Acid-resistant tubular air gap membrane distillation system

Abstract

According to the acid-resistant tubular air-gap membrane distillation system provided by the invention, the corrosion-resistant layer is arranged on the outer wall of the condensation pipe, so that corrosion of acid steam to the condensation pipe is effectively resisted, the service life of the condensation pipe is prolonged, the overall stability of the membrane distillation system is improved, and the system can continuously and stably perform concentration treatment on an acid material. As the corrosion resistance of the condensation pipe is improved, the membrane flux is increased, and the mass transfer efficiency is further improved, so that the water production efficiency in the membrane distillation process is improved. Due to the fact that corrosion of steam to the condensation pipe is effectively reduced through the anti-corrosion layer, the maintenance cost caused by replacement of the damaged condensation pipe can be reduced, the economic benefits of a membrane distillation system are improved, and application of membrane distillation in acid wastewater treatment is promoted.

Description

Technical Field

[0001] The present application relates to the technical field of membrane distillation, and in particular to an acid-resistant tubular air-gap membrane distillation system. Background Art

[0002] At present, many industrial fields involve the concentration of acidic materials. Membrane distillation is a membrane concentration and separation technology that uses hydrophobic organic polymer materials as the evaporation surface. Hydrophobic membranes have good acid resistance and are therefore considered to be a promising acidic material concentration and separation technology. Among the several operating modes of membrane distillation, air gap membrane distillation (AGMD) is an operating mode that is more friendly to the performance stability of hydrophobic membranes.

[0003] Air gap membrane distillation requires a condenser to be installed on the water production side of the tubular membrane. The steam passing through the membrane condenses on the surface of the condenser to obtain water production and achieve the concentration of the original material. However, in the process of using the air gap membrane distillation system to treat acidic materials, the water production will generally be weakly acidic, causing the condenser to be easily corroded by the acid during use, resulting in the membrane distillation system being unable to operate continuously and stably. At the same time, because the condenser is not corrosion-resistant, the membrane flux is low and the mass transfer efficiency is not high, which is not conducive to improving the water production efficiency. Summary of the invention

[0004] In order to solve the above problems, the present application provides an acid-resistant tubular air-gap membrane distillation system, which effectively resists the corrosion of the condenser by acidic steam by setting an anti-corrosion layer on the outer wall of the condenser, thereby extending the service life of the condenser, improving the overall stability of the membrane distillation system, and enabling the system to continuously and stably carry out the concentration treatment of acidic materials. Since the corrosion resistance of the condenser is improved, the membrane flux is increased, and the mass transfer efficiency is further improved, thereby improving the water production efficiency of the membrane distillation process. Also, since the anti-corrosion layer effectively reduces the corrosion of the condenser, it is possible to reduce the maintenance cost caused by replacing the damaged condenser, improve the economic benefits of the membrane distillation system, and promote the application of membrane distillation in the treatment of acidic wastewater.

[0005] The present application provides an acid-resistant tubular air-gap membrane distillation system, the system comprising: A shell (1), a first pipe member (2) and a second pipe member (3); The housing (1) comprises a first end (11) and a second end (12) which are arranged opposite to each other, the first end (11) is provided with a liquid inlet (111), and the second end (12) is provided with a liquid outlet (121); The first pipe member (2) is sleeved outside the second pipe member (3), and the shell (1) is sleeved outside the first pipe member (2); A first cavity (21) is provided between the housing (1) and the first tube (2), a second cavity (31) is provided between the first tube (2) and the second tube (3), and the liquid inlet (111) is in communication with the first cavity (21); The liquid inlet (111) is configured to transport hot acid wastewater into the first cavity (21), allowing steam to pass through the first pipe (2) into the second cavity (31), and the second pipe (3) condenses the steam; The liquid outlet (121) is configured to output the hot acid wastewater out of the first cavity (21); Wherein, the second pipe member (3) comprises a condenser tube (32) and an anti-corrosion layer (33), and the anti-corrosion layer (33) is located on the outer wall of the condenser tube (32); The anti-corrosion layer (33) is configured to resist the steam corrosion.

[0006] Furthermore, the anti-corrosion layer (33) is a mixture of polymer resin and nano chromium powder.

[0007] Furthermore, the polymer resin is at least one of epoxy resin, polyurethane resin, fluorocarbon resin, polyethylene resin and polypropylene resin.

[0008] Furthermore, the particle size of the nano chromium powder is 10 nm-100 nm.

[0009] Furthermore, the condenser (32) is made of at least one of stainless steel, copper, aluminum, titanium and nickel.

[0010] Furthermore, the anti-corrosion layer (33) has a thickness of 10 μm to 200 μm.

[0011] Furthermore, a dimension of the second cavity (31) in the thickness direction of the anti-corrosion layer (33) is 10 mm to 20 mm.

[0012] Furthermore, the orthographic projection of the anti-corrosion layer (33) on the surface of the first pipe (2) falls inside the first pipe (2); and / or the anti-corrosion layer (33) does not completely cover the outer surface of the condenser tube (32).

[0013] Furthermore, the contact angle between the water droplets on the anti-corrosion layer (33) and the surface of the anti-corrosion layer (33) is 130° to 160°.

[0014] Furthermore, the system also includes a first connector (4) and a second connector (5); The first connector (4) is respectively connected to the first end (11) and one end of the first pipe (2) aligned with the first end (11), and the second connector (5) is respectively connected to the second end (12) and one end of the first pipe (2) aligned with the second end (12); The two ends of the second pipe member (3) extending out of the first pipe member (2) are respectively embedded in the first connecting head (4) and the second connecting head (5).

