Membrane filtration assembly

Abstract

The utility model relates to the technical scheme of a filter, in particular to a membrane filtration assembly, which comprises a liquid inlet screen, a filtration layer and a filtrate screen which are stacked and alternately arranged, and the roughness of the liquid outlet surface of the filtration layer is 0.1-8 [mu] m; a non-woven structure layer allowing liquid to pass through is arranged between the filtering layer and the filtrate screen, the non-woven structure layer at least covers an effective filtering area of the filtering layer, and the roughness of the side, making contact with the liquid outlet face of the filtering layer, of the non-woven structure layer is not smaller than two times of the roughness of the filtering layer. The increase of liquid flow resistance caused by liquid pressure is reduced, and the liquid flow efficiency of the prepared filter assembly is improved.

Description

Technical Field

[0001] The present application relates to a filter technology solution, and in particular to a membrane filtration component. Background Art

[0002] Filtration using a membrane is an important process step in the field of biochemistry and chemical engineering. By using membranes with different cutoff sizes and different processes, it can achieve separation, impurity removal, concentration and other functions. In order to improve the working efficiency of the membrane filtration device and improve the stability of membrane filtration, multiple membranes can be prepared into a membrane filtration assembly. By setting a liquid inlet and a liquid outlet in the assembly and providing a stable pressure system, continuous filtration can be achieved.

[0003] A membrane package is a commonly used membrane filtration component, which is formed by encapsulating one or more filter membranes, forming a flow channel for liquid to pass through the flow guide components such as the flow guide screen in front of and behind the membrane, and connecting different liquid channels on both sides of the membrane to achieve liquid inlet and outlet. In the process of encapsulation, the membrane and the screen need to be stacked and pressed. For example, CN218190658U discloses a packaging device for a membrane package filtration unit, which has a first template and a second template for pressing the membrane package, and realizes glue injection packaging through a glue pouring channel, and then encapsulates the filter membrane and the screen into a membrane package. The membrane package also has other packaging methods, for example, pre-setting glue or film in the area to be encapsulated, and achieving sealing and bonding by melt curing, ultraviolet curing or thermal curing.

[0004] In the above preparation process, it is generally necessary to press the membrane package in the thickness direction of the membrane package to achieve good packaging and sealing effects. However, in the above scheme, during the filtration process, the liquid outlet surface of the filter layer of the filter membrane or composite filter membrane is generally convex toward the liquid outlet surface under the action of liquid pressure compared to the screen. Since the liquid outlet surface of the filter membrane is generally smoother, and the pores and fiber structure on its surface are smaller than the fiber structure of the screen, after the liquid outlet surface is attached to the screen, the screen fibers are easily embedded in the filter membrane or block the pores on the surface of the filter membrane, thereby significantly increasing the liquid flow resistance of the membrane package. Utility Model Content

[0005] In order to improve the liquid flow efficiency of the prepared filter assembly and reduce the increase in liquid flow resistance caused by liquid pressure, the present application provides a membrane filter assembly, which reduces the liquid flow resistance at the liquid outlet surface after preparation and greatly improves the filtration efficiency.

[0006] The membrane filtration component involved in the present application includes a liquid inlet screen, a filter layer and a filtrate screen which are stacked and alternately arranged, wherein the liquid inlet screen is arranged on the liquid inlet side of the filter layer, and the filtrate screen is arranged on the liquid outlet side of the filter layer; the liquid inlet screen is provided with a first packaging hole and a first connecting hole, the filtrate screen is provided with a second packaging hole and a second connecting hole, and the filter layer is provided with a liquid inlet hole and a liquid outlet hole; wherein the first packaging hole, the second connecting hole and the liquid outlet hole are connected through and through, the second packaging hole, the first connecting hole and the liquid inlet hole are connected through and through, the first packaging hole is fluid-tightly sealed with the liquid inlet screen, and the second packaging hole is fluid-tightly sealed with the filtrate screen; the roughness of the liquid outlet surface of the filter layer is 0.1 to 8 μm; a non-woven structure layer is provided between the filter layer and the filtrate screen for liquid to pass through, the non-woven structure layer at least covers the effective filtering area of ​​the filter layer, and the roughness of the side of the non-woven structure layer in contact with the liquid outlet surface of the filter layer is not less than twice the roughness of the filter layer.

