concentrated and water is enriched on the permeate side.

As shown in Figure 3, a multi-stage membrane module integrated with a semiconductor heat pump is used to make the hot side chambers of the in-situ heat transfer membrane separation units of the multi-stage membrane module integrated with the semiconductor heat pump in parallel, and the parallel ends are respectively connected to the material and liquid storage. The tank is connected to the hot-side circulation pump, and the material-liquid storage tank and the hot-side circulation pump are connected through pipelines; at the same time, the cold-side storage chambers of the in-situ heat transfer membrane separation units of the multi-stage membrane module integrated with the semiconductor heat pump are connected in parallel and in parallel. The ends are respectively connected to the permeate storage tank and the permeate circulation pump, and the permeate storage tank and the permeate circulation pump are connected through pipelines; an economical, efficient and new DCMD system is formed. The new DCMD system is mainly composed of a feed liquid storage tank 31, a hot-side circulation pump 32, a multi-stage membrane module 33 integrated with a semiconductor heat pump, a permeate storage tank 34, and a permeate circulation pump 35. The side circulation pump 32 is connected, and the hot side circulation pump 32 is connected to the material and liquid inlet channels of the multiple heat side cavities of the multi-stage membrane module 33 integrated with the semiconductor heat pump through pipes. The material-liquid outlet channel of the hot-side volume is connected to the material-liquid storage tank 31 through pipes; the permeate liquid storage tank 34 is connected to the permeate liquid circulation pump 35 through the pipes, and the permeate liquid circulation pump 35 is connected to the multi-stage membrane of the integrated semiconductor heat pump through the pipes. The permeate inlet channels of multiple cold-side containers of module 33 are connected; the permeate outlet channels of multiple cold-side containers of multiple multi-stage membrane modules 33 with integrated semiconductor heat pumps are connected to the permeate storage tank 34 through pipes, respectively.

When in use, feed the pre-prepared feed liquid to the feed liquid storage tank 31, and feed the feed liquid through the feed liquid circulation pump 32 to the hot-side volume of each stage membrane separation unit in the multi-stage membrane module 33 integrated with the semiconductor heat pump. The liquid is heated and warmed by the semiconductor heat pump assembly of this stage; the permeate in the permeate storage tank 34 is input to the cold side cavity of the membrane separation unit in the multi-stage membrane module 33 of the integrated semiconductor heat pump through the permeate circulation pump 35, The permeate in the heat transfer membrane separation unit is cooled by the semiconductor heat pump module connected to the cold-side volume; driven by the temperature difference between the two sides of the hydrophobic microporous membrane, the volatile components in the material liquid evaporate and penetrate through the hydrophobic microporous membrane. And it is condensed on the permeate side to realize the concentration of the material liquid and the output of the permeate.

Comparative Example 1

In the conventional DCMD system, the feed liquid is heated by an external heater, and the permeate is cooled by an external cooler and flows into the membrane module. In the membrane module, with the heat and mass transfer from the hot side to the cold side, the temperature of the material liquid in the hot side cavity decreases, while the temperature of the permeate in the cold side cavity increases, which reduces both sides of the DCMD membrane. Temperature difference. In addition, the polarization effect near the membrane surface further reduces the effective temperature difference between the two sides of the DCMD membrane, so the separation efficiency of traditional DCMD is lower. In order to better explain the difference between the present invention and the traditional DCMD, a traditional two-stage parallel DCMD system as shown in Fig. 4 is established.

As shown in Figure 4, the traditional DCMD system specifically includes a material-liquid storage tank 41 with a volume of 500 mL and a polypropylene material, a Cole-Parmer company's Masterflex L / S type material-liquid circulation pump 42, a 2kW electric heating system 43, and a DCMD Two-stage parallel membrane module 44, 500mL volume, permeate tank 45 made of polypropylene with overflow outlet, Masterflex L / S type permeate circulation pump 46 from Cole-Parmer Company, Polystat 12122 from Cole-Parmer Company, USA Type 58 low temperature circulating water bath 47, computer 48 for data acquisition and monitoring, and analytical balance 49 for permeate overflow measurement. The conventional DCMD two-stage parallel membrane module 44 includes a first-stage traditional DCMD membrane separation unit 441 and a second-stage traditional DCMD membrane separation unit 442 arranged in parallel. The two-stage traditional DCMD membrane separation unit has the same structure and is made of colorless and transparent plexiglass, which includes a hot-side volume 4411 and a cold-side volume 4412 each having a size of 40x40x5mm (this structure is mainly for the convenience of the present invention. It is more convenient. The width of the hot side cavity 4411 and cold side cavity 4412 is not required by the traditional DCMD system. Generally, it is much larger than this width. The following comparative examples 2 and 3 are also considered.) Porous membrane 4413 is a surface modified super-hydrophobic polyvinylidene fluoride planar membrane provided by Singapore Membrane Technology Center. Its effective size is 40x40mm and the average membrane thickness is 0.018mm. Both the cold and hot sides of the cavity are provided with fluid outlet channels 4414 and fluid. Entrance channel 4415.

