Desalination system and desalination method

A desalination system includes a water tank, a water-repellent particle layer located at a lower portion of the tank and composed of water-repellent particles, and a devolatilizing layer located below the water-repellent particle layer. Liquid is introduced to the tank, the introduced liquid is heated to be evaporated into water vapor, and the water vapor passes through the water-repellent particle layer and is liquefied at the devolatilizing layer, so that fresh water is obtained from the liquid. The desalination system further includes a liquid level controller for determining a level of the liquid introduced to the tank in accordance with information on relationship between information corresponding to an amount of the liquid introduced to the tank and a surface level of the liquid in the tank, and an introduced amount controller for adjusting the amount of the liquid introduced to the tank in accordance with the determined liquid surface level.

TECHNICAL FIELD

The technical field relates to a desalination system including water-repellent particles as well as to a desalination method.

BACKGROUND ART

Patent Literature 1 discloses a desalination system including water-repellent particles as well as a desalination method.

CITATION LIST

Patent Literature

SUMMARY OF THE INVENTION

However, there is no disclosure of a specific configuration for actual desalination.

One non-limiting and exemplary embodiment provides a desalination system and a desalination method that enable efficient desalination.

In one general aspect, the techniques disclosed here feature: A desalination system comprising:

a water tank;

a water-repellent particle layer located at a lower portion of the water tank and composed of water-repellent particles; and

a devolatilizing layer located below the water-repellent particle layer, wherein

liquid is introduced to the water tank,

the introduced liquid is heated to be evaporated into water vapor, and

the water vapor passes through the water-repellent particle layer and then, is liquefied at the devolatilizing layer to obtain fresh water from the liquid,

the desalination system further comprises:

a liquid level controller that determines a level of the liquid introduced to the water tank in accordance with information on relationship between information corresponding to an amount of the liquid introduced to the water tank and a surface level of the liquid in the water tank; and

an introduced amount controller that adjusts the amount of the liquid introduced to the water tank in accordance with the determined surface level of the liquid.

According to this aspect of the present disclosure, the liquid level controller determines the level of the liquid to be introduced to the water tank in accordance with the information on the relationship between the information corresponding to the amount of the liquid introduced to the water tank and the surface level of the liquid in the water tank, and the introduced amount controller adjusts the liquid introduced to the water tank in accordance with the determined surface level of the liquid. It is thus possible to effectively prevent breakage of the water-repellent particle layer at a concave portion and efficiently and reliably perform automatic desalination.

DETAILED DESCRIPTION

Before the description of the various embodiments proceeds, various approaches made by the inventors to accomplish the embodiments are explained.

Examples of the disclosed technique are as follows.

a water tank;

a water-repellent particle layer located at a lower portion of the water tank and composed of water-repellent particles; and

a devolatilizing layer located below the water-repellent particle layer, wherein

liquid is introduced to the water tank,

the introduced liquid is heated to be evaporated into water vapor, and

the water vapor passes through the water-repellent particle layer and then, is liquefied at the devolatilizing layer to obtain fresh water from the liquid,

the desalination system further comprises:

a liquid level controller that determines a level of the liquid introduced to the water tank in accordance with information on relationship between information corresponding to an amount of the liquid introduced to the water tank and a surface level of the liquid in the water tank; and

an introduced amount controller that adjusts the amount of the liquid introduced to the water tank in accordance with the determined surface level of the liquid.

According to this aspect of the present disclosure, the liquid level controller determines the level of the liquid to be introduced to the water tank in accordance with the information on the relationship between the information corresponding to the amount of the liquid introduced to the water tank and the surface level of the liquid in the water tank, and the introduced amount controller adjusts the liquid introduced to the water tank in accordance with the determined surface level of the liquid. It is thus possible to effectively prevent breakage of the water-repellent particle layer at a concave portion and efficiently and reliably perform automatic desalination.

2nd aspect: The desalination system according to the 1st aspect, wherein

the information corresponding to the amount of the liquid introduced to the water tank is information corresponding to a number of times of introducing the liquid to the water tank, and in information on relationship between the information corresponding to the number of times and the surface level of the liquid in the water tank, the surface level of the liquid is decreased as the number of times of introducing the liquid is larger.

According to this aspect, it is possible to estimate the depth of the concave portion at the water-repellent particle layer in accordance with the number of times of introducing the liquid to the water tank. This configuration can reduce breakage of the water-repellent particle layer.

3rd aspect: The desalination system according to the 1st aspect, wherein

when an amount of the introduced liquid per unit time is constant while a water gate located on an introduction path used for introducing the liquid to the water tank is opened, the information corresponding to the amount of the liquid introduced to the water tank is an introduced amount estimated from the number of times of opening and closing the water gate and a period of opening the water gate.

According to this aspect, it is possible to estimate the depth of the concave portion at the water-repellent particle layer, which is formed by introduction of the liquid, in accordance with the number of times of introducing the liquid to the water tank. This configuration can reduce breakage of the water-repellent particle layer.

4th aspect: The desalination system according to the 1st aspect, wherein

the information corresponding to the amount of the liquid introduced to the water tank is information corresponding to an elapsed time from the introduction of the liquid, and in information on relationship between the information corresponding to the elapsed time and the surface level of the liquid in the water tank, the surface level of the liquid is decreased as the elapsed time from the introduction of the liquid is longer.

According to this aspect, it is possible to more easily estimate the depth of the concave portion at the water-repellent particle layer, which is formed by introduction of the liquid, in accordance with the elapsed time. This configuration can reduce breakage of the water-repellent particle layer.

5th aspect: The desalination system according to any one of the 1st to 4th aspects, wherein

a level of the liquid in a case where a distance between adjacent introduction paths out of a plurality of introduction paths used for introducing the liquid to the water tank is equal to or less than a predetermined distance is smaller than a level of the liquid in a case where the distance between the adjacent introduction paths is more than the predetermined distance.

According to this aspect, it is possible to prevent the concave portion formed at the water-repellent particle layer due to overlapping of flows of the liquid introduced through the adjacent introduction paths from being deeper than the concave portion formed where flows of the liquid are not overlapped with each other. This configuration effectively can prevent likelihood of breakage of the water-repellent particle layer.

6th aspect: The desalination system according to any one of the 1st to 5th aspects, further comprising:

an impurity deposition information acquiring unit that acquires information on whether or not impurities are deposited from the liquid, wherein

the liquid level controller comprises a decision unit that determines a level of the liquid so that a level of the liquid in the water tank in a case where the impurities are deposited is higher than a level of the liquid in a case where the impurities are not deposited, in accordance with the information from the impurity deposition information acquiring unit.

According to this aspect, when acquiring from the impurity deposition information acquiring unit the information that the impurities are deposited on the liquid or in the introduction path, the decision unit in the liquid level controller determines the level of the liquid introduced to the water tank in view of the acquired information on whether or not the impurities are deposited, in accordance with the information on the relationship between the information corresponding to the amount of the liquid introduced to the water tank and the surface level of the liquid in the water tank, and the introduced amount controller adjusts the liquid introduced to the water tank in accordance with the determined surface level of the liquid. It is thus possible to effectively prevent breakage of the water-repellent particle layer at the concave portion and more efficiently and more reliably perform automatic desalination.

7th aspect: The desalination system according to the 6th aspect, wherein

the impurity deposition information acquiring unit comprises:

an imaging unit that captures an image of a surface of the water-repellent particle layer in the liquid and outputs the captured image associated with time; and

an impurity decision unit that decides whether or not the impurities are deposited from the liquid in accordance with the image captured and outputted from the imaging unit.

8th aspect: The desalination system according to the 6th aspect, wherein

the impurity deposition information acquiring unit is configured to acquire information on whether or not impurities are deposited in the introduction path used for introducing the liquid to the water tank, and

the decision unit is configured to adjust, when acquiring information from the impurity deposition information acquiring unit that the impurities are deposited, a level of the liquid in the water tank so as to be higher than a level of the liquid in a case where the impurities are not deposited.

According to this aspect, it is possible to estimate the depth of the concave portion at the water-repellent particle layer, which is formed by introduction of the liquid, in accordance with an actual environment in view of the fact that the water-repellent particles moving by introduction of the liquid vary in amount depending on deposition of impurities. This configuration can reduce breakage of the water-repellent particle layer.

9th aspect: The desalination system according to the 8th aspect, wherein

the impurity deposition information acquiring unit comprises:

a concentration measuring unit that measures concentration of the impurities in the liquid flowing in the introduction path and outputs, to the impurity deposition information acquiring unit, the measured concentration of the impurities associated with time; and

an impurity decision unit that decides whether or not the impurities are deposited from the liquid in accordance with the concentration of the impurities as outputted from the concentration measuring unit.

According to this aspect, it is possible to estimate the depth of the concave portion at the water-repellent particle layer, which is formed by introduction of the liquid, in accordance with an actual environment in view of the fact that deposition of the impurities in the introduction path decreases the flow of the liquid introduced to the water tank. This configuration can reduce breakage of the water-repellent particle layer.

10th aspect: The desalination system according to the 8th aspect, wherein

the impurity deposition information acquiring unit comprises:

an imaging unit that captures an image of the liquid flowing in the introduction path and outputs, to the impurity deposition information acquiring unit, the captured image of the liquid associated with time; and

an impurity decision unit that decides whether or not the impurities are deposited from the liquid in accordance with the image of the liquid as outputted from the imaging unit.

11th aspect: A liquid amount adjusting apparatus included in a desalination system comprising:

a water tank for containing liquid;

a water-repellent particle layer located at a lower portion of the water tank and composed of water-repellent particles; and

a devolatilizing layer located below the water-repellent particle layer, the liquid adjusting apparatus comprising:

a liquid level determining unit that determines a level of the liquid introduced to the water tank in accordance with information on relationship between information corresponding to an amount of the liquid introduced to the water tank and a surface level of the liquid in the water tank; and

an introduced amount controller that adjusts the amount of the liquid introduced to the water tank in accordance with the determined surface level of the liquid.

12th aspect: A desalination method for obtaining fresh water from liquid using a desalination apparatus comprising:

a water tank for containing liquid;

a water-repellent particle layer located at a lower portion of the water tank and composed of water-repellent particles; and

a devolatilizing layer located below the water-repellent particle layer,

the method comprising steps of:

determining, by a liquid level controller, a surface level of the liquid introduced to the water tank in accordance with information on relationship between information corresponding to an amount of the liquid introduced to the water tank and a surface level of the liquid in the water tank; and

adjusting, by an introduced amount controller, the amount of the liquid introduced to the water tank and then, placing a liquid on the water-repellent particle layer so as to be equal in level to the determined surface level of the liquid.

According to this aspect of the present disclosure, the liquid level controller determines the level of the liquid to be introduced to the water tank in accordance with the information on the relationship between the information corresponding to the amount of the liquid introduced to the water tank and the surface level of the liquid in the water tank, and the introduced amount controller adjusts the liquid introduced to the water tank in accordance with the determined surface level of the liquid. It is thus possible to effectively prevent breakage of the water-repellent particle layer at a concave portion and efficiently and reliably perform automatic desalination.