[0015] Beneficial technical effects: The present application provides an acid-resistant tubular air-gap membrane distillation system, which specifically includes a shell, a first pipe fitting and a second pipe fitting, and the first pipe fitting is sleeved outside the second pipe fitting, and the shell fitting is sleeved outside the first pipe fitting; a first cavity is arranged between the shell and the first pipe fitting, a second cavity is arranged between the first pipe fitting and the second pipe fitting, and a liquid inlet is connected to the first cavity; during implementation, hot acid wastewater is transported into the first cavity along the liquid inlet, so that the steam (mainly water vapor) in the hot acid wastewater passes through the first pipe fitting and enters the second cavity, and after cooling water is introduced into the second pipe fitting, the steam is condensed to produce water, and after the steam passes through the first pipe fitting, the concentrated hot acid wastewater is discharged from the first cavity along the liquid outlet; wherein the second pipe fitting includes a condenser and an anti-corrosion layer, and the anti-corrosion layer is arranged on the outer wall of the condenser, when the steam passes through the first pipe fitting and reaches the second cavity, the steam condenses after contacting the anti-corrosion layer to avoid direct contact of the steam with the condenser, thereby reducing the corrosion of the steam to the condenser and improving the corrosion resistance of the condenser. When the corrosion resistance of the condenser is improved, the membrane distillation system can operate stably for a long time. At the same time, due to the improved corrosion resistance of the condenser, the membrane flux during system operation increases, the mass transfer efficiency is improved, and the water production efficiency of the membrane distillation process is improved. The setting of the anti-corrosion layer can also reduce the maintenance cost caused by replacing damaged condensers, thereby improving the overall economic benefits of the membrane distillation system. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the description of the embodiments of the present application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0017] Figure 1 A schematic structural diagram of an acid-resistant tubular air-gap membrane distillation system proposed in an embodiment of the present application is shown; Figure 2 The cross-sectional structure diagram of the acid-resistant tubular air-gap membrane distillation system proposed in the embodiment of the present application is shown; Figure 3 A schematic diagram of the structure of the housing proposed in the embodiment of the present application is shown; Figure 4 A lateral schematic diagram of the contact angle of a water drop on the anti-corrosion layer proposed in an embodiment of the present application is shown; Figure 5 A schematic diagram of the structure of a first connector proposed in an embodiment of the present application is shown; Figure 6 A schematic diagram of the structure of the second connector proposed in an embodiment of the present application is shown; Figure 7 A schematic structural diagram of another acid-resistant tubular air-gap membrane distillation system proposed in an embodiment of the present application is shown.

[0018] Description of reference numerals: 1. Shell; 11. First end; 111. Liquid inlet; 12. Second end; 121. Liquid outlet; 2. a first pipe; 21. a first cavity; 3. Second pipe; 31. Second cavity; 32. Condenser tube; 33. Anticorrosion layer; 4. First connector; 5. Second connector; 51. First through slot; 52. Second through slot; 53. Water outlet; 6. Water collector; 61. Hot acid wastewater storage tank; 62. First magnetic drive pump; 63. Second magnetic drive pump; 64. First water tank; 65. Second water tank; 66. Gate valve; 67. Cold water tank; 68. First digital display thermometer; 69. Second digital display thermometer; 7. Thermometer. DETAILED DESCRIPTION

[0019] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0020] In the drawings, the size of the constituent elements, the thickness of the layer or the area may be exaggerated for the sake of clarity. Therefore, any implementation of the present disclosure is not necessarily limited to the size shown in the drawings, and the shapes and sizes of the components in the drawings do not reflect the true proportions. In addition, the drawings schematically show ideal examples, and any implementation of the present disclosure is not limited to the shapes or values ​​shown in the drawings.

[0021] In the related technologies, many industrial fields involve the concentration of acidic materials, and membrane distillation is a membrane concentration and separation technology that uses hydrophobic organic polymer materials as the evaporation surface. The hydrophobic membrane has good acid resistance, so it is considered to be a promising acidic material concentration and separation technology. Among the several operating modes of membrane distillation, air gap membrane distillation (AGMD) is an operating mode that is more friendly to the performance stability of hydrophobic membranes.

[0022] Air-gap membrane distillation requires a condensation wall (i.e., condenser) to be set up on the water-producing side of the membrane. The steam passing through the membrane condenses on the surface of the condenser to produce water and achieve the concentration of the original material. Membrane flux is the main indicator for evaluating the operating performance of the membrane distillation system. When using air-gap membrane distillation to treat acidic wastewater, membrane elements of condensers of different materials have a great influence on the condensation efficiency of the membrane distillation system. From the analysis of the mass transfer and heat transfer process of tubular membrane distillation, it can be seen that the lower the temperature of the condenser surface, the more conducive it is to the rapid condensation and liquefaction process of water vapor molecules on its surface in theory. Lowering the temperature of the condenser is mainly achieved by lowering the cooling water temperature.

[0023] However, usually, there is a certain temperature difference between the cooling water temperature and the working surface temperature of the condenser tube, and the thermal conductivity of the condenser tube material is the fundamental reason for the temperature difference. The better the thermal conductivity of the material, the lower the temperature difference. When the thermal conductivity increases to a certain extent, the temperature difference between the inner and outer walls of the condenser tube will be very small.

[0024] In the process of using the air gap membrane distillation system to treat acidic materials, the condensed water is generally weakly acidic, which makes the metal condenser tube easily corroded by the acid during use, causing the membrane distillation system to be unable to operate continuously and stably. Using organic tubes as condensers has good acid resistance, but the water production efficiency is low.

[0025] Based on the problems existing in the related technology, an embodiment of the present application provides an acid-resistant tubular air-gap membrane distillation system. By setting an anti-corrosion layer on the outer wall of the condenser, the acid resistance of the condenser can be enhanced, the membrane flux can be increased, and the mass transfer efficiency can be improved, thereby improving the overall water production efficiency of the membrane distillation system.

[0026] For specific implementation, see Figure 1 and Figure 2 , the system specifically comprises: A shell 1, a first pipe 2 and a second pipe 3; The housing 1 comprises a first end 11 and a second end 12 which are arranged opposite to each other. The first end 11 is provided with a liquid inlet 111, and the second end 12 is provided with a liquid outlet 121. The first pipe member 2 is sleeved on the outside of the second pipe member 3, and the housing 1 is sleeved on the outside of the first pipe member 2; A first cavity 21 is provided between the housing 1 and the first pipe 2, a second cavity 31 is provided between the first pipe 2 and the second pipe 3, and the liquid inlet 111 is in communication with the first cavity 21; The liquid inlet 111 is configured to transport hot acid wastewater into the first cavity 21, so that steam passes through the first pipe 2 and enters the second cavity 31, and the second pipe 3 condenses the steam; The liquid outlet 121 is configured to output the hot acid wastewater to the first cavity 21; Wherein, the second pipe member 3 includes a condenser tube 32 and an anti-corrosion layer 33, and the anti-corrosion layer 33 is located on the outer wall of the condenser tube 32; The anti-corrosion layer 33 is configured to resist the steam corrosion.

