CN108619913B - Air gap membrane distillation plant - Google Patents
Air gap membrane distillation plant Download PDFInfo
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- CN108619913B CN108619913B CN201710152985.3A CN201710152985A CN108619913B CN 108619913 B CN108619913 B CN 108619913B CN 201710152985 A CN201710152985 A CN 201710152985A CN 108619913 B CN108619913 B CN 108619913B
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
- B01D61/36—Pervaporation; Membrane distillation; Liquid permeation
- B01D61/364—Membrane distillation
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
- B01D61/36—Pervaporation; Membrane distillation; Liquid permeation
- B01D61/366—Apparatus therefor
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D63/00—Apparatus in general for separation processes using semi-permeable membranes
- B01D63/02—Hollow fibre modules
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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
- C02F1/02—Treatment of water, waste water, or sewage by heating
- C02F1/04—Treatment of water, waste water, or sewage by heating by distillation or evaporation
- C02F1/08—Thin film evaporation
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2311/00—Details relating to membrane separation process operations and control
- B01D2311/26—Further operations combined with membrane separation processes
- B01D2311/2669—Distillation
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
- Y02A20/00—Water conservation; Efficient water supply; Efficient water use
- Y02A20/124—Water desalination
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
- Y02A20/00—Water conservation; Efficient water supply; Efficient water use
- Y02A20/124—Water desalination
- Y02A20/131—Reverse-osmosis
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Abstract
The invention discloses an air gap membrane distillation device, which realizes the recycling of vapor phase change heat and improves the heat efficiency of a membrane distillation process. The air gap membrane distillation assembly designed in the invention has simple assembly process and is convenient for replacing the hollow fiber membrane in time. The device based on the membrane distillation assembly design effectively improves the integration level of a membrane distillation system, optimizes the operation flow, can carry out online cleaning and drying on the membrane distillation assembly, and reduces the operation difficulty. The membrane distillation device provided by the invention is used for treating different high-salinity wastewater, and the device is stable in operation, remarkable in desalination effect and good in produced water quality in the treatment process.
Description
Technical Field
The invention relates to a membrane distillation device, in particular to a device comprising an air gap membrane distillation assembly, which can effectively reduce the energy consumption of the membrane distillation process and improve the heat energy utilization efficiency of the process.
Background
With the annual increase of national and local environmental protection legislation standards, a large amount of salt-containing sewage generated in the production process of petrochemical enterprises cannot be directly discharged to rivers and oceans after being simply diluted and mixed. How to treat the sewage with high efficiency and then make most of the sewage capable of being recycled, and the solid-liquid separation of the concentrated solution obtained after the treatment has become a research hotspot in academia and industry. The prior technologies for carrying out advanced treatment on the salt-containing sewage include evaporation, reverse osmosis, forward osmosis, electrodialysis, membrane distillation and the like. Compared with the technologies such as evaporation, forward/reverse osmosis, electrodialysis and the like, the membrane distillation has the characteristics of higher desalination rate and water recovery rate, better water quality of produced water and the like. The technology separates two liquids with different temperatures by utilizing a microporous hydrophobic membrane (the two sides of the membrane are a raw water side and a water production side respectively), and only water vapor molecules (volatile components) can penetrate through the hydrophobic membrane from the high-temperature raw water side under the action of steam partial pressure difference generated by the solutions with different temperatures at the two sides of the membrane, and are collected at the water production side. However, the major problems that currently limit the industrialization of membrane distillation technology are that the energy consumption and cost of the process are too high, and the efficiency of heat energy utilization is low.
