Desalination system and desalination method

Abstract

To provide a desalination system and a desalination method capable of efficiently performing desalination without requiring large energy other than light energy with a simple constitution compared with a conventional one.SOLUTION: The desalination system 1 includes a heat generation part 21 containing a photothermal conversion material which generates heat by absorbing near infrared rays S1. When the heating part 21 is irradiated with light S including at least near-infrared rays S1, the heating part 21 absorbs the near-infrared rays S1 to generate heat by photothermal conversion, the raw water 2 is heated by using the generated heat to evaporate water contained in the raw water 2, and the evaporated water 3 is condensed and recovered. The photothermal conversion material is preferably a composite material containing silver nanoparticles and layered titanium dioxide.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to desalination systems and methods. [Background technology]

[0002] The shortage of fresh water, which is essential for sustaining life and for industrial activities such as industry and agriculture, is cited as one of the major issues. Fresh water, which accounts for only 0.01% of the total water on Earth, is already said to be a scarce resource.

[0003] Desalination systems that produce freshwater from raw water such as seawater are attracting attention worldwide. For example, in the "(multi-stage) flash" desalination systems widely used in oil-producing countries in the Middle East, the salt concentration of the produced freshwater is low, and large amounts of freshwater can be produced regardless of the quality of the raw water. However, the thermal efficiency is very poor, and large amounts of energy from fossil fuels, etc. are required.

[0004] Recently, instead of using fossil fuels, a "solar flash desalination system" has been proposed and put into practical use. This system uses concentrated sunlight to convert it into thermal energy, and uses solar heat to evaporate raw water, then cools and condenses the vapor to produce fresh water (see, for example, Patent Document 1 and Patent Document 2). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Special Publication No. 2022-508810 [Patent Document 2] Japanese Patent Application Laid-Open No. 2013-155993 Summary of the Invention [Problem to be solved by the invention]

[0006] However, conventional desalination systems and desalination methods that utilize solar heat, such as the above-mentioned "solar flash desalination system," currently have poor freshwater production efficiency and there is significant room for improvement. [Means for solving the problem]

[0007] (1) A desalination system according to one embodiment of the present disclosure is a desalination system including an evaporator that evaporates water in raw water. The evaporator includes a photothermal conversion material that absorbs near-infrared rays and generates heat. The evaporator includes a heat generating unit that has a photothermal conversion function that is irradiated with light containing at least the near-infrared rays and absorbs the near-infrared rays to generate heat. The generated heat is used to heat the raw water, evaporating the water in the raw water, and the evaporated water is condensed and recovered.

[0008] (2) A desalination method according to one embodiment of the present disclosure includes an evaporation step in which light containing at least near-infrared rays is irradiated onto a photothermal conversion material that generates heat by absorbing near-infrared rays, and raw water is heated by the heat generated by the photothermal conversion material absorbing the near-infrared rays to evaporate the water contained in the raw water; and a condensation step in which the evaporated water is condensed. [Effects of the Invention]

[0009] The desalination system and desalination method disclosed herein have a simpler configuration than conventional flash-type desalination systems and desalination methods, and do not require large amounts of energy other than light energy, making it possible to desalinate efficiently. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a diagram showing a desalination system (and a desalination method) according to a first embodiment of the present disclosure, and is a schematic, exemplary diagram of a desalination system. [Figure 2] FIG. 1 is a diagram illustrating an example of a composite material containing silver nanoparticles and layered titanium dioxide. [Figure 3] FIG. 1 is a schematic, exemplary diagram (cross-sectional view) of a desalination system (and a desalination method) according to a second embodiment of the present disclosure. [Figure 4]FIG. 1 shows the absorbance (extinction degree) in the wavelength region of 300 nm to 1800 nm of an Ag / TiO2 composite material prepared by chemical reduction (Example 1) and an Ag / TiO2 composite material prepared by photoreduction (Example 2). [Figure 5] FIG. 1 is a diagram showing temperature changes in a light irradiation test of test specimens of Example 1 and Comparative Example 1. [Figure 6] 1 is a diagram showing the relationship between the light irradiation time and the surface temperature of each test specimen of Example 1, Example 2, Comparative Example 1, and Comparative Example 2. FIG. [Figure 7] FIG. 1 is a diagram for explaining the apparatus and method used in the experiments of the examples, and is a diagram showing an example of an embodiment of the desalination system and desalination method of the present disclosure. [Figure 8] 1(a) is a graph showing the relationship between the light irradiation time and the water loss rate when the test specimens of Example 1, Example 2, Comparative Example 1, and Comparative Example 2 are irradiated with light in the wavelength region of 430 nm or more and 1050 nm or less, and FIG. 1(b) is a graph showing the relationship between the light irradiation time and the water loss rate when the test specimens of Example 1, Example 2, Comparative Example 1, and Comparative Example 2 are irradiated with light in the wavelength region of 610 nm or more and 1050 nm or less. [Figure 9] FIG. 1 is a diagram showing temperature changes over time in a light irradiation test in which the test specimen of Example 1 was placed in water. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the desalination system and desalination method of the present disclosure will be described with reference to Figures 1 to 9. Note that the present embodiments illustrate examples of the desalination system and desalination method of the present disclosure, and the desalination system and desalination method of the present disclosure are not necessarily limited to the following embodiments.

[0012] First Embodiment [1: Desalination system] The desalination system 1 of the first embodiment includes an evaporator (flash device) 20 that evaporates water in raw water 2, as shown in FIG.

[0013] The evaporation device 20 has a heat generating section 21 comprising a photothermal conversion material that absorbs near-infrared rays S1 and generates heat. When light S containing at least near-infrared rays S1 is irradiated onto the heat generating section 21, the photothermal conversion function causes the heat generating section 21 to absorb the near-infrared rays S1 and generate heat. The generated heat is used to heat the raw water 2, and the water (moisture) contained in the raw water 2 is evaporated.

[0014] In the desalination system 1 (and desalination method) of this embodiment, raw water 2 is heated using the heat generated by the photothermal conversion material absorbing near-infrared rays S1, so that no large amount of energy other than light energy is required. This allows the water contained in the raw water 2 to be efficiently evaporated, and the evaporated water 3 to be condensed and collected, thereby obtaining condensed water (clean water, fresh water) 4. That is, the desalination system 1 (and desalination method) of the present disclosure can perform desalination treatment efficiently with a simpler configuration than conventional solar flash desalination systems.

[0015] In this disclosure, "near-infrared light S1" refers to light in an energy region intermediate between "visible light S2" and "infrared light," specifically light having a wavelength in the range of 780 nm to 2500 nm. Furthermore, a "material that absorbs near-infrared light S1 (photothermal conversion material)" refers to a material that blocks the transmission of light in the near-infrared region (wavelength of 780 nm to 2500 nm), preferably a material in which A=Log(I0 / I)≧0.05, more preferably A≧0.1, where A is the absorbance for light with wavelengths in this near-infrared region, I0 is the amount of incident light, and I is the amount of transmitted light.

