A filter cartridge and the use of a filter cartridge

Abstract

Filter cartridge (2) structured for coalescing a dispersed phase from a mixture of the dispersed phase into a continuous phase as the mixture moves from the outside to the inside through the cartridge (2), the cartridge comprising: (a) an outer filter element (4), the outer filter element (4) comprising: (i) an outer pleated filter material (4a), the outer pleated filter (4a) having a substantially cylindrical shape, the outer pleated material (4a) comprising a composite material having a permeability of less than 0.0188 m³ / s (40 cfm); (ii) end caps (4c, 4e) attached to opposite ends of the outer pleated filter material (4a); and (b) an inner filter element (6) arranged within the outer filter element (4), the inner filter element (6) comprising: (i) an outer unfolded filter material (6a),wherein the outer unfolded filter material (6a) has a substantially cylindrical shape; (ii) an inner pleated filter material (6b) in direct or indirect contact with the outer unfolded filter material (6a), wherein the inner pleated filter material (6b) has a substantially cylindrical shape; and (iii) end caps (6c, 6d) attached to opposite ends of the outer unfolded filter material (6a) and the inner pleated filter material (6b), wherein the outer filter element (4) further comprises: (iii) an inner unfolded filter material (4b) in direct or indirect contact with the outer pleated filter material (4a) at inner fold points of the outer pleated filter material (4a), wherein the inner unfolded filter material (4b) has a substantially cylindrical shape and the end caps (4c, 4e) are attached to opposite ends of the inner unfolded filter material (4b),(iv) a support structure optionally selected from a group consisting of a permeable tube, a screen, a spring, a cage-like structure, wherein the support structure contacts the inner unfolded material (4b) of the outer filter element (4), wherein the support structure is located on the outer surface of the inner unfolded filter material (4b) of the outer filter element (4) and the inner unfolded filter material (4b) indirectly contacts the outer folded filter material (4a) of the outer filter element (4) at the inner fold points via the support structure.

Description

GENERAL STATE OF THE ARTThe field of the invention relates to filters, such as filter-in-filter cartridges, suitable for fuel-water separation, and uses thereof. The field relates in particular to a filter-in-filter fuel-water separator and particulate filters, which preferably comprise a thermoplastic material.The subject matter of the present application is related to U.S. application Ser. No. 12 / 820,791, filed Jun. 22, 2010, entitled "MODULAR FILTER ELEMENTS FOR USE IN A FILTER-IN-FILTER CARTRIDGE", and U.S. application Ser. No. 12 / 820,784, filed Jun. 22, 2010, entitled "TWO STAGE WATER SEPARATOR AND PARTICULATE FILTER", to which the present application claims priority and the contents of which are incorporated herein by reference in their entirety.Coalescers have found wide application to remove immiscible droplets from a gaseous or liquid continuous phase, such as in crankcase ventilation (CV), fuel water separation (FWS), and oil-water separation. Prior art coalescer designs involve the principles of improved droplet capture and coalescence by using graded capture (i.e., decreasing fiber diameter, pore size, and / or porosity in coalescing media) or by utilizing large depth coalescers. It is also recognized that wettability affects coalescer performance. (See, for example, U.S. Pat. No. 6767459 B1 and published U.S. Patent Applications US 2007 / 0131235 A1 and US 2007 / 0062887 A1). U.S. Patent US 5443724 A discloses that the media should have a surface energy greater than water to improve coalescer performance (i.e., the media should preferably be used by both coalescing droplets and continuous phases). U.S. Patent No. 4081373 discloses that coalescing media should be hydrophobic to remove water from fuel. Published U.S. patent application US 2006 / 0242933 A1 discloses an oil mist coalescer in which the filtering medium is oleophobic, whereby the fluid can coalesce into droplets and drain out of the filtering media.With respect to the disposal of water from fuel, there is a need to increase the disposal efficiency and to remove smaller droplets than in the past. This challenge is further enhanced by the introduction of new fuels with lower interfacial tensions and different additive packages than fuels in the past. In particular, Ultra Low Sulfur Diesel (ULSD) and biodiesel generally have lower interfacial tensions (IFT) and therefore have a smaller droplet size and more stable emulsions than previous diesel fuel. For fuels with low interfacial tension, the size of dispersed droplets is less, making it difficult to eliminate the droplets. Improved coalescence is therefore required to address these challenges. Improved coalescers containing improved coalescing media are also desirable because they allow for the use of a smaller media pack in view of improved coalescing efficiency. For fuels with lower interfacial tension, the size of the droplets is smaller, making it difficult to eliminate the droplets.Traditional fuel-water separators (FWS) are generally single stage devices designed to be used before the fuel pump. In traditional FWS, the filter media is hydrophobic with respect to the dispersed water phase and acts as a barrier. However, traditional FWS generally do not provide adequate water disposal for ULSD fuel and biodiesel with low IFTS (<15 dynes / cm) and low releasability (<50%) because their pore size is generally too large to effectively trap the small droplets. As such, a large droplet size is required for effective capture. This large droplet size is also a requirement made by the need to maintain the pressure drop across the FWS well below the 1 atmosphere available when the FWS is used in front of the fuel pump. In addition, even if the average pore size is sufficiently small, FWS media and fibrous filter media generally have a maximum pore size that is so large that excessive amounts of water pass through these large pores. In modern high pressure common rail fuel systems, where it is important to remove almost all of the undissolved water from the water flowing to the injectors, the amount of water passing through these large pores is unacceptable. In addition, in modern HPCR fuel systems, it is often desirable that the fuel-water separator be on the pump pressure side where the filter is exposed to higher pressures and the size of the water droplets is much smaller. Traditional two-stage fuel-water coalescers (FWC) are designed to be used behind the fuel pump and are generally two-stage devices for fuel, with the first stage trapping the droplets, holding them so that coalescence can occur, then releasing the enlarged droplets that are eliminated by sedimentation / settling, typically after being blocked by the second separator stage (with the second separator stage acting as an FWS). Traditional two-stage FWCs generally provide higher disposal efficiency than FWS, but generally have insufficient life due to plugging by solid particles or semi-solid particles. To varying degrees, both FWS and FWC are affected by the presence of surfactants in fuels that reduce interfacial tension, reduce droplet size, slow coalescence rate, stabilize emulsions and can be adsorbed onto media, and make them less effective. As such, there is a need for improved fuel-water separators that have high efficiency, low pressure drop, and are minimally affected by low interfacial tension and the presence of surfactants.WO 2009 / 058 598 A2 discloses a filter material for a filter system comprising a filter material capable of capturing hydrogen sulfide from a liquid, wherein the filter material is disposed between a first and a second filter mediumSUMMARY OF THE INVENTIONModular filter-in-filter elements are disclosed, namely an outer filter element and an inner filter element, that can be assembled to form a filter cartridge for use in separation methods and systems. The outer filter element typically functions as a coalescing element, the inner element typically functions as a particulate filter element, and for separating coalesced water drops from the fuel. The disclosed filter cartridges may be structured to separate water from a liquid hydrocarbon-based fuel as the fuel moves from the outside inward through the cartridge.In the disclosed cartridges, the inner filter element is located within the outer filter element. The outer filter element includes: (i) an outer pleated filter material, preferably