CN111111451A - Reduced pressure multi-effect membrane distillation method and device thereof - Google Patents
Reduced pressure multi-effect membrane distillation method and device thereof Download PDFInfo
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- CN111111451A CN111111451A CN202010050560.3A CN202010050560A CN111111451A CN 111111451 A CN111111451 A CN 111111451A CN 202010050560 A CN202010050560 A CN 202010050560A CN 111111451 A CN111111451 A CN 111111451A
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Abstract
The invention aims to provide a reduced-pressure multi-effect membrane distillation method and a device thereof.A hot feed liquid flows from top to bottom in a membrane distillation combined element, and negative pressure evaporation is generated and the temperature is reduced in the flowing process; the generated steam heats the cold fluid through the heat exchange wall and is condensed by the cold fluid; meanwhile, the cold feed liquid flows from bottom to top, and negative pressure evaporation is generated while the cold feed liquid is heated by the heat exchange wall. The evaporation cooling of the hot feed liquid and the heating of the cold feed liquid are continuous stepless processes, and efficient multi-effect evaporation can be realized. The decompression multiple-effect membrane distillation method provided by the invention has the advantages that the condensation of water vapor generated in the membrane distillation process is coupled with the heating process of the feed liquid, the membrane distillation flux is higher under the condition of high water generation ratio, and meanwhile, the consumption of external cooling water can be obviously reduced. The multi-effect membrane distillation process designed by the invention can realize the membrane distillation process with high efficiency and low energy consumption, and has high heat recovery rate.
Description
Technical Field
The invention relates to a membrane distillation method and a device thereof, in particular to a pressure reduction multi-effect membrane distillation method and a device thereof for high-salinity wastewater concentration treatment and industrial material separation and concentration.
Background
The membrane distillation technology is a novel liquid separation technology combining the membrane technology and the traditional distillation technology, and compared with a common evaporator, the most obvious characteristic of the membrane distillation is that the effective evaporation area in a unit volume is large, so that the device can efficiently operate in the evaporation process at normal pressure and lower temperature, and the equipment adopts plastic materials, thereby avoiding the corrosion problem of metal materials in the process of treating high-salinity materials. The membrane distillation is a membrane separation process which adopts a hydrophobic microporous membrane and takes the steam pressure difference at two sides of the membrane as the driving force for mass transfer. Driven by the steam pressure difference at the two sides of the microporous hydrophobic membrane, water steam passes through the hydrophobic membrane from the heated feed liquid side and is condensed into liquid. Because of the hydrophobic nature of the membrane, only water vapor can pass through the membrane pores, and feed liquid and non-volatile solutes dissolved therein cannot pass through the membrane pores, the membrane distillation process can theoretically achieve 100% removal of ions, macromolecules, colloids, cells and other non-volatile species. The microporous hydrophobic membrane plays a role in supporting and shielding between two phases in the membrane distillation process. The membrane distillation process can be carried out for treating water solution with extremely high concentration, as long as proper steam partial pressure difference is maintained on two sides of the membrane, and cheap energy sources such as solar energy, terrestrial heat, hot springs, factory waste heat, warm industrial wastewater and the like can be utilized.
Five common membrane distillation modes of operation have been developed, namely direct contact membrane distillation, air gap membrane distillation, air swept membrane distillation, vacuum membrane distillation and absorption membrane distillation. However, the membrane distillation technology has the problem of high energy consumption until now because of the phase change process in the separation process. The phase transformation heat of the water vapor in the membrane distillation process is about 2500kJ/kg and is far larger than the specific heat of the water, namely 4.2kJ/kg. Therefore, the membrane distillation process requires not only an external heat source but also a large amount of external cooling water to condense the vapor of the membrane distillation. Therefore, the recovery of the phase change heat of the water vapor in the membrane distillation process in a proper manner, the application of the phase change heat to the heating of the feed liquid and the reduction of the consumption of cooling water are one of the key problems to be solved for realizing the industrial application of the membrane distillation technology.