[0016] In the present disclosure, "raw water 2" means a substance (liquid) containing water (H2O) and components other than water (H2O).

[0017] In the present disclosure, "desalination" means obtaining a liquid with an increased content of water (H2O) from raw water 2 by reducing the content of components other than water (H2O). In other words, "desalination" in the present disclosure means producing "water 4" that is cleaner than "raw water 2," and is not necessarily limited to producing fresh water from raw water 2 such as seawater. That is, although the desalination system 1 and desalination method of the present disclosure are preferably used to produce water 4 that is suitable for drinking, they may also be applied to produce even slightly cleaner water 4 from "raw water 2," and their use does not necessarily have to be limited to producing water 4 that is suitable for drinking.

[0018] More specifically, as shown in FIG. 1, the desalination system 1 of this embodiment includes a desalination tank 10 that receives and stores raw water 2, and an evaporator 20 having a heat generating section 21 arranged so that at least a portion of the heat generating section 21 is in contact with the raw water 2 inside the desalination tank 10.

[0019] [1-1: Desalination tank] The desalination tank 10 is a treatment tank that receives and stores the raw water 2 and evaporates the water contained in the raw water 2.

[0020] The desalination tank 10 is, for example, a water tank having a substantially sealed hollow portion, and at least a part of it, such as the entire tank or the top or side surface, is formed using a transparent material that can let in light (having a near-infrared transmitting portion) so that sunlight S (at least near-infrared rays S1) can be irradiated onto the heat generating portion 21 and raw water 2 arranged inside the tank.

[0021] The raw water 2 is not particularly limited, but examples thereof include seawater, river water, lake water, rainwater, industrial wastewater, domestic wastewater, and chemically contaminated water.

[0022] Note that wastewater that has been used as cooling water may be used as raw water 2. Such wastewater is often at a higher temperature than before it was used as cooling water, which is advantageous for evaporating the water contained in raw water 2. For example, if wastewater that has been used as cooling water is returned to the natural environment, there is a concern that the surrounding water temperature will be extremely high compared to other areas, which could have an adverse effect on the ecosystem. However, by using wastewater that has been used as cooling water as raw water 2, such concerns can be alleviated or eliminated.

[0023] The desalination tank 10 is connected to a water supply device 11 having a pump, piping, on-off valves, etc. for supplying raw water 2 into the inside of the desalination tank 10, a drainage device 12 having a pump, piping, on-off valves, etc. for discharging the concentrated raw water 2 and residues after treatment outside the desalination tank 10, and a steam extraction device 13 having piping, etc. for extracting water (steam) 3 evaporated inside the desalination tank 10 to the outside of the desalination tank 10 and sending it to a heat exchanger (cooling device) 30.

[0024] [1-2: Evaporation device (flash device)] The evaporation device 20 of this embodiment includes a base material 22 and a heat generating section 21 that is integrally provided on the surface of the base material 22 and contains a photothermal conversion material that absorbs near-infrared rays S1 and generates heat.

[0025] [1-2-1: Heat generating part] In the desalination system 1 of this embodiment shown in Fig. 1, the heat generating unit 21 is provided in the form of a film on a porous substrate 22. In the configuration of this embodiment shown in Fig. 1, the heat generating unit 21 is provided on the surface of the porous substrate 22 as a coating made of a material containing a photothermal conversion material. By providing the heat generating portion 21 as a coating on the surface of the porous substrate 22 in this manner, it is possible to achieve efficient desalination while reducing the amount of photothermal conversion material used, as will be described in detail later.

[0026] The form of the heat generating portion 21 does not need to be particularly limited, and it may be provided in the form of a coating of a material containing a photothermal conversion material on the surface of the substrate 22 as in this embodiment, or it may be a molded body in which a material containing a photothermal conversion material is pre-formed into a predetermined shape.

[0027] [1-2-2: Base material] As described above, the substrate 22 of the present disclosure is made of a porous material and is a member that supports the heat generating portion 21 arranged in a membrane form and supplies water in the raw water 2 through the pores so that it comes into contact with the heat generating portion 21.

[0028] The "surface" of the porous substrate 22 includes not only the outer surface but also the inner pore surface of the substrate 22. This increases the surface area, improving the overall light-to-heat conversion efficiency and water evaporation efficiency.

[0029] Here, it is preferable that the specific gravity of the substrate 22 is smaller than the specific gravity of the raw water 2. In other words, it is preferable that the substrate 22 floats on the raw water 2.

[0030] This allows the heat generating unit 21 and therefore the evaporator 20 to be installed floating on the raw water 2, enabling the water contained in the raw water 2 to be evaporated more efficiently and simplifying and miniaturizing the desalination system 1 (see the second embodiment described later). Furthermore, it also allows for significantly improved maintainability, such as cleaning and function restoration of the evaporator 20 (heat generating unit 21 and base material 22) and the desalination system 1.

[0031] In this embodiment, the buoyancy of the substrate 22 itself causes the heat generating section 21 (evaporator 20) formed by forming a film of a photothermal conversion material (a material containing a photothermal conversion material) on the substrate 22 to float on the raw water 2. However, if the heat generating section 21 (evaporator 20) can be arranged inside the desalination tank 10 in a state similar to that in which it is floating on the raw water 2, the same effect as described above can be obtained. For example, the substrate 22 (heat generating section 21, evaporator 20) may be fixed and supported by a support member and placed on the surface of the raw water 2, or a separate floating member such as a float may be used to place the substrate 22 (heat generating section 21, evaporator 20) floating on the raw water 2. As will be described later, the heat generating section 21 (evaporator 20) does not necessarily have to be floated on the raw water 2 or fixedly supported and disposed on the water surface.

[0032] On the other hand, when a porous substrate 22 is used and the heat generating unit 21 is installed floating on the raw water 2 as in this embodiment, the water in the raw water 2 is sucked up through the pores of the substrate 22 by capillary action, reaches the heat generating unit 21, and evaporates due to the heat. At the same time, water is further sucked up through the pores to replenish the water in the raw water 2. This automatically and continuously supplies the raw water 2 to the heat generating unit 21 (photothermal conversion material) and evaporates the water efficiently. In other words, it is possible to achieve more efficient desalination treatment with the porous substrate 22 while reducing the amount of photothermal conversion material used as a coating.

[0033] The porous substrate 22 does not need to be particularly limited, but examples thereof include resin foam, sponge, porous concrete, pumice, fiber aggregates such as cotton and cloth, zeolite, and sol-gel carrier / soft material composites.

[0034] The resin constituting the resin foam does not need to be particularly limited, but examples thereof include polyurethane, polystyrene, foamed rubber, and the like.

