Patent Application
20110100900
The disclosure relates to a cross-flow filtration device for liquid filtration and, more particularly, to an improved cross-flow filtration device for separating a feed stock into a filtrate and a retentate.
Ceramic monolithic multi-channel substrates have been used to filter liquid, to remove particulate contaminants, to separate oily contaminants from aqueous solutions, and to separate and filter industrial liquid streams (see, for example, U.S. Pat. Nos. 4,983,423, 5,009,781, 5,106,502, 5,114,581, and 5,108,601). These substrates may be cross-flow filtration devices which separate a feed stock into filtrate and retentate. A feed stock passing through a monolith having passageways extending from a feed end and a retentate end may flow through the passageways, or may pass through the substrate into a filtrate collection zone and exit the substrate as a filtrate.
There exists a need to improve the performance of ceramic monolithic multi-channel substrates by increasing the capacity and efficiency of the filtration substrate or increasing the flux of liquid that may pass through the substrate. In embodiments of the present invention, surprisingly, by reducing the channel size of the passageways in a cross-flow device, the flux increases, improving the performance of the device.
Embodiments provide a monolithic multi-channel substrate 10 having a porous monolithic body or module 150 defining a plurality of flow channels 110 disposed in the body and extending longitudinally from an upstream inlet or feed end 1101 to a downstream outlet or exhaust end 1102 for filtering fluids. Porous channel walls 114 surround each of the plurality of flow channels 110. The porous body 150 further comprises a networked pore structure of interconnected pores forming torturous fluid paths or conduits 152. The tortuous paths 152 formed by the porous body 150 provide a flow path to allow a filtrate, separated from a feed stock, to flow through the fluid paths or conduits formed by the interconnecting pores of the porous material, to an exterior surface of the substrate for collection in a filtrate collector. This filtrate, which flows through the porous substrate, is separated from a retentate fluid stream which flows from an upstream or end face, through flow channels to a downstream or retentate end to be collected in a retentate collector, separate from a filtrate collector.
In use, the plurality of flow channels can receive an impure process or feed stream and the porous channel walls can separate at least a portion of the received process stream into a filtrate and a retentate whereby the separated filtrate is directed through the networked pore structure to an exterior surface of the body. The experimental monolithic multi-channel substrate, as exemplified in the following description, can be used for liquid-phase separation, in laboratory scale or in commercial scale, for extraction of one or more components from a fluid process stream.
In embodiments, the experimental cross-flow filtration device comprises a porous monolithic substrate defining a plurality of flow channels bounded by porous channel walls and extending longitudinally from an upstream inlet end to a downstream outlet end through which a portion of the process stream flows, wherein the plurality of flow channels have a cross sectional area (CSA), a cross sectional perimeter (CSP), and a hydraulic diameter Dh less than or equal to 1.1 mm, where Dh=4[(CSA)/(CSP)]. A membrane can be deposited on at least a portion of the plurality of porous flow channel walls. The membrane may be porous. According to some embodiments, the porous monolithic substrate has an aspect ratio of greater than 1.0, wherein the aspect ratio is defined as the ratio of module length 104 to part diameter 102. In still other embodiments, the porous monolithic substrate does not define a discrete conduit for receiving a purge stream.
In alternative embodiments, the cross-flow filtration device comprises a porous monolithic substrate defining a plurality of flow channels bounded by porous channel walls and extending longitudinally from an upstream inlet end to a downstream outlet end through which a portion of the process stream flows, wherein the plurality of flow channels have a cross sectional area (CSA), a cross sectional perimeter (CSP), and a hydraulic diameter Dh less than or equal to 1.10 mm, where Dh=4[(CSA)/(CSP)]. Once again, a porous membrane can be deposited on at least a portion of the plurality of porous flow channel walls. According to these embodiments, the porous monolithic substrate has an aspect ratio greater than 1.0. In an embodiment the porous monolith substrate contains one or more filtrate conduits 190 for permeate removal from the structure. In this embodiment, the porous monolithic substrate does not define a discrete conduit for receiving a purge stream.
