JP2012130874A - Fresh water generator, and fresh water generation system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fresh water generator by membrane distillation constituted of a vaporization part in which a hydrophobic porous membrane is arranged and a condensation part including a cooling surface, wherein leaked treated water is not mixed with condensation water even though the leakage of the treated water in the vaporization part occurs, and there is no need to arrange the leakage detecting means.SOLUTION: The fresh water generator has a liquid phase part in which the treated water flows, a gas phase part 1, the vaporization part constituted of the hydrophobic porous membrane, the condensation part including the cooling surface and a gas phase part 2 contacting the cooling surface, and a liquid sending means for sending the treated water to the liquid phase part. The gas phase part 1 and the gas phase part 2 are coupled so as to be able to ventilate with each other, the fresh water in the liquid is taken out as vapor from the vaporization surface where the hydrophobic porous membrane contacts the gas phase part 1, and is recovered as water by being cooled and condensed by the cooling surface. The fresh water generator is characterized in that the vaporization part and the condensation part are arranged in independent areas.

Description

  The present invention relates to a fresh water generator that extracts fresh water by membrane distillation from treated water that is not suitable for drinking, such as seawater and sewage, and a fresh water generation system using the fresh water generator.

  In recent years, water (fresh water) that can be used is separated and recovered from seawater, used domestic wastewater, well water containing toxic components such as arsenic, etc. due to the necessity of securing water resources necessary for daily life. Water production technology is being studied.

  Freshwater technology that separates and recovers fresh water that does not contain salt or toxic components from seawater, etc., is an evaporation method that cools and condenses and recovers water vapor generated from water, and reverse osmosis that passes water but does not pass salt The membrane is largely classified into a reverse osmosis method in which water is separated and recovered by applying a high pressure higher than the osmotic pressure to the membrane. As the evaporation method, in addition to the flash method, the effect can method, etc., the seawater is heated and brought into contact with one surface of a hydrophobic porous membrane that does not permeate salt but permeates water vapor, and permeates the membrane. A membrane distillation method is known in which is recovered from the other surface.

  The reverse osmosis method has an advantage that a relatively small facility scale can be obtained by using a module that does not require heat and accommodates a membrane having a large area. However, the installation costs of the high-pressure pump and the maintenance costs such as the power to operate it and the cleaning of the membrane have been pointed out as problems. On the other hand, it has been pointed out as a problem that the evaporation method requires a large capacity facility and a heat source for generating steam.

  Like the reverse osmosis method, the membrane distillation method can be made compact by modularizing the hydrophobic porous membrane, and the problem of increasing the size of the facility, which has been pointed out as a problem of the evaporation method, has been alleviated. Yes. Furthermore, since relatively low-temperature water, for example, water at 80 ° C. or lower, can be treated as compared with other evaporation methods, it is easy to clear the problem of the heat source and it is easy to reduce the operating cost by using sunlight.

  Then, the examination is performed actively, for example, in patent document 1, "The method of purifying the liquid which is the objective which produces desalinated water from seawater or blackish water or process water especially by membrane distillation" is. Are listed. Moreover, in patent document 2, the seawater desalination apparatus by the membrane distillation using sunlight as a heat source is described.

  In the fresh water generators described in these prior art documents, an evaporation section including a hydrophobic filtration membrane and a condensation section having a cooling means are provided via a gas phase section. And the water in the treated water (liquid containing water such as seawater) in contact with one surface of the hydrophobic filtration membrane permeates the membrane and is released from the other surface (evaporation surface) to the gas phase as water vapor, This water vapor is cooled by the cooling means of the condensing part, condenses and collected as fresh water.

JP 2003-51001 A (Claim 1) Japanese Patent Laid-Open No. 9-1143 (Claim 1, FIG. 1)

  The hydrophobic filtration membrane in the evaporation section ideally transmits only water vapor and does not transmit salts and the like in the treated water. However, in reality, the treated water may leak from the membrane. In particular, when seawater or wastewater, which is treated water, contains detergents, the hydrophobicity of the membrane decreases due to its surface active effect, and the treated water may permeate the membrane and enter the condensed water. is there. Since condensed water mixed with treated water can no longer be used as fresh water, for example, a sensor described in Japanese Patent No. 3223231 is provided to detect leakage of treated water, and if it leaks, measures such as interrupting the collection of condensed water are required. Met.

