CN112028181B - Low-viscosity gas bubbling vacuum enhanced direct contact membrane distillation seawater desalination device - Google Patents
Low-viscosity gas bubbling vacuum enhanced direct contact membrane distillation seawater desalination device Download PDFInfo
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- 239000013535 sea water Substances 0.000 title claims abstract description 124
- 239000012528 membrane Substances 0.000 title claims abstract description 82
- 238000004821 distillation Methods 0.000 title claims abstract description 59
- 238000010612 desalination reaction Methods 0.000 title claims abstract description 32
- 230000005587 bubbling Effects 0.000 title claims abstract description 30
- 239000013505 freshwater Substances 0.000 claims abstract description 91
- 230000002209 hydrophobic effect Effects 0.000 claims abstract description 35
- 239000012267 brine Substances 0.000 claims abstract description 14
- HPALAKNZSZLMCH-UHFFFAOYSA-M sodium;chloride;hydrate Chemical compound O.[Na+].[Cl-] HPALAKNZSZLMCH-UHFFFAOYSA-M 0.000 claims abstract description 14
- 239000007789 gas Substances 0.000 claims description 134
- 239000007788 liquid Substances 0.000 claims description 11
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 claims description 5
- 239000012510 hollow fiber Substances 0.000 claims description 3
- 239000001257 hydrogen Substances 0.000 claims description 3
- 229910052739 hydrogen Inorganic materials 0.000 claims description 3
- 239000000284 extract Substances 0.000 claims 1
- 238000000034 method Methods 0.000 abstract description 14
- 230000008569 process Effects 0.000 abstract description 10
- 230000032895 transmembrane transport Effects 0.000 abstract description 5
- 230000009471 action Effects 0.000 abstract description 4
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 31
- 239000012466 permeate Substances 0.000 description 10
- 230000004907 flux Effects 0.000 description 9
- 238000012544 monitoring process Methods 0.000 description 7
- 239000000243 solution Substances 0.000 description 7
- 230000000694 effects Effects 0.000 description 6
- 238000005728 strengthening Methods 0.000 description 4
- 230000009286 beneficial effect Effects 0.000 description 3
- 238000002347 injection Methods 0.000 description 3
- 239000007924 injection Substances 0.000 description 3
- 230000010287 polarization Effects 0.000 description 3
- 230000003321 amplification Effects 0.000 description 2
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 2
- 238000011033 desalting Methods 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000003199 nucleic acid amplification method Methods 0.000 description 2
- 239000001301 oxygen Substances 0.000 description 2
- 229910052760 oxygen Inorganic materials 0.000 description 2
- 239000000047 product Substances 0.000 description 2
- 230000002787 reinforcement Effects 0.000 description 2
- 238000012360 testing method Methods 0.000 description 2
- 238000012546 transfer Methods 0.000 description 2
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 1
- MYMOFIZGZYHOMD-UHFFFAOYSA-N Dioxygen Chemical compound O=O MYMOFIZGZYHOMD-UHFFFAOYSA-N 0.000 description 1
- 239000003570 air Substances 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 229910001873 dinitrogen Inorganic materials 0.000 description 1
- 229910001882 dioxygen Inorganic materials 0.000 description 1
- 239000003651 drinking water Substances 0.000 description 1
- 235000020188 drinking water Nutrition 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 230000008020 evaporation Effects 0.000 description 1
- 238000001704 evaporation Methods 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 238000010792 warming Methods 0.000 description 1
- 239000002699 waste material Substances 0.000 description 1
Classifications
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/44—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis
- C02F1/447—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis by membrane distillation
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
- B01D61/36—Pervaporation; Membrane distillation; Liquid permeation
- B01D61/364—Membrane distillation
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
- B01D61/36—Pervaporation; Membrane distillation; Liquid permeation
- B01D61/366—Apparatus therefor
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
- B01D61/36—Pervaporation; Membrane distillation; Liquid permeation
- B01D61/368—Accessories; Auxiliary operations
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2103/00—Nature of the water, waste water, sewage or sludge to be treated