the outer pleated filter material is polymeric material (e.g., thermoplastic material) and has a substantially cylindrical or oval shape; (ii) an inner unfolded filter material in direct or indirect contact with the outer pleated filter material at inner pleat tips of the outer pleated filter material, preferably the inner unfolded filter material is polymeric material (e.g., thermoplastic material) and has a substantially cylindrical shape; and (iii) end caps attached to opposite ends of the outer pleated filter material and the inner unfolded filter material. The inner filter element includes: (i) an outer unfolded filter material, preferably wherein the outer unfolded filter material is polymeric material (e.g., thermoplastic material), preferably hydrophobic material, and has a substantially cylindrical shape; (ii) an inner folded filter material in direct or indirect contact with the outer unfolded filter material, preferably wherein the inner folded filter material is polymeric material (e.g., thermoplastic material) and has a substantially cylindrical shape; and (iii) end caps attached to opposite ends of the outer unfolded filter material and the inner folded filter material. The outer filter element and the inner filter element may share one or both end caps. For example, one or both ends of the filter material of the outer member and one or both ends of the filter material of the inner member may be attached to the same end cap.The outer filter element of the disclosed filter cartridges includes: (iv) a support structure, which is typically a perforated or shielding material. The support structure is located on the outer surface of the inner unfolded filter material of the outer filter element. The inner unfolded filter material is in indirect contact with inner folding tips of the outer folded filter material of the outer filter element via the supporting structure. Suitable support structures may include, but are not limited to, a tube, a screen, a cage-like structure, and a spring.The outer filter element comprises outer pleated filter material, which may contain one or more layers of media material, referred to as a "nanofibrous layer", which has preferred characteristics for coalescing water droplets present in a hydrocarbon fuel as the fuel passes through the outer pleated filter material. As a rule, the nanofibre layer has an average pore size M, wherein 0.2 μm ≤ M ≤ 12.0 μm (preferably 0.2 μm ≤ M ≤ 10 μm, and particularly preferably 0.2 μm ≤ M ≤ 8.0 μm, e.g. 0.2, 0.8, 1.2, 1.6, 2.0, 2.8, 3.2, 3.6, 4.0.4.4, 4.8, 5.2, 5.6, 6.0, 6.4, 6.8, 7.2, 7.6 or 8.0 μm). The media material of the nano-fiber layer typically has a maximum pore size M M and is preferably 1≤M M / M≤3, preferably 1≤M M / M≤2 (e.g., the maximum pore sizes may include M M3, 6, 9, 12, 15, 18, 21, 24, 27, 30, 33 and 36 μm). The media material of the nanofibre layer usually contains fibres, wherein the fibres have an average diameter of below about 1 μm and in some embodiments between 0.07 μm and 1 μm (preferably between 0.15 μm and 1 μm, e.g. 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 or 1.0 μm). The media material of the nanofibre layer usually contains a polymeric non-woven material (e.g. polyamide material) which can be formed by electrobubbling. The media material has a suitable permeability. According to the invention, a permeability is below 0.0188 m3 / s (40 cfm) (preferably below about 30 cfm, more preferably below about 20 cfm, e.g. 19, 18, 17, 16, 15, 14, 13, 12, 11 or 10 cfm). The nano-fiber layer of media material has a desired thickness as measured from upstream to downstream relative to the flow through the cartridge (i.e., as measured from outside to inside). Suitable thicknesses include thicknesses between 0.05 and 0.4 mm (preferably between 0.1 and 0.3 mm, e.g., 0.10, 0.12, 0.14, 0.16, 0.18, 0.20, 0.22, 0.24, 0.26, 0.28, and 0.30 mm). The nano-fiber layer of media material preferably has a basis weight of at least about 10 gsm (or at least 20 gsm or 30 gsm).In addition to the media material nano-fiber layer of the outer pleated filter material of the outer filter element as described above, the outer pleated filter material may include additional media material layers having the same or different characteristics as the media material nano-fiber layer described above. For example, the outer pleated filter material of the outer filter element may include one or more additional layers of media material in front of or behind the above-described layer of media material. In some embodiments, the outer pleated filter material of the outer filter element includes an additional layer of media material located in front of the above-described layer of media material, namely an upstream first layer of media material and a downstream second layer of media material, as described above. The first layer and the second layer of media material have average pore sizes M 1 and M, respectively. M 2 and preferably M 1 > M 2. For example, M 1 may be at least about 2.5x, 5x, or 10x larger than M 2( e.g., M 1 ≥ 10 μm, M 1 ≥ 20 μm, or M 1 ≥ 30 μm). The additional layer of upstream media material may contain fibers, wherein the fibers have an average fiber diameter of 1-100 μm, 3-100 μm, 10-100 μm, 20-100 μm or 40-100 μm. The additional layer of upstream media material has a suitable permeability. Suitable permeability for the upstream media material may include a permeability of between about 20-500 cfm (preferably between about 30-400 cfm, more preferably between about 40-300 cfm, e.g., 50, 75, 100, 125, 150, 175, 200, 225, 250, 275, or 300 cfm).In other embodiments, the outer pleated filter material of the outer filter element includes an additional layer of media material located behind the above-described nano-fiber layer of media material, namely an upstream first layer of media material as described above and a downstream second layer of media material. The first layer and the second layer have average pore sizes M 1 and M, respectively. M 2 and preferably M 1< M 2. For example, M 2 may be at least about 2.5x, 5x, or 10x larger than M 1( e.g., M 2 ≥ 10 μm, M 2 ≥ 20 μm, or M 2 ≥ 30 μm). The additional layer of downstream media material may contain fibers, wherein the fibers have an average fiber diameter of 1-100 μm, 3-100 μm, 10-100 μm, 20-100 μm or 40-100 μm. The additional layer of downstream media material has a suitable permeability. Suitable permeability for the downstream media material may include a permeability of between about 20-500 cfm (preferably between about 30-400 cfm, more preferably between about 40-300 cfm).In further embodiments, the outer pleated filter material of the outer filter element may include an additional layer forward of the at least one layer of media material described above and an additional layer of media material rearward of the above-described nano-fiber layer of media material, namely an upstream first layer of media material, an inner second layer of media material as described above, and a downstream third layer of media material. The first layer, the second layer (i.e., a middle layer or "the nano-fiber layer" as described above), and the third layer have average pore sizes M 1, M 2 and M, respectively. M 3 and preferably M 1 > M 2 and M 3 > M 2. For example, M 1 may be at least about 2.5x, 5x, or 10x larger than M 2 and / or M 3 may be at least about 2.5x, 5x, or 10x larger than M 2( e.g., M 1 and / or M 3 ≥ 10 μm; M 1 and / or M 3 ≥ 20 μm, or M 1 and / or M 3 ≥ 30 μm). The additional layers of upstream and downstream media material may contain fibers which may be the same or different, wherein the fibers have an average fiber diameter of 1-100 μm (preferably 10-100 μm, particularly preferably 20-100 μm). The additional layers of upstream media material and downstream media material have suitable permeabilities, which may be the same or different. A suitable permeability for the upstream media material and the downstream media material may include a permeability of between about 20-500 cfm (preferably between about 30-400 cfm, more preferably between about 40-300 cfm).Where the outer pleated filter material of the outer filter element is a composite material (e.g., comprising multiple layers), the average pore sizes M for the composite material may be determined. The composite material preferably has an average pore size M, wherein 0.2 μm≤M≤12.0 μm (particularly preferably 0.2 μm≤M≤10.0 μm and particularly preferably 0.2 μm≤M≤8.0 μm). Furthermore, the composite material has a maximum pore size M M and generally 1≤M M / M≤5, preferably 1≤M M / M≤3, particularly preferably 1 <- M M / M≤2 (for example, the maximum pore sizes