[0035] The substrate 22 is preferably heat resistant. This makes it possible to prevent alteration and deterioration of the base material 22 due to solar heat or heat generated by the heat generating unit 21, thereby extending the life of the heat generating unit 21 and ultimately the entire desalination system 1.

[0036] [1-2-3: Photothermal conversion materials] As described above, the photothermal conversion material refers to a material that absorbs near-infrared rays S1 and generates heat, a material that prevents the transmission of light in the near-infrared region (wavelength of 780 nm or more and 2500 nm or less), and preferably a material in which A=Log(I0 / I)≧0.05, more preferably A≧0.1, where A is the absorbance for light with wavelengths in this near-infrared region, I0 is the amount of incident light, and I is the amount of transmitted light. With this configuration, the effects of the desalination system 1 (desalination method) of the present disclosure described above can be made more pronounced.

[0037] Examples of photothermal conversion materials include organic dye compounds, organic complex compounds, metal complex compounds, rare earth complex compounds, and metal nanoparticle materials.

[0038] Examples of organic dye compounds and organic complex compounds include cyanine dyes having an extended polymethine skeleton, phthalocyanine dyes having aluminum or zinc at the center, various naphthalocyanine compounds, nickel dithiolene complexes having a planar tetracoordinate structure, squarylium dyes, quinone compounds, diimmonium compounds, azo compounds, etc. Among these, cyanine dyes, diimmonium compounds, and squarylium dyes are preferred.

[0039] Examples of metal complex compounds include ruthenium complexes of phthalocyanine, compounds represented by the following general formula (1) and salts thereof, as described in Japanese Patent No. 5416115.

[0040] [ka] In formula (1), Nc represents a naphthalocyanine which may have a substituent, M represents a metal atom which is the central metal of the naphthalocyanine represented by Nc, a metal oxide, a metal hydroxide, or a metal halide, or a hydrogen atom, and R 1 and R 2each independently represents a hydrogen atom; a substituted or unsubstituted alkyl group; a substituted or unsubstituted aralkyl group; or a substituted or unsubstituted aryl group; A represents a bridging group; X and Y each independently represent a halogen atom; a hydroxy group; an amino group; a substituted or unsubstituted alkoxy group; a substituted or unsubstituted aryloxy group; a substituted or unsubstituted aralkyloxy group; a substituted or unsubstituted monoalkylamino group; a substituted or unsubstituted dialkylamino group; a substituted or unsubstituted arylamino group; a substituted or unsubstituted aralkylamino group; a substituted or unsubstituted alkylthio group; a substituted or unsubstituted arylthio group; or a substituted or unsubstituted aralkylthio group; k and p are all average values, k is greater than 0 and 12 or less, p is 0 or greater but less than 12, and the sum of k and p is greater than 0 and 12 or less; R 1 , R 2 Any two of the three groups, A, and B, may be bonded to form a ring.

[0041] Examples of rare earth complex compounds include compounds represented by the following general formula (2), as described in WO 2009 / 110199.

[0042] [ka] In formula (2), Ln(III) is, for example, a trivalent rare earth ion selected from the group consisting of Yb, Er, and Nd. n is an integer of 3 or greater, and X is the same or different and represents any one of a hydrogen atom, a deuterium atom, a halogen atom, a group having 1 to 20 carbon atoms, a hydroxyl group, a nitro group, an amino group, a sulfonyl group, a cyano group, a silyl group, a phosphonic acid group, a diazo group, and a mercapto group. Z is a bidentate ligand.

[0043] In the above formula (2), Z is represented, for example, by the following general formula (3).

[0044] [ka]

[0045] Examples of metal nanoparticle-based materials include copper indium sulfide (CuInS2) nanocrystals as described in "Phys. Chem. C 2015, 119, 20, 11100-11105" and composite materials containing silver nanoparticles and layered titanium dioxide.

[0046] Among these materials, a composite material containing silver nanoparticles and layered titanium dioxide is preferable as the photothermal conversion material.

[0047] FIG. 2 is a diagram schematically illustrating an example of a composite material (photothermal conversion material, material containing a photothermal conversion material) containing silver nanoparticles and layered titanium dioxide.

[0048] The composite material of this embodiment shown in Figure 2 has a structure in which silver ions are introduced into the layers (layer space) of layered titanium dioxide, i.e., a structure in which silver ions are interposed (layer space) between layered titanium dioxide (layered compound) formed by titanium dioxide crystals being formed in layers.

[0049] This composite material containing silver nanoparticles and layered titanium dioxide has excellent response characteristics to near-infrared light S1, and can make the effects of the desalination system 1 (and desalination method) of the present disclosure described above more pronounced.

[0050] Among the above-mentioned photothermal conversion materials, organic complex compounds are inexpensive, but their absorption bands are generally in the wavelength region of 1000 nm or less, and their absorption wavelength width is narrow; in other words, they only absorb a limited amount of near-infrared light S1 (their near-infrared absorption characteristics are very excellent). Furthermore, organic complex compounds tend to have poor durability, and organic dyes in particular generally have poor thermal stability.

[0051] Metal complex compounds, like organic complex compounds, only absorb a limited amount of near-infrared light S1. Furthermore, when ruthenium or rare earth metals are used, the material costs are high.

[0052] Composite materials containing copper nanoparticles as metal nanoparticles are oxidized in a short time, lose their optical response, and have poor durability.

[0053] In contrast, a composite material containing silver nanoparticles and layered titanium dioxide has excellent absorption properties over a wider range of the near-infrared region and is also highly durable.

[0054] In the above composite material, silver ions are introduced into the layers of layered titanium dioxide, which makes it possible to trap heavy metals and, for example, reduce the amount of heavy metals contained in raw water 2 after desalination. It can also be used to treat industrial wastewater, chemically polluted water, etc.

[0055] This makes it possible to reduce the impact of heavy metals on the environment when the raw water 2 is discharged after being desalination treated. The composite material of the present disclosure, which exhibits such advantageous effects, can also be suitably used for treating industrial wastewater, chemically contaminated water, and the like.

[0056] The titanium dioxide contained in the composite material has a photocatalytic function. Therefore, for example, as described below, when sunlight S is used as the light irradiated onto the heat generating unit 21, the energy of the sunlight S can be utilized more effectively. More specifically, for example, the photocatalytic function of ultraviolet rays S3 contained in sunlight S can further improve the overall light-to-heat conversion efficiency and water evaporation efficiency.

[0057] The photocatalytic function of the composite material can provide effects such as decomposing undesirable substances contained in the raw water 2 and inhibiting deterioration through self-repair (photoreduction) of the composite material, as will be described later.

[0058] A composite material containing silver nanoparticles and layered titanium dioxide can be prepared, for example, as follows.

