A spiral-wound membrane element and a method of making the same

Abstract

The application discloses a kind of spiral membrane element and its preparation method, the spiral membrane element includes spiral layer structure and water collection center pipe, the spiral layer structure includes water production flow channel cloth, first membrane, concentrated water flow channel cloth and second membrane, the water collection center pipe is placed between the water production flow channel cloth and the first or second membrane, the water collection center pipe is directly contacted with the first or second membrane and is fused;The water production flow channel cloth is placed between the first membrane and the second membrane, the upper and lower surfaces of the water production flow channel cloth respectively include first edge, second edge and third edge not provided with water collection center pipe, the first edge, second edge and third edge of the upper and lower surfaces of the water production flow channel cloth are directly contacted with the first membrane and the second membrane and are fused to form water production membrane bag.The spiral membrane element of the application has narrower connection area than traditional membrane element, and can obtain larger effective membrane use area under fixed shape.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of roll type membrane element and its preparation method. BACKGROUND

[0002] The roll type membrane element is the most widely used membrane element structure in the market. The roll type membrane element is a multilayer structure, including the concentration water channel cloth, the membrane sheet, the water production channel cloth, which are sequentially superimposed and rolled in the central water collecting pipe. The raw water is made to pass through the membrane sheet by external driving force, and then collected to the central pipe from the water production channel cloth to form water production.

[0003] However, the rolling process of the roll type membrane element is carried out by using a membrane rolling machine. First, the prepared membrane sheet, concentration water channel cloth and water production channel cloth are placed at the specified positions respectively, and then the other three ends of the folded membrane sheet connected with the water collecting pipe are sealed by using sealing glue to form a membrane bag for collecting water production, and then rolled together to form a membrane element. The traditional process has the following disadvantages: ① The glue coating process generally controls the width of the glue coating by controlling the amount of glue coating, the line of glue coating and the force of glue pressing. This requires high operation requirements for each link of the glue coating process. Therefore, it is difficult to accurately control the glue coating edge width of the membrane element. The glue coating width of the membrane element on the market is at least more than 2 cm to ensure that the membrane element will not leak during use, but this also wastes a large amount of membrane area and indirectly increases the raw material cost of production; ② The sealing glue used is a special AB glue, which needs to be prepared and used immediately, needs to accurately control the ratio of A glue and B glue, and the glue storage is very troublesome, especially the A glue is easy to absorb moisture and solidify at room temperature, which generally needs to be stored at low temperature or filled with nitrogen; ③ The glue needs at least 1-2 days to solidify, which prolongs the production cycle; ④ The connection between the water collecting central pipe and the membrane sheet also uses glue connection. In order to ensure that the water production side does not mix fresh water and concentrated water, the traditional process generally needs a large amount of glue coating at the central pipe; ⑤ The glue has the risk of releasing harmful substances, which has potential harm to operators, users and the environment.

[0004] At present, there are some improved methods for making spiral-wound membranes. CN 105479732.B "RO membrane center tube and gauze bonding mechanism" proposes a method combining ultrasonic welding with spiral bonding technology. The RO membrane center tube is first welded together with the gauze using ultrasonic welding, and then the gauze is wound on the center tube using the bonding technology. This method is complicated and requires the simultaneous use of welding and spiral bonding methods. CN 207081071.B "A method for making a spiral-wound membrane element" is divided into three steps. First, the membrane sheet material is welded to the center tube. Then, the membrane material is welded along the edge line to form a membrane bag. Finally, the membrane bag is wound on the center tube. This method is complicated, requires pre-bending of the membrane sheet material in step S20, requires the use of two sets of welding heads, and the first and second welding heads must be adapted to the shape and size of the center tube and the membrane element. Once the size of the center tube and the membrane element changes, the welding heads need to be re-made, resulting in high production costs. The welding heads are curved and difficult to process. The ultrasonic welding method is difficult to achieve a completely smooth welding surface, and in actual operation, the ultrasonic energy is easily concentrated due to the protruding defects on the welding surface, resulting in accidental penetration of the welding surface and causing leakage points. SUMMARY

[0005] To solve the above technical problems, the purpose of the present application is to provide a spiral-wound membrane element and a method for making the same.

