WO2008008749A2 - Arrangements and methods for separating water from a liquid mixture including a liquid hydrocarbon - Google Patents

Abstract

Arrangements and methods embodying the invention include a hydrocarbon barrier membrane for separating water from a liquid mixture which includes a liquid hydrocarbon as a continuous phase and water as a discontinuous phase.

Description

ARRANGEMENTS AND METHODS FOR SEPARATING WATER FROM A LIQUID MIXTURE INCLUDING A LIQUID HYDROCARBON

Technical Field

[0001] The present invention relates to arrangements and methods for separating water from a liquid mixture, which includes a liquid hydrocarbon as a continuous phase and water as a discontinuous phase. A wide variety of liquid hydrocarbons may contain water as a discontinuous phase, and removal of the water is often desirable before the liquid hydrocarbon is used for its intended purpose. For example, many oils, such as lubrication oils or hydraulic oils, may contain water as a discontinuous phase. Removal of the water from these oils protects the machinery in which the oils are used from rust and corrosion. As another example, hydrocarbon fuels, such as petroleum fuels, including, for example, kerosene, gasoline, jet fuel, diesel fuel and home heating fuel, and liquefied gas fuels, including, for example, liquefied natural gas, propane, and butane, may also contain water as a discontinuous phase. Removal of the water from the hydrocarbon fuels not only protects the engine or burner in which the fuel is used from rust and corrosion, but also enhances fuel efficiency, thereby lowering fuel costs and better utilizing a natural resource.

Summary of the Invention

[0002] In accordance with one aspect of the invention, arrangements for separating discontinuous phase water from a liquid mixture that further includes a liquid hydrocarbon as a continuous phase may comprise a hydrocarbon barrier membrane and an evaporation apparatus. The hydrocarbon barrier membrane has first and second surfaces, and the first surface fluidly communicates with the liquid mixture including the discontinuous phase water. The hydrocarbon barrier membrane allows passage of the water and resists passage of the liquid hydrocarbon. The evaporation apparatus fluidly communicates with the second surface of the hydrocarbon barrier membrane to evaporate water that passes through the hydrocarbon barrier membrane.

[0003] In accordance with another aspect of the invention, methods for separating discontinuous phase water from a liquid mixture that further includes a liquid hydrocarbon as a continuous phase may comprise contacting a first surface of a hydrocarbon barrier membrane with the liquid mixture including the discontinuous phase water. The hydrocarbon barrier membrane allows passage of the water but resists passage of the liquid hydrocarbon. The methods further comprise evaporating the water that passes through the hydrocarbon barrier membrane. [0004] In accordance with another aspect of the invention, arrangements for separating discontinuous phase water from a liquid mixture that further includes a liquid hydrocarbon as a continuous phase may comprise a hydrocarbon barrier membrane and an absorbent pad. The hydrocarbon barrier membrane has first and second surfaces, and the first surface fluidly communicates with the liquid mixture including the discontinuous phase water. The hydrocarbon barrier membrane allows passage of the water and resists passage of the liquid hydrocarbon. The absorbent pad is arranged to absorb the water which passes from the first surface to the second surface of the hydrocarbon barrier membrane.

[0005] In accordance with another aspect of the invention, arrangements for separating a discontinuous phase water from a liquid mixture that further includes a liquid hydrocarbon as a continuous phase may comprise a housing, a coalescer, and a hydrocarbon barrier membrane. The housing has an inlet for the liquid mixture, an outlet for the liquid hydrocarbon, and a water outlet for water and/or water vapor. The coalescer is positioned in the housing and fluidly communicates between the liquid mixture inlet and the liquid hydrocarbon outlet. The coalescer includes a coalescing medium which coalesces the discontinuous phase water in the liquid mixture. The hydrocarbon barrier membrane, which allows passage of water but resists passage of the liquid hydrocarbon, is also positioned in the housing and has first and second opposite surfaces. The first surface fluidly communicates with the coalesced discontinuous phase water and the second surface fluidly communicates with the water outlet.

