A three-dimensional solar evaporator with salt-oriented crystallization and automatic collection and a preparation method thereof

Abstract

This application relates to a three-dimensional solar evaporator with salt-oriented crystallization and automatic collection, and its preparation method. The three-dimensional solar evaporator includes a porous skeleton and a hydrophilic coating loaded on the outer surface of the porous skeleton. The porous skeleton includes a main skeleton and evaporation crystallization blades connected to the outer side wall of the main skeleton. The fixed end of the evaporation crystallization blade is connected to the main skeleton. At least the free end of the evaporation crystallization blade has a variable diameter shape, and the distance from the main skeleton increases from near to far. The width of the free end of the evaporation crystallization blade decreases from large to small. Therefore, the three-dimensional solar evaporator of this application can completely separate salt and water in brine, automatically collect salt, and efficiently evaporate water.

Description

Technical Field

[0001] This application relates to the field of brine evaporation technology, and more specifically, to a three-dimensional solar evaporator with salt-oriented crystallization and automatic collection, and a method for preparing the same. Background Technology

[0002] The development of modern industry and rapid population growth have left more than 30% of the world's population without reliable access to freshwater. To address this shortage, technologies such as electrically driven reverse osmosis and thermal desalination have been employed to extract freshwater from seawater. However, these methods are not only energy-intensive but also heavily reliant on fossil fuels, resulting in significant greenhouse gas emissions and a large carbon footprint. Furthermore, traditional desalination plants often discharge concentrated brine back into nearby water bodies, causing a gradual increase in salinity. Therefore, to address global challenges such as the energy crisis and environmental pollution, developing clean and environmentally friendly seawater desalination technologies driven by renewable energy has become a common goal of the international community.

[0003] In recent years, solar evaporation technology has attracted much attention due to its high solar energy conversion efficiency and low carbon emissions. Another significant feature of solar-driven evaporation technology is its ability to directly process brine solutions, achieving zero liquid discharge (ZLD) and ensuring complete separation of salt and water. However, during continuous desalination, salt crystallization occurs on the photothermal layer of the evaporator as water evaporates. This phenomenon not only reduces light absorption efficiency but also hinders the transport of brine and the release of steam, ultimately leading to evaporator performance degradation or even failure. To address the salt crystallization problem, some current methods, such as Janus structures, vertically aligned structures, and self-rotating structures, can enable efficient and continuous water evaporation while preventing salt deposition on the evaporator surface. However, these methods often cause salt to return to the large area of ​​seawater, increasing its salinity; therefore, preventing salt crystallization on the evaporator surface remains a challenge. Other methods achieve edge-preferred crystallization through effective brine management, ensuring continuous and efficient evaporation while keeping the evaporator surface clean, thus enabling the simultaneous production of salt and fresh water. However, the strong binding force between the crystallized salt and the evaporator surface hinders the natural separation of the salt. Frequent cleaning is essential to prevent the accumulation of salt caused by continuous erosion of the evaporation surface, which hinders the effective evaporation process. Furthermore, frequent cleaning not only increases labor costs but also disrupts the continuous seawater desalination process, raising the overall cost of desalination and hindering the large-scale deployment of desalination systems. Summary of the Invention

[0004] This application addresses the aforementioned deficiencies in the prior art. There is a need for a three-dimensional solar evaporator with directional salt crystallization and automatic collection, and a method for its preparation, enabling complete separation of salt and water in brine, automatic salt collection, and efficient evaporation of water.

[0005] In a first aspect, this application provides a three-dimensional solar evaporator with salt-oriented crystallization and automatic collection. The three-dimensional solar evaporator includes a porous skeleton and a hydrophilic coating loaded on the outer surface of the porous skeleton. The porous skeleton includes a main skeleton and evaporation crystallization blades connected to the outer side wall of the main skeleton. The fixed end of the evaporation crystallization blades is connected to the main skeleton. At least the free end of the evaporation crystallization blades has a variable diameter shape, and the distance from the main skeleton increases from near to far. The width of the free end of the evaporation crystallization blades decreases from large to small.

[0006] In a second aspect, this application provides a method for preparing the three-dimensional solar evaporator described in any embodiment of this application. The method includes: obtaining a main frame based on melamine foam by a rolling forming method; fixing the evaporation crystallization blades onto the main frame; spraying a hydrophilic coating onto the outer surface of the main frame and the evaporation crystallization blades; drying and reducing the coating under sunlight to obtain the three-dimensional solar evaporator.

