WO2025144798A1

WO2025144798A1 - Filtration unit with a filtration element and a screening device

Info

Publication number: WO2025144798A1
Application number: PCT/US2024/061719
Authority: WO
Inventors: Christian STAAKS; Dominik BOTSCHAFTER; Martin Heijnen; Michael Hoffmann; Michael KASSEN; Bie LI
Original assignee: DuPont Safety and Construction Inc; DDP Specialty Electronic Materials US LLC
Current assignee: DuPont Safety and Construction Inc; DDP Specialty Electronic Materials US LLC
Priority date: 2023-12-29
Filing date: 2024-12-23
Publication date: 2025-07-03
Anticipated expiration: 2026-06-29
Also published as: CN121001807A

Abstract

Provided herein is a filtration unit comprising a filtration element and a screening device. The screening device comprises screening mesh body an orifice substantially positioned in the center of the screening device, an external ring in the outer periphery of the screening device, and a screening mesh body therebetween. Further provided is a filtration system comprising a vessel, a feed port, a permeate outlet, optionally a retentate outlet, and at least a filtration unit within the vessel. For at least one of the filtration units, the screening device is positioned upstream of the filtration element.

Description

Title of the invention

Filtration unit with a filtration element and a screening device

Cross-Reference to Related Applications

The present application claims priority under 35 U.S.C. § 365(c) to International Application No. PCT/CN23/143102, filed on December 29, 2023, which in turn claims priority to U.S. Provisional Patent Appln. No. 63/477,616, filed on December 29, 2022, each of which is incorporated herein by reference in its entirety.

Field of the invention

Provided herein are filtration units comprising filtration elements and integrated pre-filters. Further provided are filtration systems comprising the filtration units. More specifically, the pre-filter comprises a screening device, which in turn comprises an orifice substantially positioned in the center of the screening device, an external ring in the outer periphery of the screening device, and a screening mesh body therebetween. The external ring comprises an outer surface that is connected to an inner surface of the filter element’s housing.

Background of the Invention

Several patents, patent applications and publications are cited in this description in order to more fully describe the state of the art to which this invention pertains. The entire disclosure of each of these patents, patent applications and publications are incorporated by reference herein.

Filtration media, for example, membranes such as reverse osmosis (RO), nanofiltration (NF), ultrafiltration (UF), microfiltration (MF), electrodialysis (ED), distillation, degassing and ion exchange membranes, is commonly and effectively used for fluid treatment. By applying a driving force, in most cases pressure, to one surface of the membrane, the membrane is able to separate a feed fluid into a permeate stream that passes through the membrane and a retentate stream that contains the filtered materials. The most important application is the purification of water, by treating process streams such as industrial waste, seawater, ground water, sewage and effluent from sewage treatment facilities. Other industrial uses include purifying and/or concentrating dairy products, fruit juices and other beverages; enzyme recovery; and dialysis. MF membranes commonly have a pore size between 0.1 micron to several microns, which can be used to remove large microbial matter such as some bacteria. UF membranes typically have a pore size between 0.1 micron to 0.01 micron, which is small enough to separate a wider range of microbes, including viruses and other pathogens, as well as macromolecules, nanoparticles, proteins, biological cell debris and so forth. NF membranes usually have a pore size between 0.001 micron to 0.01 micron, effectively to remove divalent ions, most organic molecules, nearly all viruses, and a range of salts. RO membranes generally have a pore size between 0.0001 micron to 0.001 micron, which is by far the finest membrane available in industry to remove all organic molecules, viruses and most minerals.

The membranes are susceptible to fouling and damage from larger particles. Therefore, before feeding to the filtration system, coarse screening and/or fine screening is used to treat the feed fluid to remove large particles which may damage or block the membranes in the filtration system. In general, for UF and MF systems, the pre-treatment includes self-cleaning filters with the screening size from 50 microns to 400 microns, more preferably from 100 microns to 300 microns. Often, UF and/or MF membranes are used as a pre-treatment for the finer membranes RO and NF.

Since the pre-filter used in pre-treatment is used to remove larger particles, it is easily blocked and requires frequent cleaning, for example backwash and/or chemical cleaning, to recover the original flux. UF and MF membranes are used to remove relatively large particles; regular cleaning of these membranes is also required. Normal cleaning processes for UF and MF membranes include, without limitation, backwash, air scouring, chemical enhanced backwash (CEB), and clean in place (CIP). Among the cleaning processes for UF and MF membranes, the most frequently applied one is backwash, which is normally cycled once every 20 to 60 minutes based on feed conditions. For RO and NF membranes, which are generally composite membranes, CIP is an effective cleaning process. In industrial and wastewater treatment settings, pre-treatment is performed using a separate prefilter system upstream of the filtration system, that is, the pre-treatment filter is generally separated from the downstream filtration system as a separated device. In these cases, there are usually separate and time-consuming cleaning processes for the pre-treatment filter and the filtration system. To reduce footprint of a system, the amount of piping and the number of connections, a plurality of filtration elements may be employed within a single pressure vessel to form a multi-element filtration system. In these designs, the multielement filtration system has a single set of a feed port, a permeate outlet and a retentate outlet for the multi-element pressure vessel, instead of having one set for each filtration element. Multi-element filtration systems are used widely in water treatment facilities to purify water, and also as reactors in various chemical manufacturing processes. The most commonly used commercial RO system is a multi-element filtration system comprising multiple RO elements placed horizontally in series in a pressure vessel (Figure 1a). A horizontal system with RO elements placed in parallel (Figure 1b) is also known. Similarly, commercial multi-element UF or MF systems may include horizontal elements in series (Figure 1a) or vertical elements in parallel (Figure 1c). Vertical elements may be placed in a series as well (Figure 1d). Generally horizontal multi-element UF or MF systems use inside-out membranes and vertical multi-element UF or MF systems use outside-in membranes.