Among several advantages, use of embodiments of the small-sized flow channel device having channel hydraulic diameter less than or equal to 1.8 mm, less than or equal to 1.5 mm, less than or equal to 1.25 mm, less than or equal than or equal to 1.1 mm, or less than or equal to 1.0 mm, can facilitate an increase in the surface area packing density of the module. Additionally, it was surprisingly and unexpectedly discovered, as exemplified in the following detailed description and subsequent examples, that reducing the channel size not only enhances the surface area packing density but also substantially increases permeation flux. This increase in permeation flux can be translated to a substantial increase in the filtration throughput represented by the permeation rate per unit volume of the cross-flow filtration device, and represents an increase in the efficiency of the cross-flow filtration device.
Additional embodiments and advantages of the disclosure will be set forth, in part, in the detailed description, and any claims which follow, or can be learned by practice of the disclosure. The foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive.
The accompanying drawings illustrate certain embodiments of the disclosure.
a is a perspective view of an exemplary monolithic body according to the disclosure further having a plurality of filtrate conduits 190 formed therein.
b is a cross-sectional view of the monolith body shown in
a is a graph illustration of the effect of channel size on the flux of clean water.
Low surface area packing density and high cost per unit surface area have been major barriers that hinder widespread use of inorganic cross-flow filtration devices in liquid membrane separation processes. To that end, monolith-type modules with an array of parallel membrane channels embedded in or formed from a porous solid body, typically in a cylindrical form, have been used as membrane supports for such applications. This general design advantageously offers a higher surface area and packing density than single-channel tubes of the same diameter. However, it is known that particulate retained by the membrane tends to form a filtration cake layer over time. The filtration cake layer may add flow resistance to the permeation process. In addition to surface area packing density, the channel size and shape also affect hydrodynamics and mass transfer for an actual filtration process, and thus, thickness and structures of the filtration cake layer. Embodiments of the invention disclosed in the present disclosure having small channels with round diameters shape provide solutions to these problems.
Various embodiments of the disclosure will be described in detail with reference to drawings. Reference to various embodiments does not limit the scope of the disclosure. Additionally, any examples set forth in this specification are not limiting and merely set forth some of the many possible embodiments of the invention.
The following descriptions of embodiments of the invention are provided. To this end, those skilled in the relevant art will recognize and appreciate that many changes can be made to the various embodiments of the invention described herein, while still obtaining the beneficial results of embodiments of the present invention. It will also be apparent that some of the desired benefits of embodiments can be obtained by selecting some of the features of the embodiments without utilizing other features. Accordingly, those who work in the art will recognize that many modifications and adaptations are possible and can even be desirable in certain circumstances and are a part of the present invention. Thus, the following description is provided as illustrative of the principles of the present invention and not in limitation thereof.
In this specification and in the claims which follow, reference will be made to a number of terms which shall be defined to have the following meanings:
As used herein, the singular forms “a,” “an” and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to a “component” includes embodiments having two or more such components, unless the context clearly indicates otherwise.
“Optional” or “optionally” means that the subsequently described event or circumstance can or cannot occur, and that the description includes instances where the event or circumstance occurs and instances where it does not. For example, the phrase “optional component” means that the component can or can not be present and that the description includes both embodiments of the invention including and excluding the component.
Ranges can be expressed herein as from “about” one particular value, and/or to “about” another particular value. When such a range is expressed, another embodiment includes from the one particular value and/or to the other particular value. Similarly, when values are expressed as approximations, by use of the antecedent “about,” it will be understood that the particular value forms another embodiment. It will be further understood that the endpoints of each of the ranges are significant both in relation to the other endpoint, and independently of the other endpoint.
Reference will now be made in detail to embodiments of the invention, examples of which are illustrated in the accompanying drawings. It should be noted however that the drawings are not necessarily drawn to scale.
Referring to
The monolithic body 150 can have any desired predetermined size and shape. For example, although the body or module 150 is exemplified as a cylinder with a substantially circular cross-section in
As used herein, the term hydraulic diameter (Dh) of a particular geometric element is defined by the following formula: Dh=4[cross-sectional area (CSA) of the geometric element/cross-sectional perimeter (CSP) of the geometric element]. Thus, for a two-dimensional shape, the hydraulic diameter is 4 times the surface area divided by the perimeter. For example, for a circle of diameter “d”, the hydraulic diameter Dh=4[(πd2/4)]/(πd). However, for a square of length L, hydraulic diameter Dh=4×L2/(4 L). In general, it should be understood that a hydraulic diameter bears an inverse relationship to the surface to volume ratio.