[0007] During the use of the membrane package, the liquid enters between the filtrate surfaces of adjacent filter layers through the first connecting hole, and the liquid inlet screen supports and forms a flow channel between the filtrate surfaces of adjacent filter layers. Then, under the action of external pressure, the liquid flows through the filter membrane to the liquid outlet surface of the filter membrane, and flows out through the second connecting hole under the guidance of the filtrate screen. In this process, since the liquid pressure on the liquid inlet surface of the filter layer is greater than the liquid pressure on the liquid outlet surface, the filter layer will bend toward the filtrate screen under the action of the liquid pressure. In the above process, the filtrate screen will be embedded in the surface of the filter layer. Since the fiber diameter of the screen is usually several orders of magnitude larger than the pore size of the filter layer, the screen fiber will be attached to the filter layer in a plane-like state compared to the surface of the filter layer, thereby blocking the pores on the liquid outlet surface of the filter layer and affecting the efficiency of liquid penetration.

[0008] In the above scheme, by adding a non-woven structure layer, the non-woven structure layer does not have a structure woven by warp and weft, and can be prepared by melt-blowing, spunlace, etc. Since the surface fiber thickness of the non-woven structure layer is finer than that of the screen, it is basically of a similar order of magnitude to the screen on the surface of the filter membrane, and the non-woven structure layer has a relatively rough plane, so the area of ​​its surface directly attached to the liquid outlet surface of the filter layer is smaller than that of the screen. In the case where the non-woven structure layer has a large roughness, an uneven contact surface is generated on its surface, and since the non-woven structure layer itself is relatively soft, it will not be embedded in the filter layer, and it is more difficult to block the filter holes on the liquid outlet surface of the filter layer. Therefore, compared with directly using the filtrate screen to attach to the surface of the filter layer, the scheme in this application can effectively reduce the resistance of the liquid passing through the filter layer and improve the efficiency of filtration.

[0009] Preferably, the roughness of the side of the nonwoven structure layer in contact with the liquid outlet surface of the filter layer is 5-50 μm, and the softness of the nonwoven structure layer is 80-220 mN.

[0010] A nonwoven structure layer with a roughness of 5 to 30 μm is selected so that the surface of the nonwoven structure layer has a more obvious uneven structure. Therefore, when the nonwoven structure layer and the filter layer are attached, the liquid can flow through the uneven structure on the surface of the nonwoven structure layer, and the flow of the liquid will not be blocked, so that the membrane filtration component has better liquid flow efficiency. However, the nonwoven structure layer should not have too high a roughness. When the roughness is greater than 30 μm, the filter layer is easily damaged by the nonwoven structure layer, which leads to a decrease in the interception effect of the filter membrane.

[0011] In addition, in the above scheme, a non-woven layer with a softness within a certain range is used. If the non-woven layer is too soft, it cannot support the filter layer, and then under greater pressure, the filter layer will bend to fit with the non-woven structure layer, so there will be a larger contact area between the non-woven structure layer and the filter layer, thereby blocking the pores of the filter layer at the liquid outlet surface. If the non-woven structure layer has poor softness and a harder structure, it is easy to damage the filter layer under pressure, affecting the integrity of the membrane filtration assembly.

[0012] Preferably, the ratio of the liquid outlet surface diameter of the filter layer to the fiber diameter of the nonwoven structure layer is 1:10-1000, and the average fiber diameter of the nonwoven structure layer is 5-50 μm.