- C02F2103/08—Seawater, e.g. for desalination
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2209/00—Controlling or monitoring parameters in water treatment
- C02F2209/02—Temperature
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2209/00—Controlling or monitoring parameters in water treatment
- C02F2209/03—Pressure
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2209/00—Controlling or monitoring parameters in water treatment
- C02F2209/40—Liquid flow rate
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2301/00—General aspects of water treatment
- C02F2301/04—Flow arrangements
- C02F2301/046—Recirculation with an external loop
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2301/00—General aspects of water treatment
- C02F2301/06—Pressure conditions
- C02F2301/063—Underpressure, vacuum
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2303/00—Specific treatment goals
- C02F2303/14—Maintenance of water treatment installations
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
- Y02A20/00—Water conservation; Efficient water supply; Efficient water use
- Y02A20/124—Water desalination
- Y02A20/131—Reverse-osmosis
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- Engineering & Computer Science (AREA)
- Water Supply & Treatment (AREA)
- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Life Sciences & Earth Sciences (AREA)
- Hydrology & Water Resources (AREA)
- Environmental & Geological Engineering (AREA)
- Organic Chemistry (AREA)
- Separation Using Semi-Permeable Membranes (AREA)
Abstract
本发明提供了一种低粘气体鼓泡真空强化直接接触式膜蒸馏海水淡化装置，涉及海水淡化技术领域。所述海水淡化装置包括膜蒸馏装置、低粘气体循环回路、海水循环回路和淡水循环回路；所述膜蒸馏装置包括：热海水流道、淡水流道和疏水透气膜；所述海水循环回路包括：海水加热器、海水存储罐、浓盐水存储罐、海水循环泵、第一换热器和第二换热器；所述淡水循环回路包括：淡水循环泵、淡水存储罐和真空泵；所述低粘气体循环回路包括：气体压缩机、低粘气体存储罐、气体风机。本发明不仅考虑了鼓泡过程中低粘气体对热海水湍流的持续扰动，同时在宏观压差的作用下也增强了低粘气体对蒸气跨膜输运的带动能力。
The present invention provides a low-viscosity gas bubbling vacuum enhanced direct contact membrane distillation seawater desalination device, which relates to the technical field of seawater desalination. The seawater desalination device includes a membrane distillation device, a low-viscosity gas circulation loop, a seawater circulation loop and a fresh water circulation loop; the membrane distillation device includes: a hot seawater flow channel, a fresh water flow channel and a hydrophobic breathable membrane; the seawater circulation loop includes: a seawater heater, a seawater storage tank, a concentrated brine storage tank, a seawater circulation pump, a first heat exchanger and a second heat exchanger; the fresh water circulation loop includes: a fresh water circulation pump, a fresh water storage tank and a vacuum pump; the low-viscosity gas circulation loop includes: a gas compressor, a low-viscosity gas storage tank, and a gas blower. The present invention not only takes into account the continuous disturbance of the hot seawater turbulence by the low-viscosity gas during the bubbling process, but also enhances the driving ability of the low-viscosity gas to the transmembrane transport of steam under the action of the macroscopic pressure difference.
Description
Technical Field
The invention relates to the technical field of sea water desalination, in particular to a low-viscosity gas bubbling vacuum enhanced direct contact type membrane distillation sea water desalination device.
Background
At present, pure and clean drinking water is urgently needed in many countries around the world, and water resource shortage has become a serious environmental problem further affected by global warming. With the rapid growth of the world population, desalination of sea water is increasingly considered necessary and viable. In order to further save energy and improve the quality of produced water, the membrane distillation sea water desalination technology is more and more important.
Compressed air bubbling is a means for strengthening the mass transfer process of membrane distillation seawater desalination, for example, in the patent CN101874984A and CN200810052864.2, the raw water side has stronger flowing turbulence of raw water in a membrane component due to the addition of compressed air, so that concentration polarization and temperature difference polarization of a boundary layer are reduced, and the effect of strengthening the mass transfer process is achieved.
However, the water vapor transmembrane permeation rate of the current membrane distillation seawater desalination device is still not high, and the seawater desalination efficiency needs to be improved.