Disclosure of Invention
The invention mainly aims to overcome the defects in the prior art and provide a reduced-pressure multi-effect membrane distillation method and a device thereof. By utilizing the chemical multi-effect evaporation principle, the condensation of water vapor generated in the membrane distillation process is coupled with the heating process of the feed liquid, the phase change heat of the water vapor in the membrane distillation process is recovered while the using amount of cooling water is greatly reduced, and the concentration of the feed liquid and the full utilization of the evaporation phase change heat are synchronously realized, so that the reduced-pressure multi-effect membrane distillation process is completed.
The purpose of the invention is realized by the following technical scheme.
A reduced pressure multi-effect membrane distillation device comprises a membrane distillation combined element, wherein the membrane distillation combined element is formed by sequentially arranging a hydrophobic membrane, a heat exchange wall and a hydrophobic membrane.
The cylindrical membrane distillation combined element is characterized in that an inner-layer hydrophobic membrane of a vertical flow path from top to bottom is arranged in the center of the cylindrical membrane distillation combined element, the inner-layer hydrophobic membrane is a hollow fiber hydrophobic membrane or a tubular hydrophobic membrane, a heat exchange tube is arranged outside the inner-layer hydrophobic membrane, an outer-layer hydrophobic membrane of the flow path from bottom to top is arranged outside the heat exchange tube, the outer-layer hydrophobic membrane is a tubular hydrophobic membrane, the three are sequentially arranged from inside to outside to form a combination, and one or more combinations are arranged in parallel to form the tubular membrane distillation combined element.
The plate-frame membrane distillation combined element is formed by sequentially arranging an outer-layer flat plate type hydrophobic membrane, a heat exchange plate, an inner-layer flat plate type hydrophobic membrane, a heat exchange plate and an outer-layer flat plate type hydrophobic membrane in parallel to form a combination, and one or more combinations are arranged in parallel to form a flat plate type membrane distillation combined element.
Whether it is a cylindrical membrane distillation combined element or a plate-and-frame membrane distillation combined unit, one or more membrane distillation combined elements can be connected in series to form a continuous long flow channel.
The upper inlet of a hot material liquid flow channel of an inner hydrophobic membrane of the cylindrical membrane distillation combined element is connected with a hot material liquid circulation heating device through a pipeline, the lower outlet of the hot material liquid flow channel of the inner hydrophobic membrane is communicated with a hot fluid water outlet pipeline of a heat exchanger through a pipeline and then is connected to the inlet of the lower part of a flow channel formed by the outer hydrophobic membrane and a heat exchange wall, the upper outlet of the flow channel formed by the outer hydrophobic membrane and the heat exchange wall is connected with the hot material liquid circulation heating device through a connecting pipe, the lower water outlet of a vacuum layer formed by the inner hydrophobic membrane and the heat exchange wall is connected with the hot fluid inlet of the heat exchanger through a connecting pipe, the lower water outlet of the vacuum layer formed between the outer hydrophobic membrane and a shell of the membrane distillation combined element is connected with the hot fluid inlet of the heat exchanger through a connecting pipe, a cold fluid outlet of the heat, the exhaust port of the gas-liquid separator is connected with a vacuum pump, the cold fluid inlet of the heat exchanger is connected with raw water through a centrifugal pump, one path of the hot fluid outlet of the heat exchanger is connected with a drainage pipeline, and the other path of the hot fluid outlet of the heat exchanger is connected with the inlet at the lower part of a flow channel formed by the outer hydrophobic membrane and the heat exchange wall.
The distillation method of the device is that hot feed liquid flows through a hot feed liquid flow passage of the inner hydrophobic membrane from top to bottom, and membrane distillation is carried out and the temperature is reduced under the negative pressure action of a vacuum layer between the inner hydrophobic membrane and the heat exchange wall; after the evaporated and cooled feed liquid discharges part of concentrated liquid through a concentrated water discharge valve, most of the concentrated liquid enters a cold feed liquid flow channel between an outer hydrophobic membrane and a heat exchange wall from bottom to top, membrane distillation is carried out under the negative pressure action of a vacuum layer between the outer hydrophobic membrane and a membrane distillation combined element shell, the membrane distillation is carried out simultaneously under the heating action of the heat exchange wall, the feed liquid is subjected to membrane distillation synchronously and is heated, and the concentrated feed liquid which is not evaporated returns to a hot feed liquid circulating heating device.
