CN220090665U

CN220090665U - Filtering membrane bag

Info

Publication number: CN220090665U
Application number: CN202321482893.9U
Authority: CN
Inventors: 贾建东; 陆坚
Original assignee: Hangzhou Cobetter Filtration Equipment Co Ltd
Current assignee: Hangzhou Cobetter Filtration Equipment Co Ltd
Priority date: 2023-06-10
Filing date: 2023-06-10
Publication date: 2023-11-28
Anticipated expiration: 2033-06-10

Abstract

The utility model relates to the technical field of filtering devices, in particular to a filtering membrane bag which comprises a liquid inlet screen, a filtrate screen and a filtering layer, wherein the liquid inlet screen, the filtering layer and the filtrate screen are sequentially and alternately stacked to form a filtering part with a filtering effect; the liquid inlet screen is provided with a first liquid inlet hole and a first filtrate hole, and the filtrate screen is provided with a second liquid inlet hole and a second filtrate hole; the first surrounding part is arranged on the first filtrate hole in a surrounding way, sealed between the first filtrate hole and the liquid inlet channel, and bonded and sealed on the liquid inlet surface of the filter layer; the second liquid inlet hole is provided with a second surrounding part in a surrounding mode, and the second surrounding part is sealed between the second liquid inlet hole and the filtrate flow passage and is bonded and sealed on the liquid outlet surface of the filter layer. According to the utility model, through the first surrounding part and the second surrounding part, the cohesiveness between the filter layer and the screen mesh is enhanced, so that the film package has better yield.

Description

Filtering membrane bag

Technical Field

The utility model relates to the technical field of filtering devices, in particular to a filtering membrane bag.

Background

The membrane bag is a common filter material, and the interior of the membrane bag is generally provided with a flow channel and a filter layer, wherein the flow channel comprises a liquid inlet flow channel and a filtrate flow channel, and the flow channels are respectively arranged at two sides of the filter layer. In the membrane package, the direction of the flow channel is parallel to the plane of the filter membrane, when liquid flows in the flow channel, the liquid can pass through the filter layer under the action of the shearing force of the liquid, and viruses, bacteria or other tiny particles in the liquid are trapped by the filter layer, so that the filtering effect is realized. And particles trapped in the filter layer flow out with the liquid under the flushing of the liquid flow, so that concentrated liquid and filtrate are obtained. In this process, the filter residues are not accumulated on the filter layer, and the micro filter holes on the filter layer are not blocked, so that the filter has the advantages of improving the filter effect and flux, improving the durability of the filter device, and the like.

The membrane package is generally provided with a liquid inlet hole and a liquid outlet hole, wherein the liquid inlet hole is communicated with the liquid inlet flow channel, is in fluid sealing with the filtrate flow channel, and the liquid outlet hole is communicated with the filtrate flow channel and is in fluid sealing with the liquid inlet flow channel. In the prior art, the holes and the flow channels are usually sealed through elastic extrusion sealing, and the specific method is to apply elastic sealing materials at the liquid outlet hole position of the liquid inlet screen and the liquid inlet hole position of the liquid outlet unit, and the materials penetrate into the screen and protrude out of the surface of the screen and are abutted against a filter layer (such as a filter membrane or a composite layer of a plurality of filter membranes) at the same time, so that the extrusion sealing effect is realized.

In the technical effect, the screen and the filter layer limit the relative displacement only through the abutting force in the vertical direction, the displacement of the screen and the filter layer in the direction parallel to the filter membrane is limited less, the dislocation in the horizontal direction is easy to occur in the preparation and packaging processes, and the yield of the membrane package is further affected.

Disclosure of Invention

In order to reduce offset and dislocation phenomena between a membrane layer and a screen in the preparation process of the membrane package, the utility model provides a filtering membrane package.

