US20070295674A1 - Cleaning hollow core membrane fibers using vibration - Google Patents

Abstract

A filtration system is provided with hollow membrane filter elements operable to remove solids, particulate and colloidal matter from a process fluid. Acoustic, vibration and ultrasonic energy may be used to clean exterior portions of the hollow membrane filter elements to allow substantially continuous filtration of process fluids. The filtration system may be satisfactorily used with process fluids having a relatively high concentrations of solids, particulate and colloidal matter.

Description

RELATED APPLICATIONS
• This application claims priority to U.S. Provisional Application Ser. No. 60/509,838, filed Oct. 7, 2003, and entitled “Cleaning Hollow Core Membrane Fibers Using Vibration.”
• This application claims priority to U.S. Provisional Application Ser. No. 60/509,837, filed Oct. 7, 2003, and entitled “Cleaning Hollow Core Membrane Fibers Using Acoustic Vibration Enhanced By Sound Cancellation Or Absorption.”
• This application is related to co-pending application Ser. No. 10/903,932 filed Jul. 30, 2004, and entitled “Filtration system with enhanced cleaning and dynamic fluid separation and Co-pending application Ser. No. 10/902,771 filed Jul. 30, 2004, and entitled “Filtration system and dynamic fluid separation method”/
TECHNICAL FIELD
• The present invention is related in general to the field of fluid separation, and more particularly, to fluid separation systems having hollow fiber membranes or tubes combined with enhanced cleanings of such filter elements.
BACKGROUND OF THE INVENTION
• The filtration industry is continuously looking for apparatus and methods to perform filtration for sustained periods, even when processing fluids with high amounts of solids and/or colloidal materials. A wide variety of filter media designs and configurations have been used in attempts to provide continuous filtration processes.
• This goal has led to several known techniques for continuously inhibiting the buildup of scale, solids cake or films which tend to deposit on and block passage of desired fluid flow through associated filter media. In some cases, these techniques are used intermittently, to perform what is called cyclic cleaning of filter media surfaces, usually when an associated filtration process has been suspended for such cleaning.
• Filtration systems generally require periodic removal of clogged filter media or cleaning of filter media to remove particulate matter, solids and/or colloidal matter. Such materials often build up on upstream surfaces of filter media and reduce the rate permeate or clarified fluids may flow through the filter media. Examples include buildup of mineral scale, bridged solids cake or biological films. Intermittently stopping a filtration process to manually or chemically clean upstream surfaces of filter media or to backwash clarified fluid through associated filter media is generally inefficient, labor-intensive and expensive.
• Various batch cleaning and manual cleaning techniques have been used, such as backwashing, chemical washing or hand scrubbing of filter media. Other methods for inhibiting or alleviating scaling, caking and/or filming of filter media include application of relatively violent vibration of an entire filtration device parallel to the planes of a plurality of stacked filter media and directing air or other gaseous bubbles under pressure parallel with associated filter media.
• U.S. Pat. Nos. 4,872,988; 4,952,317; 5,014,564; 5,725,767 and 6,322,698 teach relatively violent reciprocating, torsional vibration of an entire filtration devices parallel to the planes of associated stacked membranes. The patents teach shaking enclosing vessels, stacked filter leaves or plate frame filters along with associated plumbing and connecting devices, and the contained process fluid. Relatively high construction costs may be required to build structures that can withstand these constant reciprocating motions and high amounts of energy often required to generate such motion to provide commercially viable amounts of upstream membrane cleaning, for applications of sufficient value to justify the costs.
• Another method used to inhibit membrane clogging by caking, scaling or filming, is the use of air bubbling. U.S. Pat. No. 6,287,467 teaches cleaning parallel mounted flat leaf elements via air bubbling. The associated leaf filter elements generally require maintenance of uniform, structurally braced spacing between each filter leaf element to provide access for air bubbles to all membrane surfaces. The rigidly held membrane surfaces may provide a highly stable platform on which solids cake may build UP which the air bubbles can no longer remove such that manual cleaning may be required.
• Vibratory techniques such as ultrasonic excitation have been used for sensing membrane conditions, or applied to a single membrane surface, such as in small-scale laboratory explorations. U.S. Pat. No. 6,708,957; RE 37,549; U.S. Pat. Nos. 6,245,239 and 5,910,250 show the use of bubbles directed under pressure between and along upstream surfaces of clusters or skeins of hollow fiber membranes. Materials used to form hollow fiber membranes often attract the growth of scale and/or biological films such that periodic manual cleaning and/or chemical cleaning of such filter media may still be required even when bubbling techniques are used.
SUMMARY OF THE INVENTION
• In accordance with teachings of the present invention, a filtration system may be provided with at least one array or cluster of hollow fiber membranes which may be cleaned to inhibit or remove the buildup of solids cake, mineral scale and/or biological films without requiring stopping of an associated filtration process. One aspect of the invention includes either continuously or intermittently removing scale, solids cake, biological films, particulate and/or colloidal matter from exterior portions of hollow fiber membranes to maximize fluid flow through pores or openings in associated membranes and to provide substantially continuous flow of clarified fluid from an associated filtration system.
• One aspect of the present invention includes removing or inhibiting build up of mineral scale, solids cake and/or biological films that provide dynamic filtration when one or more arrays of hollow fiber membranes are used as the filter media in a high capacity, commercial filtration system. Dynamic filtration may be generally defined as the use of filter media capable of substantially continuous operation with either no interruption of an associated filtration process or substantially reduced frequency of cleaning associated filter media that interrupts and otherwise substantially continuous filtration process.
• Apparatus and methods incorporating teachings of the present invention may be used either continuously or intermittently to provide dynamic filtration depending upon characteristics of an associated filtration system, hollow fiber membranes, process fluid and desired clarified fluid flow rates. A wide variety of electrical, mechanical and electro-mechanical devices may be use to produce vibration energy in accordance with teachings of the present invention. Energy in the form of mechanically induced vibration and/or acoustically induced vibration may be used to clean hollow fiber membranes in accordance with teachings of the present invention. Sonic energy between approximately 15 and 20,000 cycles per second and ultrasonic energy generally greater than 20,000 cycles per second may be use to generate acoustically induced vibration in accordance with teachings of the present invention.
