Production process of nanofiltration membrane for extracting lithium from salt lake

Abstract

The invention provides a salt lake lithium extraction nanofiltration membrane production process, which is characterized in that drying equipment is used for heating and curing, the drying equipment comprises a pretreatment unit, the pretreatment unit comprises a liquid collection box, a conduction assembly and an extrusion assembly are arranged above the liquid collection box, and two symmetrically distributed lower water scraping assemblies are arranged below a membrane body; an upper water scraping assembly is arranged above the membrane body, and the lower water scraping assembly and the upper water scraping assembly make contact with the lower surface and the upper surface of the membrane body respectively. The extrusion assembly, the lower water scraping assembly and the upper water scraping assembly are used for carrying out water extrusion and water scraping protection treatment on a film body, the film body entering the drying oven body can be guided through the conduction assembly and the regulation and control assembly, the position of the film body is changed, water extrusion and water scraping treatment on the film body are facilitated, and the film body drying efficiency is improved. Removable liquid on the membrane body can be removed before drying, the water content of the nanofiltration membrane can be reduced, and the heating and curing effect and efficiency of the membrane body can be improved.

Description

Technical Field

[0001] This invention relates to the field of membrane manufacturing and processing, and in particular to a process for producing lithium extraction nanofiltration membranes from salt lakes. Background Technology

[0002] Lithium extraction from salt lakes, also known as brine extraction, is a metallurgical technique for extracting lithium resources from lithium-containing solutions such as brine in salt lakes. The main methods include evaporation crystallization, precipitation, solvent extraction, and ion exchange adsorption. Precipitation has become the mainstream method due to its simplicity and high efficiency, while the "adsorption + membrane" coupled process shortens the production cycle and improves lithium utilization.

[0003] Nanofiltration membranes are functional semi-permeable membranes that allow solvent molecules or certain low molecular weight solutes or low-valence ions to pass through. They are a special and promising type of separation membrane, named for the size of the substances they can retain, which is approximately nanometers in size. Nanofiltration membranes are used to remove organic matter and color from surface water, remove hardness from groundwater, partially remove dissolved salts, concentrate fruit juice, and separate useful substances from pharmaceuticals.

[0004] In the lithium extraction process from salt lakes, nanofiltration membranes are needed to treat the liquid in the salt lake to achieve efficient separation of lithium ions from other ions. During the production of nanofiltration membranes, after the interfacial polymerization reaction, a drying device is required for heating and curing. In a utility model patent entitled "Thin Film Drying Equipment" (publication number CN218973125U), an exhaust fan and a heating box are fixedly installed on the top of a support frame. The exhaust fan's outlet is connected to the heating box's inlet. The heating box's outlet is connected to the upper and lower baffles via a first hot air pipe and a second hot air pipe, respectively. This improves the uniformity of heating on both sides of the membrane and increases drying efficiency. However, in the aforementioned application, the membrane sheet taken from the interfacial polymerization reaction liquid is directly sent to the drying equipment for heating and curing. Since the membrane sheet contains a lot of liquid inside and on its surface, directly entering the drying equipment requires a longer heating time, affecting the heating and curing efficiency of the membrane sheet and resulting in greater energy consumption of the drying equipment, thereby increasing the production cost of the nanofiltration membrane sheet. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the defect of low heating and curing efficiency caused by directly feeding the membrane taken out of the liquid into the drying equipment in the prior art, and to provide a production process for lithium extraction nanofiltration membranes from salt lakes.

[0006] The present invention solves the above-mentioned technical problems through the following technical solution: This invention provides a process for producing a lithium extraction nanofiltration membrane from salt lakes, the process comprising the following steps: Step 1: Preparation of the base film. Using a film scraping device, a thin liquid film is scraped onto the support. Then, the support with the thin liquid film is immersed in a non-solvent, causing the polymer to precipitate out and form a porous membrane with a microporous structure. After cleaning and drying, the base film is obtained. Step 2: Preparation of the separation functional layer. First, the base membrane obtained in Step 1 is placed in an aqueous solution, then removed to remove excess droplets, and then immersed in an oil solution. At this time, a cross-linked network structure is formed through interfacial polymerization reaction. Then, the network structure is heated and cured, and then cleaned to obtain a nanofiltration membrane semi-finished product. Step 3: Post-processing and modification. The nanofiltration membrane semi-finished product obtained in Step 2 is modified according to functional requirements to obtain the finished nanofiltration membrane. Step 4: Assembly of spiral wound membrane elements. Cut the nanofiltration membrane sheet into the required size according to the design width, align them, lay the mesh, apply glue, and then roll them up in sequence. Finally, seal the end caps to complete the assembly.

[0007] In this technical solution, nanofiltration membranes are produced and processed through interfacial polymerization. The reaction rate is fast, the reaction conditions are mild, the phase interface reaction characteristics are excellent, the film-forming performance is outstanding, and the entire reaction operation is simple and controllable. The automatic termination mechanism is stable, preventing membrane performance degradation caused by over-polymerization and ensuring the stability and consistency of nanofiltration membrane quality.

[0008] Preferably, the specific operation steps of step one are as follows: S1. Preparation of casting solution: Dissolve the polymer in a highly polar solvent to form a homogeneous and transparent solution. S2. Film scraping: Using a precision scraper, the casting liquid is scraped onto the support to form a thin film of a specific thickness. S3, coagulation bath: The support with liquid film is immersed in a non-solvent bath. The solvent and non-solvent diffuse into each other, causing the polymer to precipitate out of the homogeneous solution and form a porous membrane with a microporous structure. S4. Post-processing: The porous membrane obtained in step S3 is cleaned and dried to obtain the base membrane.

[0009] In this technical solution, the specific operational steps for preparing the base film are defined.

