Conical solar interface evaporator with high salt deposition resistance

Abstract

The invention belongs to the field of brine evaporators, and relates to a conical solar interface evaporator with high salt deposition resistance. The evaporator comprises a hydrophobic heat insulation layer, a hydrophobic fixing layer, a water absorption layer and a hydrophobic porous evaporation layer. The hydrophobic porous evaporation layer is arranged on the hydrophobic heat insulation layer, the hydrophobic fixing layer is arranged on the hydrophobic heat insulation layer, and the hydrophilic layer is provided with a plurality of water absorption belts and is arranged between the hydrophobic porous evaporation layer and the hydrophobic fixing layer. The evaporator is simple in preparation method, solves the problem of salt deposition of a traditional evaporator in evaporation of high-concentration saline water, improves the evaporation efficiency, and can be widely applied to seawater desalination treatment as an evaporator.

Description

Technical Field

[0001] The invention belongs to the field of salt water evaporators and relates to a conical solar interface evaporator with high resistance to salt formation. Background Art

[0002] Current desalination technologies, such as reverse osmosis (RO) and low-temperature multi-effect distillation (MED), are well-established, but they rely on high-pressure pumps or heat input, resulting in high energy consumption. For example, energy consumption in RO processes accounts for 40%-50% of operating costs. Solar interfacial evaporation, a novel solar desalination method proposed by Professor Gang Chen of the Massachusetts Institute of Technology in 2014, involves floating a porous evaporator on the water surface. Photothermal conversion occurs at the water-air interface, creating a localized hot zone. Simultaneously, the porous structure within the evaporator continuously supplies water to the top hot zone through capillary action, causing evaporation. The steam condenses into fresh water for collection, while the salt remains in the residual liquid. Compared to traditional desalination technologies, this interfacial evaporation system eliminates the need for complex and expensive solar thermal collectors and power equipment, significantly reducing costs. However, when treating salty water, salt tends to crystallize at the evaporator interface, forming an insulating salt crust that reduces light absorption efficiency and hinders water evaporation. Regular cleaning is required, increasing operating and maintenance costs. Therefore, it is particularly important to develop a highly salt-tolerant solar interface evaporator. Summary of the Invention

[0003] In order to solve the above problems, the present invention aims to provide a conical solar interface evaporator with high resistance to salt deposition.

[0004] In a first aspect of the present invention, a conical solar interface evaporator is provided, wherein the conical solar interface evaporator is used to float on a salt water surface to evaporate water in the salt water, and the conical solar interface evaporator comprises:

[0005] a hydrophobic heat-insulating layer, the hydrophobic heat-insulating layer being configured to be in contact with salt water and capable of floating on the surface of the salt water;

[0006] a hydrophobic fixed layer, the hydrophobic fixed layer being arranged on the hydrophobic heat-insulating layer;

[0007] a water absorbing layer, wherein the water absorbing layer is sleeved on the upper surface of the hydrophobic fixed layer, and the lower edge of the water absorbing layer is partially in contact with the salt water;

[0008] A hydrophobic porous evaporation layer is sleeved on the upper surface of the water absorbing layer.

[0009] In some embodiments of the present invention, the hydrophobic fixed layer, the water absorbing layer and the hydrophobic porous evaporation layer all have a conical structure.

[0010] In some embodiments of the present invention, the water absorbing layer material is a hydrophilic material.

[0011] In some embodiments of the present invention, the water-absorbing layer is a conical filter paper, and a lower edge of the conical filter paper has a plurality of water-absorbing strips.

[0012] In some embodiments of the present invention, the hydrophobic insulation layer is a PS foam board.

[0013] In some embodiments of the present invention, a hole for inserting the water absorbent tape is provided on the surface of the hydrophobic heat-insulating layer.

[0014] In some embodiments of the present invention, the hydrophobic fixed layer is provided with a plurality of circular holes.

[0015] In some embodiments of the present invention, the hydrophobic fixed layer and the hydrophobic surface of the hydrophobic porous evaporation layer are formed by depositing polydopamine / silver / dodecyl mercaptan.