[0006] The present application is implemented by the following technical solutions: a spiral-wound membrane element, comprising a spiral-wound layered structure and a water collection center tube arranged in the center of the spiral-wound layered structure, the spiral-wound layered structure being wound outside the water collection center tube, the front end of the spiral-wound membrane element being the water inlet end, the rear end of the spiral-wound membrane element being the water production end and the concentrated water end, the spiral-wound layered structure comprising a water production channel cloth, a first membrane sheet, a concentrated water channel cloth and a second membrane sheet, the water collection center tube being placed between the water production channel cloth and the first or second membrane sheet, the water collection center tube being in direct contact and fusion with the first or second membrane sheet; the water production channel cloth being placed between the first membrane sheet and the second membrane sheet, the upper and lower surfaces of the water production channel cloth respectively comprising a first edge, a second edge and a third edge without the water collection center tube, the first edge, the second edge and the third edge of the upper and lower surfaces of the water production channel cloth being in direct contact and fusion with the first membrane sheet and the second membrane sheet to form a water production membrane bag.

[0007] Preferably, a desalination layer is arranged on the side of the membrane sheet facing the concentrated water channel cloth, and a water guide layer is arranged on the side of the membrane sheet facing the water production channel cloth.

[0008] Preferably, the welding edge line width of the first edge, the second edge or the third edge is between 10-25000 μm.

[0009] The present invention also provides a method for preparing a wound membrane element, comprising the following steps:

[0010] S10, rolling a first membrane sheet, a produced water flow cloth, a second membrane sheet, a concentrated water flow cloth, and a metal wire arranged at a position to be welded, for forming at least one membrane bag, onto the water collecting pipe;

[0011] S20, heating the metal wire by a welding device to melt the polymer material at the welding point of the two materials to be welded, and welding the two materials to be welded to form a membrane element.

[0012] Preferably, before step S10, the method further includes step 1, folding the diaphragm in half to form an n-shape, thereby forming a first diaphragm and a second diaphragm; step 2, placing a water production flow cloth, a concentrated water flow cloth and a water collection center pipe on the folded diaphragm; and step 3, arranging metal wires on the first side, the second side and the third side of the water production flow cloth, and extending and winding them onto the water collection center pipe.

[0013] Preferably, in the step 2, the water collecting central pipe is placed between the first membrane and the water production flow channel cloth, or between the water production flow channel cloth and the second membrane.

[0014] Preferably, after step S20, the method further includes: step 1, pulling the metal wire out of the rolled membrane element; step 2, wrapping a waterproof tape or a waterproof coating around the rolled membrane element; and step 3, providing a waterproof sealing ring around the rolled membrane element.

[0015] Preferably, the material of the metal wire is an alloy of one or more metals such as copper, aluminum, iron or nickel, the outer layer of the metal wire is covered with Teflon, the width of the metal wire is 10-20000 μm, the thickness is 10-1000 μm, and the length is the sum of the welding lengths of the first side, the second side and the third side of the water-producing flow channel cloth in the membrane bag and the length extended and wound on the water collection center pipe.

[0016] Preferably, the welding is polymer welding, including a metal wire electric heating method or a metal wire electromagnetic induction heating method.

[0017] Preferably, the welding device is a power supply device for connecting the metal wire to industrial electricity or a high-frequency electromagnetic induction coil device for connecting the metal wire to industrial electricity.

[0018] Preferably, in step S20, the width of the welding edge of the two materials to be welded is between 10-25000 μm.