The filtering membrane package comprises a liquid inlet screen, a filtering screen and a filtering layer, wherein the liquid inlet screen, the filtering layer and the filtering screen are sequentially and alternately stacked to form a filtering part with a filtering effect;

the liquid inlet screen is provided with a first liquid inlet hole and a first filtrate hole, and the filtrate screen is provided with a second liquid inlet hole and a second filtrate hole;

a filter layer is arranged between any two adjacent liquid inlet screens and filtrate screens, the filter layer is provided with a liquid inlet surface and a liquid outlet surface, a liquid inlet flow channel is formed between the liquid inlet surfaces of the two adjacent filter layers, and a filtrate flow channel is formed between the liquid outlet surfaces of the two adjacent filter layers;

the first surrounding part is arranged on the first filtrate hole in a surrounding way, is sealed between the first filtrate hole and the liquid inlet channel, and is bonded and sealed on the liquid inlet surface of the filter layer;

the second liquid inlet hole is provided with a second surrounding part in a surrounding mode, and the second surrounding part is sealed between the second liquid inlet hole and the filtrate flow passage and is bonded and sealed on the liquid outlet surface of the filter layer.

In traditional scheme, screen cloth and filter membrane are often connected through the sealed mode of extrusion, and it forms the sealed bed course that has certain elasticity on the screen cloth through specific material, under this scheme, between filter membrane and screen cloth, spacing effect is less on being parallel to the plane that the filter membrane is located, consequently the phenomenon of misalignment between filter membrane and screen cloth or filter membrane and the filter membrane appears easily, in this state, on the one hand, the decline of alignment performance leads to sealing pad and sealing pad to be unable to realize fully extruding under partial condition, and then leaves the gap between filter membrane and screen cloth, has influenced the leakproofness of membrane package. Meanwhile, insufficient alignment can also result in poor flatness of the film package during the overall pressing process.

In the above technical scheme, set up first surrounding portion and second surrounding portion respectively on first filtrate hole and second feed liquor hole, wherein first surrounding portion and second surrounding portion all adopt the mode of bonding to connect between filter layer and corresponding filter screen, can restrict filter layer, feed liquor screen cloth and filter liquor screen cloth and be on a parallel with the ascending relative displacement of filter layer direction through the tie coat for tie coat on the corresponding hole can cooperate each other better, form more firm sealing state, simultaneously, bond between tie coat and the filter membrane after, make the face have better leakproofness between runner and the hole on the filter membrane. In addition, compared with the extrusion state, the bonding state has fewer dead angles in the flow channel, and filter residues are not easy to form accumulation in the liquid inlet flow channel or the filtrate flow channel, so that the filtering and concentrating effects are also obviously improved.

In the above technical solution, the first surrounding portion and the second surrounding portion are generally made of curable glue, such as epoxy resin, polyurethane resin, etc., which can be coated on the screen, or sucked into the screen by vacuum suction, etc., and then the filter layer is stacked on the screen, and after being cured by heating, ultraviolet curing or other modes, the glue solution can bond the filter layer and the screen while sealing the corresponding holes and flow channels, thereby achieving the effect of improving the stability.

Preferably, the projections of the first surrounding part and the second surrounding part on the plane of the filter layer overlap to form an overlapping buffer part.

First, since the liquid inlet and filtrate holes are generally alternately arranged on the screen and the filter layer, bonding positions on both sides of the filter layer are located on both sides of the region with respect to positions between the liquid inlet and filtrate holes on the filter layer. The glue solution can shrink in the curing process, so that the positions between the adjacent third liquid inlet holes and the third liquid outlet holes on the filter layer can be outwards pulled by the first surrounding parts and the second surrounding parts at two sides during curing, and further, the parts of the screen mesh are twisted, deformed and even torn in the curing process, so that the integrity of the prepared film package is influenced.

In addition, to arbitrary filter layer, first surrounding portion and second surrounding portion locate the both sides of filter layer, first surrounding portion and second surrounding portion are in order to laminate with the filter layer better, and its surface can bulge in the surface of corresponding screen cloth, consequently in filter layer and screen cloth stacking process, can take place the distortion between adjacent feed liquor hole of filter layer and the filtrate hole, and then produce torque force, therefore when the filter layer texture is softer or more fragile, the membrane package suppression process leads to the fact the destruction to the structure of filter layer easily, and then influences the filter effect.