[0016] The conical solar interface evaporator according to the embodiment of the present invention has at least one of the following advantages or at least part of one of the advantages:

[0017] (1) The most important innovation of the present invention lies in the porous structure of the hydrophobic surface and the conical structure design of the evaporation layer. The hydrophobic surface and conical structure design make the temperature of the hydrophobic part and the pore wall of the evaporation layer much higher than the exposed water-absorbing layer corresponding to the position of the pores in the evaporation layer, thereby generating a temperature gradient to induce micro-convection. On the microscopic level, the shear effect of micro-convection increases the salt nucleation energy barrier, making it difficult for salt to crystallize. On the macroscopic level, the micro-flow field directionally flushes the interface, expelling free ions and subcritical crystal nuclei from the system, suppressing local supersaturation, and achieving long-term salt resistance. In addition, the hydrophobic surface of the hydrophobic fixed layer has weak adsorption to salt ions and is not easily infiltrated by salt water, reducing the risk of salt crystals nucleating and accumulating on the lower surface of the inner layer.

[0018] (2) The conical solar interface evaporator provided by the present invention is designed to have a conical evaporation layer. Compared with a planar structure, the cone has a larger evaporation area and the conical side wall induces multiple reflections of light, thereby increasing the light absorption rate and thus the evaporation rate.

[0019] (3) The hydrophobic surface of the conical solar interface evaporator provided by the present invention produces a low solid-liquid contact area. Salt ions will not accumulate on the surface of the hydrophobic evaporation layer. The salt concentration difference between the upper and lower water absorption layers due to evaporation forms Marangoni convection. Salt flows from the top of the cone to the bottom of the cone and returns to the water body, forming a dynamic and continuous salt transport cycle.

[0020] (4) In the conical solar interface evaporator and its preparation method provided in the embodiment of the present invention, the surface of the hydrophobic evaporation layer contains PDA and silver. PDA gives the device excellent photothermal conversion performance, and silver gives the device antibacterial properties, eliminating the growth of bacteria and achieving the self-cleaning property of the device. The device preparation method is simple, and solves the problem of salt formation in the evaporation of high-concentration brine in traditional evaporators, thereby laying the foundation for the treatment of high-concentration brine in seawater desalination. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] These and / or other aspects and advantages of the present invention will become apparent and readily understood from the following description of the preferred embodiments taken in conjunction with the accompanying drawings, in which:

[0022] Figure 1 A schematic diagram of the explosion structure of a conical solar interface evaporator with high salt resistance provided by an embodiment of the present invention is shown;

[0023] Figure 2 A schematic structural diagram of a conical solar interface evaporator with high salt resistance provided by an embodiment of the present invention is shown;

[0024] Figure 3 A schematic diagram of the micro-convection anti-salt principle in the evaporation hole of a conical solar interface evaporator with high salt resistance provided by an embodiment of the present invention is shown;

[0025] Figure 4 A schematic diagram of water transmission in the water absorption layer of a conical solar interface evaporator with high salt resistance (blue arrows) and a schematic diagram of salt backflow caused by concentration difference (red arrows) are shown in an embodiment of the present invention;

[0026] Figure 5 These are infrared thermal images of the comparative conical solar interface evaporator (hydrophilic evaporation layer) and the conical solar interface evaporator (hydrophobic evaporation layer) of Test Example 2 after being irradiated for 8 hours, where (a) is an infrared thermal image of the comparative example, and (b) is an infrared thermal image of the example;

[0027] Figure 6 The figures show the actual images of the comparative conical solar interface evaporator (hydrophilic evaporation layer) and the example conical solar interface evaporator (hydrophobic evaporation layer) in Test Example 2 after being irradiated for 8 hours, wherein (a) is the actual image of the comparative example, and (b) is the actual image of the example. DETAILED DESCRIPTION

[0028] To further understand the present invention, the following description is provided in conjunction with preferred embodiments. However, it should be understood that these descriptions are intended only to further illustrate the features and advantages of the present invention and are not intended to limit the scope of the present invention. The embodiments described are merely some examples of the present invention and are not intended to be exhaustive.