[0006] In accordance with another aspect of the invention, arrangements for separating a discontinuous phase water from a liquid mixture that further includes a liquid hydrocarbon as a continuous phase may comprise a coalescer and a hydrocarbon barrier membrane. The coalescer has a coalescing medium which coalesces the continuous phase water in the liquid mixture. The hydrocarbon barrier membrane has a first and second opposite surfaces, and the first surface fluidly communicates with the coalesced discontinuous phase water. The hydrocarbon barrier membrane allows passage of water and resists passage of the liquid hydrocarbon. The coalescer and the hydrocarbon barrier membrane are coupled to one another and are capable of being installed in or removed from a housing as an integral unit. [0007] In accordance with another aspect of the invention, arrangements for separating a discontinuous phase water from a liquid mixture that further includes a liquid hydrocarbon as a continuous phase may comprise a housing and a hydrocarbon barrier membrane. The hydrocarbon barrier membrane, which allows passage of water but resists passage of the liquid hydrocarbon, is positioned in the housing to define first and second volumes and has first and second opposite surfaces. The first surface fluidly communicates with the first volume and the second surface fluidly communicates with the second volume. The housing has an inlet port for the liquid mixture which fluidly communicates with the first volume and an outlet port for water and/or water vapor which fruidly communicates with the second volume but does not have an outlet port for the liquid hydrocarbon.

[0008] Arrangements and methods embodying the invention have many advantages. For example, embodiments of the invention very effectively separate the water from the liquid mixture and the liquid hydrocarbon. The liquid hydrocarbon may then be used for its intended purpose without damaging the machinery, engines, burners, or other systems in which the liquid hydrocarbon is used. Further, at least about 90% of the liquid passing through the hydrocarbon barrier membrane into the second volume may be water and only about 10% or less, for example, 1% or less, may be the liquid hydrocarbon. For many embodiments, the amount of the hydrocarbon may be considerably less than even 1%. By so effectively separating water from the liquid hydrocarbon, embodiments of the invention permit very little waste and fewer emissions of the hydrocarbon.

[0009] Further, by evaporating the water, many of the embodiments permit fast and convenient removal of the water. For example, the evaporated water vapor may simply be vented from the hydrocarbon system. For many embodiments, the evaporation apparatus may include a vacuum source which is coupled to the second surface of the hydrocarbon barrier membrane. The vacuum source effectively evaporates the water and also helps draw the water through the hydrocarbon barrier membrane, thereby enhancing the rate of removal. Additionally or alternatively, many embodiments may include an absorbent pad arranged to absorb water which passes through the hydrocarbon barrier membrane, also facilitating removal and/or evaporation of the water.

[0010] Further, arrangements which include a coalescer coupled to a hydrocarbon barrier membrane provide a very thorough removal of water from the liquid hydrocarbon. The coalescer aggregates the small immiscible droplets of water in the continuous phase liquid hydrocarbon and forms large droplets or volumes which more readily settle out of the liquid hydrocarbon onto the hydrocarbon barrier membrane. The hydrocarbon barrier membrane, in turn, very effectively separates the coalesced water from the liquid hydrocarbon. By coupling the coalescer and the hydrocarbon barrier membrane, removal of the coalescer and the hydrocarbon barrier membrane after they become fouled and reinstallation of new elements can be accomplished quickly with little down time.

DESCRIPTION OF THE DRAWINGS

[0011] Figures Ia, Ib, and Ic are representative views of separation arrangements. [0012] Figure 2 is a sectional side view of a portion of another separation arrangement. [0013] Figure 3 is a sectional side view of another separation arrangement. [0014] Figure 4 is a sectional side view of another separation arrangement. DISCLOSURE OF THE EMBODIMENTS

[0015] Arrangements for separating discontinuous phase water from a liquid mixture, which includes a liquid hydrocarbon as a continuous phase, may be embodied in any of a wide variety of ways. A few of numerous examples of separation arrangements 10 are represented in Figures Ia-Ic. Each separation arrangement 10 includes a first volume 11, which is arranged to contain the liquid mixture including the discontinuous phase water, and a second volume 12, which is arranged to receive the water from the first volume 11. The separation arrangement 10 further includes a hydrocarbon barrier membrane 13, which allows passage of the water but resists passage of the liquid hydrocarbon. The hydrocarbon barrier membrane 13 has one surface 14, e.g., an upstream or higher pressure surface, which fluidly communicates with the first volume 11 and an opposite surface 15, e.g., a downstream or lower pressure surface, which fluidly communicates with the second volume 12. [0016] In one example of a mode of operation, the upstream surface 14 of the hydrocarbon barrier membrane 13 is contacted by the liquid mixture. The nominal pressure at the upstream surface 14 may be greater than the nominal pressure at the downstream surface 15 of the hydrocarbon barrier membrane 13. The resulting differential pressure drives the discontinuous phase water from the first volume 11 through the hydrocarbon barrier membrane 13 to the second volume 12 when the discontinuous phase water contacts the upstream surface 14 of the hydrocarbon barrier membrane 13. However, the hydrocarbon barrier membrane 13 resists passage of the continuous phase liquid hydrocarbon. Consequently, substantially all of the liquid hydrocarbon is prevented from passing into the second volume 12. The liquid that passes through the hydrocarbon barrier membrane 13 may be less than about 10% liquid hydrocarbon.