The upper inlet of a hot material liquid flow channel formed by clamping two inner-layer flat hydrophobic membranes of the plate-frame type membrane distillation combined element is connected with a hot material liquid circulation heating device through a pipeline, the lower outlet of the hot material liquid flow channel is communicated with a hot fluid outlet pipeline of a heat exchanger through a pipeline and then is connected to the inlet of the lower part of a flow channel formed by clamping an outer-layer flat hydrophobic membrane and a heat exchange plate, the upper outlet of the flow channel is connected with the hot material liquid circulation heating device through a connecting pipe, the lower outlet of a vacuum layer formed by the inner-layer flat hydrophobic membrane and the heat exchange plate is connected with the hot fluid inlet of the heat exchanger through a connecting pipe, the lower outlet of the vacuum layer formed between the outer-layer flat hydrophobic membrane and a shell of the membrane distillation combined element is connected with the hot fluid inlet of the heat exchanger through a connecting pipe, a cold fluid outlet of the heat exchanger is, the exhaust port of the gas-liquid separator is connected with a vacuum pump, the cold fluid inlet of the heat exchanger is connected with raw water through a centrifugal pump, one path of the hot fluid outlet of the heat exchanger is connected with a drainage pipeline, and the other path of the hot fluid outlet of the heat exchanger is connected with the inlet at the lower part of a flow channel formed by the outer-layer flat plate type hydrophobic membrane and the heat exchange plate.
The distillation method of the device comprises the following steps: the hot feed liquid flows through a hot feed liquid flow channel formed by clamping two inner-layer flat-plate type hydrophobic membranes from top to bottom, and membrane distillation is carried out and the temperature is reduced under the negative pressure action of a vacuum layer between the inner-layer flat-plate type hydrophobic membranes and the heat exchange plate; after the evaporated and cooled feed liquid discharges part of concentrated liquid through a concentrated water discharge valve, most of the concentrated liquid enters a cold feed liquid flow channel between the outer flat-plate type hydrophobic membrane and the heat exchange plate from bottom to top, membrane distillation is carried out under the negative pressure action of a vacuum layer between the outer flat-plate type hydrophobic membrane and the membrane distillation combined element shell, meanwhile, the feed liquid is heated under the heating action of the heat exchange plate, membrane distillation is synchronously carried out on the feed liquid and the temperature is raised, and the concentrated feed liquid which is not evaporated returns to the hot feed liquid circulating heating device.
Raw water at room temperature enters from a cold fluid inlet of the heat exchanger, flows out from a hot fluid outlet of the heat exchanger after being heated, a small part of the raw water is discharged by a cooling water discharge pipe, and a large part of the raw water is combined with concentrated feed liquid flowing out from a lower opening of an inner flow passage of the inner hydrophobic membrane and then enters a flow passage formed by the outer hydrophobic membrane and the heat exchange wall from bottom to top.
The vapor generated by the evaporation of the inner and outer hydrophobic membranes respectively enters a vacuum layer formed by the inner hydrophobic membrane and the heat exchange wall, and a vacuum layer formed by the outer hydrophobic membrane and the membrane distillation combined element shell, is condensed into membrane distillation produced water, respectively enters a heat exchanger for cooling, and is collected by a water receiving container through a gas-liquid separator.