• For some applications vibration energy may be equalized, redirected or absorbed to minimize return or bounce back of vibration waves in a closed housing. Undesired return or bounce back of vibration waves may interfere with or diminish the effectiveness of primary vibration energy to produce a desired cleaning effect. Vibration energy absorbing material may be placed at selected locations within a housing to prevent or minimize undesired return of vibration waves. Also, vibration canceling drivers (mechanical or electronic) may be used to prevent or minimize undesired return of vibration waves. Various flow paths may be provided in a closed housing to return primary vibration energy to a location proximate the vibration energy source to enhance rather than diminish effectiveness of the primary vibration energy.
BRIEF DESCRIPTION OF THE DRAWINGS
• A more complete and thorough understanding of the present embodiments and advantages thereof may be acquired by referring to the following description taken in conjunction with the accompanying drawings, in which like reference numbers indicate like features, and wherein:
• FIG. 1A is a schematic drawing in section with portions broken away showing a filtration system having at least one array of hollow fiber membranes which may be used to separate a process fluid into permeate and retentate;
• FIG. 1B is a schematic drawing in section with portions broken away of a hollow fiber membrane associated with the filtration system ofFIG. 1A;
• FIG. 1C is a schematic drawing in section with portions broken away showing different positions of a hollow fiber membrane when subjected to vibration in accordance with teachings of the present invention;
• FIG. 2 is a schematic drawing in section with portions broken away showing a filtration system having at least one array of hollow fiber membranes in combination with an energy source operable to clean exterior portions of the hollow fiber membranes in accordance with teachings of the present invention;
• FIG. 3 is a schematic drawing in section and in elevation showing another example of a filtration system having at least one array of hollow fiber membranes combined with multiple energy sources operable to clean exterior portions of the associated filter media in accordance with teachings of the present invention;
• FIG. 4 is a schematic drawing in section and in elevation with portions broken away showing a filtration system having at least one array of hollow fiber membranes which may be alternately tensioned and relaxed while cleaning exterior portions of the hollow fiber membranes in accordance with teachings of the present invention;
• FIG. 5 is a schematic drawing in section and in elevation with portions broken away showing a filtration system having at least one array of hollow fiber membranes in combination with air bubbling and apparatus for cleaning exterior portions of the associated filter media in accordance with teachings of the present invention; and
• FIG. 6 is a schematic drawing in section and in elevation with portions broken away which shows a filtration system having at least one array of hollow fiber membranes which may be alternately tensioned and relaxed in combination with injecting air bubbles and acoustic or vibration ways to clean exterior portions of the associated filter media.
DETAILED DESCRIPTION OF THE INVENTION
• Preferred embodiments of the invention and its advantages are best understood by reference toFIGS. 1A-6 wherein like number refer to same and like parts.
• The term “acoustic” energy may be used to describe both sonic energy (generally equal to or less than 20,000 cycles per second) and ultrasonic energy (generally greater than 20,000 cycles per second). Acoustical vibration may be produced by sonic energy and/or ultrasonic energy.
• The term “membrane” may be used in this application to mean any material having openings or pores satisfactory for use in separating a process fluid into a clarified fluid stream and a concentrated fluid stream. Membranes satisfactory for use with filtration systems incorporating teachings of the present invention may be formed from woven materials, nonwoven materials and/or perforated plastic films. Various types of membranes may be used to form hollow fiber membranes based upon desired characteristics such as ability to separate liquids from gasses and the ability to separate suspended solids, colloidal matter and particulate matter from a fluid stream. Membrane materials may be selected with desired permeability or porosity for each application.
• The term “hollow fiber membrane” may be used to describe any generally hollow elongated tube formed from various types of membrane material. Hollow fiber membranes may also be described as “hollow fiber filter elements”, “hollow membrane tubes” and “hollow core membrane fibers”.
• Process fluid may be generally defined as a fluid stream containing liquids and/or gasses along with suspended solids, colloidal matter and/or particulate matter including, but not limited to, nanoparticles. Fluid permeable membranes may be used to separate various components of a process fluid into a clarified fluid and a concentrated fluid in accordance with teachings of the present invention. Membranes used to separate process fluids may generally be described as having an upstream side which is the side or face communicating with a process fluid. Membranes also have a downstream side or face communicating with clarified fluids removed from the process fluids.
• A hollow fiber membrane may be generally described as a hollow tube having a fluid flow path extending longitudinally therethrough. Multiple openings or pores may be formed in associated membrane material. The upstream side or upstream surface of a hollow fiber membrane is generally the exterior surface of the membrane material exposed to process fluids. The downstream side or downstream surface of a hollow fiber membrane is generally the interior surface of the membrane material. The flow path will generally collect clarified fluid which flows through the pores or openings in the membrane material. For some applications the interior surface of a hollow fiber membrane may function as the upstream side or upstream surface. However, such applications are often limited to specific types of process fluids.
• Clarified fluids may include liquids, gasses, solids, particulate matter and/or colloidal matter which has been able to pass through or permeate through openings in an associated membrane. Clarified fluids may also be referred to as “permeate” or “permeate fluids”.
• Process fluids passing over the upstream side of a membrane gradually lose associated liquids and/or gaseous components by such components permeating through openings or pores in the membrane. The remaining process fluid generally becomes relatively thicker with a higher concentration of solids, colloidal matter and/or particulate matter which will not pass through openings or pores in the membrane. The accumulation of such materials on the upstream side of a membrane may be referred to as a “retentate” or “concentrated fluid”.
• The term “fluid” may be used to include liquids, gasses or a combination of liquids and gasses.