[0029] In an embodiment of the present invention, a conical solar interface evaporator is provided. The conical solar interface evaporator is used to float on a brine surface to evaporate water in brine. The conical solar interface evaporator includes, from bottom to top, a hydrophobic insulation layer 4, a hydrophobic fixed layer 3, a water absorption layer 2, and a hydrophobic porous evaporation layer 1. The hydrophobic porous evaporation layer 1 forms a sandwich structure with the water absorption layer 2 and the hydrophobic fixed layer 3.

[0030] The hydrophobic insulating layer 4 is hydrophobic. During use, it contacts the saltwater and floats on the surface. Conventionally, since the water surface temperature is lower than the evaporation layer temperature, heat loss occurs downward, further lowering the temperature of the hydrophobic porous evaporation layer 1 and reducing evaporation efficiency. In the conical solar interface evaporator provided in this embodiment of the present invention, the hydrophobic insulating layer 4 also provides thermal insulation, physically isolating the upper evaporation interface from the water below, preventing heat loss downward through solid conduction or convection.

[0031] In some specific embodiments of the present invention, the hydrophobic heat-insulating layer 4 may be a PS foam board.

[0032] The hydrophobic fixing layer 3 is provided on the hydrophobic heat-insulating layer 4 and is used to fix the water-absorbing layer 2 .

[0033] The water-absorbing layer 2 is made of hydrophilic material. The lower edge of the water-absorbing layer 2 is partially in contact with the salt water. The water-absorbing layer 2 is sleeved on the upper surface of the hydrophobic fixed layer 3.

[0034] In some embodiments of the present invention, the hydrophobic fixed layer 3 , the water absorbing layer 2 , and the hydrophobic porous evaporation layer 1 all have a conical structure.

[0035] In some preferred embodiments of the present invention, the water absorbing layer 2 is a cone-shaped filter paper, and a plurality of water absorbing strips are provided at the lower edge of the cone-shaped filter paper. When in use, the water absorbing strips are immersed in salt water.

[0036] The hydrophobic porous evaporation layer 1 has a hydrophobic surface and is positioned over the upper surface of the water-absorbing layer 2. The pores on the surface of the hydrophobic porous evaporation layer 1 serve as evaporation pores. During use, salt water is transported upward through the lower edge of the water-absorbing layer 2, where it contacts the salt water, to the tapered interface between the two layers. Evaporated water vapor is then discharged through the pores on the surface of the hydrophobic porous evaporation layer 1.

[0037] In some embodiments of the present invention, the surface of the hydrophobic insulation layer 4 is provided with holes for inserting the water-absorbing tape. Several water-absorbing tapes along the lower edge of the water-absorbing layer 2 are inserted into the holes of the hydrophobic insulation layer 4 and immersed in brine. The brine is transported upward through the water-absorbing tapes of the water-absorbing layer 2 to the conical interface between the hydrophobic porous evaporation layer 1 and the water-absorbing layer 2. The evaporated water vapor is discharged through the evaporation holes on the surface of the hydrophobic porous evaporation layer 1.

[0038] In some embodiments of the present invention, the hydrophobic fixed layer 3 is provided with a plurality of circular holes.

[0039] In some embodiments of the present invention, the hydrophobic fixed layer 3 and the hydrophobic surface of the hydrophobic porous evaporation layer 1 are formed by depositing polydopamine / silver / dodecyl mercaptan.

[0040] The hydrophobic porous evaporation layer 1 is assembled with the water absorbing layer 2 and the hydrophobic fixed layer 3 to form a sandwich structure and placed on the hydrophobic heat-insulating layer 4. Several water absorbing strips along the lower side of the water absorbing layer 2 are inserted into the holes of the hydrophobic heat-insulating layer 4 to obtain the following: Figure 2 The overall structure of the conical solar interface evaporator is shown.

[0041] During the evaporation process of the conical solar interface evaporator provided by the embodiment of the present invention, micro convection is formed in the pores due to the hydrophobic surface and porous structure of the hydrophobic porous evaporation layer 1. Figure 3 As shown, the red arrows indicate microconvection. The specific principle is that a temperature gradient is generated between the exposed water-absorbing layer 2 and the hydrophobic porous evaporation layer 1. This temperature gradient induces microconvection, increasing the evaporation rate. Simultaneously, the shear force generated by microconvection destabilizes the system, raising the salt nucleation barrier and preventing salt crystallization. Furthermore, microconvection scours the pore walls, disrupting salt crystallization and preventing pore blockage.