13th aspect: The desalination method according to the 12th aspect, further comprising steps of:

heating to evaporate the contained liquid into water vapor; and

obtaining fresh water from the liquid by causing the water vapor to pass through the water-repellent particle layer, then reach the devolatilizing layer and be liquefied.

A first embodiment of the present disclosure is described in detail below with reference to the drawings.

Definition of Terms

The term “water repellency” means the property of repelling water in this description.

First Embodiment

In order to describe a desalination apparatus1according to the first embodiment with reference to the drawings, initially described is a desalination apparatus1A that basically functions similarly to the desalination apparatus1.FIG. 1is a sectional view of the desalination apparatus1A according to the first embodiment.

The desalination apparatus1A shown inFIG. 1includes a water tank102, a water-repellent particle layer104, and a devolatilizing layer105. The water tank102, the water-repellent particle layer104, and the devolatilizing layer105are disposed in the mentioned order from the top to the bottom.

The water tank102can have any shape in a planar view, such as a rectangular shape or a circular shape. The water tank102has an upper side wall102athat surrounds the entire side surface of the water tank102.

There can be provided a container103so as to surround the side surface of the water tank102, the side surface of the water-repellent particle layer104to be described later, and the side surface and the bottom surface of the devolatilizing layer105to be described later.

The container103shown inFIG. 1has a lower side wall103astood vertically, the upper side wall102athat is connected to the lower side wall103and is slanted so as to expand upward, and a bottom plate103bthat is connected to the lower side wall103.

The container103is formed such that surfaces other than the top surface thereof are surrounded with the upper side wall102a, the lower side wall103, and the bottom plate103b. At a lower portion of the water tank102, the lower side wall103asurrounds the entire side portions of the water-repellent particle layer104and the devolatilizing layer105to be described later and the bottom plate103bholds the bottom surface of the devolatilizing layer105. The container103is capable of reserving desalinated fresh water4gin the devolatilizing layer105.

The lower side wall103aand the upper side wall102aare each made of a water-repellent material. Examples of the lower side wall103aand the upper side wall102ainclude metal plate concrete, a waterproof sheet, clay, and the like.

Liquid poured into the water tank102forms a liquid layer (liquid)4on the top surface of the water-repellent particle layer104and in (in the space surrounded with the upper side wall102a) the water tank102.

The water tank102can optionally have an introduction path101athat is used for introducing liquid to the water tank102. If the water tank102has no introduction path101a, liquid is introduced to the water tank102from an opening provided at the top of the water tank102. Such liquid is transparent, translucent, or the like so that particle measurement is enabled as to be described later.

The water-repellent particle layer104and the upper side wall102ahave water repellency, so that liquid poured into the water tank102does not flow into the devolatilizing layer105. The liquid poured into the water tank102is provided and kept as the liquid layer4on the water-repellent particle layer104that is surrounded with the upper side wall102a. The liquid layer4is 15 to 50 cm in level (the surface level of the liquid layer4), for example. If the liquid layer4is too high (e.g. higher than 15 cm), it takes more time to heat liquid, large heat capacity is necessary, and liquid desalination efficiency thus deteriorates, as to be described later. In contrast, if the liquid layer4is too low (e.g. lower than 50 cm), liquid desalination efficiency is too low. It is possible to keep preferred desalination efficiency within the above numerical range.

The introduction path101acan optionally have a water gate101for adjusting liquid introduced to the water tank102through the introduction path101a(seeFIG. 5A). The water gate101adjusts a flow rate of liquid that is provided between the water tank102and an external tank6reserving the liquid. Examples of the external tank6include the sea, a preprocessing tank reserving seawater introduced from the sea, and a tank reserving salt water that is supplied separately.

When the water gate101is opened, the liquid is introduced from the external tank6to the water tank102through the introduction path101a. Closing the water gate101stops introduction of the liquid from the external tank6to the water tank102through the introduction path101a. A water gate controller1010functioning as an example of an introduced amount controller controls opening/closing of the water gate101.

The water gate controller1010can optionally control opening/closing of the water gate101in accordance with information inputted by a user or the like using an input unit1011. Examples of the input unit1011include a touch panel, a keyboard, a cursor, and a microphone. Information inputted by a user or the like using the input unit1011relates to opening or closing of the water gate101.

The water tank102can optionally have a heater for heating the liquid layer4in the water tank102. For example, the heater is located on the upper side wall102aof the water tank102.

The water-repellent particle layer104is located at the lower portion of the water tank102.

The water-repellent particle layer104is composed of at least a plurality of water-repellent particles, normally a large number of water-repellent particles. Such a large number of water-repellent particles are closely located to form the water-repellent particle layer104. More specifically, the surface of a water-repellent particle is in contact with surfaces of a plurality of other water-repellent particles. The water-repellent particles in contact with each other in the water-repellent particle layer104form gaps therebetween which allow water vapor formed by heating and evaporating liquid to path through.

The water-repellent particle layer104composed of the water-repellent particles is capable of decreasing entrance of liquid into the inside of the water-repellent particle layer104. The entire side surface of the water-repellent particle layer104can be surrounded with the lower side wall103a. When the water-repellent particle layer104is surrounded with the lower side wall103a, liquid can be prevented from entering the inside of the water-repellent particle layer104.

Each water-repellent particle includes a particle and a water-repellent film coating the surface of the particle.

Examples of such a particle include gravel, sand, silt, and clay. The gravel is a particle having a diameter larger than 2 mm and equal to or less than 75 mm. The sand is a particle having a diameter larger than 0.075 mm and equal to or less than 2 mm. The silt is a particle having a diameter larger than 0.005 mm and equal to or less than 0.075 mm. The clay is a particle having a diameter of 0.005 mm or less.

A water-repellent film coats the surface of each particle. The water-repellent film preferably includes a fluorocarbon group expressed by the chemical formula —(CF2)n—. In this formula, n denotes a natural number. The preferred range of n is 2 or more as well as 20 or less.

The water-repellent film is preferably bonded with the particle by means of covalent bonding. The following chemical formula (I) expresses a preferred water-repellent film.

In this formula, Q denotes hydrogen or fluorine.

m1 and m2 each independently denote 0 or a natural number of 1 or more.

In this formula, n is 2 or more as well as 20 or less.

Described below is an example of a method of producing water repellent particles.

A surface active agent expressed by the chemical formula CX3—(CH2)m1-(CF2)n-(CH2)m2-SiX3is initially dissolved in a nonaqueous solvent to prepare a surface active agent solution. In this formula, X denotes halogen, preferably chlorine.

Then, a plurality of particles are immersed in the surface active agent solution in a dry atmosphere to obtain a plurality of water-repellent particles.

For details thereof, reference can be made to U.S. Pat. No. 5,270,080 (corresponding to Japanese Examined Patent Publication No. 07-063670 B).

Examples of the material for the water-repellent film include a chlorosilane material and an alkoxysilane material. Examples of the chlorosilane material include heptadecafluoro-1,1,2,2-tetrahydrodecyltrichlorosilane and n-octadecyldimethylchlorosilane. Examples of the alkoxysilane material include n-octadecyltrimethoxysilane and nonafluorohexyltriethoxysilane.

The water-repellent particle layer104preferably has slight thermal conductivity so as to decrease thermal conduction between the water tank102and the devolatilizing layer105. The water tank102has a predetermined or higher temperature (e.g. 40 C° or more as well as 60 C° or less) in order that liquid4ais heated to water-evaporate in the water tank102. The devolatilizing layer105has a predetermined or lower temperature (e.g. 15 C° or less) so as to liquefy water vapor. The water tank102and the devolatilizing layer105are quite different from each other in temperature. Desalination efficiency can possibly deteriorate if thermal conductivity is high between the water tank102and the devolatilizing layer105.

The water-repellent particle layer104is made of the plurality of closely located water-repellent particles, among which there is air or the like. The water-repellent particle layer104is thus less thermally conductive than a film or the like made of a uniform material.

The water-repellent particle layer104is 1 cm or more and 30 cm or less in thickness, for example.

If the water-repellent particle layer104is too thin (less than 1 cm thick), water poured into the water tank102can possibly flow into the devolatilizing layer5. In contrast, if the water-repellent particle layer104is too thick (more than 30 cm thick), water vapor to be described later has difficulty to pass through the gaps in the water-repellent particle layer104.

The devolatilizing layer105is located below the water-repellent particle layer104. The devolatilizing layer105can be made of a plurality of particles to which water repellent treatment is not applied. The devolatilizing layer105can be alternatively provided as a space surrounded with the lower side wall103aand the bottom plate103b.

The entire side portion of the devolatilizing layer105can be surrounded with the lower side wall103aand the bottom portion of the devolatilizing layer105can be covered with the bottom plate103b, so that the container103is capable of reserving the fresh water4g.

Water vapor passing from the water-repellent particle layer104through the gaps in the water-repellent particle layer104and reaching the devolatilizing layer105is liquefied into liquid water (fresh water4g) in the devolatilizing layer105. Details thereof will be described later.

The devolatilizing layer105is cooled in the following manner, for example. The devolatilizing layer105is at least partially located in soil113so as to be cooled. For example, the interface between the devolatilizing layer105and the water-repellent particle layer104is made flush with the level of the ground surface, so that the devolatilizing layer105is made lower in temperature than the water-repellent particle layer104.

The devolatilizing layer105can alternatively have a cooling portion.

Described below is desalination using the desalination apparatus1A thus configured.

FIG. 2illustrates the steps of desalination by the desalination apparatus1A.

Liquid is initially poured from the external tank6through the water gate101and the introduction path101ainto the water tank102, and forms the liquid layer4on the water-repellent particle layer104provided in the water tank102. Examples of the liquid include salt water.

The liquid of the liquid layer4in the water tank102is then heated. When the liquid is heated to reach or exceed a fixed temperature, the liquid is water-evaporated. For example, the fixed temperature is set depending on the type of liquid and air pressure in accordance with the saturated water vapor pressure curve. When the liquid is salt water, the example of the fixed temperature is 50 C° or more as well as 60 C° or less.

The liquid of the liquid layer105is heated by solar light, as one example of the heating. Alternatively, the liquid of the liquid layer4is heated by the heater provided to the water tank102. Still alternatively, a heated object can be supplied to the liquid layer4so that the liquid is heated.

The water vapor evaporated from the liquid by heating the liquid then moves upward as well as downward. The water vapor moving downward passes through the gaps among the water-repellent particles in the water-repellent particle layer104and reaches the devolatilizing layer105. The water vapor passing through the gaps among the water-repellent particles in the water-repellent particle layer104is liquefied into liquid water in the devolatilizing layer105. For example, the water vapor is cooled and liquefied into liquid water in the devolatilizing layer105.

In this manner, the desalination apparatus1A generates water that includes less solid matters contained and fewer impurities dissolved in the liquid poured into the water tank102.

Examples of the impurities include ions. Examples of the liquid water obtained at the devolatilizing layer105include fresh water. The water obtained at the devolatilizing layer105is also called “distilled water”.