The traditional two-stage DCMD system shown in Figure 4 was used to desalinate and desalinate the sodium chloride aqueous solution. The sodium chloride aqueous solution was concentrated to saturation and purified water was obtained. The specific operating methods and process parameters are as follows:

The 3% sodium chloride aqueous solution prepared in advance is placed in the material liquid storage tank 41, the material liquid is sent to the electric heating system 43 through the material liquid circulation pump 42, and then input into the hot-side accommodating chambers 4411 of the two-stage parallel membrane module 44; The ultrapure water placed in the permeate storage tank 45 is sent to the low-temperature circulating water bath 47 through the permeate circulation pump 46, and is input to the cold-side accommodating chambers 4412 of the two-stage parallel membrane module 44 after being cooled by coil heat exchange. Set the flow rate of the liquid and permeate circulation pumps to 120 mL / min, adjust the electric heater 43 and the low-temperature circulating water bath 47 so that the two-stage parallel DCMD membrane module 44 has a hot-side chamber temperature of 57-59 ° C. And the permeate inlet temperature of the cold-side volume is 20 to 21 ° C. The inlet and outlet temperatures of the membrane module are collected and recorded by a computer 48. In the in-situ heat transfer membrane separation units at all levels, the temperature difference between the inlets of the hot-side and cold-side chambers is about 38 ° C. Driven by the difference in steam pressure between the hot-side and cold-side chambers, the film of the feed liquid in the hot-side chambers The surface evaporates and transfers heat and mass to the cold side, thereby increasing the permeate, and the produced permeate flows out through the overflow pipe of the permeate storage tank 45, and the amount of permeate produced per unit time is measured by the balance 49.

Under the above operating conditions, the saltwater concentration rate of the DCMD system is the amount of permeate produced per unit time, and its variation curve with time is shown in FIG. 7. The results show that the membrane distillation system can concentrate the sodium chloride aqueous solution to achieve desalination and desalination of the brine. The traditional DCMD system initially concentrated the brine at a rate of about 18 grams per hour. With the concentration of the salt solution continuously increasing, the continuous operation After 20 hours, the sodium chloride aqueous solution was nearly saturated, and the concentration ability was reduced to 13 grams per hour due to the increase in the concentration of the feed solution.

Comparative Example 2

The same traditional DCMD system as shown in Comparative Example 1 (as shown in Figure 4) was used to treat the salty wastewater of a steel plant.

The total soluble salt TDS content of wastewater is about 100g / L, mainly Mg ²⁺ , Fe ³⁺ and SO ₄ ^2- plasma.

The sample wastewater is placed in the feed liquid storage tank 41, and the feed liquid is sent to the electric heating system 43 through the feed liquid circulation pump 42 and then input into the hot-side accommodating chambers of the conventional two-stage parallel membrane module 44; The ultrapure water is sent to the low-temperature circulating water bath 47 through the permeate circulation pump 46, and is input to the cold-side accommodating chambers of the two-stage parallel membrane module 44 after being cooled by coil heat exchange. Set the flow rates of the material liquid and permeate circulation pumps to 100 mL / min, adjust the electric heater 43 and the low-temperature circulating water bath 47 so that the two-stage parallel traditional DCMD membrane module 44 has a hot-side chamber temperature of 54 ~ 55 ℃, and the permeate inlet temperature of the cold-side volume is 20 ～ 21 ℃. The inlet and outlet temperatures of the membrane module are collected and recorded by a computer 48. In a conventional DCMD membrane separation unit, the temperature difference between the inlets of the hot-side and cold-side chambers is about 34 ° C. Driven by the difference in steam pressure between the hot-side and cold-side chambers, the feed liquid evaporates on the membrane surface of the hot-side chamber and moves towards the membrane surface. The cold-side heat and mass transfer increases the permeate, and the produced permeate flows out through the overflow pipe of the permeate storage tank 45, and the amount of permeate produced per unit time is measured by the balance 49.