[0042] Because the temperature gradient between the exposed water-absorbing layer 2 and the hydrophobic porous evaporation layer 1 is a key factor in improving evaporation efficiency and reducing salt crystallization, the present invention designs the evaporation layer 1 as a hydrophobic porous conical structure. This aims to maximize the temperature of the hydrophobic portion of the hydrophobic porous evaporation layer 1 and minimize the temperature of the water-absorbing layer 2, maximizing the temperature gradient effect and enhancing microconvection. Specifically, firstly, the hydrophobic surface of the present embodiment eliminates water from the surface of the hydrophobic porous evaporation layer 1, preventing evaporation. Under sunlight, the surface absorbs heat to form a high-temperature region. At locations corresponding to the pores of the hydrophobic porous evaporation layer 1, the temperature of the exposed water-absorbing layer 2 decreases due to water evaporation. Secondly, the present embodiment designs the hydrophobic porous evaporation layer 1 into a conical structure, resulting in an overall inclined surface for all pores in any direction. Under sunlight, light is reflected within the pores of the hydrophobic porous evaporation layer 1 (regardless of their orientation), creating a light confinement effect (similar to an energy-concentrating ring), further increasing the pore wall temperature.

[0043] When in use, the conical solar interface evaporator provided by the embodiment of the present invention is placed on the surface of salt water, and the hydrophobic insulation layer 4 contacts the salt water surface. The water transmission diagram of its water absorption layer 2 (blue arrow) and the salt flushing diagram caused by the concentration difference (red arrow) are shown as follows: Figure 4As shown. Specifically, several water-absorbing strips at the bottom edge of the water-absorbing layer 2 pass through the pores of the hydrophobic insulation layer 4 and immerse themselves in the brine. The brine is then transported upward through these strips to the surface of the water-absorbing layer 2, as indicated by the blue arrows. As the evaporation process proceeds, the salt concentration at the top of the water-absorbing layer 2 gradually increases, increasing the surface tension of the brine at the top. Meanwhile, the salt concentration at the bottom of the water-absorbing layer 2 is lower, and the surface tension of the brine at the bottom is lower, creating a high concentration difference with the top of the water-absorbing layer 2. This strengthens the transport of liquid from bottom to top, diluting the high-concentration salt at the top and achieving a flushing effect. Salt then flows from the top of the cone to the bottom of the cone and returns to the water body, as indicated by the red arrows. This process forms a dynamic, continuous salt transport cycle.

[0044] Example: The porous evaporation layer is a hydrophobic surface.

[0045] (1) Design the 3D model of the evaporation layer and fixed layer of the evaporator in SolidWorks. The evaporation layer is a cone with a bottom radius of 10 mm, a height of 10 mm, and a cone angle of 90°. The cone wall thickness is 1 mm, and several circular holes with a radius of 0.25 mm are cut out on the cone wall, with a hole spacing of 0.8 mm. The fixed layer is a cone with a bottom radius of 10 mm, a height of 9 mm, and a cone angle of 90°. The cone wall thickness is 1 mm, and several circular holes with a radius of 0.25 mm are cut out on the cone wall, with a hole spacing of 0.8 mm. Import the 3D model into the light-curing printer and start printing.

[0046] (2) Soak the evaporation layer and the fixed layer in a 5% by mass NaOH solution for 20 minutes, rinse with deionized water, and dry in an oven at 60°C. Perform a hydrophobic treatment on the evaporation layer and fixed layer after alkaline treatment. The specific method is as follows: soak the evaporation layer and fixed layer after alkaline treatment in a pH = 8.5 dopamine hydrochloride and Tris-HCl composite solution, with a dopamine hydrochloride concentration of 10g / L and a Tris-HCl concentration of 10mM / L. After reacting for 24 hours, remove them, rinse with deionized water, and dry them in an oven at 60°C. Then, soak the evaporation layer and fixed layer coated with polydopamine in a silver ammonia solution for 20 minutes, then add glucose solution and react for 2 hours. The concentration of silver nitrate added to the silver ammonia solution is 5g / L, and the concentration of glucose is 10g / L. Then remove them, rinse with deionized water, and dry them in an oven at 60°C.