In the membrane distillation process, if the phase change heat released by water vapor condensation and the sensible heat contained after the water vapor is changed into liquid water can be fully utilized, the energy consumed by heating raw water can be reduced, and thus the multiple purposes of saving energy, improving the utilization efficiency of heat energy and reducing the cost of water production are achieved. The above idea can be effectively realized by developing a multi-effect membrane distillation module. The multi-effect membrane distillation subassembly adds heat recovery system in the membrane module inside promptly, utilizes vapor to heat cold feed liquid, can be with vapor condensation for liquid water and collected again when cold feed liquid temperature promotes. The essence of the multi-effect membrane distillation is innovation of air gap membrane distillation, and cold raw material liquid is used for replacing cooling water used in air gap membrane distillation, and the integration level of a membrane distillation system is improved on the basis. The conventional air gap membrane distillation has larger process mass transfer resistance due to the existence of an air gap layer, so that the water yield is lower than that of the other three types of membrane distillation. Similarly, multi-effect membrane distillation suffers from similar problems. The problem can be effectively solved by using a vacuum pump and a purge gas to strengthen the mass transfer process of the multi-effect membrane distillation so as to increase the water yield.
Chinese patent CN102107119A relates to a multi-effect membrane distillation device and a method, and the multi-effect membrane distillation device provided by the method consists of a heating evaporation zone, a main evaporation zone and a cooling evaporation zone. The water vapor generated by each stage of membrane module evaporation is condensed and cooled by the membrane module in sequence under the suction action of the vacuum pump, and finally discharged as produced water. The device can effectively utilize the phase change heat of the water vapor, but the system integration level is not high.
Chinese patent CN104261608A discloses a novel multi-effect membrane distillation assembly, which is shaped like two Y-shaped forks combined together at the lower ends, and is formed by interlacing and weaving hollow fiber membranes and hollow fiber condenser tubes which are not in contact with each other, and the design of the assembly obviously improves the heat energy utilization rate and the water generation ratio in the membrane distillation process. But the preparation process of the component is more complex; and when the surface of the membrane component is polluted to cause the reduction of the separation performance, the staggered hollow fiber membranes and the hollow fiber condenser pipes are difficult to clean and replace.
Compared with the above patent, the application relates to a membrane distillation device, realizes the recycle to vapor phase transition heat through the membrane distillation process, reduces because the energy that uses external heat exchanger to consume, improves the thermal efficiency of this process. Meanwhile, the integration level of the system is improved, the membrane module can be cleaned and dried on line, the operation difficulty can be reduced, the device is simplified, and the maintenance cost is reduced. The design of the membrane component also facilitates the timely replacement of the hollow fiber membrane in the component, and the assembly is convenient.
Disclosure of Invention
The invention aims to solve the problems of the existing multi-effect membrane distillation technology, optimize a multi-effect membrane distillation system, improve the heat energy utilization efficiency of the process, reduce the energy consumption of the multi-effect membrane distillation process and reduce the operation cost.
The invention also aims to overcome the problems of the existing multi-effect membrane distillation technology, and designs a membrane distillation assembly which is convenient for timely replacing the hollow fiber membrane in the assembly and is convenient for assembling the membrane distillation assembly.
The third purpose of the invention is to overcome the problems of the existing multi-effect membrane distillation technology, improve the integration level of the multi-effect membrane distillation system, realize the on-line cleaning and drying of the membrane distillation component, simplify the device and reduce the operation difficulty.
The purpose and the technical problem to be solved of the invention are realized by adopting the following technical scheme:
an air gap membrane distillation apparatus comprising: the membrane distillation device comprises a raw water tank 8, a membrane distillation component 18, a produced water collecting device, a cleaning tank 1 and a hot air blower 4;
the membrane distillation assembly 18 includes: a hollow metal coil 38, a hollow fiber membrane tow 39, and a membrane shell 40; the hollow fiber membrane tows 39 are located inside the hollow metal coil 38, the hollow metal coil 38 is located inside the membrane shell 40;
the lower end of the hollow metal coil 38 is a cold raw material liquid inlet 22, the upper end of the hollow metal coil 38 is a cold raw material liquid outlet 21, the top end of the hollow fiber membrane filament bundle 39 is a hot raw material liquid inlet 19, the bottom end of the hollow fiber membrane filament bundle 39 is a hot raw material liquid outlet 20, and the lower end of the side part of the membrane shell 40 is a water/steam production outlet 23;
a left water outlet of the raw water tank 8 is connected with a cold raw material liquid inlet 22 sequentially through a diaphragm pump I7, a liquid flowmeter 15 and a cartridge filter 16, and the cold raw material liquid inlet 22 is also connected with an outlet of the cleaning tank 1 and the hot air blower 4 respectively; a cold raw material liquid outlet 21 is respectively connected with a hot raw material liquid inlet 19 and an inlet of the cleaning box 1, a hot raw material liquid outlet 20 is respectively connected with an inlet of the cleaning box 1, a hot air outlet 30 and a left water inlet of the raw water box 8 through a three-way valve 29, and a produced water/steam outlet 23 is connected with an inlet of a produced water collecting device;
the produced water collecting device includes: a circulating water vacuum pump 36, a gas-water separator 35 and a produced water collecting tank 10; the inlet of the gas-water separator 35 is connected with the produced water/vapor outlet 23, the upper outlet of the gas-water separator 35 is connected with the circulating water vacuum pump 36, and the lower outlet of the gas-water separator 35 is connected with the inlet of the produced water collecting tank 10.