[0013] For the above scheme, the fiber diameter of the nonwoven structure layer is within a specific range compared to the pore size of the liquid outlet surface, so that the above fibers are neither easy to embed into the pores nor easy to block the pores of the liquid outlet surface. The fiber diameter of the above nonwoven structure layer is larger than the pore size of the liquid outlet surface of the filter layer, so the thicker the fiber, the more serious the blocking effect on the liquid outlet surface; for the filter layer with a larger liquid outlet surface diameter, it can accept thicker nonwoven structure layer fibers, thereby maintaining a good liquid flux. However, when the fibers are thinner, due to the greater pressure on the whole, it is easy for the fibers in the nonwoven structure layer to embed into the liquid outlet surface of the filter layer. After the fibers are embedded in the surface of the filter layer, they will compress the nonwoven structure layer, thereby making the nonwoven structure layer more closely fit the liquid outlet surface of the filter layer, which will also cause a decrease in filtration efficiency.

[0014] Preferably, the side of the nonwoven structure layer adjacent to the filter layer comprises monofilaments and parallel filaments, and the parallel filaments are formed by merging at least two monofilaments.

[0015] The parallel wire area can be prepared by hot pressing and other methods. The parallel wire area can further reduce the phenomenon of the surface wire structure being embedded in the filter layer, thereby improving the support effect on the filter layer. In this state, the filter layer and the non-woven structure layer have a more uniform force structure, reducing the phenomenon of the filter layer being deformed by the non-woven structure layer, further ensuring the smooth flow of the fluid structure in the filter layer. At the same time, after the non-woven structure layer forms the parallel wire area, it can also reduce the phenomenon of the wires on the surface of the non-woven structure layer being embedded in the filter layer, which overall protects the liquid surface of the filter layer and improves the liquid passage efficiency.

[0016] Preferably, the air permeability of the nonwoven structure layer is not less than 35cc / cm 2 ·s; the thickness of the nonwoven structure layer is 0.05 to 2 mm.

[0017] Since the non-woven structure layer itself also needs to pass liquid, the air permeability of the non-woven structure layer should be relatively large, otherwise it itself will easily have an adverse effect on the passage of liquid. In addition, the thickness of the non-woven structure layer should be in the range of 0.2-2mm. If the thickness of the non-woven structure layer is too large, it will produce too much resistance to the passage of liquid, and the diversion effect of the screen itself cannot be fully exerted, so the flow of liquid will also be affected. If the thickness of the non-woven structure layer is too small, the isolation effect between the filtrate screen and the filter layer cannot be achieved. During the preparation and use process, the filtrate screen will still affect the liquid outlet surface of the filter layer, which will also lead to a decrease in the liquid flow rate.

[0018] Preferably, the filter layer includes a pre-filter layer and a retention layer, a welding area is provided between the filter layer and the filtrate screen, and a welding connection structure is formed in the welding area; the projection of the non-woven structure layer on the plane where the filter layer is located at least partially covers the welding area.

[0019] The welding layer can generally be an additional polymer material, or it can be prepared by directly melting the non-woven structure layer; in the above process, since the welding process generally requires applying high temperature and high pressure to the material, it is easy to cause separation between the interception layer and the pre-filtration layer in the double-layer filter layer, which in turn leads to a deterioration in the filtration effect of the filter membrane and a reduction in integrity. After adding the non-woven structure layer, the non-woven structure layer can increase the heat conduction effect on the one hand, making it less likely to produce overheated local areas on the filter layer. At the same time, the non-woven structure layer itself has a certain flexibility, which can provide a certain displacement buffer during the process of being subjected to heat pressing, thereby reducing the layer structure separation phenomenon caused by the different forces between the interception layer and the pre-filtration layer in the horizontal direction.

[0020] In one solution of the present application, the welding area includes a first welding area surrounding the second packaging hole.

[0021] In the above solution, the welding area at least includes a first welding area surrounding the second packaging hole area. In this area, a better sealing structure is required. The use of welding can improve the sealing effect and facilitate the processing of the system.