[0019] Preferably, the welding is performed by heating the metal wire to melt the polymer material at the welding point, and after the polymer material cools down, atomic diffusion occurs in the material between the welding surfaces, and the welded polymer materials are connected by chemical bonds.

[0020] Preferably, the welding temperature is not higher than 230°C.

[0021] Preferably, the material of the membrane is a low melting point polymer material such as cellulose acetate, cellulose acetate ester, polyethylene, polysulfone, polyamide, aromatic polyamide, aromatic polyamide-hydrazide and some nitrogen-containing aromatic polymers.

[0022] Preferably, the material of the water-producing channel cloth is PP polypropylene-based low-melting-point polymer material.

[0023] Preferably, the material of the concentrated water flow cloth is PET thermoplastic polyester high melting point polymer material.

[0024] Preferably, the material of the water collecting central tube is ABS plastic.

[0025] The application of the preparation method of the present invention to the preparation of a rolled film element has the following beneficial effects:

[0026] 1. The wound membrane element of the present invention has a narrower edge welding connection area than traditional membrane elements, which can obtain a larger effective membrane usage area while maintaining a fixed shape. The present invention directly welds the diaphragm to the water collection center pipe and the water production channel cloth to the diaphragm to form a new wound membrane element structure. This eliminates the need for glue connection as in traditional methods and can reduce the width of the diaphragm edge connection area, greatly increasing the effective filtration area of ​​the diaphragm, thereby improving the filtration efficiency of the wound membrane element and enhancing its practicality.

[0027] 2. Using the polymer welding method, the range of the metal wire heating is the welding area of ​​the welding material (that is, the welding area refers to the area where the welding metal wire is arranged or the welding edge). The width of the welding edge of each membrane bag of the membrane element can be accurately controlled. Under the condition of fixed membrane element dimensions, the effective membrane area is greatly increased, and the production cost of the membrane element is reduced.

[0028] 3. By adopting the polymer welding method, the edge welding of the membrane bag can be completed quickly in a short time, with a typical welding time of less than 30 seconds, which greatly shortens the production cycle of the membrane element. Compared with the existing connection method, the water collection center tube and the membrane of the present invention are connected by polymer welding, which makes the connection uniformity and connection strength of each membrane roll surface high, and does not produce the problems of excessive material and excessive thickness at the connection between the center tube and the membrane during the membrane rolling process in the prior art. At the same time, it can meet the curvature requirements of the membrane during the membrane rolling process, will not cause damage to the membrane, and improve the product yield.

[0029] 4. Polymer welding generally regulates the weld strength of the weld surface by controlling the welding temperature and welding pressure. In this technical solution, the welding temperature is controlled by the material, cross-sectional area, channel current, and induced current frequency of the metal wire. The welding pressure is controlled by the tension between the fabrics during the membrane element rolling process and the fixing force of the waterproof coating or tape after rolling. Therefore, the membrane element rolling and material welding of this technical solution are completed simultaneously, thereby reducing the operation steps.

[0030] 5. The welding of multiple membrane bags can be completed at the same time, shortening the production cycle of membrane elements.

[0031] 6. Using polymer welding method, the polymer material is first melted and then cooled and solidified. The connection between the welding materials is a chemical bond connection, which is fast, strong and permanent.

[0032] 7. Metal wire is used as the welding element. The metal wire has good deformability and can deform along with the membrane element during the rolling process. It can adapt well to the bending and displacement changes between the diaphragms. No matter how the outer dimensions of the membrane element change, it can adapt well. There is no need to adjust the fixture or welding head and other adapter components like other process methods.

[0033] 8. There is a certain time difference between the melting and cooling of polymer materials, typically within 30 seconds. Therefore, when the membrane element is rolled and the polymer material to be welded inside the membrane element has melted but has not yet cooled, the metal wire can be quickly pulled out of the membrane element. The surface of the metal wire is coated with Teflon, which is resistant to high temperatures and does not adhere to materials. Therefore, the metal wire can be reused, reducing production costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the technical solution of the present invention, the following briefly introduces the drawings required for use in the embodiments or descriptions of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0035] Figure 1 This is a schematic diagram of the appearance structure of the rolled membrane element provided according to the first embodiment of the present application.