[0010] Preferably, the specific steps of step two are as follows: A1. Immersion in aqueous solution: Immerse the prepared base film in an aqueous solution containing aqueous monomers; A2. Remove excess droplets, take out the base film, and blow it with a rubber roller or nitrogen to remove excess aqueous solution from the surface, ensuring that only the micropores of the base film adsorb aqueous monomers. A3. Immersion in oil phase solution: Immerse the base film with aqueous phase monomers attached into an organic solution containing oil phase monomers. A4. Interfacial polymerization reaction: Aqueous monomers and oil monomers undergo instantaneous polymerization reaction at the water-oil interface to generate a cross-linked network structure film. A5. Post-processing: The membrane is removed and subjected to heat curing. Then it is rinsed with water to remove unreacted monomers and byproducts, resulting in a nanofiltration membrane semi-finished product.

[0011] In this technical solution, the specific operational steps for preparing the separated functional layer are determined.

[0012] Preferably, in step two, a drying device is used for heating and curing. The drying device includes an oven body and a movable heating component. The movable heating component is installed in the inner cavity of the oven body. The oven body is composed of multiple sections, namely, an inlet section, a preheating section, a transition section, a drying section, and an outlet section. An electric door assembly is installed between adjacent sections. The drying equipment also includes a pretreatment unit and an auxiliary unit. The pretreatment unit is located above the movable heating component and is located inside the preheating section of the oven body. The auxiliary unit is located outside the oven body and communicates with the drying section cavity of the oven body. The pretreatment unit is used to squeeze and scrape water off the membrane that needs to be heated and cured, so as to initially remove the liquid on the membrane. The auxiliary unit is used to circulate the air inside the oven body and to dry the air during circulation.

[0013] In this technical solution, the pretreatment unit is used to squeeze and scrape water from the membrane to initially remove liquid from the membrane body and surface. The auxiliary unit circulates and dries the air inside the oven body.

[0014] Preferably, the pretreatment unit includes a liquid collection tank, which is disposed above the movable heating assembly. The two sides of the liquid collection tank are respectively connected to the inner wall of the oven body. A conduction assembly and an extrusion assembly are disposed above the liquid collection tank, and the membrane passes through the space between the conduction assembly and the extrusion assembly. Two symmetrically distributed lower scraping assemblies are arranged below the membrane body. The two sides of the lower scraping assemblies are connected to the inner wall of the collection tank. An upper scraping assembly is arranged above the membrane body. The upper scraping assembly is located in the middle of the two lower scraping assemblies. The lower scraping assembly and the upper scraping assembly are in contact with the lower surface and the upper surface of the membrane body, respectively.

[0015] In this technical solution, the membrane is squeezed and scraped by the pretreatment unit to initially remove the liquid inside and on the surface of the membrane.

[0016] Preferably, the conductive assembly includes two sets of dual guide shafts, which are symmetrically distributed. Two symmetrically distributed first guide shafts and two symmetrically distributed second guide shafts are arranged between the two sets of dual guide shafts. The surfaces of the dual guide shafts, the first guide shafts and the second guide shafts are rotatably connected to the side of the liquid collection tank, and the two ends of the dual guide shafts, the first guide shafts and the second guide shafts are rotatably connected to the inner wall of the oven body.

[0017] In this technical solution, a conductive component is used to guide the membrane during transport.

[0018] Preferably, the extrusion assembly includes a first extrusion roller and a second extrusion roller, with two symmetrically distributed first extrusion rollers disposed above the film and two symmetrically distributed second extrusion rollers disposed below the film, and one first extrusion roller and one second extrusion roller forming a set of extruders; The surfaces of the first extrusion roller and the second extrusion roller are rotatably connected to the side of the liquid collection tank, and the two ends of the first extrusion roller and the second extrusion roller are rotatably connected to the inner wall of the oven body. A water-absorbing sponge pad is provided below the conduction component and the extrusion component, and the bottom of the water-absorbing sponge pad is connected to the top of the extrusion orifice plate.

[0019] In this technical solution, the liquid inside the membrane is squeezed out by an extrusion component.

[0020] Preferably, the lower wiper assembly includes a lower wiper blade, the upper end of which contacts the lower surface of the membrane, and both sides of the lower wiper blade are connected to an adaptation strip. The adaptation strip is slidably connected to the surface of the anti-detachment shaft, the bottom end of the anti-detachment shaft is connected to the top of the mounting strip, and both ends of the mounting strip are respectively connected to the inner wall of the collection tank. Multiple elastic connectors are connected between the lower wiper blade and the mounting strip; An abutment shaft is provided above the lower scraper, the abutment shaft contacts the top surface of the membrane, the surface of the abutment shaft is rotatably connected to the side of the liquid collection tank, and both ends of the abutment shaft are rotatably connected to the inner wall of the oven body.

[0021] In this technical solution, the water on the lower surface of the oven body is scraped off by the lower water scraper assembly.

[0022] Preferably, the upper wiper assembly includes two upper wiper blades distributed on the left and right, and each of the two upper wiper blades is connected to a movable connecting plate at its top. The two movable connecting plates are respectively threaded to the surfaces of two wiper threaded shafts. Each of the two wiper threaded shafts is connected to a side gear at one end. The two side gears are respectively meshed with the two sides of the central gear. The central gear is connected to the output end of the wiper power source. The wiper power source is installed on the inner wall of the protective housing. The protective housing is connected to the outside of the liquid collection tank. The inner wall of the liquid collection tank is connected to multiple anti-deviation tracks, and the surface of the anti-deviation tracks is slidably connected to the movable connecting plate.

[0023] In this technical solution, the upper scraper assembly is used to scrape off the liquid on the upper surface of the membrane.

[0024] Preferably, the preprocessing unit further includes two control components, which are located on the left and right sides of the conduction component, respectively. The control component includes a fixed frame shell, the top side of which is connected to the top of the oven body. Two symmetrically distributed control threaded shafts are rotatably connected to the inner cavity of the fixed frame shell, and the upper ends of the two control threaded shafts are connected to the synchronous component for transmission. The control threaded shaft surface is threaded with a control slider. One side of the control slider is slidably connected to the side of the fixed frame. The side of the control slider away from the fixed frame is connected to a follower side plate. The follower side plate is rotatably connected to two control shafts that are symmetrically distributed vertically. The membrane passes between the two control shafts.