By adopting the scheme that the first surrounding part and the second surrounding part are partially overlapped, on one hand, the filter membrane at the position of the overlapped buffer part is protected by the surrounding parts at two sides, the inside of the filter membrane is less in tensile force towards two sides, a buffer area is formed, the area can absorb the outward tensile force generated by the solidification of glue solution at two sides of the overlapped buffer part, the area between the third liquid inlet hole and the third liquid outlet hole on the filter layer is further protected, and the phenomena of cracking and twisting of the filter layer caused by uneven internal stress are reduced. On the other hand, the first surrounding part and the second surrounding part at the position of the overlapped buffer part can clamp the filter layer from two sides respectively, and further support the filter layer more greatly near the overlapped buffer part, so that torque force generated on the surface of the filter layer due to extrusion of the film package is reduced, the integrity of the filter layer is improved, damage or distortion of the filter layer in the processing process is reduced, and the filter performance of the film package is improved.

Preferably, the first surrounding part is an annular structure surrounding the first filtrate hole, and/or the second surrounding part is an annular structure surrounding the second liquid inlet hole.

The annular surrounding part structure can enable the peripheries of the liquid inlet holes and the filtrate holes of the screen to have more uniform stress, and the fact that the glue solution has stronger cohesive force than the filter layer under partial conditions after solidification is considered, so that the uniform stress of the first surrounding part and the second surrounding part is very important. The design annular surrounding part is more uniform in force in all directions in the curing process compared with other shapes, and the pulling force on the membrane is smaller, so that the influence on the filter layer is smaller, and the prepared membrane package has better filtering performance and integrity.

Preferably, the area of the overlapped buffer part is not more than 5% of the projection area of the first surrounding part on the filter layer, and is not more than 5% of the projection area of the second surrounding part on the filter layer.

Preferably, the width of the overlapped buffer part in the connecting line direction of the centers of the first surrounding part and the second surrounding part accounts for 0.5-10% of the sum of the apertures of the first liquid inlet holes and the first filtrate holes.

Because the torque force applied to the filter layer during the preparation of the membrane package is mainly arranged along the connecting line direction of the centers of the first surrounding part and the second surrounding part, and is alternately directed to the two sides of the filter layer. Therefore, the width of the overlap buffer portion in the center line direction of the first surrounding portion and the second surrounding portion is important for the influence of the torque force. The overlapping buffer portion can cause the increase of the total thickness of the membrane package, so that the area and the width of the overlapping buffer portion are not too large, otherwise, uneven membrane package can be caused on one hand, and then the integrity problem of the membrane package is caused, and on the other hand, excessive extrusion of the filter membrane in the filter layer is also easily caused, so that the filtering effect of the edge regions of the first surrounding portion and the second surrounding portion is affected.

Preferably, the first surrounding part protrudes out of the surface of the liquid inlet screen, and/or the second surrounding part protrudes out of the surface of the filtrate screen, and the thickness of the first surrounding part and the second surrounding part is 1-1.2 times of the thickness of the screen.

Considering that the first surrounding part and the second surrounding part are arranged on the filter layer in a staggered way, the parts protruding out of the screen mesh are not too large, if the thickness of the first surrounding part and the second surrounding part is larger than 1.2 times that of the screen mesh, the flow passage is too large, the membrane volume is increased while the filtering effect is weakened, the service efficiency is influenced, and the filter membrane is easily damaged in the process of pressing the membrane package.