  The present invention is a fresh water generation apparatus by membrane distillation comprising a condensing part including an evaporation part provided with a hydrophobic porous membrane and a cooling means, and even if leakage of treated water occurs in the evaporation part, the leaked treatment It is an object of the present invention to provide a fresh water generating device in which water is not mixed into condensed water, and therefore it is not necessary to provide leakage detection means such as the sensor.

  The present inventor has found that by providing the evaporating part and the condensing part in independent regions, mixing of the condensed and recovered water and the liquid leaking from the evaporating part can be prevented, and the present invention has been achieved. That is, the above-described problem is achieved by the configuration described below.

The invention described in claim 1
An evaporation part comprising a liquid phase part through which treated water flows, a gas phase part 1 and a hydrophobic porous membrane separating the liquid phase part and the gas phase part 1;
A condensing part including a cooling surface and a gas phase part 2 in contact with the cooling surface; and
Having liquid feeding means for feeding treated water to the liquid phase part;
The gas phase part 1 and the gas phase part 2 are connected to each other so as to be able to vent.
The water in the treated water is a fresh water generating device in which the hydrophobic porous membrane is discharged as water vapor from an evaporation surface in contact with the gas phase portion 1, cooled by the cooling surface, condensed, and recovered as water,
The water producing apparatus is characterized in that the evaporating part and the condensing part are provided in independent regions so that the water condensed and recovered and the liquid leaking from the evaporating part are not mixed.

  In this fresh water generator, since the evaporating part and the condensing part are provided in an independent region, even if treated water leaks from the evaporating part, it does not mix with the recovered condensed water. Therefore, there is no need to provide means such as a sensor for detecting leakage of treated water, and the recovery of condensed water is not interrupted by the leakage of treated water, and more stable operation can be performed.

  Furthermore, since the condensation part is independent of the evaporation part, it is easy to perform operations such as washing on the condensation part and the evaporation part independently. For example, even if leakage of treated water from the evaporation section occurs, the evaporation section can be easily washed and dried with alcohol, etc., and this washing easily restores the hydrophobicity of the hydrophobic porous membrane. Can be restored to the original state without water leakage.

  According to a second aspect of the present invention, the evaporating part bundles and stores a hydrophobic porous membrane formed in a hollow fiber shape, the treated water passes through the hollow fiber (inner lumen), and the surface of the hollow fiber is the evaporation surface. The fresh water generator according to claim 1, wherein

  It is possible to constitute the evaporation part of the fresh water generator of the present invention by a sheet-like hydrophobic porous membrane. In this case, the hydrophobic porous film on the sheet is overlaid and the cooling surface of the condensation part is provided opposite to the evaporation surface. In this structure, however, the condensation part and the evaporation part are structurally independent. It tends to be difficult. On the other hand, when the evaporation part is constituted by a module in which a hydrophobic porous membrane formed in a hollow fiber shape is bundled and stored, it is easy to make the condensation part and the evaporation part independent. In this case, it is possible to modularize the same volume with a high film filling rate, and it is preferable because the installation area of the apparatus with respect to the evaporation surface of the same area can be easily reduced.

  Further, as described later, the ratio of the area of the cooling surface to the evaporation surface is preferably large, but in the configuration in which the cooling surface of the condensing part is provided facing the evaporation surface, the ratio of the area of the cooling surface to the evaporation surface is It is about 1, and it is difficult to increase this. On the other hand, when the evaporation porous part is formed by bundling a hydrophobic porous membrane formed in a hollow fiber shape, and the condensation part is formed by bundling a hollow fiber tube, the above-mentioned area ratio and layout can be freely designed. Is preferable.

  The invention described in claim 3 is the fresh water generator according to claim 1 or 2, wherein the area of the cooling surface is 1.2 to 6 times the area of the evaporation surface. .

A membrane distillation apparatus having an evaporation part and a condensation part as described above is an excellent water production method with little initial investment. In particular, when sunlight is used as a heating means for the treated water, it is said that the operating cost is low, but the permeation flux per unit time (kg / m ² ···), which is an indicator of the rate of fresh water generation. (hr, unit area, permeation amount per unit time) was not sufficient, and it was pointed out that it was not sufficient in terms of cost for fresh water.