[0022] Furthermore, the nonwoven structure layer completely covers the first welding area.

[0023] In the above scheme, the nonwoven structure completely covers the first welding area, thereby better protecting the filter layer in the second packaging hole area. Under the protection of the nonwoven structure, the welding liquid can penetrate into the nonwoven structure layer during the welding process through the nonwoven structure layer that completely covers the first welding area, making the welding structure more solid, and also protecting the filter layer at the first welding area position (i.e., the position surrounding the liquid inlet hole) from separation of the pre-filtration layer and the retention layer, thereby improving the finished product rate of the membrane package.

[0024] In another embodiment, the nonwoven structure layer is provided with a clearance hole at the position of the first welding area, the projection of the clearance hole on the filter layer surrounds the liquid inlet hole, and the projection of the first welding area on the filter layer at least partially falls into the projection of the clearance hole on the filter layer.

[0025] In the above scheme, the second welding area surrounds the edge of the filtrate screen, and the interior thereof is the effective filtration area of ​​the filter assembly, and the outer area is directly attached to the outer edge of the filtrate screen, or is protruded from the outer edge of the filtrate screen. In the above scheme, the give way hole can better facilitate the welding of the first welding area between the filter layer and the filtrate screen, forming a direct welding effect, while also improving the welding strength and speeding up the welding efficiency, which is suitable for the filter layer structure that is not easy to separate at high temperature. At the same time, during the welding process, the second welding area around the liquid inlet hole can directly form a structure between the filter layers that is not penetrated by the non-woven structure layer and directly connected to the filter layers on both sides of the filtrate screen. In this process, the sealing performance can be improved, and the welding structure can also produce better bonding performance. A support structure directly supported between the two filter layers can be formed in the second welding area first, producing a better flow channel support effect, thereby providing better liquid flow efficiency and reducing flow resistance.

[0026] Preferably, the welding area further comprises a second welding area arranged around the edge of the screen, and the non-woven structure layer completely covers the second welding area.

[0027] In the above scheme, the non-woven structure is arranged to completely cover the second welding area, so that the second welding area penetrates through the non-woven structure layer, and the welding process is guided and buffered by the non-woven structure layer, so that during the welding process, the filter layer is not easily damaged due to local overheating in the peripheral area of ​​the screen. In addition, when the non-woven structure layer completely covers the welding area, the problems of reduced filtration area and poor packaging sealing caused by the scattering of the material after melting can be reduced.

[0028] Preferably, the first welding area and the second welding area are integrally formed.

[0029] In the above scheme, an integrally formed molten film is provided and laid on the area to be packaged, which is convenient to process and has good sealing performance after packaging.

[0030] In summary, in the above scheme, a membrane filtration component is provided, which reduces the bending of the filter layer toward the liquid outlet surface due to liquid pressure during the filtration process by setting a protective layer with a certain roughness between the filtrate surface of the filtration layer and the filtrate screen. Under the protection of the non-woven structure layer, the phenomenon of the screen fibers being embedded in the filtration layer is reduced, thereby reducing the resistance encountered during liquid filtration and improving the filtration efficiency of the liquid. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a schematic diagram of the overall structure of the membrane filtration assembly in the embodiment of the present application;

[0032] Figure 2 This is a schematic diagram of the structure of the middle layer structure stack of the membrane filtration assembly in Example 1 of the present application;

[0033] Figure 3 This is a cross-sectional view of the stacked middle structure of the membrane filtration assembly in Example 1 of the present application;

[0034] Figure 4 This is a surface SEM image of the nonwoven structure layer used in Example 1 of the present application on the side facing the filter layer;

[0035] Figure 5 This is a cross-sectional view of the stacked middle structure of the membrane filtration assembly in Example 5 of the present application.