[0059] First, a suspension of titanium dioxide exfoliates (plate-like titanium dioxide crystals) is prepared, and droplets of the suspension are dropped onto a heat-resistant substrate 22 and sintered to obtain a layered compound in which plate-like titanium dioxide crystals are formed into layers. The substrate 22 can be made of, for example, porous concrete, pumice, or metallic titanium. Alternatively, the layered compound may be dropped onto a glass or quartz plate and sintered to obtain a molded body of the layered compound.

[0060] Next, the layered compound is immersed in a silver salt solution, and the silver ions are reduced to grow silver nanoparticles between the layers (layer space), thereby producing the composite material. The reduction method used here can be chemical reduction or photoreduction, and as will be shown in the examples below, the light absorption and photothermal conversion properties of the resulting composite material can be controlled and adjusted depending on the reduction method.

[0061] In the following explanation, we will continue to use as an example a case where the photothermal conversion material is a composite material containing silver nanoparticles and layered titanium dioxide, but in the desalination system 1 and desalination method disclosed herein, the photothermal conversion material does not necessarily have to be limited to a composite material containing silver nanoparticles and layered titanium dioxide.

[0062] When the heat generating portion 21 is formed as a coating made of a photothermal conversion material (a material containing a photothermal conversion material, a composite material), a method for forming the coating may include, for example, mixing the photothermal conversion material with a binder, supplying the mixture onto the surface of the substrate 22, and forming the mixture into a film.

[0063] Examples of binders include polyvinyl alcohol, methyl cellulose, acrylic resin, and agar.

[0064] Of course, when the substrate 22 is heat-resistant (for example, porous concrete, pumice, etc.), the substrate used in producing the composite material containing silver nanoparticles and layered titanium dioxide may be used as the substrate 22. In other words, a composite material (a molded product of a layered compound) may be formed on a support (such as glass or a quartz plate) different from the substrate 22, and this composite material may be separately integrated with the substrate 22.

[0065] The thickness of the film-like photothermal conversion material (composite material, heat generating portion 21) is not particularly limited, but is preferably 0.1 μm or more and 100 μm or less, more preferably 0.5 μm or more and 50 μm or less, and even more preferably 1.0 μm or more and 10 μm or less. The photothermal conversion material containing silver nanoparticles and layered titanium dioxide (the composite material of the present disclosure, heat generating portion 21) has a thickness of 2 μm and exhibits an absorptivity of approximately 80% for near-infrared rays S1. Therefore, with this configuration, the above-mentioned effects can be made even more pronounced.

[0066] According to the desalination system 1 of the present disclosure configured as described above, it is possible to simplify and miniaturize the desalination system 1 by simply floating the evaporator 20 (heat generating unit 21) in the raw water 2. Providing the miniaturized desalination system 1 of the present disclosure to people in developing countries who have difficulty obtaining drinking water, or to people who rely on muddy water such as puddle water for daily life or drinking, can significantly improve their health and quality of life, thereby making a significant contribution.

[0067] Furthermore, even when constructing a large-scale desalination system 1 at the level of a desalination plant, the labor, time, and cost required for installation, construction, and maintenance can be reduced compared to desalination systems that use conventional RO membranes or solar-powered flash desalination systems.

[0068] Here, at least one intermediate layer may be disposed between the substrate 22 and the photothermal conversion material. The heat generating unit 21 may be configured as a molded body made of a material containing a photothermal conversion material, without including the base material 22. In this case, for example, the heat generating unit 21 may be formed by mixing the photothermal conversion material with a binder and molding the mixture. Then, by arranging the heat generating unit 21 (evaporator 20) made of a material containing the photothermal conversion material so that it is in contact with the raw water 2, it is possible to evaporate the water (moisture) in the raw water 2 by irradiating it with light S containing near-infrared rays S1. The molding method for the molded body is not particularly limited, and any known method can be used as appropriate.

[0069] The light S irradiated onto the heat generating portion 21 is not limited as long as it includes near-infrared rays S1, but may also be light including visible light rays S2. In this case, it is also possible to impart a photothermal conversion property using visible light S2, thereby improving the overall photothermal conversion efficiency and water evaporation efficiency.

[0070] Furthermore, the light S irradiated onto the heat generating portion 21 may be light containing ultraviolet rays S3. In this case, the overall light-to-heat conversion efficiency and water evaporation efficiency can be improved, and further, if the light-to-heat conversion material has a photocatalytic function, this function can be more suitably exhibited.

[0071] From the above, sunlight S can be used, for example, as the light S irradiated onto the heat generating portion 21. Near-infrared rays S1 account for approximately 40% of sunlight S, so by using a photothermal conversion material that responds to near-infrared rays S1, it is possible to effectively absorb not only visible light S2 but also the heat rays of sunlight S. This makes the above-mentioned effects even more pronounced and allows for effective use of natural energy.

[0072] The desalination system 1 may include a light collecting device (not shown) for collecting sunlight S and irradiating it on the heat generating unit 21. The light collecting device may be configured to include, as appropriate, mirrors such as a sunlight tracking reflecting mirror and a light collecting reflecting mirror that receives light reflected by the sunlight tracking reflecting mirror and reflects and irradiates the light toward the heat generating unit 21, lenses, and the like.

[0073] This allows light to be irradiated to the heat generating portion 21 more efficiently, and it becomes possible to further improve the overall light-to-heat conversion efficiency and water evaporation efficiency.

[0074] [1-3: Cooling device] The desalination system 1 of the present disclosure preferably further includes a cooling device (30) for cooling the evaporated water. By providing the cooling device (30), the evaporated water 3 can be efficiently condensed and the condensed water (clean water, fresh water) 4 can be collected.

[0075] The cooling device (30) does not need to be particularly limited, but the desalination system 1 of the present disclosure shown in FIG. 1 includes a heat exchanger 30 as the cooling device (30).

[0076] In the desalination tank 10, raw water 2 is heated and evaporated to produce water (steam) 3, which is then sent to a heat exchanger 30 by a steam extraction device 13. The heat exchanger 30 cools and condenses the steam 3 to produce liquid water (condensed water, clean water, fresh water) 4.

[0077] Cooling water 31 is introduced into the heat exchanger 30 through, for example, a cooling water inlet line, and as the cooling water 31 passes through the heat exchanger 30, it exchanges heat with the steam 3 to condense the steam 3. The heated cooling water 32 is discharged to the outside of the device through a cooling water outlet line. When seawater is used as the raw water 2, the cooling water 31 introduced into the heat exchanger 30 can be, for example, seawater pumped from the ocean. In this case, part of the used cooling water 32 discharged to the outside of the device may be supplied again to the desalination system 1 as the raw water 2.

[0078] The obtained condensed water 4 has a significantly reduced content of components other than water compared to the raw water 2.