There have been attempts to integrate pre-filters with filtration elements or systems. Examples can be seen in JP03193122, JP04338221 and CN218249518, for integrating a pre-filter to an element housing, and CN216358934, for inserting a pre-filter to the element from the side of the housing. Examples can also be seen in KR10-1303993 for integrating a screening within a vertical multi-element system, and in WO2016042179 for integrating a cylindrical pre-filter underneath above vertically arranged filtration elements.

Nevertheless, there remains a need to integrate a pre-filter with an element that is easily handled, transported, and installed into a multi-element system. Especially for a UF or MF element treating a raw liquid with relatively high turbidity, there is a need to integrate a pre-filter with the element to enable easy handling, transportation and installation into a multi-element system. In addition, there is a need to integrate the pre-filter with the filtration element or system in a simple and effective way that is essential for the element’s installation and to control the cost of the filtration system. Summary of the Invention

Accordingly, provided herein is a filtration unit comprising: a filtration element with at least one filtration membrane with a first surface which is to contact feed and a second surface which is to contact permeate, at least one end of the filtration element comprising openings to introduce feed to the first surface of the filtration membrane, and a central pipe surrounded by the filtration membrane to collect permeate; and a screening device that is preferably connected to the end of the filtration element comprising one or more openings to introduce feed to the first surface of the filtration membrane, the screening device comprising an orifice substantially positioned in the center of the screening device, an external ring in the outer periphery of the screening device, and a screening mesh body therebetween.

Preferably, the screening device is backwashable. Also preferably, the external ring defines an outer width which is greater than the width of the filtration element.

The filtration membrane may be surrounded by a housing. The external ring may comprise an inner surface connected to the housing. The external ring may further comprise an external surface with at least a supporting rib.

The inner surface of the external ring is preferably connected with the housing by optional snap-in means, corresponding grooves and protrusions, screw threads, heat welding, press welding, glue, or other non-limited ways. Preferably the inner surface of the external ring is sealed relatively to the housing of the filtration element to avoid the feed flowing to the first surface of the filtration membrane between the potential gap between the inner surface of the external ring and the housing.

The external ring may further comprise an external surface with at least a supporting rib. Preferably there are multiple supporting ribs. The multiple supporting ribs may be separated into groups and preferably the groups of the supporting ribs are placed in a uniform spacing. When two or more filtration units are placed into a common vessel, the supporting rib of the external ring may be used to face against the inner surface of the vessel, preventing the filtration unit from deviation from the required position. Optionally, the supporting rib may be a circular O-ring around the external ring to seal between the external ring and the inner surface of the vessel.

The filtration unit may further comprise two ends, and each of the two ends may comprise openings via which the feed can be introduced to the first surface of the filtration membrane. The filtration unit may further comprise two or more screening devices, and the screening devices may be placed at both sides of the filtration element. In addition, the feed flow direction of the filtration unit may be reversible. That is, the feed can be introduced from either or both sides of the filtration element.

The filtration element may be connected directly with the screening device by attaching and fixing the screening device to the filtration element, for example, the external ring of the filtration element may comprise an inner surface connected to the housing.

The filtration unit may further comprise a connector to direct the permeate collected in the central pipe of the filtration element and may further be equipped with a sealing means. The connector may connect with both the screening device and the filtration element by insertion through the orifice of the screen device and into the central pipe of the filtration element. The sealing means seals between the connector and the central pipe, forming a fluid seal between the feed and the permeate. The connector may further comprise another sealing means to seal between the connector and the orifice.

The filtration element may be connected indirectly with the screening device by fitting the connector to connect both the screening device and the filtration element separately.

The filtration membrane is selected from the group consisting of microfiltration, ultrafiltration, nanofiltration, distillation, degassing, ion exchange and reverse osmosis membranes, preferably microfiltration and ultrafiltration membranes.

The screening device may further comprise at least two layers of screening mesh bodies between the orifice and the external ring. Preferably, at least two layers of the screening mesh bodies have different screening sizes. When the filtration membrane is UF or MF membrane, the screening mesh body preferably has a screening size of between 50 microns and 400 microns, more preferably between 100 microns and 300 microns, still more preferably between 100 microns and 150 microns.

Further provided is a filtration system comprising a vessel, a feed port, a permeate outlet, optionally a retentate outlet, and one or more filtration units described herein positioned in series within the vessel, each of the filtration units comprising a filtration element with at least one filtration membrane with a first surface which is to contact feed and a second surface which is to contact permeate, at least one end of the filtration element comprising openings to introduce feed to the first surface of the filtration membrane, and a central pipe surrounded by the filtration membrane to collect permeate; and a screening device connected to the end of the filtration element comprising one or more openings to introduce feed to the first surface of the filtration membrane; the screen device comprising an orifice substantially positioned in the center of the screening device, an external ring in the outer periphery of the screening device, and a screening body positioned between the orifice and the external ring.

In some embodiments, at least two filtration units are placed in series within the vessel. The first filtration unit and the second filtration unit are positioned in this order in feed flow direction, and for the first filtration unit, the screening device is positioned upstream of the filtration element in feed flow direction, and for the second filtration unit, the screening device is positioned downstream of the filtration element in the feed flow direction. The feed flow direction of the filtration system may be reversible. Alternatively, the feed may be introduced from either or both ends of the filtration system. There may be one or more individual membrane elements positioned in series with or without integrated screening devices between the two filtration units.

The filtration element of the filtration unit within the vessel may further comprise two ends. One or both of the two ends may comprise openings via which the feed can be introduced to the first surface of the filtration membrane, and each end of the filtration element may be connected with at least one screening device. The filtration system may further comprise another feed port at the opposite end of the filtration system, and the feed may flow to either or both feed ports of the filtration system. The feed flow direction of the filtration system may be reversible.