[0036] In the figure, 1, filter layer; 11, liquid inlet hole; 12, liquid outlet hole; 2, liquid inlet screen; 21, first packaging hole; 22, first connecting hole; 3, filtrate screen; 31, second packaging hole; 32, second connecting hole; 4, non-woven structure layer; 5, welding area; 51, first welding area; 52, second welding area; 6, packaging area; 61, third welding area; 62, fourth welding area; 7, give way hole. DETAILED DESCRIPTION

[0037] The technical solution of the utility model will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments of the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0038] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0039] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installation", "connection" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0040] For the following examples, the resistance of the flow channel was measured as follows:

[0041] The flux detection method of the filter layer is as follows: refer to the test method of 5.1 pure water permeability test in GB / T 32360-2015, wherein the inlet liquid is deionized water, the operating pressure is 30psi, the operating temperature is 25°C, and the solution pH is 7.

[0042] The roughness of the filter layer and the nonwoven structure layer was measured by using an ultra-depth optical microscope VHX7000. During the measurement, the magnification of the filter layer was 300 times, and the magnification of the nonwoven structure layer was 100 times.

[0043] The softness of the nonwoven structure layer refers to the standard ASTM D6828-2002 (2011), and the test speed is 1.2 mm / s.

[0044] The SEM pore size or fiber diameter of the filter layer and the surface of the nonwoven structure can be characterized by using a scanning electron microscope to characterize the membrane structure, and then measured using computer software (such as Matlab, NIS-Elements, etc.) or manually, and corresponding calculations can be performed. In actual measurement, a certain area can be demarcated in the plane where the image is located, and operations such as drawing lines and outlining can be performed by manual marking or automatic computer marking, and then measurement can be performed.

[0045] For the above parameters, those skilled in the art can also obtain the above parameters through other measurement methods. The above measurement methods are for reference only.

[0046] In the following examples, 0.5 m 2 The membrane package with the largest filtration area is tested.

[0047] Example 1, this example relates to a membrane filtration assembly, which has a liquid inlet screen 2, a filter layer 1 and a filtrate screen 3 stacked and alternately arranged, specifically, the overall arrangement is as follows Figures 1 to 3 As shown, the inlet screen 2 is arranged on the side of the inlet surface of the filter layer 1, and the filtrate screen 3 is arranged on the side of the outlet surface of the filter layer 1. The smallest membrane filtration component can include a five-layer combination of filtrate screen 3-filter layer 1-inlet screen 2-filter layer 1-filtrate screen 3, while a larger membrane filtration component can adopt a repeated stacking structure of filtrate screen 3-filter layer 1-inlet screen 2-filter layer 1-filtrate screen 3-filter layer 1-inlet screen 2-filter layer 1 to form a filtration component system of multiple layers of filtration layer 1. Specifically, a stop layer can be set at the outermost side of the membrane filtration component to achieve the sealing of the internal space of the filtration component, or a stop piece can be not set, and the encapsulation can be achieved directly by an external fixture. In this embodiment, the filter layer 1 has a pre-filtration layer and a retention layer, wherein the pre-filtration layer is located on the side of the filter layer 1 facing the filtrate inlet screen, and the retention layer is located on the side of the filter layer 1 facing the inlet screen 2. In this embodiment, the retention layer is regenerated cellulose and the pre-filtration layer is a non-woven fabric layer. The roughness of the liquid outlet surface of the retention layer is 2.2 μm, and the average pore size of the liquid outlet surface is 20.9 nm.