may include M M3, 6, 9, 12, 15, 18, 21, 24, 27, 30, 33 and 36 μm). Preferably, the composite material has a permeability of less than about 40 cfm (more preferably less than about 30 cfm, most preferably less than about 20 cfm).The outer pleated filter material of the outer filter element typically functions to coalesce water droplets present in hydrocarbon fuel as the fuel passes through the outer pleated filter material. Optionally, the outer pleated filter material may comprise slits or holes (e.g., about 30-300 μm in size) present in the valleys of the pleats and act as release points for coalesced water drops.In another embodiment, the outer filter element optionally includes an inner unfolded filter material behind the outer folded filter material, which preferably functions as a releasing layer for coalesced water drops as the coalesced drops drain from the outer folded filter material. In some embodiments, the inner unfolded filter material has an average pore size M, where 20 μm ≤ M ≤ 100 μm (preferably 25 μm ≤ M ≤ 50 μm, and more preferably 30 μm ≤ M ≤ 40 μm). The inner unfolded filter material generally contains fibers, and preferably the fibers have an average diameter of between 10-100 μm (particularly preferably between 20-100 μm). The inner unfolded filter material typically comprises a nonwoven polymeric material (e.g., polyethylene terephthalate material). The inner unfolded filter material has a suitable permeability. Suitable permeability may include a permeability of between about 100-400 cfm (preferably between about 150-250 cfm). The inner unfolded filter material has a desired thickness as measured from upstream to downstream relative to flow through the cartridge (i.e., as measured from outside to inside). Suitable thicknesses include thicknesses between about 0.6 and 2 mm (preferably between about 0.8 and 1.2 mm).Referring now to the inner filter element, this element includes an outer unfolded filter material and an inner folded filter material (e.g., where the outer unfolded filter material contacts the inner folded filter material either directly or indirectly). Preferably, the outer unfolded filter material of the inner filter element is hydrophobic (e.g., where a water droplet in the hydrocarbon fuel has a contact angle on the outer unfolded filter material of the inner filter element that is not less than 90° (preferably not less than 120°, more preferably not less than 135°)). Preferably, the outer unfolded filter material of the inner filter element contains a thermoplastic woven mesh or screen (e.g. a mesh or screen with an opening smaller than 100 μm and preferably smaller than 50 μm). The outer unfolded filter material has a suitable permeability (e.g., between about 300-700 cfm and preferably between about 400-600 cfm).The inner filter element comprises inner pleated filter material. Typically, the inner pleated filter material of the inner filter element contains one or more layers of media material, and at least one layer of media material has an average pore size M that is less than an arbitrary average pore size of an arbitrary layer of the outer pleated filter material of the outer filter element (where, e.g., 0.2 μm≤M≤6 μm, preferably 0.2 μm≤M≤5 μm, more preferably 0.2 μm≤M≤4.0 μm, e.g., 0.2, 0.6, 0.8, 1.0, 1.6, 2.2, 2.8, 3.4 or 4.0 μm). The media material has a maximum pore size M M and typically 1 ≤ M M / M ≤ 3, preferably 1 ≤ M M / M ≤ 2. preferably the media material of the at least one layer contains fibers having an average diameter below about 1 μm (e.g., 1, 0.8, 0.6, 0.4, or 0.2 μm), and preferably the fibers are polymeric nonwoven material (e.g., polyamide material). The media material has suitable permeability. Suitable permeability may include a permeability of less than about 40 cfm (preferably less than about 20 cfm, more preferably less than about 15 cfm, more preferably less than about 10 cfm, e.g., 9, 8, 7, 6, 5 or 4 cfm). The at least one layer of media material has a desired thickness as measured from upstream to downstream relative to flow through the cartridge (i.e., as measured from outside to inside). Suitable thicknesses include thicknesses between about 0.05 and 0.4 mm (preferably between about 0.1 and 0.3 mm, e.g., 0.10, 0.12, 0.14, 0.16, 0.18, 0.20, 0.22, 0.24, 0.26, 0.28, and 0.30 mm). The at least one layer of media material is preferably a nanofibre material with a preferred basis weight (e.g. at least 10 gsm, 20 gsm or 30 gsm).In addition to the at least one layer of media material of the inner pleated filter material of the inner filter element as described above, the inner pleated filter material may include additional layers of media material having the same or different characteristics as the at least one layer of media material described above. For example, the inner pleated filter material of the inner filter element may include one or more additional layers of media material in front of or behind the above-described layer of media material. In some embodiments, the inner pleated filter material of the inner filter element includes an additional layer of media material located in front of the above-described layer of media material, namely an upstream first layer of media material and a downstream second layer of media material as described above. The first layer and the second layer of media material have average pore sizes M 1 and M, respectively. M 2 and preferably M 1 > M 2. For example, M 1 may be at least about 2.5x, 5x, or 10x larger than M 2( e.g., M 1 ≥ 10 μm, M 1 ≥ 20 μm, or M 1 ≥ 30 μm). The additional layer of upstream media material may contain fibers, wherein the fibers have an average fiber diameter of 1-100 μm, 3-100 μm, 10-100 μm, 20-100 μm or 40-100 μm). The additional layer of upstream media material has a suitable permeability. Suitable permeability for the upstream media material may include a permeability of between about 20-300 cfm (preferably between about 40-300 cfm, more preferably between about 60-300 cfm).In other embodiments, the inner pleated filter material of the inner filter element includes an additional layer of media material located behind the at least one layer of media material described above, namely an upstream first layer of media material as described above and a downstream second layer of media material. The first layer and the second layer have average pore sizes M 1 and M, respectively. M 2 and preferably M 1< M 2. For example, M 2 may be at least 2.5x, 5x, or 10x larger than M 1( e.g., M 2 ≥10 μm, M 2 ≥20 μm, or M 2 ≥30 μm). The additional layer of downstream media material may contain fibers, wherein the fibers have an average fiber diameter of 10-100 μm, 20-100 μm, or 40-100 μm). The additional layer of upstream media material has a suitable permeability. Suitable permeability for the upstream media material may include a permeability of between about 20-300 cfm (preferably between about 40-300 cfm, more preferably between about 60-300 cfm).In further embodiments, the inner pleated filter material of the inner filter element may include an additional layer forward of the above-described at least one layer of media material and an additional layer of media material rearward of the above-described at least one layer of media material, namely an upstream first layer of media material, an inner second layer of media material as described above, and a downstream third layer of media material. The first layer, the second layer (i.e., a middle layer or "the at least one layer" as described above), and the third layer have average pore sizes M 1, M 2 and M, respectively. M 3 and preferably M 1 > M 2 and M 3 > M 2. For example, M 1 may be at least about 2.5x, 5x, or 10x larger than M 2 and / or M 3 may be at least about 2.5x, 5x, or 10x larger than M 2( e.g., M 1 and / or M 3 ≥ 10 μm; M 1 and / or M 3 ≥ 20 μm, or M 1 and / or M 3 ≥ 30 μm). The additional layers of upstream and downstream media material may contain fibers which may be the same or different, wherein the fibers have an average fiber diameter of 1-100 μm, 10-100 μm, 20-100 μm or 40-100 μm. The additional layers of upstream media material and downstream media material have suitable permeabilities, which may be the same or different. A suitable permeability for the upstream media material and the downstream media material may include a permeability of between about 20-500 cfm (preferably between about 30-400 cfm, more preferably between about 40-300 cfm).Where the inner pleated filter material of the inner filter element is a composite material (e.g., comprising multiple layers), the average pore sizes M for the composite material may be determined. The composite material preferably