On the basis of the scheme, a valve I12 is arranged at a right water inlet of the raw water tank 8, an upper water outlet of the right side part of the raw water tank 8 is communicated with the atmosphere, and a lower water outlet of the right side part of the raw water tank 8 is communicated with the atmosphere through a valve II 9.
On the basis of the scheme, a temperature meter I33, a heat exchanger II 32 and a temperature meter II 31 are further arranged between the hot raw material liquid outlet 20 and the left water inlet of the raw water tank 8.
On the basis of the scheme, an outlet of the cleaning box 1 is connected with a cold raw material liquid inlet 22 sequentially through a diaphragm pump II 2, a valve IV 3, a valve VI 14, a liquid flow meter 15, a security filter 16 and a temperature meter III 17, a hot air blower 4 is connected with the cold raw material liquid inlet 22 sequentially through a valve V5, a valve VII 13, a security filter 16 and a temperature meter III 17, and a valve III 6, a valve VI 14 and a temperature meter III 17 are further arranged between a left side water outlet of the raw water box 8 and the cold raw material liquid inlet 22.
On the basis of the scheme, the cold raw material liquid outlet 21 is connected with the hot raw material liquid inlet 19 sequentially through a valve VIII 24, a thermometer IV 26, a heat exchanger I27 and a thermometer V28, and the valve VIII 24 and a valve IX 25 are sequentially arranged between the cold raw material liquid outlet 21 and the inlet of the cleaning box 1.
On the basis of the scheme, a temperature gauge VI 34 is arranged between the water/steam production outlet 23 and the inlet of the gas-water separator 35, and a valve X37 is arranged between the lower outlet of the gas-water separator 35 and the inlet of the water production collecting tank 10.
On the basis of the scheme, the cartridge filter 16 is used for filtering suspended matters in raw water.
On the basis of the scheme, the heat exchanger I27 and the heat exchanger II 32 are both coil type heat exchangers.
On the basis of the scheme, the hollow metal coil 38 is formed by rolling a hollow thin tube made of a titanium material, the hollow fiber membrane tows 39 are polypropylene hollow fiber hydrophobic membranes, two ends of each hollow fiber membrane tow 39 are sealed by epoxy resin, and the membrane shell 40 is made of organic glass.
Has the advantages that:
compared with the existing multi-effect membrane distillation system, the invention has the following advantages:
(1) the hollow fiber membrane in the membrane distillation assembly is convenient to replace and reassemble;
(2) the phase change heat of the water vapor can be fully utilized, and the heat efficiency of the membrane distillation process is improved, so that the overall energy consumption and the operating cost of the process are reduced;
(3) the membrane distillation component can be cleaned and dried on line;
(4) the system has high integration level, can save the floor area of the device and is simple and convenient to operate.
Drawings
The invention has the following drawings:
FIG. 1 is a schematic view of a vacuum-air gap membrane distillation apparatus.
FIG. 2 is a schematic view of an air gap membrane distillation assembly.
Fig. 3 is a perspective view of the assembled membrane distillation assembly.
Fig. 4 is a top view of an assembled membrane distillation assembly.