[0017] The first and second volumes of the separation arrangement may be formed in many different ways by many different structures. For example, the first and second volumes 11, 12, as well as the hydrocarbon barrier membrane 13, may be contained within the same housing 20, as shown in Figure Ia. The first and second volumes 11, 12 may then be first and second portions of the interior of the housing 20 separated by the hydrocarbon barrier membrane 13, which may be sealed to the housing 20. Alternatively, the first volume 11 may be contained within a housing 20 and the second volume 12 may be outside of the housing 20, as shown in Figure Ib. The first and second volumes 11, 12 may then be separated by a hydrocarbon barrier membrane 13, for example, that forms part of the wall of the housing 20, the first volume 11 being within the interior of the structure and the second volume 12 being on the exterior of the housing 20. Further, the first volume 11 and/or the second volume 12 may be contained within multiple housings 20a, 20b fluidly coupled to one another. The first and second volumes 11, 12 may then occupy all or a portion of the interior of one or more of the housings 20a, 20b. The hydrocarbon barrier membrane 13 separating the first and second volumes 11, 12 may be positioned in one of the housings 20a, 20b or between the housings 20a, 20b, e.g., in the fluid couplings which connect the housings 20a, 20b. In any of the embodiments, the first volume 11 may be larger than the second volume 12. Further, because the discontinuous phase water is typically more dense than the continuous phase liquid hydrocarbon, the first volume 11 may be positioned above the second volume 12, allowing the discontinuous phase water in the first volume to settle onto the upstream surface 14 of the hydrocarbon barrier membrane 13 which separates the first and second volumes 14, 15. [0018] The housing may be variously configured. For example, the housing 20 may comprise a storage container or tank for storing the liquid mixture, as shown in Figure Ia. The tank 20 may be a stationary tank, such as a larger or smaller above-ground or underground tank, or the tank may be a mobile tank, such as a railroad tank car, a tank truck, or the fuel tank of a vehicle. The tank 20 may include an inlet 21, an outlet 22, and one or more drains, e.g., a liquid mixture drain 23 and a separated water drain 24. The hydrocarbon barrier membrane 13 may be positioned in the interior of the tank 20 between the inlet 21 and the water drain 24 or it may be positioned in the wall of the tank. As another example, the housing 20 may comprise a conduit for containing a flow of the liquid mixture, as shown in Figure Ib. The conduit may be a pipe or a hose having an inlet or upstream portion 30 and an outlet or downstream portion 31. The hydrocarbon barrier membrane 13 may form part of the wall of the conduit or may be positioned in a portion, e.g., a lower portion, of the conduit with a drain. As yet another example, the housing 20b may comprise the body 32 of a device which houses the hydrocarbon barrier membrane 13, either alone, as shown in Figure Ic, or with other components. The body 32 of the device may have an inlet 33 that is coupled to a port, such as a drain port 34, of another housing 20a by any of numerous fittings. The hydrocarbon barrier membrane 13 may then be sealed within the device body 32 separating the inlet 33 from an outlet 35 or it may form part of the wall of the device body. [0019] The hydrocarbon barrier membrane 13 may be configured in numerous ways, including, for example, as a flat plate or disk, as a pleated element, e.g., a hollow, cylindrical pleated element, or as a hollow fiber element. Where the hydrocarbon barrier membrane 13 is configured as a flat plate or disk, it may be oriented generally horizontally and the upstream or higher pressure surface 14 may, for example, be the top surface of the hydrocarbon barrier membrane and the downstream or lower pressure surface may be the bottom surface. Where the hydrocarbon barrier membrane is configured as a hollow, cylindrical pleated element or as a hollow fiber element, the upstream or higher pressure surface may be the outer surface of the hydrocarbon barrier membrane and the inner surface may be the downstream or lower pressure surface, or vise versa.

[0020] The hydrocarbon barrier membrane 13 may be fashioned in a wide variety of ways, including, for example, as a multilayer composite having one or more support layers and one or more permeable membranes, including semipermeable, permselective, or porous membranes. Each support layer may comprise a woven or nonwoven fibrous or filamentous sheet or a mesh sheet or a microporous or ultraporous sheet and may be formed from a polymeric material. The support layer(s) may be positioned along the downstream or low pressure surface of the permeable membrane(s) and may serve to support the permeable membrane against the forces associated with the differential pressure across the permeable membrane. Although the support layer may be a layer separate from the permeable membrane, the support layer may alternatively be integral to the permeable membrane, e.g., the permeable membrane may be formed on or within the support layer, e.g., by solution casting or coating the permeable membrane on the support layer.