Under the above operating conditions, the wastewater treatment volume of the DCMD system is the permeate generation amount per unit time, and its variation curve with time is shown in FIG. 8. For the system described in Comparative Example 2, a conventional DCMD system with a membrane area of 32 cm ^{2 was} used for 2 hours of continuous operation, and the wastewater treatment capacity was about 14 to 15 grams per hour.

Comparative Example 3

Using the same conventional DCMD system as in Comparative Example 1 (shown in Figure 4), the milk was concentrated to increase the protein content of the milk from 5% to 10%.

The sample milk is placed in the feed liquid storage tank 41, and the feed liquid is sent to the electric heating system 43 through the feed liquid circulation pump 42 and then input into the hot-side accommodating chambers of the conventional two-stage parallel membrane module 44; The ultrapure water is sent to the low-temperature circulating water bath 47 through the permeate circulation pump 46, and is input to the cold-side accommodating chambers of the two-stage parallel membrane module 44 after being cooled by coil heat exchange. Set the flow rate of the material liquid and permeate circulation pumps to 100 mL / min, adjust the electric heater 43 and the low temperature circulating water bath 47 to make the two-stage parallel DCMD membrane module 44 feed temperature of the hot-side volume of each stage is 55-56. ℃, and the permeate inlet temperature of the cold-side volume is 20 ～ 21 ℃. The inlet and outlet temperatures of the membrane module are collected and recorded by a computer 48. In a conventional DCMD membrane separation unit, the temperature difference between the inlets of the hot-side and cold-side chambers is about 35 ° C. Driven by the difference in steam pressure between the hot-side and cold-side chambers, the feed liquid evaporates on the membrane surface of the hot-side chamber and moves towards the membrane surface. The cold-side heat and mass transfer increases the permeate, and the produced permeate flows out through the overflow pipe of the permeate storage tank 45, and the amount of permeate produced per unit time is measured by the balance 49.

Under the above operating conditions, the milk concentration rate of the DCMD system is the amount of permeate produced per unit time, and its change curve with time is shown in FIG. 9. For the conventional DCMD system with a membrane area of 32 cm ² described in Comparative Example 3, the milk concentration rate was about 13 to 14 grams per hour through continuous operation for 6 hours.

Example 1

The two-stage membrane module with integrated semiconductor heat pump shown in FIG. 5 is established according to the structure of FIGS. 1-3. The two-stage membrane module 50 with integrated semiconductor heat pump includes: an environmental heat absorption unit 51, a first-stage semiconductor heat pump module 52, and a first The first-stage in-situ heat transfer membrane separation unit 53, the second-stage semiconductor heat pump assembly 54, the second-stage in-situ heat transfer film separation unit 55, the third-stage semiconductor heat-pump assembly 56, and the ambient heat dissipation unit 57. Among them, the environmental heat absorbing unit 51 uses an aluminum natural flow fin refrigeration heat exchanger, and the fin size is 60x10x1.5mm.

The first-stage semiconductor heat pump assembly 52, the second-stage semiconductor heat pump assembly 54 and the third-stage semiconductor heat pump assembly 56 have the same structure, and all include a mounting frame and a semiconductor refrigeration sheet. The semiconductor refrigeration sheet is selected as TEC1-19006 and has a size of TEC1-19006. 40x40x4mm, mounted on heat-resistant epoxy mounting frame.

The first-stage in-situ heat-transfer membrane separation unit 53 and the second-stage in-situ heat-transfer membrane separation unit 54 have the same structure and are made of plexiglass. The dimensions of the hot-side and cold-side chambers are both 40x40x5mm. The effective volume is 8 mL (for ease of comparison, the dimensions of the membrane modules of each stage in Example 1 are the same as those described in Comparative Example 1).