Fig. 5 is a structural view of a hollow metal coil.
Fig. 6 is a schematic view of a hollow fiber membrane tow.
Fig. 7 is a schematic view of a membrane shell.
The thick solid arrows in each figure represent the flow direction of the liquid and vapor.
In the figure, 1, a cleaning box 2, a diaphragm pump II 3, a valve IV 4, a hot air blower 5, a valve V6, a valve III 7, a diaphragm pump I8, a raw water box 9, a valve II 10, a produced water collecting tank 11, raw water 12, a valve I13, a valve VII 14, a valve VI 15, a liquid flow meter 16, a security filter 17, a thermometer III 18, a membrane distillation assembly 19, a hot raw material liquid inlet 20, a hot raw material liquid outlet 21, a cold raw material liquid outlet 22, a cold raw material liquid inlet 23, a produced water/steam outlet 24, a valve VIII 25, a valve IX 26, a thermometer IV 27, a heat exchanger I28, a thermometer V29, a three-way valve 30, a hot air outlet 31, a thermometer II 32, a heat exchanger II 33, a thermometer I34, a thermometer VI 35, a gas-water separator 36, a circulating water vacuum pump 37, Valve X38, hollow metal coil pipe 39, hollow fiber membrane tow 40, membrane shell.
Detailed Description
The present invention is described in further detail below with reference to figures 1-7.
FIG. 1 shows a schematic diagram of a vacuum-air gap membrane distillation apparatus. In fig. 1, raw water 11 is passed through a diaphragm pump i 7 and a liquid flow meter 15 in a raw water tank 8 to control the flow rate, and after suspended substances are removed by a cartridge filter 16, the raw water passes through a hollow metal coil 38 of a membrane distillation module 18 from bottom to top. The raw water is gradually heated in the hollow metal coil 38 by the phase change heat released by the condensation of the high temperature steam on the coil surface. The raw water heated to a certain temperature flows out of the hollow metal coil 38 of the membrane distillation assembly 18 and is further heated to a required temperature through the heat exchanger I27 before entering the microporous hollow fiber membrane. The heated raw water passes through the hollow fiber membrane from top to bottom. The water vapor permeates the micropores on the surface of the membrane, enters the shell side (air gap layer) of the membrane distillation assembly, and is condensed and liquefied on the surface of the hollow metal coil 38 with lower temperature. The condensed water and the water vapor which is not fully condensed flow out from the bottom outlet of the shell side of the membrane distillation assembly 18, enter the gas-water separator 35, and are finally collected in the water production collecting tank 10 through the suction effect of the circulating water vacuum pump 36. In the process that the raw water flows in the hollow fiber membrane, the temperature is gradually reduced, the raw water flows out of the membrane distillation assembly 18 and then is continuously cooled to the room temperature through heat exchange with the heat exchanger II 32, and finally the raw water flows back to the raw water tank 8. The raw water level in the raw water tank 8 is controlled by appropriate water replenishment and drainage. When the device runs for a period of time and the membrane distillation assembly 18 needs to be cleaned, the corresponding valve is opened, and the membrane pump II 2 connected with the cleaning box 1 is opened, so that the cleaning liquid flows through the liquid flow meter 15 and the cartridge filter 16 and then enters the membrane distillation assembly 18. After cleaning the hollow metal coil 38 and the hollow fiber membranes, the cleaning fluid flows back to the cleaning tank 1. After the membrane distillation module 18 is cleaned, it needs to be dried to restore the hydrophobic properties of the hollow fiber membranes. The hot air provided by the hot air blower 4 in the system can dry the hollow metal coil 38 and the hollow fiber membrane in the system pipeline and membrane distillation assembly 18 on line, and the hot air is discharged from the hot air outlet 30 positioned below the membrane distillation assembly 18.
Figure 2 shows a schematic diagram of a membrane distillation assembly according to the invention. In fig. 2, the membrane distillation module 18 has a total of 5 openings, namely, a cold feed liquid inlet 22, a cold feed liquid outlet 21, a hot feed liquid inlet 19, a hot feed liquid outlet 20, and a water/water vapor production outlet 23.