[0047] (3) The dried evaporation layer and fixed layer were immersed in a 1 g / L solution of dodecanethiol and ethanol. After immersion at room temperature for 24 hours, the layers were washed with ethanol and deionized water, respectively, and dried in an oven at 60°C to obtain a hydrophobic porous evaporation layer 1 and a hydrophobic fixed layer 3. Using a contact angle meter, the contact angles of the hydrophobic porous evaporation layer 1 and the hydrophobic fixed layer 3 were both 150°, indicating that they were hydrophobic surfaces.

[0048] (4) The hydrophobic fixed layer 3 is fixed on the hydrophobic insulation layer 4, and then the filter paper is cut to form a conical water-absorbing layer 2 which is put on the hydrophobic fixed layer 3 after the hydrophobic treatment, and then the hydrophobic porous evaporation layer 1 is put on the water-absorbing layer 2 to obtain a conical solar interface evaporator.

[0049] Comparative example: the evaporation layer is a hydrophilic surface

[0050] The difference between the comparative example and the example is that in step (3), only the fixed layer was immersed in a 1 g / L solution of dodecanethiol and ethanol. The evaporating layer was not immersed. Tests using a contact angle meter showed that the contact angles of the evaporating layer were both 0°, while the contact angles of the fixed layer were both 150°, indicating that the surfaces were hydrophobic.

[0051] Test Example 1: Salt solution concentration is 3.5%

[0052] Use a xenon lamp (100mw / cm 2 The evaporator with a hydrophilic evaporation layer (comparative example) and the evaporator with a hydrophobic evaporation layer (example) were irradiated with simulated sunlight for 8 hours, and the salt solution concentration was 3.5%.

[0053] The evaporation rate was calculated by dividing the evaporation amount per unit hour by the projected area of ​​the evaporating surface. The evaporation rate of the evaporator with a hydrophobic evaporation layer obtained in the embodiment was 3.1, while the evaporation rate of the evaporator with a hydrophilic evaporation layer obtained in the comparative example was 2.6. It can be seen that the evaporation rate of the evaporator with a hydrophobic evaporation layer obtained in the embodiment is higher.

[0054] Test Example 2: Salt solution concentration is 20%

[0055] Use a xenon lamp (100mw / cm 2 The evaporator with a hydrophilic evaporation layer (comparative example) and the evaporator with a hydrophobic evaporation layer (example) were irradiated with simulated sunlight for 8 hours. The salt solution concentration was 20%. After 8 hours of irradiation, photos were taken with a thermal imager. Figure 5 As shown in the actual picture Figure 6 shown.

[0056] according to Figure 5 It can be seen that the surface center temperature of the evaporator with a hydrophobic evaporation layer (44.2°C) is higher than the surface center temperature of the evaporator with a hydrophilic evaporation layer (38.3°C). A higher surface temperature is conducive to increasing the evaporation rate. Therefore, it can be seen that the evaporation rate of the evaporator with a hydrophobic evaporation layer is higher.

[0057] The evaporation rate, calculated by dividing the evaporation volume per hour by the projected area of ​​the evaporating surface, was 2.7 for the evaporator with a hydrophobic evaporation layer obtained in the Example, while the evaporation rate for the evaporator with a hydrophilic evaporation layer obtained in the Comparative Example was 2.2. This slightly lower evaporation rate compared to a salt solution with a concentration of 3.5% is because at high salt concentrations (e.g., 20%), salt ions bind water molecules, reducing the surface vapor pressure of the solution, weakening the evaporation dynamics, and forming a high-viscosity boundary layer at the evaporation interface, which hinders the diffusion of water molecules.

[0058] according to Figure 6 It can be found that the surface of the evaporator with a hydrophilic evaporation layer has obvious salt deposition, while the surface of the evaporator with a hydrophobic evaporation layer has no obvious salt deposition. This indicates that the evaporator with a hydrophobic evaporation layer will not allow salt to accumulate on the surface and block the evaporation pores, thereby maintaining a higher evaporation rate and having better anti-salting performance.