Modification Example 1

FIG. 3is shows a desalination system2B including a desalination apparatus n according to a modification example of the desalination apparatus1A.

The water tank102can optionally have a drain pipe108aand a drain valve108used for draining liquid of the liquid layer4to the outside. When the drain valve108is opened, the liquid of the liquid layer4is drained from the water tank102. Closing the drain valve108stops draining the liquid of the liquid layer4from the water tank102. The water gate controller1010controls opening/closing of the drain valve108.

There can be optionally provided a film or another structure between the water tank102and the water-repellent particle layer104so as to allow liquid or water vapor to pass therethrough. Furthermore, there can be optionally provided a film or another structure between the water-repellent particle layer104and the devolatilizing layer105so as to allow water vapor to pass therethrough.

The water tank102can optionally have a distilled water drain pipe109and a distilled water drain valve109vused for draining distilled water in the devolatilizing layer105to the outside. When the distilled water drain valve109vis opened, distilled water in the devolatilizing layer105is drained through the distilled water drain pipe109to the outside. In contrast, closing the distilled water drain valve109vstops draining the distilled water in the devolatilizing layer105. The water gate controller1010can optionally control opening/closing of the distilled water drain valve109v.

As shown inFIG. 3, the water tank102can optionally have a lid110covering an opening in the upper side wall102a. The lid110is capable of decreasing water vapor that is released outward from the water tank102. The lid110is also capable of decreasing impurities that enter from the opening of the water tank102. When the seawater layer4is heated by solar light, the lid7is preferably transparent.

The above example refers to the case of obtaining fresh water from salt water. In another case of obtaining distilled water from not salt water but drainage water or the like containing chemical substances dissolved therein, it is also possible to decrease the chemical substances dissolved in the liquid. The desalination apparatuses1A and113are each capable of exerting similar effects as a distillation apparatus. In other words, each of the desalination apparatuses1A and1B removes impurities dissolved in liquid.

The desalination apparatuses1A and1B are configured as described above.

Described next is finding as the basis of the present disclosure, prior to disclosure of the detailed configuration of a desalination system2according to the first embodiment of the present disclosure.

(Finding as Basis of the Invention)

The present inventors have reached the finding that, when introducing liquid to the water tank102, the water-repellent particles possibly move easily so that the surface (top surface) of the water-repellent particle layer104is eroded partially.FIGS. 4A to 4Iare enlarged views each exemplifying a state where the surface of the water-repellent particle layer104is eroded partially.

FIG. 4Ashows a state before the liquid4ais introduced to the water tank102. In this figure, only part of the water tank102and the water-repellent particle layer104are enlarged in the desalination apparatus1A. Exemplified below is a case where the water-repellent particle layer104has a flat top surface and the liquid4ais introduced from the opening of the water tank102along the upper-side side wall102aof the water tank102.

FIG. 4Bshows a state where the liquid4ais introduced to the water tank102from the opening of the water tank102along the upper-side side wall102a. The downward arrow indicates the flow of the liquid4a. The dotted line in the water tank102indicates the liquid layer4that is reserved in the water tank102. When the liquid4ais introduced to the water tank102, the liquid4ais reserved to form the liquid layer4on the water-repellent particle layer104. The flow of the introduced liquid4acauses the water-repellent particles of the water-repellent particle layer104to partially fly upward and float in the liquid layer4, so as to partially erode water-repellent particles1040at the surface of a portion through which the liquid4ais introduced in the surface of the water-repellent particle layer104. The surface of the portion through which the liquid4ais introduced in the surface of the water-repellent particle layer104is eroded partially, so that the surface of the portion through which the liquid4ais introduced in the surface of the water-repellent particle layer104is partially provided with a concave portion400. In other words, the water-repellent particles1040at the surface of the water-repellent particle layer104partially move away and the surface of the water-repellent particle layer104partially has a recess (the concave portion400). The water-repellent particles1040at the water-repellent particle layer104located at the portion through which the liquid4ais introduced and where the concave portion400is provided fly upward into the liquid layer4and float in the liquid layer4.

FIG. 4Cshows a state where the liquid4ais introduced at a larger flow rate to the water tank102from the state ofFIG. 4B. Similarly toFIG. 4B, the flow of the additionally introduced liquid4afurther erodes partially the portion through which the liquid is introduced in the surface of the water-repellent particle layer104(where the concave portion400is provided). The additional introduction of the liquid4afurther increases the depth of the concave portion400. The flow of the liquid4amoves the water-repellent particles1040additionally floating in the liquid layer4mainly in the direction away from the concave portion400in the liquid layer4.

FIG. 4Dshows a state where the water-repellent particles1040floating in the liquid layer4accumulate on the surface of the portion other than the concave portion400in the surface of the water-repellent particle layer104. The water-repellent particles1040accumulate to partially form a plurality of convex portions401at the surface of the portion other than the concave portion400in the surface of the water-repellent particle layer104.

FIG. 4Eshows a state where the liquid layer4is formed to have a predetermined level (a level less than water pressure resistance). Introduction of the liquid4ato the water tank102is stopped in this state. As shown inFIGS. 4C and 4D, the liquid4aintroduced to the water tank102partially erodes the water-repellent particle layer104, so that the concave portion400and the convex portions401are formed at the surface of the water-repellent particle layer104. In other words, the top surface of the water-repellent particle layer104does not have a constant (planar) level but has the concave and convex portions of different levels, so that the level of the liquid layer4is partially different. For example, the introduced flow of the liquid4ais varied in accordance with change in level of the liquid layer4in the water tank104while the liquid4ais introduced. The water-repellent particles1040floating in the liquid layer4are accumulated at different positions of the water-repellent particle layer104due to the change in flow of the liquid4a, so that the plurality of convex portions401are formed.

Accordingly, as shown inFIG. 4E, the surface of the water-repellent particle layer104can possibly have at least one concave portion400and the plurality of convex portions401. The number of the concave portion400is not limited to1, but the surface of the water-repellent particle layer104can possibly have a plurality of concave portions400in accordance with the flow of the liquid4aintroduced to the water tank102or the method of introducing the liquid4a.

After the liquid layer4is formed as shown in FIG.4E, the desalination apparatus1A performs desalination in the steps S102and S103. The desalination evaporates the liquid of the liquid layer4into water vapor that moves away from the liquid layer4and thus decreases the level of the liquid layer4. Additional liquid4ais thus introduced to the water tank102again.

The additional liquid4aintroduced to the water tank102partially erodes the particles1040at the surface of the water-repellent particle layer104, similarly to the state shown inFIG. 4C. When the liquid4ais introduced from the same location of the water tank102, the concave portion400is increased in depth.

The water-repellent particles1040floating in the liquid layer4are accumulated on the surface of the water-repellent particle layer104to form convex portions401at the surface of the water-repellent particle layer104. The convex portions401are increased in level when the water-repellent particles1040are accumulated on the portions already provided with the convex portions401.

As shown inFIGS. 4A to 4H, the concave portion400and the plurality of convex portions401are formed at the surface of the water-repellent particle layer104when the liquid layer4is formed.

InFIG. 4I, the distance between the bottom surface (e.g. the most recessed portion) of the concave portion400and the top surface of the liquid layer4is denoted by “A”, and the distance between the top surface (e.g. the most projecting portion) of the convex portion401and the top surface of the liquid layer4is denoted by “B”. The top surface (liquid surface) of the liquid layer4is also called a “water surface”.

As described above, even when the top surface (water surface) of the liquid layer4is constant, the distance “A” between the bottom surface of the concave portion400and the water surface is larger than the distance “B” between the top surface of the convex portion401and the water surface. Pressure applied to the water-repellent particle layer104depends on the distance between the water-repellent particle layer104and the water surface, so that the concave portion400at the water-repellent particle layer104receives pressure different from pressure applied to the convex portion401at the water-repellent particle layer104.

When liquid is introduced to the water tank102with no consideration that the concave portion400and the convex portions401are formed at the surface of the water-repellent particle layer104, the liquid4aexceeding water pressure resistance is introduced at part of the water-repellent particle layer104. In such a case, the water-repellent particle layer104cannot hold the liquid4aso that the liquid enters (breaks) the water-repellent particle layer104. The phenomenon that the water-repellent particle layer104is incapable of holding liquid is also called “breakage”.

For example, when the water-repellent particle layer104is provided thereon with the liquid layer4of a predetermined level (a level less than water pressure resistance) with reference to the planar surface of the water-repellent particle layer104prior to erosion, the concave portion400receives pressure equal to or more than pressure applied to the reference planar surface (pressure exceeding water pressure resistance) and the water-repellent particle layer104can be broken at the concave portion400.

As shown inFIGS. 4F to 4H, even when the liquid4ais introduced so as to form a liquid layer4as thick as the liquid layer4prior to desalination, the water-repellent particle layer104can be possibly eroded partially so that pressure applied to the eroded portion (the concave portion400) at the water-repellent particle layer104increases to exceed predetermined water pressure resistance and the water-repellent particle layer104is broken at the concave portion400.

The liquid4aof the liquid layer4evaporates every time desalination is performed. It is thus necessary to introduction additional liquid4ato the water tank102. As shown inFIG. 4F, the additional liquid4ais introduced after desalination so that the concave portion400is deepened gradually. More specifically, the distance A between the bottom surface of the concave portion400and the top surface of the liquid layer4indicated inFIG. 4Ikeeps increasing unless water-repellent particles are supplied to repair the concave portion400at the water-repellent particle layer104.

The water pressure resistance of the water-repellent particle layer104depends on the levels of the surface of the water-repellent particle layer104and the top surface of the liquid layer4. The water-repellent particle layer104can be possibly broken if the concave portion400is deepened and the level of the liquid layer4is not adjusted to be decreased in level. The present inventors thus devised the invention of, with assumption that desalination deepens the concave portion400, adjusting the level of the liquid layer4to effectively prevent breakage of the water-repellent particle layer104at the concave portion400.

The desalination system2according to the first embodiment as shown inFIG. 5Aincludes the water tank102, the water-repellent particle layer104, the devolatilizing layer105, a liquid layer level controller106, and the water gate controller1010. The desalination system2further includes a liquid layer adjusting apparatus203that has the liquid layer level controller106, the water gate controller1010, and the like. The desalination system2also includes the desalination apparatus1that has the water tank102, the water-repellent particle layer104, and the devolatilizing layer105. The desalination apparatus1has basic functions same as those of the desalination apparatuses1A and1B already described. The desalination apparatus1is different from the desalination apparatuses1A and1B in that the desalination apparatus1includes the liquid layer level controller106in order for adjustment of the level of the liquid layer4. Configurations which are included in the desalination apparatus1B and its desalination system2B and are not mentioned in the following disclosure of the desalination apparatus1and its desalination system2are applicable where appropriate in a modification example of the first embodiment.

A system including the water tank102, the water-repellent particle layer104, the devolatilizing layer105, and the like is also called a desalination system. The liquid layer adjusting apparatus203is also called a liquid layer adjusting apparatus included in such a desalination system.