[0079] The content of components other than water (H2O) in the obtained condensed water 4 is preferably 1.0 mass % or less, more preferably 0.5 mass % or less, and even more preferably 0.1 mass % or less. This makes it possible to obtain condensed water 4 that is closer to fresh water. In other words, it is possible to generate condensed water 4 of a quality suitable for drinking.

[0080] The desalination system 1 may include a filter for removing impurities such as suspended solids (SS) and garbage from the raw water 2. When a filter is provided, impurities in the raw water 2 can be removed in advance before the desalination treatment, and the desalination treatment can be carried out more efficiently.

[0081] Depending on the type and condition of the raw water 2, it is possible that the raw water 2 may contain undesirable substances such as smelly substances (odor). In contrast, if the photothermal conversion material has a photocatalytic function, the undesirable substances in the raw water 2 can be decomposed by the photocatalytic function of the photothermal conversion material. Furthermore, if undesirable chemical substances such as heavy metals are contained in the raw water 2, they can be captured and removed by the photothermal conversion material.

[0082] Meanwhile, the desalination system 1 may be configured to perform deodorization treatment to remove odorous substances by decomposing or adsorbing them, in addition to decomposing odorous substances using the photocatalytic function of the photothermal conversion material. For example, the system may be configured to include a deodorizing device (not shown) that adsorbs odorous substances using activated carbon, through which the steam 3 and condensed water 4 pass to remove odorous substances. Furthermore, the heat exchanger 30 and the deodorizing device may be integrated, and condensation and deodorization (impurity removal) may be performed in parallel or sequentially, for example, by cooling the activated carbon in the deodorizing device to condense the steam 3. In addition, a deodorizing device that decomposes and removes odorous substances using ozone, a catalyst, ultraviolet light, or the like may be provided. Note that, in addition to deodorization, a chemical substance removal device that removes chemical substances by adsorption or the like may also be provided in the same manner as the above-mentioned deodorizing device.

[0083] Next, the desalination system 1 may include a freshwater storage tank (not shown) for temporarily storing the condensed water 4.

[0084] The desalination system 1 may include various sensors for detecting the pressure inside the desalination tank 10, the amount and temperature of the raw water 2, and a control device for controlling the operation of the desalination system 1.

[0085] Here, it is desirable to ensure stable and suitable use and operation of the desalination system 1 of the present disclosure, assuming that regular and irregular maintenance will be performed, and to extend the life of the system.

[0086] For example, if the photothermal conversion material is a composite material containing silver nanoparticles and layered titanium dioxide, the composite material will gradually oxidize and lose its light absorption ability, but by irradiating it with ultraviolet light S3, the composite material will be regenerated through the self-repair (photoreduction) action of the photocatalytic function, in other words, its light absorption ability can be restored, thereby achieving a longer lifespan.

[0087] The photothermal conversion material can be regenerated while being used in the desalination process by ultraviolet light S3 contained in sunlight S, but the photothermal conversion material may also be photoreduced and its function regenerated by, for example, recovering the heat generating unit 21 from the desalination tank 10 and separately irradiating it with ultraviolet light S3 outside the desalination tank 10. Of course, it is also possible to separately irradiate the heat generating unit 21 inside the desalination tank 10 with ultraviolet light S3 to regenerate its function.

[0088] The desalination system 1 may include a cleaning device. For example, the cleaning device may supply water in a countercurrent to the heat generating unit 21 and the base material 22 (evaporator 20), in other words, flow water from the side opposite to the side where the raw water 2 is supplied to the heat generating unit 21, thereby backwashing (backflow cleaning) the heat generating unit 21.

[0089] For example, if the base material 22 is porous and impurities such as dirt (scale) or dust adhere to the surface or the pores are clogged with impurities, the light-to-heat conversion efficiency of the heat generating portion 21 will decrease. In contrast, in the desalination system 1 of this embodiment, by cleaning the heat generating unit 21, it is possible to remove impurities that have adhered thereto, and to restore the reduced photothermal conversion efficiency.

[0090] The desalination system 1 may include an agitator (not shown) that agitates the raw water 2 inside the desalination tank 10 using aerated air, agitating blades, or the like. By agitating the raw water 2 with this agitator, it is possible to remove deposits (impurities) on the heat generating unit 21. It is also possible to prevent impurities from adhering to the heat generating unit 21.

[0091] On the other hand, impurities such as scale, algae, microorganisms, and bacteria may adhere to the evaporator 20, including the photothermal conversion material (composite material, material containing photothermal conversion material) of the heat generating portion 21 and the substrate 22, which may result in a decrease in their functionality, as described above.

[0092] In contrast, in the desalination system 1 disclosed herein, near-infrared rays S1 are irradiated and the heat generating section 21 generates heat, so in addition to the above-mentioned effects, the heat can also kill algae, microorganisms, and bacteria or inhibit their proliferation (growth), thereby realizing a desalination system 1 that is less likely to experience functional degradation.

[0093] The desalination method of the present disclosure will be described (detailed) later in the second embodiment below.

[0094] Second Embodiment Next, a second embodiment of the desalination system 1 (and desalination method) of the present disclosure will be described. Note that detailed explanations and illustrations of the same configurations as those of the first embodiment will be omitted.

[0095] The desalination system 1 of the second embodiment, like the first embodiment, has a simpler configuration than conventional systems, and by heating the raw water 2 using the heat generated when the photothermal conversion material absorbs near-infrared rays S1, it is possible to desalinate efficiently without requiring large amounts of energy other than light energy.

[0096] Specifically, FIG. 3 is a schematic, exemplary cross-sectional view of the desalination system 1 (and desalination method and other configuration examples) according to the second embodiment of the present disclosure.

[0097] In the first embodiment of the desalination system 1, the heat generating section 21 and the evaporation device 20 are constructed by providing a film of material containing a photothermal conversion material on the surface of a porous substrate 22. In this embodiment, however, a water absorbing layer (corresponding to the intermediate layer described above) 26 is provided on a plate-shaped support 25, and the substrate 22 and the heat generating section 21 containing a photothermal conversion material are arranged on the water absorbing layer 26 to construct the evaporation device 20.

[0098] In this embodiment, the support 25 is a floating body such as polystyrene foam. For example, the water-absorbing layer 26 is made of hydrophilic fibers such as water-absorbing and quick-drying polyester, cotton, or the like.

[0099] In this evaporation device 20, with the support 25 floating on the surface of the raw water 2, a portion of the support 25 is in contact with (immersed in) the raw water 2, and the water in the raw water 2 is automatically drawn up to the base material 22 side of the heat generating part 21 by the action of osmotic pressure, surface tension, capillary action, etc. This allows water to be supplied to the base material 22 continuously and efficiently.

