A multi-stage liquid supply solar photothermal evaporation device

Abstract

The application discloses a kind of multistage liquid supply solar photothermal evaporation devices, including solution holding pool and the light cover of cover being arranged in solution holding pool upper;The solution holding pool is divided into concentrated liquid area and dilute liquid area by partition;There is adaptive photothermal evaporation assembly floating in the concentrated liquid area, and the adaptive photothermal evaporation assembly includes: with the liquid in concentrated liquid area contact first-stage liquid supply module, with first-stage liquid supply module connection liquid transport module and the photothermal evaporation module on the upper surface of liquid transport module;Second-stage liquid supply module is placed in the liquid transport module, and second-stage liquid supply module is simultaneously connected with first-stage liquid supply module and liquid transport module;Second-stage liquid supply module is PNIPAAm-based temperature-sensitive hydrogel.The solar photothermal evaporation device of the application can be self-adapting to regulate and control the amount of liquid transported to the evaporation surface according to the real-time changing solar irradiance, thereby solving the problem of poor evaporation performance and low heat utilization efficiency caused by excess or insufficient liquid in the evaporation surface.

Description

Technical Field

[0001] This invention relates to a solar thermal evaporation device with multi-stage liquid supply. Background Technology

[0002] Solar energy is used to convert substances such as water in single- or multi-component liquids into steam through a liquid-vapor phase transition, which has wide applications in seawater desalination, solution concentration and regeneration, and wastewater treatment. Solar-driven interfacial evaporation technology heats only a thin layer of liquid on the surface of the water body, avoiding heat loss caused by heating the entire liquid. This reduces the energy consumed per unit volume of steam, resulting in faster response times and higher evaporation efficiency, making it possible to obtain steam even under actual outdoor low energy flux density solar irradiance.

[0003] However, in real-world environments, solar radiation intensity undergoes continuous and complex variations over time. Existing porous capillary materials transport the solution to the evaporation layer at a constant rate; therefore, excess or insufficient solution volume within the evaporation layer can occur at any time, severely impacting evaporation performance and heat utilization efficiency. Furthermore, in solar-driven interfacial evaporation, a significant portion of the heat from the photothermal evaporation surface is conducted downwards through the liquid in the evaporation device into the lower liquid pool, resulting in substantial heat loss. Summary of the Invention

[0004] Purpose of the invention: The purpose of this invention is to provide a multi-stage liquid supply solar thermal evaporation device. This device can adaptively adjust the amount of liquid transported to the evaporation surface according to the real-time changes in the intensity of sunlight, thereby solving the problems of poor evaporation performance and low heat utilization efficiency caused by excess or insufficient liquid in the evaporation surface.

[0005] Technical Solution: The solar thermal evaporation device of the present invention includes a solution holding tank and a light-transmitting cover over the solution holding tank; the solution holding tank is divided into a concentrated liquid zone and a dilute liquid zone by a partition; an adaptive photothermal evaporation component floats in the concentrated liquid zone, the adaptive photothermal evaporation component includes: a primary liquid supply module in contact with the liquid in the concentrated liquid zone, a delivery module connected to the primary liquid supply module, and a photothermal evaporation module located on the upper surface of the delivery module; a secondary liquid supply module is placed inside the delivery module, and the secondary liquid supply module is connected to both the primary liquid supply module and the delivery module; the secondary liquid supply module is a PNIPAAm-based thermosensitive hydrogel.

[0006] Among them, the sides and bottom of the adaptive photothermal evaporation component are wrapped with heat-insulating and waterproof modules. The sides and bottom of the adaptive photothermal evaporation component are tightly wrapped with heat-insulating and waterproof modules to achieve contact or suspension between the adaptive photothermal evaporation component and the liquid in the concentrated liquid area, and to greatly reduce the heat loss to the sides and bottom of the adaptive photothermal evaporation component.

[0007] The infusion module has a groove inside, and the infusion module and the primary infusion module enclose the groove to form a closed cavity, in which the secondary infusion module is embedded.