The liquid layer level controller106estimates the depth of the concave portion400at the water-repellent particle layer104formed by the liquid4aintroduced to the water tank102to determine the level of the liquid layer4in the water tank102. The liquid layer level controller106shown inFIG. 5Bincludes a liquid layer level adjusting information database106a, an information acquiring unit106b, and a decision unit (liquid layer level determining unit)106c.

The information acquiring unit106bis connected wiredly or wirelessly to the liquid layer level adjusting information database106aand the decision unit106c. The information acquiring unit106band the decision unit106care each connected wiredly or wirelessly to the water gate controller1010.

The liquid layer level adjusting information database106apreliminarily stores information (relationship information) on the relationship between information corresponding to an amount of the liquid4aintroduced to the water tank102and a predetermined level of the liquid layer4.

The information acquiring unit106bpreliminarily stores in the database106ainformation on the relationship between information on the number of times of introducing the liquid4ato the water tank102, which exemplifies information corresponding to the amount of the liquid4aintroduced to the water tank102, and the predetermined level of the liquid layer4. The information acquiring unit106balso acquires the information on the number of times of introduction from the water gate controller1010to store the acquired information.

The decision unit106crefers to the relationship information in the database106aand determines the predetermined level of the liquid layer4in accordance with the information that is acquired by the information acquiring unit106band corresponds to the amount of the liquid4aintroduced to the water tank102. For example, the decision unit106cdecreases the level of the liquid layer4as the liquid4aintroduced to the water tank102increases in amount.

The decision unit106cfurther transmits an open/close adjusting command to the water gate controller1010in order to adjust opening/closing of the water gate101or opening/closing of the drain valve108in accordance with the level of the liquid layer4as determined by the decision unit106c.

The liquid layer level controller106can alternatively include the information acquiring unit106band the decision unit (liquid layer level determining unit)106c. In this case, the information acquiring unit106band the decision unit (liquid layer level determining unit)106care each connected wiredly or wirelessly to the liquid layer level adjusting information database106ato transmit and receive information.

When the water gate101adjusts introduction of the liquid4ato the water tank102, the information corresponding to the amount of the liquid4aintroduced to the water tank102is exemplified by the number of times of opening/closing the water gate101. The amount of the liquid4aintroduced to the water tank102is in proportion to the number of times of opening/closing the water gate101. Assume that the water gate101is opened at a constant open degree (flow velocity of the liquid4a). In this case, the information acquiring unit106bacquires from the water gate controller1010information on the number of times of opening/closing the water gate101by the water gate controller1010and stores the acquired information in the database106a. The decision unit106crefers to the database106aand determines the level of the liquid layer4in accordance with the number of times of opening/closing the water gate101. The decision unit106cdecreases the level of the liquid layer4as the number of times of opening/closing the water gate101is increased.

When making decision, the decision unit106cacquires information preliminarily stored in the database106a, on the relationship between the number of times of opening/closing the water gate101and the level of the liquid layer4(in an example, see the chart inFIG. 6to be described later). The relationship information can be stored in the database106aincluded in the liquid layer level controller106, or can be acquired by the information acquiring unit106bfrom an external storage unit. The level of the liquid layer4corresponds to the surface level of the liquid4a.

The information on the relationship between the number of times of opening/closing the water gate101and the level of the liquid layer4includes an equation having the number of times of opening/closing the water gate101as a variable. One example of the equation is expressed by (the level of the liquid layer4)=30 cm−(the number of times of opening/closing the water gate101)×0.5. The database106aor the external storage unit stores this equation. The decision unit106ccan substitute the number of times of opening/closing the water gate101acquired from the information acquiring unit106bin the equation and calculate the level of the liquid layer4to determine the level of the liquid layer4.

FIG. 6shows one example of the information on the relationship between the number of times of opening/closing the water gate101and the level of the liquid layer4. It is estimated that the concave portion400is deepened as the number of times of opening/closing the water gate101increases. According to the information inFIG. 6, as the number of times of opening/closing the water gate101increases, the level of the top surface of the liquid layer4from the water-repellent particle layer104increases, and therefore the relationship information is thus configured so that the level of the liquid layer4is decreased according thereto. The information on the relationship between the number of times of opening/closing the water gate101and the level of the liquid layer4is preliminarily determined in accordance with formation speed of the concave portion400and is stored in the database106aor the external storage unit.

Another example of the information corresponding to the amount of the liquid4aintroduced to the water tank102can include an amount of opening the water gate101and a period of opening the water gate101in place of the number of times of opening/closing the water gate101. The amount of opening the water gate101can be measured by a flowmeter (not shown) or the like, and corresponds to the amount of the introduced liquid4aper unit time. The period of opening the water gate101corresponds to the period of introducing the liquid4a. In this case, the information acquiring unit106bacquires the amount of opening the water gate101and the period of opening the water gate101from the flowmeter (not shown) and the water gate controller1010.

In an exemplary case where the introduced amount of the liquid4aper unit time while the water gate101is opened is constant and the period of opening the water gate101is also constant, the decision unit106cis capable of estimating the amount of the liquid4aintroduced to the water tank102in accordance with the number of times of opening/closing the water gate101. Assume that both the maximum open degree and the opening/closing speed of the water gate101are constant in this case.

In a case where the introduced amount of the liquid4aper unit time while the water gate101is opened is constant (unchanged), the decision unit106cis capable of estimating the amount of the liquid4aintroduced to the water tank102in accordance with the number of times of opening/closing the water gate101and the period of opening the water gate101.

The number of times of opening/closing the water gate101can be replaced with the elapsed time from formation of the liquid layer4. This is effective when a constant amount of the liquid4ais introduced to the water tank102per unit elapsed time.

FIG. 7Ashows an example of information on the relationship between the elapsed time from formation of the liquid layer4and the level of the liquid layer4. The elapsed time corresponds to a period from the time of formation of the liquid layer4to the present time (when the water gate is controlled).FIG. 7Aindicates the relationship information by the day as a unit elapsed time. Examples of the unit elapsed time include the minute, hour, day, week, month, and year.

The information acquiring unit106bin the liquid layer level controller106acquires an elapsed time from a time measuring unit1061. The time measuring unit1061acquires a start time of formation of the liquid layer4and the present time (when the water gate is controlled) from the water gate controller1010, obtains the elapsed time from the formation of the liquid layer4, and transmits the obtained elapsed time to the information acquiring unit106b.

The information acquiring unit106bin the liquid layer level controller106acquires information on the relationship between the elapsed time from the formation of the liquid layer4and the level of the liquid layer4, from the database106aor the external storage unit. According to the information on the relationship between the information corresponding to the elapsed time and the surface level of the liquid layer4in the water tank102, the surface level of the liquid layer4is decreased as the elapsed time from the introduction of the liquid4ais longer.

If the decision unit106cdecides that the number of times of opening/closing the water gate101or the elapsed time is equal to or more than a predetermined value, it is estimated that the concave portion400is too deepened and the thickness of the water-repellent particle layer104is equal to or less than a certain value. The decision unit106ccan optionally transmit a stop command to the water gate controller1010to stop desalination. For example, the decision unit106ctransmits a command to the water gate controller1010so that the drain valve108is opened and the entire liquid in the water tank102is discharged from a drain port108a. A water-repellent treatment layer104is repaired after the liquid in the water tank102is discharged from the drain port108a. Such “Repair” in this case indicates a step of decreasing the depth of the concave portion400formed at the water-repellent particle layer104. Examples of specific repair include filing water-repellent particles in the concave portion400to decrease the depth of the concave portion400, or temporarily removing the entire water-repellent particle layer104and forming a new water-repellent particle layer104, or the like.

The water gate controller1010controls to independently open/close the water gate101and the drain valve108so as to adjust the level of the liquid of the liquid layer4or remove the entire liquid layer4. In an example, the water gate controller1010controls opening/closing of the water gate101, so as to adjust the amount of the liquid4aintroduced to the water tank102in accordance with the level of the liquid layer4as determined by the liquid layer level controller106.

For example, the water gate controller1010can acquire information on the level of the water surface from a water surface level measuring unit1065that measures the surface level of the liquid layer4in the water tank102.

The water surface level measuring unit1065can be embodied by a known water gauge. Examples of the water surface level measuring unit1065include an ultrasonic wave measuring unit1065a. As shown inFIG. 7B, the ultrasonic wave measuring unit1065aincludes an ultrasonic wave transmitter/receiver1065b, a time measuring unit1065c, and a calculating unit1065d. The ultrasonic wave transmitter/receiver1065bis located on the upper side wall102a. The ultrasonic wave transmitter/receiver1065btransmits an ultrasonic wave to the liquid layer4. The ultrasonic wave transmitter/receiver1065breceives an ultrasonic wave reflected at the liquid layer4. The time measuring unit1065cmeasures a period from transmission of an ultrasonic wave from the ultrasonic wave transmitter/receiver1065bto receipt of the wave. The calculating unit1065dcalculates the level of the water surface from a predetermined relationship between a time and a distance and the time measured by the time measuring unit1065c. The ultrasonic wave measuring unit1065afor transmitting and receiving an ultrasonic wave can be replaced with a laser light measuring unit for transmitting and receiving laser light.

The water gate controller1010opens the water gate101to introduction the liquid4ato the water tank102until acquiring from the level measuring unit1065information on the level of the liquid layer4as determined by the liquid layer level controller106. The water gate controller1010closes the water gate101when the level of the water surface measured by the level measuring unit1065is equal to the level of the liquid layer4determined by the liquid layer level controller106.

<Liquid Layer Level Adjustment Step by Desalination System2>

FIG. 8is a flowchart of liquid layer level adjustment step by the liquid layer adjusting apparatus203.

The information acquiring unit106bin the liquid layer level controller106initially causes the water gate controller1010to open the water gate101and acquires information corresponding to the number of times of introducing the liquid4ato the water tank102, from the water gate controller1010. As described above, examples of the information corresponding to the number of times of introducing the liquid4ato the water tank102include the number of times of opening/closing the water gate101and the elapsed time from formation of the liquid layer4. The information acquiring unit106bin the liquid layer level controller106acquires the information from the water gate controller1010.

The decision unit106cin the liquid layer level controller106subsequently determines the level of the liquid layer4in accordance with the information on the relationship between the information corresponding to the number of times of introducing the liquid4ato the water tank102and the level of the liquid layer4as stored in and read out of the database106aand the information corresponding to the number of times of introducing the liquid4ato the water tank102as acquired by the information acquiring unit106b. More specifically, the decision unit106crefers to the information on the relationship between the number of times and the level stored in the database106ain accordance with the number of times of introducing the liquid4ato the water tank102as acquired by the information acquiring unit106b, resulting in determining the level of the liquid layer4.

