JPH02277591A - Method for obtaining pure water from salt-containing water - Google Patents

Abstract

PURPOSE:To obtain pure water with a simple device at a low cost by covering a groove through which salt-contg. water is naturally or forcibly allowed to flow with a transparent film, vaporizing the water by solar heat, condensing the vapor on the film surface and collecting the condensed waterdrops flowing down on the surface. CONSTITUTION:A PVC sheet 2 is laid over a frame 1 assembled to cover a groove 4 provided on a slope 5 inclined at an angle of about 5 deg. as the root surface, side surface, groove inlet surface and groove outlet surface. Water is vaporized from the groove and condensed on the sheet part as pure water. The pure water is collected in a trough-shaped water collecting means 3 fixed to the frame 1 downwardly inclined in the flow direction of brine on the inner surface of the tent-shaped device, allowed to flow along the collecting means, and collected in a water storage means 6. Solar heat is utilized as the energy, and pure water is obtained at a low cost with this simple method.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for easily obtaining pure water from salt-containing water using simple equipment.

(Prior art) In hot and dry areas, that is, desert areas, groundwater contains salt, so not only can it not be used as daily life water, but even when water is used as a heat source, salt accumulates on the ground surface. There is a problem with salt damage to plants. Therefore, in order to obtain pure water, we used a multi-stage flash evaporation method of seawater while fishing on a boat.
Desalination methods such as ion exchange membrane method, refrigeration method, vapor compression method or reverse osmosis method are used.

(Problems to be Solved by the Invention) However, although the desalination method described above makes it possible to produce water from salt water, it requires large-scale equipment to obtain large quantities, so it is difficult to implement. This method is not easy to implement and requires a large amount of energy such as electric power, so it is expensive.

On the other hand, in the case of groundwater, the above-mentioned problems of desalination do not occur, but as mentioned above, groundwater especially in desert areas often contains salt, so it is not suitable as drinking water. When water is used for irrigation, the salt contained in the water crystallizes and forms on the ground, further forming a layer of salt that causes deterioration of the geology and causes salt damage to plants, especially vegetables. There was a problem.

The present invention has been made in view of the means for solving these problems of the prior art. The purpose is to provide a method for obtaining pure water from water.

(Means for Solving the Problems) Accordingly, the present invention covers channels through which salt-containing water flows naturally or forcibly with a transparent film, and evaporates by solar heat, condenses on the film surface, and transmits the water along the film surface. characterized in that the falling water droplets are collected in a water collecting means provided at the lower end of the film or at the end of the roof and/or by a guiding means for water droplets provided from above the roof to the water collecting means; The present invention provides a method for obtaining pure water from salt-containing water.

The grooves provided in the present invention may be formed by digging the ground or by filling earth, or may be formed by concrete, and may be straight or meandering on sloped or flat land, especially on sloped land. Well, its depth and width can be selected to suit the purpose. However, the grooves must be constructed in such a way that brine, which has become salt-enriched by evaporation of water, i.e., concentrated brine, can flow out to the outside without being covered by the film. The highly salty water flowing out from the area covered with the film may be discharged as is, or it may be collected in a reservoir and further evaporated and solidified to be used to obtain salt.

It is particularly advantageous for the transparent film used in the present invention to be weather resistant, but any type of transparent film can be used as long as it is inexpensive and can be replaced at no cost. For example, a film made of synthetic resin such as polyvinyl chloride, polyethylene, polyvinyl alcohol, polyvinyl butyral, polycarbonate, etc. can be used. The overall shape of the film when covering the grooves depends on the arrangement of the grooves, but may be tent-shaped, kamabot-shaped, or dome-shaped.

The salt-containing water flowing into the ditch may be salt-containing groundwater or seawater. Advantageously, the flow rate of the salt-containing water is such that the salt does not settle in the grooves due to concentration and has sufficient residence time for evaporation. In the case of a slope, this flow rate can be obtained by the slope, but in the case of a flat land, it is also possible to obtain this flow rate by a suitable means, such as a pump.

The water collecting means installed at the bottom end of the vinyl covering the groove can have various shapes and structures depending on the purpose of use of pure water, but when using it as domestic water, a gutter-like means is preferable, and it is preferable to collect water directly to plants. For the purpose of water supply, it is advantageous to have a funnel shape.

As a guide means for water droplets provided near the lower end of the film cover, a non-water-supplying linear object, such as a thin string-like object made of synthetic resin, which is pasted or sewn radially from the bottom to the top, is useful. . It is particularly advantageous for this means to be arranged radially above the funnel-shaped water collection means for the purpose of directly watering the plants.

As mentioned above, the pure water obtained in the present invention can be used as domestic water or water for irrigation, but it can also be used directly for plants planted inside a cover made of a film. The latter case will be explained in more detail.