has an average pore size M, wherein 0.2 μm≤M≤6.0 μm (particularly preferably 0.2 μm≤M≤5.0 μm and particularly preferably 0.2 μm≤M≤4.0 μm). M for the composite material of the inner pleated material of the inner filter element is typically less than M for the composite material of the outer pleated material of the outer filter element. The composite material of the inner pleated filter material can have a maximum pore size M M and generally 1≤M M / M≤5, preferably 1≤M M / M≤3, particularly preferably 1≤M M / M≤2. The composite material of the inner pleated filter material preferably has a permeability of below about 40 cfm (preferably below about 20 cfm, particularly preferably below about 15 cfm, particularly preferably below about 10 cfm, e.g. 9, 8, 7, 6, 5 or 4 cfm).The outer filter element and the inner filter element of the disclosed cartridges typically include pairs of end caps that are optionally shared. Typically, the outer pleated material and the optional inner unfolded material of the outer filter element are attached to the end caps of the outer filter element at the respective ends of the outer pleated material and the optional inner unfolded material of the outer filter element. Typically, the outer unfolded material and the inner folded material of the inner filter element are attached to the end caps of the inner filter element at the respective ends of the outer unfolded material and the inner folded material of the inner filter element. In some embodiments, the outer filter element and the inner filter element may share an upper or lower end cap (i.e., where the filter material of the outer filter element and the filter material of the inner filter element are both embedded in the same end cap that may be located at the top or bottom of the filter material). The end caps of the outer filter element and / or the inner filter element may be attached to the respective ends of the filter material in any suitable manner, including ways that prevent bypass of unfiltered fluid around the media. Suitable attachments include potting in an adhesive (e.g., polyurethane) or embedding the ends of the filter media into thermoplastic end caps. Preferably, the end caps of the outer filter element and / or the inner filter element comprise polymeric material (e.g., polyurethane material). In some embodiments, the end caps comprise metal end caps that contain polyurethane or another potting adhesive for the fill material.In some embodiments, the entire filter cartridge is polymeric material, such as thermoplastic material. Accordingly, the entire cartridge can be recycled or burned, the layers of media material can be more easily bonded together, with successive layers both being thermoplastic, chemical resistance and thermoplastic compatibility is typically better than other options such as cellulosic material, and further media properties such as mean pore size and distribution can be more easily controlled.The outer filter element and the inner filter element may be assembled to form a filter cartridge as contemplated herein. The disclosed cartridges may be enclosed within a containment structure such as housings known in the art. Suitable housings typically include one or more inlets for receiving fluid for filtration and one or more outlets or outlets for discharging filtered fluid (e.g., hydrocarbon liquid) and / or coalesced droplets of a dispersed phase (e.g., water).The disclosed filter cartridges can be used in systems and methods to separate a dispersed phase from a continuous phase. In some embodiments, the disclosed filter cartridges may be used in systems and methods for fuel-water separation, including systems and methods for removing water dispersed in a hydrocarbon fuel. The systems and methods may further include or utilize hydrophobic media or additional equipment positioned behind the disclosed cartridges to remove additional water from the filtered fuel. Additional means may include, but are not limited to, a gravity separator, a centrifuge, a beater, a lamella separator, an inclined stacked plate, a screen, a water absorber (e.g., a superabsorbent polymer or hydrogel), and a resting chamber. Preferably, the disclosed cartridges can be used in systems and methods that effectively remove at least about 93%, 95%, 97%, or 99% of the water dispersed in a hydrocarbon fuel.BRIEF DESCRIPTION OF THE DRAWINGSFigure 1 shows an embodiment of a filter cartridge as contemplated herein. FIG. 2 is an exploded view of the embodiment of FIG. 1. FIG. 3 shows a cross-sectional view of the embodiment of FIG. 1 taken along 3-3. FIG. 4 shows an exploded view of an embodiment of an outer member as contemplated herein. FIG. 5 shows an exploded view of an embodiment of an inner member as contemplated herein. FIG. 6 shows an exploded view of an embodiment of a fuel-water separator as contemplated herein having an outer member and an inner member. FIG. 7 shows an exploded view of an embodiment of an outer member of a fuel-water separator as contemplated herein. FIG. 8 shows an exploded view of an embodiment of an inner member of a fuel-water separator as contemplated herein. FIG. 9 shows a cross-sectional view of embodiments of an outer member of a fuel-water separator as contemplated herein, showing media layers and configuration. A. Embodiment without Supporting Center Tube or Screen. B. Embodiment with Supporting Center Tube or Screen (7) in Unfolded Media Cylinder (6). C. Embodiment with Supporting Center Tube or Screen (7) between Folded Media (1-5) and Unfolded Media Cylinders (6).FIG. 10 shows a cross-sectional view of embodiments of an inner member of a fuel-water separator as contemplated herein, showing media layers and configuration.DETAILED DESCRIPTIONModular filter-in-filter elements are disclosed, namely an outer filter element and an inner filter element, that can be assembled to form a filter cartridge for use in separation methods and systems. The modular filter-in-filter elements and filter cartridges assembled therefrom may be further described as follows.The outer filter element and the inner filter element contain or utilize media comprising one or more layers of media material for filtering a mixture of a continuous phase and a dispersed phase and coalescing the dispersed phase. Such media may be referred to herein as "coalescing media material.". As contemplated herein, the one or more layers may have a desired pore size, porosity, and fiber diameter. The one or more layers may be homogeneous (i.e., comprising a single type of material) or heterogeneous (i.e., comprising blended materials). The terms "pore size", "porosity", and "fiber diameter" may refer to "average" or "average" values for these terms (e.g., where the layer is heterogeneous or graded and "pore size", "porosity", and "fiber diameter" are reported as average pore size, average porosity, or average fiber diameter for the heterogeneous layer).The disclosed cartridges may be used in deposition processes or systems to eliminate a dispersed phase from a continuous phase. In some embodiments, the disclosed cartridges are used to separate an aqueous liquid (e.g., water) from a mixture of the aqueous liquid dispersed in a hydrocarbon liquid. As contemplated herein, a hydrocarbon liquid primarily contains hydrocarbon material, but may further contain a non-hydrocarbon material (e.g., up to about 1%, 5%, 10% or 20% non-hydrocarbon material). A hydrocarbon liquid may include a hydrocarbon fuel.The outer filter element and the inner filter element may include media, which may be a woven or nonwoven fabric. Further, the outer filter element and the inner filter element may include media that are polymeric or non-polymeric. Suitable polymeric material may include, but is not limited to, polyamide material, polyalkylene terephthalate material (e.g., polyethylene terephthalate material or polybutylene terephthalate material), polyester material, halogenated hydrocarbon material (e.g., Halar® brand ethylene chlorotrifluoroethylene (ECTFE), and polyurethane material. Polymeric materials may include thermoplastic materials.The outer filter element and the inner filter element may contain or utilize multilayer media. Such media may be formed by melt blowing two different layers of media onto each other, by a wet lay process, electro-spinning, electro-blowing, melt spinning, ultrasonic bonding, chemical bonding, physical bonding, folding or other means, or another combination.The outer filter element, the inner filter element, and the filter cartridges assembled therefrom may be utilized in filtration and coalescing systems and methods as known in the art. (See, for example, US 7527739 B2; US 