  However, the permeation flux per unit area and unit time is affected by the ratio of the area of the cooling surface (condensation surface) that cools and condenses water vapor in the condensation part to the area of the evaporation surface, and the area of the condensation surface is the evaporation surface. When the area is significantly larger than the area, the permeation flux per unit area and unit time is improved. In particular, when the area of the cooling surface is 1.2 to 6 times the area of the evaporation surface, it is preferable because an excellent permeation flux can be obtained and the enlargement of the facility can be suppressed.

  As described above, the evaporation part and the condensation part are provided in independent regions, the evaporation part is configured by bundling a hydrophobic porous membrane formed in a hollow fiber shape, and the condensation part is formed by bundling a hollow fiber tube. When comprised, it is easy to adjust the ratio between the condensation area and the evaporation area, and it is preferable because it is easy to produce a high-performance and compact fresh water generator.

  Invention of Claim 4 WHEREIN: The said hydrophobic porous membrane is the extending | stretching porous membrane of polytetrafluoroethylene, The fresh water generation of any one of Claim 1 thru | or 3 characterized by the above-mentioned. Device.

  The hydrophobic porous membrane is a membrane made of a hydrophobic material that repels water and has fine through holes (pores) for allowing water vapor to permeate. The type of the hydrophobic material and the pore diameter of the pores are selected so as to transmit water vapor that is a gas but not treated water that is a liquid (a liquid containing water). That is, from the viewpoint of easy water vapor transmission, it is preferable that the pore diameter is large. However, if the pore diameter is large, permeation (leakage) of the treated water is likely to occur. Therefore, the optimum pore diameter is selected in consideration of both.

  Further, from the viewpoint of easy permeation of water vapor, the ratio of the volume of pores to the volume of the membrane, that is, the porosity is preferably high, and the membrane is preferably thin. However, since the membrane is required to have sufficient mechanical strength to withstand the pressure received from the treated water during operation, the optimum porosity and thickness of the membrane are selected in consideration of both.

  The material of the hydrophobic porous membrane is polytetrafluoroethylene (tetrafluoroethylene resin, hereinafter referred to as PTFE), tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene / hexafluoropropylene copolymer. Polymer (FEP), tetrafluoroethylene / ethylene copolymer (ETFE), polyvinylidene fluoride (PVDF), polychlorotrifluoroethylene (PCTFE), chlorotrifluoroethylene / ethylene copolymer (ECTFE), etc., and mixtures thereof Or hydrophobic resin, such as modified resin, can be mentioned. In the present invention, PTFE (stretching method) and PVDF (solvent phase transition method) are suitable as main materials in that a porous film can be easily obtained. Among them, PTFE is hydrophobic, mechanical strength, chemical It is suitable because it can easily produce a stretched porous membrane of PTFE having a uniform pore diameter by a method (stretching method) of stretching a fusion product of PTFE fine particles while being excellent in mechanical durability (chemical resistance). .

  The invention according to claim 5 is characterized in that the liquid feeding means has means for heating the treated water by the condensation heat of water vapor generated in the condensation part. The fresh water generator described in the item.

  In order to increase the production rate of fresh water, that is, the permeation flux per unit area and unit time, it is preferable to heat the treated water before being supplied to the evaporation section. The heating means is provided. On the other hand, in the condensation part, condensation heat of water vapor is generated. By using this condensation heat as a heating means for treated water, it leads to effective use of heat (energy), and other heating means (for example, a solar heating device) ) Is preferable. As a method of heating by condensation heat of water vapor, a method of using treated water before treatment as a refrigerant for cooling the condensation surface in the condensation part can be mentioned. According to this method, heat exchange is performed on the condensation surface, the condensation surface is cooled by the low-temperature treated water, and the treated water is heated by the condensation heat.

  Invention of Claim 6 is sunlight which heats the water preparation apparatus of any one of Claim 1 thru | or 4, and the treated water sent to the said liquid feeding means with the heat | fever by sunlight It is a desalination system characterized by having a heating device.