In embodiments, the body 150 has a module hydraulic diameter 102 in a range about 10 to 200 mm. In embodiments, the body 150 has a module hydraulic diameter 102 greater than about 10 cm. As used herein, the hydraulic diameter 102 of the body or module 150 refers to the hydraulic diameter of the total module frontal area. The total module frontal area is the cross-sectional area of the module body that includes the solid matrix of porous material and the plurality of flow channel openings. For example, for a cylindrical body or module of diameter d, the total module frontal area is πd2/4.
The body 150 also has an aspect ratio of the module length 104 to the module hydraulic diameter 102 that is greater than 1. In some embodiments, the aspect ratio is greater than 3. In still other embodiments, the aspect ratio is greater than 5. For example, the module length 104 may be 30 mm while the module hydraulic diameter may be 5 mm, having an aspect ratio of 6. In embodiments, the module length 104 may be greater than 10 cm, greater than 20 cm, greater than 30 cm, or greater than 40 cm.
The plurality of flow channels 110 may be distributed in parallel and symmetrically over the module cross-section. The flow channels also extend from the module upstream inlet end 1101 to the module downstream outlet end 1102, forming a pathway through which a desired process stream can pass. In the exemplified embodiment, the flow channel cross-sectional shape is circular or rounded. However, it should be understood that the flow channel cross-section shape can be any desired elliptical or polygonal shape this is continuous and which preferably has substantially no sharp corners. Exemplary channel cross-sectional shapes include ellipses, circles, rectangle, square, pentagonal, hexagonal, octagonal, and the like.
In embodiments, the plurality of flow channels are sized and shaped to provide a channel hydraulic diameter 112 that is not greater than 1.8 mm. Similar to the calculation of the module or body hydraulic diameter, the channel hydraulic diameter is determined according to the equation: Dh=4[cross-sectional area (CSA) of the flow channel/cross-sectional perimeter (CSP) of the flow channel]. Thus, for a two-dimensional shape, the hydraulic diameter of the flow channel is 4 times the surface area divided by the perimeter. For example, for the substantially cylindrical flow channels exemplified in
In additional embodiments, the plurality of flow channels 110 are further sized and shaped to provide a flow channel density such that the open frontal area (OFA) fraction of the module 150 is in the range of from 20% to 70%. The open frontal area fraction is the ratio of overall open channel areas to the total module frontal area. For example, for an exemplary module having a total frontal cross-sectional area of 10 cm2, if the total open channel area is 5 cm2, then the open frontal area fraction is 5 cm2/10 cm2 or 50%, where the total open channel area is the sum of cross-sectional areas for all of the channels. In an exemplary and non-limiting embodiment, the plurality of flow channels 110 define a channel density in the range of about 50-800 channels/in2 (7.8-124 channels/cm2) in a module frontal area.
The flow channels are preferably distributed over the module cross-section symmetrically but may not need to be distributed uniformly. Even though the channel distribution is shown uniform in
In embodiments, the monolithic body 150 can be formed from any suitable porous material including inorganic or organic materials, or combinations or composites of organic-inorganic material. In some embodiments, the monolithic body can for example be comprised of a polymeric material. In embodiments, the polymeric material may be, for example, polysulfone, polyacylonitrile, polyvinylidenefluoride, or polyolefin. In other embodiments, the monolithic body can be comprised of metallic or ceramic materials. In an embodiment, the monolithic body is comprised of a porous ceramic material. For example, and without limitation, in some embodiments the porous monolith body 150 is made from a ceramic composition selected from mullite (3Al2O3-2SiO2), alumina (Al2O3), silica (SiO2), cordierite (2MgO—2Al2O3-5SiO2), silicon carbide (SiC), alumina-silica mixture, glasses, inorganic refractory materials and ductile metal oxides. In another embodiment, the monolith body 150 is comprised of a porous ceramic mullite, such as the mullite compositions disclosed and described in U.S. Pat. No. 6,238,618, the entire disclosure of which is incorporated by reference herein.
As noted above, the porous material which forms the module or body 150 is comprised of an interconnected matrix or network of pores which forms a networked plurality of tortuous fluid paths or conduits 152. The fluid conduits 152 are capable of directing separated filtrate that has permeated the flow channel walls to an exterior surface of the body 150 for subsequent collection or processing. According to embodiments of the disclosure, the total pore volume or porosity % P of the ceramic monolith is in the range of from 20% to 60%, including exemplary porosity values of 25%, 30%, 35%, 40%, 45%, 50% and 55%. Still further, the total porosity of the ceramic monolith can also be within a range derived from any two of the aforementioned porosity values.