7416657 B2; US 7326266 B2; US 7297279 B2; US 7235177 B2; US 7198718 B1; US 6907997 B2; US 6884349 B1; US 6811693 B2; US 6740358 B2; US 6730236 B2; US 6605224 B2; US 6517615 B2; US 6422396 B1; US 6419721 B1; US 6332987 B1; US 6302932 B1; US 6149408 A; US 6083380 A; US 6056128 A; US 5874008 A; US 5861087 A; US 580597 A; US 5762810 A; US 5750024 A; US 5656173 A; US 5643431 A; US 5616244 A; US 5575896 A; US 5565078 A; US 5500132 A; US 5480547 A; US 5480547 A; US 5468385 A; US 5454945 A; US 5454937 A; US 5439588 A; US 5417848 A; US 5401404 A; US 5242604 A; US 5174907 A; US 5156745 A; US 5112498 A; US 5080802 A; US 5068035 A; US 5037454 A; US 5006260 A; US 4888117 A; US 4790947 A; US 4759782 A; US 4643834 A; US 5156745 A; US 5112498 A; US 5080808002 A; US 5068035 A; US 5037454 A; US 5006260 A; US 4888117 A; US 47970947 A; US 4759782; US 4640781 A; US 4304671 A; US 4251369 A; US 4213863 A; US 4199447 A; US 4083778 A; US 4078965 A; US 4052316 A; US 4039441 A; US 3960719 A; US 3951814 A; and the published US applications US 2009 / 0020465 A1; US 2009 / 0134097 A1; US 2007 / 0289915 A1; US 2007 / 0107399 A1; US 2007 / 0062887 A1; US 2007 / 0062886 A1; and US 2007 / 0039865 A1; the contents of which are incorporated herein by reference in their entirety). The coalescing media disclosed herein may be prepared using methods known in the art and may include additional features disclosed in the art. (See, e.g., patents and published application references above, and U.S. Patents US 6767459 B1; US 5443724 A and US 4081373 A; and U.S. Published Patent Applications US 2007 / 0131235 A1; US 2007 / 0062887 A1 and US 2006 / 0242933 A1; the contents of which are incorporated herein by reference in their entirety.).The disclosed filter cartridges assembled therefrom may be utilized to remove a dispersed phase (e.g., water) from a continuous phase (e.g., a hydrocarbon fuel). For example, the assembled filter cartridges can be used to separate a dispersed phase from a continuous phase, wherein at least 93, 95, 97, or 99% of the dispersed phase is separated from the continuous phase after the phases have passed through the cartridges.The coalescing media described herein may comprise material having inherent hydrophilicity or hydrophobicity or inherent oleophilicity or oleophobicity. In some embodiments, the coalescing media comprises a layer of material comprising a relatively hydrophobic material relative to the dispersed phase of the mixture. In some embodiments, the outer filter element and the inner filter element comprise one or more layers of media material that are hydrophobic. The hydrophobicity characteristic of a media material may be detected by measuring a contact angle (θ) of a dispersed phase (e.g., water) in a continuous phase (e.g., hydrocarbon fuel) on the media material.Referring now to Figs. 1-5, an embodiment of an outer filter element 4, an inner filter element 6, and a filter cartridge 2 assembled therefrom is shown. The outer member 4 contains pleated filter media 4a in a cylindrical shape in direct or indirect contact with an unfolded cylinder of media 4b at the inner pleat tips of the pleated cylinder. The folded and unfolded cylinders are bonded, cast, embedded or otherwise attached at their ends to end caps (4c, top end cap, and 4e, bottom end cap) located at opposite ends of the cylinders. The top end cap 4c optionally includes a seal 4d. The unfolded cylinder 4b may be in direct or indirect contact with the inner folding tips of the folded cylinder 4a. Typically, the distance between the inner tips of the folded section and the unfolded cylinder is such that there is no significant gap or distance between the tips and the cylinder. The inner member 6 includes outer unfolded filter media 6a in a cylindrical shape in direct or indirect contact with an inner folded cylinder of media 6b. As such, the configuration of the inner member (i.e., outer unfolded filter media and inner folded filter media) is in contrast to the configuration of the outer filter member (i.e., outer folded filter media and inner unfolded filter media). The unfolded and folded cylinders are bonded, cast, embedded or otherwise attached at their ends to end caps (6c, top end cap, and 6e, bottom end cap) located at opposite ends of the cylinders.Referring now to FIGS. 6-8, an embodiment of a thermoplastic filter-in-filter fuel water separator (FWS) and a particulate filter as contemplated herein is shown. FIG. 9 shows cross-sectional views of embodiments of the outer member of the currently disclosed filter-in-filter fuel-water separator (FWS) and particulate filter. Figure 9a shows an embodiment without a central tube, screen or other support structure for the media of the outer element. FIG. 9B shows an embodiment with a center tube, screen, or other support structure for the media, positioned behind and at the unfolded media cylinder. FIG. 9C shows an embodiment with a center tube, screen, or other support structure for the media disposed between and contacting both the upstream folded media cylinders and the downstream unfolded media cylinders. In Figure 9, numerals 1-5 indicate in order from upstream to downstream the different layers of media of the folded media cylinder. Numeral 6 indicates the unfolded media and 7 indicates the structure, e.g. center tube, screen, spring, etc., supporting the media of the outer element. As shown, the folded cylinder comprises three layers of fibrous thermoplastic filter media (layers 1-3), one layer of thermoplastic nano-fiber media (layer 4) and a final layer of fibrous thermoplastic media (layer 5). The unfolded cylinder comprises a layer of fibrous thermoplastic media (layer 6) formed as a tube and placed in the folded media cylinder with its upstream face either in direct contact with the folded media cylinder or in indirect contact with the folded media cylinder via the intermediate support structure (7), as shown. The optional support structure (7) can function to prevent the unfolded cylinder from collapsing under the flow and pressure drop when the cartridge is used in a fuel-water separation system. Preferably, however, the folded and unfolded cylinders together provide sufficient strength and stiffness, making the support structure optional. In FIG. 9C, the support structure supports the folded cylinder, the inner folding tips of which are in direct contact with the support structure, while the unfolded cylinder is located inside, behind, and in direct contact with the support structure. In some embodiments, the unfolded cylinder may be thermally welded or injection molded to the thermoplastic center tube to fix it to the support structure. As a rule, the axial lengths of all 7 layers are the same. Both ends of each of the cylinders are either embedded in end caps or encapsulated in an adhesive, e.g., polyurethane, to attach the ends of the cylinders to the end caps and prevent bypass of unfiltered fluid around the media during use in a fuel-water separation system (FIGS. 1-8).The outer member of FIGS. 9B and 9C includes 6 layers of media material and a support structure. However, the outer member may contain fewer or additional layers depending on the requirements of the system in which the filter cartridge is used. For illustrative purposes only, three coalescers, designated X, Y, and Z, are described in Table 1, including the typical properties of each media layer of these coalescers.1Polybutylene terephthalate nonwoven fabric>10>50>100>250>0, 3>40±52Polybutylene terephthalate nonwoven fabric1,0-4,05,0-15,010,0-20,035-550,7-0,1527±53Polybutylene terephthalate nonwoven fabric1,0-5,015,0-30,025,0-40,075-1000,15-0,333±54Polyamide Nonwoven Fabric0,1-1,0<8, 05,0-15,05,0-20,00,1-0,25>205Nonwoven Polyethylene Terephthalate Web>4020,0-40,040-6050-750,4-0,7198±206Nonwoven Polyethylene Terephthalate Web>2025-4540-60150-2000,8-1,2100±204Polyamide Nonwoven Fabric0,1-1,0<8, 05,0-15,05,0-20,00,1-0,25>205Polyethylene terephthalate nonwoven (optional)>4020,0-40,040-6050-750,4-0,7198±206Nonwoven Polyethylene Terephthalate Web>2025-4540-60150-2000,8-1,2100±203Polybutylene terephthalate nonwoven fabric1,0-5,015,0-30,025-4075-1000,15-0,333±54Polyamide Nonwoven Fabric0,1-1,0<8, 05,0-20,05,0-20,00,1-0,25>205Polyethylene terephthalate nonwoven (optional)>4020-4040-6050-750,4-0,7198±206Nonwoven Polyethylene Terephthalate Web>2025-4540-60150-2000,8-1,2100±20The media combinations of these three coalescers reflect design choices based on the observation that in low interfacial tension systems such as ULSD and biodiesel, there is relatively little thermodynamic drive for coalescence and the kinetics of coalescence is generally slow. These coalescers are