Disclosure of Invention
(One) solving the technical problems
Aiming at the defects of the prior art, the invention provides a low-viscosity gas bubbling vacuum enhanced direct contact type membrane distillation seawater desalination device, which solves the problem that the water vapor transmembrane permeation rate of the membrane distillation seawater desalination device needs to be improved.
(II) technical scheme
The invention provides a low-viscosity gas bubbling vacuum enhanced direct contact type membrane distillation seawater desalination device, which comprises a membrane distillation device, a low-viscosity gas circulation loop, a seawater circulation loop and a fresh water circulation loop;
The membrane distillation device comprises a hot seawater flow passage, a fresh water flow passage and a hydrophobic and breathable membrane, wherein the hot seawater flow passage and the fresh water flow passage are alternately arranged side by side, and adjacent hot seawater flow passages and fresh water flow passages are separated by the hydrophobic and breathable membrane;
The seawater circulation loop comprises a seawater heater, a seawater storage tank, a strong brine storage tank, a seawater circulation pump, a first heat exchanger and a second heat exchanger;
The fresh water circulation loop comprises a fresh water circulation pump, a fresh water storage tank and a vacuum pump;
The low-viscosity gas circulation loop comprises a gas compressor, a low-viscosity gas storage tank and a gas fan;
the low-viscosity gas circulation loop is filled with low-viscosity gas, and the low-viscosity gas is non-condensable gas with lower dynamic viscosity.
Preferably, the low-viscosity gas is hydrogen.
Preferably, the fresh water storage tank is filled with gas and fresh water, the gas-liquid volume ratio is 1% -20%, and the fresh water storage tank is in a closed state, and a certain vacuum degree is formed in a fresh water circulation loop after the vacuum pump pumps air in the fresh water storage tank.
Preferably, the vacuum degree in the fresh water circulation loop is 0-0.1 MPa.
Preferably, a flow control valve is arranged behind the seawater heater.
Preferably, a gas nozzle is arranged at the low-viscosity gas inlet of the hot seawater flow passage.
Preferably, the gas nozzles are arranged side by side, the parallel distance range is 20mm-60mm, and the diameter range of the nozzles is 2mm-8mm.
Preferably, the type of the hydrophobic and breathable film depends on the direct contact form of the film distillation device, and comprises a hydrophobic and breathable flat plate film, a hydrophobic and breathable hollow fiber film and a hydrophobic and breathable tubular film.
(III) beneficial effects
The invention provides a low-viscosity gas bubbling vacuum enhanced direct contact type membrane distillation sea water desalting device. Compared with the prior art, the method has the following beneficial effects:
According to the invention, the seawater desalination device effectively combines low-viscosity gas bubbling with vacuum reinforcement, so that the transmembrane permeation rate of water vapor is greatly improved;
Compared with air, the low-viscosity gas can carry more water vapor to enter the permeation side through the hydrophobic breathable film, so that the transmembrane transport rate of the water vapor is improved, and the vapor pressure difference and the macroscopic pressure difference have little effect on the water vapor permeating through the hydrophobic breathable film, but can greatly improve the rate of the low-viscosity gas permeating through the hydrophobic breathable film, so that the water vapor quantity permeating through the hydrophobic breathable film along with the low-viscosity gas is further greatly improved, and the sea water desalination efficiency is greatly improved.
Drawings
In order to more clearly illustrate the embodiments of the invention or the technical solutions in the prior art, the drawings that are required in the embodiments or the description of the prior art will be briefly described, it being obvious that the drawings in the following description are only some embodiments of the invention, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic diagram of a low-viscosity gas bubbling vacuum enhanced direct contact membrane distillation seawater desalination plant in example 1;
wherein, the membrane distillation device 1, the hydrophobic and breathable membrane 2, the hot sea water flow channel 3, the fresh water flow channel 4, the low-viscosity gas 5, the gas compressor 6, the low-viscosity gas storage tank 7, the gas blower 8, the flow control valve 9, the sea water heater 10, the sea water storage tank 11, the strong brine storage tank 12, the sea water circulating pump 13, the heat exchanger 14, the desalination circulating pump 15, the fresh water storage tank 16, the vacuum pump 17, the gas nozzle 18, the first flowmeter Q 1, the second flowmeter Q 2, the third flowmeter Q 3, the fourth flowmeter Q 4, the fifth flowmeter Q 5, the first thermometer T 1, the second thermometer T 2, the third thermometer T 3, the fourth thermometer T 4, the fifth thermometer T 5, the sixth thermometer T 6, the first pressure gauge P 1, the second pressure gauge P 2 and the third pressure gauge P 3.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention are clearly and completely described, and it is obvious that the described embodiments are some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
The embodiment of the application solves the problem that the water vapor transmembrane permeation rate of the membrane distillation sea water desalination device needs to be improved by providing the low-viscosity gas bubbling vacuum enhanced direct contact type membrane distillation sea water desalination device.