[0007] The various embodiments of this application provide a three-dimensional solar evaporator with salt-oriented crystallization and automatic collection, and a method for preparing the same. The porous skeleton has a porous structure, allowing brine to reach the outer surface of the porous skeleton and the evaporation crystallization blades. Due to the special variable diameter shape of the free end of the evaporation crystallization blades, the brine at the free end evaporates faster, causing crystalline salt to gradually form at the position with the smallest width at the free end and automatically separate from the evaporation crystallization blades, achieving complete separation of water and salt. The brine can evaporate efficiently, avoiding salt deposition on the evaporator surface and achieving automatic salt collection. Attached Figure Description

[0008] In drawings that are not necessarily drawn to scale, the same reference numerals may describe similar parts in different views. The same reference numerals with or without letter suffixes may indicate different instances of similar parts. The drawings generally illustrate various embodiments by way of example rather than limitation and are used, together with the description and claims, to illustrate the claimed embodiments. Where appropriate, the same reference numerals are used in all drawings to refer to the same or similar parts. Such embodiments are illustrative and not intended to be exhaustive or exclusive embodiments of the apparatus or method.

[0009] Figure 1 A three-dimensional cross-sectional view of an embodiment 1 of this application is shown;

[0010] Figure 2 This diagram shows a top view of the three-dimensional solar evaporator according to Embodiment 1 of this application;

[0011] Figure 3 The diagram shows a top view of the evaporation crystallization blades and the main frame of this application at different angles. Detailed Implementation

[0012] To enable those skilled in the art to better understand the technical solutions of this application, the application will be described in detail below with reference to the accompanying drawings and specific embodiments. The embodiments of this application will be further described in detail below with reference to the accompanying drawings and specific examples, but these are not intended to limit the scope of this application.

[0013] The terms “first,” “second,” and similar terms used in this application do not indicate any order, quantity, or importance, but are merely used for distinction. Terms such as “including” or “comprising” mean that the element preceding the term covers the element listed after the term, and do not exclude the possibility of covering other elements as well.

[0014] According to an embodiment of this application, a three-dimensional solar evaporator with salt-oriented crystallization and automatic collection is provided. The three-dimensional solar evaporator includes a porous skeleton and a hydrophilic coating loaded on the outer surface of the porous skeleton. The porous skeleton includes a main skeleton and evaporation crystallization blades connected to the outer side wall of the main skeleton. The fixed end of the evaporation crystallization blade is connected to the main skeleton. At least the free end of the evaporation crystallization blade has a variable diameter shape, and the distance from the main skeleton increases from near to far. The width of the free end of the evaporation crystallization blade decreases from large to small.

[0015] The main framework and evaporation crystallization blades form a porous framework. Due to their porous structure, they can absorb brine and allow the brine to spontaneously reach the surface of the porous framework. The surface of the porous framework is coated with hydrophilic substances, which undergo photothermal conversion under sunlight, causing the water on the surface of the porous framework to evaporate continuously.

[0016] Due to the special variable diameter shape of the free end of the evaporation crystallization blades, the brine evaporates faster at the free end, causing salt crystals to gradually form at the position with the smallest width at the free end. The salt is deposited on the surface of the evaporator, and the crystallized salt block automatically separates from the evaporation crystallization blades, thereby achieving complete separation of water and salt. Water can evaporate efficiently, improving separation efficiency.

[0017] The evaporation crystallization blades are a biomimetic structure. In winter, the edges of the blades often freeze, and thinner areas cool faster at low temperatures. This rapid cooling causes water vapor to condense into ice crystals. Based on this, a three-dimensional solar evaporator structure was designed, achieving good results and facilitating the separation of salt and water in brine using solar energy. The brine concentration can range from 3.5% to 25 wt%.

[0018] Therefore, the structural design of the three-dimensional solar evaporator of this application can significantly improve the absorption of environmental energy, promote the radial transport of brine, and lead to directional salt crystallization at the edge of the biomimetic blade.

[0019] In some embodiments, the evaporation crystallization blades are triangular in shape. The width is smallest at each corner of the triangle. Using a triangular structure can significantly improve evaporation efficiency. Crystallized salt blocks can continuously appear at the corners of the free ends of the triangle and automatically detach from the evaporation crystallization blades, which is beneficial for salt collection.

[0020] In some embodiments, either side of the evaporation crystallization blade is connected to the outer wall of the main frame. For a triangular evaporation crystallization blade, any side can be connected to the outer wall of the main frame, but it is preferred that the shortest side is connected to the main frame, as the shortest side corresponds to the smallest acute angle, which is more conducive to the formation and detachment of the crystallized salt block.