designed to physically slow the passage of dispersed phase droplets in a continuous phase (e.g., dispersed water droplets in a hydrocarbon fuel) through the media and increase the concentration of the droplets locally within the coalescer to facilitate coalescence and droplet size growth.In coalescer X, at least 6 media layers with an optional support structure are used. The coalescer X may be referred to as a "speed change coalescer" (see PCT publication number WO 2010 / 042706 A1, which is incorporated herein by reference in its entirety) having a filter-in-filter configuration (see USPTO publication numbers US 2009 / 0065419 A1; US 2009 / 0250402 A1; and US 2010 / 0101993 A1, which are incorporated herein by reference in its entirety). Layer 1 functions as a prefilter and to reduce the pressure drop across the outer member. Layer 1 is further "open" than layer 2 (i.e., having a higher porosity, a larger pore size, a larger mean fiber diameter, a higher Frasing permeability, and / or a lower impurity removal efficiency). Layer 2 functions to capture fine emulsified droplets, for example water droplets, in diesel fuel which is particularly low in sulfur. Layer 2 is "narrower" than layer 3 (i.e., having a lower porosity, a smaller pore size, a smaller average fiber diameter, a lower Frasing permeability, and / or a higher impurity removal efficiency). Layer 3 functions to reduce the fluid velocity within the media and to provide a space for droplets trapped in layer 2 to drain, accumulate and coalesce. The physical properties of layer 3 are such that the fluid velocity in this layer is below the fluid velocity in layer 4. Layer 3 is further "open" than layer 4 (i.e., having a higher porosity, a larger pore size, a larger mean fiber diameter, a higher Frasing permeability, and / or a lower impurity removal efficiency). Layer 4 functions to trap droplets that have not been trapped by the preceding layers, particularly the finer droplets, and to serve as a semi-permeable barrier to the passage of trapped droplets. The function of layer 4 as a semi-permeable barrier causes droplets to concentrate and accumulate in layer 3, thereby giving the droplets more time and a greater likelihood of coalescence occurring. The function of the layer 4 as a semi-permeable barrier also results in a localized increased fluid velocity and a transient increase in drop surface area which further improves coalescence. The physical properties of layer 4 are such that the fluid velocity in this layer is higher than the fluid velocity in layer 5. layer 4 is "narrower" than layer 5 (i.e., having a lower porosity, a smaller pore size, a smaller average fiber diameter, a lower Frazier permeability, and / or a higher impurity removal efficiency). Layer 4 is typically thermoplastic nanofibre filter media with a diameter of less than 1 μm (for example to achieve the very high requirements with regard to water removal efficiency and to take into account the small droplet size for modern high pressure common rail diesel fuel systems operated with ULSD or biodiesel). Layer 5 functions to create a lower speed environment in which the coalesced droplets formed in the preceding layers may collect and drain prior to release. Layer 5 is further "open" than layer 4 (i.e., having a higher porosity, a larger pore size, a larger mean fiber diameter, a higher Frasing permeability, and / or a lower impurity removal efficiency). Layer 6 functions to provide sites for release of coalesced droplets in a low energy environment. Layer 6 is further "open" than layer 5 (higher porosity, larger pore size, larger average fiber diameter, higher Frasing permeability, and / or lower impurity removal efficiency).In coalescer Y, two or three layers of media are used with or without optional support structure. Coalescer Y may be referred to as a "single layer surface coalescer" (see USPTO application Ser. No. 61 / 178,738, filed May 15, 2009, and USPTO application Ser. No. 12 / 780,392, filed May 14, 2010, and published as USPTO publication US 2011 / 0124941 A1, which are incorporated herein by reference in their entirety) having a filter-in-filter configuration (see USPTO publication Non. US 2009 / 0065419 A1; US 2009 / 0250402 A1 and US 2010 / 0101993 A1, which are incorporated herein by reference in their entirety). In coalescer Y, the layer 4 functions to provide a semi-permeable barrier for the passage of fine emulsified droplets, thereby forcing them to concentrate at their upstream surface. As such, the droplets have sufficient time and environment to cause coalescence and droplet growth. Layer 4 is a relatively "narrow" layer with characteristics comparable to layer 4 in coalescer X or even narrower. This layer uses "screening" to prevent the passage of fine droplets and typically comprises thermoplastic nanofibre filter media having an average pore size M less than the average size of the incoming droplets and a largest to average pore size ratio of less than 3 (i.e. M M / M ≤ 3. In some embodiments there is a water drain on the upstream face of the outer element through which coalesced droplets run on the upstream surface of layer 4, while in other embodiments there may be a water drain on the downstream side of the outer element to collect coalesced water which has been forced through the media at release sites by the pressure drop across the coalescing element. Coalescer Y has an optional layer 5 to provide structural support to layer 4 if necessary and to serve as a drain path for any coalesced droplets forced through layer 4. Layer 5 connects layer 4 to release layer 6. layer 5 also functions to create a lower speed, less energy environment in which the coalesced droplets formed in the preceding layers may collect and drain through prior to release. Layer 5 is further "open" than layer 4 and is structurally stronger to provide support to layer 4 and facilitate media revision. Coalescer Y has an additional unfolded layer 6 behind layers 4 and 5 described above. layer 6 functions to provide sites for release of coalesced droplets in a low energy environment. As such, layer 6 is further "open" than layer 5.In coalescer Z, three or more layers of media are used with an optional support structure (see USPTO application Ser. No. 61 / 179,170, filed May 18, 2009; USPTO application Ser. No. 61 / 179,939, filed May 20, 2009; and USPTO application Ser. No. 12 / 780,392, filed May 14, 2010, and published as USPTO publication US 2011 / 0124941 A1, which are incorporated herein by reference in their entirety). Coalescer Z is a more complex surface coalescer than coalescer Y and has a filter-in-filter configuration (see USPTO Publication Nos. 2009 / 0065419 A1; 2009 / 0250402 A1; and 2010 / 0101993 A1, which are incorporated herein by reference in their entirety). Layer 3 functions to reduce the pressure drop across the coalescer and secondarily to serve as a particulate prefilter for the coalescer and to extend its useful life. Layer 3 is further "open" than layer 4 and has a higher capillary pressure than layer 4 (i.e., a more positive capillary pressure). The function and properties of layers 4, 5 (optional) and layer 6 are as described for coalescer Y.For all three coalescers X, Y and Z, the manner of transition from layer 5 to layer 6 is important. The layers 1-5 are generally folded. As such, the fluid flow profile within the pleat and the resistance to trapped drops causes them to accumulate in the valleys (downstream direction) of the pleats. This results in droplets concentrating in this localized area, thereby increasing coalescence by providing longer time for the droplets to coalesce before being released. It has been observed by the present inventors that the coalesced droplets are generally released from the same active areas or areas on the downstream surface of coalescers, while otherwise there is little droplet release. This suggests that after a run-through path is created by the media, it is used repeatedly. In the presently disclosed filter cartridges, preferred drainage paths terminating in larger pores are established by the direct contact of the inner pleat tips of layer 4 (for coalescers Y and Z) or layer 5 (for coalescers X, as well as Y and Z if this layer is included) to the upstream surface of the unfolded layer 6. At the point of contact between the folded and unfolded layers there is a localized disruption of the media pore structure leading to these preferred drainage paths. This results in larger droplets being released. Furthermore, these drainage paths occur at the bottoms of the fold troughs where coalesced droplets concentrate and the effect is greatest. Direct contact between layers 4 