[0021] Each permeable membrane, or the combination of the permeable membranes, is arranged to allow the passage of water and resist the passage of the liquid hydrocarbon. Each permeable membrane may be porous, e.g., nanoporous, ultraporous, or microporous, and may be formed from one or more polymeric materials. Although various permeable membranes and support layers may be useful, a hydrocarbon barrier membrane, including, for example, composite permselective membrane comprising a thin permselective layer supported on a porous support such as a microporous, ultraporous, or nanoporous support, as available from Membrane Technology and Research, Inc. of Menlo Park, California, may be used in many embodiments. Various membranes are available from Membrane Technology and Research, Inc., including, for example, a membrane available under part number M-400. [0022] The multilayer composite of the hydrocarbon barrier membrane 13 may include various other layers. For example, a cushioning layer may be positioned between the support layer and the permeable membrane. The cushioning layer may comprise a thin, smooth, nonwoven polymeric sheet that protects the permeable membrane against abrasion by the rougher support layer. Further, a filter medium may be positioned upstream of the permeable membrane. The filter medium may serve to protect the permeable membrane from particulates and other foulants. Alternatively, a filter may be positioned upstream of the separation arrangement.

[0023] In operation, a pressure differential may be applied across the hydrocarbon barrier membrane 13. The nominal pressure in the first volume 11 may be greater than the nominal pressure in the second volume 12. The nominal pressure in the first volume 11 may result from the pressure applied to the liquid mixture by, for example, pumps and/or may result from the gravity head pressure of the liquid mixture in the first volume. The pressure in the first volume, the pressure in the second volume, and the differential pressure may vary from one embodiment to another. For some embodiments, the differential pressure may be about 5 bars or less, e.g. about 3 bars or less or about 2 bars or less. For example, the nominal pressure of the liquid mixture in the first volume 11 may be on the order of about 1 bar and the nominal pressure in the second volume 12 may be approximately atmospheric pressure or less.

[0024] The liquid mixture in the first volume 11 contacts the upstream surface 14 of the hydrocarbon barrier membrane 13, which resists passage of the continuous phase liquid hydrocarbon. However, the discontinuous phase water in the liquid mixture passes through the hydrocarbon barrier membrane 13. The liquid that passes through the hydrocarbon barrier membrane 13 may be, for example, at least about 90% water and less than about 10% liquid hydrocarbon, e.g., less than about 1% liquid hydrocarbon. For many embodiments, the liquid that passes through the hydrocarbon barrier membrane 13 may be less than about 5,000 parts per million (ppm) or less than about 1,000 ppm or less than about 500 ppm or less than about 200 ppm liquid hydrocarbon. Smaller amounts of liquid hydrocarbon passing through the hydrocarbon barrier membrane 13 result in less waste, fewer emissions, and better utilization of the liquid hydrocarbon.

[0025] The water which passes through the hydrocarbon barrier membrane 13 may then be removed from the downstream surface 15. For example, the water may collect in the second volume 12, and the second volume 12 may periodically be emptied of the water. Alternatively, the second volume may be connected to a drain and the liquid water may flow into the drain.

[0026] For many embodiments, the liquid water that passes through the hydrocarbon barrier membrane 13 into the second volume 12 may be evaporated by an evaporation apparatus 40, and the resulting water vapor may be vented. The water may be evaporated from the second surface 15 of the hydrocarbon barrier membrane 13 or from elsewhere inside or out of the second volume 12. The evaporation apparatus may be variously configured. For example, the evaporation apparatus may comprise a heater that warms and evaporates the water. For many embodiments the evaporation apparatus may comprise a vacuum source 40 coupled to the second volume 12, as shown, for example, in Figures Ia and Ic. The vacuum source 40 may include, for example, a vacuum pump and may be arranged to lower the pressure in the second volume 12 to any desired pressure below atmospheric pressure. The vacuum source 40 thus provides a vacuum in the second volume 12 and very effectively evaporates the liquid water, as well as any liquid hydrocarbon, that may pass through the hydrocarbon barrier membrane 13, allowing both the water and the hydrocarbon to be exhausted as vapor and vented through a vent 39, for example, to the atmosphere. Alternatively, for a device such as a burner, a combustor, or an internal combustion engine the water vapor and any hydrocarbon vapor may be returned to the device to be combusted. In addition to being a highly effective evaporator, the vacuum source 40 has many other advantages. For example, the vacuum source 40 helps draw the discontinuous phase water through the hydrocarbon barrier membrane 13, enhancing the flux rate of the water through the hydrocarbon barrier membrane 13. Further, the vacuum source 40 may be used to evaporate even highly combustible hydrocarbons in the second volume 12. [0027] Another example of a separation arrangement 10 is shown in Figure 2. The separation arrangement 10 may comprise a coalescer 41 and a hydrocarbon barrier membrane 13 that may be physically separate from but fluidly communicates with the coalescer 41. Both the coalescer 41 and the hydrocarbon barrier membrane 13 may be removably or permanently contained in a single device body or housing 32, for example, with the coalescer 41 positioned above the hydrocarbon barrier membrane 13.