In order to improve the flow of "dead zone" and "short circuit" when the fluid enters and exits the cavity, the diameter of the hot side cavity is uniformly distributed on the side of the feed. 10 diameter environmental cooling units 57 adopts aluminum fin fan cooler, and the cooling fan comes with a standard 5V power management function, the maximum cooling power is 360W. It is a 1.8mm feed channel. Nine discharge channels with a diameter of 1.8mm are evenly distributed on the discharge side, and none of the inlet channels coincide with the axis of the outlet channel. The feed side of the cold-side cavity is evenly distributed. 1.8mm diameter feeding channels, 10 discharge channels with a diameter of 1.8mm are evenly distributed on the discharge side, and none of the inlet channels coincide with the axis of the outlet channel; for better monitoring of the membrane separation status, There are PT100 thermal resistance temperature sensors connected to the computer acquisition system in the hot-side and cold-side chambers of the in-situ heat transfer membrane separation units at all levels; the hydrophobic microporous membrane uses surface-modified super-hydrophobic polyisotropic provided by Thermo Fluoroethylene flat film (product number 88518), effective size after cutting is 40x40mm, average film thickness is 0.018mm.

Applying the present invention, the DCMD system shown in FIG. 6 was developed for desalination of sodium chloride brine according to the process shown in FIG. 3, and the purpose of the process was the same as that of Comparative Example 1, that is, the concentrated salt solution was saturated to obtain purified water.

As shown in FIG. 6, the DCMD system specifically includes a material-liquid storage tank 61 with a volume of 500 mL and a material of polypropylene, a set of Masterflex L / S type material-liquid circulation pumps 62 from the Cole-Parmer Company in the United States, and a set of FIG. 4 A two-stage membrane module 63 with integrated semiconductor heat pump shown (the specific structure is shown in Figure 5), a permeate storage tank 64 with a volume of 500 mL, made of polypropylene with an overflow outlet, and a set of Masterflex from Cole-Parmer L / S type permeate circulation pump 65; In addition, it also includes three DC adjustable power supplies 66 with a rated power of 300W, a computer 67 for data acquisition and monitoring, and an analytical balance for permeate overflow measurement. 68. An analytical balance 68 for permeate overflow measurement is connected to the permeate storage tank 64. For the connection mode of the DCMD system in this embodiment, refer to the description of FIG. 3, but the numbers of the components are modified according to the specific embodiment.

The specific operation method and process parameters of the DCMD system are as follows:

Pre-prepared 3% sodium chloride aqueous solution and ultrapure water are placed in the material liquid storage tank 61 and the permeate liquid storage tank 64, respectively. The material liquid and ultrapure water are passed through the hot-side circulation pump 62 and the cold-side circulation pump 65, respectively. The hot- and cold-side receptacles in the two-stage membrane module 63 are input. Set the output voltage of the DC power supply driven by the semiconductor heat pump components at all levels to be constant 24V, adjust the flow of the hot-side circulation pump 62 and the cold-side circulation pump 65, so that the temperature of the material liquid in the hot-side volume is stabilized at 57 ° C, and the cold-side volume The temperature of the ultrapure water in the cavity was about 20 ° C. The temperature of the cold and hot-side containers of the in-situ heat transfer membrane separation units at each level is collected and recorded by the computer 67 (the computer temperature acquisition module is connected to the thermal resistance of the two-stage membrane module at each level), and the average temperature of the hot-side storage cavity is maintained to be lower than that of the cold-side. The cavity is 37 ° C high. Driven by the vapor pressure difference between the hot side and the cold side, the feed liquid evaporates on the membrane surface of the hot side cavity and transfers heat and mass to the cold side, thereby increasing the permeate, and the produced permeate passes through the permeate storage The overflow pipe of the tank 64 flows out, and the amount of permeate generation per unit time is measured by the balance 68.

Under the above operating conditions, the saltwater concentration rate of the DCMD system is the amount of permeate produced per unit time, and its variation curve with time is shown in FIG. 7. The results show that the two-stage membrane distillation system with integrated semiconductor heat pump can concentrate the sodium chloride aqueous solution to achieve desalination of brine. For the system described in Example 1, a membrane system with a membrane area of 32 cm ² was used to initially concentrate the brine at a rate of approximately At 25 grams per hour, the salt concentration of the feed liquid is continuously increasing with concentration. After 20 hours of continuous operation, the sodium chloride aqueous solution is nearly saturated, and the concentration ability is reduced to 18 grams of water per hour due to the increase in the concentration of the feed liquid. Example 1 demonstrates that the multi-stage membrane distillation system with integrated semiconductor heat pump can run stably for a long time, and at the same time realize the concentration of sodium chloride aqueous solution and the production of pure water, thereby indicating that the method of the present invention can be expected to be applied to mineral salt recovery and seawater Desalination and other fields.