[0008] The infusion module and the primary infusion module enclose the groove to form a closed space. The inner surface of the space is tightly attached to and wraps the secondary infusion module (adaptive storage / discharge module). The primary infusion module is T-shaped and has an end with a smaller diameter and a larger height to obtain a larger heat-insulating wrapping volume.

[0009] The PNIPAAm-based thermosensitive hydrogel is PNIPAAm grafted with SA, and its preparation method specifically includes the following steps:

[0010] (1) Add the crosslinking agent N,N-methylenebisacrylamide to the NIPAAm monomer solution to obtain mixture I;

[0011] (2) Add SA to mixture I, stir continuously at room temperature, and at the same time purge nitrogen into the reaction vessel to protect the reaction environment to obtain mixture II;

[0012] (3) Dissolve ammonium persulfate in deionized water to form a solution, slowly add it to mixture II, stir evenly to obtain mixture III, pour mixture III into a mold, place the mold in an ice water environment to stand, and obtain PNIPAAm thermosensitive hydrogel.

[0013] In step (2), the amount of SA added is 15-16% of the mass of the NIPAAm monomer solution.

[0014] In step (3), the temperature of the ice water environment is no higher than 5℃.

[0015] The photothermal evaporation module is made of a capillary porous material with photothermal conversion properties or a composite porous material with nanoparticles having photothermal conversion properties attached to a porous framework; specifically, it is a wood fiber porous sponge composited with carbon nanoparticles.

[0016] The primary liquid supply module and the liquid delivery module are made of capillary porous materials with good moisture absorption, such as wood fiber or polymer fiber; specifically, they are porous sponges.

[0017] The heat-insulating and waterproof module is made of any one of the following materials: expanded polyethylene, expanded polyvinyl chloride, polyurethane foam, polystyrene foam, polypropylene foam, polyimide foam, or polyetherketone foam. The heat-insulating and waterproof module wraps the sides and bottom of the infusion module (except for the portion immersed in the concentrated liquid area) to reduce heat loss from the adaptive photothermal evaporation component to the surroundings and bottom.

[0018] Beneficial Effects: Compared with the prior art, the present invention has the following significant advantages: The device of the present invention, by employing a combined liquid supply module (primary liquid supply module and delivery module) and using a hydrogel with temperature-sensitive properties as a secondary liquid supply module, can significantly improve the evaporation efficiency of the solution. Furthermore, it can provide a corresponding solution release rate based on temperature changes caused by real-time illumination, allowing for fine adjustment of the liquid supply to the evaporation surface, achieving a match between the evaporation and replenishment volumes at the photothermal evaporation interface, and improving evaporation performance and heat utilization efficiency under different light intensities. In addition, the adaptive photothermal evaporation component in the device of the present invention also has the ability to continuously and efficiently evaporate under daytime illumination and continuously replenish and store liquid at night or on cloudy days. Finally, the adaptive photothermal evaporation component is wrapped with a heat-insulating and waterproof module, which can significantly reduce downward heat conduction loss and further improve heat utilization efficiency. The device of the present invention has significant advantages in applications such as seawater desalination and solution regeneration. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the structure of the multi-stage liquid supply solar thermal evaporation device of the present invention;

[0020] Figure 2 for Figure 1 The diagram showing the water absorption / release mechanism is shown within the corresponding dashed box.

[0021] Figure 3 This is a schematic diagram illustrating the adaptive control principle of an adaptive photothermal evaporation module.

[0022] Figure 4 Scanning electron micrographs of thermosensitive hydrogels with sodium alginate content of 0 wt% (a) and 15 wt% (b);

[0023] Figure 5 The graph shows the change in the total rate of solution transported into the evaporation module by photothermal evaporation components with different sodium alginate contents at different evaporation surface temperatures.

[0024] Figure 6 The graph shows the change in water content of thermosensitive hydrogels with different sodium alginate contents during the water absorption process.