[0021] In some embodiments, the triangular evaporation crystallization blades can be isosceles triangles or non-isosceles triangles. Furthermore, the evaporation crystallization blades are not limited to triangles; they can also be polygons, such as quadrilaterals with a pointed corner, and there can be multiple free ends, ensuring a variable diameter shape at the free ends. The included angle corresponding to the minimum width of the free end can have various values, including 15 degrees, 30 degrees, and 40 degrees.

[0022] In some embodiments, one or more evaporation crystallization blades may be provided. Multiple evaporation crystallization blades may be arranged along the axial direction of the main frame on its outer side wall, or they may form an array arrangement. For example, multiple rows of evaporation crystallization blades with equal spacing may be provided on the outer side wall of the main frame. The number of evaporation crystallization blades in each row is not limited and may be one or more, such as three or four. Two longitudinally adjacent evaporation crystallization blades in each row may be arranged close together, with spacing, or partially overlapping, among other methods.

[0023] In some embodiments, the length of the evaporation crystallization blades is 0.5-2 cm. If the blade surface of the evaporation crystallization blades is arranged radially, the length direction of the evaporation crystallization blades is consistent with the radial direction of the main frame. This length range allows for faster water evaporation at the tip of the evaporation crystallization blades, forming salt crystals and promoting the separation of salt crystals from the blades. The design of the evaporation crystallization blades increases the brine delivery and pressure at the salt crystallization point of the three-dimensional solar evaporator, enabling automatic separation of salt crystals and optimizing continuous evaporation performance.

[0024] In some embodiments, the diameter of the main frame is 1-5 cm. The brine diffuses outwards along the pores of the main frame; a suitable diameter range can improve the brine transport capacity and increase evaporation efficiency.

[0025] In some embodiments, the main frame and the evaporation crystallization blades are made of melamine foam (MF). MF has low cost, low density, superhydrophilicity, and excellent processability.

[0026] In some embodiments, the main frame is a cylindrical structure. The main frame is made of rolled melamine foam, with an opening at the top to allow sunlight to reach the inside of the main frame. Moisture continuously evaporates from the surface of the entire porous frame under sunlight.

[0027] In some embodiments, the evaporation crystallization blades are plate-like structures. When the main frame is cylindrical, the angle between the blade surface of the evaporation crystallization blade and the radial direction of the corresponding main frame is 0-90 degrees. Different evaporators may have different angles between the blade surface of the evaporation crystallization blade and the radial direction of the corresponding main frame. On the same evaporator, the blade surface of the evaporation crystallization blade and the radial direction of the corresponding main frame are the same, for example... Figure 3 As shown, the angle between the blade surface of the evaporation crystallization blade and the radial direction 3 is between 0 and 90 degrees.

[0028] In some embodiments, the height of the main frame is 1-10 cm. The height of the cylinder can be adjusted to obtain different evaporation rates and salt collection rates; a suitable cylinder height and diameter will result in a higher evaporation rate and salt collection rate.

[0029] In some embodiments, the hydrophilic coating material includes graphene oxide and cellulose nanocrystals.

[0030] According to an embodiment of this application, a method for preparing a three-dimensional solar evaporator is also provided. The method includes: obtaining a main frame based on melamine foam by a rolling forming method; fixing the evaporation crystallization blades onto the main frame; spraying a hydrophilic coating onto the outer surface of the main frame and the evaporation crystallization blades; drying and reducing the coating under sunlight to obtain a three-dimensional solar evaporator.

[0031] In some embodiments, the preparation method of the hydrophilic coating includes: mixing graphene oxide (GO) and cellulose nanocrystals (CNC) with water to form a stable suspension, and then spraying it onto the outer surface of the main framework and the evaporation crystallization blades. In some embodiments, the mass ratio of graphene oxide to cellulose nanocrystals is 50-80:50-20.

[0032] Example 1

[0033] Melamine foam (MF) is cut into 36 triangular evaporation crystallization blades and a rectangular main frame precursor, or into 9 connected parts, each of which includes 4 consecutive evaporation crystallization blades, and each evaporation crystallization blade is 1 cm long.

[0034] A stable suspension of graphene oxide (GO) and cellulose nanocrystals (CNC) was mixed at a mass ratio of 4:1, sprayed onto MF, and then air-dried and reduced by sunlight.