[0025] In this technical solution, the tension of the membrane is adjusted during the transport of the membrane by means of a control component and a synchronization component.

[0026] Based on common knowledge in the field, the above-mentioned preferred conditions can be combined arbitrarily to obtain various preferred embodiments of the present invention.

[0027] The positive and progressive effects of this invention are as follows: This invention utilizes an extrusion assembly, a lower scraping assembly, and an upper scraping assembly to perform water squeezing and scraping treatment on the membrane. Furthermore, the membrane entering the oven body can be guided and its position changed through a conduction assembly and a control assembly to facilitate water squeezing and scraping treatment. This allows removable liquids on the membrane to be removed before drying, reducing the water content of the nanofiltration membrane and thus improving the subsequent drying efficiency of the membrane, as well as the effect and efficiency of membrane heating and curing. Meanwhile, absorbent sponge pads are installed below the extrusion assembly, the lower wiper assembly, and the upper wiper assembly. The absorbent sponge pads absorb the dripping liquid in time, preventing the liquid from splashing back onto the membrane surface when it drips, and improving the liquid removal effect of the extrusion assembly, the lower wiper assembly, and the upper wiper assembly on the membrane. Furthermore, a collection component is installed, which, together with a squeezing orifice plate, squeezes the absorbent sponge pad to expel the liquid absorbed inside. The squeezed liquid is collected in the lower part of the liquid collection tank, allowing the absorbent sponge pad to be used for a long time, reducing the probability of maintenance and replacement, and improving the efficiency of membrane heating and curing. Furthermore, control components are set on both sides of the transmission component to regulate the tension of the membrane during transport, which can prevent damage to the membrane during transmission. Furthermore, the drying components circulate the hot air inside the oven body, drying the humid air before it is reintroduced. This avoids the direct discharge of hot air containing moisture, which would cause a drop in the internal temperature of the oven body. This makes the internal temperature of the oven body more stable, reduces heat loss, and makes the drying equipment more energy-efficient. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the overall process for lithium extraction nanofiltration membrane production from salt lakes, according to an embodiment of the present invention.

[0029] Figure 2 This is a schematic diagram of the overall three-dimensional structure of the lithium extraction nanofiltration membrane production process from salt lakes according to an embodiment of the present invention.

[0030] Figure 3 for Figure 2 The diagram shows the internal structure of the main oven part of the lithium extraction nanofiltration membrane production process in salt lakes.

[0031] Figure 4 for Figure 2 The diagram shows a three-dimensional structure of the pretreatment unit and oven body in the lithium extraction nanofiltration membrane production process from salt lakes.

[0032] Figure 5 for Figure 4 The diagram shows a three-dimensional structure of the pretreatment unit in the lithium extraction nanofiltration membrane production process from salt lakes.

[0033] Figure 6 for Figure 5 The diagram shows a three-dimensional structural representation of the conductive components, extrusion components, lower scraping components, upper scraping components, and collection components in the lithium extraction nanofiltration membrane production process from salt lakes.

[0034] Figure 7 for Figure 6 The diagram shows a three-dimensional structure of the scraper assembly in the lithium extraction nanofiltration membrane production process from salt lakes.

[0035] Figure 8 for Figure 6 The diagram shows a three-dimensional structure of the top water scraping component in the lithium extraction nanofiltration membrane production process from salt lakes.

[0036] Figure 9 for Figure 5 The diagram shows a three-dimensional structure of the control and synchronization components in the lithium extraction nanofiltration membrane production process from salt lakes.

[0037] Figure 10 for Figure 6The diagram shows a three-dimensional structural schematic of the collection component in the lithium extraction nanofiltration membrane production process from salt lakes.

[0038] Figure 11 for Figure 2 The diagram shows a three-dimensional structure of an auxiliary unit in the lithium extraction nanofiltration membrane production process from salt lakes.

[0039] Figure 12 for Figure 11 The diagram shows the internal structure of the drying oven in the lithium extraction nanofiltration membrane production process from salt lakes.

[0040] Explanation of reference numerals in the attached figures 1. Main body of the drying oven; 2. Mobile heating assembly; 21. Sprocket and chain drive components; 22. Heating plate assembly; 3. Electric gate assembly; 4. Liquid collecting tank; 5. Conducting assembly; 51. Dual guide shaft assembly; 52. First guide shaft; 53. Second guide shaft; 6. Extrusion assembly; 61. First extrusion roller; 62. Second extrusion roller; 63. Absorbent sponge pad; 64. Extrusion perforated plate; 7. Lower wiper assembly; 71. Lower wiper blade; 72. Adaptive strip; 73. Anti-detachment shaft; 74. Mounting strip; 75. Flexible connector; 76. Abutment shaft; 8. Upper wiper assembly; 81. Upper wiper blade; 82. Moving connecting plate; 83. Wiper threaded shaft; 84. Side gear; 85. Center gear; 86. Wiper power source; 87. Protective housing; 88. Anti-deviation track; 9. Adjustment component; 91. Fixed frame; 92. Adjustment threaded shaft; 93. Adjustment slider; 94. Follower side plate; 95. Adjustment rotating shaft; 96. Positioning track; 97. Fixed plate; 10. Synchronization component; 101. Transmission sprocket; 102. Transmission chain; 103. Driven gear; 104. Driving gear; 105. Synchronization drive source; 11. Collection component; 111. Housing assembly; 112. Power source collection; 113. Rotating drive shaft; 114. First bevel gear; 115. Second bevel gear; 116. Extrusion eccentric wheel; 12. Drying components; 121. Drying chamber; 122. Circulating fan; 123. Inlet pipe; 124. Circulation pipe; 125. Divider plate; 126. Removal rail; 127. Moisture-absorbing drying core. Detailed Implementation

[0041] The invention is further illustrated below by way of embodiments, but the invention is not limited to the scope of the embodiments described herein.

[0042] Figures 1 to 12The diagram shown is a structural schematic of an embodiment of a lithium extraction nanofiltration membrane production process from salt lakes according to the present invention.