[0048] Reference Figure 2 and Figure 3The inlet screen 2 is provided with a first packaging hole 21 and a first connecting hole 22, the filtrate screen 3 is provided with a second packaging hole 31 and a second connecting hole 32, and the filter layer 1 is provided with a liquid inlet hole 11 and a liquid outlet hole 12, wherein the first packaging hole 21, the second connecting hole 32 and the liquid outlet hole 12 are connected through and through, and the second packaging hole 31, the first connecting hole 22 and the liquid inlet hole 11 are connected through and through, and on the filter layer 1 which is rectangular as a whole, the liquid inlet hole 11 and the liquid outlet hole 12 are arranged alternately on the two opposite sides of the filter layer 1, and are both circular. During the use of the above-mentioned filter assembly, the liquid flows into the side of the filter layer 1 facing the inlet screen 2 through the first connecting hole 22 and the liquid inlet hole 11, and quickly fills the space on this side, and then passes through the filter layer 1 under the action of the tangential force, and flows into the side of the filter layer 1 facing the filtrate screen 3. In this process, solid particles exceeding the retention diameter of the filter layer 1 will be retained by the filter layer 1, thereby completing the filtering effect. After filtration, the filtrate will flow along the filtrate screen 3 and out through the liquid outlet hole 12 and the second connecting hole 32, while the residual liquid can flow out from the other liquid inlet holes 11 and the first connecting hole 22, or block the remaining first connecting holes 22 and liquid inlet holes 11 that have not entered the liquid, thereby achieving the effect of dead-end filtration.

[0049] There is a non-woven structure layer 4 between the filter layer 1 and the filtrate screen 3. The non-woven structure layer 4 is a non-woven fabric structure. Specifically, the SEM image of the non-woven structure layer 4 facing the filter layer 1 is as follows: Figure 4 As shown, it has a monofilament area and a parallel yarn area, wherein the parallel yarn area is formed by merging at least two monofilaments. The above monofilament and parallel yarn structure can be formed by heat pressing the nonwoven structure layer 4.

[0050] Reference Figure 2 and Figure 3 , there is a welding area 5 on the filtrate screen 3, the welding area 5 specifically includes a first welding area 51 surrounding the second packaging hole 31 and a second welding area 52 surrounding the edge of the filtrate screen 3, and the area on the filter layer 1 within the second welding area 52 and outside the first welding area 51 is the effective filtering area of ​​the filter layer 1, that is, only in this area can the liquid pass through the filter layer 1 and achieve filtration. The non-woven structure layer 4 is between the filter layer 1 and the filtrate screen 3, completely covering the first welding area 51, the second welding area 52 and the effective filtering area of ​​the filter layer 1, so that the first welding area 51 and the second welding area 52 both penetrate through the non-woven structure layer 4. The first welding area 51 and the second welding area 52 are attached to the filtrate screen 3 through welding sheets, and after being heated and melted, they are solidified between adjacent filter layers 1, or form a solidified packaging structure between the filter layer 1 and the outermost termination structure of the adjacent filter component, thereby realizing the fluid sealing between the second packaging hole 31 and the filtrate screen 3 and the fluid sealing between the edge area of ​​the filtrate screen 3 and the inner and outer areas of the second welding area 52.

[0051] Reference Figure 2 and Figure 3 , there is a packaging area 6 on the liquid inlet screen 2, and the packaging area 6 specifically includes a third welding area 61 surrounding the first packaging hole 21 and a fourth welding area 62 surrounding the edge of the liquid inlet screen 2. The third welding area 61 and the fourth welding area 62 are formed by melting and bonding the welding sheet preset on the liquid inlet screen 2 between the filter layers 1 on both sides of the liquid inlet screen 2, wherein the third welding area 61 can achieve fluid sealing between the first packaging hole 21 and the liquid inlet screen 2, and the fourth packaging area 6 can achieve fluid sealing between the inside and outside of the fourth packaging area 6 on the liquid inlet screen 2. In this embodiment, the first welding area 51 and the second welding area 52 are integrally formed by melting a whole welding sheet, and the third welding area 61 and the fourth welding area 62 are integrally formed by melting a whole welding sheet.

[0052] It should be noted that in Figure 3 For the convenience of display, in this application, the packaging area and the welding area are drawn in a transparent state, and each layer structure is separated. In fact, the layers can be tightly fitted.