[0025] Figure 7 A comparison chart showing the evaporation rates of evaporators with different structures under different light intensities. Detailed Implementation

[0026] like Figure 1As shown, the solar thermal evaporation device of the present invention includes a solution holding tank 8 and a light-transmitting cover 6 covering the solution holding tank 8; the solution holding tank 8 is divided into a concentrated liquid zone 7 and a dilute liquid zone 9 by an annular partition 12; an adaptive solar thermal evaporation component floats in the concentrated liquid zone 7; the adaptive solar thermal evaporation component includes a primary liquid supply module 3 in contact with the liquid in the concentrated liquid zone 7, a liquid delivery module 2 connected to the primary liquid supply module 3, and a solar thermal evaporation module 1 located on the upper surface of the liquid delivery module 2; a secondary liquid supply module 4 is placed in the liquid delivery module 2, and the secondary liquid supply module 4 is simultaneously connected to the primary liquid supply module 7. Module 3 is connected to infusion module 2; the secondary infusion module 4 is a PNIPAAm-based thermosensitive hydrogel; that is, the top of the adaptive photothermal evaporation assembly is photothermal evaporation module 1, and the upper surface of photothermal evaporation module 1 is a light-absorbing layer; the upper surface of infusion module 2 is in close contact with photothermal evaporation module 1; infusion module 2 has a groove, and infusion module 2 and primary infusion module 3 enclose the groove to form a closed cavity, in which secondary infusion module 4 is embedded, tightly wrapped inside in infusion module 2, while the bottom surface of secondary infusion module 4 is in close contact with the upper surface of primary infusion module 3. Primary infusion module 3 includes a smaller diameter and a larger height end, which extends into the solution in the concentrate zone 7 to continuously absorb and supply solution into the adaptive photothermal evaporation assembly.

[0027] The sides and bottom of the adaptive photothermal evaporation module are tightly wrapped by the heat insulation and waterproof module 5 to achieve contact or suspension between the adaptive photothermal evaporation module and the solution in the solution supply tank (concentrated liquid area 7), and to greatly reduce the loss of heat to the sides and bottom of the adaptive photothermal evaporation module.

[0028] In this embodiment, the photothermal evaporation module 1 is made of porous wood fiber sponge composed of carbon nanoparticles (prepared using the method disclosed in the literature titled "Scalable and high-efficiency lignocellulose sponge-based evaporators for solar-driven desalination and desiccant regeneration"); the primary liquid supply module 3 and the liquid delivery module 2 are both made of porous wood fiber sponge; and the heat insulation and waterproofing module 5 is made of expandable polystyrene foam board (EPS board). The PNIPAAm-based thermosensitive hydrogel is a thermosensitive hydrogel modified with SA, wherein, during the preparation of the thermosensitive hydrogel, the amount of SA added is 15% of the mass of the NIPAAm (N-isopropylacrylamide) monomer solution.

[0029] The thermosensitive hydrogel PNIPAAm with an SA addition of 15 wt% is prepared by the following method:

[0030] (1) Add the crosslinking agent BIS (N,N-methylenebisacrylamide) to the NIPAAm (N-isopropylacrylamide) monomer solution to obtain mixture I;

[0031] (2) Add SA (sodium alginate) to mixture I, stir continuously at room temperature, and at the same time purge nitrogen into the reaction vessel to protect the reaction environment, to obtain mixture II;

[0032] (3) Dissolve APS (ammonium persulfate) in a quantitative amount of deionized water to form an APS solution, slowly add it to mixture II, stir evenly to obtain mixture III, pour mixture III into a mold, place the mold in a 5°C ice water environment and let it stand for 24 hours to obtain PNIPAAm thermosensitive hydrogel with adaptive transport properties.

[0033] The NIPAAm monomer solution contains 8% NIPAAm monomer by mass; in mixture I, the crosslinking agent BIS is added at a mass ratio of 1:0.025 to NIPAAm monomer by mass (1g and 0.025g respectively); in mixture II, SA is added at 15% of the mass of the NIPAAm monomer solution; and the APS solution contains 1% APS by mass.