[0035] The rectangular main frame is rolled into a cylindrical structure (1 cm in diameter and 5 cm in height), and six interconnected evaporation and crystallization blades are evenly fixed to the cylinder around its perimeter using thin nickel wires, assembling a three-dimensional solar evaporator. Figure 1 and Figure 2 As shown.

[0036] Example 2

[0037] Melamine foam (MF) is cut into 24 triangular evaporation crystallization blades and a rectangular main frame precursor, or into 6 connected parts, each of which includes 4 consecutive evaporation crystallization blades, and each evaporation crystallization blade is 1 cm long.

[0038] A stable suspension of graphene oxide (GO) and cellulose nanocrystals (CNC) was mixed at a mass ratio of 4:1, sprayed onto MF, and then air-dried and reduced by sunlight.

[0039] The rectangular main frame is rolled into a cylindrical structure (1cm in diameter and 5cm in height), and six connected evaporation crystallization blades are fixed at equal intervals around the cylinder to assemble a three-dimensional solar evaporator.

[0040] Example 3

[0041] Melamine foam (MF) is cut into 12 triangular evaporation crystallization blades and a rectangular main frame precursor, or into 3 connected parts, each of which includes 4 consecutive evaporation crystallization blades, and each evaporation crystallization blade is 1 cm long.

[0042] A stable suspension of graphene oxide (GO) and cellulose nanocrystals (CNC) was mixed at a mass ratio of 4:1, sprayed onto MF, and then air-dried and reduced by sunlight.

[0043] The rectangular main frame is rolled into a cylindrical structure (1cm in diameter and 5cm in height), and six connected evaporation crystallization blades are fixed at equal intervals around the cylinder to assemble a three-dimensional solar evaporator.

[0044] Example 4

[0045] Melamine foam (MF) is cut into 36 triangular evaporation crystallization blades and a rectangular main frame precursor, or into 9 connected parts, each of which includes 4 consecutive evaporation crystallization blades, and each evaporation crystallization blade is 1 cm long.

[0046] A stable suspension of graphene oxide (GO) and cellulose nanocrystals (CNC) was mixed at a mass ratio of 4:1, sprayed onto MF, and then air-dried and reduced by sunlight.

[0047] The rectangular main frame is rolled into a cylindrical structure (2cm in diameter and 5cm in height), and six connected evaporation crystallization blades are fixed at equal intervals around the cylinder to assemble a three-dimensional solar evaporator.

[0048] Example 5

[0049] Melamine foam (MF) is cut into 24 triangular evaporation crystallization blades and a rectangular main frame precursor, or into 6 connected parts, each of which includes 4 consecutive evaporation crystallization blades, and each evaporation crystallization blade is 1 cm long.

[0050] A stable suspension of graphene oxide (GO) and cellulose nanocrystals (CNC) was mixed at a mass ratio of 4:1, sprayed onto MF, and then air-dried and reduced by sunlight.

[0051] The rectangular main frame is rolled into a cylindrical structure (2cm in diameter and 5cm in height), and four connected evaporation crystallization blades are fixed to the cylinder at equal intervals with thin nickel wires to assemble a three-dimensional solar evaporator.

[0052] Example 6

[0053] Melamine foam (MF) is cut into 12 triangular evaporation crystallization blades and a rectangular main frame precursor, or into 3 connected parts, each of which includes 4 consecutive evaporation crystallization blades, and each evaporation crystallization blade is 1 cm long.

[0054] A stable suspension of graphene oxide (GO) and cellulose nanocrystals (CNC) was mixed at a mass ratio of 4:1, sprayed onto MF, and then air-dried and reduced by sunlight.

[0055] The rectangular main frame is rolled into a cylindrical structure (2cm in diameter and 5cm in height), and five connected evaporation crystallization blades are fixed to the cylinder at equal intervals with thin nickel wires to assemble a three-dimensional solar evaporator.