The filtration element is preferably connected directly with the screening device by attaching and fixing the screening device to the filtration element, for example, the external ring of the filtration element may comprise an inner surface connected to the housing.

The filtration unit may further comprise a connector to direct the permeate collected in the central pipe of the filtration element and equipped with a sealing means; and the connector connects with both the screening device and the filtration element by inserting it through the orifice of the screen device and into the central pipe of the filtration element. The sealing means seals between the connector and the central pipe, forming a fluid seal between the feed and the permeate. The connector may further comprise another sealing means to seal between the connector and the orifice.

The external ring may further comprise an external surface. The inner surface of the external ring is preferably connected with the housing by optionally snap-in means, corresponding grooves and protrusions, screw thread, heat welding, press welding, glue, and other non-limited ways. Preferably the inner surface of the external ring is sealed relatively to the housing of the filtration element to avoid the feed flowing to the first surface of the filtration membrane between the potential gap between the inner surface of the external ring and the housing. The external ring may further comprise an external surface with at least a supporting rib. Preferably there are multiple supporting ribs. The multiple supporting ribs may be separated into groups and preferably the groups of the supporting ribs are placed in a uniform spacing. When the filtration unit is placed into a common vessel, the supporting rib of the external ring may be used to face against the inner surface of the vessel, preventing the filtration unit from deviation from the required position. Optionally, the supporting rib may be a circular O-ring around the external ring to seal between the external ring and the inner surface of the vessel.

The external ring may further comprise an inner surface connected to the housing by optionally snap-in means, corresponding grooves and protrusions, screw thread, heat welding, press welding, glue, and other non-limited ways. Preferably the inner surface of the external ring is sealed relatively to the housing of the filtration element to avoid the feed flowing to the first surface of the filtration membrane between the potential gap between the inner surface of the external ring and the housing.

When the filtration element is optionally connected indirectly with the screening device by fitting a connector to connect both the screening device and the filtration element separately, the inner surface of the external ring is not necessarily connected to the housing.

The connector may be used to direct the permeate collected in the central pipe of the filtration element and may also be equipped with a sealing means. There could be a first connector connecting with only one filtration element. There could also be a second connector connecting with two filtration elements, i.e., one filtration element on each side of the connector. The first connector and the second connector preferably comprise sealing means to seal between the connector and the central pipe of the filtration element, forming a fluid seal between the feed and the permeate. The first connector may further comprise another sealing means to seal between the connector and the orifice. The second connector may further comprise another sealing means to seal between the connector and the orifice.

The filtration membrane is selected from the group of microfiltration, ultrafiltration, nanofiltration, distillation, degassing, ion exchange and reverse osmosis membranes, preferably microfiltration and ultrafiltration membranes. The type of membrane is selected independently for each membrane element in the filtration units.

The screening device may further comprise at least two layers of screening mesh bodies between the orifice and the external ring. And at least two layers of the screening mesh bodies have different screening sizes. When the filtration membrane is UF or MF membrane, the screening mesh body preferably has a screening size of between 50 microns and 400 microns, more preferably between 100 microns and 300 microns, still more preferably between 100 microns and 150 microns.

The advantages and features of novelty that characterize the invention are pointed out with particularity in the claims annexed hereto and forming a part hereof. For a better understanding of the invention, its advantages, and the objects obtained by its use, however, reference should be made to the drawings which form a further part hereof, and to the accompanying descriptive matter, in which there is illustrated and described one or more preferred embodiments of the invention.

Brief Description of the Drawings

Figures 1 a, 1b, and 1 c are sectional views that illustrate different types of multielement filtration systems of the prior art.

Figures 2a, 2b, and 2c are perspective views that illustrate a filtration unit as described herein.

Figures 3a through 3d are elevations that illustrate the front view of a screening device as described herein. Figure 3d is a partial elevation view of the screening device depicted in use in Figure 2b.

Figures 4a through 4d are perspective views that illustrate several connectors as described herein.

Figures 5a through 5d are section views that illustrate filtration systems with at least one filtration unit.

Figures 6a and 6b are partial views that illustrate a cross-section of a filtration system as described herein with at least two filtration units.

Figures 7a, 7b, and 7c are sectional views that illustrate filtration systems of the prior art in an original feed flow direction, a reversed feed flow direction, and feed flow from two ends of a filtration system.

Figure 8b is a sectional view that illustrates an embodiment of the filtration system as described herein. Figure 8a is a partial view of the sectional view depicted in Figure 8b. Figure 9b is a sectional view that illustrates an embodiment of the filtration system as described herein. Figure 9a is a partial view of the sectional view depicted in Figure 9b.

Figures 10a is a sectional view, and Figures 10b and 10c are partial sectional views that illustrate three further embodiments of the filtration system as described herein.

Detailed Description of the Invention

Referring now to the drawings, wherein like reference numerals designate corresponding structure throughout the views, and referring in particular to Figures 2 and 3, a filtration unit 10 comprises a filtration element 2 with at least one filtration membrane 9 (see Figure 5) with a first surface which is to contact feed and a second surface which is to contact permeate, at least one end 110 of the filtration element comprising openings 12 to introduce feed to the first surface of the filtration membrane, and a central pipe 8 surrounded by the filtration membrane 9 to collect permeate; and a screening device 21 comprising an orifice 23 substantially positioned in the central part of the screening device 21, an external ring 25 in the outer periphery of the screening device 21, and a screening mesh body 22 therebetween.