[0036] Figure 2 This is a process flow chart for preparing a rolled membrane element according to the first embodiment of the present application.

[0037] Figure 3 This is a schematic diagram of the internal structure of a rolled membrane element provided according to the first embodiment of the present application.

[0038] Figure 4This is a process flow chart for preparing a spiral membrane element according to the second embodiment of the present application.

[0039] Figure 5 This is a schematic diagram of the internal structure of a roll-type membrane element provided according to the second embodiment of the present application. DETAILED DESCRIPTION

[0040] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0041] Reference Manual Figure 1 A rolled membrane element comprises a rolled layered structure, a water collecting central pipe (6) arranged in the center of the rolled layered structure, and a waterproof sealing accessory arranged on the outside of the rolled layered structure. The rolled layered structure is wound around the outside of the water collecting central pipe (6). The front end of the rolled membrane element is a water inlet end (7), and a sealing ring (5) is arranged near the water inlet end. The rear end of the rolled membrane element is a water production end (8) and a concentrated water end (9). The rolled layered structure comprises a water production flow channel cloth (4), a first membrane The membrane (2), the concentrated water flow cloth (1) and the second membrane (3), the water collecting center pipe (6) is placed between the first membrane (2) and the produced water flow cloth (4), or between the produced water flow cloth (4) and the second membrane (3); a desalination layer is set on the side of the first membrane (2) facing the concentrated water flow cloth (1), and a water guide layer is set on the side of the first membrane (2) facing the produced water flow cloth (4), and the rolled layer structure is wound around the water collecting center pipe (6). ), the upper and lower surfaces of the water-producing duct cloth (4) respectively include a first side (41), a second side (42) and a third side (43) where a water collecting center pipe is not provided, the first side (41), the second side (42) and the third side (43) of the upper surface of the water-producing duct cloth (4) are directly in contact with and welded to the first diaphragm (2), and the first side (41), the second side (42) and the third side (43) of the lower surface of the water-producing duct cloth (4) are directly in contact with and welded to the second diaphragm (3), and at the same time, the water-producing duct cloth (4) is directly in contact with and welded to the second diaphragm (3). The water flow channel cloth (4) is also directly contacted and welded with the welding area of ​​the water collection center pipe (6), that is, the first side, the second side and the third side of the upper and lower surfaces of the water production channel cloth (4) are directly contacted and welded with the relative contact surfaces of the first diaphragm (2) and the second diaphragm (3) in a glue-free manner, and are connected with the welding area of ​​the water collection center pipe to form a single water production membrane bag. The surface of the water collection center pipe is provided with an axial through hole, and the through hole is connected with the water production side of the water production membrane bag and the water production end of the water collection center pipe.

[0042] Furthermore, the width of the welding edge of the first side (41), the second side (42) or the third side (43) is between 10-25000 μm.

[0043] Furthermore, a waterproof tape or a waterproof film may be wrapped around the rolled layered structure.

[0044] Furthermore, the number of membrane bags in the membrane element can be 1-30. Figure 4 In the embodiment shown in , the number of film bags stacked in sequence is 2. As the number of film bags increases, the film bags can be stacked in sequence on the central tube according to the schematic diagram of the accompanying drawings.

[0045] Furthermore, the first membrane or the second membrane is one of a reverse osmosis rolled membrane element, a nanofiltration rolled membrane element and an ultrafiltration rolled membrane element.

[0046] Furthermore, the first diaphragm (2) and the second diaphragm (3) are formed by folding the diaphragm in half, and the first diaphragm (2) and the second diaphragm (3) are folded in half to form an n-type state.