[0043] A process for producing lithium-ion nanofiltration membranes from salt lakes, comprising the following steps: Step 1: Preparation of the base film. Using a film scraping device, a thin liquid film is scraped onto the support. Then, the support with the thin liquid film is immersed in a non-solvent, causing the polymer to precipitate out and form a porous membrane with a microporous structure. After cleaning and drying, the base film is obtained. Step 2: Preparation of the separation functional layer. First, the base membrane obtained in Step 1 is placed in an aqueous solution, then removed to remove excess droplets, and then immersed in an oil solution. At this time, a cross-linked network structure is formed through interfacial polymerization reaction. Then, the network structure is heated and cured, and then cleaned to obtain a nanofiltration membrane semi-finished product. Step 3: Post-processing and modification. The nanofiltration membrane semi-finished product obtained in Step 2 is modified according to functional requirements to obtain the finished nanofiltration membrane. Step 4: Assembly of spiral wound membrane elements. Cut the nanofiltration membrane sheet into the required size according to the design width, align them, lay the mesh, apply glue, and then roll them up in sequence. Finally, seal the end caps to complete the assembly.

[0044] In this technical solution, nanofiltration membranes are produced and processed through interfacial polymerization. The reaction rate is fast, the reaction conditions are mild, the phase interface reaction characteristics are excellent, the film-forming performance is outstanding, and the entire reaction operation is simple and controllable. The automatic termination mechanism is stable, preventing membrane performance degradation caused by over-polymerization and ensuring the stability and consistency of nanofiltration membrane quality.

[0045] The specific steps for step one are as follows: S1. Preparation of casting solution: Dissolve the polymer in a highly polar solvent to form a homogeneous and transparent solution, such as dissolving polysulfone in N-methylpyrrolidone. S2. Film scraping: Using a precision scraper, the casting liquid is scraped onto the support to form a thin film of a specific thickness. The support can be a clean nonwoven fabric or polyester fiber support. S3, coagulation bath: The support with liquid film is immersed in a non-solvent bath. The solvent and non-solvent diffuse into each other, causing the polymer to precipitate out of the homogeneous solution and form a porous membrane with a microporous structure. The aforementioned non-solvents are typically water; S4. Post-processing: The porous membrane obtained in step S3 is cleaned and dried to obtain the base membrane.

[0046] In this technical solution, the specific operational steps for preparing the base film are defined.

[0047] The specific steps for step two are as follows: A1. Immersion in aqueous solution: Immerse the prepared base film in an aqueous solution containing aqueous monomers; Aqueous monomers are usually nucleophilic molecules containing multiple amine groups (-NH2), the most commonly used being piperazine; A2. Remove excess droplets, take out the base film, and blow it with a rubber roller or nitrogen to remove excess aqueous solution from the surface, ensuring that only the micropores of the base film adsorb aqueous monomers. A3. Immersion in oil phase solution: Immerse the base film with aqueous phase monomers attached into an organic solution containing oil phase monomers. The organic solutions, such as n-hexane and ISOPAR G (isoparaffin solvent), have an oil phase monomer that is an electrophilic molecule containing multiple acyl chloride groups (-COCl), the most commonly used being trimesoyl chloride; A4. Interfacial polymerization reaction: Aqueous monomers and oil monomers undergo instantaneous polymerization reaction at the water-oil interface to generate a cross-linked network structure film. That is, piperazine in the aqueous phase and pyromellitic methyl chloride in the oil phase undergo an instantaneous polymerization reaction at the water-oil interface to generate a cross-linked polyamide film; A5. Post-processing: Take out the above membrane, heat and solidify it, then rinse it with water to remove unreacted monomers and by-products, and obtain nanofiltration membrane semi-finished product. The purpose of rinsing with water is to remove unreacted monomers and byproducts.

[0048] In this technical solution, the specific operational steps for preparing the separated functional layer are determined.

[0049] The production process of lithium extraction nanofiltration membrane from salt lakes includes drying equipment, rinsing tank equipment, interface polymerization equipment, and other reaction equipment. The drying equipment includes a drying oven body 1 and a mobile heating component 2. The mobile heating component 2 is installed in the inner cavity of the drying oven body 1. The drying oven body 1 is composed of multiple structural sections, namely, an inlet section, a preheating section, a transition section, a drying section, and an outlet section. An electric door assembly 3 is installed between adjacent structural sections. The drying equipment also includes a pretreatment unit and an auxiliary unit. The pretreatment unit is located above the movable heating component 2 and is located in the preheating section of the oven body 1. The auxiliary unit is located outside the oven body 1 and is connected to the drying section cavity of the oven body 1. The pretreatment unit is used to squeeze and scrape water off the membrane that needs to be heated and cured, and to initially remove the liquid from the membrane. The auxiliary unit is used to circulate the air inside the oven body 1 and to dry the air during circulation.

[0050] The oven body 1 has inlets and outlets on both sides, and each inlet and outlet is rotatably connected to two symmetrically distributed anti-scratch rotating shafts.

[0051] Heating devices are installed inside the main body of the oven 1.

[0052] The mobile heating assembly 2 includes two symmetrically distributed sprocket and chain drive components 21. Each sprocket and chain drive component 21 is composed of multiple sprockets and chains. Multiple sprockets on the same side are respectively engaged with the chains. Multiple sprockets on the same side are connected by chain drive. The outer side of the sprocket is rotatably connected to the support frame. The support frame is connected to the inner wall of the oven body 1. The outer side of one sprocket on the same side is connected to the output end of the motor. The motor is installed at the support frame. Multiple heating plate assemblies 22 are connected between the chains on both sides.

[0053] The heating plate assembly 22 is made of high-temperature resistant material and is treated to be waterproof and prevent it from being viewed from above.

[0054] In use, the heating plate assembly 22 rotates with the sprocket and chain drive component 21 to circulate and heat the inside of the oven body 1. The heating speed is fast and the heating is uniform, which can improve the drying efficiency of the film.

[0055] In this technical solution, the pretreatment unit is used to squeeze and scrape water from the membrane to initially remove liquid from the membrane body and surface. The auxiliary unit circulates and dries the air inside the oven body 1.