Membrane distillation produced water in each stage of membrane distillation combined elements is sequentially communicated through a communicating pipe and is finally pumped out by a produced water pump;
the vacuum degree control of the shell pass of each stage of membrane distillation combined element is realized through the liquid level difference of the inlet and the outlet of the water production communicating pipe in each stage of membrane distillation combined element and the vacuum pump;
the raw water is tap water, seawater, high salinity water or chemical product solution needing concentration or desalination treatment
The core characteristic of the reduced-pressure multi-effect membrane distillation method is as follows: in the membrane distillation combined element, hot feed liquid flows from top to bottom, and negative pressure evaporation is generated in the flowing process and the temperature is reduced; the generated steam heats the cold fluid through the heat exchange wall and is condensed by the cold fluid; meanwhile, the cold feed liquid flows from bottom to top, and negative pressure evaporation is generated while the cold feed liquid is heated by the heat exchange wall. The evaporation cooling of the hot feed liquid and the heating of the cold feed liquid are continuous stepless processes, and efficient multi-effect evaporation can be realized. The condensation of water vapor generated in the membrane distillation process is coupled with the heating process of the feed liquid, so that the phase change heat of the water vapor in the membrane distillation process is recovered while the using amount of cooling water is greatly reduced, and the full utilization of the phase change heat of the feed liquid concentration and evaporation is synchronously realized, thereby completing the pressure-reducing multi-effect membrane distillation process.
In order to improve the water generation ratio of the pressure-reducing multi-effect membrane distillation process, namely reduce the consumption of cooling water and synchronously realize the full utilization of evaporation phase change heat, the length of the membrane distillation combined element is longer than that of a conventional pressure-reducing membrane distillation component. The length of the conventional vacuum membrane distillation assembly is generally not more than 100 cm, and the length of the membrane distillation assembly element proposed by the present invention is 100 to 200 cm. If the length of a single membrane distillation combination element does not exceed 100 cm, a plurality of membrane distillation combination elements can be connected in series to form a continuous long flow channel.
The hydrophobic membrane used in the invention can be a hollow fiber hydrophobic membrane, and can also adopt tubular, plate-and-frame flat-plate and spiral hydrophobic membranes.
The heat exchanger used in the invention can be a shell and tube type or a flat plate type. The heat exchange material can be a metal material, and can also be plastic, such as polypropylene, polyvinylidene fluoride, polytetrafluoroethylene and the like. If the plastic hollow fiber is adopted, the plastic hollow fiber with better heat-conducting property and a gap structure is preferably adopted. If polyvinylidene fluoride plastic hollow fiber obtained through wet spinning has a porosity which can reach more than 80%, when the polyvinylidene fluoride plastic hollow fiber is used, liquid water is filled in the porosity, the heat-conducting property of the polyvinylidene fluoride plastic hollow fiber can be obviously improved, and the heat exchange efficiency is improved.
The membrane distillation combined element can adopt a heat exchange tube or a heat exchange plate.
The invention has the advantages and beneficial effects that:
the reduced-pressure multi-effect membrane distillation method provided by the invention couples the water vapor condensation in the membrane distillation process with the feed liquid heating process, has higher membrane distillation flux under the condition of high water generation ratio, and simultaneously obviously reduces the consumption of external cooling water. The multi-effect membrane distillation process designed by the invention can realize the membrane distillation process with high efficiency and low energy consumption, and has high heat recovery rate.
Drawings
FIG. 1 is a schematic view of a reduced-pressure multi-effect membrane distillation apparatus of the present invention.
Fig. 2 is a schematic diagram showing the configuration of the cylindrical membrane distillation combination unit 33.
Fig. 3 is a schematic structural diagram of a cylindrical membrane distillation assembly unit formed by arranging a plurality of cylindrical membrane distillation assembly units 33 in parallel in the housing 9.
FIG. 4 is a schematic diagram showing the construction of a plate-and-frame membrane distillation combined unit according to the present invention. Like fig. 3, a plurality of flat-plate type membrane distillation combination units arranged in parallel form a membrane distillation combination element.