[0100] The water absorption layer 26 only needs to have a water absorption and water supply function that automatically transports and diffuses the water in the raw water 2 so that it comes into contact with the substrate 22 and ultimately the heat generating portion 21, and there is no need to particularly limit its material or configuration.

[0101] <Other> As described above, in the desalination system 1 of the embodiments (first embodiment and second embodiment), the substrate 22 and support 25 on which the film-like heat generating section 21 is provided are floated on the raw water 2, and the raw water 2 is sucked up from below by capillary action, water absorption, etc. and supplied to the heat generating section 21.

[0102] On the other hand, the desalination system 1 of the present disclosure is not limited to this, and for example, a raw water supply pipe may be provided above the heat generating unit 21, and raw water 2 or the water in the raw water 2 may be intermittently or continuously supplied from the raw water supply pipe toward the heat generating unit 21, where it is evaporated and condensed to obtain condensed water 4.

[0103] Also, for example, the heat generating unit 21 may be placed in the raw water 2, and the heat generating unit 21 may generate heat in the raw water 2 using a photothermal conversion function, thereby heating the raw water 2 (water contained in the raw water 2) and obtaining steam 3.

[0104] As described above, the desalination system 1 of the present disclosure can achieve efficient and effective desalination with a much simpler configuration than conventional flash desalination systems. Therefore, it is not subject to significant limitations on application conditions and can be deployed and utilized in an appropriate location. For example, the desalination system 1 of the present disclosure can be suitably transported, installed, and used as a small-scale purified water / fresh water production device for personal use in developing countries, mountainous areas, outdoors such as on a boat or camping, or as a purified water / fresh water production device for large-scale plants.

[0105] Furthermore, the desalination system 1 of the present disclosure may be installed, for example, on the rooftop, roof, or balcony of a building. This allows the heat generating unit 21 to absorb heat rays contained in sunlight S, thereby effectively suppressing the temperature rise of the entire building in addition to the above-mentioned effects.

[0106] [2] Desalination method Here, the desalination method of the present disclosure will be described.

[0107] The desalination method disclosed herein includes an evaporation step in which light S containing at least near-infrared rays S1 is irradiated onto a photothermal conversion material that absorbs near-infrared rays S1 and generates heat, and raw water 2 is heated with the heat generated by the photothermal conversion material absorbing the near-infrared rays S1 to evaporate the water contained in the raw water 2, and a condensation step in which the evaporated water 3 is condensed.

[0108] In other words, in the desalination method disclosed herein, the raw water 2 is heated using the heat generated by the photothermal conversion material absorbing near-infrared rays S1, thereby efficiently evaporating the water contained in the raw water 2 and efficiently desalination it without requiring any large amount of energy other than light energy.

[0109] The desalination method of the present disclosure can be implemented using, for example, the desalination system 1 of the first or second embodiment described above.

[0110] [2-1] Evaporation process As shown in Figure 1, in the method of desalination using the desalination system 1 of the first embodiment, the base material 22 of the evaporator 20 arranged inside the desalination tank 10 is in contact with the raw water 2, so that the water in the raw water 2 reaches the heat generating section 21 through the pores of this base material 22. At this time, the heat generating unit 21 is irradiated with near-infrared rays S1 (and visible light S2 and ultraviolet light S3) through the transparent member of the desalination tank 10.

[0111] In the evaporation process, light S containing near-infrared rays S1 is irradiated onto the photothermal conversion material of the heat generating section 21, which absorbs near-infrared rays S1 and generates heat, and the heat generated by the photothermal conversion material absorbing the near-infrared rays S1 heats the raw water 2, thereby evaporating the water contained in the raw water 2.

[0112] Next, in a method of desalination using the desalination system 1 of the second embodiment, as shown in FIG. 3, water in the raw water 2 is drawn up by the water absorption layer 26 of the evaporator 20 and reaches the heat generating part 21 through the substrate 22.

[0113] At this time, the water absorption layer 26 is made of hydrophilic fibers such as water-absorbing, quick-drying polyester, cotton, etc., and has water absorption and supply functions, and is arranged with a part of it in contact with and immersed in the raw water 2. Therefore, the water in the raw water 2 is absorbed by the water absorption layer 26, pulled up through the water absorption layer 26, and automatically fed so as to come into contact with the substrate 22 and ultimately the heat generating part 21.

[0114] The heat generating portion 21 is irradiated with near-infrared rays S1 (and visible light S2 and ultraviolet light S3) through the transparent member of the desalination tank 10, as described above.

[0115] As a result, in the evaporation step, light S containing at least near-infrared rays S1 is irradiated onto the photothermal conversion material of heat generating portion 21, which absorbs near-infrared rays S1 and generates heat, and the photothermal conversion material absorbs the near-infrared rays S1, causing heat generation in heat generating portion 21. Therefore, water supplied to heat generating portion 21 through water absorption layer 26 and substrate 22 is sequentially evaporated by the heat of heat generating portion 21.

[0116] [2-2] Condensation process In the condensation process, the water (steam) 3 evaporated by the evaporator 20 is discharged from the desalination tank 10 to the outside, where it is cooled and condensed by the heat exchanger 30 of the cooling device, thereby obtaining liquid water (condensed water, purified water, fresh water) 4.

[0117] It should be noted that the steam 3 released from the desalination tank 10 to the outside does not necessarily have to be forcibly cooled and condensed by a cooling device. For example, the steam 3 released from the desalination tank 10 to the outside may be automatically condensed by utilizing the difference in temperature, or the temperature difference between day and night, to obtain the condensed water 4. That is, as long as it is possible to lower the temperature of the vapor 3 and cause it to be condensed, there is no need to particularly limit the means and configuration of the condensation step. [Example]

[0118] Hereinafter, examples of the desalination system and desalination method of the present disclosure will be shown and described in more detail. In this example, treatments and measurements for which no temperature conditions are specified were carried out at room temperature (23° C.).

[0119] [3] Preparation of test specimen (Example 1: Preparation of test specimen of Example 1) A composite material (heat generating part 21) containing silver nanoparticles and layered titanium dioxide as a photothermal conversion material was prepared as a test piece (sample, test piece). In the following description, the composite material (21) comprising silver nanoparticles and layered titanium dioxide is also referred to as "Ag / TiO2 composite material."

[0120] In Example 1, in producing a test specimen of the Ag / TiO2 composite material, first, a suspension of titanium dioxide exfoliates (plate-like titanium dioxide crystals) was prepared, and droplets of the suspension were dropped onto a glass substrate and sintered to obtain a layered compound consisting of a plurality of titanium dioxide exfoliates (plate-like titanium dioxide crystals) stacked together.