The technical scheme in the embodiment of the application aims to solve the technical problems, and the overall thought is as follows:
After the seawater under the atmospheric pressure is heated by a seawater heater, high-temperature seawater is taken as feed liquid to be pumped into a hot seawater flow channel by a seawater circulating pump, low-viscosity gas in a low-viscosity gas storage tank is blown into the feed liquid through a plurality of gas nozzles, and low-temperature fresh water with a certain vacuum degree is pumped into a fresh water flow channel by a fresh water circulating pump.
Due to the total pressure and vapor pressure differences, a portion of the water vapor and low-viscosity gas flows from the feed side membrane surface to the permeate side membrane surface, and the water vapor condenses when it encounters low-temperature fresh water, while the low-viscosity gas flows upward and is discharged from the membrane distillation apparatus. The fresh water tank, which is isolated from the outside atmosphere, is filled with water and a small amount of air, which is kept at a certain vacuum level by a vacuum pump, thereby creating a low pressure state for the fresh water flow. The first heat exchanger and the second heat exchanger respectively preheat seawater by utilizing strong brine and fresh water discharged by the membrane distillation device, and the preheated seawater enters the membrane distillation device after being reheated by a seawater heater. Meanwhile, the circulating fresh water is cooled before entering the membrane distillation device, low-viscosity gas which is discharged through the membrane distillation device and has vapor on the surface is compressed to the atmospheric pressure by the gas compressor and then cooled, and the vapor is separated from the low-viscosity gas and serves as a part of aquatic products. Necessary parameter monitoring meters (thermometers, manometers, flowmeters) are provided to test the temperature, pressure and flow of each circuit at a certain location, and data is also used for the flow control valve to maintain the set value of each parameter under given conditions.
The low-viscosity gas is used as bubbling gas, and a certain vacuum negative pressure is manufactured on the permeation side, so that the low-viscosity gas can optimize the raw water flow state, and can generate the water vapor portability strengthening effect of the transmembrane flow, and the strengthening effect of the bubbling process is further improved.
In order to better understand the above technical solutions, the following detailed description will refer to the accompanying drawings and specific embodiments.
Example 1:
As shown in FIG. 1, the invention provides a low-viscosity gas bubbling vacuum enhanced direct contact type membrane distillation seawater desalination device, which comprises a Membrane Distillation (MD) device 1, a low-viscosity gas circulation loop, a seawater circulation loop and a fresh water circulation loop;
The membrane distillation device 1 comprises a hot seawater flow passage 3, a fresh water flow passage 4 and a hydrophobic and breathable membrane 2, wherein the hot seawater flow passage 3 and the fresh water flow passage 4 are alternately arranged side by side, and the adjacent hot seawater flow passage 3 and the fresh water flow passage 4 are separated by the hydrophobic and breathable membrane 2;
the seawater circulation loop comprises a seawater heater 10, a seawater storage tank 11, a strong brine storage tank 12, a seawater circulation pump 13, a first heat exchanger 14a and a second heat exchanger 14b, wherein the seawater circulation loop is used for sequentially communicating the seawater storage tank 11, the first heat exchanger 14a, the seawater circulation pump 13, the second heat exchanger 14b, the seawater heater 10, a hot seawater runner 3, the first heat exchanger 14a and the strong brine storage tank 12 through pipelines;
the seawater is preheated by the seawater storage tank 11 through the first heat exchanger 14a and the second heat exchanger 14b and heated by the seawater heater 10 under the driving of the seawater circulating pump 13, then is input into the hot seawater flow channel 3, and the strong brine obtained by membrane distillation is injected into the strong brine storage tank 12 after heat exchange between the hot seawater flow channel 3 and the seawater just pumped out of the seawater storage tank 11 through the first heat exchanger 14 a;