[0028] The coalescer 41 may have a hollow, generally cylindrical configuration. The housing 32 may have an inlet port 33 for the liquid mixture and the inlet port may communicate with the interior of the coalescer 41. The housing 32 may also have an outlet port 36 for the liquid hydrocarbon and the outlet port may be near the top of the housing communicating with the exterior of the coalescer 41. The inlet and outlet ports may be configured as connector fittings allowing the separation arrangement to be connected to the remainder of a hydrocarbon fluid system. The coalescer 41, which includes a coalescing medium 42, aggregates small immiscible droplets of the discontinuous phase water in the continuous phase liquid hydrocarbon and forms larger droplets or volumes of water. The larger droplets or volumes of the more dense water more readily settle through the less dense liquid hydrocarbon to the hydrocarbon barrier membrane 13. A wide variety of coalescers and coalescing media may be selected for the separation arrangement 10, including those disclosed in United States Patent No. US 6,332,987 Bl, which is incorporated by reference. [0029] In addition to the coalescer 41 and the hydrocarbon barrier membrane 13, the separation arrangement 10 may also include a more rigid support element 43 which is positioned along the downstream surface 15 of the hydrocarbon barrier membrane 13. The support element 43 firmly supports the hydrocarbon barrier membrane 13 against the forces associated with the differential pressures. The support element 43 may have through holes, such as perforations or slots, or may be coarsely porous, allowing the separated water to pass through the support element 43 into the second volume 12.

[0030] The hydrocarbon barrier membrane 13 and the support element 43 may be sealed to the housing 32 in a variety of ways. For example, an O-ring seal assembly 44 may be fitted between the hydrocarbon barrier membrane 13/support element 43 and a lower portion of the housing 32. The housing 32 then defines a first volume 11 beyond, e.g., above, the upstream surface 14 of the hydrocarbon barrier membrane 13 and a second volume 12 beyond, e.g., below, the downstream surface 15 of the hydrocarbon barrier assembly 13. The housing 32 includes a water outlet port 35 for water or water vapor which fluidly communicates with the second volume 12, and the water outlet 35 may be coupled to a vacuum source (not shown). The water outlet 35 may also be configured as a connector fitting.

[0031] In operation, a liquid mixture, which includes discontinuous phase water and a continuous phase liquid hydrocarbon, e.g., a hydrocarbon fuel such as diesel fuel, may be directed along a flow path through the housing 32 of the separation arrangement 10. For example, the coalescer 41 may be sealed to the top of the housing 32 with the interior of the coalescer 41 fluidly communicating with an inlet 33 at the top of the housing 32. The liquid mixture may be directed through the inlet 33 into the interior of the coalescer 41 and then radially outwardly through the coalescer 41, coalescing the discontinuous phase water in the continuous phase liquid hydrocarbon. The less dense liquid hydrocarbon may pass upwardly within the first volume 11 along the flow path between the housing 32 and the coalescer 41 to an outlet 36 in the top of the housing 32. The more dense coalesced water passes downwardly within the first volume 11 along the outside surface of the coalescer 41 to the bottom of the coalescer 41, where the coalesced water settles by gravity into the lower portion of the first volume 11 and contacts the upstream surface 14 of the hydrocarbon barrier membrane 13. The nominal pressure in the first volume 11 may, for example, be on the order of about one bar, and the vacuum pressure in the second volume 12 may, for example, be in the range from about 0.25 bar or less to about 0.99 bar or more. The differential pressure across the hydrocarbon barrier membrane 13 drives the coalesced water from the upstream surface 14 to the downstream surface 15 of the hydrocarbon barrier membrane 13. For some embodiments, on the order of about 1 ml/hr of water may be removed from the liquid hydrocarbon through the hydrocarbon barrier membrane. For other embodiments, the removal rate may be lower or higher. While the water is removed from the liquid mixture, the hydrocarbon barrier membrane 13 resists passage of the liquid hydrocarbon. For example, less than 10% of the liquid passing through the hydrocarbon barrier membrane 13 may be liquid hydrocarbon, as previously described.