• The term “housing” may be used to describe any container, tank, chamber, vessel, pressure vessel, cartridge, surrounding housing, frame assembly or any other structure suitable for holding an array of hollow fiber membranes in accordance with teachings of the present invention. Some housings may be open to ambient pressure or may be disposed within a reservoir holding process fluid. Other housing may be capable of holding a positive pressure or a vacuum depending upon requirements of an associated filtration process.
• To achieve sufficient surface area for high capacity, commercial filtration applications, multiple flat sheets of filter membranes are frequently collected together within a single filtration device. Various techniques may be used to combine flat sheet filter membranes such as parallel stacks mounted either horizontally or vertically or winding relatively long sheets of flat filter membrane material into various spiral configurations. To achieve sufficient surface area for high capacity, commercial scale filtration systems, a plurality of hollow fiber membranes may be bundled together in parallel arrays or clusters. Such arrays or clusters may sometimes be referred to as “skeins”.
• Some filtration systems may be formed with a plurality of hollow fiber membranes having only one end of each hollow fiber membrane attached to a single end cap. The opposite end of the hollow fiber membranes may be sealed or closed to prevent undesired fluid flow therethrough. Various features of the present invention may be used with arrays of hollow fiber membranes having only one end cap or a pair of end caps.
• The filtration systems shown in FIGS.1A and2-6, include a plurality ofhollow fiber membranes50 with opposite ends of eachhollow fiber membrane50 attached torespective end caps42 and44. Various features of the present invention, described with respect to hollowfiber membrane array40, may also be satisfactorily used to with hollow fiber membrane arrays attached to only a single end cap (not expressly shown). Mounting elements other thanend caps42 and44 may be satisfactorily used.
• One example of a filtration system having an array or cluster of hollow fiber membranes is shown in FIG.1A. For this example filtration system orfluid separation system20 may includehousing30 with one or more hollowfiber membrane arrays40 disposed therein. Hollowfiber member array40 includes a plurality of individual hollow fiber membranes ortubes50 attached to and bonded withrespective end caps42 and44. Various techniques may be satisfactorily used to couple respective ends of eachhollow fiber membrane50 withend caps42 and44. Some types of end caps may be referred to as “potting heads”. See for example U.S. Pat. No. 5,445,771 entitled “Process For Preparing Hollow Fiber Separatory Devices”; U.S. Pat. No. 6,656,356 entitled “Aerated Immersed Membrane System”; U.S. Pat. No. 6,685,832 entitled “Method Of Potting Hollow Fiber Membranes” and U.S. Pat. No. 6,739,459 entitled “Filter Element Including Bonded End Caps And Support Core”.
• Housing30 preferably includes at least a first inlet for process fluid, a first outlet for permeate or clarified fluid and a second outlet for retentate or concentrated fluid. For embodiments such as shown inFIG. 1A,housing30 includesprocess fluid inlet22, clarifiedfluid outlet24 andretentate outlet26. For some applications, fluids with increased density and any solids, scale or biological films separated from the process fluid may collect along lower portions ofhousing30. Therefore,concentrated fluid outlet26 may be formed proximate the lower portion ofhousing30.
• Housing30 may either be open to the atmosphere or may be capable of operating as a pressure vessel depending upon characteristics of the associated process fluid and fluid separation process.
• End cap44 may include multiple flow paths (not expressly shown) communicating with respectivefluid flow paths62 formed within eachhollow fiber membrane50.End cap44 may function as a permeate or clarified fluid collecting manifold to direct clarified fluid flow from respectivefluid flow paths62 to conduits extending betweenend cap44 and clarifiedfluid outlet24. For some applications,end cap42 may also function as a clarified fluid collecting manifold and may be operably coupled with an associated clarified fluid outlet (not expressly shown). Subject to variations in the type of process fluid, associated fluid flow rates and fluid pressure withhousing30, end caps42 and44 may be used to maintain relatively constant tension onhollow fiber membranes50.
• Eachhollow fiber membrane50 may have a generally circular configuration defined in part bylongitudinal axis52. SeeFIGS. 1B and 1C. Eachhollow fiber membrane50 may include generallycylindrical wall54 having a plurality of pores or opening56 disposed therein.Openings56 preferably extend fromexterior surface58 throughwall54 tointerior surface60.Interior surface60 defines in partfluid flow path62 extending generally longitudinally through eachhollow fiber membrane50 approximately parallel withlongitudinal axis52. For many applications the dimensions and configurations of each pore oropening58 may vary alongwall54, particularly for hollow fiber membranes formed from nonwoven materials. See, for example, U.S. Pat. No. 6,770,202 entitled “Porous Membrane”.
• For purposes of illustrating various features of the present invention,hollow fiber membrane50 is shown inFIGS. 1B and 1C with a generally circular cross section relative tolongitudinal axis52. However, the configuration ofhollow fiber membranes50 may vary substantially. For example,hollow fiber membranes50 may have oval, elliptical and/or circular cross sections depending upon the type of material used to form eachhollow fiber membrane50. The type of process fluid and associated operating pressure offiltration system20 may also vary the configuration ofhollow fiber membranes50.
• Arrows70 as shown inFIGS. 1B and 1C indicate the general direction of vibration energy which may be applied tohollow fiber membrane50 in accordance with teachings of the present invention. The vibration energy may be produced by a mechanical energy source or an acoustic energy source. Exterior portions ofhollow fiber membrane50 immediately adjacent to oncoming acoustical energy or vibration energy may be described as leadingface72. Exterior portions ofhollow fiber membrane50 opposite from the direction of acoustical energy or vibration may be described as trailingface74.Exterior portions76 and78 ofhollow fiber membrane50 may be described as “side faces”.
• As shown inFIG. 1C, vibration energy may have multiple effects upon exterior portions ofhollow fiber membrane50. One cleaning effect includes reciprocating movement or bouncing ofhollow fiber membrane50 as represented bydotted lines50aand50bin response to vibration energy directed generally perpendicular tolongitudinal axis52. A second cleaning effect includes turbulent scouring of side faces76 and78.
• Vibration energy and/or acoustical energy may cause movement of process fluids, scale, solid cakes and/or biological films disposed onexterior surface58 and may also movehollow fiber membrane50. The process fluid, scale, solids cake, biological film andhollow fiber membrane50 may each have different rates of movement which results in lifting or removing scale, solids cake and/or biological film from leadingface72 and trailingface74. The difference in inertia or mass of the process fluid, any scale, solids and/or biological film and each hollow fiber membrane may produce leading face turbulence and trailing face turbulence in response to acoustic and/or vibration energy. Such cleaning effects promote dynamic filtration of the process fluid.