[0034] In the solar thermal evaporation device of this invention, the solar thermal evaporation component has an adaptive control function, that is, it can adaptively adjust the liquid flow rate transported to the solar thermal evaporation module 1 according to changes in sunlight. During the day when there is sunlight, the solar thermal evaporation module 1 absorbs solar radiation, converts it into heat, and evaporates the water in the solution; the primary liquid supply module 3 absorbs the solution from the solution supply tank (concentrated liquid zone 7) using capillary principle and transports it to the secondary liquid supply module 4 and the delivery module 2 through its upper surface; the secondary liquid supply module 4 regulates the release or storage of the solution inside it through thermal response effect, and provides different rates of solution release according to temperature changes; the delivery module 2 absorbs the constant amount of solution provided by the primary liquid supply module 3 and the different amounts of solution released by the secondary liquid supply module 4 through the contact interface 10, so that the solution evaporation rate matches the delivery rate of the solution transported to the solar thermal evaporation module 1, so as to achieve adaptive control of solution evaporation and liquid supply and transport volume at the vapor-liquid interface of the solar thermal evaporation device under varying solar radiation conditions.

[0035] The adaptive control method of the photothermal evaporation component of this invention for the solution is as follows: Figures 2-3As shown, the contact interface 10 serves as an adaptive solution transport channel between the thermosensitive hydrogel substrate 101 of the secondary liquid supply module 4 and the wood fiber porous sponge substrate 104 of the infusion module 2. Near the contact interface 10, the mass changes of the solution 102 within the pores of the thermosensitive hydrogel and the solution 103 within the pores of the wood fiber porous sponge are generally conserved. Under no light conditions (Case 1), the temperature (i.e., internal temperature) of the thermosensitive hydrogel substrate 101 is below the critical temperature. The mass of the solution in the saturated thermosensitive hydrogel and the capillary porous material remains unchanged, and they are in dynamic equilibrium. Under light conditions (Case 2), the temperature of the thermosensitive hydrogel substrate 101 rises to the internal temperature A, which is higher than the critical temperature. At this time, the saturated thermosensitive hydrogel changes from hydrophilic to hydrophobic and shrinks its pore volume to release the stored solution. The released solution is driven by the wettability gradient into the pores of the capillary porous material with constant hydrophilicity and is further transported upward by capillary action. When the light intensity further increases, the temperature of the thermosensitive hydrogel substrate 101 rises to the internal temperature B, which is higher than the internal temperature A (Case 3). At this time, the hydrophobicity of the thermosensitive hydrogel and the degree of pore volume shrinkage further increase, and more solution is released into the pores of the wood fiber porous sponge than in Case 2.

[0036] The PNIPAAm (poly-N-isopropylacrylamide)-based thermosensitive hydrogel used in this invention is a thermosensitive hydrogel modified with SA (sodium alginate). In the preparation process of PNIPAAm (poly-N-isopropylacrylamide)-based thermosensitive hydrogel, the mass of SA added is 15% of the mass of N-isopropylacrylamide monomer.

[0037] Figure 4 Microstructure diagrams of thermosensitive hydrogels with SA contents of 0 wt% and 15 wt% are shown. Figure 3 It is known that the addition of SA can significantly increase the pore size inside the thermosensitive hydrogel, which significantly improves the storage and release rates of liquid in the pores. Therefore, grafting SA can improve the solution release rate and water absorption rate of PNIPAAm-based thermosensitive hydrogels at the same temperature and for the same water absorption time.

[0038] pass Figure 5It can be seen that when the temperature is below the critical temperature (approximately 32°C), it can be considered as a day without sunlight. The total rate at which the solution is transported to the photothermal evaporation module 1 remains relatively stable at a low value. This transport process mainly relies on the solution absorbed from the primary liquid supply module 3 by the liquid delivery module 2. When the surface temperature exceeds the critical temperature, the secondary liquid supply module 4 releases the solution, and the total rate at which the solution is transported to the photothermal evaporation module 1 increases significantly. Above the critical temperature, the total transport rate of the solution increases linearly with further increases in temperature. Therefore, using the temperature-sensitive hydrogel of this invention enables the photothermal evaporation component to achieve a match between the total transport rate and the evaporation rate at surface temperatures corresponding to different light intensities.