Although not depicted herein, the filtration membrane 9 may be potted by any suitable material, for example by a polymeric material, at one or both ends 110 of the filtration element 2. The external ring 25 comprises an inner surface 252 and an external surface 253. The external surface preferably comprises at least a supporting rib 251 . The supporting rib 251 may be extended along the feed direction or around at least as part of the outer periphery of the external ring 25 to fit into the vessel 3. Alternatively, the supporting rib(s) 251 may be disposed in a direction that is perpendicular to the feed flow, or in a diagonal direction that is intermediate between the feed flow direction and its perpendicular. Preferably there are multiple supporting ribs 251 which are separated into groups and preferably the groups of the supporting ribs 251 are placed in a relatively uniform spacing. When the filtration unit is placed into a common vessel 3, the supporting rib(s) 251 of the external ring 25 may be used to face against the inner surface of the vessel 3 (see Figures 5 and 9a). The functions of the supporting rib(s) 251 may include, without limitation, one or both of supporting the filtration element 2 and preventing the filtration unit 10 from deviation from the required or pre-set position. Alternatively, as shown in Figures 9a and 9b, the supporting rib 251 may comprise a circular O-ring around the outer periphery of the external ring 25 to seal between the external ring 25 and the inner surface of the vessel 3. The vessel 3 may optionally be a pressure vessel.

Referring now to Figure 2a, the filtration membrane 9 (shown in Figures 5 and 6) may be surrounded by a housing 11. The housing 11 may be a polymeric or metal tube, a cylindrical polymeric or metal netting, a spiral-wound non-woven fabric, a winding band, a combination of two or more of these types of housing, or any other suitable means to surround the filtration membrane 9. The housing 11 may be permanent or temporary. For example, the housing 11 may be dissolved in water and washed away after the filtration element 2 is put into operation.

Alternatively, the filtration element 2 may not be equipped with a housing 11. In such configurations (not depicted), the external ring 25 is disposed on one end 110 of the filtration element 2. When the filtration elements 2 are installed in a common vessel 3, the supporting rib(s) 251 on the external surface 253 of the external ring 25 form a fluid-tight seal between the external ring 25 and the inner surface of the vessel; in another embodiment, the supporting rib(s) 251 help to create a space between the filtration element 2 and inner surface of the vessel 3 for bypass flow.

The inner surface 252 of the external ring 25 may be connected to the housing 11 by optional snap-in means, corresponding grooves and protrusions, screw threads, heat welding, press welding, glue, a combination of two or more of these methods, or other non-limited ways. Preferably the inner surface 252 of the external ring 25 is sealed relatively to the housing 11 of the filtration element 2 to avoid the feed flowing to the first surface of the filtration membrane 9 between the potential gap between the inner surface 252 of the external ring 25 and the housing 11. An example of this configuration is depicted in Figure 8a.

Referring now to Figure 3, the screening device 21 comprises an orifice 23 substantially positioned in the center of the screening device 21 , an external ring 25 disposed along the outer periphery of the screening device 21 , and a screening mesh body 22 therebetween. The feed flows through the screening mesh body 22, into the openings 12 in one end 110 of the filtration element 2 (see Figure 2c, depicting the filter element 2 without the screening device 21 affixed) and then to the first surface of the filtration membrane 9. A general description of filter membranes and their operation is set forth in R.W. Baker “Membrane Technology and Applications,” 3rd edition, John Wiley & Sons, Ltd. (Hoboken, NJ, 2012), for example (hereinafter “Baker”). Briefly, part of the feed passes through the filtration membrane 9 from the first surface to the second surface as a permeate. The permeate is collected in central pipe 8. Preferably the inner diameter of the orifice 23 is sized appropriately to facilitate withdrawing the permeate that has collected in the central pipe 8. For example, in some configurations (not depicted) the central pipe 8 may extend through the orifice 23; in other configurations, a connector 261,262 may extend through the orifice 23, as depicted in Figure 2a, for example. The remainder of the feed does not pass through the filter membrane 9; rather, it becomes a retentate stream that contains the filtered materials. The retentate stream may be discharged as waste. Alternatively, it may undergo one or more additional purification methods, or it may be recycled through the filtration element 2 alone or in combination with another fluid to create a new feed flow.

The screening mesh body 22 may comprise a coarse screen (low mesh number) to remove large particles which may damage or block the filtration membranes 9 in the filtration element 2. Alternatively, the screening mesh body 22 may comprise a fine screen (high mesh number) to remove both larger and smaller particles from the raw feed. A suitable range of mesh opening sizes is 10 pm to 1000 pm, although smaller or larger sizes may be appropriate. Those of skill in the art are capable of determining suitable mesh number(s) based on the size(s) of material to be filtered from the feed stream. Ideally there is a seal (not shown) around the orifice 23 to prevent the feed from flowing into the filtration element 2 through the space around the orifice 23. The orifice 23 is preferably in the center of the screening device 21. As shown in Figure 2a and Figure 3a, the periphery of the screening mesh body 22 comprises an external ring 25 that secures the screening mesh body 22 in place in a position within the feed flow that is upstream of the filtration element(s) 2, i.e., before the feed flow enters the filtration element(s) 2. Also notably, the screening device 21 may comprise a single piece only (Figure 3a, 3b), or it may comprise several pieces joined or held together (Figure 3c).

As shown in Figure 2a and Figures 3b, 3c, and 3d, the screening device 21 may further comprise supporting beams 24 in the area of the screening mesh body 22 as a reinforcement to strengthen the screening device 21 or, as shown in Figure 3c, as a combination part for several pieces to form a screening device 21. Different parts of the screening device 21 may be formed into one piece by the action of an adhesive, by tongue-and-groove construction, by snap-in means, or by other connecting means (not shown). It may be preferable for the polymeric parts of the screening device 21 to be formed as one piece and combined by suitable means with the other parts made of non-polymeric materials. The screening device 21 may be formed as one piece by injection molding, by other types of molding, or by 3D printing in one or more pieces, for example.