• Acoustical energy and/or vibration energy may also create shear forces between the process fluid and side faces76 and78. The resulting shear forces may result in turbulent flow of process fluid adjacent to side faces76 and78 which lifts or removes any scale, solids cake and/or biological film disposed thereon.Arrows80 inFIG. 1C indicate such turbulent flow. Cleaning effects associated with turbulent flow adjacent to side faces76 and78 also promote dynamic filtration of the process fluid.
• Applying vibration energy to an array ofhollow fiber membranes50 in accordance with teachings of the present invention may also result in scraping or scrubbing of adjacent exterior surfaces ofhollow fiber membranes50. Movement ofhollow fiber membranes50 such as shown inFIG. 1C may result in multiple contacts or jostling of adjacenthollow fiber membranes50 with each other. This third cleaning effect may promote dynamic filtration of the process fluid.
• As discussed later in more detail, alternatively relaxing and tensioninghollow fiber membranes50 may result in exterior portions of adjacenthollow fiber membranes50 scraping or scouring one another which provides a fourth cleaning effect especially when acoustical energy and/or vibration energy is being applied. SeeFIGS. 4 and 6. Teachings of the present invention may be used to provide at least four (4) effects to clean or inhibit deposits of scale, solids cake and/or biological films on exterior portions ofhollow fiber membranes50.
• Most commercial large scale filtrations systems which contain either multiple flat sheets of membrane material or multiple arrays of hollow fiber membranes must be periodically cleaned to remove solids cake, mineral scale and/or biological films from upstream surfaces of associated filter media. Various examples of apparatus and methods for cleaning exterior portions (upstream surfaces) of hollow fiber membranes during dynamic filtration in accordance with teachings of the present invention are shown inFIGS. 2-6.
• Filtration system120aas shown inFIG. 2 combines various features of previously describedfiltration system20 withmechanical vibration system100. As previously noted, the present invention may be used with housings having various configurations. For purposes of describing various features of the present invention as represented by filtration system120,housing30amay be described as having a generally cylindrical configuration defined in part bywall32,first end closure34 andsecond end closure36.Cylindrical wall32 andend closures34 and36 may be satisfactorily formed from a wide variety of materials.
• Mechanical vibration system100 preferably includesvibration driver102 and at least oneconnector104 operable to transmit vibration energy fromdriver102 to endclosure34.Connector104 may be a plunger, piston rod or motor driven shaft.Vibration driver102 may be generally described as a linear, reciprocating mechanical driver.Vibration driver102 may include an air powered vibration generator, a motor (electrical or hydraulic) powered vibration generator or any other mechanism satisfactory for producing linear reciprocating motion ofconnector104.
• End closure34 may sometimes be described as a diaphragm operable to transmit vibration energy represented bywaves70a. Hollowfiber membrane array40 is preferably aligned withend closure34 such that vibration energy may be directed substantially normal to or perpendicular with leadingface72 of eachhollow fiber membrane50.End cap42 and44 may be securely attached with interior portions ofwall32 to maintain substantially constant tension onhollow fiber membranes50.
• Vibration waves70amay be projected along approximately the full length of eachhollow fiber membrane50. For embodiments such as shown inFIG. 2end caps42 and44 may be generally described as “stationary mounting heads” which cooperate with each other to maintain a predetermined amount of tension on associatedhollow fiber membranes50.
• For some applicationsmechanical vibration system100 may includecontrol system110.Control system110 may include one or more permeateflow rate sensors112 operably coupled withpermeate outlet24.Flow rate sensor112 may be used to detect permeate rate fromoutlet24 and any changes in permeate flow rate.Sensor112 communicates this information tologic control device114 which may include instructions to increase or decrease the amplitude and frequency of vibration energy produced byvibration driver102 to increase or decrease cleaning of associatedhollow fiber membranes50 as appropriate.
• When the increase vibration energy has removed any scale, solid cakes and/or biological materials from the exterior portions ofhollow fiber membranes50,flow rate sensor112 may detect the resulting increased permeate fluid flow rate and signal this change tologic control device114.Logic control device114 may then send a signal tovibration driver102 to change the frequency and/or amplitude of vibration energy applied to exterior surfaces ofhollow fiber membranes50 to reduce the unnecessary energy use. Such changes may be made continuously or at selected time intervals. For some applications, flow rate sensors (not expressly shown) may also be coupled withprocess fluid inlet22 andretentenate outlet26. Information from these sensors may also be communicated tologic control device114 to regulate the amplitude and frequency of vibration energy produced byvibration driver102.
• For some applications secondary vibration driver or vibration canceling106 may be operably engaged withend closure36. At least oneconnector108 may transmit vibration energy fromdriver106 to endclosure34.Secondary vibration driver106 andconnector108 may include similar features and characteristics as previously described with respect tovibration driver102 andconnector104. When vibration waves70areach end closure36 opposite fromvibration driver102,control system110 may send an appropriate signal to secondaryvibration canceling driver106 to actively equalize, cancel or reduce any vibration waves reflected fromenclosure36. Relativelysmall waves70b, as shown inFIG. 2, represent the effect ofsecondary vibration driver106 equalizing, canceling or reducing primary vibration energy reflected fromend closure36.
• For someapplications control system110 may send signals fromlogic control device114 to bothprimary vibration driver102 andsecondary vibration driver106. One or more sensors (not expressly shown) may be disposed onend closure36 to detect primary vibration waves70aand provide an appropriate signal to controlsystem110. As a result, any changes in the amplitude and/or frequency of primary vibration waves70aor initiation of vibration waves70amay result in real-time changes represented by secondary vibration waves70b.