  This fresh water generation system is characterized in that a solar heating device is used as a heating means (heating means provided in the liquid feeding means) of the treated water in the fresh water generator of the present invention. This system is expected to slightly increase the installation cost related to the solar heating device, but it has a significant effect on lowering the cost for heating at the time of fresh water generation, enabling a reduction in operating cost and reducing the overall processing cost. It is preferable because

  The fresh water generator of the present invention is a fresh water generator by membrane distillation consisting of an evaporation part provided with a hydrophobic porous membrane and a condensation part including a cooling surface, but even if leakage of treated water occurs in the evaporation part The leaked treated water is not mixed into the condensed water. Therefore, it is not necessary to provide a leakage detection means, and operation stoppage due to leakage does not occur. The fresh water generation system of the present invention that combines the fresh water generator and the solar heating device can reduce the operating cost together with the above-described features.

It is a partially cutaway sectional view showing typically an example of the fresh water generator of the present invention. It is a cross-sectional view which shows the other example of the fresh water generator of this invention typically. It is a figure which shows typically the other example of the fresh water generator of this invention. It is a figure which shows typically the other example of the fresh water generator of this invention. It is a graph which shows the permeation | transmission flux obtained by the reference example 1, and the relationship of a condensation area / evaporation area. It is a figure which shows typically the module of the fresh water generator used in the Example. It is a graph which shows the salinity change of the water collect | recovered from the evaporation part and the condensation part at the time of performing film | membrane distillation in an Example.

  Next, the form for implementing this invention is demonstrated concretely. Note that the present invention is not limited to this form, and can be changed to other forms as long as the gist of the present invention is not impaired.

  The treated water to be treated by the fresh water generator of the present invention includes minerals and salts that exceed the limit of intake or use, heavy metals such as arsenic, bacteria such as algae and Escherichia coli, viruses and other harmful and harmful components to the human body. Examples include wells, rivers, water intake from the sea, domestic wastewater, etc. that are not suitable for drinking and domestic water. For example, the fresh water generator of the present invention can be applied to seawater desalination, purification of arsenic-contaminated well water in Bangladesh, well water containing salt in Egyptian deserts, drinking water, and the like. As the liquid feeding means for supplying the treated water to the liquid phase part, the same means as the liquid feeding means in the conventional membrane distillation, for example, a pump can be used. As the heating means usually provided in the liquid feeding means, the same means as the heating means in the conventional membrane distillation can be used, but it is preferable to combine the solar heating device as described above.

  The stretched porous body made of PTFE suitably used as the hydrophobic porous membrane used in the present invention can be obtained, for example, as follows.

  Add 20-30 parts by weight of kerosene as an auxiliary agent to PTFE fine powder, mix it so that shearing force is not applied as much as possible by rotating the container, and shape it into a desired shape such as sheet or hollow fiber by ram extrusion. . Due to the pressure applied during the extrusion and the shearing force applied during the deformation, bonds due to molecular entanglement are generated on the surface of the fine powder particles.

  Next, the extrudate is dried in a hot air circulating furnace at 60 to 80 ° C. until the auxiliary agent is removed, and then stretched while being heated. At this time, the bond between the PTFE fine particles generated by extrusion receives a tension in the drawing direction, and the fibers are drawn from the crystals of the PTFE fine particles. The PTFE molded product after stretching has a porous structure composed of the drawn fibers and the space between the drawn fibers. After that, heating to a temperature higher than the melting point of PTFE melts a part of the fiber, and a structure called a nodule is formed by adhering in the vertical direction to the stretch, and this is cooled and fixed. It becomes a PTFE porous body which is constructed and has mechanical strength as a whole.

  A conventional desalination apparatus using membrane distillation, for example, bundles a plurality of porous PTFE hollow fibers and a plurality of impervious pipes such as metal pipes, and stores them in an outer cylinder. The gap between the yarns and the gap between the hollow fiber bundle and the outer cylinder are filled and sealed with resin or the like to form an evaporation portion and a condensation portion. Furthermore, the lumen of the porous PTFE hollow fiber and the lumen of the impervious tube are opened and isolated in separate rooms so that the treated water and the cooling water are not mixed.

  Alternatively, in order to simplify the structure, only the porous PTFE hollow fiber is put in the outer cylinder, and the outer cylinder is made into a double structure instead of the impervious tube, and cooling water is placed in the gap between the inside and the outside. The method of flowing is also adopted. However, this method has a simple structure, but has a problem that it is difficult to increase the condensation area with respect to the evaporation area. Accordingly, a method of increasing the cooling surface by using a cooling surface inside the outer cylinder as a pleat is conceivable.