The screening device 21 may comprise one or more organic materials, one or more inorganic materials, or a combination of one or more organic materials and one or more inorganic materials. Organic materials suitable for use in the screening device 21 include, without limitation, any suitable polymer such as, for example, polyolefins (including fluorinated polyolefins), polyamides, polyacrylates, polyesters, copolyesters such as Tritan™ (available from the Eastman Chemical Co. of Kingsport, TN), polysulfones (PS), polyethersulfones (PES), sulfonated polyethersulfone (SPS), celluloses, polycarbonates (PC), polytetrafluoroethylene (PTFE), polychlorotrifluoro-ethylene (PCTFE), fluorinated ethylene polymer (FEP), polyvinylidene fluoride (PVDF), polyvinyl chloride (PVC), polyacrylonitrile (PAN), acrylonitrile butadiene styrene (ABS) and a combination of two or more of these polymers. Inorganic materials suitable for use in the screening device 21 include, without limitation, metals such as stainless steel, ceramic components such as aluminum oxide, zirconium oxide, silicon oxide and the like, and a combination of two or more of these materials. Preferably the surrounding of the orifice 23, the supporting beams 24, and the external ring 25 are made from organic materials. Preferably the screening mesh body 22 is made from inorganic materials.

Filtration membranes 9 suitable for use in the filtration units described herein are described in Baker, cited above. Briefly, the filtration membrane 9 may include one or more of, or one or more types of, microfiltration, ultrafiltration, nanofiltration, distillation, degassing, ion exchange and reverse osmosis membranes. Preferably the filtration membrane 9 is selected from microfiltration and ultrafiltration membranes. The filtration membrane 9 may comprise organic or inorganic materials or a combination of the two. Organic materials suitable for use in the filtration membrane 9 include, without limitation, any suitable polymer such as, for example, polyolefins (including fluorinated polyolefins), polyamides, polyacrylates, polyesters, copolyesters including Tritan™ , polysulfones (PS), polyethersulfones (PES), sulfonated polyethersulfone (SPS), celluloses, polycarbonates, polytetrafluoroethylene (PTFE), polychlorotrifluoro-ethylene (PCTFE), fluorinated ethylene polymer (FEP), polyvinylidene fluoride (PVDF), polyvinyl chloride (PVC), polyacrylonitrile (PAN), and the like, and a combination of two or more of these polymers. Inorganic materials suitable for use in the filtration membrane 9 include, without limitation, a ceramic membrane made of any suitable material such as aluminum oxide, zirconium oxide, silicon oxide, and the like, and combinations of two or more of these materials. The ceramic membrane may be synthesized by a sintering method, a sol-gel method, a phase separation method, a vapor deposition method, or another suitable method known in the art. The filtration membrane 9 may be of any suitable shape such as hollow fibers, tubes, multi-bore fibers, knitted fibers, spiral sheets, pleated sheets and flat sheets. In elements with more than one membrane 9, the membranes may be the same or different.

Referring now to Figure 2c, one or both ends 110 of the filtration element 2 comprise one or more openings 12 to introduce feed to the first surface of the filtration membrane 9. Referring to Figure 5b and 5c, a filtration unit 10 may comprise two or more screening devices 21 , 2T on both ends 110 of the filtration element(s) 2. As discussed above, one or more screening devices 21, 2T may be located at a single end 110 of the filtration element 2, as depicted in Figures 5a and 5c. Alternatively, each end 110 of the filtration element 2 may be connected with at least one screening device 21, 21’, as depicted in Figures 5b and 5d. The two or more screening devices 21 , 2T can be placed together in parallel aligned by the orifices 23, as depicted in Figure 6b. The two or more screening devices 21 , 21’ may be the same, or they may have different screen sizes, material types, or shapes. The feed flow direction of the filtration unit 10 may be reversible. Alternatively, the feed can be introduced from either or both sides of the filtration unit 10.

The filtration element 2 is preferably connected directly with the screening device 21 by attaching and fixing the screening device 21 to the filtration element 2, for example by fixing the external ring 25 to the housing 11 , as depicted in Figure 2. Referring now to Figure 4, suitable connectors 261, 262 may be used to direct the permeate collected in the central pipe 8 of the filtration element 2 to the next filtration unit 10 in series or to a permeate outlet 5 as shown in Figure 1 , for example. Alternatively, the filtration unit 10 may use the connector 261, 262 to connect both the filtration element 2 and the screening device 21 so that the filtration element 2 is connected indirectly with the screening device 21 whose external ring 25 has no direct connection to the housing 11 of the filtration element 2, by fitting the connector 261, 262 to connect both the screening device 21 and the filtration element 2 separately. This configuration is shown in Figure 9.

As shown in Figure 4, the connector 261, 262 may be a hollow tube with a hollow chamber 28. The connector 261 , 262 directs the permeate collected in the central pipe 8 of the filtration element 2 and is equipped with at least one sealing means 27. Any suitable sealing means 27 may be used. Preferably, the sealing means forms a fluid-tight seal. For example, two or more O-rings, preferably deformable or elastic O-rings, are depicted in Figures 4a to 4d. Also preferably, the O-rings are seated, so that they remain in place on the connector 261, 262 when it is attached to the central pipe 8. The connector 261, 262 connects with both the screening device 21 and the filtration element 2 by inserting through the orifice 23 of the screen device 21 and inserting into the central pipe 8 of the filtration element 2. In this preferred configuration, the sealing means 27 seals between the connector 261, 262 and the central pipe 8, forming a fluid seal between the feed and the permeate. The first type of connector 261 has sealing means 27 at one end (Figure 4b, 4d) to connect to and seal with only one filtration membrane 2. The second type of connector 262 has sealing means 27 at both ends (Figure 4a, 4c) and each end of the connector 262 connects to and seals with one filtration membrane 2. The connector 261 , 262 may further comprise a protruded base 29 for a screening device 21 to align with and/or rest on. Such protruded base 29 may also enable a constant spacing between neighboring filtration elements 2 on both sides of the protruded base 29. The first connector 261 may further comprise an additional part or be connected to an additional part of the filtration system 1 , such as a cover 31 shown in Figure 8a and Figure 9a. The connector 261, 262 may further comprise another sealing means (not shown) to seal between the connector 261 , 262 and the orifice 23.