[0056] Experimental Example

[0057] The three-dimensional solar evaporators of each embodiment were placed in a high-concentration brine solution. In this experiment, the brine concentration was 23 wt%, with the bottom of the main frame in contact with the water and the upper evaporation portion exposed to the air. A heat insulation plate was used to separate the evaporation components, preventing the salt crystals from the evaporation crystallization blades from falling back into the brine. Under the same indoor and outdoor sunlight conditions, each three-dimensional solar evaporator exhibited an extremely high evaporation rate of 3.6–8.4 kg m³. -2 h -1 And a significant salt collection rate of 0.5–1.1 kg m - 2 h -1 In Example 1, the evaporation rate was 8.4 kg m³. -2 h -1 The salt collection rate was 1.1 kg m³. -2 h -1 Example 2: Evaporation rate was 6.5 kg m³. -2 h -1 The salt collection rate was 0.9 kg m³. -2 h -1 Example 3: Evaporation rate was 4.4 kg m³. -2 h -1 The salt collection rate is 0.6 kg m -2 h -1 Example 4: Evaporation rate was 6.2 kg m³. -2 h -1 The salt collection rate is 0.8 kg m -2 h -1 Example 5: Evaporation rate was 4.8 kg m³. -2 h -1 The salt collection rate was 0.7 kg m³. -2 h -1 Example 6: Evaporation rate was 3.6 kg m³. -2 h -1 The salt collection rate is 0.5 kg m -2 h -1 The unique self-separation property of salt on the biomimetic blades enables the three-dimensional solar evaporator to maintain continuous seawater desalination indefinitely. In a continuous evaporation test lasting up to 200 hours, it not only maintained a stable evaporation rate but also successfully achieved zero liquid discharge (ZLD) desalination. Furthermore, the three-dimensional solar evaporator demonstrated a performance of 3.50 kg m³ in outdoor testing. -2 h -1 The extremely high water output and 0.6 kg m -2 h -1 The salt collection rate is high. Therefore, it can be used for continuous solar desalination and ZLD brine treatment.

[0058] Furthermore, although exemplary embodiments have been described herein, their scope includes any and all embodiments based on this application that have equivalent elements, modifications, omissions, combinations (e.g., schemes involving intersections of various embodiments), adaptations, or alterations. Elements in the claims will be interpreted broadly based on the language used in the claims and are not limited to the examples described in this specification or during the implementation of this application, which will be interpreted as non-exclusive. Therefore, this specification and examples are intended to be considered illustrative only, and the true scope and spirit are indicated by the following claims and the full scope of their equivalents.

[0059] The above description is intended to be illustrative and not restrictive. For example, the above examples (or one or more of them) can be used in combination with each other. Other embodiments may be used by those skilled in the art upon reading the above description. Furthermore, in the above detailed description, various features may be grouped together to simplify the application. This should not be construed as an intention that a feature of an unclaimed application is necessary for any claim. Rather, the subject matter of this application may be less than all the features of an embodiment of a particular application. Thus, the following claims are incorporated herein by reference as examples or embodiments, wherein each claim is independently considered as a separate embodiment, and these embodiments are contemplated as being possible in various combinations or arrangements. The scope of the invention should be determined by reference to the appended claims and the full scope of their equivalents.

[0060] The above embodiments are merely exemplary embodiments of this application and are not intended to limit the present invention. The scope of protection of the present invention is defined by the claims. Those skilled in the art can make various modifications or equivalent substitutions to the present invention within the spirit and scope of this application, and such modifications or equivalent substitutions should also be considered to fall within the scope of protection of the present invention.

Claims

1. A three-dimensional solar evaporator with salt-oriented crystallization and automatic collection, characterized in that, The three-dimensional solar evaporator includes a porous skeleton and a hydrophilic coating loaded on the outer surface of the porous skeleton. The porous skeleton includes a main skeleton and evaporation crystallization blades connected to the outer side wall of the main skeleton. The main skeleton is a cylindrical structure, and the evaporation crystallization blades are triangular sheet-like structures. Any side of the evaporation crystallization blades is connected to the outer side wall of the main skeleton. The main frame and the evaporation crystallization blades are made of melamine foam; The hydrophilic coating is made of graphene oxide and cellulose nanocrystals.

2. The three-dimensional solar evaporator according to claim 1, characterized in that, The length of the evaporation crystallization blade along the radial direction of the main skeleton is 0.5-2 cm.

3. The three-dimensional solar evaporator according to claim 1, characterized in that, The diameter of the main frame is 1-5cm.

4. The method for preparing the three-dimensional solar evaporator according to any one of claims 1-3, characterized in that, The preparation method includes: obtaining a main frame based on melamine foam by curling; fixing the evaporation crystallization blades onto the main frame; spraying a hydrophilic coating onto the outer surface of the main frame and the evaporation crystallization blades, drying and reducing them under sunlight to obtain a three-dimensional solar evaporator.

5. The preparation method according to claim 4, characterized in that, The preparation method of the hydrophilic coating includes: mixing graphene oxide and cellulose nanocrystals with water to form a stable suspension; and spraying the stable suspension onto the outer surface of the main frame and the evaporation crystallization blades.

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