[0027] It should be noted that the shell 1 is a tube with a hollow structure, and both ends of the shell are set to be open; the cross-sectional shape of the shell can be circular, rectangular, diamond-shaped, etc.; In one case, when the shell 1 is placed vertically on the ground, the first end 11 is the lower end of the shell 1, and the second end 12 is the upper end of the shell 1, so that the liquid inlet 111 is located at the lower end of the shell 1, and the liquid outlet 121 is located at the upper end of the shell 1, so as to realize the bottom-up transportation of hot acid wastewater, so as to make full use of the gravity effect, so that the hot acid wastewater moves slowly in the shell 1, so as to achieve a more uniform temperature distribution; the liquid inlet 111 is set at the lower end of the shell 1, and during the transportation process, the steam in the hot acid wastewater will be gradually released in the rising process and pass through the first pipe 2, so as to avoid the accumulation of steam in the shell 1; In another case, when the shell 1 is placed vertically on the ground, the first end 11 is the upper end of the shell 1 and the second end 12 is the lower end of the shell 1, so that the liquid inlet 111 is located at the upper end of the shell 1 and the liquid outlet 121 is located at the lower end of the shell 1, so that the hot acid wastewater is transported from top to bottom, so that the suspended matter or heavier impurities in the hot acid wastewater are more likely to be deposited at the bottom of the shell 1 due to gravity, and are not easy to gradually accumulate during the flow process, thereby reducing the risk of sediment and scaling inside the hot pipe, which helps to keep the system clean and efficient. The first pipe fitting 2 is a pipe body composed of a tubular membrane, which is synthesized from glass fiber and cast on a support body such as non-woven fabric, plastic, ceramic or stainless steel. The inner diameter is between 400 mm and 450 mm, and the length is between 0.3 m and 0.4 m. It can withstand high pressure and temperature and is suitable for various complex process conditions. The inner diameter of the first pipe fitting 2 can be 400 mm, 410 mm, 420 mm, 430 mm, 440 mm, and 450 mm. The length of the first pipe 2 can be 0.3 m, 0.32 m, 0.34 m, 0.36 m, 0.38 m, or 0.4 m; The cross-sectional shape of the first pipe member 2 can be circular, rectangular, elliptical, diamond-shaped, etc.; The length of the first pipe 2 is the same as that of the shell 1, that is, the end faces of both ends of the first pipe 2 are flush with the end face of the first end 11 and the end face of the second end 12, respectively, to ensure that the steam in the first cavity 21 can contact with the first pipe 2 and permeate through the first pipe 2; The second pipe member 3 is a hollow pipe body made of metal. The two opposite ends of the second pipe member 3 are set to be open, so as to facilitate the transportation of cooling water in the second pipe member 3. The first cavity 21 is located between the inner wall of the shell 1 and the outer wall of the first pipe 2, and the vertical distance between the inner wall of the shell 1 and the outer wall of the first pipe 2 is 5 mm to 20 mm; for example, the vertical distance between the inner wall of the shell 1 and the outer wall of the first pipe 2 can be 5 mm, 8 mm, 10 mm, 12 mm, 15 mm, 17 mm, or 20 mm; The first cavity 21 is a closed cavity; The second cavity 31 is located between the inner wall of the first pipe 2 and the surface of the anti-corrosion layer 33, and the vertical distance between the inner wall of the first pipe 2 and the surface of the anti-corrosion layer 33 is 5 mm to 20 mm; for example, the vertical distance between the inner wall of the first pipe 2 and the surface of the anti-corrosion layer 33 can be 5 mm, 8 mm, 10 mm, 12 mm, 16 mm, 18 mm, or 20 mm; The second cavity 21 is a closed cavity; The anti-corrosion layer 33 can be made by coating, specifically, coating the anti-corrosion material on the outer wall of the condenser 32, and forming the anti-corrosion layer 33 after solidification; the outer wall of the condenser 32 refers to the side wall of the condenser 32 close to the first pipe 2.

[0028] When using the system, see Figure 2 and Figure 3 , the hot acid wastewater can be sent upward into the first cavity 21 along the liquid inlet 111, the steam in the hot acid wastewater moves upward and reaches the second cavity 31 through the first pipe 2, and cooling water is introduced into the condenser 32 to cool and condense the steam in the second cavity 31. Part of the water produced by condensation adheres to the surface of the anti-corrosion layer 33, and the other part flows downward and is stored in the second cavity 31. After the steam is removed, the concentrated hot acid wastewater is discharged from the first cavity 21 along the liquid outlet 121. Then, new hot acid wastewater continues to be transported along the liquid inlet 111 to form a cycle in the system to continuously condense steam and produce water.

[0029] By providing the anti-corrosion layer 33, it is possible to prevent steam or condensed water droplets from directly contacting the surface of the condenser tube 32, thereby reducing the corrosion of the condenser tube 32 by steam or condensed water, and improving the anti-corrosion performance of the condenser tube 32. After the anti-corrosion performance of the condenser tube 32 is improved, it can maintain stable cooling for a longer time. By continuously circulating and replacing the cooling water in the condenser tube 32, the temperature difference between the second cavity 31 and the inside of the condenser tube 32 is gradually reduced, and the temperature difference between the first cavity 21 and the inside of the second cavity 31 is gradually increased. Since the steam temperature is high, the high-temperature fluid usually tends to move to the side with a low temperature, so that more steam passes through the first pipe 2 to reach the second cavity 31 for condensation, so as to increase the membrane flux of the first pipe 2, and more steam exchanges heat with the condenser tube 32, so that the mass transfer efficiency is improved, thereby improving the overall water production efficiency of the system. Finally, the provision of the anti-corrosion layer 33 effectively reduces the corrosion of the condenser tube 32, so that the maintenance cost caused by replacing the damaged condenser tube 32 can be reduced, thereby improving the economic benefits of the membrane distillation system.

[0030] Among them, thermal acid wastewater refers to wastewater containing certain acids and with a pH value lower than 6. According to the type and concentration of acid, acid wastewater can be divided into the following categories: Inorganic acid wastewater and organic acid wastewater mainly contain inorganic acids, such as sulfuric acid, hydrochloric acid, nitric acid, etc.; organic acid wastewater mainly contains organic acids, such as esterification wastewater discharged by some chemical companies; acidic wastewater mainly comes from mine drainage, hydrometallurgy, steel rolling, surface acid treatment of steel and non-ferrous metals, chemicals, acid making, pharmaceuticals, dyes: acidic wastewater generated in the production process of these industries, electrolysis, electroplating: acidic wastewater generated in the process of electrolysis and electroplating, etc.

[0031] In specific implementation, the temperature of the hot acid wastewater can be 50 ℃~80 ℃, and the flow rate of the hot acid wastewater can be 1 L / min~3 L / min. For example, the temperature of the hot acid wastewater can be 50 ℃, 55 ℃, 60 ℃, 65 ℃, 70 ℃, 75 ℃, 80 ℃; the flow rate of the hot acid wastewater can be 1 L / min, 1.5 L / min, 2 L / min, 2.5 L / min, 3 L / min.

[0032] In specific implementation, the higher the temperature of the hot acid wastewater, the greater its saturated vapor pressure, thereby enhancing the driving force for evaporation. In the air gap membrane distillation system provided in the embodiment of the present application, a higher temperature helps to generate more steam, thereby increasing the water production flux. By setting the flow rate of the hot acid wastewater, it can be ensured that the hot acid wastewater is fully in contact with and flows on the surface of the first pipe 2, which helps to uniformly generate and transmit steam.