[0047] The rolled membrane element of the present invention directly welds the diaphragm to the water collection center pipe and the water production flow channel cloth to the diaphragm to form a new type of rolled membrane element structure. It does not need to use glue to connect as in the traditional method, and can reduce the width of the edge connection area of ​​the diaphragm, so that the effective filtration area of ​​the diaphragm is greatly increased, thereby improving the filtration efficiency of the rolled membrane element, reducing costs, and having strong practicality.

[0048] The preparation method of the spiral membrane element will be described in detail below.

[0049] First embodiment

[0050] Figure 2 This is a flow chart of the preparation process of the first type of rolled membrane element provided in the first embodiment of the present application.

[0051] Please refer to Figure 2 and Figure 3 In this embodiment, the preparation process of the spiral membrane element is achieved as follows:

[0052] Step S001, folding the membrane in half to form an n-type, forming a first membrane (2) and a second membrane (3);

[0053] Step S002, placing the water collection central pipe (6) between the first membrane (2) and the water production channel cloth (4);

[0054] Step S003, arranging the metal wire (A) on the first side (41), the second side (42), and the third side (43) of the water production channel cloth (4), and extending and winding the metal wire (A) onto the water collection central pipe (6);

[0055] Step S10, rolling the membrane sheet for forming the membrane bag, the produced water flow channel cloth (4), the concentrated water flow channel cloth (1) and the metal wire (A) arranged at the welding position onto the water collection central pipe (6);

[0056] Step S20, using a welding device to heat the metal wire (A) to melt the polymer material at the welding point of the two materials to be welded (i.e., the water production channel cloth and the membrane, or the membrane and the water collection center pipe), thereby connecting the two materials to be welded to form a membrane bag;

[0057] Step S301, extracting the metal wire from the rolled membrane element;

[0058] Step S302: Wrapping a waterproof tape or a waterproof film around the rolled membrane element;

[0059] Step S303: a waterproof sealing ring is provided outside the rolled membrane element.

[0060] In step S001, a first membrane (2) and a second membrane (3) are formed in a membrane folded in half to form an n-shaped membrane. Water-conducting layers are provided on the opposing surfaces of the first membrane (2) and the second membrane (3). A water production flow channel cloth (4) is sandwiched between the opposing first membrane (2) and the second membrane (3). A concentrated water flow channel cloth (1) is placed on the outside of the first membrane (2) or the outside of the second membrane (3). A desalination layer is provided on the outside of the first membrane and the outside of the second membrane.

[0061] In step S002, a water collecting central pipe is inserted into the bent folded membrane.

[0062] In step S003, the metal wires are respectively arranged on the first side (41), the second side (42) and the third side (43) of the upper and lower surfaces of the water production channel cloth, and are extended and wound on the water collection central pipe (6).

[0063] In step S10, the materials forming a single membrane bag are wound together on the water collecting central pipe (6) with the concentrated water flow channel cloth (1), the first membrane sheet (2), the produced water flow channel cloth (4), the second membrane sheet (3) and the metal wire (A) arranged on the produced water flow channel cloth from top to bottom; in step S10, the tension between the materials when the single membrane bag materials are wound on the water collecting central pipe should be controlled, which will affect the welding pressure in the subsequent welding process.

[0064] In step S20, the heating temperature of the metal wire is adjusted by adjusting the current, supply voltage, and / or electromagnetic induction frequency of the welding device, so that the polymer material on the welding surface is melted and then solidified and connected together after cooling. Before welding, some parameter calculations need to be prepared and calculated according to the calculation formula , where R is the resistance of the wire, C is the correction coefficient (set between 1 and 2), u is the voltage, t is the welding time (controlled within 30 seconds), m is the weight of the weld (set as weld cross-sectional area × weld length × weld density), C p is the specific heat capacity of the welding material, T is the initial temperature of the weld (set to room temperature 25 ℃), and T0 is the melting point of the weld; according to The resistance of the metal wire can be calculated, where ρ is the resistivity of the material selected for the metal wire, l is the length of the metal wire, and s is the cross-sectional area of ​​the metal wire; through the above two formulas, the welding voltage can be set according to the metal wire length and cross-sectional area, material, welding polymer material, etc. specified in the early stage; according to the above method, the present invention can conveniently achieve rapid welding for different welding polymer materials and different membrane element sizes.