FIG. 3 shows a perspective view of an assembled membrane distillation assembly of the present invention; FIG. 4 is a top view of an assembled membrane distillation assembly; FIG. 5 is a view of the structure of a hollow metal coil; FIG. 6 is a schematic view of a hollow fiber membrane tow; fig. 7 is a schematic view of a membrane shell.
The invention will now be further described with reference to the accompanying figures 1 to 7 and specific examples.
The operation process comprises the following steps:
(1) checking to ensure that all the parts are connected correctly and tightly without leakage; and closing the valves IV 3, V5, VII 13 and IX 25 of the cleaning and drying pipelines.
(2) And opening a valve I12 at the raw water inlet, closing a valve II 9, adding the raw water amount in the raw water tank 8 to 70L, and then closing the valve I12.
(3) The valve III 6, the valve VI 14, the valve VIII 24 and the valve X37 are opened to communicate the three-way valve 29 with the raw water tank 8. The diaphragm pump I7 is started, and the raw water in the raw water tank 8 is controlled in flow rate by the liquid flowmeter 15. The raw water is filtered by the cartridge filter 16 before entering the membrane distillation assembly 18, and the filter element aperture of the cartridge filter 16 is 0.5 μm. Temperature gauge iii 17 is used to monitor the temperature of the raw water before it enters the hollow metal coil 38 of the membrane distillation module 18. The temperature gauge IV 26 and the temperature gauge V28 are respectively used for monitoring the temperature of the raw water after passing through the hollow metal coil 38 and the temperature of the raw water before entering the microporous hollow fiber membrane of the membrane distillation assembly 18 after the heat exchange of the raw water is carried out through the heat exchanger I27. The heat exchanger I27 is a coil heat exchanger. The temperature table II 31 is used for monitoring the temperature of the raw water after flowing out of the membrane distillation assembly 18. The temperature meter I33 is used for measuring the temperature of raw water which flows back to the raw water tank 8 after being cooled by the heat exchanger II 32. The hollow metal coil 38 of the membrane distillation assembly 18 is made by rolling a hollow thin tube of titanium material with an inner diameter of 2 mm and an outer diameter of 4 mm. The cross-sectional outer diameter of the hollow metal coil 38 is 54 mm and the number of turns is 95. The distillation membrane module 18 uses a polypropylene (PP) hollow fiber hydrophobic membrane, the inner diameter is 1.8 mm, the outer diameter is 2.7 mm, the porosity is 73.9%, the average pore diameter is 0.238 μm, and the contact angle of the membrane surface is 148 °. The two ends of the hollow fiber membrane are sealed with epoxy resin, and the excess parts of the two ends of the cured membrane are cut off to prepare a hollow fiber membrane tow 39 for standby. The membrane shell 40 of the membrane distillation assembly 18 is made of plexiglass and has a length of 400mm, an inner diameter of 60 mm and a thickness of 4 mm.The hollow fiber membrane tows 39, the hollow metal coil 38 and the membrane shell 40 are assembled to obtain the membrane distillation component 18, and the total area of the inner membrane of the membrane distillation component 18 is 0.2 m2. In order to avoid heat loss, the membrane distillation assembly 18 and the pipeline are wrapped by heat insulation materials. And the raw water flows out of the membrane distillation assembly 18 and then enters the heat exchanger II 32 for heat exchange and temperature reduction. The heat exchanger II 32 is a coil type heat exchanger. And finally the raw water flows back to the raw water tank 8. After the system operates stably for a period of time, the circulating water vacuum pump 36 is turned on. The produced water and a small part of the uncondensed water vapor firstly enter the gas-water separator 35 under the pumping action of the pump and then are collected by the produced water collecting tank 10. The temperature table VI 34 is used for monitoring the temperature of the membrane distillation produced water. After the system produces water for a period of time, when finding that the liquid level in the raw water tank 8 descends, open valve I12 and carry out water replenishing to the raw water tank 8.