[0033] In a specific implementation, the temperature of the cooling water may be 0°C to 35°C, and the flow rate of the cooling water may be 2 L / min to 4 L / min. For example, the temperature of the cooling water may be 0°C, 5°C, 10°C, 15°C, 20°C, 25°C, 30°C, 35°C, and the flow rate of the cooling water may be 2 L / min, 2.3 L / min, 2.5 L / min, 2.8 L / min, 3 L / min, 3.5 L / min, 3.8 L / min, 4 L / min.

[0034] In specific implementation, the lower the temperature of the cooling water, the stronger its condensation ability. In the air gap membrane distillation system provided in the embodiment of the present application, the lower temperature of the cooling water helps to condense the steam faster, thereby improving the condensation efficiency. The heat transfer effect between the cooling water and the steam can be enhanced by setting a higher cooling water flow rate, because the increase in flow rate helps to speed up the speed of heat transfer.

[0035] In some embodiments, see Figure 2 The anti-corrosion layer 33 is a mixture of polymer resin and nano chromium powder.

[0036] In specific implementation, the polymer resin, i.e., the high polymer resin, has good corrosion resistance and film-forming properties, and can protect the condenser 32 from corrosion by water generated by steam or condensation. In addition, the polymer resin has strong adhesion to the substrate, i.e., the anti-corrosion layer 33 has strong adhesion to the outer wall of the condenser 32, which prevents the anti-corrosion layer 33 from peeling off or falling off after the system has been running for a period of time, enhances the stability of the anti-corrosion layer 33, and enables it to protect the condenser 32 for a long time, thereby extending the service life of the condenser 32. By adding nano-chromium powder to the polymer resin, the corrosion resistance and hardness of the anti-corrosion layer 33 can be significantly improved. Among them, the shape of the nano-chromium powder can be spherical, flaky, etc.

[0037] The use of polymer resin and nano-chromium powder in combination can form a composite organic anti-corrosion layer 33 with excellent corrosion resistance on the condenser 32, which can more effectively isolate the direct contact between the acidic steam and the substrate of the condenser 32, thereby significantly extending the service life of the condenser 32. As a matrix material, the polymer resin has good adhesion and plasticity, and can firmly fix the nano-chromium powder on the outer wall of the condenser 32, further improving the adhesion of the composite organic anti-corrosion layer 33, and making it more durable and not easy to fall off or crack. Even in an acidic environment, the anti-corrosion layer 33 can maintain its integrity and effectiveness, ensuring the long-term stable operation of the condenser 32. The addition of nano-chromium powder can also optimize the microstructure of the anti-corrosion layer 33, making it more dense and uniform. This change in microstructure helps to improve the anti-permeability and corrosion resistance of the anti-corrosion layer 33, and further enhance its protection against acidic steam.

[0038] In some embodiments, the polymer resin is at least one of an epoxy resin, a polyurethane resin, a fluorocarbon resin, a polyethylene resin, and a polypropylene resin.

[0039] During specific implementation, epoxy resin has good corrosion resistance and adhesion, and can fit tightly with the second pipe fitting 3 for a long time; polyurethane resin has good weather resistance and strong film-forming ability, and can be suitable for condenser tubes 32 made of different materials; fluorocarbon resin has extremely low surface energy, excellent weather resistance and corrosion resistance, and can achieve good anti-corrosion performance; polyethylene resin, especially high-density polyethylene (HDPE) and ultra-high molecular weight polyethylene (UHMWPE), has excellent wear resistance and corrosion resistance, not only can achieve corrosion resistance, but also has less wear during use and can be used for a long time; polypropylene resin has good chemical resistance and low cost. Using polypropylene resin to prepare the anti-corrosion layer 33 helps to reduce costs.

[0040] For specific implementation, see Figure 2 Preferably, the polymer resin is a fluorocarbon resin. Because the fluorocarbon resin has an extremely low surface energy, the surface contact angle of the anti-corrosion layer 33 made of the fluorocarbon resin is significantly increased, thereby enhancing the hydrophobicity of the surface of the anti-corrosion layer 33, making it more difficult for water droplets generated by condensation to adhere to the surface of the anti-corrosion layer 33, and keeping the surface of the anti-corrosion layer 33 smooth, thereby enhancing the mass transfer efficiency of the condenser 32 through the anti-corrosion layer 33 to the outside, increasing the temperature difference between the first cavity 21 and the second cavity 31, making it easier for steam to flow to the second cavity 31, thereby increasing the membrane flux of the first pipe 2 and improving the water production rate.

[0041] In some embodiments, the particle size of the nano-chromium powder is 10 nm-100 nm. For example, the particle size of the nano-chromium powder can be 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, or 100 nm.

[0042] By setting the nano-chromium powder to have a smaller particle size to provide a larger specific surface area, the interaction between the nano-chromium powder and the polymer resin matrix is ​​enhanced, thereby improving the corrosion resistance and hardness of the anti-corrosion layer 33, so that the anti-corrosion layer 33 can better protect the condenser 32 in a complex environment.

[0043] In some embodiments, see Figure 2 and Figure 3, the thickness of the anti-corrosion layer 33 is 10 μm to 200 μm. For example, the thickness of the anti-corrosion layer 33 can be 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, 110 μm, 120 μm, 130 μm, 140 μm, 150 μm, 160 μm, 170 μm, 180 μm, 190 μm, or 200 μm.

[0044] By setting the thickness of the anti-corrosion layer 33, in the air-gap membrane distillation system provided in the embodiment of the present application, the anti-corrosion layer 33 has a sufficient thickness to resist the erosion of the acidic steam, which can not only provide an effective barrier to prevent the acidic steam from directly contacting the substrate of the condenser 32, but also maintain the stability of its corrosion resistance during long-term use, thereby extending the service life of the condenser 32; Limiting the thickness of the anti-corrosion layer 33 to the range of 10 μm to 200 μm can achieve a balance between performance and cost while ensuring corrosion resistance. The anti-corrosion layer 33 of this thickness is neither too thick, which increases unnecessary costs, nor too thin, which affects corrosion resistance. By limiting the thickness of the anti-corrosion layer 33 to the range of 10 μm to 200 μm, it can be ensured that the anti-corrosion layer 33 provides effective corrosion resistance while minimizing the impact on heat transfer efficiency, allowing sufficient heat to pass through, thereby ensuring that the condenser 32 can efficiently condense steam into water.

[0045] In some embodiments, see Figure 2 The condenser 32 is made of at least one of stainless steel, copper, aluminum, titanium and nickel.