Referring now to Figure 5 and Figure 6, the first connector 261 is connected to the filtration element 2 by inserting the end with sealing means 27 into the central pipe 8 of the filtration element 2. In this preferred configuration, the sealing means 27 forms a fluid seal, that is, a seal that is not permeable by gas or liquid, between the feed and the permeate. The first connector 261 is connected to the screening device 21 by inserting one end of the first connector 261 through the orifice 23 of the screening device 21 . As shown in Figure 5a and 5b, the filtration element 2 may be connected indirectly to the screening device 21 via the first connector 261, which may connect separately to each of the screening device 21 and the filtration element 2. In this configuration, the external ring 25 has no direct connection to the housing 11 of the filtration element 2 (as depicted in Fig. 9a), and the first connector 261 also helps to direct the permeate collected in the central pipe 8 to a further step in the purification process or to a storage vessel, for example. As shown in Figures 5c and 5d , a filtration system 1 that has a direct connection between the filtration element 2 and the screening device 21 (depicted as an orthogonal portion of the screening device 21) may also comprise a first connector 261 to direct the permeate collected in the central pipe 8 of the filtration element 2 to a further step in the purification process or to a storage vessel, for example.

Optionally, without a first connector 261 , the filtration element 2 comprises a protrusion (not shown) that is suitable to connect with the screening device 21 by inserting the protrusion through the orifice 23 of the screening device 21.

Referring now to Figures 5(a-d), further provided herein is a filtration system 1 comprising a vessel 3, two ends 112 of the vessel 3 with multiple ports including a feed port 4, a permeate outlet 5, and optionally a retentate outlet 6, and at least one filtration unit 10 as described herein (shown in Figure 2, for example) within the vessel 3, said system comprising a filtration unit 10 which comprises a filtration element 2 with at least one filtration membrane 9 with a first surface which is to contact feed and a second surface which is to contact permeate, at least one end 110 of the filtration element 2 comprising openings 12 (shown in Figure 2c) to introduce feed to the first surface of the filtration membrane, and a central pipe 8 surrounded by the filtration membrane(s) 9 to collect permeate; and a screening device 21 connected to the end 110 of the filtration element 2 comprising one or more openings 12 to introduce feed to the first surface of the filtration membrane(s) 9; wherein the screening device 21 comprises an orifice 23 substantially positioned in the central part of the screening device 21, an external ring 25 disposed along the outer periphery of the screening device 21 , and a screening mesh body 22 disposed between the between the orifice 23 and the external ring 25.

In some preferred configurations, at least one filtration unit 10 is positioned at the outermost edge of the feed side of the filtration system 1, and the screening device 21 of the one filtration unit 10 is positioned upstream of the filtration element 2 in feed flow direction.

The screening device 21 may comprise at least two layers of screening mesh bodies 22 between the orifice 23 and the external ring 25, wherein the layers of the screening mesh bodies 22 have screening sizes that are the same or different. When the filtration membrane is UF or MF membrane, the screening mesh body 22 preferably has a screening size of between 50 microns and 400 microns, more preferably between 100 microns and 300 microns, still more preferably between 100 microns and 150 microns.

To reduce the physical footprint of a filtration system, it is known to place at least two filtration units 10 within the vessel 3, as shown in Figures 1a through 1d. Significantly, the configurations shown in Figures 1a through 1d apply equally well to the filtration units and filtration systems provided herein. For example, the filtration units 10 may be positioned in series in a horizontal direction (as shown in Figures 1a and 1b) or in a vertical direction (as shown in Figures 1c and 1d). There is preferably an air inlet port 7 for the vertical system, as shown in Figure 1c and Figure 1d. Preferably the filtration units 10 are positioned in series in horizontal direction, as illustrated in Figure 1a. Also depicted in Figures 1 a through 1 d are feed inlet 4, permeate outlet 5, and retentate outlet 6.

As shown in Figure 6, Figure 8b, and Figure 9b, at least two filtration units 10 may be placed in series in horizontal direction within the vessel 3. Preferably, at least one screening device 21 is positioned before the feed inlet 4 of the first filtration unit 10 (configuration not shown). Alternatively, a screening device 21 may be placed upstream of the first filtration unit 10 in the feed flow direction. For example, in Figure 8b, a screening device 21 is positioned before each filtration unit 10 in the feed flow direction. In Figure 9b, a screening device 21 is positioned before the first filtration unit 10 and another screening device 2T is positioned after the last filtration unit 10 in the filtration system 1. Again, the ordering of the filtration units is in the direction of the feed flow. Significantly in this connection, the feed flow direction of the filtration system 1 is reversible. That is, as depicted in Figure 7, the feed can be introduced from the feed port 4 for some period of operation, and then the feed can be reversed and introduced from the feed port 4’ for another period of operation. Alternatively, the feed can be introduced from either or both sides of the filtration system 1 , for example from either or both of the feed ports 4, 4’. Referring now to Figure 6b, the first connector 261 is connected to the feed inlet 4, and the second connector 262 is connected to two filtration elements 2, 2”. Each end of the second connector 262 is connected to one filtration element 2 by inserting the end with sealing means 27 into the central pipe 8 of the filtration elements 2, 2’. Sealing means 27 preferably forms a fluid seal, that is, a seal that is not permeable by gas or liquid, between the feed and the permeate within the filtration system 1. In some preferred configurations, such as the one shown in Figure 6b, the second connector 262 is connected to two screening devices 21, 21’. In this preferred configuration, each end of the second connector 262 is connected to a screening device 21, 21’ by inserting one end of the second connector 262 through the orifice 23, 23’ of each screening device 21, 21’.