Compared with the conventional membrane distillation system described in Comparative Example 1, the present invention has higher membrane separation efficiency. For the same membrane material and membrane area, under the same operating conditions as shown in FIG. 7, the concentration capacity of the sodium chloride solution of Example 1 is increased by more than 1/3 than that of Comparative Example 1. This is because the two-stage membrane module with integrated semiconductor heat pump described in Example 1 (as shown in FIG. 5) applied the "in-situ heat transfer" method and optimized the flow channel design scheme, thereby effectively improving the heat and mass transfer efficiency. .

Comparing the two systems of Fig. 6 and Fig. 4, since the present invention (as shown in Fig. 6) integrates the feed liquid heating system and the permeate liquid cooling system into an integrated multi-stage membrane module, the system configuration requires only two storage tanks and Two circulation pumps greatly reduce the space requirements for system implementation; more importantly, the present invention uses an economical and compact semiconductor heat pump assembly instead of the two systems of heater and cooler, and uses the heat pump process to achieve cold and heat The integration of energy has effectively improved the comprehensive energy utilization rate of the system. Compared to existing membrane distillation systems with integrated semiconductor heat pumps, such as Chinese invention patent applications CN105709601A, CN206652392U, CN205461826U, CN105749752A, CN106582292A, and CN203155103U, etc., the multi-stage membrane module of the present invention (as shown in Figure 1, Figure 2 and Figure 5) (Shown in Figure 3) and the membrane distillation system (shown in Figures 3 and 6) built thereby not only avoids the use of compressors, cold and heat exchangers and other components necessary in traditional heat pump methods, but also avoids the use of complex membrane groups The components effectively reduce the module size, thereby significantly reducing the complexity and cost of the system configuration, which is convenient for the system to be enlarged and applied to the actual industrial field.

Example 2

The same DCMD system as in Example 1 was used to treat the same salt-containing wastewater from a steel plant as described in Comparative Example 2.

Using a similar operation method as in Example 1, the salt-containing wastewater and the ultrapure water were respectively placed in the material liquid storage tank 61 and the permeate liquid storage tank 64, and the material liquid (salt-containing wastewater) and the ultrapure water were passed through the hot-side circulation pump, respectively. 62 and the cold-side circulation pump 65 are input to the hot-side and cold-side accommodating chambers in the two-stage membrane module 63, respectively. Set the output voltage of the DC power supply driven by the semiconductor heat pump components at all levels to be constant 24V, adjust the flow of the hot-side circulation pump 62 and the cold-side circulation pump 65 so that the temperature of the hot and cold-side chambers and the temperature of the cold-side chamber entering the membrane module are as described in Comparative Example 2. The temperature of the feed liquid and the permeate is the same, that is, the temperature of the hot side cavity is 54 to 55 ° C, and the temperature of the cold side cavity is 20 to 21 ° C. The temperature of the cold and hot-side containers of the in-situ heat transfer membrane separation units at each level is collected and recorded by the computer 67 (the computer temperature acquisition module is connected to the thermal resistance of the two-stage membrane module at each stage), and the average temperature of the hot-side volume is maintained to be lower than that of the cold-side The cavity is 34 ° C high. Driven by the vapor pressure difference between the hot side and the cold side, the feed liquid evaporates on the membrane surface of the hot side cavity and transfers heat and mass to the cold side, thereby increasing the permeate, and the produced permeate passes through the permeate storage The overflow pipe of the tank 64 flows out, and the amount of permeate generation per unit time is measured by the balance 68.

Under the above operating conditions, the wastewater treatment volume of the DCMD system is the permeate generation amount per unit time, and its variation curve with time is shown in FIG. 8. The results show that the two-stage membrane distillation system with integrated heat pump can stably process salt-containing wastewater. For the system described in Example 2, a membrane system with a membrane area of 32 cm ² was continuously operated for 2 hours and the wastewater treatment capacity was stabilized at 19-20 grams. This indicates that the method of the present invention can be expected to be applied to the fields of saline wastewater treatment and the like.