[0046] For example, the condenser 32 may be made of stainless steel, or may be made of an alloy such as copper, aluminum, or nickel.

[0047] During implementation, the condenser tube 32 made of different materials has a great influence on the condensation efficiency of the membrane distillation system. From the analysis of the mass transfer and heat transfer process of tubular membrane distillation, the lower the temperature of the outer surface of the condenser tube 32, the more conducive it is for the steam molecules to undergo a rapid condensation and liquefaction process on its surface, and lowering the temperature of the condenser tube 32 is mainly achieved by lowering the cooling water temperature. Under normal circumstances, there is a certain temperature difference between the cooling water temperature and the working surface temperature of the condenser tube 32, and the thermal conductivity of the material of the condenser tube 32 is the fundamental reason for the temperature difference. The better the thermal conductivity of the material, the lower the temperature difference. Therefore, using a metal with a large thermal conductivity (the above-mentioned stainless steel, copper, aluminum, titanium and nickel and other metals) to make the condenser tube 32 is conducive to enhancing the membrane flux of the distillation of the first pipe 2. When the thermal conductivity increases to a certain extent, the temperature difference between the inner and outer walls of the condenser tube 32 will be very small. Therefore, using at least one material such as stainless steel, aluminum, copper, etc. provided in the embodiment of the present application to form the condenser tube 32 can achieve a higher water production efficiency at a lower cost. Furthermore, the metal selected in the embodiment of the present application is relatively cheap, but has a high thermal conductivity, thereby reducing the cost of using the system without affecting the membrane flux.

[0048] In some embodiments, see Figure 2 The size of the second cavity 31 in the thickness direction of the anti-corrosion layer 33 is 10 mm to 20 mm.

[0049] It should be noted that the dimension of the second cavity 31 in the thickness direction of the anti-corrosion layer 33 represents: the vertical distance between the outer wall of the anti-corrosion layer 33 and the inner wall of the first pipe 2 .

[0050] The size of the second cavity 31 in the thickness direction of the anti-corrosion layer 33 can be 10 mm, 12 mm, 14 mm, 16 mm, 18 mm, or 20 mm.

[0051] By setting the size of the second cavity 31 within the range of 10 mm to 20 mm, the steam can have enough space to be evenly distributed and flow in the second cavity 31, thereby optimizing the steam transmission process. If the cavity size is set too small, the contact pressure between the first pipe 2 and the condenser 32 will increase, resulting in instability or deformation of the system structure; while an excessively large cavity size will reduce the compactness and strength of the system. Therefore, setting the size of the second cavity 31 within the range of 10 mm to 20 mm can ensure the smooth progress of the steam transmission and condensation process while maintaining structural stability and strength.

[0052] In some embodiments, see Figure 2 , the orthographic projection of the anti-corrosion layer 33 on the surface of the first pipe 2 falls inside the first pipe 2 ; and / or, the anti-corrosion layer 33 does not completely cover the outer surface of the condenser tube 32 .

[0053] It should be noted that when the length of the condenser 32 is the same as that of the first pipe fitting 2, the orthographic projection of the anti-corrosion layer 33 on the surface of the first pipe fitting 2 falls inside the first pipe fitting 2, indicating that the anti-corrosion layer 33 wraps the entire outer wall of the condenser 32, thereby achieving more comprehensive protection for the condenser 32.

[0054] When both ends of the condenser tube 32 extend out of the shell 1, the anti-corrosion layer 33 does not completely cover the outer surface of the condenser tube 32, specifically, the anti-corrosion layer 33 only covers the positive projection area of ​​the first pipe 2 on the condenser tube 32. Since the outer surfaces of both ends of the condenser tube 32 extending out of the shell 1 will not directly contact the steam or water generated by condensation, there is no need to set the anti-corrosion layer 33 for protection, which is conducive to reducing costs and improving the economic benefits of system applications.

[0055] In some embodiments, see Figure 2 and Figure 4 The contact angle between the water droplets on the anti-corrosion layer 33 and the surface of the anti-corrosion layer 33 is 130°~160°.

[0056] Figure 4 The R shown in the figure represents the contact angle, and W represents the water droplet. The contact angle between the water droplet on the anti-corrosion layer 33 and the surface of the anti-corrosion layer 33 can be 130°, 135°, 140°, 145°, 150°, 155°, or 160°.

[0057] In specific implementation, in the air gap membrane distillation process of the present application, the water droplets generated by condensation need to be formed on the surface of the anti-corrosion layer 33 and then desorbed in order to be collected. The embodiment of the present application selects a polymer resin and a nano-chromium powder compound so that the contact angle between the anti-corrosion layer 33 and the water droplets is larger, so that the adhesion between the water droplets and the anti-corrosion layer 33 is relatively reduced, and the water droplets are more easily desorbed from the surface of the anti-corrosion layer 33, thereby improving the collection efficiency of the condensed water droplets; A larger contact angle also helps to reduce the residue and accumulation of condensed water droplets on the surface of the anti-corrosion layer 33. When the contact angle between the water droplets and the surface of the anti-corrosion layer 33 is larger, the shape of the water droplets will be closer to a sphere, making it easier for them to roll and slide on the surface of the anti-corrosion layer 33, preventing the water droplets from forming a continuous liquid film on the surface of the anti-corrosion layer 33, reducing the obstruction of the liquid film to steam transmission, and improving the steam transmission efficiency and condensation effect; When the contact angle between the condensed water droplets and the surface of the anti-corrosion layer 33 is large, the thermal resistance between the water droplets and the anti-corrosion layer 33 will be relatively small, and heat will be more easily transferred from the steam to the condensed water droplets, thereby improving the heat transfer efficiency of the condensation process.

[0058] In some embodiments, see Figure 2 and Figure 5 , the system further comprises a first connector 4 and a second connector 5; The first connector 4 is respectively connected to the first end 11 and one end of the first pipe 2 aligned with the first end 11, and one end of the second connector is respectively connected to the second end 12 and one end of the first pipe 2 aligned with the second end 12; Two ends of the second pipe member 3 extending out of the first pipe member 2 are respectively embedded in the first connector 4 and the second connector 5 .

[0059] It should be noted that the cross-sectional shape of the first connector 4 is a circular ring, and the cross-sectional shape of the second connector 5 is also a circular ring; The lower end surface of the first connector 4 and the end surface of the first end 11 are both coated with sealant, and a sealed connection is formed after bonding; The upper end surface of the second connector 5 and the end surface of the second end 12 are both coated with sealant, and a sealed connection is formed after bonding; The end surface of the first pipe member 2, which is aligned with the first end 11, is adhered to the lower end surface of the first connector 4 by means of sealing glue; The end surface of one end of the first pipe member 2 aligned with the second end 12 is adhered to the upper end surface of the second connector 5 by means of sealing adhesive.