• Vibration energy whether mechanical or acoustical will generally be more effective if the vibration energy is applied uniformly to exterior portions of all hollow fiber membranes disposed within a housing. The use ofvibration canceling driver106 andcontrol system110 in accordance with teachings of the present invention may result in substantial reduction and/or elimination of interference waves70bassociated with vibration energy returning from or bouncing back fromend closure36. As discussed later with respect tofiltration system120binFIG. 3, vibration energy absorbing material may also be disposed within selected portions of a housing to substantially reduce or eliminate undesired return or bounce back of primary vibration energy. As a result, the present invention allows primary vibration energy (vibration waves70a) to produce optimum cleaning and/or unclogging of exterior portions of associatedhollow fiber membranes50.
• The following methods and techniques may be used in accordance with teachings of the present invention to reduce, continuously cancel, absorb or redirect primary vibration energy such energy arrives at portions of an associated housing generally located opposite from an associated primary vibration driver. As previously noted, one or more sensing devices may be located at various positions withinhousing30ato detect and measure primary vibration waves70a. Generally such sensing devices will be located opposite fromprimary vibration driver102. This location will often be at the greatest distance withinhousing30afromprimary vibration driver102. One or moresecondary vibration drivers106 may be located approximately opposite fromprimary vibration driver102.Control system110 may be used to continuously interpret data from associated sensors and provide operating instructions tosecondary vibration driver106 to adjust its associated vibration energy output to actively cancel, equalize or substantially reduce primary vibration waves70aas they reachend closure36. The previous comments have been made with respect to mechanical vibration driver such as shown inFIG. 2. However, a primary electrical vibration driver and a secondary electrical vibration driver may also be used to equalize, cancel or reduce primary vibration waves in accordance with teachings of the present invention.
• Filtration system120b, as shown inFIG. 3, combines various features of previously describedfiltration system20 withelectrical vibration system130 having an array of piezo-electric transducers132. For some applications piezo-electric transducers132 may be used to produce sonic energy in the frequency range of approximately fifteen (15) to twenty thousand (20,000) cycles per second to inducevibration waves70a. For other applications piezo-electric transducers132 may be used to produce ultrasonic energy (greater than 20,000 cycles per second). The sonic energy may have a generally constant frequency or a variable frequency as appropriate for optimum cleaning of associatedhollow fiber membranes50.
• The amplitude and frequency of the acoustic energy may be adjusted to produce desired vibration ofhollow fiber membranes50. For some applications the amplitude and/or frequency of sonic signals produced bytransducers132 may remain constant. For other applications the amplitude and frequency may be intermittently or continuously variable depending upon requirements of an associated dynamic filtration process. A wide variety of electrical energy drivers may be satisfactorily used withprimary filtration system120b. The present invention is not limited to piezo-electric transducers132.
• Housing30bmay have various configurations, including generallycylindrical wall32. However,end closure34bmay be modified to accommodate attachment of piezo-electric transducers132.End closure36bor various other satisfactory end enclosures may be installed withinhousing30b. For some applications, one or more layers of vibrationenergy absorbing material134 may be disposed on interior portions ofend closure36bopposite fromtransducers132. Vibrationenergy absorbing material134 may be located and tuned for optimum results. As a result of attaching vibrationenergy absorbing material134 withend closure36b, the amplitude ofwaves70breflected fromend closure36bmay be substantially reduced or eliminated.
• For other applications, an array of piezo-electric transducers (not expressly shown) may be attached withend closure36bfor use in canceling vibration waves70aas previously described with respect tofiltration system120a. A control system (not expressly shown) may also be used to vary the amplitude and/or frequency of primary sonic energy produced bytransducers132. For the embodiment shown inFIG. 3,housing30bmay include one ormore vents38 which are open to ambient air pressure exterior tohousing30. For other applications piezo-electric transducers132 may be satisfactorily used in a sealed or closed housing.
• For someapplications housing30bor any other housing formed in accordance with teachings of the present invention may include one or more return paths (not expressly shown) to direct primary vibration waves70afromend closure36bto endclosure34bproximate piezo-electric transducers132. The returned paths may be separate passageways disposed on the exterior ofhousing30b. The return paths may be filled with various fluids to provide optimum return of primary vibration waves70a. As a result, return waves70bmay be substantially reduced or eliminated. The returned vibration waves may be synchronized with primary vibrations waves70abeing generated bytransducers132. Also, by returning substantial amounts of primary vibration waves70a, the efficiency of an associated primary vibration driver may be enhanced. For other applications one or more passageways or openings may be provided withinhousing30bto return primary vibration energy or to direct such primary vibration energy to escape fromhousing30b.
• Filtration system120c, as shown inFIG. 4, combines various features of the previously describedfiltration system120awith variable tensioning ofhollow fiber membranes50.Housing30cpreferably includeswall32cwhich has been modified to accommodate variable tensioning of hollowfiber membrane array40c. For embodiments, such as shown inFIG. 4, end caps42cand44cmay be modified to allow reciprocating longitudinally movement relative to each other and adjacent portions ofwall32c. Movement ofend caps42cand44crelative to each other may vary both the length and cross section of attachedhollow fiber membranes50.
• For some applications,brackets142 and144 may be securely attached with adjacent portions ofwall32c. End caps42cand42cmay be slidably retained withinrespective brackets142 and144. Various types of electrical and/or mechanical motors (not expressly shown) may be attached withrespective shafts146, extending fromend caps42cand44cthroughrespective openings148 in adjacent portions ofwall32c. For some applications, eachshaft146 may includehollow flow path24cextending therethrough to allow communication of clarified fluid or permeate fromfluid flow path62 of eachhollow fiber membrane50.
• Vibration wave a70aproduced byvibration driver102 may be combined with physical interference or physical scouring associated with alternately tensioning and relaxinghollow fiber membrane50. Variable tensioning plus applying vibration energy generally perpendicular tolongitudinal axis52 ofhollow fiber membranes50 will increase shaking and shearing actions to remove any scale, solids cake and/or biological films from exterior portions ofhollow fiber membranes50. Filtration system120 may also include previously describedcontrol system110 andvibration canceling driver106. Also, variable tensioning ofhollow fiber membranes50 may be satisfactorily used with an electrical vibration system.