The main reference numbers in the figures illustrate: 1 is a hot feed liquid circulating heating tank, 2 is a circulating water pump, 3 is a circulating flow control valve, 4 is a circulating flow meter, 5 is a connecting pipe, 6 is a hot feed liquid inlet, 7 is a connecting pipe, 8 is an outer layer reflux liquid outlet, 9 is a membrane distillation combined unit shell, 10 is an inner layer hydrophobic membrane, 11 is a heat exchange wall, 12 is an outer layer hydrophobic membrane, 13 is a membrane distillation produced water outlet of the outer layer hydrophobic membrane, 14 is a connecting pipe, 15 is a membrane distillation produced water outlet of the inner layer hydrophobic membrane, 16 is a connecting pipe, 17 is a heat exchanger, 18 is a vacuum pump, 19 is a gas-liquid separator, 20 is a water receiving container, 21 is a cold fluid inlet of the heat exchanger, 22 is a raw water centrifugal pump, 23 is a connecting pipe, 24 is a drain valve, 25 is a cooling water discharge pipe, 26 is a hot fluid outlet of the heat exchanger, 27 is a concentrated water discharge valve, 28, 29 and 30 are connecting pipes, 31 is an inner layer cold feed liquid, 33 is a unit of membrane distillation combination, which comprises an inner hydrophobic membrane, a heat exchange tube and an outer tubular hydrophobic membrane, a plurality of combination units arranged in parallel form a membrane distillation combination, and 34 is a three-way valve.
Detailed Description
The present invention is further illustrated by the following specific examples, which are intended to be illustrative, not limiting and are not intended to limit the scope of the invention.
A pressure-reducing multi-effect membrane distillation device is shown in figure 1 and comprises a plurality of membrane distillation combined elements, a circulating water pump 2, a vacuum pump 18, a hot feed liquid circulating heating device 1, a heat exchanger 17, a raw water centrifugal pump 22, a gas-liquid separator 19, valves and connecting pipes among the valves.
A plurality of membrane distillation combined units 33 are arranged in parallel in the shell 9 to form a membrane distillation combined element, as shown in figure 3, the most central part of each membrane distillation combined unit 33 is an inner hydrophobic membrane 10 with a vertical flow path from top to bottom, the outer surface of the membrane distillation combined unit is a tubular heat exchange wall 11, and the outer surface of the heat exchange wall is an outer hydrophobic membrane 12 with a flow path from bottom to top, as shown in figures 2 and 3 (cylindrical shape) and figure 4 (plate frame type).
The upper part of the shell 9 is provided with a hot feed liquid inlet 6 and an outer layer reflux liquid outlet 8, the lower part is provided with an inner layer cold feed liquid outlet 31, an inner layer membrane distillation produced water outlet 15, an outer layer cold feed liquid inlet 32 and an outer layer distillation produced water outlet 13.
The hot feed liquid inlet 6 is connected with the hot feed liquid circulating water heating tank 1 through a connecting pipe 5 outside the shell 9, a circulating water pump 2, a circulating flow control valve 3 and a circulating flow meter 4 are installed on the connecting pipe 5, an inner layer cold feed liquid outlet 31 is connected with the connecting pipe 30, the connecting pipe 30 is divided into two branch pipes, one branch pipe is provided with a concentrated water discharge valve 27, the other branch pipe is connected with one inlet of a three-way valve 34, the other inlet of the three-way valve 34 is connected with a connecting pipe 28, the outlet of the three-way valve 34 is connected with an outer layer cold feed liquid inlet 32 through the connecting pipe 29, the outer layer cold feed liquid inlet 32 is a flow passage inlet formed by an outer layer hydrophobic membrane 12 and a heat exchange wall 11, and an outer layer reflux liquid outlet 8 is connected with.
The inner membrane distilled water outlet 15 is connected with the connecting pipe 14 through the connecting pipe 16. The outer layer distilled water outlet 13 is connected with a connecting pipe 14. The connecting pipe 14 is connected with a hot fluid inlet of the heat exchanger 17, a cold fluid outlet of the heat exchanger 17 is connected with a gas-liquid separator 19, a water outlet of the gas-liquid separator 19 is connected with a water receiving container 20, and an air outlet of the gas-liquid separator 19 is connected with a vacuum pump 18. A cold fluid inlet 21 of the heat exchanger 17 is connected with raw water through a centrifugal pump 22, a hot fluid outlet 26 of the heat exchanger 17 is connected with a connecting pipe 23, the connecting pipe 23 is divided into two branches, one branch pipe 28 is connected with a three-way valve 34, and a drain valve 24 is arranged on the other branch pipe 25.