The fresh water circulation loop comprises a fresh water circulation pump 15, a fresh water storage tank 16 and a vacuum pump 17, wherein the fresh water circulation loop sequentially communicates the fresh water storage tank 16, the fresh water runner 4, the fresh water circulation pump 15, the second heat exchanger 14b and the fresh water storage tank 16 through pipelines to form a loop, the fresh water storage tank 16 is provided with the vacuum pump 17, and the vacuum pump 17 keeps the fresh water storage tank 16 under a certain vacuum degree and provides negative pressure for the fresh water runner 4;
the fresh water in the fresh water storage tank 16 flows into the fresh water runner 4 through a pipeline, the fresh water in the fresh water runner 4 is pumped into the second heat exchanger 14b through the fresh water circulating pump 15, and after heat exchange is carried out between the fresh water and the seawater in the second heat exchanger 14b, the fresh water flows back to the fresh water storage tank 16;
the low-viscosity gas circulation loop comprises a gas compressor 6, a low-viscosity gas storage tank 7 and a gas fan 8, wherein the low-viscosity gas storage tank 7 is sequentially communicated with the gas fan 8 and the hot seawater flow channel 3 through a pipeline, a gas discharge pipe of the fresh water flow channel 4 is communicated with the gas compressor 6, and the gas compressor 6 is communicated with the low-viscosity gas storage tank 7 after being converged with the gas discharge pipe of the hot seawater flow channel 3 through a pipeline to form a loop;
the low-viscosity gas circulation loop is filled with low-viscosity gas 5, and the low-viscosity gas 5 is non-condensable gas with lower dynamic viscosity;
The low-viscosity gas 5 is input into the hot seawater flow channel 3 from the low-viscosity gas storage tank 7 through the gas blower 8, part of the low-viscosity gas passes through the hydrophobic and breathable film 2 to enter the fresh water flow channel 4, the rest of the low-viscosity gas remains in the hot seawater flow channel 3, the low-viscosity gas 5 exhausted from the fresh water flow channel 4 is pressurized by the gas compressor 6 and then is converged with the low-viscosity gas 5 exhausted from the hot seawater flow channel 3, and the low-viscosity gas returns to the low-viscosity gas storage tank 7.
As shown in fig. 1, a flow control valve 9 is arranged behind the seawater heater 10, and the flow control valve 9 controls the rate of seawater entering the hot seawater flow channel 3.
As shown in fig. 1, a gas nozzle 18 is disposed at the low-viscosity gas inlet of the hot seawater flow channel 3, and the low-viscosity gas 5 is injected into the hot seawater flow channel 3 through the gas nozzle 18.
As shown in FIG. 1, the gas nozzles 18 are arranged side by side with a side-by-side pitch ranging from 20mm to 60mm and a nozzle diameter ranging from 2mm to 8mm.
The fresh water storage tank 16 is filled with gas and fresh water, the gas-liquid volume ratio is 1% -20%, the fresh water storage tank is in a closed state, the vacuum pump 17 pumps air in the fresh water storage tank 16 and then forms fresh water with a certain vacuum degree on the fresh water circulation side, and the vacuum degree is 0-0.1 MPa.
The low-pressure low-viscosity gas 5 discharged from the fresh water flow passage 4 is pressurized to about 0.1MPa by the gas compressor 6.
The membrane distillation apparatus 1 is not limited to a flat plate type, and may be a tube type or the like.
The type of the hydrophobic and breathable membrane 2 depends on the direct contact form of the membrane distillation device 1, and can be a hydrophobic and breathable flat plate membrane, a hydrophobic and breathable hollow fiber membrane, a hydrophobic and breathable tubular membrane and other forms of membranes.
Various homemade and commercially available hydrophobic breathable films that meet the functional needs of the present application can be used in the present application.
The devices in the three circulation loops of the present application are connected by pipes, which may be various flexible or rigid pressure-resistant pipes, with flexible materials being preferred.