[0032] The vacuum pressure drawn in the second volume 12 by the vacuum source aids in drawing the water through the hydrocarbon barrier membrane 13 and also aids in the removal of the water by enhancing the evaporation rate of the water. To facilitate removal of the water from the hydrocarbon barrier membrane 13 and/or to further facilitate evaporation, the separation assembly 10 may include an absorbent pad, e.g., a coarsely porous absorbent pad 50 that may be readily wetted by the water. The pad 50 may be spaced from the downstream surface 15 of the hydrocarbon barrier membrane 13 to facilitate the flow of coalesced water through the membrane 13. Alternatively, the pad may abut the downstream surface of the hydrocarbon barrier membrane. The pad 50 absorbs liquid water from the downstream surface 15 of hydrocarbon barrier membrane 13, pulling liquid away from the hydrocarbon barrier membrane 13. As the liquid water and any entrained liquid hydrocarbon pass from the downstream surface 15 of the hydrocarbon barrier membrane 13 through the support element 43 into the pad 50, the liquid spreads out along the interior surfaces of the coarse pores in the pad 50 and may be more readily evaporated. The water vapor and any hydrocarbon vapor may then be exhausted by the vacuum source from the second volume 12 through the water outlet 35 and vented, for example, to the atmosphere. [0033] Another example of a separation arrangement 10 is shown in Figure 3. The separation arrangement 10 may include a hydrocarbon barrier membrane 13 and a support element 43 removably or permanently positioned within a housing 32 between an inlet port 33 for the liquid mixture and a water outlet port 35 for water or water vapor. The housing 32 does not include and is free of any outlet port for the liquid hydrocarbon. The hydrocarbon barrier membrane 13 and the support element 43 may be sealed to the housing 32 in various ways. For example, the housing 32 may bear against the outer peripheral region of the hydrocarbon barrier membrane 13, forming a compression seal 45. The first volume 11 extends beyond the upstream surface 14 of the hydrocarbon barrier membrane 13 and the second volume 12 extends beyond the downstream surface 15. A coarsely porous absorbent pad 50 may be positioned in the housing 32 in the second volume 12 spaced from the downstream surface 15 of the hydrocarbon barrier membrane 13. The spacing between the pad 50 and the hydrocarbon barrier membrane 13 may be maintained by a rigid perforated spacer 51.

[0034] The separation arrangement 10 may also include a change-out indicator 52 that indicates when the hydrocarbon barrier membrane 13 can be replaced. The change-out indicator 52 may be variously configured. For example, the change-out indicator 52 may comprise a material that changes color on exposure to the hydrocarbon. Various materials, including, for example, bromine chloride or iodine pentoxide, may be used in a variety of forms. For example, the material may be coated on the inner surface of the housing in the second volume. In the illustrated embodiment, the material may be coated on a substrate 53, such as fibers and beads, which are positioned in the second volume 12, e.g., between the coarse pad 50 and a porous or perforated plate or disk 54. A transparent portion 55 of the housing 32 may permit observation of the change in color of the substrate 53 as the material is exposed over time to the small amounts of the hydrocarbon in the second volume 12. [0035] In operation, the separation arrangement 10 may be coupled to another component in a hydrocarbon fluid system. For example, the separation arrangement 10 may be connected via the inlet fitting 33 to a drain fitting of a coalescer assembly (not shown) in a diesel fuel system of a vehicle. The upstream surface 14 of the hydrocarbon barrier membrane 13 may then fluidly communicate with the downstream surface of the coalescer, and the first volume 11 may extend from the separation arrangement 10 into the coalescer assembly. The outlet fitting 35 of the separation arrangement 10 may be coupled to a vacuum source (not shown), such as a vacuum pump on the vehicle.

[0036] As the liquid mixture, e.g., the continuous phase diesel fuel and the discontinuous phase water, is directed through the fuel system, it passes through the coalescer. The continuous phase diesel fuel continues through the coalescer assembly to the engine, while the coalesced, discontinuous phase water settles through the first volume 11 from the coalescer assembly through the connection between the coalescer assembly and the separation arrangement 10 into the separation arrangement 10.

[0037] Within the first volume 11 in the separation arrangement 10, the coalesced water settles and contacts the upstream surface 14 of the hydrocarbon barrier membrane 13. The differential pressure, e.g., about 3 bar or less, across the hydrocarbon barrier membrane 13 drives the coalesced water to the downstream surface 15 of the hydrocarbon barrier membrane 13, while the hydrocarbon barrier membrane 13 resists passage of the liquid hydrocarbon, which remains in the first volume 11. For example, less than 10% of the liquid passing through the hydrocarbon barrier membrane 13 may be liquid hydrocarbon, as previously described.