[0056] The pretreatment unit includes a liquid collection tank 4, which is located above the movable heating component 2. The two sides of the liquid collection tank 4 are connected to the inner wall of the oven body 1, respectively. A conduction component 5 and an extrusion component 6 are arranged above the liquid collection tank 4, and the membrane passes through the space between the conduction component 5 and the extrusion component 6. Two symmetrically distributed lower wiper components 7 are provided below the membrane body. The two sides of the lower wiper components 7 are connected to the inner wall of the collection tank 4. An upper wiper component 8 is provided above the membrane body. The upper wiper component 8 is located in the middle of the two lower wiper components 7. The lower wiper components 7 and the upper wiper component 8 are in contact with the lower surface and the upper surface of the membrane body, respectively.

[0057] A drain pipe assembly is installed on one side of the liquid collection tank 4, and the end of the drain pipe assembly away from the liquid collection tank 4 extends to the outside of the oven body 1.

[0058] The drain pipe assembly is used to drain the liquid collected in the collection tank 4.

[0059] In this technical solution, the membrane is squeezed and scraped by the pretreatment unit to initially remove the liquid inside and on the surface of the membrane.

[0060] In use, the membrane first enters the oven body 1, then passes through the first control component 9, the conduction component 5, the extrusion component 6, and the second control component 9 in sequence, and then exits the oven body 1, so that the membrane is conveyed within the oven body 1. During the conveying process, the conduction component 5 guides and changes the conveying direction of the membrane to facilitate subsequent squeezing and scraping operations. At the same time, as the membrane is conveyed, the extrusion component 6 squeezes the membrane to squeeze out the liquid inside the membrane. The lower scraping component 7 and the upper scraping component 8 scrape the upper and lower surfaces of the membrane to initially remove excess liquid from the membrane.

[0061] The conductive assembly 5 includes two sets of double guide shaft groups 51, which are symmetrically distributed. Two symmetrically distributed first guide shafts 52 and two symmetrically distributed second guide shafts 53 are arranged between the two sets of double guide shaft groups 51. The surfaces of the double guide shaft groups 51, the first guide shafts 52 and the second guide shafts 53 are rotatably connected to the side of the liquid collection tank 4, and the two ends of the double guide shaft groups 51, the first guide shafts 52 and the second guide shafts 53 are rotatably connected to the inner wall of the oven body 1.

[0062] The dual guide shaft assembly 51 consists of two shafts, one above the other.

[0063] In this technical solution, the conductive component 5 is used to guide the membrane during transport.

[0064] The extrusion assembly 6 includes a first extrusion roller 61 and a second extrusion roller 62. Two symmetrically distributed first extrusion rollers 61 are arranged in contact above the film body, and two symmetrically distributed second extrusion rollers 62 are arranged below the film body. A first extrusion roller 61 and a second extrusion roller 62 form a set of extruders. The surfaces of the first extrusion roller 61 and the second extrusion roller 62 are rotatably connected to the side of the liquid collection tank 4, and the two ends of the first extrusion roller 61 and the second extrusion roller 62 are rotatably connected to the inner wall of the oven body 1. A water-absorbing sponge pad 63 is provided below the conduction component 5 and the extrusion component 6, and the bottom of the water-absorbing sponge pad 63 is connected to the top of the extrusion orifice plate 64.

[0065] In this technical solution, the liquid inside the membrane is squeezed out by the extrusion component 6.

[0066] In use, the membrane passes between the first extrusion roller 61 and the second extrusion roller 62. At this time, the first extrusion roller 61 and the second extrusion roller 62 squeeze the membrane to squeeze out the liquid inside the membrane. The squeezed liquid is absorbed by the absorbent sponge pad 63.

[0067] The lower wiper assembly 7 includes a lower wiper blade 71. The upper end of the lower wiper blade 71 contacts the lower surface of the membrane. Adaptive strips 72 are connected to both sides of the lower wiper blade 71. The adaptive strips 72 are slidably connected to the surface of the anti-detachment shaft 73. The bottom end of the anti-detachment shaft 73 is connected to the top of the mounting strip 74. The two ends of the mounting strip 74 are respectively connected to the inner wall of the liquid collection tank 4. Multiple elastic connectors 75 connect the lower wiper blade 71 and the mounting strip 74; An abutment shaft 76 is provided above the lower scraper 71. The abutment shaft 76 contacts the top surface of the membrane. The surface of the abutment shaft 76 is rotatably connected to the side of the liquid collection tank 4. Both ends of the abutment shaft 76 are rotatably connected to the inner wall of the oven body 1.

[0068] The anti-detachment shaft 73 has a T-shaped cross-section.

[0069] In this technical solution, the water on the lower surface of the oven body 1 is scraped off by the lower scraper assembly 7.

[0070] As the membrane moves and is conveyed, the upper part of the lower scraper 71 contacts the lower surface of the membrane using the elastic connector 75 and other structures. The lower scraper 71 scrapes away the liquid on the lower surface of the membrane, and the scraped liquid drips down and is absorbed by the absorbent sponge pad 63.

[0071] The upper wiper assembly 8 includes two upper wiper blades 81 distributed on the left and right. Each of the two upper wiper blades 81 is connected to a movable connecting plate 82 at the top. The two movable connecting plates 82 are respectively threaded to the surfaces of two wiper threaded shafts 83. Each of the two wiper threaded shafts 83 is connected to a side gear 84 at one end. The two side gears 84 are respectively meshed with the two sides of the middle gear 85. The middle gear 85 is connected to the output end of the wiper power source 86. The wiper power source 86 is installed on the inner wall of the protective housing 87. The protective housing 87 is connected to the outside of the liquid collection tank 4. The inner wall of the liquid collection tank 4 is connected with multiple anti-deviation rails 88, and the surface of the anti-deviation rails 88 is slidably connected to the movable connecting plate 82.

[0072] The two ends of the scraper threaded shaft 83 are rotatably connected to the two sides of the liquid collection tank 4.