• Fluid filtration system120d, as shown inFIG. 5, combines various features previously describedfiltration system120aalong with agas bubbling system150.
• Housing30emay include various features as previously described with respect tohousing30a. However, for embodiments such as shown inFIG. 5,housing30emay be oriented withend closures34 and36, extending generally vertically relative to wall32d.End cap42dmay be modified to accommodate gas flow frommanifold152.Gas bubbling system150 may include asource154 of relatively high pressure gas. One ormore regulators156 may be used to control the flow of gas fromsource154 tomanifold152. One ormore conduits158 may be used tocouple regulator156 withmanifold152.Insert gas source154 may provide nitrogen, air and any other suitable gas tomanifold152.
• Vibration waves70afromvibration driver102 may be projected generally perpendicular with respect to the exterior portions ofhollow fiber membranes50. Gas bubbles frommanifold152 may flow generally parallel withhollow fiber membranes50. The gas bubbles cooperate with the perpendicular vibration waves to increase scouring or cleaning of exterior portions ofhollow fiber membranes50.
• Filtration system120eas shown inFIG. 6 combines various features of previously describedfiltration systems120cand120d. Exterior portions ofhollow fiber membranes50 may be cleaned by using a combination of vibration energy produced byvibration device102, gas bubbles frommanifold152 flowing generally parallel with exterior portions ofhollow fiber membranes50 and reciprocating movement ofend cap44cto produce alternative tensioning and relaxing of attachedhollow fiber membranes50.
• For some applications the removal of scale, solids cake and/or biological films may be further enhanced by using water jets (not expressly shown) or other suitable pumps (not expressly shown) to direct fluid flow generally parallel with exterior portions ofhollow fiber membranes50. Such fluid flow may be used either intermittently or continuously. Also, such fluid flow may be used in combination with bubbles frommanifold52, alternatively tensioning and relaxinghollow fiber membranes50 and/or applying vibration energy thereto. For still other applications process fluids may be directed through one or more inlet tubes (not expressly shown) to locations disposed within each hollowfiber membrane array40. As a result, inbound movement or flow of process fluid may be used to assist with transport of any scale, solids cake and/or biological films removed from exterior portions ofhollow fiber membranes50 by any of the previously described cleaning effects.
• Filtration systems120a,120b,120c,120dand120emay be used to treat a wide variety of process fluids. Such filtration systems may include one or more arrays of hollow fiber membranes. The arrays may be mounted in side by side relationships in a housing or in a cassette (not expressly shown). The cassette may be placed in a relatively open or unrestricted reservoir. Such cassettes may also be placed in and removed from pressurized or closed housings.
• For some applications one end of the hollow fiber membranes may be attached to a mounting element such as an end cap. The hollow fiber membranes may hang from the one mounting element. For other applications both ends of the hollow fiber membranes may be attached to respective mounting elements such as a pair of end caps spaced from each other. The mounting elements may apply relatively preset or constant tension to the associated hollow fiber membranes. For still other applications both ends of the hollow fiber membranes may be attached to mounting elements operable to apply variable tension to the associated hollow fiber membranes. The amount of tension may be varied substantially continuously or may be varied intermittently during an associated dynamic filtration process.
• Previously describedfiltration systems120a,120b,120c,120dand120emay be further modified to improve associated dynamic filtration processes by applying a source of vacuum to associated clarified fluid outlets and/or applying pressure to associated process fluid inlets. Increasing the differential pressure applied to exterior portions of hollow fiber membranes may be used to increase the flow rate of clarified fluid or permeate through associatedmembrane walls54. The amount of differential pressure may be regulated to leave selected retentate components on exterior portions of the associatedhollow fiber membranes50.
• Filtration systems incorporating teachings of the present invention may be used for the following applications.
• Applications in water and wastewater treatment for municipal purposes such as:
• drinking water treatment;
• reverse osmosis reject concentration;
• reclaimed water treatment;
• primary and secondary wastewater treatment; and
• primary and secondary wastewater treatment sludge concentration.
• Applications for water and wastewater treatment for industrial purposes such as:
• ultra-pure water polishing;
• process water purification;
• car wash wastewater treatment and reuse;
• industrial laundry wastewater treatment and reuse;
• boiler feed water treatment;
• industrial wastewater pretreatment;
• sludge de-watering; and
• scrubber effluent treatment and concentration.
• Applications for water and wastewater treatment for agricultural purposes such as:
• irrigation water treatment and reuse;
• confined animal feeding operation wastewater treatment and reuse; and
• aquaculture water treatment and reuse.
• Applications in bio-manufacturing such as concentration of pharmaceutical and biotechnology products.
• Applications in food and beverage processing such as:
• ultra-pure water polishing;
• juice concentration; and
• wastewater treatment and reuse.
• Applications in chemical manufacturing and process industry such as:
• concentration of high solids;
• calcium carbonate;
• titanium dioxide;
• latex emulsion and catalysts;
• acid clarification;
• metal hydroxide treatment;
• colloidal silica filtration;
• separation of othalic acid catalyst fines;
• sodium hydroxide recovery; and
• applications in paints and pigments industry such as white water treatment and organic and inorganic pigment washing and concentration.
• Applications in the pulp and paper industry such as:
• white water treatment;
• box and bag plant effluent treatment;
• bleach plant effluent treatment
• black liquor treatment;
• paper coating effluent treatment; and
• green liquor treatment.
• Applications in the petroleum production and refining industry such as:
• recycling of petroleum;
• drilling muds;
• brine extraction;
• cracking catalyst removal;
• treatment of injection water;
• produced water;
• completion fluids;
• process water; and
• refinery wastewater treatment and reuse.
• Applications in mining industry such as:
• mineral clay de-watering;
• red mud recovery;
• mining and milling effluent treatment; and
• mine tailing processing and size classification.
• Other continuous filtration applications for the chemical industry, kaolin manufacture, metal casting industry, sludges from waste gas scrubbing, aluminum industry, steel industry and other materials processing industries.
• Although the present invention and its advantages have been described in detail, it should be understood that various changes, substitutions and alternations can be made herein without departing from the spirit and scope of the invention as defined by the following claims.