Preferably, a first peripheral part is arranged between the liquid inlet screen and the filter layer in the area surrounding the edge of the liquid inlet screen, and is used for limiting liquid from flowing into gaps between the outer casing shell and the liquid inlet screen and between the liquid inlet screen and the filter layer from the liquid inlet channel, and the first peripheral part is connected with all the first surrounding parts;

and a second peripheral part is arranged between the filtrate screen and the filter layer in the area surrounding the edge of the filtrate screen and used for limiting liquid from flowing into gaps between the outer casing and the liquid inlet screen as well as between the filtrate screen and the filter layer from the filtrate flow channel, and the second peripheral part is connected with all the second surrounding parts.

The first peripheral portion and the second peripheral portion may be applied to the liquid inlet screen and the filtrate screen in a similar manner to the first surrounding portion and the second surrounding portion, and sealing effect is achieved. In the above technical solution, the first peripheral portion and the second peripheral portion limit the contact of the filtrate with the housing outside the filter layer, reducing the risk of filtrate confusion and contamination.

Preferably, the liquid inlet screen is provided with a first protruding part which partially or completely surrounds the liquid inlet screen outside the first peripheral part, the first protruding part is embedded in the outer casing, and/or the filtrate screen is provided with a second protruding part which partially or completely surrounds the filtrate screen outside the second peripheral part, and the second protruding part is embedded in the outer casing.

The protruding part is arranged outside the screen mesh, the protruding part is embedded in the shell, and the shell can be made of hot melt injection molding sealing glue or other methods. In this structure, the casing can fix and seal feed liquor screen cloth and filtrate screen cloth, has better leakproofness and stability.

Preferably, the first peripheral portion is adhesively sealed between the liquid inlet screen and the filter layer, and/or the second peripheral portion is adhesively sealed between the filtrate screen and the filter layer.

The first peripheral part and the second peripheral part are connected with the screen cloth and the filter layer in a bonding mode, so that the bonding strength between the screen cloth and the filter layer is further improved, and meanwhile, the force in the horizontal direction is equally divided into a larger area. In this case, when the filter layer receives a force parallel to the filter layer, the first and second peripheral portions of the edges thereof can uniformly receive these external forces, thereby reducing

Preferably, the projection of the first peripheral portion and the projection of the first surrounding portion on the plane of the filter membrane are connected smoothly, and the projection of the second peripheral portion and the projection of the second surrounding portion on the plane of the filter membrane are connected smoothly.

In the technical scheme, dead angles formed in the flow channels are fewer, liquid cannot form accumulation in the dead angles, and therefore the flow speed, the loading capacity and the effective filtering area of the membrane package are improved.

In summary, the filtering membrane package of the utility model adopts the two-side point adhesive sealing mode to connect the screen mesh and the filtering layer, so that the sealing property and stability between the screen mesh and the filtering layer can be considered, the filtering layer is not easy to deviate from the screen mesh in the direction parallel to the filtering layer, and the membrane package has better stability, yield and integrity.

Drawings

FIG. 1 is a schematic view of the appearance of a film package in example 1;

FIG. 2 is an overall schematic of the feed, filtration and filtrate screens of example 1;

FIG. 3 is a schematic view of the structure of example 1 after the feed, filtrate and filter layers are stacked;

fig. 4 is a schematic view of the projection of the filter layer and the first and second surrounding portions on the filter layer in embodiment 2.

In the figure, 1, a liquid inlet screen; 11. a first liquid inlet hole; 12. a first filtrate aperture; 13. a first surrounding portion; 14. a first outer peripheral portion; 15. a first protrusion; 2. a filtrate screen; 21. a second liquid inlet hole; 22. a second filtrate aperture; 23. a second surrounding portion; 24. a second outer peripheral portion; 25. a second protruding portion; 3. a filter layer; 31. an overlap buffer section; 32. a third liquid inlet hole; 33. a third filtrate aperture; 4. a housing.

Detailed Description

The following description of the embodiments of the present utility model will be made apparent and fully in view of the accompanying drawings, in which some, but not all embodiments of the utility model are shown. All other embodiments, which can be made by those skilled in the art based on the embodiments of the utility model without making any inventive effort, are intended to be within the scope of the utility model.