As shown in fig. 1, the seawater input pipe of the membrane distillation apparatus 1 is provided with a first flowmeter Q 1 for monitoring the seawater injection rate of the membrane distillation apparatus 1, the seawater discharge pipe of the membrane distillation apparatus 1 is provided with a second flowmeter Q 2 for monitoring the seawater discharge rate of the membrane distillation apparatus 1, the fresh water input pipe of the membrane distillation apparatus 1 is provided with a third flowmeter Q 3 for monitoring the fresh water injection rate of the membrane distillation apparatus 1, the fresh water discharge pipe of the membrane distillation apparatus 1 is provided with a fourth flowmeter Q 4 for monitoring the fresh water discharge rate of the membrane distillation apparatus 1, and the low-viscosity gas input pipe of the membrane distillation apparatus 1 is provided with a fifth flowmeter Q 5 for monitoring the low-viscosity gas injection rate of the membrane distillation apparatus 1.
As shown in fig. 1, a first thermometer T 1 is disposed behind the seawater heater 10, a second thermometer T 2 is disposed on the seawater outlet pipe of the membrane distillation apparatus 1, a third thermometer T 3 is disposed on the fresh water inlet pipe of the second heat exchanger 14b, a fourth thermometer T 4 is disposed on the fresh water outlet pipe of the second heat exchanger 14b, a fifth thermometer T 5 is disposed on the seawater inlet pipe of the second heat exchanger 14b, and a sixth thermometer T 6 is disposed on the seawater outlet pipe of the second heat exchanger 14 b.
As shown in fig. 1, the fresh water storage tank 16 is provided with a first pressure gauge P 1, the membrane distillation apparatus 1 is provided with a second pressure gauge P 2, and the low-viscosity gas storage tank 7 is provided with a third pressure gauge P 3.
The working principle of the application is as follows:
After the seawater under the atmospheric pressure is heated by the seawater heater 10, high-temperature seawater is pumped into the hot seawater flow channel 3 as feed liquid by the seawater circulating pump 13, the low-viscosity gas 5 in the low-viscosity gas storage tank 7 is blown into the feed liquid through the plurality of gas nozzles 18, and the low-temperature fresh water with a certain vacuum degree is pumped into the fresh water flow channel 4 by the fresh water circulating pump 15.
Due to the presence of the total pressure and vapor pressure difference, a part of the water vapor and the low-viscosity gas 5 flow from the feed-side membrane surface to the permeate-side membrane surface, and the water vapor condenses when it encounters low-temperature fresh water, and the low-viscosity gas 5 flows upward and is discharged from the membrane distillation apparatus 1. The fresh water tank 16, which is isolated from the outside atmosphere, is filled with water and a small amount of air, which is kept under a certain vacuum by the vacuum pump 17, creating a low pressure state for the fresh water flow. The first heat exchanger 14a and the second heat exchanger 14b preheat seawater by using strong brine and fresh water discharged from the membrane distillation apparatus 1, respectively, and the preheated seawater is reheated by the seawater heater 10 and then enters the membrane distillation apparatus 1. Meanwhile, the circulated fresh water is cooled before entering the membrane distillation apparatus 1, the low-viscosity gas discharged through the membrane distillation apparatus 1 and having vapor attached to the surface thereof is compressed to atmospheric pressure by the gas compressor 6 and then cooled, and the vapor is separated from the low-viscosity gas and serves as a part of the aquatic product. The necessary parameter monitoring meters (thermometer T 1-T6, manometer P 1-P3, flow meter Q 1-Q5) are set to test the temperature, pressure and flow rate of each circuit at a certain position shown in fig. 1, and the data is also used for the flow control valve 9 to maintain the set value of each parameter under given conditions.
Example 2:
based on example 1, the low-viscosity gas 5 was hydrogen gas, and table 1 was prepared by comparing with nitrogen gas, air, oxygen gas as bubbling gas and no bubbling gas, respectively.