Claims (32)

1-5. (canceled)

6. A filtration system operable to separate a process fluid into a clarified fluid and a concentrated fluid comprising:

a housing having at least one inlet operable to receive the process fluid;

the housing having at least a first outlet for the concentrated fluid and a second outlet for the clarified fluid;

at least one array of hollow fiber membranes disposed within the housing;

each hollow fiber element having a first end and a second end spaced from each other;

exterior portions of each hollow fiber element exposed to contact with the process fluid and operable to separate the process fluid into the concentrated fluid and the clarified fluid;

a flow path coupling interior portions of each hollow fiber membrane with the second outlet to allow clarified fluid to exit from the housing; and

a first energy source operable to vibrate the hollow fiber membranes without interruption of an associated filtration process.

7. The filtration system ofclaim 6 further comprising:

a plurality of conduits disposed within the housing; and

the conduits operable to inject gas bubbles into the process fluid contained within the housing.

8. The filtration system ofclaim 6 wherein the housing further comprises at least one flexible portion generally aligned with each array of hollow fiber membranes to facilitate vibratory cleaning of associated hollow fiber membranes.

9. The filtration system ofclaim 8 further comprising a second flexible portion disposed in the housing generally opposite from the first flexible portion.

10. The filtration system ofclaim 9 further comprising a second energy source coupled with the flexible outer wall and operable to regulate vibration of the hollow fiber membranes.

11. A method for separating a process fluid stream into a clarified fluid stream and a concentrated fluid stream comprising:

communicating the process fluid to at least one inlet of a filtration system;

directing the process fluid to contact at least one skein of hollow fiber membrane disposed within the housing;

separating the clarified fluid from the process fluid by the clarified fluid flowing through an exterior surface of each hollow fiber membrane to a respective interior flow path disposed within each hollow fiber membrane;

directing the clarified fluid from the interior flow path of each hollow fiber membrane to at least a first outlet from the housing;

directing the concentrated fluid to at least a second outlet from the housing; and

applying energy to each skein of hollow fiber membranes to remove or inhibit buildup of scale, solids cake or film on exterior portions of the associated hollow membrane tubes.

12. The method ofclaim 11 further comprising directing sonic energy to clean exterior portions of the associated hollow membrane tubes.

13. The method ofclaim 11 further comprising directing ultrasonic energy to clean exterior portions of the associated hollow membrane tubes.

14. The method ofclaim 11 further comprising directing mechanical fibration energy to clean exterior portions of the associated hollow fiber membranes.

15. The method ofclaim 11 further comprising combining a first method for cleaning each skein with a second method for cleaning each skein.

16. The method ofclaim 11 further comprising alternatively tensioning and relaxing the hollow fiber membranes disposed within each skein to remove or inhibit any buildup of scale, solids cake or film on exterior portions of the hollow fiber membranes.

17. The method ofclaim 11 further comprising moving mounting elements attached to respective ends of each skein to remove or inhibit buildup of scale, solids cake or film on exterior portions of the hollow fiber membranes by changing the shape of the hollow fiber membranes.