[0121] Next, this layered compound was immersed in a silver nitrate solution to allow a saturation amount of silver ions to be adsorbed onto the surface of the plate-like titanium dioxide crystals. It is believed that by immersing the layered compound in a silver nitrate solution, a saturated amount of silver ions can be adsorbed onto the surfaces of all the plate-like titanium dioxide crystals. Next, the silver ions were "chemically reduced" by immersing the material in a 0.1 mol / L aqueous solution of sodium tetrahydroborate for 30 minutes, producing an Ag / TiO2 composite material in which silver nanoparticles grew between the layers (layer spaces) of multiple titanium dioxide exfoliated crystals (layered crystals of plate-shaped titanium dioxide exfoliated crystals).

[0122] Then, a plate-shaped test piece (heat generating part 21) measuring 20 mm in length, 20 mm in width, and 1 mm in thickness was obtained by depositing the Ag / TiO2 composite material on a glass substrate (glass piece).

[0123] (Example 2: Preparation of test specimen of Example 2) An Ag / TiO2 composite material was prepared and a test piece was obtained in the same manner as in Example 1, except that when growing silver nanoparticles, the silver ions were reduced by "photoreduction" utilizing the photocatalytic properties of titanium dioxide instead of "chemical reduction."

[0124] (Comparative Example 1: Preparation of Test Specimen for Comparative Example 1) In this example, a comparative example test piece was also prepared as a sample for comparison. In Comparative Example 1, a plate-shaped glass piece measuring 20 mm in length, 20 mm in width, and 1 mm in thickness was prepared and used as a test specimen.

[0125] (Comparative Example 2) In this example, a test specimen was obtained by preparing a glass piece similar to that in Comparative Example 1, dropping droplets of the same titanium dioxide exfoliation suspension as in Example 1 onto one surface of the glass piece, and sintering the glass piece. That is, the test specimen in Comparative Example 2 was a glass substrate having one surface coated or covered with a layered compound composed of a plurality of titanium dioxide exfoliations (plate-like titanium dioxide crystals) stacked on top of each other.

[0126] [4] Evaluation of light absorption properties using reduction methods FIG. 4 shows the test results of examining the absorbance (extinction rate) in the wavelength range of 300 nm to 1800 nm for the specimen of Example 1 prepared by chemical reduction and the specimen of Example 2 prepared by photoreduction in the preparation of the Ag / TiO2 composite material.

[0127] From Figure 4, it was confirmed that the optical absorption properties of the Ag / TiO2 composite material obtained differ depending on the reduction method used in the preparation of the Ag / TiO2 composite material.

[0128] [5] Evaluation of photothermal conversion properties Next, the photothermal conversion characteristics of each of the test specimens of Example 1, Example 2, Comparative Example 1, and Comparative Example 2 were confirmed and evaluated.

[0129] In this test, the test specimen was placed on black paper and irradiated with light from above using a xenon lamp "MAX-303" (wavelength 430nm to 1050nm: near-infrared S1 + visible light S2) for 5 minutes. Before and after irradiation with light, the surface temperature of the test specimen and the surface temperature of the black paper portion exposed from the test specimen when viewed in plan were measured and evaluated. The surface temperature of the black paper before irradiation was 21.0°C.

[0130] FIG. 5 is a diagram showing temperature changes in the light irradiation test of each test specimen of Example 1 and Comparative Example 1.

[0131] In Example 1, which used an Ag / TiO2 composite material, the surface temperature of the test specimen after light irradiation was 38.1°C, and the surface temperature of the black paper was 22.1°C. Although the black paper showed only a temperature increase of about 1°C when irradiated with light, the test specimen showed a temperature increase of up to about 17°C. The test results demonstrate that the Ag / TiO2 composite material of Example 1 exhibits extremely excellent photothermal conversion properties (heat generation properties) when irradiated with near-infrared rays S1.

[0132] On the other hand, in the test piece of Comparative Example 1, the surface temperature of the test piece (23.6°C) was lower than the surface temperature of the black paper part (28.7°C). This is presumably because the glass absorbed heat.

[0133] Next, FIG. 6 is a diagram showing the relationship between the light irradiation time and the surface temperature of each test specimen of Example 1, Example 2, Comparative Example 1, and Comparative Example 2.

[0134] From Figure 6, it was confirmed that the test specimens of Example 1 and Example 2, which used the Ag / TiO2 composite material, had higher surface temperatures than the test specimen of Comparative Example 1, which used glass, and the test specimen of Comparative Example 2, which used a titanium dioxide peeled material, and thus exhibited excellent photothermal conversion properties (heat generation properties).

[0135] Furthermore, the specimen of Example 1, which was prepared by chemical reduction, had a higher surface temperature than the specimen of Example 2, which was prepared by photoreduction, confirming that producing an Ag / TiO2 composite material using chemical reduction can achieve better photothermal conversion properties (heat generation properties).

[0136] [6] Water heating experiment (test) Next, a water heating experiment was carried out using the test specimens of Example 1, Example 2, Comparative Example 1, and Comparative Example 2. FIG. 7 is a diagram for explaining the apparatus and method used in the experiment, and also shows an example of an embodiment of the desalination system 1 and desalination method of the present disclosure.

[0137] 3 mL of water (raw water 2) was stored in a plastic container, and a test specimen was placed in the water. The entire container was covered with a PET bottle cover (desalination tank 10), and a cut filter (irradiation light selection device 40) was placed on top of the cover.

[0138] The cut filter 40 is, for example, a UV cut filter manufactured by Asahi Spectroscopy Co., Ltd., and cuts out ultraviolet rays S3 contained in the irradiated light S. As a result, only light S in the range from infrared rays (near-infrared rays S1) to visible light S2 is selectively irradiated onto the test specimen.

[0139] In this state, the test specimen was irradiated with light S from a predetermined light source through a cut filter 40, and the mass of the water (raw water 2) in the plastic container was measured to determine the rate of water loss.

[0140] Fig. 8(a) is a diagram showing the relationship between the light irradiation time and the rate of reduction of water 2 when light S in the wavelength region of 430 nm or more and 1050 nm or less is irradiated to each of the test specimens of Example 1, Example 2, Comparative Example 1, and Comparative Example 2. Fig. 8(b) is a diagram showing the relationship between the light irradiation time and the rate of reduction of water 2 when light S in the wavelength region of 610 nm or more and 1050 nm or less is irradiated to each of the test specimens of Example 1, Example 2, Comparative Example 1, and Comparative Example 2.

[0141] 8, it was confirmed that in both Example 1 and Example 2, the water reduction rate was higher than in Comparative Examples 1 and 2, and that it was possible to efficiently heat and evaporate water 2. Furthermore, for the Ag / TiO2 composite material, it was confirmed that the test specimen of Example 2, which was produced by photoreduction, was able to heat and evaporate water 2 more efficiently than the test specimen of Example 1, which was produced by chemical reduction.

[0142] Next, FIG. 9 is a diagram showing the temperature change state for each irradiation time in a light irradiation test in water 2 using the test specimen of Example 1.