[0073] In this technical solution, the upper scraper assembly 8 is used to scrape off the liquid on the upper surface of the membrane.

[0074] In use, the wiper power source 86 drives the central gear 85 to rotate, which in turn drives the side gears 84 on both sides to rotate. When the side gears 84 rotate, they drive the corresponding wiper thread shafts 83 to rotate. When the wiper thread shafts 83 rotate, they drive the movable connecting plate 82 to move along the anti-deviation track 88, which in turn drives the upper wiper plate 81 to move in the same direction. The upper wiper plate 81 is used to scrape off the liquid on the upper surface of the membrane. The scraped liquid drips down and is absorbed by the absorbent sponge pad 63. In use, the upper wiper blades 81 at the two wiper thread shafts 83 move in opposite directions, and the two upper wiper blades 81 moving alternately can more thoroughly scrape the liquid off the upper surface of the membrane.

[0075] The preprocessing unit also includes two control components 9, which are located on the left and right sides of the conduction component 5, respectively. The control component 9 includes a fixed frame 91, the top side of which is connected to the top of the oven body 1. Two symmetrically distributed control threaded shafts 92 are rotatably connected to the inner cavity of the fixed frame 91, and the upper ends of the two control threaded shafts 92 are connected to the synchronous component 10 for transmission. The surface of the adjusting threaded shaft 92 is threaded with an adjusting slider 93. One side of the adjusting slider 93 is slidably connected to the side of the fixed frame 91. The side of the adjusting slider 93 away from the fixed frame 91 is connected to a follower side plate 94. Two adjusting shafts 95 are symmetrically distributed on one side of the follower side plate 94. The membrane passes between the two adjusting shafts 95.

[0076] In this technical solution, the tension of the membrane is adjusted during the transport of the membrane by the control component 9 and the synchronization component 10.

[0077] The fixed frame 91 has an inverted U-shaped cross-section, and sliding openings are provided on both inner sides of the fixed frame 91. One side of the adjusting slider 93 is slidably connected to the inner side of the fixed frame 91 through the sliding opening.

[0078] Multiple positioning rails 96 are connected to the inner wall of the fixed frame 91, and the surface of the positioning rails 96 is slidably connected to the control slider 93.

[0079] The inner wall of the fixed frame 91 is connected to two symmetrically distributed fixed plates 97. The surface of the adjusting threaded shaft 92 is rotatably connected to the fixed plate 97. The top of the positioning track 96 is connected to the bottom of the fixed plate 97.

[0080] When the control slider 93 moves, it moves along the positioning track 96. The positioning track 96 limits the movement trajectory of the control slider 93, making the movement of the control slider 93 more stable.

[0081] The synchronization component 10 includes two transmission sprockets 101, which are respectively connected to the surface of the regulating threaded shaft 92. The lower end of the regulating threaded shaft 92 is rotatably connected to the inner wall of the fixed frame 91. The sides of the two transmission sprockets 101 are meshed with the transmission chain 102. The two transmission sprockets 101 are connected by transmission through the transmission chain 102. One of the adjusting threaded shafts 92 has a driven gear 103 connected to its surface. The side of the driven gear 103 meshes with the side of the driving gear 104. The driving gear 104 is connected to the output end of the synchronous drive source 105, which is mounted on the inner wall of the fixed frame 91.

[0082] In use, the synchronous drive source 105 drives the drive gear 104 to rotate, which in turn drives the driven gear 103 to rotate, which in turn drives the corresponding regulating threaded shaft 92 to rotate, which in turn drives the corresponding transmission sprocket 101 to rotate. At this time, the transmission chain 102 rotates, which in turn drives another transmission sprocket 101 to rotate, which in turn drives another regulating threaded shaft 92 to rotate, so that the two regulating threaded shafts 92 can rotate simultaneously. When the control threaded shaft 92 rotates, it drives the control slider 93 to move along the positioning track 96, thereby driving the follower side plate 94 to move in the same direction, and then driving the control shaft 95 to move in the same direction. The tension of the membrane during conveying can be adjusted by adjusting the height of the control shafts 95 on the left and right sides.

[0083] A collection component 11 is provided above the absorbent sponge pad 63. The collection component 11 includes a mounting housing 111, which is connected to the outside of the liquid collection tank 4. A collection power source 112 is installed in the inner cavity of the mounting housing 111. A rotary drive shaft 113 is connected to the output end of the collection power source 112. The end of the rotary drive shaft 113 away from the collection power source 112 is rotatably connected to the inner wall of the mounting housing 111. Multiple first bevel gears 114 are connected to the surface of the rotary transmission shaft 113. Second bevel gears 115 are respectively meshed with the sides of the multiple first bevel gears 114. Each side of the multiple second bevel gears 115 is connected to a squeezing eccentric wheel 116. The surface of the squeezing eccentric wheel 116 is in contact with the top surface of the water-absorbing sponge pad 63. One end of the squeezing eccentric wheel 116 is rotatably connected to the inner wall of one side of the liquid collection tank 4, and the other end is rotatably connected to the other side of the liquid collection tank 4.

[0084] During use, the absorbent sponge pad 63 absorbs the liquid extruded by the first extrusion roller 61 and the second extrusion roller 62, as well as the liquid scraped out by the lower scraper assembly 7 and the upper scraper assembly 8, to prevent the liquid from splashing back onto the membrane when it drips, and to prevent it from affecting the effect of the extrusion assembly 6 and the lower scraper assembly 7 on the removal of liquid from the membrane. When the absorbent sponge pad 63 absorbs liquid, the power source 112 drives the rotary transmission shaft 113 to rotate, which in turn drives multiple first bevel gears 114 to rotate, which in turn drives the corresponding second bevel gears 115 to rotate, thereby driving the corresponding extrusion eccentric wheel 116 to rotate. The extrusion eccentric wheel 116, together with the extrusion orifice plate 64, extrudes the absorbent sponge pad 63, squeezes out the liquid absorbed by the absorbent sponge pad 63, and collects it in the lower part of the inner cavity of the liquid collection tank 4.