[0065] The schematic diagram of the membrane element structure obtained by the rapid preparation method of the wound membrane element is shown in Figure 3 :

[0066] The membrane element includes a membrane bag. The materials forming a single membrane bag are, from top to bottom, concentrated water flow cloth, a first diaphragm, a water production flow cloth, and a second diaphragm, which are stacked and wound on the water collection center pipe in sequence; the first edge, the second edge and the third edge of the upper and lower surfaces of the water production flow cloth are connected to the diaphragm by the welding method, and the relative diaphragms bent on the water collection center pipe are connected to the water collection center pipe by the welding method, thereby forming an integrated envelope structure with the U-shaped folding position of the first diaphragm and the second diaphragm as the outlet, and the water production flow cloth is sandwiched in the middle and sealed on three sides. The water production side of the envelope is connected to the water production end of the water collection center pipe.

[0067] The material of the metal wire is one or an alloy of several metals such as copper, aluminum, iron or nickel. The outer layer of the metal wire is covered with Teflon. The width of the metal wire is 10-20000 μm, the thickness is 10-1000 μm, and the length is the sum of the welding lengths of the first side, the second side and the third side of the water production flow cloth in the membrane bag and the length extended and wound on the water collection center pipe.

[0068] The welding method refers to polymer welding, including wire heating by electrical current or electromagnetic induction. This method involves heating the wire to melt the polymer material at the weld. After the polymer material cools, atomic diffusion occurs between the weld surfaces, creating a chemical bond between the polymer materials. The welding temperature is no higher than 230°C.

[0069] The rapid preparation method of the rolled membrane element also includes the welding device being a power supply device externally connected to industrial electricity with a metal wire or a high-frequency electromagnetic induction coil device externally connected to industrial electricity.

[0070] The material of the membrane is low-melting-point high-molecular material such as cellulose acetate, cellulose acetate ester, polyethylene, polysulfone, polyamide, aromatic polyamide, aromatic polyamide-hydrazide and some nitrogen-containing aromatic polymers.

[0071] The material of the water production channel cloth is PP polypropylene low-melting-point high-molecular material.

[0072] The material of the concentrated water channel cloth is PET thermoplastic polyester high-melting-point high-molecular material.

[0073] The material of the water collection center pipe is ABS plastic.

[0074] Second embodiment

[0075] Figure 4 The process flow chart of the preparation method of the first type of roll-type membrane element provided in the second embodiment of the present application.

[0076] Please refer to Figure 4 and Figure 5 In the present embodiment, the preparation process of the roll-type membrane element is different from that of the first embodiment in that:

[0077] In step S002, the water collection center pipe is placed between the water production channel cloth and the second membrane.

[0078] The other steps are the same as those of the first embodiment, and will not be described here.

[0079] However, the operation details of some steps are not the same, which are listed as follows:

[0080] In step S001, the n-shaped membrane folded by folding is formed with a first membrane and a second membrane, the opposite surfaces of which are respectively provided with a desalination layer, and a concentrated water channel cloth is arranged between the opposite first membrane and second membrane, a water production channel cloth is placed outside the first membrane or outside the second membrane, and a water guide layer is arranged outside the first membrane and the second membrane.

[0081] In step S002, the water collection center pipe is placed on the folded and bent folded membrane, that is, between the water production channel cloth and the second membrane.

[0082] In step S003, the metal wires are arranged on the first edge, the second edge and the third edge of the upper and lower surfaces of the water production channel cloth, and are extended and wound on the water collection center pipe.