[0053] In this embodiment, non-woven fabrics of different batches were used as the non-woven structure layer, and the fiber diameter, roughness, softness and thickness thereof, as well as the flux of the membrane filtration assembly finally prepared are shown in Table 1.

[0054] Table 1

[0055]

[0056]

[0057] Example 2, based on Example 1, the filter layer is replaced, wherein the filter membrane retention layer in this application is PES, the pre-filtration layer is UPE, the roughness of the liquid outlet surface is 0.8μm, and the liquid outlet surface diameter is 15.5nm.

[0058] In this embodiment, non-woven fabrics of different batches were used as the non-woven structure layer, and the fiber diameter, roughness, softness and thickness thereof, as well as the flux of the membrane filtration assembly finally prepared are shown in Table 2.

[0059] Table 2

[0060]

[0061] Example 3, based on Example 1, a single-layer regenerated cellulose virus removal membrane is selected as the filter layer, the roughness of the liquid outlet surface of the filter layer is 4.4 μm, and the SEM pore size of the liquid outlet surface is 21.4 nm.

[0062] In this embodiment, non-woven fabrics of different batches were used as the non-woven structure layer, and the fiber diameter, roughness, softness and thickness thereof, as well as the flux of the membrane filtration assembly finally prepared are shown in Table 3.

[0063] Table 3

[0064]

[0065]

[0066] From the experimental data in Tables 1 to 3, it can be seen that the fibers of the nonwoven structure layer cannot be too fine. Too fine fibers will increase the specific surface area in the system and cause the liquid path to be tortuous. From the experimental data, it can be seen that when the fiber diameter of the nonwoven structure layer is less than 5 μm, it will have an adverse effect on the flux. Further, the surface roughness of the nonwoven structure layer should be controlled within 5 to 30 μm. Too large or too small will cause a decrease in the flux. In addition, when the surface roughness of the nonwoven structure layer should be controlled within 5 to 30 μm, when the roughness of the filter layer outlet surface is large, the roughness of the nonwoven structure layer should be maintained at not less than twice the roughness of the filter layer outlet surface, and the softness should be controlled within 80 to 220 mN.

[0067] The non-woven structure layer being too thick or too thin will also affect the liquid flux. A non-woven structure layer that is too thin will weaken the protective effect of the non-woven structure layer, making the screen itself easily affect the filtration layer, while a non-woven structure layer that is too thick will lead to a decrease in liquid passage efficiency.

[0068] Example 4, based on Example 1, uses a non-woven structure layer with a different structure. Specifically, the side of the non-woven structure layer facing the filter layer is not hot pressed, so its surface has only a single-filament area and no parallel-filament area.

[0069] In this embodiment, non-woven fabrics of different batches were used as the non-woven structure layer, and the fiber diameter, roughness, softness and thickness thereof, as well as the flux of the membrane filtration assembly finally prepared are shown in Table 4.

[0070] Table 4

[0071]

[0072] By comparing Example 4 with Example 1, it can be seen that when the surface roughness and fiber diameter of the non-woven structure layer are relatively close, the non-woven structure layer with a single-filament and parallel-filament structure on the surface can further reduce the resistance of the liquid during filtration and improve the efficiency of the liquid flow, so its reflux flow rate is larger.

[0073] In Example 5, compared with Example 1, the coverage area of ​​the nonwoven structure layer 4 is adjusted as follows:

[0074] In this embodiment, refer to Figure 5 As shown, the nonwoven structure layer 4 completely covers the second welding area 52 and the effective filtering area of ​​the filter layer 1, but does not cover the first welding area 51. Specifically, the nonwoven structure layer 4 opens a clearance hole 7 in the area corresponding to the first welding area 51, and the second welding area 52 passes through the clearance hole 7, directly penetrates the filtrate screen 3, and is bonded to the liquid outlet surface of the filter layer 1.