In the description of the present utility model, it should be noted that the directions or positional relationships indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. are based on the directions or positional relationships shown in the drawings, are merely for convenience of describing the present utility model and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a specific orientation, be configured and operated in a specific orientation, and thus should not be construed as limiting the present utility model. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.

In the description of the present utility model, it should be noted that, unless explicitly specified and limited otherwise, the terms "mounted," "connected," and "connected" are to be construed broadly, and may be either fixedly connected, detachably connected, or integrally connected, for example; can be mechanically or electrically connected; can be directly connected or indirectly connected through an intermediate medium, and can be communication between two elements. The specific meaning of the above terms in the present utility model will be understood in specific cases by those of ordinary skill in the art.

In the following examples, the integrity test was performed by the seed air diffusion flow test, with the following specific experimental methods:

the prepared filter element was wetted with water, the liquid inlet end of the element was connected to compressed air, and a pressure of 0.1mPa was applied to the liquid inlet end, and then the air flow rate was measured at the liquid outlet end to evaluate the integrity. The smaller the air flow, the better the integrity of the film package.

In the following examples, the filter elements were each prepared with a membrane area of 0.46m ² And (3) packaging the filtering membrane, wherein in the case, the qualified product is obtained when the liquid outlet end has the air flow rate of less than or equal to 50mL/min, and the lower the air flow rate is, the better the integrity is.

Embodiment 1, a filtration membrane package, referring to fig. 1, comprises a liquid inlet screen 1, a filtrate screen 2 and a filtration layer 3 stacked, wherein the liquid inlet screen 1, the filtrate screen 2 and the filtration layer 3 are rectangular, the liquid inlet screen 1 and the filtrate screen 2 are alternately arranged, and for any adjacent liquid inlet screen 1 and filtrate screen 2, a filtration layer 3 is arranged between the two. A liquid inlet channel is formed between the liquid inlet surfaces of two adjacent filter layers 3, and a filtrate channel is formed between the liquid outlet surfaces of two adjacent filter layers 3. The above-described stacked structure repeatedly forms a filter unit similar to a rectangular parallelepiped, and the filter unit is covered by the housing 4, so that the filter membrane pack in this embodiment can be obtained.

The liquid inlet screen 1 is provided with a first liquid inlet hole 11 and a first filtrate hole 12, wherein the first liquid inlet hole 11 and the first filtrate hole 12 are alternately arranged on two opposite sides of the liquid inlet screen 1 along the liquid inlet screen 1. The filtrate screen 2 is provided with a second liquid inlet hole 21 and a second filtrate hole 22, the filter layer 3 is provided with a third liquid inlet hole 32 and a third filtrate hole 33, wherein the first liquid inlet hole 11, the second liquid inlet hole 21 and the third liquid inlet hole 32 are opposite and communicated with a liquid inlet end on the shell 4; the first filtrate hole 12, the second filtrate hole 22 and the third filtrate hole 33 are opposite and communicated with the filtrate outlet end of the shell 4.

A first surrounding part 13 is arranged on the liquid inlet screen 1 at a position surrounding the first filtrate hole 12, and the first surrounding part 13 is sealed between the first filtrate hole 12 and the liquid inlet channel and is bonded and sealed on the liquid inlet surface of the filter layer 3. A second surrounding part 23 is arranged on the filtrate screen 2 at a position surrounding the second liquid inlet hole 21, and the second surrounding part 23 is sealed between the second liquid inlet hole 21 and the filtrate flow passage and is bonded and sealed with the liquid outlet surface of the filter layer 3. The first surrounding portion 13 and the second surrounding portion 23 are each obtained by applying a glue solution to the screen and allowing it to penetrate the screen. In the actual process, the liquid inlet screen 1 or the filtrate screen 2 is paved at a specific position, then the first surrounding part 13 or the second surrounding part 23 is coated on the screen, the filter layer 3 is paved above the screen, and then the filter layer 3 is heated and solidified, so that the adhesion between the screen and the filter layer 3 can be realized. In this embodiment, all set up the surrounding portion that is used for bonding the filter layer on feed liquor screen cloth and filtrate screen cloth, make feed liquor screen cloth, filtrate sun-out and filtration membrane bond together for the membrane package has in the installation, is difficult for taking place the skew between feed liquor screen cloth, filtrate screen cloth and the filter layer, and then has improved leakproofness, integrality and the yields of membrane package.