[0083] In step S10, the material forming the single membrane bag is wound on the water collection center pipe (6) together with the water production channel cloth (4), the second membrane (3), the concentrated water channel cloth (1), the first membrane (2) and the metal wires (A) arranged on the water production channel cloth from top to bottom.

[0084] The schematic diagram of the membrane element structure obtained by the rapid preparation method of the wound membrane element is shown in Figure 4 :

[0085] The schematic diagram shows that the materials forming a single membrane bag are stacked and wound on the water collection center pipe (6) in sequence from top to bottom, namely, a water production flow channel cloth (4), a second membrane sheet (3), a concentrated water flow channel cloth (1), and a first membrane sheet (2); the first side (41), the second side (42), and the third side (43) of the upper and lower surfaces of the water production flow channel cloth (4) are connected to the membrane sheets by the welding method, and the bent membrane sheets are connected to the water collection center pipe (3) by the welding method, thereby forming an envelope structure with three sides sealed with the water production flow channel cloth sandwiched in the middle and the U-shaped folded position of the first membrane sheet and the second membrane sheet as the outlet, and the water production side of the envelope is connected to the water production end of the center pipe.

[0086] Preferably, when the roll-type membrane element is manufactured by the preparation method of this embodiment, the number of membrane bags in the membrane element can be 1-30 pages. Figure 5 In the embodiment shown in , the number of film bags stacked in sequence is 2. As the number of film bags increases, the film bags can be stacked in sequence on the central tube according to the schematic diagram of the accompanying drawings.

[0087] We then conducted reverse osmosis desalination tests on membrane elements with the same external dimensions but prepared using the traditional glue bonding method and the polymer welding method described in this technical method. The experimental results are described below.

[0088] Operating conditions were based on GB / T 32373-2015, Test Methods for Reverse Osmosis Membranes: a reverse osmosis operating pressure of 5.5 MPa, influent water containing 32,000 mg / L sodium chloride, a test water temperature of 25°C, and an influent flow rate of 450 L / H. Specific test data are shown in Table 1.

[0089] Table 1 Reverse osmosis desalination experiment of membrane elements prepared by different preparation methods

[0090]

[0091] Among them, desalination rate = (influent conductivity - produced water conductivity) / influent conductivity × 100%.

[0092] From the data, it can be seen that the polymer welding method, when the membrane element has the same external dimensions, can achieve a larger water production per unit time because the effective membrane area is larger, which is twice the water production of the traditional method.

[0093] The foregoing description shows and describes preferred embodiments of the present invention. As previously mentioned, it should be understood that the present invention is not limited to the form disclosed herein and should not be construed as excluding other embodiments. Instead, the present invention can be used in various other combinations, modifications, and environments and can be modified within the scope of the inventive concept described herein by the teachings above or by techniques or knowledge in the relevant art. Modifications and variations made by those skilled in the art without departing from the spirit and scope of the present invention are intended to be within the scope of the appended claims.

Claims

1. A method for preparing a wound membrane element, characterized in that: The following steps are included: S10, rolling a first membrane sheet, a produced water flow channel cloth, a second membrane sheet, a concentrated water flow channel cloth, and a metal wire arranged at a location to be welded, for forming at least one membrane bag, onto a water collection central pipe; S20, heating a metal wire by a welding device to melt the polymer material at the welding point of the two materials to be welded, and welding the two materials to be welded to form a membrane element; then, pulling the metal wire out of the rolled membrane element; Among them, the water collecting central tube is directly contacted and welded with the first or second diaphragm, and the upper and lower surfaces of the water production duct cloth respectively include a first side, a second side and a third side where the water collecting central tube is not set. Metal wires are arranged on the first side, the second side and the third side of the water production duct cloth, and extend and wind around the water collecting central tube.