[0039] based on Figure 6 It can be seen that, through 1000W / m 2 To simulate daytime evaporation, the adaptive photothermal evaporation module was subjected to evaporation for 7 hours under varying light intensity. The remaining water content of the temperature-sensitive hydrogel was then used as the initial water content for nighttime water absorption. Since increasing the SA content expands the pore size, the increase in water content over the same absorption time increases with increasing SA content. After 16 hours of water absorption, the water content of the temperature-sensitive hydrogel with 15 wt% SA content increased by 53.3%, reaching 83.2%.

[0040] Figure 7 The evaporation rates of evaporators with different structures under different light intensities were compared. The adaptive structure evaporator, 3D channel evaporator, and combined channel evaporator of this invention all have the same immersion depth h. w The height h1 above the water surface. The materials of the infusion module and photothermal evaporation module are the same for all three structures. Specifically, the interior of the 3D channel and the combined channel is made of porous sponge and does not contain the temperature-sensitive hydrogel of this invention. Furthermore, the 3D channel does not have a primary infusion module; its infusion module is in direct contact with the water at the bottom. It was observed that the evaporation rate of all three structures increases with increasing light intensity. The evaporation rate of the combined channel (including the T-shaped primary infusion module (porous sponge) and the infusion module) is 500, 1000, 1500, and 2000 W / m. 2 Under varying light intensities, the evaporation rates of the two channels were increased by 7.9%, 10.7%, 17.6%, and 7.8% respectively compared to the 3D channel, showing a trend of initial increase followed by decrease. The increase in evaporation rate is mainly due to the design of the primary liquid supply module reducing heat loss through conduction to the bottom water. The subsequent decrease is due to the fixed total transport rate of the combined channel leading to water shortage and drying of the evaporation surface under high light intensity. The evaporation rate of the adaptive structure of this invention is 500, 1000, 1500, and 2000 W / m². 2 The light intensities reached 1.04, 2.21, 2.92 and 3.70 kg / m², respectively. 2The efficiency of the h-channel was improved by 26.16%, 48.28%, 47.97%, and 47.87% respectively compared to the 3D channel. Therefore, the adaptive structure evaporation device of the present invention can effectively overcome the defects of excessive or insufficient water in the photothermal evaporation module under different light intensities.

[0041] The solar thermal evaporation device of this invention is applied to seawater desalination.

[0042] Seawater stored in the concentrated liquid zone 7 is introduced into the adaptive photothermal evaporation assembly via capillary action from the primary supply module 3. A certain amount of seawater is stored in the secondary supply module 4, the delivery module 2, and the photothermal evaporation module 1. When illumination begins, the surface temperature of the photothermal evaporation module 1 rises, transferring heat to the secondary supply module 4. The secondary supply module 4 adjusts its internal temperature according to the real-time changes in light intensity, thus providing a corresponding seawater release rate into the delivery module 2. Simultaneously, the primary supply module 3 continuously supplies seawater at a constant rate into the delivery module 2, which in turn supplies seawater to the photothermal evaporation module 1 for continuous and efficient evaporation. The water vapor generated by evaporation collects on the inner wall of the evaporation chamber's light-transmitting cover 6, gradually cooling into liquid water and flowing back to the desalinated liquid zone 9 by gravity. During daytime illumination, the secondary supply module 4 shrinks in volume due to the continuous release of seawater and becomes unsaturated. After the sunlight exposure ends, the ambient temperature drops, causing the internal temperature of the secondary liquid supply module 4 to fall below the critical temperature and become hydrophilic. The infusion module 2 and the primary liquid supply module 3 will continuously supply seawater to the secondary liquid supply module 4 through the contact interface 10 until the secondary liquid supply module 4 reaches saturation. This completes the day-night seawater desalination cycle.

[0043] The solar thermal evaporation device of this invention is applied to the regeneration of dehumidification solutions.