[0143] As can be seen from Figure 9, before light irradiation, the temperature of the center of the test piece was about 17°C, lower than the surrounding water temperature. However, when light S was irradiated, the temperature of the test piece rose to over 25°C, higher than the surrounding water temperature. This also raised the water temperature to over 20°C, confirming that water 2 could be heated effectively.

[0144] The above description of the examples has demonstrated that the desalination system 1 and desalination method of the present disclosure can realize a heat generating unit 21 with excellent photothermal conversion properties (heat generating properties) that generates heat by irradiating light S containing at least near-infrared rays S1 using a photothermal conversion material that absorbs near-infrared rays S1. It has also been fully demonstrated that clean water 4 can be efficiently and effectively produced and recovered by heating and evaporating water 2 using heat generated by the heat generating unit 21 upon irradiation with near-infrared rays S1, and then cooling and condensing the vapor 3.

[0145] The above describes embodiments and examples of the desalination system and desalination method disclosed herein. However, the desalination system and desalination method according to the present invention do not need to be limited to the contents shown in the above embodiments and examples, and can be modified as appropriate within the scope of the spirit thereof.

[0146] For example, in addition to the evaporation and condensation steps described above, the desalination method may include other steps, such as a pretreatment step, an intermediate treatment step, and a post-treatment step, to obtain more suitable purified water 4 in an efficient and effective manner.

[0147] In Figure 7 of the embodiment, the desalination system 1 according to the present disclosure is illustrated as being configured such that a PET bottle (desalination tank 10) is formed with an opening on the bottom surface, and a test specimen (heat generating part 21, evaporator 20) is immersed in water (raw water 2) stored in a plastic container inside the PET bottle. Alternatively, the desalination system 1 according to the present disclosure may be configured by directly pouring and storing water (2) into a plastic bottle (10) with the bottom opening closed, and inserting and disposing test specimens (21, 20) into the plastic bottle (10). In this case, the desalination system 1 according to the present disclosure may be configured by providing an openable / closable opening (enabling the interior of the plastic bottle (10) to be sealed / opened) at the top of the plastic bottle (10) for pouring and discharging water 2 into and from the inside of the plastic bottle (10), inserting and removing test specimens (21, 22), and extracting the generated steam 3. With this configuration, for example, a portable and easily transportable desalination system 1 can be realized.

[0148] Furthermore, the desalination tank 10 (shell body, etc.) may be configured to have a translucent heat insulating layer such as a vacuum layer to enhance thermal efficiency, thereby enabling the evaporation efficiency to be improved.

[0149] Furthermore, the desalination tank 10 may be configured with a pressure regulator for increasing the pressure inside the tank 10 to improve evaporation efficiency, and for drawing the evaporated water 3 to the outside of the tank 10 and reducing the pressure to improve condensation efficiency. A cooling device may be configured including this pressure regulator. In this configuration, simply by controlling the pressure, the inside of the desalination tank 10 can be pressurized, thereby increasing the thermal efficiency and therefore the evaporation efficiency. In addition, when the high-pressure inside of the desalination tank 10 is opened, the evaporated water 3 can be automatically drawn out from the desalination tank 10, and this opening automatically reduces the pressure of the evaporated water 3, allowing the condensed water 4 to be obtained. This makes it possible to increase the efficiency of producing the condensed water 4. Furthermore, it is possible to eliminate the need for cooling by the heat exchanger 30 and reduce the energy required for cooling. [Explanation of symbols]

[0150] 1. Desalination system 2 Raw water 3 Evaporated water (steam) 4 Liquid water (condensed water, clean water, fresh water) 10 Desalination Tank 11 Water supply equipment 12 Drainage system 13 Steam pumping device 20 Evaporator (Flash device) 21 Heat generating part 22 Base material 25 Support 26 Water absorption layer 30 Heat exchanger (cooling device) 31 Cooling water 32 Used cooling water 40 Cut filter (irradiation light selection device) S light (sunlight) S1 near infrared S2 visible light S3 UV

Claims

1. A desalination system including an evaporator that evaporates water in raw water, The evaporation device is a heat generating section that includes a photothermal conversion material that absorbs near-infrared rays and generates heat, and that has a photothermal conversion function of absorbing the near-infrared rays and generating heat when irradiated with light that includes at least the near-infrared rays; The raw water is heated using the generated heat, the water in the raw water is evaporated, and the evaporated water is condensed and recovered. Desalination system.

2. The photothermal conversion material is a composite material containing silver nanoparticles and layered titanium dioxide. The desalination system of claim 1 .

3. The composite material comprises: a layered compound in which titanium dioxide crystals are formed in layers; The silver nanoparticles present in the layer spaces of the layered compound, The desalination system of claim 2 .

4. The heat generating unit is disposed inside the desalination tank, and the desalination tank stores the raw water. The desalination tank includes a near-infrared transmitting portion for transmitting light including at least near-infrared rays from the outside and irradiating the heat-generating portion inside the desalination tank. The desalination system of claim 1 .

5. The evaporation device is The heat generating portion is provided in the form of a coating on the surface of a porous substrate. The desalination system of claim 1 .

6. The evaporation device is At least a portion of the porous substrate is in contact with the raw water, and at least a portion of the heat generating portion is disposed above the surface of the raw water. The desalination system of claim 5 .

7. The evaporation device is The substrate has a specific gravity smaller than that of the raw water and is disposed in a floating state in the raw water. The desalination system of claim 5 .

8. The evaporation device is The porous substrate; The heat generating portion is provided on the surface of the base material; a support that supports the heat generating unit and the substrate in a floating state in the raw water so that the heat generating unit and the substrate are disposed above the surface of the raw water; a water absorption layer interposed between the substrate and the support, in contact with the raw water, for supplying water in the raw water to the substrate or the heat generating part; The desalination system of claim 5 .

9. The silver nanoparticles are a product of chemical reduction of silver ions. The desalination system of claim 2 .

10. The silver nanoparticles are a product of photoreduction of silver ions. The desalination system of claim 2 .

11. a cooling device for condensing the evaporated water; a deodorizing device for removing odorous substances contained in the evaporated water, The cooling device and the deodorizing device are integrally provided so that condensation and deodorization are performed in parallel or in sequence. The desalination system of claim 1 .

12. the light includes near-infrared light, visible light, and ultraviolet light, an irradiation light selecting device for irradiating the heat generating portion with the near-infrared light while blocking at least one of the visible light and the ultraviolet light; The desalination system of claim 1 .

13. an evaporation step of irradiating a photothermal conversion material that absorbs near-infrared rays and generates heat with light containing at least the near-infrared rays, and heating raw water with the heat generated by the photothermal conversion material absorbing the near-infrared rays to evaporate the water contained in the raw water; A condensation step of condensing the evaporated water. Desalination method.

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