The device comprises the following process flows:
the hot feed liquid in the hot feed liquid circulating water heating tank 1 sequentially passes through a circulating water pump 2 to increase pressure, a valve 3 to control the flow of the hot feed liquid and a flowmeter 4, flows through an inner hydrophobic membrane 10 in an inner membrane distillation combined element in a shell 9 from top to bottom from a hot feed liquid inlet 6 of the shell 9 through a connecting pipe 5, and is subjected to membrane distillation and cooled by a heat exchange wall 11 under the negative pressure action of a vacuum layer between the inner hydrophobic membrane 10 and the heat exchange wall 11 to form membrane distillation water. The material liquid after being evaporated and cooled in the hydrophobic membrane 10 in the inner layer flows out from an inner layer cold material liquid outlet 31 of the shell 9, part of the concentrated liquid is discharged through the concentrated water discharge valve 27, most of the concentrated liquid passes through the connecting pipes 30 and 29 and passes through an outer layer cold material liquid inlet 32 at the lower end of the shell 9 and enters a flow channel formed by the outer layer hydrophobic membrane 12 and the heat exchange wall 11 of the membrane distillation combined element from bottom to top, membrane distillation is performed under the negative pressure action of the vacuum layer between the outer layer hydrophobic membrane 12 and the shell, and the material liquid is heated under the heating action of the heat exchange wall 11, namely, the material liquid is subjected to membrane distillation synchronously and is heated and heated by the heat exchange wall 11, the concentrated material liquid which is not evaporated is returned to the hot material liquid circulating water heating tank 1 from an outer layer reflux liquid outlet 8 of the shell.
The water vapor generated by the membrane distillation of the inner hydrophobic membrane 10 is condensed by the heat exchange wall 11 to become membrane distillation produced water, flows through the connecting pipe 16 and the connecting pipe 14 from the inner membrane distillation produced water outlet 15 at the lower end of the shell 9, enters the heat exchanger 17 from top to bottom for cooling, passes through the gas-liquid separator 19, and is collected by the water receiving container 20. The water vapor generated by the membrane distillation of the outer hydrophobic membrane 12 flows from the outer distilled water outlet 13 at the lower side of the shell 9, passes through the connecting pipe 14, enters the heat exchanger 17 from top to bottom for cooling and condensation, passes through the gas-liquid separator 19, and is collected by the water receiving container 20.
The raw water at room temperature enters from a cold fluid inlet 21 at the lower end of the heat exchanger 17 after the pressure of the raw water is raised by a raw water centrifugal pump 22, the raw water is heated and flows into a connecting pipe 23 from a hot fluid outlet 26 of the heat exchanger 17, part of the raw water is used as cooling water, the discharge amount of the raw water is controlled by a drain valve 24 and is discharged by a cooling water discharge pipe 25, and the rest of the raw water is merged with concentrated raw water after membrane distillation of the inner hydrophobic membrane 10 at a three-way valve by a connecting pipe 28 and enters. Similarly, the liquid enters a flow channel formed by the outer hydrophobic membrane 12 and the heat exchange wall 11 from bottom to top through an outer layer cold liquid inlet 32 at the lower end of the shell 9, membrane distillation is carried out under the negative pressure of a vacuum layer between the outer hydrophobic membrane 12 and the shell, and the liquid is heated by the heat exchange wall 11 at the same time, namely, the liquid is subjected to membrane distillation synchronously and is heated, and the non-evaporated concentrated liquid returns to the hot liquid circulating water heating tank 1 from an outer layer distillate outlet 8 of the shell 9 through a connecting pipe 7.
The vacuum layer between the inner hydrophobic membrane 10 and the heat exchange wall 11 and the vacuum layer between the outer hydrophobic membrane 12 and the shell are provided with vacuum pumps 18, and the uncondensed gas in the membrane distillation device is discharged out of the membrane distillation system by the vacuum pumps 18.