In the filtration system 1 depicted in Figure 9b, one or more individual filtration elements 2”, 2’” may be positioned in series between two filtration units 10, 10’. This filtration system 1 further comprises two or more second connectors 262 to connect the membrane elements 2, 2’, 2”, 2’” in adjacent pairs. In addition, in this configuration the filtration elements 2, 2’ of the filtration units 10, 10’ are connected indirectly with the screening devices 21, 21’ by fitting connectors 261, 26T to connect both the screening devices 21, 21’ and the filtration elements 2, 2’, optionally connecting them one by one or separately. The partial view shown in Figure 9a illustrates in cross-section the external ring 25, its external surface 253, and at least one supporting rib 251, which is depicted here as a circular protrusion or O-ring that extends around the outer circumference of the external ring 25 to seal between the external ring 25 and the inner surface of the vessel 3.

Referring once more to Figure 8b, in an alternative configuration of filtration system 1, two or more filtration units 10, 10’, 10”, 10’” are positioned in series, each filtration unit 10, 10’, 10”, 10’” comprises two or more screening devices 21 , 2T, 21”, 2T”, and each end 110 of each filtration element 2, 2’, 2”, 2’” is connected with at least one screening device 21, 2T, 21”, 2T”. In this configuration, the filtration system 1 further comprises a second connector 262 to connect every two neighboring filtration units 10, 10’, 10”, 10’”. Optionally, the filtration units 10, 10’, 10” are connected directly with the screening devices 21,21’. As shown in Figure 8a, the inner surface 252 of the external ring 25 of the screening device 2T is connected with the housing 11 , for example by optional snap-in means, corresponding grooves and protrusions, screw threads, heat welding, press welding, glue, by another suitable means known in the art, or by a combination of two or more of these methods. When the screening device 21 is fixed directly to the housing 11 of the filtration element 2, the filtration unit 10 can be transported and installed conveniently as a single unit without the need of managing the filtration element 2 and the screening device 21 separately. Preferably the inner surface 252 of the external ring 25 is sealed relatively to the housing 11 of the filtration element 2 in a fluid-tight seal, to avoid the feed flowing to the first surface of the filtration membrane 9 between the inner surface of the external ring 25 and the housing 11. In Fig. 8a, the fluid-tight seal 26 is depicted as a circular protrusion along the inner circumference of external ring 25.

Referring now to Figure 10a, a filtration system 1 is depicted that is similar to that depicted in Figure 5d, except that there are two screening devices 21 ,21 ’ at each end 115,115’ of the system. In Figure 10b, a filtration system 1 is depicted that is similar to that shown in Figure 6a, except that there are two screening devices 21 ,21 ’ at the depicted end 115 of the system. In Figure 10c, a filtration system 1 is depicted that is similar to that shown in Figure 6b, except that there are two screening devices 21,21’ at the depicted end 115 of the system.

The filtration membrane 9 is selected from the group of MF, UF, NF, distillation, degassing, ion exchange and RO membranes. The type of membrane is selected independently for each filtration unit. Stated alternatively, the filtration units may include the same type or different types of the filtration membranes. Preferably the filtration membrane 9 is selected from MF and UF. Normal cleaning processes for UF and MF include backwash, air scouring, chemical enhanced backwash (CEB), cleaning in place (CIP), and other methods known to those of skill in the art. The most frequently applied cleaning process is backwash, which is typically conducted once every 20 to 60 minutes based on feed conditions. With the filtration unit 10 and filtration system 1 described herein, when cleaning such as backwash is applied to clean the MF and/or UF membranes, the same cleaning process is simultaneously applied to the screening device 21. Therefore, no separate cleaning steps or additional cleaning agents are needed to clean the screening device 21 and the filtration element 2, which largely reduces the maintenance time and cost, and highly improves the operation efficiency. Furthermore, the filtration elements 2 described herein enable one-control-philosophy for the filtration unit 10 with both screening device 21 and filtration element 2. The term “one-control-philosophy” refers to systems that can be operated in the same manner as a system that includes only UF capability without additional operational changes.

In a multi-element filtration system 1, the filtration membranes 9 of different filtration elements 2 may have the same or different materials, pore sizes, morphologies, dimensions, and shapes, etc. Different filtration elements 2 in the filtration system 1 may have the same or different configurations, membranes, membrane areas, etc. For example, as shown in Figure 6, a downstream filtration element 2” may have filtration membranes 9’ with larger or smaller pore sizes than that of the filtration membrane 9 in an upstream filtration element 2.