[0075] In this embodiment, the nonwoven structural layer selected is the same as that of the experimental group 1-1 in Example 1, and its measured flux is 98.5LMH / 30psi.

[0076] It should be noted that in Figure 5 For the convenience of display, in this application, the packaging area and the welding area are drawn in a transparent state, and each layer structure is separated. In fact, the layers can be tightly fitted.

[0077] The above-mentioned implementation modes are only preferred implementation modes of the present invention, and cannot be used to limit the protection scope of the present invention. Any non-substantial changes and substitutions made by technicians in this field on the basis of the present invention shall fall within the scope of protection required by the present invention.

Claims

1. A membrane filtration assembly, comprising a liquid inlet screen, a filter layer and a filtrate screen stacked and alternately arranged, wherein the liquid inlet screen is arranged on the liquid inlet side of the filter layer, and the filtrate screen is arranged on the liquid outlet side of the filter layer; the liquid inlet screen has a first packaging hole and a first connecting hole, the filtrate screen has a second packaging hole and a second connecting hole, and the filter layer has a liquid inlet hole and a liquid outlet hole; wherein, The first packaging hole, the second connecting hole and the liquid outlet hole are connected through and through, the second packaging hole, the first connecting hole and the liquid inlet hole are connected through and through, the first packaging hole is fluid-tightly sealed with the liquid inlet screen, and the second packaging hole is fluid-tightly sealed with the filtrate screen; characterized in that: The roughness of the liquid outlet surface of the filter layer is 0.1 to 8 μm; a non-woven structure layer is provided between the filter layer and the filtrate screen for liquid to pass through, the non-woven structure layer at least covers the effective filtration area of ​​the filter layer, and the roughness of the side of the non-woven structure layer in contact with the liquid outlet surface of the filter layer is not less than twice the roughness of the filter layer.

2. A membrane filtration assembly according to claim 1, characterized in that: The roughness of the side of the nonwoven structure layer contacting the liquid outlet surface of the filter layer is 5-50 μm, and the softness of the nonwoven structure layer is 80-220 mN.

3. A membrane filtration assembly according to claim 1, characterized in that: The ratio of the surface diameter of the liquid outlet of the filter layer to the fiber diameter of the nonwoven structure layer is 1:10-1000, and the average fiber diameter of the nonwoven structure layer is 5-50 μm.

4. A membrane filtration assembly according to claim 1, characterized in that: The nonwoven structure layer has monofilaments and parallel yarns on one side adjacent to the filter layer, wherein the parallel yarns are formed by combining at least two monofilaments.

5. A membrane filtration assembly according to claim 1, characterized in that: The air permeability of the nonwoven structural layer is not less than 35cc / cm 2 ·s; the thickness of the nonwoven structure layer is 0.05 to 2 mm.

6. A membrane filtration assembly according to claim 1, characterized in that: The filter layer comprises a pre-filter layer and a retention layer. A welding area is provided between the filter layer and the filtrate screen, and a welding connection structure is formed in the welding area. The projection of the nonwoven structure layer on the plane where the filter layer is located at least partially covers the welding area.

7. A membrane filtration assembly according to claim 6, characterized in that: The welding area includes a first welding area surrounding the second packaging hole.

8. A membrane filtration assembly according to claim 7, characterized in that: Therefore the nonwoven structure layer completely covers the first welding area.

9. A membrane filtration assembly according to claim 7, characterized in that: The nonwoven structure layer is provided with a clearance hole at the position of the first welding area, the projection of the clearance hole on the filter layer surrounds the liquid inlet hole, and the projection of the first welding area on the filter layer at least partially falls into the projection of the clearance hole on the filter layer.

10. A membrane filtration assembly according to any one of claims 8 or 9, characterized in that: The welding area further comprises a second welding area arranged around the edge of the screen, and the nonwoven structure layer completely covers the second welding area.

11. A membrane filtration assembly according to claim 10, characterized in that: The first welding area and the second welding area are integrally formed.

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