(4) The membrane distillation unit was shut down. Heating of the raw water by the heat exchanger i 27 was stopped. The membrane pump i 7 is closed as well as valve iii 6, valve vi 14 and valve viii 24. When the membrane distillation module 18 is no longer producing water, the circulating water vacuum pump 36 and valve x 37 are turned off.
(5) And (5) cleaning the membrane distillation device. First, a hydrochloric acid solution having a pH of about 2 is prepared in a cleaning tank 1. The valves IX 25, VI 14 and VIII 24 were opened, the other valves remaining closed. The three-way valve 29 is turned to the side communicating with the cleaning tank 1. And opening the diaphragm pump II 2, cleaning the system by using acid liquor for 30 minutes, and then draining the acid liquor in the cleaning tank 1. And (3) preparing sodium hydroxide alkaline liquor with the pH value of about 11.5, cleaning the system for 30 minutes, and draining the alkaline liquor in the cleaning tank 1. And then, washing the system by using clear water until the pH value of the cleaning solution is recovered to about 7.
(6) And (5) drying the membrane distillation device. The valves V5, VII 13 and VIII 24 are opened, and the other valves are kept closed. The three-way valve 29 is screwed to the hot air outlet 30 side. And (4) opening the hot air blower 4, and blowing hot air to dry the system for about 15 minutes.
The first embodiment is as follows:
the multi-effect membrane distillation system has a wide application prospect, and can greatly reduce the water production cost and simplify the operation flow on the basis of the traditional membrane distillation process. In areas with scarce fresh water resources but abundant bitter water, the technology can be used for preparing drinking water and water for life and production. In addition, the multi-effect membrane distillation system can also be used for treating high-salinity wastewater generated in the petroleum and chemical industry, and the economical efficiency of the process can be obviously improved in a chemical plant capable of providing waste heat.
The prepared conductivity is 5000 mu S cm-1The NaCl salt solution (2) as raw water, the flow rate of which is controlled to 100 L.h by the liquid flowmeter (15)-1The vacuum degree provided by the circulating water vacuum pump 36 is-0.09 MPa. After the device stably operates, the temperature of raw water before entering the membrane distillation assembly 18 is read by a temperature meter III 17 to be 30 ℃. The temperature of the raw water flowing out of the hollow metal coil 38 of the membrane distillation assembly 18 is read by the temperature gauge IV 26 to be about 60 ℃. After the raw water is heated by the heat exchanger I27, the temperature of the raw water is controlled at 80 ℃. After the raw water flows out of the membrane distillation module 18 through the hollow fiber membranes, the temperature is reduced to 45 ℃. After further cooling by the heat exchanger II 32, the temperature of the raw water becomes about 31 ℃, and the raw water flows back to the raw water tank 8. The stable membrane flux obtained by the experiment is 32 L.m-2·h-1The conductivity of the produced water is kept at 20 mu S cm-1Hereinafter, the salt rejection is more than 99.6%, and the water yield ratio is about 3.1. After the device is stably operated for one week, the membrane flux is reduced to 28 L.m-2·h-1The conductivity of the produced water can still be kept at 20 mu S cm-1Hereinafter, the salt rejection was always higher than 99%.
Note that:
(1) after the multi-effect membrane distillation device is operated for a long time, when the conductivity of the produced water is found to be higher than 100 mu S-cm-1Or when the membrane flux significantly declines to 50% or more of the steady value, the apparatus needs to be cleaned, and the cleaning process refers to the operation process (5) in the embodiment. And (3) drying the device in time after cleaning to recover the hydrophobicity of the hollow fiber membrane, wherein the drying process refers to the step (6) of the operation process in the embodiment.
(2) After the membrane distillation device operates for a period of time, when the liquid level in the raw water tank 8 is found to be reduced, the valve I12 is opened to supplement water to the raw water tank 8.
(3) Attention is paid to the heat preservation of the membrane distillation assembly 18 and the pipeline, and heat loss is reduced.
(4) The cartridge of the cartridge filter 16 needs to be replaced at intervals.