Referring now to Figures 7a, 7b, and 7c, it is significant that these drawings illustrate filtration systems that are known in the art. Nevertheless, the construction of filter systems designed for reversible feed flow apply equally to the filtration elements and filtration systems described herein, for example those depicted in Figures 8b and 9b. In these configurations, the feed flow direction of the filtration unit 10 and the filtration system 1 is reversible. Also significantly, reversing the flow in this manner is one mechanism by which the screening device(s) 21 may be backwashed. As shown in Figure 7a, the filtration system 1 comprises a vessel 3, two ends 112 of the vessel 3 with multiple ports including a feed port 4, a permeate outlet 5, optionally a retentate outlet 6, a first filtration unit 10, and at least a second filtration unit 10’. When the feed flow reverses compared with the flow direction in Figure 7a, the filtration system 1 operates in the configuration depicted in Figure 7b, in which the filtration system 1 comprises a vessel 3, two ends 112 of the vessel 3 with multiple ports including a feed port 4’, which functions as a retentate outlet 6 in the configuration depicted in Figure 7a; a retentate outlet 6’, which functions as a feed port 4 in the configuration depicted in Figure 7a; a permeate outlet 5, which retains the same function as in the configuration depicted in Figure 7a; a first filtration unit 10; and at least a second filtration unit 10’. As shown in Figure 7c, in another configuration the filtration system 1 comprises a vessel 3, two ends 112 of the vessel 3 with multiple ports including feed ports 4, 4’, a permeate outlet 5, a retentate outlet 6, and at least two filtration units 10, 10’. In this configuration, the feed is introduced from the feed ports 4, 4’ from both sides of the filtration system 1. There may also be permeate outlets 5 positioned on one or both ends 115 of the filtration system 1 ; alternatively, a plug 30 may be inserted in one end of the central pipe 8 to seal between the permeate and the feed or the retentate, as shown in Figure 5a and Figure 5c. As shown in Figure 8 and Figure 9, the external ring 25 may preferably have an inner diameter that is greater than the outer diameter of the filtration element 2. In the depicted configuration, the external ring 25, directly or indirectly connecting to the filtration element 2, establishes a gap between the filtration element 2 and the vessel 3. In some configurations, this gap may prevent the contents of the filtration element 2 from being pumped into the vessel 3. In a preferred configuration, shown in Figure 8, there is also a gap between the external ring 25 and the inner surface of the vessel 3. This gap may prevent the screening device 21 from expanding and pressing against the vessel 3, thus possibly deforming and disrupting other seals or connections in the system. Such unwanted expansion may be the result of exposure to solvents or to excessive heat.

While certain of the preferred embodiments of the present invention have been described and specifically exemplified above, it is not intended that the invention be limited to such embodiments. Rather, it is to be understood that even though numerous characteristics and advantages of the present invention have been set forth in the foregoing description, together with details of the structure and function of the invention, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.

Numbers for reference

Claims

1. A filtration unit comprising: a filtration element comprising at least one filtration membrane with a first surface for contacting feed and a second surface for contacting permeate; wherein at least one end of the filtration element comprises one or more openings to introduce feed to the first surface of the filtration membrane; and wherein the filtration element further comprises a central pipe surrounded by the filtration membrane to collect permeate; and a screening device connected to the end of the filtration element that comprises the one or more openings; wherein the screening device comprises an orifice substantially positioned in the center of the screening device, an external ring positioned along the outer periphery of the screening device, and a screening mesh body disposed between the orifice and the external ring, and optionally wherein the external ring defines an outer width which is greater than the width of the filtration element.

2. The filtration unit of claim 1 , wherein the external ring comprises an external surface comprising at least a supporting ridge.

3. The filtration unit of claim 1 or claim 2, wherein the filtration membrane is surrounded by a housing; the external ring comprises an inner surface; and the inner surface is connected to the housing.

4. The filtration unit of any of claims 1 , 2, or 3, wherein the filtration element comprises two ends, and the two ends comprise openings via which the feed can be introduced to the first surface of the filtration membrane; wherein the filtration unit comprises two or more screening devices; and wherein each end of the filtration element is connected to at least one screening device.

5. The filtration unit of any preceding claim, wherein the feed flow direction of the filtration unit is reversible.

6. The filtration unit of any preceding claim, further comprising a first connector to direct the permeate collected in the central pipe of the filtration element; wherein the first connector is equipped with a sealing means; wherein the first connector connects with both the screening device and the filtration element by inserting through the orifice of the screen device and inserting into the central pipe of the filtration element; and wherein the sealing means seals between the first connector and the central pipe, forming a fluid seal between the feed and the permeate.

7. The filtration unit of claim 6, wherein the first connector further comprises a second sealing means to seal between the first connector and the orifice.

8. The filtration unit of any preceding claim, wherein the inner surface of the external ring is sealed against the housing of the filtration element.

9. The filtration unit of any preceding claim, wherein the screening device comprises at least two layers of screening mesh bodies.

10. The filtration unit of any preceding claim, wherein the at least two layers of the screening mesh bodies have different screening sizes.

11 . The filtration unit of any preceding claim, wherein at least one of the screening mesh body layers has a screening size of between 50 microns and 400 microns.

12. The filtration unit of any preceding claim, wherein at least one of the screening mesh body layers has a screening size of between 100 microns and 300 microns.

13. The filtration unit of any preceding claim, wherein the filtration membrane is selected from the group consisting of reverse osmosis membranes, nanofiltration membranes, ultrafiltration membranes, microfiltration membranes, electrodialysis membranes, distillation membranes, degassing membranes, ion exchange membranes, and combinations of two or more of these membranes; preferably the group consisting of microfiltration membranes, ultrafiltration membranes, and both microfiltration membranes and ultrafiltration membranes.

14. The filtration unit of any preceding claim, wherein the screening device is backwashable.

15. A filtration system comprising a vessel, said vessel comprising two ends, wherein at least one of the two sides ends is equipped with multiple ports including one or more of a feed port, a permeate outlet, and optionally a retentate outlet, and wherein at least one filtration unit of any preceding claim is placed within the vessel.

16. The filtration system of claim 15, comprising at least two filtration units, wherein one screening device of one filtration unit is positioned next to each end of the filtration system.

17. The filtration system of claim 15 or claim 16, that comprises at least two feed ports, wherein at least two of the feed ports are positioned on different ends of the filtration system, and wherein the feed flows to at least two feed ports on different ends of the filtration system.

18. The filtration system of claim 15, 16, or 17, wherein the feed flow direction of the filtration system is reversible.

19. The filtration system of any of claims 15 to 18, wherein the external ring comprises an external surface comprising at least a supporting ridge to face against the inner surface of the vessel.