  The fresh water generator of the present invention can also adopt the same structure as the conventional fresh water generator by membrane distillation as described above, but evaporates so that the water condensed and recovered and the liquid leaking from the evaporation section do not mix. Preferably, the bundle of PTFE porous body hollow fibers and the like and the bundle of impervious tubes such as metal tubes are provided separately in order to provide the part and the condensing part in independent regions. In order to prevent the water collected by condensation and the liquid leaking from the evaporation part from mixing, the evaporation part has a leakage liquid recovery part for recovering the liquid leaking from the hydrophobic porous membrane, and the condensation is performed. More preferably, the part has a condensed water recovery part for recovering the condensed water, and the leaked liquid recovery part and the condensed water recovery part are separated. By adopting such a structure, even if the waterproof property of the PTFE porous body is lowered and leakage of treated water occurs, it is easy to avoid mixing water before treatment into the treated water.

  As an example of the sheet module used in the fresh water generator of the present invention, it consists of a flow path of treated water, a porous PTFE sheet, a gap where condensed water is generated, a metal plate, an impermeable sheet, and a flow path of cooling water. Can be mentioned in the above-mentioned order in the form of a layer, and this layer can be stacked several times. However, in the case of a sheet module, there is a problem that it is difficult to manufacture a structure in which the evaporation portion and the condensation portion are provided in independent regions.

  FIG. 1 is a partially cutaway cross-sectional view schematically showing an example of the fresh water generator of the present invention. This fresh water generator has an evaporation section 1 formed by bundling a plurality of hollow fibers made of a hydrophobic porous membrane, and a condensing section 2 having a plurality of bundles formed by bundling a plurality of metallic pipes. Centering on the part 1, it is provided in the outer cylinder 21 so that the condensing part 2 may become the outer side. That is, the evaporation part and the condensing part are arrange | positioned in the independent area | region. The space 3 in the outer cylinder 21 corresponds to the gas phase portion 1 and also to the gas phase portion 2 in claim 1 since it is a space where the evaporation portion 1 and the condensation portion 2 are in contact with each other.

  Both ends of the evaporation unit 1 (hollow fiber) are connected to the treated water chambers 5 and 6, respectively. The treated water chamber 5 is provided with a pipe 4 and the treated water chamber 6 is provided with a pipe 7. The treated water is heated and passed through the pipe 4 and the treated water chamber 5 and passed through the evaporation section 1 (hollow fiber). Since the treated water flows in the hollow fiber lumen forming the evaporation part 1, it corresponds to the liquid phase part in claim 1. The water in the treated water passed through the evaporation part 1 (hollow fiber) permeates through the hydrophobic porous membrane as water vapor and is released into the space 3 (gas phase part 1). The treated water that has passed through the hollow fiber lumen is discharged through the treated water chamber 6 and the pipe 7.

  A bundle of metallic pipes constituting the condensing part 2 is provided so as to pass through the treated water chamber 5 and the treated water chamber 6. In this metallic pipe, cooling water flows in the direction indicated by the arrow in the figure, and the water vapor released into the space 3 (gas phase portion 1) passes through the pipe surface (cooling surface) through which the cooling water passes. ) To cool and condense.

  The fresh water generator of this figure is provided vertically so that the treated water chamber 5 is on the top and the treated water chamber 6 is on the bottom. Accordingly, the condensed water condensed on the pipe surface moves downward and is stored in the condensed water recovery unit 10 provided in the lower portion of the space 3. The condensed water recovery unit 10 is provided with a pipe 11, and the stored condensed water (fresh water) is recovered from the pipe 11 at appropriate times and used as fresh water.

  In the fresh water generator shown in this figure, a leaked liquid recovery unit 8 is provided below the evaporation unit 1 and on the treated water chamber 6. The leaked liquid recovery unit 8 is a container for storing the leaked liquid, and even if the treated water leaks from the evaporation unit 1, the leaked liquid travels through the hollow fiber and falls into the leaked liquid recovery unit 8. It does not mix with the condensed water stored in the water recovery unit 10. The leaked liquid (treated water) stored in the leaked liquid recovery unit 8 is discharged through the leaked liquid discharge pipe 9.