[0060] See also Figure 2 and Figure 6 The second pipe 3 extending from both ends of the first pipe 2 is embedded in the first connector 4 and the second connector 5, and the opening portion extends upward from the first connector 4 and downward from the second connector 5, respectively, so as to facilitate the delivery of cooling water; The width x of the hollow structure inside the first connector 4 along the horizontal direction is greater than the width of the condenser tube 32 along the horizontal direction. This allows the condenser tube 32 to slide vertically downward into the first pipe 2 during installation, and the upper and lower ends of the condenser tube 32 can extend out of the first connector 4 and the second connector 5 respectively. The dimension of the second connector 5 along the horizontal direction x is smaller than the dimension of the hollow structure inside the shell 1 along the horizontal direction x, so that the second connector 5 can slide into the shell 1 along the vertical direction y until the second connector 5 slides downward out of the shell 1 .

[0061] In the specific implementation, the first pipe fitting 2 of appropriate size is cut, where the length of the first pipe fitting 2 is the same as that of the shell 1, and then the two ends of the first pipe fitting 2 are respectively glued to the lower end face of the first connector 4 and the upper end face of the second connector 5 with sealant to form a sealed connection. The connected second connector 5 is first placed downward into the shell 1, and then the first connector 4 is pressed, and the first connector 4 drives the first pipe fitting 2 to slide downward into the shell 1. Until the second connector 5 slides out of the shell 1, the first end 11 end face and the second end 12 end face of the shell 1 are sealed and connected to the lower end face of the first connector 4 and the upper end face of the second connector 5 respectively with sealant. Then insert the condenser 32 coated with the anti-corrosion layer 33 downward into the first connector 4, and slide it downward into the space surrounded by the first pipe fitting 2 until the lower end of the condenser 32 extends out of the second connector 5. It is necessary to ensure that the two ends of the condenser 32 extend out of the first connector 4 and the second connector 5 respectively along the vertical direction y, and then use sealant to embed the condenser 32 into the first connector 4 and the second connector 5 to bond them to achieve a sealed connection, that is, assemble an acid-resistant tubular air gap membrane distillation system.

[0062] By providing the first connector 4 and the second connector 5, the first pipe 2 and the housing 1 can be firmly connected to ensure that the size of the internal space of the first cavity 21 remains unchanged. The use of sealant also achieves a close fit between the end faces, thereby greatly improving the sealing of the system to prevent steam leakage and ensure the continuity and stability of the membrane distillation process; By extending the first connector 4 and the second connector 5 from both ends of the condenser 32, the first connector 4 and the second connector 5 not only provide stable support for the second pipe 3, but also enable cooling water to smoothly enter and exit the condenser 32, thereby improving the cooling water transportation efficiency.

[0063] In some embodiments, see Figure 2 and Figure 6 The second connector 5 includes a first through groove 51 and a second through groove 52. The first through groove 51 is larger than the second through groove 52 in the horizontal direction. The first through groove 51 is located above the second through groove 52. The condensation tube 32 is fixedly connected to the second through groove 52 by a sealant. The first through groove 51 is communicated with the second cavity 31; The second connector 5 is provided with a water outlet 53 , which is communicated with the first through groove 51 .

[0064] In specific implementation, the water generated by condensation in the second cavity 31 flows downward into the first through groove 51 and then discharged along the water outlet 53. This is to facilitate timely discharge of the generated water and avoid excessive water accumulation in the second cavity 31 to affect the mass transfer process.

[0065] In some embodiments, see Figure 2 and Figure 7, the system also includes a produced water collector 6, a hot acid wastewater storage tank 61, a first magnetic drive pump 62, a second magnetic drive pump 63, a first water tank 64, a second water tank 65, a gate valve 66, a cold water tank 67, a first digital display thermometer 68, a second digital display thermometer 69 and a plurality of thermometers 7; The water production collector 6 is connected to the water outlet 53 to recover the water discharged from the second cavity 31, so as to avoid excessive water accumulation in the second cavity 31 and affect the subsequent condensation water production, thereby ensuring the continuous and stable operation of the system.

[0066] The hot acid wastewater storage tank 61 is connected to the liquid inlet 111, and the first magnetic-driven pump 62 is arranged on the pipeline connecting the hot acid wastewater storage tank 61 and the liquid inlet 111; during implementation, the first magnetic-driven pump 62 is started, and the first magnetic-driven pump 62 transports the hot acid wastewater in the hot acid wastewater storage tank 61 along the liquid inlet 111 to the first cavity 21.

[0067] The hot acid wastewater storage tank 61 is also connected to the liquid outlet 121 to recover the concentrated hot acid wastewater discharged from the first cavity 21 along the liquid outlet 121, and the recovered hot acid wastewater is mixed with the material in the hot acid wastewater storage tank 61 to continue to participate in the next concentration process.

[0068] The first water tank 64 is arranged on the pipeline connecting the hot acid wastewater storage tank 61 and the liquid outlet 121, and the liquid inlet end of the first water tank 64 is connected to the liquid outlet 121, and the liquid outlet end is connected to the hot acid wastewater storage tank 61. During implementation, the concentrated hot acid wastewater outputted from the liquid outlet 121 first enters the first water tank 64 for water replenishment, and the hot acid wastewater after water replenishment then enters the hot acid wastewater storage tank 61 along the first water tank 64, evaporates to obtain more steam after being heated, and when it is transported to the first cavity 21 for the next time, more steam can pass through the first pipe 2 to reach the second cavity 31 for condensation and water production, thereby increasing the membrane flux, and at the same time, more steam can take away more easily evaporated waste materials in the hot acid wastewater, so that the purity of the acid in the concentrated hot acid wastewater is higher.

[0069] The gate valve 66 is disposed on the connecting pipeline between the liquid outlet of the first water tank 64 and the hot acid wastewater storage tank 61 to control the flow rate of the material flowing back into the hot acid wastewater storage tank 61 .

[0070] One end of the cold water tank 67 is connected to the opening at the lower end of the condenser 32, and the other end is connected to the opening at the upper end of the condenser 32, so that the cooling water can be transported along the lower end opening of the condenser 32 to the inside of the condenser 32, and then discharged along the upper end opening and returned to the cold water tank 67, forming a reciprocating cycle to keep the temperature inside the condenser 32 always low and avoid it from rising due to the influence of steam, thereby reducing the temperature difference between the second cavity 31 and the inside of the condenser 32 and maintaining a stable condensation effect.