The decision unit106csubsequently transmits a command (signal) to the water gate controller1010in order to adjust opening/closing of the water gate101or opening/closing of the drain valve108in accordance with the level of the liquid layer4as determined by the decision unit106c. Upon receipt of the command from the decision unit106c, the water gate controller1010adjusts opening/closing of the water gate101in accordance with the level of the liquid layer4as determined by the decision unit106c. More specifically, for example, the decision unit106ccalculates the time of opening the water gate101until the liquid layer4reaches the determined level, and controls the water gate controller1010to open the water gate101during the calculated time.

It is thus possible to effectively prevent breakage of the water-repellent particle layer104at the concave portion400and efficiently and reliably perform automatic desalination.

Modification Example 2

According to the first embodiment and the modification example 1, the water gate controller1010controls to open the single water gate101and introduction the liquid4ato the water tank102through the single introduction path101a. Alternatively, a plurality of water gates101can be opened so that liquid4ais introduced to the water tank102through a plurality of introduction paths101a. In such a case where the liquid4ais introduced from the plurality of introduction paths101ato the water tank102, the information on the relationship between the information corresponding to the number of times of introducing the liquid4aand the level of the liquid layer4can be set in view of the number of the introduction paths101aused for introducing the liquid4a.

For example, each ofFIGS. 9A and 9Bis a top view showing a state where the liquid4ais introduced to the water tank102. In this case, the introduction paths101ainclude three introduction paths1021a,1021b, and1021cand the water gates101include three water gates101-1,101-2, and101-3.

The water tank102shown inFIGS. 9A and 9Cis provided on the side wall with the three introduction paths1021a,1021b, and1021c. The introduction paths1021a,1021b, and1021care connected to the three water gates101-1,101-2, and101-3, respectively, that are controlled to open and close by the water gate controller1010. The water gates101-1,101-2, and101-3are each connected to the external tank6. When the water gate controller1010opens each of the water gates101-1,101-2, and101-3, the liquid4ain the external tank6is introduced to the water tank102. Closing each of the water gates101-1,101-2, and101-3stops introduction of the liquid4afrom the external tank6to the water tank102.

FIG. 9Ashows a state where the liquid4ais introduced simultaneously to the water tank102through the three introduction paths1021a,1021b, and1021c.FIG. 9Bis an enlarged top view showing a flow of the liquid4athrough one of the introduction paths in the state ofFIG. 9A.FIG. 9Cshows a state where the liquid4ais introduced simultaneously to the water tank102through the two introduction paths1021aand1021cat the both ends out of the three introduction paths1021a,1021b, and1021c. InFIGS. 9A and 9C, shaded regions A indicate the flows of the liquid4aintroduced to the water tank102through the three introduction paths1021a,1021b, and1021cand through the two introduction paths1021aand1021c, respectively.

The liquid4aintroduced through each of the introduction paths1021a,1021b, and1021cforms a flow expanding in a fan shape or the like (e.g. an inverted trapezoidal shape) and is reserved in the water tank102. For example, a predetermined region (the region indicated inFIG. 9A) forming the flow of the liquid has a fan shape (e.g. an inverted trapezoidal shape) having the center at an opening of each of the introduction paths.

When the flows of the introduced liquid4aexpand, the flows of the liquid introduced through the plurality of introduction paths can be possibly overlapped in some regions. Shaded regions B inFIG. 9Aeach indicate a portion where the flows of the liquid4aintroduced to the water tank102through the two adjacent introduction paths1021aand1021bor1021band1021cout of the three introduction paths1021a,1021b, and1021care overlapped with each other. In each of the shaded regions B (hereinafter, also called an overlapped region B) it is assumed that the amount of the introduced liquid4ais larger than that in a region other than the overlapped region B and the concave portion400is deepened partially.

Whether or not there is the shaded region B depends on whether or not the predetermined regions (the shaded regions A shown inFIG. 9A) forming the flows of the liquid4aintroduced through the respective introduction paths are overlapped with each other.

FIG. 9Bshows the enlarged shaded region A indicating the flow of the liquid introduced through the introduction path1021ainFIG. 9A(this applies to each of the introduction paths1021band1021c). The shaded region A indicating the flow of the liquid4aincludes a shaded region D formed in the direction of introducing the liquid4athrough the introduction path1021a(in the direction of the opening of the introduction path1021a) (e.g. upward in the up-down direction inFIG. 9B), a shaded region C expanded rightward from the direction of introducing the liquid4a, and a shaded region E expanded leftward from the direction of introducing the liquid4a. In the direction perpendicular (e.g. the right-left direction inFIG. 9B) to the direction (e.g. upward in the up-down direction inFIG. 9B) of introducing the liquid4athrough the introduction path1021ainFIG. 92, the shaded region C has a maximum length L2, the shaded region D has a maximum length L3, the shaded region E has a maximum length L4, and the shaded region A (including the shaded regions C, D, and E) has a maximum length L5.

The areas of the shaded regions C and D depend on the amount of the introduced liquid4aper unit time or the like. The shaded regions C and E shown inFIG. 9Bare bilaterally symmetric. The shaded regions C and E can be asymmetric depending on the positional relationship between the introduction path1021aand the introduction path1021bor the direction of the opening of the introduction path1021a.

When the shaded regions C and E formed by the liquid4aintroduced through the adjacent introduction paths are overlapped with each other, the shaded region B shown inFIG. 9Ais formed. More specifically, the shaded region B is formed when the sum of the vertical maximum length L4of the region E expanded from the direction of introducing the liquid4athrough the introduction path1021a(the direction of the opening of the introduction path1021a) (e.g. upward in the up-down direction inFIG. 9A) and the vertical maximum length L2of the region C expanded from the direction of introducing the liquid4athrough the introduction path1021bis larger than the distance between these adjacent introduction paths.

For example, inFIG. 9A, the shaded region B is formed when the distance obtained by adding the maximum length (e.g. the length L4inFIG. 9B) of the region E expanded leftward from the shaded region A in the direction perpendicular (e.g. the right-left direction inFIG. 9A) to the direction of introducing the liquid4athrough the introduction path1021aand the maximum length (e.g. the length L2inFIG. 9B) of the region C expanded rightward from the shaded region A in the direction perpendicular to the direction of introducing the liquid4athrough the introduction path1021bis smaller than a distance L1between the opening of the introduction path1021aand the opening of the introduction path1021b.

More specifically, the following is applicable when the liquid4aintroduced through any two introduction paths forms the shaded regions A in the inverted trapezoidal shapes of the same areas as shown inFIG. 9C. InFIG. 9C, the amounts of the liquid4aintroduced through the introduction paths1021aand1021care equal per unit time. The liquid4aintroduced through each of the introduction paths1021aand1021cforms the shaded region A having the inverted trapezoidal shape of the same area.

The distance L1between the adjacent introduction paths is defined as a gap between the end, close to the center introduction path1021b, of the opening of the right-end introduction path1021aand the end, close to the center introduction path1021b, of the opening of the left-end introduction path1021cinFIG. 9C. Lines extended upward from the end, close to the center introduction path1021b, of the opening of the right-end introduction path1021a, as well as from the end of the upper bottom (the lower side inFIG. 9C) of the inverted trapezoidal shape of the shaded region A of the liquid4aflown out through the right-end introduction path1021a, and the lower bottom (the upper side inFIG. 9C) of the inverted trapezoidal shape cross to form a right triangle Ti. The distance L2at the bottom side of the right triangle is assumed to be the maximum width L2of the region A of the liquid4aflown out of the opening of the right-end introduction path1021aso as to expand toward the opening of the center introduction path1021b. The overlapped shaded region B is formed if the maximum width L2is larger than a half of the distance L1between the adjacent openings (seeFIG. 9A). In contrast, the overlapped shaded region B is not formed if the maximum width L2is smaller than a half of the distance L1between the adjacent openings (seeFIG. 9C).

In other words, if the distance L1between the plurality of introduction paths used for introducing the liquid4ais equal to or less than a predetermined distance, the liquid4aintroduced through these introduction paths forms an overlapped portion. If the distance L1between the plurality of introduction paths used for introducing the liquid4ais more than the predetermined distance, the liquid4aintroduced through these introduction paths does not form any overlapped portion. The predetermined distance can be decided depending on the amount of the introduced liquid or the direction of the opening of the introduction path.

At the water-repellent particle layer104receiving the flow indicated by the shaded region B, the flows of the liquid4athrough the two introduction paths1021aand1021bor the two introduction paths1021band1021cform the deeper concave portion400in the water-repellent particle layer104. Meanwhile, at the water-repellent particle layer104receiving the flow indicated by the shaded region A, the flow of the liquid4athrough any one of the introduction paths1021a,1021b, and1021cforms the concave portion400in the water-repellent particle layer104.

When introducing the liquid4aof a similar amount to the water tank102, the concave portion400formed at the water-repellent particle layer104receiving the flows of the liquid4aindicated by the vertically hatched region B is deeper than the concave portion400formed at the water-repellent particle layer104receiving the flow of the liquid4aindicated by the horizontally hatched region A.

Accordingly, the decision unit106ccan optionally change the information on the relationship between the information corresponding to the amount of the liquid4aintroduced to the water tank102and the level of the liquid layer4in accordance with the distance between the plurality of introduction paths used for introducing the liquid4ato the water tank102. For example, the decision unit106csets the level of the liquid layer4in the case where the distance L1between the adjacent introduction paths is equal to or less than the predetermined distance so as to be higher than the level of the liquid layer4in the case where the distance L1between the adjacent introduction paths is more than the predetermined distance.

The predetermined distance is dependent on the difference in level between the bottom surface of the introduction path and the water surface, the amount of the introduced liquid4aper unit time, or the like. The predetermined distance is 1 m, for example.

FIG. 10Aexemplifies values before and after change of the relationship information on the level of the liquid layer4in accordance with the distance L1between the plurality of introduction paths used for introducing the liquid4ato the water tank102. The information on the relationship between the number of times of opening/closing the water gate101and the level of the liquid layer4after the change (see the right chart inFIG. 10A) includes the levels of the liquid layer4higher than those in the relationship information on the level of the liquid layer4before the change (see the right and left charts inFIG. 10A).

In an example, the level of the liquid layer4in the case where the number of times of opening/closing the water gate101before the change is 1 is lower by 0.5 cm than the level of the liquid layer4in the case where the number of opening/closing times is 0. Meanwhile, the level of the liquid layer4in the case where the number of times of opening/closing the water gate101after the change is 1 is lower by 0.2 cm than the level of the liquid layer4in the case where the number of opening/closing times is 0. In summary, the change in level of the liquid layer4each time the number of times of opening/closing the water gate101increases in the relationship information after the change is smaller than the change in level of the liquid layer4in the relationship information before the change. The level of the liquid layer4is changed largely by decreasing the change in level of the liquid layer4(the amount of decreasing the level of the liquid layer4).

If there is a portion (the overlapped region B) receiving the flows of water through the plurality of introduction paths, the level of the liquid layer4can be obtained by adding a predetermined value as a safety coefficient for prevention of breakage to the reference level of the liquid layer4.