  The water in the treated water sent to the liquid phase part 1 is released into the space 3 as water vapor, but the released water vapor is cooled and condensed on the cooling surface of the condensation part in contact with the space 3. The cooling surface is not particularly limited as long as it is sufficiently cooled to condense water vapor, and may be a plate that is in contact with the refrigerant at one end and cooled by heat transmission from the one end. However, in order to increase the cooling efficiency, a method of cooling by making one surface of a metal plate or tube with good thermal conductivity or the surface of the tube a cooling surface and flowing a coolant or cooling water to the other surface is preferable. As described above, treated water before heating is preferably used as the refrigerant and the cooling water. The water vapor in the gas phase part 2 is cooled and condensed by the cooling surface and recovered as water.

  FIG. 2 is a cross-sectional view schematically showing another example of the fresh water generator of the present invention. In this example, as in the example of FIG. 1, an evaporation part and a condensation part are provided in a cylindrical outer cylinder, and the evaporation part is arranged at the center and the condensation part is arranged around the evaporation part. That is, the evaporation part and the condensing part are arrange | positioned in the independent area | region. As in the example of FIG. 1, the evaporation part is formed by a plurality of hollow fibers made of a hydrophobic porous membrane, and the condensation part is formed by a plurality of metal pipes (cooling pipes). Cooling water flows in the metallic pipe, treated water flows in the hollow fiber, and the water in the treated water becomes steam and is discharged from the outer surface of the hollow fiber into the gas phase portion 1, and in the gas phase portion 2. The water vapor is cooled and condensed by a metallic pipe (cooling pipe).

  The fresh water generator of this example is also provided so that the hollow fiber and the cooling pipe are vertical. Although not shown in the figure, a leaked liquid recovery section having the same cross section as that of the gas phase section 1 is provided immediately below the gas phase section 1, and a cross section of the gas phase section 2 is provided immediately below the gas phase section 2. The condensed water recovery part having the same cross section is provided separately so that the leaked liquid from the evaporation part (hollow fiber) does not mix with the condensed water. Further, as is apparent from the figure, the condensation area of the condensation part is larger than the evaporation area of the evaporation part, and a large permeation flux is obtained.

  FIG. 3 is a diagram schematically showing another example of the fresh water generator of the present invention. This fresh water generator is an example in which an evaporation section made up of a bundle of hollow fibers and a condensation section made up of a bundle of metal pipes are provided in parallel. FIG. 3 (a) is an example in which an evaporation part and a condensation part are provided in parallel in one cylinder, and FIG. 3 (b) is an evaporation in each of two cylinders connected to each other so as to allow ventilation. It is the example which provided the part and the condensing part in parallel. That is, the evaporation part and the condensation part are provided independently in the region.

  The treatment water passes through the hollow of the hollow fiber and the cooling water passes through the lumen of the metal pipe, as in the example of FIGS. The fresh water generator of this example is also provided so that the hollow fiber and the cooling pipe are vertical. The water vapor released to the gas phase 1 in the evaporation part moves to the gas phase 2 as indicated by the arrow in the figure, and is cooled and condensed on the surface of the metal pipe, and then condenses on the surface of the metal pipe. Is stored in a condensed water recovery unit provided in the lower part of the water, and is recovered by the pipe 1 installed in the condensed water recovery unit and used as fresh water.

  A leaked liquid recovery unit is provided below the evaporation unit. When treated water leaks from a hollow fiber or the like, the leaked liquid travels through the hollow fiber or the like and is stored in the leaked liquid recovery unit, and is discharged through the pipe 2 installed in the leaked liquid recovery unit.

  FIG.3 (c) is sectional drawing of the leaking liquid collection | recovery part, condensed water collection | recovery part, and its vicinity of the example of Fig.3 (a). As is apparent from this figure, the condensed water recovery part and the leaked liquid recovery part are separated, and the leaked liquid is not mixed with the condensed water.

  FIG. 4 is a diagram schematically showing another example of the fresh water generator of the present invention. In this example, an evaporating part composed of a bundle of hollow fibers and a condensing part composed of a bundle of metal pipes are provided in different outer cylinders. The outer cylinder in which the evaporation part is provided and the outer cylinder in which the condensation part is provided are connected by a ventilation pipe so as to allow ventilation. That is, the evaporation part and the condensation part are provided independently in the region.