The temperature of the hot feed liquid at the hot feed liquid inlet 6 of the shell 9 is controlled to be 70-95 ℃, the specific temperature is determined according to the heat source and the property of the feed liquid, the temperature of the cold feed liquid outlet 31 at the inner layer of the lower end of the shell 9 is controlled to be 30-50 ℃, and the temperature of the return liquid outlet 8 at the outer layer of the shell 9 is controlled to be 2-20 ℃ lower than the temperature of the hot feed liquid inlet 6.
The lower end of the membrane distillation combined element, the inner layer membrane distillation water production outlet 15 and the lower outer layer distillation water production outlet 13 are provided with high vacuum degree as much as possible so as to improve the membrane distillation water production.
The temperature of the hot fluid outlet 26 of the heat exchanger 17 is controlled to be 30-50 ℃, the liquid level in the hot liquid circulating water heating tank 1 is kept constant, and the redundant raw water is returned to the source of the raw water through the drain pipe 25 under the control of the drain valve 24.
In the hot feed liquid circulating water heating tank, the feed liquid can be heated by electric heating, steam heating, hot water heating and the like.
Through the control, the water making ratio of the membrane distillation device can reach more than 20 at most. According to the conventional vacuum membrane distillation process, one part of membrane distillation produced water is obtained, about 30 parts of cooling water is required, and according to the process of the present invention, even no cooling water may be required, i.e., the amount of water discharged from the line 25 via the valve 24 is even zero.
The content that is not described in the embodiments of the present invention is the prior art, and therefore, the description thereof is omitted.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention in any way, and any simple modifications and variations of the embodiments according to the technical spirit of the present invention are still within the scope of the technical solution of the present invention.
Claims (10)
1. A decompression multi-effect membrane distillation device is characterized in that: the membrane distillation combined element is formed by sequentially arranging a hydrophobic membrane, a heat exchange wall and a hydrophobic membrane.
2. The reduced-pressure, multi-effect membrane distillation apparatus of claim 1, wherein: the membrane distillation combined element is cylindrical or flat.
3. The reduced-pressure, multi-effect membrane distillation apparatus of claim 1, wherein: the hydrophobic membrane is a hollow fiber hydrophobic membrane or a tubular hydrophobic membrane or a flat plate type hydrophobic membrane.
4. The reduced-pressure, multi-effect membrane distillation apparatus of claim 1, wherein: the heat exchange wall is a heat exchange tube or a heat exchange plate.
5. A reduced pressure multi-effect membrane distillation apparatus according to any one of claims 1 to 4, wherein: the membrane distillation combined element is cylindrical, an inner hydrophobic membrane of a vertical flow path from top to bottom is arranged in the center, the inner hydrophobic membrane is a hollow fiber hydrophobic membrane or a tubular hydrophobic membrane, a heat exchange tube is arranged outside the inner hydrophobic membrane, an outer hydrophobic membrane of the flow path from bottom to top is arranged outside the heat exchange tube, the outer hydrophobic membrane is a tubular hydrophobic membrane, the three are sequentially arranged from inside to outside to form a combination, and one or more combinations are arranged in parallel to form the tubular membrane distillation combined element.
6. The reduced-pressure, multi-effect membrane distillation apparatus of claim 5, wherein: one or more membrane distillation combined elements are connected in series to form a continuous long flow channel.
7. The reduced-pressure, multi-effect membrane distillation apparatus of claim 5, wherein: the upper inlet of a hot material liquid flow channel of an inner hydrophobic membrane of the membrane distillation combined element is connected with a hot material liquid circulation heating device through a pipeline, the lower outlet of the hot material liquid flow channel of the inner hydrophobic membrane is communicated with a hot fluid outlet pipeline of a heat exchanger through a pipeline and then is connected to the inlet of the lower part of a flow channel formed by the outer hydrophobic membrane and a heat exchange wall, the upper outlet of the flow channel formed by the outer hydrophobic membrane and the heat exchange wall is connected with the hot material liquid circulation heating device through a connecting pipe, the lower water outlet of a vacuum layer formed by the inner hydrophobic membrane and the heat exchange wall is connected with the hot fluid inlet of the heat exchanger through a connecting pipe, the lower water outlet of the vacuum layer formed between the outer hydrophobic membrane and a shell of the membrane distillation combined element is connected with the hot fluid inlet of the heat exchanger through a connecting pipe, a cold fluid outlet of the heat exchanger, the exhaust port of the gas-liquid separator is connected with a vacuum pump, the cold fluid inlet of the heat exchanger is connected with raw water through a centrifugal pump, one path of the hot fluid outlet of the heat exchanger is connected with a drainage pipeline, and the other path of the hot fluid outlet of the heat exchanger is connected with the inlet at the lower part of a flow channel formed by the outer hydrophobic membrane and the heat exchange wall.