Example two:
the conductivity of the solution used is 26000 mu S cm-1The natural gas production wastewater is used as raw water, and the flow rate of the raw water is controlled to be 100 L.h by a liquid flowmeter 15-1The vacuum degree provided by the circulating water vacuum pump 36 is-0.09 MPa. After the device stably operates, the temperature of raw water before entering the membrane distillation assembly 18 is read by a temperature meter III 17 to be 30 ℃. The temperature of the raw water flowing out of the hollow metal coil 38 of the membrane distillation assembly 18 is read by the temperature gauge IV 26 to be about 62 ℃. After the raw water is heated by the heat exchanger I27, the temperature of the raw water is controlled at 80 ℃. After the raw water flows out of the membrane distillation module 18 through the hollow fiber membranes, the temperature is reduced to 50 ℃. After further cooling by the heat exchanger II 32, the temperature of the raw water becomes about 30 ℃, and the raw water flows back to the raw water tank 8. The stable membrane flux obtained by the experiment is 27 L.m-2·h-1The conductivity of the produced water is maintained at 100-200 mu S-cm-1The salt rejection rate is about 99.5%, and the water generation ratio is about 2.5.
Example three:
using a conductivity of 110 mS cm-1The alkaline residue wastewater is used as raw water, and the flow rate of the raw water is controlled to be 100 L.h by a liquid flow meter 15-1The vacuum degree provided by the circulating water vacuum pump 36 is-0.09 MPa. After the device stably operates, the temperature of raw water before entering the membrane distillation assembly 18 is read by a temperature meter III 17 to be 30 ℃. The temperature of the raw water flowing out of the hollow metal coil 38 of the membrane distillation assembly 18 is read by the temperature gauge iv 26 to be about 61 ℃. After the raw water is heated by the heat exchanger I27, the temperature of the raw water is controlled at 80 ℃. After the raw water flows out of the membrane distillation module 18 through the hollow fiber membranes, the temperature drops to 52 ℃. After further cooling by the heat exchanger II 32, the temperature of the raw water becomes about 30 ℃, and the raw water flows back to the raw water tank 8. The stable membrane flux obtained by the experiment is 22 L.m-2·h-1The conductivity of the produced water is maintained at 100 mu S cm-1About, the salt rejection was 99.9%, and the fresh water ratio was about 2.1.
Example four:
the conductivity of the used solution is 59000 mu S cm-1The pretreated desulfurization waste water was used as raw water, and the flow rate of the raw water was controlled to 100 L.h by the liquid flowmeter 15-1The vacuum degree provided by the circulating water vacuum pump 36 is-0.09 MPa. After the device stably operates, the temperature of raw water before entering the membrane distillation assembly 18 is read by a temperature meter III 17 to be 30 ℃. The temperature of the raw water flowing out of the hollow metal coil 38 of the membrane distillation assembly 18 is read by the temperature gauge iv 26 to be about 59 ℃. After the raw water is heated by the heat exchanger I27, the temperature of the raw water is controlled at 80 ℃. After the raw water flows out of the membrane module distillation member 18 through the hollow fiber membrane, the temperature is reduced to 50 ℃. After further cooling by the heat exchanger II 32, the temperature of the raw water becomes about 30 ℃, and the raw water flows back to the raw water tank 8. The stable membrane flux obtained by the experiment is 25 L.m-2·h-1The conductivity of the produced water is kept at 120 mu S cm-1About, the salt rejection is above 99.5%, and the water yield ratio is about 2.3.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not intended to limit the scope of the present invention, so that all equivalent variations made by using the contents of the specification and drawings are included in the scope of the present invention.
Those not described in detail in this specification are within the skill of the art.