or 5 and layer 6 is not required to achieve this result. For example, the inner pleat tips of the most downstream layer of the pleated section may directly contact the porous support structure 7, which in turn is in direct contact with layer 6 on its downstream side, as shown in FIG. 9C.The inner member of the presently disclosed filter cartridge functions to separate coalesced water droplets from the fuel and to remove fine solid contaminants from the fluid. The inner member comprises an outer unfolded cylinder in direct contact with an inner folded cylinder. Typically, the axial lengths of both unfolded and folded cylinders are the same. Both ends of each of the cylinders are either embedded in end caps or cast in an adhesive, e.g., polyurethane, to attach the ends of the cylinders to the end caps and to prevent bypass of unfiltered fluid around the media during use in a fuel-water separation system (FIGS. 1-8).The inner member typically includes at least 4 layers of media material (FIG. 10 ). The purpose of the first layer, layer A, is to separate coalesced (water) droplets from the continuous phase (fuel). This layer preferably comprises a thermoplastic fabric grid in the form of a tube which repels the droplets and allows them to drain freely from the surface. Layer A is located outside the inner folded cylinder and is in direct contact therewith. The lattice opening of this layer is generally below 100 μm and preferably below 50 μm. The function of the pleated layers is to trap solid contaminants and droplets that have not been removed by the downstream layers of the outer filter element. The first two of these folded layers, layers B and C in Figure 10 and Table 2, are transition layers that function to reduce pressure drop, provide further disposal of droplets and droplets, and reduce solids collection on the following nanofibrous filtration layer, layer D. Layer B also facilitates the preparation and processing of the composite material.A. APolyethylene terephthalate fabric screen*30-5030-50400-6000,03-0,137110B. BPolybutylene terephthalate nonwoven fabric>10>50>100225-3250,3-0,548±10C. CPolybutylene terephthalate nonwoven fabric1,0-5,05,0-15,010,0-25,035-550,1-0,338±10D. DPolyamide Nonwoven Fabric0,1-0,81,0-8,01,0-10,03,0-20,00,1-0,3>20E. ENonwoven Polyethylene Terephthalate Web>4020-3540-6550-750,45-0, 65198±20These layers have properties similar to layers 1 and 2 in the outer member. The next folded layer, layer D in FIG. 10 and Table 2, functions as a highly efficient filter for fine particles (e.g., particles having a diameter of 4 μm or smaller). For high pressure common rail applications, very high particulate removal efficiencies as low as 4 μm are typically required to protect the fuel injectors. The layers before layer D function primarily to eliminate and deposit droplets. Layer D functions to protect the downstream system from contamination by fine solids. Layer D also functions to eliminate droplets that may have passed through the preceding layers. Preferably, layer D is "narrower" than any of the other layers of the outer member or the inner member and contains thermoplastic nanofibre filter media having a diameter of less than 1 μm. At a minimum, layer D of the inner element is as "narrow" as layer 4 of the outer element. The final layer, layer E, functions to support the preceding layers without significantly increasing the pressure drop. Layer E is a relatively "open" medium of sufficient strength and stiffness to support the downstream layers under use conditions and to facilitate processing of the media of the inner member.

Claims

A filter cartridge (2) structured to coalesce a dispersed phase from a dispersed phase mixture in a continuous phase as the mixture moves from the outside inward through the cartridge (2), the cartridge comprising: (a) an outer filter element (4), the outer filter element (4) comprising: (i) an outer pleated filter material (4a), the outer pleated filter (4a) having a substantially cylindrical shape, the outer pleated material (4a) comprising a composite material having a permeability of less than 0.0188 m 3 / s (40 cfm); (ii) end caps (4c, 4e) attached to opposite ends of the outer pleated filter material (4a); (b) an inner filter element (6) disposed in the outer filter element (4), the inner filter element (6) comprising: (i) an outer unfolded filter material (6a), the outer unfolded filter material (6a) having a substantially cylindrical shape; (ii) an inner folded filter material (6b) in direct or indirect contact with the outer unfolded filter material (6a), the inner folded filter material (6b) having a substantially cylindrical shape; and (iii) end caps (6c, 6d) attached to opposite ends of the outer unfolded filter material (6a) and the inner folded filter material (6b), wherein the outer filter element (4) further comprises: (iii) an inner unfolded filter material (4b) in direct or indirect contact with the outer folded filter material (4a) at inner folding tips of the outer folded filter material (4a), wherein the inner unfolded filter material (4b) has a substantially cylindrical shape and the end caps (4c, 4e) are attached to opposite ends of the inner unfolded filter material (4b), (iv) a support structure optionally selected from a group consisting of a permeable tube, a screen, a spring, a cage-like structure, wherein the support structure contacts the inner unfolded material (4b) of the outer filter element (4), wherein the support structure is located on the outer surface of the inner unfolded filter material (4b) of the outer filter element (4) and the inner unfolded filter material (4b) indirectly contacts the outer folded filter material (4a) of the outer filter element (4) at the inner folding tips via the support structure.A cartridge according to claim 1, wherein the outer pleated filter material (4a) of the outer filter element (4) has slits or holes in valleys of the pleated filter material (4a).A cartridge according to claim 1, wherein the outer pleated filter material (4a) of the outer filter element (4) comprises a polymeric material.A cartridge according to claim 3, wherein the polymeric material is a thermoplastic material.A cartridge according to claim 1, wherein the inner unfolded filter material (4b) of the outer filter element (4) comprises a polymeric material.A cartridge according to claim 5, wherein the polymeric material is a thermoplastic material.A cartridge according to claim 1, wherein the outer unfolded filter material (6a) of the inner filter element (6) comprises a polymeric material.A cartridge according to claim 7, wherein the polymeric material is a thermoplastic material.A cartridge according to claim 1, wherein the inner pleated material (6b) of the inner filter element (6) comprises a polymeric material.A cartridge according to claim 9, wherein the polymeric material is a thermoplastic material.A cartridge according to claim 1, wherein the entire cartridge (2) is a polymeric material.A cartridge according to claim 11, wherein the polymeric material is a thermoplastic material.A cartridge according to claim 1, wherein the outer pleated filter material (4a) has an average pore size M, where 0.2 μm ≤ M ≤ 12.0 μm, and the outer pleated material (4a) has a maximum pore size M M where 1 ≤ M M / M ≤ 5.A cartridge according to claim 13, wherein the outer pleated material (4a) has a maximum pore size M M where 1 ≤ M M / M ≤ 3.A cartridge according to claim 13, wherein the outer pleated material (4a) has a maximum pore size M M where 1 ≤ M M / M ≤ 2.A cartridge according to claim 1, wherein at least one layer of the outer pleated filter material (4a) has an average pore size M, and 0.2 μm ≤ M ≤ 12.0 μm.The cartridge of claim 16, wherein the at least one layer has a maximum pore size M M and 1 ≤ M M / M ≤ 3.The cartridge of claim 16, wherein the at least one layer has a maximum pore size M M and 1 ≤ M M / M ≤ 2.A cartridge according to claim 16, wherein the at least one layer comprises fibres having an average diameter between 0.07 μm and 1 μm.The cartridge of claim 19, wherein the fibers comprise a polymeric material.A cartridge according to claim 20, wherein the polymeric material is a thermoplastic material.A cartridge according to claim 20, wherein the polymeric material is a polyamide.The cartridge of claim 16, wherein the media material of the at least one layer has a permeability of less than about 40 cfm.The cartridge of claim 16, wherein the at least one layer is a nano-fiber material having a basis weight of at least about 10 gsm.A cartridge according to claim 16, wherein the at least one layer has a thickness, as measured from upstream to downstream, of