[0059] The conical solar interface evaporator according to the embodiment of the present invention has at least one of the following advantages or at least part of one of the advantages:

[0060] (1) The most important innovation of this patent lies in the porous structure of the hydrophobic surface and the conical structure design of the evaporation layer. The hydrophobic surface and conical structure design make the temperature of the hydrophobic part and the pore wall of the evaporation layer much higher than the exposed water-absorbing layer corresponding to the position of the pores in the evaporation layer, thereby generating a temperature gradient to induce micro-convection. On the microscopic level, the shear effect of micro-convection increases the salt nucleation energy barrier, making it difficult for salt to crystallize. On the macroscopic level, the micro-flow field directionally flushes the interface, expelling free ions and subcritical crystal nuclei from the system, suppressing local supersaturation, and achieving long-term salt resistance. In addition, the hydrophobic surface of the hydrophobic fixed layer has weak adsorption to salt ions and is not easily infiltrated by salt water, reducing the risk of salt crystals nucleating and accumulating on the lower surface of the inner layer.

[0061] (2) The conical solar interface evaporator provided by the present invention is designed to have a conical evaporation layer. Compared with a planar structure, the cone has a larger evaporation area and the conical side wall induces multiple reflections of light, thereby increasing the light absorption rate and thus the evaporation rate.

[0062] (3) The hydrophobic surface of the conical solar interface evaporator provided by the present invention produces a low solid-liquid contact area. Salt ions will not accumulate on the surface of the hydrophobic evaporation layer. The salt concentration difference between the upper and lower water absorption layers due to evaporation forms Marangoni convection. Salt flows from the top of the cone to the bottom of the cone and returns to the water body, forming a dynamic and continuous salt transport cycle.

[0063] (4) In the conical solar interface evaporator and its preparation method provided in the embodiment of the present invention, the surface of the hydrophobic evaporation layer contains PDA and silver. PDA gives the device excellent photothermal conversion performance, and silver gives the device antibacterial properties, eliminating the growth of bacteria and achieving the self-cleaning property of the device. The device preparation method is simple, and solves the problem of salt formation in the evaporation of high-concentration brine in traditional evaporators, thereby laying the foundation for the treatment of high-concentration brine in seawater desalination.

[0064] The foregoing description is merely a preferred embodiment of the present invention, and the scope of protection of the present invention is not limited to the foregoing embodiment. Persons skilled in the art will appreciate that modifications may be made to these embodiments without departing from the principles and spirit of the overall concept of the present invention, and such modifications should be considered to fall within the scope of protection of the present invention. The scope of the present invention is defined by the claims and their equivalents.

Claims

1. A conical solar interface evaporator with high resistance to salt formation, wherein the conical solar interface evaporator is used to float on a salt water surface to evaporate water in salt water, characterized in that: The conical solar interface evaporator comprises: a hydrophobic heat-insulating layer, the hydrophobic heat-insulating layer being configured to be in contact with salt water and capable of floating on the surface of the salt water; a hydrophobic fixed layer, the hydrophobic fixed layer being arranged on the hydrophobic heat-insulating layer; a water absorbing layer, wherein the water absorbing layer is sleeved on the upper surface of the hydrophobic fixed layer, and the lower edge of the water absorbing layer is partially in contact with the salt water; A hydrophobic porous evaporation layer is sleeved on the upper surface of the water absorbing layer.

2. The conical solar interface evaporator according to claim 1, characterized in that: The hydrophobic fixed layer, the water absorbing layer and the hydrophobic porous evaporation layer all have a conical structure.

3. The conical solar interface evaporator according to claim 1, characterized in that: The water absorption layer is a conical filter paper, and the lower edge of the conical filter paper is provided with a plurality of water absorption belts.

4. The conical solar interface evaporator according to claim 1, characterized in that: The hydrophobic heat-insulating layer is a PS foam board.

5. The conical solar interface evaporator according to claim 1, characterized in that: The surface of the hydrophobic heat-insulating layer is provided with holes for inserting the water-absorbing tape.

6. The conical solar interface evaporator according to claim 1, characterized in that: The hydrophobic fixed layer is provided with a plurality of circular holes.

7. The conical solar interface evaporator according to claim 1, characterized in that: The hydrophobic fixed layer and the hydrophobic surface of the hydrophobic porous evaporation layer are formed by depositing polydopamine / silver / dodecyl mercaptan.

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