TABLE 1 relationship between permeation flux and bubbling gas
As can be seen from table 1, the lower the dynamic viscosity of the bubbling gas, the greater the permeation flux of the membrane distillation apparatus, in the case where the feed-liquid side velocity, feed-liquid side temperature, feed-liquid side pressure, permeation side velocity, permeation side temperature, and permeation side pressure are all the same. Namely, the low-viscosity gas can carry more water vapor to permeate the hydrophobic breathable film to enter the permeation side, so that the transmembrane transport rate of the water vapor is greatly improved.
In addition, it can be seen from the comparison of the bubbling gas not used and the bubbling gas used in table 1:
the hydrogen with low dynamic viscosity is used as bubbling gas, and the permeation flux of the membrane distillation device is far greater than that of the membrane distillation device without bubbling gas under the condition that a certain vacuum degree is provided on the permeation side, so that the amplification reaches 108%.
Even if the bubbling gas is oxygen (the dynamic viscosity of oxygen is higher than that of air), the permeation flux of the membrane distillation device greatly exceeds that of the bubbling gas, and the amplification reaches 44% under the condition that a certain vacuum degree is provided on the permeation side.
However, in the case where the permeate side does not provide a vacuum degree, i.e., the permeate side pressure is 101325Pa, the feed side and the permeate side no longer have a macroscopic pressure difference, and even if hydrogen gas is used as the bubbling gas, the permeate flux of the membrane distillation apparatus is increased by only 4% relative to the permeate flux without the bubbling gas. The difference was significant compared to the 108% flux increase before the comparison.
In summary, only the bubbling gas adopts the low-viscosity gas 5 and is matched with the permeation side to provide negative pressure, so that the permeation flux of the membrane distillation device can be greatly improved, and the principle is as follows:
Compared with air, the low-viscosity gas 5 can carry more water vapor to enter the permeation side through the hydrophobic breathable film, so that the transmembrane transport rate of the water vapor is improved, the negative pressure provided by the permeation side enables the feed liquid side and the permeation side to generate a pressure difference, and the pressure difference has little effect on the water vapor to permeate the hydrophobic breathable film, but can greatly improve the rate of the low-viscosity gas to permeate the hydrophobic breathable film, so that the water vapor quantity along with the low-viscosity gas to permeate the hydrophobic breathable film is further improved, and the sea water desalination efficiency is greatly improved.
In summary, compared with the prior art, the invention has the following beneficial effects:
1. According to the embodiment of the invention, the seawater desalination device greatly improves the transmembrane permeation rate of water vapor by effectively combining low-viscosity gas bubbling with vacuum reinforcement;
Compared with air, the low-viscosity gas can carry more water vapor to enter the permeation side through the hydrophobic breathable film, so that the transmembrane transport rate of the water vapor is improved, and the vapor pressure difference and the macroscopic pressure difference have little effect on the water vapor permeating through the hydrophobic breathable film, but can greatly improve the rate of the low-viscosity gas permeating through the hydrophobic breathable film, so that the water vapor quantity permeating through the hydrophobic breathable film along with the low-viscosity gas is further improved, and the seawater desalination efficiency is greatly improved.
2. In the embodiment of the invention, the turbulence degree of hot seawater is obviously increased after the low-viscosity gas is introduced, the thermal boundary layers at the two sides of the membrane are reduced, the temperature polarization phenomenon is effectively weakened, and the increase of flux causes the surfaces at the two sides of the membrane to absorb or release more heat, so that the evaporation efficiency of the process is improved.
3. In the embodiment of the invention, the existence of the first heat exchanger and the second heat exchanger can fully recover the residual heat of the discharged strong brine and fresh water, preheat the seawater, greatly improve the effective heat consumption of the whole process and save energy, the strong brine generated in the membrane distillation process is stored by the strong brine storage tank, the strong brine can be further recycled, the resource utilization rate is increased, and the low-viscosity gas in the whole process can be recycled without unnecessary resource waste.
It is noted that relational terms such as first and second, and the like are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Moreover, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises an element.
The foregoing embodiments are merely for illustrating the technical solution of the present invention, but not for limiting the same, and although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those skilled in the art that modifications may be made to the technical solution described in the foregoing embodiments or equivalents may be substituted for parts of the technical features thereof, and that such modifications or substitutions do not depart from the spirit and scope of the technical solution of the embodiments of the present invention in essence.
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