In embodiments, the pore volume of the monolithic body 150 has pores having pore diameter sizes in the range of from 2 μm to 20 μm, including exemplary pore diameter sizes of 3 μm, 5 μm, 7 μm, 9 μm, 11 μm, 13 μm, 15 μm, 17 μm, and even 19 μm. Still further, the total porosity of the monolithic body can be in a range derived from any two of the above mentioned porosity values.
The pore size and total porosity % P are values that can be quantified using conventionally known measurement methods and models. For example, the pore size and porosity can be measured by standardized techniques, such as mercury porosimetry and nitrogen adsorption.
The module or body 150 can be prepared by any conventionally known casting or extrusion methods. For example, the module or body can be comprised of a sintered ceramic composition having mullite as its primary phase. The sintered ceramic can be prepared from an extrudable plasticized batch composition comprised of ceramic forming raw materials, an organic binder system, and an optional liquid vehicle. The extrudable mixture can be extruded to form a green body of the desired configuration. The green body can be dried and fired for a time and at temperature sufficient to form a sintered ceramic structure. The filtrate conduits can be formed in the monolith, for example, at the time of manufacture by extrusion or by other means after extrusion. Exemplary plasticized batch compositions and manufacturing processes for preparing the monolithic structures of the instant disclosure are those disclosed and described in U.S. Pat. No. 6,238,618, the entire disclosure of which is incorporated by reference herein.
For processing fluid streams in applications such as coarse microfiltration, extraction, fluid mixing, and the like, the porous monolith body 150 can be used by itself in the absence of an added membrane layer. However, for other fluid stream processing applications, a porous membrane can be deposited on at least a portion of the porous flow channel walls.
If desired, an optional intermediate layer 160 of porous materials that may have smaller pore sizes than the pores of the monolith matrix can be deposited onto the channel wall 114 of the substrate or matrix body portion 150 and can be used alone or with a membrane film 140. In embodiments, these layers, 160 and 140, may be referred to as membranes, coatings, films, coating layers or coating films. The coating layer 160 can serve one or more possible functions. In some embodiments, the coating 160 can be applied to modify the flow channel shape and wall texture, including such parameters as pore size, surface smoothness, and the like. In other embodiments, the coating layer 160 can be used to strengthen the monolithic body 150. In still further embodiments, the coating layer 160 can be used to enhance the membrane deposition efficiency and adhesion.
In embodiments, the porous coating layer 160 may be deposited such that it exhibits a layer thickness in the range of from about 5 to 150 μm. Further, the pore volume of the optional coating layer 160 may be comprised of pore sizes in the range of from 2 nm to about 500 nm. In embodiments, the porous coating layer has a total pore volume % P having pores having an average pore size diameter of less than 200 nm. Thus, one or more intermediate porous coating layers 160 can optionally be disposed on the inner surfaces or walls 114 of the plurality of feed flow channels 110 to form a nano- or meso-porous layer.
In embodiments, the optional layer 160 may be comprised of a material selected from the group consisting of alumina, silica, mullite, glass, zirconia, titania, or a combination of any two or more thereof. In an additional embodiment, the intermediate layer 160 is comprised of alumina, zirconia, silica or titania. The intermediate coating layer 160 may be applied by conventionally known wet chemistry methods such as a conventional sol-gel process.
Optionally, an additional membrane film 140 providing a separation function can be further applied onto the optional intermediate coating layer 160 or directly on the inner surfaces or walls 114 of the plurality of feed flow channels 110 of the monolithic body 150. To that end, because the layer 160 can be used alone, without another layer, the term “membrane” as used herein refers to embodiments comprising the use of the layer 160 alone, use of the layer 140 alone, or the use of both layers 140 and 160. Multiple layers of membrane may be present. The membrane 140 can be comprised of inorganic or organic materials. For example, in some embodiments, the membrane film 140 can be a dense layer, or a non-metallic dense film that allows permeation of certain molecules in a mixture, such as SiC, or glass. In still other embodiments, the membrane film 140 can be a micro-porous layer comprised of, for example, zeolite, zirconia, alumina, silica, titania, or glass. These exemplary microporous membrane materials can be used to provide a separation function in the molecular size level. In still further embodiments, the membrane layer 140 can be a polymeric membrane film. When present, the porous membrane layer 140 is preferably deposited such that it exhibits a layer thickness in the range of from about 1 to 20 μm. Further, the pore volume of the optional additional membrane layer 140 is preferably comprised of pore sizes less than about 200 nm.