Compared with the conventional membrane distillation system described in Comparative Example 2, the present invention has higher membrane separation efficiency. As shown in FIG. 8, the membrane module described in Example 2 and Comparative Example 2 have the same membrane area, and the processing capacity of the salt-containing wastewater has increased by more than 40% under the same feed temperature. This is due to Example 1 The two-stage membrane module of the integrated heat pump (as shown in FIG. 5) applies the “in-situ heat transfer” method and optimizes the flow channel design scheme, thereby effectively improving the heat and mass transfer efficiency of the process.

The method of the invention has the advantages of economy and easy configuration, and it is expected to be applied to practical industrial fields through multi-stage amplification.

Example 3

The milk described in Comparative Example 3 was concentrated using the same DCMD system as in Example 1.

Using a similar operation method as in Example 1, the milk sample and ultrapure water were placed in the feed liquid storage tank 61 and the permeate liquid storage tank 64, respectively. The feed liquid (milk) and ultrapure water were passed through the hot-side circulation pump 62 and cold respectively. The side circulation pump 65 is input into a hot-side and a cold-side volume in the two-stage membrane module 63, respectively. Set the output voltage of the DC power supply driven by the semiconductor heat pump components at all levels to be constant 24V, adjust the flow of the hot-side circulation pump 62 and the cold-side circulation pump 65, so that the temperature of the hot and cold side chambers and the hot and cold sides described in Comparative Example 3 The inlet temperature of the cavity is the same, that is, the temperature on the hot side is 55 to 56 ° C, and the temperature on the cold side is 20 to 21 ° C. The temperature of the cold and hot-side containers of the in-situ heat transfer membrane separation units at each level is collected and recorded by a computer 67 (the computer temperature acquisition module is connected to the thermal resistance of the two-stage membrane module at each level), and the average temperature of the hot-side cavity is maintained to be lower than that of the cold-side The cavity is 35 ° C high. Driven by the vapor pressure difference between the hot side and the cold side, the feed liquid evaporates on the membrane surface of the hot side cavity and transfers heat and mass to the cold side, thereby increasing the permeate, and the produced permeate passes through the permeate storage The overflow pipe of the tank 64 flows out, and the amount of permeate generation per unit time is measured by the balance 68.

Under the above operating conditions, the milk concentration of the DCMD system is the amount of permeate produced per unit time, and its change curve with time is shown in FIG. 9. The results show that the two-stage membrane distillation system with integrated heat pump can stably concentrate milk. For the system described in Example 3, a membrane system with a membrane area of 32 cm ² was continuously operated for 7 hours and the milk concentration was stabilized at 20 to 22 g / hour. This shows that the method of the present invention is expected to be applied to the field of food concentration such as milk juice.

Compared with the conventional membrane distillation system described in Comparative Example 3, the present invention has higher membrane separation efficiency. As shown in FIG. 9, the membrane modules described in Example 3 and Comparative Example 3 have the same membrane area, and the processing capacity of milk increases by nearly 50% under the same feed temperature condition. This is due to the integration described in Example 1. The two-stage membrane module of the heat pump (as shown in Figure 5) applied the "in-situ heat transfer" method and optimized the flow channel design scheme, thereby effectively improving the heat and mass transfer efficiency of the process.

The invention also has the advantages of economy and easy configuration, and is expected to be applied to the actual industrial production field through multi-stage amplification.

Those skilled in the art should understand that the present invention is not limited by the embodiments. Any modification, equivalent replacement and improvement made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

A multi-stage membrane module integrated with a semiconductor heat pump is characterized in that it is mainly composed of an environmental heat absorption unit, an environmental heat dissipation unit and a multi-stage membrane module, and each stage membrane module includes a semiconductor heat pump module and an in-situ heat transfer membrane separation unit;

The in-situ heat transfer membrane separation unit includes a hydrophobic microporous membrane, a hot-side volume, a cold-side volume, a material liquid inlet channel, a material liquid outlet channel, a permeate liquid inlet channel, and a permeate liquid outlet channel. A hot-side volume and a cold-side volume are provided on both sides; one end of the hot-side volume is provided with a material-liquid inlet channel and the other end is provided with a volume-liquid outlet channel; one end of the cold-side volume is provided with a permeate inlet channel and the other There are permeate outlet channels;