[0071] The second water tank 65 is connected to the connecting pipeline between the upper opening of the condenser tube 32 and the cold water tank 67. During implementation, part of the cooling water in the condenser tube 32 will remain on the inner wall of the condenser tube 32. In order to ensure sufficient cooling water, the cooling water discharged from the upper opening of the condenser tube 32 is first transported to the second water tank 65 for water replenishment, and then refluxed into the cold water tank 67 together, and it is convenient to replenish the cooling water in time to ensure that the system can operate continuously and stably. At the same time, due to the heat release during steam condensation, the cooling water temperature inside the condenser tube 32 is slightly increased. If it is directly refluxed into the cold water tank 67, it is easy to cause the temperature in the cold water tank 67 to increase. Therefore, the second water tank 65 is set to cool the cooling water drawn out of the condenser tube 32 to ensure that the cooling water temperature refluxed into the cold water tank 67 is low enough.

[0072] The second magnetically driven pump 63 is disposed on the connecting pipe between the upper opening of the condenser tube 32 and the second water tank 65. Since the cooling water in the condenser tube 32 is transported from bottom to top, the second magnetically driven pump 63 is disposed to ensure that the cooling water has sufficient power, so as to timely extract the cooling water in the condenser tube 32 and transport it to the first water tank 64, so as to avoid the cooling water from accumulating in the condenser tube 32 due to insufficient power, thereby affecting the temperature inside the condenser tube 32.

[0073] The first digital thermometer 68 is arranged on the connecting pipe between the upper end opening of the condenser 32 and the second water tank 65 to monitor the temperature of the upper end opening of the condenser 32 in real time. The temperature is the same as the temperature of the cooling water discharged from the condenser 32. The measurement is used to ensure that the temperature inside the condenser 32 is suitable for condensation, and timely adjust it by delivering cooling water of different temperatures to keep the temperature difference between the condenser 32 and the inside of the second cavity 31 very small to achieve the best condensation effect.

[0074] The second digital display thermometer 69 is arranged on the connecting pipeline between the first magnetic drive pump 62 and the liquid inlet 111, and monitors the temperature of the hot acid wastewater entering the first cavity 21 through the liquid inlet 111 in real time. If the temperature is too low, it is adjusted in time to ensure that the hot acid wastewater can generate sufficient steam after entering the first cavity 21.

[0075] A plurality of thermometers 7 are respectively arranged on the connecting pipe between the liquid outlet 121 and the first water tank 64, on the connecting pipe between the liquid inlet 111 and the hot acid wastewater storage tank 61, on the connecting pipe between the lower end opening of the condenser 32 and the cold water tank 67, and on the connecting pipe between the upper end opening of the condenser 32 and the second water tank 65; The multiple thermometers 7 are respectively used to detect the temperature of the concentrated hot acid wastewater (which is also the temperature inside the first cavity 21), the temperature of the liquid inlet 111, the temperature of the cooling water entering the condenser 32, and the temperature of the cooling water discharged from the condenser 32, so as to timely adjust the temperature of the hot acid wastewater and the cooling water, so that the temperature inside the first cavity 21, the second cavity 31 and the condenser 32 is always maintained within the specified temperature.

[0076] In the specific implementation, the first magnetic drive pump 62 is started to transport the hot acid wastewater in the hot acid wastewater storage tank 61 to the first cavity 21 along the liquid inlet 111, and then the cooling water in the cold water tank 67 is transported into the condenser 32 along the lower end opening of the condenser 32; The steam in the hot acid wastewater passes through the first pipe 2 and reaches the second cavity 31 to condense and produce water. Part of the produced water adheres to the surface of the anti-corrosion layer 33, and the other part flows downward into the second through groove 52, and is finally discharged through the water outlet 53 to the produced water collector 6 for storage; The cooling water in the condenser tube 32 is pumped into the second water tank 65 along the upper opening by the second magnetic drive pump 63. After cooling, the cooling water flows into the cooling water tank together with the water in the second water tank 65. The cold water tank 67 then delivers new cooling water into the condenser tube 32 along the lower opening of the condenser tube 32, thus forming a cycle. The concentrated hot acid wastewater enters the first water tank 64 along the liquid outlet 121, and flows into the hot acid wastewater storage tank 61 for storage after water replenishment. The hot acid wastewater storage tank 61 then pumps the new hot acid wastewater into the first cavity 21 through the first magnetic drive pump 62, forming a cycle in sequence; During the operation of the system, the multiple thermometers 7, the first digital display thermometer 68 and the second digital display thermometer 69 are all in the start-up state. The first digital display thermometer 68 and the second digital display thermometer 69 monitor the temperature of the hot acid wastewater input into the first cavity 21 and the temperature of the cooling water in real time. When the temperature exceeds or falls below the specified range, the hot acid wastewater in the hot acid wastewater storage tank 61 is heated in time, and the cooling water in the cold water tank 67 is cooled, so as to ensure that the system can continuously and stably carry out the concentration treatment of the hot acid wastewater. The gate valve 66 is closed only when the liquid level in the hot acid wastewater storage tank 61 exceeds a limit value, and the concentrated hot acid wastewater discharged from the liquid outlet 121 is first stored in the first water tank 64. After the liquid level in the hot acid wastewater storage tank 61 drops, the gate valve 66 is started to replenish the hot acid wastewater in time to ensure continuous operation of the system.

[0077] The following is a detailed description of an acid-resistant tubular air-gap membrane distillation system provided by the present application through specific embodiments.

[0078] Example 1 like Figures 1 to 6 The structural diagram of the acid-resistant tubular air-gap membrane distillation system is shown.