18. The method ofclaim 11 further comprising producing vibration energy using an air powered vibration driver.

19. The method ofclaim 11 further comprising producing reciprocating linear mechanical vibration using a motor powered vibration driver.

20. The method ofclaim 11 further comprising directing reciprocating energy selected from the group consisting of mechanical and acoustical vibration to generate friction between the process fluid and exterior portions of the hollow fiber membranes resulting from the process fluid and the hollow fiber membranes moving at different rates.

21. The method ofclaim 11 further comprising:

directing the energy in a direction generally perpendicular with the hollow fiber membranes; and

directing gas bubbles in a direction generally parallel with the hollow fiber membranes whereby the vibration energy and the flow of bubbles cooperate with each other to enhance cleaning exterior portions of the hollow fiber membranes.

22. The method ofclaim 11 further comprising cleaning exterior portions of the hollow fiber membranes by applying vibration energy to produce leading face turbulence and trailing face turbulence adjacent to exterior portions of the hollow fiber membranes.

23. The method ofclaim 11 further comprising cleaning exterior portions of the hollow fiber membranes by applying vibration energy to produce side face turbulence adjacent to respective exterior portions of the hollow fiber membranes.

24. The method ofclaim 11 further comprising cleaning exterior portions of the hollow fiber membranes by applying vibration energy to produce scouring and scrubbing of exterior portions of the hollow fiber membranes resulting from physical contact and jostling between adjacent hollow fiber membranes.

25. A filtration system operable to separate a process fluid into selected components comprising:

a housing having at least one inlet operable to receive the process fluid;

the housing having at least a first outlet for a concentrated fluid and a second outlet for a clarified fluid;

at least one array of hollow fiber membranes disposed within the housing;

each hollow fiber membranes having a first end and a second end spaced from each other;

each hollow fiber membranes having an interior fluid flow path operable to receive clarified fluid;

exterior portions of each hollow fiber element exposed to contact with the process fluid and operable to separate the process fluid into the concentrated fluid and the clarified fluid;

a first flow path coupling the concentrated fluid with the first outlet;

a second flow path coupling interior portions of each hollow filter element with the second outlet to allow clarified fluid to exit the housing; and

a vibration energy source operable to vibrate exterior portions of each hollow fiber membrane without interruption of an association filtration process.

26. The filtration system ofclaim 25 further comprising the housing selected from the group consisting of a generally rectangular shaped tank, a generally circular shaped tank, a generally oval shaped tank or a pressurized tank.

27. The filtration system ofclaim 25 further comprising:

the vibration energy source selected from the group consisting of a linear reciprocating mechanical vibrator, a first ultrasonic vibrator, a first sonic vibrator and a first plurality of piezo-electric transducers; and

a system for managing vibration energy selected from the group consisting of energy absorbing material disposed within the housing, a linear reciprocating mechanical vibrator, a second linear reciprocating mechanical vibrator disposed opposite from the first linear reciprocating linear vibrator, a second ultrasonic vibrator disposed in the housing opposite from the first ultrasonic mechanical vibrator, a second sonic vibrator disposed in the housing opposite from the first sonic vibrator and a second plurality of piezo-electric transducers disposed in the housing opposite from the first plurality of piezo-electric transducers.

28. The filtration system ofclaim 25 further comprising a low pressure vacuum source operably coupled with the second outlet to assist with clarified fluid flow through the interior flow path of each hollow fiber tube.

29. The filtration system ofclaim 25 further comprising energy absorbing material disposed within the housing opposite from vibration the energy source.

30. A method for forming a filtration system operable to separate a process fluid into selected components comprising:

forming a housing having at least one inlet operable to receive a process fluid;

forming at least a first outlet from the housing for a retentate fluid to exit from the housing;

forming at least one second outlet from the housing for a permeate fluid to exit the housing;

forming at least one array of hollow fiber membranes;

installing the at least one array of hollow fiber membranes in the housing;

connecting at least one conduit with an interior flow path disposed within each hollow fiber membrane to allow communication of permeate fluid to the second outlet from the housing; and

installing at least one primary energy source coupled with the housing to apply primary vibration energy to the hollow fiber membranes to clean any scale, solids cake and biological film from exterior portions of the hollow fiber membranes.

31. The method ofclaim 30 further comprising:

attaching the hollow fiber membranes with a first end cap and a second end cap; and

installing the first end cap and the second cap within respective portions of the housing operable to move the end caps relative to each other to change the frequency rate associated with the hollow fiber membranes to induce rubbing between adjacent hollow fiber membranes to remove any scale, solids cake or biological film disposed on exterior portions of the hollow fiber membranes.

32. The method ofclaim 30 further comprising attaching a source of gas bubbles with the housing operable direct gas bubbles generally parallel with exterior portions of the hollow fiber membranes.

33. The method ofclaim 30 further comprising placing energy absorbing material within the housing to absorb primary vibration energy after the primary vibration energy has cleaned exterior portions of the hollow fiber membranes.

34. The method ofclaim 30 further comprising:

installing at least one secondary energy source coupled with the housing to apply vibration energy thereto; and

installing a control system connected with the primary energy source and the secondary energy source to equalize, cancel or reduce primary vibration energy after the primary vibration energy has cleaned exterior portions of the hollow fiber membranes.

35. The method ofclaim 30 further comprising forming one or more passageways extending from the housing to allow escape of primary vibration energy after the primary vibration energy has cleaned exterior portions of the hollow fiber membranes.

36. The method ofclaim 30 further comprising installing one or more flow paths operable to return primary vibration energy to a location proximate the primary energy source after the primary vibration energy has cleaned exterior portions of the hollow fiber membrane.

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