  The treatment water passes through the hollow of the hollow fiber and the cooling water passes through the lumen of the metal pipe as in the above example. Arrow (1) in the figure indicates the flow of treated water, and arrow (2) indicates the flow of cooling water. The water vapor released to the gas phase 1 in the evaporation section moves to the gas phase 2 through the vent pipe, and is cooled and condensed on the surface of the metal pipe.

  Fig.4 (a) is a top view of the fresh water generator of this example, and FIG.4 (b) is a side view. As shown in FIG. 4 (b), both the evaporating part and the condensing part have a downward inclined part, and the bottom part (lowermost part) has a condensed water recovery pipe or a leakage liquid discharge pipe. is doing. Condensed water generated in the condensing part moves to the bottom due to the inclination, and is recovered from the condensed water recovery pipe and used as fresh water. Further, when the treated water leaks from the hollow fiber or the like, the leaked liquid moves to the bottom due to the inclination and is discharged from the leaked liquid discharge pipe. Therefore, the leakage liquid is not mixed with the condensed water.

Reference example 1
It is made of expanded PTFE porous material (PTFE porous material hollow fiber poreflon TB-2311-200 manufactured by Sumitomo Electric Industries) having a pore size of 2.0 μm and an open area ratio of 79%, and has an outer diameter of 2.3 mm and an inner diameter of 1.1 mm. The yarn was used as a hydrophobic porous body. By flowing seawater with an initial temperature (temperature of the hollow fiber inlet) of 75 ° C. through the lumen of the hollow fiber, water vapor released from the outer surface of the hollow fiber to the gas phase part is cooled on the inner surface of the stainless steel container cooled with ice water. It was condensed and collected. A value obtained by converting the weight of the collected water into the inner surface area and unit time of the hydrophobic porous hollow fiber was defined as a permeation flux.

  The permeation flux was measured by varying the ratio (condensation area / evaporation area) of the inner surface area (evaporation area) of the hydrophobic porous hollow fiber to the inner surface area (condensation area) of the stainless steel container. FIG. 5 is a graph showing the relationship between the permeation flux obtained by this experiment and the condensation area / evaporation area.

  Referring to FIG. 5, the change in the permeation flux with respect to the condensation area / evaporation area is based on the slope of the change, and the area A where the condensation area / evaporation area is less than 1.2, the area C exceeding 6, and the area in between The region A can be divided into three regions B, and the region A less than 1.2 and the region C exceeding 6 have a small inclination. In the region A, the ratio of the condensation area to the evaporation area is small, so even if it evaporates, the condensation is rate-determined and the recovery of fresh water is difficult to proceed. In the region C, the condensation ability is sufficient, but the evaporation cannot catch up with it and It is thought that the recovery of fresh water is difficult to proceed.

  The result of FIG. 5 shows that the condensation area / evaporation area is preferably 1.2 or more in order to obtain a high permeation flux. On the other hand, if the condensation area is increased, the equipment becomes larger. In the region C where the condensation area / evaporation area exceeds 6, the permeation flux value tends to saturate even if the condensation area / evaporation area is increased, although the improvement in the permeation flux is small, although the size of the facility increases. is there. Therefore, considering the overall efficiency, the condensation area / evaporation area is preferably 6 or less.

  The reason why the condensation efficiency is several times lower than the evaporation efficiency is considered as follows. At the gas-liquid interface on the inner surface of the hydrophobic porous membrane where evaporation occurs, even if the heat of vaporization is lost and water temperature drops locally, new warm water is supplied by the flow of warm seawater and the temperature is constantly recovered . On the other hand, on the condensing surface, vaporization heat is released when water vapor becomes water, so the temperature of the condensing surface rises, but before the heat escapes to the cooling water on the back side of the metal surface, the heat conduction of the metal wall is reduced. In addition, the water generated on the condensation surface usually stays there until it flows as water droplets under its own weight, which is considered to be less efficient than the constantly updated evaporation surface.

  An evaporation module (evaporation part) in which 30 hollow fiber-like porous membranes (TB-2311-200) same as those in the reference example are bundled and accommodated in a vinyl chloride tube having an inner diameter of 20 mm, and 121 stainless tubes having an inner diameter of 1 mm and an outer diameter of 2 mm. A condensing module (condensation part) bundled and accommodated in a vinyl chloride tube having an inner diameter of 40 mm was produced and arranged as shown in FIG. The principle of separating the evaporation part and the condensation part is the same as in FIG. FIG. 6A is a diagram schematically showing a longitudinal section, and FIG. 6B is a diagram schematically showing a transverse section.