There is a semiconductor heat pump module between the adjacent two-stage membrane modules. The heat-absorbing surface of the semiconductor heat pump module is attached to the cold-side volume of the upper-stage membrane module, and the heat-dissipating surface of the semiconductor heat pump module is attached to the hot-side of the next-stage membrane module. On the cavity; the distance from the heat dissipation surface of the semiconductor heat pump component to the hydrophobic microporous membrane is 1 to 5 mm on the hot side cavity; the distance from the heat absorption surface of the semiconductor heat pump component to the hydrophobic microporous membrane is 1 ~ 5mm; the environmental heat absorption unit is close to the heat absorption surface of the semiconductor heat pump module on the hot side cavity of the first-stage membrane module, and the heat dissipation surface of the semiconductor heat pump module is connected to the heat side cavity of the first-stage membrane module; The unit is closely attached to the heat radiation surface of the semiconductor heat pump component on the cold side cavity of the last stage membrane module, and the heat absorption surface of the semiconductor heat pump component is connected to the cold side cavity of the last stage membrane module.
The multi-stage membrane module integrated with a semiconductor heat pump according to claim 1, characterized in that a plurality of material liquid inlet channels and material liquid outlet channels are respectively provided at both ends of the hot-side storage cavity, and any material liquid inlet channel and The axis of any material liquid outlet channel is not collinear.
The multi-stage membrane module with integrated semiconductor heat pump according to claim 1, characterized in that a plurality of permeate inlet channels and permeate outlet channels are provided at both ends of the cold-side storage cavity, and any one of the permeate inlet channels is provided. Non-collinear with the axis of any permeate outlet channel.
The multi-stage membrane module with integrated semiconductor heat pump according to claim 1, wherein the ambient heat absorption unit uses a natural convection air heat exchanger, and the ambient heat dissipation unit uses a forced convection air radiator.
The multi-stage membrane module with integrated semiconductor heat pump according to claim 4, wherein the natural convection air heat exchanger uses a natural flow fin refrigeration heat exchanger; and the forced convection air radiator uses aluminum fins Fan cooler.
The multi-stage membrane module with integrated semiconductor heat pump according to claim 4, characterized in that the semiconductor heat pump modules each include a mounting frame and a semiconductor refrigerating sheet, wherein the semiconductor refrigerating sheet selects a model number of TEC1-19006 with a size of 40x40x4mm. Embedded in a heat-resistant epoxy mounting frame.
The multi-stage membrane module with integrated semiconductor heat pump according to claim 1, wherein the hydrophobic microporous membrane is a surface-modified super-hydrophobic polyvinylidene fluoride planar membrane, and the average membrane thickness is 0.018 mm.
The application of a multi-stage membrane module with integrated semiconductor heat pump in a direct contact membrane distillation system according to claim 1, characterized in that the multi-stage membrane module with integrated semiconductor heat pump and accessories form a direct contact membrane distillation system. The contact membrane distillation system is mainly composed of a material-liquid storage tank, a hot-side circulation pump, a multi-stage membrane module integrated with a semiconductor heat pump, a permeate storage tank, and a permeate circulation. The material-liquid storage tank is connected to the hot-side circulation pump through a pipeline. The side circulation pump is connected to the material liquid inlet channels of the multiple hot side chambers of the multi-stage membrane module integrated with the semiconductor heat pump through pipes, and the material liquid outlet channels of the multiple heat side chambers of the multi-stage membrane module integrated with the semiconductor heat pump pass through. The pipeline is connected to the material liquid storage tank; the permeate storage tank is connected to the permeate circulation pump through the pipeline, and the permeate circulation pump is connected to the permeate inlet channels of the multiple cold-side compartments of the multi-stage membrane module integrated with the semiconductor heat pump through the pipeline respectively ; The permeate outlet channels of the multiple cold-side accommodating cavities of multiple multi-stage membrane modules with integrated semiconductor heat pumps are connected to the permeate storage tank through pipes, respectively.
The application of a multi-stage membrane module with an integrated semiconductor heat pump in a direct contact membrane distillation system according to claim 8, characterized in that the feed liquid storage tank is charged with seawater, sewage or liquid food to be concentrated; Add ultrapure water to the liquid storage tank to achieve seawater desalination, sewage treatment or food concentration.
The application of a multi-stage membrane module with an integrated semiconductor heat pump in a direct contact membrane distillation system according to claim 9, wherein the liquid food to be concentrated is milk.