2. The method for preparing a spiral membrane element according to claim 1, characterized in that: The rolled membrane element includes a rolled layered structure and a water collection center tube arranged in the center of the rolled layered structure. The rolled layered structure is wrapped around the outside of the water collection center tube. The front end of the rolled membrane element is the water inlet end, and the rear end of the rolled membrane element is the water production end and the concentrated water end. The rolled layered structure includes a water production flow channel cloth, a first diaphragm, a concentrated water flow channel cloth and a second diaphragm. The water collection center tube is placed between the water production flow channel cloth and the first or second diaphragm; the water production flow channel cloth is placed between the first diaphragm and the second diaphragm, and the first edge, second edge and third edge of the upper and lower surfaces of the water production flow channel cloth are directly contacted and welded with the first diaphragm and the second diaphragm respectively to form a water production membrane bag; the welding edge line width of the first edge, the second edge or the third edge is between 10-25000μm.

3. The method for preparing a spiral membrane element according to claim 1, characterized in that: A desalination layer is provided on the side of the membrane facing the concentrated water flow channel cloth, and a water guide layer is provided on the side of the membrane facing the produced water flow channel cloth.

4. The method for preparing a spiral membrane element according to claim 1, wherein: Before step S10, the method further includes step 1, folding the membrane in half to form an n-shape, forming a first membrane and a second membrane; and step 2, placing a produced water flow cloth, a concentrated water flow cloth and a water collection central pipe on the folded membrane.

5. The method for preparing a spiral membrane element according to claim 1, characterized in that: The water collecting central pipe is placed between the first membrane and the water production flow channel cloth, or between the water production flow channel cloth and the second membrane.

6. The method for preparing a spiral membrane element according to claim 1, wherein: After step S20, the method further includes: step S302, wrapping a waterproof tape or a waterproof film around the rolled membrane element; and step S303, providing a waterproof sealing ring around the rolled membrane element.

7. The method for preparing a spiral membrane element according to claim 1, wherein: The material of the metal wire is an alloy of one or more metals such as copper, aluminum, iron or nickel. The outer layer of the metal wire is covered with Teflon. The width of the metal wire is 10-20000μm, the thickness is 10-1000μm, and the length is the sum of the welding lengths of the first side, the second side and the third side of the water-producing flow channel cloth in the membrane bag and the length extended and wound on the water collection center pipe.

8. The method for preparing a spiral membrane element according to claim 1, wherein: The welding is polymer welding, including a metal wire electric heating method or a metal wire electromagnetic induction heating method.

9. The method for preparing a spiral membrane element according to claim 1, wherein: The welding device is a power supply device for connecting the metal wire to industrial electricity or a high-frequency electromagnetic induction coil device for connecting the metal wire to industrial electricity.

10. The method for preparing a spiral membrane element according to claim 1, wherein: In step S20, the width of the welding edge of the two materials to be welded is between 10-25000 μm.

11. The method for preparing a spiral membrane element according to claim 1, wherein: The welding process heats the metal wire to melt the polymer material at the welding point. After the polymer material cools down, atomic diffusion occurs in the material between the welding surfaces, and the welded polymer materials are connected by chemical bonds.

12. The method for preparing a spiral membrane element according to claim 1, wherein: The welding temperature is not higher than 230℃.

13. The method for preparing a spiral membrane element according to claim 1, wherein: The material of the membrane is a low melting point polymer material, including cellulose acetate, cellulose acetate ester, polyethylene, polysulfone, polyamide, aromatic polyamide, aromatic polyamide-hydrazide or nitrogen-containing aromatic polymer.

14. The method for preparing a spiral membrane element according to claim 1, wherein: The material of the water-producing channel cloth is PP polypropylene low melting point polymer material.

15. The method for preparing a spiral membrane element according to claim 1, wherein: The material of the concentrated water flow cloth is PET thermoplastic polyester high melting point polymer material.

16. The method for preparing a spiral membrane element according to claim 1, characterized in that: The material of the water collecting central pipe is ABS plastic.

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