between 0.05 and 0.4 mm.A cartridge according to claim 16, wherein the outer pleated filter material (4a) includes an upstream first layer of medium material having an average pore size M 1 and a downstream second layer of medium material having an average pore size M 2 and wherein M 1 > M 2.The cartridge of claim 26, wherein M 1 is at least 2.5 times greater than M 2.A cartridge according to claim 26, wherein 0.2 μm ≤ M 2 ≤ 12.0 μm.A cartridge according to claim 26, wherein M 1 ≥ 15 μm.A cartridge according to claim 26, wherein 30 μm ≥ M 1 ≥ 15 μm.The cartridge of claim 26, wherein the first layer comprises media having an average fiber diameter of 1-100 μm.The cartridge of claim 26, wherein the first layer comprises media having a permeability between 0.0189 m 3 / s (40 cfm) and 0.0566 m 3 / s (120 cfm).A cartridge according to claim 26, comprising an upstream first layer of medium material having an average pore size M 1, an intermediate second layer of medium material having an average pore size M 2 and a downstream third layer of medium material having an average pore size M 3, wherein M 1 > M 2 and M 3 > M 2.A cartridge according to claim 33, wherein M 3 ≥ 15 μm.A cartridge according to claim 33, wherein 60 μm ≥ M 3 ≥ 15 μm.The cartridge of claim 33, wherein the third layer comprises media having an average fiber diameter greater than about 20 μm.The cartridge of claim 33, wherein the third layer comprises media having a permeability between 0.0189 m 3 / s (40 cfm) and 0.0944 m 3 / s (200 cfm).A cartridge according to claim 1, wherein the outer pleated filter material (4a) is formed by obtaining a first media material and a second media material and physically or chemically coupling the first media material and the second media material in layers.A cartridge according to claim 26, wherein the outer pleated filter material (4a) is formed by obtaining a first media material and a second media material and physically or chemically coupling the first media material and the second media material in layers.A cartridge according to claim 1, wherein the outer pleated filter material (4a) is formed by electrobubbling one media material and combining the electrobubbled media material and another media material into layers.A cartridge according to claim 26, wherein the outer pleated filter material (4a) is formed by electrobubbling one media material and combining the electrobubbled media material and another media material into layers.The cartridge of claim 1, wherein the cartridge (2) is configured to coalesce water dispersed in a continuous phase of a hydrocarbon fuel.A cartridge according to claim 42 wherein the outer unfolded filter material (6a) of the inner filter element (6) is hydrophobic.A cartridge according to claim 42 wherein a drop of water in the hydrocarbon fuel has a contact angle on the outer unfolded filter material (6a) of the inner filter element (6) which is not less than 90°.A cartridge according to claim 1, wherein the outer unfolded filter material (6a) of the inner filter element (6) comprises a thermo plastic mesh with a mesh opening below 100 μm.A cartridge according to claim 1, wherein the inner pleated material (6b) of the inner element (6) comprises a composite material having a permeability of below 0.00844 m 3 / s (20 cfm).A cartridge according to claim 50, wherein the inner pleated material (6b) has an average pore size M, where 0.2 μm ≤ M ≤ 6.0 μm, and the inner pleated material (6b) has a maximum pore size M M where 1 ≤ M M / M ≤ 5.A cartridge according to claim 51, wherein the inner pleated material (6b) has a maximum pore size M M where 1 ≤ M M / M ≤ 3.A cartridge according to claim 51, wherein the inner pleated material (6b) has a maximum pore size M M where 1 ≤ M M / M ≤ 2.A cartridge according to claim 1, wherein at least one layer of inner pleated filter material (6b) has an average pore size M which is less than any average pore size of any layer of outer pleated filter material (4a) of the outer filter element (4).A cartridge according to claim 50, wherein 0.2 μm ≤ M ≤ 6.0 μm.A cartridge according to claim 50, wherein the at least one layer comprises fibers having an average diameter below about 1 μm.A cartridge according to claim 50, wherein the fibres of the inner pleated filter element (6b) comprise a polymeric material.A cartridge according to claim 53, wherein the polymeric material is a thermoplastic material.A cartridge according to claim 53, wherein the polymeric material is a polyamide.A cartridge according to claim 50, wherein the media material of the at least one layer of inner pleated filter material (6b) is a nano-fibre material having a basis weight of at least 10 gsm.A cartridge according to claim 50, wherein the material of the at least one layer of inner pleated filter material (6b) has a thickness, as measured from upstream to downstream, of between 0.05 and 0.4 mm.A cartridge according to claim 50, wherein an upstream first layer of inner pleated media filter material (6b) has an average pore size M 1 and a downstream second layer of inner pleated media filter material (6b) has average pore sizes M 2 and wherein M 1 > M 2.The cartridge of claim 58, wherein M 1 is at least 2.5 times greater than M 2.A cartridge according to claim 58, wherein 0.2 μm ≤ M 2 ≤ 6.0 μm.A cartridge according to claim 58, wherein 5.0 μm ≤ M 1 ≤ 15.0 μm.The cartridge of claim 58, wherein the downstream second layer of media material has a permeability between 0.0014158 m 3 / s (3.0 cfm) and 0.009439 m 3 / s (20.0 cfm).The cartridge of claim 58, wherein the upstream first layer of media material has a permeability between 0.0118 m 3 / s (25 cfm) and 0.0307 m 3 / s (65 cfm).A cartridge according to claim 58, wherein an upstream first layer of inner pleated media filter material (6b) has an average pore size M 1 a middle second layer of inner pleated media filter material (6b) has an average pore size M 2 and a downstream third layer of inner pleated media filter material (6b) has an average pore size M 3 and wherein M 1 > M 2 and M 3 > M 2.A cartridge according to claim 64, wherein M 3 ≥ 15 μm.A cartridge according to claim 64, wherein 75 μm ≥ M 3 ≥ 15 μm.The cartridge of claim 64, wherein the third layer comprises media having an average fiber diameter above about 40 μm.The cartridge of claim 64, wherein the third layer of media material has a permeability of between 0.0189 m 3 / s (40 cfm) and 0.0378 m 3 / s (80 cfm).A cartridge according to claim 1, wherein the outer member (4) and the inner member (6) share both end caps.A cartridge according to claim 1, wherein the end caps (4c, 4e) comprise a polymeric material.The cartridge of claim 70, wherein the polymeric material is a thermoplastic material.The cartridge of claim 70, wherein the polymeric material is a polyurethane material.The cartridge of claim 1, wherein: the outer pleated material (4a) has an average pore size M, where 0.2 μm ≤ M ≤ 12.0 μm; and the outer pleated material (4a) has a maximum pore size M M where 1 ≤ M M / M ≤ 3; wherein: the inner pleated material (6b) has an average pore size M, where 0.2 μm ≤ M ≤ 6.0 μm; the inner pleated material (6b) has a maximum pore size M M where 1 ≤ M M / M ≤ 3; and the inner pleated material (6b) has a permeability below 0.00944 m 3 / s (20 cfm).The cartridge of claim 1, contained within a housing, the housing having an upstream inlet structured to receive the mixture, a downstream outlet structured to discharge the mixture after coalescing the dispersed phase, and optionally a downstream outlet structured to discharge the coalesced dispersed phase.Use of a cartridge according to claim 1 in a fuel-water separation system.The use of claim 75 wherein the fuel-water separation system is structured to remove water dispersed in a hydrocarbon fuel.The use of claim 75 wherein the fuel-water separation system further comprises a hydrophobic medium for removing water positioned behind the cartridge.Use according to claim 75, wherein the fuel-water separation system further comprises additional means for removing water positioned behind the filter cartridge (2), said means being selected from a group consisting of a gravity separator, a centrifuge, a beater, a lamella separator, an inclined stacked plate, a screen, a water absorber and a resting chamber.Use of a cartridge according to claim 1 in a method of removing water dispersed in a hydrocarbon fuel, the method comprising passing a mixture comprising hydrocarbon fuel and water dispersed in the hydrocarbon fuel through the filter cartridge (2) and removing at least about 95% of the water dispersed in the hydrocarbon fuel.

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