  A 3.5% sodium chloride aqueous solution (artificial seawater) at 75 ° C. is flowed into the lumen of the hollow fiber-like porous membrane of the evaporation module at a rate of 0.2 m / s, and into the stainless tube lumen of the condensation module. Was cooled by flowing 5 ° C. cooling water at a flux of 0.05 m / s, and water collected in each module was collected 30 minutes after the start of the experiment. Thereafter, an experiment similar to the above was performed except that 100 ppm of household detergent (main component allylether ether sulfate sodium salt) was added to the artificial seawater. Water collected in each module was collected every 30 minutes, and the electricity stored in each module was collected. The salinity was measured from the conductivity.

  120 minutes after the start of operation (90 minutes after the addition of household detergent), the evaporation module is removed from the experimental system, immersed in 2-propanol for 5 minutes, then immersed in tap water for 5 minutes, and the water is changed. The mixture was further left to stand for 60 minutes and then dried overnight in a constant temperature bath at 60 ° C. The above experiment using artificial seawater (no household detergent) was performed again by attaching the evaporation module to the experimental system. The change in salinity concentration in the above experiment is shown in FIG. That is, FIG. 7 shows that when membrane distillation was performed, a surfactant was mixed into artificial seawater to intentionally generate seawater leakage, and then leakage recovery processing was performed by washing the module. It is a graph which shows the salinity concentration change of the water collect | recovered from the evaporation part and condensation part before and behind.

  While only artificial seawater was flowing, salt was not detected from the water in the evaporation module. However, salt was gradually detected after putting household detergent into artificial seawater, and artificial seawater became hydrophobic. It was shown that it leaked out of the porous porous membrane. Thereafter, when the evaporation module is washed with alcohol and water, salt detection from the water accumulated in the evaporation module is lost. From this result, it is shown that the hollow fiber-like hydrophobic porous material in the evaporation module easily recovers the water retention by simple cleaning. On the other hand, the water in the condensation module has not detected salinity through experiments, and in the desalination apparatus shown in FIG. 6, the evaporation unit and the condensation unit are provided in independent regions. It is shown that even if the treated water) leaks, it does not mix with the produced water (condensed water).

1. Evaporator 2 2. Condensation part Space 4.7. Piping 5.6. Treated water chamber 8. Leakage liquid recovery unit9. Leakage liquid discharge pipe 10. Condensed water recovery unit 21. Outer cylinder

Claims (6)

An evaporation part comprising a liquid phase part through which treated water flows, a gas phase part 1 and a hydrophobic porous membrane separating the liquid phase part and the gas phase part 1;
A condensing part including a cooling surface and a gas phase part 2 in contact with the cooling surface; and
Having liquid feeding means for feeding treated water to the liquid phase part;
The gas phase part 1 and the gas phase part 2 are connected to each other so as to be able to vent.
The water in the treated water is a fresh water generating device in which the hydrophobic porous membrane is discharged as water vapor from an evaporation surface in contact with the gas phase portion 1, cooled by the cooling surface, condensed, and recovered as water,
A fresh water generator characterized in that an evaporating part and a condensing part are provided in an independent region so that water condensed and recovered and liquid leaking from the evaporating part are not mixed.   The said evaporation part bundles and stores the hydrophobic porous membrane formed in the shape of a hollow fiber, treated water passes through the hollow fiber lumen, and the hollow fiber surface is an evaporation surface. Fresh water generator.   The fresh water generating apparatus according to claim 1 or 2, wherein an area of the cooling surface is 1.2 to 6 times an area of the evaporation surface.   The fresh water generating device according to any one of claims 1 to 3, wherein the hydrophobic porous membrane is a stretched porous membrane of polytetrafluoroethylene.   The fresh water generator according to any one of claims 1 to 4, wherein the liquid feeding means includes means for heating the treated water by the condensation heat of water vapor generated in the condensation part.   5. A water freshening device according to claim 1, and a solar heating device that heats treated water to be fed to the liquid feeding means with heat from sunlight. Fresh water system.

Images