[0085] The auxiliary unit includes two drying components 12, each of which includes a drying chamber 121 connected to the outside of the oven body 1. A maintenance door is installed on the side of the drying oven 121 away from the main body of the oven 1.

[0086] A circulating fan 122 is installed on one side of the drying oven 121, and the outlet end of the circulating fan 122 is connected to the inner cavity of the drying oven 121. The inlet end of the circulating fan 122 is connected to an inlet pipe 123. The end of the inlet pipe 123 away from the circulating fan 122 is connected to the top of the oven body 1. The inner cavity of the circulating fan 122 is connected to the inner cavity of the oven body 1. A circulating pipe 124 is connected to the top of the drying oven 121. The end of the circulating pipe 124 away from the drying oven 121 is connected to the top of the oven body 1. The inner cavity of the oven body 1 and the inner cavity of the drying oven 121 are connected through the circulating pipe 124. The inner wall of the drying oven 121 is connected to two symmetrically distributed partition plates 125. The partition plate 125 near the circulating fan 122 has an upper connecting port on its upper side, and the partition plate 125 near the circulating pipe 124 has a lower connecting port on its lower side. The inner wall of the drying chamber 121 and the side of the partition plate 125 are connected to two symmetrically distributed disassembly rails 126. A moisture-absorbing drying core 127 is slidably arranged inside the disassembly rails 126. The top and bottom surfaces of the moisture-absorbing drying core 127 are slidably connected to the two disassembly rails 126.

[0087] The installation of the disassembly rail 126 allows the moisture-absorbing drying core 127 to be maintained and replaced.

[0088] In use, the circulating fan 122 makes the airflow circulate between the oven body 1, the inlet pipe 123, the drying chamber 121, and the circulating pipe 124. When the airflow enters the drying chamber 121, it passes through three moisture-absorbing drying cores 127 in sequence under the separation of the partition plate 125. The moisture-absorbing drying cores 127 absorb moisture and dry the airflow. The moisture-absorbing and dried airflow is then sent into the oven body 1. This avoids the direct discharge of hot air with moisture, which would cause the temperature inside the oven body 1 to drop. This makes the temperature inside the oven body 1 more stable, reduces heat loss, and makes the drying equipment more energy-efficient.

[0089] The wiper power source 86, synchronous drive source 105, and power collection source 112 are motor sets or other devices that can output rotational kinetic energy.

[0090] The elastic connector 75 is a spring or other component with elastic reset function.

[0091] While specific embodiments of the present invention have been described above, those skilled in the art should understand that these are merely illustrative examples, and the scope of protection of the present invention is defined by the appended claims. Those skilled in the art can make various changes or modifications to these embodiments without departing from the principles and essence of the present invention, but all such changes and modifications fall within the scope of protection of the present invention.

Claims

1. A process for producing a nanofiltration membrane for lithium extraction from salt lakes, characterized in that: The production process comprises the following operation steps: Step one, preparation of the base film, using a film scraping device to scrape a thin liquid film on the support body, then immersing the support body with the thin liquid film into a non-solvent to make the polymer precipitate to form a porous film with a microporous structure, then cleaning and drying to obtain the base film; Step two, preparation of the separation functional layer, first immersing the base film obtained in step one into an aqueous phase solution, then taking out and removing excess liquid drops, then immersing into an oil phase solution, at this time, a cross-linked network structure is formed through interfacial polymerization, then the network structure is heated and solidified, then cleaned to obtain a nanofiltration membrane sheet semi-finished product; Step three, post-treatment and modification, modifying the nanofiltration membrane sheet semi-finished product obtained in step two according to functional requirements to obtain a nanofiltration membrane sheet finished product; Step four, assembly of the roll-type membrane element, cutting the nanofiltration membrane sheet finished product into the required size according to the designed width, then laying the separation net, then coating glue, then sequentially rolling, end cap packaging and processing to complete the assembly.

2. The process for producing a nanofiltration membrane for lithium extraction from salt lakes according to claim 1, characterized in that: The specific operation steps of step one are: S1, casting solution preparation, dissolving the polymer in a strong polar solvent to form a uniform transparent solution; S2, film scraping, using a precision scraper to scrape a thin liquid film with a specific thickness on the support body; S3, coagulation bath, immersing the support body with the liquid film into a non-solvent bath, the solvent and the non-solvent diffuse with each other, causing the polymer to precipitate from the homogeneous solution to form a porous film with a microporous structure; S4, post-treatment, cleaning and drying the porous film obtained in step S3 to obtain the base film.

3. The process for producing a nanofiltration membrane for lithium extraction from salt lakes according to claim 1, characterized in that: The specific operation steps of step two are: A1, immersing the aqueous phase solution, immersing the prepared base film into an aqueous solution containing an aqueous phase monomer; A2, removing excess liquid drops, taking out the base film and removing the excess aqueous phase solution on the surface by using a rubber roller or nitrogen blowing to ensure that only the micropores of the base film adsorb the aqueous phase monomer; A3, immersing the oil phase solution, immersing the base film with the aqueous phase monomer into an organic solution containing an oil phase monomer; A4, interfacial polymerization, the aqueous phase monomer and the oil phase monomer instantaneously polymerize on the water-oil interface to generate a cross-linked network structure film; A5, post-treatment, taking out the above film, heating and solidifying, then washing with water to remove unreacted monomers and by-products to obtain a nanofiltration membrane sheet semi-finished product.

4. The process for producing a nanofiltration membrane for lithium recovery from salt lakes according to claim 1, characterized in that: The heating and solidification in step two is performed by using a drying equipment, the drying equipment comprises a drying oven main body (1) and a movable heating assembly (2), the movable heating assembly (2) is installed at the inner cavity of the drying oven main body (1), the drying oven main body (1) is composed of multiple segments, which are an entering segment, a preheating segment, a transition segment, a drying segment and an outlet segment, and an electric door group (3) is installed between adjacent two segments; The drying equipment further comprises a pretreatment unit and an auxiliary unit, the pretreatment unit is arranged above the movable heating assembly (2), and the pretreatment unit is arranged in the preheating segment of the drying oven main body (1), the auxiliary unit is arranged outside the drying oven main body (1) and communicates with the inner cavity of the drying segment of the drying oven main body (1); The preprocessing unit is used for extruding and water scraping operation of the film body which needs to be heated and solidified, and preliminarily removing the liquid on the film body; The auxiliary unit is used for circulating the air in the oven body (1) and drying the air during the circulation.