For this purpose, it is particularly advantageous to provide the water drop guiding means radially on top of the funnel-shaped water collection means by gluing thin synthetic resin lobes. In this case, the size of the guide means is determined according to the amount of water required by the plants. Plant seeds or the plants themselves are sown or planted at the point where the pure water reaching the funnel-like collection means from the guide means is absorbed into the ground. In this way, plants can be watered even in hot and dry areas without any difficulty or great expense. Of course,
The formation of salt crystal layers, which is a drawback when using groundwater as is, can be avoided.

In addition to the plant water supply means described here, pure water collected by the gutter-like water supply means described above can be used as irrigation water.

Plants suitable for growing in hot, dry areas with this type of water supply include tomatoes, cucumbers, lettuce, eggplants,
Examples include vegetables such as watermelon and cabbage, fruits such as melon, and various trees.

The soil for planting plants may be any of sandy soil to clayey soil.

Furthermore, if the soil temperature becomes too high, the absorbed water will quickly evaporate, so it is advantageous to suppress the rise in soil temperature as much as possible. As a means of suppressing this rise in soil temperature,
It is particularly advantageous to cover at least part of the ground surface other than the ditch and where the plants are planted with a radiant heat shielding sheet, for example a silver sheet, for shielding radiant heat from the sun. The sheet may be of any material as long as it can shield radiant heat from the sun, but from the viewpoint of ease of construction and cost, it is preferable to use a sheet made of synthetic resin with good sheet processability, such as polyvinyl chloride or polyethylene. is advantageous. Depending on the application, a surfactant may be applied to the sheet to prevent water droplets from falling.

Depending on the application, a water repellent may also be applied to promote the formation of water droplets.

The method of the invention will be explained in more detail below with the aid of the drawings: FIG. 1 is a schematic perspective view of a long tent-like device for carrying out the method of the invention, and FIG. -A line cross-sectional view.

In Figures 1 and 2, (1) means a frame assembled so as to wrap around a groove (4) provided in a slope (5) with an inclination angle of 5''; A polyvinyl chloride sheet (2) is stretched over the roof surface, side surfaces, and one groove entrance surface on the higher side of one slope and one groove exit surface on the lower side of one slope.(3) is a tent. A gutter-like water collection means is shown on the inner surface of the device, which is attached to an inclined frame (1) that descends in the direction of flow of the salt water.Pure water that evaporates from the grooves and condenses on the sheet is collected by this water collection means. The water flows in an inclined direction along the water collecting means and is collected in the water collecting means (6). This water collecting means may be located inside or outside the tent, but in either case, In order to reduce the amount of evaporation, it is desirable to have a small evaporation surface and/or to use a heat insulating material.

Particularly advantageous is a container or tank made of an inorganic material, such as ceramics or concrete, which is closed except for the part into which the pure water from the water collection means flows.

The sheet stretched over the frame may be tensioned with some slack to serve as a guide path for condensate water, and/or the sheet may be radially thread-like guiding means extending from bottom to top as described above - not shown. It is also possible to attach a -.

The present invention will be explained in more detail with reference to examples below: (Example) As an experiment to demonstrate the method of the present invention, an experimental apparatus for carrying out the method of the present invention was constructed. We analyzed its heat balance by filling a groove with water and exposing it to sunlight.

This experiment was conducted in Tokyo. The frame of this device was made of aluminum, and the films used were anti-drop vinyl chloride film and droplet-forming vinyl chloride film.

The floor of the device consists of expanded polyethylene. In addition, the length of the groove of the device is 176C11, the height of the tip of the frame is 68C+a at the start end and 53C11 at the end, and the height of the gutter is 23C at the start end.
As, the end was 8 CI, and the width of the water collection device was 91 cm.

The heat balance of the device is shown by the following formula; R= Rx + Qc + Qd + Qv (1)
Each term is the heat fraction, R is the total amount of heat obtained by radiation, Rx is the amount of heat used to evaporate water, Qc is the amount of heat lost by convection, Qd is the amount of heat escaping underground by heat transfer, and Q
v is the amount of heat lost due to ventilation.

The total number of heat radiation is shown by the following formula; R= Rs + Rls - Rlh (2) where R
s-AIXtXs.

Rs is the amount of short-wave radiant heat projected onto the device, AI is the floor area, t is the transmittance of the covering material (in this case, vinyl chloride film) for short-wave radiation, and S is the amount of short-wave radiant heat outside the device.

The heat fraction Qc is calculated by the following formula; Qc = 8z X hc
-Ta) (3) Az is the surface area of the device (3,2
3rIf), hc is the convective heat transfer coefficient, given by hc = 4.0 + wind speed. For analysis of the convective heat transfer coefficient, the average wind speed during the day was estimated to be 4.0 m/sec.