[0038] Within the second volume 12 in the separation arrangement 10, the coalesced water and any entrained liquid hydrocarbon may fall onto the coarse pad 50. The vacuum pressure drawn in the second volume 12 by the vacuum source facilitates the evaporation of the coalesced water and the liquid hydrocarbon from the pad 50 and elsewhere in the second volume 12. The water vapor and the hydrocarbon vapor, as well as some liquid water and liquid hydrocarbon, may then be drawn into the change-out indicator 52. As the hydrocarbon contacts the substrate 53, the material on the substrate 53 may change color. As more of the hydrocarbon contacts the substrate, more of the material changes color. If a significant amount of the material changes color, the separation arrangement 10 may be replaced by a new separation arrangement 10. From the change-out indicator 52, the water vapor and the hydrocarbon vapor may be exhausted by the vacuum source from the second volume 12 through the water outlet 35 and vented, for example, to the atmosphere. [0039] Various aspects of the invention have been disclosed with reference to several embodiments. However, the invention is not limited to the disclosed embodiments. For instance, one or more of the features of any embodiment may be eliminated without departing from the scope of the invention. For example, the coarse pad 50 may be eliminated from the embodiments shown in Figures 2 and 3 without departing from the scope of the invention. Further, one or more features of any embodiment may be combined with one or more features of any other embodiment without departing from the scope of the invention. For example, the change-out indicator 52 of the embodiment shown in Figure 3 may be combined with the embodiment shown in Figure 2, or the coalescer 41 of the embodiment shown in Figure 2 may be combined with the embodiment shown in Figure 3, without departing from the scope of the invention. In addition, very different embodiments may be implemented without departing from the scope of the invention. For example, the separation arrangement 10 shown in Figure 3 may be connected to a storage container for a liquid hydrocarbon, rather than a coalescer assembly, and may be used, for example, to separate discontinuous phase water that settles to the bottom of the storage container. As another example, the separation arrangement 10 shown in Figure 2 may be modified by arranging the coalescer 41 and the hydrocarbon barrier membrane 13 as a single integral unit. For many embodiments the unit may be removably contained within the housing, allowing a spent or fouled unit to be removed and a new unit to be installed. The coalescer and the hydrocarbon barrier membrane may be arranged as a unit in a wide variety of ways. For example, one of the coalescer and the hydrocarbon barrier membrane may be hollow and the other may be nested inside the hollow one. Alternatively, both may be hollow and joined end to end such that the fluid mixture flows radially out of (or into) the coalescer and the coalesced water then flows radially into (or out of) the hydrocarbon barrier membrane. In the separation arrangement 10 shown in Figure 4, the hydrocarbon barrier membrane 13 may be attached to the bottom of the coalescer 41 by a perforated sleeve 60 that extends from the O-ring assembly 44 to the blind end cap of the coalescer 41, forming a single, integral unit 61. All other aspects of the structure and operation of the separation arrangement 10 shown in Figure 4 may be identical to those of the separation arrangement 10 shown in Figure 2. The present invention is thus not restricted to the particular embodiments which have been disclosed but includes all modifications, combinations, and different embodiments that fall within the scope of the claims.

Claims

1. An arrangement for separating water from a liquid mixture including a liquid hydrocarbon as a continuous phase and water as a discontinuous phase, the arrangement comprising: a hydrocarbon barrier membrane having first and second opposite surfaces, the first surface being arranged to fluidly communicate with the liquid mixture including the discontinuous phase water, wherein the hydrocarbon barrier membrane allows passage of the water and resists passage of the liquid hydrocarbon, and an evaporation apparatus fluidly communicating with the second surface of the hydrocarbon barrier membrane to evaporate water that passes through the hydrocarbon barrier membrane.

2. The arrangement of claim 1 wherein the evaporation apparatus includes a vacuum source.

3. The arrangement of claim 1 or 2 further comprising a vent arranged to vent evaporated water to the atmosphere.

4. The arrangement of any preceding claim further comprising an absorbent pad arranged to receive water that passes through the hydrocarbon barrier membrane.

5. The arrangement of any preceding claim further comprising a change-out indicator fluidly communicating with the second surface of the hydrocarbon barrier membrane.

6. The arrangement of any preceding claim further comprising a coalescer fluidly communicating with the first surface of the hydrocarbon barrier membrane, the coalescer coalescing the water in the liquid mixture.