Alternatively, the database106aor the external storage unit can store both of the information on the relationship between the information corresponding to the amount of the liquid4aintroduced to the water tank102and the surface level of the liquid4ain the water tank102in the case where there is the portion (the overlapped portion B) receiving flows of water from a plurality of introduction paths and the information on the relationship between the information corresponding to the amount of the liquid4aintroduced to the water tank102and the surface level of the liquid4ain the water tank102in the case where there is not the portion (the overlapped region B) receiving flows of water from a plurality of introduction paths.

The information acquiring unit106bin the liquid layer level controller106acquires information on opening/closing of each of the water gates101-1,101-2, and101-3from the water gate controller1010. If the distance L1between the plurality of introduction paths on which the water gates101are opened is equal to or less than the predetermined distance, the decision unit106cdetermines the level of the liquid layer4in accordance with the information on the relationship between the information corresponding to the amount of the liquid4aintroduced to the water tank102and the surface level of the liquid4ain the water tank102in the case where there is a portion receiving flows of water from a plurality of introduction paths. If the distance L1between the plurality of introduction paths on which the water gates101are opened is more than the predetermined distance, the decision unit106cdetermines the level of the liquid layer4in accordance with the information on the relationship between the information corresponding to the amount of the liquid4aintroduced to the water tank102and the surface level of the liquid4ain the water tank102in the case where there is no portion receiving flows of water from a plurality of introduction paths.

If the a large amount of water vapor is generated from the liquid4ain the water tank102because of high temperature or another reason, a user or the like is capable of commanding, using the input unit1011, the water gate controller1010to increase the amount of the introduced liquid4aper unit time. For example, the liquid4ais introduced to the water tank102through a plurality of introduction paths. More specifically, as shown inFIG. 9A, the liquid4ais introduced to the water tank102through the three introduction paths1021a,1021b, and1021c.

If the temperature of the liquid4aintroduced to the water tank102is lower than the temperature of the liquid4aof the liquid layer4, the temperature of the liquid layer4is decreased by a large amount of introduced liquid4a. For example, a command can be issued to decrease the amount of the introduced liquid4aper unit time so as to decrease the temperature of the liquid layer4as less as possible. In this case, a user or the like causes, using the input unit1011, the water gate controller1010to introduction the liquid4ato the water tank102through introduction paths1021of a number as less as possible. More specifically, as shown inFIG. 9C, the liquid4ais introduced to the water tank102through the two introduction paths1021aand1021cat the both ends without using the center introduction path1021b.

Force generated by the flow of the liquid4aand applied to the water-repellent particle layer104is dispersed as the number of using introduction paths increases. In this case, the number of concave portions400is increased and each of the concave portions400is decreased in depth. For example, the decision unit106ccan increase the level of the liquid layer4as a larger number of introduction paths are used for introduction of the liquid4a. More specifically, the decision unit106cdecreases the level of the liquid layer4as the number of the introduction paths are larger, with reference to the information on the relationship between the information corresponding to the amount of the liquid4aintroduced to the water tank102and the level of the liquid layer4as indicated inFIG. 6. If the distance L1between the plurality of introduction paths is equal to or less than a predetermined value, the decision unit106cdecreases the level of the liquid layer4as compared with the case where the distance L1between the plurality of introduction paths is more than the predetermined value.

According to the first embodiment, the liquid layer level controller106determines the level of the liquid4aintroduced to the water tank102in accordance with the information on the relationship between the information corresponding to the amount of the liquid4aintroduced to the water tank102and the surface level of the liquid4ain the water tank102, and the water gate controller1010adjusts the liquid4aintroduced to the water tank102in accordance with the determined surface level of the liquid4a. It is thus possible to effectively prevent breakage of the water-repellent particle layer104at the concave portion400and efficiently and reliably perform automatic desalination.

Second Embodiment

Continuous desalination can possibly increase concentration of impurities dissolved in liquid in the water tank102and deposit the impurities on the water-repellent particle layer104. For example, liquid of the liquid layer4is partially evaporated, so that the concentration of the impurities dissolved in the liquid layer4is increased and the impurities are deposited and accumulated on the surface of the water-repellent particle layer104. In short, impurities2000are deposited when the concentration of the impurities in the liquid layer4exceeds saturated concentration.

FIG. 10Bshows a state where the impurities2000are deposited on the water-repellent particle layer104. The impurities2000are accumulated on the surface of the water-repellent particle layer104. In this case, the impurities2000are deposited and accumulated on a slanted surface of the convex portion401, a slanted surface of the concave portion400, and the like, in the surface of the water-repellent particle layer104. The impurities2000accumulated on the slanted surface of the convex portion401is assumed to be moved from the slanted surface of the convex portion401to the slanted surface of the concave portion400due to gravity. The impurities2000on the surface of the concave portion400are assumed to be relatively more than the impurities2000on the surface of the convex portion401.

FIG. 10Cshows a state where the liquid4ais introduced to the water tank102when the impurities2000are deposited on the water-repellent particle layer104. The flow of the liquid4aintroduced to the water tank102shifts the impurities2000accumulated on the concave portion400in the liquid layer4, similarly to the water-repellent particles1040at the concave portion400.

FIG. 10Dshows a state where the liquid4ais introduced to the water tank102when the impurities2000are not deposited on the water-repellent particle layer104. The water-repellent particles1040floating in the liquid in the water tank102in the state shown inFIG. 10Care smaller in amount than the water-repellent particles1040in the state shown inFIG. 10D.

In the state shown inFIG. 10C, the impurities2000are deposited on the water-repellent particle layer104. Accordingly, the impurities2000accumulated on the concave portion400are shifted in the liquid layer4by the flow of the liquid and then the water-repellent particles1040at the concave portion400are shifted in the liquid layer4. That is, force generated by the flow of the liquid is applied also for shifting the impurities2000at the concave portion400. The amount of the moving water-repellent particles1040at the concave portion400is smaller than that of the case where the impurities2000are not deposited.

In a desalination system3according to the second embodiment, the decision unit106cacquires, from an impurity deposition information acquiring unit232to be described later, information on whether or not the impurities2000are deposited, and determines the level of the liquid layer4in the water tank102in view of the information on whether or not the impurities are deposited. For example, when acquiring from the impurity deposition information acquiring unit232information that the impurities2000are deposited, the level of the liquid layer44in the water tank102is adjusted to be higher than the level of the liquid layer4in the state where the impurities2000are not deposited.

FIGS. 11A and 11Beach show the desalination system3according to the second embodiment. The desalination system3shown inFIG. 11Aincludes the water tank102, the water-repellent particle layer104, the devolatilizing layer105, and a liquid layer adjusting apparatus231. As shown inFIGS. 11A and 11B, the liquid layer adjusting apparatus231in the desalination system3includes a liquid layer level controller206, the water gate controller1010, the impurity decision unit2063, either one of a concentration measuring unit2061and an imaging unit2062, and the like.

The liquid layer level controller206is configured similarly to the liquid layer level controller106, and includes a liquid layer level adjusting information database206a, an information acquiring unit206b, and a decision unit (liquid layer level determining unit)206c. The information acquiring unit206bis connected wiredly or wirelessly to the liquid layer level adjusting information database206aand the decision unit206c. The information acquiring unit206band the decision unit206care each connected wiredly or wirelessly to the water gate controller1010. The liquid layer level controller206is different from the liquid layer level controller106only in reference information for decision and decision contents.

The impurity decision unit2063is connected wiredly or wirelessly to the concentration measuring unit2061or the imaging unit2062. The exemplified impurity deposition information acquiring unit232includes either one of the concentration measuring unit2061and the imaging unit2062, and the impurity decision unit2063.

The liquid layer adjusting apparatus231is also called a liquid layer adjusting system included in the desalination system3.

The concentration measuring unit2061measures concentration of the impurities2000in the liquid of the liquid layer4. The concentration measuring unit2061can possibly acquire time from a time measuring unit233for measuring time and transmit, to the impurity decision unit2063, the measured concentration of the impurities2000associated with the time.

The concentration measuring unit2061is located inside the water tank102as well as inside the liquid layer4.FIG. 12Aexemplifies the concentration measuring unit2061located in the liquid layer4. Out of the liquid of the liquid layer4, liquid located close to the water-repellent particle layer104contains impurities of the highest concentration. The concentration measuring unit2061is thus located close to the water-repellent particle layer104, for example. More specifically, the concentration measuring unit2061is located in contact with the water-repellent particle layer104.

The imaging unit2062captures an image of the surface of the water-repellent particle layer104. The imaging unit2062can possibly acquire time from the time measuring unit233for measuring time and transmit, to the impurity decision unit2063, the captured image associated with the time.

The imaging unit2062is located so as to capture an image of the surface of the water-repellent particle layer104. More specifically, as shown inFIG. 12B, the imaging unit2062is located inside the liquid layer4so as to be less influenced by light that is reflected at the surface of the liquid layer4.

The impurity decision unit2063decides whether or not the impurities2000having dissolved in the liquid are deposited on the water-repellent particle layer104.

The impurity decision unit2063decides whether or not concentration of the impurities2000measured by the concentration measuring unit2061is within a predetermined concentration range. If the measured concentration is within the predetermined concentration range, the impurity decision unit2063decides that the impurities2000are deposited. If the measured concentration is not within the predetermined concentration range, the impurity decision unit2063decides that the impurities2000are not deposited. The predetermined concentration range is equal to or covers up to saturated concentration from concentration that is equal to or smaller by a predetermined degree than the saturated concentration. The exemplary predetermined concentration range covers from a concentration lower by 3% than saturated concentration to the saturated concentration.

If the concentration of the liquid layer4is within the predetermined concentration range for at least a predetermined period, the impurity decision unit2063can decide that the impurities2000are deposited. The impurity decision unit2063can decide the amount of the deposited impurities2000in accordance with the length of the predetermined period as well as with the information on whether or not the impurities2000are deposited.

The impurity decision unit2063acquires the predetermined concentration range that is stored in a reference storage unit2063a. The liquid impurity decision unit2063itself can include the reference storage unit2063a(illustrated outside the impurity decision unit2063inFIG. 11Afor better comprehension), or the impurity decision unit2063can acquire the predetermined concentration range from the reference storage unit that is provided externally. The reference storage unit2063acan store the predetermined period in addition to the predetermined concentration range.

The impurity decision unit2063decides whether or not the impurities2000are contained in accordance with the image captured by the imaging unit2062. The impurity decision unit2063decides whether or not the impurities2000are contained in accordance with whether or not the captured image includes color of the impurities2000preliminarily dissolved in the liquid. The impurity decision unit2063can refer to brightness information when the impurities2000and the water-repellent particles have the same color.

The impurity decision unit2063can decide the amount of the deposited impurities2000in accordance with the amount of the impurities2000in the captured image. The amount of the impurities2000in the captured image can be expressed by a ratio of the impurities2000to the image or an area of the impurities2000.

The impurity decision unit2063acquires predetermined color or brightness of the impurities2000that is stored in the reference storage unit2063a. The impurity decision unit2063can include the reference storage unit2063a(illustrated outside the impurity decision unit2063inFIG. 11Afor better comprehension), or the impurity decision unit2063can acquire color or brightness of the impurities2000in a predetermined image from the external reference storage unit. The reference storage unit2063acan store, in addition to predetermined color or brightness of the impurities2000, a predetermined ratio of the impurities2000or a predetermined area of the impurities2000.