The heat fraction Od escaping underground by conduction is expressed by the following formula % formula % Here, AI is the floor area of the equipment (1.6 rrr), and d
2 is the thickness of the floor made of foamed polyethylene (d2・0.0
5a+), L is the thermal conductivity of polyethylene foam (L・0.
033 Kcal/m/hr-C), Tp and Tu are the trench and underground temperatures, respectively.

The amount of long wavelength radiant heat (Rls) falling from the atmosphere to the device is given by the following formula; RIs=83X to s XTa'
1+0.58X (ea)"")
-'), el is the long-wavelength radiation absorption of vinyl chloride film (0,95), Ta is the air temperature, ea is the vapor pressure of the air (m), ■ is the view factor between the roof of the equipment and the sky. (view factor) (0,80).

The amount of long-wavelength radiation heat (Rlh) from the device toward the sky is expressed by the following formula; Rlh , ^3 X e2 X Ts ' X V
(6) Here, Ts is the surface temperature (K) of the cover film,
e2 is the luminous intensity of the film (0,95).

Using the above formula, we will analyze the heat balance using the data obtained from measurements in Tokyo. FIG. 3 shows temperature changes inside and outside the device and changes in radiant heat during the day. Figure 4 shows the heat fractions of this device. According to heat balance analysis, 60-70% of the solar heat was captured in the device, and that energy was used as heat to evaporate water. Water evaporates from the gutter due to solar heat. The water vapor is cooled on the surface of the vinyl chloride film and becomes pure water. The rate of water production depends on cooling at the film surface, ie, heat transfer by convection and long-wavelength radiation heat. The amount of solar heat taken in by this device was 8843 Kcal/day. The amount of water obtained from the device is 2125 zf /+"/day, which is equal to 1206 cal/m"/day. Therefore, the solar efficiency of the device is 22%.

Back Facility: The apparatus described in FIGS. 1 and 2 was installed in the sandy soil of Sotoboso, a Chiba region, and the method of the present invention was carried out during the summer season (mid-August).

The heat balance of the water collection system was analyzed by filling a trench with seawater and exposing it to sunlight.

The frame of this device was made of aluminum, and the film used was a vinyl chloride film coated with a surfactant and a vinyl chloride film coated with a water repellent. A silver polyvinyl chloride sheet was placed over the areas where the grooves were not provided. The length of the groove is 27.6-, the width is 7.5 m, and the depth is 20 cm. The height of the tip of the frame is 3.
The height of the gutter is 1.8m at the beginning and 0.7m at the end.

The width of the device was 9 m.

The amount of water flowing into the groove was 2027 minutes. The amount of pure water collected in the water storage means was about 3 tons at 80:00 sunshine hours.

Real 1LL car Eggplants were grown using the apparatus of Example 2.

However, the following points of the apparatus described in Example 2 are changed: There is no gutter-like water collection means, and funnel-like water collection means are placed at the frame at 3 ra intervals, and the funnel-like water collection means are added dropwise. It is attached with a clamp so that the mouth is 20all away from the frame, and a collective terminal bundle of thin rope-like guides hangs down from the inverted conical mouth of the funnel-like object, and the rope-like guide has a thickness of 3
mtm-, 8 lobes of length 3 ra are applied to the film at an angle of 8° to each other and extending in the direction of the top of the roof. Then, a thin lobe-like object with a thickness of 3 m111 that reaches all the way to the ground was lowered into the inlet of the funnel-like object. Eggplant seedlings (average height: 15 cm) were planted 5 cva away from the end of the rope.

When an experiment was conducted for 3 weeks under the same conditions as in Example 2,
Eggplant seedlings grew to an average capacity of 20.5 ca+.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing an example of an apparatus used in the method of the present invention, and FIG. 2 is a cross-sectional view taken along the line A--A of the apparatus. FIG. 3 is a graph showing temperature changes inside and outside the device during the day, FIG. 4 is a graph showing each heat fraction of the experimental device used in Example 1, and FIG. 1 is a graph representing the cumulative amount of water collected by the device. The symbols in Figures 1 and 2 have the following meanings: 1...Frame, 2...Film, 3...Gutter-like water collection means, 4...Gutter, 5...Ground. 6...Water storage means. Diagram

Claims (1)

[Claims] A transparent film is used to cover the grooves through which salt-containing water flows naturally or forcibly, and to prevent water droplets from being evaporated by solar heat, condensed on the film surface, and flowing down the film surface. A method for obtaining pure water from saline water, characterized in that it is collected in a water collection means and/or by a guide means for water droplets provided from above the roof to the water collection means.