7. An arrangement for separating water from a liquid mixture including a liquid hydrocarbon as a continuous phase and water as a discontinuous phase, the arrangement comprising: a hydrocarbon barrier membrane having first and second opposite surfaces, the first surface being arranged to fluidly communicate with the liquid mixture including the discontinuous phase water, wherein the hydrocarbon barrier membrane allows passage of the water and resists passage of the liquid hydrocarbon, and an absorbent pad arranged to absorb water which passes from the first surface to the second surface of the hydrocarbon barrier membrane.

8. The arrangement of claim 7 wherein the pad is spaced from the second surface of the hydrocarbon barrier membrane.

9. A method for separating water from a liquid mixture including a liquid hydrocarbon as a continuous phase and water as a discontinuous phase, the arrangement comprising: contacting a first surface of a hydrocarbon barrier membrane with the liquid mixture including the discontinuous phase water, wherein the hydrocarbon barrier membrane allows passage of the water and resists passage of the liquid hydrocarbon, and evaporating the water that passes through the hydrocarbon barrier membrane.

10. The method of claim 9 wherein evaporating the water includes evaporating the water in a vacuum.

11. The method of claim 9 or 10 further comprising absorbing water that passes through the hydrocarbon barrier membrane in an absorbent pad.

12. The method of any of claims 9-11 further comprising venting the evaporated water to the atmosphere.

13. The method of any of claims 9-12 further comprising coalescing the water in the liquid mixture before contacting the first surface of the hydrocarbon barrier membrane with the liquid mixture.

14. An arrangement for separating water from a liquid mixture including a liquid hydrocarbon as a continuous phase and water as a discontinuous phase, the arrangement comprising: a housing including an inlet for the liquid mixture, an outlet for the liquid hydrocarbon, and a water outlet for water and/or water vapor; a coalescer having a coalescing medium which coalesces the discontinuous phase water in the liquid mixture, wherein the coalescer is positioned in the housing and fluidly communicates between the liquid mixture inlet and the liquid hydrocarbon outlet; and a hydrocarbon barrier membrane which allows passage of water and resists passage of the liquid hydrocarbon, wherein the hydrocarbon barrier membrane is positioned in the housing and has first and second opposite surfaces, the first surface fluidly communicating with the coalesced discontinuous phase water and the second surface fluidly communicating with the water outlet.

15. The arrangement of claim 14 wherein the coalescer is positioned above the hydrocarbon barrier membrane.

16. The arrangement of claim 14 or 15 further comprising a vacuum source fluidly communicating with the second surface of the hydrocarbon barrier membrane.

17. The arrangement of claim 14 or 15 further comprising an evaporation apparatus arranged to evaporate water that passes through the hydrocarbon barrier membrane.

18. The arrangement of claim 17 further comprising a vent arranged to vent evaporated water to the atmosphere.

19. The arrangement of any of claims 14-18 wherein the coalescer and the hydrocarbon barrier membrane are coupled as an integral unit.

20. The arrangement of any of claims 14-19 further comprising a change-out indicator fluidly communicating with the second surface of the hydrocarbon barrier membrane.

21. An arrangement for separating water from a liquid mixture including a liquid hydrocarbon as a continuous phase and water as a discontinuous phase, the arrangement comprising: a coalescer having a coalescing medium which coalesces the continuous phase water in the liquid mixture and a hydrocarbon barrier membrane which allows passage of water and resists passage of the liquid hydrocarbon, the hydrocarbon barrier membrane having first and second opposite surfaces, the first surface fluidly communicating with the coalesced discontinuous phase water, wherein the coalescer and the hydrocarbon barrier membrane are coupled to one another and are installable in or removable from a housing as an integral unit.

22. The arrangement of claim 21 wherein the coalescer is positioned above the hydrocarbon barrier membrane.

23. An arrangement for separating water from a liquid mixture including a liquid hydrocarbon as a continuous phase and water as a discontinuous phase, the arrangement comprising: a housing and a hydrocarbon barrier membrane positioned in the housing to define first and second volumes in the housing, wherein the hydrocarbon barrier membrane allows passage of the water and resists passage of the liquid hydrocarbon, wherein the hydrocarbon barrier membrane has first and second opposite surfaces, the first surface fluidly communicating with the first volume and the second surface fluidly communicating with the second volume, wherein the housing includes an inlet port for the liquid mixture, the inlet port fluidly communicating with the first volume, and an outlet port for water and/or water vapor, the outlet port fluidly communicating with the second volume, and wherein the housing is free of an outlet port for the liquid hydrocarbon.

24. The arrangement of claim 23 further comprising an absorbent pad disposed in the housing in the second volume.

25. The arrangement of claim 23 or 24 further comprising a change-out indicator operatively associated with the second volume.