The liquid layer level controller206acquires, from the impurity decision unit2063, information on whether or not the impurities2000having dissolved in the liquid are deposited on the water-repellent particle layer104, estimates the depth of the concave portion400at the water-repellent particle layer104formed by introduction of the liquid4ato the water tank102in accordance with the acquired information on whether or not the impurities are deposited, and determines the level of the liquid layer4in the water tank102.

For example, the impurity decision unit2063can acquire concentration information from the concentration measuring unit2061for measuring a concentration of liquid and decide whether or not there are the impurities, and then, the liquid layer level controller206can acquire information thereon. If the concentration measured by the concentration measuring unit2061is equal to a saturated concentration at least for a predetermined period, the impurity decision unit2063decides that the impurities2000are deposited. Alternatively, the imaging unit2062captures an image of the surface of the water-repellent particle layer104and the impurity decision unit2063decides whether or not there are impurities in accordance with the captured image.

For example, the impurity decision unit2063preliminarily stores sizes or shapes of the deposited impurities2000as information on the impurities2000. The impurity decision unit2063analyzes the captured image and acquires information on whether or not the impurities2000are deposited. The impurity decision unit2063can preliminarily store a shape of a particle forming the water-repellent particle layer104, to decide that the impurities2000are deposited when a lump of a different shape is detected. The impurity decision unit2063can alternatively obtain the amount of the impurities2000from the number or the area of the deposited impurities2000in the image captured by the imaging unit2062.

The decision unit206cin the liquid layer level controller206changes the information on the relationship between the information corresponding to the number of times of introducing the liquid to the water tank102and the level of the liquid of the liquid layer4in accordance with the decision information on whether or not the impurities2000are deposited as decided by the impurity decision unit2063, and then, determines the level of the liquid layer4. For example, if the impurity decision unit2063decides that the impurities2000are deposited, the liquid layer level controller206controls the water gate controller1010so as to increase the level of the liquid in comparison to the case where the impurities2000are not deposited. If a large amount of impurities2000are deposited on the water-repellent particle layer104, a movement amounts of water-repellent particles are decreased and the concave portion400formed by introduction of the liquid4ato the water tank102is less deeper than the concave portion400formed by introduction of the liquid4ato the water tank102in a case where the impurities2000are not deposited on the water-repellent particle layer104. It is thus possible to increase the level of the liquid. In contrast, if the impurity decision unit2063decides that the impurities2000are not deposited, the decision unit206cin the liquid layer level controller206does not change the level of the liquid. The decision information on whether or not the impurities2000are deposited is not necessarily binary information. When the impurity decision unit2063decides that the impurities2000are deposited, the decision unit206cin the liquid layer level controller206can decide the level of the liquid layer4in accordance with the amount of the deposited impurities2000.

FIG. 13is a flowchart of liquid layer level adjustment by the liquid layer adjusting apparatus231in the desalination system3.

The information acquiring unit206bin the liquid layer level controller206initially causes the water gate controller1010to open the water gate101and acquires information corresponding to the number of times of introducing the liquid4ato the water tank102, from the water gate controller1010. As described above, examples of the information corresponding to the number of times of introducing the liquid4ato the water tank102include the number of times of opening/closing the water gate101or the elapsed time from formation of the liquid layer4. The information acquiring unit206bin the liquid layer level controller206acquires the information from the water gate controller1010.

The decision unit206cin the liquid layer level controller206subsequently acquires from the impurity deposition information acquiring unit232information on whether or not the impurities2000are deposited, and changes as necessary, in accordance with the acquired information, the information on the relationship between the information corresponding to the number of times of introducing the liquid to the water tank102and the level of the liquid layer4, which is stored in the database206aor the external storage unit and read out by the decision unit206c. For example, when acquiring from the impurity deposition information acquiring unit232information that the impurities2000are not deposited in the liquid layer4, the decision unit206cin the liquid layer level controller206does not change the relationship information. In contrast, when acquiring from the impurity deposition information acquiring unit232information that the impurities2000are deposited in the liquid layer4, the decision unit206cin the liquid layer level controller206changes the relationship information as described above.

The decision unit206cin the liquid layer level controller206subsequently determines the level of the liquid layer4in accordance with the information, which is changed in step S301or is not changed with no necessity, on the relationship between the information corresponding to the number of times of introducing the liquid to the water tank102and the level of the liquid layer4and the acquired information corresponding to the number of times of introducing the liquid to the water tank102. More specifically, when changed in step S301, the decision unit206crefers to the information on the relationship between the number of times and the level as changed in step S301to determine the level of the liquid layer4in accordance with the number of times of introducing the liquid4ato the water tank102as acquired by the information acquiring unit206b. When not changed in step S301, the decision unit206crefers to the information on the relationship between the number of times and the level as stored in the database206aor the external storage unit to determine the level of the liquid layer4in accordance with the number of times of introducing the liquid4ato the water tank102that is acquired by the information acquiring unit206b.

The decision unit206csubsequently transmits a command to the water gate controller1010in order to adjust opening/closing of the water gate101or opening/closing of the drain valve108in accordance with the level of the liquid layer4determined by the decision unit206c. Upon receipt of the command from the decision unit206c, the water gate controller1010adjusts opening/closing of the water gate101in accordance with the level of the liquid layer4determined by the decision unit206c. More specifically, for example, the decision unit206ccalculates the period of opening the water gate101until the liquid layer4reaches the level determined by the decision unit206c, and controls the water gate controller1010to open the water gate101during the calculated period.

It is thus possible to effectively prevent breakage of the water-repellent particle layer104at the concave portion400and efficiently and reliably perform automatic desalination.

According to the second embodiment, when acquiring from the impurity deposition information acquiring unit232the information that the impurities2000are deposited in the liquid layer4, the decision unit206cin the liquid layer level controller206determines the level of the liquid4aintroduced to the water tank102in view of the acquired information on whether or not the impurities are deposited, in accordance with the information on the relationship between the information corresponding to the amount of the liquid4aintroduced to the water tank102and the surface level of the liquid4ain the water tank102, and the water gate controller1010adjusts the liquid4aintroduced to the water tank102in accordance with the determined surface level of the liquid4a. It is thus possible to effectively prevent breakage of the water-repellent particle layer104at the concave portion400and more efficiently and more reliably perform automatic desalination.

Third Embodiment

The liquid4acan be possibly heated partially to be water-evaporated while the liquid4ais flowing in the water tank102. The liquid4atemporarily exceeds a saturated concentration, so that the impurities2000are deposited in the introduction path101a. The flow of the liquid4ais changed by the impurities2000that are deposited in the introduction path101aused for introducing the liquid4ato the water tank102, and the flow of the liquid4aintroduced to the water tank102is also changed. More specifically, if a large amount of impurities2000are deposited in the introduction path101a, a less amount of liquid4aflows in the introduction path101a.

In a desalination system7according to the third embodiment, an introduction path impurity deposition information acquiring unit332acquires information on whether or not the impurities2000are deposited in the introduction path101a, and the decision unit106cdetermines the level of the liquid layer4in accordance with the acquired information. For example, when acquiring from the introduction path impurity deposition information acquiring unit332information that the impurities2000are deposited, the level of the liquid layer4in the water tank102is adjusted to be higher than the level of the liquid layer4in the state where the impurities2000are not deposited.

FIGS. 14A and 14Beach show the desalination system7according to the third embodiment. The desalination system7includes the water tank102, the water-repellent particle layer104, the devolatilizing layer105, and a liquid layer adjusting apparatus241. The liquid layer adjusting apparatus241in the desalination system7includes a liquid layer level controller306, the water gate controller1010, an impurity decision unit3063, either one of a concentration measuring unit3061and an imaging unit3062, and the like.

The liquid layer level controller306is configured similarly to the liquid layer level controller106, and includes a liquid layer level adjusting information database306a, an information acquiring unit306b, and a decision unit (liquid layer level determining unit)306c. The information acquiring unit306bis connected to the liquid layer level adjusting information database306aand the decision unit306c. The information acquiring unit306band the decision unit306care each connected to the water gate controller1010. The liquid layer level controller306is different from the liquid layer level controller106only in reference information for decision and decision contents.

The impurity decision unit3063is connected wiredly or wirelessly to the concentration measuring unit3061or the imaging unit3062. The exemplified impurity deposition information acquiring unit332includes either one of the concentration measuring unit3061and the imaging unit3062, and the impurity decision unit3063.

The liquid layer adjusting apparatus241is also called a liquid layer adjusting system included in the desalination system7.

The concentration measuring unit3061measures concentration of the impurities2000in the liquid4aflowing in the introduction path101a. The concentration measuring unit3061can possibly acquire time from a time measuring unit233for measuring time and transmit, to the impurity decision unit3063, the measured concentration of the impurities2000associated with the time.

As shown inFIG. 14A, the concentration measuring unit3061is located in the introduction path101a. In an example, the concentration measuring unit3061is located in the introduction path101aat a portion or in the vicinity thereof for introducing liquid to the water tank102.

The imaging unit3062captures an image of the liquid4aflowing in the introduction path101a. The imaging unit3062can possibly acquire time from the time measuring unit233for measuring time and transmit, to the impurity decision unit3063, the captured image associated with the time.

As shown inFIG. 14A, the imaging unit3062is located in the introduction path101aso as to capture an image of a flow of the liquid4ain the introduction path101aalong the introduction path101a. For example, the imaging unit3062is located along the introduction path101aat a portion close to the water gate101in the introduction path101atoward the water tank102, so as to capture an image of a state of the liquid4aflowing in the introduction path101afrom the water gate101toward the water tank102. In an example, a member of the introduction path101ais made different in color from the liquid and the impurities2000, so that the impurities2000can be easily detected in the captured image.

The impurity decision unit3063decides whether or not the impurities2000having dissolved in the liquid4aare deposited in the introduction path101a.

The impurity decision unit3063decides whether or not concentration of the impurities2000measured by the concentration measuring unit3061is within a predetermined concentration range. If the measured concentration is within the predetermined concentration range, the impurity decision unit3063decides that the impurities2000are deposited. If the measured concentration is not within the predetermined concentration range, the impurity decision unit3063decides that the impurities2000are not deposited. The predetermined concentration range covers up to a saturated concentration from concentration that is smaller by a predetermined degree than the saturated concentration. The exemplary predetermined concentration range covers from a concentration lower by 3% than a saturated concentration to the saturated concentration.

If the concentration of the liquid layer4is within the predetermined concentration range for at least a predetermined period, the impurity decision unit3063can decide that the impurities2000are deposited. The impurity decision unit3063can decide the amount of the deposited impurities in accordance with the length of the predetermined period as well as with the information on whether or not the impurities2000are deposited.