8. A reduced pressure multi-effect membrane distillation apparatus according to any one of claims 1 to 4, wherein: the membrane distillation combined element is a plate frame type and is formed by sequentially arranging an outer flat plate type hydrophobic membrane, a heat exchange plate, an inner flat plate type hydrophobic membrane, the heat exchange plate and an outer flat plate type hydrophobic membrane in parallel to form a combination, and one or more combinations are arranged in parallel to form a flat plate type membrane distillation combined element.
9. The reduced-pressure, multi-effect membrane distillation apparatus of claim 8, wherein: the upper inlet of a hot material liquid flow channel formed by clamping two inner-layer flat-plate type hydrophobic membranes of the membrane distillation combined element is connected with a hot material liquid circulation heating device through a pipeline, the lower outlet of the hot material liquid flow channel is communicated with a hot fluid outlet pipeline of a heat exchanger through a pipeline and then is connected to the inlet of the lower part of a flow channel formed by clamping an outer-layer flat-plate type hydrophobic membrane and a heat exchange plate, the upper outlet of the flow channel is connected with the hot material liquid circulation heating device through a connecting pipe, the lower outlet of a vacuum layer formed by the inner-layer flat-plate type hydrophobic membrane and the heat exchange plate is connected with the hot fluid inlet of the heat exchanger through a connecting pipe, the lower outlet of the vacuum layer formed between the outer-layer flat-plate type hydrophobic membrane and a shell of the membrane distillation combined element is connected with the hot fluid inlet of the heat exchanger through a connecting pipe, the exhaust port of the gas-liquid separator is connected with a vacuum pump, the cold fluid inlet of the heat exchanger is connected with raw water through a centrifugal pump, one path of the hot fluid outlet of the heat exchanger is connected with a drainage pipeline, and the other path of the hot fluid outlet of the heat exchanger is connected with the inlet at the lower part of a flow channel formed by the outer-layer flat plate type hydrophobic membrane and the heat exchange plate.
10. The distillation method of a reduced-pressure multi-effect membrane distillation apparatus according to claims 7 and 9, wherein: the hot feed liquid flows through the hot feed liquid flow channel of the inner-layer hydrophobic membrane/the inner-layer flat-plate hydrophobic membrane from top to bottom, and under the negative pressure action of the vacuum layer between the inner-layer hydrophobic membrane/the inner-layer flat-plate hydrophobic membrane and the heat exchange wall, membrane distillation is carried out and the temperature is reduced; after the evaporated and cooled feed liquid discharges part of the concentrated liquid through a concentrated water discharge valve, most of the concentrated liquid enters a cold feed liquid flow channel between an outer layer hydrophobic membrane/an outer layer flat plate type hydrophobic membrane and a heat exchange wall from bottom to top, membrane distillation is carried out under the negative pressure of a vacuum layer between the outer layer hydrophobic membrane/the outer layer flat plate type hydrophobic membrane and a membrane distillation combined element shell, meanwhile, the membrane distillation is carried out under the heating action of the heat exchange wall, the feed liquid is subjected to the membrane distillation synchronously and is heated, and the concentrated feed liquid which is not evaporated returns to a hot feed liquid circulating heating device.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN113461245A (en) * | 2021-08-02 | 2021-10-01 | 兰州理工大学 | Solar-driven salt-containing water film distillation and purification device |
| CN115259287A (en) * | 2022-09-03 | 2022-11-01 | 南华大学 | High-yield tubular membrane distillation membrane device and wastewater concentration method |
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