[0079] 1. The upper end surface of the first pipe fitting 2 is bonded to the lower end surface of the first connector 4 by means of a sealant, and the lower end surface of the first pipe fitting 2 is bonded to the upper end surface of the second connector 5 by means of a sealant to form a sealed connection; 2. Place the connected second connector 5 downward into the housing 1, and then press the first connector 4. The first connector 4 drives the first pipe 2 to slide downward into the housing 1, so that the first cavity 21 is automatically formed between the outer wall of the first housing 1 and the inner wall of the housing 1; 3. Until the second connector 5 slides out of the housing 1, the first end 11 of the housing 1 is bonded to the lower end of the first connector 4 by means of sealant to form a sealed connection, and the second end 12 is bonded to the upper end of the second connector 5 by means of sealant to form a sealed connection; 4. Then, insert the condenser tube 32 coated with the anti-corrosion layer 33 downward into the first connector 4, and press hard until the lower end of the condenser tube 32 extends out of the second connector 5. Here, it is necessary to ensure that the upper end of the condenser tube 32 extends out of the first connector 4 and the lower end extends out of the second connector 5. Then, use sealant to embed the condenser tube 32 into the first connector 4 and the second connector 5 to seal the part, so that the second cavity 31 is automatically formed between the surface of the anti-corrosion layer 33 and the outer wall of the first pipe 2, so as to form the following: Figure 1 and Figure 2 The acid-resistant tubular air-gap membrane distillation system shown, wherein the anti-corrosion layer 33 is a mixture of fluorocarbon resin and nano-chromium powder with a particle size of 30 nm, the thickness of the anti-corrosion layer 33 is set to 129 μm, the condenser 32 is made of stainless steel, the length of the condenser 32 is 16 mm, and the thickness is 2.5 mm; 5. Cooling water at a temperature of 20°C is conveyed upward to the inside of the condenser tube 32 along the opening at the lower end of the condenser tube 32 at a flow rate of 3 L / min, and hot acid wastewater at a temperature of 60°C is conveyed upward to the first cavity 21 along the liquid inlet 111 at a flow rate of 2 L / min, so that the steam passes through the first pipe 2 to reach the second cavity 31 and adheres to the anti-corrosion layer 33, and the water generated by condensation flows downward into the second through groove 52 of the second connector 5, and is finally discharged along the water outlet 53; 6. The concentrated hot acid wastewater is discharged from the first cavity 21 along the liquid outlet 121; 7. Repeat steps 5 and 6 until all hot acid wastewater is concentrated.

[0080] Comparative Example 1 was set based on Example 1.

[0081] Comparative Example 1 The only difference between Comparative Example 1 and Example 1 is that no anti-corrosion layer 33 is provided on the condenser tube 32 used in Comparative Example 1, and the other steps are the same as those in Example 1.

[0082] According to experimental verification, the system membrane flux of Example 1 during operation increased by 13.56% compared with that of Comparative Example 1. It is proved that the anti-corrosion layer 33 provided in Example 1 of the present application can not only achieve the anti-corrosion effect, but also increase the membrane flux of the system, thereby improving the mass transfer efficiency and water production efficiency.

[0083] In summary, the acid-resistant tubular air-gap membrane distillation system provided in the embodiment of the present application effectively resists the corrosion of the condenser by acidic steam by setting an anti-corrosion layer on the outer wall of the condenser, thereby extending the service life of the condenser, improving the overall stability of the membrane distillation system, and enabling the system to continuously and stably carry out the concentration treatment of acidic materials. Since the corrosion resistance of the condenser is improved, the membrane flux is increased, and the mass transfer efficiency is further improved, thereby improving the water production efficiency of the membrane distillation process. In addition, since the anti-corrosion layer effectively reduces the corrosion of the condenser, it is possible to reduce the maintenance cost caused by replacing damaged condensers, improve the economic benefits of the membrane distillation system, and promote the application of membrane distillation in the treatment of acidic wastewater.

[0084] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0085] Although the preferred embodiments of the present application have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the embodiments of the present application.

[0086] Finally, it should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or terminal device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or terminal device. In the absence of further restrictions, the elements defined by the sentence "including one..." do not exclude the existence of other identical elements in the process, method, article or terminal device including the elements.

[0087] The above is a detailed introduction to an acid-resistant tubular air-gap membrane distillation system provided by the present application. Specific examples are used in this article to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only used to help understand the method of the present application and its core idea; at the same time, for general technical personnel in this field, according to the idea of ​​the present application, there will be changes in the specific implementation method and application scope. In summary, the content of this specification should not be understood as a limitation on the present application.

Claims

1. An acid-resistant tubular air-gap membrane distillation system, characterized in that: The system comprises: A shell (1), a first pipe member (2) and a second pipe member (3); The housing (1) comprises a first end (11) and a second end (12) which are arranged opposite to each other, the first end (11) is provided with a liquid inlet (111), and the second end (12) is provided with a liquid outlet (121); The first pipe member (2) is sleeved outside the second pipe member (3), and the shell (1) is sleeved outside the first pipe member (2); A first cavity (21) is provided between the housing (1) and the first tube (2), a second cavity (31) is provided between the first tube (2) and the second tube (3), and the liquid inlet (111) is in communication with the first cavity (21); The liquid inlet (111) is configured to transport hot acid wastewater into the first cavity (21), allowing steam to pass through the first pipe (2) into the second cavity (31), and the second pipe (3) condenses the steam; The liquid outlet (121) is configured to output the hot acid wastewater out of the first cavity (21); Wherein, the second pipe member (3) comprises a condenser tube (32) and an anti-corrosion layer (33), and the anti-corrosion layer (33) is located on the outer wall of the condenser tube (32); The anti-corrosion layer (33) is configured to resist the steam corrosion.

2. The acid-resistant tubular air-gap membrane distillation system according to claim 1, characterized in that: The anti-corrosion layer (33) is a mixture of polymer resin and nano chromium powder.

3. The acid-resistant tubular air-gap membrane distillation system according to claim 2, characterized in that: The polymer resin is at least one of epoxy resin, polyurethane resin, fluorocarbon resin, polyethylene resin and polypropylene resin.

4. The acid-resistant tubular air-gap membrane distillation system according to claim 2, characterized in that: The particle size of the nano chromium powder is 10 nm-100 nm.

5. The acid-resistant tubular air-gap membrane distillation system according to claim 1, characterized in that: The condenser (32) is made of at least one of stainless steel, copper, aluminum, titanium and nickel.

6. The acid-resistant tubular air-gap membrane distillation system according to claim 1, characterized in that: The thickness of the anti-corrosion layer (33) is 10 μm to 200 μm.

7. The acid-resistant tubular air-gap membrane distillation system according to claim 6, characterized in that: The size of the second cavity (31) in the thickness direction of the anti-corrosion layer (33) is 10 mm to 20 mm.

8. The acid-resistant tubular air-gap membrane distillation system according to claim 1, characterized in that: The orthographic projection of the anti-corrosion layer (33) on the surface of the first pipe (2) falls inside the first pipe (2); and / or the anti-corrosion layer (33) does not completely cover the outer surface of the condenser tube (32).

9. The acid-resistant tubular air-gap membrane distillation system according to claim 1, characterized in that: The contact angle between the water droplets on the anti-corrosion layer (33) and the surface of the anti-corrosion layer (33) is 130° to 160°.

10. The acid-resistant tubular air-gap membrane distillation system according to any one of claims 1 to 9, characterized in that: The system further comprises a first connector (4) and a second connector (5); The first connector (4) is respectively connected to the first end (11) and one end of the first pipe (2) aligned with the first end (11), and the second connector (5) is respectively connected to the second end (12) and one end of the first pipe (2) aligned with the second end (12); The two ends of the second pipe member (3) extending out of the first pipe member (2) are respectively embedded in the first connecting head (4) and the second connecting head (5).

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