The impurity decision unit3063acquires the predetermined concentration range that is stored in a reference storage unit3063a. The liquid impurity decision unit3063itself can include the reference storage unit3063a(illustrated outside the impurity decision unit3063inFIG. 14Afor better comprehension), or the impurity decision unit3063can acquire the predetermined concentration range from the reference storage unit that is provided externally. The reference storage unit3063acan store the predetermined period in addition to the predetermined concentration range.

The impurity decision unit3063alternatively decides whether or not the impurities2000are contained in accordance with the image captured by the imaging unit3062. The impurity decision unit3063decides whether or not the impurities2000are contained in accordance with whether or not the captured image includes color of the impurities2000preliminarily dissolved in the liquid4a. The impurity decision unit3063can refer to brightness information when the impurities2000and the water-repellent particles have the same color.

The impurity decision unit3063can decide the amount of the deposited impurities2000in accordance with the amount of the impurities2000in the captured image. The amount of the impurities2000in the captured image can be expressed by a ratio of the impurities2000to the image or an area of the impurities.

The impurity decision unit3063acquires predetermined color or brightness of the impurities2000that is stored in the reference storage unit3063a. The impurity decision unit3063can include the reference storage unit3063a(illustrated outside the impurity decision unit3063inFIG. 14Afor better comprehension), or the impurity decision unit3063can acquire color or brightness of the impurities2000in a predetermined image from the external reference storage unit. The reference storage unit3063acan store a predetermined ratio of the impurities2000or a predetermined area of the impurities in addition to predetermined color or brightness of the impurities2000.

The liquid layer level controller306acquires, from the impurity decision unit3063, information on whether or not the impurities2000having dissolved in the liquid4aare deposited in the introduction path101a, estimates the depth of the concave portion400at the water-repellent particle layer104formed by the changed flow of the liquid4adue to deposition of the impurities2000in the introduction path101ain accordance with the acquired information on whether or not the impurities are deposited, and determines the level of the liquid layer4in the water tank102.

For example, the impurity decision unit3063can acquire concentration information from the concentration measuring unit3061for measuring concentration of liquid and then, decide whether or not there are the impurities, and thereafter, the liquid layer level controller306can acquire information thereon. If the concentration measured by the concentration measuring unit3061is equal to a saturated concentration at least for a predetermined period, the impurity decision unit3063decides that the impurities2000are deposited. Alternatively, the imaging unit captures a flow of the liquid4ain the introduction path101aand the impurity decision unit3063decides whether or not there are impurities in accordance with the captured image.

For example, the impurity decision unit3063preliminarily stores sizes or shapes of the deposited impurities2000as information on the impurities2000. The impurity decision unit3063analyzes the captured image and the impurity decision unit2063acquires information on whether or not the impurities2000are deposited. The impurity decision unit3063can preliminarily store a shape of a particle forming the water-repellent particle layer104, to determine that the impurities2000are deposited when a lump of a different shape is detected. The imaging unit3062can alternatively capture an image to obtain the amount of the impurities2000from the number or the area of the deposited impurities2000in the image captured by the imaging unit3062.

The decision unit306cin the liquid layer level controller306changes the information on the relationship between the information corresponding to the number of times of introducing the liquid to the water tank102and the level of the liquid of the liquid layer4in accordance with the decision information on whether or not the impurities2000are deposited as decided by the impurity decision unit3063, and determines the level of the liquid layer4. For example, if the impurity decision unit3063decides that the impurities2000are deposited, the liquid layer level controller306controls the water gate controller1010so as to increase the level of the liquid in comparison to the case where the impurities2000are not deposited. When a large amount of impurities2000are deposited in the introduction path101a, the liquid4aintroduced to the water tank102is smaller in amount than the liquid4aintroduced to the water tank102in the case where the impurities2000are not deposited in the introduction path101a. The concave portion400formed at the water-repellent particle layer104is thus decreased in depth and the liquid can be increased in level. In contrast, if the impurity decision unit3063decides that the impurities2000are not deposited, the decision unit306cin the liquid layer level controller306does not change the level of the liquid. The decision information on whether or not the impurities2000are deposited is not necessarily binary information. When the impurity decision unit2063decides that the impurities2000are deposited, the decision unit306cin the liquid layer level controller306can determine the level of the liquid layer4in accordance with the amount of the deposited impurities2000.

The steps of liquid layer level adjustment by the liquid layer adjusting apparatus241are similar, as to be described below, to those of the liquid layer level adjustment by the liquid layer adjusting apparatus231in the desalination system3according to the second embodiment as illustrated inFIG. 13. These steps are thus described with reference toFIG. 13.

The information acquiring unit306bin the liquid layer level controller306causes the water gate controller1010to open the water gate101and acquires information corresponding to the number of times of introducing the liquid4ato the water tank102from the water gate controller1010. As described above, examples of the information corresponding to the number of times of introducing the liquid4ato the water tank102include the number of times of opening/closing the water gate101and the elapsed time from formation of the liquid layer4. The information acquiring unit306bin the liquid layer level controller306acquires the information from the water gate controller1010.

The decision unit306cin the liquid layer level controller306subsequently acquires from the impurity deposition information acquiring unit332information on whether or not the impurities2000are deposited, and changes as necessary, in accordance with the acquired information, the information on the relationship between the information corresponding to the number of times of introducing the liquid to the water tank102and the level of the liquid layer4, which is stored in the database306aand read out by the decision unit306c. For example, when acquiring from the impurity deposition information acquiring unit332information that the impurities2000are not deposited in the introduction path101a, the decision unit306cin the liquid layer level controller306does not change the relationship information. In contrast, when acquiring from the impurity deposition information acquiring unit332information that the impurities2000are deposited in the introduction path101a, the decision unit306cin the liquid layer level controller306changes the relationship information as described above.

The decision unit306cin the liquid layer level controller306subsequently determines the level of the liquid layer4in accordance with the information, which is changed in step S301or is not changed with no necessity, on the relationship between the information corresponding to the number of times of introducing the liquid to the water tank102and the level of the liquid layer4and the acquired information corresponding to the number of times of introducing the liquid to the water tank102. More specifically, when changed in step S301, the decision unit306crefers to the information on the relationship between the number of times and the level as changed in step S301to determine the level of the liquid layer4in accordance with the number of times of introducing the liquid4ato the water tank102that is acquired by the information acquiring unit306b. When not changed in step S301, the decision unit306crefers to the information on the relationship between the number of times and the level that is stored in the database306ato determine the level of the liquid layer4in accordance with the number of times of introducing the liquid4ato the water tank102that is acquired by the information acquiring unit306b.

The decision unit306csubsequently transmits a command to the water gate controller1010in order to adjust opening/closing of the water gate101or opening/closing of the drain valve108in accordance with the level of the liquid layer4determined by the decision unit306c. Upon receipt of the command from the decision unit306c, the water gate controller1010adjusts opening/closing of the water gate101in accordance with the level of the liquid layer4determined by the decision unit306c. More specifically, for example, the decision unit306ccalculates the time of opening the water gate101until the liquid layer4reaches the level determined by the decision unit306c, and controls the water gate controller1010to open the water gate101during the calculated time.

It is thus possible to effectively prevent breakage of the water-repellent particle layer104at the concave portion400and efficiently and reliably perform automatic desalination.

According to the third embodiment, when acquiring from the introduction path impurity deposition information acquiring unit332the information that the impurities2000are deposited in the introduction path101a, the decision unit306cin the liquid layer level controller306determines the level of the liquid4aintroduced to the water tank102in accordance with the information on the relationship between the information corresponding to the introduction amount of the liquid4aintroduced to the water tank102and the surface level of the liquid4ain the water tank102, and the water gate controller1010adjusts the liquid4aintroduced to the water tank102in accordance with the determined surface level of the liquid4a. It is thus possible to effectively prevent breakage of the water-repellent particle layer104at the concave portion400and more efficiently and more reliably perform automatic desalination.

Other Embodiments

FIG. 15exemplifies a hardware configuration of the liquid layer level controller106in the liquid layer adjusting apparatus203. The liquid layer level controller106includes an antenna3006, a receiving circuit3005, and a CPU3001. For example, the antenna3006receives information transmitted from an antenna of the water gate controller1010, and the receiving circuit3005receives the information. The receiving circuit3005and the CPU3001are connected to each other by a bus3011so as to transmit and receive data therebetween. The information received from the water gate controller1010is transmitted from the receiving circuit3005to the CPU3001by way of the bus3011.

The CPU3001configuring the liquid layer level controller106executes a program3003stored in a RAM3002. The program3003includes a processing procedure illustrated in the flowchart ofFIG. 8or the like. The program3003can be alternatively stored in a ROM3004.

The liquid layer level controller206or306is configured similarly to the liquid layer level controller106. The program3003includes a processing procedure illustrated inFIG. 13or the like instead ofFIG. 8.

Though the present disclosure has been described above based on the above first to third embodiments, the present disclosure should not be limited to the above-described first to third embodiments. For example, the present disclosure also includes the following cases.

Part or entirety of each of the above-described controllers (control devices) is actually a computer system that includes, for example, a microprocessor, ROM, RAM, hard disk unit, display unit, keyboard, mouse, and the like. A computer program is stored on the RAM or the hard disk unit. Functions of each of the controllers (control devices) can be achieved by the microprocessor operating according to the computer program. The computer program mentioned here is a combination of a plurality of instruction codes that indicate commands to a computer for achieving predetermined functions.

For example, each component can be implemented as a result that a program executing section (part/unit) such as a CPU reads and executes software programs recorded in a recording medium such as a hard disk or semiconductor memory. Here, software that implements a part or entirety of the desalination system according to each of the above-mentioned embodiments is a following program. That is, such a program for the desalination system is a program for the desalination system, causing a computer to function as:

a liquid level controller that determines a level of the liquid introduced to the water tank in accordance with information on relationship between information corresponding to an amount of the liquid introduced to the water tank and a surface level of the liquid in the water tank; and

an introduced amount controller that adjusts the amount of the liquid introduced to the water tank in accordance with the determined surface level of the liquid.

In addition, it may be possible to execute the program by downloading it from a server or reading it from a predetermined storage medium (an optical disc such as a CD-ROM, a magnetic disc, a semiconductor memory, or the like).

Further, one or more computers can be used to execute the program. That is, centralized processing or distributed processing can be performed.

By properly combining the arbitrary embodiment(s) or modification(s) of the aforementioned various embodiments and modifications, the effects possessed by the embodiment(s) or modification(s) can be produced.

INDUSTRIAL APPLICABILITY

In the desalination system and the desalination method according to the present disclosure, the level of the liquid introduced to the water tank is determined in accordance with the information on the relationship between the information corresponding to the amount of the liquid introduced to the water tank and the surface level of the liquid in the water tank, so as to previously prevent breakage of the water-repellent particle layer and efficiently and reliably perform automatic desalination. The desalination system and the desalination method are applicable to a desalination system for desalinating liquid and a method thereof, for example.

The entire disclosure of Japanese Patent Application No. 2013-007554 filed on Jan. 18, 2013, including specification, claims, drawings, and summary are incorporated herein by reference in its entirety.