[0044] The low-solution dehumidifying solution stored in the concentrated liquid zone 7 is introduced into the adaptive photothermal evaporation component via capillary action from the primary liquid supply module 3. The secondary liquid supply module 4, the delivery module 2, and the photothermal evaporation module 1 all store a certain amount of low-solution dehumidifying solution. When illumination begins, the surface temperature of the photothermal evaporation module 1 rises, transferring heat to the secondary liquid supply module 4. The secondary liquid supply module 4 adjusts its internal temperature according to the real-time changes in light intensity, thus providing a corresponding solution release rate into the delivery module 2. Simultaneously, the primary liquid supply module 3 continuously provides a constant rate of solution into the delivery module 2, which then supplies the solution to the photothermal evaporation module 1 for continuous and efficient evaporation. The water vapor generated by evaporation collects on the inner wall of the evaporation chamber's light-transmitting cover 6, gradually cooling into liquid water and flowing back to the dilute liquid zone 9 by gravity for collection. After daytime illumination ends, the dehumidifying solution in the concentrated liquid zone 7, after concentration regeneration, is collected and replaced with a new solution to be treated. The regeneration cycle of the dehumidification solution is completed after new low-concentration solution is added to the secondary liquid supply module 4.

Claims

1. A multi-stage liquid supply solar thermal evaporation device, comprising a solution holding tank (8) and a light-transmitting cover (6) covering the solution holding tank (8); the solution holding tank (8) is divided into a concentrated liquid zone (7) and a dilute liquid zone (9) by a partition (12); characterized in that: An adaptive photothermal evaporation assembly floats in the concentrated liquid zone (7). The adaptive photothermal evaporation assembly includes: a primary liquid supply module (3) in contact with the liquid in the concentrated liquid zone (7), an infusion module (2) connected to the primary liquid supply module (3), and a photothermal evaporation module (1) located on the upper surface of the infusion module (2). A secondary liquid supply module (4) is placed in the infusion module (2). The secondary liquid supply module (4) is connected to both the primary liquid supply module (3) and the infusion module (2). The secondary liquid supply module (4) is a PNIPAAm-based thermosensitive hydrogel. The PNIPAAm-based thermosensitive hydrogel is PNIPAAm grafted with sodium alginate SA. The photothermal evaporation module (1) is a porous sponge made of wood fibers composite with carbon nanoparticles. The primary liquid supply module (3) and the infusion module (2) are made of wood fibers or polymer fibers.

2. The solar thermal evaporation device according to claim 1, characterized in that: Thermal insulation and waterproof modules are wrapped around the sides and bottom of the adaptive photothermal evaporation assembly (5).

3. The solar thermal evaporation device according to claim 1, characterized in that: The infusion module (2) has a groove inside, and the infusion module (2) and the primary infusion module (3) enclose the groove to form a closed cavity, and the secondary infusion module (4) is embedded in the cavity.

4. The solar thermal evaporation device according to claim 3, characterized in that: The primary liquid supply module (3) is T-shaped, and the end of the primary liquid supply module (3) extends into the concentrated liquid zone (7) on the side away from the infusion module (2).

5. The solar thermal evaporation device according to claim 1, characterized in that: The PNIPAAm-based thermosensitive hydrogel was prepared by the following method, with the following specific steps: (1) N,N-methylenebisacrylamide, a crosslinking agent, was added to the NIPAAm monomer solution to obtain mixture I; (2) Sodium alginate SA was added to mixture I, and the mixture was stirred continuously at room temperature. At the same time, nitrogen gas was introduced into the reaction vessel to protect the reaction environment, resulting in mixture II; (3) Ammonium persulfate was dissolved in deionized water to form a solution, which was slowly added to mixture II and stirred evenly to obtain mixture III. Mixture III was poured into a mold, and the mold was placed in an ice water environment to stand, resulting in PNIPAAm-based thermosensitive hydrogel.

6. The solar thermal evaporation device according to claim 5, characterized in that: In step (2), the amount of sodium alginate SA added is 15-16% of the mass of the NIPAAm monomer solution.

7. The solar thermal evaporation device according to claim 5, characterized in that: In step (3), the temperature of the ice water environment is no higher than 5℃.

8. The solar thermal evaporation device according to claim 2, characterized in that: The heat insulation and waterproof module (5) is made of any one of the following materials: foamed polyethylene, foamed polyvinyl chloride, polyurethane foam, polystyrene foam, polypropylene foam, polyimide foam or polyetherketone foam.

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