Claims (7)
1. An air gap membrane distillation apparatus, characterized in that: the method comprises the following steps: the device comprises a raw water tank (8), a membrane distillation assembly (18), a produced water collecting device, a cleaning tank (1) and a hot air blower (4);
the membrane distillation assembly (18) comprises: a hollow metal coil (38), a hollow fiber membrane tow (39) and a membrane shell (40); the hollow fiber membrane tows (39) are located inside a hollow metal coil (38), the hollow metal coil (38) being located inside a membrane shell (40);
the lower end of the hollow metal coil pipe (38) is a cold raw material liquid inlet (22), the upper end of the hollow metal coil pipe (38) is a cold raw material liquid outlet (21), the top end of the hollow fiber membrane filament bundle (39) is a hot raw material liquid inlet (19), the bottom end of the hollow fiber membrane filament bundle (39) is a hot raw material liquid outlet (20), and the lower end of the side part of the membrane shell (40) is a water/steam outlet (23);
a left water outlet of the raw water tank (8) is connected with a cold raw material liquid inlet (22) sequentially through a diaphragm pump I (7), a liquid flowmeter (15) and a security filter (16), and the cold raw material liquid inlet (22) is also connected with an outlet of the cleaning tank (1) and the hot air blower (4) respectively; a cold raw material liquid outlet (21) is respectively connected with a hot raw material liquid inlet (19) and an inlet of the cleaning box (1), a hot raw material liquid outlet (20) is respectively connected with an inlet of the cleaning box (1), a hot air outlet (30) and a left water inlet of the raw water box (8) through a three-way valve (29), and a produced water/steam outlet (23) is connected with an inlet of a produced water collecting device;
the produced water collecting device includes: a circulating water vacuum pump (36), a gas-water separator (35) and a produced water collecting tank (10); an inlet of the gas-water separator (35) is connected with a water/steam production outlet (23), an outlet at the upper end of the gas-water separator (35) is connected with a circulating water vacuum pump (36), and an outlet at the lower end of the gas-water separator (35) is connected with an inlet of a water production collection tank (10);
a temperature meter I (33), a heat exchanger II (32) and a temperature meter II (31) are also arranged between the hot raw material liquid outlet (20) and the left water inlet of the raw water tank (8);
an outlet of the cleaning box (1) is connected with a cold raw material liquid inlet (22) sequentially through a diaphragm pump II (2), a valve IV (3), a valve VI (14), a liquid flow meter (15), a security filter (16) and a thermometer III (17), a hot air blower (4) is connected with the cold raw material liquid inlet (22) sequentially through a valve V (5), a valve VII (13), the security filter (16) and the thermometer III (17), and a valve III (6), a valve VI (14) and a thermometer III (17) are further arranged between a left side water outlet of the raw water box (8) and the cold raw material liquid inlet (22);
and the cold raw material liquid outlet (21) is connected with the hot raw material liquid inlet (19) sequentially through a valve VIII (24), a thermometer IV (26), a heat exchanger I (27) and a thermometer V (28), and the valve VIII (24) and a valve IX (25) are sequentially arranged between the cold raw material liquid outlet (21) and the inlet of the cleaning box (1).
2. The air gap membrane distillation apparatus of claim 1, wherein: a valve I (12) is arranged at a right water inlet of the raw water tank (8), a water outlet in the right side of the raw water tank (8) is communicated with the atmosphere, and a water outlet in the right side of the raw water tank (8) is communicated with the atmosphere through a valve II (9).
3. The air gap membrane distillation apparatus of claim 1, wherein: a temperature gauge VI (34) is arranged between the water/steam production outlet (23) and the inlet of the gas-water separator (35), and a valve X (37) is arranged between the outlet at the lower end of the gas-water separator (35) and the inlet of the water production collecting tank (10).
4. The air gap membrane distillation apparatus of claim 1, wherein: the cartridge filter (16) is used for filtering suspended matters in raw water.
5. The air gap membrane distillation apparatus of claim 1, wherein: the heat exchanger I (27) is a coil type heat exchanger.
6. The air gap membrane distillation apparatus of claim 1, wherein: and the heat exchanger II (32) is a coil type heat exchanger.
7. The air gap membrane distillation apparatus of claim 1, wherein: the hollow metal coil pipe (38) is formed by rolling a titanium hollow thin pipe, the hollow fiber membrane tows (39) are polypropylene hollow fiber hydrophobic membranes, two ends of each hollow fiber membrane tow (39) are sealed by epoxy resin, and the membrane shell (40) is made of organic glass.
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