The arrangement of the first surrounding portion 13 and the second surrounding portion 23 on the filter layer 3 is as shown in fig. 2, the projections of the adjacent first surrounding portion 13 and second surrounding portion 23 on the same side of the filter layer 3 on the filter layer 3 have overlapping buffer portions 31 overlapping each other, in the embodiment, the aperture of the first filtrate hole 12 is 8mm, the aperture of the first liquid inlet hole 11 is 12mm, the outer diameter of the first surrounding portion 13 is 13mm, the outer diameter of the second surrounding portion 23 is 18mm, and the width of the overlapping buffer portion 31 in the direction of the line connecting the centers of the first surrounding portion 13 and the second surrounding portion 23 is 1mm. Through the setting of overlapping buffer portion, internal stress that each component shrinkage force difference produced and the influence of the torque force that first surrounding portion 11, second surrounding portion 12 and then produced on filter layer 3 are pressed filter layer 3 both sides at filter layer 3 when the membrane package solidification has been reduced in the membrane package installation, has improved the yields of membrane package.

Referring to fig. 1 to 2, the liquid inlet screen 1 has a first outer peripheral portion 14 surrounding the liquid inlet screen 1 at an edge position thereof, and the filtrate screen 2 has a second outer peripheral portion 24 surrounding the filtrate screen 2 at an edge position thereof. In the present embodiment, the first outer peripheral portion 14 is connected to all the first surrounding portions 13 with the connecting portion being smooth and free from dead angles, and the second outer peripheral portion 24 is connected to all the second surrounding portions 23 with the connecting portion being smooth and free from dead angles. In the present embodiment, the first surrounding portion 13 and the first outer peripheral portion 14 protrude from the liquid inlet screen 1 toward the filter layer 3 side and have the same thickness, and the thickness protruding from the liquid inlet screen 1 is 0.1 times the thickness of the liquid inlet screen 1 itself. The second surrounding portion 23 and the second peripheral portion 24 protrude from the filtrate screen 2 toward the filter layer 3 side and have the same thickness, and the thickness protruding from the filtrate screen 2 is 0.1 times the thickness of the filtrate screen 2 itself.

Referring to fig. 1 to 2, in the present embodiment, the edge of the liquid inlet screen 1 has a first protrusion 15 protruding from the first outer peripheral portion 14, the edge of the filtrate screen 2 has a second protrusion 25 protruding from the second outer peripheral portion 24, and when the liquid inlet screen 1, the filtrate screen 2 and the filter layer 3 are stacked, projections of the edge of the filter layer 3, the outer edge of the first outer peripheral portion 14 and the outer edge of the second outer peripheral portion 24 on a plane on which the filter layer 3 lies overlap, and both the first protrusion 15 and the second protrusion 25 are embedded in the side wall of the housing 4.

Embodiment 2 differs from embodiment 1 in that the first surrounding portion 13 and the second surrounding portion 23 are tangent circles on the filter portion, and do not have the overlap buffer portion 31, wherein projections of the filter layer 3 and the first surrounding portion 13 and the second surrounding portion 23 on the filter layer 3 are specifically shown in fig. 4.

Embodiment 3 is different from embodiment 1 in that the width of the overlap buffer portion 31 in the direction of the line connecting the centers of the first surrounding portion 13 and the second surrounding portion 23 is 0.5mm.

Embodiment 4 is different from embodiment 1 in that the width of the overlap buffer portion 31 in the direction of the line connecting the centers of the first surrounding portion 13 and the second surrounding portion 23 is 0.1mm.