5. The process for producing a nanofiltration membrane for lithium extraction from salt lakes according to claim 4, characterized by the fact that: The preprocessing unit includes a liquid collecting tank (4) which is arranged above the moving heating assembly (2), and the two sides of the liquid collecting tank (4) are connected with the inner wall of the oven body (1), and the upper part of the liquid collecting tank (4) is provided with a conduction assembly (5) and an extrusion assembly (6), and the film body passes between the conduction assembly (5) and the extrusion assembly (6). The lower part of the film body is provided with two symmetrically distributed lower water scraping assemblies (7), the two sides of the lower water scraping assembly (7) are connected with the inner wall of the liquid collecting tank (4), and the upper part of the film body is provided with an upper water scraping assembly (8), the upper water scraping assembly (8) is arranged at the middle position of the two lower water scraping assemblies (7), and the lower water scraping assembly (7) and the upper water scraping assembly (8) are respectively connected with the lower surface and the upper surface of the film body.

6. The process for producing a nanofiltration membrane for lithium extraction from salt lakes according to claim 5, characterized by the fact that: The conduction assembly (5) includes two groups of double guide shaft groups (51), the two groups of double guide shaft groups (51) are symmetrically distributed, and the positions between the two double guide shaft groups (51) are provided with two symmetrically distributed first guide shafts (52) and two symmetrically distributed second guide shafts (53), the surfaces of the double guide shaft groups (51), the first guide shaft (52) and the second guide shaft (53) are respectively rotatably connected with the side of the liquid collecting tank (4), and the two ends of the double guide shaft groups (51), the first guide shaft (52) and the second guide shaft (53) are rotatably connected with the inner wall of the oven body (1).

7. The process for producing a nanofiltration membrane for lithium extraction from salt lakes according to claim 5, characterized by the fact that: The extrusion assembly (6) includes a first extrusion roller (61) and a second extrusion roller (62), the upper part of the film body is provided with two symmetrically distributed first extrusion rollers (61), the lower part of the film body is provided with two symmetrically distributed second extrusion rollers (62), and one first extrusion roller (61) and one second extrusion roller (62) form a group of extruders. The surfaces of the first extrusion roller (61) and the second extrusion roller (62) are respectively rotatably connected with the side of the liquid collecting tank (4), and the two ends of the first extrusion roller (61) and the second extrusion roller (62) are rotatably connected with the inner wall of the oven body (1). The lower part of the conduction assembly (5) and the extrusion assembly (6) is provided with a water absorbing sponge pad (63), and the bottom of the water absorbing sponge pad (63) is connected with the top of the extrusion hole plate (64).

8. The process for producing a nanofiltration membrane for lithium recovery from salt lakes according to claim 5, characterized by the fact that: The lower water scraping assembly (7) includes a lower water scraping plate (71), the upper end of the lower water scraping plate (71) is in contact with the lower surface of the film body, the two sides of the lower water scraping plate (71) are connected with an adaptive strip (72), the adaptive strip (72) is slidably connected with the surface of an anti-coming-off shaft (73), the bottom end of the anti-coming-off shaft (73) is connected with the top of a mounting strip (74), and the two ends of the mounting strip (74) are respectively connected with the inner wall of the liquid collecting tank (4). A plurality of elastic connecting pieces (75) are connected between the lower water scraping plate (71) and the mounting strip (74). The lower wiper plate (71) is provided with an abutting shaft (76) above it, the abutting shaft (76) is in contact with the top surface of the film body, the surface of the abutting shaft (76) is rotatably penetrated and connected with the side surface of the liquid collecting tank (4), and the both ends of the abutting shaft (76) are rotatably connected with the inner wall of the oven main body (1).

9. The process for producing a nanofiltration membrane for lithium recovery from salt lakes according to claim 5, characterized by the fact that: The upper wiper assembly (8) comprises two upper wiper plates (81) distributed left and right, and the top of each of the two upper wiper plates (81) is connected with a moving connecting plate (82), and the surface of each of the two moving connecting plates (82) is threadedly connected with a wiper threaded shaft (83); One end of each of the two wiper threaded shafts (83) is connected with a side gear (84), and the two side gears (84) are meshingly connected with the two sides of a middle gear (85), the middle gear (85) is connected with the output end of a wiper power source (86), the wiper power source (86) is mounted on the inner wall of a protective shell (87), and the protective shell (87) is connected with the outer side of the liquid collecting tank (4); The inner wall of the liquid collecting tank (4) is connected with a plurality of anti-deviation tracks (88), and the surface of the anti-deviation track (88) is slidably penetrated and connected with the moving connecting plate (82).

10. The process for producing a nanofiltration membrane for lithium recovery from salt lakes as claimed in claim 5, characterized by the fact that: The pretreatment unit further comprises two regulating assemblies (9), and the two regulating assemblies (9) are respectively located on the left and right sides of the conducting assembly (5); The regulating assembly (9) comprises a fixed frame shell (91), the top side of the fixed frame shell (91) is connected with the top of the oven main body (1), and the inner cavity of the fixed frame shell (91) is rotatably connected with two symmetrically distributed regulating threaded shafts (92), and the upper end of each of the two regulating threaded shafts (92) is drivingly connected with a synchronous assembly (10); The surface of the regulating threaded shaft (92) is threadedly connected with a regulating sliding block (93), one side of the regulating sliding block (93) is slidably penetrated and connected with the side surface of the fixed frame shell (91), and the side of the regulating sliding block (93) away from the fixed frame shell (91) is connected with a follow-up side plate (94), one side of the follow-up side plate (94) is rotatably connected with two regulating rotating shafts (95) symmetrically distributed above and below, and the film body passes between the two regulating rotating shafts (95).

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