In embodiments, the substrate can be used for separating, purifying, filtering, or other processing functions for a variety of liquid-phase mixtures through a plurality of tortuous paths 152 through the matrix of the porous body portion 150 having membraned sections 1521 and a non-membraned porous body sections 1522. In general, the concept of tortuosity, is defined as the difference between the length of a flow path which a given portion of a fluid or a mixture of fluids will travel through the passage formed by the channel as a result of changes in direction of the channel and/or changes in channel cross-sectional area versus the length of the path traveled by a similar portion of the mixture in a channel of the same overall length without changes in direction or cross-sectional area, in other words, a straight channel of unaltered cross-sectional area. The deviations from a straight or linear path, of course, result in a longer or more tortuous path and the greater the deviations from a linear path the longer the traveled path will be.
In embodiments, the membrane module 10 has a structure that in use can be placed vertically as shown in
With reference to
In some embodiments, the filtrate conduits 190 may extend longitudinally from the upstream inlet or feed end to the downstream outlet or exhaust end of the structure. Alternatively, at least one of the filtrate conduits can extend longitudinally with the one or more flow channels along at least a portion of its length. As further shown in
In embodiments of the present invention, which provide filtrate conduits 190, blocked at both a feed end 1101 and an outlet end 1102 with barriers 194, received process stream enters the monolith 150 at the inlet end 1101 of the monolith. A portion of the received process stream, the retentate, flows through the monolith 150 through flow channels 110, to the exit end 1102 as shown by arrow 225 in
The filtrate conduits 190 provide flow paths of lower flow resistance than that of flow channels 110 through the porous material, and the structure is constructed such that the filtrate conduits are distributed among the passageways to provide low pressure drop flow paths from the passageways through the porous material to nearby filtrate conduits. The plurality of filtrate conduits can carry filtrate from within the structure toward a filtrate collection zone 300 (see
In embodiments, filtrate conduits 190 may be absent (as shown in
In some embodiments, it is also contemplated that the porous monolithic substrates of the disclosure specifically do not define a discrete conduit for receiving a second stream of fluid, separate from the process or fluid stream, for example a purge stream. Such exemplary discrete conduits for receiving a purge stream are described and disclosed in U.S. Pat. No. 7,169,213. For example, it is surprisingly found that embodiments of the present invention operate favorably without the need for a second fluid stream, introduced to the monolith through a discrete purge stream conduit, flowing through the monolith to act as a purge stream or a sweep stream to force the flow of filtrate through the monolith body, into the filtrate conduits 190, and out of the monolith through the slots 192. This feature, a separate fluid stream to sweep the filtrate through the monolith body, is an example of a feature that may be necessary to allow a larger diameter part, larger in diameter than, for example, 5 cm, 10 cm, 15 cm or 20 cm, to operate in the absence of slots 192.
In use, the cross-flow filtration device can be used for separation processes wherein the mixed feedstream 180 is a liquid-phase stream, such as a water-based solution containing other larger components. The larger components can be larger molecules and/or particulates. Thus, a water mixture can have finely-dispersed oil droplets from an industrial waste water stream. Water mixtures can have particulates such as in a beverage juice. Water mixtures can have macro molecules such as proteins. Embodiments of the cross-flow filtration device are appropriate for separation processes with water as the permeate, because water as the smallest molecule the liquid mixture would have a larger permeability through the substrate matrix than the other components. Moreover, the cross-flow filtration device is also particularly preferred for separation processes of liquid mixtures involving organic solvents where the organic solvent is the permeate. The liquid-phase stream could be an organic solvent-based solution containing other larger components.
For a body 150 having a given monolith hydraulic diameter and open frontal area fraction, the surface area packing density of the module increases with decreasing channel size. Thus, the use of the small-sized flow channels having channel hydraulic diameter less than or equal to 1.1 mm facilitates an increase in the surface area packing density of the module. However, it was surprisingly found as exemplified in the following examples, that reducing the channel size not only enhances the surface area packing density but also substantially increases permeation flux, which can be translated to substantial increase in the filtration throughput represented by the permeation rate per unit volume of the membrane module.