Embodiment 5 is different from embodiment 1 in that the width of the overlap buffer portion 31 in the direction of the line connecting the centers of the first surrounding portion 13 and the second surrounding portion 23 is 2mm.

In the above-mentioned embodiment, all encircle the portion through first and encircle the portion and bond filter layer and screen cloth, first encircle the portion and encircle the portion with the second and strengthened filter layer and feed liquor screen cloth, filtrate between the screen cloth bonding performance, make overall structure more firm, the integrality of membrane package is higher. The integrity and film package yields for examples 1-5 are shown in table 1.

TABLE 1

Numbering device	Integrity (mL/min)	Yield (%)
			Example 1	31.0	＞99
Example 2	33.9	96.5
			Example 3	30.7	＞99
Example 4	31.2	＞99
			Example 5	31.5	＞99

From the above experimental data, it can be seen that the film package structures in examples 1 to 5 all have better integrity (average value of 30 samples), and higher yield. Compared with the embodiment 2, the film package prepared in other embodiments has higher yield, and the fact that a certain overlapped buffer part is arranged proves that the internal stress of the film package in the pressing process can be effectively reduced, and the yield of the film package is further improved.

The above embodiments are only preferred embodiments of the present utility model, and the scope of the present utility model is not limited thereto, but any insubstantial changes and substitutions made by those skilled in the art on the basis of the present utility model are intended to be within the scope of the present utility model as claimed.

Claims

1. The filtering membrane bag comprises a liquid inlet screen and a filtering liquid screen, and a filtering layer, wherein the liquid inlet screen, the filtering layer and the filtering liquid screen are sequentially stacked alternately to form a filtering part with a filtering effect;

the method is characterized in that:

2. The filter membrane pack of claim 1, wherein projections of the first and second loop portions onto a plane of the filter layer overlap to form an overlap buffer.

3. A filtration membrane pack according to claim 2, wherein the first surrounding portion is an annular structure surrounding the first filtrate aperture and/or the second surrounding portion is an annular structure surrounding the second filtrate aperture.

4. A filtration membrane pack according to claim 2, wherein the area of the overlapping buffer is no more than 5% of the projected area of the first surrounding portion on the filtration layer, and no more than 5% of the projected area of the second surrounding portion on the filtration layer.

5. A filtration membrane pack according to claim 2, wherein the width of the overlap buffer portion in the direction of the line between the centers of the first and second surrounding portions is 0.5-10% of the sum of the pore diameters of the first liquid inlet pore and the first filtrate pore.

6. The filtration membrane pack of claim 1, wherein the first surrounding portion protrudes from the surface of the liquid inlet screen and/or the second surrounding portion protrudes from the surface of the filtrate screen, and the thickness of the first surrounding portion and the second surrounding portion is 1 to 1.2 times the thickness of the screen.

7. A filtration membrane pack according to claim 1, wherein a first peripheral portion is further provided between the liquid inlet screen and the filtration layer in a region surrounding the edge of the liquid inlet screen for restricting liquid from flowing from the liquid inlet channel into the gap between the outer casing and the liquid inlet screen, the filtrate screen, the first peripheral portion being connected to all of the first surrounding portions;

8. The filtration membrane pack of claim 7, wherein the liquid feed screen is provided with a first protrusion partially or entirely surrounding the liquid feed screen outside the first peripheral portion, the first protrusion being embedded in the outer housing, and/or the filtrate screen is provided with a second protrusion partially or entirely surrounding the filtrate screen outside the second peripheral portion, the second protrusion being embedded in the outer housing.

9. The filtration membrane pack of claim 7, wherein the first peripheral portion is adhesively sealed between the feed screen and the filtration layer and/or the second peripheral portion is adhesively sealed between the filtrate screen and the filtration layer.

10. The filter membrane pack of claim 7, wherein the first peripheral portion and the first circumferential portion are smoothly connected in projection on a plane in which the filter membrane is located, and the second peripheral portion and the second circumferential portion are smoothly connected in projection on a plane in which the filter membrane is located.