It will be apparent to those skilled in the art that various modifications and variations can be made to the described embodiments to include processing applications, such as sensors, without departing from the spirit and scope of the invention. Thus it is intended that the present invention include modifications and variations of the described embodiments.
To further illustrate embodiments, the following examples are put forth so as to provide those of ordinary skill in the art with a description of how embodiments of the cross-flow filtration device are made and evaluated. They are intended to be purely exemplary of the invention and are not intended to limit the scope of what the inventors regard as their invention. Unless indicated otherwise, parts are parts by weight, temperature is ° C. or is at ambient temperature, and pressure is at or near atmospheric.
A comparative cylindrical monolith support was prepared by a conventional extrusion process utilizing a circular extrusion die. The comparative cylindrical monolith had a hydraulic diameter of about 1.08 inches and a module length of 12 inches. The module comprised 60 square flow channels having a channel width of 1.85 mm. The flow channels were uniformly distributed over the cross-sectional area of the module. The resulting module had a surface area of 1.46 ft2 (0.135 m2) and an open frontal area of 205.4 mm2. The comparative monolith did not have slots or filtrate conduits.
The monolith support was formed of a porous mullite material having a mean pore size of about 4.5 μm and total porosity of about 40%. The surface of the flow channel walls were first pre-coated with a mixture of zircon and alpha-alumina followed by a layer comprised of a mixture of alpha-alumina and zirconia to provide an intermediate porous coating. The resulting intermediate porous coating was comprised of a mean pore opening in the range of about 50 to 200 nm. A top layer coating of titania was finally applied to provide an outer membrane layer having a mean pore opening of about 10 nm.
An experimental cylindrical monolith support (a cross-flow filtration device according to embodiments of the present invention) was prepared by an extrusion process utilizing a circular extrusion die. The experimental cylindrical monolith had a hydraulic diameter of about 9.7 mm and a module length of 133 mm. The module comprised 19 rounded flow channels each having a channel diameter of 0.88 mm. The flow channels were uniformly distributed over the cross-sectional area of the module. The resulting module had a surface area of 0.0070 m2 and an open frontal area of 11.61 mm2. In this embodiment, the experimental monolith did not have slots or filtrate conduits.
The experimental monolith support was formed of a porous mullite material having a mean pore size of about 4.5 μm and total porosity of about 40%. The surface of the flow channel walls were first pre-coated with a mixture of zircon and alpha-alumina followed by a layer comprised of a mixture of alpha-alumina and zirconia to provide an intermediate porous coating. The resulting intermediate porous coating had a mean pore opening in the range of about 50 to 200 nm. A top layer coating of titania was finally applied to provide an outer membrane layer. In this manner, three membrane coated monolithic bodies were prepared having top layer membrane coatings with pore openings of about 200 nm, 50 nm, and 10 nm respectively.
Utilizing comparative and experimental monolithic bodies prepared according to Examples 1 and 2 above, filtration testing was conducted over a cross-flow filtration apparatus 200 as schematically illustrated in
For each filtration test, for both the comparative and the experimental monolithic, membrane body 150 was housed in a vessel 210, as shown in
Flux values were calculated according to the following equation:
where “Fp”=Permeation flow rate and “SAM”=Membrane surface area.
Permeance was calculated by the following equation:
where “TMPavg”=Average trans-membrane pressure as calculated by the equation:
where “PF,in”=Inlet pressure; “PF,out”=Outlet pressure; and Po=Pressure on the permeation side.
The Cross-flow linear velocity was calculated by the following equation:
where “Rin”=Cross-flow rate and “SAopen”=Total cross-sectional area of open channels.
Based upon the filtration test procedures described above,
Still further, it was expected that process flux (flow normalized to membrane surface area) on the paint test would be independent of membrane channel size and, as such, throughput flow would be strictly proportional to membrane surface area.
Without intending to be bound or limited by theory, it is believed that the difference in the filtration performance between two different sizes of membrane channels may be explained by difference in the filtration cake layer. As schematically illustrated in
This application claims the benefit of U.S. Provisional Application Ser. No. 61/125,707 filed Apr. 28, 2008 and entitled “Monolith Membrane Module for Liquid Filtration”.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/US09/02587 | 4/28/2009 | WO | 00 | 12/7/2010 |
| Number | Date | Country | |
|---|---|---|---|
| 61125707 | Apr 2008 | US |
